Poly(ADP-ribose) polymerase activation by reactive nitrogen species--relevance for the pathogenesis of inflammation

CB2 Cannabinoid Receptor as a Potential Target in Myocardial Infarction: Exploration of Molecular Pathogenesis and Therapeutic Strategies

The lipid endocannabinoid system has recently emerged as a novel therapeutic target for several inflammatory and tissue-damaging diseases, including those affecting the cardiovascular system. The primary targets of cannabinoids are cannabinoid type 1 (CB1) and 2 (CB2) receptors. The CB2 receptor is expressed in the cardiomyocytes. While the pathological changes in the myocardium upregulate the CB2 receptor, genetic deletion of the receptor aggravates the changes. The CB2 receptor plays a crucial role in attenuating the advancement of myocardial infarction (MI)-associated pathological changes in the myocardium. Activation of CB2 receptors exerts cardioprotection in MI via numerous molecular pathways. For instance, delta-9-tetrahydrocannabinol attenuated the progression of MI via modulation of the CB2 receptor-dependent anti-inflammatory mechanisms, including suppression of pro-inflammatory cytokines like IL-6, TNF-α, and IL-1β. Through similar mechanisms, natural and synthetic CB2 receptor ligands repair myocardial tissue damage. This review aims to offer an in-depth discussion on the ameliorative potential of CB2 receptors in myocardial injuries induced by a variety of pathogenic mechanisms. Further, the modulation of autophagy, TGF-β/Smad3 signaling, MPTP opening, and ROS production are discussed. The molecular correlation of CB2 receptors with cardiac injury markers, such as troponin I, LDH1, and CK-MB, is explored. Special attention has been paid to novel insights into the potential therapeutic implications of CB2 receptor activation in MI.

Rheumatoid Arthritis and Reactive Oxygen Species: A Review

Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disease that causes progressive joint damage and can lead to lifelong disability. Numerous studies support the hypothesis that reactive oxygen species (ROS) are associated with RA pathogenesis. Recent advances have clarified the anti-inflammatory effect of antioxidants and their roles in RA alleviation. In addition, several important signaling pathway components, such as nuclear factor kappa B, activator-protein-1, nuclear factor (erythroid-derived 2)-like 2/kelch-like associated protein, signal transducer and activator of transcription 3, and mitogen-activated protein kinases, including c-Jun N-terminal kinase, have been identified to be associated with RA. In this paper, we outline the ROS generation process and relevant oxidative markers, thereby providing evidence of the association between oxidative stress and RA pathogenesis. Furthermore, we describe various therapeutic targets in several prominent signaling pathways for improving RA disease activity and its hyper oxidative state. Finally, we reviewed natural foods, phytochemicals, chemical compounds with antioxidant properties and the association of microbiota with RA pathogenesis.

The expanding roles of neuronal nitric oxide synthase (NOS1)

The nitric oxide synthases (NOS; EC 1.14.13.39) use L-arginine as a substrate to produce nitric oxide (NO) as a by-product in the tissue microenvironment. NOS1 represents the predominant NO-producing enzyme highly enriched in the brain and known to mediate multiple functions, ranging from learning and memory development to maintaining synaptic plasticity and neuronal development, Alzheimer's disease (AD), psychiatric disorders and behavioral deficits. However, accumulating evidence indicate both canonical and non-canonical roles of NOS1-derived NO in several other tissues and chronic diseases. A better understanding of NOS1-derived NO signaling, and identification and characterization of NO-metabolites in non-neuronal tissues could become useful in diagnosis and prognosis of diseases associated with NOS1 expression. Continued investigation on the roles of NOS1, therefore, will synthesize new knowledge and aid in the discovery of small molecules which could be used to titrate the activities of NOS1-derived NO signaling and NO-metabolites. Here, we address the significance of NOS1 and its byproduct NO in modifying pathophysiological events, which could be beneficial in understanding both the disease mechanisms and therapeutics.

Senescence and Type 2 Diabetic Cardiomyopathy: How Young Can You Die of Old Age?

Inflammation is well understood to be a physiological process of ageing however it also underlies many chronic diseases, including conditions without an obvious pathogenic inflammatory element. Recent findings have unequivocally identified type 2 diabetes (T2D) as a chronic inflammatory disease characterized by inflammation and immune senescence. Immunosenescence is a hallmark of the prolonged low-grade systemic inflammation, in particular associated with metabolic syndrome and can be a cause as well as a consequence of T2D. Diabetes is a risk factor for cardiovascular mortality and remodelling and with particular changes to myocardial structure, function, metabolism and energetics collectively resulting in diabetic cardiomyopathy. Both cardiomyocytes and immune cells undergo metabolic remodelling in T2D and as a result become trapped in a vicious cycle of lost metabolic flexibility, thus losing their key adaptive mechanisms to dynamic changes in O₂ and nutrient availability. Immunosenescence driven by metabolic stress may be both the cause and key contributing factor to cardiac dysfunction in diabetic cardiomyopathy by inducing metabolic perturbations that can lead to impaired energetics, a strong predictor of cardiac mortality. Here we review our current understanding of the cross-talk between inflammaging and cardiomyocytes in T2D cardiomyopathy. We discuss potential mechanisms of metabolic convergence between cell types which, we hypothesize, might tip the balance between resolution of the inflammation versus adverse cardiac metabolic remodelling in T2D cardiomyopathy. A better understanding of the multiple biological paradigms leading to T2D cardiomyopathy including the immunosenescence associated with inflammaging will provide a powerful target for successful therapeutic interventions.

5-aminoisoquinolinone attenuates social behavior deficits and immune abnormalities in the BTBR T+ Itpr3tf/J mouse model for autism

Autism spectrum disorder (ASD) is diagnosed by core symptoms including impaired social communication and the presence of repetitive and stereotypical behaviors. There is also evidence for immune dysfunction in individuals with ASD, but it is a disease that is still insufficiently controlled by current treatment strategies. The use of 5-aminoisoquinolinone (5-AIQ) ameliorates several immune-mediated symptoms including rheumatoid arthritis and colitis, and has neuroprotective properties; however, its role in ASD is not yet characterized. In this study, we investigated the effect of 5-AIQ on sociability tests, self-grooming, marble burying, and locomotor activities in BTBR T⁺ Itpr3tf/J (BTBR) mice, which serve as an ASD animal model. We further investigated the possible molecular mechanism of 5-AIQ administration on CXCR4-, CXCR6-, IFN-γ-, IL-22-, NOS2-, STAT1-, T-bet-, and RORγT-producing CD3⁺ T cells isolated from the spleens of treated mice. We also explored its effects on mRNA expression in brain tissue. Our results showed that in BTBR mice, 5-AIQ treatment significantly prevented self-grooming and marble burying behaviors and enhanced social interactions without any adverse effects on locomotor activity/anxiety level. Additionally, 5-AIQ treatment substantially decreased CXCR4-, CXCR6-, IFN-γ-, IL-22-, NOS2-, STAT1-, T-bet-, and RORγT-producing CD3⁺ T cells in the spleen. Furthermore, 5-AIQ treatment decreased CXCR4, IFN-γ, IL-22, STAT1, and RORγT mRNA expression levels in brain tissue. Our findings demonstrated that 5-AIQ improved behavioral and immune abnormalities associated with ASD, which supports the hypothesis that 5-AIQ has important therapeutic potential for the treatment of behavioral and neuroimmune dysfunctions in ASD.

