Scoparone alleviates aortic aneurysm formation by inhibiting smooth muscle cell phenotypic switching and inflammation...

Key pathophysiological mechanisms such as chronic inflammation, oxidative stress, and vascular smooth muscle cells (VSMCs) phenotypic change are vital in defining abdominal aortic aneurysm (AAA). In traditional Chinese medicine, scoparone, or 6,7-dimethoxycoumarin, is the essential mixture found in the herb Artemisia capillaries Thunb (Yin chen hao), used for treating disorders related to the liver, bile, and inflammation. The potential of scoparone to protect against AAA and the mechanisms behind it have yet to be clarified.

Our investigation focused on understanding the impact of scoparone on AAA formation and the processes behind it.

The AAA model in mice was established with porcine pancreatic elastase (PPE), and ultrasound was used to assess scoparone's therapeutic effects. The morphological impact of scoparone on AAA formation was assessed using hematoxylin-eosin (HE) and Verhoeff-Van Gieson (VVG) staining. Later, network pharmacology, molecular docking, and molecular dynamics simulation were employed to determine scoparone's key molecular targets against AAA, with the target effects being verified in vitro and in vivo.

In this study, we showed that scoparone inhibited PPE-induced AAA formation and elastin degradation in mice. By utilizing network pharmacology, molecular docking, and molecular dynamics simulation, we identified the mammalian target of rapamycin (mTOR) signaling pathway as a potential target for scoparone in addressing AAA. Experiments conducted both in vivo and in vitro further validated that scoparone inhibited mTOR signaling pathway activation and VSMCs phenotypic switching, the evidence is seen in the reduced phosphorylation ratios of S6 and S6K, the increased expression of VSMCs contractile markers including α-smooth muscle actin (α-SMA), smooth muscle 22 (SM22), and calponin 1 (CNN1), and the decreased levels of synthetic markers such as osteopontin (OPN) and Krüppel-like factor 4 (KLF4). However, these effects were abolished by application of mTOR inhibitor - rapamycin. Additionally, scoparone also reduced the infiltration and M1 polarization of macrophage and the production of inflammation-related cytokines like tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1β.

Scoparone inhibited the development of AAA in mice by: (i) blocking the phenotypic change of VSMCs via suppression of the mTOR pathway; and (ii) decreasing macrophage infiltration, M1 polarization, and the release of inflammatory cytokines.