Role of transient receptor potential vanilloid 2 in LPS-induced cytokine production in macrophages

K Yamashiro, T Sasano, K Tojo, I Namekata… - Biochemical and …, 2010 - Elsevier
K Yamashiro, T Sasano, K Tojo, I Namekata, J Kurokawa, N Sawada, T Suganami, Y Kamei…
Biochemical and biophysical research communications, 2010Elsevier
There is considerable evidence indicating that intracellular Ca2+ participates as a second
messenger in TLR4-dependent signaling. However, how intracellular free Ca2+
concentrations ([Ca2+] i) is increased in response to LPS and how they affect cytokine
production are poorly understood. Here we examined the role of transient receptor potential
(TRP), a major Ca2+ permeation pathway in non-excitable cells, in the LPS-induced
cytokine production in macrophages. Pharmacologic experiments suggested that TRPV …
There is considerable evidence indicating that intracellular Ca2+ participates as a second messenger in TLR4-dependent signaling. However, how intracellular free Ca2+ concentrations ([Ca2+]i) is increased in response to LPS and how they affect cytokine production are poorly understood. Here we examined the role of transient receptor potential (TRP), a major Ca2+ permeation pathway in non-excitable cells, in the LPS-induced cytokine production in macrophages. Pharmacologic experiments suggested that TRPV family members, but neither TRPC nor TRPM family members, are involved in the LPS-induced TNFα and IL-6 production in RAW264 macrophages. RT-PCR and immunoblot analyses showed that TRPV2 is the sole member of TRPV family expressed in macrophages. ShRNA against TRPV2 inhibited the LPS-induced TNFα and IL-6 production as well as IκBα degradation. Experiments using BAPTA/AM and EGTA, and Ca2+ imaging suggested that the LPS-induced increase in [Ca2+]i involves both the TRPV2-mediated intracellular and extracellular Ca2+ mobilizations. BAPTA/AM abolished LPS-induced TNFα and IL-6 production, while EGTA only partially suppressed LPS-induced IL-6 production, but not TNFα production. These data indicate that TRPV2 is involved in the LPS-induced Ca2+ mobilization from intracellular Ca2+ store and extracellular Ca2+. In addition to Ca2+ mobilization through the IP3-receptor, TRPV2-mediated intracellular Ca2+ mobilization is involved in NFκB-dependent TNFα and IL-6 expression, while extracellular Ca2+ entry is involved in NFκB-independent IL-6 production.
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