Functional Two-Way Crosstalk Between Brain and Lung: The Brain-Lung Axis

COVID-19 influenced gut dysbiosis, post-acute sequelae, immune regulation, and therapeutic regimens

The novel coronavirus disease 2019 (COVID-19) pandemic outbreak caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has garnered unprecedented global attention. It caused over 2.47 million deaths through various syndromes such as acute respiratory distress, hypercoagulability, and multiple organ failure. The viral invasion proceeds through the ACE2 receptor, expressed in multiple cell types, and in some patients caused serious damage to tissues, organs, immune cells, and the microbes that colonize the gastrointestinal tract (GIT). Some patients who survived the SARS-CoV-2 infection have developed months of persistent long-COVID-19 symptoms or post-acute sequelae of COVID-19 (PASC). Diagnosis of these patients has revealed multiple biological effects, none of which are mutually exclusive. However, the severity of COVID-19 also depends on numerous comorbidities such as obesity, age, diabetes, and hypertension and care must be taken with respect to other multiple morbidities, such as host immunity. Gut microbiota in relation to SARS-CoV-2 immunopathology is considered to evolve COVID-19 progression via mechanisms of biochemical metabolism, exacerbation of inflammation, intestinal mucosal secretion, cytokine storm, and immunity regulation. Therefore, modulation of gut microbiome equilibrium through food supplements and probiotics remains a hot topic of current research and debate. In this review, we discuss the biological complications of the physio-pathological effects of COVID-19 infection, GIT immune response, and therapeutic pharmacological strategies. We also summarize the therapeutic targets of probiotics, their limitations, and the efficacy of preclinical and clinical drugs to effectively inhibit the spread of SARS-CoV-2.

Focus on brain-lung crosstalk: Preventing or treating the pathological vicious circle between the brain and the lung

Recently, there has been increasing attention to bidirectional information exchange between the brain and lungs. Typical physiological data is communicated by channels like the circulation and sympathetic nervous system. However, communication between the brain and lungs can also occur in pathological conditions. Studies have shown that severe traumatic brain injury (TBI), cerebral hemorrhage, subarachnoid hemorrhage (SAH), and other brain diseases can lead to lung damage. Conversely, severe lung diseases such as acute respiratory distress syndrome (ARDS), pneumonia, and respiratory failure can exacerbate neuroinflammatory responses, aggravate brain damage, deteriorate neurological function, and result in poor prognosis. A brain or lung injury can have adverse effects on another organ through various pathways, including inflammation, immunity, oxidative stress, neurosecretory factors, microbiome and oxygen. Researchers have increasingly concentrated on possible links between the brain and lungs. However, there has been little attention given to how the interaction between the brain and lungs affects the development of brain or lung disorders, which can lead to clinical states that are susceptible to alterations and can directly affect treatment results. This review described the relationships between the brain and lung in both physiological and pathological conditions, detailing the various pathways of communication such as neurological, inflammatory, immunological, endocrine, and microbiological pathways. Meanwhile, this review provides a comprehensive summary of both pharmacological and non-pharmacological interventions for diseases related to the brain and lungs. It aims to support clinical endeavors in preventing and treating such ailments and serve as a reference for the development of relevant medications.

Exposure to Environmental Toxins: Potential Implications for Stroke Risk via the Gut- and Lung-Brain Axis

Recent evidence indicates that exposure to environmental toxins, both short-term and long-term, can increase the risk of developing neurological disorders, including neurodegenerative diseases (i.e., Alzheimer's disease and other dementias) and acute brain injury (i.e., stroke). For stroke, the latest systematic analysis revealed that exposure to ambient particulate matter is the second most frequent stroke risk after high blood pressure. However, preclinical and clinical stroke investigations on the deleterious consequences of environmental pollutants are scarce. This review examines recent evidence of how environmental toxins, absorbed along the digestive tract or inhaled through the lungs, affect the host cellular response. We particularly address the consequences of environmental toxins on the immune response and the microbiome at the gut and lung barrier sites. Additionally, this review highlights findings showing the potential contribution of environmental toxins to an increased risk of stroke. A better understanding of the biological mechanisms underlying exposure to environmental toxins has the potential to mitigate stroke risk and other neurological disorders.

