Increased glycolysis is an early consequence of palmitate lipotoxicity mediated by redox signaling.

Exposure to toxic levels of fatty acids (lipotoxicity) leads to cell damage and death and is involved in the pathogenesis of the metabolic syndrome. Since the metabolic consequences of lipotoxicity are still poorly understood, we studied the bioenergetic effects of the saturated fatty acid palmitate, quantifying changes in mitochondrial morphology, real-time oxygen consumption, ATP production sources, and extracellular acidification in hepatoma cells. Surprisingly, glycolysis was enhanced by the presence of palmitate as soon as 1 h after stimulus, while oxygen consumption and oxidative phosphorylation were unchanged, despite overt mitochondrial fragmentation. Palmitate only induced mitochondrial fragmentation if glucose and glutamine were available, while glycolytic enhancement did not require glutamine, showing it is independent of mitochondrial morphological changes. Redox state was altered by palmitate, as indicated by NAD(P)H quantification. Furthermore, the mitochondrial antioxidant mitoquinone, or a selective inhibitor of complex I electron leakage (S1QEL) further enhanced palmitate-induced glycolysis. Our results demonstrate that palmitate overload and lipotoxicity involves an unexpected and early increase in glycolytic flux, while, surprisingly, no changes in oxidative phosphorylation are observed. Interestingly, enhanced glycolysis involves signaling by mitochondrially-generated oxidants, uncovering a novel regulatory mechanism for this pathway.

Administration of branched-chain amino acids increases the susceptibility to lipopolysaccharide-induced inflammation in young Wistar rats.

Maple Syrup Urine Disease (MSUD) is an inborn error of the metabolism caused by defects in the branched a-ketoacid dehydrogenase complex (BCKDC), leading to the accumulation of branched chain amino acids (BCAAs) (leucine, isoleucine and valine). Patients with MSUD present a series of neurological dysfunction. Recent studies have been associated the brain damage in the MSUD with inflammation and immune system activation. MSUD patients die within a few months of life due to recurrent metabolic crises and neurologic deterioration, often precipitated by infection or other stresses. In this regard, our previous results showed that the inflammatory process, induced by lipopolysaccharide (LPS), associated with high levels of BCAAs causes blood-brain barrier (BBB) breakdown due to hyperactivation of MMPs. Thus, we hypothesize that the synergistic action between high concentrations of BCAAs (H-BCAAs) and LPS on BBB permeability and hyperactivation of MMPs could be through an increase in the production of cytokines and RAGE protein levels. We observed that high levels of BCAA in infant rats are related to increased brain inflammation induced by LPS administration. In addition, BCAA exposure led to an increase on brain RAGE expression of young rats. The brain inflammation was characterized by enhanced levels of interleukin 1 ß (IL-1ß), interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α) and Interferon- γ (IFN-γ), and decreased content of interleukin-10 (IL-10). Therefore, MSUD is associated with a more intense neuroinflammation induced by LPS infection.

Retinoic acid downregulates thiol antioxidant defences and homologous recombination while promotes A549 cells sensitization to cisplatin.

Recent studies have investigated the use of retinoic acid (RA) molecule in combined chemotherapies to cancer cells as an attempt to increase treatment efficiency and circumvent cell resistance. Positive results were obtained in clinical trials from lung cancer patients treated with RA and cisplatin. Meanwhile, the signalling process that results from the interaction of both molecules remains unclear. One of the pathways that RA is able to modulate is the activity of NRF2 transcription factor, which is highly associated with tumour progression and resistance. Therefore, the aim of this work was to investigate molecular mechanism of RA and cisplatin co-treatment in A549 cells, focusing in NRF2 pathway. To this end, we investigated NRF2 and NRF2-target genes expression, cellular redox status, cisplatin-induced apoptosis, autophagy and DNA repair through homologous recombination. RA demonstrated to have an inhibitory effect over NRF2 activation, which regulates the expression of thiol antioxidants enzymes. Moreover, RA increased reactive species production associated with increased oxidation of thiol groups within the cells. The expression of proteins associated with DNA repair through homologous recombination was also suppressed by RA pre-treatment. All combined, these effects appear to create a more sensitive cellular environment to cisplatin treatment, increasing apoptosis frequency. Interestingly, autophagy was also increased by combination therapy, suggesting a resistance mechanism by A549 cells. In conclusion, these results provided new information about molecular mechanisms of RA and cisplatin treatment contributing to chemotherapy optimization.

Guarana supplementation attenuated obesity, insulin resistance, and adipokines dysregulation induced by a standardized human Western diet via brown adipose tissue activation.

Obesity is a metabolic disorder associated with adverse health consequences that has increased worldwide at an epidemic rate. This has encouraged many people to utilize nonprescription herbal supplements for weight loss without knowledge of their safety or efficacy. However, mounting evidence has shown that some herbal supplements used for weight loss are associated with adverse effects. Guarana seed powder is a popular nonprescription dietary herb supplement marketed for weight loss, but no study has demonstrated its efficacy or safety when administered alone. Wistar rats were fed four different diets (low-fat diet and Western diet with or without guarana supplementation) for 18 weeks. Metabolic parameters, gut microbiota changes, and toxicity were then characterized. Guarana seed powder supplementation prevented weight gain, insulin resistance, and adipokine dysregulation induced by Western diet compared with the control diet. Guarana induced brown adipose tissue expansion, mitochondrial biogenesis, uncoupling protein-1 overexpression, AMPK activation, and minor changes in gut microbiota. Molecular docking suggested a direct activation of AMPK by four guarana compounds tested here. We propose that brown adipose tissue activation is one of the action mechanisms involved in guarana supplementation-induced weight loss and that direct AMPK activation may underlie this mechanism. In summary, guarana is an attractive potential therapeutic agent to treat obesity.

