Novel role of group VIB Ca2+-independent phospholipase A2 gamma in leukocyte-endothelial cell interactions: An intravital microscopic study in rat mesentery

作者：Kojima Mitsuaki; Aiboshi Junichi^*; Shibata Masahiro; Kobayashi Tetsuyuki; Otomo Yasuhiro

来源：Journal of Trauma and Acute Care Surgery, 2015, 79(5): 782-789.

DOI：10.1097/TA.0000000000000845

• Calcium-independent phospholipase A(2)
• intravital microscopy
• (2)-integrin
• adherence
• rats

BACKGROUND Phospholipase A(2) (PLA(2)) is associated with a variety of inflammatory processes related to polymorphonuclear neutrophil (PMN)-endothelial cell interactions. However, the cellular and molecular mechanisms underlying the interactions and the causative isoform(s) of PLA(2) remain elusive. In addition, we recently showed that calcium-independent PLA(2) (iPLA(2)), but not cytosolic PLA(2) (cPLA(2)), is responsible for the cytotoxic functions of human PMN including respiratory bursts, degranulation, and chemotaxis. We therefore hypothesized that iPLA(2) is a prerequisite for the PMN recruitment cascade into the site of inflammation. The aim of this study was to elucidate the roles of the three major phospholipases A(2), iPLA(2), cPLA(2) and secretory PLA(2), in leukocyte rolling and adherence and in the surface expression of (2)-integrins in vivo and in vitro in response to well-defined stimuli.
METHODS Male Wistar rats were pretreated with PLA(2) inhibitors selective for iPLA(2), iPLA(2), cPLA(2), or secretory PLA(2). Leukocyte rolling/adherence in the mesenteric venules superfused with platelet-activating factor (PAF) were quantified by intravital microscopy. Furthermore, isolated human PMNs or whole blood were incubated with each PLA(2) inhibitor and then activated with formyl-methionyl-leucyl-phenylalanine (fMLP) or PAF. PMN adherence was assessed by counting cells bound to purified fibrinogen, and the surface expression of lymphocyte function-associated antigen 1 and macrophage antigen 1 (Mac-1) was measured by flow cytometry.
RESULTS The iPLA(2)-specific inhibitor almost completely inhibited the fMLP/PAF-induced leukocyte adherence in vivo and in vitro and also decreased the fMLP/PAF-stimulated surface expression of Mac-1 by 60% and 95%, respectively. In contrast, the other inhibitors did not affect these cellular functions.
CONCLUSION iPLA(2) seems to be involved in leukocyte/PMN adherence in vivo and in vitro as well as in the up-regulation of Mac-1 in vitro in response to PAF/fMLP. This enzyme is therefore likely to be a major regulator in the PMN recruitment cascade.

• 出版日期2015-11