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

Protective effects of FK 506 against haemorrhagic shock-induced microvascular hyperpermeability

Microvascular hyperpermeability, the excessive leakage of fluid and proteins from the intravascular space to the interstitium, is a devastating clinical concern in haemorrhagic shock (HS), sepsis, burn and so forth. Previous studies have shown that HS-induced microvascular hyperpermeability is associated with activation of the mitochondria-mediated 'intrinsic' apoptotic signalling cascade and caspase-3 mediated disruption of the endothelial cell barrier. In this study, our objective was to test if FK506, an immunomodulator that is also known to protect mitochondria, would protect barrier functions and decrease vascular hyperpermeability following HS by acting on this pathway. FK506 (25 µM) was given 10 minutes before the shock period in a rat model of HS. The HS model was a non-traumatic/fixed pressure model of hypovolemic shock developed by withdrawing blood to reduce the mean arterial pressure to 40 mm Hg for 60 minutes. The mesenteric post-capillary venules were monitored for changes in permeability using intravital microscopic imaging. The changes in mitochondrial transmembrane potential (MTP) were determined using the cationic dye 5,5',6,6' tetrachoro-1,1',3,3' tetraethyl benzimidazolyl carbocyanine iodide (JC-1), that was superfused on the mesenteric vasculature followed by intravital imaging. The mesenteric caspase-3 activity was measured fluorometrically. Haemorrhagic shock induced a significant increase in hyperpermeability compared to the sham-control group and FK506 treatment decreased HS-induced hyperpermeability significantly (P < .05). FK506 dampened HS-induced loss of MTP and elevation of caspase-3 activity significantly (P < .05). FK506 has protective effects against HS-induced microvascular hyperpermeability. The maintenance of the MTP and protection against caspase-3 mediated endothelial cell barrier disruption are possible mechanisms by which FK506 attenuates HS-induced hyperpermeability. FK506, currently used in clinical settings as an immunomodulator, needs to be explored further for its therapeutic usefulness against HS-induced vascular hyperpermeability and associated complications.

Transcriptome Analysis Revealed Inflammation Is Involved in the Impairment of Human Umbilical Vein Endothelial Cells Induced by Post-hemorrhagic Shock Mesenteric Lymph

Vascular endothelial injury caused by post-hemorrhagic shock mesenteric lymph (PHSML) return is an important manifestation during refractory hemorrhagic shock. Using human umbilical vein endothelial cells (HUVECs) and transcriptome analysis, this study sought to investigate the molecular mechanism underlying the adverse effect of PHSML on vascular endothelium. Post-hemorrhagic shock mesenteric lymph was collected from male rats after they underwent hemorrhagic shock and following resuscitation, while normal mesenteric lymph (NML) was harvested from sham rats. Human umbilical vein endothelial cells were incubated with the culture medium containing either 10% phosphate buffered saline (Control), NML, or PHSML for 3 h, and then were harvested for RNA sequencing. In comparison with NML treated cells, 37 genes were differentially expressed in PHSML-treated HUVECs, including 32 upregulated genes and five downregulated genes. These differentially expressed genes were mainly enriched in inflammatory pathways, including signaling pathways for activation of the NOD-like receptors, NF-κB, and TNF. Furthermore, we found that C-C motif chemokine ligand 2 (CCL2) was increased significantly after PHSML treatment, and Bindarit, a CCL2 production inhibitor, attenuated the damage of HUVECs induced by PHSML. The results provide molecular evidence on vascular endothelium damage caused by PHSML. C-C motif chemokine ligand 2 might represent a new target for reducing vascular injury after severe hemorrhagic shock.

