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Systemic inhibition of NF-kappaB activation protects from silicosis.

Di Giuseppe M, Gambelli F, Hoyle GW, Lungarella G, Studer SM, Richards T, Yousem S, McCurry K, Dauber J, Kaminski N, Leikauf G, Ortiz LA - PLoS ONE (2009)

Bottom Line: At the time of lung transplantation, we found the lungs of silica-exposed subjects to contain multiple foci of inflammatory cells and silicotic nodules with proximal TNFalpha expressing macrophage and NF-kappaB activation in epithelial cells.Using a mouse experimental model in which the endotracheal instillation of silica reproduces the silica-induced lung injury observed in humans we found that systemic inhibition of NF-kappaB activation with a pharmacologic inhibitor (BAY 11-7085) of IkappaB alpha phosphorylation decreased silica-induced inflammation and collagen deposition.In contrast, transgenic mice expressing a dominant negative IkappaB alpha mutant protein under the control of epithelial cell specific promoters demonstrate enhanced apoptosis and collagen deposition in their lungs in response to silica.

View Article: PubMed Central - PubMed

Affiliation: Division of Occupational and Environmental Medicine, Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.

ABSTRACT

Background: Silicosis is a complex lung disease for which no successful treatment is available and therefore lung transplantation is a potential alternative. Tumor necrosis factor alpha (TNFalpha) plays a central role in the pathogenesis of silicosis. TNFalpha signaling is mediated by the transcription factor, Nuclear Factor (NF)-kappaB, which regulates genes controlling several physiological processes including the innate immune responses, cell death, and inflammation. Therefore, inhibition of NF-kappaB activation represents a potential therapeutic strategy for silicosis.

Methods/findings: In the present work we evaluated the lung transplant database (May 1986-July 2007) at the University of Pittsburgh to study the efficacy of lung transplantation in patients with silicosis (n = 11). We contrasted the overall survival and rate of graft rejection in these patients to that of patients with idiopathic pulmonary fibrosis (IPF, n = 79) that was selected as a control group because survival benefit of lung transplantation has been identified for these patients. At the time of lung transplantation, we found the lungs of silica-exposed subjects to contain multiple foci of inflammatory cells and silicotic nodules with proximal TNFalpha expressing macrophage and NF-kappaB activation in epithelial cells. Patients with silicosis had poor survival (median survival 2.4 yr; confidence interval (CI): 0.16-7.88 yr) compared to IPF patients (5.3 yr; CI: 2.8-15 yr; p = 0.07), and experienced early rejection of their lung grafts (0.9 yr; CI: 0.22-0.9 yr) following lung transplantation (2.4 yr; CI:1.5-3.6 yr; p<0.05). Using a mouse experimental model in which the endotracheal instillation of silica reproduces the silica-induced lung injury observed in humans we found that systemic inhibition of NF-kappaB activation with a pharmacologic inhibitor (BAY 11-7085) of IkappaB alpha phosphorylation decreased silica-induced inflammation and collagen deposition. In contrast, transgenic mice expressing a dominant negative IkappaB alpha mutant protein under the control of epithelial cell specific promoters demonstrate enhanced apoptosis and collagen deposition in their lungs in response to silica.

Conclusions: Although limited by its size, our data support that patients with silicosis appear to have poor outcome following lung transplantation. Experimental data indicate that while the systemic inhibition of NF-kappaB protects from silica-induced lung injury, epithelial cell specific NF-kappaB inhibition appears to aggravate the outcome of experimental silicosis.

