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) polymerase inhibition: past, present and future

The process of poly(ADP-ribosyl)ation and the major enzyme that catalyses this reaction, poly(ADP-ribose) polymerase 1 (PARP1), were discovered more than 50 years ago. Since then, advances in our understanding of the roles of PARP1 in cellular processes such as DNA repair, gene transcription and cell death have allowed the investigation of therapeutic PARP inhibition for a variety of diseases - particularly cancers in which defects in DNA repair pathways make tumour cells highly sensitive to the inhibition of PARP activity. Efforts to identify and evaluate potent PARP inhibitors have so far led to the regulatory approval of four PARP inhibitors for the treatment of several types of cancer, and PARP inhibitors have also shown therapeutic potential in treating non-oncological diseases. This Review provides a timeline of PARP biology and medicinal chemistry, summarizes the pathophysiological processes in which PARP plays a role and highlights key opportunities and challenges in the field, such as counteracting PARP inhibitor resistance during cancer therapy and repurposing PARP inhibitors for the treatment of non-oncological diseases.

Exploration of the nicotinamide-binding site of the tankyrases, identifying 3-arylisoquinolin-1-ones as potent and selective inhibitors in vitro

Tankyrases-1 and -2 (TNKS-1 and TNKS-2) have three cellular roles which make them important targets in cancer. Using NAD(+) as a substrate, they poly(ADP-ribosyl)ate TRF1 (regulating lengths of telomeres), NuMA (facilitating mitosis) and axin (in wnt/β-catenin signalling). Using molecular modelling and the structure of the weak inhibitor 5-aminoiso quinolin-1-one, 3-aryl-5-substituted-isoquinolin-1-ones were designed as inhibitors to explore the structure-activity relationships (SARs) for binding and to define the shape of a hydrophobic cavity in the active site. 5-Amino-3-arylisoquinolinones were synthesised by Suzuki-Miyaura coupling of arylboronic acids to 3-bromo-1-methoxy-5-nitro-isoquinoline, reduction and O-demethylation. 3-Aryl-5-methylisoquinolin-1-ones, 3-aryl-5-fluoroisoquinolin-1-ones and 3-aryl-5-methoxyisoquinolin-1-ones were accessed by deprotonation of 3-substituted-N,N,2-trimethylbenzamides and quench with an appropriate benzonitrile. SAR around the isoquinolinone core showed that aryl was required at the 3-position, optimally with a para-substituent. Small meta-substituents were tolerated but groups in the ortho-positions reduced or abolished activity. This was not due to lack of coplanarity of the rings, as shown by the potency of 4,5-dimethyl-3-phenylisoquinolin-1-one. Methyl and methoxy were optimal at the 5-position. SAR was rationalised by modelling and by crystal structures of examples with TNKS-2. The 3-aryl unit was located in a large hydrophobic cavity and the para-substituents projected into a tunnel leading to the exterior. Potency against TNKS-1 paralleled potency against TNKS-2. Most inhibitors were highly selective for TNKSs over PARP-1 and PARP-2. A range of highly potent and selective inhibitors is now available for cellular studies.

The potential of PARP inhibitors in neuro-oncology

DNA damaging agents have an integral role in the treatment of brain tumors. Recent advances in our understanding of how cancer cells repair DNA damage have made it possible to consider modification of the DNA damage response as a way in which resistance to radiotherapy and chemotherapy might be overcome. PARP inhibitors are potent but nontoxic drugs that inhibit repair of DNA single-strand breaks and increase the cytotoxic effects of radiotherapy and alkylating chemotherapy agents, including temozolomide. PARP inhibitors have potential applications in neuro-oncology because there is increasing evidence that their radio- and chemo-sensitizing effects are tumor specific. This review explores the mechanisms of action of PARP inhibitors and describes their putative mechanisms of radio- and chemo-sensitization in the context of CNS oncology. The authors go on to review their development in recent clinical trials, with a focus on glioblastoma.

Insights into the binding of PARP inhibitors to the catalytic domain of human tankyrase-2

The poly(ADP-ribose) polymerase (PARP) family represents a new class of therapeutic targets with diverse potential disease indications. PARP1 and PARP2 inhibitors have been developed for breast and ovarian tumors manifesting double-stranded DNA-repair defects, whereas tankyrase 1 and 2 (TNKS1 and TNKS2, also known as PARP5a and PARP5b, respectively) inhibitors have been developed for tumors with elevated β-catenin activity. As the clinical relevance of PARP inhibitors continues to be actively explored, there is heightened interest in the design of selective inhibitors based on the detailed structural features of how small-molecule inhibitors bind to each of the PARP family members. Here, the high-resolution crystal structures of the human TNKS2 PARP domain in complex with 16 various PARP inhibitors are reported, including the compounds BSI-201, AZD-2281 and ABT-888, which are currently in Phase 2 or 3 clinical trials. These structures provide insight into the inhibitor-binding modes for the tankyrase PARP domain and valuable information to guide the rational design of future tankyrase-specific inhibitors.

Poly(ADP-ribose) polymerase inhibition improves endothelin-1-induced endothelial dysfunction in rat thoracic aorta

AIM

The aim of this study was to investigate whether poly(ADP-ribose) polymerase (PARP) inhibition improves endothelin-1 (ET-1)-induced endothelial dysfunction (ED).

METHODS

Isolated rat thoracic aorta rings were incubated with ET-1 (10 nmol/L) in the presence or absence of either polyethylene glycol-superoxide dismutase (PEG-SOD; a cell-permeable superoxide radical scavenger, 41 U/mL) plus apocynin (a NADPH oxidase inhibitor, 300 µmol/L) or PJ34 (an inhibitor of polyADP-ribose polymerase, 3 µmol/L) for 18 h. Isometric tension studies were performed in response to acetylcholine (ACh; an endothelium-dependent vasodilator), sodium nitroprusside (SNP; an endothelium-independent vasodilator), and phenylephrine (Phe). PARP-1 and PAR (an end-product of PARP activity) expressions were evaluated by both Western blot and immunohistochemistry.

RESULTS

Incubation of thoracic aorta rings with ET-1 resulted in a significant inhibition of the response to ACh, while SNP-induced relaxation was unaffected. The contractile response to Phe increased in arteries that were incubated with ET-1. PARP-1 and PAR expressions increased after ET-1 incubation. The diminished vasoreactivity as well as changes in expressions of PARP-1 and PAR in ET-1-incubated vessels were improved by both PEG-SOD plus apocynin and PJ34.

CONCLUSION

Our studies demonstrate that ED induced by ET-1 seems to be effected via oxidative stress in the thoracic aorta endothelium with subsequent activation of the PARP pathway.

