3-Aminobenzamide, an inhibitor of poly (ADP-ribose) synthetase, improves hemodynamics and prolongs survival in a porcine model of hemorrhagic shock

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.

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).

Thalidomide suppresses sclerosing encapsulating peritonitis in a rat experimental model

Peritoneal dialysis is an alternative treatment of patients with end-stage renal disease. Sclerosing encapsulating peritonitis is a life-threatening complication of continuous ambulatory peritoneal dialysis. The aim of the present study was to evaluate the effect of thalidomide, which is used for the treatment of various inflammatory and autoimmune diseases, on the development of sclerosing encapsulating peritonitis induced by chlorhexidine gluconate (CG). A peritoneal fibrosis model was established using rats treated intraperitoneally with injections of CG. Thalidomide was administered orally at a dose of 100 mg/kg three times per week. When compared with CG-treated rats, thalidomide (100 mg/kg orally)-treated mice subjected to CG-induced peritoneal fibrosis experienced a significantly lower rate in the extent and severity of histological signs of peritoneal injury. Thalidomide also caused a substantial reduction of 1) the rise in myeloperoxidase activity (mucosa); 2) the expression in the tissue of TNF-alpha, IL-1beta, transforming growth factor-beta, and vascular endothelial growth factor; 3) the increase in staining (immunohistochemistry) for nitrotyrosine and for poly(ADP ribose), as well as 4) the nuclear factor-kappaB activation caused by CG in the peritoneum. Thus, thalidomide treatment reduces the degree of peritoneal fibrosis caused by CG. We propose that this evidence may help clarify the potential therapeutic actions of thalidomide in patients with peritoneal fibrosis.

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 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.

Role of poly(ADP-ribose) polymerase 1 (PARP-1) in cardiovascular diseases: the therapeutic potential of PARP inhibitors

Accumulating evidence suggests that the reactive oxygen and nitrogen species are generated in cardiomyocytes and endothelial cells during myocardial ischemia/reperfusion injury, various forms of heart failure or cardiomyopathies, circulatory shock, cardiovascular aging, diabetic complications, myocardial hypertrophy, atherosclerosis, and vascular remodeling following injury. These reactive species induce oxidative DNA damage and consequent activation of the nuclear enzyme poly(ADP-ribose) polymerase 1 (PARP-1), the most abundant isoform of the PARP enzyme family. PARP overactivation, on the one hand, depletes its substrate, NAD+, slowing the rate of glycolysis, electron transport, and ATP formation, eventually leading to the functional impairment or death of the endothelial cells and cardiomyocytes. On the other hand, PARP activation modulates important inflammatory pathways, and PARP-1 activity can also be modulated by several endogenous factors such as various kinases, purines, vitamin D, thyroid hormones, polyamines, and estrogens, just to mention a few. Recent studies have demonstrated that pharmacological inhibition of PARP provides significant benefits in animal models of cardiovascular disorders, and novel PARP inhibitors have entered clinical development for various cardiovascular indications. Because PARP inhibitors can enhance the effect of anticancer drugs and decrease angiogenesis, their therapeutic potential is also being explored for cancer treatment. This review discusses the therapeutic effects of PARP inhibitors in myocardial ischemia/reperfusion injury, various forms of heart failure, cardiomyopathies, circulatory shock, cardiovascular aging, diabetic cardiovascular complications, myocardial hypertrophy, atherosclerosis, vascular remodeling following injury, angiogenesis, and also summarizes our knowledge obtained from the use of PARP-1 knockout mice in the various preclinical models of cardiovascular diseases.

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.

Protective effects of PARP inhibition on liver microcirculation and function after haemorrhagic shock and resuscitation in male rats

OBJECTIVE

The aim of this study was to investigate the impact of the water-soluble poly-(ADP)-ribose-polymerase (PARP) inhibitor 5-aminoisoquinolinone (5-AIQ) on liver microcirculation and function after haemorrhagic shock and resuscitation.

DESIGN

Controlled, randomized animal study.

SETTING

University animal care facility and research laboratory.

SUBJECT

Male Sprague-Dawley rats were subjected to haemorrhagic shock for 1 h, followed by resuscitation with shed blood and crystalloid solution for a total of 5 h.

