Structural studies with crotoxin B from Crotalus durissus collilineatus venom suggest a heterodimeric assembly formed by two new isoforms.

In accidents involving Crotalus snakes, the crotoxin complex (CTX) plays lethal action due to its neurotoxic activity. On the other hand, CTX have potential biotechnological application due to its anti-tumoral, anti-inflammatory, antimicrobial, analgesic and immunomodulatory properties. CTX is a heterodimer composed of Crotoxin A (CA or crotapotin), the acidic nontoxic and non-enzymatic component and; Crotoxin B (CB), a basic, toxic and catalytic PLA2. Currently, there are two classes of CTX isoforms, whose differences in their biological activities have been attributed to features presented in CB isoforms. Here, we present the crystal structure of CB isolated from the Crotalus durissus collilineatus venom. It amino acid sequence was assigned using the SEQUENCE SLIDER software, which revealed that the crystal structure is a heterodimer composed of two new CB isoforms (colCB-A and colCB-B). Bioinformatic and biophysical analyses showed that the toxin forms a tetrameric assembly in solution similar to CB from Crotalus durissus terrificus venom, despite some differences observed at the dimeric interface. By the previously proposed classification, the colCB-B presents features of the class I isoforms while colCB-A cannot be classified into classes I and II based on its amino acid sequence. Due to similar features observed for other CB isoforms found in the NCBI database and the results obtained for colCB-A, we suggest that there are more than two classes of CTX and CB isoforms in crotalic venoms.

Exosome Liberation by Human Neutrophils under L-Amino Acid Oxidase of Calloselasma rhodostoma Venom Action.

L-Amino acid oxidase (LAAO) is an enzyme found in snake venom that has multifaceted effects, including the generation of hydrogen peroxide (H2O2) during oxidative reactions, leading to various biological and pharmacological outcomes such as apoptosis, cytotoxicity, modulation of platelet aggregation, hemorrhage, and neutrophil activation. Human neutrophils respond to LAAO by enhancing chemotaxis, and phagocytosis, and releasing reactive oxygen species (ROS) and pro-inflammatory mediators. Exosomes cellular nanovesicles play vital roles in intercellular communication, including immune responses. This study investigates the impact of Calloselasma rhodostoma snake venom-derived LAAO (Cr-LAAO) on human neutrophil exosome release, including activation patterns, exosome formation, and content. Neutrophils isolated from healthy donors were stimulated with Cr-LAAO (100 µg/mL) for 3 h, followed by exosome isolation and analysis. Results show that Cr-LAAO induces the release of exosomes with distinct protein content compared to the negative control. Proteomic analysis reveals proteins related to the regulation of immune responses and blood coagulation. This study uncovers Cr-LAAO's ability to activate human neutrophils, leading to exosome release and facilitating intercellular communication, offering insights into potential therapeutic approaches for inflammatory and immunological disorders.

Therapeutic applications of snake venoms: An invaluable potential of new drug candidates.

Animal venoms and their chemical compounds have aroused both empirical and scientific attention for ages. However, there has been a significant increase in scientific investigations in recent decades, allowing the production of various formulations that are helping in the development of many important tools for biotechnological, diagnostic, or therapeutic use, both in human and animal health, as well as in plants. Venoms are composed of biomolecules and inorganic compounds that may have physiological and pharmacological activities that are not related to their principal actions (prey immobilization, digestion, and defense). Snake venom toxins, mainly enzymatic and non-enzymatic proteins, and peptides have been identified as potential prototypes for new drugs and/or models for the development of pharmacologically active structural domains for the treatment of cancer, cardiovascular diseases, neurodegenerative and autoimmune diseases, pain, and infectious-parasitic diseases. This minireview aims to provide an overview of the biotechnological potential of animal venoms, with a focus on snakes, and to introduce the reader to the fascinating world of Applied Toxinology, where animal biodiversity can be used to develop therapeutic and diagnostic applications for humans.

