Expression profiles for macrophage alternative activation genes in AD and in mouse models of AD

Identification of a dysfunctional microglial population in human Alzheimer's disease cortex using novel single-cell histology image analysis

In Alzheimer's disease (AD), microglia are affected by disease processes, but may also drive pathogenesis. AD pathology-associated microglial populations have been identified with single-cell RNA-Seq, but have not been validated in human brain tissue with anatomical context. Here, we quantified myeloid cell markers to identify changes in AD pathology-associated microglial populations. We performed fluorescent immunohistochemistry on normal (n = 8) and AD (n = 8) middle temporal gyri, co-labelling the pan-myeloid cell marker, Iba1, with one of 11 markers of interest (MOIs): CD45, HLA-DR, CD14, CD74, CD33, CD206, CD32, CD163, P2RY12, TMEM119, L-Ferritin. Novel image analyses quantified the single-cell abundance of Iba1 and each MOI. Each cell was gated into one Iba1-MOI population (Iba1^low MOI^high, Iba1^high MOI^high, or Iba1^high MOI^low) and the abundance of each population was compared between AD and control. Triple-labelling of L-Ferritin and Iba1 with a subset of MOIs was performed to investigate L-Ferritin-MOI co-expression on Iba1^low cells. Iba1^low MOI^high myeloid cell populations delineated by MOIs CD45, HLA-DR, CD14, CD74, CD33, CD32, and L-Ferritin were increased in AD. Further investigation of the Iba1^low MOI^high populations revealed that their abundances correlated with tau, but not amyloid beta, load in AD. The Iba1^low microglial population highly expressed L-Ferritin, reflecting microglial dysfunction. The L-Ferritin^high CD74^high HLA-DR^high phenotype of the Iba1^low population mirrors that of a human AD pathology-associated microglial subpopulation previously identified using single-cell RNA-Seq. Our high-throughput immunohistochemical data with anatomical context support the microglial dysfunction hypothesis of AD.

TREM2 overexpression rescues cognitive deficits in APP/PS1 transgenic mice by reducing neuroinflammation via the JAK/STAT/SOCS signaling pathway

Overactivated microglia and neuroinflammation are considered to play a crucial role in the progression of Alzheimer's disease (AD). Triggering receptor expressed on myeloid cells-2 (TREM2), a type I transmembrane receptor, expressed uniquely by microglia in the brain, is involved in the neuroinflammatory responses of AD. In this study, to further explore the precise effects of TREM2 on neuroinflammation and the underlying mechanisms in AD, we employed a lentiviral-mediated strategy to overexpress TREM2 in the brain of APPswe/PS1dE9 (APP/PS1) transgenic mice and cultured BV2 cells. Our results showed that TREM2 overexpression rescued cognitive deficits, decreased β-amyloid (Aβ) plaques deposition, reduced synaptic and neuronal loss, as well as ameliorated neuroinflammation. The mechanistic study revealed that these protective effects were likely attributed to inhibition of neuroinflammatory responses through the JAK/STAT/SOCS signaling pathway and subsequent attenuation of pro-inflammatory cytokines. Furthermore, suppression of neuroinflammation might be ascribed to activation of the M2 microglia, as the levels of M2 phenotype markers Arg-1, IL-10 and Ym1 were markedly increased. Similarly, overexpression of TREM2 in BV2 cells also promoted M2 polarization and led to the alleviation of M1 microglial inflammatory responses through JAK/STAT/SOCS signaling pathway, suggesting that TREM2 is an important factor in shifting the microglia from M1 to M2 phenotype. Taken together, our results further provide insights into the role of TREM2 in AD pathogenesis and highlight TREM2 as a potential target against AD.

The Role of Microglia in Perioperative Neurocognitive Disorders

Perioperative neurocognitive disorder (PND) is a common phenomenon associated with anesthesia and surgery and has been frequently described in the elderly and susceptible individuals. Microglia, which are the brain’s major resident immune cells, play critical roles in maintaining neuronal homeostasis and synaptic plasticity. Accumulating evidence suggests microglial dysfunction occurring after anesthesia and surgery might perturb neuronal function and induce PND. This review aims to provide an overview of the involvement of microglia in PND to date. Possible cellular and molecular mechanisms regarding the connection between microglial activation and PND are discussed.

DHCR24 overexpression modulates microglia polarization and inflammatory response via Akt/GSK3β signaling in Aβ25-35 treated BV-2 cells

Microglial phenotypic polarization, divided into pro-inflammatory "M1" phenotype and anti-inflammatory "M2" phenotype, played a crucial role in the pathogenesis of Alzheimer's disease (AD). Facilitating microglial polarization from M1 to M2 phenotype was shown to alleviate AD-associate pathologic damage, and modulator of the microglial phenotype has become a promising therapeutic approach for the treatment of AD. Previous little evidence showed that DHCR24 (3-β-hydroxysteroid-Δ-24-reductase), also known as seladin-1 (selective Alzheimer's disease indicator-1), exerted potential anti-inflammatory property, however, the link between DHCR24 and microglial polarization has never been reported. Thus, the role of DHCR24 in microglial polarization in amyloid-beta 25-35 (Aβ_25-35) treated BV-2 cells was evaluated in this study. Our results demonstrated that Aβ_25-35 aggravated inflammatory response and facilitated the transition of microglia phenotype from M2 to M1 in BV-2 cells, by upregulating M1 marker (i-NOS, IL-1β and TNF-α) and downregulating M2 marker (arginase-1, IL-4 and TGF-β). DHCR24 overexpression by lentivirus transfection could significantly reverse these effects, meanwhile, activated Akt/GSK3β signaling pathway via increasing the protein expression of P-Akt and P-GSK3β. Furthermore, when co-treated with Akt inhibitor MK2206, the effect of DHCR24 was obviously reversed. The study exhibited the neuroprotective function of DHCR24 in AD-related inflammatory injury and provided a novel therapeutic target for AD in the future.

Significance of Blood and Cerebrospinal Fluid Biomarkers for Alzheimer's Disease: Sensitivity, Specificity and Potential for Clinical Use

Alzheimer's disease (AD) is the most common type of dementia, affecting more than 5 million Americans, with steadily increasing mortality and incredible socio-economic burden. Not only have therapeutic efforts so far failed to reach significant efficacy, but the real pathogenesis of the disease is still obscure. The current theories are based on pathological findings of amyloid plaques and tau neurofibrillary tangles that accumulate in the brain parenchyma of affected patients. These findings have defined, together with the extensive neurodegeneration, the diagnostic criteria of the disease. The ability to detect changes in the levels of amyloid and tau in cerebrospinal fluid (CSF) first, and more recently in blood, has allowed us to use these biomarkers for the specific in-vivo diagnosis of AD in humans. Furthermore, other pathological elements of AD, such as the loss of neurons, inflammation and metabolic derangement, have translated to the definition of other CSF and blood biomarkers, which are not specific of the disease but, when combined with amyloid and tau, correlate with the progression from mild cognitive impairment to AD dementia, or identify patients who will develop AD pathology. In this review, we discuss the role of current and hypothetical biomarkers of Alzheimer's disease, their specificity, and the caveats of current high-sensitivity platforms for their peripheral detection.

