Effect of ethanol consumption on adult rat liver mitochondrial populations analyzed by flow cytometry

Chronic ethanol consumption increases myocardial mitochondrial DNA mutations: a potential contribution by mitochondrial topoisomerases

AIMS

Alcoholic cardiomyopathy (ACM) presents as decreased myocardial contractility, arrhythmias and secondary non-ischemic dilated cardiomyopathy leading to heart failure. Mitochondrial dysfunction is known to have a significant role in the development and complications of ACM. This study investigated if chronic ethanol feeding promoted myocardial mitochondrial topoisomerase dysfunction as one underlying cause of mitochondrial DNA (mtDNA) damage and mitochondrial dysfunction in ACM.

METHODS

The impact of chronic ethanol exposure on the myocardial mitochondria was examined in both neonatal cardiomyocytes using 50 mM ethanol for 6 days and in rats assigned to control or ethanol feeding groups for 4 months.

RESULTS

Chronic ethanol feeding led to significant (P < 0.05) decreases in M-mode Fractional Shortening, ejection fraction, and the cardiac output index as well as increases in Tau. Ethanol feeding promoted mitochondrial dysfunction as evidenced by significantly decreased left ventricle cytochrome oxidase activity and decreases in mitochondrial protein content. Both in rats and in cultured cardiomyocytes, chronic ethanol presentation significantly increased mtDNA damage. Using isolated myocardial mitochondria, both mitochondrial topoisomerase-dependent DNA cleavage and DNA relaxation were significantly altered by ethanol feeding.

CONCLUSION

Chronic ethanol feeding compromised cardiovascular and mitochondrial function as a result of a decline in mtDNA integrity that was in part the consequence of mitochondrial topoisomerase dysfunction. Understanding the regulation of the mitochondrial topoisomerases is critical for protection of mtDNA, not only for the management of alcoholic cardiomyopathy, but also for the many other clinical treatments that targets the topoisomerases in the alcoholic patient.

Impaired development of mitochondria plays a role in the central nervous system defects of fetal alcohol syndrome

BACKGROUND

Alcohol consumption during pregnancy can induce a wide spectrum of adverse effects in offspring. Microcephaly and mental retardation are two major defects of central nervous system (CNS). Most mechanism studies of alcohol-related CNS defects have been focused on the morphologically abnormal tissues, and more attention has been paid to nuclear alteration as opposed to organelle development.

METHODS

A mouse model of fetal alcohol syndrome (FAS) was used to investigate the effect of alcohol on fetal cerebral mitochondria development. Pregnant mice were given different doses of ethanol intragastrically from GD6 to GD15. Fetal cerebral mitochondria were isolated and analyzed on GD18.

RESULTS

Excessive cell apoptosis was found in the cerebra of prenatal alcohol exposure fetuses. Proliferation and differentiation of fetal cerebral mitochondria were inhibited by alcohol. Affected mitochondrial volume constriction and adenosine triphosphate (ATP) accumulation, reduced activities of respiratory chain complex I and IV and ATP synthase were detected in the cerebral tissue without obvious malformed appearance.

CONCLUSIONS

Impaired mitochondria development plays a role in the CNS defects induced by prenatal alcohol exposure.

Flow cytometric analysis of isolated liver mitochondria to detect changes relevant to cell death

BACKGROUND

Mitochondria are key players in many forms of cell death, and mitochondrial production of reactive oxygen species (ROS), membrane depolarization, permeability changes, and release of apoptogenic proteins are involved in these processes. Flow cytometric analysis of isolated mitochondria enables parallel analysis of mitochondrial structure and function in individual mitochondria, and small mitochondrial samples are sufficient for analysis. This article describes a well-characterized protocol for flow cytometric analysis of isolated liver mitochondria that can be used to detect mitochondrial alterations relevant to cell death.

METHODS

Fluorescent probes were used to selectively stain mitochondria (nonyl acridine orange), and to measure membrane potential (tetramethylrhodamine-methyl-ester, 1,1',3,3,3',3'-hexamethylindodicarbocyanine-iodide), as well as production of ROS (2',7'-dichlorodihydrofluorescein-diacetate). Calcium-induced mitochondrial swelling was detected as a decrease in SSC. To ensure optimal concentrations of all probes, the effect on mitochondrial respiration was evaluated.

RESULTS

This protocol can be used to determine the purity of the mitochondrial preparation, to detect calcium-induced morphological changes, small mitochondrial de- and hyperpolarizations, as well as physiological changes in ROS generation.

