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Background: M2 macrophages have important roles in diseases such as tumours, cardiovascular diseases and renal diseases. This study aimed to determine the effects and protective mechanism of M2 macrophages against oxidative stress injury and apoptosis induced by calcium oxalate crystals (CaOx) in renal tubular epithelial cells (HK-2) under coculture conditions. Methods: THP-1 cells were induced to differentiate into M2 macrophages by using phorbol-12-myristate-13-acetate, IL-4 and IL-13. Morphological features were observed by microscopy. Phenotypic markers were identified by reverse transcription-polymerase chain reaction, Western blot and enzyme-linked immunosorbent assay (ELISA). HK-2 cells were treated with 0.5 mg/mL CaOx crystals and co-cultured with M2 macrophages or apocynin. The viability of HK-2 cells was detected by CCK-8 assay. The lactate dehydrogenase (LDH) activity of HK-2 cells was analysed using a microplate reader. The apoptosis of HK-2 cells was examined by flow cytometry and Hoechst 33258 staining. Reactive oxygen species (ROS) expression and mitochondrial membrane potential in HK-2 cells were detected by a fluorescence microplate reader. Western blot analysis was conducted to detect the expression of p47phox, Bcl-2, cleaved caspase-3, cytochrome c, p38 MAPK, phospho-p38 MAPK, Akt and phospho-Akt. Results: The results of morphology, reverse transcription-polymerase chain reaction, Western blot and ELISA showed that THP-1 cells were successfully polarised to M2 macrophages. The results of co-culture suggested that M2 macrophages or apocynin significantly increased the cell viability and decreased the LDH activity and apoptosis rate after HK-2 cells were challenged with CaOx crystals. The expression of the p47phox protein and the concentration of ROS were reduced, the release of mitochondrial membrane potential and the expression of the Bcl-2 protein were upregulated and the protein expression of cleaved caspase-3 and cytochrome c was downregulated. The expression of the phosphorylated form of p38 MAPK increased. Under coculture conditions with M2 macrophages, the Akt protein of HK-2 cells treated with CaOx crystals was dephosphorylated, but the phosphorylated form of Akt was not reduced by apocynin. Conclusions: M2 macrophages reduced the oxidative stress injury and apoptosis of HK-2 cells by downregulating the activation of NADPH oxidase, reducing the production of ROS, inhibiting the phosphorylation of p38 MAPK and enhancing the phosphorylation of Akt. We have revealed one of the possible mechanisms by which M2 macrophages reduce the formation of kidney stones. [ABSTRACT FROM AUTHOR]

Background/Aims: Nephrolithiasis is a common and frequently occurring disease, its exact pathogenesis is remains unclear. Emerging data suggest that autophagy plays a vital role in the pathophysiological processes of kidney diseases. Therefore, this study was designed to investigate the potential role of autophagy in the formation of calcium oxalate (CaOx) kidney stones in rat model. Methods: Thirty-two rats were randomly divided into four groups (eight rats/group): untreated control group, stone model group, rapamycin-treated group, chloroquine-treated group. Rat models of CaOx nephrolithiasis was administration of 0.75% ethylene glycol (EG) in their drinking water for 4 weeks. Western blot and transmission electron microscope (TEM) were used to detect the expression of autophagy related protein LC3-II, BECN1 and p62 and autophagic vacuoles respectively. Renal function was evaluated by measuring the levels of serum CRE and BUN. Renal tubular injury markers NGAL and Kim-1 was determined by ELISA kits. Von Kossa staining was used to assess crystal deposits and histological tissue injury. TUNEL staining was employed to assess apoptosis of the renal tubular cell. Results: Compare with the controls, the expression of autophagy related protein LC3-II, BECN1 and number of autophagic vacuoles were increased significantly, whereas the p62 protein level was decreased in the stone model group. The levels of apoptosis, serum CRE and BUN, NGAL and Kim-1 in the stone model group were increased compared with the control group and crystals deposition and renal injury were increased significantly. However, the levels of autophagy, kidney injury and crystal deposition were decreased by chloroquine but increased by rapamycin. Conclusion: These findings suggested that rats were administration of ethylene glycol could lead to the formation of CaOx nephrolithiasis and autophagy activation. Inhibiting autophagy could be an effective therapeutic approach for decreasing the formation of nephrolithiasis. [ABSTRACT FROM AUTHOR]