INTERVENTIONS

The PARP inhibitor 5-AIQ (3 mg/kg; n=7) or vehicle (n=7) was administered 5 min prior to resuscitation. Sham-operated animals without induction of shock served as controls (n=7).

MEASUREMENTS AND RESULTS

Using intravital fluorescence microscopy hepatic microcirculation was assessed at baseline, end of shock phase as well as 1 h and 5 h after resuscitation. Systemic arterial blood pressure and bile flow were continuously monitored. 5-AIQ treatment attenuated shock/resuscitation-induced increase of intrahepatic leukocyte-endothelial cell interaction with a marked reduction of both sinusoidal leukostasis and venular leukocyte adherence. Moreover, nutritive perfusion was found improved, guaranteeing sufficient oxygen supply to tissue, as indicated by low NADH autofluorescence, which was not different to that in controls. Most notably, excretory liver function reached baseline level over 5 h of reperfusion in 5-AIQ-treated animals.

CONCLUSIONS

In the present setting of shock/resuscitation in male rats the PARP inhibitor 5-AIQ proved to be very effective in ameliorating compromised liver microcirculation and function. Further research has to confirm that PARP inhibition is a suitable tool in the acute treatment of patients suffering from reduced circulating blood volume and thus microcirculatory organ dysfunction.

Inhibition of Poly (ADP-ribose) Synthetase Improves Pulmonary Arterial Endothelium-Dependent Relaxation After Ischemic-Reperfusion Injury of Splanchnic Artery in Rats

The role of poly (adenosine diphosphate-ribose) synthetase (PARS) in the contractile and relaxant responses of pulmonary arteries injured by ischemia and reperfusion (IR) of splanchnic artery has not been evaluated. We examined these responses by using 3-aminobenzamide, a pharmacological inhibitor of PARS. IR models in rats were induced by clamping the superior mesenteric artery for 60 min, followed by release of the clamp for 60 min. In the 2 treated groups, 5 or 10 mg/kg of 3-aminobenzamide was administered as an IV bolus at 10 min before reperfusion, followed by infusion rates of 5 and 10 mg.kg(-1).h(-1), respectively, during the period of reperfusion (IR + PARS inhibitor 5 and 10 groups). In the vehicle-treated group, 3-aminobenzamide was not given, but IV saline was administered (IR group). In the control group, surgery was performed, but the superior mesenteric artery was not occluded (sham group). The pulmonary arteries were isolated, and effects of drugs were evaluated in vitro. The IR group showed no attenuation of the contractile responses of the pulmonary artery to phenylephrine. The relaxant responses to endothelium-dependent vasodilators, acetylcholine, and A23187 in the IR group were significantly inhibited when compared with the sham group. The reduction in the relaxant response to endothelium-dependent vasodilators was improved in the IR + PARS inhibitor 5 and 10 groups when compared with the IR group. We concluded that IR attenuated the relaxant responses of the pulmonary artery to endothelium-dependent vasodilators and that PARS inhibitors ameliorate the reduction in the relaxant response.

Shock, inflammation and PARP

The activation of poly(ADP-ribose) polymerase (PARP) is well considered to play an important role in various patho-physiological conditions like inflammation and shock. A vast amount of circumstantial evidence implicates oxygen-derived free radicals (especially, superoxide and hydroxyl radical) and high-energy oxidants (such as peroxynitrite) as mediators of inflammation and shock. ROS (e.g., superoxide, peroxynitrite, hydroxyl radical and hydrogen peroxide) are all potential reactants capable of initiating DNA single strand breakage, with subsequent activation of the nuclear enzyme poly(ADP-ribose) synthetase (PARS), leading to eventual severe energy depletion of the cells, and necrotic-type cell death. During the last years, numerous experimental studies have clearly demonstrated the beneficial effects of PARP inhibition in cell cultures through rodent models and more recently in pre-clinical large animal models of acute and chronic inflammation. The aim of this review is to describe recent experimental evidence implicating PARP as a pathophysiological modulator of acute and chronic inflammation.

