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BackgroundThe neglected human diseases caused by trypanosomatids are currently treated with toxic therapy with limited efficacy. In search for novel anti-trypanosomatid agents, we showed previously that the Crotalus viridis viridis (Cvv) snake venom was active against infective forms of Trypanosoma cruzi. Here, we describe the purification of crovirin, a cysteine-rich secretory protein (CRISP) from Cvv venom with promising activity against trypanosomes and Leishmania.Methodology/Principal FindingsCrude venom extract was loaded onto a reverse phase analytical (C8) column using a high performance liquid chromatographer. A linear gradient of water/acetonitrile with 0.1% trifluoroacetic acid was used. The peak containing the isolated protein (confirmed by SDS-PAGE and mass spectrometry) was collected and its protein content was measured. T. cruzi trypomastigotes and amastigotes, L. amazonensis promastigotes and amastigotes and T. brucei rhodesiense procyclic and bloodstream trypomastigotes were challenged with crovirin, whose toxicity was tested against LLC-MK2 cells, peritoneal macrophages and isolated murine extensor digitorum longus muscle. We purified a single protein from Cvv venom corresponding, according to Nano-LC MS/MS sequencing, to a CRISP of 24,893.64 Da, henceforth referred to as crovirin. Human infective trypanosomatid forms, including intracellular amastigotes, were sensitive to crovirin, with low IC50 or LD50 values (1.10–2.38 µg/ml). A considerably higher concentration (20 µg/ml) of crovirin was required to elicit only limited toxicity on mammalian cells.ConclusionsThis is the first report of CRISP anti-protozoal activity, and suggests that other members of this family might have potential as drugs or drug leads for the development of novel agents against trypanosomatid-borne neglected diseases.

Altogether, our results give support for the popular use of HA extracts in cases of accidents with snakes, suggesting that it can be used as an adjunct in the management of venomous snakebites.

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In the present work we investigated the toxic activities of two Bothrops snake venoms using in vivo and in vitro experimental protocols in mice and tested the protective effect of dexamethasone (DEXA) in different conditions, comparing it with the polyvalent antivenom. We also expanded the investigations on the antiophidic effect of the Eclipta prostrata (EP) crude extract. The administration of Bothrops jararaca and Bothrops jararacussu snake venoms induced muscle damage demonstrated in vivo by the elevation on plasma creatine kinase (CK) activity in mice and by the decrease in CK content in the extensor digitorum longus (EDL) muscle of these animals, and in vitro by the increase in the rate of CK release from the isolated EDL muscle. We also observed inflammatory response following perimuscular injection of B. jararacussu venom (1.0 mg/kg). Treatment with DEXA (1.0 mg/kg) preserved over 50% of the EDL muscle CK content in vivo when evaluated 24 and 72 h after the injection of B. jararacussu venom in mice, and likewise reduced about 20% of the edema induced by this venom. DEXA reduced in 50% the presence of inflammatory cells and their activity in EDL muscle. The EP extract (50 mg/kg) showed similar ability in preventing the induction of edema and the decrease in muscle CK content, and its association with DEXA showed additive effect. EP reduced over 77% of the plasma CK activity induced by the B. jararacussu venom. In the in vitro experiments, DEXA was not able to change the rate of CK release from EDL muscles exposed to 25 μg/mL of B. jararacussu venom, neither to prevent the fall in the amplitude of the indirectly evoked twitch at the phrenic-diaphragm preparation. EP extract showed otherwise a protective effect on these protocols, reaching up to 100% of protection when concentrations of 50.0 and 100.0 μg/mL were used. Altogether our results show that inflammation is at least in part responsible for the tissue damage induced by Bothrops snake venoms, once the steroidal anti-inflammatory drug dexamethasone was able to decrease the myotoxic effects of these venoms, by reducing the inflammatory response to the venom injection.

We investigated a synthetic coumestan named LQB93 and similar compounds abilities to antagonize activities of Bothrops jararacussu and Bothrops jararaca crude venoms in different protocols. The antimyotoxic activity was evaluated in vitro by the rate of release of creatine kinase (CK) from isolated mouse extensor digitorum longus muscle (EDL) induced by B. jararacussu (25 g/ml). For in vivo studies, B. jararacussu venom (1.0 mg/kg) was preincubated with LQB93 (0.1-30 mg/kg), during 30 min, for later injection in mouse tight and evaluation of the antimyotoxic and anti-edematogenic effects. LQB93 antagonized in vitro, the increase of CK release from the EDL muscle (IC(50)=0.0291 M). It also showed in vivo, antimyotoxic and anti-edematogenic effects that were dose-dependent with ID50 of 0.17 mg/kg and 0.14 mg/kg, respectively. The hemorrhage induced by B. jararaca (1.0 mg/kg) venom in the mouse skin, was abolished by LQB93 (10.0 mg/kg) preincubated with venom. Like wedelolactone, LQB93 protected rat isolated heart on a Langendorff preparation, from the cardiotoxicity of B. jararacussu venom. LQB93 inhibit the effects of Bothrops venoms like wedelolactone, a natural compound isolated from the plant Eclipta prostrata.

Altogether, our results show that Combretum leprosum extract can inhibit different activities of two important Brazilian snake venoms, giving support for its popular use in folk medicine in the management of venomous snakebites.