Schwann cells in the normal and pathological lung microenvironment

The lungs are a key organ in the respiratory system. They are regulated by a complex network of nerves that control their development, structure, function, and response to various pathological stimuli. Accumulating evidence suggests the involvement of a neural mechanism in different pathophysiological conditions in the lungs and the development and progression of common respiratory diseases. Lung diseases are the chief source of death globally. For instance, lung cancer is the second most commonly diagnosed malignancy, after prostate cancer in men and breast cancer in women, and is the most lethal cancer worldwide. However, although airway nerves are accepted as a mechanistically and therapeutically important feature that demands appropriate emphasizing in the context of many respiratory diseases, significantly less is known about the role of the neuroglial cells in lung physiology and pathophysiology, including lung cancer. New data have uncovered some cellular and molecular mechanisms of how Schwann cells, as fundamental components of the peripheral nervous system, may regulate lung cancer cells' survival, spreading, and invasiveness in vitro and in vivo. Schwann cells control the formation and maintenance of the lung cancer microenvironment and support metastasis formation. It was also reported that the number of lung cancer-associated Schwann cells correlates with patients' survival. Different factors secreted by Schwann cells, including microRNA, are known to sharpen the lung cancer environment by regulating the tumor-neuro-immune axis. Further clinical and experimental studies are required to elucidate the detailed role of Schwann cells in creating and maintaining pulmonary tumor-neuro-immune axis, which will advance our understanding of the pathogenesis of lung cancer and may inform therapeutic hypotheses aiming neoplasms and metastases in the lung.

First Exploration of the Altered Microbial Gut-Lung Axis in the Pathogenesis of Human Refractory Chronic Cough

PURPOSE

Cough represents a natural mechanism that plays an important defensive role in the respiratory tract, but in some conditions, it may become persistent, nonproductive, and harmful. In general, refractory chronic cough (RCC) occurs in about 20% of individuals; hence, we aimed to assess the presence of altered gut-lung communication in RCC patients through a compositional and functional characterization of both gut (GM) and oral microbiota (OM).

METHODS

16S rRNA sequencing was used to characterize both GM and OM composition of RCC patients and healthy controls (HC). PICRUST2 assessed functional changes in microbial communities while gas chromatography was used to evaluate fecal short-chain fatty acid levels and serum-free fatty acid (FFA) abundances.

RESULTS

In comparison with HC, RCC patients reported increased saliva alpha-diversity and statistically significant beta-diversity in both GM and OM. Also, a, respectively, significant increased or reduced Firmicutes/Bacteroidota ratio in stool and saliva samples of RCC patients has been shown, in addition to a modification of the abundances of several taxa in both GM and OM. Moreover, a potential fecal over-expression of lipopolysaccharide biosynthesis and lipoic acid metabolism pathways and several differences in serum FFA levels have been reported in RCC patients than in HC.

CONCLUSION

Since differences in both GM and OM of RCC patients have been documented, these findings could provide new information about RCC pathogenesis and also pave the way for the development of novel nutritional or pharmacological interventions for the management of RCC through the restoration of eubiotic gut-lung communication.

Immune regulation of the gut-brain axis and lung-brain axis involved in ischemic stroke

Local ischemia often causes a series of inflammatory reactions when both brain immune cells and the peripheral immune response are activated. In the human body, the gut and lung are regarded as the key reactional targets that are initiated by brain ischemic attacks. Mucosal microorganisms play an important role in immune regulation and metabolism and affect blood-brain barrier permeability. In addition to the relationship between peripheral organs and central areas and the intestine and lung also interact among each other. Here, we review the molecular and cellular immune mechanisms involved in the pathways of inflammation across the gut-brain axis and lung-brain axis. We found that abnormal intestinal flora, the intestinal microenvironment, lung infection, chronic diseases, and mechanical ventilation can worsen the outcome of ischemic stroke. This review also introduces the influence of the brain on the gut and lungs after stroke, highlighting the bidirectional feedback effect among the gut, lungs, and brain.

