Mitochondria: A mirror into cellular dysfunction in heart disease

Metabolic response to radiation therapy in cancer

Tumor metabolism has emerged as a hallmark of cancer and is involved in carcinogenesis and tumor growth. Reprogramming of tumor metabolism is necessary for cancer cells to sustain high proliferation rates and enhanced demands for nutrients. Recent studies suggest that metabolic plasticity in cancer cells can decrease the efficacy of anticancer therapies by enhancing antioxidant defenses and DNA repair mechanisms. Studying radiation-induced metabolic changes will lead to a better understanding of radiation response mechanisms as well as the identification of new therapeutic targets, but there are few robust studies characterizing the metabolic changes induced by radiation therapy in cancer. In this review, we will highlight studies that provide information on the metabolic changes induced by radiation and oxidative stress in cancer cells and the associated underlying mechanisms.

Ameliorating Effects of Ginger on Isoproterenol-Induced Acute Myocardial Infarction in Rats and its Impact on Cardiac Nitric Oxide

Background:

Myocardial infarction is a major heart disease and is considered a significant reason for mortality and morbidity around the world. The model of Isoproterenol (ISO)-induced myocardial infarction provides a supported method for investigating the impacts of numerous possible cardioprotective bioactive substances. Nitric Oxide (NO) could react with reactive oxygen intermediates and free radicals to create harmful species. For several years, researchers have investigated the use of herbs and natural products as antioxidants to protect the body's organs against toxins and drug metabolites. However, studies on the antioxidant effects of ginger against cardiotoxicity induced by drugs and toxic agents remain insufficient, especially its effects on NO.

Aims and Objectives:

This study aimed to investigate the possible antioxidant and protective role of ginger in ISO-induced acute myocardial infarction in experimental rats. Special emphasis was given to the impact of ginger on NO levels.

Materials and Methods:

Forty adult male albino rats were used in this study. The animals were randomly divided into four equal groups. Group I served as control and received a normal mouse diet. Group II received ginger extract orally, Group III received normal diet for eight weeks, followed by ISO administration subcutaneously to induce myocardial infarction, Group IV received ginger extracts, followed by ISO.

Results and Conclusions:

The results of this study illustrated ginger's protective role against ISO-induced acute myocardial infarction. This role is mainly due to ginger's antioxidant and anti-inflammatory properties. We assume that sufficient intake of ginger by individuals who are regularly exposed to ISO would be beneficial in overcoming the cardiotoxicity of ISO. The effects of ginger may take place through inhibition of NOS enzymes, which needs further immunohistochemical and biochemical studies to reveal the underlying different mechanisms of the effects of ginger at the molecular and structural levels.

Correlation between the blood level of irisin and the severity of acute myocardial infarction in exercise-trained rats

Background Acute myocardial infarction is a major cause of death all over the world. Irisin is a novel myokine released after exercise. This work aimed to study the correlation between the serum irisin level and the severity of the acute myocardial infarction in the exercise-trained rats. Methods Forty-eight male rats were classified into four groups (12 for each): group I, control sedentary (C); group II, exercise-trained (EX) (swimming for 8 weeks); group III, isoprenaline-induced infarct (MI); and group IV, exercise-trained infarct (EX-MI) (swimming for 8 weeks followed by isoprenaline-induced infarction). ECG was recorded at start and end of the study, before and after induction of infarction. The serum level of irisin, lipid peroxidation [malondialdehyde (MDA)], total antioxidant status (TAS), creatine phosphokinase-MB (CK-MB), and troponin I was determined. The hearts were excised for histopathology and immunohistochemistry for caspase-3. Results The infarct rats showed significant prolongation in QTc interval and elevation in the ST segment as well as significant elevation of serum CK-MB, troponin I, and MDA, whereas TAS and serum irisin level were significantly decreased. With exercise, we observed a high positive correlation between the serum irisin and QRS duration (+0.643), amplitude (+0.860), and TAS (+0.887). In addition, there was a high negative correlation between the serum irisin and ST elevation (-0.865), QTc (-0.886), CK-MB (-0.891), troponin (-0.882), and MDA (-0.868). This was confirmed by the negative correlation between serum irisin and both collagen deposition and caspase-3 expression (-0.823 and -0.822, respectively). Conclusions We recommend regular exercise or taking recombinant irisin as a supplement to protect at-risk individuals against acute myocardial infarction.

