Inhibition of Neurotoxic Secretory Phospholipases A(2) Enzymatic, Edematogenic, and Myotoxic Activities by Harpalycin 2, an Isoflavone Isolated from Harpalyce brasiliana Benth

Unraveling snake venom phospholipase A2: an overview of its structure, pharmacology, and inhibitors

Snake bite is a neglected disease that affects millions of people worldwide. WHO reported approximately 5 million people are bitten by various species of snakes each year, resulting in nearly 1 million deaths and an additional three times cases of permanent disability. Snakes utilize the venom mainly for immobilization and digestion of their prey. Snake venom is a composition of proteins and enzymes which is responsible for its diverse pharmacological action. Snake venom phospholipase A2 (SvPLA2) is an enzyme that is present in every snake species in different quantities and is known to produce remarkable functional diversity and pharmacological action like inflammation, necrosis, myonecrosis, hemorrhage, etc. Arachidonic acid, a precursor to eicosanoids, such as prostaglandins and leukotrienes, is released when SvPLA2 catalyzes the hydrolysis of the sn-2 positions of membrane glycerophospholipids, which is responsible for its actions. Polyvalent antivenom produced from horses or lambs is the standard treatment for snake envenomation, although it has many drawbacks. Traditional medical practitioners treat snake bites using plants and other remedies as a sustainable alternative. More than 500 plant species from more than 100 families reported having venom-neutralizing abilities. Plant-derived secondary metabolites have the ability to reduce the venom's adverse consequences. Numerous studies have documented the ability of plant chemicals to inhibit the enzymes found in snake venom. Research in recent years has shown that various small molecules, such as varespladib and methyl varespladib, effectively inhibit the PLA2 toxin. In the present article, we have overviewed the knowledge of snake venom phospholipase A2, its classification, and the mechanism involved in the pathophysiology of cytotoxicity, myonecrosis, anticoagulation, and inflammation clinical application and inhibitors of SvPLA2, along with the list of studies carried out to evaluate the potency of small molecules like varespladib and secondary metabolites from the traditional medicine for their anti-PLA2 effect.

Purification, Characterization and Evaluation of the Antitumoral Activity of a Phospholipase A2 from the Snake Bothrops moojeni

Nature presents a wide range of biomolecules with pharmacological potential, including venomous animal proteins. Among the protein components from snake venoms, phospholipases (PLA₂) are of great importance for the development of new anticancer compounds. Thus, we aimed to evaluate the PLA₂ anticancer properties from Bothrops moojeni venom. The crude venom was purified through three chromatographic steps, monitored by enzymatic activity and SDS-PAGE (12%). The purified PLA₂ denominated BmPLA2 had its molecular mass and N-terminal sequence identified by mass spectrometry and Edman degradation, respectively. BmPLA2 was assayed against human epithelial colorectal adenocarcinoma cells (Caco-2), human rhabdomyosarcoma cells (RD) and mucoepidermoid carcinoma of the lung (NCI-H292), using human fibroblast cells (MRC-5) and microglia cells (BV-2) as a cytotoxicity control. BmPLA2 presented 13,836 Da and a 24 amino acid-residue homologue with snake PLA₂, which showed a 90% similarity with other Bothrops moojeni PLA₂. BmPLA2 displayed an IC₅₀ of 0.6 µM against Caco-2, and demonstrated a selectivity index of 1.85 (compared to MRC-5) and 6.33 (compared to BV-2), supporting its selectivity for cancer cells. In conclusion, we describe a new acidic phospholipase, which showed antitumor activity and is a potential candidate in the development of new biotechnological tools.

Plant-Derived Toxin Inhibitors as Potential Candidates to Complement Antivenom Treatment in Snakebite Envenomations

Snakebite envenomations (SBEs) are a neglected medical condition of global importance that mainly affect the tropical and subtropical regions. Clinical manifestations include pain, edema, hemorrhage, tissue necrosis, and neurotoxic signs, and may evolve to functional loss of the affected limb, acute renal and/or respiratory failure, and even death. The standard treatment for snake envenomations is antivenom, which is produced from the hyperimmunization of animals with snake toxins. The inhibition of the effects of SBEs using natural or synthetic compounds has been suggested as a complementary treatment particularly before admission to hospital for antivenom treatment, since these alternative molecules are also able to inhibit toxins. Biodiversity-derived molecules, namely those extracted from medicinal plants, are promising sources of toxin inhibitors that can minimize the deleterious consequences of SBEs. In this review, we systematically synthesize the literature on plant metabolites that can be used as toxin-inhibiting agents, as well as present the potential mechanisms of action of molecules derived from natural sources. These findings aim to further our understanding of the potential of natural products and provide new lead compounds as auxiliary therapies for SBEs.

Plants and Phytocompounds Active Against Bothrops Venoms

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Snakebite envenomation is an important health problem in tropical countries, with severe human and social consequences. In Latin America, the Bothrops species constitute the main threat to humans, and the envenomation caused by these species quickly develops into severe local tissue damage, including swelling, hemorrhaging, myonecrosis, skin ulceration, and pain. The systemic effects of envenomation are usually neutralized by antivenom serum therapy, despite its intrinsic risks. However, neutralization of local tissue damage remains a challenge. To improve actual therapy, two major alternatives are proposed: the rational design of new specific antibodies for most of the tissue damaging/ poor immunogenic toxins, or the search for new synthetic or natural compounds which are able to inhibit these toxins and complement the serum therapy. Natural compounds isolated from plants, mainly from those used in folk medicine to treat snakebite, are a good choice for finding new lead compounds to improve snakebite treatment and minimize its consequences for the victims. In this article, we reviewed the most promising plants and phytocompounds active against bothropic venoms.

