Induction of lipid peroxidation by oxalate in experimental rat urolithiasis

The function of lipid peroxidation and the antiperoxidative enzymes of rat liver and kidney were studied in stone formation induced by intraperitoneal administration of sodium oxalate (7 mg/100 g body weight). The animals sacrificed 3 and 12 h after administration of sodium oxalate had higher level of malondialdehyde in liver and kidney than control animals. A significantly pronounced release of malondialdehyde was observed in treated liver and kidney homogenates when incubated with either ferrous sulphate or hydrogen peroxide compared to control liver and kidney. Superoxide dismutase activity was increased only in liver and not in kidney in treated animals compared to the control. A highly significant decrease in catalase activity was observed in both liver and kidney of treated animals.     

Induction of oxalate binding by lipid peroxidation in rat kidney mitochondria.

Enhanced oxalate binding (150-180% of control) was observed in kidney, liver, brain and heart, after subjecting them to lipid peroxidation in presence of iron. Kidney mitochondrial oxalate binding was stimulated by different promoters, and the order of stimulation was Fe2+ greater than t-BH greater than ascorbic acid greater than Fe3+ greater than H2O2. Oxalate binding was maximum when iron concentration was between 1-2 mM. The iron-induced oxalate binding was inhibited by reduced glutathione, beta-mercaptoethanol, alpha-tocopherol and hydroxyl ion scavengers, histidine and mannitol. Catalase inhibited both Fe(2+)-H2O2 induced oxalate binding and lipid peroxidation reactions, suggesting that the induced oxalate binding in mitochondria was mediated through the hydroxyl radical reaction mechanism.     

Fungal physiology and the formation of calcium oxalate films on stone monuments

Summary Extensive, uniform, yellow-brown films are observed on many monuments. The origin of these films, composed predominantly of calcium oxalate, has been investigated by several authors. Oxalate film formation may be related, in some cases, to the activity of such microorganisms as fungi, which presumably form oxalic acid via the metabolic transformation of organic substances already present on the stone. The present work provides an overview of the physiological factors affecting oxalate synthesis by fungi and of oxalic acid in fungi metabolism.     

Ferroptosis in calcium oxalate kidney stone formation and the possible regulatory mechanism of ANKRD1

The objective of this study was to explore the role of ferroptosis in the formation of calcium oxalate (CaOx) kidney stones and the regulatory mechanism of the ankyrin repeat domain 1 (ANKRD1) gene. The study found that the Nrf2/HO-1 and p53/SLC7A11 signaling pathways were activated in the kidney stone model group, and the expression of the ferroptosis marker proteins SLC7A11 and GPX4 was significantly reduced, while the expression of ACSL4 was significantly increased. The expression of the iron transport-related proteins CP and TF increased significantly, and Fe²⁺ accumulated in the cell. The expression of HMGB1 increased significantly. In addition, the level of intracellular oxidative stress was increased. The gene with the most significant difference caused by CaOx crystals in HK-2 cells was ANKRD1. Silencing or overexpression of ANKRD1 by lentiviral infection technology regulated the expression of the p53/SLC7A11 signaling pathway, which regulated the ferroptosis induced by CaOx crystals. In conclusion, CaOx crystals can mediate ferroptosis through the Nrf2/HO-1 and p53/SLC7A11 pathways, thereby weakening the resistance of HK-2 cells to oxidative stress and other unfavorable factors, enhancing cell damage, and increasing crystal adhesion and CaOx crystal deposition in the kidney. ANKRD1 participates in the formation and development of CaOx kidney stones by activating ferroptosis mediated by the p53/SLC7A11 pathway.     

Engineering calcium oxalate crystal formation in Arabidopsis

Many plants accumulate crystals of calcium oxalate. Just how these crystals form remains unknown. To gain insight into the mechanisms regulating calcium oxalate crystal formation, a crystal engineering approach was initiated utilizing the non-crystal-accumulating plant, Arabidopsis. The success of this approach hinged on the ability to transform Arabidopsis genetically into a calcium oxalate crystal-accumulating plant. To accomplish this transformation, two oxalic acid biosynthetic genes, obcA and obcB, from the oxalate-secreting phytopathogen, Burkholderia glumae were inserted into the Arabidopsis genome. The co-expression of these two bacterial genes in Arabidopsis conferred the ability not only to produce a measurable amount of oxalate but also to form crystals of calcium oxalate. Biochemical and cellular studies of crystal accumulation in Arabidopsis revealed features that are similar to those observed in the cells of crystal-forming plants. Thus, it appears that at least some of the basic components that comprise the calcium oxalate crystal formation machinery are conserved even in non-crystal-accumulating plants.     