Anti-inflammatory, Antithrombotic and Cardiac Remodeling Preventive Effects of Eugenol in Isoproterenol-Induced Myocardial Infarction in Wistar Rat

This study aimed to evaluate the antithrombotic, anti-inflammatory and anti-cardiac remodeling properties of eugenol in isoproterenol-induced myocardial infarction in rats. Male Wistar rats were randomly divided into four groups, control, iso [100 mg/kg body weight was injected subcutaneously into rats at an interval of 24 h for 2 days (6th and 7th day) to induce MI] and pretreated animals with clopidogrel (0.2 mg/kg) and eugenol (50 mg/kg) orally for 7 days and intoxicated with isoproterenol (Iso + Clop) and (Iso + EG) groups. Isoproterenol-induced myocardial infarcted rats showed notable changes in the ECG pattern, increase in heart weight index, deterioration in the hemodynamic function and rise in plasma level of troponin-T, CK-MB and LDH and ALT by 316, 74, 172 and 45 %, respectively, with histological myocardium necrosis and cells inflammatory infiltration. In addition, significant increases in plasma levels of inflammatory biomarkers such as fibrinogen, α1, α2, β1, β2 and γ globulins with decrease level of albumin were observed in infarcted rats as compared to normal ones. Else, the angiotensin-converting enzyme (ACE) activity in plasma, kidney and heart of the isoproterenol-induced rats was significantly increased by 34, 47 and 93 %, respectively, as compared to normal group. However, the administration of eugenol induced a clear improvement in cardiac biomarkers injury, reduced inflammatory mediators proteins, increased heart activities of superoxide dismutase and glutathione peroxidase with reduce in thiobarbituric acid-reactive substances content and inhibition of ventricular remodeling process through inhibition of ACE activity. Overall, eugenol evidences high preventive effects from cardiac remodeling process.

Protective Effect of Hydroxytyrosol Against Cardiac Remodeling After Isoproterenol-Induced Myocardial Infarction in Rat

The present study aimed to investigate the cardioprotective effect of hydroxytyrosol (HT) against isoproterenol-induced myocardial infarction in rats. Male rats were randomly divided into four groups, control, isoproterenol (Isop) and pretreated animals with HT in two different doses (2 and 5 mg/kg) orally for 7 days and intoxicated with isoproterenol (Isop + HT1) and (Isop + HT2) groups. Myocardial infarction in rats was induced subcutaneously by isoproterenol (100 mg/kg, s.c.) at an interval of 24 h on 6th and 7th day. On 8th day, electrocardiographic (ECG) pattern, gravimetric and biochemical parameters were assessed. Isoproterenol exhibited changes in ECG pattern, including significant ST-segment elevation and increase in the serum troponin-T level by 317 % as compared to control rats. Moreover, cardiac injury markers (creatine kinase-MB, lactate dehydrogenase, alanine aminotransferase) underwent a notable rise in serum of infarcted animals. Else, a disturbance in lipids profile and significant increase in lipase and angiotensin-converting enzyme (ACE) activities and heart weight ratio were observed in isoproterenol group. However, pre- and co-treatment with HT (2 and 5 mg/kg) improved the myocardium injury, restored the hemodynamic function and inhibited the ACE activity that prevent cardiac hypertrophy and remodeling. Overall, these findings demonstrated that HT exerted a potent cardioprotective effect against isoproterenol-induced myocardial infarction.

