Autophagy-endoplasmic reticulum stress inhibition mechanism of superoxide dismutase in the formation of calcium oxalate kidney stones

Sulfated Pelvetia siliquosa Polysaccharides Inhibit CaOx Stone Formation by Inhibiting Calcium Oxalate Crystallization, Cellular Inflammation, and Crystal Adhesion

Hyperoxaluria can easily induce calcium oxalate (CaOx) crystals and cause cell damage, thereby increasing the risk of kidney stone formation. In this study, three sulfated Pelvetia siliquosa polysaccharides (PSPs) were obtained by the sulfur trioxide-pyridine method. The antioxidant activity of PSPs and the inhibitory effects of PSPs on CaOx crystallization, cellular oxidative damage, and cellular inflammation were explored in vitro, and PSPs were used to treat hyperoxaluria-induced crystallization model mice in order to validate the stone-preventive effect of PSPs in vivo. PSPs can inhibit CaOx crystal formation, as well as reduce reactive oxygen species (ROS) levels through their own antioxidant properties and up-regulation of antioxidant enzyme (SOD and CAT) expression, which in turn reduces the release of lactate dehydrogenase (LDH) and malondialdehyde (MDA), improves lysosomal integrity, cellular morphology, and cytoskeleton, inhibits the decrease of mitochondrial membrane potential, reduces adhesion protein (CD44 and OPN) expression, alleviates cellular inflammatory factor (IL-6, TNF-α, and IL-1β) levels, and inhibits apoptosis. PSP3, which has the highest degree of sulfation, had the best protection capacity. PSP3 also showed good antistone ability in mice, and it may be a potential drug for kidney stone prevention.

Combination drug therapy prevents CIAKI by suppressing ER stress-induced apoptosis

Contrast-induced acute kidney injury (CIAKI) is an important clinical complication that occurs after the application of contrast agent in percutaneous coronary intervention. The pathogenesis of CIAKI is complex. Studies have shown that cell apoptosis induced by endoplasmic reticulum stress (ERS) plays an important role in renal tubular injury in CIAKI. These findings suggest that atorvastatin, probucol and alprostadil can inhibit renal tubular cell apoptosis to prevent CIAKI. However, there is no specific research on the above effects of drug combinations. Therefore, this study aimed to establish a rat CIAKI model with meglumine diatrizoate and add drug intervention to compare the influence of combined drugs with that of atorvastatin alone on CIAKI via the inhibition of ERS-specific molecular chaperones. Fifty Wistar rats were randomly divided into 5 groups: Group A + CC (atorvastatin group, n = 10); Group PA + CC (probucol + atorvastatin group, n = 10); Group AA + CC (alprostadil + atorvastatin group, n = 10); Group PCC (contrast group, n = 10); and Group NCC (control group, n = 10). Among the five groups, Group PCC presented the significantly highest creatinine increase rate and protein and nucleic acid expression levels, with the most severe cell injury and apoptosis observed via HE and TUNEL staining. Compared with those in the atorvastatin group, the rate of increase in creatinine and protein expression in the combined treatment groups were decreased to some extent, and the histological morphology was also improved. This was especially evident in Group AA + CC. Renal cell apoptosis induced by the ERS pathway may play an important role in the pathogenesis of CIAKI induced by meglumine diatrizoate. Atorvastatin, probucol and alprostadil can prevent the occurrence of CIAKI, and the ERS-induced apoptosis pathway is involved in this mechanism. The protective effect of probucol or alprostadil combined with atorvastatin on CIAKI may be stronger than that of atorvastatin alone, with a greater effect of the combination of alprostadil and atorvastatin.

Association between atherosclerosis and the development of multi-organ pathologies

Atherosclerosis is a chronic inflammatory disease affecting the vascular system, characterised by the accumulation of modified lipoproteins, immune cell aggregation and the development of fibrous tissue within blood vessel walls. As atherosclerosis impacts blood vessels, its adverse effects may manifest across various tissues and organs. In this review, we examine the association of atherosclerosis with Alzheimer's disease, stroke, pancreatic and thyroid dysfunction, kidney stones and chronic kidney diseases. In several cases, the reciprocal causative effect of these diseases on the progression of atherosclerosis is also discussed. Particular attention is given to common risk factors, biomarkers and identified molecular mechanisms linking the pathophysiology of atherosclerosis to the dysfunction of multiple tissues and organs. Understanding the role of atherosclerosis and its associated microenvironmental conditions in the pathology of multi-organ disorders may unveil novel therapeutic avenues for the prevention and treatment of cardiovascular and associated diseases.

Sigma-1 receptor exerts protective effects on ameliorating nephrolithiasis by modulating endoplasmic reticulum-mitochondrion association and inhibiting endoplasmic reticulum stress-induced apoptosis in renal tubular epithelial cells

Oxalate-induced damage to renal tubular epithelial cells (RTECs) is an essential factor in the incident kidney stone, but the specific mechanism is unclear. Recent research has pinpointed interacting areas within the endoplasmic reticulum and mitochondria, called mitochondria-associated membranes (MAMs). These studies have linked endoplasmic reticulum stress (ERS) and oxidative imbalance to kidney disease development. The sigma-1 receptor (S1R), a specific protein found in MAMs, is involved in various physiological processes, but its role in oxalate-induced kidney stone formation remains unclear. In this study, we established cellular and rat models of oxalate-induced kidney stone formation to elucidate the S1R's effects against ERS and apoptosis and its mechanism in oxalate-induced RTEC injury. We found that oxalate downregulated S1R expression in RTECs and escalated oxidative stress and ERS, culminating in increased apoptosis. The S1R agonist dimemorfan up-regulated S1R expression and mitigated ERS and oxidative stress, thereby reducing apoptosis. This protective effect was mediated through S1R inhibition of the CHOP pathway. Animal experiments demonstrated that S1R's activation attenuated oxalate-induced kidney injury and alleviated kidney stone formation. This is the first study to establish the connection between S1R and kidney stones, suggesting S1R's protective role in inhibiting ERS-mediated apoptosis to ameliorate kidney stone formation.

Mitochondrial dysfunction and NLRP3 inflammasome: key players in kidney stone formation

The mitochondrion serves as a critical intracellular organelle, engaging in essential roles in the regulation of energy production, oxidative stress management, calcium homeostasis, and apoptosis. One such disease that has been particularly associated with these functions is kidney stone disease (KSD), specifically calcium oxalate (CaOx). It is underpinned by oxidative stress and tissue inflammation. Recent studies have shed light on the vital involvement of mitochondrial dysfunction, the nucleotide-binding domain and leucine-rich repeat containing protein 3 (NLRP3) inflammasome, endoplasmic reticulum stress and subsequent cell death in CaOx crystal retention and aggregation. These processes are pivotal in the pathogenesis of kidney stone formation. This review focuses on the pivotal roles of mitochondria in renal cell functions and provides an overview of the intricate interconnectedness between mitochondrial dysfunction and NLRP3 inflammasome activation in the context of KSD. It is essential to recognise the utmost significance of gaining a comprehensive understanding of the mechanisms that safeguard mitochondrial function and regulate the NLRP3 inflammasome. Such knowledge carries significant scientific implications and opens up promising avenues for the development of innovative strategies to prevent the formation of kidney stones.

