Hyperoxaluria is well known to cause renal injury and end-stage kidney disease. Previous studies suggested that acetate treatment may improve the renal function in hyperoxaluria rat model. However, its underlying mechanisms remain largely unknown. Using an ethylene glycol (EG)-induced hyperoxaluria rat model, we find the oral administration of 5% acetate reduced the elevated serum creatinine, urea, and protected against hyperoxaluria-induced renal injury and fibrosis with less infiltrated macrophages in the kidney. Treatment of acetate in renal tubular epithelial cells in vitro decrease the macrophages recruitment which might have reduced the oxalate-induced renal tubular cells injury. Mechanism dissection suggests that acetate enhanced acetylation of Histone H3 in renal tubular cells and promoted expression of miR-493-3p by increasing H3K9 and H3K27 acetylation at its promoter region. The miR-493-3p can suppress the expression of macrophage migration inhibitory factor (MIF), thus inhibiting the macrophages recruitment and reduced oxalate-induced renal tubular cells injury. Importantly, results from the in vivo rat model also demonstrate that the effects of acetate against renal injury were weakened after blocking the miR-493-3p by antagomir treatment. Together, these results suggest that acetate treatment ameliorates the hyperoxaluria-induced renal injury via inhibiting macrophages infiltration with change of the miR-493-3p/MIF signals. Acetate could be a new therapeutic approach for the treatment of oxalate nephropathy.

Glyoxylate is a toxic metabolite because of its rapid conversion into oxalate, as catalyzed by the ubiquitous enzyme lactate dehydrogenase. This requires the presence of efficient glyoxylate detoxification systems in multiple subcellular compartments, as glyoxylate is produced in peroxisomes, mitochondria, and the cytosol. Alanine glyoxylate aminotransferase (AGT) and glyoxylate reductase/hydroxypyruvate reductase (GRHPR) are the key enzymes involved in glyoxylate detoxification. Bi-allelic mutations in the genes coding for these enzymes cause primary hyperoxaluria type 1 (PH1) and 2 (PH2), respectively. Glyoxylate is derived from various sources, including 4-hydroxyproline, which is degraded in mitochondria, generating pyruvate and glyoxylate, as catalyzed by the mitochondrial enzyme 4-hydroxy-2-oxoglutarate aldolase (HOGA); however, counterintuitively, a defect in HOGA1 is the molecular basis of primary hyperoxaluria type 3 (PH3). Irrespective of its underlying cause, hyperoxaluria in humans leads to nephrocalcinosis, recurrent urolithiasis, and kidney damage, which may culminate in kidney failure requiring combined liver-kidney transplantation in severely affected patients. In the past few years, therapeutic options, especially for primary hyperoxaluria type 1 (PH1), have greatly been improved thanks to the introduction of two RNAi-based therapies that inhibit either the production of glycolate oxidase (lumasiran) or lactate dehydrogenase (nedosiran). While lumasiran only targets PH1 patients, nedosiran was specifically developed to target all three subtypes of PH. Inspired by the findings reported in the literature that nedosiran effectively reduced urinary oxalate excretion in PH1 patients but not in PH2 or PH3 patients, we have now revisited glyoxylate metabolism in humans and performed a thorough literature study which revealed that glyoxylate/oxalate metabolism is not confined to the liver but instead involves multiple different organs. This new view on glyoxylate/oxalate metabolism in humans may well explain the disappointing results of nedosiran in PH2 and PH3, and provides new clues for the future generation of new therapeutic strategies for PH2 and PH3.

