[Show abstract][Hide abstract] ABSTRACT: Background: The impact of nicorandil as adjunctive therapy for percutaneous coronary intervention (PCI) in patients with ST-elevation myocardial infarction (STEMI) is controversial. We performed 15O-labeled water positron emission tomography (PET) to quantify regional myocardial perfusion in patients with STEMI who received nicorandil or no adjunctive therapy during PCI. Methods: PCI was performed within 8. h after STEMI onset in 33 patients. 14 patients received intracoronary nicorandil 2. mg immediately after recanalization of the culprit lesion (Nico group). After 3-4. weeks, PET was performed in which myocardial blood flow (MBF) was measured at baseline and during adenosine triphosphate (ATP)-induced hyperemia. Myocardial vascular resistance (MVR) was calculated for all segments. Data were obtained from the reperfused (Rep) and normal segments (Cont) in each patient. Results: In patients not given nicorandil (No-Nico group), the MBF was significantly lower in Rep than that in Cont at baseline and during hyperemia (Cont vs. Rep: 0.82 ± 0.14 vs. 0.68 ± 0.11, P= 0.001, ATP-Cont vs. ATP-Rep: 2.00 ± 0.72 vs. 1.52 ± 0.61, P= 0.017), which was restored in the Nico group (Cont vs. Rep: 0.79 ± 0.17 vs. 0.78 ± 0.20; ATP-Cont vs. ATP-Rep: 2.02 ± 0.84 vs. 1.84 ± 0.62). MVR was elevated in Rep at baseline and during hyperemia in the No-Nico group. MVR elevation in Rep was prevented in the Nico group. Conclusions: 15O-labeled water PET was feasible for segmental analysis of MBF during the subacute phase of STEMI. It revealed that intracoronary administration of nicorandil to STEMI patients who underwent PCI prevented MVR elevation and thus restored MBF in the reperfused segments to a level similar to that in the normal segments.
[Show abstract][Hide abstract] ABSTRACT: Steroid hormones synthesized in and secreted from peripheral endocrine glands pass through the blood-brain barrier and play a role in the central nervous system. In addition, the brain possesses an inherent endocrine system and synthesizes steroid hormones known as neurosteroids. Increasing evidence shows that neuroactive steroids protect the central nervous system from various harmful stimuli. Reports show that the neuroprotective actions of steroid hormones attenuate oxidative stress. In this review, we summarize the antioxidative effects of neuroactive steroids, especially 17β-estradiol and progesterone, on neuronal injury in the central nervous system under various pathological conditions, and then describe our recent findings concerning the neuroprotective actions of 17β-estradiol and progesterone on oxidative neuronal injury induced by organometallic compounds, tributyltin, and methylmercury.
Preview · Article · Mar 2015 · Oxidative medicine and cellular longevity
[Show abstract][Hide abstract] ABSTRACT: Growing evidence shows that steroid hormones, especially 17β-estradiol (E2), protect neuronal cells by attenuating excess activation of microglia. However, the use of E2 in the clinic is controversial because of its peripheral actions in reproductive organs and its potential to increase risk for endometrial cancer and breast cancer. Selective estrogen-receptor modulators (SERMs) bind to estrogen receptors (ERs), but their effects as ER agonists or antagonists are dependent on the target tissue. SERMs pose very little cancer risk as a result of their anti-estrogen action in reproductive organs, but their action in the brain is not well understood. In this study, we investigated the effects of SERMs tamoxifen (Tam) and raloxifene (Rlx) on microglial activation and subsequent neuronal injury. Tam and Rlx suppressed the increases in proinflammatory cytokines and chemokine expression that were induced by lipopolysaccharide (LPS) in rat primary microglia cultures. The microglial-conditioned media pretreated with Tam or Rlx significantly attenuated cellular injury in SH-SY5Y cells elicited by microglial-conditioned media treated with LPS alone. Rat primary microglia expressed ERα and ERβ primarily in the nucleus, and thus we examined the involvement of ERs in the suppressive action of Tam and Rlx on microglial activation using a pure ER antagonist, ICI182,780. Pretreatment with ICI182,780 abolished the suppressive effects of SERMs on microglial activation, as well as their protective action on SH-SY5Y cells. A luciferase assay using a vector with 3 estrogen response elements (EREs) revealed that Tam and Rlx activated ERE-mediated transcription in rat primary microglia. Taken together, these results suggest that Tam and Rlx suppress microglial activation and subsequent neuronal cell death via an ER-mediated transcription pathway. SERMs could represent a novel therapeutic strategy for disorders of the central nervous system based on their ability to suppress neuroinflammation.
