OBJECTIVETo explore the effect and mechanism of vitamin D supplementation in early life on rat asthma model.

METHODThirty two sex-mature, female Wistar rats were randomly divided into a control group (n = 8), a low dose group (n = 8), a medium dose group (n = 8) and a high dose group (n = 8). From the seventh day of pregnancy on, the rats in each group were given different doses of vitamin D by intragastric administration, until the offspring rats were 21 days old. The rats in the control group were fed with DMSO-PBS. After the offsprings were weaned, 8 rats were randomly selected from each group. The number of male and female rats was equal. The rats were sensitized to ovalbumin (OVA) and challenged with aerosol OVA to establish the asthma model. The lung tissues were examined for pathologic changes after HE staining. ELISA was used to determine the concentrations of IL-10 in serum and BALF. Immunohistochemical staining methods were used to measure the expression of intercellular adhesion molecule-1 (ICAM-1) in lung tissues.

RESULT(1) Pathologic changes of lung tissues: compared with the control group, light microscope (LM) showed that eosinophil cells infiltration and the airway inflammation decreased in the low dose and medium dose groups, but increased in the high dose group. (2) The concentrations of IL-10 in serum and BALF: In serum, compared with the control group [(18.7 +/- 4.7) pg/ml], the concentrations of IL-10 in the low dose group [(30.2 +/- 2.8) pg/ml, P < 0.05] and the medium dose group [(51.5 +/- 6.6) pg/ml, P < 0.05] were significantly increased. And the IL-10 level of medium dose group was higher than that of the low dose group (P < 0.05). In BALF, compared with the control group [(59.1 +/- 14.4) pg/ml], the concentrations of IL-10 in the medium dose group [(90.0 +/- 14.3) pg/ml, P < 0.05] was significantly increased. There were no significant changes in the low dose group [(58.1 +/- 3.4) pg/ml, P > 0.05], whereas in the high dose group [(45.3 +/- 6.5) pg/ml, P < 0.05] the level significantly decreased. (2) The expression of ICAM-1 in lung tissues: compared with the control group, there were no significant changes in the low dose group (P > 0.05). The expression of ICAM-1 was significantly decreased in the medium dose group (P < 0.05). In the high dose group, the expression of ICAM-1 was significantly increased (P > 0.05).

CONCLUSIONAdequate intervention with 1,25(OH)2D3 in the early life could alleviate the inflammation in the lung tissues, reduces eosinophil cell infiltration in rat asthma model. However, overdose might play a detrimental role. Its mechanism may be associated with the effect of 1,25(OH)2D3 on IL-10 secretion and the expression of ICAM-1.