Delayed graft function (DGF) after kidney transplantation heralds a worse prognosis. In patients with hyperoxaluria, the incidence of DGF is high. Oxalic acid is a waste product that accumulates when kidney function decreases. We hypothesize that residual diuresis and accumulated waste products influence the DGF incidence. Patients transplanted between 2018-2022 participated in the prospective cohort study. Pre-transplant concentrations of oxalic acid and its precursors were determined. Data on residual diuresis and other recipient, donor or transplant related variables were collected. 496 patients were included, 154 were not on dialysis. Oxalic acid, and glyoxylic acid, were above upper normal concentrations in 98.8%, and 100% of patients. Residual diuresis was ≤150 mL/min in 24% of patients. DGF occurred in 157 patients. Multivariable binary logistic regression analysis demonstrated a significant influence of dialysis type, recipient BMI, donor type, age, and serum creatinine on the DGF risk. Residual diuresis and glycolic acid concentration were inversely proportionally related to this risk, glyoxylic acid directly proportionally. Results in the dialysis population showed the same results, but glyoxylic acid lacked significance. In conclusion, low residual diuresis is associated with increased DGF incidence. Possibly accumulated waste products also play a role. Pre-emptive transplantation may decrease the incidence of DGF.

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.

The present study aimed to evaluate the role and mechanism of ferrostatin‑1 (Fer‑1) in oxalate (Ox)‑induced renal tubular epithelial cell injury, fibrosis, and calcium oxalate (CaOx) stone formation. A CaOx model in mice kidneys was established via intraperitoneal injection of 80 mg/kg glyoxylic acid for 14 days. The mice were randomly divided into three groups (n=6), namely, the control (Con), the CaOx group, and the CaOx + Fer‑1 group. Cultured human renal tubular epithelial cells (HK‑2 cells) were randomly divided into three groups (n=3), namely, the control (Con), the Ox group, and the Ox + Fer‑1 group. The levels of heme oxygenase 1 (HO‑1), superoxide dismutase 2 (SOD2), glutathione peroxidase 4 (GPX4), and solute carrier family 7 member 11 (SLC7A11) were assessed by immunofluorescence and western blot analysis. Renal tubular injury and apoptosis were evaluated by H&E and TUNEL staining. Kidney interstitial fibrosis was evaluated by Masson and Sirius red staining, and the levels of E‑cadherin, vimentin and α‑SMA were detected by immunofluorescence or western blot analysis. Mitochondrial structure was observed using a transmission electron microscope. The levels of reactive oxygen species (ROS) were determined by flow cytometry and CaOx stone formation was evaluated by von Kossa staining. The results revealed that in comparison with the Con group, mitochondrial injury under glyoxylic acid treatment was observed by TEM. The expression of GPX4 and SLC7A11 in the CaOx and Ox groups was downregulated (P<0.05), whereas the expression of HO‑1 and SOD2 was upregulated (P<0.05). Renal tissue damage, apoptosis of renal tubular epithelial cells, and interstitial fibrosis were increased in the CaOx and Ox groups (P<0.05). In comparison with the CaOx or Ox group, the expression of GPX4 and SLC7A11 in the CaOx + Fer‑1 or Ox + Fer‑1 group was upregulated (P<0.05), whereas that of HO‑1 and SOD2 was downregulated (P<0.05). Renal tissue damage, apoptosis of renal tubular epithelial cells and interstitial fibrosis were decreased following Fer‑1 treatment (P<0.05). The ROS level was also decreased following Fer‑1 treatment. Moreover, CaOx stone formation was decreased in the CaOx + Fer‑1 group (P<0.05). In conclusion, Fer‑1 alleviated Ox‑induced renal tubular epithelial cell injury, fibrosis, and CaOx stone formation by inhibiting ferroptosis.

We recently reported the case of a patient who experienced three consecutive episodes of acute kidney injury, all of them following a "Brazilian" hair-straightening treatment. The cream used for the straightening procedure contained glyoxylic acid. To examine possible underlying mechanisms causing kidney injury, four groups of mice were exposed to topical application of (i) the straightening product, (ii) a cream containing 10% glyoxylic acid, (iii) a cream containing 10% glycolic acid or (iv) a control cream. Application of glycolic acid slightly increased urine oxalate excretion, while glyoxylic acid and the straightening product dramatically increased urine oxalate excretion and caused calcium oxalate nephropathy after transcutaneous absorption. Thus, glyoxylic acid was presumptively absorbed through the skin, metabolized to oxalate and promoted crystallization of calcium oxalate in urine. Hence, cosmetic products containing glyoxylic acid may induce acute kidney injury and should be discontinued. Further studies are needed to investigate the metabolism of glycolic acid and glyoxylic acid following topical application.

