Protein kinase C inhibitors stimulate arachidonic and docosahexaenoic acids release from uterine stromal cells through a Ca²⁺‐independent pathway

Abstract

The mechanisms underlying arachidonic acid (AA) release by uterine stromal (U sss ) cells were studied. Stimulation of AA release by calcium ionophore and PMA are inhibited by various PKC inhibitors and by calcium deprivation. These results suggest the involvement of an AA-specific cPLA P as the release of docosahexaenoic acid (DHA) from prelabelled cells is much lower than the release of AA. The results also show a more original stimulation of AA and DHA release induced by PKC inhibitors, which is insensitive to calcium deprivation. This stimulation is not due to acyltransferase inhibition, suggesting the participation of a Ca 2+ -independent PLA P (iPLA P ). However, iPLA P activity measured in U sss cells is inhibited by the specific iPLA P inhibitor, BEL, and is not stimulated by PKC inhibitors, in contrast with the AA and DHA release. It seems therefore that this iPLA P cannot be involved in this mechanism. The participation of another iPLA P , BEL-insensitive, is discussed.z 1998 Federation of European Biochemical Societies.

Molecular Circuits of Resolution: Formation and Actions of Resolvins and Protectins

“…We recorded the exudate volume at 2 h after inflammation (0.47 Ϯ 0.02 ml) and estimated that the exudate levels of unesterified DHA, EPA, and AA were 141, 172, and 218 nM, respectively, and may reflect stimulated release of EPA and DHA from lipid storage sites. The early involvement of iPLA 2 , a calcium-insensitive phospholipase A 2 that can release DHA (33), in AA release was recently demonstrated in acute pleural inflammation (34). In this respect, we found via proteomic analysis that S100A9, a known AA-binding protein (35), was present in the exudate within 2 h after initiation of inflammation and reached maximal at the onset of R i , paralleling the PMN infiltration time course (Figs.…”

Hydrogen Peroxide Activation of Ca2+-Independent Phospholipase A2 in Uterine Stromal Cells

“…Moreover, preincubation of cells with 50 M BEL for 30 min, a very effective concentration to inhibit iPLA 2 activity (Table 2), caused a significant decreased release of [ (Table 1). This is consistent with previous results suggesting the participation of a BEL-insensitive iPLA 2 to this mechanism (17). The presence of both BEL-sensitive and -insensitive iPLA 2, demonstrated in bovine brain (28,29), has still to be formally established in U III cells and the regulatory mechanism of these enzymes by PKC should be clarified.…”

“…Indeed, enhanced basal and H 2 O 2 responses were observed after exposure to AA-COCF 3 (ϩ65% and ϩ56%, respectively, Table 1 (Fig. 1, right panel), arguing against the involvement of cPLA 2 , as this enzyme hardly releases DHA compared to AA (17,26).…”

“…In other cell systems, the mechanism of oxidant-induced AA release appears to be independent of Ca 2ϩ , resulting either from the activation of an iPLA 2 (12)(13)(14) or the inhibition of AA esterification into phospholipids (15,16). Since rat uterine stromal cell in culture (U III cells) possess different PLA 2 including secretory PLA 2 , iPLA 2 , and cPLA 2 (17)(18)(19), it was of interest to investigate the ability of H 2 O 2 to stimulate AA release from these cells and to identify the target. We found that H 2 O 2 -induced AA release was independent of intracellular Ca 2ϩ concentration and was not inhibited by cPLA 2 inhibitors, nor by PKC inhibitors or by PKC down-regulation.…”

Involvement of calcium‐independent phospholipase A2 in uterine stromal cell phospholipid remodelling

“…Recent studies from our group have shown that a Ca 2+ ‐independent PLA 2 enzyme is responsible for basal release of AA and docosahexaenoic acid (DHA) in unstimulated rat uterine stromal (U III ) cells [30]. We also found a specific pattern for AA and DHA distribution within phospholipid classes of these cells [31].…”