C-X-C chemokine receptor type 4 promotes tubular cell senescence and renal fibrosis through ß-catenin-inhibited fatty acid oxidation.

The prevalence of chronic kidney disease (CKD) is highly increasing. Renal fibrosis is a common pathological feature in various CKD. Previous studies showed tubular cell senescence is highly involved in the pathogenesis of renal fibrosis. However, the inducers of tubular senescence and the underlying mechanisms have not been fully investigated. C-X-C motif chemokine receptor 4 (CXCR4), a G-protein-coupled seven-span transmembrane receptor, increases renal fibrosis and plays an important role in tubular cell injury. Whereas, whether CXCR4 could induce tubular cell senescence and the detailed mechanisms have not studied yet. In this study, we adopted adriamycin nephropathy and 5/6 nephrectomy models, and cultured tubular cell line. Overexpression or knockdown of CXCR4 was obtained by injection of related plasmids. We identified CXCR4 increased in injury tubular cells. CXCR4 was expressed predominantly in renal tubular epithelial cells and co-localized with adipose differentiation-related protein (ADRP) as well as the senescence-related protein P16INK4A . Furthermore, we found overexpression of CXCR4 greatly induced the activation of ß-catenin, while knockdown of CXCR4 inhibited it. We also found that CXCR4 inhibited fatty acid oxidation and triggered lipid deposition in tubular cells. To inhibit ß-catenin by ICG-001, an inhibitor of ß-catenin, could significantly block CXCR4-suppressed fatty acid oxidation. Taken together, our results indicate that CXCR4 is a key mediator in tubular cell senescence and renal fibrosis. CXCR4 promotes tubular cell senescence and renal fibrosis by inducing ß-catenin and inhibiting fatty acid metabolism. Our findings provide a new theory for tubular cell injury in renal fibrosis.

Klotho accelerates the progression of polycystic ovary syndrome through promoting granulosa cell apoptosis and inflammation.

The morbidity of polycystic ovary syndrome (PCOS) is in highly increasing rate nowadays. PCOS not only affects the fertility in women, but also threatens the health of whole life. Hence, to find the prognostic risk factors is of great value. However, the effective predictors in clinical practice of PCOS are still in blackness. In this study, we found Klotho was increased in FF (Follicular Fluid) and primary luteinized granulosa cells (GCs) from PCOS patients with hyperandrogenism. Furthermore, we found follicular Klotho was negatively correlated with numbers of mature oocytes, and positively correlated with serum testosterone, LH, and LH/FSH levels menstrual cycle and number of total antral follicles in PCOS patients. In primary luteinized GCs, the increased Klotho was accompanied with upregulation of cell apoptosis and inflammation-related genes. In ovaries of PCOS mice and cultured human KGN cell line, Klotho was up-regulated and accompanied by apoptosis, inflammation and mitochondrial dysfunction. Therefore, our findings suggest new mechanisms for granulosa cell injury and revealed to target inhibit Klotho maybe a new therapeutic strategy for treatment of PCOS.

Serum granulosa cell-derived TNF-α promotes inflammation and apoptosis of renal tubular cells and PCOS-related kidney injury through NF-κB signaling.

Polycystic ovary syndrome (PCOS) is a disorder with endocrinal and metabolic problems in reproductive aged women. Evidence shows that PCOS is in a high prone trend to develop kidney diseases. In this study, we investigated the mediators responsible for PCOS-related kidney injury. We found that tumor necrosis factor (TNF-α) levels were significantly increased in serum and primary cultured granulosa cells (GCs) from PCOS patients. Serum TNF-α levels were positively correlated with serum testosterone and luteinizing hormone (LH)/follicle-stimulating hormone (FSH) ratio, suggesting its positive role in the severity of PCOS. Serum TNF-α levels were also positively correlated with the levels of urinary KapU, LamU, α1-MU and ß2-MU, the markers for renal tubular cell-derived proteinuria. We established a PCOS mouse model by resection of the right kidney, followed by daily administration of dihydrotestosterone (DHT, 27.5 µg, i.p.) from D7 for 90 days. We found that TNF-α levels were significantly increased in the ovary and serum of the mice, accompanied by increased renal tubular cell apoptosis, inflammation and fibrosis in kidneys. Furthermore, the receptor of TNF-α, tumor necrosis factor receptor 1 (TNFR1), was significantly upregulated in renal tubular cells. We treated human ovarian granulosa-like tumor cells (KGN) with DHT (1 µg/ml) in vitro, the conditioned medium derived from the granulosa cell culture greatly accelerated apoptotic injury in human proximal tubular epithelial cells (HKC-8), which was blocked after knockdown of TNF-α in KGN cells. Furthermore, knockdown of TNFR1 in renal tubular epithelial cells greatly ameliorated cell injury induced by granulosa cell-derived conditioned medium. These results suggest that serum TNF-α plays a key role in mediating inflammation and apoptosis in renal tubular cells associated with PCOS-related kidney injury.

