Ramon Róseo Paula Pessoa Bezerra de Menezes

Bothrops leucurus venom induces nephrotoxicity in the isolated perfused kidney and cultured renal tubular epithelia

Bites from snake (Bothrops genus) cause local tissue damage and systemic complications, which include alterations such as hemostatic system and acute renal failure (ARF). Recent studies suggest that ARF pathogenesis in snakebite envenomation is multifactorial and involves hemodynamic disturbances, immunologic reactions and direct nephrotoxicity. The aim of the work was to investigate the effects of the Bothrops leucurus venom (BlV) in the renal perfusion system and in cultured renal tubular cells of the type MDCK (Madin-Darby Canine kidney). BlV (10 μg/mL) reduced the perfusion pressure at 90 and 120 min. The renal vascular resistance (RVR) decreased at 120 min of perfusion. The effect on urinary flow (UF) and glomerular filtration rate (GFR) started 30 min after BlV infusion, was transient and returned to normal at 120 min of perfusion. It was also observed a decrease on percentual tubular transport of sodium (%TNa(+)) at 120 min and of chloride (%TCl(-)) at 60 and 90 min. The treatment with BlV caused decrease in cell viability to the lowest concentration tested with an IC(50) of 1.25 μg/mL. Flow cytometry with annexin V and propidium iodide showed that cell death occurred predominantly by necrosis. However, a cell death process may involve apoptosis in lower concentrations. BlV treatment (1.25 μg/mL) led to significant depolarization of the mitochondrial membrane potential and, indeed, we found an increase in the expression of cell death genes in the lower concentrations tested. The venom also evoked an increase in the cytosolic Ca(2+) in a concentration dependent manner, indicating that Ca(2+) may participate in the venom of B. leucurus effect. The characterization of the effects in the isolated kidney and renal tubular cells gives strong evidences that the acute renal failure induced by this venom is a result of the direct nephrotoxicity which may involve the cell death mechanism.

Syndecan-1 in Acute Decompensated Heart Failure – Association With Renal Function and Mortality –

BACKGROUND Heart failure (HF) is a leading cause of hospitalization throughout the world, and the mortality rate remains elevated. HF is frequently complicated by acute kidney injury (AKI), worsening the patients prognosis. There have been no studies evaluating the role that endothelial glycocalyx damage plays in HF patients and its association with AKI and mortality. METHODS AND RESULTS We measured several endothelial biomarkers in 201 consecutive patients with acute decompensated HF (ADHF) during emergency department (ED) admission. In-hospital mortality, AKI development and 6-month mortality rates were assessed. ADHF patients with worsening renal function had higher levels of syndecan-1 but not those patients with stable chronic kidney disease. Syndecan-1 levels during ED admission were predictive for AKI during the hospital stay (AUC 0.741, P<0.001) and had an even better discriminatory capacity in more severe AKI (AUC 0.812, P<0.001). Additionally, after adjusting for several confounding factors, including biomarkers of endothelial function and endothelial cell activation, syndecan-1 remained associated with in-hospital mortality rates. On a Cox multivariate analysis regression, syndecan-1 was associated with 6-month mortality rates. CONCLUSIONS The concentration of syndecan-1, a marker of glycocalyx damage measured during ED admission, is valuable in assessing the risk of developing AKI and in-hospital mortality. Its association with mortality is strong after 6-month follow-up.

Antiparasitic effect of Dinoponera quadriceps giant ant venom

Neglected tropical diseases (NTD) are treated with toxic therapy of limited efficacy. Previously, we studied the antimicrobial effect of Dinoponera quadriceps venom (DqV) against bacteria. To continue the study, we report in this short communication the antimicrobial effect of DqV against Leishmania amazonensis and Trypanosoma cruzi. DqV inhibits the promastigote forms of L. amazonensis and all T. cruzi developmental forms, with low toxicity in host cells. DqV causes cell death in T. cruzi through necrotic and apoptotic mechanisms observed by staining the cells with annexin V-FITC (AX) and propidium iodide (PI), loss of mitochondrial membrane potential by flow cytometry analyses and confocal microscopy and morphological alterations, such as loss of membrane integrity and cell shrinkage by scanning electron microscopy (SEM). In conclusion, we suggest there is an antimicrobial effect also on parasites.

