Hypoxia increases group IIA phospholipase A(2) expression under inflammatory conditions in rat renal mesangial cells.
Hypoxia evokes a common mechanism of oxygen sensing mediated by hypoxia-inducible transcription factors (HIF) in many mammalian cells. This study investigated the effect of hypoxia on group-IIA secretory phospholipase A(2) (sPLA(2)-IIA) expression in renal mesangial cells. Stimulation of cells with IL-1beta under normoxic conditions (21% O(2)) is known to induce expression and secretion of the group sPLA(2)-IIA. This induction is further enhanced by constantly reducing the O(2) concentration to 1% O(2), and is accompanied by increased sPLA(2) activity. To see whether hypoxia potentiates IL-1beta-induced sPLA(2)-IIA gene expression, a 2.67-kb fragment of the rat sPLA(2)-IIA promoter was fused to a luciferase reporter construct and used to transfect mesangial cells. Hypoxia alone is not able to activate the sPLA(2) promoter, whereas it significantly enhances IL-1beta-stimulated promoter activity. A deletion mutant of the promoter that lacks the two putative hypoxia responsive elements (HRE) is devoid of the potentiating effect of hypoxia. Moreover, site-directed mutagenesis of either of the two HRE is sufficient to abolish the potentiating effect of hypoxia. Electrophoretic mobility shift assays show that HIF-2alpha, which is the only HIF subtype expressed in mesangial cells, binds to both HRE in the sPLA(2)-IIA promoter. In summary, the data show that in an inflammatory setting hypoxia is able to potentiate sPLA(2)-IIA expression and activity in renal mesangial cells, and thereby may critically contribute to enhanced formation of inflammatory lipid mediators seen in a diverse range of kidney diseases.
Petry
Claudia
C
Pharmazentrum Frankfurt, Klinikum der Johann Wolfgang Goethe-Universität, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany.
Huwiler
Andrea
A
Eberhardt
Wolfgang
W
Kaszkin
Marietta
M
Pfeilschifter
Josef
J
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D015687:Cell Hypoxia; D002478:Cells, Cultured; D054501:Group II Phospholipases A2; D007249:Inflammation / Q000378:metabolism; D050527:Mesangial Cells / Q000378:metabolism*; D010741:Phospholipases A / Q000096:biosynthesis* / Q000378:metabolism; D051381:Rats; D014157:Transcription Factors / Q000502:physiology; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D054501:Group II Phospholipases A2; D010741:Phospholipases A; D014157:Transcription Factors; D000099162:Endothelial PAS Domain-Containing Protein 1