Hydroxyapatite nanoparticles (HAP) have been widely used in various fields because of their natural biological origin and functional properties. The emerging evidence on their toxicities has attracted research interest. HAP-induced vascular smooth muscle cell (VSMC) damage is a key step in vascular calcification (VC), particularly in patients with chronic kidney disease. However, the injury effects and mechanism of action of HAP on VSMCs have not been extensively investigated. This study comprehensively characterized commercially available HAP and investigated its adverse biological effects in cultured A7R5 cells. In vitro experiments revealed that internalized HAP was localized in lysosomes, followed by the release of Ca ²⁺ owing to the low pH microenvironment. Upon Ca ²⁺ homeostasis, Ca ²⁺ enters the mitochondria, leading to the simultaneous generation of reactive oxygen species (ROS). ROS subsequently attack mitochondrial transmembrane potentials, promote mitochondrial ROS production, and oxidize mitochondrial DNA (Ox-mtDNA). Mitochondrial permeability-transition pores open, followed by the release of more Ox-mtDNA from the mitochondria into the cytosol due to the redox imbalance. This activates NLRP3/caspase-1/gasdermin D-dependent pyroptosis and finally excretes inflammatory factors to induce VC; an antioxidant could rescue this process. It has been suggested that HAP could induce an imbalance in intracellular Ca ²⁺ homeostasis in A7R5 cells, followed by the promotion of mitochondrial dysfunction and cell pyroptosis, finally enhancing VC. To detect the in vivo toxicity of HAP, mice were treated with Cy7-labelled HAP NPs for 24 h. In vivo results also demonstrated that HAP accumulated in the kidneys, accompined with increased Ca concentration, upregulated oxidative stress-related factor and kidney damage. Overall, our research elucidates the mechanism of calcium homeostasis and redox imbalance, providing insights into the prevention of HAP-induced cell death.

Background: Recommended regular saline flushing presents clinical ineffectiveness for hemodialysis (HD) patients at high risk of bleeding with heparin contraindication. Regional citrate anticoagulation (RCA) has previously been used with a Ca²⁺containing dialysate with prefiltered citrate in one arm (RCA-one). However, anticoagulation is not always achievable and up to 40% results in serious clotting in the venous expansion chamber. In this study, we have transferred one-quarter of the TSC from the prefiltered to the post filter based on RCA-one, which we have called RCA-two. The objective of this study was to compare the efficacy and safety of RCA-two with either saline flushing or RCA-one in HD patients with a high bleeding risk.Method: In this investigator-initiated, multicenter, controlled, prospective, randomized clinical trial, 52 HD patients (77 sessions) were randomized to the RCA-2 and RCA-one group in part one of the trial, and 45 patients (64 sessions) were randomized to the RCA-2 and saline group in part two of the trial. Serious clotting events, adverse events and blood analyses were recorded.Results: Serious clotting events in the RCA-two group were significantly lower compared with the RCA-one and saline group (7.89% vs. 30.77%,P = 0.011; 3.03% vs. 54.84%,P < 0.001, respectively). The median circuit survival time was 240 min (IQR 240 to 240) in the RCA-two group, was significantly longer than 230 min (IQR 155 to 240,P < 0.001) in the RCA-one group and 210 min (IQR 135 to 240,P = 0.003) in the saline group. The majority of the AEs were hypotension, hypoglycemia and chest tightness, most of which were mild in intensity. Eight patients (20.51%) in the RCA-one group, 4 patients (12.90%) in the saline group and 10 patients (26.31%) in the RCA-two group,P > 0.05.Conclusions: Our data demonstrated that the modified anticoagulation protocol was more effective and feasible during hemodialysis therapy for patients at high risk of bleeding.Trial registration: GDREC,GDREC2017250H. Registered February 2, 2018; retrospectively registered.

Background: Arteriovenous fistulas (AVF) have been the main vascular accesses for haemodialysis patients, but the maintenance after maturation poses serious challenges. Arm exercises promote the maturation of AVFs. However, few studies have evaluated the effect of arm exercise on matured AVF and addressed the intervention for late fistula failure. Objectives: The study was conducted to explore the effect of dumbbell exercise on mature AVF. Methods: 86 participants undergoing haemodialysis with AVFs were randomized into the control group and experimental group. The experimental group held 6-pound dumbbells on non-dialysis days for 3 months, while the control group squeezed rubber balls. Results: For blood flow of draining vein (DV; primary outcome), the between-group effects, interaction effect and time effect showed significant differences. A significant increase in blood flow of DV was observed in the dumbbell group at the 3rd month (mean difference, 359.50 [111.90–829.05] mL/min; p = 0.001). The difference in blood flow of AVF proximal artery, blood flow of brachial artery, the diameter of DV and the incidence of adverse events at 3 months (secondary outcomes) between the 2 groups was insignificant. Conclusion: Prolonged training with arm exercises is essential for patients with AVFs though the fistula has matured. The designed dumbbell exercise is an economical, effective intervention to maintain the function of AVF, especially for patients with potential reduction of access blood flow and no percutaneous transluminal angioplasty indication.

Introduction: Restoration of podocyte autophagy is considered as a feasible strategy for the treatment of diabetic kidney disease (DKD). This study aimed at investigating the protective effect and potential mechanism of vitamin D on podocyte injury of DKD. Methods: Type 2 diabetic db/db mice received intraperitoneal injections of vitamin D analog paricalcitol 400 ng/kg per day for 16 weeks. Immortalized mouse podocytes were cultured in high glucose (HG) medium with active vitamin D3 calcitriol or autophagy inhibitor 3-methyladenine. Renal function and urine albumin creatinine ratio were assessed at week 24. HE, PAS staining, and electron microscopy were used to evaluate renal histopathology and morphological changes. Immunohistochemistry, immunofluorescence, and Western blot were used to evaluate protein expression of nephrin and podocin in kidney tissue and podocytes. The expression of autophagy-related proteins (LC3, Beclin-1, Vps34) and apoptosis-related proteins (cleaved caspase-3, Bax) was determined by Western blotting. Podocyte apoptosis was further evaluated by using flow cytometer. Results: Albuminuria in a db/db mouse model was markedly attenuated after treatment with paricalcitol. This was accompanied by alleviation of mesangial matrix expansion and podocyte injury. Besides, the impaired autophagy in podocytes under diabetic conditions was also markedly enhanced after paricalcitol or calcitriol treatment, accompanied by restored decreased podocyte slit diaphragm proteins podocin and nephrin. Furthermore, the protective effect of calcitriol against HG-induced podocyte apoptosis could be abated by autophagy inhibitor 3-methyladenine. Conclusion: Vitamin D ameliorates podocyte injury of DKD by enhancing podocyte autophagy activity, which may become a potential candidate autophagy activator for the therapeutic interventions for DKD.