Inhibition of ischemia/reperfusion-induced damage by dexamethasone in isolated working rat hearts: the role of cytochrome c release

Prolonged exposure to the synthetic glucocorticoid dexamethasone induces brain damage via oxidative stress and apoptotic response in adult Daniorerio

Due to its extensive use as a painkiller, anti-inflammatory, and immune modulatory agent, as well as its effectiveness in treating severe COVID-19, dexamethasone, a synthetic glucocorticoid, has gained attention not only for its impact on public health but also for its environmental implications. Various studies have reported its presence in aquatic environments, including urban waters, surface samples, sediments, drinking water, and wastewater effluents. However, limited information is available regarding its toxic effects on nontarget aquatic organisms. Therefore, this study aimed to investigate the mechanism of toxicity underlying dexamethasone-induced brain damage in the bioindicator Danio rerio following long-term exposure. Adult zebrafish were treated with environmentally relevant concentrations of dexamethasone (20, 40, and 60 ng L-1) for 28 days. To elucidate the possible mechanisms involved in the toxicity of the pharmaceutical compound, we conducted a behavioral test battery (Novel Tank and Light and Dark tests), oxidative stress biomarkers, acetylcholinesterase enzyme activity quantification, histopathological analysis, and gene expression analysis using qRT-PCR (p53, bcl-2, bax, caspase-3, nrf1, and nrf2).The results revealed that the pharmaceutical compound could produce anxiety-like symptoms, increase the oxidative-induced stress response, decrease the activity of acetylcholinesterase enzyme, and cause histopathological alterations, including perineuronal vacuolization, granular and molecular layers deterioration, cell swallowing and intracellular spaces. The expression of genes involved in the apoptotic process (p53, bax, and casp-3) and antioxidant defense (nrf1 and nrf2) was upregulated in response to oxidative damage, while the expression of the anti-apoptotic gene bcl-2 was down-regulated indicating that the environmental presence of dexamethasone may pose a threat to wildlife and human health.

COX5A Alleviates Doxorubicin-Induced Cardiotoxicity by Suppressing Oxidative Stress, Mitochondrial Dysfunction and Cardiomyocyte Apoptosis

Doxorubicin (DOX) as a chemotherapeutic agent can cause mitochondrial dysfunction and heart failure. COX5A has been described as an important regulator of mitochondrial energy metabolism. We investigate the roles of COX5A in DOX-induced cardiomyopathy and explore the underlying mechanisms. C57BL/6J mice and H9c2 cardiomyoblasts were treated with DOX, and the COX5A expression was assessed. An adeno-associated virus serum type 9 (AAV9) and lenti-virus system were used to upregulate COX5A expression. Echocardiographic parameters, morphological and histological analyses, transmission electron microscope and immunofluorescence assays were used to assess cardiac and mitochondrial function. In a human study, we found that cardiac COX5A expression was dramatically decreased in patients with end-stage dilated cardiomyopathy (DCM) compared to the control group. COX5A was significantly downregulated following DOX stimulation in the heart of mice and H9c2 cells. Reduced cardiac function, decreased myocardium glucose uptake, mitochondrial morphology disturbance, reduced activity of mitochondrial cytochrome c oxidase (COX) and lowered ATP content were detected after DOX stimulation in mice, which could be significantly improved by overexpression of COX5A. Overexpression of COX5A effectively protected against DOX-induced oxidative stress, mitochondrial dysfunction and cardiomyocyte apoptosis in vivo and in vitro. Mechanistically, the phosphorylation of Akt (Thr308) and Akt (Ser473) were also decreased following DOX treatment, which could be reserved by the upregulation of COX5A. Furthermore, PI3K inhibitors abrogated the protection effects of COX5A against DOX-induced cardiotoxicity in H9c2 cells. Thus, we identified that PI3K/Akt signaling was responsible for the COX5A-mediated protective role in DOX-induced cardiomyopathy. These results demonstrated the protective effect of COX5A in mitochondrial dysfunction, oxidative stress, and cardiomyocyte apoptosis, providing a potential therapeutic target in DOX-induced cardiomyopathy.

