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ABSTRACT: Oxidative stress and inflammation are known to be associated with age-related macular degeneration (AMD). Retinal pigment epithelial (RPE) cells play the principal role in the immune defense of macula, and their dysfunction is a crucial event leading to clinically relevant changes seen in AMD. In the present study, we have examined the ability of oxidative stress to activate inflammasome signaling in the human ARPE-19 cells by adding the lipid peroxidation end product 4-hydroxynonenal (HNE) to cell cultures pre-treated or not treated with the endotoxin, LPS. Our results indicate that LPS and HNE significantly increased the production of IL-6 and IL-18, respectively. LPS treatment preceding HNE induced an even greater increase in the production of IL-18 than HNE alone. In addition to IL-18, HNE significantly increased the production of IL-1β. The productions of IL-1β and IL-18 were reduced in the cell cultures pre-treated with the Caspase-1 inhibitor. PCR analysis revealed that HNE induced an over 5-fold increase in the amount of NLRP3 mRNA compared to control cells; LPS had no effect. In conclusion, our present data suggest that oxidative stress can activate NLRP3 inflammasomes in RPE cells which occupy center stage in the pathogenesis of AMD.
Immunology letters 06/2012; 147(1-2):29-33. · 2.91 Impact Factor
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ABSTRACT: The lack of substrate-bound crystal structures of SIRT1 and SIRT2 complicates the drug design for these targets. In this work, we aim to study whether SIRT3 could serve as a target structure in the design of substrate based pseudopeptidic inhibitors of SIRT1 and SIRT2. We created a binding hypothesis for pseudopeptidic inhibitors, synthesized a series of inhibitors, and studied how well the fulfillment of the binding criteria proposed by the hypothesis correlated with the in vitro inhibitory activities. The chosen approach was further validated by studying docking results between 12 different SIRT3, Sir2Tm, SIRT1 and SIRT2 X-ray structures and homology models in different conformational forms. It was concluded that the created binding hypothesis can be used in the design of the substrate based inhibitors of SIRT1 and SIRT2 although there are some reservations, and it is better to use the substrate-bound structure of SIRT3 instead of the available apo-SIRT2 as the target structure.
Journal of Medicinal Chemistry 09/2011; 54(19). · 4.80 Impact Factor
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ABSTRACT: Sirtuins catalyze the NAD(+) dependent deacetylation of N(epsilon)-acetyl lysine residues to nicotinamide, O'-acetyl-ADP-ribose (OAADPR) and N(epsilon)-deacetylated lysine. Here, an easy-to-synthesize Ac-Ala-Lys-Ala sequence has been used as a probe for the screening of novel N(epsilon)-modified lysine containing inhibitors against SIRT1 and SIRT2. N(epsilon)-Selenoacetyl and N(epsilon)-isothiovaleryl were the most potent moieties found in this study, comparable to the widely studied N(epsilon)-thioacetyl group. The N(epsilon)-3,3-dimethylacryl and N(epsilon)-isovaleryl moieties gave significant inhibition in comparison to the N(epsilon)-acetyl group present in the substrates. In addition, the studied N(epsilon)-alkanoyl, N(epsilon)-alpha,beta-unsaturated carbonyl and N(epsilon)-aroyl moieties showed that the acetyl binding pocket can accept rather large groups, but is sensitive to even small changes in electronic and steric properties of the N(epsilon)-modification. These results are applicable for further screening of N(epsilon)-acetyl analogues.
