Melatonin effects on pulmonary tissue in the experimental model of Hepatopulmonary Syndrome

Vildagliptin ameliorates intrapulmonary vasodilatation and angiogenesis in chronic common bile duct ligation-induced hepatopulmonary syndrome in rat

INTRODUCTION

Experimental hepatopulmonary syndrome (HPS) is best reproduced in the rat common bile duct ligation (CBDL) model. Vildagliptin (Vild) is an anti-hyperglycemic drug that exerts beneficial anti-inflammatory, anti-oxidant and anti-fibrotic effects. Therefore, the present search aimed to explore the possible effectiveness of Vild in CBDL-induced HPS model.

METHODS

Four groups of male Wistar rats which weigh 220-270 g were used, including the normal control group, the sham control group, the CBDL group and CBDL+Vild group. The first three groups received i.p. saline, while the last group was treated with i.p. Vild (10 mg/kg/day) from the 15th to 28th day of the experiment.

RESULTS

CBDL decreased the survivability and body weight of rats, increased diameter of the pulmonary vessels, and altered the arterial blood gases and the liver function parameters. Additionally, it increased the pulmonary expressions of endothelin-1 (ET-1) and tumor necrosis factor-α (TNF-α) mRNA as well as endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS) and vascular endothelial growth factor-A (VEGF-A) proteins. The CBDL rats also exhibited elevation of the pulmonary interleukin-6 (IL-6), dipeptidyl peptidase-4 (DPP-4) and nitric oxide (NO) levels along with reduction of the pulmonary total anti-oxidant capacity and glucagon-like peptide-1 (GLP-1) levels. Vild mitigated these alterations and improved the histopathological abnormalities caused by CBDL.

CONCLUSION

Vild effectively attenuated CBDL-induced HPS through its anti-oxidant and anti-inflammatory effects along with its modulatory effects on ET-1/NOS/NO and TNF-α/IL-6/VEGF-A signaling implicated in the regulation of intrapulmonary vasodilatation and angiogenesis, respectively.

Effect of melatonin on oxidative stress indicators in animal models of fibrosis: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

Imbalance of oxidative stress has been detected in a range of fibrotic diseases. Melatonin as an indoleamine hormone plays an important role in regulating the circadian rhythm of human, while in recent years, its antioxidant effect has also attracted increasing attention. This study aimed to perform a systematic review and meta-analysis to comprehensively evaluate the antioxidant effect of melatonin in animal models of fibrosis.

METHODS

The PubMed, Cochrane Library, EMBASE, Web of Science, China National Knowledge Infrastructure (CNKI), Wanfang database, China Science and Technology Journal Database (VIP), and SinoMed databases were searched from inception to March 1st, 2022 to retrieve eligible studies that evaluated the effect of melatonin supplementation on the levels of malondialdehyde (MDA), lipid peroxidation (LPO), nitric oxide (NO), superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GPx), and catalase (CAT) in animal models of fibrosis.

RESULTS

A total of 64 studies were included in this meta-analysis. The results showed that melatonin supplementation significantly reduced the levels of oxidative indicators including MDA (P < 0.00001), LPO (P < 0.00001) and NO (P < 0.0001), and elevated the levels of antioxidant indicators including GSH (P < 0.00001), GPx (P < 0.00001) and SOD (P < 0.00001) in fibrotic diseases.

CONCLUSIONS

Our research findings showed that melatonin supplementation could significantly reduce the levels of oxidative indicators including MDA, LPO and NO and elevate the levels of antioxidant indicators including GSH, GPx and SOD so as to correct oxidative stress in animal models of fibrosis. However, no significant changes were observed in CAT level. More clinical studies are needed to further confirm the beneficial role of melatonin in fibrotic diseases.

Quercetin ameliorates acute lung injury in a rat model of hepatopulmonary syndrome

BACKGROUND

Common bile duct ligation (BDL) is a rat experimental model to induce biliary cirrhosis. Lung fibrosis and pulmonary vascular angiogenesis and congestion are the most common complications of biliary cirrhosis that is known as hepatopulmonary syndrome. The aim of the present work is to investigate the acute lung injury in a BDL model and to investigate the possible protective effect of quercetin on this injury.

