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Lee EY, Kim J, Prado-Rico JM, Du G, Lewis MM, Kong L, Yanosky JD, Eslinger P, Kim BG, Hong YS, Mailman RB, Huang X. Effects of mixed metal exposures on MRI diffusion features in the medial temporal lobe. Neurotoxicology 2024; 105:196-207. [PMID: 39395642 DOI: 10.1016/j.neuro.2024.10.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2024] [Revised: 09/01/2024] [Accepted: 10/08/2024] [Indexed: 10/14/2024]
Abstract
BACKGROUND Environmental exposure to metal mixtures is common and may be associated with increased risk for neurodegenerative disorders including Alzheimer's disease. This study examined associations of mixed metal exposures with medial temporal lobe (MTL) MRI structural metrics and neuropsychological performance. METHODS Metal exposure history, whole blood metal, MRI R1 (1/T1) and R2* (1/T2*) metrics (estimates of brain Mn and Fe, respectively), and neuropsychological tests were obtained from subjects with/without a history of mixed metal exposure from welding fumes (42 exposed subjects; 31 controls). MTL structures (hippocampus, entorhinal and parahippocampal cortices) were assessed by morphologic (volume or cortical thickness) and diffusion tensor imaging [mean (MD), axial (AxD), radial diffusivity (RD), and fractional anisotropy (FA)] metrics. In exposed subjects, effects of mixed metal exposure on MTL structural and neuropsychological metrics were examined. RESULTS Compared to controls, exposed subjects displayed higher MD, AxD, and RD throughout all MTL ROIs (p's<0.001) with no morphological differences. They also had poorer performance in processing/psychomotor speed, executive, and visuospatial domains (p's<0.046). Long-term mixed metal exposure history indirectly predicted lower processing speed performance via lower parahippocampal FA (p's<0.023). Higher entorhinal R1 and whole blood Mn and Cu levels predicted higher entorhinal diffusivity (p's<0.043) and lower Delayed Story Recall performance (p=0.007). DISCUSSION Mixed metal exposure predicted certain MTL structural and neuropsychological features that are similar to those detected in Alzheimer's disease at-risk populations. These data warrant follow-up as they may illuminate a potential path for environmental exposure to brain changes associated with Alzheimer's disease-related health outcomes.
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Niu W, Lam JSW, Vu T, Du G, Fan H, Zheng L. Mechanistic diversity and functional roles define the substrate specificity and ligand binding of bacterial PGP phosphatases. J Biol Chem 2024; 300:107959. [PMID: 39510191 PMCID: PMC11629553 DOI: 10.1016/j.jbc.2024.107959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2024] [Revised: 10/24/2024] [Accepted: 10/26/2024] [Indexed: 11/15/2024] Open
Abstract
Phosphatidylglycerol is a critical membrane phospholipid in microorganisms, synthesized via the dephosphorylation of phosphatidylglycerol-phosphate (PGP) by three membrane-bound phosphatases: PgpA, PgpB, and PgpC. While any one of these enzymes can produce phosphatidylglycerol at WT levels, the reason for the presence of all three in bacteria remains unclear. To address this question, we characterized these phosphatases in vitro to uncover their mechanistic differences. Our assays demonstrated that all three enzymes catalyze the hydrolysis of PGP but exhibit distinct substrate selectivity. PgpB displays a broad substrate range, dephosphorylating various lipid phosphates, while PgpA and PgpC show a higher specificity for lysophosphatidic acid and PGP. Notably, PgpA also effectively dephosphorylates soluble metabolites, such as glycerol-3-phosphate and glyceraldehyde-3-phosphate, suggesting its unique substrate-binding mechanism that relies on precise recognition of the glycerol head group rather than the fatty acid. Inhibitor screening with synthetic substrate analogs revealed that PgpB is inhibited by lipid-like compounds XY-14 and XY-55, whereas PgpA and PgpC are unaffected. Structural analysis and mutational studies identified two charged residues at the catalytic site entry for inhibitor binding in PgpB and support the notion that the PgpB maintains a large substrate binding site to accommodate multiple ligand binding conformations. These findings underscore the distinct substrate recognition mechanisms and possible functional roles of PgpA, PgpB, and PgpC in bacterial lipid metabolism and offer insights for developing novel inhibitors targeting bacterial membrane phospholipid biosynthesis.
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Lewis MM, Mailman RB, Cheng XV, Du G, Zhang L, Li C, De Jesus S, Tabbal SD, Li R, Huang X. Clinical progression of Parkinson's disease in the early 21st century: Insights from the accelerating medicine partnership (AMP-PD) data. Parkinsonism Relat Disord 2024; 130:107186. [PMID: 39541725 DOI: 10.1016/j.parkreldis.2024.107186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2024] [Revised: 10/22/2024] [Accepted: 10/23/2024] [Indexed: 11/16/2024]
Abstract
BACKGROUND Parkinson's disease (PD) therapeutic strategies have evolved since levodopa introduction in mid 1900s. To understand their impact and research gaps, this study delineated the clinical progression of PD in recent years. METHODS Using Accelerating Medicine Partnership-PD (AMP-PD) data harmonized from seven biomarker discovery studies (2010-2020), we extracted: overall [Schwab and England (S&E), PD Questionnaire (PDQ-39)]; motor [Movement Disorders Society Unified PD Rating Scale (MDS-UPDRS)-II and -III and Hoehn & Yahr (HY)]; and non-motor [MDS-UPDRS-I, University of Pennsylvania Smell Identification Test (UPSIT), Montreal Cognitive Assessment (MoCA), and Epworth Sleepiness Scale (ESS)] scores. Age at diagnosis was set as 0 years, and data were tracked for 15 subsequent years. RESULTS Among 3001 PD cases identified to be suitable for this study, 2838 are white, 1843 are males, with a mean age at diagnosis was 60.2 ± 10.3 years. At baseline evaluation, the disease duration was 9.9 ± 6.0 years overall, 1915 within 0-5, 541 with 6-10, 254 within 11-15, and 163 greater than 15 years. Participants largely reported independence (S&E, 5y: 86.6 ± 12.3; 10y: 78.9 ± 19.3; 15y: 78.5 ± 17.0) and good quality of life (PDQ-39, 5y: 15.5 ± 12.3; 10y: 22.1 ± 15.8; 15y: 24.3 ± 14.4). Motor scores displayed a linear progression, whereas non-motor scores plateaued ∼10-15 years. Younger onset age and female correlated with slower progression. CONCLUSIONS Twenty-first century PD patients remain largely independent in the first decade of disease at tertiary subspecialty care and research centers. There are data gaps for those who are non-whites or longer PD duration, and sensible metrics that can gauge non-motor progression when PD is beyond 10 years.