The CXCR4-AT1 axis plays a vital role in glomerular injury via mediating the crosstalk between podocyte and mesangial cell.

Glomeruli stand at the center of nephrons to accomplish filtration and albumin interception. Podocytes and mesangial cells are the major constituents in the glomeruli. However, their interdependency in glomerular injury has rarely been reported. Herein, we investigated the role of C-X-C chemokine receptor type 4 (CXCR4) in mediating the crosstalk between podocytes and mesangial cells. We found CXCR4 and angiotensin II (AngII) increased primarily in injured podocytes. However, type-1 receptor of angiotensin II (AT1) and stromal cell-derived factor 1α (SDF-1α), a ligand of CXCR4, were evidently upregulated in mesangial cells following the progression of podocyte injury. Ectopic expression of CXCR4 in 5/6 nephrectomy mice increased the decline of renal function and glomerular injury, accelerated podocyte injury and mesangial cell activation, and initiated CXCR4-AT1 axis signals. Additionally, treatment with losartan, an AT1 blocker, interrupted the cycle of podocyte injury and mesangial matrix deposition triggered by CXCR4. Podocyte-specific ablation of CXCR4 gene blocked podocyte injury and mesangial cell activation. In vitro, CXCR4 overexpression induced oxidative stress and renin angiotensin system (RAS) activation in podocytes, and triggered the communication between podocytes and mesangial cells. In cultured mesangial cells, AngII treatment induced the expression of SDF-1α, which was secreted into the supernatant to further promote oxidative stress and cell injury in podocytes. Collectively, these results demonstrate that the CXCR4-AT1 axis plays a vital role in glomerular injury via mediating pathologic crosstalk between podocytes and mesangial cells. Our findings uncover a novel pathogenic mechanism by which the CXCR4-AT1 axis promotes glomerular injury.

CXC Chemokine Receptor 2 Accelerates Tubular Cell Senescence and Renal Fibrosis via ß-Catenin-Induced Mitochondrial Dysfunction.

Renal fibrosis is a common feature of various chronic kidney diseases (CKD). However, its underlying mechanism has not been totally clarified. C-X-C motif chemokine receptor (CXCR) family plays a role in renal fibrosis, however, detailed mechanisms have not been elucidated. Here, we report that CXCR2 has a potential role in tubular cell senescence and renal fibrosis, and is associated with ß-catenin-activated mitochondrial dysfunction. CXCR2 is one of most increased members among CXCR family in unilateral ureteral obstruction (UUO) mice. CXCR2 was expressed primarily in tubules and co-localized with p16INK4A, a cellular senescence marker, and ß-catenin. Administration of SB225002, a selective CXCR2 antagonist, significantly inhibited the activation of ß-catenin signaling, restored mitochondrial function, protected against tubular cell senescence and renal fibrosis in unilateral ureteral obstruction (UUO) mice. In unilateral ischemia-reperfusion injury (UIRI) mice, treatment with interlukin-8 (IL-8), the ligand of CXCR2, further aggravated ß-catenin activation, mitochondrial dysfunction, tubular cell senescence and renal fibrosis, whereas knockdown of p16INK4A inhibited IL-8-induced these effects. In vitro, SB225002 inhibited mitochondrial dysfunction and tubular cell senescence. Furthermore, ICG-001, a ß-catenin signaling blocker, significantly retarded CXCR2-induced cellular senescence and fibrotic changes. These results suggest that CXCR2 promotes tubular cell senescence and renal fibrosis through inducing ß-catenin-activated mitochondrial dysfunction.

ß-catenin-controlled tubular cell-derived exosomes play a key role in fibroblast activation via the OPN-CD44 axis.

