Inhibition of neutrophil migration and oxygen free radical release by metipranolol and timolol

Mitochondrial Effects of Common Cardiovascular Medications: The Good, the Bad and the Mixed

Mitochondria are central organelles in the homeostasis of the cardiovascular system via the integration of several physiological processes, such as ATP generation via oxidative phosphorylation, synthesis/exchange of metabolites, calcium sequestration, reactive oxygen species (ROS) production/buffering and control of cellular survival/death. Mitochondrial impairment has been widely recognized as a central pathomechanism of almost all cardiovascular diseases, rendering these organelles important therapeutic targets. Mitochondrial dysfunction has been reported to occur in the setting of drug-induced toxicity in several tissues and organs, including the heart. Members of the drug classes currently used in the therapeutics of cardiovascular pathologies have been reported to both support and undermine mitochondrial function. For the latter case, mitochondrial toxicity is the consequence of drug interference (direct or off-target effects) with mitochondrial respiration/energy conversion, DNA replication, ROS production and detoxification, cell death signaling and mitochondrial dynamics. The present narrative review aims to summarize the beneficial and deleterious mitochondrial effects of common cardiovascular medications as described in various experimental models and identify those for which evidence for both types of effects is available in the literature.

[Mechanisms of adrenergic β-antagonist for wounds and its application prospect in diabetic foot ulcers]

Objective

To review the research progress of adrenergic β-antagonists on wounds and diabetic chronic cutaneous ulcers healing in recent years, and to investigate its application prospect in diabetic foot ulcer (DFU).

Methods

The latest literature about the role of adrenergic β-antagonists in wounds and diabetic chronic cutaneous ulcers healing was extensively reviewed, and the mechanisms of adrenergic β-antagonists for wounds and its potential benefit for DFU were analyzed thoroughly.

Results

The adrenergic β-antagonists can accelerate the wound healing. The possible mechanisms include accelerating re-epithelialization, promoting angiogenesis, improving neuropathy, and regulating inflammation and growth factors, etc. At present clinical research data showed that the adrenergic β-antagonists may be an adjuvant treatment for diabetic chronic cutaneous ulcers.

Conclusion

Adrenergic β-antagonists maybe promote the healing of wounds and diabetic chronic cutaneous ulcers. However, more long-term follow-up and high-quality randomized control studies are needed to further verify their efficacy and safety for DFU.

Melatonin inhibits granulocyte adhesion to ICAM via MT3/QR2 and MT2 receptors

Neutrophils are cells of the innate immune system that first respond and arrive to the site of infection. Melatonin modulates acute inflammatory responses by interfering with leukocyte recruitment. It is known that melatonin modulates granulocyte migration though the endothelial layer thereby acting on the endothelial cell. Here we investigated whether melatonin could modulate granulocyte infiltration by acting directly on granulocytes. Granulocyte infiltration into the peritoneal cavity was investigated in mice kept at normal light/dark conditions and mice kept under constant lighting. To induce migration of neutrophils from the blood into the injury site via the endothelial layer, a bacterial product N-formyl-l-methionyl- l-leucyl- l-phenylalanine (fMLP) was injected into the peritoneal cavity. We found that the number of infiltrated granulocytes during the dark time was lower than that during the light time. It did not depend on circadian time. Moreover, the expression of an adhesion molecule, CD18, on granulocytes, was also lower during the dark time as compared with the light time. We have found that melatonin inhibited fMLP-induced CD18 up-regulation. Importantly, melatonin also inhibited the integrin-mediated granulocyte adhesion to intercellular adhesion molecule-coated plates. This study additionally showed that melatonin receptors MT2 and MT3/quinone reductase 2 (QR2) are expressed on granulocytes. Interestingly, melatonin increases the expression of its MT3/QR2 receptor. The fMLP-mediated CD18 up-regulation was inhibited by melatonin via MT2 receptor and the integrin-mediated granulocyte adhesion was inhibited by melatonin via MT3/QR2 and MT2 receptors. In conclusion, we show that melatonin suppresses granulocyte migration via endothelium by acting directly on granulocytes.

Todralazine protects zebrafish from lethal effects of ionizing radiation: role of hematopoietic cell expansion

