HAO1-Mediated Oxalate Metabolism Promotes Lung Pre-Metastatic Niche Formation by Inducing Neutrophil Extracellular Traps

Background Metabolic reprogramming has been shown to be involved in cancer-induced PMN formation, but the underlying mechanisms have been insufficiently explored. Methods HAO1 expression in lung tissues and alveolar epithelial cells were deteted by qPCR and Western blotting. The effect of HAO1 on the lung metastasis of cancer was investigated by orthotropic metastasis assay. Lungs and cells oxalate levels were determined using an oxalate assay kit. The effect of oxalate on neutrophil extracellular trap formation was investigated by immunofluorescence. The effect of oxalate on proliferation of breast cancer cells was revealed by immunofluorescence by colony formation assay. Results HAO1 was up-regulated in the alveolar epithelial cells of mice bearing metastatic breast cancer cells at the pre-metastatic stage. Upregulation of HAO1 led to oxalate accumulation in lung tissues and alveolar epithelial cells. Pharmacologic inhibition of HAO1 could effectively suppress the lung oxalate accumulation induced by primary cancer. Lung oxalate accumulation induced NET formation by activating NADPH oxidase. Lung oxalate accumulation promoted the proliferation of metastatic cancer cells by activating the MAPK signaling pathway. Breast cancer cells induced HAO1 expression and oxalate accumulation in alveolar epithelial cells by activating TLR3-IRF3 signaling. Conclusion These findings underscore the role of HAO1-mediated oxalate metabolism in cancer-induced lung PMN formation and metastasis. HAO1 could be an appealing therapeutic target for preventing lung metastasis of cancer.

Regulation of Oxalate Metabolism in Spinach Revealed by RNA-Seq-Based Transcriptomic Analysis

Although spinach (Spinacia oleracea L.) is considered to be one of the most nutrient-rich leafy vegetables, it is also a potent accumulator of anti-nutritional oxalate. Reducing oxalate content would increase the nutritional value of spinach by enhancing the dietary bioavailability of calcium and other minerals. This study aimed to investigate the proposed hypothesis that a complex network of genes associated with intrinsic metabolic and physiological processes regulates oxalate homeostasis in spinach. Transcriptomic (RNA-Seq) analysis of the leaf and root tissues of two spinach genotypes with contrasting oxalate phenotypes was performed under normal physiological conditions. A total of 2308 leaf- and 1686 root-specific differentially expressed genes (DEGs) were identified in the high-oxalate spinach genotype. Gene Ontology (GO) analysis of DEGs identified molecular functions associated with various enzymatic activities, while KEGG pathway analysis revealed enrichment of the metabolic and secondary metabolite pathways. The expression profiles of genes associated with distinct physiological processes suggested that the glyoxylate cycle, ascorbate degradation, and photorespiratory pathway may collectively regulate oxalate in spinach. The data support the idea that isocitrate lyase (ICL), ascorbate catabolism-related genes, and acyl-activating enzyme 3 (AAE3) all play roles in oxalate homeostasis in spinach. The findings from this study provide the foundation for novel insights into oxalate metabolism in spinach.

MO311THE ASSOCIATION BETWEEN NEPHROTIC-RANGE PROTEINURIA AND OXALATE METABOLISM VIOLATION IN PATIENTS WITH PRIMARY GLOMERULONEPHRITIS

Background and Aims There is a general lack of scientific research on oxalate metabolism in primary glomerulonephritis (PGN) patients. The present study aimed to evaluate plasma oxalic acid (POx) concentration and urinary oxalate (UOx) excretion in PGN patients and determine the role of nephrotic syndrome in oxalate metabolism, which has never before been reported. Method A total of 100 participants were enrolled in this cross-sectional single-center study, including 76 PGN patients aged 41 ± 1.83 years and 24 healthy volunteers on a free-choice diet who served as a control reference group to evaluate POx concentration. Among the patients were 53 (69.7 %) patients with nephrotic syndrome (NS) and biopsy-proven PGN and 23 (30.3 %) patients with a clinical diagnosis of PGN. All patients were treated according to KDIGO Clinical Practice Guidelines for Glomerulonephritis. In addition to routine hematological and biochemical tests, POx concentration and UOx excretion were found in all study participants. POx was measured spectrophotometrically using a commercially available kit (MAK315, Sigma, Spain). Daily UOx excretion was determined using an oxalate oxidase/peroxidase reagent (BioSystems, Spain). Urine protein excretion (UPE) was measured in a 24-h urine collection. The glomerular filtration rate (GFR) was calculated using the CKD-EPI formula. The data were presented as the median and the interquartile ranges [Me (Q25-Q75)] and compared using the Mann-Whitney test. The Spearman correlation test and the partial correlation coefficient were used to evaluate the association between the examined markers. Results POx concentration was significantly higher in the patients with PGN compared with the healthy volunteers: 29.9 (14.9-51.7) vs 18.9 (16.2-23.8) µmol/L, p = 0.01. Although the patients with NS demonstrated a statistically higher GFR level compared with the patients with mild proteinuria [70.5 (47-87) vs 50 (22-76.2) mL/min/1.73 m2, p = 0.01], these patients also had the highest POx level (Fig. 1). Moreover, POx concentration was significantly associated with GFR (r = -0.27, p = 0.005), serum phosphate (r = 0.26, p = 0.007) and UPE (Fig. 2) levels. No significant differences were found in UOx excretions between the groups. However, the higher level of UPE was, the higher level of UOx was observed in the PGN patients with NS (Fig. 3). The partial correlation analysis confirmed a strong association between UPE and POx concentration independently of the patients’ age, gender, GFR and serum phosphate levels (r = 0.22, p = 0.04). Conclusion Nephrotic-range proteinuria was significantly associated with the elevation of POx concentration and UOx excretion in the PGN patients. More research with a larger cohort is needed to confirm this preliminary evidence and validate NS as a risk factor for oxalate metabolism violation in PGN patients.

