Proteasomes are a key component of the ubiquitin-proteasome system, which plays a central role in the degradation of most intracellular proteins. Several types of proteasomes exist, with the constitutive proteasome and the immunoproteasome being the most commonly represented. When proteasomes are found outside the cells, in blood plasma or other bodily fluids, they are referred to as circulating proteasomes. Their concentrations are often elevated under various pathological conditions, suggesting their potential as novel biomarkers for disease monitoring. Chronic inflammatory bowel diseases (IBD), are characterized by persistent inflammation of the gastrointestinal tract. There diagnosing and monitoring is a complex and time-consuming process, involving assessment of clinical symptoms, laboratory analysis of inflammatory markers in blood, stool testing, and endoscopic and histological examination of the affected intestinal tissue. In this master's thesis, we investigated whether circulating proteasomes could serve as diagnostic markers of IBDs. The aim of our study was to determine whether there is an association between the concentration or enzymatic activity of circulating proteasomes and the level of inflammation in patients with IBD, before and during treatment with biologic therapies. We focused on two proteolytically active subunits – beta5c and beta5i. The concentrations of these subunits were measured in selected plasma samples using the ELISA method, while their enzymatic activity was assessed through fluorescence-based kinetic measurements. The results were compared to values of biochemical inflammation markers and further correlated with clinical scoring systems (MAYO and HBI), which are used to evaluate disease activity. Patients donated blood before the start of the study (time point 1), after 6-12 weeks (time point 2), and finally after 24-36 weeks (time point 3). Based on our analyses, we found that the concentrations of the beta5c and beta5i subunits in patients with ulcerative colitis (UC) at the second time point negatively correlated with calprotectin levels, whereas the activity of the β5 subunits at the third time point showed a positive correlation with calprotectin in these patients. In patients with Crohn’s disease (CD), no association was observed between the beta5c and beta5i subunits and calprotectin, suggesting that circulating subunits may serve as potencial markers for distinguishing between CD and UC. No statistically significant correlations were observed between the concentration and activity of circulating proteasomes and other inflammatory markers, such as total bilirubin, CRP, albumin, and platelet count, in patients with imflammatory bowel disease at the second and third time points. Further studies including a larger number of patients and a broader range of clinical variables will be needed to gain a clearer understanding of the role of circulating proteasomes in these diseases.
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