Melatonin promotes Bax sequestration to mitochondria reducing cell susceptibility to apoptosis via the lipoxygenase metabolite 5-hydroxyeicosatetraenoic acid

Revealing Melatonin's Mysteries: Receptors, Signaling Pathways, and Therapeutics Applications

Melatonin (5-methoxy-acetyl tryptamine) is a sleep-inducing hormone, and the pineal gland produces it in response to the circadian clock of darkness. In the body, MT1 and MT2 receptors are mostly found, having an orthosteric pocket and ligand binding determinants. Melatonin acts by binding on melatonin receptors, intracellular proteins, and orphan nuclear receptors. It inhibits adenyl cyclase and activates phospholipase C, resulting in gene expression and an intracellular alteration environment. Melatonin signaling pathways are also associated with other intracellular signaling pathways, i. e., cAMP/PKA and MAPK/ERK pathways. Relative expression of different proteins depends on the coupling profile of G protein, accounting pharmacology of the melatonin receptor bias system, and mediates action in a Gi-dependent manner. It shows antioxidant, antitumor, antiproliferative, and neuroprotective activity. Different types of melatonin agonists have been synthesized for the treatment of sleeping disorders. Researchers have developed therapeutics that target melatonin signaling, which could benefit a wide range of medical conditions. This review focuses on melatonin receptors, pharmacology, and signaling cascades; it aims to provide basic mechanical aspects of the receptor's pharmacology, melatonin's functions in cancer and neurodegenerative diseases, and any treatments and drugs designed for these diseases. This will allow a basic comparison between the receptors in question, highlighting any parallels and differences that may exist and providing fundamental knowledge about these receptors to future researchers.

Melatonin ameliorates retinal ganglion cell senescence and apoptosis in a SIRT1-dependent manner in an optic nerve injury model

Melatonin is involved in exerting protective effects in aged-related and neurodegenerative diseases through a silent information regulator type 1 (SIRT1)-dependent pathway. However, little was known about the impact of melatonin on retinal ganglion cell (RGC) senescence and apoptosis following optic nerve crush (ONC). Thus, this study aimed to examine the effects of melatonin on RGC senescence and apoptosis after ONC and investigate the involvement of SIRT1 in this process. To study this, an ONC model was established. EX-527, an inhibitor of SIRT1, was injected intraperitoneally into mice. And melatonin was administrated abdominally into mice after ONC every day. Hematoxylin & eosin staining, retina flat-mounts and optical coherence tomography were used to evaluate the loss of retina cells/neurons. Pattern electroretinogram (p-ERG) was performed to evaluate the function of RGCs. Immunofluorescence and western blot were used to evaluate protein expression. SA-β-gal staining was employed to detect senescent cells. The results demonstrated that melatonin partially rescued the expression of SIRT1 in RGC 3 days after ONC. Additionally, melatonin administration partly rescued the decreased RGC number and ganglion cell complex thickness observed 14 days after ONC. Melatonin also suppressed ONC-induced senescence and apoptosis index. Furthermore, p-ERG showed that melatonin improved the amplitude of P50, N95 and N95/P50 following ONC. Importantly, the protective effects of melatonin were reversed when EX-527 was administered. In summary, this study revealed that melatonin attenuated RGC senescence and apoptosis through a SIRT1-dependent pathway after ONC. These findings provide valuable insights for the treatment of RGC senescence and apoptosis.

Melatonin Alleviates Lipopolysaccharide-Induced Abnormal Pregnancy through MTNR1B Regulation of m6A

Pregnancy is a highly intricate and delicate process, where inflammation during early stages may lead to pregnancy loss or defective implantation. Melatonin, primarily produced by the pineal gland, exerts several pharmacological effects. N6-methyladenosine (m6A) is the most prevalent mRNA modification in eukaryotes. This study aimed to investigate the association between melatonin and m6A during pregnancy and elucidate the underlying protective mechanism of melatonin. Melatonin was found to alleviate lipopolysaccharide (LPS)-induced reductions in the number of implantation sites. Additionally, it mitigated the activation of inflammation, autophagy, and apoptosis pathways, thereby protecting the pregnancy process in mice. The study also revealed that melatonin regulates uterine m6A methylation levels and counteracts abnormal changes in m6A modification of various genes following LPS stimulation. Furthermore, melatonin was shown to regulate m6A methylation through melatonin receptor 1B (MTNR1B) and subsequently modulate inflammation, autophagy, and apoptosis through m6A. In conclusion, our study demonstrates that melatonin protects pregnancy by influencing inflammation, autophagy, and apoptosis pathways in an m6A-dependent manner via MTNR1B. These findings provide valuable insights into the mechanisms underlying melatonin's protective effects during pregnancy and may have implications for potential therapeutic strategies in managing pregnancy-related complications.

