Effect of topically applied cyclosporin A on arachidonic acid (AA)- and tetradecanoylphorbol acetate (TPA)-induced dermal inflammation in mouse ear

Topical cyclosporin A (CsA) was compared with dexamethasone, indomethacin and phenidone in edema, increases in vascular permeability, eicosanoids and cell-influx induced by arachidonic acid (AA) and tetradecanoylphorbol acetate (TPA) in mouse ears. CsA ED(50) on AA-edema (7.7 micrograms/ear) was similar to dexamethasone and lower than indomethacin and phenidone. CsA ED(50) in TPA edema (21 micrograms/ear) was higher than dexamethasone and lower than indomethacin or phenidone. All drugs equally reduce the AA-induced increase in vascular permeability, but CsA and dexamethasone had more activity on TPA. AA-increase in vascular 6-keto-PGF1 alpha was reduced by dexamethasone, indomethacin and phenidone but not by CsA; only phenidone reduced LTB4. TPA-increase in 6-keto-PGF1 alpha was reduced by CsA and indomethacin while CsA, dexamethasone and phenidone decreased LTB4. CsA, indomethacin and phenidone, but not dexamethasone, suppressed AA-neutrophil influx. In TPA-ears all drugs produced similar reduction in neutrophil influx. CsA was shown to be a good topical anti-inflammatory drug.     

Dendritic orientation of thalamocortical projection neurons in the ventrobasal complex of macaques

The present study measured the production of eicosanoids in the gerbil brain during early reperfusion after either a 3-h unilateral carotid occlusion (UCO, model of focal ischemia) or a 10-min bilateral carotid occlusion (BCO, model of global ischemia). Arachidonic acid (AA) metabolites were examined to determine if pretreatment with the 21-aminosteroid lipid peroxidation inhibitor U-74006F (tirilazad mesylate) could influence postreperfusion synthesis of brain eicosanoids. In the 3-h UCO focal ischemia model, there was an early (5-min) postreperfusion elevation in brain levels of PGF2 alpha, TXB2 and LTC4 (P < 0.05 vs. sham for all three eicosanoids). LTB4 also rose but not significantly. On the other hand, PGE2 and 6-keto-PGF1 alpha tended to decrease during ischemia and at 5-min postreperfusion (P < 0.05 vs. sham for PGE2). Pretreatment with known neuroprotective doses of U-74006F in this model (10 mg/kg i.p. 10 min before and again immediately upon reperfusion) did not affect the increase in PGF2 alpha or TXB2 but significantly blunted the elevations in LTC4 and LTB4. The postreperfusion decrease in PGE2 was also attenuated. In the 10-min BCO global ischemia model, there was also an increase in each of the measured eicosanoids, except LTB4, at 5 min after reperfusion. Pretreatment with U-74006F (10 mg/kg i.p. 10 min before ischemia) selectively decreased the rise in LTC4 but did not significantly affect the other eicosanoids. In contrast, the antioxidant actually caused a significant enhancement of the postreperfusion increase in PGE2 vs. vehicle-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regulatory interactions between inducible nitric oxide synthase and eicosanoids in glomerular immune injury

In a rat model of glomerular immune injury induced by administration of anti-glomerular basement membrane antibody and resembling human rapidly progressive glomerulonephritis, we explored whether activation of inducible nitric oxide synthase (iNOS) regulates synthesis of eicosanoids originating from cyclooxygenation or lipoxygenation of arachidonic acid. At early stages (24 hr) of injury, inhibition of iNOS using the selective inhibitor L-N6-(1-iminoethyl) lysine (L-NIL) at doses sufficient to reduce urinary excretion of nitrate/nitrite, reduced glomerular synthesis of the prostaglandins PGE2 and PGI2, but had no effect on that of thromboxane A2 (TxA2). The syntheses of 5-hydroxyeicosatetraenoic acid (HETE), 15-HETE and leukotriene B4 (LTB4) were also reduced. That of 12-HETE remained unchanged. We also explored the effect of arachidonate cyclooxygenation and lipoxygenation eicosanoids on iNOS expression. Administration of the cyclooxygenase (COX) inhibitor, indomethacin, at doses sufficient to inhibit glomerular prostaglandin synthesis, increased iNOS mRNA levels in glomeruli. Administration of the 5-lipoxygenase (5-LO) inhibitor, MK-0591, at doses sufficient to inhibit glomerular LTB4 synthesis also increased iNOS mRNA. The effect of 5-LO inhibition on iNOS expression was more pronounced than that of COX inhibition. In nephritic animals given the iNOS inhibitor, L-NIL, or indomethacin proteinuria worsened. In those given the 5-lipoxygenase inhibitor there was no change in urine protein excretion. These observations point to regulatory interactions between the arachidonic acid and the L-arginine: NO pathways in glomerulonephritis. These interactions are of importance in considering antiinflammatory strategies based on inhibition of iNOS or of specific eicosanoids.     

