Mitochondrial Dysfunction and Kidney Stone Disease

RUNX3 alleviates mitochondrial dysfunction and tubular damage by inhibiting TLR4/NF-κB signalling pathway in diabetic kidney disease

AIM

The impaired function of tubular mitochondria is critical in diabetic kidney disease (DKD) progression. RUNX3 is down-regulated in DKD models. We intend to explore the effects of RUNX3 on mitochondrial dysfunction and renal tubule injury in DKD and related mechanisms.

METHODS

The development of diabetes models involved injecting mice with streptozotocin while treating HK-2 cells with high glucose (HG). By using immunohistochemical techniques, the renal localizations of RUNX3 were identified. Levels of adenosine triphosphate (ATP), mitochondrial membrane potential, and biochemical index were detected by appropriate kits. Reactive oxygen species (ROS) generation was assessed with dihydroethidium and MitoSOX Red staining. Apoptosis was assessed by flow cytometry and TUNEL. RUNX3 ubiquitination was measured.

RESULTS

RUNX3 was mainly present in renal tubules. Overexpressing RUNX3 increased Mfn2, Mfn1, ATP levels, and mitochondrial membrane potential, reduced Drp1 and ROS levels and cell apoptosis, as well as Cyt-C release into the cytoplasm. RUNX3 overexpression displayed a reduction in urinary albumin to creatinine ratio, Hemoglobin A1c, serum creatinine, and blood urea nitrogen. Overexpressing TLR4 attenuated the inhibitory effect of RUNX3 overexpression on mitochondrial dysfunction and cell apoptosis. HG promoted RUNX3 ubiquitination and SMURF2 expression. RUNX3 knockdown cancelled the inhibitory effect of SMURF2 on mitochondrial dysfunction and cell apoptosis.

CONCLUSION

SMURF2 interference inhibits RUNX3 ubiquitination and TLR4/NF-κB signalling pathway, thereby alleviating renal tubule injury.

Inhibitory effect of Incarvillea diffusa Royle extract in the formation of calcium oxalate nephrolithiasis by regulating ROS-induced Nrf2/HO-1 pathway in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Calcium oxalate (CaOx) kidney stones are widely acknowledged as the most prevalent type of urinary stones, with high incidence and recurrence rates. Incarvillea diffusa Royle (ID) is a traditionally used medicinal herb in the Miao Minzu of Guizhou province, China, for treating urolithiasis. However, the active components and the underlying mechanism of its pharmacodynamic effects remain unclear.

AIM OF THE STUDY

This study aimed to investigate the potential inhibitory effect of the active component of ID on the formation of CaOx nephrolithiasis and elucidate the underlying mechanism.

MATERIALS AND METHODS

In vivo, a CaOx kidney stone model was induced in Sprague-Dawley (SD) rats using an ethylene glycol and ammonium chloride protocol for four weeks. Forty-eight male SD rats were randomly assigned to 6 groups (n = 8): blank group, model group, apocynin group, and low, medium, and high dose of ID's active component (IDW) groups. After three weeks of administration, rat urine, serum, and kidney tissues were collected. Renal tissue damage and crystallization, Ox, BUN, Ca2+, CRE, GSH, MDA, SOD contents, and levels of IL-1β, IL-18, MCP-1, caspase-1, IL-6, and TNF-α in urine, serum, and kidney tissue were assessed using HE staining and relevant assay kits, respectively. Protein expression of Nrf2, HO-1, p38, p65, and Toll-4 in kidney tissues was quantified via Western blot. The antioxidant capacities of major compounds were evaluated through DPPH, O2·-, and ·OH radical scavenging assays, along with their effects on intracellular ROS production in CaOx-induced HK-2 cells.

RESULTS

We found that IDW could significantly reduce the levels of CRE, GSH, MDA, Ox, and BUN, and enhancing SOD activity. Moreover, it could inhibit the secretion of TNF-α, IL-1β, IL-18, MCP-1, caspase-1, and decreased protein expression of Nrf2, HO-1, p38, p65, and Toll-4 in renal tissue. Three major compounds isolated from IDW exhibited promising antioxidant activities and inhibited intracellular ROS production in CaOx-induced HK-2 cells.

CONCLUSIONS

IDW facilitated the excretion of supersaturated Ca2+ and decreased the production of Ox, BUN in SD rat urine, and mitigated renal tissue damage by regulating Nrf2/HO-1 signaling pathway. Importantly, the three major compounds identified as active components of IDW contributed to the inhibition of CaOx nephrolithiasis formation. Overall, IDW holds significant potential for treating CaOx nephrolithiasis.

Lycopene from tomatoes and tomato products exerts renoprotective effects by ameliorating oxidative stress, apoptosis, pyroptosis, fibrosis, and inflammatory injury in calcium oxalate nephrolithiasis: the underlying mechanisms

Several mechanisms underlying nephrolithiasis, one of the most common urological diseases, involve calcium oxalate formation, including oxidative stress, inflammatory reactions, fibrosis, pyroptosis, and apoptosis. Although lycopene has strong antioxidant activity, its protective effects against CaOx-induced injury have not yet been reported. This study aimed to systematically investigate the protective effects of lycopene and explore its mechanisms and molecular targets. Crystal deposition, renal function, oxidative stress, inflammatory response, fibrosis, pyroptosis, and apoptosis were assessed to evaluate the renoprotective effects of lycopene against crystal formation in a CaOx rat model and oxalate-stimulated NRK-52E and HK-2 cells. Lycopene markedly ameliorated crystal deposition, restored renal function, and suppressed kidney injury by reducing oxidative stress, apoptosis, inflammation, fibrosis, and pyroptosis in the rats. In cell models, lycopene pretreatment reversed reactive oxygen species increase, apoptotic damage, intracellular lactate dehydrogenase release, cytotoxicity, pyroptosis, and extracellular matrix deposition. Network pharmacology and proteomic analyses were performed to identify lycopene target proteins under CaOx-exposed conditions, and the results showed that Trappc4 might be a pivotal target gene for lycopene, as identified by cellular thermal shift assay and surface plasmon resonance analyses. Based on molecular docking, molecular dynamics simulations, alanine scanning mutagenesis, and saturation mutagenesis, we observed that lycopene directly interacts with Trappc4 via hydrophobic bonds, which may be attributed to the PHE4 and PHE142 residues, preventing ERK1/2 or elevating AMPK signaling pathway phosphorylation events. In conclusion, lycopene might ameliorate oxalate-induced renal tubular epithelial cell injury via the Trappc4/ERK1/2/AMPK pathway, indicating its potential for the treatment of nephrolithiasis.

