Melatonin ameliorates nickel induced autophagy in mouse brain: diminution of oxidative stress

Melatonin is a Neuroprotective and Antioxidant Agent against Neurotoxicity Induced by an Intrahippocampal Injection of Nickel in Rats

The investigation into the hippocampal function and its response to heavy metal exposure is crucial for understanding the mechanisms underlying neurotoxicity, this can potentially inform strategies for mitigating the adverse effects associated with heavy metal exposure. Melatonin is an essential neuromodulator known for its efficacy as an antioxidant. In this study, we aimed to determine whether melatonin could protect against Nickel (Ni) neurotoxicity. To achieve this, we performed an intracerebral injection of Ni (300 µM NiCl2) into the right hippocampus of male Wistar rats, followed by melatonin treatment. Based on neurobehavioral and neurobiochemical assessments, our results demonstrate that melatonin efficiently enhances Ni-induced behavioral dysfunction and cognitive impairment. Specifically, melatonin treatment positively influences anxious behavior, significantly reduces immobility time in the forced swim test (FST), and improves learning and spatial memory abilities. Moreover, neurobiochemical assays revealed that melatonin treatment modulates the Ni-induced alterations in oxidative stress balance by increasing antioxidant enzyme activities, such as superoxide dismutase (SOD) and catalase (CAT). Additionally, we observed that melatonin significantly attenuated the increased levels of lipid peroxidation (LPO) and nitric oxide (NO). In conclusion, the data from this study suggests that melatonin attenuates oxidative stress, which is the primary mechanism responsible for Ni-induced neurotoxicity. Considering that the hippocampus is the main structure involved in the pathology associated with heavy metal intoxication, such as Ni, these findings underscore the potential therapeutic efficacy of melatonin in mitigating heavy metal-induced brain damage.

Exogenous Melatonin Alleviates Atrazine-Induced Glucose Metabolism Disorders in Mice Liver via Suppressing Endoplasmic Reticulum Stress

Atrazine (ATZ) is a widely used herbicide that has toxic effects on animals. Melatonin (MLT) is a natural hormone with strong antioxidant properties. However, the effect of MLT on the glucose metabolism disorder caused by ATZ is still unclear. Mice were divided into four groups randomly and given 21 days of gavage: blank control group (Con), 5 mg/kg MLT group (MLT), 170 mg/kg ATZ group (ATZ), and 170 mg/kg ATZ and 5 mg/kg MLT group (ATZ + MLT). The results show that ATZ alters mRNA levels of metabolic enzymes related to glycogen synthesis and glycolysis and increased metabolites (glycogen, lactate, and pyruvate). ATZ causes abnormalities in glucose metabolism in mouse liver, interfering with glycemia regulation ability. MLT can regulate the endoplasmic reticulum to respond to disordered glucose metabolism in mice liver. This study suggested that MLT has the power to alleviate the ATZ-induced glycogen overdeposition and glycolytic deficit.

Melatonin alleviates 3,3',4,4',5-pentachlorobenzene induced colon injury by relieving oxidative stress

3,3',4,4',5-pentachlorobiphenyl (PCB126) is widely distributed, non-degradable and bioaccumulative, which can affect the function of tissues and organs of the living organisms. Melatonin (MT) is a sort of indole neurohormone that is mainly secreted by the pineal gland. Numerous studies have shown that MT can alleviate intestinal injury through various mechanisms such as antioxidant, anti-inflammatory, and anti-apoptosis. For the above reasons, the aim of this study is to explore the mechanism of intestinal injury in mice after exposure to PCB126 as well as the antagonistic effect of MT. Mice were respectively fed PCB126 (0.326 mg/kg) and/or MT (10 mg/kg) in vivo. In vitro, colonic epithelial cells (MCEC) were treated with PCB126 (150 μM) and/or MT (2 mM). We found that the microscopic structure of colon tissue was impaired after exposure to PCB126. The levels of oxidative stress, the protein and mRNA levels of expression of inflammatory related factors were significantly increased and the expression levels of intestinal tight junction protein were decreased. Notably, MT can promote Nrf2/HO-1 expression level and reduce the colonic injury caused by PCB126. Further in vitro treatment with reactive oxygen species inhibitors (NAC) showed that it significantly alleviated PCB126-induced in MCEC cell damage. In summary, the above results suggested that MT alleviates PCB126-induced colon inflammation by inhibiting the overproduction of reactive oxygen species (ROS) and up-regulating the expression level of intestinal tight junction protein. Our results contribute to the further comprehension of the intestinal toxicity effects of PCB126 and the significant role of MT in preserving the mechanisms of intestinal injury.

