Role of Exogenous Melatonin on Cell Proliferation and Oxidant/Antioxidant System in Aluminum-Induced Renal Toxicity

Empagliflozin and pirfenidone confer renoprotection through suppression of glycogen synthase kinase-3β and promotion of tubular regeneration in rats with induced metabolic syndrome

Metabolic syndrome (MetS) is largely coupled with chronic kidney disease (CKD). Glycogen synthase kinase-3β (GSK-3β) pathway drives tubular injury in animal models of acute kidney injury; but its contribution in CKD is still elusive. This study investigated the effect empagliflozin and/or pirfenidone against MetS-induced kidney dysfunction, and to clarify additional underpinning mechanisms particularly the GSK-3β signaling pathway. Adult male rats received 10%w/v fructose in drinking water for 20 weeks to develop MetS, then treated with either drug vehicle, empagliflozin (30 mg/kg/day) and/or pirfenidone (100 mg/kg/day) via oral gavage for subsequent 4 weeks, concurrently with the high dietary fructose. Age-matched rats receiving normal drinking water were used as controls. After 24 weeks, blood and kidneys were harvested for subsequent analyses. Rats with MetS showed signs of kidney dysfunction, structural changes and interstitial fibrosis. Activation of GSK-3β, decreased cyclinD1 expression and enhanced apoptotic signaling were found in kidneys of MetS rats. There was abundant alpha-smooth muscle actin (α-SMA) expression along with up-regulation of TGF-β1/Smad3 in kidneys of MetS rats. These derangements were almost alleviated by empagliflozin or pirfenidone, with evidence that the combined therapy was more effective than either individual drug. This study emphasizes a novel mechanism underpinning the beneficial effects of empagliflozin and pirfenidone on kidney dysfunction associated with MetS through targeting GSK-3β signaling which can mediate the regenerative capacity, anti-apoptotic effects and anti-fibrotic properties of such drugs. These findings recommend the possibility of using empagliflozin and pirfenidone as promising therapies for management of CKD in patients with MetS.

A review of the epidemiological and laboratory evidence of the role of aluminum exposure in pathogenesis of cardiovascular diseases

The objective of the present study was to review the epidemiological and laboratory evidence on the role of aluminum (Al) exposure in the pathogenesis of cardiovascular diseases. Epidemiological data demonstrated an increased incidence of cardiovascular diseases (CVD), including hypertension and atherosclerosis in occupationally exposed subjects and hemodialysis patients. In addition, Al body burden was found to be elevated in patients with coronary heart disease, hypertension, and dyslipidemia. Laboratory studies demonstrated that Al exposure induced significant ultrastructural damage in the heart, resulting in electrocardiogram alterations in association with cardiomyocyte necrosis and apoptosis, inflammation, oxidative stress, inflammation, and mitochondrial dysfunction. In agreement with the epidemiological findings, laboratory data demonstrated dyslipidemia upon Al exposure, resulting from impaired hepatic lipid catabolism, as well as promotion of low-density lipoprotein oxidation. Al was also shown to inhibit paraoxonase 1 activity and to induce endothelial dysfunction and adhesion molecule expression, further promoting atherogenesis. The role of Al in hypertension was shown to be mediated by up-regulation of NADPH-oxidase, inhibition of nitric oxide bioavailability, and stimulation of renin-angiotensin-aldosterone system. It has been also demonstrated that Al exposure targets cerebral vasculature, which may be considered a link between Al exposure and cerebrovascular diseases. Findings from other tissues lend support that ferroptosis, pyroptosis, endoplasmic reticulum stress, and modulation of gut microbiome and metabolome are involved in the development of CVD upon Al exposure. A better understanding of the role of the cardiovascular system as a target for Al toxicity will be useful for risk assessment and the development of treatment and prevention strategies.

