Dexamethasone rapidly inhibits glucose uptake via non-genomic mechanisms in contracting myotubes

The Use of Albuterol/Budesonide as Reliever Therapy to Reduce Asthma Exacerbations

Prevention of asthma exacerbations and reduction of systemic corticosteroid burden remain unmet needs in asthma. US asthma guidelines recommend concomitant short-acting β2-agonist (SABA) and inhaled corticosteroid (ICS) as an alternative reliever at step 2. The Food and Drug Administration approved a pressurized metered-dose inhaler containing albuterol and budesonide for as-needed treatment or prevention of bronchoconstriction and for reducing exacerbation risk in patients with asthma aged ≥18 years. This combination is approved for use as a reliever with or without maintenance therapy, but it is not indicated for maintenance therapy (or for single maintenance and reliever therapy). Intervening with as-needed SABA-ICS during the window of opportunity to reduce inflammation during loss of asthma control can reduce exacerbation risk, by exerting both genomic and nongenomic anti-inflammatory effects. We propose that the use of albuterol-budesonide rather than albuterol as a reliever to manage episodic symptoms driven by acute bronchoconstriction and airway inflammation can improve outcomes. This combination approach, shown to decrease asthma exacerbations and oral corticosteroid burden in patients with moderate-to-severe asthma, represents a paradigm shift for asthma treatment in the United States. Further safety and efficacy studies should provide evidence that this type of reliever should be standard of care.

Short-term exposure to dexamethasone at environmentally relevant concentrations impairs embryonic development in Cyprinus carpio: Bioconcentration and alteration of oxidative stress-related gene expression patterns

In recent years and as a result of the Covid-19 pandemic, the consumption of dexamethasone (DXE) has increased. This favors that this corticosteroid is highly released in aquatic environments, generating deleterious effects in aquatic organisms. The information on the toxic effects of DXE in the environment is still limited. Thus, the objective of this work was to determine whether DXE at short-term exposure can cause alterations to embryonic development and alteration of oxidative stress-related gene expression patterns in Cyprinus carpio. For this purpose, common carp embryos (2 hpf) were exposed to realistic concentrations of DXE until 96 hpf. Alterations to embryonic development were evaluated at 12, 24, 48, 72 and 96 hpf. In addition, oxidative stress in carp embryos at 72 and 96 hpf was evaluated by cellular oxidation biomarkers (lipoperoxidation level, hydroperoxide and carbonyl protein content) and antioxidant enzymes activities (superoxide dismutase and catalase). Oxidative stress-related gene expression (sod, cat and gpx1) was also evaluated. Our results showed that DXE concentrations above 35 ng/L are capable of producing alterations to embryonic development in 50 % of the embryo population. Furthermore, DXE was able to induce alterations such as scoliosis, hypopigmentation, craniofacial malformations, pericardial edema and growth retardation, leading to the death of half of the population at 50 ng/L of DXE. Concerning oxidative stress, the results demonstrated that DXE induce oxidative damage on the embryos of C. carpio. In conclusion, DXE is capable of altering embryonic development and generating oxidative stress in common carp C. carpio.

Treating the Side Effects of Exogenous Glucocorticoids; Can We Separate the Good From the Bad?