Gestational Hypoxia and Developmental Plasticity

Hypoxia is one of the most common and severe challenges to the maintenance of homeostasis. Oxygen sensing is a property of all tissues, and the response to hypoxia is multidimensional involving complicated intracellular networks concerned with the transduction of hypoxia-induced responses. Of all the stresses to which the fetus and newborn infant are subjected, perhaps the most important and clinically relevant is that of hypoxia. Hypoxia during gestation impacts both the mother and fetal development through interactions with an individual's genetic traits acquired over multiple generations by natural selection and changes in gene expression patterns by altering the epigenetic code. Changes in the epigenome determine "genomic plasticity," i.e., the ability of genes to be differentially expressed according to environmental cues. The genomic plasticity defined by epigenomic mechanisms including DNA methylation, histone modifications, and noncoding RNAs during development is the mechanistic substrate for phenotypic programming that determines physiological response and risk for healthy or deleterious outcomes. This review explores the impact of gestational hypoxia on maternal health and fetal development, and epigenetic mechanisms of developmental plasticity with emphasis on the uteroplacental circulation, heart development, cerebral circulation, pulmonary development, and the hypothalamic-pituitary-adrenal axis and adipose tissue. The complex molecular and epigenetic interactions that may impact an individual's physiology and developmental programming of health and disease later in life are discussed.

Bone marrow and adipose mesenchymal stem cells attenuate cardiac fibrosis induced by methotrexate in rats

Mesenchymal stem cells (MSCs) are an ideal adult stem cell with capacity for self-renewal and differentiation with an extensive tissue distribution. The present study evaluates the therapeutic effects of bone marrow mesenchymal stem cells (BM-MSCs) or adipose-derived mesenchymal stem cells (AD-MSCs) against the development of methotrexate (MTX)-induced cardiac fibrosis versus dexamethasone (DEX). Rats were allocated into five groups; group 1, received normal saline orally; group 2, received MTX (14 mg/kg/week for 2 weeks); groups 3 and 4, treated once with 2 × 10⁶ cells of MTX + BM-MSCs and MTX + AD-MSCs, respectively; and group 5, MTX + DEX (0.5 mg/kg, for 7 days, P.O.). MTX induced cardiac fibrosis as marked changes in oxidative biomarkers and elevation of triglyceride, cholesterol, aspartate aminotransferase, gamma-glutamyl transferase, creatine kinase, and caspase-3, as well as deposited collagen. These injurious effects were antagonized after treatment with MSCs. So, MSCs possessed antioxidant, antiapoptotic, as well antifibrotic effects, which will perhaps initiate them as notable prospective for the treatment of cardiac fibrosis.

Effect of Glucocorticoids on Ultrastructure of Myocardial Muscle in the Course of Experimentally Induced Acute Myocardial Ischemia

The search for effective methods of myocardial cytoprotection against ischemia is the most significant issue in modern cardiology and cardiac surgery. Glucocorticoids are deemed very strong modulators of inflammatory response and thus can potentially protect heart muscle from postreperfusion injury and myocardial ischemia during cardiac surgery. Ultrastructural examination of the left ventricle heart samples revealed that the intravenous application of dexamethasone and hydrocortisone proved to exert cytoprotective effect on cardiomyocytes during experimentally induced acute ischemia in rats.

Changes in Energy Levels by Dexamethasone in Ischemic Hearts and Brains in Male Mice

BACKGROUND

Glucocorticoids have been shown to alleviate ischemia-induced myocardial injury, while aggravating neuronal damage caused by ischemia. As energy failure is a predominant factor in cellular viability, we examined the effects of glucocorticoids on energy utilization in the mouse heart and brain.

METHODS

Seventy-two male ddY mice were assigned to 1 of 3 groups: saline (S), dexamethasone (a glucocorticoid without mineralocorticoid activity, 5 mg/kg) (D), and metyrapone (a potent inhibitor of the synthesis of glucocorticoids, 100 mg/kg) (M) groups (n=24 in each). Three hours after intraperitoneal administration, all animals were decapitated, and the heads were frozen in liquid nitrogen after 0, 0.5, 1, or 2 minutes (n=6 in each). The hearts were immediately removed and frozen in liquid nitrogen after 0, 5, 10, or 20 minutes of incubation at 37°C (n=6 in each). The concentrations of adenylates and monoamines were determined by high-performance liquid chromatography.