Diabetes is known to increase the risk of kidney stones, but the influence of antidiabetic drugs on this risk remains uncertain. Genetic instruments for antidiabetic drugs were identified as variants, which were associated with both the expression of genes encoding target proteins of drugs and glycated hemoglobin level (HbA1c). Here, we investigated the effect of antidiabetic drugs on kidney stones in a mendelian randomization (MR) framework, and further explore the potential effect on CaOx stone rat models induced by glyoxylic acid. Genetically proxied thiazolidinediones (PPARG agonists) significantly reduced the risk of kidney stones (OR = 0.42; P=0.004) per 1-SD decrement in HbA1c, while no significant association was noted in sulfonylureas, SGLT2 inhibitors, or GLP-1 analogs. Other antidiabetic drugs were not analyzed due to unclear pharmacological targets or no identified instruments. Additionally, PPARG agonists pioglitazone ameliorated CaOx nephrocalcinosis in glyoxylic acid-induced rats. The summary-data-based MR (SMR) results showed that PPARG mRNA expression in blood or kidney was not associated with kidney stone risk, and thus we performed mediation MR of PPARG agonists, circulating metabolites, and kidney stones. Among 249 circulating metabolites, we identified an indirect effect of PPARG agonists on kidney stones through increasing phospholipids to total lipids ratio in very large VLDL, with a mediated proportion of 6.87% (P = 0.018). Our study provided evidence that PPARG agonists reduced the risk of kidney stones partially via regulating lipid metabolism, and PPARG agonists may be a promising study subject in clinical studies for the prevention of kidney stones.

BACKGROUND AND AIMS:Nephrolithiasis is a common renal disease with no effective medication. Sodium-glucose cotransporter-2 (SGLT2) inhibitors, an anti-diabetic agent, have diuretic and anti-inflammatory properties and could prevent nephrolithiasis. Here, we investigated the potential of SGLT2 inhibition against nephrolithiasis using large-scale epidemiological data, animal models, and cell culture experiments. METHODS:This study included the data of diabetic patients (n = 1,538,198) available in the Japanese administrative database and divided them according to SGLT2 inhibitor prescription status. For animal experiments, renal calcium oxalate stones were induced by ethylene glycol in Sprague-Dawley rats, and phlorizin, an SGLT1/2 inhibitor, was used for the treatment. The effects of SGLT2-specific inhibition for renal stone formation were assessed in SGLT2-deficient mice and a human proximal tubular cell line, HK-2. RESULTS:Nephrolithiasis prevalence in diabetic men was significantly lower in the SGLT2 inhibitor prescription group than in the non-SGLT2 inhibitor prescription group. Phlorizin attenuated renal stone formation and downregulated the kidney injury molecule 1 (Kim1) and osteopontin (Opn) expression in rats, with unchanged water intake and urine volume. It suppressed inflammation and macrophage marker expression, suggesting the role of the SGLT2 inhibitor in reducing inflammation. SGLT2-deficient mice were resistant to glyoxylic acid-induced calcium oxalate stone formation with reduced Opn expression and renal damages. High glucose-induced upregulation of OPN and CD44 and cell surface adhesion of calcium oxalate reduced upon SGLT2-silencing in HK-2 cells. CONCLUSION:Overall, our findings identified that SGLT2 inhibition prevents renal stone formation and may be a promising therapeutic approach against nephrolithiasis.

