Poly(Adp-ribose) synthetase inhibition prevents lipopolysaccharide-induced peroxynitrite mediated damage in diaphragm

Ascorbate protects against vascular leakage in cecal ligation and puncture-induced septic peritonitis

Vascular leakage in multiple organs is a characteristic pathological change in sepsis. Our recent study revealed that ascorbate protects endothelial barrier function in microvascular endothelial cell monolayers through inhibiting serine/threonine protein phosphatase 2A (PP2A) activation (Han M, Pendem S, Teh SL, Sukumaran DK, Wu F, Wilson JX. Free Radic Biol Med 48: 128-135, 2010). The present study addressed the mechanism of protection by ascorbate against vascular leakage in cecal ligation and puncture (CLP)-induced septic peritonitis in mice. CLP caused NADPH oxidase activation and endothelial nitric oxide synthase (eNOS) uncoupling to produce superoxide, increased NO production by inducible NOS (iNOS) and neuronal NOS (nNOS) activity, and elevated 3-nitrotyrosine (a product of peroxynitrite) formation and PP2A activity in the hindlimb skeletal muscles at 12 h after CLP. The increase in PP2A activity was associated with decreased levels of phosphorylated serine and threonine in occludin, which was immunoprecipitated from freshly harvested endothelial cells of the septic skeletal muscles. Moreover, CLP increased the vascular permeability to fluorescent dextran and Evans blue dye in skeletal muscles. An intravenous bolus injection of ascorbate (200 mg/kg body wt), given 30 min prior to CLP, prevented eNOS uncoupling, attenuated the increases in iNOS and nNOS activity, decreased 3-nitrotyrosine formation and PP2A activity, preserved the phosphorylation state of occludin, and completely inhibited the vascular leakage of dextran and Evans blue. A delayed ascorbate injection, given 3 h after CLP, also prevented the vascular permeability increase. We conclude that ascorbate injection protects against vascular leakage in sepsis by sequentially inhibiting excessive production of NO and superoxide, formation of peroxynitrite, PP2A activation, and occludin dephosphorylation. Our study provides a scientific basis for injection of ascorbate as an adjunct treatment for vascular leakage in sepsis.

Molecular biology of inflammation and sepsis: a primer

BACKGROUND

Remarkable progress has been made during the last decade in defining the molecular mechanisms that underlie septic shock. This rapidly expanding field is leading to new therapeutic opportunities in the management of severe sepsis.

AIM

To provide the clinician with a timely summary of the molecular biology of sepsis and to better understand recent advances in sepsis research.

DATA SELECTION

Medline search of relevant publications in basic mechanisms of sepsis/severe sepsis/septic shock, and selected literature review of other manuscripts about the signalosome, inflammasome, apoptosis, or mechanisms of shock. DATA SYNTHESIS AND FINDINGS: The identification of the toll-like receptors and the associated concept of innate immunity based upon pathogen- or damage-associated molecular pattern molecules allowed significant advances in our understanding of the pathophysiology of sepsis. The essential elements of the inflammasome and signal transduction networks responsible for activation of the host response have now been characterized. Apoptosis, mitochondrial dysfunction, sepsis-related immunosuppression, late mediators of systemic inflammation, control mechanisms for coagulation, and reprogramming of immune response genes all have critical roles in the development of sepsis.

CONCLUSIONS

Many of these basic discoveries have direct implications for the clinical management of sepsis. The translation of these "bench-to-bedside" findings into new therapeutic strategies is already underway. This brief review provides the clinician with a primer into the basic mechanisms responsible for the molecular biology of sepsis, severe sepsis, and septic shock.

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.

Poly (adp-ribose) synthetase inhibition reduces oxidative and nitrosative organ damage after thermal injury

Poly (ADP-ribose) synthetase (PARS) is a nuclear enzyme activated by DNA single-strand breakage, which can be triggered by reactive oxygen and nitrogen species. Activation of this enzyme depletes the intracellular concentration of energetic substrates such as nicotinamide adenine dinucleotide (NAD). Eventually, this process results in cell dysfunction and cell death. PARS inhibitors have successfully shown benefits in several experimental models of ischemia-reperfusion injury, inflammation, and sepsis. In our experimental study, we investigated the role of 3-aminobenzamide (3-AB), a nonspecific PARS inhibitor, in systemic organ damage after burn. Twenty-four Wistar rats were randomly divided into three groups. The sham group (n=8) was exposed to 21 degrees C water, and the burn group (n=8) and the burn-plus-3-AB group (n=8) were exposed to boiling water for 12 s to produce a full-thickness burn of 35-40% of total body surface area. In the burn-plus-3-AB group, 3-AB 10 mg/kg was given intraperitoneally 10 min before thermal injury. Twenty-four hours later, tissue samples were obtained for biochemical analysis from lung, intestine, and kidney. In the burn group, tissue malondialdehyde, myeloperoxidase, and 3-nitrotyrosine levels in all organs were significantly increased compared with the sham group (p<0.05). Pretreatment with 3-AB significantly reduced burn-induced organ damage (p<0.05). These data provide evidence of the relationship between the PARS pathway and lipid peroxidation in systemic organ damage after thermal injury.