Neuroinflammation in dementia with Lewy bodies: a human post-mortem study

Dementia with Lewy bodies (DLB) is the second most common neurodegenerative cause of dementia, behind Alzheimer's disease (AD). It is now established that cerebral inflammation has a key role in the aetiology and progression of AD, but this has yet to be confirmed in DLB. We aimed to determine the neuroinflammatory profile in the cerebral cortex of a large cohort of DLB cases. Thirty post-mortem confirmed DLB cases and twenty-nine matched controls were immunolabelled (Brodmann area 21) and quantified for: neuropathology-αSYN, Aβ, P-tau; microglial phenotype-Iba1, HLA-DR, CD68, FcƴR (CD64, CD32a, CD32b, CD16); presence of T lymphocytes-CD3; and anti-inflammatory markers-IL4R, CHI3L1. Status spongiosis, as a marker of neuropil degeneration, was quantified using Haematoxylin and Eosin staining. We found no significant difference between groups in protein load for Iba1, HLA-DR, CD68, CD64, CD32b, IL4R, or CHI3L1, despite increased neuropathology in DLB. CD32a load was significantly lower, and CD16 load higher, in DLB compared with controls. There was no difference in status spongiosis between groups. Significantly more DLB cases than controls showed T-lymphocyte recruitment. Overall, we conclude that microglial activation is not a prominent feature of DLB, and that this may be associated with the relatively modest neuropil degeneration observed in DLB. Our findings, based on the largest post-mortem cohort to date exploring neuroinflammation in DLB, demonstrate a dissociation between protein deposition, neurodegeneration and microglial activation. The relative preservation of cortical structures in DLB suggests the dementia could be more amenable to potential therapies.

Neuroprotective modulation of microglia effector functions following priming with interleukin 4 and 13: current limitations in understanding their mode-of-action

In recent years the long-standing theory of microglia's properties for dual polarization towards a pro- or anti-inflammatory phenotype has been deeply challenged. Furthermore, the elucidation of microglia ontogenesis exposed intrinsic differences between microglia and peripheral myeloid cells, thereby further underscoring the need to re-evaluate microglia-specific activation behavior, especially within an inflamed central nervous system (CNS) environment. This review critically summarizes recent literature on the in vitro and in vivo response of murine microglia to the immune-modulatory cytokines interleukin 4 (IL4) and interleukin 13 (IL13), i.e. those driving the so-called anti-inflammatory phenotype. Here we highlight several pivotal factors that may influence experimental outcome and/or interpretation of in vitro and in vivo studies evaluating microglia's phenotypical and functional properties upon IL4/IL13 treatment. Finally, the current therapeutic relevance of IL4/IL13-induced microglia activation in both acute and chronic CNS disorders is discussed.

Altered brain arginine metabolism with age in the APPswe/PSEN1dE9 mouse model of Alzheimer's disease

Amyloid-beta (Aβ) cleaved from amyloid precursor protein (APP) has been proposed to play a central and causative role in the aetiology of Alzheimer's disease (AD). APP_swe/PSEN1_dE9 (APP/PS1) transgenic mice display chronic Aβ accumulation and deposition in the brain. L-arginine is a semi-essential amino acid with a number of bioactive metabolites, and altered arginine metabolism has been implicated in the pathogenesis and/or the development of AD. This study systematically investigated how arginine metabolic profiles changed in the frontal cortex, hippocampus, parahippocampal region and cerebellum of male APP/PS1 mice at 4, 9 and 17 months of age relative to their sex- and age-matched wildtype controls. Immunohistochemistry demonstrated age-related Aβ deposition in the brain. High-performance liquid chromatography and mass spectrometry revealed age-related increases in glutamine, spermidine and spermine in APP/PS1 mice in a region-specific manner. Notably, genotype-related increases in spermine were found in the frontal cortex at the 9-month age point and in the frontal cortex, hippocampus and parahippocampal region at 17 months of age. Given the existing literature indicating the role of polyamines (spermine in particular) in modulating the aggregation and toxicity of Aβ oligomers, increased spermidine and spermine levels in APP/PS1 mice may be a neuroprotective mechanism to combat Aβ toxicity. Future research is required to better understand the functional significance of these changes.

Modulation of microglial phenotypes improves sepsis-induced hippocampus-dependent cognitive impairments and decreases brain inflammation in an animal model of sepsis

BACKGROUND

In order to modulate microglial phenotypes in vivo, M1 microglia were depleted by administration of gadolinium chloride and the expression of M2 microglia was induced by IL-4 administration in an animal model of sepsis to better characterize the role of microglial phenotypes in sepsis-induced brain dysfunction.

METHODS

Wistar rats were submitted to sham or cecal ligation and perforation (CLP) and treated with IL-4 or GdCl3. Animals were submitted to behavioral tests 10 days after surgery. In a separated cohort of animals at 24 h, 3 and 10 days after surgery, hippocampus was removed and cytokine levels, M1/M2 markers and CKIP-1 levels were determined.

RESULTS

Modulation of microglia by IL-4 and GdCl3 was associated with an improvement in long-term cognitive impairment. When treated with IL-4 and GdCl3, the reduction of pro-inflammatory cytokines was apparent in almost all analyzed time points. Additionally, CD11b and iNOS were increased after CLP at all time points, and both IL-4 and GdCl3 treatments were able to reverse this. There was a significant decrease in CD11b gene expression in the CLP+GdCl3 group. IL-4 treatment was able to decrease iNOS expression after sepsis. Furthermore, there was an increase of CKIP-1 in the hippocampus of GdCl3 and IL-4 treated animals 10 days after CLP induction.

CONCLUSIONS

GdCl3 and IL-4 are able to manipulate microglial phenotype in an animal models of sepsis, by increasing the polarization toward an M2 phenotype IL-4 and GdCl3 treatment was associated with decreased brain inflammation and functional recovery.

An Update of Palmitoylethanolamide and Luteolin Effects in Preclinical and Clinical Studies of Neuroinflammatory Events

The inflammation process represents of a dynamic series of phenomena that manifest themselves with an intense vascular reaction. Neuroinflammation is a reply from the central nervous system (CNS) and the peripheral nervous system (PNS) to a changed homeostasis. There are two cell systems that mediate this process: the glia of the CNS and the lymphocites, monocytes, and macrophages of the hematopoietic system. In both the peripheral and central nervous systems, neuroinflammation plays an important role in the pathogenesis of neurodegenerative diseases, such as Parkinson’s and Alzheimer’s diseases, and in neuropsychiatric illnesses, such as depression and autism spectrum disorders. The resolution of neuroinflammation is a process that allows for inflamed tissues to return to homeostasis. In this process the important players are represented by lipid mediators. Among the naturally occurring lipid signaling molecules, a prominent role is played by the N-acylethanolamines, namely N-arachidonoylethanolamine and its congener N-palmitoylethanolamine, which is also named palmitoylethanolamide or PEA. PEA possesses a powerful neuroprotective and anti-inflammatory power but has no antioxidant effects per se. For this reason, its co-ultramicronization with the flavonoid luteolin is more efficacious than either molecule alone. Inhibiting or modulating the enzymatic breakdown of PEA represents a complementary therapeutic approach to treating neuroinflammation. The aim of this review is to discuss the role of ultramicronized PEA and co-ultramicronized PEA with luteolin in several neurological diseases using preclinical and clinical approaches.

Robust neuroinflammation and perivascular pathology in rTg-DI rats, a novel model of microvascular cerebral amyloid angiopathy

BACKGROUND

Cerebral amyloid angiopathy (CAA) is a common cerebral small vessel disease of the aged and a prominent comorbidity of Alzheimer's disease (AD). CAA can promote a variety of vascular-related pathologies including neuroinflammation, cerebral infarction, and hemorrhages, which can all contribute to vascular cognitive impairment and dementia (VCID). Our understanding of the pathogenesis of CAA remains limited and further investigation of this condition requires better preclinical animal models that more accurately reflect the human disease. Recently, we generated a novel transgenic rat model for CAA (rTg-DI) that develops robust and progressive microvascular CAA, consistent microhemorrhages and behavioral deficits.

METHODS

In the current study, we investigated perivascular pathological processes that accompany the onset and progressive accumulation of microvascular CAA in this model. Cohorts of rTg-DI rats were aged to 3 months with the onset of CAA and to 12 months with advanced stage disease and then quantitatively analyzed for progression of CAA, perivascular glial activation, inflammatory markers, and perivascular stress.