Role of poly (ADP-ribose)-polymerase and its signaling pathway with renin-angiotensin aldosterone system in renal diseases

Poly(ADP-ribose) polymerase (PARP), a ubiquitous, chromatin-bound enzyme, plays a crucial role in many processes, including DNA repair, cell death, metabolism, and inflammatory responses, by activating DNA repair pathways responsible for cellular survival. Renin-angiotensin-aldosterone system (RAAS) genes encode renin, angiotensinogen, angiotensin-converting enzyme, angiotensin type-1 receptor and aldosterone synthase gene. RAAS is a hormone system which acts on multiple physiologic pathways primarily by regulating blood pressure, electrolyte and fluid homeostasis in mammals, but also by local autocrine and paracrine actions. The current status quo of scientific evidence shows that there might be a signaling pathway between PARP and RAAS. Herein, we review the role of PARP and its signaling pathways with RAAS in renal diseases.

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.

PARP-1 regulates expression of TGF-β receptors in T cells

Transforming growth factor-β (TGF-β) receptors (TβRs) are essential components for TGF-β signal transduction in T cells, yet the mechanisms by which the receptors are regulated remain poorly understood. We show here that Poly(ADP-ribose) polymerase-1 (PARP-1) regulates TGF-β receptor I (TβRI) and II (TβRII) expression in CD4(+) T cells and subsequently affects Smad2/3-mediated TGF-β signal transduction. Inhibition of PARP-1 led to the upregulation of both TβRI and TβRII, yet the underlying molecular mechanisms were distinct. PARP-1 selectively bound to the promoter of TβRII, whereas the enzymatic activity of PARP-1 was responsible for the inhibition of TβRI expression. Importantly, inhibition of PARP-1 also enhanced expression of TβRs in human CD4(+) T cells. Thus, PARP-1 regulates TβR expression and TGF-β signaling in T cells.

Potential role of poly(ADP-ribose) polymerase (PARP) activation in methotrexate-induced nephrotoxicity and tubular apoptosis

Nephrotoxicity is one of the serious dose-limiting complications of methotrexate (MTX) when used in the treatment of various malignancies and nononcological diseases. The aim of this study was to investigate the role of poly(adenosine diphosphate ribose) polymerase (PARP) activity in MTX-induced nephrotoxicity. Rats were divided into 4 groups as control, MTX treated (MTX, 7 mg/kg per d, intraperitoneally [ip], once daily for 3 consecutive days), MTX plus 1,5-isoquinelinediol (ISO, a PARP inhibitor, 3 mg/kg per d, i.p.) treated, or ISO treated. Histopathology of kidneys was evaluated by light microscopy. Terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling assay was used to analyze apoptosis in kidney sections. Blood urea nitrogen (BUN), serum creatinine, and urinary N-acetyl-β-d-glucosaminidase (NAG) were used as biochemical markers of MTX-induced renal injury. Our results showed that MTX administration significantly increased BUN, serum creatinine, and urinary NAG levels. The PARP-1 and PAR (a product of PARP activity) expression and apoptotic cell death were also markedly increased in renal tubules after MTX administration. The ISO treatment attenuated MTX-induced renal injury, as indicated by BUN and serum creatinine levels, urinary NAG excretion, and renal histology. The PARP inhibitor treatment reduced PARP-1 and PAR expression to levels similar to that of controls. These results revealed that ISO may have a protective effect against the nephrotoxic effects of MTX by inhibiting PARP activation. This is the first study that demonstrates the role of PARP activation in MTX-induced nephrotoxicity and tubular apoptosis.

Cellular bioenergetics is regulated by PARP1 under resting conditions and during oxidative stress

PURPOSE

The goal of the current studies was to elucidate the role of the principal poly(ADP-ribose)polymerase isoform, PARP1 in the regulation of cellular energetics in endothelial cells under resting conditions and during oxidative stress.

METHODS

We utilized bEnd.3 endothelial cells and A549 human transformed epithelial cells. PARP1 was inhibited either by pharmacological inhibitors or by siRNA silencing. The Seahorse XF24 Extracellular Flux Analyzer was used to measure indices of mitochondrial respiration (oxygen consumption rate) and of glycolysis (extracellular acidification rate). Cell viability, cellular and mitochondrial NAD(+) levels and mitochondrial biogenesis were also measured.

RESULTS

Silencing of PARP1 increased basal cellular parameters of oxidative phosphorylation, providing direct evidence that PARP1 is a regulator of mitochondrial function in resting cells. Pharmacological inhibitors of PARP1 and siRNA silencing of PARP1 protected against the development of mitochondrial dysfunction and elevated the respiratory reserve capacity in endothelial and epithelial cells exposed to oxidative stress. The observed effects were unrelated to an effect on mitochondrial biogenesis. Isolated mitochondria of A549 human transformed epithelial cells exhibited an improved resting bioenergetic status after stable lentiviral silencing of PARP1; these effects were associated with elevated resting mitochondrial NAD+ levels in PARP1 silenced cells.

CONCLUSIONS

PARP1 is a regulator of basal cellular energetics in resting endothelial and epithelial cells. Furthermore, endothelial cells respond with a decrease in their mitochondrial reserve capacity during low-level oxidative stress, an effect, which is attenuated by PARP1 inhibition. While PARP1 is a regulator of oxidative phosphorylation in resting and oxidatively stressed cells, it only exerts a minor effect on glycolysis.

5-Benzamidoisoquinolin-1-ones and 5-(ω-carboxyalkyl)isoquinolin-1-ones as isoform-selective inhibitors of poly(ADP-ribose) polymerase 2 (PARP-2)

PARP-2 is a member of the poly(ADP-ribose) polymerase family, with some activities similar to those of PARP-1 but with other distinct roles. Two series of isoquinolin-1-ones were designed, synthesized, and evaluated as selective inhibitors of PARP-2, using the structures of the catalytic sites of the isoforms. A new efficient synthesis of 5-aminoisoquinolin-1-one was developed, and acylation with acyl chlorides gave 5-acylaminoisoquinolin-1-ones. By examination of isoquinolin-1-ones with carboxylates tethered to the 5-position, Heck coupling of 5-iodoisoquinolin-1-one furnished the 5-CH═CHCO(2)H compound for reduction to the 5-propanoic acid. Alkylation of 5-aminoisoquinolin-1-one under mildly basic conditions, followed by hydrolysis, gave 5-(carboxymethylamino)isoquinolin-1-one, whereas it was alkylated at 2-N with methyl propenoate and strong base. Compounds were assayed in vitro for inhibition of PARP-1 and PARP-2, using FlashPlate and solution-phase assays, respectively. The 5-benzamidoisoquinolin-1-ones were more selective for inhibition of PARP-2, whereas the 5-(ω-carboxyalkyl)isoquinolin-1-ones were less so. 5-Benzamidoisoquinolin-1-one is the most PARP-2-selective compound (IC(50(PARP-1))/IC(50(PARP-2)) = 9.3) to date, in a comparative study.