First Annual PACT Act Research Symposium on Veterans Health: A Colorado PACT Act Collaboration (CoPAC) Initiative

In response to the Sergeant First Class Heath Robinson Honoring our Promise to Address Comprehensive Toxics (PACT) Act being signed into law, several research groups in Colorado organized the First Annual PACT Act Research Symposium for Veteran Health. The 2-day symposium was interested in research relevant to military exposures with a primary focus on respiratory and mental health. Information on the PACT Act, data sources in the Department of Veteran Affairs and DOD, and research opportunities at the Veteran Affairs were presented. The morning session centered on respiratory health, highlighting research conducted over the last two decades regarding deployment-related respiratory diseases. Despite the high prevalence of mental health disorders among Veterans, information presented during the afternoon sessions on mental health highlighted the dearth of research to date regarding psychological health and military-related exposures. Policymakers, clinicians, and researchers were encouraged to adopt a life-course approach when conceptualizing physical and psychological exposures. On the second day of meetings, a smaller group of participants discussed next steps in military exposure research, as well as priorities for future research. Per the latter, recommendations for future research were made regarding the need for more precise exposure characterization, longitudinal data collection, and efforts to increase understanding regarding disease pathogenesis, as well as the impact of exposures across multiple organs. Such efforts will require interdisciplinary collaboration.

Left cardiac vagotomy rapidly reduces contralateral cardiac vagal electrical activity in anesthetized Göttingen minipigs

BACKGROUND

The impact of acute unilateral injury on spontaneous electrical activity in both vagus nerves at the heart level is poorly understood. We investigated the immediate neuroelectrical response after right or left cardiac vagal nerve transection (VNTx) by recording spiking activity of each heart vagus nerve (VN).

METHODS

Fourteen male Göttingen minipigs underwent sternotomy. Multi-electrode cuffs were implanted below the cut level to record vagal electroneurographic signals during electrocardiographic and hemodynamic monitoring, before and immediately after cardiac VNTx (left: L-cut, n = 6; right: R-cut, n = 8).

RESULTS

Left cardiac VNTx significantly reduced multi-unit electrical activity (MUA) firing rate in the vagal stump (-30.7% vs pre-cut) and intact right VN (-21.8% vs pre-cut) at the heart level, without affecting heart rate, heart rate variability, or hemodynamics. In contrast, right cardiac VNTx did not acutely alter MUA in either VN but slightly increased (p < 0.022) the root mean square of successive RR interval differences (rMSSD), an index of parasympathetic outflow, without affecting hemodynamics.

CONCLUSIONS

Our study reveals an early left-lateralized pattern in vagal spiking activity following unilateral cardiac vagotomy. These findings enhance understanding of the neuroelectrical response to vagal injury and provide insights into preserving vagal outflow after unilateral cardiac vagotomy. Importantly, monitoring spiking activity of the cardiac right VN may predict onset of left vagal pathway injury, which is detrimental to cardiac patients and can occur as a complication of catheter ablation for atrial fibrillation.

Radiotracers for Imaging of Inflammatory Biomarkers TSPO and COX-2 in the Brain and in the Periphery

Inflammation involves the activation of innate immune cells and is believed to play an important role in the development and progression of both infectious and non-infectious diseases such as neurodegeneration, autoimmune diseases, pulmonary and cancer. Inflammation in the brain is marked by the upregulation of translocator protein (TSPO) in microglia. High TSPO levels are also found, for example, in macrophages in cases of rheumatoid arthritis and in malignant tumor cells compared to their relatively low physiological expression. The same applies for cyclooxgenase-2 (COX-2), which is constitutively expressed in the kidney, brain, thymus and gastrointestinal tract, but induced in microglia, macrophages and synoviocytes during inflammation. This puts TSPO and COX-2 in the spotlight as important targets for the diagnosis of inflammation. Imaging modalities, such as positron emission tomography and single-photon emission tomography, can be used to localize inflammatory processes and to track their progression over time. They could also enable the monitoring of the efficacy of therapy and predict its outcome. This review focuses on the current development of PET and SPECT tracers, not only for the detection of neuroinflammation, but also for emerging diagnostic measures in infectious and other non-infectious diseases such as rheumatic arthritis, cancer, cardiac inflammation and in lung diseases.