RESULTS

In the heart, the adenosine 5'-triphosphate (ATP) concentration did not differ among the 3 groups at 0 minute of ischemia (3 h of S, D, or M treatment). Ischemia for 5 minutes decreased the ATP content to 21% of the basal level in the S group. The ATP decrease was suppressed by either the D or M treatment, such that after 5 minutes ATP levels were 63% and 64% of each basal level, respectively. In the brain, the ATP level in the M group was 62% of that in the S group at 0 minute of ischemia, and the 5'-monophosphate (AMP) level was 276% of that in the S group. Brain dopamine metabolism was facilitated by dexamethasone, and suppressed by metyrapone.

CONCLUSIONS

The relationship between effects of glucocorticoids on ischemia-induced changes in energy levels and cellular viability was not clearly elucidated.

Antenatal hypoxia induces epigenetic repression of glucocorticoid receptor and promotes ischemic-sensitive phenotype in the developing heart

Large studies in humans and animals have demonstrated a clear association of an adverse intrauterine environment with an increased risk of cardiovascular disease later in life. Yet mechanisms remain largely elusive. The present study tested the hypothesis that gestational hypoxia leads to promoter hypermethylation and epigenetic repression of the glucocorticoid receptor (GR) gene in the developing heart, resulting in increased heart susceptibility to ischemia and reperfusion injury in offspring. Hypoxic treatment of pregnant rats from day 15 to 21 of gestation resulted in a significant decrease of GR exon 14, 15, 16, and 17 transcripts, leading to down-regulation of GR mRNA and protein in the fetal heart. Functional cAMP-response elements (CREs) at -4408 and -3896 and Sp1 binding sites at -3425 and -3034 were identified at GR untranslated exon 1 promoters. Hypoxia significantly increased CpG methylation at the CREs and Sp1 binding sites and decreased transcription factor binding to GR exon 1 promoter, accounting for the repression of the GR gene in the developing heart. Of importance, treatment of newborn pups with 5-aza-2'-deoxycytidine reversed hypoxia-induced promoter methylation, restored GR expression and prevented hypoxia-mediated increase in ischemia and reperfusion injury of the heart in offspring. The findings demonstrate a novel mechanism of epigenetic repression of the GR gene in fetal stress-mediated programming of ischemic-sensitive phenotype in the heart.

Cardiovascular effects of low versus high-dose beta-carotene in a rat model

β-carotene (BC), a lipid-soluble tetraterpene precursor to vitamin A, widely distributed in plants, including many used in human diet, has well-known health-enhancing properties, including reducing risk of and treatment for certain diseases. Nevertheless, BC may also act to promote disease through the activity of BC derivatives that form in the presence of external toxicants such as cigarette smoke and endogenously-produced reactive oxygen species. The present investigation evaluates the dose-dependent cardioprotective and possibly harmful properties of BC in a rat model. Adult male rats were gavage-fed BC for 4 weeks, at dosages of either 0, 30 or 150 mg/kg/day. Then, hearts excised from the animals were mounted in a "working heart" apparatus and subjected to 30 min of global ischemia, followed by 120 min of reperfusion. A panel of cardiac functional evaluations was conducted on each heart. Infarct size and total antioxidant capacity of the myocardium were assessed. Heart tissue content of heme oxygenase-1 (HO-1) by Western blot analysis; and potential direct cytotoxic effects of BC by MTT assay were evaluated. Hearts taken from rats receiving 30 mg/kg/day BC exhibited significantly improved heart function at lower reperfusion times, but lost this protection at higher BC dosage and longer reperfusion times. Myocardial HO-1 content was significantly elevated dose-responsively to both BC dosage. Finally, in vitro evaluation of BC on H9c2 cells showed that the agent significantly improved vitality of these cells in a dose range of 2.5-10 μM. Although data presented here do not allow for a comprehensive mechanistic explanation for reduced cardioprotection at high dose BC, it is speculated that since Fe2+ produced as a metabolite of HO-1 activity, may determine whether BC acts as an antioxidant or prooxidant agent, the strong induction of this enzyme in response to ischemia/reperfusion-induced oxidative stress may account for the high-dose BC loss of cardioprotection.

