Snakebite envenoming is a
neglected tropical disease affecting millions of people every year, especially in vulnerable rural populations in the developing world. Viperid snakes cause envenomings characterized by a complex pathophysiology which includes local and systemic
hemorrhage due to the action of
snake venom metalloproteinases (SVMPs). The pathogenesis of SVMP-induced systemic
hemorrhage has not been investigated in detail. This study explored the pulmonary
hemorrhage induced in a murine model by a P-III SVMP from the
venom of Crotalus simus. Histological analysis revealed extravasation in the lungs as early as 15 min after
intravenous injection of the toxin, and
hemorrhage increased at 360 min. Western blot analysis demonstrated the cleavage of basement membrane (BM)
proteins in lung homogenates and in bronchoalveolar lavage fluid, implying an enzymatic disruption of this extracellular matrix structure at the capillary-alveolar barrier. Likewise, alveolar
edema was observed, with an increment in
protein concentration in the bronchoalveolar lavage fluid, and a neutrophil-rich inflammatory infiltrate was present in the parenchyma of the lungs as part of the inflammatory reaction. Pretreatment of mice with
indomethacin,
pentoxifylline and an anti-neutrophil antibody resulted in a significant decrease in pulmonary
hemorrhage at 360 min. These findings suggest that this P-III SVMP induces
acute lung injury through the direct action of this
enzyme in the capillary-alveolar barrier integrity, as revealed by BM degradation, and as a consequence of the inflammatory reaction that develops in lung tissue. Our findings provide novel clues to understand the mechanism of action of hemorrhagic SVMPs in the lungs.