Autophagy upregulation and loss of NF-κB in oxidative stress-related immunodeficient SAMP8 mice

Efficacy of Melatonin in Animal Models of Subarachnoid Hemorrhage: A Systematic Review and Stratified Meta-Analysis

Background and Purpose: Subarachnoid hemorrhage (SAH) is a severe disease characterized by sudden headache, loss of consciousness, or focal neurological deficits. Melatonin has been reported as a potential neuroprotective agent of SAH. It provides protective effects through the anti-inflammatory effects or the autophagy pathway. Our systematic review aims to evaluate the efficacy of melatonin administration on experimental SAH animals and offer support for the future clinical trial design of the melatonin treatment following SAH.

Methods: The following online databases were searched for experimentally controlled studies of the effect of melatonin on SAH models: PubMed, Web of Knowledge, Embase, and China National Knowledge Infrastructure (all until March 2021). The melatonin effect on the brain water content (BWC) and neurological score (NS) were compared between the treatment and control groups using the standardized mean difference (SMD).

Results: Our literature identified 160 possible articles, and most of them were excluded due to duplication (n = 69) and failure to meet the inclusion criteria (n = 56). After screening the remaining 35 articles in detail, we excluded half of them because of no relevant outcome measures (n = 16), no relevant interventions (n = 3), review articles (n = 1), duplicated publications (n = 1), and studies on humans or cells (n = 2). Finally, this systematic review contained 12 studies between 2008 and 2018. All studies were written in English except for one study in Chinese, and all of them showed the effect of melatonin on BWC and NS in SAH models.

Conclusion: Our research shows that melatonin can significantly improve the behavior and pathological results of SAH animal models. However, due to the small number of studies included in this meta-analysis, the experimental design and experimental method limitations should be considered when interpreting the results. Significant clinical and animal studies are still required to evaluate whether melatonin can be used in the adjuvant treatment of clinical SAH patients.

Senescence-accelerated mouse prone 8 (SAMP8) mice exhibit reduced entoconid in the lower second molar

OBJECTIVE

The position and size of the major cusps in mammalian molars are arranged in a characteristic pattern that depends on taxonomy. In humans, the cusp which locates distally within each molar is smaller than the mesially located cusp, which is referred to as "distal reduction". Although this concept has been well-recognized, it is still unclear how this reduction occurs. Current study examined whether senescence-accelerating mouse prone 8 (SAMP8) mice could be a possible animal model for studying how the mammalian molar cusp size is determined.

DESIGN

SAMP8 mice were compared with parental control (SAMR1) mice. Microcomputed tomography images of young and aged mice were captured to observe molar cusp morphologies. Cusp height from cement-enamel junction and mesio-distal length of molars were measured. The statistical comparison of the measurements was performed by Mann-Whitney U test.

RESULTS

SAMP8 mice showed reduced development of the disto-lingual cusp (entoconid) of lower second molar when compared with SAMR1 mice. The enamel thickness and structure was disturbed at entoconid, and aged SAMP8 mice displayed severe wear of the entoconid in lower second molar. These phenotypes were observed on both sides of the lower second molar.

CONCLUSIONS

In addition to the general senescence phenotype observed in SAMP8 mice, this strain may genetically possess molar cusp phenotypes which is determined prenatally. Further, SAMP8 mice would be a potential model strain to study the genetic causes of the distal reduction of molar cusp size.

