ω-Hydroxylation Activith toward leukotriene B₄ and Polyunsaturated Fatty Acids in the Human Hepatoblastoma Cell Line, HepG2, and Human Lung Adenocarcinoma Cell Line, A549

Abstract

The addition of glucose to the culture medium of HepG2 or A549 cells for 22h caused a dose-dependent increase in leukotriene B₄ ω-hydroxylation activity in the homogenate. The addition of genistein to the culture medium of HepG2 or A 549 cells for 22h caused a dose-dependent decrease in the activity, although the number of living cells was not influenced by the addition of genistein. The inhibition by genistein was reversed by removal of genistein from the culture medium in 22h. The specific leukotriene B₄ ω-hydroxylation activity was high in the nuclear envelope fraction of HepG2 or A 549 cells, and a large portion of the activity was concentrated in the nuclear envelope fraction. In the nuclear envelope fraction, leukotriene B₄ ω-hydroxylation activity was accompanied by high polyunsaturated fatty acid ω-hydroxylation activity. The apparent K_m values for arachidonic acid and leukotriene B₄ in the fractions of HepG2 or A 549 cells were 25 and 50μM, or 22 and 66μM, respectively. The V_max values were 222 and 104 pmol/min/mg protein, or 175 and 370 pmol/min/mg protein, respectively. NADPH-dependent ω-hydroxyla-tion of LTB₄ in the nuclear envelope fraction of HepG2 or A 549 cells was strongly inhibited by metyrapone and CO. The expression of cytochrome P 450 4F2 mRNAs was detected in HepG2 and A 549 cells, and thus the arachidonic acid and leukotriene B₄ ω-hydroxylation activities in the nuclear envelope fractions of HepG2 and A 549 cells are likely due to cytochrome P 450 4F2.