Heme: The Lord of the Iron Ring

Heme is an iron-protoporphyrin complex with an essential physiologic function for all cells, especially for those in which heme is a key prosthetic group of proteins such as hemoglobin, myoglobin, and cytochromes of the mitochondria. However, it is also known that heme can participate in pro-oxidant and pro-inflammatory responses, leading to cytotoxicity in various tissues and organs such as the kidney, brain, heart, liver, and in immune cells. Indeed, heme, released as a result of tissue damage, can stimulate local and remote inflammatory reactions. These can initiate innate immune responses that, if left uncontrolled, can compound primary injuries and promote organ failure. In contrast, a cadre of heme receptors are arrayed on the plasma membrane that is designed either for heme import into the cell, or for the purpose of activating specific signaling pathways. Thus, free heme can serve either as a deleterious molecule, or one that can traffic and initiate highly specific cellular responses that are teleologically important for survival. Herein, we review heme metabolism and signaling pathways, including heme synthesis, degradation, and scavenging. We will focus on trauma and inflammatory diseases, including traumatic brain injury, trauma-related sepsis, cancer, and cardiovascular diseases where current work suggests that heme may be most important.

The influence of a supervised group exercise intervention combined with active lifestyle recommendations on breast cancer survivors' health, physical functioning, and quality of life indices: study protocol for a randomized and controlled trial

Background

Most cancer patients, under active treatment or not, are sedentary, despite increasing scientific and clinical understanding of the benefits of exercise and physical activity, such as improving quality of life, limiting disease symptoms, decreasing cancer recurrence, and increasing overall survival. Studies have shown that both supervised exercise and unsupervised physical activity programs have low adherence and limited long-term benefits among cancer survivors. Therefore, interventions focused on increasing physical activity levels have clinical and psychological relevance. The present study will examine the feasibility and efficacy of an intervention that combines supervised group exercise with active lifestyle recommendations, analyzing its clinical, psychological, physiological, functional, and immunological effects in breast cancer survivors.

Methods

Women aged 35–75 years who have completed chemotherapy, radiotherapy, and surgery for breast cancer will be recruited from the Cancer Institute of the State of Sao Paulo (ICESP) and take part in a 16-week, parallel-group, randomized, and controlled trial. They will receive a booklet with recommendations for achieving a physically active lifestyle by increasing overall daily movement and undertaking at least 150 min/week of structured exercise. Then, they will be randomized into two groups: the supervised group will take part in two canoeing group exercise sessions every week, and the unsupervised group will increase their overall physical activity level by any means, such as active commuting, daily activities, or home-based exercise. Primary outcome includes aerobic capacity. Secondary outcomes are physical activity, physical functioning, self-reported quality of life, fatigue, presence of lymphedema, body composition, immune function, adherence to physical activity guidelines, and perceptions of self-image.

Discussion

Results should contribute to advance knowledge on the impact of a supervised group exercise intervention to improve aspects related to health, physical functioning, and quality of life in female breast cancer survivors.

Trial registration

Brazilian Registry of Clinical Trials Number: RBR-3fw9xf. Retrospectively Registered on 27 December 2018. Items from the World Health Organization Trial Registration Data Set can be accessed on http://www.ensaiosclinicos.gov.br/rg/RBR-3fw9xf/.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05843-z.

Aerobic exercise training prevents skeletal myopathy by myomiRs regulation in heart failure

Introduction

Heart failure (HF) is the endpoint of systemic arterial hypertension. Exercise intolerance is a common symptom, partly due, to changes in the skeletal muscle mass (SM) and fiber type profile. Otherwise, aerobic exercise training (ET) has been used as an important non-pharmacological therapy in HF. MyomiRs are a muscle-specific class of miRNAs, which regulate genes that inhibiting the expression of proteins in pathological and physiological conditions controlling phenotypic changes in the SM, however little is known about these changes in ET-induced HF

Purpose

To elucidate the molecular mechanisms of ET involved in the metabolic alterations of SM in HF rats of hypertensive etiology.