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Niu W, Vu T, Du G, Bogdanov M, Zheng L. Lysophospholipid remodeling mediated by the LplT and Aas protein complex in the bacterial envelope. J Biol Chem 2024; 300:107704. [PMID: 39173951 PMCID: PMC11416262 DOI: 10.1016/j.jbc.2024.107704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2024] [Revised: 08/12/2024] [Accepted: 08/13/2024] [Indexed: 08/24/2024] Open
Abstract
Lysophospholipid transporter LplT and acyltransferase Aas consist of a lysophospholipid-remodeling system ubiquitously found in gram-negative microorganisms. LplT flips lysophospholipid across the inner membrane which is subsequently acylated by Aas on the cytoplasmic membrane surface. Our previous study showed that the proper functioning of this system is important to protecting Escherichia coli from phospholipase-mediated host attack by maintaining the integrity of the bacterial cell envelope. However, the working mechanism of this system is still unclear. Herein, we report that LplT and Aas form a membrane protein complex in E. coli which allows these two enzymes to cooperate efficiently to move lysophospholipids across the bacterial membrane and catalyze their acylation. The direct interaction of LplT and Aas was demonstrated both in vivo and in vitro with a binding affinity of 2.3 μM. We found that a cytoplasmic loop of LplT adjacent to the exit of the substrate translocation pathway plays an important role in maintaining its interaction with Aas. Aas contains an acyl-acyl carrier protein synthase domain and an acyl-transferase domain. Its interaction with LplT is mediated exclusively by its transferase domain. Mutations within the three loops near the putative catalytic site of the transferase domain, respectively, disrupt its interaction with LplT and lysophospholipid acylation activity. These results support a hypothesis of the functional coupling mechanism, in which LplT directly interacts with the transferase domain of Aas for specific substrate membrane migration, providing synchronization of substrate translocation and biosynthetic events.
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Johnson ML, Lewis MM, Wang EW, Jellen LC, Du G, De Jesus S, Kong L, Pu C, Huang X. Neuropathological findings and in vivo imaging correlates of the red nucleus compared to those of the substantia nigra pars compacta in parkinsonisms. Parkinsonism Relat Disord 2024; 125:107043. [PMID: 38896976 PMCID: PMC11283947 DOI: 10.1016/j.parkreldis.2024.107043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 06/03/2024] [Accepted: 06/14/2024] [Indexed: 06/21/2024]
Abstract
INTRODUCTION The substantia nigra pars compacta (SNc) is the key pathologic locus in neurodegenerative parkinsonian disorders. Recently, in vivo susceptibility MRI metrics were associated with postmortem glial cell density and tau burden in the SNc of parkinsonism subjects. This study investigated the red nucleus (RN), another iron-rich region adjacent to the SNc and a potential site of higher functionality in parkinsonisms. METHODS In vivo MRI and postmortem data were obtained from 34 parkinsonism subjects and 3 controls. Neuron density, glial cell density, and percentages of area occupied by α-synuclein and tau were quantified using digitized midbrain slides. R2* and quantitative susceptibility mapping (QSM) metrics in the RN and SNc were derived from multi-gradient echo images. Histopathology data were compared between the RN and SNc using paired t-tests. MRI-histology associations were analyzed using partial Pearson correlations. RESULTS The RN had greater neuron (t23 = 3.169, P = 0.004) and glial cell densities (t23 = 2.407, P = 0.025) than the SNc, whereas the SNc had greater α-synuclein (t28 = 4.614, P < 0.0001) and tau burden (t24 = 4.513, P = 0.0001). In both the RN (R2*: r = 0.47, P = 0.043; QSM: r = 0.52, P = 0.024) and SNc (R2*: r = 0.57, P = 0.01; QSM: r = 0.58, P = 0.009), MRI values were associated with glial cell density but not neuron density or α-synuclein (Ps > 0.092). QSM associated with tau burden (r = 0.49, P = 0.038) in the SNc, but not the RN. CONCLUSIONS The RN is resilient to parkinsonian-related pathological processes compared to the SNc, and susceptibility MRI captured glial cell density in both regions. These findings help to further our understanding of the underlying pathophysiological processes in parkinsonisms.
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Li YE, Norris DM, Xiao FN, Pandzic E, Whan RM, Fok S, Zhou M, Du G, Liu Y, Du X, Yang H. Phosphatidylserine regulates plasma membrane repair through tetraspanin-enriched macrodomains. J Cell Biol 2024; 223:e202307041. [PMID: 38530252 PMCID: PMC10964951 DOI: 10.1083/jcb.202307041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 11/30/2023] [Accepted: 03/11/2024] [Indexed: 03/27/2024] Open
Abstract
The integrity of the plasma membrane is critical to cell function and survival. Cells have developed multiple mechanisms to repair damaged plasma membranes. A key process during plasma membrane repair is to limit the size of the damage, which is facilitated by the presence of tetraspanin-enriched rings surrounding damage sites. Here, we identify phosphatidylserine-enriched rings surrounding damaged sites of the plasma membrane, resembling tetraspanin-enriched rings. Importantly, the formation of both the phosphatidylserine- and tetraspanin-enriched rings requires phosphatidylserine and its transfer proteins ORP5 and ORP9. Interestingly, ORP9, but not ORP5, is recruited to the damage sites, suggesting cells acquire phosphatidylserine from multiple sources upon plasma membrane damage. We further demonstrate that ORP9 contributes to efficient plasma membrane repair. Our results thus unveil a role for phosphatidylserine and its transfer proteins in facilitating the formation of tetraspanin-enriched macrodomains and plasma membrane repair.
