Ana S. Almeida

Glutathionylation of Adenine Nucleotide Translocase Induced by Carbon Monoxide Prevents Mitochondrial Membrane Permeabilization and Apoptosis

The present work demonstrates the ability of CO to prevent apoptosis in a primary culture of astrocytes. For the first time, the antiapoptotic behavior can be clearly attributed to the inhibition of mitochondrial membrane permeabilization (MMP), a key event in the intrinsic apoptotic pathway. In isolated non-synaptic mitochondria, CO partially inhibits (i) loss of potential, (ii) the opening of a nonspecific pore through the inner membrane, (iii) swelling, and (iv) cytochrome c release, which are induced by calcium, diamide, or atractyloside (a ligand of ANT). CO directly modulates ANT function by enhancing ADP/ATP exchange and prevents its pore-forming activity. Additionally, CO induces reactive oxygen species (ROS) generation, and its prevention by β-carotene decreases CO cytoprotection in intact cells as well as in isolated mitochondria, revealing the key role of ROS. On the other hand, CO induces a slight increase in mitochondrial oxidized glutathione, which is essential for apoptosis modulation by (i) delaying astrocytic apoptosis, (ii) decreasing MMP, and (iii) enhancing ADP/ATP translocation activity of ANT. Moreover, CO and GSSG trigger ANT glutathionylation, a post-translational process regulating protein function in response to redox cellular changes. In conclusion, CO protects astrocytes from apoptosis by preventing MMP, acting on ANT (glutathionylation and inhibition of its pore activity) via a preconditioning-like process mediated by ROS and GSSG.

Carbon Monoxide Modulates Apoptosis by Reinforcing Oxidative Metabolism in Astrocytes: ROLE OF Bcl-2*

Background: Low doses of carbon monoxide (CO) prevent apoptosis in several cell models, including astrocytes. Results: CO improves cytochrome c oxidase (COX) activity and induces mitochondrial biogenesis. Bcl-2 expression and interaction with COX is involved in CO signaling. Conclusion: CO stimulates oxidative phosphorylation, improves metabolism, and prevents astrocytic apoptosis. Significance: Metabolism modulation can be a potential strategy against cerebral ischemia. Modulation of cerebral cell metabolism for improving the outcome of hypoxia-ischemia and reperfusion is a strategy yet to be explored. Because carbon monoxide (CO) is known to prevent cerebral cell death; herein the role of CO in the modulation of astrocytic metabolism, in particular, at the level of mitochondria was investigated. Low concentrations of CO partially inhibited oxidative stress-induced apoptosis in astrocytes, by preventing caspase-3 activation, mitochondrial potential depolarization, and plasmatic membrane permeability. CO exposure enhanced intracellular ATP generation, which was accompanied by an increase on specific oxygen consumption, a decrease on lactate production, and a reduction of glucose use, indicating an improvement of oxidative phosphorylation. Accordingly, CO increased cytochrome c oxidase (COX) enzymatic specific activity and stimulated mitochondrial biogenesis. In astrocytes, COX interacts with Bcl-2, which was verified by immunoprecipitation; this interaction is superior after 24 h of CO treatment. Furthermore, CO enhanced Bcl-2 expression in astrocytes. By silencing Bcl-2 expression with siRNA transfection, CO effects in astrocytes were prevented, namely: (i) inhibition of apoptosis, (ii) increase on ATP generation, (iii) stimulation of COX activity, and (iv) mitochondrial biogenesis. Thus, Bcl-2 expression is crucial for CO modulation of oxidative metabolism and for conferring cytoprotection. In conclusion, CO protects astrocytes against oxidative stress-induced apoptosis by improving metabolism functioning, particularly mitochondrial oxidative phosphorylation.

Carbon Monoxide Targeting Mitochondria

Mitochondria present two key roles on cellular functioning: (i) cell metabolism, being the main cellular source of energy and (ii) modulation of cell death, by mitochondrial membrane permeabilization. Carbon monoxide (CO) is an endogenously produced gaseoustransmitter, which presents several biological functions and is involved in maintaining cell homeostasis and cytoprotection. Herein, mitochondrion is approached as the main cellular target of carbon monoxide (CO). In this paper, two main perspectives concerning CO modulation of mitochondrial functioning are evaluated. First, the role of CO on cellular metabolism, in particular oxidative phosphorylation, is discussed, namely, on: cytochrome c oxidase activity, mitochondrial respiration, oxygen consumption, mitochondrial biogenesis, and general cellular energetic status. Second, the mitochondrial pathways involved in cell death inhibition by CO are assessed, in particular the control of mitochondrial membrane permeabilization.