Role of Txnrd3 in NiCl2-induced kidney cell apoptosis in mice: Potential therapeutic effect of melatonin

Nickel (Ni) exposure is a significant risk factor for kidney dysfunction and oxidative stress injury in humans. Thioredoxin reductase 3 (Txnrd3), an important enzyme in animals, plays a role in maintaining cellular homeostasis and regulating oxidative stress. However, its protective effect against kidney injury has been determined. Melatonin (Mel) has antioxidant and anti-apoptotic effects and therefore may be a preventive and therapeutic agent for kidney injury. Our study aimed to investigate the roles of Mel and Txnrd3 in the treatment of nickel-induced renal injury. We divided 80 wild-type mice and 80 Txnrd3 -/- mice (C57BL/6 N) into a control group treated with saline, Ni group treated with 10 mg/kg NiCl2, Mel group treated with 2 mg/kg Mel, and Ni + Mel group given NiCl2 and Mel for 21 days. Histopathological and ultrastructural observation of the kidney showed that nuclei were wrinkled and mitochondrial cristae were broken in the Ni group, and these changes were significantly attenuated by Mel treatment. Mitochondrial and nuclear damage improved significantly in the Ni + Mel and Txnrd3-/- Ni + Mel groups. Furthermore, NiCl2 exposure decreased T-AOC, SOD, and GSH activities in the kidney. The decreases in antioxidant enzyme activity were attenuated by Mel, and these improvements were abolished by Txnrd3 knockout. NiCl2-induced increases in the mRNA and protein levels of apoptosis factors (Bax, Cyt-c, caspase-3, and caspase-9) were attenuated by Mel treatment, and Txnrd3 knockout abolished the repressive effect of Mel on apoptosis genes. Overall, we concluded that Mel improves oxidative stress and apoptosis induced by NiCl2 by regulating Txnrd3 expression in the kidney. Our results provide evidence for the role of Mel in NiCl2-induced kidney injury and identify Txnrd3 as a potential therapeutic target for renal injury.

Txnrd3 knockout enhancement of lung injury induced by Ni exposure via the VEGF-VEGFR-2 axis and alleviation of this effect by melatonin

Ni exposure leads to respiratory diseases in mice. Txnrd3 has been shown to have a protective effect on the body, but there is a paucity of empirical research focusing specifically on lung tissue. Melatonin possesses potent antioxidant, anti-inflammatory, and anti-fibrotic effects. By regulating inflammation-related factors, melatonin can activate the VEGF signaling pathway, ultimately alleviating lung injuries caused by Ni exposure. One hundred and sixty 8-week-old C57BL/6N mice, that were wild-type or Txnrd3-/- mice and 25-30 g in weight, were randomly divided into eight groups, including the NC group, Ni group, melatonin-treated group, and Ni plus melatonin group. Ni (10 mg/kg) was gavaged, and melatonin (2 mg/kg) was administered for 21 days. Inflammatory cells were found in the bronchioles of Txnrd3-/- mice under Ni exposure. Ultrastructural examination revealed that the homozygous-Ni group had a high amount of collagen fibers. The antioxidant capacity studies also revealed that mice lungs underwent oxidative stress. The results of qRT-PCR and WB showed that Ni induced an inflammatory response, which was also aggravated in Txnrd3-/- mice. Melatonin can effectively reduce the above symptoms. In conclusion, Ni causes lung injury by activating the VEGF-VEGFR-2 pathway and Txnrd3 knockout aggravates injury after Ni exposure.

The role of selenoprotein M in nickel-induced pyroptosis in mice spleen tissue via oxidative stress

Nickel (Ni) is a heavy metal element and a pollutant that threatens the organism's health. Melatonin (Mel) is an antioxidant substance that can be secreted by the organism and has a protective effect against heavy metals. Selenoprotein M (SelM) is a selenoprotein widely distributed of the body, and its role is to protect these tissues from oxidative damage. To study the mechanism of Ni, Mel, and SelM in mouse spleen, 80 SelM^+/+ wild-type and 80 SelM^-/- homozygous mice were divided into 8 groups with 20 mice in each group. The Ni group was intragastric at a concentration of 10 mg/kg, while the Mel group was intragastric at 2 mg/kg. Mice were injected with 0.1 mL/10 g body weight for 21 days. Histopathological and ultrastructural observations showed the changes in Ni, such as the destruction of white and red pulp and the appearance of pyroptosomes. SelM knockout showed more severe injury, while Mel could effectively interfere with Ni-induced spleen toxicity. The results of antioxidant capacity determination showed that Ni could cause oxidative stress in the spleen, and Mel could also effectively reduce oxidative stress. Finally, Ni exposure increased the expression levels of the pyroptotic genes, including apoptosis-associated speck protein (ASC), absent in melanoma-2 (AIM2), NOD-like receptor thermal protein domain-associated protein 3 (NLRP3), Caspase-1, interleukin- (IL-) 18, and IL-1β (p < 0.05). Loss of SelM significantly increased these (p < 0.05), while Mel decreased the alleviated impact of Ni. In conclusion, the loss of SelM aggravated Ni-induced pyroptosis of the spleen via activating oxidative stress, which was alleviated by Mel, but the effect of Mel was not obvious in the absence of SelM, which reflected the important role of SelM in Ni-induced pyroptosis.

