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Interleukin 12 p40 production by barrier epithelial cells during airway inflammation.

Walter MJ, Kajiwara N, Karanja P, Castro M, Holtzman MJ - J. Exp. Med. (2001)

Bottom Line: To better determine how this epithelial system operates in vivo, we analyzed its behavior in mouse models that allow for in vitro versus in vivo comparison and genetic modification.Induction of IL-12 p40 was even further increased in IL-12 p35-deficient mice, and in this case, was associated with increased mortality and epithelial macrophage accumulation.Taken together, these results suggest a novel role for epithelial-derived IL-12 p40 in modifying the level of airway inflammation during mucosal defense and disease.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.

ABSTRACT
Human airway epithelial cells appear specially programmed for expression of immune response genes implicated in immunity and inflammation. To better determine how this epithelial system operates in vivo, we analyzed its behavior in mouse models that allow for in vitro versus in vivo comparison and genetic modification. Initial comparisons indicated that tumor necrosis factor alpha induction of epithelial intercellular adhesion molecule 1 required sequential induction of interleukin (IL)-12 (p70) and interferon gamma, and unexpectedly localized IL-12 production to airway epithelial cells. Epithelial IL-12 was also inducible during paramyxoviral bronchitis, but in this case, initial IL-12 p70 expression was followed by 75-fold greater expression of IL-12 p40 (as monomer and homodimer). Induction of IL-12 p40 was even further increased in IL-12 p35-deficient mice, and in this case, was associated with increased mortality and epithelial macrophage accumulation. The results placed epithelial cell overgeneration of IL-12 p40 as a key intermediate for virus-inducible inflammation and a candidate for epithelial immune response genes that are abnormally programmed in inflammatory disease. This possibility was further supported when we observed IL-12 p40 overexpression selectively in airway epithelial cells in subjects with asthma and concomitant increases in airway levels of IL-12 p40 (as homodimer) and airway macrophages. Taken together, these results suggest a novel role for epithelial-derived IL-12 p40 in modifying the level of airway inflammation during mucosal defense and disease.

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Viral induction of IL-12 p40 without a change in constitutive p35 expression in airway epithelial cells. Wild-type C57BL/6J mice underwent intranasal inoculation with SdV (5,000 EID50 in 30 μl of PBS), and lungs were removed and fixed in formalin on day 1, 3, 5, and 8 after inoculation. In each case, tissue was immunostained for IL-12 P-40 and p35 as described in the legend to Fig. 3 and similarly for viral protein (labeled SdV) using rat anti-SdV pAb. In mice inoculated with UV-inactivated Sdv, IL-12 p40 immunostaining was not detected and IL-12 p35 constitutive immunostaining was unchanged from untreated control mice (not shown). Control rat, goat, or rabbit nonimmune IgG gave no signal above background (data not shown). Bar, 20 μm.
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Figure 4: Viral induction of IL-12 p40 without a change in constitutive p35 expression in airway epithelial cells. Wild-type C57BL/6J mice underwent intranasal inoculation with SdV (5,000 EID50 in 30 μl of PBS), and lungs were removed and fixed in formalin on day 1, 3, 5, and 8 after inoculation. In each case, tissue was immunostained for IL-12 P-40 and p35 as described in the legend to Fig. 3 and similarly for viral protein (labeled SdV) using rat anti-SdV pAb. In mice inoculated with UV-inactivated Sdv, IL-12 p40 immunostaining was not detected and IL-12 p35 constitutive immunostaining was unchanged from untreated control mice (not shown). Control rat, goat, or rabbit nonimmune IgG gave no signal above background (data not shown). Bar, 20 μm.

Mentions: In other systems, IL-12 is selectively produced by immune cells, especially antigen-presenting cells, and production depends on induction of the IL-12 p40 subunit in the context of constitutive p35 expression 16. However, when we submitted tracheal and lung tissue from TNF-α–treated mice to immunohistochemistry, we found that airway epithelial cells were the predominant site of induction of IL-12 p40 expression (Fig. 3). We also found constitutive IL-12 p35 expression in airway epithelial as well as other parenchymal and immune cells (Fig. 3). To next determine whether a more natural stimulus of airway inflammation might cause similar upregulation of IL-12 expression, we examined the response to an inoculum of Sdv (5,000 EID50) that causes reversible tracheobronchitis and bronchiolitis with transient epithelial expression of SdV protein (that is maximal at day 5 and undetectable by day 8 after viral inoculation) and mononuclear cell influx that is limited to the adjacent bronchovascular tissue compartment (Fig. 4, and data not shown). In this setting, we found that induction of IL-12 p40 was again localized to airway epithelial cells, rather than adjacent mononuclear cells, and was colocalized (temporally and spatially) with SdV protein expression, whereas constitutive expression of IL-12 p35 remained unchanged in all cell populations (Fig. 4). Thus, airway epithelial cells (rather than immune cells) appear to be the major cellular source for IL-12 p40 production during airway inflammatory conditions initiated by TNF-α administration or respiratory viral infection.


