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Abstract
As a natural analogue of glutamate, l-theanine is the unique amino acid derivative in green tea. Although its underlining mechanisms are not yet clear, it has been suggested that l-theanine treatment may prove beneficial to patients with neurodegenerative diseases. In this study, we investigated the neuroprotective effect and its mechanism of l-theanine in an in vitro model of Alzheimer's disease by using the human APP (Swedish mutation) transgenic SH-SY5Y cell. Amyloid beta (Abeta) neurotoxicity was triggered by l-glutamate in this cell line. Additionally, l-theanine significantly attenuated l-glutamate-induced apoptosis at similar levels to those seen with the NMDA receptor inhibitor MK-801 in the stably expressing APP Swedish mutation SH-SY5Y cells which over-generated Abeta. Meanwhile, the activation of c-Jun N-terminal kinase and caspase-3 induced by l-glutamate was suppressed by l-theanine. We also found that cells treated with l-theanine showed decreased production of nitric oxide resulting from the down-regulated protein levels of inducible nitric oxide synthase (iNOS) and neuronal nitric oxide synthase (nNOS). These results indicate that the inhibition of the NMDA subtype of glutamate receptors and its related pathways is the crucial point of the neuroprotective effect of l-theanine in the cell model. Thus, our present study supports the notion that l-theanine may provide effective prophylaxis and treatment for Alzheimer's disease.
... L-TH can alleviate Aβ-induced oxidative stress and activate ERK1/p38MAPK and NF-κB pathways to inhibit neuronal cell death (Kim et al. 2009). Furthermore, L-TH showed anti-neurotoxicity induced by L-glutamate on APPsw-overexpressing SH-SY5Y cells by overactivating the NMDA receptor and its associated pathways (Di et al. 2010). As a natural antagonist of glutamate, L-TH can prevent the increase of Aβ secretion caused by excessive activation of NMDA receptors, regulate Ca 2+and NO-related cell signaling pathways, and protect nerve cells from apoptosis (Di et al. 2010). ...
... Furthermore, L-TH showed anti-neurotoxicity induced by L-glutamate on APPsw-overexpressing SH-SY5Y cells by overactivating the NMDA receptor and its associated pathways (Di et al. 2010). As a natural antagonist of glutamate, L-TH can prevent the increase of Aβ secretion caused by excessive activation of NMDA receptors, regulate Ca 2+and NO-related cell signaling pathways, and protect nerve cells from apoptosis (Di et al. 2010). L-TH also shows anti-inflammatory effects by reducing the expression of the inflammation-related factors TNF-α and IL-1β (Park et al. 2018). ...
... Caffeine reduces the damage to mitochondrial electron transport by reducing the formation of ROS to prevent the activation of caspase-3 (Dragicevic et al. 2012). L-TH can inhibit caspase activation induced by L-glutamate (Di et al. 2010). PQQ derivatives can improve metabolic circulation through BBB to effectively protect neurons (Murray 2020). ...
Alzheimer's disease (AD) has brought a heavy burden to society as a representative neurodegenerative disease. The etiology of AD combines multiple factors, concluding family, gender, head trauma, diseases and social psychology. There are multiple hypotheses explaining the pathogenesis of AD such as β-amyloid (Aβ) deposition and tau hyperphosphorylation, which lead to extracellular amyloid plaques and neurofibrillary tangles in neurons. The existing therapeutic drugs have several disadvantages including single target, poor curative effect, and obvious side effects. Tea contains many bioactive components, such as tea polyphenols (TPP), L-theanine (L-TH), tea pigment, tea polysaccharides and caffeine. The epidemiological investigations have shown that drinking tea can reduce the risk of AD. The mechanisms of tea active ingredients in the prevention and regulation of AD includes reducing the generation and aggregation of Aβ; inhibiting tau aggregation and hyperphosphorylation; inhibiting neuronal apoptosis and regulate neurotransmitters; relieving oxidative stress and neuroinflammation as well as the regulation of intestinal flora. This review summarizes the different signaling pathways that tea active ingredients regulate AD. Furthermore, we propose the main limitations of current research and future research directions, hoping to contribute to the development of natural functional foods based on tea active ingredients in the prevention and treatment of AD.
... Aβ 1-42 concentration in the cerebral cortex and hippocampus was reportedly significantly decreased in mice fed Ltheanine for 5 weeks [33]. We found that the concentrations of AGEs and Aβ 1-42 were significantly increased when induced with D-galactose and then decreased after L-theanine treatment, which is consistent with the fact that nutritional intervention with L-theanine effectively reduced the amount of AGEs and Aβ 1-42 in brain tissues [33,34]. Progressive cognitive impairment is also related to dynamic changes in ACh and AChE activity [35]. ...
... Similarly, our results showed that L-theanine inhibited the AChE activity and restored normal levels of ACh in brain tissues, thereby repressing the damage caused by AGEs and Aβ 1-42 . These findings were consistent with the fact that Oxidative Medicine and Cellular Longevity L-theanine blocked the increase in Aβ 1-42 content and AChE activity induced by external stress and prevented AD [33,34,36]. ...
... Apoptosis is an active form of programmed cell death, which is closely related to AD lesions and is regulated by 7 Oxidative Medicine and Cellular Longevity specific proteins, including Bcl proteins and caspases [54]. Cho and Di reported that L-theanine has antineuronal apoptosis effects, suggesting applications in the prevention and treatment of neurodegenerative diseases [34,55]. L-Theanine inhibited the expression of the apoptotic proteins, including Bax and cleaved-caspase-3. ...
The maintenance of homeostasis is essential for mitigating stress and delaying degenerative diseases such as Alzheimer's disease (AD). AD is generally defined as the abnormal production of β-amyloid (Aβ) and advanced glycation end products (AGEs). The effects of l-theanine on Aβ and AGE generation were investigated in this study. Decreased AGEs and Aβ 1-42 levels were reflected by increased acetylcholine (ACh) concentration and acetylcholinesterase (AChE) activity inhibition compared to model rats. l-Theanine also inhibited nuclear factor-κB (p65) protein expression by activating sirtuin1 (SIRT1), reducing inflammatory factor expression, and downregulating the mRNA and protein expression of AGE receptors (RAGE). Superoxide dismutase 2 and catalase protein expressions were markedly upregulated by l-theanine, whereas oxidative stress-related injury was alleviated. The expression of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) was also found to be increased. H&E staining showed that the apoptosis of hippocampal neurons was mitigated by decreased Bax and cleaved-caspase-3 protein expression and the increase of Bcl-2 protein expression. Moreover, l-theanine increased the gene and protein expression of brain-derived neurotrophic factor (BDNF). These findings suggest that the potential preventive effects of l-theanine against AD may be attributed to its regulation of SIRT1 and BDNF proteins and its mitigation of AGEs/RAGE signaling pathways in the brain tissue of AD model rats.
... The results of HAL treatment affecting the production of TBARS in rat striatum are shown in Figure 3. HAL treatment (1 mg/kg for 21 days) induced a significant increase in the TBARS level in rat striatum (t-test, P < 0.001). The two-way ANOVA revealed significant main effects of groups (C vs. H) (F [1,36] =78.35, P < 0.001; partial Eta squared = 0.716) and LT treatment (F [2,36] = 25.86, ...
... The effects of HAL on the NO production in rat striatum are shown in Figure 7. HAL treatment (1 mg/kg for 21 days) significantly increased the NO concentration in rat striatum (t-test, P < 0.001). The two-way ANOVA revealed significant main effects of groups (C vs. H) (F [1,36] =168.92, P < 0.001; partial Eta squared = 0.851) and LT treatment (F [2,36] = 55.72, ...
... Data were analyzed using two-way ANOVA, post hoc with one-way ANOVA and Tukey pairwise tests (**P < 0.01, ***P < 0.001 by comparing within the group; ## P < 0.01, ### P < 0.001 by comparing to the C) rats to reduce oxidative stress, thus preventing and the subsequent cytotoxic injury. [36,37] The nNOS isoform of NOS produces toxic effect through NO. Therefore, LT's inhibition on nNOS may be one of its neuroprotective mechanisms. ...
Having powerful antioxidative properties, L-theanine (LT), one of the major amino acid components in green tea, has potent anti-oxidative and neuroprotective effects. In this study, we examined the potential protective effects of LT on haloperidol (HAL)-induced orofacial dyskinesia (OD) in rats. HAL treatment (1 mg/kg intraperitoneally for 21 days) induced OD; significant increases (P < 0.001) in the frequency of vacuous chewing movement and tongue protrusion as well as the duration of facial twitching. LT treatment (100 mg/kg orally for 35 days, starting 14 days before HAL injection) was able to prevent most of the HAL-induced OD. LT treatment was also able to reduce the lipid peroxidation production and nitric oxide (NO) level, and enhance the antioxidation power in striatum from rats with HAL treatment. In order to examine the implication of NO pathway activity in HAL treatment, either NO precursor (L-arginine) or NO synthase inhibitor (L-NAME) was co-pretreated with LT; NO precursor treatment eliminated the protective effect of LT, in contrast to that NO synthase inhibitor treatment significantly potentiated the LT effects on behavioral and biochemical protection in HAL-treated rats. These results suggested that the NO pathway was implicated, at least in part, in the HAL-induced OD, as well as in the protective effect of LT in treating HAL-induced OD. The above evidence provides a clinically relevant value for LT in delaying or treating tardive dyskinesia.
... As described previously, over-stimulation of the NMDA receptor will lead to calcium influx, ROS production, neuro toxicity induced by Aβ, and eventually accelerate the Aβ production. Based on those findings, L-theanine may have neuroprotective activities against the Aβ and L-glutamate induced neurotoxicity and these hypotheses were supported by recent studies [156]. ...
... In the APPsw cell model, cell viability was improved by Ltheanine. L-glutamate induced apoptosis and caspase-3 activation was suppressed by L-theanine, and these effects may be associated with the inhibition of nitric oxide (NO) overproduction, NMDA receptor over-activation, the disturbance of calcium homeostasis and the related pathways [156,157]. In addition, it was also discovered that L-theanine may inhibit the extracellular signal-regulated kinase (ERK) and p38 MAPK pathway induced by Aβ 42 , and the activity of NF-κB, which lead to the reduction of Aβ 42 in cortex and hippocampus and eventually attenuate the learning and memory impairment induced by Aβ 42 in AD mice models. ...
P>Alzheimer’s disease (AD) is a progressive and deadly neurodegenerative disease that is characterized by memory loss, cognitive impairment and dementia. Several hypotheses have been proposed for the pathogenesis based on the pathological changes in the brain of AD patients during the last few decades. Unfortunately, there is no effective agents/therapies to prevent or control AD at present. Currently, only a few drugs, which function as acetylcholinesterase (AChE) inhibitors or N-methyl-Daspartate (NMDA) receptor antagonists, are available to alleviate symptoms.
Since many small molecule natural products have shown their functions as agonists or antagonists of receptors, as well as inhibitors of enzymes and proteins in the brain during the development of central nervous system (CNS) drugs, it is likely that natural products will play an important role in anti-AD drug development. We review recent papers on using small molecule natural products as drug candidates for the treatment of AD. These natural products possess antioxidant, anti-inflammatory, anticholinesterase, anti-amyloidogenic and neuroprotective activities. Moreover, bioactive natural products intended to be used for preventing AD, reducing the symptoms of AD and the new targets for treatment of AD are summarized.</P
... Activation of the JNK and p38 pathways further induce the stimulation of effector caspases, including Caspase-3 [39,40]. Previous studies have also reported that L-theanine exerts anti-apoptosis effects by suppressing the activation of JNK or p38 and NF-kB in H 2 O 2 -induced hepatocytes [23], L-glutamate-induced human Amyloid-beta A4 protein (Swedish mutation) transgenic SH-SY5Y cells [41], Ab1-42-induced human neuroblastoma cells [29], and mouse brain nerve cells [29] due to its ROS-scavenging ability. L-theanine pretreatment also protects PC12 cells from apoptosis by depressing cadmium-induced protein phosphorylation of ERK, JNK, Akt, p38, and the ratio of Bax/Bcl-2 and recovering mitochondrial dysfunction [33]. ...
... Our results show that L-theanine pretreatment did not affect the phosphorylation of JNK and p38, indicating that JNK and p38 are not involved in the regulation of H 2 O 2 -induced apoptosis in H9C2 cells. These results are not consistent with previous findings [16,22,23,29,30,33,41] and this discrepancy might be due to the difference in cell models or the dose of L-theanine used. Furthermore, other proteins, such as ERK, NF-kB, and mitochondrial apoptotic pathways, including Bax/Bcl-2 and PI3K/AKT, may also play an anti-apoptosis role. ...
Background
L-theanine is a non-protein amino acid in green tea, and its hepatoprotection and neuroprotection have been verified. However, whether L-theanine can prevent cardiomyocytes from apoptosis is unclear yet. This study evaluated the protective effects of L-theanine on H2O2-induced heart injury in vitro.
Material/Methods
The certified H9C2 cells were pretreated with L-theanine (0 mM, 4 mM, 8 mM, and 16 mM) for 24 h, followed by 160 μM H2O2 solution for 4 h. The cell viability and antioxidant indices were assayed. Quantitative evaluation of apoptosis was performed by flow cytometric analysis. Nuclear morphology of the cells was monitored by 4′,6-diamidino-2-phenylindole staining. Expression of Caspase-3, poly ADP-ribose polymerase (PARP), c-Jun N-terminal kinase (JNK), and mitogen-activated protein kinase p38 was assayed by Western blot.