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Tian J, Zhao T, Tu R, Zhang B, Huang Y, Shen Z, Wang Y, Du G. Achromobacter species (sp.) outbreak caused by hospital equipment containing contaminated water: risk factors for infection. J Hosp Infect 2024; 146:141-147. [PMID: 38403082 DOI: 10.1016/j.jhin.2024.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 01/30/2024] [Accepted: 02/07/2024] [Indexed: 02/27/2024]
Abstract
BACKGROUND Nosocomial outbreaks of urinary tract infections caused by Achromobacter spp. have been rare in recent decades. AIM To identify the origin of an Achromobacter sp. outbreak, conduct multi-modal infection control measures, and finally to stop the outbreak. To this end, an epidemiological outbreak investigation and risk factor analysis were performed. METHODS Achromobacter sp. was detected in 22 patients in our urology wards and six environmental cultures of specimens obtained from the operating rooms. Strains isolated were submitted for antimicrobial susceptibility testing. An on-site epidemiological investigation, evaluation of patient medical records, and environmental sampling were performed to identify the source of the outbreak, and implementation of infection control intervention. A case-control study was performed to analyse the potential risk factors. FINDINGS Environmental sampling showed that the source of the infection for 22 patients was an ISA-IIIA-type medical pressurizer containing contaminated water. A case-control analysis showed that the risk factors for infection were: diagnosis of kidney/ureteral stones, surgery, placement of a double-J stent, and history of hospitalization in the past three months. CONCLUSION It was concluded that the outbreak occurred in patients who underwent internal lithotripsy and double-J stent placement, due to contact transmission with the contaminated sensor and connecting tubes of the ISA-IIIA-type medical pressurizer.
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Lee EY, Kim J, Prado-Rico JM, Du G, Lewis MM, Kong L, Yanosky JD, Eslinger P, Kim BG, Hong YS, Mailman RB, Huang X. Effects of mixed metal exposures on MRI diffusion features in the medial temporal lobe. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2023.07.18.23292828. [PMID: 37503124 PMCID: PMC10371112 DOI: 10.1101/2023.07.18.23292828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Background Environmental exposure to metal mixtures is common and may be associated with increased risk for neurodegenerative disorders including Alzheimer's disease. Objective This study examined associations of mixed metal exposures with medial temporal lobe (MTL) MRI structural metrics and neuropsychological performance. Methods Metal exposure history, whole blood metal, and neuropsychological tests were obtained from subjects with/without a history of mixed metal exposure from welding fumes (42 exposed subjects; 31 controls). MTL structures (hippocampus, entorhinal and parahippocampal cortices) were assessed by morphologic (volume, cortical thickness) and diffusion tensor imaging [mean (MD), axial (AD), radial diffusivity (RD), and fractional anisotropy (FA)] metrics. In exposed subjects, correlation, multiple linear, Bayesian kernel machine regression, and mediation analyses were employed to examine effects of single- or mixed-metal predictor(s) and their interactions on MTL structural and neuropsychological metrics; and on the path from metal exposure to neuropsychological consequences. Results Compared to controls, exposed subjects had higher blood Cu, Fe, K, Mn, Pb, Se, and Zn levels (p's<0.026) and poorer performance in processing/psychomotor speed, executive, and visuospatial domains (p's<0.046). Exposed subjects displayed higher MD, AD, and RD in all MTL ROIs (p's<0.040) and lower FA in entorhinal and parahippocampal cortices (p's<0.033), but not morphological differences. Long-term mixed-metal exposure history indirectly predicted lower processing speed performance via lower parahippocampal FA (p=0.023). Higher whole blood Mn and Cu predicted higher entorhinal diffusivity (p's<0.043) and lower Delayed Story Recall performance (p=0.007) without overall metal mixture or interaction effects. Discussion Mixed metal exposure predicted MTL structural and neuropsychological features that are similar to Alzheimer's disease at-risk populations. These data warrant follow-up as they may illuminate the path for environmental exposure to Alzheimer's disease-related health outcomes.
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Lee EY, Kim J, Prado-Rico JM, Du G, Lewis MM, Kong L, Kim BG, Hong YS, Yanosky JD, Mailman RB, Huang X. Higher hippocampal diffusivity values in welders are associated with greater R2* in the red nucleus and lower psychomotor performance. Neurotoxicology 2023; 96:53-68. [PMID: 36966945 PMCID: PMC10445214 DOI: 10.1016/j.neuro.2023.03.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 02/17/2023] [Accepted: 03/22/2023] [Indexed: 04/05/2023]
Abstract
INTRODUCTION Chronic excessive welding exposure may be related to higher metal accumulation and structural differences in different subcortical structures. We examined how welding affected brain structures and their associations with metal exposure and neurobehavioral consequences. METHODS Study includes 42 welders and 31 controls without a welding history. Welding-related structural differences were assessed by volume and diffusion tensor imaging (DTI) metrics in basal ganglia, red nucleus (RN), and hippocampus. Metal exposure was estimated by both exposure questionnaires and whole blood metal levels. Brain metal accumulations were estimated by R1 (for Mn) and R2* (for Fe). Neurobehavioral status was assessed by standard neuropsychological tests. RESULTS Compared to controls, welders displayed higher hippocampal mean (MD), axial (AD), and radial diffusivity (RD) (p's < 0.036), but similar DTI or volume in other ROIs (p's > 0.117). Welders had higher blood metal levels (p's < 0.004), higher caudate and RN R2* (p's < 0.014), and lower performance on processing/psychomotor speed, executive function, and visuospatial processing tasks (p's < 0.046). Higher caudate and RN R2* were associated with higher blood Fe and Pb (p's < 0.043), respectively. RN R2* was a significant predictor of all hippocampal diffusivity metrics (p's < 0.006). Higher hippocampal MD and RD values were associated with lower Trail Making Test-A scores (p's < 0.025). A mediation analysis of both groups revealed blood Pb indirectly affected hippocampal diffusivity via RN R2* (p's < 0.041). DISCUSSION Welding-related higher hippocampal diffusivity metrics may be associated with higher RN R2* and lower psychomotor speed performance. Future studies are warranted to test the role of Pb exposure in these findings.
