Protective alpha1-antitrypsin effects in autoimmune vasculitis are compromised by methionine oxidation

BACKGROUND

Anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitidies (AAV) are life-threatening systemic autoimmune conditions. ANCA directed against proteinase 3 (PR3) or myeloperoxidase (MPO) bind their cell surface-presented antigen, activate neutrophils and cause vasculitis. An imbalance between PR3 and its major inhibitor α1-antitrypsin (AAT) was proposed to underlie PR3- but not MPO-AAV. We measured AAT and PR3 in healthies and AAV patients and studied protective AAT effects pertaining to PR3- and MPO-ANCA.

METHODS

Plasma and blood neutrophils were assessed for PR3 and AAT. Wild-type, mutant, and oxidation-resistant AAT species were produced to characterize AAT-PR3 interactions by flow cytometry, immunoblotting, FRET assays, and surface plasmon resonance measurements. Neutrophil activation was measured using the ferricytochrome C assay and AAT methionine-oxidation by Parallel Reaction Monitoring.

RESULTS

We found significantly increased PR3 and AAT pools in both PR3- and MPO-AAV patients, however, only in PR3-AAV did the PR3 pool correlate with ANCA titer, inflammatory response and disease severity. Mechanistically, AAT prevented PR3 from binding to CD177, thereby reducing neutrophil surface antigen for ligation by PR3-ANCA. Active PR3-AAV patients showed critical methionine-oxidation in plasma AAT that was recapitulated by ANCA-activated neutrophils. The protective PR3-related AAT effects were compromised by methionine-oxidation in the AAT reactive center loop but preserved when two critical methionines were substituted by valine and leucine.

CONCLUSION

Pathogenic differences between PR3- and MPO-AAV are related to AAT regulation of membrane-PR3, attenuating neutrophil activation by PR3- rather than MPO-ANCA. Oxidation-resistant AAT could serve as adjunctive therapy in PR3-AAV.

Blood pressure responses to acute exercise in type A females

Cardiovascular responses to moderate steady state exercise were studied in type A females. Twenty-one women, ages 18 to 43 years (mean 29.7 +/- 2.0), were divided into type A (n = 11) and type B (n = 10) groups by means of the Jenkins Activity Survey (JAS). Baseline measurement included EMG, BP, and psychometric data. Subjects exercised on a treadmill at 60% VO2 peak for 20 min. Postexercise systolic and diastolic BP (SBP, DBP) reductions were similar in the type A and type B groups [111/72 to 104/66 and 108/70 to 98/62 mmHg, respectively, (F(1, 38) = 4.03, p < 0.05]. However, DBP responses during exercise for type B, but not the type A, were lower [71 +/- 2 to 60 +/- 2 mmHg, preexercise to steady state exercise, (F(1, 38) = 7.14, p < 0.01]. Also, steady state exercise SBP was lower in type B compared to type A [159 +/- 3 vs. 150 +/- 4 mmHg, (F(1, 38) = 3.97, p < 0.05]. These data with psychometric data, suggest that hemodynamic and other physiological responses to exercise in females vary according to behavioral types associated with differing physiology.