Nephroprotective effects of (−)-α-bisabolol against ischemic-reperfusion acute kidney injury

BACKGROUND Ischemia/reperfusion (I/R) in kidney is commonly related to acute kidney injury (AKI), essentially through oxidative stress. (-)-α-Bisabolol is a sesquiterpene isolated from the essential oil of a variety of plants, including chamomile, which has important antioxidant activity. STUDY DESIGN This study intends to evaluate the nephroprotective activity of (-)-α-bisabolol (Bis) in both in vivo and in vitro models of kidney I/R. METHODS Male Wistar rats were submitted to right nephrectomy, followed by ischemia by clamping of the renal artery in the left kidney for 60min. and 48h of reperfusion. The animals were treated orally with Bis (100mg/kg) or vehicle for 24h after reperfusion, and placed in metabolic cages, to evaluate water consumption, diuresis, urinary osmolality, classic biochemical markers and urinary KIM-1 (kidney injury molecule-1). Additionally, the left kidney was collected for histological evaluation and determination of glutathione (GSH) and Thiobarbituric Acid Reactive Substances (TBARS) levels. Tubular epithelial cells LLC-MK2 were used to assess Bis effect on in vitro I/R, by MTT assay. It was performed the cellular respiration tests by flow cytometry: evaluation of the production of cytoplasmic reactive oxygen species by DCFH-DA assay and mitochondrial transmembrane potential analysis with the dye rhodamine 123. RESULTS I/R caused alterations in diuresis, water intake, urinary osmolality, plasmatic creatinine, urea and uric acid, creatinine clearance, proteinuria and microalbuminuria. Treatment with Bis ameliorated all of these parameters. Also, KIM-1 level enhanced by I/R was also diminished in groups treated with Bis. The histological examination showed that Bis attenuated the morphological changes caused by I/R, markedly vascular congestion and intratubular deposits of proteinaceous material. Additionally, Bis was able to reduce the changes observed in TBARS and GSH levels in kidney tissue. In in vitro assay, Bis was capable to partially protect the cell lineage against cell damage induced by I/R. CONCLUSION (-)-α-Bisabolol has a nephroprotective effect in kidney I/R, with antioxidant effect. Moreover, this result seems to be associated to a direct protective effect on tubular epithelia.

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.

Evaluation of KIM-1 as an early biomarker of snakebite-induced AKI in mice

ABSTRACT Acute kidney injury (AKI) is one of the most important complications of bothropic poisoning and its early identification remains challenging. The nephrotoxicity of Bothrops insularis venom (BinsV) was previously described by our research group. In this study, we continued to evaluate the effect of BinsV on kidney function in mice and LLC‐MK2 proximal tubule cells, evaluating KIM‐1 protein as an early AKI biomarker. Male Swiss mice were inoculated with BinsV intramuscularly and observed for 24 h in a metabolic cage model. Urine and blood were collected for biochemical analyses and the kidneys were examined for oxide‐reducing balance and submitted to histological analysis. LLC‐MK2 cells incubated with BinsV were assessed for cell viability and cell death mechanism by flow cytometry. Histological analysis of the kidneys indicated AKI and the oxide‐reducing analyses demonstrated a decreasing in reduced glutathione (GSH) levels and an increasing on Malondialdehyde (MDA) levels. BinsV was cytotoxic to LLC‐MK2 and the cytometry analyses suggested necrosis. Within 24 h after the envenomation, urinary creatinine did not increase, but the urinary levels of KIM‐1 increased. In conclusion, we found AKI evidence in the kidney tissue and the increase in the KIM‐1 levels suggest it can be used as an early AKI biomarker. HighlightsBothrops insularis venom (BinsV) is nephrotoxic.BinsV induces Acute Kidney Injury in mice.Discrepancies were observed between plasmatic creatinine and histological findings.Urinary KIM‐1 was increased in mice inoculated with BinsV after 24 h.Urinary KIM‐1 was suggested as specific and early AKI biomarker on envenomation.

Insights into the candidacidal mechanism of Ctn[15–34] – a carboxyl-terminal, crotalicidin-derived peptide related to cathelicidins

Purpose. Ctn[15‐34], a carboxyl‐terminal fragment of crotalicidin (a cathelicidin from the venom gland of a South American rattlesnake), has shown antifungal activity against clinical and standard strains of Candida species. The aim of the present work was to investigate the underlying mechanisms of the candidicidal activity of Ctn[15‐34]. Methodology. The time‐kill profile and drug synergism were evaluated by means of a microdilution assay and multi‐parametric flow cytometry. The presumptive interaction of Ctn[15‐34] with lipid membranes was estimated in vitro with a lipid‐mimic compound, the chromogenic substance 4‐nitro‐3‐(octanoyloxy)benzoic acid (4N3OBA). Results/Key findings. The absorbance increment (at 425 nm) indicated a concentration‐ and time‐dependent in‐solution association between Ctn[15‐34] and 4N3OBA. The interaction of Ctn[15‐34] with Candida cells was confirmed by flow cytometric measurements with the 5(6)‐carboxyfluorescein‐labelled peptide (CF‐Ctn[15‐34]). Analysis of the killing time of Candida exposed to Ctn[15‐34] and amphotericin B (AMB) showed that both the peptide and polyene drug reduce the number of c.f.u. but in mechanistically different ways. The Ctn[15‐34] peptide alone caused yeast cell membrane disruption, which was confirmed by lactate dehydrogenase leakage and biomarkers of cell death mediated by necrosis. Conclusion. Overall, Ctn[15‐34] displays a synergistic antifungal activity with AMB, an effect that can be further developed into a multi‐target therapeutic option with other antimycotics currently in use.