Resveratrol inhibits calcium oxalate crystal growth, reduces adhesion to renal cells and induces crystal internalization into the cells, but promotes crystal aggregation

Resveratrol is a natural phenolic compound that belongs to stilbenoid group found in diverse plants. Health benefits and therapeutic potentials of resveratrol have been widely recognized in various diseases. In kidney stone disease, it can alleviate oxalate-induced hyperproduction of free radicals in renal epithelial cells. Nevertheless, its direct effects on calcium oxalate (CaOx) crystal, which is the major stone component, remained unclear. This study therefore addressed the direct effects of resveratrol (at 1, 10 or 100 μM) on each step of CaOx kidney stone formation. The results revealed that resveratrol had no significant effects on CaOx crystallization. However, resveratrol significantly decreased CaOx crystal growth and adhesion to renal epithelial cells at all concentrations, and induced crystal internalization into the cells (a process related to crystal degradation by endolysosomes) in a concentration-dependent manner. On the other hand, resveratrol promoted crystal aggregation. These data indicate that resveratrol serves as a dual modulator on CaOx stone formation. While it inhibits CaOx stone development by reducing crystal growth and adhesion to renal cells and by inducing crystal internalization into the cells, resveratrol promotes crystal aggregation, which is one of the mechanisms leading to kidney stone formation.

Carboxymethylated Rhizoma alismatis polysaccharides reduces the risk of calcium oxalate stone formation by reducing cellular inflammation and oxidative stress

This study aims to elucidate the mechanism and potential of Rhizoma alismatis polysaccharides (RAPs) in preventing oxidative damage to human renal proximal tubule epithelial cells. The experimental approach involved incubating HK-2 cells with 100 nm calcium oxalate monohydrate for 24 h to establish a cellular injury model. Protection was provided by RAPs with varying carboxyl group contents: 3.57%, 7.79%, 10.84%, and 15.33%. The safeguarding effect of RAPs was evaluated by analyzing relevant cellular biochemical indicators. Findings demonstrate that RAPs exhibit notable antioxidative properties. They effectively diminish the release of reactive oxygen species, lactate dehydrogenase, and malondialdehyde, a lipid oxidation byproduct. Moreover, RAPs enhance superoxide dismutase activity and mitochondrial membrane potential while attenuating the permeability of the mitochondrial permeability transition pore. Additionally, RAPs significantly reduce levels of inflammatory factors, including NLRP3, TNF-α, IL-6, and NO. This reduction corresponds to the inhibition of overproduced pro-inflammatory mediator nitric oxide and the caspase 3 enzyme, leading to a reduction in cellular apoptosis. RAPs also display the ability to suppress the expression of the HK-2 cell surface adhesion molecule CD44. The observed results collectively underscore the substantial anti-inflammatory and anti-apoptotic potential of all four RAPs. Moreover, their capacity to modulate the expression of cell surface adhesion molecules highlights their potential in inhibiting the formation of kidney stones. Notably, RAP3, boasting the highest carboxyl group content, emerges as the most potent agent in this regard.

N-acetylcysteine regulates oxalate induced injury of renal tubular epithelial cells through CDKN2B/TGF-β/SMAD axis

This study was aimed to investigate the preventive effects of N-acetyl-L-cysteine (NAC) against renal tubular cell injury induced by oxalate and stone formation and further explore the related mechanism. Transcriptome sequencing combined with bioinformatics analysis were performed to identify differentially expressed gene (DEG) and related pathways. HK-2 cells were pretreated with or without antioxidant NAC/with or silencing DEG before exposed to sodium oxalate. Then, the cell viability, oxidative biomarkers of superoxidase dismutase (SOD) and malondialdehyde (MDA), apoptosis and cell cycle were measured through CCK8, ELISA and flow cytometry assay, respectively. Male SD rats were separated into control group, hyperoxaluria (HOx) group, NAC intervention group, and TGF-β/SMAD pathway inhibitor group. After treatment, the structure changes and oxidative stress and CaOx crystals deposition were evaluated in renal tissues by H&E staining, immunohistochemical and Pizzolato method. The expression of TGF-β/SMAD pathway related proteins (TGF-β1, SMAD3 and SMAD7) were determined by Western blot in vivo and in vitro. CDKN2B is a DEG screened by transcriptome sequencing combined with bioinformatics analysis, and verified by qRT-PCR. Sodium oxalate induced declined HK-2 cell viability, in parallel with inhibited cellular oxidative stress and apoptosis. The changes induced by oxalate in HK-2 cells were significantly reversed by NAC treatment or the silencing of CDKN2B. The cell structure damage and CaOx crystals deposition were observed in kidney tissues of HOx group. Meanwhile, the expression levels of SOD and 8-OHdG were detected in kidney tissues of HOx group. The changes induced by oxalate in kidney tissues were significantly reversed by NAC treatment. Besides, expression of SMAD7 was significantly down-regulated, while TGF-β1 and SMAD3 were accumulated induced by oxalate in vitro and in vivo. The expression levels of TGF-β/SMAD pathway related proteins induced by oxalate were reversed by NAC. In conclusion, we found that NAC could play an anti-calculus role by mediating CDKN2B/TGF-β/SMAD axis.

Spaceflight causes strain-dependent gene expression changes associated with lipid and extracellular matrix dysregulation in the mouse kidney in vivo

To explore new worlds we must ensure humans can survive and thrive in the space environment. Incidence of kidney stones in astronauts is a major risk factor associated with long term missions, caused by increased blood calcium levels due to bone demineralisation triggered by microgravity and space radiation. Transcriptomic changes have been observed in other tissues during spaceflight, including the kidney. We analysed kidney transcriptome patterns in two different strains of mice flown on the International Space Station, C57BL/6J and BALB/c. Here we show a link between spaceflight and transcriptome patterns associated with dysregulation of lipid and extracellular matrix metabolism and altered transforming growth factor-beta signalling. A stronger response was seen in C57BL/6J mice than BALB/c. Genetic differences in hyaluronan metabolism between strains may confer protection against extracellular matrix remodelling through downregulation of epithelial-mesenchymal transition. We intend for our findings to contribute to development of new countermeasures against kidney disease in astronauts and people here on Earth.

Highlights

Spaceflight has a significant effect on gene expression in the kidney.Responses in the BALB/c indicate milder transcriptomic perturbations than C57BL/6J.Lipid metabolism was altered in both strains of mice.Extracellular matrix metabolism and TGF-β signalling up in BALB/c down in C57BL/6J.Reduced gene expression of hyaluronan synthesis pathway in BALB/c but not in C57BL/6J.

