Inhibition on calcium oxalate crystallization and repair on injured renal epithelial cells of degraded soybean polysaccharide

Quercus dentata Thunb. leaves extract inhibits CaOx crystallization and ameliorates ethylene glycol-induced CaOx kidney stones via the OPN/CD44 and NLRP3 pathways

ETHNOPHARMACOLOGICAL RELEVANCE

The leaves of Quercus dentata Thunb. (QD), a member of the Fagaceae family and genus Quercus, with distributions in China, Japan, Korea, and other regions. As recorded in the Ben Cao Gang Mu (Compendium of Materia Medica) and other classical Chinese medical texts, QD has been traditionally employed in Traditional Chinese Medicine (TCM) for their hemostatic and diuretic effects and has been used to treat urinary stones (Lin Zheng). It is also the main ingredient of the Mishitong capsule (MST), a Chinese patent drug, used for kidney stones and ureteral stones. Nonetheless, the specific active ingredients and the mechanisms of QD in treating kidney stones remain to be elucidated, which is crucial for advancing the scientific understanding and clinical application of this traditional medicine.

AIM OF STUDY

This study aimed to identify the active constituents of QD water extract (QDWE), explore its inhibitory effects on kidney stones through in vitro and in vivo studies, and elucidate the underlying mechanisms of the OPN/CD44 axis and the NLRP3 signaling pathway to provide a full understanding of its potential as a novel treatment approach against kidney stones.

MATERIALS AND METHODS

The micromolecular components in the supernatant of QDWE (QDS) were analyzed by UPLC-Q-Exactive-Orbitrap-MS and the monosaccharide composition of the macromolecular polysaccharide components in the crude polysaccharide (QDP) was determined by pre-column derivatization in HPLC. The effects of QDWE, QDS and QDP on the shape, size, and structure of calcium oxalate (CaOx) crystals in vitro were explored by XRD, FTIR and SEM. The effects of QDWE, QDS and QDP on CaOx kidney stones in SD rats induced by ethylene glycol and VD3 were compared in vivo. Furthermore, the underlying mechanisms of OPN/CD44 and NLRP3 pathways were investigated by Western blot analysis.

RESULTS

There were 32 compounds identified in QDS. The monosaccharide composition ratio of QDP was Man: L-Rha: D-GlcA: D-GalA: D-Glc: D-Gal: L-Ara = 1.01: 22.52: 8.27: 38.61: 3.43: 17.80: 6.38, indicating a mixture of pectin-type acidic heteropolysaccharides. QDP had a more significant inhibitory effect on CaOx crystals in vitro than QDWE, which can inhibit the formation of CaOx monohydrate crystals (COM) and convert them into thermodynamically unstable CaOx dihydrate (COD) crystals. The high dose of QDWE exhibited significant in vivo efficacy (P < 0.05), including anti-calculus, diuretic effects, and kidney protection, marked by decreased calcification and stone formation, alongside improved kidney vitality. Furthermore, the protective effects of QDWE were demonstrated to be associated with the OPN/CD44 and NLRP3 pathways.

CONCLUSION

The studies identified and analyzed the active constituents of QDWE. Among these, QDP significantly inhibited CaOx crystal generation in vitro and could be a potential component for the treatment of urinary stones in QDWE. Moreover, the results indicated that QDWE had a remarkable therapeutic effect on CaOx stones by modulating the OPN/CD44 axis to affect stone formation and the NLRP3 signaling pathway to mediate inflammation, providing an experimental basis for the mechanism of anti-urinary stone and deep development of QD.

Targeting urinary calcium oxalate crystallization with inulin-type AOFOS from Aspidopterys obcordata Hemsl. for the management of rat urolithiasis

ETHNOPHARMACOLOGICAL RELEVANCE

Calcium oxalate crystals play a key role in the development and recurrence of kidney stones (also known as urolithiasis); thus, inhibiting the formation of these crystals is a central focus of urolithiasis prevention and treatment. Previously, we reported the noteworthy in vitro inhibitory effects of Aspidopterys obcordata fructo oligosaccharide (AOFOS), an active polysaccharide of the traditional Dai medicine Aspidopterys obcordata Hemsl. (commonly known as Hei Gai Guan), on the growth of calcium oxalate crystals.

AIM OF THE STUDY

To investigated the effectiveness and mechanism of AOFOS in treating kidney stones.

