Artemia salina as an animal model for the preliminary evaluation of snake venom-induced toxicity

Assessment of the Artemia salina toxicity assay as a substitute of the mouse lethality assay in the determination of venom-induced toxicity and preclinical efficacy of antivenom

Mice are routinely used in snake venom research but are costly and subject to pain and suffering. The crustacean Artemia salina could be an alternative to mice, but data to support its adoption in snake venom research is limited. The aim of the present study was to evaluate the suitability of A. salina as a surrogate of mice in assessing the toxicity of venoms and the preclinical efficacy of antivenoms. The toxicity of venoms from 22 snakes of medical importance in sub-Saharan Africa was evaluated in mice (intraperitoneally; i.p. and intravenously; i.v.) and in A. salina. Subsequently, the capacity of a commercial antivenom to neutralize the toxicity of these venoms in mice and A. salina was investigated. There was a positive correlation between the i.v. median lethal doses (LD50s) and the i.p. LD50s in mice (r = 0.804; p < 0.0001), a moderate correlation between the i.v. LD50s in mice and the median lethal concentrations (LC50s) in A. salina (r = 0.606; p = 0.003), and a moderate correlation between the i.p. LD50s in mice and the LC50s in A. salina (r = 0.426; p = 0.048). Moreover, there was a strong correlation between the i.p. median effective doses (ED50s) and the i.v. ED50s in mice (r = 0.941, p < 0.0001), between the i.p. ED50s in mice and the ED50s in A. salina (r = 0.818, p < 0.0001), and between the i.v. ED50s in mice and the ED50s in A. salina (r = 0.972, p < 0.0001). These findings present A. salina as a promising candidate for reducing reliance on mice in snake venom research. Future investigations should build upon these findings, addressing potential limitations and expanding the scope of A. salina in venom research and antivenom development.

Exploring nature's antidote: unveiling the inhibitory potential of selected medicinal plants from Kisumu, Kenya against venom from some snakes of medical significance in sub-Saharan Africa

Background: The present study investigated the efficacy of Conyza bonariensis, Commiphora africana, Senna obtusifolia, Warburgia ugandensis, Vernonia glabra, and Zanthoxylum usambarense against Bitis arietans venom (BAV), Naja ashei venom (NAV), and Naja subfulva venom (NSV). Methods: 40 extracts and fractions were prepared using n-hexane, dichloromethane, ethyl acetate, and methanol. In vitro efficacy against snake venom phospholipase A2 (svPLA2) was determined in 96-well microtiter and agarose-egg yolk coagulation assays. in vivo efficacy against venom-induced cytotoxicity was determined using Artemia salina. Two commercial antivenoms were used for comparison. Results: The 96-well microtiter assay revealed poor svPLA2 inhibition of BAV by antivenom (range: 20.76% ± 13.29% to 51.29% ± 3.26%) but strong inhibition (>90%) by dichloromethane and hexane fractions of C. africana, hexane and ethyl acetate extracts and fraction of W. ugandensis, dichloromethane fraction of V. glabra, and the methanol extract of S. obtusifolia. The methanol extract and fraction of C. africana, and the hexane extract of Z. usambarense strongly inhibited (>90%) svPLA2 activity in NAV. The hexane and ethyl acetate fractions of V. glabra and the dichloromethane, ethyl acetate, and methanol extracts of C. africana strongly inhibited (>90%) svPLA2 in NSV. The agarose egg yolk coagulation assay showed significant inhibition of BAV by the dichloromethane fraction of C. africana (EC50 = 3.51 ± 2.58 μg/mL), significant inhibition of NAV by the methanol fraction of C. africana (EC50 = 7.35 ± 1.800 μg/mL), and significant inhibition of NSV by the hexane extract of V. glabra (EC50 = 7.94 ± 1.50 μg/mL). All antivenoms were non-cytotoxic in A. salina but the methanol extract of C. africana and the hexane extracts of V. glabra and Z. usambarense were cytotoxic. The dichloromethane fraction of C. africana significantly neutralized BAV-induced cytotoxicity, the methanol fraction and extract of C. africana neutralized NAV-induced cytotoxicity, while the ethyl acetate extract of V. glabra significantly neutralized NSV-induced cytotoxicity. Glycosides, flavonoids, phenolics, and tannins were identified in the non-cytotoxic extracts/fractions. Conclusion: These findings validate the local use of C. africana and V. glabra in snakebite but not C. bonariensis, S. obtusifolia, W. ugandensis, and Z. usambarense. Further work is needed to isolate pure compounds from the effective plants and identify their mechanisms of action.