Bioorganic & medicinal chemistry 08/2010; 18(15):5616-25. · 2.82 Impact Factor
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ABSTRACT: Clusterin is a secreted molecular chaperone, also called apolipoprotein J. Recent genetic studies have demonstrated that clusterin is a significant susceptibility gene for late-onset Alzheimer's disease (AD). Clusterin shares several properties with apolipoprotein E, a well-known risk gene for AD, i.e. they bind to amyloid-beta peptides and are present in neuritic plaques, enhance the clearance of amyloid-beta peptides in brain, and are included in lipid particles and thus regulate cholesterol traffic. Biochemical studies indicate that clusterin can prevent the progress of AD pathogenesis. We have observed earlier that histone deacetylase (HDAC) inhibitors can induce the expression of clusterin in several neuroblastoma and glioma cell lines. Recent studies have revealed that valproic acid, a common and well-tolerated drug for epilepsy and bipolar disorders, is a potent HDAC inhibitor. In this study, we examined whether valproic acid can induce the expression of clusterin in human astrocytes. Our results demonstrated that valproic acid is a potent inducer of clusterin expression and secretion in human astrocytes at the therapeutical concentrations. Another clinically used HDAC inhibitor, the cancer drug, Vorinostat (SAHA, suberoylanilide hydroxamic acid), also robustly stimulated the expression of clusterin in human astrocytes. One could postulate that valproic acid may be able to prevent amyloid-beta aggregation in AD, as observed in transgenic AD mice, by increasing clusterin expression.
Neuroscience Letters 03/2010; 475(2):64-8. · 2.11 Impact Factor
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ABSTRACT: N()-Thioacetyl-lysine-containing tri-, tetra-, and pentapeptides, based on the alpha-tubulin and p53 protein sequences, were studied as SIRT1 and SIRT2 inhibitors. The potency of the pentapeptides depended on the selection of the side chains. The removal of N- and C-terminal residues of the pentapeptides yielded tripeptides with retained SIRT1 inhibitory activity but decreased SIRT2 inhibitory activity. The most potent SIRT1 inhibitors were equipotent with the reference compound (6-chloro-2,3,4,9-tetrahydro-1H-carbazole-1-carboxamide) with the IC(50) values of 180-330 nM.
Journal of Medicinal Chemistry 05/2009; 52(7):2153-6. · 4.80 Impact Factor
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ABSTRACT: Nϵ-Thioacetyl-lysine-containing tri-, tetra-, and pentapeptides, based on the α-tubulin and p53 protein sequences, were studied as SIRT1 and SIRT2 inhibitors. The potency of the pentapeptides depended on the selection of the side chains. The removal of N- and C-terminal residues of the pentapeptides yielded tripeptides with retained SIRT1 inhibitory activity but decreased SIRT2 inhibitory activity. The most potent SIRT1 inhibitors were equipotent with the reference compound (6-chloro-2,3,4,9-tetrahydro-1H-carbazole-1-carboxamide) with the IC50 values of 180−330 nM.
04/2009;
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ABSTRACT: The inflammatory process has a fundamental role in the pathogenesis of Alzheimer's disease (AD). Recent studies indicate that inflammation is not merely a bystander in neurodegeneration but a powerful pathogenetic force in the disease process. Increased production of amyloid-beta peptide species can activate the innate immunity system via pattern recognition receptors (PRRs) and evoke Alzheimer's pathology. We will focus on the role of innate immunity system of brain in the initiation and the propagation of inflammatory process in AD. We examine here in detail the significance of amyloid-beta oligomers and fibrils as danger-associated molecular patterns (DAMPs) in the activation of a wide array of PRRs in glial cells and neurons, such as Toll-like, NOD-like, formyl peptide, RAGE and scavenger receptors along with complement and pentraxin systems. We also characterize the signaling pathways triggered by different PRRs in evoking inflammatory responses. In addition, we will discuss whether AD pathology could be the outcome of chronic activation of the innate immunity defence in the brain of AD patients.
