Correction: LRRK2 kinase plays a critical role in manganese-induced inflammation and apoptosis in microglia.

[This corrects the article DOI: 10.1371/journal.pone.0210248.].

Manganese phosphorylates Yin Yang 1 at serine residues to repress EAAT2 in human H4 astrocytes.

Impairment of the astrocytic glutamate transporter excitatory amino acid transporter 2 (EAAT2) is associated with neurological disorders such as Parkinson's disease (PD), Alzheimer's disease (AD), and manganism, a neurological disorder caused by overexposure to manganese (Mn) which shares the features of sporadic PD. Mechanisms of Mn-induced neurotoxicity include dysregulation of EAAT2 following activation of the transcription factor Yin Yang 1 (YY1) by transcriptional upregulation, but the posttranslational mechanisms by which YY1 is activated to repress EAAT2 remain to be elucidated. In the present study, we tested if Mn activates YY1 through posttranslational phosphorylation in cultured H4 human astrocytes, leading to EAAT2 repression. The results demonstrate that Mn exposure induced phosphorylation of YY1 at serine residues via kinases Aurora B kinase (AurkB) and Casein kinase II (CK2), leading to YY1 nuclear translocation, YY1/HDAC interactions, binding to the EAAT2 promoter, and consequent decreases in EAAT2 promoter activity and mRNA/protein levels. Although further studies are warranted to fully elucidate the mechanisms of Mn-induced YY1 phosphorylation and resultant EAAT2 impairment, our findings indicate that serine phosphorylation of YY1 via AurkB and CK2 is critical, at least in part, to its activation and transcriptional repression of EAAT2.

Manganese-induced reactive oxygen species activate IκB kinase to upregulate YY1 and impair glutamate transporter EAAT2 function in human astrocytes in vitro.

Dysregulation of the astrocytic glutamate transporter excitatory amino acid transporter 2 (EAAT2) is associated with several neurological disorders, including Parkinson's disease, Alzheimer's disease, and manganism, the latter induced by chronic exposure to high levels of manganese (Mn). Mechanisms of Mn-induced neurotoxicity include impairment of EAAT2 function secondary to the activation of the transcription factor Yin Yang 1 (YY1) by nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). However, the upstream mechanisms by which Mn-induced NF-κB activates YY1 remain to be elucidated. In the present study, we used the H4 human astrocyte cell line to test if Mn activates YY1 through the canonical NF-κB signaling pathway, leading to EAAT2 repression. The results demonstrate that Mn exposure induced phosphorylation of the upstream kinase IκB kinase (IKK-ß), leading to NF-κB p65 translocation, increased YY1 promoter activity, mRNA/protein levels, and consequently repressed EAAT2. Results also demonstrated that Mn-induced oxidative stress and subsequent TNF-α production were upstream of IKK-ß activation, as antioxidants attenuated Mn-induced TNF-α production and IKK-ß activation. Moreover, TNF-α inhibition attenuated the Mn-induced activation of IKK-ß and YY1. Taken together, Mn-induced oxidative stress and TNF-α mediates activation of NF-κB signaling and YY1 upregulation, leading to repression of EAAT2. Thus, targeting reactive oxygen species (ROS), TNF-α and IKK-ß may attenuate Mn-induced YY1 activation and consequent EAAT2 repression.

Astrocyte-specific deletion of the transcription factor Yin Yang 1 in murine substantia nigra mitigates manganese-induced dopaminergic neurotoxicity.

