Recent advances in managing and understanding nephrolithiasis/nephrocalcinosis

New insight into oxidative stress and inflammatory responses to kidney stones: Potential therapeutic strategies with natural active ingredients

Kidney stones, a prevalent urological disorder, are closely associated with oxidative stress (OS) and the inflammatory response. Recent research in the field of kidney stone treatment has indicated the potential of natural active ingredients to modulate OS targets and the inflammatory response in kidney stones. Oxidative stress can occur through various pathways, increasing the risk of stone formation, while the inflammatory response generated during kidney stone formation further exacerbates OS, forming a detrimental cycle. Both antioxidant systems related to OS and inflammatory mediators associated with inflammation play roles in the pathogenesis of kidney stones. Natural active ingredients, abundant in resources and possessing antioxidative and anti-inflammatory properties, have the ability to decrease the risk of stone formation and improve prognosis by reducing OS and suppressing pro-inflammatory cytokine expression or pathways. Currently, numerous developed natural active ingredients have been clinically applied and demonstrated satisfactory therapeutic efficacy. This review aims to provide novel insights into OS and inflammation targets in kidney stones as well as summarize research progress on potential therapeutic strategies involving natural active ingredients. Future studies should delve deeper into exploring efficacy and mechanisms of action of diverse natural active ingredients, proposing innovative treatment strategies for kidney stones, and continuously uncovering their potential applications.

Tea and coffee consumption and the risk of urinary stones-a systematic review of the epidemiological data

OBJECTIVE

To explore the relationship between the consumption of coffee and tea with urolithiasis. We evaluated large epidemiological and small clinical studies to draw conclusions regarding their lithogenic risk.

METHODS

A systematic review was performed using the Medline and Scopus databases, in concordance with the PRISMA statement. English, French, and Spanish language studies regarding the consumption of caffeinated and decaffeinated coffee and tea, and the relationship to urinary stone disease were reviewed. Case reports and letters, unpublished studies, posters, and comments were excluded.

RESULTS

As per the inclusion criteria, 13 studies were included in the final review. Most studies, including four large prospective studies and one meta-analysis, reported a reduced risk of stone formation for coffee and tea. Caffeine has a diuretic effect and increases the urinary excretion of calcium, but if these losses are compensated for, moderate caffeine intakes may have little or no deleterious effects. Green and Herbal teas infused for short time had low oxalate content compared to black tea.

CONCLUSION

There is no evidence that moderate consumption of coffee raises the risk for stone formation in healthy individuals, provided the recommended daily fluid intake is maintained. The currently available literature supports in general a protective role for tea against the stone formation, mainly for green tea. However, heterogeneity of published data and lack of standardization needs to be addressed before final and clear conclusions can be given to patients and to the public in general.

Idiopathic Osteoporosis and Nephrolithiasis: Two Sides of the Same Coin?

Idiopathic osteoporosis and nephrolithiasis are formidable health problems showing a progressive increase in their incidence and prevalence in the last decades. These temporal trends were observed in both pediatric and adult populations worldwide. Epidemiological and experimental studies indicate that both disorders show several common pathogenic environmental and genetic factors. In this review, we analyzed the clinical characteristics common to the two disorders and the state-of-the-art knowledge regarding the genetic predisposition and the environmental factors recognized as triggers in adult and pediatric ages. As a result of this work, we propose to consider idiopathic nephrolithiasis and osteoporosis as two possible expressions of a unique clinical syndrome. Accordingly, the clinical approach to both disorders should be modified in order to program an efficient primary and secondary prevention strategy.

Relationship of endoscopic lesions of the renal papilla with type of renal stone and 24 h urine analysis

Background

Our purpose was to study the relationship of the 3 different types of endoscopic calcifications of the renal papilla (Randall’s plaque, intratubular calcification, papillary crater) with the type of stone and urine analysis.

Methods

This prospective study examined 41 patients (age range: 18 to 80 years) who received retrograde intrarenal surgery (RIRS) for renal lithiasis (mean stone size: 15.3 ± 7.2 mm). The renal papilla injuries were endoscopically classified as Randall’s plaque, intratubular calcification, or papillary crater. Calculi were classified as uric acid, calcium oxalate monohydrate (COM; papillary and cavity), calcium oxalate dihydrate (COD), or calcium phosphate (CP). A 24 h urine analysis of calcium, oxalate, citrate, phosphate, and pH was performed in all patients. The relationship of each type of papillary injury with type of stone and urine chemistry was determined. Fisher’s exact test and Student’s t-test were used to determine the significance of relationships, and a p value below 0.05 was considered significant.

