Objective: To investigate effects of repeated SEB exposure on airway remodeling in OVA-induced chronic allergic asthma model.
Methods: BALB/c mice were intra-peritoneally sensitized with ovalbumin (OVA)-aluminum hydroxide at days 0 and 14, and were intra-nasally challenged with OVA and/or SEB for the next 6 weeks(50 ug OVA, 10 or 100 ng of SEB, 3 times per week over a period, total 18 exposure). At 8 weeks, mice were sacrificed and assessed for histopathology, bronchoalveolar lavage fluid (BALF) cell counts, lung cytokines, methacholine airway hyper-responsiveness (AHR), and serum immunoglobulins.
Results: OVA sensitization followed by repeated OVA exposure resulted in the development of Th2 asthma and inflammation, including BALF cell counts, lung cytokines, histopathology, AHR and serum immunoglobulins. However, repeated SEB exposure did not aggravate OVA-induced pathologic changes, or induce any remarkable pathologic changes when administered alone. Serum total IgE levels were also not influenced by repeated SEB exposure. Rather, chronic repeated SEB-exposed mice showed lower levels of lung inflammation and remodeling, but higher levels of IL-10 and TGF-β, compared to non-SEB-exposed mice.
Conclusion: The present study demonstrates unpredicted suppressive effects of chronic repeated exposure of SEB in allergic asthma models, leading to the speculation that SEB exerts bi-directional effects depending on the timing of exposure. The mechanisms of anti-inflammatory effects warrant further investigation.