Melatonin Alleviates Hypoxia-Induced Apoptosis of Granulosa Cells by Reducing ROS and Activating MTNR1B-PKA-Caspase8/9 Pathway.

In mammalian ovaries, the avascular environment within follicular cavity is supposed to cause hypoxic status in granulosa cells (GCs), leading to apoptotic cell death accompanied by cumulative reactive oxygen species (ROS) production. Melatonin (N-acetyl-5-methoxytryptamine, MT), a broad-spectrum antioxidant that exists in porcine follicle fluid, was suggested to maintain GCs survival under stress conditions. In this study, using the established hypoxic model (1% O2) of cultured porcine GCs, we explored the effect of MT on GCs apoptosis. The results showed that MT restored cell viability and reduced the apoptosis of GCs during hypoxia exposure. In addition, GCs treated with MT exhibited decreased ROS levels and increased expression of antioxidant enzymes including heme oxygenase-1 (HO-1), glutathione S-transferase (GST), superoxide dismutase 1 (SOD1), and catalase (CAT) upon hypoxia incubation. Moreover, the hypoxia-induced expression of cleaved caspase 3, 8, and 9 was significantly inhibited after MT treatment. In contrast, blocking melatonin receptor 2 (MTNR1B) with a competitive antagonist 4-phenyl-2-propionamidotetralin (4P-PDOT) diminished the inhibitory effects of MT on caspase 3 activation. By detecting levels of protein kinase (PKA), a downstream kinase of MTNR1B, we further confirmed the involvement of MT-MTNR1B signaling in mediating GCs protection during hypoxia stress. Together, the present data provide mechanistic evidence suggesting the role of MT in defending GCs from hypoxia-induced apoptosis.

Autophagy-Lysosome Pathway in Renal Tubular Epithelial Cells Is Disrupted by Advanced Glycation End Products in Diabetic Nephropathy.

It has been suggested that autophagy protects renal tubular epithelial cells (TECs) from injury in diabetic nephropathy (DN). However, the manner in which the autophagy-lysosome pathway is changed in this state remains unclear. In this study of DN, we investigated the autophagic activity and lysosomal alterations in vivo and in vitro. We found that autophagic vacuoles and SQSTM1-positive proteins accumulated in TECs from patients with DN and in human renal tubular epithelial cell line (HK-2 cells) treated with advanced glycation end products (AGEs), the important factors that involved in the pathogenesis of DN. In HK-2 cells, exposure to AGEs caused a significant increase in autophagosomes but a marked decrease in autolysosomes, and the lysosomal turnover of LC3-II was not observed, although LC3-II puncta were co-localized with the irregular lysosomal-associated membrane protein1 granules after AGEs treatment. Furthermore, lysosomal membrane permeabilization was triggered by AGEs, which likely resulted in a decrease in the enzymatic activities of cathepsin B and cathepsin L, the defective acidification of lysosomes, and suppression of the lysosomal degradation of DQ-ovalbumin. Oxidative stress evoked by AGEs-receptor for AGE interaction likely played an important role in the lysosomal dysfunction. Additionally, ubiquitinated proteins were co-localized with SQSTM1-positive puncta and accumulated in HK-2 cells after exposure to AGEs, indicating blocked degradation of SQSTM1-positive and ubiquitinated aggregates. Taken together, the results show that lysosomal membrane permeabilization and lysosomal dysfunction are triggered by AGEs, which induce autophagic inactivation in TECs from patients with DN. Disruption of the autophagy-lysosome pathway should be focused when studying the mechanisms underlying DN.

The expression of renal Epstein-Barr virus markers in patients with lupus nephritis.

