Mirian M. Mendes

Snake Venom L-Amino Acid Oxidases: Trends in Pharmacology and Biochemistry

L-amino acid oxidases are enzymes found in several organisms, including venoms of snakes, where they contribute to the toxicity of ophidian envenomation. Their toxicity is primarily due to enzymatic activity, but other mechanisms have been proposed recently which require further investigation. L-amino acid oxidases exert biological and pharmacological effects, including actions on platelet aggregation and the induction of apoptosis, hemorrhage, and cytotoxicity. These proteins present a high biotechnological potential for the development of antimicrobial, antitumor, and antiprotozoan agents. This review provides an overview of the biochemical properties and pharmacological effects of snake venom L-amino acid oxidases, their structure/activity relationship, and supposed mechanisms of action described so far.

BthMP: a new weakly hemorrhagic metalloproteinase from Bothrops moojeni snake venom

In this work, a new weakly hemorrhagic metalloproteinase (BthMP) was purified from Bothrops moojeni snake venom. This enzyme was homogeneous by native and SDS-PAGE. It showed a polypeptide chain of 23.5kDa, pI=7.1, and N-terminal blocked. BthMP is comprised of high proteolytic activity on casein, fibrin and bovine fibrinogen, with no coagulating, esterase or phospholipase A(2) activities; it was inhibited by EDTA, EGTA and 1,10-phenanthroline and maintained its activity on pH from 7.0 to 9.0 and temperature from 5-40 degrees C. Assays with metal ions showed that Ca(2+) is an activator, whereas Zn(2+) and Hg(2+) inhibited about 50 and 80% of its activity, respectively. The edema evidenced the important role of the toxin in the inflammatory activity of the venom. BthMP also caused unclotting, and provoked histological alterations in the gastrocnemius muscle of mice inducing hemorrhage, necrosis and leukocytic infiltrate. The molecular mass and the inhibition assays suggest that the metalloproteinase BthMP belongs to class P-I of SVMPs.

Anti-snake venom properties of Schizolobium parahyba (Caesalpinoideae) aqueous leaves extract.

Many medicinal plants have been recommended for the treatment of snakebites. The aqueous extracts prepared from the leaves of Schizolobium parahyba (a plant found in Mata Atlantica in Southeastern Brazil) were assayed for their ability to inhibit some enzymatic and biological activities induced by Bothrops pauloensis and Crotalus durissus terrificus venoms as well as by their isolated toxins neuwiedase (metalloproteinase), BnSP‐7 (basic Lys49 PLA2) and CB (PLA2 from crotoxin complex). Phospholipase A2, coagulant, fibrinogenolytic, hemorrhagic and myotoxic activities induced by B. pauloensis and C. d. terrificus venoms, as well as by their isolated toxins were significantly inhibited when different amounts of S. parahyba were incubated previously with these venoms and toxins before assays. However, when S. parahyba was administered at the same route as the venoms or toxins injections, the tissue local damage, such as hemorrhage and myotoxicity was only partially inhibited. The study also evaluated the inhibitory effect of S. parahyba upon the spreading of venom proteins from the injected area into the systemic circulation. The neutralization of systemic alterations induced by i.m. injection of B. pauloensis venom was evaluated by measuring platelet and plasma fibrinogen levels which were significantly maintained when S. parahyba extract inoculation occurred at the same route after B. pauloensis venom injection. In conclusion, the observations confirmed that the aqueous extract of S. parahyba possesses potent snake venom neutralizing properties. It may be used as an alternative treatment to serum therapy and as a rich source of potential inhibitors of toxins involved in several physiopathological human and animal diseases. Copyright

Purification and functional characterization of a new metalloproteinase (BleucMP) from Bothrops leucurus snake venom