Tannic acid antagonizes atrazine exposure-induced autophagy and DNA damage crosstalk in grass carp hepatocytes via NO/iNOS/NF-κB signaling pathway to maintain stable immune function

Atrazine (ATR) is a herbicide widely used in grass crops. The pollution of the soil and water environment is extremely harmful to aquatic animals and their offspring. iNOS/NO upregulation, DNA damage and cellular autophagy affect the immune function of fish liver cells. The effects of ATR at exposure doses on grass carp hepatocytes in terms of autophagy and DNA damage effects in genotoxicity, as well as the antagonistic effects of TAN on the above phenotypes and the internal mechanisms are not known. Therefore, we constructed control (Con group), ATR exposure (ATR group), TAN exposure (TAN group) and mixed group (ATR + TAN group) models on grass carp hepatocytes. Validation was performed by comet assay, MDC staining, qRT-PCR and protein blotting assay as well as iNOS/NO indicator levels and expression of immune factors as these experimental methods. Our data indicate that iNOS/NO assay kit measured that ATR treatment resulted in a significant increase in iNOS/NO activity and levels in grass carp hepatocytes (p < 0.05). We also found that NO/iNOS/NF-κB pathway genes were significantly activated (p < 0.05) at the exposure dose of ATR (3 μg mL-1). In addition, the proportion of cells that died due to DNA damage, autophagy, and immunotoxic effects was significantly increased at the exposure dose of ATR. Comet assay protein blotting detected increased DNA damage in cells at the ATR exposure dose (p < 0.05). MDC staining and qRT-PCR and protein blotting to detect the proportion of autophagic cells and autophagy-related genes also appeared upregulated at the exposed dose of ATR (p < 0.05). In brief, this study showed that ATR exposure caused cellular DNA damage and autophagy via the NO/iNOS/NF-κB axis, which led to immunotoxic effects and eventual death of grass carp hepatocytes. The present study facilitates the demonstration of the molecular mechanism of TAN alleviation of ATR cytotoxicity from the perspective of NO-mediated iNOS/NF-κB axis. It provides insights into the protection of farmed fish from agricultural contaminants and opens up new horizons in the use of natural plant-derived monomers for the clinical treatment of antagonistic triazine pesticide poisoning.

Melatonin Protects Against Titanium Oxide-Induced Neurotoxicity: Neurochemical, Neurobehavioral, and Histopathological Evidences

titania (titanium dioxide, TiO₂) is known to induce neurotoxicity and CNS dysfunctions. Numerous studies have explored the neuroprotective effects of melatonin against neurotoxicity. This study evaluates the potential of melatonin to protect against titania-induced neurotoxicity and the role of the Keap1/Nrf2/ARE signaling pathway. One group of animals were treated with Titania (0.045 and 0.075 g/rat) alone while the other with added melatonin (1 mg/kg and 3 mg/kg) and behavioral alterations were assessed using OFT (open field test). Neurochemical and histopathological changes were also studied in the hippocampus by analyzing kelch ECH associating protein 1 (Keap1), nuclear factor erythroid 2-related factor 2 (Nrf2), and antioxidant response element (ARE). It was seen that the animals with added Melatonin had improved behavioral scores in the OFT, like anxiety and motor dysfunction triggered by TiO₂. Melatonin also reduced lipid peroxidation, ROS, GSSG, IL1β, TNFα, Bax, and Keap1 levels, but boosted GSH, GPx, GR, SOD,IL10,IL4, Bcl2, Nrf2, and ARE levels and improved quadruple mitochondrial enzyme complex activity in titania-treated animals. Histopathological examination showed melatonin induced cytoprotection against vacuolization and necrosis in granular cells of DG and pyramidal cells of CA1 area of the hippocampus. In our study, pretreatment with melatonin reduced titania-induced neurotoxicity in the hippocampus through a mechanism potentially mediated by the Keap-1/Nrf2/ARE pathway.

Chlorpyrifos exposure induces calcium-dependent necrosis in carp (Cyprinus carpio) lymphocytes via the inhibition of T cell receptor gamma (TCR γ)

The insecticide chlorpyrifos plays an important role in agricultural production and is widely used because of its excellent insecticidal ability. However, the mechanism by which chlorpyrifos causes lymphocyte death remains unclear. In this study, transcriptomic techniques were used to analyze the head kidney tissues of carp (Cyprinus carpio) treated with chlorpyrifos. Subsequently, we screened out differentially expressed genes (DEGs) and performed the corresponding processing in the head kidney lymphocyte. Then, the intracellular calcium content and necrosis were detected by fluorescence staining, real-time fluorescence quantitative PCR, and flow cytometry. Our results showed that the expression of T cell receptor gamma (TCR γ) was significantly decreased, and TCR γ was inhibited after chlorpyrifos treatment. Also, TCR γ significantly increased the abundance of calcium channel messenger RNA (mRNA). To verify this result, we established the TCR γ overexpression group and found that the reverse results were observed in TCR γ of in the overexpression group. The results of cytoplasmic calcium concentration detection, calcium staining, and flow cytometry confirmed the conclusion of increased calcium in the cytoplasm. The function of TCR γ significantly enhanced the mRNA expression levels of necrosis-related genes, and this conclusion was evidenced by the result of necrotic flow detection. Our results showed that chlorpyrifos could inhibit TCR γ in carp lymphocytes and induce calcium-dependent necrosis.