Preventive Pharmacological Therapy and Risk of Recurrent Urinary Stone Disease.

BACKGROUND: Urinary stone disease is a prevalent condition associated with a high recurrence risk. Preventive pharmacological therapy has been proposed to reduce recurrent stone episodes. However, limited evidence exists regarding its effectiveness, contributing to its underutilization by physicians. This study aimed to evaluate the association between preventive pharmacological therapy (thiazide diuretics, alkali therapy, and uric acid-lowering medications) and clinically significant urinary stone disease recurrence. METHODS: Using data from the Veterans Health Administration, adults with an index episode of urinary stone disease from 2012 through 2019 and at least one urinary abnormality (hypercalciuria, hypocitraturia, or hyperuricosuria) on 24-hour urine collection were included. The primary outcome was a composite variable representing recurrent stone events that resulted in emergency department visits, hospitalizations, or surgery for urinary stone disease. Cox proportional hazards regression was performed to estimate the association between preventive pharmacological therapy use and recurrent urinary stone disease while adjusting for relevant baseline patient characteristics. RESULTS: Among the cohort of patients with urinary abnormalities ( n =5637), treatment with preventive pharmacological therapy was associated with a significant 19% lower risk of recurrent urinary stone disease during the 12-36-month period after the initial urine collection (hazard ratio, 0.81; 95% confidence interval, 0.65 to 1.00; P = 0.0496). However, the effectiveness of preventive pharmacological therapy diminished over longer follow-up periods (12-48 and 12-60 months after the urine collection) and did not reach statistical significance. When examining specific urinary abnormalities, only alkali therapy for hypocitraturia was associated with a significant 26% lower recurrence risk within the 12-36-month timeframe (hazard ratio, 0.74; 95% confidence interval, 0.56 to 0.97; P = 0.03). CONCLUSIONS: When considering all urinary abnormalities together, this study demonstrates that the use of preventive pharmacological therapy is associated with a lower risk of clinically significant recurrent episodes of urinary stone disease in the 12-36 month timeframe after urine collection, although only the association with the use of alkali therapy for hypocitraturia was significant when individual abnormalities were examined.

Identification of Pax protein inhibitors that suppress target gene expression and cancer cell proliferation.

The Pax family of developmental control genes are frequently deregulated in human disease. In the kidney, Pax2 is expressed in developing nephrons but not in adult proximal and distal tubules, whereas polycystic kidney epithelia or renal cell carcinoma continues to express high levels. Pax2 reduction in mice or cell culture can slow proliferation of cystic epithelial cells or renal cancer cells. Thus, inhibition of Pax activity may be a viable, cell-type-specific therapy. We designed an unbiased, cell-based, high-throughput screen that identified triazolo pyrimidine derivatives that attenuate Pax transactivation ability. We show that BG-1 inhibits Pax2-positive cancer cell growth and target gene expression but has little effect on Pax2-negative cells. Chromatin immunoprecipitation suggests that these inhibitors prevent Pax protein interactions with the histone H3K4 methylation complex at Pax target genes in renal cells. Thus, these compounds may provide structural scaffolds for kidney-specific inhibitors with therapeutic potential.

From single nucleotide polymorphism to transcriptional mechanism: a model for FRMD3 in diabetic nephropathy.

Genome-wide association studies have proven to be highly effective at defining relationships between single nucleotide polymorphisms (SNPs) and clinical phenotypes in complex diseases. Establishing a mechanistic link between a noncoding SNP and the clinical outcome is a significant hurdle in translating associations into biological insight. We demonstrate an approach to assess the functional context of a diabetic nephropathy (DN)-associated SNP located in the promoter region of the gene FRMD3. The approach integrates pathway analyses with transcriptional regulatory pattern-based promoter modeling and allows the identification of a transcriptional framework affected by the DN-associated SNP in the FRMD3 promoter. This framework provides a testable hypothesis for mechanisms of genomic variation and transcriptional regulation in the context of DN. Our model proposes a possible transcriptional link through which the polymorphism in the FRMD3 promoter could influence transcriptional regulation within the bone morphogenetic protein (BMP)-signaling pathway. These findings provide the rationale to interrogate the biological link between FRMD3 and the BMP pathway and serve as an example of functional genomics-based hypothesis generation.

