The type I interferon antiviral response in the choroid plexus and the cognitive risk in COVID-19

Type I Interferon Signalling and Ischemic Stroke: Mechanisms and Therapeutic Potentials

Type I interferon (IFN-I) signalling is intricately involved in the pathogenesis of multiple infectious diseases, autoimmune diseases, and neurological diseases. Acute ischemic stroke provokes overactivation of IFN-I signalling within the injured brain, particularly in microglia. Following cerebral ischemia, damage-associated molecular patterns (DAMPs) released from injured neural cells elicit marked proinflammatory episodes within minutes. Among these, self-nucleic acids, including nuclear DNA and mitochondrial DNA (mtDNA), have been recognized as a critical alarm signal to fan the flames of neuroinflammation, predominantly via inducing IFN-I signalling activation in microglia. The concept of interferon-responsive microglia (IRM), marked by upregulation of a plethora of IFN-stimulated genes, has been emergingly elucidated in ischemic mouse brains, particularly in aged ones. Among the pattern recognition receptors responsible for IFN-I induction, cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) plays integral roles in potentiating microglia-driven neuroinflammation and secondary brain injury after cerebral ischemia. Here, we aim to provide an up-to-date review on the multifaceted roles of IFN-I signalling, the detailed molecular and cellular mechanisms leading to and resulting from aberrant IFN-I signalling activation after cerebral ischemia, and the therapeutic potentials. A thorough exploration of these above points will inform our quest for IFN-based therapies as effective immunomodulatory therapeutics to complement the limited repertoire of thrombolytic agents, thereby facilitating the translation from bench to bedside.

Type I interferon signalling and interferon-responsive microglia in health and disease

Recent evidence suggests that type I interferon (IFN-I) signalling extends beyond its canonical roles in antiviral defence and immunomodulation. Over the past decade, dysregulated IFN-I signalling has been linked to genetic disorders and neurodegenerative diseases, where it may contribute to neurological impairments. Microglia have emerged as key mediators of IFN-I responses in the central nervous system. A distinct transcriptional state responsive to interferons has recently been identified in microglia. The activation of the IFN-I pathway in these cells is now recognised as pivotal in both development and neurodegeneration. This review is divided into two main sections: the first examines the broader role of IFN-I signalling in the central nervous system, particularly its contribution to neurological dysfunction; the second focuses on the specific state of interferon-responsive microglia, exploring its mechanisms and relevance in neurodegenerative conditions. Finally, we discuss how these areas intersect and their implications for both healthy and diseased states.

Choroid plexus volume is enlarged in long COVID and associated with cognitive and brain changes

Patients with post-COVID condition (PCC) present with diverse symptoms which persist at long-term after SARS-CoV-2 infection. Among these symptoms, cognitive impairment is one of the most prevalent and has been related to brain structural and functional changes. The underlying mechanisms of these cognitive and brain alterations remain elusive but neuroinflammation and immune mechanisms have been majorly considered. In this sense, the choroid plexus (ChP) volume has been proposed as a marker of neuroinflammation in immune-mediated conditions and the ChP epithelium has been found particularly susceptible to the effects of SARS-CoV-2. The objective was to investigate the ChP in PCC and evaluate its relationships with cognition, brain, and immunological alterations. One-hundred and twenty-nine patients with PCC after a mean of 14.79 ± 7.17 months of evolution since the infection and 36 healthy controls were recruited. Participants underwent a neuropsychological, and neuroimaging assessment and immunological markers evaluation. Results revealed ChP volume enlargement in PCC compared to healthy controls. The ChP enlargement was associated with cognitive dysfunction, grey matter volume reduction in frontal and subcortical areas, white matter integrity and diffusivity changes and functional connectivity changes. These ChP changes were also related to intermediate monocytes levels. Findings suggest that the ChP integrity may play a relevant role in the pathophysiology of cognitive deficits and the observed brain changes in PCC. The previously documented function of the ChP in maintaining brain homeostasis and regulating the entry of immune cells into the brain supports the presence of neuroinflammatory mechanisms in this disorder.