Reactive Oxygen Species: A Key Hallmark of Cardiovascular Disease

Cardiovascular diseases (CVDs) have been the prime cause of mortality worldwide for decades. However, the underlying mechanism of their pathogenesis is not fully clear yet. It has been already established that reactive oxygen species (ROS) play a vital role in the progression of CVDs. ROS are chemically unstable reactive free radicals containing oxygen, normally produced by xanthine oxidase, nicotinamide adenine dinucleotide phosphate oxidase, lipoxygenases, or mitochondria or due to the uncoupling of nitric oxide synthase in vascular cells. When the equilibrium between production of free radicals and antioxidant capacity of human physiology gets altered due to several pathophysiological conditions, oxidative stress is induced, which in turn leads to tissue injury. This review focuses on pathways behind the production of ROS, its involvement in various intracellular signaling cascades leading to several cardiovascular disorders (endothelial dysfunction, ischemia-reperfusion, and atherosclerosis), methods for its detection, and therapeutic strategies for treatment of CVDs targeting the sources of ROS. The information generated by this review aims to provide updated insights into the understanding of the mechanisms behind cardiovascular complications mediated by ROS.

Post-Translational Modifications of Cardiac Mitochondrial Proteins in Cardiovascular Disease: Not Lost in Translation

Protein post-translational modifications (PTMs) are crucial in regulating cellular biology by playing key roles in processes such as the rapid on and off switching of signaling network and the regulation of enzymatic activities without affecting gene expressions. PTMs lead to conformational changes in the tertiary structure of protein and resultant regulation of protein function such as activation, inhibition, or signaling roles. PTMs such as phosphorylation, acetylation, and S-nitrosylation of specific sites in proteins have key roles in regulation of mitochondrial functions, thereby contributing to the progression to heart failure. Despite the extensive study of PTMs in mitochondrial proteins much remains unclear. Further research is yet to be undertaken to elucidate how changes in the proteins may lead to cardiovascular and metabolic disease progression in particular. We aimed to summarize the various types of PTMs that occur in mitochondrial proteins, which might be associated with heart failure. This study will increase the understanding of cardiovascular diseases through PTM.

The physiological significance of a coronary stenosis differentially affects contractility and mitochondrial function in viable chronically dysfunctional myocardium

The reversibility of viable dysfunctional myocardium after revascularization is variable and the reasons for this are unknown. Using 2D-DIGE, we tested the hypothesis that this could reflect the extent of molecular remodeling of myocardial tissue in the absence of infarction. Swine with a progressive left anterior descending (LAD) stenosis were studied 2 months (n = 18) or 3 months (n = 22) post-instrumentation. Coronary flow reserve (vasodilated/rest) was severely reduced at 2 months (LAD 2.6 ± 0.4 versus 5.1 ± 0.4 in normal, p < 0.05) and became critically impaired after 3 months (LAD 1.1 ± 0.2, p < 0.05 vs. 2 months). Despite progression in stenosis severity, reductions in wall thickening at 2 months (LAD 37 ± 4% vs. remote 86 ± 9%, p < 0.05) were unchanged at 3 months (LAD 32 ± 3%, p = ns). Contractile dysfunction was primarily related to reductions (LAD/normal) in contractile proteins which were not affected by stenosis severity (e.g., troponin T, 2 months 0.82 ± 0.03 vs. 0.74 ± 0.03 at 3 months, p-ns). In contrast, mitochondrial function and proteins were normal at 2 months but declined with progression to a critical stenosis (state 3 respiration at 3 months 145 ± 13 vs. 216 ± 5 ng-atoms O2 mg(-1) min(-1) at 2 months, p < 0.05). In a similar fashion, increases in stress (e.g., αB-crystalline 2.13 ± 0.2 vs. 1.17 ± 0.13 at 2 months, p < 0.05) and cytoskeletal proteins (e.g., desmin 1.63 ± 0.12 vs. 1.24 ± 0.10 at 2 months, p < 0.05) only developed with more advanced remodeling from a critical stenosis. We conclude that similar degrees of chronic contractile dysfunction can have diverse intrinsic molecular adaptations to ischemia. This spectrum of adaptations may underlie variability in the time course and extent of reversibility in viable chronically dysfunctional myocardium after revascularization.

