Understanding the role of Poly(ADP-ribose) polymerase (PARP1) and PARP inhibitors in viral infection and pathogenesis

Poly (ADP-ribose) polymerase 1 (PARP1) is a post-translational modifying enzyme and is also known to act as transcription factor and co-activator. PARP1 has been shown to be involved with diseases resulting in increased inflammation and several viral diseases have also been associated with PARP1 activation. PARP1 facilitates influenza A virus entry in host cells by degrading interferon receptor type I. PARP1 regulates expression of NFkB and downstream cytokine production and its inhibition is known to attenuate the expression of inflammatory cytokines. Thus, PARP1 plays an important role in host-pathogen interactions and pathogenesis. Moreover, pre-clinical and in vitro studies have shown that PARP1 inhibition may affect viability of several viruses including affecting replication of the SARS-CoV virus, a distant relative of the SARS-CoV-2 virus, the one which caused the SARS epidemic of 2002. Covid-19 has been declared a global pandemic; with symptoms of the disease now not limited to respiratory distress alone. Severe inflammation is observed in the lungs leading to a surge of cytokine release systemically, affecting heart function, ischemia and stroke. Inflammatory cytokines which are associated with severe comorbidities and mortalities due to chronic diseases are being upregulated in an acute fashion. There is no immediate treatment, and only palliative care is being provided. The current review will discuss mechanisms of PARP1 activation during viral infection, inflammatory diseases, cytokine expression and possibility of PARP1 in regulating cytokine storm and hyper-inflammation seen with Covid-19.