Mitochondrial regulatory mechanisms in spinal cord injury: A narrative review

Spinal cord injury is a severe central nervous system injury that results in the permanent loss of motor, sensory, and autonomic functions below the level of injury with limited recovery. The pathological process of spinal cord injury includes primary and secondary injuries, characterized by a progressive cascade. Secondary injury impairs the ability of the mitochondria to maintain homeostasis and leads to calcium overload, excitotoxicity, and oxidative stress, further exacerbating the injury. The defective mitochondrial function observed in these pathologies accelerates neuronal cell death and inhibits regeneration. Treatment of spinal cord injury by preserving mitochondrial biological function is a promising, although still underexplored, therapeutic strategy. This review aimed to explore mitochondrial-based therapeutic advances after spinal cord injury. Specifically, it briefly describes the characteristics of spinal cord injury. It then broadly discusses the drugs used to protect the mitochondria (e.g., cyclosporine A, acetyl-L-carnitine, and alpha-tocopherol), phenomena associated with mitochondrial damage processes (e.g., mitophagy, ferroptosis, and cuproptosis), mitochondrial transplantation for nerve cell regeneration, and innovative mitochondrial combined protection therapy.

Melatonin Type 2 Receptor Activation Regulates Blue Light Exposure-Induced Mouse Corneal Epithelial Damage by Modulating Impaired Autophagy and Apoptosis

The MT1/2 receptors, members of the melatonin receptor, belong to G protein-coupled receptors and mainly regulate circadian rhythms and sleep in the brain. Previous studies have shown that in many other cells and tissues, such as HEK293T cells and the retina, MT1/2 receptors can be involved in mitochondrial homeostasis, antioxidant, and anti-inflammatory responses. In our study, we aimed to investigate the effects of blue light (BL) exposure on the expression of melatonin and its receptors in the mouse cornea and to evaluate their functional role in corneal epithelial damage. After exposing 8-week-old C57BL/6 mice to BL at 25 and 100 J/cm² twice a day for 14 days, a significant increase in the expression of 4-HNE and MT2 was observed in the cornea. MT2 antagonist-treated mice exposed to BL showed an increased expression of p62 and decreased expression of BAX and cleaved caspase 3 compared with mice exposed only to BL. In addition, MT2 antagonist-treated mice showed more enhanced MDA and corneal damage. In conclusion, BL exposure can induce MT2 expression in the mouse cornea. MT2 activation can modulate impaired autophagy and apoptosis by increasing the expression of BAX, an apoptosis activator, thereby regulating the progression of corneal epithelial damage induced by BL exposure.

Hypoxia: Role of SIRT1 and the protective effect of resveratrol in ovarian function

Background

Ovarian function is closely related to the degree of vascular network development surrounding the ovary. Maternal aging‐related construction defects in this vascular network can cause ovarian hypoxia, which impedes oocyte nutrient supply, leading to physiological changes in the ovaries and oocytes. The anti‐aging gene Sirtuin 1 (SIRT1) senses and adapts to ambient stress and is associated with hypoxic environments and mitochondrial biogenesis.

Methods

The present study is a literature review focusing on investigations involving the changes in SIRT1 and mitochondrial expression during hypoxia and the cytoprotective effects of the SIRT1 activator, resveratrol.

Main findings

Hypoxia suppresses SIRT1 and mitochondrial expression. Resveratrol can reverse the hypoxia‐induced decrease in mitochondrial and SIRT1 activity. Resveratrol suppresses the production of hypoxia‐inducible factor‐1α and vascular endothelial growth factor proteins.

Conclusion

Resveratrol exhibits protective activity against hypoxic stress and may prevent hypoxia‐ or aging‐related mitochondrial dysfunction. Resveratrol treatment may be a potential option for infertility therapy.

