Isolation, homology modeling and renal effects of a C-type natriuretic peptide from the venom of the Brazilian yellow scorpion (Tityus serrulatus)

Mammalian natriuretic peptides (NPs) have been extensively investigated for use as therapeutic agents in the treatment of cardiovascular diseases. Here, we describe the isolation, sequencing and tridimensional homology modeling of the first C-type natriuretic peptide isolated from scorpion venom. In addition, its effects on the renal function of rats and on the mRNA expression of natriuretic peptide receptors in the kidneys are delineated. Fractionation of Tityusserrulatus venom using chromatographic techniques yielded a peptide with a molecular mass of 2190.64Da, which exhibited the pattern of disulfide bridges that is characteristic of a C-type NP (TsNP, T. serrulatus Natriuretic Peptide). In the isolated perfused rat kidney assay, treatment with two concentrations of TsNP (0.03 and 0.1μg/mL) increased the perfusion pressure, glomerular filtration rate and urinary flow. After 60min of treatment at both concentrations, the percentages of sodium, potassium and chloride transport were decreased, and the urinary cGMP concentration was elevated. Natriuretic peptide receptor-A (NPR-A) mRNA expression was down regulated in the kidneys treated with both concentrations of TsNP, whereas NPR-B, NPR-C and CG-C mRNAs were up regulated at the 0.1μg/mL concentration. In conclusion, this work describes the isolation and modeling of the first natriuretic peptide isolated from scorpion venom. In addition, examinations of the renal actions of TsNP indicate that its effects may be related to the activation of NPR-B, NPR-C and GC-C. © 2013 Elsevier Ltd.

Role of cholinergic and adrenergic pathways of the medial septal area in the control of water intake and renal excretion in rats

In this study, we investigated an interaction between noradrenergic and cholinergic pathways of the medial septal area (MSA) on the control of water intake and urinary electrolyte excretion by means of injection of their respective agonists. Noradrenaline (a nonspecific α-adrenergic agonist) and clonidine (an α2-adrenergic agonist), but not phenylephrine (an α1-adrenergic agonist), induced natriuresis and kaliuresis. α-Adrenergic activation had no effect on the natriuresis and kaliuresis induced by carbachol (a cholinergic agonist) and it inhibited the antinatriuresis and antikaliuresis induced by isoproterenol (a ß-adrenergic agonist). Interactions related to volume excretion are complex. α-Adrenergic activation induced a mild diuresis and inhibited the antidiuresis induced by isoproterenol, but phenylephrine combined with carbachol induced antidiuresis. The water intake induced by carbachol was inhibited by clonidine and noradrenaline, but not phenylephrine. These results show an asymmetry in the interaction between α-adrenergic and cholinergic receptors concerning water intake and electrolyte excretion. © 1992.

Role of α1-, and α2- and β-adrenoceptors of the median preoptic area on the water intake, renal excretion, and arterial pressure induced by ANG II

The present experiments were conducted to investigate the role of the α1-, α2- and β-adrenergic receptors of the median preoptic area (MnPO) on the water intake and urinary electrolyte excretion, elicited by central injections of angiotensin II (ANG II). Prazosin (an α1-adrenergic receptor antagonist) and yohimbine (an α2-adrenergic receptor antagonist) antagonized the water ingestion, Na +, K +, and urine excretion induced by ANG II. Administration of propranolol, a β-adrenergic receptor antagonist increased the Na +, K +, and urine excretion induced by ANG II. Previous treatment with prazosin and yohimbine reduced the pressor responses to ANG II. These results suggest that the adrenergic neurotransmission in the MnPO may actively participate in ANG II-induced dipsogenesis, natriuresis, kaliuresis, diuresis and pressor responses in a process that involves α1-, α2-, and β-adrenoceptors.

