Bradykinin-stimulated release of [3H]arachidonic acid from phospholipids of HSDM1C1 cells: comparison of diacyl phospholipids and plasmalogens as sources of prostaglandin precursors

Kallikrein-kinin system activation in Crohn's disease: differences in intestinal and systemic markers

OBJECTIVES

Observations in experimental models and in human ulcerative colitis suggest that activation of the kallikrein-kinin system plays a role in the pathogenesis of inflammatory bowel disease. The aim of this study was to assess activation of the plasma and tissue kallikrein-kinin system in Crohn's disease.

METHODS

We studied plasma inflammatory and contact system parameters in 36 patients with Crohn's disease and in 36 control subjects with noninflammatory GI diseases. We also obtained tissue samples from the involved intestine of 12 patients with Crohn's disease, and from normal peritumoral tissue (12 patients) and diverticulitis tissue (seven patients) as controls. Full-thickness sections were tested for intestinal tissue kallikrein reactivity with a specific antibody.

RESULTS

In Crohn's disease patients and controls, plasma levels of prekallikrein, factor XI, high molecular weight kininogen and its cleaved form were normal. Crohn's disease patients had significantly higher levels of antigen and functional Cl-inhibitor (+22%, +12%) than did controls (p = 0.005, p = 0.004). After surgical resection, antigen and functional Cl-inhibitor significantly decreased in Crohn's disease patients (-22%, -15%; p = 0.035, p = 0.006). Intestinal tissue kallikrein immunoreactivity was absent (75%) or weak (25%) in the goblet cells from Crohn's disease tissue sections but was normal in controls, with a highly significant difference in the staining score (p = 0.0001). Intestinal tissue kallikrein immunoreactivity in the interstitium was higher in Crohn's disease than in normal and diverticulitis samples (p = 0.0001 and p = 0.001, respectively).

CONCLUSIONS

Our observations suggest that intestinal tissue kallikrein is involved in the inflammatory process in Crohn's disease. The lack of contact system activation in peripheral blood might be related to the high plasma levels of Cl-inhibitor, the most important inhibitor of the contact system in the circulation.

Evidence that bradykinin stimulates renal prostaglandin synthesis by a mechanism distinct from that of other vasoactive substances

Arginine-vasopressin (AVP), angiotensin II (AII), and norepinephrine (NE) are known to stimulate prostaglandin (PG) synthesis in the intact rat kidney perfused with Tyrode's solution by a mechanism that requires intracellular Ca2+, while PG synthesis elicited by bradykinin (BK) is independent of Ca2+. To elucidate further the differences in the mechanism of action of BK and other vasoactive agents, in this preparation we have investigated the effect of caffeine, an agent known to interfere with the uptake and storage of Ca2+ in intracellular sites, on renal output of PGE2 and 6-keto-PGF1 alpha elicited by AVP, AII, NE, and BK; various combinations of the maximal doses of BK, AII, AVP, and NE on renal PG synthesis; and RHC 80267, an inhibitor of diglyceride and monoglyceride lipase, on the output of PGs produced by these vasoactive agents. Infusion of 1 mM caffeine inhibited PG output elicited by AVP, AII, and NE but not that caused by BK in the absence of extracellular Ca2+. Combined administration of maximal doses of BK (2.8 nmol) with that of AII (0.28 nmol), AVP (0.27 nmol), or NE (3.2 nmol) but not AVP and AII, NE and AVP, or NE and AII produced an additive effect on renal PG output in the presence or absence of Ca2+. The renal vasoconstrictor effect of AVP, AII, and NE produced in the presence of Ca2+ was not additive and remained unaltered when given together with BK.(ABSTRACT TRUNCATED AT 250 WORDS)

Bradykinin-induced cyclic AMP accumulation in mouse fibrosarcoma independent of prostaglandin E2 formation

The relationship between bradykinin (BK)-induced prostaglandin E2 (PGE2) and cyclic AMP syntheses in mouse fibrosarcoma cells (HSDM1C1) was investigated. Maximal BK-induced increases in cyclic AMP preceded increases in PGE2 production. PGE2 synthesis reached maximum at a much lower concentration of BK than cyclic AMP synthesis. Indomethacin completely inhibited BK-induced PGE2 production, but did not influence the cyclic AMP levels. Arachidonic acid in the medium induced PGE2 production in large quantities, but increased cyclic AMP accumulation only slightly. A high PGE2 concentration increased cyclic AMP levels only slightly. Theophylline increased basal and BK-mediated cyclic AMP levels, but did not affect PGE2 production at all. These results indicate that BK-evoked PGE2 and cyclic AMP syntheses in HSDM1C1 are not dependent upon each other.

