A snake venom group IIA PLA with immunomodulatory activity induces formation of lipid droplets containing 15-d-PGJ in macrophages.

Crotoxin B (CB) is a catalytically active group IIA sPLA from Crotalus durissus terrificus snake venom. In contrast to most GIIA sPLAs, CB exhibits anti-inflammatory effects, including the ability to inhibit leukocyte functions. Lipid droplets (LDs) are lipid-rich organelles associated with inflammation and recognized as a site for the synthesis of inflammatory lipid mediators. Here, the ability of CB to induce formation of LDs and the mechanisms involved in this effect were investigated in isolated macrophages. The profile of CB-induced 15-d-PGJ (15-Deoxy-Delta-12,14-prostaglandin J) production and involvement of LDs in 15-d-PGJ biosynthesis were also investigated. Stimulation of murine macrophages with CB induced increased number of LDs and release of 15-d-PGJ. LDs induced by CB were associated to PLIN2 recruitment and expression and required activation of PKC, PI3K, MEK1/2, JNK, iPLA and PLD. Both 15-d-PGJ and COX-1 were found in CB-induced LDs indicating that LDs contribute to the inhibitory effects of CB by acting as platform for synthesis of 15-d-PGJ, a pro-resolving lipid mediator. Together, our data indicate that an immunomodulatory GIIA sPLA can directly induce LD formation and production of a pro-resolving mediator in an inflammatory cell and afford new insights into the roles of LDs in resolution of inflammatory processes.