It is estimated that 2% to 3% of the population are currently prescribed systemic or topical glucocorticoid treatment. The potent anti-inflammatory action of glucocorticoids to deliver therapeutic benefit is not in doubt. However, the side effects associated with their use, including central weight gain, hypertension, insulin resistance, type 2 diabetes (T2D), and osteoporosis, often collectively termed iatrogenic Cushing's syndrome, are associated with a significant health and economic burden. The precise cellular mechanisms underpinning the differential action of glucocorticoids to drive the desirable and undesirable effects are still not completely understood. Faced with the unmet clinical need to limit glucocorticoid-induced adverse effects alongside ensuring the preservation of anti-inflammatory actions, several strategies have been pursued. The coprescription of existing licensed drugs to treat incident adverse effects can be effective, but data examining the prevention of adverse effects are limited. Novel selective glucocorticoid receptor agonists and selective glucocorticoid receptor modulators have been designed that aim to specifically and selectively activate anti-inflammatory responses based upon their interaction with the glucocorticoid receptor. Several of these compounds are currently in clinical trials to evaluate their efficacy. More recently, strategies exploiting tissue-specific glucocorticoid metabolism through the isoforms of 11β-hydroxysteroid dehydrogenase has shown early potential, although data from clinical trials are limited. The aim of any treatment is to maximize benefit while minimizing risk, and within this review we define the adverse effect profile associated with glucocorticoid use and evaluate current and developing strategies that aim to limit side effects but preserve desirable therapeutic efficacy.

Diclofenac and dexamethasone modulate the effect of cannabidiol on the rat colon motility ex vivo

Introduction

Due to the growing interest in the use of cannabinoids in supportive therapies, they are increasingly used together with anti-inflammatory drugs. Cannabinoids inhibit gastrointestinal motility, while steroidal and nonsteroidal anti-inflammatory drugs influence motility in other ways. The aim of the research was to study the interactions between cannabidiol (CBD) and these two classes of anti-inflammatory drugs in the context of gastrointestinal motility. Dexamethasone (DEX) was selected as a steroidal drug and diclofenac (DCF) as a nonsteroidal counterpart.

Material and Methods

The experiments were performed on isolated rat colon strips in isometric conditions. The contractile response to acetylcholine (ACh) (1 μM) was measured with no substance applied as a control value and was measured after application of CBD (80 μM), DEX (100 μM), DCF (100 μM), or a combination of these substances.

Results

Cannabidiol strongly inhibited intestinal motility mediated by ACh application, DCF inhibited it non-significantly, while DEX intensified it. When CBD was co-administered with DEX, the combination inhibited intestinal motility non-significantly relative to the ACh-only control. Co-administration of CBD with DCF inhibited motility more than when these substances were administered separately.

Conclusion

Inhibition of the intestinal response to ACh is likely due to the synergistic effect of CBD and endogenous cannabinoids. Dexamethasone lessened the inhibitory effect of CBD, likely because of diminished availability of the arachidonic acid necessary for endogenous cannabinoid synthesis. However, diclofenac may increase endogenous cannabinoid synthesis, because of the greater availability of arachidonic acid caused by DCF blocking the cyclooxygenation pathway.

Mitochondrial ROS Accumulation Contributes to Maternal Hypertension and Impaired Remodeling of Spiral Artery but Not IUGR in a Rat PE Model Caused by Maternal Glucocorticoid Exposure

Increased maternal glucocorticoid levels have been implicated as a risk factor for preeclampsia (PE) development. We found that pregnant rats exposed to dexamethasone (DEX) showed hallmarks of PE features, impaired spiral artery (SA) remodeling, and elevated circulatory levels of sFlt1, sEng IL-1β, and TNFα. Abnormal mitochondrial morphology and mitochondrial dysfunction in placentas occurred in DEX rats. Omics showed that a large spectrum of placental signaling pathways, including oxidative phosphorylation (OXPHOS), energy metabolism, inflammation, and insulin-like growth factor (IGF) system were affected in DEX rats. MitoTEMPO, a mitochondria-targeted antioxidant, alleviated maternal hypertension and renal damage, and improved SA remodeling, uteroplacental blood flow, and the placental vasculature network. It reversed several pathways, including OXPHOS and glutathione pathways. Moreover, DEX-induced impaired functions of human extravillous trophoblasts were associated with excess ROS caused by mitochondrial dysfunction. However, scavenging excess ROS did not improve intrauterine growth retardation (IUGR), and elevated circulatory sFlt1, sEng, IL-1β, and TNFα levels in DEX rats. Our data indicate that excess mitochondrial ROS contributes to trophoblast dysfunction, impaired SA remodeling, reduced uteroplacental blood flow, and maternal hypertension in the DEX-induced PE model, while increased sFlt1 and sEng levels and IUGR might be associated with inflammation and an impaired energy metabolism and IGF system.

