OBJECTIVETo investigate the regulative mechanism of the diterpene phenol extract of Rosmarinus Officinalis (DERO) on the imbalance of collagen metabolism of the lung tissue in pulmonary fibrosis rats.

METHODSFifty healthy Sprague-Dawley rats were randomly divided into the normal saline group (NS), the bleomycin-induced lung injury group (BLM), the low dose DERO group (at the daily dose of 50 mg/kg), the moderate dose DERO group (at the daily dose of 100 mg/kg), and the high dose DERO group (at the daily dose of 200 mg/kg), 10 in each group (abbreviated as DERO 1, 2, 3, respectively). The pulmonary fibrosis rat model was prepared by disposable intratracheal instillation of bleomycin. DERO was administered by gastrogavage as intervention during the repairing process of lung injury. On the morning of the 29th day, the rats' lung tissue was extracted. The karyocyte number, collagen protein, type I collagen (collagen I) and transforming growth factor-beta type II receptor (TGFbetaR II), Smad4 mRNA expressions were semi-quantitatively determined using tissue microarray, HE staining, collagen fiber dyeing, immunohistochemical assay, and in situ hybridization. Using real-time fluorescent quantification RT-PCR, the mRNA expression of transforming growth factor-beta1 (TGF-beta1) were detected.

RESULTSCompared with the NS group, the collagen deposition of the lung tissue was obvious and the inflammatory infiltration was more severe in the BLM group (P < 0.05, P < 0.01). There was no statistical difference in the aforesaid 4 indices between the DERO1 group and the BLM group (P > 0.05). The collagen deposition and the inflammatory infiltration were obviously alleviated in the DERO2 and DERO3 groups (P < 0.05, P < 0.01). Compared with the NS group, the mRNA expressions of collagen-I, TGF-beta1 R II, Smad4, and TGF-beta1 were obviously up-regulated in the BLM group (P < 0.05, P < 0.01). Compared with the BLM group, the aforesaid four indices were not statistically changed in the DERO1 group (P > 0.05). But the mRNA expressions of collagen-I, TGF-beta1 R II, Smad4, and TGF-beta1 were obviously downregulated in the DERO2 and DERO3 groups (P < 0.05, P < 0.01). But the down-regulation of Smad4 expression was not obvious in the DERO2 and the DERO3 groups (P > 0.05). Compared with the DERO1 group, the mRNA expressions of collagen-I, TGF-beta1, R II, TGFbeta1 were all obviously lower in the DERO2 and the DERO3 groups (P < 0.05). But there was no statistical difference in the aforesaid 4 indices between the DERO2 group and the DERO3 group (P > 0.05).

CONCLUSIONSDERO could regulate imbalanced collagen metabolism of pulmonary fibrosis. It could inhibit excessive deposition of collagen fibers, especially excessive deposition of collagen- I. Its mechanisms might be realized by inhibiting up-regulation of TGF-beta1 and TGFbetaR II mRNA expressions, thus interfering the activation of TGF-beta-Smad signaling pathway on target genes, especially on type I procollagen target gene.