Prostaglandin actions in established insect cell lines.

Prostaglandins (PGs) are oxygenated metabolites of arachidonic acid (AA) and two other C20 polyunsaturated fatty acids that serve as biochemical signals mediating physiological functions. We reported that PGs influence protein expression in insect cell lines, which prompted the question: do PGs influence cell proliferation or viability in insect cell lines? Here, we report on the outcomes of experiments designed to address the question in cell lines from three insect orders: Hemiptera (squash bug, Anasa tristis, BCIRL-AtE-CLG15A), Coleoptera (red flour beetle, Tribolium castaneum, BCIRL-TcA-CLG1), and Lepidoptera (tobacco budworm, Heliothis virescens, BCIRL-HvAM1). Treating the insect cell lines with PGA1, PGA2, or PGD2 led to dose-dependent reductions in cell numbers. All three cell lines were sensitive to PGA1 and PGA2 (IC50s = 9.9 to 26.9 μM) and were less sensitive to PGD2 (IC50s = 31.6 to 104.7 μM). PG treatments also led to cell death at higher concentrations, as seen in mammalian cell lines. PGE1, PGE2, and PGF2α treatments did not influence AtE-CLG15A or HvAM1 cell numbers at lower concentrations, but led to dose-related reductions in TcA-CLG1 cells at higher concentrations. Similar treatments with pharmaceutical inhibitors of PG biosynthesis also led to reduced cell numbers: MAFP (inhibits phospholipase A2), indomethacin (inhibits PG biosynthesis), and esculetin (inhibits lipoxygenase). Because these pharmaceuticals are used to relieve inflammation and other medical issues in human medicine, they are not toxic to animal cells. We infer PGs are necessary in optimal quantities for ongoing homeostatic functions in established cell lines; in quantities outside the optimal concentrations, PGs are deleterious.