Incorporation of α‐linolenic acid and linoleic acid into human respiratory epithelial cell lines

Abstract

Animal and human studies designed to examine the effects of alpha-linolenic acid (ALA) and linoleic acid (LA) supplementation on the fatty acid composition of plasma and tissues have demonstrated a marked difference in incorporation into phospholipids of these 18-carbon precursors of the long-chain polyunsaturates. Whereas tissue phospholipid levels are linearly related to dietary ALA and LA, the levels of tissue LA can be 10-fold higher than tissue ALA even when dietary levels are equivalent. There is some dispute whether this disparity is due to ALA being more rapidly metabolized to its products or substantially oxidized by the liver, or whether LA but not ALA is readily incorporated into cellular phospholipids. We examined the level of incorporation of polyunsaturated fatty acids into human respiratory epithelial cell lines (A549, 16HBE) by determining the dose-dependent incorporation of ALA and LA as free fatty acid (5-150 microg FFA/mL). Cell membrane phospholipid ALA and LA were both increased up to approximately 20-30% total fatty acids, with a concomitant decrease predominantly in monounsaturated membrane fatty acids, before significant toxicity was observed (50 microg/mL). Our data support the concept that rather than any inherent inability by human cells to incorporate ALA into membrane phospholipids, the lack of ALA content in human and animal tissues in vivo is due to the rapid metabolism or oxidation of this fatty acid in the liver.

Polyunsaturated fatty acids regulate cytokine and prostaglandin E2 production by respiratory cells in response to mast cell mediators

“…The degree to which each of the FFA, excluding CLA, was incorporated into the A549 cells has been reported previously (11,12). As with all other FFA used in this project, each CLA isomer was readily incorporated dose-dependently into the cell membranes of the A549 respiratory epithelial cells.…”

“…Each of the CLA isomers was incorporated proportionally to the content of the FFA mixture, resulting in a majority of 9-cis,11-trans CLA (~45%) and 10-trans,12-cis CLA (~35%) with the remaining isomers making up the final 20% of the total CLA increase. The incorporation of each of the FA-ALA, LA, OA, EPA, AA, DHA, and CLA-into the membranes of A549 cells at maximum incorporation (50 µg/mL FFA; 20-25% total phospholipids) (11,12) resulted in a significant decrease in the production of IL-8 when compared with approximately 50% maximum incorporation (10 µg/mL FFA) (Fig. 3B).…”

“…1) (Nu-Chek-Prep Inc., Elysian, MN), or oleic acid (OA; 18:1n-9) (ICN Pharmaceuticals Inc., Costa Mesa, CA) as FFA solubilized in 100% ethanol. These FA concentrations result in approximately 50% incorporation and maximal incorporation, as described previously (11,12). Briefly, incorporation of FFA was determined in separate triplicate experiments.…”

“…Mast cells are one of the primary contributors to this via release of pre-formed histamine, tryptase, and chymase, as well as by producing cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-4, and IL-5. These mast cell products are responsible for increasing vascular permeability, Th2 lymphocyte development, and eosinophil attraction leading to bronchoconstriction; and the upregulation of a number of secondary inflammatory and chemotactic products including PGE 2 , IL-1β, TNF-α, IL-8, and regulation on activation, normal T cell-expressed and -secreted (RANTES). This study used a model developed in our laboratory (11,12) of in vitro FA manipulation in a respiratory cell line (A549) to examine the hypothesis that changes in membrane PUFA would significantly alter the production of inflammatory mediators in response to mediators of allergic disease. We examined the effect of manipulation of membrane phospholipid on the production of cytokines (IL-1β, TNF-α, IL-8, RANTES) and PGE 2 by respiratory epithelial cells in response to stimulation by mast cell mediators of allergic disease (histamine, TNF-α, IL-4, IL-5).…”

Modulation of respiratory syncytial virus‐induced prostaglandin E2 production by n−3 long‐chain polyunsaturated fatty acids in human respiratory epithelium

“…Cellular lipids were extracted using the method described by Broekhuyse (12). The phospholipid fraction was separated via TLC, the lipids were transesterified, and the FAME were separated and quantified as described previously (13). Statistical analysis.…”