Protective Effects of 18β-Glycyrrhetinic Acid on Monocrotaline-Induced Pulmonary Arterial Hypertension in Rats

Figures

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  FIGURE 1. Structure of 18β-glycyrrhetinic acid. The molecular formula for 18β-glycyrrhetinic acid is C30H46O4, and the molecular weight is 470.68.

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  FIGURE 2. Experimental design. PAH model of rats was established by single subcutaneous injection of MCT (60 mg/kg). After 21 days, 18β-GA (100, 50, and 25 mg/kg/day) was intragastrically administered. At the end of the treatment, lung structure and function were evaluated through various experimental methods.

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  FIGURE 3. Survival analysis of all rats. Data are expressed as mean ± SEM (n = 20). #p < 0.05 vs. control group, ∗p < 0.05 vs. MCT group. MCT, monocrotaline; 18β-GA, 18β-glycyrrhetinic acid.

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  FIGURE 4. Effect of 18β-glycyrrhetinic acid treatment on MCT-induced pulmonary arterial hypertension. (A) Effect of 18β-glycyrrhetinic acid on mean pulmonary arterial pressure (mPAP). (B) Effect of 18β-glycyrrhetinic acid on right ventricular systolic pressure (RVSP). (a) Control group; (b) MCT group; (c) 18β-GA 25 mg/kg group; (d) 18β-GA 50 mg/kg group; (e) 18β-GA 100 mg/kg group; (f) Sildenafil 30 mg/kg group. Data are expressed as mean ± SEM (n = 10). ##p < 0.01 vs. control group, ∗p < 0.05, ∗∗p < 0.01 vs. MCT group. MCT, monocrotaline; 18β-GA, 18β-glycyrrhetinic acid; mPAP, mean pulmonary arterial pressure; RVSP, right ventricular systolic pressure.

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  FIGURE 5. Effect of 18β-glycyrrhetinic acid on right ventricular hypertrophy index (RVHI). Data are expressed as mean ± SEM (n = 10). ##p < 0.01 vs. control group, ∗p < 0.05, ∗∗p < 0.01 vs. MCT group. MCT, monocrotaline; 18β-GA, 18β-glycyrrhetinic acid; RVHI, right ventricular hypertrophy index.

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  FIGURE 6. Effect of 18β-glycyrrhetinic acid on MCT-induced pulmonary vascular remodeling. Representative photomicrographs of pulmonary small arteries by H&E staining (A) and Masson staining (B) (magnification 400×): (a) control group; (b) MCT group; (c) 18β-GA 25 mg/kg group; (d) 18β-GA 50 mg/kg group; (e) 18β-GA 100 mg/kg group; (f) Sildenafil 30 mg/kg group. (C) Left: Effect of 18β-GA on WT%, Right: Effect of 18β-GA on WA%. Data are expressed as mean ± SEM (n = 10). ##p < 0.01 vs. control group, ∗p < 0.05, ∗∗p < 0.01 vs. MCT group. MCT, monocrotaline; 18β-GA, 18β-glycyrrhetinic acid; WT%, the ratio of the vascular walls thickness; WA%, the ratio of the vascular wall area.

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  FIGURE 7. Ultrathin cross-sections of the pulmonary vascular in rats were examined under transmission electron microscopy (6,000× magnification; bar = 5,000 nm). (A) Control group; (B) MCT group; (C) 18β-GA 25 mg/kg group; (D) 18β-GA 50 mg/kg group; (E) 18β-GA 100 mg/kg group; (F) Sildenafil 30 mg/kg group. Endothelial cell (thick arrow), smooth muscle cell (thin arrow), and elastic membrane (arrow head). MCT, monocrotaline; 18β-GA, 18β-glycyrrhetinic acid.

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  FIGURE 8. Effect of 18β-glycyrrhetinic acid on oxidative stress induced by MCT. (A) Effect of 18β-glycyrrhetinic acid on T-AOC expression. (B) Effect of 18β-glycyrrhetinic acid on SOD expression. (C) Effect of 18β-glycyrrhetinic acid on GSH-PX expression. (D) Effect of 18β-glycyrrhetinic acid on MDA expression. (E) Effect of 18β-glycyrrhetinic acid on CAT expression. Data are expressed as mean ± SEM (n = 10). ##p < 0.01 vs. control group, ∗∗p < 0.01 vs. MCT group. T-AOC, total antioxidant capacity; SOD, determine superoxide dismutase; GSH-PX, glutathione peroxidase; MDA, malonyldialdehyde; CAT, catalase; MCT, monocrotaline; 18β-GA, 18β-glycyrrhetinic acid.

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  FIGURE 9. Effects of 18β-glycyrrhetinic acid on NOX-2 and NOX-4 expression. (A) Representative Western blot band of NOX-2 activation in the lung tissues. (B) Representative Western blot band of NOX-4 activation in the lung tissues. Data are expressed as mean ± SEM (n = 10). ##p < 0.01 vs. control group, ∗p < 0.05, ∗∗p < 0.01 vs. MCT group. NOX-2, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-2; NOX-4, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-4; MCT, monocrotaline; GA, 18β-glycyrrhetinic acid.