Choroid Plexus Pathophysiology

This review examines the roles of the choroid plexus (ChP) in central nervous system (CNS) pathology, emphasizing its involvement in disease mechanisms and therapeutic potential. Structural changes in the human ChP have been reported across various diseases in case reports and descriptive work, but studies have yet to pin down the physiological relevance of these changes. We highlight primary pathologies of the ChP, as well as their significance in neurologic disorders, including stroke, hydrocephalus, infectious diseases, and neurodegeneration. Synthesizing recent research, this review positions the ChP as a critical player in CNS homeostasis and pathology, advocating for enhanced focus on its mechanisms to unlock new diagnostic and treatment strategies and ultimately improve patient outcomes in CNS diseases. Whether acting as a principal driver of disease, a gateway for pathogens into the CNS, or an orchestrator of neuroimmune processes, the ChP holds tremendous promise as a therapeutic target to attenuate a multitude of CNS conditions.

The impact of COVID-19 on accelerating of immunosenescence and brain aging

The COVID-19 pandemic, caused by the novel coronavirus SARS-CoV-2, has profoundly impacted global health, affecting not only the immediate morbidity and mortality rates but also long-term health outcomes across various populations. Although the acute effects of COVID-19 on the respiratory system have initially been the primary focus, it is increasingly evident that the virus can have significant impacts on multiple physiological systems, including the nervous and immune systems. The pandemic has highlighted the complex interplay between viral infection, immune aging, and brain health, that can potentially accelerate neuroimmune aging and contribute to the persistence of long COVID conditions. By inducing chronic inflammation, immunosenescence, and neuroinflammation, COVID-19 may exacerbate the processes of neuroimmune aging, leading to increased risks of cognitive decline, neurodegenerative diseases, and impaired immune function. Key factors include chronic immune dysregulation, oxidative stress, neuroinflammation, and the disruption of cellular processes. These overlapping mechanisms between aging and COVID-19 illustrate how the virus can induce and accelerate aging-related processes, leading to an increased risk of neurodegenerative diseases and other age-related conditions. This mini-review examines key features and possible mechanisms of COVID-19-induced neuroimmune aging that may contribute to the persistence and severity of long COVID. Understanding these interactions is crucial for developing effective interventions. Anti-inflammatory therapies, neuroprotective agents, immunomodulatory treatments, and lifestyle interventions all hold potential for mitigating the long-term effects of the virus. By addressing these challenges, we can improve health outcomes and quality of life for millions affected by the pandemic.

IRF3 regulates neuroinflammatory responses and the expression of genes associated with Alzheimer's disease

The pathological role of interferon signaling is emerging in neuroinflammatory disorders, yet, the specific role of Interferon Regulatory Factor 3 (IRF3) in neuroinflammation remains poorly understood. Here, we show that global IRF3 deficiency delays TLR4-mediated signaling in microglia and attenuates the hallmark features of LPS-induced inflammation such as cytokine release, microglial reactivity, astrocyte activation, myeloid cell infiltration, and inflammasome activation. Moreover, expression of a constitutively active IRF3 (S388D/S390D: IRF3-2D) in microglia induces a transcriptional program reminiscent of the Activated Response Microglia and the expression of genes associated with Alzheimer's disease, notably apolipoprotein-e. Using bulk-RNAseq of IRF3-2D brain myeloid cells, we identified Z-DNA binding protein-1 (ZBP1) as a target of IRF3 that is relevant across various neuroinflammatory disorders. Lastly, we show IRF3 phosphorylation and IRF3-dependent ZBP1 induction in response to Aβ in primary microglia cultures. Together, our results identify IRF3 as an important regulator of LPS and Aβ -mediated neuroinflammatory responses and highlight IRF3 as a central regulator of disease-specific gene activation in different neuroinflammatory diseases.