HO-1 and CD39: It Takes Two to Protect the Realm

Cellular protective mechanisms exist to ensure survival of the cells and are a fundamental feature of all cells that is necessary for adapting to changes in the environment. Indeed, evolution has ensured that each cell is equipped with multiple overlapping families of genes that safeguard against pathogens, injury, stress, and dysfunctional metabolic processes. Two of the better-known enzymatic systems, conserved through all species, include the heme oxygenases (HO-1/HO-2), and the ectonucleotidases (CD39/73). Each of these systems generates critical bioactive products that regulate the cellular response to a stressor. Absence of these molecules results in the cell being extremely predisposed to collapse and, in most cases, results in the death of the cell. Recent reports have begun to link these two metabolic pathways, and what were once exclusively stand-alone are now being found to be intimately interrelated and do so through their innate ability to generate bioactive products including adenosine, carbon monoxide, and bilirubin. These simple small molecules elicit profound cellular physiologic responses that impact a number of innate immune responses, and participate in the regulation of inflammation and tissue repair. Collectively these enzymes are linked not only because of the mitochondria being the source of their substrates, but perhaps more importantly, because of the impact of their products on specific cellular responses. This review will provide a synopsis of the current state of the field regarding how these systems are linked and how they are now being leveraged as therapeutic modalities in the clinic.

Poly(ADP-ribose) polymerase inhibition suppresses inflammation and promotes recovery from adrenal injury in a rat model of acute necrotizing pancreatitis

Background

Poly(ADP-ribose) polymerase (PARP) participates in multi-organ failure in various inflammatory diseases including acute necrotizing pancreatitis (ANP). Since pancreatitis-associated adrenal insufficiency is partly caused by inflammatory damage to the adrenal cortex, we examined whether PARP antagonism could alleviate adrenal insufficiency in a rat model of ANP.

Methods

ANP was induced by retrograde infusion of sodium taurocholate into the bile-pancreatic duct. At 30 min prior to taurocholate infusion, rats were pretreated with the PARP inhibitor 3-Aminobenzamide (3-AB, 20 mg/kg) or vehicle. Pancreatic pathological injury, adrenal histology, neutrophil infiltration, cell apoptosis, and serum corticosterone level were assessed at various times points. Activities of poly(ADP-ribosyl)ated protein (PAR), nuclear factor-kappaB (NF-kB), tumor necrosis factor-α (TNF-α), intercellular adhesion molecule-1 (ICAM-1) and inducible nitric oxide synthase (iNOS) in the adrenal were also examined.

Results

PARP overactivation in ANP rats is associated with reduced serum corticosterone level and marked cellular alterations in adrenocortical tissue. Inflammatory stress caused by ANP reduced adrenal corticosterone release. 3-AB reduced the activation of PARP and inflammatory markers, decreased myeloperoxidase activity, attenuated adrenal morphologic lesions and cells apoptosis, simultaneously improved the impaired adrenal function.

Conclusions

Our data demonstrate the involvement of PARP overactivation in the pathogenesis of adrenal dysfunction after ANP. PARP inhibition may suppress inflammation and promote functional recovery from adrenal injury.

RECOMBINANT BCL-XL ATTENUATES VASCULAR HYPERPERMEABILITY IN A RAT MODEL OF HEMORRHAGIC SHOCK

Following hemorrhagic shock (HS), vascular hyperpermeability, that is, the leakage of fluid, nutrients and proteins into the extravascular space occurs primarily due to the disruption of the endothelial cell–cell adherens junctional complex. Studies from our laboratory demonstrate that activation of the mitochondria-mediated ‘intrinsic’ apoptotic signaling cascade has a significant role in modulating HS-induced hyperpermeability. Here we report the novel use of recombinant Bcl-xL, an anti-apoptotic protein, to control HS-induced vascular hyperpermeability. Our results corroborate involvement of vascular hyperpermeability and apoptotic signaling. HS (the mean arterial pressure (MAP) was reduced to 40 mm Hg for 60 min followed by resuscitation to 90 mm Hg for 60 min) in rats resulted in vascular hyperpermeability as determined by intravital microscopy. Treatment of Bcl-xL (2.5 µg/ml of rat blood in non-lipid cationic polymer, i.v.) before, during and even after HS attenuated or reversed HS-induced vascular hyperpermeability significantly (P<0.05). Conversely, treatment using Bcl-xL inhibitors, 2-methoxy antimycin (2-OMeAA) and ABT 737, significantly increased vascular hyperpermeability compared with sham (P<0.05). Bcl-xL treatment also decreased the amount of fluid volume required to maintain a MAP of 90 mm Hg during resuscitation (P<0.05). HS resulted in an increased mitochondrial reactive oxygen species formation, reduction of ΔΨm, mitochondrial release of cytochrome c and significant activation of caspase-3 (P<0.05). All of these effects were significantly inhibited by Bcl-xL pre-treatment (P<0.05). Our results show that recombinant Bcl-xL is effective against HS-induced vascular hyperpermeability that appears to be mediated through the preservation of ΔΨm and subsequent prevention of caspase-3 activation.

