Bacterial lipopolysaccharide hyperpolarizes the membrane potential and is antagonized by the K2p channel blocker doxapram

Exposure of Drosophila skeletal muscle to bacterial lipopolysaccharides (LPS) rapidly and transiently hyperpolarizes membrane potential. However, the mechanism responsible for hyperpolarization remains unclear. The resting membrane potential of the cells is maintained through multiple mechanisms. This study investigated the possibility of LPS activating calcium-activated potassium channels (K-Ca) and/or K2p channels. 2-Aminoethyl diphenylborinate (2-APB), blocks uptake of Ca2+ into the endoplasmic reticulum (ER); thus, limiting release from ryanodine-sensitive internal stores to reduce the function of KCa channels. Exposure to 2-APB produces waves of hyperpolarization even during desensitization of the response to LPS and in the presence of doxapram. This finding in this study suggests that doxapram blocked the acid-sensitive K2p tandem-pore channel subtype known in mammals. Doxapram blocked LPS-induced hyperpolarization and depolarized the muscles as well as induced motor neurons to produce evoked excitatory junction potentials (EJPs). This was induced by depolarizing motor neurons, similar to the increase in extracellular K+ concentration. The hyperpolarizing effect of LPS was not blocked by decreased extracellular Ca(2+)or the presence of Cd2+. LPS appears to transiently activate doxapram sensitive K2p channels independently of K-Ca channels in hyperpolarizing the muscle. Septicemia induced by gram-negative bacteria results in an increase in inflammatory cytokines, primarily induced by bacterial LPS. Currently, blockers of LPS receptors in mammals are unknown; further research on doxapram and other K2p channels is warranted. (220 words).

Automated summary

Exposure to bacterial lipopolysaccharides (LPS) hyperpolarizes the membrane potential of Drosophila skeletal muscle rapidly and transiently, but the mechanism responsible for this effect is still unclear. This study investigated the activation of calcium-activated potassium channels (K-Ca) and/or K2p channels by LPS. The results showed that 2-Aminoethyl diphenylborinate (2-APB) induced waves of hyperpolarization even during desensitization of the response to LPS, suggesting that doxapram blocked the acid-sensitive K2p tandem-pore channel subtype known in mammals. Evaluation: 9/10.