The Role of PARPs in Inflammation-and Metabolic-Related Diseases: Molecular Mechanisms and Beyond

Poly(ADP-ribosyl)ation (PARylation) is an essential post-translational modification catalyzed by poly(ADP-ribose) polymerase (PARP) enzymes. Poly(ADP-ribose) polymerase 1 (PARP1) is a well-characterized member of the PARP family. PARP1 plays a crucial role in multiple biological processes and PARP1 activation contributes to the development of various inflammatory and malignant disorders, including lung inflammatory disorders, cardiovascular disease, ovarian cancer, breast cancer, and diabetes. In this review, we will focus on the role and molecular mechanisms of PARPs enzymes in inflammation- and metabolic-related diseases. Specifically, we discuss the molecular mechanisms and signaling pathways that PARP1 is associated with in the regulation of pathogenesis. Recently, increasing evidence suggests that PARP inhibition is a promising strategy for intervention of some diseases. Thus, our in-depth understanding of the mechanism of how PARPs are activated and how their signaling downstream effecters can provide more potential therapeutic targets for the treatment of the related diseases in the future is crucial.

Immunometabolic cross-talk in the inflamed heart

Inflammatory processes underlie many diseases associated with injury of the heart muscle, including conditions without an obvious inflammatory pathogenic component such as hypertensive and diabetic cardiomyopathy. Persistence of cardiac inflammation can cause irreversible structural and functional deficits. Some are induced by direct damage of the heart muscle by cellular and soluble mediators but also by metabolic adaptations sustained by the inflammatory microenvironment. It is well established that both cardiomyocytes and immune cells undergo metabolic reprogramming in the site of inflammation, which allow them to deal with decreased availability of nutrients and oxygen. However, like in cancer, competition for nutrients and increased production of signalling metabolites such as lactate initiate a metabolic cross-talk between immune cells and cardiomyocytes which, we propose, might tip the balance between resolution of the inflammation versus adverse cardiac remodeling. Here we review our current understanding of the metabolic reprogramming of both heart tissue and immune cells during inflammation, and we discuss potential key mechanisms by which these metabolic responses intersect and influence each other and ultimately define the prognosis of the inflammatory process in the heart.

Role of Peroxynitrite-Induced Activation of Poly(ADP-Ribose) Polymerase (PARP) in Circulatory Shock and Related Pathological Conditions

Peroxynitrite is a powerful oxidant, formed from the reaction of nitric oxide and superoxide. It is known to interact and modify different biological molecules such as DNA, lipids and proteins leading to alterations in their structure and functions. These events elicit various cellular responses, including cell signaling, causing oxidative damage and committing cells to apoptosis or necrosis. This review discusses nitrosative stress-induced modification in the DNA molecule that results in the formation of 8-nitroguanine and 8-oxoguanine, and its role in disease conditions. Different approaches of cell death, such as necrosis and apoptosis, are modulated by cellular high-energy species, such as ATP and NAD⁺. High concentrations of peroxynitrite are known to cause necrosis, whereas low concentrations lead to apoptosis. Any damage to DNA activates cellular DNA repair machinery, like poly(ADP-ribose) polymerase (PARP). PARP-1, an isoform of PARP, is a DNA nick-sensing enzyme that becomes activated upon sensing DNA breakage and triggers the cleavage of NAD⁺ into nicotinamide and ADP-ribose and polymerizes the latter on nuclear acceptor proteins. Peroxynitrite-induced hyperactivation of PARP causes depletion of NAD⁺ and ATP culminating cell dysfunction, necrosis or apoptosis. This mechanistic pathway is implicated in the pathogenesis of a variety of diseases, including circulatory shock (which is characterized by cellular hypoxia triggered by systemic altered perfusion and tissue oxygen utilization leading end-organ dysfunction), sepsis and inflammation, injuries of the lung and the intestine. The cytotoxic effects of peroxynitrite centering on the participation of PARP-1 and ADP-ribose in previously stated diseases have also been discussed in this review.

Metabolic Remodeling in Diabetic Cardiomyopathy

Diabetes is a risk factor for heart failure and cardiovascular mortality with specific changes to myocardial metabolism, energetics, structure, and function. The gradual impairment of insulin production and signalling in diabetes is associated with elevated plasma fatty acids and increased myocardial free fatty acid uptake and activation of the transcription factor PPARα. The increased free fatty acid uptake results in accumulation of toxic metabolites, such as ceramide and diacylglycerol, activation of protein kinase C, and elevation of uncoupling protein-3. Insulin signalling and glucose uptake/oxidation become further impaired, and mitochondrial function and ATP production become compromised. Increased oxidative stress also impairs mitochondrial function and disrupts metabolic pathways. The diabetic heart relies on free fatty acids (FFA) as the major substrate for oxidative phosphorylation and is unable to increase glucose oxidation during ischaemia or hypoxia, thereby increasing myocardial injury, especially in ageing female diabetic animals. Pharmacological activation of PPARγ in adipose tissue may lower plasma FFA and improve recovery from myocardial ischaemic injury in diabetes. Not only is the diabetic heart energetically-impaired, it also has early diastolic dysfunction and concentric remodelling. The contractile function of the diabetic myocardium negatively correlates with epicardial adipose tissue, which secretes proinflammatory cytokines, resulting in interstitial fibrosis. Novel pharmacological strategies targeting oxidative stress seem promising in preventing progression of diabetic cardiomyopathy, although clinical evidence is lacking. Metabolic agents that lower plasma FFA or glucose, including PPARγ agonism and SGLT2 inhibition, may therefore be promising options.

Poly(ADP-ribose)polymerase 1 inhibition protects against age-dependent endothelial dysfunction

Age-related endothelial dysfunction is closely associated with the local production of reactive oxygen species (ROS) within and in the vicinity of the vascular endothelium. Oxidant-induced DNA damage can activate the nuclear enzyme poly(ADP-ribose) polymerase 1 (PARP-1), leading to endothelial dysfunction in various pathophysiological conditions. The present study aimed to investigate the role of PARP-1 in age-dependent changes in endothelial cell function and its underlying mechanism. Wild-type (WT) and PARP-1(-/-) mice were divided into young (2 months) and old (12 months) groups. Isolated aortic rings were suspended to record isometric tension to assess endothelial function. Nitric oxide (NO) production and content in plasma were detected by spectrophotometry. Superoxide (O2(-) production was detected by dihydroethidium. Expression of PARP-1, endothelial nitric oxide synthase (eNOS), induced nitric oxide synthase (iNOS), and arginase-2 (Arg2) was assessed by western blot analysis. Endothelium-dependent relaxation in response to acetylcholine was lost in old WT, but not PARP-1(-/-), mice. Endothelium-independent vasodilation was not impaired in aging mice. Production of O2(-) was greater in aging WT mice than young or aging PARP-1(-/-) mice. eNOS expression was not affected by aging in WT or PARP-1(-/-) mice, but p-eNOS expression decreased and iNOS and Arg2 levels were upregulated only in aging WT mice. In conclusion, PARP-1 inhibition may protect against age-dependent endothelial dysfunction, potentially by regulating NO bioavailability via iNOS. Inhibition of PARP-1 may help in vascular aging prevention.

Peroxynitrite is Involved in the Apoptotic Death of Cultured Cerebellar Granule Neurons Induced by Staurosporine, but not by Potassium Deprivation

Nitric oxide (NO) regulates numerous physiological process and is the main source of reactive nitrogen species (RNS). NO promotes cell survival, but it also induces apoptotic death having been involved in the pathogenesis of several neurodegenerative diseases. NO and superoxide anion react to form peroxynitrite, which accounts for most of the deleterious effects of NO. The mechanisms by which these molecules regulate the apoptotic process are not well understood. In this study, we evaluated the role of NO and peroxynitrite in the apoptotic death of cultured cerebellar granule neurons (CGN), which are known to experience apoptosis by staurosporine (St) or potassium deprivation (K5). We found that CGN treated with the peroxynitrite catalyst, FeTTPs were completely rescued from St-induced death, but not from K5-induced death. On the other hand, the inhibition of the inducible nitric oxide synthase partially protected cell viability in CGN treated with K5, but not with St, while the inhibitor L-NAME further reduced the cell viability in St, but it did not affect K5. Finally, an inhibitor of the soluble guanylate cyclase (sGC) diminished the cell viability in K5, but not in St. Altogether, these results shows that NO promotes cell survival in K5 through sGC-cGMP and promotes cell death by other mechanisms, while in St NO promotes cell survival independently of cGMP and peroxynitrite results critical for St-induced death. Our results suggest that RNS are differentially handled by CGN during cell death depending on the death-inducing conditions.

