Mechanism of Porphyra Yezoensis Polysaccharides in Inhibiting Hyperoxalate-Induced Renal Injury and Crystal Deposition.

Oxidative damage to the kidneys is a primary factor in the occurrence of kidney stones. This study explores the inhibitory effect of Porphyra yezoensis polysaccharides (PYP) on oxalate-induced renal injury by detecting levels of oxidative damage, expression of adhesion molecules, and damage to intracellular organelles and revealed the molecular mechanism by molecular biology methods. Additionally, we validated the role of PYP in vivo using a crystallization model of hyperoxalate-induced rats. PYP effectively scavenged the overproduction of reactive oxygen species (ROS) in HK-2 cells, inhibited the adhesion of calcium oxalate (CaOx) crystals on the cell surface, unblocked the cell cycle, restored the depolarization of the mitochondrial membrane potential, and inhibited cell death. PYP upregulated the expression of antioxidant proteins, including Nrf2, HO-1, SOD, and CAT, while decreasing the expression of Keap-1, thereby activating the Keap1/Nrf2 signaling pathway. PYP inhibited CaOx deposition in renal tubules in the rat crystallization model, significantly reduced high oxalate-induced renal injury, decreased the levels of the cell surface adhesion proteins, improved renal function in rats, and ultimately inhibited the formation of kidney stones. Therefore, PYP, which has crystallization inhibition and antioxidant properties, may be a therapeutic option for the treatment of kidney stones.

Corn Silk Polysaccharides with Different Carboxyl Contents Reduce the Oxidative Damage of Renal Epithelial Cells by Inhibiting Endocytosis of Nano-calcium Oxalate Crystals.

OBJECTIVE: Renal epithelial cell injury and cell-crystal interaction are closely related to kidney stone formation. METHODS: This study aims to explore the inhibition of endocytosis of nano-sized calcium oxalate monohydrate (nano-COM) crystals and the cell protection of corn silk polysaccharides (CCSPs) with different carboxyl contents (3.92, 7.75, 12.90, and 16.38%). The nano-COM crystals protected or unprotected by CCSPs were co-cultured with human renal proximal tubular epithelial cells (HK-2), and then the changes in the endocytosis of nano-COM and cell biochemical indicators were detected. RESULTS: CCSPs could inhibit the endocytosis of nano-COM by HK-2 cells and reduce the accumulation of nano-COM in the cells. Under the protection of CCSPs, cell morphology is restored, intracellular superoxide dismutase levels are increased, lipid peroxidation product malondialdehyde release is decreased, and mitochondrial membrane potential and lysosomal integrity are increased. The release of Ca2+ ions in the cell, the level of cell autophagy, and the rate of cell apoptosis and necrosis are also reduced. CCSPs with higher carboxyl content have better cell protection abilities. CONCLUSION: CCSPs could inhibit the endocytosis of nano-COM crystals and reduce cell oxidative damage. CCSP3, with the highest carboxyl content, shows the best biological activity.

Cell Protection and Crystal Endocytosis Inhibition by Sulfated Laminaria Polysaccharides Against Nano-COM-Induced Oxidative Damage in Renal Epithelial Cells.

Background: The damage to renal tubular epithelial cells is closely related to the formation of kidney stones. At present, research on drugs that can protect cells from damage remains limited. Methods: This study aims to explore the protective effects of four different sulfate groups (-OSO3 -) of Laminaria polysaccharides (SLPs) on human kidney proximal tubular epithelial (HK-2) cells and determine the difference in the endocytosis of nano-sized calcium oxalate monohydrate (COM) crystals before and after protection. COM with a size of 230 ± 80 nm was used to damage HK-2 cells to establish a damage model. The protection capability of SLPs (LP0, SLP1, SLP2, and SLP3) with -OSO3 - contents of 0.73, 15, 23, and 31%, respectively, against COM crystal damage and the effect of SLPs on the endocytosis of COM crystals were studied. Results: Compared with that of the SLP-unprotected COM-injured group, the cell viability of the SLP-protected group was improved, healing capability was enhanced, cell morphology was restored, production of reactive oxygen species was reduced, mitochondrial membrane potential and lysosome integrity were increased, intracellular Ca2+ level and autophagy were decreased, cell mortality was reduced, and internalized COM crystals were lessened. The capability of SLPs to protect cells from damage and inhibit the endocytosis of crystals in cells enhanced with an increase in the -OSO3 - content of SLPs. Conclusions: SLPs with a high -OSO3 - content may become a potential green drug for preventing the formation of kidney stones.