Catalytically Active Snake Venom PLA2 Enzymes: An Overview of Its Elusive Mechanisms of Reaction.

Snake venom-secreted phospholipase A2 (svPLA2) enzymes, both catalytically active and inactive, are a central component in envenoming. These are responsible for disrupting the cell membrane's integrity, inducing a wide range of pharmacological effects, such as the necrosis of the bitten limb, cardiorespiratory arrest, edema, and anticoagulation. Although extensively characterized, the reaction mechanisms of enzymatic svPLA2 are still to be thoroughly understood. This review presents and analyses the most plausible reaction mechanisms for svPLA2, such as the "single-water mechanism" or the "assisted-water mechanism" initially proposed for the homologous human PLA2. All of the mechanistic possibilities are characterized by a highly conserved Asp/His/water triad and a Ca2+ cofactor. The extraordinary increase in activity induced by binding to a lipid-water interface, known as "interfacial activation," critical for the PLA2s activity, is also discussed. Finally, a potential catalytic mechanism for the postulated noncatalytic PLA2-like proteins is anticipated.

Phenotypic, functional and plasticity features of human PBMCs induced by venom secreted PLA2s.

Bothrops venom contains a high amount of secreted phospholipase A2 (sPLA2s) enzymes responsible for the inflammatory reaction and activation of leukocytes in cases of envenoming. PLA2s are proteins that have enzymatic activity and can hydrolyze phospholipids at the sn-2 position, thereby releasing fatty acids and lysophospholipids precursors of eicosanoids, which are significant mediators of inflammatory conditions. Whether these enzymes have a role in the activation and function of peripheral blood mononuclear cells (PBMCs) is not known. Here we show for the first time how two secreted PLA2s (BthTX-I and BthTX-II) isolated from the venom of Bothrops jararacussu affect the function and polarization of PBMCs. Neither BthTX-I nor BthTX-II exhibited significant cytotoxicity to isolated PBMCs compared with the control at any of the time points studied. RT-qPCR and enzyme-linked immunosorbent assays were used to determine changes in gene expression and the release of pro-inflammatory (TNF-α, IL-6, and IL-12) and anti-inflammatory (TGF-ß and IL-10) cytokines, respectively, during the cell differentiation process. Lipid droplets formation and phagocytosis were also investigated. Monocytes/macrophages were labeled with anti-CD14, -CD163, and -CD206 antibodies to assay cell polarization. Both toxins caused a heterogeneous morphology (M1 and M2) on days 1 and 7 based on immunofluorescence analysis, revealing the considerable flexibility of these cells even in the presence of typical polarization stimuli. Thus, these findings indicate that the two sPLA2s trigger both immune response profiles in PBMCs indicating a significant degree of cell plasticity, which may be crucial for understanding the consequences of snake envenoming.

Structural basis of the myotoxic inhibition of the Bothrops pirajai PrTX-I by the synthetic varespladib.

Varespladib (LY315920) is a potent inhibitor of human group IIA phospholipase A2 (PLA2) originally developed to control inflammatory cascades of diseases associated with high or dysregulated levels of endogenous PLA2. Recently, varespladib was also found to inhibit snake venom PLA2 and PLA2-like toxins. Herein, ex vivo neuromuscular blocking activity assays were used to test the inhibitory activity of varespladib. The binding affinity between varespladib and a PLA2-like toxin was quantified and compared with other potential inhibitors for this class of proteins. Crystallographic and bioinformatic studies showed that varespladib binds to PrTX-I and BthTX-I into their hydrophobic channels, similarly to other previously characterized PLA2-like myotoxins. However, a new finding is that an additional varespladib binds to the MDiS region, a particular site that is related to muscle cell disruption by these toxins. The present results further advance the characterization of the molecular interactions of varespladib with PLA2-like myotoxins and provide additional evidence for this compound as a promising inhibitor candidate for different PLA2 and PLA2-like toxins.