Melatonin/Nrf2/NLRP3 Connection in Mouse Heart Mitochondria during Aging

Aging is a major risk for cardiovascular diseases (CVD). Age-related disorders include oxidative stress, mitochondria dysfunction, and exacerbation of the NF-κB/NLRP3 innate immune response pathways. Some of the molecular mechanisms underlying these processes, however, remain unclear. This study tested the hypothesis that NLRP3 inflammasome plays a role in cardiac aging and melatonin is able to counteract its effects. With the aim of investigating the impact of NLRP3 inflammasome and the actions and target of melatonin in aged myocardium, we analyzed the expression of proteins implied in mitochondria dynamics, autophagy, apoptosis, Nrf2-dependent antioxidant response and mitochondria ultrastructure in heart of wild-type and NLRP3-knockout mice of 3, 12, and 24 months-old, with and without melatonin treatment. Our results showed that the absence of NLRP3 prevented age-related mitochondrial dynamic alterations in cardiac muscle with minimal effects in cardiac autophagy during aging. The deficiency of the inflammasome affected Bax/Bcl2 ratio, but not p53 or caspase 9. The Nrf2-antioxidant pathway was also unaffected by the absence of NLRP3. Furthermore, NLRP3-deficiency prevented the drop in autophagy and mice showed less mitochondrial damage than wild-type animals. Interestingly, melatonin treatment recovered mitochondrial dynamics altered by aging and had few effects on cardiac autophagy. Melatonin supplementation also had an anti-apoptotic action in addition to restoring Nrf2-antioxidant capacity and improving mitochondria ultrastructure altered by aging.

Understanding Epigenetics in the Neurodegeneration of Alzheimer's Disease: SAMP8 Mouse Model

Epigenetics is emerging as the missing link among genetic inheritance, environmental influences, and body and brain health status. In the brain, specific changes in nucleic acids or their associated proteins in neurons and glial cells might imprint differential patterns of gene activation that will favor either cognitive enhancement or cognitive loss for more than one generation. Furthermore, derangement of age-related epigenetic signaling is appearing as a significant risk factor for illnesses of aging, including neurodegeneration and Alzheimer’s disease (AD). In addition, better knowledge of epigenetic mechanisms might provide hints and clues in the triggering and progression of AD. Intense research in experimental models suggests that molecular interventions for modulating epigenetic mechanisms might have therapeutic applications to promote cognitive maintenance through an advanced age. The SAMP8 mouse is a senescence model with AD traits in which the study of epigenetic alterations may unveil epigenetic therapies against the AD.

Oxidative-Inflammatory Stress in Immune Cells from Adult Mice with Premature Aging

Oxidative and inflammatory stresses are closely related processes, which contribute to age-associated impairments that affect the regulatory systems such as the immune system and its immunosenescence. Therefore, the aim of this work was to confirm whether an oxidative/inflammatory stress occurs in immune cells from adult mice with premature aging, similar to that shown in leukocytes from chronologically old animals, and if this results in immunosenescence. Several oxidants/antioxidants and inflammatory/anti-inflammatory cytokines were analyzed in peritoneal leukocytes from adult female CD1 mice in two models of premature aging—(a) prematurely aging mice (PAM) and (b) mice with the deletion of a single allele (hemi-zygotic: HZ) of the tyrosine hydroxylase (th) gene (TH-HZ), together with cells from chronologically old animals. Several immune function parameters were also studied in peritoneal phagocytes and lymphocytes. The same oxidants and antioxidants were also analyzed in spleen and thymus leukocytes. The results showed that the immune cells of PAM and TH-HZ mice presented lower values of antioxidant defenses and higher values of oxidants/pro-inflammatory cytokines than cells from corresponding controls, and similar to those in cells from old animals. Moreover, premature immunosenescence in peritoneal leukocytes from both PAM and TH-HZ mice was also observed. In conclusion, adult PAM and TH-HZ mice showed oxidative stress in their immune cells, which would explain their immunosenescence.

The role and therapeutic potential of melatonin in age-related ocular diseases

The eye is continuously exposed to solar UV radiation and pollutants, making it prone to oxidative attacks. In fact, oxidative damage is a major cause of age-related ocular diseases including cataract, glaucoma, age-related macular degeneration, and diabetic retinopathy. As the nature of lens cells, trabecular meshwork cells, retinal ganglion cells, retinal pigment epithelial cells, and photoreceptors is postmitotic, autophagy plays a critical role in their cellular homeostasis. In age-related ocular diseases, this process is impaired, and thus, oxidative damage becomes irreversible. Other conditions such as low-grade chronic inflammation and angiogenesis also contribute to the development of retinal diseases (glaucoma, age-related macular degeneration and diabetic retinopathy). As melatonin is known to have remarkable qualities such as antioxidant/antinitridergic, mitochondrial protector, autophagy modulator, anti-inflammatory, and anti-angiogenic, it can represent a powerful tool to counteract all these diseases. The present review analyzes the role and therapeutic potential of melatonin in age-related ocular diseases, focusing on nitro-oxidative stress, autophagy, inflammation, and angiogenesis mechanisms.

