Roles of tumor necrosis factor and macrophages in lipopolysaccharide-induced accumulation of neutrophils in cutaneous air pouches

Brazilian Red Propolis shows antifungal and immunomodulatory activities against Paracoccidioides brasiliensis

ETHNOPHARMACOLOGICAL RELEVANCE

Paracoccidioidomycosis (PCM) is a systemic mycosis with high prevalence in South America and especially in Brazil with severe clinical consequences that need broadened therapeutic options. Propolis is a natural resin from bees used in folk medicine for centuries with the first report in the ancient history of Egypt by Eberly papyrus, in Middle-Ages used to wash the newborn's umbilical cord and World War II as antiseptic or antibiotics. Nowadays it is a natural product worldwide consumed as food and traditionally used for oral and systemic diseases as an anti-inflammatory, antimicrobial, antifungal, and other diseases. Brazilian red propolis (BRP) is a new type of propolis with a distinguished chemical profile and biological activities from propolis (green) with pharmacological properties such as antimicrobial, anti-inflammatory, antioxidant, and others.

AIM OF STUDY

Thus, the main purpose of this study was to investigate the direct in vitro and ex vivo effect of BRP on Paracoccidioides brasiliensis.

MATERIAL AND METHODS

Antifungal activity of different concentrations of BRP on a virulent P. brasiliensis isolate (Pb18) was evaluated using the microdilution technique. Also, mice splenic cells co-cultured with Pb18 were treated with BRP at different times and concentrations (only Pb18 = negative control). Mice were inoculated with Pb18 and treated with different concentrations of BRP (50-500 mg/mL) in a subcutaneous air pouch. In this later experimental model, macroscopic characteristics of the air pouch were evaluated, and cellular exudate was collected and analyzed for cellular composition, mitochondrial activity, total protein reactive oxygen specimens (ROS), and nitric oxide production, as well as the number of viable fungal cells.

RESULTS

The in vitro experiments showed remarkable direct antifungal activity of BRP, mainly with the highest concentration employed (500 mg/mL), reducing the number of viable cells to 10% of the original inoculum after 72 h incubation. The splenocytes co-cultivation assays showed that BRP had no cytotoxic effect on these cells, on the contrary, exerted a stimulatory effect. This stimulation was also observed on the PMNs at the air pouch, as verified by production of ROS and total proteins and mitochondrial activity. This activation resulted in enhanced fungicidal activity, mainly with the 500 mg/mL concentration of BRP. An anti-inflammatory effect was also detected, as verified by the smaller volume of the BRP-treated air pouch as well as by an earlier shift from neutrophils to mononuclear cells present in the infection site.

CONCLUSION

Our results strongly suggest, for the first time in the literature, that Brazilian Red propolis has four protective mechanisms in experimental paracoccidioidomycosis: activating neutrophils, exerting a direct antifungal effect, preventing fungal dissemination, and controlling excessive inflammation process.

Resistance to P. brasiliensis Experimental Infection of Inbred Mice Is Associated with an Efficient Neutrophil Mobilization and Activation by Mediators of Inflammation

Paracoccidioidomycosis (PCM) is a systemic fungal infection, endemic in Brazil, that leads to severe morbidity and even mortality if not correctly treated. Patients may respond differently to PCM depending on the pattern of the acquired immune response developed. The onset of protective immune response is notably mediated by neutrophils (PMN) that play an important role through directly killing the fungi and also by interacting with other cell types to modulate the acquired protective immune response that may follow. In that way, this study aimed to present and compare different experimental models of PCM (intraperitoneal and subcutaneous) regarding PMN production and maturation inside femoral bone marrow and also PMN infiltration in peritoneal and subcutaneous exudates of resistant and susceptible mice. We also assessed the fungal colony forming units and the levels of soluble inflammatory mediators (LTB4, KC, IFN-γ, GM-CSF, and IL-10) inside subcutaneous air-pouches to compare the efficiency of the PMN present at this site in relation to the two main neutrophil functions: initial lysis of the invading pathogen and modulation of the acquired immune response. P. brasiliensis inoculated intraperitoneally was able to disseminate to the bone marrow of susceptible mice, causing a more marked alteration of PMN production and maturation than that observed after resistant mice infection by the same route. Subcutaneous air-pouch inoculation of P. brasiliensis elicited a controlled and limited infection that produced a PMN-rich exudate, thus favoring the study of the interaction between the fungus and the neutrophils. Susceptible mice produced higher numbers of PMN; however, these cells were less effective in killing the fungi. Inflammatory cytokines were more pronounced in resistant mice, which supports their PCM raised resistance.

