Spermine isolated and identified as the major trypanocidal compound from the snake venom of Eristocophis macmahoni causes autophagy in Trypanosoma brucei

Antiprotozoal Effect of Snake Venoms and Their Fractions: A Systematic Review

Background: Protozoal infection is a lingering public health issue of great concern, despite efforts to produce drugs and vaccines against it. Recent breakthrough research has discovered alternative antiprotozoal agents encompassing the use of snake venoms and their components to cure these infections. This study collated the existing literature to examine the antiprotozoal effect of snake venoms and their fractions. Methods: We conducted a systematic review following the PRISMA guidelines. The PubMed and Embase databases were searched from their inception until 13 October 2021. Articles were screened at the title, abstract and full-text phases. Some additional studies were obtained through the manual search process. Results: We identified 331 studies via the electronic database and manual searches, of which 55 reporting the antiprotozoal effect of snake venoms and their components were included in the review. Around 38% of studies examined the effect of whole crude venoms, and a similar percentage evaluated the effect of a proportion of enzymatic phospholipase A2 (PLA2). In particular, this review reports around 36 PLA2 activities and 29 snake crude venom activities. We also report the notable phenomenon of synergism with PLA2 isoforms of Bothrops asper. Importantly, limited attention has been given so far to the antiprotozoal efficacies of metalloproteinase, serine protease and three-finger toxins, although these venom components have been identified as significant components of the dominant venom families. Conclusion: This study highlights the impact of snake venoms and their fractions on controlling protozoal infections and suggests the need to examine further the effectiveness of other venom components, such as metalloproteinase, serine protease and three-finger toxins. Future research questions in this field must be redirected toward synergism in snake venom components, based on pharmacological usage and in the context of toxicology. Ascertaining the effects of snake venoms and their components on other protozoal species that have not yet been studied is imperative.

Effect of Bitis gabonica and Dendroaspis angusticeps snake venoms on apoptosis-related genes in human thymic epithelial cells

Background:

Certain environmental toxins permanently damage the thymic epithelium, accelerate immune senescence and trigger secondary immune pathologies. However, the exact underlying cellular mechanisms and pathways of permanent immune intoxication remain unknown. The aim of the present study was to demonstrate gene expressional changes of apoptosis-related cellular pathways in human thymic epithelial cells following exposure to snake venom from Bitis gabonica and Dendroaspis angusticeps.

Methods:

Snake venoms were characterized by analytical methods including reversed phase high-performance liquid chromatography and sodium dodecyl sulphate-polyacrylamide gel electrophoresis, then applied on human thymic epithelial cells (1889c) for 24 h at 10 μg/mL (as used in previous TaqMan Array study). Gene expressional changes restricted to apoptosis were assayed by TaqMan Array (Human Apoptosis Plate).

Results:

The most prominent gene expressional changes were shown by CASP5 (≈ 2.5 million-fold, confirmed by dedicated quantitative polymerase chain reaction) and CARD9 (0.016-fold) for B. gabonica, and BIRC7 (6.46-fold) and CASP1 (0.30-fold) for D. angusticeps.

Conclusion:

The observed apoptotic environment suggests that pyroptosis may be the dominant pathway through which B. gabonica and D. angusticeps snake venoms trigger thymic epithelial apoptosis following envenomation.

Polyamines as Snake Toxins and Their Probable Pharmacological Functions in Envenomation