Association between cardiometabolic index and kidney stone from NHANES: a population-based study

Purpose

The Cardiometabolic Index (CMI) is a novel marker of visceral obesity and dyslipidemia. Our study aimed to explore the association between CMI and kidney stones among US adults.

Methods

This cross-sectional study was conducted among adults with complete records of CMI and kidney stones information from the 2011 to 2018 National Health and Nutrition Examination Survey (NHANES). Inverse probability treatment weighting (IPTW) was used to balance the baseline characteristics of the study population. The independent relationship between CMI and kidney stones was evaluated using IPTW-adjusted multivariate logistic regression, restricted cubic splines (RCS), and subgroup analysis.

Results

A total of 9,177 participants, with an average CMI of 0.72 (0.99), were included in this study. The IPTW-adjusted logistic regression revealed that CMI was an independent risk factor for kidney stones. The adjusted odds ratio (OR) for kidney stones were 1.39 (95% CI: 1.24 - 1.56, P < 0.001) for the second CMI tertile and 1.31 (95% CI: 1.17 - 1.47, P < 0.001) for the third CMI tertile, compared with the first CMI tertile. A linear relationship between CMI levels and kidney stone risk was observed in the RCS analysis. Subgroup analysis showed that the association between CMI levels and kidney stone risk remained stable across groups.

Conclusions

A positive association between CMI level and the risk of kidney stones was observed among US adults in our study. Further large-scale prospective studies are needed to validate our findings.

Screening of oxalate-degrading probiotics and preventive effect of Lactiplantibacillus plantarum AR1089 on kidney stones

Calcium oxalate stone is the main type of kidney stone, so far there is no specific drug treatment. Here, we screened for oxalate-degrading probiotics and evaluated the potential preventive effect of lactic acid bacteria in rats with hyperoxaluria-induced kidney stones. The oxalate degradation efficiencies of the probiotics were determined to be 5-20% by in vitro experiments, of which the degradation efficiencies of Lactiplantibacillus plantarum AR342 and L. plantarum AR1089 were 17.32% and 14.15%, respectively. Through animal experiments, we found that L. plantarum AR1089 significantly attenuated kidney injury, as demonstrated by improving renal dysfunction and renal fibrosis, lowering creatinine and urea nitrogen levels. L. plantarum AR1089 was also effective in decreasing the number of calcium oxalate crystals in the urine and kidneys as well as ameliorating oxidative stress as evidenced by lowering the level of MDA and decreasing the level of SOD and CAT. Moreover, supplementation of L. plantarum AR1089 inhibited renal crystalline deposition by down-regulating the expression of KIM-1, OPN and MCP-1, and prevented hyperoxaluria-induced kidney stones by regulating the gut microbiota. Taken together, the present study shows that oral administration of L. plantarum AR1089, by attenuating kidney injury and regulating gut microbiota, is a potential therapy to reduce calcium oxalate crystals and prevent the progression of kidney stones.

Mitochondrial dysfunction in kidney stones and relief of kidney stones after reducing mtROS

Mitochondria are essential organelles because they generate the energy required for cellular functions. Kidney stones, as one of the most common urological diseases, have garnered significant attention. In this study, we first collected peripheral venous blood from patients with kidney stones and used qRT-PCR to detect mitochondrial DNA (mtDNA) copy number as a means of assessing mitochondrial function in these patients. Subsequently, through Western blotting, qPCR, immunofluorescence, immunohistochemistry, and transmission electron microscopy, we examined whether calcium oxalate crystals could cause mitochondrial dysfunction in the kidney in both in vitro and in vivo. We then examined the intersection of the DEGs obtained by transcriptome sequencing of the mouse kidney stone model with mitochondria-related genes, and performed KEGG and GO analyses on the intersecting genes. Finally, we administered the mitochondrial ROS scavenger Mito-Tempo in vivo and observed its effects. Our findings revealed that patients with kidney stones had a reduced mtDNA copy number in their peripheral venous blood compared to the control group, suggesting mitochondrial dysfunction in this population. This conclusion was further validated through in vitro and in vivo experiments. Enrichment analyses revealed that the intersecting genes were closely related to metabolism. We observed that after mitochondrial function was preserved, the deposition of calcium oxalate crystals decreased, and the kidney damage and inflammation caused by them were also alleviated. Our research indicates that kidney stones can cause mitochondrial dysfunction. After clearing mtROS, the damage and inflammation caused by kidney stones are reversed, providing new insights into the prevention and treatment of kidney stones.

Machine learning and 4D-LFQ quantitative proteomic analysis explore the molecular mechanism of kidney stone formation

Background

Nephrolithiasis, a common and chronic urological condition, exerts significant pressure on both the general public and society as a whole. The precise mechanisms of nephrolith formation remain inadequately comprehended. Nevertheless, the utilization of proteomics methods has not been employed to examine the development of renal calculi in order to efficiently hinder and manage the creation and reappearance of nephrolith. Nowadays, with the rapid development of proteomics techniques, more efficient and more accurate proteomics technique is utilized to uncover the mechanisms underlying diseases. The objective of this study was to investigate the possible alterations of HK-2 cells when exposed to varying amounts of calcium oxalate (CaOx). The aim was to understand the precise development of stone formation and recurrence, in order to find effective preventive and treatment methods.

Methods

To provide a complete view of the proteins involved in the development of nephrolithiasis, we utilized an innovative proteomics method called 4D-LFQ proteomic quantitative techniques. HK-2 cells were selected as our experimental subjects. Three groups (n = 3) of HK-2 cells were treated with intervention solutions containing 0 (negative control, NC), 1 mM, and 2 mM CaOx, respectively. For the proteins that showed differential expression, various analyses were conducted including examination of Gene Ontology (GO), Clusters of Orthologous Groups of proteins (KOG), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, enrichment analysis of protein domains, and hierarchical clustering analysis. The STRING database was used to identify the interaction network of the chosen proteins. Candidate proteins were validated using parallel reaction monitoring (PRM) in the end.

Results

All three groups verified the repeatability of samples. According to the results of 4D-LFQ proteomic quantitative analysis, there were 120, 262, and 81 differentially expressed proteins (DEPs) in the 1 mM-VS-NC, 2 mM-VS-NC, and 2 mM-VS-1mM conditions, respectively. According to GO annotation, the functional enrichment analysis indicates that the differentially expressed proteins (DEPs) were notably enriched in promoting cell migration and the extracellular matrix, among other functions. Analysis of enrichment, based on the KEGG pathway, revealed significant enrichment of DEPs in complement and coagulation cascades, as well as in ECM-receptor (extracellular matrix-receptor) interaction and other related pathways. 14 DEPs of great interest were selected as candidate proteins, including FN1, TFRC, ITGA3, FBN1, HYOU1, SPP1, HSPA5, COL6A1, MANF, HIP1R, JUP, AXL, CTNNB1 and DSG2.The data from PRM demonstrated the variation trend of 14 DEPs was identical as 4D-LFQ proteomic quantitative analysis.