Disturbances of Hormonal Circadian Rhythms by Light Pollution

The circadian rhythms evolved to anticipate and cope with cyclic changes in environmental conditions. This adaptive function is currently compromised by increasing levels of artificial light at night (ALAN), which can represent a risk for the development of diseases of civilisation. The causal links are not completely understood, and this featured review focuses on the chronodisruption of the neuroendocrine control of physiology and behaviour by dim ALAN. The published data indicate that low levels of ALAN (2-5 lux) can attenuate the molecular mechanisms generating circadian rhythms in the central oscillator, eliminate the rhythmic changes in dominant hormonal signals, such as melatonin, testosterone and vasopressin, and interfere with the circadian rhythm of the dominant glucocorticoid corticosterone in rodents. These changes are associated with a disturbed daily pattern of metabolic changes and behavioural rhythms in activity and food and water intake. The increasing levels of ALAN require the identification of the pathways mediating possible negative consequences on health to design effective mitigation strategies to eliminate or minimise the effects of light pollution.

Role of glucocorticoid and mineralocorticoid receptors in rainbow trout (Oncorhynchus mykiss) skeletal muscle: A transcriptomic perspective of cortisol action

Cortisol is an essential regulator of neuroendocrine stress responses in teleost. Cortisol performs its effects through the modulation of glucocorticoid receptor (GR) and mineralocorticoid receptor (MR), activating gene expression. Until now the contribution of both receptors in the global transcriptional response in teleost skeletal muscle has not been explored. To understand in a comprehensive and global manner how GR and MR modulates the skeletal muscle transcriptomic response, we performed RNA-seq analysis. Juvenile rainbow trout (Oncorhynchus mykiss) pretreated with a suppressor of endogenous cortisol production were intraperitoneally injected with cortisol (10 mg/kg). We also included a treatment with mifepristone (GR antagonist) and eplerenone (MR antagonist) in the presence or absence of cortisol. cDNA libraries were constructed from the skeletal muscle of rainbow trout groups: vehicle, cortisol, mifepristone, eplerenone, mifepristone/cortisol and eplerenone/cortisol. RNA-seq analysis revealed that 135 transcripts were differentially expressed in cortisol vs. mifepristone/cortisol group, mainly associated to inflammatory response, ion transmembrane transport, and proteolysis. In the other hand, 68 transcripts were differentially expressed in cortisol vs. eplerenone/cortisol group, mainly associated to muscle contraction, and regulation of cell cycle. To validate these observations, we performed in vitro experiments using rainbow trout myotubes. In myotubes treated with cortisol, we found increased expression of cxcr2, c3, and clca3p mediated by GR, associated with inflammatory response, proteolysis, and ion transmembrane transport, respectively. Contrastingly, MR modulated the expression of myh2 and gadd45g mainly associated with muscle contraction and regulation of cell cycle, respectively. These results suggest that GR and MR have a differential participation in the physiological response to stress in teleost skeletal muscle.

Characteristics of the Protocols Used in Electrical Pulse Stimulation of Cultured Cells for Mimicking In Vivo Exercise: A Systematic Review, Meta-Analysis, and Meta-Regression

While exercise benefits a wide spectrum of diseases and affects most tissues and organs, many aspects of its underlying mechanistic effects remain unsolved. In vitro exercise, mimicking neuronal signals leading to muscle contraction in vitro, can be a valuable tool to address this issue. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for this systematic review and meta-analysis, we searched EMBASE and PubMed (from database inception to 4 February 2022) for relevant studies assessing in vitro exercise using electrical pulse stimulation to mimic exercise. Meta-analyses of mean differences and meta-regression analyses were conducted. Of 985 reports identified, 41 were eligible for analysis. We observed variability among existing protocols of in vitro exercise and heterogeneity among protocols of the same type of exercise. Our analyses showed that AMPK, Akt, IL-6, and PGC1a levels and glucose uptake increased in stimulated compared to non-stimulated cells, following the patterns of in vivo exercise, and that these effects correlated with the duration of stimulation. We conclude that in vitro exercise follows motifs of exercise in humans, allowing biological parameters, such as the aforementioned, to be valuable tools in defining the types of in vitro exercise. It might be useful in transferring obtained knowledge to human research.

