Pharmacological characterization of a novel metal-based proteasome inhibitor Na-AuPT for cancer treatment.

The ubiquitin-proteasome system (UPS) is essential for maintaining cell homeostasis by orchestrating the protein degradation, but is impaired in various diseases, including cancers. Several proteasome inhibitors, such as bortezomib, are currently used in cancer treatment, but associated toxicity limits their widespread application. Recently metal complex-based drugs have attracted great attention in tumor therapy; however, their application is hindered by low water-solubility and poor absorbency. Herein, we synthesized a new type of gold (I) complex named Na-AuPT, and further characterized its anticancer activity. Na-AuPT is highly water-soluble (6 mg/mL), and it was able to potently inhibit growth of a panel of 11 cancer cell lines (A549, SMMC7721, H460, HepG2, BEL7402, LNCap, PC3, MGC-803, SGC-7901, U266, and K562). In A549 and SMMC7721 cells, Na-AuPT (in a range of 2.5-20 µM) inhibited the UPS function in a dose-dependent fashion by targeting and inhibiting both 20 S proteasomal proteolytic peptidases and 19 S proteasomal deubiquitinases. Furthermore, Na-AuPT induced caspase-dependent apoptosis in A549 and SMMC7721 cells, which was prevented by the metal chelator EDTA. Administration of Na-AuPT (40 mg · kg-1 · d-1, ip) in nude mice bearing A549 or SMMC7721 xenografts significantly inhibited the tumor growth in vivo, accompanied by increased levels of total ubiquitinated proteins, cleaved caspase 3 and Bax protein in tumor tissue. Moreover, Na-AuPT induced cell death of primary mononuclear cells from 5 patients with acute myeloid leukemia ex vivo with an average IC50 value of 2.46 µM. We conclude that Na-AuPT is a novel metal-based proteasome inhibitor that may hold great potential for cancer therapy.

[Effect of heat shock response on the cleavage of nucleolin induced by oxidative stress].

OBJECTIVE: To observe the cleavage of nucleolin (C23) during apoptosis induced by oxidative stress and to clarify the effect of heat shock response (HSR) on the cleavage of nucleolin and its possible molecular mechanism. METHODS: We added 0.5 mmol/L peroxide hydrogen (H2O2 ) into cultured cells to mimic oxidative stress. Apoptosis and cleavage of C23 were detected using caspase-3 colorimetric assay and Western blotting respectively. HSR was performed to observe the effect of HSR on cleavage of C23 induced by oxidative stress, and over-expressions of HSP70 and HSP25 were detected by Western blotting. RESULTS: Activity of caspase-3 increased significantly after 2 hours of 0.5 mmol/L H2O2 treatment, and reached the peak after 12 hours. The cleavage of C23 appeared 30 minutes to 1 hour after the treatment of H2O2 as indicated by a cleaved fragmentation of 80 kD, which was significantly inhibited by HSR. Moreover, HSR could induce HSP70 and HSP25 over-expressions. CONCLUSION: Oxidative stress can induce the activation of caspase-3, cleavage of C23, and apoptosis. HSR can significantly inhibit the cleavage of C23 induced by oxidative stress, which is related to the over-expressions of HSP70, HSP25, and other stress proteins.

[Heat shock pretreatment in inhibiting myocardical apoptosis induced by ischemia-reperfusion and its mechanism].

OBJECTIVE: To explore the mechanisms of myocardial apoptosis during myocardial ischemia-reperfusion injury and to further clarify the molecular mechanisms by which heat shock pretreatment in inhibiting myocardial apoptosis induced by ischemia-reperfusion injury. METHODS: Myocardial ischemia-reperfusion injury was induced by the occlusion of left anterior descending branch of the coronary artery. Apoptosis was evaluated by DNA laddering assay and the activities of caspase 3, 8, or 9 was measured with Caspase Colorimetric Assay Kit. Expression of heat shock proteins was detected by Western blotting analysis. To explore the effect of heat shock pretreatment on myocardium against apoptosis, mice were pretreated with whole body hyperthermia before the myocardial ischemia-reperfusion injury. RESULTS: Ischemia-reperfusion injury induced myocardial apoptosis and activation of caspase-3,8,9. Heat shock pretreatment induced the expression of several family members of heat shock proteins and inhibited myocardial apoptosis and activation of the above caspases. CONCLUSION: Mitochondria and death receptor signaling pathways play important roles in myocardial apoptosis induced by ischemia-reperfusion injury. Heat shock pretreatment may increase the expression of several HSP, and inhibit the activation of both mitochondria and death receptor signaling pathways and apoptosis in cardiomyocytes induced by myocardial ischemia-reperfusion injury.