Gestational exposure to cadmium alters crucial offspring rat brain enzyme activities: the role of cadmium-free lactation

Curcumin protects against aging-related stress and dysfunction through autophagy activation in rat brain

BACKGROUND

Curcumin (Curcuma longa) is a well-known medicinal plant that induces autophagy in various model species, helping maintain cellular homeostasis. Its role as a caloric restriction mimetic (CRM) is being investigated. This study explores the potential of curcumin (CUR), as a CRM, to provide neuroprotection in D galactose induced accelerated senescence model of rats through modulation of autophagy. For six weeks, male rats received simultaneous supplementation of D-gal (300 mg/kg b.w., subcutaneously) and CUR (200 mg/kg b.w., oral).

METHOD AND RESULTS

The oxidative stress indices, antioxidants, and electron transport chain complexes in brain tissues were measured using standard methods. Reverse transcriptase-polymerase chain reaction (RT-PCR) gene expression analysis was used to evaluate the expression of autophagy, neuroprotection, and aging marker genes. Our results show that curcumin significantly (p ≤ 0.05) enhanced the level of antioxidants and considerably lowered the level of oxidative stress markers. Supplementing with CUR also increased the activity of electron transport chain complexes in the mitochondria of aged brain tissue, demonstrating the antioxidant potential of CUR at the mitochondrial level. CUR was found to upregulate the expression of the aging marker gene (SIRT-1) and the genes associated with autophagy (Beclin-1 and ULK-1), as well as neuroprotection (NSE) in the brain. The expression of IL-6 and TNF-α was downregulated.

CONCLUSION

Our findings demonstrate that CUR suppresses oxidative damage brought on by aging by modulating autophagy. These findings imply that curcumin might be beneficial for neuroprotection in aging and age-related disorders.

Environmental exposure of the general population to cadmium as a risk factor of the damage to the nervous system: A critical review of current data

Nowadays, more and more attention has been focused on the risk of the neurotoxic action of cadmium (Cd) under environmental exposure. Due to the growing incidence of nervous system diseases, including neurodegenerative changes, and suggested involvement of Cd in their aetiopathogenesis, this review aimed to discuss critically this element neurotoxicity. Attempts have been made to recognize at which concentrations in the blood and urine Cd may increase the risk of damage to the nervous system and compare it to the risk of injury of other organs and systems. The performed overview of the available literature shows that Cd may have an unfavourable impact on the human's nervous system at the concentration >0.8 μg Cd/L in the urine and >0.6 μg Cd/L in the blood. Because such concentrations are currently noted in the general population of industrialized countries, it can be concluded that environmental exposure to this xenobiotic may create a risk of damage to the nervous system and be involved in the aetiopathogenesis of neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease, as well as worsening cognitive and behavioural functions. The potential mechanism of Cd neurotoxicity consists in inducing oxidative stress, disrupting the activity of enzymes essential to the proper functioning of the nervous system and destroying the homoeostasis of bioelements in the brain. Thus, further studies are necessary to recognize accurately both the risk of nervous system damage in the general population due to environmental exposure to Cd and the mechanism of this action.

Alternate day fasting and time-restricted feeding may confer similar neuroprotective effects during aging in male rats

Age associated neurodegenerative changes are acknowledged to play a causative role in a majority of neurological diseases that accompany aging in organisms. To alleviate the deteriorative effects of aging in the brain, we investigated the effects oftwo types of intermittent fasting (IF) methods: alternate day fasting (ADF) and time- restricted feeding (TRF) in young (3 months) and old (24 months) in male Wistar rats comparing the results with age matched controls. The evaluation of biomarkers of oxidative stress showed significant decline in the old (ADF and TRF) groups in addition to up regulation in antioxidant levels. It was observed that ADF and TRF methods helped reduce ROS accumulation in the mitochondria and increased the activity of the electron transport chain complexes especially C-I and III. Gene expression analysis of autophagy genes like beclin and LC3B showed upregulated expression in ADF and TRF group. Sirtuin1 expression too significantly increased during fasting in both young and old groups showing fasting induced protection from aging. Histological analysis of sections of cerebral cortex and CA1 area provide evidence that fasting protected neurons against degeneration with age. Our results prompt us to conclude that the efficacy of these fasting methods ADF and TRF are reliable anti- aging strategies with respect to dietary restriction interventions. Moreover, both these methods compete closely in conferring protection from oxidative stress and inducing neuroprotective changes in brain of aged rats when compared to their young counterparts.