The Chemically-Modified Tetracycline COL-3 and Its Parent Compound Doxycycline Prevent Microglial Inflammatory Responses by Reducing Glucose-Mediated Oxidative Stress

We used mouse microglial cells in culture activated by lipopolysaccharide (LPS) or α-synuclein amyloid aggregates (αSa) to study the anti-inflammatory effects of COL-3, a tetracycline derivative without antimicrobial activity. Under LPS or αSa stimulation, COL-3 (10, 20 µM) efficiently repressed the induction of the microglial activation marker protein Iba-1 and the stimulated-release of the pro-inflammatory cytokine TNF-α. COL-3′s inhibitory effects on TNF-α were reproduced by the tetracycline antibiotic doxycycline (DOX; 50 µM), the glucocorticoid dexamethasone, and apocynin (APO), an inhibitor of the superoxide-producing enzyme NADPH oxidase. This last observation suggested that COL-3 and DOX might also operate themselves by restraining oxidative stress-mediated signaling events. Quantitative measurement of intracellular reactive oxygen species (ROS) levels revealed that COL-3 and DOX were indeed as effective as APO in reducing oxidative stress and TNF-α release in activated microglia. ROS inhibition with COL-3 or DOX occurred together with a reduction of microglial glucose accumulation and NADPH synthesis. This suggested that COL-3 and DOX might reduce microglial oxidative burst activity by limiting the glucose-dependent synthesis of NADPH, the requisite substrate for NADPH oxidase. Coherent with this possibility, the glycolysis inhibitor 2-deoxy-D-glucose reproduced the immunosuppressive action of COL-3 and DOX in activated microglia. Overall, we propose that COL-3 and its parent compound DOX exert anti-inflammatory effects in microglial cells by inhibiting glucose-dependent ROS production. These effects might be strengthened by the intrinsic antioxidant properties of DOX and COL-3 in a self-reinforcing manner.

20(s)‑ginseonside‑Rg3 modulation of AMPK/FoxO3 signaling to attenuate mitochondrial dysfunction in a dexamethasone‑injured C2C12 myotube‑based model of skeletal atrophy in vitro

Muscle atrophy, a side effect from administration of the anti-inflammatory medication dexamethasone (DEX), is preventable by concomitant administration of the major monomeric constituent of Panax ginseng C.A. Meyer, 20(S)-ginsenoside Rg3 (S-Rg3). Putative S-Rg3-associated prevention of DEX-induced muscle atrophy may involve S-Rg3 mitigation of DEX-induced mitochondrial dysfunction. In the present study, MTT assays revealed enhanced cell viability following S-Rg3 treatment of DEX-injured C2C12 myotubes. Subsequent PCR and western blotting results demonstrated S-Rg3-induced reduction of expression of muscle atrophy F-box protein (atrogin-1) and muscle RING-finger protein-1, proteins previously linked to muscle atrophy. Additionally, S-Rg3 treatment of DEX-injured myotubes led to aggregation of Rg3 monomers in cells and dose-dependent increases in cellular mitochondrial basal respiratory oxygen consumption rate and intracellular ATP levels compared with their levels in untreated DEX-injured myotubes. In addition, S-Rg3 treatment significantly reversed DEX-induced reductions of expression of key mitochondrial respiratory electron transport chain subunits of protein complexes II, III and V in DEX-injured myotube cells. Furthermore, S-Rg3 alleviation of mitochondrial dysfunction associated with DEX-induced injury of C2C12 myotubes was linked to S-Rg3-associated decreases in both forkhead box O3 (FoxO3) protein expression and phosphorylation of AMP-activated protein kinase (AMPK). Collectively, these results implicate S-Rg3 modulation of signaling within the AMPK-FoxO3 pathway as a putative mechanism underlying S-Rg3 alleviation of DEX-induced muscle atrophy.