Results
Compared to the H2O2 treatment, all doses of L-theanine treatments increased the cell viability, glutathione level, and the activities of glutathione peroxidase and superoxide dismutase (P<0.001). The contents of reactive oxygen species, nitric oxide, and oxidized glutathione were decreased by L-theanine treatments (P<0.001). Meanwhile, L-theanine treatments decreased the apoptosis ratio of H2O2-induced H9C2 cells (P<0.001). Pro-Caspase-3 expression was upregulated and cleavaged-PARP expression was inhibited by L-theanine (P<0.001). However, the phosphorylation of JNK and p38 was not affected by L-theanine treatments (P>0.05).
Conclusions
These data indicate that L-theanine pretreatment prevents H2O2-induced apoptosis in H9C2 cells, probably via antioxidant capacity improvement. Therefore, it might be a promising potential drug candidate for prophylaxis of ischemia/reperfusion-induced heart diseases.
... In addition, L-theanine inhibits oxidative stress, neuroinflammation and down regulates the protein level of iNOS under pathophysiological conditions (Jiang et al., 2012;Tsai et al., 2016). L-theanine has been reported to provide neuroprotection against cerebral ischemia-reperfusion (IR) injury in rats (Zukhurova et al., 2013), rotenone induced neuronal death in SH-SY5Y cell lines (Di et al., 2010), 3-NP induced striatal toxicity in rats (Thangarajan et al., 2014;Jamwal et al., 2017), and amyloid-βeta induced cognitive dysfunction and oxidative stress in mice (Kim et al., 2010). On the basis of these findings, the present study sought to evaluate the anti-oxidant and anti-inflammatory potential of L-theanine against QA induced striatal neurotoxicity and neurochemical alteration in rats. ...
... Moreover, Ltheanine has ability to enhance the level of brain NE, dopamine, 5-HT, GABA, promotes brain derived neurotrophic factor (BDNF), glial cell derived neurotrophic factor (GDNF) and nerve growth factor (NGF) formation (Kiramura and Murata, 1986;Ritsner et al., 2010;Yamada et al., 2005). L-theanine decreases iNOS and neuronal nitric oxide synthase (nNOS) protein activity (Di et al., 2010). In addition to this, recent reports from other labs concluded that L-theanine provides neuroprotection against Aluminium induced neurotoxicity, PCBs (Aroclor 1254) induced neuroinflammation and enhances motor activity in Drosophila male flies (Yang et al., 2013). ...
L-theanine has been documented to possess anti-oxidant, anti-inflammatory and neuroprotective potential in various animal models of neurological disorders. The present study was anticipated to investigate the effect of L-theanine against quinolinic acid induced motor deficits, oxido-nitrosative stress, neuro-inflammation and neurotransmitters alteration in rats. Rats were stereotaxically injected QA (200 nmol/2 µl saline; intrastriatal); bilaterally on 0 day and L-theanine (25 & 50 mg/kg; p.o.) was administered for 21 days starting from day 1 of QA injection. Either, L-NAME (10 mg/kg; i.p.), a nitric oxide synthase inhibitor and L-arginine (50 mg/kg; i.p.), a nitric oxide synthase precursor were administered with L-theanine in respective groups. Behavioral observations were evaluated on weekly basis using rota-rod, grip strength, narrow beam walking and open field test. QA treatment induces significant alteration in body weight, motor coordination, oxidative defense, pro-inflammatory cytokines and striatal neurotransmitters level. L-theanine treatment alone, at both the tested doses, significantly attenuated QA induced alterations. In addition, treatment of L-theanine with L-NAME significantly enhances the protective effect of L-theanine whereas treatment of L-theanine with L-arginine significantly ameliorated the protective effect of L-theanine. The protective effect of L-theanine is attributed to its anti-oxidant, anti-inflammatory and modulatory effect on nitric oxide pathway and neurotransmitters level in striatum. This suggests use of L-theanine in the clinical settings of HD.
... As seen with the structure of l-GLN, a free carboxylic acid moiety is absent from the gamma carbon position in l-theanine (Fig. 1). Although l-theanine has been thought to modulate both neurotransmission and neurotoxicity mediated by l-GLU in the literature [4,5], the aforementioned structural similarity gives rise to an idea that l-GLN would be at least in part responsible for particular pharmacological properties of l-theanine, besides l-GLU, in the brain. ...
... The green tea amino acid l-theanine is thus supposed to be an inhibitor of Slc38a1 capable of transporting l-GLN across plasma membranes in neurons and astroglia. The aforementioned low affinity and clear structural discrimination are not in favor of an idea for l-theanine to be a modulator of the activity of particular ionotropic receptor subtypes for l-GLU in the brain as described previously [4,5]. ...
L-Theanine (=γ-glutamylethylamide) is an amino acid ingredient in green tea with a structural analogy to L-glutamine (L-GLN) rather than L-glutamic acid (L-GLU), with regards to the absence of a free carboxylic acid moiety from the gamma carbon position. L-theanine markedly inhibits [(3)H]L-GLN uptake without affecting [(3)H]L-GLU uptake in cultured neurons and astroglia. In neural progenitor cells with sustained exposure to L-theanine, upregulation of the L-GLN transporter isoform Slc38a1 expression and promotion of both proliferation and neuronal commitment are seen along with marked acceleration of the phosphorylation of mammalian target of rapamycin (mTOR) and relevant downstream proteins. Stable overexpression of Slc38a1 leads to promotion of cellular growth with facilitated neuronal commitment in pluripotent embryonic carcinoma P19 cells. In P19 cells stably overexpressing Slc38a1, marked phosphorylation is seen with mTOR and downstream proteins in a fashion insensitive to the additional stimulation by L-theanine. The green tea amino acid L-theanine could thus elicit pharmacological actions to up-regulate Slc38a1 expression for activation of the mTOR signaling pathway required for cell growth together with accelerated neurogenesis after sustained exposure in undifferentiated neural progenitor cells. In this review, I summarize a novel pharmacological property of the green tea amino acid L-theanine for embryonic and adult neurogenesis with a focus on the endogenous amino acid analog L-GLN. A possible translational strategy is also discussed on the development of dietary supplements and nutraceuticals enriched of L-theanine for the prophylaxis of a variety of untoward impairments and malfunctions seen in patients with different neurodegenerative and/or neuropsychiatric disorders.
... In this regard, several investigations revealed the protective effects of EGCG (1e100 mM) and epicatechin (100 mM) against toxicity induced by glutamate exposure (5 mM and 100 mg/ml, respectively) in HT22 cells, mouse hippocampal cell line, due to their antioxidant properties (Lee et al., 2015;Fu and Koo, 2006;Li et al., 2005). In the other study, it has been shown that L-theanine protected cells against glutamate-induced excitotoxicity by inhibiting N-methyl-D-aspartate (NMDA) receptor and related pathways (Di et al., 2010). However, Mazzio et al. showed no significant protection against glutamate-induced toxicity in PC12 cells using catechin, EGCG and GT treatments (Mazzio et al., 2001). ...
... Chung Wei et al. recently showed that anti-oxidative effects of EGCG could protect EOC 13.31 cells, mouse immortalized microglia cells, from Ab-induced microglial inflammation and neurotoxicity (Cheng- Chung Wei et al., 2016). It has been implicated that neuroprotective effects of GT and its derivatives against Ab are attributed to their anti-oxidative function (Choi et al, 2001(Choi et al, , 2014Cuevas et al., 2009;Bastianetto et al., 2008;He et al., 2011;Jo et al., 2011;Kim et al., 2009), inhibition of the NMDA receptors (Di et al., 2010) and glycogen synthase kinase 3 beta (GSK3b) (Lin et al., 2009b), activation of a7 nicotinic acetylcholine receptors (nAChR) (Zhang et al., 2014b), protein kinase C (PKC) (Levites et al., 2003;Jang et al., 2007), phosphoinositide 3kinase (PI3K)/AKT signaling pathway (Zhang et al., 2014b;Qin et al., 2012) as well as suppression of c-Abl/FE65 nuclear translocation (Lin et al., 2009b), ERK/p38 (Kim et al., 2009), NF-kappa B (Kim et al., 2009) and MAPK pathway (Cheng- Chung Wei et al., 2016). More importantly, it has been discussed that GT has a potential role in inhibition of Ab fibril/oligomers formation (Bastianetto et al., 2008(Bastianetto et al., , 2009(Bastianetto et al., , 2006Harvey et al., 2011) and production of non-toxic amyloid oligomers (Lopez del Amo et al., 2012). ...
Toxins are natural or chemical poisonous substances with severe side effects on health. Humans are generally exposed by widespread toxic contaminations via air, soil, water, food, fruits and vegetables. Determining a critical antidote agent with extensive effects on different toxins is an ultimate goal for all toxicologists. Traditional medicine is currently perceived as a safe and natural approach against toxins. In this regard, we focused on the protective effects of green tea (Camellia sinensis) and its main components such as catechin, epicatechin, epicatechin gallate, gallocatechin, epigallocatechin and epigallocatechin gallate as a principal source of antioxidants against both natural and chemical toxins. This literate review demonstrates that protective effects of green tea and its constituents were mainly attributed to their anti-oxidative, radical scavenging, chelating, anti-apoptotic properties and modulating inflammatory responses. Although, some studies reveal they have protective effects by increasing toxin metabolism and neutralizing PLA2, proteases, hyaluronidase and l-amino acid oxidase enzymes.
... L-theanine is also reported to induce reduction in glutamate reuptake by inhibition of glutamate transporter [22]. Ltheanine inhibits activation of c-Jun N-terminal kinase and caspase-3 induced by L-glutamate [31]. Also, L-theanine decreased the production of NO induced by glutamate by downregulation of inducible nitric oxide synthase (iNOS) and neuronal nitric oxide synthase (nNOS) protein activity [31]. ...
... Ltheanine inhibits activation of c-Jun N-terminal kinase and caspase-3 induced by L-glutamate [31]. Also, L-theanine decreased the production of NO induced by glutamate by downregulation of inducible nitric oxide synthase (iNOS) and neuronal nitric oxide synthase (nNOS) protein activity [31]. In addition to this, L-theanine has been reported to boost locomotor activity in Drosophila male flies [32]. ...
L-theanine is unique amino acid which readily crosses blood brain barrier and possesses neuroprotective potential against neurodegenerative disorders including Huntington disease (HD). HD is characterized by selective loss of GABAergic medium spiny neurons. 3-nitropropionic acid (3-NP) induces a spectrum of HD-like neuropathology in rat striatum and widely used as experimental tool to study HD. Therefore, the present study was intended to investigate the effect of L-theanine against 3-NP-induced striatal toxicity and to explore its possible mechanism. Rats were administered with 3-NP for 21 days. L-theanine was given once a day, 1 h prior to 3-NP treatment for 21 days and L-NAME (10 mg/kg, i.p.), NO inhibitor and L-arginine (50 mg/kg; i.p.), NO precursor were administered 1 h prior to L-theanine treatment. Body weight and behavioral observation were made on weekly basis. On the 22nd day, animals were sacrificed, and the striatum was isolated for biochemical (LPO, GSH, and nitrite), pro-inflammatory cytokines and neurochemical analysis. 3-NP treatment significantly altered body weight, locomotor activity, motor coordination, mitochondrial complex-II activity, oxidative defense, pro-inflammatory mediators, and striatal neurotransmitters level. L-theanine pre-treatment (25 and 50 mg/kg/day, p.o.) significantly prevented these alterations. In addition, concurrent treatment of L-NAME with L-theanine (25 mg/kg/day, p.o.) significantly enhanced protective effect of L-theanine (25 mg/kg/day, p.o.) whereas concurrent treatment of L-arginine with L-theanine (50 mg/kg/day, p.o.) significantly ameliorated the protective effect of L-theanine (50 mg/kg/day, p.o.). The neuroprotective potential of L-theanine involves inhibition of detrimental nitric oxide production and prevention of neurotransmitters alteration in the striatum.
... In addition to the beneficial effects such as enhancement of relaxation and improvement of concentration and learning ability (Egashira et al., 2008;Gomez-Ramirez, Kelly, Montesi, & Foxe, 2008;Juneja, Chu, Okubo, Nagato, & Yokogoshi, 1999;Yamada et al., 2008), theanine has been found beneficial in many aspects including the prevention of certain cancers (Sadzuka, Sugiyama, Miyagishima, Nozawa, & Hirota, 1996) and regulation of blood pressure (Yokogoshi et al., 1995), promotion of weight loss (Zhent et al., 2005) and enhancement of the performance of the immune system (Bukowski & Percival, 2008). It is also linked with neuroprotective effects such as Parkinson disease and Alzheimer disease (Di et al., 2010;Il Kim et al., 2009;Yamada et al., 2009). Recently it has been reported that theanine may inhibit nicotine addiction and possess the antidepressant effect (Egashira et al., 2008;Yan et al., 2010;Yin et al., 2011). ...
... It is also linked with neuroprotective effects such as Parkinson disease and Alzheimer disease (Di et al., 2010;Il Kim et al., 2009;Yamada et al., 2009). Recently it has been reported that theanine may inhibit nicotine addiction and possess the antidepressant effect (Egashira et al., 2008;Yan et al., 2010;Yin et al., 2011). However, only a few studies have reported on the beneficial properties of theanine on stress resistance. ...
... The chemical structure of theanine is similar to that of glutamate and glutamine, and theanine can easily cross the blood-brain barrier [4]. In the central nervous system, it is believed that theanine competitively antagonizes glutamine and inhibits glutamine transporters, thereby suppressing excitatory neurotransmission of glutamate [5][6]. Through this mechanism, theanine is thought to exert physiological effects. ...