Progress in Neurobiology 03/2009; 87(3):181-94. · 8.87 Impact Factor
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ABSTRACT: The endoplasmic reticulum (ER) is involved in several crucial cellular functions, e.g. protein folding and quality control, maintenance of Ca2+ balance, and cholesterol synthesis. Many genetic and environmental insults can disturb the function of ER and induce ER stress. ER contains three branches of stress sensors, i.e. IRE1, PERK and ATF6 transducers, which recognize the misfolding of proteins in ER and activate a complex signaling network to generate the unfolded protein response (UPR). Alzheimer's disease (AD) is a progressive neurodegenerative disorder involving misfolding and aggregation of proteins in conjunction with prolonged cellular stress, e.g. in redox regulation and Ca2+ homeostasis. Emerging evidence indicates that the UPR is activated in neurons but not in glial cells in AD brains. Neurons display pPERK, peIF2alpha and pIRE1alpha immunostaining along with abundant diffuse staining of phosphorylated tau protein. Recent studies have demonstrated that ER stress can also induce an inflammatory response via different UPR transducers. The most potent pathways are IRE1-TRAF2, PERK-eIF2alpha, PERK-GSK-3, ATF6-CREBH, as well as inflammatory caspase-induced signaling pathways. We will describe the mechanisms which could link the ER stress of neurons to the activation of the inflammatory response and the evolution of pathological changes in AD.
Journal of Neuroinflammation 01/2009; 6:41. · 3.83 Impact Factor
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ABSTRACT: The aging process involves changes in immune regulation, i.e. adaptive immunity declines whereas innate immunity becomes activated. NF-kappaB signaling is the master regulator of the both immune systems. Two recent articles highlight the role of the NF-kappaB system in aging and immune responses. Adler et al showed that the NF-kappaB binding domain is the genetic regulatory motif which is most strongly associated with the aging process. Kwon et al studying HIV-1 infection and subsequent immune deficiency process demonstrated that HIV-1 Tat protein binds to SIRT1 protein, a well-known longevity factor, and inhibits the SIRT1-mediated deacetylation of the p65 component of the NF-kappaB complex. As a consequence, the transactivation efficiency of the NF-kappaB factor was greatly potentiated, leading to the activation of immune system and later to the decline of adaptive immunity. These observations support the scenario where immune responses and aging process can be enforced by the potentiation of NF-kappaB transactivation efficiency. Longevity factors, such as SIRT1 and its activators, might regulate the efficiency of the NF-kappaB signaling, the major outcome of which is inflamm-aging via proinflammatory responses.
BioEssays 10/2008; 30(10):939-42. · 4.95 Impact Factor
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ABSTRACT: Genetic and molecular studies have confirmed the central role of amyloid-beta production and fibrillation in the pathogenesis of Alzheimer's disease (AD). However, the pathological pathways from amyloid-beta peptide oligomerization to the major pathological hallmarks of AD, such as neurofibrillary tangles, inflammation and loss of cholinergic neurons, are largely unknown. The innate immunity defence system utilizes pattern recognition receptors to respond to a variety of danger- and pathogen-associated molecular structures. Amyloid-beta oligomers and fibrils and their cellular effects can activate the innate immunity defence and induce inflammatory and apoptotic responses in human brain. Amyloid-beta oligomers can interfere with many aspects of neuronal membrane functions and can evoke potassium (K+) efflux from neurons. A low K+ concentration is a potent activator for the NALP1 inflammasomes, which then stimulate caspase-1 to cleave the proforms of IL-1beta and IL-18 cytokines. Interestingly, recent observations have demonstrated that amyloid-beta fibrils can activate NALP3 inflammasomes Via the lysosomal damage in mouse microglia. We will review here the activation mechanisms of NALP inflammasomes in neurons and microglia and several downstream effects in brain demonstrating that toxic amyloid-beta oligomers and fibrils can light afire in inflammasomes and induce Alzheimer's pathology.
Journal of Cellular and Molecular Medicine 10/2008; 12(6A):2255-62. · 4.13 Impact Factor
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Päivi H Kiviranta,
Heikki S Salo,
Jukka Leppänen,
Valtteri M Rinne,
Sergiy Kyrylenko,
Erkki Kuusisto, Tiina Suuronen,
Antero Salminen,
Antti Poso,
Maija Lahtela-Kakkonen,
Erik A A Wallén
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ABSTRACT: SIRT2 inhibitors with a N-(3-phenylpropenoyl)-glycine tryptamide backbone were studied. This backbone has been developed in our group, and it is derived from a compound originally found by virtual screening. In addition, compounds with a smaller 3-phenylpropenoic acid tryptamide backbone were also included in the study. Binding modes for the new compounds and the previously reported compounds were analyzed with molecular modelling methods. The approach, which included a combination of molecular dynamics, molecular docking and cluster analysis, showed that certain docking poses were favourable despite the conformational variation in the target protein. The N-(3-phenylpropenoyl)-glycine tryptamide backbone is also a good backbone for SIRT2 inhibitors, and the series of compounds includes several potent SIRT2 inhibitors.