Interleukin 12 p40 production by barrier epithelial cells during airway inflammation.

Walter MJ, Kajiwara N, Karanja P, Castro M, Holtzman MJ - J. Exp. Med. (2001)

Viral induction of IL-12 p40 without a change in constitutive p35 expression in airway epithelial cells. Wild-type C57BL/6J mice underwent intranasal inoculation with SdV (5,000 EID50 in 30 μl of PBS), and lungs were removed and fixed in formalin on day 1, 3, 5, and 8 after inoculation. In each case, tissue was immunostained for IL-12 P-40 and p35 as described in the legend to Fig. 3 and similarly for viral protein (labeled SdV) using rat anti-SdV pAb. In mice inoculated with UV-inactivated Sdv, IL-12 p40 immunostaining was not detected and IL-12 p35 constitutive immunostaining was unchanged from untreated control mice (not shown). Control rat, goat, or rabbit nonimmune IgG gave no signal above background (data not shown). Bar, 20 μm.
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Related In: Results  -  Collection

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Figure 4: Viral induction of IL-12 p40 without a change in constitutive p35 expression in airway epithelial cells. Wild-type C57BL/6J mice underwent intranasal inoculation with SdV (5,000 EID50 in 30 μl of PBS), and lungs were removed and fixed in formalin on day 1, 3, 5, and 8 after inoculation. In each case, tissue was immunostained for IL-12 P-40 and p35 as described in the legend to Fig. 3 and similarly for viral protein (labeled SdV) using rat anti-SdV pAb. In mice inoculated with UV-inactivated Sdv, IL-12 p40 immunostaining was not detected and IL-12 p35 constitutive immunostaining was unchanged from untreated control mice (not shown). Control rat, goat, or rabbit nonimmune IgG gave no signal above background (data not shown). Bar, 20 μm.
Mentions: In other systems, IL-12 is selectively produced by immune cells, especially antigen-presenting cells, and production depends on induction of the IL-12 p40 subunit in the context of constitutive p35 expression 16. However, when we submitted tracheal and lung tissue from TNF-α–treated mice to immunohistochemistry, we found that airway epithelial cells were the predominant site of induction of IL-12 p40 expression (Fig. 3). We also found constitutive IL-12 p35 expression in airway epithelial as well as other parenchymal and immune cells (Fig. 3). To next determine whether a more natural stimulus of airway inflammation might cause similar upregulation of IL-12 expression, we examined the response to an inoculum of Sdv (5,000 EID50) that causes reversible tracheobronchitis and bronchiolitis with transient epithelial expression of SdV protein (that is maximal at day 5 and undetectable by day 8 after viral inoculation) and mononuclear cell influx that is limited to the adjacent bronchovascular tissue compartment (Fig. 4, and data not shown). In this setting, we found that induction of IL-12 p40 was again localized to airway epithelial cells, rather than adjacent mononuclear cells, and was colocalized (temporally and spatially) with SdV protein expression, whereas constitutive expression of IL-12 p35 remained unchanged in all cell populations (Fig. 4). Thus, airway epithelial cells (rather than immune cells) appear to be the major cellular source for IL-12 p40 production during airway inflammatory conditions initiated by TNF-α administration or respiratory viral infection.

Bottom Line: To better determine how this epithelial system operates in vivo, we analyzed its behavior in mouse models that allow for in vitro versus in vivo comparison and genetic modification.Induction of IL-12 p40 was even further increased in IL-12 p35-deficient mice, and in this case, was associated with increased mortality and epithelial macrophage accumulation.Taken together, these results suggest a novel role for epithelial-derived IL-12 p40 in modifying the level of airway inflammation during mucosal defense and disease.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.

ABSTRACT
Human airway epithelial cells appear specially programmed for expression of immune response genes implicated in immunity and inflammation. To better determine how this epithelial system operates in vivo, we analyzed its behavior in mouse models that allow for in vitro versus in vivo comparison and genetic modification. Initial comparisons indicated that tumor necrosis factor alpha induction of epithelial intercellular adhesion molecule 1 required sequential induction of interleukin (IL)-12 (p70) and interferon gamma, and unexpectedly localized IL-12 production to airway epithelial cells. Epithelial IL-12 was also inducible during paramyxoviral bronchitis, but in this case, initial IL-12 p70 expression was followed by 75-fold greater expression of IL-12 p40 (as monomer and homodimer). Induction of IL-12 p40 was even further increased in IL-12 p35-deficient mice, and in this case, was associated with increased mortality and epithelial macrophage accumulation. The results placed epithelial cell overgeneration of IL-12 p40 as a key intermediate for virus-inducible inflammation and a candidate for epithelial immune response genes that are abnormally programmed in inflammatory disease. This possibility was further supported when we observed IL-12 p40 overexpression selectively in airway epithelial cells in subjects with asthma and concomitant increases in airway levels of IL-12 p40 (as homodimer) and airway macrophages. Taken together, these results suggest a novel role for epithelial-derived IL-12 p40 in modifying the level of airway inflammation during mucosal defense and disease.

Show MeSH
Related in: MedlinePlus