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-1 inhibitor ameliorates dextran sulfate sodium-induced colitis in mice by regulating the balance of Th17/Treg cells and inhibiting the NF-κB signaling pathway

Poly(ADP-ribose) polymerase-1 (PARP-1) plays a critical role in inflammatory pathways. The PARP-1 inhibitor, 5-aminoisoquinolinone (5-AIQ), has been demonstrated to exert significant pharmacological effects. The present study aimed to further examine the potential mechanisms of 5-AIQ in a mouse model of dextran sodium sulfate (DSS)-induced colitis. Colitis conditions were assessed by changes in weight, disease activity index, colon length, histopathology and pro-inflammatory mediators. The colonic expression of PARP/NF-κB and STAT3 pathway components was measured by western blot analysis. Flow cytometry was used to analyze the proportion of T helper 17 cells (Th17) and regulatory T cells (Tregs) in the spleen. Western blot analysis and reverse transcription-quantitative PCR were employed to determine the expression of the transcription factors retinoic acid-related orphan receptor and forkhead box protein P3. The results demonstrated that 5-AIQ reduced tissue damage and the inflammatory response in mice with experimental colitis. Moreover, 5-AIQ increased the proportion of Treg cells and decreased the percentage of Th17 cells in the spleen. Furthermore, following 5-AIQ treatment, the main components of the PARP/NF-κB and STAT3 pathways were downregulated. Collectively, these results demonstrate that the PARP-1 inhibitor, 5-AIQ, may suppress intestinal inflammation and protect the colonic mucosa by modulating Treg/Th17 immune balance and inhibiting PARP-1/NF-κB and STAT3 signaling pathways in mice with experimental colitis.

In vitro effects of poly(ADP-ribose) polymerase inhibitors on the production of tumor necrosis factor-α by interferon- γ - and lipopolysaccharide-stimulated peripheral blood mononuclear cells of horses

OBJECTIVE

To evaluate effects of poly(ADP-ribose) polymerase-1 (PARP1) inhibitors on the production of tumor necrosis factor-α (TNF-α) by interferon-γ (IFN-γ)- and lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells (PBMCs) of horses as an in vitro model of inflammation in horses.

SAMPLE

1,440 samples of PBMCs from 6 healthy research horses.

PROCEDURES

From heparinized whole blood samples, PBMC cultures were obtained. An initial dose-response trial on 48 PBMC samples from 2 horses (24 samples each) was used to determine concentrations of IFN-γ and LPS for use as low- and high-level stimulation concentrations. Seventy-two PBMC samples from 6 horses were assigned equally to 1 of 4 PARP1 inhibition categories: no PARP1 inhibitor (PARP1 inhibition control); 2-((R)-2-methylpyrrolidin-2-yl)-1H-benzimidazole-4-carbozamide dihydrochloride (ABT888);4-(3-(1-(cyclopropanecarbonyl)piperazine-4-carbonyl)-4-fluorobenzyl)phthalazin-1(2H)-one (AZD2281); or N-(6-oxo-5,6-dihydrophenanthridin-2-yl) -N,N-dimethylacetamide hydrochloride (PJ34). Samples of PBMCs from each horse and each PARP1 inhibition category were then assigned to 1 of 3 levels of IFN-γ and LPS stimulation: none (control), low stimulation, or high stimulation. After a 24-hour incubation period, a TNF-α ELISA was used to measure TNF-α concentration in the supernatant. Results were compared across treatments and for each horse. Data were analyzed with repeated-measures ANOVA.

RESULTS

Median TNF-α concentration was significantly lower for PJ34-treated, high-level stimulated PBMCs than for PARP1 inhibition control, high-level stimulated PBMCs; however, no other meaningful differences in TNF-α concentration were detected among the inhibition and stimulation combinations.

CONCLUSIONS AND CLINICAL RELEVANCE

Findings suggested that PJ34 PARP1 inhibition may reduce TNF-α production in horses, a potential benefit in reducing inflammation and endotoxin-induced damage in horses.

The activity and inhibition of poly(ADP-ribose) polymerase-1 in equine peripheral blood mononuclear cells in vitro

OBJECTIVES

To evaluate the poly (ADP-ribose) polymerase-1 (PARP1) enzyme and its inhibition in horses and explore its potential as a novel therapeutic target for equine intestinal ischemia-reperfusion injury by (1) identifying poly (ADP-ribose) (PAR) as an indication of PARP1 activation in equine cells using available immunoblot analytical techniques, (2) inducing PARP1 activation in an in vitro oxidative DNA damage model, (3) and demonstrating the inhibition of PARP1 in equine cells using commercially available PARP1 inhibitors.

DESIGN

Experimental study.

ANIMALS

Blood samples were collected from systemically healthy ponies (n = 3) and horses (n = 3).

INTERVENTIONS

(1) Equine peripheral blood mononuclear cells were exposed to 3 different concentrations of hydrogen peroxide (H2 O2 ) and were lysed at specific time points. PARP1 activity was then assessed by using immunoblot analyses to determine PAR levels. (2) Equine peripheral blood mononuclear cells were preincubated with defined concentrations of PARP1 inhibitors prior to H2 O2 -mediated PARP1 stimulation. PAR levels reflecting PARP1 activity were determined using immunoblot analyses.

