Tanshinone IIA suppresses FcεRI-mediated mast cell signaling and anaphylaxis by activation of the Sirt1/LKB1/AMPK pathway.

AMP-activated protein kinase (AMPK) and its upstream mediators liver kinase B1 (LKB1) and sirtuin 1 (Sirt1) are generally known as key regulators of metabolism. We have recently reported that the AMPK pathway negatively regulates mast cell activation and anaphylaxis. Tanshinone IIA (Tan IIA), an active component of Salvia miltiorrhiza extract that is currently used for the treatment of cardiovascular and cerebrovascular diseases, shows anti-diabetic activity and improves insulin resistance in db/db mice through activation of AMPK. The aim of this study was to evaluate the anti-allergic activity of Tan IIA in vivo and to investigate the underlying mechanism in vitro in the context of AMPK signaling. The anti-allergic effect of Tan IIA was evaluated using mouse bone marrow-derived mast cells (BMMCs) from AMPKα2-/- or Sirt1-/- mice, or BMMCs transfected with siRNAs specific for AMPKα2, LKB1, or Sirt1. AMPKα2-/- and Sirt1-/- mice were used to confirm the anti-allergic effect of Tan IIA in anaphylaxis in vivo. Tan IIA dose-dependently inhibited FcεRI-mediated degranulation and production of eicosanoids and cytokines in BMMCs. These inhibitory effects were diminished by siRNA-mediated knockdown or genetic deletion of AMPKα2 or Sirt1. Moreover, Tan IIA inhibited a mast cell-mediated local passive anaphylactic reaction in wild-type mice, but not in AMPKα2-/- or Sirt1-/- mice. In conclusion, Tan IIA suppresses FcεRI-mediated mast cell activation and anaphylaxis through activation of the inhibitory Sirt1-LKB1-AMPK pathway. Thus, Tan IIA may be useful as a new therapeutic agent for mast cell-mediated allergic diseases.

Saucerneol F inhibits tumor necrosis factor-α and IL-6 production by suppressing Fyn-mediated pathways in FcεRI-mediated mast cells.

The aim of this study was to investigate the effect of saucerneol F (SF) on the productions of the pro-inflammatory cytokines, TNF-α and IL-6, in IgE/Ag-induced mouse bone marrow-derived mast cells (BMMCs). SF dose-dependently suppressed the transcriptions of these pro-inflammatory cytokines. To identify the molecular mechanisms responsible for these suppressions, we examined the effect of SF on three important transcription factors; activator protein-1 (AP-1), nuclear factor-κB (NF-κB), and STAT5. It was found that SF inhibited the nuclear translocation of the p65 subunit of NF-κB to the nucleus and its DNA-binding ability. SF also attenuated mitogen-activated protein kinase (MAPK)-mediated AP-1 activation and STAT5 activation. Biochemical analysis of FcεRI-mediated signaling pathways demonstrated that SF inhibited the phosphorylation of Fyn and multiple downstream signaling processes, including Syk, Gab2, and the Akt/IKK/IκB and MAPK pathways. Taken together, our results suggest that SF inhibits the production of pro-inflammatory cytokines by suppressing Fyn kinase-dependent signaling events.

Pimaric acid from Aralia cordata has an inhibitory effect on TNF-α-induced MMP-9 production and HASMC migration via down-regulated NF-κB and AP-1.

Many studies have indicated that activation of matrix metalloproteinase (MMP)-9 and smooth muscle cell (SMC) migration are involved in neointimal formation and atherosclerosis. In this study, we revealed that pimaric acid (PiMA) purified from Aralia cordata had an inhibitory effect on MMP-9 production and migration of human aortic smooth muscle cells (HASMCs) induced by tumor necrosis factor (TNF)-α. Down-regulated MMP-9 mRNA transcription was detected in PiMA-treated cells using RT-PCR and the luciferase-tagged MMP-9 promoter assay. Results of an electrophoretic mobility shift assay indicated that PiMA-treated HASMCs showed decreased binding activity of nuclear factor (NF)-κB and activator protein-1 transcription factors. A Western-blot analysis using nuclear extract demonstrated that PiMA reduced the levels of NF-κB p65, c-Fos, p-c-Jun, Jun-D, and p-ATF2 proteins in the nucleus. In addition, TNF-α stimulated mitogen activated protein kinase (MAPK) containing extracellular signal regulated kinase 1 and 2, p38, and c-Jun N-terminal kinase was inhibited by PiMA. Using the Transwell system, we found that PiMA inhibited TNF-α stimulated HASMC migration/invasion in a dose-dependent manner. To confirm whether MAPK mediated MMP-9 expression, we used MAPK inhibitors including U0126, SB253580, and SP600125 and found that those inhibitors reduced MMP-9 expression and HASMC migration/invasion. These results suggest that PiMA has potent anti-atherosclerotic activity with inhibitory action on MMP-9 production and cell migration in TNF-α-induced HASMCs.

Citreorosein, a naturally occurring anthraquinone derivative isolated from Polygoni cuspidati radix, attenuates cyclooxygenase-2-dependent prostaglandin D2 generation by blocking Akt and JNK pathways in mouse bone marrow-derived mast cells.

In this study, we examined the effects of citreorosein (CIT), an anthraquinone component of Polygoni cuspidati radix (P. cuspidati, Polygonaceae), on cyclooxygenase (COX)-2 dependent prostaglandin (PG)D2 generation in mast cells, central effector cells of allergy and other inflammatory diseases. CIT strongly inhibited COX-2-dependent PGD2 generation in a concentration-dependent manner in mouse bone marrow-derived mast cells (BMMCs) stimulated with stem cell factor (SCF)/IL-10/LPS. In an effort to identify the mechanisms underlying the inhibition of COX-2-dependent PGD2 generation by CIT, we examined the effects of this compound on MAP kinases, Akt and NF-κB signaling pathways, which are essential for COX-2 induction. CIT inhibited nuclear translocation of the nuclear factor (NF)-κB p65 subunit and its cognate DNA-binding activity, which correlated with its inhibitory effects on the phosphorylation of Akt and IKK and subsequent phosphorylation and degradation of IκB. Furthermore, CIT significantly attenuated the DNA binding of activator protein (AP)-1 that regulates COX-2 expression through the reduction of the phosphorylation of c-Jun. Moreover, inhibition of PGD2 generation by CIT was accompanied by a decrease in phosphorylation of cytosolic phospholipase A2α. Taken together, the present study suggests that CIT represents a potential therapeutic approach for the treatment of inflammatory diseases.