Medroxyprogesterone Acetate Impairs Amyloid Beta Degradation in a Matrix Metalloproteinase-9 Dependent Manner

Exposure to endogenous and exogenous sex hormones and reproductive history influence prognosis in women with ALS

INTRODUCTION/AIMS

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with a higher incidence in men suggesting an influence of sex steroids. Our objective was to investigate past exposure to endogenous and synthetic steroids in female ALS patients and controls.

METHODS

We administered a questionnaire to 158 postmenopausal women (75 ALS patients and 83 controls). We calculated reproductive time span (RTS), lifetime endogenous estrogen (LEE) and progesterone exposures (LPE), oral contraceptive pill (OCP) use, and reproductive history.

RESULTS

ALS patients showed shorter LEE and LPE, a lower proportion of breast cancer, and 11% showed no history of pregnancies vs. 4% of controls. Odds ratios (ORs) showed that <17 y of LEE and a delayed menarche (>13 y) constitute risk factors for ALS [OR = 2.1 (95% confidence interval {CI}, 1.08-4.2); and OR = 2.4 (95% CI, 1.1-5.1) respectively]. According to Cox survival analysis, for each year the LEE increased over 17 y, it was independently associated with longer survival [hazard ratio (HR) = 0.37 (95% CI, 0.16-0.85)] after adjusting for smoking, age and site of onset. Multivariate regression analysis demonstrated that for each month using OCP for longer than 40 mo increased the risk of ALS [adjusted OR = 4.1 (95% CI, 1.2-13.8)].

DISCUSSION

Thus, longer exposure to endogenous female sex steroids increased survival and reduced ALS susceptibility. In contrast, longer exposure to synthetic sex steroids showed a negative impact by reducing the production of endogenous female sex steroids or due to crossover with other steroid receptors. Given the neuroprotective effects of sex steroids, we suggest that abnormalities of neuroendocrine components may alter motor function in women with ALS.

Advances in Amyloid-β Clearance in the Brain and Periphery: Implications for Neurodegenerative Diseases

This review examines the role of impaired amyloid-β clearance in the accumulation of amyloid-β in the brain and the periphery, which is closely associated with Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA). The molecular mechanism underlying amyloid-β accumulation is largely unknown, but recent evidence suggests that impaired amyloid-β clearance plays a critical role in its accumulation. The review provides an overview of recent research and proposes strategies for efficient amyloid-β clearance in both the brain and periphery. The clearance of amyloid-β can occur through enzymatic or non-enzymatic pathways in the brain, including neuronal and glial cells, blood-brain barrier, interstitial fluid bulk flow, perivascular drainage, and cerebrospinal fluid absorption-mediated pathways. In the periphery, various mechanisms, including peripheral organs, immunomodulation/immune cells, enzymes, amyloid-β-binding proteins, and amyloid-β-binding cells, are involved in amyloid-β clearance. Although recent findings have shed light on amyloid-β clearance in both regions, opportunities remain in areas where limited data is available. Therefore, future strategies that enhance amyloid-β clearance in the brain and/or periphery, either through central or peripheral clearance approaches or in combination, are highly encouraged. These strategies will provide new insight into the disease pathogenesis at the molecular level and explore new targets for inhibiting amyloid-β deposition, which is central to the pathogenesis of sporadic AD (amyloid-β in parenchyma) and CAA (amyloid-β in blood vessels).

Association of Apolipoprotein E4-related Microvascular Disease in the Alzheimer's Disease Hippocampal CA1 Stratum Radiatum

Current data suggest a hypothesis of vascular pathogenesis for the development and progression of Alzheimer's disease (AD). To investigate this, we studied the association of apolipoprotein E4 (APOE4) gene on microvessels in human autopsy-confirmed AD with and without APOE4, compared with age/sex-matched control (AC) hippocampal CA1 stratum radiatum. AD arterioles (without APOE4 gene) had mild oxidative stress and loss of vascular endothelial growth factor (VEGF) and endothelial cell density, reflecting aging progression. In AD + APOE4, an increase in strong oxidative DNA damage marker 8-hydroxy-2'-deoxyguanosine (8-OHdG), VEGF, and endothelial cell density were associated with increased diameter of arterioles and perivascular space dilation. In cultured human brain microvascular cells (HBMECs), treatment of ApoE4 protein plus amyloid-β (Aβ) oligomers increased superoxide production and the apoptotic marker cleaved caspase 3, sustained hypoxia inducible factor-1α (HIF-1α) stability that was associated with an increase in MnSOD, VEGF, and cell density. This cell over-proliferation was inhibited with the antioxidants N-acetyl cysteine and MnTMPyP, the HIF-1α inhibitor echinomycin, the VEGFR-2 receptor blocker SU1498, the protein kinase C (PKC) ε knock-down (KD) and the extracellular signal-regulated kinase 1/2 (ERK) inhibitor FR180204. The PKCε KD and echinomycin decreased VEGF and/or ERK. In conclusion, AD capillaries and arterioles in hippocampal CA1 stratum radiatum of non-APOE4 carriers are related with aging, while those in APOE4 carriers with AD are related with pathogenesis of cerebrovascular disease.