RESULTS

The rTg-DI rats developed early-onset and robust accumulation of microvascular amyloid. As the disease progressed, rTg-DI rats exhibited increased numbers of astrocytes and activated microglia which were accompanied by expression of a distinct subset of inflammatory markers, perivascular pericyte degeneration, astrocytic caspase 3 activation, and disruption of neuronal axonal integrity.

CONCLUSIONS

Taken together, these results demonstrate that rTg-DI rats faithfully mimic numerous aspects of human microvascular CAA and provide new experimental insight into the pathogenesis of neuroinflammation and perivascular stress associated with the onset and progression of this condition, suggesting new potential therapeutic targets for this condition. The rTg-DI rats provide an improved preclinical platform for developing new biomarkers and testing therapeutic strategies for microvascular CAA.

Association of Neutrophil-Lymphocyte Ratio with Mild Cognitive Impairment in Elderly Chinese Adults: A Case-control Study

Background:

Inflammation plays a significant role in the pathophysiology of cognitive impairment in previous studies. Neutrophil-lymphocyte ratio (NLR) is a reliable measure of systemic inflammation.

Objective:

The aim of this study was to investigate the association between NLR and mild cognitive impairment (MCI), and further to explore the diagnostic potential of the inflammatory markers NLR for the diagnosis of MCI in elderly Chinese individuals.

Methods:

186 MCI subjects and 153 subjects with normal cognitive function were evaluated consecutively in this study. Neutrophil (NEUT) count and Lymphocyte (LYM) count were measured in fasting blood samples. The NLR was calculated by dividing the absolute NEUT count by the absolute LYM count. Multivariable logistic regression was used to evaluate the potential association between NLR and MCI. NLR for predicting MCI was analyzed using Receiver Operating Characteristic (ROC) curve analysis.

Results:

The NLR of MCI group was significantly higher than that of subjects with normal cognitive function (2.39 ± 0.55 vs. 1.94 ± 0.51, P < 0.001). Logistic regression analysis showed that higher NLR was an independent risk factor for MCI (OR: 4.549, 95% CI: 2.623-7.889, P < 0.001). ROC analysis suggested that the optimum NLR cut-off point for MCI was 2.07 with 73.66% sensitivity, 69.28% specificity, 74.48% Positive Predictive Values (PPV) and 68.36% negative predictive values (NPV). Subjects with NLR ≥ 2.07 showed higher risk relative to NLR < 2.07 (OR: 5.933, 95% CI: 3.467-10.155, P < 0.001).

Conclusion:

The elevated NLR is significantly associated with increased risk of MCI. In particular, NLR level higher than the threshold of 2.07 was significantly associated with the probability of MCI.

YKL-39 as a Potential New Target for Anti-Angiogenic Therapy in Cancer

YKL-39 belongs to the evolutionarily conserved family of Glyco_18-containing proteins composed of chitinases and chitinase-like proteins. Chitinase-like proteins (CLPs) are secreted lectins that lack hydrolytic activity due to the amino acid substitutions in their catalytic domain and combine the functions of cytokines and growth factors. One of the major cellular sources that produce CLPs in various pathologies, including cancer, are macrophages. Monocytes recruited to the tumor site and programmed by tumor cells differentiate into tumor-associated macrophages (TAMs), which are the primary source of pro-angiogenic factors. Tumor angiogenesis is a crucial process for supplying rapidly growing tumors with essential nutrients and oxygen. We recently determined that YKL-39 is produced by tumor-associated macrophages in breast cancer. YKL-39 acts as a strong chemotactic factor for monocytes and stimulates angiogenesis. Chemotherapy is a common strategy to reduce tumor size and aggressiveness before surgical intervention, but chemoresistance, resulting in the relapse of tumors, is a common clinical problem that is critical for survival in cancer patients. Accumulating evidence indicates that TAMs are essential regulators of chemoresistance. We have recently found that elevated levels of YKL-39 expression are indicative of the efficiency of the metastatic process in patients who undergo neoadjuvant chemotherapy. We suggest YKL-39 as a new target for anti-angiogenic therapy that can be combined with neoadjuvant chemotherapy to reduce chemoresistance and inhibit metastasis in breast cancer patients.

Expression and functions of cellular prion proteins in immunocytes

Prion diseases are fatal neurodegenerative processes caused by the accumulation of the pathological prion protein, PrP^Sc . While pathological lesions are limited to the central nervous system (CNS), disease-specific proteins accumulate and replicate in secondary lymphoid organs prior to neuroinvasion, and their replication there depends on the abundance of cellular prion protein (PrP^C ). PrP^C is expressed in both central and peripheral lymphoid tissues, and up- or downregulates innate and adaptive immune responses. In addition to prion diseases, PrP^C is also immunologically involved in other neurological disorders and infectious diseases, including Alzheimer's disease and human immunodeficiency virus infection. Herein, we summarize the expression and functions of PrP^C in various immunocytes, as well as its immunological and pathological roles in neurodegeneration and infection.

HHV-6A infection induces amyloid-beta expression and activation of microglial cells

BACKGROUND

The control of viral infections in the brain involves the activation of microglial cells, the macrophages of the brain that are constantly surveying the central nervous system, and the production of amyloid-beta (Aβ) as an anti-microbial molecule. Recent findings suggest a possible implication of HHV-6A in AD. We evaluated the effect of HHV-6A infection on microglial cell expression Aβ and the activation status, determined by TREM2, ApoE, cytokines, and tau expression.

METHODS

We have infected microglial cells (HMC3, ATCC®CRL-3304), in monolayer and human peripheral blood monocyte-derived microglia (PBM-microglia) spheroid 3D model, with HHV-6A (strain U1102) cell-free virus inocula with 100 genome equivalents per 1 cell. We collected the cells 1, 3, 7, and 14 days post-infection (d.p.i.) and analyzed them for viral DNA and RNA, ApoE, Aβ (1-40, 1-42), tau, and phospho-tau (Threonine 181) by real-time immunofluorescence and cytokines by immunoenzymatic assay.

RESULTS

We observed a productive infection by HHV-6A. The expression of Aβ 1-42 increased from 3 d.p.i., while no significant induction was observed for Aβ 1-40. The HHV-6A infection induced the activation (TREM2, IL-1beta, ApoE) and migration of microglial cells. The secretion of tau started from 7 d.p.i., with an increasing percentage of the phosphorylated form.

CONCLUSIONS

In conclusion, microglial cells are permissive to HHV-6A infection that induces the expression of Aβ and an activation status. Meanwhile, we hypothesize a paracrine effect of HHV-6A infection that activates and induces microglia migration to the site of infection.

Friend, Foe or Both? Immune Activity in Alzheimer's Disease

Alzheimer's disease (AD) is marked by the presence of amyloid beta (Aβ) plaques, neurofibrillary tangles (NFT), neuronal death and synaptic loss, and inflammation in the brain. AD research has, in large part, been dedicated to the understanding of Aβ and NFT deposition as well as to the pharmacological reduction of these hallmarks. However, recent GWAS data indicates neuroinflammation plays a critical role in AD development, thereby redirecting research efforts toward unveiling the complexities of AD-associated neuroinflammation. It is clear that the innate immune system is intimately associated with AD progression, however, the specific roles of glia and neuroinflammation in AD pathology remain to be described. Moreover, inflammatory processes have largely been painted as detrimental to AD pathology, when in fact, many immune mechanisms such as phagocytosis aid in the reduction of AD pathologies. In this review, we aim to outline the delicate balance between the beneficial and detrimental aspects of immune activation in AD as a more thorough understanding of these processes is critical to development of effective therapeutics for AD.