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Clara cell expression of a dominant-negative (dn) IκBα protein alters TNFα, and MMP2, but not α1(I) collagen and TIMP-1, mRNA expression in response to silica.Densitometry analysis of Northern blots of TNF, α1(I) collagen, MMP2, TIMP-1, and 18S (loading control) mRNA expression in CCSP-dnIκB mouse lung 28 days following the intratracheal injection of saline as control, or silica as described in the Methods section. Compared to their wild type littermates, CCSP-dnIkB transgenic mice significantly inhibited (P<0.05) the enhanced expression of TNFα and MMP2 mRNA induced by silica in the mouse lung. Figure illustrate results obtained from five set of mice exposed to silica or saline as control. * Indicates statistically significant difference compared to saline treated mice. † Indicates statistically significant difference compared to wild-type non-transgenic mice.
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pone-0005689-g007: Clara cell expression of a dominant-negative (dn) IκBα protein alters TNFα, and MMP2, but not α1(I) collagen and TIMP-1, mRNA expression in response to silica.Densitometry analysis of Northern blots of TNF, α1(I) collagen, MMP2, TIMP-1, and 18S (loading control) mRNA expression in CCSP-dnIκB mouse lung 28 days following the intratracheal injection of saline as control, or silica as described in the Methods section. Compared to their wild type littermates, CCSP-dnIkB transgenic mice significantly inhibited (P<0.05) the enhanced expression of TNFα and MMP2 mRNA induced by silica in the mouse lung. Figure illustrate results obtained from five set of mice exposed to silica or saline as control. * Indicates statistically significant difference compared to saline treated mice. † Indicates statistically significant difference compared to wild-type non-transgenic mice.

Mentions: CCSP-dnIκBα mice reacted to silica exposure with decreased lung inflammation as compared to littermate controls (Table 4). This attenuated inflammatory response was associated decreased TNFα transcripts and inflammatory cell infiltration [(Vv(f)] at 28 d after silica exposure (Table 4). In contrast to these effects on inflammation, lung hydroxyproline deposition increased in CCSP-dnIκBα mice than in littermate controls (Table 4). Similarly, CCSP-dnIκBα mice and wild-type littermate mice had nearly equivalent increases in collagen and TIMP1 transcripts. However, silica-induced lung MMP2 transcripts were less in CCSP-dnIκBα mice as compared to C57BL/6 mice (Figure 7). Because NF-κB can function as an anti-apoptotic factor, we evaluated the effect of expressing the dnIκBα mutant in the lung epithelium of these transgenic mice. CCSP-dnIκBα mice had increased apoptosis (TUNEL positive cells) in their lungs when compared to their non-transgenic littermate controls (Table 4). SPC-dnIκBα mice reacted to silica exposure similar to that of CCSP-dnIκBα mice. SPC-dnIκBα mice had decreased infiltrating cells, but accumulated increased hydroxyproline and TUNEL positive cells in their lungs when compared to littermate controls (Table 5).


Systemic inhibition of NF-kappaB activation protects from silicosis.

Di Giuseppe M, Gambelli F, Hoyle GW, Lungarella G, Studer SM, Richards T, Yousem S, McCurry K, Dauber J, Kaminski N, Leikauf G, Ortiz LA - PLoS ONE (2009)

Clara cell expression of a dominant-negative (dn) IκBα protein alters TNFα, and MMP2, but not α1(I) collagen and TIMP-1, mRNA expression in response to silica.Densitometry analysis of Northern blots of TNF, α1(I) collagen, MMP2, TIMP-1, and 18S (loading control) mRNA expression in CCSP-dnIκB mouse lung 28 days following the intratracheal injection of saline as control, or silica as described in the Methods section. Compared to their wild type littermates, CCSP-dnIkB transgenic mice significantly inhibited (P<0.05) the enhanced expression of TNFα and MMP2 mRNA induced by silica in the mouse lung. Figure illustrate results obtained from five set of mice exposed to silica or saline as control. * Indicates statistically significant difference compared to saline treated mice. † Indicates statistically significant difference compared to wild-type non-transgenic mice.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2682759&req=5

