NOX-dependent reactive oxygen species production underlies arrhythmias susceptibility in dexamethasone-treated rats

NADPH Oxidases: From Molecular Mechanisms to Current Inhibitors

NADPH oxidases (NOXs) form a family of electron-transporting membrane enzymes whose main function is reactive oxygen species (ROS) generation. Strong evidence suggests that ROS produced by NOX enzymes are major contributors to oxidative damage under pathologic conditions. Therefore, blocking the undesirable actions of these enzymes is a therapeutic strategy for treating various pathological disorders, such as cardiovascular diseases, inflammation, and cancer. To date, identification of selective NOX inhibitors is quite challenging, precluding a pharmacologic demonstration of NOX as therapeutic targets in vivo. The aim of this Perspective is to furnish an updated outlook about the small-molecule NOX inhibitors described over the last two decades. Structures, activities, and in vitro/in vivo specificity are discussed, as well as the main biological assays used.

Dexamethasone-Induced Arterial Stiffening Is Attenuated by Training due to a Better Balance Between Aortic Collagen and Elastin Levels

PURPOSE

Although the cardioprotective benefits of exercise training are well known, the effects of training on dexamethasone (DEX)-induced arterial stiffness are still unclear. This study was aimed at investigating the mechanisms induced by training to prevent DEX-induced arterial stiffness.

METHODS

Wistar rats were allocated into 4 groups and submitted to combined training (aerobic and resistance exercises, on alternate days, 60% of maximal capacity, for 74 d) or were kept sedentary: sedentary control rats (SC), DEX-treated sedentary rats (DS), combined training control (CT), and DEX-treated trained rats (DT). During the last 14 d, rats were treated with DEX (50 μg/kg per body weight, per day, s.c.) or saline.

RESULTS

DEX increased PWV (+44% vs +5% m/s, for DS vs SC, p<0.001) and increased aortic COL 3 protein level (+75%) in DS. In addition, PWV was correlated with COL3 levels (r=0.682, p<0.0001). Aortic elastin and COL1 protein levels remained unchanged. On the other hand, the trained and treated groups showed lower PWV values (-27% m/s, p<0.001) vs DS and lower values of aortic and femoral COL3 compared with DS.

CONCLUSION

As DEX is widely used in several situations, the clinical relevance of this study is that the maintenance of good physical capacity throughout life can be crucial to alleviate some of its side effects, such as arterial stiffness.

Apitherapy combination improvement of blood pressure, cardiovascular protection, and antioxidant and anti-inflammatory responses in dexamethasone model hypertensive rats

Hypertension-induced ventricular and vascular remodeling causes myocardial infarction, heart failure, and sudden death. Most available pharmaceutical products used to treat hypertension lead to adverse effects on human health. Limited data is available on apitherapy (bee products) combinations for treatment of hypertension. This study aims to evaluate the antihypertensive effects of combinations of natural apitherapy compounds used in the medical sector to treat a variety of diseases. Rats were assigned into six groups consisting of one control group and five hypertensive groups where hypertension (blood pressure > 140/90) was induced with dexamethasone. One of these groups was used as a hypertension model, while the remaining four hypertensive groups were treated with a propolis, royal jelly, and bee venom combination (PRV) at daily oral doses of 0.5, 1.0, and 2.0 mg/kg, and with losartan 10 mg/kg. The PRV combination at all doses decreased arterial blood pressure below the suboptimal value (p < 0.001), and PRV combination treatment improved dexamethasone-induced-ECG changes. The same treatment decreased angiotensin-II, endothelin-1, and tumor growth factor β serum levels in hypertensive rats. Additionally, PRV combination improved histopathological structure, and decreased serum levels of NF-kB and oxidative stress biomarkers. We concluded that PRV combination therapy may be used as a potential treatment for a variety of cardiovascular diseases.

