Effect of human recombinant interleukin-I alpha on release of prostacyclin from human endothelial cells

Incubation of human recombinant IL-1 alpha (hrIL-1 alpha) with cultured human endothelial cells induced a dose- and time-dependent increase in the release of prostacyclin (PGI2). Above a dose of hrIL-1 alpha 0.05 units/ml and following a variable lag phase of between 2 and 4 h, PGI2 release (measured as the stable hydrolysis product 6-keto-prostaglandin F1 alpha) was detected in the culture supernatant and levels continued to rise throughout a 48-h incubation. The release of PGI2 required the continued presence of hrIL-1 alpha, did not demonstrate tachyphylaxis and was not reduced by pre-incubation with the protein synthesis inhibitors cycloheximide, tunicamycin and actinomycin or by the calmodulin antagonist trifluoroperazine. The relationship of these results to ultraviolet radiation induced erythema is discussed.