Stimulation of prostaglandin biosynthesis mediates gastroprotective effect of rebamipide in rats

The concept that gastroprotection by agents such as mild irritants, antacids, or sucralfate is prostaglandin (PG)-mediated has been challenged recently. These agents do not reproducibly stimulate prostaglandin formation, and indomethacin does not effectively attenuate their protective potency. Rebamipide is a novel antiulcer compound. This study was designed to clarify whether eicosanoids contribute to the gastroprotective activity of the drug. In the rat stomach, rebamipide (100 and 500 mg/kg, intraperitoneally) slightly increased release of PGE2, 6-keto-PGF1 alpha, thromboxane B2, and the metabolite 15-keto-13,14-dihydro-PGE2 from mucosal fragments incubated ex vivo and significantly enhanced secretion of these products into the lumen, resulting in gastric juice eicosanoid levels exceeding those in controls several-fold. Mucosal formation of leukotriene (LT) C4 was not affected by rebamipide. Rebamipide caused substantial protection against gastric damage produced by ethanol, which was antagonized by pretreatment with indomethacin (0.1-5 mg/kg, subcutaneously). The dose-response relationship of indomethacin for inhibition of prostaglandin formation and rebamipide-induced protection correlated well and 5 mg/kg indomethacin completely prevented the protective effect of rebamipide. The results indicate that: (1) in contrast to most other protective agents, protection by rebamipide involves the endogenous prostaglandin system; (2) the increase in prostaglandin formation results from stimulation of biosynthesis, and not inhibition of degradation; (3) gastroprotection by rebamipide occurs despite increased thromboxane formation and is not associated with reduced generation of LTC4; and (4) determinations of gastric juice eicosanoids seem to be particularly useful to evaluate effects of agents increasing formation of cyclooxygenase products in the stomach.     

Differing profiles of prostaglandin formation inhibition between selective prostaglandin H synthase-2 inhibitors and conventional NSAIDs in inflammatory and non-inflammatory sites of the rat

The present study examined the inhibitory profiles of NS-398 and nimesulide against prostaglandin (PG) formation in inflammatory and non-inflammatory sites, and compared them with those of aspirin and indomethacin. In vitro, indomethacin inhibited PGH synthase (PGHS)-1 and PGHS-2 almost equally, while NS-398 and nimesulide inhibited only PGHS-2. NS-398 (1, 10 mg/kg) and nimesulide (3 mg/kg) slowed the rate of plasma exudation and thus the exudate accumulation in rat carrageenin-induced pleurisy. Aspirin (30, 100 mg/kg) and indomethacin (10 mg/kg) also reduced this rate. NS-398 and nimesulide reduced the PGE2 more potently than TXB2 and 6-keto-PGF1 alpha in the exudate. However, aspirin and indomethacin did not exhibit this selectivity. The levels of PGE2 correlated significantly with the plasma exudation rate. Moreover, nimesulide (3 mg/kg) did not affect PGE2 formation in rat stomachs injected with 1 M NaCl solution, while indomethacin (10 mg/kg) reduced it. Thus, NS-398 and nimesulide exhibit different inhibitory profiles from aspirin and indomethacin against PG formation. These results suggest that PGE2 may be produced by PGHS-2 in the inflammatory site, and may play a more prominent role than PGI2 in plasma exudation.     