Perflubron emulsion improves hepatic microvascular integrity and mitochondrial redox state after hemorrhagic shock

Hemorrhagic shock is associated with decreased systemic oxygen delivery, but also with impaired microvascular perfusion, which can result in diminished local oxygen availability even in the presence of adequate cardiac output after resuscitation. Beside surgical interventions to control blood loss, transfusion of stored packed red blood cells represents the current standard of care in the management of severe hemorrhagic shock. Because stored red blood cells are less deformable and show a higher O2 affinity that affects the O2 off-load to tissues, perfluorocarbon-based artificial oxygen carriers might improve local O2 delivery under these conditions. To test this, rats were subjected to hemorrhagic shock (1 h, mean arterial pressure [MAP] 30-35 mmHg) and were resuscitated with fresh whole blood, pentastarch, stored red blood cells, perflubron emulsion (2.7 and 5.4 g/kg body weight) together with pentastarch, or stored red blood cells together with 2.7 g/kg perflubron emulsion. Hepatic microcirculation, tissue oxygenation, and mitochondrial redox state were investigated by intravital microscopy. In addition, hepatocellular function and liver enzyme release were determined. After hemorrhagic shock and resuscitation with perflubron emulsion, volumetric sinusoidal blood flow was significantly increased compared with resuscitation with stored red blood cells. Furthermore, resuscitation with perflubron emulsion resulted in higher hepatic tissue PO2 and normalized mitochondrial redox potential, which was accompanied by lessened hepatocellular injury as well as improved liver function. These results indicate that, in this model of hemorrhagic shock, asanguineous fluid resuscitation with addition of perflubron emulsion is superior to stored blood or pentastarch alone with respect to increased local O2 availability on the cellular level. This effect is primarily due to improved restoration of hepatic microcirculatory integrity.

Pyruvate prevents poly-ADP ribose polymerase (PARP) activation, oxidative damage, and pyruvate dehydrogenase deactivation during hemorrhagic shock in swine

The inadequate availability of fuel substrates and sharp decline in cellular ATP have been implicated in a cascade of events associated with cell death and organ failure during hemorrhagic shock (HS). In this in vivo swine model of severe prolonged HS, the effect of exogenous pyruvate administration on various markers of cell damage in brain and liver was examined. Thirty minutes after the start of controlled arterial hemorrhage, 30% sodium pyruvate, 10% saline, or 0.9% saline was administered via jugular vein. Four hours after the initiation of hemorrhage, tissue samples from brain and liver were obtained and examined for the cellular and molecular markers of cellular damage. Results of our study suggest that pyruvate prevents loss of total NAD content, cleavage of poly-ADP ribose polymerase (PARP), and inhibits lipid peroxidation in both the brain and liver of swine during prolonged severe HS. We conclude that there are multiple mechanisms by which pyruvate can possibly prevent cell damage caused during HS.

Nicotinamide increases systemic vascular resistance in ovine endotoxemia

OBJECTIVE

The nuclear enzyme Poly(ADP-Ribose)-Polymerase (PARP) has been hypothesized as playing a major role in various forms of inflammation. PARP activation is induced by DNA strand breakage and can result in intracellular energy depletion and, ultimately, cell death. Further, it is thought to influence cardiovascular function and organ failure in endotoxemia. Here, we investigated the effect of the PARP inhibitor nicotinamide on cardiovascular and liver function in healthy and chronically endotoxemic sheep.

DESIGN

Prospective controlled trial.

SETTING

University research laboratory.

SUBJECTS

12 female adult sheep.

INTERVENTIONS

Six healthy sheep, instrumented for chronic study, received nicotinamide intravenously as a bolus of 40 mg/kg followed by a continuous infusion of 10 mg.kg(-1).h(-1); six animals received the vehicle. One hour after bolus application, a continuous infusion of endotoxin ( Salmonella typhosa, 10 ng.kg(-1).min(-1)) was started. Hemodynamic parameters were determined before and during endotoxemia.

MEASUREMENTS AND RESULTS

Treatment with nicotinamide resulted in a significantly higher systemic vascular resistance index and lower cardiac index in endotoxemic animals, but not in controls. It also attenuated endotoxin-induced increase in gamma-glutamyl transferase.

CONCLUSIONS

The PARP inhibitor nicotinamide attenuates impairment of cardiovascular function during endotoxemia. In addition, PARP activation may be involved in endotoxin-induced liver injury.