RSK2 promotes melanoma cell proliferation and vemurafenib resistance via upregulating cyclin D1.

BRAF inhibitors are commonly used in targeted therapies for melanoma patients harboring BRAFV600E mutant. Despite the benefit of vemurafenib therapy, acquired resistance during or after treatment remains a major obstacle in BRAFV600E mutant melanoma. Here we found that RSK2 is overexpressed in melanoma cells and the high expression of RSK2 indicates poor overall survival (OS) in melanoma patients. Overexpression of RSK2 leads to vemurafenib resistance, and the deletion of RSK2 inhibits cell proliferation and sensitizes melanoma cells to vemurafenib. Mechanistically, RSK2 enhances the phosphorylation of FOXO1 by interacting with FOXO1 and promoting its subsequent degradation, leading to upregulation of cyclin D1 in melanoma cells. These results not only reveal the presence of a RSK2-FOXO1-cyclin D1 signaling pathway in melanoma, but also provide a potential therapeutic strategy to enhance the efficacy of vemurafenib against cancer.

Carboxymethylation of Desmodium styracifolium Polysaccharide and Its Repair Effect on Damaged HK-2 Cells.

Objective: Desmodium styracifolium is the best traditional medicine for treating kidney calculi in China. This study is aimed at increasing the carboxyl (-COOH) content of D. styracifolium polysaccharide (DSP0) and further increasing its antistone activity. Methods: DSP0 was carboxymethylated with chloroacetic acid at varying degrees. Then, oxalate-damaged HK-2 cells were repaired with modified polysaccharide, and the changes in biochemical indices before and after repair were detected. Results: Three modified polysaccharides with 7.45% (CDSP1), 12.2% (CDSP2), and 17.7% (CDSP3) -COOH are obtained. Compared with DSP0 (-COOH content = 1.17%), CDSPs have stronger antioxidant activity in vitro and can improve the vitality of damaged HK-2 cells. CDSPs repair the cell morphology and cytoskeleton, increase the cell healing ability, reduce reactive oxygen species and nitric oxide levels, increase mitochondrial membrane potential, limit autophagy level to a low level, reduce the eversion of phosphatidylserine in the cell membrane, weaken the inhibition of oxalate on DNA synthesis, restore cell cycle to normal state, promote cell proliferation, and reduce apoptosis/necrosis. Conclusion: The carboxymethylation modification of DSP0 can improve its antioxidant activity and enhance its ability to repair damaged HK-2 cells. Among them, CDSP2 with medium -COOH content has the highest activity of repairing cells, whereas CDSP3 with the highest -COOH content has the highest antioxidant activity. This difference may be related to the active environment of polysaccharide and conformation of the polysaccharide and cell signal pathway. This result suggests that Desmodium styracifolium polysaccharide with increased -COOH content may have improved potential treatment and prevention of kidney calculi.

Interaction between nanometer calcium oxalate and renal epithelial cells repaired with carboxymethylated polysaccharides.

OBJECTIVE: Injury of renal tubular epithelial cells (HK-2) is an important cause of kidney stone formation. In this article, the repairing effect of polysaccharide (PCP0) extracted from the traditional Chinese medicine Poria cocos and its carboxymethylated derivatives on damaged HK-2 cells was studied, and the differences in adhesion and endocytosis of the cells to nanometer calcium oxalate monohydrate (COM) before and after repair were explored. METHODS: Sodium oxalate (2.8 mmol/L) was used to damage HK-2 cells to establish a damage model, and then Poria cocos polysaccharides (PCPs) with different carboxyl (COOH) contents were used to repair the damaged cells. The changes in the biochemical indicators of the cells before and after the repair and the changes in the ability to adhere to and internalize nano-COM were detected. RESULTS: The natural PCPs (PCP0, COOH content = 2.56%) were carboxymethylated, and three carboxylated modified Poria cocos with 7.48% (PCP1), 12.07% (PCP2), and 17.18% (PCP3) COOH contents were obtained. PCPs could repair the damaged HK-2 cells, and the cell viability was enhanced after repair. The cell morphology was gradually repaired, the proliferation and healing rate were increased. The ROS production was reduced, and the polarity of the mitochondrial membrane potential was restored. The level of intracellular Ca2+ ions decreased, and the autophagy response was weakened. CONCLUSION: The cells repaired by PCPs inhibited the adhesion to nano-COM and simultaneously promoted the endocytosis of nano-COM. The endocytic crystals mainly accumulated in the lysosome. Inhibiting adhesion and increasing endocytosis could reduce the nucleation, growth, and aggregation of cell surface crystals, thereby inhibiting the formation of kidney stones. With the increase of COOH content in PCPs, its ability to repair damaged cells, inhibit crystal adhesion, and promote crystal endocytosis all increased, that is, PCP3 with the highest COOH content showed the best ability to inhibit stone formation.