The present understanding of the cellular characteristics and communications in crystal nephropathy is limited. Here, molecular and cellular studies combined with single-cell RNA sequencing (scRNA-seq) were performed to investigate the changes in cell components and their interactions in glyoxylate-induced crystallized kidneys to provide promising treatments for crystal nephropathy. The transcriptomes of single cells from mouse kidneys treated with glyoxylate for 0, 1, 4, or 7 days were analyzed via 10× Genomics, and the single cells were clustered and characterized by the Seurat pipeline. The potential cellular interactions between specific cell types were explored by CellChat. Molecular and cellular findings related to macrophage-to-epithelium crosstalk were validated in sodium oxalate (NaOx)-induced renal tubular epithelial cell injury in vitro and in glyoxylate-induced crystal nephropathy in vivo. Our established scRNA atlas of glyoxylate-induced crystalline nephropathy contained 15 cell populations with more than 40000 single cells, including relatively stable tubular cells of different segments, proliferating and injured proximal tubular cells, T cells, B cells, and myeloid and mesenchymal cells. In this study, we found that Mrc1 macrophages, as a subtype of myeloid cells, increased in both the number and percentage within the myeloid population as crystal-induced injury progresses, and distinctly express IGF1, which induces the activation of a signal pathway to dominate a significant information flow towards injured and proliferating tubule cells. IGF1 promoted the repair of damaged tubular epithelial cells induced by NaOx in vitro, as well as the repair of damaged tubular epithelial cells and the recovery of disease outcomes in glyoxylate-induced nephrolithic mice in vivo. After constructing a cellular atlas of glyoxylate-induced crystal nephropathy, we found that IGF1 derived from Mrc1 macrophages attenuated crystal nephropathy through promoting renal tubule cell proliferation via the AKT/Rb signaling pathway. These findings could lead to the identification of potential therapeutic targets for the treatment of crystal nephropathy.

PURPOSE:The availability of various transgenic and knockout mice provides an excellent opportunity to better understand the pathophysiology of calcium oxalate stone disease. However, attempts to produce calcium oxalate nephrolithiasis in mice have not been successful. We hypothesized that calcium oxalate nephrolithiasis in mice requires increasing urine calcium and oxalate excretion, and experimentally induced hyperoxaluria alone is not sufficient. To provide evidence we induced hyperoxaluria by administering hyperoxaluria inducing agents in normocalciuric and hypercalciuric mice, and investigating various aspects of nephrolithiasis. MATERIALS AND METHODS:We administered ethylene glycol, glyoxylate or hydroxyl proline via diet in male and female normocalciuric B6 mice, and in hypercalciuric sodium phosphate co-transporter type 2 a -/- mice for 4 weeks. We collected 24-hour urine samples on days 0, 3, 7, 14, 21 and 28, and analyzed them for pH, creatinine, lactate dehydrogenase calcium and oxalate. Kidneys were examined using light microscopy. Urine was examined for crystals using light and scanning electron microscopy. RESULTS:Hypercalciuric mice on hydroxyl proline did not tolerate treatment and were sacrificed before 28 days. All mice on ethylene glycol, glyoxylate or hydroxyl proline became hyperoxaluric and showed calcium oxalate crystalluria. No female, normocalciuric or hypercalciuric mice showed renal calcium oxalate crystal deposits. Calcium oxalate nephrolithiasis developed in all mice on glyoxylate and in some on ethylene glycol. In all mice the kidneys showed epithelial injury. Male mice particularly on glyoxylate had more renal injury and inflammatory cell migration into the interstitium around the crystal deposits. CONCLUSIONS:Results confirm that hyperoxaluria induction alone is not sufficient to create calcium oxalate nephrolithiasis in mice. Hypercalciuria is also required. Kidneys in male mice are more prone to injury than those in female mice and are susceptible to calcium oxalate crystal deposition. Perhaps epithelial injury promotes crystal retention. Thus, calcium oxalate nephrolithiasis in mice is gender dependent, and requires hypercalciuria and hyperoxaluria.

