SUMO-conjugating enzyme UBE2I inhibition alleviates asthma progression: effects on BHLHE40 and M2 macrophage polarization.

Abstract

BACKGROUND: Perturbation of macrophage homeostasis is a key mechanism of airway inflammation in asthma. Ubiquitin conjugating enzyme E2 I (UBE2I), a SUMO E2 conjugating enzyme involved in macrophage M2 polarization, has an unclear role in asthma. METHODS: Mouse asthma was induced by intraperitoneal OVA and Al(OH)sensitization, followed by 1% OVA inhalation. H&E and PAS staining evaluated lung pathological changes. UBE2I expression in lungs was detected using qRT-PCR and western blotting, and immunofluorescence determined UBE2I and CD68 expression. For cell studies, primary BMDMs were stimulated with IL-4 for M2 polarization. Co-IP assay evaluated UBE2I and BHLHE40 interaction and BHLHE40's SUMOylation. Luciferase reporter assay determined the binding of BHLHE40 to NRTN promoter. For in vivo studies, leukocyte cell types in BALF were determined using Wright-Giemsa staining. ELISA detected IL-4, IL-5, IL-13, YM1 (BALF) and IgE (serum). RESULTS: In the lungs of asthmatic mice and IL-4-induced BMDMs, UBE2I expression was up-regulated and BHLHE40 SUMOylation mediated by SUMO-1 was enhanced. Depletion of UBE2I in BMDMs decreased BHLHE40 SUMOylation and promoted NRTN transcription. UBE2I depletion down-regulated Arg1, CD206, Fizz1, and YM1 expression, which were reversed by NRTN knockdown. Importantly, UBE2I depletion in mice attenuated allergic response, evidenced by improved airway narrowing, reduced goblet cell hyperplasia and inflammatory cell infiltration, and decreased IL-4, IL-5 and IL-13 in BALF and IgE in serum. CONCLUSIONS: Our study suggests that UBE2I depletion inhibited M2 macrophage polarization to reduce airway inflammation via inhibiting BHLHE40 SUMOylation and promoting NRTN, implicating UBE2I as a promising therapeutic target in asthma.