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TNF‐α modulates the Na + / K + ATPase and the Na + K + 2Cl − symporter in LLC‐PK 1 cells
Author(s) -
Ramia N. F.,
Kreydiyyeh S. I.
Publication year - 2009
Publication title -
european journal of clinical investigation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.164
H-Index - 107
eISSN - 1365-2362
pISSN - 0014-2972
DOI - 10.1111/j.1365-2362.2009.02098.x
Subject(s) - symporter , microbiology and biotechnology , apoptosis , caspase , tumor necrosis factor alpha , chemistry , programmed cell death , biology , endocrinology , biochemistry , transporter , gene
Background Tumour necrosis factor alpha (TNF‐α) has been implicated in the development of diabetic nephropathy and the accompanying increase in sodium retention. Inhibition of renal Na + /K + ATPase was reported to accompany cell death. As TNF is known to induce both apoptosis and cell survival, this work investigated the effect and mechanism of action of TNF‐α on the Na + /K + ATPase and the Na + K + 2Cl − symporter using LLC‐PK 1 cells, a porcine renal proximal tubules cell line. Materials and methods Cells were incubated for 2 h with TNF‐α in presence and absence of pyrrolidinedithiocarbamate, SP600125 and FK009, respective inhibitors of the transcription factor nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐κB), c‐Jun N‐terminal kinase (JNK) and caspases. The activity of the pump was assayed by measuring the ouabain‐inhibitable release of inorganic phosphate. Changes in its expression and the expression of the symporter were monitored by western blot analysis. Results TNF‐α up‐regulated both transporters. NF‐κB, JNK and the caspases were all mediators of the cytokine action. TNF up‐regulated the Na + /K + pump by stimulating JNK which in turn, activated NF‐κB and inhibited the caspases. TNF effect on the cotransporter was also mediated via activation of JNK which however inhibited NF‐κB and by so doing prevented activation of caspases. As caspases were demonstrated to down‐regulate the two transporters, their inhibition by TNF is responsible for the observed up‐regulatory effect. Conclusions It was concluded that the Na + /K + ATPase and Na + K + 2Cl − are both targets of TNF‐α and the effect of the cytokine favours cell survival over cell death.