Conclusion

Proteomics studies of CaOx-induced HK-2 cells using 4D-LFQ proteomic quantitative analysis and PRM may help to provide crucial potential target proteins and signaling pathways for elucidating the mechanism of nephrolithiasis and better treating nephrolithiasis.

Investigating the attenuating effects of metformin-loaded selenium nanoparticles coupled with Myrtus communis L. flower extract on CaOx deposition in male Sprague Dawley rat kidneys via regulating MAPK signaling pathway

Kidney stones are a foremost clinical concern in urology with CaOx crystals accounting for roughly 80% of these renal formations. This research endeavor seeks to ascertain the protective effects of Metformin-encapsulated selenium nanoparticles (M@Se NPs), combined with a 55% hydroethanolic flower extract from Myrtus communis L. (MCL) in countering the formation of kidney stones in Male Sprague Dawley rats. The particle's diameter was measured to be 39 nm and 13.8 nm from DLS and HR-TEM analysis. Rat groups administered with the MCL-M@Se NPs (1:1.5:1) exhibited reduced renal stone formation in urine and serum analysis compared to the negative control group. Histological evaluations of kidney samples using H&E, and MTS staining indicated a subdued presence of ECM deposition in contrast to other rat groups. Conclusively, the protective mechanism of MCL-M@Se NPs against CaOx stone damage can be confidently attributed to the obstruction of the MAPK signaling pathway.

Remodeling brain pathological microenvironment to lessen cerebral ischemia injury by multifunctional injectable hydrogels

Ischemia stroke is one of the leading causes of death and disability worldwide. Owing to the limited delivery efficiency to the brain caused by the blood-brain barrier (BBB) and off-target effects of systemic treatment, it is crucial to develop an in situ drug delivery system to improve the therapeutic effect in ischemic stroke. Briefly, we report a multifunctional in situ hydrogel delivery system for the co-delivery of reactive oxygen species (ROS)-responsive nanoparticles loaded with atorvastatin calcium (DSPE-se-se-PEG@AC NPs) and β-nerve growth factor (NGF), which is expected to remodel pathological microenvironment for improving cerebral ischemia injury. The in vitro results exhibited the multifunctional hydrogel scavenged oxygen-glucose deprivation (OGD)-induced free radical, rescued the mitochondrial function, and maintained the survival and function of neurons, hence reducing neuronal apoptosis and neuroinflammation, consequently relieving ischemia injury in hippocampal neurons cell line (HT22). In the rat ischemia stroke model, the hydrogel significantly minified cerebral infarction by regulating inflammatory response, saving apoptotic neurons, and promoting angiogenesis and neurogenesis. Besides, the hydrogel distinctly improved the rats' neurological deficits after cerebral ischemia injury over the long-term observation. In conclusion, the in-situ hydrogel platform has demonstrated promising therapeutic effects in both in vitro and in vivo studies, indicating its potential as a new and effective therapy.

Ferroptosis and its emerging role in kidney stone formation

Kidney stone is a common and highly recurrent disease in urology, and its pathogenesis is associated with various factors. However, its precise pathogenesis is still unknown. Ferroptosis describes a form of regulated cell death that is driven by unrestricted lipid peroxidation, which does not require the activation of caspase and can be suppressed by iron chelators, lipophilic antioxidants, inhibitors of lipid peroxidation, and depletion of polyunsaturated fatty acids. Recent studies have shown that ferroptosis plays a crucial role in kidney stone formation. An increasing number of studies have shown that calcium oxalate, urate, phosphate, and selenium deficiency induce ferroptosis and promote kidney stone formation through mechanisms such as oxidative stress, endoplasmic reticulum stress, and autophagy. We also offered a new direction for the downstream mechanism of ferroptosis in kidney stone formation based on the "death wave" phenomenon. We reviewed the emerging role of ferroptosis in kidney stone formation and provided new ideas for the future treatment and prevention of kidney stones.

Spectroscopic investigation of phase transformation of calcium oxalate dehydrates (renal calculi) using acidic Bryophyllum pinnatom powder

Urolithiasis is one of most common renal disorders, characterized by the formation of kidney stones (renal calculi) through the crystallization process within the urinary system. The frequently observed renal calculi are calcium oxalate renal calculi and treatment is done by shock wave method or lithotripsy which is harmful for other cells of the internal system. The objective of this work was to evaluate in vitro diagnosis of calcium oxalate kidney stones in the aqueous solution of Bryophyllum pinnatum. The B. pinnatum powder was mixed in apple cider vinegar and lemon juice separately to make solution 1 and 2 respectively. Apple cider vinegar and lemon juice were used as solvents due to their acidic and body compatible nature. Two surgically removed stones was dipped in solution 1 and 2. After two weeks, kidney stone of weight 2.7 g is completely dissolved in solution 2 while a considerable weight reduction of other kidney stone has been observed in solution 1. Fourier transform infrared (FTIR) spectroscopy results show the presence of two strong absorption peaks at 610 and 912 (cm-1) in both solutions after dissolution of urinary stones are related to calcium oxalate dehydrate (COD). Raman spectra further confirm the dissolution of COD in solution having Raman shifts at 504 and 910 (cm-1). Cluster formation and aggregation of particles has been observed in scanning electron microscopy images. This in vitro study proves that a mixture of Bryophyllum pinnatum powder and lemon juice is a best remedy to remove kidney stones.

Protective Effect of Alkaline Mineral Water on Calcium Oxalate-Induced Kidney Injury in Mice

Background

Kidney stone disease induces chronic renal insufficiency by crystal-induced renal tubular epithelial cell injury. It has been reported that the prevalence of kidney stone disease is increasing, accompanied by the high recurrence rate. Alkaline mineral water has been reported to possess beneficial effects to attenuate inflammation. Here, we explored the potential protective effects and underlying mechanisms of alkaline mineral water against calcium oxalate-induced kidney injury.

Methods

We performed the mice kidney stone model by administering glyoxylate at 100 mg/kg once daily for 7 days. To assess the effects of alkaline mineral water on oxalate-induced kidney injury, mice drank different water (distilled water, natural mineral water at pH = 8.0, as well as natural mineral water at pH = 9.3) for 7 days, respectively, followed by glyoxylate exposure. After collection, crystal formation, kidney injury and cell apoptosis, fibrosis, oxidative stress, as well as inflammation were measured.

Results

Our results showed that glyoxylate treatment led to kidney crystal formation and fibrosis, which can be attenuated by drinking alkaline mineral water. Furthermore, alkaline mineral water also reduced kidney injury and cell apoptosis, oxidative stress, and inflammation.

Conclusion

Alkaline mineral water supplement prevents progression of glyoxylate-induced kidney stones through alleviating oxidative stress and inflammation.