Uptake and subcellular distribution of [3H]arachidonic acid in murine fibrosarcoma cells measured by electron microscope autoradiography

We have used quantitative electron microscope autoradiography to study uptake and distribution of arachidonate in HSDM1C1 murine fibrosarcoma cells and in EPU-1B, a mutant HSDM1C1 line defective in high affinity arachidonate uptake. Cells were labeled with [3H]arachidonate for 15 min, 40 min, 2 h, or 24 h. Label was found almost exclusively in cellular phospholipids; 92-96% of incorporated radioactivity was retained in cells during fixation and tissue processing. All incorporated radioactivity was found to be associated with cellular membranes. Endoplasmic reticulum (ER) contained the bulk of [3H]arachidonate at all time points in both cell types, while mitochondria, which contain a large portion of cellular membrane, were labeled slowly and to substantially lower specific activity. Plasma membrane (PM) also labeled slowly, achieving a specific activity only one-sixth that of ER at 15 min in HSDM1C1 cells (6% of total label) and one-third of ER in EPU-1B (10% of total label). Nuclear membrane (NM) exhibited the highest specific activity of labeling at 15 min in HSDM1C1 cells (twice that of ER) but was not preferentially labeled in the mutant. Over 24 h, PM label intensity increased to that of ER in both cell lines. However, NM activity diminished in HSDM1C1 cells by 24 h to a small fraction of that in ER. In response to agonists, HSDM1C1 cells release labeled arachidonate for eicosanoid synthesis most readily when they have been labeled for short times. Our results therefore suggest that NM and ER, sites of cyclooxygenase in murine fibroblasts, are probably sources for release of [3H]arachidonate, whereas PM and mitochondria are unlikely to be major sources of eicosanoid precursors.

Characterization of an arachidonic acid-selective acyl-CoA synthetase from murine T lymphocytes

Evidence is presented that the murine thymoma EL4 and cytotoxic T lymphocyte clones possess two distinct long-chain fatty acyl-CoA synthetase activities. One enzyme shows activity toward a broad spectrum of fatty acid substrates, similar to the long-chain fatty acyl-CoA synthetase from rat liver. The other enzyme is selective for arachidonic acid and related fatty acids. Fatty acid competition studies using EL4 microsomes demonstrate that [14C]palmitoyl-CoA synthesis (Km = 13 +/- 1 microM, Vmax = 7 +/- 1 nmol/mg per min) is inhibited by unlabeled palmitate, oleate, linoleate or linolenate (Ki = 15-25 microM) and weakly by arachidonate (Ki greater than 100 microM). Similar inhibition is observed for the activation of [14C]oleate (Km = 31 +/- 3 microM, Vmax = 6 +/- 2 nmol/mg per min). On the other hand, [14C]arachidonyl-CoA synthetase (Km = 15 +/- 3 microM, Vmax = 13 +/- 2 nmol/mg per min) is inhibited by unlabeled arachidonic acid (Ki = 20 microM) but not by unlabeled palmitate, oleate, linoleate and linolenate. The description of arachidonoyl-CoA synthetase in cytotoxic T lymphocyte clones represents the first example of a cell with little or no capacity to synthesize arachidonic acid metabolites, yet which possesses a selective esterification mechanism for the fatty acid. Studies on the specificity of the arachidonic acid-selective acyl-CoA synthetase utilized arachidonic acid metabolites and structurally related fatty acids and yielded two points of interest: (1) metabolism of arachidonic acid to monohydroxy fatty acids (HETEs) resulted in compounds with significantly decreased ability to be activated by the arachidonate-selective acyl-CoA synthetase; (2) arachidonate was a much better substrate than was 5,8,11-eicosatrienoic acid (Km = 41 microM), the fatty acid which accumulates during essential fatty acid deficiency. The possible role of an arachidonic acid-selective acyl-CoA synthetase in lymphocyte activation and as a homeostatic mechanism during essential fatty acid deficiency is discussed.

Synthesis of prostaglandin F by cultured human endometrial cells

Human endometrial cells were dispersed with collagenase and maintained in culture overnight. The synthesis of PGF by the dispersed cells incubated at 37 degrees C in serum-free medium was stimulated by estradiol (10(-7)M - 10(-5)M), histamine (5X10(-7)M - 5X10(-5)M), bradykinin (10(-6)M), phorbol myristate (PMA, 3X10(-8)M) and arachidonate (5X10(-6)M). Preincubation of the cells for 3 h with cortisol (5X10(-7)M - 5X10(-5)M), progesterone (10(-6)M) or mepacrine (10(-6)M - 2X10(-4)M) inhibited the response to histamine, bradykinin and PMA but not to arachidonate. Perfusion of the cultured cells in filtration chambers yielded similar results to those obtained in the incubation system but differences in the onset and duration of the responses to stimuli were found. In the perifusion system the responses to histamine and bradykinin were rapid and of short duration (peak response in less than 60 min) while the responses to PMA and arachidonate were of longer duration with a slower onset. We conclude that these observations using dispersed endometrial cells are consistent with previous work showing that histamine, bradykinin and PMA act by stimulating acylhydrolase activity, thereby liberating precursors such as arachidonic acid which are converted to prostaglandins by the cyclo-oxygenase complex.