Results

The most common injury was tubular calcification (78%), followed by Randall’s plaque (58%), and papillary crater (39%). There was no significant relationship of Randall’s plaque with type of stone. However, endoscopic intratubular calcification (p = 0.025) and papillary crater (p = 0.041) were more common in patients with COD and CP stones. There were also significant relationships of papillary crater with hypercalciuria (p = 0.036) and hyperoxaluria (p = 0.024), and of Randall’s plaque with hypocitraturia (p = 0.005).

Conclusions

There are certain specific relationships between the different types of papillary calcifications that were endoscopically detected with stone chemistry and urine analysis. COD and CP stones were associated with endoscopic tubular calcifications and papillary craters. Hypercalciuria was associated with tubular calcification, and hypocitraturia was associated with Randall’s plaque.

Human proximal tubular cells can form calcium phosphate deposits in osteogenic culture: role of cell death and osteoblast-like transdifferentiation

Nephrocalcinosis is a clinicopathological entity characterized by microscopic calcium crystals in the renal parenchyma, within the tubular lumen or in the interstitium. Crystal binding to tubular cells may be the cause underlying nephrocalcinosis and nephrolithiasis. Pathological circumstances, such as acute cortical necrosis, may induce healthy cells to acquire a crystal-binding phenotype. The present study aimed to investigate whether human renal proximal tubular cells (HK-2 cells) can form calcium phosphate deposits under osteogenic conditions, and whether apoptosis and/or osteogenic-like processes are involved in cell calcification. HK-2 cells were cultured in standard or osteogenic medium for 1, 5, and 15 days. Von Kossa staining and ESEM were used to analyze crystal deposition. Apoptosis was investigated, analyzing caspase activation by in-cell Western assay, membrane translocation of phosphotidylserine by annexin V-FITC/propidium iodide staining, and DNA fragmentation by TUNEL assay. qRT/PCR, immunolabeling and cytochemistry were performed to assess osteogenic activation (Runx2, Osteonectin, Osteopontin and ALP), and early genes of apoptosis (BAX, Bcl-2). HK-2 cell mineralization was successfully induced on adding osteogenic medium. Calcium phosphate deposition increased in a time-dependent manner, and calcified cell aggregates exhibited characteristic signs of apoptosis. At 15 days, calcifying HK-2 cells revealed osteogenic markers, such as Runx2, ALP, osteonectin and osteopontin. Monitoring the processes at 1, 5, and 15 days showed apoptosis starting already after 5 days of osteogenic induction, when the first small calcium phosphate crystals began to appear on areas where cell aggregates were in apoptotic conditions. The cell death process proved caspase-dependent. The importance of apoptosis was reinforced by the time-dependent increase in BAX expression, starting from day 1. These findings strongly support the hypothesis that apoptosis triggered HK-2 calcification even before any calcium phosphate crystal deposition or acquisition of an osteogenic phenotype.

The potential effects of dietary food and beverage intakes on the risk of kidney stone formation

ABSTRACT Objective To determine the effect of nutritional habits on kidney stone formation and recurrence. Methods This study was conducted on 44 healthy individuals and 44 patients diagnosed with nephrolithiasis and aging between 20 and 65 years. Participants shared their salt consumption habits, daily fluid consumption amounts and general information about themselves in a questionnaire form. In addition, food and beverage consumption frequencies of participants were recorded through a food frequency questionnaire. Results Salt consumption frequencies of patients are higher than that of healthy individuals in both genders (p<0.05). It was found out that male individuals in the patient group salt dishes without tasting more frequently (p<0.05). Daily total water consumption of both genders in patient group is lower than that of healthy individuals (p<0.05). Meat consumption of male patients (51.6±31.35g/day) was found to be higher than that of healthy group (34.1±22.58g/day) (p<0.05). Additionally, individuals in the patient group consume less stinging nettle, corn, plum, loquat, orange juice and lemonade than healthy individuals (p<0.05). Conclusion Results of the study showed that total fluid intake, salt consumption habits, and vegetable, fruit and beverage consumption may be correlated with stone formation risk and nutrition habits may affect stone recurrence.

