Group I mGlu receptor stimulation inhibits activation-induced cell death of human T lymphocytes.
1. The effects of L-glutamate on activation-induced cell death (AICD) of human activated (1 microg ml(-1) phytohemagglutinin plus 2 U ml(-1) interleukin-2; 8 days) T lymphocytes were studied by measuring anti-CD3 monoclonal antibody (10 microg ml(-1); 18 h)-induced cell apoptosis (Annexin V and propidium iodide staining). 2. L-Glutamate (1 x 10(-8)-1 x 10(-4) M) significantly (P < or = 0.01) inhibited AICD in a concentration-dependent manner (EC50=6.3 x 10(-8) M; maximum inhibition 54.8+/-6.3% at 1 x 10(-6) M). 3. The L-glutamate inhibitory effect was pharmacologically characterized as mediated by group I mGlu receptors, since mGlu receptor agonists reproduced this effect. The EC50 values were: 3.2 x 10(-7) M for (1S,3R)-ACPD; 4.5 x 10(-8) M for quisqualate; 1.0 x 10(-6) M for (S)-3,5-DHPG; 2.0 x 10(-5) M for CHPG. 4. Group I mGlu receptor antagonists inhibited the effects of quisqualate 1.0 x 10(-6) M. The IC50 values calculated were: 8.7 x 10(-5), 4.3 x 10(-6) and 6.3 x 10(-7) M for AIDA, LY 367385 and MPEP, respectively. 5. L-Glutamate (1 x 10(-6) M; 18 h) significantly (P < or = 0.05) inhibited FasL expression (40.8+/-11.3%) (cytofluorimetric analysis), whereas it did not affect Fas signalling. 6. Expression of both mGlu1 and mGlu5 receptor mRNA by T lymphocytes and T-cell lines, as demonstrated by reverse transcriptase-PCR analysis, suggests that L-glutamate-mediated inhibition of AICD was exerted on T cells. 7. These data depict a novel role for L-glutamate in the regulation of the immune response through group I mGlu receptor-mediated mechanisms.
Chiocchetti
Annalisa
A
Interdisciplinary Research Center of Autoimmune Diseases, Department of Medical Sciences, Eastern Piedmont University, Via Solaroli, 17, 28100 Novara, Italy.
Miglio
Gianluca
G
Mesturini
Riccardo
R
Varsaldi
Federica
F
Mocellin
Marco
M
Orilieri
Elisabetta
E
Dianzani
Chiara
C
Fantozzi
Roberto
R
Dianzani
Umberto
U
Lombardi
Grazia
G
D017209:Apoptosis / Q000187:drug effects*; D001565:Benzoates / Q000494:pharmacology; D002478:Cells, Cultured; D053222:Fas Ligand Protein / Q000032:analysis; D018698:Glutamic Acid / Q000494:pharmacology*; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D008213:Lymphocyte Activation; D012333:RNA, Messenger / Q000032:analysis; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology*
D001565:Benzoates; D053222:Fas Ligand Protein; D012333:RNA, Messenger; D018094:Receptors, Metabotropic Glutamate; C104077:metabotropic glutamate receptor type 1; C079694:alpha-methyl-4-carboxyphenylglycine; D018698:Glutamic Acid; D005998:Glycine