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

Decoding mechanisms and protein markers in lung-brain axis

BACKGROUND

The lung-brain axis represents a complex bidirectional communication network that is pivotal in the crosstalk between respiratory and neurological functions. This review summarizes the current understanding of the mechanisms and protein markers that mediate the effects of lung diseases on brain health.

MAIN FINDINGS

In this review, we explore the mechanisms linking lung injury to neurocognitive impairments, focusing on neural pathways, immune regulation and inflammatory responses, microorganism pathways, and hypoxemia. Specifically, we highlight the role of the vagus nerve in modulating the central nervous system response to pulmonary stimuli; Additionally, the regulatory function of the immune system is underscored, with evidence suggesting that lung-derived immune mediators can traverse the blood-brain barrier, induce neuroinflammation and cognitive decline; Furthermore, we discuss the potential of lung microbiota to influence brain diseases through microbial translocation and immune activation; Finally, the impact of hypoxemia is examined, with findings indicating that it can exacerbate cerebral injury via oxidative stress and impaired perfusion. Moreover, we analyze how pulmonary conditions, such as pneumonia, ALI/ARDS, and asthma, contribute to neurological dysfunction. Prolonged mechanical ventilation can also contribute to cognitive impairment. Conversely, brain diseases (e.g., stroke, traumatic brain injury) can lead to acute respiratory complications. In addition, protein markers such as TLR4, ACE2, A-SAA, HMGB1, and TREM2 are crucial to the lung-brain axis and correlate with disease severity. We also discuss emerging therapeutic strategies targeting this axis, including immunomodulation and microbiome engineering. Overall, understanding the lung-brain interplay is crucial for developing integrated treatment strategies and improving patient outcomes. Further research is needed to elucidate the molecular mechanisms and foster interdisciplinary collaboration.

Inter-organ correlation based multi-task deep learning model for dynamically predicting functional deterioration in multiple organ systems of ICU patients

BACKGROUND

Functional deterioration (FD) of various organ systems is the major cause of death in ICU patients, but few studies propose effective multi-task (MT) model to predict FD of multiple organs simultaneously. This study propose a MT deep learning model named inter-organ correlation based multi-task model (IOC-MT), to dynamically predict FD in six organ systems.

METHODS

Three public ICU databases were used for model training and validation. The IOC-MT was designed based on the routine MT deep learning framework, but it used a Graph Attention Networks (GAT) module to capture inter-organ correlation and an adaptive adjustment mechanism (AAM) to adjust prediction. We compared the IOC-MT to five single-task (ST) baseline models, including three deep models (LSTM-ST, GRU-ST, Transformer-ST) and two machine learning models (GRU-ST, RF-ST), and performed ablation study to assess the contribution of important components in IOC-MT. Model discrimination was evaluated by AUROC and AUPRC, and model calibration was assessed by the calibration curve. The attention weight and adjustment coefficient were analyzed at both overall and individual level to show the AAM of IOC-MT.

RESULTS

The IOC-MT had comparable discrimination and calibration to LSTM-ST, GRU-ST and Transformer-ST for most organs under different gap windows in the internal and external validation, and obviously outperformed GRU-ST, RF-ST. The ablation study showed that the GAT, AAM and missing indicator could improve the overall performance of the model. Furthermore, the inter-organ correlation and prediction adjustment of IOC-MT were intuitive and comprehensible, and also had biological plausibility.

CONCLUSIONS

The IOC-MT is a promising MT model for dynamically predicting FD in six organ systems. It can capture inter-organ correlation and adjust the prediction for one organ based on aggregated information from the other organs.

Pulmonary microbiota disruption by respiratory exposure to carbon quantum dots induces neuronal damages in mice

Given the fact that carbon quantum dots (CQDs) have been commercially produced in quantities, it is inevitable to make their ways into environment and interact closely with the public. Even though CQDs in the environment have been reported to damage the central nervous system, the underlying mechanisms of neurotoxic effects of CQDs following respiratory exposure is still not clear. Intranasal instilled CQDs, mimicking respiratory exposure, induces neurobehavioral impairments associated with neuronal cell death of ferroptosis and disulfidptosis that is regulated by metabolic reprogramming of glutathione and cysteine pathways in the cortex and hippocampus where CQDs were hardly accumulated. Therefore, further exploration found that dysbiosis in the lung microbiome was found specifically manipulated by CQDs, which correlated with systemic and neuroinflammatory responses, implicating a lung-brain axis other than gut-brain axis as a critical pathway through which microbiota dysbiosis may impact neurological health after respiratory exposure to CQDs. This study pioneers the exploration of the neurological consequences of inhaled CQDs in the environment through the regulation of microbiome-lung-brain axis, which is key in understanding the mechanistic link between CQDs exposure and neurotoxicity. The findings could develop potential strategies for mitigating the neurological effects of CQDs even other types of nanoparticles.

Serum RIPK1, Acute Lung Injury, and Outcomes in Severe Traumatic Brain Injury: A Multicenter Prospective Study

Background

Receptor-interacting protein kinase-1 (RIPK1), a regulator of necroptosis, is involved in acute brain injury and acute lung injury (ALI). Here, serum RIPK1 levels were measured after severe traumatic brain injury (sTBI), with an endeavor to unveil its prognostic implications and mediation effects of ALI.