Structural and functional studies of a snake venom phospholipase A2-like protein complexed to an inhibitor from Tabernaemontana catharinensis.

Snake envenomation is an ongoing global health problem and tropical neglected disease that afflicts millions of people each year. The only specific treatment, antivenom, has several limitations that affects its proper distribution to the victims and its efficacy against local effects, such as myonecrosis. The main responsible for this consequence are the phospholipases A2 (PLA2) and PLA2-like proteins, such as BthTX-I from Bothrops jararacussu. Folk medicine resorts to plants such as Tabernaemontana catharinensis to palliate these and other snakebite effects. Here, we evaluated the effect of its root bark extract and one of its isolated compounds, 12-methoxy-4-methyl-voachalotine (MMV), against the in vitro paralysis and muscle damage induced by BthTX-I. Secondary and quaternary structures of BthTX-I were not modified by the interaction with MMV. Instead, this compound interacted in an unprecedented way with the region inside the toxin hydrophobic channel and promoted a structural change in Val31, loop 58-71 and Membrane Disruption Site. Thus, we hypothesize that MMV inhibits PLA2-like proteins by preventing entrance of fatty acid into the hydrophobic channel. These data may explain the traditional use of T. catharinensis extract and confirm MMV as a promising candidate to complement antivenom or a structural guide to develop more effective inhibitors.

Antileishmanial activity, cytotoxicity and cellular response of amphotericin B in combination with crotamine derived from Crotalus durissus terrificus venom using in vitro and in silico approaches.

OBJECTIVE: To investigate the in vitro activity, synergism, cytotoxicity and cellular immunological response, as well as the molecular affinity between amphotericin B (AmB) and crotamine (CTA), derived from Crotalus durissus terrificus venom against Leishmania amazonensis. METHODS: This study performed the inhibition of promastigotes and amastigotes' growth under different concentrations of the drug and pharmacological combinations (AmB + CTA) based on the Berimbaum method (synergism study). The lactate dehydrogenase (LDH) quantification method was used to determine the cytotoxicity of the drug and combinations employing four cell lines (J774, HepG2, VERO, and C2C12). Following, the levels of Tumour Necrose Factor-alpha (TNF-α) and Interleukin-12 (IL-12) cytokines, using enzyme-linked immunosorbent assay (ELISA) and nitrites, as an indirect measure of Nitric Oxide (NO), using the Griess reaction were assessed in the supernatants of infected macrophages. In silico approach (molecular docking and dynamics) and binding affinity (surface plasmon resonance) between the drug and toxin were also investigated. RESULTS: CTA enhanced AmB effect against promastigote and amastigote forms of L. amazonensis, decreased the drug toxicity in different cell lines and induced the production of important Th1-like cytokines and NO by infected macrophages. The pharmacological combination also displayed consistent molecular interactions with low energy of coupling and a concentration-dependent profile. CONCLUSION: Our data suggest that this pharmacological approach is a promising alternative treatment against L. amazonensis infection due to the improved activity (synergistic effect) achieved against the parasites' forms and to the decreased cytotoxic effect.

Anti-Metalloprotease P-I Single-Domain Antibodies: Tools for Next-Generation Snakebite Antivenoms.

In order to address the global antivenom crisis, novel antivenoms need to present high therapeutic efficacy, broad neutralization ability against systemic and local damage, sufficient safety, and cost-effectiveness. Due to biological characteristics of camelid single-domain antibodies (VHH) such as high affinity, their ability to penetrate dense tissues, and facility for genetic manipulation, their application in antivenoms has expanded considerably. VHHs that are active against the metalloprotease BjussuMP-II from the snake Bothrops jararacussu were selected. After isolation of BjussuMP-II, a camelid was immunized with the purified toxin in order to construct the recombinant phage library. Following a round of biopanning, 52% of the selected clones were able to recognize BjussuMP-II in an ELISA assay. After sequencing, seven sequence profiles were identified. One selected clone (VHH61) showed cross-reactivity to B. brazili venom, but did not recognize the Crotalus and Lachesis genera, indicating specificity for the Bothrops genus. Through in vitro tests, the capacity to neutralize the toxicity triggered by BjussuMP-II was observed. Circular dichroism spectroscopy indicated a robust secondary structure for VHH61, and the calculated melting temperature (T M) for the clone was 56.4°C. In silico analysis, through molecular docking of anti-BjussuMP-II VHHs with metalloprotease, revealed their potential interaction with amino acids present in regions critical for the toxin's conformation and stability. The findings suggest that anti-BjussuMP-II VHHs may be beneficial in the development of next-generation antivenoms.