A fibrino(geno)lytic nonhemorrhagic metalloproteinase (BleucMP) was purified from Bothrops leucurus snake venom by two chromatographic steps procedure on DEAE-Sephadex A-25 followed by CM-Sepharose Fast Flow column. BleucMP represented 1.75% (w/w) of the crude venom and was homogeneous on SDS-PAGE. BleucMP analyzed by MALDI TOF/TOF, showed a molecular mass of 23,057.54Da and when alkylated and reduced, the mass is 23,830.40Da. Their peptides analyzed in MS (MALDI TOF\TOF) showed significant score when compared with those of other proteins by NCBI-BLAST2 alignment display. As regards their proteolytic activities, BleucMP efficiently acted on fibrinogen, fibrin, and was inhibited by EDTA and 1.10-phenanthroline. This enzyme was also able to decrease significantly the plasma fibrinogen level provoking blood incoagulability, however was devoid of hemorrhagic activity when tested in the mice skin and did not induce relevant biochemical, hematological and histopathological alterations in mice. The aspects addressed in this paper provide data on the effect of BleucMP in envenomation from B. leucurus snakes in order to better understand the effects caused by snake venom metalloproteinase.

Neutralization of pharmacological and toxic activities of bothrops snake venoms by Schizolobium parahyba (Fabaceae) aqueous extract and its fractions.

The aqueous extract prepared from Schizolobium parahyba (Sp) leaves, a native plant from Atlantic Forest (Brazil), was tested to analyse its ability to inhibit some biological and enzymatic activities induced by Bothrops alternatus (BaltCV) and Bothrops moojeni (BmooCV) snake venoms. Sp inhibited 100% of lethality, blood incoagulability, haemorrhagic and indirect haemolytic activities at a 1:10 ratio (venom/extract, w/w), as well as coagulant activity at a 1:5 ratio (venom/extract, w/w) induced by both venoms. BaltCV fibrinogenolytic activity was also neutralized by Sp at a 1:10 ratio, resulting in total protection of fibrinogen Bbeta chain and partial protection of Aalpha chain. Interaction tests have demonstrated that, at certain extract/proteins ratios, Sp precipitates proteins non-specifically suggesting the presence of tannins, which are very likely responsible for the excellent inhibiting effects of the analysed ophidian activities. Sp aqueous extract chromatography on Sephadex LH-20 was carried out aiming at the separation of these compounds that mask the obtained results. Thus, the fractionation of Sp resulted in three fractions: F1 (methanolic fraction); F2 (methanol:water fraction, 1:1 v/v); and F3 (aqueous fraction). These fractions were analysed for their ability to inhibit the BaltCV fibrinogenolytic activity. F1 inhibited 100% the venom fibrinogenolytic activity without presenting protein precipitation effect; F2 showed only partial inhibition of this venom activity. Finally, F3 did not inhibit fibrinogen proteolysis, but presented strong protein precipitating action. We conclude that Sp aqueous extract, together with tannins, also contains other compounds that can display specific inhibitory activity against snake venom toxins.

Protective Effect of Schizolobium parahyba Flavonoids Against Snake Venoms and Isolated Toxins

Four compounds (isoquercitrin, myricetin-3-O-glucoside, catechin and gallocatechin) were isolated from lyophilized aqueous extract of Schizolobium parahyba leaves by chromatography on Sephadex LH-20, followed by semipreparative HPLC using a C-18 column, and identified by 1H and 13C NMR. The compounds were then, tested against hemorrhagic and fibrinogenolytic activities of Bothrops crude venoms and isolated metalloproteinases. The inhibitors neutralized the biological and enzymatic activities of Bothrops venoms and toxins isolated from B. jararacussu and B. neuwiedi venoms. The results showed that gallocatechin and myricetin-3-O-glucoside are good inhibitors of hemorrhagic and fibrinogenolytic activities of metalloproteinases, respectively. Gallocatechin also inhibited the myotoxic activity of both B. alternatus venom and BnSP-6 (Lys49 PhospholipaseA2 from B. neuwiedi). Circular dichroism and docking simulation studies were performed in order to investigate the possible interaction between BnSP-6 and gallocatechin. This is the first time these compounds and their anti-ophidian properties are reported for S. parahyba species. Forthcoming studies involving X-ray co-crystallization, will be of great importance for the development of new therapeutic agents for the treatment of ophidian accidents and for the better understanding of the structure/function relationship of venom toxins.