Neuroinflammation as a Factor of Neurodegenerative Disease: Thalidomide Analogs as Treatments

Neuroinflammation is initiated when glial cells, mainly microglia, are activated by threats to the neural environment, such as pathogen infiltration or neuronal injury. Although neuroinflammation serves to combat these threats and reinstate brain homeostasis, chronic inflammation can result in excessive cytokine production and cell death if the cause of inflammation remains. Overexpression of tumor necrosis factor-α (TNF-α), a proinflammatory cytokine with a central role in microglial activation, has been associated with neuronal excitotoxicity, synapse loss, and propagation of the inflammatory state. Thalidomide and its derivatives, termed immunomodulatory imide drugs (IMiDs), are a class of drugs that target the 3'-untranslated region (3'-UTR) of TNF-α mRNA, inhibiting TNF-α production. Due to their multi-potent effects, several IMiDs, including thalidomide, lenalidomide, and pomalidomide, have been repurposed as drug treatments for diseases such as multiple myeloma and psoriatic arthritis. Preclinical studies of currently marketed IMiDs, as well as novel IMiDs such as 3,6'-dithiothalidomide and adamantyl thalidomide derivatives, support the development of IMiDs as therapeutics for neurological disease. IMiDs have a competitive edge compared to similar anti-inflammatory drugs due to their blood-brain barrier permeability and high bioavailability, with the potential to alleviate symptoms of neurodegenerative disease and slow disease progression. In this review, we evaluate the role of neuroinflammation in neurodegenerative diseases, focusing specifically on the role of TNF-α in neuroinflammation, as well as appraise current research on the potential of IMiDs as treatments for neurological disorders.

Status of inflammation and alcohol use in a 6-month follow-up study of patients with major depressive disorder

INTRODUCTION

The studies on the relationship between alcohol consumption, the status of inflammation, and depression have produced conflicting results. In this study, we followed patients with major depressive disorders by monitoring biomarkers of inflammation together with biomarkers of heavy alcohol use.

METHOD

The levels of IL-6 (interleukin-6), IL-8 (interleukin-8), hs-CRP (high sensitivity C-reactive protein), YKL-40 (also known as Chitinase-3-like protein 1 or CHI3L1), and biomarkers of alcohol consumption and liver status (GT, CDT, ALT, alkaline phosphatase) were measured at baseline and after 6 months of psychiatric treatment from 242 patients suffering from current major depressive disorder (MDD) with (n = 99) or without (n = 143) alcohol use disorder (AUD).

RESULTS

At baseline, the patients with MDD + AUD showed higher levels of inflammatory biomarkers IL-6 (p < 0.001), hs-CRP (p < 0.01), YKL-40 (p < 0.05), and biomarkers of alcohol consumption, than the corresponding group of non-AUD patients. These differences disappeared during follow-up and recovery from depression. The level of IL-8 decreased significantly in both AUD (p < 0.05) and non-AUD (p < 0.05) patients. During follow-up, the biomarkers of alcohol consumption, GT and CDT, in AUD patients were found to decrease in parallel with serum YKL-40 levels.

CONCLUSIONS

Alcohol consumption appears to modulate the status of inflammation in depressive patients. A more systematic use of biomarkers of inflammation together with biomarkers of alcohol consumption and liver status may prove to be of value in a more comprehensive assessment and treatment of patients with depression.

The role of innate immune responses and neuroinflammation in amyloid accumulation and progression of Alzheimer's disease

Alzheimer's disease (AD) is characterized by amyloid beta (Aβ) accumulation, tau pathology and neuroinflammation. Recently, there has been considerable interest in the role of neuroinflammation in directly contributing to the progression of AD. Studies in mice and humans have identified a role for microglial cells, the resident innate immune cells of the central nervous system, in AD. Activated microglia are a key hallmark of the disease and the secretion of proinflammatory cytokines by microglia may result in a positive feedback loop between neurons and microglia, resulting in ongoing low-grade inflammation. Traditionally, the pathways of Aβ production and neuroinflammation have been considered independently; however, recent studies suggest that these processes may converge to promote the pathology associated with AD. Here we review the importance of inflammation and microglia in AD development and effects of inflammatory responses on cellular pathways of neurons, including Aβ generation.

Microglial motility in Alzheimer's disease and after Aβ42 immunotherapy: a human post-mortem study

Microglial function is highly dependent on cell motility, with baseline motility required for homeostatic surveillance activity and directed motility to migrate towards a source of injury. Experimental evidence suggests impaired microglial motility in Alzheimer’s disease (AD) and therefore we have investigated whether the expression of proteins associated with motility is altered in AD and affected by the Aβ immunotherapy using post-mortem brain tissue of 32 controls, 44 AD cases, and 16 AD cases from our unique group of patients immunised against Aβ42 (iAD).

Sections of brain were immunolabelled and quantified for (i) the motility-related microglial proteins Iba1, cofilin 1 (CFL1), coronin-1a (CORO1A) and P2RY12, and (ii) pan-Aβ, Aβ42 and phosphorylated tau (ptau). The neuroinflammatory environment was characterised using Meso Scale Discovery multiplex assays. The expression of all four motility-related proteins was unmodified in AD compared with controls, whereas Iba1 and P2RY12, the homeostatic markers, were increased in the iAD group compared with AD. Iba1 and P2RY12 showed significant positive correlations with Aβ in controls but not in the AD or iAD groups. Pro- and anti-inflammatory proteins were increased in AD, whereas immunotherapy appears to result in a slightly less pro-inflammatory environment.

Our findings suggest that as Aβ appears during the ageing process, the homeostatic Iba1 and P2RY12 –positive microglia respond to Aβ, but this response is absent in AD. Aβ-immunisation promoted increased Iba1 and P2RY12 expression, likely reflecting increased baseline microglial motility but without restoring the profile observed in controls.

Efficacy and mechanism of cGAMP to suppress Alzheimer's disease by elevating TREM2

Innate immune responses are considered to play crucial roles in the progression of Alzheimer's disease (AD). Recently, immunotherapy is emerging as an innovative and highly conceivable strategy for AD treatment. The cGAMP-STING-IRF3 signaling pathway plays a pivotal role in mediating innate immune responses. In this study, we provide pioneering investigation to find that the STING stimulator, cGAMP, significantly ameliorates cognitive deficits, improves pathological changes, decreases Aβ plaque load and reduces neuron apoptosis in APP/PS1 transgenetic mice. The stimulation of cGAMP-STING-IRF3 pathway induces expression of triggering receptor expressed on myeloid cells 2 (TREM2), and the overexpression of TREM2 further decreases Aβ deposition and neuron loss while improves AD pathomorphology and cognitive impairment. Additionally, TREM2 regulates microglia polarization from M1 towards M2 phenotype thereby achieves reduction of neuroinflammation in AD. These findings support that the enhancement of TREM2 exerts beneficial effects in ameliorating AD development. Taken together, our results demonstrate that cGAMP is a potential candidate for applications in Alzheimer's disease immunotherapy.

Understanding Epigenetics in the Neurodegeneration of Alzheimer's Disease: SAMP8 Mouse Model

Epigenetics is emerging as the missing link among genetic inheritance, environmental influences, and body and brain health status. In the brain, specific changes in nucleic acids or their associated proteins in neurons and glial cells might imprint differential patterns of gene activation that will favor either cognitive enhancement or cognitive loss for more than one generation. Furthermore, derangement of age-related epigenetic signaling is appearing as a significant risk factor for illnesses of aging, including neurodegeneration and Alzheimer’s disease (AD). In addition, better knowledge of epigenetic mechanisms might provide hints and clues in the triggering and progression of AD. Intense research in experimental models suggests that molecular interventions for modulating epigenetic mechanisms might have therapeutic applications to promote cognitive maintenance through an advanced age. The SAMP8 mouse is a senescence model with AD traits in which the study of epigenetic alterations may unveil epigenetic therapies against the AD.