Methods

In this multicenter prospective study, serum RIPK1 levels were gauged in 100 healthy individuals and 158 sTBI patients in need of decompressive craniectomy for brain herniation. The collected materials encompassed the Glasgow Coma Scale (GCS), pupil enlargement status, basal cisternal shapes, ALI, etc. The extended Glasgow outcome scale (GOSE) was employed for estimating neurological impairments at posttraumatic 180-day mark. Multifactorial analytical methods were applied to assess relevancies.

Results

Patients, as opposed to controls, had markedly raised serum RIPK1 levels, with the even substantially higher levels in those with lower GCS scores, bilateral pupil enlargement or obliterated basal cisterns. Using restricted cubic spline, RIPK1 levels were linearly related to occurrent risks of the four outcome variables of interest, that is 180-day death, overall survival, poor prognosis (GOSE scores 1-4) and ALI. RIPK1 levels independently predicted these outcome variables. RIPK1 levels had noninteractional effects with age, sex, hypertension, diabetes, smoking and alcohol habits in terms of its association with these outcome variables. RIPK1 levels exhibited high discriminatory efficiency for these outcome variables under the receiver operating characteristic curve. RIPK1 levels, via partial mediation by ALI, were associated with death and poor prognosis of patients.

Conclusion

Elevated serum RIPK1 levels of patients with sTBI may be highly related to trauma severity, and risks of poor outcomes and ALI; and ALI partially explains the links between serum RIPK1 levels, death and poor prognosis, substantializing serum RIPK1 as a serological prognostic predictor of good prospect in sTBI.

Association of serum galectin3 levels with six-month functional outcome of severe traumatic brain injury and the mediation effect of acute lung injury: A two-center prospective cohort study

BACKGROUND

Severe traumatic brain injury (sTBI) is frequently complicated with acute lung injury (ALI). Galectin3 poses a pivotal role in acute brain injury and non-traumatic ALI. Here, serum galectin3 was quantified with an intent to unravel its prognostic significance and mediation effects of ALI in humans with sTBI.

METHODS

Serum galectin3 levels were detected in 295 patients with sTBI and 124 healthy subjects in this prospective cohort study. The Glasgow Coma Scale (GCS) scores and Rotterdam computed tomography (CT) scores were recorded. The extended Glasgow outcome scale (GOSE) scores of 1-4 at six-month mark after sTBI signified a poor prognosis. Results were verified by employing multivariate methods.

RESULTS

Patients, relative to controls, exhibited pronouncedly incremental serum galectin3 levels. Serum galectin3 levels were linearly and independently relevant to GCS, Rotterdam CT, GOSE scores, and the likelihoods of ALI and poor prognosis. Serum galectin3 levels negligibly interacted with age, sex, hypertension, diabetes, smoking and alcohol habits in predicting ALI and poor prognosis. Serum galectin3 levels efficaciously discriminated probabilities of ALI and poor prognosis. Within the context of propensity score matching, a worse prognosis was evidently occupied by patients with higher serum galectin3 levels. Serum galectin3 levels, in conjunction with GCS, Rotterdam CT scores and ALI, were consolidated to construct a prognosis model, and along with GCS and Rotterdam CT scores, to configure an ALI model. Both models were visually represented by the monogram, and were operated efficiently in the assessment of various statistical metrics. Moreover, ALI partially mediated association of serum galectin3 levels with poor prognosis.

CONCLUSIONS

Elevated serum galectin3 levels after sTBI may be significantly pertinent to trauma intensity, ALI and poor prognosis, and its association with poor prognosis may be in part mediated by ALI, substantializing serum galectin3 as an encouraging prognostic predictor of sTBI.

Fingolimod Suppresses NLRP3 Inflammasome Activation and Alleviates Oxidative Stress in Traumatic Brain Injury-Induced Acute Lung Injury

Background

Acute lung injury (ALI) is a serious yet common complication in patients with traumatic brain injury (TBI), often associated with poor prognosis. The development of TBI-induced ALI is closely associated with excessive oxidative stress and NLRP3 inflammasome activation. Fingolimod, an immunomodulatory agent, has been reported to attenuate inflammatory responses, restore blood-brain barrier integrity, reduce cerebral edema, and mitigate associated neurological deficits.

Objective

This study aimed to investigate the mechanistic role of NLRP3 inflammasome activation in TBI-induced ALI and to evaluate the therapeutic potential of fingolimod in targeting this inflammatory pathway.

Results

A rat TBI model was established using the classical free-fall method, and animals were treated with fingolimod (0.5 or 1 mg/kg) daily for three days. The TBI model rats presented with clear signs of histopathological pulmonary damage, an increase in the permeability of capillaries in the lung, and pulmonary edema that coincided with significantly increased NLRP3, caspase-1, and ASC expression in lung tissue samples. This overexpression of NLRP3 inflammasome machinery resulted in the release of IL-1β. Fingolimod treatment, however, reversed all of these effects such that it suppressed NLRP3 activity and normalized levels of IL-1β, leading to the alleviation of inflammation. In line with these results, LPS and nigericin (NLRP3 agonist)-treated NR8383 cells treated using fingolimod exhibited reductions in reactive oxygen species production and NLRP3 inflammasome activation.

Conclusion

These findings suggest that NLRP3 inflammasome activation and oxidative stress are key mediators of TBI-induced ALI. Fingolimod exerts protective effects against this condition by inhibiting NLRP3 inflammasome activation, highlighting its potential as a therapeutic agent for TBI-associated pulmonary complications.