MAPK3 and systemic sclerosis: Furthermore, the NE-induced IL-6 mRNA and secreted protein levels in the normal and SSc fibroblasts was enhanced by the MEK/ERK inhibitor, PD98059 (Fig. 3E,F), thus suggesting that the NE-induced phosphorylation of ERK1/2 via ARα inhibits IL-6 production in SSc fibroblasts.