Low-level laser therapy to the mouse femur enhances the fungicidal response of neutrophils against Paracoccidioides brasiliensis

Neutrophils (PMN) play a central role in host defense against the neglected fungal infection paracoccidioidomycosis (PCM), which is caused by the dimorphic fungus Paracoccidioides brasiliensis (Pb). PCM is of major importance, especially in Latin America, and its treatment relies on the use of antifungal drugs. However, the course of treatment is lengthy, leading to side effects and even development of fungal resistance. The goal of the study was to use low-level laser therapy (LLLT) to stimulate PMN to fight Pb in vivo. Swiss mice with subcutaneous air pouches were inoculated with a virulent strain of Pb or fungal cell wall components (Zymosan), and then received LLLT (780 nm; 50 mW; 12.5 J/cm2; 30 seconds per point, giving a total energy of 0.5 J per point) on alternate days at two points on each hind leg. The aim was to reach the bone marrow in the femur with light. Non-irradiated animals were used as controls. The number and viability of the PMN that migrated to the inoculation site was assessed, as well as their ability to synthesize proteins, produce reactive oxygen species (ROS) and their fungicidal activity. The highly pure PMN populations obtained after 10 days of infection were also subsequently cultured in the presence of Pb for trials of protein production, evaluation of mitochondrial activity, ROS production and quantification of viable fungi growth. PMN from mice that received LLLT were more active metabolically, had higher fungicidal activity against Pb in vivo and also in vitro. The kinetics of neutrophil protein production also correlated with a more activated state. LLLT may be a safe and non-invasive approach to deal with PCM infection.

PCM triggers a typical granulomatous inflammatory reaction with PMN playing a major role; these inflammatory cells are crucial in the initial stages of PCM, participating in the innate immune reaction and also directing the acquired immune response in the later stages. In some PCM patients, these immune mechanisms are insufficient to eradicate the infection, and need to be boosted with antifungal drugs that have to be administered for long periods and can show serious side-effects. We aimed to develop a novel and safe way to activate PMN through low-level laser irradiation of the bone marrow in the mouse femoral medulla. LLLT increased PMN viability and activation, shown by a significantly greater production of protein and ROS, as well as a higher fungicidal capacity; PMN even retained their higher metabolic activity and fungicidal ability after a second exposure to the pathogenic fungus in vitro. This is the first time that LLLT has been shown to increase the immune response against a fungal infection, and could be a promising and safe technique to be used with antifungal drugs in PCM.

The LPS-induced neutrophil recruitment into rat air pouches is mediated by TNFalpha: likely macrophage origin

The role of resident cells during the lipopolysaccharide (LPS)-induced neutrophil recruitment into rat air pouches was investigated. In this model, LPS (Escherichia coli, O55: B5 strain; 2-2000 ng) induced a dose- and time-dependent neutrophil recruitment accompanied by the generation of a tumour necrosis factor-alpha (TNFalpha)-like activity. Dexamethasone (0.05-5 mug) and cycloheximide (6 ng), injected 2 h before LPS into the pouches, inhibited the neutrophil recruitment and the generation of the TNFalpha-like activity, while the H1-receptor antagonist mepyramine (1 and 4 mg/kg, i.p., 0.5 h before LPS) and the PAF-receptor antagonist WEB 2170 (0.05 and 1 mg/kg, i.p., 0.5 h before LPS) had no effect. Purified alveolar macrophages (AM) were used to replenish the pouches of cycloheximide-treated recipient rats. AM provided by PBS-treated animals led to the recovery of the LPS-induced neutrophil recruitment and of the TNFalpha-like formation contrasting with those from cycloheximide-treated animals (1 mg/kg, i.p.). When delivered in situ, liposome-encapsulated clodronate, a macrophage depletor, significantly impaired both the LPSinduced neutrophil recruitment and the TNFalpha-like activity. An anti-murine TNFalpha polyclonal antibody (0.5 h before LPS) was also effective. These results emphasize the pivotal role of macrophages for LPS-induced neutrophil recruitment via the formation of TNFalpha.