Functional decorations: post-translational modifications and heart disease delineated by targeted proteomics

The more than 300 currently identified post-translational modifications (PTMs) provides great scope for subtle or dramatic alteration of protein structure and function. Furthermore, the rapid and transient nature of many PTMs allows efficient signal transmission in response to internal and environmental stimuli. PTMs are predominantly added by enzymes, and the enzymes responsible (such as kinases) are thus attractive targets for therapeutic interventions. Modifications can be grouped according to their stability or transience (reversible versus irreversible): irreversible types (such as irreversible redox modifications or protein deamidation) are often associated with aging or tissue injury, whereas transient modifications are associated with signal propagation and regulation. This is particularly important in the setting of heart disease, which comprises a diverse range of acute (such as ischemia/reperfusion), chronic (such as heart failure, dilated cardiomyopathy) and genetic (such as hypertrophic cardiomyopathy) disease states, all of which have been associated with protein PTM. Recently the interplay between diverse PTMs has been suggested to also influence cellular function, with cooperation or competition for sites of modification possible. Here we discuss the utility of proteomics for examining PTMs in the context of the molecular mechanisms of heart disease.

Radiation-induced signaling results in mitochondrial impairment in mouse heart at 4 weeks after exposure to X-rays

Backround

Radiation therapy treatment of breast cancer, Hodgkin's disease or childhood cancers expose the heart to high local radiation doses, causing an increased risk of cardiovascular disease in the survivors decades after the treatment. The mechanisms that underlie the radiation damage remain poorly understood so far. Previous data show that impairment of mitochondrial oxidative metabolism is directly linked to the development of cardiovascular disease.

Methodology/Principal findings

In this study, the radiation-induced in vivo effects on cardiac mitochondrial proteome and function were investigated. C57BL/6N mice were exposed to local irradiation of the heart with doses of 0.2 Gy or 2 Gy (X-ray, 200 kV) at the age of eight weeks, the control mice were sham-irradiated. After four weeks the cardiac mitochondria were isolated and tested for proteomic and functional alterations. Two complementary proteomics approaches using both peptide and protein quantification strategies showed radiation-induced deregulation of 25 proteins in total. Three main biological categories were affected: the oxidative phophorylation, the pyruvate metabolism, and the cytoskeletal structure. The mitochondria exposed to high-dose irradiation showed functional impairment reflected as partial deactivation of Complex I (32%) and Complex III (11%), decreased succinate-driven respiratory capacity (13%), increased level of reactive oxygen species and enhanced oxidation of mitochondrial proteins. The changes in the pyruvate metabolism and structural proteins were seen with both low and high radiation doses.

Conclusion/Significance

This is the first study showing the biological alterations in the murine heart mitochondria several weeks after the exposure to low- and high-dose of ionizing radiation. Our results show that doses, equivalent to a single dose in radiotherapy, cause long-lasting changes in mitochondrial oxidative metabolism and mitochondria-associated cytoskeleton. This prompts us to propose that these first pathological changes lead to an increased risk of cardiovascular disease after radiation exposure.

Delayed preconditioning by sevoflurane elicits changes in the mitochondrial proteome in ischemia-reperfused rat hearts

BACKGROUND

Delayed myocardial preconditioning by volatile anesthetics involves changes in DNA transcription and translation. Mitochondria play a central role in myocardial ischemia/reperfusion (I/R) injury and in ischemic or pharmacologic preconditioning. In this study, we investigated whether there are alterations in myocardial mitochondrial protein expression after volatile anesthetic preconditioning (APC) to examine the underlying mechanisms of delayed cardioprotection.

