Collagen tripeptide alleviates allergic rhinitis symptoms in mice

Background and objectives: Collagen tripeptide (CTP) is a collagen hydrolysate containing high concentrations of tripeptides with glycine-X-Y sequences. Residues X and Y are arbitrary but often occupied by proline, hydroxyproline, and/or alanine. CTP has excellent skin permeability and promotes the synthesis of hyaluronic acid. Further, CTP is reported to exert an anti-inflammatory effect on atopic dermatitis. Based on these reports, we evaluated the effect of CTP on allergic rhinitis, an inflammatory diseasefinal, using a mouse model of ovalbumin-induced rhinitis. In addition, we examined the effect of CTP on the immune system in the mouse spleen. Methods:To prepare the rhinitis model, BALB/c female mice were sensitized with ovalbumin (OVA). CTP was dissolved in tap water and given ad libitum from a water bottle. Control mice received tap water only. CTP administration was continued for 5 weeks from the day of first sensitization in the study of preventive efficacy, and for 4 weeks from the time when rhinitis worsened in the study of therapeutic efficacy. Some mice were given normal collagen peptide (CP), which did not contain CTP. Rhinitis symptoms (sneezing and nasal rubbing) were observed once weekly. The plasma levels of OVA-specific IgE antibodies (OVA-IgE) were measured over time. After a final observation of rhinitis symptoms, mice were deeply anesthetized, and their spleens were removed. By real-time PCR, mRNA levels in the spleen were analyzed, with a focus on the master transcription factors of helper T (Th) cells. Results: Repeated administration of OVA resulted in exacerbation of rhinitis symptoms and a marked increase in OVA-IgE levels. CTP administration prevented and treated the symptoms of rhinitis and reduced the OVA-IgE levels. Regarding therapeutic efficacy, rhinitis symptoms were alleviated for more than 4 weeks after cessation of CTP administration. In contrast, CP had no effect on rhinitis symptoms. Real-time PCR revealed that CTP decreased the activity of type 2 Th cells and of follicular helper T cells. Conclusions: These findings suggest that CTP exerts an anti-rhinitis effect by restoring the Th-cell composition.