Synthesis of 4-alkyl-, 4-aryl- and 4-arylamino-5-aminoisoquinolin-1-ones and identification of a new PARP-2 selective inhibitor

The considerable interest in substituted isoquinolin-1-ones related to 5-aminoisoquinolin-1-one (5-AIQ) as drugs points to a need for an efficient and straightforward synthesis of the 4,5-disubstituted bicycles. Bromination of 5-nitroisoquinolin-1-one gave 4-bromo-5-nitroisoquinolin-1-one but neither this nor 5-amino-4-bromoisoquinolin-1-one would participate in Pd-catalysed couplings. Protection of the lactam as 1-methoxy- and 1-benzyloxy-4-bromo-5-nitroisoquinolines, however, permitted Stille, Suzuki and Buchwald-Hartwig couplings to take place in high yields, insensitive to electronic demands and severe steric bulk in the arylboronic acids. Lithiation of 4-bromo-1-methoxy-5-nitroisoquinoline and quench with iodomethane gave 1-methoxy-4-methyl-5-nitroisoquinoline in low yield. Demethylation of the 1-methoxy-4-substituted-5-nitroisoquinolines with hydrogen bromide gave 4-substituted-5-nitroisoquinolin-1-ones, whereas hydrogenolytic debenzylation was achieved with simultaneous reduction of the 5-nitro group. 5-Amino-4-(4-trifluoromethylphenyl)isoquinolin-1-one was identified as a new potent and selective inhibitor of poly(ADP-ribose)polymerase-2 (PARP-2).

PolyADP-ribosylation is required for pronuclear fusion during postfertilization in mice

Background

During fertilization, pronuclear envelope breakdown (PNEB) is followed by the mingling of male and female genomes. Dynamic chromatin and protein rearrangements require posttranslational modification (PTM) for the postfertilization development.

Methodology/Principal Findings

Inhibition of poly(ADP-ribose) polymerase activity (PARylation) by either PJ-34 or 5-AIQ resulted in developmental arrest of fertilized embryos at the PNEB. PARylation inhibition affects spindle bundle formation and phosphorylation of Erk molecules of metaphase II (MII) unfertilized oocytes. We found a frequent appearance of multiple pronuclei (PN) in the PARylation-inhibited embryos, suggesting defective polymerization of tubulins. Attenuated phosphorylation of lamin A/C by PARylation was detected in the PARylation-inhibited embryos at PNEB. This was associated with sustained localization of heterodomain protein 1 (HP1) at the PN of the one-cell embryos arrested by PARylation inhibition.

Conclusions/Significance

Our findings indicate that PARylation is required for pronuclear fusion during postfertilization processes. These data further suggest that PARylation regulates protein dynamics essential for the beginning of mouse zygotic development. PARylation and its involving signal-pathways may represent potential targets as contraceptives.

Role of the poly(ADP-ribose)polymerase activity in vancomycin-induced renal injury

The aim of the present study was to investigate the role of poly(ADP-ribose)polymerase (PARP) activity in vancomycin (VCM)-induced renal injury and to determine whether 1,5-isoquinelinediol (ISO), a PARP inhibitor agent, could be offered as an alternative therapy in VCM-induced renal impairment. Rats were divided into four groups as follows: (i) control (Group 1); (ii) VCM-treated (Group 2); (iii) VCM plus ISO-treated (Group 3); and (iv) ISO-treated (Group 4). VCM (200mg/kg, i.p., twice daily) was administered to Groups 2 and 3 for 7 days. ISO (3mg/kg/day, i.p.) treatment was started 24h before the first administration of VCM and continued for 8 days. After the 14th VCM injection, the animals were placed in metabolic cages to collect urine samples. All the rats were sacrificed by decapitation, blood samples were taken in tubes and kidneys were excised immediately. Blood urea nitrogen (BUN) and plasma creatinine, and urinary N-acetyl-beta-d-glucosaminidase (NAG, a marker of renal tubular injury) were used as markers of VCM-induced renal injury in rats. Light microscopy was used to evaluate semi-quantitative analysis of the kidney sections. Poly(ADP-ribose) (PAR, the product of activated PARP) and PARP-1 expressions in renal tissues were demonstrated by immunohistochemistry and Western blot. VCM administration increased BUN levels from 8.07+/-0.75 mg/dL to 53.87+/-10.11 mg/dL. The plasma creatinine levels were 0.8+/-0.04 mg/dL and 3.38+/-0.51 mg/dL for the control and VCM-treated groups, respectively. Also, urinary excretion of NAG was increased after VCM injection. Besides, there was a significant dilatation of the renal tubules, eosinophilic casts within some tubules, desquamation and vacuolization of renal tubule epithelium, and interstitial tissue inflammation in VCM-treated rats. In VCM-treated rats, both PAR and PARP-1 expressions were increased in renal tubular cells. ISO treatment attenuated VCM-induced renal injury, as indicated by BUN and plasma creatinine levels, urinary NAG excretion, and renal histology. PARP inhibitor treatment also decreased PAR and PARP-1 protein expressions similar to that of controls. Herewith, the overactivation of the PARP pathway may have a role in VCM-induced renal impairment and pharmacological inhibition of this pathway might be an effective intervention to prevent VCM-induced acute renal injury.

Design, synthesis, and evaluation in vitro of quinoline-8-carboxamides, a new class of poly(adenosine-diphosphate-ribose)polymerase-1 (PARP-1) inhibitor

Poly(ADP-ribose)polymerase-1 is an important target enzyme in drug design; inhibitors have a wide variety of therapeutic activities. A series of quinoline-8-carboxamides was designed to maintain the required pharmacophore conformation through an intramolecular hydrogen bond. 3-Substituted quinoline-8-carboxamides were synthesized by Pd-catalyzed couplings (Suzuki, Sonogashira, Stille) to 3-iodoquinoline-8-carboxamide, an efficient process that introduces diversity in the final step. 2-Substituted quinoline-8-carboxamides were prepared by selective Pd-catalyzed couplings at the 2-position of 2,8-dibromoquinoline, followed by lithium-bromine exchange of the intermediate 2-(alkyl/aryl)-8-bromoquinolines and reaction with trimethylsilyl isocyanate. The intramolecular hydrogen bond was confirmed by X-ray and by NMR. The SAR of the 3-substituted compounds for inhibition of human recombinant PARP-1 activity showed a requirement for a small narrow group. Substituents in the 2-position increased potency, with the most active 2-methylquinoline-8-carboxamide having IC(50) = 500 nM (IC(50) = 1.8 microM for 5-aminoisoquinolin-1-one (5-AIQ, a standard water-soluble inhibitor)).

