Identification and Characterization of Novel Caspase Inhibitors: The Unforeseen Effects of NSAIDs

Soti, Subada

Undergraduate Honors Thesis

Identification and Characterization of Novel Caspase Inhibitors: The Unforeseen Effects of NSAIDs Public Deposited

Analytics

Citations

Citeable URL: https://scholar.colorado.edu/concern/undergraduate_honors_theses/0c483j844

Abstract

Proper regulation of cell death and the inflammatory mechanism leading to cell death is vital for the development and homeostasis of living organisms. Dysregulation of cell death leads to cancer, neurodegenerative disorders, and inflammatory conditions such as sepsis. Caspases are major players of cell death. In gram-negative bacteria induced sepsis, LPS directly binds to caspase-4 and 5 to induce pyroptosis. With the hypothesis that inhibition of caspase-4 may be required to provide protection from sepsis, the first goal of this research is to identify and characterize novel small molecules that inhibit caspase-4. Additionally, nonsteriodal anti-inflammatory drugs (NSAIDs) provide analgesic and antipyretic effects, but the mechanism of their adverse side effects such as the gastrointestinal bleeding and development of ulcers is unknown. With the hypothesis that NSAIDs mechanism may involve caspases, the second goal of this research is to study the effect of NSAIDs on caspases. 3700 compounds from the Soft Focus Protease/Kinase Library (P/K) and Prestwick Chemical Library (FDA) were screened against caspase-4 activity using a Caspase-Glo enzymatic activity assay. Two compounds from P/K were identified as promising caspase-4 specific inhibitors. FDA screen revealed that 56% of the top caspase-4 inhibitors were NSAIDs. Further characterization of six diverse NSAIDs revealed NSAIDs are pan-caspase inhibitors and that their IC₅₀ values are lower than the average concentration present in blood. Considering that the knockout of mice-homologous caspase-4 increased susceptibility of bacterial infection in mice gut and knockout of caspase-1 increased tumorogenesis in mice, NSAIDs being pan-caspase inhibitors has serious implications for NSAIDs’ side effects. This study supports the hypothesis that caspases may be involved in the mechanism of side effects of NSAIDs.

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