Role of MAPK-mediated endoplasmic reticulum stress signaling in the heart during aging in senescence-accelerated prone mice

Heart failure is typically related to aging as there is a definite relationship between age-related changes in the heart and the pathogenesis of heart failure. We have previously reported the involvement of p38 mitogen-activated protein kinase protein in cardiac function using animal models of heart failure. To further understand its relationship with aging-induced heart failure, we have compared its expression in the hearts of senescence accelerated-prone (SAMP8) mice and their control (SAMR1) with normal aging behavior. We have identified its activation along with reduced expression of 14-3-3η protein in SAMP8 mice hearts than in SAMR1 mice. To reveal the downstream signaling, we have measured the endoplasmic reticulum stress marker proteins along with some inflammatory and apoptosis markers and identified a significant increase in SAMP8 mice hearts than that of SAMR1. In addition, we have performed comet assay and revealed a significant DNA damage in the cardiomyocytes of SAMP8 mice when compared with SAMR1 mice. All these results demonstrate the role of 14-3-3η protein and the downstream mitogen-activated protein kinase-mediated endoplasmic reticulum stress, and apoptosis and DNA damage in aging-induced cardiac malfunction in SAMP8 mice. Thus targeting this signaling might be effective in treating age-related cardiac dysfunction. © 2016 BioFactors, 42(4):368-375, 2016.

The anti-aging effects of LW-AFC via correcting immune dysfunctions in senescence accelerated mouse resistant 1 (SAMR1) strain

Although there were considerable advances in the anti-aging medical field, it is short of therapeutic drug for anti-aging. Mounting evidence indicates that the immunosenescence is the key physiopathological mechanism of aging. This study showed the treatment of LW-AFC, an herbal medicine, decreased the grading score of senescence, increased weight, prolonged average life span and ameliorated spatial memory impairment in 12- and 24-month-old senescence accelerated mouse resistant 1 (SAMR1) strain. And these anti-aging effects of LW-AFC were more excellent than melatonin. The administration of LW-AFC enhanced ConA- and LPS-induced splenocyte proliferation in aged SAMR1 mice. The treatment of LW-AFC not only reversed the decreased the proportions of helper T cells, suppressor T cells and B cells, the increased regulatory T cells in the peripheral blood of old SAMR1 mice, but also could modulate the abnormal secretion of IL-1β, IL-2, IL-6, IL-17, IL-23, GM-CSF, IFN-γ, TNF-α, TNF-β, RANTES, eotaxin, MCP-1, IL-4, IL-5, IL-10 and G-CSF. These data indicated that LW-AFC reversed the immunosenescence status by restoring immunodeficiency and decreasing chronic inflammation and suggested LW-AFC may be an effective anti-aging agent.

Inflammation, But Not Telomere Length, Predicts Successful Ageing at Extreme Old Age: A Longitudinal Study of Semi-supercentenarians

To determine the most important drivers of successful ageing at extreme old age, we combined community-based prospective cohorts: Tokyo Oldest Old Survey on Total Health (TOOTH), Tokyo Centenarians Study (TCS) and Japanese Semi-Supercentenarians Study (JSS) comprising 1554 individuals including 684 centenarians and (semi-)supercentenarians, 167 pairs of centenarian offspring and spouses, and 536 community-living very old (85 to 99 years). We combined z scores from multiple biomarkers to describe haematopoiesis, inflammation, lipid and glucose metabolism, liver function, renal function, and cellular senescence domains. In Cox proportional hazard models, inflammation predicted all-cause mortality with hazard ratios (95% CI) 1.89 (1.21 to 2.95) and 1.36 (1.05 to 1.78) in the very old and (semi-)supercentenarians, respectively. In linear forward stepwise models, inflammation predicted capability (10.8% variance explained) and cognition (8(.)6% variance explained) in (semi-)supercentenarians better than chronologic age or gender. The inflammation score was also lower in centenarian offspring compared to age-matched controls with Δ (95% CI) = - 0.795 (- 1.436 to - 0.154). Centenarians and their offspring were able to maintain long telomeres, but telomere length was not a predictor of successful ageing in centenarians and semi-supercentenarians. We conclude that inflammation is an important malleable driver of ageing up to extreme old age in humans.

