Dessapt Cecile, Baradez Marc Olivier, Hayward Anthea, Dei Cas Alessandra, Thomas Stephen M, Viberti Giancarlo, Gnudi Luigi
King's College London, UK.
Nephrol Dial Transplant. 2009 Sep;24(9):2645-55. doi: 10.1093/ndt/gfp204. Epub 2009 May 6.
Podocyturia is a marker of diabetic nephr- opathy, a possible determinant of its progression and a powerful risk factor for cardiovascular disease. A reduction in podocyte adhesion to the glomerular basement membrane (GBM) via downregulation of alpha3beta1 integrin expression, the main podocyte anchoring dimer to the GBM, may represent one of the mechanisms of podocyturia in glomerular disease. This study investigated the role of mechanical forces and transforming growth factor beta1 (TGFbeta1) in podocyte adhesion and integrin expression.
Conditionally immortalized murine podocytes were exposed to mechanical stretch and/or TGFbeta1 for 48 h. Podocyte adhesion, apoptosis and alpha3beta1 integrin expression were assessed.
Stretch and TGFbeta1 significantly reduced podocyte adhesion and alpha3beta1 integrin expression, events paralleled by increased apoptosis. Blockade of beta1 integrin, with a specific antibody, demonstrated a reduced podocyte adhesion indicating that beta1 integrin downregulation was required for the loss of podocyte adhesion. This was linked to an increase in podocyte apoptosis. The role of apoptosis in podocyte adhesion was further investigated using caspase-3 inhibitors. Podocyte apoptosis inhibition did not affect stretch- and TGFbeta1-mediated integrin downregulation and the loss of podocyte adhesion, suggesting that alpha3beta1 integrin downregulation is sufficient to alter cell adhesion. Although stretch significantly increased podocyte TGFbeta type I, II and III receptors but not podocyte TGFbeta1 secretion, the combination of stretch and TGFbeta1 did not show any additive or synergistic effects on podocyte adhesion and alpha3beta1 integrin expression.
These results suggest that downregulation of alpha3beta1 integrin expression, by mechanical forces or TGFbeta1, is per se sufficient to reduce podocyte adhesion. Apoptosis may represent a parallel important determinant of the podocyte loss from the GBM.
足细胞尿是糖尿病肾病的一个标志物，可能是其病情进展的一个决定因素，也是心血管疾病的一个强大危险因素。通过下调α3β1整合素表达（足细胞锚定到肾小球基底膜（GBM）的主要二聚体）来降低足细胞与GBM的黏附，可能是肾小球疾病中足细胞尿的机制之一。本研究调查了机械力和转化生长因子β1（TGFβ1）在足细胞黏附和整合素表达中的作用。
将条件永生化小鼠足细胞暴露于机械拉伸和/或TGFβ1 48小时。评估足细胞黏附、凋亡和α3β1整合素表达。
拉伸和TGFβ1显著降低足细胞黏附和α3β1整合素表达，这些事件伴随着凋亡增加。用特异性抗体阻断β1整合素，显示足细胞黏附减少，表明β1整合素下调是足细胞黏附丧失所必需的。这与足细胞凋亡增加有关。使用半胱天冬酶-3抑制剂进一步研究凋亡在足细胞黏附中的作用。抑制足细胞凋亡并不影响拉伸和TGFβ1介导的整合素下调以及足细胞黏附丧失，表明α3β1整合素下调足以改变细胞黏附。虽然拉伸显著增加足细胞TGFβⅠ型、Ⅱ型和Ⅲ型受体，但不增加足细胞TGFβ1分泌，拉伸和TGFβ1的组合对足细胞黏附和α3β1整合素表达未显示任何相加或协同作用。
这些结果表明，机械力或TGFβ1导致的α3β1整合素表达下调本身足以降低足细胞黏附。凋亡可能是足细胞从GBM丢失的一个平行重要决定因素。