The emerging role of exosomes in communication between the periphery and the central nervous system

Exosomes, membrane-enclosed vesicles, are secreted by all types of cells. Exosomes can transport various molecules, including proteins, lipids, functional mRNAs, and microRNAs, and can be circulated to various recipient cells, leading to the production of local paracrine or distal systemic effects. Numerous studies have proved that exosomes can pass through the blood-brain barrier, thus, enabling the transfer of peripheral substances into the central nervous system (CNS). Consequently, exosomes may be a vital factor in the exchange of information between the periphery and CNS. This review will discuss the structure, biogenesis, and functional characterization of exosomes and summarize the role of peripheral exosomes deriving from tissues like the lung, gut, skeletal muscle, and various stem cell types in communicating with the CNS and influencing the brain's function. Then, we further discuss the potential therapeutic effects of exosomes in brain diseases and the clinical opportunities and challenges. Gaining a clearer insight into the communication between the CNS and the external areas of the body will help us to ascertain the role of the peripheral elements in the maintenance of brain health and illness and will facilitate the design of minimally invasive techniques for diagnosing and treating brain diseases.

Inhibition of S100A9 alleviates neurogenic pulmonary edema after subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Neurogenic pulmonary edema (NPE) frequently arises as a complication subsequent to subarachnoid hemorrhage (SAH). Heterodimers of S100A8 and S100A9 are commonly formed, thereby initiating an inflammatory reaction through receptor binding on the cell surface. Paquinimod serves as a specific inhibitor of S100A9. The objective of this investigation is to assess the impact of Paquinimod administration and S100A9 knockout on NPE following SAH.

METHODS

In this study, SAH models of C57BL/6J wild-type (WT) and S100A9 knockout mice were established through intravascular perforation. These models were then divided into several groups, including the WT-sham group, S100A9-KO-sham group, WT-SAH group, WT-SAH + Paquinimod group, and S100A9-KO-SAH group. After 24 h of SAH induction, pulmonary edema was assessed using the lung wet-dry weight method and Hematoxylin and eosin (HE) staining. Additionally, the expression levels of various proteins, such as interleukin-1β (IL-1β), tumor necrosis factor α (TNF-α), occludin, claudin-3, Bax, Bcl-2, TLR4, MYD88, and pNF-κB, in lung tissue were analyzed using western blot and immunofluorescence staining. Lung tissue apoptosis was detected by TUNEL staining.

RESULTS

Firstly, our findings indicate that the knockout of S100A9 has a protective effect on early brain injury following subarachnoid hemorrhage (SAH). Additionally, the reduction of brain injury after SAH can also alleviate neurogenic pulmonary edema (NPE). Immunofluorescence staining and western blot analysis revealed that compared to SAH mice with wild-type S100A9 expression (WT-SAH), the lungs of S100A9 knockout SAH mice (S100A9-KO-SAH) and mice treated with Paquinimod exhibited decreased levels of inflammatory molecules (IL-1β and TNF-α) and increased levels of tight junction proteins. Furthermore, the knockout of S100A9 resulted in upregulated expression of the apoptotic-associated protein Bax and down-regulated expression of Bcl-2. Furthermore, a decrease in TLR4, MYD88, and phosphorylated pNF-κB was noted in S100A9-KO-SAH and Paquinimod treated mice, indicating the potential involvement of the TLR4/MYD88/NF-κB signaling pathway in the inhibition of the protective effect of S100A9 on NPE following SAH.

CONCLUSION

The knockout of S100A9 not only ameliorated initial cerebral injury following subarachnoid hemorrhage (SAH), but also mitigated SAH-associated neurogenic pulmonary edema (NPE). Additionally, Paquinimod was found to diminish NPE. These findings imply a correlation between the central nervous system and peripheral organs, highlighting the potential of safeguarding the brain to mitigate harm to peripheral organs.

