Oroxylin A induces G2/M phase cell-cycle arrest via inhibiting Cdk7-mediated expression of Cdc2/p34 in human gastric carcinoma BGC-823 cells

SIRT3 Activation a Promise in Drug Development? New Insights into SIRT3 Biology and Its Implications on the Drug Discovery Process

Sirtuins catalyze deacetylation of lysine residues with a NAD+-dependent mechanism. In mammals, the sirtuin family is composed of seven members, divided into four subclasses that differ in substrate specificity, subcellular localization, regulation, as well as interactions with other proteins, both within and outside the epigenetic field. Recently, much interest has been growing in SIRT3, which is mainly involved in regulating mitochondrial metabolism. Moreover, SIRT3 seems to be protective in diseases such as age-related, neurodegenerative, liver, kidney, heart, and metabolic ones, as well as in cancer. In most cases, activating SIRT3 could be a promising strategy to tackle these health problems. Here, we summarize the main biological functions, substrates, and interactors of SIRT3, as well as several molecules reported in the literature that are able to modulate SIRT3 activity. Among the activators, some derive from natural products, others from library screening, and others from the classical medicinal chemistry approach.

Long-Term Exposure to Oroxylin A Inhibits Metastasis by Suppressing CCL2 in Oral Squamous Cell Carcinoma Cells

Oroxylin A (Oro-A), the main bioactive flavonoid extracted from Scutellaria radix, has been reported to inhibit migration in various human cancer cell models. In this study, we further explored the anti-migration effects of Oro-A on oral squamous cell carcinoma (OSCC) cells and investigated the underlying mechanisms. A 24-h (short-term) exposure of OSCC cells to non-cytotoxic concentrations (5⁻20 μM) of Oro-A significantly suppressed cell migration according to a wound-healing assay. Furthermore, a 30-day exposure (long-term) to Oro-A (20 μM), which did not exhibit a cytotoxic effect on OSCC cells, significantly suppressed cell migration more than short-term Oro-A exposure. To uncover the molecular mechanisms underlying the inhibitory effect of long-term Oro-A exposure on OSCC migration, a cDNA microarray and the Ingenuity software were used. Overall, 112 upregulated and 356 downregulated genes were identified in long-term Oro-A-exposed cells compared with untreated OSCC cells. Among them, 75 genes were reported to be associated with cancer cell migration. Consistent with the cDNA microarray results, we found that the expression levels of several cell migration-related genes, such as LCN2, ID-1, MDK, S100A9 and CCL2, were significantly decreased in long-term Oro-A-exposed OSCC cells using a quantitative real-time polymerase chain reaction (Q-PCR) assay. The Western blotting and enzyme-linked immunosorbent assay (ELISA) results also demonstrated that CCL2 expression at the mRNA and protein levels was significantly decreased in long-term Oro-A-exposed OSCC cells compared with untreated OSCC cells. Moreover, the expression levels of downstream CCL2 targets, including p-ERK1/2, NFκB, MMP2, and MMP9, were also decreased in long-term Oro-A-exposed OSCC cells. Further, Oro-A treatment suppressed in vivo metastasis. These results suggest that long-term Oro-A treatment inhibits metastasis via CCL2 signaling in OSCC cells.

VDAC1 as Pharmacological Target in Cancer and Neurodegeneration: Focus on Its Role in Apoptosis

Cancer and neurodegeneration are different classes of diseases that share the involvement of mitochondria in their pathogenesis. Whereas the high glycolytic rate (the so-called Warburg metabolism) and the suppression of apoptosis are key elements for the establishment and maintenance of cancer cells, mitochondrial dysfunction and increased cell death mark neurodegeneration. As a main actor in the regulation of cell metabolism and apoptosis, VDAC may represent the common point between these two broad families of pathologies. Located in the outer mitochondrial membrane, VDAC forms channels that control the flux of ions and metabolites across the mitochondrion thus mediating the organelle's cross-talk with the rest of the cell. Furthermore, the interaction with both pro-apoptotic and anti-apoptotic factors makes VDAC a gatekeeper for mitochondria-mediated cell death and survival signaling pathways. Unfortunately, the lack of an evident druggability of this protein, since it has no defined binding or active sites, makes the quest for VDAC interacting molecules a difficult tale. Pharmacologically active molecules of different classes have been proposed to hit cancer and neurodegeneration. In this work, we provide an exhaustive and detailed survey of all the molecules, peptides, and microRNAs that exploit VDAC in the treatment of the two examined classes of pathologies. The mechanism of action and the potential or effectiveness of each compound are discussed.

