Inflammatory effects of acetylglycerylether phosphorylcholine: vascular permeability increase and induction of pleurisy in rats

Roles for the kallikrein-kinin system in inflammatory exudation and pain: lessons from studies on kininogen-deficient rats

Roles for the kallikrein-kinin system in inflammation have been investigated extensively, and many reviews on this topic have been published during the 50 years since the discovery of bradykinin in 1949. Recent progress in the field has been remarkable with the help of experiments using gene-targetted transgenic or knockout mice, which have added further valuable information in addition to previous results obtained from pharmacological and biochemical studies using purified and isolated components of the system. Furthermore, much knowledge has been accumulated as a result of the development of various bradykinin agonists and antagonists. In this review, we focused on the data obtained from the kininogen-deficient rat, which is a natural mutant, and discuss the results in comparison with those from bradykinin receptor knockout mice. These data have clarified that endogenous bradykinin exerts a most important role in inflammatory exudation along with prostanoids, preferentially to histamine, serotonin, or neuropeptides. In inflammatory pain perception also, bradykinin produced in the local perivascular spaces stimulates polymodal pain receptors in conjunction with co-helpers such as prostanoids, vanilloids, and neuropeptides. These important roles are concluded based on consistent results obtained from experiments using several antagonists of bradykinin, kininogen-deficient rats, and bradykinin receptor knockout mice.

Anti-inflammatory and analgesic effects of paeonol in carrageenan-evoked thermal hyperalgesia

1. Paeonol was tested for its anti-inflammatory and analgesic effects in a rat model of carrageenan-evoked thermal hyperalgesia. The possible mechanisms involved in these effects were also investigated. 2. Pre- and post-treatment with paeonol (30, 50 or 100 mg kg(-1), i.p.) dose-dependently inhibited the carrageenan-evoked thermal hyperalgesia. 3. Treatment with paeonol dose-dependently inhibited tumour necrosis factor-alpha (TNF-alpha) and interleukin-lbeta (IL-1beta) formation, but enhanced IL-10 production in the rat paw exudates both at the early (1.5 h) and late phase (4 h) after carrageenan injection. However, inhibition of IL-6 formation by paeonol was only observed at the late phase. 4. Paeonol dose-dependently decreased the formation of prostaglandin E(2) (PGE(2)) in rat paw exudates with a greater inhibition at the late phase. However, inhibition of nitrate generation was observed only during the late phase (at 4 h after carrageenan injection), accompanied by an attenuation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein expression in paw tissue. 5. Elevated myeloperoxidase activity, an indicator of neutrophil infiltration, in carrageenan-injected paws was also dose-dependently reduced in paeonol-treated rats. 6. Our results suggest that the mechanisms by which paeonol exerts its anti-inflammatory and analgesic effects in this inflammatory model may be associated with decreased production of proinflammatory cytokines, NO and PGE(2) and increased production of IL-10, an anti-inflammatory cytokine, in carrageenan-injected rat paws. In addition, attenuation of the elevated iNOS and COX-2 protein expression as well as neutrophil infiltration in carrageenan-injected paws may also be involved in the beneficial effects of paeonol.

Regulation of TNFalpha and interleukin-10 production by prostaglandins I(2) and E(2): studies with prostaglandin receptor-deficient mice and prostaglandin E-receptor subtype-selective synthetic agonists

To know which receptors of prostaglandins are involved in the regulation of TNFalpha and interleukin 10 (IL-10) production, we examined the production of these cytokines in murine peritoneal macrophages stimulated with zymosan. The presence of PGE(2) or the PGI(2) analog carbacyclin in the medium reduced the TNFalpha production to one-half, whereas IL-10 production increased several fold; and indomethacin caused the reverse effects, suggesting that endogenous prostaglandins may have a regulatory effect on the cytokine production. Among prostaglandin E (EP) receptor-selective synthetic agonists, EP2 and EP4 agonists caused down-regulation of the zymosan-induced TNFalpha production, but up-regulation on the IL-10 production; while EP1 and EP3 agonists showed no effect. Macrophages harvested from prostaglandin I (IP) receptor-deficient mice showed the up- and down-regulatory effects on the cytokine production by the EP2 and EP4 agonists or PGE(2), but no effect was obtained by carbacyclin. On the contrary, macrophages from EP2-deficient mice showed the effect by PGE(2), carbacyclin, and the EP4 agonist, but not by the EP2 agonist; and the cells from EP4-deficient mice showed the effect by PGE(2), carbacyclin, and EP2 agonist, but not by the EP4 agonist. These functional effects of prostaglandins well accorded with the mRNA expression of TNFalpha and IL-10 when such expression was examined by the RT-PCR method. The peritoneal macrophages from normal mice expressed IP, EP2, and EP4 receptors, but not EP1 and EP3, when examined by RT-PCR. Thus the results suggest that PGI(2) and PGE(2) generated simultaneously with cytokines by macrophages treated with zymosan may influence the cytokine production through IP, EP2, and EP4 receptors.