METHODS

Thirty-six Sprague-Dawley rats were randomly assigned to 1 of 3 groups (n = 12 for each group). Rats in the delayed APC group were exposed to sevoflurane (2.5% for 60 minutes) 24 hours before myocardial ischemia was induced. Myocardial ischemia in the I/R and APC groups was induced by left coronary artery occlusion for 30 minutes, followed by 120 minutes of reperfusion. The control group received no treatment. The mitochondria fractions were prepared by differential centrifugation with density gradient isolation for proteomic analysis. Two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization with time-of-flight mass spectrometry was used to identify differences in the protein expression from mitochondria of the rat hearts.

RESULTS

Fifteen differentially expressed mitochondrial proteins between the APC group and I/R group were identified and the expression patterns of 2 of the proteins were confirmed by Western blot analysis. These proteins were associated with mitochondrial substrate metabolism, respiration, and adenosine triphosphate (ATP)/adenosine diphosphate transport. The modifications of the mitochondrial proteome suggest an enhanced capacity of mitochondria to maintain myocardial ATP levels after I/R injury.

CONCLUSION

Delayed sevoflurane myocardial preconditioning induces mitochondrial proteome remodeling, which mainly involves proteins that are related to ATP generation and transport. Therefore, proteomic changes related to bioenergetic balance may be the mechanistic basis of delayed anesthetic myocardial preconditioning.

Ellagic acid ameliorates isoproterenol induced oxidative stress: Evidence from electrocardiological, biochemical and histological study

The present study was designed to evaluate the cardioprotective effects of ellagic acid against isoproterenol induced myocardial infarction in rats by studying electrocardiography, blood pressure, cardiac markers, lipid peroxidation, antioxidant defense system and histological changes. Male Wistar rats were treated orally with ellagic acid (7.5 and 15mg/kg) daily for a period of 10 days. After 10 days of pretreatment, isoproterenol (100mg/kg) was injected subcutaneously to rats at an interval of 24h for 2 days to induce myocardial infarction. Isoproterenol administered rats showed significant changes in the electrocardiogram pattern, arterial pressure, and heart rate. Isoproterenol-induced rats also showed significant (P<0.05) increase in the levels of serum troponin-I, creatine kinase, lactate dehydrogenase, C-reactive protein, plasma homocysteine, heart tissue thiobarbituric acid reactive substances and lipid hydro peroxides. The activities/levels of antioxidant system were decreased in isoproterenol-induced rats. The histopathological findings of the myocardial tissue evidenced myocardial damage in isoproterenol induced rats. The oral pretreatment of ellagic acid restored the pathological electrocardiographic patterns, regulated the arterial blood pressures and heart rate in the isoproterenol induced myocardial infarcted rats. The ellagic acid pretreatment significantly reduced the levels of biochemical markers, lipid peroxidation and significantly increased the activities/levels of the antioxidant system in the isoproterenol induced rats. An inhibited myocardial necrosis was evidenced by the histopathological findings in ellagic acid pretreated isoproterenol induced rats. Our study shows that oral pretreatment of ellagic acid prevents isoproterenol induced oxidative stress in myocardial infarction.

Parallel proteomics to improve coverage and confidence in the partially annotated Oryctolagus cuniculus mitochondrial proteome

