Hereditary deficiency of the protein α-1 antitrypsin (AAT) causes a chronic lung disease in humans that is characterized by excessive mobilization of neutrophils into the lung. However, the reason for the increased neutrophil burden has not been fully elucidated. In this study we have demonstrated using human neutrophils that serum AAT coordinates both CXCR1- and soluble immune complex (sIC) receptor–mediated chemotaxis by divergent pathways. We demonstrated that glycosylated AAT can bind to IL-8 (a ligand for CXCR1) and that AAT–IL-8 complex formation prevented IL-8 interaction with CXCR1. Second, AAT modulated neutrophil chemotaxis in response to sIC by controlling membrane expression of the glycosylphosphatidylinositol-anchored (GPI-anchored) Fc receptor FcγRIIIb. This process was mediated through inhibition of ADAM-17 enzymatic activity. Neutrophils isolated from clinically stable AAT-deficient patients were characterized by low membrane expression of FcγRIIIb and increased chemotaxis in response to IL-8 and sIC. Treatment of AAT-deficient individuals with AAT augmentation therapy resulted in increased AAT binding to IL-8, increased AAT binding to the neutrophil membrane, decreased FcγRIIIb release from the neutrophil membrane, and normalization of chemotaxis. These results provide new insight into the mechanism underlying the effect of AAT augmentation therapy in the pulmonary disease associated with AAT deficiency.

Apoptosis is a distinct mechanism by which eukaryotic cells die. Neutrophils (PMN) play a fundamental role in the systemic inflammatory response syndrome. Clearance of PMN during resolution of the acute inflammatory process occurs by apoptosis, but factors inducing this process are unknown. The aims of this study were to determine whether PMN ingestion of Escherichia coli would result in PMN apoptosis and whether the mechanism was related to the respiratory burst. PMN from 10 healthy volunteers were cultured with different ratios of PMN:E. coli (1:0 to 1:25) for 12 h. Apoptosis was then assessed by propidium iodide DNA staining, morphology, gel electrophoresis, and Fc γ RIII expression. There was a significant induction of PMN apoptosis on incubation with E. coli at a ratio of 1:10 and 1:25 PMN:E. coli as well as decreases in Fc γ RIII. This correlated with increased ingestion of FITC-labeled E. coli and intracellular reactive oxygen intermediates after a 2-h coculture. To clarify the role of reactive oxygen intermediates in E. coli-induced PMN apoptosis, we assessed the effects of the antioxidants catalase, DMSO, glutathione, and N-acetylcysteine. There was a significant decrease in E. coli-induced PMN apoptosis on incubation with DMSO (1.0%), glutathione (25 mM), and N-acetylcysteine (25 mM) compared with control PMN:E. coli. This study demonstrates for the first time that E. coli induces PMN apoptosis through an oxygen-dependent mechanism. The removal of effete PMN by the process of apoptosis rather than necrosis may be teleologically beneficial during Gram-negative septicemia.

Research from JAMA Surgery — Immune Function in Patients Undergoing Open vs Laparoscopic Cholecystectomy

There is increasing evidence that vascular endothelial growth factor (VEGF) has autocrine as well as paracrine functions in tumour biology. Vascular endothelial growth factor-mediated cell survival signalling occurs via the classical tyrosine kinase receptors Flt-1, KDR/Flk-1 and the more novel neuropilin (NP) receptors, NP-1 and NP-2. A 24-mer peptide, which binds to neuropilin-1, induced apoptosis of murine and human breast carcinoma cells, whereas a peptide directed against KDR had no effect. Both anti-NP1 and anti-KDR peptides induced endothelial cell apoptosis. Confocal microscopy using 5-(6)-carboxyfluorescein-labelled peptides showed that anti-NP1 bound to both tumour and endothelial cells, whereas anti-KDR bound endothelial cells only. This study demonstrates that NP-1 plays an essential role in autocrine antiapoptotic signalling by VEGF in tumour cells and that NP1-blockade induces tumour cell and endothelial cell apoptosis. Specific peptides can therefore be used to target both autocrine (tumour cells) and paracrine (endothelial cells) signalling by VEGF.