MATERIALS AND METHODS

A kidney stones rats model was developed, followed by examining AOFOS transport dynamics and effectiveness in live rats. Additionally, a correlation between the polysaccharide and calcium oxalate crystals was studied by combining crystallization experiments with density functional theory calculations.

RESULTS

The results showed that the polysaccharide was transported to the urinary system. Furthermore, their accumulation was inhibited by controlling their crystallization and modulating calcium ion and oxalate properties in the urine. Consequently, this approach helped effectively prevent kidney stone formation in the rats.

CONCLUSIONS

The present study emphasized the role of the polysaccharide AOFOS in modulating crystal properties and controlling crystal growth, providing valuable insights into their potential therapeutic use in managing kidney stone formation.

Correlation between interfacial layer properties and physical stability of food emulsions: current trends, challenges, strategies, and further perspectives

Emulsions are thermodynamically unstable systems that tend to separate into two immiscible phases over time. The interfacial layer formed by the emulsifiers adsorbed at the oil-water interface plays an important role in the emulsion stability. The interfacial layer properties of emulsion droplets have been considered the cutting-in points that influence emulsion stability, a traditional motif of physical chemistry and colloid chemistry of particular significance in relation to the food science and technology sector. Although many attempts have shown that high interfacial viscoelasticity may contribute to long-term emulsion stability, a universal relationship for all cases between the interfacial layer features at the microscopic scale and the bulk physical stability of the emulsion at the macroscopic scale remains to be established. Not only that, but integrating the cognition from different scales of emulsions and establishing a unified single model to fill the gap in awareness between scales also remain challenging. In this review, we present a comprehensive overview of recent progress in the general science of emulsion stability with a peculiar focus on interfacial layer characteristics in relation to the formation and stabilization of food emulsions, where the natural origin and edible safety of emulsifiers and stabilizers are highly requested. This review begins with a general overview of the construction and destruction of interfacial layers in emulsions to highlight the most important physicochemical characteristics of interfacial layers (formation kinetics, surface load, interactions among adsorbed emulsifiers, thickness and structure, and shear and dilatational rheology), and their roles in controlling emulsion stability. Subsequently, the structural effects of a series of typically dietary emulsifiers (small-molecule surfactants,proteins, polysaccharides, protein-polysaccharide complexes, and particles) on oil-water interfaces in food emulsions are emphasized. Finally, the main protocols developed for modifying the structural characteristics of adsorbed emulsifiers at multiple scales and improving the stability of emulsions are highlighted. Overall, this paper aims to comprehensively study the literature findings in the past decade and find out the commonality of multi-scale structures of emulsifiers, so as to deeply understand the common characteristics and emulsification stability behaviour of adsorption emulsifiers with different interfacial layer structures. It is difficult to say that there has been significant progress in the underlying principles and technologies in the general science of emulsion stability over the last decade or two. However, the correlation between interfacial layer properties and physical stability of food emulsions promotes revealing the role of interfacial rheological properties in emulsion stability, providing guidance on controlling the bulk properties by tuning the interfacial layer functionality.

Antioxidant Activities and Cytotoxicity of the Regulated Calcium Oxalate Crystals on HK-2 Cells of Polysaccharides from Gracilaria lemaneiformis with Different Molecular Weights

The antioxidant activities of seven degraded products (GLPs) with different molecular weights (M_w) of polysaccharides from Gracilaria lemaneiformis were compared. The M_w of GLP1-GLP7 were 106, 49.6, 10.5, 6.14, 5.06, 3.71 and 2.42 kDa, respectively. The results show that GLP2 with M_w = 49.6 kDa had the strongest scavenging capacity for hydroxyl radical, DPPH radical, ABTS radical and reducing power. When M_w < 49.6 kDa, the antioxidant activity of GLPs increased with the increase in M_w, but when M_w increased to 106 kDa, their antioxidant activity decreased. However, the ability of GLPs to chelate Fe²⁺ ions increased with the decrease in polysaccharide M_w, which was attributed to the fact that the polysaccharide active groups (-OSO₃^- and -COOH) were easier to expose, and the steric hindrance was smaller when GLPs chelated with Fe²⁺. The effects of GLP1, GLP3, GLP5 and GLP7 on the crystal growth of calcium oxalate (CaOx) were studied using XRD, FT-IR, Zeta potential and thermogravimetric analysis. Four kinds of GLPs could inhibit the growth of calcium oxalate monohydrate (COM) and induce the formation of calcium oxalate dihydrate (COD) in varying degrees. With the decrease in M_w of GLPs, the percentage of COD increased. GLPs increased the absolute value of the Zeta potential on the crystal surface and reduced the aggregation between crystals. Cell experiments showed that the toxicity of CaOx crystal regulated by GLPs to HK-2 cells was reduced, and the cytotoxicity of CaOx crystal regulated by GLP7 with the smallest M_w was the smallest, which was consistent with the highest SOD activity, the lowest ROS and MDA levels, the lowest OPN expression level and the lowest cell necrosis rate. These results suggest that GLPs, especially GLP7, may be a potential drug for the prevention and treatment of kidney stones.