Incorporation of fatty acids into phospholipids in L cells stimulated by antibody

Binding antibodies to surface membranes stimulated incorporation of fatty acids (FA) into phospholipids of L cells. Antibodies stimulated at least a 3.4-fold greater incorporation of arachidonic acid into phosphatidylinositol than into any other class of phospholipid when compared on a molar basis (p less than 0.003). This enhanced incorporation was selective, depending on the character of the FA, because antibodies stimulated the incorporation of arachidonic acid at least 2.4-fold more than oleic acid, palmitic acid or stearic acid (p less than 0.001). Surprisingly, an antibody-stimulated incorporation of palmitic acid into sphingomyelin (SM) was at least 2.2-fold greater than that into any other class of phospholipid (p less than 0.001) and the antibody-stimulated incorporation of palmitic acid into SM was at least 60-fold greater than that of arachidonic acid, stearic or oleic acid (p less than 0.001). Nontoxic doses of ethylenediamine tetraacetic acid (EDTA), dexamethasone, 4-bromophenacylbromide and indomethacin inhibited the antibody-stimulated incorporation of arachidonic acid into cellular phospholipids, principally phosphatidylinositol (PI), and similarly inhibited the antibody stimulation of DNA synthesis. We conclude that when antibody binds to surface antigens on L cells, a rapid and selective incorporation of fatty acids into certain cellular phospholipids occurs, possibly mediated by calcium-dependent phospholipases. Degradation products of arachidonic acid, i.e., prostaglandins, may be important in these antibody stimulation events, as well. These early changes in phospholipid metabolism may serve as an important signal or mechanism for the subsequent stimulation of DNA synthesis in L cells.

Bradykinin-stimulated differential incorporation of arachidonic acid into lipids of kidney cortex and medulla

We investigated bradykinin-induced changes in the turnover of arachidonate in renal lipids of the perfused rabbit kidney. Upon hormone stimulation, this cellular system undergoes only transient dynamic changes in arachidonic acid metabolism; no loss of bradykinin effect on arachidonate release and prostaglandin generation is shown upon repeated hormone administrations during 8-9 hr of perfusion. Ureter-obstructed rabbit kidneys were perfused for 5-6 hr and then saline or bradykinin in saline was administered, followed after 10 sec by pulse labelling with [14C]arachidonate. The pattern of distribution of [14C]arachidonate in lipid fractions of the cortex showed that bradykinin caused a 2 to 2.5-fold increase in the relative incorporation of arachidonic acid into phosphatidylinositol (PI), phosphatidic acid (PA), diglyceride (DG) and triglyceride (TG) fractions and a concomitant decrease in its incorporation into phosphatidylcholine (PC) and phosphatidylethanolamine (PE). In contrast, in the medulla hormone administration caused a marked increase of arachidonate incorporation into PI and PC, and a decrease in incorporation into PE, PA, DG and TG. This differential arachidonate labelling of cortical vs medullary lipids following bradykinin stimulation suggests that the hormone activates different lipolytic processes in cortex and medulla, and promotes hydrolysis of arachidonic acid from different phospholipid pools.

Bradykinin-stimulated electrolyte secretion in rabbit and guinea pig intestine. Involvement of arachidonic acid metabolites

Bradykinin (BK) increases short-circuit current (Isc) when added to the serosal side of rabbit or guinea pig ileum or rabbit colon. Significant effects on Isc are seen at concentrations as low as 10(-10) M. Anion substitution experiments and unidirectional 36Cl flux measurements indicate that this effect of BK on Isc is due to Cl secretion. The effect of BK on Isc can be partially blocked (60-70% inhibition) by cyclooxygenase inhibitors (indomethacin and/or naproxen) and completely blocked by the phospholipase inhibitor, mepacrine. The combined cyclooxygenase/lipoxygenase inhibitors BW 755 and eicosa-5,8,11,14-tetraynoic acid (ETYA) also completely block the effect of BK on Isc but the slow-reacting substance of anaphylaxis (SRS-A) antagonist FPL 55712 has no effect. None of the above inhibitors diminish the effect on Isc of other exogenously added secretory stimuli such as vasoactive intestinal peptide (VIP), theophylline, or prostaglandin E2 (PGE2). Prior desensitization of rabbit ileum to PGE2 blocks the effect on Isc of BK but not those of VIP or theophylline. Conversely, prior desensitization of rabbit ileum to BK greatly reduces the effect of PGE2 on Isc. BK also stimulates the synthesis of PGE2 in rabbit ileal and colonic mucosa and this effect can be blocked by prior addition of either indomethacin or mepacrine. These effects of BK are similar to those of exogenously added arachidonic acid (AA). AA also stimulates Cl secretion and increases PGE2 synthesis and its effect on Isc can be inhibited by prior desensitization to PGE2 or by prior addition of indomethacin. The above results indicate that BK stimulates active Cl secretion in both small and large intestine and suggest that this effect is due to the intracellular release of AA. Although the prostaglandins appear to be the major products of AA metabolism contributing to the secretory response, lipoxygenase products may also play a role.