Glucocorticoids as an emerging pharmacologic agent for cardiopulmonary resuscitation

Although cardiac arrest (CA) constitutes a major health problem with dismal prognosis, no specific drug therapy has been shown to improve survival to hospital discharge. CA causes adrenal insufficiency which is associated with poor outcome and increased mortality. Adrenal insufficiency may manifest as an inability to increase cortisol secretion during and after cardiopulmonary resuscitation (CPR). Several studies suggest that glucocorticoids during and after CPR seem to confer benefits with respect to return of spontaneous circulation (ROSC) rates and long term survival. They have beneficial hemodynamic effects that may favor their use during CPR and in the early post-resuscitation period. Moreover, they have anti-inflammatory and anti-apoptotic properties that improve organ function by reducing ischemia/reperfusion (I/R) injury. However, glucocorticoid supplementation has shown conflicting results with regard to survival to hospital discharge and neurological outcome. The purpose of this article is to review the pathophysiology of hypothalamic-pituitary-adrenal (HPA) axis during CPR. Furthermore, this article reviews the effects of glucocorticoids use during CRP and the post-resuscitation phase.

Glucocorticoid modulates angiotensin II receptor expression patterns and protects the heart from ischemia and reperfusion injury

Glucocorticoid regulates angiotensin II receptor (ATR) expression via activating glucocorticoid receptors and binding to glucocorticoid response elements. The regulation of ATR by glucocorticoids in the context of myocardial injury from ischemia/reperfusion (I/R) is yet to be elucidated. The present study determined the role of ATR in glucocorticoid-induced cardiac protection. Adult male rats were administered once a day i.p. 1 mg/kg/day dexamethasone or dexamethasone plus 10 mg/kg/day RU486 for 5 days. Hearts were then isolated and subjected to I/R injury in a Langendorff preparation. Dexamethasone treatment significantly decreased I/R injury and improved post-ischemic recovery of cardiac function. Dexamethasone increased glucocorticoid receptor binding to glucocorticoid response elements at AT_1aR and AT₂R promoters, resulting in a significant increase in expression of AT₁R protein but a decrease in AT₂R expression in the heart. In addition, dexamethasone treatment significantly increased PKCε expression and p-PKCε protein abundance. These dexamethasone-mediated effects were blocked by RU486. More importantly, blockade of AT₁R and AT₂R with losartan and PD123319 abrogated dexamethasone-induced protection of the heart from I/R injury. The results indicate that glucocorticoid promotes a cardioprotective phenotype associated with the upregulation of AT₁R and PKCε and downregulation of AT₂R in the heart.

Glucocorticoids Activate Cardiac Mineralocorticoid Receptors During Experimental Myocardial Infarction

Myocardial ischemia-reperfusion leads to significant changes in redox state, decreased postischemic functional recovery, and cardiomyocyte apoptosis, with development and progression of heart failure. Ischemia-reperfusion in the isolated perfused rat heart has been used as a model of heart failure. Clinically, mineralocorticoid receptor blockade in heart failure decreases morbidity and mortality versus standard care alone. The effects of corticosteroids on infarct area and apoptosis were determined in rat hearts subjected to 30 minutes of ischemia and 2.5 hours of reperfusion. Both aldosterone and cortisol increased infarct area and apoptotic index, an effect half-maximal between 1 and 10 nM and reversed by spironolactone. Dexamethasone and mifepristone aggravated infarct area and apoptotic index, similarly reversed by spironolactone. Spironolactone alone reduced infarct area and apoptotic index below ischemia-reperfusion alone, in hearts from both intact and adrenalectomized rats. The present study shows that cardiac damage is aggravated by activation of mineralocorticoid receptors by aldosterone or cortisol or of glucocorticoid receptors by dexamethasone. Mifepristone unexpectedly acted as a glucocorticoid receptor agonist, for which there are several precedents. Spironolactone protected cardiomyocytes via inverse agonist activity at mineralocorticoid receptors, an effect near maximal at a relatively low dose (10 nM). Spironolactone acts not merely by excluding corticosteroids from mineralocorticoid receptors but as a protective inverse agonist at low concentration. Mineralocorticoid receptor antagonists may, thus, provide an additional therapeutic advantage in unstable angina and acute myocardial infarction.

