Effect of lifestyle on age-related mitochondrial protein oxidation in mice cardiac muscle

Long-term effects of the chronic administration of doxorubicin on aged skeletal muscle: An exploratory study in mice

The widely used chemotherapeutic drug doxorubicin (DOX) has been associated with adverse effects on the skeletal muscle, which can persist for years after the end of the treatment. These adverse effects may be exacerbated in older patients, whose skeletal muscle might already be impaired by aging. Nonetheless, the mediators responsible for DOX-induced myotoxicity are still largely unidentified, particularly the ones involved in the long-term effects that negatively affect the quality of life of the patients. Therefore, this study aimed to investigate the long-term effects of the chronic administration of DOX on the soleus muscle of aged mice. For that and to mimic the clinical regimen, a dose of 1.5 mg kg-1 of DOX was administered two times per week for three consecutive weeks in a cumulative dose of 9 mg kg-1 to 19-month-old male mice, which were sacrificed two months after the last administration. Body wasting and the atrophy of the soleus muscle, as measured by a decrease in the cross-sectional area of the soleus muscle fibers, were identified as long-term effects of DOX administration. The atrophy observed was correlated with increased reactive oxygen species production and caspase-3 activity. An impaired skeletal muscle regeneration was also suggested due to the correlation between satellite cells activation and the soleus muscle fibers atrophy. Systemic inflammation, skeletal muscle energy metabolism and neuromuscular junction-related markers do not appear to be involved in the long-term DOX-induced skeletal muscle atrophy. The data provided by this study shed light on the mediators involved in the overlooked long-term DOX-induced myotoxicity, paving the way to the improvement of the quality of life and survival rates of older cancer patients.

Mitochondrial remodeling underlying age-induced skeletal muscle wasting: let's talk about sex

Sarcopenia is associated with reduced quality of life and premature mortality. The sex disparities in the processes underlying sarcopenia pathogenesis, which include mitochondrial dysfunction, are ill-understood and can be decisive for the optimization of sarcopenia-related interventions. To improve the knowledge regarding the sex differences in skeletal muscle aging, the gastrocnemius muscle of young and old female and male rats was analyzed with a focus on mitochondrial remodeling through the proteome profiling of mitochondria-enriched fractions. To the best of our knowledge, this is the first study analyzing sex differences in skeletal muscle mitochondrial proteome remodeling. Data demonstrated that age induced skeletal muscle atrophy and fibrosis in both sexes. In females, however, this adverse skeletal muscle remodeling was more accentuated than in males and might be attributed to an age-related reduction of 17beta-estradiol signaling through its estrogen receptor alpha located in mitochondria. The females-specific mitochondrial remodeling encompassed increased abundance of proteins involved in fatty acid oxidation, decreased abundance of the complexes subunits, and enhanced proneness to oxidative posttranslational modifications. This conceivable accretion of damaged mitochondria in old females might be ascribed to low levels of Parkin, a key mediator of mitophagy. Despite skeletal muscle atrophy and fibrosis, males maintained their testosterone levels throughout aging, as well as their androgen receptor content, and the age-induced mitochondrial remodeling was limited to increased abundance of pyruvate dehydrogenase E1 component subunit beta and electron transfer flavoprotein subunit beta. Herein, for the first time, it was demonstrated that age affects more severely the skeletal muscle mitochondrial proteome of females, reinforcing the necessity of sex-personalized approaches towards sarcopenia management, and the inevitability of the assessment of mitochondrion-related therapeutics.

Exercise Training Impacts Cardiac Mitochondrial Proteome Remodeling in Murine Urothelial Carcinoma

Cardiac dysfunction secondary to cancer may exert a negative impact in patients’ tolerance to therapeutics, quality of life, and survival. The aim of this study was to evaluate the potential therapeutic effect of exercise training on the heart in the setting of cancer, after diagnosis. Thus, the molecular pathways harbored in heart mitochondria from a murine model of chemically-induced urothelial carcinoma submitted to 8-weeks of high intensity treadmill exercise were characterized using mass spectrometry-based proteomics. Data highlight the protective effects of high intensity exercise training in preventing left ventricle diastolic dysfunction, fibrosis, and structural derangement observed in tumor-bearing mice. At the mitochondrial level, exercise training counteracted the lower ability to produce ATP observed in the heart of animals with urothelial carcinoma and induced the up-regulation of fatty acid oxidation and down-regulation of the biological process “cardiac morphogenesis”. Taken together, our data support the prescription of exercise training after cancer diagnosis for the management of disease-related cardiac dysfunction.