Chemical Composition and Anti-Urolithiatic Activity of Extracts from Argania spinosa (L.) Skeels Press-Cake and Acacia senegal (L.) Willd

Ethnobotanical studies have reported the traditional medicinal uses of Acacia senegal (L.) Willd. and Argania spinosa (L.) Skeels against kidney stone formation and other chronic kidney diseases. The present work is undertaken to study the litholytic activity and the inhibiting activity of calcium oxalate crystallization by bioactive compounds identified in Argania spinosa (L.) Skeels press-cake (residue of Argan oil) and in Acacia senegal (L.) Willd. The litholytic activity was studied in vitro on cystine and uric acid stones using a porous bag and an Erlenmeyer glass. The study of the inhibiting activity of calcium oxalate crystallization, was based on temporal measurements of the optical density, registered at a 620 nm wavelength for 30 min using an ultraviolet−visible spectrophotometer. The silylation method was performed to identify phytochemicals, followed by gas chromatography coupled with mass spectrophotometry (GC/MS) analysis. The results show significant litholytic activity of Argania Spinosa press-cake hydro-ethanolic extract on uric acid and cystine stones, respectively, with dissolution rates (DR) of 86.38% and 60.42% versus 3.23% and 9.48% for the hydro-ethanolic extract of Acacia senegal exudate. Furthermore, the percentages of nucleation inhibition are 83.78% and 43.77% (p ˂ 0.05) for Argania spinosa and Acacia senegal, respectively. The results point to the detection of 17 phytochemicals in Argania spinosa press-cake extract, the majority of which are phenolic acids and have potent anti-urolithiatic action.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Chemical Compounds Identification and Antioxidant and Calcium Oxalate Anticrystallization Activities of Punica granatum L

The plant Punica granatum L. has several biological activities and a great curative and preventive power against chronic diseases. For this purpose, the objective of this work is to valorize the fruit peel of this plant in the field of phytomedicine, by quantifying and identifying its bioactive compounds and by evaluating their antioxidant and anticrystallization activities against calcium oxalate. This comparative study has been carried out by hydroalcoholic extract (E.PG) and infusion (I.PG) of the plant. The quantification of the phenolic compounds has been performed by spectrophotometric methods, and the chemical species identification has been performed by UPLC-PDA-ESI-MS. Moreover, the examination of the antioxidant activity has been executed by both methods of DPPH and FRAP. The crystallization inhibition has been studied in vitro by the turbidimetric model. The characterization of the synthesized crystals has been accomplished by microscopic observation and by Fourier Transform Infrared Spectroscopy. The results found show the comparable importance of the two plant extracts in the elimination of free radicals; the values of the half maximal inhibitory concentration "IC50" obtained are in the order of 60.87 ± 0.27 and 59.91 ± 0.83 μg/mL by the DPPH method and in the order of 42.17 ± 7.46 and 79.77 ± 6.91 μg/mL by the FRAP method, for both E.PG and I.PG, respectively. Furthermore, the inhibition percentages of calcium oxalate crystallization are in the range of 98.11 ± 0.17 and 98.22 ± 0.71% against the nucleation and in the order of 88.98 ± 0.98 and 88.78 ± 2.48% against the aggregation, for E.PG and I.PG, respectively. These results prove the richness of the plant in bioactive compounds, offering an antioxidant and anticrystallization capacity; therefore, it can be used in the treatment and/or the prevention of stone formation.