The dinoponeratoxin peptides from the giant ant Dinoponera quadriceps display in vitro antitrypanosomal activity

Abstract The crude venom of the giant ant Dinoponera quadriceps is a cocktail of polypeptides and organic compounds that shows antiparasitic effects against Trypanosoma cruzi, the causative agent of Chagas disease. In order to investigate the venom-derived components responsible for such antitrypanosomal activity, four dinoponeratoxins (DnTxs) were identified, namely M-PONTX-Dq3a, -Dq3b, -Dq3c and -Dq4e, that are diverse in size, net charge, hydrophobicity and propensity to interact with eukaryote cell membranes. These peptides were tested against epimastigote, trypomastigote and amastigote forms of benznidazole (Bz)-resistant Y strain of T. cruzi and in mammalian host cells. The M-PONTX-Dq3a and -Dq4e inhibited all developmental forms of T. cruzi, including amastigotes, the responsible form for the maintenance of infection on chronic phase of the disease. The M-PONTX-Dq3a showed the highest selectivity index (SI) (80) and caused morphological alterations in T. cruzi, as observed by scanning electron microscopy (SEM), and induced cell death through necrosis, as seen by multiparametric flow cytometry analysis with specific biochemical markers. Altogether, the D. quadriceps venom appears as a source for the prospection of trypanocidal peptides and the M-PONTX-Dq3a arises as a candidate among the dinoponeratoxin-related peptides in the development of compounds against Chagas disease.

Involvement of Nitric Oxide on Bothropoides insularis Venom Biological Effects on Murine Macrophages In Vitro

Viperidae venom has several local and systemic effects, such as pain, edema, inflammation, kidney failure and coagulopathy. Additionally, bothropic venom and its isolated components directly interfere on cellular metabolism, causing alterations such as cell death and proliferation. Inflammatory cells are particularly involved in pathological envenomation mechanisms due to their capacity of releasing many mediators, such as nitric oxide (NO). NO has many effects on cell viability and it is associated to the development of inflammation and tissue damage caused by Bothrops and Bothropoides venom. Bothropoides insularis is a snake found only in Queimada Grande Island, which has markedly toxic venom. Thus, the aim of this work was to evaluate the biological effects of Bothropoides insularis venom (BiV) on RAW 264.7 cells and assess NO involvement. The venom was submitted to colorimetric assays to identify the presence of some enzymatic components. We observed that BiV induced H2O2 production and showed proteolytic and phospholipasic activities. RAW 264.7 murine macrophages were incubated with different concentrations of BiV and then cell viability was assessed by MTT reduction assay after 2, 6, 12 and 24 hours of incubation. A time- and concentration-dependent effect was observed, with a tendency to cell proliferation at lower BiV concentrations and cell death at higher concentrations. The cytotoxic effect was confirmed after lactate dehydrogenase (LDH) measurement in the supernatant from the experimental groups. Flow cytometry analyses revealed that necrosis is the main cell death pathway caused by BiV. Also, BiV induced NO release. The inhibition of both proliferative and cytotoxic effects with L-NAME were demonstrated, indicating that NO is important for these effects. Finally, BiV induced an increase in iNOS expression. Altogether, these results demonstrate that B. insularis venom have proliferative and cytotoxic effects on macrophages, with necrosis participation. We also suggest that BiV acts by inducing iNOS expression and causing NO release.

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

ABSTRACT Components from animal venoms may vary according to the snakes 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 &mgr;g/mL for BjSv and 1.18 &mgr;g/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. HighlightsBothrops jararaca venoms from south and southeast Brazil have different renal effects.B. jararaca venom (Bjv) from south is more nephrotoxic than from Bjv from southeast.Bjv from south showed characteristics of renal injury on isolated kidney.Bjv from southeast showed a diuretic effect on isolated kidney.Bjv from south showed a higher necrotic profile than Bjv from southeast in MDCK cells.