High activity before breeding improves reproductive performance by enhancing mitochondrial function and biogenesis

Understanding of physiological responses of organisms is typically based on data collected during an isolated event. Although many fundamental insights have been gained from these studies, evaluating the response to a single event ignores the fact that each individual has experienced a unique set of events throughout its life that may have altered its physiology. The idea that prior experiences can influence subsequent performance is known as a carry-over effect. Carry-over effects may explain much of the variation in performance found among individuals. For example, high physical activity has been shown to improve mitochondrial respiratory function and biogenesis and reduce oxidative stress, and has been linked to improved health and longevity. In this study, we asked whether the bioenergetic differences between active and inactive individuals carry over to impact performance in a subsequent reproductive event and alter a female's reproductive outcome. Female mice that had access to a running wheel for a month before mating gave birth to a larger litter and weaned a heavier litter, indicating that high physical activity had a positive carry-over effect to reproduction. Mice that ran also displayed higher mitochondrial respiration and biogenesis with no changes in endogenous antioxidant enzymes. These results provide a mechanistic framework for how the conditions that animals experience before breeding can impact reproductive outcomes.

Exercise: Teaching myocytes new tricks

Endurance exercise training promotes numerous cellular adaptations in both cardiac myocytes and skeletal muscle fibers. For example, exercise training fosters changes in mitochondrial function due to increased mitochondrial protein expression and accelerated mitochondrial turnover. Additionally, endurance exercise training alters the abundance of numerous cytosolic and mitochondrial proteins in both cardiac and skeletal muscle myocytes, resulting in a protective phenotype in the active fibers; this exercise-induced protection of cardiac and skeletal muscle fibers is often referred to as "exercise preconditioning." As few as 3-5 consecutive days of endurance exercise training result in a preconditioned cardiac phenotype that is sheltered against ischemia-reperfusion-induced injury. Similarly, endurance exercise training results in preconditioned skeletal muscle fibers that are resistant to a variety of stresses (e.g., heat stress, exercise-induced oxidative stress, and inactivity-induced atrophy). Many studies have probed the mechanisms responsible for exercise-induced preconditioning of cardiac and skeletal muscle fibers; these studies are important, because they provide an improved understanding of the biochemical mechanisms responsible for exercise-induced preconditioning, which has the potential to lead to innovative pharmacological therapies aimed at minimizing stress-induced injury to cardiac and skeletal muscle. This review summarizes the development of exercise-induced protection of cardiac myocytes and skeletal muscle fibers and highlights the putative mechanisms responsible for exercise-induced protection in the heart and skeletal muscles.

Effect of reproductive ageing on pregnant mouse uterus and cervix

KEY POINTS

Older pregnant women have a greater risk of operative delivery, still birth and post-term induction. This suggests that maternal age can influence the timing of birth and processes of parturition. We have found that increasing maternal age in C57BL/6J mice is associated with prolongation of gestation and length of labour. Older pregnant mice also had delayed progesterone withdrawal and impaired myometrial function. Uterine ageing and labour dysfunction should be investigated further in older primigravid women.

ABSTRACT

Advanced maternal age (≥35 years) is associated with increased rates of operative delivery, stillbirth and post-term labour induction. The physiological causes remain uncertain, although impaired myometrial function has been implicated. To investigate the hypothesis that maternal age directly influences successful parturition, we assessed the timing of birth and fetal outcome in pregnant C57BL/6J mice at 3 months (young) and 5 months (intermediate) vs. 8 months (older) of age using infrared video recording. Serum progesterone profiles, myometrium and cervix function, and mitochondrial electron transport chain complex enzymatic activities were also examined. Older pregnant mice had a longer mean gestation and labour duration (P < 0.001), as well as reduced litter size (P < 0.01) vs. 3-month-old mice. Older mice did not exhibit the same decline in serum progesterone concentrations as younger mice. Cervical tissues from older mice were more distensible than younger mice (P < 0.05). Oxytocin receptor and connexin-43 mRNA expression were reduced in the myometrium from 8-month-old vs. 3-month-old mice (P < 0.05 and P < 0.01 respectively) in tandem with more frequent but shorter duration spontaneous myometrial contractions (P < 0.05) and an attenuated contractile response to oxytocin. Myometrial mitochondrial copy number was reduced in older mice, although there were no age-induced changes to the enzymatic activities of the mitochondrial electron transport chain complexes. In conclusion, 8-month-old mice provide a useful model of reproductive ageing. The present study has identified potential causes of labour dysfunction amenable to investigation in older primigravid women.

