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CD44 is protective during hyperoxia-induced lung injury
Gerritje J W van der Windt1, Marcel Schouten, Sacha Zeerleder
1Center for Infection and Immunity Amsterdam, University of Amsterdam, The Netherlands.
Summary
CD44 protein protects against lung injury caused by high oxygen levels. CD44 deficiency leads to increased inflammation and cell death, highlighting its protective role in acute lung injury.
Area of Science:
- Pulmonary Medicine
- Cell Biology
- Immunology
Background:
- Supplemental oxygen is crucial for acute lung injury (ALI) patients but can exacerbate lung inflammation.
- CD44, a transmembrane adhesion molecule, regulates leukocyte trafficking and is implicated in inflammatory responses.
Purpose of the Study:
- To investigate the role of CD44 in hyperoxia-induced acute lung injury.
- To determine if CD44 deficiency exacerbates lung injury and mortality under hyperoxic conditions.
Main Methods:
- Comparison of wild-type and CD44 knockout (KO) mice exposed to hyperoxia (>95% oxygen).
- Assessment of survival rates, neutrophil infiltration (bronchoalveolar space and lung parenchyma), inflammatory cytokine levels (IL-6, keratinocyte-derived chemokine) in bronchoalveolar lavage fluid (BALF).
- Evaluation of vascular leak, type II respiratory epithelial cell injury, bronchial epithelial cell death, and BALF nucleosome levels.
Main Results:
- CD44 KO mice exhibited significantly higher mortality (37.5%) compared to wild-type mice under hyperoxia.
- CD44 deficiency led to increased neutrophil influx into the bronchoalveolar space, suggesting impaired containment in the lung interstitium.
- Elevated IL-6 and keratinocyte-derived chemokine levels, increased vascular permeability, and enhanced type II respiratory epithelial cell injury were observed in CD44 KO mice.
- CD44 KO mice showed increased bronchial epithelial cell necrosis and a trend toward higher BALF nucleosome levels, indicating greater cell death.
- Hyaluronic acid (HA) concentrations increased in BALF of CD44 KO mice during hyperoxia, suggesting impaired HA clearance by CD44.
Conclusions:
- CD44 plays a critical protective role against hyperoxia-induced acute lung injury and mortality.
- CD44 deficiency impairs neutrophil containment, increases inflammation, and exacerbates epithelial cell injury and death.
- CD44's ability to clear hyaluronic acid from the bronchoalveolar space is a key mechanism in its protective effect against hyperoxic lung injury.
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