Alteration of thromboxane A2/prostacyclin and their effect on spinal cord blood flow in experimental spinal cord injury in rats

In order to document the contribution of Thromboxane (TXA2) and Prostacyclin (PGI2) to the secondary damage following spinal cord injury (SCI) and their effects on spinal cord blood flow (SCBF), the alteration of SCBF, TXB2 and 6-keto-PGF1 alpha concentration in injury site (T13-L1) and adjacent cords (upper: T12, under: L2) were studied using a rat SCI model induced by Allen's weight drop method (50g-cm). The result showed that after SCI the SCBF in injury site significantly reduced during 1-2 hrs and reduced further during 4-8 hrs. The SCBF in adjacent cords also decreased during 4-8 hrs. TXB2 levels significantly increased at 1 hr and reached peak value at 4 hrs. The 6-keto-PGF1 alpha concentration also significantly increased at 1 hr and maintained that level for 24 hrs. The TXB2/6-keto-PGF1 alpha ratio was significantly elevated at 1 hr and reached its peak at 4 hrs after SCI, then gradually decreased to the preinjury level during 8-24 hrs. The negative correlation of SCBF with TXB2 concentration and TXB2/6-keto-PGF1 alpha ratio were appeared. The experimental results indicated that the imbalance of TXB2/6-keto-PGF1 alpha could be the main cause of microcirculatory disturbance and secondary damage in SCI.     

Increased production of eicosanoids, TXA2, PGI2 and LTC4 in experimental spinal cord injuries

Arachidonate metabolites have many kinds of bioactivities. Thromboxane A2 (TXA2) stimulates platelet aggregation and vasoconstriction, whereas prostaglandin I2 (PGI2) antagonises its activities. Thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) are determined in biological materials. Production of TXB2, 6-keto-PGF1 alpha and leukotriene C4 (LTC4), which have potent vascular permeability, was measured by radioimmunoassay in experimental spinal cord injured animals. TXB2 level in the rat spinal cord reached a peak concentration of 133.6 +/- 3.8 pmol/g cord, and 6-keto-PGF1 alpha increased to 26.2 +/- 11.7 pmol/g cord 5 minutes after the injury. There was good correlation between TXB2 production and vascular damage as monitored by fluorescein uptake. When OKY-046 ((E)-3-[4-(1-imidazolylmethyl) phenyl]-2-propenoic acid), which selectively inhibits TXA2 synthetase activity, was administered 10 minutes before injury, the increase in TXB2 production was inhibited by more than 80%, but the degree of vascular damage was reduced by only 40%. In the guinea pig spinal cord, LTC4 levels reached a peak concentration of 2.2 +/- 0.4 pmol/g cord 10 minutes after compression, while that of TXB2 reached 146.8 +/- 6.2 pmol/g cord. The increased production of TXB2 was correlated with the degree of compression injury while that of LTC4 production did not. These findings suggest that vasoactive eicosanoids, TXA2, PGI2 and LTC4, play important roles in secondary damage following spinal cord injury, although their roles may be different among species of animals.     

Eicosanoid synthesis by warm- and cold-acclimated American bullfrog (Rana catesbeiana) brain

