Upregulation of heme oxygenase-1 as a host mechanism for protection against nitric oxide-induced damage in human renal epithelial cells.
OBJECTIVE
To examine whether urinary tract infection-associated stimuli could regulate heme oxygenase-1 (HO-1) expression and to asses the significance of HO-1 in protecting urinary tract epithelial cells against nitric oxide (NO)-induced damage.


METHODS
Heme oxygenase-1 expression was investigated in the human renal epithelial cell line A498 in response to the uropathogenic Escherichia coli (UPEC) strain IA2, the NO-donor DETA/NONOate (DETA/NO), and proinflammatory cytokines (interleukin-1beta, tumor necrosis factor-alpha, and interferon-gamma) using reverse transcriptase polymerase chain reaction and Western blot analysis. Cell viability was examined by the trypan blue exclusion test and light microscopy.


RESULTS
The HO-1 inducer hemin and DETA/NO increased HO-1 expression in A498 cells, and glutathione depletion further increased HO-1 expression in response to DETA/NO and hemin. Stimulation with a UPEC strain or cytokines did not upregulate HO-1 expression. The cytokines induced inducible NO synthase expression and caused an increase in nitrite production. Hemin significantly decreased cytokine-induced NO production (P <0.001). DETA/NO decreased the cell viability by approximately 75%, but hemin was able to attenuate DETA/NO-induced cell damage.


CONCLUSIONS
The expression of HO-1 increased in human renal epithelial cells in response to NO, and the expression was further enhanced in glutathione-depleted cells. The bacteria per se or proinflammatory cytokines were not able to upregulate HO-1. Heme oxygenase-1 protects the cells against NO by feedback inhibition of NO production and by decreasing cell damage.
Svensson
Lovisa
L
School of Pure and Applied Natural Science, University of Kalmar, Kalmar, Sweden.
Mohlin
Camilla
C
Persson
Katarina
K
D000704:Analysis of Variance; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D051547:Heme Oxygenase-1 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D006427:Hemin / Q000494:pharmacology; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D007668:Kidney / Q000166:cytology; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis / Q000378:metabolism*; D011336:Probability; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation; D014552:Urinary Tract Infections / Q000201:enzymology* / Q000517:prevention & control*
D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D006427:Hemin; D007371:Interferon-gamma; D051547:Heme Oxygenase-1