Modification of lymphocyte DNA synthesis by alpha 1-antitrypsin

Alpha-1 Antitrypsin Augmentation Inhibits Proteolysis of Neutrophil Membrane Voltage-Gated Proton Channel-1 in Alpha-1 Deficient Individuals

Background and Objectives: Alpha-1 antitrypsin is a serine protease inhibitor that demonstrates an array of immunomodulatory functions. Individuals with the genetic condition of alpha-1 antitrypsin deficiency (AATD) are at increased risk of early onset emphysematous lung disease. This lung disease is partly driven by neutrophil mediated lung destruction in an environment of low AAT. As peripheral neutrophil hyper-responsiveness in AATD leads to excessive degranulation and increased migration to the airways, we examined the expression of the membrane voltage-gated proton channel-1 (HVCN1), which is integrally linked to neutrophil function. The objectives of this study were to evaluate altered HVCN1 in AATD neutrophils, serine protease-dependent degradation of HVCN1, and to investigate the ability of serum AAT to control HVCN1 expression. Materials and Methods: Circulating neutrophils were purified from AATD patients (n = 20), AATD patients receiving AAT augmentation therapy (n = 3) and healthy controls (n = 20). HVCN1 neutrophil expression was assessed by flow cytometry and Western blot analysis. Neutrophil membrane bound elastase was measured by fluorescence resonance energy transfer. Results: In this study we demonstrated that HVCN1 protein is under-expressed in AATD neutrophils (p = 0.02), suggesting a link between reduced HVCN1 expression and AAT deficiency. We have demonstrated that HVCN1 undergoes significant proteolytic degradation in activated neutrophils (p < 0.0001), primarily due to neutrophil elastase activity (p = 0.0004). In addition, the treatment of AATD individuals with AAT augmentation therapy increased neutrophil plasma membrane HVCN1 expression (p = 0.01). Conclusions: Our results demonstrate reduced levels of HVCN1 in peripheral blood neutrophils that may influence the neutrophil-dominated immune response in the AATD airways and highlights the role of antiprotease treatment and specifically AAT augmentation therapy in protecting neutrophil membrane expression of HVCN1.

T lymphocyte subset profile and serum alpha-1-antitrypsin in pathogenesis of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is an inflammatory disorder characterized by the presence of non-fully reversible airflow limitation. The study was undertaken to investigate the involvement of alpha-1-antitrypsin (alpha(1)AT) and T lymphocyte subsets in the pathogenesis of COPD. Blood samples of 50 subjects, including 25 healthy volunteers and 25 patients with COPD, were analysed. Serum trypsin inhibitory capacity (STIC) was determined by enzymatic assay. CD4(+) and CD8(+) T lymphocytes were enumerated in heparinized blood using a fluorescence activated cell sorter counter. The STIC in COPD patients was found to be decreased significantly than in controls (P < 0.01). In COPD patients with lower expression levels of alpha(1)AT, a highly significant decrease in the number of CD4(+) T lymphocytes (P < 0.0009) and CD4/CD8 ratio was observed compared with control subjects (P < 0.008). The mean +/- standard error of CD8(+) lymphocytes was found to be little different (only marginally decreased) in COPD patients compared to healthy controls; however, an alteration in the individual count of CD8(+) lymphocytes cells was observed in COPD patients. Using linear regression analysis, a negative correlation was observed between STIC and CD4(+) lymphocytes and CD8(+) lymphocytes (r = -0.40, P < 0.04; r = -0.42, P < 0.03, respectively) in COPD patients. An alteration in alpha(1)AT and T lymphocyte subsets in COPD patients suggested that interplay of these factors may be responsible for the progression of COPD.

Growth stimulation of human keratinocytes by tissue inhibitor of metalloproteinases

Human recombinant tissue inhibitor of metalloproteinases (rTIMP) at 0.2-4.6 microM was found to stimulate the growth of normal human keratinocytes, in primary cultures on a plastic support, and to markedly increase their growth on a tridimensional culture system, the skin equivalent, as shown by histology, DNA measurements, and planimetry. In contrast, rTIMP had no effect on the growth of normal human fibroblasts. The growth of keratinocytes on extracellular matrix components produced by keratinocytes cultured in the presence or absence of rTIMP was similar, suggesting that rTIMP does not stimulate keratinocyte growth by modifying either the quantity or the composition of the extracellular matrix deposited. rTIMP was labeled with 125iodine in order to study its interaction with keratinocytes in culture. Binding of (125I) rTIMP to keratinocytes was found to be temperature and time dependent. Under steady-state conditions at 22 degrees C, one class of specific rTIMP binding sites was identified with KD of 8.7 nM and 135,000 sites/cell. Such findings are in keeping with the known potentiating effect of TIMP on erythroid precursors, and indicate that this protein has at least two distinct activities.

The effect of alpha 2HS glycoprotein on lymphocyte reactivity to phytohemagglutinin

The effect of alpha 2HS glycoprotein on lymphocyte reactivity to phytohemagglutinin (PHA) was investigated. The results show that alpha 2HS glycoprotein, rather than enhancing lymphocyte reactivity to PHA as suggested by earlier correlation studies, inhibits such reactivity. Experiments suggest that this inhibition is unlikely to be the result of alpha 2HS glycoprotein binding either PHA or 3H-thymidine but is more likely to act at the cellular level.