Oxidative stress, redox signaling, and autophagy: cell death versus survival

SIGNIFICANCE

The molecular machinery regulating autophagy has started becoming elucidated, and a number of studies have undertaken the task to determine the role of autophagy in cell fate determination within the context of human disease progression. Oxidative stress and redox signaling are also largely involved in the etiology of human diseases, where both survival and cell death signaling cascades have been reported to be modulated by reactive oxygen species (ROS) and reactive nitrogen species (RNS).

RECENT ADVANCES

To date, there is a good understanding of the signaling events regulating autophagy, as well as the signaling processes by which alterations in redox homeostasis are transduced to the activation/regulation of signaling cascades. However, very little is known about the molecular events linking them to the regulation of autophagy. This lack of information has hampered the understanding of the role of oxidative stress and autophagy in human disease progression.

CRITICAL ISSUES

In this review, we will focus on (i) the molecular mechanism by which ROS/RNS generation, redox signaling, and/or oxidative stress/damage alter autophagic flux rates; (ii) the role of autophagy as a cell death process or survival mechanism in response to oxidative stress; and (iii) alternative mechanisms by which autophagy-related signaling regulate mitochondrial function and antioxidant response.

FUTURE DIRECTIONS

Our research efforts should now focus on understanding the molecular basis of events by which autophagy is fine tuned by oxidation/reduction events. This knowledge will enable us to understand the mechanisms by which oxidative stress and autophagy regulate human diseases such as cancer and neurodegenerative disorders.

Melatonin-enhanced autophagy protects against neural apoptosis via a mitochondrial pathway in early brain injury following a subarachnoid hemorrhage

Melatonin is a strong antioxidant that has beneficial effects against early brain injury (EBI) following a subarachnoid hemorrhage (SAH) in rats; protection includes reduced mortality and brain water content. The molecular mechanisms underlying these clinical effects in the SAH model, however, have not been clearly identified. This study was undertaken to determine the influence of melatonin on neural apoptosis and the potential mechanism of these effects in EBI following SAH using the filament perforation model of SAH in male Sprague Dawley rats. Melatonin (150 mg/kg) or vehicle was given via an intraperitoneal injection 2 hr after SAH induction. Brain samples were extracted 24 hr after SAH. The results show that melatonin treatment markedly reduced caspase-3 activity and the number of TUNEL-positive cells, while the treatment increased the LC3-II/LC3-I, an autophagy marker, which indicated that melatonin-enhanced autophagy ameliorated apoptotic cell death in rats subjected to SAH. To further identify the mechanism of autophagy protection, we demonstrated that melatonin administration reduced Bax translocation to the mitochondria and the release of cytochrome c into the cytosol. Taken together, this report demonstrates that melatonin improved the neurological outcome in rats by protecting against neural apoptosis after the induction of filament perforation SAH; moreover, the mechanism of these antiapoptosis effects was related to the enhancement of autophagy, which ameliorated cell apoptosis via a mitochondrial pathway.

Senescence-Accelerated Mice P8: A Tool to Study Brain Aging and Alzheimer's Disease in a Mouse Model

The causes of aging remain unknown, but they are probably intimately linked to a multifactorial process that affects cell networks to varying degrees. Although a growing number of aging and Alzheimer’s disease (AD) animal models are available, a more comprehensive and physiological mouse model is required. In this context, the senescence-accelerated mouse prone 8 (SAMP8) has a number of advantages, since its rapid physiological senescence means that it has about half the normal lifespan of a rodent. In addition, according to data gathered over the last five years, some of its behavioral traits and histopathology resemble AD human dementia. SAMP8 has remarkable pathological similarities to AD and may prove to be an excellent model for acquiring more in-depth knowledge of the age-related neurodegenerative processes behind brain senescence and AD in particular. We review these facts and particularly the data on parameters related to neurodegeneration. SAMP8 also shows signs of aging in the immune, vascular, and metabolic systems, among others.