Macrophage-specific metalloelastase (MMP-12) truncates and inactivates ELR+ CXC chemokines and generates CCL2, -7, -8, and -13 antagonists: potential role of the macrophage in terminating polymorphonuclear leukocyte influx

Through the activity of macrophage-specific matrix metalloproteinase-12 (MMP-12), we found that macrophages dampen the lipopolysaccharide (LPS)-induced influx of polymorphonuclear leukocytes (PMNs)-thus providing a new mechanism for the termination of PMN recruitment in acute inflammation. MMP-12 specifically cleaves human ELR(+) CXC chemokines (CXCL1, -2, -3, -5, and -8) at E-LR, the critical receptor-binding motif or, for CXCL6, carboxyl-terminal to it. Murine (m) MMP-12 also cleaves mCXCL1, -2, and -3 at E-LR. MMP-12-cleaved mCXCL2 (macrophage-inflammatory protein-2 [MIP-2]) and mCXCL3 (dendritic cell inflammatory protein-1 [DCIP-1]) lost chemotactic activity. Furthermore, MMP-12 processed and inactivated monocyte chemotactic proteins CCL2, -7, -8, and -13 at position 4-5 generating CCR antagonists. Indeed, PMNs and macrophages in bronchoalveolar lavage fluid were significantly increased 72 hours after intranasal instillation of LPS in Mmp12(-/-) mice compared with wild type. Specificity occurred at 2 levels. Macrophage MMP-1 and MMP-9 did not cleave in the ELR motif. Second, unlike human ELR(+)CXC chemokines, mCXCL5 (LPS-induced CXC chemokine [LIX]) was not inactivated. Rather, mMMP-12 cleavage at Ser4-Val5 activated the chemokine, promoting enhanced PMN early infiltration in wild-type mice compared with Mmp12(-/-) mice 8 hours after LPS challenge in air pouches. We propose that the macrophage, specifically through MMP-12, assists in orchestrating the regulation of acute inflammatory responses by precise proteolysis of ELR(+)CXC and CC chemokines.

A role for adrenoceptors in the regulation of pleural neutrophilia induced by LPS

The role of catecholamines in regulating pleural neutrophilia evoked by intrathoracic (i.t.) injection of lipopolysaccharide (LPS) was investigated in Wistar rats by means of surgical adrenalectomy, depletion of catecholamine stores or adrenoceptor blockade. Treatment of animals with a single dose of LPS evoked a dramatic increase in the number of pleural neutrophils concomitant with an increase in the number of these cells in blood at 4 h. Although blood neutrophilia was drastically reduced when catecholamine stores were depleted with intraperitoneal (i.p.) injection of reserpine, pleural neutrophilia was not modified. However, the i.t. injection of reserpine reduced the increase in pleural neutrophils after LPS stimulation. Adrenalectomy failed to inhibit the increase in neutrophil counts in the blood or pleural cavity after LPS challenge. Pretreatment with intravenous (i.v.) injection of prazosin, an alpha(1)/alpha(2B) antagonist, reduced LPS-induced blood but not pleural neutrophilia. On the other hand, although pleural neutrophilia was not affected by systemic pretreatment with the alpha(2)-adrenoceptor antagonist, yohimbine, the local treatment (i. t. injection) with this antagonist markedly reduced the increase in pleural neutrophil counts observed after stimulation by LPS. In contrast, pleural neutrophilia induced by i.t injection of formyl-methionyl-leucyl-phenylalanine (fMLP) was not modified by local treatment with yohimbine. Taken together, our results suggest that catecholamines, through activation of alpha(1) and alpha(2)-adrenoceptors, play a role in the regulation of blood and pleural neutrophilia observed during the inflammatory response evoked by LPS in the pleural cavity.

