Infiltration of neutrophils by intrapleural injection of tumour necrosis factor, interleukin-1, and interleukin-8 in rats, and its modification by actinomycin D

The future of chemical pleurodesis: A review of novel and investigational sclerosant agents

Chemical pleurodesis is a technique in which an injurious and inflammatory substance is instilled into the pleural cavity to cause adhesion and fibrosis. It is commonly used in the management of recurrent malignant pleural effusions. Historically, many different types of sclerosants have been described, though only a few, including talc, the tetracycline derivatives, and anti-septic compounds such as silver nitrate and iodopovidone, have found their way into mainstream use. However, over the past several years, there has been increasing interest in alternative pleurodesis agents. In this review, we will explore future directions in the field, with an eye toward novel and investigational agents.

Thirty-five years since the discovery of chemotactic cytokines, interleukin-8 and MCAF: A historical overview

Inflammation is a host defense response to various invading stimuli, but an excessive and persistent inflammatory response can cause tissue injury, which can lead to irreversible organ damage and dysfunction. Excessive inflammatory responses are believed to link to most human diseases. A specific type of leukocyte infiltration into invaded tissues is required for inflammation. Historically, the underlying molecular mechanisms of this process during inflammation were an enigma, compromising research in the fields of inflammation, immunology, and pathology. However, the pioneering discovery of chemotactic cytokines (chemokines), monocyte-derived neutrophil chemotactic factor (MDNCF; interleukin [IL]-8, CXCL8) and monocyte chemotactic and activating factor (MCAF; monocyte chemotactic factor 1 [MCP-1], CCL2) in the late 1980s finally enabled us to address this issue. In this review, we provide a historical overview of chemokine research over the last 35 years.

Tumour necrosis factor-α (TNF-α) enhances dietary carcinogen-induced DNA damage in colorectal cancer epithelial cells through activation of JNK signaling pathway

Colorectal cancer (CRC) is the third most common cancer worldwide and the second leading cause of cancer death. Benzo[a]pyrene (BaP) and 2-amino-1-methyl-6-phenylimidazol [4,5-b] pyridine (PhIP) present in cooked meat are pro-carcinogens and considered to be potential risk factors for CRC. Their carcinogenic and mutagenic effects require metabolic activation primarily by cytochrome P450 1 family enzymes (CYPs); the expression of these enzymes can be modulated by aryl hydrocarbon receptor (AhR) activation and the tumour microenvironment, involving mediators of inflammation. In this study, we hypothesized that tumour necrosis factor-α (TNF-α), a key mediator of inflammation, modulates BaP- and PhIP-induced DNA damage in colon cancer epithelial cells. Importantly, we observed that TNF-α alone (0.1-100 pg/ml) induced DNA damage (micronuclei formation) in HCT-116 cells and co-treatment of TNF-α with BaP or PhIP showed higher levels of DNA damage compared to the individual single treatments. TNF-α alone or in combination with BaP or PhIP did not affect the expression levels of CYP1A1 and CYP1B1 (target genes of AhR signaling pathways). The DNA damage induced by TNF-α was elevated in p53 null HTC-116 cells compared to wild type cells, suggesting that TNF-α-induced DNA damage is suppressed by functional p53. In contrast, p53 status failed to affect BaP and PhIP induced micronucleus frequency. Furthermore, JNK and NF-κB signaling pathway were activated by TNF-α treatment but only inhibition of JNK significantly reduced TNF-α-induced DNA damage. Collectively, these findings suggest that TNF-α induced DNA damage involves JNK signaling pathway rather than AhR and NF-κB pathways in colon cancer epithelial cells.