Role of melatonin in the regulation of autophagy and mitophagy: a review

Oxidative stress plays an essential role in triggering many cellular processes including programmed cell death. Proving a relationship between apoptosis and reactive oxygen species has been the goal of numerous studies. Accumulating data point to an essential role for oxidative stress in the activation of autophagy. The term autophagy encompasses several processes including not only survival or death mechanisms, but also pexophagy, mitophagy, ER-phagy or ribophagy, depending of which organelles are targeted for specific autophagic degradation. However, whether the outcome of autophagy is survival or death and whether the initiating conditions are starvation, pathogens or death receptors, reactive oxygen species are invariably involved. The role of antioxidants in the regulation of these processes, however, has been sparingly investigated. Among the known antioxidants, melatonin has high efficacy and, in both experimental and clinical situations, its protective actions against oxidative stress are well documented. Beneficial effects against mitochondrial dysfunction have also been described for melatonin; thus, this indoleamine seems to be linked to mitophagy. The present review focuses on data and the most recent advances related to the role of melatonin in health and disease, on autophagy activation in general, and on mitophagy in particular.

Melatonin-induced autophagy protects against human prion protein-mediated neurotoxicity

  Melatonin has neuroprotective effects in the models of neurodegenerative disease including Alzheimer's and Parkinson's disease. Several studies have shown that melatonin prevents neurodegeneration by regulation of mitochondrial function. However, the protective action of melatonin has not been reported in prion disease. We investigated the influence of melatonin on prion-mediated neurotoxicity. Melatonin rescued neuronal cells from PrP(106-126)-induced neurotoxicity by prevention of mitochondrial dysfunction. Moreover, the protective effect of melatonin against mitochondrial dysfunction was related with autophagy activation. Melatonin-treated cells were dose-dependently increased in LC3-II, an autophagy marker. Melatonin-induced autophagy prevented a PrP(106-126)-induced reduction in mitochondrial potential and translocation of Bax to the mitochondria and cytochrome c release. On the other hand, downregulation of autophagy protein 5 with Atg5 siRNA or the autophagy blocker 3-methyladenine prevented the melatonin-mediated neuroprotective effects. This is the first report demonstrating that treatment with melatonin appears to protect against prion-mediated neurotoxicity and that the neuroprotection is induced by melatonin-mediated autophagy signals. The results of this study suggest that regulation of melatonin is a therapeutic strategy for prion peptide-induced apoptosis.

Beneficial actions of melatonin in the management of viral infections: a new use for this "molecular handyman"?

Melatonin (N‐acetyl‐5‐methoxytryptamine) is a multifunctional signaling molecule that has a variety of important functions. Numerous clinical trials have examined the therapeutic usefulness of melatonin in different fields of medicine. Clinical trials have shown that melatonin is efficient in preventing cell damage under acute (sepsis, asphyxia in newborns) and chronic states (metabolic and neurodegenerative diseases, cancer, inflammation, aging). The beneficial effects of melatonin can be explained by its properties as a potent antioxidant and antioxidant enzyme inducer, a regulator of apoptosis and a stimulator of immune functions. These effects support the use of melatonin in viral infections, which are often associated with inflammatory injury and increases in oxidative stress. In fact, melatonin has been used recently to treat several viral infections, which are summarized in this review. The role of melatonin in infections is also discussed herein. Copyright © 2012 John Wiley & Sons, Ltd.

New paradigms in chronic intestinal inflammation and colon cancer: role of melatonin

In intestinal bowel disease (IBD), immune-mediated conditions exert their effects through various cells and proinflammatory mediators. Recent data support a participation of the endoplasmic reticulum stress and mitochondrial dysfunctions in IBD. Moreover, it is evident that chronic degenerative pathologies, including IBD, share comparable disease mechanisms with alteration in the autophagy mechanisms. Chronic inflammation in IBD exposes these patients to a number of signals known to have tumorigenic effects. This circuitry of inflammation and cancer modifies apoptosis and autophagy, and promotes cellular cycle progression, invasion, and angiogenesis. Melatonin has been shown as a specific antioxidant reducing oxidative damage in both lipid and aqueous cell environments. However, several studies provide further insight into the molecular mechanisms of melatonin action in the colon. In this line, recent data suggest that melatonin modulates autophagy and sirtuin activity. An anti-autophagic property of melatonin has been demonstrated, and it could contribute to its anti-oncogenic activity. Nevertheless, there is no information about whether antitumoral effects of melatonin on colon cancer are dependent on autophagy. Sirtuins have pleiotropic effects on cancer development, being reported both as facilitator and as suppressor of colon cancer development. Sirtuins and melatonin are connected through the circadian clock machinery, and melatonin seems able to correct the alterations in sirtuin activity associated with several pathological conditions. Autophagy and sirtuin activities are linked through 5'AMP-activated protein kinase (AMPK) activation, which switches on autophagy and increases sirtuin. The effect of melatonin on AMPK and the impact of this effect on IBD and colon cancer remain an open question.