Cortisol rapidly stimulates calcium waves in the developing trunk muscle of zebrafish

Glucocorticoids (GCs) play a role in stress coping by activating the glucocorticoid receptor (GR), a ligand-bound transcription factor. GCs also exert rapid effects that are nongenomic by modulating second messenger signaling, including Ca²⁺. However, the mechanism of action of GCs in modulating cytoplasmic free calcium level ([Ca²⁺]i) is unclear. We hypothesized that cortisol increases ([Ca²⁺]i) in zebrafish (Danio rerio) muscle, and this is independent of GR activation. Indeed, cortisol rapidly stimulated ([Ca²⁺]i) rise in the developing trunk muscle (DTM), and this response was not abolished in the GR knockout zebrafish. The rapid cortisol-induced ([Ca²⁺]i) rise was reduced with EGTA, and completely abolished by the pharmacological inhibition of the calcium release-activated calcium channel (CRACC). Also, cortisol stimulation rapidly increased the expression of Orai1, the pore forming protein subunit of CRACC, in the DTM. Altogether, rapid nongenomic action of cortisol on muscle function may involve Ca²⁺ signaling by CRACC gating in zebrafish.

20(S)-ginsenoside Rg3 promotes myoblast differentiation and protects against myotube atrophy via regulation of the Akt/mTOR/FoxO3 pathway

We previously found that 20(S)-ginsenoside Rg3 (S-Rg3) promotes myoblast differentiation via an unknown mechanism. Here we measured levels of myosin heavy chain (MHC) and myogenin, markers of myoblast differentiation, using Western blot analysis and immunofluorescence staining. Notably, S-Rg3 treatment of C2C12 myoblasts led to increased muscle differentiation and protection from muscle atrophy in a dexamethasone (DEX)-treated C2C12 myotube-based muscle atrophy model. This effect was likely caused by S-Rg3 treatment-induced promotion of Akt/mTOR phosphorylation and inhibition of FoxO3 nuclear transcription. Additionally, S-Rg3 treatment also led to increased fruit fly climbing distances (Drosophila melanogaster) and prevented muscle atrophy in aged fruit flies. Our study provides a mechanistic framework for understanding how S-Rg3 enhances myoblast differentiation and inhibits myotube atrophy through activation of the Akt/mTOR/FoxO3 signaling pathway, as demonstrated in vitro in C2C12 cells and in vivo in fruit flies.

Early transcriptomic responses associated with the membrane-initiated action of cortisol in the skeletal muscle of rainbow trout (Oncorhynchus mykiss)

Cortisol is a critical neuroendocrine regulator of the stress response in fish. Cortisol practically affects all tissues by interacting with an intracellular receptor and modulating target gene expression. However, cortisol also interacts with components of the plasma membrane in a nongenomic process that activates rapid signaling. Until now, the implication of this novel cortisol signaling for the global transcriptional response has not been explored. In the present work, we evaluated the effects of the membrane-initiated actions of cortisol on the in vivo transcriptome of rainbow trout ( Oncorhynchus mykiss) skeletal muscle. RNA-Seq analyses were performed to examine the transcriptomic changes in rainbow trout stimulated by physiological concentrations of cortisol and cortisol coupled with bovine serum albumin (cortisol-BSA), a membrane-impermeable analog of cortisol. A total of 660 million paired-ends reads were generated. Reads mapped onto the reference genome revealed that 1,737; 897; and 1,012 transcripts were differentially expressed after 1, 3, and 9 h of cortisol-BSA treatment, respectively. Gene Ontology analysis showed that this novel action of cortisol modulates several biological processes, such as mRNA processing, ubiquitin-dependent protein catabolic processes, and transcription regulation. In addition, a KEGG analysis revealed that focal adhesion was the main signaling pathway that was upregulated at all the times tested. Taking these results together, we propose that the membrane-initiated cortisol action contributes significantly in the regulation of stress-mediated gene expression.