Serum HDL partially mediates the association between exposure to volatile organic compounds and kidney stones: A nationally representative cross-sectional study from NHANES

Environmental exposure to volatile organic compounds (VOCs) is ubiquitous, and this study explored whether exposure to VOCs is associated with the risk of kidney stones. We performed a nationally representative US cross-sectional study using data from five survey cycles (2011-2020) of the National Health and Nutrition Examination Survey (NHANES) program. Exposure to VOCs was determined by urine creatinine-corrected metabolites of VOCs (mVOCs). In total 5505 participants and 15 urine mVOCs were included for analysis, and the prevalence of kidney stones was 9.57 % (527/5505). Multivariable logistic regression showed that urine AMCC (parent VOCs (pVOCs): N, N-Dimethylformamide), 3,4-MHA (pVOCs: xylene), MA (pVOCs: ethylbenzene; styrene), DHBMA (pVOCs: 1,3-butadiene), HMPMA (pVOCs: crotonaldehyde) and 2HPMA (pVOCs: propylene oxide) were significantly associated with an increased risk of kidney stones in US general population. Sub-analysis revealed that there was a more pronounced association in women and the overweight/obesity group (body mass index ≥ 25). Moreover, the weighted quantile sum (WQS) regression model and the Bayesian kernel machine regression (BKMR) model consistently identified a positive association between co-exposure to VOCs and the risk of kidney stones, in which AMCC played the most important role among the 15 mVOCs. Mediation analysis further identified serum high-density lipoprotein cholesterol (HDL) as a mediator of the association between VOC co-exposure and kidney stones. Our study draws attention to the previously unknown positive associations between non-occupational VOC exposure and the risk of kidney stones in the general population. However, further studies are required to clarify the existence of such causation.

Quercetin inhibits calcium oxalate crystallization and growth but promotes crystal aggregation and invasion

Recent evidence has shown an association between kidney stone pathogenesis and oxidative stress. Many anti-oxidants have been studied with an aim for stone prevention. Quercetin, a natural flavonol, is one among those eminent anti-oxidants with satisfactory anti-inflammatory property to cope with renal tissue injury in kidney stone disease. Nevertheless, its direct effect (if any) on calcium oxalate (CaOx) crystals and the stone formation mechanism had not been previously explored. This study has addressed the ability of quercetin at various concentrations (2.5, 5, 10, 20, 40, 80 and 160 μM) to directly modulate CaOx crystallization, growth, aggregation, adhesion on kidney cells, and invasion through the matrix. The data have shown that quercetin significantly inhibits CaOx crystallization and crystal growth but promotes crystal aggregation in concentration-dependent manner. However, quercetin at all these concentrations do not affect CaOx adhesion on kidney cells. For the invasion, quercetin at all concentrations constantly promotes CaOx invasion through the matrix without concentration-dependent pattern. These discoveries have demonstrated for the first time that quercetin has direct but dual modulatory effects on CaOx crystals. While quercetin inhibits CaOx crystallization and growth, on the other hand, it promotes CaOx crystal aggregation and invasion through the matrix. These data highlight the role for quercetin in direct modulation of the CaOx crystals that may intervene the stone pathogenesis.

Hydroxycitric acid prevents hyperoxaluric-induced nephrolithiasis and oxidative stress via activation of the Nrf2/Keap1 signaling pathway

Nephrolithiasis is a common and frequently-occurring disease in the urinary system with high recurrence. The present study aimed to explore the protective effect and underlying mechanism of hydroxycitric acid (HCA) in hyperoxaluria-induced nephrolithiasis in vitro and in vivo. Crystal deposition and pathophysiological injury in rat models of glyoxylate-induced nephrolithiasis were examined using H&E staining. Cell models of nephrolithiasis were established by oxalate-treated renal tubular epithelial cells. The levels of oxidative stress indexes were determined by ELISA kits. Cell proliferation in vivo and in vitro was evaluated using a cell counting kit-8 (CCK-8) assay and Ki-67 cell proliferation detection kit. Cell apoptosis was measured by flow cytometry and TUNEL staining. The protein levels were examined by western blotting. Our results showed that HCA administration significantly reduced crystal deposition and kidney injury induced by glyoxylate. HCA also alleviated oxidative stress via upregulating the antioxidant enzyme activities of superoxide dismutase (SOD) and catalase (CAT) and reducing the malondialdehyde (MDA) content. Moreover, HCA treatment promoted cell proliferation and inhibited apoptosis of renal tubular epithelial cells exposed to hyperoxaluria. Of note, Nrf2 activator dimethyl fumarate (DMF) exerted the same beneficial effects as HCA in nephrolithiasis. Mechanistically, HCA prevented crystal deposition and oxidative stress induced by hyperoxaluria through targeting the Nrf2/Keap1 antioxidant defense pathway, while knockdown of Nrf2 significantly abrogated these effects. Taken together, HCA exhibited antioxidation and anti-apoptosis activities in nephrolithiasis induced by hyperoxaluria via activating Nrf2/Keap1 pathway, suggesting that it may be an effective therapeutic agent for the prevention and treatment of nephrolithiasis.

Oxalate (dys)Metabolism: Person-to-Person Variability, Kidney and Cardiometabolic Toxicity

Oxalate is a metabolic end-product whose systemic concentrations are highly variable among individuals. Genetic (primary hyperoxaluria) and non-genetic (e.g., diet, microbiota, renal and metabolic disease) reasons underlie elevated plasma concentrations and tissue accumulation of oxalate, which is toxic to the body. A classic example is the triad of primary hyperoxaluria, nephrolithiasis, and kidney injury. Lessons learned from this example suggest further investigation of other putative factors associated with oxalate dysmetabolism, namely the identification of precursors (glyoxylate, aromatic amino acids, glyoxal and vitamin C), the regulation of the endogenous pathways that produce oxalate, or the microbiota's contribution to oxalate systemic availability. The association between secondary nephrolithiasis and cardiovascular and metabolic diseases (hypertension, type 2 diabetes, and obesity) inspired the authors to perform this comprehensive review about oxalate dysmetabolism and its relation to cardiometabolic toxicity. This perspective may offer something substantial that helps advance understanding of effective management and draws attention to the novel class of treatments available in clinical practice.

Calcineurin B inhibits calcium oxalate crystallization, growth and aggregation via its high calcium-affinity property

Calcineurin inhibitors (CNIs) are widely used in organ transplantation to suppress immunity and prevent allograft rejection. However, some transplant patients receiving CNIs have hypocitraturia, hyperoxaluria and kidney stone with unclear mechanism. We hypothesized that CNIs suppress activities of urinary calcineurin, which may serve as the stone inhibitor. This study aimed to investigate effects of calcineurin B (CNB) on calcium oxalate monohydrate (COM) stone formation. Sequence and structural analyses revealed that CNB contained four EF-hand (Ca2+-binding) domains, which are known to regulate Ca2+ homeostasis and likely to affect COM crystals. Various crystal assays revealed that CNB dramatically inhibited COM crystallization, crystal growth and crystal aggregation. At an equal amount, degrees of its inhibition against crystallization and crystal growth were slightly inferior to total urinary proteins (TUPs) from healthy subjects that are known to strongly inhibit COM stone formation. Surprisingly, its inhibitory effect against crystal aggregation was slightly superior to TUPs. While TUPs dramatically inhibited crystal-cell adhesion, CNB had no effect on this process. Ca2+-affinity assay revealed that CNB strongly bound Ca2+ at a comparable degree as of TUPs. These findings indicate that CNB serves as a novel inhibitor of COM crystallization, growth and aggregation via its high Ca2+-affinity property.

