Tetrahydropalmatine promotes macrophage autophagy by inhibiting the AMPK/mTOR pathway to attenuate atherosclerosis.

Background: Atherosclerosis (AS) is a chronic progressive arterial disease that is associated with macrophage autophagy and AMP-activated protein kinase (AMPK)/mechanistic target of the rapamycin (mTOR) pathway. Tetrahydropalmatine (THP) can activate AMPK-dependent autophagy. We aim to study the mechanism of macrophage autophagy mediated by THP in the treatment of AS via the AMPK/mTOR pathway.

Methods: High-fat diet apolipoprotein E-deficient mice and ox-LDL-induced RAW264.7 cells were used to mimic the AS model, then THP was administered. Cell viability was detected by MTT. Pathological aorta lesions were detected using Hematoxylin and Eosin, Masson, and oil red staining. Lipid metabolism indices and inflammatory factors were measured using ELISA. A transmission electron microscope was used to observe autophagosomes. Autophagy and AMPK/mTOR pathway protein expression was detected by immunofluorescence and Western blot. The AMPK inhibitor 9-β-d-Arabinofuranosyl Adenine (Ara-A) was used to validate the effect of THP. The mRNA expression of Beclin-1 and MCP-1 was detected by q-PCR.

Results: THP administration regulated lipid metabolism by lowering total cholesterol, triacylglycerol, low-density lipoprotein, and high-density lipoprotein levels, and suppressed aortic damage. THP suppressed aortic damage and regulated lipid metabolism by altering serum lipid levels. THP reduced inflammation and macrophage CD68 expression. Twenty μg/mL THP reduced cell viability. THP decreased cholesterol uptake and increased efflux, promoting autophagy. THP increased autophagosome number, LC3B expression, and autophagy markers p-AMPK/AMPK and LC3-II/LC3-I. THP also decreased p-mTOR/mTOR and P62. THP increased Beclin-1 mRNA expression and decreased MCP-1 mRNA expression. Ara-A reversed THP's effects.

Conclusion: THP promotes macrophage autophagy by inhibiting the AMPK/mTOR pathway to attenuate AS.