Deterioration of neuroimmune homeostasis in Alzheimer's Disease patients who survive a COVID-19 infection

Growing evidence has implicated systemic infection as a significant risk factor for the development and advancement of Alzheimer's disease (AD). With the emergence of SARS-CoV-2 (COVID-19) and the resultant pandemic, many individuals from the same aging population vulnerable to AD suffered a severe systemic infection with potentially unidentified long-term consequences for survivors. To study the impact of COVID-19 survival on the brain's intrinsic immune system in a population also suffering from AD, we profiled post-mortem brain tissue from patients in the UF Neuromedicine Human Brain and Tissue Bank with a diagnosis of AD who survived a COVID-19 infection (COVID-AD) and contrasted our findings with AD patients who did not experience a COVID-19 infection, including a group of brain donors who passed away before arrival of SARS-CoV-2 in the United States. We assessed disease-relevant protein pathology and microglial and astrocytic markers by quantitative immunohistochemistry and supplemented these data with whole tissue gene expression analysis performed on the NanoString nCounter® platform. COVID-AD patients showed slightly elevated Aβ burden in the entorhinal, fusiform, and inferior temporal cortices compared to non-COVID-AD patients, while tau pathology burden did not differ between groups. Analysis of microglia revealed a significant loss of microglial homeostasis as well as exacerbated microgliosis in COVID-AD patients compared to non-COVID-AD patients in a brain region-dependent manner. Furthermore, COVID-AD patients showed reduced cortical astrocyte numbers, independent of functional subtype. Transcriptomic analysis supported these histological findings and, in addition, identified a dysregulation of oligodendrocyte and myelination pathways in the hippocampus of COVID-AD patients. In summary, our data demonstrate a profound impact of COVID-19 infection on neuroimmune and glial pathways in AD patients persisting for months post-infection, highlighting the importance of peripheral to central neuroimmune crosstalk in neurodegenerative diseases.

Long COVID as a disease of accelerated biological aging: An opportunity to translate geroscience interventions

It has been four years since long COVID-the protracted consequences that survivors of COVID-19 face-was first described. Yet, this entity continues to devastate the quality of life of an increasing number of COVID-19 survivors without any approved therapy and a paucity of clinical trials addressing its biological root causes. Notably, many of the symptoms of long COVID are typically seen with advancing age. Leveraging this similarity, we posit that Geroscience-which aims to target the biological drivers of aging to prevent age-associated conditions as a group-could offer promising therapeutic avenues for long COVID. Bearing this in mind, this review presents a translational framework for studying long COVID as a state of effectively accelerated biological aging, identifying research gaps and offering recommendations for future preclinical and clinical studies.

The immune and metabolic milieu of the choroid plexus as a potential target in brain protection

The brain's choroid plexus (CP), which operates as an anatomical and functional 'checkpoint', regulates the communication between brain and periphery and contributes to the maintenance of healthy brain homeostasis throughout life. Evidence from mouse models and humans reveals a link between loss of CP checkpoint properties and dysregulation of the CP immune milieu as a conserved feature across diverse neurological conditions. In particular, we suggest that an imbalance between different immune signals at the CP, including CD4+ T cell-derived cytokines, type-I interferon, and complement components, can perpetuate brain inflammation and cognitive deterioration in aging and neurodegeneration. Furthermore, we highlight the role of CP metabolism in controlling CP inflammation, and propose that targeting molecules that regulate CP metabolism could be effective in safeguarding brain function.

SARS-CoV-2-Induced Type I Interferon Signaling Dysregulation in Olfactory Networks Implications for Alzheimer's Disease