Mitochondria-derived vesicles and their potential roles in kidney stone disease

Recent evidence has shown significant roles of mitochondria-derived vesicles (MDVs) in mitochondrial quality control (MQC) system. Under mild stress condition, MDVs are formed to carry the malfunctioned mitochondrial components, such as mitochondrial DNA (mtDNA), peptides, proteins and lipids, to be eliminated to restore normal mitochondrial structure and functions. Under severe oxidative stress condition, mitochondrial dynamics (fission/fusion) and mitophagy are predominantly activated to rescue mitochondrial structure and functions. Additionally, MDVs generation can be also triggered as the major MQC machinery to cope with unhealthy mitochondria when mitophagy is unsuccessful for eliminating the damaged mitochondria or mitochondrial fission/fusion fail to recover the mitochondrial structure and functions. This review summarizes the current knowledge on MDVs and discuss their roles in physiologic and pathophysiologic conditions. In addition, the potential clinical relevance of MDVs in therapeutics and diagnostics of kidney stone disease (KSD) are emphasized.

Himalayan Citrus jambhiri juice reduced renal crystallization in nephrolithiasis by possible inhibition of glycolate oxidase and matrix metalloproteinases

ETHNOPHARMACOLOGICAL RELEVANCE

Citrus fruits are a very rich source of electrolytes and citric acid. They have been used traditionally for treating urinary ailments and renal stones. Citrus jambhiri is indigenously used as a diuretic.

AIM OF THE STUDY

Present study aimed at establishing the antiurolithiatic potential of the juice of Citrus jambhiri fruits along with the elucidation of the mechanism involved in the urolithiasis disease defying activity.

METHODS

The antiurolithiatic activity was established by means of nucleation, growth and aggregation assay in the in vitro settings and by means of ethylene glycol mediated calcium oxalate urolithiasis in the male Wistar rats. Docking studies were performed in an attempt to determine the mechanism of the antiurolithiatic action.

RESULTS

Present study revealed the role of C. jambhiri fruit juice in reducing nucleation, growth and aggregation of calcium oxalate crystals by possible reduction in the urinary supersaturation relative to calcium oxalate and raising the zeta potential of the calcium oxalate crystals. C. jambhiri fruit juice treatment in experimental rats produced significant amelioration of hypercalciuria, hyperoxaluria, hyperphosphaturia, hyperproteinuria, hyperuricosuria, hypocitraturia and hypomagnesiuria and ion activity product of calcium oxalate. It exhibited nephroprotection against calcium oxalate crystals induced renal tubular dilation and renal tissue deterioration. Docking studies further revealed high binding potential of the phytoconstituents of C. jambhiri viz. narirutin, neohesperidin, hesperidin, rutin and citric acid with glycolate oxidase and matrix metalloproteinase-9.

CONCLUSION

C. jambhiri fruit juice possesses excellent antiurolithiatic activity. The study reveals antiurolithiatic mechanism that involves restoration of equilibrium between the promoters and inhibitors of stone formation; and inhibition of matrix metalloproteinases and glycolate oxidase.

Increased renal uptake and urine excretion of oxidized LDL is possibly associated with formation of large calcium oxalate nephrolithiasis: a preliminary study

PURPOSE

Growing evidence have suggested an association between nephrolithiasis and cardiovascular disease (CVD) with unclear mechanism. Oxidized low-density lipoproteins (oxLDL) induces atherosclerosis and was found to be the possible link between these two diseases. Our study aimed to examine the serum, urine and kidney expression of oxLDL in relation to large calcium oxalate (CaOx) renal stone disease.

METHODS

A total of 67 large CaOx dominant renal stone patients and 31 stone-free controls were enrolled in the prospective case-control study. All participants were without known CVD history. Serum, urine, and kidney biopsy were collected before and during percutaneous nephrolithotomy, respectively. Enzyme-linked immunosorbent assays were used to assess serum and urine oxLDL, lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), and high-sensitivity C-reactive protein (hsCRP).

RESULTS

There was no significantly difference in circulating oxLDL, but serum hsCRP was significantly near two-fold higher in nephrolithiasis patients. Serum hsCRP was also correlated with stone maximal length. Urine oxLDL was significantly higher in the nephrolithiasis group and correlated with serum hsCRP and stone maximal length. Increased oxLDL uptake in kidney was found in nephrolithiasis patients, whereas no significantly renal expression of oxLDL was observed in controls.

CONCLUSIONS

The renal uptake of oxLDL with increased oxLDL excretion from large CaOx renal stone formers, independent of increased circulating oxLDL, is a novel pathological finding in kidney stone disease and brings attention to the possible involvement of renal steatosis in the process of urolithiasis formation.

Protective efficacy of Schizandrin B on ameliorating nephrolithiasis via regulating GSK3β/Nrf2 signaling-mediated ferroptosis in vivo and in vitro

Schizandrin B (SchB) protects against oxidative, inflammatory, and ferroptotic injury. Oxidative stress and inflammation are indispensably involved in nephrolithiasis and ferroptosis also plays an important role in stone formation. It is unclear whether SchB can ameliorate nephrolithiasis; its underlying mechanism is also unknown. First, we employed bioinformatics to investigate the mechanisms of nephrolithiasis. To evaluate the efficacy of SchB, HK-2 cell models of oxalate-induced damage, Erastin-induced ferroptosis, and the Sprague Dawley rat model of Ethylene Glycol-induced nephrolithiasis were established. Then, Nrf2 siRNA and GSK3β overexpression plasmids were transfected into HK-2 cells to elucidate the role of SchB in regulating oxidative stress-mediated ferroptosis. In our study, oxidative stress and inflammation were strongly associated with nephrolithiasis. Administration of SchB attenuated the cell viability, dysfunctional mitochondria, oxidative stress and inflammatory response in vitro and alleviated renal injury and crystal deposition in vivo. SchB treatment also reduced the levels of cellular Fe²⁺ accumulation, lipid peroxidation and MDA, and regulated ferroptosis-related proteins, including XCT, GPX4, FTH1 and CD71, in Erastin-induced or oxalate-induced HK-2 cells. Mechanistically, SchB facilitated Nrf2 nuclear translocation, and silencing Nrf2 or overexpressing GSK3β worsened oxalate-induced oxidative injury and abolished the beneficial effect of SchB against ferroptosis in vitro. To summarize, SchB could alleviate nephrolithiasis by positively regulating GSK3β/Nrf2 signaling-mediated ferroptosis.

Proteomics and transcriptomics profiling reveals distinct aspects of kidney stone related genes in calculi rats

BACKGROUNDS

Kidney stone also known as urolithiasis or nephrolithiasis, is one of the oldest diseases known to medicine, however, the gene expression changes and related kidney injury remains unclear.