The ability to decipher the dynamic protein component of any system is determined by the inherent limitations of the technologies used, the complexity of the sample, and the existence of an annotated genome. In the absence of an annotated genome, large-scale proteomic investigations can be technically difficult. Yet the functional and biological species differences across animal models can lead to selection of partially or nonannotated organisms over those with an annotated genome. The outweighing of biology over technology leads us to investigate the degree to which a parallel approach can facilitate proteome coverage in the absence of complete genome annotation. When studying species without complete genome annotation, a particular challenge is how to ensure high proteome coverage while meeting the bioinformatic stringencies of high-throughput proteomics. A protein inventory of Oryctolagus cuniculus mitochondria was created by overlapping "protein-centric" and "peptide-centric" one-dimensional and two-dimensional liquid chromatography strategies; with additional partitioning into membrane-enriched and soluble fractions. With the use of these five parallel approaches, 2934 unique peptides were identified, corresponding to 558 nonredundant protein groups. 230 of these proteins (41%) were identified by only a single technical approach, confirming the need for parallel techniques to improve annotation. To determine the extent of coverage, a side-by-side comparison with human and mouse cardiomyocyte mitochondrial studies was performed. A nonredundant list of 995 discrete proteins was compiled, of which 244 (25%) were common across species. The current investigation identified 142 unique protein groups, the majority of which were detected here by only one technical approach, in particular peptide- and protein-centric two-dimensional liquid chromatography. Although no single approach achieved more than 40% coverage, the combination of three approaches (protein- and peptide-centric two-dimensional liquid chromatography and subfractionation) contributed 96% of all identifications. Parallel techniques ensured minimal false discovery, and reduced single peptide-based identifications while maximizing sequence coverage in the absence of the annotated rabbit proteome.

Novel O-palmitolylated beta-E1 subunit of pyruvate dehydrogenase is phosphorylated during ischemia/reperfusion injury

BACKGROUND

During and following myocardial ischemia, glucose oxidation rates are low and fatty acids dominate as a source of oxidative metabolism. This metabolic phenotype is associated with contractile dysfunction during reperfusion. To determine the mechanism of this reliance on fatty acid oxidation as a source of ATP generation, a functional proteomics approach was utilized.

RESULTS

2-D gel electrophoresis of mitochondria from working rat hearts subjected to 25 minutes of global no flow ischemia followed by 40 minutes of aerobic reperfusion identified 32 changes in protein abundance compared to aerobic controls. Of the five proteins with the greatest change in abundance, two were increased (long chain acyl-coenzyme A dehydrogenase (48 +/- 1 versus 39 +/- 3 arbitrary units, n = 3, P < 0.05) and alpha subunit of ATP synthase (189 +/- 15 versus 113 +/- 23 arbitrary units, n = 3, P < 0.05)), while two were decreased (24 kDa subunit of NADH-ubiquinone oxidoreductase (94 +/- 7 versus 127 +/- 9 arbitrary units, n = 3, P < 0.05) and D subunit of ATP synthase (230 +/- 11 versus 368 +/- 47 arbitrary units, n = 3, P < 05)). Two forms of pyruvate dehydrogenase betaE1 subunit, the rate-limiting enzyme for glucose oxidation, were also identified. The protein level of the more acidic form of pyruvate dehydrogenase was reduced during reperfusion (37 +/- 4 versus 56 +/- 7 arbitrary units, n = 3, P < 05), while the more basic form remained unchanged. The more acidic isoform was found to be O-palmitoylated, while both isoforms exhibited ischemia/reperfusion-induced phosphorylation. In silico analysis identified the putative kinases as the insulin receptor kinase for the more basic form and protein kinase Czeta or protein kinase A for the more acidic form. These modifications of pyruvate dehydrogenase are associated with a 35% decrease in glucose oxidation during reperfusion.

CONCLUSIONS

Cardiac ischemia/reperfusion induces significant changes to a number of metabolic proteins of the mitochondrial proteome. In particular, ischemia/reperfusion induced the post-translational modification of pyruvate dehydrogenase, the rate-limiting step of glucose oxidation, which is associated with a 35% decrease in glucose oxidation during reperfusion. Therefore these post-translational modifications may have important implications in the regulation of myocardial energy metabolism.