Metabolic changes in kidney stone disease

Kidney stone disease (KSD) is one of the earliest medical diseases known, but the mechanism of its formation and metabolic changes remain unclear. The formation of kidney stones is a extensive and complicated process, which is regulated by metabolic changes in various substances. In this manuscript, we summarized the progress of research on metabolic changes in kidney stone disease and discuss the valuable role of some new potential targets. We reviewed the influence of metabolism of some common substances on stone formation, such as the regulation of oxalate, the release of reactive oxygen species (ROS), macrophage polarization, the levels of hormones, and the alternation of other substances. New insights into changes in substance metabolism changes in kidney stone disease, as well as emerging research techniques, will provide new directions in the treatment of stones. Reviewing the great progress that has been made in this field will help to improve the understanding by urologists, nephrologists, and health care providers of the metabolic changes in kidney stone disease, and contribute to explore new metabolic targets for clinical therapy.

Ferroptosis in calcium oxalate kidney stone formation and the possible regulatory mechanism of ANKRD1

The objective of this study was to explore the role of ferroptosis in the formation of calcium oxalate (CaOx) kidney stones and the regulatory mechanism of the ankyrin repeat domain 1 (ANKRD1) gene. The study found that the Nrf2/HO-1 and p53/SLC7A11 signaling pathways were activated in the kidney stone model group, and the expression of the ferroptosis marker proteins SLC7A11 and GPX4 was significantly reduced, while the expression of ACSL4 was significantly increased. The expression of the iron transport-related proteins CP and TF increased significantly, and Fe²⁺ accumulated in the cell. The expression of HMGB1 increased significantly. In addition, the level of intracellular oxidative stress was increased. The gene with the most significant difference caused by CaOx crystals in HK-2 cells was ANKRD1. Silencing or overexpression of ANKRD1 by lentiviral infection technology regulated the expression of the p53/SLC7A11 signaling pathway, which regulated the ferroptosis induced by CaOx crystals. In conclusion, CaOx crystals can mediate ferroptosis through the Nrf2/HO-1 and p53/SLC7A11 pathways, thereby weakening the resistance of HK-2 cells to oxidative stress and other unfavorable factors, enhancing cell damage, and increasing crystal adhesion and CaOx crystal deposition in the kidney. ANKRD1 participates in the formation and development of CaOx kidney stones by activating ferroptosis mediated by the p53/SLC7A11 pathway.

The role of autophagy in calcium oxalate kidney stone: A systematic review of the literature

Background: Calcium oxalate kidney stone is one of the common diseases in the urinary system and has a high recurrence rate. Currently, the pathogenesis of kidney stone and the methods to prevent recurrence are still being investigated. Autophagy, as an event of cellular self-repair, has received attention in the field of kidney stone in recent years. In some current studies, autophagy has shown destructiveness and protectiveness in the pathogenesis of kidney stone. The inhibition or promotion of autophagy may be a key target for future kidney stone therapy. This systematic literature review discusses the function of autophagy in kidney stone pathogenesis in the context of current research and synthesizes the evidence analysis to provide a basis for new future therapies.

Method: We systematically reviewed the literature during September 2021 according to the Preferred Reporting Items for Systematic Evaluation and Meta-Analysis (PRISMA) guidelines. Articles on studying the role of autophagy in the pathogenesis of calcium oxalate kidney stone were extracted from PubMed, MEDLINE, Embase and Scopus, including in vivo versus in vitro experiments. The study topic, language and publication date were not restricted. Two authors (Li and Zhou) searched and screened the literature.

Results: We screened 18 articles from the 33 collected articles, of which 6 conducted in vitro cellular studies, four conducted animal studies, eight conducted cellular studies with animal studies, and five studied human specimens. In early studies, the literature generally concluded that autophagy is deleterious in the development of kidney stone. In 2020, the idea of the protectiveness of autophagy associated with kidney stone was first proposed and focused on targeting transcription factor EB. In addition, the interaction of autophagy with other cellular events and the regulation of signaling molecules are focused on in this paper.

Conclusion: This systematic review provides advances in research on the role of autophagy in renal calculi. The current studies suggest that both upregulation and downregulation of autophagy may ameliorate injury in kidney stone models. The authors prefer the upregulation of autophagy as a future research direction for kidney stone treatment.

4-PBA rescues hyperoxaluria induced nephrolithiasis by modulating urinary glycoproteins: Cross talk between endoplasmic reticulum, calcium homeostasis and mitochondria

AIM

Urinary glycoproteins such as Tamm Horsfall Protein (THP) and Osteopontin (OPN) are well established key regulators of renal stone formation. Additionally, recent revelations have highlighted the influence of Endoplasmic Reticulum (ER) and mitochondria of crucial importance in nephrolithiasis. However, till date conclusive approach highlighting the influence of ER stress on urinary glycoproteins and chaperone in nephrolithiasis remains elusive. Therefore, the present study was focussed on deciphering the possible effect of 4-PBA mitigating ER stress on urinary glycoproteins and calnexin (chaperone) with emphasis on interlinking calcium homeostasis in hyperoxaluric rats.

MATERIAL AND METHODS

Post 9 days of treatment, animals were sacrificed, and renal tissues were investigated for urinary glycoproteins, calnexin, calcium homeostasis, ER environment, redox status, and mitochondrial linkage.

KEY FINDINGS

4-PBA appreciably reversed the altered levels of THP, OPN, and calnexin observed along with curtailing the disrupted calcium homeostasis when assessed for SERCA activity and intra-cellular calcium levels. Additionally, significant improvement in the perturbed ER environment as verified by escalated ER stress markers, disturbed protein folding-aggregation-degradation (congo red assay) pathway, and redox status was found post 4-PBA intervention. Interestingly, linkage of ER stress and mitochondria was established under hyperoxaluric conditions when assessed for protein levels of VDAC1 and GRP75.

SIGNIFICANCE

4-PBA treatment resulted in rectifying the repercussions of ER-mitochondrial caused distress when assessed for protein folding/aggregation/degradation events along with disturbed calcium homeostasis. The present study advocates the necessity to adopt a holistic vision towards hyperoxaluria with emphasis on glycoproteins and ER environment.