Dynamics of action of a Lys-49 and an Asp-49 PLA2s on inflammasome NLRP3 activation in murine macrophages.

Phospholipases A2 (PLA2s) are proteins found in snake venoms with hemolytic, anticoagulant, myotoxic, edematogenic, bactericidal and inflammatory actions. In Bothrops jararacussu snake venom were isolated a Lys49-PLA2 (BthTX-I) and an Asp49-PLA2 (BthTX-II) with myotoxic and inflammatory actions. Both PLA2s can activate the NLRP3 inflammasome, an intracytoplasmic platform that recognizes molecules released when tissue is damaged liberating IL-1ß that contributes to the inflammatory response observed in envenoming. The dynamic of action of BthTX-I and BthTX-II in both thioglycollate (TG)-elicited macrophages and C2C12 myoblasts and the involvement of EP1 and EP2 receptors, and PGE2 in NLRP3 inflammasome activation were evaluated. Both toxins induced PGE2 liberation and inflammasome components (NLRP3, Caspase-1, ASC, IL-1ß, and IL18), IL-6, P2X7, COX-1, COX-2, EP2 and EP4 gene expression in TG-elicited macrophages but not in C2C12 myoblasts. EP2 (PF04418948) and EP4 (GW627368X) inhibitors abolished this effect. Both PLA2s also induced NLRP3 inflammasome protein expression that was abolished with the inhibitors used. Immunofluorescence and IL-1ß assays confirmed the NLRP3 activation in TG-elicited macrophages with the participation of both EP2 and EP4 receptors confirming their involvement in this effect. All in all, BthTX-I and BthTX-II activate macrophages and induce the NLRP3 inflammasome complex activation with the participation of the PGE2 via COX pathway and EP2 and EP4, both PGE2 receptors, contributing to the local inflammatory effects observed in envenoming.

Light Emitting Diode Photobiomodulation Enhances Oxidative Redox Capacity in Murine Macrophages Stimulated with Bothrops jararacussu Venom and Isolated PLA2s.

Photobiomodulation therapy associated with conventional antivenom treatment has been shown to be effective in reducing the local effects caused by bothropic venoms in preclinical studies. In this study, we analyzed the influence of photobiomodulation using light emitting diode (LED) on the oxidative stress produced by murine macrophages stimulated with Bothrops jararacussu venom and it isolated toxins BthTX-I and BthTX-II. Under LED treatment, we evaluated the activity of the antioxidant enzymes catalase, superoxide dismutase, and peroxidase as well as the release of hydrogen peroxide and the enzyme lactate dehydrogenase. To investigate whether NADPH oxidase complex activation and mitochondrial pathways could contribute to hydrogen peroxide production by macrophages, we tested the effect of two selective inhibitors, apocynin and CCCP3, respectively. Our results showed that LED therapy was able to decrease the production of hydrogen peroxide and the liberation of lactate dehydrogenase, indicating less cell damage. In addition, the antioxidant enzymes catalase, superoxide dismutase, and peroxidase increased in response to LED treatment. The effect of LED treatment on macrophages was inhibited by CCCP3, but not by apocynin. These findings show that LED photobiomodulation treatment protects macrophages, at least in part, by reducing oxidative stress caused B. jararacussu venom and toxins.