Type I interferon signaling (IFN-I) perturbations are major drivers of COVID-19. Dysregulated IFN-I in the brain, however, has been linked to both reduced cognitive resilience and neurodegenerative diseases such as Alzheimer's. Previous works from our group have proposed a model where peripheral induction of IFN-I may be relayed to the CNS, even in the absence of fulminant infection. The aim of our study was to identify significantly enriched IFN-I signatures and genes along the transolfactory route, utilizing published datasets of the nasal mucosa and olfactory bulb amygdala transcriptomes of COVID-19 patients. We furthermore sought to identify these IFN-I signature gene networks associated with Alzheimer's disease pathology and risk. Gene expression data involving the nasal epithelium, olfactory bulb, and amygdala of COVID-19 patients and transcriptomic data from Alzheimer's disease patients were scrutinized for enriched Type I interferon pathways. Gene set enrichment analyses and gene-Venn approaches were used to determine genes in IFN-I enriched signatures. The Agora web resource was used to identify genes in IFN-I signatures associated with Alzheimer's disease risk based on its aggregated multi-omic data. For all analyses, false discovery rates (FDR) <0.05 were considered statistically significant. Pathways associated with type I interferon signaling were found in all samples tested. Each type I interferon signature was enriched by IFITM and OAS family genes. A 14-gene signature was associated with COVID-19 CNS and the response to Alzheimer's disease pathology, whereas nine genes were associated with increased risk for Alzheimer's disease based on Agora. Our study provides further support to a type I interferon signaling dysregulation along the extended olfactory network as reconstructed herein, ranging from the nasal epithelium and extending to the amygdala. We furthermore identify the 14 genes implicated in this dysregulated pathway with Alzheimer's disease pathology, among which HLA-C, HLA-B, HLA-A, PSMB8, IFITM3, HLA-E, IFITM1, OAS2, and MX1 as genes with associated conferring increased risk for the latter. Further research into its druggability by IFNb therapeutics may be warranted.

SARS-CoV-2 induces blood-brain barrier and choroid plexus barrier impairments and vascular inflammation in mice

The coronavirus disease of 2019 (COVID-19) pandemic has led to more than 700 million confirmed cases and nearly 7 million deaths. Although severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) virus mainly infects the respiratory system, neurological complications are widely reported in both acute infection and long-COVID cases. Despite the success of vaccines and antiviral treatments, neuroinvasiveness of SARS-CoV-2 remains an important question, which is also centered on the mystery of whether the virus is capable of breaching the barriers into the central nervous system. By studying the K18-hACE2 infection model, we observed clear evidence of microvascular damage and breakdown of the blood-brain barrier (BBB). Mechanistically, SARS-CoV-2 infection caused pericyte damage, tight junction loss, endothelial activation and vascular inflammation, which together drive microvascular injury and BBB impairment. In addition, the blood-cerebrospinal fluid barrier at the choroid plexus was also impaired after infection. Therefore, cerebrovascular and choroid plexus dysfunctions are important aspects of COVID-19 and may contribute to neurological complications both acutely and in long COVID.

Type I interferon signaling, cognition and neurodegeneration following COVID-19: update on a mechanistic pathogenetic model with implications for Alzheimer's disease

COVID-19's effects on the human brain reveal a multifactorial impact on cognition and the potential to inflict lasting neuronal damage. Type I interferon signaling, a pathway that represents our defense against pathogens, is primarily affected by COVID-19. Type I interferon signaling, however, is known to mediate cognitive dysfunction upon its dysregulation following synaptopathy, microgliosis and neuronal damage. In previous studies, we proposed a model of outside-in dysregulation of tonic IFN-I signaling in the brain following a COVID-19. This disruption would be mediated by the crosstalk between central and peripheral immunity, and could potentially establish feed-forward IFN-I dysregulation leading to neuroinflammation and potentially, neurodegeneration. We proposed that for the CNS, the second-order mediators would be intrinsic disease-associated molecular patterns (DAMPs) such as proteopathic seeds, without the requirement of neuroinvasion to sustain inflammation. Selective vulnerability of neurogenesis sites to IFN-I dysregulation would then lead to clinical manifestations such as anosmia and cognitive impairment. Since the inception of our model at the beginning of the pandemic, a growing body of studies has provided further evidence for the effects of SARS-CoV-2 infection on the human CNS and cognition. Several preclinical and clinical studies have displayed IFN-I dysregulation and tauopathy in gene expression and neuropathological data in new cases, correspondingly. Furthermore, neurodegeneration identified with a predilection for the extended olfactory network furthermore supports the neuroanatomical concept of our model, and its independence from fulminant neuroinvasion and encephalitis as a cause of CNS damage. In this perspective, we summarize the data on IFN-I as a plausible mechanism of cognitive impairment in this setting, and its potential contribution to Alzheimer's disease and its interplay with COVID-19.

