Clinical Severity of β-thalassaemia/Hb E Disease Is Associated with Differential Activities of the Calpain-Calpastatin Proteolytic System

Abstract

Earlier observations in the literature suggest that proteolytic degradation of excess unmatched α-globin chains reduces their accumulation and precipitation in β-thalassaemia erythroid precursor cells and have linked this proteolytic degradation to the activity of calpain protease. The aim of this study was to correlate the activity of calpain and its inhibitor, calpastatin, with different degrees of disease severity in β-thalassaemia. CD34+ cells were enriched from peripheral blood of healthy individuals (control group) and patients with mild and severe clinical presentations of β0-thalassaemia/Hb E disease. By ex vivo cultivation promoting erythroid cell differentiation for 7 days, proerythroblasts, were employed for the functional characterization of the calpain-calpastatin proteolytic system. In comparison to the control group, enzymatic activity and protein amounts of μ-calpain were found to be more than 3-fold increased in proerythroblasts from patients with mild clinical symptoms, whereas no significant difference was observed in patients with severe clinical symptoms. Furthermore, a 1.6-fold decrease of calpastatin activity and 3.2-fold accumulation of a 34 kDa calpain-mediated degradation product of calpastatin were observed in patients with mild clinical symptoms. The increased activity of calpain may be involved in the removal of excess α-globin chains contributing to a lower degree of disease severity in patients with mild clinical symptoms.

Methods to develop a scoring system for disease severity classification: More than clinical experience and expertise

“…Thus, a binary logistic regression model could be used to assess the impact of variables with the need for treatment as a response variable, and then the coefficients obtained from the logistic regression should be multiplied by a scaling factor to produce a scoring system that required whole integers for all the criterions, which are associated with specific risk factors identified at patients' initial assessments. Furthermore, previous studies have reported that other factors, including age at disease presentation, age at receiving first blood transfusion, requirement for transfusion and laboratory parameters like calpain activation may correlate with NTDT [3,4]. Therefore, it would be more relevant if the authors had taken all the possible factors associated with the disease into consideration during the selecting candidate variables for a disease severity scoring system.…”