Microcystin-LR (MC-LR) Triggers Inflammatory Responses in Macrophages
Robin C. Su, Joshua D. Breidenbach, Khaled Alganem, Fatimah K. Khalaf, Benjamin W. French, Prabhatchandra Dube, Deepak Malhotra, Robert E. McCullumsmith, John B. Presloid, R. Mark Wooten, David J. Kennedy, Steven T. Haller
Abstract
We were the first to previously report that microcystin-LR (MC-LR) has limited effects within the colons of healthy mice but has toxic effects within colons of mice with pre-existing inflammatory bowel disease. In the current investigation, we aimed to elucidate the mechanism by which MC-LR exacerbates colitis and to identify effective therapeutic targets. Through our current investigation, we report that there is a significantly greater recruitment of macrophages into colonic tissue with pre-existing colitis in the presence of MC-LR than in the absence of MC-LR. This is seen quantitatively through IHC staining and the enumeration of F4/80-positive macrophages and through gene expression analysis for Cd68, Cd11b, and Cd163. Exposure of isolated macrophages to MC-LR was found to directly upregulate macrophage activation markers Tnf and Il1b. Through a high-throughput, unbiased kinase activity profiling strategy, MC-LR-induced phosphorylation events were compared with potential inhibitors, and doramapimod was found to effectively prevent MC-LR-induced inflammatory responses in macrophages.