Spinal cord injury: pathophysiology, treatment strategies, associated challenges, and future implications

Axonal regeneration and formation of tripartite (axo-glial) junctions at damaged sites is a prerequisite for early repair of injured spinal cord. Transplantation of stem cells at such sites of damage which can generate both neuronal and glial population has gained impact in terms of recuperation upon infliction with spinal cord injury. In spite of the fact that a copious number of pre-clinical studies using different stem/progenitor cells have shown promising results at acute and subacute stages, at the chronic stages of injury their recovery rates have shown a drastic decline. Therefore, developing novel therapeutic strategies are the need of the hour in order to assuage secondary morbidity and effectuate improvement of the spinal cord injury (SCI)-afflicted patients' quality of life. The present review aims at providing an overview of the current treatment strategies and also gives an insight into the potential cell-based therapies for the treatment of SCI.

Cerebrospinal fluid biomarkers for understanding multiple aspects of Alzheimer's disease pathogenesis

Alzheimer's disease (AD) is a multifactorial age-related brain disease. Numerous pathological events run forth in the brain leading to AD. There is an initial long, dormant phase before the clinical symptoms become evident. There is a need to diagnose the disease at the preclinical stage since therapeutic interventions are most likely to be effective if initiated early. Undoubtedly, the core cerebrospinal fluid (CSF) biomarkers have a good diagnostic accuracy and have been used in clinical trials as end point measures. However, looking into the multifactorial nature of AD and the overlapping pathology with other forms of dementia, it is important to integrate the core CSF biomarkers with a broader panel of other biomarkers reflecting different aspects of pathology. The review is focused upon a panel of biomarkers that relate to different aspects of AD pathology, as well as various studies that have evaluated their diagnostic potential. The panel includes markers of neurodegeneration: neurofilament light chain and visinin-like protein (VILIP-1); markers of amyloidogenesis and brain amyloidosis: apolipoproteins; markers of inflammation: YKL-40 and monocyte chemoattractant protein 1; marker of synaptic dysfunction: neurogranin. These markers can highlight on the state and stage-associated changes that occur in AD brain with disease progression. A combination of these biomarkers would not only aid in preclinical diagnosis, but would also help in identifying early brain changes during the onset of disease. Successful treatment strategies can be devised by understanding the contribution of these markers in different aspects of disease pathogenesis.

In vitro models to study insulin and glucocorticoids modulation of trimethyltin (TMT)-induced neuroinflammation and neurodegeneration, and in vivo validation in db/db mice

Brain susceptibility to a neurotoxic insult may be increased in a compromised health status, such as metabolic syndrome. Both metabolic syndrome and exposure to trimethyltin (TMT) are known to promote neurodegeneration. In combination the two factors may elicit additive or compensatory/regulatory mechanisms. Combined effects of TMT exposure (0.5-1 μM) and mimicked metabolic syndrome-through modulation of insulin and glucocorticoid (GC) levels-were investigated in three models: tridimensional rat brain cell cultures for neuron-glia effects; murine microglial cell line BV-2 for a mechanistic analysis of microglial reactivity; and db/db mice as an in vivo model of metabolic syndrome. In 3D cultures, low insulin condition significantly exacerbated TMT's effect on GABAergic neurons and promoted TMT-induced neuroinflammation, with increased expression of cytokines and of the regulator of intracellular GC activity, 11β-hydroxysteroid dehydrogenase 1 (11β-Hsd1). Microglial reactivity increased upon TMT exposure in medium combining low insulin and high GC. These results were corroborated in BV-2 microglial cells where lack of insulin exacerbated the TMT-induced increase in 11β-Hsd1 expression. Furthermore, TMT-induced microglial reactivity seems to depend on mineralocorticoid receptor activation. In diabetic BKS db mice, a discrete exacerbation of TMT neurotoxic effects on GABAergic neurons was observed, together with an increase of interleukin-6 (IL-6) and of basal 11β-Hsd1 expression as compared to controls. These results suggest only minor additive effects of the two brain insults, neurotoxicant TMT exposure and metabolic syndrome conditions, where 11β-Hsd1 appears to play a key role in the regulation of neuroinflammation and of its protective or neurodegenerative consequences.

Novel Sustainable-by-Design HDAC Inhibitors for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) represents a global problem, with an estimation of the majority of dementia patients in low- and middle-income countries by 2050. Thus, the development of sustainable drugs has attracted much attention in recent years. In light of this, taking inspiration from the HDAC inhibitor vorinostat (1), we develop the first HDAC inhibitors derived from cashew nut shell liquid (CNSL), an inexpensive agro-food waste material. CNSL derivatives 8 and 9 display a HDAC inhibitory profile similar to 1, together with a more promising safety for 9 compared to 1. Moreover, both compounds and particularly 9 were able to effectively modulate glial cell-induced inflammation and to revert the pro-inflammatory phenotype. All these results demonstrate that the use of inexpensive food waste materials could be successfully applied for the development of accessible and sustainable drug candidates for the treatment of AD.

Altered Expression of Urea Cycle Enzymes in Amyloid-β Protein Precursor Overexpressing PC12 Cells and in Sporadic Alzheimer's Disease Brain

Urea cycle enzymes may play important yet poorly characterized roles in Alzheimer's disease (AD). Our previous results showed that amyloid-β (Aβ) affects urea cycle enzymes in rat pheochromocytoma (PC12) cells. The aim of the present study was to investigate the changes in arginases, other urea cycle enzymes, and nitric oxide synthases (NOSs) in PC12 cells transfected with AβPP bearing the double 'Swedish' mutation (APPsw, K670M/N671L) and in postmortem sporadic AD brain hippocampus; the mutation intensifies Aβ production and strongly associates with AD neuropathology. mRNA expression was analyzed using real-time PCR in cell cultures and DNA microarrays in hippocampal CA1 area of human AD brains. Arginase activity was measured spectrophotometrically, and arginine, ornithine, and citrulline levels by high-performance liquid chromatography. Our data demonstrated that the expression and activity of arginases (Arg1 and Arg2), as well as the expression of argininosuccinate synthase (Ass) were significantly reduced in APPsw cells compared to control. However, argininosuccinate lyase (Asl) was upregulated in APPsw cells. Real-time PCR analysis revealed significant elevation of neuronal nitric oxide synthase (Nnos) mRNA in APPsw cells, without changes in the endothelial Enos, whereas inducible Inos was undetectable. The changes were found to follow closely those observed in the human hippocampal CA1 region of sporadic AD brains. The changes in enzyme expression were accompanied in APPsw cells by significantly elevated citrulline, ornithine, and arginine. Our findings demonstrate that AβPP/Aβ alters arginine metabolism and induces a shift of cellular homeostasis that may support the oxidative/nitrosative stress observed in AD.

The Gut-Brain Axis, Paving the Way to Brain Cancer

The gut-brain axis formed by blood and lymphatic vessels paves the way for microbiota to impact the brain. Bacterial populations in the gut are a good candidate for a nongenetic factor contributing substantively to brain tumor development and to the success of therapy. Specifically, suppression of the immune system and induction of inflammation by microbiota sustain proliferative signaling, limit cell death, and induce angiogenesis as well as invasiveness. In addition, altered microbial metabolites and their levels could stimulate cell proliferation. We propose here a novel gear model connecting these complex interdisciplinary fields. Our model may impact mechanistic studies of brain cancer and better treatment outcomes through precision oncology.