L-theanine (theanine), one of the ingredients of green tea, had been proven to have anti-anxiety, anti-stress, memory, cognitive, and sleep improvement effects in most clinical trials. However, these effects have shown efficacy at a dose of 200–400 mg of theanine a day. In this study, we explored the sleep-improving effects of a lower dose (100 mg/day) of theanine. A double-blind, randomized crossover study was conducted on 25 middle-aged and older males. Participants were randomly assigned to Groups A and B. Group A took theanine first, and Group B took theanine later in the intervention period. The participants took theanine/placebo for one week. Electroencephalogram (EEG) parameters were measured with a monitoring device during sleep, and subjective sleep quality after waking up was evaluated using a questionnaire. Following the statistical analysis between interventions, subgroup analyses according to the participants’ background information were conducted on the representative sleep parameters of non-REM sleep, REM sleep, and wakefulness. Of the 25 participants, three withdrew from this study. In the sleep analysis, there was no significant difference in all sleep parameters between the theanine and placebo periods. In particular, the difference in the percentage of nonREM sleep in stage 2 per sleep duration was not significant (p = 0.053). However, subgroup analysis of the results showed that the percentage of non-REM sleep in stage 2 in groups aged <50 years was higher in theanine than that of the placebo, and in groups with green tea consumption habit of <3 to 4 days per week (p = 0.018, 0.048). The intake of 100 mg/day of theanine does not have an effect on sleep improvement. However, subgroup analyses showed that theanine had an improved effect in stage 2 non-REM sleep according to age and green tea consumption habit.
... Therefore, the balance of glutamate level is crucial for synaptic plasticity and neuronal survival (Bin Ibrahim et al., 2022;Hayashi, 2022). In AD, this balance is disappeared, which ends to induction of glutamateinduced excitotoxicity (Di et al., 2010). During this condition, the pyramidal cells would be eliminated due to generation of various free radicals, mitochondrial dysfunction, and induction of apoptosis and necrosis factors (Lai et al., 2014;Verma et al., 2022). ...
Memory impairment is one of the main complications of Alzheimer’s disease (AD). This condition can be induced by hyper-stimulation of N-Methyl-D-aspartate receptors (NMDARs) of glutamate in the hippocampus, which ends up to pyramidal neurons determination. The release of neurotransmitters relies on voltage-gated calcium channels (VGCCs) such as P/Q-types. Omega-lycotoxin-Gsp2671e (OLG1e) is a P/Q-type VGCC modulator with high affinity and selectivity. This bio-active small protein was purified and identified from the Lycosa praegrandis venom. The effect of this state-dependent low molecular weight P/Q-type calcium modulator on rats was investigated via glutamate-induced excitotoxicity by N-Methyl-D-aspartate. Also, Electrophysiological amplitude of field excitatory postsynaptic potentials (fEPSPs) in the input–output and Long-term potentiation (LTP) curves were recorded in mossy fiber and the amount of synaptophysin (SYN), synaptosomal-associated protein, 25 kDa (SNAP-25), and synaptotagmin 1(SYT1) genes expression were measured using Real-time PCR technique for synaptic quantification. The outcomes of the current study suggest that OLG1e as a P/Q-type VGCC modulator has an ameliorative effect on excitotoxicity-induced memory defects and prevents the impairment of pyramidal neurons in the rat hippocampus.
... The mutated APP is primarily processed by β-secretase and therefore causes elevated level of Aβ and the transcriptional regulator AICD via the amyloidogenic processing pathway [56][57][58][59]. SH-SY5Y cells expressing the APPswe mutation are a commonly accepted cellular AD-model and frequently used in AD research, for example in the context of oxidative stress [60][61][62][63][64][65][66][67]. Importantly, this cell line has been characterized for its suitability to be used as a familial AD model, for details please see [61]. ...
Oxidative stress is closely linked to Alzheimer’s disease (AD), and is detected peripherally as well as in AD-vulnerable brain regions. Oxidative stress results from an imbalance between the generation and degradation of reactive oxidative species (ROS), leading to the oxidation of proteins, nucleic acids, and lipids. Extensive lipid changes have been found in post mortem AD brain tissue; these changes include the levels of total phospholipids, sphingomyelin, and ceramide, as well as plasmalogens, which are highly susceptible to oxidation because of their vinyl ether bond at the sn-1 position of the glycerol-backbone. Several lines of evidence indicate that a deficiency in the neurotropic vitamin B12 is linked with AD. In the present study, treatment of the neuroblastoma cell line SH-SY5Y with vitamin B12 resulted in elevated levels of phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, and plasmalogens. Vitamin B12 also protected plasmalogens from hydrogen peroxide (H2O2)-induced oxidative stress due to an elevated expression of the ROS-degrading enzymes superoxide-dismutase (SOD) and catalase (CAT). Furthermore, vitamin B12 elevates plasmalogen synthesis by increasing the expression of alkylglycerone phosphate synthase (AGPS) and choline phosphotransferase 1 (CHPT1) in SH-SY5Y cells exposed to H2O2-induced oxidative stress.
... Pretreatment with the amino acid has been shown to block the toxin-induced down-regulation of ERK1/2 and BDNF in SH-SY5Y cells [73]. Theanine has also shown to exert its neuroprotective effect in case of Alzheimer's disease as Di et al. in his in-vitro experiment showed that administration of Theanine attenuates glutamate-induced amyloid β neurotoxicity, as well as apoptosis in human APP transgenic SH-SY5Y cells as well as it, suppressed the activation of c Jun Nterminal kinase, caspase-3 [74]. Kakuda et al., 2002). ...
Neurodegenerative diseases involve a heterogeneous group of disorders characterized by progressive impairment and degeneration of nerve structure and function, eventually leading towards the death of certain parts of the CNS and brain. The most common form of neurodegenerative diseases includes Alzheimer's disease (AD) leading towards progressive loss of memory, Parkinson's disease (PD) causing impairment in movements, Huntington's disease (HD) affecting the ability to walk, talk and think. The pathogenesis of these diseases mainly AD and PD are complex and there is no such cure for these diseases as the drugs that are currently in use shown to have an adverse effect on these diseases. However epidemiological studies have shown that consumption of tea has therapeutic effects in treating those neurodegenerative diseases especially the major tea components i.e. Catechins, Caffeine, Theanine, TFs in elderly persons. The major tea components are antioxidants which help to combat oxidative stress, the major reason behind all those neurodegenerative diseases, regulating signaling pathways as well as helps in metal chelation. The objective of this review is to summarize all the available information on different bioactive components of tea in the treatment of different neurodegenerative diseases.
... Confirming our results, the work of Di and colleagues supports the neuroprotective effect of TEA against GLU-induced excitotoxicity, through the modulation of NMDA receptor in the APP transgenic SH-SY5Y cells. [27] Similarly, MOE counteracted the toxic effect produced by GLU in neuronal cells. This activity could be related to the presence of honokiol in the extract. ...
Objectives:
The exposure of neurons to an excessive excitatory stimulation induces the alteration of the normal neuronal function. Mood disorders are among the first signs of alterations in the central nervous system function. Magnolia officinalis bark extract has been extensively used in the traditional medicine systems of several countries, showing several pharmacological activities. Honokiol, the main constituent of M. officinalis, is a GABA modulator and a CB1 agonist, which is deeply investigated for its role in modulating mood disorders.
Methods:
Thus, we evaluated the possible neuroprotective effect of a standardized M. officinalis bark extract (MOE), enriched in honokiol, and its effect on animal mood behavioural tests and in an in vitro model of excitotoxicity.
Key findings:
MOE showed neuroprotective effect using SH-SY5Y cells, by normalizing brain-derived neurotrophic factor release. Then, we tested the effect of MOE in different behavioural tests evaluating anxiety and depression and we observed a selective anxiolytic-like effect. Finally, we confirmed the involvement of CB1 in the final effect of MOE by the co-administration of the CB1 antagonist, AM251.
Conclusion:
These results suggest that MOE could be considered an effective and safe anxiolytic candidate with neuroprotective activity.
... Prolonged exposure to NMDA for 24 hours promotes the synthesis and subsequent processing of APP in a dose-dependent manner, thereby increasing the production of soluble Aβ 40 and Aβ 42 in mouse cortical cultures of neurons (Lesné et al., 2005a). Aβ oligomers trigger neurotoxicity in vitro and in vivo (Lesné et al., 2005b;Bordji et al., 2011;Rudy et al., 2015;Tanokashira et al., 2017); however, cells expressing basal levels of wild-type APP produce very low levels of Aβ peptides (Podlisny et al., 1995;Meli et al., 2014), and long exposure to glutamate for 12 hours only moderately increases the secretion of Aβ in cells overexpressing mutated APP (Di et al., 2010). Together, our results suggest that the 20-min exposure to glutamate used in vitro was likely insufficient to induce significant production and oligomerization of Aβ peptides. ...
Subcommissural organ (SCO)-spondin is a brain-specific glycoprotein produced during embryogenesis, that strongly contributes to neuronal development. The SCO becomes atrophic in adults, halting SCO-spondin production and its neuroprotective functions. Using rat and human neuronal cultures, we evaluated the neuroprotective effect of an innovative peptide derived from SCO-spondin against glutamate excitotoxicity. Primary neurons were exposed to glutamate and treated with the linear (NX210) and cyclic (NX210c) forms of the peptide. Neuronal survival and neurite networks were assessed using immunohistochemistry or biochemistry. The mechanism of action of both peptide forms was investigated by exposing neurons to inhibitors targeting receptors and intracellular mediators that trigger apoptosis, neuronal survival, or neurite growth. NX210c promoted neuronal survival and prevented neurite network retraction in rat cortical and hippocampal neurons, whereas NX210 was efficient only in neuronal survival (cortical neurons) or neurite networks (hippocampal neurons). They triggered neuroprotection via integrin receptors and γ-secretase substrate(s), activation of the PI3K/mTOR pathway and disruption of the apoptotic cascade. The neuroprotective effect of NX210c was confirmed in human cortical neurons via the reduction of lactate dehydrogenase release and recovery of normal basal levels of apoptotic cells. Together, these results show that NX210 and NX210c protect against glutamate neurotoxicity through common and distinct mechanisms of action and that, most often, NX210c is more efficient than NX210. Proof of concept in central nervous system animal models are under investigation to evaluate the neuroprotective action of SCO-spondin-derived peptide.
... These effects were attributed to antioxidant, anti-inflammatory, and relaxant activities (Jiang et al. 2012;Chatterjee et al. 2014;Tadesse et al. 2015). l-Theanine has been used as a treatment for various diseases in China due to its anti-inflammatory and anti-oxidant effects (Di et al. 2010;Yan et al. 2017;Zeng et al. 2018). In a recent study, l-theanine was shown to suppress airway inflammation in ovalbumin-induced allergic asthma and inhibited TNF-α-induced NF-kB activation in Human lung carcinoma cells (Hwang et al. 2017). ...
The aim of this study is to evaluate the anti-inflammatory and protective effects of l-theanine in inflammatory bowel disease (IBD) and to identify the underlying molecular mechanisms. Rats were pre-treated with l-theanine at 0, 50, 200, or 800 mg/kg/day. IBD was induced in rats using dextran sulfate sodium (DSS). Histopathological analysis suggests that l-theanine can suppress DSS-induced IBD with significant inhibition of inflammation in large and small intestinal tissues. Moreover, the 200 mg/kg/day l-theanine-treated DSS group had higher body and small intestine weights, a lower disease activity index and expression of inflammatory factors than the DSS group without pre-treatment. In RNA sequencing and tandem mass tag labeling analyses, large number of mRNAs and proteins expression level differed when compared with the DSS-induced rats with and without 200 mg/kg/day l-theanine pre-treatment. Moreover, Kyoto Encyclopedia of Genes and Genomes pathway analysis indicates the anti-inflammatory activities of l-theanine in DSS-induced IBD, with a high representation of genes in “Cholesterol metabolism” and “Retinol metabolism” pathways. Analysis of protein–protein interaction networks further indicates the involvement of these two pathways. These studies suggest that medium-dose l-theanine pre-treatment could ameliorate DSS-induced IBD through molecular mechanisms involving cholesterol and retinol metabolism.
... Recent studies showed that L-theanine had neuroprotective effects on injured neurons and could improve learning and memory functions in the developing rat brain [12][13][14][15] . As a natural glutamate analog, L-theanine's neuroprotective effect is proved to be mainly mediated by its antagonistic action on glutamate receptors, such as AMPA, kainate and NMDA receptors 16,17) , and regulation on the release and neurotransmission of glutamate 9,[18][19][20][21] . ...