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.

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.

The effect of erythropoietin on microcirculation perfusion and tissue bioenergetics of the small intestine in a hemorrhagic shock and resuscitation rat model

BACKGROUND

Erythropoietin (EPO) can exert acute hemodynamic and anti-inflammatory effects in addition to erythropoiesis. We tested the hypothesis that EPO given at resuscitation with saline will improve capillary perfusion and tissue oxygenation in the gut using a hemorrhagic shock model.

METHODS

Sprague-Dawley rats were bled 30 mL/kg to maintain a mean arterial blood pressure of 40 mm Hg for 50 minutes and then randomized to one of four resuscitation groups (n = 6 per group): blood, blood + recombinant human EPO (rHuEPO), saline, and saline + rHuEPO. Intravenous rHuEPO (1,000 U/kg) was given at the start of resuscitation. Intravital microscopy was used to measure perfused capillary density, flow motion of red blood cell (RBC), and tissue NADH fluorescence 60 minutes after resuscitation. Venous oxygenation saturation (Svo2) was also measured in a second experiment.

RESULTS

In the blood +/- rHuEPO resuscitation group, the perfused capillary density, RBC flow motion scores, and NADH fluorescence returned to near normal values. The saline + rHuEPO group compared with the saline group demonstrated an increased RBC flow motion score (2.32 vs. 1.60; p < 0.01); however, the perfused capillary density was not significantly increased (23.03 Cap/mm vs. 21.61 Cap/mm; p = 0.40). The saline + rHuEPO group also demonstrated statistically significant lower NADH fluorescence than the saline group after shock following resuscitation (110% +/- 3.64% vs. 122% +/- 4.26%; p < 0.05) suggesting decreased tissue dysoxia. The Svo2 in the saline + rHuEPO group was higher when compared with the saline group (45% vs. 38% by continuous oximetry; 38% vs. 29% by co-oximetry; p < 0.05).

CONCLUSION

Our results suggest that the addition of rHuEPO at the time of saline resuscitation may have beneficial effects in hemorrhagic shock by improving tissue perfusion and decreasing dysoxia in the gut.

(-)-Deprenyl inhibits vascular hyperpermeability after hemorrhagic shock

Recent studies from our laboratory demonstrated the involvement of endothelial cell reactive oxygen species (ROS) formation and activation of apoptotic signaling in vascular hyperpermeability after hemorrhagic shock (HS). The objective of this study was to determine if (-)-deprenyl, an antioxidant with antiapoptotic properties, would attenuate HS-induced vascular hyperpermeability. In rats, HS was induced by withdrawing blood to reduce the MAP to 40 mmHg for 60 min followed by resuscitation for 60 min. To study hyperpermeability, we injected the rats with fluorescein isothiocyanate--albumin (50 mg/kg), and the changes in integrated optical intensity of the mesenteric postcapillary venules were obtained intravascularly and extravascularly using intravital microscopy. Mitochondrial ROS formation and mitochondrial transmembrane potential (DeltaPsim) were studied using dihydrorhodamine 123 and JC-1, respectively. Mitochondrial release of cytochrome c was determined using enzyme-linked immunosorbent assay and caspase-3 activity by a fluorometric assay. Parallel studies were performed in rat lung microvascular endothelial cells using proapoptotic BAK as inducer of hyperpermeability. Hemorrhagic shock induced vascular hyperpermeability, mitochondrial ROS formation, DeltaPsim decrease, cytochrome c release, and caspase-3 activation (P G 0.05). (-)-Deprenyl (0.15 mg/kg) attenuated all these effects (P < 0.05). Similarly in rat lung microvascular endothelial cells, (-)-deprenyl attenuated BAK peptide-induced monolayer hyperpermeability (P < 0.05), ROS formation, DeltaPsim decrease, cytochrome c release (P<0.05), and caspase-3 activation (P < 0.05). The protective effects of (-)-deprenyl on vascular barrier functions may be due to its protective effects on DeltaPsim, thereby preventing mitochondrial release of cytochrome c and caspase-3--mediated disruption of endothelial adherens junctions.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Cyclosporine A prevents vascular hyperpermeability after hemorrhagic shock by inhibiting apoptotic signaling

