15-HETE-substituted diglycerides selectively regulate PKC isotypes in human tracheal epithelial cells

Area of Science:

• Cell Biology
• Biochemistry
• Respiratory Medicine

Background:

• Human tracheal epithelial (TE) cells incorporate 15-hydroxyeicosatetraenoic acid (15-HETE), a lipoxygenase product, into phosphatidylinositol (PI).
• The functional significance of this lipid modification in TE cells remains largely unexplored.

Purpose of the Study:

• To investigate the generation of 15-HETE-substituted diglycerides (DGs) from 15-HETE-PI.
• To determine if these 15-HETE-DGs modulate protein kinase C (PKC) isotype activity in human TE cells.

Main Methods:

• Primary human TE cells were incubated with radiolabeled 15-HETE and stimulated with platelet-activating factor (PAF).
• Lipid products, including DGs and phospholipids, were analyzed using chromatography.
• PKC isotype expression and activity were assessed via Western blotting and in vitro assays.

Main Results:

• PAF stimulation mobilized radiolabel from PI, leading to the transient increase of 15-HETE-DGs.
• Cell-generated 15-HETE-DGs selectively activated PKC-alpha and inhibited PKC-alpha, -delta, -betaI, and -betaII activation by diacylglycerol.
• Multiple PKC isotypes (alpha, betaI, betaII, delta, epsilon, zeta) were detected in human TE cells.

Conclusions:

• 15-HETE-DGs are generated in response to receptor-mediated signaling in human TE cells.
• These lipids can modulate the activity of various PKC isotypes.
• This suggests an intracellular autocrine signaling role for 15-HETE in human airway epithelium.