Insights of local tissue damage and regeneration induced by BnSP-7, a myotoxin isolated from Bothrops (neuwiedi) pauloensis snake venom.

Envenomations caused by Bothrops snake venoms are characterized by prominent local tissue damage due to myonecrosis, hemorrhage, edema and acute muscle damage which is widely correlated with phospholipases A2 (PLA2). In the present study, the progression of local tissue damage and inflammation induced by BnSP-7, a myotoxin isolated from Bothrops (neuwiedi) pauloensis snake venom, was evaluated. Local tissue damages characterized by edema, necrosis and inflammation were evaluated until 24 h after inoculation of BnSP-7. The regeneration of myofibers, analyzed by light microscopy, was observed from 72 h to 2 weeks post-inoculation of toxin. MMP-2 was expressed in gastrocnemius muscle at all time points tested, while the expression of MMP-9 increased expressively at the same time interval of regenerating muscle, suggesting the involvement of MMP-9 in the regeneration process. The production of pro-inflammatory cytokines was also increased, whereas IL-1 beta showed the highest level. Modification of BnSP-7 with BPB decreased the release of IL-8, IL-6 and IL-1 beta when compared to native BnSP-7. These data suggest that BnSP-7 acts as pro-inflammatory incentives (mediators), inducing MMP and cytokine production from the inflammatory and satellite cells, and thus it may play an important role in inflammatory process and, consequently, in the evolution of local tissue damage and regeneration.

Effects of Schizolobium parahyba Extract on Experimental Bothrops Venom-Induced Acute Kidney Injury

Background Venom-induced acute kidney injury (AKI) is a frequent complication of Bothrops snakebite with relevant morbidity and mortality. The aim of this study was to assess the effects of Schizolobium parahyba (SP) extract, a natural medicine with presumed anti-Bothrops venom effects, in an experimental model of Bothrops jararaca venom (BV)-induced AKI. Methodology Groups of 8 to 10 rats received infusions of 0.9% saline (control, C), SP 2 mg/kg, BV 0.25 mg/kg and BV immediately followed by SP (treatment, T) in the doses already described. After the respective infusions, animals were assessed for their glomerular filtration rate (GFR, inulin clearance), renal blood flow (RBF, Doppler), blood pressure (BP, intra-arterial transducer), renal vascular resistance (RVR), urinary osmolality (UO, freezing point), urinary neutrophil gelatinase-associated lipocalin (NGAL, enzyme-linked immunosorbent assay [ELISA]), lactate dehydrogenase (LDH, kinetic method), hematocrit (Hct, microhematocrit), fibrinogen (Fi, Klauss modified) and blinded renal histology (acute tubular necrosis score). Principal Findings BV caused significant decreases in GFR, RBF, UO, HcT and Fi; significant increases in RVR, NGAL and LDH; and acute tubular necrosis. SP did not prevent these changes; instead, it caused a significant decrease in GFR when used alone. Conclusion SP administered simultaneously with BV, in an approximate 10∶1 concentration, did not prevent BV-induced AKI, hemolysis and fibrinogen consumption. SP used alone caused a decrease in GFR.

Acute toxicity of Schizolobium parahyba aqueous extract in mice.

The herbal extract of Schizolobium parahyba leaves is used commonly in the Brazil central region to treat snakebites. This study evaluates the acute toxicological effects of Schizolobium parahyba aqueous extract in mice 24 h after intraperitoneal administration. Acute toxicity was evaluated using biochemical, hematological and histopathological assays. Alterations in the levels of transaminases, bilirubin, albumin and prothrombrin time were observed, and these are likely to occur due to hepatic injury, which was confirmed by light microscopy. Liver histopathological analysis revealed the presence of lymph plasmocitary inflammatory infiltrate, but no other histopathological alterations were observed in any of the other organs analysed. The data confirm the low toxicity of the extract of Schizolobium parahyba and provide a model for the selection of a dose that does not cause injuries in the organism. Copyright