Role of alveolar macrophages in innate immunity in neonates: evidence for selective lipopolysaccharide binding protein production by rat neonatal alveolar macrophages

As the first line of defense against inhaled substances, alveolar macrophages (AM) play a crucial role in maintaining lung homeostasis. This is achieved via phagocytosis of foreign material and the secretion of a wide range of mediator molecules, including those involved in neutrophil recruitment. Neonates are known to manifest increased susceptibility to lung infections, and we hypothesize that this may be due in part to a deficiency in the function of AM. We report here that although recruitment of neutrophils into the respiratory tract of newborn animals in response to Moraxalla catarrhalis exposure is greatly delayed and diminished, AM from newborn animals have greater phagocytic capacity when compared with those from adult animals. Additionally, newborn AM respond normally to lipopolysaccharide (LPS) via production of a variety of chemokines, including macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, monocyte chemotactic protein-1, gro/ cytokine-induced neutrophil chemoattractant, MIP-2, and tumor necrosis factor-alpha. We have also demonstrated an LPS inducible expression of messenger RNA for LPS binding protein (LBP) in neonatal AM that was not observed in AM from adult animals or in peritoneal macrophages. We speculate that local production of LBP by AM may be a significant factor in the neonatal immunologic response to infections, providing a compensatory mechanism for the deficiency in specific neonatal immunity during this period of development when the newborn is being exposed to a range of potentially pathogenic materials for the first time.

Role of Resident Peritoneal Macrophages and Mast Cells in Chemokine Production and Neutrophil Migration in Acute Inflammation: Evidence for an Inhibitory Loop Involving Endogenous IL-10

The roles played by resident macrophages (Mφ) and mast cells (MCs) in polymorphonuclear leukocyte (PMN) accumulation and chemokine production within the mouse peritoneal cavity in response to administration of zymosan (0.2 and 1 mg), LPS (1 mg/kg), and thioglycolate (0.5 ml of a 3% suspension) were investigated. A marked reduction (>95%) in intact MC numbers was obtained by pretreatment with the MC activator compound 48/80, whereas resident Mφ were greatly diminished (>85%) by a 3-day treatment with liposomes encapsulating the cytotoxic drug dichloromethylene-bisphosphonate. No modulation of thioglycolate-induced inflammation was seen with either pretreatment. Removal of either MCs or Mφ attenuated LPS-induced PMN extravasation without affecting the levels of the chemokines murine monocyte chemoattractant protein-1 and KC measured in the lavage fluids. In contrast, MC depletion inhibited PMN accumulation and murine monocyte chemoattractant protein-1 and KC production in the zymosan peritonitis model. Removal of Mφ augmented the accumulation of PMN elicited by the latter stimulus. This was due to an inhibitory action of Mφ-derived IL-10 because there was 1) a time-dependent release of IL-10 in the zymosan exudates; 2) a reduction in IL-10 levels following Mφ, but not MC, depletion; and 3) an increased PMN influx and chemokine production in IL-10 knockout mice. In conclusion, we propose a stimulus-dependent role of resident MCs in chemokine production and the existence of a regulatory loop between endogenous IL-10 and the chemokine-mediated cellular component of acute inflammation.

Endotoxin-stimulated alveolar macrophage recruitment of neutrophils and modulation with exogenous surfactant

OBJECTIVE

To determine whether endotoxin-stimulated alveolar macrophages would attract neutrophils and whether exogenous surfactant treatment would modulate this chemoattraction.

DESIGN

Alveolar macrophages were harvested from bronchoalveolar lavage fluid and neutrophils from the blood of anesthetized guinea pigs.

SUBJECTS

Hartley guinea pigs.

INTERVENTIONS

Alveolar macrophages were suspended in RPMI 1640 and stimulated with 1 microg/mL of lipopolysaccharide (LPS), the supernatant removed and the alveolar macrophages were incubated in either RPMI or RPMI with surfactant at two different doses (292 microg/mL or 875 microg/mL) for 16 hrs.

MEASUREMENTS AND MAIN RESULTS

The supernatant was extracted from the alveolar macrophages and placed in a chemotaxis plate and the migration of neutrophils was measured. Chemotaxis of all cell types to be tested was measured by a change of absorbance on a microplate reader set at 492 nm. Results were compared with alveolar macrophages not stimulated with LPS, RPMI alone, and N formyl-methionyl-leucyl-phenylalanine (FMLP). The supernatant of the stimulated alveolar macrophages increased neutrophil chemotaxis as compared with unstimulated alveolar macrophages, and RPMI (p < .05). Surfactant treatment with 292 microg/mL significantly decreased LPS-stimulated alveolar macrophages induced neutrophil chemotaxis. Treatment with 875 microg/mL of surfactant did not alter neutrophil chemotaxis.

