Condensed Tannin Promotes the Release of Arachidonic Acid from Rabbit Resident Alveolar Macrophages

Abstract

The condensed tannin present in cotton mill dust profoundly alters the functional capabilities of resident alveolar macrophages. Previous studies from this laboratory have shown that in vitro exposure of rabbit resident alveolar macrophages to condensed tannin significantly inhibits the ability of these cells to produce reactive oxygen intermediates or to ingest particles. In the present study, we demonstrate that condensed tannin also alters arachidonic acid (C20:4) metabolism in these cells. Exposure of rabbit resident alveolar macrophages to condensed tannin results in the time- and dose-dependent release of C20:4 from the membrane phospholipids. The release of C20:4 occurred only at tannin concentrations greater than 25 micrograms/ml and was maximal 90 min after the onset of exposure. The EC50 for release was 75 micrograms/ml. Exposure to 100 micrograms/ml tannin resulted in the release of 20 +/- 3% of the [14C]C20:4 incorporated in the cell membrane. In comparison, exposure to 160 micrograms/ml zymosan resulted in the release of 14 +/- 4% of the [14C]C20:4. For both tannin and zymosan, phosphatidylcholine and phosphatidylinositol were the principal sources of the released C20:4. Approximately 63% of the C20:4 released after zymosan stimulation was further metabolized, mainly via the cyclooxygenase pathway. The major metabolites were 6-keto-prostaglandin F1 alpha, prostaglandin F2 alpha, and prostaglandin E2. In contrast, only 24% of the C20:4 released by tannin was subsequently further metabolized. The metabolites formed were essentially evenly distributed between products of the cyclooxygenase pathway and the lipoxygenase pathway. Exposure of alveolar macrophages to 50 micrograms/ml tannin for 30 min reduced the ability of the cells to subsequently incorporate C20:4 by 50 to 70%. In contrast, exposure of the cells to 160 mg/ml zymosan for 30 min had only a minimal effect on the subsequent ability of these cells to incorporate C20:4. These results indicate that tannin promotes C20:4 release, at least in part, by inhibiting its reacylation back into phospholipids, a mechanism that differs from that of zymosan.

Candida albicans induces the release of inflammatory mediators from human peripheral blood monocytes

“…The adherent cells were cultured for two hours in mixed media containing 0.1% fatty acid free BSA and 0.1-0.2 #Ci/ml of [IgC]-AA (1.9 Bq/mmol, New England Nuclear, Boston, Massachusetts) at 37~ The cells were then washed with HBSS to remove free AA. Previous studies have demonstrated that incubation for two hours results in the incorporation of greater than 60% of the added AA [30].…”

“…have shown that the release of AA from mononuclear cells provides a reliable measure of eicosanoid metabolism in response to a variety of stimuli [11,30]. Monocytes were plated in 24-well tissue culture plates (316,000 cells/well), and incubated for one hour at 37 ~ The cells were subsequently washed with HBSS to remove nonadherent cells.…”

“…Control monocytes were incubated without any C. albicans. In parallel wells, monocytes were also stimulated with calcium ionophore A23187 (10 #M/ml) (Sigma Corp., St. Louis, Missouri), a well established stimulant of AA release [30]. The monocytes were cultured for 90 minutes at 37~ and the medium removed and centrifuged (1000 x g for 10 minutes) to pellet any nonadherent cells.…”

Preventive and curative effect of the methanolic extract of Ajuga iva on collagen induced arthritis in rats

“…[26] In fact, the phenolic compounds have been mentioned to exert an anti-inflammatory effect. [27][28] The variation of the weight of the rats constitutes a significant parameter. Effectively, a difference between the growth of the arthritic and normal rats was noted.…”

Mass determination of the fatty acids released from tannin‐stimulated rabbit alveolar macrophages

“…Several of the inflammatory mediators released following tannin inhalation suggested the involvement of alveolar macrophages (2). Subsequent in vitro studies have shown that condensed tannin can profoundly change the functional capacity of alveolar macrophages (3)(4)(5)(6)(7)(8).…”