Protein kinase C inhibition enhances platelet-activating factor-induced eicosanoid production in human eosinophils

Am J Respir Cell Mol Biol. 1998 Jan;18(1):136-44. doi: 10.1165/ajrcmb.18.1.2817.

Abstract

Previous investigations have suggested that protein kinase C (PKC) may regulate guinea pig eosinophil responses through a suppressive "negative feedback" mechanism. Using the selective PKC inhibitors bisindolylmaleimide I (Bis I, GF 109203X) and calphostin C, we examined the role of PKC in platelet-activating factor (PAF)-induced respiratory burst and generation of arachidonic acid metabolites in human peripheral blood eosinophils. Bis I inhibited PAF-induced generation of superoxide anion with substantially lower potency (geometric mean IC50 = 1.41 microM, 95% CI 0.94-2.11 microM) than it exhibited against responses to the phorbol esters 4-beta-phorbol 12-myristate 13-acetate (PMA; IC50 = 0.25 microM, 0.09-0.72 microM; P < 0.01) and 4-beta-phorbol 12,13-dibutyrate (IC50 = 0.48 microM, 0.20-1.14 microM; P < 0.05). The production of thromboxane (measured as TxB2) induced by 1 microM PAF was increased significantly by Bis I at concentrations of 1 microM (162 +/- 7.5% of control PAF response; P < 0.01) and 10 microM (194 +/- 17%; P < 0.001); TxB2 release induced by PMA was unaffected by concentrations of Bis I up to 1 microM and inhibited by 10 microM Bis I (48 +/- 11%; P < 0.05). Bis I (1 microM) significantly increased both thromboxane and leukotriene C4 (LTC4) production induced by 2 microM (P < 0.01 and P < 0.05, respectively) or 20 microM PAF (both P < 0.001). The actions of Bis I on PAF-stimulated thromboxane and leukotriene production were mimicked by a second PKC inhibitor, calphostin C, whereas the non-PKC-inhibitory analog, bisindolylmaleimide V, caused no enhancement of TxB2 or LTC4 production. The increase in intracellular free calcium induced by 1 microM PAF was heightened and prolonged in cells pre-treated with 1 microM Bis I or 1 microM calphostin C (peak increase, P < 0.05 for both drugs; level 60 s after addition of PAF, P < 0.001 and P < 0.05 for Bis I and calphostin C, respectively; time to return to 50% of peak, P < 0.05 for Bis I). We conclude that PKC inhibition causes augmentation of thromboxane and LTC4 production in PAF-stimulated human eosinophils despite suppressing respiratory burst activity, indicating that different signaling pathways predominate in these two responses and that PKC mediates a suppression of an early stage in an alternative pathway of activation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Arachidonic Acid / metabolism
  • Calcium / metabolism
  • Catalase / pharmacology
  • Eicosanoids / biosynthesis*
  • Enzyme Inhibitors / pharmacology*
  • Eosinophils / drug effects
  • Eosinophils / metabolism*
  • Female
  • Humans
  • Indoles / pharmacology
  • Leukotriene C4 / biosynthesis
  • Male
  • Maleimides / pharmacology
  • Naphthalenes / pharmacology
  • Phorbol 12,13-Dibutyrate / pharmacology
  • Platelet Activating Factor / pharmacology*
  • Protein Kinase C / antagonists & inhibitors*
  • Protein Kinase C / physiology
  • Respiratory Burst / drug effects
  • Superoxides / metabolism
  • Tetradecanoylphorbol Acetate / pharmacology
  • Thromboxane B2 / biosynthesis

Substances

  • Eicosanoids
  • Enzyme Inhibitors
  • Indoles
  • Maleimides
  • Naphthalenes
  • Platelet Activating Factor
  • Superoxides
  • Arachidonic Acid
  • Leukotriene C4
  • Phorbol 12,13-Dibutyrate
  • Thromboxane B2
  • Catalase
  • Protein Kinase C
  • calphostin C
  • bisindolylmaleimide
  • Tetradecanoylphorbol Acetate
  • Calcium