Differential Effects of Pyrazinamide and Clofibrate on Gene Expression of Rat Hepatic a-Amino-b-Carboxymuconate-e-Semialdehyde Decarboxylase, a Key Enzyme of the Tryptophan-NAD Pathway

Abstract

Hepatic α-amino-β-carboxymuconate-e-semialdehyde decarboxylase (ACMSD) [EC4.1.1.45] plays a key role in regulating NAD biosynthesis from tryptophan. The aim of this study was to evaluate the ACMSD mRNA expression after pyrazinamide or peroxisome proliferators ingestion. When rats were fed a control (pyrazinamide- and clofibrate-free) diet, 1% pyrazinamide- or 0.24% clofibrate-containing diets for 8 days, hepatic ACMSD activity and mRNA in rats consuming the clofibrate-containing diet was strongly suppressed, as compared with those fed the control and pyrazinamide diet. Pyrazinamide suppressed liver and kidney ACMSD activities, but did not affect ACMSD mRNA. Blood NAD was increased in the clofibrate and pyrazinamide groups. Shifting from the control diet to a clofibrate diet suppressed ACMSD mRNA strongly at day 1 and continued through day 4. However ACMSD activity decreased gradually. In rats fed with several kinds of peroxisome-proliferator-containing diets such as phthalate ester, bezafibrate, Wy-14,643, 2-(-4-chlorophenoxy) propionic acid, or dehydroisoandrosterone for 8 days, hepatic ACMSD mRNA was drastically decreased by all the peroxisome proliferators. These results suggest that the transcription level of hepatic ACMSD is modulated by peroxisome proliferators, and the fluctuation of the hepatic ACMSD mRNA expression was followed by that of the ACMSD activity. However, pyrazinamide does not affect the transcription level of hepatic ACMSD.