Peripheral Inflammation and Demyelinating Diseases

The Association among Hypothalamic Subnits, Gonadotropic and Sex Hormone Plasmas Levels in Alzheimer's Disease

This study investigates the sex-specific role of the Hypothalamic-Pituitary-Gonadal axis in Alzheimer's disease progression, utilizing ADNI1 data for 493 individuals, analyzing plasma levels of gonadotropic and sex hormones, and examining neurodegeneration-related brain structures. We assessed plasma levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), progesterone (P4), and testosterone (T), along with volumetric measures of the hippocampus, entorhinal cortex, and hypothalamic subunits, to explore their correlation with Alzheimer's disease markers across different cognitive statuses and sexes. Significant cognitive status effects were observed for all volumetric measures, with a distinct sex-by-cognitive status interaction for hypothalamic volume, indicating a decrease in males but not in females across cognitive impairment stages. Regression analyses showed specific hypothalamic subunit volume related to hormone levels, accounting for up to approximately 40% of the variance (p < 0.05). The findings highlight sex differences in neurodegeneration and hormonal regulation, suggesting potential for personalized treatments and advancing the understanding of Alzheimer's disease etiology.

Peripheral inflammation is a potential etiological factor in Alzheimer's disease

Peripheral inflammation could constitute a risk factor for AD. This review summarizes the research related to peripheral inflammation that appears to have a relationship with Alzheimer's disease. We find there are significant associations between AD and peripheral infection induced by various pathogens, including herpes simplex virus type 1, cytomegalovirus, Epstein-Barr virus, human immunodeficiency virus, severe acute respiratory syndrome coronavirus 2, Porphyromonas gingivalis, Helicobacter pylori, and Toxoplasma gondii. Chronic inflammatory diseases are also reported to contribute to the pathophysiology of AD. The mechanisms by which peripheral inflammation affects the pathophysiology of AD are complex. Pathogen-derived neurotoxic molecule composition, disrupted BBB, and dysfunctional neurogenesis may all play a role in peripheral inflammation, promoting the development of AD. Anti-pathogenic medications and anti-inflammatory treatments are reported to decrease the risk of AD. Studies that could improve understanding the associations between AD and peripheral inflammation are needed. If our assumption is correct, early intervention against inflammation may be a potential method of preventing and treating AD.

Extracellular vesicles from hyperammonemic rats induce neuroinflammation in hippocampus and impair cognition in control rats

Patients with liver cirrhosis show hyperammonemia and peripheral inflammation and may show hepatic encephalopathy with cognitive impairment, reproduced by rats with chronic hyperammonemia. Peripheral inflammation induces neuroinflammation in hippocampus of hyperammonemic rats, altering neurotransmission and leading to cognitive impairment. Extracellular vesicles (EVs) may transmit pathological effects from the periphery to the brain. We hypothesized that EVs from peripheral blood would contribute to cognitive alterations in hyperammonemic rats. The aims were to assess whether EVs from plasma of hyperammonemic rats (HA-EVs) induce cognitive impairment and to identify the underlying mechanisms. Injection of HA-EVs impaired learning and memory, induced microglia and astrocytes activation and increased TNFα and IL-1β. Ex vivo incubation of hippocampal slices from control rats with HA-EVs reproduced these alterations. HA-EVs increased membrane expression of TNFR1, reduced membrane expression of TGFβR2 and Smad7 and IκBα levels and increased IκBα phosphorylation. This led to increased activation of NF-κB and IL-1β production, altering membrane expression of NR2B, GluA1 and GluA2 subunits, which would be responsible for cognitive impairment. All these effects of HA-EVs were prevented by blocking TNFα, indicating that they were mediated by enhanced activation of TNFR1 by TNFα. We show that these mechanisms are very different from those leading to motor incoordination, which is due to altered GABAergic neurotransmission in cerebellum. This demonstrates that peripheral EVs play a key role in the transmission of peripheral alterations to the brain in hyperammonemia and hepatic encephalopathy, inducing neuroinflammation and altering neurotransmission in hippocampus, which in turn is responsible for the cognitive deficits.

Elevated monocyte to high-density lipoprotein cholesterol ratio correlates with clinical severity in acute inflammatory demyelinating polyradiculoneuropathy patients

While monocyte to high-density lipoprotein cholesterol ratio (MHR) has been reported to be associated with nervous system lesions, the role of MHR has not been determined in patients with Guillain-Barré Syndrome (GBS). The purpose of our study was to explore the role of MHR in patients with GBS. A total of 52 GBS patients were involved in the study retrospectively, including patients with acute inflammatory demyelinating polyradiculoneuropathy (AIDP), acute motor axonal neuropathy (AMAN), and acute motor sensory axonal neuropathy (AMSAN). We used Hughes Functional Grading Scale (HFGS) score to evaluate functional status in GBS patients. Among patients with different subtypes of GBS, MHR was significantly elevated in those with demyelination compared to patients without demyelination (p < 0.001); AIDP patients had an increased MHR compared with AMAN or AMSAN patients (p = 0.001; p = 0.013). There was a positive correlation between MHR and HFGS score (r = 0.463, p = 0.006) in AIDP patients, but not in AMAN or AMSAN. Multiple linear regression analysis revealed that MHR was independently associated with HFGS score (beta = 0.405, p = 0.013) in AIDP patients. Our study suggests that MHR as an inflammatory marker is elevated in patients with AIDP compared to AMAN or AMSAN patients, while MHR has a positive correlation with clinical severity in AIDP patients, suggesting that MHR may provide an additional information to reflect the pathophysiology of AIDP.