Glucocorticoid protects rodent hearts from ischemia/reperfusion injury by activating lipocalin-type prostaglandin D synthase-derived PGD2 biosynthesis

Lipocalin-type prostaglandin D synthase (L-PGDS), which was originally identified as an enzyme responsible for PGD2 biosynthesis in the brain, is highly expressed in the myocardium, including in cardiomyocytes. However, the factors that control expression of the gene encoding L-PGDS and the pathophysiologic role of L-PGDS in cardiomyocytes are poorly understood. In the present study, we demonstrate that glucocorticoids, which act as repressors of prostaglandin biosynthesis in most cell types, upregulated the expression of L-PGDS together with cytosolic calcium-dependent phospholipase A2 and COX2 via the glucocorticoid receptor (GR) in rat cardiomyocytes. Accordingly, PGD2 was the most prominently induced prostaglandin in vivo in mouse hearts and in vitro in cultured rat cardiomyocytes after exposure to GR-selective agonists. In isolated Langendorff-perfused mouse hearts, dexamethasone alleviated ischemia/reperfusion injury. This cardioprotective effect was completely abrogated by either pharmacologic inhibition of COX2 or disruption of the gene encoding L-PGDS. In in vivo ischemia/reperfusion experiments, dexamethasone reduced infarct size in wild-type mice. This cardioprotective effect of dexamethasone was markedly reduced in L-PGDS-deficient mice. In cultured rat cardiomyocytes, PGD2 protected against cell death induced by anoxia/reoxygenation via the D-type prostanoid receptor and the ERK1/2-mediated pathway. Taken together, these results suggest what we believe to be a novel interaction between glucocorticoid-GR signaling and the cardiomyocyte survival pathway mediated by the arachidonic acid cascade.

Dexamethasone-induced cardioprotection: a role for the phosphatase MKP-1?

AIMS

Previous studies suggested that p38 MAPK activation during sustained myocardial ischaemia and reperfusion was harmful. We hypothesize that attenuation of p38MAPK activity via dephosphorylation by the dual-specificity phosphatase MKP-1 should be protective against ischaemia/reperfusion injury. Since the glucocorticoid, dexamethasone, induces the expression of MKP-1, the aim of this study was to determine whether upregulation of this phosphatase by dexamethasone protects the heart against ischaemia/reperfusion injury.

MAIN METHODS

Male Wistar rats were treated with dexamethasone (3 mg/kg/day ip) for 10 days, before removal of the hearts for Western blot (ip Dex-P) or perfusion in the working mode (ip Dex+P). Hearts were subjected to 20 min global or 35 min regional ischaemia (36.5 degrees C) and 30 or 120 min reperfusion. In a separate series, dexamethasone (1 microM) was added to the perfusate for 10 min (Pre+Dex) before or after (Rep+Dex) ischaemia.

KEY FINDINGS

Dexamethasone, administered intraperitoneally or added directly to the perfusate, significantly improved post-ischaemic functional recovery and reduced infarct size compared to untreated controls (p<0.05). These were associated with enhanced up-regulation of MKP-1 protein expression (arbitrary units (mean+/-SD): Untreated: 1; ip Dex-P: 2.59+/-0.22; ip Dex+P: 1.51+/-0.22; Pre+Dex: 4.11+/-0.73, Rep+15'Dex: 1.51+/-0.14; untreated vs. all groups, p<0.05) and attenuation of p38 MAPK activation (p<0.05) in all dexamethasone-treated groups, except for Rep+10'Dex. ERK and PKB/Akt activation were unchanged.

SIGNIFICANCE

Dexamethasone-induced cardioprotection was associated with upregulation of the phosphatase MKP-1 and inactivation of pro-apoptotic p38 MAPK.