Is oxidized low-density lipoprotein the connection between atherosclerosis, cardiovascular risk and nephrolithiasis?

Nephrolithiasis is considered a systemic disease. A link has been established between nephrolithiasis, cardiovascular disease (CVD), the metabolic syndrome and atherosclerosis. A significant correlation has been found between the high levels of oxidized low-density lipoprotein (oxLDL) and CVD and atherosclerosis, including coronary and femoral artery disease. To the best of our knowledge, oxLDL has not been evaluated in patients with nephrolithiasis. This study aimed to evaluate serum levels of oxLDL, anti-oxLDL antibodies (oxLDL-ab) and other markers of atherosclerosis in patients with nephrolithiasis, according to the severity of the disease. The population sample consisted of 94 patients of 30-70 years of age with no symptoms of CVD who presented with renal calculi documented by ultrasonography, abdominal X-ray or computed tomography. The patients were divided into two groups: Group 1 (≥ 3 stones) and Group 2 (1-2 stones). A comparison control group was formed with 21 healthy individuals. Enzyme-linked immunosorbent assays were used to assess oxLDL and oxLDL-ab. Lipid peroxidation indexes were also analyzed. Median serum oxLDL values were higher in Groups 1 and 2 compared to the control group (≥ 3 stones, p = 0.02; 1-2 stones, p = 0.03). Median serum anti-oxLDL antibody levels were lower in the patients in Group 1 compared to the controls (p = 0.03). There was no significant difference in the oxLDL/oxLDL-ab ratio between patients and controls. These findings suggest that this may be the link between nephrolithiasis and the greater incidence of atherosclerosis and cardiovascular disease in patients with kidney stones.

Potassium Citrate Supplementation Decreases the Biochemical Markers of Bone Loss in a Group of Osteopenic Women: The Results of a Randomized, Double-Blind, Placebo-Controlled Pilot Study

The relationship involving acid-base imbalance, mineral metabolism and bone health status has previously been reported but the efficacy of the alkalizing supplementation in targeting acid overload and preventing bone loss has not yet been fully elucidated. In this randomized, double-blind, placebo-controlled study, the hypothesis that potassium citrate (K citrate) modifies bone turnover in women with postmenopausal osteopenia was tested. Three hundred and ten women were screened; 40 women met the inclusion criteria and were randomly assigned to the treatment or the placebo group. They were treated with K citrate (30 mEq day⁻¹) or a placebo in addition to calcium carbonate (500 mg day⁻¹) and vitamin D (400 IU day⁻¹). At baseline and time points of 3 and 6 months, serum indicators of renal function, electrolytes, calciotropic hormones, serum bone turnover markers (BTMs) (tartrate-resistant acid phosphatase 5b (TRACP5b), carboxy-terminal telopeptide of type I collagen (CTX), bone alkaline phosphatase (BAP), procollagen type 1 N terminal propeptide (PINP)), and urine pH, electrolytes, and citrate were measured. The follow-up was completed by 17/20 patients in the “K citrate” group and 18/20 patients in the “placebo” group. At baseline, 90% of the patients exhibited low potassium excretion in 24 h urine samples, and 85% of cases had at least one urine parameter associated with low-grade acidosis (low pH, low citrate excretion). After treatment, CTX and BAP decreased significantly in both groups, but subjects with evidence of low-grade acidosis gained significant benefits from the treatment compared to the placebo. In patients with low 24h-citrate excretion at baseline, a 30% mean decrease in BAP and CTX was observed at 6 months. A significant reduction was also evident when low citrate (BAP: −25%; CTX: −35%) and a low pH (BAP: −25%; CTX: −30%) were found in fasting-morning urine. In conclusion, our results suggested that K citrate supplementation improved the beneficial effects of calcium and vitamin D in osteopenic women with a documented potassium and citrate deficit, and a metabolic profile consistent with low-grade acidosis.

Increased amount and duration of tea consumption may be associated with decreased risk of renal stone disease

PURPOSE

Previous studies have looked into the association between tea consumption and renal stone disease, but the impact of tea consumption over time has not yet been fully clarified. Our study aimed to examine the amount and duration of tea consumption concomitantly in relation to the risk of renal stone disease.