[Inflammation-allergy and prostanoids. (1). Prostanoids in experimental inflammatory reaction]

It is known that prostaglandins (PGs) modify the inflammatory reaction in concert with other biologically active mediators. However, characteristics of these interactions or modulating actions have not yet been clarified well. Recently, the production of mice with specific receptor deficiencies by using the gene targeting procedure for PG receptors has accelerated elucidation of the roles of PGs through correlation of their phenotypes and experimental features. Here I discuss roles of PGs in experimental paw edema, the writhing reaction of a pain model, and regulation of cytokine production, as determined using some PG-receptor-deficient mice. From the experiment of carrageenin-induced paw edema in IP receptor-deficient mice, with an indomethacin or bradykinin antagonist, we conclude that bradykinin initially induces paw swelling and then stimulates the release PGI2, which in turn enhances the swelling with bradykinin. By comparing the writhing responses in IP-deficient and wild-type mice, we found that PGI2 is a main mediator for this pain reaction. However, in the LPS-pretreated mice, not only PGI2 but also other PGs produced by COX-2 may be involved in pain induction. Production of TNF alpha and IL-10 was modified with PGI2 or PGE2; the production of TNF alpha was down-regulated by the stimulation via IP-, EP2- or EP4 receptor, but that of IL-10 was up-regulated by these receptors, resulting in an anti-inflammatory effect.

Potentiation of the pro-inflammatory effects of bradykinin by inhibition of angiotensin-converting enzyme and aminopeptidase P in rat paws

The influence of some peptidase inhibitors on oedema and plasma extravasation induced by bradykinin and carrageenan in rat paw was evaluate. Bradykinin-induced oedema in normal rats was increased by o-phenanthroline (3.10(-2) M), by captopril (10(-6) M to 10(-4) M), by lisinopril (10(-6) M to 10(-4), or by lisinopril (10(-5) M) in combination with apstatin (8.10(-5) M or 1.4 10(-4) M). It was not modified by phosphoramidon (10(-6) M to 10(-5) M) and by diprotin A (10(-3) M). It was increased by mergepta at high concentrations (2.10(-4) M). Mergepta did not increase the potentiating effect of captopril. Carrageenan-oedema in normal rats was increased by captopril (10(-5) M), lisinopril (10(-5) M) and apstatin (1.4 10(-4) M. It was not modified by mergepta (10(-4) M), phosphoramidon (10 (-5) M) and diprotin A (109-3) M). Des-Arg1-bradykinin and Des-Arg9-bradykinin have low oedema-promoting effects. Captopril (10(-5) M) increased the effects of bradykinin but not those of carrageenan in kininogen-deficit Brown Norway rats. Angiotensin-converting enzyme and aminopeptidase P appear to be main kinin-inactivating enzymes in rat paws. Carboxypeptidase N, neutral endopeptidase 24.11 and dipeptidyl(amino)peptidase IV do not play a significant role in this inactivation.

The mediators involved in endotoxin-induced vascular permeability increase in the rat skin and their interactions

The injection of lipopolysaccharide (LPS) from E. Coli into the dorsal skin of rats caused a dose-dependent increase in vascular permeability as measured by the extravasation over a 40-min period of intravenously injected dye. This increase caused by LPS was attenuated by pretreatment with the bradykinin (BK) receptor antagonist HOE140, the selective platelet-activating factor (PAF) antagonist TCV309, and by combined treatment with mepyramine and methysergide. Combined treatment with HOE140 and TCV309 resulted in further suppression than that achieved with a single treatment alone. By the simultaneous pretreatment with all antagonists, the response was almost totally abolished. On the other hand, indomethacin also inhibited the response induced by LPS, but not those induced by BK and PAF itself. A small dose of BK or histamine synergistically potentiated the effect of PAF when simultaneously injected. These results suggest that BK, PAF, histamine/serotonin and prostaglandins are involved in the LPS-induced increase in vascular permeability, where PAF, in addition to its direct action, potentiates the response to BK and histamine, and prostaglandins potentiate the actions of other mediators without its direct action.

