Inhibition of inducible nitric oxide synthase and interleukin-1β expression by tunicamycin in cultured glial cells exposed to lipopolysaccharide.

Endoplasmic reticulum (ER) stress has recently been implicated in human diseases such as Alzheimer׳s disease (AD) and Parkinson׳s disease (PD). However, the link between the immune system, ER stress, and the development of neurodegenerative diseases has not yet been clarified in detail. Mouse primary cultured astrocytes were treated with lipopolysaccharide (LPS) and/or tunicamycin (Tm), and inducible nitric oxide synthase (iNOS) and interleukin (IL)-1β levels were then measured using RT-PCR, ELISA, and Western blotting. Activation of the immune system by LPS triggered inflammatory responses in astrocytes, as measured by the induction of iNOS and IL-1β. Tm-induced ER stress inhibited the LPS-induced expression of IL-1β and iNOS at the protein level. On the other hand, ER stress alone did not induce the expression of IL-1β or iNOS. The inhibitory effect of ER stress on iNOS and IL-1β may not be mediated transcriptionally as we did not observe inhibition at the mRNA level. LPS-induced iNOS protein levels were attenuated by the Tm post-treatment in the absence of LPS. Overall, these results suggest that ER stress negatively regulates the expression of IL-1β and iNOS in LPS-activated astrocytes.