Previous studies in bullfrogs have demonstrated the presence of leukotriene (LT)C4 binding sites in the brain. However, synthesis of eicosanoids by brain tissue has not been examined. Because prostaglandin (PG) synthesis differs in warm- and cold-acclimated bullfrog lung tissue, this study compared the synthesis of prostaglandins and leukotrienes in brains from warm-(22 degrees C) and cold-acclimated (5 degrees C) animals. Initial experiments determined that leukotriene and prostaglandin production rates were greatest during the initial 30 min time period. Therefore, tissues were incubated in Munsick's solution and gassed with 95% O2, 5% CO2 for 30 min. Media were analyzed by radioimmunoassay for LTC4, LTB4, PGE2, PGF2 alpha, TXB2, and 6-keto PGF1 alpha. In warm-acclimated bullfrog brains, production was as follows: LTC4 > PGE2 > 6-keto PGF1 alpha, thromboxane (TX)B2, LTB4, and PGF2 alpha. Brain tissues from cold-acclimated animals incubated at 22 degrees C produced significantly greater quantities of PGE2 and 6-keto PGF1 alpha than did brains from warm-acclimated animals. Stimulation of TXB2 levels was observed when the animal was stunned with a blow to the head prior to decapitation. Indomethacin, a cyclooxygenase inhibitor, decreased prostaglandin but not leukotriene synthesis. Epinephrine (4 x 10(-8) M), the amphibian sympathetic postganglionic neurotransmitter, stimulated leukotriene synthesis by brains from warm-acclimated bullfrogs, and the effect was blocked with the 5-lipoxygenase inhibitor MK-886 (5 x 10(-5) M). These results clearly indicate that the bullfrog brain synthesized both leukotrienes and prostaglandins. Further studies are necessary to determine their function in the amphibian central nervous system.     

Prostaglandins and thromboxanes in amniotic fluid during rivanol-induced abortion and labour

Abortion or delivery were induced by extra-amniotic instillation of Rivanol during the second trimester in twelve patients and during the third trimester in two patients with fetal death and one patient with fetal acrania. Serial sampling of amniotic fluid was performed through a transabdominal catheter and the levels of free arachidonic acid (AA), prostaglandin F2 alpha (PGF2 alpha), prostaglandin E2 (PGE2), 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane B2 (TXB2) were determined. The levels of AA, PGF2 alpha, PGE2, 6-keto-PGF1 alpha and TXB2 in amniotic fluid increased significantly during induction with the exception of AA in fetal death which was high and remained constant during induction. Furthermore, PGF2 alpha, 6-keto-PGF1 alpha and TXB2 were all significantly correlated to AA. These observations suggested that free AA is released during Rivanol-induction of abortion and labour giving an increased synthesis of PGF2 alpha, PGE2 prostacyclin and thromboxane A2 in the fetal membranes and the decidua but not in the fetus. This increase might be relevant for the initiation and progress of abortion and labour in these patients.     

Toxoplasma gondii alters eicosanoid release by human mononuclear phagocytes: role of leukotrienes in interferon gamma-induced antitoxoplasma activity

Toxoplasma gondii tachyzoites markedly alter the profile of eicosanoids released by human mononuclear phagocytes. Freshly isolated, 2-h adherent human monocytes release both cyclooxygenase (e.g., thromboxane [TX] B2, prostaglandin [PG] E2) and 5-lipoxygenase (e.g., leukotriene [LT] B4, LTC4) products of arachidonic acid metabolism after stimulation by the calcium ionophore A23187 or ingestion of opsonized zymosan particles or heat-killed T. gondii. However, after incubation with viable T. gondii, normal and chronic granulomatous disease monocytes release only the cyclooxygenase products TXB2 and PGE2 and fail to form LTB4, LTC4, or other 5-lipoxygenase products. Monocytes maintained in culture for 5 d lose this capacity to release TXB2 and PGE2 after incubation with T. gondii. T. gondii significantly inhibit calcium ionophore A23187-induced LTB4 release by monocyte-derived macrophages; heat-killed organisms do not affect this calcium ionophore A23187-induced release of LTB4. T. gondii-induced inhibition of LTB4 release by calcium ionophore A23187-stimulated monocyte-derived macrophage is reversed by interferon (IFN)-gamma treatment of the monolayers. LTB4 induced extensive damage to the cellular membranes and cytoplasmic contents of the organisms as observed by transmission electron microscopy. Exogenous LTB4 (10(-6) M) induced intracellular killing of ingested T. gondii by non-IFN-gamma-treated monocyte-derived macrophages. IFN-gamma-induced antitoxoplasma activity in monocyte-derived macrophages was inhibited by the selective 5-lipoxygenase inhibitor zileuton but not by the cyclooxygenase inhibitor indomethacin. These findings suggest a novel role for 5-lipoxygenase arachidonic acid products in human macrophage IFN-gamma-induced antitoxoplasma activity.     