Predictive Modeling and Integrated Risk Assessment of Postoperative Mortality and Pneumonia in Traumatic Brain Injury Patients through Clustering and Machine Learning: Retrospective Study

This study harnessed machine learning to forecast postoperative mortality (POM) and postoperative pneumonia (PPN) among surgical traumatic brain injury (TBI) patients. Our analysis centered on the following key variables: Glasgow Coma Scale (GCS), midline brain shift (MSB), and time from injury to emergency room arrival (TIE). Additionally, we introduced innovative clustered variables to enhance predictive accuracy and risk assessment. Exploring data from 617 patients spanning 2012 to 2022, we observed that 22.9% encountered postoperative mortality, while 30.0% faced postoperative pneumonia (PPN). Sensitivity for POM and PPN prediction, before incorporating clustering, was in the ranges of 0.43-0.82 (POM) and 0.54-0.76 (PPN). Following clustering, sensitivity values were 0.47-0.76 (POM) and 0.61-0.77 (PPN). Accuracy was in the ranges of 0.67-0.76 (POM) and 0.70-0.81 (PPN) prior to clustering and 0.42-0.73 (POM) and 0.55-0.73 (PPN) after clustering. Clusters characterized by low GCS, small MSB, and short TIE exhibited a 3.2-fold higher POM risk compared to clusters with high GCS, small MSB, and short TIE. In summary, leveraging clustered variables offers a novel avenue for predicting POM and PPN in TBI patients. Assessing the amalgamated impact of GCS, MSB, and TIE characteristics provides valuable insights for clinical decision making.

Neurological disorders after severe pneumonia are associated with translocation of endogenous bacteria from the lung to the brain

Neurological disorders are a common feature in patients who recover from severe acute pneumonia. However, the underlying mechanisms remain poorly understood. Here, we show that the neurological syndromes after severe acute pneumonia are partly attributed to the translocation of endogenous bacteria from the lung to the brain during pneumonia. Using principal components analysis, similarities were found between the brain's flora species and those of the lungs, indicating that the bacteria detected in the brain may originate from the lungs. We also observed impairment of both the lung-blood and brain-blood barriers, allowing endogenous lung bacteria to invade the brain during pneumonia. An elevated microglia and astrocyte activation signature via bacterial infection-related pathways was observed, indicating a bacterial-induced disruption of brain homeostasis. Collectively, we identify endogenous lung bacteria that play a role in altering brain homeostasis, which provides insight into the mechanism of neurological syndromes after severe pneumonia.

Multiorgan talks in the presence of brain injury

PURPOSE OF REVIEW

The brain is the command center of the rest of the body organs. The normal multiorgan talks between the brain and the rest of the body organs are essential for the normal body homeostasis. In the presence of brain injury, the disturbed talks between the brain and the rest of body organs will result in several pathological conditions. The aim of this review is to present the most recent findings for the pathological conditions that would result from the impaired multiorgan talks in the presence of brain injury.

RECENT FINDINGS

The brain injury such as in acute ischemic stroke, subarachnoid hemorrhage and traumatic brain injury will result in cascade of pathological talks between the brain and the rest of body organs. These pathological talks could result in pathological conditions such as cardiomyopathy, acute lung and kidney injuries, impaired liver functions, and impaired gut barrier permeability as well.

SUMMARY

Better understanding of the pathological conditions that could result from the impaired multiorgan talks in the presence of brain injury will open the doors for precise targeted therapies in the future for myriad of pathological conditions.

Emerging role of the host microbiome in neuropsychiatric disorders: overview and future directions

The human body harbors a diverse ecosystem of microorganisms, including bacteria, viruses, and fungi, collectively known as the microbiota. Current research is increasingly focusing on the potential association between the microbiota and various neuropsychiatric disorders. The microbiota resides in various parts of the body, such as the oral cavity, nasal passages, lungs, gut, skin, bladder, and vagina. The gut microbiota in the gastrointestinal tract has received particular attention due to its high abundance and its potential role in psychiatric and neurodegenerative disorders. However, the microbiota presents in other body tissues, though less abundant, also plays crucial role in immune system and human homeostasis, thus influencing the development and progression of neuropsychiatric disorders. For example, oral microbiota imbalance and associated periodontitis might increase the risk for neuropsychiatric disorders. Additionally, studies using the postmortem brain samples have detected the widespread presence of oral bacteria in the brains of patients with Alzheimer's disease. This article provides an overview of the emerging role of the host microbiota in neuropsychiatric disorders and discusses future directions, such as underlying biological mechanisms, reliable biomarkers associated with the host microbiota, and microbiota-targeted interventions, for research in this field.