Orexin-A Regulates Follicular Growth, Proliferation, Cell Cycle and Apoptosis in Mouse Primary Granulosa Cells via the AKT/ERK Signaling Pathway

Granulosa cells (GCs) are essential for follicular growth, development, and atresia. The orexin-A (OXA) neuropeptide is widely involved in the regulation of various biological functions. OXA selectively binds to orexin receptor type 1 (OX1R) and mediates all its biological actions via OX1R. This study aimed to explore the expression of OXA and OX1R and their regulatory role in GCs proliferation, cell cycle progression, apoptosis, oocyte maturation, and underlying molecular mechanisms of these processes and elucidate its novel signaling pathway. Western blotting and RT-qPCR showed that OXA and OX1R were expressed during different developmental stages of GCs, and siRNA transfection successfully inhibited the expression of OX1R at the translational and transcriptional levels. Flow cytometry revealed that OX1R knockdown upregulated GCs apoptosis and triggered S-phase arrest in cell cycle progression. RT-qPCR and Western blotting showed significantly reduced expression of Bcl-2 and elevated expression of Bax, caspase-3, TNF-α, and P21 in OX1R-silenced GCs. Furthermore, the CCK-8 assay showed that knockdown of OX1R suppressed GCs proliferation by downregulating the expression of PCNA, a proliferation marker gene, at the translational and transcriptional levels. Western blotting revealed that knockdown of OX1R resulted in a considerable decrease of the phosphorylation level of the AKT and ERK1/2 proteins, indicating that the AKT/ERK1/2 pathway is involved in regulating GCs proliferation and apoptosis. In addition, OX1R silencing enhanced the mRNA expression of GDF9 and suppressed the mRNA expression of BMP15 in mouse GCs. Collectively, these results reveal a novel regulatory role of OXA in the development of GCs and folliculogenesis by regulating proliferation, apoptosis, and cell cycle progression. Therefore, OXA can be a promising therapeutic agent for female infertility.

Luzindole and 4P-PDOT block the effect of melatonin on bovine granulosa cell apoptosis and cell cycle depending on its concentration

Granulosa cells play an essential physiological role in mediating the follicle development and survival or apoptosis of granulosa cells dictate the follicle development or atresia. The aim of this study was to investigate the role of high dose (10-5 M) and low dose (10-9 M) melatonin in bovine granulosa cells, and assess whether MT1 and MT2 inhibiter affect granulosa cells response to melatonin. We found that the high dose (10-5 M) and low dose (10-9 M) both could act as an essential role in modulating granulosa cells apoptosis, cell cycle and antioxidant. The beneficial effect could be related to that melatonin promoted the expression of Bcl2, Bcl-xl, SOD1 and GPX4, and inhibited Bax, caspase-3 and p53 expression. Moreover P21 expression was decreased in granulosa cells treated with the high dose (10-5 M) melatonin and increased in that treated with the low dose (10-9 M) melatonin. To further reveal the role of MT1 and MT2 in mediating the effect of melatonin on granulosa cells apoptosis, cell cycle and antioxidant, we found that the luzindole and 4P-PDOT did not affect the effect of high dose (10-5 M) melatonin on regulating Bcl2, Bax, caspase-3, SOD1, GPX4 and p53 expression, while blocked its effect on modulating Bcl-xl and P21expression. However, luzindole and 4P-PDOT disturbed the effect of low dose (10-9 M) melatonin on regulating Bcl2, Bax, caspase-3, Bcl-xl, SOD1, GPX4, and p53 expression. In conclusion, these results reveal that the effect of low dose (10-9 M) melatonin on granulosa cells apoptosis are mediated by MT1 and MT2, and the high dose (10-5 M) melatonin affect the granulosa cells apoptosis by other pathway, besides MT1 and MT2. Moreover MT1 and MT2 may work in concert to modulate bovine granulosa cells function by regulating cellular progression and apoptosis.

The Molecular Mechanism of Aluminum Phosphide poisoning in Cardiovascular Disease: Pathophysiology and Diagnostic Approach

Nowadays, poisoning with metal phosphides, especially aluminum phosphide (ALP), is one of the main health threats in human societies. Patients suffer from significant complications due to this type of poisoning, and the heart is one of the main organs targeted by ALP. Therefore, in this study, we discussed the effect of phosphine on cardiac function. This study is based on data obtained from PubMed, between 2002 and 2020. The key keywords included "Aluminum phosphide," "Oxidative Stress," "Mitochondria," "Cardiovascular disease," and "Treatment." The results showed that ALP produced reactive oxygen species (ROS) due to mitochondrial dysfunction. ROS production leads to red blood cell hemolysis, decreased ATP production, and induction of apoptosis in cardiomyocytes, which eventually results in cardiovascular disease. Since ALP has the most significant effect on cardiomyocytes, the use of appropriate treatment strategies to restore cell function can increase patients' survival.

