Role of poly-ADP ribosyltransferase activation in the vascular contractile and energetic failure elicited by exogenous and endogenous nitric oxide and peroxynitrite

Role of Gasotransmitters in Inflammatory Edema

Significance: Nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) are, to date, the identified members of the gasotransmitter family, which consists of gaseous signaling molecules that play central roles in the regulation of a wide variety of physiological and pathophysiological processes, including inflammatory edema. Recent Advances: Recent studies show the potential anti-inflammatory and antiedematogenic effects of NO-, CO-, and H2S-donors in vivo. In general, it has been observed that the therapeutical effects of NO-donors are more relevant when administered at low doses at the onset of the inflammatory process. Regarding CO-donors, their antiedematogenic effects are mainly associated with inhibition of proinflammatory mediators (such as inducible NO synthase [iNOS]-derived NO), and the observed protective effects of H2S-donors seem to be mediated by reducing some proinflammatory enzyme activities. Critical Issues: The most recent investigations focus on the interactions among the gasotransmitters under different pathophysiological conditions. However, the biochemical/pharmacological nature of these interactions is neither general nor fully understood, although specifically dependent on the site where the inflammatory edema occurs. Future Directions: Considering the nature of the involved mechanisms, a deeper knowledge of the interactions among the gasotransmitters is mandatory. In addition, the development of new pharmacological tools, either donors or synthesis inhibitors of the three gasotransmitters, will certainly aid the basic investigations and open new strategies for the therapeutic treatment of inflammatory edema. Antioxid. Redox Signal. 40, 272-291.

Effects of the PARP Inhibitor Olaparib on the Response of Human Peripheral Blood Leukocytes to Bacterial Challenge or Oxidative Stress

Prior studies demonstrate the activation of poly-(ADP-ribose) polymerase 1 (PARP1) in various pathophysiological conditions, including sepsis. We have assessed the effect of olaparib, a clinically used PARP1 inhibitor, on the responses of human peripheral blood leukocytes (PBMCs) obtained from healthy volunteers in response to challenging with live bacteria, bacterial lipopolysaccharide (LPS), or oxidative stress (hydrogen peroxide, H₂O₂). The viability of PBMCs exposed to olaparib or to the earlier generation PARP inhibitor PJ-34 (0.1–1000 µM) was monitored using Annexin V and 7-aminoactinomycin D. To evaluate the effects of olaparib on the expression of PARP1 and its effects on protein PARylation, PBMCs were stimulated with Staphylococcus aureus with or without olaparib (1–10 μM). Changes in cellular levels of nicotinamide adenine dinucleotide (NAD⁺) and adenosine triphosphate (ATP), as well as changes in mitochondrial membrane potential (MMP), were measured in PBMCs exposed to H₂O₂. Bacterial killing was evaluated in PBMCs and polymorphonuclear leukocytes (PMNs) incubated with S. aureus. Cytokine production was measured in supernatants using a cytometric bead array. Reactive oxygen species (ROS), nitric oxide (NO) production, and phagocytic activity of monocytes and neutrophils were measured in whole blood. For ROS and NO production, samples were incubated with heat-killed S. aureus; phagocytic activity was assessed using killed Escherichia coli conjugated to FITC. Olaparib (0.1–100 µM) did not adversely affect lymphocyte viability. Olaparib also did not interfere with PARP1 expression but inhibits S. aureus-induced protein PARylation. In cells challenged with H₂O₂, olaparib prevented NAD⁺ and ATP depletion and attenuated mitochondrial membrane depolarization. LPS-induced production of TNF-α, MIP-1α, and IL-10 by PBMCs was also reduced by olaparib. Monocytes and neutrophils displayed significant increases in the production of ROS and NO after stimulation with S. aureus and phagocytic (E. coli) and microbicidal activity, and these responses were not suppressed by olaparib. We conclude that, at clinically relevant concentrations, olaparib exerts cytoprotective effects and modulates inflammatory cytokine production without exerting adverse effects on the cells’ ability to phagocytose or eradicate pathogens. The current data support the concept of repurposing olaparib as a potential experimental therapy for septic shock.

Repurposing of Clinically Approved Poly-(ADP-Ribose) Polymerase Inhibitors for the Therapy of Sepsis

ABSTRACT

Sepsis' pathogenesis involves multiple mechanisms that lead to a dysregulation of the host's response. Significant efforts have been made in search of interventions that can reverse this situation and increase patient survival. Poly (ADP-polymerase) (PARP) is a constitutive nuclear and mitochondrial enzyme, which functions as a co-activator and co-repressor of gene transcription, thus regulating the production of inflammatory mediators. Several studies have already demonstrated an overactivation of PARP1 in various human pathophysiological conditions and that its inhibition has benefits in regulating intracellular processes. The PARP inhibitor olaparib, originally developed for cancer therapy, paved the way for the expansion of its clinical use for nononcological indications. In this review we discuss sepsis as one of the possible indications for the use of olaparib and other clinically approved PARP inhibitors as modulators of the inflammatory response and cellular dysfunction. The benefit of olaparib and other clinically approved PARP inhibitors has already been demonstrated in several experimental models of human diseases, such as neurodegeneration and neuroinflammation, acute hepatitis, skeletal muscle disorders, aging and acute ischemic stroke, protecting, for example, from the deterioration of the blood-brain barrier, restoring the cellular levels of NAD+, improving mitochondrial function and biogenesis and, among other effects, reducing oxidative stress and pro-inflammatory mediators, such as TNF-α, IL1-β, IL-6, and VCAM1. These data demonstrated that repositioning of clinically approved PARP inhibitors may be effective in protecting against hemodynamic dysfunction, metabolic dysfunction, and multiple organ failure in patients with sepsis. Age and gender affect the response to PARP inhibitors, the mechanisms underlying the lack of many protective effects in females and aged animals should be further investigated and be cautiously considered in designing clinical trials.

Poly(ADP-Ribose) Polymerase Inhibition in Acute Lung Injury. A Reemerging Concept

PARP1, the major isoform of a family of ADP-ribosylating enzymes, has been implicated in the regulation of various biological processes including DNA repair, gene transcription, and cell death. The concept that PARP1 becomes activated in acute lung injury (ALI) and that pharmacological inhibition or genetic deletion of this enzyme can provide therapeutic benefits emerged over 20 years ago. The current article provides an overview of the cellular mechanisms involved in the pathogenetic roles of PARP1 in ALI and provides an overview of the preclinical data supporting the efficacy of PARP (poly[ADP-ribose] polymerase) inhibitors. In recent years, several ultrapotent PARP inhibitors have been approved for clinical use (for the therapy of various oncological diseases): these newly-approved PARP inhibitors were recently reported to show efficacy in animal models of ALI. These observations offer the possibility of therapeutic repurposing of these inhibitors for patients with ALI. The current article lays out a potential roadmap for such repurposing efforts. In addition, the article also overviews the scientific basis of potentially applying PARP inhibitors for the experimental therapy of viral ALI, such as coronavirus disease (COVID-19)-associated ALI.