Comparison of the adhesion and endocytosis of calcium oxalate dihydrate to HK-2 cells before and after repair by Astragalus polysaccharide

This work investigated the effects of repairing injured renal proximal tubular epithelial (HK-2) cells by using three Astragalus polysaccharides (APS) with different molecular weights and the adhesion and endocytosis of HK-2 cells to the calcium oxalate dihydrate (COD) nanocrystals before and after repair to develop new products that can protect against kidney stones. HK-2 cells cultured in vitro were injured with 2.6 mmol/L oxalic acid to establish a damaged cell model. Three kinds of APS (APS0, APS1, and APS2 with molecular weights of 11.03, 4.72, and 2.60 kDa, respectively) were used to repair the damaged cells. The changes in the adhesion and endocytosis of 100 nm COD crystals to cells before and after the repair were detected. After the repair of HK-2 cells by the APS, the speed of wound healing of the damaged HK-2 cells increased, and the amount of phosphatidylserine (PS) ectropion decreased. In addition, the proportion of cells with adhered COD crystals decreased, whereas the proportion of cells with internalized crystals increased. As a result of the repair activity, APS can inhibit the adhesion and promote the endocytosis of COD nanocrystals to damaged cells. APS1, which had a moderate molecular weight, displayed the strongest abilities to repair the cells, inhibit adhesion, and promote endocytosis. Thus, APS, particularly APS1, may serve as potential green drugs for preventing kidney stones.

Phytochemical screening and inhibitory activity of oxalocalcic crystallization of Arbutus unedo L. leaves

The present study is focused on the experimental verification of the efficiency of Arbutus unedo L. leaves against the crystallization of calcium oxalate. The inhibition of crystallization has been studied in vitro with the absence and the presence of the different concentrations of the infusion and hydroalcoholic extract of the plant. This study consists of measuring, using a UV-Visible spectrophotometer, the temporal evolution of the optical density at λ = 620 nm corresponding to the crystals formation. The latter have been characterized by microscopic observation using an optical microscope, and by Fourier Transform Infrared Spectroscopy (FT-IR). The results suggest a greater effectiveness of the plant infusion with respect to the hydroalcoholic extract against crystallization or nucleation at percentages of 69.41 ± 0.24 or 19.76 ± 0.27% and at 93.92 ± 2.61 and 45.16 ± 3.06% against the aggregation, for both the infusion and the hydroalcoholic extract respectively. A. unedo leaves is a very promising and effective remedy against the crystallization of calcium oxalate and especially in the aggregation stage.

Synthesis and characterization of a new soluble soybean polysaccharide-iron(III) complex using ion exchange column

A new ion exchange column method was investigated to synthesize the soluble soybean polysaccharide-iron(III) complex (SSPS-FeIII1) using soluble soybean polysaccharides (SSPS). The feasibility of ion exchange column reaction was explored firstly. Results indicated the D730 anion macroporous adsorption resin could effectively absorb SSPS and the static adsorption saturation time was 20h. The iron content of the complex reached up to 15.07% when trisodium citrate concentration was 2mg/mL. The structure of SSPS-FeIII complex synthesized by this method (SSPS-FeIII12) was compared with that prepared by trisodium citrate - ferric chloride method (SSPS-FeIII23). UV-vis absorption spectra, FI-IR spectra and XRD patterns confirmed that both hydroxyl groups and carboxyl groups in SSPS were involved in the coordination reaction and the iron core of SSPS-FeIII1 was a polymerized β- FeOOH structure. Those results indicated that the ion exchange column method could effectively prepare the SSPS-FeIII complex.

The study of the inhibitory effect of calcium oxalate monohydrate's crystallization by two medicinal and aromatic plants: Ammi visnaga and Punica granatum

INTRODUCTION

Urinary lithiasis is a recurrent disease defined by the presence of calculi in the urinary tract. Most urinary calculi have as a major component calcium oxalate which occurs mainly in two crystalline forms: Calcium oxalate monohydrate (whewellite) and calcium oxalate dihydrate (weddellite). The target behind, this work is to study the inhibiting effect of the calcium oxalate's crystallization by the extract of the Ammi visnaga and the Punica granatum.

METHODS

The inhibition of crystallization has been studied in vitro with both the absence and the presence of the different concentrations of the extracts of the two plants. This study consists in measurement, with the UV-Visible spectrophotometer, the temporal evolution of the optical density at λ equal to 620nm corresponding to the formation of the crystals due to the mixing of metastable solutions of calcium and oxalate. The characterization of the crystals is carried out in parallel by both the Fourier transform infrared spectra (FT-IR) and the observation of the crystals with the help of an optical microscope. In this respect, the inhibition percentages were calculated from the turbidity slopes in the presence and absence of the extract.

