BRG1 accelerates mesothelial cell senescence and peritoneal fibrosis by inhibiting mitophagy through repression of OXR1.

Peritoneal mesothelial cell senescence promotes the development of peritoneal dialysis (PD)-related peritoneal fibrosis. We previously revealed that Brahma-related gene 1 (BRG1) is increased in peritoneal fibrosis yet its role in modulating peritoneal mesothelial cell senescence is still unknown. This study evaluated the mechanism of BRG1 in peritoneal mesothelial cell senescence and peritoneal fibrosis using BRG1 knockdown mice, primary peritoneal mesothelial cells and human peritoneal samples from PD patients. The augmentation of BRG1 expression accelerated peritoneal mesothelial cell senescence, which attributed to mitochondrial dysfunction and mitophagy inhibition. Mitophagy activator salidroside rescued fibrotic responses and cellular senescence induced by BRG1. Mechanistically, BRG1 was recruited to oxidation resistance 1 (OXR1) promoter, where it suppressed transcription of OXR1 through interacting with forkhead box protein p2. Inhibition of OXR1 abrogated the improvement of BRG1 deficiency in mitophagy, fibrotic responses and cellular senescence. In a mouse PD model, BRG1 knockdown restored mitophagy, alleviated senescence and ameliorated peritoneal fibrosis. More importantly, the elevation level of BRG1 in human PD was associated with PD duration and D/P creatinine values. In conclusion, BRG1 accelerates mesothelial cell senescence and peritoneal fibrosis by inhibiting mitophagy through repression of OXR1. This indicates that modulating BRG1-OXR1-mitophagy signaling may represent an effective treatment for PD-related peritoneal fibrosis.

Brahma-related gene 1 acts as a profibrotic mediator and targeting it by micheliolide ameliorates peritoneal fibrosis.

BACKGROUND: Progressive peritoneal fibrosis is a worldwide public health concern impacting patients undergoing peritoneal dialysis (PD), yet there is no effective treatment. Our previous study revealed that a novel compound, micheliolide (MCL) inhibited peritoneal fibrosis in mice. However, its mechanism remains unclear. Brahma-related gene 1 (BRG1) is a key contributor to organ fibrosis, but its potential function in PD-related peritoneal fibrosis and the relationship between MCL and BRG1 remain unknown. METHODS: The effects of MCL on BRG1-induced fibrotic responses and TGF-ß1-Smads pathway were examined in a mouse PD model and in vitro peritoneal mesothelial cells. To investigate the targeting mechanism of MCL on BRG1, coimmunoprecipitation, MCL-biotin pulldown, molecular docking and cellular thermal shift assay were performed. RESULTS: BRG1 was markedly elevated in a mouse PD model and in peritoneal mesothelial cells cultured in TGF-ß1 or PD fluid condition. BRG1 overexpression in vitro augmented fibrotic responses and promoted TGF-ß1-increased-phosphorylation of Smad2 and Smad3. Meanwhile, knockdown of BRG1 diminished TGF-ß1-induced fibrotic responses and blocked TGF-ß1-Smad2/3 pathway. MCL ameliorated BRG1 overexpression-induced peritoneal fibrosis and impeded TGF-ß1-Smad2/3 signaling pathway both in a mouse PD model and in vitro. Mechanically, MCL impeded BRG1 from recognizing and attaching to histone H3 lysine 14 acetylation by binding to the asparagine (N1540) of BRG1, in thus restraining fibrotic responses and TGF-ß1-Smad2/3 signaling pathway. After the mutation of N1540 to alanine (N1540A), MCL was unable to bind to BRG1 and thus, unsuccessful in suppressing BRG1-induced fibrotic responses and TGF-ß1-Smad2/3 signaling pathway. CONCLUSION: Our research indicates that BRG1 may be a crucial mediator in peritoneal fibrosis and MCL targeting N1540 residue of BRG1 may be a novel therapeutic strategy to combat PD-related peritoneal fibrosis.

FOXO3a accumulation and activation accelerate oxidative stress-induced podocyte injury.

Podocyte injury is the primary cause of glomerular injury in diabetic nephropathy (DN). Advanced oxidation protein products (AOPPs), the triggers and markers of oxidative stress in DN, have been linked to podocyte damage. However, the underlying mechanism is not yet clear. Here, we investigated the potential role of FOXO3a, a key transcription factor in the response to stress, in mediating AOPPs-induced podocyte injury. We found that FOXO3a expression was increased in the glomeruli of kidney biopsies from patients with DN and it was positively correlated with proteinuria. The serum from patients with DN significantly increased FOXO3a and its downstream genes FasL and Bim, thereby inducing the high level of cleaved caspase3 and the loss of nephrin and podocin expressions in podocytes. Blockade of AOPPs signaling by a neutralizing antibody against the receptor of advanced glycation end products (αRAGE) abolished the effect of DN serum on podocytes, confirming the pathogenic role of AOPPs in DN serum. Downregulation of FOXO3a decreased AOPPs-induced podocyte apoptosis and restored the levels of podocyte markers nephrin and podocin, and upregulation of FOXO3a exacerbated these changes in podocytes after AOPPs treatment. Furthermore, FOXO3a specifically activated proapoptotic genes in podocytes only in the presence of AOPPs. Mechanistically, AOPPs increased the FOXO3a protein levels by inhibiting their autophagic degradation in a ROS/mTOR-dependent manner. Moreover AOPPs activated the accumulated FOXO3a by maintaining FOXO3a in the nucleus, and this process was dependent on ROS-mediated AKT signaling deactivation. These studies suggest that FOXO3a plays a critical role in mediating AOPPs-induced podocyte injury and reveal a new mechanistic linkage of oxidative stress, FOXO3a activation and podocyte injury in DN.