Toxicity Evaluation of Anti-cholinesterasic Amphibian Extracts by MTT and an Optimized Artemia salina Test

The amphibian skin is an important source of bioactive compounds. Recently, our workgroup reported the bioactivity of new extracts from the Hylidae, Microhylidae and Leptodactylidae families against several pathways involved in Alzheimer's disease. However, since cytotoxicity can be a limiting factor for their applicability, we evaluated the toxicity of nine amphibian skin extracts with reported anticholinesterase activity, using the traditional MTT assay and an optimized Artemia salina test. The proposed improvement, guided by experimental design, aims to reduce the amount of biological sample needed. Overall, we proved that the active extracts were non-toxic at effective concentration against cholinesterases (AChE/BChE), positioning the amphibian skin as a promising and preliminary safe source of bioactive compounds in the anti-Alzheimer's treatment. Interestingly, we demonstrated that both toxicity assays can discriminate between toxic and non-toxic samples. We propose the A. salina bioassay as a reliable and cost-effective alternative for early toxicity screening.

Chemical characterization, antioxidant activity, and cytotoxicity of fatty acids methyl esters from Handroanthus impetiginosus (Mart. ex DC.) Mattos (Bignoniaceae) seeds

Handroanthus impetiginosus, popularly known as "ipê-roxo", is used in folk medicine to treat skin inflammations, infections, stomach diseases, and cancer. Fatty acid methyl esters (FAMEs) obtained from the esterification reaction of fatty acids (FA) found in the hexane extract (HE) of seeds of H. impetiginosus were identified by gas chromatography-mass spectrometry (GC-MS). The antioxidant and cytotoxic activities of the HE and FAMEs were evaluated. Methyl palmitate, methyl linoleate, methyl oleate, and methyl stearate were the major FAMEs obtained from the HE. The samples, especially the HE, exhibited a significant antioxidant potential analyzed by ferric reducing ability power (FRAP) assay. In the A. salina larvae bioassay, the HE showed no cytotoxic effects, but the FAMEs exhibited a high toxicity. This study reported, for the first time, the antioxidant and cytotoxic activities of the HE and FAMEs obtained from H. impetiginosus seeds.

In vitro biofilm inhibition efficacy of Aerva lanata flower extract against Gram negative and Gram-positive biofilm forming bacteria and toxicity analysis using Artemia salina

A biofilm consists of Gram positive and Gram-negative bacteria enclosed in a matrix. Industrial biofouling is caused by biofilms, which can exhibit antimicrobial resistance during infections. Many biofilm studies find that nearly all biofilm communities consist of Gram positive and Gram-negative bacteria. It is therefore necessary to better understand the conserved themes in biofilm formation to develop therapeutics based on biofilm formation. Plant extracts can effectively combat pathogenic bacterial biofilms. This study evaluated the antibacterial and antibiofilm activity of Aerva lanata flower extract against Staphylococcus aureus and Pseudomonas aeruginosa. Methanol extract of dried A. lanata flower was tested against S. aureus and P. aeruginosa to determine the antibacterial activity (10, 25, 50, 75, 100 μg/mL) resulted in a maximum of 0.5-1 log reduction and 2 log reduction in comparison to the control or untreated bacterial cells respectively. A. lanata showed maximum biofilm inhibition up to 1.5-fold and 1-fold against P. aeruginosa and S. aureus. Light microscopic analysis of biofilm treated with A. lanata extract showed efficient distortion of the biofilm matrix. Further, the in vivo analysis of A. lanata in the Artemia salina brine shrimp model showed >50% survival and thus proving the efficacy of A. lanata extract in rescuing the brine shrimps against P. aeruginosa and S. aureus infection.

