B cell-derived anti-beta 2 glycoprotein I antibody mediates hyperhomocysteinemia-aggravated hypertensive glomerular lesions by triggering ferroptosis

Hyperhomocysteinemia (HHcy) is a risk factor for chronic kidney diseases (CKDs) that affects about 85% CKD patients. HHcy stimulates B cells to secrete pathological antibodies, although it is unknown whether this pathway mediates kidney injury. In HHcy-treated 2-kidney, 1-clip (2K1C) hypertensive murine model, HHcy-activated B cells secreted anti-beta 2 glycoprotein I (β₂GPI) antibodies that deposited in glomerular endothelial cells (GECs), exacerbating glomerulosclerosis and reducing renal function. Mechanistically, HHcy 2K1C mice increased phosphatidylethanolamine (PE) (18:0/20:4, 18:0/22:6, 16:0/20:4) in kidney tissue, as determined by lipidomics. GECs oxidative lipidomics validated the increase of oxidized phospholipids upon Hcy-activated B cells culture medium (Hcy-B CM) treatment, including PE (18:0/20:4 + 3[O], PE (18:0a/22:4 + 1[O], PE (18:0/22:4 + 2[O] and PE (18:0/22:4 + 3[O]). PE synthases ethanolamine kinase 2 (etnk2) and ethanolamine-phosphate cytidylyltransferase 2 (pcyt2) were increased in the kidney GECs of HHcy 2K1C mice and facilitated polyunsaturated PE synthesis to act as lipid peroxidation substrates. In HHcy 2K1C mice and Hcy-B CM-treated GECs, the oxidative environment induced by iron accumulation and the insufficient clearance of lipid peroxides caused by transferrin receptor (TFR) elevation and down-regulation of SLC7A11/glutathione peroxidase 4 (GPX4) contributed to GECs ferroptosis of the kidneys. In vivo, pharmacological depletion of B cells or inhibition of ferroptosis mitigated the HHcy-aggravated hypertensive renal injury. Consequently, our findings uncovered a novel mechanism by which B cell-derived pathogenic anti-β₂GPI IgG generated by HHcy exacerbated hypertensive kidney damage by inducing GECs ferroptosis. Targeting B cells or ferroptosis may be viable therapeutic strategies for ameliorating lipid peroxidative renal injury in HHcy patients with hypertensive nephropathy.

Serum homocysteine is associated with tubular interstitial lesions at the early stage of IgA nephropathy

BACKGROUND

The association between homocysteine (Hcy) and IgA nephropathy (IgAN) is not well understood. We aimed to investigate the relationship between Hcy and clinicopathologic features in IgAN patients.

METHODS

A total of 337 IgAN patients and 150 sex- and age- matched healthy controls were enrolled in this single-center retrospective study. According to Hcy ≤ 10 μmol/L or > 10 μmol/L, patients were divided into low and high Hcy groups. Multivariate logistic regression was performed to explore the risk factors for elevated Hcy.

RESULTS

Serum Hcy was higher in IgAN patients than in healthy controls [11.6 (9.1,15.3) vs. 8.8 (7.5,10.6) μmol/L, P < 0.001], unanimously in the subgroup of 156 patients with a normal estimated glomerular filtration rate (eGFR) (≥ 90 ml/min/1.73 m²) [9.9 (7.6,12.4) vs. 8.8 (7.5,10.6) μmol/L, P < 0.001]. Compared to the low Hcy group, serum creatinine (Scr), blood urine nitrogen (BUN), uric acid (UA), endocapillary hypercellularity (E) and tubular atrophy/interstitial fibrosis lesion (T) were higher in the high Hcy group. Hcy levels were positively correlated with Scr, BUN, UA, 24-h urine protein, and E and T lesions, but negatively correlated with eGFR and superoxide dismutase (SOD). In the subgroup with normal eGFR, patients with higher Hcy were persistent with higher Scr, BUN and T lesions. A multivariate logistic regression model showed that the risk of elevated Hcy in patients with pathological T increased by 2.87-fold. T lesions could better predict high Hcy, with an odds ratio (OR) of 14.20 in the subgroup with normal eGFR.