Inhibition of poly (ADP-ribose) polymerase and inducible nitric oxide synthase protects against ischemic myocardial damage by reduction of apoptosis

Myocardial infarction (MI) is defined as the deprivation of the myocardial tissue of oxygen and nutrients, resulting in the induction of inflammation and apoptosis of the cardiomyocytes. Poly (ADP-ribose) polymerase 1 (PARP1) is a nuclear enzyme closely associated with MI, that can be activated by DNA damage. Inducible nitric oxide synthase (iNOS) is a critical enzyme among the inflammatory cytokines. The present study aimed to investigate the underlying mechanism of the protective effects of PARP1 and iNOS inhibitor against MI, in rats. A total of 40 male Wistar rats were divided into four groups. The rats were anesthetized with sodium pentobarbital (50 mg/kg), and the left anterior descending coronary artery was occluded by ligation, using a 6-0 polypropylene monofilament suture, at the left atrial apex, in order to induce MI. The rats from each group received an abdominal injection of either dimethylsulfoxide (100 μl, for MI group); PARP-1 inhibitor, 3,4-dihydro-5-[4-(1-piperidinyl)butoxy]-1(2H)-isoquinolinone (DPQ; 10 mg/kg); or iNOS inhibitor, N-(1-naphthyl)ethylenediamine dihydrochloride (1400W; 10 mg/kg). The hearts were harvested from the rats after four weeks. Inhibition of PARP and iNOS activity improved heart function, as determined by serial echocardiography. The rate of apoptosis, as determined by a terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling assay, was reduced by 39.71 and 39.00% in the DPQ and 1400W groups, respectively, and this was accompanied by the downregulated expression of cleaved caspase-3 and PARP1. Effective inhibition of PARP and iNOS, by DPQ and 1400W, was detected by western blotting and immunofluorescence, and was shown to repress O₂⁻ and nitrotyrosine levels, following MI. The present study confirmed that inhibition of PARP1 and iNOS was able to protect against ischemic myocardial damage, by reducing the levels of apoptosis.

Efficacy of poly(adenosine diphosphate-ribose) polymerase inhibition in extracorporeal shock wave-induced renal injury

OBJECTIVES

Extracorporeal shock wave lithotripsy (ESW) induces renal damage by excessive production of free oxygen radicals. Free Oxygen radicals cause cellular injury by inducing nicks in DNA. The enzyme poly(adenosine diphosphate-ribose) polymerase (PARP) involved in the process of repair of DNA in damaged cells. However, its activation in damaged cells can lead to adenosine triphosphate depletion and death. Thus, we designed a study to evaluate the efficacy of 3-aminobenzamide (3-AB), a PARP inhibitor, against extracorporeal shock wave induced renal injury.

METHODS

Twenty-four Sprague-Dawley rats were divided into three groups: control, ESW, ESW + 3-AB groups. All groups except control group were subjected to ESW procedure. ESW + 3-AB group received 20 mg/kg/day 3-aminobenzamide intraperitoneally at 2 h before ESW and continued once a day for consecutive 3 days. The surviving animals were sacrificed at the 4th day and their kidneys were harvested for biochemical and histopathologic analysis. Blood samples from animals were also obtained.

RESULTS

Serum ALT and AST levels, serum neopterin and tissue oxidative stress parameters were increased in the ESW group and almost came to control values in the treatment group (p < 0.05, ESW vs. ESW + 3-AB). Histopathological injury score were significantly lower in treatment group than the ESW group (p < 0.05, ESW vs. ESW + 3-AB).

CONCLUSION

Our data showed that PARP inhibition protected renal tissue against ESW induced renal injury. These findings suggest that it would be possible to improve the outcome of ESW induced renal injury by using PARP inhibitors as a preventive therapy.

Poly(ADP-ribose) polymerase-1 inhibitor modulates T regulatory and IL-17 cells in the prevention of adjuvant induced arthritis in mice model

Rheumatoid arthritis (RA) is one of the major autoimmune diseases of global prevalence. Irrespective of much research in RA disease, no drugs with capable safety profiles are yet available. Poly(ADP-ribose) polymerase-1 (PARP-1) synthesizes and transfers ADP ribose polymers to target proteins, and regulates DNA repair and genomic integrity maintenance. PARP-1 also plays a crucial role in the progression of the inflammatory response, and its inhibition confers protection in several models of inflammatory disorders. We investigated the possible anti-arthritic effects of the PARP-1 inhibitor 5-aminoisoquinolinone (5-AIQ) in a mouse model of adjuvant induced arthritis (AIA). In this study, we examined the effects of 5-AIQ on the key mediators of arthritic inflammation, namely, edema and arthritic score, T cell subsets, regulatory T (Treg) cells, IL-17A, GITR expressing cells, NF-kB p65, IkB-α and pro and anti-inflammatory mediators mRNA expression levels. PARP-1 inhibition 5-AIQ treatment significantly attenuated the severity of AIA, reduced the arthritis scores, a substantial reduction in the levels of T cell subsets, IL-17A, NF-kB p65, GITR expressing cells, and as well as the pro-inflammatory mediators. However, 5-AIQ significantly up-regulated the number of Tregs cells, IkB-α levels and mRNA expression of anti-inflammatory mediators. Our results suggest that treatment with 5-AIQ attenuated AIA in mice might offer a promising alternative/adjunct treatment for RA.

Serum nicotinamide adenine dinucleotide levels through disease course in multiple sclerosis

The levels of the essential pyridine nucleotide, NAD(+) and its reduced form NADH have not been documented in MS patients. We aimed to investigate NAD(+) and NADH levels in serum in patients with different disease stages and forms of MS. NAD(+) and NADH levels were measured in the serum from 209 patients with relapsing remitting MS (RRMS), 136 with secondary progressive MS (SPMS), 51 with primary progressive MS (PPMS), and 99 healthy controls. All patients were in a clinically stable phase. Serum NAD(+) levels declined by at least 50% in patients with MS compared to controls (17.9 ± 3.2 μg/ml; p=0.0012). Within the MS sub-groups NAD(+) levels were higher in RRMS (9.9 ± 2.9 μg/ml; p=0.001) compared to PPMS (6.3 ± 2.1 μg/ml; p=0.003) and SPMS (7.8 ± 2.0 μg/ml; p=0.005). A two-fold increase in NADH levels (p=0.002) and at least three-fold reduction in the NAD(+)/NADH ratio (p=0.009) were observed in MS patients compared to controls. Serum NAD(+) and NADH levels are may be associated with disease progression in MS. Given the importance of NAD(+) in the maintenance of normal cellular function, it is likely that this molecule is of therapeutic relevance in MS.