Targeted co-delivery of methotrexate and chloroquine via a pH/enzyme-responsive biocompatible polymeric nanohydrogel for colorectal cancer treatment

Application of conventional chemotherapy regardless of its unique effectiveness have been gradually being edged aside due to limited targeting capability, lack of selectivity and chemotherapy-associated side effects. To this end, colon-targeted nanoparticles via combination therapy have shown great therapeutic potential against cancer. Herein, pH/enzyme-responsive biocompatible polymeric nanohydrogels based on poly(methacrylic acid) (PMAA) containing methotrexate (MTX) and chloroquine (CQ) were fabricated. PMAA-MTX-CQ exhibited high drug loading capacity of which MTX was 4.99% and was CQ 25.01% and displayed pH/enzyme-triggered drug release behavior. Higher CQ release rate (76%) under simulated acidic microenvironment of tumor tissue whereas 39% of CQ was released under normal physiological conditions. Intestinally, MTX release was facilitated in the presence of proteinase K enzyme. TEM image demonstrated spherical morphology with particle size of less than 50 nm. In vitro and in vivo toxicity assessments indicated that developed nanoplatforms possessed great biocompatibility. These nanohydrogels did not cause any adverse effects against Artemia Salina and HFF2 cells (around 100% cell viability) which highlight the safety of prepared nanohydrogels. There was no death in mice received different concentrations of nanohydrogel through oral administration and less than 5% hemolysis was found in red blood cells incubated with PMAA nanohydrogels. In vitro anti-cancer results showed that combination therapy based on PMAA-MTX-CQ can effectively suppress the growth of SW480 colon cancer cells (29% cell viability) compared to monotherapy. Altogether, these findings suggest that pH/enzyme-responsive PMAA-MTX-CQ could effectively inhibit cancer cell growth and progression via site-specific delivery of its cargo in a safe and controlled manner.

Chitosan (CS)/Hydroxyapatite (HA)/Tricalcium Phosphate (β-TCP)-Based Composites as a Potential Material for Pulp Tissue Regeneration

This research focused on developing new materials for endodontic treatments to restore tissues affected by infectious or inflammatory processes. Three materials were studied, namely tricalcium phosphate β-hydroxyapatite (β-TCP), commercial and natural hydroxyapatite (HA), and chitosan (CS), in different proportions. The chemical characterization using infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis confirmed the composition of the composite. Scanning electron microscopy (SEM) demonstrated that the design and origin of the HA, whether natural or commercial, did not affect the morphology of the composites. In vitro studies using Artemia salina (A. salina) indicated that all three experimental materials were biocompatible after 24 h, with no significant differences in mortality rate observed among the groups. The subdermal implantation of the materials in block form exhibited biocompatibility and biodegradability after 30 and 60 days, with the larger particles undergoing fragmentation and connective tissue formation consisting of collagen type III fibers, blood vessels, and inflammatory cells. The implanted material continued to undergo resorption during this process. The results obtained in this research contribute to developing endodontic technologies for tissue recovery and regeneration.

Effects on cell cycle progression and cytoskeleton organization of five Bothrops spp. venoms in cell culture-based assays

Snake envenomation is a neglected tropical disease. In Brazil, the Bothrops genus is responsible for about 86% of snakebite accidents. Despite extensive evidence of the cytotoxicity of snake venoms, the cellular and molecular mechanisms involved are not fully understood, especially regarding the effects on cell cycle progression and cytoskeleton organization. Traditionally, the effectiveness and quality control tests of venoms and antivenoms are assessed by in vivo assays. Despite this, there is a rising effort to develop surrogate in vitro models according to the 3R principle (Replacement, Reduction, and Refinement). In this study, we treated rat liver cells (BRL-3A) with venoms from five Bothrops species (B. jararaca, B. jararacussu, B. moojeni, B. alternatus, and B. neuwiedi) and analyzed cell viability and IC50 by MTT assay, cell cycle phases distribution by flow cytometry, and morphology and cytoskeleton alterations by immunofluorescence. In addition, we evaluated the correlation between IC50 and the enzymatic and biological activities of each venom. Our results indicated that Bothrops spp. venoms decreased the cell viability of rat liver BRL-3A cells. The rank order of potency was B. jararacussu > B. moojeni > B. alternatus > B. jararaca > B. neuwiedi. The mechanisms of cytotoxicity were related to microtubules and actin network disruption, but not to cell cycle arrest. No clear correlation was found between the IC50 and retrieved literature data of in vitro enzymatic and in vivo biological activities. This work contributed to understanding cellular and molecular mechanisms underlying the Bothrops spp. venom cytotoxicity, which can help to improve envenomation treatment, as well as disclose potential therapeutic properties of snake venoms.

