Octylphenol (OP) alters the expression of members of the amyloid protein family in the hypothalamus of the snapping turtle, Chelydra serpentina serpentina

Current understandings and perspectives of petroleum hydrocarbons in Alzheimer's disease and Parkinson's disease: a global concern

Over the last few decades, the global prevalence of neurodevelopmental and neurodegenerative illnesses has risen rapidly. Although the aetiology remains unclear, evidence is mounting that exposure to persistent hydrocarbon pollutants is a substantial risk factor, predisposing a person to neurological diseases later in life. Epidemiological studies correlate environmental hydrocarbon exposure to brain disorders including neuropathies, cognitive, motor and sensory impairments; neurodevelopmental disorders like autism spectrum disorder (ASD); and neurodegenerative disorders like Alzheimer's disease (AD) and Parkinson's disease (PD). Particulate matter, benzene, toluene, ethylbenzene, xylenes, polycyclic aromatic hydrocarbons and endocrine-disrupting chemicals have all been linked to neurodevelopmental problems in all class of people. There is mounting evidence that supports the prevalence of petroleum hydrocarbon becoming neurotoxic and being involved in the pathogenesis of AD and PD. More study is needed to fully comprehend the scope of these problems in the context of unconventional oil and natural gas. This review summarises in vitro, animal and epidemiological research on the genesis of neurodegenerative disorders, highlighting evidence that supports inexorable role of hazardous hydrocarbon exposure in the pathophysiology of AD and PD. In this review, we offer a summary of the existing evidence gathered through a Medline literature search of systematic reviews and meta-analyses of the most important epidemiological studies published so far.

Role of environmental pollutants in Alzheimer's disease: a review

Neurodegenerative disorders are commonly erratic influenced by various factors including lifestyle, environmental, and genetic factors. In recent observations, it has been hypothesized that exposure to various environmental factors enhances the risk of Alzheimer's disease (AD). The exact etiology of Alzheimer's disease is still unclear; however, the contribution of environmental factors in the pathology of AD is widely acknowledged. Based on the available literature, the review aims to culminate in the prospective correlation between the various environmental factors and AD. The prolonged exposure to the various well-known environmental factors including heavy metals, air pollutants (particulate matter), pesticides, nanoparticles containing metals, industrial chemicals results in accelerating the progression of AD. Common mechanisms have been documented in the field of environmental contaminants for enhancing amyloid-β (Aβ) peptide along with tau phosphorylation, resulting in the initiation of senile plaques and neurofibrillary tangles, which results in the death of neurons. This review offers a compilation of available data to support the long-suspected correlation between environmental risk factors and AD pathology. Graphical abstract .

Stem Cells as Potential Targets of Polyphenols in Multiple Sclerosis and Alzheimer's Disease

Alzheimer's disease (AD) and multiple sclerosis are major neurodegenerative diseases, which are characterized by the accumulation of abnormal pathogenic proteins due to oxidative stress, mitochondrial dysfunction, impaired autophagy, and pathogens, leading to neurodegeneration and behavioral deficits. Herein, we reviewed the utility of plant polyphenols in regulating proliferation and differentiation of stem cells for inducing brain self-repair in AD and multiple sclerosis. Firstly, we discussed the genetic, physiological, and environmental factors involved in the pathophysiology of both the disorders. Next, we reviewed various stem cell therapies available and how they have proved useful in animal models of AD and multiple sclerosis. Lastly, we discussed how polyphenols utilize the potential of stem cells, either complementing their therapeutic effects or stimulating endogenous and exogenous neurogenesis, against these diseases. We suggest that polyphenols could be a potential candidate for stem cell therapy against neurodegenerative disorders.

Fertaric Acid Protects from Octylphenol-Related Hepatotoxicity in Rats: Biochemical, Molecular, and Histopathological Studies