Blot-MS of Carbonylated Proteins: A Tool to Identify Oxidized Proteins

The efficiency of proteostasis regulation declines during aging and the failure of protein homeostasis is common in age-related diseases. Protein oxidation is a major contributor to the loss of proteome homeostasis, also called "proteostasis," precluding protein misfolding and aggregation. So, the identification of the molecular pathways impaired by protein oxidation will increase the understanding of proteostasis and the pathophysiological conditions related to the loss of proteostasis. Sample derivatization with dinitrophenyl hydrazine and western blot immunoassay detection of carbonylated proteins (commonly known as Oxyblot™) coupled to mass spectrometry (blot-MS) is an attractive methodological approach to identify proteins that are more prone to carbonylation, a typical oxidative modification of amino acid residues. The integration of blot-MS data of carbonylated proteins with bioinformatics tools allows the identification of the biological processes more affected by protein oxidation and that, eventually, result in the loss of proteostasis.In this chapter, we describe a blot-MS methodology to identify the proteins more prone to oxidation in biological samples, as cell and tissue extracts, and biofluids. Analysis of mitochondria isolated from cardiac tissue is provided as an example. Bioinformatic strategy to deal with data retrieved from blot-MS experiments are proposed for the identification of relevant biological processes modulated by oxidative stress stimuli.

Mechanisms of exercise-induced cardioprotection

Myocardial ischemia-reperfusion (IR) injury can cause ventricular cell death and is a major pathological event leading to morbidity and mortality in those with coronary artery disease. Interestingly, as few as five bouts of exercise on consecutive days can rapidly produce a cardiac phenotype that resists IR-induced myocardial injury. This review summarizes the development of exercise-induced cardioprotection and the mechanisms responsible for this important adaptive response.

Molecular insights into mitochondrial dysfunction in cancer-related muscle wasting

Alterations in muscle mitochondrial bioenergetics during cancer cachexia were previously suggested; however, the underlying mechanisms are not known. So, the goal of this study was to evaluate mitochondrial phospholipid remodeling in cancer-related muscle wasting and its repercussions to respiratory chain activity and fiber susceptibility to apoptosis. An animal model of urothelial carcinoma induced by exposition to N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN) and characterized by significant body weight loss due to skeletal muscle mass decrease was used. Morphological evidences of muscle atrophy were associated to decreased respiratory chain activity and increased expression of mitochondrial UCP3, which altogether highlight the lower ability of wasted muscle to produce ATP. Lipidomic analysis of isolated mitochondria revealed a significant decrease of phosphatidic acid, phosphatidylglycerol and cardiolipin in BBN mitochondria, counteracted by increased phosphatidylcholine levels. Besides the impact on membrane fluidity, this phospholipid remodeling seems to justify, at least in part, the lower oxidative phosphorylation activity observed in mitochondria from wasted muscle and their increased susceptibility to apoptosis. Curiously, no evidences of lipid peroxidation were observed but proteins from BBN mitochondria, particularly the metabolic ones, seem more prone to carbonylation with the consequent implications in mitochondria functionality. Overall, data suggest that bladder cancer negatively impacts skeletal muscle activity specifically by affecting mitochondrial phospholipid dynamics and its interaction with proteins, ultimately leading to the dysfunction of this organelle. The regulation of phospholipid biosynthetic pathways might be seen as potential therapeutic targets for the management of cancer-related muscle wasting.

Cardiac aging and insulin resistance: could insulin/insulin-like growth factor (IGF) signaling be used as a therapeutic target?

Intrinsic cardiac aging is an independent risk factor for cardiovascular disease and is associated with structural and functional changes that impede cardiac responses to stress and to cardio-protective mechanisms. Although systemic insulin resistance and the associated risk factors exacerbate cardiac aging, cardiac-specific insulin resistance without confounding systemic alterations, could prevent cardiac aging. Thus, strategies aimed to reduce insulin/insulin-like growth factor (IGF) signaling in the heart prevent cardiac aging in lower organisms and in mammals but the mechanisms underlying this protection are not fully understood. In this review, we describe the impact of aging on the cardiovascular system and discuss the mounting evidence that reduced insulin/IGF signaling in the heart could alleviate age-associated alterations and preserve cardiac performance.

Proteomic analyses of age related changes in A.BY/SnJ mouse hearts

Background

A.BY/SnJ mice are used to study pathological alterations in the heart due to enteroviral infections. Since age is a well-known factor influencing the susceptibility of mice to infection, response to stress and manifestation of cardiovascular diseases, the myocardial proteome of A.BY/SnJ mice aged 1 and 4 months was comparatively studied using two dimensional-differential in-gel electrophoresis (2D-DIGE) and liquid chromatography tandem mass spectrometry (LC-MS/MS).