Differential impacts of brain stem oxidative stress and nitrosative stress on sympathetic vasomotor tone

Based on work-done in the rostral ventrolateral medulla (RVLM), this review presents four lessons learnt from studying the differential impacts of oxidative stress and nitrosative stress on sympathetic vasomotor tone and their clinical and therapeutic implications. The first lesson is that an increase in sympathetic vasomotor tone because of augmented oxidative stress in the RVLM is responsible for the generation of neurogenic hypertension. On the other hand, a shift from oxidative stress to nitrosative stress in the RVLM underpins the succession of increase to decrease in sympathetic vasomotor tone during the progression towards brain stem death. The second lesson is that, by having different cellular sources, regulatory mechanisms on synthesis and degradation, kinetics of chemical reactions, and downstream signaling pathways, reactive oxygen species and reactive nitrogen species should not be regarded as a singular moiety. The third lesson is that well-defined differential roles of oxidative stress and nitrosative stress with distinct regulatory mechanisms in the RVLM during neurogenic hypertension and brain stem death clearly denote that they are not interchangeable phenomena with unified cellular actions. Special attention must be paid to their beneficial or detrimental roles under a specific disease or a particular time-window of that disease. The fourth lesson is that, to be successful, future antioxidant therapies against neurogenic hypertension must take into consideration the much more complicated picture than that presented in this review on the generation, maintenance, regulation or modulation of the sympathetic vasomotor tone. The identification that the progression towards brain stem death entails a shift from oxidative stress to nitrosative stress in the RVLM may open a new vista for therapeutic intervention to slow down this transition.

The PARP inhibitor olaparib exerts beneficial effects in mice subjected to cecal ligature and puncture and in cells subjected to oxidative stress without impairing DNA integrity: A potential opportunity for repurposing a clinically used oncological drug for the experimental therapy of sepsis

Poly(ADP-ribose) polymerase (PARP) is involved in the pathogenesis of cell dysfunction, inflammation and organ failure during septic shock. The goal of the current study was to investigate the efficacy and safety of the clinically approved PARP inhibitor olaparib in experimental models of oxidative stress in vitro and in sepsis in vivo. In mice subjected to cecal ligation and puncture (CLP) organ injury markers, circulating and splenic immune cell distributions, circulating mediators, DNA integrity and survival was measured. In U937 cells subjected to oxidative stress, cellular bioenergetics, viability and DNA integrity were measured. Olaparib was used to inhibit PARP. The results show that in adult male mice subjected to CLP, olaparib (1-10 mg/kg i.p.) improved multiorgan dysfunction. Olaparib treatment reduced the degree of bacterial CFUs. Olaparib attenuated the increases in the levels of several circulating mediators in the plasma. In the spleen, the number of CD4+ and CD8+ lymphocytes were reduced in response to CLP; this reduction was inhibited by olaparib treatment. Treg but not Th17 lymphocytes increased in response to CLP; these cell populations were reduced in sepsis when the animals received olaparib. The Th17/Treg ratio was lower in CLP-olaparib group than in the CLP control group. Analysis of miRNA expression identified a multitude of changes in spleen and circulating white blood cell miRNA levels after CLP; olaparib treatment selectively modulated these responses. Olaparib extended the survival rate of mice subjected to CLP. In contrast to males, in female mice olaparib did not have significant protective effects in CLP. In aged mice olaparib exerted beneficial effects that were less pronounced than the effects obtained in young adult males. In in vitro experiments in U937 cells subjected to oxidative stress, olaparib (1-100 μM) inhibited PARP activity, protected against the loss of cell viability, preserved NAD⁺ levels and improved cellular bioenergetics. In none of the in vivo or in vitro experiments did we observe any adverse effects of olaparib on nuclear or mitochondrial DNA integrity. In conclusion, olaparib improves organ function and extends survival in septic shock. Repurposing and eventual clinical introduction of this clinically approved PARP inhibitor may be warranted for the experimental therapy of septic shock.

The role of the exogenous supply of adenosine triphosphate in the expression of Bax and Bcl2L1 genes in intestinal ischemia and reperfusion in rats 1

PURPOSE

To investigate the role of the exogenous supply of adenosine triphosphate (ATP) in the expression of Bax and Bcl2L1 genes in intestinal ischemia and reperfusion (IR) in rats.

METHODS

The study was designed as a randomized controlled trial with a blinded assessment of the outcome. Eighteen adult male Wistar-EPM1 rats were housed under controlled temperature and light conditions (22-23°C, 12 h light/dark cycle). The animals were randomly divided into 3 groups: 1. Sham group (SG): no clamping of the superior mesenteric artery; 2. Ischemia and reperfusion group (IRG): 3. Ischemia and reperfusion plus ATP (IRG + ATP). ATP was injected in the femoral vein before and after ischemia. Afterwards, intestinal segments were appropriately removed and processed for Endothelial Cell Biology Rat RT2 Profiler PCR Array.

RESULTS

ATP promoted the upregulation of Bcl2L1 gene expression, whereas it did not have significant effects on Bax gene expression. In addition, the relation of Bax/Bcl2L1 gene expression in the IRG group was 1.39, whereas it was 0.43 in the IRG + ATP group. Bcl2L1 plays a crucial role in protecting against intestinal apoptosis after ischemia and reperfusion. Increased Bcl2L1 expression can inhibit apoptosis while decreased Bcl2L1 expression can trigger apoptosis.

CONCLUSION

Adenosine triphosphate was associated with antiapoptotic effects on the rat intestine ischemia and reperfusion by upregulating of Bcl2L1 gene expression.

Beneficial treatment effects of dietary nitrate supplementation on testicular injury in streptozotocin-induced diabetic male rats

RESEARCH QUESTION

Do low doses of dietary nitrate help to attenuate the progression of diabetic reproductive disorders in streptozotocin-induced diabetic male rats?

DESIGN

Fifty male Wistar rats were divided into five groups: controls receiving distilled water; controls receiving 100 mg/l nitrate in distilled water; diabetic rats receiving distilled water; diabetic rats receiving insulin 2-4 U/day of neutral protamine hagedorn insulin; and diabetic rats receiving 100 mg/l nitrate in distilled water. Diabetes was induced by 45 mg/kg streptozotocin. Nitrate and insulin treatment were started 4 weeks after diabetes induction for 8 weeks. Serum insulin, nitrogen oxide, stereology of testis, apoptosis, sperm parameters, and mRNA expression of Pdcd4, Pacs2, p53 and miR-449a were assessed at the end of the study.

RESULTS

Blood glucose, apoptotic index of seminiferous tubules and expression of p53, Pdcd4, and Pacs2 mRNA were significantly higher in the diabetic rats (P < 0.001). Decreased body weight, serum insulin and nitrogen oxide level, and miR-449a were observed in the diabetic group (P < 0.01 for insulin; P < 0.001 for others). Most sperm parameters and stereological results differed between diabetic and control rats; nitrate recovered almost all these alterations, including dead spermatozoa, sperm motility grade, sperm deformity index, spermatozoa with damaged DNA, malformations in abnormal spermatozoa, total volume of seminiferous tubule, germinal epithelium, capsule, lumen, interstitial tissue, seminiferous tubule diameter, germinal epithelium height, the number of spermatogenic, Sertoli and Leydig cells.

CONCLUSIONS

Treatment with sodium nitrate could modulate apoptosis, which is a major cause of diabetic testicular disorder. These experiments suggest that nitric oxide plays an important role in the function of the reproductive system.

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.

Causes of upregulation of glycolysis in lymphocytes upon stimulation. A comparison with other cell types

In this review, we revisit the metabolic shift from respiration to glycolysis in lymphocytes upon activation, which is known as the Warburg effect in tumour cells. We compare the situation in lymphocytes with those in several other cell types, such as muscle cells, Kupffer cells, microglia cells, astrocytes, stem cells, tumour cells and various unicellular organisms (e.g. yeasts). We critically discuss and compare several explanations put forward in the literature for the observation that proliferating cells adopt this apparently less efficient pathway: hypoxia, poisoning of competitors by end products, higher ATP production rate, higher precursor supply, regulatory effects, and avoiding harmful effects (e.g. by reactive oxygen species). We conclude that in the case of lymphocytes, increased ATP production rate and precursor supply are the main advantages of upregulating glycolysis.