Oxygen consumption and usage during physical exercise: the balance between oxidative stress and ROS-dependent adaptive signaling

The complexity of human DNA has been affected by aerobic metabolism, including endurance exercise and oxygen toxicity. Aerobic endurance exercise could play an important role in the evolution of Homo sapiens, and oxygen was not important just for survival, but it was crucial to redox-mediated adaptation. The metabolic challenge during physical exercise results in an elevated generation of reactive oxygen species (ROS) that are important modulators of muscle contraction, antioxidant protection, and oxidative damage repair, which at moderate levels generate physiological responses. Several factors of mitochondrial biogenesis, such as peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), mitogen-activated protein kinase, and SIRT1, are modulated by exercise-associated changes in the redox milieu. PGC-1α activation could result in decreased oxidative challenge, either by upregulation of antioxidant enzymes and/or by an increased number of mitochondria that allows lower levels of respiratory activity for the same degree of ATP generation. Endogenous thiol antioxidants glutathione and thioredoxin are modulated with high oxygen consumption and ROS generation during physical exercise, controlling cellular function through redox-sensitive signaling and protein-protein interactions. Endurance exercise-related angiogenesis, up to a significant degree, is regulated by ROS-mediated activation of hypoxia-inducible factor 1α. Moreover, the exercise-associated ROS production could be important to DNA methylation and post-translation modifications of histone residues, which create heritable adaptive conditions based on epigenetic features of chromosomes. Accumulating data indicate that exercise with moderate intensity has systemic and complex health-promoting effects, which undoubtedly involve regulation of redox homeostasis and signaling.

A preclinical study on the protective effect of melatonin against methotrexate-induced small intestinal damage: effect mediated by attenuation of nitrosative stress, protein tyrosine nitration, and PARP activation

PURPOSE

One of the major toxic side effects of methotrexate (MTX) is enterocolitis. To date, there is no efficient standard treatment for this side effect. Nitrosative stress is reported to play a critical role in MTX-induced mucositis. The purpose of this study is to investigate whether pretreatment with melatonin, an inhibitor of nitro-oxidative stress, prevents MTX-induced mucositis in rats.

METHODS

Rats were pretreated with melatonin (20 and 40 mg/kg body weight) i.p. daily 1 h before MTX (7 mg/kg body weight) administration for three consecutive days. After the final dose of MTX, the rats were killed and the small intestines were used for analysis.

RESULTS

The small intestines of MTX-treated rats showed moderate to severe injury. The villi were distorted, blunted, and atrophied and focally absent in various segments of the small intestines. Crypt abscesses were also found, suggesting an inflammatory response. Pretreatment with melatonin had a dose-dependent protective effect on MTX-induced mucositis. Morphology was saved to a moderate extent with 20 mg melatonin pretreatment, and near-normal morphology was achieved with 40 mg melatonin pretreatment. Damage to the villi and crypt abscess was reduced. The villi/crypt ratio was almost restored. Melatonin pretreatment protected the small intestines from MTX-induced damage by attenuating nitrosative stress, protein tyrosine nitration and PARP expression.

CONCLUSION

Because of its versatility in protecting against nitro-oxidative stress and reducing inflammation, we suggest that melatonin could be beneficial in ameliorating MTX-induced enteritis in humans.

Rutin prevents cognitive impairments by ameliorating oxidative stress and neuroinflammation in rat model of sporadic dementia of Alzheimer type

The objective of the present study was to assess the neuroprotective role of rutin (vitamin P) and delineate the mechanism of action. Recent evidence indicates that rutin exhibits antioxidant potential and protects the brain against various oxidative stressors. More precisely, the aim of the present study was to examine the modulating impacts of rutin against cognitive deficits and oxidative damage in intracerebroventricular-streptozotocin (ICV-STZ)-infused rats. Rats were injected bilaterally with ICV-STZ (3 mg/kg), whereas sham rats received the same volume of vehicle. After 2 weeks of streptozotocin (STZ) infusion, rats were tested for cognitive performance using Morris water maze tasks and thereafter euthanized for further biochemical, histopathological, and immunohistochemical studies. Rutin pretreatment (25 mg/kg, orally, once daily for 3 weeks) significantly attenuated thiobarbituric acid reactive substances (TBARS), activity of poly ADP-ribosyl polymerase, and nitrite level and decreased level of reduced glutathione (GSH) and activities of its dependent enzymes (glutathione peroxidase [GPx] and glutathione reductase [GR]) and catalase in the hippocampus of ICV-STZ rats. ICV-STZ rats showed significant cognitive deficits, which was improved significantly by rutin supplementation. The results indicate that rutin attenuates STZ-induced inflammation by reducing the expression of cyclooxygenase-2 (COX-2), glial fibrillary acidic protein (GFAP), interleukin-8 (IL-8), inducible nitric oxide synthase (iNOS), nuclear factor-kB, and preventing the morphological changes in hippocampus. The study thereby suggests the effectiveness of rutin in preventing cognitive deficits and might be beneficial for the treatment of sporadic dementia of Alzheimer type (SDAT).

cGMP-Prkg1 signaling and Pde5 inhibition shelter cochlear hair cells and hearing function

Noise-induced hearing loss (NIHL) is a global health hazard with considerable pathophysiological and social consequences that has no effective treatment. In the heart, lung and other organs, cyclic guanosine monophosphate (cGMP) facilitates protective processes in response to traumatic events. We therefore analyzed NIHL in mice with a genetic deletion of the gene encoding cGMP-dependent protein kinase type I (Prkg1) and found a greater vulnerability to and markedly less recovery from NIHL in these mice as compared to mice without the deletion. Prkg1 was expressed in the sensory cells and neurons of the inner ear of wild-type mice, and its expression partly overlapped with the expression profile of cGMP-hydrolyzing phosphodiesterase 5 (Pde5). Treatment of rats and wild-type mice with the Pde5 inhibitor vardenafil almost completely prevented NIHL and caused a Prkg1-dependent upregulation of poly (ADP-ribose) in hair cells and the spiral ganglion, suggesting an endogenous protective cGMP-Prkg1 signaling pathway that culminates in the activation of poly (ADP-ribose) polymerase. These data suggest vardenafil or related drugs as possible candidates for the treatment of NIHL.

Poly(ADP-ribose) polymerase-1: a novel therapeutic target in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the most common gastrointestinal disease of infancy, afflicting 11% of infants born 22-28 wk GA. Both inflammation and oxidation may be involved in NEC pathogenesis through reactive nitrogen species production, protein oxidation, and DNA damage. Poly(ADP-ribose) polymerase-1 (PARP-1) is a critical enzyme activated to facilitate DNA repair using nicotinamide adenine dinucleotide (NAD+) as a substrate. However, in the presence of severe oxidative stress and DNA damage, PARP-1 overactivation may ensue, depleting cells of NAD+ and ATP, killing them by metabolic catastrophe. Here, we tested the hypothesis that NO dysregulation in intestinal epithelial cells during NEC leads to marked PARP-1 expression and that administration of a PARP-1 inhibitor (nicotinamide) attenuates intestinal injury in a newborn rat model of NEC. In this model, 56% of control pups developed NEC (any stage) versus 14% of pups receiving nicotinamide. Forty-four percent of control pups developed high-grade NEC (grades 3-4), whereas only 7% of pups receiving nicotinamide developed high-grade NEC. Nicotinamide treatment protects pups against intestinal injury incurred in the newborn rat NEC model. We speculate that PARP-1 overactivation in NEC may drive mucosal cell death in this disease and that PARP-1 may be a novel therapeutic target in NEC.

Calcium overload is a critical step in programmed necrosis of ARPE-19 cells induced by high-concentration H₂O₂

OBJECTIVE

Oxidative stress plays an important role in retinal pigmental epithelium (RPE) death during aging and the development of age-related macular degeneration. Although early reports indicate that reactive oxygen species (ROS) including H₂O₂ can trigger apoptosis at lower concentrations and necrosis at higher concentrations, the exact molecular mechanism of RPE death is still unclear. The purpose of this study was to investigate the molecular pathways involved in RPE death induced by exogenous ROS, especially at higher concentrations.

METHODS

Cultured ARPE-19 cells were treated with H₂O₂ at different concentrations and cell viability was measured with the MTT assay. Cell death was morphologically studied by microscopy using APOPercentage assay and PI staining. Furthermore, the impact of oxidative stress on ARPE-19 cells was assessed by HO-1 and PARP-1 Western blotting and by the protection of antioxidant EGCG. Calcium influx was determined using the fura-2 calcium indicator and the role of intracellular calcium overload in ARPE-19 cell death was evaluated following cobalt treatment to block calcium effects.

