Augmented responses to ozone in obese carboxypeptidase E-deficient mice

We reported previously that mice obese as a result of leptin deficiency (ob/ob) have enhanced ozone (O3)-induced airway hyperresponsiveness (AHR) and inflammation compared with wild-type (C57BL/6) controls. To determine whether this increased response to O3 was independent of the modality of obesity, we examined O3-induced AHR and inflammation in Cpe(fat) mice. These mice are obese as a consequence of a mutation in the gene encoding carboxypeptidase E (Cpe), an enzyme important in processing prohormones and proneuropeptides involved in satiety and energy expenditure. Airway responsiveness to intravenous methacholine, measured by forced oscillation, was increased in Cpe(fat) vs. wild-type mice after air exposure. In addition, compared with air exposure, airway responsiveness was increased 24 h after O3 exposure (2 ppm for 3 h) in Cpe(fat) but not in wild-type mice. Compared with air-exposed controls, O3 exposure increased bronchoalveolar lavage fluid (BALF) protein, IL-6, KC, MIP-2, MCP-1, and soluble TNF receptors (sTNFR1 and sTNFR2) as well as BALF neutrophils. With the exception of sTNFR1 and sTNFR2, all of these outcome indicators were greater in Cpe(fat) vs. wild-type mice. Serum sTNFR1, sTNFR2, MCP-1, leptin, and blood leukocytes were elevated in Cpe(fat) compared with wild-type mice even in the absence of O3 exposure, similar to the chronic systemic inflammation observed in human obesity. These results indicate that increased O3-induced AHR and inflammation are consistent features of obese mice, regardless of the modality of obesity. These results also suggest that chronic systemic inflammation may enhance airway responses to O3 in obese mice.     

CXCR2 is essential for maximal neutrophil recruitment and methacholine responsiveness after ozone exposure

Ozone (O(3)), a common air pollutant, induces airway inflammation and airway hyperresponsiveness. In mice, the neutrophil chemokines KC and macrophage inflammatory protein-2 (MIP-2) are expressed in the lungs following O(3) exposure. The purpose of this study was to determine whether CXCR2, the receptor for these chemokines, is essential to O(3)-induced neutrophil recruitment, injury to lungs, and increases in respiratory system responsiveness to methacholine (MCh). O(3) exposure (1 ppm for 3 h) increased the number of neutrophils in the bronchoalveolar lavage fluid (BALF) of wild-type (BALB/c) and CXCR2-deficient mice. However, CXCR2-deficient mice had significantly fewer emigrated neutrophils than did wild-type mice. The numbers of neutrophils in the blood and concentrations of BALF KC and MIP-2 did not differ between genotypes. Together, these data suggest CXCR2 is essential for maximal chemokine-directed migration of neutrophils to the air spaces. In wild-type mice, O(3) exposure increased BALF epithelial cell numbers and total protein levels, two indirect measures of lung injury. In contrast, in CXCR2-deficient mice, the number of BALF epithelial cells was not increased by O(3) exposure. Responses to inhaled MCh were measured by whole body plethysmography using enhanced pause as the outcome indicator. O(3) exposure increased responses to inhaled MCh in both wild-type and CXCR2-deficient mice 3 h after O(3) exposure. However, at 24 h after exposure, responses to inhaled MCh were elevated in wild-type but not CXCR2-deficient mice. These results indicate CXCR2 is essential for maximal neutrophil recruitment, epithelial cell sloughing, and persistent increases in MCh responsiveness after an acute O(3) exposure.     

