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An inhibitor of poly (ADP-ribose) synthetase activity reduces contractile dysfunction and preserves high energy phosphate levels during reperfusion of the ischaemic rat heart.

ABSTRACT: The cardioprotective properties of inhibition of poly (ADP-ribose) synthetase (PARS) were investigated in the isolated perfused heart of the rat. Hearts were perfused in the Langendorff mode and subjected to 23 min total global ischaemia and reperfused for 60 min. Left ventricular function was assessed by means of an intra-ventricular balloon. High energy phosphates were measured by 31P-NMR spectroscopy. Intracellular levels of NAD were measured by capillary electrophoresis of perchloric acid extracts of hearts at the end of reperfusion. Reperfusion in the presence of the PARS inhibitor 1,5 didroxyisoquinoline (ISO, 100 microM) attenuated the mechanical dysfunction observed following 1 h of reperfusion; 27+/-13 and 65+/-8% recovery of preischaemic rate pressure product for control and 100 microM ISO, respectively. This cardioprotection was accompanied by a preservation of intracellular high-energy phosphates during reperfusion; 38+/-2 vs 58+/-4% (P<0.05) of preischaemic levels of phosphocreatine (PCr) for control and 100 microM ISO respectively and 23+/-1 vs 31+/-3% (P < 0.05) of preischaemic levels of ATP for control and 100 microM ISO respectively. Cellular levels of NAD were higher in ISO treated hearts at the end of reperfusion; 2.56+/-0.45 vs 4.76+/-1.12 micromoles g(-1) dry weight (P<0.05) for control and ISO treated. These results demonstrate that the cardioprotection afforded by inhibition of PARS activity with ISO is accompanied by a preservation of high-energy phosphates and cellular NAD levels and suggest that the mechanism responsible for this cardioprotection may involve prevention of intracellular ATP depletion.

SUBMITTER: Docherty JC

PROVIDER: S-EPMC1760665 | biostudies-other | 1999 Jul

REPOSITORIES: biostudies-other

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Project description:BackgroundInitiation, amplitude, duration and termination of transforming growth factor ? (TGF?) signaling via Smad proteins is regulated by post-translational modifications, including phosphorylation, ubiquitination and acetylation. We previously reported that ADP-ribosylation of Smads by poly(ADP-ribose) polymerase 1 (PARP-1) negatively influences Smad-mediated transcription. PARP-1 is known to functionally interact with PARP-2 in the nucleus and the enzyme poly(ADP-ribose) glycohydrolase (PARG) can remove poly(ADP-ribose) chains from target proteins. Here we aimed at analyzing possible cooperation between PARP-1, PARP-2 and PARG in regulation of TGF? signaling.MethodsA robust cell model of TGF? signaling, i.e. human HaCaT keratinocytes, was used. Endogenous Smad3 ADP-ribosylation and protein complexes between Smads and PARPs were studied using proximity ligation assays and co-immunoprecipitation assays, which were complemented by in vitro ADP-ribosylation assays using recombinant proteins. Real-time RT-PCR analysis of mRNA levels and promoter-reporter assays provided quantitative analysis of gene expression in response to TGF? stimulation and after genetic perturbations of PARP-1/-2 and PARG based on RNA interference.ResultsTGF? signaling rapidly induces nuclear ADP-ribosylation of Smad3 that coincides with a relative enhancement of nuclear complexes of Smads with PARP-1 and PARP-2. Inversely, PARG interacts with Smads and can de-ADP-ribosylate Smad3 in vitro. PARP-1 and PARP-2 also form complexes with each other, and Smads interact and activate auto-ADP-ribosylation of both PARP-1 and PARP-2. PARP-2, similar to PARP-1, negatively regulates specific TGF? target genes (fibronectin, Smad7) and Smad transcriptional responses, and PARG positively regulates these genes. Accordingly, inhibition of TGF?-mediated transcription caused by silencing endogenous PARG expression could be relieved after simultaneous depletion of PARP-1.ConclusionNuclear Smad function is negatively regulated by PARP-1 that is assisted by PARP-2 and positively regulated by PARG during the course of TGF? signaling.

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An inhibitor of poly (ADP-ribose) synthetase activity reduces contractile dysfunction and preserves high energy phosphate levels during reperfusion of the ischaemic rat heart.

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