Association Between IFN-γ Gene Polymorphisms and IgA Nephropathy in a Chinese Han Population.

BACKGROUND/AIMS: IFN-γ was reported to be involved in the development and progression of Immunoglobulin A nephropathy (IgAN), however, few studies have investigated the association between IFN-γ polymorphisms and IgAN. Therefore, we performed a case-control study to assess the association between IFN-γ polymorphisms and the risk of IgAN. METHODS: Sequenom MassARRAY was used to genotype two SNPs (rs1861494 and rs2430561) in 351 patients with IgAN and 310 healthy controls. Associations were evaluated as odd ratios (OR) with 95% confidence intervals (CI). RESULTS: No association was found between IFN-γ rs1861494 and IgAN risk or clinical parameters. For rs2430561, the AA genotype was more common in patients with IgAN, compared with controls (AT vs. AA: OR = 0.57, P = 0.035). IFN-γ-rs2430561 T allele may be a protective factor for IgAN susceptibility (T vs. A: OR = 0.59, P = 0.04). Subgroup analysis based on clinical features revealed no significant association between rs2430561 polymorphism and clinical data such as gender, 24-h urine protein, blood pressure, Oxford classifcation and estimated glomerular fltration rate. IgAN patients had a higher IFN-γ serum level than healthy controls and patients with rs1861494 AA genotype had a higher IFN-γ serum level compared with those with AG/GG genotypes. CONCLUSIONS: IFN-γ polymorphisms may be involved in the development and progression of IgAN.

Therapeutic Effects of FK506 on IgA Nephropathy Rat.

BACKGROUND/AIMS: FK506 is an immunosuppressive drug and a calcineurin inhibitor that has been widely used in kidney disease in recent years. FK506 shows a wide range of biological and pharmaceutical effects; however, the mechanism of its anti- proliferative effect has not been well elucidated. An IgA nephropathy (IgAN) model was used to generate a mesangial cell proliferation model. This study aims to examine the effect of FK506 on IgAN rats and the underlying mechanisms. METHODS: Hematuria, proteinuria and renal function were measured. To observe the pathological conditions, we performed HE (hematoxylin - eosin) and PAS (periodic acid - schiff) staining. Transcription and protein expression levels were detected by qRT - PCR (quantitative real-time polymerase chain reaction) and Wb (western blotting). The location and semi-quantitative expression levels of TRPCs, CaN (Calcineurin) and α-SMA were examined by IHC (Immunohistochemical staining). RESULTS: We found that FK506 could improve hematuria, proteinuria and renal function, especially in the HF (high-dose FK506) groups. Renal pathological changes were ameliorated in the treatment groups. FK506 could significantly decrease TRPCs, CaN, phosphorylation of ERK1/2 and α-SMA expression. CONCLUSION: Taken together, these results suggest that the therapeutic effect of FK506 on IgAN might be partially associated with the down-regulated expression of TRPC channels, CaN and phosphorylation of ERK1/2.

TIPE2, a novel biomarker for clinical chronic kidney allograft rejection.

Tumor necrosis factor-a--induced protein 8-like 2 (TIPE2) has an essential role in immune homeostasis, yet the relationship between TIPE2 expression and allograft rejection has not been addressed. Dependent on clinical diagnosis, 96 kidney transplant recipients were divided into three groups, long-term survival group, acute rejection group (AR) and chronic rejection group (CR). Thirty-two healthy volunteers were used as a control group. The expression of TIPE2 in peripheral blood mononuclear cells (PBMC) and kidney biopsy samples was performed using reverse transcript-polymerase chain reaction, immunohistochemistry and immunofluorescence. The expression of TIPE2 in PBMC of CR group was significantly higher than that of the healthy control (P < 0.001), but TIPE2 expression in AR group was lower than that of control individuals (P < 0.05). The renal expression of TIPE2 in allograft tissue of CR was significantly lower and its expression in AR slightly lower than in normal kidneys. The positive correlation between TIPE2 expression in PBMCs and the CR of allo-kidney grafts indicates that detection of TIPE2 in the blood samples may be used as one of the diagnosis molecular markers in clinical monitoring kidney chronic rejection.