Full-text · Article · Oct 2014 · The Journal of Steroid Biochemistry and Molecular Biology
[Show abstract][Hide abstract] ABSTRACT: Regulatory T cells (Tregs) play a crucial role in the negative regulation of immune responses. Recent studies suggest that Tregs are involved in the pathogenesis of atherosclerosis and myocarditis. Here, we investigated the involvement of Tregs on worsening heart failure (HF) in patients with reduced ejection fraction (HF-REF). The study population consisted of 32 HF-REF patients who were hospitalized for worsening HF, and 18 control subjects. Cardiac function was evaluated by echocardiography. A single venous blood sample was collected before discharge. Circulating T cells were evaluated by flow cytometry. Tregs were defined as CD4(+)CD25(+)Foxp3(+)T cells, and the correlations between the frequency of Tregs and CRP, IL-6 and several echoparameters were analysed. Furthermore, all HF-REF patients were followed up to 12 months from discharge to examine the predictors of recurrent hospitalization.In HF-REF patients, Tregs were significantly decreased (5.9 ± 1.4 versus 8.0 ± 2.2%, P < 0.01), while CD4(+)HLADR(+)T cells were increased (10.1 ± 5.4 versus 7.3 ± 3.1%, P < 0.05), compared with controls. Tregs were negatively correlated with left ventricular end-diastolic dimension, and levels of CRP and IL-6. Eleven of 32 HF-REF patients were rehospitalized for worsening HF within 12 months. Multivariate Cox regression analysis showed that CD4/CD8 and frequency of Tregs were independent predictors for recurrent hospitalization. Furthermore, HF-REF patients expressing under 6% Treg/CD4(+)T cells showed a significantly higher incidence of recurrent hospitalization for worsening HF within 12 months.Our data suggest that Tregs might be involved in the pathogenesis of decompensated HF, and may be a novel predictor of poor prognosis in HF-REF patients.
No preview · Article · May 2014 · International Heart Journal
[Show abstract][Hide abstract] ABSTRACT: Genetic deficiencies in transcription factors can lead to the loss of certain types of cells and tissue. The steroidogenic tissue-specific nuclear receptor Ad4BP/SF-1 (NR5A1) is one such gene, because mice in which this gene is disrupted fail to develop the adrenal gland and gonads. However, the specific role of Ad4BP/SF-1 in these biological events remains unclear. Here we use chromatin immunoprecipitation sequencing to show that nearly all genes in the glycolytic pathway are regulated by Ad4BP/SF-1. Suppression of Ad4BP/SF-1 by small interfering RNA reduces production of the energy carriers ATP and nicotinamide adenine dinucleotide phosphate, as well as lowers expression of genes involved in glucose metabolism. Together, these observations may explain tissue dysgenesis as a result of Ad4BP/SF-1 gene disruption in vivo. Considering the function of estrogen-related receptor α, the present study raises the possibility that certain types of nuclear receptors regulate sets of genes involved in metabolic pathways to generate energy carriers.
[Show abstract][Hide abstract] ABSTRACT: Neuroactive steroids are reported to protect neurons from various harmful compounds; however, the protective mechanisms remain largely unclear. In this study, we examined the suppressive effects of 17β-estradiol (E2) on tributyltin (TBT)-induced neurotoxicity.
Organotypic hippocampal slices were prepared from neonatal rats and then cultured. Cell death was assayed by propidium iodide uptake. Levels of reactive oxygen species (ROS) were determined by dihydroethidium staining. Protein phosphorylation was evaluated by immunoblotting.