Collagenase-induced oedema in the rat paw and the kinin system

Collagenase (100 micrograms) induced a large plasma extravasation, during the first 15 min after its injection in rat paw, associated with the rapid development of oedema which subsided after 6 h. The extent of the oedema was similar in normal and kininogen-deficient rats. The swelling induced in normal rats was reduced by HOE 140 (D-Arg[Hyp3,Thi5,D-Tic7,Oic8]bradykinin), a bradykinin B2 receptor antagonist, and by three serine protease inhibitors, soybean trypsin inhibitor (SBTI), Leucaena leucocephala trypsin inhibitor 1 (LLTI-1) and Leucaena leucocephala trypsin inhibitor 2 (LLTI-2). These agents had no effect on the oedema induced in kininogen-deficient rats. The swelling was also reduced by methysergide, indomethacin, ketoprofen and methylprednisolone. It was increased by heparin, but it was not modified by mepyramine, WEB 2086 (3-[4-(2-chlorophenyl)-9-methyl-6H-thieno[3,2-f][1,2,4]-triazolo- [4,3-a][1,4]-diazepine-2-yl]-1-(4-morpholinyl)-1-propanone) and NG-nitro-L-arginine. In vitro, collagenase did not release kinins from rat plasma or from purified T-kininogen. LLTI-1 and LLTI-2 did not inhibit collagenase activity for one of its specific substrates. Kinins are thus involved in the development of collagenase oedema in normal rats. Their generation would be indirect following changes in matrix proteins in extravascular spaces. Nevertheless, kinins are not the decisive mediators of the swelling. Serotonin, possibly released from platelets, and prostanoids participate in the inflammatory process.

Platelet activating factor and the responses of rat isolated stomach strip to prostaglandin E2

The effect of platelet activating factor (PAF) on contractions evoked by acetylcholine, 5-hydroxytryptamine (5-HT) and prostaglandin E2 (PGE2) was studied in-vitro on rat stomach strip. Addition of PAF to the organ bath increased PGE- but not 5-HT- or acetylcholine-evoked responses. The effect of PAF was unaffected by atropine, methysergide or indomethacin, but prevented by a specific PAF receptor antagonist BN 52021. The data support a specific interaction between PAF and PGE2 on rat stomach strip.

Influence of a long-acting bradykinin antagonist, Hoe 140, on some acute inflammatory reactions in the rat

We studied the influence of Hoe 140, a bradykinin antagonist, on inflammatory reactions induced in rats. Hoe 140 reduced paw oedema induced by bradykinin alone, bradykinin plus prostaglandin (PG) E1, carrageenan, urate crystals or urate crystals plus captopril. The inhibitory effect of Hoe 140 lasted for at least 4 h. Hoe 140 also reduced plasma exudation in sponges implanted in the back of the rat. However it did not modify paw oedema induced by zymosan or by heating the paw at 55 degrees C for 30 s. Carrageenan oedema developed to a small extent in kininogen-deficient rats while the swelling induced by heating the paw of kininogen-deficient rats was the same as that measured in normal animals. Hoe 140 had no effect on the slight swelling induced by carrageenan in kininogen-deficient rats. We conclude that the kinin system is involved in inflammatory reactions induced by carrageenan, urate crystals, sponge implantation but not by zymosan and scalding.