Protection of endotoxin-induced oxidative renal tissue damage of rats by vitamin E or/and EGb 761 treatment

The aim of the present study was to evaluate the possible protective effects of vitamin E and EGb 761 treatments, alone or in combination, against oxidative renal tissue damage in experimentally induced endotoxaemic rats. Fifty healthy male Wistar albino rats, weighing 150-250 g and averaging 12 weeks old, were allotted randomly into one of five experimental groups: A (untreated), B (endotoxaemic), C (endotoxaemic + vitamin E treated), D (endotoaxemic + EGb 761 treated) and E (endotoxaemic + vitamin E and EGb 761 treated), each containing ten animals. Group A received only an intraperitoneal (i.p.) injection of 2 ml of normal saline solution and served as the control. Groups B, C, D and E were administrated a single i.p. injection of 0.5 ml of endotoxin solution. In addition, groups C, D and E received i.p. injections of 600 mg kg(-1) body mt. of vitamin E and oral extract of 50 mg kg(-1) body wt. of EGb 761, alone or in combination, immediately after the endotoxin injection. The experiment lasted for 24 h. At the end of the experiment blood and tissue samples were obtained for biochemical and histopathological investigation. Endotoxin injection produced renal damage, increased lipid peroxidation and decreased antioxidant enzyme activity. Vitamin E or/and EGb 761 treatment decreased lipid peroxidation, increased antioxidant enzyme activity and also prevented renal tissue damage in experimentally induced endotoxaemic rats. In conclusion, vitamin E and EGb 761 treatment, alone or in combination, appears to be beneficial in preventing endotoxin-induced oxidative renal tissue damage and therefore shows potential for clinical use.

Inhibition of poly(ADP-ribose) polymerase attenuates lung tissue damage after hind limb ischemia-reperfusion in rats

The objective of this study was to investigate the effects of 3-aminobenzamide (3-AB) on tissue damage in lung after hind limb ischemia-reperfusion (I/R), by assessing blood biochemical assay and histopathological analysis. Thirty-five adult Wistar rats were divided into five groups. After application of anaesthesia both hind limbs were occluded with tourniquets. Following ischemia period for 60 min, the tourniquets were removed allowing reperfusion for 120 min. The IR group received 0.5 ml of saline while the IR+AB group received 3-AB (10 mgkg(-1) intraperitoneally). The IR+DMSO group was given 0.5 ml 10% DMSO 30 min before the removal of the tourniquets. The control group received 0.5 ml saline and the AB group received 0.5 ml 3-AB (10 mgkg(-1)) intraperitoneally. At the end of the reperfusion period, mid-line sternotomy was performed. Blood samples were taken with cardiac puncture. Bronchoalveolar lavage (BAL) of the left lung was performed with saline. Right lung was preserved for histopathological evaluation and biochemical examination. Lung tissue malondialdehyde (MDA) and 3-nitrotyrosine levels, myeloperoxidase and Na+/K+ ATP-ase activities, wet to dry weight ratios, and plasma and BAL fluid MDA levels were determined. Histopathological evaluation was performed, too. Hind limb IR caused significant increase in the lung tissue 3-NT to total tyrosine ratio (p = 0.014), wet to dry weight ratio (p = 0.000), MPO activity (p = 0.000), and MDA levels (p = 0.000). The animals treated with 3-AB showed a statistically significant decrease in these values (p < 0.05). Na+/K+ ATP-ase activity which was found to be decreased significantly with IR, returned to near normal levels with 3-AB treatment. Additionally, lung tissue injury in IR group characterized with moderate interstitial congestion and neutrophil infiltration, showed remarkable amelioration following 3-AB treatment. Our results strongly support the view that poly(ADP-ribose) polymerase (PARP) plays an important role in the inflammatory process in hind limb I/R-induced lung injury and as a PARP inhibitor, 3-AB seems to have a potential to treat this inflammatory injury.