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

OBJECTIVE: The formation of kidney stone is closely related to cell injury and crystal adhesion. METHOD: The sulfur trioxide-pyridine method was used to sulfate raw Undaria pinnatifida polysaccharide (UPP) with a molecular weight (Mw) of 8.33 kDa. Four polysaccharides with the sulfate group (-OSO3-) contents of 1.59% (UPP0), 6.03% (UPP1), 20.83% (UPP2), and 36.39% (UPP3) were obtained. The antioxidant activity of the four UPPs, the difference in oxidative damage inflicted by nano-CaOx monohydrate (nano-COM) on human proximal tubular epithelial (HK-2) cells before and after protection by UPPs, and the inhibitory effect on nano-COM adhesion were explored. RESULTS: Structural characterization showed that sulfation was successful. As the -OSO3- content in the UPPs was increased, the antioxidant activity and capability of the UPPs to regulate the growth of calcium oxalate (CaOx) crystals gradually increased. The damage caused by nano-COM crystals to HK-2 cells under protection by UPPs was weakened. This effect enhanced cell viability, enabled the maintenance of good cell morphology, reduced reactive oxygen species (ROS) levels, and inhibited the decrease in mitochondrial membrane potential, as well as decreased the eversion of phosphatidylserine (PS) and the expression of the adhesion proteins osteopontin (OPN), heat shock protein (HSP 90), and Annexin A1 (ANXA1). The adhesion of nano-COM to HK-2 cells was inhibited under the protection by UPPs. CONCLUSION: UPP3 with the highest content of -OSO3- presented the best antioxidant activity and crystal regulation ability, while UPP2 with the second highest -OSO3- content showed optimal cell protection ability and crystal adhesion inhibition ability. The biological activity of UPPs was regulated by Mw and -OSO3- content. UPP2 with moderate -OSO3- content may become a potential drug for preventing CaOx stones.

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.

Regulation of Laminaria Polysaccharides with Different Degrees of Sulfation during the Growth of Calcium Oxalate Crystals and their Protective Effects on Renal Epithelial Cells.

The original Laminaria polysaccharide (LP0) was sulfated using the sulfur trioxide-pyridine method, and four sulfated Laminaria polysaccharides (SLPs) were obtained, namely, SLP1, SLP2, SLP3, and SLP4. The sulfated (-OSO3 -) contents were 8.58%, 15.1%, 22.8%, and 31.3%, respectively. The structures of the polysaccharides were characterized using a Fourier transform infrared (FT-IR) spectrometer and nuclear magnetic resonance (NMR) techniques. SLPs showed better antioxidant activity than LP0, increased the concentration of soluble Ca2+ in the solution, reduced the amount of CaOx precipitation and degree of CaOx crystal aggregation, induced COD crystal formation, and protected HK-2 cells from damage caused by nanometer calcium oxalate crystals. These effects can inhibit the formation of CaOx kidney stones. The biological activity of the polysaccharides increased with the content of -OSO3 -, that is, the biological activities of the polysaccharides had the following order: LP0 < SLP1 < SLP2 < SLP3 < SLP4. These results reveal that SLPs with high -OSO3 - contents are potential drugs for effectively inhibiting the formation of CaOx stones.

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 â†’ 3)-linked ß-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.

Carboxymethylation of Corn Silk Polysaccharide and Its Inhibition on Adhesion of Nanocalcium Oxalate Crystals to Damaged Renal Epithelial Cells.

