Ahmed M U, Hazeki K, Hazeki O, Katada T, Ui M
Ui Laboratory, Institute of Physical and Chemical Research, Wako-shi, Japan.
J Biol Chem. 1995 Oct 6;270(40):23816-22. doi: 10.1074/jbc.270.40.23816.
Superoxide anion and arachidonic acid were produced in guinea pig neutrophils in response to a chemotactic peptide formyl-methionyl-leucyl-phenylalanine (fMLP). Both responses were markedly, but the former response to a phorbol ester was not at all, inhibited when the cellular cAMP level was raised by prostaglandin E1 combined with a cAMP phosphodiesterase inhibitor. Increasing cAMP was also inhibitory to fMLP-induced activation of phosphatidylinositol (PI) 3-kinase and Ca2+ influx without any effect on the cation mobilization from intracellular stores. The fMLP-induced respiratory burst was abolished when PI 3-kinase was inhibited by wortmannin or LY294002, but was not affected when Ca2+ influx was inhibited. On the contrary, fMLP released arachidonic acid from the cells treated with the PI 3-kinase inhibitors as well as from non-treated cells, but it did not so when cellular Ca2+ uptake was prevented. The chemotactic peptide activated PI 3-kinase even in cells in which the receptor-mediated intracellular Ca2+ mobilization and respiratory burst were both abolished by exposure of the cells to a permeable Ca(2+)-chelating agent. Thus, stimulation of fMLP receptors gave rise to dual effects, activation of PI 3-kinase and intracellular Ca2+ mobilization; both effects were necessary for the fMLP-induced respiratory burst. Increasing cellular cAMP inhibited the respiratory burst and arachidonic acid release as a result of the inhibitions of PI 3-kinase and Ca2+ influx, respectively, in fMLP-treated neutrophils.
豚鼠嗜中性粒细胞在受到趋化肽甲酰甲硫氨酰亮氨酰苯丙氨酸（fMLP）刺激时会产生超氧阴离子和花生四烯酸。当用前列腺素E1联合环磷酸腺苷（cAMP）磷酸二酯酶抑制剂提高细胞内cAMP水平时，这两种反应均受到显著抑制，但前一种对佛波酯的反应则完全不受影响。增加cAMP对fMLP诱导的磷脂酰肌醇（PI）3激酶激活和Ca2+内流也有抑制作用，而对细胞内储存阳离子的动员没有任何影响。当用渥曼青霉素或LY294002抑制PI 3激酶时，fMLP诱导的呼吸爆发被消除，但当Ca2+内流受到抑制时则不受影响。相反，fMLP能从经PI 3激酶抑制剂处理的细胞以及未处理的细胞中释放花生四烯酸，但当细胞Ca2+摄取被阻止时则不会如此。即使在细胞通过暴露于可渗透的Ca(2+)螯合剂而使受体介导的细胞内Ca2+动员和呼吸爆发均被消除的情况下，趋化肽仍能激活PI 3激酶。因此，fMLP受体的刺激产生了双重作用，即激活PI 3激酶和细胞内Ca2+动员；这两种作用对于fMLP诱导的呼吸爆发都是必需的。增加细胞内cAMP分别通过抑制fMLP处理的嗜中性粒细胞中的PI 3激酶和Ca2+内流，从而抑制了呼吸爆发和花生四烯酸释放。