Manganese (Mn)-induced neurotoxicity resembles Parkinson's disease (PD), but the mechanisms underpinning its effects remain unknown. Mn dysregulates astrocytic glutamate transporters, GLT-1 and GLAST, and dopaminergic function, including tyrosine hydroxylase (TH). Our previous in vitro studies have shown that Mn repressed GLAST and GLT-1 via activation of transcription factor Yin Yang 1 (YY1). Here, we investigated if in vivo astrocytic YY1 deletion mitigates Mn-induced dopaminergic neurotoxicity, attenuating Mn-induced reduction in GLAST/GLT-1 expression in murine substantia nigra (SN). AAV5-GFAP-Cre-GFP particles were infused into the SN of 8-week-old YY1 flox/flox mice to generate a region-specific astrocytic YY1 conditional knockout (cKO) mouse model. 3 weeks after adeno-associated viral (AAV) infusion, mice were exposed to 330 µg of Mn (MnCl2 30 mg/kg, intranasal instillation, daily) for 3 weeks. After Mn exposure, motor functions were determined in open-field and rotarod tests, followed by Western blotting, quantitative PCR, and immunohistochemistry to assess YY1, TH, GLAST, and GLT-1 levels. Infusion of AAV5-GFAP-Cre-GFP vectors into the SN resulted in region-specific astrocytic YY1 deletion and attenuation of Mn-induced impairment of motor functions, reduction of TH-expressing cells in SN, and TH mRNA/protein levels in midbrain/striatum. Astrocytic YY1 deletion also attenuated the Mn-induced decrease in GLAST/GLT-1 mRNA/protein levels in midbrain. Moreover, YY1 deletion abrogated its interaction with histone deacetylases in astrocytes. These results indicate that astrocytic YY1 plays a critical role in Mn-induced neurotoxicity in vivo, at least in part, by reducing astrocytic GLAST/GLT-1. Thus, YY1 might be a potential target for treatment of Mn toxicity and other neurological disorders associated with dysregulation of GLAST/GLT-1.

The transcription factor REST up-regulates tyrosine hydroxylase and antiapoptotic genes and protects dopaminergic neurons against manganese toxicity.

Dopaminergic functions are important for various biological activities, and their impairment leads to neurodegeneration, a hallmark of Parkinson's disease (PD). Chronic manganese (Mn) exposure causes the neurological disorder manganism, presenting symptoms similar to those of PD. Emerging evidence has linked the transcription factor RE1-silencing transcription factor (REST) to PD and also Alzheimer's disease. But REST's role in dopaminergic neurons is unclear. Here, we investigated whether REST protects dopaminergic neurons against Mn-induced toxicity and enhances expression of the dopamine-synthesizing enzyme tyrosine hydroxylase (TH). We report that REST binds to RE1 consensus sites in the TH gene promoter, stimulates TH transcription, and increases TH mRNA and protein levels in dopaminergic cells. REST binding to the TH promoter recruited the epigenetic modifier cAMP-response element-binding protein-binding protein/p300 and thereby up-regulated TH expression. REST relieved Mn-induced repression of TH promoter activity, mRNA, and protein levels and also reduced Mn-induced oxidative stress, inflammation, and apoptosis in dopaminergic neurons. REST reduced Mn-induced proinflammatory cytokines, including tumor necrosis factor α, interleukin 1ß (IL-1ß), IL-6, and interferon γ. Moreover, REST inhibited the Mn-induced proapoptotic proteins Bcl-2-associated X protein (Bax) and death-associated protein 6 (Daxx) and attenuated an Mn-induced decrease in the antiapoptotic proteins Bcl-2 and Bcl-xL. REST also enhanced the expression of antioxidant proteins, including catalase, NF-E2-related factor 2 (Nrf2), and heme oxygenase 1 (HO-1). Our findings indicate that REST activates TH expression and thereby protects neurons against Mn-induced toxicity and neurological disorders associated with dopaminergic neurodegeneration.

Role of Astrocytes in Manganese Neurotoxicity Revisited.

