Approximately 30% of traumatic brain injured patients suffer from acute lung injury or acute respiratory distress syndrome. Our previous work revealed that extracellular vesicle (EV)-mediated inflammasome signaling plays a crucial role in the pathophysiology of traumatic brain injury (TBI)-induced lung injury. Here, serum-derived EVs from severe TBI patients were analyzed for particle size, concentration, origin, and levels of the inflammasome component, an apoptosis-associated speck-like protein containing a caspase-recruiting domain (ASC). Serum ASC levels were analyzed from EV obtained from patients that presented lung injury after TBI and compared them to EV obtained from patients that did not show any signs of lung injury. EVs were co-cultured with lung human microvascular endothelial cells (HMVEC-L) to evaluate inflammasome activation and endothelial cell pyroptosis. TBI patients had a significant increase in the number of serum-derived EVs and levels of ASC. Severe TBI patients with lung injury had a significantly higher level of ASC in serum and serum-derived EVs compared to individuals without lung injury. Only EVs isolated from head trauma patients with gunshot wounds were of neural origin. Delivery of serum-derived EVs to HMVEC-L activated the inflammasome and resulted in endothelial cell pyroptosis. Thus, serum-derived EVs and inflammasome proteins play a critical role in the pathogenesis of TBI-induced lung injury, supporting activation of an EV-mediated neural-respiratory inflammasome axis in TBI-induced lung injury.

Traumatic brain injury (TBI) patients frequently develop cardiopulmonary system complications such as acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). However, the mechanism by which TBI causes ALI/ARDS is not fully understood. Here, we used a severe TBI model to examine the effects of a low-molecular-weight heparin, enoxaparin, on inflammasome activation and lung injury damage. We investigated whether enoxaparin inhibits ALI and inflammasome signaling protein expression in the brain and lungs after TBI in mice. C57/BL6 mice were subjected to severe TBI and were treated with vehicle or 1 mg/kg of enoxaparin 30 min after injury. Lung and brain tissue were collected 24 h post-TBI and were analyzed by immunoblotting for expression of the inflammasome proteins, caspase-1 and interleukin (IL)-1β. In addition, lung tissue was collected for histological analysis to determine ALI scoring and neutrophil and macrophage infiltration post-injury. Our data show that severe TBI induces increased expression of inflammasome proteins caspase-1 and IL-1β in the brain and lungs of mice after injury. Treatment with enoxaparin attenuated inflammasome expression in the brain and lungs 24 h after injury. Enoxaparin significantly decreased ALI score as well as neutrophil and macrophage infiltration in lungs at 24 h after injury. This study demonstrates that enoxaparin attenuates ALI and inhibits inflammasome expression in the brain and lungs after TBI. These findings support the hypothesis that inhibition of the neural-respiratory inflammasome axis that is activated after TBI may have therapeutic potential.

There is a growing body of evidence that the delivery of cell-derived exosomes normally involved in intracellular communication can reduce secondary injury mechanisms after brain and spinal cord injury and improve outcomes. Exosomes are nanometer-sized vesicles that are released by Schwann cells and may have neuroprotective effects by reducing post-traumatic inflammatory processes as well as promoting tissue healing and functional recovery. The purpose of this study was to evaluate the beneficial effects of human Schwann-cell exosomes (hSC-Exos) in a severe model of penetrating ballistic-like brain injury (PBBI) in rats and investigate effects on multiple outcomes. Human Schwann cell processing protocols followed Current Good Manufacturing Practices (cGMP) with exosome extraction and purification steps approved by the Food and Drug Administration for an expanded access single ALS patient Investigational New Drug. Anesthetized male Sprague-Dawley rats (280–350g) underwent PBBI surgery or Sham procedures and, starting 30 min after injury, received either a dose of hSC-Exos or phosphate-buffered saline through the jugular vein. At 48h after PBBI, flow cytometry analysis of cortical tissue revealed that hSC-Exos administration reduced the number of activated microglia and levels of caspase-1, a marker of inflammasome activation. Neuropathological analysis at 21 days showed that hSC-Exos treatment after PBBI significantly reduced overall contusion volume and decreased the frequency of Iba-1 positive activated and amoeboid microglia by immunocytochemical analysis. This study revealed that the systemic administration of hSC-Exos is neuroprotective in a model of severe TBI and reduces secondary inflammatory injury mechanisms and histopathological damage. The administration of hSC-Exos represents a clinically relevant cell-based therapy to limit the detrimental effects of neurotrauma or other progressive neurological injuries by impacting multiple pathophysiological events and promoting neurological recovery.

