Characterization of Thiomuscimol: A Novel Small Molecule Pyroptosis Inhibitor

Abstract

Pyroptosis, a form of pro-inflammatory programmed cell death mediated by caspase- 1 and dependent on gasdermin D, is a crucial element of the innate immune response. Pyroptosis arises from activation of sensor proteins which respond to threats to host health, leading to the formation of multiprotein complexes known as inflammasomes that induce production of pro-inflammatory cytokines. The downstream effects of pyroptosis such as cell rupture and the release of inflammatory signals are implicated in the progression of a number of diseases, indicating that having the ability to control pyroptosis has great therapeutic potential. GABAA receptor agonist muscimol inhibits pyroptotic lysis. The goal of this thesis was to better understand the mechanism of the muscimol analog thiomuscimol, which inhibits pyroptosis in a unique manner. We used Salmonella typhimurium and anthrax lethal toxin as pyroptosis inducers, and we identified the target concentrations of thiomuscimol and that the effects of thiomuscimol were not due to cytotoxicity nor were boosted by a pretreatment. Then we determined that thiomuscimol binds in a reversible manner, and that it inhibits caspase-3 in addition to caspase-1.Finally, we determined that thiomuscimol is capable of both diffuse active caspase-1 inhibition as well as foci-bound caspase-1 inhibition. Together, these results provide insight into thiomuscimol’s mechanism, contributing to the understanding of small molecule pyroptosis inhibition.