Interleukin-1β and Tumor Necrosis Factor-α Produce Distinct, Time-dependent Patterns of Acute Arthritis in the Rat Knee

Interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) synergistically induce and sustain arthritis. Two competing hypotheses of arthritis induction are 1) that TNF preferentially mediates inflammation, whereas IL-1 impels bone destruction, or 2) that either cytokine controls the entire process. In this study, these propositions were tested in two experiments by instilling IL-1β or TNF-α into one knee of Lewis rats ( n = 6/group) to incite arthritis, after which semiquantitative scores for inflammation, bone resorption, osteoclasts, and cartilage integrity were acquired. In the induction study, IL-1β or TNF-α (3, 10, or 30 μg) was given once to incite arthritis. After 2 days, IL-1β induced significant, dose-dependent increases in inflammation (mild to marked), bone resorption (minimal to moderate), and osteoclasts (minimal to moderate). In contrast, TNF-α induced minimal to mild inflammation but had little impact on resorption or osteoclasts. Both IL-1 and TNF (≥10 μg) yielded mild cartilage degeneration. Most lesion scores in TNF-treated rats were significantly lower than those in animals given the same dose of IL-1β. In the persistence study, rats were injected once with IL-1 or TNF (10 μg) and maintained for 2, 3, or 7 days. IL-1β significantly enhanced inflammation (all 3 days), bone resorption (days 2 and 3), osteoclasts (days 2 and 3), and cartilage matrix loss (days 2 and 3), whereas TNF-α augmented inflammation (days 2 and 3) and cartilage degeneration (day 2) but not bone resorption or osteoclasts. Thus, both IL-1β and TNF-α can launch inflammation, but IL-1β drives skeletal destruction.

Neutrophil chemorepulsion in defined interleukin-8 gradients in vitro and in vivo

We report for the first time that primary human neutrophils can undergo persistent, directionally biased movement away from a chemokine in vitro and in vivo, termed chemorepulsion or fugetaxis. Robust neutrophil chemorepulsion in microfluidic gradients of interleukin-8 (IL-8; CXC chemokine ligand 8) was dependent on the absolute concentration of chemokine, CXC chemokine receptor 2 (CXCR2), and was associated with polarization of cytoskeletal elements and signaling molecules involved in chemotaxis and leading edge formation. Like chemoattraction, chemorepulsion was pertussis toxin-sensitive and dependent on phosphoinositide-3 kinase, RhoGTPases, and associated proteins. Perturbation of neutrophil intracytoplasmic cyclic adenosine monophosphate concentrations and the activity of protein kinase C isoforms modulated directional bias and persistence of motility and could convert a chemorepellent to a chemoattractant response. Neutrophil chemorepulsion to an IL-8 ortholog was also demonstrated and quantified in a rat model of inflammation. The finding that neutrophils undergo chemorepulsion in response to continuous chemokine gradients expands the paradigm by which neutrophil migration is understood and may reveal a novel approach to our understanding of the homeostatic regulation of inflammation.

Increased expression of chemokine KC, an interleukin-8 homologue, in a model of oxygen-induced retinopathy

PURPOSE

The purpose of this study was to determine the retinal expression of angiogenic chemokines/cytokines in a mouse model of oxygen-induced retinopathy.

METHODS

C57BL/6 (B6) mice were exposed to 75% oxygen from postnatal day 7 (P7) to P12 and then recovered in room air. Reverse transcription-polymerase chain reaction (RT-PCR) was used to determine relative mRNA levels of KC, macrophage inflammatory protein-2 (MIP-2), interleukin-1alpha (IL-1alpha), and interferon gamma (IFN-gamma). Immunohistochemistry was used to localize KC in the retina. IL-1alpha was also injected into the vitreous of mouse eyes, and KC expression was examined by RT-PCR, enzyme-linked immunosorbent assay (ELISA), and immunohistochemistry.

RESULTS

KC expression at both the mRNA and protein levels was increased in P14, P17, and P21 of hyperoxia-injured eyes. KC immunoreactivity was localized along the nerve fiber layer and in radial Müller cell processes. IL-1alpha mRNA was modestly increased in hyperoxia-injured eyes on P14 and P17. INF-gamma mRNA was not detected in the retina. Adult mouse eyes injected with IL-1alpha demonstrated increased levels of both KC mRNA and protein, with KC immunoreactivity localized to Müller cell processes.