Hypertension: Causes and Consequences of Circadian Rhythms in Blood Pressure

Hypertension is extremely common, affecting approximately 1 in every 2 adults globally. Chronic hypertension is the leading modifiable risk factor for cardiovascular disease and premature mortality worldwide. Despite considerable efforts to define mechanisms that underlie hypertension, a potentially major component of the disease, the role of circadian biology has been relatively overlooked in both preclinical models and humans. Although the presence of daily and circadian patterns has been observed from the level of the genome to the whole organism, the functional and structural impact of biological rhythms, including mechanisms such as circadian misalignment, remains relatively poorly defined. Here, we review the impact of daily rhythms and circadian systems in regulating blood pressure and the onset, progression, and consequences of hypertension. There is an emphasis on the impact of circadian biology in relation to vascular disease and end-organ effects that, individually or in combination, contribute to complex phenotypes such as cognitive decline and the loss of cardiac and brain health. Despite effective treatment options for some individuals, control of blood pressure remains inadequate in a substantial portion of the hypertensive population. Greater insight into circadian biology may form a foundation for novel and more widely effective molecular therapies or interventions to help in the prevention, treatment, and management of hypertension and its related pathophysiology.

IRF3 regulates neuroinflammatory responses and the expression of genes associated with Alzheimer's disease

The pathological role of interferon signaling is emerging in neuroinflammatory disorders, yet, the specific role of Interferon Regulatory Factor 3 (IRF3) in neuroinflammation remains poorly understood. Here, we show that global IRF3 deficiency delays TLR4-mediated signaling in microglia and attenuates the hallmark features of LPS-induced inflammation such as cytokine release, microglial reactivity, astrocyte activation, myeloid cell infiltration, and inflammasome activation. Moreover, expression of a constitutively active IRF3 (S388D/S390D:IRF3-2D) in microglia induces a transcriptional program reminiscent of the Activated Response Microglia and the expression of genes associated with Alzheimer's Disease, notably apolipoprotein-e. Lastly, using bulk-RNAseq of IRF3-2D brain myeloid cells, we identified Z-DNA binding protein-1 as a target of IRF3 that is relevant across various neuroinflammatory disorders. Together, our results identify IRF3 as an important regulator of LPS-mediated neuroinflammatory responses and highlight IRF3 as a central regulator of disease-specific gene activation in different neuroinflammatory diseases.

Brain Pathology in COVID-19: Clinical Manifestations and Potential Mechanisms

Neurological manifestations of coronavirus disease 2019 (COVID-19) are less noticeable than the respiratory symptoms, but they may be associated with disability and mortality in COVID-19. Even though Omicron caused less severe disease than Delta, the incidence of neurological manifestations is similar. More than 30% of patients experienced "brain fog", delirium, stroke, and cognitive impairment, and over half of these patients presented abnormal neuroimaging outcomes. In this review, we summarize current advances in the clinical findings of neurological manifestations in COVID-19 patients and compare them with those in patients with influenza infection. We also illustrate the structure and cellular invasion mechanisms of SARS-CoV-2 and describe the pathway for central SARS-CoV-2 invasion. In addition, we discuss direct damage and other pathological conditions caused by SARS-CoV-2, such as an aberrant interferon response, cytokine storm, lymphopenia, and hypercoagulation, to provide treatment ideas. This review may offer new insights into preventing or treating brain damage in COVID-19.

Choroid plexus volume is increased in mood disorders and associates with circulating inflammatory cytokines

