Abstract
Purpose: :
Pollen is the most ubiquitous allergen triggering seasonal rhinitis, conjunctivitis and asthma, as well as exacerbating atopic dermatitis. However, the underlying mechanism by which pollen induces Th2-dominant allergic inflammation is largely unknown. This study was to explore the direct effects of short ragweed (SRW) pollen on expression and production of pro-allergic cytokines (TSLP and IL-33) and chemokines by mouse ocular surface mucosa and dendritic cells (DCs).
Methods: :
BALB/c mice at 8-10 weeks of age were topically exposed for 2-24 hours to aqueous extract of defatted SRW pollen (SRWe) at 150µg/5µl/eye, or by PBS as controls. The corneal epithelial and conjunctival tissues were collected for evaluation. Bone marrow cells were isolated from femur bone of BALB/c mouse, and cultured in RPMI1640 medium supplemented with 10% FBS, 20 ng/ml rmGM-CSF and 5 ng/ml rmIL-4 for 8-10 days. The induced immature DCs (iDCs) were treated with SRWe (1-50 µg/ml) for 4-24 hours. The mRNA expression was determined by reverse transcription and real time PCR. The protein production was measured by immunohistochemical staining, ELISA or Western blot.
Results: :
In ocular surface tissue of BALB/c mice topically exposed to SRWe, the expression of TSLP and IL-33 mRNA was significantly stimulated to 2-3, and 3-5 fold, respectively with the peak levels at 8 hours, compared with PBS treated control mice. The stimulated levels were higher in conjunctiva than in corneal epithelium. SRWe was found to promote maturation of iDCs, evidenced by increased expression of CD80 and CD86. SRWe also stimulated the expression of TSLP and IL-33 up to 2.5-5 and 4-8 fold, respectively, with the peak levels at 4 hours. Interestingly, SRWe dramatically stimulated the expression of inflammatory cytokines (TNF-α, IL-1β, IL-6) and chemokines (CCL2, CCL11, CCL17 and CCL22) by corneal and conjunctival epithelia in vivo, as well as by DCs in vitro. These stimulations were confirmed at protein levels.
Conclusions: :
These findings demonstrate that SRW pollen directly stimulates production of pro-allergic cytokines (TSLP and IL-33), inflammatory cytokines and chemokines in ocular surface mucosal epithelia in vivo and DCs in vitro, which may contribute to allergic inflammation triggered by SRW pollen.
Keywords: conjunctivitis • inflammation • immunomodulation/immunoregulation