Transient loss of prostaglandin synthetic capacity in rabbit iris-ciliary body following anterior chamber paracentesis

The trauma-induced acute ocular inflammatory response has been characterized by investigating the kinetics of blood-aqueous barrier (BAB) breakdown, prostaglandin (PG) accumulation in the aqueous humor, and cyclooxygenase (PGH synthase) activity of the iris-ciliary body (ICB) following paracentesis in the NZA rabbit. BAB breakdown was assessed by quantifying plasma protein extravasation into the anterior chamber. PGE2 and 6-keto-PGF(1alpha) concentrations in the aqueous humor were quantified by radioimmunoassay. The capacity of ICB tissue homogenates to generate eicosanoids from exogenously supplied [I-14C]-arachidonic acid was assessed radiometrically by HPLC. Paracentesis resulted in a rapid and dramatic increase in aqueous humor PGE2 concentrations. Within 10 minutes, PGE2 concentrations increased 937-fold, from 6.2+/-4.9 pg/ml to maximal concentrations of 5810+/-3829 pg/ml. PG synthesis was followed temporally by an increase in aqueous humor protein, with peak levels (53.1 mg/ml) achieved within 30 minutes post paracentesis. Both PGE2 and protein levels gradually declined to near baseline levels 48 hours after trauma. ICB homogenates from naive animals produced significant amounts of eicosanoids (total PG=2.95 nmol/ 10 min/100 mg tissue). HHT (12 hydroxy-heptadecatrienoic acid) was produced in the greatest quantity, followed by PGE2alpha, PGI2, and TXB2/ PGF2 . Notably, following paracentesis, eicosanoid synthesis by the isolated ICB was observed to diminish abruptly. Formation of all eicosanoids was uniformly reduced by approximately 40% five minutes following paracentesis, with an 81% decrease in synthetic activity at 15 minutes. Eicosanoid synthetic capacity was only restored to baseline 48 hours post paracentesis. These findings suggest that, following ocular trauma, temporal changes occur in ICB PG synthetic activity that may impact on the selection of an optimal dosing paradigm for efficacy testing of topically administered NSAIDs.     

Medication errors: the problem and its scope

OBJECTIVE AND DESIGN: In the present study, we investigated the role of mast cells in a model of polyacrylamide gel (PAG)-induced inflammation in mice. SUBJECTS: Balb/c mice and two strains of mast cell deficient mice (WBB6F1/J-W/Wv, WCB6F1/J-S1/S1d). TREATMENT: Various quantities of polyacrylamide gel (Bio-Gel P4) were injected subcutaneously in the backs of mice. METHODS: Five hours after the injection of PAG the animals were euthanized, the injection sites lavaged and levels of LTB4, PGE2, TNF alpha and cells were determined. RESULTS: Subcutaneous injection of PAG caused a time-dependent response characterized by the accumulation of inflammatory cells peaking at 10 h and the formation of LTB4, PGE2 and TNF alpha, peaking at 5 h. PAG injection into W/Wv or SL/SLd mice (mice lacking mast cells) resulted in an attenuated response, i.e. LTB4 levels were reduced by 60% and minimal cell influx was seen. The lack of mast cells caused about a 30% reduction in the levels of TNF alpha found. CONCLUSIONS: These data suggest that mast cells play a prominent role in the PMN influx, TNF alpha production and eicosanoid formation in the PAG-induced inflammatory response.     