Patients with Alzheimer's disease (AD) suffering from post-stroke gut dysfunction present with worsened neurological outcomes. This study investigated the role of stool-derived extracellular vesicle (EV)-mediated inflammasome signaling in the gut-brain axis following photothrombotic stroke (PTS) in aged 3xTg- AD and wildtype (WT) mice. Western Blot and immunohistochemical analyses evaluated inflammasome signaling proteins, Gasdermin D (GSDMD), and Aβ in intestinal and cortical tissues. Gut permeability was measured using a FITC-dextran assay 3 days post PTS. Adoptive transfer experiments assessed the impact of stool-derived EVs from PTS mice on inflammasome signaling in recipient naïve 3xTg and WT mice. At 3 days, 3xTg-PTS mice demonstrated significantly impaired sensorimotor Rotarod performance compared to WT-PTS mice. Both WT and 3xTg PTS mice had deficits compared to 3xTg and WT sham mice using the Open Field or Novel Object Recognition tests. Compared to WT- PTS mice, 3xTg-PTS mice had disrupted gut morphology at 1-month post-PTS, as well as increased gut permeability at 72 h. Immunohistochemical analysis also revealed activated microglial morphology and presence of GSDMD and Aβ in the brain and intestines post-PTS in 3xTg and WT mice. Adoptive transfer of stool-derived EVs from PTS mice to WT mice induced elevated levels of inflammasome signaling proteins in recipient cerebral cortices. These findings indicate an important role of stool-derived EV inflammasome signaling and pyroptosis in disruption of the bidirectional gut-brain axis after stroke leading to exacerbation of AD pathology in aged WT and 3xTg mice.

Cerebrovascular stroke patients exhibit an increased incidence of cardiac arrhythmias. The pathomechanisms underlying post-traumatic cardiac dysfunction include a surge of catecholamines and an increased systemic inflammatory response, but whether inflammasome activation contributes to cardiac dysfunction remains unexplored. Here, we used a mouse model of photothrombotic stroke (PTS) to investigate the role of inflammasome activation in post-stroke cardiac dysfunction by catecholamines and to evaluate the effectiveness of the inflammasome inhibitor IC100 on inflammasome activation. To evaluate functional electrophysiological changes in the heart by catecholamine treatment, we recorded action potential duration in excised zebrafish hearts with and without IC100 treatment. We show that PTS induced AIM2 inflammasome activation in atria and ventricles that was significantly reduced by administration of IC100. Injection of epinephrine into naïve mice induced a significant increase in AIM2, IL-1b and caspase-8 in atria. Treatment of excised zebrafish hearts with epinephrine shortened the action potential duration and this shortening that was reduced by IC100. These findings indicate that stroke initiates a catecholamine surge that induces inflammasome activation and pyroptosis in the heart that is blocked by IC100, thus providing a framework for the development of therapeutics for stroke-related cardiovascular injury.

Traumatic brain injury (TBI) pathology is significantly mediated by an inflammatory response involving inflammasome activation, resulting in the release of interleukin (IL)-1β and pyroptotic cell death through gasdermin-D (GSDMD) cleavage. Inflammasome components are transported through extracellular vesicles (EVs) to mediate systemic inflammation in peripheral organs, including the gut. The purpose of this study was to determine the protective effect of GSDMD knockout (KO) on TBI-induced inflammasome activation, EV signaling, and gut function. GSDMD-KO and C57BL6 (WT) mice were subjected to the controlled cortical impact model of TBI. Cytokine expression was assessed with electrochemiluminescent immunoassay and immunoblotting of the cerebral cortex and gut. EVs were examined for pathology-associated markers using flow cytometry, and gut permeability was determined. GSDMD-KO attenuated IL-1β and IL-6 expression in the cerebral cortex and reduced IL-1β and IL-18 in the gut 3 days post-injury. GSDMD-KO mice had decreased neuronal- and gut-derived EVs compared to WT mice post-TBI. GSDMD-KO EVs also had decreased IL-1β and different surface marker expression post-TBI. GSDMD-KO mice had decreased gut permeability after TBI. These data demonstrate that GSDMD ablation improves post-TBI inflammation and gut pathology, suggesting that GSDMD may serve as a potential therapeutic target for the improvement of TBI-associated pathologies.