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Am J Transl Res 2013;5(5):530-542
Original Article
Regulation of Monocyte Chemotactic Protein-1 secretion by the Two-
Pore-Domain Potassium (K2P) channel TREK-1 in human alveolar
epithelial cells
Andreas Schwingshackl, Bin Teng, Manik Ghosh, Christopher M Waters
Departments of Pediatrics, Physiology, Medicine, University of Tennessee Health Science Center, Memphis, TN
38103, USA
Received June 14, 2013; Accepted July 23, 2013; Epub August 15, 2013; Published August 30, 2013
Abstract: We recently proposed a role for the 2-pore-domain K+ (K2P) channel TREK-1 in the regulation of
cytokine release from alveolar epithelial cells (AECs) by demonstrating decreased IL-6 secretion from TREK-1
deficient cells, but the effects of altered TREK-1 expression on other inflammatory mediators remain poorly
understood. We now examined the role of TREK-1 in TNF-α-induced MCP-1 release from human A549 cells. We
hypothesized that TREK-1 regulates TNF-α-induced MCP-1 secretion via c-Jun N-terminal kinases (JNK)- and
protein kinase-C (PKC)-dependent pathways. In contrast to IL-6 secretion, we found that TREK-1 deficiency
resulted in increased MCP-1 production and secretion, although baseline MCP-1 gene expression was
unchanged in TREK-1 deficient cells. In contrast to TREK-1 deficient AECs, overexpression of MCP-1 had no
effect on MCP-1 secretion. Phosphorylation of JNK1/2/3 was increased in TREK-1 deficient cells upon TNF-α
stimulation, but pharmacological inhibition of JNK1/2/3 decreased MCP-1 release from both control and TREK-1
deficient cells. Similarly, pharmacological inhibition of PKC decreased MCP-1 secretion from control and TREK-1
deficient cells, suggesting that alterations in JNK and PKC signaling pathways were unlikely the cause for the
increased MCP-1 secretion from TREK-1 deficient cells. Furthermore, MCP-1 secretion from control and TREK-1
deficient cells was independent of extracellular Ca2+ but sensitive to inhibition of intracellular Ca2+ reuptake
mechanisms. In summary, we report for the first time that TREK-1 deficiency in human AECs resulted in
increased MCP-1 production and secretion, and this effect appeared unrelated to alterations in JNK-, PKC- or
Ca2+-mediated signaling pathways in TREK-1 deficient cells. (AJTR1306002).
Keywords: TREK-1, MCP-1, TNF-α, chemokine, epithelium, acute lung injury
Address correspondence to: Dr. Andreas Schwingshackl, Department of Pediatrics, University of Tennessee
Health Science Center, 50 North Dunlap, Suite 346R, Memphis, TN 38103. Tel: 901-287-6303; Fax: 901-287-
6336; E-mail: aschwing@uthsc.edu
Original Article
Regulation of Monocyte Chemotactic Protein-1 secretion by the Two-
Pore-Domain Potassium (K2P) channel TREK-1 in human alveolar
epithelial cells
Andreas Schwingshackl, Bin Teng, Manik Ghosh, Christopher M Waters
Departments of Pediatrics, Physiology, Medicine, University of Tennessee Health Science Center, Memphis, TN
38103, USA
Received June 14, 2013; Accepted July 23, 2013; Epub August 15, 2013; Published August 30, 2013
Abstract: We recently proposed a role for the 2-pore-domain K+ (K2P) channel TREK-1 in the regulation of
cytokine release from alveolar epithelial cells (AECs) by demonstrating decreased IL-6 secretion from TREK-1
deficient cells, but the effects of altered TREK-1 expression on other inflammatory mediators remain poorly
understood. We now examined the role of TREK-1 in TNF-α-induced MCP-1 release from human A549 cells. We
hypothesized that TREK-1 regulates TNF-α-induced MCP-1 secretion via c-Jun N-terminal kinases (JNK)- and
protein kinase-C (PKC)-dependent pathways. In contrast to IL-6 secretion, we found that TREK-1 deficiency
resulted in increased MCP-1 production and secretion, although baseline MCP-1 gene expression was
unchanged in TREK-1 deficient cells. In contrast to TREK-1 deficient AECs, overexpression of MCP-1 had no
effect on MCP-1 secretion. Phosphorylation of JNK1/2/3 was increased in TREK-1 deficient cells upon TNF-α
stimulation, but pharmacological inhibition of JNK1/2/3 decreased MCP-1 release from both control and TREK-1
deficient cells. Similarly, pharmacological inhibition of PKC decreased MCP-1 secretion from control and TREK-1
deficient cells, suggesting that alterations in JNK and PKC signaling pathways were unlikely the cause for the
increased MCP-1 secretion from TREK-1 deficient cells. Furthermore, MCP-1 secretion from control and TREK-1
deficient cells was independent of extracellular Ca2+ but sensitive to inhibition of intracellular Ca2+ reuptake
mechanisms. In summary, we report for the first time that TREK-1 deficiency in human AECs resulted in
increased MCP-1 production and secretion, and this effect appeared unrelated to alterations in JNK-, PKC- or
Ca2+-mediated signaling pathways in TREK-1 deficient cells. (AJTR1306002).
Keywords: TREK-1, MCP-1, TNF-α, chemokine, epithelium, acute lung injury
Address correspondence to: Dr. Andreas Schwingshackl, Department of Pediatrics, University of Tennessee
Health Science Center, 50 North Dunlap, Suite 346R, Memphis, TN 38103. Tel: 901-287-6303; Fax: 901-287-
6336; E-mail: aschwing@uthsc.edu
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