Computer analysis of single neuron activity during conditioned feeding task

Human recombinant tumor necrosis factors alpha and beta (TNF-alpha and TNF-beta), at and above 1 ng/ml (approximately equal to 70 pM), caused a dose- and time-dependent enhancement of 45Ca release from neonatal mouse calvarial bones in vitro. In addition, TNF-alpha and TNF-beta (3-100 ng/ml) caused a dose-dependent stimulation of prostaglandin E2 (PGE2) formation in the calvarial bones. TNF-alpha also enhanced the biosynthesis of PGI2, as assessed by analysis of the stable breakdown product 6-keto-PGF1 alpha. The stimulatory actions of TNF-alpha and TNF-beta on PGE2 formation was maximal at 12 h. Indomethacin, flurbiprofen, and meclofenamic acid, three structurally unrelated nonsteroidal antiinflammatory drugs, abolished PGE2 biosynthesis induced by TNF-alpha and TNF-beta (100 ng/ml). The 45Ca release stimulated by TNF-alpha and TNF-beta (100 ng/ml), however, was only slightly reduced by indomethacin, flurbiprofen, and meclofenamic acid. The partial inhibitory effect of indomethacin on 45Ca release was seen over a wide range of TNF-alpha concentrations, without affecting the concentration producing half-maximal stimulatory response. TNF-alpha and TNF-beta (100 ng/ml) stimulated bone matrix breakdown, as assessed by analysis of the release of 3H from bone prelabeled with [3H]proline. Also, the stimulatory effect of TNF-alpha and TNF-beta on bone matrix degradation was partially reduced by indomethacin. Hydrocortisone (1 microM) and dexamethasone (0.1 microM) abolished TNF-alpha- and TNF-beta-induced production of PGE2. In contrast to the cyclooxygenase inhibitors, the corticosteroids did not affect the stimulatory action by the cytokines on 45Ca release.(ABSTRACT TRUNCATED AT 250 WORDS)     

The molecular and functional characterization of E2F-5 transcription factor

1. Endotoxaemia is associated with the expression of the inducible isoform of cyclo-oxygenase, cyclo-oxygenase-2 (COX-2), and an overproduction of arachidonic acid (AA) metabolites. The role of the AA metabolites generated by COX-2 in the circulatory failure and multiple organ dysfunction caused by endotoxin is unclear. Dexamethasone prevents the expression of COX-2 and exerts beneficial effects in animal models of shock. 2. Here we compare the effects of two inhibitors of COX-2 activity, namely NS-398 (5 mg kg(-1), i.p., n=7) and SC-58635 (3 mg kg(-1), i.p., n=9) with those of dexamethasone (3 mg kg(-1), i.p., n=9) on the circulatory failure and organ dysfunction caused by lipopolysaccharide (LPS, E. coli, 6 mg kg(-1), i.v., n=11) in the rat. 3. Endotoxaemia for 6 h caused hypotension, acute renal dysfunction, hepatocellular injury, pancreatic injury and an increase in the plasma levels of 6-keto-PGF1alpha (indicator of the induction of COX-2) and nitrite/nitrate (indicator of the induction of iNOS). 4. Pretreatment of rats with dexamethasone attenuated the hypotension, the renal dysfunction, the hepatocellular and pancreatic injury and the induction of COX-2 and iNOS caused by LPS. In contrast, inhibition of COX-2 activity with SC-58635 or NS-398 neither attenuated the circulatory failure nor the multiple organ failure caused by endotoxin. 5. Thus, the prevention of the circulatory failure and the multiple organ injury/dysfunction caused by dexamethasone in the rat is not due to inhibition of the activity of COX-2. Our results suggest that an enhanced formation of eicosanoids by COX-2 does not contribute to the development of organ injury and/or dysfunction in rats with endotoxaemia.     

Sulindac causes rapid regression of preexisting tumors in Min/+ mice independent of prostaglandin biosynthesis