The neurodevelopmental toxicity of isoflurane has been proved by many studies, which makes it essential to explore the underline mechanisms and search for protective agents to attenuate its neurotoxcity. Accumulating evidence showed that L-theanine had neuroprotective effects on injured neurons and the developing brain. The present study was designed to investigate whether L-theanine could attenuate isoflurane-induced damage in neural stem cells and cognitive impairment in young mice, and to discuss the role of Akt/GSK-3β signaling pathway in this process. Multipotential neural stem cells (NSCs) and C57BL/6J mice were treated with either gas mixture, isoflurane, or L-theanine 30 min prior to isoflurane exposure, respectively. NSC viability was detected by CCK-8 assay. NSC proliferation and apoptosis were assessed by immunofluorescence and TUNEL assay, respectively. The levels of cleaved caspase-3 and p-Akt and p-GSK-3β in NSCs were tested by Western blotting. Cognitive function of mice was tested by Morris Water Maze at postnatal day (P) 30-35. The results indicated that isoflurane exposure inhibited NSC viability and proliferation, promoted NSC apoptosis as well as increased caspase-3 activation and down-regulated the expressions of p-Akt and p-GSK-3β in NSCs, and that isoflurane exposure on neonatal mice would induce late cognitive impairment. Pretreatment with L-theanine could attenuate isoflurane-caused damage in NSCs and cognitive deficits in young mice. Addinonally, the protective effects of L-theanine on isoflurane-injured NSCs could be reversed by Akt inhibitor Triciribine. Our data showed that pretreatment with L-theanine eliminated the NSC damage and cognitive impairment induced by isoflurane exposure, and that the neuroprotective effect of L-theanine was associated with the Akt/GSK-3β signaling pathway.
... However, theanine is a weak displacer of ligand binding to different neurotoxic ionotropic Glu receptor subtypes in rat cortical synaptic membranes (Kakuda et al., 2002). Although theanine has been thought to modulate both neurotransmission and neurotoxicity mediated by Glu in the literature (Di et al., 2000;Ota et al., 2015), the close structural similarity gives rise to an idea that GLN would be at least in part responsible for particular pharmacological properties of theanine, besides Glu, in the brain. ...
The green tea amino acid theanine is abundant in green tea rather than black and oolong teas, which are all made of the identical tea plant “Chanoki” (Camellia sinensis). Theanine has a molecular structure close to glutamine (GLN) compared to glutamic acid (Glu), in terms of the absence of a free carboxylic acid moiety from the gamma carbon position. Theanine efficiently inhibits [3H]GLN uptake without affecting [3H]Glu uptake in rat brain synaptosomes. In contrast to GLN, however, theanine markedly stimulates the abilities to replicate and to commit to a neuronal lineage following prolonged exposure in cultured neural progenitor cells (NPCs) prepared from embryonic and adult rodent brains. Upregulation of transcript expression is found for one of the GLN transporter isoforms, Slc38a1, besides the promotion of both proliferation and neuronal commitment along with acceleration of the phosphorylation of mechanistic target of rapamycin (mTOR) and relevant downstream proteins, in murine NPCs cultured with theanine. Stable overexpression of Slc38a1 similarly facilitates both cellular replication and neuronal commitment in pluripotent embryonic carcinoma P19 cells. In P19 cells with
stable overexpression of Slc38a1, marked phosphorylation is seen for mTOR and downstream proteins in a manner insensitive to further additional phosphorylation by theanine. Taken together, theanine would exhibit a novel pharmacological property to up-regulate Slc38a1 expression for activation of the intracellular mTOR signaling pathway required for neurogenesis after sustained exposure in undifferentiated NPCs in the brain. In this review, a novel neurogenic property of the green tea amino acid theanine is summarized for embryonic and adult neurogenesis with a focus on the endogenous amino acid GLN on the basis of our accumulating evidence to date.
... Indeed, L-THE has been reported to prevent neurotoxicity and environmental toxin-induced neuronal cell death ( Table 2). The neuroprotective effects of L-THE have been described in human nSH-SY5Y cells in which L-THE was able to counteract L-glutamate-induced neurotoxicity, which in turn may provide effective prophylaxis and treatment for AD (Di et al., 2010). Similarly, in vitro Current evidence also suggests that L-THE counteracts aluminium toxicity in the brain. ...
l‐Theanine (l‐THE) is a nonproteinogenic amino acid derived from green tea (Camellia sinensis), which exhibits strong antioxidant‐like properties and contributes to the favourable umami taste sensation. Several studies have reported that the consumption of this amino acid has many therapeutic effects, including improvements in brain and gastrointestinal function, cancer drug therapeutic efficacies, antihypertensive effects, and improved immune function. Considering the recent Western commercialisation and popularity of green tea consumption as a nootropic agent in humans, the aims of this review were to consolidate the existing knowledge from ex vivo and in vitro animal models and attempt to highlight the applicability of l‐THE towards the human clinical trials. Considering the anti‐inflammatory and antioxidants effects of l‐THE presented in the current review, further research must translate the existing knowledge gained from animal and cell models to exploring the potential metabolic health benefits and moderating effects on the pathogenesis of conditions such as obesity, arthritis, depression, and type 2 diabetes in human trials. This will bridge the gap in literature and provide more insights into the mechanisms driving pathologies characterised by the inflammatory response and oxidative stress.
... Another nootropic compound "L-theamine" protects SH-SY5Y cells against glutamate-induced toxicity through inhibition of Nmethyl-D-aspartate (NMDA) glutamate subtype of receptors and related pathways. Hence, L-theamine may serve as prophylaxis and treatment for AD 57 . Further, Piracetam exerts its neuroprotective effects on PC12 cells, SH-SY5Y cells, and SH-SY5Y APPwt cells by improving synaptic plasticity, maintaining mitochondrial dynamic and neuritogenesis 58 . ...
Background: The nootropic or simply known as smart drug is a common term given to any compound that is responsible for enhancing mental capability or performance. Alzheimer's disease is characterized clinically by lose of cognitive abilities and pathologically by two hallmark lesions, neurofibrillary tangles and senile plaques. It is unfortunate that AD has no cure yet. In this review attempt has been made to elucidate the general views on AD pathogenic hypotheses and common nootropics being used in AD research. Methods: Articles from credible scientific data bases such as Sciencdirect, Scopus Pubmed, and Google scholar were searched and retrieved using keywords nootropics', Alzheimer's disease', amyloid beta hypotheses', tau hypotheses', cholinergic hypotheses', oxidative stress' and cognitive impairments'. Results: The nootropics act as Ca-channel blockers, AChE inhibitors, glysine antagonists, antioxidants, serotonergic, dopaminergic and glutamic acid receptors antagonists. Conclusion: Based on the available literature searched, there is no doubts the nootropics are attenuating cognitive deficits in both preclinical and clinical studies on AD.
... В этой же работе было отмечено снижение экспрессии внеклеточной сигнальной киназы (ERK), митогенактивируемой протеинкиназы p38, а также индуцируемой βА-активности ядерного фактора транскрипции NF-κβ. В другой работе [33] изучался нейропротективный эффект теанина в модели БА на культуре трансгенных клеток SH-SY5Y, в которой глутамат запускал механизм нейротоксичности βА. При этом введение теанина значительно снижало индуцированный глутаматом апоптоз (в сходных дозах с соединением МК-801, ингибитором NMDA-рецепторов). ...
Theanine is an analog of glutamate and the major aminoacid in green tea. It has received growing attention in recent years because of its beneficial effects on the central nervous system. Theanine was shown to increase levels of brain-derived neurotrophic factor and to stimulate neurogenesis. Anti-stress and calming effects of theanine are the most apparent and well-studied. A number of studies showed neuroprotective effects of theanine after an ischemic cerebral injury or the exposure to toxic chemicals. It also improved cognitive function including attention, memory and learning. Recent studies demonstrated a promising role of theanine in augmentation therapy for major depressive disorder and schizophrenia. Theoretical grounds for using theanine in treatment of bipolar disorder, anxiety disorder and some neurodegenerative disorders are discussed.
... Amyloid beta (Ab) neurotoxicity was triggered by L-glutamate in SH-SY5Y cell line. 63 The cells were treated with test compounds, at 25 mM concentration, and incubated for 2 h. Aer incubation, cells were treated with a medium containing 100 mM of L-glutamate and le for an additional 24 h. ...
Ligand-based and energy-optimized structure-based approaches were considered to obtain excellent candidates as AChE inhibitors. The known AChE inhibitors were utilized to develop a pharmacophore hypothesis, HPRRR and X-ray crystallographic structures of AChE were used to produce three e-pharmacophore hypotheses viz. AHHRR, AHRR, and DHRR. Based on in silico approaches, we came across eight structurally diverse hits as non-competitive AChE inhibitors with good ADME properties. The best four hits, ZINC20592007, ZINC05354646, ZINC20649934, and ZINC39154782 were non-toxic, neuroprotective, and were selective AChE inhibitors (IC 50 values 482 AE 1.88 nM, 580 AE 1.63 nM, 854 AE 2.65 nM, and 636 AE 1.79 nM respectively). The hits showed non-competitive inhibition of AChE at PAS site with attractive K i values (0.21 AE 0.027 mM, 0.27 AE 0.064 mM, 0.3 AE 0.018 mM, and 0.28 AE 0.032 mM for ZINC20592007, ZINC05354646, ZINC20649934, and ZINC39154782 respectively), and increased the cholinergic activity as well as inhibited Ab aggregation.
... 9 Its neuroprotective actions may rely on interference with ionotropic or metabotropic glutamate receptormediated neuronal processes. 10,11 The prevention of ischemic damage in the gerbil hippocampus could be attributed to the blockade of AMPA receptors, which actively contribute to ischemic injury. 7,12 In addition, L-theanine may also modulate GABAergic transmission to produce neuroprotection under ischemia as evidenced in mice. ...
L-Theanine (or L-γ-N-ethyl-glutamine) is the major amino acid found in Camellia sinensis. It has received much attention because of its pleiotropic physiological and pharmacological activities leading to health benefits in humans, especially. We describe here a new, easy, efficient and environmentally-friendly chemical synthesis of L-Theanine and L-γ-N-propyl-Gln and their corresponding D isomers. L-Theanine, and its derivatives obtained so far, exhibited partial co-agonistic action at N-methyl-D-aspartate (NMDA) receptors, with no detectable agonist effect at other glutamate receptors, on cultured hippocampal neurons. This activity was retained on NMDA receptors expressed in Xenopus oocytes. In addition, both GluN2A and GluN2B containing NMDA receptors were equally modulated by L-Theanine. The stereochemical change from L-Theanine to D-Theanine along to the substitution of the ethyl for a propyl moiety in the γ-N position of L- and D-Theanine significantly enhanced the biological efficacy, as measured on cultured hippocampal neurons. L-Theanine structure thus represents an interesting backbone to develop novel NMDA receptor modulators.
... Interestingly, theanine binds to glutamate receptors, AMPA, kainite, and NMDA receptors (Kakuda et al., 2002;Maruyama and Takeda 1994), and a previous study demonstrated that iontophoretically applied glutamate induced the amplitude of excitatory junctional potentials was reversible inhibited by theanine, implicating theanine as a glutamate antagonist (Shinozaki and Ishida 1978). Di et al., (2010) also reported that theanine attenuates L-glutamate-induced apoptosis via NMDA receptor-related signaling pathways. In the present study, we found that (i) the relative magnitude of inhibition by theanine of SpVc WDR neuronal discharge frequency was significantly greater for noxious than non-noxious stimulation; (ii) the mean firing frequency of SpVc WDR neurons responding to iontophoretic application of glutamate was inhibited by 13 intravenous administration of theanine; (iii) there was no significant difference in mean discharge frequency between noxious mechanical stimulation (60 g) and iontophoretic application of glutamate (50 nA); and, (iv) the mean firing frequency of SpVc WDR neurons responding to iontophoretic application of 50-nA glutamate was significantly inhibited by intravenous administration of theanine, with the maximal inhibition of discharge frequency observed by 5 min and reversed within 10 min. ...
Theanine is a non-dietary amino acid linked to the modulation of synaptic transmission in the central nervous system, although the acute effects of theanine in vivo, particularly on nociceptive transmission in the trigeminal system, remain to be determined. The present study investigated whether acute intravenous theanine administration to rats attenuates the excitability of wide dynamic range (WDR) spinal trigeminal nucleus caudalis (SpVc) neurons in response to nociceptive and non-nociceptive mechanical stimulation in vivo. Extracellular single unit recordings were made from 15 SpVc neurons in response to orofacial mechanical stimulation of pentobarbital-anesthetized rats, and responses to non-noxious and noxious mechanical stimuli were analyzed. The mean firing frequency of SpVc WDR neurons in response to all mechanical stimuli was dose-dependently inhibited by theanine (10, 50, and 100mM, i.v.) with the maximum inhibition of discharge frequency reached within 5min. These inhibitory effects were reversed after approximately 10min. The relative magnitude of theanine’s inhibition of SpVc WDR neuronal discharge frequency was significantly greater for noxious than non-noxious stimulation. Iontophoretic application of L-glutamate induced the mean firing frequency of SpVc WDR neuron responding to noxious mechanical stimulation was also inhibited by intravenous administration of 100mM theanine. These results suggest that acute intravenous theanine administration suppresses glutaminergic noxious synaptic transmission in the SpVc, implicating theanine as a potential complementary and alternative therapeutic agent for the treatment of trigeminal nociceptive pain.
... However, recent studies point to more complex effects. In an in vitro model of AD using the human APP transgenic SH-SY5Y cell, Aβ neurotoxicity was triggered by L-glutamate [307]. ...
Phytochemicals are plant-derived non-nutritive molecules that have the ability to provide protection against a wide range of neurodegenerative disorders. Common components that contribute to the neurodegeneration in these conditions involve oxidative and/or inflammatory insults. Extensive studies have shown that phytochemicals like resveratrol, curcumin, sulforaphanes, and catechins can prevent neurodegeneration through their antioxidative and anti-inflammatory properties. They exert their beneficial effects by modulating specific targets, which can include sirtuins, adenosine monophosphate-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), forkhead box-O (FOXO), NF-kB, histone deacetylases, insulin-like growth factor 1 (IGF-1), and Nrf2/ARE pathways. In this chapter, emphasis is placed on the molecular targets involved in the action of various phytochemicals that prevent or suppress the onset of different neurodegenerative disorders.
