Cigarette Smoke-Induced Alterations in Frontal White Matter Lipid Profiles Demonstrated by MALDI-Imaging Mass Spectrometry: Relevance to Alzheimer's Disease

Lipidome changes in alcohol-related brain damage

Alcohol-related brain injury is characterized by cognitive deficits and brain atrophy with the prefrontal cortex particularly susceptible. White matter in the human brain is lipid rich and a major target of damage from chronic alcohol abuse; yet, there is sparse information on how these lipids are affected. Here, we used untargeted lipidomics as a discovery tool to describe these changes in the prefrontal, middle temporal, and visual cortices of human subjects with alcohol use disorder and controls. Significant changes to the lipidome, predominantly in the prefrontal and visual cortices, and differences between the white and grey matter of each brain region were identified. These effects include broad decreases to phospholipids and ceramide, decreased polyunsaturated fatty acids, decreased sphingadiene backbones, and selective decreases in cholesteryl ester fatty acid chains. Our findings show that chronic alcohol abuse results in selective changes to the neurolipidome, which likely reflects both the directs effects on the brain and concurrent effects on the liver.

Chemical analysis of the human brain by imaging mass spectrometry

Analysis of the chemical makeup of the brain enables a deeper understanding of several neurological processes. Molecular imaging that deciphers the spatial distribution of neurochemicals with high specificity and sensitivity is an exciting avenue in this aspect. The past two decades have witnessed a significant surge of mass spectrometry imaging (MSI) that can simultaneously map the distribution of hundreds to thousands of biomolecules in the tissue specimen at a fairly high resolution, which is otherwise beyond the scope of other molecular imaging techniques. In this review, we have documented the evolution of MSI technologies in imaging the anatomical distribution of neurochemicals in the human brain in the context of several neuro diseases. This review also addresses the potential of MSI to be a next-generation molecular imaging technique with its promising applications in neuropathology.

Independent and Combined Effects of Nicotine or Chronic Tobacco Smoking and HIV on the Brain: A Review of Preclinical and Clinical Studies

Tobacco smoking is highly prevalent among HIV-infected individuals. Chronic smokers with HIV showed greater cognitive deficits and impulsivity, and had more psychopathological symptoms and greater neuroinflammation than HIV non-smokers or smokers without HIV infection. However, preclinical studies that evaluated the combined effects of HIV-infection and tobacco smoking are scare. The preclinical models typically used cell cultures or animal models that involved specific HIV viral proteins or the administration of nicotine to rodents. These preclinical models consistently demonstrated that nicotine had neuroprotective and anti-inflammatory effects, leading to cognitive enhancement. Although the major addictive ingredient in tobacco smoking is nicotine, chronic smoking does not lead to improved cognitive function in humans. Therefore, preclinical studies designed to unravel the interactive effects of chronic tobacco smoking and HIV infection are needed. In this review, we summarized the preclinical studies that demonstrated the neuroprotective effects of nicotine, the neurotoxic effects of the HIV viral proteins, and the scant literature on nicotine or tobacco smoke in HIV transgenic rat models. We also reviewed the clinical studies that evaluated the neurotoxic effects of tobacco smoking, HIV infection and their combined effects on the brain, including studies that evaluated the cognitive and behavioral assessments, as well as neuroimaging measures. Lastly, we compared the different approaches between preclinical and clinical studies, identified some gaps and proposed some future directions. Graphical abstract Independent and combined effects of HIV and tobacco/nicotine. Left top and bottom panels: Both clinical studies of HIV infected persons and preclinical studies using viral proteins in vitro or in vivo in animal models showed that HIV infection could lead to neurotoxicity and neuroinflammation. Right top and bottom panels: While clinical studies of tobacco smoking consistently showed deleterious effects of smoking, clinical and preclinical studies that used nicotine show mild cognitive enhancement, neuroprotective and possibly anti-inflammatory effects. In the developing brain, however, nicotine is neurotoxic. Middle overlapping panels: Clinical studies of persons with HIV who were smokers typically showed additive deleterious effects of HIV and tobacco smoking. However, in the preclinical studies, when nicotine was administered to the HIV-1 Tg rats, the neurotoxic effects of HIV were attenuated, but tobacco smoke worsened the inflammatory cascade.