Altered neurovascular coupling and brain arginine metabolism in endothelial nitric oxide synthase deficient mice

Nitric oxide (NO) produced by endothelial NO synthase (eNOS) is a key regulator of cerebral blood flow (CBF) dynamics. Mice with eNOS deficiency (eNOS^-/-) display age-related increases in amyloid beta in the brain and memory deficits, implicating eNOS dysfunction in the neuropathogenesis and/or development of Alzheimer's disease (AD). The present study systematically investigated behavioural, CBF and brain arginine metabolic profile changes in male and female wildtype (WT) and eNOS^-/- mice at 14 months of age. eNOS^-/- mice displayed altered behaviour in the Y-maze and open field tests. A real-time microcirculation imager revealed a significant sex difference in the basal CBF and significantly increased perfusion response to whisker stimulations in the Barrel cortex in both male and female eNOS^-/- mice relative to their sex-matched WT controls. The treatment of 7-nitroindazole blocked the increased perfusion response to whisker stimulations in eNOS^-/- mice. Neurochemically, the most intriguing changes were markedly reduced glutamine levels in both male and female eNOS^-/- mice in the frontal cortex, hippocampus, parahippocampal region and cerebellum. These findings demonstrate altered behavioural function, neurovascular coupling and brain arginine metabolism (glutamine in particular) under the condition of eNOS deficiency, which further supports the role of eNOS dysfunction in the AD neuropathogenesis.

Restoration of aberrant mTOR signaling by intranasal rapamycin reduces oxidative damage: Focus on HNE-modified proteins in a mouse model of down syndrome

Increasing evidences support the notion that the impairment of intracellular degradative machinery is responsible for the accumulation of oxidized/misfolded proteins that ultimately results in the deposition of protein aggregates. These events are key pathological aspects of "protein misfolding diseases", including Alzheimer disease (AD). Interestingly, Down syndrome (DS) neuropathology shares many features with AD, such as the deposition of both amyloid plaques and neurofibrillary tangles. Studies from our group and others demonstrated, in DS brain, the dysfunction of both proteasome and autophagy degradative systems, coupled with increased oxidative damage. Further, we observed the aberrant increase of mTOR signaling and of its down-stream pathways in both DS brain and in Ts65Dn mice. Based on these findings, we support the ability of intranasal rapamycin treatment (InRapa) to restore mTOR pathway but also to restrain oxidative stress resulting in the decreased accumulation of lipoxidized proteins. By proteomics approach, we were able to identify specific proteins that showed decreased levels of HNE-modification after InRapa treatment compared with vehicle group. Among MS-identified proteins, we found that reduced oxidation of arginase-1 (ARG-1) and protein phosphatase 2A (PP2A) might play a key role in reducing brain damage associated with synaptic transmission failure and tau hyperphosphorylation. InRapa treatment, by reducing ARG-1 protein-bound HNE levels, rescues its enzyme activity and conceivably contribute to the recovery of arginase-regulated functions. Further, it was shown that PP2A inhibition induces tau hyperphosphorylation and spatial memory deficits. Our data suggest that InRapa was able to rescue PP2A activity as suggested by reduced p-tau levels. In summary, considering that mTOR pathway is a central hub of multiple intracellular signaling, we propose that InRapa treatment is able to lower the lipoxidation-mediated damage to proteins, thus representing a valuable therapeutic strategy to reduce the early development of AD pathology in DS population.

A metabolomic approach to identifying biomarkers in blood of Alzheimer's disease

Objective

This study aims to identify metabolites with altered levels of expression in patients with early and progressive stages of Alzheimer's disease (AD).

Methods

All participants of the study underwent genetic screening and were diagnosed using both neuropsychological assessment and amyloid imaging before metabolome analysis. According to these assessments, the patients were classified as normal (n = 15), with mild cognitive impairment (n = 10), and with AD (n = 15).

Results

Using a targeted metabolomic approach, we found that plasma levels of C3, C5, and C5-DC acylcarnitines, arginine, phenylalanine, creatinine, symmetric dimethylarginine (SDMA) and phosphatidylcholine ae C38:2 were significantly altered in patients with early and progressive stages of AD. We created a predictive model based on the decision tree that included three main parameters: age, arginine and C5 plasma concentrations. The model distinguished AD patients from other participants with 60% sensitivity and 86.7% specificity. For healthy controls, the sensitivity was 85.7% and specificity was 61.5%. Multivariate ROC analysis to develop a decision tree showed that our model reached moderate diagnostic power in differentiating between older adults who are cognitively normal (AUC = 0.77) and those with AD (AUC = 0.72).

Interpretation

The plasma levels of arginine and valeryl carnitine, together with subject age, are promising as biomarkers for the diagnosis of AD in older adults.

Development and Characterization of a Novel Monoclonal Antibody Against Chitinase-like Protein CHID1 Applicable for Immunohistochemistry on Formalin Fixed Paraffin-Embedded Sections

CHID1 has been recently described as a predictive marker of different malignant tumors. Thus, monoclonal antibodies (mAbs) for CHID1 detection in different human liquids and in tissues are an important tool for the diagnosis of CHID1-positive cancers. However, only few mAbs have been established to date. In this study we describe the generation of a new hybridoma clone 3D4 producing anti-CHID1 antibodies. 3D4 mAb specifically binds human CHID1 and was successfully used in enzyme-linked immunosorbent assay, immunoblotting, immunofluorescence on paraformaldehyde-fixed cells, and in immunohistochemistry of paraffin-embedded tissue specimens. These results indicate that this new anti-CHID1 mAb 3D4 will be useful in the diagnosis of CHID1-related cancers and is a strong tool for both basic and clinical research on chitinase-like proteins.

Microglial overexpression of fALS-linked mutant SOD1 induces SOD1 processing impairment, activation and neurotoxicity and is counteracted by the autophagy inducer trehalose

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease. Mutations in the gene encoding copper/zinc superoxide dismutase-1 (SOD1) are responsible for most familiar cases, but the role of mutant SOD1 protein dysfunction in non-cell autonomous neurodegeneration, especially in relation to microglial activation, is still unclear. Here, we focused our study on microglial cells, which release SOD1 also through exosomes. We observed that in rat primary microglia the overexpression of the most-common SOD1 mutations linked to fALS (G93A and A4V) leads to SOD1 intracellular accumulation, which correlates to autophagy dysfunction and microglial activation. In primary contact co-cultures, fALS mutant SOD1 overexpression by microglial cells appears to be neurotoxic by itself. Treatment with the autophagy-inducer trehalose reduced mutant SOD1 accumulation in microglial cells, decreased microglial activation and abrogated neurotoxicity in the co-culture model. These data suggest that i) the alteration of the autophagic pathway due to mutant SOD1 overexpression is involved in microglial activation and neurotoxicity; ii) the induction of autophagy with trehalose reduces microglial SOD1 accumulation through proteasome degradation and activation, leading to neuroprotection. Our results provide a novel contribution towards better understanding key cellular mechanisms in non-cell autonomous ALS neurodegeneration.

In utero exposure to fine particulate matter results in an altered neuroimmune phenotype in adult mice

Environmental exposure to air pollution has been linked to a number of health problems including organ rejection, lung damage and inflammation. While the deleterious effects of air pollution in adult animals are well documented, the long-term consequences of particulate matter (PM) exposure during animal development are uncertain. In this study we tested the hypothesis that environmental exposure to PM 2.5 μm in diameter in utero promotes long term inflammation and neurodegeneration. We evaluated the behavior of PM exposed animals using several tests and observed deficits in spatial memory without robust changes in anxiety-like behavior. We then examined how this affects the brains of adult animals by examining proteins implicated in neurodegeneration, synapse formation and inflammation by western blot, ELISA and immunohistochemistry. These tests revealed significantly increased levels of COX2 protein in PM2.5 exposed animal brains in addition to changes in synaptophysin and Arg1 proteins. Exposure to PM2.5 also increased the immunoreactivity for GFAP, a marker of activated astrocytes. Cytokine concentrations in the brain and spleen were also altered by PM2.5 exposure. These findings indicate that in utero exposure to particulate matter has long term consequences which may affect the development of both the brain and the immune system in addition to promoting inflammatory change in adult animals.

