Arachidonic Acid Metabolism in Cultured Mouse Keratinocytes

Abstract

We attempted to characterize the general features of arachidonate metabolism in cultured mouse keratinocytes. The cells labeled with [3H]arachidonate were stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA), ionophore A23187, and fetal bovine serum (FBS). Common to the three substances, phosphatidylinositol, phosphatidylethanolamine, and phosphatidylcholine almost equally served as sources of arachidonate liberated by the action of phospholipase A2. The stimulation of phospholipase A2 action was observed in the order of A23187 greater than FBS greater than TPA. When stimulated by TPA or A23187, the radioactivity released into the extracellular medium was mostly found in prostaglandin (PG) E2. Formation of other PGs and hydroxyeicosatetraenoate (HETE) was extremely limited. In the case of stimulation by FBS, however, the released radioactivity was mainly associated with non-converted arachidonate. FBS also inhibited the TPA- and A23187-induced conversion of arachidonate to PGE2. Phospholipid degradation induced by the three stimulators was similarly dependent on extracellular Ca2+. The stimulation by FBS and A23187 was suppressed by calmodulin antagonists, though the effect of A23187 was much more sensitive to the antagonists when compared to that of FBS. We observed more than additive effects of the three stimulators when tested together.

Anti-inflammatory Activity of Crude Extract and Fractions of Nectandra falcifolia Leaves

“…On the other hand, the edema of the ear induced by local application of croton oil involves the activation of phospholipase A 2 and, consequently, biosynthesis of prostaglandins and leucotriens. 27,28) From the data of this study, we cannot conclude clearly which pro-inflammatory mediator of agent is inhibited by the extract. Particularly in the pleurisy model utilized, although the extract did not reduce the concentration of total nitrate in the pleural exudates, we cannot discard the possibility that this mediator participates in the inflammatory response.…”

Differential Utilization of Linoleic and Arachidonic Acid by Cultured Human Keratinocytes

“…Thus it is possi ble that the increased incorporation into PL in lifted cultures reflects an increased eicosanoid synthesis and AA turnover. While both Punnonen et al [30] and Kondoh et al [31] observed relatively high incorporation of AA into PL (85 and 95% at 24 and 16 h, respec tively) they employed much lower concentra tions of AA.…”

Anti-inflammatory activity of the extract, fractions and amides from the leaves of Piper ovatum Vahl (Piperaceae)

“…The mechanism of croton oil-induced inflammation involves an increase in phospholipase A-2 activity (Kondoh et al, 1985;McColl et al, 1986), which in turn leads to the release of arachidonic acid and subsequent biosynthesis of leukotrienes and prostaglandins (Ashendel and Boutwell, 1979;Furstenberger and Marks, 1980), which also involves the lipooxygenase pathway. Arachidonic acid metabolites have been firmly shown to act as mediators of the inflammatory response via cyclooxygenase and lipooxygenase activity, and have therefore been a target for the development of therapeutic agents (Inoue et al, 1989).…”