METHODS

A calculi rat model was developed via ethylene glycol- and ammonium chloride-induction. Integrated proteomic and transcriptomic analysis was performed to characterize the distinct gene expression profiles in the kidney of calculi rat. Differential expressed genes (DEGs) were sub-clustered into distinct groups according to the consistency of transcriptome and proteome. Gene Ontology and KEGG pathway enrichment was performed to analyze the functions of each sub-group of DEGs. Immunohistochemistry was performed to validated the expression of identified proteins.

RESULTS

Five thousand eight hundred ninety-seven genes were quantified at both transcriptome and proteome levels, and six distinct gene clusters were identified, of which 14 genes were consistently dysregulated. Functional enrichment analysis showed that the calculi rat kidney was increased expression of injured & apoptotic markers and immune-molecules, and decreased expression of solute carriers & transporters and many metabolic related factors.

CONCLUSIONS

The present proteotranscriptomic study provided a data resource and new insights for better understanding of the pathogenesis of nephrolithiasis, will hopefully facilitate the future development of new strategies for the recurrence prevention and treatment in patients with kidney stone disease.

Maternal family history of urolithiasis is associated with earlier age of onset of stone disease

PURPOSE

To evaluate the impact of detailed family history on the severity of disease and age of onset in patients with urolithiasis.

METHODS

Prospectively collected data from a single institution between October 2015 and December 2020 were analyzed. Our primary endpoint was the number of patients experiencing at least one recurrent stone during the follow-up period.

RESULTS

Of 1566 patients analyzed, 603 (39%) reported at least one family member with a history of stones. The percentage of patients experiencing at least one recurrent stone event was higher in patients with a family history of stones (38%) compared to those without a family history of stones (28%) over a median follow-up period of 8 months (p = 0.001). On multivariate analysis, the presence of any family history of urolithiasis increased risk of recurrent stone events (odds ratio [OR] 1.62, p < 0.001). The presence of both a first- and a second-degree relative with urolithiasis was associated with higher odds for a recurrent stone event (OR 2.17; p = 0.003) and a younger age of onset for stones, (OR 3.32; < 0.001). A maternal-side relative with stones conferred a higher odds ratio for younger age of first onset of stones (OR 2.93; p < 0.001).

CONCLUSION

Any family history of kidney stone disease imparts an increased risk of recurrent stone event and an earlier age of onset for urolithiasis. The presence of both first- and second-degree relatives or a maternal-side relative with kidney stones may be a predictor for an earlier age of onset for urolithiasis.

A pilot dynamic analysis of formative factors of nephrolithiasis related to metabolic syndrome: evidence in a rat model

Introduction and objective

To examine the dynamic changes in the formative factors of nephrolithiasis and the final micromorphological changes in an obesity-initiated metabolic syndrome (MS) rat model.

Methods

Forty five-week-old male Sprague–Dawley (SD) rats were randomly divided into four groups: the regular diet group (RD), high-fat diet group (HFD), regular diet with drug (ethylene glycol and ammonium chloride) group (RDD), and high-fat diet with drug group (HFDD). A dynamic assessment of MS components (body weight (BW), body length (BL), Lee’s index (LI), blood glucose (BG), total cholesterol (TC), and triglycerides (TGs)) and stone-forming factors (urinary pH, urinary calcium, and urinary oxalate acid) was carried out. In addition, the levels of oxidative stress (OS) markers (CAT, SOD, TAC, GSH-PX, and MDA) were measured, and histological analysis was carried out at the end of 16 weeks.

Results

MS-related parameters, such as BW, LI, BG, TC, and TG, were significantly higher in HFD-fed rats than in RD-fed rats (p < 0.001). In the HFDD group, significantly lower urinary pH, hyperoxaluria, and hypocalciuria were noted in the dynamic assessment of stone-forming factors (p < 0.001). CAT, TAC, and MDA were notably changed in the HFD-fed groups, particularly the HFDD rats. Histological analysis showed that the renal tubules of HFDD rats had the highest scores for both inflammation and renal crystallization deposition (p < 0.05).

Conclusions

Our results suggest that male SD rats with MS are prone to developing nephrolithiasis. Validation in an in vivo model may lead to an understanding of the underlying pathophysiological mechanisms of action of MS-related nephrolithiasis in humans.

Key messages

Male SD rats with metabolic syndrome are more prone to developing calcium oxalate nephrolithiasis after treatment with ethylene glycol and ammonium chloride compared to control lean rats.

MS-related nephrolithiasis in rats induced by ethylene glycol and ammonium chloride is mainly related to increased hyperoxaluria and inflammation and decreased antioxidant levels.

High-fat diet-fed SD rats treated with ethylene glycol and ammonium chloride are a stable and valid in vivo model for understanding the potential mechanism of action of MS-related nephrolithiasis.

Nephro-protective effect of Daphnetin in hyperoxaluria-induced rat renal injury via alterations of the gut microbiota

It is well proved that hyperoxaluria induces the renal injury and finally causes the end stage kidney disease. Daphnetin (coumarin derivative) already confirmed renal protective effect in renal model, but hyperoxaluria protective effect still unexplore. The objective of this research was to scrutinize the renal protective effect of daphnetin against ethylene glycol (GC)-induced hyperoxaluria via altering the gut microbiota. GC (1% v/v) was used for the induction of hyperoxaluria in the rats and the rats were received the oral administration of daphnetin (5, 10 and 15 mg/kg). The body and renal weight were assessed. Urine, renal, inflammatory cytokines, antioxidant, inflammatory parameters, and gut microbiota were appraised. Daphnetin effectually improved the body weight and reduced the renal weight. Its also remarkably boosted the magnesium, calcium, citrate level and suppressed the level of uric acid and oxalate formation. Daphnetin significantly (p < .001) ameliorate the level of urinary kidney injury molecule 1 (KIM-1), blood urea nitrogen (BUN), urea, serum creatinine (Scr), neutrophil gelatinase-associated lipocalin (NGAL) and uric acid along with inflammatory cytokines and inflammatory mediators. Daphnetin considerably repressed the malonaldehyde (MDA) level, protein carbonyl and improved the level of glutathione reductase (GR), superoxide dismutase (SOD), glutathione (GSH) and catalase (CAT). Daphnetin treatment considerably altered the microbial composition of different bacteria at phylum, genus and family level. Daphnetin significantly suppressed the Firmicutes relative abundance and boosted the Bacteroidetes relative abundance. Our result clearly indicated that daphnetin remarkably ameliorates the GC induced hyperoxaluria in rats via altering the oxidative stress, inflammatory reaction and gut microbiota. PRACTICAL APPLICATION: Nephrotoxicity is a serious health disease worldwide. We induce the renal toxicity in the experimental rats using the ethylene glycol and scrutinized the renal protective effect of daphnetin. Daphnetin considerably suppress the renal, urine parameters. For estimation the underlying mechanism, we estimated the gut microbiota in all group rats. Daphnetin remarkably altered the level of gut microbiota and suggesting the renal protective effect.