CONCLUSIONS

Oxygen-induced injury to the developing retina results in the induction of the CXC chemokine KC at both the mRNA and protein levels during the peak time points of neovascularization, suggesting a possible role in the pathogenesis of retinopathy of prematurity.

Reduced infiltration and increased apoptosis of leukocytes at sites of inflammation by systemic administration of a membrane-permeable IkappaBalpha repressor

OBJECTIVE

NF-kappaB activation is associated with several inflammatory disorders, including rheumatoid arthritis (RA), making this family of transcription factors a good target for the development of antiinflammatory treatments. Although inhibitors of the NF-kappaB pathway are currently available, their specificity has not been adequately determined. IkappaBalpha is a physiologic inhibitor of NF-kappaB and a potent repressor experimentally when expressed in a nondegradable form. We describe here a novel means for specifically regulating NF-kappaB activity in vivo by administering a chimeric molecule comprising the super-repressor IkappaBalpha (srIkappaBalpha) fused to the membrane-transducing domain of the human immunodeficiency virus Tat protein (Tat-srIkappaBalpha).

METHODS

The Wistar rat carrageenan-induced pleurisy model was used to assess the effects of in vivo administration of Tat-srIkappaBalpha on leukocyte infiltration and on cytokine and chemokine production.

RESULTS

Systemic administration of Tat-srIkappaBalpha diminished infiltration of leukocytes into the site of inflammation. Analysis of the recruited inflammatory cells confirmed uptake of the inhibitor and reduction of the NF-kappaB activity. These cells exhibited elevated caspase activity, suggesting that NF-kappaB is required for the survival of leukocytes at sites of inflammation. Analysis of exudates, while showing decreases in the production of the proinflammatory cytokines tumor necrosis factor alpha and interleukin-1beta, also revealed a significant increase in the production of the neutrophil chemoattractants cytokine-induced neutrophil chemoattractant 1 (CINC-1) and CINC-3 compared with controls. This result could reveal a previously unknown feedback mechanism in which infiltrating leukocytes may down-regulate local production of these chemokines.

CONCLUSION

These results provide new insights into the etiology of inflammation and establish a strategy for developing novel therapeutics by regulating the signaling activity of pathways known to function in RA.

Selective transport of cytokine-induced neutrophil chemoattractant from the lung to the blood facilitates pulmonary neutrophil recruitment

The CXC chemokines cytokine-induced neutrophil chemoattractant (CINC) and macrophage inflammatory protein-2 (MIP-2) are potent neutrophil chemoattractants in rats. We have previously shown that CINC, unlike MIP-2 and most other proinflammatory cytokines, is elevated in the systemic circulation in response to an intratracheal (IT) challenge. Therefore, we hypothesized that CINC generated within the lung selectively enters the vascular compartment to facilitate pulmonary neutrophil recruitment. Rats were administered IT LPS, and plasma CINC and MIP-2 levels were measured 90 min and 4 h after injection, along with mRNA expression in lung, spleen, liver, and kidney. Ninety minutes and 4 h after IT LPS, CINC and MIP-2 mRNA expression were largely confined to lung homogenate, but of the two chemokines, only CINC was present in plasma. In separate experiments, rats received IT injections of recombinant CINC and/or MIP-2. Here, plasma levels of CINC, but not MIP-2, were significantly increased throughout the 4-h observation period. This finding was verified by individually administering125I-labeled forms of each chemokine. Instillation of recombinant MIP-2 or CINC into the lung increased the number of neutrophils recovered in bronchoalveolar lavage fluid at 4 h, and this effect was enhanced when both chemokines were administered together. In addition, intravenous (IV) CINC, but not IV MIP-2, increased pulmonary neutrophil recruitment in response to IT MIP-2. Our results show that CINC, in contrast to MIP-2, is selectively transported from the lung to the systemic circulation, where it promotes neutrophil migration into the lung in response to a chemotactic stimulus.

