Lipid peroxidation and growth inhibition of human microvascular endothelial cells

Peroxidation products of polyunsaturated fatty acids may cause growth inhib ition of cells in culture. This study was carried out to elucidate to what extent peroxidation products may be found in growth media, with and without cells and albumin, using thiobarbituric acid-reactive substances (TBARS) a nd protein carbonyl groups as measures of peroxidation. The growth of human microvascular endothelial cells was studied as influenced by docosahexaeno ic (C22:6. Or - 3), arachidonic acid (C20:4, n - 6), and serum albumin. Cel l growth was strongly inhibited by the fatty acids, and the inhibition was related to the concentration of TBARS in the medium. Defatted albumin (0.5 g/100 nil) nullified the increase of TBARS in the medium and released the g rowth inhibition by the fatty acids. With polyunsaturated fatty acids (PUFA ) there was a time- and concentration-dependent increase in media TBARS, ob served both with and without cells, but the TBARS increase was somewhat gre ater in the presence of cells. Surprisingly, TBARS in cell-free media also increased somewhat upon increasing the albumin concentration from 0.5 to 5 g/100 nil, and the TBARS increase differed among various preparations of al bumin. Unexpectedly, the albumin that had not been defatted gave the lowest TBARS values. The amount of protein carbonyl groups did not differ among v arious albumin preparations. It is concluded that PUFA may autooxidize in m edia used for cell cultures, and thereby cause an unspecific growth inhibit ion, which can be prevented by a low albumin concentration. However, even d efatted albumin preparations may contain lipid peroxidation products, the c auses and implications of which remain to be elucidated.