Depressed patients exhibit altered levels of immune-inflammatory markers both in the peripheral blood and in the cerebrospinal fluid (CSF) and inflammatory processes have been widely implicated in the pathophysiology of mood disorders. The Choroid Plexus (ChP), located at the base of each of the four brain ventricles, regulates the exchange of substances between the blood and CSF and several evidence supported a key role for ChP as a neuro-immunological interface between the brain and circulating immune cells. Given the role of ChP as a regulatory gate between periphery, CSF spaces and the brain, we compared ChP volumes in patients with bipolar disorder (BP) or major depressive disorder (MDD) and healthy controls, exploring their association with history of illness and levels of circulating cytokines. Plasma levels of inflammatory markers and MRI scans were acquired for 73 MDD, 79 BD and 72 age- and sex-matched healthy controls (HC). Patients with either BD or MDD had higher ChP volumes than HC. With increasing age, the bilateral ChP volume was larger in patients, an effect driven by the duration of illness; while only minor effects were observed in HC. Right ChP volumes were proportional to higher levels of circulating cytokines in the clinical groups, including IFN-γ, IL-13 and IL-17. Specific effects in the two diagnostic groups were observed when considering the left ChP, with positive association with IL-1ra, IL-13, IL-17, and CCL3 in BD, and negative associations with IL-2, IL-4, IL-1ra, and IFN-γ in MDD. These results suggest that ChP could represent a reliable and easy-to-assess biomarker to evaluate the brain effects of inflammatory status in mood disorders, contributing to personalized diagnosis and tailored treatment strategies.

Cullin5 drives experimental asthma exacerbations by modulating alveolar macrophage antiviral immunity

Asthma exacerbations caused by respiratory viral infections are a serious global health problem. Impaired antiviral immunity is thought to contribute to the pathogenesis, but the underlying mechanisms remain understudied. Here using mouse models we find that Cullin5 (CUL5), a key component of Cullin-RING E3 ubiquitin ligase 5, is upregulated and associated with increased neutrophil count and influenza-induced exacerbations of house dust mite-induced asthma. By contrast, CUL5 deficiency mitigates neutrophilic lung inflammation and asthma exacerbations by augmenting IFN-β production. Mechanistically, following thymic stromal lymphopoietin stimulation, CUL5 interacts with O-GlcNAc transferase (OGT) and induces Lys48-linked polyubiquitination of OGT, blocking the effect of OGT on mitochondrial antiviral-signaling protein O-GlcNAcylation and RIG-I signaling activation. Our results thus suggest that, in mouse models, pre-existing allergic injury induces CUL5 expression, impairing antiviral immunity and promoting neutrophilic inflammation for asthma exacerbations. Targeting of the CUL5/IFN-β signaling axis may thereby serve as a possible therapy for treating asthma exacerbations.

The regulation of antiviral innate immunity through non-m6A RNA modifications

The post-transcriptional RNA modifications impact the dynamic regulation of gene expression in diverse biological and physiological processes. Host RNA modifications play an indispensable role in regulating innate immune responses against virus infection in mammals. Meanwhile, the viral RNAs can be deposited with RNA modifications to interfere with the host immune responses. The N6-methyladenosine (m6A) has boosted the recent emergence of RNA epigenetics, due to its high abundance and a transcriptome-wide widespread distribution in mammalian cells, proven to impact antiviral innate immunity. However, the other types of RNA modifications are also involved in regulating antiviral responses, and the functional roles of these non-m6A RNA modifications have not been comprehensively summarized. In this Review, we conclude the regulatory roles of 2'-O-methylation (Nm), 5-methylcytidine (m5C), adenosine-inosine editing (A-to-I editing), pseudouridine (Ψ), N1-methyladenosine (m1A), N7-methylguanosine (m7G), N6,2'-O-dimethyladenosine (m6Am), and N4-acetylcytidine (ac4C) in antiviral innate immunity. We provide a systematic introduction to the biogenesis and functions of these non-m6A RNA modifications in viral RNA, host RNA, and during virus-host interactions, emphasizing the biological functions of RNA modification regulators in antiviral responses. Furthermore, we discussed the recent research progress in the development of antiviral drugs through non-m6A RNA modifications. Collectively, this Review conveys knowledge and inspiration to researchers in multiple disciplines, highlighting the challenges and future directions in RNA epitranscriptome, immunology, and virology.

