Hava Yolu Epitel Hücrelerinde Alerjen Proteazların Matriks Proteazların Salımı Üzerine Olan Etkileri

Abstract

Asthma is an important respiratory disease that has a higher incidence in children and has increased in recent years in our country. Allergens are the main environmental factors which trigger asthma. While allergens with protease activity are categorized to 6 main groups (serine, cysteine, threonine, aspartate, glutamate, and metalloprotease), there also allergens with no proteolytic activity.

Inflammation, which begins when allergens enter the body through the receptors on epithelial cells or disrupted epithelial barrier, leads to airway remodelling by activating various mechanisms such as epithelial cell hyperplasia, sub-epithelial fibrosis and smooth muscle cell hyperplasia.

In airway remodeling, in addition to changes is epithelial cell, fibroblast and smooth muscle cell, there are also deteriorations in the content and structure of extracellular matrix. These deteriorations occur by degradation of molecules such as collagen, fibronectin, laminin, and aggrecan. The protease group responsible for the cleavage of these molecules in airway remodeling is matrix metalloproteases.

Matrix metalloproteases (MMPs), zinc-activated endopeptidases, are effective on molecules that regulate cellular activity such as cytokines and growth factors, as well as exerting destructive effects on extracellular matrix components. Thus, they participate in metabolic events taking place in different cells such as epithelial cells, fibroblasts and smooth muscle cells. Of the 28 matrix metalloproteases identified to date, MMP-2 and MMP-9, which breaks the gelatin molecule, and MMP-12, which breaks the collagen molecule, have been shown to play an important role in asthma. Inadequate expression of MMPs by the source cells or failure to fully perform protease activity by degrading molecules leads to disruption of the balance between extracellular matrix production and lung fibrillation breakdown and eventually causes structural disruption in the lung. Although there are publications in the literature indicating the association between bronchial epithelial cells and MMP-9, information on MMP-2 and MMP-12 released by airway epithelial cells in response to allergen exposure is extremely inadequate.

In this study, BEAS-2B bronchial epithelial cells were stimulated seperately with cysteine protease allergen Der p 1, serine protease allergen Der p 6, and Der p 2 allergen with no protease activity, allergens derived from Dermatophagoides pteronyssinus. Changes in expression of MMP-2, MMP-9, and MMP-12 levels occuring after allergen stimulation were investigated at RNA level by using PCR and at protein level by using ELISA method.

It has been established that cysteine protease Der p 1 is effective on MMP-2 and MMP-9 gene expression, while non-proteolytic Der p 2 have an impact on MMP-2, only. Also, Der p 6 has been shown to be effective on MMP-2, MMP-9, and MMP-12 after 24 hour allergen exposure. Besides, heat inactivated allerges are also shown to be effective on MMP genes. Amount of MMP-9 protein released from cells are shown to be increased after both Der p 1 and Der p 2 stimulation, whereas stimulation with Der p 6 decreased release of MMP-9. According to these results, it can be concluded that allergens exposed to bronchial cells play a role in airway remodeling by affecting MMP release through their protease activities and/or epithelial cell receptor interactions.