The purpose of this study was to explore the repair effect of carboxymethyl-modified corn silk polysaccharide (CSP) on oxidatively damaged renal epithelial cells and the difference in adhesion between cells and calcium oxalate crystals. The CSP was degraded and modified through carboxymethylation. An oxidatively damaged cell model was constructed by oxalate damage to human kidney proximal tubular epithelial (HK-2) cells. Then, the damaged cells were repaired by modified polysaccharides, and the changes in biochemical indexes and adhesion ability between cells and crystals before and after repair were detected. Four modified polysaccharides with carboxyl group (-COOH) contents of 3.92% (CSP0), 7.75% (CCSP1), 12.90% (CCSP2), and 16.38% (CCSP3) were obtained. Compared with CSP0, CCSPs had stronger antioxidant activity, could repair damaged HK-2 cells, and could reduce phosphorylated serine eversion on the cell membrane, the expression of osteopontin (OPN) and Annexin A1, and crystal adhesion. However, its effect on the expression of hyaluronic acid synthase was not substantial. The carboxymethyl modification of the CSP can improve its ability to repair cells and inhibit crystal adhesion and aggregation. A high carboxymethylation degree results in strong polysaccharide activity. CCSPs are expected to reduce the risk of kidney stone formation and recurrence.

Protective Effect of Degraded Porphyra yezoensis Polysaccharides on the Oxidative Damage of Renal Epithelial Cells and on the Adhesion and Endocytosis of Nanocalcium Oxalate Crystals.

The protective effects of Porphyra yezoensis polysaccharides (PYPs) with molecular weights of 576.2 (PYP1), 105.4 (PYP2), 22.47 (PYP3), and 3.89 kDa (PYP4) on the oxidative damage of human kidney proximal tubular epithelial (HK-2) cells and the differences in adherence and endocytosis of HK-2 cells to calcium oxalate monohydrate crystals before and after protection were investigated. Results showed that PYPs can effectively reduce the oxidative damage of oxalic acid to HK-2 cells. Under the preprotection of PYPs, cell viability increased, cell morphology improved, reactive oxygen species levels decreased, mitochondrial membrane potential increased, S phase cell arrest was inhibited, the cell apoptosis rate decreased, phosphatidylserine exposure reduced, the number of crystals adhered to the cell surface reduced, but the ability of cells to endocytose crystals enhanced. The lower the molecular weight, the better the protective effect of PYP. The results in this article indicated that PYPs can reduce the risk of kidney stone formation by protecting renal epithelial cells from oxidative damage and reducing calcium oxalate crystal adhesion, and PYP4 with the lowest molecular weight may be a potential drug for preventing kidney stone formation.

Inhibition of Calcium Oxalate Formation and Antioxidant Activity of Carboxymethylated Poria cocos Polysaccharides.

Three carboxymethylated Poria cocos polysaccharides (PCP-C1, PCP-C2, and PCP-C3) with -COOH contents of 6.13%, 10.24%, and 16.22%, respectively, were obtained by carboxymethylation of the original polysaccharide (PCP-C0), which has a molecular weight of 4 kDa and a carboxyl (-COOH) content of 2.54%. The structure of the PCP-Cs was characterized by FT-IR, 1H NMR, and 13C NMR spectra. The four PCP-Cs exhibited antioxidant activity, and their ability to scavenge radicals (hydroxyl and DPPH) and chelate ferrous ions was positively correlated with the degree of carboxymethylation. As the content of -COOH groups in the PCP-Cs increases, their ability to regulate the growth of calcium oxalate (CaOx) crystals was enhanced, thus inhibiting the growth of calcium oxalate monohydrate (COM) crystals and inducing the formation of more calcium oxalate dihydrate (COD) crystals. The formed CaOx crystal was more round and blunt, the absolute value of the Zeta potential on the crystal surface increased, and the aggregation between crystals was inhibited. Thermogravimetric analysis curves showed that the proportions of PCP-C0, PCP-C1, PCP-C2, and PCP-C3 incorporated into the crystal were 20.52%, 15.60%, 10.65%, and 9.78%, respectively, in the presence of 0.4 g/L PCP-Cs. PCP-C protection resisted oxidative damages of human kidney proximal tubular epithelial cells (HK-2) caused by oxalate, resulting in increased cell viability and superoxide dismutase activity and decreased reactive oxygen species levels, malondialdehyde content, and 8-hydroxy-deoxyguanosine expression. Hence, PCP-Cs, especially PCP-C3, can inhibit the formation of CaOx crystals and may have the potential to be an alternative antistone drug.