Increased pulmonary responses to acute ozone exposure in obese db/db mice

Epidemiological studies indicate the incidence of asthma is increased in obese and overweight humans. Responses to ozone (O(3)), an asthma trigger, are increased in obese (ob/ob) mice lacking the satiety hormone leptin. The long form of leptin receptor (Ob-R(b)) is required for satiety; mice lacking this receptor (db/db mice) are also substantially obese. Here, wild-type (WT) and db/db mice were exposed to air or O(3) (2 ppm) for 3 h. Airway responsiveness, measured by the forced oscillation technique, was greater in db/db than WT mice after air exposure. O(3)-induced increases in pulmonary resistance and airway responsiveness were also greater in db/db mice. BALF eotaxin, IL-6, KC, and MIP-2 increased 4 h after O(3) exposure and subsided by 24 h, whereas protein and neutrophils continued to increase through 24 h. For each outcome, the effect of O(3) was significantly greater in db/db than WT mice. Previously published results obtained in ob/ob mice were similar except for O(3)-induced neutrophils and MIP-2, which were not different from WT mice. O(3) also induced pulmonary IL-1beta and TNF-alpha mRNA expression in db/db but not ob/ob mice. Leptin was increased in serum of db/db mice, and pulmonary mRNA expression of short form of leptin receptor (Ob-R(a)) was similar in db/db and WT mice. These data confirm obese mice have innate airway hyperresponsiveness and increased pulmonary responses to O(3). Differences between ob/ob mice, which lack leptin, and db/db mice, which lack Ob-R(b) but not Ob-R(a), suggest leptin, acting through Ob-R(a), can modify some pulmonary responses to O(3).     

Effect of obesity on pulmonary inflammation induced by acute ozone exposure: role of interleukin-6

To determine the role of interleukin (IL)-6 in the increased ozone (O3)-induced inflammation and injury observed in obese vs. lean mice, lean wild-type and leptin-deficient obese (ob/ob) mice were injected with anti-IL-6 antibody (Ab) or isotype control Ab 24 h before exposure to either O3 (2 ppm for 3 h) or room air. Four or 24 h after O3 exposure, bronchoalveolar lavage (BAL) was performed, and the lungs were harvested for Western blotting. Anti-IL-6 Ab caused substantial reductions in O3-induced increases in BAL IL-6 in mice of both genotypes. Four hours following O3, ob/ob mice had increased BAL neutrophils compared with controls, and anti-IL-6-Ab virtually abolished this difference. At 24 h, O3-induced increases in BAL protein and BAL serum albumin were augmented in ob/ob vs. wild-type mice, and anti-IL-6 Ab ablated these obesity-related differences in epithelial barrier injury. O3 increased tyrosine phosphorylation of STAT-3 and STAT-1. There was no effect of obesity on STAT-3 phosphorylation, whereas obesity decreased STAT-1 expression, resulting in reduced STAT-1 phosphorylation. IL-6 neutralization did not alter STAT-3 or STAT-1 phosphorylation in ob/ob or wild-type mice. O3 increased BAL leukemia inhibitory factor (LIF) to a greater extent in obese than in lean mice, and LIF may account for effects on STAT phosphorylation. Our results suggest that IL-6 plays a complex role in pulmonary responses to O3, a role that differs between wild-type and ob/ob mice. Moreover, obesity-related differences in activation of STAT proteins may contribute to some of the differences in the response of obese vs. lean mice.     

Intranasal mite allergen induces allergic asthma-like responses in NC/Nga mice

Airway responses induced by intranasal administration of mite allergen without adjuvant were studied in NC/Nga mice. A crude extract of Dermatophagoides farinae (Df) was administered for 5 consecutive days and a single intranasal challenge booster dose was given 1 week after the last sensitization. 24 h after the single challenge, the airway hyperresponsiveness (AHR) was measured and the bronchoalveolar lavage fluid (BALF) was analyzed for numbers of eosinophils and neutrophils, and both cytokine and chemokine levels. There were marked increases in number of eosinophils in the BALF, AHR, Th2 cytokines (IL-5 and IL-13), and chemokine (eotaxin-1 and eotaxin-2) levels in the BALF following Df exposure. C57BL/6N, A/J, BALB/c, and CBA/JN mouse strains were also exposed to Df crude extract, but all of the measured responses were strongest in NC/Nga mice. Furthermore, Df-exposed NC/Nga mice showed the goblet cell hyperplasia, pulmonary eosinophilic inflammation, and increases in both total serum IgE and Df-specific IgG1. After intranasal exposure of NC/Nga mice to crude extract of Dermatophagoides pteronyssinus, the BALF eosinophilia and AHR were similar to responses induced by Df. None of the study parameters were increased in response to intranasal exposure to ovalbumin. These data demonstrated that NC/Nga mice developed allergic asthma-like responses after intranasal exposure to mite allergens.     