The endocrine-disrupting chemical 4-tert-octylphenol (OP) can mimic estrogen and testosterone hormones and threaten health; fertaric acid (FA) is a hydroxycinnamic acid found in grapefruit. This study aimed to investigate whether FA has a protective effect on 4-tert-octylphenol-related hepatotoxicity. Thirty male albino rats were divided into 5 equal groups of 6 rats each as follows: control group-administrated orally with 1 ml saline 3 days/week for 4 weeks; corn oil group-administrated orally with 1 ml corn oil 3 days/week for 4 weeks; FA-treated group-administrated orally with FA (45 mg /kg body weight) dissolved in saline 3 days/week for 4 weeks; OP-treated group-administrated orally with OP (40 mg /kg body weight) dissolved in corn oil 3 days/week for 4 weeks; FA + OP-treated group-administrated orally with FA (45 mg /kg body weight) dissolved in saline 3 days/week for 4 weeks then administrated orally with OP (40 mg/kg body weight) dissolved in corn oil 3 days/week for another 4 weeks. The results obtained showed that OP-exposed rats had significant increase in serum aspartate aminotransferase, alanine aminotransferase, γ-glutamyl transferase, lactate dehydrogenase, bilirubin, serum and liver tumor necrosis factor-α, interleukin-1β and malondialdehyde, serum interleukin-6 and interleukin-10 and significant decrease in serum alkaline phosphatase, acid phosphatase, serum and liver superoxide dismutase, glutathione peroxidase, and catalase. OP caused an inhibitory action on the gene expression of liver proteins. Rats treated with FA before OP exposure had near-normal values. In addition, FA prevented the degradation of liver deoxyribonucleic acid (DNA), and DNA reformation occurred. In conclusion, FA protects from dangerous OP-related hepatic effects, and these results were supported by molecular and histological investigations.

Neuroendocrine disruption of organizational and activational hormone programming in poikilothermic vertebrates

In vertebrates, sexual differentiation of the reproductive system and brain is tightly orchestrated by organizational and activational effects of endogenous hormones. In mammals and birds, the organizational period is typified by a surge of sex hormones during differentiation of specific neural circuits; whereas activational effects are dependent upon later increases in these same hormones at sexual maturation. Depending on the reproductive organ or brain region, initial programming events may be modulated by androgens or require conversion of androgens to estrogens. The prevailing notion based upon findings in mammalian models is that male brain is sculpted to undergo masculinization and defeminization. In absence of these responses, the female brain develops. While timing of organizational and activational events vary across taxa, there are shared features. Further, exposure of different animal models to environmental chemicals such as xenoestrogens such as bisphenol A-BPA and ethinylestradiol-EE2, gestagens, and thyroid hormone disruptors, broadly classified as neuroendocrine disrupting chemicals (NED), during these critical periods may result in similar alterations in brain structure, function, and consequently, behaviors. Organizational effects of neuroendocrine systems in mammals and birds appear to be permanent, whereas teleost fish neuroendocrine systems exhibit plasticity. While there are fewer NED studies in amphibians and reptiles, data suggest that NED disrupt normal organizational-activational effects of endogenous hormones, although it remains to be determined if these disturbances are reversible. The aim of this review is to examine how various environmental chemicals may interrupt normal organizational and activational events in poikilothermic vertebrates. By altering such processes, these chemicals may affect reproductive health of an animal and result in compromised populations and ecosystem-level effects.

Role of environmental contaminants in the etiology of Alzheimer's disease: a review

Alzheimer's dis ease (AD) is a leading cause of mortality in the developed world with 70% risk attributable to genetics. The remaining 30% of AD risk is hypothesized to include environmental factors and human lifestyle patterns. Environmental factors possibly include inorganic and organic hazards, exposure to toxic metals (aluminium, copper), pesticides (organochlorine and organophosphate insecticides), industrial chemicals (flame retardants) and air pollutants (particulate matter). Long term exposures to these environmental contaminants together with bioaccumulation over an individual's life-time are speculated to induce neuroinflammation and neuropathology paving the way for developing AD. Epidemiologic associations between environmental contaminant exposures and AD are still limited. However, many in vitro and animal studies have identified toxic effects of environmental contaminants at the cellular level, revealing alterations of pathways and metabolisms associated with AD that warrant further investigations. This review provides an overview of in vitro, animal and epidemiological studies on the etiology of AD, highlighting available data supportive of the long hypothesized link between toxic environmental exposures and development of AD pathology.

