Qing Miao

Curcumin promotes apoptosis by activating the p53-miR-192-5p/215-XIAP pathway in non-small cell lung cancer

Curcumin has attracted increasing interest as an anti-cancer drug for decades. The mechanisms of action involve multiple cancer-related signaling pathways. Recent studies highlighted curcumin has epigenetic regulatory effects on miRNA in cancers. In the present study, we demonstrated the proapoptotic effects of curcumin in vitro and in vivo. miRNA microarray and qPCR indicated that miR-192-5p and miR-215 were the most responsive miRNAs upon curcumin treatment in H460 and A427 cells. Functional studies showed miR-192-5p/215 were putative tumor suppressors in non-small cell lung cancer. Curcumin also promoted miR-192-5p/215 expressions in A549 cells (p53 wild type) but not in H1299 cells (p53-null). Conditional knockdown of p53 by tetracycline inducible expression system significantly abrogated curcumin-induced miR-192-5p/215 upregulation in the p53 wild-type H460, A427 and A549 cells. Conversely, ectopic expression of exogenous wild-type but not R273H mutant p53 in the p53-null H1299 cells enabled miR-192-5p/215 response to curcumin treatment. The proapoptotic effects of curcumin also depended on miR-192-5p/215 induction, and antagonizing miR-192-5p/215 expression attenuated curcumin-induced apoptosis in H460, A427 and A549 cells, but not in H1299 cells. Finally, X-linked inhibitor of apoptosis (XIAP) is proved to be a novel transcriptional target of miR-192-5p/215. Taken together, this study highlights that the proapoptotic effects of curcumin depend on miR-192-5p/215 induction and the p53-miR-192-5p/215-XIAP pathway is an important therapeutic target for non-small cell lung cancer.

Curcumin reverses cis-platin resistance and promotes human lung adenocarcinoma A549/DDP cell apoptosis through HIF-1α and caspase-3 mechanisms.

Curcumin, a yellow pigment derived from Curcuma longa Linn, has been favored by the Eastern as dietary ingredients for centuries. During the past decade, extensive investigations have revealed curcumin sensitized various chemotherapeutic agents in human breast, colon, pancreas, gastric, liver, brain and hematological malignant disorders in vivo and in vitro. Several pathways and specific targets including NF-κB, STAT3, COX-2, Akt and multidrug resistant protein have been identified to facilitate curcumin as a chemosensitizer. Recent studies suggest HIF-1α participated in the development of drug resistance in cancer cells and targeting HIF-1α either by RNAi or siRNA successfully overcame chemotherapeutic resistance. To investigate the mechanism basis of curcumin as a chemosensitizer in lung cancer, we examined curcumins effects on HIF-1α in cis-platin (DDP) sensitive A549 and resistant A549/DDP cell lines by RT-PCR and Western blot. HIF-1α in A549/DDP cells was found to be overexpressed at both mRNA and protein levels together with a poor response to DDP. Results from transient transfection and flow cytometry showed the HIF-1α abnormality contributed to DDP resistance in A549/DDP lung cancer cells. Combined curcumin and DDP treatment markedly inhibited A549/DDP cells proliferation, reversed DDP resistance and triggered apoptotic death by promoting HIF-1α degradation and activating caspase-3, respectively. Expression of HIF-1α-dependent P-gp also seemed to decrease as response to curcumin in a dose-dependent manner. Our findings shed light on drug resistant reversing effect of curcumin in lung cancer cells by inhibiting HIF-1α expression and activating caspase-3.

Cardioprotective effect of polydatin against ischemia/reperfusion injury: Roles of protein kinase C and mito KATP activation

Polydatin preconditioning (PPC) has been reported to be protective against brain and intestine ischemia/reperfusion injury (I/R injury), but whether polydatin exerts cardioprotective effect against myocardial ischemia/reperfusion and the underlying mechanisms remain unclear. Previous studies have demonstrated that oxidative stress plays an important role in the process of I/R. Elevation of oxidative agents and decline in anti-oxidant substance would promote I/R. Meanwhile, the activation of PKC signaling seems to mediate the cardioprotective effects of many drugs by alleviating Ca(2+) influx. In the present study, we reported for the first time that intravenous administration of polydatin before I/R significantly limited the infarct size, creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) leakage from the damaged myocardium after I/R. The activity of SOD and the content of MDA remarkably changed in the presence of polydatin as well. However, the cardiac function-preserving and myocardial enzymes leakage-limiting effects of polydatin vanished in the presence of PKC inhibitors and mito K(ATP) channel blockers. But there was not a significant change in the activity of SOD and MDA content. We therefore conclude that PPC exerts cardioprotective effect by the activation of PKC-K(ATP)-dependent signaling and the direct anti-oxidative stress mechanisms.