Role of neuroinflammation in neurodegeneration development

Studies in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease and Amyotrophic lateral sclerosis, Huntington's disease, and so on, have suggested that inflammation is not only a result of neurodegeneration but also a crucial player in this process. Protein aggregates which are very common pathological phenomenon in neurodegeneration can induce neuroinflammation which further aggravates protein aggregation and neurodegeneration. Actually, inflammation even happens earlier than protein aggregation. Neuroinflammation induced by genetic variations in CNS cells or by peripheral immune cells may induce protein deposition in some susceptible population. Numerous signaling pathways and a range of CNS cells have been suggested to be involved in the pathogenesis of neurodegeneration, although they are still far from being completely understood. Due to the limited success of traditional treatment methods, blocking or enhancing inflammatory signaling pathways involved in neurodegeneration are considered to be promising strategies for the therapy of neurodegenerative diseases, and many of them have got exciting results in animal models or clinical trials. Some of them, although very few, have been approved by FDA for clinical usage. Here we comprehensively review the factors affecting neuroinflammation and the major inflammatory signaling pathways involved in the pathogenicity of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis. We also summarize the current strategies, both in animal models and in the clinic, for the treatment of neurodegenerative diseases.

Beyond the classical amyloid hypothesis in Alzheimer's disease: Molecular insights into current concepts of pathogenesis, therapeutic targets, and study models

Alzheimer's disease (AD) is one of the progressive neurodegenerative disorders and the most common cause of dementia in the elderly worldwide causing difficulties in the daily life of the patient. AD is characterized by the aberrant accumulation of β-amyloid plaques and tau protein-containing neurofibrillary tangles (NFTs) in the brain giving rise to neuroinflammation, oxidative stress, synaptic failure, and eventual neuronal cell death. The total cost of care in AD treatment and related health care activities is enormous and pharmaceutical drugs approved by Food and Drug Administration have not manifested sufficient efficacy in protection and therapy. In recent years, there are growing studies that contribute a fundamental understanding to AD pathogenesis, AD-associated risk factors, and pharmacological intervention. However, greater molecular process-oriented research in company with suitable experimental models is still of the essence to enhance the prospects for AD therapy and cell lines as a disease model are still the major part of this milestone. In this review, we provide an insight into molecular mechanisms, particularly the recent concept in gut-brain axis, vascular dysfunction and autophagy, and current models used in the study of AD. Here, we emphasized the importance of therapeutic strategy targeting multiple mechanisms together with utilizing appropriate models for the discovery of novel effective AD therapy. This article is categorized under: Neurological Diseases > Molecular and Cellular Physiology.

The Role of Extracellular Matrix in Human Neurodegenerative Diseases

The dense neuropil of the central nervous system leaves only limited space for extracellular substances free. The advent of immunohistochemistry, soon followed by advanced diagnostic tools, enabled us to explore the biochemical heterogeneity and compartmentalization of the brain extracellular matrix in exploratory and clinical research alike. The composition of the extracellular matrix is critical to shape neuronal function; changes in its assembly trigger or reflect brain/spinal cord malfunction. In this study, we focus on extracellular matrix changes in neurodegenerative disorders. We summarize its phenotypic appearance and biochemical characteristics, as well as the major enzymes which regulate and remodel matrix establishment in disease. The specifically built basement membrane of the central nervous system, perineuronal nets and perisynaptic axonal coats can protect neurons from toxic agents, and biochemical analysis revealed how the individual glycosaminoglycan and proteoglycan components interact with these molecules. Depending on the site, type and progress of the disease, select matrix components can either proactively trigger the formation of disease-specific harmful products, or reactively accumulate, likely to reduce tissue breakdown and neuronal loss. We review the diagnostic use and the increasing importance of medical screening of extracellular matrix components, especially enzymes, which informs us about disease status and, better yet, allows us to forecast illness.

