Search Results (6)

Background: Common forms of pathological crystals are uric acid or urates, which are responsible for gout, urolithiasis, and other conditions. Methods: We used a kinetic–turbidimetric crystallization assay to evaluate the effect of ten specific methylxanthines on the crystallization of monosodium urate, potassium urate, and ammonium urate in conditions that mimicked urine. We also studied the effect of different levels of 7-methylxanthine in the presence of other biological compounds (albumin and hyaluronic acid) on the solubility of monosodium urate in conditions that mimicked synovial fluid. Results: The results showed that 7-methylxanthine in the range of 16.61–49.84 mg/L inhibited the crystallization of each urate when the initial urate concentration was 3 × 10⁻³ M (500 mg/L) and the conditions mimicked urine, and that the greatest inhibitory effect was for monosodium urate. In addition, 7-methylxanthine at a concentration of 25 mg/L totally prevented the crystallization of monosodium urate at an initial urate concentration of 2.38 × 10⁻³ M (400 mg/L) in conditions that mimicked synovial fluid. Moreover, at a low concentration of 7-methylxanthine, albumin and hyaluronic acid increased this inhibitory effect. Conclusions: Our in vitro results demonstrate that 7-methylxanthine inhibits the crystallization of urates in conditions that mimic synovial fluid and urine. Full article

Urolithiasis is a complex and multifactorial disease characterized by the formation of calculi at the urinary tract level. Conventional therapeutic prophylaxis relies on the use of Ca-blockers, alkalis, diuretics, and anti-edema agents, but their prolonged utilization is often limited by several side effects. In this scenario, the aim of the present work was the design of an innovative multi-component nutraceutical formulation (NF) for the management of urinary stones consisting of a synergistic combination of natural aqueous extracts of Oreganum vulgare L. (1% of saponin), Urtica dioica (0.8% of β-sitosterol), Phyllanthus niruri (15% of tannins w/w), and Ceterach officinarum in association with bromelain, K, and Mg citrate. To assess the potential of NF also in the treatment of uric acid (UA) stones, the effects on the expression of the cellular UA transporters OAT1 and URAT1 were investigated in a renal tubular cell line. In addition, the myorelaxant effect of NF was investigated in a human pulmonary artery smooth muscle cell (HPASMC) model resulting in a decreased muscle contractility of −49.4% (p < 0.01) compared to the control. The treatment with NF also showed a valuable inhibition of in vitro calcium-oxalate crystal formation, both in prevention (−52.3% vs. control, p < 0.01) and treatment (−70.8% vs. control, p < 0.01) experiments. Finally, an ischemic reperfusion rat model was used to evaluate the NF anti-edema effects, resulting in a reduction in the edema-related vascular permeability (Normalized Gray Levels, NGL = 0.40 ± 0.09, p < 0.01, −67.1% vs. untreated rats). In conclusion, the present NF has shown to be a promising natural alternative for managing urinary tract stones. Full article

Uric acid (UA) forms monosodium urate (MSU) crystals to exert proinflammatory actions, thus causing gout arthritis, urolithiasis, kidney disease, and cardiovascular disease. UA is also one of the most potent antioxidants that suppresses oxidative stress. Hyper andhypouricemia are caused by genetic mutations or polymorphism. Hyperuricemia increases urinary UA concentration and is frequently associated with urolithiasis, which is augmented by low urinary pH. Renal hypouricemia (RHU) is associated with renal stones by increased level of urinary UA, which correlates with the impaired tubular reabsorption of UA. Hyperuricemia causes gout nephropathy, characterized by renal interstitium and tubular damage because MSU precipitates in the tubules. RHU is also frequently associated with tubular damage with elevated urinary beta2-microglobulin due to increased urinary UA concentration, which is related to impaired tubular UA reabsorption through URAT1. Hyperuricemia could induce renal arteriopathy and reduce renal blood flow, while increasing urinary albumin excretion, which is correlated with plasma xanthine oxidoreductase (XOR) activity. RHU is associated with exercise-induced kidney injury, since low levels of SUA could induce the vasoconstriction of the kidney and the enhanced urinary UA excretion could form intratubular precipitation. A U-shaped association of SUA with organ damage is observed in patients with kidney diseases related to impaired endothelial function. Under hyperuricemia, intracellular UA, MSU crystals, and XOR could reduce NO and activate several proinflammatory signals, impairing endothelial functions. Under hypouricemia, the genetic and pharmacological depletion of UA could impair the NO-dependent and independent endothelial functions, suggesting that RHU and secondary hypouricemia might be a risk factor for the loss of kidney functions. In order to protect kidney functions in hyperuricemic patients, the use of urate lowering agents could be recommended to target SUA below 6 mg/dL. In order to protect the kidney functions in RHU patients, hydration and urinary alkalization may be recommended, and in some cases an XOR inhibitor might be recommended in order to reduce oxidative stress. Full article

