Effects of cilostazol, a Phosphodiesterase-3 inhibitor, on kidney function and redox imbalance in acute kidney injury caused by Bothrops alternatus venom.

The mechanisms of pathogenesis of acute kidney injury (AKI) in snakebites is multifactorial and involves hemodynamic disturbances, with release of free radical causing cytotoxic effects. The phosphodiesterase-3 (PDE3) inhibitor, Cilostazol, has been reported to provide protection against renal oxidative stress. OBJECTIVE: We evaluated the protective effects of cilostazol against Bothrops alternatus snake venom (BaV)-induced nephrotoxicity. METHODS: Wistar rat kidneys (n = 6, 260-300 g) were isolated and perfused with Krebs-Henseleit solution containing 6 g/100 mL of bovine serum albumin. After 30 min, the kidneys were perfused with BaV to a final concentration of 1 and 3 µg/mL, and subsequently evaluated for perfusion pressure (PP), renal vascular resistance (RVR), urinary flow (UF), glomerular filtration rate (GFR), and percentage of electrolyte tubular sodium and chloride transport (%TNa+, %TCl-). Oxidative stress and renal histological analyses were performed. RESULTS: BaV caused a reduction in all the evaluated renal parameters (PP, RVR, GFR, UF, %TNa+, and %TCl-). Although only the effects on PP and UF were reversed with cilostazol treatment, the decrease in the malondialdehyde levels, without changes in glutathione levels, further reduced the venom-induced renal tissue changes. CONCLUSION: Our data suggest that PDE3 is involved in BaV-induced nephrotoxicity, as cilostazol administration significantly ameliorated these effects.

Pain modulated by Bothrops snake venoms: Mechanisms of nociceptive signaling and therapeutic perspectives.

Snake venoms are substances mostly composed by proteins and peptides with high biological activity. Local and systemic effects culminate in clinical manifestations induced by these substances. Pain is the most uncomfortable condition, but it has not been well investigated. This review discusses Bothrops snakebite-induced nociception, highlighting molecules involved in the mediation of this process and perspectives in treatment of pain induced by Bothrops snake venoms (B. alternatus, B. asper, B. atrox, B. insularis, B. jararaca, B. pirajai, B. jararacussu, B. lanceolatus, B. leucurus, B. mattogrossensis, B. moojeni). We highlight, the understanding of the nociceptive signaling, especially in snakebite, enables more efficient treatment approaches. Finally, future perspectives for pain treatment concerning snakebite patients are discussed.

Phosphodiesterase-5 inhibitor sildenafil attenuates kidney injury induced by Bothrops alternatus snake venom.

Acute kidney injury pathogenesis in envenoming by snakes is multifactorial and involves immunologic reactions, hemodynamic disturbances, and direct nephrotoxicity. Sildenafil (SFC), a phosphodiesterase 5 inhibitor, has been reported to protect against pathological kidney changes. OBJECTIVE: This study aimed to investigate the protective effect of sildenafil against Bothrops alternatus snake venom (BaV)-induced nephrotoxicity. METHODS: Kidneys from Wistar rats (n = 6, weighing 260-300 g) were isolated and divided into four groups: (1) perfused with a modified Krebs-Henseleit solution (MKHS) containing 6 g% of bovine serum albumin; (2) administered 3 µg/mL SFC; (3) perfused with 3 µg/mL BaV; and (4) administered SFC + BaV, both at 3 µg/mL. Subsequently, the perfusion pressure (PP), renal vascular resistance (RVR), urinary flow (UF), glomerular filtration rate (GFR), and percentage of electrolyte tubular sodium and chloride transport (%TNa+, %TCl-, respectively) were evaluated. The cyclic guanosine monophosphate (cGMP) levels were analyzed in the perfusate, and the kidneys were removed to perform oxidative stress and histopathological analyses. RESULTS: All renal parameters evaluated were reduced with BaV. In the SFC + BaV group, SFC restored PP to normal values and promoted a significant increase in %TNa+ and %TCl-. cGMP levels were increased in the SFC + BaV group. The oxidative stress biomarkers, malondialdehyde (MDA) and glutathione (GSH), were reduced by BaV. In the SFC + BaV group, a decrease in MDA without an increase in GSH was observed. These findings were confirmed by histological analysis, which showed improvement mainly in tubulis. CONCLUSION: Our data suggest the involvement of phosphodiesterase-5 and cGMP in BaV-induced nephrotoxicity since its effects were attenuated by the administration of SFC.

Bothrops pauloensis snake venom-derived Asp-49 and Lys-49 phospholipases A2 mediates acute kidney injury by oxidative stress and release of inflammatory cytokines.