n-3 Polyunsaturated Fatty Acids Modulate LPS-Induced ARDS and the Lung-Brain Axis of Communication in Wild-Type versus Fat-1 Mice Genetically Modified for Leukotriene B4 Receptor 1 or Chemerin Receptor 23 Knockout

Specialized pro-resolving mediators (SPMs) and especially Resolvin E1 (RvE1) can actively terminate inflammation and promote healing during lung diseases such as acute respiratory distress syndrome (ARDS). Although ARDS primarily affects the lung, many ARDS patients also develop neurocognitive impairments. To investigate the connection between the lung and brain during ARDS and the therapeutic potential of SPMs and its derivatives, fat-1 mice were crossbred with RvE1 receptor knockout mice. ARDS was induced in these mice by intratracheal application of lipopolysaccharide (LPS, 10 µg). Mice were sacrificed at 0 h, 4 h, 24 h, 72 h, and 120 h post inflammation, and effects on the lung, liver, and brain were assessed by RT-PCR, multiplex, immunohistochemistry, Western blot, and LC-MS/MS. Protein and mRNA analyses of the lung, liver, and hypothalamus revealed LPS-induced lung inflammation increased inflammatory signaling in the hypothalamus despite low signaling in the periphery. Neutrophil recruitment in different brain structures was determined by immunohistochemical staining. Overall, we showed that immune cell trafficking to the brain contributed to immune-to-brain communication during ARDS rather than cytokines. Deficiency in RvE1 receptors and enhanced omega-3 polyunsaturated fatty acid levels (fat-1 mice) affect lung-brain interaction during ARDS by altering profiles of several inflammatory and lipid mediators and glial activity markers.

Effect of Low Doses of Dexamethasone on Experimental Pulmonary Tuberculosis

Tuberculosis (TB) is the deadliest disease caused by a bacterial agent. Glucocorticoids (GCs) have a typical anti-inflammatory effect, but recently it has been shown that they can present proinflammatory activity, mainly by increasing molecules from innate immunity. In the current study, we evaluated the effect of low doses of dexamethasone on Mycobacterium tuberculosis in vivo and in vitro. We used an established mice model of progressing tuberculosis (TB) in the in vivo studies. Intratracheal or intranasal dexamethasone therapy administered with conventional antibiotics in the late stage of the disease decreased the lung bacilli load and lung pneumonia, and increased the survival of the animals. Finally, the treatment decreased the inflammatory response in the SNC and, therefore, sickness behavior and neurological abnormalities in the infected animals. In the in vitro experiments, we used a cell line of murine alveolar macrophages infected with Mtb. Low-dose dexamethasone treatment increased the clearance capacity of Mtb by MHS macrophages, MIP-1α, and TLR2 expression, decreased proinflammatory and anti-inflammatory cytokines, and induced apoptosis, a molecular process that contributes to the control of the mycobacteria. In conclusion, the administration of low doses of dexamethasone represents a promising adjuvant treatment for pulmonary TB.

Clinical Implications of the Association between Respiratory and Gastrointestinal Disorders in Migraine and Non-Migraine Headache Patients

Headaches, particularly migraine, are associated with gastrointestinal (GI) disorders. In addition to the gut-brain axis, the lung-brain axis is suspected to be involved in the relationship between pulmonary microbes and brain disorders. Therefore, we investigated possible associations of migraine and non-migraine headaches (nMH) with respiratory and GI disorders using the clinical data warehouse over 11 years. We compared data regarding GI and respiratory disorders, including asthma, bronchitis, and COPD, among patients with migraine, patients with nMH, and controls. In total, 22,444 patients with migraine, 117,956 patients with nMH, and 289,785 controls were identified. After adjustment for covariates and propensity score matching, the odds ratios (ORs) for asthma (1.35), gastroesophageal reflux disorder (1.55), gastritis (1.90), functional GI disorder (1.35), and irritable bowel syndrome (1.76) were significantly higher in patients with migraine than in controls (p = 0.000). The ORs for asthma (1.16) and bronchitis (1.33) were also significantly higher in patients with nMH than in controls (p = 0.0002). When the migraine group was compared with the nMH group, only the OR for GI disorders was statistically significant. Our findings suggest that migraine and nMH are associated with increased risks of GI and respiratory disorders.

