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

Effects of Tityus stigmurus (Thorell 1876) (Scorpiones: Buthidae) venom in isolated perfused rat kidneys

ABSTRACT Scorpions belonging to the Tityus genus are of medical interest in Brazil. Among them, Tityus stigmurus is the main scorpion responsible for stings in the Northeast region. After a sting, the scorpion venom distributes rapidly to the organs, reaching the kidneys quickly. However, there are few studies concerning the renal pathophysiology of scorpion poisoning. In this study, we evaluated the effects of T. stigmurus venom (TsV) on renal parameters in isolated rat kidneys. Wistar rats (n = 6), weighing 250-300 g, were perfused with Krebs-Henseleit solution containing 6 g/100 mL bovine serum albumin. TsV at 0.3 and 1.0 &#956;g/mL was tested, and the effects on perfusion pressure (PP), renal vascular resistance (RVR), urinary flow (UF), glomerular filtration rate (GFR), and electrolyte excretion were analyzed. Effects were observed only at TsV concentration of 1.0 &#956;g/mL, which increased PP (controlPP40' = 92.7 ± 1.95; TsVPP40' = 182.0 ± 4.70* mmHg, *p < 0.05), RVR (controlRVR40' = 3.28 ± 0.23 mmHg; TstRVR40' = 6.76 ± 0.45* mmHg, *p < 0.05), UF (controlUF50' = 0.16 ± 0.04; TstUF50' = 0.60 ± 0.10* mL/g/min,*p < 0.05), GFR and electrolyte excretion, with histological changes that indicate renal tubular injury. In conclusion, T. stigmurus venom induces a transient increase in PP with tubular injury, both of which lead to an augmented electrolyte excretion

Renal Tubular Dysfunction in Sickle Cell Disease

Background/Aims: Kidney abnormalities are one of the main chronic complications of sickle cell disease (SCD). The aim of this study is to investigate the occurrence of renal tubular abnormalities among patients with SCD. Methods: This is a prospective study with 26 SCD adult patients in Brazil. Urinary acidification and concentration tests were performed using calcium chloride (CaCl2), after a 12h period of water and food deprivation. Fractional excretion of sodium (FENa), transtubular potassium gradient (TTKG) and solute free water reabsorption (TcH2O) were calculated. The SCD group was compared to a group of 15 healthy volunteers (control group). Results: Patient`s average age and gender were similar to controls. Urinary acidification deficit was found in 10 SCD patients (38.4%), who presented urinary pH >5.3 after CaCl2 test. Urinary osmolality was significantly lower in SCD patients (355±60 vs. 818±202mOsm/kg, p=0.0001, after 12h period water deprivation). Urinary concentration deficit was found in all SCD patients (100%). FENa was higher among SCD patients (0.75±0.3 vs. 0.55±0.2%, p=0.02). The TTKG was higher in SCD patients (5.5±2.5 vs. 3.0±1.5, p=0.001), and TcH2O was lower (0.22±0.3 vs. 1.1±0.3L/day, p=0.0001). Conclusions: SCD is associated with important kidney dysfunction. The main abnormalities found were urinary concentrating and incomplete distal acidification defect. There was also an increase in the potassium transport and decrease in water reabsorption, evidencing the occurrence of distal tubular dysfunction

Action of anti-bothropic factor isolated from Didelphis marsupialis on renal effects of Bothrops erythromelas venom

