High glucose stimulates cell proliferation and Collagen IV production in rat mesangial cells through inhibiting AMPK-K signaling.

PURPOSE

The present study investigated the putative mechanisms underlying effects of K channel on high glucose (HG)-induced mesangial cell proliferation and tissue inhibitors of metalloproteinases (TIMP)-2 and Collagen IV production.

METHODS

Rat mesangial cells were subjected to whole cell patch clamp to record the K channel currents under high glucose (HG, 30 mM) condition. Cell proliferation was measured using a CCK-8 assay. The production of TIMP-2 and Collagen IV and AMP-activated protein kinase (AMPK)-signaling pathway activity was assessed by ELISA and Western blotting, respectively. AMPK agonist (AICAR) was used to analyze the role of this kinase. The expression of K subunit (Kir6.1, Kir6.2, SUR1, SUR2A and SUR2B) was examined using quantitative real-time PCR (RT-PCR).

RESULTS

We found that HG was significant decreases in the expression of Kir6.1, SUB2A and SUB2B, three subunits of K, TIMP-2 production, K channel activity and AMPK activity, while it promoted the cell proliferation and Collagen IV production in rat mesangial cells. Pretreatment with K selective opener (diazoxide, DZX) significantly inhibited HG-induced mesangial cell proliferation, Collagen IV production and decrease in K channel activity in rat mesangial cells, which were reversed by pretreatment of 5-hydroxydecanoate, a selective inhibitor of K. Moreover, AICAR pretreatment inhibited HG-induced decrease in K channel activity.

CONCLUSIONS

Taken together, activating AMPK-K signaling may protect against HG-induced mesangial cell proliferation and Collagen IV production, and, thereby, provides new insights into the molecular mechanisms underlying early diabetic nephropathy (DN).