BACKGROUND

Hemorrhagic shock (HS) is associated with the activation of caspase-dependent or -independent apoptotic signaling pathways, disruption of endothelial cell adherens junctions, and vascular hyperpermeability. Recent studies have suggested that the vascular hyperpermeability observed after HS is associated with activation of the intrinsic apoptotic signaling cascade resulting in caspase-mediated cleavage of endothelial cell adherens proteins and subsequent cell-cell detachment. We hypothesized that cyclosporine A (CsA) would attenuate vascular hyperpermeability after HS by protecting mitochondrial transition pores and thereby preventing the activation of caspase-mediated apoptotic signaling. The objective of this study was to determine the effect of CsA on, HS-induced hyperpermeability, mitochondrial membrane depolarization, mitochondrial release of cytochrome c, and caspase 3 activation.

METHODS

HS was induced in Sprague-Dawley rats by withdrawing blood to reduce the mean arterial pressure to 40 mm Hg for 60 minutes. CsA (10 microL/mL) was given 10 minutes before the shock period. The mesenteric postcapillary venules of the proximal ileum were monitored for permeability changes using intravital microscopy. The changes in mitochondrial transmembrane potential were determined using the cationic dye JC-1. Mitochondrial release of cytochrome c in to the cytosol was detected using ELISA. Caspase-3 activity was measured using a fluorometric assay.

RESULTS

HS induced vascular hyperpermeability, release of cytochrome c, and activation of caspase-3 (p < 0.05). CsA (10 microL/mL) attenuated HS-induced hyperpermeability (p < 0.05) and prevented HS-induced decrease in mitochondrial transmembrane potential. CsA treatment decreased the HS-induced rise in cytosolic cytochrome c levels and caspase-3 activity (p < 0.05).

CONCLUSIONS

These findings demonstrate that CsA protects mitochondrial permeability transition pores to prevent HS-induced release of cytochrome c and caspase-3 activation.

Marinobufagenin causes endothelial cell monolayer hyperpermeability by altering apoptotic signaling

Marinobufagenin (MBG) is an endogenous mammalian cardiotonic steroid that is involved in the inhibition of the sodium pump Na(+)/K(+)-ATPase. Increased plasma levels of MBG have been reported in patients with preeclampsia. MBG increases microvascular barrier permeability in an animal model of preeclampsia. However, the mechanism by which MBG impairs endothelial permeability is unknown. We utilized rat lung microvascular endothelial cells (RLMEC) to examine alterations in MBG-induced monolayer permeability and the effect of MBG on the phosphorylation status of ERK1/2, Jnk, and p38. Apoptosis was evaluated by examining alterations in caspases 3/7, 8, and 9 and annexin-V staining. We also examined the effect of MBG on the endothelial adherens junctions of the RLMEC monolayer. MBG inhibited the proliferation, and increased the monolayer permeability, of RLMEC. These actions of MBG were attenuated by ERK, p38, and pan caspase inhibition. MBG significantly decreased the phosphorylation of ERK1/2 and activated the phosphorylation of Jnk and p38. MBG also significantly increased the expression of caspases 3/7, 8, and 9, indicating the activation of apoptosis. MBG-induced apoptosis signaling was not observed in cells pretreated with a p38 inhibitor. MBG treatment induced the disruption of endothelial cell junctions. This effect was prevented by a pan caspase inhibitor. In conclusion, 1) MBG induced an impairment of RLMEC proliferation; 2) the bufadienolide also caused endothelial hyperpermeability; and 3) these effects of MBG were mediated by the downregulation of ERK1/2, the upregulation of Jnk and p38, by the activation of apoptosis, and by the disruption of endothelial cell junctions.