The establishment of an experimental animal model would be useful to study the mechanism of kidney stone formation. A calcium kidney stone model in rats induced by ethylene glycol has been used for research; however, to investigate the genetic basis affecting kidney stone formation, which will contribute to preventive medicine, the establishment of a kidney stone model in mice is essential. This study indicates the optimum conditions for inducing calcium oxalate stones in normal mouse kidney. Various doses of oxalate precursors, ethylene glycol, glycolate and glyoxylate, were administered either by free drinking or intraabdominal injection for 2 months as a preliminary study. Stone formation was detected with light microscopy, polarized light optical microscopy and electron microscopy. Stone components were detected with X-ray diffraction analysis. The expression of osteopontin (OPN), a major stone-related protein, was detected with immunohistochemical staining, in situ hybridization and quantitative reverse transcriptase polymerase chain reaction. Kidney stones were not detected in ethylene glycol- or glycolate-treated groups even at the highest dose of LD(50). Whereas, numerous kidney stones were detected in glyoxylate-treated mice (more than 60 mg/kg) at 3, 6 and 9 days after glyoxylate were administered intraabdominally. However, the number of kidney stones decreased gradually at day 12, and was hardly detected at day 15. The stone component was further analyzed as calcium oxalate monohydrate. A dramatic increase in the expression of OPN was observed by the administration of glyoxylate. We established a mouse kidney stone experimental system in this study. The difficulty of inducing kidney stones suggested that mice have greater intrinsic ability to prevent stone formation with hyperoxaluric stress than rats. The differing response to hyperoxaluric stress between mice and rats possibly contributes to the molecular mechanism of kidney stone formation and will aid preventive medicine in the future.

Oxidative stress and inflammatory response are closely related to nephrolithiasis. This study is aimed at exploring whether rosiglitazone (ROSI), a regulator of macrophage (Mp) polarization, could reduce renal calcium oxalate (CaOx) deposition by ameliorating oxidative stress and inflammatory response. Male C57 mice were equally and randomly divided into 7 groups. Kidney sections were collected on day 5 or day 8 after treatment. Pizzolato staining and polarized light optical microscopy were used to detect crystal deposition. PAS staining and TUNEL assay were performed to assess the tubular injury and cell apoptosis, respectively. Gene expression was assessed by immunohistochemistry, immunofluorescence, ELISA, qRT-PCR, and Western blot. The reactive oxygen species (ROS) level was assessed using a fluorescence microplate and fluorescence microscope. Hydrogen peroxide (HO), malonaldehyde (MDA), and glutathione (GSH) were evaluated to determine oxidative stress. Lactic dehydrogenase (LDH) activity was examined to detect cell injury. Adhesion of CaOx monohydrate (COM) crystals to HK-2 cells was detected by crystal adhesion assay. HK-2 cell death or renal macrophage polarization was assessed by flow cytometry. , renal crystal deposition, tubular injury, crystal adhesion, cell apoptosis, oxidative stress, and inflammatory response were significantly increased in the 7-day glyoxylic acid- (Gly-) treated group but were decreased in the ROSI-treated groups, especially in the groups pretreated with ROSI. Moreover, ROSI significantly reduced renal Mp aggregation and M1Mp polarization but significantly enhanced renal M2Mp polarization. In vitro, ROSI significantly suppressed renal injury, apoptosis, and crystal adhesion of HK-2 cells and markedly shifted COM-stimulated M1Mps to M2Mps, presenting an anti-inflammatory effect. Furthermore, ROSI significantly suppressed oxidative stress by promoting the Nrf2/HO-1 pathway in HK-2 cells. These findings indicate that ROSI could ameliorate renal tubular injury that resulted from oxidative stress and inflammatory response by suppressing M1Mp polarization and promoting M2Mp polarization. Therefore, ROSI is a potential therapeutic and preventive drug for CaOx nephrolithiasis.

