Olanzapine Induces Inflammation and Immune Response via Activating ER Stress in the Rat Prefrontal Cortex

Antipsychotics, in particular olanzapine, are first-line medications for schizophrenia. The prefrontal cortex (PFC) is an important region for antipsychotics' therapeutic effects. The PFC inflammatory and immune pathways are associated with schizophrenia pathogenesis. However, the effect of antipsychotics on the inflammatory and immune pathways in the PFC remains unclear. We aimed to examined the time-dependent effect of olanzapine on inflammatory and immune markers in the PFC of rats. Since the inflammatory and immune pathways are related to endoplasmic reticulum (ER) stress, we further investigated whether or not olanzapine-induced inflammation and immune responses were related to ER stress.

Expression of pro-inflammatory markers including IkappaB kinase β (IKKβ), nuclear factor kappa B (NFκB), tumor necrosis factor α (TNF-α), interleukin-6 (IL-6) and IL-1β, and immune-related proteins including inducible nitric oxide synthase (iNOS), toll-like receptor 2 (TLR2) and cluster of differentiation 14 (CD14) were examined by Western blotting.

Olanzapine treatments for 1, 8 and 36 days significantly activated the inflammatory IKKβ/NFκB signaling, and increased the expression of TNF-α, IL-6, IL-1β and immune-related proteins such as iNOS, TLR4 and CD14. Olanzapine treatment for 1 day, 8 and 36 days also induced ER stress in the PFC. Co-treatment with an ER stress inhibitor, 4-phenylbutyrate, inhibited olanzapine-induced inflammation and the immune response in the PFC.

These results suggested olanzapine exposure could be a factor that induces central inflammation and immunological abnormities in schizophrenia subjects. Olanzapine induces PFC inflammation and immune response, possibly via activating ER stress signaling.