Pretreatment of the slices with E2 dose-dependently attenuated the neuronal injury induced by TBT. An estrogen receptor antagonist, ICI182,780 abrogated these neuroprotective effects. The de novo protein synthesis inhibitors actinomycin D and cycloheximide showed no effects on the neuroprotective mechanism, indicating that a nongenomic pathway acting via the estrogen receptor may be involved in the neuroprotection conferred by E2. E2 suppressed the ROS production and lipid peroxidation induced by TBT, and these effects were almost completely canceled by ICI182,780. TBT decreased Akt phosphorylation, and this reduction was suppressed by E2. An Akt inhibitor, triciribine, attenuated the decreases in both the ROS production and neuronal injury mediated by E2.
E2 enhances the phosphorylation of Akt, thereby attenuating the oxidative stress and subsequent neuronal injury induced by TBT.
[Show abstract][Hide abstract] ABSTRACT: An enzymatic activity of cytochrome P450 was first identified as a component of adrenal steroidogenesis by Estabrook and his coworkers in 1963. The adrenal glands and gonads synthesize large amounts of steroid hormones and secrete them for systemic circulation. Two decades later, regional steroidogenesis in the brain was well established by Baulieu and his coworkers. Brain-synthesized steroids were termed neurosteroids. Recently, regional steroidogenesis has been reported in various organs, including the heart, lung, pancreas, and intestine. The locally synthesized steroids are present at low levels and may function as paracrine modulators.
Neurosteroids exert various important modulatory effects on brain functions and diseases. This chapter presents evidence for the regulation of neurosteroidogenesis and the protective functions of brain-synthesized steroids in the rat hippocampus.
(1) Rat hippocampal cultured slices synthesized testosterone and 17β-estradiol as neurosteroids. Retinoic acid stimulated the synthesis of sex steroids via transcriptional activation of cytochromes P450(17α) and P450arom. (2) The housing conditions of immature rats strongly affected the hippocampal steroid synthesis by alteration of mRNA levels for steroidogenic enzymes. (3) De novo synthesized estradiol self-protected rat hippocampal cultured slices from methylmercury toxicity by an estrogen receptor-mediated mechanism. (4) The neuroprotective effect of progesterone against tributyltin in the rat hippocampal slices was not mediated by a progesterone receptor but by allopregnanolone, which was synthesized from progesterone.
[Show abstract][Hide abstract] ABSTRACT: Ca(2+)/calmodulin-dependent protein kinase phosphatase (CaMKP/PPM1F) and its nuclear homolog CaMKP-N (PPM1E) are Ser/Thr protein phosphatases that belong to the PPM family. CaMKP-N is expressed in the brain and undergoes proteolytic processing to yield a C-terminally truncated form. The physiological significance of this processing, however, is not fully understood. Using a wheat-embryo cell-free protein expression system, we prepared human CaMKP-N (hCaMKP-N(WT)) and the truncated form, hCaMKP-N(1-559), to compare their enzymatic properties using a phosphopeptide substrate. The hCaMKP-N(1-559) exhibited a much higher V max value than the hCaMKP-N(WT) did, suggesting that the processing may be a regulatory mechanism to generate a more active species. The active form, hCaMKP-N(1-559), showed Mn(2+) or Mg(2+)-dependent phosphatase activity with a strong preference for phospho-Thr residues and was severely inhibited by NaF, but not by okadaic acid, calyculin A, or 1-amino-8-naphthol-2,4-disulfonic acid, a specific inhibitor of CaMKP. It could bind to postsynaptic density and dephosphorylate the autophosphorylated Ca(2+)/calmodulin-dependent protein kinase II. Furthermore, it was inactivated by H2O2 treatment, and the inactivation was completely reversed by treatment with DTT, implying that this process is reversibly regulated by oxidation/reduction. The truncated CaMKP-N may play an important physiological role in neuronal cells.