Antioxidants inhibit the inflammatory and apoptotic processes in an intermittent hypoxia model of sleep apnea

BACKGROUND

Sleep apnea causes intermittent hypoxia (IH). We aimed to investigate the proteins related to oxidative stress, inflammation and apoptosis in liver tissue subjected to IH as a simulation of sleep apnea in conjunction with the administration of either melatonin (MEL, 200 μL/kg) or N-acetylcysteine (NAC, 10 mg/kg).

METHODS

Seventy-two adult male Balb-C mice were divided: simulation of IH (SIH), SIH + MEL, SIH + NAC, IH, IH + MEL and IH + NAC. The animals were subjected to simulations of sleep apnea for 8 h a day for 35 days. The data were analyzed with ANOVA and Tukey tests with the significance set at p < 0.05.

RESULTS

In IH, there was a significant increase in oxidative stress and expression of HIF-1a. In addition, we observed increase in the activation levels of NF-kB. This increase may be responsible for the increased expression of TNF-alpha and iNOS as well as the significant increase of VEGF signaling and expression of caspase-3 and caspase-6, which suggests an increase in apoptosis. In the groups treated with antioxidants, the analysis showed that the enzyme activity and protein levels were similar to those of the non-simulated group.

CONCLUSIONS

Thus, we show that IH causes liver inflammation and apoptosis, which may be protected with either MEL or NAC.

Pelagia noctiluca (Scyphozoa) crude venom injection elicits oxidative stress and inflammatory response in rats

Cnidarian toxins represent a rich source of biologically active compounds. Since they may act via oxidative stress events, the aim of the present study was to verify whether crude venom, extracted from the jellyfish Pelagia noctiluca, elicits inflammation and oxidative stress processes, known to be mediated by Reactive Oxygen Species (ROS) production, in rats. In a first set of experiments, the animals were injected with crude venom (at three different doses 6, 30 and 60 µg/kg, suspended in saline solution, i.v.) to test the mortality and possible blood pressure changes. In a second set of experiments, to confirm that Pelagia noctiluca crude venom enhances ROS formation and may contribute to the pathophysiology of inflammation, crude venom-injected animals (30 µg/kg) were also treated with tempol, a powerful antioxidant (100 mg/kg i.p., 30 and 60 min after crude venom). Administration of tempol after crude venom challenge, caused a significant reduction of each parameter related to inflammation. The potential effect of Pelagia noctiluca crude venom in the systemic inflammation process has been here demonstrated, adding novel information about its biological activity.

Uric acid in multiple sclerosis

Peroxynitrite, a reactive oxidant formed by the reaction of nitric oxide with superoxide at sites of inflammation in multiple sclerosis (MS), is capable of damaging tissues and cells. Uric acid, a natural scavenger of peroxynitrite, reduces inflammatory demyelination in experimental allergic encephalomyelitis. Some studies reported lower serum levels of uric acid in MS patients compared with controls, whereas other studies found no difference. A critical appraisal of these studies favors the view that reduced uric acid in MS is secondary to its peroxynitrite scavenging activity during inflammatory disease activity, rather than a primary deficiency. Serum uric acid levels could be used as a biomarker for monitoring disease activity in MS. Therapeutic strategies aimed at raising serum uric acid levels may have a glial/neuroprotective effect on MS patients.

Therapeutic applications of PARP inhibitors: anticancer therapy and beyond

The aim of this article is to describe the current and potential clinical translation of pharmacological inhibitors of poly(ADP-ribose) polymerase (PARP) for the therapy of various diseases. The first section of the present review summarizes the available preclinical and clinical data with PARP inhibitors in various forms of cancer. In this context, the role of PARP in single-strand DNA break repair is relevant, leading to replication-associated lesions that cannot be repaired if homologous recombination repair (HRR) is defective, and the synthetic lethality of PARP inhibitors in HRR-defective cancer. HRR defects are classically associated with BRCA1 and 2 mutations associated with familial breast and ovarian cancer, but there may be many other causes of HRR defects. Thus, PARP inhibitors may be the drugs of choice for BRCA mutant breast and ovarian cancers, and extend beyond these tumors if appropriate biomarkers can be developed to identify HRR defects. Multiple lines of preclinical data demonstrate that PARP inhibition increases cytotoxicity and tumor growth delay in combination with temozolomide, topoisomerase inhibitors and ionizing radiation. Both single agent and combination clinical trials are underway. The final part of the first section of the present review summarizes the current status of the various PARP inhibitors that are in various stages of clinical development. The second section of the present review summarizes the role of PARP in selected non-oncologic indications. In a number of severe, acute diseases (such as stroke, neurotrauma, circulatory shock and acute myocardial infarction) the clinical translatability of PARP inhibition is supported by multiple lines of preclinical data, as well as observational data demonstrating PARP activation in human tissue samples. In these disease indications, PARP overactivation due to oxidative and nitrative stress drives cell necrosis and pro-inflammatory gene expression, which contributes to disease pathology. Accordingly, multiple lines of preclinical data indicate the efficacy of PARP inhibitors to preserve viable tissue and to down-regulate inflammatory responses. As the clinical trials with PARP inhibitors in various forms of cancer progress, it is hoped that a second line of clinical investigations, aimed at testing of PARP inhibitors for various non-oncologic indications, will be initiated, as well.

Simulating sleep apnea by exposure to intermittent hypoxia induces inflammation in the lung and liver

Sleep apnea is a breathing disorder that results from momentary and cyclic collapse of the upper airway, leading to intermittent hypoxia (IH). IH can lead to the formation of free radicals that increase oxidative stress, and this mechanism may explain the association between central sleep apnea and nonalcoholic steatohepatitis. We assessed the level of inflammation in the lung and liver tissue from animals subjected to intermittent hypoxia and simulated sleep apnea. A total of 12 C57BL/6 mice were divided into two groups and then exposed to IH (n = 6) or a simulated IH (SIH) (n = 6) for 35 days. We observed an increase in oxidative damage and other changes to endogenous antioxidant enzymes in mice exposed to IH. Specifically, the expression of multiple transcription factors, including hypoxia inducible factor (HIF-1α), nuclear factor kappa B (NF-κB), and tumor necrosis factor (TNF-α), inducible NO synthase (iNOS), vascular endothelial growth factor (VEGF), and cleaved caspase 3 were shown to be increased in the IH group. Overall, we found that exposure to intermittent hypoxia for 35 days by simulating sleep apnea leads to oxidative stress, inflammation, and increased activity of caspase 3 in the liver and lung.

Inhibition of poly(ADP-ribose) polymerase attenuates acute kidney injury in sodium taurocholate-induced acute pancreatitis in rats

OBJECTIVES

The aim of our present study was to investigate the efficacy of poly(adenosine diphosphate-ribose) polymerase (PARP) inhibition in the development of acute kidney injury in an experimental model of severe acute pancreatitis induced by retrograde infusion of sodium taurocholate into the bile-pancreatic duct.

METHODS

Severity of pancreatitis was evaluated by serum amylase, lipase, tumor necrosis factor α, interleukin-1β, interleukin-6, and histological grading. The following markers of renal dysfunction and injury were measured: serum creatinine level, urea nitrogen level, myeloperoxidase activity, and histology. Activation of PARP, intercellular adhesion molecule-1, and P-selectin protein in the kidney was studied using Western blot analysis.

