Poly (ADP-ribose) polymerase-1 inhibition increases expression of heat shock proteins and attenuates heat stroke-induced liver injury

Objective: Heat stroke is a life-threatening illness characterized by an increased core body temperature as a result of exposure to high ambient temperature. Despite advances in supportive care, heat stroke is often fatal, and no specific and effective therapies exist. The pathophysiological responses to heat stroke involve a systemic inflammatory response and a disseminated intravascular coagulation in the host, which lead to a multiorgan dysfunction syndrome. Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear DNA-binding protein that has been shown to play a relevant role in cell necrosis and organ failure in various diseases associated with inflammation. Therefore, we set out to investigate whether inhibition of PARP activity might affect the heat stroke-induced injury. Design: Controlled animal study. Setting: Research laboratory of an academic institution. Subjects: PARP-1-deficient mice (Parp-1(-/-)) and wild-type mice (C57BL/6J). Interventions: Wild-type mice untreated or treated with either PJ34 or 3-AB, two generic PARP inhibitors, and Parp-1(-/-) mice were subjected to heat exposure as a model to study heal stroke. Measurements and Main Results: We measured rectal temperature, serum interleukin-1 beta and interleukin-6, liver histology, and heat shock proteins expression. We found that the heat stroke-induced injury was attenuated in mice lacking PARP-1 and was markedly reduced in wild-type mice treated with PARP inhibitors. Interestingly, heat-induced expression of heat shock proteins 27 and 70 was boosted after PARP inhibition. Indeed, PARP inhibition increased expression of heat shock proteins 27 and 70 even in the absence of heat exposure. Accordingly, PARP inhibition increased thermal tolerance that may contribute to attenuate the clinical effects of heat stroke, resulting in increased survival. Conclusions: Our results find a new protective function of PARP inhibitors and support their potential therapeutic application in the treatment of heat stroke.