Antigen microarrays identify unique serum autoantibody signatures in clinical and pathologic subtypes of multiple sclerosis

Multiple sclerosis (MS) is a chronic relapsing disease of the central nervous system (CNS) in which immune processes are believed to play a major role. To date, there is no reliable method by which to characterize the immune processes and their changes associated with different forms of MS and disease progression. We performed antigen microarray analysis to characterize patterns of antibody reactivity in MS serum against a panel of CNS protein and lipid autoantigens and heat shock proteins. Informatic analysis consisted of a training set that was validated on a blinded test set. The results were further validated on an independent cohort of relapsing-remitting (RRMS) samples. We found unique autoantibody patterns that distinguished RRMS, secondary progressive (SPMS), and primary progressive (PPMS) MS from both healthy controls and other neurologic or autoimmune driven diseases including Alzheimer's disease, adrenoleukodystropy, and lupus erythematosus. RRMS was characterized by autoantibodies to heat shock proteins that were not observed in PPMS or SPMS. In addition, RRMS, SPMS, and PPMS were characterized by unique patterns of reactivity to CNS antigens. Furthermore, we examined sera from patients with different immunopathologic patterns of MS as determined by brain biopsy, and we identified unique antibody patterns to lipids and CNS-derived peptides that were linked to each type of pathology. The demonstration of unique serum immune signatures linked to different stages and pathologic processes in MS provides an avenue to monitor MS and to characterize immunopathogenic mechanisms and therapeutic targets in the disease.

Imidazoquinolinone, imidazopyridine, and isoquinolindione derivatives as novel and potent inhibitors of the poly(ADP-ribose) polymerase (PARP): a comparison with standard PARP inhibitors

We have identified three novel structures for inhibitors of the poly(ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA and implicated in DNA repair, apoptosis, organ dysfunction or necrosis. 2-[4-(5-Methyl-1H-imidazol-4-yl)-piperidin-1-yl]-4,5-dihydro-imidazo[4,5,1-i,j]quinolin-6-one (BYK49187), 2-(4-pyridin-2-yl-phenyl)-4,5-dihydro-imidazo[4,5,1-i,j]quinolin-6-one (BYK236864), 6-chloro-8-hydroxy-2,3-dimethyl-imidazo-[1,2-alpha]-pyridine (BYK20370), and 4-(1-methyl-1H-pyrrol-2-ylmethylene)-4H-isoquinolin-1,3-dione (BYK204165) inhibited cell-free recombinant human PARP-1 with pIC(50) values of 8.36, 7.81, 6.40, and 7.35 (pK(i) 7.97, 7.43, 5.90, and 7.05), and murine PARP-2 with pIC(50) values of 7.50, 7.55, 5.71, and 5.38, respectively. BYK49187, BYK236864, and BYK20370 displayed no selectivity for PARP-1/2, whereas BYK204165 displayed 100-fold selectivity for PARP-1. The IC(50) values for inhibition of poly(ADP-ribose) synthesis in human lung epithelial A549 and cervical carcinoma C4I cells as well in rat cardiac myoblast H9c2 cells after PARP activation by H(2)O(2) were highly significantly correlated with those at cell-free PARP-1 (r(2) = 0.89-0.96, P < 0.001) but less with those at PARP-2 (r(2) = 0.78-0.84, P < 0.01). The infarct size caused by coronary artery occlusion and reperfusion in the anesthetized rat was reduced by 22% (P < 0.05) by treatment with BYK49187 (3 mg/kg i.v. bolus and 3 mg/kg/h i.v. during 2-h reperfusion), whereas the weaker PARP inhibitors, BYK236864 and BYK20370, were not cardioprotective. In conclusion, the imidazoquinolinone BYK49187 is a potent inhibitor of human PARP-1 activity in cell-free and cellular assays in vitro and reduces myocardial infarct size in vivo. The isoquinolindione BYK204165 was found to be 100-fold more selective for PARP-1. Thus, both compounds might be novel and valuable tools for investigating PARP-1-mediated effects.

Bench-to-bedside review: latest results in hemorrhagic shock

Hemorrhagic shock is a leading cause of death in trauma patients worldwide. Bleeding control, maintenance of tissue oxygenation with fluid resuscitation, coagulation support, and maintenance of normothermia remain mainstays of therapy for patients with hemorrhagic shock. Although now widely practised as standard in the USA and Europe, shock resuscitation strategies involving blood replacement and fluid volume loading to regain tissue perfusion and oxygenation vary between trauma centers; the primary cause of this is the scarcity of published evidence and lack of randomized controlled clinical trials. Despite enormous efforts to improve outcomes after severe hemorrhage, novel strategies based on experimental data have not resulted in profound changes in treatment philosophy. Recent clinical and experimental studies indicated the important influences of sex and genetics on pathophysiological mechanisms after hemorrhage. Those findings might provide one explanation why several promising experimental approaches have failed in the clinical arena. In this respect, more clinically relevant animal models should be used to investigate pathophysiology and novel treatment approaches. This review points out new therapeutic strategies, namely immunomodulation, cardiovascular maintenance, small volume resuscitation, and so on, that have been introduced in clinics or are in the process of being transferred from bench to bedside. Control of hemorrhage in the earliest phases of care, recognition and monitoring of individual risk factors, and therapeutic modulation of the inflammatory immune response will probably constitute the next generation of therapy in hemorrhagic shock. Further randomized controlled multicenter clinical trials are needed that utilize standardized criteria for enrolling patients, but existing ethical requirements must be maintained.

