Evidence that histamine does not participate in carrageenan-induced pleurisy in rat

Resident pleural macrophages are key orchestrators of neutrophil recruitment in pleural inflammation

RATIONALE

The role played by resident pleural macrophages in the initiation of pleural inflammation is currently unclear.

OBJECTIVE

To evaluate the role of resident pleural macrophages in the initiation of inflammation.

METHODS

We have used a conditional macrophage ablation strategy to determine the role of resident pleural macrophages in the regulation of neutrophil recruitment in a murine model of experimental pleurisy induced by the administration of carrageenan and formalin- fixed Staphylococcus aureus.

MEASUREMENTS AND MAIN RESULTS

Conditional macrophage ablation mice express the human diphtheria toxin receptor under the control of the CD11b promoter such that the administration of diphtheria toxin induces ablation of nearly 97% of resident macrophages. Ablation of resident pleural macrophages before the administration of carrageenan or S. aureus dramatically reduced neutrophil influx into the pleural cavity. In the carrageenan model, the reduction in neutrophil infiltration was associated with marked early reduction in the level of macrophage inflammatory protein 2 as well as reduced levels of various cytokines, including tumor necrosis factor alpha, interleukin 6, and interleukin 10. Adoptive transfer of nontransgenic macrophages partially restored neutrophil infiltration. We also stimulated macrophage-depleted and nondepleted pleural cell populations with carrageenan in vitro and determined the production of chemokines and cytokines. Chemokine and cytokine production was markedly reduced by macrophage depletion, reinforcing the role of resident pleural macrophages in the generation of mediators that initiate acute inflammation.

CONCLUSION

These studies indicate a critical role for resident pleural macrophages in sensing perturbation to the local microenvironment and orchestrating subsequent neutrophil infiltration.

Critical role of histamine H4 receptor in leukotriene B4 production and mast cell-dependent neutrophil recruitment induced by zymosan in vivo

The recently identified histamine receptor, H4, was shown to be primarily expressed on leukocytes and has been implicated in the activation of lymphocytes, eosinophils, and mast cells in vitro. Its function in vivo, however, has not yet been characterized. We present evidence for a critical role of H4 receptor in the mast cell-dependent recruitment of neutrophils. Mice injected with zymosan into the pleural cavity developed massive neutrophilia within hours after challenge. Neutrophilia was dose-dependently reduced when mice were pretreated with thioperamide, a known H(3/4) receptor antagonist, whereas H1 and H2 receptor antagonists lacked efficacy. Similarly, a 70 to 80% reduction in neutrophils in the pleural cavity compared with wild-type animals was noted in mice lacking mast cells (W/W(v) mice); mice deficient in MyD88 (MyD88(-/-)); a critical component of the signaling cascade of the major receptor for zymosan, toll-like receptor 2 (TLR2); or in mice pretreated with a functionally antagonistic anti-TLR2 antibody. The residual 20% neutrophil infiltration seen in mast cell-deficient and MyD88(-/-) mice was not further reduced by thioperamide. Neutrophilia was completely restored by transferring wild-type bone marrow-derived mast cells into MyD88(-/-) or W/W(v) mice. Interestingly, when neutrophilia was evoked by carrageenan injection, mast cell depletion and thioperamide had no effect. Various inflammatory mediators were detectable in the pleural cavity of zymosan-challenged mice. Upon pretreatment with thioperamide, reduced levels of the neutrophil chemoattractant leukotriene B4 were observed, providing a mechanistic explanation for the prevention of neutrophilia by H4 receptor antagonism.

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.

Downward regulation of neutrophil infiltration by endogenous histamine without affecting vascular permeability responses in air-pouch-type carrageenin inflammation in rats

The role of histamine in neutrophil infiltration and vascular permeability response in carrageenin air pouch inflammation in rats was examined. Injection of carrageenin solution into an air pouch induced a gradual increase in histamine content in the pouch fluid and histidine decarboxylase activity of pouch wall tissues, with a maximum attained at 24 h. Local administration of the H2 antagonists cimetidine and famotidine, but not the H1 antagonist pyrilamine, induced an increase in neutrophil infiltration at 24 h. Both types of histamine antagonists failed to suppress the vascular permeability response. In addition, H2 antagonists attenuated the inhibitory effect of indomethacin on neutrophil infiltration without affecting the indomethacin-induced suppression of vascular permeability response. These results suggest that histamine produced in the inflammatory locus exerts a downward regulation of neutrophil infiltration through H2 receptors but does not play any significant role in the vascular permeability response. Furthermore, the inhibition by indomethacin of neutrophil infiltration might be ascribed to the increase in histamine level in the pouch fluid.

