Assessment of Platelet Mitochondrial Respiration in a Pediatric Population: A Pilot Study in Healthy Children and Children with Acute Lymphoblastic Leukemia.

Characterization of mitochondrial respiration in peripheral blood cells has recently emerged as a potential biomarker for the assessment of the severity of hematological malignancies (HM) in adults. Whether changes in platelet respiratory function occur in children with or without HM it is unknown. The present pilot study was double-aimed: (i) to investigate whether platelet respiration is age-dependent in non-HM children and (ii) to assess the platelet mitochondrial respiration in children with newly diagnosed acute lymphoblastic leukemia (ALL). Blood samples obtained from age-grouped children (10-11, 13-14 and 16-17 years) with non-HM and children with ALL (10-11 years) were used to isolate platelets via differential centrifugation. High-resolution respirometry studies of isolated platelets were performed according to a protocol adapted to evaluate complex I and II-supported respiration. An age-related decrease in respiration was observed in the non-HM pediatric population and had comparable values for the 13-14 and 16-17 years. groups. In children with ALL, a significant increase in C I-supported active respiration and decrease in maximal noncoupled respiration were found at the disease onset. In conclusion, in a pediatric population, platelet mitochondrial respiration is age-dependent. Platelet respiratory dysfunction occurs in children with newly-diagnosed ALL, an observation that warrants further investigation of this change as a disease biomarker.

Pleiotropic Effects of Eugenol: The Good, the Bad, and the Unknown.

Phytocompounds and medicinal herbs were used in traditional ancient medicine and are nowadays increasingly screened in both experimental and clinical settings due to their beneficial effects in several major pathologies. Similar to the drug industry, phytotherapy is interested in using nanobased delivery systems to view the identification and characterization of the cellular and molecular therapeutic targets of plant components. Eugenol, the major phenolic constituent of clove essential oil, is a particularly versatile phytochemical with a vast range of therapeutic properties, among which the anti-inflammatory, antioxidant, and anticarcinogenic effects have been systematically addressed. In the past decade, with the emerging understanding of the role of mitochondria as critical organelles in the pathophysiology of noncommunicable diseases, research regarding the role of phytochemicals as modulators of bioenergetics and metabolism is on a rise. Here, we present a brief overview of the major pharmacological properties of eugenol, with special emphasis on its applications in dental medicine, and provide preliminary data regarding its effects, alone, and included in polyurethane nanostructures, on mitochondrial bioenergetics, and glycolysis in human HaCaT keratinocytes.

Stimulation of P2Y11 receptor protects human cardiomyocytes against Hypoxia/Reoxygenation injury and involves PKCε signaling pathway.

Sterile inflammation is a key determinant of myocardial reperfusion injuries. It participates in infarct size determination in acute myocardial infarction and graft rejection following heart transplantation. We previously showed that P2Y11 exerted an immunosuppressive role in human dendritic cells, modulated cardiofibroblasts' response to ischemia/reperfusion in vitro and delayed graft rejection in an allogeneic heterotopic heart transplantation model. We sought to investigate a possible role of P2Y11 in the cellular response of cardiomyocytes to ischemia/reperfusion. We subjected human AC16 cardiomyocytes to 5 h hypoxia/1 h reoxygenation (H/R). P2Y11R (P2Y11 receptor) selective agonist NF546 and/or antagonist NF340 were added at the onset of reoxygenation. Cellular damages were assessed by LDH release, MTT assay and intracellular ATP level; intracellular signaling pathways were explored. The role of P2Y11R in mitochondria-derived ROS production and mitochondrial respiration was investigated. In vitro H/R injuries were significantly reduced by P2Y11R stimulation at reoxygenation. This protection was suppressed with P2Y11R antagonism. P2Y11R stimulation following H2O2-induced oxidative stress reduced mitochondria-derived ROS production and damages through PKCε signaling pathway activation. Our results suggest a novel protective role of P2Y11 in cardiomyocytes against reperfusion injuries. Pharmacological post-conditioning targeting P2Y11R could therefore contribute to improve myocardial ischemia/reperfusion outcomes in acute myocardial infarction and cardiac transplantation.

Methylene blue improves mitochondrial respiration and decreases oxidative stress in a substrate-dependent manner in diabetic rat hearts.

Diabetic cardiomyopathy has been systematically associated with compromised mitochondrial energetics and increased generation of reactive oxygen species (ROS) that underlie its progression to heart failure. Methylene blue is a redox drug with reported protective effects mainly on brain mitochondria. The purpose of the present study was to characterize the effects of acute administration of methylene blue on mitochondrial respiration, H2O2 production, and calcium sensitivity in rat heart mitochondria isolated from healthy and 2 months (streptozotocin-induced) diabetic rats. Mitochondrial respiratory function was assessed by high-resolution respirometry. H2O2 production and calcium retention capacity were measured spectrofluorimetrically. The addition of methylene blue (0.1 µmol·L-1) elicited an increase in oxygen consumption of mitochondria energized with complex I and II substrates in both normal and diseased mitochondria. Interestingly, methylene blue elicited a significant increase in H2O2 release in the presence of complex I substrates (glutamate and malate), but had an opposite effect in mitochondria energized with complex II substrate (succinate). No changes in the calcium retention capacity of healthy or diabetic mitochondria were found in the presence of methylene blue. In conclusion, in cardiac mitochondria isolated from diabetic and nondiabetic rat hearts, methylene blue improved respiratory function and elicited a dichotomic, substrate-dependent effect on ROS production.