The chemistry of snake venom and its medicinal potential.

The fascination and fear of snakes dates back to time immemorial, with the first scientific treatise on snakebite envenoming, the Brooklyn Medical Papyrus, dating from ancient Egypt. Owing to their lethality, snakes have often been associated with images of perfidy, treachery and death. However, snakes did not always have such negative connotations. The curative capacity of venom has been known since antiquity, also making the snake a symbol of pharmacy and medicine. Today, there is renewed interest in pursuing snake-venom-based therapies. This Review focuses on the chemistry of snake venom and the potential for venom to be exploited for medicinal purposes in the development of drugs. The mixture of toxins that constitute snake venom is examined, focusing on the molecular structure, chemical reactivity and target recognition of the most bioactive toxins, from which bioactive drugs might be developed. The design and working mechanisms of snake-venom-derived drugs are illustrated, and the strategies by which toxins are transformed into therapeutics are analysed. Finally, the challenges in realizing the immense curative potential of snake venom are discussed, and chemical strategies by which a plethora of new drugs could be derived from snake venom are proposed.

Inflammasome NLRP3 activation induced by Convulxin, a C-type lectin-like isolated from Crotalus durissus terrificus snake venom.

Convulxin (CVX), a C-type lectin-like protein isolated from the venom of the snake species, Crotalus durissus terrificus, stimulates platelet aggregation by acting as a collagen receptor agonist for glycoprotein VI found in the platelets. The effect of CVX on platelets has been studied, but its effect on human peripheral blood mononuclear cells (PBMCs) remains unclear. Given the significance of PBMCs in inflammation, this study explored the effect of CVX on PBMCs, specifically regarding NLRP3 inflammasome activation by assessing cell viability, ability to induce cell proliferation, reactive oxygen species (ROS) and nitric oxide production, interleukin (IL)-2 and IL-10 secretion, NLRP3 complex activation, and the role of C-type lectin-like receptors (CTLRs) in these. CVX was not toxic to PBMCs at the investigated concentrations and did not increase PBMC growth or IL-2 release; however, CVX induced IL-10 release and ROS generation via monocyte activation. It also activated the NLRP3 complex, resulting in IL-1ß induction. Furthermore, the interaction between CVX and Dectin-2, a CTLR, induced IL-10 production. CVX interaction with CTLR has been demonstrated by laminarin therapy. Because of the involvement of residues near the Dectin-2 carbohydrate-recognition site, the generation of ROS resulted in inflammasome activation and IL-1ß secretion. Overall, this work helps elucidate the function of CVX in immune system cells.

NLRP3 inflammasome activation in human peripheral blood mononuclear cells induced by venoms secreted PLA2s.

Bothropic venoms contains high amount of secreted phospholipases A2 (sPLA2s) that play a significant role in leukocyte activation and inflammation. Monocytes and lymphocytes are highly functional immune system cells that mediate and provide efficient responses during the inflammation. NLRP3 inflammasome is a multiprotein complex found in immune system cells that is triggered by pathogen- and damage-associated molecular patterns, PAMPs and DAMPs, respectively. PLA2s' effect on human peripheral blood mononuclear cells (PBMCs) is still incompletely understood. PBMCs were isolated by density gradient and incubated with RPMI (control), LPS, BthTX-I (PLA2-Lys49) or BthTX-II (PLA2-Asp49) isolated from Bothrops jararacussu venom, to evaluate viability, and the results showed that there was no cell death. RT-qPCR and immunoblot were used to assess the gene and protein expression of NLRP3 components. Results indicated that there was substantial amplification of ASC, Caspase-1, IL-6, and IL-1ß in 1 h and NLRP3 in 2 h. Protein expression was measured, and the results revealed substantial expression of the NLRP3 inflammasome complex after 4 h. IL-1ß and LDH was quantified in the supernatant of the cells. Taken together, the findings demonstrate that BthTX-I and BthTX-II activate the NLRP3 inflammasome complex in human PBMCs and contribute to the inflammatory response seen in envenoming.

