Lipopolysaccharide increases Na(+),K(+)-pump, but not ENaC, expression in guinea-pig airway epithelium.
Earlier, we found in functional experiments that lipopolysaccharide (LPS; 4mg/kg; i.p.) hyperpolarized the epithelium by stimulating the transepithelial transport of Na(+) in guinea-pig tracheal epithelium. Epithelial sodium channel (ENaC) activity and Na(+),K(+)-pump activity were increased. In this study, we hypothesized that LPS increases the expression of ENaC and the Na(+),K(+)-pump in the epithelium and investigated the levels of transcription and protein abundance. Using qPCR, the effects of LPS on the transcription of αENaC, α(1) Na(+),K(+)-pump, COX-2, eNOS, iNOS, IL-1β, and TNF-α were measured at 3 and 18h. In the epithelium, LPS increased the transcription of COX-2, IL-1β, and, to a nonsignificant extent, TNF-α at 3h, but not at 18h. In alveolar macrophages, TNF-α, and, to a nonsignificant extent, COX-2 and IL-1β were up-regulated at 3h, but not at 18h. Even though LPS stimulated the transcription of some genes, αENaC and α(1) Na(+),K(+)-ATPase transcription were not affected. The expressions of α-, β-, and γ-ENaC and α(1) Na(+),K(+)-pump from the tracheal epithelium and kidney cortex/medulla were investigated by western blotting. All three ENaC subunits were detected as cleavage fragments, yet LPS had no effect on their expression. LPS increased the expression of the α(1) subunit and the α(1), α(2), and α(3) subunits, collectively, of the Na(+),K(+)-pump. Taken together, these data indicate that LPS increases Na(+) transport downstream of the genetic level, in part, by stimulating the expression of the Na(+),K(+)-pump.
Department of Basic Pharmaceutical Sciences, West Virginia University, Morgantown, WV 26505, USA.
Michael W
MW
Dodrill
Donald H
DH
Beezhold
Terence
T
Meighan
Michael L
ML
Kashon
Jeffrey S
JS
Fedan
D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D053503:Epithelial Sodium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D006168:Guinea Pigs; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D051381:Rats; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*; D014132:Trachea / Q000187:drug effects* / Q000378:metabolism*
D053503:Epithelial Sodium Channels; D008070:Lipopolysaccharides; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase