The role of the novel small molecule QUIN-A in suppressing neuroinflammation and its target

•MyD88 is an important regulatory protein of neuroinflammation. Targeting MyD88 can inhibit TLR4 Signal transduction.•QUIN-A is a targeted inhibitor of MyD88, which can inhibit neuroinflammation.•QUIN-A is a potential anti-inflammatory small molecule, which is worthy of further study. Myeloid differentiation protein 88 (MyD88) is an important accessory protein of Toll-like receptor 4 (TLR4) Signal. Inhibiting MyD88 protein can inhibit the activation of TLR4 Signal, so it is particularly important to explore the small molecule inhibitor of MyD88. This study discovered that a kind of quinazoline derivative small molecule (QUIN-A) specifically suppressed MyD88. lipopolysaccharide（LPS） was used to induce inflammatory response in microglial cells BV2. Thereafter, cell apoptosis was detected by flow cytometry, propidium iodide（PI） staining, and Hoechst 33342 staining, while the levels of inflammatory factors were measured through enzyme linked immunosorbent assay (ELISA). In addition, the expression of superoxidedismutase（SOD）and Malondialdehyde（MDA）was detected by test kit, respectively, whereas that of TLR4 and MyD88 was observed by immunofluorescence (IF) staining, and the levels of TLR4 and MyD88 proteins were analyzed through Western blotting (WB) assay. The results suggested that QUIN-A suppressed the inflammatory injury in BV2 cells, decreased the cell apoptosis level and reduced the inflammatory factor levels in the culture medium. Besides, the expression levels of TLR4 and MyD88 in cells were down-regulated. In animal experiments, QUIN-A reduced the inflammatory factor levels in cerebrospinal fluid (CSF), but it did not significantly affect the serum inflammatory factors. At the same time, QUIN-A down-regulated the expression of TLR4 and MyD88 proteins. By pull-down assay, we discovered that QUIN-A specifically bound to MyD88 and served as the inhibitor of MyD88. QUIN-A bound to MyD88 and suppressed the transduction of TLR4 signal, thus exerting the anti-inflammation effect.