RESULTS

The results obtained were more effective, especially for Punica granatum with percentages of 97.8±0.12 and 83.46±1.34% against nucleation and aggregation, respectively, the order of Ammi visnaga was as follow: 73.25±0.81 and 59.44±3.3%. Thus, all correlation coefficients are greater than 0.95 and all coefficients of variation are less than 10%.

CONCLUSIONS

The prevention and treatment of urinary lithiasis and especially in the case of recurrence by plants remains an alternative choice for medical methods. This study justified the efficacy of the plants Ammi visnaga and in particular Punica granatum against the crystallization of calcium oxalate.

LEVEL OF EVIDENCE

3.

Effects of plant polysaccharides with different carboxyl group contents on calcium oxalate crystal growth

The effects of five plant polysaccharides (PPSs) with molecular weights of ∼4000 Da and different carboxylic group (–COOH) contents on the crystal growth of calcium oxalate (CaOx) were comparatively studied.

Protective Effects of Degraded Soybean Polysaccharides on Renal Epithelial Cells Exposed to Oxidative Damage

This study aimed to investigate the protective effects of degraded soybean polysaccharides (DSP) on oxidatively damaged African green monkey kidney epithelial (Vero) cells. Low DSP concentration (10 μg/mL) elicited an evident protective effect on H₂O₂-induced cell injury (0.3 mmol/L). The cell viabilities of the H₂O₂-treated group and the DSP-protected group were 57.3 and 93.1%, respectively. The cell viability decreased to 88.3% when the dosage was increased to 100 μg/mL. DSP protected Vero cells from H₂O₂-mediated oxidative damage by enhancing cellular superoxide dismutase activity and total antioxidant capacity and by decreasing malonaldehyde content and lactate dehydrogenase release. The H₂O₂-treated cells stimulated the aggregation of calcium oxalate monohydrate crystals. DSP could also reduce the crystal size, decrease the attached crystal content, and prevent the cell aggregation by alleviating oxidative injury and lipid peroxidation, enhancing antioxidant capacity, and decreasing hyaluronan expression on cellular surfaces. The internalization ability of the injured cells was improved after these cells were exposed to DSP solution. The regulation ability of DSP-repaired cells on calcium oxalate dihydrate formation, crystal attachment, aggregation, and internalization was lower than that of normal cells but was higher than that of the injured cells. DSP may be a potential green drug to prevent calcium oxalate (CaOx) stone formation because DSP could protect cells from oxidative damage and inhibit CaOx crystal formation.

Repair Effect of Seaweed Polysaccharides with Different Contents of Sulfate Group and Molecular Weights on Damaged HK-2 Cells

The structure⁻activity relationships and repair mechanism of six low-molecular-weight seaweed polysaccharides (SPSs) on oxalate-induced damaged human kidney proximal tubular epithelial cells (HK-2) were investigated. These SPSs included Laminaria japonica polysaccharide, degraded Porphyra yezoensis polysaccharide, degraded Gracilaria lemaneiformis polysaccharide, degraded Sargassum fusiforme polysaccharide, Eucheuma gelatinae polysaccharide, and degraded Undaria pinnatifida polysaccharide. These SPSs have a narrow difference of molecular weight (from 1968 to 4020 Da) after degradation by controlling H₂O₂ concentration. The sulfate group (⁻SO₃H) content of the six SPSs was 21.7%, 17.9%, 13.3%, 8.2%, 7.0%, and 5.5%, respectively, and the ⁻COOH contents varied between 1.0% to 1.7%. After degradation, no significant difference was observed in the contents of characteristic ⁻SO₃H and ⁻COOH groups of polysaccharides. The repair effect of polysaccharides was determined using cell-viability test by CCK-8 assay and cell-morphology test by hematoxylin-eosin staining. The results revealed that these SPSs within 0.1⁻100 μg/mL did not express cytotoxicity in HK-2 cells, and each polysaccharide had a repair effect on oxalate-induced damaged HK-2 cells. Simultaneously, the content of polysaccharide ⁻SO₃H was positively correlated with repair ability. Furthermore, the low-molecular-weight degraded polysaccharides showed better repair activity on damaged HK-2 cells than their undegraded counterpart. Our results can provide reference for inhibiting the formation of kidney stones and for developing original anti-stone polysaccharide drugs.

