Activation of cellular functions in macrophages by venom secretory Asp-49 and Lys-49 phospholipases A(2)

Area of Science:

• Immunology
• Biochemistry
• Toxicology

Background:

• Snake venom components, particularly phospholipase A(2) myotoxins, play significant roles in envenomation.
• Understanding the immunomodulatory effects of snake venom toxins is crucial for developing effective antivenoms and therapeutics.

Purpose of the Study:

• To investigate the in vitro effects of myotoxin III (MT-III), an Asp-49 catalytically-active phospholipase A(2), and myotoxin II (MT-II), a Lys-49 variant, on macrophage phagocytosis and hydrogen peroxide production.
• To determine the cytotoxic concentrations of MT-II and MT-III on mouse peritoneal macrophages.

Main Methods:

• Isolation of myotoxin II (MT-II) and myotoxin III (MT-III) from Bothrops asper snake venom.
• Assessment of cytotoxicity of MT-II and MT-III on mouse peritoneal macrophages.
• Measurement of phagocytosis mediated by Fcgamma, complement, mannose, and beta-glucan receptors.
• Quantification of hydrogen peroxide (H(2)O(2)) production by thioglycollate-elicited macrophages stimulated with MT-II and MT-III.

Main Results:

• MT-II and MT-III exhibited cytotoxicity at concentrations above 25 microg/ml.
• At non-cytotoxic concentrations, MT-II stimulated phagocytosis via Fcgamma, complement, mannose, and beta-glucan receptors.
• MT-III stimulated phagocytosis primarily through mannose and beta-glucan receptors.
• Both myotoxins induced H(2)O(2) release; MT-III was a more potent stimulator than MT-II across tested concentrations.

Conclusions:

• At non-cytotoxic concentrations, MT-II and MT-III activate macrophage defense mechanisms.
• These myotoxins upregulate phagocytosis, particularly via mannose and beta-glucan receptors.
• MT-II and MT-III effectively stimulate the respiratory burst, leading to increased H(2)O(2) production.