Bioorganic & medicinal chemistry 10/2008; 16(17):8054-62. · 2.82 Impact Factor
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ABSTRACT: Estrogen has a variety of neuroprotective effects but the molecular basis of its function is still mainly unclear. Estrogen
receptor (ER) signaling is highly dependent on posttranslational modifications and the assembly of coactivator and corepressor
complexes. Several proteins involved in ERα signaling have recently been found to be acetylated, including ERα itself and
Hsp90, a key chaperone in the functional regulation of ERα. ERα complexes also contain histone deacetylases (HDAC) which repress
transactivation. Our purpose was to clarify the role of protein acetylation and Hsp90 function in the ERE-mediated ERα signaling
in neuronal HN10 cells. We observed that increasing protein/histone acetylation status with trichostatin A, a potent HDAC
inhibitor, increased the 17β-estradiol (E2)-induced transactivation of ERE-driven luciferase in non-transfected cells, and
even more extensively in pERα-transfected cells. E2-induced ERE-driven transactivation was blocked by ICI 182.780. Several
ER antagonists, such as raloxifene and tamoxifen, were unresponsive. Valproate, an antiepileptic drug which is recently characterized
as a HDAC inhibitor, was also able to potentiate the E2-induced ERE-transactivation. Inhibition of the function of Hsp90 chaperone
with geldanamycin strongly inhibited the E2-induced ERE-transactivation. Overexpression of SIRT2 protein deacetylase did not
inhibit the acetylation-potentiated ERE-driven transactivation indicating that SIRT2 deacetylase is not involved in ERα signaling.
Our results reveal that ERα signaling is dependent on protein acetylation and epigenetic regulation.
Neurochemical Research 08/2008; 33(9):1768-1775. · 2.24 Impact Factor
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ABSTRACT: A new inhibitor for human sirtuin type proteins 1 and 2 (SIRT1 and SIRT2) was discovered through virtual database screening in search of new scaffolds. A series of compounds was synthesized based on the hit compound (3-[[3-(4-tert-butylphenyl)1,2,4-oxadiazole-5-carbonyl]amino]-1-[3-(trifluoromethyl)phenyl]thiourea). The most potent compound in the series was nearly as potent as the reference compound (6-chloro-2,3,4,9-tetrahydro-1H-carbazole-1-carboxamide).
Journal of Medicinal Chemistry 08/2008; 51(15):4377-80. · 4.80 Impact Factor
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ABSTRACT: Alzheimer's disease is a neurodegenerative disorder where the cognitive deficit is the hallmark symptom reflecting the progression of the disease. Synaptic dysfunction is a sensitive parameter of the AD pathology. Rho GTPases and the Rho kinases, ROCK1/2, and PAK1-3, are important regulators of synaptic plasticity, especially in maintaining the actin cytoskeleton of dendritic spines. Recent studies have revealed that beta-amyloid oligomers can inhibit PAK and stimulate ROCK-mediated signaling. Both of these effects enhance the disassembly of synaptic actin filaments and ultimately evoke synaptic loss. Brain tissue in AD recognizes the beta-amyloid peptide oligomers as foreign protein particles and mounts an inflammatory defense via Toll-like receptor (TLR) signaling which causes synaptic impairment. We will review here the dysfunction of ROCK, PAK, and Toll signaling associated with AD pathology. The protection of synapses in AD may provide new therapeutic approaches to combatting the cognitive impairment in AD.