Association between sleep duration and kidney stones in 34 190 American adults: A cross-sectional analysis of NHANES 2007-2018

OBJECTIVE

To explore the association between sleep duration and kidney stones among United States adults.

PARTICIPANTS AND METHODS

This cross-sectional study is based on National Health and Nutrition Examination Surveys (NHANES) 2007-2018. Participants aged 20 years and above who self-reported history of kidney stones and sleep duration were included. Weighted proportions, multivariable analysis, and piecewise linear regression were used to evaluate the associations between sleep duration and kidney stones, while adjusting for gender, age, race, poverty income ratio, body mass index, education, marital status, trouble sleeping, smoking, alcohol and some comorbidities. Stratified logistic regression models were used in subgroup analyses and included all potential confounding factors above.

RESULTS

Of the 34,190 participants, the overall weighted kidney stone prevalence was 9.73%, weighted mean age was 47.67 ± 16.99 years, and mean sleep duration was 7.15 ± 1.44 hours. The fully adjusted multivariable model demonstrated that people with normal (7-9 hours) and long (>9 hours) sleep duration had 17% and 20% lower odds of kidney stone prevalence than people with short sleep duration (<7 hours), respectively. However, fitting a smooth curve showed a nonlinear association between sleep duration and kidney stones. A piecewise linear regression model showed that one hour longer sleep duration was associated with 7% lower kidney stone prevalence for people with short sleep duration and with 22% higher prevalence for participants with long sleep duration. However, for people with normal sleep duration, increasing sleep duration was nonsignificantly associated with lower prevalence of kidney stones. Subgroup analysis showed no significant interaction effects.

CONCLUSIONS

There is a curvilinear relationship between sleep duration and kidney stones. Normal sleep duration is associated with lower prevalence of kidney stones than short sleep duration. This study provides new insight into potential strategies for the prevention and treatment of kidney stones.

Inhibition of sodium-glucose cotransporter 2 suppresses renal stone formation

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.

CAV1 alleviated CaOx stones formation via suppressing autophagy-dependent ferroptosis

Background

Calcium oxalate (CaOx) is the most common type of kidney stone, but the mechanism of CaOx stones formation remains unclear. The injury of renal cells such as ferroptosis and autophagy has been considered a basis for stones formation.

Methods

We conducted transmission electron microscope (TEM), reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), and C11-BODIPY analysis to explore whether CaOx could induce autophagy-dependent ferroptosis in vivo and in vitro. To explore the possible mechanism, we conducted bioinformatic analysis of patients with or without CaOx stones, Western blot and qPCR were used to identify the different genes we found in bioinformatic analysis.

Results

In our study, we found that CaOx could induce autophagy-dependent ferroptosis no matter in vivo or in vitro, which might finally lead to urolithiasis. Bioinformatic analysis of the GSE73680 dataset indicated that the expression of caveolin-1 (CAV1) was higher in control patients than CaOx stone patients, the STRING database indicated that CAV1 might interact with low density lipoprotein receptro-related protein 6 (LRP6), Gene Set Enrichment Analysis (GSEA) showed that the WNT pathway positively associated with the control group while negatively related to the stone group, and LRP6 was the core gene of the WNT pathway. Western blot found that CAV1, LRP6, and Wnt/β-Catenin were decreased in Human Kidney2 (HK2) cells stimulated with CaOx. Furthermore, the WNT pathway was considered to be involved in autophagy and ferroptosis.

Conclusions

We presumed that CAV1 could ameliorate autophagy-dependent ferroptosis through the LRP6/Wnt/β-Catenin axis, and finally alleviate CaOx stone formation.

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.

HydroZitLa inhibits calcium oxalate stone formation in nephrolithic rats and promotes longevity in nematode Caenorhabditis elegans

Low fluid intake, low urinary citrate excretion, and high oxidative stress are main causative factors of calcium oxalate (CaOx) nephrolithiasis. HydroZitLa contains citrate and natural antioxidants and is developed to correct these three factors simultaneously. Antioxidants theoretically can prolong the lifespan of organisms. In this study, we preclinically investigated the antilithogenic, lifespan-extending and anti-aging effects of HydroZitLa in HK-2 cells, male Wistar rats, and Caenorhabditis elegans. HydroZitLa significantly inhibited CaOx crystal aggregation in vitro and reduced oxidative stress in HK-2 cells challenged with lithogenic factors. For experimental nephrolithiasis, rats were divided into four groups: ethylene glycol (EG), EG + HydroZitLa, EG + Uralyt-U, and untreated control. CaOx deposits in kidneys of EG + HydroZitLa and EG + Uralyt-U rats were significantly lower than those of EG rats. Intrarenal expression of 4-hydroxynonenal in EG + HydroZitLa rats was significantly lower than that of EG rats. The urinary oxalate levels of EG + HydroZitLa and EG + Uralyt-U rats were significantly lower than those of EG rats. The urinary citrate levels of EG + HydroZitLa and EG + Uralyt-U rats were restored to the level in normal control rats. In C. elegans, HydroZitLa supplementation significantly extended the median lifespan of nematodes up to 34% without altering feeding ability. Lipofuscin accumulation in HydroZitLa-supplemented nematodes was significantly lower than that of non-supplemented control. Additionally, HydroZitLa inhibited telomere shortening, p16 upregulation, and premature senescence in HK-2 cells exposed to lithogenic stressors. Conclusions, HydroZitLa inhibited oxidative stress and CaOx formation both in vitro and in vivo. HydroZitLa extended the lifespan and delayed the onset of aging in C. elegans and human kidney cells. This preclinical evidence suggests that HydroZitLa is beneficial for inhibiting CaOx stone formation, promoting longevity, and slowing down aging.

Plants Used in Mexican Traditional Medicine for the Management of Urolithiasis: A Review of Preclinical Evidence, Bioactive Compounds, and Molecular Mechanisms

Urolithiasis (UL) involves the formation of stones in different parts of the urinary tract. UL is a health problem, and its prevalence has increased considerably in developing countries. Several regions use plants in traditional medicine as an alternative in the treatment or prevention of UL. Mexico has known about the role of traditional medicine in the management of urinary stones. Mexican traditional medicine uses plants such as Argemone mexicana L., Berberis trifoliata Hartw. ex Lindl., Costus mexicanus Liebm, Chenopodium album L., Ammi visnaga (L.) Lam., Eysenhardtia polystachya (Ortega) Sarg., Selaginella lepidophylla (Hook. & Grev.) Spring, and Taraxacum officinale L. These plants contain different bioactive compounds, including polyphenols, flavonoids, phytosterols, saponins, furanochromones, alkaloids, and terpenoids, which could be effective in preventing the process of stone formation. Evidence suggests that their beneficial effects might be associated with litholytic, antispasmodic, and diuretic activities, as well as an inhibitory effect on crystallization, nucleation, and aggregation of crystals. The molecular mechanisms involving these effects could be related to antioxidant, anti-inflammatory, and antimicrobial properties. Thus, the review aims to summarize the preclinical evidence, bioactive compounds, and molecular mechanisms of the plants used in Mexican traditional medicine for the management of UL.