Chronic Oral Administration of Aluminum Hydroxide Stimulates Systemic Inflammation and Redox Imbalance in BALB/c Mice

The present study is aimed at investigating the long-term effects of the aluminum hydroxide administration in the small intestine, lung, liver, and kidney of male BALB/c mice. The mice received via orogastric gavage phosphate buffered or 10 mg/kg aluminum hydroxide 3 times a week for 6 months. Administration of aluminum hydroxide decreased hemoglobin, hematocrit, and erythrocyte. In the blood, kidney and liver function markers were evaluated, and long-term administration of aluminum hydroxide led to an increase in AST levels and a decrease in urea levels. The animals exposed to aluminum showed higher lipid and protein oxidation in all the organs analyzed. In relation to the enzymes involved in antioxidant defense, the lungs showed lower superoxide dismutase (SOD) and catalase activity and a lower reduced and oxidized glutathione (GSH/GSSG) ratio. In the liver, aluminum administration led to a decrease in catalase activity and the GSH/GSSG ratio. Lower catalase activity was observed in the small intestine, as well as in the lungs and liver. In addition to alterations in antioxidant defense, increased levels of the chemokine CCL-2 were observed in the lungs, lower levels of IL-10 in the liver and small intestine, and decreased levels of IL-6 in the intestine of the animals that received aluminum hydroxide for 6 months. Long-term exposure to aluminum promoted steatosis in the liver. In the kidneys, mice treated with aluminum presented a decreased glomerular density than in the naive control group. In the small intestine, exposure caused villi shortening. Our results indicate that long-term oral administration of aluminum hydroxide provokes systemic histological damage, inflammation, and redox imbalance.

Ferroptosis as a mechanism of non-ferrous metal toxicity

Ferroptosis is a recently discovered form of regulated cell death, implicated in multiple pathologies. Given that the toxicity elicited by some metals is linked to alterations in iron metabolism and induction of oxidative stress and lipid peroxidation, ferroptosis might be involved in such toxicity. Although direct evidence is insufficient, certain pioneering studies have demonstrated a crosstalk between metal toxicity and ferroptosis. Specifically, the mechanisms underlying metal-induced ferroptosis include induction of ferritinophagy, increased DMT-1 and TfR cellular iron uptake, mitochondrial dysfunction and mitochondrial reactive oxygen species (mitoROS) generation, inhibition of Xc-system and glutathione peroxidase 4 (GPX4) activity, altogether resulting in oxidative stress and lipid peroxidation. In addition, there is direct evidence of the role of ferroptosis in the toxicity of arsenic, cadmium, zinc, manganese, copper, and aluminum exposure. In contrast, findings on the impact of cobalt and nickel on ferroptosis are scant and nearly lacking altogether for mercury and especially lead. Other gaps in the field include limited studies on the role of metal speciation in ferroptosis and the critical cellular targets. Although further detailed studies are required, it seems reasonable to propose even at this early stage that ferroptosis may play a significant role in metal toxicity, and its modulation may be considered as a potential therapeutic tool for the amelioration of metal toxicity.

Melatonin as a powerful antioxidant

Melatonin is a hormone that has many body functions and, for several decades, its antioxidant potential has been increasingly talked about. There is a relationship between failure in melatonin production in the pineal gland, an insufficient supply of this hormone to the body, and the occurrence of free radical etiology diseases such as neurodegenerative diseases, cardiovascular diseases, diabetes, cancer and others. Despite the development of molecular biology, numerous in vitro and in vivo studies, the exact mechanism of melatonin antioxidant activity is still unknown. Nowadays, the use of melatonin supplementation is more and more common, not only to prevent insomnia, but also to slow down the aging process and provide protection against diseases. The aim of this study is to get acquainted with current reports on melatonin, antioxidative mechanisms and their importance in diseases of free radical etiology.