Methods

The study was approved by the animal ethics committee (USP-No. 2020/01). 20 male rats, spontaneously hypertensive (SHR), and 10 Wistar Kyoto rats (WKY), SHR controls, nine-months-old, were divided into three groups: sedentary WKY (WKY-S), sedentary SHR (SHR-S), and trained (SHR-T). The ET consisted of swimming sessions with 60 minutes, 1x/day, 5x/week, for 10 weeks, with 5% of body overload. After ET protocol, blood pressure (BP), cardiac morphology and function (Echocardiography), exercise tolerance test, maximal oxygen uptake (VO2 peak), mitochondrial oxygen consumption (Oroboros), immunohistochemistry of the SM, expression of miRNAs (RT-qPCR) were evaluated. Statistical analyzes were performed by one-way ANOVA followed by the Tukey test. The results were expressed as mean ± standard error.

Results

ET reduced blood pressure levels and cardiac dysfunction in SHR-T compared to SHR-S. The SHR-S group covered smaller distance in the exercise tolerance test (255±22 meters) compared to the WKY-S (419±19 meters, p<0.0001), however ET reestablished the exercise tolerance (SHR-T: 365±20 meters; SHR-S: p<0.001 and WKY-S: p>0.05). The HF induced changes in type I and II fibers composition (I: 73±0.6% and II: 24±0.9%), VO2 peak (50±1.5 mL kg–1 min–1), mitochondrial oxygen consumption (State 3: 3.0±0.2 nmol O2 min–1 mg protein–1) and myomiRs expression (miRNA-208b: 65±4%, -499: 73±5%, -1: 153±10%) in the soleus muscle of SHR-S compared to WKY-S (I: 94±0.6%, II: 6±0.6%, p<0.001; VO2 peak: 59±2.3 mL kg–1 min–1, p<0.01; State 3: 4.0±0.2 nmol O2 min–1 mg protein–1, p<0.05; miRNAs: p<0.01). ET minimized changes in metabolic profile by counteract the muscle fiber type switching, and the oxygen consumption impairment, and myomiRs expression dysregulation (I: 90±0.5%, II: 9±0.6%, SHR-S p<0.01; VO2 peak: 79±2.4 mL kg–1 min–1, SHR-S: p<0.0001; State 3: 5.45±0.32 nmol O2 min–1 mg protein–1, SHR-S: p<0.0001; miRNA-208b: 91±5%, -499: 106±8%, -1: 100±9%; SHR-S: p<0.01).

Conclusions

ET reestablished structural and metabolic changes in SM, resulting from the progression of HF, through the regulation of myomiRs, improving exercise tolerance.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): The Coordination for the Improvement of Higher Education Personnel (CAPES): Academic Excellence Program (Proex).

β2-Adrenergic Signaling Modulates Mitochondrial Function and Morphology in Skeletal Muscle in Response to Aerobic Exercise

The molecular mechanisms underlying skeletal muscle mitochondrial adaptations induced by aerobic exercise (AE) are not fully understood. We have previously shown that AE induces mitochondrial adaptations in cardiac muscle, mediated by sympathetic stimulation. Since direct sympathetic innervation of neuromuscular junctions influences skeletal muscle homeostasis, we tested the hypothesis that β₂-adrenergic receptor (β₂-AR)-mediated sympathetic activation induces mitochondrial adaptations to AE in skeletal muscle. Male FVB mice were subjected to a single bout of AE on a treadmill (80% Vmax, 60 min) under β₂-AR blockade with ICI 118,551 (ICI) or vehicle, and parameters of mitochondrial function and morphology/dynamics were evaluated. An acute bout of AE significantly increased maximal mitochondrial respiration in tibialis anterior (TA) isolated fiber bundles, which was prevented by β₂-AR blockade. This increased mitochondrial function after AE was accompanied by a change in mitochondrial morphology towards fusion, associated with increased Mfn1 protein expression and activity. β₂-AR blockade fully prevented the increase in Mfn1 activity and reduced mitochondrial elongation. To determine the mechanisms involved in mitochondrial modulation by β₂-AR activation in skeletal muscle during AE, we used C2C12 myotubes, treated with the non-selective β-AR agonist isoproterenol (ISO) in the presence of the specific β₂-AR antagonist ICI or during protein kinase A (PKA) and Gα_i protein blockade. Our in vitro data show that β-AR activation significantly increases mitochondrial respiration in myotubes, and this response was dependent on β₂-AR activation through a Gα_s-PKA signaling cascade. In conclusion, we provide evidence for AE-induced β₂-AR activation as a major mechanism leading to alterations in mitochondria function and morphology/dynamics. β₂-AR signaling is thus a key-signaling pathway that contributes to skeletal muscle plasticity in response to exercise.