Low bone mineral density, renal dysfunction, and fracture risk in HIV infection: a cross-sectional study

BACKGROUND: Reduced bone mineral density (BMD) is common in adults infected with human immunodeficiency virus (HIV). The role of proximal renal tubular dysfunction (PRTD) and alterations in bone metabolism in HIV-related low BMD are incompletely understood. METHODS: We quantified BMD (dual-energy x-ray absorptiometry), blood and urinary markers of bone metabolism and renal function, and risk factors for low BMD (hip or spine T score, -1 or less) in an ambulatory care setting. We determined factors associated with low BMD and calculated 10-year fracture risks using the World Health Organization FRAX equation. RESULTS: We studied 153 adults (98% men; median age, 48 years; median body mass index, 24.5; 67 [44%] were receiving tenofovir, 81 [53%] were receiving a boosted protease inhibitor [PI]). Sixty-five participants (42%) had low BMD, and 11 (7%) had PRTD. PI therapy was associated with low BMD in multivariable analysis (odds ratio, 2.69; 95% confidence interval, 1.09-6.63). Tenofovir use was associated with increased osteoblast and osteoclast activity (P< or = .002). The mean estimated 10-year risks were 1.2% for hip fracture and 5.4% for any major osteoporotic fracture. CONCLUSIONS: In this mostly male population, low BMD was significantly associated with PI therapy. Tenofovir recipients showed evidence of increased bone turnover. Measurement of BMD and estimation of fracture risk may be warranted in treated HIV-infected adults.

Effects of chronic renal disease on the transport of vitamin A in plasma and urine of dogs

OBJECTIVE To determine plasma and urine concentrations of retinol, retinyl esters, retinol-binding protein (RBP), and Tamm-Horsfall protein (THP) in dogs with chronic renal disease (CRD). ANIMALS 17 dogs with naturally developing CRD and 21 healthy control dogs. PROCEDURE A diagnosis of CRD was established on the basis of clinical signs, plasma concentrations of creatinine and urea, and results of urinalysis. Concentrations of retinol and retinyl esters were measured by use of reverse-phase high-performance liquid chromatography. Concentrations of RBP and THP were measured by use of sensitive ELISA systems. RESULTS Dogs with CRD had higher plasma concentrations of retinol, which were not paralleled by differences in plasma concentrations of RBP. Calculated ratio of urinary total vitamin A (sum of concentrations of retinol and retinyl esters to creatinine concentration) and ratio of the concentration of urinary retinyl esters to creatinine concentration did not differ between groups. However, we detected a significantly higher retinol-to-creatinine ratio in the urine of dogs with CRD, which was paralleled by a higher urinary RBP-to-creatinine ratio. Thus, in dogs with CRD, the estimated fractional clearance of total vitamin A, retinol, and RBP was increased. Furthermore, dogs with CRD had a reduced urinary THP-to-creatinine ratio. CONCLUSIONS AND CLINICAL RELEVANCE Results of this study documented that CRD affects the concentrations of retinol in plasma and urine of dogs. Analysis of the data indicates that measurement of urinary RBP and urinary THP concentrations provides valuable information that can be helpful in follow-up monitoring of dogs with CRD.

Associations of Urinary Uromodulin with Clinical Characteristics and Markers of Tubular Function in the General Population

BACKGROUND AND OBJECTIVES Allelic variants in UMOD, the gene coding for uromodulin, are associated with rare tubulointerstitial kidney disorders and risk of CKD and hypertension in the general population. The factors associated with uromodulin excretion in the normal population remain largely unknown, and were therefore explored in this study. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Urinary uromodulin excretion was measured using a validated ELISA in two population-based cohorts that included more than 6500 individuals. The Swiss Kidney Project on Genes in Hypertension study (SKIPOGH) included 817 adults (mean age±SD, 45±17 years) who underwent renal ultrasonography and performed a 24-hour urine collection. The Cohorte Lausannoise study included 5706 adults (mean age, 53±11 years) with fresh spot morning urine samples. We calculated eGFRs using the CKD-Epidemiology Collaboration formula and by 24-hour creatinine clearance. RESULTS In both studies, positive associations were found between uromodulin and urinary sodium, chloride, and potassium excretion and osmolality. In SKIPOGH, 24-hour uromodulin excretion (median, 41 [interquartile range, 29-57] mg/24 h) was positively associated with kidney length and volume and with creatinine excretion and urine volume. It was negatively associated with age and diabetes. Both spot uromodulin concentration and 24-hour uromodulin excretion were linearly and positively associated (multivariate analyses) with eGFR<90 ml/min per 1.73 m(2). CONCLUSION Age, creatinine excretion, diabetes, and urinary volume are independent clinical correlates of urinary uromodulin excretion. The associations of uromodulin excretion with markers of tubular functions and kidney dimensions suggest that it may reflect tubule activity in the general population.

