Alterations induced by chronic lead exposure on the cells of circadian pacemaker of developing rats

Effects of postnatal exposure to cadmium on male sexual incentive motivation and copulatory behavior: Estrogen and androgen receptors expression in adult brain rat

There are numerous evidence showing that cadmium (Cd) is an endocrine disruptor that exerts multiple toxic effects at different reproductive levels, including male sexual behavior (MSB). The effect of early exposure to Cd on sexual incentive motivation (SIM) and MSB in adult stage, and the immunoreactivity of receptors for hormones such as estrogens and androgens in brain regions that are relevant for the SIM and MSB display, have not been studied until now. The present study evaluated the effects of 0.5 and 1 mg/kg CdCl2 from day 1-56 of postnatal life on SIM and MSB in adults rats, as well as serum testosterone concentrations, Cd concentration in blood, testis, and brain areas, and the immunoreactivity in estrogen receptors (ER-α and -β), and androgen receptor (AR) in the olfactory bulbs (OB), medial preoptic area (mPOA), and medial amygdala (MeA). Our results showed that both doses of Cd decreased SIM and MSB, accompanied by low serum concentrations of testosterone. Also, there was a significant reduction in immunoreactivity of ER-α and AR in mPOA, and a significant reduction in AR in MeA on male rats treated with Cd 1 mg/kg. These results show that exposure to high doses of Cd in early postnatal life could alter the correct integration of hormonal signals in the brain areas that regulate and display SIM and MSB in adult male rats.

Redox Regulatory Changes of Circadian Rhythm by the Environmental Risk Factors Traffic Noise and Air Pollution

Significance: Risk factors in the environment such as air pollution and traffic noise contribute to the development of chronic noncommunicable diseases. Recent Advances: Epidemiological data suggest that air pollution and traffic noise are associated with a higher risk for cardiovascular, metabolic, and mental disease, including hypertension, heart failure, myocardial infarction, diabetes, arrhythmia, stroke, neurodegeneration, depression, and anxiety disorders, mainly by activation of stress hormone signaling, inflammation, and oxidative stress. Critical Issues: We here provide an in-depth review on the impact of the environmental risk factors air pollution and traffic noise exposure (components of the external exposome) on cardiovascular health, with special emphasis on the role of environmentally triggered oxidative stress and dysregulation of the circadian clock. Also, a general introduction on the contribution of circadian rhythms to cardiovascular health and disease as well as a detailed mechanistic discussion of redox regulatory pathways of the circadian clock system is provided. Future Directions: Finally, we discuss the potential of preventive strategies or "chrono" therapy for cardioprotection. Antioxid. Redox Signal. 37, 679-703.

Physiological Alterations of Subchronic Lead Exposure Induced Degeneration of Epithelial Cells in Proximal Tubules and the Remedial Effect of Curcumin-III in Meriones shawi: a Possible Link with Vasopressin Release

At the industrial working conditions, lead exposure could induce several alterations for the human body. Subchronic lead exposure is linked with several injuries including cerebral and renal dysfunctions. The present work discusses the effects of subchronic lead toxicity (3 g/l) in drinking water during the period of treatment (6 weeks) on vasopressin system and epithelial cells in proximal tubules. Also, we aimed to evaluate the protective effect of curcumin-III administered orally by gavage (30 mg/kg BW), against subchronic Pb exposure in Meriones shawi. The biochemical and histopathological examinations demonstrate renal damages induced by lead toxicity. In addition, the behavioral and immunohistochemical studies revealed that Pb neurotoxicity exhibited an anxious behavior with a significant elevation of the vasopressin (AVP) staining within the paraventricular nuclei. The study showed also curcumin-III restored the renal alterations with an anxiolytic effect. Moreover, it restored the AVP level in the studying nuclei. Our work supports a possible link between AVP release and epithelial degeneration in the proximal tubules, and shows a new pharmacological effect of curcumin-III as an anxiolytic agent against lead toxicity.