Mitochondrial Pathophysiology on Chronic Kidney Disease

In healthy kidneys, interstitial fibroblasts are responsible for the maintenance of renal architecture. Progressive interstitial fibrosis is thought to be a common pathway for chronic kidney diseases (CKD). Diabetes is one of the boosters of CKD. There is no effective treatment to improve kidney function in CKD patients. The kidney is a highly demanding organ, rich in redox reactions occurring in mitochondria, making it particularly vulnerable to oxidative stress (OS). A dysregulation in OS leads to an impairment of the Electron transport chain (ETC). Gene deficiencies in the ETC are closely related to the development of kidney disease, providing evidence that mitochondria integrity is a key player in the early detection of CKD. The development of novel CKD therapies is needed since current methods of treatment are ineffective. Antioxidant targeted therapies and metabolic approaches revealed promising results to delay the progression of some markers associated with kidney disease. Herein, we discuss the role and possible origin of fibroblasts and the possible potentiators of CKD. We will focus on the important features of mitochondria in renal cell function and discuss their role in kidney disease progression. We also discuss the potential of antioxidants and pharmacologic agents to delay kidney disease progression.

Emerging connections between gut microbiome bioenergetics and chronic metabolic diseases

The conventional viewpoint of single-celled microbial metabolism fails to adequately depict energy flow at the systems level in host-adapted microbial communities. Emerging paradigms instead support that distinct microbiomes develop interconnected and interdependent electron transport chains that rely on cooperative production and sharing of bioenergetic machinery (i.e., directly involved in generating ATP) in the extracellular space. These communal resources represent an important subset of the microbial metabolome, designated here as the "pantryome" (i.e., pantry or external storage compartment), that critically supports microbiome function and can exert multifunctional effects on host physiology. We review these interactions as they relate to human health by detailing the genomic-based sharing potential of gut-derived bacterial and archaeal reference strains. Aromatic amino acids, metabolic cofactors (B vitamins), menaquinones (vitamin K2), hemes, and short-chain fatty acids (with specific emphasis on acetate as a central regulator of symbiosis) are discussed in depth regarding their role in microbiome-related metabolic diseases.

Oxidative Modifications Switch Modulatory Activities of Urinary Proteins From Inhibiting to Promoting Calcium Oxalate Crystallization, Growth, and Aggregation

The incidence/prevalence of kidney stone disease has been increasing around the globe, but its pathogenic mechanisms remained unclear. We evaluated effects of oxidative modifications of urinary proteins on calcium oxalate (CaOx) stone formation processes. Urinary proteins derived from 20 healthy individuals were modified by performic oxidation, and the presence of oxidatively modified urinary proteins was verified, quantified, and characterized by Oxyblot assay and tandem MS (nanoLC-electrospray ionization-linear trap quadrupole-Orbitrap-MS/MS). Subsequently, activities of oxidatively modified urinary proteins on CaOx stone formation processes were examined. Oxyblot assay confirmed the marked increase in protein oxidation level in the modified urine. NanoLC-electrospray ionization-linear trap quadrupole-Orbitrap-MS/MS identified a total of 193 and 220 urinary proteins in nonmodified and modified urine samples, respectively. Among these, there were 1121 and 5297 unambiguous oxidatively modified peptides representing 42 and 136 oxidatively modified proteins in the nonmodified and modified urine samples, respectively. Crystal assays revealed that oxidatively modified urinary proteins significantly promoted CaOx crystallization, crystal growth, and aggregation. By contrast, the nonmodified urinary proteins had inhibitory activities. This is the first direct evidence demonstrating that oxidative modifications of urinary proteins increase the risk of kidney stone disease by switching their modulatory activities from inhibiting to promoting CaOx crystallization, crystal growth, and aggregation.

Antioxidant activity of sulfated Porphyra yezoensis polysaccharides and their regulating effect on calcium oxalate crystal growth

The nucleation, growth and aggregation of calcium oxalate (CaOx) crystals and the oxidative damage of renal tubular epithelial cells are the key factors to induce kidney stones. In this study, degraded Porphyra yezoensis polysaccharide (PYP0) with 14.14% sulfate group (-OSO₃^-) content was modified via the sulfur trioxide-pyridine method to obtain three kinds of sulfated P. yezoensis polysaccharides (PYPs), namely, PYPS1, PYPS2, and PYPS3, with -OSO₃^- group contents of 17.11%, 20.28%, and 27.14% respectively. Fourier transform infrared spectroscopy, ¹H NMR, and ¹³C NMR analyses showed that the -OSO₃^- groups replaced the hydroxyl groups at the C2, C4, and C6 positions on (1 → 3)-linked β-D-galactose, the basic structural skeleton unit of PYP0. The antioxidant activity of the PYPSs increased after sulfation, and their scavenging capacity for OH and DPPH free radicals was enhanced with the increase in their -OSO₃^- group content. Calcium oxalate (CaOx) crystal growth experiments showed that sulfated PYPs promoted the conversion of the thermodynamically stable and sharp CaOx monohydrate (COM) crystals into the thermodynamically unstable and round CaOx dihydrate crystals. With the increase in the -OSO₃^- group content of the polysaccharides, the concentration of soluble Ca²⁺ ions in the supernatant increased and the amount of CaOx precipitate decreased. PYPs were nontoxic to human kidney proximal tubular epithelial cells (HK-2) and could protect HK-2 from oxidative damage caused by nano-COM and reduce the level of reactive oxygen species in cells. PYPS3, which had the highest degree of sulfation, had the best protective capability. The results of this work showed that sulfation improved the biological activity of PYPs. This study could provide inspiration for the development of new drugs for the prevention and treatment of kidney stones.

Effects of secretome derived from macrophages exposed to calcium oxalate crystals on renal fibroblast activation

The association between kidney stone disease and renal fibrosis has been widely explored in recent years but its underlying mechanisms remain far from complete understanding. Using label-free quantitative proteomics (nanoLC-ESI-LTQ-Orbitrap MS/MS), this study identified 23 significantly altered secreted proteins from calcium oxalate monohydrate (COM)-exposed macrophages (COM-MP) compared with control macrophages (Ctrl-MP) secretome. Functional annotation and protein-protein interactions network analysis revealed that these altered secreted proteins were involved mainly in inflammatory response and fibroblast activation. BHK-21 renal fibroblasts treated with COM-MP secretome had more spindle-shaped morphology with greater spindle index. Immunofluorescence study and gelatin zymography revealed increased levels of fibroblast activation markers (α-smooth muscle actin and F-actin) and fibrotic factors (fibronectin and matrix metalloproteinase-9 and -2) in the COM-MP secretome-treated fibroblasts. Our findings indicate that proteins secreted from macrophages exposed to COM crystals induce renal fibroblast activation and may play important roles in renal fibrogenesis in kidney stone disease.

