Effect of Retinoic Acid in a Mouse Model of Allergic Rhinitis.
OBJECTIVE
All-trans retinoic acid (ATRA) modulates immune responses by affecting T cells. Several studies have revealed that allergic inflammation of the lower airways is negatively associated with the vitamin A concentration. However, the role of ATRA in allergic inflammation of the upper airways is unclear. We investigated the effects of ATRA in an allergic rhinitis mouse model.


METHODS
BALB/c mice except control groups (CON group) were sensitized with and challenged intra-nasally with Dermatophagoides farina (AR group). The ATRA groups were administered ATRA intraperitoneally. The steroid groups were administered steroid intranasally (ST group). Allergic symptoms and the average eosinophil number were counted. Cytokines and transcription factors were measured by Real-Time PCR and Western blotting. Der f-specific immunoglobulin E (IgE) was measured. Flow cytometry results of CD4⁺CD25⁺Foxp3⁺ T cells were analyzed.


RESULTS
The symptom scores were lower in the ATRA group than in the AR group and higher than in the CON group. The levels of IgE were lower in the ATRA group than in the AR group and higher than in the CON and ST groups. The levels of Foxp3, TGF-β, and IL-10 mRNA, as well as the percentage of CD4⁺CD25⁺Foxp3⁺ T cells, were higher in the ATRA group than in theAR group. In the ATRA group the levels of IFN-γ mRNA were higher, and the levels of GATA-3 and IL-4 mRNA, and ROR-γt were lower. In Western blotting analyses, the expression patterns of all factors, except Foxp3, showed similar to those of mRNA expression.


CONCLUSIONS
ATRA has anti-allergic effects in an allergic rhinitis model, and its underlying mechanisms mainly include the induction of regulatory T cells and the inhibition of Th2 responses.
Department of Otolaryngology-Head and Neck Surgery, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Suwon, Korea.
Hye Lim
HL
Son
Department of Otolaryngology-Head and Neck Surgery, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
Hyang Rim
HR
Park
Department of Otolaryngology-Head and Neck Surgery, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Suwon, Korea.
Yong Jin
YJ
Park
Department of Otolaryngology-Head and Neck Surgery, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea. kshent@catholic.ac.kr.
Soo Whan
SW
Kim
Allergic rhinitis; Th17 cells; Th2 cells; all-trans retinoic acid; regulatory T cells