OUP accepted manuscript

Healthy soil is foundational to human health. Healthy soil is needed to grow crops, provides food, and sustains populations. It supports diverse ecosystems and critical ecological services such as pollination. It stores water and prevents floods. It captures carbon and slows global climate change. Soil pollution is a great and growing threat to human health. Soil may be polluted by heavy metals, organic chemicals such as pesticides, biological pathogens, and micro/nanoplastic particles. Pollution reduces soil's ability to yield food. It results in food crop contamination and disease. Soil pollutants wash into rivers causing water pollution. Deforestation causes soil erosion, liberates sequestered pollutants, and generates airborne dust. Pollution of air, water, and soil is responsible for at least 9 million deaths each year. More than 60% of pollution-related disease and death is due to cardiovascular disease. Recognizing the importance of pollution to human health, the European Commission and the EU Action Plan for 2050: A Healthy Planet for All, have determined that air, water, and soil pollution must be reduced to levels that cause no harm to human or ecosystem health. We are thus required to create a toxic-free environment, respect the concept of a safe operating space for humanity, and sustain the health of our planet for future generations. This review article summarizes current knowledge of the links between soil health and human health and discusses the more important soil pollutants and their health effects.

Disrupted Sleep Homeostasis and Altered Expressions of Clock Genes in Rats with Chronic Lead Exposure

Sleep disturbance is one of the neurobehavioral complications of lead neurotoxicity. The present study evaluated the impacts of chronic lead exposure on alteration of the sleep–wake cycle in association with changes of clock gene expression in the hypothalamus. Sprague–Dawley rats with chronic lead exposure consumed drinking water that contained 250 ppm of lead acetate for five weeks. Electroencephalography and electromyography were recorded for scoring the architecture of the sleep–wake cycle in animals. At six Zeitgeber time (ZT) points (ZT2, ZT6, ZT10, ZT14, ZT18, and ZT22), three clock genes, including rPer1, rPer2, and rBmal1b, were analyzed. The rats with chronic lead exposure showed decreased slow wave sleep and increased wakefulness in the whole light period (ZT1 to ZT12) and the early dark period (ZT13 to ZT15) that was followed with a rebound of rapid-eye-movement sleep at the end of the dark period (ZT22 to ZT24). The disturbance of the sleep–wake cycle was associated with changes in clock gene expression that was characterized by the upregulation of rPer1 and rPer2 and the feedback repression of rBmal1b. We concluded that chronic lead exposure has a negative impact on the sleep–wake cycle in rats that predominantly disrupts sleep homeostasis. The disruption of sleep homeostasis was associated with a toxic effect of lead on the clock gene expression in the hypothalamus.

A Health Risk Assessment of Lead and Other Metals in Pharmaceutical Herbal Products and Dietary Supplements Containing Ginkgo biloba in the Mexico City Metropolitan Area

The use of the medicinal plant Ginkgo biloba has increased worldwide. However, G. biloba is capable of assimilating both essential and toxic metals, and the ingestion of contaminated products can cause damage to health. The aim of this study was to investigate the safety of manganese (Mn), copper (Cu), lead (Pb), arsenic (As), and cadmium (Cd) in 26 items containing Ginkgo biloba (pharmaceutical herbal products, dietary supplements, and traditional herbal remedies) purchased in the metropolitan area of Mexico City. Metal analysis was performed using a graphite furnace atomic absorption spectrometer. All of the products were contaminated with Pb, 54% of them with As, and 81% with Cd. The lowest values of Pb, As, and Cd were detected in pharmaceutical herbal products > dietary supplements > traditional herbal remedies. The daily intake dose (DID) of pharmaceutical herbal products was within the established limits for the five metals. Dietary supplements and traditional herbal remedies exceeded the DID limits for Pb. The hazard quotients estimation and non-carcinogenic cumulative hazard estimation index for Mn, As, and Cd indicated no human health risk. Our results suggest that products containing G. biloba for sale in Mexico are not a health risk.