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 as a potential target for the treatment of acute renal injury caused by lipopolysaccharide

Recent studies have clearly reported that there is a relationship between endotoxemia and acute renal injury. The aim of this study was to investigate whether treatment with the new potent PARP inhibitor PJ34 could prevent the acute renal injury induced by lipopolysaccharide (LPS). Endotoxemia was induced by LPS injection (10 mg/kg, i.v.). LPS increased blood urea nitrogen (BUN) levels from 22 +/- 0.54 mg/dL to 45.7 +/- 5.79 mg/dL (p < 0.05). The plasma creatinine levels were 0.38 +/- 0.02 mg/dL and 0.47 +/- 0.03 mg/dL for the control and LPS groups, respectively. In addition, urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG, a marker of renal tubular damage) was increased after LPS injection. By light microscopy, structural renal damage was observed in the LPS-treated group. However, PJ34 treatment (10 mg/kg, i.p.) attenuated LPS-induced renal injury, as indicated by plasma BUN and creatinine levels, urinary NAG excretion, and renal histology. These results indicated that the overactivation of the PARP pathway may have a role in LPS-induced renal impairment. Hence, pharmacological inhibition of this pathway might be an effective intervention to prevent endotoxin-induced acute renal injury.

Novel pharmacological approaches to the treatment of renal ischemia-reperfusion injury: a comprehensive review

Renal ischemia-reperfusion (I-R) contributes to the development of ischemic acute renal failure (ARF). Multi-factorial processes are involved in the development and progression of renal I-R injury with the generation of reactive oxygen species, nitric oxide and peroxynitrite, and the decline of antioxidant protection playing major roles, leading to dysfunction, injury, and death of the cells of the kidney. Renal inflammation, involving cytokine/adhesion molecule cascades with recruitment, activation, and diapedesis of circulating leukocytes is also implicated. Clinically, renal I-R occurs in a variety of medical and surgical settings and is responsible for the development of acute tubular necrosis (a characteristic feature of ischemic ARF), e.g., in renal transplantation where I-R of the kidney directly influences graft and patient survival. The cellular mechanisms involved in the development of renal I-R injury have been targeted by several pharmacological interventions. However, although showing promise in experimental models of renal I-R injury and ischemic ARF, they have not proved successful in the clinical setting (e.g., atrial natriuretic peptide, low-dose dopamine). This review highlights recent pharmacological developments, which have shown particular promise against experimental renal I-R injury and ischemic ARF, including novel antioxidants and antioxidant enzyme mimetics, nitric oxide and nitric oxide synthase inhibitors, erythropoietin, peroxisome-proliferator-activated receptor agonists, inhibitors of poly(ADP-ribose) polymerase, carbon monoxide-releasing molecules, statins, and adenosine. Novel approaches such as recent research involving combination therapies and the potential of non-pharmacological strategies are also considered.

Formation of 3-Aryl-5-nitroisocoumarins from 5-Nitroisocoumarins and Aromatic Acyl Chlorides under Friedel−Crafts Conditions

Treatment of 5-nitroisocoumarin with aromatic acyl chlorides under Friedel-Crafts conditions gives 3-aryl-5-nitroisocoumarins, rather than the expected 4-acyl-5-nitroisocoumarins. This procedure was optimized for reaction temperature (150 degrees C), solvent (nitrobenzene), and Lewis acid (SnCl4). Reaction of 5-nitroisocoumarin with [13C]-carbonyl benzoyl chloride under the optimum conditions gave 5-nitro-3-phenylisocoumarin in which the 13C is located at the 3-C of the heterocycle, indicating that the benzoyl carbon framework is incorporated intact.

Combination therapy of poly (ADP-ribose) polymerase inhibitor 3-aminobenzamide and gemcitabine shows strong antitumor activity in pancreatic cancer cells

BACKGROUND AND AIM

Poly (ADP-ribose) polymerase (PARP) inhibitors such as 3-aminobenzamide (3-ABA) enhance the in vitro cytotoxicity of DNA mono-functional alkylating agents such as radiation or chemotherapeutic agents. The aim of this study was to test an approach combining the PARP inhibitor 3-ABA with standard gemcitabine therapy in human pancreatic cancer cells.

METHODS

Cell viability was determined by proliferation assay (XTT). Cell-cycle analysis (FACS), ELISA (M30 Apoptosense), Western blot for caspase 8 and PARP, and electron microscopy were used to identify apoptosis. Tumor growth and survival was assessed in nude mice by subcutaneously injected Capan-1 cells. In addition, Ki67 staining was performed on tumors for cell proliferation and in vivo apoptosis induction was measured by TUNEL assay and ELISA.

RESULTS

Combination therapy of gemcitabine and 3-ABA suppressed tumor cell growth more than gemcitabine alone in XTT, FACS and ELISA analysis.

CONCLUSION

This in vivo study demonstrated a significantly reduced tumor weight and increased survival up to 40 days after cell inoculation with combination therapy compared to animals treated with PBS, gemcitabine or 3-ABA alone. Furthermore, TUNEL assay revealed a significant apoptosis induction and reduced proliferation in the combination group.

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.

Effects of 3-aminobenzamide, an inhibitor of poly (ADP-ribose) polymerase, in a mouse model of acute pancreatitis induced by cerulein

Poly (ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the colon injury associated with experimental colitis. The aim of the present study was to examine the effects of 3-aminobenzamide (3-AB), an inhibitor of PARP activity, in the development of acute pancreatitis caused by cerulein in mice. Intraperitoneal injection of cerulein in mice resulted in severe, acute pancreatitis characterized by oedema, neutrophil infiltration and necrosis and elevated serum levels of amylase and lipase. Infiltration of pancreatic and lung tissue with neutrophils (measured as increase in myeloperoxidase activity) was associated with enhanced expression of the intercellular adhesion molecule-1 (ICAM-1) and P-selectin. Immunohistochemical examination demonstrated a marked increase in the staining (immunoreactivity) for transforming growth factor-beta (TGF-beta) and vascular endothelial growth factor (VEGF) in the pancreas of cerulein-treated mice in comparison to sham-treated mice. Acute pancreatitis in vehicle-treated mice was also associated with a significant mortality (40% survival at 5 days after cerulein administration). In contrast, (1) the degree of pancreatic inflammation and tissue injury (histological score), (2) upregulation/formation of ICAM-1 and P-selectin, (4) neutrophils infiltration and (5) the expression of TGF-beta and VEGF was markedly reduced in pancreatic tissue obtained from cerulein-treated mice which have been treated with 3-AB. These findings provide the evidence that PARP inhibition reduce the degree of pancreas injury caused by acute pancreatitis induced by cerulein administration.

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.