METHODS

Twenty-four adult male albino rats of the Wister strain (weighing 150-250 g). Animals were divided into 3 groups, with 8 rats each: Group I: Sham-operated group (control). Group II: Bile duct ligation group (BDL) sacrificed after 28 days from the surgery. Group III: Quercetin-treated bile duct ligation group (Q-BDL) was given orally by gastric gavage in a dose of 50 mg/kg/day, starting from the 4th day of the operation until the 28th day. At the end of the experiment, at day 28, all rats were sacrificed. Lung specimens were processed to measure Endothelin B receptor gene expression by PCR, lung surfactant by ELISA, "eNO" s by immunohistochemistry. Histological assessment was done using; H&E, Masson's trichrome, PAS, toluidine blue-stained semi-thin sections, transmission electron microscope. Histomorphometric and statistical studies were done.

RESULTS

BDL group showed significant increase in lung index together with mononuclear cellular infiltration denoting lung inflammatory state. Also, the significant increase in pulmonary endothelial nitric oxide synthase ("eNO" s) area percent and endothelin B receptor (ET_B) gene expression indicates enhanced angiogenesis. Pulmonary surfactant concentration was significantly decreased together with thickening of interalveolar septa denoting lung injury and fibrosis. Quercetin led to significant decrease in lung index, pulmonary "eNO" s area percent, ET_B gene expression and significant increase in pulmonary surfactant concentration. Quercetin treatment improved histological changes and morphometric measurements, limited mononuclear cellular infiltration and decreased perivascular and perialveolar collagen deposition.

CONCLUSION

Quercetin ameliorates the hepatopulmonary syndrome-induced lung injury through its anti-inflammatory, antioxidative and antifibrotic effects.

Beneficial effects of melatonin on liver fibrosis: A systematic review of current biological evidence

Hepatic fibrosis is a reversible response to either acute or chronic cellular injury from a wide variety of etiologies, characterized by excessive deposition of extracellular matrix resulting in liver dysfunction and cirrhosis. Melatonin (N‐acetyl‐5‐methoxytryptamine), the main product secreted by the pineal gland, is a multitasking indolamine with important physiological functions such as anti‐inflammatory and antioxidant actions, modulation of circadian rhythms, and immune system enhancement. Among the numerous biological activities of melatonin, its antifibrotic effects have received increasingly more attention. In this study, we performed a systematic review of publications of the last 10 years evaluating the mechanisms of action of melatonin against liver fibrosis. The study protocol was registered at PROSPERO (CRD42022304744). Literature research was performed employing PubMed, Scopus, and Web of Science (WOS) databases, and after screening, 29 articles were included. Results from the selected studies provided denoted the useful actions of melatonin on the development, progression, and evolution of liver fibrosis. Melatonin antifibrotic effects in the liver involved the reduction of profibrogenic markers and modulation of several cellular processes and molecular pathways, mainly acting as an antioxidant and anti‐inflammatory agent. In addition, the indolamine influenced different molecular processes, such as hepatocyte apoptosis, modulation of autophagy and mitophagy, restoration of circadian rhythms, and modulation of microRNAs, among others. Although some limitations have been found regarding variability in the study design, the findings here summarized display the potential role of melatonin in ameliorating the development of liver fibrosis and its possible progression to liver cirrhosis and hepatocarcinoma.