Investigation of Precise Molecular Mechanistic Action of Tobacco-Associated Carcinogen `NNK´ Induced Carcinogenesis: A System Biology Approach

Cancer is the second deadliest disease listed by the WHO. One of the major causes of cancer disease is tobacco and consumption possibly due to its main component, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). A plethora of studies have been conducted in the past aiming to decipher the association of NNK with other diseases. However, it is strongly linked with cancer development. Despite these studies, a clear molecular mechanism and the impact of NNK on various system-level networks is not known. In the present study, system biology tools were employed to understand the key regulatory mechanisms and the perturbations that will happen in the cellular processes due to NNK. To investigate the system level influence of the carcinogen, NNK rewired protein–protein interaction network (PPIN) was generated from 544 reported proteins drawn out from 1317 articles retrieved from PubMed. The noise was removed from PPIN by the method of modulation. Gene ontology (GO) enrichment was performed on the seed proteins extracted from various modules to find the most affected pathways by the genes/proteins. For the modulation, Molecular COmplex DEtection (MCODE) was used to generate 19 modules containing 115 seed proteins. Further, scrutiny of the targeted biomolecules was done by the graph theory and molecular docking. GO enrichment analysis revealed that mostly cell cycle regulatory proteins were affected by NNK.

The 20-Year Voyage Aboard the Journal of Alzheimer's Disease: Docking at 'Type 3 Diabetes', Environmental/Exposure Factors, Pathogenic Mechanisms, and Potential Treatments

The Journal of Alzheimer’s Disease (JAD), founded in 1998, played a pivotal role in broadening the field of research on Alzheimer’s disease (AD) by publishing a diverse range of clinical, pathological, molecular, biochemical, epidemiological, experimental, and review articles from its birth. This article recounts my own journey as an author who contributed articles to JAD over the 20 years of the journal’s existence. In retrospect, it seems remarkable that a considerable body of work that originated from our group marks a trail that began with studies of vascular, stress, and mitochondrial factors in AD pathogenesis, exploded into the concept of ‘Type 3 Diabetes’, and continued with the characterization of how environmental, exposure, and lifestyle factors promote neurodegeneration and which therapeutic strategies could reverse the neurodegeneration cascade.

Insight into the internal structure of amyloid-β oligomers by isotope-edited Fourier transform infrared spectroscopy

Isotope-edited infrared spectroscopy reveals the structural unit of amyloid-β oligomers.

Independent and Combined Effects of Chronic HIV-Infection and Tobacco Smoking on Brain Microstructure

HIV-infected individuals (HIV+) have 2-3 times higher prevalence of tobacco smoking than the general U.S. population. This study aims to evaluate the independent and combined effects of tobacco-smoking and HIV-infection on brain microstructure and cognition using a 2 × 2 design. 21 HIV + Smokers, 25 HIV + Nonsmokers, 25 Seronegative (SN)-Smokers and 23 SN-Nonsmokers were evaluated using diffusion tensor imaging. Fractional anisotropy (FA), mean (MD), radial (RD) and axial (AD) diffusivity were assessed in 8 major cerebral fiber tracts and 5 subcortical regions. Cognitive performance in 7 neurocognitive domains was also assessed. Compared to SN, HIV+ had higher AD in genu of corpus callosum (GCC, p = 0.002). Smokers also had higher diffusivities in GCC, splenium of corpus callosum (SCC), anterior corona radiata (ACR), sagittal stratum (SS) and superior fronto-occipital fasciculus (SFO), than Nonsmokers (p-values<0.001-0.003). Tobacco-Smoking and HIV-infection showed synergistic effects on AD_SS (p = 0.002) and RD_SFO (p = 0.02), but opposite effects in FA_putamen (p = 0.024). Additive effects from HIV+ and Tobacco-Smoking were observed in 9 other white matter tracts, with highest diffusivities and lowest FA in HIV + Smokers. Higher diffusivities in the GCC, SCC, ACR and SS predicted poorer cognitive performance across all participants (p ≤ 0.001). Higher AD_GCC also predicted slower Speed of information processing and poorer Fluency and Attention only in HIV + Smokers (p = 0.001-0.003). Chronic tobacco smoking and HIV-infection appear to have additive and synergistic adverse effects on brain diffusivities, suggesting greater neuroinflammation, which may contribute to poorer cognition. Therefore, chronic tobacco-smoking may be a risk factor for HIV-associated neurocognitive disorders. Graphical Abstract ᅟ.

