Glutamine prevents late-phase anaphylaxis via MAPK phosphatase 1-dependent cytosolic phospholipase A₂ deactivation

Background: Cytosolic phospholipase A₂ (cPLA₂) plays a key role in the development of late-phase anaphylaxis. L-Glutamine (Gln), a nonessential amino acid, has anti-inflammatory activity via inhibiting cPLA₂. Methods: We used a penicillin-induced murine model of anaphylaxis, and late-phase anaphylaxis was quantified by measuring the increase in the hematocrit (Ht) value. Various inhibitors, small interfering RNA, and knockout mice were used in inhibition experiments. Phosphorylation and protein expression of cPLA₂, ERK, and MAPK phosphatase 1 (MKP-1) were detected by Western blotting. Results: Leukotriene (LT) B₄ was found to be another potent inducer of late-phase anaphylaxis besides the known mediator platelet-activating-factor (PAF). Gln efficiently prevented late-phase anaphylaxis when it was administered up to 3 h after challenge injection via inhibiting cPLA₂. Inhibition studies indicated that p38 MAPK was the major upstream regulator of cPLA₂. Gln dephosphorylated p38 and cPLA₂ via up-regulating the negative regulator of p38 MAPK, i.e., MKP-1 protein. MKP-1 blockade abrogated all the effects of Gln. Conclusion: Of the cPLA₂ metabolites, PAF and LTB₄ play a key role in the development of late-phase anaphylaxis, and Gln prevents the reaction via MKP-1-dependent deactivation of cPLA₂.