Ketoconazole attenuates radiation-induction of tumor necrosis factor.
OBJECTIVE
Previous work has demonstrated that inhibitors of phospholipase A2 attenuate ionizing radiation induced arachidonic acid production, protein kinase C activation and prevent subsequent induction of the tumor necrosis factor gene. Because arachidonic acid contributes to radiation-induced tumor necrosis factor expression, we analyzed the effects of agents which alter arachidonate metabolism on the regulation of this gene.


METHODS
Phospholipase A2 inhibitors quinicrine, bromphenyl bromide, and pentoxyfylline or the inhibitor of lipoxygenase (ketoconazole) or the inhibitor of cyclooxygenase (indomethacin) were added to cell culture 1 h prior to irradiation.


RESULTS
Radiation-induced tumor necrosis factor gene expression was attenuated by each of the phospholipase A2 inhibitors (quinicrine, bromphenyl bromide, and pentoxyfylline). Furthermore, ketoconazole attenuated X ray induced tumor necrosis factor gene expression. Conversely, indomethacin enhanced tumor necrosis factor expression following irradiation.


CONCLUSIONS
The finding that radiation-induced tumor necrosis factor gene expression was attenuated by ketoconazole suggests that the lipoxygenase pathway participates in signal transduction preceding tumor necrosis factor induction. Enhancement of tumor necrosis factor expression by indomethacin following irradiation suggests that prostaglandins produced by cyclooxygenase act as negative regulators of tumor necrosis factor expression. Inhibitors of tumor necrosis factor induction ameliorate acute and subacute sequelae of radiotherapy. We propose therefore, that ketoconazole may reduce acute radiation sequelae such as mucositis and esophagitis through a reduction in tumor necrosis factor induction or inhibition of phospholipase A2 in addition to its antifungal activity.
Department of Radiation and Cellular Oncology, University of Chicago, IL 60637.
D E
DE
Hallahan
S
S
Virudachalam
D W
DW
Kufe
R R
RR
Weichselbaum
D016718:Arachidonic Acid / Q000378:metabolism; D015152:Blotting, Northern; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects / Q000528:radiation effects; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects / Q000528:radiation effects*; D016758:Genes, jun / Q000528:radiation effects; D006801:Humans; D007654:Ketoconazole / Q000494:pharmacology*; D007951:Leukemia, Myeloid / Q000235:genetics / Q000378:metabolism; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D010741:Phospholipases A / Q000037:antagonists & inhibitors; D054467:Phospholipases A2; D015398:Signal Transduction / Q000502:physiology / Q000528:radiation effects; D014407:Tumor Cells, Cultured / Q000528:radiation effects; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000235:genetics*
D016861:Cyclooxygenase Inhibitors; D018076:DNA, Complementary; D016859:Lipoxygenase Inhibitors; D014409:Tumor Necrosis Factor-alpha; D016718:Arachidonic Acid; D010741:Phospholipases A; D054467:Phospholipases A2; D007654:Ketoconazole