Effects of graphene oxide slice on neuro-immunity modulation of microglia cells

Background Graphene oxide (GO) is widely applied to neuroscience. Recent studies have shown that GO can regulate the nervous system, but there are limited reports about the mechanism underlying its neuro-immunity modulation.

Objective This experiment is designed to investigate the regulation of GO towards M1/M2 polarization of microglia induced by lipopolysaccharide (LPS) and interleukin-4 (IL-4).

Methods BV2 cells cultured on GO substrate and control medium were added with 20μg·L^-1 LPS and IL-4 respectively to induce M1/M2 phenotype of BV2 cells, and were divided into blank control group, GO control group, LPS control group, IL-4 control group, GO-LPS group, and GO-IL-4 group. After 24 h of incubation, the number of cells was counted. The expression levels of M1 markerstumor necrosis factor α (TNF-α), inducible nitric oxide synthase (iNOS), and cytokine CD86 and M2 markersrecombinant human arginase-1 (Arg1), interleukin-10 (IL-10), and cytokine CD206) were detected by real-time fluorescence quantitative PCR (RT-qPCR) and flow cytometry, and the NO concentration in supernatant was measured by spectrophotometry.

Results After the designed GO treatment, the number of BV2 cells was decreased (218.13±8.77 and 175.63±8.24) compared with the blank control group (P < 0.05). The mRNA expression levels of M1 markers TNF-α (8.16±0.26 and 5.35±0.42), iNOS (45.64±2.03 and 30.39±1.84), CD86 positive rate(14.65±0.85)% and (10.29±0.46)%, and NO production(19.62±1.07) μmol·L^-1 and (8.37±1.25) μmol·L^-1 were all decreased in the GO-LPS group, as well as the mRNA expression levels of M2 marker IL-10 (1.63±0.09 and 2.09±0.15) increased, compared with the LPS control group (P < 0.05). Under the IL-4 inducement, the mRNA expression level of M1 marker iNOS was upregulated (0.41±0.03 and 1.05±0.07), the levels of Arg1 (201.63±12.31 and 4.74±0.38) and IL-10 (2.63±0.14 and 0.71±0.13) were downregulated, and the positive rate(17.01±1.03)% and (3.66±0.41)% and average fluorescence intensity (8 893.2±347.62 and 1 299.9±159.67) in the GO-IL-4 group (P < 0.01).

Conclusion GO inhibits the growth of BV2 cells and regulates the activation of microglia to resist the effects of LPS/IL-4 induced microglial polarization.