Subventricular zone lipidomic architecture loss in Huntington's disease

The human subventricular zone (SVZ) has a defined cytological and neurochemical architecture, with four constituent laminae that act in concert to support its neurogenic activity. Lipidomic specialisation has previously been demonstrated in the neurologically normal human SVZ, with enrichment of functionally important lipid classes in each lamina. The SVZ is also responsive to neurodegenerative disorders, where thickening of the niche and enhanced proliferation of resident cells were observed in Huntington's disease (HD) brains. In this study, we hypothesised lipidomic changes in the HD SVZ. Using matrix-assisted laser desorption/ionisation (MALDI) imaging mass spectrometry, this analysis shows differences in the lipidomic architecture in the post-mortem Vonsattel grade III cases. Relative to matched, neurologically normal specimens (N = 4), the lipidomic signature of the HD SVZ (N = 4) was characterized by loss of sulfatides and triglycerides in the myelin layer, with an ectopic and focal accumulation of sphingomyelins and ceramide-1-phosphate observed in this lamina. A striking loss of lipidomic patterning was also observed in the ependymal layer, where the local abundance of phosphatidylinositols was significantly reduced in HD. This comprehensive spatially resolved lipidomic analysis of the human HD SVZ identifies alterations in lipid architecture that may shed light on the mechanisms of SVZ responses to neurodegeneration in HD. Open Science: This manuscript was awarded with the Open Materials Badge. For more information see: https://cos.io/our-services/open-science-badges/.

Imaging mass spectrometry of frontal white matter lipid changes in human alcoholics

BACKGROUND

Chronic alcohol use disorders (AUD) are associated with white matter (WM) degeneration with altered myelin integrity. Matrix assisted laser desorption ionization-imaging mass spectrometry (MALDI-IMS) enables high throughput analysis of myelin lipid biochemical histopathology to help characterize disease mechanisms.

PURPOSE

This study utilized MALDI-IMS to investigate frontal lobe WM myelin lipid abnormalities in AUD.

METHODS

Standardized cores of formalin-fixed WM from Brodmann Area 4 (BA4) and BA8/9 of 20 postmortem AUD and 19 control adult human brains were embedded in carboxymethyl-cellulose, cryo-sectioned (8 μm), thaw-mounted onto indium tin oxide (ITO) -coated glass slides, and sublimed with 2,5-dihydroxybenzxoic acid (DHB) matrix. Lipids were imaged by MALDI-time of flight in the negative ionization mode. Data were visualized with FlexImaging software v4.0 and analyzed with ClinProTools v3.0.

RESULTS

Principal component analysis (PCA) and data bar plots of MALDI-IMS data differentiated AUD from control WM. The dominant effect of AUD was to broadly reduce expression of sphingolipids (sulfatides and ceramides) and phospholipids. Data bar plots demonstrated overall similar responses to AUD in BA4 and BA8/9. However, differential regional effects of AUD on WM lipid profiles were manifested by non-overlapping expression or discordant responses to AUD for a subset of lipid ions.

CONCLUSIONS

Human AUD is associated with substantial inhibition of frontal lobe WM lipid expression with regional variability in these effects. MALDI-IMS can be used to characterize the nature of AUD-associated lipid biochemical abnormalities for correlation with lifetime exposures and WM degeneration, altered gene expression, and responses to abstinence or treatment.

Progressive white matter atrophy with altered lipid profiles is partially reversed by short-term abstinence in an experimental model of alcohol-related neurodegeneration

Chronic ethanol exposure causes white matter (WM) atrophy and degeneration with major impairments in the structural integrity of myelin. Since myelin is composed of oligodendrocyte lipid-rich membranes, understanding the consequences and reversibility of alcohol-related oligodendrocyte dysfunction in relation to myelin structure could provide new insights into the pathogenesis of WM degeneration and potential strategies for treatment. Adult male Long Evans rats were pair-fed with isocaloric liquid diets containing 0% or 26% ethanol (caloric) for 3 or 8 weeks. During the last 2 weeks of feeding, the ethanol groups were binged with 2 g/kg of ethanol by intraperitoneal (i.p.) injection on Mondays, Wednesdays, and Fridays; controls were treated with i.p. saline. For recovery effects, at the 6-week time point, ethanol exposures were tapered over 2 days, and then discontinued, rendering the rats ethanol-free for 12 days. Anterior corpus callosum WM lipid ion profiles were analyzed using matrix-assisted laser desorption ionization-imaging mass spectrometry (MALDI-IMS) and correlated with histopathology. Ethanol exposures caused progressive atrophy and reductions in myelin staining intensity within the corpus callosum, whereas short-term recovery partially reversed those effects. MALDI-IMS demonstrated striking ethanol-associated alterations in WM lipid profiles characterized by reduced levels of phosphatidylinositols, phosphatidylserines, phosphatidylethanolamines, and sulfatides, and partial "normalization" of lipid expression with recovery. Ethanol exposure duration and recovery responses were further distinguished by heatmap hierarchical dendrogram and PCA plots. In conclusion, chronic+binge ethanol exposures caused progressive, partially reversible WM atrophy with myelin loss associated with reduced expression of WM phospholipids and sulfatides. The extent of WM lipid abnormalities suggests that ethanol broadly impairs molecular and biochemical functions regulating myelin synthesis, degradation, and maintenance in oligodendrocytes.

