Evaluation and Characterization of Post-Stroke Lung Damage in a Murine Model of Cerebral Ischemia

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.

Mechanisms of inflammation after ischemic stroke in brain-peripheral crosstalk

Stroke is a devastating disease with high morbidity, disability, and mortality, among which ischemic stroke is more common. However, there is still a lack of effective methods to improve the prognosis and reduce the incidence of its complications. At present, there is evidence that peripheral organs are involved in the inflammatory response after stroke. Moreover, the interaction between central and peripheral inflammation includes the activation of resident and peripheral immune cells, as well as the activation of inflammation-related signaling pathways, which all play an important role in the pathophysiology of stroke. In this review, we discuss the mechanisms of inflammatory response after ischemic stroke, as well as the interactions through circulatory pathways between peripheral organs (such as the gut, heart, lung and spleen) and the brain to mediate and regulate inflammation after ischemic stroke. We also propose the potential role of meningeal lymphatic vessels (MLVs)-cervical lymph nodes (CLNs) as a brain-peripheral crosstalk lymphatic pathway in ischemic stroke. In addition, we also summarize the mechanisms of anti-inflammatory drugs in the treatment of ischemic stroke.

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.

Acute brain injury increases pulmonary capillary permeability via sympathetic activation-mediated high fluid shear stress and destruction of the endothelial glycocalyx layer

Neurogenic pulmonary edema secondary to acute brain injury (ABI) is a common and fatal disease condition. However, the pathophysiology of brain-lung interactions is incompletely understood. This study aims to investigate whether sympathetic activation-mediated high fluid shear stress after ABI would damage pulmonary endothelial glycocalyx thus leading to increased pulmonary capillary permeability. The tricuspid annular plane systolic excursion (TAPSE) was detected in a rat model of controlled cortical impact (CCI) and CCI + transection of the cervical sympathetic trunk (TCST). Changes in pulmonary capillary permeability were assessed by analyzing the Evans blue, measuring the dry/wet weight ratio of the lungs and altering protein levels in the bronchoalveolar lavage fluid (BALF). The parallel-plate flow chamber system was used to simulate the fluid shear stress in vitro. Western blotting and immunofluorescence staining were used to determine the expression levels of hyaluronan-binding protein (CEMIP), syndecan-1 and tight junction proteins (TJPs, including claudin-5 and occludin). TCST could restrain cardiac overdrive and sympathetic activation in a rat model of CCI. Compared to the CCI group, the CCI + TCST group showed a reduction of CEMPI (which degrades hyaluronic acid), along with an increase of syndecan-1 and TJPs. CCI + TCST group presented decreasing pulmonary capillary permeability. In vitro, high shear stress (HSS) increased the expression of CEMIP and reduced syndecan-1 and TJPs, which was coordinated with the results in vivo. Our findings show that sympathetic activation-mediated high fluid shear stress after ABI would damage pulmonary endothelial glycocalyx thus leading to increased pulmonary capillary permeability.