The Johns Hopkins Clinical Compound Library (JHCCL), a collection of Food and Drug Administration (FDA)-approved small molecules (1400), was screened in silico for identification of novel β2AR blockers and tested for hematopoietic stem cell (HSC) expansion and radioprotection in zebrafish embryos. Docking studies, followed by the capacity to hasten erythropoiesis, identified todralazine (Binding energy, -8.4 kcal/mol) as a potential HSC-modulating agent. Todralazine (5 μM) significantly increased erythropoiesis in caudal hematopoietic tissue (CHT) in wild-type and anemic zebrafish embryos (2.33- and 1.44-folds, respectively) when compared with untreated and anemic control groups. Todralazine (5 μM) treatment also led to an increased number of erythroid progenitors, as revealed from the increased expression of erythroid progenitor-specific genes in the CHT region. Consistent with these effects, zebrafish embryos, Tg(cmyb:gfp), treated with 5 μM todralazine from 24 to 36 hours post fertilization (hpf) showed increased (approximately two-folds) number of HSCs at the aorta-gonad-mesonephros region (AGM). Similarly, expression of HSC marker genes, runx1 (3.3-folds), and cMyb (1.41-folds) also increased in case of todralazine-treated embryos, further supporting its HSC expansion potential. Metoprolol, a known beta blocker, also induced HSC expansion (1.36- and 1.48-fold increase in runx1 and cMyb, respectively). Todralazine (5 μM) when added 30 min before 20 Gy gamma radiation, protected zebrafish from radiation-induced organ toxicity, apoptosis, and improved survival (80% survival advantage over 6 days). The 2-deoxyribose degradation test further suggested hydroxyl (OH) radical scavenging potential of todralazine, and the same is recapitulated in vivo. These results suggest that todralazine is a potential HSC expanding agent, which might be acting along with important functions, such as antioxidant and free radical scavenging, in manifesting radioprotection.

Application of a nitric oxide sensor in biomedicine

In the present study, we describe the biochemical properties and effects of nitric oxide (NO) in intact and dysfunctional arterial and venous endothelium. Application of the NO electrochemical sensor in vivo and in vitro in erythrocytes of healthy subjects and patients with vascular disease are reviewed. The electrochemical NO sensor device applied to human umbilical venous endothelial cells (HUVECs) and the description of others NO types of sensors are also mentioned.

ß-blocker timolol prevents arrhythmogenic Ca²⁺ release and normalizes Ca²⁺ and Zn²⁺ dyshomeostasis in hyperglycemic rat heart

Defective cardiac mechanical activity in diabetes results from alterations in intracellular Ca(2+) handling, in part, due to increased oxidative stress. Beta-blockers demonstrate marked beneficial effects in heart dysfunction with scavenging free radicals and/or acting as an antioxidant. The aim of this study was to address how β-blocker timolol-treatment of diabetic rats exerts cardioprotection. Timolol-treatment (12-week), one-week following diabetes induction, prevented diabetes-induced depressed left ventricular basal contractile activity, prolonged cellular electrical activity, and attenuated the increase in isolated-cardiomyocyte size without hyperglycemic effect. Both in vivo and in vitro timolol-treatment of diabetic cardiomyocytes prevented the altered kinetic parameters of Ca(2+) transients and reduced Ca(2+) loading of sarcoplasmic reticulum (SR), basal intracellular free Ca(2+) and Zn(2+) ([Ca(2+)]i and [Zn(2+)]i), and spatio-temporal properties of the Ca(2+) sparks, significantly. Timolol also antagonized hyperphosphorylation of cardiac ryanodine receptor (RyR2), and significantly restored depleted protein levels of both RyR2 and calstabin2. Western blot analysis demonstrated that timolol-treatment also significantly normalized depressed levels of some [Ca(2+)]i-handling regulators, such as Na(+)/Ca(2+) exchanger (NCX) and phospho-phospholamban (pPLN) to PLN ratio. Incubation of diabetic cardiomyocytes with 4-mM glutathione exerted similar beneficial effects on RyR2-macromolecular complex and basal levels of both [Ca(2+)]i and [Zn(2+)]i, increased intracellular Zn(2+) hyperphosphorylated RyR2 in a concentration-dependent manner. Timolol also led to a balanced oxidant/antioxidant level in both heart and circulation and prevented altered cellular redox state of the heart. We thus report, for the first time, that the preventing effect of timolol, directly targeting heart, seems to be associated with a normalization of macromolecular complex of RyR2 and some Ca(2+) handling regulators, and prevention of Ca(2+) leak, and thereby normalization of both [Ca(2+)]i and [Zn(2+)]i homeostasis in diabetic rat heart, at least in part by controlling the cellular redox status of hyperglycemic cardiomyocytes.

Effects of the aquatic contaminant human pharmaceuticals and their mixtures on the proliferation and migratory responses of the bioindicator freshwater ciliate Tetrahymena

An increasing attention is paid to the potential harmful effects of aquatic contaminant pharmaceuticals exerted on both biosystems and humans. In the present work the effects of 14 pharmaceuticals including NSAIDs, antibiotics, β-blockers and a frequently used X-ray contrast media on the proliferation and migratory behavior of the freshwater ciliate Tetrahymena pyriformis was investigated. Moreover, the mixture toxicity of four selected pharmaceuticals (diclofenac, ibuprofen, metoprolol and propranolol) was evaluated in binary mixtures using full factorial experimental design. Our results showed that the sensitivity of Tetrahymena to NSAIDs and β-blockers (EC(50) ranged from 4.8 mg L(-1) to 308.1 mg L(-1)) was comparable to that of algal or Daphnia bioassays. Based on these elevated EC(50) values acute toxic effects of these pharmaceuticals to T. pyriformis are unlikely. Antibiotics and the contrast agent sodium-diatrizoate had no proliferation inhibiting effect. Chemotactic response of Tetrahymena was more sensible than proliferation as significant chemorepellent action was observed in the environmentally realistic concentration range for acetylsalicylic acid, diclofenac, fenoprofen, paracetamol, metoprolol, propranolol, timolol and trimethoprim (Chemotaxis Index ranged from 63% to 88%). Mixture toxicity experiments resulted in a complex, concentration dependent interaction type pattern with antagonism being the predominant interaction type (59%) followed by additivity (37%) and synergism (4%). Hence the concept of concentration addition validated for NSAIDs in other organisms cannot be adopted for this ciliate. In summary authors suggest Tetrahymena as a sensible model of testing aquatic contaminants as well as underline the significance using more specific endpoints to understand the complex mechanisms investigated.