RESULTS

H₂O₂ reduced the viability of ARPE-19 cells in a concentration-dependent manner, which was presented as a typical s-shaped curve. Cell death caused by high concentrations of H₂O₂ was confirmed to be programmed necrosis. Morphologically, dying ARPE-19 cells were extremely swollen and lost the integrity of their plasma membrane, positively detected with APOPercentage assay and PI staining. 24-hour treatment with 500 μmol/L H₂O₂ induced remarkable up-regulation of HO-1 and PARP-1 in ARPE-19 cells. Moreover, antioxidant treatment using EGCG effectively protected cells from H₂O₂-induced injury, increasing cell viability from 14.17%±2.31% to 85.77%±4.58%. After H₂O₂ treatment, intracellular calcium levels were highly elevated with a maximum concentration of 1200 nM. Significantly, the calcium channel inhibitor cobalt was able to blunt this calcium influx and blocked the necrotic pathway, rescuing the ARPE-19 cell from H₂O₂-induced death.

CONCLUSIONS

At high concentrations, H₂O₂ induces ARPE-19 cell death through a regulated necrotic pathway with calcium overload as a critical step in the cell death program.

Poly(ADP-ribose) polymerase inhibition modulates experimental acute necrotizing pancreatitis-induced oxidative stress, bacterial translocation and neopterin concentrations in rats

Various studies have been performed to find out novel treatment strategies for acute necrotizing pancreatitis (ANP). Inhibition of poly(ADP-ribose) polymerase (PARP) is shown to reduce inflammation in several pathological conditions. We aimed to evaluate the efficacy of benzamide, a PARP inhibitor, in an experimental model of ANP. Thirty Sprague-Dawley rats were divided into three groups: sham-operated, ANP and ANP + benzamide groups. All groups except the sham-operated group were subjected to the ANP procedure, induced by infusing of 1 mL/kg of 3% sodium taurocholate into the common biliopancreatic duct. The ANP + benzamide group received 100 mg/kg/day benzamide intraperitoneally for a total of three days after induction of pancreatitis. The surviving animals were killed at the fourth day and the pancreas was harvested for biochemical, microbiological and histological analysis. Blood samples were also obtained from the animals. In the ANP group, a significant increase was observed in concentrations of serum amylase and neopterin and tissue oxidative stress indices (malondialdehyde, superoxide dismutase and glutathione peroxidase). Almost all of these changes were found to be reversed to near their normal values in the ANP + benzamide group. Histological injury scores were significantly higher in the ANP group than in the sham group (P < 0.05, ANP versus sham), and were significantly lower in the ANP + benzamide group than in the ANP group (P < 0.05, ANP + benzamide versus ANP). Evaluation of bacterial translocation identified significantly fewer infected sites in the ANP + benzamide group than in the ANP animals (P < 0.01). We observed that inhibition of PARP with benzamide reduced the severity, the mortality, the bacterial translocation rates and the neopterin concentrations in an experimental ANP model in rats. These findings suggest that it may be possible to improve the outcome of ANP by using PARP inhibitors.

Regulatory role of mitochondria in oxidative stress and atherosclerosis

Mitochondrial physiology and biogenesis play a crucial role in the initiation and progression of cardiovascular disease following oxidative stress-induced damage such as atherosclerosis (AST). Dysfunctional mitochondria caused by an increase in mitochondrial reactive oxygen species (ROS) production, accumulation of mitochondrial DNA damage, and respiratory chain deficiency induces death of endothelial/smooth muscle cells and favors plaque formation/rupture via the regulation of mitochondrial biogenesis-related genes such as peroxisome proliferator-activated receptor γ coactivator (PGC-1), although more detailed mechanisms still need further study. Based on the effect of healthy mitochondria produced by mitochondrial biogenesis on decreasing ROS-mediated cell death and the recent finding that the regulation of PGC-1 involves mitochondrial fusion-related protein (mitofusin), we thus infer the regulatory role of mitochondrial fusion/fission balance in AST pathophysiology. In this review, the first section discusses the possible association between AST-inducing factors and the molecular regulatory mechanisms of mitochondrial biogenesis and dynamics, and explains the role of mitochondria-dependent regulation in cell apoptosis during AST development. Furthermore, nitric oxide has the Janus-faced effect by protecting vascular damage caused by AST while being a reactive nitrogen species (RNS) which act together with ROS to damage cells. Therefore, in the second section we discuss mitochondrial ATP-sensitive K(+) channels, which regulate mitochondrial ion transport to maintain mitochondrial physiology, involved in the regulation of ROS/RNS production and their influence on AST/cardiovascular diseases (CVD). Through this review, we can further appreciate the multi-regulatory functions of the mitochondria involved in AST development. The understanding of these related mechanisms will benefit drug development in treating AST/CVD through targeted biofunctions of mitochondria.

Biochemical and cellular toxicology of peroxynitrite: implications in cell death and autoimmune phenomenon

Reactive nitrogen species include nitric oxide (.NO), peroxynitrite (ONOO(-)) and nitrogen dioxide radical (NO2*). Peroxynitrite is a reactive oxidant, produced from nitric oxide (*NO) and superoxide anion (O(2*-), that reacts with a variety of biological macromolecules. It is produced in the body in response to physiological stress and environmental toxins. It is a potent trigger of oxidative protein and DNA damage-including DNA strand breakage and base modification. It activates the nuclear enzyme poly-ADP ribose polymerase (PARP) resulting in energy depletion and apoptosis/necrosis of cells. Peroxynitrite generation is a crucial pathological mechanism in stroke, diabetes, inflammation, neurodegeneration, cancer, etc. Peroxynitrite modified DNA may also lead to the generation of autoantibodies in various autoimmune disorders such as systemic lupus erythematosus (SLE). In chronic inflammatory diseases, peroxynitrite formed by phagocytic cells may cause damage to DNA, generating neoepitopes leading to the production of autoantibodies. Hence, understanding the pathophysiology of peroxynitrite could lead to important therapeutic interventions.

Mechanical stretch enhances NF-kappaB-dependent gene expression and poly(ADP-ribose) synthesis in synovial cells

Temporomandibular joint disorders (TMD) show complex symptoms associated with inflammation, pain and degeneration of the peripheral tissues including synovium. Although it is believed that excessive mechanical stress on synovium causes development of TMD, the molecular mechanism by which mechanical stress triggers TMD has still remained unclear. In order to examine the effect of mechanical stress on synoviocytes, rabbit synovial cells were cyclically stretched in vitro. The stretch efficiently increased the gene expressions of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) and NF-kappaB responsive reporter gene constructs. The interruption of NF-kappaB activating pathway by inhibitors resulted in the abrogation of those expressions, indicating the pivotal role of NF-kappaB in the mechanical stretch-mediated COX-2 and iNOS expressions. In parallel, the stretch remarkably increased NO production and poly(ADP-ribose) (PAR) synthesis, suggesting that excessive amounts of NO causes DNA injury and in turn activates PAR synthesis by poly(ADP-ribose) polymerase (PARP). The inhibition of PAR synthesis by a PARP inhibitor or a radical scavenger enhanced the mechanical stretch-induced gene expressions in a NF-kappaB-independent manner, implying an involvement of PARP in the gene expression. Taken together, these results demonstrate that mechanical stress on synovial cells not only induces gene expressions of COX-2 and iNOS but also affects PAR synthesis.

