Doxorubicin induces ZAKα overexpression with a subsequent enhancement of apoptosis and attenuation of survivability in human osteosarcoma cells

Naringin against doxorubicin-induced hepatotoxicity in mice through reducing oxidative stress, inflammation, and apoptosis via the up-regulation of SIRT1

Clinical application of doxorubicin is limited because of its potential side effects. The present study examined whether naringin had protective actions on doxorubicin-induced liver injury. Male BALB/c mice and alpha mouse liver 12 (AML-12) cells were used in this paper. The results showed that AML-12 cells treated with naringin significantly reduced cell injury, reactive oxygen species release and apoptosis level; Moreover, naringin notably alleviated liver injury by decreasing aspartate transaminase, alanine transaminase and malondialdehyde, and increasing superoxide dismutase, glutathione and catalase levels. Mechanism researches indicated that naringin increased the expression levels of sirtuin 1 (SIRT1), and inhibited the downstream inflammatory, apoptotic and oxidative stress signaling pathways. Further validation was obtained by knocking down SIRT1 in vitro, which proved the effects of naringin on doxorubicin-induced liver injury. Therefore, naringin is a valuable lead compound for preventing doxorubicin-induced liver damage by reducing oxidative stress, inflammation, and apoptosis via up-regulation of SIRT1.

Selective Activation of ZAK β Expression by 3-Hydroxy-2-Phenylchromone Inhibits Human Osteosarcoma Cells and Triggers Apoptosis via JNK Activation

Although various advancements in radical surgery and neoadjuvant chemotherapy have been developed in treating osteosarcoma (OS), their clinical prognosis remains poor. A synthetic chemical compound, 3-hydroxylflavone, that is reported to regulate ROS production is known to inhibit human bone osteosarcoma cells. However, its role and mechanism in human OS cells remains unclear. In this study, we have determined the potential of 3-Hydroxy-2-phenylchromone (3-HF) against OS using human osteosarcoma (HOS) cells. Our previous studies showed that Zipper sterile-alpha-motif kinase (ZAK), a kinase member of the MAP3K family, was involved in various cellular events such as cell proliferation and cell apoptosis, and encoded two transcriptional variants, ZAKα and β. In this study, we show that 3-HF induces the expression of ZAK and thereby enhances cellular apoptosis. Using gain of function and loss of function studies, we have demonstrated that ZAK activation by 3-HF in OS cells is confined to a ZAKβ form that presumably plays a leading role in triggering ZAKα expression, resulting in an aggravated cancer apoptosis. Our results also validate ZAKβ as the predominant form of ZAK to drive the anticancer mechanism in HOS cells.

Fisetin activates Hippo pathway and JNK/ERK/AP-1 signaling to inhibit proliferation and induce apoptosis of human osteosarcoma cells via ZAK overexpression

Osteosarcoma (OS) is a tumor entity that can cause a large number of cancer-related deaths. Although chemotherapy can decrease proliferation and increase apoptosis of human OS cells, the clinical prognosis remains poor. Fisetin is a flavonol found in fruits and vegetables and is reported to inhibit cell growth in numerous cancers. But the molecular mechanism underlying fisetin in human OS cells is not clear. It is known that sterile-alpha motif and leucine zipper containing kinase (ZAK), a kinase in the MAP3K family, is involved in various cell processes, including proliferation and apoptosis. In our lab, we have demonstrated that overexpression of ZAK can induce apoptosis in human OS cells. In the previous studies, MAP4K, the upstream of MAP3K, can act in parallel to MST1/2 to activate LATS1/2 in the Hippo pathway. Turning on the Hippo pathway can decrease proliferation and otherwise cause cell apoptosis in cancer cells. In this study, we found that fisetin can upregulate ZAK expression to induce the Hippo pathway and mediate the activation of JNK/ERK, the downstream of ZAK, to trigger cell apoptosis via AP-1 dependent manner in human OS cells. These findings reveal a novel molecular mechanism underlying fisetin effect on human OS cells.