Expression Of Toll-Like Receptor 2, Toll-Like Receptor 3 And Toll-Like Receptor 4 In Experimental Allergic Rhinitis In Rats

Background and purposesAllergic rhinitis remains a major cause of morbidity in the world. Despite the widespread prevalence of this disease, the genetic and environmental determinants that contribute to progression of allergic rhinitis remain poorly understood. Toll-like receptors enable the host to recognize a large number of pathogen associated molecular patterns such as bacterial lipopolysaccharide, viral RNA, CpG-containing DNA and flagellin. Their recognization has recently emerged as key receptors of the innate immune system. And the activation of TLR-dependent signaling pathways results in the expression of effector molecules, such as cytokines and chemokines, which contributes to the activation of the antigen-specific adaptive immune response. Toll-like receptors have also been shown to play a pivotal role in both innate and adaptive immune responses. The role of Toll-like receptors as a primary part of our microbe defense system has been shown in several studies, but their possible function as mediators in allergy remains to be established. It has been suggested that pathogens or their products elicit Th1 immune responses, which down-regulate the Th2 cells, a hallmark of allergic disease. However, recent studies suggest that a simple change in the ratio of Th1 and Th2 cytokines does not account for the ability of pathogens to protect against the progression of allergy. The present study was designed to examine the expression of Toll-like receptors 2, 3 and 4 in the nasal mucosa of rats with allergic rhinitis, which were sensitized and challenged with the allergen ovalbumin(OVA). Materials and methods1. Developing the animal model of allergic rhinitis. 46 Wistar rats were divided randomly into three groups : AR group ( group A) was immunized by intraperitoneal injection and intranasal instillation of ovalbumin (OVA) . Normal control group ( group B) was administered by intraperitoneal injection and intranasal instillation of physiological saline .and the other six rats (group C) remained as an untouched healthy control group.2. All groups were analyzed for the allergic parameters described below before sacrifice respectively.3. The expression of TLR₂,TLR₃ and TLR₄ was detected by immunohistochemistry in rat nasal mucosa of all the groups.Results1. The success of developing animal model of allergic rhinitis indicated the rats after intraperitoneal injection and intranasal instillation of ovalbumin (OVA) did show allergic rhinitis.2. The Animal models of allergic rhinitis were made successfully in group A. TLR₂ expressed in all the groups. TLR₃ showed no expression in three groups. TLR₄ expressed in the three groups. The expression of TLR₂ and TLR₃ in all the groups showed no significant difference ( P > 0.05) . The expression of TLR₄ in group A was significantly higher than that in group B and group C ( P < 0.05 ) .Conclusions1.The rhinitis sympton confirms that the rates experienced allergic rhinitis after intraperitoneal injection and intranasal instillation of ovalbumin (OVA).2. The expression of TLR₄ increased in rat nasal mucosa with experimental allergic rhinitis. It suggests that TLR₄ have an effect on allergic inflammation. The expression of TLR₂ and TLR₃ showed no difference in all the groups , so it needs to further study the relationship between TLR₂ or TLR₃ and allergic inflammation.