The Protective Effects of Melatonin on Aluminum-Induced Hepatotoxicity and Nephrotoxicity in Rats

Aluminum (Al) is a ubiquitous element with known toxicity for both humans and animals. Herein, we aimed to investigate the potential role of melatonin (MEL) in hepatotoxicity and nephrotoxicity following aluminum chloride (AlCl₃) treatment in rats. Adult male rats were treated with AlCl₃ (34 mg/kg bwt) for eight weeks. Exposure to AlCl₃ enhanced the serum activities of the liver transaminases (alanine aminotransferase and aspartate aminotransferase) and increased the level of bilirubin, in addition to the serum kidney function markers urea and creatinine. AlCl₃ intoxication boosted oxidative stress, as evidenced by increases in the levels of lipid peroxidation (LPO) and nitric oxide (NO) along with simultaneous decreases in the levels of glutathione (GSH), various antioxidant enzymes, and Nrf2 mRNA expression. MEL (5 mg/kg bwt) treatment repressed LPO and NO levels, whereas it augmented GSH content. The activities of the antioxidant enzymes GPx, SOD, CAT, and GR were also restored concomitantly when MEL was administered before AlCl₃. MEL also suppressed the apoptotic effect of AlCl₃ by enhancing Bcl-2 protein expression in the liver and kidney and decreasing the expression levels of proinflammatory cytokines. Histopathological findings in the liver and kidney tissues confirmed the beneficial effect of MEL against AlCl₃ toxicity. These findings indicate that MEL prevents AlCl₃ toxicity by enhancing the antioxidant defense system.

Cellular Mechanisms of Melatonin: Insight from Neurodegenerative Diseases

Neurodegenerative diseases are the second most common cause of death and characterized by progressive impairments in movement or mental functioning in the central or peripheral nervous system. The prevention of neurodegenerative disorders has become an emerging public health challenge for our society. Melatonin, a pineal hormone, has various physiological functions in the brain, including regulating circadian rhythms, clearing free radicals, inhibiting biomolecular oxidation, and suppressing neuroinflammation. Cumulative evidence indicates that melatonin has a wide range of neuroprotective roles by regulating pathophysiological mechanisms and signaling pathways. Moreover, melatonin levels are decreased in patients with neurodegenerative diseases. In this review, we summarize current knowledge on the regulation, molecular mechanisms and biological functions of melatonin in neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, vascular dementia and multiple sclerosis. We also discuss the clinical application of melatonin in neurodegenerative disorders. This information will lead to a better understanding of the regulation of melatonin in the brain and provide therapeutic options for the treatment of various neurodegenerative diseases.

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.

Melatonin and non-small cell lung cancer: new insights into signaling pathways

Non-small-cell lung cancer (NSCLC) is a type of malignancy with progressive metastasis having poor prognosis and lowered survival resulting from late diagnosis. The therapeutic approaches for the treatment of this incurable cancer are chemo- and radiotherapy. Since current treatments are insufficient and because of drug-induced undesirable side effects and toxicities, alternate treatments are necessary and critical. The role of melatonin, produced in and released from the pineal gland, has been documented as a potential therapy for NSCLC. Melatonin prevents tumor metastasis via inducing apoptosis processes and restraining the autonomous cell proliferation. Moreover, melatonin inhibits the progression of tumors due to its oncostatic, pro-oxidant and anti-inflammatory effects. As a result, the combined treatment with melatonin and chemotherapy may have a synergistic effect, as with some other tumors, leading to a prolonged survival and improved quality of life in patients with NSCLC. This review summarizes the available data, based on the molecular mechanisms and related signaling pathways, to show how melatonin and its supplementation function in NSCLC.

Nicotinamide adenine dinucleotide emerges as a therapeutic target in aging and ischemic conditions

Nicotinamide adenine dinucleotide (NAD⁺) has been described as central coenzyme of redox reactions and is a key regulator of stress resistance and longevity. Aging is a multifactorial and irreversible process that is characterized by a gradual diminution in physiological functions in an organism over time, leading to development of age-associated pathologies and eventually increasing the probability of death. Ischemia is the lack of nutritive blood flow that causes damage and mortality that mostly occurs in various organs during aging. During the process of aging and related ischemic conditions, NAD⁺ levels decline and lead to nuclear and mitochondrial dysfunctions, resulting in age-related pathologies. The majority of studies have shown that restoring of NAD⁺ using supplementation with intermediates such as nicotinamide mononucleotide and nicotinamide riboside can be a valuable strategy for recovery of ischemic injury and age-associated defects. This review summarizes the molecular mechanisms responsible for the reduction in NAD⁺ levels during ischemic disorders and aging, as well as a particular focus is given to the recent progress in the understanding of NAD⁺ precursor's effects on aging and ischemia.

