[Effects of calcitonin gene-related peptide on eIF3a and p27 expression in bleomycin-induced pulmonary fibrosis of rats].

Objective: To observe the effects of calcitonin gene-related peptide (CGRP) on eukaryotic translation initiation factor 3a (eIF3a) and p27 expression in bleomycin-induced pulmonary fibrosis of rats and its possible mechanism.

Methods: Twenty-four male SD rats weighing 180~220 g were randomly divided into three groups (=8):control group, bleomycin group, bleomycin plus capsaicin group. Bleomycin (5 mg/kg) was used to induce pulmonary fibrosis rat model. Rats were given capsaicin (50 mg/kg·d) by subcutaneous injections 4 days before to deplete endogenous CGRP. At the end of experiments, blood samples were collected from carotid artery to determinate the plasma levels of CGRP by ELISA. The cells were divided into 6 groups as follows:control group, transforming growth factor-β1 (TGF-β1) group, +CGRP (1, 10, 100 nmol/L) group, +CGRP 100 nmol/L and CGRP8-37 1 mol/L group respectively(=9). TGF-β1 (5 ng/ml) stimulated proliferation of pulmonary fibroblasts and proliferation was measured by BrdU marking. The expression levels of eIF3a, p27, α-smooth muscle actin (α-SMA) and collagen Ⅰ were detected by immunohistochemisty, real-time PCR or Western blot.

Results: The expressions of eIF3a, α-SMA, and collagen I were increased and the expression of p27 was decreasing in pulmonary fibrosis rats induced by bleomycin. Exogenous application of CGRP significantly inhibited TGF-β1-induced proliferation and differentiation of pulmonary fibroblasts and the expressions of α-SMA, collagen I and eIF3a, and upregulated the expression of p27. All these effects of CGRP were abolished in the presence of CGRP8-37.

Conclusions: These results suggest that endogenous CGRP is related to the development of pulmonary fibrosis induced by bleomycin, and the inhibitory effect of CGRP on proliferation of lung fibroblasts involves the eIF3a/p27 signaling pathway.