Biochemical indices of urine in children with allergic diseases of airways

Currently, unsatisfactory control of the course of allergic diseases of airways (ADA) remains. There is data on the potential involvement of urate and oxalate metabolism in the pathogenesis of ADA, which determines the need to study the corresponding biomarkers. Aim of the work - to evaluate the daily urinary excretion of urates and oxalates in ADA children. Materials and methods. We examined 100 children aged 2 to 9 years, boys - 22, girls - 78, with symptoms of crystalluria. The children were divided into the main group (42 children) and the comparison group (58 people). The main group included patients with established diagnoses of ADA, and the comparison group included patients without ADA. A biochemical study of daily urine was performed in all cases. Results. It was found that the daily excretion of oxalates in ADA patients was significantly increased compared to the control, 26.5 [22.1; 32.6] mg/day and 23.3 [20.1; 27.6] mg/day, respectively. Daily urate excretion in patients of the main group was also significantly increased compared to the control, both in absolute numbers - 1.45 [1.13; 2.13] mmol/day and 1.17 [0.89; 1.5] mmol/day, respectively (p = 0.005), and in normalized to the body surface area units. Conclusion. A statistically significant increase in daily urate excretion was found in ADA children. The clinical and pathogenetic significance of this phenomenon in children with ADA requires further study.

Microbial contributions to oxalate metabolism in health and disease

Over-accumulation of oxalate in humans may lead to nephrolithiasis and nephrocalcinosis. Humans lack endogenous oxalate degradation pathways (ODP), but intestinal microbiota can degrade oxalate and protect against its absorption. However, the particular microbes that actively degrade oxalate in vivo are ill-defined, which restricts our ability to disentangle the underlying taxonomic contributions. Here we leverage large-scale multi-omics data (>3000 samples from >1000 subjects) to show that the human microbiota in health harbors diverse ODP-encoding microbial species, but an oxalate autotroph-Oxalobacter formigenes- dominates this function transcriptionally. Patients with Inflammatory Bowel Disease (IBD) are at significantly increased risk for disrupted oxalate homeostasis and calcium-oxalate nephrolithiasis. Here, by analyzing multi-omics data from the iHMP-IBD study, we demonstrate that the oxalate degradation function conferred by the intestinal microbiota is severely impaired in IBD patients. In parallel, the enteric oxalate levels of IBD patients are significantly elevated and associated with intestinal disease severity, which is consistent with the clinically known nephrolithiasis risk. The specific changes in ODP expression by several important taxa suggest that they play different roles in the IBD-induced nephrolithiasis risk.

Metabolism of Oxalate in Humans: A Potential Role Kynurenine Aminotransferase/Glutamine Transaminase/Cysteine Conjugate Betalyase Plays in Hyperoxaluria

Hyperoxaluria, excessive urinary oxalate excretion, is a significant health problem worldwide. Disrupted oxalate metabolism has been implicated in hyperoxaluria and accordingly, an enzymatic disturbance in oxalate biosynthesis can result in the primary hyperoxaluria. Alanine-glyoxylate aminotransferase-1 and glyoxylate reductase, the enzymes involving glyoxylate (precursor for oxalate) metabolism, have been related to primary hyperoxalurias. Some studies suggest that other enzymes such as glycolate oxidase and alanine-glyoxylate aminotransferase-2 might be associated with primary hyperoxaluria as well, but evidence of a definitive link is not strong between the clinical cases and gene mutations. There are still some idiopathic hyperoxalurias, which require a further study for the etiologies. Some aminotransferases, particularly kynurenine aminotransferases, can convert glyoxylate to glycine. Based on biochemical and structural characteristics, expression level, and subcellular localization of some aminotransferases, a number of them appear able to catalyze the transamination of glyoxylate to glycine more efficiently than alanine glyoxylate aminotransferase-1. The aim of this minireview is to explore other undermining causes of primary hyperoxaluria and stimulate research toward achieving a comprehensive understanding of underlying mechanisms leading to the disease. Herein, we reviewed all aminotransferases in the liver for their functions in glyoxylate metabolism. Particularly, kynurenine aminotransferase-I and III were carefully discussed regarding their biochemical and structural characteristics, cellular localization, and enzyme inhibition. Kynurenine aminotransferase-III is, so far, the most efficient putative mitochondrial enzyme to transaminate glyoxylate to glycine in mammalian livers, which might be an interesting enzyme to look for in hyperoxaluria etiology of primary hyperoxaluria and should be carefully investigated for its involvement in oxalate metabolism.