Neuroprotective effects of tetramethylpyrazine against dopaminergic neuron injury in a rat model of Parkinson's disease induced by MPTP.

Parkinsons disease (PD) is the second most prevalent progressive neurodegenerative disease. Although several hypotheses have been proposed to explain the pathogenesis of PD, apoptotic cell death and oxidative stress are the most prevalent mechanisms. Tetramethylpyrazine (TMP) is a biological component that has been extracted from Ligusticum wallichii Franchat (ChuanXiong), which exhibits anti-apoptotic and antioxidant roles. In the current study, we aimed to investigate the possible protective effect of TMP against dopaminergic neuron injury in a rat model of Parkinsons disease induced by MPTP and to elucidate probable molecular mechanisms. The results showed that TMP could notably prevent MPTP-induced dopaminergic neurons damage, reflected by improvement of motor deficits, enhancement of TH expression and the content of dopamine and its metabolite, DOPAC. We observed MPTP-induced activation of mitochondrial apoptotic death pathway, evidenced by up-regulation of Bax, down-regulation of Bcl-2, release of cytochrome c and cleavage of caspase 3, which was significantly inhibited by TMP. Moreover, TMP could prevent MPTP-increased TBARS level and MPTP-decreased GSH level, indicating the antioxidant role of TMP in PD model. And the antioxidant role of TMP attributes to the prevention of MPTP-induced reduction of Nrf2 and GCLc expression. In conclusion, in MPTP-induced PD model, TMP prevents the down-regulation of Nrf2 and GCLc, maintaining redox balance and inhibiting apoptosis, leading to the attenuation of dopaminergic neuron damage. The effectiveness of TMP in treating PD potentially leads to interesting therapeutic perspectives.

Anticancer Effects of Bufalin on Human Hepatocellular Carcinoma HepG2 Cells: Roles of Apoptosis and Autophagy

The traditional Chinese medicine bufalin, extracted from toad’s skin, has been demonstrated to exert anticancer activities in various kinds of human cancers. The mechanisms of action lie in its capacity to induce apoptosis, or termed type I programmed cell death (PCD). However, type II PCD, or autophagy, participates in cancer proliferation, progression, and relapse, as well. Recent studies on autophagy seem to be controversial because of the dual roles of autophagy in cancer survival and death. In good agreement with previous studies, we found that 100 nM bufalin induced extensive HepG2 cell apoptosis. However, we also noticed bufalin triggered autophagy and enhanced Beclin-1 expression, LC3-I to LC3-II conversion, as well as decreased p62 expression and mTOR signaling activation in HepG2 cells. Blockage of autophagy by selective inhibitor 3-MA decreased apoptotic ratio in bufalin-treated HepG2 cells, suggesting a proapoptotic role of bufalin-induced autophagy. Furthermore, we investigated the underlying mechanisms of bufalin-induced autophagy. Bufalin treatment dose-dependently promoted AMPK phosphorylation while AMPK inhibition by compound C significantly attenuated bufalin-induced autophagy. Taken together, we report for the first time that bufalin induces HepG2 cells PCD, especially for autophagy, and the mechanism of action is, at least in part, AMPK-mTOR dependent.

Proliferation-Attenuating and Apoptosis-Inducing Effects of Tryptanthrin on Human Chronic Myeloid Leukemia K562 Cell Line in Vitro

Tryptanthrin, a kind of indole quinazoline alkaloid, has been shown to exhibit anti-microbial, anti-inflammation and anti-tumor effects both in vivo and in vitro. However, its biological activity on human chronic myeloid leukemia cell line K562 is not fully understood. In the present study, we investigated the proliferation-attenuating and apoptosis-inducing effects of tryptanthrin on leukemia K562 cells in vitro and explored the underlying mechanisms. The results showed that tryptanthrin could significantly inhibit K562 cells proliferation in a time- and dose-dependent manner as evidenced by MTT assay and flow cytometry analysis. We also observed pyknosis, chromatin margination and the formation of apoptotic bodies in the presence of tryptanthrin under the electron microscope. Nuclei fragmentation and condensation by Hoechst 33258 staining were detected as well. The amount of apoptotic cells significantly increased whereas the mitochondrial membrane potential decreased dramatically after tryptanthrin exposure. K562 cells in the tryptanthrin treated group exhibited an increase in cytosol cyt-c, Bax and activated caspase-3 expression while a decrease in Bcl-2, mito cyt-c and pro-caspase-3 contents. However, the changes of pro-caspase-3 and activated caspase-3 could be abolished by a pan-caspase inhibitor ZVAD-FMK. These results suggest that tryptanthrin has proliferation-attenuating and apoptosis-inducing effects on K562 cells. The underlying mechanism is probably attributed to the reduction in mitochondria membrane potential, the release of mito cyt-c and pro-caspase-3 activation.