Tubular injury and peripheral fibroblast activation are the hallmarks of chronic kidney disease (CKD), suggesting intimate communication between the two types of cells. However, the underlying mechanisms remain to be determined. Exosomes play a role in shuttling proteins and other materials to recipient cells. In our study, we found that exosomes were aroused by ß-catenin in renal tubular cells. Osteopontin (OPN), especially its N-terminal fragment (N-OPN), was encapsulated in ß-catenin-controlled tubular cell-derived exosome cargo, and subsequently passed to fibroblasts. Through binding with CD44, exosomal OPN promoted fibroblast proliferation and activation. Gene deletion of ß-catenin in tubular cells (Ksp-ß-catenin-/- ) or gene ablation of CD44 (CD44-/- ) greatly ameliorated renal fibrosis. Notably, N-OPN was carried by exosome and secreted into the urine of patients with CKD, and negatively correlated with kidney function. The urinary exosomes from patients with CKD greatly accelerated renal fibrosis, which was blocked by CD44 deletion. These results suggest that exosome-mediated activation of the OPN/CD44 axis plays a key role in renal fibrosis, which is controlled by ß-catenin.

Klotho retards renal fibrosis through targeting mitochondrial dysfunction and cellular senescence in renal tubular cells.

Chronic kidney disease (CKD) has a high prevalence worldwide and is an intricate issue to whole medical society. Renal fibrosis is the common pathological feature for various kinds of CKD. As an anti-aging protein, Klotho is predominantly expressed in renal tubular epithelial cells. Reports show Klotho could retard age-related renal fibrosis. Mitochondrial dysfunction plays an important role in cellular senescence. However, the role of Klotho in mitochondrial dysfunction in CKD has not yet been determined. In this study, we treated unilateral ischemia-reperfusion (UIRI) mice and cultured human renal tubular epithelial cells (HKC-8) with Klotho. We assessed renal fibrosis, cellular senescence, and Wnt/ß-catenin signaling. We also focused on mitochondrial function assessment. In UIRI mice, ectopic expression of Klotho greatly retarded fibrotic lesions and the activation of Wnt/ß-catenin signaling. Interestingly, Klotho significantly preserved mitochondrial mass, inhibited mitochondrial reactive oxygen species (ROS) production and restored the expression of mitochondrial respiration chain complex subunits. Consequently, Klotho restrained cellular senescence. In HKC-8 cells, Klotho significantly inhibited Wnt1- and Wnt9a-induced mitochondrial injury, cellular senescence, and fibrotic lesions. These results suggest Klotho has a protective role in renal function through targeted protection on mitochondria. This further broads the understanding of the beneficial efficacies of Klotho in CKD.

Serum testosterone acts as a prognostic indicator in polycystic ovary syndrome-associated kidney injury.

Polycystic ovary syndrome (PCOS) is closely related with the onset and development of metabolic abnormalities. However, the correlation between PCOS and kidney injury has not been clarified, and the underlying mechanism remains unknown. Herein, we performed a prospective survey in 55 PCOS and 69 healthy participants. Furthermore, the correlation analyses between serum testosterone and renal functional manifestations of patients and healthy subjects, including urinary albumin to creatinine ratio (UACR), urinary κ-light chains (KapU), urinary λ-light chains (LamU), urinary α1-microglobulin (α1-MU), and urinary ß2-microglobulin (ß2-MU), were analyzed. Compared with that in normal subjects, the levels of serum testosterone and UACR were significantly higher in PCOS patients. Serum testosterone is significantly correlated with the disease severity of PCOS. Although urinary excretions of KapU, LamU, α1-MU, and ß2-MU did not increase in PCOS patients, they had a significantly positive correlation with the extent of serum testosterone in PCOS patients. IN vitro, primary cultured human ovary granulosa cells (GCs) were isolated from the follicular fluid (FF) extracting from PCOS patients and controls. FF, especially which extracted from PCOS patients with a high expression of serum testosterone, significantly induced cell apoptosis and inflammation in human GCs. To examine the communication between PCOS and kidney injury, a human proximal tubular epithelial cell line (HKC-8) was cultured and administered FF. Interestingly, FF from PCOS patients with a higher level of serum testosterone induced fibrotic lesions in HKC-8 cells. These data suggest serum testosterone plays a critical role in PCOS and PCOS-associated kidney injury. Serum testosterone may serve as a promising indicator for kidney fibrotic injury outcomes in PCOS patients.