RESULTS

3-Aminobenzamide attenuated the following: (1) serum amylase, lipase, and renal dysfunction; (2) serum concentrations of proinflammatory cytokines; (3) pancreatic and renal pathological injury; (4) renal myeloperoxidase activity; and (5) activation of PARP, intercellular adhesion molecule-1, and P-selectin in the kidney.

CONCLUSIONS

Our results suggest that PARP activation may contribute to kidney injury and that PARP inhibitors may be beneficial in renal disorders associated with severe acute pancreatitis.

Brain stem oxidative stress and its associated signaling in the regulation of sympathetic vasomotor tone

There is now compelling evidence from studies in humans and animals that overexcitation of the sympathetic nervous system plays an important role in the pathogenesis of cardiovascular diseases. An excellent example is neurogenic hypertension, in which central sympathetic overactivation is involved in the development, staging, and progression of the disease, and one of the underlying mechanisms involves oxidative stress in key brain stem sites that are engaged in the regulation of sympathetic vasomotor tone. Using the rostral ventrolateral medulla (RVLM) and nucleus tractus solitarii (NTS) as two illustrative brain stem neural substrates, this article provides an overview of the impact of reactive oxygen species and antioxidants on RVLM and NTS in the pathogenesis of neurogenic hypertension. This is followed by a discussion of the redox-sensitive signaling pathways, including several kinases, ion channels, and transcription factors that underpin the augmentation in sympathetic vasomotor tone. In addition, the emerging view that brain stem oxidative stress is also causally related to a reduction in sympathetic vasomotor tone and hypotension during brain stem death, methamphetamine intoxication, and temporal lobe status epilepticus will be presented, along with the causal contribution of the oxidant peroxynitrite formed by a reaction between nitric oxide synthase II (NOS II)-derived nitric oxide and superoxide. Also discussed as a reasonable future research direction is dissection of the cellular mechanisms and signaling cascades that may underlie the contributory role of nitric oxide generated by different NOS isoforms in the differential effects of oxidative stress in the RVLM or NTS on sympathetic vasomotor tone.

Involvement of nitrosative stress in experimental periodontitis in diabetic rats

AIM

Periodontal disease is highly prevalent and severe in diabetic patients, and is considered one of the diabetic complications. To elucidate how periodontitis progresses in diabetes, we examined an animal model of periodontitis in diabetic rats.

MATERIALS AND METHODS

Two weeks after the induction of diabetes by streptozotocin, surgical nylon thread was ligated around the cervical portion of the unilateral maxillary second molar to induce periodontitis. Periodontitis was evaluated 2 weeks after the ligation by gingival blood flow, mRNA expressions, Western blot analysis, histological examination and micro CT.

RESULTS

Ligation-induced severe periodontitis in the diabetic rats, which was apparently shown by the increase of TNF-α and iNOS mRNA expressions and inflammatory cell infiltration in the gingiva and alveolar bone loss. The number of nitrotyrosine, a footprint of nitrosative stress, -positive cells was significantly higher in the periodontitis of the diabetic rats compared with that in the normal rats. Western blot analysis confirmed that the nitrotyrosine was increased in the periodontitis of the diabetic rats.

CONCLUSIONS

This is the first study to confirm increased nitrosative stress due to periodontitis in diabetic rats. Nitrosative stress may play a crucial role in the exacerbation of periodontitis in diabetic patients.

Poly(ADP-ribose) polymerase-1 is a key mediator of cisplatin-induced kidney inflammation and injury

Cisplatin is a commonly used chemotherapeutic drug, the clinical use of which is limited by the development of dose-dependent nephrotoxicity. Enhanced inflammatory response, oxidative stress, and cell death have been implicated in the development of cisplatin-induced nephropathy; however, the precise mechanisms are elusive. Overactivation of the nuclear enzyme poly(ADP-ribose) polymerase-1 (PARP-1) by oxidative DNA damage under various pathological conditions promotes cell death and up-regulation of key proinflammatory pathways. In this study, using a well-established model of nephropathy, we have explored the role of PARP-1 in cisplatin-induced kidney injury. Genetic deletion or pharmacological inhibition of PARP-1 markedly attenuated the cisplatin-induced histopathological damage, impaired renal function (elevated serum BUN and creatinine levels), and enhanced inflammatory response (leukocyte infiltration; TNF-α, IL-1β, F4/80, adhesion molecules ICAM-1/VCAM-1 expression) and consequent oxidative/nitrative stress (4-HNE, 8-OHdG, and nitrotyrosine content; NOX2/NOX4 expression). PARP inhibition also facilitated the cisplatin-induced death of cancer cells. Thus, PARP activation plays an important role in cisplatin-induced kidney injury, and its pharmacological inhibition may represent a promising approach to preventing the cisplatin-induced nephropathy. This is particularly exciting because several PARP inhibitors alone or in combination with DNA-damaging anticancer agents show considerable promise in clinical trials for treatment of various malignancies (e.g., triple-negative breast cancer).

Activation of TNFR1 ectodomain shedding by mitochondrial Ca2+ determines the severity of inflammation in mouse lung microvessels

Shedding of the extracellular domain of cytokine receptors allows the diffusion of soluble receptors into the extracellular space; these then bind and neutralize their cytokine ligands, thus dampening inflammatory responses. The molecular mechanisms that control this process, and the extent to which shedding regulates cytokine-induced microvascular inflammation, are not well defined. Here, we used real-time confocal microscopy of mouse lung microvascular endothelium to demonstrate that mitochondria are key regulators of this process. The proinflammatory cytokine soluble TNF-α (sTNF-α) increased mitochondrial Ca2+, and the purinergic receptor P2Y2 prolonged the response. Concomitantly, the proinflammatory receptor TNF-α receptor-1 (TNFR1) was shed from the endothelial surface. Inhibiting the mitochondrial Ca2+ increase blocked the shedding and augmented inflammation, as denoted by increases in endothelial expression of the leukocyte adhesion receptor E-selectin and in microvascular leukocyte recruitment. The shedding was also blocked in microvessels after knockdown of a complex III component and after mitochondria-targeted catalase overexpression. Endothelial deletion of the TNF-α converting enzyme (TACE) prevented the TNF-α receptor shedding response, which suggests that exposure of microvascular endothelium to sTNF-α induced a Ca2+-dependent increase of mitochondrial H2O2 that caused TNFR1 shedding through TACE activation. These findings provide what we believe to be the first evidence that endothelial mitochondria regulate TNFR1 shedding and thereby determine the severity of sTNF-α-induced microvascular inflammation.

Pathophysiological roles of peroxynitrite in circulatory shock

Peroxynitrite is a reactive oxidant produced from nitric oxide and superoxide, which reacts with proteins, lipids, and DNA, and promotes cytotoxic and proinflammatory responses. Here, we overview the role of peroxynitrite in various forms of circulatory shock. Immunohistochemical and biochemical evidences demonstrate the production of peroxynitrite in various experimental models of endotoxic and hemorrhagic shock both in rodents and in large animals. In addition, biological markers of peroxynitrite have been identified in human tissues after circulatory shock. Peroxynitrite can initiate toxic oxidative reactions in vitro and in vivo. Initiation of lipid peroxidation, direct inhibition of mitochondrial respiratory chain enzymes, inactivation of glyceraldehyde-3-phosphate dehydrogenase, inhibition of membrane Na+/K+ ATPase activity, inactivation of membrane sodium channels, and other oxidative protein modifications contribute to the cytotoxic effect of peroxynitrite. In addition, peroxynitrite is a potent trigger of DNA strand breakage, with subsequent activation of the nuclear enzyme poly(ADP-ribose) polymerase, which promotes cellular energetic collapse and cellular necrosis. Additional actions of peroxynitrite that contribute to the pathogenesis of shock include inactivation of catecholamines and catecholamine receptors (leading to vascular failure) and endothelial and epithelial injury (leading to endothelial and epithelial hyperpermeability and barrier dysfunction), as well as myocyte injury (contributing to loss of cardiac contractile function). Neutralization of peroxynitrite with potent peroxynitrite decomposition catalysts provides cytoprotective and beneficial effects in rodent and large-animal models of circulatory shock.