Acute renal failure is the most common complication in the lethal cases caused by snakebites in Brazil. Among the Brazilian venom snakes, Bothrops erythromelas is responsible for the majority of accidents in Northeastern Brazil. Didelphis marsupialis serum could inhibit myonecrotic, hemorrhagic, edematogenic hyperalgesic and lethal effects of envenomation determined by ophidian bites. In the present study, we evaluated the action of the anti-bothropic factor isolated from D. marsupialis on the renal effects promoted by B. erythromelas venom without systemic interference. Isolated kidneys from Wistar rats were perfused with Krebs-Henseleit solution containing 6% bovine serum albumin. We analyzed renal perfusion pressure (PP), renal vascular resistance (RVR), glomerular filtration rate (GFR), urinary flow (UF), and the percentages of sodium and potassium tubular transport (%TNa +, %TK +). The B. erythromelas venom (10 μg mL -1) decreased the PP (ct=108.71±5.09 mmHg; BE=65.21±5.6 mmHg*) and RVR (ct=5.76±0.65 mmHg mL -1 g -1 min -1; BE=3.10±0.45 mmHg mL -1 g -1 min -1*) . On the other hand, the GFR decreased at 60 min (ct 60=0.76±0. 07 mL g -1 min -1; BE 60=0.42±0.12 mL g -1 min -1*) and increased at 120 min (ct 120=0.72±0.01 mL g -1 min -1; BE 120=1.24±0.26 mL g -1 min -1*). The UF increased significantly when compared with the control group (ct=0.14±0.01 mL g -1 min -1; BE=0.47±0.08 mL g -1 min -1*). The venom reduced the %TNa + (ct 90=79.18±0.88%; BE 90=58.35±4.86%*) and %TK + (ct 90=67.20±4.04%; BE 90=57. 32±5.26%*) The anti-bothropic factor from D. marsupialis (10 μg mL -1) incubated with B. erythromelas venom (10 μg mL -1) blocked the effects on PP, RVR, %TNa +, and %TK +, but was not able to reverse the effects in UF and GFR promoted by venom alone. However, the highest concentration of D. marsupialis serum (30 μg mL -1) reversed all the renal effects induced by the venom. In conclusion, B. erythromelas venom altered all the renal functional parameters evaluated and the anti-bothropic factor from D. marsupialis was able to inhibit the effects induced by the venom in isolated kidney. © 2005 Elsevier Ltd. All rights reserved

Larvicidal activity of the water extract of Moringa oleifera seeds against Aedes aegypti and its toxicity upon laboratory animals

In this work, biological effects of the water extract of Moringa oleifera seeds (WEMOS) were assessed on eggs and 3rd instar larvae of Aedes aegypti and on its toxicity upon laboratory animals (Daphnia magna, mice and rats). Crude WEMOS showed a LC50 value of 1260µg/mL, causing 99.2 ± 2.9% larvae mortality within 24 h at 5200µg/mL, though this larvicidal activity has been lost completely at 80ºC/10 min. WEMOS did not demonstrate capacity to prevent egg hatching. After extensive dialyses of the crude WEMOS into watersoluble dialyzable (DF) and nondyalizable (NDF) fractions, only DF maintained its efficacy to kill larvae. Acute toxicity evaluations on daphnids (EC50 of 188.7µg/mL) and mice (LD50 of 446.5 mg/kg body weight) pointed out to low toxicity. Despite the thymus hypertrophy, WEMOS revealed to be harmless in orally and subacutelytreated rats. In conclusion, WEMOS has thermostable bioactive compounds against Ae. aegypti larvae with apparent molecular mass lower than 12 kDa and moderately toxic potential.<br>Neste trabalho, o extrato aquoso das sementes de Moringaoleifera (EASMO) foi avaliado quanto aos seus efeitos biológicos sobre ovos e larvas de Aedes aegypti no 3ºestágio de desenvolvimento e sua toxicidade sobre animais de laboratório(Daphnia magna, camundongos e ratos). O EASMO bruto revelou uma CL50 de 1.260 µg/mL, causando 99, 2 ± 2, 9% de mortalidade em 24 h na concentração de 5.200 µg/mL, embora o mesmo não tenha sido capaz de impedir a eclosão dos ovos. A atividade larvicida extinguiu-se após aquecimento do extrato a 80ºC/10 min. Diálises sucessivas do EASMO bruto resultaram em duas frações solúveis em água (Fração dializável, FD; Fração nãodializável, FND), dentre as quais apenas a FD mostrou ação larvicida. Testes de toxicidade aguda realizadosem dáfnias (CE50 de 188, 7 µg/mL) e camundongos (DL50 de446,5 mg/kg de peso corpóreo) evidenciaram baixa toxicidade. Apesar da hipertrofia tímica, o EASMO mostrou ser atóxicoapós tratamento subagudo via oral em ratos. Conclui-se, portanto, que o EASMO apresenta substâncias com capacida de larvicida contra Ae. aegypti, as quais possuem massa molecular aparente menor que 12 kDa e potencial tóxico moderado