The repositioned drugs disulfiram/diethyldithiocarbamate combined to benznidazole: Searching for Chagas disease selective therapy, preventing toxicity and drug resistance

Chagas disease (CD) affects at least 6 million people in 21 South American countries besides several thousand in other nations all over the world. It is estimated that at least 14,000 people die every year of CD. Since vaccines are not available, chemotherapy remains of pivotal relevance. About 30% of the treated patients cannot complete the therapy because of severe adverse reactions. Thus, the search for novel drugs is required. Here we tested the benznidazole (BZ) combination with the repositioned drug disulfiram (DSF) and its derivative diethyldithiocarbamate (DETC) upon Trypanosoma cruzi in vitro and in vivo. DETC-BZ combination was synergistic diminishing epimastigote proliferation and enhancing selective indexes up to over 10-fold. DETC was effective upon amastigotes of the BZ- partially resistant Y and the BZ-resistant Colombiana strains. The combination reduced proliferation even using low concentrations (e.g., 2.5 µM). Scanning electron microscopy revealed membrane discontinuities and cell body volume reduction. Transmission electron microscopy revealed remarkable enlargement of endoplasmic reticulum cisternae besides, dilated mitochondria with decreased electron density and disorganized kinetoplast DNA. At advanced stages, the cytoplasm vacuolation apparently impaired compartmentation. The fluorescent probe H2-DCFDA indicates the increased production of reactive oxygen species associated with enhanced lipid peroxidation in parasites incubated with DETC. The biochemical measurement indicates the downmodulation of thiol expression. DETC inhibited superoxide dismutase activity on parasites was more pronounced than in infected mice. In order to approach the DETC effects on intracellular infection, peritoneal macrophages were infected with Colombiana trypomastigotes. DETC addition diminished parasite numbers and the DETC-BZ combination was effective, despite the low concentrations used. In the murine infection, the combination significantly enhanced animal survival, decreasing parasitemia over BZ. Histopathology revealed that low doses of BZ-treated animals presented myocardial amastigote, not observed in combination-treated animals. The picrosirius collagen staining showed reduced myocardial fibrosis. Aminotransferase de aspartate, Aminotransferase de alanine, Creatine kinase, and urea plasma levels demonstrated that the combination was non-toxic. As DSF and DETC can reduce the toxicity of other drugs and resistance phenotypes, such a combination may be safe and effective.

Mechanism of ketotifen fumarate inhibiting renal calcium oxalate stone formation in SD rats

OBJECTIVES

To investigate the inhibitory effect of ketotifen fumarate (KFA), a mast cell membrane stabilizer, on renal calcium oxalate stone (CaOx) formation and its possible molecular mechanism.

METHODS

We used the Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) database for functional and pathway enrichment analyses of osteopontin (OPN), CD44 and fibronectin (FN). Blood biochemistry, reactive oxygen species ratio (ROS), mast cells, proteins (CD44, OPN and FN) and OPN receptor integrin family genes were detected by ELISA, flow cytometry, immunohistochemistry and RT-QPCR, respectively.

RESULTS

The crystal area of CaOx in the KFA and Control group was significantly smaller than that in the Model group. The number of activated mast cells, the expression levels of OPN and CD44 in the Control and KFA groups were significantly lower than those in the Model group, and the percentage of ROS in the KFA group was also significantly lower than that in the Model group. The mRNA expression levels of ITGB1, ITGA9, ITGAV and ITGA4 genes in the prominent OPN receptor integrin family increased significantly in the Model group.

CONCLUSIONS

Ketotifen can effectively inhibit the crystal formation of CaOx and reduce the inflammatory response of tissue in SD rats. The mechanism may be to reduce the infiltration and activation of mast cells in renal tissue and down-regulate the expression of OPN, CD44 and FN in renal tubules and renal interstitium. And affect the synthesis of integrins (ITGA9, ITGA4, ITGAV, ITGB1, ITGB3 and ITGB5) and ROS.

Amphotericin B and Curcumin Co-Loaded Porous Microparticles as a Sustained Release System against Candida albicans

Amphotericin B (AMB) is an antifungal drug used for serious fungal infections. However, AMB has adverse reactions such as nephrotoxicity, which limit the clinical application of AMB alone or in combination with other antifungal drugs. Nano or micro drug delivery systems (DDS) have been proven to be effective in reducing the toxic and side effects of drugs. Further, the combination of AMB with other compounds with antifungal activity, such as curcumin (CM), may enhance the synergistic effects. Herein, AMB and CM were co-loaded into porous poly (lactic-co-glycolic acid) (PLGA) microparticles (MPs) to prepare AMB/CM-PLGA MPs. The AMB/CM-PLGA MPs showed a remarkably reduced hemolysis (62.2 ± 0.6%) compared to AMB (80.9 ± 1.1%). The nephrotoxicity of AMB/CM-PLGA MPs is significantly lower than that of AMB. In vitro, AMB/CM-PLGA MPs had better inhibitory effects on the adhesion and biofilm formation of Candida albicans compared with AMB. Experiments on mice infected with C. albicans showed that AMB/CM-PLGA MPs have a better therapeutic effect than AMB in vivo. In summary, AMB/CM-PLGA MPs may be a novel and promising therapeutic candidate for fungal infection.

Role of ROS-Induced NLRP3 Inflammasome Activation in the Formation of Calcium Oxalate Nephrolithiasis

Calcium oxalate nephrolithiasis is a common and highly recurrent disease in urology; however, its precise pathogenesis is still unknown. Recent research has shown that renal inflammatory injury as a result of the cell-crystal reaction plays a crucial role in the development of calcium oxalate kidney stones. An increasing amount of research have confirmed that inflammation mediated by the cell-crystal reaction can lead to inflammatory injury of renal cells, promote the intracellular expression of NADPH oxidase, induce extensive production of reactive oxygen species, activate NLRP3 inflammasome, discharge a great number of inflammatory factors, trigger inflammatory cascading reactions, promote the aggregation, nucleation and growth process of calcium salt crystals, and ultimately lead to the development of intrarenal crystals and even stones. The renal tubular epithelial cells (RTECs)-crystal reaction, macrophage-crystal reaction, calcifying nanoparticles, endoplasmic reticulum stress, autophagy activation, and other regulatory factors and mechanisms are involved in this process.

Sulfated Undaria pinnatifida polysaccharide inhibits the formation of kidney stones by inhibiting HK-2 cell damage and reducing the adhesion of nano‑calcium oxalate crystals

OBJECTIVE

The formation of kidney stone is closely related to cell injury and crystal adhesion.

METHOD

The sulfur trioxide-pyridine method was used to sulfate raw Undaria pinnatifida polysaccharide (UPP) with a molecular weight (Mw) of 8.33 kDa. Four polysaccharides with the sulfate group (-OSO3-) contents of 1.59% (UPP0), 6.03% (UPP1), 20.83% (UPP2), and 36.39% (UPP3) were obtained. The antioxidant activity of the four UPPs, the difference in oxidative damage inflicted by nano-CaOx monohydrate (nano-COM) on human proximal tubular epithelial (HK-2) cells before and after protection by UPPs, and the inhibitory effect on nano-COM adhesion were explored.

RESULTS

Structural characterization showed that sulfation was successful. As the -OSO3- content in the UPPs was increased, the antioxidant activity and capability of the UPPs to regulate the growth of calcium oxalate (CaOx) crystals gradually increased. The damage caused by nano-COM crystals to HK-2 cells under protection by UPPs was weakened. This effect enhanced cell viability, enabled the maintenance of good cell morphology, reduced reactive oxygen species (ROS) levels, and inhibited the decrease in mitochondrial membrane potential, as well as decreased the eversion of phosphatidylserine (PS) and the expression of the adhesion proteins osteopontin (OPN), heat shock protein (HSP 90), and Annexin A1 (ANXA1). The adhesion of nano-COM to HK-2 cells was inhibited under the protection by UPPs.