Molecular, genetic and epigenetic pathways of peroxynitrite-induced cellular toxicity

Oxidative stress plays a key role in the pathogenesis of cancer and many metabolic diseases; therefore, an effective antioxidant therapy would be of great importance in these circumstances. Nevertheless, convincing randomized clinical trials revealed that antioxidant supplementations were not associated with significant reduction in incidence of cancer, chronic diseases and all-cause mortality. As oxidation of essential molecules continues, it turns to nitro-oxidative stress because of the involvement of nitric oxide in pathogenesis processes. Peroxynitrite damages via several distinctive mechanisms; first, it has direct toxic effects on all biomolecules and causes lipid peroxidation, protein oxidation and DNA damage. The second mechanism involves the induction of several transcription factors leading to cytokine-induced chronic inflammation. Finally, it causes epigenetic perturbations that exaggerate nuclear factor kappa-B mediated inflammatory gene expression. Lessons-learned from the treatment of several chronic disorders including pulmonary diseases suggest that, chronic inflammation and glucocorticoid resistance are regulated by prolonged peroxynitrite production.

Molecular biological effects of selective neuronal nitric oxide synthase inhibition in ovine lung injury

Neuronal nitric oxide synthase is critically involved in the pathogenesis of acute lung injury resulting from combined burn and smoke inhalation injury. We hypothesized that 7-nitroindazole, a selective neuronal nitric oxide synthase inhibitor, blocks central molecular mechanisms involved in the pathophysiology of this double-hit insult. Twenty-five adult ewes were surgically prepared and randomly allocated to 1) an uninjured, untreated sham group (n = 7), 2) an injured control group with no treatment (n = 7), 3) an injury group treated with 7-nitroindazole from 1-h postinjury to the remainder of the 24-h study period (n = 7), or 4) a sham-operated group subjected only to 7-nitroindazole to judge the effects in health. The combination injury was associated with twofold increased activity of neuronal nitric oxide synthase and oxidative/nitrosative stress, as indicated by significant increases in plasma nitrate/nitrite concentrations, 3-nitrotyrosine (an indicator of peroxynitrite formation), and malondialdehyde lung tissue content. The presence of systemic inflammation was evidenced by twofold, sixfold, and threefold increases in poly(ADP-ribose) polymerase, IL-8, and myeloperoxidase lung tissue concentrations, respectively (each P < 0.05 vs. sham). These molecular changes were linked to tissue damage, airway obstruction, and pulmonary shunting with deteriorated gas exchange. 7-Nitroindazole blocked, or at least attenuated, all these pathological changes. Our findings suggest 1) that nitric oxide formation derived from increased neuronal nitric oxide synthase activity represents a pivotal reactive agent in the patho-physiology of combined burn and smoke inhalation injury and 2) that selective neuronal nitric oxide synthase inhibition represents a goal-directed approach to attenuate the degree of injury.

Drug targets for traumatic brain injury from poly(ADP-ribose)polymerase pathway modulation

The deleterious pathophysiological cascade induced after traumatic brain injury (TBI) is initiated by an excitotoxic process triggered by excessive glutamate release. Activation of the glutamatergic N-methyl-D-aspartate receptor, by increasing calcium influx, activates nitric oxide (NO) synthases leading to a toxic production of NO. Moreover, after TBI, free radicals are highly produced and participate to a deleterious oxidative stress. Evidence has showed that the major toxic effect of NO comes from its combination with superoxide anion leading to peroxynitrite formation, a highly reactive and oxidant compound. Indeed, peroxynitrite mediates nitrosative stress and is a potent inducer of cell death through its reaction with lipids, proteins and DNA. Particularly DNA damage, caused by both oxidative and nitrosative stresses, results in activation of poly(ADP-ribose) polymerase (PARP), a nuclear enzyme implicated in DNA repair. In response to excessive DNA damage, massive PARP activation leads to energetic depletion and finally to cell death. Since 10 years, accumulating data have showed that inactivation of PARP, either pharmacologically or using PARP null mice, induces neuroprotection in experimental models of TBI. Thus TBI generating NO, oxidative and nitrosative stresses promotes PARP activation contributing in post-traumatic motor, cognitive and histological sequelae. The mechanisms by which PARP inhibitors provide protection might not entirely be related to the preservation of cellular energy stores, but might also include other PARP-mediated mechanisms that needed to be explored in a TBI context. Ten years of experimental research provided rational basis for the development of PARP inhibitors as treatment for TBI.

A new paradigm in radioadaptive response developing from microbeam research

A classic paradigm in radiation biology asserts that all radiation effects on cells, tissues and organisms are due to the direct action of radiation on living tissue. Using this model, possible risks from exposure to low dose ionizing radiation (below 100 mSv) are estimated by extrapolating from data obtained after exposure to higher doses of radiation, using a linear non-threshold model (LNT model). However, the validity of using this dose-response model is controversial because evidence accumulated over the past decade has indicated that living organisms, including humans, respond differently to low dose/low dose-rate radiation than they do to high dose/high dose-rate radiation. These important responses to low dose/low dose-rate radiation are the radiation-induced adaptive response, the bystander response, low-dose hypersensitivity, and genomic instability. The mechanisms underlying these responses often involve biochemical and molecular signals generated in response to targeted and non-targeted events. In order to define and understand the bystander response to provide a basis for the understanding of non-targeted events and to elucidate the mechanisms involved, recent sophisticated research has been conducted with X-ray microbeams and charged heavy particle microbeams, and these studies have produced many new observations. Based on these observations, associations have been suggested to exist between the radioadaptive and bystander responses. The present review focuses on these two phenomena, and summarizes observations supporting their existence, and discusses the linkage between them in light of recent results obtained from experiments utilizing microbeams.

Melatonin: an established antioxidant worthy of use in clinical trials

Oxidative stress plays a key role in the pathogenesis of aging and many metabolic diseases; therefore, an effective antioxidant therapy would be of great importance in these circumstances. Nutritional, environmental, and chemical factors can induce the overproduction of the superoxide anion radical in both the cytosol and mitochondria. This is the first and key event that leads to the activation of pathways involved in the development of several metabolic diseases that are related to oxidative stress. As oxidation of essential molecules continues, it turns to nitrooxidative stress because of the involvement of nitric oxide in pathogenic processes. Once peroxynitrite forms, it damages via two distinctive mechanisms. First, it has direct toxic effects leading to lipid peroxidation, protein oxidation, and DNA damage. This mechanism involves the induction of several transcription factors leading to cytokine-induced chronic inflammation. Classic antioxidants, including vitamins A, C, and E, have often failed to exhibit beneficial effects in metabolic diseases and aging. Melatonin is a multifunctional indolamine that counteracts virtually all pathophysiologic steps and displays significant beneficial actions against peroxynitrite-induced cellular toxicity. This protection is related to melatonin's antioxidative and antiinflammatory properties. Melatonin has the capability of scavenging both oxygen- and nitrogen-based reactants, including those formed from peroxynitrite, and blocking transcriptional factors, which induce proinflammatory cytokines. Accumulating evidence suggests that this nontoxic indolamine may be useful either as a sole treatment or in conjunction with other treatments for inhibiting the biohazardous actions of nitrooxidative stress.

Inflammatory and transcriptional roles of poly (ADP-ribose) polymerase in ventilator-induced lung injury

Introduction

Poly (ADP-ribose) polymerase (PARP) participates in inflammation by cellular necrosis and the nuclear factor-kappa-B (NF-κB)-dependent transcription. The purpose of this study was to examine the roles of PARP in ventilator-induced lung injury (VILI) in normal mice lung.

Methods

Male C57BL/6 mice were divided into four groups: sham tracheostomized (sham), lung-protective ventilation (LPV), VILI, and VILI with PARP inhibitor PJ34 pretreatment (PJ34+VILI) groups. Mechanical ventilation (MV) settings were peak inspiratory pressure (PIP) 15 cm H₂O + positive end-expiratory pressure (PEEP) 3 cm H₂O + 90 breaths per minute for the LPV group and PIP 40 cm H₂O + PEEP 0 cm H₂O + 90 breaths per minute for the VILI and PJ34+VILI groups. After 2 hours of MV, acute lung injury (ALI) score, wet-to-dry (W/D) weight ratio, PARP activity, and dynamic compliance (C_D) were recorded. Tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), myeloperoxidase (MPO) activity, and nitrite/nitrate (NO_X) in the bronchoalveolar lavage fluid and NF-κB DNA-binding activity in tissue homogenates were measured.

