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alpha2, 6 sialylation of transferrin and total serum glycoproteins in COPD patients

Many pathophysiological conditions, particularly those involving inflammation, were shown to be associated with disruption of glycan processing and therefore resulting in aberrant protein glycosylation. Inflammation is one of the main characteristics of chronic obstructive pulmonary disease (COPD), slowly progressive disease of airways characterized by a gradual loss of lung function. COPD is one of the major global health problems and its prevalence is constantly increasing. Although numerous glycoproteins were shown to play important roles in pathogenesis of COPD, the available information on glycosylation in this disease is extremely scarce. Transferrin is a serum glycoprotein with two N-linked oligosaccharide chains, bi- or three- anntenary structures each terminating in sialic acid. In healthy individuals N-glycosylation of transferrin has very small intra- and interindividual variations. Since many studies suggested changes of transferrin glycosylation in various diseases, in our work we examined the level of α 2, 6 sialylation of transferrin and total serum glycoproteins in subjects having COPD. Our study included 30 healthy individuals (age 55, 7± 8, 7 of which 10 smokers, 5 ex-smokers, 15 non smokers) and 29 individuals diagnosed as having COPD (age 67, 1± 7, 5 of which 19 smokers, 5 ex-smokers, 5 no smokers). For the analysis of the sialic acid level on serum transferrin we developed lectin based ELISA with immobilized antibodies. The level of α 2, 6 sialylation of total serum proteins was tested using slot blot method followed by lectin-chemiluminescence detection. Since Sambucus nigra agglutinin lectin specifically recognises α 2, 6 linked sialic acid it was used in both methods. Results were analysed using parametric test. Sialylation of transferrin in COPD patients was 13% lower (P=0, 0004), while the total serum silaic acid level was 15% lower than in controls (P=0, 0019). The difference is present even when the age was taken into account. Smoking had no influence. These results suggested changes in protein glycosylation in COPD patients and offer a good basis for further investigation and improvement of diagnostic approach in COPD. Since transferrin is shown to reflect pretty well a defect in N-glycosylation of many other glycoproteins, development of a novel assay for transferrin sialylation represents a contribution to the analysis of glycosylation changes in general.

sialic acid; transferrin; serum proteins; COPD

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