RESUMEN
Toll-like receptors are an integral part of innate immunity in the central nervous system (CNS); they orchestrate a robust defense in response to both exogenous and endogenous danger signals. Recently, toll-like receptor 4 (TLR4) has emerged as a therapeutic target for the treatment of CNS-related diseases such as sepsis and chronic pain. We herein report a chemical biology approach by using a rationally designed peptide inhibitor to disrupt the TLR4-MD2 association, thereby blocking TLR4 signaling.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/antagonistas & inhibidores , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Péptidos/farmacología , Receptor Toll-Like 4/antagonistas & inhibidores , Receptor Toll-Like 4/metabolismo , Proteínas Adaptadoras Transductoras de Señales/química , Animales , Línea Celular , Biología Computacional , Antígeno 96 de los Linfocitos , Ratones , Modelos Moleculares , Péptidos/síntesis química , Unión Proteica/efectos de los fármacos , Conformación Proteica , Receptor Toll-Like 4/químicaRESUMEN
Recent data suggest that opioids can activate immune-like cells of the central nervous system (glia). This opioid-induced glial activation is associated with decreased analgesia, owing to the release of proinflammatory mediators. Here, we examine in rats whether the putative microglial inhibitor, minocycline, may affect morphine-induced respiratory depression and/or morphine-induced reward (conditioned place preference). Systemic co-administration of minocycline significantly attenuated morphine-induced reductions in tidal volume, minute volume, inspiratory force, and expiratory force, but did not affect morphine-induced reductions in respiratory rate. Minocycline attenuation of respiratory depression was also paralleled with significant attenuation by minocycline of morphine-induced reductions in blood oxygen saturation. Minocycline also attenuated morphine conditioned place preference. Minocycline did not simply reduce all actions of morphine, as morphine analgesia was significantly potentiated by minocycline co-administration. Lastly, morphine dose-dependently increased cyclooxygenase-1 gene expression in a rat microglial cell line, an effect that was dose-dependently blocked by minocycline. Together, these data support that morphine can directly activate microglia in a minocycline-suppressible manner and suggest a pivotal role for minocycline-sensitive processes in the mechanisms of morphine-induced respiration depression, reward, and pain modulation.