Panax ginseng Total Protein Facilitates Recovery from Dexamethasone-Induced Muscle Atrophy through the Activation of Glucose Consumption in C2C12 Myotubes

Background

The clinical anti-inflammatory drug dexamethasone (DEX) can cause many side effects such as muscle atrophy for long-term use. Muscle atrophy induced by DEX may be caused by decrease of glucose consumption. Panax ginseng C.A. Meyer was previously considered to be an antiatrophic agent for glucocorticoid- (GC-) treated therapies. As one of the main components, it remains unclear whether ginseng total protein (GP) facilitates recovery from muscle atrophy induced by DEX.

Methods

In this study, GP was extracted and purified with Sephadex-G50. C2C12 myoblasts was induced with 2% horse serum to differentiate into C2C12 myotubes. Cell viability was analyzed by the MTT assay, and Ca²⁺ concentration was analyzed by a flow cytometer. The release of lactic dehydrogenase (LDH) and the glucose consumption were analyzed by spectrophotometry. The phosphorylation of AMP-activated protein kinase (AMPK), phosphoinositide 3-kinase (PI3K), and protein kinase B (Akt) and the expression of glucose transporter 4 (GLUT4) were analyzed by Western blotting. The phosphorylation of AS160 was quantified by Immunofluorescence staining.

Results

We found that GP increased cell viability and increased myotube diameter in high-dose DEX-treated C2C12 myotubes for 24 h, but this activity was not found in the enzymatic hydrolyzed GP group. GP reduced muscle atrophy by decreasing the expression of key proteins such as muscle RING-finger protein-1 and muscle atrophy F-box, reducing the Ca²⁺ concentration, and decreasing the release of LDH in DEX-injured C2C12 myotubes. Moreover, GP improved glucose consumption and increased the phosphorylation of AMPK, PI3K, Akt, and AS160 and the expression of GLUT4 in DEX-treated C2C12 myotubes.

Conclusion

The results of this study suggest that GP has effects on recovering DEX-induced muscle atrophy and cell injury, which may improve glucose consumption via the AMPK and PI3K/Akt pathways in high-dose DEX-treated C2C12 myotubes. This study provides in vitro mechanistic insights into the recovery of muscle atrophy with GP treatment.

Nongenomic glucocorticoid effects and their mechanisms of action in vertebrates

Glucocorticoids (GC) act on multiple organ systems to regulate a variety of physiological processes in vertebrates. Due to their immunosuppressive and anti-inflammatory actions, glucocorticoids are an attractive target for pharmaceutical development. Accordingly, they are one of the most widely prescribed classes of therapeutics. Through the classical mechanism of steroid action, glucocorticoids are thought to mainly affect gene transcription, both in a stimulatory and suppressive fashion, regulating de novo protein synthesis that subsequently leads to the physiological response. However, over the past three decades multiple lines of evidence demonstrate that glucocorticoids may work through rapid, nonclassical mechanisms that do not require alterations in gene transcription or translation. This review assimilates evidence across the vertebrate taxa on the diversity of nongenomic actions of glucocorticoids and the membrane-associated cellular mechanisms that may underlie rapid glucocorticoid responses to include potential binding sites characterized to date.

