Inhibition of autophagy ameliorates pulmonary microvascular dilation and PMVECs excessive proliferation in rat experimental hepatopulmonary syndrome.

Duo Xu,Jianteng Gu,Lin Chen,Bin Yi,Karine Belguise,Kaizhi Lu,Bing Chen,Xiaobo Wang

doi:10.1038/srep30833

Abstract

Hepatopulmonary syndrome (HPS) is a defective liver-induced pulmonary vascular disorder with massive pulmonary microvascular dilation and excessive proliferation of pulmonary microvascular endothelial cells (PMVECs). Growing evidence suggests that autophagy is involved in pulmonary diseases, protectively or detrimentally. Thus, it is interesting and important to explore whether autophagy might be involved in and critical in HPS. In the present study, we report that autophagy was activated in common bile duct ligation (CBDL) rats and cultured pulmonary PMVECs induced by CBDL rat serum, two accepted in vivo and in vitro experimental models of HPS. Furthermore, pharmacological inhibition of autophagy with 3-methyladenine (3-MA) significantly alleviated pathological alterations and typical symptom of HPS in CBDL rats in vivo, and consistently 3-MA significantly attenuated the CBDL rat serum-induced excessive proliferation of PMVECs in vitro. All these changes mediated by 3-MA might explain the observed prominent improvement of pulmonary appearance, edema, microvascular dilatation and arterial oxygenation in vivo. Collectively, these results suggest that autophagy activation may play a critical role in the pathogenesis of HPS, and autophagy inhibition may have a therapeutic potential for this disease.

Highlights

Our previous research demonstrated that the common bile duct ligation (CBDL) rat serum induces the excessive proliferation of pulmonary microvascular endothelial cells (PMVECs) in vitro, which could contribute to the Hepatopulmonary syndrome (HPS)-associated angiogenesis, a highly complicated and regulated process to form new vessels and capillary networks[18,19,20]
Our results demonstrated that the protein levels of LC3B and Beclin-1 in the lung tissues were significantly increased and peaked at 2-week CBDL rats; oppositely, the protein levels of p62 in lung tissues were significantly decreased and dropped to minimal in 2-week CBDL rats; the positive or negative changes of all these proteins showed a slightly reduction in 4-week CBDL rats, and all these temporal changes are consistent with our observation of autophagosome formation (Fig. 1B)
Our results demonstrated that the protein levels of LC3B and Beclin-1 in cultured PMVECs were significantly increased and peaked at 24 h after the CBDL rat serum stimulation, while the protein levels of p62 were significantly decreased and dropped to minimal at 24 h after the CBDL rat serum stimulation (Fig. 2B,C)

Summary

Introduction

Our previous research demonstrated that the common bile duct ligation (CBDL) rat serum induces the excessive proliferation of pulmonary microvascular endothelial cells (PMVECs) in vitro, which could contribute to the HPS-associated angiogenesis, a highly complicated and regulated process to form new vessels and capillary networks[18,19,20]. We hypothesized that the initial autophagy activation may play a pivotal role in the pathological alterations of HPS. To address this hypothesis, we assessed whether autophagy level is increased in both CBDL rats and cultured PMVECs under the stimulation of CBDL rat serum, and whether autophagy inhibition could affect the pathological status of HPS in both in vivo and in vitro models

Methods

Results

Conclusion