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Wang EW, Brown GL, Lewis MM, Jellen LC, Pu C, Johnson ML, Chen H, Kong L, Du G, Huang X. Susceptibility Magnetic Resonance Imaging Correlates with Glial Density and Tau in the Substantia Nigra Pars Compacta. Mov Disord 2023; 38:464-473. [PMID: 36598274 PMCID: PMC10445152 DOI: 10.1002/mds.29311] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Revised: 12/13/2022] [Accepted: 12/16/2022] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Susceptibility magnetic resonance imaging (MRI) is sensitive to iron-related changes in the substantia nigra pars compacta (SNc), the key pathologic locus of parkinsonisms. It is unclear, however, if iron deposition in the SNc is associated with its neurodegeneration. OBJECTIVE The objective of this study was to test whether susceptibility MRI metrics in parkinsonisms are associated with SNc neuropathologic features of dopaminergic neuron loss, gliosis, and α-synuclein and tau burden. METHODS This retrospective study included 27 subjects with both in vivo MRI and postmortem data. Multigradient echo imaging was used to derive the apparent transverse relaxation rate (R2*) and quantitative susceptibility mapping (QSM) in the SNc. Archived midbrain slides that were stained with hematoxylin and eosin, anti-α-synuclein, and anti-tau were digitized to quantify neuromelanin-positive neuron density, glial density, and the percentages of area occupied by positive α-synuclein and tau staining. MRI-histology associations were examined using Pearson correlations and regression. RESULTS Twenty-four subjects had postmortem parkinsonism diagnoses (Lewy body disorder, progressive supranuclear palsy, multiple system atrophy, and corticobasal degeneration), two had only Alzheimer's neuropathology, and one exhibited only mild atrophy. Among all subjects, both R2* and QSM were associated with glial density (r ≥ 0.67; P < 0.001) and log-transformed tau burden (r ≥ 0.53; P ≤ 0.007). Multiple linear regression identified glial density and log-transformed tau as determinants for both MRI metrics (R2 ≥ 0.580; P < 0.0001). Neither MRI metric was associated with neuron density or α-synuclein burden. CONCLUSIONS R2* and QSM are associated with both glial density and tau burden, key neuropathologic features in the parkinsonism SNc. © 2023 International Parkinson and Movement Disorder Society.
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Brown G, Hakun J, Lewis MM, De Jesus S, Du G, Eslinger PJ, Kong L, Huang X. Frontostriatal and limbic contributions to cognitive decline in Parkinson's disease. J Neuroimaging 2023; 33:121-133. [PMID: 36068704 PMCID: PMC9840678 DOI: 10.1111/jon.13045] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 08/21/2022] [Accepted: 08/22/2022] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND AND PURPOSE The circuitry underlying heterogenous cognitive profiles in Parkinson's disease (PD) remains unclear. The purpose of this study is to investigate whether structural changes in frontostriatal and limbic pathways contribute to different cognitive trajectories in PD. METHODS We obtained clinical and multimodal MRI data from 120 control and 122 PD subjects without dementia or severe motor disability. T1/T2-weighted images estimated volume, and diffusion imaging evaluated fractional anisotropy (FA) of frontostriatal (striatum and frontostriatal white matter [FSWM]) and limbic (hippocampus and fornix) structures. Montreal Cognitive Assessment (MoCA) gauged total and domain-specific (attention/executive and memory) cognitive function. Linear mixed-effects models were used to compare MRI and cognitive progression over 4.5 years between controls and PD and evaluate associations between baseline MRI and cognitive changes in PD. RESULTS At baseline, control and PD groups were comparable, except PD participants had smaller striatal volume (p < 0.001). Longitudinally, PD showed faster decline in hippocampal volume, FSWM FA, and fornix FA (ps < .016), but not striatal volume (p = .218). Total and domain-specific MoCA scores declined faster in PD (ps < .030). In PD, lower baseline hippocampal volume (p = .005) and fornix FA (p = .032), but not striatal volume (p = .662) or FSWM FA (p = .143), were associated with faster total MoCA decline. Baseline frontostriatal metrics of striatal volume and FSWM FA were associated with faster attention/executive decline (p < .038), whereas lower baseline hippocampal volume was associated with faster memory decline (p = .005). CONCLUSION In PD, frontostriatal structural metrics are associated with attention/executive tasks, whereas limbic changes correlated with faster global cognitive decline, particularly in memory tasks.
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Xiong J, Luu TTT, Venkatachalam K, Du G, Zhu MX. Glutamine Produces Ammonium to Tune Lysosomal pH and Regulate Lysosomal Function. Cells 2022; 12:cells12010080. [PMID: 36611873 PMCID: PMC9819001 DOI: 10.3390/cells12010080] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 12/21/2022] [Accepted: 12/21/2022] [Indexed: 12/28/2022] Open
Abstract
Glutamine is one of the most abundant amino acids in the cell. In mitochondria, glutaminases 1 and 2 (GLS1/2) hydrolyze glutamine to glutamate, which serves as the precursor of multiple metabolites. Here, we show that ammonium generated during GLS1/2-mediated glutaminolysis regulates lysosomal pH and in turn lysosomal degradation. In primary human skin fibroblasts BJ cells and mouse embryonic fibroblasts, deprivation of total amino acids for 1 h increased lysosomal degradation capacity as shown by the increased turnover of lipidated microtubule-associated proteins 1A/1B light chain 3B (LC3-II), several autophagic receptors, and endocytosed DQ-BSA. Removal of glutamine but not any other amino acids from the culture medium enhanced lysosomal degradation similarly as total amino acid starvation. The presence of glutamine in regular culture media increased lysosomal pH by >0.5 pH unit and the removal of glutamine caused lysosomal acidification. GLS1/2 knockdown, GLS1 antagonist, or ammonium scavengers reduced lysosomal pH in the presence of glutamine. The addition of glutamine or NH4Cl prevented the increase in lysosomal degradation and curtailed the extension of mTORC1 function during the early time period of amino acid starvation. Our findings suggest that glutamine tunes lysosomal pH by producing ammonium, which regulates lysosomal degradation to meet the demands of cellular activities. During the early stage of amino acid starvation, the glutamine-dependent mechanism allows more efficient use of internal reserves and endocytosed proteins to extend mTORC1 activation such that the normal anabolism is not easily interrupted by a brief disruption of the amino acid supply.
