Gut microbiota modification suppresses the development of pulmonary arterial hypertension in an SU5416/hypoxia rat model

Abstract

The pathogenesis of pulmonary arterial hypertension is closely associated with dysregulated inflammation. Recently, abnormal alterations in gut microbiome composition and function were reported in a pulmonary arterial hypertension experimental animal model. However, it remains unclear whether these alterations are a result or the cause of pulmonary arterial hypertension. The purpose of this study was to investigate whether alterations in the gut microbiome affected the hemodynamics in SU5416/hypoxia rats. We used the SU5416/hypoxia rat model in our study. SU5416/hypoxia rats were treated with a single SU5416 injection (30 mg/kg) and a three-week hypoxia exposure (10% O₂). Three SU5416/hypoxia rats were treated with a combination of four antibiotics (SU5416/hypoxia + ABx group) for four weeks. Another group was exposed to hypoxia (10% O₂) without the SU5416 treatment, and control rats received no treatment. Fecal samples were collected from each animal, and the gut microbiota composition was analyzed by 16S rRNA sequencing. The antibiotic treatment significantly suppressed the vascular remodeling, right ventricular hypertrophy, and increase in the right ventricular systolic pressure in SU5416/hypoxia rats. 16S rRNA sequencing analysis revealed gut microbiota modification in SU5416/hypoxia + ABx group. The Firmicutes-to-Bacteroidetes ratio in SU5416/hypoxia rats was significantly higher than that in control and hypoxia rats. Compared with the control microbiota, 14 bacterial genera, including Bacteroides and Akkermansia, increased, whereas seven bacteria, including Rothia and Prevotellaceae, decreased in abundance in SU5416/hypoxia rats. Antibiotic-induced modification of the gut microbiota suppresses the development of pulmonary arterial hypertension. Dysbiosis may play a causal role in the development and progression of pulmonary arterial hypertension.

Keywords: dysbiosis; inflammation; pathogenesis; pulmonary hypertension experimental; vascular remodeling.

Fig. 1.

Study protocol. One week before the beginning of the study, all rats were acclimatized in normoxic (Nx) conditions. The control group remained in Nx conditions. A second group of rats was exposed to hypoxia (10% O₂) for three weeks but did not receive SU5416 injection. A third group of rats received a subcutaneous injection of SU5416 (30 mg/kg) followed by exposure to hypoxia (10% O₂) for three weeks (Su/Hx group). A fourth group of rats received antibiotic treatment one week before and four weeks after receiving the SU5416 injection and exposure to hypoxia (Su/Hx + Abx group).

Fig. 2.

Comparison of the hemodynamics and body weights among control, Su/Hx, and Su/Hx + Abx rats. (a) Right ventricular systolic pressure (RVSP). (b) The ratio of the right ventricle weight to left ventricle and septum weights (RV/LV + S). (c) Body weights of the four groups. Su/Hx: SU5416/hypoxia; Su/Hx + ABx: SU5416/hypoxia rats treated with antibiotics. *p < 0.05, vs. control; ^#p < 0.05, vs. Hx rats; †p < 0.05, vs. Su/Hx rats.

Fig. 3.

Vascular remodeling in control, Su/Hx, and Su/Hx + ABx rats. (a) Representative images showing each grade of vascular remodeling. Scale bars show 50 µm. (b) The proportion of each grade of vascular remodeling among the three groups. Su/Hx: SU5416/hypoxia; Su/Hx + ABx: SU5416/hypoxia rats treated with antibiotics. *p < 0.05, vs. control; ^#p < 0.05, vs. Hx rats; †p < 0.05, vs. Su/Hx rats.

Fig. 4.

Gut microbiota compositions. (a) The gut microbiota compositions at the beginning of the study. (b) The gut microbiota compositions after three weeks of hypoxic exposure. (c) The Firmicutes-to-Bacteroidetes (F/B) ratios in control, hypoxia, and Su/Hx groups at three weeks. (d) The bacterial numbers in fecal samples at three weeks. Su/Hx: SU5416/hypoxia; Su/Hx + ABx: SU5416/hypoxia rats treated with the antibiotic cocktail. *p < 0.05, vs. control; ^#p < 0.05, vs. Hx rats; †p < 0.05, vs. Su/Hx rats.

Fig. 5.

Differences in gut microbiota between control and Su/Hx rats at three weeks. (a) Principal coordinates analysis (PCoA). (b) Dendrogram of the two groups. (c) The compositions of gut microbiota at the phylum level. *p < 0.05, vs. control. (d) Significantly increased and decreased genera in Su/Hx rats compared with those in the control group. Su/Hx: SU5416/hypoxia.