The proatherosclerotic function of indoleamine 2, 3-dioxygenase 1 in the developmental stage of atherosclerosis.

The discrepancy of indoleamine 2, 3-dioxygenase 1 (IDO1) function in atherosclerosis has been noted. Compared to the protective effect of IDO1 against established atherogenesis, the role of IDO1 in the developmental process of atherosclerosis is still unclear. Here, the expression patterns and activities of IDO1 and its isoenzyme tryptophan 2,3-dioxygenase (TDO) in aortas and blood samples of patients with atherosclerosis were investigated. IDO1 and TDO were colocalized with CD3-positive lymphocytes and CD68-positive macrophages in atherosclerotic lesions. The expression and activity of IDO1 and TDO increased with the grade of the histological classification in early atherosclerosis (grade I, II), but the increase did not continue in advanced atherosclerosis (grade III). Treatment of THP-1 macrophages (THP-M) with oxidized low-density lipoprotein (oxLDL) induced the expression of IDO1 via the PI3K/Akt/NF-κB pathway, indicating the potential function of IDO1 in foam cells. Before and after treatment with oxLDL on THP-M, IFN-γ-induced IDO1 exhibited different degrees of promotion on foaming, inflammatory factor production and cell apoptosis. Finally, we found that the IDO1 inhibitor 1-methyl-tryptophan could elevate the high-density lipoprotein cholesterol level in serum and reduce the area of the aortic atherosclerotic lesions in high-fat diet-fed ApoE-/- mice. Our study indicated that IDO1 played a complicated and unfixed role in the entire process of atherogenesis, despite the atheroprotective role in established atherosclerosis. IDO1 also had proatherosclerotic functions in the developmental stages of atherosclerosis. Modulation of IDO1 could be a good method for alleviating atherosclerosis.

Tryptophan 2,3-dioxygenase inhibitory activities of tryptanthrin derivatives.

Tryptophan 2,3-dioxygenase (TDO) is becoming a promising therapeutic target due to its involvement in cancer and neurodegenerative diseases. Development of efficient TDO inhibitors is a prime strategy in disease treatment. However, the lack of a TDO inhibitor bioassay system slows the progress of TDO inhibitor research. Herein, an active recombinant human TDO (hTDO) was prepared under optimal expression conditions, an enzymatic assay was optimized, and two cellular assays of TDO activity were developed. Then, the potential TDO inhibitory activities of nine tryptanthrin derivatives (5a-5i) were evaluated, and the inhibitory constants (Ki), enzymatic and cellular half maximal inhibitory concentrations (IC50) were measured, and the type of inhibition was determined. The tryptanthrins had various levels of TDO inhibitory activities; tryptanthrins with a substituent at 8-position had stronger inhibitory activities than the other derivatives. Moreover, most of the compounds, except 5g and 5h, exhibited better inhibitory activities than the previously reported TDO inhibitor LM10. Furthermore, the molecular docking study of compounds 5c and 5d revealed that the O atom of the tryptanthrin ring is directed toward the heme iron (Fe) of hTDO via strong coordination interactions. These findings suggest that tryptanthrin and its derivatives have the potential to be developed as promising molecules for TDO-related target therapy.