Anticancer Effect and Apoptosis Induction of Gambogic Acid in Human Leukemia Cell Line K562 In Vitro

BACKGROUND

The aim of this study was to investigate the anticancer effect and related mechanisms of gambogic acid (GA), a traditional Chinese medicine, on human leukemia cell line K562, together with the effect on bone marrow mononuclear cells (MNCs).

MATERIAL AND METHODS

K562 cells and MNCs were treated with various concentrations and treatment times of GA. Inhibitory rate was detected by use of the Cell Counting Kit-8 (CCK-8) assay. Apoptosis was analyzed by morphological detection, Annexin-V/PI doubling staining, and TUNEL assays. The expression changes of pivotal proteins were evaluated by Western blotting.

RESULTS

GA not only suppressed cell proliferation, but also induced apoptosis of K562 cells in a dose-dependent manner. While it did not significantly inhibit cell proliferation of MNCs, it did induce apoptosis in a dose-dependent manner. CCK-8 assay revealed that the proliferation of K562 cells was significantly inhibited when the concentration of GA was more than 0.5 μM. Morphological detection showed the nuclei became denser and more intense orange in K562 cells after GA treatment compared with the untreated group. The expression levels of BCL-2, nuclear factor-κB (NF-κB), c-myc, phosphatidylinositol3-kinase (PI3K), and phosphorylation of serine-threonine kinase (p-AKT) were down-regulated by GA.

CONCLUSIONS

GA significantly suppressed the proliferation of K562 cells, but has less effect on MNCs. The inhibition of K562 cells proliferation and apoptosis induced by GA might be related to the down-regulation of BCL-2, NF-κB, c-myc, PI3K, and p-AKT.

Oroxylum indicum (L.) Kurz, an important Asian traditional medicine: from traditional uses to scientific data for its commercial exploitation

ETHNOPHARMACOLOGICAL RELEVANCE

Oroxylum indicum\ (L.) Kurz has been used for centuries as a traditional medicine in Asia in ethnomedicinal systems for the prevention and treatment of several diseases, such as jaundice, arthritic and rheumatic problems, gastric ulcers, tumors, respiratory diseases, diabetes, and diarrhea and dysentery, among others. The present review provides scientific evidence supporting the therapeutic potency of the plant for ethnomedicinal uses and identifies gaps for future research to facilitate commercial exploitation.

METHODS

This review is based on available information on traditional uses and phytochemical, pharmacological, clinical and toxicity data for Oroxylum indicum that was collected from electronic (SciFinder, PubMed, Science Direct, and ACS, among others) and library searches.

KEY FINDING

A variety of traditional medicinal uses of Oroxylum indicum in different Southeast and South Asian countries have been reported in books describing the uses of these plants. Phytochemical investigations of the different parts of the plant resulted in identification of approximately 111 compounds, among which flavonoids, naphthalenoids and cyclohexylethanoids are the predominant groups. The crude extracts and their isolates exhibit a wide spectrum of in vitro and in vivo pharmacological activities involving antimicrobial, anti-inflammatory, anti-arthritic, anticancer, anti-ulcer, hepatoprotective, antidiabetic, antidiarrheal and antioxidant activities. Flavonoids are the major constituents of all parts of the plant. From a toxicity perspective, only aqueous and ethanolic extracts of stem bark, root bark and fruits have been assessed and found to be safe. The major flavonoids of the stem bark, such as baicalein, chrysin and oroxylin A, were reported for the first time as natural flavonoids with potent inhibitory activity against endoprotease enzymes and proprotein convertases, which play a key role in the growth of cancer and in viral and bacterial infections. Flavonoids are the active components of bioactive extracts. Several Ayurvedic medicines have been formulated either singly using this plant or along with other herbs for the treatment of different diseases.

CONCLUSIONS

Pharmacological results have supported some traditional medicinal uses of Oroxylum indicum. Several extracts and their isolates have been reported to exhibit interesting pharmacological properties. These components could be useful as sources of modern medicines following future detailed studies to elucidate their underlying mechanisms, toxicity, synergistic effects and clinical trials. Attention should also be focused on pharmacological studies investigating the traditional uses of the plant, which have not been yet addressed, as well as clinical studies investigating commercial Ayurvedic medicines and other ethnomedicinal preparations in human subjects based on this plant to confirm the safety and quality of the preparations.

