AMPK-deficiency forces metformin-challenged cancer cells to switch from carbohydrate metabolism to ketogenesis to support energy metabolism.

Epidemiologic studies in diabetic patients as well as research in model organisms have indicated the potential of metformin as a drug candidate for the treatment of various types of cancer, including breast cancer. To date most of the anti-cancer properties of metformin have, in large part, been attributed either to the inhibition of mitochondrial NADH oxidase complex (Complex I in the electron transport chain) or the activation of AMP-activated kinase (AMPK). However, it is becoming increasingly clear that AMPK activation may be critical to alleviate metabolic and energetic stresses associated with tumor progression suggesting that it may, in fact, attenuate the toxicity of metformin instead of promoting it. Here, we demonstrate that AMPK opposes the detrimental effects of mitochondrial complex I inhibition by enhancing glycolysis at the expense of, and in a manner dependent on, pyruvate availability. We also found that metformin forces cells to rewire their metabolic grid in a manner that depends on AMPK, with AMPK-competent cells upregulating glycolysis and AMPK-deficient cell resorting to ketogenesis. In fact, while the killing effects of metformin were largely rescued by pyruvate in AMPKcompetent cells, AMPK-deficient cells required instead acetoacetate, a product of fatty acid catabolism indicating a switch from sugar to fatty acid metabolism as a central resource for ATP production in these cells. In summary, our results indicate that AMPK activation is not responsible for metformin anticancer activity and may instead alleviate energetic stress by activating glycolysis.

Dihydrocaffeic Acid Prevents UVB-Induced Oxidative Stress Leading to the Inhibition of Apoptosis and MMP-1 Expression via p38 Signaling Pathway.

Chronic UVB exposure promotes oxidative stress, directly causes molecular damage, and induces aging-related signal transduction, leading to skin photoaging. Dihydrocaffeic acid (DHCA) is a phenolic compound with potential antioxidant capacity and is thus a promising compound for the prevention of UVB-induced skin photodamage. The aim of this study was to evaluate the antioxidant and protective effect of DHCA against oxidative stress, apoptosis, and matrix metalloproteinase (MMP) expression via the mitogen-activated protein kinase (MAPK) signaling pathway on L929 fibroblasts irradiated with UVB. DHCA exhibited high antioxidant capacity on 2,2-diphenyl-1-picrylhydrazyl (DPPH•), 2,2-azinobis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS•+), and xanthine/luminol/xanthine oxidase (XOD) assays and reduced UVB-induced cell death in the neutral red assay. DHCA also modulated oxidative stress by decreasing intracellular reactive oxygen species (ROS) and extracellular hydrogen peroxide (H2O2) production, enhancing catalase (CAT) and superoxide dismutase (SOD) activities and reduced glutathione (GSH) levels. Hence, cellular damage was attenuated by DHCA, including lipid peroxidation, apoptosis/necrosis and its markers (loss of mitochondria membrane potential, DNA condensation, and cleaved caspase 9 expression), and MMP-1 expression. Furthermore, DHCA reduced the phosphorylation of MAPK p38. These findings suggest that DHCA can be used in the development of skin care products to prevent UVB-induced skin damage.

Design of composite microparticle systems based on pectin and waste material of propolis for modified l-alanyl-l-glutamine release and with immunostimulant activity.

Catabolic conditions like acquired immunodeficiency syndrome, cancer, and burn can cause immunosuppression. Amino acids such as alanine and glutamine are essential for the activity of the immune system. Propolis is immunostimulant and the waste of propolis extraction has been reused with technological and therapeutic purposes. Therefore, this study describes the association of propolis byproduct extract (BPE) with pectin to prepare spray-dried microparticles containing the dipeptide l-alanyl-l-glutamine as stimulant systems of neutrophils. The use of a factorial design allowed selecting the best formulation, which was characterized by morphology, size, and entrapment efficiency analyses. In addition, the systems were characterized by thermal and X-ray diffraction analysis, Fourier-transform infrared spectroscopy, in vitro drug release, and in vitro cytotoxicity and stimulation test of neutrophils. Small well-structured microparticles with good entrapment efficiency values were achieved. Thermal stability of formulation was observed, and it was proved that pectin, BPE and l-alanyl-l-glutamine were dispersed throughout the matrix. The drug was released from the microparticles during 24 h governed by swelling and diffusion. The drug-loaded formulations showed a significant stimulating effect on neutrophils. These structures could increase the activity of immune cells, and other in vitro and in vivo studies should be performed in the future.

Artepillin C Induces Selective Oxidative Stress and Inhibits Migration and Invasion in a Comprehensive Panel of Human Cervical Cancer Cell Lines.

BACKGROUND: Artepillin C (3,5-diprenyl-4-hydroxycinnamic acid) is the main bioactive component of Brazilian green propolis, and possesses, among other things, anticancer properties. However, to the best of our knowledge, there are no studies of artepillin C in cervical cancer. METHOD: To explore a new therapeutic candidate for cervical cancer, we have evaluated the effects of artepillin C on cellular viability in a comprehensive panel of human cervical cancer-derived cell lines including HeLa (human papillomavirus/HPV 18-positive), SiHa (HPV 16-positive), CaSki (HPV 16- and 18-positive) and C33A (HPV-negative) cells compared to a spontaneously immortalized human epithelial cell line (HaCaT). RESULTS: Our results demonstrated that artepillin C had a selective effect on cellular viability and could induce apoptosis possibly by intrinsic pathway, likely a result of oxidative stress, in all cancer-derived cell lines but not in HaCaT. Additionally, artepillin C was able to inhibit the migration and invasion of cancer cells. CONCLUSION: Thus, artepillin C appears to be a promising new candidate as an anticancer drug for cervical cancer induced by different HPV types.

