Age-related lung changes linked to altered lysosomal protease profile, histology, and ultrastructure.

Introduction: The aging process is intricately linked to alterations in cellular and tissue structures, with the respiratory system being particularly susceptible to age-related changes. Therefore, this study aimed to profile the activity of proteases using activity-based probes in lung tissues of old and young rats, focusing on the expression levels of different, in particular cathepsins G and X and matrix Metalloproteinases (MMPs). Additionally, the impact on extracellular matrix (ECM) components, particularly fibronectin, in relation to age-related histological and ultrastructural changes in lung tissues was investigated.

Materials and methods: Lung tissues from old and young rats were subjected to activity-based probe profiling to assess the activity of different proteases. Expression levels of cathepsins G and X were quantified, and zymography was performed to evaluate matrix metalloproteinases activity. Furthermore, ECM components, specifically fibronectin, were examined for signs of degradation in the old lung tissues compared to the young ones. Moreover, histological, immunohistochemical and ultrastructural assessments of old and young lung tissue were also conducted.

Results: Our results showed that the expression levels of cathepsins G and X were notably higher in old rat lung tissues in contrast to those in young rat lung tissues. Zymography analysis revealed elevated MMP activity in the old lung tissues compared to the young ones. Particularly, significant degradation of fibronectin, an essential ECM component, was observed in the old lung tissues. Numerous histological and ultrastructural alterations were observed in old lung tissues compared to young lung tissues.

Discussion and conclusion: The findings indicate an age-related upregulation of cathepsins G and X along with heightened MMP activity in old rat lung tissues, potentially contributing to the degradation of fibronectin within the ECM. These alterations highlight potential mechanisms underlying age-associated changes in lung tissue integrity and provide insights into protease-mediated ECM remodeling in the context of aging lungs.