Involvement of platelet-activating factor in zymosan-induced rat pleurisy

The role of platelet-activating factor (PAF) in inflammatory reactions was studied in zymosan-induced rat pleurisy. Pleurisy was induced by injection of a 2% zymosan suspension into the pleural cavity of rats. The time course of pleural exudate accumulation, the exudation rate, and exudate leukocyte numbers were followed then for 96 hr. Peak pleural exudate accumulation was about 3 mL at 24 hr, whereas the exudation rate increased biphasically with peaks at 0.5 hr and 5 hr. The migration of leukocytes into the pleural cavity increased with time up to 48 hr. The polymorphonuclear leukocytes were the dominant white cells in the exudate between 5 and 16 hr, but mononuclear leukocytes started to outnumber them around 24 hr. Pretreatment with cyproheptadine (5 mg/kg), an inhibitor of both histamine and serotonin, significantly suppressed pleural fluid accumulation and the exudation rate at 0.5 hr. The PAF antagonist CV-6209 (1 mg/kg) significantly suppressed pleural fluid accumulation and the exudation rate at both 0.5 and 5 hr. At either time point, the parameters were not suppressed by indomethacin. We detected PAF activity in the high-performance liquid chromatography (HPLC) fraction (with a retention time corresponding to that of authentic PAF) of the exudates at 0.5 hr, 5 hr, and 16 hr using an aggregation bioassay with washed rabbit platelets. The results suggest that in zymosan-induced rat pleurisy, histamine and/or serotonin are the main mediators of exudation at 0.5 hr and that PAF may be partly responsible for exudation at 0.5 hr and later at 5 hr to 16 hr.

Phorbol ester stimulates PAF synthesis via the activation of protein kinase C in rat leukocytes

When rat pleural mononuclear leukocytes were stimulated with 1 microM phorbol myristate acetate (PMA), platelet-activating factor (PAF)-like activity was detected in the supernatant and the cellular fractions of the incubation mixture, as measured by rabbit platelet aggregation. C16PAF activity peaked at 30 min in both fractions. Acetyltransferase activity in the microsomal fraction of the stimulated cells also increased rapidly and showed a peak at 10 min. A protein kinase C inhibitor, staurosporine, and an inhibitor of phospholipase A2, p-bromophen-acylbromide, inhibited stimulated PAF formation in both fractions. Staurosporine also inhibited PMA induced acetyltransferase activity. The data suggest that PMA stimulates PAF synthesis by the remodeling pathway in rat pleural cells through activation of both phospholipase A2 and acetyltransferase, and that the acetyltransferase, in turn, may be activated through activation of protein kinase C.

Vascular permeability increase in the mouse paw during the passive anaphylaxis reaction

Assessment of mouse paw edema induced by the passive allergic reaction was made by the previously reported dye-leakage method. The edema was induced by the injection of antiserum against ovalbumin into the paw, followed by the intravenous injection of ovalbumin 10 min before or 72 hr later. The latter reaction may be mainly mediated by heat-labile IgE. Both of the edemas were suppressed by pretreatment with mepyramine, methysergide, PAF-antagonists, or dexamethasone, and the latter suppressed by the lipoxygenase inhibitor AA-861, suggesting that histamine, serotonin, PAF, and leukotrienes are involved in exudate formation in these edemas.

Distinct stimulatory effect of platelet-activating factor on prostaglandin I2 and thromboxane A2 biosynthesis by rat dental pulp

Platelet-activating factor (PAF-acether), but not lyso PAF, stimulated the production of both PGI2 and TXA2 by rat dental pulp tissue in vitro. However, there were differences in the dose- and time-dependence of the stimulatory effects. PAF-acether antagonists, Bn 52021, CV 3988 and kadsurenone, dose dependently inhibited PAF-acether-induced PG production. BN 52021, CV 3988 also dose dependently inhibited TX production, but kadsurenone was almost without effect on TX production. Pretreatment of the tissues with PAF-acether or phorbol 12-myristate 13-acetate completely abolished the effect of the second challenge with PAF-acether. The stimulatory effects of PAF-acether and the calcium ionophore A23187 on PGI2 production were completely blocked by removal of extracellular calcium, whereas the effects on TXA2 production were not. TMB-8, an intracellular calcium antagonist, completely inhibited PAF-acether-induced PG production, whereas it slightly inhibited TX production. H-7, a protein kinase C inhibitor, and neomycin, a phospholipase C inhibitor, completely inhibited PAF-acether-induced PG and TX production, whereas W-7, a calmodulin inhibitor, did not. These results suggest that PAF-acether stimulates PGI2 and TXA2 production in rat dental pulp by interacting with distinct PAF-acether receptors, and that these receptors are coupled to independent signal transduction pathways which have a different dependence on extra- and intracellular calcium.

