Effect and mechanism of acupuncture on airway smooth muscle relaxation during acute asthma attack in rats.

OBJECTIVES: To explore the effect and mechanism of acupuncture at "Feishu" (BL 13) and "Dingchuan" (EX-B 1), and "Kongzui" (LU 6) and "Yuji" (LU 10) for relaxing the airway smooth muscle in the rats during acute asthma attack and compare the effect among the two pairs of acupoints and the acupoints combination.

METHODS: Forty SD male rats with SPF grade were randomly divided into a blank group, a model group, a pair-point A group (acupuncture at "Feishu" [BL 13] and "Dingchuan" [EX-B 1]), a pair-point B group (acupuncture at "Kongzui" [LU 6] and "Yuji" [LU 10]) and a point combination group (acupuncture at "Feishu" [BL 13] , "Dingchuan" [EX-B 1], "Kongzui" [LU 6] and "Yuji" [LU 10]), with 8 rats in each group. Except the rats in the blank group, the model of acute asthma attack was induced by ovalbumin (OVA) combined with aluminum hydroxide gel in the rest groups. Started on the 15th day of modeling, except in the blank group and the model group, acupuncture was delivered in the other groups, 30 min in each intervention, once daily, for 14 days. In each group, the latent period of asthma inducing was measured; the lung resistance (LR) and dynamic lung compliance (Cdyn) were determined using lung function detector; the levels of endothelin-1 (ET-1), tumor necrosis factor-α (TNF-α), cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in serum and bronchoalveolar lavage fluid (BALF) were measured by ELISA; with Masson staining and electron microscopy adopted, the morphology and ultrastructure of airway smooth muscle of the rats were observed; the mRNA and protein expressions of ET-1 and beta-2 adrenergic receptor (β2 -AR) were detected by quantitative real-time fluorescence and Western blot, respectively.

RESULTS: Compared with the blank group, the latent period of asthma inducing was shortened ( P< 0.05), RL increased and Cdyn decreased ( P< 0.05) with the different concentrations of methacholine (0.025 mg/kg, 0.05 mg/kg, 0.1 mg/kg, 0.2 mg/kg) in the model group. In the pair-point A group, the pair-point B group and the point combination group, the latent period of asthma inducing was prolonged ( P< 0.05), RL decreased and Cdyn increased ( P< 0.05) with different concentrations of methacholine when compared with those in the model group; and the latent period of asthma inducing in the point combination group was longer than that in the pair-point A group ( P <0.05). Compared with the blank group, the levels of ET-1, TNF-α and cGMP in the serum and BALF were elevated ( P <0.05), and those of cAMP reduced ( P< 0.05) in the model group. The levels of ET-1, TNF-α and cGMP in the serum and BALF were reduced ( P< 0.05), and those of cAMP elevated ( P <0.05) in the pair-point A group, the pair-point B group and the point combination group when compared with those in the model group. In the blank group, the lung tissue was normal structurally. In the model group, the collagen fibers were proliferated increasingly, the smooth muscle was thickened, the mitochondria were swollen, and their cristae disrupted and reduced massively. In the pair-point B group, the collagen fibers were proliferated, the smooth muscle was thicker compared with that in the blank group, the mitochondria were mildly swollen and their cristae disrupted partially. In the pair-point A group and the point combination group, the lung tissue changes were obviously alleviated in comparison with the model group, the mitochondria were slightly swollen and their cristae disrupted occasionally. Compared with the blank group, the mRNA and protein expression of ET-1 increased and that of β2 -AR decreased in the lung tissue of the model group ( P< 0.05). In the pair-point A group, the pair-point B group and the point combination group, the mRNA and protein expression of ET-1 was reduced and that of β2 -AR elevated in the lung tissue when compared with those in the model group ( P< 0.05). In comparison with the pair-point A group, the mRNA expression of β2 -AR was elevated in the point combination group ( P< 0.05). When compared with the pair-point B group, the mRNA expression of β2 -AR increased, the protein expression of ET-1 decreased ( P <0.05) in the point combination group.

CONCLUSIONS: Acupuncture at "Feishu" (BL 13) and "Dingchuan" (EX-B 1), "Kongzui" (LU 6) and "Yuji" (LU 10), two pairs of acupoints relieves the airway smooth muscle spasm in the rats during acute asthma attack, which may be related to inhibiting the mRNA and protein expression of ET-1 to reduce the excretion of ET-1 and TNF-α; while enhancing the mRNA and protein expression of β2 -AR to balance the levels of cAMP and cGMP. The effect is optimal when acupuncture is delivered at two pairs of acupoints simultaneously.