Mannheimia haemolyticaleukotoxin-induced increase in leukotriene B₄production by bovine neutrophils is mediated by a sustained and excessive increase in intracellular calcium concentration

Abstract

Isolated bovine neutrophils were used to study the relationship between the duration and magnitude of the Mannheimia haemolytica leukotoxin-induced increase in intracellular calcium concentration and leukotriene B 4 synthesis. In contrast to recombinant human C 5a , which caused a transient, small increase in intracellular calcium concentration and no effects on leukotriene B 4 synthesis, exposure of neutrophils to leukotoxin resulted in a rapid, sustained, large increase in intracellular calcium concentration, followed by leukotriene B 4 synthesis. This leukotoxin-induced response was similar to those produced by the calcium ionophore, A23187, and phorbol myristate acetate, which also caused significant leukotriene B 4 production. Manipulation of the duration and magnitude of leukotoxin-and A23187-induced intracellular calcium concentration increase confirmed that a high and sustained intracellular calcium concentration was necessary to stimulate production of leukotriene B 4 , which is believed to play an important role in the pathogenesis of pulmonary M. haemolytica infection.

Store-operated calcium entry mediates intracellular alkalinization, ERK1/2, and Akt/PKB phosphorylation in bovine neutrophils

“…SOCE is considered a potential target for therapeutic interventions in inflammatory diseases [35], as PMN Ca 2ϩ influx is increased in some infectious diseases and inflammatory processes, i.e., bacterial pneumonia [35,36]. In other cellular responses, such as pH i changes, MAPK and PI-3K phosphorylation is activated simultaneously in neutrophils and contributes to the tissue injury [37][38][39].…”

P2Y1and Cysteinyl Leukotriene Receptors Mediate Purine and Cysteinyl Leukotriene Co-Release in Primary Cultures of Rat Microglia

“…4B (Fig. 5) It has been reported that glial cells can release ATP in both Ca't-dependent (14) and Ca't-independent (58) manner, and that calcium has a pivotal role in the biosynthetic production of leukotrienes (16). To examine the potential role of intracellular Ca (Fig.…”

Contribution of intracellular calcium stores to an increase in cytosolic calcium concentration induced byMannheimia haemolyticaleukotoxin

“…The present study con¢rmed that, in addition to in£ux of extracellular Ca 2þ , release of stored intracellular Ca 2þ via both ryanodine-and IP 3 -sensitive Ca 2þ channels contributes to LKT-induced increase in [Ca 2þ ] i . Previous studies have demonstrated that this high and sustained [Ca 2þ ] i is necessary to stimulate production of LTB 4 [8], which is correlated with development of acute, exudative M. haemolytica infection [3]. .…”

“…Furthermore, this reliance on extracellular Ca 2þ has been correlated with increased [Ca 2þ ] i , suggesting that LKT induces an in£ux of Ca 2þ across the plasma membrane. However, comparison between the e¡ects of various neutrophil activators, including LKT, A23187, and recombinant human C 5a , on the rate and degree of increase in [Ca 2þ ] i has indicated that the response to LKT cannot be explained entirely by in£ux of extracellular Ca 2þ across the plasma membrane, down a concentration gradient, because the rate at which [Ca 2þ ] i increases is too rapid to be explained by the ¢rst-order kinetics characteristic of di¡usional processes [8]. The present study con¢rmed that, in addition to in£ux of extracellular Ca 2þ , release of stored intracellular Ca 2þ via both ryanodine-and IP 3 -sensitive Ca 2þ channels contributes to LKT-induced increase in [Ca 2þ ] i .…”

“…A previous study concluded that increased cytosolic calcium concentration ([Ca 2þ ] i ) serves as a necessary signal transduction event in LKTinduced LTB 4 production and membrane damage [7], and that in£ux of extracellular Ca 2þ across the plasma membrane contributes to an increase in [Ca 2þ ] i in neutrophils exposed to LKT. However, comparison of LKT-induced e¡ects with those caused by other stimulators, including A23187, suggested that di¡usion of extracellular Ca 2þ down a concentration gradient does not fully explain the speci¢c pattern of LKT-induced [Ca 2þ ] i increase [8] and that release and re-uptake of Ca 2þ stored intracellularly may also be involved. Therefore, the speci¢c objective of this study was to assess the importance of intracellular Ca 2þ stores in increased [Ca 2þ ] i induced by LKT.…”