Isotoosendanin inhibits triple-negative breast cancer metastasis by reducing mitochondrial fission and lamellipodia formation regulated by the Smad2/3-GOT2-MYH9 signaling axis.

Triple-negative breast cancer (TNBC) is incurable and prone to widespread metastasis. Therefore, identification of key targets for TNBC progression is urgently needed. Our previous study revealed that isotoosendanin (ITSN) reduced TNBC metastasis by targeting TGFßR1. ITSN is currently used as an effective chemical probe to further discover the key molecules involved in TNBC metastasis downstream of TGFßR1. The results showed that GOT2 was the gene downstream of Smad2/3 and that ITSN decreased GOT2 expression by abrogating the activation of the TGF-ß-Smad2/3 signaling pathway through directly binding to TGFßR1. GOT2 was highly expressed in TNBC, and its knockdown decreased TNBC metastasis. However, GOT2 overexpression reversed the inhibitory effect of ITSN on TNBC metastasis both in vitro and in vivo. GOT2 interacted with MYH9 and hindered its binding to the E3 ubiquitin ligase STUB1, thereby reducing MYH9 ubiquitination and degradation. Moreover, GOT2 also enhanced the translocation of MYH9 to mitochondria and thus induced DRP1 phosphorylation, thereby promoting mitochondrial fission and lamellipodia formation in TNBC cells. ITSN-mediated inhibition of mitochondrial fission and lamellipodia formation was associated with reduced GOT2 expression. In conclusion, ITSN prevented MYH9-regulated mitochondrial fission and lamellipodia formation in TNBC cells by enhancing MYH9 protein degradation through a reduction in GOT2 expression, thus contributing to its inhibition of TNBC metastasis.

[Effect of forsythiaside A against CCl_4-induced liver fibrosis in mice and its mechanism].

This study aims to investigate the efficacy of forsythiaside A(FTA) against CCl_4-induced liver fibrosis and the mechanism. Specifically, activities of serum alanine/aspartate aminotransferase(ALT/AST) and hydroxyproline(HYP) level in liver were detected, and pathological morphology of liver was observed based on hematoxylin-eosin(HE) staining, Masson's trichrome staining, and Sirius red staining of liver. On this basis, the effect of FTA on liver fibrosis was evaluated. The mRNA expression of actin alpha 2/α-smooth muscle actin(Acta2/α-SMA), transforming growth factor ß(Tgfß), collagen Ⅰ alpha 1(Col1 a1), and collagen Ⅲ alpha 1(Col3 a1) in liver tissue and hepatic stellate cells(HSC) was determined by qPCR, and the protein expression of α-SMA in liver tissue and HSC was measured by Western blot to assess the inhibition of FTA on HSC activation. The protein expression of α-SMA, vi-mentin(Vim), vascular endothelial cadherin(Ve-cadherin), and platelet endothelial cell adhesion molecule-1(PECAM-1/CD31) was measured by Western blot to evaluate the reverse of endothelial-mesenchymal transition(EMT) by FTA. The efficacy of FTA in relieving CCl_4-induced liver fibrosis was evidenced by the alleviation of hepatocyte necrosis, liver inflammation, and hepatic collagen deposition. FTA decreased the mRNA expression of Acta2, Tgfß, Col1 a1, and Col3 a1 and protein expression of α-SMA both in vivo and in vitro. FTA reversed the increase of α-SMA and Vim and the decrease of CD31 and Ve-cadherin in livers from mice treated with CCl_4. Therefore, FTA alleviated CCl_4-induced liver fibrosis in mice via suppressing HSC activation and reversing EMT.

Quercetin attenuates toosendanin-induced hepatotoxicity through inducing the Nrf2/GCL/GSH antioxidant signaling pathway.

Toosendanin (TSN) is the main active compound in Toosendan Fructus and Meliae Cortex, two commonly used traditional Chinese medicines. TSN has been reported to induce hepatotoxicity, but its mechanism remains unclear. In this study, we demonstrated the critical role of nuclear factor erythroid 2-related factor 2 (Nrf2) in protecting against TSN-induced hepatotoxicity in mice and human normal liver L-02 cells. In mice, administration of TSN (10 mg/kg)-induced acute liver injury evidenced by increased serum alanine/aspartate aminotransferase (ALT/AST) and alkaline phosphatase (ALP) activities, and total bilirubin (TBiL) content as well as the histological changes. Furthermore, TSN markedly increased liver reactive oxygen species (ROS) and malondialdehyde (MDA) levels, and decreased liver glutathione (GSH) content and Nrf2 expression. In L-02 cells, TSN (2 µM) time-dependently reduced glutamate-cysteine ligase (GCL) activity and cellular expression of the catalytic/modify subunit of GCL (GCLC/GCLM). Moreover, TSN reduced cellular GSH content and the increased ROS formation, and time-dependently decreased Nrf2 expression and increased the expression of the Nrf2 inhibitor protein kelch-like ECH-associated protein-1 (Keap1). Pre-administration of quercetin (40, 80 mg/kg) effectively inhibited TSN-induced liver oxidative injury and reversed the decreased expression of Nrf2 and GCLC/GCLM in vivo and in vitro. In addition, the quercetin-provided protection against TSN-induced hepatotoxicity was diminished in Nrf2 knock-out mice. In conclusion, TSN decreases cellular GSH content by reducing Nrf2-mediated GCLC/GCLM expression via decreasing Nrf2 expression. Quercetin attenuates TSN-induced hepatotoxicity by inducing the Nrf2/GCL/GSH antioxidant signaling pathway. This study implies that inducing Nrf2 activation may be an effective strategy to prevent TSN-induced hepatotoxicity.