Endothelial-Specific Loss of Sphingosine-1-Phosphate Receptor 1 Increases Vascular Permeability and Exacerbates Bleomycin-induced Pulmonary Fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive disease which leads to significant morbidity and mortality from respiratory failure. The two drugs currently approved for clinical use slow the rate of decline in lung function but have not been shown to halt disease progression or reverse established fibrosis. Thus, new therapeutic targets are needed. Endothelial injury and the resultant vascular permeability are critical components in the response to tissue injury and are present in patients with IPF. However, it remains unclear how vascular permeability affects lung repair and fibrosis following injury. Lipid mediators such as sphingosine-1-phosphate (S1P) are known to regulate multiple homeostatic processes in the lung including vascular permeability. We demonstrate that endothelial cell-(EC) specific deletion of the S1P receptor 1 (S1PR1) in mice (EC-S1pr1-/-) results in increased lung vascular permeability at baseline. Following a low-dose intratracheal bleomycin challenge, EC-S1pr1-/- mice had increased and persistent vascular permeability compared with wild-type mice, which was strongly correlated with the amount and localization of resulting pulmonary fibrosis. EC-S1pr1-/- mice also had increased immune cell infiltration and activation of the coagulation cascade within the lung. However, increased circulating S1P ligand in ApoM-overexpressing mice was insufficient to protect against bleomycin-induced pulmonary fibrosis. Overall, these data demonstrate that endothelial cell S1PR1 controls vascular permeability in the lung, is associated with changes in immune cell infiltration and extravascular coagulation, and modulates the fibrotic response to lung injury.

Targeting the Linear Ubiquitin Assembly Complex to Modulate the Host Response and Improve Influenza A Virus Induced Lung Injury.

Influenza virus infection is characterized by symptoms ranging from mild congestion and body aches to severe pulmonary edema and respiratory failure. While the majority of those exposed have minor symptoms and recover with little morbidity, an estimated 500,000 people succumb to IAV-related complications each year worldwide. In these severe cases, an exaggerated inflammatory response, known as "cytokine storm", occurs which results in damage to the respiratory epithelial barrier and development of acute respiratory distress syndrome (ARDS). Data from retrospective human studies as well as experimental animal models of influenza virus infection highlight the fine line between an excessive and an inadequate immune response, where the host response must balance viral clearance with exuberant inflammation. Current pharmacological modulators of inflammation, including corticosteroids and statins, have not been successful in improving outcomes during influenza virus infection. We have reported that the amplitude of the inflammatory response is regulated by Linear Ubiquitin Assembly Complex (LUBAC) activity and that dampening of LUBAC activity is protective during severe influenza virus infection. Therapeutic modulation of LUBAC activity may be crucial to improve outcomes during severe influenza virus infection, as it functions as a molecular rheostat of the host response. Here we review the evidence for modulating inflammation to ameliorate influenza virus infection-induced lung injury, data on current anti-inflammatory strategies, and potential new avenues to target viral inflammation and improve outcomes.

La infección por el virus de la gripe se caracteriza por síntomas que van desde la congestión leve y los dolores corporales hasta el edema pulmonar grave y la insuficiencia respiratoria. Aunque que la mayoría de las personas expuestas presentan síntomas leves y se recuperan con poca morbilidad, se estima que cada año 500.000 personas en todo el mundo fallecen por las complicaciones relacionadas con esta infección. En estos casos graves, se produce una respuesta inflamatoria exagerada, conocida como «tormenta de citocinas¼, que causa daños en la barrera epitelial respiratoria y el desarrollo del síndrome de distrés respiratorio agudo. Los datos de estudios retrospectivos en humanos, así como de modelos animales experimentales de infección por el virus de la gripe, resaltan la delgada línea que existe entre una respuesta inmunitaria excesiva y una inadecuada, cuando la respuesta del huésped debe mantener el equilibrio entre el aclaramiento viral y la inflamación exagerada. Los moduladores farmacológicos de la inflamación actuales, incluidos los corticoides y las estatinas, no han tenido éxito a la hora de mejorar los resultados de la infección por el virus de la gripe. Hemos publicado que la amplitud de la respuesta inflamatoria está regulada por la actividad del complejo de ensamblaje de cadenas lineales de ubiquitina (LUBAC, por sus siglas en inglés) y que la atenuación de la actividad de LUBAC protege durante la infección grave por este virus. La modulación terapéutica de la actividad de LUBAC puede ser crucial para mejorar los resultados, ya que funciona como un reóstato molecular de la respuesta del huésped. Aquí revisamos la evidencia al respecto de la modulación de la inflamación para mejorar el daño pulmonar inducido por la infección por el virus de la gripe, los datos sobre las estrategias antiinflamatorias actuales y las posibles nuevas vías para tratar la inflamación viral y mejorar los resultados.