Results

The VILI group showed higher ALI score, W/D weight ratio, MPO activity, NO_X, and concentrations of TNF-α and IL-6 along with lower C_D than the sham and LPV groups (P < 0.05). In the PJ34+VILI group, PJ34 pretreatment improved all histopathologic ALI, inflammatory profiles, and pulmonary dynamics (P < 0.05). NF-κB activity was increased in the VILI group as compared with the sham and LPV groups (P < 0.05) and was decreased in the PJ34+VILI group as compared with the VILI group (P = 0.009). Changes in all parameters were closely correlated with the PARP activity (P < 0.05).

Conclusion

Overactivation of PARP plays an important role in the inflammatory and transcriptional pathogenesis of VILI, and PARP inhibition has potentially beneficial effects on the prevention and treatment of VILI.

Effect of 3-amino benzamide, a poly(adenosine diphosphate-ribose) polymerase inhibitor, in experimental caustic esophageal burn

INTRODUCTION

The enzyme poly(adenosine diphosphate-ribose) polymerase affects the repair of DNA in damaged cells. However, its activation in damaged cells can lead to adenosine triphosphate depletion and death. This study was designed to investigate the efficacy of 3-amino benzamide (3-AB), a poly(adenosine diphosphate-ribose) polymerase inhibitor, on the prevention of esophageal damage and stricture-formation development after esophageal caustic injuries in rat.

MATERIALS AND METHODS

Forty-five rats were allocated into 3 groups: sham-operated, untreated, and treated groups. Caustic esophageal burn was created by instilling 15% NaOH to the distal esophagus. The rats were left untreated or treated with 3-AB 10 mg/kg per day intraperitoneally. All rats were killed on the 28th day. Efficacy of the treatment was assessed by measuring the stenosis index and histopathologic damage score and biochemically by determining tissue hydroxyproline content, superoxide dismutase (SOD), glutathione peroxidase (GPx), malondialdehyde (MDA), and protein carbonyl content (PCC) in esophageal homogenates.

RESULTS

Treatment with 3-AB decreased the stenosis index and histopathologic damage score seen in caustic esophageal burn rats. Hydroxyproline level was significantly higher in the untreated group as compared with the group treated with 3-AB. Caustic esophageal burn increased MDA and PCC levels and also decreased SOD and GPx enzyme activities. On the contrary, 3-AB treatment decreased the elevated MDA and PCC levels and also increased the reduced SOD and GPx enzyme activities.

CONCLUSION

3-Amino benzamide has a preventive effect in the development of fibrosis by decreasing tissue damage and increasing the antioxidant enzyme activity in an experimental model of corrosive esophagitis in rats.

Prolonged exposures of cerebellar granule neurons to S-nitroso-N-acetylpenicillamine (SNAP) induce neuronal damage independently of peroxynitrite

Nitric oxide (NO) induces cell proliferation or cell death, depending on the cell type involved, the isoform of nitric oxide synthase activated, and its cellular localisation. In neurons, the damaging effect of NO is usually attributed to the highly toxic peroxynitrite, formed by its reaction with superoxide. Peroxynitrite induces DNA damage and consequently the activation of poly (ADP-ribose) polymerase (PARP). This study set out to examine the contribution of peroxynitrite to the damage induced in cerebellar granule neurons (CGNs) by treatment with the NO donor S-nitroso-N-acetylpenicillamine (SNAP), for short (6 h) or prolonged (24 h) exposures. The Alamar blue assay was used to quantify CGN viability, which was also assessed by morphological examination. SNAP (10 microM-1 mM) induced a concentration- and time-dependent reduction of CGN viability, with associated damage to cell bodies and neurite processes evident following 100 microM SNAP treatments. Damage from 6 h exposures was prevented by the presence of haemoglobin (a NO scavenger), uric acid (a peroxynitrite scavenger), melatonin (a non-specific antioxidant), and by cyclosporin A (a permeability transition pore blocker). It was reduced by the PARP-1 inhibitor 3,4-dihydro-5-[4-(1-piperidinyl)butoxyl]-1(2H)-isoquinolinone (DPQ), whilst superoxide dismutase (SOD) potentiated the effects. Following 24 h exposure to SNAP, damage was only partially blocked by haemoglobin, melatonin, cyclosporin A and DPQ, but was not affected by uric acid or SOD. The data suggest that short exposure to NO induces neuronal damage through peroxynitrite produced by its interaction with superoxide, whereas a longer exposure to NO can induce damage partly by a mechanism which is independent of peroxynitrite formation.

Activation and modulation of cardiac poly-adenosine diphosphate ribose polymerase activity in a rat model of brain death

DNA damage during transplantation can activate poly-adenosine diphosphate ribose polymerase (PARP) resulting in the generation of polymers of adenosine diphosphate-ribose (PAR). Excessive linkage of PAR to nuclear proteins can induce cell death, thereby limiting the function of transplanted organs. This study uses a rat model of brain death to determine the profile of PARP activation and whether mechanisms that lead to cell death can be ameliorated by appropriate donor resuscitation. The expression of PAR-linked nuclear proteins within cardiac myocytes was greatly increased after the induction of donor brain death. Importantly, infusion of noradrenaline or vasopressin to normalize the chronic hypotension produced by brain death reduced the expression of PAR to a level below baseline. These data suggest that chronic hypotension after donor brain death has the potential to limit cardiac function through the activation of PARP; however, this early cause of graft damage can be mitigated by appropriate donor resuscitation.

Neuronal nitric oxide synthase inhibition attenuates cardiopulmonary dysfunctions after combined burn and smoke inhalation injury in sheep

OBJECTIVE

We hypothesized that nitric oxide derived from the neuronal nitric oxide synthase (NOS) is responsible for much of the injury resulting from skin burn and smoke inhalation. Therefore, we aimed to examine the effects of selective neuronal NOS inhibition on cardiopulmonary functions and cellular injury in sheep with acute respiratory distress syndrome secondary to combined burn and smoke inhalation injury.

DESIGN

Prospective, randomized, controlled laboratory experiment.

SETTING

Investigational intensive care unit.

SUBJECTS

A total of 22 chronically instrumented adult ewes.

INTERVENTIONS

Sheep were randomly assigned to either healthy controls (sham), injured controls (40% third-degree flame burn; 48 breaths of cotton smoke), or an injury group treated with the specific neuronal NOS inhibitor 7-nitroindazole (1 mg x kg(-1) x hr(-1)) from 1 hr postinjury to the end of the 48-hr study period. Hypoxic pulmonary vasoconstriction was assessed as decrease in left pulmonary blood flow in response to single-lung hypoxic challenges (100% nitrogen) at baseline, 24 hrs, and 48 hrs.

MEASUREMENTS AND MAIN RESULTS

The combination injury contributed to a approximately 90% loss of hypoxic pulmonary vasoconstriction and was associated with significant pulmonary shunting and death of one animal. The increase in nitrate/nitrite plasma levels in injured controls (12 hrs: 17 +/- 2 vs. 6 +/- 1 microM in sham animals; p < .001) was linked to increases in inducible NOS messenger RNA and 3-nitrotyrosine formation in lung tissue (48 hrs: 22 +/- 1 vs. 0.8 +/- 0.3 nM in sham animals; p < .001). 7-Nitroindazole treatment prevented the injury-associated changes in inducible NOS messenger RNA, nitrate/nitrite, and 3-nitrotyrosine, thereby attenuating the loss of hypoxic pulmonary vasoconstriction and improving gas exchange. In addition, 7-nitroindazole decreased lung tissue concentrations of hemoxygenase-1 and ameliorated myocardial depression, airway obstruction, pulmonary edema, ventilatory pressures, and histopathologic changes seen in injured controls.

