THI is a trace component present in the industrially produced food colorant caramel color III. It acts as an immunosuppressant by inhibiting the enzyme sphingosine 1-phosphate lyase (S1PL) which fragments S1P to hexadecenal and phosphoethanolamine. Administration of THI in drinking water to mice (50 µg/mL) resulted in decreased S1PL activity, increased S1P levels in lymphoid tissues and reduced egress of CD4+ and CD8+ T cells (lymphopenia).
References
1) J. T. Bagdanoff, et al. Inhibition of Sphingosine-1-phosphate Lyase for the Treatment of Autoimmune Disorders. J. Med. Chem. 2009, 52, 3941-3953. 2) G.F. Houben, et al. Effects of Ammonia Caramel and Tetrahydroxybutylimidazole on the Immune System of Rats. Arch. Toxicol., 1989, 13, 183-187. 3) S.R. Schwab, et al. ''Lymphocyte Sequestration Through S1P Lyase Inhibition and Disruption of S1P Gradients. Science 2005, 309, 1735-1739.