CONCLUSION

UPP3 with the highest content of -OSO3- presented the best antioxidant activity and crystal regulation ability, while UPP2 with the second highest -OSO3- content showed optimal cell protection ability and crystal adhesion inhibition ability. The biological activity of UPPs was regulated by Mw and -OSO3- content. UPP2 with moderate -OSO3- content may become a potential drug for preventing CaOx stones.

Exosomes derived from calcium oxalate-treated macrophages promote apoptosis of HK-2 cells by promoting autophagy

Calcium oxalate (CaOx) crystals are the main component of kidney stones. Macrophages have the function of eliminating these crystals, and the underlying mechanism remains unclear. Here, we attempted to determine the role of macrophage-derived exosomes exposed to CaOx crystals in regulating apoptosis of human proximal tubular cells (HK-2). Exosomes (CaOx-Exo) were isolated from CaOx-treated macrophages and then incubated with HK-2 cells. CaOx-Exo treatment reduced cell viability and promoted apoptosis of HK-2 cells. The expression of Caspase-3 and Bax was increased, and Bcl-2 expression was decreased in HK-2 cells following CaOx-Exo treatment. Moreover, CaOx-Exo treatment caused an increase of LC3-II/LC3-I ratio and Beclin-1 expression and a downregulation of p62 in HK-2 cells. GFP-LC3 puncta were increased in HK-2 cells following CaOx-Exo treatment. Additionally, CaOx-Exo-treated HK-2 cells were treated with 3-methyladenine (3-MA) to inhibit autophagy activity. 3-MA treatment weakened the impact of CaOx-Exo on cell viability and apoptosis of HK-2 cells. 3-MA treatment also reduced the LC3-II/LC3-I ratio and Beclin-1 expression and enhanced p62 expression in CaOx-Exo-treated HK-2 cells. In conclusion, these data demonstrated that exosomes derived from CaOx-treated macrophages promote apoptosis of HK-2 cells by promoting autophagy. Thus, this work suggests that macrophage-derived exosomes may play a vital role in CaOx-induced human proximal tubular cell damage.

Regulatory Effects of Damaged Renal Epithelial Cells After Repair by Porphyra yezoensis Polysaccharides with Different Sulfation Degree on the Calcium Oxalate Crystal-Cell Interaction

BACKGROUND

The interaction between urinary microcrystals and renal epithelial cells is closely related to kidney stone formation. However, the mechanism of cell state changes that affect crystal-cell interaction remains unclear.

METHODS

This study investigated the relationship between the sulfate group (-OSO3 -) content in Porphyra yezoensis polysaccharide (PYP) and the ability to repair damaged cells, as well as the changes in cell adhesion and endocytosis of nano-calcium oxalate monohydrate (COM) crystals before and after PYP repair of damaged renal tubular epithelial cells. The sulfur trioxide-pyridine method was used to sulfate PYP (-OSO3 - content of 14.14%), and two kinds of sulfated PYPs with -OSO3 - content of 20.28% (SPYP1) and 27.14% (SPYP2) were obtained. The above three PYPs were used to repair oxalate-damaged human proximal tubular epithelial cells (HK-2), and the changes in the biochemical indicators of the cells before and after the repair and the changes in cell adhesion and endocytosis of nano-COM crystals were detected.

RESULTS

After repair by PYPs, the cell viability increased, the number of reactive oxygen species decreased, and the reduction of mitochondrial membrane potential and the release of intracellular Ca2+ were suppressed. The cells repaired by PYPs inhibited the adhesion of nano-COM crystals while promoting the endocytosis of the adhered crystals. The endocytosed crystals mainly accumulated in the lysosome. The ability of PYPs to repair cell damage, inhibit crystal adhesion, and promote crystal endocytosis was enhanced when the -OSO3 - content increased. Among them, SPYP2 with the highest -OSO3 - content showed the best biological activity.

CONCLUSION

SPYP2 showed the best ability to repair damaged cells, followed by SPYP1 and PYP. SPYP2 may become a potential green drug that inhibits the formation and recurrence of calcium oxalate stones.

ER Stress in Cardiometabolic Diseases: From Molecular Mechanisms to Therapeutics

The endoplasmic reticulum (ER) hosts linear polypeptides and fosters natural folding of proteins through ER-residing chaperones and enzymes. Failure of the ER to align and compose proper protein architecture leads to accumulation of misfolded/unfolded proteins in the ER lumen, which disturbs ER homeostasis to provoke ER stress. Presence of ER stress initiates the cytoprotective unfolded protein response (UPR) to restore ER homeostasis or instigates a rather maladaptive UPR to promote cell death. Although a wide array of cellular processes such as persistent autophagy, dysregulated mitophagy, and secretion of proinflammatory cytokines may contribute to the onset and progression of cardiometabolic diseases, it is well perceived that ER stress also evokes the onset and development of cardiometabolic diseases, particularly cardiovascular diseases (CVDs), diabetes mellitus, obesity, and chronic kidney disease (CKD). Meanwhile, these pathological conditions further aggravate ER stress, creating a rather vicious cycle. Here in this review, we aimed at summarizing and updating the available information on ER stress in CVDs, diabetes mellitus, obesity, and CKD, hoping to offer novel insights for the management of these cardiometabolic comorbidities through regulation of ER stress.

Oxalate Activates Autophagy to Induce Ferroptosis of Renal Tubular Epithelial Cells and Participates in the Formation of Kidney Stones

Renal tubular epithelial cell damage is the basis for the formation of kidney stones. Oxalate can induce human proximal tubular (HK-2) cells to undergo autophagy and ferroptosis. The present study was aimed at investigating whether the ferroptosis of HK-2 cells induced by oxalate is caused by the excessive activation of autophagy. We treated HK-2 cells with 2 mmol/L of oxalate to establish a kidney stone model. First, we tested the degree of oxidative damage and the level of autophagy and ferroptosis in the control group and the oxalate intervention group. We then knocked down and overexpressed the BECN1 gene and knocked down the NCOA4 gene in HK-2 cells, followed by redetection of the above indicators. We confirmed that oxalate could induce autophagy and ferroptosis in HK-2 cells. Moreover, after oxalate treatment, overexpression of the BENC1 gene increased cell oxidative damage and ferroptosis. In addition, knockdown of NCOA4 reversed the effect of oxalate-induced ferroptosis in HK-2 cells. Our results show that the effects of oxalate on the ferroptosis of HK-2 cells are caused by the activation of autophagy, and knockdown of the NCOA4 could ameliorate this effect.