Involvement of vitronectin in lipopolysaccaride-induced acute lung injury

Vitronectin is present in large concentrations in serum and participates in regulation of humoral responses, including coagulation, fibrinolysis, and complement activation. Because alterations in coagulation and fibrinolysis are common in acute lung injury, we examined the role of vitronectin in LPS-induced pulmonary inflammation. Vitronectin concentrations were significantly increased in the lungs after LPS administration. Neutrophil numbers and proinflammatory cytokine levels, including IL-1beta, MIP-2, KC, and IL-6, were significantly reduced in bronchoalveolar lavage fluid from vitronectin-deficient (vitronectin(-/-)) mice, as compared with vitronectin(+/+) mice, after LPS exposure. Similarly, LPS induced increases in lung edema, myeloperoxidase-concentrations, and pulmonary proinflammatory cytokine concentrations were significantly lower in vitronectin(-/-) mice. Vitronectin(-/-) neutrophils demonstrated decreased KC-induced chemotaxis as compared with neutrophils from vitronectin(+/+) mice, and incubation of vitronectin(+/+) neutrophils with vitronectin was associated with increased chemotaxis. Vitronectin(-/-) neutrophils consistently produced more TNF-alpha, MIP-2, and IL-1beta after LPS exposure than did vitronectin(+/+) neutrophils and also showed greater degradation of IkappaB-alpha and increased LPS-induced nuclear accumulation of NF-kappaB compared with vitronectin(+/+) neutrophils. These findings provide a novel vitronectin-dependent mechanism contributing to the development of acute lung injury.     

Ozone-induced lung inflammation and hyperreactivity are mediated via tumor necrosis factor-alpha receptors

This study was designed to investigate the mechanisms through which tumor necrosis factor (Tnf) modulates ozone (O(3))-induced pulmonary injury in susceptible C57BL/6J (B6) mice. B6 [wild-type (wt)] mice and B6 mice with targeted disruption (knockout) of the genes for the p55 TNF receptor [TNFR1(-/-)], the p75 TNF receptor [TNFR2(-/-)], or both receptors [TNFR1/TNFR2(-/-)] were exposed to 0.3 parts/million O(3) for 48 h (subacute), and lung responses were determined by bronchoalveolar lavage. All TNFR(-/-) mice had significantly less O(3)-induced inflammation and epithelial damage but not lung hyperpermeability than wt mice. Compared with air-exposed control mice, O(3) elicited upregulation of lung TNFR1 and TNFR2 mRNAs in wt mice and downregulated TNFR1 and TNFR2 mRNAs in TNFR2(-/-) and TNFR1(-/-) mice, respectively. Airway hyperreactivity induced by acute O(3) exposure (2 parts/million for 3 h) was diminished in knockout mice compared with that in wt mice, although lung inflammation and permeability remained elevated. Results suggested a critical role for TNFR signaling in subacute O(3)-induced pulmonary epithelial injury and inflammation and in acute O(3)-induced airway hyperreactivity.     

Ozone causes lipid peroxidation but little antioxidant depletion in exercising and nonexercising hamsters.

