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.

Nephrotoxicity induced by the venom of Hypnale hypnale from Sri Lanka: Studies on isolated perfused rat kidney and renal tubular cell lines.

The hump-nosed pit viper Hypnale hypnale is responsible for a high number of snakebite cases in southwestern India and Sri Lanka. Although most patients only develop local signs and symptoms of envenoming, there is a growing body of evidence indicating that these envenomings may be associated with systemic alterations, including acute kidney injury. In this study we evaluated the renal toxicity of H. hypnale venom by using a perfused isolated rat kidney system and by assessing cytotoxicity in two different renal tubular cell lines in culture. The venom caused alterations in several renal functional parameters, such as reduction on perfusion pressure, renal vascular resistance, and sodium and chloride tubular transport, whereas glomerular filtration rate and urinary flow initially decreased and then increased after venom perfusion. In addition, this venom was cytotoxic to proximal and distal renal tubular cells in culture, with predominance of necrosis over apoptosis. Moreover, the venom affected the mitochondrial membrane potential and induced an increment in reactive oxygen species in these cells. Taken together, our results demonstrate a nephrotoxic activity of H. hypnale venom in these experimental models, in agreement with clinical observations.

High Salt Intake Promotes Different Responses to Urodilatin and Uroguanylin in the Isolated Rat Kidney.

Urodilatin (UD) and uroguanylin (UGN) have been implicated in the regulation of salt and water homeostasis, particularly in the balance handling of salt intake. In this sense, the aim of the present work was to study the main effects of these peptides in kidneys from animals subjected to high NaCl (2%) intake, during 10 days in metabolic cages. The control group received only normal water, whereas the treated group drank 2% solution of NaCl (NaCl 2%). In addition, we studied effect of subthreshold UD (0.14 nM) and UGN (0.06 µM) doses in NaCl 2% after a 30-min control period. Kidney perfusion was performed with Krebs-Henseleit containing 6 g% bovine albumin previously dialyzed. The effects of UD (0.14 nM) promoted reduction of PP, RVR, and UF in the NaCl 2% group. We also observed an increase in %TNa+ and %TCl-. The main effects of UGN in NaCl 2% were increase in PP, UF, and GFR, followed by a reduction in %TNa+ and %TCl-. After an increased intake of salt, physiological pathways are activated and regulated in order to eliminate excess sodium. In this study, we observed that in a subthreshold dose, UD does not promotes natriuresis and diuresis, suggesting that UGN is an important hormone in inducing salt excretion in a chronic salt overload. Therefore, the effects herein described may play a contributory role in the regulation of kidney function after ingestion of salty meals.

Differences between renal effects of venom from two Bothrops jararaca populations from southeastern and southern Brazil.

Components from animal venoms may vary according to the snake's age, gender and region of origin. Recently, we performed a proteomic analysis of Bothrops jararaca venom from southern (BjSv) and southeastern (BjSEv) Brazil, showing differences in the venom composition, as well as its biological activity. To continue the study, we report in this short communication the different effects induced by the BjSEv and BjSv on isolated kidney and MDCK renal cells. BjSEv decreased perfusion pressure (PP) and renal vascular resistance (RVR) and increased urinary flow (UF) and glomerular filtration rate (GFR), while BjSv did not alter PP and RVR and reduced UF and GFR. Both types of venom, more expressively BjSEv, reduced %TNa+, %TK+ and %Cl-. In MDCK cells, the two types of venom showed cytotoxicity with IC50 of 1.22 µg/mL for BjSv and 1.18 µg/mL for BjSEv and caused different profiles of cell death, with BjSv being more necrotic. In conclusion, we suggest that BjSv is more nephrotoxic than BjSEv.

Bothrops erythromelas () venom induces apoptosis on renal tubular epithelial cells.

Bothrops erythromelas is responsible for a large number of snakebite incidents in Northeastern Brazil. Previously, we showed the effects of whole B. erythromelas venom in an isolated kidney model. To continue the study with B. erythromelas venom, the present work aims to study the effects of this venom on MDCK tubular epithelial cells and assess gene expression involved in kidney injury, aiming at elucidating the mechanisms responsible for renal toxicity. Cytotoxicity in MDCK cells showed an IC50 of 93 µg/mL and predominant apoptotic involvement demonstrated by flow cytometry assays and expression of caspase-3 and caspase-8. In conclusion, we suggest that Bothropoides erythromelas venom causes apoptosis with involvement of the caspases, probably through the extrinsic pathway.

Study of the safety of methylphenidate: Focus on nephrotoxicity aspects.

AIMS: Methylphenidate (MPD) is increasingly prescribed for the treatment of Attention Deficit Hyperactivity Disorder and there are concerns about its appropriate use. Furthermore, little is known about the potential nephrotoxicity in patients using MPD. This study aimed to investigate the safety of MPD, with focus on the possible effects of this drug on renal function. MAIN METHODS: We investigated the effects of MPD on renal perfusion system and renal tubular cells through in vivo and in vitro experimental models. KEY FINDINGS: In the in vivo experiments, 24 h and 48 h after MPD administration, urea, creatinine, creatinine clearance, and the fractional excretion of sodium and potassium were not changed. In the isolated kidney perfusion, MPD significantly reduced urinary flow, glomerular filtration rate and the percentage of tubular sodium transport. However, the perfusion pressure, renal vascular resistance and the percentage of tubular potassium transport were unchanged in this system. In the canine renal epithelial cell line MDCK culture, MPD was not cytotoxic and, in histopathological analysis, MPD did not promote alterations. SIGNIFICANCE: Our findings suggest a possible nephrotoxic effect of MPD, since it altered renal function by reducing the glomerular activity, urinary flow and sodium transport. These effects need to be further investigated in order to minimize potential harms associated with the use of MPD.

l-amino acid oxidase from Bothrops marajoensis causes nephrotoxicity in isolated perfused kidney and cytotoxicity in MDCK renal cells.

Renal alterations caused by Bothrops venom and its compounds are studied to understand these effects and provide the best treatment. Previously, we studied the renal effect of the whole venom of Bothrops marajoensis and its phospholipase A2 (PLA2), but these effects could not to be attributed to PLA2. To continue the study, we report in this short communication the effects of l-amino acid oxidase from B. marajoensis venom (LAAOBm) on renal function parameter alterations observed in the same model of isolated perfused kidney, as well as the cytotoxic effect on renal cells. LAAOBm caused a decrease in PP, RVR, UF, GFR, %TNa(+) and %TCl(-), very similar to the effects of whole venom using the same model. We also demonstrated its cytotoxicity in MDCK cells with IC50 of 2.5 µg/mL and late apoptotic involvement demonstrated by flow cytometry assays. In conclusion, we suggested that LAAOBm is a nephrotoxic compound of B. marajoensis venom.