Inhibitory effects of berberine on proinflammatory M1 macrophage polarization through interfering with the interaction between TLR4 and MyD88

Abstract

BackgroundsInflammation is recognized as the key pathological mechanism of type 2 diabetes. The hypoglyceamic effects of berberine (BBR) are related to the inhibition of the inflammatory response, but the mechanism is not completely clear.MethodsThe inflammatory polarization of Raw264.7 cells and primary peritoneal macrophages were induced by LPS, and then effects and underlying mechanisms of BBR were explored. An inflammatory model was established by LPS treatment at different concentrations for different treatment time. An ELISA assay was used to detect the secretions of TNF-α. RT-PCR was applied to detect M1 inflammatory factors. The F4/80+ ratio and CD11c+ ratio of primary peritoneal macrophages were determined by flow cytometry. The expressions of p-AMPK and TLR4 were detected by Western blot. The cytoplasmic and nuclear distributions of NFκB p65 were observed by confocal microscopy. The binding of TLR4 to MyD88 was tested by CoIP, and the affinity of BBR for TLR4 was assessed by molecular docking.ResultsUpon exposure to LPS, the secretion of TNF-α and transcription of inflammatory factors in macrophages increased, cell morphology changed and protrusions appeared gradually, the proportion of F4/80+CD11c+ M1 macrophages increased, and the nuclear distribution of NFκB p65 increased. BBR pretreatment partially inhibited the changes mentioned above. However, the expression of TLR4 and p-AMPK did not change significantly after LPS intervention for 3 h. Meanwhile, CoIP showed that the interaction between TLR4 and MyD88 increased, and BBR inhibited the binding. Molecular docking suggested that BBR might interact with TLR4.ConclusionsInflammatory changes were induced in macrophages after LPS stimulation for 3 h, and BBR pretreatment inhibited inflammatory polarization. BBR might interact with TLR4 and disturb TLR4/MyD88/NFκB signalling pathway, and it might be the mechanism by which BBR attenuated inflammation in the early phase.

Berberine Alleviates Insulin Resistance and Inflammation via Inhibiting the LTB4–BLT1 Axis

“…Recent studies showed that BBR decreased hyperglycemia, alleviated insulin resistance, and inhibited lipid synthesis possibly via the activation of adenosine monophosphate-activated protein kinase (AMPK) ( Turner et al, 2008 ). Our previous study demonstrated that the MyD88/NF-κB pathway was the target inflammation pathway of BBR ( Gong et al, 2019 ). The MyD88/NF-κB pathway was also known as the downstream pathway of the LTB4 pathway ( Sánchez-Galán et al, 2009 ), which was verified in our study.…”

TLR7 modulating B-cell immune responses in the spleen of C57BL/6 mice infected with Schistosoma japonicum

“…TLRs–MyD88–NF-κB p65 was the most classical signaling pathway to stimulate APCs [ 49 , 50 ]. It is also reported that the TLR-MyD88-STAT3 pathway could be activated in human B cells to boost antibody production [ 51 ].…”

Macrophage Polarization and Its Role in Liver Disease

“…Recently, a variety of drugs have been shown to inhibit M1 macrophage polarization by inhibiting the TLR4/NF-κB signaling pathway. For example, berberine could competitively inhibit the combination of TLR4 and MyD88 to inhibit the TLR4/MyD88/NF-κB signaling pathway, thus inhibiting M1 macrophage polarization ( 37 ). Similarly, quercetin downregulated the expression of NF-κB and IRF5, and then inhibited the activity of upstream TLR4/MyD88 to inhibit M1 polarization ( 38 , 39 ).…”