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de Freitas PB, Freitas SMSF, Prado-Rico JM, Lewis MM, Du G, Yanosky JD, Huang X, Latash ML. Synergic control in asymptomatic welders during multi-finger force exertion and load releasing while standing. Neurotoxicology 2022; 93:324-336. [PMID: 36309163 PMCID: PMC10398836 DOI: 10.1016/j.neuro.2022.10.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 10/21/2022] [Accepted: 10/22/2022] [Indexed: 11/06/2022]
Abstract
Motor synergies, i.e., neural mechanisms that organize multiple motor elements to ensure stability of actions, are affected by several neurological condition. Asymptomatic welders showed impaired synergy controlling the stability of multi-finger action compared to non-welders and this impairment was associated with microstructural damage in the globus pallidus. We further explored the effect of welding-related metal exposure on multi-finger synergy and extended our investigation to posture-stabilizing synergy during a standing task. Occupational, MRI, and performance-stabilizing synergies during multi-finger accurate force production and load releasing while standing were obtained from 29 welders and 19 age- and sex-matched controls. R2* and R1 relaxation rate values were used to estimate brain iron and manganese content, respectively, and diffusion tensor imaging was used to reflect brain microstructural integrity. Associations of brain MRI (caudate, putamen, globus pallidus, and red nucleus), and motor synergy were explored by group status. The results revealed that welders had higher R2* values in the caudate (p = 0.03), putamen (p = 0.01), and red nucleus (p = 0.08, trend) than controls. No group effect was revealed on multi-finger synergy index during steady-state phase of action (ΔVZss). Compared to controls, welders exhibited lower ΔVZss (-0.106 ± 0.084 vs. 0.160 ± 0.092, p = 0.04) and variance that did not affect the performance variable (VUCM, 0.022 ± 0.003 vs. 0.038 ± 0.007, p = 0.03) in the load releasing, postural task. The postural synergy index, ΔVZss, was associated negatively with higher R2* in the red nucleus in welders (r = -0.44, p = 0.03), but not in controls. These results suggest that the synergy index in the load releasing during a standing task may reflect welding-related neurotoxicity in workers with chronic metals exposure. This finding may have important clinical and occupational health implications.
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Zhou H, Zhang Z, Yang S, Gong X, Liu Y, Du G, Chen J. Logistic regression analysis of risk factors for intra-abdominal hypertension after giant ventral hernia repair: a retrospective cohort study. Hernia 2022; 27:305-309. [PMID: 36169738 DOI: 10.1007/s10029-022-02667-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 08/17/2022] [Indexed: 11/26/2022]
Abstract
BACKGROUND Intra-abdominal hypertension (IAH) is a classical complication after giant ventral hernia surgery and may lead to abdominal compartment syndrome (ACS). Assessment of risk factors and prevention of IAH/ACS are essential for hernia surgeons. METHODS We performed a retrospective study including 58 giant ventral hernia patients in our center between Jan 1, 2017, and Mar 1, 2022, we recorded age, gender, chronic obstructive pulmonary disease (COPD), coronary heart disease (CHD), hypertension, type 2 diabetes mellitus (T2DM), hypoproteinemia, body mass index (BMI), the ratio of hernia sac volume to abdominal cavity volume (HSV/ACV), defect width, tension reduction procedure (TRP), positive fluid balance (PFB) and IAH of these patients and analyzed the data using univariate and multivariate logistic regression to screen the risk factors for IAH after surgery. RESULTS The multivariate analysis showed that HSV/ACV ≥ 25%, hypoproteinemia, and PFB were independent risk factors for the occurrence of IAH after giant ventral hernia repair (P = 0.025, 0.016, 0.017, respectively). We did not find any correlation between postoperative IAH and the patient's age, gender, COPD, CHD, hypertension, T2DM, BMI, defect width, TRP, and PFB. CONCLUSION Identifying risk factors is of great significance for the early identification and prevention of IAH/ACS. We found that HSV/ACV ≥ 25%, hypoproteinemia, and PFB were independent risk factors for IAH after giant ventral hernia repair.
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Du G, Wang E, Sica C, Chen H, De Jesus S, Lewis MM, Kong L, Connor J, Mailman RB, Huang X. Dynamics of Nigral Iron Accumulation in Parkinson's Disease: From Diagnosis to Late Stage. Mov Disord 2022; 37:1654-1662. [PMID: 35614551 PMCID: PMC9810258 DOI: 10.1002/mds.29062] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 04/08/2022] [Accepted: 05/02/2022] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Higher nigral iron has been reported in Parkinson's disease (PD). OBJECTIVE The aim is to understand the dynamics of nigral iron accumulation in PD and its association with drug treatment. METHODS Susceptibility magnetic resonance imaging data were obtained from 79 controls and 18 drug-naive (PDDN ) and 87 drug-treated (PDDT ) PD patients. Regional brain iron in basal ganglia and cerebellar structures was estimated using quantitative susceptibility mapping. Nigral iron was compared between PDDN and PDDT subgroups defined by disease duration (early [PDE, <2 years], middle [PDM, 2-6 years], and later [PDL, >6 years]). Associations with both disease duration and types of antiparkinson drugs were explored using regression analysis. RESULTS Compared to controls, PDDN had lower iron in the substantia nigra (P = 0.018), caudate nucleus (P = 0.038), and globus pallidus (P = 0.01) but not in the putamen or red nucleus. In contrast, PDDT had higher iron in the nigra (P < 0.001) but not in other regions, compared to either controls or PDDN . Iron in the nigra increased with disease duration (PDE > PDDN [P = 0.001], PDM > PDE [P = 0.045]) except for PDM versus PDL (P = 0.226). Levodopa usage was associated with higher (P = 0.013) nigral iron, whereas lower nigral iron was correlated with selegiline usage (P = 0.030). CONCLUSION Nigral iron is lower before the start of dopaminergic medication and then increases throughout the disease until it plateaus at late stages, suggesting increased iron may not be an etiological factor. Interestingly, PD medications may have differential associations with iron accumulation that need further investigation. © 2022 International Parkinson and Movement Disorder Society.
