Tumor necrosis factor primes polymorphonucleotides (PMN) for receptor mediated stimulation (eg according to C5a or fMLP).

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Tumor necrosis factor primes polymorphonucleotides (PMN) for receptor mediated stimulation (eg according to C5a or fMLP), which might contribute to the pathogenesis of ARDS. We previously reported that primed PMN stimulated with fMLP have increased release of independent arachidonic acid (AA) and eicosanoids (5-HETE, [LTBsub4]) using PMN-labelled for 30 min with [sup.3]H-AA (which labels primarily PC and PI phospholipids). Thus, primed PMN could provide a source of the AA and [LTBsub4] which come to passs during ARDS. Many aspects of in the same state [i]or[/i] condition events remain uncertain, including the mass of AA releasd according to such cells and the specific phospholipase [A.sub.2] involved.

To determine the event of priming on receptor-stimulated AA release, we quantitated the mass of AA released by way of stimulation of resting or TNF-primed PMN using negative ion chemical ionization gas chromatography/mass spectrometry Resting PMN contained 6 to 18 pmol exempt AA per 2.5 x [10sup7] PMN which was doubled after fMLP stimulation. Primed PMN stimulated by the agency of fMLP, released 360 to 620 pmol AA, with peak AA occurring 1 to 2 min poststimulation, followed on a rapid decline. Thus, primed PMN release about 20-fold more AA than unprimed PMN after receptor stimulation.

The [PLA.sub.2](s) responsible for AA release in of that kind cells are unknown. The AA release from PMN is known to be [Ca.sup.++]-dependent. sum of two units [Ca.sup.++]-dependent [PLA.sub.2](s), defined in other small rooms are candidate enzymes for the activity in primed PMN: (1) an 85 kd cytosolic [PLA.sub.2] ([cPLA.sub.2]), and (2) a 14 kd clump 2 [PLA.sub.2] which is hided by some cells ([sPLA.sub.2]). Enzymatic assays could distinguish [sPLA.sub.2] and [cPLA.sub.2] activities by way of sensitivity to acid or dithiothreitol, and at sensitivity to anti-[sPLA.sub.2] and anti-[cPLA.sub.2] blocking antibodies. the one and the other [sPLA.sub.2] and [cPLA.sub.2] activities were not absent in PMN disrupted by [Nsub2] cavitation or on sonication. Both activities were approximately doubled on priming the PMN prior to disruption. Using several antibodies to probe Western obliterates we identified [PLA.sub.2] proteins of the one and the other the [sPLA.sub.2] and [cPLA.sub.2] symbols The presence of mRNA for the cytosolic [PLA.sub.2] in PMN was identified at reverse transcriptase PCR, indicating the PMN enzyme is homologous to the [cPLA.sub.2] clon from U937 macrophages. Although enzymatic assays and Western tarnishs indicated the presence of a clump 2 [PLA.sub.2], no [sPLA.sub.2] mRNA was detectable on RT-PCR in resting or primed PMN or in HL-60 small rooms (undifferentiated and at 3 and 5 days of differentiation), suggesting that the PMN enzyme is distinct from the known arrange 2 [sPLA.sub.2] identified in other enclosed spaces (platelets, liver cells, etc).

To subject of attention regulation of the [PLA.sub.2](s) activated in primed lonely dwellings we developed a model of PMN permeabilized with Staphylococcus [alpha] toxin to cogitation regulation of [PLA.sub.2]s with soft molecular weight cofactors.[1,2] Using lonely dwellings labelled with [sup.3]H-AA, we had previously set up that in unprimed, permeabilized PMN there was a G protein-dependent and [Ca.sup.++]-dependent activation of [PLA.sub.2] with release of [LTBsub4] (from 27 [+ or -] 075 percent of label in [LTBsub4] in directs to 6.1 [+ or -] 065 percent after activation with 10 [mu]M GTP[gamma]S, [Ca.sup.++] and 1 [mu]M fMLP) and that maximal [LTBsub4] release occurr in personality of 500 to 750 nM [Ca.sup.++], with no further increase at higher (05 to 1 mM) [Ca.sup.++] horizontals We have begun studies of mass of AA released according to such cells and have cause to growed a method of prime (with TNF) then permeabilize the confined apartments and then activate with GTP[gamma]S and [Ca.sup.++]. In like primed, permeabilized cells, nanomalor [Ca.sup.++] (500 to 750 nM) supported activation of [PLA.sub.2] to release 44 [+ or -] 18 pmole AA/2.5 x [10sup7] PMN in 2 min; however, this was no higher than the AA released from unprimed ascendency cells. In contrast, at higher (05 to 1 mM) [Ca.sup.++], primed permeabilized PMN released 185 [+ or -] 26 pmole AA (N = 3) The data are preliminary on the contrary suggest that optimal [PLA.sub.2] activity in primed PMN requires millimolar [Ca.sup.++], rather than the nanomolar [Ca.sup.++] typical of PMN cytosol. This would be more compatible with a part for a group 2 [PLA.sub.2] than for the cytosolic [PLA.sub.2], at least as the pair of these [PLA.sub.2]s have been characterized in other cells

Thus, there are pair [PLA.sub.2]s in PMN which may be differentially regulated and either of which may be primed through TNF. The [cPLA.sub.2] is the same as the enzyme in other small rooms but the specific [sPLA.sub.2] in PMN remains to be determined.

REFERENCES

[1] J Biol Chem 1992; 267:323

[2] J Biol Chem 1992; 267:25141

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