Systemic and hepatosplanchnic hemodynamic and metabolic effects of the PARP inhibitor PJ34 during hyperdynamic porcine endotoxemia

Activation of the poly(ADP-ribose)polymerase (PARP), a highly energy-consuming DNA-repairing enzyme, plays a crucial role in the pathogenesis of multiorgan failure. Most results, however, were derived from experiments with hypodynamic shock states characterized by a markedly decreased cardiac output (CO) and/or using a pretreatment approach. Therefore, we investigated the effects of the novel potent and selective PARP-1 inhibitor PJ34 in a posttreatment model of long-term, volume-resuscitated porcine endotoxemia. Anesthetized, mechanically ventilated and instrumented pigs received continuous intravenous (i.v.) lipopolysaccharide (LPS) over 24 h. Hydroxyethyl starch was administered to maintain a mean arterial pressure > 65 mmHg. After 12 h of LPS infusion, the animals were randomized to receive either vehicle (Control, n = 9) or i.v. PJ34 (n = 6; 10 mg/kg over 1 h followed by 2 mg/kg/h until the end of the experiment). Measurements were performed before as well as at 12, 18, and 24 h of LPS infusion. In all animals CO increased because of reduced systemic vascular resistance (SVR) and fluid resuscitation. PJ34 further raised CO (P < 0.05 vs. control group) as the result of a higher stroke volume indicating its positive inotropic effect. In addition, it diminished the rise in the ileal mucosal-arterial PCO2 gap, which returned to baseline levels at 24 h of LPS, and improved the gut lactate balance (P = 0.093 PJ34 vs. control) together with significantly lower portal venous lactate/pyruvate ratios. By contrast, it failed to influence the LPS-induced derangements of liver metabolism. Incomplete PARP inhibition because of dilutional effects and/or an only partial efficacy when used in post-treatment approaches may account for this finding.

Protective effect of a novel, potent inhibitor of poly(adenosine 5'-diphosphate-ribose) synthetase in a porcine model of severe bacterial sepsis

OBJECTIVE

To determine whether activation of the nuclear enzyme poly(adenosine 5'-diphosphate [ADP]-ribose) synthetase (PARS) contributes to mortality rate, myocardial dysfunction, and cardiovascular collapse in a porcine model of sepsis induced by implantation of an infected clot.

DESIGN

Prospective, random animal study.

SETTING

Research laboratory at Rush Presbyterian St. Luke's Medical Center.

SUBJECTS

Twenty pigs were chronically instrumented with intracardiac transducers to measure left ventricular pressure, sonomicrometer crystals in the left ventricle to measure short axis diameter, an ultrasonic flow meter to measure cardiac output, and catheters in the pulmonary artery and aorta to measure blood pressures and collect samples.

INTERVENTIONS

By using a randomized study design, we administered either the novel potent PARS inhibitor PJ34 (10 mg/kg for 1 hr, 2 mg x kg(-1) x hr(-1) for 96 hrs) or vehicle to pigs immediately before intraperitoneal implantation of Escherichia coli 0111.B4 (2.3 +/- 0.1 x 10(10) colony-forming units/kg)-laden fibrin clots to produce peritonitis and bacteremia.

MEASUREMENTS AND MAIN RESULTS

In vehicle-treated pigs, 12% survival was recorded at 24 hrs, whereas 83% and 66% survival was recorded in the PJ34-treated animals at 24 and 96 hrs, respectively (p <.05). PJ34 treatment attenuated bacteremia-induced increases in systemic and pulmonary vascular resistances. In controls, peritonitis induced rapid increase in plasma tumor necrosis factor-alpha. PJ34 treatment significantly attenuated this cytokine response. The formation of peroxynitrite and the activation of PARS were confirmed in hearts and lungs of the septic pigs by the immunohistochemical detection of nitrotyrosine and poly(ADP-ribose), respectively. Inhibition of PARS with PJ34 abolished poly(ADP-ribose) formation in septic animals.

CONCLUSIONS

Treatment with a potent PARS inhibitor improved survival and cardiovascular status and attenuated an important mediator component of the inflammatory response in a lethal porcine model of sepsis.

