[Losartan inhibited angiotensin induced human lung fibroblast transformation and collagen synthesis]

To observe the induction of cell transdifferentiation, connective tissue growth factor (CTGF) expression and collagen production of human lung fibroblast (HLF) by angiotensin II (Ang II), and to investigate the inhibitory effect of Ang II receptor antagonist-losartan on this process.

HLF cells were cultured and divided into a control group, an Ang II treated group, an Ang II + losartan co-incubated group and a losartan group. The marker of myofibroblast-alpha-smooth muscle actin (alpha-SMA) was detected by immunofluorescence and Western blot respectively, and the expression of CTGF mRNA and protein level were measured by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry respectively. Groups of Ang II and Ang II + losartan incubated with CTGF phosphothioate antisense, sense and random oligonucleotides transfected HLFs respectively, and collagen I (Col) I mRNA and alpha-SMA expression level were compared. The amount of hydroxyproline in the cell culture was measured by colorimetric assay.

In the Ang II group, CTGF mRNA level (0.82 +/- 0.07) was significantly higher than the control group (0.29 +/- 0.05), the Ang II + Losartan group (0.51 +/- 0.04) and the Losartan group (0.26 +/- 0.04). The CTGF protein level in the Ang II group (0.24 +/- 0.05) was increased as compared to the other groups. In the Ang II group, Col I mRNA (1.03 +/- 0.12) and amount of hydroxyproline (0.62 +/- 0.01 ng/ml) were significantly different as compared with the other three groups. The alpha-SMA expression level (1.14 +/- 0.15) and Col I mRNA (0.30 +/- 0.04) of HLF cells transfected with antisense oligonucleotide incubated with Ang II decreased significantly as compared to those of sense and random oligonucleotide transfected cells. Alpha-SMA expression level (0.85 +/- 0.09) and Col I mRNA (0.20 +/- 0.02) of Losartan + Ang II co-incubated antisense oligonucleotide transfected HLF cells decreased significantly as compared to Ang II treated alone.

Ang II promoted HLF cell transdifferentiation into myofibroblasts and increased collagen production through induction of CTGF expression. Blocking CTGF expression decreased Ang II induced transdifferentiation. Losartan blocked Ang II induced HLF cell transdifferentiation and collagen production.