Uremic anorexia and gastrointestinal motility dysfunction correlate with the changes of ghrelin system in hypothalamus.

AIM: Ghrelin can act as a signal for meal initiation and play a role in the regulation of gastrointestinal (GI) motility via hypothalamic circuit. This study investigated the correlation between changes of hypothalamic ghrelin system and GI motility dysfunction and anorexia in rats with chronic renal failure (CRF). METHODS: Sprague-Dawley (SD) rats (male/female 1:1, 180 ± 20 g) were randomly classified into a CRF group and control group (n = 8 per group). 5/6 nephrectomy was used to construct the CRF model. When plasma creatinine concentration (PCr) and blood urea nitrogen (BUN) in the CRF group were twice higher than the normal, food intake (g/24 h) and gastrointestinal interdigestive myoelectric complex (IMC) were detected. Then all rats were killed for assessment of the mRNA expression of ghrelin and growth hormone secretagogue receptor (GHS-R) in hypothalamus using reverse transcription-polymerase chain reaction. Analysis of variance, Student-Newman-Keuls-q-test and Correlation Analysis were used to do statistical analysis. P < 0.05 was considered as statistically significant. RESULTS: Compared to the control group, the CRF group was obviously decreased in the food intake (g/24 h), the phase III duration and amplitude and the ghrelin and GHS-R expression in the hypothalamus (P < 0.05). There was a positive correlation between them (P < 0.05). CONCLUSION: Changes of ghrelin and GHS-R in the hypothalamus correlate with gastrointestinal motility dysfunction and anorexia in rats with CRF.

Chronic renal failure impacts the expression of ghrelin and its receptor in hypothalamus and hippocampus.

BACKGROUND/AIMS: Ghrelin plays a central role in the regulation of gastrointestinal (GI) motility. This study aimed to investigate the expression of ghrelin and growth hormone secretagogue receptor (GHSR) in the central nervous system of rats with chronic renal failure (CRF). METHODS: Sprague-Dawley rats (male, 180 ± 20 g, n = 24) were treated by 5/6 nephrectomy to construct CRF model. As their plasma creatinine concentration and blood urea nitrogen were maintained more than double the normal level for 2 weeks, they were killed for assessing the expression of ghrelin and GHSR in hypothalamus and hippocampus using immunohistochemistry and real-time polymerase chain reaction (RT-PCR). The rats (male, 180 ± 20 g, n = 24) treated by Sham operation served as a control. One-way analysis of variance and Student-Newman-Keuls q test were used to analyze group difference and a p-value of <0.05 was considered as statistically significant. RESULTS: Compared with the controls, the ghrelin and GHSR expression was obviously increased in the hippocampus (p < 0.05) but decreased in the hypothalamus of rats with CRF (p < 0.05). CONCLUSIONS: CRF was found to impact the expression of ghrelin and GHSR in hypothalamus and hippocampus. This might be associated with the CRF-induced GI motility dysfunction.

Citrate Attenuates Adenine-Induced Chronic Renal Failure in Rats by Modulating the Th17/Treg Cell Balance.

Citrate is commonly used as an anticoagulant in hemodialysis for chronic renal failure (CRF) and for the regulation of the immune dysfunction in CRF patients. The objective of this study was to investigate the effect of citrate on the balance of T helper 17 (Th17) and regulatory T (Treg) cells in CRF. The levels of blood urea nitrogen (BUN) and serum creatinine (Scr) were significantly increased in the CRF model group compared to the control group, and were decreased in the citrate-treated groups. Citrate treatment inhibited the viability of Th17 cells while elevating the viability of Treg cells in CRF rats. Moreover, Th17-related cytokines significantly decreased while the Treg-related cytokines significantly increased with citrate treatment. Moreover, citrate had a negative influence on the deviation of Th17/Treg cells in CRF rats. Therefore, our study suggests that citrate had an anti-inflammatory effect on CRF through the modulation of the Th17/Treg balance.

