Alpha-1-Antitrypsin Ameliorates Diffuse Alveolar Hemorrhage in the Pristane Induced Lupus Model

Abstract

Abstract Diffuse alveolar hemorrhage (DAH) is a fatal complication of lupus with >50% mortality in humans. DAH can be induced in B6 mice by a single intraperitoneal (i.p.) injection of pristane. Human alpha-1-antitrypsin (hAAT) is an anti-inflammatory and immuno-regulatory protein. In this study, we investigated the protective effect of treatment with hAAT against pristane induced DAH development in B6, as well as in AAT-deficient (AAT-Ko) and hAAT transgenic (hAAT-Tg) mice. First, we characterized activated splenocytes from B6 and hAAT-Tg mice. We found that TNF-α production was significantly lower in the B cells, CD4+ and CD8+ T cells from hAAT-Tg mice as compared to B6 mice. Conversely, the frequency of CD4+CD25+ and CD4+CD25−IL-10+cells was significantly higher in hAAT-Tg than that in B6 mice. To test the effect of hAAT on DAH development, we treated B6 mice with or without hAAT (2mg/mouse/2 d) and induced DAH by a pristane injection. Two weeks after induction, control B6 mice showed severe lung hemorrhage, while hAAT treatment prevented lung hemorrhage. To investigate the mechanisms responsible for protection, we induced DAH in B6, AAT-Ko and hAAT-Tg mice. One week after induction, the frequencies of pro-inflammatory CD11b−Ly6Chi, pDCA-1+CD11clo, CD11c+CD11b+ and neutrophils were significantly lower in the peritoneal exudate cells of hAAT-Tg mice as compared to B6 and AAT-Ko mice. Moreover, the frequency of CD11b+Ly6Clow cells were significantly increased in hAAT-Tg. These results showed for the first time that hAAT has a therapeutic potential for the treatment of DAH by modulating myeloid cell phenotypes.