Several lines of evidence strongly link prostaglandins (PGs) and leukotrienes (LTs) to cancer of the intestine. Several studies have reported a 40-50% reduction in mortality from colorectal cancer in individuals who routinely consume nonsteroidal anti-inflammatory drugs, possibly by inhibiting cyclooxygenase activity. However, the role of eicosanoids in this process is still unclear. The heterozygote Min/+ mouse model, like patients with familial adenomatous polyposis, carries a nonsense mutation in the adenomatous polyposis coli (APC) gene that results in the spontaneous development of intestinal adenomas (100% incidence). This study investigated the association between eicosanoid biosynthesis, intestinal tumor load, and the chemotherapeutic effect of the nonsteroidal anti-inflammatory drug sulindac during early and preexisting phases of tumor growth and development as well as residual effects after drug withdrawal. Administration of sulindac (320 ppm) to Min/+ mice reduced the tumor number by 95% but did not alter the levels of PGE2 and LTB4 in intestinal tissues. Increasing PGE2 and LTB4 levels by 44% with dietary arachidonic acid supplementation had no effect on tumor number or size. When sulindac was added to the arachidonic acid-supplemented diet, tumor number was reduced by 82%, whereas eicosanoid levels remained elevated. In Min/+ mice with established tumors, treatment with sulindac for 4 days reduced tumor number by 75%, and continual administration of sulindac was necessary to maintain a reduced tumor load. In summary, alterations in eicosanoid formation were not correlated with tumor number or size in the Min/+ mouse model; thus, the antitumor effect of sulindac seems to be PG independent.     

Dietary monounsaturated n-3 and n-6 long-chain polyunsaturated fatty acids affect cellular antioxidant defense system in rats with experimental ulcerative colitis induced by trinitrobenzene sulfonic acid

The intrarectal administration of trinitrobenzene sulfonic acid in rats induces ulcerative colitis, which results in histological alterations of colonic mucosa, severe modification of the cellular antioxidant defense system, and enhanced production of inflammatory eicosanoids. This study evaluated the influence of different dietary fatty acids, i.e., monounsaturated, n-3, and n-3 + n-6 polyunsaturated fatty acids, on the recovery of the colonic mucosa histological pattern, the cellular antioxidant defense system of colon, and PGE2 and LTB4 colonic mucosa contents in a model of ulcerative colitis induced by intrarectal administration of trinitrobenzene sulfonic acid. Administration of dietary n-3 polyunsaturated fatty acids led to a minimum stenosis score, a higher histological recovery, lower colon alkaline phosphatase and gamma-glutamyltranspeptidase activities, and lower mucosal levels of PGE2 and LTB4 compared with the other two experimental groups. However, glutathione transferase, glutathione reductase, glutathione peroxidase, and catalase activities were lower in the group treated with n-3 polyunsaturated fatty acids than in the groups fed with either the monounsaturated or the n-6 + n-3 polyunsaturated enriched diet. We conclude that n-3 polyunsaturated fatty acids can be administered to prevent inflammation in ulcerative colitis, but they cause a decrease in the colonic antioxidant defense system, promoting oxidative injury at the site of inflammation.     

Renal tubular transport of prostaglandins: inhibition by probenecid and indomethacin

With use of the Sperber technique in chickens, labeled prostaglandin E2 and F2alpha were infused and resulted in renal tubular excretion of the label into the urine. A labeled metabolite, 12,14-dihydro,15-keto-PGF2alpha, was infused exogenously and this label was also excreted by active tubular transport. Tubular excretion of the label from PGE2, PGF2alpha, and 13,14-dihydro,15-keto-PGF2alpha was inhibited by probenecid, indomethacin, and PAH. The PAH was 10 times weaker as an inhibitor than probenecid and indomethacin. These results indicate that the prostaglandins are actively transported across the renal tubule by the classic anionic transport system which transports PAH. Since the transport of the prostaglandins is blocked by nonsteroidal anti-inflammatory agents such as indomethacin, the anti-inflammatory action of indomethacin may be produced not only by the inhibition of prostaglandin synthesis but also by restriction of the distribution of endogenous prostaglnadins. Thin-layer chromatography of an ethyl acetate extract of urine collected during infusion of [3H]PGF2alpha revealed three discrete radioactive peaks, one of which corresponded to authentic PGF2alpha. This signified tubular excretion of PGF2alpha. One metabolite in the ethyl acetate extract was found to be of renal origin.     

