Age-related expression, enzymatic solubility and modification with advanced glycation end-products of fibrillar...

Changes in the expression of fibrillar collagens and post-translational modifications with advanced glycation end-products (AGEs) are often associated with tissue aging. Less is known about age-related changes in mouse lung tissue. Therefore, we studied the expression level and AGE load of fibrillar collagens in lungs from young (≤6 months), adult (15 months) and old (≥25 months) mice. The mRNA expression level was reduced in adult and old mice compared with the young. Old mice also showed a reduced protein level, whereas the adults even had more collagen protein. Fractionating of the fibrillar collagens into enzyme-soluble and insoluble collagens revealed a reduced solubility of collagens in old age. The enzymatic solubility of fibrillar collagens correlated inversely with the AGE load in the insoluble collagen as detected by the AGE-related fluorescence. While the intensity of the AGE-related fluorescence was increased in fibrillar collagens in response to age, the fluorescing AGE variant argpyrimidine was less affected. In summary, aging causes a reduced expression, lower enzymatic solubility and increased AGE load of fibrillar collagens in mouse lung tissue, but not all changes occur gradually with age.