Melatonin exerts neuroprotection in a chronodisrupted rat model through reduction in oxidative stress and modulation of autophagy

Circadian disruption due to artificial light affects cellular redox homeostasis and may lead to neurodegenerative diseases. The aim of the present study was to investigate the effect of continuous light exposure (CLE) and continuous dark exposure (CDE) along with melatonin supplementation on neuronal redox status, mitochondrial complexes, membrane bound transporters, inflammation, autophagy and neurodegeneration in chronodisrupted model of rat. In the study artificial light of white LED bulb with 500 lux intensity was used. Melatonin (10 mg/kg b.w., orally) was supplemented to control and CLE groups for 10 days. Standard protocols were employed to measure pro-oxidants, non-enzymatic antioxidants, and mitochondrial complexes in brain tissues. Membrane-bound ion transporter activities were evaluated in the crude synaptosomes. Gene expression analysis was performed to assess the expression of inflammatory, autophagy and neuronal marker genes. Histopathological changes in cerebral cortex and different hippocampus regions of the brain were studied. Melatonin exerted a significant normalization of redox status biomarkers in brain tissue. Further melatonin restored the activities of mitochondrial complexes and synaptosomal membrane bound ion transporters. RT-PCR data revealed that melatonin downregulated the expression of inflammatory (TNF-α, IL-6) autophagy (Atg-3, Beclin-1) and neurodegenerative genes (Ngb and NSE) in CLE group. Melatonin also preserved the histology architecture in cerebral cortex and hippocampus. Our results indicate that melatonin exerts a potent neuroprotective effect through reduction of oxidative stress, inflammation and autophagy. Melatonin supplementation might be a promising neurotherapeutic in the treatment neurodegenerative disorders caused by circadian disturbances.

Effect of pinealectomy and melatonin supplementation on metallothionein, ZnT2, ZIP2, ZIP4 and zinc levels in rat small intestine

We investigated the relations among levels of metallothionein (MT); zinc (Zn) transport proteins, ZnT2, ZIP2 (ZRT and IRT-like proteins); and ZIP4, which enable Zn absorption in the small intestine of rats. We also investigated tissue Zn levels in the small intestine. We used four groups of adult male rats: group 1, control; group 2, pinealectomy (Px); group 3, Px + melatonin (MEL); group 4, MEL only. Animals in groups 3 and 4 were administered 5 mg/kg/day MEL for four weeks. At the end of the study, all animals were sacrificed and samples of duodenum, jejunum and ileum were harvested to analyze ZnT2, ZIP2, ZIP4 and MT levels using immunohistochemistry, and tissue Zn levels were measured by atomic absorption spectrophotometry. The lowest ZnT2 levels in the duodenum, jejunum and ileum, and the lowest ZIP2 levels in the duodenum and ileum were found in group 2. The lowest ZIP4 levels were found in the duodenum and jejunum, and the lowest MT levels in the duodenum and ileum were found in group 2. The highest MT values in the ileum were found in group 4. We found that ZnT2, ZIP2, ZIP4 and MT levels were reduced in the ileum compared to controls following Px, but levels approached control values after MEL administration. By its effects on ZnT2, ZIP2, ZIP4 and MT levels, MEL participates in the absorption of Zn in the rat small intestine.

Melatonin alleviates aluminium chloride-induced immunotoxicity by inhibiting oxidative stress and apoptosis associated with the activation of Nrf2 signaling pathway

The present study aimed to investigate whether melatonin (MT) treatment can attenuate immunotoxicity induced by aluminum chloride (AlCl₃) in rat spleen. Forty-eight healthy male Wistar rats were randomly allocated and treated with AlCl₃ and/or MT. Rats were orally administered with AlCl₃ for 90 days, from 61st days, rats were injected intraperitoneally with MT for 30 days. Firstly, we found that MT relieved the AlCl₃-induced immunosuppression by improving spleen structural damage, CD3⁺ and CD4⁺ T lymphocyte subsets, IL-2 and TNF-α mRNA expressions and decreasing CD8⁺ T lymphocyte subsets. Secondly, MT attenuated the AlCl₃-induced oxidative stress in rat spleen by decreasing the levels of ROS and MDA, while increasing the activities of SOD and CAT. Thirdly, MT relieved the AlCl₃-induced apoptosis in rat spleen by increasing the MMP and Bcl-2 mRNA and protein expressions, while decreasing apoptosis rates, activity of Caspase-3 and pro-apoptotic gene expression. Finally, MT increased Nrf2 nuclear translocation, and Nrf2 target genes (HO-1, NQO1, SOD1 and CAT) mRNA expressions in the spleen of AlCl₃-exposed rat. These results suggest that MT may alleviate AlCl₃-induced immunotoxicity by inhibiting oxidative stress and apoptosis associated with the activation of Nrf2 signaling pathway, which could lay the foundation for the treatment of AlCl₃ immunotoxicity.