Review on the extraction, characterization and application of soybean polysaccharide

In this review, we critically appraise the latest literature on the extraction and the structural features of SPS, and provide a perspective on the biological applications of SPS.

Concave urinary crystallines: direct evidence of calcium oxalate crystals dissolution by citrate in vivo

The changes in urinary crystal properties in patients with calcium oxalate (CaOx) calculi after oral administration of potassium citrate (K₃cit) were investigated via atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray powder diffractometry (XRD), and zeta potential analyzer. The AFM and SEM results showed that the surface of urinary crystals became concave, the edges and corners of crystals became blunt, the average size of urinary crystallines decreased significantly, and aggregation of urinary crystals was reduced. These changes were attributed to the significant increase in concentration of excreted citrate to 492 ± 118 mg/L after K₃cit intake from 289 ± 83 mg/L before K₃cit intake. After the amount of urinary citrate was increased, it complexed with Ca²⁺ ions on urinary crystals, which dissolved these crystals. Thus, the appearance of concave urinary crystals was a direct evidence of CaOx dissolution by citrate in vivo. The XRD results showed that the quantities and species of urinary crystals decreased after K₃cit intake. The mechanism of inhibition of formation of CaOx stones by K₃cit was possibly due to the complexation of Ca²⁺ with citrate, increase in urine pH, concentration of urinary inhibitor glycosaminoglycans (GAGs), and the absolute value of zeta potential after K₃cit intake.

Changes in urinary nanocrystallites in calcium oxalate stone formers before and after potassium citrate intake

The property changes of urinary nanocrystallites in 13 patients with calcium oxalate (CaOx) stones were studied before and after ingestion of potassium citrate (K3cit), a therapeutic drug for stones. The analytical techniques included nanoparticle size analysis, transmission electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The studied properties included the components, morphologies, zeta potentials, particle size distributions, light intensity autocorrelation curves, and polydispersity indices (PDIs) of the nanocrystallites. The main components of the urinary nanocrystallites before K3cit intake included uric acid, β-calcium phosphate, and calcium oxalate monohydrate. After K3cit intake, the quantities, species, and percentages of aggregated crystals decreased, whereas the percentages of monosodium urate and calcium oxalate dehydrate increased, and some crystallites became blunt. Moreover, the urinary pH increased from 5.96 ± 0.43 to 6.46 ± 0.50, the crystallite size decreased from 524 ± 320 nm to 354 ± 173 nm, and the zeta potential decreased from -4.85 ± 2.87 mV to -8.77 ± 3.03 mV. The autocorrelation curves became smooth, the decay time decreased from 11.4 ± 3.2 ms to 4.3 ± 1.7 ms, and the PDI decreased from 0.67 ± 0.14 to 0.53 ± 0.19. These changes helped inhibit CaOx calculus formation.

Interaction between submicron COD crystals and renal epithelial cells

Objectives

This study aims to investigate the adhesion characteristics between submicron calcium oxalate dihydrate (COD) with a size of 150 ± 50 nm and African green monkey kidney epithelial cells (Vero cells) before and after damage, and to discuss the mechanism of kidney stone formation.

Methods

Vero cells were oxidatively injured by hydrogen peroxide to establish a model of injured cells. Scanning electron microscopy was used to observe Vero–COD adhesion. Inductively coupled plasma emission spectrometry was used to quantitatively measure the amount of adhered COD microcrystals. Nanoparticle size analyzer and laser scanning confocal microscopy were performed to measure the change in the zeta potential on the Vero cell surface and the change in osteopontin expression during the adhesion process, respectively. The level of cell injury was evaluated by measuring the changes in malonaldehyde content, and cell viability during the adhesion process.

Results

The adhesion capacity of Vero cells in the injury group to COD microcrystals was obviously stronger than that of Vero cells in the control group. After adhesion to COD, cell viability dropped, both malonaldehyde content and cell surface zeta potential increased, and the fluorescence intensity of osteopontin decreased because the osteopontin molecules were successfully covered by COD. Submicron COD further damaged the cells during the adhesion process, especially for Vero cells in the control group, leading to an elevated amount of attached microcrystals.

Conclusion

Submicron COD can further damage injured Vero cells during the adhesion process. The amount of attached microcrystals is proportional to the degree of cell damage. The increased amount of microcrystals that adhered to the injured epithelial cells plays an important role in the formation of early-stage kidney stones.