Regulation of c-Ret in the developing kidney is responsive to Pax2 gene dosage.

During kidney development, Pax2 and Pax8 are expressed very early in the mammalian nephric duct and both precede the expression of receptor tyrosine kinase, c-Ret. However, in Pax2-/- mutant mice, expression of c-Ret is lost after embryonic day 10.5. As the Ret/Gdnf pathway is necessary for renal development and there is a temporal and spatial relationship of Pax2 and c-Ret expression in the developing genito-urinary system, we postulate that Pax2 is necessary for c-Ret expression in the developing kidney. In vitro, Pax2 protein is capable of physically interacting with a c-RET promoter, and both Pax2 and Pax8 can activate the expression of a reporter gene driven by the c-RET promoter. Compound heterozygous null mice (Pax2+/-: Ret+/-) display an increased incidence of unilateral and bilateral renal agenesis, and smaller kidneys with fewer nephrons. Furthermore, the expression of Gdnf is reduced 2-3-fold, whereas c-Ret expression is reduced 9-47-fold in Pax2 heterozygous embryonic kidneys as detected by real-time quantitative RT (QRT)-PCR. The data demonstrate that Pax2 plays an integral role in the initiation and maintenance of the Ret/Gdnf pathway by not only activating the ligand of the pathway, but by also enhancing the expression of the pathway receptor Ret. The effects of reduced Pax2 gene dosage are thus amplified resulting in a haploinsufficient phenotype.

The cysteine-rich domain protein KCP is a suppressor of transforming growth factor beta/activin signaling in renal epithelia.

The transforming growth factor beta (TGF-beta) superfamily, including the bone morphogenetic protein (BMP) and TGF-beta/activin A subfamilies, is regulated by secreted proteins able to sequester or present ligands to receptors. KCP is a secreted, cysteine-rich (CR) protein with similarity to mouse Chordin and Xenopus laevis Kielin. KCP is an enhancer of BMP signaling in vertebrates and interacts with BMPs and the BMP type I receptor to promote receptor-ligand interactions. Mice homozygous for a KCP null allele are hypersensitive to developing renal interstitial fibrosis, a disease stimulated by TGF-beta but inhibited by BMP7. In this report, the effects of KCP on TGF-beta/activin A signaling are examined. In contrast to the enhancing effect on BMPs, KCP inhibits both activin A- and TGF-beta1-mediated signaling through the Smad2/3 pathway. These inhibitory effects of KCP are mediated in a paracrine manner, suggesting that direct binding of KCP to TGF-beta1 or activin A can block the interactions with prospective receptors. Consistent with this inhibitory effect, primary renal epithelial cells from KCP mutant cells are hypersensitive to TGF-beta and exhibit increased apoptosis, dissociation of cadherin-based cell junctions, and expression of smooth muscle actin. Furthermore, KCP null animals show elevated levels of phosphorylated Smad2 after renal injury. The ability to enhance BMP signaling while suppressing TGF-beta activation indicates a critical role for KCP in modulating the responses between these anti- and profibrotic cytokines in the initiation and progression of renal interstitial fibrosis.

Kielin/chordin-like protein, a novel enhancer of BMP signaling, attenuates renal fibrotic disease.

The bone morphogenetic proteins (BMPs) profoundly affect embryonic development, differentiation and disease. BMP signaling is suppressed by cysteine-rich domain proteins, such as chordin, that sequester ligands from the BMP receptor. We describe a novel protein, KCP, with 18 cysteine-rich domains. Unlike chordin, KCP enhances BMP signaling in a paracrine manner. Smad1-dependent transcription and phosphorylated Smad1 (P-Smad1) levels are increased, as KCP binds to BMP7 and enhances binding to the type I receptor. In vivo, Kcp(-/-) mice are viable and fertile. Because BMPs have a pivotal role in renal disease, we examined the phenotype of Kcp(-/-) mice in two different models of renal injury. Kcp(-/-) animals show reduced levels of P-Smad1, are more susceptible to developing renal interstitial fibrosis, are more sensitive to tubular injury and show substantial pathology after recovery. The data indicate an important role for KCP in attenuating the pathology of renal fibrotic disease.