Naizhen Wang

Elevated CO2 selectively inhibits interleukin-6 and tumor necrosis factor expression and decreases phagocytosis in the macrophage

Elevated blood and tissue CO2, or hypercapnia, is common in severe lung disease. Patients with hypercapnia often develop lung infections and have an increased risk of death following pneumonia. To explore whether hypercapnia interferes with host defense, we studied the effects of elevated PCO2 on macrophage innate immune responses. In differentiated human THP‐1 macrophages and human and mouse alveolar macrophages stimulated with lipopolysaccharide (LPS) and other Toll‐like receptor ligands, hypercapnia inhibited expression of tumor necrosis factor and interleukin (IL)‐6, nuclear factor (NF)‐KB‐dependent cytokines critical for antimicrobial host defense. Inhibition of IL‐6 expression by hypercapnia was concentration dependent, rapid, reversible, and independent of extracellular and intracellular acidosis. In contrast, hypercapnia did not down‐regulate IL‐10 or interferon‐ß, which do not require NF‐κB. Notably, hypercapnia did not affect LPS‐induced degradation of IκBα, nuclear translocation of RelA/p65, or activation of mitogen‐activated protein kinases, but it did block IL‐6 promoter‐driven luciferase activity in mouse RAW 264.7 macrophages. Elevated PCO2 also decreased phagocytosis of opsonized polystyrene beads and heat‐killed bacteria in THP‐1 and human alveolar macrophages. By interfering with essential innate immune functions in the macrophage, hypercapnia may cause a previously unrecognized defect in resistance to pulmonary infection in patients with advanced lung disease.—Wang, N., Gates, K. L., Trejo, H., Favoreto, Jr., S., Schleimer, R P., Sznajder, J. I., Beitel, G. J., Sporn, P. H. S. Elevated CO2 selectively inhibits interleukin‐6 and tumor necrosis factor expression and decreases phagocytosis in the macrophage. FASEB J. 24, 2178–2190 (2010). www.fasebj.org

Hypercapnia Alters Expression of Immune Response, Nucleosome Assembly and Lipid Metabolism Genes in Differentiated Human Bronchial Epithelial Cells

Hypercapnia, the elevation of CO2 in blood and tissues, commonly occurs in severe acute and chronic respiratory diseases, and is associated with increased risk of mortality. Recent studies have shown that hypercapnia adversely affects innate immunity, host defense, lung edema clearance and cell proliferation. Airway epithelial dysfunction is a feature of advanced lung disease, but the effect of hypercapnia on airway epithelium is unknown. Thus, in the current study we examined the effect of normoxic hypercapnia (20% CO2 for 24 h) vs normocapnia (5% CO2), on global gene expression in differentiated normal human airway epithelial cells. Gene expression was assessed on Affymetrix microarrays, and subjected to gene ontology analysis for biological process and cluster-network representation. We found that hypercapnia downregulated the expression of 183 genes and upregulated 126. Among these, major gene clusters linked to immune responses and nucleosome assembly were largely downregulated, while lipid metabolism genes were largely upregulated. The overwhelming majority of these genes were not previously known to be regulated by CO2. These changes in gene expression indicate the potential for hypercapnia to impact bronchial epithelial cell function in ways that may contribute to poor clinical outcomes in patients with severe acute or advanced chronic lung diseases.

44 AMBIENT PARTICULATE MATTER INDUCES MYOFIBROBLAST DIFFERENTIATION VIA MACROPHAGE-DEPENDENT TRANSFORMING GROWTH FACTOR b TYPE I (ALK5) SIGNALING.

Rationale Increased levels of ambient particulate matter have been associated with increased pulmonary morbidity and mortality. To investigate if particulate matter induces airway remodeling, we studied the effects of particulate matter (< 10 μm in diameter) collected from Dusseldorf, Germany (DPM), on fibroblast to myofibroblast differentiation. Methods Human fetal lung fibroblasts (IMR-90) were grown to subconfluence, serum-starved for 48 hours, and exposed to either TGF-b1 (2 ng/mL), DPM, or conditioned medium from human monocytic (THP-1) cells exposed to DPM. The role of TGF-b1 signaling was assessed by the addition of SB431542 (10 μM), a TGF-b type I (ALK5) receptor inhibitor. After 48 hours, cells were lysed and analyzed by immunoblot for a-smooth muscle actin (aSMA), a marker of myofibroblast differentiation. Results Direct exposure of IMR-90 cells to DPM did not increase aSMA expression. However, conditioned medium of THP-1 cells exposed to DPM induced increased aSMA expression in fibroblasts. This increase was blocked by the ALK5 inhibitor SB431542. Conclusions Ambient particulate matter triggers macrophage-dependent induction of myofibroblast differentiation via ALK5 receptor signaling. We speculate that particulate matter induces airway remodeling.