The chemistry of snake venom and its medicinal potential.

The fascination and fear of snakes dates back to time immemorial, with the first scientific treatise on snakebite envenoming, the Brooklyn Medical Papyrus, dating from ancient Egypt. Owing to their lethality, snakes have often been associated with images of perfidy, treachery and death. However, snakes did not always have such negative connotations. The curative capacity of venom has been known since antiquity, also making the snake a symbol of pharmacy and medicine. Today, there is renewed interest in pursuing snake-venom-based therapies. This Review focuses on the chemistry of snake venom and the potential for venom to be exploited for medicinal purposes in the development of drugs. The mixture of toxins that constitute snake venom is examined, focusing on the molecular structure, chemical reactivity and target recognition of the most bioactive toxins, from which bioactive drugs might be developed. The design and working mechanisms of snake-venom-derived drugs are illustrated, and the strategies by which toxins are transformed into therapeutics are analysed. Finally, the challenges in realizing the immense curative potential of snake venom are discussed, and chemical strategies by which a plethora of new drugs could be derived from snake venom are proposed.

Synergism of in vitro plasmodicidal activity of phospholipase A2 isoforms isolated from panamanian Bothrops asper venom.

Bothrops asper is one of the most important snake species in Central America, mainly because of its medical importance in countries like Ecuador, Panama and Costa Rica, where this species causes a high number of snakebite accidents. Several basic phospholipases A2 (PLA2s) have been previously characterized from B. asper venom, but few studies have been carried out with its acidic isoforms. In addition, since snake venom is a rich source of bioactive substances, it is necessary to investigate the biotechnological potential of its components. In this context, this study aimed to carry out the biochemical characterization of PLA2 isoforms isolated from B. asper venom and to evaluate the antiparasitic potential of these toxins. The venom and key fractions were subjected to different chromatographic steps, obtaining nine PLA2s, four acidic ones (BaspAc-I, BaspAc-II, BaspAc-III and BaspAc-IV) and five basic ones (BaspB-I, BaspB-II, BaspB-III, BaspB-IV and BaspB-V). The isoelectric points of the acidic PLA2s were also determined, which presented values ranging between 4.5 and 5. The findings indicated the isolation of five unpublished isoforms, four Asp49-PLA, corresponding to the group of acidic isoforms, and one Lys49-PLA2-like. Acidic PLA2s catalyzed the degradation of all substrates evaluated; however, for the basic PLA2s, there was a preference for phosphatidylglycerol and phosphatidic acid. The antiparasitic potential of the toxins was evaluated, and the acidic PLA2s demonstrated action against the epimastigote forms of T. cruzi and promastigote forms of L. infantum, while the basic PLA2s BaspB-II and BaspB-IV showed activity against P. falciparum. The results indicated an increase of up to 10 times in antiplasmodial activity, when the Asp49-PLA2 and Lys49-PLA2 were associated with one another, denoting synergistic action between these PLA2 isoforms. These findings correspond to the first report of synergistic antiplasmodial action for svPLA2s, demonstrating that these molecules may be important targets in the search for new antiparasitic agents.

Gallic acid anti-myotoxic activity and mechanism of action, a snake venom phospholipase A2 toxin inhibitor, isolated from the medicinal plant Anacardium humile.