Neuroinflammation and blood-brain barrier disruption following traumatic brain injury: Pathophysiology and potential therapeutic targets

Traumatic Brain Injury (TBI) is the most frequent cause of death and disability in young adults and children in the developed world, occurring in over 1.7 million persons and resulting in 50,000 deaths in the United States alone. The Centers for Disease Control and Prevention estimate that between 3.2 and 5.3 million persons in the United States live with a TBI-related disability, including several neurocognitive disorders and functional limitations. Following the primary mechanical injury in TBI, literature suggests the presence of a delayed secondary injury involving a variety of neuroinflammatory changes. In the hours to days following a TBI, several signaling molecules and metabolic derangements result in disruption of the blood-brain barrier, leading to an extravasation of immune cells and cerebral edema. The primary, sudden injury in TBI occurs as a direct result of impact and therefore cannot be treated, but the timeline and pathophysiology of the delayed, secondary injury allows for a window of possible therapeutic options. The goal of this review is to discuss the pathophysiology of the primary and delayed injury in TBI as well as present several preclinical studies that identify molecular targets in the potential treatment of TBI. Additionally, certain recent clinical trials are briefly discussed to demonstrate the current state of TBI investigation.

Systemic infection modifies the neuroinflammatory response in late stage Alzheimer's disease

Clinical studies indicate that systemic infections accelerate cognitive decline in Alzheimer’s disease. Animal models suggest that this may be due to enhanced pro-inflammatory changes in the brain. We have performed a post-mortem human study to determine whether systemic infection modifies the neuropathology and in particular, neuroinflammation, in the late-stage of the disease.

Sections of cerebral cortex and underlying white matter from controls and Alzheimer's patients who died with or without a terminal systemic infection were immunolabelled and quantified for: (i) Αβ and phosphorylated-tau; (ii) the inflammation-related proteins Iba1, CD68, HLA-DR, FcγRs (CD64, CD32a, CD32b, CD16), CHIL3L1, IL4R and CCR2; and (iii) T-cell marker CD3. In Alzheimer's disease, the synaptic proteins synaptophysin and PSD-95 were quantified by ELISA, and the inflammatory proteins and mRNAs by MesoScale Discovery Multiplex Assays and qPCR, respectively.

Systemic infection in Alzheimer's disease was associated with decreased CD16 (p = 0.027, grey matter) and CD68 (p = 0.015, white matter); increased CD64 (p = 0.017, white matter) as well as increased protein expression of IL6 (p = 0.047) and decreased IL5 (p = 0.007), IL7 (p = 0.002), IL12/IL23p40 (p = 0.001), IL15 (p = 0.008), IL16 (p < 0.001) and IL17A (p < 0.001). Increased expression of anti-inflammatory genes CHI3L1 (p = 0.012) and IL4R (p = 0.004) were detected in this group. T-cell recruitment to the brain was reduced when systemic infection was present. However, exposure to systemic infection did not modify the pathology. In Alzheimer's disease, CD68 (p = 0.026), CD64 (p = 0.002), CHI3L1 (p = 0.016), IL4R (p = 0.005) and CCR2 (p = 0.010) were increased independently of systemic infection.

Our findings suggest that systemic infections modify neuroinflammatory processes in Alzheimer's disease. However, rather than promoting pro-inflammatory changes, as observed in experimental models, they seem to promote an anti-inflammatory, potentially immunosuppressive, environment in the human brain.

Polarization of Microglia to the M2 Phenotype in a Peroxisome Proliferator-Activated Receptor Gamma-Dependent Manner Attenuates Axonal Injury Induced by Traumatic Brain Injury in Mice

Increasing evidence indicates that activated microglia play an important role in the inflammatory response following traumatic brain injury (TBI). Inhibiting M1 and stimulating M2 activated microglia have demonstrated protective effects in several animal models of central nervous system diseases. However, it is not clear whether the polarization of microglia to M2 attenuates axonal injury following TBI. In this study, we used a lateral fluid percussion injury device to induce axonal injury in mice. Mice were randomly assigned to the sham, TBI, TBI + rosiglitazone (peroxisome proliferator-activated receptor gamma [PPAR-γ] agonist), and TBI + GW9662 (PPAR-γ antagonist) groups. Axonal injury was assessed using immunohistochemical staining for beta amyloid precursor protein. The inflammatory response was assessed by enzyme-linked immunosorbent assay, microglia polarization was assessed using specific markers of M1 and M2 microglia, and neurological function was assessed using the neurological severity score. Following TBI, microglia of the M1 phenotype increased significantly, while those of the M2 phenotype decreased. Rosiglitazone-induced PPAR-γ activation promoted microglia polarization to the M2 phenotype, which reduced the inflammatory response, attenuated axonal injury in the cerebral cortex, and improved neurological function. Conversely, GW9662 inhibited the polarization of microglia to M2 and aggravated inflammation and axonal injury. Our in vitro findings in lipopolysaccharide-induced microglia were consistent with those of our in vivo experiments. In conclusion, the polarization of microglia to the M2 phenotype via PPAR-γ activation attenuated axonal injury following TBI in mice, which may be a potential therapeutic approach for TBI-induced axonal injury.

Inflammation, neurodegeneration and protein aggregation in the retina as ocular biomarkers for Alzheimer's disease in the 3xTg-AD mouse model

Alzheimer's disease (AD) is the most common cause of dementia in the elderly. In the pathogenesis of AD a pivotal role is played by two neurotoxic proteins that aggregate and accumulate in the central nervous system: amyloid beta and hyper-phosphorylated tau. Accumulation of extracellular amyloid beta plaques and intracellular hyper-phosphorylated tau tangles, and consequent neuronal loss begins 10–15 years before any cognitive impairment. In addition to cognitive and behavioral deficits, sensorial abnormalities have been described in AD patients and in some AD transgenic mouse models. Retina can be considered a simple model of the brain, as some pathological changes and therapeutic strategies from the brain may be observed or applicable to the retina. Here we propose new retinal biomarkers that could anticipate the AD diagnosis and help the beginning and the follow-up of possible future treatments. We analyzed retinal tissue of triple-transgenic AD mouse model (3xTg-AD) for the presence of pathological hallmarks during disease progression. We found the presence of amyloid beta plaques, tau tangles, neurodegeneration, and astrogliosis in the retinal ganglion cell layer of 3xTg-AD mice, already at pre-symptomatic stage. Moreover, retinal microglia in pre-symptomatic mice showed a ramified, anti-inflammatory phenotype which, during disease progression, switches to a pro-inflammatory, less ramified one, becoming neurotoxic. We hypothesize retina as a window through which monitor AD-related neurodegeneration process.

Dihydromyricetin inhibits microglial activation and neuroinflammation by suppressing NLRP3 inflammasome activation in APP/PS1 transgenic mice

BACKGROUND

Activated microglia-mediated inflammation plays a key role in the pathogenesis of Alzheimer's disease (AD). In addition, chronic activation of NLRP3 inflammasomes triggered by amyloid β peptide (Aβ) in microglia contributes to persistent neuroinflammation. Here, the primary goal was to assess whether Dihydromyricetin (DHM), a plant flavonoid compound, is effective therapies for AD; it is crucial to know whether DHM will affect microglial activation and neuroinflammation in APP/PS1 transgenic mice.

METHODS

After DHM was intraperitoneally injected in APP/PS1 double-transgenic mice, we assessed the effect of DHM on microglial activation, the expression of NLRP3 inflammasome components, and the production of inflammatory cytokine IL-1β by immunofluorescence and Western blot. To determine whether DHM play roles in the Aβ production and deposition, amyloid β protein precursor (APP) and β-site APP cleaving enzyme1 (BACE1), as well as neprilysin (NEP), were detected by Western blot. Finally, behavior was tested by Morris Water Maze to illustrate whether DHM treatment has a significantly positive effect on ameliorating the memory and cognition deficits in AD.

