Nimodipine reduces microglial activation in vitro as evidenced by morphological phenotype, phagocytic activity and high-throughput RNA sequencing.

BACKGROUND AND PURPOSE: Nimodipine, an L-type voltage-gated calcium channel blocker, is an approved cerebral vasorelaxant. We hypothesized that nimodipine attenuates the pro-inflammatory shift in microglial phenotypes. Here, we analysed the effects of nimodipine on morphological and functional microglial phenotypes as well as their transcriptomic profile.

EXPERIMENTAL APPROACH: Live brain slice preparations from C57BL/6 mice and primary microglia cultures from neonatal Sprague Dawley rats were used. Microglia were activated either by ischemia or lipopolysaccharide (LPS), and preparations were treated with nimodipine (5-10-20 μM). Microglial morphological phenotypes, phagocytic activity, Iba1 expression and TNF-α levels were evaluated. Total RNA was isolated from monocultures and processed for next generation RNA sequencing.

KEY

RESULTS

LPS resulted in a pro-inflammatory microglial phenotype, affecting the expression of cytokines, the complement system and phagocytosis-related genes. LPS increased the transcription of ionotropic purinergic and TRP channels but decreased the expression of voltage- and ligand-gated calcium channels, down-regulated the expression of Ryr and IP3 receptors and increased transcription of the SERCA calcium pump. Nimodipine suppressed the amoeboid morphological transformation and phagocytosis and altered the expression of 110 genes in the opposite direction to LPS activation, of which at least 20 were associated with the microglial immune response, seven with cell adhesion and two with autophagy regulation.

CONCLUSION AND IMPLICATIONS: The effect of nimodipine goes beyond cerebral vasorelaxation. Nimodipine attenuates microglial activation by modulating Ca2+-dependent gene expression involved in intracellular signalling cascades to drive microglial immune responses. Consideration should be given to expanding the use of nimodipine beyond vasorelaxation.