Evaluation of Usnea barbata (L.) Weber ex F.H. Wigg Extract in Canola Oil Loaded in Bioadhesive Oral Films for Potential Applications in Oral Cavity Infections and Malignancy

Usnea lichens are known for their beneficial pharmacological effects with potential applications in oral medicine. This study aims to investigate the extract of Usnea barbata (L.) Weber ex F.H. Wigg from the Călimani Mountains in canola oil as an oral pharmaceutical formulation. In the present work, bioadhesive oral films (F-UBO) with U. barbata extract in canola oil (UBO) were formulated, characterized, and evaluated, evidencing their pharmacological potential. The UBO-loaded films were analyzed using standard methods regarding physicochemical and pharmacotechnical characteristics to verify their suitability for topical administration on the oral mucosa. F-UBO suitability confirmation allowed for the investigation of antimicrobial and anticancer potential. The antimicrobial properties against Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27353, Candida albicans ATCC 10231, and Candida parapsilosis ATCC 22019 were evaluated by a resazurin-based 96-well plate microdilution method. The brine shrimp lethality assay (BSL assay) was the animal model cytotoxicity prescreen, followed by flow cytometry analyses on normal blood cells and oral epithelial squamous cell carcinoma CLS-354 cell line, determining cellular apoptosis, caspase-3/7 activity, nuclear condensation and lysosomal activity, oxidative stress, cell cycle, and cell proliferation. The results indicate that a UBO-loaded bioadhesive film’s weight is 63 ± 1.79 mg. It contains 315 µg UBO, has a pH = 6.97 ± 0.01, a disintegration time of 124 ± 3.67 s, and a bioadhesion time of 86 ± 4.12 min, being suitable for topical administration on the oral mucosa. F-UBO showed moderate dose-dependent inhibitory effects on the growth of both bacterial and fungal strains. Moreover, in CLS-354 tumor cells, F-UBO increased oxidative stress, diminished DNA synthesis, and induced cell cycle arrest in G0/G1. All these properties led to considering UBO-loaded bioadhesive oral films as a suitable phytotherapeutic formulation with potential application in oral infections and neoplasia.

Preclinical efficacy testing of three antivenoms against Naja ashei venom-induced lethality

This study aimed to determine the efficacy of Inoserp, Vins bioproducts, and South African Institute of Medical Research (SAIMR) polyvalent antivenoms in neutralizing Naja ashei venom-induced lethality in mice. The neutralization efficacy of the antivenoms were expressed as effective dose, median effective ratio, potency, normalized potency, volume, and the number of vials of antivenom required to neutralize 100 mg of Naja ashei venom (NAV).

Evaluation of lethality and cytotoxic effects induced by Naja ashei (large brown spitting cobra) venom and the envenomation-neutralizing efficacy of selected commercial antivenoms in Kenya

Neutralization of lethality in mice model at the preclinical level has been established by the World Health Organization as the gold standard for the evaluation of antivenom efficacy. The assessment of the neutralization profiles of antivenoms helps to discern the efficacy or otherwise of these antivenoms at neutralizing the toxic effects induced by medically significant snake venoms. However, for many antivenoms, information on their preclinical efficacy remains limited. Therefore, to strengthen global efforts at reducing the impact of snakebite envenoming, the provision of information on the preclinical efficacy of antivenoms, especially in parts of the world where antivenom availability and accessibility is problematic, including sub-Saharan Africa is crucial. This study presents the lethal and toxic activities of N. ashei venom and the neutralizing capacity of two commonly used commercial antivenoms in Kenya; VINS™ and Inoserp™. Median lethal dose (LD50), minimum necrotizing dose (MND) and minimum edema-forming dose (MED) of N. ashei venom as well as the neutralization of these effects were evaluated in mice. The LD50 of N. ashei venom was found to be 4.67 (3.34-6.54) mg/kg while MND and MED were 11.00 μg and 0.80 μg respectively. Both VINS™ and Inoserp™ antivenoms demonstrated capacity to neutralize the lethal and toxic effects induced by Naja ashei venom albeit at varying efficacies. Our results thus confirm the toxic effects of N. ashei venom as previously observed with other Naja sp. venoms and also underscore the relevance of para-specific neutralizing capacity of antivenoms in the design of antivenoms.