Vascular leak in a rat model of preeclampsia

BACKGROUND/AIMS

Preeclampsia is a hypertensive disorder which develops de novo in women during pregnancy. The urinary excretion of the cardiotonic steroid, marinobufagenin (MBG), is increased prior to the development of hypertension. Preeclamptic patients are volume expanded but much of the excess salt and water appears to be located primarily in the interstitial space. Therefore, 'capillary leak' syndrome has been postulated in this disorder.

METHODS

We evaluated the vascular leakage in normal rats following MBG injection and in a rat model of human preeclampsia. We measured the changes in light intensity comparing that in the intravascular to the extravascular space by assessing 'leak' of fluorescein-labeled albumin (FITC-albumin) from mesenteric postcapillary venules.

RESULTS

FITC-albumin extravasation continued to increase in a time-dependent fashion after MBG infusion and was significant (p < 0.05) at 60 min of observation when compared to sham rats. We also observed a significant difference in 'vascular leakage' in preeclamptic rats compared to control non-pregnant and normal pregnant groups starting at 20 min after the FITC-albumin infusion.

CONCLUSION

We propose that MBG is involved in the production of a 'vascular leak' in our rat model of preeclampsia.

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-1 and its clinical applications in brain injury

Traumatic brain injury (TBI) is a devastating occurrence that may result in short- and long-term complications. Oxidative stress (an imbalance between oxidants and antioxidants) plays a critical role in the development of secondary injuries following TBI and, consequently, in patient outcomes. Secondary injuries resulting from oxidative stress produce DNA strand breaks that activate poly(adenosine diphosphate [ADP]-ribose) polymerase-1 (PARP-1) and produce another level of injury. PARP-1 functions as a DNA-damage sensor and signaling molecule. In response to the severe DNA damage after brain injury, PARP-1 becomes overactivated and depletes the cells' energy sources, which leads to cellular and neuronal death. Recently, PARP-1 inhibition has been studied in various animal models of brain injury with promising results. TBI treatments based on PARP-1 inhibition in humans are far from the clinical arena, although descriptive studies of PARP-1 activation in humans are beginning to emerge. Nurses should become involved in this area of collaborative research in human response to brain injury by helping design and implement safe and meaningful clinical trials.

Ischemia/Reperfusion of the Liver Induces Heart Injury in Rats

OBJECTIVE

We evaluated the cardiovascular injury induced by ischemia and reperfusion (I/R) of the liver by measuring changes in blood levels of cardiac troponin I (cTNI), an index of cardiovascular injury, as well as levels of selected indicators of an inflammatory response.

MATERIALS AND METHODS

Ischemia was induced in the rat liver by clamping the common hepatic artery and portal vein for 40 minutes, after which flow was restored, and the liver reperfused for 90 minutes. Blood samples were collected prior to ischemia and after reperfusion. cTNI as well as levels of tumor necrosis factor alpha (TNFalpha), hydroxyl radical (.OH), nitric oxide (NO), and alanine transferase (ALT) were measured.

RESULTS

I/R of the liver induced a significant increase in ALT (P<.001). Increased cTNI levels (P<.05) were associated with inflammatory responses, such as elevated levels of TNFalpha (P<.001), . OH (P<.001), and NO (P<.001). After administration of 3-aminobenzamide, a poly(ADP-ribose) polymerase (PARP) inhibitor, liver and heart injuries were significantly attenuated (P<.05).

CONCLUSIONS

I/R-induced liver injury was associated with cardiovascular injury, perhaps resulting from inflammatory responses triggered by elevated levels of reactive radical species of nitric oxide, superoxide, and peroxynitrite, by which PARP was activated. 3-Aminobenzamide, significantly attenuated I/R-induced liver and heart injuries.

Increased poly(ADP-ribose) polymerase activity during porcine hemorrhagic shock is transient and predictive of mortality

AIM OF THE STUDY

The aim of our study was to compare poly(ADP-ribose) polymerase (PARP) activity levels in a porcine model of hemorrhagic shock and resuscitation.

