Ephedrae herba (Mao) decreased histamine content in RBL-2H3 cells.

The effect of Ephedrae herba (Mao) on histamine content was investigated. When rat basophilic leukemia (RBL-2H3) cells were incubated for 48 h with Mao, Mao decreased histamine content in a concentration-dependent manner. However, the ratio of released histamine to total histamine was scarcely affected by Mao treatment when RBL-2H3 cells were stimulated by ionomycin. On the other hand, the content of ß-hexosaminidase, another marker of degranulation, was only slightly decreased by Mao. The expression level of the active form (53 kDa) of L-histidine decarboxylase, the enzyme which synthesizes histamine, was partially suppressed by Mao. Furthermore, Mao significantly suppressed proliferation of RBL-2H3 cells in a concentration-dependent manner. The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine revealed an increasing effect of Mao on cAMP level in RBL-2H3 cells. Since this result suggested that Mao may stimulate adenylate cyclase, we evaluated the effect of adenylate cyclase inhibitor SQ 22536 on Mao-induced decrease in histamine content. As a result, we showed that SQ 22536 did not have a reducing effect of Mao. From these results it is understood that Mao decreased histamine content by inhibiting cell proliferation and expression of histidine decarboxylase. However, these effects are not related to the increase in cAMP.

Inhibitory effect of Mao-Bushi-Saishin-to on prostaglandin E2 synthesis in C6 rat glioma cells.

Effect of Mao-Bushi-Saishin-to (Ma-Huang-Fu-Zi-Xi-Xin-Tang: MBS) on prostaglandin E(2) (PGE(2)) production was investigated using C6 rat glioma cells. Mao or Saishin inhibited histamine-induced PGE(2) production while MBS slightly decreased and Bushi increased it. MBS and Mao inhibited and Bushi enhanced A23187-induced PGE(2) production while Saishin had no effect. Concomitantly, Mao inhibted, but Bushi fascilitated, histamine- and A23187-induced phosphorylation of extracellular signal-regulated kinase (ERK)1/2. Treatment of MBS, Mao and also Saishin increased cAMP content. From these results, MBS inhibit PGE(2) production in C6 cells, mainly due to Mao but also due to Saishin at least in part, and the counteraction of Bushi. The former effect is mediated by formation of cAMP and resulting inhibition of ERK1/2-phosphorylation.

Ephedrae herba in Mao-Bushi-Saishin-To inhibits IgE-mediated histamine release and increases cAMP content in RBL-2H3 cells.

Acute effect of Mao-Bushi-Saishin-To (Ma-Huang-Fu-Zi-Xi-Xin-Tang in Chinese: MBS) on histamine release was investigated. The IgE-mediated anaphylaxic response in Wistar rats was significantly suppressed by MBS and Mao. However, Saishin and Bushi had no or little effect on the antigen-mediated anaphylaxic reaction. Mao as well as MBS but not Saishin nor Bushi inhibited IgE-mediated histamine release from rat basophilic leukemia (RBL-2H3) cells. Consistently, MBS and Mao but not Bushi nor Saishin increased cAMP levels in RBL-2H3 cells. However, ephedrine, methylephedrine, and pseudoephedrine, the main components in Mao, did not affect histamine release. From these results, increase of cAMP levels may account for the inhibitory effect of Mao on histamine release. Furthermore, these inhibitory actions of MBS were mainly due to Mao with an ingredient(s) different from ephedrines.