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  • Title: Tumor necrosis factor-alpha potentiates RhoA-mediated monocyte transmigratory activity in vivo at a picomolar level.
    Author: Lim S, Ryu J, Shin JA, Shin MJ, Ahn YK, Kim JJ, Han KH.
    Journal: Arterioscler Thromb Vasc Biol; 2009 Dec; 29(12):2138-45. PubMed ID: 19745197.
    Abstract:
    OBJECTIVE: The serum level of tumor necrosis factor-alpha (TNF-alpha) is in the picomolar range under inflammatory conditions. We investigated whether these picomolar levels of TNF-alpha directly modulate the functional activities of circulating monocytes. METHODS AND RESULTS: In THP-1 monocytes treated with TNF-alpha (1 to 100 pmol/L/30 minutes), cytosolic RhoA small GTPase rapidly translocated to the plasma membrane via functionally active ezrin/radixin/moesin (ERM) complex, a cytoskeletal linker, and subsequent actin polymerization through NF-kappaB activation. The threonine phosphorylation of ERM was accomplished by the activation of TNF receptor type I (TNFRI) and signaling pathways involving PI3K and an atypical PKC; ie, PKCzeta. The TNF-alpha-treated monocytes (10 pmol/L) displayed more potent and prolonged generation of GTP-bound RhoA in response to secondary stimulation with RhoA-activating monocyte chemoattractant protein-1 (MCP-1). Clearly, human circulating monocytes preconditioned by 10 pmol/L TNF-alpha augmented MCP-1-mediated chemotaxis and firm adhesion on VCAM-1 and ICAM-1 in vitro and ex vivo. The elevation of serum TNF-alpha (>5 pmol/L within 16 hours), which was introduced by intraperitoneal injection of mouse-specific TNF-alpha to C57/BL6 mice, enhanced the number of CD80+ monocytes transmigrating to the JE/MCP-1-injected intraperitoneal space. CONCLUSIONS: Picomolar concentrations of TNF-alpha in the bloodstream may prime the RhoA-dependent activities of circulating monocytes to enhance recruitment to active inflammatory foci.
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