The effect of purinergic signaling via the P2Y11 receptor on vascular function in a rat model of acute inflammation.

There is a growing body of evidence pointing to the role of purinergic signaling in the development and progression of various conditions that have inflammation as a common pathogenetic denominator. The aim of the present study was to assess the involvement of P2Y11 purinergic receptors in the regulation of vascular function in aortic segments obtained using an experimental model of acute inflammation, the lipopolysaccharide (LPS, 8 mg/kg, i.p)-treated rats. Twelve hours after LPS administration, thoracic aortas were isolated and used for studies of vascular reactivity in the organ bath and for the measurement of reactive oxygen species (ROS) generation, respectively. LPS treatment significantly increased contractility to phenylephrine and attenuated the endothelium-dependent relaxation of the vascular segments in response to acetylcholine; an increased production of hydrogen peroxide (H2O2) was also recorded. The P2Y11 activator, NF546, decreased the LPS-induced aortic H2O2 release and partially normalized the vasomotor function, namely reduced contractility and improved relaxation. The effect was abolished by co-treatment with the P2Y11 inhibitor, NF340, and also after endothelium denudation. Importantly, NF546 did not elicit an antioxidant effect by acting as a H2O2 scavenger, suggesting that the beneficial outcome of this treatment on the vasculature is the consequence of P2Y11 stimulation. In conclusion, purinergic P2Y11 receptors stimulation improves vascular function and mitigates oxidative stress in the setting of acute systemic inflammation, revealing salutary effects and therapeutic potential in pathologies associated with endothelial dysfunction.

The Role of Mitochondrial Reactive Oxygen Species in Cardiovascular Injury and Protective Strategies.

Ischaemia/reperfusion (I/R) injury of the heart represents a major health burden mainly associated with acute coronary syndromes. While timely coronary reperfusion has become the established routine therapy in patients with ST-elevation myocardial infarction, the restoration of blood flow into the previously ischaemic area is always accompanied by myocardial injury. The central mechanism involved in this phenomenon is represented by the excessive generation of reactive oxygen species (ROS). Besides their harmful role when highly generated during early reperfusion, minimal ROS formation during ischaemia and/or at reperfusion is critical for the redox signaling of cardioprotection. In the past decades, mitochondria have emerged as the major source of ROS as well as a critical target for cardioprotective strategies at reperfusion. Mitochondria dysfunction associated with I/R myocardial injury is further described and ultimately analyzed with respect to its role as source of both deleterious and beneficial ROS. Furthermore, the contribution of ROS in the highly investigated field of conditioning strategies is analyzed. In the end, the vascular sources of mitochondria-derived ROS are briefly reviewed.

Acute inhibition of monoamine oxidase and ischemic preconditioning in isolated rat hearts: interference with postischemic functional recovery but no effect on infarct size reduction.

Monoamine oxidases (MAOs) have recently emerged as important mitochondrial sources of oxidative stress in the cardiovascular system. Generation of reactive oxygen species during the brief episodes of ischemic preconditioning (IPC) is responsible for the cardioprotection at reperfusion. The aim of this study was to assess the effects of two MAO inhibitors (clorgyline and pargyline) on the IPC-related protection in isolated rat hearts. Animals subjected to 30 min global ischemia and 120 min reperfusion were assigned to the following groups: (i) Control, no additional intervention; (ii) IPC, 3 cycles of 5 min ischemia and 5 min reperfusion before the index ischemia; (iii) IPC-clorgyline, IPC protocol bracketed for 5 min with clorgyline (50 µmol/L); (iv) IPC-pargyline, IPC protocol bracketed for 5 min with pargyline (0.5 mmol/L). The postischemic functional recovery was assessed by the left ventricular developed pressure (LVDP) and the indices of contractility (+dLVP/dt max) and relaxation (-dLVP/dt max). Infarct size (IS) was quantified by TTC staining. In both genders, IPC significantly improved functional recovery that was further enhanced in the presence of either clorgyline or pargyline. IS reduction was comparable among all the preconditioned groups, regardless of the presence of MAO inhibitors. In isolated rat hearts, acute inhibition of MAOs potentiates the IPC-induced postischemic functional recovery without interfering with the anti-necrotic protection.

Monoamine oxidases are novel sources of cardiovascular oxidative stress in experimental diabetes.

Diabetes mellitus (DM) is widely recognized as the most severe metabolic disease associated with increased cardiovascular morbidity and mortality. The generation of reactive oxygen species (ROS) is a major event causally linked to the development of cardiovascular complications throughout the evolution of DM. Recently, monoamine oxidases (MAOs) at the outer mitochondrial membrane, with 2 isoforms, MAO-A and MAO-B, have emerged as novel sources of constant hydrogen peroxide (H2O2) production in the cardiovascular system via the oxidative deamination of biogenic amines and neurotransmitters. Whether MAOs are mediators of endothelial dysfunction in DM is unknown, and so we studied this in a streptozotocin-induced rat model of diabetes. MAO expression (mRNA and protein) was increased in both arterial samples and hearts isolated from the diabetic animals. Also, H2O2 production (ferrous oxidation - xylenol orange assay) in aortic samples was significantly increased, together with an impairment of endothelium-dependent relaxation (organ-bath studies). MAO inhibitors (clorgyline and selegiline) attenuated ROS production by 50% and partially normalized the endothelium-dependent relaxation in diseased vessels. In conclusion, MAOs, in particular the MAO-B isoform, are induced in aortas and hearts in the streptozotocin-induced diabetic rat model and contribute, via the generation of H2O2, to the endothelial dysfunction associated with experimental diabetes.