CONCLUSIONS

Flow cytometry is a very useful tool to simultaneously analyze several mitochondrial parameters that are important in the induction of mitochondria-mediated cell death.

Flow cytometric analysis of mitochondria from CA1 and CA3 regions of rat hippocampus reveals differences in permeability transition pore activation

Mitochondria are important in the pathophysiology of several neurodegenerative diseases, and mitochondrial production of reactive oxygen species (ROS), membrane depolarization, permeability changes and release of apoptogenic proteins are involved in these processes. Following brain insults, cell death often occurs in discrete regions of the brain, such as the subregions of the hippocampus. To analyse mitochondrial structure and function in such subregions, only small amounts of mitochondria are available. We developed a protocol for flow cytometric analysis of very small samples of isolated brain mitochondria, and analysed mitochondrial swelling and formation of ROS in mitochondria from the CA1 and CA3 regions of the hippocampus. Calcium-induced mitochondrial swelling was measured, and fluorescent probes were used to selectively stain mitochondria (nonyl acridine orange), to measure membrane potential (tetramethylrhodamine-methyl-ester, 1,1',3,3,3',3'-hexamethylindodicarbocyanine-iodide) and to measure production of ROS (2',7'-dichlorodihydrofluorescein-diacetate). We found that formation of ROS and mitochondrial permeability transition pore activation were higher in mitochondria from the CA1 than from the CA3 region, and propose that differences in mitochondrial properties partly underlie the selective vulnerability of the CA1 region to brain insults. We also conclude that flow cytometry is a useful tool to analyse the role of mitochondria in cell death processes.

Flow cytometry of isolated mitochondria during development and under some pathological conditions

Mitochondria play an essential role in the generation of the energy needed for eukaryotic cell life and in the release of molecules involved in initiation of cell death. Here we review the changes in isolated mitochondrial fluorescent populations as distinguished by flow cytometry during postnatal development and their regulation by thyroid hormones and catecholamines. The use of flow cytometry in the study of mitochondrial changes occurring under hypothyroidism, alcohol abuse and aging is also reviewed.

Alcohol-induced thymocyte apoptosis is accompanied by impaired mitochondrial function

This study examines the effects of chronic alcohol consumption on thymic apoptosis with or without pretreatment with E. coli lipopolysaccharide (LPS). Apoptotic cell death of thymocytes was monitored by DNA fragments in gel electrophoresis and the appearance of apoptotic cells by flow cytometry. Changes in mitochondrial membrane potential (MMP), as indicated by 3,3'-dihexyloxacarbocyanine iodide [DiOC6(3)] uptake, and hydrogen peroxide (H2O2) production as indicated by oxidation of 2',7'-dichlorofluresin diacetate (DCFH-DA), were used to assess altered mitochondrial function. Glutathione levels were also determined to obtain information concerning alterations in the antioxidant potential in the cells. Male Sprague-Dawley rats, fed a nutritionally adequate liquid diet for 8-9 weeks, were divided in four groups: 1) saline-injected, diet controls; 2) LPS-injected, diet controls; 3) saline-injected, alcohol-consuming; and 4) LPS-injected, alcohol-consuming animals. LPS (0.5 mg/kg in 4 ml saline) or saline (4 ml) was continuously infused i.v. for 12 h before the experiments. The results showed that the weight and cell numbers of thymus from the chronic alcoholic rats were significantly less than values found in diet controls. Administration of LPS aggravated thymic apoptosis, as indicated by the presence of significant DNA fragments in gel electrophoresis and increased rate of apoptotic cells in flow cytometry. The alcohol-induced apoptotic changes were also accompanied by decreased MMP, indicating impaired mitochondrial function. Although H2O2 production by the total thymocyte population did not show marked changes among the experimental groups, the subpopulation of thymocytes exhibiting low H2O2 production was increased markedly in the LPS-treated groups. Ethanol consumption or LPS treatment decreased total glutathione concentration in the thymocytes. In summary, 1) chronic administration of alcohol induces atrophy of the thymus gland; 2) apoptosis is a major factor in thymic atrophy under these conditions; 3) chronic alcohol consumption is accompanied by alterations in mitochondrial function of the thymocytes, as indicated by decreased MMP and an increase in the low H2O2-producing cell subpopulation; 4) chronic alcohol abuse may impair intracellular defense mechanisms as reflected by the depletion of the intracellular antioxidant, glutathione; and 5) administration of LPS further enhances thymic apoptosis in chronic alcohol-consuming rats, suggesting that the dual insults of infection and chronic alcoholism exaggerate in vivo immunosuppression.