Targeting the Linear Ubiquitin Assembly Complex to Modulate the Host Response and Improve Influenza A Virus Induced Lung Injury.

Influenza virus infection is characterized by symptoms ranging from mild congestion and body aches to severe pulmonary edema and respiratory failure. While the majority of those exposed have minor symptoms and recover with little morbidity, an estimated 500,000 people succumb to IAV-related complications each year worldwide. In these severe cases, an exaggerated inflammatory response, known as "cytokine storm", occurs which results in damage to the respiratory epithelial barrier and development of acute respiratory distress syndrome (ARDS). Data from retrospective human studies as well as experimental animal models of influenza virus infection highlight the fine line between an excessive and an inadequate immune response, where the host response must balance viral clearance with exuberant inflammation. Current pharmacological modulators of inflammation, including corticosteroids and statins, have not been successful in improving outcomes during influenza virus infection. We have reported that the amplitude of the inflammatory response is regulated by Linear Ubiquitin Assembly Complex (LUBAC) activity and that dampening of LUBAC activity is protective during severe influenza virus infection. Therapeutic modulation of LUBAC activity may be crucial to improve outcomes during severe influenza virus infection, as it functions as a molecular rheostat of the host response. Here we review the evidence for modulating inflammation to ameliorate influenza virus infection-induced lung injury, data on current anti-inflammatory strategies, and potential new avenues to target viral inflammation and improve outcomes.

La infección por el virus de la gripe se caracteriza por síntomas que van desde la congestión leve y los dolores corporales hasta el edema pulmonar grave y la insuficiencia respiratoria. Aunque que la mayoría de las personas expuestas presentan síntomas leves y se recuperan con poca morbilidad, se estima que cada año 500.000 personas en todo el mundo fallecen por las complicaciones relacionadas con esta infección. En estos casos graves, se produce una respuesta inflamatoria exagerada, conocida como «tormenta de citocinas¼, que causa daños en la barrera epitelial respiratoria y el desarrollo del síndrome de distrés respiratorio agudo. Los datos de estudios retrospectivos en humanos, así como de modelos animales experimentales de infección por el virus de la gripe, resaltan la delgada línea que existe entre una respuesta inmunitaria excesiva y una inadecuada, cuando la respuesta del huésped debe mantener el equilibrio entre el aclaramiento viral y la inflamación exagerada. Los moduladores farmacológicos de la inflamación actuales, incluidos los corticoides y las estatinas, no han tenido éxito a la hora de mejorar los resultados de la infección por el virus de la gripe. Hemos publicado que la amplitud de la respuesta inflamatoria está regulada por la actividad del complejo de ensamblaje de cadenas lineales de ubiquitina (LUBAC, por sus siglas en inglés) y que la atenuación de la actividad de LUBAC protege durante la infección grave por este virus. La modulación terapéutica de la actividad de LUBAC puede ser crucial para mejorar los resultados, ya que funciona como un reóstato molecular de la respuesta del huésped. Aquí revisamos la evidencia al respecto de la modulación de la inflamación para mejorar el daño pulmonar inducido por la infección por el virus de la gripe, los datos sobre las estrategias antiinflamatorias actuales y las posibles nuevas vías para tratar la inflamación viral y mejorar los resultados.

The Rho Kinase Isoforms ROCK1 and ROCK2 Each Contribute to the Development of Experimental Pulmonary Fibrosis.