Contribution of Non-canonical Cortisol Actions in the Early Modulation of Glucose Metabolism of Gilthead Sea Bream (Sparus aurata)

Teleost fish are exposed to diverse stressors in farming and wildlife conditions during their lifespan. Cortisol is the main glucocorticoid hormone involved in the regulation of their metabolic acclimation under physiological stressful conditions. In this context, increased plasma cortisol is associated with energy substrate mobilization from metabolic tissues, such as liver and skeletal muscle, to rapidly obtain energy and cope with stress. The metabolic actions of cortisol have primarily been attributed to its genomic/classic action mechanism involving the interaction with intracellular receptors, and regulation of stress-responsive genes. However, cortisol can also interact with membrane components to activate rapid signaling pathways. In this work, using the teleost fish gilthead sea bream (Sparus aurata) as a model, we evaluated the effects of membrane-initiated cortisol actions on the early modulation of glucose metabolism. For this purpose, S. aurata juveniles were intraperitoneally administrated with cortisol and with its membrane impermeable analog, cortisol-BSA. After 1 and 6 h of each treatment, plasma cortisol levels were measured, together with glucose, glycogen and lactate in plasma, liver and skeletal muscle. Transcript levels of corticosteroids receptors (gr1, gr2, and mr) and key gluconeogenesis (g6pc and pepck)- and glycolysis (pgam1 and aldo) related genes in the liver were also measured. Cortisol and cortisol-BSA administration increased plasma cortisol levels in S. aurata 1 h after administration. Plasma glucose levels enhanced 6 h after each treatment. Hepatic glycogen content decreased in the liver at 1 h of both cortisol and cortisol-BSA administration, while increased at 6 h due to cortisol but not in response to cortisol-BSA. Expression of gr1, g6pc, pgam1, and aldo were preferentially increased by cortisol-BSA in the liver. Taking all these results in consideration, we suggest that non-canonical cortisol mechanisms contribute to the regulation of the early glucose metabolism responses to stress in S. aurata.

Non-genomic Effects of Glucocorticoids: An Updated View

Glucocorticoid (GC) anti-inflammatory effects generally require a prolonged onset of action and involve genomic processes. Because of the rapidity of some of the GC effects, however, the concept that non-genomic actions may contribute to GC mechanisms of action has arisen. While the mechanisms have not been completely elucidated, the non-genomic effects may play a role in the management of inflammatory diseases. For instance, we recently reported that GCs 'rapidly' enhanced the effects of bronchodilators, agents used in the treatment of allergic asthma. In this review article, we discuss (i) the non-genomic effects of GCs on pathways relevant to the pathogenesis of inflammatory diseases and (ii) the putative role of the membrane GC receptor. Since GC side effects are often considered to be generated through its genomic actions, understanding GC non-genomic effects will help design GCs with a better therapeutic index.

Mechanisms for the species difference between mouse and pig oocytes in their sensitivity to glucorticoids

Although in vitro exposure to physiological concentrations of glucorticoids did not affect maturation of mouse oocytes, it significantly inhibited nuclear maturation of pig oocytes. Studies on this species difference in oocyte sensitivity to glucocorticoids will contribute to our understanding of how stress/glucocorticoids affect oocytes. We showed that glucorticoid receptors (NR3C1) were expressed in both oocytes and cumulus cells (CCs) of both pigs and mice; however, while cortisol inhibition of oocyte maturation was overcome by NR3C1 inhibitor RU486 in pigs, it could not be relieved by RU486 in mice. The mRNA level of 11β-hydroxysteroid dehydrogenase 1 (HSD11B1) was significantly higher than that of HSD11B2 in pig cumulus-oocyte complexes (COCs), whereas HSD11B2 was exclusively expressed in mouse COCs. Pig and mouse cumulus-denuded oocytes (DOs) expressed HSD11B2 predominantly and exclusively, respectively. In the presence of cortisol, although inhibiting HSD11B2 decreased maturation rates of COCs in both species, inhibiting HSD11B1 improved maturation of pig COCs while having no effect on mouse COCs. Cortisol-cortisone interconversion observation confirmed high HSD11B1 activities in pig oocytes but none in mouse oocytes, a higher HSD11B2 activity in mouse than in pig oocytes, and a rapid cortisol-cortisone interconversion in pig COCs catalyzed by HSD11B1 from CCs and HSD11B2 from DOs. In conclusion, the species difference in glucocorticoid sensitivity between pig and mouse oocytes is caused by their different contents/ratios of HSD11B1 and HSD11B2, which maintain different concentrations of active glucocorticoids. While cortisol inhibited pig oocytes by interacting with NR3C1, glucocorticoid suppression of mouse oocytes was apparently not mediated by NR3C1.

