OBJECTIVETo observe the effects and related mechanisms of fasudil on monocrotaline-induced pulmonary arterial hypertension (PAH) in rats.

METHODSA total of 56 healthy male Sprague-Dawley rats were randomly divided into 5 groups: 4 weeks control group (N4), 4 weeks PAH group (M4), 8 weeks control group (N8), 8 weeks PAH group (M8), 8 weeks PAH and fasudil group (F8). PAH was induced by subcutaneous injection of monocrotaline (50 mg/kg). Animals in F8 group received intraperitoneal injection of fasudil hydrochloride (15 mg×kg(-1)×d(-1)) from the end of the 4th week to the end of the 8th week. Rats in control groups and PAH groups received equal volume saline injection. Polyethylene catheters were inserted into the RV through the jugular vein for right ventricular systolic pressure (RVSP) and mean pulmonary artery pressure (mPAP) measurements after various treatment protocols. RV hypertrophy index [RV/(LV+S)] was also measured. Arteries of 50 to 150 µm were evaluated for the median wall thickness and wall area by HE staining as follows: percent wall thickness (WT%) = [(medial thickness×2/external diameter)]×100 and percent wall area (WA%) = (wall area/total area)×100%. The mRNA expression of ROCK-1 in lung tissue was analyzed by reverse transcription-polymerase chain reaction (RT-PCR). The protein expressions of ROCK-1 and MYPT-1 in lung tissue were analyzed by Western blot and MYPT-1 phosphorylation, respectively.

RESULTSForty-one rats survived and mortality rate was zero in N4, N8 and M4 groups. Survival rate was significantly higher in F8 group compared to M8 group (75.00% vs. 31.25%, P < 0.05). At the end of the 4th week, RVSP [(62.25 ± 3.24) vs. (31.33 ± 2.35) mm Hg(1 mm Hg = 0.133 kPa)], mPAP [(36.38 ± 2.31) vs.(20.32 ± 1.81) mm Hg], [RV/(LV+S)] (0.5648 ± 0.0580 vs. 0.3458 ± 0.0455), WT% [(25.63 ± 5.35)% vs.(13.38 ± 3.45)%], WA% [(60.36 ± 2.51)% vs. (38.42 ± 2.84)%] were all significantly higher in M4 group than in N4 group (all P < 0.01). RVSP [(54.64 ± 4.11) vs. (67.37 ± 4.68) mm Hg], mPAP [(26.25 ± 2.32) vs. (39.83 ± 1.83) mm Hg], and markedly relieve [RV/(LV+S)] (0.3985 ± 0.0210 vs. 0.7600 ± 0.0341), WT% [(15.64 ± 2.81)% vs. (28.26 ± 4.38)%], WA% [(40.35 ± 2.82)% vs. (68.83 ± 1.63)%] were all significantly lower in F8 group than in M8 group (all P < 0.05) while the expression of ROCK-1 mRNA (1.2139 ± 0.1778 vs. 1.6839 ± 0.3251, P < 0.01), and the protein expression of ROCK-1 and MYPT-1 as well as the extent of MYPT-1 phosphorylation were all downregualted in F8 group compared to M8 group (all P < 0.01).

CONCLUSIONSFasudil can effectively reverse the MCT-induced PAH in rats via downregulating ROCK-1 and MYPT-1.