Constitutive apoptosis in equine peripheral blood neutrophils in vitro

Timothy J Brazil,Padraic M Dixon,Christopher Haslett,Joanna Murray,Bruce C Mcgorum

doi:10.1016/j.tvjl.2014.08.029

Timothy J Brazil, Padraic M Dixon + Show 3 more

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https://doi.org/10.1016/j.tvjl.2014.08.029

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Abstract

The aim of this study was to characterise constitutive apoptosis in equine peripheral blood neutrophils, including assessment of factors that potentially modulate neutrophil survival through alteration of the rate of constitutive apoptosis. Cells underwent spontaneous time-dependent constitutive apoptosis when aged in culture for up to 36 h, developing the structural and functional features of apoptosis observed in many cell types, including human neutrophils. Neutrophils undergoing apoptosis also had diminished zymosan activated serum (ZAS)-stimulated chemiluminescence, but maintained responsiveness to phorbol myristate acetate (PMA). The constitutive rate of equine neutrophil apoptosis was promoted by lipopolysaccharide (LPS), tumour necrosis factor α and phagocytosis of opsonised ovine erythrocytes, while it was inhibited by dexamethasone and ZAS (a source of C5a). Formyl-Met-Leu-Phe, leukotriene B4, platelet activating factor and PMA had no demonstrable effect on equine neutrophil apoptosis. There was a difference between equine and human neutrophil apoptosis in response to LPS and the time-dependence of the response to dexamethasone.

Highlights

Equine neutrophils play a key role in host defence, and contribute to host tissue injury through secretion of pro-inflammatory and histotoxic agents (Morris, 1991; Moore et al, 1995; de la Rebière de Pouyade and Serteyn, 2011)
Despite loss of small pseudopodia found in freshly isolated cells (Fig. 2)
zymosan activated serum (ZAS) inhibited equine neutrophil apoptosis at 8 h (% apoptosis: control 9.8 ± 2.0%, ZAS 5.6 ± 2.0%; P < 0.05, n = 4) and 20 h

Summary

Introduction

Equine neutrophils play a key role in host defence, and contribute to host tissue injury through secretion of pro-inflammatory and histotoxic agents (Morris, 1991; Moore et al, 1995; de la Rebière de Pouyade and Serteyn, 2011). This has prompted investigation into the role of neutrophil apoptosis in equine pulmonary (Turlej et al, 2001; Brazil et al, 2005; Lavoie-Lamoureux et al, 2012), gastrointestinal (Krista, 2012) and orthopaedic (Kim et al, 2003) diseases. Stimuli used were phorbol myristate acetate (PMA), zymosan activated serum (ZAS, a source of C5a), the bacterial product formyl-Met-Leu-Phe (fMLP), leukotriene B4 (LTB4), platelet activating factor (PAF), tumour necrosis factor α (TNF-α), lipopolysaccharide (LPS), dexamethasone (DEX) and phagocytosis of opsonised ovine erythrocytes

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