MATERIALS AND METHODS

We designed a prospective, comparative randomized survival study of hemorrhagic shock using 20 male Yorkshire-Landrace pigs (15-25 kg). In 16 pigs after splenectomy, we induced hemorrhagic shock to a mean arterial pressure of 50 mm Hg ( approximately 35% bleed). Pigs were randomized to receive normotensive resuscitation (SBP 90 mm Hg), mild hypotensive resuscitation (SBP 80 mm Hg), moderate hypotensive resuscitation (SBP 65 mm Hg), or no resuscitation (n=4 in each group). We also included a group of sham animals that were instrumented and had a splenectomy but not bled (n=4). Muscle and liver biopsies were taken prior to hemorrhage, after 45 min of shock, and 8, 24, and 48 h after resuscitation. PARP activity levels in biopsies were measured using chemical quantitation of NAD+.

RESULTS

Irrespective of our resuscitation strategy or outcome, both muscle and liver PARP activity levels rose after 45 min of shock and then returned to baseline. Excluding our control animals, PARP activity levels were significantly higher during shock in non-survivors compared to survivors.

CONCLUSIONS

In our model of porcine hemorrhagic shock, PARP activity levels increased during hemorrhagic shock. However, this increase in PARP activity levels was transient as they returned to baseline regardless of resuscitation strategy. Interestingly, PARP activity levels were significantly higher during hemorrhagic shock in non-survivors compared to survivors. These findings suggest that PARP activity may be a part of initial pathways leading from hemorrhagic shock to death.

Apoptotic signaling induces hyperpermeability following hemorrhagic shock

Hemorrhagic shock (HS) disrupts the endothelial cell barrier, resulting in microvascular hyperpermeability. Recent studies have also demonstrated that activation of the apoptotic signaling cascade is involved in endothelial dysfunction, which may result in hyperpermeability. Here we report involvement of the mitochondrial "intrinsic" pathway in microvascular hyperpermeability following HS in rats. HS resulted in the activation of the mitochondrial intrinsic pathway, as is evident from an increase in the proapoptotic Bcl-2 family member BAK, release of mitochondrial cytochrome c into the cytoplasm, and activation of caspase-3. This, along with the in vivo transfection of the proapoptotic peptide BAK (BH3), resulted in hyperpermeability (as visualized by intravital microscopy), release of mitochondrial cytochrome c into the cytoplasm, and activation of caspase-3. Conversely, transfection of the BAK (BH3) mutant had no effect on hyperpermeability. Together, these results demonstrate involvement of the mitochondrial intrinsic apoptotic pathway in HS-induced hyperpermeability and that the attenuation of this pathway may provide an alternative strategy in preserving vascular barrier integrity.

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.

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.

Poly(ADP-ribose) polymerases: homology, structural domains and functions. Novel therapeutical applications

Poly(ADP-ribose) polymerases (PARPs) are a family of enzymes, which show differences in structure, cellular location and functions. However, all these enzymes possess poly(ADP-ribosyl)ation activity. Overactivation of PARP enzymes has been implicated in the pathogenesis of several diseases, including stroke, myocardial infarction, diabetes, shock, neurodegenerative disorder and allergy. The best studied of these enzymes (PARP-1) is involved in the cellular response to DNA damage so that in the event of irreparable DNA damage overactivation of PARP-1 leads to necrotic cell death. Inhibitors of PARP-1 activity in combination with DNA-binding antitumor drugs may constitute a suitable strategy in cancer chemotherapy. In addition, PARP inhibitors may be also useful to restore cellular functions in several pathophysiological states and diseases. This review gives an update of the state-of-the-art concerning PARP enzymes and their exploitation as pharmacological targets in several illnesses.

Mechanisms of postburn intestinal barrier dysfunction in the rat: Roles of epithelial cell renewal, E-cadherin, and neutrophil extravasation*

OBJECTIVE

Our group has previously shown that the intestinal epithelium exhibits increased postburn barrier permeability and bacterial translocation associated with deranged neutrophil activity. The purpose of this investigation is to explore possible underlying intestinal structural mechanisms, leading to those functional changes with emphasis on (1) neutrophil influx and extravasation in the intestinal lamina propria 1-3 days after burn and (2) enterocyte proliferation, migration, apoptosis, and E-cadherin junctional epithelium levels 3 days after burn.

