Abstract
In the current study, we sought to investigate whether lysed Enterococcus faecalis FK-23 (LFK), a heat-killed probiotic preparation, attenuated eosinophil influx into the upper airway and had immunomodulatory activity in a murine allergic rhinitis model. Eighteen BALB/c mice were divided into three groups; the ovalbumin (OVA)-sensitized/challenged group, which received saline orally for 6 weeks (OVA group), the OVA-sensitized/challenged group, which received LFK orally for 6 weeks (LFK-fed group), and the non-sensitized group, which received saline for 6 weeks (saline control group). Nasal rubbing and sneezing were monitored during the study. After the final challenge, interleukin (IL)-4, interferon (IFN)-γ, and OVA-specific IgE levels in the sera and splenocyte culture supernatants were determined, eosinophilic infiltrate into the upper airway was quantified, and splenic CD4+CD25+ regulatory T cells (Tregs) were examined by flow cytometry. We found that nasal rubbing was significantly reduced in LFK-fed mice compared to the OVA group on d 27 and 35, and sneezing was significantly inhibited by LFK administration for 35 d. LFK-fed mice had significantly less eosinophil influx into the nasal mucosa than the OVA group. There were no significant differences between the LFK-fed group and OVA group in the serum and splenocyte culture supernatant levels of IL-4, IFN-γ, and OVA-specific IgE. Interestingly, the LFK-fed mice had a significantly greater percentage of splenic CD4+CD25+ Tregs than OVA group. Our results indicate that oral administration of LFK may alleviate nasal symptoms, reduce nasal eosinophilia, and increase the percentage of CD4+CD25+ Tregs in experimental allergic rhinitis.
Highlights
The utilization of probiotics to promote human health has been proposed for many years[1]
Nasal rubbing increased gradually after intranasal challenge in the OVA group and was significantly alleviated in the lysed Enterococcus faecalis FK-23 (LFK)-fed mice compared to the OVA group on d 27 (P = 0.015) and d 35 (P = 0.008) but not on d 21 (P = 0.289) (Fig. 2)
IL-4 was decreased, albeit not significantly, in the LFK-fed mice compared to the OVA group (P = 0.207)
Summary
The utilization of probiotics to promote human health has been proposed for many years[1]. In addition to the effects in the gut, there is increasing evidence that probiotics may be beneficial in the regulation of systemic immune responses[4,5] and in the resistance to the development of allergies[6,7]. This has led to increasing interest in the role of probiotics in the protection against the manifestations of allergic disease. Animal experiments have demonstrated that certain lactic acid bacteria strains, e.g., Lactobacillus reuteri (L. reuteri) and L. casei, can attenuate allergic airway responses[13,14] and protect against respiratory pathogens[15]
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