Alterations of mitochondrial function in sepsis and critical illness

PURPOSE OF REVIEW

Septic shock is the consequence of a conflict between a pathogenic agent and the immune system of the host. This conflict induces an immune-mediated cytokine storm, with a whole-body inflammatory response often leading to multiple organ failure. Although extensively studied, the pathophysiology of sepsis-associated multiorgan failure remains unknown. One postulated mechanism is changes in mitochondrial function with an inhibition of mitochondrial respiratory chain and a decrease of oxygen utilization.

RECENT FINDINGS

Mitochondrion is a key organelle in supplying energy to the cell according to its metabolic need. Hypoxia and a number of the mediators implicated in sepsis and in the associated systemic inflammatory response have been demonstrated to directly impair mitochondrial function. A large body of evidence supports a key role of the peroxynitrite, which can react with most of the components of the electron transport chain, in the mitochondrial dysfunction.

SUMMARY

A pivotal role is suggested for mitochondrial dysfunction during the occurrence of multiorgan failure. Understanding the precise effect of sepsis on the mitochondrial function and the involvement of mitochondria in the development of multiple organ failure is fundamental. More human studies are thus necessary to clarify the mitochondrial dysfunction in the various phases of sepsis (early and late phase) before testing therapeutic strategies targeting mitochondria.

Inhibition of matrix metalloproteinase activity in vivo protects against vascular hyporeactivity in endotoxemia

Persistent arterial hypotension is a hallmark of sepsis and is believed to be caused, at least in part, by excess nitric oxide (NO). NO can combine with superoxide to produce peroxynitrite, which activates matrix metalloproteinases (MMPs). Whether MMP inhibition in vivo protects against vascular hyporeactivity induced by endotoxemia is unknown. Male Sprague-Dawley rats were administered either bacterial lipopolysaccharide (LPS, 4 mg/kg ip) or vehicle (pyrogen-free water). Later (30 min), animals received the MMP inhibitor doxycycline (4 mg/kg ip) or vehicle (pyrogen-free water). After LPS injection (6 h), animals were killed, and aortas were excised. Aortic rings were mounted in organ baths, and contractile responses to phenylephrine or KCl were measured. Aortas and plasma were examined for MMP activity by gelatin zymography. Aortic MMP and inducible nitric oxide synthase (iNOS) were examined by immunoblot and/or immunohistochemistry. Doxycycline prevented the LPS-induced development of ex vivo vascular hyporeactivity to phenylephrine and KCl. iNOS protein was significantly upregulated in aortic homogenates from endotoxemic rats; doxycycline did not alter its level. MMP-9 activity was undetectable in aortic homogenates from LPS-treated rats but significantly upregulated in the plasma; this was attenuated by doxycycline. Plasma MMP-2 activities were unchanged by LPS. Specific MMP-2 activity was increased in aortas from LPS-treated rats. This study demonstrates the in vivo protective effect of the MMP inhibitor doxycycline against the development of vascular hyporeactivity in endotoxemic rats.

A randomized, placebo-controlled trial to evaluate the tolerability, safety, pharmacokinetics, and pharmacodynamics of a potent inhibitor of poly(ADP-ribose) polymerase (INO-1001) in patients with ST-elevation myocardial infarction undergoing primary percutaneous coronary intervention: results of the TIMI 37 trial

BACKGROUND

Reperfusion injury is a significant complication of the management of ST-elevation MI (STEMI). INO-1001 is a potent inhibitor of poly(ADP-ribose) polymerase (PARP), a mediator of oxidant-induced myocyte dysfunction during reperfusion.

METHODS & RESULTS

We assessed the safety and pharmacokinetics of INO-1001 in a randomized, placebo-controlled, single-blind, dose-escalating trial in 40 patients with STEMI undergoing primary percutaneous coronary intervention within 24 h of onset. INO-1001 was well-tolerated. A trend toward more frequent transaminitis was observed with 800 mg. Plasma from INO1001-treated patients reduced in vitro PARP activity >90% at all doses. Serial C-reactive protein and IL-6 levels showed a trend toward blunting of inflammation with INO-1001. The apparent median terminal half-life (t(1/2)) of INO-1001 was 7.5 (25th, 75th: 5.9, 10.2) h.

CONCLUSIONS

The results from this first trial of INO-1001 in STEMI support future investigation of INO-1001 as a novel treatment for reperfusion injury.

Poly(ADP-ribose) polymerase: a new therapeutic target?

PURPOSE OF REVIEW

To overview the emerging data in the literature showing the role of poly(ADP-ribose) polymerase (PARP) in the pathogenesis of critical illness.

RECENT FINDINGS

PARP, an abundant nuclear enzyme involved in DNA repair and transcriptional regulation, is now recognized as a key regulator of cell survival and cell death in response to noxious stimuli in various forms of cardiovascular collapse. PARP becomes activated in response to oxidative DNA damage and depletes cellular energy pools, thus leading to cellular dysfunction in various tissues. The activation of PARP may also induce various cell death processes, and promotes an inflammatory response. In circulatory shock PARP plays a crucial role both in the development of early cardiovascular dysfunction and in the delayed systemic inflammatory response syndrome with associated multiple organ failure. Inhibition of PARP activity is protective in various models of circulatory shock.

SUMMARY

A solid body of literature supports the view that PARP is an important target for therapeutic intervention in critical illness.

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.

Effects of bioactive ceramics on the pathogenesis of rat vascular smooth muscle cells treated with phorbol 12-myristate 13-acetate

Vascular smooth muscle cells (VSMCs) play a pivotal role in vascular injury through proliferation and migration. Pro-inflammatory cytokines and cyclooxygenase (COX)-2 and nitric oxide synthase (NOS) are highly associated with the pathogenesis of VSMCs. We investigated the effect of bioactive ceramics on the expression of inflammatory cytokines, COX-2, and inducible NOS (iNOS) induced by phorbol 12-myristate 13-acetate (PMA) in rat VSMCs. The ceramics inhibited mRNA expression of IL-1beta, TNF-alpha, IL-6, COX-2, and iNOS. Prostaglandin release was also diminished by the ceramics. The bioactive ceramics effect on cytokines, COX-2, and iNOS expression was achieved by inhibition of NF-kappaB activity. Interestingly, the ceramics-induced up-regulation of expression of endothelial NOS resulted in an increase of nitric oxide production. Thus, bioactive ceramics may have dual effects on the pathogenesis of VSMCs by regulation of NF-kappaB activity and NO production.

[Microcirculatory disturbance in the course of acute pancreatitis]

Although as many studies are sacrificed to acute pancreatitis (AP), the pathogenesis of the disease remains undiscovered. The microcirculatory disturbances during AP as a cause of necrotic changes in the parenchyma of the gland, described first time by Panum in 1886, have become again a very attractive theory. In the last decades, several studies were done to prove that microcirculatory impairment plays a crucial role in pathogenesis of severe AP. It had been proved that many mediators play important roles in this process including nitric oxide and endothelin balance. Vasoconstriction and vasodilatation named "vascular game" caused by cytokine accumulation and lower oxygenation of the tissue gives very interesting basis for theories about creating pancreatic necrosis. The severity of the course of AP also determinates damage of the microcirculation of the lungs, the liver and the bowels which leads to SIRS, MODS and MOF. The new experimental dates seems to be very promising and can became a basis for developing a new strategy of treatment in the most severe cases of AP. In this article we present up-to-date information about these theories and concepts.