Role of Melatonin in Aluminum-Related Neurodegenerative Disorders: a Review

Aluminum (Al), a potentially neurotoxic element, provokes various adverse effects on human health such as dialysis dementia, osteomalacia, and microcytic anemia. It has been also associated with serious neurodegenerative diseases such as Alzheimer's disease (AD), amyotrophic lateral sclerosis, and Parkinsonism dementia of Guam. The "aluminum hypothesis" of AD assumes that the metal complexes can potentiate the rate of aggregation of amyloid-β (Aβ), enhancing the toxicity of this peptide, and being able of contributing to the pathogenesis of AD. It has been supported by a number of analytical, epidemiological, and neurotoxicological studies. On the other hand, melatonin (Mel) is a potent direct free radical scavenger and indirect antioxidant, which acts increasing the activity of important related antioxidant enzymes, and preventing oxidative stress and cell death of neurons exposed to Aβ-induced neurotoxicity. Therefore, Mel might be useful in the treatment of AD by reducing the Aβ generation and by inhibiting mitochondrial cell death pathways. The present review on the role of Mel in Al-related neurodegenerative disorders concludes that the protective effects of this hormone, together with its low toxicity, support the administration of Mel as a potential supplement in the treatment of neurological disorders, in which oxidative stress is involved.

The role of heat shock protein 70 in oxidant stress and inflammatory injury in quail spleen induced by cold stress

The aim of this study was to investigate the role of heat shock protein 70 (Hsp70) in oxidative stress and inflammatory damage in the spleen of quails which were induced by cold stress. One hundred ninety-two 15-day-old male quails were randomly divided into 12 groups and kept at 12 ± 1 °C to examine acute and chronic cold stress. We first detected the changes in activities of antioxidant enzymes in the spleen tissue under acute and chronic cold stress. The activities of glutathione peroxidase (GSH-Px) fluctuated in acute cold stress groups, while they were significantly decreased (p < 0.05) after chronic cold stress. The activities of superoxide dismutase (SOD), inducible nitric oxide synthase (iNOS), and nitric oxide (NO) content were decreased significantly (p < 0.05) in both of the acute and chronic cold stress groups. Malondialdehyde (MDA) content was significantly increased (p < 0.05) under cold stress except the 0.5 h group of acute cold stress. Besides, histopathological analysis showed that quail's spleen tissue was inflammatory injured seriously in both the acute and chronic cold stress groups. Additionally, the inflammatory factors (cyclooxygenase-2 (COX-2), prostaglandin E synthase (PTGES), iNOS, nuclear factor-kappa B (NF-κB), and tumor necrosis factor-a (TNF-α)) and Hsp70 mRNA levels were increased in both of the acute and chronic cold stress groups compared with the control groups. These results suggest that oxidative stress and inflammatory injury could be induced by cold stress in spleen tissues of quails. Furthermore, the increased expression of Hsp70 may play a role in protecting the spleen against oxidative stress and inflammatory damage caused by cold stress.

Dietary Sources and Bioactivities of Melatonin

Insomnia is a serious worldwide health threat, affecting nearly one third of the general population. Melatonin has been reported to improve sleep efficiency and it was found that eating melatonin-rich foods could assist sleep. During the last decades, melatonin has been widely identified and qualified in various foods from fungi to animals and plants. Eggs and fish are higher melatonin-containing food groups in animal foods, whereas in plant foods, nuts are with the highest content of melatonin. Some kinds of mushrooms, cereals and germinated legumes or seeds are also good dietary sources of melatonin. It has been proved that the melatonin concentration in human serum could significantly increase after the consumption of melatonin containing food. Furthermore, studies show that melatonin exhibits many bioactivities, such as antioxidant activity, anti-inflammatory characteristics, boosting immunity, anticancer activity, cardiovascular protection, anti-diabetic, anti-obese, neuroprotective and anti-aging activity. This review summaries the dietary sources and bioactivities of melatonin, with special attention paid to the mechanisms of action.