... L-theanine at the dose 2 and 4 mg/ kg reduce amyloid β (Aβ) (amino acid range: 1-42) levels and accompanying amyloid β peptide (amino acid range: 1-42) induced neural cell death in cortex and hippocampus of mice brain. Moreover, it has positive effects on memory, may be mediated by suppression of ERK/p38 (Extracellular Signal-Regulated kinase/ p38) and NF-kappa ß as well as reduction of macromolecular oxidative damage62 . It can protect the APP (Swedish mutation) transgenic SH-SY5Y cell against glutamate induced excitotoxicity via inhibition of NMDA receptor pathway63 . ...
L-theanine, an important constituent of the tea, is consumed daily throughout the world and is said to greatly contribute to the umami taste of tea. The objective of this review is to summarize the currently available information of L-theanine with reference to health benefits. Relevant keywords like " Tea " , " L-theanine " and " health benefits " were used for the extraction and subsequent analysis of the biomedical literature in the field. Two search engines, Google and Pubmed were used for that purpose. It is expected that the review update the basic features of L-theanine as well as, the current status pertaining to the role of the L-theanine in human health.
... [13,14] It also has various healthful effects such as cardiovascular protection, neuroprotection, anti-oxidant, anti-stress, anti-cancer, anti-inflammatory and antithrombogenic effects. [15][16][17][18][19][20][21][22][23][24][25][26] Although regular dietary of green tea may have valuable effects on health, however drinking too much can lead to an oxidative stress in the liver. [27,28] L.Theanine [LT], the responsible substance is a unique amino acid, found only in tea plant. ...
Postoperative pain is always not well controlled by current analgesics. Green tea is supposed to have analgesic and
relaxing effect. This study assessed the effect of green tea on post-operative pain and anxiety in tibia surgery. A randomized double blind controlled trial has been conducted from May to September 2015in the north of Iran after being registered in Iranian Registry of Clinical Trials. Sixty eligible patients have randomly been assigned to either green tea (G) or placebo (P) group in quadripartite blocks. Pain severity and anxiety based on visual analogue scale (VAS)and State Trait Anxiety Inventory (STAI)were measured and compared two hours before surgery and drink intake (T0), after recovery filling Aldrete criteria(T1) and eight hours after the end of surgery (T2).Statistical analysis was performed by Chi-square test and repeated measurement in SPSS version 20. In the group of G and P 36 and 32patients remained with mean age of 36.76±1 0.96 and 41.26±11.44 years (p=0.120). Respectively 69.4% (n=25) and 75% (n=24) of participants were menin groups (p=0.787) and the mean of Body Mass Index (BMI) was
27.81±3.88 and 28.27±5.37 (p=0.706). There was no significant difference in VAS score in each group and also
between two groups in three measurement point times. The difference of STAI was significant in each group (p=0.001) and between two groups (p=0.01) in three measurement point times. Green tea could diminish postoperative anxiety but not post-operative pain.
... L-theanine (N-ethyl-L-glutamine), a unique non-protein amino acid found only in green tea (Camellia sinensis) and comprising 1e2% of the dry weight of the leaf, has antioxidative properties (Li et al., 2012), as well as immune modulating (Li et al., 2016), hepatoprotective (P erez-Vargas et al., 2016), and neuroprotective effects (Kim et al., 2009). Furthermore, L-theanine has been shown to markedly decrease nitric oxide production via the downregulation of inducible nitric oxide synthase (iNOS) in glutamate-induced SH-SY5Y cells (Di et al., 2010). Liu et al. (2009) proposed that L-theanine attenuates b-amyloid-induced neurotoxicity through a reduction in ROS production and inactivation of the NF-kB pathways, and inhibits the growth of human leukemia and lung cancer cells. ...
L-theanine, a water-soluble amino acid isolated from green tea (Camellia sinensis), has anti-inflammatory activity, antioxidative properties, and hepatoprotective effects. However, the anti-allergic effect of L-theanine and its underlying molecular mechanisms have not been elucidated. In this study, we investigated the protective effects of L-theanine on asthmatic responses, particularly airway inflammation and oxidative stress modulation in an ovalbumin (OVA)-induced murine model of asthma. Treatment with L-theanine dramatically attenuated the extensive trafficking of inflammatory cells into bronchoalveolar lavage fluid (BALF). Histological studies revealed that L-theanine significantly inhibited OVA-induced mucus production and inflammatory cell infiltration in the respiratory tract and blood vessels. L-theanine administration also significantly decreased the production of IgE, monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-4, IL-5, IL-13, tumor necrosis factor-alpha (TNF-α), and interferon-gamma (INF-γ) in BALF. The lung weight decreased with L-theanine administration. L-theanine also markedly attenuated the OVA-induced generation of reactive oxygen species and the activation of nuclear factor kappa B (NF-κB) and matrix metalloprotease-9 in BALF. Moreover, L-theanine reduced the TNF-α-induced NF-κB activation in A549 cells. Together, these results suggest that L-theanine alleviates airway inflammation in asthma, which likely occurs via the oxidative stress-responsive NF-κB pathway, highlighting its potential as a useful therapeutic agent for asthma management.
... These findings further support the anti-stress effects of L-theanine. a complex range of neurochemical actions associated with L-theanine administration, including inhibiting glutamate reuptake [8], increasing brain GABA [9] and striatum dopamine and glycine concentrations [4,10], while serotonin levels were reported to decrease globally, with region-specific increases in the striatum, hippocampus and hypothalamus [4,11]. Longer term L-theanine administration has demonstrated additional actions, including facilitating long-term potentiation and an increase in brain-derived neurotrophic factor (BDNF) expression in the hippocampus over three to four weeks [12,13], as well as mounting evidence supporting a neuroprotective effect [7,14,15]. ...
L-theanine (γ-glutamylethylamide) is an amino acid found primarily in the green tea plant. This study explored the effects of an L-theanine-based nutrient drink on mood responses to a cognitive stressor. Additional measures included an assessment of cognitive performance and resting state alpha oscillatory activity using magnetoencephalography (MEG). Thirty-four healthy adults aged 18–40 participated in this double-blind, placebo-controlled, balanced crossover study. The primary outcome measure, subjective stress response to a multitasking cognitive stressor, was significantly reduced one hour after administration of the L-theanine drink when compared to placebo. The salivary cortisol response to the stressor was reduced three hours post-dose following active treatment. No treatment-related cognitive performance changes were observed. Resting state alpha oscillatory activity was significantly greater in posterior MEG sensors after active treatment compared to placebo two hours post-dose; however, this effect was only apparent for those higher in trait anxiety. This change in resting state alpha oscillatory activity was not correlated with the change in subjective stress response or the cortisol response, suggesting further research is required to assess the functional relevance of these treatment-related changes in resting alpha activity. These findings further support the anti-stress effects of L-theanine.
... Studies on the biological activities of L-theanine have mainly focused on its neuroprotective effects (for example see Haskell et al., 2008;Nathan et al., 2006), especially on how it acts antagonistically against the stimulatory effects of caffeine in the nervous system (Bryan, 2008;Haskell et al., 2008). Because the structure of L-theanine is similar to that of glutamic acid, it can bind to the glutamate receptor and trigger a series of corresponding physiological reactions (Di et al., 2010). ...
... In addition to the properties described above, green tea and its components may exert neuroprotective effects through a variety of other mechanisms. These include green tea extract-and L-theaninemediated regulation of the secretion of stress hormones that influence cognitive function, including corticosterone [119,120]; EGCG-mediated reduction of amyloid-induced mitochondrial dysfunction [121]; inhibition of glutamate dehydrogenase [122,123], 3,4-dihydroxyphenylalanine decarboxylase [124], and histone acetyltransferase [125]; inhibition of fatty acid synthase by catechins [126,127]; interactions between catechin derivatives and opioid/cannabinoid receptors [128,129]; and L-theanine-mediated modulation of glutamatergic [130], GABAergic [131], dopaminergic [132], and serotoninergic neurotransmission in the brain [132][133][134]. Caffeine is also a psychoactive ingredient of green tea [76] and this stimulates cholinergic neurons by acting as a non-selective antagonist of adenosine A1 and A2A receptors [135]. ...
The prevalence of cognitive dysfunction, and particularly dementia, is increasing rapidly among older adults worldwide. There is currently no cure for dementia. In this situation, pharmaceutical and non-pharmaceutical combination therapies capable of preventing or slowing the progression of cognitive dysfunction are important. Nutritional intervention provides an important non-pharmaceutical approach in clinical practice. Green tea has the potential to contribute to this nutritional approach. Experimental studies in vitro and in vivo have suggested that green tea and its components could affect cognition via several potential mechanisms; these include its antioxidant and anti-inflammatory properties, protein kinase C activation, and acetylcholinesterase inhibition. Although several epidemiological and interventional studies in humans have suggested an association between tea consumption and cognition, not all studies have reported consistent findings. The present review summarizes experimental studies of the mechanisms involved in these effects and clinical studies of green tea consumption and cognition. This review provides a basis for the development of an evidence-based approach to the use of green tea and its ingredients in individuals with cognitive dysfunction.
... Cadmium increased CaM function and induced [Ca 2? ]i elevation, induced ROS and activated MAPK and mTOR pathways, thereby leading to caspase-dependent apoptosis of neuronal cells [26]. Both L-Glutamate and Ab could induce a rise in calcium levels along with overactivation of the NMDA receptor in APPsw cells, while L-theanine as NMDA antagonists attenuated this rise in calcium concentration [34,35]. These suggest that inhibition of the calcium influx is one of potential mechanisms by which L-theanine exerts a protective effect against cadmium remains to be determined. ...
L-Theanine is an amino acid derivative from green tea. The present work was aimed at the effect of L-theanine on neuron-like rat pheochromocytoma (PC12) cells stimulated with cadmium chloride. Treatment with L-theanine before cadmium exposure increased cell viability; the experiments of Annexin V/PI staining indicated that L-theanine inhibited cadmium-induced cell apoptosis. Meanwhile, L-theanine decreased ROS production and protected from cadmium-induced disruption of mitochondrial transmembrane potential. Compared with cadmium-treated cells, L-theanine could also decrease the ratio of Bax/Bcl-2, as well as the level of cleaved caspase-9, caspase-3 and poly(ADP-ribose) polymerase. Furthermore, L-theanine depresses cadmium-induced up regulation of phosphorylations of PI3K/Akt, MAPK ERK1/2, and JNK signaling. These data suggest that L-theanine pretreatment reduces severity of cadmium toxicity probably via antioxidant action. Therefore, it may be concluded that L-theanine could be exploited for prevention of cadmium-induced diseases.
... Even doses as low as 1 mg of L-Theanine per kg of body weight reduce the sizes of cerebral infarcts following middle cerebral artery occlusion in mice [37]. L-Theanine also attenuated neurotoxicity of rotenone and dieldrin-induced DNA fragmentation and apoptotic death in cultured neural cells [38], as well as L-glutamate-induced amyloid beta neurotoxicity [39]. Moreover, L-Theanine is reported to facilitate neurogenesis in the hippocampus of rats following treatment, leading to enhanced memory [40]. ...
Genetic studies indicate that aging is modulated by a great number of genetic pathways. We have used Drosophila longevity and stress assays to test a multipath intervention strategy. To carry out this strategy, we supplemented the flies with herbal extracts (SC100) that are predicted to modulate the expression of many genes involved in aging and stress resistance, such as mTOR, NOS, NF-KappaB, and VEGF. When flies were housed in large cages with SC100 added, daily mortality rates of both male and female flies were greatly diminished in mid to late life. Surprisingly, SC100 also stabilized midlife mortality rate increases so as to extend the maximum life span substantially beyond the limits previously reported for D. melanogaster. Under these conditions, SC100 also promoted robust resistance to partial starvation stress and to heat stress. Fertility was the same initially in both treated and control flies, but it became significantly higher in treated flies at older ages as the fertility of control flies declined. Mean and maximum life spans of flies in vials at the same test site were also extended by SC100, but the life spans were short in absolute terms. In contrast, at an independent test site where stress was minimized, the flies exhibited much longer mean life spans, but the survival curves became highly rectangular and the effects of SC100 on both mean and maximum life spans declined greatly or were abolished. The data indicate that SC100 is a novel herbal mix with striking effects on enhancing Drosophila stress resistance and life span in some environments, while minimizing mid to late life mortality rates. They also show that the environment and other factors can have transformative effects on both the length and distribution of survivorship, and on the ability of SC100 to extend the life span.
... According to Yokogoshi and collaborators [108], Ltheanine is partially transported to the brain via a leucinepreferring transporter system and can cross the BBB exercising protective and preventive effects on neuronal cell death. The benefits of L-theanine for health are reported to be associated with regulation of blood pressure, effective prophylaxis and treatment for neurodegenerative diseases, among others [109][110][111]. ...
Diabetes mellitus (DM) is a metabolic disease that is rapidly increasing and has become a major public health problem. Type 2 DM (T2DM) is the most common type, accounting for up to 90-95% of the new diagnosed DM cases. The brain is very susceptible to glucose fluctuations and hyperglycemia-induced oxidative stress (OS). It is well known that DM and the risk of developing neurodegenerative diseases are associated. Tea, Camellia sinensis L., is one of the most consumed beverages. It contains several phytochemicals, such as polyphenols, methylxanthines (mainly caffeine) and L-theanine that are often reported to be responsible for tea’s health benefits, including in brain. Tea phytochemicals have been reported to be responsible for tea’s significant antidiabetic and neuroprotective properties and antioxidant potential. Epidemiological studies have shown that regular consumption of tea has positive effects on DM-caused complications and protects the brain against oxidative damage, contributing to an improvement of the cognitive function. Among the several reported benefits of tea consumption, those related with neurodegenerative diseases are of great interest. Herein, we discuss the potential beneficial effects of tea consumption and tea phytochemicals on DM and how their action can counteract the severe brain damage induced by this disease.