Exercise training delays cardiac remodeling in a mouse model of cancer cachexia

AIMS

We aimed to investigate the impact of cancer cachexia and previous aerobic exercise training (AET) on cardiac function and structure in tumor bearing mice.

MAIN METHODS

Colon adenocarcinoma cells 26 (CT26) were subcutaneously injected in BALB/c mice to establish robust cancer cachexia model. AET was performed on a treadmill during 45 days, 60 min/5 days per week. Cardiac function was evaluated by echocardiography and cardiac morphology was assessed by light microscopy. The protein expression levels of mitochondrial complex were analyzed by Western blotting. The mRNA levels of genes related to cardiac remodeling and autophagy were analyzed by quantitative Real-Time PCR.

KEY FINDINGS

Our data confirms CT26 tumor bearing mice as a well-characterized and robust model of cancer cachexia. CT26 mice exhibited cardiac remodeling and dysfunction characterized by cardiac atrophy and impaired left ventricle ejection fraction paralleled by cardiac necrosis, inflammation and fibrosis. AET partially reversed the left ventricle ejection fraction and led to significant anti-cardiac remodeling effect associated reduced necrosis, inflammation and cardiac collagen deposition in CT26 mice. Reduced TGF-β1 mRNA levels, increased mitochondrial complex IV protein levels and partial recovery of BNIP3 mRNA levels in cardiac tissue were associated with the cardiac effects of AET in CT26 mice. Thus, we suggest AET as a powerful regulator of key pathways involved in cardiac tissue homeostasis in cancer cachexia.

SIGNIFICANCE

Our study provides a robust model of cancer cachexia, as well as highlights the potential and integrative effects of AET as a preventive strategy for reducing cardiac damage in cancer cachexia.

Lack of β2-AR improves exercise capacity and skeletal muscle oxidative phenotype in mice

β(2)-adrenergic receptor (β(2)-AR) agonists have been used as ergogenics by athletes involved in training for strength and power in order to increase the muscle mass. Even though anabolic effects of β(2)-AR activation are highly recognized, less is known about the impact of β(2)-AR in endurance capacity. We presently used mice lacking β(2)-AR [β(2)-knockout (β(2) KO)] to investigate the role of β(2)-AR on exercise capacity and skeletal muscle metabolism and phenotype. β(2) KO mice and their wild-type controls (WT) were studied. Exercise tolerance, skeletal muscle fiber typing, capillary-to-fiber ratio, citrate synthase activity and glycogen content were evaluated. When compared with WT, β(2) KO mice displayed increased exercise capacity (61%) associated with higher percentage of oxidative fibers (21% and 129% of increase in soleus and plantaris muscles, respectively) and capillarity (31% and 20% of increase in soleus and plantaris muscles, respectively). In addition, β(2) KO mice presented increased skeletal muscle citrate synthase activity (10%) and succinate dehydrogenase staining. Likewise, glycogen content (53%) and periodic acid-Schiff staining (glycogen staining) were also increased in β(2) KO skeletal muscle. Altogether, these data provide evidence that disruption of β(2)-AR improves oxidative metabolism in skeletal muscle of β(2) KO mice and this is associated with increased exercise capacity.