Corticosterone rapidly improves the endurance of high-intensity exercise (swimming) via nongenomic mechanisms in mice

BACKGROUND

Glucocorticoids (GCs) take a pivotal role during the stress response. Some clinical studies suggest short-term GCs intake improves exercise endurance. However, whether the rapid nongenomic effects of GCs are involved in acute exercise is still unknown. Here, we aimed to reveal the potential nongenomic effects of GCs in skeletal muscle of mice during exercise.

METHODS

Adrenalectomized mice subjected to a weight-loaded forced swim were used for detecting the changes of time to exhaustion. Corticosterone (CORT) and other drugs were injected via the coccygeal vein before swimming. After exhaustion, the injury of skeletal muscle, nitric oxide generation, blood glucose and lactic acid were determined.

RESULTS

The results demonstrated that CORT rapidly extended the time to exhaustion within 30 min (~30%), which could not be abolished by glucocorticoid receptor antagonist RU486. Pretreatment with the nitric oxide synthesis inhibitor L-NAME prior to CORT administration further increased exercise tolerance compared to the increase caused by CORT alone. Moreover, CORT contributed to protecting skeletal muscle from injury and maintaining blood glucose.

CONCLUSIONS

Considered together, our results suggest that GCs rapidly improve exercise tolerance via its nongenomic mechanism, which is associated with the inhibition of nitric oxide generation. Pretreatment of GCs may be helpful to enhance exercise tolerance during acute exercise.

Insulin resistance enhances the mitogen-activated protein kinase signaling pathway in ovarian granulosa cells

The ovary is the main regulator of female fertility. Granulosa cell dysfunction may be involved in various reproductive endocrine disorders. Here we investigated the effect of insulin resistance on the metabolism and function of ovarian granulosa cells, and dissected the functional status of the mitogen-activated protein kinase signaling pathway in these cells. Our data showed that dexamethasone-induced insulin resistance in mouse granulosa cells reduced insulin sensitivity, accompanied with an increase in phosphorylation of p44/42 mitogen-activated protein kinase. Furthermore, up-regulation of cytochrome P450 subfamily 17 and testosterone and down-regulation of progesterone were observed in insulin-resistant mouse granulosa cells. Inhibition of p44/42 mitogen-activated protein kinase after induction of insulin resistance in mouse granulosa cells decreased phosphorylation of p44/42 mitogen-activated protein kinase, downregulated cytochrome P450 subfamily 17 and lowered progesterone production. This insulin resistance cell model can successfully demonstrate certain mechanisms such as hyperandrogenism, which may inspire a new strategy for treating reproductive endocrine disorders by regulating cell signaling pathways.

Electrical pulse stimulation of cultured skeletal muscle cells as a model for in vitro exercise - possibilities and limitations

The beneficial health-related effects of exercise are well recognized, and numerous studies have investigated underlying mechanism using various in vivo and in vitro models. Although electrical pulse stimulation (EPS) for the induction of muscle contraction has been used for quite some time, its application on cultured skeletal muscle cells of animal or human origin as a model of in vitro exercise is a more recent development. In this review, we compare in vivo exercise and in vitro EPS with regard to effects on signalling, expression level and metabolism. We provide a comprehensive overview of different EPS protocols and their applications, discuss technical aspects of this model including critical controls and the importance of a proper maintenance procedure and finally discuss the limitations of the EPS model.