Joint toxicity of lead and cadmium on the behavior of zebrafish larvae: An antagonism

Although the individual toxicity of lead (Pb) and cadmium (Cd) was intensively studied, little is known about their joint toxicity on the development of circadian behavioral rhythm. Therefore, we co-exposed zebrafish to Pb and Cd to investigate the alterations of behavioral rhythm and the potential mechanism. Inductively coupled plasma mass spectrometry analysis was used to detect the internal exposure level of heavy metals. The behavioral rhythm was monitored by a video-track tracking system. The changes of gene expression regarding melatonin-related molecules and clock genes were analyzed by quantitative polymerase chain reaction and JTK-Cycle analysis. The results showed that the level of Pb2+ and Cd2+ accumulated in the co-exposure group were significantly lower than that in the Pb or Cd group. Exposed to Pb reduced the locomotor activity; the behavioral rhythms were disrupted by Cd, while the pattern in the co-exposure group showed an antagonistic effect on locomotor activity and behavioral rhythm. The expression rhythm of aanat1 was disturbed and the expression levels of mtnr1aa and mtnr1bb were decreased by co-exposure treatment, but mtnr1c was increased in Pb and Cd group, respectively. Exposure to Cd caused the disruption of expression rhythm in clock genes, like clock1b, clock2, and cry1b, while only the rhythm of clock2 was disrupted in the co-exposure group. The results suggest that the behavioral rhythm disruption caused by Cd exposure is associated with the disturbance of certain circadian genes, whereas Pb exposure only abates the locomotor activity; an antagonistic effect on the behavioral pattern when co-exposed zebrafish larvae to Pb and Cd.

Chronic lead exposure alters photic entrainment of locomotor activity rhythm and neuronal photoactivation in the suprachiasmatic nucleus of the adult rat

Chronic lead (Pb) exposure affects the circadian physiological processes regulated by suprachiasmatic nucleus (SCN), which is synchronized (entrainment) by light. Disorders in the entrainment capacity of an organism alter its performance to interact with the environment, thus affecting its health status. The objectives of the present study were to evaluate whether chronic early Pb exposure affects the entrainment of the circadian rhythm of locomotor activity by light and to explore the possible mechanisms involved. Adult male Wistar rats, control and chronically exposed to Pb (320 ppm) in drinking water from gestation to adult age, were used. Assessment of the metal level showed a significant increase of Pb in the blood, hypothalamus and prefrontal cortex of the experimental rats. Continuous registrations of locomotor activity (12 h:12 h light-dark cycle) depicted that Pb induces important delay of this activity when the light was turned off. The Pb exposed animals entrained faster with a photoperiod delay of 6 h, (lights on at 13:00 h), and maintained the significant delay in the onset of activity at lights out. In continuous darkness, the animals were exposed to a light pulse at circadian time 23. This resulted in a significant decrease of photo-stimulated neurons (immunoreactivity to c-Fos) in the SCN of the metal-exposed animals. These results show that chronic early Pb exposure alters the photic entrainment of the rhythm of locomotor activity, which is evidenced by a significant decrease in both the number of photo-stimulated neurons and neuronal population (Nissl stain) of the SCN.

Ferulic acid exerts Nrf2-dependent protection against prenatal lead exposure-induced cognitive impairment in offspring mice

