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Interstitial collagen turnover during airway remodeling in acute and chronic experimental asthma

View Article: PubMed Central - PubMed

ABSTRACT

Asthma airway remodeling is characterized by the thickening of the basement membrane (BM) due to an increase in extracellular matrix (ECM) deposition, which contributes to the irreversibility of airflow obstruction. Interstitial collagens are the primary ECM components to be increased during the fibrotic process. The aim of the present study was to examine the interstitial collagen turnover during the course of acute and chronic asthma, and 1 month after the last exposure to the allergen. Guinea pigs sensitized to ovalbumin (OVA) and exposed to 3 further OVA challenges (acute model) or 12 OVA challenges (chronic model) were used as asthma experimental models. A group of animals from either model was sacrificed 1 h or 1 month after the last OVA challenge. Collagen distribution, collagen content, interstitial collagenase activity and matrix metalloproteinase (MMP)-1, MMP-13 and tissue inhibitor of metalloproteinase (TIMP)-1 protein expression levels were measured in the lung tissue samples from both experimental models. The results revealed that collagen deposit in bronchiole BM, adventitial and airway smooth muscle layers was increased in both experimental models as well as lung tissue collagen concentration. These structural changes persisted 1 month after the last OVA challenge. In the acute model, a decrease in collagenase activity and in MMP-1 concentration was observed. Collagenase activity returned to basal levels, and an increase in MMP-1 and MMP-13 expression levels along with a decrease in TIMP-1 expression levels were observed in animals sacrificed 1 month after the last OVA challenge. In the chronic model, there were no changes in collagenase activity or in MMP-13 concentration, although MMP-1 expression levels increased. One month later, an increase in collagenase activity was observed, although MMP-1 and TIMP-1 levels were not altered. The results of the present study suggest that even when the allergen challenges were discontinued, and collagenase activity and MMP-1 expression increased, fibrosis remained, contributing to the irreversibility of bronchoconstriction.

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Related in: MedlinePlus

MMP and TIMP-1 protein expression levels in tissue samples from the 35 day asthma experimental model. (A) Active MMP-1 and MMP-13 forms were observed in all samples assayed (56- and 45-kDa bands, respectively). Pro-MMP-13 was identified in tissue samples from group II (60-kDa band). TIMP-1 was present as a 28-kDa band in the majority of tissue samples. Bands of larger weight which correspond to TIMP-1 polymers or complexes were also observed. (B) Densitometry analysis showed a significant increase in MMP-1 expression levels in samples belonging to group III as compared with group II (*P=0.013). Group II MMP-13 expression levels were significantly higher, as compared with those of group III (**P=0.003). TIMP-1 expression levels were significantly increased in group II, as compared with TIMP-1 expression levels in the tissue samples of control animals (group I; ***P=0.01). Bars represent the mean ± standard error. MMP, matrix metalloproteinase; TIMP, tissue inhibitors of metalloproteinase.
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f6-etm-0-0-3509: MMP and TIMP-1 protein expression levels in tissue samples from the 35 day asthma experimental model. (A) Active MMP-1 and MMP-13 forms were observed in all samples assayed (56- and 45-kDa bands, respectively). Pro-MMP-13 was identified in tissue samples from group II (60-kDa band). TIMP-1 was present as a 28-kDa band in the majority of tissue samples. Bands of larger weight which correspond to TIMP-1 polymers or complexes were also observed. (B) Densitometry analysis showed a significant increase in MMP-1 expression levels in samples belonging to group III as compared with group II (*P=0.013). Group II MMP-13 expression levels were significantly higher, as compared with those of group III (**P=0.003). TIMP-1 expression levels were significantly increased in group II, as compared with TIMP-1 expression levels in the tissue samples of control animals (group I; ***P=0.01). Bars represent the mean ± standard error. MMP, matrix metalloproteinase; TIMP, tissue inhibitors of metalloproteinase.

Mentions: Western blot assays revealed the presence of MMP-1 as a band of 56-kDa which corresponds to the MMP-1 active form. This band was found in tissue homogenates from guinea pigs from every one of the 3 groups in the 35 day experimental model (Fig. 6A). MMP-1 densitometry analysis demonstrated a significant decrease in MMP-1 expression levels in tissue from group II animals, as compared with tissue samples from group III (49,325.3±3,319.9 and 97,338.1±1,038.1 DU, respectively; P=0.013; Fig. 6B). There were no significant differences in MMP-1 concentration between group II and group I (76,641.7±4,250 DU).