Canthin-6-one (CO) from Picrasma quassioides (D.Don) Benn. ameliorates lipopolysaccharide (LPS)-induced astrocyte activation and associated brain endothelial disruption

BACKGROUND

Canthin-6-one (CO) is an active ingredient found in Picrasma quassioides (D.Don) Benn. (PQ) that displays various biological activities including anti-inflammatory properties. Several studies reported PQ displayed neuroprotective activities, but its effects on astrocytes have not yet been investigated. Astrocytes are crucial regulators of neuroinflammatory responses under pathological conditions in the central nervous system (CNS). Proinflammatory astrocytes can induce the blood-brain barrier (BBB) breakdown, which plays a key role in the progression of neurodegenerative disorder (ND).

PURPOSE

This study aims to investigate the anti-neuroinflammatory effects of CO in LPS-induced astrocyte activation and its underlying mechanisms in protecting the blood-brain barrier (BBB) in vitro.

METHODS

Mouse astrocytes (C8-D1A) were activated with lipopolysaccharide (LPS) with or without CO pretreatment. Effects of CO on astrocyte cell viability, secretions of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β) and nitric oxide (NO) were determined. Intracellular transcriptions and translations of proinflammatory mediators, molecular signaling, [Ca²⁺] and the levels of reactive oxygen species (ROS) were evaluated by RT-PCR, western blotting, and flow cytometry, respectively. Astrocyte-conditioned medium (ACM) was further prepared for incubating endothelial monolayer (bEnd.3) grown on transwell. Endothelial disruptions were evaluated by transendothelial electrical resistance (TEER), FITC-dextran permeability and monocyte adhesion assays. Endothelial tight junctions (TJs) and molecular signaling pathways were evaluated by immunofluorescence staining and western blotting.

RESULTS

CO attenuated LPS-induced expression of astrocytic proinflammatory mediators (TNF-α, IL-1β, IL-6, NO) and inhibited deleterious molecular activities including inducible nitric oxide synthase (iNOS), p-NFκB and p-STAT3 in astrocytes. Incubation of ACM collected from CO-treated astrocytes significantly ameliorated endothelial disruptions, reduced expressions of endothelial cytokine receptors (IL-6R, gp130 (IL-6RB), TNFR and IL-1R), suppressed proinflammatory pathways, MAPKs (p-AKT, p-MEK, p-ERK, p-p38, p-JNK) and p-STAT3, restored endothelial stabilizing pathways (p-Rac 1) and upregulated beneficial endothelial nitric oxide synthase (eNOS).

CONCLUSION

Our study demonstrates for the first time CO exhibited potent protective effects against astrocyte-mediated proinflammatory responses and associated endothelial barrier disruptions.

The Role of a Pathological Interaction between β-amyloid and Mitochondria in the Occurrence and Development of Alzheimer's Disease

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases in existence. It is characterized by an impaired cognitive function that is due to a progressive loss of neurons in the brain. Extracellular β-amyloid (Aβ) plaques are the main pathological features of the disease. In addition to abnormal protein aggregation, increased mitochondrial fragmentation, altered expression of the genes involved in mitochondrial biogenesis, disruptions in the ER-mitochondria interaction, and mitophagy are observed. Reactive oxygen species are known to affect Aβ expression and aggregation. In turn, oligomeric and aggregated Aβ cause mitochondrial disorders. In this review, we summarize available knowledge about the pathological effects of Aβ on mitochondria and the potential molecular targets associated with proteinopathy and mitochondrial dysfunction for the pharmacological treatment of Alzheimer's disease.

Classical HDACs in the regulation of neuroinflammation

Neuroinflammation is a key factor of the pathology of various neurological diseases (brain injury, depression, neurodegenerative diseases). It is a complex and orderly process that relies on various types of glial cells and peripheral immune cells. Inhibition of neuroinflammation can reduce the severity of neurological diseases. The initiation, progression, and termination of inflammation require gene activation, epigenetic modification, transcriptional translation, and post-translational regulation, all of which are tightly regulated by different enzymes. Epigenetics refers to the regulation of epigenetic gene expression by epigenetic changes (DNA methylation, histone modification, and non-coding RNAs such as miRNA) that are not dependent on changes in gene sequence and are heritable. Histone deacetylases (HDACs) are a group of important enzymes that regulate epigenetics. They can remove the acetyl group on the lysine ϵ-amino group of the target protein, thereby affecting gene transcription or altering protein activity. HDACs are involved in the regulation of immunity and inflammation. HDAC inhibitor (HDACi) has also become a new hotspot in the research of anti-inflammatory drugs. Therefore, the aim of the current review is to discuss and summarize the role and mechanism of different HDACs in neuroinflammation and the corresponding role of HDACi in neurological diseases, and to providing new ideas for future research on neuroinflammation-related diseases and drug development.