Sarcopenia, oxidative stress and inflammatory process in muscle of cirrhotic rats - Action of melatonin and physical exercise

Sarcopenia is one of the most common features of cirrhosis, contributing to morbidity and mortality in this population. We aimed to evaluate the effect of melatonin (MLT) and exercise (EX) on the quadriceps muscle in rats with biliary cirrhosis induced by bile duct ligation (BDL). We used 48 males (mean weight = 300 g), divided into eight groups. A 20 mg/Kg MLT dose was administered via i.p. (1 x daily), and the EX, the animals were set to swim in couples for 10 min each day. Upon completion, blood, liver, and quadriceps samples were taken for analysis. In the liver enzymes analysis and comet assay results, a reduction was observed in the groups treated with MLT with/or EX comparing to the BDL group. In the evaluation of substances that react to thiobarbituric acid (TBARS), nitric oxide levels (NO), and tumor necrosis factor-alpha levels (TNF-α), there was a significant increase in the BDL group and a reduction in the treated groups. In the activity of the superoxide dismutase enzyme (SOD) and interleukin-10 levels (IL-10) concentrations, there was a significant increase in the treated groups of the BDL group. Histological analysis revealed muscle hypotrophy in the BDL group in comparison with the control group (CO) and increased muscle mass in the treated groups. There was an increase in weight gain and phase angle in the groups treated with MLT with/or EX comparing to the BDL group. We suggest that treatments may contribute to the reduction of muscle changes in cirrhotic patients.

Pineal hormone melatonin as an adjuvant treatment for COVID‑19 (Review)

The beneficial properties of the pineal hormone, melatonin, as a neuroprotective and cardioprotective agent, have been previously identified. Furthermore, melatonin plays essential roles in biological rhythms resynchronization, sleep initiation/maintenance and metabolic, ocular, rheumatological diseases. In addition to these functions, melatonin is known to exert immunomodulation, anti-inflammatory and anti-oxidative effects. Due to these properties, coupled with its non-toxic nature, melatonin has been suggested to limit viral infections; however, melatonin cannot be classified as a viricidal drug. In addition, the recent increase in the number of clinical trials on melatonin's role, as an adjuvant treatment for COVID-19, has resurged the interest of the scientific community in this hormone. The present short review aimed to improve the understanding of the antiviral/anti-COVID-19 profile of melatonin and the clinical trials that have recently been conducted, with respect to its co-administration in treating individuals with COVID-19.

Is Melatonin the Cornucopia of the 21st Century?

Melatonin, an indoleamine hormone produced and secreted at night by pinealocytes and extra-pineal cells, plays an important role in timing circadian rhythms (24-h internal clock) and regulating the sleep/wake cycle in humans. However, in recent years melatonin has gained much attention mainly because of its demonstrated powerful lipophilic antioxidant and free radical scavenging action. Melatonin has been proven to be twice as active as vitamin E, believed to be the most effective lipophilic antioxidant. Melatonin-induced signal transduction through melatonin receptors promotes the expression of antioxidant enzymes as well as inflammation-related genes. Melatonin also exerts an immunomodulatory action through the stimulation of high-affinity receptors expressed in immunocompetent cells. Here, we reviewed the efficacy, safety and side effects of melatonin supplementation in treating oxidative stress- and/or inflammation-related disorders, such as obesity, cardiovascular diseases, immune disorders, infectious diseases, cancer, neurodegenerative diseases, as well as osteoporosis and infertility.

Lungs as target of COVID-19 infection: Protective common molecular mechanisms of vitamin D and melatonin as a new potential synergistic treatment

COVID-19 pandemic has a high mortality rate and is affecting practically the entire world population. The leading cause of death is severe acute respiratory syndrome as a consequence of exacerbated inflammatory response accompanied by uncontrolled oxidative stress as well as the inflammatory reaction at the lung level. Until now, there is not a specific and definitive treatment for this pathology that worries the world population, especially the older adults who constitute the main risk group. In this context, it results in a particular interest in the evaluation of the efficacy of existing pharmacological agents that may be used for overcoming or attenuating the severity of this pulmonary complication that has ended the lives of many people worldwide. Vitamin D and melatonin could be good options for achieving this aim, taking into account that they have many shared underlying mechanisms that are able to modulate and control the immune adequately and oxidative response against COVID-19 infection, possibly even through a synergistic interaction. The renin-angiotensin system exaltation with consequent inflammatory response has a leading role in the physiopathology of COVID-19 infection; and it may be down-regulated by vitamin D and melatonin in many organs. Therefore, it is also essential to analyze this potential therapeutic association and their relation with RAS as part of this new approach.