Changes in the activity of lysosomal cysteine proteases of plasma mononuclear and polymorphonuclear blood leukocytes in Alzheimer’s disease

Abstract

Aim. To study the level of activity of lysosomal cysteine proteases (cathepsins H, B, L) in blood plasma and fractionated leukocytes (polymorphonuclear and mononuclear) in patients with Alzheimer’s disease in comparison with similar indicators in persons without signs of neurodegeneration as a possible marker of Alzheimer’s disease development and diagnosis. Materials and methods. The spectrofluorimetric study of cathepsins B, L, H activity level in plasma and fractionated leukocytes was conducted in 22 patients diagnosed with Alzheimer’s disease in comparison with the same indicators in 22 patients matched by sex, age and associated diseases with patients of the observation group, but having no signs of neurodegeneration. Results. The activity of all three enzymes, and especially cathepsin H, increased significantly in blood plasma. A significant increase is also noted in the activity of cathepsins H, B, and L in homogenates of fractionated leukocytes. At the same time, in both polymorphonuclear and mononuclear leukocytes the greatest degree of changes is demonstrated by the activity of cathepsin B, and the least is the activity of cathepsin L. Given the available data on an increased cathepsin B activity in the cerebrospinal fluid of patients with Alzheimer’s disease, we can assume a correlation between the state of lysosomal proteases activity in the Central nervous system and in the peripheral blood cells. Conclusion. Alzheimer’s disease is associated with increased activity of cysteine cathepsins in plasma, polymorphonuclear and mononuclear leukocytes of peripheral blood, which can be considered as one of the possible markers of development and diagnosis of the disease.