Drugs modulating the biological effects of peroxynitrite and related nitrogen species

The term "reactive nitrogen species" includes nitrogen monoxide, commonly called nitric oxide, and some other remarkable chemical entities (peroxynitrite, nitrosoperoxycarbonate, etc.) formed mostly from nitrogen monoxide itself in biological environments. Regardless of the specific mechanisms implicated in their effects, however, it is clear that an integrated pharmacological approach to peroxynitrite and related species is only just beginning to take shape. The array of affected chemical and pathological processes is extremely broad. One of the most conspicuous mechanisms observed thus far has been the scavenging of the peroxynitrite anion by molecules endowed with antioxidant activity. This discovery has in turn lent great significance to several naturally occurring and synthetic antioxidants, which usually protect not only against oxidative reactions, but also from nitrating ones, both in vitro and in vivo. This has proven to be beneficial in different tissues, especially within the central nervous system. Taking these results and those of other biochemical investigations into account, many research lines are currently in progress to establish the true potential of reactive nitrogen species deactivators in the therapy of neurological diseases, ischemia-reperfusion damage, renal failure, and lung injury, among others.

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.

Effect of poly(ADP-ribosyl)ation inhibitors on the genotoxic effects of the boron neutron capture reaction

The boron neutron capture (BNC) reaction results from the interaction of 10B with low-energy thermal neutrons and gives rise to highly damaging lithium and alpha-particles. In this work the genotoxicity caused by the BNC reaction in V79 Chinese hamster cells was evaluated in the presence of poly(ADP-ribosyl)ation inhibitors. Poly(ADP-ribose) polymerase-1 (PARP-1), the most important member of the PARP enzyme family, is considered to be a constitutive factor of the DNA damage surveillance network present in eukaryotic cells, acting through a DNA break sensor function. Inhibition of poly(ADP-ribosyl)ation was achieved with the classical compound 3-aminobenzamide (3-AB), and with two novel and very potent inhibitors, 5-aminoisoquinolinone (5-AIQ) and PJ-34. Dose-response increases in the frequencies of aberrant cells excluding gaps (%ACEG) and chromosomal aberrations excluding gaps per cell (CAEG/cell) were observed for increasing exposures to the BNC reaction. The presence of 3-AB did not increase the %ACEG or CAEG/cell, nor did it change the pattern of the induced chromosomal aberrations. Results with 5-AIQ and PJ-34 were in agreement with the results obtained with 3-AB. We further studied the combined effect of a PARP inhibitor and a DNA-dependent protein kinase (DNA-PK) inhibitors (3-AB and wortmannin, respectively) on the genotoxicity of the BNC reaction, by use of the cytokinesis-block micronucleus assay. DNA-PK is also activated by DNA breaks and binds DNA ends, playing a role of utmost importance in the repair of double-strand breaks. Our results show that the inhibition of poly(ADP-ribosyl)ation does not particularly modify the genotoxicity of the BNC reaction, and that PARP inhibition together with a concomitant inhibition of DNA-PK revealed barely the same sensitizing effect as DNA-PK inhibition per se.

Inhibitors of poly(ADP-ribose) polymerase modulate signal transduction pathways and the development of bleomycin-induced lung injury

Poly(ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the tissue injury associated with inflammation. The aim of our study was to evaluate the therapeutic efficacy of in vivo inhibition of PARP in an experimental model of lung injury caused by bleomycin administration. Mice subjected to intratracheal administration of bleomycin developed significant lung injury and apoptosis (measured by Annexin V coloration). An increase of immunoreactivity to nitrotyrosine and PARP, as well as a significant loss of body weight and mortality, was observed in the lung of bleomycin-treated mice. Administration of the two PARP inhibitors 3-aminobenzamide (3-AB) or 5-aminoisoquinolinone (5-AIQ) significantly reduced the 1) loss of body weight, 2) mortality rate, 3) infiltration of the lung with polymorphonuclear neutrophils (myeloperoxidase activity), 4) edema formation, and 5) histological evidence of lung injury. Administration of 3-AB and 5-AIQ also markedly reduced nitrotyrosine formation and PARP activation. These results demonstrate that treatment with PARP inhibitors reduces the development of inflammation and tissue injury events induced by bleomycin administration in the mice.

Effects of inhibition of poly(adenosine diphosphate-ribose) synthase on acute cardiac allograft rejection

BACKGROUND

Nitric oxide synthase (NOS)-2 is expressed during acute cardiac allograft rejection in association with death of heart muscle cells. The nuclear enzyme poly(adenosine diphosphate [ADP]-ribose) synthase (PARS) is activated by agonists such as NO and peroxynitrite, which cause single-strand DNA breaks; PARS, in turn can promote both necrosis and apoptosis. To investigate the hypothesis that NO produced by NOS-2 in cardiomyocytes activates PARS and contributes to heart muscle cell death by apoptosis, experiments were performed using a heterotopic rat abdominal heart transplant model and cytokine-stimulated heart muscle cells in tissue culture.

METHODS

Cardiac allografts were treated after transplantation with either the PARS inhibitor 5-aminoisoquinolinone at 3 mg/kg subcutaneously daily or with vehicle. Isolated purified adult rat cardiomyocytes incubated with cytokines to induce NOS-2 were treated in vitro with another PARS inhibitor, 3-aminobenzamide (3AB).

RESULTS

PARS inhibition increased cardiac-allograft survival from 6 +/- 2 to 10 +/- 3 days (n=6, n=6, P<0.05). The inflammatory infiltrate, NOS-2-positive macrophages, myocyte apoptosis, and myocyte content of nitrotyrosine and poly(ADP-ribose) were significantly decreased in PARS inhibited allografts at day 5 posttransplantation. Similarly, apoptosis and PARS activity were diminished in cytokine-stimulated adult rat cardiomyocytes when either 3AB or L-NMMA were applied.

CONCLUSIONS

The data indicate that PARS activation occurs during acute cardiac-allograft rejection and contributes significantly to the inflammatory response and to the death of cardiac muscle cells by apoptosis. They suggest that PARS inhibition combined with immunosuppression might enhance salvage of heart-muscle cells during acute cardiac-allograft rejection.

5-Aminoisoquinolinone reduces colon injury by experimental colitis

Poly (ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the colon injury associated with experimental colitis. The aim of the present study was to examine the effects of 5-aminoisoquinolinone (5-AIQ), a novel and potent inhibitor of PARP activity, in the development of experimental colitis. To address this question, we used an experimental model of colitis, induced by dinitrobenzene sulfonic acid (DNBS). Compared with DNBS-treated mice, mice treated with 5-AIQ (3 mg/kg i.p.) or 3-aminobenzamide (3-AB; 10 mg/kg i.p. twice a day) and subjected to DNBS-induced colitis experienced a significantly lower rate in the extent and severity of the histological signs of colon injury. DNBS-treated mice experienced diarrhea and weight loss. Four days after administration of DNBS, the mucosa of the colon exhibited large areas of necrosis. Neutrophil infiltration (determined by histology as well as an increase in myeloperoxidase [MPO] activity in the mucosa) was associated with an up-regulation of intercellular adhesion molecule-1 (ICAM-1). Immunohistochemistry for PAR showed an intense staining in the inflamed colon. On the contrary, the treatment of DNBS-treated mice with 5-AIQ or with 3-AB significantly reduced the degree of hemorrhagic diarrhea and weight loss caused by administration of DNBS. 5-AIQ also caused a substantial reduction in the degree of colon injury, in the rise in MPO activity (mucosa), in the increase in staining (immunohistochemistry) for PAR, as well as in the up-regulation of ICAM-1 caused by DNBS in the colon. Thus, 5-AIQ treatment reduces the degree of colitis caused by DNBS. We propose that 5-AIQ treatment may be useful in the treatment of inflammatory bowel disease.