MEASUREMENTS AND MAIN RESULTS

Commercially available anti-PAR antibodies were used successfully to identify equine PAR. There was a significant increase in PAR accumulation following treatment with H2 O2 . All of the tested PARP inhibitors significantly reduced PAR accumulation to or below basal levels following treatment with H2 O2 .

CONCLUSIONS

This proof of principle study demonstrated that PAR, an indicator of PARP1 activity, can be identified in the equine species using immunoblot techniques, that equine PARP1 can be activated by H2 O2 -induced DNA damage, and that this activation can be inhibited by PARP1 enzyme inhibitors. The data suggest that the PARP1 pathway plays a role in the equine cellular response to oxidative DNA damage and supports its potential as a novel therapeutic target. Further research documenting an increase in PAR levels in vivo and the efficacy of PARP1 inhibitors in an equine intestinal ischemia-reperfusion model is needed.

5-AIQ inhibits H2O2-induced apoptosis through reactive oxygen species scavenging and Akt/GSK-3β signaling pathway in H9c2 cardiomyocytes

Poly(adenosine 5'-diphosphate ribose) polymerase (PARP) is a nuclear enzyme activated by DNA strand breaks and plays an important role in the tissue injury associated with ischemia and reperfusion. The aim of the present study was to investigate the protective effect of 5-aminoisoquinolinone (5-AIQ), a PARP inhibitor, against oxidative stress-induced apoptosis in H9c2 cardiomyocytes. 5-AIQ pretreatment significantly protected against H2O2-induced cell death, as determined by the XTT assay, cell counting, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay, and Western blot analysis of apoptosis-related proteins such as caspase-3, Bax, and Bcl-2. Upregulation of antioxidant enzymes such as manganese superoxide dismutase and catalase accompanied the protective effect of 5-AIQ on H2O2-induced cell death. Our data also showed that 5-AIQ pretreatment protected H9c2 cells from H2O2-induced apoptosis by triggering activation of Akt and glycogen synthase kinase-3β (GSK-3β), and that the protective effect of 5-AIQ was diminished by the PI3K inhibitor LY294002 at a concentration that effectively abolished 5-AIQ-induced Akt and GSK-3β activation. In addition, inhibiting the Akt/GSK-3β pathway by LY294002 significantly attenuated the 5-AIQ-mediated decrease in cleaved caspase-3 and Bax activation and H9c2 cell apoptosis induction. Taken together, these results demonstrate that 5-AIQ prevents H2O2-induced apoptosis in H9c2 cells by reducing intracellular reactive oxygen species production, regulating apoptosis-related proteins, and activating the Akt/GSK-3β pathway.

Therapeutic effect of a poly(ADP-ribose) polymerase-1 inhibitor on experimental arthritis by downregulating inflammation and Th1 response

Poly(ADP-ribose) polymerase-1 (PARP-1) synthesizes and transfers ADP ribose polymers to target proteins, and regulates DNA repair and genomic integrity maintenance. PARP-1 also plays a crucial role in the progression of the inflammatory response, and its inhibition confers protection in several models of inflammatory disorders. Here, we investigate the impact of a selective PARP-1 inhibitor in experimental arthritis. PARP-1 inhibition with 5-aminoisoquinolinone (AIQ) significantly reduces incidence and severity of established collagen-induced arthritis, completely abrogating joint swelling and destruction of cartilage and bone. The therapeutic effect of AIQ is associated with a striking reduction of the two deleterious components of the disease, i.e. the Th1-driven autoimmune and inflammatory responses. AIQ downregulates the production of various inflammatory cytokines and chemokines, decreases the antigen-specific Th1-cell expansion, and induces the production of the anti-inflammatory cytokine IL-10. Our results provide evidence of the contribution of PARP-1 to the progression of arthritis and identify this protein as a potential therapeutic target for the treatment of rheumatoid arthritis.

PARP inhibition reduces acute colonic inflammation in rats

Poly(ADP-ribose) polymerases (PARP) comprise a family of enzymes which catalyse poly(ADP-ribosyl)ation of DNA-binding proteins. Multiple researches indicate the importance of PARP in promoting cell recruitment and thereby inducing organ injury in various forms of inflammation, such as colitis. We have evaluated the effects of two PARP inhibitors, nicotinamide and 1,5-dihydroxyisoquinoline, in acute colitis induced by trinitrobenzensulfonic acid (TNBS) in rats. Nicotinamide (20-40 mg/kg) and 1,5-dihydroxyisoquinoline (4-8 mg/kg) were administered 48, 24 and 1 h prior to the induction of colitis as well as 24 h later. 48 h after colitis induction the lesions were blindly scored and quantified as ulcer index. Histological study and colonic inflammation were assessed by gross appearance and myeloperoxidase (MPO) activity. Prostaglandin E2 (PGE2) synthesis and, cyclooxygenase-1 and cyclooxygenase-2 expressions by Western blotting and immunohistochemistry were also performed. Inflammation following TNBS induction was characterized by increased colonic wall thickness, oedema, diffuse inflammatory cells infiltration in the mucosa and necrosis. Furthermore, increased MPO activity, cyclooxygenase-2 expression and PGE2 synthesis were significantly augmented after TNBS instillation. On the contrary, treatment with 1,5-dihydroxyisoquinoline significantly reduced the degree of colon injury and also caused a substantial reduction in the rise in MPO activity, in the increase of staining for cyclooxygenase-2, as well as in the up-regulation of PGE2 caused by TNBS in the colon. Although nicotinamide significantly did not reduce macroscopic damage, it decreased both MPO activity and PGE2 colonic levels. In conclusion, we demonstrated that PARP inhibition can exert beneficial effects in experimental colitis and may, therefore, be useful in the treatment of ulcerative colitis.

