Tight junction plays important roles in regulating paracellular transports and maintaining cell polarity. Calcium oxalate monohydrate (COM) crystals, the major crystalline composition of kidney stones, have been demonstrated to be able to cause tight junction disruption to accelerate renal cell injury. However, the cellular signaling involved in COM crystal-induced tight junction disruption remains largely to be investigated. In the present study, we proved that COM crystals induced tight junction disruption by activating ROS/Akt/p38 MAPK pathway. Treating Madin–Darby canine kidney (MDCK) cells with COM crystals induced a substantial increasing of ROS generation and activation of Akt that triggered subsequential activation of ASK1 and p38 mitogen-activated protein kinase (MAPK). Western blot revealed a significantly decreased expression of ZO-1 and occludin, two important structural proteins of tight junction. Besides, redistribution and dissociation of ZO-1 were observed by COM crystals treatment. Inhibition of ROS by N-acetyl-l-cysteine (NAC) attenuated the activation of Akt, ASK1, p38 MAPK, and down-regulation of ZO-1 and occludin. The redistribution and dissociation of ZO-1 were also alleviated by NAC treatment. These results indicated that ROS were involved in the regulation of tight junction disruption induced by COM crystals. In addition, the down-regulation of ZO-1 and occludin, the phosphorylation of ASK1 and p38 MAPK were also attenuated by MK-2206, an inhibitor of Akt kinase, implying Akt was involved in the disruption of tight junction upstream of p38 MAPK. Thus, these results suggested that ROS-Akt-p38 MAPK signaling pathway was activated in COM crystal-induced disruption of tight junction in MDCK cells.
To our knowledge our findings are the first to show that oxalate induced increased reactive oxygen species generation impairs aminophospholipid translocase activity and decreased aminophospholipid translocase activity has a role in hyperoxaluria promoted calcium oxalate urolithiasis by facilitating phosphatidylserine redistribution in renal epithelial cells.
Background/Aims: Renal calculi represent a prevalent disorder associated with mineral deposition in renal calyces and the pelvis. Aberrant microRNA (miRNA) expression is implicated in renal injury. This study investigated the mechanism of miR-141-3p in calcium oxalate (CaOx) crystals-induced renal tubular epithelial cell (RTEC) injury.
Methods: Human RTECs HK-2 cells were treated with CaOx crystals to induce RTEC injury. Cell viability was evaluated using CCK-8 assay and apoptosis was measured using flow cytometry. The contents of lactate dehydrogenase (LDH), malondialdehyde (MDA), superoxide dismutase (SOD), IL-1β, and IL-18 were measured using ELISA kits. The expressions of NLRP3, cleaved caspase-1, and GSDMD-N were detected using Western blot. miR-141-3p and NLRP3 expressions were determined using RT-qPCR. The binding of miR-141-3p and NLRP3 was validated using a dual-luciferase assay. The role of NLRP3 in the protection of miR-141-3p on RTEC injury was verified using functional rescue experiments.
Results: CaOx crystals induced RTEC injury, manifested as attenuated cell viability, enhanced apoptosis, elevated intracellular LDH and MDA levels, and decreased SOD level. Pyroptosis of RTECs was enhanced by CaOx crystal induction, evidenced by elevated expressions of cleaved caspase-1, GSDMD-N, IL-1β, and IL-18. miR-141-3p expression was reduced in CaOx crystals-induced RTECs. miR-141-3p overexpression alleviated CaOx crystals-induced RTEC injury and suppressed pyroptosis of RTECs. miR-141-3p bound to NLRP3 and thereby repressed NLRP3 expression. NLRP3 overexpression reversed the protective effect of miR-141-3p overexpression on RTECs.
Conclusion: miR-141-3p repressed NLRP3-mediated pyroptosis by suppressing NLRP3 expression, thus protecting CaOx crystals-induced RTEC injury.
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