The Bone-Protective Effect of Genistein in the Animal Model of Bilateral Ovariectomy: Roles of Phytoestrogens and PTH/PTHR1 Against Post-Menopausal Osteoporosis

Genistein, a major phytoestrogen of soy, is considered a potential drug for the prevention and treatment of post-menopausal osteoporosis. Mounting evidence suggested a positive correlation between genistein consumption and bone health both in vivo and in vitro. Earlier studies have revealed that genistein acted as a natural estrogen analogue which activated estrogen receptor and exerted anti-osteoporotic effect. However, it remains unclear whether PTH, the most crucial hormone that regulates mineral homeostasis, participates in the process of genistein-mediated bone protection. In the present study, we compared the therapeutic effects between genistein and nilestriol and investigated whether PTH and its specific receptor PTHR1 altered in response to genistein-containing diet in the animal model of ovariectomy. Our results showed that genistein administration significantly improved femoral mechanical properties and alleviates femoral turnover. Genistein at all doses (4.5 mg/kg, 9.0 mg/kg and 18.0 mg/kg per day, respectively) exerted improved bending strength and b-ALP limiting effects than nilestriol in the present study. However, genistein administration did not exert superior effects on bone protection than nilestriol. We also observed circulating PTH restoration in ovariectomized rats receiving genistein at the dose of 18 mg/kg per day. Meanwhile, PTHR1 abnormalities were attenuated in the presence of genistein as confirmed by RT-PCR, Western blot and immunohistochemistry. These findings strongly support the idea that besides serving as an estrogen, genistein could interact with PTH/PTHR1, causing a superior mineral restoring effect than nilestriol on certain circumstance. In conclusion, our study reported for the first time that the anti-osteoporotic effect of genistein is partly PTH/PTHR1-dependent. Genistein might be a potential option in the prevention and treatment of post-menopausal osteoporosis with good tolerance, more clinical benefits and few undesirable side effects.

Tetramethylpyrazine (TMP) exerts antitumor effects by inducing apoptosis and autophagy in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common types of liver cancers with high recurrence rate and mortality rate. Recent studies have indicated that tetramethylpyrazine (TMP), a purified chemical extracted from Ligusticum wallichii Franchat (ChuanXiong), possessed antitumor effects on HCC, but detailed mechanism remains unclear. Our study aims at investigating the antitumor effect of TMP on HCC and its underlying mechanism. We found that TMP inhibited cell proliferation of HepG2 cells in a dose-dependent way, and xenograft tumor models also indicated that high concentrations of TMP administration inhibited tumor growth. Next, flow cytometric analysis and transmission electron microscope images showed that TMP enhanced cell apoptosis in HepG2 cells, and western blot results showed that TMP promoted cleavage of caspase-3 and PARP in vitro and in vivo. We also found that TMP caused autophagy in HCC in vitro and in vivo. In order to examine the role of autophagy in TMP-induced apoptosis, 3-methyladenine (3-MA) was used to block the action of autophagy. Our data showed TMP-induced autophagy might be a pro-apoptosis process in HCC. Furthermore, the results of anti-oxidative enzymes and oxidation-sensitive fluorescent probe 2, 7-dichlorofluorescein diacetate (DCFH-DA) indicated that TMP induced ROS generation and inhibition of ROS diminished the anticancer function of TMP. In conclusion, our studies provide new insights into the mechanisms underlying the antitumor effect of TMP and suggest that TMP can be a novel therapeutic regimen for HCC.

Polydatin Attenuates Hypoxic Pulmonary Hypertension and Reverses Remodeling through Protein Kinase C Mechanisms

Hypoxic pulmonary hypertension is a life-threatening emergency if untreated. Consistent pulmonary hypertension also leads to arteries and ventricular remodeling. The clinical therapeutic strategy for pulmonary hypertension and the corresponding remodeling mainly interacts with NO, angiotensin II (Ang II) and elevated endothelin (ET) targets. In the present study, we evaluated the effects of polydatin on hypoxia-induced pulmonary hypertension. It was observed that polydatin attenuated hypoxic pulmonary hypertension, reversed remodeling, and regulated NO, Ang II, ET contents in the serum and lung samples. However, forced activation of PKC signaling by its selective activator thymeleatoxin (THX) could abate the effects of polydatain. These results suggest that polydatin might be a promising candidate for hypoxic pulmonary treatment through interaction with PKC mechanisms.