Ganglioside GM3 inhibits the high glucose- and TGF-β1-induced proliferation of rat glomerular mesangial cells

Abrupt proliferation of glomerular mesangial cells (GMCs) is a common feature in the early stage of diabetic glomerulopathy, and ganglioside GM3 (NeuAcα3Galβ4Glcβ1Cer) is thought to regulate the proliferation of many cell types. Recently, we have reported ganglioside GM3 as a modulator of glomerular hypertrophy in streptozotocin-induced diabetic rats [Kwak, D.H., Rho, Y.I., kwon, O.D., Ahn, S.H., Song, J.H., Choo, Y.K., Kim, S.J., Choi, B.K., Jung, K.Y., 2003. Decreases of ganglioside GM3 in streptozotocin-induced diabetic glomeruli of rats. Life Sciences 72, 1997-2006]. This study examined whether modulation of cellular ganglioside GM3 could regulate the high glucose- and transforming growth factor-β1 (TGF-β1)-induced proliferation of GMCs. To pharmacologically modulate the cellular ganglioside GM3, GMCs originated from rat kidneys were cultured with exogenous ganglioside GM3 or d-threo-PDMP, an inhibitor of ganglioside synthesis, in the RPMI 1640 media containing normal (5.6 mM, NG) or high (25 mM, HG) glucose. HG, TGF-β1 (10 ng/ml) and d-threo-PDMP (20 μM) significantly stimulated the mesangial cell proliferation, whereas these increments were remarkable attenuated by exogenous ganglioside mixture (0.1–0.2 mg/ml) or GM3 (20–100 μM) in a dose-dependent manner. The mesangial cell proliferation caused by HG, TGF-β1 and d-threo-PDMP was closely correlated with decreases in both cellular sialic acid contents and ganglioside GM3 synthase activity. Based upon the mobility on high-performance thin-layer chromatography (HPTLC), GMCs showed a complex pattern of ganglioside expression that consisted, at least, of five different components of gangliosides, mainly ganglioside GM3. HG, TGF-β1 and d-threo-PDMP induced a significant reduction of ganglioside expression with apparent changes in the composition of ganglioside GM3, and semi-quantitative analysis by HPTLC showed that ganglioside GM3 expression reduced to about 35–54% of control. These results provide a pathophysiological link between mesangial cell proliferation and ganglioside GM3 expression, indicating that exogenously added ganglioside GM3 inhibits the high-ambient glucose- and TGF-β1-induced proliferation of cultured GMCs.