Manganese (Mn) overexposure is a public health concern due to its widespread industrial usage and the risk for environmental contamination. The clinical symptoms of Mn neurotoxicity, or manganism, share several pathological features of Parkinson's disease (PD). Biologically, Mn is an essential trace element, and Mn in the brain is preferentially localized in astrocytes. This review summarizes the role of astrocytes in Mn-induced neurotoxicity, specifically on the role of neurotransmitter recycling, neuroinflammation, and genetics. Mn overexposure can dysregulate astrocytic cycling of glutamine (Gln) and glutamate (Glu), which is the basis for Mn-induced excitotoxic neuronal injury. In addition, reactive astrocytes are important mediators of Mn-induced neuronal damage by potentiating neuroinflammation. Genetic studies, including those with Caenorhabditis elegans (C. elegans) have uncovered several genes associated with Mn neurotoxicity. Though we have yet to fully understand the role of astrocytes in the pathologic changes characteristic of manganism, significant strides have been made over the last two decades in deciphering the role of astrocytes in Mn-induced neurotoxicity and neurodegeneration.

Astrocytic Oxidative/Nitrosative Stress Contributes to Parkinson's Disease Pathogenesis: The Dual Role of Reactive Astrocytes.

: Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide; it is characterized by dopaminergic neurodegeneration in the substantia nigra pars compacta, but its etiology is not fully understood. Astrocytes, a class of glial cells in the central nervous system (CNS), provide critical structural and metabolic support to neurons, but growing evidence reveals that astrocytic oxidative and nitrosative stress contributes to PD pathogenesis. As astrocytes play a critical role in the production of antioxidants and the detoxification of reactive oxygen and nitrogen species (ROS/RNS), astrocytic oxidative/nitrosative stress has emerged as a critical mediator of the etiology of PD. Cellular stress and inflammation induce reactive astrogliosis, which initiates the production of astrocytic ROS/RNS and may lead to oxidative/nitrosative stress and PD pathogenesis. Although the cause of aberrant reactive astrogliosis is unknown, gene mutations and environmental toxicants may also contribute to astrocytic oxidative/nitrosative stress. In this review, we briefly discuss the physiological functions of astrocytes and the role of astrocytic oxidative/nitrosative stress in PD pathogenesis. Additionally, we examine the impact of PD-related genes such as α-synuclein, protein deglycase DJ-1( DJ-1), Parkin, and PTEN-induced kinase 1 (PINK1) on astrocytic function, and highlight the impact of environmental toxicants, such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), rotenone, manganese, and paraquat, on astrocytic oxidative/nitrosative stress in experimental models.

The role of astrocytic glutamate transporters GLT-1 and GLAST in neurological disorders: Potential targets for neurotherapeutics.

Glutamate is the primary excitatory neurotransmitter in the central nervous system (CNS) which initiates rapid signal transmission in the synapse before its re-uptake into the surrounding glia, specifically astrocytes. The astrocytic glutamate transporters glutamate-aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) and their human homologs excitatory amino acid transporter 1 (EAAT1) and 2 (EAAT2), respectively, are the major transporters which take up synaptic glutamate to maintain optimal extracellular glutamic levels, thus preventing accumulation in the synaptic cleft and ensuing excitotoxicity. Growing evidence has shown that excitotoxicity is associated with various neurological disorders, including amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), manganism, ischemia, schizophrenia, epilepsy, and autism. While the mechanisms of neurological disorders are not well understood, the dysregulation of GLAST/GLT-1 may play a significant role in excitotoxicity and associated neuropathogenesis. The expression and function of GLAST/GLT-1 may be dysregulated at the genetic, epigenetic, transcriptional or translational levels, leading to high levels of extracellular glutamate and excitotoxicity. Consequently, understanding the regulatory mechanisms of GLAST/GLT-1 has been an area of interest in developing therapeutics for the treatment of neurological disorders. Pharmacological agents including ß-lactam antibiotics, estrogen/selective estrogen receptor modulators (SERMs), growth factors, histone deacetylase inhibitors (HDACi), and translational activators have shown significant efficacy in enhancing the expression and function of GLAST/GLT-1 and glutamate uptake both in vitro and in vivo. This comprehensive review will discuss the regulatory mechanisms of GLAST/GLT-1, their association with neurological disorders, and the pharmacological agents which mediate their expression and function. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.

LRRK2 kinase plays a critical role in manganese-induced inflammation and apoptosis in microglia.