Protective Effects of Vitamin C, Alone or in Combination with Vitamin A, on Endotoxin-Induced Oxidative Renal Tissue Damage in Rats

This study was designed to investigate the protective effects of vitamin C and vitamin A on oxidative renal tissue damage. Male Wistar rats were given an intraperitoneal injection of 0.5 ml saline (control) or 0.5 ml solution of lipopolysaccharide (10 mg/kg), which caused endotoxemia. Immediately (within 5 min) after the endotoxin injection, the endotoxemic rats were untreated or treated with intraperitoneal injection of vitamin A (195 mg/kg bw), vitamin C (500 mg/kg bw) or their combination. After 24 hours, tissue and blood samples were obtained for histopathological and biochemical investigation. Endotoxin injection caused renal tissue damage and increased erythrocyte and tissue malondialdehyde (MDA) and serum nitric oxide (NO), urea and creatinine concentrations, but decreased the superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) activities compared to the parameters of control animals. Treatment with vitamin C or with vitamins C and A significantly decreased the MDA levels and serum NO, urea and creatinine levels, recovered the antioxidant enzyme activities (SOD, GSH-Px and CAT), and prevented the renal tissue damage in endotoxemic rats. In contrast, vitamin A alone did not change the altered parameters except for creatinine levels. Notably, the better effects were observed when vitamins A and C given together. It is concluded that vitamin C treatment, alone or its combination with vitamin A, may be beneficial in preventing endotoxin-induced oxidative renal tissue damage and shows potential for clinical use.

The role of poly(ADP-ribose) synthetase inhibition on the intestinal mucosal barrier after thermal injury

Oxidative and nitrosative stressor agents can trigger DNA strand breakage, which then activates the nuclear enzyme poly(ADP-ribose) synthetase (PARS). Activation of the enzyme depletes the intracellular concentration of energetic substrates such as nicotinamide adenine dinucleotide (NAD). This process can result in cell dysfunction and cell death. PARS inhibitors have been successfully used in ischemia-reperfusion injury, inflammation and sepsis in several experimental models. In our experimental study, we investigated the role of 3-aminobeanzamide (3-AB), a non-specific PARS inhibitor, on the intestinal mucosal barrier after burn injury. Twenty-four Wistar rats were randomly divided into three groups. The sham group (n = 8) was exposed to 21 degrees C water while the burn group (n = 8) and the burn + 3-AB group (n = 9) were exposed to boiling water for 12s to produce a full thickness burn in 35-40% of total body surface area. In the burn + 3-AB group, 10mg/kg of 3-AB was given intraperitoneally 10min before thermal injury. Twenty-four hours later, tissue samples from mesenteric lymph nodes (MLN), spleen and liver were obtained under sterile conditions for microbiological analysis and ileum samples were obtained for biochemical and histopathological analysis. In burn group, the incidence of bacteria isolated from MLN and spleen was significantly higher than other groups (P < 0.05). 3-AB pre-treatment prevented burn induced bacterial translocation and it significantly reduced burn induced intestinal injury. Tissue malondialdehyde and 3-nitrotyrozine levels were found significantly lower than that of the burn group. These data suggest that the relationship between PARS pathway and lipid peroxidation in intestinal tissue and PARS has a role in intestinal injury caused by thermal injury.

Mitochondrial dysfunction in sepsis

Sepsis is an increasingly common problem, particularly among critically ill patients. Mechanisms by which sepsis induces organ dysfunction have not been elucidated. The coexisting findings (unique to sepsis) of metabolic acidosis yet increased tissue oxygen tensions suggest cellular availability but decreased use of oxygen (tissue dysoxia). Because mitochondria use more than 90% of total body oxygen consumption for adenosine triphosphate (ATP) generation, a bioenergetic abnormality is implied. Cell and animal data have shown that nitric oxide (and its metabolites), produced in considerable excess in patients with sepsis, can affect oxidative phosphorylation by inhibiting several of its component respiratory enzymes. Human data are scarce. However, in skeletal muscle biopsies taken from patients with sepsis, we have recently demonstrated a relationship between increased nitric oxide production, antioxidant depletion, reduced respiratory chain complex I activity, and low ATP levels. These findings correlated with severity of disease and outcome and support the notion that mitochondrial dysfunction resulting in bioenergetic failure may be an important factor in the pathophysiology of sepsis-associated multiorgan failure. However, a reasonable argument can be made that the reduction in energy supply could represent a last-ditch adaptive response to ongoing inflammation, resulting in a cellular shutdown analogous to hibernation that allows eventual restoration of organ function and long-term survival in patients fit enough to survive the acute phase.