... Theanine has also found to link with providing effective prophylaxis and treatment for Alzheimer's disease, Downloaded by [Figure 4 Mechanism of theanine to protect normal tissue from doxorubicin (DOX) toxicity via the changing glutathione (GSH) level (Wan et al., 2009b). regulating blood pressure, promoting the weight loss and improving the immune system (Yokogoshi and Kobayashi, 1998; Rogers et al., 2007; Di et al., 2010; Takagi et al., 2010). ...
Tea has been widely consumed around the world for thousands of years and drinking tea is a daily habit for people of all ages. Tea is a major source of flavanoids, which have become well known as antioxidants. Tea also contains caffeine and theanine, which have been found to associate with health benefits. Many animal and epidemiological studies have been conducted to investigate the link between tea consumption and human health. However, common questions that arise about tea consumption include: whether all teas are the same, why drinking tea is linked with health benefits, how do the different ways of tea preparation impact on availability of tea components, how much and how long a person should consume tea to obtain health benefits, and whether there is any negative health effect associated with drinking tea. To answer these questions, this paper outlines the tea components and their link to human health, discusses major factors affecting availability of tea components in a tea cup, and reviews the latest epidemiological evidence linking tea consumption to human health.
Tea is prepared from the young leaves, buds, stalks of the plant Camellia sinensis. The cultivation process of tea plants and the habit of tea drinking were initiated in China from ancient times. Now, the consumption of tea is very popular throughout the world and it is an integral part of our social culture. Tea contains polyphenolic compounds (catechins and epicatechins), theaflavins, flavonol glycosides, L-theanine, caffeine, theobromine, and volatile organic substances. These bioactive components are responsible for the astringency, flavor, aroma, and taste of the tea as well as its health beneficial effects. Moreover, tea has several medicinal values. The phytochemical components are involved in the prevention and cure of many illnesses like cardiovascular diseases, malignancy, digestive dysfunction, and metabolic disorders like obesity, diabetes. Tea flavonoids show strong antioxidant properties. Caffeine and other methylxanthine regulate the intracellular second messenger levels. Additionally, catechins exhibit anti-inflammatory effects. All these multidimensional actions make some positive attributes in favor of neuroprotection, cardioprotection, and cancer prevention. Various approaches are also taken to use tea ingredients as an adjuvant in cancer therapy. This review emphasizes the importance of bioactive components, and their health promotional activities.
• KEY TEACHING POINTS
• Origin and brief history of tea.
• Processing steps and characteristics of different types of teas.
• Bioactive components of teas (green and black tea), their biochemical characteristics and health promotional effects.
• Role of different bioactive components to control the various physiological and metabolic disorders.
• Possibilities of use of tea component in cancer therapy.
Meta-analyses of tea consumption and reduced risk of Parkinson's disease have thrown light in the pathway of exploring beneficial properties of tea components. On the basis of dry mass, a typical black or green tea beverage contains approximately 6% of free amino acids, which impart high quality, taste and distinctive aroma to the tea infusion. L-theanine (chemically known as γ-glutamylethylamide) is a non-proteinogenic amino acid of tea that takes part in the biosynthesis of its polyphenols. Recently discovered neuroprotective effects of L-theanine can be attributed to its structural analogy with glutamate, the principal excitatory neurotransmitter in brain. This unique amino acid also bears a potential to ameliorate the pathophysiological changes associated with Parkinson's disease as it displays antioxidant and anti-inflammatory properties, improves motor behavioral abnormalities, increases dopamine availability and may cause a favorable downshift in neurodegeneration due to glutamate excitotoxicity. To gain an explicit understanding of the role of L-theanine, this review article is the first one to focus on its mechanism of neuromodulatory action and to critically evaluate the possibilities of employing this bioactive amide in the forage of anti-Parkinsonian medication. We also hypothesize the idea of L-theanine being a potent natural agent against L-DOPA induced dyskinesia, since long-term reliance on dopamine replacement therapy is linked with elevation in glutamate receptor activity.
Context: Currently, there is no treatment that can stop the progression of Alzheimer’s disease. We have used transgenic Drosophila melanogaster models and machine learning to develop an eight component botanical mixture (Geneaire™ ReBuilder™) that targets multiple genetic pathways involved in brain aging and dementia that are homologous between Drosophila and humans.
Objective: To test the effects of ReBuilder on the cognitive function of subjects diagnosed with mild or moderate Alzheimer’s disease.
Methods: We recruited 50 subjects with mild to moderate AD to participate in a double-blind, placebo-controlled clinical study. During the 12-month pilot study, the subjects were evaluated quarterly on the Mini Mental State Exam (MMSE), Alzheimer’s Disease Cooperative Study’s Activities of Daily Living (ADCS-ADL), and the Clinical Dementia Rating Sum of Boxes (CDR-SB).
Results: The addition of ReBuilder to subjects’ existing Namenda and Exelon regimens stabilized cognitive decline in patients with mild AD and slowed cognitive decline in patients with moderate AD.
Conclusions: These results were observed in both sexes and in all ages tested. Importantly, no adverse side effects attributable to ReBuilder were reported. The results of this clinical pilot warrant further study of ReBuilder in AD.
As two natural oligosaccharide esters, 3,6?-Disinapoyl sucrose (DISS) and tenuifolisideA (TFSA) are originating from the root of Polygala tenuifolia Willd, a traditional Chinese medicine used in treatment of mental disorders. Previous reports have shown that both of them possess in vitro neuroprotective effects by stimulating different upstream pathways related with cyclic AMP-responsive element-binding protein (CREB). In the present study, we investigated the additive neuroprotective effects of DISS and TFSA on Glu-induced damage of SY5Y cells and purposed the possible underlying mechanism. The interaction between DISS and TFSA showed a clear-cut synergistic effect as evidenced by combination index (CI). Additional evidence from biochemical (NOS activity) assays confirmed their additive inhibition on the Glu-induced NOS hyperactivation. Moreover, we showed that co-treatment of DISS and TFSA resulted in an additively up-regulated phosphorylation of CREB as well as increased expressions of CRTC1 and BDNF. Neuroprotective effects of DISS and TFSA on Glu-induced decrease in cell viability were blocked by MAPK/ERK1/2 inhibitor (U0126) and PI3-K inhibitor (LY290042). Nevertheless, the CRTC1 or BDNF expression induced by these two compounds was significantly reduced in the presence of either ERK or PI3-K inhibitor, indicating that the two oligosaccharide esters shared some common pathways in the regulation of CREB-BDNF pathway. Taken together, we, for the first time, showed that DISS and TFSA exerted the additive neuroprotective effects on CREB-BDNF signaling pathway through complementary mechanisms.
Typical drinks of the Mediterranean diet, associated with convivial meals, are wine (in non-Muslim countries)—consumed during main courses—and infusions and coffee, generally consumed after the meal. Many herbal infusions of wild weeds are often related to folk medicine. None of these drinks provide major nutrients in significant amounts, and their effects on health result from the presence of minor components. Coffee is a very popular drink, consumed all over the world in many different ways: brewed, filtered or prepared using particular techniques. Italians popularised the ‘espresso’ coffee, produced from a blend of selected proportions of ‘Robusta’ and ‘Arabica’ grains. Coffee became popular for its stimulant properties attributed to caffeine, which is thought to improve mental acuity, particularly in the elderly, and recent studies suggest that moderate coffee consumption may reduce the risk of stroke. On the other hand, tea (the infusion of the leaves of Camellia sinensis) provides a wide range of bioactive compounds. Tea is rich in catechins and derivatives as well as in other flavonoids; it also provides two stimulant compounds: caffeine and theobromine (in lower amounts than coffee). While black tea is predominant in Europe, green tea is preferred in the south of the Mediterranean Sea; the difference between both types of tea relies on the existence of an oxidation step during manufacturing of black tea. Regular tea consumption has been associated with a decreased rate of some non-communicable diseases and may also be helpful in weight control. Herbal infusions, sometimes called medicinal teas, have been used since immemorial times, mostly for curative purposes. The most popular herbal infusions, in the countries referred in the current work, are chamomile (Chamaemelum nobile), lemon balm and balm mint (variant of Melissa officinalis), lemon verbena (Aloysia triphylla) and lemon peel (Citrus limon). Their antioxidant and anti-inflammatory properties have been attributed to different flavonoids and essential oils. In its turn, wine is one of the oldest fermented drinks, admired for its flavour and health-promoting effects, particularly in the improvement of cardiovascular health. Wine making and consumption is a mixture of science, culture and art. A wine is chosen to complement a meal and should be consumed in moderate amounts.
Pregnenolone (PREG) and L-Theanine (LT) have shown ameliorative effects on various schizophrenia symptoms. This is the first study to evaluate the efficacy and safety of augmentation of antipsychotic treatment among patients with chronic schizophrenia or schizoaffective disorder with PREG - LT.
Double-blind, placebo-controlled trial of PREG - LT or placebo augmentation was conducted for 8 weeks with 40 chronic DSM-IV schizophrenia and schizoaffective disorder patients with suboptimal response to antipsychotics. Oral PREG (50 mg/day) with LT (400 mg/day) or placebo were added to a stable regimen of antipsychotic medication from March 2011 to October 2013. The participants were rated using the Scale for the Assessment of Negative Symptoms (SANS), Hamilton Scale for Anxiety (HAM-A), and Positive and Negative Syndrome Scale (PANSS) scales bi-weekly. The decrease of SANS and HAM-A scores were the co-primary outcomes. Secondary outcomes included assessments of general functioning and side effects.
Negative symptoms such as blunted affect, alogia, and anhedonia (SANS) were found to be significantly improved, with moderate effect sizes among patients who received PREG-LT, in comparison with the placebo group. Add-on PREG-LT also significantly associated with a reduction of anxiety scores such as anxious mood, tension, and cardiovascular symptoms (HAM-A), and elevation of general functioning (GAF). Positive symptoms, antipsychotic agents, concomitant drugs, and illness duration did not associate significantly with effect of PREG-LT augmentation. PREG-LT was well-tolerated.
Pregnenolone with L-Theanine augmentation may offer a new therapeutic strategy for treatment of negative and anxiety symptoms in schizophrenia and schizoaffective disorder. Further studies are warranted.
clinicaltrials.gov Identifier: NCT01831986.
Although glutamate is one of the most important excitatory neurotransmitters of the central nervous system, its excessive extracellular concentration leads to uncontrolled continuous depolarization of neurons, a toxic process called, excitotoxicity. In excitotoxicity glutamate triggers the rise of intracellular Ca 2+ levels, followed by up regulation of nNOS, dysfunction of mitochondria, ROS production, ER stress, and release of lysosomal enzymes. Excessive calcium concentration is the key mediator of glutamate toxicity through over activation of ionotropic and metabotropic receptors. In addition, glutamate accumulation can also inhibit cystine (CySS) uptake by reversing the action of the CySS/glutamate antiporter. Reversal of the antiporter action reinforces the aforementioned events by depleting neurons of cysteine and eventually glutathione's reducing potential. Various cell lines have been employed in the pursuit to understand the mechanism(s) by which excitotoxicity affects the cells leading them ultimately to their demise. In some cell lines glutamate toxicity is exerted mainly through over activation of NMDA, AMPA, or kainate receptors whereas in other cell lines lacking such receptors, the toxicity is due to glutamate induced oxidative stress. However, in the greatest majority of the cell lines ionotropic glutamate receptors are present, co-existing to CySS/glutamate antiporters and metabotropic glutamate receptors, supporting the assumption that excitotoxicity effect in these cells is accumulative. Different cell lines differ in their responses when exposed to glutamate. In this review article the responses of PC12, SH-SY5Y, HT-22, NT-2, OLCs, C6, primary rat cortical neurons, RGC-5, and SCN2.2 cell systems are systematically collected and analyzed.
The beneficial effects of theanine in tea are reported on many aspects. Here we report that theanine can extend nematode Caenorhabditis elegans lifespan under stress. Theanine (100 mg/mL) significantly increased the mean longevity of C. elegans by 12.8% and 21.3% under heat stress and oxidative stress, respectively. However, theanine treatment did not increase survival of C. elegans under normal culture condition. Further studies showed that theanine mediated lifespan extension under heat stress was involved in heat shock protein-16.2 (HSP-16.2) up-regulating expression.
The benefits of tea for human health are widely accepted all over the world. L-Theanine, a nonprotein amino acid found in tea plants, is the major tea component that contributes to the unique pleasing taste of tea. L-Theanine has been shown to promote relaxation, enhance cognitive performance and act antagonistically against the excitement induced by caffeine. Recently, it was found that L-Theanine had inhibitory effect on nicotine dependence. This paper reviews the neuroprotective properties of L-Theanine and discusses the inhibitory effects of L-Theanine on nicotine dependence.