Long-term exposure to elevated levels of manganese (Mn) causes manganism, a neurodegenerative disorder with Parkinson's disease (PD)-like symptoms. Increasing evidence suggests that leucine-rich repeat kinase 2 (LRRK2), which is highly expressed in microglia and macrophages, contributes to the inflammation and neurotoxicity seen in autosomal dominant and sporadic PD. As gene-environment interactions have emerged as important modulators of PD-associated toxicity, LRRK2 may also mediate Mn-induced inflammation and pathogenesis. In this study, we investigated the role of LRRK2 in Mn-induced toxicity using human microglial cells (HMC3), LRRK2-wild-type (WT) and LRRK2-knockout (KO) RAW264.7 macrophage cells. Results showed that Mn activated LRRK2 kinase by phosphorylation of its serine residue at the 1292 position (S1292) as a marker of its kinase activity in macrophage and microglia, while inhibition with GSK2578215A (GSK) and MLi-2 abolished Mn-induced LRRK2 activation. LRRK2 deletion and its pharmacological inhibition attenuated Mn-induced apoptosis in macrophages and microglia, along with concomitant decreases in the pro-apoptotic Bcl-2-associated X (Bax) protein. LRRK2 deletion also attenuated Mn-induced production of reactive oxygen species (ROS) and the pro-inflammatory cytokine TNF-α. Mn-induced phosphorylation of mitogen-activated protein kinase (MAPK) p38 and ERK signaling proteins was significantly attenuated in LRRK2 KO cells and GSK-treated cells. Moreover, inhibition of MAPK p38 and ERK as well as LRRK2 attenuated Mn-induced oxidative stress and cytotoxicity. These findings suggest that LRRK2 kinase activity plays a critical role in Mn-induced toxicity via downstream activation of MAPK signaling in macrophage and microglia. Collectively, these results suggest that LRRK2 could be a potential molecular target for developing therapeutics to treat Mn-related neurodegenerative disorders.

The role of posttranslational modifications of α-synuclein and LRRK2 in Parkinson's disease: Potential contributions of environmental factors.

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease (AD), and the most prevalent movement disorder. PD is characterized by dopaminergic neurodegeneration in the substantia nigra, but its etiology has yet to be established. Among several genetic variants contributing to PD pathogenesis, α-synuclein and leucine-rich repeat kinase (LRRK2) are widely associated with neuropathological phenotypes in familial and sporadic PD. α-Synuclein and LRRK2 found in Lewy bodies, a pathogenic hallmark of PD, are often posttranslationally modified. As posttranslational modifications (PTMs) are key processes in regulating the stability, localization, and function of proteins, PTMs have emerged as important modulators of α-synuclein and LRRK2 pathology. Aberrant PTMs altering phosphorylation, ubiquitination, nitration and truncation of these proteins promote PD pathogenesis, while other PTMs such as sumoylation may be protective. Although the causes of many aberrant PTMs are unknown, environmental risk factors may contribute to their aberrancy. Environmental toxicants such as rotenone and paraquat have been shown to interact with these proteins and promote their abnormal PTMs. Notably, manganese (Mn) exposure leads to a PD-like neurological disorder referred to as manganism-and induces pathogenic PTMs of α-synuclein and LRRK2. In this review, we highlight the role of PTMs of α-synuclein and LRRK2 in PD pathogenesis and discuss the impact of environmental risk factors on their aberrancy.

(S)He's Gotta Have It: Emotion Regulation, Emotional Expression, and Sexual Risk Behavior in Emerging Adult Couples.

Emotion regulation and emotional expression may be important factors which contribute to sexual risk behavior among emerging adults, yet research exploring their relation is limited. Further, the influence of a romantic partner is unclear. The current study aims to a) investigate association between emotional difficulties and sexual risk behavior (e.g. sexual compulsivity and sensation-seeking) and b) explore the influence of a romantic partner on individual sexual risk. Participants were 49 couples (n=98) participating in a randomized control pilot intervention. Results demonstrated that individual and partner emotional difficulties were associated with sexual risk behavior. Results did not vary by gender.