Results

Complementary analyses by 2D-DIGE and gel-free LC-MS/MS revealed 96 distinct proteins displaying age associated alterations in their levels. Proteins related to protein transport, and transport chain, lipid metabolism and fatty acid transport showed significant changes in 4 months old mouse hearts compared to juvenile hearts. Proteins involved in lipid metabolism and transport were identified at significantly higher levels in older mice and dysregulation of proteins of the respiratory transport chain were observed.

Conclusion

The current proteomics study discloses age dependent changes occurring in the hearts already in young mice of the strain A.BY/SnJ. Besides alterations in protein transport, we provide evidence that a decrease of ATP synthase in murine hearts starts already in the first months of life, leading to well-known low expression levels manifested in old mice thereby raising the possibility of reduced energy supply. In the first few months of murine life this seems to be compensated by an increased lipid metabolism. The functional alterations described should be considered during experimental setups in disease related studies.

Lipidomic characterization of streptozotocin-induced heart mitochondrial dysfunction

Myocardial mitochondria dysfunction seems to represent an important pathogenic factor underlying cardiomyopathy, a common complication of type 1 diabetes mellitus (T1DM). Despite significant progress in the understanding of the molecular mechanisms of mitochondrial function in the heart, the interplay between phospholipids and membrane proteins of this organelle is still poorly comprehended. Using a well-characterized animal model of T1DM obtained by the administration of streptozotocin, phospholipid profiling of isolated mitochondria was performed using MS-based approaches, which was analyzed together with oxidative phosphorylation (OXPHOS) complexes activities and their susceptibility to oxidation, and the expression of cytochrome c, the uncoupling protein UCP-3 and the mitochondrial transcription factor Tfam. Although in higher amounts, mitochondria from T1DM heart presented lower OXPHOS activity and lower transcription ability. This profile was related to phospholipid (PL) remodeling characterized by higher phosphatidylcholine levels, lower phosphatidylglycerol, phosphatidylinositol and sphingomyelin content, higher amounts of long fatty acyl side chains and increased lipid peroxidation, particularly of cardiolipin (CL). CL peroxidation was paralleled by lower cytochrome c content. Though in higher levels, UCP-3 does not seem to protect heart mitochondrial PL and membrane proteins from the oxidative damage induced by four weeks of hyperglycemia. Taken together, our data suggest that PL remodeling of heart mitochondria is an early event in T1DM pathogenesis and is related with OXPHOS dysfunction.

Temporal patterns of tyrosine nitration in embryo heart development

Tyrosine nitration is a biomarker for the production of peroxynitrite and other reactive nitrogen species. Nitrotyrosine immunoreactivity is present in many pathological conditions including several cardiac diseases. Because the events observed during heart failure may recapitulate some aspects of development, we tested whether nitrotyrosine is present during normal development of the rat embryo heart and its potential relationship in cardiac remodeling through apoptosis. Nitric oxide production is highly dynamic during development, but whether peroxynitrite and nitrotyrosine are formed during normal embryonic development has received little attention. Rat embryo hearts exhibited strong nitrotyrosine immunoreactivity in endocardial and myocardial cells of the atria and ventricles from E12 to E18. After E18, nitrotyrosine staining faded and disappeared entirely by birth. Tyrosine nitration in the myocardial tissue coincided with elevated protein expression of nitric oxide synthases (eNOS and iNOS). The immunoreactivity for these NOS isoforms remained elevated even after nitrotyrosine had disappeared. Tyrosine nitration did not correlate with cell death or proliferation of cardiac cells. Analysis of tryptic peptides by MALDI-TOF showed that nitration occurs in actin, myosin, and the mitochondrial ATP synthase α chain. These results suggest that reactive nitrogen species are not restricted to pathological conditions but may play a role during normal embryonic development.

Protein carbonylation and metabolic control systems

Oxidative stress is linked to the production of reactive lipid aldehydes that non-enzymatically alkylate cysteine, histidine, or lysine residues in a reaction termed protein carbonylation. Reactive lipid aldehydes and their derivatives are detoxified via a variety of phase I and phase II systems, and when antioxidant defenses are compromised or oxidative conditions are increased, protein carbonylation is increased. The resulting modification has been implicated as causative in a variety of metabolic states including neurodegeneration, muscle wasting, insulin resistance, and aging. Although such modifications usually result in loss of protein function, protein carbonylation may be regulatory and activate signaling pathways involved in antioxidant biology and cellular homeostasis.