Albumin-globulin ratio and mortality in patients on peritoneal dialysis: a retrospective study.

BACKGROUND: Albumin-globulin ratio (AGR), a variable based on serum albumin and non-albumin proteins, has been demonstrated as a predictor of mortality in patients with malignant neoplasm. The aim of this study was to evaluate the prognostic value of AGR on peritoneal dialysis (PD) patients. METHODS: We retrospectively analyzed 602 incident PD patients from January 1st, 2008, to December 31st, 2017, at our center and followed them until December 31st, 2018. Kaplan-Meier curves and multivariate Cox regression models were applied to analyze the association between AGR and all-cause of mortality and cardiovascular mortality. RESULTS: The median follow-up time was 32.17 (interquartile range = 32.80) months. During follow-up, 131 (21.8%) patients died, including 57 patients (43.5%) who died due to cardiovascular diseases. Kaplan-Meier curves showed that patients with AGR > 1.26 had better rates of survival than those with AGR ≤ 1.25 (p < 0.001). After adjusting for potential confounders, the lower AGR level was significantly associated with an increased all-cause and cardiovascular mortality [hazard ratio (HR): 1.57, 95% confidence interval (CI): 1.07-2.32, p = 0.022 and HR: 2.01, 95% CI: 1.10-3.69, p = 0.023 respectively]. CONCLUSIONS: Patients with a low AGR level had an increased all-cause and cardiovascular mortality. AGR may be a useful index in identifying patients on PD at risk for CVD and all-cause of mortality.

Association of total testosterone, free testosterone, bioavailable testosterone, sex hormone-binding globulin, and hypertension.

Low testosterone has been inversely associated with hypertension. Our objective was to determine the associations between total testosterone (TT), free testosterone (FT), bioavailable testosterone (BioT), sex hormone-binding globulin (SHBG), and hypertension. Two hundred fifty-three men were enrolled in this study. TT and SHBG were measured by chemiluminescent immunoassay, and FT and BioT were calculated. Hypertension was defined as systolic blood pressure (SBP) ≥140 mm Hg and/or diastolic blood pressure (DBP) ≥90 mm Hg. Our results showed that hypertensive men had higher SHBG levels, and lower FT and BioT, compared to normotensive men. FT and BioT were inversely associated with SBP and DBP after adjusting for covariates (age, smoking, alcohol consumption, and physical activity). Furthermore, there was a significant decrease in the odds ratios for hypertension in the third and fourth quartiles of BioT and FT, compared to the lowest quartile before and after adjusting for covariates. In contrast, the OR for hypertension in the third quartile of SHBG was lower than the highest quartile. Our data show that FT and BioT are inversely correlated with SBP, DBP, and hypertension in men.

Association of total testosterone, free testosterone, bioavailable testosterone and sex hormone-binding globulin with hepatic steatosis and the ratio of aspartate aminotransferase to alanine aminotransferase.

Several articles have shown the inverse association between total testosterone (TT) or sex hormone-binding globulin (SHBG) and hepatic steatosis. No articles report associations of TT, SHBG, free testosterone (FT), and bioavailable testosterone (BioT) with aspartate aminotransferase (AST)/alanine aminotransferase (ALT) ratios. Therefore, we investigated the associations of TT, FT, BioT and SHBG with hepatic steatosis and AST/ALT ratios. A total of 218 men were enrolled. We diagnosed hepatic steatosis by ultrasound. TT and SHBG showed a reduced risk for hepatic steatosis when analyzed with or without adjusting for age, smoking, alcohol consumption and physical activity. Compared with the lowest quartile, the ORs for hepatic steatosis in the third and fourth quartiles (0.32 [95% CI: 0.14-0.75] and 0.27 [95% CI: 0.10-0.73], respectively) of SHBG were significantly lower after adjustments. The OR for hepatic steatosis in the fourth quartile of TT (0.41 [95% CI: 0.17-0.95]) was significantly lower than in the lowest quartile after adjustments. The mean AST/ALT ratios in men with hepatic steatosis were lower than those without hepatic steatosis (0.83 and 1.04, respectively), due to the elevated ALT levels in hepatic steatosis groups. Furthermore, TT and SHBG were positively associated with AST/ALT ratios with and without adjustments. In conclusion, higher TT and SHBG levels in men are associated with the reduced risk of hepatic steatosis and elevated AST/ALT ratios, independent of age, smoking, alcohol consumption and physical activity.

Reference values for serum levels of cholesteryl ester transfer protein and its distribution characteristics in healthy Chinese children and newborns.

