Daily Ards Research Analysis

Cytopathic tau variants are recovered from the lung, circulation, and brain following lower respiratory tract infection. Cytopathic tau injures the lung and brain, yet its cellular origin during infection is unknown. Here, we assessed whether lung capillary endothelium is a source of cytopathic tau that contributes to brain injury during infection. Alveolar-capillary permeability was higher in tau knockout than wild type mice following sublethal Pseudomonas aeruginosa infection, indicating endogenously expressed tau contributes to integrity of the lung's gas exchange unit. Hippocampal long-term potentiation was inhibited following sublethal infection in wild type but not tau knockout mice, even though the blood-brain barrier was not overtly disrupted. Tau expression solely in lung capillaries of tau knockout mice was sufficient to restore alveolar-capillary barrier integrity and impair hippocampal long-term potentiation following sublethal infection. Thus, endogenous lung capillary endothelial tau preserves alveolar-capillary integrity, yet it is a source of cytopathic tau that injures the brain during pneumonia.

Secondary bacterial pneumonia following influenza A virus (IAV) infection markedly exacerbates lung inflammation and contributes to acute respiratory distress syndrome (ARDS); however, the immunologic pathways that drive lung injury and determine protective versus pathogenic inflammation remain incompletely defined. Using a clinically relevant murine model of sublethal IAV infection followed by methicillin-resistant Staphylococcus aureus (MRSA) challenge under antibiotic therapy, this study investigated the dynamic role of type I interferon (IFN-I) signaling in disease progression. The findings demonstrate that IFN-I exerts dual and contrasting effects on the host inflammatory response: it enhances myeloid-derived TNF-α while indirectly suppressing T cell-derived IFN-γ. Reporter mouse models identified recruited monocytes and dendritic cells (DCs) as the primary IFN-I-targeted populations, whereas neutrophils, T cells, and alveolar macrophages exhibited limited direct responsiveness. Myeloid-specific deletion of IFNAR1 reduced TNF-α production, restrained inflammatory monocyte differentiation, and improved survival without disrupting IFN-γ and IL-10 balance. Temporal IFNAR1 blockade further revealed that early IFN-I signaling supports alveolar macrophage maintenance and primes monocytes/DCs for immune activation, whereas sustained signaling during bacterial superinfection drives persistent monocyte chemoattractant production, excessive monocyte activation, and delayed resolution of inflammation. Collectively, these findings position IFN-I as a temporal immune rheostat-protective during acute viral infection but pathogenic when prolonged-and define a therapeutic window in which selective IFNAR inhibition enhances host antibacterial defense, either alone or in combination with antibiotic therapy. These insights highlight a promising immunomodulatory strategy to improve outcomes in severe viral-bacterial pneumonia and ARDS.

Unremitting increases in lung vascular permeability is the pathophysiological hallmark of acute lung injuries (ALI) and drives both severity and mortality. Therapies with the capacity to quickly restore vascular integrity in ALI remains a serious unmet need. Our laboratory was first to report both the vascular barrier-protective effects of sphingosine-1 -phosphate (S1P) and S1P analogues, such as Tysiponate (TySIP), and the efficacy of peptide inhibitors (PIK) of non-muscle myosin light chain kinase (nmMLCK) as dual complementary strategies to reduce vascular permeability. The current study evaluates a novel nanocarrier (NTyP-100) containing conjugated TySIP and encargoed PIK as a pharmacologic approach to vascular barrier restoration in rodent models of LPS-induced ALI. NTyP-100 (or controls) was delivered IV to wild-type C57BL/6J mice exposed to a "one-hit" lipopolysaccharide (LPS, 18 h) ALI model or to Sprague-Dawley (SD) rats challenged by a "two-hit" ALI model combining LPS (18 h) and exposure to high tidal volume mechanical ventilation (MV, 4 h). Compared to TySIP or PIK alone, IV NTyP-100 produced the highest reduction (∼40%) in inflammatory injury in murine and rat ALI models (H&E, IHC p-MLC staining, BAL cells) with marked reductions in vascular leak (Evan Blue Dye leakage, BAL protein) and biochemical indices of inflammation. Genomic studies underscored NTyP-100 attenuation of ALI-mediated dysregulated barrier-regulatory signaling pathways (inflammatory response, innate immunity, TNF, IL-17, apoptosis). These studies demonstrate the successful therapeutic targeting of vascular barrier properties and supports the NTyP-100 nanocarrier as a strategy to address the unmet need for novel therapeutics that mitigate inflammatory injury and vascular permeability.