Fibroblast growth factor 23 and markers of mineral metabolism in individuals with preserved renal function

Fibroblast growth factor 23 (FGF23) is a bone-derived hormone that regulates phosphate homeostasis. Circulating FGF23 is elevated in chronic kidney disease (CKD) and independently associated with poor renal and cardiovascular outcomes and mortality. Because the study of FGF23 in individuals with normal renal function has received little attention, we examined in a large, population based study of 1128 participants the associations of FGF23 with markers of mineral metabolism and renal function. The median estimated glomerular filtration rate (eGFR) of the cohort was 105 ml/min per 1.73 m2, and the median plasma FGF23 was 78.5 RU/ml. FGF23 increased and plasma 1,25-dihydroxyvitamin D3 decreased significantly below an eGFR threshold of 102 and 99 ml/min per 1.73 m2, respectively. In contrast, plasma parathyroid hormone increased continuously with decreasing eGFR and was first significantly elevated at an eGFR of 126 ml/min per 1.73 m2. On multivariable analysis adjusting for sex, age, body mass index, and GFR, FGF23 was negatively associated with 1,25-dihydroxyvitamin D3, and urinary absolute and fractional calcium excretion but not with serum calcium or parathyroid hormone. We found a positive association of FGF23 with plasma phosphate, but no association with urinary absolute or fractional phosphate excretion and, unexpectedly, a positive association with tubular maximum phosphate reabsorption/GFR. Thus, in the absence of CKD, parathyroid hormone increases earlier than FGF23 when the eGFR decreases. The increase in FGF23 occurs at a higher eGFR threshold than previously reported and is closely associated with a decrease in 1,25-dihydroxyvitamin D3. We speculate that the main demonstrable effect of FGF23 in the setting of preserved renal function is suppression of 1,25-dihydroxyvitamin D3 rather than stimulation of renal phosphate excretion.

Renal function and cardiovascular risk markers in a remote Australian Aboriginal community

Background. Australian Aborigines living in remote areas have exceedingly high rates of renal failure together with increased cardiovascular morbidity and mortality. To examine the basis of this association, we studied markers of renal function and cardiovascular (CV) risk in a coastal Aboriginal community in a remote area of the Northern Territory of Australia. End-stage renal disease (ESRD) incidence rates in that community are 15 times the national non-Aboriginal rate and CV mortality rates in the region are increased 5-fold. Methods. A cross-sectional community survey was conducted. Markers of early renal disease examined included urine albumin/creatinine ratio (ACR), serum creatinine concentration and calculated glomerular filtration rate (GFR). CV risk markers included blood pressure as well as measures of glycaemia, diabetes and serum lipids. Results. The study group included 237 people, 58% of the adult population of the community. The crude prevalence of microalbuminuria (urine ACR: 3.4-33.9 g/mol, 30-299 mg/g) was 31% and of overt albuminuria (urine ACR: greater than or equal to34 g/mol, greater than or equal to300 mg/g), 13%. The prevalence of overt albuminuria increased with age, but the prevalence of microalbuminuria was greatest in the 45-54 year age group. Microalbuminuria was associated with increasing body mass index, whereas overt albuminuria was associated with increasing glycated haemoglobin (HbA1c) and systolic blood pressure and a history of diabetes. The prevalence of elevated serum creatinine concentration (greater than or equal to120 mumol/l) was 10%. GFR (calculated using the MDRD equation) was <60 ml/min/1.73m(2) in 12% and 60-79 ml/min/1.73 m(2) in a further 36% of the study population. Although many people with albuminuria had well preserved GFRs, mean GFR was lower in people with higher levels of albuminuria. Conclusions. The high prevalence of markers of renal disease in this community was consistent with their high rates of ESRD. The distribution of microalbuminuria suggested a 'cohort effect', representing a group who will progress to overt albuminuria. The powerful association of renal disease markers with CV risk factors confirms a strong link between renal and CV disease in the early, asymptomatic stages of each. Thus, pathologic albuminuria, in part, might be a manifestation of the metabolic/haemodynamic syndrome and both conditions might arise out of a common menu of risk factors. Hence, a single agenda of primary and secondary intervention may benefit both.