Development and characterization of a tissue culture cell line with essential fatty acid deficiency

We have developed an essential fatty acid-deficient cell line from a parental cell line, HSDM1C1, which metabolizes arachidonic acid to prostaglandin E2 (PGE2). This cell line, designated EFD-1, is depleted of arachidonate, is unable to synthesize PGE2 in response to bradykinin, and has changes in fatty acid composition characteristic of tissues from animals with essential fatty acid deficiency. Within 15 min of repletion by arachidonate, the ability to synthesize PGE2 is restored. Linoleate also is able to restore PGE2 synthesis, indicating that deficient cells contain both the rate-limiting delta 6 desaturase enzyme and the delta 5 desaturase enzyme, which are required to form arachidonate. When parental cells are incubated in lipid-free medium, there is rapid induction of the ability to convert linoleate to arachidonate. Arachidonate prevents this induction, suggesting that icosanoid precursor availability controls the rate of arachidonate formation.

Bradykinin-stimulated prostaglandin E2 production by endothelial cells and its modulation by antiinflammatory compounds

Prostaglandin production was studied in cultures of pig aorta endothelial cells using radioimmunoassay, radiochromatography, and smooth muscle bioassay. PGE2 was produced in higher concentrations than other prostaglandins. Bradykinin produced a rapid dose-related stimulation of PGE2 production. These results provided the basis for establishment of a simplified test system for investigating new compounds which alter prostaglandin synthesis and might therefore affect inflammatory response. It was also observed that these endothelial cells do not metabolize prostaglandins via 15-hydroxyprostaglandin dehydrogenase.

Steady-state fluorescence polarization (FP) of 1,6-diphenyl-1,3,5-hexatriene (dph)-labelled platelets in the presence of bradykinin (bk)

Steady-state fluorescence polarization (FP) decreases, when 1,6-diphenyl-1,3,5-hextriene (dph) labelled platelets are exposed to bradykinin (bk). At pH 8, the dose-response curve is bell-shaped with an optimum bk effect at 10(-7) M. In contrast to the ricinoleic-acid ester of glycerin-polyethyleneglycol, cremophor EL (CEL), bk is no more effective when platelets are pretreated with 10(-5) M p-bromophenacylbromide (B phi B). These results suggest that platelets are target cells for the peptide bk, which induces an FP decrease indirectly by stimulating the release of non-saturated fatty acids in the platelet membrane.

Effect of incubation of guinea-pig taenia coli in potassium-free media on arachidonate release and lipid metabolism

We studied the effects of immersion of guinea-pig taenia coli strips in potassium-free media on arachidonate stores and other lipid fractions. Control studies obtained with the strips in Krebs solution showed that greater than 97% of arachidonate was found esterified in phospholipid with the following distribution: phosphatidylethanolamine greater than phosphatidylcholine greater than phosphatidylserine plus phosphatidylinositol. 30 min incubation of the strips with [3H]arachidonate complexed to albumin resulted in incorporation of this isotope into phospholipid and neutral lipid fractions, phosphatidylcholine greater than neutral lipid greater than phosphatidylserine plus phosphatidylinositol greater than phosphatidylethanolamine. 30 min incubations with 32PO4(2-)-resulted in an isotope incorporation into phospholipids, phosphatidylcholine greater than phosphatidylserine plus phosphatidylinositol greater than phosphatidylethanolamine. After 'loading' with [3H]arachidonate and 32P, placing the strips in potassium-free media caused the following: there was an increased release of [3H]arachidonate from the tissue into the bathing solution. [3H]Arachidonate and 32P radioactivity in phosphatidylinositol fell without a change in phosphatidylinositol content. [3H]Arachidonate and 32P radioactivity in other phospholipid fractions was unchanged. Arachidonate specific activity fell and arachidonate content increased in the phosphatidylserine plus phosphatidylinositol fraction. [3]Arachidonate in neutral lipid did not change significantly. We conclude that exposure of taenia coli to potassium-free media activates turnover of phosphatidylinositol, which results in release of arachidonate.