Objective This study was designed to investigate the immunoregulatory role of α-galactosylceramide (α-GalCer), a ligand for invariant natural killer T (iNKT) cells, on experimental autoimmune myocarditis (EAM) induced in Balb/c mice, and to explore the underlying mechanisms of its action.
Methods Balb/c mice were immunised on day 0 with porcine cardiac myosin to establish the EAM model. All the immunised mice were divided into two groups, the α-GalCer treated group and the EAM group. A dose of α-GalCer (2 μg/mouse/injection) or vehicle (1% phosphate-buffered saline, PBS) was given intraperitoneally at the time of immunisation, and then α-GalCer or PBS was injected on alternate days for 6 weeks. Untreated Balb/c mice (n=10) served as normal controls.
Results All animals were euthanised 1 day after the last injection. Myocardial inflammation was evaluated by H & E staining and the expression levels of C/EBPβ and α-SMA were determined by immunohistochemistry. CD4 CD25 Foxp3+ Tregs and iNKT cells were analysed and sorted by flow cytometry. Western blot analysis was performed to detect MMP-2 and MMP-9 protein expression. Following α-GalCer treatment for 6 weeks, myocardial inflammation improved significantly in the α-GalCer treated group compared to the EAM group. The proportions of CD4 CD25 Foxp3+ regulatory T cells and NK1.1+ iNKT cells were statistically increased in the α-GalCer treated group compared to the EAM and normal control groups. In contrast to the EAM group, α-GalCer treatment significantly increased myocardial MMP-2 and MMP-9 expression. Expression of C/EBPβ increased significantly in the EAM group compared to the α-GalCer treated group and the normal control group. In contrast, the expression of α-SMA in the myocardium did not differ significantly among the three groups.
Conclusion This study demonstrated that α-GalCer alleviates experimental autoimmune myocarditis in Balb/c mice. Thus, α-GalCer represents a potential therapeutic target for autoimmune-inflammation mediated cardiac damage. This study revealed that α-GalCer protects experimental autoimmune myocarditis through upregulation of the proportion of iNKT and Tregs and increased expression of myocardial MMP-2 and MMP-9.