Alfa-lipoic acid protects testosterone secretion pathway and sperm quality against 4-tert-octylphenol induced reproductive toxicity

The protective effect of α-lipoic acid (LA) (50 mg/kg bw) against 4-tert-octylphenol (OP) (50 mg/kg bw) induced reproductive toxicity in male rats was studied. LA was injected 1h prior to OP administration three times a week. OP caused significant increase in oxidative stress in hypothalamus and epididymal sperm, disturbed hormonal levels in serum, decreased sperm quality, increased DNA fragmentation and loss of 35 and 95 kDa proteins in sperm, as well as elevated proliferating index in testis. LA protected against oxidative stress through promoting the levels of glutathione and glutathione-S-transferase in hypothalamus and sperm. In addition, LA prevented the decrease in testosterone, dehydroepiandrosterone sulfate, 3β-hydroxysteroid dehydrogenase, and inhibited the elevations in sex-hormone-binding globulin levels and showed normal sperm quality. LA modulated proliferation of germ cell, protected against DNA fragmentation and maintained membrane protein organization in the sperm. In conclusion, LA normalized oxidative stress and protected testosterone synthesis pathway across hypothalamus-testicular axis and sperm quality indicating its defensive influence against OP-induced oxidative reproductive dysfunction in male rats.

Neuroendocrine disruption: more than hormones are upset

Only a small proportion of the published research on endocrine-disrupting chemicals (EDC) directly examined effects on neuroendocrine processes. There is an expanding body of evidence that anthropogenic chemicals exert effects on neuroendocrine systems and that these changes might impact peripheral organ systems and physiological processes. Neuroendocrine disruption extends the concept of endocrine disruption to include the full breadth of integrative physiology (i.e., more than hormones are upset). Pollutants may also disrupt numerous other neurochemical pathways to affect an animal's capacity to reproduce, develop and grow, or deal with stress and other challenges. Several examples are presented in this review, from both vertebrates and invertebrates, illustrating that diverse environmental pollutants including pharmaceuticals, organochlorine pesticides, and industrial contaminants have the potential to disrupt neuroendocrine control mechanisms. While most investigations on EDC are carried out with vertebrate models, an attempt is also made to highlight the importance of research on invertebrate neuroendocrine disruption. The neurophysiology of many invertebrates is well described and many of their neurotransmitters are similar or identical to those in vertebrates; therefore, lessons learned from one group of organisms may help us understand potential adverse effects in others. This review argues for the adoption of systems biology and integrative physiology to address the effects of EDC. Effects of pulp and paper mill effluents on fish reproduction are a good example of where relatively narrow hypothesis testing strategies (e.g., whether or not pollutants are sex steroid mimics) have only partially solved a major problem in environmental biology. It is clear that a global, integrative physiological approach, including improved understanding of neuroendocrine control mechanisms, is warranted to fully understand the impacts of pulp and paper mill effluents. Neuroendocrine disruptors are defined as pollutants in the environment that are capable of acting as agonists/antagonists or modulators of the synthesis and/or metabolism of neuropeptides, neurotransmitters, or neurohormones, which subsequently alter diverse physiological, behavioral, or hormonal processes to affect an animal's capacity to reproduce, develop and grow, or deal with stress and other challenges. By adopting a definition of neuroendocrine disruption that encompasses both direct physiological targets and their indirect downstream effects, from the level of the individual to the ecosystem, a more comprehensive picture of the consequences of environmentally relevant EDC exposure may emerge.

Fluorescent RNA arbitrarily primed polymerase chain reaction. A new differential display approach to detect contaminant-induced alterations of gene expression in wildlife species

Differential display polymerase chain reaction (PCR) can facilitate the identification of novel molecular end points related to contaminant exposure in a wide range of species. To date, various differential display methodologies have been described in detail. Herein, we describe a modification of the RNA arbitrarily primed PCR (RAP-PCR) method that involves the fluorescent labeling of cDNA transcripts via 5' rhodamine-labeled 18-mer arbitrary primers. These arbitrary primers typically bind to the coding regions of cDNA, which simplifies the downstream identification of contaminant-responsive genes. The technique has been aptly named fluorescent RNA arbitrarily primed PCR, FRAP-PCR, and has been successfully utilized with several avian species and RNA sources (e.g., cultured cells, tissue). This straightforward, safe, and cost-effective approach represents a useful alternative to the radiometric-based RAP-PCR method.

