Effect of L-tryptophan supplementation on eosinophils and eotaxin in guinea pigs

Eosinophilia Myalgia Syndrome is a hypereosinophilic disorder that appears to result from the ingestion of the dietary supplement L-tryptophan by susc eptible individuals. It is unclear if this disease results from tryptophan, contaminants found in tryptophan, individual predisposition (such as immun e status and allergies), or some combination of effects. To evaluate effect s of L-tryptophan on eosinophil migration, guinea pigs were compared with o r without supplemental tryptophan (0.4 g/kg/day), with or without immune se nsitization, and with or without immune challenge. Eosinophil counts were o btained from bone marrow, blood, lung, and bronchial alveolar lavage fluid (BAL), Lung cells were obtained to measure eotaxin concentrations in supern ates and lysates with or without antigen and calcium ionophore challenge us ing direct ELISA. Skin biopsies were taken from both non-injected and antig en injection sites. The tryptophan supplemented, antigen-sensitized/antigen -challenged guinea pigs showed a significant decrease in blood eosinophils, compared to control (cellulose) supplemented antigen-sensitized/antigen-ch allenged guinea pigs [(0.086 +/- 0.023) x 10(6) vs (0.147 +/- 0.021) x 10(6 ) eosinophils/ml recovered, respectively] with a significant increase in BA L eosinophils [(0.052 +/- 0.008)x 10(6) vs (0.033 +/- 0.005) x 10(6) eosino phils/ml recovered, respectively]. Unchallenged lung cell lysates from tryp tophan-supplemented guinea pigs contained significantly less eotaxin compar ed to cellulose-supplemented guinea pigs regardless of whether they were se nsitized (0.006 +/- 0.002 vs 0.027 +/- 0.008 ng/10(6) cells, respectively). No differences were observed in skin biopsies between cellulose and trypto phan groups. These results suggest that L-tryptophan-supplemented guinea pi gs have altered eotaxin regulation, a potential mechanism by which human ov erconsumption of tryptophan dietary supplements could lead to hypereosinoph ilic disorders in susceptible individuals.