[Eosinophils apoptosis, fas mRNA and bcl-2 mRNA expressions in asthma model of young rat and effects of achyranthes bidentata polysaccharides].

OBJECTIVE

Asthma is a chronic respiratory tract disorder characterized by airway hyperreaction (AHR), persistent airway inflammation, high serum IgE, overproduction of IL-4, IL-5 and IL-13 by allergen-specific Th2 cells. The morbidity and mortality of asthma have continued to increase despite the use of currently available therapeutic agents. The reputed effects of traditional Chinese medicines (TCMs) have led to increasing use of TCMs for treatment of asthma throughout the world. The aims of this study were to investigate in asthma model of young rat the mRNA expressions of apoptotic gene fas and bcl-2, eosinophils (EOS) apoptosis in airway, and effects of achyranthes bidentata polysaccharides (ABPS), a group of polysaccharides extracted from TCM Achyranthes bidentata blume, on treatment of asthma.

METHODS

Fifty Sprague-Dawley (SD) rats were divided into five groups, 10 rats per group. Asthma in rats was induced by intraperitioneal sensitization and challenge with nebulized ovalbumin (OVA). A pretreatment with ABPS [50 mg/(kg x d)] was done according to three different schedules: consecutively 3 days at sensitization (T1), at challenge (T2) or both of the two periods (T3). Sham-treated rats (A) and naive rats (C) served as controls. The animals were sacrificed 24 hours after the last challenge. The mRNA expression of bcl-2 and fas in eosinophils presenting in airway and the apoptosis of eosinophils in airway were assessed by using in situ hybridization with oligonucleotide probe and TUNEL methods, respectively.

RESULTS

(1) Twenty-four hours after the last antigen challenge, the mRNA expression of fas in eosinophils presenting in airway significantly decreased in group A [(43.4 +/- 10.0)%] compared with that in group C [(73.2 +/- 11.9)%] (P < 0.01). ABPS could increase the fas mRNA expression significantly in all the three groups [(59.0 +/- 8.1)%, (57.5 +/- 9.6)%, (76.2 +/- 2.7)%], compared with that in group A (P < 0.05, P < 0.05, P < 0.01, respectively). The expression of the bcl-2 mRNA in group C was (47.9 +/- 8.7)%, it was elevated to (67.4 +/- 7.3)% in group A (P < 0.01). The expression of the bcl-2 mRNA in ABPS treated T1 and T3 groups was significantly lowered [(57.7 +/- 12.7)%, (57.3 +/- 6.8)%, P < 0.05], but not in T2 group [(72.4 +/- 6.7)%]. (2) In group A, the EOS presenting in the airway increased significantly, but there were few apoptotic EOS; the percentage of apoptotic eosinophil was distinctly lower in group A than that in group C [(5.3 +/- 2.2)% vs. (15.9 +/- 2.4)%, P < 0.01]. Compared with that in group A, the eosinophil apoptosis ratio in those ABPS treated groups T1, T3 was evidently elevated [(8.7 +/- 2.9)%, (9.8 +/- 2.2)%, P < 0.05, P < 0.05], but ABPS treated at challenge (T2) could not change the eosinophil apoptosis ratio significantly (P > 0.05).

CONCLUSION

(1) In asthmatic rat, the expressions of the genes fas and bcl-2 mRNA in EOS were changed evidently and the ratio of EOS apoptotosis reduced greatly. (2) ABPS could enhance the apoptosis of EOS by upregulating the expression of the genes fas and bcl-2 mRNA.