Human mini-brains for reconstituting central nervous system disorders

Neurological disorders in the central nervous system (CNS) are progressive and irreversible diseases leading to devastating impacts on patients' life as they cause cognitive impairment, dementia, and even loss of essential body functions. The development of effective medicines curing CNS disorders is, however, one of the most ambitious challenges due to the extremely complex functions and structures of the human brain. In this regard, there are unmet needs to develop simplified but physiopathologically-relevant brain models. Recent advances in the microfluidic techniques allow multicellular culture forming miniaturized 3D human brains by aligning parts of brain regions with specific cells serving suitable functions. In this review, we overview designs and strategies of microfluidics-based human mini-brains for reconstituting CNS disorders, particularly Alzheimer's disease (AD), Parkinson's disease (PD), traumatic brain injury (TBI), vascular dementia (VD), and environmental risk factor-driven dementia (ERFD). Afterward, the applications of the mini-brains in the area of medical science are introduced in terms of the clarification of pathogenic mechanisms and identification of promising biomarkers. We also present expanded model systems ranging from the CNS to CNS-connecting organ axes to study the entry pathways of pathological risk factors into the brain. Lastly, the advantages and potential challenges of current model systems are addressed with future perspectives.

A Prospect to Ameliorate Affective Symptoms and to Enhance Cognition in Long COVID Using Auricular Transcutaneous Vagus Nerve Stimulation

Long COVID, the postviral disorder caused by COVID-19, is expected to become one of the leading causes of disability in Europe. The cognitive consequences of long COVID have been described as "brain fog" and characterized by anxiety and depression, and by cognitive deficits. Long COVID is assumed to be a complex condition arising from multiple causes, including persistent brainstem dysfunction and disrupted vagal signaling. We recommend the potential application of auricular transcutaneous vagus nerve stimulation (atVNS) as an ADD-ON instrument to compensate for the cognitive decline and to ameliorate affective symptoms caused by long COVID. This technique enhances vagal signaling by directly activating the nuclei in the brainstem, which are hypoactive in long COVID to enhance mood and to promote attention, memory, and cognitive control-factors affected by long COVID. Considering that atVNS is a non-pharmacological intervention, its ADD-ON to standard pharmaceutical agents will be useful for non-responders, making of this method a suitable tool. Given that atVNS can be employed as an ecological momentary intervention (EMI), we outline the translational advantages of atVNS in the context of accelerating the cognitive and affective recovery from long COVID.

Mapping brain endophenotypes associated with idiopathic pulmonary fibrosis genetic risk

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a serious disease of the lung parenchyma. It has a known polygenetic risk, with at least seventeen regions of the genome implicated to date. Growing evidence suggests linked multimorbidity of IPF with neurodegenerative or affective disorders. However, no study so far has explicitly explored links between IPF, associated genetic risk profiles, and specific brain features.

METHODS

We exploited imaging and genetic data from more than 32,000 participants available through the UK Biobank population-level resource to explore links between IPF genetic risk and imaging-derived brain endophenotypes. We performed a brain-wide imaging-genetics association study between the presence of 17 known IPF risk variants and 1248 multi-modal imaging-derived features, which characterise brain structure and function.

FINDINGS

We identified strong associations between cortical morphological features, white matter microstructure and IPF risk loci in chromosomes 17 (17q21.31) and 8 (DEPTOR). Through co-localisation analysis, we confirmed that cortical thickness in the anterior cingulate and more widespread white matter microstructure changes share a single causal variant with IPF at the chromosome 8 locus. Post-hoc preliminary analysis suggested that forced vital capacity may partially mediate the association between the DEPTOR variant and white matter microstructure, but not between the DEPTOR risk variant and cortical thickness.

INTERPRETATION

Our results reveal the associations between IPF genetic risk and differences in brain structure, for both cortex and white matter. Differences in tissue-specific imaging signatures suggest distinct underlying mechanisms with focal cortical thinning in regions with known high DEPTOR expression, unrelated to lung function, and more widespread microstructural white matter changes consistent with hypoxia or neuroinflammation with potential mediation by lung function.

FUNDING

This study was supported by the NIHR Nottingham Biomedical Research Centre and the UK Medical Research Council.