In the Brazilian Amazon, Bothrops atrox snakebites are frequent, and patients develop tissue damage with blisters sometimes observed in the proximity of the wound. Antivenoms do not seem to impact blister formation, raising questions regarding the mechanisms underlying blister formation. Here, we launched a clinical and laboratory-based study including five patients who followed and were treated by the standard clinical protocols. Blister fluids were collected for proteomic analyses and molecular assessment of the presence of venom and antivenom. Although this was a small patient sample, there appeared to be a correlation between the time of blister appearance (shorter) and the amount of venom present in the serum (higher). Of particular interest was the biochemical identification of both venom and antivenom in all blister fluids. From the proteomic analysis of the blister fluids, all were observed to be a rich source of damage-associated molecular patterns (DAMPs), immunomodulators, and matrix metalloproteinase-9 (MMP-9), suggesting that the mechanisms by which blisters are formed includes the toxins very early in envenomation and continue even after antivenom treatment, due to the pro-inflammatory molecules generated by the toxins in the first moments after envenomings, indicating the need for local treatments with anti-inflammatory drugs plus toxin inhibitors to prevent the severity of the wounds.

Snake venom metalloproteinases (SVMPs) play an important role in local tissue damage of snakebite patients, mostly by hydrolysis of basement membrane (BM) components. We evaluated the proinflammatory activity of SVMPs Atroxlysin-Ia (ATXL) and Batroxrhagin (BATXH) from Bothrops atrox venom and their hydrolysis products of Matrigel. BALB/c mice were injected with SVMPs (2 μg), for assessment of paw edema and peritoneal leukocyte accumulation. Both SVMPs induced edema, representing an increase of ~70% of the paw size. Leukocyte infiltrates reached levels of 6 × 10⁶ with ATXL and 5 × 10⁶ with BATXH. TNF-α was identified in the supernatant of BATXH—or venom-stimulated MPAC cells. Incubation of Matrigel with the SVMPs generated fragments, including peptides from Laminin, identified by LC–MS/MS. The Matrigel hydrolysis peptides caused edema that increased 30% the paw size and promoted leukocyte accumulation (4–5 × 10⁶) to the peritoneal cavity, significantly higher than Matrigel control peptides 1 and 4 h after injection. Our findings suggest that ATXL and BATXH are involved in the inflammatory reaction observed in B. atrox envenomings by direct action on inflammatory cells or by releasing proinflammatory peptides from BM proteins that may amplify the direct action of SVMPs through activation of endogenous signaling pathways.