3-Bromopyruvate, a caloric restriction mimetic, exerts a mitohormetic effect to provide neuroprotection through activation of autophagy in rats during aging

In the present study, attempts have been made to evaluate the potential role of 3 Bromopyruvate (3-BP) a glycolytic inhibitor and a caloric restriction mimetic (CRM), to exert neuroprotection in rats during aging through modulation of autophagy. Young male rats (4 months), and naturally aged (22 months) male rats were supplemented with 3-BP (30 mg/kg b.w., orally) for 28 days. Our results demonstrate a significant increase in the antioxidant biomarkers (ferric reducing antioxidant potential level, total thiol, superoxide dismutase, and catalase activities) and a decrease in the level of pro-oxidant biomarkers such as protein carbonyl after 3-BP supplementation in brain tissues. A significant increase in reactive oxygen species (ROS) was observed due to the mitohormetic effect of 3-BP supplementation in the treated rats. Furthermore, the 3-BP treatment also enhanced the activities of electron transport chain complexes I and IV in aged brain mitochondria thus proving its antioxidant potential at the level of mitochondria. Gene expression analysis with reverse transcriptase-polymerase chain reaction (RT-PCR) was performed to assess the expression of autophagy, neuroprotective and aging marker genes. RT-PCR data revealed that 3-BP up-regulated the expression of autophagy markers genes (Beclin-1 and LC3 β), sirtuin-1, and neuronal marker gene (NSE), respectively in the aging brain. The results suggest that 3-BP induces a mitohormetic effect through the elevation of ROS which reinforces defensive mechanism(s) targeted at regulating autophagy. These findings suggest that consistently low-dose 3-BP may be beneficial for neuroprotection during aging and age-related disorders.

Age-dependent effect of continuous 'artificial light at night' on circadian rhythm in male rats: neuroprotective role of melatonin

Circadian disruption due to artificial light at night (ALAN) is an alarming threat to modern society. In the present study we evaluated the protective effect of melatonin on age dependent redox insults and neurochemical deficits induced by ALAN in the brain of chronodisrupted rat model. Young (3 months) and old (22 months) male Wistar rats were exposed to ALAN along with melatonin supplementation (10 mg Kg^-1, oral) for 10 days. Results demonstrated significant increment in the pro-oxidant biomarkers: reactive oxygen species, lipid hydroperoxidation, protein carbonyl, nitric oxide while suppression in the total thiol, ferric reducing antioxidant potential level, superoxide dismutase and catalase activities in the brain of ALAN exposed groups with higher amplitude in aged rats. Further these oxidative modifications were protected by subsequent administration of melatonin. Mitochondrial complexes (C-I to C-IV) activity was significantly altered in young and old ALAN exposed groups with melatonin showing protective effect. Histopathological analysis show dense cytosolic staining and neuronal degeneration in cerebral cortex and different hippocampus regions with greater extent in old ALAN rats effectively moderated by melatonin supplementation. RT-PCR data analysis revealed melatonin effectively downregulated neuroinflammatory (IL-6, TNF α) and neurodegenerative marker (Ngb) while upregulating the aging (Sirt 1) gene expression in both young and old melatonin supplemented ALAN exposed groups. Our results may help in understanding the degree of ALAN induced photo-oxidative damage in neuronal redox homeostasis during aging. We also show that melatonin supplementation might provide a basis for amelioration of oxidative disturbances to improve circadian entrainment in aged populations.

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.

Spermidine, a caloric restriction mimetic, provides neuroprotection against normal and D-galactose-induced oxidative stress and apoptosis through activation of autophagy in male rats during aging

Spermidine (SPD) is a natural polyamine present in all living organisms and is involved in the maintenance of cellular homeostasis by inducing autophagy in different model organisms. Its role as a caloric restriction mimetic (CRM) is still being investigated. We have undertaken this study to investigate whether SPD, acting as a CRM, can confer neuroprotection in D-galactose induced accelerated senescence model rat and naturally aged rats through modulation of autophagy and inflammation. Young male rats (4 months), D-gal induced (500 mg/kg b.w., subcutaneously) aging and naturally aged (22 months) male rats were supplemented with SPD (10 mg/kg b.w., orally) for 6 weeks. Standard protocols were employed to measure prooxidants, antioxidants, apoptotic cell death and electron transport chain complexes in brain tissues. Gene expression analysis with reverse transcriptase-polymerase chain reaction (RT-PCR) was performed to assess the expression of autophagy and inflammatory marker genes. Our data demonstrate that SPD significantly (p ≤ 0.05) decreased the level of pro-oxidants and increased the level of antioxidants. SPD supplementation also augmented the activities of electron transport chain complexes in aged brain mitochondria thus proving its antioxidant potential at the level of mitochondria. RT-PCR data revealed that SPD up-regulated the expression of autophagy genes (ATG-3, Beclin-1, ULK-1 and LC3B) and down-regulated the expression of the inflammatory gene (IL-6) in aging brain. Our results provide first line of evidence that SPD provides neuroprotection against aging-induced oxidative stress by regulating autophagy, antioxidants level and also reduces neuroinflammation. These results suggest that SPD may be beneficial for neuroprotection during aging and age-related disorders.