Prenatal and/or early postnatal exposure to lead (Pb) may be associated with deficits in cognitive function in the toddler offspring, and oxidative stress likely play a central role in mediating these adverse effects. Here, we tested the hypothesis that ameliorative effect of ferulic acid (FA) on lead-induced cognitive deficits attributed to its antioxidant properties in a nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-dependent manner in the context of prenatal Pb exposure. To test this hypothesis, Nrf2 knockout and C57BL/6 wild type mouse dams were exposed/unexposed to PbAc (250 ppm) during gestation day 5 to postnatal day 14 via drinking water, and FA (50 mg/kg)/vehicle was administered orally to dams for 31 d. Spatial learning and memory in pups was assessed by Morris water maze. Biochemical assays, real-time PCR, western blot techniques were employed to evaluate oxidative stress and signaling pathways in the brain of pups. We report that lead acetate (PbAc) leads to deficits in cognitive functions in offspring, which were partially attenuated by FA (P<.05). In parallel, pretreatment with FA also significantly inhibited the PbAc-induced oxidative stress, as indicated by a change in NAD+/NADH ratio, glutathione (GSH) and malondialdehyde contents (all P<.05). Interestingly, FA significantly elevated the glutamate cysteine ligase and heme oxygenase 1 at levels of transcription and translation in both mice exposed and unexposed to Pb, increasing de novo synthesis of GSH (all P<.05). Furthermore, maternal FA administration activates extracellular signal-regulated kinases 1 and 2 and promotes more Nrf2 nuclear accumulation by increasing the Nrf2 total protein in brain of offspring mice (all P<.05). Conversely, FA failed to influence Pb-induced both memory deficits and oxidative stress in offspring of Nrf2 knockout mice (all P≥.05), suggesting that Nrf2 is essential in mediating the cognition-enhancing and antioxidant effects of FA. Overall, our results demonstrate that FA protects against Pb-induced offspring's cognitive deficits, suggesting that it is a promising candidate for the treatment of Pb toxicity.

Lead (Pb) exposure induces physiological alterations in the serotoninergic and vasopressin systems causing anxiogenic-like behavior in Meriones shawi: Assessment of BDMC as a neuroprotective compound for Pb-neurotoxicity and kidney damages

BACKGROUND

Studies have shown that lead (Pb) is one of hazardous heavy metals with various adverse effects on human health including mental health; Pb can induce psychiatric disorders like anxiety. In the present work, we examined the potential of bisdemethoxycurcumin (BDMC) as a neuroprotective agent against lead induced anxiety inMeriones shawi (M. shawi).

METHODS

We asses, the potential of three consecutive day exposure to Pb (25 mg/kg body weight) in inducing anxiogenic effect, serotoninergic and vasopressinergic disruptions inM. shawi. This was done using neurobehavioral tests (open field, elevated plus maze), immunohistochemestry by anti-serotonin (5-HT), and anti-vasopressin (AVP) antibodies. We also measured the possible restorative potential of BDMC (30 mg/kg body weight), delivered by oral gavage. After that, a biochemical and histopathological studies were done.

RESULTS

Our results showed that lead exposure for three consecutive days increases significantly the 5-HT-immunoreactivity in dorsal raphe nucleus (DRN) accompanied with a significant enhancement of AVP-immunoreactivity in the cell bodies and fibers in the supraoptic (SON) and paraventricular (PVN) nuclei of the hypothalamus. In the collecting tube, AVP binds to the V2 receptor of the epithelial cells and increases the water permeability. Our results showed clearly the epithelial cells degeneration after lead exposure, then we suggest that the increased AVP could be a response to the hydric balance disrupted after degenerative effect of lead exposure on epithelial cells. BDMC produced an anxiolytic effect in meriones. Moreover, it restored 5-HT and AVP immunoreactivity within studying nuclei. The biochemical and histopathological studies showed that Pb induced renal damages. In addition, BDMC restored the renal alterations.

CONCLUSION

According to the obtained results, we suggest new pharmacological effects of BDMC; while it has an anxiolytic effect against Pb-induced anxiety by working on serotoninergic and vasopressinergic systems with an obvious restoration of the renal injuries induced by lead exposure.

Kynurenine Pathway as a New Target of Cognitive Impairment Induced by Lead Toxicity During the Lactation