Role of nuclear factor-kappaB in gastric ulcer healing in rats

We investigated the role of nuclear factor-kappaB (NF-kappaB) in gastric ulcer healing in rats. NF-kappaB was activated in ulcerated tissue but not in normal mucosa, and the level of the activation was decreased with ulcer healing. NF-kappaB activation was observed in fibroblasts, monocytes/macrophages, and neutrophils. Treatment of gastric fibroblasts, isolated from the ulcer base, with interleukin-1beta activated NF-kappaB and the subsequently induced cyclooxygenase-2 and cytokine-induced neutrophil chemoattractant-1 (CINC-1) mRNA expression. Inhibition of activated NF-kappaB action resulted in suppression of both their mRNA expression and increases in PGE(2) and CINC-1 levels induced by interleukin-1beta. Persistent prevention of NF-kappaB activation caused an impairment of ulcer healing in rats. Gene expression of interleukin-1beta, CINC-1, cyclooxygenase-2, and inducible nitric oxide synthase in ulcerated tissue had been inhibited before the delay in ulcer healing became manifest. The increased levels of cyclooxygenase-2 protein and PGE(2) production were also reduced. These results demonstrate that NF-kappaB, activated in ulcerated tissue, might upregulate the expression of healing-promoting factors responsible for gastric ulcer healing in rats.

Role of neutrophil elastase in endotoxin-induced mucus hypersecretion in rat nasal epithelium

In the present study, hypertrophic and metaplastic changes of goblet cells were induced in rat nasal epithelium by intranasal instillation of endotoxin or elastase. A significant increase in the amount of intraepithelial mucosubstance was observed after 24 hours during 3 days of instillation. The elastase-induced mucus production was not inhibited in neutrophil-depleted rats, but the endotoxin-induced change was significantly inhibited. Intranasal instillation of the neutrophil elastase inhibitor ONO-5046 partially inhibited the endotoxin-induced mucus production. Epithelial mucus secretion was evaluated by the temporary decrease in the amount of intraepithelial mucosubstance. The endotoxin-induced mucus secretion peaked 3 to 6 hours after intranasal instillation, coinciding with the peak of the intraepithelial neutrophil infiltration. The elastase-induced mucus secretion peaked 1 to 3 hours after intranasal instillation; intraepithelial neutrophil infiltration was not induced by elastase. These results indicate that neutrophil elastase is an important mediator of the intraepithelial mucus synthesis and secretion induced by endotoxin.

Are the anti-inflammatory effects of dexamethasone responsible for inhibition of the induction of enzymes involved in prostanoid formation in rat carrageenin-induced pleurisy?

Since anti-inflammatory steroids modulate multiple gene expression, including the expression of prostaglandin H synthase-2 and phospholipase A(2), at the molecular level, we studied the effects of dexamethasone on rat carrageenin-induced pleurisy to elucidate whether regulation of phospholipase A(2) and prostaglandin H synthase-2 expression is the primary mechanism of its anti-inflammatory action. Suppression of plasma exudation by a lower dose of dexamethasone (0.3 mg/kg) was almost equal to that by aspirin (100 mg/kg), but that by higher dexamethasone doses (3 and 30 mg/kg) was considerably stronger, suggesting the involvement of effects other than that on prostanoid formation. The lower dose of dexamethasone also significantly reduced the pleural exudate neutrophil count and prostanoid levels. However, this dose affected neither the prostaglandin H synthase-2 level nor the phospholipase A(2) activity in the exudate cells. The prostaglandin H synthase-2 level was affected only at the higher doses, while phospholipase A(2) activity was not. These results suggest that the anti-inflammatory effects of dexamethasone in acute inflammation cannot be ascribed to direct interference with prostanoid formation via suppression of phospholipase A(2) and prostaglandin H synthase-2 expression.

