Objective

To evaluate the effects of Bushen Gubiao Recipe (BGR), a compound traditional Chinese herbal medicine, on toll-like receptor 4 (TLR4) signaling pathway and CD4 ⁺CD25 ⁺foxp3 ⁺regulatory T cells (CD4 ⁺CD25 ⁺foxp3 ⁺Tregs) in mice with recurrent respiratory tract infections (RRTIs).

Methods

A mouse model of kidney-yang deficiency which simulated physical characteristics of RRTIs was established by intraperitoneal injection of hydrocortisone for 14 d. The model mice were divided into 4 groups, model group, high-dose BGR group, low-dose BGR group, and nucleic acid and casein oral solution group. They were administered respectively with distilled water, high-dose BGR (50 g/kg body weight), low-dose BGR (25 g/kg body weight) and nucleic acid and casein oral solution. Besides, a normal control group was set up and gastrogavaged with distilled water. The effect of intervention was evaluated 4 weeks later by estimating the changes in behaviors of mice. Expressions of TLR4 and nuclear factor-kappa B (NF-κB) p65 in lung tissue were detected by immunohistochemical SABC method, the expression of TLR4 mRNA in lung tissue was detected by fluorescence quantitative-polymerase chain reaction (FQ-PCR), and the level of blood CD4 ⁺CD25 ⁺foxp3 ⁺ Tregs was determined by flow cytometry.

Results

A kidney-yang deficiency mouse model with RRTIs was successfully established by intraperitoneal injection of hydrocortisone. BGR could improve the abnormal behavioral condition of the mice and enhance the expressions of TLR4 and NF-κB p65 in the lung tissue. Expression of TLR4 mRNA in high-dose BGR group was higher than that in model group (P<0.05), while the difference was not statistically significant between high-dose BGR group and low-dose BGR group (P>0.05). Levels of CD4 ⁺CD25 ⁺foxp3 ⁺Tregs in high-dose BGR group and nucleic acid and casein oral solution group were lower than that in model group (P<0.05), while the difference was not statistically significant between high-dose BGR group and low-dose BGR group (P>0.05).

Conclusion

BGR can improve the behavior of the kidney-yang deficiency mice, and improve the innate immune function by up-regulating TLR/NF-κB signaling pathway. BGR can adjust the immune imbalance of T-helper cell (Th) 1/Th2 through reducing the activity of CD4 ⁺ CD25 ⁺foxp3 ⁺Tregs and enhancing the immune response of Th1 type.

Key words: Chinese herbal drugs, Bushen Gubiao Recipe, Respiratory tract infections, Toll-like receptor 4, T-lymphocytes, regulatory, Nuclear factor-kappa B, Mice