CONCLUSIONS

Alveolar macrophages stimulation with LPS increased the chemotaxis of neutrophils. Treatment with surfactant at a concentration of 875 microg/mL did not alter neutrophil migration; however, treatment with 292 microg/mL significantly decreased neutrophil chemotaxis suggesting that at low concentrations, surfactant inhibits chemokine release and may reduce pulmonary neutrophil sequestration in vivo.

Endogenous tumor necrosis factor (TNF) alpha mediates neutrophil accumulation at the mid-phase of a murine model of Pseudomonas aeruginosa pneumonia

To determine the role of endogenous tumor necrosis factor (TNF) alpha on neutrophil influx into the lungs in acute Pseudomonas aeruginosa pneumonia, we evaluated TNF alpha activity, inflammatory cell response and neutrophil chemotactic activity in the bronchoalveolar lavage fluids (BALFs) of P. aeruginosa-infected mice. In the case of fatal pneumonia, the TNF alpha activity in the BALFs appeared within 3 hr, peaked at 6-12 hr and attenuated within 24 hr after intratracheal challenging, while no TNF alpha activity was detected in the plasma. The elevation of TNF alpha activity in the BALFs was closely associated with neutrophil accumulation. Mirroring the TNF alpha activity response and the influx of neutrophils into the murine airway, the number of neutrophils in the BALFs increased within 3 hr, peaked at 6-12 hr and remained elevated up to 24 hr after challenging. Neutralization of the TNF alpha activity in the BALFs with anti-murine TNF antiserum decreased the level of neutrophil migration by BALF 45.0-49.7% at 6 hr and 49.3-54.2% at 12 hr, while the neutralizing antiserum had no effect on the level of neutrophil migration by BALFs at 3 and 24 hr. Furthermore, the intravenous administration of anti-murine TNF antiserum 2 hr before challenging significantly inhibited neutrophil migration into the lungs of mice with sublethal pneumonia (P < 0.05; compared with mice receiving pre-immune serum). These data suggest that intra-alveolar TNF alpha plays an important role in causing lung neutrophil accumulation at the mid-phase of murine P. aeruginosa pneumonia.

The role of lymphocytes in the neutrophil migration induced by ovalbumin in immunized rats

In the present study, we investigated the role of resident cells in the neutrophil migration induced by ovalbumin (OVA) in immunized rats. OVA administration induced dose-dependent neutrophil migration, which was inhibited by pretreating the animals with dexamethasone, but not with indomethacin or BW 70C. Lymphocytes, but not macrophages or mast cells, obtained from sensitized animals and stimulated in vitro with OVA released a factor that induced neutrophil migration in vivo and in vitro. Both the release of this factor in vitro and the neutrophil migration induced in vivo were inhibited by dexamethasone, thus explaining the inhibitory effect of glucocorticoids on the neutrophil migration induced by OVA in immunized animals. Neither indomethacin nor BW 70C had any such effect. The fact that actinomycin D also inhibited the release of the factor from OVA-stimulated lymphocytes suggests that this substance is of a proteinaceous nature. The importance of lymphocytes for neutrophil recruitment in OVA-immunized rats was supported by the fact that homologous lymphocyte transfer into air pouches rendered these cavities responsive to OVA. Lymphocytes obtained from naive rats and stimulated with the lectins concanavalin A (Con A) or phytohaemagglutinin (PHA) were also able to release a factor that induced neutrophil migration in vivo. In vitro incubation of the supernatant from OVA-stimulated lymphocytes with antisera to interleukin-1 beta (IL-1 beta), IL-8 and tumour necrosis factor-alpha (TNF-alpha) did not inhibit the neutrophil chemotactic activity. These data suggest that IL-1 beta, IL-8 and TNF-alpha are not involved in the neutrophil chemotactic activity of the supernatant. Overall, these results indicate the importance of lymphocyte participation in neutrophil recruitment during inflammatory immune reaction, through the release of a neutrophil chemotactic factor different from IL-1 beta, IL-8 and TNF-alpha.