2 -Deoxy - d-glucose at chronic low dose acts as a caloric restriction mimetic through a mitohormetic induction of ROS in the brain of accelerated senescence model of rat

INTRODUCTION

Aging induces significant molecular alteration in brain morphology. Glycolytic inhibitor 2-Deoxy-d-glucose (2-DG) is considered to act as a caloric restriction mimetic (CRM) but it is correlated with elevated mortality risk in rats at persistent high dosage.

MATERIALS AND METHODS

In young and d-galactose induced accelerated senescent rat aging models, we tested a persistent low-dose dietary 2-DG administration and evaluated various aging biomarkers in brain tissue.

RESULTS

A significant increase in reactive oxygen species (ROS) was observed in 2-DG treated (both young and accelerated senescent rat model). Increased Ferric reducing antioxidant potential (FRAP) value, Superoxide Dismutase (SOD), Catalase (CAT), and activity of mitochondrial complexes I and IV was observed. There was also significant improvements in the autophagy expression of genes (Beclin-1 and Atg-3) after 2- DG treatment.

CONCLUSION

We propose that 2-DG induces a mitohormetic effect through elevation of ROS which reinforces defensive mechanism(s) through increased FRAP, SOD, CAT and autophagy gene expression. Our observations indicate that a consistently low dose 2-DG could be a valuable CRM.

Maternal cadmium exposure in the mouse leads to increased heart weight at birth and programs susceptibility to hypertension in adulthood

Cadmium (Cd) is a toxic heavy metal ubiquitous in the environment. Maternal exposure to Cd is associated with fetal growth restriction, trace element deficiencies, and congenital malformations. Cd exposure during adulthood is associated with cardiovascular disease (CVD); however, the effects of maternal Cd exposure on offspring cardiovascular development and disease are not well-understood. Utilizing a mouse model of maternal Cd exposure, we show that offspring born to Cd-exposed mothers have increased heart weights at birth and susceptibility to hypertension during adulthood. Despite inefficient maternal-fetal transfer of Cd, maternal Cd alters fetal levels of essential trace elements including a deficiency in iron, which is required for cardiovascular system development, oxygen homeostasis, and cellular metabolism. RNA-seq on newborn hearts identifies differentially expressed genes associated with maternal Cd exposure that are enriched for functions in CVD, hypertension, enlarged hearts, cellular energy, and hypoxic stress. We propose that a maternal Cd exposure-induced iron deficiency leads to altered cellular metabolic pathways and hypoxic conditions during fetal development; this stress may contribute to increased heart weight at birth and the programming of susceptibility to hypertension in adulthood. These studies will give insights into potential mechanisms through which maternal Cd exposure impacts cardiovascular development and disease.

N-acetyl-l-cysteine attenuates oxidative damage and neurodegeneration in rat brain during aging

N-acetyl-l-cysteine (NAC) is a precursor of cysteine, which is known to increase the level of glutathione (GSH) in the brain. Several neurodegenerative changes linked to oxidative stress take place in the aging brain. This study aimed to assess the neuroprotective effect of NAC supplementation on age-dependent neurodegeneration in the rat brain. Young (4 months) and old (24 months) Wistar rats (n = 6 rats/group) were supplemented with NAC (100 mg/kg b.w. orally) for 14 days. Enzymatic and nonenzymatic antioxidants such as superoxide dismutase and catalase, and GSH and total thiol respectively, prooxidants such as protein carbonyl, advanced oxidation protein products, reactive oxygen species, and malondialdehyde were assessed in the brain homogenates. Furthermore, nitric oxide level, acetylcholinesterase activity, and Na⁺/K⁺-ATPase activity were measured and gene expression studies were also performed. The results indicated that NAC augmented the level of enzymatic and nonenzymatic antioxidants with a significant reduction in prooxidant levels in old rats. NAC supplementation also downregulated the expression of inflammatory markers (TNF-α, IL-1β, IL-6) and upregulated the expression of marker genes associated with aging (sirtuin-1) and neurodegeneration (neuron-specific enolase, neuroglobin, synapsin-I, myelin basic protein 2) in old rats. The present findings support a neuroprotective role of NAC which has therapeutic implication in controlling age-related neurological disorders.

