Poly(ADP-ribose) polymerase (PARP)-1, an enzyme that catalyzes the attachment of ADP ribose to target proteins, acts as a component of enhancer/promoter regulatory complexes. In the present study, we show that pharmacologic inhibition of PARP-1 with 3,4-dihydro-5-[4-(1-piperidinyl)butoxyl]-1(2H)-isoquinolinone (DPQ) results in a strong delay in tumor formation and in a dramatic reduction in tumor size and multiplicity during 7,12-dimethylbenz(a)anthracene plus 12-O-tetradecanoylphorbol-13-acetate-induced skin carcinogenesis. This observation was parallel with a reduction in the skin inflammatory infiltrate in DPQ-treated mice and tumor vasculogenesis. Inhibition of PARP also affected activator protein-1 (AP-1) activation but not nuclear factor-KB (NF-KB). Using cDNA expression array analysis, a substantial difference in key tumor-related gene expression was found between chemically induced mice treated or not with PARP inhibitor and also between wild-type and parp-1 knockout mice. Most important differences were found in gene expression for Nfkbiz, S100a9, Hif-1a, and other genes involved in carcinogenesis and inflammation. These results were corroborated by real-time PCR. Moreover, the transcriptional activity of hypoxia-inducible factor-1A (HIF-1A) was compromised by PARP inhibition or in PARP-1-deficient cells, as measured by gene reporter assays and the expression of key target genes for HIF-1A. Tumor vasculature was also strongly inhibited in PARP-1-deficient mice and by DPQ. In summary, this study shows that inhibition of PARP on itself is able to control tumor growth, and PARP inhibition or genetic deletion of PARP-1 prevents from tumor promotion through their ability to cooperate with the activation AP-1, NF-KB, and HIF-1A.

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.

Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear protein that, once activated by genotoxic agents, modulates the activity of several nuclear proteins including itself. Previous studies have established that PARP-1 inhibition may provide benefit in the treatment of different diseases, particularly those involving a hypoxic situation, in which an increased oxidative and nitrosative stress occurs. One of the most important transcription factors involved in the response to the hypoxic situation is the hypoxia-inducible factor-1 (HIF-1). The activity of HIF-1 is determined by the accumulation of its alpha subunit which is regulated, in part, by oxidative stress (ROS) and nitric oxide (NO), both of them highly dependent on PARP-1. Besides, HIF-1alpha can be induced by iron chelators such as deferoxamine (DFO). In this sense, the therapeutical use of DFO to strengthen the post-hypoxic response has recently been proposed. Taking into account the increasing interest and potential clinical applications of PARP inhibition and DFO treatment, we have evaluated the impact of PARP-1 on HIF-1alpha accumulation induced by treatment with DFO. Our results show that, in DFO treated cells, PARP-1 gene deletion or inhibition decreases HIF-1alpha accumulation. This lower HIF-1alpha stabilization is parallel to a decreased inducible NO synthase induction and NO production, a higher response of some antioxidant enzymes (particularly glutathione peroxidase and glutathione reductase) and a lower ROS level. Taken together, these results suggest that the absence of PARP-1 modulates HIF-1 accumulation by reducing both NO and oxidative stress.

Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear protein that once activated by genotoxic agents, modulates its own activity and that of several other nuclear proteins. The absence or pharmacological inhibition of this protein has been proven to be beneficial in the treatment of different diseases involving a hypoxic situation. We previously reported that PARP-1 modulates the hypoxia-inducible factor-1 (HIF-1) response in vitro, but this effect has not yet been demonstrated in vivo. The brain is especially susceptible to hypoxic injury, and the present study demonstrates that PARP-1 plays a major role in the post-hypoxic response of HIF-1alpha in the cerebral cortex. Immediate post-hypoxic HIF-1alpha accumulation was higher in the presence of PARP-1, and this differential response was mediated by nitric oxide and to a lesser extent, reactive oxygen species. PARP-1 was also found to induce a more rapid but less sustained HIF-1 transcriptional activity by up-regulating the factor inhibiting HIF. The implication of PARP-1 in these results was further demonstrated by pharmacologically inhibiting PARP in wild-type mice. In conclusion, our data suggest that PARP-1 has an important regulatory role in the in vivo response of brain HIF-1 to hypoxia/reoxygenation.

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The physiological response to hypobaric hypoxia represents a complex network of biochemical pathways in which the nitrergic system plays an important role. Previous studies have provided evidence for an interplay between the hypoxia-inducible factor-1 (HIF-1) and poly(ADP-ribose) polymerase-1 (PARP-1) under hypoxia. Here, we evaluate the potential involvement of nitric oxide (NO) in the cross talk between these two proteins. With this aim, we studied comparatively the effect of pharmacological inhibitors of NO production or PARP activity in the response of the mouse cerebral cortex to 4 h of exposure to a simulated altitude of 31,000 ft. Particularly, we analyzed the NO and reactive oxygen species production, the expression of NO synthase (NOS) isoforms, PARP-1 activity, HIF-1α expression and HIF-1 transcriptional activity, the protein level of the factor inhibiting HIF, and, finally, beclin-1 and fractin expression, as markers of cellular damage. Our results demonstrate that the reduction of NO level did not affect reactive oxygen species production but significantly 1) dampened the posthypoxic increase in neuronal NOS and inducible NOS expression without altering endothelial NOS protein level; 2) prevented PARP activation; 3) decreased HIF-1α response to hypoxia; 4) achieved a higher long-term HIF-1 transcriptional activity by reducing factor inhibiting HIF expression; and 5) reduced hypoxic damage. The pharmacological inhibition of PARP reproduced the NOS expression pattern and the HIF-1α response observed in NOS-inhibited mice, supporting its involvement in the NO-dependent regulation of hypoxia. As a whole, these results provide new data about the molecular mechanism underlying the beneficial effects of controlling NO production under hypobaric hypoxic conditions.

We aimed to test exercise-induced adaptations on skeletal muscle when quercetin is supplemented. Four groups of rats were tested: quercetin sedentary, quercetin exercised, placebo sedentary, and placebo exercised. Treadmill exercise training took place 5 days a week for 6 weeks. Quercetin groups were supplemented with quercetin, via gavage, on alternate days throughout the experimental period. Sirtuin 1 (SIRT1), peroxisome proliferator-activated receptor γ coactivator-1α mRNA levels, mitochondrial DNA (mtDNA) content, and citrate synthase (CS) activity were measured on quadriceps muscle. Redox status was also quantified by measuring muscle antioxidant enzymatic activity and oxidative damage product, such as protein carbonyl content (PCC). Quercetin supplementation increased oxidative damage in both exercised and sedentary rats by inducing higher amounts of PCC (P < 0.001). Quercetin supplementation caused higher catalase (P < 0.001) and superoxide dismutase (P < 0.05) activity in the non-exercised animals, but not when quercetin is supplemented during exercise. Quercetin supplementation increased SIRT1 expression, but when quercetin is supplemented during exercise, this effect is abolished (P < 0.001). The combination of exercise and quercetin supplementation caused lower (P < 0.05) mtDNA content and CS activity when compared with exercise alone. Quercetin supplementation during exercise provides a disadvantage to exercise-induced muscle adaptations.

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