BACKGROUND:Primary hyperoxaluria is a rare genetic disorder of glyoxylate metabolism that results in overproduction of oxalate. The disease is characterized by severe calcium oxalate nephrolithiasis and nephrocalcinosis, resulting in end-stage renal disease (ESRD) early in life. Most patients eventually require dialysis and kidney transplantation, usually in combination with the replacement of the liver. Reduction of urinary oxalate levels can efficiently decrease calcium oxalate depositions; yet, no treatment is available that targets oxalate biosynthesis. In previous in vitro studies, we demonstrated that pyridoxamine can trap reactive carbonyl compounds, including intermediates of oxalate biosynthesis. METHODS:The effect of PM on urinary oxalate excretion and kidney crystal formation was determined using the ethylene glycol rat model of hyperoxaluria. Animals were given 0.75% to 0.8% ethylene glycol in drinking water to establish and maintain hyperoxaluria. After 2 weeks, pyridoxamine treatment (180 mg/day/kg body weight) started and continued for an additional 2 weeks. Urinary creatinine, glycolate, oxalate, and calcium were measured along with the microscopic analysis of kidney tissues for the presence of calcium oxalate crystals. RESULTS:Pyridoxamine treatment resulted in significantly lower (by approximately 50%) levels of urinary glycolate and oxalate excretion compared to untreated hyperoxaluric animals. This was accompanied by a significant reduction in calcium oxalate crystal formation in papillary and medullary areas of the kidney. CONCLUSION:These results, coupled with favorable toxicity profiles of pyridoxamine in humans, show promise for therapeutic use of pyridoxamine in primary hyperoxaluria and other kidney stone diseases.

Recent reports have described acute kidney injury in otherwise healthy individuals after exposure to hair-straightening products. In this issue, Robert et al. help elucidate the underlying mechanisms in a murine model that replicates the human pathology. Cutaneous absorption of glyoxylic acid from hair-straightening products and its subsequent conversion to oxalate are identified as crucial steps in the development of oxalate nephropathy. This newly described "skin-kidney" axis expands our understanding of oxalate metabolism, calls for additional studies to explore susceptibility to acute kidney injury following cutaneous glyoxylate exposure, and warrants vigilance around the use of these products.

BACKGROUND:High prevalence and reoccurrence rate of nephrolithiasis bring about serious socioeconomic and healthcare burden, necessitating the need of effective therapeutic agents. Previous study revealed that gallic acid (GAL) alters the nucleation pathway of calcium oxalate (CaOx). On the other hand, it appears protective role against oxidative injury. Whether GAL could protect against crystal-induced lesion in vivo, and its underlying mechanism is yet unsolved. PURPOSE:This study aims to investigate the protective effects of GAL on the crystal-induced renal injury and its underlying mechanism in the mouse model of stone formation induced by glyoxylic acid. STUDY DESIGN AND METHODS:The mouse model of stone formation was established via successive intraperitoneal injection of glyoxylate. Proximal tubular epithelial cell line HK-2 treated with calcium oxalate monohydrate (COM) was used as in vitro model. The protective role of GAL on nephrolithiasis was tested by determination of tubular injury, crystal deposition and adhesion, levels of inflammatory cytokines, macrophage infiltration and the redox status of kidney. In vitro, effect of GAL on the ROS level and oxidative tubular injury induced by COM were detected, as well as major antioxidant pathway Nrf2/HO-1. RESULTS:Administration of GAL alleviates the renal deposition and adhesion of CaOx stone. Meanwhile, GAL ameliorates the inflammation and renal tubular injury. Level of intracellular ROS, osteopontin and CD44 are reduced, either in the mouse model of stone formation or in the COM-treated HK-2 cells after treatment of GAL. Mechanistically, GAL activates Nrf2/HO-1 pathway in HK-2 cells. Silencing Nrf2 abrogates the protective effect of GAL on the oxidative injury and adhesion of COM in HK-2 cells. CONCLUSION:Taken together, our study demonstrates the protective effect of GAL on the deposition of kidney stone and consequent tubular injury. Induction of the antioxidant pathway Nrf2/HO-1 was found to decrease the level of ROS and oxidative injury, thus implying that GAL could be a potential therapeutic agent for the treatment of nephrolithiasis.

