Bradykinin reduces growth factor-induced glomerular ERK1/2 phosphorylation

Abstract

Several experimental data report both mitogenic and antimitogenic effects of bradykinin (BK). To conciliate these apparent opposite effects, we hypothesized that, depending on cell context activation, BK could reduce the mitogenic effect of growth factors. Therefore, in the present study we assessed the existence of possible negative cross talk between BK and potential pathogenic growth factors in freshly isolated rat glomeruli (IG). Next, we determined whether this cross talk could be pharmacologically recruited during angiotensin-converting enzyme (ACE) inhibition in the diabetic rat. In IG from normal rats, BK, via activation of the B2 kinin receptor (B2R), causes a transient stimulation of ERK1/2 phosphorylation, whereas it inhibits ERK1/2 phosphorylation induced by IGF-1, PDGF-BB, VEGF, or basic FGF. The reduction of growth factor-induced ERK1/2 phosphorylation is abolished by an inhibitor of tyrosine phosphatase. In glomeruli from diabetic rats, hyperglycemia increased the phosphorylation level of ERK-1/2 as well as oxidative stress. The reversal of these events by ACE inhibition is mediated via B2R activation. These observations are consistent with a potential therapeutic role of BK and B2R during glomerulosclerosis.

ACE inhibitor reduces growth factor receptor expression and signaling but also albuminuria through B2-kinin glomerular receptor activation in diabetic rats

“…The rats were anesthetized intraperitoneally with 65 mg/kg pentobarbital sodium (Sanofi, Montpellier, France). After complete exsanguination, the kidneys were quickly removed and the glomeruli were isolated as routinely performed in the laboratory by graded sieving (3). Briefly, the cortex was forced through three consecutive steel sieves with decreasing mesh sizes (180, 125, and 75 m) to harvest ϳ12,000 glomeruli/kidney.…”

“…Equal amounts of proteins (25 g) were separated by SDS-PAGE in Tris-glycine buffer under a 150-V, 30-mA current in a Bio-Rad miniature transfer gel apparatus (Mini-Protean, Bio-Rad Laboratories, Richmond, CA) on a 10% SDS-polyacrylamide gel as routinely performed in the laboratory and recently described (3). Proteins were then transferred to a nitrocellulose membrane (Amersham, Orsay, France) in Tris-glycine-methanol buffer under a 100-V, 300-mA current in a Bio-Rad miniature transfer gel apparatus (Mini-Protean, Bio-Rad Laboratories).…”

Bradykinine et néphroprotection

“…Par ailleurs, la BK est capable de réduire l'auto-phosphorylation du récepteur de l'EGF sur la cellule mésangiale [23]. Nous avons montré, chez le rat diabétique, que l'expression des récepteurs glomérulaires de certaines cytokines (IGF-1, insulin-like growth factor -1, TGF-β, transforming growth factor) est augmentée lors du blocage du RB2 [28]. Ces travaux sont par ailleurs en accord avec une observation récente indiquant que la surexpression du récepteur du TGF-β est augmentée chez les souris n'exprimant plus le RB2 [29].…”

“…Inversement, une aggravation du profil du stress oxydant a été décrite chez les souris n'exprimant pas le RB2 [29]. Enfin, chez le rat diabétique, notre groupe a décrit une augmentation de l'accumulation de protéines complexées à des dérivés 4-HNE (index de la peroxidation lipidique) lors du blocage du RB2 [28]. L'activation du RB2 pourrait donc contrôler en partie le stress oxydant, vraisemblablement par la production tonique de NO.…”

“…Bien que l'idée qu'une stimulation du RB2 de la BK puisse induire des effets thérapeutiques bénéfiques reste encore novatrice, ce concept émerge finalements des travaux de plusieurs groupes indépendants [28,29,[32][33][34]. Plusieurs agonistes non peptidiques sont disponibles et ont été testés dans des modèles différents [38][39][40].…”