A novel small-molecule PCSK9 inhibitor E28362 ameliorates hyperlipidemia and atherosclerosis.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to the epidermal growth factor precursor homologous domain A (EGF-A) of low-density lipoprotein receptor (LDLR) in the liver and triggers the degradation of LDLR via the lysosomal pathway, consequently leading to an elevation in plasma LDL-C levels. Inhibiting PCSK9 prolongs the lifespan of LDLR and maintains cholesterol homeostasis in the body. Thus, PCSK9 is an innovative pharmacological target for treating hypercholesterolemia and atherosclerosis. In this study, we discovered that E28362 was a novel small-molecule PCSK9 inhibitor by conducting a virtual screening of a library containing 40,000 compounds. E28362 (5, 10, 20 µM) dose-dependently increased the protein levels of LDLR in both total protein and the membrane fraction in both HepG2 and AML12 cells, and enhanced the uptake of DiI-LDL in AML12 cells. MTT assay showed that E28362 up to 80 µM had no obvious toxicity in HepG2, AML12, and HEK293a cells. The effects of E28362 on hyperlipidemia and atherosclerosis were evaluated in three different animal models. In high-fat diet-fed golden hamsters, administration of E28362 (6.7, 20, 60 mg·kg-1·d-1, i.g.) for 4 weeks significantly reduced plasma total cholesterol (TC), triglyceride (TG), low-density lipoprotein-cholesterol (LDL-C) and PCSK9 levels, and reduced liver TC and TG contents. In Western diet-fed ApoE-/- mice (20, 60 mg·kg-1·d-1, i.g.) and human PCSK9 D374Y overexpression mice (60 mg·kg-1·d-1, i.g.), administration of E28362 for 12 weeks significantly decreased plasma LDL-C levels and the area of atherosclerotic lesions in en face aortas and aortic roots. Moreover, E28362 significantly increased the protein expression level of LDLR in the liver. We revealed that E28362 selectively bound to PCSK9 in HepG2 and AML12 cells, blocked the interaction between LDLR and PCSK9, and induced the degradation of PCSK9 through the ubiquitin-proteasome pathway, which finally resulted in increased LDLR protein levels. In conclusion, E28362 can block the interaction between PCSK9 and LDLR, induce the degradation of PCSK9, increase LDLR protein levels, and alleviate hyperlipidemia and atherosclerosis in three distinct animal models, suggesting that E28362 is a promising lead compound for the treatment of hyperlipidemia and atherosclerosis.

Effect of annonaceous acetogenin mimic AA005 on proliferative inhibition of leukemia cells in vitro and its possible mechanisms / 中国实验血液学杂志

This study was aimed to investigate the biological behavior of annonaceous acetogenin mimic AA005 in various kinds of leukemia cells and further elaborated its possible mechanisms in acute promyelocytic leukemia (APL) cell line NB4. The proliferative inhibition of leukemia cells was measured by CCK-8 method. Cell death was determined by trypan blue. Cell morphological features of NB4 treated with AA005 were examined by microscopy after Wright's staining. The form of cell death was measured by flow cytometry. Proteins PARP-1 and caspase-3 were detected by Western blot. Flow cytometry was used to detect the cell cycle arrest induced by AA005 of low concentration. The results showed that AA005 (> 200 nmol/L) significantly inhibited proliferation of all tested leukemia cell lines in a concentration-dependent manner. The vast majority of cells went to die after leukemia cell lines of NB4, U937 and K562 were treated with different concentration of AA005 for 48 h. Typical morphologic changes significantly appeared in NB4 cells after AA005 treatment. AA005 almost simultaneously induced early apoptosis and late apoptosis. The little cleavage of PARP-1 and activation of caspase-3 happened in AA005-induced cell death, and caspase-3 inhibitor Z-VAD-fmk could not block the cell death. The non-toxic concentrations of AA005 (< 200 nmol/L) caused NB4 cells G(2)/M-phase arrest. It is concluded that annonaceous acetogenin mimic AA005 induces significant proliferative inhibition of various leukemia cell lines in a concentration-dependent manner, which may be associated with cell death and G(2)/M-phase arrest induced by AA005.