While decades of research have focused on snake venom proteins, far less attention has been paid to small organic venom constituents. Using mostly pooled samples, we surveyed 31 venoms (six elapid, six viperid, and 19 crotalid) for spermine, spermidine, putrescine, and cadaverine. Most venoms contained all four polyamines, although some in essentially trace quantities. Spermine is a potentially significant component of many viperid and crotalid venoms (≤0.16% by mass, or 7.9 µmol/g); however, it is almost completely absent from elapid venoms assayed. All elapid venoms contained larger molar quantities of putrescine and cadaverine than spermine, but still at levels that are likely to be biologically insignificant. As with venom purines, polyamines impact numerous physiological targets in ways that are consistent with the objectives of prey envenomation, prey immobilization via hypotension and paralysis. Most venoms probably do not contain sufficient quantities of polyamines to induce systemic effects in prey; however, local effects seem probable. A review of the pharmacological literature suggests that spermine could contribute to prey hypotension and paralysis by interacting with N-methyl-d-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, nicotinic and muscarinic acetylcholine receptors, γ-Aminobutyric acid (GABA) receptors, blood platelets, ryanodine receptors, and Ca²⁺-ATPase. It also blocks many types of cation-permeable channels by interacting with negatively charged amino acid residues in the channel mouths. The site of envenomation probably determines which physiological targets assume the greatest importance; however, venom-induced liberation of endogenous, intracellular stores of polyamines could potentially have systemic implications and may contribute significantly to envenomation sequelae.

Extreme venom variation in Middle Eastern vipers: a proteomics comparison of Eristicophis macmahonii, Pseudocerastes fieldi and Pseudocerastes persicus

Venoms of the viperid sister genera Eristicophis and Pseudocerastes are poorly studied despite their anecdotal reputation for producing severe or even lethal envenomations. This is due in part to the remote and politically unstable regions that they occupy. All species contained are sit and wait ambush feeders. Thus, this study examined their venoms through proteomics techniques in order to establish if this feeding ecology, and putatively low levels of gene flow, have resulted in significant variations in venom profile. The techniques indeed revealed extreme venom variation. This has immediate implications as only one antivenom is made (using the venom of Pseudocerastes persicus) yet the proteomic variation suggests that it would be of only limited use for the other species, even the sister species Pseudocerastes fieldi. The high degree of variation however also points toward these species being rich resources for novel compounds which may have use as lead molecules in drug design and development.

BIOLOGICAL SIGNIFICANCE

These results show extreme venom variation between these closely related snakes. These results have direct implications for the treatment of the envenomed patient.

Autophagy in Trypanosoma brucei: amino acid requirement and regulation during different growth phases

Autophagy in the protozoan parasite, Trypanosoma brucei, may be involved in differentiation between different life cycle forms and during growth in culture. We have generated multiple parasite cell lines stably expressing green fluorescent protein- or hemagglutinin-tagged forms of the autophagy marker proteins, TbAtg8.1 and TbAtg8.2, in T. brucei procyclic forms to establish a trypanosome system for quick and reliable determination of autophagy under different culture conditions using flow cytometry. We found that starvation-induced autophagy in T. brucei can be inhibited by addition of a single amino acid, histidine, to the incubation buffer. In addition, we show that autophagy is induced when parasites enter stationary growth phase in culture and that their capacity to undergo starvation-induced autophagy decreases with increasing cell density.

Extensive inter- and intraspecific venom variation in closely related parasites targeting the same host: the case of Leptopilina parasitoids of Drosophila

The arms race between immune suppressive parasites that produce virulence factors and hosts that evolve resistance to these factors is suggested to be a key driver for the diversification of both partners. However, little is known regarding the diversity of virulence factors in closely related parasites or the mechanisms underlying the variation of virulence. One of the best-described model to address this issue is the interaction between Leptopilina parasitic wasps and their Drosophila hosts, in which variation of virulence is well documented. Thanks to a combined transcriptomic and proteomic approach, we have identified the main secreted proteins in the venom of Leptopilina heterotoma (Gotheron strain, 66 proteins) and of two well-characterized strains of Leptopilina boulardi, ISm and ISy (65 and 49 proteins, respectively). Results revealed significant quantitative differences in venom components between the L. boulardi strains, in agreement with their different virulence properties. Strikingly, the two related Leptopilina species did not share any abundant venom protein. The main identified proteins in L. boulardi were RhoGAPs and serpins while an aspartylglucosaminidase (AGA) was found abundant in L. heterotoma. The extensive quantitative variation observed between these species may be related with their use of different virulence strategies and/or to differences in their host range (specialist versus generalist). Altogether, our data suggests that parasitoid venom can quickly evolve, mainly through rapid changes in regulation of gene expression. It also evidences venom evolutionary processes largely described in other venomous animals i.e. the convergent recruitment of venom proteins between phylogenetically unrelated organisms, and the role of duplications in the emergence of multigenic families of virulence factors.