Endotoxin administration to humans primes alveolar macrophages for increased production of inflammatory mediators

To elucidate potential mechanisms of the acute lung injury associated with endotoxemia, we evaluated the effect of intravenously administered endotoxin on the ability of alveolar macrophages isolated by bronchoalveolar lavage from normal subjects to produce inflammatory mediators. Within 1 hr of endotoxin (4 ng/kg body weight) administration, all 12 study subjects developed constitutional symptoms and leukopenia, and within 3 hr, low-grade fever. Resolution of symptoms and fever by 6 hr was accompanied by systemic granulocytosis. Although intravenously administered endotoxin appeared to activate a subset of circulating monocytes, it did not alter the bronchoalveolar lavage cell number, phenotype (95% macrophages), or constitutively expressed high levels of surface HLA-DR and O2-. In contrast, intravenous endotoxin primed the alveolar macrophages for enhanced lipopolysaccharide-induced secretion of interleukin-1 (11.8 to 25.8 U/ml; P = 0.04), tumor necrosis factor-alpha (titer, 6.8 to 13.6; P = 0.20), and prostaglandin E2 (38.4 to 116.3 ng/ml; P = 0.035). These results demonstrate that low-dose intravenous endotoxin primes human alveolar macrophages, which are already differentiated in situ, for enhanced secretion of inflammatory mediators. Such mediators may contribute to the pulmonary changes associated with endotoxemia and acute lung injury.

Blockade by fenspiride of endotoxin-induced neutrophil migration in the rat

Fenspiride, an antiinflammatory drug with low anti-cyclooxygenase activity, administered orally at 60-200 mg/kg inhibited neutrophil migration into peritoneal and air pouches cavities as well as exudation into peritoneal cavities induced by endotoxin but not induced by carrageenin. Up to 100 microM, fenspiride failed to inhibit the in vitro release of a neutrophil chemotactic activity by endotoxin-stimulated macrophages and the in vivo migration into the peritoneal cavities induced by the supernatant of those macrophages. The release of tumour necrosis factor by stimulated macrophages was inhibited by fenspiride in a dose-dependent manner. These results suggest that the antiinflammatory effects of fenspiride are associated with the inhibition of the tumour necrosis factor release by resident macrophages.

Interferon-gamma (IFN-gamma) and macrophage inflammatory proteins (MIP)-1 and -2 are involved in the regulation of the T cell-dependent chronic peritoneal neutrophilia of mice infected with mycobacteria

In mycobacterial infections of mice there is a chronic, immune-mediated mobilization of neutrophils to the infectious site. In this study we evaluated the role played by cytokines in the chronic peritoneal neutrophilia which occurs in mice intraperitoneally infected with Mycobacterium bovis BCG or M. avium. Antibodies to IFN-gamma and to MIP-1 and -2 were effective in reducing peritoneal neutrophilia when given during the infection. Whereas the former antibody was only effective when given early, the latter two were effective when administered late in infection, suggesting the MIPs were direct mediators of neutrophil recruitment. Recombinant IFN-gamma given intraperitoneally induced the accumulation of neutrophils and primed the peritoneal cells for an enhanced recruitment of neutrophils. Our data show that chronic neutrophilia during mycobacterial infection is regulated by different cytokines acting at different stages and levels of neutrophil recruitment.

IL-8 causes in vivo neutrophil migration by a cell-dependent mechanism

A dose-dependent neutrophil migration was observed following the injection of recombinant interleukin-8 (rIL-8) into rat peritoneal cavities. This finding contrasts with the inability of rIL-8 to induce neutrophil emigration into subcutaneous air-pouches. Pre-treatment of the animals with dexamethasone (0.5 mg/kg, s.c.) or depletion of the peritoneal resident cell population abolished the neutrophil migration induced by rIL-8 and by recombinant interleukin-1 beta (rIL-1 beta). Different from that which occurs with rIL-1 beta, neutrophil migration induced by rIL-8 was not enhanced by an increase in the peritoneal macrophage population. Transference of homologous total resident peritoneal cells to the air-pouch rendered this cavity responsive to the chemotactic effect of rIL-8 and potentiated the neutrophil migration induced by rIL-1. Our results show that both rIL-8 and rIL-1 beta are able to induce in vivo neutrophil migration by an indirect mechanism, dependent on resident cells. Neither macrophages nor lymphocytes seem to be involved in the rIL-8 chemotactic effect. However, peritoneal resident mast cells may be implicated in this mechanism. These cells, when stimulated in vitro by rIL-8, released a factor that when injected into peritoneal and air-pouch cavities induced neutrophil migration.