SERPINB1 upregulation is associated with in vivo complex formation with neutrophil elastase and cathepsin G in a baboon model of bronchopulmonary dysplasia

Abstract

Bronchopulmonary dysplasia (BPD) continues to be a major cause of morbidity in premature infants. An imbalance between neutrophil elastase and its inhibitors has been implicated in BPD. Serine protease inhibitor (SERPIN)B1 is an inhibitor of neutrophil proteases, including neutrophil elastase (NE) and cathepsin G (cat G). Recent studies suggest that SERPINB1 could provide protection in the airways by regulating excess protease activity associated with inflammatory lung disorders. In this study, we determined the distribution and ontogeny of SERPINB1 in the baboon lung and characterized the expression of SERPINB1 in baboon models of BPD. SERPINB1 expression was detected in the conducting airway and glandular epithelial cells in addition to neutrophils, macrophages, and mast cells. SERPINB1 mRNA and protein expression increased with advancing gestational age and in the new BPD model. In contrast, SERPINB1 expression levels were decreased in the old BPD model. Furthermore, SERPINB1 was detected as a high-molecular-mass (HMM) complex in lung tissue and bronchoalveolar lavage fluid samples from the BPD group. Analysis of the HMM complex by coimmunoprecipitation showed that these complexes were formed between SERPINB1 and NE or cat G. High-performance liquid chromatography (HPLC) ion trap mass spectrometry verified the presence of SERPINB1 in HMM complexes. Finally, NE activity level was compared between new and old baboon models of BPD and was found to be significantly lower in new BPD. Thus SERPINB1 upregulation in new BPD may be protective by contributing to the regulation of neutrophil proteases NE and cat G.

Surfactant Protein-D Inhibits Lung Inflammation Caused by Ventilation in Premature Newborn Lambs

“…NE is a potent serine proteinase, responsible for tissue destruction in adult lung with emphysema (36). In the preterm newborn lung, increased NE activity affects lung remodeling and increases alveolar epithelial apoptosis and the development of BPD (15,16).…”

“…Total inflammatory cell numbers as well as neutrophils were significantly decreased by rhSP-D ( Figure 4A). Increased NE activity has been associated with development of BPD (15,16). The addition of rhSP-D to Survanta decreased NE activity in the lung ( Figure 4B).…”

“…Lung tissue of the right lower lobe was frozen in liquid nitrogen for RNA isolation and measurement of neutrophil elastase (NE) activity (14,15). NE activity was assessed by a spectrophotometric assay using chromogenic substrate specific for NE: N-methoxy-succinyl-Ala-Ala-Pro-Val pNA (16 Lung tissue of the right middle lobe was homogenized in 0.9% NaCl and supernatant after centrifugation at 1,000 3 g for 15 minutes was frozen for ELISA of proinflammatory cytokine proteins (5,7). Bronchoalveolar lavage fluid (BALF) was recovered from the left lung (7) for further analyses.…”

Intracellular and extracellular serpins modulate lung disease

“…89 Yasumatsu et al probed SERPINB1 function in the established baboon BPD model. 90,91 As in humans, SERPINB1 was localized to bronchial and glandular epithelial cells, as well as mast cells, neutrophils and macrophages in the baboon lung.…”

“…90 These results suggested that SERPINB1 function in the newborn lung is critical as an antipeptidase shield against elastases associated with inflammation and responsible for lung injury.…”