The effect of dexamethasone on CRH and prostanoid production from human term placenta

The human placenta at term produces large quantities of corticotropin releasing hormone (CRH) and prostanoids. These hormones play an important role in the maintenance of pregnancy, and the initiation and progress of labor; yet little is known of factors affecting their regulation and the interrelationship of CRH and prostanoid production. In these studies we have investigated the effect of dexamethasone on the production of CRH and prostanoids from fresh human term placental tissues. The basal release of prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), thromboxane B2 (TxB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) from human term placental explants increased from the fifth hour in culture, while the release of 13,14-dihydro-15-keto-PGF2 alpha (PGFM) was not significantly changed during this period. The addition of dexamethasone (10(-8) M) to the perifusing medium resulted in a rapid and dramatic inhibition of PGE2, PGF2 alpha, PGFM, TxB2 and 6-keto-PGF1 alpha release. On the other hand, CRH release was not significantly changed throughout the seven hours of incubation with dexamethasone. These data demonstrate that glucocorticoids at physiologic concentrations can inhibit human term placental prostanoid production, and thus glucocorticoid production may play an important role in the physiological regulation of placental prostanoid production in the human placenta. However, dexamethasone did not alter CRH release, demonstrating that the inhibition of placental prostanoids by dexamethasone is not a CRH mediated event.     

Prostaglandin synthesis by cumulus-oocyte complexes: effects on in vitro fertilization in mice

Cumulus-oocyte complexes, obtained from superovulated Balb/C virgin female mice, released to the incubation media significant amounts of PGE1, PGE2 and PGF2 alpha, as estimated by bioassay. Fertilization rates in vitro decreased sharply when cumulus-oocyte complexes were treated with indomethacin (10(-6) M) and then inseminated with 5000 sperm per oocyte. In order to explore if the reduced prostaglandin (PG) concentration was responsible for diminished fertilization rates, PGE1, PGE2 and PGF2 alpha (10(-9) M) were added to the fertilization media of treated oocytes. PGE1 and PGE2 but not PGF2 alpha returned fertilization rates to control levels. Besides, PGE1 (10(-9) M) enhanced fertilization rates with reduced sperm numbers (1000 sperm per oocyte) of untreated cumulus-oocyte complexes. In conclusion, PG synthesis and release of mouse cumulus-oocyte complexes affects fertilization in vitro, and it is suggested that PGs of the E series modulate sperm function at the moment of fertilization.     

Increased LTB4 metabolites and PGD2 in BAL fluid after methacholine challenge in asthmatic subjects

The bronchoconstrictor potency of inhaled methacholine is widely used to assess airway responsiveness. However, evidence has accumulated that methacholine inhalation challenge may lead to an inflammatory response in the lower respiratory tract. We therefore compared cellular, leukotriene and prostanoid profiles in bronchoalveolar lavages (BAL) obtained five hours after methacholine challenge to control lavages without prior challenge. Eight subjects with asymptomatic to mild bronchial asthma and nine nonatopic healthy controls were enrolled in the study. Without prior challenge, the percentage of BAL eosinophils was higher in the asthmatic subjects ((mean +/- SD), 1.1 +/- 0.9%) than in the control subjects (0.1 +/- 0.1%. Leukotriene B4 (LTB4), and its omega-oxidation products (20-OH-LTB4 and 20-COOH-LTB4) were the only leukotrienes detectable in the baseline BAL fluids in five of the eight asthmatic patients. After methacholine challenge, no change in BAL cell profile occurred, but in the asthmatic patients, the total amounts of LTB4 and its omega-oxidation products rose from 0.52 +/- 0.50 ng.ml-1 (pre-challenge) to 1.55 +/- 1.32 ng.ml-1 (post-challenge), and prostaglandin D2 (PGD2) rose from 49.1 +/- 15.7 (pre-challenge) to 94.4 +/- 25.4 pg.ml-1 (post-challenge), with no change in 6-keto-PGF1 alpha, thromboxane B2 (TXB2), and prostaglandins F2 alpha and E2 (PGF2 alpha and PGE2). In the healthy controls, no consistent change in BAL cell profile and mediators occurred after methacholine provocation. We conclude that inhaled methacholine stimulates LTB4 and PGD2 release in asthmatics, but not in healthy controls, without affecting the number of inflammatory cells in BAL fluid.