Protective effects of GPR120 agonist-programmed macrophages on renal interstitial fibrosis in unilateral ureteral obstruction (UUO) rats.

Macrophages in the kidney play different roles in renal interstitial fibrosis (RIF) depending on their phenotypes. M2 phenotype macrophages are believed to protect the kidney against RIF. Free fatty acid receptor GPR120 is expressed in macrophages, and its activation induces macrophage transition to M2 phenotype. In this study, the effects of GPR120 agonist-programmed macrophages on RIF were investigated. The peritoneal macrophages collected from rats were incubated with GPR120 agonist TUG891 in vitro for 24 h, and then they were transplanted autologously to the kidney with ureteral obstruction by intrarenal injection for 7 days on the same day following unilateral ureteral obstruction (UUO) operation. RIF was identified by Masson trichrome histological staining, and the expression of RIF-related proteins was analyzed by immunohistochemistry and western blot. It was observed that TUG891-programmed macrophages up-regulated the expression of CD206 and arginase-1 while the expression of interleukin-6 and tumor necrosis factor-α were down-regulated. RIF in rats was significantly increased following UUO, which was markedly alleviated by TUG891-programmed macrophages but not untreated macrophages. TUG891-programmed macrophages inhibited the abnormal expression of TGF-ß1 and SMAD2. The abnormal expression of epithelial-mesenchymal transition (EMT)-related proteins including vimentin, α-SMA and ß-catenin was also significantly decreased in rats with transplantation of TUG891-programmed macrophages as compared to UUO rats. This study suggests that autologous administration of peritoneal macrophages programmed in vitro by GPR120 agonist to kidney has a protective effect against RIF following UUO.

Epithelial C5aR1 Signaling Enhances Uropathogenic Escherichia coli Adhesion to Human Renal Tubular Epithelial Cells.

Recent work in a murine model of ascending urinary tract infection has suggested that C5a/C5aR1 interactions play a pathogenic role in the development of renal infection through enhancement of bacterial adhesion/colonization to renal tubular epithelial cells (RTECs). In the present study, we extended these observations to human. We show that renal tubular epithelial C5aR1 signaling is involved in promoting uropathogenic Escherichia coli (UPEC) adhesion/invasion of host cells. Stimulation of primary cultures of RTEC with C5a resulted in significant increases in UPEC adhesion/invasion of the RTEC. This was associated with enhanced expression of terminal α-mannosyl residues (Man) (a ligand for type 1 fimbriae of E. coli) in the RTEC following C5a stimulation. Mechanism studies revealed that C5aR1-mediated activation of ERK1/2/NF-κB and upregulation of proinflammatory cytokine production (i.e., TNF-α) is at least partly responsible for the upregulation of Man expression and bacterial adhesion. Clinical sample studies showed that C5aR1 and Man were clearly detected in the renal tubular epithelium of normal human kidney biopsies, and UPEC bound to the epithelium in a d-mannose-dependent manner. Additionally, C5a levels were significantly increased in urine of urinary tract infection patients compared with healthy controls. Our data therefore demonstrate that, in agreement with observations in mice, human renal tubular epithelial C5aR1 signaling can upregulate Man expression in RTEC, which enhances UPEC adhesion to and invasion of RTEC. It also suggests the in vivo relevance of upregulation of Man expression in renal tubular epithelium by C5a/C5aR1 interactions and its potential impact on renal infection.

C5aR1 promotes acute pyelonephritis induced by uropathogenic E. coli.

C5a receptor 1 (C5aR1) is a G protein-coupled receptor for C5a and also an N-linked glycosylated protein. In addition to myeloid cells, C5aR1 is expressed on epithelial cells. In this study, we examined the role of C5aR1 in bacterial adhesion/colonization of renal tubular epithelium and addressed the underlying mechanisms of this role. We show that acute kidney infection was significantly reduced in mice with genetic deletion or through pharmacologic inhibition of C5aR1 following bladder inoculation with uropathogenic E. coli (UPEC). This was associated with reduced expression of terminal α-mannosyl residues (Man; a ligand for type 1 fimbriae of E. coli) on the luminal surface of renal tubular epithelium and reduction of early UPEC colonization in these mice. Confocal microscopy demonstrated that UPEC bind to Man on the luminal surface of renal tubular epithelium. In vitro analyses showed that C5a stimulation enhances Man expression in renal tubular epithelial cells and subsequent bacterial adhesion, which, at least in part, is dependent on TNF-α driven by C5aR1-mediated intracellular signaling. Our findings demonstrate a previously unknown pathogenic role for C5aR1 in acute pyelonephritis, proposing a potentially novel mechanism by which C5a/C5aR1 signaling mediates upregulation of carbohydrate ligands on renal tubules to facilitate UPEC adhesion.

Premature senescence and cellular phenotype transformation of mesangial cells induced by TGF-B1.

BACKGROUND: Transforming growth factor-ß1 (TGF-ß1) is a polypeptide member of the transforming growth factor ß superfamily of cytokines and performs many cellular functions. Its overexpression may lead to renal fibrosis. AIM: This study planed to investigate the effects of TGF-ß1 on the cell cycle and phenotype of mesangial cells. METHODS: Rat mesangial cells were cultured together with different concentrations (0, 1, 2, 5, and 10 ng/mL) of TGF-ß1 for specified times from 0 min to 72 h. 0 ng/mL TGF-ß1 and 0 min served as controls. Cell cycles were assessed by flow cytometry and α-smooth muscle actin expression (α-SMA) protein expression by western blot analysis. All data were presented as Mean ± SD. Statistical analysis was performed by using one-way analysis of variance and correlation analysis. Results were considered significant at p < 0.05. RESULTS: After 15 min of co-culture with different concentrations of TGF-ß1, the percentage of mesangial cells in G0/G1 phase was significantly elevated compared to the control (p < 0.05). 12 h co-culture induced cell hyperplasia, 24 h co-culture obvious up-regulation of α-SMA (p < 0.01) and one or two cells' myofibroblast phenotype transition, and 36 h co-culture several cells' phenotype transition. Correlation analysis prompted that the TGF-ß1-induced premature aging was time-dependent (p < 0.01). CONCLUSION: TGF-ß1 may induce mesangial cells' premature senescence and myofibroblast-like phenotype transformation time-dependently, which may contribute to the development of early stage of glomerulosclerosis.

Uremic anorexia and ghrelin expression in the amygdala.

BACKGROUND/AIMS: Ghrelin can act as a signal for mealtime hunger and meal initiation. Amygdala is indispensable in appetitive behavior motivated by learned emotions. This study was to investigate the alteration of ghrelin in the amygdala of rats with chronic renal failure (CRF) and its relation with uremic anorexia. METHODS: SD rats were randomly classified into CRF group and control group (n=16 per group). The CRF model was constructed using 5/6 nephrectomy. When plasma creatinine (PCr) and blood urea nitrogen (BUN) in the CRF group were twice more than the normal level, food intake (g/24h) was measured and then all rats were killed for detection of ghrelin protein expression in the amygdala using immunohistochemical analysis and mRNA expression using RT-PCT. Statistics was conducted with one-way analysis of variance, Student-Newman-Keuls-q test and correlation analysis. RESULTS: By the 8th week after the surgery, the BUN and PCr of CRF rats exceeded double the normal level, and their food intake was obviously decreased compared with the controls (P<0.05). The protein and mRNA expression of ghrelin in the amygdala of CRF group were significantly reduced, and there was a positive correlation between this reduction and the decrease in food intake (P<0.05). CONCLUSION: The reduction of amygdala's ghrelin in CRF rats may be associated with uremic anorexia.