Kidney stone proteomics: an update and perspectives

INTRODUCTION

Main problems of kidney stone disease are its increasing prevalence and high recurrence rate after calculi removal in almost all areas around the globe. Despite enormous efforts in the past, its pathogenic mechanisms remain unclear and need further elucidations. Proteomics has thus become an essential tool to unravel such sophisticated disease mechanisms at cellular, subcellular, molecular, tissue, and whole organism levels.

AREAS COVERED

This review provides abrief overview of kidney stone disease followed by updates on proteomics for investigating urinary stone modulators, matrix proteins, cellular responses to different types/doses of calcium oxalate (CaOx) crystals, sex hormones and other stimuli, crystal-cell interactions, crystal receptors, secretome, and extracellular vesicles (EVs), all of which lead to better understanding of the disease mechanisms. Finally, the future challenges and translation of these obtained data to the clinic are discussed.

EXPERT OPINION

Knowledge from urinary proteomics for exploring the important stone modulators (either inhibitors or promoters) will be helpful for early detection of asymptomatic cases for prompt prevention of symptoms, complications, and new stone formation. Moreover, these modulators may serve as the new therapeutic targets in the future for successful treatment and prevention of kidney stone disease by medications or other means of intervention.

Downregulation of inflammatory mediators by ethanolic extract of Bergenia ligulata (Wall.) in oxalate injured renal epithelial cells

ETHNOPHARMACOLOGICAL RELEVANCE

In the Indian traditional system of medicine, Bergenia ligulata (Wall.) Engl. has been used for treatment of urolithiasis. Its efficacious nature has led to its incorporation in various commercial herbal formulations such as Cystone and Neeri which are prescribed for kidney related ailments.

AIM OF THE STUDY

To assess whether ethanolic extract of B. ligulata can mitigate the cascade of inflammatory responses that cause oxidative stress and ultimately cell death in renal epithelial cells exposed to hyperoxaluric conditions.

MATERIAL AND METHODS

Bioactivity guided fractionation using solvents of varying polarities was employed to evaluate the potential of the extracts of B. ligulata to inhibit the crystallization process. Modulation of crystal morphology was visualized through Scanning electron microscopy (SEM) analysis. Cell death was assessed using flow cytometry based assays. Alteration in the inflammatory mediators was evaluated using real time PCR and immunocytochemistry. Phytochemical characterization of the ethanolic extract was carried out using FTIR, LC-MS and GC-MS.

RESULTS

Bioactivity guided fractionation for the assessment of antilithiatic activity revealed dose dependent inhibition of nucleation and aggregation process of calcium oxalate crystals in the presence of various extracts, however ethanolic extract showed maximum inhibition and was chosen for further experiments. Studies on renal epithelial NRK-52E cells showed, cytoprotective efficacy of B. ligulata extract against oxalate injury. SEM anaysis further revealed the potential of the extract to modulate the crystal structure and adhesion to renal cell surface. Exposure of the renal cells to the extract led to conversion of the calcium oxalate monohydrate (COM) crystals to the less injurious calcium oxalate dihydrate (COD) form. Expression analysis for oxidative stress and inflammatory biomarkers in NRK-52E cells revealed up-regulation of Mitogen activated protein kinase (MAPK), Osteopontin (OPN) and Nuclear factor- ĸB (NF-ĸB), in response to calcium oxalate insult; which was drastically reduced in the presence of B. ligulata extract. Flow cytometric evaluation pointed to caspase 3 mediated apoptotic cell death in oxalate injured cells, which was attenuated by B. ligulata extract.

CONCLUSION

Considering the complex multifactorial etiology of urolithiasis, ethanolic extract from B. ligulata can be a promising option for the management of kidney stones, as it has the potential to limit inflammation and the subsequent cell death.

Dual modulatory effects of diosmin on calcium oxalate kidney stone formation processes: Crystallization, growth, aggregation, crystal-cell adhesion, internalization into renal tubular cells, and invasion through extracellular matrix

Diosmin is a natural flavone glycoside (bioflavonoid) found in fruits and plants with several pharmacological activities. It has been widely used as a dietary supplement or therapeutic agent in various diseases/disorders. Although recommended, evidence of its protective mechanisms against kidney stone disease (nephrolithiasis/urolithiasis), especially calcium oxalate (CaOx) monohydrate (COM) that is the most common type, remained unclear. In this study, we thus systematically evaluated the effects of diosmin (at 2.5-160 nM) on various stages of kidney stone formation processes, including COM crystallization, crystal growth, aggregation, crystal-cell adhesion, internalization into renal tubular cells and invasion through extracellular matrix (ECM). The results showed that diosmin had dose-dependent modulatory effects on all the mentioned COM kidney stone processes. Diosmin significantly increased COM crystal number and mass during crystallization, but reduced crystal size and growth. While diosmin promoted crystal aggregation, it inhibited crystal-cell adhesion and internalization into renal tubular cells. Finally, diosmin promoted crystal invasion through the ECM. Our data provide evidence demonstrating both inhibiting and promoting effects of diosmin on COM kidney stone formation processes. Based on these dual modulatory activities of diosmin, its anti-urolithiasis role is doubtful and cautions should be made for its use in kidney stone disease.

Calcium oxalate monohydrate crystal disrupts tight junction via F-actin reorganization

Tight junction is an intercellular protein complex that regulates paracellular permeability and epithelial cell polarization. This intercellular barrier is associated with actin filament. Calcium oxalate monohydrate (COM), the major crystalline composition in kidney stones, has been shown to disrupt tight junction but with an unclear mechanism. This study aimed to address whether COM crystal disrupts tight junction via actin deregulation. MDCK distal renal tubular epithelial cells were treated with 100 μg/ml COM crystals for 48 h. Western blot analysis revealed that level of a tight junction protein, zonula occludens-1 (ZO-1), significantly decreased, whereas that of β-actin remained unchanged after exposure to COM crystals. Immunofluorescence study showed discontinuation and dissociation of ZO-1 and filamentous actin (F-actin) expression at the cell border. In addition, clumping of F-actin was found in some cytoplasmic areas of the COM-treated cells. Moreover, transepithelial resistance (TER) was reduced by COM crystals, indicating the defective barrier function of the polarized cells. All of these COM-induced defects could be completely abolished by pretreatment with 20 μM phalloidin, an F-actin stabilizer, 2-h prior to the 48-h crystal exposure. These findings indicate that COM crystal does not reduce the total level of actin but causes tight junction disruption via F-actin reorganization.