Participation of mitogen-activated protein kinase in thapsigargin- and TPA-induced histamine production in murine macrophage RAW 264.7 cells

1 Stimulation of the murine macrophage cell line RAW 264.7 with thapsigargin, an endomembrane Ca2+-ATPase inhibitor, induced histamine production in a time- and concentration-dependent manner. 2 The protein kinase C activator, 12-O-tetradecanoylphorbol 13-acetate (TPA), also enhanced histamine production. 3 alpha-Fluoromethylhistidine, a suicide substrate of L-histidine decarboxylase (HDC), suppressed the thapsigargin (30 nM)- and TPA (30 nM)-induced histamine production. 4 Both thapsigargin (30 nM) and TPA (30 nM) induced phosphorylation of p44/p42 MAP kinase and p38 MAP kinase. 5 PD98059, a specific inhibitor of MEK-1 which phosphorylates p44/p42 MAP kinase, strongly suppressed both the thapsigargin (30 nM)- and TPA (30 nM)-induced histamine production, whereas SB203580, a specific inhibitor of p38 MAP kinase, inhibited them only partially. 6 The other MEK-1 inhibitor, U-0126, also inhibited both the thapsigargin- and TPA-induced histamine production in a concentration-dependent manner. 7 Thapsigargin (30 nM) and TPA (30 nM) increased the levels of HDC mRNA at 4 h, but PD98059 suppressed both the thapsigargin- and TPA-induced increases in the HDC mRNA level. 8 These findings indicate that thapsigargin and TPA induce histamine production in RAW 264.7 cells by increasing the level of HDC mRNA, and that both the thapsigargin- and TPA-induced histamine production are regulated largely by p44/p42 MAP kinase and partially by p38 MAP kinase.