Regulation of Inflammatory Cytokine Production by MKP‐5 in Macrophages

Mitogen-activated protein kinases (MAPKs) include p38 MAPKs, c-Jun N-terminal kinases (JNKs) and Extracellular signal-regulated kinases (ERKs), and they regulate many cell processes, such as cell division, differentiation and release of inflammatory mediators. MAPK activity is controlled by mitogen-activated protein kinase phosphatases (MKPs), a phosphatase family with 11 members. MKP-1 is the most studied member of MKP family, and it is one of the anti-inflammatory factors induced by glucocorticoids. Less is known about the other MAPK phosphatases although they hold a promise as anti-inflammatory drug targets. In this study, we investigated the effect of MKP-5 on MAPK phosphorylation and cytokine production in J774 mouse macrophages. We used MKP-5 siRNA and an MKP-5 inhibitor (AS077234-4) to modulate MKP-5 function. We found that MKP-5 controlled p38 MAPK phosphorylation, but not that of JNK or ERK. In addition, the production of IL-6 and TNF was suppressed by MKP-5 in macrophages. Our results introduce a novel concept that compounds able to enhance MKP-5 expression and/or activity hold anti-inflammatory potential, because MKP-5 down-regulates the release of inflammatory mediators by controlling p38 MAPK activity.