Mannose receptor modulates macrophage polarization and allergic inflammation through miR-511-3p

Mannose receptor (MRC1/CD206) has been suggested to mediate allergic sensitization and asthma to multiple glycoallergens, including cockroach allergens.

We sought to determine the existence of a protective mechanism through which MRC1 limits allergic inflammation through its intronic miR-511-3p.

We examined MRC1-mediated cockroach allergen uptake by lung macrophages and lung inflammation using C57BL/6 wild-type (WT) and Mrc1^-/- mice. The role of miR-511-3p in macrophage polarization and cockroach allergen-induced lung inflammation in mice transfected with adeno-associated virus (AAV)-miR-511-3p (AAV-cytomegalovirus-miR-511-3p-enhanced green fluorescent protein) was analyzed. Gene profiling of macrophages with or without miR-511-3p overexpression was also performed.

Mrc1^-/- lung macrophages showed a significant reduction in cockroach allergen uptake compared with WT mice, and Mrc1^-/- mice had an exacerbated lung inflammation with increased levels of cockroach allergen-specific IgE and T_H2/T_H17 cytokines in a cockroach allergen-induced mouse model compared with WT mice. Macrophages from Mrc1^-/- mice showed significantly reduced levels of miR-511-3 and an M1 phenotype, whereas overexpression of miR-511-3p rendered macrophages to exhibit a M2 phenotype. Furthermore, mice transfected with AAV-miR-511-3p showed a significant reduction in cockroach allergen-induced inflammation. Profiling of macrophages with or without miR-511-3p overexpression identified 729 differentially expressed genes, wherein expression of prostaglandin D₂ synthase (Ptgds) and its product PGD₂ were significantly downregulated by miR-511-3p. Ptgds showed a robust binding to miR-511-3p, which might contribute to the protective effect of miR-511-3p. Plasma levels of miR-511-3p were significantly lower in human asthmatic patients compared with nonasthmatic subjects.

These studies support a critical but previously unrecognized role of MRC1 and miR-511-3p in protection against allergen-induced lung inflammation.