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Prado-Rico JM, Lee EY, Wang EW, Yanosky JD, Kong L, Chen H, Navas-Acien A, Du G, Lewis MM, Mailman RB, Huang X. Higher R2* in the Red Nucleus Is Associated With Lead Exposure in an Asymptomatic Welder Cohort. Toxicol Sci 2022; 187:345-354. [PMID: 35357496 PMCID: PMC9154244 DOI: 10.1093/toxsci/kfac035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Lead is a nonessential metal and may be a coexposure in welding fumes. Preclinical data indicate lead may affect iron regulation. The current study investigated blood lead concentrations and their association with brain iron accumulation in workers with chronic welding fume exposure, with a focus on iron-rich subcortical regions of the cerebellum and basal ganglia. Occupational exposure, whole blood metal, and brain MRI data were obtained from 29 controls and 42 welders. R2* (1/T2*) and R1 (T1 relaxation rate) values were used to estimate brain iron and manganese content, respectively. Blood metals and brain R2* (in the red nucleus [RN], dentate nucleus, caudate, putamen, globus pallidus, and substantia nigra) were compared between groups. Associations between brain R2* values and exposure metrics were tested within each group, and analyses were adjusted for potential confounders. Welders had significantly higher levels of whole blood lead, manganese, iron, and copper. Welders also had higher R2* RN (p = .002), but not R1. A 2nd-order polynomial modeled the association between R2* RN and a long-term welding exposure metric. In welders, but not controls, R2* RN was associated positively with whole blood lead (r = 0.54, p = .003), and negatively with whole blood manganese (r = -0.43, p = .02). Higher blood Pb and lower blood Mn independently accounted for variance in high RN R2*. Together, these data suggest that higher RN R2* values may mark lead exposure in welders. Because lead is a known neurotoxicant, additional studies are warranted to confirm this finding, and ascertain its scientific and public/occupational health implications.
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Lewis MM, Albertson RM, Du G, Kong L, Foy A, Huang X. Parkinson’s Disease Progression and Statins: Hydrophobicity Matters. JOURNAL OF PARKINSON'S DISEASE 2022; 12:821-830. [PMID: 34958045 PMCID: PMC10141621 DOI: 10.3233/jpd-212819] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Background: Recent randomized clinical trials using hydrophobic statins reported no influence on Parkinson’s disease (PD) clinical progression. Hydrophobicity is a key determinant for blood-brain barrier penetrance. Objective: Investigate a potential effect of statins on PD progression. Methods: Statin use was determined at baseline and subtyped according to hydrophobicity in 125 PD patients participating in the PD Biomarker Program (PDBP, 2012–2015) at our site. Clinical (N = 125) and susceptibility MRI (N = 86) data were obtained at baseline and 18-months. Movement Disorders Society-Unified PD Rating Scales were used to track progression of non-motor (MDS-UPDRS-I) and motor (MDS-UPDRS-II) symptoms, and rater-based scores (MDS-UPDRS-III) of patients in the “on” drug state. R2* values were used to capture pathological progression in the substantia nigra. Associations between statin use, its subtypes, and PD progression were evaluated with linear mixed effect regressions. Results: Compared to statin non-users, overall statin or lipophilic statin use did not significantly influence PD clinical or imaging progression. Hydrophilic statin users, however, demonstrated faster clinical progression of non-motor symptoms [MDS-UPDRS-I (β= 4.8, p = 0.010)] and nigral R2* (β= 3.7, p = 0.043). A similar trend was found for MDS-UPDRS-II (β= 3.9, p = 0.10), but an opposite trend was observed for rater-based MDS-UPDRS-III (β= –7.3, p = 0.10). Compared to lipophilic statin users, hydrophilic statin users also showed significantly faster clinical progression of non-motor symptoms [MDS-UPDRS-I (β= 5.0, p = 0.020)], but R2* did not reach statistical significance (β= 2.5, p = 0.24). Conclusion: This study suggests that hydrophilic, but not lipophilic, statins may be associated with faster PD progression. Future studies may have clinical and scientific implications.
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Brown G, Du G, Farace E, Lewis MM, Eslinger PJ, McInerney J, Kong L, Li R, Huang X, De Jesus S. Subcortical Iron Accumulation Pattern May Predict Neuropsychological Outcomes After Subthalamic Nucleus Deep Brain Stimulation: A Pilot Study. JOURNAL OF PARKINSON'S DISEASE 2022; 12:851-863. [PMID: 34974437 PMCID: PMC9181238 DOI: 10.3233/jpd-212833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Background: Neuropsychological outcomes after deep brain stimulation (DBS) are variable and may arise from the heterogeneous neuropathological processes in Parkinson’s disease (PD). Objective: To explore if brain iron accumulation patterns and its region-specific alterations relate to neuropsychological outcomes post-DBS. Methods: Thirty-two PD subjects were identified from our database with susceptibility MRI prior to bilateral subthalamic nucleus (STN) DBS between 2011–2016. Demographic (age, sex, education), clinical information (disease duration, neuropsychological scores), and R2* (susceptibility MRI measure reflecting iron) in 11 subcortical regions of interest were obtained. Neuropsychological outcomes were defined as changes in psychomotor speed, executive function, attention, memory, and depression by subtracting pre- and post-DBS scores. A penalized logistic analysis was used to identify the best pre-DBS clinical and R2* predictors for each neuropsychological domain. Pearson’s partial correlations explored R2* associations with neuropsychological outcomes. Results: Combined clinical and MRI metrics were associated better with neuropsychological outcomes (R2≥0.373, p-value≤0.008) than either alone. Adding R2* metrics increased prediction of executive function (R2=0.455, p=0.008) and attention (R2=0.182, p=0.018) outcomes over clinical metrics alone. Specifically, R2* in the substantia nigra, caudate, STN, and hippocampus improved prediction of executive function, and in the putamen for attention. Interestingly, higher caudate R2* correlated with better executive function (p=0.043), whereas higher putamen R2* associated with worsening attention (p=0.018). Conclusions: Brain iron accumulation patterns, captured by susceptibility MRI, may add value to clinical evaluation in predicting neuropsychological outcomes post-DBS in PD. Further studies are warranted to validate these findings and understand the region-specific relationships between iron and DBS outcomes.