The aim of this study was to investigate the role of renal Epstein-Barr virus (EBV) infection in the pathogenesis of lupus nephritis (LN). A total of 58 renal tissue samples from patients with LN, seven normal renal tissue samples from patients with non-glomerular hematuria and 37 renal tissue samples from patients with minimal change nephropathy were collected. The expression of EBV-latent membrane protein-1 (EBV-LMP1) and EBV-encoded RNA 1 (EBER-1) in the renal tissue was examined by immunohistochemistry (IHC) and in situ hybridization (ISH), respectively. The sera levels of anti-nuclear antibody as well as antibodies to extractable nuclear antigen in patients with LN were also measured. An equivalence test showed that the results from the IHC and the ISH analyses had strong agreement. The positive rates of renal EBER-1 and EBV-LMP1 in the LN patients were significantly higher than those of the normal and minimal change nephropathy patients (P<0.001), while no significant difference was identified between those of the normal and minimal change nephropathy groups (P>0.05). The positive rates of EBV-LMP1 and EBER-1 in the renal tissues of patients with LN were not determined to be significantly different between the relapse (immunosuppressant-treated) and initial onset (non-treated) patients, between the patients with and without concurrent infection, and among the patients with different age ranges (P>0.05). The proportion of LN patients positive for anti-Sm antibody was significantly higher in the renal EBV-positive group than in the EBV-negative group (P<0.05), while the proportions of LN patients positive for the other autoantibodies that were examined were not identified to be significantly different between these two groups (P>0.05). The present study shows that renal EBV infection may contribute to the pathogenesis of LN by inducing anti-Sm antibody production.

Continuation of immunosuppressive treatment may be necessary in IgA nephropathy patients with remission of proteinuria: Evaluation by repeat renal biopsy.

The present study aimed to evaluate the effects of an individualized, low-dose multi-drug immunosuppressive regimen for the treatment of immunoglobulin A nephropathy (IgAN). A preliminary investigation of the course of IgAN following immunosuppressive treatment was conducted based on repeat renal biopsies. Clinical and pathological data of 17 patients with IgAN who received repeat renal biopsies were analyzed retrospectively. In addition to basic treatment, 16 patients regularly received an individualized low-dose immunosuppressive regimen according to their clinical manifestations and pathological patterns following the first biopsy. Clinical parameters, including 24-h urinary protein excretion and levels of serum albumin, uric acid and total cholesterol were collected. Glomerular deposits of IgA and C3, as well as the activity and chronicity indexes of renal lesions were evaluated by semi-quantitative methods. The 24-h urinary protein excretion of the patients decreased significantly from the first biopsy (2.53±2.17 g/day) to the repeated biopsy (0.26±0.55 g/day) (P<0.001). Deposits of IgA and C3 in the glomerulus were persistent, but were reduced in quantity at the second biopsy. Although active renal lesions were observed in the majority of patients, the activity index decreased significantly from 3.18±1.33 prior to therapy to 2.47±0.80 following therapy (P<0.05), while the chronicity index did not change significantly (2.59±2.00 versus 2.76±1.89, respectively). The individualized, low-dose multi-drug immunosuppressive regimen used in the present study significantly minimized proteinuria, stabilized renal function and alleviated histological lesions in patients with IgAN without causing overt adverse effects during the short-term follow-up. In addition to proteinuria, renal pathological changes should be appraised when considering the withdrawal of immunosuppressants from IgAN treatment.

Epithelial-mesenchymal transdifferentiation of renal tubular epithelial cells induced by urinary proteins requires the activation of PKC-α and ßI isozymes.