pone-0005689-g007: Clara cell expression of a dominant-negative (dn) IκBα protein alters TNFα, and MMP2, but not α1(I) collagen and TIMP-1, mRNA expression in response to silica.Densitometry analysis of Northern blots of TNF, α1(I) collagen, MMP2, TIMP-1, and 18S (loading control) mRNA expression in CCSP-dnIκB mouse lung 28 days following the intratracheal injection of saline as control, or silica as described in the Methods section. Compared to their wild type littermates, CCSP-dnIkB transgenic mice significantly inhibited (P<0.05) the enhanced expression of TNFα and MMP2 mRNA induced by silica in the mouse lung. Figure illustrate results obtained from five set of mice exposed to silica or saline as control. * Indicates statistically significant difference compared to saline treated mice. † Indicates statistically significant difference compared to wild-type non-transgenic mice.
Mentions: CCSP-dnIκBα mice reacted to silica exposure with decreased lung inflammation as compared to littermate controls (Table 4). This attenuated inflammatory response was associated decreased TNFα transcripts and inflammatory cell infiltration [(Vv(f)] at 28 d after silica exposure (Table 4). In contrast to these effects on inflammation, lung hydroxyproline deposition increased in CCSP-dnIκBα mice than in littermate controls (Table 4). Similarly, CCSP-dnIκBα mice and wild-type littermate mice had nearly equivalent increases in collagen and TIMP1 transcripts. However, silica-induced lung MMP2 transcripts were less in CCSP-dnIκBα mice as compared to C57BL/6 mice (Figure 7). Because NF-κB can function as an anti-apoptotic factor, we evaluated the effect of expressing the dnIκBα mutant in the lung epithelium of these transgenic mice. CCSP-dnIκBα mice had increased apoptosis (TUNEL positive cells) in their lungs when compared to their non-transgenic littermate controls (Table 4). SPC-dnIκBα mice reacted to silica exposure similar to that of CCSP-dnIκBα mice. SPC-dnIκBα mice had decreased infiltrating cells, but accumulated increased hydroxyproline and TUNEL positive cells in their lungs when compared to littermate controls (Table 5).

Bottom Line: At the time of lung transplantation, we found the lungs of silica-exposed subjects to contain multiple foci of inflammatory cells and silicotic nodules with proximal TNFalpha expressing macrophage and NF-kappaB activation in epithelial cells.Using a mouse experimental model in which the endotracheal instillation of silica reproduces the silica-induced lung injury observed in humans we found that systemic inhibition of NF-kappaB activation with a pharmacologic inhibitor (BAY 11-7085) of IkappaB alpha phosphorylation decreased silica-induced inflammation and collagen deposition.In contrast, transgenic mice expressing a dominant negative IkappaB alpha mutant protein under the control of epithelial cell specific promoters demonstrate enhanced apoptosis and collagen deposition in their lungs in response to silica.

View Article: PubMed Central - PubMed

Affiliation: Division of Occupational and Environmental Medicine, Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.

ABSTRACT

Background: Silicosis is a complex lung disease for which no successful treatment is available and therefore lung transplantation is a potential alternative. Tumor necrosis factor alpha (TNFalpha) plays a central role in the pathogenesis of silicosis. TNFalpha signaling is mediated by the transcription factor, Nuclear Factor (NF)-kappaB, which regulates genes controlling several physiological processes including the innate immune responses, cell death, and inflammation. Therefore, inhibition of NF-kappaB activation represents a potential therapeutic strategy for silicosis.

Methods/findings: In the present work we evaluated the lung transplant database (May 1986-July 2007) at the University of Pittsburgh to study the efficacy of lung transplantation in patients with silicosis (n = 11). We contrasted the overall survival and rate of graft rejection in these patients to that of patients with idiopathic pulmonary fibrosis (IPF, n = 79) that was selected as a control group because survival benefit of lung transplantation has been identified for these patients. At the time of lung transplantation, we found the lungs of silica-exposed subjects to contain multiple foci of inflammatory cells and silicotic nodules with proximal TNFalpha expressing macrophage and NF-kappaB activation in epithelial cells. Patients with silicosis had poor survival (median survival 2.4 yr; confidence interval (CI): 0.16-7.88 yr) compared to IPF patients (5.3 yr; CI: 2.8-15 yr; p = 0.07), and experienced early rejection of their lung grafts (0.9 yr; CI: 0.22-0.9 yr) following lung transplantation (2.4 yr; CI:1.5-3.6 yr; p<0.05). Using a mouse experimental model in which the endotracheal instillation of silica reproduces the silica-induced lung injury observed in humans we found that systemic inhibition of NF-kappaB activation with a pharmacologic inhibitor (BAY 11-7085) of IkappaB alpha phosphorylation decreased silica-induced inflammation and collagen deposition. In contrast, transgenic mice expressing a dominant negative IkappaB alpha mutant protein under the control of epithelial cell specific promoters demonstrate enhanced apoptosis and collagen deposition in their lungs in response to silica.

Conclusions: Although limited by its size, our data support that patients with silicosis appear to have poor outcome following lung transplantation. Experimental data indicate that while the systemic inhibition of NF-kappaB protects from silica-induced lung injury, epithelial cell specific NF-kappaB inhibition appears to aggravate the outcome of experimental silicosis.

Show MeSH
Related in: MedlinePlus