Ginsenoside Rb1 alleviates aluminum chloride-induced rat osteoblasts dysfunction

Osteoblasts dysfunction, induced by aluminum (Al), plays a critical role in the osteoporosis etiology. Ginsenoside Rb1 (Rb1) has the therapeutic properties for osteoporosis. This study aimed to assess the efficiency of Rb1 in ameliorating Al-induced osteoblasts dysfunction. The osteoblasts were divided into four groups: Rb1-treated group (RG, 0.0145mg/mL Rb1), control group (CG, 0), AlCl₃-treated group (AG, 0.126mg/mL AlCl₃·6H₂O), AlCl₃+Rb1-treated group (ARG, 0.0145mg/mL Rb1 and 0.126mg/mL AlCl₃·6H₂O). After 24h of culture, the osteoblasts viability, the transforming growth factor-β1 (TGF-_β1), bone morphogenetic protein-2 (BMP-2), the insulin-like growth factor I (IGF-I), core-binding factor α1 (Cbfα1) mRNA expressions, glutathione perioxidase (GSH-P_x) and superoxide dismutase (SOD) activities, and reactive oxygen species (ROS) concentration were determined. The osteoblasts ultrastructural features were also observed. In the ARG, the osteoblasts viability, TGF-_β1, BMP-2, IGF-I and Cbfα1 mRNA expressions and the GSH-P_x and SOD activities were significantly increased, the ROS concentration was significantly decreased, and osteoblasts histology lesion was attenuated compared with the AG. These results demonstrated that Rb1 could significantly reverse osteoblasts viability and osteoblasts growth regulation factor, inhibit oxidative stress, and attenuate histology lesion in the osteoblasts with AlCl₃. These results indicate that Rb1 can effectively alleviate the AlCl₃-induced osteoblasts dysfunction.

Melatonin: an ancient molecule that makes oxygen metabolically tolerable

Melatonin is remarkably functionally diverse with actions as a free radical scavenger and antioxidant, circadian rhythm regulator, anti-inflammatory and immunoregulating molecule, and as an oncostatic agent. We hypothesize that the initial and primary function of melatonin in photosynthetic cyanobacteria, which appeared on Earth 3.5-3.2 billion years ago, was as an antioxidant. The evolution of melatonin as an antioxidant by this organism was necessary as photosynthesis is associated with the generation of toxic-free radicals. The other secondary functions of melatonin came about much later in evolution. We also surmise that mitochondria and chloroplasts may be primary sites of melatonin synthesis in all eukaryotic cells that possess these organelles. This prediction is made on the basis that mitochondria and chloroplasts of eukaryotes developed from purple nonsulfur bacteria (which also produce melatonin) and cyanobacteria when they were engulfed by early eukaryotes. Thus, we speculate that the melatonin-synthesizing actions of the engulfed bacteria were retained when these organelles became mitochondria and chloroplasts, respectively. That mitochondria are likely sites of melatonin formation is supported by the observation that this organelle contains high levels of melatonin that are not impacted by blood melatonin concentrations. Melatonin has a remarkable array of means by which it thwarts oxidative damage. It, as well as its metabolites, is differentially effective in scavenging a variety of reactive oxygen and reactive nitrogen species. Moreover, melatonin and its metabolites modulate a large number of antioxidative and pro-oxidative enzymes, leading to a reduction in oxidative damage. The actions of melatonin on radical metabolizing/producing enzymes may be mediated by the Keap1-Nrf2-ARE pathway. Beyond its direct free radical scavenging and indirect antioxidant effects, melatonin has a variety of physiological and metabolic advantages that may enhance its ability to limit oxidative stress.