Assessment of estrogenic endocrine-disrupting chemical actions in the brain using in vivo somatic gene transfer

Estrogenic endocrine-disrupting chemicals abnormally stimulate vitellogenin gene expression and production in the liver of many male aquatic vertebrates. However, very few studies demonstrate the effects of estrogenic pollutants on brain function. We have used polyethylenimine-mediated in vivo somatic gene transfer to introduce an estrogen response element-thymidine kinase-luciferase (ERE-TK-LUC) construct into the brain. To determine if waterborne estrogenic chemicals modulate gene transcription in the brain, we injected the estrogen-sensitive construct into the brains of Nieuwkoop-Faber stage 54 Xenopus laevis tadpoles. Both ethinylestradiol (EE2; p < 0.002) and bisphenol A (BPA; p < 0.03) increased luciferase activity by 1.9- and 1.5-fold, respectively. In contrast, low physiologic levels of 17ss-estradiol had no effect (p > 0.05). The mixed antagonist/agonist tamoxifen was estrogenic in vivo and increased (p < 0.003) luciferase activity in the tadpole brain by 2.3-fold. There have been no previous reports of somatic gene transfer to the fish brain; therefore, it was necessary to optimize injection and transfection conditions for the adult goldfish (Carassius auratus). Following third brain ventricle injection of cytomegalovirus (CMV)-green fluorescent protein or CMV-LUC gene constructs, we established that cells in the telencephalon and optic tectum are transfected. Optimal transfections were achieved with 1 microg DNA complexed with 18 nmol 22 kDa polyethylenimine 4 days after brain injections. Exposure to EE2 increased brain luciferase activity by 2-fold in males (p < 0.05) but not in females. Activation of an ERE-dependent luciferase reporter gene in both tadpole and fish indicates that waterborne estrogens can directly modulate transcription of estrogen-responsive genes in the brain. We provide a method adaptable to aquatic organisms to study the direct regulation of estrogen-responsive genes in vivo.

Molecular markers of endocrine disruption in aquatic organisms

A wide range of organic contaminant compounds prevalent in the aquatic environment has been shown to exhibit hormone-disrupting activity. The actual potency of such compounds are low compared with endogenous hormones, such as 17beta-estradiol, but may still produce detrimental biological effects. Induced hormone levels are routinely measured using commercial testing kits, though these fail to relate to actual effects. Field and laboratory studies on the biological effects of environmental estrogens have, in the past, largely relied on assays of vitellogenin (vtg) induction in male fish, reduced growth in testes formation, and intersex incidence. Here, we critically review the current and potential application of molecular techniques in assessing the adverse biological reproductive effects of endocrine-disrupting chemicals in aquatic organisms. The role of fish (estrogen, androgen, and progestogen) hormone receptors and invertebrate (ecdysone) hormone receptor, egg production (vtg and chorion) proteins, steroid biosynthesis enzymes (aromatase, sulfotransferase, and hydroxysteroid dehydrogenase), DNA damage, apoptosis, and their potential development as biomarkers are discussed in turn. In each case, the sequences characterized are presented and homologies across species are highlighted. Molecular methods of gauging vtg and zona radiata (ZR) expression and protein concentrations have included immunoassay and reverse transcription polymerase chain reaction (RT-PCR). Suggestions for the isolation for key gene expression products (aromatase, ZR, and vtg, for instance), from a wider range of fish species using degenerate primers, are given. Endocrine disruption in invertebrates has received less attention compared with fish, partly because the knowledge regarding invertebrate endocrinology is limited. Here we review and suggest alternate isolation strategies for key players in the imposex induction process: vitellin (Vn), aromatase, and Ala-Pro-Gly-Trp (APGW) amide neurohormone. Current molecular-level techniques rely on ligand-binding assays, enzyme-linked immunosorbent assay (ELISA), and, more recently, gene expression. In the future, more reliance will be placed on the development of gene expression assays using reporter systems combined with cross-species PCR-based or polyclonal antibody-based assays. We discuss the use of recombinant receptors as a means of primary screening of environmental samples for estrogenicity and antiestrogenicity, which avoids species and seasonal variation in receptor response to ligand binding, a recognized problem of earlier bioassays. Most exciting is the potential that microarray and proteomics approaches have to offer. Such techniques are now used routinely in medical research to identify specific genes and proteins affected by treatment with endocrine disruptors, including estradiol. The technique has yet to be used to screen aquatic organisms, but it has the potential to implicate previously unsuspected estradiol-sensitive genes that may later become molecular markers of endocrine disruption.