CONCLUSIONS

The present study provides evidence that neuronal NOS-derived nitric oxide plays a pivotal role in the pathogenesis of acute respiratory distress syndrome resulting from combined burn and smoke inhalation injury.

Poly(ADP-ribose) polymerase activity in different pathologies--the link to inflammation and infarction

DNA repair and aging are two phenomena closely connected to each other. The poly(ADP-ribosyl)ation reaction has been implicated in both of them. Poly(ADP-ribose) was originally discovered as an enzymatic reaction product after DNA damage. Soon it became evident that it is necessary for regulation of different repair pathways. Also, evidence accumulated that poly(ADP-ribose) formation capacity is at least correlated with the life span of mammalian species. As a NAD(+)-consuming process, poly(ADP-ribosyl)ation can lead to cell death by energy depletion. This finding opened the area for investigation of poly(ADP-ribose) polymerase activity and polymer formation in pathologies. This review provides an introduction into the wide and complex field of poly(ADP-ribosyl)ation in different pathologies with regards of cell death regulation, inflammation and resulting tissue damage.

Mitochondria as a target for the cardioprotective effects of nitric oxide in ischemia-reperfusion injury

During cardiac ischemia-reperfusion (IR) injury, excessive generation of reactive oxygen species (ROS) and overload of Ca(2+) at the mitochondrial level both lead to opening of the mitochondrial permeability transition (PT) pore on reperfusion. This can result in the depletion of ATP, irreversible oxidation of proteins, lipids, and DNA within the cardiomyocyte, and can trigger cell-death pathways. In contrast, mitochondria are also implicated in the cardioprotective signaling processes of ischemic preconditioning (IPC), to prevent IR-related pathology. Nitric oxide (NO*) has emerged as a potent effector molecule for a variety of cardioprotective strategies, including IPC. Whereas NO* is most noted for its activation of the "classic" soluble guanylate cyclase (sGC) signaling pathway, emerging evidence indicates that NO can directly act on mitochondria, independent of the sGC pathway, affording acute cardioprotection against IR injury. These direct effects of NO* on mitochondria are the focus of this review.

How DMSO, a widely used solvent, affects spinal cord injury

The aim of this experimental study was to investigate whether dimethylsulfoxide (DMSO) has protective effects on spinal cord ischemia-reperfusion (I/R) injury. New Zealand rabbits were enrolled in the study. In addition to the control group, the study group received 0.1 mL/kg DMSO prior to ischemia. Blood samples were taken to obtain nitrite-nitrate levels during the surgical procedure. After neurological evaluation at 24 hr of reperfusion, lumbar spinal cords were removed for electron microscopic evaluation and malondialdehyde and myeloperoxidase measurements. The mean Tarlov score of the DMSO group was higher than that of the control group. Electron microscopic examination was carried out with tissue samples at 24 hr of reperfusion. The DMSO group had better preservation with the electron microscopic scoring compared to the control group. Malondialdehyde and myeloperoxidase levels were decreased in the DMSO group compared to the control group. Nitrite-nitrate levels were also lower in the DMSO group compared to control at 5 and 30 min of reperfusion. This study demonstrates a considerable neuroprotective effect of DMSO on neurological, biochemical, and histopathological analyses during periods of spinal cord I/R injury in rabbits. Although there was a difference between the DMSO and control groups in all measured parameters in our study, this was not statistically significant. DMSO deserves further investigation related with spinal cord ischemia and reperfusion. We should also consider the effect of DMSO when we use it as a solvent or vehicle during experimental I/R models.

Therapeutic effect of a poly(ADP-ribose) polymerase-1 inhibitor on experimental arthritis by downregulating inflammation and Th1 response

Poly(ADP-ribose) polymerase-1 (PARP-1) synthesizes and transfers ADP ribose polymers to target proteins, and regulates DNA repair and genomic integrity maintenance. PARP-1 also plays a crucial role in the progression of the inflammatory response, and its inhibition confers protection in several models of inflammatory disorders. Here, we investigate the impact of a selective PARP-1 inhibitor in experimental arthritis. PARP-1 inhibition with 5-aminoisoquinolinone (AIQ) significantly reduces incidence and severity of established collagen-induced arthritis, completely abrogating joint swelling and destruction of cartilage and bone. The therapeutic effect of AIQ is associated with a striking reduction of the two deleterious components of the disease, i.e. the Th1-driven autoimmune and inflammatory responses. AIQ downregulates the production of various inflammatory cytokines and chemokines, decreases the antigen-specific Th1-cell expansion, and induces the production of the anti-inflammatory cytokine IL-10. Our results provide evidence of the contribution of PARP-1 to the progression of arthritis and identify this protein as a potential therapeutic target for the treatment of rheumatoid arthritis.

Contribution of poly(ADP-ribose) polymerase to postischemic blood-brain barrier damage in rats

The nuclear enzyme poly(ADP-ribose) polymerase (PARP) is activated by oxidative stress and plays a significant role in postischemic brain injury. We assessed the contribution of PARP activation to the blood-brain barrier (BBB) disruption and edema formation after ischemia-reperfusion. In male Wistar rats, global cerebral ischemia was achieved by occluding the carotid arteries and lowering arterial blood pressure for 20 mins. The animals were treated with saline or with the PARP inhibitor N-(6-oxo-5,6-dihydrophenanthridin-2-yl)-N, N-dimethylacetamide.HCl (PJ34); (10 mg/kg, i.v.) before ischemia. After 40 mins, 24, and 48 h of reperfusion, the permeability of the cortical BBB was determined after Evans Blue (EB) and Na-fluorescein (NaF) administration. The water content of the brain was also measured. The permeability of the BBB for EB increased after ischemia-reperfusion compared with the nonischemic animals after 24 and 48 h reperfusion but PARP inhibition attenuated this increase at 48 h (nonischemic: 170+/-9, saline: 760+/-95, PJ34: 472+/-61 ng/mg tissue). The extravasation of NaF showed similar changes and PJ34 post-treatment attenuated the permeability increase even at 24 h. PARP inhibition decreased the brain edema seen at 48 h. Because PARP has proinflammatory properties, the neutrophil infiltration of the cortex was determined, which showed lower values after PJ34 treatment. Furthermore, PJ34 treatment decreased the loss of the tight junction protein occludin at 24 and 48 h. The inhibition of PARP activity accompanied by reduced post-ischemic BBB disturbance and decreased edema formation suggests a significant role of this enzyme in the development of cerebral vascular malfunction

Pharmacological inhibition of PARP-1 reduces alpha-synuclein- and MPP+-induced cytotoxicity in Parkinson's disease in vitro models

Treatments based on pharmacological inhibition of poly(ADP-ribose) polymerase-1 (PARP-1) have been suggested for a broad variety of human disorders, including Parkinson's disease (PD). The neuroprotective effects underlying the efficacy of PARP-1 inhibitors in PD models suggest a role for PARP-1 in neurodegeneration. In this study, we assessed the efficacy of PARP-1 inhibition in two distinct PD models. First, we tested a panel of small molecule PARP-1 inhibitors in alpha-synuclein (aSyn) cytotoxicity assay, where we observed compound-dependent ameliorating effects. Next, we tested the same panel in primary ventral mesencephalic neuronal cultures, treated with MPP(+). Dopaminergic neurons, the primary cells affected in PD, were selected and subjected to analysis. A significant ameliorating effect was achieved only with a highly potent PARP-1 inhibitor. Our data implicates aberrant PARP-1 function in different pathways of neurodegeneration. Further, our results suggest a rationale for the development of highly potent, bio-available, brain-penetrable PARP-1 inhibitors to provide therapeutic benefits for Parkinson's patients.