Melatonin attenuates caspase-dependent apoptosis in the thoracic aorta by regulating element balance and oxidative stress in pinealectomised rats

The aim of this study was to explain the possible mechanisms by which melatonin deficiency results in cardiovascular injury and to investigate the effects of melatonin administration on important signalling pathways and element equilibrium in the thoracic aorta (TA). For this purpose, we analysed the cellular and molecular effects of melatonin deficiency or administration on oxidative stress, DNA damage, molecular chaperone response, and apoptosis induction in TA tissues of pinealectomised rats using ELISA, RAPD, qRT-PCR, and Western blot assays. The results showed that melatonin deficiency led to an imbalance in essential element levels, unfolded or misfolded proteins, increased lipid peroxidation, and selectively induced caspase-dependent apoptosis in TA tissues without significantly affecting the Bcl-2/BAX ratio (2.28 in pinealectomised rats, 2.73 in pinealectomised rats treated with melatonin). In pinealectomised rats, the genomic template stability (80.22%) was disrupted by the significantly increased oxidative stress, and heat shock protein 70 (20.96-fold), TNF-α (1.73-fold), caspase-8 (2.03-fold), and caspase-3 (2.87-fold) were markedly overexpressed compared with the sham group. Melatonin treatment was protective against apoptosis and inhibited oxidative damage. In addition, melatonin increased the survivin level and improved the regulation of element equilibrium in TA tissues. The results of the study indicate that melatonin deficiency induces TNF-α-related extrinsic apoptosis signals and that the administration of pharmacological doses of melatonin attenuates cardiovascular toxicity by regulating the increase in the rate of apoptosis caused by melatonin deficiency in TA tissue of Sprague–Dawley rats.

RNAi-mediated knockdown of MTNR1B without disrupting the effects of melatonin on apoptosis and cell cycle in bovine granulose cells

Melatonin is well known as a powerful free radical scavenger and exhibits the ability to prevent cell apoptosis. In the present study, we investigated the role of melatonin and its receptor MTNR1B in regulating the function of bovine granulosa cells (GCs) and hypothesized the involvement of MTNR1B in mediating the effect of melatonin on GCs. Our results showed that MTNR1B knockdown significantly promoted GCs apoptosis but did not affect the cell cycle. These results were further verified by increasing the expression of pro-apoptosis genes (BAX and CASP3), decreasing expression of the anti-apoptosis genes (BCL2 and BCL-XL) and anti-oxidant genes (SOD1 and GPX4) without affecting cell cycle factors (CCND1, CCNE1 and CDKN1A) and TP53. In addition, MTNR1B knockdown did not disrupt the effects of melatonin in suppressing the GCs apoptosis or blocking the cell cycle. Moreover, MTNR1B knockdown did not affect the role of melatonin in increasing BCL2, BCL-XL, and CDKN1A expression, or decreasing BAX, CASP3, TP53, CCND1 and CCNE1 expression. The expression of MTNR1A was upregulated after MTNR1B knockdown, and melatonin promoted MTNR1A expression with or without MTNR1B knockdown. However, despite melatonin supplementation, the expression of SOD1 and GPX4 was still suppressed after MTNR1B knockdown. In conclusion, these findings indicate that melatonin and MTNR1B are involved in BCL2 family and CASP3-dependent apoptotic pathways in bovine GCs. MTNR1A and MTNR1B may coordinate the work of medicating the appropriate melatonin responses to GCs.

Melatonin diminishes oxidative damage in sperm cells, improving assisted reproductive techniques

Sperm preparation procedures are a potential generator of oxidative stress-induced DNA damage, which leads to a dramatic drop in fertility. An increasing number of studies suggest that melatonin reduces the oxidative stress induced by manipulation. However, very little is known about the preservative role of melatonin in sperm preparation medium during assisted reproduction procedures. For this aim to be achieved, semen was divided into two fractions and preincubated with and without 1 mM melatonin. Afterwards, both fractions were divided into two subfractions to perform swim-up in the presence and absence of 1 mM melatonin. Labeling with anti-CD46 and antiactive caspase-3 allowed the monitoring of acrosome reaction and apoptosis by flow cytometry. Sperm DNA fragmentation and compaction were analyzed through propidium iodide staining. The normozoospermic and oligozoospermic samples that were preincubated with melatonin underwent a significant increase in the ratio of adequate spermatozoa and a reduction of caspase-3 activation. Additionally, preincubation with melatonin enhanced the migration of sperm cells with compacted DNA in oligozoospermic samples (P < 0.05) and prevented DNA fragmentation in normozoospermic samples (P < 0.05). In light of the current results, the cytoprotective capacity and innocuousness of melatonin make it a great candidate to be applied in assisted reproduction techniques in order to prevent triaogenic oxidative damage.