Biochemical and Biophysical Research Communications 08/2008; 371(4):587-90. · 2.48 Impact Factor
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ABSTRACT: Several research models have shown that if cellular stress induces the heat shock response then this will suppress the NF-kappaB-mediated inflammatory response. The NF-kappaB signaling pathway mediates both stress signals and innate immunity signals. Heat shock proteins HSP70 and HSP90 regulate several signaling cascades to maintain cellular homeostasis. Recent studies have revealed that HSP70 and HSP90 proteins regulate the function of the IKK complex which is the major activator of the NF-kappaB complex. The heat shock response can cause the dissociation of the IKK complex, composed of protein kinase subunits IKKalpha and IKKbeta and the regulatory unit NEMO, and inhibit the activation of NF-kappaB signaling. Suppression of immune signaling during cellular stress may be a useful feedback response for helping cells to survive tissue injury. Furthermore, IKKalpha and IKKbeta kinases are important activators of tumorigenesis and hence the inhibition of long-term activation of the IKK complex by HSP70 and HSP90 proteins may prevent cancer development during chronic inflammation.
Immunology Letters 05/2008; 117(1):9-15. · 2.53 Impact Factor
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ABSTRACT: Innate and adaptive immunity are the major defence mechanisms of higher organisms against inherent and environmental threats. Innate immunity is present already in unicellular organisms but evolution has added novel adaptive immune mechanisms to the defence armament. Interestingly, during aging, adaptive immunity significantly declines, a phenomenon called immunosenescence, whereas innate immunity seems to be activated which induces a characteristic pro-inflammatory profile. This process is called inflamm-aging. The recognition and signaling mechanisms involved in innate immunity have been conserved during evolution. The master regulator of the innate immunity is the NF-kB system, an ancient signaling pathway found in both insects and vertebrates. The NF-kB system is in the nodal point linking together the pathogenic assault signals and cellular danger signals and then organizing the cellular resistance. Recent studies have revealed that SIRT1 (Sir2 homolog) and FoxO (DAF-16), the key regulators of aging in budding yeast and Caenorhabditis elegans models, regulate the efficiency of NF-kB signaling and the level of inflammatory responses. We will review the role of innate immunity signaling in the aging process and examine the function of NF-kB system in the organization of defence mechanisms and in addition, its interactions with the protein products of several gerontogenes. Our conclusion is that NF-kB signaling seems to be the culprit of inflamm-aging, since this signaling system integrates the intracellular regulation of immune responses in both aging and age-related diseases.
Ageing Research Reviews 05/2008; 7(2):83-105. · 6.17 Impact Factor
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ABSTRACT: Activation of NF-kappaB transcription factor signaling is one of the hallmarks of genotoxic stress. Recently, the NEMO shuttle was revealed to mediate this nucleo-cytoplasmic signaling linking DNA damage to the activation of NF-kappaB system. DNA damage is the causative factor of several segmental progeroid syndromes, such as Werner syndrome and Hutchinson-Gilford syndrome. Although the gene defects have been well characterized, the molecular mechanisms of premature aging process still need to be defined. Here we review the details of the NEMO shuttle, a dual-signal sensor linking DNA damage to NF-kappaB activation, and present evidence for the hypothesis that DNA damage in progeroid syndromes may activate the NEMO shuttle and subsequently increase the pressure on the activation of NF-kappaB system evoking a premature aging phenotype. The NEMO shuttle may link genotoxic stress to the activation of the innate immunity system and cause premature aging via inflamm-aging process.
