Phosphatidylserine eversion regulated by phospholipid scramblase activated by TGF-β1/Smad signaling in the early stage of kidney stone formation

The mechanism underlying phosphatidylserine eversion in renal tubule cells following calcium oxalate-mediated damage remains unclear; therefore, we investigated the effects of TGF-β1/Smad signaling on phosphatidylserine eversion in the renal tubule cell membrane during the early stage of kidney stone development. In a rat model of early stage of calcium oxalate stone formation, phosphatidylserine eversion on the renal tubular cell membrane was detected by flow cytometry, and the expression of TGF-β1 (transforming growth factor-β1), Smad7, and phospholipid scramblase in the renal tubular cell membrane was measured by western blotting. We observed that the TGF-β1/Smad signaling pathway increased phosphatidylserine eversion at the organism level. The results of in vitro studies demonstrated that oxalate exposure to renal tubule cells induced TGF-β1 expression, increasing phospholipid scramblase activity and phosphatidylserine eversion in the renal tubule cell membrane. These results indicate that TGF-β1 stimulates phosphatidylserine eversion by increasing the phospholipid scramblase activity in the renal tubule cell membrane during the early stage of kidney stone development. The results of this study form a basis for further detailed research on the development of therapeutic agents that specifically treat urolithiasis and exert fewer adverse effects.

Phosphate Metabolism and Pathophysiology in Parathyroid Disorders and Endocrine Tumors

The advent of new insights into phosphate metabolism must urge the endocrinologist to rethink the pathophysiology of widespread disorders, such as primary hyperparathyroidism, and also of rarer endocrine metabolic bone diseases, such as hypoparathyroidism and tumor-induced hypophosphatemia. These rare diseases of mineral metabolism have been and will be a precious source of new information about phosphate and other minerals in the coming years. The parathyroid glands, the kidneys, and the intestine are the main organs affecting phosphate levels in the blood and urine. Parathyroid disorders, renal tubule defects, or phosphatonin-producing tumors might be unveiled from alterations of such a simple and inexpensive mineral as serum phosphate. This review will present all these disorders from a ‘phosphate perspective’.

Autophagy in Cisplatin Nephrotoxicity during Cancer Therapy

Cisplatin is a widely used chemotherapeutic agent but its clinical use is often limited by nephrotoxicity. Autophagy is a lysosomal degradation pathway that removes protein aggregates and damaged or dysfunctional cellular organelles for maintaining cell homeostasis. Upon cisplatin exposure, autophagy is rapidly activated in renal tubule cells to protect against acute cisplatin nephrotoxicity. Mechanistically, the protective effect is mainly related to the clearance of damaged mitochondria via mitophagy. The role and regulation of autophagy in chronic kidney problems after cisplatin treatment are currently unclear, despite the significance of research in this area. In cancers, autophagy may prevent tumorigenesis, but autophagy may reduce the efficacy of chemotherapy by protecting cancer cells. Future research should focus on developing drugs that enhance the anti-tumor effects of cisplatin while protecting kidneys during cisplatin chemotherapy.

Autophagy gene ATG7 regulates albumin transcytosis in renal tubule epithelial cells

Receptor-mediated albumin transport in proximal tubule epithelial cells (PTECs) is important to control proteinuria. Autophagy is an evolutionarily conserved degradation pathway and its role in intracellular trafficking through interaction with the endocytic pathway has recently been highlighted. Here, we determined whether autophagy regulates albumin transcytosis in PTECs and suppresses albumin-induced cytotoxicity using human proximal tubule (HK-2) cells. Neonatal Fc-receptor (FcRn), a receptor for albumin transcytosis, partially co-localized with autophagosomes. Recycling of FcRn was attenuated and FcRn accumulated in autophagy related 7 (ATG7) knockdown HK-2 cells. Co-localization of FcRn with RAB7-positive late endosomes and RAB11-positive recycling endosomes was reduced in ATG7 knockdown cells, resulting in decreased recycling of FcRn to the plasma membrane. In ATG7 knockdown cells, albumin transcytosis was significantly reduced and intracellular albumin accumulation was increased. Finally, release of KIM-1, a marker of tubule injury, from ATG7 knockdown cells was increased in response to excess albumin. In conclusion, suppression of autophagy in tubules impairs FcRn transport, thereby inhibiting albumin transcytosis. The resulting accumulation of albumin induces cytotoxicity in tubules.

Marrow-Derived Mesenchymal Stem Cells Transfected with Survinvin Gene Protect Kidney from ischemia-reperfusion Injury in Rats

Objective: To investigate the survival ability of bone marrow Mesenchymal stem cells (MSCs) transfected with survinvin gene in the microenvironment of renal ischemia,and to study the ability and mechanism of repairing renal ischemia-reperfusion injury in rats.Method: Mesenchymal stem cells (MSCs) from bone marrow of male Sprague–Dawley rat were infected with the self‐inactive lentiviral vector and transfected with the Survinvin gene recombinant vector and then EGFP-tagged. After amplification and culture, they were detected by green fluorescence and then retained.48 specific pathogen-free C57BL/6J mice were randomly divided into 4 groups of 12 each. Rats in the control group were only surgically exposed. The other 3 groups were surgically exposed and the bilateral renal arteries were clamped for 45 minutes to restore blood supply, and models of renal ischemia-reperfusion were established. There were control group,ischemia reperfusion group(Marked as IR group), empty virus transfection transplantation group(Marked as MSCs group) or survinvin gene transfection transplantation group(Marked as SVV/MSCs group), and sequentially injected with normal saline,normal saline,1×106 MSCs infected with the self‐inactive lentiviral vector or 1×106 survivin gene-expressing MSCs. At different time points of 1d, 3d, 7d, 14d, collect serum to test blood urea nitrogen detection, to cut the rat kidney section for quantitative analysis, HE staining to observe renal issues changes and the degree of renal tubular damage and IL-10 by using ELISA detection. Result: The MSCs with resuscitation and expansion culture had strong proliferation and good fluorescence. The creatinine urea nitrogen level in the MSCs group and SVV/MSCs group was significantly lower than that in the IR group and control group (p<0.01 or p<0.05). The pathological damage score of HE staining in the kidney was lighter in the stem cell transplantation group, and the SVV/MSCs group was significantly lower than the other two groups (p<0.01 or p<0.05). On the 3rd and 14th day, the number of transplanted cells in the kidney tissue was much higher in the SVV/MSCs group than in the MSCs group. The MSCs expressing EGFP were mainly distributed around the glomerulus, the small vessel inner wall, and the interstitial between the renal tubule and the renal tubule. However, MSCs expressing EGFP were hardly seen on the inner wall of the renal tubule. The levels of protective factors IL-10 increased after renal ischemic injury. SVV/MSCs group was also significantly more than IR group or MSCs group (P<0.01 or p<0.05). And there was no statistical difference from the normal control group on the 14th day.Conclusion: Transfection of Survinifin gene can increase the survival ability of MSCs in ischemic kidney. After transplantation, MSCs are not directly differentiated into injured tubular endothelial cells, which further promote the repair of kidney damage through its strong paracrine effect.