Effects of Selenized Astragalus Polysaccharide on the Adhesion and Endocytosis of Nanocalcium Oxalate Dihydrate after the Repair of Damaged HK-2 Cells.

An oxidative damage model of human proximal renal epithelial cells (HK-2) was established using oxalate damage. The repair effects of Astragalus polysaccharide (APS) and selenized APS (Se-APS) on damaged HK-2 cells were investigated. Differences in the adhesion and endocytosis of HK-2 cells to calcium oxalate dihydrate crystals with a size of approximately 100 nm before and after APS and Se-APS repair were also explored. The results showed that after being repaired by APS and Se-APS, HK-2 cells exhibited increased cell viability, restored cell morphology, reduced reactive oxygen species level, increased mitochondrial membrane potential, reduced phosphatidylserine eversion, and osteopontin expression. Moreover, the amount of adherent crystals on the cell surface decreased, but the amount of endocytic crystals increased. At the same concentration, Se-APS exhibited better repair effects on the damaged HK-2 cells than APS. All these findings revealed that Se-APS may be a potential drug candidate for inhibiting the formation of kidney stones.

Ligand and adjuvant dual-assisted synthesis of highly luminescent and stable Cs4PbBr6 nanoparticles used in LEDs.

We developed a new ligand and adjuvant dual-assisted room temperature colloidal method for the synthesis of highly luminescent and stable Cs4PbBr6 nanoparticles, in which acetone, oleamine (OM) and oleic acid (OA) were used as precursors, while water and dimethyl sulfoxide (DMSO) were used as adjuvants. In this process, we explored the influencing factors of process parameters (such as the amount of water, the standing time of precursors, and the molar ratio of raw materials), and found that Cs4PbBr6 synthesized by water + DMSO can not only change the morphology and promote crystallization but also improve the lattice strain, reduce the lattice defects and optimize the passivation effect, so as to improve the luminescence properties. Simultaneously, we also found that the pc-LED made of Cs4PbBr6 can still emit bright green light after 4344 h of operation, showing excellent stability and making it promising for solid-state lighting application. This method also provides an important reference value for solving the hydrolysis property of perovskites.

Improvement in optical properties of Cs4PbBr6 nanocrystals using aprotic polar purification solvent.

We demonstrate the influence mechanism on the optical property of Cs4PbBr6 during purification of solution with different protonated levels and polarities. During the purification process, organic groups originating from oleic acid (OA) and PbBr impurity on the surface of Cs4PbBr6 nanocrystals can be removed using high polarity aprotic and protonic solvents, and the number of Br vacancies (V Br) can be reduced. The protonic polar solvent can not only etch the organic groups on the surface of nanocrystals, causing surface reconstruction and particle growth of nanocrystals, but also enter into the lattice of Cs4PbBr6 and react with the embedded CsPbBr3. However, aprotic polar solvent decreases the particle size of Cs4PbBr6 nanocrystals with the increase in the solvent polarity. The optical properties of Cs4PbBr6 can be effectively improved using aprotic polar solvents as a purification solvent, which is very significant to improve the luminescence efficiency of perovskites.

Porphyra yezoensis polysaccharide and potassium citrate synergistically inhibit calcium oxalate crystallization induced by renal epithelial cells and cytotoxicity of the formed crystals.

Mineralization crystallization is considered to be the initial stage of stone formation. However, the formation of crystals and subsequent cell damage have rarely been investigated. An oxidatively damaged cell model was established using oxalic acid to injure human proximal tubular epithelial cells (HK-2). Subsequently, CaOx crystallization was induced by adding 2.0 mmol/L sodium oxalate solution. We compared the synergistic effects of PYPs with molecular weights of 49.54 kDa (PYP1) and 4.02 kDa (PYP2) and K3Cit on the inhibition of CaOx crystallization and studied the nucleation, growth, and retention process of CaOx crystals on the cell surface and the subsequent damage of the formed crystals to the cells. Normal HK-2 cells mainly induced the formation of CaOx dihydrate (COD), whereas the damaged cells mainly induced the formation of CaOx monohydrate (COM) crystals. Under the protection of PYPs, the state of cells was improved, and the proportion of COD crystals in the formed crystals increased. Small-molecular-weight PYP2 exhibited better abilities of inhibiting CaOx crystallization and improving cell state compared with PYP1. Under the synergistic effects of PYPs and K3Cit, the number of formed crystals was obviously reduced, and the size was obviously decreased. PYPs can repair damaged cells and inhibit the conversion of COD phase to COM phase. K3Cit can obviously inhibit the nucleation of CaOx crystal and reduce the amount of crystal formation. The repair of damaged cells by PYPs and the synergistic inhibition of CaOx crystallization by PYPs and K3Cit reduce cell damage and crystal formation on the cell surface. By simultaneously repairing damaged cells and inhibiting crystallization, this strategy is expected to exert a desirable effect in preventing the formation and recurrence of stones.