Potential Benefits of Peroxynitrite

Peroxynitrite (PN) is generated by the reaction of nitric oxide (NO) and superoxide in one of the most rapid reactions in biology. Studies have reported that PN is a cytotoxic molecule that contributes to vascular injury in a number of disease states. However, it has become apparent that PN has beneficial effects including vasodilation, inhibition of platelet aggregation, inhibition of inflammatory cell adhesion, and protection against ischemia/reperfusion injury in the heart. It is our hypothesis that PN may serve to inactivate superoxide and prolong the actions of NO in the circulation. This manuscript reviews the beneficial effects of PN in the cardiovascular system.

Human serum albumin improves arterial dysfunction during early resuscitation in mouse endotoxic model via reduced oxidative and nitrosative stresses

Human serum albumin (HSA) is used as a resuscitation fluid in sepsis. This study investigated the potential protective properties of HSA on vascular function in a mouse endotoxic model in terms of oxidative and nitrosative stresses. Swiss mice were treated with either lipopolysaccharide (LPS) (50 mg/kg i.p.) or vehicle. One and five hours later, mice were infused with HSA (4%, 10 ml/kg), normal saline (0.9% NaCl, 30 ml/kg), or no fluid. Six hours after treatment, vascular reactivity was assessed on aortae and small mesenteric arteries. Measurements of NO and superoxide anion (O2(-)) by spin trapping and nuclear factor (NF)-kappaB, inducible NO synthase (iNOS), and peroxynitrite by Western blotting and immunohistochemical studies were conducted. HSA partially prevented the reduction of blood pressure induced by LPS and completely prevented both vascular hyporeactivity to phenylephrine and myogenic tone as well as endothelial dysfunction induced by the endotoxin. This was associated with a decreased up-regulation of NF-kappa B, iNOS, and peroxynitrite in the vascular wall. LPS-induced tissue increases in both NO and O2(-) production was decreased by HSA. These data demonstrate the protective effect of HSA treatment in experimental endotoxic shock by reducing the inflammatory process leading to oxidative and nitrosative stresses and vascular hyporeactivity.

Peroxynitrite: biochemistry, pathophysiology and development of therapeutics

Peroxynitrite--the product of the diffusion-controlled reaction of nitric oxide with superoxide radical--is a short-lived oxidant species that is a potent inducer of cell death. Conditions in which the reaction products of peroxynitrite have been detected and in which pharmacological inhibition of its formation or its decomposition have been shown to be of benefit include vascular diseases, ischaemia-reperfusion injury, circulatory shock, inflammation, pain and neurodegeneration. In this Review, we first discuss the biochemistry and pathophysiology of peroxynitrite and then focus on pharmacological strategies to attenuate the toxic effects of peroxynitrite. These include its catalytic reduction to nitrite and its isomerization to nitrate by metalloporphyrins, which have led to potential candidates for drug development for cardiovascular, inflammatory and neurodegenerative diseases.

Poly (ADP-ribose) polymerase activation and circulatory shock

Sepsis is associated with increased production of reactive oxidant species. Oxidative and nitrosative stress can lead to activation of the nuclear enzyme poly (ADP-ribose) polymerase (PARP), with subsequent loss of cellular functions. Activation of PARP may dramatically lower the intracellular concentration of its substrate, NAD thus slowing the rate of glycolysis, electron transport and subsequently ATP formation. This process can result in cell dysfunction and cell death. In addition, PARP enhances the expression of various pro-inflammatory mediators, via activation of NF-kappaB, MAP kinase and AP-1 and other signal transduction pathways. Preclinical studies in various rodent and large animal models demonstrate that PARP inhibition or PAR deficiency exerts beneficial effects on the haemodynamic and metabolic alterations associated with septic and haemorrhagic shock. Recent human data also support the role of PARP in septic shock: In a retrospective study in 25 septic patients, an increase in plasma troponin level was related to increased mortality risk. In patients who died, significant myocardial damage was detected, and histological analysis of heart showed inflammatory infiltration, increased collagen deposition, and derangement of mitochondrial criptae. Immunohistochemical staining for poly(ADP-ribose) (PAR), the product of activated PARP was demonstrated in septic hearts. There was a positive correlation between PAR staining and troponin I; and a correlation of PAR staining and LVSSW. Thus, there is significant PARP activation in animal models subjected to circulatory shock, as well as in the hearts of septic patients. Based on the interventional studies in animals and the correlations observed in patients we propose that PARP activation may be, in part responsible for the cardiac depression and haemodynamic failure seen in humans with severe sepsis. Interestingly, recent studies reveal that the protective effects of PARP inhibitors are predominant in male animals, and are not apparent in female animals. Oestrogen, by providing a baseline inhibitory effect on PARP activation, may be partially responsible for this gender difference.

Nitric oxide and peroxynitrite in health and disease

The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.

N-acetylcysteine prevents nitrosative stress-associated depression of blood pressure and heart rate in streptozotocin diabetic rats

Previous studies have indicated that cardiovascular abnormalities such as depressed blood pressure and heart rate occur in streptozotocin (STZ) diabetic rats. Chronic diabetes, which is associated with increased expression of inducible nitric oxide synthase (iNOS) and oxidative stress, may produce peroxynitrite/nitrotyrosine and cause nitrosative stress. We hypothesized that nitrosative stress causes cardiovascular depression in STZ diabetic rats and therefore can be corrected by reducing its formation. Control and STZ diabetic rats were treated orally for 9 weeks with N-acetylcysteine (NAC), an antioxidant and inhibitor of iNOS. At termination, the mean arterial blood pressure (MABP) and heart rate (HR) were measured in conscious rats. Nitrotyrosine and endothelial nitric oxide synthase (eNOS) and iNOS expression were assessed in the heart and mesenteric arteries by immunohistochemistry and Western blot experiments. Untreated diabetic rats showed depressed MABP and HR that was prevented by treatment with NAC. In untreated diabetic rats, levels of 15-F(2t)-isoprostane, an indicator of lipid peroxidation increased, whereas plasma nitric oxide and antioxidant concentrations decreased. Furthermore, decreased eNOS and increased iNOS expression were associated with elevated nitrosative stress in blood vessel and heart tissue of untreated diabetic rats. N-acetylcysteine treatment of diabetic rats not only restored the antioxidant capacity but also reduced the expression of iNOS and nitrotyrosine and normalized the expression of eNOS to that of control rats in heart and superior mesenteric arteries. The results suggest that nitrosative stress depress MABP and HR following diabetes. Further studies are required to elucidate the mechanisms involved in nitrosative stress mediated depression of blood pressure and heart rate.