Activation of PPAR-γ inhibits PDGF-induced proliferation of mouse renal fibroblasts.

Recent studies have shown that activation of peroxisome proliferators activated receptor-γ (PPAR-γ) ameliorates renal interstitial fibrosis (RIF) in animal model. Yet, the underlying molecular mechanisms remain still largely unknown. Here, we investigated the hypothesis that activation of PPAR-γ regulates renal remodeling by modulating proliferation of primary cultured renal fibroblasts. In our present study, platelet-derived growth factor-AA (PDGF-AA), a key isoform of PDGF superfamily as mitogen in RIF, was applied to stimulate renal fibroblasts, the selective inhibitor or sequence specific siRNA of PI3K, skp2 or PPAR-γ was used to investigate the involvement of above molecular mediators in PDGF-AA-induced cell proliferation. Our results demonstrate that PDGF-AA induced proliferation of renal fibroblasts by activating PI3K/AKT signaling and resultant skp2 production. Pre-stimulation of cells with rosiglitazone or adenovirus carrying PPAR-γ cDNA (AdPPAR-γ) blocked PDGF-AA-stimulated cell proliferation, this effect was particularly coupled to PPAR-γ inhibition of AKT phosphorylation and skp2 expression. Inhibition of PPAR-γ by GW9662 restored the suppression of activated PPAR-γ on phosphorylation of AKT and subsequent skp2 production. Our results indicate that activation of PI3K/AKT signaling and resultant skp2 generation mediated PDGF-induced proliferation of renal fibroblasts. Activation of PPAR-γ inhibited cell proliferation by inhibition of AKT phosphorylation and its down-streams.

TLR1 polymorphism rs4833095 as a risk factor for IgA nephropathy in a Chinese Han population: A case-control study.

Toll-like receptors (TLRs) are a family of transmembrane receptors, and play a vital role in recognizing invading pathogens and activating innate immunity. Previous studies indicated that TLR1 single nucleotide polymorphisms (SNPs) might be associated with the risk of IgA nephropathy (IgAN). This study aims to investigate the relationship between TLR1 SNPs (rs4833095 and rs5743557) and IgAN in a Chinese Han population. This case-control study included 351 patients with IgAN and 310 healthy controls. Two SNPs (rs4833095 and rs5743557) of TLR1 were genotyped by Sequenom MassARRAY. Odds ratios (OR) with 95% confidence intervals (CI) were used to assess the relationship with IgAN. We found that both allele and genotype frequencies of rs5743557 were not associated with IgAN risk. Rs4833095 increased IgAN risk compared with controls in the allele, dominant and log-additive models (P = 0.04, 0.04 and 0.03, respectively). Further haplotype analysis revealed that the Trs4833095Trs5743557 haplotype may be a risk factor for IgAN (OR = 1.28; 95% CI = 1.01-1.63; P = 0.046). Furthermore, rs4833095 was associated with Lee's grades (OR = 1.75; 95% CI = 1.03-2.96; P = 0.04). However, there was no significant association between the genotype distributions of rs5743557 and clinical parameters of IgAN such as gender, 24 hour urine protein, blood pressure, and Lee's grades. Taken together, these findings suggest that the TLR1 rs4833095 polymorphism may play a role in the development and progression of IgAN.

Activation of AMPK by metformin inhibits TGF-ß-induced collagen production in mouse renal fibroblasts.