Melatonin as a mitochondrial protector in neurodegenerative diseases

Mitochondria are crucial organelles as their role in cellular energy production of eukaryotes. Because the brain cells demand high energy for maintaining their normal activities, disturbances in mitochondrial physiology may lead to neuropathological events underlying neurodegenerative conditions such as Alzheimer's disease, Parkinson's disease and Huntington's disease. Melatonin is an endogenous compound with a variety of physiological roles. In addition, it possesses potent antioxidant properties which effectively play protective roles in several pathological conditions. Several lines of evidence also reveal roles of melatonin in mitochondrial protection, which could prevent development and progression of neurodegeneration. Since the mitochondrial dysfunction is a primary event in neurodegeneration, the neuroprotection afforded by melatonin is thereby more effective in early stages of the diseases. This article reviews mechanisms which melatonin exerts its protective roles on mitochondria as a potential therapeutic strategy against neurodegenerative disorders.

Aspartate β-hydroxylase disrupts mitochondrial DNA stability and function in hepatocellular carcinoma

The mechanism of aberrant mitochondrial genome and function in hepatocellular carcinoma (HCC) remains largely unknown. Our previous study demonstrated an increased expression of aspartate β-hydroxylase (ASPH) in HCC tissues, which was associated with tumor invasiveness and a worse prognosis. Currently, we unexpectedly observed the presence of ASPH in purified mitochondrial protein fraction. In addition, immunostaining of both exogenously and endogenously expressed ASPH showed a colocalization with mitochondrial biomarkers. This study aimed to investigate whether the mitochondrial ASPH is involved in mitochondrial malfunction in HCC. Our results showed that ASPH overexpression in HCC tissues was correlated with decreased copy numbers of displacement loop (D-loop) and NADH dehydrogenase subunit 1 (ND-1) and enhanced D-loop mutation, suggesting the disrupted mitochondrial DNA (mtDNA) stability. The reduced mtDNA copy numbers were associated with aggressive clinicopathological features of HCC. The loss of mtDNA integrity induced by enforced expression of ASPH was accompanied with mitochondrial dysfunction, which was characterized by the aberrant mitochondrial membrane potential, decreased ATP generation and enhanced reactive oxygen species. In contrast, knocking down ASPH by siRNA in HCC cell lines showed the opposite impact on mtDNA integrity and function. Mass spectrometry and co-immunoprecipitation further identified that ASPH interacted with histone H2A member X (H2AX). ASPH overexpression diminished the interaction between H2AX and mitochondrial transcription factor A (mtTFA), an important DNA-binding protein for mtDNA replication, which then reduced the binding of mtTFA to D-loop region. Collectively, our results demonstrate that ASPH overexpression disrupts the mtDNA integrity through H2AX-mtTFA signal, thereby affecting mitochondrial functions in HCC.

On the mechanisms of melatonin in protection of aluminum phosphide cardiotoxicity

Aluminum phosphide (AlP), one of the most commonly used pesticides worldwide, has been the leading cause of self-poisoning mortalities among many Asian countries. The heart is the main organ affected in AlP poisoning. Melatonin has been previously shown to be beneficial in reversing toxic changes in the heart. The present study reveals evidence on the probable protective effects of melatonin on AlP-induced cardiotoxicity in rats. The study groups included a control (almond oil only), ethanol 5% (solvent), sole melatonin (50 mg/kg), AlP (16.7 mg/kg), and 4 AlP + melatonin groups which received 20, 30, 40 and 50 mg/kg of melatonin by intraperitoneal injections following AlP treatment. An electronic cardiovascular monitoring device was used to record the electrocardiographic (ECG) parameters. Heart tissues were studied in terms of oxidative stress biomarkers, mitochondrial complexes activities, ADP/ATP ratio and apoptosis. Abnormal ECG records as well as declined heart rate and blood pressure were found to be related to AlP administration. Based on the results, melatonin was highly effective in controlling AlP-induced changes in the study groups. Significant improvements were observed in the activities of mitochondrial complexes, oxidative stress biomarkers, the activities of caspases 3 and 9, and ADP/ATP ratio following treatment with melatonin at doses of 40 and 50 mg/kg. Our results indicate that melatonin can counteract the AlP-induced oxidative damage in the heart. This is mainly done by maintaining the normal balance of intracellular ATP as well as the prevention of oxidative damage. Further research is warranted to evaluate the possibility of using melatonin as an antidote in AlP poisoning.