Imaging mass spectrometry (IMS) of cortical lipids from preclinical to severe stages of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease affecting millions of patients worldwide. Previous studies have demonstrated alterations in the lipid composition of lipid extracts from plasma and brain samples of AD patients. However, there is no consensus regarding the qualitative and quantitative changes of lipids in brains from AD patients. In addition, the recent developments in imaging mass spectrometry methods are leading to a new stage in the in situ analysis of lipid species in brain tissue slices from human postmortem samples. The present study uses the matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS), permitting the direct anatomical analysis of lipids in postmortem brain sections from AD patients, which are compared with the intensity of the lipid signal in samples from matched subjects with no neurological diseases. The frontal cortex samples from AD patients were classified in three groups based on Braak's histochemical criteria, ranging from non-cognitively impaired patients to those severely affected. The main results indicate a depletion of different sulfatide lipid species from the earliest stages of the disease in both white and gray matter areas of the frontal cortex. Therefore, the decrease in sulfatides in cortical areas could be considered as a marker of the disease, but may also indicate neurochemical modifications related to the pathogenesis of the disease. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

Hippocampal lipid differences in Alzheimer's disease: a human brain study using matrix-assisted laser desorption/ionization-imaging mass spectrometry

INTRODUCTION

Alzheimer's disease (AD), the leading cause of dementia, is pathologically characterized by β-amyloid plaques and tau tangles. However, there is also evidence of lipid dyshomeostasis-mediated AD pathology. Given the structural diversity of lipids, mass spectrometry is a useful tool for studying lipid changes in AD. Although there have been a few studies investigating lipid changes in the human hippocampus in particular, there are few reports on how lipids change in each hippocampal subfield (e.g., Cornu Ammonis [CA] 1-4, dentate gyrus [DG] etc.). Since each subfield has its own function, we postulated that there could be lipid changes that are unique to each.

METHODS

We used matrix-assisted laser desorption/ionization-imaging mass spectrometry to investigate specific lipid changes in each subfield in AD. Data from the hippocampus region of six age- and gender-matched normal and AD pairs were analyzed with SCiLS lab 2015b software (SCiLS GmbH, Germany; RRID:SCR_014426), using an analysis workflow developed in-house. Hematoxylin, eosin, and luxol fast blue staining were used to precisely delineate each anatomical hippocampal subfield. Putative lipid identities, which were consistent with published data, were assigned using MS/MS.

RESULTS

Both positively and negatively charged lipid ion species were abundantly detected in normal and AD tissue. While the distribution pattern of lipids did not change in AD, the abundance of some lipids changed, consistent with trends that have been previously reported. However, our results indicated that the majority of these lipid changes specifically occur in the CA1 region. Additionally, there were many lipid changes that were specific to the DG.

CONCLUSIONS

Matrix-assisted laser desorption/ionization-imaging mass spectrometry and our analysis workflow provide a novel method to investigate specific lipid changes in hippocampal subfields. Future work will focus on elucidating the role that specific lipid differences in each subfield play in AD pathogenesis.

Smoking and Cerebral Oxidative Stress and Air Pollution: A Dreadful Equation with Particulate Matter Involved and One More Powerful Reason Not to Smoke Anything!

Smoking has serious health effects. Cigarettes, including tobacco, marijuana, and electronic nicotine delivery systems are very effective ways to inhale harmful amounts of fine and ultrafine particulate matter. Does size matter? Yes, indeed! The smaller the particle you inhale, the higher the ability to produce reactive oxygen species and to readily access the brain. In this issue of the Journal of Alzheimer's Disease, Durazzo provides evidence of an association between active cigarette tobacco smoking in cognitively-normal elders and increased cerebral oxidative stress, while in actively smoking Alzheimer's disease (AD) patients, the association was also seen with smaller left and total hippocampal volumes. This paper has highly relevant results of interest across the US and the world because millions of people are active smokers and they have other genetic and environmental risk factors that could play a key role in the development/worsening of brain oxidative stress and neurodegeneration. Smoking basically anything producing aerosols with particulate matter in the fine and ultrafine size range is detrimental to your brain. Marijuana and e-cigarette use has grown steadily among adolescents and young adults. Smoking-related cerebral oxidative stress is a potential mechanism promoting AD pathology and increased risk for AD. Current knowledge also relates fine and ultrafine particles exposures influencing neurodevelopmental processes in utero. The results from Durazzo et al. should be put in a broader context, a context that includes evaluating the oxidative stress of nano-aerosols associated with cigarette emissions and their synergistic effects with air pollution exposures. AD is expected to increase in the US threefold by the year 2050, and some of these future AD patients are smoking and vaping right now. Understanding the impact of everyday exposures to long-term harmful consequences for brain health is imperative.