Regulation of the ischemia-induced autophagy-lysosome processes by nitrosative stress in endothelial cells

The cellular mechanisms that underlie the diverse nitrosative stress-mediated cellular events associated with ischemic complications in endothelial cells are not yet clear. To characterize whether autophagic elements are associated with the nitrosative stress that causes endothelial damage after ischemia injury, an in vitro sustained oxygen-glucose deprivation (OGD) and an in vivo microsphere embolism model were used in the present study. Consistent with OGD-induced peroxynitrite formation, a rapid induction of microtubule-associated protein 1 light chain 3 (LC3)-I/II conversion and green fluorescent protein-LC3 puncta accumulation were observed in endothelial cells. The Western blot analyses indicated that OGD induced elevations in lysosome-associated membrane protein 2 and cathepsin B protein levels. Similar results were observed in the microvessel insult model, following occlusion of the microvessels using microsphere injections in rats. Furthermore, cultured endothelial cells treated with peroxynitrite (1-50 μm) exhibited a concentration-dependent change in the pattern of autophagy-lysosome signaling. Intriguingly, OGD-induced autophagy-lysosome processes were attenuated by PEP-19 overexpression and by a small-interfering RNA (siRNA)-mediated knockdown of eNOS. The importance of nitrosative stress in ischemia-induced autophagy-lysosome cascades is further supported by our finding that pharmacological inhibition of nitrosative stress by melatonin partially inhibits the ischemia-induced autophagy-lysosome cascade and the degradation of the tight junction proteins. Taken together, the present results demonstrate that peroxynitrite-mediated nitrosative stress at least partially potentiates autophagy-lysosome signaling during sustained ischemic insult-induced endothelial cell damage.

Phytic acid as a potential treatment for alzheimer's pathology: evidence from animal and in vitro models

Alzheimer's disease (AD) causes progressive, age-dependent cortical and hippocampal dysfunction leading to abnormal intellectual capacity and memory. We propose a novel protective treatment for AD pathology with phytic acid (inositol hexakisphosphate), a phytochemical found in food grains and a key signaling molecule in mammalian cells. We evaluated the protective and beneficial effects of phytic acid against amyloid-β (Aβ) pathology in MC65 cells and the Tg2576 mouse model. In MC65 cells, 48-72-hour treatment with phytic acid provided complete protection against amyloid precursor protein-C-terminal fragment-induced cytotoxicity by attenuating levels of increased intracellular calcium, hydrogen peroxide, superoxide, Aβ oligomers, and moderately upregulated the expression of autophagy (beclin-1) protein. In a tolerance paradigm, wild type mice were treated with 2% phytic acid in drinking water for 70 days. Phytic acid was well tolerated. Ceruloplasmin activity, brain copper and iron levels, and brain superoxide dismutase and ATP levels were unaffected by the treatment. There was a significant increase in brain levels of cytochrome oxidase and a decrease in lipid peroxidation with phytic acid administration. In a treatment paradigm, 12-month old Tg2576 and wild type mice were treated with 2% phytic acid or vehicle for 6 months. Brain levels of copper, iron, and zinc were unaffected. The effects of phytic acid were modest on the expression of AβPP trafficking-associated protein AP180, autophagy-associated proteins (beclin-1, LC3B), sirtuin 1, the ratio of phosphorylated AMP-activated protein kinase (PAMPK) to AMPK, soluble Aβ1-40, and insoluble Aβ1-42. These results suggest that phytic acid may provide a viable treatment option for AD.