The immature brain is especially vulnerable to lead (Pb²⁺) toxicity, which is considered an environmental neurotoxin. Pb²⁺ exposure during development compromises the cognitive and behavioral attributes which persist even later in adulthood, but the mechanisms involved in this effect are still unknown. On the other hand, the kynurenine pathway metabolites are modulators of different receptors and neurotransmitters related to cognition; specifically, high kynurenic acid levels has been involved with cognitive impairment, including deficits in spatial working memory and attention process. The aim of this study was to evaluate the relationship between the neurocognitive impairment induced by Pb²⁺ toxicity and the kynurenine pathway. The dams were divided in control group and Pb²⁺ group, which were given tap water or 500 ppm of lead acetate in drinking water ad libitum, respectively, from 0 to 23 postnatal day (PND). The poison was withdrawn, and tap water was given until 60 PND of the progeny. The locomotor activity in open field, redox environment, cellular function, kynurenic acid (KYNA) and 3-hydroxykynurenine (3-HK) levels as well as kynurenine aminotransferase (KAT) and kynurenine monooxygenase (KMO) activities were evaluated at both 23 and 60 PND. Additionally, learning and memory through buried food location test and expression of KAT and KMO, and cellular damage were evaluated at 60 PND. Pb²⁺ group showed redox environment alterations, cellular dysfunction and KYNA and 3-HK levels increased. No changes were observed in KAT activity. KMO activity increased at 23 PND and decreased at 60 PND. No changes in KAT and KMO expression in control and Pb²⁺ group were observed, however the number of positive cells expressing KMO and KAT increased in relation to control, which correlated with the loss of neuronal population. Cognitive impairment was observed in Pb²⁺ group which was correlated with KYNA levels. These results suggest that the increase in KYNA levels could be a mechanism by which Pb²⁺ induces cognitive impairment in adult mice, hence the modulation of kynurenine pathway represents a potential target to improve behavioural alterations produced by this environmental toxin.

Influence of mental stress and environmental toxins on circadian clocks: Implications for redox regulation of the heart and cardioprotection

Risk factors in the environment such as air pollution and mental stress contribute to the development of chronic non-communicable disease. Air pollution was identified as the leading health risk factor in the physical environment, followed by water pollution, soil pollution/heavy metals/chemicals and occupational exposures, however neglecting the non-chemical environmental health risk factors (e.g. mental stress and noise). Epidemiological data suggest that environmental risk factors are associated with higher risk for cardiovascular, metabolic and mental diseases, including hypertension, heart failure, myocardial infarction, diabetes, arrhythmia, stroke, depression and anxiety disorders. We provide an overview on the impact of the external exposome comprising risk factors/exposures on cardiovascular health with a focus on dysregulation of stress hormones, mitochondrial function, redox balance and inflammation with special emphasis on the circadian clock. Finally, we assess the impact of circadian clock dysregulation on cardiovascular health and the potential of environment-specific preventive strategies or "chrono" therapy for cardioprotection. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc.

Circadian Clock Protein Content and Daily Rhythm of Locomotor Activity Are Altered after Chronic Exposure to Lead in Rat

Lead exposure has been reported to produce many clinical features, including parkinsonism. However, its consequences on the circadian rhythms are still unknown. Here we aimed to examine the circadian rhythms of locomotor activity following lead intoxication and investigate the mechanisms by which lead may induce alterations of circadian rhythms in rats. Male Wistar rats were injected with lead or sodium acetate (10 mg/kg/day, i.p.) during 4 weeks. Both groups were tested in the “open field” to quantify the exploratory activity and in the rotarod to evaluate motor coordination. Then, animals were submitted to continuous 24 h recordings of locomotor activity under 14/10 Light/dark (14/10 LD) cycle and in complete darkness (DD). At the end of experiments, the clock proteins BMAL1, PER1-2, and CRY1-2 were assayed in the suprachiasmatic nucleus (SCN) using immunohistochemistry. We showed that lead significantly reduced the number of crossing in the open field, impaired motor coordination and altered the daily locomotor activity rhythm. When the LD cycle was advanced by 6 h, both groups adjusted their daily locomotor activity to the new LD cycle with high onset variability in lead-intoxicated rats compared to controls. Lead also led to a decrease in the number of immunoreactive cells (ir-) of BMAL1, PER1, and PER2 without affecting the number of ir-CRY1 and ir-CRY2 cells in the SCN. Our data provide strong evidence that lead intoxication disturbs the rhythm of locomotor activity and alters clock proteins expression in the SCN. They contribute to the understanding of the mechanism by which lead induce circadian rhythms disturbances.