[Show abstract][Hide abstract] ABSTRACT: Quinones are widely distributed in nature, and some quinone compounds are used as therapeutic agents such as anti-cancer, anti-malarial or anti-bacterial drugs. However, their therapeutic use is limited in some cases because the use of most quinones is accompanied by adverse effects derived from their cytotoxicity, especially for hepatocytes. Two mechanisms have been proposed to explain quinone toxicity: oxidative stress via redox cycle and the arylation/alkylation of intracellular nucleophiles. A drug metabolizing enzyme, cytochrome P450 is closely involved in the hepatotoxicity of therapeutic agents in general, but quinone hepatotoxicity has been considered not to contribute to cytochrome P450 because the structure of quinone is not modified by cytochrome P450 and thus quinone compounds are thought to be metabolized mainly via a conjugation process. However, we have recently shown that quinone hepatotoxicity is enhanced under conditions of cytochrome P450 inhibition, indicating clearly the involvement of cytochrome P450 in quinone hepatotoxicity. Here, we revisit the generally accepted mechanisms of quinone hepatotoxicity and propose the importance of cytochrome P450 systems in quinone-induced hepatotoxicity on the basis of our recent work.
[Show abstract][Hide abstract] ABSTRACT: Dysfunction of the blood-brain barrier (BBB) is one of the major pathophysiological consequences of epilepsy. The increase in the permeability caused by BBB failure is thought to contribute to the development of epileptic outcomes. We developed a method by which the BBB permeability can be demonstrated by gadolinium-enhanced T1 weighted imaging (GdET1WI). The present study examined the changes in the BBB permeability in mice with generalized convulsive seizures (GCS) induced by acute pentylentetrazole (PTZ) injection. At fifteen minutes after PTZ-induced GCS, the BBB temporarily leaks BBB-impermeable contrast agent into the parenchyma of the diencephalon, hippocampus and cerebral cortex in mice, and the loss of BBB integrity was gradually recovered by 24 hours. The temporary BBB failure is a critical link to the glutamatergic activities that occur following the injection of PTZ. PTZ activates the glutamatergic pathway via the NMDA receptor, then nitric oxide (NO) is generated by NMDA receptor-coupled neuronal NO synthase (nNOS). To examine the influence of nNOS-derived NO induced by PTZ on the increases of the BBB permeability, GdET1WI was performed using conventional nNOS gene-deficient mice with or without PTZ injection. The failure of the BBB induced by PTZ was completely protected by nNOS deficiency in the brain. These results suggest that nNOS-derived excess NO in the glutamatergic pathway plays a key role in the failure of the BBB during PTZ-induced GCS. The levels of NO synthetized by nNOS in the brain may represent an important target for the future development of drugs to protect the BBB.
[Show abstract][Hide abstract] ABSTRACT: Abstract Oxidative stress is considered to be related to the onset and/or progression of Alzheimer's disease (AD), but there is insufficient evidence of its role(s). In this study, we evaluated the relationships between the brain redox state and cognitive function using a triple transgenic mouse model of AD (3xTg-AD mouse). One group of 3xTg-AD mice started to receive an α-tocopherol-supplemented diet at two months of age, and another group of 3xTg-AD mice was fed a normal diet. The levels of α-tocopherol, reduced glutathione, oxidized glutathione and lipid peroxidation were decreased in the cerebral cortex and hippocampus at four months of age in the 3xTg-AD mice fed a normal diet. These reductions were abrogated by the supplementation of α-tocopherol in the diet. During Morris water maze testing, the 3xTg-AD mice did not exhibit cognitive impairment at four months of age, but started to show cognitive dysfunction at six months of age, and α-tocopherol supplementation suppressed this dysfunction. Magnetic resonance imaging (MRI) using 3-hydroxymethyl-proxyl as a probe showed decreases in the signal intensity in the brains of 3xTg-AD mice at four months of age, and this reduction was clearly attenuated by α-tocopherol supplementation. Taken together, these findings suggest that oxidative stress can be associated with the cognitive impairment in 3xTg-AD mice. Furthermore, MRI might be a powerful tool to noninvasively evaluate the increases in reactive radicals, especially those occurring during the early stages of AD.
