Ginsenoside Rg1 ameliorated experimental colitis by regulating the balance of M1/M2 macrophage polarization and the homeostasis of intestinal flora

Abstract Background: Aberrant M1/M2 macrophage polarization and intestinal flora disruption are involved in the pathological processes associated with ulcerative colitis (UC). Ginsenoside Rg1 has good immunomodulatory and anti-inflammatory effects and is effective in treating UC of humans and animals. However, it is unclear how ginsenoside Rg1 regulate the homeostasis of M1/M2 macrophage polarization and intestinal flora.Methods: BALB/c mice were randomly divided into 4 groups: Control, DSS, DSS+Rg1, DSS+Y27632 groups. In this study, experiment colitis was induced in BALB/c mice using sodium dextran sulfate (DSS). Mice of DSS+Rg1, DSS+Y27632 groups were treated respectively with ginsenoside Rg1 and Rock inhibitor Y27632 for 14 consecutive days. On day 21, all mice were sacrificed. Histopathological analysis of the colon tissues was performed by Hematoxylin Eosin sinning. Cytokines (IL-6, IL-33, CCL-2, TNF-α, IL-4 and IL-10) were detected by Elisa. Flow cytometry was used to analyse macrophage activation and M1/M2 macrophage polarisation. Western blotting were applied to detect the levels of Macrophage polarization-associated protein (Arg-1, MIF-1, PIM-1, TLR2) and Nogo-B/RhoA signaling molecules (Rock1, RhoA and Nogo-B). The fecal microbial populations were analyzed using 16S gene sequencing. Results: After ginsenoside Rg1 and Y27632 treatment, the changes of body weight, colon length, colonic weight index and colonic mucosal injury of colitis mice were effectively improved, accompanied by less ulcer formation and inflammatory cell infiltration, lower levels of pro-inflammatory cytokines (IL-6, IL-33, CCL-2, TNF-α) and higher anti-inflammatory cytokines (IL-4 and IL-10). Importantly, the percentage of CD11b+F4/80+, CD11b+F4/80+Tim-1+, CD11b+F4/80+TLR4+, and CD11b+F4/80+iNOS+ cells and the expression levels of MIF-1 and PIM-1 proteins were down-regulated significantly after ginsenoside Rg1 and Y27632 treatment, and CD11b+F4/80+CD206+ and CD11b+F4/80+CD163+ cells and Arg-1 up-regulated significantly. Intestinal flora composition were effectively improved after administration of ginsenoside Rg1. The Nogo-B/RchoA signaling pathway were obviously inhibited after ginsenoside Rg1 and Y27632 treatment, and the levels of Rock1, RhoA and Nogo-B proteins were significantly reduced. Conclusions: Ginsenoside Rg1 has the protective effect on UC by inhibiting macrophage activation, restoring the balance of M1/M2 macrophage polarization, and improving intestinal flora composition, associated with inhibition of the Nogo-B/RhoA signaling pathway.

AbstractThe decrease of neurotransmitter dopamine (DA) levels in the intestine is closely related to the development of inflammatory bowel disease (IBD). However, the functional relevance and underlying mechanistic basis of the effects of DA signaling on IBD remains unclear. Here, we observed that the DRD5 receptor is highly expressed in colonic macrophages, and the deficiency of DA-DRD5 signaling exacerbated experimental colitis. Moreover, DA-DRD5 signaling can inhibit M1 by negatively regulating NF-κB signaling but promote M2 macrophage polarization through activation of the CREB pathway, respectively. The deficiency of DRD5 signaling increased colonic M1 macrophages but reduced M2 cells during colitis. Additionally, the administration of a D1-like agonist that has a higher affinity to DRD5 can attenuate the colitogenic phenotype of mice. Collectively, these findings provide the first demonstration of DA-DRD5 signaling in colonic macrophages controlling the development of colitis by regulating M1/M2 macrophage polarization.

Curcumin has shown good efficacy in mice with experimental colitis and in patients with ulcerative colitis, but the mechanism of action through the regulation of M1/M2 macrophage polarization has not been elaborated. The ulcerative colitis was modeled by dextran sulfate sodium; colitis mice were orally administrated with curcumin (10 mg/kg/day) or 5-ASA (300 mg/kg/day) for 14 consecutive days. After curcumin treatment, the body weight, colon weight and length, colonic weight index, and histopathological damage in colitis mice were effectively improved. The concentrations of proinflammatory cytokines IL-1β, IL-6, and CCL-2 in the colonic tissues of colitis mice decreased significantly, while anti-inflammatory cytokines IL-33 and IL-10 increased significantly. Importantly, macrophage activation was suppressed and M1/M2 macrophage polarization was regulated in colitis mice, and the percentage of CD11b+F4/80+ and CD11b+F4/80+TIM-1+ and CD11b+F4/80+iNOS+ decreased significantly and CD11b+F4/80+CD206+ and CD11b+F4/80+CD163+ increased significantly. Additionally, curcumin significantly downregulated CD11b+F4/80+TLR4+ macrophages and the protein levels of TLR2, TLR4, MyD88, NF-κBp65, p38MAPK, and AP-1 in colitis mice. Our study suggested that curcumin exerted therapeutic effects in colitis mice by regulating the balance of M1/M2 macrophage polarization and TLRs signaling pathway.

Background: Nucleolin has multiple functions within cell survival and proliferation pathways. Our previous studies have revealed that nucleolin can significantly reduce myocardial ischemia-reperfusion injury by promoting myocardial angiogenesis and reducing myocardial apoptosis. In this study, we attempted to determine the role of nucleolin in myocardial infarction (MI) injury recovery and the underlying mechanism. Methods: Male BALB/c mice aged 6–8 weeks were used to set up MI models by ligating the left anterior descending coronary artery. Nucleolin expression in the heart was downregulated by intramyocardial injection of a lentiviral vector expressing nucleolin-specific small interfering RNA. Macrophage infiltration and polarization were measured by real-time polymerase chain reaction, flow cytometry, and immunofluorescence. Cytokines were detected by enzyme-linked immunosorbent assay. Results: Nucleolin expression in myocardium after MI induction decreased a lot at early phase and elevated at late phase. Nucleolin knockdown impaired heart systolic and diastolic functions and decreased the survival rate after MI. Macrophage infiltration increased in the myocardium after MI. Most macrophages belonged to the M1 phenotype at early phase (2 days) and the M2 phenotype increased greatly at late phase after MI. Nucleolin knockdown in the myocardium led to a decrease in M2 macrophage polarization with no effect on macrophage infiltration after MI. Furthermore, Notch3 and STAT6, key regulators of M2 macrophage polarization, were upregulated by nucleolin in RAW 264.7 macrophages. Conclusions: Lack of nucleolin impaired heart function during recovery after MI by reducing M2 macrophage polarization. This finding probably points to a new therapeutic option for ischemic heart disease.