Platelet activating factor is produced during infectious peritonitis in CAPD patients

Peritonitis, a frequent complication of continuous ambulatory peritoneal dialysis (CAPD), is a model of inflammation which provides the opportunity to recover the exudate fluid. To date, various endogenous mediators (histamine, bradykinin, activated complement factors, prostanoids) have been implicated in the mediation of peritoneal inflammation and increased peritoneal permeability. In the present study, a lipid compound with physicochemical and biological characteristics similar to platelet activating factor (PAF) (1-0-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine) was extracted in significant amounts from the dialysate of eight out of nine peritonitis episodes in seven CAPD patients (Group A; 6771.4 +/- 3025.9 pM, mean +/- SEM at the first exchange during peritonitis). The amounts of PAF recovered in the first exchange dialysate from patients of Group A were linearly correlated with the loss of albumin (y = -3157.64 + 91.4x; r = 0.7394; N = 9; P less than 0.03) and number of leukocytes (y = 902.45 + 1.52x; r = 0.7576 N = 9; P less than 0.02). PAF was not detectable in the dialysate fluid from patients of Group A after recovery. Twelve patients on CAPD who had no past or present history of peritonitis (Group B) were used as controls; no PAF (9 patients) or only minimal amounts (3 patients: 7.0 pM; 23.0 pM; 70.0 pM) of this mediator were detected. This is the first direct demonstration of the local generation of PAF in a septic inflammatory reaction involving the peritoneal serosa in man. PAF produced by various cell types (neutrophils, peritoneal macrophages, endothelial cells) during peritoneal inflammation may contribute to the increased permeability of the peritoneal vascular bed.

Role of high molecular weight (HMW)-kininogen in inflammatory exudation: evidence with the studies of the HMW-kininogen deficient rat

Role of the kallikrein-kinin system in inflammation has been studied in rat model of inflammation, such as paw edema and pleurisy. Previous works suggested involvement of HMW-kininogen and activation of plasma kallikrein system in the carrageenin-induced rat pleurisy at early phase. This study clearly demonstrates the involvement of HMW-kininogen in carrageenin-induced rat paw edema and carrageenin-induced rat pleurisy by using congenitally deficient rat strain in plasma HMW-kininogen. Conclusion is the followings: 1. Significantly less reactivity was noticed in the deficient strain, B/N-Ka, in comparison with normal strain, B/N-Ki, when carrageenin-paw edema or carrageenin- and kaolin-pleurisies were induced. 2. Pretreatment with captopril enhanced the paw swelling as well as pleural fluid accumulation in normal strain but no enhancement was observed in the deficient strain. These results indicate that HMW-kininogen is responsible to inflammatory exudation. 3. T-kinin may not be involved in these inflammations, since the deficient strain owns normal plasma level of T-kininogen.

Detection of platelet-activating factor in exudates of rats with phorbol myristate acetate-induced pleurisy

PAF-likely activity, detected as aggregation of washed platelets, was found in the exudate of rats with pleurisy induced by phorbol myristate acetate (PMA, 1 nmol). At 30 min after the injection of PMA, 400-500 pg of PAF was detected in the pleural exudate. An extract of the exudate was made and analysed by HPLC and by rabbit platelet aggregation. The activity was characterized as that of PAF as a result of the inhibition seen with the PAF-antagonist CV-3988 and the loss of activity by treatment with phospholipase A2. Indirect evidence was previously reported in that CV-3988 suppressed the pleural fluid accumulation in the pleurisy induced by PMA. Taken together these facts it indicates that PAF could be an important mediator of acute inflammation, especially of the plasma exudation resulting from an increase in vascular permeability. Evidence that pleural cells produce PAF was also examined in an in vitro experiment. PAF was found in the supernatant and cellular fractions of the incubation mixture of the pleural cells from normal rats when stimulated by PMA (1 microM) or A23187 (5 microM), and the results indicate that the pleural cells produce PAF and release a portion of it.

Characterization of the activity of a platelet activating factor antagonist, CV-3988

CV-3988 inhibited the vascular permeability increase induced by C16-PAF and C18-PAF in rat skin in a dose-dependent manner. The inhibition was shown to be specific and competitive with PAF on its receptor by the following observations: parallel shift of the dose-response curve; crossing of double reciprocal plots on the intersection of the ordinate; and no inhibition on other autacoids such as bradykinin, histamine, 5-hydroxytryptamine and LTC4. PAF-induced blood pressure fall in rats was also suppressed by pretreatment with CV-3988 selectively.