Intracortical Ceramides Prime Microglia Activation and Anxiety-like Behavior in Mice

Ceramides (CER) are bioactive lipids involved in inflammation, stress response, and metabolism. Ceramide dysregulation in the brain has been linked to neuroinflammation and psychiatric-related behaviors. Here, we aimed to elucidate the role of intracortical long-chain ceramides on microglia activation and neuroinflammation leading to anxiety-like behavior in mice.

Mice received a stereotaxic microinjection of C16:0, C18:0, C22:0, C24:0, and C24:1 ceramides into the M1 cortical nucleus, and behavioral phenotyping was performed using the elevated plus maze (EPM), open field (OF), and light-dark box (LDB) tests to assess anxiety-like traits. Proinflammatory profile and microglial activation were determined by qPCR for IL6, IL1B, TNFα, and TREM2; CD68 markers; and histological analysis using H&E, Nissl, and Iba1 immunostaining for microglial morphology.

Intracortical long-chain ceramides prime anxiety-like behavior in mice, as evidenced by reduced time on the open arms during the EPM, decreased exploration in the OF, and increased preference for the dark compartment during the LDB. Also, long-chain ceramides promoted upregulation of TNFα, IL6, IL1B, TREM2, and CD68 gene expression in the M1 cortical nucleus. Histological analysis revealed increased glial density without significant neuronal loss, while robust microglial amoeboid morphology was evidenced by Iba1 staining. Biological modeling supports the association of ceramide administration into the M1 cortical nucleus and proinflammatory profiles and microglial activation with anxiety-like behavior in mice.

Long-chain ceramide inoculation into the M1 cortical nucleus promotes anxiety-like behavior in mice, likely driven by neuroinflammatory mechanisms involving microglial activation.

Ceramides modulate neuroimmune activation and contribute to anxiety susceptibility in mice, offering new insights into lipid-mediated pathways underlying neuropsychiatric disorders.