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.

5-aminoisoquinolin-1(2H)-one, a water-soluble poly (ADP-ribose) polymerase (PARP) inhibitor reduces the evolution of experimental periodontitis in rats

BACKGROUND

Poly (ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the tissue injury associated with ischaemia-reperfusion and inflammation. Recent studies have demonstrated that PARP activation plays a crucial role in the pathogenesis of acute periodontal injury.

AIM

We have investigated the effect of 5-aminoisoquinolin-1(2H)-one (5-AIQ), a water-soluble PARP inhibitor, in a rat model of periodontitis.

MATERIALS AND METHODS

Periodontitis was induced in rats by placing a 2/0 braided silk ligature around the lower left first molar. At day eight, the gingivomucosal tissue encircling the mandibular first molar was removed for biochemical and histological analysis.

RESULTS AND CONCLUSIONS

Ligation significantly induced an increased neutrophil infiltration and a positive staining for PARP activation. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone destruction. Intraperitonial injection of 5-aminoisoquinolin-1(2H)-one (5-AIQ) (5 mg/kg daily for eight days) significantly decreased all of the parameters of inflammation as described above. This suggests that inhibition of PARP may represent a novel approach for the treatment of periodontal disease.

Anti-inflammatory effects of PJ34, a poly(ADP-ribose) polymerase inhibitor, in transient focal cerebral ischemia in mice

BACKGROUND AND PURPOSE

Activation of poly(ADP-ribose) polymerase (PARP) is deleterious during cerebral ischemia. We assessed the influence of PARP activation induced by cerebral ischemia on the synthesis of proinflammatory mediators including the cytokines, tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) and the adhesion molecules, E-selectin and intercellular adhesion molecule-1 (ICAM-1).

EXPERIMENTAL APPROACH

Ischemia was induced by intravascular occlusion of the left middle cerebral artery for 1 h in male Swiss mice anaesthetized with ketamine and xylazine. The PARP inhibitor PJ34 (1.25-25 mg kg(-1)) was administered intraperitoneally 15 min before and 4 hours after, the onset of ischemia. Animals were killed 6 h or 24 h after ischemia and cerebral tissue removed for analysis.

KEY RESULTS

Ischemia increased TNF-alpha protein in cerebral tissue at 6 and 24 h after ischemia. All doses of PJ34 blocked the increase in TNF-alpha at 6 h and 25 mg kg(-1) PJ34 had a sustained effect for up to 24 h. Quantitative real time polymerase chain reaction showed that PJ34 (25 mg kg(-1)) reduced the increase in TNF-alpha mRNA by 70% at 6 h. PJ34 also prevented the increase in mRNAs encoding IL-6 (-41%), E-selectin (-81%) and ICAM-1 (-54%). PJ34 (25 mg kg(-1)) reduced the infarct volume (-26%) and improved neurological deficit, 24 h after ischemia.

CONCLUSIONS AND IMPLICATIONS

PJ34 inhibited the increase in the mRNAs of four inflammatory mediators, caused by cerebral ischemia. The contribution of this effect of PJ34 to neuroprotection remains to be clarified.

PARG activity mediates intestinal injury induced by splanchnic artery occlusion and reperfusion

Poly (ADP-ribosyl)ation, an early post-translational modification in response to DNA damage, is catalyzed by poly (ADP-ribose) polymerase (PARP-1) and catabolized by poly(ADP-ribose) glycohydrolase (PARG). The aim of this study was to investigate the role of PARG on the modulation of the inflammatory response caused by splanchnic ischemia and reperfusion. SAO shock in rats and wild-type (WT) mice was associated with a significant neutrophil infiltration in the ileum and production of tumor necrosis factor-alpha (TNF-alpha). Reperfused ileum tissue sections from SAO-shocked WT mice and rats showed positive staining for P-selectin and ICAM-1 localized mainly in the vascular endothelial cells. Genetic disruption of the PARG gene in mice or pharmacological inhibition of PARG by PARG inhibitors significantly improved the histological status of the reperfused tissues associated with reduced expression of P-selectin and ICAM-1, neutrophil infiltration into the reperfused intestine, and TNF-alpha production. These results suggest that PARG activity modulates the inflammatory response in ischemia/reperfusion and participates in end (target) organ damage under these conditions.

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.

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.