Acetaminophen-mediated cardioprotection via inhibition of the mitochondrial permeability transition pore-induced apoptotic pathway

Our laboratory has previously reported that acetaminophen confers functional cardioprotection following cardiac insult, including ischemia/reperfusion, hypoxia/reoxygenation, and exogenous peroxynitrite administration. In the present study, we further examined the mechanism of acetaminophen-mediated cardioprotection following ischemia/reperfusion injury. Langendorff-perfused guinea pig hearts were exposed to acute treatment with acetaminophen (0.35 mM) or vehicle beginning at 15 min of a 30-min baseline stabilization period. Low-flow global myocardial ischemia was subsequently induced for 30 min followed by 60 min of reperfusion. At the completion of reperfusion, hearts were homogenized and separated into cytosolic and mitochondrial fractions. Mitochondrial swelling and mitochondrial cytochromec release were assessed and found to be significantly and completely reduced in acetaminophen- vs. vehicle-treated hearts following reperfusion. In a separate group of hearts, ventricular myocytes were isolated and subjected to fluorescence-activated cell sorting. Acetaminophen-treated hearts showed a significant decrease in late stage apoptotic myocytes compared with vehicle-treated hearts following injury (58 +/- 1 vs. 81 +/- 5%, respectively). These data, together with electron micrograph analysis, suggest that acetaminophen mediates cardioprotection, in part, via inhibition of the mitochondrial permeability transition pore and subsequent apoptotic pathway.

Improvement of chronic heart failure by dexamethasone is not associated with downregulation of leptin in rats

AIM

To demonstrate the hypothesis that dexamethasone (Dex) could improve chronic heart failure (CHF) by inhibiting the downstream signaling transduction of leptin but had no influence on the upregulation of leptin and its receptor in myocardium.

METHODS

CHF was induced by left coronary artery ligation for 6 weeks. CHF rats were treated with Dex 50 mg.kg/d. Hemodynamics, histology, reactive oxygen species (ROS)-related parameters, and leptin concentrations in serum were measured. The mRNA expression of matrix metalloproteinases (MMP)2/9, tissue inhibitor of metalloproteinases (TIMP)1/2, tumor necrosis factor (TNF)-alpha, and OB-Rb were measured by RT-PCR.

RESULTS

In the CHF rats, hemodynamic functions were deteriorated, which was accompanied with myocardium remodeling and histological changes. CHF rats showed hyperleptinemia and excessive ROS in the serum, and the upregulation of MMP-2/9, TNF-alpha, and leptin receptor mRNA and downregulation of TIMP-1/2 mRNA in the myocardium compared with the sham operation group. Dex treatment significantly ameliorated CHF in association with the reversion of the abnormalities of MMP-2/9, TIMP-1/2, TNF-alpha, and ROS. But Dex had no influence on the hyperleptinemia and the upregulated leptin and its receptor in the myocardium during CHF.

CONCLUSION

Dex improves CHF by inhibiting TNF-alpha, MMP-2, MMP-9, and ROS. Dex had no effects on upregulated leptin and its receptor expression and hyperleptinemia induced by CHF.

Effect of dexamethasone on germ cell apoptosis in the contralateral testis after testicular ischemia-reperfusion injury in the rat

OBJECTIVE

To evaluate the effect of dexamethasone on spermatogenesis and germ cell apoptosis in the ipsilateral and contralateral testis after testicular ischemia-reperfusion (IR) in rats.

DESIGN

Laboratory study.

SETTING

Medical research laboratory in a university setting.

ANIMAL(S)

Forty adult Sprague-Dawley rats weighing 250-280 g.

INTERVENTION(S)

Testicular IR, treatment with dexamethasone (10 mg per kilogram of body weight).

MAIN OUTCOME MEASURE(S)

Testicular germ cell apoptosis was assessed by deoxyuridine nick-end labeling immunohistochemical assay.

RESULT(S)

Testicular ischemia in rats led to histological damage in the ipsilateral testis. In the contralateral testis, minimal damage was observed. Germ cell apoptosis in both the ischemic and the contralateral testis increased significantly after IR. Treatment with dexamethasone did not change germ cell apoptosis in ischemic testis but decreased germ cell apoptosis in the contralateral testis.

CONCLUSION(S)

Glucocorticoids may be beneficial for spermatogenesis after testicular IR by decreasing germ cell apoptosis in the contralateral testis.