METHODS

A total of 13,842 subjects who underwent health check-ups were recruited. Average tea consumption per day was defined as the amount of tea consumption per day multiplied by the frequency per week divided by seven. A "cup" was defined as 120 mL for each Chinese traditional teapot," and "cup-year" was calculated by multiplying the number of daily cups and the years of tea consumption to express the cumulative dose of tea consumption over time. The diagnosis of renal stone disease was established based on the results of abdominal sonography.

RESULTS

The amount of daily tea consumption was 119.2 ± 306.8 and 131.7 ± 347.3 mL in groups with and without renal stone disease. After adjusting for other clinical variables, daily tea consumption ≥ 240 mL vs. none was related to lower risk of renal stone disease (OR = 0.84, CI 0.71-0.99, p = 0.037). In another model, the associated risk of renal stone disease decreased significantly with tea consumption ≥ 20 cup-year (OR = 0.79, CI 0.66-0.94, p = 0.008), but not < 20 cup-year (OR = 0.92, CI 0.78-1.09, p = 0.34).

CONCLUSIONS

Daily tea consumption ≥ 240 mL (two cups) was associated with a lower risk of renal stone disease. Tea consumption ≥ 20 cup-year also had a decreased associated risk of renal stone disease.

Caspase-independent programmed cell death triggers Ca2PO4 deposition in an in vitro model of nephrocalcinosis

Nephrocalcinosis involves the deposition of microscopic crystals in the tubular lumen or interstitium. While the clinical, biochemical, and genetic aspects of the diseases causing nephrocalcinosis have been elucidated, little is known about the cellular events in this calcification process. We previously reported a phenomenon involving the spontaneous formation of Ca2PO4 nodules in primary papillary renal cells from a patient with medullary nephrocalcinosis harboring a rare glial cell-derived neurotrophic factor (GDNF) gene variant. We also demonstrated that cultivating GDNF-silenced human kidney-2 (HK-2) cells in osteogenic conditions for 15 days triggered Ca2PO4 deposits. Given the reportedly close relationship between cell death and pathological calcification, aim of the present study was to investigate whether apoptosis is involved in the calcification of GDNF-silenced HK-2 cells under osteogenic conditions. Silenced and control cells were cultured in standard and osteogenic medium for 1, 5, and 15 days, and any Ca2PO4 deposition was identified by means of von Kossa staining and environmental SEM (ESEM) analyses. Based on the results of annexin V and propidium iodide (PI) analysis, and terminal deoxynucleotidyl transferase dUTP-biotin nick end labeling (TUNEL) assay, the silenced cells in the osteogenic medium showed a significant increase in the percentage of cells in the late phase of apoptosis and an increased Ca2PO4 deposition at 15 days. The results of quantitative real-time PCR (qRT-PCR) of BAX and BCL2, and in-cell Western analysis of caspases indicated that the cell death process was independent of caspase-3, -6, -7, and -9 activation, however. Using this model, we provide evidence of caspase-independent cell death triggering the calcification process in GDNF-silenced HK-2 cells.

Caffeine prevents kidney stone formation by translocation of apical surface annexin A1 crystal-binding protein into cytoplasm: In vitro evidence

Recent large 3 cohorts have shown that caffeinated beverage consumption was associated with lower risk of kidney stone disease. However, its protective mechanisms remained unknown and had not been previously investigated. We thus evaluated protective effects of caffeine (1 μM–10 mM) on calcium oxalate monohydrate (COM) kidney stone formation, using crystallization, crystal growth, cell-crystal adhesion, Western blotting, and immunofluorescence assays. The results showed that caffeine reduced crystal number but, on the other hand, increased crystal size, resulting in unchanged crystal mass, consistent with crystal growth that was not affected by caffeine. However, caffeine significantly decreased crystal-binding capacity of MDCK renal tubular cells in a dose-dependent manner. Western blotting and immunofluorescence study of COM crystal-binding proteins revealed significantly decreased level of annexin A1 on apical surface and its translocation into cytoplasm of the caffeine-treated cells, but no significant changes in other COM crystal-binding proteins (annexin A2, α-enolase, HSP70, and HSP90) were observed. Moreover, caffeine decreased intracellular [Ca²⁺] but increased [Ca²⁺] secretory index. Taken together, our findings showed an in vitro evidence of the protective mechanism of caffeine against kidney stone formation via translocation of annexin A1 from apical surface into cytoplasm to reduce the crystal-binding capacity of renal tubular epithelial cells.