Galectin-9 Inhibits Glomerular Hypertrophy in db/db Diabetic Mice via Cell-Cycle–Dependent Mechanisms

Galectins are β-galactoside–binding lectins that are involved in various biologic processes, such as apoptosis, cell proliferation, and cell-cycle regulation. Galectin-9 (Gal-9) was identified previously and demonstrated to have apoptotic potential to thymocytes in mice and activated CD8 + T cells in nephrotoxic serum nephritis model. In this study, the effect of Gal-9 on G1-phase cell-cycle arrest, one of the hallmark pathologic changes in early diabetic nephropathy, was investigated. Eight-week-old male db/db mice received injections of recombinant Gal-9 or vehicle for 8 wk. The injection of Gal-9 into db/db mice significantly inhibited glomerular hypertrophy and mesangial matrix expansion and reduced urinary albumin excretion. Gal-9 reduced glomerular expression of TGF-β1 and the number of p27 Kip1 - and p21 Cip1 -positive cells in glomeruli. Double staining with nephrin and type IV collagen revealed that podocytes were mainly positive for p27 Kip1 . For further confirming the cell-cycle regulation by Gal-9, conditionally immortalized mouse podocyte cells were cultured under 5.5 and 25 mM d-glucose supplemented with Gal-9. Cell-cycle distribution analyses revealed that Gal-9 maintained further progression of cell cycle from the G1 phase. Gal-9 reversed the high-glucose–mediated upregulation of p27 Kip1 and p21 Cip1 and inhibited cell-cycle–dependent hypertrophy, i.e. , reduced [ 3 H]proline incorporation. The data suggest that Gal-9 plays a central role in inducing their successful progression from G1 to G2 phase by suppressing glomerular expression of TGF-β1 and inhibition of cyclin-dependent kinase inhibitors. Gal-9 may give an impetus to develop new therapeutic tools targeted toward diabetic nephropathy.