Proteomic Profiling of the Dystrophin-Deficient MDX Heart Reveals Drastically Altered Levels of Key Metabolic and Contractile Proteins

Although Duchenne muscular dystrophy is primarily classified as a neuromuscular disease, cardiac complications play an important role in the course of this X-linked inherited disorder. The pathobiochemical steps causing a progressive decline in the dystrophic heart are not well understood. We therefore carried out a fluorescence difference in-gel electrophoretic analysis of 9-month-old dystrophin-deficient versus age-matched normal heart, using the established MDX mouse model of muscular dystrophy-related cardiomyopathy. Out of 2,509 detectable protein spots, 79 2D-spots showed a drastic differential expression pattern, with the concentration of 3 proteins being increased, including nucleoside diphosphate kinase and lamin-A/C, and of 26 protein species being decreased, including ATP synthase, fatty acid binding-protein, isocitrate dehydrogenase, NADH dehydrogenase, porin, peroxiredoxin, adenylate kinase, tropomyosin, actin, and myosin light chains. Hence, the lack of cardiac dystrophin appears to trigger a generally perturbed protein expression pattern in the MDX heart, affecting especially energy metabolism and contractile proteins.

Proteomic DIGE analysis of the mitochondria-enriched fraction from aged rat skeletal muscle

Skeletal muscle aging is associated with a loss in tissue mass and contractile strength, as well as fiber type shifting and bioenergetic adaptation processes. Since mitochondria represent the primary site for energy generation via oxidative phosphorylation, we investigated potential changes in the expression pattern of the mitochondrial proteome using the highly sensitive DIGE approach. The comparative analysis of the mitochondria-enriched fraction from young adult versus aged muscle revealed an age-related change in abundance for 39 protein species. MS technology identified the majority of altered proteins as constituents of muscle mitochondria. An age-dependent increase was observed for NADH dehydrogenase, the mitochondrial inner membrane protein mitofilin, peroxiredoxin isoform PRX-III, ATPase synthase, succinate dehydrogenase, mitochondrial fission protein Fis1, succinate-coenzyme A ligase, acyl-coenzyme A dehydrogenase, porin isoform VDAC2, ubiquinol-cytochrome c reductase core I protein and prohibitin. Immunoblotting, enzyme testing and confocal microscopy were used to validate proteomic findings. The DIGE-identified increase in key mitochondrial elements during aging agrees with the concept that sarcopenia is associated with a shift to a slower contractile phenotype and more pronounced aerobic-oxidative metabolism. This suggests that mitochondrial markers are reliable candidates that should be included in the future establishment of a biomarker signature of skeletal muscle aging.

Mitochondrial proteomics on human fibroblasts for identification of metabolic imbalance and cellular stress

Background

Mitochondrial proteins are central to various metabolic activities and are key regulators of apoptosis. Disturbance of mitochondrial proteins is therefore often associated with disease. Large scale protein data are required to capture the mitochondrial protein levels and mass spectrometry based proteomics is suitable for generating such data. To study the relative quantities of mitochondrial proteins in cells from cultivated human skin fibroblasts we applied a proteomic method based on nanoLC-MS/MS analysis of iTRAQ-labeled peptides.

Results

When fibroblast cultures were exposed to mild metabolic stress – by cultivation in galactose medium- the amount of mitochondria appeared to be maintained whereas the levels of individual proteins were altered. Proteins of respiratory chain complex I and IV were increased together with NAD⁺-dependent isocitrate dehydrogenase of the citric acid cycle illustrating cellular strategies to cope with altered energy metabolism. Furthermore, quantitative protein data, with a median standard error below 6%, were obtained for the following mitochondrial pathways: fatty acid oxidation, citric acid cycle, respiratory chain, antioxidant systems, amino acid metabolism, mitochondrial translation, protein quality control, mitochondrial morphology and apoptosis.

Conclusion

The robust analytical platform in combination with a well-defined compendium of mitochondrial proteins allowed quantification of single proteins as well as mapping of entire pathways. This enabled characterization of the interplay between metabolism and stress response in human cells exposed to mild stress.