UBC13 and COOH-terminus of HSP70 interacting protein (CHIP) are required for growth hormone receptor endocytosis

Background: The scientific question that we address is how cytokine receptors organize their degradation. Results: CHIP and Ubc13 are required for GH receptor endocytosis, implicating Lys63-specific ubiquitination. Conclusion: This study shows how two ubiquitin ligases act in concert to allow receptor endocytosis. Significance: Understanding this mechanism enables drug design to control GH signaling in fighting cancer and cachexia. Growth hormone receptor (GHR) endocytosis is a highly regulated process that depends on the binding and activity of the multimeric ubiquitin ligase, SCFβTrCP (Skp Cullin F-box). Despite a specific interaction between β-transducin repeat-containing protein (βTrCP) and the GHR, and a strict requirement for ubiquitination activity, the receptor is not an obligatory target for SCFβTrCP-directed Lys48 polyubiquitination. We now show that also Lys63-linked ubiquitin chain formation is required for GHR endocytosis. We identified both the ubiquitin-conjugating enzyme Ubc13 and the ubiquitin ligase COOH terminus of Hsp70 interacting protein (CHIP) as being connected to this process. Ubc13 activity and its interaction with CHIP precede endocytosis of GHR. In addition to βTrCP, CHIP interacts specifically with the cytosolic tails of the dimeric GHR, identifying both Ubc13 and CHIP as novel factors in the regulation of cell surface availability of GHR.

Carbon monoxide prevents hepatic mitochondrial membrane permeabilization

BackgroundLow concentrations of carbon monoxide (CO) protect hepatocytes against apoptosis and confers cytoprotection in several models of liver. Mitochondria are key organelles in cell death control via their membrane permeabilization and the release of pro-apoptotic factors.ResultsHerein, we show that CO prevents mitochondrial membrane permeabilization (MMP) in liver isolated mitochondria. Direct and indirect approaches were used to evaluate MMP inhibition by CO: mitochondrial swelling, mitochondrial depolarization and inner membrane permeabilization. Additionally, CO increases mitochondrial reactive oxygen species (ROS) generation, and their scavenging, by ß-carotene addition, decreases CO protection, which reveals the key role of ROS. Interestingly, cytochrome c oxidase transiently responds to low concentrations of CO by decreasing its activity in the first 5 min, later on there is an increase of cytochrome c oxidase activity, which were detected up to 30 min.ConclusionCO directly prevents mitochondrial membrane permeabilization, which might be implicated in the hepatic apoptosis inhibition by this gaseoustransmitter.

Carbon monoxide and mitochondria—modulation of cell metabolism, redox response and cell death

Carbon monoxide (CO) is an endogenously produced gasotransmitter, which is associated with cytoprotection and cellular homeostasis in several distinct cell types and tissues. CO mainly targets mitochondria because: (i) mitochondrial heme-proteins are the main potential candidates for CO to bind, (ii) many COs biological actions are dependent on mitochondrial ROS signaling and (iii) heme is generated in the mitochondrial compartment. Mitochondria are the key cell energy factory, producing ATP through oxidative phosphorylation and regulating cell metabolism. These organelles are also implicated in many cell signaling pathways and the production of reactive oxygen species (ROS). Finally, mitochondria contain several factors activating programmed cell death pathways, which are released from the mitochondrial inter-membrane space upon mitochondrial membrane permeabilization. Therefore, disclosing CO mode of action at mitochondria opens avenues for deeper understanding COs biological properties. Herein, it is discussed how CO affects the three main aspects of mitochondrial modulation of cell function: metabolism, redox response and cell death.

Carbon monoxide improves neuronal differentiation and yield by increasing the functioning and number of mitochondria.