Activation of the unfolded protein response contributed to the selective cytotoxicity of oroxylin A in human hepatocellular carcinoma HepG2 cells

Hepatocellular carcinoma (HCC) is a refractory malignancy with a high incidence and large mortality. Current strategy for the chemotherapy of HCC focuses on developing agents with better efficacy and lower toxicity. In this study, we demonstrated that the natural flavonoid oroxylin A preferentially inhibited the viability of HCC cell line HepG2 but not the normal hepatic cell line L02. In HepG2 but not L02 cells, oroxylin A induced substantial production of intracellular H₂O₂ and inordinate activation of the PERK-eIF2α-ATF4-CHOP branch of the unfolded protein response (UPR) pathway, which resulted in the induction of TRB3 and causal reduction of p-AKT1/2/3 (Ser473). Moreover, these effects were eliminated by either the stable knockdown of CHOP or the pretreatment and then co-incubation with the specific H₂O₂ scavenger catalase. These results indicated that the H₂O₂-triggered overactivation of the UPR pathway and causal inactivation of AKT signaling contributed to the preferential cytotoxicity of oroxylin A in malignant HepG2 cells. Therefore, present study proposed an underlying molecular mechanism that implicated the selective antitumor effect of oroxylin A and recommended oroxylin A as a prospect for improving the current chemotherapeutic strategy for the treatment of HCC.

Beclin 1-mediated autophagy in hepatocellular carcinoma cells: implication in anticancer efficiency of oroxylin A via inhibition of mTOR signaling

Autophagy is a tightly-regulated catabolic process that involves the degradation of intracellular components via lysosomes. Although the pivotal role of autophagy in cell growth, development, and homeostasis has been well understood, its function in cancer prevention and intervention remains to be delineated. The aim of this study was to investigate the function and mechanism of autophagy induced by oroxylin A, a natural mono-flavonoid extracted from Scutellariae radix. We found for the first time that oroxylin A induced Beclin 1-mediated autophagy in human hepatocellular carcinoma HepG2 cells. Time-lapse video microscopy and western blotting studies showed that treatment of cells with 80 μM oroxylin A resulted in the conversion of water soluble MAP-LC3 (LC3-I) to the lipidated and autophagosome-associated form (LC3-II) after 12hours; then autophagosome-lysosome fusion and lysosome degradation after 24 hours was required in oroxylin A-mediated cell death. This induction was associated with the suppressing of PI3K-PTEN-Akt-mTOR signaling pathway by oroxylin A. Our results also showed that autophagy took place before noticeable apoptosis can be observed. It was further demonstrated that oroxylin A-triggered autophagy contributed to cell death using over-expression of autophagy-related gene (Atg5 and Atg7) and inhibition of autophagy by siBeclin 1 and 3-methyladenine (3-MA). In vivo study, oroxylin A inhibited xenograft tumor growth and induced obvious autophagy in tumors. Taken together, we conclude that oroxylin A exhibits autophagy-mediated antitumor activity in a dose and time-dependent manner in vivo and in vitro. These findings define and support a novel function of autophagy in promoting death of hepatocellular carcinoma cells.

Synthesis and biological evaluation of 7-O-modified oroxylin A derivatives

Oroxylin A (5,7-dihydroxy-6-methoxyflavone) is a naturally occurring monoflavonoid isolated from the root of Scutellaria baicalensis Georgi, and exhibits potent anticancer activities in vitro and in vivo. In this study, we synthesized three series of oroxylin derivatives by connecting a nitrogen-containing hydrophilic, heterocyclic ring to the C7-OH via a varying length of carbon chain. All the derivatives were screened for anti-proliferative activities against three tumor cell lines. Some of the derivatives displayed higher activities compared to oroxylin A. The most potent antitumor compound, 5f, also induced apoptosis in HepG2 cell. The difference of 5f between the inhibiting rates of cell proliferation and the apoptotic rates indicated that 5f was more likely to be a necrosis-inducing agent or both apoptosis/necrosis inducer.

Activation of AMP-activated protein kinase contributes to doxorubicin-induced cell death and apoptosis in cultured myocardial H9c2 cells

Despite its potent antitumor effect, clinical use of Doxorubicin is limited because of serious side effects including myocardial toxicity. Understanding the cellular mechanism involved in this process in a better manner is beneficial for optimizing Doxorubicin treatment. In the current study, the authors focus on the AMP-activated protein kinase (AMPK) in the said process. In this study, the authors discovered for the first time that Doxorubicin induces AMPK activation in cultured rat embryonic ventricular myocardial H9c2 cells. Reactive oxygen species (ROS)-dependent LKB1 activation serves as the upstream signal for AMPK activation by Doxorubicin. Evidence in support of the activation of AMPK contributing to Doxorubicin-induced H9c2 cell death/apoptosis--probably by modulating multiple downstream signal targets, including regulating JNK, p53, and inhibiting mTORC1--is provided in this article.