DESIGN

Freshly isolated ileum specimens were quick frozen, then cut by a cryostat into 30-micron-thick sections. Sections from day 1 postburn rats were immunostained with (1) anti-granulocyte or anti-elastase antibodies to assess neutrophil influx or (2) combined anti-granulocyte and anti-von Willebrand factor double immunolabeling to compare levels of neutrophil extravasation. Sections from day 3 postburn rats were immunostained with (1) bromodeoxyuridine immunohistochemistry 1, 3, 6, or 18 hrs after bromodeoxyuridine injection to assess enterocyte proliferation and migration, (2) cytokeratin-18 M30-immunohistochemistry to compare levels of enterocyte apoptosis, and (3) E-cadherin immunohistochemistry to compare junctional E-cadherin integrity. Ileal myeloperoxidase activity and bacterial translocation of Enterococcus faecalis were assessed biochemically and by E. faecalis-specific bacterial cultures, respectively, in day 3 postburn rats.

SETTING

: Research laboratories in a medical center and an academic institution.

SUBJECTS

Male Sprague-Dawley rats given sham treatment or treatment as a burn model with full-thickness skin scald over 30% total body surface area.

CONCLUSIONS

We report (1) increased levels of neutrophil influx and extravasation in villi lamina propriae, including elastase-positive cells (postburn day 1), (2) heightened levels of intestinal myeloperoxidase activity (postburn day 3), (3) decreased levels of epithelial cell proliferation, migration, and E-cadherin (postburn day 3), and (4) increased enterocyte apoptosis and E. faecalis bacterial translocation (postburn day 3). Based on these structural and functional abnormalities, we propose a mechanism for burn injury-related intestinal barrier dysfunction that includes increased trans- and para-cellular leakage caused by impaired enterocyte renewal and decreased junctional E-cadherin levels subsequent to increased neutrophil influx and extravasation within the villus lamina propria microenvironment.

Poly(ADP-ribose) polymerase and renal hypothermic preservation injury

The nuclear enzyme poly(ADP-ribose) polymerase (PARP) has been implicated in ischemia-reperfusion injury in many tissues under normothermic conditions. The purpose of this study was to determine whether PARP contributes to mechanisms of the hypothermic ischemia-reperfusion injury that occurs when kidneys are cold stored for transplantation. Cortical tissue slice PARP enzyme activity rose significantly with prolonged cold storage and was dependent on both reperfusion and preservation quality. However, prior exposure to warm ischemia abrogated this increase. PARP protein increased with cold storage but was not dependent on reperfusion. PARP enzyme activity rose quickly after reperfusion in buffer and was not different when whole blood was used. Addition of exogenous hydrogen peroxide (3 mM) to normal renal slices significantly increased PARP activity over 4 h in the cortex but not in the medulla, but the medullary basal PARP synthesis rate was five times higher than that in the cortex. However, the reactive oxygen species (ROS) inhibitors catalase (2,000 U/ml), Trolox (200 microM), and DMSO (15 mM) did not reduce reperfusion-induced PARP activity in cold-stored cortical slices. Finally, PARP inhibitors potentiated preservation injury in isolated canine proximal renal tubules. In conclusion, canine renal PARP enzyme activity rises with prolonged cold storage after reperfusion and may play a protective rather than an injurious role in hypothermic preservation for transplantation. ROS are sufficient but not necessary to activate PARP under these conditions.