The process of cell differentiation goes hand‐in‐hand with metabolic adaptations, which are needed to provide energy and new metabolites. Carbon monoxide (CO) is an endogenous cytoprotective molecule able to inhibit cell death and improve mitochondrial metabolism. Neuronal differentiation processes were studied using the NT2 cell line, which is derived from human testicular embryonic teratocarcinoma and differentiates into post‐mitotic neurons upon retinoic acid treatment. CO‐releasing molecule A1 (CORM‐A1) was used do deliver CO into cell culture. CO treatment improved NT2 neuronal differentiation and yield, since there were more neurons and the total cell number increased following the differentiation process. CO supplementation enhanced the mitochondrial population in post‐mitotic neurons derived from NT2 cells, as indicated by an increase in mitochondrial DNA. CO treatment during neuronal differentiation increased the extent of the classical metabolic change that occurs during neuronal differentiation, from glycolytic to more oxidative metabolism, by decreasing the ratio of lactate production and glucose consumption. The expression of pyruvate and lactate dehydrogenases was higher, indicating an augmented oxidative metabolism. Moreover, these findings were corroborated by an increased percentage of 13C incorporation from [U‐13C]glucose into the tricarboxylic acid cycle metabolites malate and citrate, and also glutamate and aspartate in CO‐treated cells. Finally, under low levels of oxygen (5%), which enhances glycolytic metabolism, some of the enhancing effects of CO on mitochondria were not observed. In conclusion, our data show that CO improves neuronal and mitochondrial yield by stimulation of tricarboxylic acid cycle activity, and thus oxidative metabolism of NT2 cells during the process of neuronal differentiation.

Carbon monoxide reverses the metabolic adaptation of microglia cells to an inflammatory stimulus

ABSTRACT Microglia fulfill important immunological functions in the brain by responding to pathological stresses and modulating their activities according to pro‐ or anti‐inflammatory stimuli. Recent evidence indicates that changes in metabolism accompany the switch in microglia activation state, favoring glycolysis over oxidative phosphorylation when cells exhibit a pro‐inflammatory phenotype. Carbon monoxide (CO), a byproduct of heme breakdown by heme oxygenase, exerts anti‐inflammatory action and affects mitochondrial function in cells and tissues. In the present study, we analyzed the metabolic profile of BV2 and primary mouse microglia exposed to the CO‐releasing molecules CORM‐401 and CORM‐A1 and investigated whether CO affects the metabolic adaptation of cells to the inflammatory stimulus lipopolysaccharide (LPS). Microglia respiration and glycolysis were measured using an Extracellular Flux Analyzer to provide a real‐time bioenergetic assessment, and biochemical parameters were evaluated to define the metabolic status of the cells under normal or inflammatory conditions. We show that CO prevents LPS‐induced depression of microglia respiration and reduction in ATP levels while altering the early expression of inflammatory markers, suggesting the metabolic changes induced by CO are associated with control of inflammation. CO alone affects microglia respiration depending on the concentration, as low levels increase oxygen consumption while higher amounts inhibit respiration. Increased oxygen consumption was attributed to an uncoupling activity observed in cells, at the molecular level (respiratory complex activities) and during challenge with LPS. Thus, application of CO is a potential countermeasure to reverse the metabolic changes that occur during microglia inflammation and in turn modulate their inflammatory profile. HIGHLIGHTSMicroglia cells change their metabolic profile when exposed to LPS.CO prevents the LPS‐induced depression of microglia respiration and ATP levels.CO action relies on mechanisms involving uncoupling and modulation of glycolysis.

Role of Cell Metabolism and Mitochondrial Function During Adult Neurogenesis

Brain is the major consumer of glucose in the human body, whose pattern of consumption changes through lifetime, decreasing during adolescence up to adulthood. This evidence leads to the hypothesis that, in cerebral developmental stages, glycolysis might be the driving force for the high-energy requirement. Furthermore, several studies claim that neurogenesis process is accompanied by a shift into mitochondrial oxidative metabolism. Herein, we discuss recent work about cell metabolism during neuronal differentiation process, in particular the mitochondrial role in cellular bioenergy dynamics.

Anti-Tuberculosis Activity Present in a Unique Marine Bacteria Collection from Portuguese Deep Sea Hydrothermal Vents

Anti-Tuberculosis Activity Present in a Unique Marine Bacteria Collection from Portuguese Deep Sea Hydrothermal Vents Natural product drug discovery from untapped sources of microorganisms, such as the oceans, is full of innovative solutions and is again becoming increasingly explored by the pharmaceutical industry. In fact, interesting bioactivities such as anti-tumour, anti-microtubule and anti-proliferative have been successfully identified in the marine environment. Antibiotic properties of marine products, in particular, have been shown to be effective against several microbial infections and should be further explored for the treatment of infectious diseases such as Tuberculosis, which have become a great threat to global health.