Time course analyses of kinins and other mediators in plasma exudation of rat kaolin-induced pleurisy

Pleurisy was induced in rats by an intrapleural injection of 0.5 ml of 1% kaolin. The exudation of plasma into the pleural cavity showed two peaks at 20 min and 3-5 h after the kaolin injection. The volume of the pleural fluid increased gradually up to 5 h. The effects of treatment with mepyramine, methysergide, captopril, bromelain and indomethacin suggested that the early phase (20 min) of exudation was mediated mainly by kinins, histamine and 5-HT, and that the late phase (3 h) was mediated by prostaglandins (PGs) and possibly kinins. We measured the levels of histamine, kinin and PG in the pleural exudate to verify the involvement of the mediators mentioned above. Intracellular histamine levels decreased markedly and extracellular histamine levels increased significantly 20 min after the induction of kaolin pleurisy. Only threshold levels of kinin were detected after the induction of pleurisy. Captopril treatment, however, increased kinin levels which peaked at 20 min and decreased rapidly thereafter. Levels of 6-keto-PGF1 alpha and thromboxane B2 showed a peak at 20 min, whereas levels of PGE2 increased gradually from 20 min to 5 h. These results indicate that kaolin-induced pleurisy is a kinin-related inflammation and could be used as a model for studying the in vivo interaction of the kallikrein-kinin system and PGs at inflammatory sites.

Carrageenan-stimulated release of arachidonic acid and of lactate dehydrogenase from rat pleural cells

Cells isolated from the rat pleural cavity consist mainly of macrophages, mast cells, eosinophils, and lymphocytes. Isolated pleural cells labeled with [14C]arachidonic acid released appreciable amounts (approximately 12%) of radiolabel upon exposure to pharmacological concentrations of carrageenan (1-100 micrograms/ml). The release of radiolabel was decreased by an inhibitor of phospholipase A2 (p-bromophenacyl bromide) but not by an inhibitor of arachidonate cyclooxygenase (indomethacin). The released products were arachidonic acid and, to a much lesser extent, prostaglandin E2 and leukotriene C4. The release of radiolabel was associated with release of cytosolic lactate dehydrogenase over the same range of carrageenan concentrations. Time-course studies indicated that release of radiolabel preceded that of lactate dehydrogenase. Since p-bromophenacyl bromide blocked stimulated release of radiolabel but did not prevent release of lactate dehydrogenase, it is unlikely that increase in arachidonate causes carrageenan-induced cell damage. Nevertheless, the question of whether the activation of phospholipase A2 in the pleural cells, most probably the macrophages, was sufficient to initiate the carrageenan-induced inflammatory response requires further study. Cytotoxicity which was apparent with as little as 5 micrograms/ml of carrageenan, may have been a significant consequence of carrageenan action.

Mast cells in newly formed lining tissue during acute inflammation: a six day air pouch model in the mouse

Connective tissue mast cells were topographically and quantitatively studied in the newly formed lining tissue of six day old air pouches induced in the dorsal surface of mice. The results showed that the number of mast cells in the cavities innermost lining increased after injection of carrageenan into the cavity. Degranulation of mast cells was also observed. Variations in mast cell numbers in the lining seemed to correlate with the histamine content. These findings suggest that mast cells not only participate in the initiation of the early phase of acute inflammation but also appear to play an important part in regulating and prolonging more chronic inflammatory reactions.

The effects of histamine and serotonin on polymorphonuclear leukocyte accumulation in the rat

Histamine and serotonin were evaluated for their effects on rat polymorphonuclear leukocyte (PMN) accumulation in vivo and PMN migration in vitro. Both of the mediators inhibited the accumulation of PMNs when injected into the pleural cavity in a saline vehicle, and reduced the PMN content of the peripheral blood. Histamine also reduced the cellular influx when administered in combination with an intrapleural injection of carrageenan. Peripheral blood leukocytes removed from rats injected intrapleurally with histamine and carrageenan had a lesser chemotactic responsiveness compared with those removed from rats injected only with carrageenan. The effects of histamine in reducing PMN accumulation was abolished by treatment with cimetidine, an H2 antagonist, but not by treatment with chlorpheniramine, an H1 antagonist. These results suggest that a local release of histamine may play a role in reducing cellular infiltration into an inflammatory site.