Increased lipid peroxidation in the erythrocytes of kidney stone formers

The level of lipid peroxidation was significantly increased in erythrocytes and erythrocyte membrane in patients with stone disease. Increased activities of catalase and acetylcholinesterase in the erythrocyte membrane were observed, while hemolysate displayed no significant change in superoxide dismutase activity. The amount of phospholipids in the RBC membrane of patients was significantly increased. Peroxidation was stimulated by oxalate in vitro and was further enhanced in the presence of ferrous ion. The changes in lipid peroxidation and antioxidant enzymes are suggestive of chemical alteration of the RBC membrane during urolithiasis.     

Intracrystalline proteins and the hidden ultrastructure of calcium oxalate urinary crystals: implications for kidney stone formation

The external appearance of urinary calcium oxalate (CaOx) crystals suggests that they are solid, homogeneous structures, despite their known association with proteins. Our aim was to determine whether proteins comprising the organic matrix of CaOx crystals are superficial or intracrystalline in order to clarify the role of urinary proteins in the formation of kidney stones. CaOx crystals were precipitated from centrifuged and filtered, or ultrafiltered, healthy human urine. They were then treated with dilute NaOH to remove bound proteins, partially demineralized with EDTA, or fractured and subjected to limited proteolysis before examination by low-resolution scanning electron microscopy or field emission scanning electron microscopy. Crystals precipitated from centrifuged and filtered urine had a complex interior network of protein distributed throughout the mineral phase, which appeared to comprise closely packed subcrystalline particles stacked in an orderly array among an amorphous organic matrix. This ultrastructure was not evident in crystals deposited in the absence of macromolecules, which were completely solid. This is the first direct evidence that crystals generated from cell-free systems contain significant amounts of protein distributed throughout a complex internal cribriform ultrastructure. Combined with mineral erosion in the acidic lysosomal environment, proteins inside CaOx crystals would render them susceptible to attack by urinary and intracellular renal proteases and facilitate their further dissolution or disruption into small particles and ions for removal by exocytosis. The findings also have broader ramifications for industry and the materials sciences, as well as the development and resorption of crystals in biomineralization systems throughout nature.     

植物乳酸杆菌对小鼠草酸钙结石的干预效果

【背景】草酸钙结石是一种临床常见且易复发的疾病,由于结石质地坚硬,只能通过外科手术的方法治疗,给患者带了很大的痛苦。已有研究证实,肠道菌群可影响草酸钙结石的形成,降低草酸钙结石的发病率。【目的】探究植物乳杆菌对小鼠草酸钙结石的干预效果。【方法】体外实验：在MRS培养基中加入0.02 mol/L草酸钠,制备菌株筛选培养基（MRS-OX）。接种200μL的3.48×10¹²CFU/L植物乳杆菌悬液至MRS-OX制备含菌培养基（B+MRS-OX）。将等体积MRS-OX和B+MRS-OX于37°C恒温培养2 d,测剩余草酸浓度。体内实验：以10周龄雄性昆明小鼠为实验动物,随机分为对照组、植物乳杆菌组、结石组和植物乳杆菌干预组,每组5只小鼠。通过乙醛酸诱导小鼠建立草酸钙结石模型,并给予200μL的3.48×10¹²CFU/L植物乳杆菌进行干预治疗以观察其预防小鼠草酸钙结石的效果。实验结束后,绘制各组小鼠平均体重变化趋势图并计算小鼠肾脏脏器指数,检测每只小鼠血液学指标和氧化应激指标总超氧化物歧化酶（superoxide dismutase,SOD）和丙二...     

Role of lipid peroxidation in iron-induced cellular calcium overload

Calcium overload is the common pathway leading to cell injury. The role of iron-induced lipid peroxidation in the modification of Ehrlich carcinoma cells calcium homeostasis has been studied. There is a lack of correlation between that modification and the value of lipid peroxidation. The stability characteristics of low-mol-weight iron complexes affect lipid peroxidation and, to a lesser extent, cellular calcium uptake. Lipid peroxidation appears not as a triggering factor of cellular calcium homeostasis modification, but as a concomitant phenomenon.     