Health of Children Living Near Coal Ash

Coal ash, generated from coal combustion, is composed of small particles containing metals and other elements, such as metalloids. Coal ash is stored in open-air impoundments, frequently near communities. The objective of this study was to evaluate the prevalence of health and sleep problems in children living near coal ash and compare these prevalences to children not living near coal ash. In 2013 to 2014, we conducted a cross-sectional survey in a community adjacent to coal ash storage sites and a community not exposed to coal ash. Overall, 111 children who lived near coal ash were in the study; 55.9% (62) were males, 44.1% (49) were females, and the mean age was 10.3 years (SD = 3.9). Descriptive statistics and logistic regression were used to compare the prevalence of health and sleep problems. Attention-deficit hyperactivity disorder (P = .02), gastrointestinal problems (P = .01), difficulty falling asleep (P = .007), frequent night awakenings (P < .001), teeth grinding (P = .03), and complaint of leg cramps (P < .001) were significantly greater in the children living near coal ash. When adjusting for covariates, the odds of allergies excluding asthma, attention-deficit hyperactivity disorder, gastrointestinal problems, difficulty falling asleep, frequent night awakenings, sleep talking, and complaint of leg cramps were greater in children living near coal ash compared to children not living near coal ash (nonexposed). Several components of coal ash, such as heavy metals like lead, mercury, and arsenic, may be associated with health and sleep problems in children. More research is needed to investigate this relationship.

Neonatal exposure to monosodium glutamate induces morphological alterations in suprachiasmatic nucleus of adult rat

Neonatal exposure to monosodium glutamate (MSG) induces circadian disorders in several physiological and behavioural processes regulated by the suprachiasmatic nucleus (SCN). The objective of this study was to evaluate the effects of neonatal exposure to MSG on locomotor activity, and on morphology, cellular density and expression of proteins, as evaluated by optical density (OD), of vasopressin (VP)-, vasoactive intestinal polypeptide (VIP)- and glial fibrillary acidic protein (GFAP)-immunoreactive cells in the SCN. Male Wistar rats were used: the MSG group was subcutaneously treated from 3 to 10 days of age with 3.5 mg/g/day. Locomotor activity was evaluated at 90 days of age using 'open-field' test, and the brains were processed for immunohistochemical studies. MSG exposure induced a significant decrease in locomotor activity. VP- and VIP-immunoreactive neuronal densities showed a significant decrease, while the somatic OD showed an increase. Major axes and somatic area were significantly increased in VIP neurons. The cellular and optical densities of GFAP-immunoreactive sections of SCN were significantly increased. These results demonstrated that newborn exposure to MSG induced morphological alterations in SCN cells, an alteration that could be the basis for behavioural disorders observed in the animals.

Neurotoxic effect of lead on rats: Relationship to Apoptosis

BACKGROUND

Lead toxicity has been subjected to intensive research work, but some aspects of its mechanism needs to be elucidated.

OBJECTIVES

In the current study we aim to investigate the impact of lead toxicity on some different intermediates of apoptotic signaling pathway in experimental rats.

DESIGN AND METHODS

We measured caspase-8 and caspase-9 [by chemilumenescence], Bax and Bcl-2 [by ELISA] in Experimental rats, injected intraperitoneally with lead acetate for 7days at the dosage of 25, 50 and l00 mg/kg body weight and compared to control rats injected with deionized distilled water instead. instead.

RESULTS

Lead acetate significantly increased the levels of caspase 8, caspase 9 and Bax in liver, kidney and brain of experimental animals especially those with high doses. Meanwhile, caspase 8 and Bax significantly increased in brain tissue at low dose of lead, while Bcl-2 significantly increased only with advanced toxicity. Furthermore, Bax/bcl2 ratio was significantly high in kidney (p<0.05), liver (p<0.01) and brain (p<0.01) at higher doses of lead toxicity. However, brain tissues showed significant Bax/Bcl2 ratio (p<0.05) at low lead dose. A significant positive correlation was noticed between the blood level of lead and enzymatic level of caspase 8, caspase 9 and Bax in different tissues.

CONCLUSION

: we concluded that lead might have toxic effect through intrinsic and extrinsic induction of apoptotic pathway with prominent effect on brain tissue even at low dose.