Gongronema latifolium leaf extract protects against dexamethasone-induced myocardial cell injury via cardiac oxido-inflammatory molecules modulation

The use of glucocorticoids in the treatment of inflammatory disorders can result in myocardial injury. This study was carried out to investigate the protective effects of ethanolic leaf extract of Gongronema latifolium (GL) in dexamethasone (DEX)-induced myocardial injury. Wistar rats were assigned to 4 groups (n = 6) namely, control, GL, DEX, and DEX+GL groups. DEX (35 μg/kg body weight) was administered subcutaneously to induce myocardial injury, while GL leaf extract (200 mg/kg body weight) was administered orally. Both agents were administered to their respective groups for 14 days. DEX (p < .05) decreased nitric oxide and increased angiotensin-converting enzyme activity compared with the control. Serum superoxide dismutase activity and bilirubin level were decreased (p < .05), while malondialdehyde level was increased (p < .05) in the DEX group. Serum liver enzymes, inflammatory biomarkers (C-reactive protein and interleukin-6), and cardiac injury biomarkers (creatinine kinase, cardiac troponin-T, and lactate dehydrogenase) were significantly (p < .05) increased in the DEX group relative to the control. Administration of GL leaf extract attenuated these changes significantly. The study therefore suggests that GL is beneficial in the treatment of myocardial injury via the downregulation of high serum concentration of cardiac biomarkers, oxidative stress markers, and inflammatory biomarkers released as a result of the insult caused by glucocorticoid administration. PRACTICAL APPLICATIONS: In this study, we demonstrated that prolonged use of dexamethasone resulted in myocardial cell injury via increased production of reactive oxygen species, inflammatory biomarkers, and inhibition of nitric oxide, a potent vasodilator. The leaves extract of Gongronema latifolium elicits the anti-inflammatory and cardioprotective potential as an efficient inhibitor of free radicals with good antioxidant properties. The study provides scientific evidence of the therapeutic ability of the extract of G. latifolium in the treatment of DEX-induced myocardial injury and could be a drug candidate for the treatment of myocardial injury and inflammation in humans.

Advances in the study of nicotinamide adenine dinucleotide phosphate oxidase in myocardial remodeling

Myocardial remodeling is a key pathophysiological basis of heart failure, which seriously threatens human health and causes a severe economic burden worldwide. During chronic stress, the heart undergoes myocardial remodeling, mainly manifested by cardiomyocyte hypertrophy, apoptosis, interstitial fibrosis, chamber enlargement, and cardiac dysfunction. The NADPH oxidase family (NOXs) are multisubunit transmembrane enzyme complexes involved in the generation of redox signals. Studies have shown that NOXs are highly expressed in the heart and are involved in the pathological development process of myocardial remodeling, which influences the development of heart failure. This review summarizes the progress of research on the pathophysiological processes related to the regulation of myocardial remodeling by NOXs, suggesting that NOXs-dependent regulatory mechanisms of myocardial remodeling are promising new therapeutic targets for the treatment of heart failure.

Benefits of combined exercise training on arterial stiffness and blood pressure in spontaneously hypertensive rats treated or not with dexamethasone

Dexamethasone (DEX)-induced arterial stiffness is an important side-effect, associated with hypertension and future cardiovascular events, which can be counteracted by exercise training. The aim of this study was to evaluate the mechanisms induced by combined training to attenuate arterial stiffness and hypertension in spontaneously hypertensive rats treated or not with dexamethasone. Spontaneously hypertensive rats (SHR) underwent combined training for 74 days and were treated with dexamethasone (50 µg/kg s. c.) or saline solution during the last 14 days. Wistar rats were used as controls. Echocardiographic parameters, blood pressure (BP) and pulse wave velocity (PWV), as well as histological analyses of the heart and aorta, carotid and femoral arteries were performed. At the beginning, SHR had higher BP and PWV compared with Wistar rats. After 60 days, while BP increased in sedentary SHR, combined exercise training decreased BP and PWV. After 74d, the higher BP and PWV of sedentary SHR was accompanied by autonomic imbalance to the heart, cardiac remodeling, and higher arterial collagen deposition. DEX treatment did not change these parameters. On the other hand, trained SHR had reduced BP and PWV, which was associated with better autonomic balance to the heart, reduced myocardial collagen deposition, as well as lower arterial collagen deposition. The results of this study suggest that combined training, through the reduction of aortic collagen deposition, is an important strategy to reduce arterial stiffness in spontaneously hypertensive rats, and these lower responses were maintained regardless of dexamethasone treatment.