Full-text · Article · Jun 2013 · Free Radical Research
[Show abstract][Hide abstract] ABSTRACT: Estrogen, a class of female sex steroids, is neuroprotective. Estrogen is synthesized in specific areas of the brain. There is a possibility that the de novo synthesized estrogen exerts protective effect in brain, although direct evidence for the neuroprotective function of brain-synthesized estrogen has not been clearly demonstrated. Methylmercury (MeHg) is a neurotoxin that induces neuronal degeneration in the central nervous system. The neurotoxicity of MeHg is region-specific, and the molecular mechanisms for the selective neurotoxicity are not well defined. In this study, the protective effect of de novo synthesized 17β-estradiol on MeHg-induced neurotoxicity in rat hippocampus was examined.
Neurotoxic effect of MeHg on hippocampal organotypic slice culture was quantified by propidium iodide fluorescence imaging. Twenty-four-hour treatment of the slices with MeHg caused cell death in a dose-dependent manner. The toxicity of MeHg was attenuated by pre-treatment with exogenously added estradiol. The slices de novo synthesized estradiol. The estradiol synthesis was not affected by treatment with 1 µM MeHg. The toxicity of MeHg was enhanced by inhibition of de novo estradiol synthesis, and the enhancement of toxicity was recovered by the addition of exogenous estradiol. The neuroprotective effect of estradiol was inhibited by an estrogen receptor (ER) antagonist, and mimicked by pre-treatment of the slices with agonists for ERα and ERβ, indicating the neuroprotective effect was mediated by ERs.
Hippocampus de novo synthesized estradiol protected hippocampal cells from MeHg-induced neurotoxicity via ERα- and ERβ-mediated pathways. The self-protective function of de novo synthesized estradiol might be one of the possible mechanisms for the selective sensitivity of the brain to MeHg toxicity.
[Show abstract][Hide abstract] ABSTRACT: Increasing evidence shows that progesterone, a neuroactive steroid, has protective actions in central nervous system, but there is little evidence to show the protective mechanism of progesterone on neurotoxicity induced by environmental chemicals. In this study, we examined the effects of progesterone on neuronal injury induced by tributyltin (TBT) in rat hippocampal slices. Treatment with progesterone dose-dependently suppressed hippocampal neuronal injury induced by TBT. The neuroprotective action of progesterone was completely cancelled with pretreatment by finasteride, a 5α-reductase inhibitor, but it was not affected by mifepristone, a progesterone receptor antagonist, or by SU-10603, a cytochrome P450 17α inhibitor. The content of allopregnanolone in the slices was significantly increased by treatment with progesterone, and this increment was greatly suppressed with a pretreatment of finasteride. Treatment with allopregnanolone attenuated neuronal injury induced by TBT in a dose-dependent manner. The neuroprotective effects not only of progesterone but also of allopregnanolone were cancelled by bicuculline, a potent gamma-aminobutyric acid A (GABA(A)) receptor antagonist. Pretreatment with muscimol, a GABA(A) receptor agonist, attenuated hippocampal neuronal injury elicited by TBT. Taken together, allopregnanolone converted from progesterone in hippocampal slices could protect neurons from TBT-induced neurotoxicity due to a GABA(A) receptor-dependent mechanism. One of the physiological roles of neuroactive steroids might be neuroprotection from environmental chemicals.
No preview · Article · Dec 2012 · The Journal of steroid biochemistry and molecular biology
[Show abstract][Hide abstract] ABSTRACT: Treatment of intracerebral hemorrhage is often pointless, although considerable effort has been devoted to developing treatments for ischemic stroke. The purpose of this study was to determine the influence of drugs in improving neurological outcomes with pharmaceutical therapy after intracerebral hemorrhage. The free-radical hypothesis for intracerebral hemorrhage is based on the cytotoxicity triggered by blood components and its degradation products, such as heme and iron as a potent pro-oxidant atom. Sulfaphenazole (SPZ) has a different mechanism such as reactive oxygen species scavenging, in addition to the inhibition of superoxide production by cytochrome P450. The present study investigated the properties of SPZ in collagenase-induced intracerebral hemorrhage rat brain damage. The results show that systemic SPZ treatment after intracerebral hemorrhage reduces striatal dysfunction, the elevation of lipid peroxidation, and brain edema in the rat. These results suggest that SPZ is a potentially effective therapeutic approach for intracerebral hemorrhage as the effect of SPZ was initiated for either 1 h or 3 d post-intracerebral hemorrhage.