Whey protein concentrate supplementation protects rat brain against aging-induced oxidative stress and neurodegeneration

Whey protein concentrate (WPC) is a rich source of sulfur-containing amino acids and is consumed as a functional food, incorporating a wide range of nutritional attributes. The purpose of this study is to evaluate the neuroprotective effect of WPC on rat brain during aging. Young (4 months) and old (24 months) male Wistar rats were supplemented with WPC (300 mg/kg body weight) for 28 days. Biomarkers of oxidative stress and antioxidant capacity in terms of ferric reducing antioxidant potential (FRAP), lipid hydroperoxide (LHP), total thiol (T-SH), protein carbonyl (PC), reactive oxygen species (ROS), nitric oxide (NO), and acetylcholinesterase (AChE) activity were measured in brain of control and experimental (WPC supplemented) groups. In addition, gene expression and histopathological studies were also performed. The results indicate that WPC augmented the level of FRAP, T-SH, and AChE in old rats as compared with the old control. Furthermore, WPC-treated groups exhibited significant reduction in LHP, PC, ROS, and NO levels in aged rats. WPC supplementation also downregulated the expression of inflammatory markers (tumor necrosis factor alpha, interleukin (IL)-1β, IL-6), and upregulated the expression of marker genes associated with autophagy (Atg3, Beclin-1, LC3B) and neurodegeneration (neuron specific enolase, Synapsin-I, MBP-2). The findings suggested WPC to be a potential functional nutritional food supplement that prevents the progression of age-related oxidative damage in Wistar rats.

Disruption of the zinc metabolism in rat fœtal brain after prenatal exposure to cadmium

This study was carried out to investigate the effects of maternal Cd and/or Zn exposure on some parameters of Zn metabolism in fetal brain of Wistar rats. Thus, female controls and other exposed by the oral route during the gestation period to Cd (50 mg CdCl2/L) and/or Zn (ZnCl2 60 mg/L) were used. The male fetuses at age 20 days of gestation (GD20) were sacrificed and their brains were taken for histological, chemical and molecular analysis. Zn depletion was observed in the brains of fetuses issued from mothers exposed to Cd. Histological analysis showed that Cd exposure induces pyknosis in cortical region and CA1 region of the hippocampus compared to controls. Under Cd exposure, we noted an overexpression of the genes coding for membrane transporter involved in the intracellular incorporation of Zn (ZIP6) associated with inhibition of that encoding the transporters involved in the output of the Zn into the extracellular medium (ZnT1 and ZnT3). A decrease in the expression of the gene encoding the neuro-trophic factor (BDNF) associated with overexpression of the encoding the metal regulatory transcription factor 1 (MTF1), factor involved in the homeostasis of Zn, was also noted in Cd group. Interestingly, Zn supply provided a total or partial restauration of the changes induced by the Cd exposure. The depletion of brain Zn contents as well as the modification of the profile of expression of genes encoding membrane Zn transporters, suggest that the toxicity of Cd observed in fetal brain level are mediated, in part, by impairment of Zn metabolism.

Exposure to ethanol during neurodevelopment modifies crucial offspring rat brain enzyme activities in a region-specific manner

The experimental simulation of conditions falling within "the fetal alcohol spectrum disorder" (FASD) requires the maternal exposure to ethanol (EtOH) during crucial neurodevelopmental periods; EtOH has been linked to a number of neurotoxic effects on the fetus, which are dependent upon the extent and the magnitude of the maternal exposure to EtOH and for which very little is known with regard to the exact mechanism(s) involved. The current study has examined the effects of moderate maternal exposure to EtOH (10 % v/v in the drinking water) throughout gestation, or gestation and lactation, on crucial 21-day-old offspring Wistar rat brain parameters, such as the activities of acetylcholinesterase (AChE) and two adenosine triphosphatases (Na(+),K(+)-ATPase and Mg(2+)-ATPase), in major offspring CNS regions (frontal cortex, hippocampus, hypothalamus, cerebellum and pons). The implemented experimental setting has provided a comparative view of the neurotoxic effects of maternal exposure to EtOH between gestation alone and a wider exposure timeframe that better covers the human third trimester-matching CNS neurodevelopment period (gestation and lactation), and has revealed a CNS region-specific susceptibility of the examined crucial neurochemical parameters to the EtOH exposure schemes attempted. Amongst these parameters, of particular importance is the recorded extensive stimulation of Na(+),K(+)-ATPase in the frontal cortex of the EtOH-exposed offspring that seems to be a result of the deleterious effect of EtOH during gestation. Although this stimulation could be inversely related to the observed inhibition of AChE in the same CNS region, its dependency upon the EtOH-induced modulation of other systems of neurotransmission cannot be excluded and must be further clarified in future experimental attempts aiming to simulate and to shed more light on the milder forms of the FASD-related pathophysiology.