Manganese superoxide dismutase (SOD2): is there a center in the universe of mitochondrial redox signaling?

It is becoming increasingly clear that mitochondria drive cellular functions and in vivo phenotypes by directing the production rate and abundance of metabolites that are proposed to function as signaling molecules (Chandel 2015; Selak et al. 2005; Etchegaray and Mostoslavsky 2016). Many of these metabolites are intermediates that make up cellular metabolism, part of which occur in mitochondria (i.e. the TCA and urea cycles), while others are produced "on demand" mainly in response to alterations in the microenvironment in order to participate in the activation of acute adaptive responses (Mills et al. 2016; Go et al. 2010). Reactive oxygen species (ROS) are well suited for the purpose of executing rapid and transient signaling due to their short lived nature (Bae et al. 2011). Hydrogen peroxide (H2O2), in particular, possesses important characteristics including diffusibility and faster reactivity with specific residues such as methionine, cysteine and selenocysteine (Bonini et al. 2014). Therefore, it is reasonable to propose that H2O2 functions as a relatively specific redox signaling molecule. Even though it is now established that mtH2O2 is indispensable, at least for hypoxic adaptation and energetic and/or metabolic homeostasis (Hamanaka et al. 2016; Guzy et al. 2005), the question of how H2O2 is produced and regulated in the mitochondria is only partially answered. In this review, some roles of this indispensable signaling molecule in driving cellular metabolism will be discussed. In addition, we will discuss how H2O2 formation in mitochondria depends on and is controlled by MnSOD. Finally, we will conclude this manuscript by highlighting why a better understanding of redox hubs in the mitochondria will likely lead to new and improved therapeutics of a number of diseases, including cancer.

Oxidative Stress Triggered by Apigenin Induces Apoptosis in a Comprehensive Panel of Human Cervical Cancer-Derived Cell Lines.

Recently, the cytotoxic effects of apigenin (4',5,7-trihydroxyflavone), particularly its marked inhibition of cancer cell viability both in vitro and in vivo, have attracted the attention of the anticancer drug discovery field. Despite this, there are few studies of apigenin in cervical cancer, and these studies have mostly been conducted using HeLa cells. To evaluate the possibility of apigenin as a new therapeutic candidate for cervical cancer, we evaluated its cytotoxic effects in a comprehensive panel of human cervical cancer-derived cell lines including HeLa (human papillomavirus/HPV 18-positive), SiHa (HPV 16-positive), CaSki (HPV 16 and HPV 18-positive), and C33A (HPV-negative) cells in comparison to a nontumorigenic spontaneously immortalized human epithelial cell line (HaCaT). Our results demonstrated that apigenin had a selective cytotoxic effect and could induce apoptosis in all cervical cancer cell lines which were positively marked with Annexin V, but not in HaCaT (control cells). Additionally, apigenin was able to induce mitochondrial redox impairment, once it increased ROS levels and H2O2, decreased the Δψm, and increased LPO. Still, apigenin was able to inhibit migration and invasion of cancer cells. Thus, apigenin appears to be a promising new candidate as an anticancer drug for cervical cancer induced by different HPV genotypes.

Caveolin-1 regulates cancer cell metabolism via scavenging Nrf2 and suppressing MnSOD-driven glycolysis.

Aerobic glycolysis is an indispensable component of aggressive cancer cell metabolism. It also distinguishes cancer cells from most healthy cell types in the body. Particularly for this reason, targeting the metabolism to improve treatment outcomes has long been perceived as a potentially valuable strategy. In practice, however, our limited knowledge of why and how metabolic reprogramming occurs has prevented progress towards therapeutic interventions that exploit the metabolic peculiarities of tumors. We recently described that in breast cancer, MnSOD upregulation is both necessary and sufficient to activate glycolysis. Here, we focused on determining the molecular mechanisms of MnSOD upregulation. We found that Caveolin-1 (Cav-1) is a central component of this mechanism due to its suppressive effects of NF-E2-related factor 2 (Nrf2), a transcription factor upstream of MnSOD. In transformed MCF10A(Er/Src) cells, Cav-1 loss preceded the activation of Nrf2 and its induction of MnSOD expression. Consistently, with previous observations, MnSOD expression secondary to Nrf2 activation led to an increase in the glycolytic rate dependent on mtH2O2 production and the activation of AMPK. Moreover, rescue of Cav-1 expression in a breast cancer cell line (MCF7) suppressed Nrf2 and reduced MnSOD expression. Experimental data were reinforced by epidemiologic nested case-control studies showing that Cav-1 and MnSOD are inversely expressed in cases of invasive ductal carcinoma, with low Cav-1 and high MnSOD expression being associated with lower 5-year survival rates and molecular subtypes with poorest prognosis.