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Home > Medical Professionals > Research Initiatives Conference > Poster Abstracts Accepted > Crawford PJ34, A Potent Poly ADP-Ribose Inhibitor

PJ34, A Potent Poly ADP-Ribose Inhibitor, Confers Local, But Not Systemic Protection In A Murine Model Of Bilateral Critical Limb Ischemia-Reperfusion

Robert S Crawford, Hassan Albadawi, Fateh Entabi, John Jones, Marvin Atkins, Juan D Pedraza, Glenn M LaMuraglia, Michael T Watkins
Massachusetts General Hospital, Boston, MA

Introduction: Poly ADP-Ribose Polymerase (PARP) inhibition has been shown to be protective in numerous animal models of sepsis, hemodynamic shock and ischemia-reperfusion (IR). The concept that inhibition of PARP, an essential nuclear repair enzyme, should be protective against ischemic stress seems paradoxical. These experiments were designed to investigate the effects of a PARP inhibitor, PJ34 on local and systemic responses to bilateral limb IR.
Methods: Two groups of C57BL6 mice underwent 2.5 hours of bilateral limb ischemia, followed by 48 hours of reperfusion. The treatment group (PJ, n=20) received PJ34 (15 mg/kg/dose) 1hr before, just prior to reperfusion, and at 3 hours post-reperfusion. Control group (NS, n=24) received normal saline at the same intervals. Surviving mice were sacrificed at 48 hours reperfusion. KC (murine analogue of human IL-8, pg/mg protein) and Myeloperoxidase (MPO, a neutrophil marker, ng/mg protein) were assayed (by ELISA) from muscle extracts as markers of local inflammation. The systemic effects of reperfusion were evaluated using non-invasive quantitative assessment of global perfusion via Laser Doppler Imaging (LDI, flux units/cm2) of the tail at baseline, 2.5 hrs ischemia, 4, 24 and 48 hrs reperfusion. Vascular endothelial growth factor (VEGF, a pro-angiogenic growth factor, pg/ml) and KC (pg/ml) were also measured in the serum, along with KC levels in the kidney and liver as indices of systemic inflammation. Results were analyzed using unpaired t-test. Mortality was assessed using χ².
Results: Local Response: Muscle KC from PJ34 treated animals was significantly lower than NS mice (24±4 vs. 66±20, p=0.03). Decreased muscle MPO levels in the PJ treated mice (95±14 vs. 134±16, p=0.11) were not statistically significant. Systemic Response: Mortality among the PJ treated mice was greater than the NS mice (PJ: 60%, (12/20) vs. NS: 16.8% (4/24), p=0.025). All PJ and NS mice died between 4 and 24 hours reperfusion. In PJ mice after 4 and 24 hours reperfusion, LDI was significantly less than NS mice (p=0.001, p=0.02). By 48 hours reperfusion, tail LDI among surviving mice was no different between PJ, NS mice, although both were lower than pre-ischemic measurements. Also at 48 hrs, the levels of KC in the serum, kidney and liver were not different between the PJ and NS treated mice. Serum VEGF levels were not different between PJ34 (71 ±5) and saline (76 ±6) treated animals.
Conclusions: These data suggest that PJ34 adequately ameliorates a robust local cytokine response but not the systemic response to limb reperfusion injury. Mortality following IR appears to occur between 4 and 24 hours reperfusion, when the LDI remains markedly diminished compared to baseline and NS treated conditions. PJ34 treatment may interfere with systemic mediators essential for surviving the stress associated with limb reperfusion