During the formation of kidney stones, the interaction between crystals and tubular epithelial cells (TECs) leads to tubular injury and dysfunction, which in turn promote stone formation. However, the molecular mechanisms underlying these changes in TECs remain elusive. Drug screening revealed that JQ1 inhibited the adhesion of calcium oxalate (CaOx) crystals to TECs. Its therapeutic effect is further confirmed in a glyoxylic acid-induced CaOx crystal deposition mouse model. Utilizing epigenomic and transcriptomic profiling, dynamic enhancer landscape and gene expression program associated with nephrolithiasis are charted. Bioinformatic analysis pinpointing the RXRα as a central transcription factor (TF) modulating enhancer activity. Importantly, the animal studies revealed that RXRα deletion promoted the CaOx crystal deposition, while its activation by Bexarotene (Bex), an FDA-approved drug, mitigated this progression. Mechanistically, under normal circumstances, RXRα inhibited nephrolithiasis-promoting genes by recruiting the HDAC3/SMART complex to repress enhancer activity. Yet, with the progression of CaOx crystal deposition, RXRα expression decreased, leading to enhancer activation and subsequent upregulation of nephrolithiasis-promoting genes. In summary, the work illustrates an epigenetic mechanism underlying TECs fate transition during CaOx crystal deposition and highlights the therapeutic potential of JQ1 and Bex in managing kidney stone diseases.

BACKGROUND:Kidney stones are composed of approximately 70-80% calcium oxalate. However, the exact mechanism of formation of calcium oxalate kidney stones remains unclear. In this study, we investigated the roles of endoplasmic reticulum stress (ERS), reactive oxygen species (ROS), and the NF-κB signalling pathway in the pathogenesis of oxalate-induced renal tubular epithelial cell injury and its possible molecular mechanisms. METHODS:We established a model to evaluate the formation of kidney stones by intraperitoneal injection of glyoxylic acid solution into mice and assessed cell morphology, apoptosis, and the expression levels of ERS, ROS, and NF-κB signalling pathway-related proteins in mouse renal tissues. Next, we treated HK-2 cells with potassium oxalate to construct a renal tubular epithelial cell injury model. We detected the changes in autophagy, apoptosis, and mitochondrial membrane potential and investigated the ultrastructure of the cells by transmission electron microscopy. Western blotting revealed the expression levels of apoptosis and autophagy proteins; mitochondrial structural and functional proteins; and ERS, ROS, and NF-κB (p65) proteins. Lastly, we studied the downregulation of NF-κB activity in HK-2 cells by lentivirus interference and confirmed the interaction between the NF-κB signalling and ERS/ROS pathways. RESULTS:We observed swelling of renal tissues, increased apoptosis of renal tubular epithelial cells, and activation of the ERS, ROS, and NF-κB signalling pathways in the oxalate group. We found that oxalate induced autophagy, apoptosis, and mitochondrial damage in HK-2 cells and activated the ERS/ROS/NF-κB pathways. Interestingly, when the NF-κB signalling pathway was inhibited, the ERS/ROS pathway was also inhibited. CONCLUSION:Oxalate induces HK-2 cell injury through the interaction between the NF-κB signalling and ERS/ROS pathways.

OBJECTIVE:To investigate the role of inflammatory reactions and oxidative stress injury in the mechanisms of ceftriaxone calcium crystal-induced acute kidney injury (AKI) both in vivo and in vitro. METHODS:Male Sprague Dawley rats were randomly divided into five groups of ten each according to different concentrations of ceftriaxone and calcium. Based on the levels of serum creatinine (Scr) and blood urea nitrogen (BUN), the AKI group was chosen for the subsequent experiments. Kidney histological examination and immunohistochemistry were performed. The expression of NLRP3 and IL-1 protein and the concentrations of oxidative stress markers such as ROS, MDA, and HO in kidney tissues were estimated. In parallel, HK-2 human renal proximal tubule cells were exposed to ceftriaxone calcium crystals. The mRNA expression levels of NLRP3 and IL-1 and the concentrations of oxidative stress markers were evaluated. Finally, cell viability and rat survival were also assessed. RESULTS:The results showed that significantly increased Scr and BUN levels, consistent with morphological changes and kidney stones, were found in the rats that received the highest concentration of ceftriaxone (1000 mg/kg) combined with calcium (800 mg/kg). The activation of the NLRP3 inflammasome axis and the marked elevation of MDA, HO, and ROS levels were observed both in vivo and in vitro. High expression of Nrf2, HO-1, and NQO1 was also documented. In addition, cell apoptosis and rat mortality were promoted by ceftriaxone calcium crystals. CONCLUSIONS:Notably, we found that ceftriaxone-induced urolithiasis was associated with a high risk of AKI and NLRP3-mediated inflammasome and oxidative stress injury were of major importance in the pathogenesis.

