Assessment of platelet respiration as emerging biomarker of disease.

Mitochondrial dysfunction is currently acknowledged as a central pathomechanism of most common diseases of the 21(st) century. Recently, the assessment of the bioenergetic profile of human peripheral blood cells has emerged as a novel research field with potential applications in the development of disease biomarkers. In particular, platelets have been successfully used for the ex vivo analysis of mitochondrial respiratory function in several acute and chronic pathologies. An increasing number of studies support the idea that evaluation of the bioenergetic function in circulating platelets may represent the peripheral signature of mitochondrial dysfunction in metabolically active tissues (brain, heart, liver, skeletal muscle). Accordingly, impairment of mitochondrial respiration in peripheral platelets might have potential clinical applicability as a diagnostic and prognostic tool as well as a biomarker in treatment monitoring. The aim of this minireview is to summarize current information in the field of platelet mitochondrial dysfunction in both acute and chronic diseases.

Assessment of Mitochondrial Dysfunction and Monoamine Oxidase Contribution to Oxidative Stress in Human Diabetic Hearts.

Mitochondria-related oxidative stress is a pathomechanism causally linked to coronary heart disease (CHD) and diabetes mellitus (DM). Recently, mitochondrial monoamine oxidases (MAOs) have emerged as novel sources of oxidative stress in the cardiovascular system and experimental diabetes. The present study was purported to assess the mitochondrial impairment and the contribution of MAOs-related oxidative stress to the cardiovascular dysfunction in coronary patients with/without DM. Right atrial appendages were obtained from 75 patients randomized into 3 groups: (1) Control (CTRL), valvular patients without CHD; (2) CHD, patients with confirmed CHD; and (3) CHD-DM, patients with CHD and DM. Mitochondrial respiration was measured by high-resolution respirometry and MAOs expression was evaluated by RT-PCR and immunohistochemistry. Hydrogen peroxide (H2O2) emission was assessed by confocal microscopy and spectrophotometrically. The impairment of mitochondrial respiration was substrate-independent in CHD-DM group. MAOs expression was comparable among the groups, with the predominance of MAO-B isoform but no significant differences regarding oxidative stress were detected by either method. Incubation of atrial samples with MAOs inhibitors significantly reduced the H2O2 in all groups. In conclusion, abnormal mitochondrial respiration occurs in CHD and is more severe in DM and MAOs contribute to oxidative stress in human diseased hearts with/without DM.

BIOENERGETIC CHARACTERIZATION OF H9C2 CELLS USING THE EXTRACELLULAR FLUX ANALYZER.

UNLABELLED: The aim of the present work was to standardize the working methodology for assessing the bioenergetic profile of H9c2 cardiomyoblasts cells, with reference to the optimization of cell seeding number and the establishment of favorable concentrations for the classic modulators of mitochondrial respiratory function, in particular the one of a classical uncoupler, FCCP. MATERIAL AND METHODS: The extracellular flux analyzer (XF, Seahorse Bioscience) is a novel high-throughput instrument able to monitor the metabolism of living cells by simultaneously measuring mitochondrial respiration and glycolysis. The in vitro platform will be further used to better understand the pathophysiology and the unrecognized side effects of drugs currently used in the therapy of major cardiovascular diseases. CONCLUSIONS: In the long run, characterization of novel pharmacological agents' effects on other cell lines, including tumoral ones, will be also considered.

Monoamine oxidase--a inhibition reverses endothelial dysfunction in hypertensive rat aortic rings.

AIM: Monoamine oxidases (MAOs) are mitochondrial enzymes, with 2 isoforms, A and B that convert biogenic amines to their corresponding aldehydes via a reaction that produces hydrogen peroxide. Since MAO-A is the predominant form at vascular level we hypothesized that MAO-A-dependent H2O2 production may contribute to the development of endothelial dysfunction and, MAOs inhibition could improve the vascular function, respectively. MATERIAL AND METHODS: To this aim aortic rings were isolated from female adult spontaneously hypertensive rats (SHR) and their corresponding (Wistar-Kyoto) controls. The effect of MAO-A inhibitor, clorgyline (10 micromol/l) on endothelium-dependent relaxation (EDR) in response to acetylcholine and endothelium-independent relaxation in response to sodium nitroprusside, was studied in isolated phenylephrine-preconstricted aortic segments in the presence of indometacine (10 micromol/l). RESULTS: In hypertensive group EDR was significantly decreased - maximal relaxation (% of KCI, mean +/- SD) being 37 +/- 3.5 in SHR vs. 3.7 +/- 1.8 in controls. If experiments were done in the presence of clorgyline, EDR in control segments was unaffected. However, the compound restored normal EDR in aortic segments from hypertensive rats (maximal relaxation % of KCI, 13.7 +/- 2.3). CONCLUSIONS: Inhibition of the MAO-A isoform might be useful in restoring endothelium-dependent relaxation in this experimental model of hypertension in rat.