Inhibitors of Poly(ADP-Ribose) Polymerase Modulate Signal Transduction Pathways and Secondary Damage in Experimental Spinal Cord Trauma

Poly(ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the tissue injury associated with stroke and neurotrauma. The aim of our study was to evaluate the therapeutic efficacy of in vivo inhibition of PARP in an experimental model of spinal cord trauma, which was induced by the application of vascular clips (force of 24g) to the dura via a four-level T5-T8 laminectomy. Spinal cord injury in mice resulted in severe trauma characterized by edema, neutrophil infiltration (measured as an increase in myeloperoxidase activity), and apoptosis (measured by terminal deoxynucleotidyltransferase-mediated UTP end labeling coloration). Infiltration of spinal cord tissue with neutrophils was associated with a marked increase in immunoreactivity for poly(ADP-ribose) (PAR), index of PARP activation, in the spinal cord tissue. These inflammatory events were associated with the activation of nuclear factor-kappaB (NF-kappaB) at 4 h after spinal cord damage. Treatment of the mice with the PARP inhibitors 3-aminobenzamide (3-AB) or 5-aminoisoquinolinone (5-AIQ) significantly reduced the degree of 1) spinal cord inflammation and tissue injury (histological score), 2) PAR formation, 3) neutrophil infiltration, and 4) apoptosis. Treatment with these PARP inhibitors also reduced DNA binding of NF-kappaB and inhibitory kappaB degradation. In a separate set of experiments, we have also demonstrated that PARP inhibitors significantly ameliorated the recovery of limb function (evaluated by motor recovery score). Taken together, our results clearly demonstrate that treatment with PARP inhibitors reduces the development of inflammation and tissue injury events associated with spinal cord trauma.

Alpha1-acid-glycoprotein protects against trauma-hemorrhagic shock

BACKGROUND

Recent studies have shown that the acute phase protein alpha(1)-acid-glycoprotein (AAG) directly modifies endothelial cell responsiveness and is a crucial factor for maintaining endothelial barrier function. We hypothesized that the addition of AAG to the resuscitation fluid will prevent edema formation, increases circulating blood volume, and reduces tissue inflammation following soft tissue trauma and hemorrhagic shock.

MATERIALS AND METHODS

Male Sprague-Dawley rats (338 +/- 28 g) underwent a 5-cm midline laparotomy (i.e., induction of soft tissue trauma) and were bled to and maintained at a mean arterial pressure of 35 mm Hg for 90 min. The rats were then resuscitated with four times the shed blood volume with Ringer's lactate containing 200 mg/kg AAG or the same amount of albumin. At 6 h after resuscitation, organ wet-to-dry weight ratios and circulating blood volume (Evans blue dilution) were determined. Neutrophil accumulation (myeloperoxidase activity, MPO) and tissue lipid peroxidation (thiobarbituric acid reactive substances) were also measured in the lungs, liver, and intestine.

RESULTS

Administration of AAG during the resuscitation significantly increased circulating blood volume and reduced edema formation, neutrophil accumulation, and lipid peroxidation. Interestingly, concomitant plasma IL-6 levels increased while TNF-alpha levels were not significantly affected.

CONCLUSIONS

Since addition of AAG to the resuscitation fluid increased circulating blood volume, reduced edema formation, and neutrophil accumulation following trauma and hemorrhagic shock, supplementation of this acute phase protein appears to be a potential adjunct to prevent capillary leakage in patients undergoing major traumatic injury.

Beneficial effects of 5-aminoisoquinolinone, a novel, potent, water-soluble, inhibitor of poly (ADP-ribose) polymerase, in a rat model of splanchnic artery occlusion and reperfusion

Poly(ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the tissue injury associated with ischemia-reperfusion and inflammation. Splanchnic artery occlusion and reperfusion causes an enhanced formation of reactive oxygen species which contribute to the pathophysiology of shock. The aim of the present study was to investigate the effects of 5-aminoisoquinolinone (5-AIQ), a potent water-soluble inhibitor of poly(ADP-ribose) polymerase (PARP), in the pathogenesis of splanchnic artery occlusion shock. Splanchnic artery occlusion shock was induced in rats by clamping both the superior mesenteric artery and the celiac artery for 45 min, followed thereafter by release of the clamp (reperfusion). At 60 min after reperfusion, all animals were sacrificed for histological examination and biochemical studies. Treatment of rats with 5-AIQ (3 mg/kg i.v.), attenuated the fall of mean arterial blood pressure caused by splanchnic artery occlusion shock. 5-AIQ also attenuated the ileum injury as well as the increase in the tissue levels of myeloperoxidase and malondialdehyde caused by splanchnic artery occlusion shock in the ileum. The immunohistochemical examination also demonstrated a marked increase in the immunoreactivity to PAR, nitrotyrosine, and intercellular adhesion molecule (ICAM-1) in the necrotic ileum from splanchnic artery occlusion-shocked rats. 5-AIQ treatment significantly reduced the increase of positive staining for PAR, nitrotyrosine and ICAM-I. In conclusion, these results show that 5-AIQ, a new water-soluble potent inhibitor of poly(ADP-ribose) polymerase, exerts multiple protective effects in splanchnic artery occlusion/reperfusion shock.

Tempol, an intracelullar free radical scavenger, reduces liver injury in hepatic ischemia-reperfusion in the rat

Liver ischemia is of clinical interest because of its role in liver failure and also hepatic graft rejection. The generation of reactive oxygen species contributes to the injury that follows ischemia-reperfusion. One therapy utilizes the administration of antioxidants; however, only limited experience suggests a potential benefit of systemic administration of these compounds. To overcome the limitations of these compounds, small molecules with improved cell membrane permeability characteristics and higher potency, such as tempol, are being tested in vivo. Tempol, a membrane-permeable radical scavenger, interferes with the formation or the effects of many radicals, including superoxide anions, hydroxyl radicals, and peroxynitrite. The aim of this study was to investigate the effects of tempol in an in vivo rat model of liver ischemia-reperfusion injury. Male Wistar rats were pretreated with tempol (30 mg/kg, i.v.) 5 minutes prior to liver ischemia (for 30 minutes) and reperfusion (for 2 hours). The liver injury was assessed by measuring serum levels of transaminases, lactate dehydrogenase, and gamma-glutamyl transferase. Tempol significantly mitigated the increase in transaminases, lactate dehydrogenase, and gamma-glutamyl transferase following liver ischemia-reperfusion, suggesting an improvement in liver function and resistance to injury.