Extracellular HSP70 Activates ERK1/2, NF-kB and Pro-Inflammatory Gene Transcription Through Binding with RAGE in A549 Human Lung Cancer Cells.

BACKGROUND/AIMS: Heat shock protein 70 (HSP70) has been recently described with extracellular actions, where it is actively released in inflammatory conditions. Acting as DAMPs (damage associated molecular pattern), extracellular HSP70 (eHSP70) interacts with membrane receptors and activates inflammatory pathways. At this context, the receptor for advanced glycation endproducts (RAGE) emerges as a possible candidate for interaction with eHSP70. RAGE is a pattern-recognition receptor and its expression is increased in several diseases related to a chronic pro-inflammatory state. One of the main consequences of RAGE ligand-binding is the ERK1/2 (extracellular signal-regulated kinases)-dependent activation of NF-kB (nuclear factor kappa B), which leads to expression of TNF-α (tumor necrosis factor alpha) and other cytokines. The purpose of this work is to elucidate if eHSP70 is able to evoke RAGE-dependent signaling using A549 human lung cancer cells, which constitutively express RAGE. METHODS: Immunoprecipitation and protein proximity assay were utilized to demonstrate the linkage between RAGE and eHSP70. To investigate RAGE relevance on cell response to eHSP70, siRNA was used to knockdown the receptor expression. Signaling pathways activation were evaluated by western blotting, gene reporter luciferase and real time quantitative PCR. RESULTS: Protein eHSP70 shown to be interacting physically with the receptor RAGE in our cell model. Treatment with eHSP70 caused ERK1/2 activation and NF-κB transactivation impaired by RAGE knockdown. Moreover, the stimulation of pro-inflammatory cytokines expression by eHSP70 was inhibited in RAGE-silenced cells. Finally, conditioned medium of eHSP70-treated A549 cells caused differential effects in monocytes cytokine expression when A549 RAGE expression is inhibited. CONCLUSIONS: Our results evidence eHSP70 as a novel RAGE agonist capable of influence the cross-talk between cancer and immune system cells.

NRF2 Mediates Neuroblastoma Proliferation and Resistance to Retinoic Acid Cytotoxicity in a Model of In Vitro Neuronal Differentiation.

Retinoic acid (RA) morphogenetic properties have been used in different kinds of therapies, from neurodegenerative disorders to some types of cancer such as promyelocytic leukemia and neuroblastoma. However, most of the pathways responsible for RA effects remain unknown. To investigate such pathways, we used a RA-induced differentiation model in the human neuroblastoma cells, SH-SY5Y. Our data showed that n-acetyl-cysteine (NAC) reduced cells' proliferation rate and increased cells' sensitivity to RA toxicity. Simultaneously, NAC pre-incubation attenuated nuclear factor erythroid 2-like factor 2 (NRF2) activation by RA. None of these effects were obtained with Trolox® as antioxidant, suggesting a cysteine signalization by RA. NRF2 knockdown increased cell sensibility to RA after 96 h of treatment and diminished neuroblastoma proliferation rate. Conversely, NRF2 overexpression limited RA anti-proliferative effects and increased cell proliferation. In addition, a rapid and non-genomic activation of the ERK 1/2 and PI3K/AKT pathways revealed to be equally required to promote NRF2 activation and necessary for RA-induced differentiation. Together, we provide data correlating NRF2 activity with neuroblastoma proliferation and resistance to RA treatments; thus, this pathway could be a potential target to optimize neuroblastoma chemotherapeutic response as well as in vitro neuronal differentiation protocols.

Reverse engineering the neuroblastoma regulatory network uncovers MAX as one of the master regulators of tumor progression.

Neuroblastoma is the most common extracranial tumor and a major cause of infant cancer mortality worldwide. Despite its importance, little is known about its molecular mechanisms. A striking feature of this tumor is its clinical heterogeneity. Possible outcomes range from aggressive invasion to other tissues, causing patient death, to spontaneous disease regression or differentiation into benign ganglioneuromas. Several efforts have been made in order to find tumor progression markers. In this work, we have reconstructed the neuroblastoma regulatory network using an information-theoretic approach in order to find genes involved in tumor progression and that could be used as outcome predictors or as therapeutic targets. We have queried the reconstructed neuroblastoma regulatory network using an aggressive neuroblastoma metastasis gene signature in order to find its master regulators (MRs). MRs expression profiles were then investigated in other neuroblastoma datasets so as to detect possible clinical significance. Our analysis pointed MAX as one of the MRs of neuroblastoma progression. We have found that higher MAX expression correlated with favorable patient outcomes. We have also found that MAX expression and protein levels were increased during neuroblastoma SH-SY5Y cells differentiation. We propose that MAX is involved in neuroblastoma progression, possibly increasing cell differentiation by means of regulating the availability of MYC:MAX heterodimers. This mechanism is consistent with the results found in our SH-SY5Y differentiation protocol, suggesting that MAX has a more central role in these cells differentiation than previously reported. Overexpression of MAX has been identified as anti-tumorigenic in other works, but, to our knowledge, this is the first time that the link between the expression of this gene and malignancy was verified under physiological conditions.