Ginkgo biloba exocarp extracts induces apoptosis in Lewis lung cancer cells involving MAPK signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

A fruit of Ginkgo biloba L. is known as Ginkgo nuts. It is an edible traditional Chinese medicine, and could be used for the treatment of cancer thousands of years ago in China. The extracts prepared from the exocarp of Ginkgo biloba (Ginkgo biloba exocarp extracts, GBEE) has the effects of anti-cancer, immune promotion, anti-aging and etc.

AIM OF STUDY

To study the effects of GBEE inducing apoptosis in Lewis lung cancer (LLC) cells and the role of Mitogen-activated protein kinase(MAPK) signaling pathways in it.

MATERIALS AND METHODS

The LLC solid tumor model was established in C57BL/6J mice. The tumor-bearing mice were randomly divided into 5 groups. A normal control group without tumor cells was established additionally. There were 10 mice in each group, and they were dosed 24h after inoculation. The GBEE (50, 100, 200mg/kg b.w.) groups were dosed by intragastric gavage (i.g.). The mice in positive control group were intraperitoneal (i.p.) injected with cyclophosphamide (CPA) at a dose of 20mg/kg (b.w.). The model control group and the normal control group were both given normal saline (NS) by i.g.. All the groups were dosed at a volume of 0.1mL/10g (b.w.), once a day for 18d. The day after the last administration, the transplanted tumors was stripped and weighed, and the inhibition rate was calculated. In vitro experiments, MTT method was applied to detect the effects of GBEE on LLC cells and primary cultured mouse lung cells. Annexin V-FITC/PI method was used to detect the apoptosis rate of LLC cells. Rhodamine 123 method was used to detect the Mitochondrial transmembrane potential (MTP). Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to detect the levels of Fas mRNA. Western Blot was used to detect the expression of Bax, Bcl-2, Cyt C, cleaved Caspase-3 and MAPK proteins in the corresponding parts of LLC cells.

RESULTS

GBEE (50-200mg/kg) inhibited the growth of LLC transplanted tumors with a dose-effect relationship. GBEE (5-160µg/mL) inhibited the proliferation of LLC cells in vitro with the half maximal inhibitory concentration (IC50) value of 162.43µg/mL, while it had no significant inhibitory effects on the primary cultured mouse lung cells. After GBEE (10, 20 and 40µg/mL) acted on the LLC cells, the apoptosis rate was increased and the MTP was decreased. The ratio of Bax/Bcl-2 was increased in the cells. Meanwhile, it also promoted the translocation of Bax/Bcl-2 in mitochondrial membrane and the release of Cyt C from mitochondria to cytosol. In addition, it up-regulated the cleaved-Caspase-3 protein expression. The mRNA levels of Fas and the protein levels of Fas, FasL and p-p38 in the cells were both increased. The levels of p-ERK1/2 and p-JNK1/2 protein were down-regulated but the p38, ERK1/2 and JNK1/2 were not significantly changed.

CONCLUSIONS

GBEE induces apoptosis in LLC cells via mitochondrial-mediated intrinsic pathway and death receptor-mediated extrinsic pathway, which may be closely relevant to the regulation of MAPK signaling pathways.

Antioxidative, membrane protective and antiapoptotic effects of melatonin, in silico study of physico-chemical profile and efficiency of nanoliposome delivery compared to betaine

Hepatoprotective effects of melatonin mediated by the inhibition of apoptotic and oxidative processes and activation of survival pathways, in comparison with betaine, were studied in mouse hepatocytes undergone Fas-ligand apoptosis.

A review of the protective role of melatonin during phosphine-induced cardiotoxicity: focus on mitochondrial dysfunction, oxidative stress and apoptosis

OBJECTIVES

Acute poisoning with aluminium phosphide (AlP) is a major cause of mortality in developing countries. AlP mortality is due to cardiac dysfunction leading to cardiomyocyte death. The main mechanism is an inhibition of cytochrome c oxidase in the cardiomyocyte mitochondria, resulting in a decreased ATP production and oxidative stress. Unfortunately, the administration of exogenous drugs does not meet the desired requirements of an effective therapy. Melatonin is an amphiphilic molecule and can easily pass through all cellular compartments with the highest concentration recorded in mitochondria. It is known as a vigorous antioxidant, acting as a potent reactive oxygen species (ROS) scavenger. Our aim is to summarize the mechanisms by which melatonin may modulate the deteriorating effects of AlP poisoning on cardiac mitochondria.