Amyloid beta ()-induced neurotoxicity is a major pathological mechanism of Alzheimer's disease (AD). In this study, we investigated the inhibitory effect of L-theanine, a component of green tea (Camellia sinensis) on -induced neurotoxicity and oxidative damages of macromolecules. L-theanine inhibited -induced generation of reactive oxygen species, and activation of extracellular signal-regulated kinase and p38 mitogenic activated protein kinase as well as the activity of nuclear factor kappa-B. L-theanine also signifi cantly reduced oxidative protein and lipid damage, and elevated glutathione level. Consistent with the reduced neurotoxic signals, L-theanine (10-50 /ml) concomitantly attenuated (5 )-induced neurotoxicity in SK-N-MC and SK-N-SH human neuroblastoma cells. These data indicate that L-theanine on -induced neurotoxicity prevented oxidative damages of neuronal cells, and may be useful in the prevention and treatment of neurodegenerative disease like AD.
A new family of highly fluorescent indicators has been synthesized for biochemical studies of the physiological role of cytosolic free Ca2+. The compounds combine an 8-coordinate tetracarboxylate chelating site with stilbene chromophores. Incorporation of the ethylenic linkage of the stilbene into a heterocyclic ring enhances the quantum efficiency and photochemical stability of the fluorophore. Compared to their widely used predecessor, “quin2”, the new dyes offer up to 30-fold brighter fluorescence, major changes in wavelength not just intensity upon Ca2+ binding, slightly lower affinities for Ca2+, slightly longer wavelengths of excitation, and considerably improved selectivity for Ca2+ over other divalent cations. These properties, particularly the wavelength sensitivity to Ca2+, should make these dyes the preferred fluorescent indicators for many intracellular applications, especially in single cells, adherent cell layers, or bulk tissues.
We have characterized amyloid β peptide (Aβ. concentration, Aβ deposition, paired helical filament formation, cerebrovascular amyloid angiopathy, apolipoprotein E (ApoE) allotype, and synaptophysin concentration in entorhinal cortex and superior frontal gyrus of normal elderly control (ND) patients, Alzheimer's disease (AD. patients, and high pathology control (HPC) patients who meet pathological criteria for AD but show no synapse loss or overt antemortem symptoms of dementia. The measures of Aβ deposition, Aβ-immunoreactive plaques with and without cores, thioflavin histofluorescent plaques, and concentrations of insoluble Aβ, failed to distinguish HPC from AD patients and were poor correlates of synaptic change. By contrast, concentrations of soluble Aβ clearly distinguished HPC from AD patients and were a strong inverse correlate of synapse loss. Further investigation revealed that Aβ40, whether in soluble or insoluble form, was a particularly useful measure for classifying ND, HPC, and AD patients compared with Aβ42. Aβ40 is known to be elevated in cerebrovascular amyloid deposits, and Aβ40 (but not Aβ42) levels, cerebrovascular amyloid angiopathy, and ApoE4 allele frequency were all highly correlated with each other. Although paired helical filaments in the form of neurofibrillary tangles or a penumbra of neurites surrounding amyloid cores also distinguished HPC from AD patients, they were less robust predictors of synapse change compared with soluble Aβ, particularly soluble Aβ40. Previous experiments attempting to relate Aβ deposition to the neurodegeneration that underlies AD dementia may have failed because they assayed the classical, visible forms of the molecule, insoluble neuropil plaques, rather than the soluble, unseen forms of the molecule.
A new family of highly fluorescent indicators has been synthesized for biochemical studies of the physiological role of cytosolic free Ca2+. The compounds combine an 8-coordinate tetracarboxylate chelating site with stilbene chromophores. Incorporation of the ethylenic linkage of the stilbene into a heterocyclic ring enhances the quantum efficiency and photochemical stability of the fluorophore. Compared to their widely used predecessor, "quin2", the new dyes offer up to 30-fold brighter fluorescence, major changes in wavelength not just intensity upon Ca2+ binding, slightly lower affinities for Ca2+, slightly longer wavelengths of excitation, and considerably improved selectivity for Ca2+ over other divalent cations. These properties, particularly the wavelength sensitivity to Ca2+, should make these dyes the preferred fluorescent indicators for many intracellular applications, especially in single cells, adherent cell layers, or bulk tissues.
In Alzheimer's disease, β-amyloid (Aβ) plaques are surrounded by activated astrocytes and microglia. A growing body of evidence
suggests that these activated glia contribute to neurotoxicity through the induction of inflammatory cytokines such as interleukin
(IL)-1β and tumor necrosis factor-α (TNFα) and the production of neurotoxic free radicals, mediated in part by the expression
of inducible nitric-oxide synthase (iNOS). Here, we address the possibility that Aβ-stimulated iNOS expression might result
from an initial induction of IL-1β and TNFα. We find that in Aβ-stimulated astrocyte cultures, IL-1β and TNFα production occur
before iNOS production, new protein synthesis is required for increased iNOS mRNA levels, and the IL-1 receptor antagonist
IL-1ra can inhibit nitrite accumulation. Likewise, dominant-negative mutants of tumor necrosis factor-α receptor-associated
factor (TRAF) 6, TRAF2, and NFκB-inducing kinase (NIK), intracellular proteins involved in IL-1 and TNFα receptor signaling
cascades, inhibit Aβ-stimulated iNOS promoter activity. Our data suggest that Aβ stimulation of astrocyte iNOS is mediated
in part by IL-1β and TNFα, and involves a TRAF6-, TRAF2-, and NIK-dependent signaling mechanism.
Increasing evidence suggests an important role of mitochondrial dysfunction in the pathogenesis of Alzheimer's disease. Thus, we investigated the effects of acute and chronic exposure to increasing concentrations of amyloid beta (Abeta) on mitochondrial function and nitric oxide (NO) production in vitro and in vivo. Our data demonstrate that PC12 cells and human embryonic kidney cells bearing the Swedish double mutation in the amyloid precursor protein gene (APPsw), exhibiting substantial Abeta levels, have increased NO levels and reduced ATP levels. The inhibition of intracellular Abeta production by a functional gamma-secretase inhibitor normalizes NO and ATP levels, indicating a direct involvement of Abeta in these processes. Extracellular treatment of PC12 cells with comparable Abeta concentrations only leads to weak changes, demonstrating the important role of intracellular Abeta. In 3-month-old APP transgenic (tg) mice, which exhibit no plaques but already detectable Abeta levels in the brain, reduced ATP levels can also be observed showing the in vivo relevance of our findings. Moreover, we could demonstrate that APP is present in the mitochondria of APPsw PC12 cells. This presence might be directly involved in the impairment of cytochrome c oxidase activity and depletion of ATP levels in APPsw PC12 cells. In addition, APPsw human embryonic kidney cells, which produce 20-fold increased Abeta levels compared with APPsw PC12 cells, and APP tg mice already show a significantly decreased mitochondrial membrane potential under basal conditions. We suggest a hypothetical sequence of pathogenic steps linking mutant APP expression and amyloid production with enhanced NO production and mitochondrial dysfunction finally leading to cell death.
Universally accepted neuropathologic criteria for differentiating Alzheimer disease (AD) from healthy brain aging do not exist. We tested the hypothesis that Bielschowsky silver stained total, cored, and neuritic senile plaques (TSPs, CSPs, and NSPs, respectively), rather than neurofibrillary tangles (NFTs), best discriminate between the 2 conditions using rigorously defined nondemented (n = 7) and AD (n = 35) subjects with no known co-morbidities. We compared lesions in 3 neocortical regions, in hippocampal CA1, and in entorhinal cortex in 19 men and 13 women between 74 and 86 years at death. The Clinical Dementia Rating (CDR) was used to assess degree of cognitive impairment within a year of demise. Neocortical TSP measures provided the highest correlation with expiration CDR: area under the curve (AUC) = 0.986 with 97.8% sensitivity at 90% specificity with an estimated cut-point of 6.0 TSP/ mm2. All SP measures yielded higher estimated AUC and sensitivity for 90% specificity compared to NFTs. Derived TSP cut-points applied to 149 persons with clinical AD regardless of their neuropathologic diagnosis yielded a sensitivity of 97% and specificity of 84% for TSPs in the 3 neocortical areas. Thus cut-points based on both diffuse and neuritic SP in neocortical regions distinguished nondemented and AD subjects with high sensitivity and specificity.
The tumor suppressor and transcription factor p53 is a key modulator of cellular stress responses, and activation of p53 can trigger apoptosis in many cell types including neurons. Apoptosis is a form of programmed cell death that occurs in neurons during development of the nervous system and may also be responsible for neuronal deaths that occur in neurological disorders such as stroke, and Alzheimer's and Parkinson's diseases. p53 production is rapidly increased in neurons in response to a range of insults including DNA damage, oxidative stress, metabolic compromise, and cellular calcium overload. Target genes induced by p53 in neurons include those encoding the pro-apoptotic proteins Bax and the BH3-only proteins PUMA and Noxa. In addition to such transcriptional control of the cell death machinery, p53 may more directly trigger apoptosis by acting at the level of mitochondria, a process that can occur in synapses (synaptic apoptosis). Preclinical data suggest that agents that inhibit p53 may be effective therapeutics for several neurodegenerative conditions.
In an investigation of the mechanisms of the neuroprotective effects of theanine (gamma-glutamylethylamide) in brain ischemia, inhibition by theanine of the binding of [H-3](RS)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), [H-3]kainate, and [H-3](E)-3-(2-phenyl-2-carboxyethenyl)-4,6-dichloro-1-H-indole-2- carboxylic acid (MDL 105,519) to glutamate receptors was studied in terms of its possible inhibiting effects on the three receptor subtypes (AMPA, kainate, and NMDA glycine), with rat cortical neurons. Theanine bound the three receptors, but its IC50 of theanine was 80- to 30,000-fold less than that of L-glutamic acid.
The compound 13-l-hydroperoxylinoleic acid (LOOH) triggered the death of clonal rat pheochromocytoma PC12h cells (LD50=about 8 μM). LOOH induced nuclear condensation and DNA fragmentation, which was prevented by cycloheximide (a protein synthesis inhibitor) and NGF, indicating that LOOH triggered apoptosis in PC12h cells. LOOH produced reactive oxygen species (ROS) in PC12h cells in a time- and dose-dependent manner, as measured by flow cytometry using the ROS-specific fluorescent indicator, 6-carboxy-2,7-dichorodihydrofluorescein diacetate, di(acetoxymethyl ester) (C-DCDHF-DA). Antioxidants such as N,N′-diphenyl-p-phenylenediamine (DPPD), vitamin E and N-acetylcysteine, and a ferric iron chelator, deferoxamine, inhibited the LOOH-triggered apoptosis and simultaneously decreased the generation of ROS, whereas an inhibitor of glutathione synthesis, buthionine sulfoximine (BSO), enhanced the apoptosis and increased the generation of ROS. These results indicate that LOOH triggers the apoptosis of PC12h cells by increasing the production of ROS. A confocal analysis with the Ca2+-specific fluorescent indicator, fluo-3, demonstrated that LOOH at concentrations up to 200 μM, did not increase the intracellular Ca2+ concentration. These data indicate that LOOH induces apoptosis of PC12h cells through the enhanced production of ROS, not through increasing the permeability of Ca2+.
Theanine is the main amino acid component in tea. It usually constitutes between 1 and 2% of the dry weight of the tea leaves. It is as prevalent in tea as all other free amino acids combined. Both enantiomers of theanine were found to have a similar sweet taste, with little or no aftertaste. It was found that black and half-green teas (except for Formosa Oolong) contained as much, or more, theanine as green teas. No correlation was found between the absolute concentration of theanine in tea and its enantiomeric composition. An inverse correlation was found between certain grades of tea (e.g., pekoe, Flowery Orange Pekoe, etc.) and the percent of d-theanine present. This could provide the basis for a reproducible, scientific method to grade and/or evaluate teas. Theanine slowly racemizes in aqueous solution. It also undergoes hydrolysis, particularly at basic pH values. By monitoring these processes, information may be gleaned on the production, storage, handling, and shipping of tea and tea products. Keywords: Racemization; beverage; d-amino acid; tea grades; cyclodextrin column; column switching
Excitotoxicity refers to the ability of glutamate or related excitatory amino acids to mediate the death of central neurons under certain conditions, for example, after intense exposure. Such excitotoxic neuronal death may contribute to the pathogenesis of brain or spinal cord injury associated with several human disease states. Excitotoxicity has substantial cellular specificity and, in most cases, is mediated by glutamate receptors. On average, NMDA receptors activation may be able to trigger lethal injury more rapidly than AMPA or kainate receptor activation, perhaps reflecting a greater ability to induce calcium influx and subsequent cellular calcium overload. It is possible that excitotoxic death may share some mechanisms with other forms of neuronal death. © 1992 John Wiley & Sons, Inc.
Since ancient times, it has been said that drinking green tea brings relaxation. The substance that is responsible for a sense of relaxation, is theanine. Theanine is a unique amino acid found almost solely in tea plants and the main component responsible for the exotic taste of ‘green’ tea. It was found that L-theanine administered intraperitoneally to rats reached the brain within 30 min without any metabolic change. Theanine also acts as a neurotransmitter in the brain and decreased blood pressure significantly in hypertensive rats. In general, animals always generate very weak electric pulses on the surface of the brain, called brain waves. Brain waves are classified into four types, namely α,β,δ and θ-waves, based on mental conditions. Generation of α-waves is considered to be an index of relaxation. In human volunteers, α-waves were generated on the occipital and parietal regions of the brain surface within 40 min after the oral administration of theanine (50–200 mg), signifying relaxation without causing drowsiness. With the successful industrial production of L-theanine, we are now able to supply Suntheanine™ (trade name of L-theanine) which offers a tremendous opportunity for designing foods and medical foods targeting relaxation and the reduction of stress. Taiyo Kagaku Co., Ltd, Japan won the 1998 ‘Food Ingredient Research Award’ for development of Suntheanine™ at Food Ingredients in Europe (Frankfurt). The judges felt it was a particularly well-documented and fascinating piece of research.
