Sirtuin functions and modulation: from chemistry to the clinic

Sirtuins are NAD+ -dependent histone deacetylases regulating important metabolic pathways in prokaryotes and eukaryotes and are involved in many biological processes such as cell survival, senescence, proliferation, apoptosis, DNA repair, cell metabolism, and caloric restriction. The seven members of this family of enzymes are considered potential targets for the treatment of human pathologies including neurodegenerative diseases, cardiovascular diseases, and cancer. Furthermore, recent interest focusing on sirtuin modulators as epigenetic players in the regulation of fundamental biological pathways has prompted increased efforts to discover new small molecules able to modify sirtuin activity. Here, we review the role, mechanism of action, and biological function of the seven sirtuins, as well as their inhibitors and activators

Possible physiopathological roles of the transglutaminase activity in the etiopathogenesis of human neurodegenerative diseases

Transglutaminases are ubiquitous enzymes which catalyze post-translational modifications of proteins. The main activity of these enzymes is the cross-linking of glutaminyl residues of a protein/peptide substrate to lysyl residues of a protein/peptide co-substrate. In addition to lysyl residues, other second nucleophilic co-substrates may include monoamines or polyamines (to form mono- or bi-substituted /crosslinked adducts) or –OH groups (to form ester linkages). In the absence of co-substrates, the nucleophile may be water, resulting in the net deamidation of the glutaminyl residue. Transglutaminase activity has been suggested to be involved in molecular mechanisms responsible for both physiological or pathological processes. For example, neurodegenerative diseases, such as Alzheimer’s Disease, Parkinson’s Disease, supranuclear palsy, Huntington’s Disease and other polyglutamine diseases, are characterized in part by aberrant cerebral transglutaminase activity and by increased cross-linked proteins in affected brains. This review focuses on the possible molecular mechanisms responsible for such diseases and on the possible therapeutic effects of transglutaminase inhibitors for patients with diseases characterized by aberrant transglutaminase activity

Curcumin (Diferulolylmethane) Reduces Transglutaminase 2 Overexpression Induced by Retinoic Acid in Human Nervous Cell Lines

Abstract Objectives: Curcumin, a naturally occurring compound derived from turmeric (Curcuma longa) has long been suggested to have strong therapeutic or preventive potential against human diseases because of its antioxidative, anticancerous, and anti-inflammatory effects. Curcumin is known to exert anti-inflammatory effects by interrupting NF-κB signaling at multiple levels. Many observations indicate that curcumin shows its valuable potential by inhibiting the activity of I-κB kinase. Transglutaminase 2 (TG2) expression is increased in inflammatory diseases. Data in the literature suggest that this enzyme activates the proinflammatory transcriptional factor NF-κB by inducing the polymerization of its inhibitory subunit I-κBα, which in turn results in the dissociation of NF- κB and its translocation to the nucleus, where it is capable of upregulating host inflammatory genes. Interestingly, NF-κB regulatory response elements are also present in the TG2 promoter, suggesting a possible role for this pathway in the mechanism responsible for chronic inflammation. On the basis of these literature data, our objective was to analyze the effects of curcumin on TG2 expression in human nervous cell lines. Methods: Human nervous cell lines were treated with curcumin alone or in association with retinoic acid in order to induce TG2 overexpression. TG2 levels were analyzed by Western blot and real-time PCR analyses. Results: Curcumin was able to downregulate the expression of TG2 in human nervous cell lines, which was also the case after treatment with retinoic acid. Conclusions: These results suggest a possible use of curcumin in reducing TG2 overexpression in human nervous cells

Possible pathophysiological roles of transglutaminase-catalyzed reactions in the pathogenesis of human neurodegenerative diseases

Transglutaminases (TG, E.C. 2.3.2.13) are related and ubiquitous enzymes that catalyze the cross linking of a glutaminyl residue of a protein/peptide substrate to a lysyl residue of a protein/peptide co-substrate. These enzymes are also capable of catalyzing other post-translational reactions important for cell life. The distribution and the physiological roles of human TGs have been widely studied in numerous cell types and tissues and recently their roles in several diseases have begun to be identified. It has been hypothesized that transglutaminase activity is directly involved in the pathogenetic mechanisms responsible for several human diseases. In particular, tissue TG (tTG, TG2), a member of the TG enzyme family, has been recently shown to be involved in the molecular mechanisms responsible for a very widespread human pathology, Celiac Disease (CD), one of the most common food intolerances described in the western population. The main food agent that provokes the strong and diffuse clinical symptoms has been known for several years to be gliadin, a protein present in a very large number of human foods derived from vegetables. Recently, some biochemical and immunological aspects of this very common disease have been clarified, and “tissue” transglutaminase, a multifunctional and ubiquitous enzyme, has been identified as one of the major factors. The aim of this review is to summarize the most recent findings concerning the relationships between the biochemical properties of the transglutaminase activity and the basic molecular mechanisms responsible for some human diseases, with particular reference to neuropsychiatric disorders. Possible molecular links between CD and neuropsychiatric disorders, and the use of transglutaminase inhibitors are also discussed

Transglutaminase inhibition: A therapy to protect cells from death in neurodegeneration?

""Transglutaminases (TGs; E.C. 2.3.2.13) are ubiquitous. enzymes which catalyze post-translational modifications. of proteins. TGs and TG-catalyzed post-translational. modifications of proteins have been shown to be involved. in the molecular mechanisms responsible for several. human diseases. In particular, TG activity has been. hypothesized to also be involved also in the molecular. mechanisms responsible for human neurodegenerative. diseases. In support of this hypothesis, Basso et al. recently demonstrated that the TG inhibition protects. against oxidative stress-induced neuronal death, suggesting. that multiple TG isoforms participate in oxidative. stress-induced cell death and that nonselective TG. isoform inhibitors will be most effective in fighting oxidative. death in neurological disorders. In this commentary,. we discuss the possible molecular mechanisms by. which TG activity could be involved in the pathogenesis. of neurological diseases, with particular reference to. neurodegenerative diseases, and the possible involvement. of multiple TG isoforms expressed simultaneously. in the nervous system in these diseases. Moreover,. therapeutic strategies based on the use of selective or. nonselective TG inhibitors for the amelioration of the symptoms of patients with neurological diseases, characterized. by aberrant TG activity, are also discussed."

Possible role of the transglutaminase-catalyzed reactions in the pathogenesis of neurodegenerative diseases

Transglutaminases are ubiquitous enzymes which catalyze posttranslational modifications of proteins. The main activity of these enzymes is the cross-linking of glutaminyl residues of a protein/ peptide substrate to lysyl residues of a protein/peptide co-substrate. In addition to lysyl residues, other second nucleophilic cosubstrates may include monoamines or polyamines (to form monoor bi-substituted/crosslinked adducts) or –OH groups (to form ester linkages). In absence of co-substrates, the nucleophile may be water, resulting in the net deamidation of the glutaminyl residue. Transglutaminase activity has been suggested to be involved in molecular mechanisms responsible for both physiological and pathological processes. For example, neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, supranuclear palsy, Huntington’s disease and other polyglutamine diseases, are characterized in part by aberrant cerebral transglutaminase activity and by increased cross-linked proteins in affected brains. This review focuses on the possible molecular mechanisms responsible for such diseases and on the possible therapeutic effects of transglutaminase inhibitors for patients with diseases characterized by aberrant transglutaminase activity