Involvement of MAPKs in ICAM-1 Expression in Glomerular Endothelial Cells in Diabetic Nephropathy

Inflammatory processes are involved in the pathogenesis of diabetic nephropathy. The aim of this study was to clarify the role of mitogen-activated protein kinase (MAPK) pathways for induction of intercellular adhesion molecule-1 (ICAM-1) expression in glomerular endothelial cells under diabetic conditions. We examined the expression of ICAM-1 in the kidneys of experimental diabetic rats. Human glomerular endothelial cells (GE cells) were exposed to normal glucose concentration, high glucose concentration (HG), or high mannitol concentration (HM), and then the expression of the ICAM-1 protein and the phosphorylation of the 3 subfamilies of mitogen-activated protein kinase (MAPK) were determined using Western blot analysis. Next, to evaluate the involvement of MAPKs in HG- or HM-induced ICAM-1 expression, we preincubated GE cells with the inhibitors for ERK, p38 or JNK 1h prior to the application of glucose or mannitol. Expression of ICAM-1 was increased in the glomeruli of diabetic rats. Both HG and HM induced ICAM-1 expression and phosphorylation of ERK1/2, p38 and JNK in GE cells. Expression of ICAM-1 was significantly attenuated by inhibitors of ERK, p38 and JNK. We conclude that activation of ERK1/2, p38 and JNK cascades may be involved in ICAM-1 expression in glomerular endothelial cells under diabetic conditions

Nuclear Hormone Receptor Expression in Mouse Kidney and Renal Cell Lines

Nuclear hormone receptors (NHRs) are transcription factors that regulate carbohydrate and lipid metabolism, immune responses, and inflammation. Although several NHRs, including peroxisome proliferator-activated receptor-γ (PPARγ) and PPARα, demonstrate a renoprotective effect in the context of diabetic nephropathy (DN), the expression and role of other NHRs in the kidney are still unrecognized. To investigate potential roles of NHRs in the biology of the kidney, we used quantitative real-time polymerase chain reaction to profile the expression of all 49 members of the mouse NHR superfamily in mouse kidney tissue (C57BL/6 and db/m), and cell lines of mesangial (MES13), podocyte (MPC), proximal tubular epithelial (mProx24) and collecting duct (mIMCD3) origins in both normal and high-glucose conditions. In C57BL/6 mouse kidney cells, hepatocyte nuclear factor 4α, chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) and COUP-TFIII were highly expressed. During hyperglycemia, the expression of the NHR 4A subgroup including neuron-derived clone 77 (Nur77), nuclear receptor-related factor 1, and neuron-derived orphan receptor 1 significantly increased in diabetic C57BL/6 and db/db mice. In renal cell lines, PPARδ was highly expressed in mesangial and proximal tubular epithelial cells, while COUP-TFs were highly expressed in podocytes, proximal tubular epithelial cells, and collecting duct cells. High-glucose conditions increased the expression of Nur77 in mesangial and collecting duct cells, and liver x receptor α in podocytes. These data demonstrate NHR expression in mouse kidney cells and cultured renal cell lines and suggest potential therapeutic targets in the kidney for the treatment of DN

The Macrophage Is a Key Factor in Renal Injuries Caused by Glomerular Hyperfiltration

Glomerular hyperfiltration is a common pathway leading to glomerulosclerosis in various kinds of kidney diseases. The 5/6 renal ablation is an established experimental animal model for glomerular hyperfiltration. On the other hand, low-grade inflammation is also a common mechanism for the progression of kidney diseases including diabetic nephropathy and atherosclerosis. Here we analyzed the gene expression profile in the remnant kidney tissues of 5/6 nephrectomized mice using a DNA microarray system and compared it with that of sham-operated control mice. The 5/6 nephrectomized mice showed glomerular hypertrophy and an increase in the extracellular matrix in the glomeruli. DNA microarray analysis indicated the up-regulated expression of various kinds of genes related to the inflammatory process in remnant kidneys. We confirmed the up-regulated expression of platelet factor-4, and monocyte chemoattractant protein-1, 2, and 5 in remnant kidneys by RT-PCR. The current results suggest that the inflammatory process is involved in the progression of glomerulosclerosis and is a common pathway of the pathogenesis of kidney disease