Evaluation of anti-inflammatory activity and molecular docking study of new aza-bicyclic isoxazoline acylhydrazone derivatives

The aim of this study was to investigate the anti-inflammatory effects of two new isoxazoline-acylhydrazone derivatives: N'-(4-methoxybenzylidene)-6-(4-nitro-benzoyl)-3a,5,6,6a-tetrahydro-4H-pyrrolo[3,2-d]isoxazole-3-carbohydrazide (R-123) and N'-(4-chlorobenzylidene)-6-(4-chlorobenzoyl)-3a,5,6,6a-tetrahydro-4H-pyrrolo[3,2-d]isoxazole-3-carbohydrazide (R-99). An air pouch induced by carrageenan was used for screening the best dose of R-99 and R-123. Using this mouse model, leukocyte migration and cytokine levels (TNF-α and IL-1β) were determined. Paw edema induced by several phlogistic agents and vascular permeability induced by acetic acid were employed to investigate the mechanism of action of the isoxazoline-acylhydrazone derivatives. A docking study was performed with the human histamine H1 receptor to investigate potential antihistaminic activity. Treatment with the compounds reduced leukocyte migration in the air pouch at all doses tested. TNF-α and IL-1β levels were similarly reduced by the two compounds. Vasoactive amines were inhibited in models of paw edema induced by several agents and vascular permeability induced by acetic acid. The docking study suggests that R-99 and R-123 may be inhibitors of the histamine H1 receptor. In conclusion, the results indicate that R-99 and R-123 exhibit promising anti-inflammatory activity related to their ability to inhibit TNF-α, IL-1β, and vasoactive amine production, as well as reduce leukocyte migration and inhibit mast cell degranulation.

Evaluation of Rhamnetin as an Inhibitor of the Pharmacological Effect of Secretory Phospholipase A2

Rhamnetin (Rhm), 3-O-methylquercetin (3MQ), and Rhamnazin (Rhz) are methylated derivatives of quercetin commonly found in fruits and vegetables that possess antioxidant and anti-inflammatory properties. Phospholipase A2 (PLA2) displays several important roles during acute inflammation; therefore, this study aimed at investigating new compounds able to inhibit this enzyme, besides evaluating creatine kinase (CK) levels and citotoxicity. Methylated quercetins were compared with quercetin (Q) and were incubated with secretory PLA2 (sPLA2) from Bothrops jararacussu to determine their inhibitory activity. Cytotoxic studies were performed by using the J774 cell lineage incubated with quercertins. In vivo tests were performed with Swiss female mice to evaluate decreasing paw edema potential and compounds’ CK levels. Structural modifications on sPLA2 were made with circular dichroism (CD). Despite Q and Rhz showing greater enzymatic inhibitory potential, high CK was observed. Rhm exhibited sPLA2 inhibitory potential, no toxicity and, remarkably, it decreased CK levels. The presence of 3OH on the C-ring of Rhm may contribute to both its anti-inflammatory and enzymatic inhibition of sPLA2, and the methylation of ring A may provide the increase in cell viability and low CK level induced by sPLA2. These results showed that Rhm can be a candidate as a natural compound for the development of new anti-inflammatory drugs.

Isoflavones: Anti-Inflammatory Benefit and Possible Caveats

Inflammation, a biological response of body tissues to harmful stimuli, is also known to be involved in a host of diseases, such as obesity, atherosclerosis, rheumatoid arthritis, and even cancer. Isoflavones are a class of flavonoids that exhibit antioxidant, anticancer, antimicrobial, and anti-inflammatory properties. Increasing evidence has highlighted the potential for isoflavones to prevent the chronic diseases in which inflammation plays a key role, though the underlying mechanisms remain unclear. Recently, some studies have raised concerns about isoflavones induced negative effects like carcinogenesis, thymic involution, and immunosuppression. Therefore, this review aims to summarize the anti-inflammatory effects of isoflavones, unravel the underlying mechanisms, and present the potential health risks.

An evaluation of 3-rhamnosylquercetin, a glycosylated form of quercetin, against the myotoxic and edematogenic effects of sPLA 2 from Crotalus durissus terrificus

This paper shows the results of quercitrin effects on the structure and biological activity of secretory phospholipase (sPLA₂) from Crotalus durissus terrificus, which is the main toxin involved in the pharmacological effects of this snake venom. According to our mass spectrometry and circular dichroism results, quercetin was able to promote a chemical modification of some amino acid residues and modify the secondary structure of C. d. terrificus sPLA₂. Moreover, molecular docking studies showed that quercitrin can establish chemical interactions with some of the crucial amino acid residues involved in the enzymatic activity of the sPLA₂, indicating that this flavonoid could also physically impair substrate molecule access to the catalytic site of the toxin. Additionally, in vitro and in vivo assays showed that the quercitrin strongly diminished the catalytic activity of the protein, altered its Vmax and Km values, and presented a more potent inhibition of essential pharmacological activities in the C. d. terrificus sPLA₂, such as its myotoxicity and edematogenic effect, in comparison to quercetin. Thus, we concluded that the rhamnose group found in quercitrin is most likely essential to the antivenom activities of this flavonoid against C. d. terrificus sPLA₂.