Atorvastatin treatment ameliorates cardiac function and remodeling induced by isoproterenol attack through mitigation of ferroptosis

Ferroptosis has been identified as an important role in damaged heart. Meanwhile, statin therapy has been reported to be beneficial for the treatment of heart failure(HF) under different conditions. However, the beneficial effects of statin treatment on regulation of ferroptosis in failing heart is unveiled. The aim of this study is to explore the protective efficacy of atorvastatin against the ferroptosis related signaling pathway in isoproterenol(ISO)-induced HF. We found that ATV and ferrostatin-1(Fer-1,as a positive control) significantly improved ISO-decreased cell viability and cell survival by reducing oxidative stress and Fe²⁺-dependent lipid peroxidation in H9C2 cells. Additionally, ISO triggered marked ferritinophagy accompanied by up-regulating protein levels of LC3BII,NCOA4 and Beclin1 and down-regulating protein levels of P62 and FTH1 in damaged cells, which nevertheless was significantly blocked by administration of ATV and these results were in parallel with the results obtained after 3-methyadenine(3-MA) treatment. Consistently, C57BL/6J mice were used in used in this study and administered 5 mg/kg/day ISO for 2 weeks to simulate cardiac injury. 20 mg/kg/day ATV treatment for 2 weeks simultaneously markedly improved cardiac dysfunction and remodeling induced by ISO attack. ATV showed significantly protective effects through suppressing the activation of ferroptosis related signaling, as evidenced by decreasing the mRNA levels of PTGS2(a marker of ferroptosis), contents of malonaldehyde and protein levels of NOX4 and increasing the contents of glutathione(GSH), the ratio of GSH/GSSG and protein levels of GPX4 and SLC7A11. Moreover, ISO evidently triggered degradation of FTH1 in failing heart. However, ATV significantly prevented these changes in damaged heart. Overall, these results reveal atorvastatin suppresses ferroptosis and exhibits protective effect on failing myocardium of mice after ISO insult though inhibiting ferritinophagy-mediated ferroptosis, which might be a potential therapeutic strategy in the prevention of ISO-associated cardiomyopathy.

The Role of miR-34c-5p in Osteogenic Differentiation of Bone Marrow Mesenchymal Stem Cells

Background and Objectives

Osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) plays a critical role in the success of lumbar spinal fusion with autogenous bone graft. This study aims to explore the role and specific mechanism of miR-34c-5p in osteogenic differentiation of BMSCs.

Methods and Results

Rabbit model of lumbar fusion was established by surgery. The osteogenic differentiation dataset of mesenchymal stem cells was obtained from the Gene Expression Omnibus (GEO) database, and differentially expressed miRNAs were analyzed using R language (limma package). The expressions of miR-34c-5p, miR-199a-5p, miR-324-5p, miR-361-5p, RUNX2, OCN and Bcl-2 were determined by qRT-PCR and Western blot. ELISA, Alizarin red staining and CCK-8 were used to detect the ALP content, calcium deposition and proliferation of BMSCs. The targeted binding sites between miR-34c-5p and Bcl-2 were predicted by the Target database and verified using dual-luciferase reporter assay. MiR-34c-5p expression was higher in rabbit lumbar fusion model and differentiated BMSCs than normal rabbit or BMSCs. The content of ALP and the deposition of calcium increased with the osteogenic differentiation of BMSCs. Upregulation of miR-34c-5p reduced cell proliferation and promoted ALP content, calcium deposition, RUNX2 and OCN expression compared with the control group. The effects of miR-34c-5p inhibitor were the opposite. In addition, miR-34c-5p negatively correlated with Bcl-2. Upregulation of Bcl-2 reversed the effects of miR-34c-5p on ALP content, calcium deposition, and the expressions of RUNX2 and OCN.

Conclusions

miR-34c-5p could promote osteogenic differentiation and suppress proliferation of BMSCs by inhibiting Bcl-2.

Potential Roles of Endoplasmic Reticulum Stress and Cellular Proteins Implicated in Diabesity

The role of the endoplasmic reticulum (ER) has evolved from protein synthesis, processing, and other secretory pathways to forming a foundation for lipid biosynthesis and other metabolic functions. Maintaining ER homeostasis is essential for normal cellular function and survival. An imbalance in the ER implied stressful conditions such as metabolic distress, which activates a protective process called unfolded protein response (UPR). This response is activated through some canonical branches of ER stress, i.e., the protein kinase RNA-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1α (IRE1α), and activating transcription factor 6 (ATF6). Therefore, chronic hyperglycemia, hyperinsulinemia, increased proinflammatory cytokines, and free fatty acids (FFAs) found in diabesity (a pathophysiological link between obesity and diabetes) could lead to ER stress. However, limited data exist regarding ER stress and its association with diabesity, particularly the implicated proteins and molecular mechanisms. Thus, this review highlights the role of ER stress in relation to some proteins involved in diabesity pathogenesis and provides insight into possible pathways that could serve as novel targets for therapeutic intervention.

Regulation of endoplasmic reticulum stress on the damage and apoptosis of renal tubular epithelial cells induced by calcium oxalate crystals

This study aimed to observe whether calcium oxalate (CaOx) crystals can induce the activation of endoplasmic reticulum (ER) stress in human renal cortex proximal tubule epithelial (HK-2) cells and to explore the regulatory of ER stress on the damage and apoptosis of HK-2 cells induced by CaOx crystals. We detected the optimal CaOx crystal concentration and intervention time by Western blot. ER stress modifiers tunicamycin (TM) and 4-phenylbutyric acid (4-PBA) were used to regulate the ER stress of HK-2 cells. The activities of ER stress marker proteins GRP78 and CHOP were evaluated by Western blot and immunohistochemistry. Western blot and TUNEL staining were used to detect cell apoptosis. We observed cell-crystal adhesion with an optical microscope. Lactate dehydrogenase (LDH) test kit and IL-1β enzyme-linked immunosorbent assay kit were used to detect and evaluate HK-2 cell damage. We found that the expression of ER stress marker proteins GRP78 and CHOP gradually increased with the increase in CaOx crystal concentration and intervention time and reached the maximum at 2.0 mmol/L and 24 h. The use of ER stress modifiers TM and 4-PBA can effectively regulate the ER stress level induced by CaOx crystals, and the level of apoptosis is positively correlated with the level of ER stress. 4-PBA pretreatment remarkably reduced cell-crystal adhesion and the secretions of IL-1β and LDH, whereas the results of TM pretreatment were the opposite. In summary, the damage and apoptosis of HK-2 cells induced by CaOx crystals are closely related to the level of ER stress. Inhibiting the ER stress of HK-2 cells can substantially reduce the cell damage and apoptosis induced by CaOx crystals.

The effects of glycaemic variability on intimal hyperplasia and plaque stability after stenting via autophagy-mediated G3BP1/NLRP3 inflammasome

Background

The objective of this study was to investigate the effects of glycaemic variability (GV) on intimal hyperplasia and plaque stability after coronary stenting via autophagy-mediated G3BP1/NLRP3 inflammasome signalling.

Methods

In the clinical study, between July 2017 and December 2017, 95 patients with acute myocardial infarction (AMI) and diabetes mellitus (DM) comorbidity received stent implantation. The patients were followed up for 2 years after discharge. The patients were divided into a low-GV (n=61) and high-GV (n=34) group, and the incidence of recurrent AMI was measured. In the animal study, thirteen pigs were divided into a sham (n=3), low-GV DM (n=5) and high-GV DM group (n=5). Intima samples were analysed by optical coherence tomography 22 weeks after coronary stenting. Becn1, LC3B, p62, G3BP1 and NLRP3 protein levels in the intima were examined by western blot. In vitro experiments with THP-1 cells were also conducted.