RESULTS

Dihydromyricetin treatment significantly ameliorated memory and cognition deficits and decreased the number of activated microglia in the hippocampus and cortex of APP/PS1 mice. In addition, APP/PS1 mice show reduced activation of NLRP3 inflammasomes and reduced expression of NLRP3 inflammasome components. Furthermore, DHM could promote clearance of Aβ, a trigger for NLRP3 inflammasome activation, by increasing levels of NEP and shift microglial conversion to the M2-specific agrinase-1-positive cell phenotype, which enhances microglial clearance of Aβ and its aggregates but not production of Aβ.

CONCLUSION

Taken together, our findings suggest that DHM prevents progression of AD-like pathology through inhibition of NLRP3 inflammasome-based microglia-mediated neuroinflammation and may be a promising therapeutic drug for treating AD.

YKL-40 as a Potential Biomarker and a Possible Target in Therapeutic Strategies of Alzheimer's Disease

Background:

Growing body of evidence suggests that the pathogenesis of Alzheimer’s disease (AD), a progressing neurodegenerative condition, is not limited to the neuronal compartment, but also involves various immunological mechanisms. Insoluble Aβ aggregates in the brain can induce the activation of microglia, resulting in the synthesis of proinflammatory mediators, which further can stimulate astrocytic expression of YKL-40. Therefore, the aim of the current review is to present up-to-date data about the role of YKL-40 as a biomarker of AD as well as the possibility of therapeutic strategies targeting neuroinflammation.

Objective/Methods:

We searched PubMed articles for the terms “YKL-40”, “neurodegeneration”, “neuroinflammation” and “Alzheimer’s disease”, and included papers focusing on this review’s scope.

Results:

Recent studies indicate that CSF concentrations of YKL-40 were significantly higher in AD patients than in cognitively normal individuals and correlated with dementia biomarkers, such as tau proteins and amyloid beta. Determination of YKL-40 CSF concentration may be also helpful in differentiation between types of dementia and in the distinction of patients in the stable phase of MCI from those who progressed to dementia. Moreover, significantly increased levels of YKL-40 mRNA were found in AD brains in comparison with non-demented controls. Additionally, it was suggested that anti-inflammatory treatment might relief the symptoms of AD and slow its progression.

Conclusion:

Based on the recent knowledge, YKL-40 might be useful as a possible biomarker in the diagnosis and prognosis of AD. Modulation of risk factors and targeting of immune mechanisms, including systemic inflammation could lead to future preventive or therapeutic strategies for AD.

Arginase: A Multifaceted Enzyme Important in Health and Disease

The arginase enzyme developed in early life forms and was maintained during evolution. As the last step in the urea cycle, arginase cleaves l-arginine to form urea and l-ornithine. The urea cycle provides protection against excess ammonia, while l-ornithine is needed for cell proliferation, collagen formation, and other physiological functions. In mammals, increases in arginase activity have been linked to dysfunction and pathologies of the cardiovascular system, kidney, and central nervous system and also to dysfunction of the immune system and cancer. Two important aspects of the excessive activity of arginase may be involved in diseases. First, overly active arginase can reduce the supply of l-arginine needed for the production of nitric oxide (NO) by NO synthase. Second, too much l-ornithine can lead to structural problems in the vasculature, neuronal toxicity, and abnormal growth of tumor cells. Seminal studies have demonstrated that increased formation of reactive oxygen species and key inflammatory mediators promote this pathological elevation of arginase activity. Here, we review the involvement of arginase in diseases affecting the cardiovascular, renal, and central nervous system and cancer and discuss the value of therapies targeting the elevated activity of arginase.

Use of Eflornithine (DFMO) in the Treatment of Early Alzheimer's Disease: A Compassionate Use, Single-Case Study

Background: Recent genome-wide association screening (GWAS) studies have linked Alzheimer's disease (AD) neuropathology to gene networks that regulate immune function. Kan et al. recently reported that Arg1 (an anti-inflammatory gene that codes for arginase-1) is expressed in parts of the brain associated with amyloidosis prior to the onset of neuronal loss, suggesting that chronic brain arginine deprivation promotes AD-related neuropathology. They blocked arginine catabolism in their mouse AD model by administration of eflornithine (DFMO) to juvenile animals, effectively blocking the expression of AD-related amyloid pathology as the mice aged. We report results from a single-case study in which DFMO was administered, for the first time, in an attempt to slow progression of AD in a single woman with multi-domain, amnestic MCI who was unable to tolerate an acetylcholinesterase inhibitor. Methods: Patient C.S. is a 74-year old female with a 5-year history of cognitive decline who was placed on DFMO (500 mg b.i.d.) for 12 months, with amyloid PET scans (baseline and 12-months), APOE genotyping and neuropsychological exams at baseline, 3, 9, and 12 months. Results: C.S. suffered continued cognitive decline over 12 months, including progressive worsening of orientation, social functions and ability to engage in IADL's. She also showed progressive decline on measures of episodic memory and executive function. Florbetapir PET imaging yielded elevated total neocortical SUVr scores at both baseline (SUVr = 1.55) and at 12 months (SUVr = 1.69). Conclusions: We report a first attempt at using DFMO to slow AD progression. This 12-month single-case trial did not halt continued amyloidosis nor cognitive decline. Although this trial was predicated on data reported by Kan et al. (2015) showing that DFMO administered to juvenile AD-prone mice led to diminished amyloid aggregation, this attempt to treat an older mild AD patient may not be a fair test of Kan et al.'s model and results. A future trial might seek to block amyloidosis in young adults who are autosomal gene carriers for early onset AD, or perhaps in adults who are very clearly in the pre-clinical disease stage. Trial Registration: This trial was registered as a Compassionate Use IND #128888 with the United States Food and Drug Administration (FDA).

Markers of microglia in post-mortem brain samples from patients with Alzheimer's disease: a systematic review

Neuroinflammation is proposed as one of the mechanisms by which Alzheimer's disease pathology, including amyloid-β plaques, leads to neuronal death and dysfunction. Increases in the expression of markers of microglia, the main neuroinmmune cell, are widely reported in brains from patients with Alzheimer's disease, but the literature has not yet been systematically reviewed to determine whether this is a consistent pathological feature. A systematic search was conducted in Medline, Embase and PsychINFO for articles published up to 23 February 2017. Papers were included if they quantitatively compared microglia markers in post-mortem brain samples from patients with Alzheimer's disease and aged controls without neurological disease. A total of 113 relevant articles were identified. Consistent increases in markers related to activation, such as major histocompatibility complex II (36/43 studies) and cluster of differentiation 68 (17/21 studies), were identified relative to nonneurological aged controls, whereas other common markers that stain both resting and activated microglia, such as ionized calcium-binding adaptor molecule 1 (10/20 studies) and cluster of differentiation 11b (2/5 studies), were not consistently elevated. Studies of ionized calcium-binding adaptor molecule 1 that used cell counts almost uniformly identified no difference relative to control, indicating that increases in activation occurred without an expansion of the total number of microglia. White matter and cerebellum appeared to be more resistant to these increases than other brain regions. Nine studies were identified that included high pathology controls, patients who remained free of dementia despite Alzheimer's disease pathology. The majority (5/9) of these studies reported higher levels of microglial markers in Alzheimer's disease relative to controls, suggesting that these increases are not solely a consequence of Alzheimer's disease pathology. These results show that increased markers of microglia are a consistent feature of Alzheimer's disease, though this seems to be driven primarily by increases in activation-associated markers, as opposed to markers of all microglia.