Evidence for Concurrent Effects of Exposure to Environmental Cadmium and Lead on Hepatic CYP2A6 Phenotype and Renal Function Biomarkers in Non Smokers

We examined the interrelationships between phenotype of hepatic cytochrome P450 2A6 (CYP2A6), nephropathy, and exposure to cadmium and lead in a group of 118 healthy Thai men and women who had never smoked. Their urinary Cd excretion ranged from 0.05 to 2.36 mug/g creatinine, whereas their urinary Pb excretion ranged from 0.1 to 12 mug/g creatinine. Average age and Cd burden of women and men did not differ. Women, however, on average showed a 46% higher urinary Pb excretion (p < 0.001) and lower zinc status, suggested by lower average serum Zn and urinary Zn excretion compared with those in men. Cd-linked nephropathy was detected in both men and women. However, Pb-linked nephropathy was seen only in women, possibly because of higher Pb burden coupled with lower protective factors, notably of Zn (P < 0.001), in women compared with men. In men, Pb burden showed a negative association with CYP2A6 activity (adjusted beta = -0.29, p = 0.003), whereas Cd burden showed a positive association with CYP2A6 activity (adjusted beta = 0.38, p = 0.001), suggesting opposing effects of Cd and Pb on hepatic CYP2A6 phenotype. The weaker correlation between Cd burden CYP2A6 activity in women despite similarity in Cd burden between men and women is consistent with opposing effects of Pb and Cd on hepatic CYP2A6 phenotypic expression. A positive correlation between Cd-linked nephropathy (urinary N-acetyl-beta-D-glucosaminidase excretion) and CYP2A6 activity in men (r = 0.39, p = 0.002) and women (r = 0.37, p = 0.001) suggests that Cd induction of hepatic CYP2A6 expression and Cd-linked nephropathy occurred simultaneously.

Baseline serum lipids and renal function in chronic kidney disease patients entering the LORD trial

Objective: Previous studies investigating associations between serum lipids and renal disease have generally not taken into account dietary intake or physical activity - both known to influence circulating lipids. Furthermore, inclusion of patients on HMG-CoA reductase inhibitors may also have influenced findings due to the pleiotropic effect of this medication. Therefore, the aim of this study is to determine the relationships between serum lipids and renal function in a group of patients not taking lipid-lowering medication and taking into account dietary intake and physical activity. Methods: Data from 100 patients enrolled in the Lipid Lowering and Onset of Renal Disease (LORD) trial were used in this study. Patients were included with serum creatinine > 120 mu mol/l, and excluded if they were taking lipid-lowering medication. Unadjusted and adjusted relationships were determined between fasting serum lipid concentrations (total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides and total cholesterol/HDL ratio) and measures of renal function (estimated glomerular filtration rate (eGFR), creatinine clearance and serum creatinine) and urinary protein excretion. Results: Significant (p < 0.05) negative unadjusted relationships were found between lipids (total cholesterol, LDL and HDL cholesterol) and serum creatinine. In support of these findings, logarithmically-transformed lipids (total cholesterol, LDL and HDL cholesterol) were significantly associated with eGFR and creatinine clearance although the effects were of a smaller magnitude. Adjustment for dietary saturated fat intake and physical activity did not substantially change these effects. Conclusion: These data do not support the premise that lipids are associated with renal dysfunction in patients with normocholesterolemia.

Defining a 3-dimensional (3D) in vitro model to study immune cell and renal cell interactions

This study aimed to develop a 3-Dimensional (D) hydrogel system for the co-culture of autologous human renal and immune cells. Previous studies have shown that human renal epithelial cells are able to modulate autologous immune cell responses. However, these studies were undertaken in a standard 2D culture system. The 3D model was developed to re-capitulate these observations within a more physiological relevant in vivo like environment.