Mast cell amines and the oedema induced by zymosan and carrageenans in rats

Cimetidine and metiamide suppressed the paw swelling induced in rats by low doses of histamine while these H2 antagonists had little effect on the oedema induced by 100 micrograms of histamine and inhibited by mepyramine. When administered 0.5 h before the inflammagens, H2 antagonists reduced the oedema induced by zymosan and iota carrageenan; they had a slight effect on the oedema induced by lambda and kappa carrageenans and no effect on the oedema induced by compound 48/80. When administered 18 h before the inflammagens, cimetidine greatly increased zymosan oedema and slightly increased lambda carrageenan oedema. Mepyramine, methysergide or depletion of the 5-hydroxytryptamine stores in mast cells by pretreatment with reserpine inhibited the oedema induced by compound 48/80 and zymosan but did not affect the oedema induced by lambda and kappa carrageenans. Histamine may play a dual role in inflammatory reactions. Mast cell amines take a part in the development of zymosan oedema though they play a minor role in the oedema induced by the carrageenans.

Inflammatory response induced by intrapleural injection of antiserum to IgE in rat. An evaluation of the role of histamine

Intrapleural injection of antiserum to rat IgE (anti-IgE) into rats resulted in release of histamine from mast cells and rapid effusion of fluid and plasma proteins into the pleural cavity. By 4 hr this was followed by infiltration of neutrophils. These responses were dependent on the amount of anti-IgE injected, and maximal responses were greater than those obtained with compound 48/80. The effusion of fluid and protein, but not the infiltration of cells, was partially suppressed by prior treatment with the H1 histamine receptor antagonist mepyramine (5 mg/kg, s.c.) or the H2 antagonist metiamide (100 mg/kg, s.c.) and was almost totally suppressed (85-88%) when both drugs were administered simultaneously. Neither methysergide (1 and 4 mg/kg, s.c.) nor indomethacin (5 and 10 mg/kg, i.v.) had an effect on the responses to anti-IgE. Although it seemed likely that histamine was a primary mediator of increased vascular permeability, the intrapleural injection of histamine agonists or histamine in large amounts (50 micrograms) provoked a much less intense response than did anti-IgE. The effects of injected histamine may not, therefore, mimic those induced by histamine released from mast cells in situ. The intrapleural injection of histamine releasers such as anti-IgE may serve as a useful model to test the therapeutic efficacy of antihistamine drugs. The present results also confirm previous reports that localized neutrophil infiltration occurs after mast cell degranulation.

Effect of indomethacin on generation of chemotactic activity in inflammatory exudates induced by carrageenan

Chemotactic activity of protein origin was demonstrated in carrageenan-induced pleural exudates by the chemotactic response of neutrophils in the modified Boyden chamber. The activity was partly neutralized by monospecific antisera to complement component 5 and was destroyed by trypsin and chymotrypsin treatment but it differed from that in rat serum or plasma in that it was stable for 30 min at 56 degrees C. Indomethacin (5 mg/kg i.v.) reduced equally protein content (56%) and total chemotactic activity (58%); i.e., chemotactic activity/mg of exudate protein was unchanged. Intrapleural injection of autologous or homologous serum also induced an infiltration of neutrophils; the protein content of the pleural fluid decreased by 60-70% in 4 h, whereas with carrageenan there was a progressive increase in exudate protein. When serum was injected in two doses to maintain protein levels comparable to those found following carrageenan injection, the number of neutrophils in the exudates was also comparable. In contrast to carrageenan, the response to serum was not inhibited by indomethacin. From these and other data we suggest that the exudate chemotactic activity is generated from plasma protein and that indomethacin acts primarily to reduce extravasation of plasma and consequently generation of chemotactic activity.

Carrageenan-induced oedema in the rat paw - histamine participation

Participation of histamine in the inflammatory reaction produced by carrageenan was studied. Mepyramine did not influence the course of the inflammatory reaction. In contrast to when mepyramine was used, there was a significant inhibition of carrageenan oedema when cimetidine was used. Pretreatment of animals with compound 48/80 significantly reduced the oedema formation. Neither mepyramine nor cimetidine reversed the inhibition of rat paw swelling produced by histamine liberators. It is concluded that histamine participates in carrageenan oedema via its H2-receptors and that the anti-inflammatory effect of compound 48/80 is not connected with the 'anti-inflammatory' action of liberated histamine.