HYDROXYNONENAL, A COMPONENT OF CLASTOGENIC FACTORS

Exposure of human lymphocyte cultures to superoxide generated by the xanthine-xanthine oxidase (X-XO) system, resulted in formation of a clastogenic factor (CF), as expected from previous work (refs. 13,14). We speculated that arachidonic acid (AA). the major polyunsaturated fatty acid of biological membranes, was oxidized via the cyclooxygenase-lipoxygenase pathways or nonenzymatically by oxygen free radicals in the culture medium to products with clastogenic properties. In the present study, we analyzed CF for AA-derived products and tested corresponding commercial standards for their clastogenic properties. The results show that prostaglandins, thromboxane, and H(P)ETEs were not increased in supernatants from X-XO treated cultures compared to untreated cultures. Synthetic H(P)ETEs added to the medium of lymphocyte cultures were only slightly or not clastogenic. In contrast hereto, the degradation product 4-hydroxynonenal was found in 50% of CF samples, while it was absent in all 43 control samples. The kinetics of detectability in the culture medium was similar to that of CF. Also, the clastogenic effect of synthetic 4-hydroxynonenal at concentrations as low as 0.1-mu-M suggested that this aldehyde, known for its genotoxic effects. was a clastogenic component of CF. The indirect action mechanisms of 4-hydroxynonenal via inactivation of functional SH groups in DNA polymerases, may explain why chromatid-type damage is predominant in lymphocytes exposed to CF in the Go-G1 phase of the cell cycle. This particularly was already stressed 20 years ago in the first observations of radiation-induced CF. However, 4-hydroxynonenal is not the only clastogenic component of CF. Clastogenic activity was distributed over several fractions, when the eluant was tested mL per mL in the cytogenetic test system. This additional clastogenic material needs further study.