Neuronal loss is prominent in Alzheimer’s disease (AD), and its mechanisms remain unresolved. Apoptotic cell death has been implicated on the basis of studies demonstrating DNA fragmentation and an up-regulation of proapoptotic proteins in the AD brain. However, DNA fragmentation in neurons is too frequent to account for the continuous neuronal loss in a degenerative disease extending over many years. Furthermore, the typical apoptotic morphology has not been convincingly documented in AD neurons with fragmented DNA. We report the detection of the activated form of caspase-3, the central effector enzyme of the apoptotic cascade, in AD and Down’s syndrome (DS) brain using an affinity-purified antiserum. In AD and DS, single neurons with apoptotic morphology showed cytoplasmic immunoreactivity for activated caspase-3, whereas no neurons were labeled in age-matched controls. Apoptotic neurons were identified at an approximate frequency of 1 in 1100 to 5000 neurons in the cases examined. Furthermore, caspase-3 immunoreactivity was detected in granules of granulovacuolar degeneration. Our results provide direct evidence for apoptotic neuronal death in AD with a frequency compatible with the progression of neuronal degeneration in this chronic disease and identify autophagic vacuoles of granulovacuolar degeneration as possible means for the protective segregation of early apoptotic alterations in the neuronal cytoplasm.
Modern chromatographic techniques such as high-performance liquid chromatography are currently the most helpful approach to the routine analysis of and research of non-volatile tea constituents. Using these techniques some errors in the more classical analytical techniques could be detected. Unfortunately, some of these methods of analysis are still in widespread use, even as official methods. However, knowledge of especially the polyphenols in tea is still lacking, and for many of the minor polyphenols no chromatographic methods for the determination exist.
We present here both linear regressions and multivariate analyses correlating three global neuropsychological tests with a number of structural and neurochemical measurements performed on a prospective series of 15 patients with Alzheimer's disease and 9 neuropathologically normal subjects. The statistical data show only weak correlations between psychometric indices and plaques and tangles, but the density of neocortical synapses measured by a new immunocytochemical/densitometric technique reveals very powerful correlations with all three psychological assays. Multivariate analysis by stepwise regression produced a model including midfrontal and inferior parietal synapse density, plus inferior parietal plaque counts with a correlation coefficient of 0.96 for Mattis's Dementia Rating Scale. Plaque density contributed only 26% of that strength.
A convenient way to estimate the number of viable cells growing in microtitre tray wells is to use a colorimetric assay and an automatic microplate scanning spectrophotometer. One such assay, developed by Mosmann, depends on the reduction by living cells of tetrazolium salt, MTT, to form a blue formazan product. However the original technique has several technical limitations, namely a less than optimal sensitivity, a variable background due to protein precipitation on adding an organic solvent to dissolve the blue formazan product, and a low solubility of the product. These problems have been overcome by the following modifications: avoidance of serum in the incubation medium, thus overcoming precipitation problems in the organic solvent; avoidance of phenol red in the incubation medium, thus avoiding the use of acid in the final solvent which altered the spectral properties of the formazan; elimination of the medium containing MTT after the reaction and subsequent use of pure propanol or ethanol to rapidly solubilize the formazan; use of a higher concentration of MTT; use of half-area microtitre trays to increase the spectrophotometer readings from a given amount of formazan; use of a more judicious reference wavelength in a dual wavelength spectrophotometer. With these modifications the reliability and sensitivity of the test have been increased to the point where it can in many cases replace the [3H]thymidine uptake assay to measure cell proliferation or survival in growth factor or cytotoxicity assays. Examples of its use in IL-2 assays are given.
A tetrazolium salt has been used to develop a quantitative colorimetric assay for mammalian cell survival and proliferation. The assay detects living, but not dead cells and the signal generated is dependent on the degree of activation of the cells. This method can therefore be used to measure cytotoxicity, proliferation or activation. The results can be read on a multiwell scanning spectrophotometer (ELISA reader) and show a high degree of precision. No washing steps are used in the assay. The main advantages of the colorimetric assay are its rapidity and precision, and the lack of any radioisotope. We have used the assay to measure proliferative lymphokines, mitogen stimulations and complement-mediated lysis.
Effects of an excitatory amino acid, glutamate, and of ionotropic and metabotropic glutamate receptor agonists on the levels of free intracellular calcium, and their specific receptor binding in human SH-SY5Y neuroblastoma cells were studied. The calcium response was always biphasic, except for AMPA, suggesting both stimulatory and inhibitory effects on free intracellular calcium upon glutamate receptor stimulation, both with ionotropic and metabotropic glutamate receptor agonists. Specific binding of glutamate and other glutamate receptor agonists, together with the biphasic calcium response, suggests that human SH-SY5Y neuroblastoma cells express both ionotropic and metabotropic glutamate receptors. These findings shed new light on the use of human SH-SY5Y neuroblastoma cells as a human neuronal tumor cell model.
One of the clinical manifestations of Alzheimer's disease is the deposition of the 39-43 residue amyloid-β (Aβ) peptide in aggregated fibrils in senile plaques. Characterization of the aggregation behavior of Aβ is one of the critical issues in understanding the role of Aβ in the disease process. Using solution hydrodynamics, Aβ was observed to form three types of species in phosphate-buffered saline: insoluble aggregates with sedimentation coefficients of ~50,000 S and molecular masses of ~109 Da, 'soluble aggregates' with sedimentation coefficients of ~30 S and masses of ~106 Da, and monomer. When starting from monomer, the aggregation kinetics of Aβ 1-40 (Aβ40) and Aβ 1-42 (Aβ42), alone and in combination, reveal large differences in the tendency of these peptides to aggregate as a function of pH and other solution conditions. At pH 4.1 and 7.0-7.4, aggregation is significantly slower than at pH 5 and 6. Under all conditions, aggregation of the longer Aβ42 was more rapid than Aβ40. Oxidation of Met- 35 to the sulfoxide in Aβ40 enhances the aggregation rate over that of the nonoxidized peptide. Aggregation was found to be dependent upon temperature and to be strongly dependent on peptide concentration and ionic strength, indicating that aggregation is driven by a hydrophobic effect. When Aβ40 and Aβ42 are mixed together, Aβ40 retards the aggregation of Aβ42 in a concentration-dependent manner. Shorter fragments have a decreasing ability to interfere with Aβ42 aggregation. Conversely, the rate of aggregation of Aβ40 can be significantly enhanced by seeding slow aggregating solutions with preformed aggregates of Aβ42. Taken together, the inhibition of Aβ42 aggregation by Aβ40, the seeding of Aβ40 aggregation by Aβ42 aggregates, and the chemical oxidation of Aβ40 suggest that the relative abundance and rates of production of different-length Aβ and its exposure to radical damage may be factors in the accumulation of Aβ in plaques in vivo.
Alzheimer's disease (AD) is defined by degeneration of specific populations of neurons and the presence of insoluble aggregates of cytoskeletal proteins and amyloid beta-peptide (A beta) within affected brain regions. Alzheimer's disease does not appear to result from a single alteration, but in some cases of inherited AD a specific genetic defect can precipitate the disease. In this article, metabolic compromise, altered metabolism of the beta-amyloid precursor protein (beta APP), and an excitotoxic form of neuronal injury are considered central to the pathogenesis AD. The hypothesis is forwarded that destabilization of neuronal Ca2+ homeostasis underlies neuronal degeneration and that multiple age-associated and/or genetic alterations contribute to the loss of Ca2+ homeostasis. Recent studies showed that the secreted forms of beta APP (APPss) stabilize intracellular free calcium levels ([Ca2+]i) and protect neurons against excitotoxic insults. In contrast, A beta which arises from alternative processing of beta APP forms free radical peptides and aggregates that destabilize [Ca2+]i and make neurons vulnerable to metabolic insults. Increased expression (eg, Down's syndrome) or altered processing (eg, beta APP mutations) of beta APP may increase the A beta/APPs ratio. The death of neurons in AD most likely has an excitotoxic component because: the vulnerable neurons possess high levels of glutamate receptors; experimentally induced excitotoxicity shows several features similar to those of neurofibrillary tangles; and A beta can destabilize [Ca2+]i homeostasis and render neurons vulnerable to neurofibrillary degeneration. Selective vulnerability may result from cell type-specific differences in expression of proteins involved in regulating [Ca+]i. In addition, many intercellular signals are involved in determining whether a neuron is able to maintain [Ca2+]i within a range of concentrations conducive to cell survival and adaptive plasticity. In this regard, it was recently shown that several growth factors can stabilize [Ca]i and protect neurons against excitotoxic injury and A beta toxicity. Age-related changes in the brain (eg, ischemic conditions, reduced glucose uptake, and increased glucocorticoid levels) may compromise the mechanisms that normally regulate [Ca2+]i adaptively.
Although a consensus on the primary mechanism(s) of neuronal degeneration in AD has not yet been reached, several potential pathogenic mechanisms have emerged. The involvement of APP and Aβ in the neurodegenerative process and their relationship to the tau-related neurofibrillary pathology are central issues. The pathogenic mechanism associated with inheritance of the ApoE4 allele remains to be determined, although initial investigations implicate effects on Aβ or possibly tau. Increasing evidence implicates oxidative stress in the neurodegenerative process, although this has yet to be convincingly linked to specific molecular mechanisms. Most importantly, the recent identification of new AD susceptibility genes promises to rapidly advance our understanding of the primary neurodegenerative mechanisms. In the broader context of human neurobiology, AD poses fundamental questions about how the brain ages and why the systems subserving memory and cognition are selectively vulnerable. The potential to answer these questions and treat this devastating illness makes this an exciting time in AD research.
To understand the mechanism of interaction of the dopamine D2L receptors with NMDA receptors, we have developed a model by transfecting human neuroblastoma SH-SY5Y cells with the human dopamine D2L receptor gene. In vitro blockade of NMDA receptors by the specific antagonists MK-801 and (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP) on human neuroblastoma SH-SY5Y cells expressing human dopamine D2L receptors resulted in a significant increase in the density of D2L receptors without a significant change in receptor affinity. Moreover, the dopamine receptor mRNA level increased by approximately 50% by the blockade of NMDA with MK-801. These results suggest a possible interaction of NMDA and dopamine D2L receptors in neuroblastoma SH-SY5Y cells. This system would serve as an excellent model to study the molecular mechanisms involved in the interaction of these two receptors.
Cerebral deposition of the amyloid beta protein (A beta) is an early and invariant feature of Alzheimer disease (AD). Whereas the 40-amino acid form of A beta (A beta 40) accounts for approximately 90% of all A beta normally released from cells, it appears to contribute only to later phases of the pathology. In contrast, the longer more amyloidogenic 42-residue form (A beta 42), accounting for only approximately 10% of secreted A beta, is deposited in the earliest phase of AD and remains the major constituent of most amyloid plaques throughout the disease. Moreover, its levels have been shown to be increased in all known forms of early-onset familial AD. Thus, inhibition of A beta 42 production is a prime therapeutic goal. The same protease, gamma-secretase, is assumed to generate the C termini of both A beta 40 and A beta 42. Herein, we analyze the effect of the compound MDL 28170, previously suggested to inhibit gamma-secretase, on beta-amyloid precursor protein processing. By immunoprecipitating conditioned medium of different cell lines with various A beta 40- and A beta 42-specific antibodies, we demonstrate a much stronger inhibition of the gamma-secretase cleavage at residue 40 than of that at residue 42. These data suggest that different proteases generate the A beta 40 and A beta 42 C termini. Further, they raise the possibility of identifying compounds that do not interfere with general beta-amyloid precursor protein metabolism, including A beta 40 production, but specifically block the generation of the pathogenic A beta 42 peptide.
Recent data in cell culture has shown that brain neurons are particularly vulnerable to degeneration by apoptosis. Further the inducers that activate the program (e.g. beta-amyloid, oxidatative damage, low energy metabolism) correspond to conditions present in the Alzheimer's disease (AD) brain. This suggests the possibility that apoptosis may be one of the mechanisms contributing to neuronal loss in this disease. Indeed, some neurons in vulnerable regions of the AD brain show evidence of DNA damage, nuclear apoptotic bodies, chromatin condensation, and the induction of select genes characteristic of apoptosis in cell culture and animal models. This suggests the existence of apoptosis in the AD brain, a hypothesis also consistent with evolving research in one of the regulatory functions of the presenilin genes. On the other hand, DNA damage is present in the majority of neurons in vulnerable regions in early and mild cases. In most tissues, cells in fully activated apoptosis degenerate and are removed within hours to days and thus it seems all DNA damage is unlikely to signify terminal apoptosis. The presence of extensive DNA damage suggests an acceleration of damage, faulty repair process, loss of protective mechanisms, or an activation and arrest of aspects of the apoptotic program. DNA damage is unlikely to be an artifact of postmortem delay or agonal state. The existence of protective mechanisms for neurons may exist as these cells are nondividing and essential. In this context it is interesting that Bcl-2 is upregulated in most neurons with DNA damage. Further, at least one DNA repair enzyme is also upregulated. Thus it appears as if neurons are in a struggle between degeneration and repair. As research advances it is critical to reduce the stimuli that cause the neuronal damage and discover the key intervention points to assist neurons in the repair processes.