CONCLUSIONS

Pathologic T was an independent risk factor associated with elevated Hcy, especially at the early stage of IgAN.

Hyperhomocysteinemia-Induced Oxidative Stress Aggravates Renal Damage in Hypertensive Rats

BACKGROUND

Hyperhomocysteinemia (HHcy) plays a synergistic role with hypertension in vascular injury; however, the relationship between HHcy and hypertension in renal injury remains unclear. Here, we sought to evaluate the relationship between HHcy and hypertension in the context of renal injury and to elucidate the mechanism of action underlying this relationship.

METHODS

Wistar Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) were randomized into WKY, WKY + HHcy, SHR, and SHR + HHcy groups. Blood pressure, plasma homocysteine, serum malondialdehyde (MDA), serum superoxide dismutase (SOD), urinary albumin creatinine ratio (UACR), and glomerular filtration rate (GFR) were measured. Renal histopathology and expression levels of NOX2, NOX4, and nephrin in the kidneys were examined.

RESULTS

The WKY + HHcy and SHR groups exhibited lower serum SOD and GFR levels, relative to the WKY group, along with higher levels of both serum MDA and UACR. Higher mRNA and protein expression levels of NOX2 and NOX4, along with lower expression levels of nephrin, were observed in the kidneys of WKY + HHcy and SHR rats, relative to WKY controls, respectively. Similar effects were observed in the SHR + HHcy group, relative to the SHR group and WKY + HHcy group, respectively. Periodic acid-Schiff staining showed an increase in the glomerular extracellular matrix in the WKY + HHcy and SHR + HHcy groups compared with their respective controls.

CONCLUSIONS

HHcy appears to synergistically increase hypertensive renal damage by enhancing oxidative stress.

The Relationship Between Homocysteine, Blood Pressure Variability, and Left Ventricular Hypertrophy in Patients with Essential Hypertension: An Observational Study

INTRODUCTION

This study aimed to investigate the relationship between homocysteine (Hcy) and blood pressure variability (BPV) and the relationship between Hcy and left ventricular hypertrophy (LVH) in 102 patients with essential hypertension.

METHODS

The 102 patients were divided into the Hcy < 10 μmol/L group (n = 47) and the Hcy ≥ 10 μmol/L group (n = 55) according to Hcy concentration. The differences between Hcy and BPV and Hcy and LVH were compared between the two groups. Finally, the correlations between Hcy and BPV and between Hcy and LVH were analyzed.

RESULTS

The results showed that there were significant differences between Hcy and BPV and between Hcy and LVH in the two groups. Hcy correlated positively with the coefficient of variation in nighttime diastolic blood pressure and night systolic blood pressure standard deviation (nDBPSD), with correlation coefficients of 0.331 and 0.303 (P < 0.001). At the same time, Hcy correlated positively with interventricular septal thickness and left ventricular posterior wall thickness, which were indicators of LVH, with correlation coefficients of 0.350 and 0.352 (P < 0.001).

CONCLUSIONS

There was a correlation between Hcy and BPV and between Hcy and LVH. Attention should also be paid to blood Hcy and BPV for patients with essential hypertension.

Correlation between serum homocysteine level and ulcerative colitis: A meta-analysis

Background: The aim of the present meta-analysis was to investigate the correlation of serum homocysteine (Hcy) concentration and ulcerative colitis (UC) through pooling all the relevant publications.

Methods The electronic databases of PubMed, EMBase, Web of Science, Google Scholar, CBM, and CNKI were systematic searched with the text words of homocysteine/Hcy, ulcerative colitis/UC, and inflammatory bowel disease. The correlation between serum Hcy and UC were demonstrated by stand mean difference (SMD) and corresponding 95% confidence interval (95% CI). The publication bias was evaluated by Egger’s line regression test and Begg’s funnel plot.

Results After systematic searching the related electronic databases of PubMed, EMBase, Web of Science, Google Scholar, CBM, and CNKI, eighteen publications relevant to serum Hcy and UC were included in the present meta-analysis. The serum Hcy leves were 14.01±2.76 and 10.31±1.59 μmol/L for UC groups and healthy controls respectively with statistical difference (p<0.05). Significant heterogeneity was found (I2=94.5%, p<0.001) among the included studies. Therefore, the SMD was pooled through the random effect model. The pooled SMD was 1.20 (95% CI: 0.89-1.51), indicating that serum Hcy levels were significant higher in UC groups compared to healthy controls with statistical difference (Z=7.52, P<0.001). Egger’s line regression test indicated no publications bias (t=1.45, p=0.17).