Altered hippocampal GR/KCC2 signaling mediates susceptibility to convulsion in male offspring following dexamethasone exposure during pregnancy in rats

Epidemiological research suggests that convulsions may have an intrauterine developmental origin related to the application of dexamethasone, an artificially synthesized glucocorticoid. Here, using a rat animal model of prenatal dexamethasone exposure (PDE) we confirm that PDE can cause susceptibility to convulsions in male offspring and explore the epigenetic programming mechanism underlying this effect related to intrauterine type 2K⁺-Cl^- cotransporter (KCC2). Wistar rats were injected with dexamethasone (0.2mg/kg/d) subcutaneously during the gestational days (GD) 9-20 and part of the offspring was given lithium pilocarpine (LiPC) at postnatal week 10. Our results showed that male offspring of the PDE+LiPC group exhibited convulsions susceptibility, as well as increased hippocampal gamma-aminobutyric acid (GABA) and intracellular chloride ions level and decreased GABA receptor expression. The offspring also showed a decrease of hippocampal KCC2 H3K14ac levels and KCC2 expression. PDE male fetal rats (GD20) showed similar changes to male offspring after birth and exhibited an increased expression of glucocorticoid receptor (GR) and histone deacetylase type 2 (HDAC2). We observed effects consistent with those observed in PDE fetal rats following in vitro dexamethasone treatment of the fetal rat hippocampal neuron H19-7 cell line, and the effects could be reversed by treatment with a GR inhibitor (RU486) or HDAC2 inhibitor (romidepsin). Taken together, this study confirmed that PDE causes a reduction of H3K14ac levels in the KCC2 promoter region caused by activation of fetal hippocampal GR-HDAC2-KCC2 signaling. We proposed that this abnormal epigenetic modification is the mechanism underlying offspring convulsions susceptibility. CATEGORIES: mechanism of toxicity.

Dexamethasone attenuates the modulatory effect of the insular cortex on the baroreflex in anesthetized rat

The arterial baroreflex (BR) is an important neural mechanism for the stabilization of arterial pressure (AP). It is known that the insular cortex (IC) and other parts of the central autonomic network (CAN) are able to modulate the BR arc, altering baroreflex sensitivity (BRS). In addition, the sensitivity of the BR changes under the influence of hormones, in particular glucocorticoids (GC). It has been suggested that GC may influence BRS by altering the ability of the IC to modulate the BR. This hypothesis has been tested in experiments on rats anesthetized with urethane. It was found that microelectrostimulation of the visceral area in the left IC causes a short-term drop in AP, which is accompanied by bradycardia, and impairs BRS. The synthetic GC dexamethasone (DEX) did not significantly affect the magnitude of depressor responses but increased BRS and impaired the effect of IC stimulation on the BR. The results obtained confirm the hypothesis put forward and suggest that GC can attenuate the inhibitory effects of the IC on the BR arc, thereby enhancing the sensitivity of the BR.

Potential Adverse Effects of Dexamethasone Therapy on COVID-19 Patients: Review and Recommendations