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Jellen LC, Lewis MM, Du G, Wang X, Galvis MLE, Krzyzanowski S, Capan CD, Snyder AM, Connor JR, Kong L, Mailman RB, Brundin P, Brundin L, Huang X. Low plasma serotonin linked to higher nigral iron in Parkinson's disease. Sci Rep 2021; 11:24384. [PMID: 34934078 PMCID: PMC8692322 DOI: 10.1038/s41598-021-03700-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Accepted: 11/18/2021] [Indexed: 12/30/2022] Open
Abstract
A growing body of evidence suggests nigral iron accumulation plays an important role in the pathophysiology of Parkinson's disease (PD), contributing to dopaminergic neuron loss in the substantia nigra pars compacta (SNc). Converging evidence suggests this accumulation might be related to, or increased by, serotonergic dysfunction, a common, often early feature of the disease. We investigated whether lower plasma serotonin in PD is associated with higher nigral iron. We obtained plasma samples from 97 PD patients and 89 controls and MRI scans from a sub-cohort (62 PD, 70 controls). We measured serotonin concentrations using ultra-high performance liquid chromatography and regional iron content using MRI-based quantitative susceptibility mapping. PD patients had lower plasma serotonin (p < 0.0001) and higher nigral iron content (SNc: p < 0.001) overall. Exclusively in PD, lower plasma serotonin was correlated with higher nigral iron (SNc: r(58) = - 0.501, p < 0.001). This correlation was significant even in patients newly diagnosed (< 1 year) and stronger in the SNc than any other region examined. This study reveals an early, linear association between low serotonin and higher nigral iron in PD patients, which is absent in controls. This is consistent with a serotonin-iron relationship in the disease process, warranting further studies to determine its cause and directionality.
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Cai M, Wang Z, Luu TTT, Zhang D, Finke B, He J, Tay LWR, Di Paolo G, Du G. PLD1 promotes reactive oxygen species production in vascular smooth muscle cells and injury-induced neointima formation. Biochim Biophys Acta Mol Cell Biol Lipids 2021; 1867:159062. [PMID: 34610470 DOI: 10.1016/j.bbalip.2021.159062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 08/28/2021] [Accepted: 08/31/2021] [Indexed: 10/20/2022]
Abstract
Phospholipase D (PLD) generates the signaling lipid phosphatidic acid (PA) and has been known to mediate proliferation signal in vascular smooth muscle cells (VSMCs). However, it remains unclear how PLD contributes to vascular diseases. VSMC proliferation directly contributes to the development and progression of cardiovascular disease, such as atherosclerosis and restenosis after angioplasty. Using the mouse carotid artery ligation model, we find that deletion of Pld1 gene inhibits neointima formation of the injuried blood vessels. PLD1 deficiency reduces the proliferation of VSMCs in both injured artery and primary cultures through the inhibition of ERK1/2 and AKT signals. Immunohistochemical staining of injured artery and flow cytometry analysis of VSMCs shows a reduction of the levels of reactive oxygen species (ROS) in Pld1-/- VSMCs. An increase of intracellular ROS by hydrogen peroxide stimulation restored the reduced activities of ERK and AKT in Pld1-/- VSMCs, whereas a reduction of ROS by N-acetyl-l-cysteine (NAC) scavenger lowered their activity in wild-type VSMCs. These results indicate that PLD1 plays a critical role in neointima, and that PLD1 mediates VSMC proliferation signal through promoting the production of ROS. Therefore, inhibition of PLD1 may be used as a therapeutic approach to suppress neointimal formation in atherosclerosis and restenosis after angioplasty.
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Kalam A, Al-Sehemi A, Alrumman S, Du G, Assiri M, Hesham AEL. Antibacterial studies of bio-functionalized carbon decorated silver nanoparticles (AgNPs). J INDIAN CHEM SOC 2021. [DOI: 10.1016/j.jics.2021.100155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Han F, Brown GL, Zhu Y, Belkin-Rosen AE, Lewis MM, Du G, Gu Y, Eslinger PJ, Mailman RB, Huang X, Liu X. Decoupling of Global Brain Activity and Cerebrospinal Fluid Flow in Parkinson's Disease Cognitive Decline. Mov Disord 2021; 36:2066-2076. [PMID: 33998068 PMCID: PMC8453044 DOI: 10.1002/mds.28643] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 04/19/2021] [Accepted: 04/26/2021] [Indexed: 11/07/2022] Open
Abstract
BACKGROUND Deposition and spreading of misfolded proteins (α-synuclein and tau) have been linked to Parkinson's disease cognitive dysfunction. The glymphatic system may play an important role in the clearance of these toxic proteins via cerebrospinal fluid (CSF) flow through perivascular and interstitial spaces. Recent studies discovered that sleep-dependent global brain activity is coupled to CSF flow, which may reflect glymphatic function. OBJECTIVE The objective of this current study was to determine if the decoupling of brain activity-CSF flow is linked to Parkinson's disease cognitive dysfunction. METHODS Functional and structural MRI data, clinical motor (Unified Parkinson's Disease Rating Scale), and cognitive (Montreal Cognitive Assessment [MoCA]) scores were collected from 60 Parkinson's disease and 58 control subjects. Parkinson's disease patients were subgrouped into those with mild cognitive impairment (MoCA < 26), n = 31, and those without mild cognitive impairment (MoCA ≥ 26), n = 29. The coupling strength between the resting-state global blood-oxygen-level-dependent signal and associated CSF flow was quantified, compared among groups, and associated with clinical and structural measurements. RESULTS Global blood-oxygen-level-dependent signal-CSF coupling decreased significantly (P < 0.006) in Parkinson's disease patients showing mild cognitive impairment, compared with those without mild cognitive impairment and controls. Reduced global blood-oxygen-level-dependent signal-CSF coupling was associated with decreased MoCA scores present in Parkinson's disease patients (P = 0.005) but not in controls (P = 0.65). Weaker global blood-oxygen-level-dependent signal-CSF coupling in Parkinson's disease patients also was associated with a thinner right entorhinal cortex (Spearman's correlation, -0.36; P = 0.012), an early structural change often seen in Alzheimer's disease. CONCLUSIONS The decoupling between global brain activity and associated CSF flow is related to Parkinson's disease cognitive impairment. © 2021 International Parkinson and Movement Disorder Society.