Profound cardioprotection with timolol in a female rat model of aging-related altered left ventricular function

Increasing evidence shows a marked beneficial effect with β-blockers in heart dysfunction via scavenging reactive oxygen species. Previously we showed that chronic treatment with either timolol or propranolol possessed similar beneficial effects for heart function in male rats as age increased, whereas only timolol exerted similar benefits in female rats. Therefore, in this study, we aimed first to examine the cellular bases for age-related alterations in excitation–contraction coupling in ventricular myocytes from female rats and, second, to investigate the hypothesis that age-related changes in [Ca2+]ihomeostasis and receptor-mediated system can be prevented with chronic timolol treatment. Chronic timolol treatment of 3-month-old female rats abolished age-related decrease in left ventricular developed pressure and the attenuated responses to β-adrenoreceptor stimulation. It also normalized the altered parameters of [Ca2+]itransients, decreased Ca2+loading of sarcoplasmic reticulum and increased basal [Ca2+]i, and decreased L-type Ca2+currents in 12-month-old female rats compared with the 3-month-old group. Adenylyl cyclase activity, β-adrenoreceptor affinity to its agonist, and β-adrenoreceptor density of the 12-month-old group are normalized to those of the 3-month-old group. Moreover, timolol treatment prevented dysfunction of the antioxidant system, including increased lipid peroxidation, decreased ratio of reduced glutathione to oxidized glutathione, and decreased activities of thioredoxin reductase and glucose-6-phosphate dehydrogenase, in the left ventricle of hearts from the 12-month-old group. Our data confirmed that aging-related early myocardial impairment is primarily related to a dysfunctional antioxidant system and impairment of Ca2+homeostasis, which can be prevented with chronic timolol treatment.

Metoprolol treatment decreases tissue myeloperoxidase activity after spinal cord injury in rats

Neutrophil infiltration has been reported to play an important role in spinal cord injury (SCI). In addition to their cardioprotective effects, beta-blockers have been found to have neuroprotective effects on the central nervous system, but their effect on SCI has not yet been studied. In the current study, we investigated the effect of metoprolol on myeloperoxidase (MPO) activity, a marker of neutrophil activation, in the spinal cord after experimental SCI in rats. Rats were divided into six groups: controls received only laminectomy and spinal cord samples were taken immediately; the sham operated group received laminectomy, and spinal cord samples were taken 4h after laminectomy; the trauma only group underwent a 50g/cm contusion injury but received no medication; and three other groups underwent trauma as for the trauma group, and received 30mg/kg methylprednisolone, 1mg/kg metoprolol, or 1mL saline, respectively. All the medications were given intraperitoneally as single doses, immediately after trauma. Spinal cord samples were taken 4h after trauma and studied for MPO activity. The results showed that tissue MPO activity increased after injury. Both metoprolol and methylprednisolone treatments decreased MPO activity, indicating a reduction in neutrophil infiltration in damaged tissue. The effect of metoprolol on MPO activity was found to be similar to methylprednisolone. In view of these data, we conclude that metoprolol may be effective in protecting rat spinal cord from secondary injury.

Antioxidant activity of timolol on endothelial cells and its relevance for glaucoma course

PURPOSE

A growing evidence in the scientific literature suggests that oxidative damage plays a pathogenic role in primary open-angle glaucoma. Therefore, it is of interest to test whether drugs effective against glaucoma display antioxidant activity. We test the hypothesis that the classic beta-blocker therapy for glaucoma with timolol involves the activation of antioxidant protective mechanisms towards endothelial cells.

METHODS

Oxidative stress was induced in cultured human endothelial cells by iron/ascorbate with or without timolol pretreatment. Analysed parameters included cell viability (neutral red uptake and tetrazolium salt tests), lipid peroxidation (thiobarbituric reactive substances), and occurrence of molecular oxidative damage to DNA (8-hydroxy-2'-deoxyguanosine).

RESULTS

Oxidative stress decreased 1.8-fold cell viability, increased 3.0-fold lipid peroxidation and 64-fold oxidative damage to DNA. In the presence of timolol, oxidative stress did not modify cell viability, whereas lipid peroxidation was increased 1.3-fold, and DNA oxidative damage 3.6-fold only.

CONCLUSIONS

The obtained results indicate that timolol exerts a direct antioxidant activity protecting human endothelial cells from oxidative stress. These cells employ mechanisms similar to those observed in the vascular endothelium. It is hypothesized that this antioxidant activity is involved in the therapeutic effect of this drug against glaucoma.