The biphasic effect of calcium on lipid peroxidation

Mechanisms underlying Ca2+ effects on lipid peroxidation (LPO) induced in liposomes (from egg yolk lecithin) and ufasomes (from linolenic acid and methyl linolenate) with the aid of an O2-(.) -generating system (Fe2+ + ascorbate) were studied. It was shown that stimulation of LPO by low Ca2+ concentrations (10(-6)-10(-5)M) was due to its ability to release Fe2+ ions bound to negatively charged (phosphate or carboxylic) lipid groups (of lecithin or linolenic acid), thus increasing the concentration of catalytically active Fe2+. The inhibitory effect of high Ca2+ concentrations was caused by its interaction with superoxide anion radicals and was not observed in LPO systems independent of O2- generation (e.g., Fe2+ + cumol hydroperoxide).     

Ecological approach to the genesis of calcium oxalate patinas on stone monuments

Summary The genesis of calcium oxalate patinas on stone monuments gives rise to controversial opinions. One of the proposed hypotheses links this phenomenon to the past presence of lichens on the exposed surfaces of monuments. However, the growth of a biological species cannot occur if environmental conditions are not compatible with its autoecology. Analysis of variations of the environmental factors that can act as «limiting factors» shows that in most monuments, the various exposures are not always compatible with biological growth. The environmental factor that seems to be the most limiting is the amount of surface water that is frequently below the range of tolerance of even the most xerophylous species. In the case of Trajan's column in Rome, the distribution of oxalate layers shows an opposite trend with respect to what we would expect for lichen colonization. Presently other kinds of biological colonization cannot be excluded.     

Sialylation of urinary prothrombin fragment 1 is implicated as a contributory factor in the risk of calcium oxalate kidney stone formation

Urinary glycoproteins are important inhibitors of calcium oxalate crystallization and adhesion of crystals to renal cells, both of which are key mechanisms in kidney stone formation. This has been attributed to glycosylation of the proteins. In South Africa, the black population rarely form stones (incidence < 1%) compared with the white population (incidence 12-15%). A previous study involving urinary prothrombin fragment 1 from both populations demonstrated superior inhibitory activity associated with the protein from the black group. In the present study, we compared N-linked and O-linked oligosaccharides released from urinary prothrombin fragment 1 isolated from the urine of healthy and stone-forming subjects in both populations to elucidate the relationship between glycosylation and calcium oxalate stone pathogenesis. The O-glycans of both control groups and the N-glycans of the black control samples were significantly more sialylated than those of the white stone-formers. This demonstrates a possible association between low-percentage sialylation and kidney stone disease and provides a potential diagnostic method for a predisposition to kidney stones that could lead to the implementation of a preventative regimen. These results indicate that sialylated glycoforms of urinary prothrombin fragment 1 afford protection against calcium oxalate stone formation, possibly by coating the surface of calcium oxalate crystals. This provides a rationale for the established roles of urinary prothrombin fragment 1, namely reducing the potential for crystal aggregation and inhibiting crystal-cell adhesion by masking the interaction of the calcium ions on the crystal surface with the renal cell surface along the nephron.     

Recombinant Lactobacillus plantarum expressing and secreting heterologous oxalate decarboxylase prevents renal calcium oxalate stone deposition in experimental rats

Background

Calcium oxalate (CaOx) is the major constituent of about 75% of all urinary stone and the secondary hyperoxaluria is a primary risk factor. Current treatment options for the patients with hyperoxaluria and CaOx stone diseases are limited. Oxalate degrading bacteria might have beneficial effects on urinary oxalate excretion resulting from decreased intestinal oxalate concentration and absorption. Thus, the aim of the present study is to examine the in vivo oxalate degrading ability of genetically engineered Lactobacillus plantarum (L. plantarum) that constitutively expressing and secreting heterologous oxalate decarboxylase (OxdC) for prevention of CaOx stone formation in rats. The recombinants strain of L. plantarum that constitutively secreting (WCFS1OxdC) and non-secreting (NC8OxdC) OxdC has been developed by using expression vector pSIP401. The in vivo oxalate degradation ability for this recombinants strain was carried out in a male wistar albino rats. The group I control; groups II, III, IV and V rats were fed with 5% potassium oxalate diet and 14^th day onwards group II, III, IV and V were received esophageal gavage of L. plantarum WCFS1, WCFS1OxdC and NC8OxdC respectively for 2-week period. The urinary and serum biochemistry and histopathology of the kidney were carried out. The experimental data were analyzed using one-way ANOVA followed by Duncan’s multiple-range test.