The envenomation caused by the Bothrops pauloensis snake leads to severe local and systemic effects including acute kidney injury. In this study, we investigated the renal effects by phospholipases A2 (PLA2s), divided into two main subgroups, Asp-49 and Lys-49, isolated from the Bothrops pauloensis snake venom (BpV) in isolated rat kidney system. Both PLA2s (3 µg/mL), added alone to the perfusion system and analyzed for 120 min, had significant effects on isolated rat kidney. Asp-49 reduced Glomerular Filtration Rate (GFR) at 60, 90 and 120 min, and the percentage of total tubular sodium transport (%TNa+) and potassium transport (%TK+) at 120 min. Lys-49 increased Perfusion Pressure (PP) at 120 min and reduced GFR, %TNa+ and the percentage of total tubular chloride transport (%TCl-) at 60, 90 and 120 min. Cytokine release in the kidney tissues were increased with Asp-49 PLA2 (IL-10) and Lys-49 PLA2 (TNF-α, IL-1ß, IL-10). Both increased MPO activity. Asp-49 PLA2 decreased Glutathione (GSH) and increased nitrite levels, while Lys-49 PLA2 increased Malondialdehyde (MDA), GSH and nitrite levels. Histological analysis of the perfused kidneys revealed the presence of glomerular degeneration and atrophy, deposit of proteinaceous material in Bowman's space and intratubular with both PLA2s. These findings indicated that both PLA2s modified the functional parameters in an isolated perfused kidney model with increased oxidative stress and cytokine release. PLA2s are one of the components at high concentration in BpV and our results provide important knowledge about their involvement with the nephrotoxic mechanism.

Renal effects of venoms of Mexican coral snakes Micrurus browni and Micrurus laticollaris.

The Micrurus snake venoms mainly cause systemic complications, essentially neurotoxicity. Previous studies, however, have described that they are involved in the occurrence of acute kidney injury (AKI) in animal models. AKI pathogenesis in snakebites is multifactorial and involves immunological reactions, hemodynamic disturbances, and direct nephrotoxicity. The aim of this study was to compare the nephrotoxic effects of coral snake venoms from M. browni (MbV) and M. laticollaris (MlV) on the proximal tubular epithelial cell line (LLC-MK2) and isolated perfused kidney. Using an MTT assay, both venoms significantly reduced cell viability at higher concentrations (25-100 µg/mL). MlV (10 µg/mL) increased the perfusion pressure (PP) at 60, 90 and 120 min, while the MbV did it only at 90 and 120 min. Renal vascular resistance (RVR) decreased at 60 min and increased at 120 min with MbV, but decreased at 60, 90 and 120 min with MlV. Urinary flow (UF) alterations were not observed with MlV, but MbV elevated them at 90 and 120 min. Both venoms significantly decreased the glomerular filtration rate (GFR), %TNa+, %TK+ and %TCl- levels as of 60 min of perfusion. Oxidative stress analysis revealed that both venoms behaved similarly, reducing glutathione and increasing malondialdehyde levels. Kidney injury is not usually described in clinical cases of Micrurus snakebites. However, the potential for nephrotoxicity should be considered in the overall picture of envenomation.

Toxicidade oral aguda e avaliação dos efeitos pressóricos e renais causados pela oncocalyxona A / Acute oral toxicity and assessment of blood pressure and kidney effects caused by oncocalyxone A

Neste estudo propõe-se avaliar os efeitos toxicológicos, pressóricos e renais da onco-A em modelos animais in vivo e ex vivo. A Oncocalyxona A (onco-A) isolada de Auxemma oncocalyx foi estudada nas doses 1, 3, e 10 µg/mL. Utilizou-se camundongos Swiss fêmeas (20-25g) para o teste de toxicidade oral aguda. Os dados foram comparados por teste t de Student, Two-Way ANOVA e pós-teste de Bonferroni (p<0,05). Foi estimado uma DL50 ˃ 2000 mg/kg, os tecidos pulmonar, renal e cardíaco demonstraram alterações histológicas. Sobre os níveis pressóricos de ratos, a onco-A ocasionou redução significativa da pressão arterial média, alterou os níveis de creatinina e, observou-se alterações histológicas nos tecidos cardíaco e renal. Em perfusão de rim isolado a onco-A causou aumento na pressão de perfusão, fluxo urinário e resistência vascular renal. O ritmo de filtração glomerular encontrou-se reduzido nas concentrações de 1 µg/mL e 10 µg/mL e aumentado para a dose de 3 µg/mL. As fotomicrografias do tecido renal após a perfusão demonstraram alterações histológicas significativas induzidas pela onco-A. Pode-se inferir que, embora a onco-A tenha apresentado baixa letalidade em todos os protocolos experimentais realizados, mostrou evidências de toxicidade pulmonar, renal e cardíaca.