Inflammatory Response Leads to Neuronal Death in Human Post-Mortem Cerebral Cortex in Patients with COVID-19

The recent coronavirus disease of 2019 (COVID-19) pandemic has adversely affected people worldwide. A growing body of literature suggests the neurological complications and manifestations in response to COVID-19 infection. Herein, we explored the inflammatory and immune responses in the post-mortem cerebral cortex of patients with severe COVID-19. The participants comprised three patients diagnosed with severe COVID-19 from March 26, 2020, to April 17, 2020, and three control patients. Our findings demonstrated a surge in the number of reactive astrocytes and activated microglia, as well as low levels of glutathione along with the upregulation of inflammation- and immune-related genes IL1B, IL6, IFITM, MX1, and OAS2 in the COVID-19 group. Overall, the data imply that oxidative stress may invoke a glial-mediated neuroinflammation, which ultimately leads to neuronal cell death in the cerebral cortex of COVID-19 patients.

Relevant mediators involved in and therapies targeting the inflammatory response induced by activation of the NLRP3 inflammasome in ischemic stroke

The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) inflammasome is a member of the NLR family of inherent immune cell sensors. The NLRP3 inflammasome can detect tissue damage and pathogen invasion through innate immune cell sensor components commonly known as pattern recognition receptors (PRRs). PRRs promote activation of nuclear factor kappa B (NF-κB) pathways and the mitogen-activated protein kinase (MAPK) pathway, thus increasing the transcription of genes encoding proteins related to the NLRP3 inflammasome. The NLRP3 inflammasome is a complex with multiple components, including an NAIP, CIITA, HET-E, and TP1 (NACHT) domain; apoptosis-associated speck-like protein containing a CARD (ASC); and a leucine-rich repeat (LRR) domain. After ischemic stroke, the NLRP3 inflammasome can produce numerous proinflammatory cytokines, mediating nerve cell dysfunction and brain edema and ultimately leading to nerve cell death once activated. Ischemic stroke is a disease with high rates of mortality and disability worldwide and is being observed in increasingly younger populations. To date, there are no clearly effective therapeutic strategies for the clinical treatment of ischemic stroke. Understanding the NLRP3 inflammasome may provide novel ideas and approaches because targeting of upstream and downstream molecules in the NLRP3 pathway shows promise for ischemic stroke therapy. In this manuscript, we summarize the existing evidence regarding the composition and activation of the NLRP3 inflammasome, the molecules involved in inflammatory pathways, and corresponding drugs or molecules that exert effects after cerebral ischemia. This evidence may provide possible targets or new strategies for ischemic stroke therapy.

Severe Acute Respiratory Syndrome Coronavirus 2 Impact on the Central Nervous System: Are Astrocytes and Microglia Main Players or Merely Bystanders?

With confirmed coronavirus disease 2019 (COVID-19) cases surpassing the 18 million mark around the globe, there is an imperative need to gain comprehensive understanding of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although the main clinical manifestations of COVID-19 are associated with respiratory or intestinal symptoms, reports of neurological signs and symptoms are increasing. The etiology of these neurological manifestations remains obscure, and probably involves several direct pathways, not excluding the direct entry of the virus to the central nervous system (CNS) through the olfactory epithelium, circumventricular organs, or disrupted blood–brain barrier. Furthermore, neuroinflammation might occur in response to the strong systemic cytokine storm described for COVID-19, or due to dysregulation of the CNS rennin-angiotensin system. Descriptions of neurological manifestations in patients in the previous coronavirus (CoV) outbreaks have been numerous for the SARS-CoV and lesser for Middle East respiratory syndrome coronavirus (MERS-CoV). Strong evidence from patients and experimental models suggests that some human variants of CoV have the ability to reach the CNS and that neurons, astrocytes, and/or microglia can be target cells for CoV. A growing body of evidence shows that astrocytes and microglia have a major role in neuroinflammation, responding to local CNS inflammation and/or to disbalanced peripheral inflammation. This is another potential mechanism for SARS-CoV-2 damage to the CNS. In this comprehensive review, we will summarize the known neurological manifestations of SARS-CoV-2, SARS-CoV and MERS-CoV; explore the potential role for astrocytes and microglia in the infection and neuroinflammation; and compare them with the previously described human and animal CoV that showed neurotropism to propose possible underlying mechanisms.

Thioredoxin-1 Protects Spinal Cord from Demyelination Induced by Methamphetamine through Suppressing Endoplasmic Reticulum Stress and Inflammation

Methamphetamine (METH) is a psychostimulant abused around the world. Emerging evidence indicates that METH causes brain damage. However, there are very few reports on METH-induced demyelination. Thioredoxin-1 (Trx-1) is a redox regulating protein and plays the roles in protecting neurons from various stresses. However, whether Trx-1 resists demyelination induced by METH has not been reported. In this study, we found that METH-induced thin myelin sheaths in spinal cord, whereas Trx-1 overexpression transgenic (TG) mice restored the myelin sheaths thickness. The expressions of myelin-associated glycoprotein, myelin basic protein, and cyclin-dependent kinase 5 were decreased by METH, whereas these alterations were blocked in Trx-1 TG mice. The expressions of procaspase-12 and procaspase-3 were decreased by METH, the expression of calpain1 was increased by METH, whereas the alterations were suppressed in Trx-1 TG mice. As same as, the expressions of the extracellular signal-regulated kinase, nuclear factor κB, tumor necrosis factor-alpha, and interleukin-1beta were induced by METH, which were suppressed in Trx-1 TG mice. These data suggest that Trx-1 may play a critical role in resisting the METH-mediated demyelination in spinal cord through regulating endoplasmic reticulum stress and inflammation pathways.