Poly(adenosine 5'-diphosphate) ribose polymerase activation as a cause of metabolic dysfunction in critical illness

Poly(adenosine 5'-diphosphate) ribose polymerase is a nuclear enzyme activated in response to genotoxic stress induced by a variety of DNA damaging agents. Several oxygen and nitrogen-centered free radicals, notably peroxynitrite, are strong inducers of DNA damage and poly(adenosine 5'-diphosphate) ribose polymerase activation in vitro and in vivo. Activation of this nuclear enzyme depletes the intracellular stores of its substrate nicotinamide adenine dinucleotide, slowing the rate of glycolysis, mitochondrial electron transport and adenosine triphosphate formation. This process triggers a severe energetic crisis within the cell, leading to acute cell dysfunction and cell necrosis. Poly(adenosine 5'-diphosphate) ribose polymerase also plays an important role in the regulation of inflammatory cascades, through a functional association with various transcription factors and transcription co-activators. Recent works identified this enzyme as a critical mediator of cellular metabolic dysfunction, inflammatory injury, and organ damage in conditions associated with overwhelming oxidative stress, including systemic inflammation, circulatory shock, and ischemia-reperfusion. Accordingly, pharmacological inhibitors of poly(adenosine 5'-diphosphate) ribose polymerase protect against cell death and tissue injury in such conditions, and may therefore represent novel therapeutic tools to limit multiple organ damage and dysfunction in critically ill patients.

Activation of poly(ADP-ribose) polymerase in severe hemorrhagic shock and resuscitation

This study examines activation of poly(ADP-ribose) polymerase (PARP) in the ileum during hemorrhage and resuscitation and determines if inhibition of PARP reduces organ dysfunction and metabolic acidosis. Awake, nonheparinized rats were hemorrhaged (40 mmHg, 60 min). Resuscitation used Ringer's solution (2 1/3 x shed volume) and packed red blood cells (2/3 shed volume). Ileal PARP activity was elevated at the end of hemorrhage (3.6-fold) and 10 min of resuscitation (5-fold). The subsequent decline in PARP activity observed after 60 min of resuscitation was not due to cleavage by caspase-3. Ileum permeability increased 10-fold and circulating liver enzymes increased 4- to 6-fold following 60 min of resuscitation in animals pretreated with 3-aminobenzoic acid, a structural analog that does not inhibit PARP. Pretreatment with 3-aminobenzamide (3-AB), a PARP inhibitor, reduced these changes, whereas posttreatment with a bolus of 3-AB was ineffective. Metabolic acidosis, accumulation of lactate, and base deficit was reduced by pretreatment with 3-AB. PARP is activated in the ileum by hemorrhage and by resuscitation. Activation of PARP contributes to organ dysfunction in the ileum and liver and appears to be central to the development of metabolic acidosis.

Protection against hemorrhagic shock in mice genetically deficient in poly(ADP-ribose)polymerase

Hemorrhagic shock (HS) and resuscitation leads to widespread production of oxidant species. Activation of the enzyme poly(ADP-ribose) polymerase (PARP) has been shown to contribute to cell necrosis and organ failure in various disease conditions associated with oxidative stress. We tested the hypothesis whether PARP activation plays a role in the multiple organ dysfunction complicating HS and resuscitation in a murine model of HS and resuscitation by using mice genetically deficient in PARP (PARP(-/-)) and their wild-type littermates (PARP(+/+)). Animals were bled to a mean blood pressure of 45 mmHg (1 mmHg = 133 Pa) and resuscitated after 45 min with isotonic saline (2x volume of shed blood). There was a massive activation of PARP, detected by poly(ADP-ribose) immunohistochemistry, which localized to the areas of the most severe intestinal injury, i.e., the necrotic epithelial cells at the tip of the intestinal villi, and colocalized with tyrosine nitration, an index of peroxynitrite generation. Intestinal PARP activation resulted in gut hyperpermeability, which developed in PARP(+/+) but not PARP(-/-) mice. PARP(-/-) mice were also protected from the rapid decrease in blood pressure after resuscitation and showed an increased survival time, as well as reduced lung neutrophil sequestration. The beneficial effects of PARP suppression were not related to a modulation of the NO pathway nor to a modulation of signaling through IL-6, which similarly increased in both PARP(+/+) and PARP(-/-) mice exposed to HS. We propose that PARP activation and associated cell injury (necrosis) plays a crucial role in the intestinal injury, cardiovascular failure, and multiple organ damage associated with resuscitated HS.

