The effects of bupivacaine and brevetoxin on RAW 264.7 macrophage inflammatory responses are not modulated by plasma membrane voltage-gated sodium ion channels 2231

Abstract Description Macrophages are leukocytes that are an integral part of the innate immune system. Recently, we have shown that the red tide toxin, brevetoxin, and the local anesthetic, bupivacaine, modulate the release of inflammatory cytokines from RAW 264.7 macrophage cells. Both bupivacaine and brevetoxin bind to voltage-gated sodium ion channels (VGSCs), found on the plasma membrane. In this study, we determine if the mechanism of action of brevetoxin and bupivacaine on macrophage cells is through the modulation of VGSCs by conducting whole-cell patch-clamp electrophysiology experiments. Activation and inactivation patch-clamp protocols were conducted to measure gating properties of VGSCs on RAW 264.7 macrophages in the presence and absence of lipopolysaccharide, a macrophage activator, as well as control neuronal pituitary GH3 cells that are known to express native VGSCs. Our study reveals that GH3 cell VGSCs are affected by both bupivacaine and brevetoxin. Bupivacaine served as a sodium channel antagonist as sodium ion currents were blocked in GH3 cells. Unlike bupivacaine, brevetoxin activated the VGSCs in GH3 cells. On the other hand, it was shown that macrophage cells do not express any VGSCs on their plasma membrane as no sodium ion currents were detected upon depolarizing test pulses. The data in this study illustrates that brevetoxin and bupivacaine effects on inflammatory responses from macrophage cells are not due to modulation of plasma membrane bound VGSCs. Funding Sources This study was supported by the Holmes Development Fund Grant from the Whitaker Center at FGCU Topic Categories Innate Immune Responses and Host Defense: Molecular Mechanisms (INM)