5-Aminoisoquinolinone, a novel inhibitor of poly(adenosine disphosphate-ribose) polymerase, reduces microvascular liver injury but not mortality rate after hepatic ischemia-reperfusion*

OBJECTIVE

The aim of this study was to investigate the impact of the novel, potent, water-soluble inhibitor of poly(adenosine diphosphate-ribose) polymerase (PARP) 5-aminoisoquinolinone (5-AIQ) on hepatic microcirculation, hepatocellular injury, and survival in a murine model of hepatic ischemia-reperfusion.

DESIGN

Randomized animal study.

SETTING

Research laboratory.

SUBJECTS

C57BL6 mice were subjected to warm either partial (90 mins) or total (75 mins) ischemia of the liver.

INTERVENTIONS

Either PARP inhibitor 5-AIQ (3 mg/kg) or vehicle was administered to mice intravenously immediately before the start of reperfusion. Sham-operated animals served as controls.

MEASUREMENTS AND MAIN RESULTS

As shown by intravital fluorescence microscopy after 30-60 mins of reperfusion, ischemia-reperfusion significantly enhanced platelet- and leukocyte-endothelial cell interactions in hepatic microvessels and impaired sinusoidal perfusion. Hepatocellular injury was characterized by an increase in the number of necrotic and apoptotic cells, dramatic elevation of aspartate aminotransferase/alanine aminotransferase serum activity, and lipid peroxidation in liver tissue. 5-AIQ treatment attenuated ischemia-reperfusion-induced increases in the numbers of adherent platelets and leukocytes as well as of necrotic and apoptotic cells and ameliorated perfusion failure. Furthermore, PARP inhibition prevented the increase in aspartate aminotransferase activity after ischemia-reperfusion but did not affect postischemic alanine aminotransferase release. However, no protective impact of 5-AIQ on postischemic oxidative stress was observed. Although PARP inhibition did not alter the survival percentage after ischemia-reperfusion (22% in both groups), this approach prolonged survival from 1 to 24 hrs (ischemia-reperfusion + vehicle) up to 48-72 hrs in the treated group.

CONCLUSIONS

PARP inhibition with 5-AIQ during hepatic ischemia-reperfusion attenuates microvascular injury and reduces the extent of necrotic/apoptotic cell damage but does not protect from oxidative injury and does not improve postoperative survival rate.

5-Aminoisoquinolinone reduces renal injury and dysfunction caused by experimental ischemia/reperfusion

BACKGROUND

Poly (ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the development of ischemia/reperfusion (I/R) injury. The aim of this study was to investigate the effects of a water-soluble and potent PARP inhibitor, 5-aminoisoquinolinone (5-AIQ), on the renal injury and dysfunction caused by oxidative stress of the rat kidney in vitro and in vivo.

METHODS

Primary cultures of rat renal proximal tubular cells, subjected to oxidative stress caused by hydrogen peroxide (H2O2), were incubated with increasing concentrations of 5-AIQ (0.01 to 1 mmol/L) after which PARP activation, cellular injury, and cell death were measured. In in vivo experiments, anesthetized male Wistar rats were subjected to renal bilateral ischemia (45 minutes) followed by reperfusion (6 hours) in the absence or presence of 5-AIQ (0.3 mg/kg) after which renal dysfunction, injury and PARP activation were assessed.

RESULTS

Incubation of proximal tubular cells with H2O2 caused a substantial increase in PARP activity, cellular injury, and cell death, which were all significantly reduced in a concentration-dependent by 5-AIQ [inhibitory concentration 50 (IC50) approximately 0.03 mmol/L]. In vivo, renal I/R resulted in renal dysfunction, injury, and PARP activation, primarily in the proximal tubules of the kidney. Administration of 5-AIQ significantly reduced the biochemical and histologic signs of renal dysfunction and injury and markedly reduced PARP activation caused by I/R.

CONCLUSION

This study demonstrates that 5-AIQ is a potent, water soluble inhibitor of PARP activity, which can significantly reduce (1) cellular injury and death caused to primary cultures of rat proximal tubular cells by oxidative stress in vitro, and (2) renal injury and dysfunction caused by I/R of the kidney of the rat in vivo.

Characterization of human brain nicotinamide 5'-mononucleotide adenylyltransferase-2 and expression in human pancreas

NMNAT (nicotinamide 5'-mononucleotide adenylyltransferase; EC 2.7.7.1) catalyses the transfer of the adenylyl group from ATP to NMN to form NAD. We have cloned a novel human NMNAT cDNA, designated hNMNAT-2, from human brain. The cDNA contains a 924 bp open reading frame that encodes a 307 amino acid peptide that was expressed as a histidine-patch-containing thioredoxin fusion protein. Expressed hNMNAT-2 shared only 35% amino acid sequence homology with the human NMNAT enzyme (hNMNAT-1), but possessed enzymic activity comparable with hNMNAT-1. Using human genomic databases, hNMNAT-2 was localized to chromosome 1q25 within a 171 kb gene, whereas hNMNAT-1 is on chromosome 1p32-35. Northern blot analysis revealed highly restricted expression of hNMNAT-2 to brain, heart and muscle tissues, which contrasts with the wide tissue expression of hNMNAT-1; different regions of the brain exhibited differential expression of hNMNAT-2. Substitution mutations of either of two invariant residues, His-24 or Trp-92, abolished enzyme activity. Anti-peptide antibody to a unique epitope within hNMNAT-2 was produced, and immunohistochemical analysis of sections of normal adult human pancreas revealed that hNMNAT-2 protein was markedly expressed in the islets of Langerhans. However, the pancreatic exocrine cells exhibited weak expression of hNMNAT-2 protein. Sections of pancreas from insulinoma patients showed strong expression of hNMNAT-2 protein in the insulin-producing tumour cells, whereas acinar cells exhibited relatively low expression of hNMNAT-2 protein. These data suggest that the unique tissue-expression patterns of hNMNAT-2 reflect distinct functions for the isoforms in the regulation of NAD metabolism.