Results

In the high-GV group, patients exhibited a higher recurrent AMI, greater neointimal thickness, increased p62 and NLRP3 expression, and decreased Becn1, LC3B and G3BP1 expression compared with the low-GV group (P<0.05). The effects of high GV could be abolished by rapamycin but were aggravated by 3-methyladenine.

Conclusions

GV might impact the intimal hyperplasia and plaque stability via autophagy-mediated G3BP1/NLRP3 inflammasome signalling. GV and the autophagy-mediated G3BP1/NLRP3 inflammasome may be promising targets for the treatment of coronary heart disease.

Mechanisms of star fruit (Averrhoa carambola) toxicity: A mini-review

The star fruit (Averrhoa carambola) is consumed in high amounts in Asia and Central/South America. It contains oxalic acid and caramboxin. In some individuals, its ingestion may lead to nephrotoxicity and neurotoxicity. The nephrotoxic effect is due to oxalate deposition in renal tubules resulting in acute tubular necrosis and interstitial nephritis. Although uraemic encephalopathy secondary to acute kidney injury may play a role, a shift to an excitatory state of the central nervous system (CNS) by caramboxin through activation of excitatory neuroreceptors and inhibition of GABA receptors leads to mental confusion, seizures and status epilepticus seen with star fruit intoxication. In this mini-review, we discuss the mechanisms of star fruit-related toxicity.

Taurine suppresses ROS-dependent autophagy via activating Akt/mTOR signaling pathway in calcium oxalate crystals-induced renal tubular epithelial cell injury

Oxidative stress and autophagy are the key promoters of calcium oxalate (CaOx) nephrolithiasis. Taurine is an antioxidant that plays a protective role in the pathogenesis of kidney disease. Previous studies found that taurine suppressed cellular oxidative stress, and inhibited autophagy activation. However, the effect of taurine on CaOx kidney stone formation remains unknown. In the present work, we explored the regulatory effects of taurine on CaOx crystals-induced HK-2 cell injury. Results showed that pretreatment with taurine significantly enhanced the viability of HK-2 cells and ameliorated kidney tissue injury induced by CaOx crystals. Taurine also markedly reduced the levels of inflammatory cytokines, apoptosis, and CaOx crystals deposition. Furthermore, we observed that taurine supplementation alleviated CaOx crystals-induced autophagy. Mechanism studies showed that taurine reduced oxidative stress via increasing SOD activity, reducing MDA concentration, alleviating mitochondrial oxidative injury, and decreasing the production of intracellular ROS. Taurine treatment also effectively activated Akt/mTOR signaling pathway in CaOx crystals-induced HK-2 cells both in vitro and in vivo. In summary, the current study shows that taurine inhibits ROS-dependent autophagy via activating Akt/mTOR signaling pathway in CaOx crystals-induced HK-2 cell and kidney injury, suggesting that taurine may serve as an effective therapeutic agent for the treatment of CaOx nephrolithiasis.

Melatonin inhibits oxalate-induced endoplasmic reticulum stress and apoptosis in HK-2 cells by activating the AMPK pathway

Background: Deposition of various crystal and organic substances in the kidney can lead to kidney stone formation. Melatonin is an effective endogenous antioxidant that can prevent crystalluria and kidney damage due to crystal formation and aggregation. In this study, we investigated the mechanism by which melatonin inhibits endoplasmic reticulum (ER) stress and apoptosis. Methods: We treated HK-2 cells with oxalate to establish an in vitro kidney stone model, and treated these cells with different concentrations of melatonin (0, 5, 10, 20 μmol/L) and the AMP-activated protein kinase (AMPK) inhibitor Compound C. We measured levels of stress response markers including reactive oxygen species (ROS), lactate dehydrogenase (LDH), glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA), catalase (CAT), and factors in the stress response pathway, such as ATF6, GRP78, DDIT3, PERK, p-PERK, IRE1, p-IRE1, XBP1s, AMPK, and p-AMPK, using real time-PCR, western blot, and immunofluorescence analyzes. We measured mitochondrial membrane potential and caspases-3 activity using the CCK8, enzyme-linked immunosorbent, and flow cytometry assays to assess HK-2 cell viability and apoptosis. Results: Melatonin improved the total antioxidant capacity (T-AOC) of the HK-2 cells, as evidenced by the dose-dependent reduction in apoptosis, ROS levels, and protein expression of ATF6, GRP78, DDIT3, p-PERK, p-IRE1, XBP1s, caspase-12, cleaved caspase-3 and cleaved caspase-9. Addition of the AMPK inhibitor, Compound C, partially reversed the protective effect of melatonin. Conclusion: Our study revealed that the protective effects of melatonin on oxalate-induced ER stress and apoptosis is partly dependent on AMPK activation in HK-2 cells. These findings provide insight into the prevention and treatment of kidney stones.

Atorvastatin inhibits renal inflammatory response induced by calcium oxalate crystals via inhibiting the activation of TLR4/NF-κB and NLRP3 inflammasome

This study aimed to investigate the renal protective effect of atorvastatin (ATV) on the kidney inflammation induced by calcium oxalate (CaOx) crystals. A cell model of cell-crystal interactions and a rat model of CaOx kidney stone were established. The expressions of TLR4, NF-κB, NLRP3, and cleaved caspase-1 in cells and rat kidney tissues were detected using Western blot, immunohistochemical, and/or immunofluorescence. The concentrations of malondialdehyde (MDA), superoxide dismutase (SOD), reactive oxygen species (ROS) in cells, and lactic acid dehydrogenase (LDH) in the culture medium were measured. The secreted levels of interleukin (IL)-1β, IL-18, IL-6, and tumor necrosis factor-α (TNF-α) were examined by ELISA. The serum levels of creatinine (CRE) and blood urea nitrogen (BUN) were measured. von Kossa staining was used for the evaluation of renal lens deposition. The CaOx model group showed significantly decreased SOD level; increased concentrations of MDA; ROS and LDH; elevated expressions of TLR4, NF-κB, NLRP3, and cleaved caspase-1; and the elevated release of IL-1β, IL-18, IL-6, and TNF- α as compared to the control group. The treatment with ATV significantly inhibited the formation of CaOx kidney stone by increasing the level of SOD; downregulating MDA, ROS, and LDH; inhibiting the expressions of TLR4, NF-κB, NLRP3 and cleaved caspase-1; and blocking the secretion of inflammatory cytokines. In addition, the serum levels of CRE and BUN, and the intrarenal crystal deposition were also significantly decreased in ATV-treated rats. In summary, oxidative stress, TLR4/NF-κB, and NLRP3 inflammasome pathways are involved in renal inflammatory responses induced by CaOx crystals. ATV treatment significantly suppressed oxidative stress, inhibited the activation of TLR4/NF-κB and NLRP3 inflammasome pathways, and decreased the release of inflammatory mediators, thereby ameliorating CaOx crystal-induced damage and crystal deposition in HK-2 cells and rat kidney tissues.