Gut-brain pathogenesis of post-acute COVID-19 neurocognitive symptoms

Approximately one third of non-hospitalized coronavirus disease of 2019 (COVID-19) patients report chronic symptoms after recovering from the acute stage of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Some of the most persistent and common complaints of this post-acute COVID-19 syndrome (PACS) are cognitive in nature, described subjectively as "brain fog" and also objectively measured as deficits in executive function, working memory, attention, and processing speed. The mechanisms of these chronic cognitive sequelae are currently not understood. SARS-CoV-2 inflicts damage to cerebral blood vessels and the intestinal wall by binding to angiotensin-converting enzyme 2 (ACE2) receptors and also by evoking production of high levels of systemic cytokines, compromising the brain's neurovascular unit, degrading the intestinal barrier, and potentially increasing the permeability of both to harmful substances. Such substances are hypothesized to be produced in the gut by pathogenic microbiota that, given the profound effects COVID-19 has on the gastrointestinal system, may fourish as a result of intestinal post-COVID-19 dysbiosis. COVID-19 may therefore create a scenario in which neurotoxic and neuroinflammatory substances readily proliferate from the gut lumen and encounter a weakened neurovascular unit, gaining access to the brain and subsequently producing cognitive deficits. Here, we review this proposed PACS pathogenesis along the gut-brain axis, while also identifying specific methodologies that are currently available to experimentally measure each individual component of the model.

Endothelial type I interferon response and brain diseases: identifying STING as a therapeutic target

The endothelium layer lining the inner surface of blood vessels serves relevant physiological functions in all body systems, including the exchanges between blood and extravascular space. However, endothelial cells also participate in innate and adaptive immune response that contribute to the pathophysiology of inflammatory disorders. Type I Interferon (IFN) signaling is an inflammatory response triggered by a variety of pathogens, but it can also be induced by misplaced DNA in the cytosol caused by cell stress or gene mutations. Type I IFN produced by blood leukocytes or by the endothelium itself is well-known to activate the interferon receptor (IFNAR) in endothelial cells. Here, we discuss the induction of type I IFN secretion and signaling in the endothelium, specifically in the brain microvasculature where endothelial cells participate in the tight blood-brain barrier (BBB). This barrier is targeted during neuroinflammatory disorders such as infection, multiple sclerosis, Alzheimer's disease and traumatic brain injury. We focus on type I IFN induction through the cGAS-STING activation pathway in endothelial cells in context of autoinflammatory type I interferonopathies, inflammation and infection. By comparing the pathophysiology of two separate infectious diseases-cerebral malaria induced by Plasmodium infection and COVID-19 caused by SARS-CoV-2 infection-we emphasize the relevance of type I IFN and STING-induced vasculopathy in organ dysfunction. Investigating the role of endothelial cells as active type I IFN producers and responders in disease pathogenesis could lead to new therapeutic targets. Namely, endothelial dysfunction and brain inflammation may be avoided with strategies that target excessive STING activation in endothelial cells.

Single-cell multiomic analysis reveals the involvement of Type I interferon-responsive CD8+ T cells in amyloid beta-associated memory loss

Alzheimer's disease (AD) is the leading cause of dementia worldwide, but there are limited therapeutic options and no current cure. While the involvement of microglia in AD has been highly appreciated, the role of other innate and adaptive immune cells remains largely unknown, partly due to their scarcity and heterogeneity. This study aimed to study non-microglial immune cells in wild type and AD-transgenic mouse brains across different ages. Our results uncovered the presence of a unique CD8+ T cell population that were selectively increased in aging AD mouse brains, here referred to as "disease-associated T cells (DATs)". These DATs were found to express an elevated tissue-resident memory and Type I interferon-responsive gene signature. Further analysis of aged AD mouse brains showed that these CD8+ T cells were not present in peripheral or meningeal tissues. Preventing CD8+ T cell development in AD-transgenic mice via genetic deletion of beta-2 microglobulin ( B2m ) led to a reduction of amyloid-β plaque formation in aged mice, and improved memory in AD-transgenic mice as early as four months of age. The integration of transcriptomic and epigenomic profiles at the single-cell level revealed potential transcription factors that reshape the regulomes of CD8+ T cells. These findings highlight a critical role for DATs in the progression of AD and provide a new avenue for treatment.