Pulmonary fibrosis is thought to result from dysregulated wound repair after repetitive lung injury. Many cellular responses to injury involve rearrangements of the actin cytoskeleton mediated by the two isoforms of the Rho-associated coiled-coil-forming protein kinase (ROCK), ROCK1 and ROCK2. In addition, profibrotic mediators such as transforming growth factor-ß, thrombin, and lysophosphatidic acid act through receptors that activate ROCK. Inhibition of ROCK activation may be a potent therapeutic strategy for human pulmonary fibrosis. Pharmacological inhibition of ROCK using nonselective ROCK inhibitors has been shown to prevent fibrosis in animal models; however, the specific roles of each ROCK isoform are poorly understood. Furthermore, the pleiotropic effects of this kinase have raised concerns about on-target adverse effects of ROCK inhibition such as hypotension. Selective inhibition of one isoform might be a better-tolerated strategy. In the present study, we used a genetic approach to determine the roles of ROCK1 and ROCK2 in a mouse model of bleomycin-induced pulmonary fibrosis. Using ROCK1- or ROCK2-haploinsufficient mice, we found that reduced expression of either ROCK1 or ROCK2 was sufficient to protect them from bleomycin-induced pulmonary fibrosis. In addition, we found that both isoforms contribute to the profibrotic responses of epithelial cells, endothelial cells, and fibroblasts. Interestingly, ROCK1- and ROCK2-haploinsufficient mice exhibited similar protection from bleomycin-induced vascular leak, myofibroblast differentiation, and fibrosis; however, ROCK1-haploinsufficient mice demonstrated greater attenuation of epithelial cell apoptosis. These findings suggest that selective inhibition of either ROCK isoform has the potential to be an effective therapeutic strategy for pulmonary fibrosis.

HIF and HOIL-1L-mediated PKCζ degradation stabilizes plasma membrane Na,K-ATPase to protect against hypoxia-induced lung injury.

Organisms have evolved adaptive mechanisms in response to stress for cellular survival. During acute hypoxic stress, cells down-regulate energy-consuming enzymes such as Na,K-ATPase. Within minutes of alveolar epithelial cell (AEC) exposure to hypoxia, protein kinase C zeta (PKCζ) phosphorylates the α1-Na,K-ATPase subunit and triggers it for endocytosis, independently of the hypoxia-inducible factor (HIF). However, the Na,K-ATPase activity is essential for cell homeostasis. HIF induces the heme-oxidized IRP2 ubiquitin ligase 1L (HOIL-1L), which leads to PKCζ degradation. Here we report a mechanism of prosurvival adaptation of AECs to prolonged hypoxia where PKCζ degradation allows plasma membrane Na,K-ATPase stabilization at ∼50% of normoxic levels, preventing its excessive down-regulation and cell death. Mice lacking HOIL-1L in lung epithelial cells (CreSPC/HOIL-1Lfl/fl ) were sensitized to hypoxia because they express higher levels of PKCζ and, consequently, lower plasma membrane Na,K-ATPase levels, which increased cell death and worsened lung injury. In AECs, expression of an α1-Na,K-ATPase construct bearing an S18A (α1-S18A) mutation, which precludes PKCζ phosphorylation, stabilized the Na,K-ATPase at the plasma membrane and prevented hypoxia-induced cell death even in the absence of HOIL-1L. Adenoviral overexpression of the α1-S18A mutant Na,K-ATPase in vivo rescued the enhanced sensitivity of CreSPC/HOIL-1Lfl/fl mice to hypoxic lung injury. These data suggest that stabilization of Na,K-ATPase during severe hypoxia is a HIF-dependent process involving PKCζ degradation. Accordingly, we provide evidence of an important adaptive mechanism to severe hypoxia, whereby halting the exaggerated down-regulation of plasma membrane Na,K-ATPase prevents cell death and lung injury.

Identification of novel small molecules that elevate Klotho expression.

The absence of Klotho (KL) from mice causes the development of disorders associated with human aging and decreased longevity, whereas increased expression prolongs lifespan. With age, KL protein levels decrease, and keeping levels consistent may promote healthier aging and be disease-modifying. Using the KL promoter to drive expression of luciferase, we conducted a high-throughput screen to identify compounds that activate KL transcription. Hits were identified as compounds that elevated luciferase expression at least 30%. Following validation for dose-dependent activation and lack of cytotoxicity, hit compounds were evaluated further in vitro by incubation with opossum kidney and Z310 rat choroid plexus cells, which express KL endogenously. All compounds elevated KL protein compared with control. To determine whether increased protein resulted in an in vitro functional change, we assayed FGF23 (fibroblast growth factor 23) signalling. Compounds G-I augmented ERK (extracellular-signal-regulated kinase) phosphorylation in FGFR (fibroblast growth factor receptor)-transfected cells, whereas co-transfection with KL siRNA (small interfering RNA) blocked the effect. These compounds will be useful tools to allow insight into the mechanisms of KL regulation. Further optimization will provide pharmacological tools for in vivo studies of KL.