Structure and activity cyclase activated of OK-GC: A kidney receptor-guanylate cyclase activated by guanylin peptides

Uroguanylin, guanylin, and lymphoguanylin are small peptides that activate renal and intestinal receptor guanylate cyclases (GC). They are structurally similar to bacterial heat-stable enterotoxins (ST) that cause secretory diarrhea. Uroguanylin, guanylin, and ST elicit natriuresis, kaliuresis, and diuresis by direct actions on kidney GC receptors. A 3,762-bp cDNA characterizing a uroguanylin/guanylin/ST receptor was isolated from opossum kidney (OK) cell RNA/cDNA. This kidney cDNA (OK-GC) encodes a mature protein containing 1,049 residues sharing 72.4�75.8% identity with rat, human, and porcine forms of intestinal GC-C receptors. COS or HEK-293 cells expressing OK-GC receptor protein were activated by uroguanylin, guanylin, or ST13 peptides. The 3.8-kb OK-GC mRNA transcript is most abundant in the kidney cortex and intestinal mucosa, with lower mRNA levels observed in urinary bladder, adrenal gland, and myocardium and with no detectable transcripts in skin or stomach mucosa. We propose that OK-GC receptor GC participates in a renal mechanism of action for uroguanylin and/or guanylin in the physiological regulation of urinary sodium, potassium, and water excretion. This renal tubular receptor GC may be a target for circulating uroguanylin in an endocrine link between the intestine and kidney and/or participate in an intrarenal paracrine mechanism for regulation of kidney function via the intracellular second messenger, cGMP.

Structure and activity of OK-GC: a kidney receptor guanylate cyclase activated by guanylin peptides

Uroguanylin, guanylin, and lymphoguanylin are small peptides that activate renal and intestinal receptor guanylate cyclases (GC). They are structurally similar to bacterial heat-stable enterotoxins (ST) that cause secretory diarrhea. Uroguanylin, guanylin, and ST elicit natriuresis, kaliuresis, and diuresis by direct actions on kidney GC receptors. A 3,762-bp cDNA characterizing a uroguanylin/guanylin/ST receptor was isolated from opossum kidney (OK) cell RNA/cDNA. This kidney cDNA (OK-GC) encodes a mature protein containing 1,049 residues sharing 72.4-75.8% identity with rat, human, and porcine forms of intestinal GC-C receptors. COS or HEK-293 cells expressing OK-GC receptor protein were activated by uroguanylin, guanylin, or ST13 peptides. The 3.8-kb OK-GC mRNA transcript is most abundant in the kidney cortex and intestinal mucosa, with lower mRNA levels observed in urinary bladder, adrenal gland, and myocardium and with no detectable transcripts in skin or stomach mucosa. We propose that OK-GC receptor GC participates in a renal mechanism of action for uroguanylin and/or guanylin in the physiological regulation of urinary sodium, potassium, and water excretion. This renal tubular receptor GC may be a target for circulating uroguanylin in an endocrine link between the intestine and kidney and/or participate in an intrarenal paracrine mechanism for regulation of kidney function via the intracellular second messenger, cGMP.

Inibidores do co-transportador renal de sódio-glicose 2

Projeto de Pós-Graduação/Dissertação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Ciências Farmacêuticas

Targeting death receptors in bladder, prostate and renal cancer

PURPOSE: We describe key components of normal and aberrant death receptor pathways, the association of these abnormalities with tumorigenesis in bladder, prostate and renal cancer, and their potential application in novel therapeutic strategies targeted toward patients with cancer.

MATERIALS AND METHODS: A MEDLINE literature search of the key words death receptors, TRAIL (tumor necrosis factor related apoptosis inducing ligand), FAS, bladder, prostate, renal and cancer was done to obtain information for review. A brief overview of the TRAIL and FAS death receptor pathways, and their relationship to apoptosis is described. Mechanisms that lead to nonfunction of these pathways and how they may contribute to tumorigenesis are linked. Current efforts to target death receptor pathways as a therapeutic strategy are highlighted.

RESULTS: Activation of tumor cell expressing death receptors by cytotoxic immune cells is the main mechanism by which the immune system eliminates malignant cells. Death receptor triggering induces a caspase cascade, leading to tumor cell apoptosis. Receptor gene mutation or hypermethylation, decoy receptor or splice variant over expression, and downstream inhibitor interference are examples of the ways that normal pathway functioning is lost in cancers of the bladder and prostate. Targeting death receptors directly through synthetic ligand administration and blocking downstream inhibitor molecules with siRNA or antisense oligonucleotides represent novel therapeutic strategies under development.

CONCLUSIONS: Research into the death receptor pathways has demonstrated the key role that pathway aberrations have in the initiation and progression of malignancies of the bladder, prostate and kidney. This new understanding has resulted in exciting approaches to restore the functionality of these pathways as a novel therapeutic strategy.