Hypouricemia is recognized as a rare disorder, defined as a serum uric acid level of 2.0 mg/dL or less. Hypouricemia is divided into an overexcretion type and an underproduction type. The former typical disease is xanthinuria, and the latter is renal hypouricemia (RHUC). The frequency of nephrogenic hypouricemia due to a deficiency of URAT1 is high in Japan, accounting for most asymptomatic and persistent cases of hypouricemia. RHUC results in a high risk of exercise-induced acute kidney injury and urolithiasis. It is vital to promote research on RHUC, as this will lead not only to the elucidation of its pathophysiology but also to the development of new treatments for gout and hyperuricemia. Full article

Renal hypouricemia (RHUC) is caused by an inherited defect in the main reabsorption system of uric acid, SLC22A12 (URAT1) and SLC2A9 (GLUT9). RHUC is characterized by a decreased serum uric acid concentration and an increase in its excreted fraction. Patients suffer from hypouricemia, hyperuricosuria, urolithiasis, and even acute kidney injury. We report clinical, biochemical, and genetic findings in a cohort recruited from the Košice region of Slovakia consisting of 27 subjects with hypouricemia and relatives from 11 families, 10 of whom were of Roma ethnicity. We amplified, directly sequenced, and analyzed all coding regions and exon–intron boundaries of the SLC22A12 and SLC2A9 genes. Sequence analysis identified dysfunctional variants c.1245_1253del and c.1400C>T in the SLC22A12 gene, but no other causal allelic variants were found. One heterozygote and one homozygote for c.1245_1253del, nine heterozygotes and one homozygote for c.1400C>T, and two compound heterozygotes for c.1400C>T and c.1245_1253del were found in a total of 14 subjects. Our result confirms the prevalence of dysfunctional URAT1 variants in Roma subjects based on analyses in Slovak, Czech, and Spanish cohorts, and for the first time in a Macedonian Roma cohort. Although RHUC1 is a rare inherited disease, the frequency of URAT1-associated variants indicates that this disease is underdiagnosed. Our findings illustrate that there are common dysfunctional URAT1 allelic variants in the general Roma population that should be routinely considered in clinical practice as part of the diagnosis of Roma patients with hypouricemia and hyperuricosuria exhibiting clinical signs such as urolithiasis, nephrolithiasis, and acute kidney injury. Full article

Renal hypouricemia (RHUC) is caused by an inherited defect in the main (reabsorptive) renal urate transporters, URAT1 and GLUT9. RHUC is characterized by decreased concentrations of serum uric acid and an increase in its excretion fraction. Patients suffer from hypouricemia, hyperuricosuria, urolithiasis, and even acute kidney injury. We report the clinical, biochemical, and genetic findings of a pediatric patient with hypouricemia. Sequencing analysis of the coding region of SLC22A12 and SLC2A9 and a functional study of a novel RHUC1 variant in the Xenopus expression system were performed. The proband showed persistent hypouricemia (67–70 µmol/L; ref. range 120–360 µmol/L) and hyperuricosuria (24–34%; ref. range 7.3 ± 1.3%). The sequencing analysis identified common non-synonymous allelic variants c.73G > A, c.844G > A, c.1049C > T in the SLC2A9 gene and rare variants c.973C > T, c.1300C > T in the SLC22A12 gene. Functional characterization of the novel RHUC associated c.973C > T (p. R325W) variant showed significantly decreased urate uptake, an irregular URAT1 signal on the plasma membrane, and reduced cytoplasmic staining. RHUC is an underdiagnosed disorder and unexplained hypouricemia warrants detailed metabolic and genetic investigations. A greater awareness of URAT1 and GLUT9 deficiency by primary care physicians, nephrologists, and urologists is crucial for identifying the disorder. Full article