Effects of 5-aminoisoquinolinone, a water-soluble, potent inhibitor of the activity of poly (ADP-ribose) polymerase on the organ injury and dysfunction caused by haemorrhagic shock

Poly (ADP-ribose) synthetase (PARP) is a nuclear enzyme activated by strand breaks in DNA, which are caused inter alia by reactive oxygen species (ROS). Here we report on (i) a new synthesis of a water-soluble and potent PARP inhibitor, 5-aminoisoquinolinone (5-AIQ) and (ii) investigate the effects of 5-AIQ on the circulatory failure and the organ injury/dysfunction caused by haemorrhage and resuscitation in the anaesthetized rat. Exposure of human cardiac myoblasts (Girardi cells) to hydrogen peroxide (H(2)O(2), 3 mM for 1 h, n=9) caused a substantial increase in PARP activity. Pre-treatment of these cells with 5-AIQ (1 microM - 1 mM, 10 min prior to H(2)O(2)) caused a concentration-dependent inhibition of PARP activity (IC(50): approximately 0.01 mM, n=6). Haemorrhage and resuscitation resulted (within 4 h after resuscitation) in a delayed fall in blood pressure (circulatory failure) as well as in rises in the serum levels of (i) urea and creatinine (renal dysfunction), (ii) aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyl-transferase (gamma-GT) (liver injury and dysfunction), (iii) lipase (pancreatic injury) and (iv) creatine kinase (CK) (neuromuscular injury) (n=10). Administration (5 min prior to resuscitation of 5-AIQ) (0.03 mg kg(-1) i.v., n=8, or 0.3 mg kg(-1) i.v., n=10) reduced (in a dose-related fashion) the multiple organ injury and dysfunction, but did not affect the circulatory failure, associated with haemorrhagic shock. Thus, 5-AIQ abolishes the multiple organ injury caused by severe haemorrhage and resuscitation.

Effects of inhibitors of the activity of poly (ADP-ribose) synthetase on the organ injury and dysfunction caused by haemorrhagic shock

1 Poly (ADP-ribose) synthetase (PARS) is a nuclear enzyme activated by strand breaks in DNA, which are caused by reactive oxygen species (ROS). Here we investigate the effects of the PARS inhibitors 3-aminobenzamide (3-AB), nicotinamide and 1,5-dihydroxyisoquinoline (ISO) on the circulatory failure and the organ injury/dysfunction caused by haemorrhage and resuscitation in the anaesthetized rat. 2 Haemorrhage (sufficient to lower mean arterial blood pressure to 50 mmHg for 90 min) and subsequent resuscitation with shed blood resulted (within 4 h after resuscitation) in a delayed fall in blood pressure to 66+/-4 mmHg (control, n=13). This circulatory failure was not affected by administration (5 min prior to resuscitation) of 3-AB (10 mg kg-1 i.v., n=7), nicotinamide (10 mg kg-1 i.v., n=6) or ISO (3 mg kg-1 i.v., n=6). 3 Haemorrhage and resuscitation also resulted in rises in the serum levels of urea and creatinine. This renal dysfunction was attenuated by 3-AB and nicotinamide, but not by nicotinic acid (n=7), an inactive analogue of nicotinamide. Although ISO (n=6) also attenuated the renal dysfunction caused by haemorrhage and resuscitation, its vehicle (10% DMSO, n=4) had the same effect. 4 Haemorrhagic shock resulted in enhanced serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lipase, indicating the development of hepatocellular and pancreatic injury, respectively. Similarly, haemorrhagic shock also resulted in an increase in the serum levels of creatine kinase (CK) indicating the development of neuromuscular injury. This was attenuated by 3-AB and nicotinamide, but not by nicotinic acid. Although ISO also attenuated the liver, pancreatic and neuromuscular injury caused by haemorrhagic shock, its vehicle had the same effect. 5 Thus, activation of PARS contributes to the organ injury and dysfunction caused by haemorrhage and resuscitation in the rat.