Accumulation of mesangial matrix is a pivotal event in the pathophysiology of diabetic nephropathy. The molecular triggers for matrix production are still being defined. Here, suppression subtractive hybridization identified 15 genes differentially induced when primary human mesangial cells are exposed to high glucose (30 mM versus 5 mM) in vitro. These genes included (a) known regulators of mesangial cell activation in diabetic nephropathy (fibronectin, caldesmon, thrombospondin, and plasminogen activator inhibitor-1), (b) novel genes, and (c) known genes whose induction by high glucose has not been reported. Prominent among the latter were genes encoding cytoskeleton-associated proteins and connective tissue growth factor (CTGF), a modulator of fibroblast matrix production. In parallel experiments, elevated CTGF mRNA levels were demonstrated in glomeruli of rats with streptozotocin-induced diabetic nephropathy. Mannitol provoked less mesangial cell CTGF expression in vitro than high glucose, excluding hyperosmolality as the key stimulus. The addition of recombinant CTGF to cultured mesangial cells enhanced expression of extracellular matrix proteins. High glucose stimulated expression of transforming growth factor ␤1 (TGF-␤1), and addition of TGF-␤1 to mesangial cells triggered CTGF expression. CTGF expression induced by high glucose was partially suppressed by anti-TGF-␤1 antibody and by the protein kinase C inhibitor GF 109203X. Together, these data suggest that 1) high glucose stimulates mesangial CTGF expression by TGF␤1-dependent and protein kinase C dependent pathways, and 2) CTGF may be a mediator of TGF␤1-driven matrix production within a diabetic milieu.

The presence of Desulfovibrio subspecies is increased in ulcerative colitis and the data presented suggest that these bacteria represent an increased percentage of the colonic microbiome in acute ulcerative colitis.

Connective tissue growth factor (CTGF) is a member of an emerging family of immediate-early gene products that coordinate complex biological processes during differentiation and tissue repair. Here we describe the role of CTGF in integrin-mediated adhesive signaling and the production of extracellular matrix components in human mesangial cells. The addition of CTGF to primary mesangial cells induced fibronectin production, cell migration, and cytoskeletal rearrangement. These functional responses were associated with recruitment of Src and phosphorylation of p42/44 MAPK and protein kinase B. The inhibition of CTGF-induced p42/44 MAPK or phosphatidylinositol 3-kinase (PI3K)/protein kinase B pathway activities abrogated the induction of fibronectin expression. In addition, anti-␤ 3 integrin antibodies attenuated the activation of both the p42/44 MAPK and protein kinase B and the increase in fibronectin levels. CTGF also induced mesangial cell migration via a ␤ 3 integrin-dependent mechanism that was similarly sensitive to the inhibition of the p42/44 MAPK and PI3K pathways, and it promoted the adhesion of the mesangial cells to type I collagen via up-regulation of ␣ 1 integrin. Transient actin cytoskeletal disassembly was observed following treatment with the ligand over the course of a 24-h period. CTGF induced the loss of focal adhesions from the mesangial cell as evidenced by the loss of punctate vinculin. However, these processes are p42/44 MAPK and PI3K pathway-independent. Our data support the hypothesis that CTGF mediates a number of its biological effects by the induction of signaling processes via ␤ 3 integrin. However, others such as actin cytoskeleton disassembly are modulated in a ␤ 3 integrin/MAPK/PI3K-independent manner, indicating that CTGF is a complex pleiotropic factor with the potential to amplify primary pathophysiological responses.

Lipoxins, which are endogenously produced lipid mediators, promote the resolution of inflammation, and may inhibit fibrosis, suggesting a possible role in modulating renal disease. Here, lipoxin A4 (LXA 4 ) attenuated TGF-b1-induced expression of fibronectin, N-cadherin, thrombospondin, and the notch ligand jagged-1 in cultured human proximal tubular epithelial (HK-2) cells through a mechanism involving upregulation of the microRNA let-7c. Conversely, TGF-b1 suppressed expression of let-7c. In cells pretreated with LXA 4 , upregulation of let-7c persisted despite subsequent stimulation with TGF-b1. In the unilateral ureteral obstruction model of renal fibrosis, let-7c upregulation was induced by administering an LXA 4 analog. Bioinformatic analysis suggested that targets of let-7c include several members of the TGF-b1 signaling pathway, including the TGF-b receptor type 1. Consistent with this, LXA 4 -induced upregulation of let-7c inhibited both the expression of TGF-b receptor type 1 and the response to TGF-b1. Overexpression of let-7c mimicked the antifibrotic effects of LXA 4 in renal epithelia; conversely, anti-miR directed against let-7c attenuated the effects of LXA 4 . Finally, we observed that several let-7c target genes were upregulated in fibrotic human renal biopsies compared with controls. In conclusion, these results suggest that LXA 4 -mediated upregulation of let-7c suppresses TGF-b1-induced fibrosis and that expression of let7c targets is dysregulated in human renal fibrosis.

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