BACKGROUND:Hereditary renal hypouricemia type 1 (RHUC1) is caused by URAT1/SLC22A12 dysfunction, resulting in urolithiasis and exercise-induced AKI (EIAKI). However, because there is no useful experimental RHUC1 animal model, the precise pathophysiologic mechanisms underlying EIAKI have yet to be elucidated. We established a high HPRT activity - double knockout (DKO) mouse as a novel RHUC1 animal model for investigating the cause of EIAKI and the potential therapeutic effect of xanthine oxidoreductase inhibitors (XOIs). METHODS:The novel - DKO mice were used in a forced swimming test as loading exercise to explore the onset mechanism of EIAKI and evaluate related purine metabolism and renal injury parameters. RESULTS:- DKO mice had uricosuric effects and elevated levels of plasma creatinine and BUN as renal injury markers, and decreased creatinine clearance observed in a forced swimming test. In addition, - DKO mice had increased NLRP3 inflammasome activity and downregulated levels of Na-K-ATPase protein in the kidney, as Western blot analysis showed. Finally, we demonstrated that topiroxostat and allopurinol, XOIs, improved renal injury and functional parameters of EIAKI. CONCLUSIONS:- DKO mice are a useful experimental animal model for human RHUC1. The pathogenic mechanism of EIAKI was found to be due to increased levels of IL-1 NLRP3 inflammasome signaling and Na-K-ATPase dysfunction associated with excessive urinary urate excretion. In addition, XOIs appear to be a promising therapeutic agent for the treatment of EIAKI.

INTRODUCTION:Acute kidney injury (AKI) is a prevalent renal disorder. The occurrence of AKI may promote the formation of renal calcium oxalate stones by exerting continuous effects on renal tubular epithelial cells (TECs). We aimed to delineate the molecular interplay between AKI and nephrolithiasis. METHODS:A mild (20 min) and severe (30 min) renal ischemia-reperfusion injury model was established in mice. Seven days after injury, calcium oxalate stones were induced using glyoxylate (Gly) to evaluate the impact of AKI on the formation of kidney stones. Transcriptome sequencing was performed on TECs to elucidate the relationship between AKI severity and kidney stones. Key transcription factors (TFs) regulating differential gene transcription levels were identified using motif analysis, and pioglitazone, ginkgetin, and fludarabine were used for targeted therapy to validate key TFs as potential targets for kidney stone treatment. RESULTS:Severe AKI led to increased deposition of calcium oxalate crystals in renal, impaired kidney function, and upregulation of kidney stone-related gene expression. In contrast, mild AKI was associated with decreased crystal deposition, preserved kidney function, and downregulation of similar gene expression. Transcriptomic analysis revealed that genes associated with inflammation and cell adhesion pathways were significantly upregulated after severe AKI, while genes related to energy metabolism pathways were significantly upregulated after mild AKI. An integrative bioinformatic analysis uncovered a TF regulatory network within TECs, pinpointing that PKNOX1 was involved in the upregulation of inflammation-related genes after severe AKI, and inhibiting PKNOX1 function with pioglitazone could simultaneously reduce the increase of calcium oxalate crystals after severe AKI in kidney. On the other hand, motif analysis also revealed the protective role of STAT1 in the kidneys after mild AKI, enhancing the function of STAT1 with ginkgetin could reduce kidney stone formation, while the specific inhibitor of STAT1, fludarabine, could eliminate the therapeutic effects of mild AKI on kidney stones. CONCLUSION:Inadequate repair of TECs after severe AKI increases the risk of kidney stone formation, with the upregulation of inflammation-related genes regulated by PKNOX1 playing a role in this process. Inhibiting PKNOX1 function can reduce kidney stone formation. Conversely, after mild AKI, effective cell repair through upregulation of STAT1 expression can protect TEC function and reduce stone formation, and activating STAT1 function can also achieve the goal of treating kidney stones.