Differential effect of p38 and MK2 kinase inhibitors on the inflammatory and toxicity biomarkers in vitro

Background: Many inflammatory responses including chemotaxis, production of nitric oxide, and modulation of pro-inflammatory cytokines in immunological cells are mediated by p38MAPK. Due to its pivotal role, p38MAPK has been extensively explored as a molecular target for inhibition of chronic inflammation; however, it has not been successful so far due to serious toxicity issues. Among several downstream substrates of p38, mitogen-activated protein kinase-activated protein kinase 2 (MK2) has been reported to be a direct and essential downstream component in regulation of innate immune and inflammatory responses. Thus, in this study, we aimed to understand relative molecular differences between p38 and MK2 kinase inhibition in terms of a comparative anti-inflammatory potential along with molecular regulation of toxicity biomarkers such as Phospho c-Jun N-Terminal Kinase (pJNK), caspase-3, and hepatic enzyme levels in relevant human cells in vitro. Results: Both p38 and MK2 inhibitors attenuated lipopolysaccharide-induced pro-inflammatory biomarkers expression. In addition, both these kinase inhibitors inhibited release of Th1 and Th17 cytokines in phytohemagglutinin-induced cells with MK2 inhibitor showing a better potency for inhibition of Th1 cytokine release, interferon-γ. In the mechanistic differentiation studies, p38 inhibitors displayed an increase in pJNK and caspase-3 activity in U937 cells and elevation in aspartate transaminase enzyme in HepG2 cells, whereas MK2 inhibitor did not show such adverse toxic effects. Conclusion: Taken together, inhibition of MK2 kinase can be a relatively preferred strategy as an anti-inflammatory therapy over direct inhibition of p38 kinase in p38MAPK pathway.