Snakebite envenoming is the cause of an ongoing health crisis in several regions of the world, particularly in tropical and neotropical countries. This scenario creates an urgent necessity for new practical solutions to address the limitations of current therapies. The current study investigated the isolation, phytochemical characterization, and myotoxicity inhibition mechanism of gallic acid (GA), a myotoxin inhibitor obtained from Anacardium humile. The identification and isolation of GA was achieved by employing analytical chromatographic separation, which exhibited a compound with retention time and nuclear magnetic resonance spectra compatible with GA's commercial standard and data from the literature. GA alone was able to inhibit the myotoxic activity induced by the crude venom of Bothrops jararacussu and its two main myotoxins, BthTX-I and BthTX-II. Circular dichroism (CD), fluorescence spectroscopy (FS), dynamic light scattering (DLS), and interaction studies by molecular docking suggested that GA forms a complex with BthTX-I and II. Surface plasmon resonance (SPR) kinetics assays showed that GA has a high affinity for BthTX-I with a KD of 9.146 × 10-7 M. Taken together, the two-state reaction mode of GA binding to BthTX-I, and CD, FS and DLS assays, suggest that GA is able to induce oligomerization and secondary structure changes for BthTX-I and -II. GA and other tannins have been shown to be effective inhibitors of snake venoms' toxic effects, and herein we demonstrated GA's ability to bind to and inhibit a snake venom PLA2, thus proposing a new mechanism of PLA2 inhibition, and presenting more evidence of GA's potential as an antivenom compound.

Engineering of single-domain antibodies for next-generation snakebite antivenoms.

Given the magnitude of the global snakebite crisis, strategies to ensure the quality of antivenom, as well as the availability and sustainability of its supply are under development by several research groups. Recombinant DNA technology has allowed the engineering of monoclonal antibodies and recombinant fragments as alternatives to conventional antivenoms. Besides having higher therapeutic efficacy, with broad neutralization capacity against local and systemic toxicity, novel antivenoms need to be safe and cost-effective. Due to the biological and physical chemical properties of camelid single-domain antibodies, with high volume of distribution to distal tissue, their modular format, and their versatility, their biotechnological application has grown considerably in recent decades. This article presents the most up-to-date developments concerning camelid single-domain-based antibodies against major toxins from snake venoms, the main venomous animals responsible for reported envenoming cases and related human deaths. A brief discussion on the composition, challenges, and perspectives of antivenoms is presented, as well as the road ahead for next-generation antivenoms based on single-domain antibodies.

Photobiomodulation induces murine macrophages polarization toward M2 phenotype.

Photobiomodulation using light-emitting diode (LED) treatment has analgesic and anti-inflammatory effects which can be an effective therapeutic associated with serum therapy for local treatment of snakebites. Here we explored the effects of LED treatment on isolated macrophage under Bothrops jararacussu venom. Results showed that LED induced IL-6 and TNF-α genes down-regulation and, TGF and ARG1 genes up-regulation which indicates a polarization of macrophages to an M2 phenotype contributing to both tissue repair and resolution of inflammation.

Antileishmanial activity evaluation of a natural amide and its synthetic analogs against Leishmania (V.) braziliensis: an integrated approach in vitro and in silico.

Leishmaniasis is considered a neglected disease, which makes it an unattractive market for the pharmaceutical industry; hence, efforts in the search for biologically active substances are hampered by this lack of financial motivation. Thus, in the present study, we report the leishmanicidal activity and the possible mechanisms of action of compounds with promising activity against the species Leishmania (V.) braziliensis, the causative agent of the skin disease leishmaniasis. The natural compound 1a (piplartine) and the analog 2a were the most potent against promastigote forms with growth inhibition values for 50% of the parasite population (IC50) = 8.58 and 11.25 µM, respectively. For amastigote forms, the ICa50 values were 1.46 and 16.7 µM, respectively. In the molecular docking study, piplartine showed favorable binding energy (-7.13 kcal/mol) and with 50% inhibition of trypanothione reductase (IC50) = 91.1 µM. Preliminary investigations of the mechanism of action indicate that piplartine increased ROS levels, induced loss of cell membrane integrity, and caused accumulation of lipid bodies after 24 h of incubation at its lowest effective concentration (IC50), which was not observed for the synthetic analog 2a. The mode of action for the leishmanicidal activity of piplartine (1a) was assigned to involve affinity for the trypanothione reductase of Leishmania (V.) braziliensis TR.