Cadmium exposure during lactation causes learning and memory-impairment in F1 generation mice: amelioration by quercetin

Cadmium (Cd) is a known pollutant present in the environment at low levels and is reported to affect reproduction in many ways. The present study was undertaken to explore the effect of Cd in F1 generation mice on cognitive parameters, and to further investigate whether quercetin could modulate these effects. In this study, female lactating mice were exposed to cadmium for seven days just after delivery. The new born pups in their adulthood were tested for learning and memory parameters by passive avoidance task and Morris water maze (MWM) test. It was observed that pups exposed to Cd showed significant impairment of memory in step down latency test, which was reversed by quercetin (100 mg/kg). In MWM test for spatial memory, animals exposed to Cd exhibited increased escape latency, which was reversed by quercetin (50 mg/kg) significantly. Quercetin alone (50 and 100 mg/kg) also demonstrated improved spatial memory, and showed improved retention memory in the passive avoidance paradigm at dose 50 mg/kg. On testing oxidative stress parameters, we observed significantly increased malondialdehyde (MDA) levels in brain tissue of Cd-treated mice. Moreover, co-treatment with quercetin (50 mg/kg) and Cd significantly reduced these MDA levels. The other doses (25 and 100 mg/kg) also showed reduction in MDA levels as compared to the group exposed to Cd alone, though the difference was not statistically significant. Hence, this study highlights the possibility of cognitive impairment in adulthood if there is Cd exposure during lactation and oxidative stress could possibly attribute to this effect.

Postnuclear supernatants of rat brain regions as substrates for the in vitro assessment of cadmium-induced neurotoxicity on acetylcholinesterase activity

Acetylcholinesterase (AChE) activity is thought to be a major neurotoxicity biomarker. Considering the recently highlighted controversy over the use of AChE activity as a biomarker for the neurotoxicity induced by cadmium (Cd; a major environmental contaminant), we have evaluated the in vitro effects of different concentrations of Cd on AChE activity in postnuclear supernatants of brain regions of newborn, 21-day-old, and adult male Wistar rats. Our findings demonstrate that Cd is a consistent inhibitor of AChE activity at concentrations higher than 10(-3) M as well as that, at a concentration of 10(-2) M, Cd induces an almost absolute inhibition of this crucial enzyme in the examined postnuclear supernatants. These findings confirm previous in vitro experiments of ours, but are not in full agreement with the available in vivo findings; in fact, they underline that this in vitro approach to Cd-induced neurotoxicity does not produce the distinctive brain region-specific responses in terms of AChE activity that we have recently observed in vivo. Our study does not support the use of AChE activity as a biomarker for the assessment of Cd-induced neurotoxicity in rat brain-derived postnuclear supernatants, at least under the examined in vitro experimental conditions.

Developmental neurotoxicity of cadmium on enzyme activities of crucial offspring rat brain regions

Cadmium (Cd) is an environmental contaminant known to exert significant neurotoxic effects on both humans and experimental animals. The aim of this study was to shed more light on the effects of gestational (in utero) and lactational maternal exposure to Cd (50 ppm of Cd as Cd-chloride in the drinking water) on crucial brain enzyme activities in important rat offspring brain regions (frontal cortex, hippocampus, hypothalamus, pons and cerebellum). Our study provides a brain region-specific view of the changes in the activities of three crucial brain enzymes as a result of the developmental neurotoxicity of Cd. Maternal exposure to Cd during both gestation and lactation results into significant changes in the activities of acetylcholinesterase and Na(+),K(+)-ATPase in the frontal cortex and the cerebellum of the offspring rats, as well as in a significant increase in the hippocampal Mg(2+)-ATPase activity. These brain-region-specific findings underline the need for further research in the field of Cd-induced developmental neurotoxicity. Deeper understanding of the mechanisms underlying the neurodevelopmental deficits taking place due to in utero and early age exposure to Cd could shed more light on the causes of its well-established cognitive implications.