A self-produced trigger for biofilm disassembly that targets exopolysaccharide

Biofilms are structured communities of bacteria that are held together by an extracellular matrix consisting of protein and exopolysaccharide. Biofilms often have a limited lifespan, disassembling as nutrients become exhausted and waste products accumulate. D-amino acids were previously identified as a self-produced factor that mediates biofilm disassembly by causing the release of the protein component of the matrix in Bacillus subtilis. Here we report that B. subtilis produces an additional biofilm-disassembly factor, norspermidine. Dynamic light scattering and scanning electron microscopy experiments indicated that norspermidine interacts directly and specifically with exopolysaccharide. D-amino acids and norspermidine acted together to break down existing biofilms and mutants blocked in the production of both factors formed long-lived biofilms. Norspermidine, but not closely related polyamines, prevented biofilm formation by B. subtilis, Escherichia coli, and Staphylococcus aureus.

Targeting essential pathways in trypanosomatids gives insights into protozoan mechanisms of cell death

Apoptosis is a normal component of the development and health of multicellular organisms. However, apoptosis is now considered a prerogative of unicellular organisms, including the trypanosomatids of the genera Trypanosoma spp. and Leishmania spp., causative agents of some of the most important neglected human diseases. Trypanosomatids show typical hallmarks of apoptosis, although they lack some of the key molecules contributing to this process in metazoans, like caspase genes, Bcl-2 family genes and the TNF-related family of receptors. Despite the lack of these molecules, trypanosomatids appear to have the basic machinery to commit suicide. The components of the apoptotic execution machinery of these parasites are slowly coming into light, by targeting essential processes and pathways with different apoptogenic agents and inhibitors. This review will be confined to the events known to drive trypanosomatid parasites to apoptosis.

L-amino acid oxidase activity present in fractions of Bothrops jararaca venom is responsible for the induction of programmed cell death in Trypanosoma cruzi

Bothrops jararaca venom induces programmed cell death in epimastigotes of Trypanosoma cruzi. Here we fractionated the venom and observed that the anti-T. cruzi activity was associated with fractions that present L-amino acid oxidase (L-AAO) activity. L-AAO produces H(2)O(2), which is highly toxic. The addition of catalase to the medium, a H(2)O(2) scavenger, reverted the killing capacity of venom fractions. The anti-T. cruzi activity was also abolished when parasites were cultured in a medium without hydrophobic amino acids that are essential for L-AAO activity. These results were confirmed with a commercial purified L-AAO. Treatment for 24 h with fractions that present L-AAO activity induced parasites cytoplasmic retraction, mitochondrial swelling and DNA fragmentation, all morphological characteristics of programmed cell death. Similar changes were also observed when parasites were treated with H(2)O(2). These results indicate that H(2)O(2), the product of L-AAO reaction, induces programmed cell death explaining the anti-T. cruzi activity of B. jararaca venom.

Neuropeptides kill African trypanosomes by targeting intracellular compartments and inducing autophagic-like cell death

Trypanosoma brucei is the causative agent of African sleeping sickness. Available treatments are ineffective, toxic and susceptible to resistance by the parasite. Here we show that various endogenous neuropeptides act as potent antitrypanosome agents. Neuropeptides exerted their trypanolytic activity through an unusual mechanism that involves peptide uptake by the parasite, disruption of lysosome integrity and cytosolic accumulation of glycolytic enzymes. This promotes an energetic metabolism failure that initiates an autophagic-like cell death. Neuropeptide-based treatment improved clinical signs in a chronic model of trypanosomiasis by reducing the parasite burden in various target organs. Of physiological importance is the fact that hosts respond to trypanosome infection producing neuropeptides as part of their natural innate defense. From a therapeutic point of view, targeting of intracellular compartments by neuropeptides suppose a new promising strategy for the treatment of trypanosomiasis.