Proteinuria is a common feature for almost all glomerular diseases and reflects the severity of the glomerular lesion. The presence of a large amount of proteins in tubular fluid, however, may also contribute to the development of RIF (renal interstitial fibrosis). Endocytosis of albumin in proximal tubular cells triggers PKC (protein kinase C)-dependent generation of reactive oxygen species and secretion of chemokines. As a family including 12 isozymes, which PKC isozymes participate in RIF is still unclear. EMT (epithelial-mesenchymal transdifferentiation) of RTECs (renal tubular epithelial cells) plays a crucial role in the progress of RIF induced by proteinuria. In the present study, we investigated the role of classical PKC isozymes in the proteinuria-induced EMT of RTECs. Employing immunochemical staining, we found that PKC-α, -ßI and -ßII were expressed in glomerulus and in RTECs in both normal and diseased renal tissues, while PKC-γ was only expressed in podocytes in the glomerulus. Treatment of HK-2 cells with extracted urinary proteins resulted in EMT, as evidenced by morphological changes, decreased E-cadherin expression, increased α-SMA (α-smooth muscle actin) expression, as well as production of type I collagen and fibronectin. Western blot analysis of PKC isozymes in the cytosolic compared with membrane fraction revealed translocation of PKC-α and -ßI, but not PKC-ßII, in HK-2 cells undergoing EMT. Pretreatment with selective PKC-α inhibitor G-6976 or PKC-ß inhibitor significantly attenuated EMT induced by urinary proteins. In summary, the present study suggested that PKC-α and -ßI play critical roles in the EMT of RTECs in response to urinary proteins.

Thiazolidinedione attenuate proteinuria and glomerulosclerosis in Adriamycin-induced nephropathy rats via slit diaphragm protection.

AIM: The slit diaphragm (SD) of podocyte impairment contributes to massive proteinuria and progressive glomerulosclerosis in many human glomerular diseases. The aim of the study was to determine if thiazolidinedione (TZD) reduce proteinuria and glomerulosclerosis in focal segmental glomerulosclerosis (FSGS) by preserving the structure and function of SD. METHODS: Adriamycin-induced FSGS rat models were employed. Urinary protein content was measured dynamically during the experiment. Additional biochemical parameters in serum samples were measured after the animals were killed. Glomerular sclerosis index (SI) and podocyte foot processes fusion rate (PFR) were evaluated. The protein and mRNA expressing levels of nephrin, podocin and CD2-associated protein (CD2AP) in glomeruli were assessed by immunohistochemistry and real-time quantitative polymerase chain reaction, respectively. The density of podocytes was also evaluated after anti-Wilms' tumour-1 immunohistochemical staining. RESULTS: Rosiglitazone treatment partially reduced proteinuria, but did not significantly affect the serum levels of triglyceride, cholesterol, albumin, glucose, urea nitrogen and creatinine in Adriamycin-induced FSGS rats. Glomerular SI and podocyte foot PFR were significantly attenuated by rosiglitazone treatment. Rosiglitazone prevented the reduction of nephrin, podocin and CD2AP protein expression induced by Adriamycin, however, the mRNA expression levels of these SD-related markers did not change significantly. Rosiglitazone therapy did not reverse Adriamycin-mediated reduction of the density of podocytes. CONCLUSIONS: The study data suggest that TZD are promising therapeutic agents on FSGS, and the mechanism may be mediated in part by directly protecting the structure and function of SD.

[The effect of IL-18 on E-cadherin expression and its possible intracellular pathway in HK-2 cells].

AIM: To explore the effect of NF-kappaB signaling pathway in interleukin-18-induced transdifferentiation in renal proximal tubular cells. METHODS: In IL-18 stimulation groups, HK-2 cells were challenged with different concentrations (0, 1, 10, 100 microg/L) of IL-18 for 72 h; In SN50 preincubation groups, HK-2 cells were incubated with 100 mg/L SN50 for 30 min before IL-18 was added. At the end of the incubation, the expression of E-cadherin was determined by the combination of immunocytochemistry and RT-PCR. RESULTS: Percentage of E-cadherin positive expression HK-2 cells was decreased by IL-18 in dosage dependant manner. Expression of E-cadherin mRNA in HK-2 cells was also decreased by IL-18 in dosage dependant manner. Recovered the mostly part of expression of E-cadherin was found after HK-2 cells were pretreated with SN50. CONCLUSION: IL-18-induced transdifferentiation of RTECs is suppressed by blocking NF-kappaB signaling pathway. IL-18-induced transdifferentiation of RTECs at least is partly via NF-kappaB pathway.