Enhanced survival of lung granulocytes in an animal model of asthma: evidence for a role of GM-CSF activated STAT5 signalling pathway

Abstract

Background-As granulocyte/macrophage colony stimulating factor (GM-CSF) mediated delay of granulocyte apoptosis contributes to the accumulation of inflammatory cells at the site of inflammation in many diseases, we sought to determine whether asthma is also associated with a GM-CSF dependent increase in lung granulocyte survival. Moreover, because GM-CSF mediates its eVects through activation of signal transducer and activator of transcription 5 (STAT5), we also investigated the potential role of STAT5 in allergic inflammation. Methods-Blood granulocytes were recovered from six healthy and six heaves aVected horses, a model of asthma. Lung granulocytes were obtained by bronchoalveolar lavage (BAL) from the same horses. Granulocytes were cultured in the presence or absence of anti-GM-CSF receptor antibodies for diVerent times and apoptosis was determined using the Annexin-V/propidium iodide detection method. Nuclear protein extracts from cultured granulocytes were analysed for STAT5 binding activity by electrophoretic mobility shift assay. Results-BAL fluid granulocytes from heaves aVected horses demonstrated a significant delay in apoptosis compared with blood granulocytes from the same horses and blood and BAL fluid granulocytes from healthy horses. Conversely, the rate of apoptosis in blood granulocytes from healthy and heaves aVected horses was comparable. The enhanced survival of BAL fluid granulocytes from aVected horses was suppressed in the presence of antibodies directed against GM-CSF receptors. Increased levels of active STAT5 were found in BAL fluid granulocytes from heaves aVected horses and were markedly reduced after treatment with anti-GM-CSF receptor antibodies. Conclusions-These data indicate that granulocyte survival is enhanced in the lung of heaves aVected horses and suggest a role for a GM-CSF activated STAT5 pathway in delaying apoptosis of lung granulocytes in this model of asthma. (Thorax 2001;56:696-702)

Reduced spontaneous apoptosis in peripheral blood neutrophils during exacerbation of COPD

“…In a recent study, TURLEJ et al [16] found an increased resistance to apoptosis in alveolar neutrophils from heaves-affected horses; heaves is regarded to be an animal model for COPD or asthma [10]. The authors could not detect a significant difference in resistance to apoptosis of peripheral blood neutrophils.…”

Nitric oxide: a key regulator of myeloid inflammatory cell apoptosis

“…Delayed apoptosis of activated granulocytes has been reported to occur in a number of inflammatory conditions in humans or animal models, 5,52 including rheumatoid arthritis, 53 acute pancreatitis, 54 bacterial pneumonia, 55 inflammatory bowel disease, 56 asthma, [57][58][59] and following surgery. 60,61 Failure of these cells to undergo programmed cell death and to be cleared by phagocytes allows persistent and inappropriate inflammation to occur, as activated granulocytes release a number of proinflammatory mediators, which may contribute significantly to the aetiology of the disease.…”

Early onset airway obstruction in response to organic dust in the horse

“…The late-phase response comprises airway obstruction, airway inflammation, and airway hyperreactivity. RAO has been suggested to be the most similar naturally occurring disease in animals to human asthma (35) and has been used as model of human asthma (2,6,17,39).…”