Local Administration of the Poly ADP-Ribose Polymerase (PARP) Inhibitor, PJ34 During Hindlimb Ischemia Modulates Skeletal Muscle Reperfusion Injury

Background: PARP stabilizes DNA and modulates inflammation in murine models of sepsis, stroke, and myocardial infarction. Previous studies have shown that systemic PARP inhibition before hindlimb ischemia preserves tissue viability and modulates cytokine synthesis during reperfusion. The purpose of this study was to determine whether intra-muscular (IM) administration of PJ34, a potent inhibitor of PARP, after the onset of acute hindlimb ischemia (post hoc) modulates the local production of inflammatory mediators during ischemia/reperfusion (I/R). Materials and methods: The control tension tourniquet was used to establish unilateral hindlimb ischemia in mice for 3 h followed by 48 h I/R. The treatment group (PJ) received IM PJ34 (10 mg/kg) in the affected hindlimb 90 min into ischemia whereas the control group (UN) received IM saline (150 uL) at the same time point. Skeletal muscle viability (MTT mitochondrial activity), local neutrophil chemoattractant protein (KC), Interleukin 6 (IL-6), Interleukin 1β (IL-1β), and Myeloperoxidase (MPO) levels were measured in protein extracts after the reperfusion period. Results: Muscle viability (102% ± 10 PJ, 78% ± 4 UN, P = 0.04), IL-B (21.1 ± 1.3 PJ, 15.5 ± 1.0 UN, P = 0.02), and IL-6 levels (16.3 ± 1.2 PJ, 10.9 ± 1.4 UN, P = 0.04) after 48 I/R were significantly higher in PJ. KC and MPO levels were higher in PJ but neither reached statistical significance. Conclusions: Post hoc PJ34 therapy appears to protect skeletal muscle from I/R injury despite increased levels of local cytokines. These initial findings support the role of local post hoc therapy in the treatment of acute limb threatening ischemia suggesting that further study of this novel therapy is warranted.