Bradykinin reduces growth factor-induced glomerular ERK1/2 phosphorylation

Area of Science:

• Nephrology
• Endocrinology
• Molecular Biology

Background:

• Bradykinin (BK) has demonstrated both mitogenic and antimitogenic effects.
• The interaction between BK and growth factors in glomerular cells requires further elucidation.
• Understanding these interactions may reveal therapeutic targets for kidney diseases.

Purpose of the Study:

• To investigate the negative cross-talk between BK and mitogenic growth factors in rat glomeruli.
• To determine if angiotensin-converting enzyme (ACE) inhibition can pharmacologically recruit this cross-talk in diabetic rats.
• To explore the role of BK and its B(2) receptor (B(2)R) in diabetic glomerulosclerosis.

Main Methods:

• Isolated rat glomeruli (IG) were used to assess ERK1/2 phosphorylation.
• BK, growth factors (IGF-1, PDGF-BB, VEGF, bFGF), B(2)R antagonist, and tyrosine phosphatase inhibitor were applied.
• Diabetic rat models were used to evaluate the effects of ACE inhibition.

Main Results:

• In normal glomeruli, BK transiently stimulated ERK1/2 phosphorylation but inhibited growth factor-induced phosphorylation.
• This inhibitory effect was dependent on tyrosine phosphatase activity.
• In diabetic glomeruli, hyperglycemia increased ERK1/2 phosphorylation and oxidative stress, which was reversed by ACE inhibition via B(2)R activation.

Conclusions:

• BK, through B(2)R activation, can inhibit growth factor signaling in glomeruli.
• ACE inhibition leverages this BK-mediated pathway to counteract hyperglycemia-induced damage in diabetic nephropathy.
• These findings support a potential therapeutic role for BK and B(2)R activation in managing glomerulosclerosis.