Evaluation of Cathepsin D activity in spleen and bone marrow in experimental immunodeficiency and under treatment with sulfated polysaccharides

Abstract

Introduction: The cellular lysosomal system represents one of the key enzymatic protection mechanisms of the body. Cathepsin D (CatD) is a normal and major component of lysosomes. CatD manages protein turnover degrading misfolded and aggregated proteins and favors apoptosis in the case of proteostasis disruption. Proteostasis refers to the regulation of the cellular concentration, folding, interactions and localization of each of the proteins that comprise the proteome. However, when CatD regulation is affected, it can contribute to numerous disorders [Jackson MP, Hewitt EW (2016)]. Thereby, studying the mechanisms of action of sulfated polysaccharides (SPS) of local origin on CatD activity in various pathological conditions is of particular interest. Materials and Methods: Immunodeficiency was modeled in laboratory rats by biweekly injections of cyclophosphamide solution (50 mg/kg) for two weeks. SPS at doses of 50 and 125 mg/kg, dissolved in 20 mL of beef broth, were administered enterally on a daily basis. The collection and preparation of spleen and bone marrow (BM) were conducted under specific conditions to assess CatD activity. The evaluation of CatD activity was based on the enzyme's ability to cleave the hemoglobin molecule, resulting in acid-soluble derivatives, whose quantity is directly proportional to enzyme activity. This was assessed using a Synergy H1 Hybrid Reader (BioTek Instruments, USA). Statistical analysis was performed using the software programs "StatsDirect" and "Statistica 6.0". Results: In rats with immunodeficiency, CatD activity exhibited an increasing trend in spleen, while in BM, it was particularly elevated, exceeding control values by twofold (p<0.05). Treatment with SPS at a dose of 125 mg/kg led to a significant reduction (39%, p<0.01) in CatD activity in the spleen. In BM, CatD levels tended toward normalization only when SPS was administered at a dose of 50 mg/kg. Conclusions: The administration of SPS in experimental immunodeficiency resulted in a decrease in CatD values, which could potentially reduce the intensity of inflammation and reduce a lot a disorder at cellular and molecular level. Therefore, targeting CatD could provide significant diagnostic benefits and new avenues of therapy.