Mesothelial cell apoptosis is confirmed in vivo by morphological change in cytokeratin distribution

Apoptosis of mesothelial cells has been demonstrated in vitro but not in vivo. To identify apoptotic pleural cells as mesothelial, we used cytokeratin as a marker and found a striking spheroid, aggregated appearance of cytokeratin in apparently apoptotic mesothelial cells. In in vitro studies, we found that the aggregated cytokeratin pattern correlated with apoptosis in primary mesothelial cells from mice, rabbits, and humans and was not seen with necrosis. In in vivo studies in mice, we then used this cytokeratin pattern to identify and quantitate apoptotic mesothelial cells. Apoptotic mesothelial cells were best harvested by pleural lavage, indicating that they were loosely adherent or nonadherent. Instillation of RPMI 1640 medium or wollastonite for 24 h induced apoptosis in 0.1 +/- 0. 1 (SE) and 1.0 +/- 0.7%, respectively, of all mesothelial cells recovered, whereas instillation of known apoptotic stimuli, crocidolite asbestos (25 microg) for 24 h or actinomycin D plus murine tumor necrosis factor-alpha for 12 h, induced apoptosis in 5. 1 +/- 0.5 and 22.4 +/- 4.5%, respectively (significantly greater than in control experiments, P < 0.05). By analysis of cytokeratin staining, mesothelial cell apoptosis has been confirmed in vivo.

Cytokine-induced neutrophil chemoattractants in healing of gastric ulcers in rats: expression of >40-kDa chemoattractant in delayed ulcer healing by indomethacin

We examined the roles of cytokine-induced neutrophil chemoattractants (CINCs) in neutrophil infiltration of ulcerated gastric tissue in rats. Neutrophil chemotactic and myeloperoxidase (MPO) activities were negligible in the normal mucosa but were markedly elevated by ulceration. The activities decreased with spontaneous ulcer healing, but remained quite high when the healing was prevented by indomethacin. Neither CINC-1 nor CINC-2alpha was detected, and CINC-3 was negligible in the normal mucosa. The expression of these CINCs was also promoted by ulceration, but the expression patterns during ulcer healing were apparently different among them. The change in net content of CINCs was well associated with those in chemotactic and MPO activities during spontaneous healing. The chemotactic activity due to the net CINCs was equivalent to most parts of the activity extracted from the tissue. On the other hand, indomethacin did not affect CINC expression, compared with that in spontaneous healing, but induced the expression of high-molecular-weight (>40-kDa) chemoattractant when ulcer healing was impaired. The chemotactic activity due to >40-kDa chemoattractant was equivalent to the activity extracted from the tissue. We conclude that CINCs play crucial roles in neutrophil infiltration of ulcerated gastric tissue in the spontaneous healing in rats and that the expression of CINCs might be differentially regulated. Furthermore, the >40-kDa chemoattractant might be the predominant contributor to the increased neutrophil infiltration in the delayed healing by indomethacin.

Mechanism of suppressed neutrophil mobilization in a mouse model for binge drinking: role of glucocorticoids

The goals of this study were to determine if suppression of neutrophil accumulation and TNF-alpha production in the peritoneal cavity occurs in mice exposed to a chemical stressor [ethanol (EtOH)], to evaluate the role of EtOH-induced increases in endogenous glucocorticoids in any such suppression, and to determine if decreased tumor necrosis factor-alpha (TNF-alpha) production is responsible for decreases in neutrophil accumulation in EtOH-treated mice. An inflammatory response induced in the peritoneal cavity of mice by administration of heat-killed Propionibacterium acnes (P. acnes) was suppressed by a single dose of EtOH given 1 h before administration of the bacteria, as indicated by decreased accumulation of neutrophils in the peritoneal cavity. The concentration of TNF-alpha in the peritoneal cavity was also decreased by EtOH, but exogenous TNF-alpha did not prevent the suppression of neutrophil accumulation. The glucocorticoid antagonist RU-486 did not prevent the suppression of neutrophil accumulation in mice treated with EtOH, but RU-486 did block suppression of neutrophil accumulation caused by administration of exogenous corticosterone. The suppression of neutrophil accumulation caused by exogenous corticosterone was less than produced by EtOH. These observations suggest that the increase in endogenous corticosterone induced by EtOH may explain some of the suppression of neutrophil accumulation, but other neuroendocrine mediators (or EtOH per se) are sufficient to cause the full suppressive effect when the action of corticosterone is blocked by RU-486. The results also demonstrate that EtOH decreases TNF-alpha production, but this is not the mechanism by which neutrophil accumulation is decreased in this model.