AIMS: To clarify whether activation of adenosine monophosphate-activated protein kinase (AMPK) by metformin inhibits transforming growth factor beta (TGF-ß)-induced collagen production in primary cultured mouse renal fibroblasts and further to address the molecular mechanisms. MAIN METHODS: Primary cultured mouse renal fibroblasts were stimulated with TGF-ß1 and the sequence specific siRNA of Smad3 or connective tissue growth factor (CTGF) was applied to investigate the involvement of these molecular mediators in TGF-ß1-induced collagen type I production. Cells were pre-incubated with AMPK agonist metformin or co-incubated with AMPK agonist metformin and AMPK inhibitor Compound C before TGF-ß1 stimulation to clarify whether activation of AMPK inhibition of TGF-ß1-induced renal fibroblast collagen type I expression. KEY FINDINGS: Our results demonstrate that TGF-ß1 time- and dose-dependently induced renal fibroblast collagen type I production; TGF-ß1 also stimulated Smad3-dependent CTGF expression and caused collagen type I generation; this effect was blocked by knockdown of Smad3 or CTGF. Activation of AMPK by metformin reduced TGF-ß1-induced collagen type I production by suppression of Smad3-driven CTGF expression. SIGNIFICANCE: This study suggests that activation of AMPK might be a novel strategy for the treatment of chronic kidney disease (CKD) partially by inhibition of renal interstitial fibrosis (RIF).

Inhibition of the K+ channel K(Ca)3.1 reduces TGF-ß1-induced premature senescence, myofibroblast phenotype transition and proliferation of mesangial cells.

OBJECTIVE: K(Ca)3.1 channel participates in many important cellular functions. This study planned to investigate the potential involvement of K(Ca)3.1 channel in premature senescence, myofibroblast phenotype transition and proliferation of mesangial cells. METHODS & MATERIALS: Rat mesangial cells were cultured together with TGF-ß1 (2 ng/ml) and TGF-ß1 (2 ng/ml) + TRAM-34 (16 nM) separately for specified times from 0 min to 60 min. The cells without treatment served as controls. The location of K(Ca)3.1 channels in mesangial cells was determined with Confocal laser microscope, the cell cycle of mesangial cells was assessed with flow cytometry, the protein and mRNA expression of K(Ca)3.1, α-smooth muscle actin (α-SMA) and fibroblast-specific protein-1 (FSP-1) were detected with Western blot and RT-PCR. One-way analysis of variance (ANOVA) and Student-Newman-Keuls-q test (SNK-q) were used to do statistical analysis. Statistical significance was considered at P<0.05. RESULTS: Kca3.1 channels were located in the cell membranes and/or in the cytoplasm of mesangial cells. The percentage of cells in G0-G1 phase and the expression of K(ca)3.1, α-SMA and FSP-1 were elevated under the induction of TGF-ß1 when compared to the control and decreased under the induction of TGF-ß1+TRAM-34 when compared to the TGF-ß1 induced (P<0.05 or P<0.01). CONCLUSION: Targeted disruption of K(Ca)3.1 inhibits TGF-ß1-induced premature aging, myofibroblast-like phenotype transdifferentiation and proliferation of mesangial cells.

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.

[Effect of ghrelin on duodenal migrating myoelectric complex in rats with chronic renal failure].

OBJECTIVE: To investigate the effect of ghrelin on duodenal migrating myoelectric complex (MMC) in rats with chronic renal failure (CRF). METHODS: Thirty healthy male SD rats were randomly assigned into sham-operated group (n=6) and CRF group (n=24), and the latter group was divided into 4 subgroups according to ghrelin doses administered with or without pretreatment with the receptor antagonist D-Lys(3)-GHRP-6. After a 18-h fasting, the rats with or without pretreatment with D-Lys(3)-GHRP-6 were given subcutaneous injections of ghrelin at different doses to observe the changes in duodenal MMC recorded using a multi lead physiological recording system. RESULTS: Ghrelin significantly increased the MMC cycle duration and dose-dependently enhanced the frequency, amplitude and percentage of phase III MMC cycle. This effect was inhibited by the pretreatment with ghrelin receptor antagonist D-Lys(3)-GHRP-6. CONCLUSION: Ghrelin can promote gastrointestinal motilities of rats with CRF, and the receptor of ghrelin can regulate the activity of MMC.