Interstitial collagen turnover during airway remodeling in acute and chronic experimental asthma
MMP and TIMP-1 protein expression levels in tissue samples from the 35 day asthma experimental model. (A) Active MMP-1 and MMP-13 forms were observed in all samples assayed (56- and 45-kDa bands, respectively). Pro-MMP-13 was identified in tissue samples from group II (60-kDa band). TIMP-1 was present as a 28-kDa band in the majority of tissue samples. Bands of larger weight which correspond to TIMP-1 polymers or complexes were also observed. (B) Densitometry analysis showed a significant increase in MMP-1 expression levels in samples belonging to group III as compared with group II (*P=0.013). Group II MMP-13 expression levels were significantly higher, as compared with those of group III (**P=0.003). TIMP-1 expression levels were significantly increased in group II, as compared with TIMP-1 expression levels in the tissue samples of control animals (group I; ***P=0.01). Bars represent the mean ± standard error. MMP, matrix metalloproteinase; TIMP, tissue inhibitors of metalloproteinase.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4998200&req=5

f6-etm-0-0-3509: MMP and TIMP-1 protein expression levels in tissue samples from the 35 day asthma experimental model. (A) Active MMP-1 and MMP-13 forms were observed in all samples assayed (56- and 45-kDa bands, respectively). Pro-MMP-13 was identified in tissue samples from group II (60-kDa band). TIMP-1 was present as a 28-kDa band in the majority of tissue samples. Bands of larger weight which correspond to TIMP-1 polymers or complexes were also observed. (B) Densitometry analysis showed a significant increase in MMP-1 expression levels in samples belonging to group III as compared with group II (*P=0.013). Group II MMP-13 expression levels were significantly higher, as compared with those of group III (**P=0.003). TIMP-1 expression levels were significantly increased in group II, as compared with TIMP-1 expression levels in the tissue samples of control animals (group I; ***P=0.01). Bars represent the mean ± standard error. MMP, matrix metalloproteinase; TIMP, tissue inhibitors of metalloproteinase.
Mentions: Western blot assays revealed the presence of MMP-1 as a band of 56-kDa which corresponds to the MMP-1 active form. This band was found in tissue homogenates from guinea pigs from every one of the 3 groups in the 35 day experimental model (Fig. 6A). MMP-1 densitometry analysis demonstrated a significant decrease in MMP-1 expression levels in tissue from group II animals, as compared with tissue samples from group III (49,325.3±3,319.9 and 97,338.1±1,038.1 DU, respectively; P=0.013; Fig. 6B). There were no significant differences in MMP-1 concentration between group II and group I (76,641.7±4,250 DU).

View Article: PubMed Central - PubMed

ABSTRACT

Asthma airway remodeling is characterized by the thickening of the basement membrane (BM) due to an increase in extracellular matrix (ECM) deposition, which contributes to the irreversibility of airflow obstruction. Interstitial collagens are the primary ECM components to be increased during the fibrotic process. The aim of the present study was to examine the interstitial collagen turnover during the course of acute and chronic asthma, and 1 month after the last exposure to the allergen. Guinea pigs sensitized to ovalbumin (OVA) and exposed to 3 further OVA challenges (acute model) or 12 OVA challenges (chronic model) were used as asthma experimental models. A group of animals from either model was sacrificed 1 h or 1 month after the last OVA challenge. Collagen distribution, collagen content, interstitial collagenase activity and matrix metalloproteinase (MMP)-1, MMP-13 and tissue inhibitor of metalloproteinase (TIMP)-1 protein expression levels were measured in the lung tissue samples from both experimental models. The results revealed that collagen deposit in bronchiole BM, adventitial and airway smooth muscle layers was increased in both experimental models as well as lung tissue collagen concentration. These structural changes persisted 1 month after the last OVA challenge. In the acute model, a decrease in collagenase activity and in MMP-1 concentration was observed. Collagenase activity returned to basal levels, and an increase in MMP-1 and MMP-13 expression levels along with a decrease in TIMP-1 expression levels were observed in animals sacrificed 1 month after the last OVA challenge. In the chronic model, there were no changes in collagenase activity or in MMP-13 concentration, although MMP-1 expression levels increased. One month later, an increase in collagenase activity was observed, although MMP-1 and TIMP-1 levels were not altered. The results of the present study suggest that even when the allergen challenges were discontinued, and collagenase activity and MMP-1 expression increased, fibrosis remained, contributing to the irreversibility of bronchoconstriction.

No MeSH data available.


Related in: MedlinePlus