Effects of SA6541, a leukotriene A4 hydrolase inhibitor, and indomethacin on carrageenan-induced murine dermatitis

We investigated the effects of S-(4-dimethylaminobenzyl)-N-[(2S)-3-mercapto-2-methylpropionyl]-L- cysteine (SA6541), a potent leukotriene A4 hydrolase inhibitor. on early phase of carrageenan-induced dermatitis model. Carrageenan injection induced edema and neutrophil influx in the mouse ear. SA6541 inhibited edema formation and neutrophil influx. SA6541 also inhibited leukotriene B4 production but not prostaglandin E2 production in the mouse ear. On the other hand, indomethacin inhibited edema formation but not neutrophil influx. Indomethacin also inhibited prostaglandin E2 production but not leukotriene B4 production. Combination therapy with SA6541 and indomethacin strongly inhibited edema formation in comparison with treatment with either agent alone. These results suggest that leukotriene B4 may be important in the pathogenesis of dermatitis.

Possible participation of macrophage inflammatory protein 2 in neutrophil infiltration in allergic inflammation in rats

Recombinant rat macrophage inflammatory protein 2 (MIP-2) was prepared from E. coli transfected with a glutathione-S-transferase (GST)-MIP-2 fusion protein expression vector. A polyclonal antibody to rat MIP-2 was then obtained from rabbits by immunization with recombinant rat MIP-2. Using the polyclonal antibody which selectively suppressed neutrophil chemotactic activity of MIP-2, the role of MIP-2 in neutrophil infiltration in allergic inflammation in rats was studied. In an air pouch-type allergic inflammation model in rats, neutrophil infiltration into the pouch fluid increased with time after antigen challenge. Neutrophil chemotactic activity in the pouch fluid collected 8 h after antigen challenge was diminished by anti-MIP-2 antibody. In addition, when leukocytes that had infiltrated into the pouch fluid collected 4 h after antigen challenge were incubated, neutrophil chemotactic activity in the conditioned medium increased time-dependently, and the activity was neutralized by anti-MIP-2 antibody. Furthermore, when anti-MIP-2 antibody was injected into the pouch 6 h after antigen challenge, neutrophil infiltration into the pouch fluid during the next 2 h was suppressed. These findings indicate that MIP-2 plays an important role in neutrophil infiltration in rat allergic inflammation.

Sequential release of TNFalpha and phospholipase A(2) in a rat model of LPS-induced pleurisy

The levels of extracellular phospholipase A₂ (sPLA₂) and TNFα, and cell accumulation were measured in the pleural washings obtained at different times following the induction of Escherichia coli lipopolysaccharide (LPS, 100 μg/cavity) pleurisy in rats. TNFα peaked at 2 hours (3036 ± 160.3 units/ml) and decreased thereafter. Conversely, levels of sPLA₂ peaked at 48 hours (1.97 ± 0.64 ng/ml) and were increased further (14.02 ± 4.16 ng/ml) by pretreatment with anti-TNFα antibody. Cell accumulation was not affected by antibody pretreatment. These data indicate that the sPLA₂ enzyme is involved in LPS-induced pleurisy. The enzyme seems not to be stimulated by TNFα which may be involved in the downregulation of sPLA₂ in this model of inflammation.