KEY FINDINGS

Melatonin not only mitigates the inhibition of respiratory chain complexes, but also increases ATP generation. Moreover, it can directly inhibit the mitochondrial permeability transition pore (mPTP) opening, thus preventing apoptosis. In addition, melatonin inhibits the release of cytochrome c from mitochondria to hinder caspase activation leading to cell survival.

SUMMARY

Based on the promising effects of melatonin on mitochondria, melatonin may mitigate AlP-induced cardiotoxicity and might be potentially suggested as cardioprotective in AlP-intoxicated patients.

Cell type-dependent ROS and mitophagy response leads to apoptosis or necroptosis in neuroblastoma

A limiting factor in the therapeutic outcome of children with high-risk neuroblastoma is the intrinsic and acquired resistance to common chemotherapeutic treatments. Here we investigated the molecular mechanisms by which the hemisynthetic cardiac glycoside UNBS1450 overcomes this limitation and induces differential cell death modalities in both neuroblastic and stromal neuroblastoma through stimulation of a cell-type-specific autophagic response eventually leading to apoptosis or necroptosis. In neuroblastic SH-SY5Y cells, we observed a time-dependent production of reactive oxygen species that affects lysosomal integrity inducing lysosome-associated membrane protein 2 degradation and cathepsin B and L activation. Subsequent mitochondrial membrane depolarization and accumulation of mitochondria in phagophores occurred after 8h of UNBS1450 treatment. Results were confirmed by mitochondrial mass analysis, electron microscopy and co-localization of mitochondria with GFP-LC3, suggesting the impaired clearance of damaged mitochondria. Thus, a stress-induced defective autophagic flux and the subsequent lack of clearance of damaged mitochondria sensitized SH-SY5Y cells to UNBS1450-induced apoptosis. Inhibition of autophagy with small inhibitory RNAs against ATG5, ATG7 and Beclin-1 protected SH-SY5Y cells against the cytotoxic effect of UNBS1450 by inhibiting apoptosis. In contrast, autophagy progression towards the catabolic state was observed in stromal SK-N-AS cells: here reactive oxygen species (ROS) generation remained undetectable preserving intact lysosomes and engulfing damaged mitochondria after UNBS1450 treatment. Moreover, autophagy inhibition determined sensitization of SK-N-AS to apoptosis. We identified efficient mitophagy as the key mechanism leading to failure of activation of the apoptotic pathway that increased resistance of SK-N-AS to UNBS1450, triggering rather necroptosis at higher doses. Altogether we characterize here the differential modulation of ROS and mitophagy as a main determinant of neuroblastoma resistance with potential relevance for personalized anticancer therapeutic approaches.

HDAC1 inhibition by melatonin leads to suppression of lung adenocarcinoma cells via induction of oxidative stress and activation of apoptotic pathways

Melatonin is an indoleamine synthesized in the pineal gland that shows a wide range of physiological and pharmacological functions, including anticancer effects. In this study, we investigated the effect of melatonin on drug-induced cellular apoptosis against the cultured human lung adenocarcinoma cells and explored the role of histone deacetylase (HDAC) signaling in this process. The results showed that melatonin treatment led to a dose- and time-dependent decrease in the viability of human A549 and PC9 lung adenocarcinoma cells. Additionally, melatonin exhibited potent anticancer activity in vitro, as evidenced by reductions of the cell adhesion, migration, and the intracellular glutathione (GSH) level and increases in the apoptotic index, caspase 3 activity, and reactive oxygen species (ROS) in A549 and PC9 cells. Melatonin treatment also influenced the expression of HDAC-related molecules (HDAC1 and Ac-histone H3), upregulated the apoptosis-related molecules (PUMA and Bax), and downregulated the proliferation-related molecule (PCNA) and the anti-apoptosis-related molecule (Bcl2). Furthermore, the inhibition of HDAC signaling using HDAC1 siRNA or SAHA (a potent pan-inhibitor of HDACs) sensitized A549 and PC9 cells to the melatonin treatment. In summary, these data indicate that in vitro-administered melatonin is a potential suppressor of lung adenocarcinoma cells by the targeting of HDAC signaling and suggest that melatonin in combination with HDAC inhibitors may be a novel therapeutic intervention for human lung adenocarcinoma.