In the context of the coronavirus disease 2019 (COVID-19) pandemic, the global healthcare community has raced to find effective therapeutic agents against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To date, dexamethasone is the first and an important therapeutic to significantly reduce the risk of death in COVID-19 patients with severe disease. Due to powerful anti-inflammatory and immunosuppressive effects, dexamethasone could attenuate SARS-CoV-2-induced uncontrolled cytokine storm, severe acute respiratory distress syndrome and lung injury. Nevertheless, dexamethasone treatment is a double-edged sword, as numerous studies have revealed that it has significant adverse impacts later in life. In this article, we reviewed the literature regarding the adverse effects of dexamethasone administration on different organ systems as well as related disease pathogenesis in an attempt to clarify the potential harms that may arise in COVID-19 patients receiving dexamethasone treatment. Overall, taking the threat of COVID­19 pandemic into account, we think it is necessary to apply dexamethasone as a pharmaceutical therapy in critical patients. However, its adverse side effects cannot be ignored. Our review will help medical professionals in the prognosis and follow-up of patients treated with dexamethasone. In addition, given that a considerable amount of uncertainty, confusion and even controversy still exist, further studies and more clinical trials are urgently needed to improve our understanding of the parameters and the effects of dexamethasone on patients with SARS-CoV-2 infection.

Differential effects of dexamethasone on arterial stiffness, myocardial remodeling and blood pressure between normotensive and spontaneously hypertensive rats

Dexamethasone (DEX)-induced hypertension is observed in normotensive rats, but little is known about the effects of DEX on spontaneously hypertensive animals (SHR). This study aimed to evaluate the effects of DEX on hemodynamics, cardiac hypertrophy and arterial stiffness in normotensive and hypertensive rats. Wistar rats and SHR were treated with DEX (50 μg/kg s.c., 14 d) or saline. Pulse wave velocity (PWV), echocardiographic parameters, blood pressure (BP), autonomic modulation and histological analyses of heart and thoracic aorta were performed. SHR had higher BP compared with Wistar, associated with autonomic unbalance to the heart. Echocardiographic changes in SHR (vs. Wistar) were suggestive of cardiac remodeling: higher relative wall thickness (RWT, +28%) and left ventricle mass index (LVMI, +26%) and lower left ventricle systolic diameter (LVSD, -19%) and LV diastolic diameter (LVDD, -10%), with slightly systolic dysfunction and preserved diastolic dysfunction. Also, SHR had lower myocardial capillary density and similar collagen deposition area. PWV was higher in SHR due to higher aortic collagen deposition. DEX-treated Wistar rats presented higher BP (~23%) and autonomic unbalance. DEX did not change cardiac structure in Wistar, but PWV (+21%) and aortic collagen deposition area (+21%) were higher compared with control. On the other side, DEX did not change BP or autonomic balance to the heart in SHR, but reduced RWT and LV collagen deposition area (-12% vs. SHR_CT ). In conclusion, the results suggest a differential effect of dexamethasone on arterial stiffness, myocardial remodeling and blood pressure between normotensive and spontaneously hypertensive rats.

Inclusion complex with β-cyclodextrin is a key determining factor for the cardioprotection induced by usnic acid

Ischemia-reperfusion (I/R) injury causes oxidative stress, leading to severe cardiac dysfunction. Thus, biologically active compounds with antioxidant properties may be viewed as a promising therapeutic strategy against oxidative-related cardiac disorders. Usnic acid (UA), a natural antioxidant, was complexed with β-cyclodextrin (βCD) to improve its bioavailability. Wistar male rats were orally treated with the free form of UA (50 mg/kg) or the inclusion complex UA/βCD (50 mg/kg) for seven consecutive days. Afterward, hearts were subjected to I/R injury, and the cardiac contractility, rhythmicity, infarct size, and antioxidant enzyme activities were evaluated. Here, we show that neither UA nor UA/βCD treatments developed signs of toxicity. After I/R injury, animals treated with UA/βCD showed improved post-ischemic cardiac functional recovery while the release of cell injury biomarkers decreased. Following reduced cardiac damage, a lower incidence of ventricular arrhythmias and smaller myocardial infarct size were associated with reduced lipid peroxidation, along with preserved activity of antioxidant enzymes compared to untreated rats. Surprisingly, uncomplexed UA did not protect hearts against IR injury. Altogether, our results indicate that the inclusion complex UA/βCD is a critical determining factor responsible for the cardioprotection action of UA, suggesting the involvement of an antioxidant-dependent mechanisms. Moreover, our findings support that UA/βCD is a structurally engineered compound with active cardioprotective properties.