Inhibition of poly(adp-ribose) polymerase reduces cardiomyocytic apoptosis after global cardiac arrest under cardiopulmonary bypass

Cardiomyocytic apoptosis occurs after cardiopulmonary bypass (CPB) despite the use of perfusion techniques and cardioplegic solutions. Reactive oxygen species (ROS) cause single-strand DNA breaks and activate nuclear poly(ADP-ribose) polymerase (PARP), which leads to cellular damage. Therefore, the inhibition of PARP might protect cardiomyocytes from oxidative injuries. In this study, experiments were designed to determine whether a PARP inhibitor could decrease the myocardial ischemia/reperfusion injury after cardioplegia-induced global cardiac arrest under CPB, attenuate the appearance of cardiomyocytic apoptosis, and decrease damage from ROS. New Zealand white rabbits (10 in each group) were subjected to total CPB. Rabbits were weaned from CPB and reperfused for 4 h before the hearts were harvested. 3-Aminobenzamide and/or 3-aminobenzoic acid was added to the cardioplegic solution. The ascending aorta was cross-clamped for 60 min while intermittent cold crystalloid cardioplegic solution was infused into the aortic root every 20 min. The reperfused hearts were harvested and studied for evidence of apoptosis using the TUNEL method and Western blot analyses. The oxidative insults were checked using ELISA to detect plasma isoprostane and cytokines levels. The occurrence of cardiomyocytic apoptosis was significantly less in PARP inhibitor recipients than in PARP-inhibitor-naive controls. Plasma isoprostane and various cytokines were significantly elevated in PARP-inhibitor-naive controls but significantly reduced in PARP inhibitor recipients. Western blot analysis revealed similar patterns. PARP inhibitor-supplemented crystalloid cardioplegic solution diminished postischemic cardiomyocytic apoptosis and ROS-mediated injuries after global cardiac arrest under CPB, possibly via inhibiting both caspase-dependent and -independent apoptotic pathways, which also preserved postischemic myocardial contractility.

Potential role of poly(adenosine 5'-diphosphate-ribose) polymerase activation in the pathogenesis of myocardial contractile dysfunction associated with human septic shock

OBJECTIVE

Sepsis is associated with increased production of superoxide and nitric oxide, with consequent peroxynitrite generation. Cardiodepression is induced in the heart during oxidative stress associated with septic shock. Oxidative and nitrosative stress can lead to activation of the nuclear enzyme poly(adenosine 5'-diphosphate [ADP]-ribose) polymerase (PARP), with subsequent loss of myocardial contractile function. The aim of the study was to investigate whether cardiodepression found in septic patients is associated with plasma markers of myocardial necrosis and with myocardial PARP activation.

DESIGN

Prospective and observational study.

SETTING

University hospital intensive care unit for clinical and surgical patients.

PATIENTS

Twenty-five patients older than 18 yrs presenting with severe sepsis or septic shock. Patients with history of chronic heart failure, cancer, coronary artery disease, diabetes, or acquired immune deficiency syndrome were excluded.

INTERVENTIONS

Patients were followed for 28 days, and biochemical and hemodynamic data were collected on days 1, 3, and 6 of sepsis. The groups were survivors and nonsurvivors, defined only after the end of clinical patient evolution. Heart sections from patients who died were analyzed with hematoxylin-eosin and Picro Sirius-Red immunostaining and with electron microscopy.

MEASUREMENTS AND MAIN RESULTS

The study population included 25 individuals, of whom 12 (48%) died during the 6 days of follow-up. The initial data of the inflammation marker C-reactive protein and Acute Physiologic and Chronic Health. Evaluation severity were similar in both groups (nonsurvivors, 26 +/- 2; survivors, 24 +/- 5; NS). Overall, an increase in plasma troponin level was related to increased mortality risk. In patients who died, significant myocardial damage was detected, and histologic analysis of heart sections showed inflammatory infiltration, increased collagen deposition, and derangement of mitochondrial cristae. Immunohistochemical staining for poly(ADP-ribose) (PAR), the product of activated PARP, was demonstrated in septic hearts. There was a positive correlation between PAR staining densitometry and troponin I (r(2) = 0.73; p < .05), and the correlation of PAR staining densitometry and left ventricular systolic stroke work index was r(2) = 0.33 (p = .0509).

CONCLUSION

There is significant PARP activation in the hearts of septic patients with impaired cardiac function. We hypothesize that PARP activation may be partly responsible for the cardiac depression seen in humans with severe sepsis.

Tyrphostin AG 126 reduces intestinal ischemia-reperfusion injury in the rat

In this study, we evaluated the effect of tyrphostin AG126, a tyrosine kinase inhibitor, in the splanchnic artery occlusion (SAO) shock mediated injury. SAO shock was induced in rats by clamping both the superior mesenteric artery and the celiac trunk for 45 min. After 1 h of reperfusion, SAO shocked rats developed a significant fall in mean arterial blood pressure. Ileum analysis revealed that SAO shock is characterized by a significant (P<0.01) induction in TNF-alpha and IL-1 ileum levels, while immunohistochemistry examination of necrotic ileum demonstrated a marked increase in the immunoreactivity in intracellular adhesion molecule (ICAM-1) and nitrotyrosine formation. A significant increase in myeloperoxidase activity (P<0.01) was also observed in rats subjected to ischemia-reperfusion injury. Tyrphostin AG126, given intraperitoneally 30 min before ischemia at the dose of 5 mg/kg, significantly improved mean arterial blood pressure, markedly reduced TNF-alpha and IL-1beta levels and the positive staining of ICAM-1 into the reperfused ileum. Tyrphostin AG126 significantly improved the histological status of the reperfused tissue. In conclusion, this study demonstrates that tyrphostin AG126 exerts multiple protective effects in splanchnic artery occlusion/reperfusion shock and suggests that this tyrosine kinase inhibitor may be a candidate for consideration as a therapeutic intervention for ischemia-reperfusion injury.

New insights on brain stem death: From bedside to bench

As much as brain stem death is currently the clinical definition of death in many countries and is a phenomenon of paramount medical importance, there is a dearth of information on its mechanistic underpinnings. A majority of the clinical studies are concerned only with methods to determine brain stem death. Whereas a vast amount of information is available on the cellular and molecular mechanisms of cell death, rarely are these studies directed specifically towards the understanding of brain stem death. This review presents a framework for translational research on brain stem death that is based on systematically coordinated clinical and laboratory efforts that center on this phenomenon. It begins with the identification of a novel clinical marker from patients that is related specifically to brain stem death. After realizing that this "life-and-death" signal is related to the functional integrity of the brain stem, its origin is traced to the rostral ventrolateral medulla (RVLM). Subsequent laboratory studies on this neural substrate in animal models of brain stem death provide credence to the notion that both "pro-life" and "pro-death" programs are at work during the progression towards death. Those programs (mitochondrial functions, nitric oxide, peroxynitrite, superoxide anion, coenzyme Q10, heat shock proteins and ubiquitin-proteasome system) hitherto identified from the RVLM are presented, along with their cellular and molecular mechanisms. It is proposed that outcome of the interplay between the "pro-life" and "pro-death" programs (dying) in this neural substrate determines the final fate of the individual (being dead). Thus, identification of additional programs in the RVLM and delineation of their regulatory mechanisms should shed new lights on future directions for clinical management of life-and-death.