OBJECTIVE: To investigate the distribution characteristics of serum CETP levels in childhood. DESIGN AND METHODS: CETP was measured in 912 healthy children and 40 cord blood with an ELISA. RESULTS: CETP was skewed in children with a median of 2.48 (2.5-97.5 percentiles: 0.56-6.96) mg/L. CETP in cords was much lower than in children, and was lower in younger children (<1 year) than in elder children. CONCLUSIONS: CETP is lowest at birth and sharply rises to maximum levels in infancy.

Effect of hypoalbuminemia on the increased serum cholesteryl ester transfer protein concentration in children with idiopathic nephrotic syndrome.

OBJECTIVES: To examine the alteration of cholesteryl ester transfer protein (CETP) mass with the regression of albumin level in childhood nephrotic syndrome (NS) in order to clarify the effect of albumin on CETP in NS. DESIGN AND METHODS: Serum concentrations of CETP, kidney parameters and lipid traits were determined in 110 children with idiopathic NS and 150 control subjects. Of the NS patients, 69 children with an active phase formed group 1, and 41 in remission formed group 2. RESULTS: Group 1 presented severe hypoalbuminemia and hyperlipidemia, while group 2 exhibited marked recovery in both serum albumin level and lipid/lipoprotein profile. CETP concentration was significantly higher in group 1 (7.36+/-2.43 mg/L, compared with controls 3.38+/-1.83 mg/L, P<0.0001), and declined to within normal range in group 2 (2.91+/-1.77 mg/L). CETP concentration had a strong inverse correlation with serum albumin level (r=-0.688, P<0.0001) in NS patients. Furthermore, when multiple linear regression analysis was performed, in which albumin, proteinuria, lipid traits, and prednisone dose were treated as independent variables, albumin was the only variable showing a significant correlation with CETP in the NS patients (R(2)=0.587, beta=-0.475, P<0.0001). CONCLUSIONS: The results demonstrate that the decreased serum albumin level might be a main determinant of the increased CETP concentration in pediatric NS.

CETP gene mutation (D442G) increases low-density lipoprotein particle size in patients with coronary heart disease.

BACKGROUND: Small, dense low-density lipoprotein (LDL) in subjects with the atherogenic pattern B has been established as a risk factor of atherosclerosis. Cholesteryl ester transfer protein (CETP) plays an important role in the transfer and exchange of cholesteryl esters and triglycerides between the lipoprotein classes of human plasma. It has been shown that CETP can also change the particle size of high-density lipoprotein (HDL) and LDL subfractions in vitro. Previous clinical studies about CETP gene mutations mainly focused on abnormalities in HDL, few involved those in LDL. OBJECTIVES: To investigate the effect of the D442G mutation in the CETP gene on major peak size of LDL particles in patients with coronary heart diseases (CHD). METHODS: D442G mutation in the CETP gene was detected using the PCR-RFLP. LDL particles sizes were analyzed by 2-16% nondenaturing polyacrylamide gradient gels in CHD patients with D442G mutation in the CETP gene. RESULTS: Six heterozygotes and one homozygote were found to have the D442G mutation among 200 CHD patients. The frequency of this mutation was 3.5%. The major peak size of LDL in patients with gene mutation (n=7) was significantly larger than that in patients without the mutation (n=40) (26.92 +/- 0.79 nm vs. 25.71 +/- 0.66 nm, respectively; P<0.01). All the patients with the gene mutation expressed pattern A, whereas only about half of the patients without the mutation expressed this pattern. The patients with gene mutation had decreased plasma CETP concentration, while increased concentration of HDL-C and apolipoprotein A-I compared with controls. CONCLUSIONS: CETP gene mutation (D442G) increases LDL particle size. This suggests that CETP play an antiatherogenic role.

Cholesteryl ester transfer protein levels and gene deficiency in Chinese patients with cardio-cerebrovascular diseases.

OBJECTIVE: To detect cholesteryl ester transfer protein (CETP) levels, frequencies of CETP D442G and I 14A mutations and characteristics of abnormal lipids in patients with cardio-cerebro vascular diseases. METHODS: Ninety-four myocardial infarction (MI) patients, 110 stroke patients and 335 healthy controls were selected. The CETP concentration was determined using ELISA. The CETP activity was measured using a substrate of (14)C-radiolabeled discoidal bilayer particles. The CETP gene mutations were detected by PCR-RFLP. RESULTS: The CETP concentrations in the MI and stroke group, were higher than those in the controls. The gene mutation frequencies of D442G in the MI, stroke and control group were 3.5%, 3.6% and 5%, respectively, and the frequencies of I 14A were 1.05%, 0.91% and 1%, respectively. One case of D442G homozygote was detected in the healthy group. The frequency of two CETP gene mutations showed no significant difference among the patients and controls. The CETP concentration and activity in subjects with CETP mutations were one-third of those in the control group. The level of HDL-C, apo-A1 increased in the mutation subjects, while the TG level decreased. CONCLUSIONS: The CETP level increased significantly in patients with cardio-cerebrovascular diseases. The carriers of CETP deficiency had CETP and lipid abnormalities.