Insulin-like growth factor binding protein-3 mediates cytokine-induced mesangial cell apoptosis

Quantified by DNA fragmentation ELISA and Annexin V flow cytometry, apoptosis occurred in rat mesangial cells (RMC) exposed to 2 μg/mL IGFBP-3 for 24 h under high ambient or standard glucose. Anti-sense IGFBP-3 oligo at 10 μg/mL significantly inhibited apoptosis induced by 100 ng/mL TNF-α, serum-free conditions, or high (25 mM) glucose. Increased IGFBP-3 release associated with high ambient glucose or TNF-α was inhibited by pre-treatment with anti-sense oligo. Under serum-free conditions, recombinant human IGFBP-3 blocked Akt phosphorylation at threonine 308 (pThr308), whereas anti-sense oligo treatment was associated with enhanced pThr308 activity. In summary, these data support a novel mechanism for TNF-α-induced mesangial cell apoptosis mediated by IGFBP-3 and present regulation of pThr308 activity as a novel mechanism underlying IGFBP-3 action.