Beneficial pleiotropic actions of melatonin in an experimental model of septic shock in mice: regulation of pro-/anti-inflammatory cytokine network, protection against oxidative damage and anti-apoptotic effects

Septic shock, the most severe problem of sepsis, is a lethal condition caused by the interaction of a pathogen-induced long chain of sequential intracellular events in immune cells, epithelium, endothelium, and the neuroendocrine system. The lethal effects of septic shock are associated with the production and release of numerous pro-inflammatory biochemical mediators including cytokines, nitric oxide and toxic oxygen and nitrogen radicals, together with development of massive apoptosis. As melatonin has remarkable properties as a cytokine modulator, antioxidant and anti-apoptotic agent, the present study was designed to evaluate the possible protective effect of melatonin against LPS-induced septic shock in Swiss mice. We observed that intraperitoneally (i.p.) administered-melatonin (10 mg/kg) 30 min prior, and 1 hr after i.p. LPS injection (0.75 mg/animal) markedly protected mice from the LPS lethal effects with 90% survival rates for melatonin and 20% for LPS-injected mice after 72 hr. The melatonin effect was mediated by modulating the release of pro-/anti-inflammatory cytokine levels, protection from oxidative damage and counteracting apoptotic cell death. Melatonin was able to partially counteract the increase in LPS-induced pro-inflammatory cytokine levels such as tumor necrosis factor-alpha, IL-12 and interferon-gamma at the local site of injection, while it increased the production of the anti-inflammatory cytokine IL-10 both locally and systemically. Furthermore, melatonin inhibited the LPS-induced nitrite/nitrate and lipid peroxidation levels in brain and liver and counteracted the sepsis-associated apoptotic process in spleen. In conclusion, we have demonstrated that melatonin improves the survival of mice with septic shock via its pleiotropic functions as an immunomodulator, antioxidant and anti-apoptotic mediator.

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

Oxidative and nitrosative stress triggers DNA strand breakage, which then activates the nuclear enzyme poly(ADP-ribose) polymerase (PARP). Nitrogen-derived reactive oxidant species capable of involving DNA single strand breakage and PARP activation include peroxynitrite (the reaction product of nitric oxide and superoxide), but not nitric oxide per se. Activation of PARP may dramatically lower the intracellular concentration of its substrate, nicotinamide adenine dinucleotide, thus slowing the rate of glycolysis, electron transport, and subsequently ATP formation. This process can result in cell dysfunction and cell death. Here we review the role of reactive nitrogen species in the process of PARP activation, followed by the effect of pharmacological inhibition or genetic inactivation of PARP on the course of various forms of inflammation.

Cardioprotective effects of poly(ADP-ribose) polymerase inhibition

Free radical and oxidant production in cardiac myocytes during ischemia/reperfusion, cardiomyopathy, cardiotoxic drug exposure and ageing leads to DNA strand-breakage which activates the nuclear enzyme poly(ADP-ribose) polymerase (PARP) and initiates an energy consuming, inefficient cellular metabolic cycle with transfer of the ADP-ribosyl moiety of NAD+ to protein acceptors. These processes lead to the functional impairment of the myocytes and promote myocyte death. During the last decade a growing number of experimental studies demonstrated the beneficial effects of PARP inhibition in cell cultures through rodent models and more recently in pre-clinical large animal models of regional and global ischemia/reperfusion injury and various forms of heart failure. The current article provides an overview of the experimental evidence implicating PARP as a pathophysiological modulator of cardiac myocyte injury in vitro and in vivo.

Inhibition of poly(ADP-ribose) polymerase prevents vascular hyporesponsiveness induced by lipopolysaccharide in isolated rat aorta

Recent studies clearly show that there is a relationship between endotoxemia and impaired vascular responsiveness. The aim of this study was to investigate whether treatment with the new potent PARP inhibitor PJ34 could prevent the vascular hyporesponsiveness induced by lipopolysaccharide (LPS). Endotoxemia was induced in rats by LPS injection (20 mgkg-1, i.p.). Administration of LPS caused a decrease in mean blood pressure and an increase in heart rate. In endothelium-denuded rings of thoracic aorta from untreated rats, contractile responses to KCl and phenylephrine decreased after LPS injection. Furthermore, there was a significant loss of endothelium-dependent vasodilatation in response to acetylcholine in LPS-treated rats. The animals pretreated with PJ34 (10 mgkg-1, i.p., 30 min before LPS injection), the effect of LPS on vascular responsiveness was lower than the untreated ones. Pretreating the animals with PJ34 before the LPS challenge prevented the decline in mean blood pressure. However, this did not result in significant changes to the heart rate. The inhibitory effect of LPS treatment on both KCl- and phenylephrine-induced contraction responses was significantly antagonized by PJ34. Additionally, pretreatment of the rats with PJ34 attenuated the LPS-induced endothelial dysfunction in endothelium-intact aorta rings. This study demonstrates that PARP activation in the vascular system is an important contributory factor to the impaired vascular responsiveness associated with endotoxic shock. Hence, the pharmacological inhibition of PARP pathway might be an effective intervention to prevent endotoxin-induced vascular hyporesponsiveness.

Amentoflavone inhibits the induction of nitric oxide synthase by inhibiting NF-κB activation in macrophages

Amentoflavone is a bi-flavonoid compound with anti-fungal and anti-inflammatory activities. We isolated amentoflavone from Selaginella tamariscina (Selaginellaceae) and studied its effects on nuclear factor-kappaB (NF-kappaB)-mediated inducible nitric oxide synthase (iNOS) gene expression in RAW 264.7 cells. Amentoflavone inhibited the production of nitric oxide in a concentration-dependent manner and also blocked the lipopolysaccharide (LPS)-induced expression of inducible nitric oxide synthase (iNOS). To clarify the mechanistic basis for its inhibition of iNOS induction, we examined the effect of amentoflavone on the transactivation of iNOS gene by luciferase reporter activity using -1.59 kb flanking region. Amentoflavone potently suppressed the reporter gene activity. The LPS-induced activation of NF-kappaB was also found to be significantly blocked by amentoflavone, but AP-1 activation was unaffected. Furthermore, the nuclear translocation of p65 by LPS was inhibited by amentoflavone. NF-kappaB activation is controlled by the phosphorylation and subsequent degradation of I-kappaBalpha, and the cytosolic degradation of I-kappaBalpha was found to be inhibited by amentoflavone. These findings suggest that the inhibition of LPS-induced NO formation by amentoflavone is due to its inhibition of NF-kappaB by blocking I-kappaBalpha degradation, which may be the mechanistic basis of the anti-inflammatory effects of amentoflavone.

Poly(ADP-ribose) polymerase inhibitor PJ-34 reduces mesenteric vascular injury induced by experimental cardiopulmonary bypass with cardiac arrest

The aim of this study was to investigate effects of poly(ADP-ribose) polymerase (PARP) inhibition on mesenteric vascular function and metabolism in an experimental model of cardiopulmonary bypass (CPB) with cardiac arrest. Twelve anesthetized dogs underwent 90-min hypothermic CPB. After 60 min of cardiac arrest, reperfusion was started for 40 min following application of either saline vehicle (control, n = 6) or a potent PARP inhibitor, PJ-34 (10 mg/kg iv bolus and 0.5 mg.kg(-1).min(-1) infusion for 20 min, n = 6). PJ-34 led to better recovery of cardiac output (2.2 +/- 0.1 vs. 1.8 +/- 0.2 l/min in control) and mesenteric blood flow (175 +/- 38 vs. 83 +/- 4 ml/min, P < 0.05 vs. control) after reperfusion. The impaired vasodilator response of the superior mesenteric artery to acetylcholine, assessed in the control group after CPB (-32.8 +/- 3.3 vs. -57.6 +/- 6.6% at baseline, P < 0.05), was improved by PJ-34 (-50.3 +/- 3.6 vs. -54.3 +/- 4.1% at baseline, P < 0.05 vs. control). Although plasma nitrate/nitrite concentrations were not significantly different between groups, mesenteric nitric oxide synthase activity was increased in the PJ-34 group (P < 0.05). Moreover, the treated group showed a marked attenuation of mesenteric venous plasma myeloperoxidase levels after CPB compared with the control group (75 +/- 1 vs. 135 +/- 9 ng/ml, P < 0.05). Pharmacological PARP inhibition protects against development of post-CPB mesenteric vascular dysfunction by improving hemodynamics, restoring nitric oxide production, and reducing neutrophil adhesion.