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Venkatraman G, Tang X, Du G, Parisentti AM, Hemmings DG, Brindley DN. Lysophosphatidate Promotes Sphingosine 1-Phosphate Metabolism and Signaling: Implications for Breast Cancer and Doxorubicin Resistance. Cell Biochem Biophys 2021; 79:531-545. [PMID: 34415509 DOI: 10.1007/s12013-021-01024-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 07/09/2021] [Indexed: 10/20/2022]
Abstract
Lysophosphatidate (LPA) and sphingosine 1-phosphate (S1P) promote vasculogenesis, angiogenesis, and wound healing by activating a plethora of overlapping signaling pathways that stimulate mitogenesis, cell survival, and migration. As such, maladaptive signaling by LPA and S1P have major effects in increasing tumor progression and producing poor patient outcomes after chemotherapy and radiotherapy. Many signaling actions of S1P and LPA are not redundant; each are vital in normal physiology and their metabolisms differ. In the present work, we studied how LPA signaling impacts S1P metabolism and signaling in MDA-MB-231 and MCF-7 breast cancer cells. LPA increased sphingosine kinase-1 (SphK1) synthesis and rapidly activated cytosolic SphK1 through association with membranes. Blocking phospholipase D activity attenuated the LPA-induced activation of SphK1 and the synthesis of ABCC1 and ABCG2 transporters that secrete S1P from cells. This effect was magnified in doxorubicin-resistant MCF-7 cells. LPA also facilitated S1P signaling by increasing mRNA expression for S1P1 receptors. Doxorubicin-resistant MCF-7 cells had increased S1P2 and S1P3 receptor expression and show increased LPA-induced SphK1 activation, increased expression of ABCC1, ABCG2 and greater S1P secretion. Thus, LPA itself and LPA-induced S1P signaling counteract doxorubicin-induced death of MCF-7 cells. We conclude from the present and previous studies that LPA promotes S1P metabolism and signaling to coordinately increase tumor growth and metastasis and decrease the effectiveness of chemotherapy and radiotherapy for breast cancer treatment.
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Metz C, Oyanadel C, Jung J, Retamal C, Cancino J, Barra J, Venegas J, Du G, Soza A, González A. Phosphatidic acid-PKA signaling regulates p38 and ERK1/2 functions in ligand-independent EGFR endocytosis. Traffic 2021; 22:345-361. [PMID: 34431177 DOI: 10.1111/tra.12812] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Revised: 07/27/2021] [Accepted: 08/16/2021] [Indexed: 12/16/2022]
Abstract
Ligand-independent epidermal growth factor receptor (EGFR) endocytosis is inducible by a variety of stress conditions converging upon p38 kinase. A less known pathway involves phosphatidic acid (PA) signaling toward the activation of type 4 phosphodiesterases (PDE4) that decrease cAMP levels and protein kinase A (PKA) activity. This PA/PDE4/PKA pathway is triggered with propranolol used to inhibit PA hydrolysis and induces clathrin-dependent and clathrin-independent endocytosis, followed by reversible accumulation of EGFR in recycling endosomes. Here we give further evidence of this signaling pathway using biosensors of PA, cAMP, and PKA in live cells and then show that it activates p38 and ERK1/2 downstream the PKA inhibition. Clathrin-silencing and IN/SUR experiments involved the activity of p38 in the clathrin-dependent route, while ERK1/2 mediates clathrin-independent EGFR endocytosis. The PA/PDE4/PKA pathway selectively increases the EGFR endocytic rate without affecting LDLR and TfR constitute endocytosis. This selectiveness is probably because of EGFR phosphorylation, as detected in Th1046/1047 and Ser669 residues. The EGFR accumulates at perinuclear recycling endosomes colocalizing with TfR, fluorescent transferrin, and Rab11, while a small proportion distributes to Alix-endosomes. A non-selective recycling arrest includes LDLR and TfR in a reversible manner. The PA/PDE4/PKA pathway involving both p38 and ERK1/2 expands the possibilities of EGFR transmodulation and interference in cancer.
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Wang EW, Trojano ML, Lewis MM, Du G, Chen H, Brown GL, Jellen LC, Song I, Neely E, Kong L, Connor JR, Huang X. HFE H63D Limits Nigral Vulnerability to Paraquat in Agricultural Workers. Toxicol Sci 2021; 181:47-57. [PMID: 33739421 DOI: 10.1093/toxsci/kfab020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Paraquat is an herbicide whose use is associated with Parkinson's disease (PD), a neurodegenerative disorder marked by neuron loss in the substantia nigra pars compacta (SNc). We recently observed that the murine homolog to the human H63D variant of the homeostatic iron regulator (HFE) may decrease paraquat-associated nigral neurotoxicity in mice. The present study examined the potential influence of H63D on paraquat-associated neurotoxicity in humans. Twenty-eight paraquat-exposed workers were identified from exposure histories and compared with 41 unexposed controls. HFE genotypes, and serum iron and transferrin were measured from blood samples. MRI was used to assess the SNc transverse relaxation rate (R2*), a marker for iron, and diffusion tensor imaging scalars of fractional anisotropy (FA) and mean diffusivity, markers of microstructural integrity. Twenty-seven subjects (9 exposed and 18 controls) were H63D heterozygous. After adjusting for age and use of other PD-associated pesticides and solvents, serum iron and transferrin were higher in exposed H63D carriers than in unexposed carriers and HFE wildtypes. SNc R2* was lower in exposed H63D carriers than in unexposed carriers, whereas SNc FA was lower in exposed HFE wildtypes than in either unexposed HFE wildtypes or exposed H63D carriers. Serum iron and SNc FA measures correlated positively among exposed, but not unexposed, subjects. These data suggest that H63D heterozygosity is associated with lower neurotoxicity presumptively linked to paraquat. Future studies with larger cohorts are warranted to replicate these findings and examine potential underlying mechanisms, especially given the high prevalence of the H63D allele in humans.
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