Results

Recombinants L. plantarum constitutively express and secretes the functional OxdC and could degrade the oxalate up to 70–77% under in vitro. The recombinant bacterial treated rats in groups IV and V showed significant reduction of urinary oxalate, calcium, uric acid, creatinine and serum uric acid, BUN/creatinine ratio compared to group II and III rats (P < 0.05). Oxalate levels in kidney homogenate of groups IV and V were showed significant reduction than group II and III rats (P < 0.05). Microscopic observations revealed a high score (4+) of CaOx crystal in kidneys of groups II and III, whereas no crystal in group IV and a lower score (1+) in group V.

Conclusion

The present results indicate that artificial colonization of recombinant strain, WCFS1OxdC and NC8OxdC, capable of reduce urinary oxalate excretion and CaOx crystal deposition by increased intestinal oxalate degradation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-014-0086-y) contains supplementary material, which is available to authorized users.     

Effect of calcium on lipid peroxidation in plasma membranes]

Process of nonenzymatic peroxidation of lipids in the plasma membranes of thymocytes has been studied as affected by Ca2+. It is established that at calcium concentrations to 900 microM peroxidation gets more intensive; at higher concentrations of the intensity of this process falls.     

Isolation of Medicago truncatula mutants defective in calcium oxalate crystal formation

Plants accumulate crystals of calcium oxalate in a variety of shapes, sizes, amounts, and spatial locations. How and why many plants form crystals of calcium oxalate remain largely unknown. To gain insight into the regulatory mechanisms of crystal formation and function, we have initiated a mutant screen to identify the genetic determinants. Leaves from a chemically mutagenized Medicago truncatula population were visually screened for alterations in calcium oxalate crystal formation. Seven different classes of calcium oxalate defective mutants were identified that exhibited alterations in crystal nucleation, morphology, distribution and/or amount. Genetic analysis suggested that crystal formation is a complex process involving more than seven loci. Phenotypic analysis of a mutant that lacks crystals, cod 5, did not reveal any difference in plant growth and development compared with controls. This finding brings into question the hypothesized roles of calcium oxalate formation in supporting tissue structure and in regulating excess tissue calcium.     

Expression of heterologous oxalate decarboxylase in HEK293 cells confers protection against oxalate induced oxidative stress as a therapeutic approach for calcium oxalate stone disease

Oxalates stimulate alterations in renal epithelial cells and thereby induce calcium oxalate (CaOx) stone formation. Bacillus subtilis YvrK gene encodes for oxalate decarboxylase (OxdC) which degrades oxalate to formate and CO₂. The present work is aimed to clone the oxdC gene in a mammalian expression vector pcDNA and transfect into Human Embryonic Kidney 293 (HEK293) cells and evaluate the oxdC expression, cell survival rate and oxalate degrading efficiency. The results indicate cell survival rate of HEK293/pcDNAOXDC cells pre-incubated with oxalate was enhanced by 28%. HEK293/pcDNAOXDC cells expressing OxdC treated with oxalate, significantly restored antioxidant activity, mitochondrial membrane potential and intracellular reactive oxygen species (ROS) generation compared with HEK293/pcDNA. Apoptotic marker caspase 3 downregulation illustrates HEK293/pcDNAOXDC cells were able to survive under oxalate-mediated oxidative stress. The findings suggest HEK293 cells expressing oxdC capable of degrading oxalate protect cells from oxidative damage and thus serve as a therapeutic option for prevention of CaOx stone disease.

     

Calcium in lipid peroxidation: does calcium interact with superoxide?

Using a pulse radiolysis approach to generate and observe superoxide anions (O2-.) in the absence and presence of calcium, we have attempted to verify the recent hypothesis of Babizhayev (Arch. Biochem. Biophys. 266, 446-451, 1988) of a Ca2(+)-O2-. interaction during lipid peroxidation. We could not observe rapid scavenging of O2-. or complex formation with Ca2+ to account for an inhibitory effect of this cation on lipid peroxidation. Neither could we agree that the stimulatory effect is due to liberation of catalytic ferrous iron from weak complexes by Ca2+. Drawing on reports in the literature, we propose an alternate explanation for the apparent stimulation of lipid peroxidation by low Ca2+ concentrations. In our view, this is not a direct effect, but reflects independently initiated processes of lipid peroxidation and Ca2+ translocation, which interact subsequently in a synergistic manner. The reported inhibition at high Ca2+ concentrations is considered an artifact as it was observed at levels far in excess of those relevant to animal systems (but not necessarily in some plant compartments).