The involvement of chemokines in inflammation is well established, but their functional role in disease progression, and particularly in the development of fibrosis, is not yet understood. To investigate the functional role that the chemokines monocyte chemoattractant protein–1 (MCP-1) and RANTES play in inflammation and the progression to fibrosis during crescentic nephritis we have developed and characterized a murine model for this syndrome. Significant increases in T-lymphocytes and macrophages were observed within glomeruli and interstitium, paralleled by an induction of mRNA expression of MCP-1 and RANTES, early after disease initiation. Blocking the function of MCP-1 or RANTES resulted in significant decreases in proteinuria as well as in numbers of infiltrating leukocytes, indicating that both MCP-1 and RANTES (regulated upon activation in normal T cells expressed and secreted) play an important role in the inflammatory phase of crescentic nephritis. In addition, neutralization of MCP-1 resulted in a dramatic decrease in both glomerular crescent formation and deposition of type I collagen. These results highlight a novel role for MCP-1 in crescent formation and development of interstitial fibrosis, and indicate that in addition to recruiting inflammatory cells this chemokine is critically involved in irreversible tissue damage.

Intrinsic glomerular cells in a diabetic milieu have transcriptional activation of genes that influence the development of diabetic nephropathy. The cellular repertoire of microRNAs can regulate translation of these expressed genes into proteins. Fibronectin is a key matrix protein accumulated in excess in diabetic nephropathy. Here, we exposed cultured human and mouse mesangial cells to high glucose and transforming growth factor-beta to simulate the diabetic milieu. In these conditions in vitro, as well as in mouse diabetic nephropathy models in vivo, microRNA-377 was consistently up-regulated relative to controls. Through a combination of computational and biological approaches, we identified relevant miR-377 target genes. Although fibronectin was induced by miR-377, it was not a direct target of miR-377. However, miR-377 led to reduced expressions of p21-activated kinase and superoxide dismutase, which enhanced fibronectin protein production. Thus, overexpression of miR-377 in diabetic nephropathy indirectly leads to increased fibronectin protein production; as such, miR-377 can have a critical role in the pathophysiology of this prevalent human disease.

1,25-Dihydroxyvitamin D3 negatively regulates the renin-angiotensin system (RAS), which plays a critical role in the development of diabetic nephropathy. We tested if mice lacking the vitamin D receptor (VDR) are more susceptible to hyperglycemia-induced renal injury. Diabetic VDR knockout mice developed more severe albuminuria and glomerulosclerosis due to increased glomerular basement membrane thickening and podocyte effacement. More fibronectin (FN) and less nephrin were expressed in the VDR knockout mice compared to diabetic wild-type mice. In receptor knockout mice, increased renin, angiotensinogen, transforming growth factor-beta (TGF-beta), and connective tissue growth factor accompanied the more severe renal injury. 1,25-Dihydroxyvitmain D3 inhibited high glucose (HG)-induced FN production in cultured mesangial cells and increased nephrin expression in cultured podocytes. 1,25-Dihydroxyvitmain D3 also suppressed HG-induced activation of the RAS and TGF-beta in mesangial and juxtaglomerular cells. Our study suggests that receptor-mediated vitamin D actions are renoprotective in diabetic nephropathy.

Abstract. In previous work, it was demonstrated that apoptosis occurs in the kidney during LPS-induced acute renal failure (ARF). However, the relative importance of apoptosis in LPSinduced ARF remained unproven. Because the caspase enzyme cascade is responsible for carrying out apoptosis, it was hypothesized that treatment with a caspase inhibitor would protect mice from LPS-induced ARF. C57BL/6 mice received an injection of LPS and were treated with either the broad-spectrum caspase inhibitor z-VAD-fmk or vehicle and compared with unmanipulated mice. LPS induced a significant increase in caspase-3 activity in vehicle-treated mice, which was significantly inhibited by z-VAD. Mice that were treated with z-VAD were protected from ARF and demonstrated significantly less apoptosis as measured by both terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining and DNA laddering.