Conclusion: Serum Hcy levels were usually elevated in UC patients, which indicates that Hcy may play an important role in UC development and may be used as a serological biomarker for UC diagnosis.

Genetically elevated circulating homocysteine concentrations increase the risk of diabetic kidney disease in Chinese diabetic patients

Diabetic kidney disease (DKD) is a devastating and frequent complication of diabetes mellitus. Here, we first adopted methylenetetrahytrofolate reductase (MTHFR) gene C677T polymorphism as an instrument to infer the possible causal relevance between circulating homocysteine and DKD risk in a Chinese population and next attempted to build a risk prediction model for DKD. This is a hospital‐based case‐control association study. Total 1107 study participants were diagnosed with type 2 diabetes mellitus, including 547 patients with newly diagnosed and histologically confirmed DKD. MTHFR gene C677T polymorphism was determined using the TaqMan method. Carriers of 677TT genotype (14.55 μmol/L) had significantly higher homocysteine concentrations than carriers of 677CT genotype (12.88 μmol/L) (P < 0.001). Carriers of 677TT genotype had a 1.57‐fold increased risk of DKD (odds ratio: 1.57, 95% CI: 1.21‐2.05, P = 0.001) relative to carriers of 677CT genotype after adjusting for confounders. Mendelian randomization analysis revealed that the odds ratio for DKD relative to diabetes mellitus per 5 μmol/L increment of circulating homocysteine concentrations was 3.86 (95% confidence interval: 1.21‐2.05, P < 0.001). In the Logistic regression analysis, hypertension, homocysteine and triglyceride were significantly associated with an increased risk of DKD and they constituted a risk prediction model with good test performance and discriminatory capacity. Taken together, our findings provide evidence that elevated circulating homocysteine concentrations were causally associated with an increased risk of DKD in Chinese diabetic patients.

Regulation of TGF-β1 on PI3KC3 and its role in hypertension-induced vascular injuries

The aim of the present study was to investigate the expression and role of transforming growth factor (TGF)-β1/phosphatidylinositol 3-kinase catalytic subunit type 3 (PI3KC3) in the peripheral blood in patients with hypertension. A total of 28 patients with primary hypertension and 20 healthy control subjects were included. Peripheral blood samples were collected. The mRNA and protein expression levels were detected by reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. Cell counting kit-8 assay, Transwell chamber assay and flow cytometry were performed to detect the cell proliferation, migration ability and cellular apoptosis, respectively. Laser scanning confocal microscopy was used to detect the intracellular autophagosomes. The expression of TGF-β1 was significantly elevated, whereas the expression of PI3KC3 was significantly downregulated in the patients with hypertension compared with controls. There was negative correlation between the TGF-β1 and PI3KC3 expression. Following treatment with TGF-β1, the protein expression of PI3KC3 was significantly decreased in human umbilical vein endothelial cells (HUVECs), and the autophagic activity was significantly decreased. Furthermore, following the treatment of TGF-β1 the proliferation of HUVECs was significantly reduced in the HUVECs, the hypoxia-induced apoptosis rates were significantly elevated and the number of penetrating cells were significantly declined (indicating declined migration ability). However, the overexpression of PI3KC3 significantly ameliorated the proliferation, migration ability and hypoxia tolerance of TGF-β1-treated HUVECs. In conclusion, the present results indicated that TGF-β1 expression was elevated in the peripheral blood in hypertensive patients and negatively correlated with the PI3KC3 expression; and that TGF-β1 regulates the PI3KC3 signaling pathway to inhibit the autophagic activity of vascular endothelial cells, and regulate the cell proliferation, migration and anti-apoptosis ability, thus aggregating the endothelial cell injuries in hypertension. The results of the current study revealed a novel mechanism of TGF-β1 in the regulation of endothelial cell injury in hypertension, which may provide a potential target for disease therapy.