Pyruvate improves redox status and decreases indicators of hepatic apoptosis during hemorrhagic shock in swine

Previous studies have shown that the liver is the first organ to display signs of injury during hemorrhagic shock. We examined the mechanism by which pyruvate can prevent liver damage during hemorrhagic shock in swine anesthetized with halothane. Thirty minutes after the induction of a 240-min controlled arterial hemorrhage targeted at 40 mmHg, hypertonic sodium pyruvate (0.5 g. kg(-1). h(-1)) was infused to achieve an arterial concentration of 5 mM. The volume and osmolality effects of pyruvate were matched with 10% saline (HTS) and 0.9% saline (NS). Although the peak hemorrhage volume increased significantly in both the pyruvate and HTS group, only the pyruvate treatment was effective in delaying cardiovascular decompensation. In addition, pyruvate effectively maintained the NADH/NAD redox state, as evidenced by increased microdialysate pyruvate levels and a significantly lower lactate-to-pyruvate ratio. Pyruvate also prevented the loss of intracellular antioxidants (GSH) and a reduction in the GSH-to-GSSG ratio. These beneficial effects on the redox environment decreased hepatic cellular death by apoptosis. Pyruvate significantly increased the ratio of Bcl-Xl (antiapoptotic molecule)/Bax (proapoptotic molecule), prevented the release of cytochrome c from mitochondria, and decreased the fragmentation of caspase 3 and poly(ADP ribose) polymerase (DNA repair enzyme). These beneficial findings indicate that pyruvate infused 30 min after the onset of severe hemorrhagic shock is effective in maintaining the redox environment, preventing the loss of the key antioxidant GSH, and decreasing early apoptosis indicators.

Poly(ADP-ribose) polymerase triggers the microvascular mechanisms of hepatic ischemia-reperfusion injury

Activation of poly(ADP-ribose) polymerase (PARP) mediates oxidative stress-induced cell injury. We tested the hypothesis that PARP contributes to ischemia-reperfusion (I/R) damage of the liver by triggering the mechanisms of microcirculatory failure. Leukocyte- and platelet-endothelial cell interactions as well as sinusoidal perfusion were analyzed by intravital fluorescence microscopy after lobar hepatic I/R (90 min/30 min) in C57BL/6 x 129/Sv wild-type (PARP+/+) and PARP-deficient (PARP-/-) mice. Hepatic I/R induced leukocyte/platelet-endothelial cell interactions and tissue injury in PARP+/+ mice, as indicated by impaired sinusoidal perfusion and increased alanine aminotransferase (ALT)/aspartate aminotransferase (AST) serum activities. In PARP-/- mice, however, the postischemic increase in the numbers of rolling/adherent leukocytes and platelets was significantly lower. In addition, I/R-induced translocation of CD62P as well as mRNA expression of CD62E, CD54, and CD106 were attenuated. The degree of perfusion failure was reduced and the increase in the ALT/AST activities was lower in PARP-/- mice compared with PARP+/+ mice. We conclude that PARP contributes to hepatic microvascular injury by triggering the expression/translocation of adhesion molecules and modulating leukocyte/platelet-endothelial cell interactions.

Potential clinical applications of poly(ADP-ribose) polymerase (PARP) inhibitors

Poly(ADP-ribose) polymerases (PARPs) are defined as cell signaling enzymes that catalyze the transfer of ADP-ribose units from NAD(+)to a number of acceptor proteins. PARP-1, the best characterized member of the PARP family, that presently includes six members, is an abundant nuclear enzyme implicated in cellular responses to DNA injury provoked by genotoxic stress (oxygen radicals, ionizing radiations and monofunctional alkylating agents). Due to its involvement either in DNA repair or in cell death, PARP-1 is regarded as a double-edged regulator of cellular functions. In fact, when the DNA damage is moderate, PARP-1 participates in the DNA repair process. Conversely, in the case of massive DNA injury, elevated PARP-1 activation leads to rapid NAD(+)/ATP consumption and cell death by necrosis. Excessive PARP-1 activity has been implicated in the pathogenesis of numerous clinical conditions such as stroke, myocardial infarction, shock, diabetes and neurodegenerative disorders. PARP-1 could therefore be considered as a potential target for the development of pharmacological strategies to enhance the antitumor efficacy of radio- and chemotherapy or to treat a number of clinical conditions characterized by oxidative or NO-induced stress and consequent PARP-1 activation. Moreover, the discovery of novel functions for the multiple members of the PARP family might lead in the future to additional clinical indications for PARP inhibitors.