A new insight into the cellular mechanisms of envenomation: Elucidating the role of extracellular vesicles in Loxoscelism

A review on snake venom extracellular vesicles: Past to present

Around 95% of snake venom is protein. Along with the soluble proteins, snake venom also contains proteins encapsulated in vesicles known as Snake Venom Extracellular Vesicles (SVEV). SVEVs are nano-sized membrane-bound vesicles released from the snake venom gland cells. The available published research works on SVEVs are minimal. Extracellular vesicles in the Snake Venom gland were initially discovered during the histopathological analysis of the Crotalus durissus terrificus snakes' venom gland. Later, various techniques were employed to isolate and characterize the SVEVs. The cargo of SVEV consists of a variety of proteins like Phospholipase A-2, C-type Lectins, L-Amino Acid Oxidase, Cysteine-Rich Secretory Proteins, Serine Proteinases, Dipeptidyl Peptidase-IV, Aminopeptidase-A, Ecto-5'-nucleotidases, Disintegrins. Proteomic data revealed the presence of some exclusive proteins in the SVEVs, and the other proteins are in varying concentrations in the SVEVs compared to their whole Venom. Interaction of SVEVs with mammalian cell lines showed the disruption of primary physiological functions leads to host immune modulation, and long-term effects of envenoming. Snakebite victim's blood showed variations in the specific Extracellular vesicle concentration. It has been hypothesized that SVEVs are responsible for long-term toxicity. The current review focuses on the various techniques adopted to isolate and characterize SVEVs and discusses the exclusiveness and variations of SVEV proteins and their role in snakebites.

[Loxoscelism with acute compartment síndrome: A case report with successful conclusion]

BACKGROUND

Loxoscelism is a toxic clinical condition caused by the bite of spiders of the genus Loxosceles, with wide distribution throughout the world.1 Phospholipase D is responsible for dermonecrosis, inflammation, platelet aggregation, hemolysis, alteration of vascular permeability, cytotoxicity, nephrotoxicity, acute renal failure, among other symptoms involved with this protein.

CASE REPORT

27-year-old male patient, who began with a sudden episode of intense pain in the right hand, in the metacarpus and metacarpophalangeal joints. On clinical examination, the upper extremity was noted to have increased volume, extensive edema, hyperemia, and increased local temperature; The lesion progressed to extensive necrosis. Fasciotomies were performed, from distal to proximal, and release of the second and third finger compartment through longitudinal radial and ulnar incisions. A skin autograft was placed, obtained from the anterior surface of the right thigh. Opioid analgesics, non-steroidal anti-inflammatory drugs, corticosteroids, and antibiotics were administered. The skin biopsy reported: inflammatory infiltrate with neutrophils, ulceration, and bacterial colonies. After 27 days he had a favorable evolution, so he was discharged to his home, with follow-up by staff from the Outpatient Service.

CONCLUSION

Cutaneous loxoscelism, as a cause of acute compartment syndrome of the hand, is rare, but should be considered in an area endemic for Loxosceles spp. Surgical decompression of the affected compartments represents a decisive factor in the treatment of patients.

Extracellular Vesicles from Bothrops jararaca Venom Are Diverse in Structure and Protein Composition and Interact with Mammalian Cells

Snake venoms are complex cocktails of non-toxic and toxic molecules that work synergistically for the envenoming outcome. Alongside the immediate consequences, chronic manifestations and long-term sequelae can occur. Recently, extracellular vesicles (EVs) were found in snake venom. EVs mediate cellular communication through long distances, delivering proteins and nucleic acids that modulate the recipient cell's function. However, the biological roles of snake venom EVs, including possible cross-organism communication, are still unknown. This knowledge may expand the understanding of envenoming mechanisms. In the present study, we isolated and characterized the EVs from Bothrops jararaca venom (Bj-EVs), giving insights into their biological roles. Fresh venom was submitted to differential centrifugation, resulting in two EV populations with typical morphology and size range. Several conserved EV markers and a subset of venom related EV markers, represented mainly by processing enzymes, were identified by proteomic analysis. The most abundant protein family observed in Bj-EVs was 5'-nucleotidase, known to be immunosuppressive and a low abundant and ubiquitous toxin in snake venoms. Additionally, we demonstrated that mammalian cells efficiently internalize Bj-EVs. The commercial antibothropic antivenom partially recognizes Bj-EVs and inhibits cellular EV uptake. Based on the proteomic results and the in vitro interaction assays using macrophages and muscle cells, we propose that Bj-EVs may be involved not only in venom production and processing but also in host immune modulation and long-term effects of envenoming.