RSK2 protects human breast cancer cells under endoplasmic reticulum stress through activating AMPKα2-mediated autophagy.

Autophagy can protect stressed cancer cell by degradation of damaged proteins and organelles. However, the regulatory mechanisms behind this cellular process remain incompletely understood. Here, we demonstrate that RSK2 (p90 ribosomal S6 kinase 2) plays a critical role in ER stress-induced autophagy in breast cancer cells. We demonstrated that the promotive effect of RSK2 on autophagy resulted from directly binding of AMPKα2 in nucleus and phosphorylating it at Thr172 residue. IRE1α, an ER membrane-associated protein mediating unfolded protein response (UPR), is required for transducing the signal for activation of ERK1/2-RSK2 under ER stress. Suppression of autophagy by knockdown of RSK2 enhanced the sensitivity of breast cancer cells to ER stress both in vitro and in vivo. Furthermore, we demonstrated that inhibition of RSK2-mediated autophagy rendered breast cancer cells more sensitive to paclitaxel, a chemotherapeutic agent that induces ER stress-mediated cell death. This study identifies RSK2 as a novel controller of autophagy in tumor cells and suggests that targeting RSK2 can be exploited as an approach to reinforce the efficacy of ER stress-inducing agents against cancer.

Size-Dependent Cytotoxicity of Hydroxyapatite Crystals on Renal Epithelial Cells.

BACKGROUND: Hydroxyapatite (HAP) is a common component of most idiopathic calcium oxalate (CaOx) stones and is often used as a nidus to induce the formation of CaOx kidney stones. METHODS: This work comparatively studies the cytotoxicity of four kinds of HAP crystals with different sizes (40 nm to 2 µm), namely, HAP-40 nm, HAP-70 nm, HAP-1 µm, and HAP-2 µm, on human renal proximal tubular epithelial cells (HK-2). RESULTS: HAP crystals reduce the viability and membrane integrity of HK-2 cells in a concentration-dependent manner and consequently cause cytoskeleton damage, cell swelling, increased intracellular reactive oxygen species level, decreased mitochondrial membrane potential, increased intracellular calcium concentration, blocked cell cycle and stagnation in G0/G1 phase, and increased cell necrosis rate. HAP toxicity to HK-2 cells increases with a decrease in crystal size. CONCLUSION: Cell damage caused by HAP crystals increases the risk of kidney stone formation.

Degraded Porphyra yezoensis polysaccharide protects HK-2 cells and reduces nano-COM crystal toxicity, adhesion and endocytosis.

We studied the protection of degraded Porphyra yezoensis polysaccharide (PYP) on human proximal tubular epithelial cells (HK-2) from cytotoxicity of nano-calcium oxalate monohydrate (COM) crystal, and the regulation of adhesion and endocytosis of the COM crystal. Four degraded fractions, namely, PYP1, PYP2, PYP3, and PYP4, were successfully obtained, with molecular weights (Mws) of 576.2, 49.5, 12.6, and 4.02 kDa, respectively. PYP protection reduced the crystal toxicity, prevented the destruction of cell morphology and cytoskeleton, inhibited the production of reactive oxygen species and the decline of lysosomal integrity, and reduced the expression of osteopontin and transmembrane protein (CD44). PYPi inhibited the adhesion and endocytosis of HK-2 cells by nano-COM. Endocytic COM crystals were accumulated in the lysosomes. With decreasing molecular weight, the ability of PYP to reduce cell damage and inhibit cell adhesion and endocytosis increased. PYP4, which has the smallest molecular weight, weaker intramolecular hydrogen bonds and more reducing groups, showed the best biological activity. PYPi can reduce the oxidative damage of the crystal to the cell, inhibit the adhesion and endocytosis of the crystal, and reduce the risk of kidney stone formation. Therefore, PYP, especially PYP4, has potential for use as a green drug to inhibit the formation and recurrence of calcium oxalate stones.