Exercise interrupts ongoing glucocorticoid-induced muscle atrophy and glutamine synthetase induction

Contractile regulation of the glucocorticoid-sensitive transcriptome in young and aged skeletal muscle

Elevated glucocorticoids alter the skeletal muscle transcriptome to induce a myopathy characterized by muscle atrophy, muscle weakness, and decreased metabolic function. These effects are more likely to occur and be more severe in aged muscles. Resistance exercise can blunt the development of glucocorticoid myopathy in young muscle, but the potential to oppose the signals initiating myopathy in aged muscle is unknown. To answer this, young (4-mo-old) and aged (24-to 25-mo-old) male C57BL/6 mice were randomized to receive either an intraperitoneal (IP) injection of dexamethasone (DEX; 2 mg/kg) or saline as a control. Two hours postinjections, the tibialis anterior (TA) muscles of mice were subjected to unilateral high-force contractions. Muscles were harvested 4 h later. The glucocorticoid- and contraction-sensitive genes were determined by RNA sequencing. The number of glucocorticoid-sensitive genes was similar between young and aged muscle. Contractions opposed changes to more glucocorticoid-sensitive genes in aged muscle, with this outcome primarily occurring when hormone levels were elevated. Glucocorticoid-sensitive gene programs opposed by contractions were primarily related to metabolism in young mice and muscle size regulation and inflammation in aged mice. In silico analysis implied peroxisome proliferator-activated receptor gamma-1 (PPARG) contributed to the contraction-induced opposition of glucocorticoid-sensitive genes in aged muscle. Increasing PPARG expression in the TA of aged mice using adeno-associated virus serotype 9 partially counteracted the glucocorticoid-induced reduction in runt-related transcription factor 1 (Runx1) mRNA content, recapitulating the effects observed by contractions. Overall, these data contribute to our understanding of the contractile regulation of the glucocorticoid transcriptome in aged skeletal muscle.NEW & NOTEWORTHY We establish the extent to which muscle contractions oppose changes to the glucocorticoid-sensitive transcriptome in both young and aged muscle. We also identify peroxisome proliferator-activated receptor gamma (PPARG) as a transcription factor likely contributing to contraction-induced opposition to the glucocorticoid transcriptome in aged muscle. Overall, these data contribute to our understanding of the contractile regulation of the glucocorticoid transcriptome.

Steroid myopathy and rehabilitation in patients with cancer

Steroids are broadly used in oncology, despite known adverse events such as glucocorticosteroid-induced myopathy (SM). To date there are no accepted guidelines on the diagnosis and treatment of SM. The purpose of this review is to provide up-to-date information regarding SM with emphasis on neuro-oncology and hematopoietic stem cell transplant patients, given they are at high risk of experiencing SM following routine treatment with steroids. Our work is a combination of a comprehensive narrative review regarding etiology, pathogenesis, incidence, clinical presentation and treatment options for SM and a scoping review on exercise therapy for SM. We have identified 24 in vivo studies of different exercise modalities in the settings of glucocorticosteroid treatment. Twenty of 24 studies demonstrated decreased muscle catabolism with exercise training. Both endurance and resistance exercises at mild to moderate intensity were beneficial. The value of high-intensity activities remains questionable as it may worsen muscle atrophy. Rehabilitation interventions, along with pharmacologic and dietary considerations, may be beneficial in preventing or reversing SM. Potential adverse events of some of these interventions and expected caveats in translating findings in preclinical models to human settings warrant caution and demand controlled clinical studies.

The Increased Endogenous Sulfur Dioxide Acts as a Compensatory Mechanism for the Downregulated Endogenous Hydrogen Sulfide Pathway in the Endothelial Cell Inflammation

Endogenous hydrogen sulfide (H₂S) and sulfur dioxide (SO₂) are regarded as important regulators to control endothelial cell function and protect endothelial cell against various injuries. In our present study, we aimed to investigate the effect of endogenous H₂S on the SO₂ generation in the endothelial cells and explore its significance in the endothelial inflammation in vitro and in vivo. The human umbilical vein endothelial cell (HUVEC) line (EA.hy926), primary HUVECs, primary rat pulmonary artery endothelial cells (RPAECs), and purified aspartate aminotransferase (AAT) protein from pig heart were used for in vitro experiments. A rat model of monocrotaline (MCT)-induced pulmonary vascular inflammation was used for in vivo experiments. We found that endogenous H₂S deficiency caused by cystathionine-γ-lyase (CSE) knockdown increased endogenous SO₂ level in endothelial cells and enhanced the enzymatic activity of AAT, a major SO₂ synthesis enzyme, without affecting the expressions of AAT1 and AAT2. While H₂S donor could reverse the CSE knockdown-induced increase in the endogenous SO₂ level and AAT activity. Moreover, H₂S donor directly inhibited the activity of purified AAT protein, which was reversed by a thiol reductant DTT. Mechanistically, H₂S donor sulfhydrated the purified AAT1/2 protein and rescued the decrease in the sulfhydration of AAT1/2 protein in the CSE knockdown endothelial cells. Furthermore, an AAT inhibitor l-aspartate-β-hydroxamate (HDX), which blocked the upregulation of endogenous SO₂/AAT generation induced by CSE knockdown, aggravated CSE knockdown-activated nuclear factor-κB pathway in the endothelial cells and its downstream inflammatory factors including ICAM-1, TNF-α, and IL-6. In in vivo experiment, H₂S donor restored the deficiency of endogenous H₂S production induced by MCT, and reversed the upregulation of endogenous SO₂/AAT pathway via sulfhydrating AAT1 and AAT2. In accordance with the results of the in vitro experiment, HDX exacerbated the pulmonary vascular inflammation induced by the broken endogenous H₂S production in MCT-treated rat. In conclusion, for the first time, the present study showed that H₂S inhibited endogenous SO₂ generation by inactivating AAT via the sulfhydration of AAT1/2; and the increased endogenous SO₂ generation might play a compensatory role when H₂S/CSE pathway was downregulated, thereby exerting protective effects in endothelial inflammatory responses in vitro and in vivo.

Corticosteroid-induced adverse events in adults: frequency, screening and prevention

Corticosteroids represent the most important and frequently used class of anti-inflammatory drugs and are the reference therapy for numerous neoplastic, immunological and allergic diseases. However, their substantial efficacy is often counter-balanced by multiple adverse events. These corticosteroid-induced adverse events represent a broad clinical and biological spectrum from mild irritability to severe and life-threatening adrenal insufficiency or cardiovascular events. The purpose of this article is to provide an overview of the available data regarding the frequency, screening and prevention of the adverse events observed in adults during systemic corticosteroid therapy (topically administered corticosteroids are outside the remit of this review). These include clinical (i.e. adipose tissue redistribution, hypertension, cardiovascular risk, osteoporosis, myopathy, peptic ulcer, adrenal insufficiency, infections, mood disorders, ophthalmological disorders, skin disorders, menstrual disorders, aseptic necrosis, pancreatitis) and biological (i.e. electrolytes homeostasis, diabetogenesis, dyslipidaemia) events. Lastly, data about the prescription of corticosteroids during pregnancy are provided. This review underscores the absence of data on many of these adverse events (e.g. lipodystrophy, dyslipidaemia). Our intent is to present to practitioners data that can be used in a practical way to both screen and prevent most of the adverse events observed during systemic corticosteroid therapy.