Biochemical and Biophysical Research Communications 04/2008; 367(4):715-8. · 2.48 Impact Factor
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[show abstract]
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ABSTRACT: Estrogen has a variety of neuroprotective effects but the molecular basis of its function is still mainly unclear. Estrogen receptor (ER) signaling is highly dependent on posttranslational modifications and the assembly of coactivator and corepressor complexes. Several proteins involved in ER alpha signaling have recently been found to be acetylated, including ER alpha itself and Hsp90, a key chaperone in the functional regulation of ER alpha. ER alpha complexes also contain histone deacetylases (HDAC) which repress transactivation. Our purpose was to clarify the role of protein acetylation and Hsp90 function in the ERE-mediated ER alpha signaling in neuronal HN10 cells. We observed that increasing protein/histone acetylation status with trichostatin A, a potent HDAC inhibitor, increased the 17beta-estradiol (E2)-induced transactivation of ERE-driven luciferase in non-transfected cells, and even more extensively in pER alpha-transfected cells. E2-induced ERE-driven transactivation was blocked by ICI 182.780. Several ER antagonists, such as raloxifene and tamoxifen, were unresponsive. Valproate, an antiepileptic drug which is recently characterized as a HDAC inhibitor, was also able to potentiate the E2-induced ERE-transactivation. Inhibition of the function of Hsp90 chaperone with geldanamycin strongly inhibited the E2-induced ERE-transactivation. Overexpression of SIRT2 protein deacetylase did not inhibit the acetylation-potentiated ERE-driven transactivation indicating that SIRT2 deacetylase is not involved in ER alpha signaling. Our results reveal that ER alpha signaling is dependent on protein acetylation and epigenetic regulation.
Neurochemical Research 03/2008; 33(9):1768-75. · 2.24 Impact Factor
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ABSTRACT: We have recently discovered collagen XVII to be present in neurons of the human central nervous system. Collagen XVII has previously been primarily studied in the field of dermatopathology since it is abundantly expressed in the skin, which, like the nervous system, is ectodermal in origin. A link between dermatopathological and neurological entities has been implied due to clinical case studies revealing an association between bullous pemphigoid and age-related neurodegenerative disorders. The objective of this study was to assess the distribution of collagen XVII in the human brain in relation to normal ageing. Post-mortem brain tissue was obtained from 11 neurologically unimpaired subjects who had died from cardiovascular causes at the age of 17 to 78 years. Collagen XVII expression in various neuroanatomical regions, representing essentially the entire human brain, was then assessed using immunohistochemistry. We found collagen XVII to be expressed widely in the brain and to be located primarily in the soma and proximal axons of neurons. In contrast, glial cells did not express collagen XVII. The expression varied strikingly between different neuroanatomical regions, being most notable in motor nuclei and Betz cells followed by pyramidal neurons. There was no correlation between collagen XVII expression and variables such as gender, age at death, post-mortem delay and fixation time whereas a mode of death leading to notable neuronal ischemia depleted the protein expression. Many neurodegenerative disorders display a specific pattern of neuroanatomical involvement, thus the regionally variable expression of collagen XVII offers new prospects for research.
Brain Research 08/2007; 1158:50-6. · 2.73 Impact Factor
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ABSTRACT: Age-related macular degeneration (AMD) is the leading cause of blindness worldwide. AMD is characterized by the deposition of drusen aggregates under the retinal pigment epithelium (RPE). Clusterin/apo J, a multifunctional secreted chaperone, is one of the major proteins accumulating in drusen deposits. The regulation of clusterin expression is not well characterized but the promoter of clusterin contains a CpG-rich methylation domain. Since aging affects both DNA methylation and histone acetylation status, the epigenetic regulation might have an important role in clusterin/apo J expression. Our purpose was to elucidate whether the induction of DNA hypomethylation with 5-aza-2'-deoxycytidine (AZA) and histone hyperacetylation with trichostatin A (TSA) could affect the clusterin transcription, protein levels, and secretion in retinal pigment epithelial cells. We observed that both TSA and AZA treatments induced a prominent increase in the expression levels of clusterin mRNA and protein in ARPE-19 cells, as well as in the secretion of clusterin protein. Furthermore, valproic acid, an antiepileptic drug and a recently identified inhibitor of histone deacetylases (HDAC), induced a significant increase in clusterin protein expression and secretion in retinal pigment epithelial cells. HDAC inhibitors are characterized as inhibitors of angiogenesis, and clusterin as a complement inhibitor. Our results indicate that epigenetic factors regulate the clusterin expression of RPE cells and thus might affect the pathogenesis of AMD via the inhibition of angiogenesis and inflammation.
Biochemical and Biophysical Research Communications 07/2007; 357(2):397-401. · 2.48 Impact Factor
