The Study of the Effects of (1S,2E,4R,6R,-7E,11E)-2,7,11-cembratriene-4,6-diol on Microglia Polarization Using an Ischemia in vitro Mode

(1S, 2E, 4R, 6R,-7E, 11E)-2, 7, 11-cembratriene-4, 6-diol (4R) is one of the cembranoids found in tobacco leaves. Previous studies have found that 4R protected acute rat hippocampal slices against neurotoxicity induced by N-methyl-D-aspartate (NMDA) and against the toxic organophosphorus compounds paraoxon and diisopropylfluorophosphate (DFP). Furthermore, 4R reduced the infarct size in a rodent ischemic stroke model and neurodegeneration caused by DFP and 6-hydroxydopamine (6-OHDA). The present study expanded our previous study focusing on the effect of 4R in N9 cells (murine-derived microglia cell line) polarization. The results showed that 4R promoted M2 activation of N9 cells and inhibited M1 activation of N9 cells induced by lipopolysaccharide (LPS) or oxygen glucose deprivation (OGD). LPS or OGD-induced M1 activation marker-inducible nitric oxide synthase (iNOS) of N9 cells was attenuated by 1uM of 4R treatment, which was 69.4% and 56.4% of vehicle control, respectively. In addition, 1uM 4R promoted M2 activation marker-Argnase-1 of N9 cells under LPS or OGD conditions, which was 192.7% and 188.0% of vehicle control, respectively. Furthermore, the conditioned medium of 4R-treated post-OGD N9 cells protected neuro2a cells from OGD-induced injury. The cells viability increased by 54.5% by treatment with the conditioned medium of 4R-treated post-OGD N9 cells compared with the conditioned medium from post-OGD N9 cells without 4R. Furthermore, cytokines release measured by ELISA showed that 4R increased anti-inflammatory cytokine IL-10 production and inhibited pro-inflammatory cytokine TNF-alpha release from N9 cells induced by OGD.;In conclusion, the present study indicates that 4R exhibits anti-inflammatory properties by modulating polarization of microglia toward M2 subtype.