Modulation of colony stimulating factor-induced murine myeloid colony formation by S-peptido-lipoxygenase products

Prompted by the observation that the selective blockade of lipoxygenase pathway by known inhibitors of this pathway inhibited the colony stimulating factor (CSF)-induced colony formation in both mouse and human marrow cells and the fact that this inhibitory effect could be reversed by a crude total lipoxygenase extract from an incubation of rat peritoneal neutrophils and arachidonic acid, we investigated which of the two major classes of lipoxygenase products, mono- and dihydroxy fatty acids (5S-hydroxyeicosatetraenoic acid and 5S-, 12R-dihydroxyeicosatetraenoic acid) and the S-peptidohydroxy fatty acids (leukotrienes C4 and D4), is involved in the modulation of CSF-induced colony formation by mouse marrow cells. Data from incubations with synthetic lipoxygenase products revealed that (a) the culture of mouse marrow cells in the presence of varying amounts of purified CSF-I (Mia PaCa 2) with a low concentration (5 micrograms/ml) of nordihydroguaretic acid consistently suppressed CSF-induced colony formation by approximately 40-50%. This concentration of nordihydroguaretic acid selectively inhibits only the lipoxygenase pathway; (b) additions of two S-peptido-hydroxy fatty acids [5S-hydroxy-6R-S-glutathionyl-7,9,11,14-(E,E,Z,Z)-eicosatetraenoic acid and 5S-hydroxy-6R-S-cysteinglycyl-7,9,11,14-(E,E,Z,Z)-eicosatetraenoic acid] to these partially suppressed colonies restored the CSF-induced colony formation to control levels in a dose-dependent manner; and (c) additions of two mono- and dihydroxy acids, 5S-hydroxyeicosatetraenoic acid and 5S-12R-dihydroxyeicosatetraenoic acid [5S, 12R-dihydroxy-6,8,10,14-(Z,E,E,Z)-eicosatetraenoic acid], failed to restore the nordihydroguaretic acid inhibited colony formation. These novel observations underscore the importance of these peptido-5-hydroxy fatty acids and the lipoxygenase pathway in the mechanism of CSF-induced colony formation in mouse marrow cells.