Ozone (O(3)), a major component of urban air pollution, is a strong oxidizing agent that can cause lung injury and inflammation. In the present study, we investigated the effect of inhalation of O(3) on levels of F(2)-isoprostanes in bronchoalveolar lavage fluid (BALF) and on levels of antioxidants in the BALF and plasma of hamsters. Because antioxidants, including urate, ascorbate, GSH, and vitamin E, defend the lungs by reacting with oxidizing agents, we expected to find a decrease in antioxidant levels after O(3) exposure. Similarly, we expected an increase in the levels of F(2)-isoprostanes, which are lipid peroxidation products. Exposure to 1.0 or 3.0 parts/million (ppm) O(3) for 6 h resulted in an increase in BALF neutrophil numbers, an indicator of acute inflammation, as well as elevation of BALF F(2)-isoprostanes. The higher dose of O(3) caused an increase in the BALF level of urate and a decrease in the plasma level of ascorbate, but 1.0 ppm O(3) had no effect on BALF or plasma antioxidant levels. Exposure to 0.12 ppm O(3) had no effect on BALF neutrophils or F(2)-isoprostanes nor on BALF and plasma antioxidants. We also investigated the effect of O(3) exposure of hamsters during exercise on F(2)-isoprostane and antioxidant levels. We found that exposure to 1.0 ppm O(3) during 1 h of exercise on a laddermill increased BALF levels of F(2)-isoprostanes but had no effect on BALF neutrophils or on BALF and plasma antioxidants. These results indicate that O(3) induces inflammation and biomolecule oxidation in the lungs, whereas extracellular antioxidant levels are relatively unchanged.     

Hyaluronan signaling during ozone-induced lung injury requires TLR4, MyD88, and TIRAP

Ozone exposure is associated with exacerbation of reactive airways disease. We have previously reported that the damage-associated molecular pattern, hyaluronan, is required for the complete biological response to ambient ozone and that hyaluronan fragments signal through toll-like receptor 4 (TLR4). In this study, we further investigated the role of TLR4 adaptors in ozone-induced airway hyperresponsiveness (AHR) and the direct response to hyaluronan fragments (HA). Using a murine model of AHR, C57BL/6J, TLR4-/-, MyD88-/-, and TIRAP-/- mice were characterized for AHR after exposure to either ozone (1 ppm × 3 h) or HA fragments. Animals were characterized for AHR with methacholine challenge, cellular inflammation, lung injury, and production of pro-inflammatory cytokines. Ozone-exposed C57BL/6J mice developed cellular inflammation, lung injury, pro-inflammatory cytokines, and AHR, while mice deficient in TLR4, MyD88 or TIRAP demonstrated both reduced AHR and reduced levels of pro-inflammatory cytokines including TNFα, IL-1β, MCP-1, IL-6 and KC. The level of hyaluronan was increased after inhalation of ozone in each strain of mice. Direct challenge of mice to hyaluronan resulted in AHR in C57BL/6J mice, but not in TLR4-/-, MyD88-/-, or TIRAP-/- mice. HA-induced cytokine production in wild-type mice was significantly reduced in TLR4-/-, MyD88-/-, or TIRAP-/- mice. In conclusion, our findings support that ozone-induced airway hyperresponsiveness is dependent on the HA-TLR4-MyD88-TIRAP signaling pathway.     

Dietary galacto-oligosaccharides prevent airway eosinophilia and hyperresponsiveness in a murine house dust mite-induced asthma model

Background

Allergic asthma is strongly associated with the exposure to house dust mite (HDM) and is characterized by eosinophilic pulmonary inflammation and airway hyperresponsiveness (AHR). Recently, there is an increased interest in using dietary oligosaccharides, also known as prebiotics, as a novel strategy to prevent the development of, or reduce, symptoms of allergy.

Aim

We investigated the preventive capacity of dietary galacto-oligosaccharides (GOS) compared to an intra-airway therapeutic treatment with budesonide on the development of HDM-induced allergic asthma in mice.

Methods

BALB/c mice were intranasally sensitized with 1 μg HDM on day 0 followed by daily intranasal challenge with PBS or 10 μg HDM on days 7 to 11. Two weeks prior to the first sensitization and throughout the experiment mice were fed a control diet or a diet containing 1% GOS. Reference mice were oropharyngeally instilled with budesonide (500 μg/kg) on days 7, 9, 11, and 13, while being fed the control diet. On day 14, AHR was measured by nebulizing increasing doses of methacholine into the airways. At the end of the experiment, bronchoalveolar lavage fluid (BALF) and lungs were collected.

Results

Sensitization and challenge with HDM resulted in AHR. In contrast to budesonide, dietary intervention with 1% GOS prevented the development of AHR. HDM sensitization and challenge resulted in a significant increase in BALF leukocytes numbers, which was suppressed by budesonide treatment and dietary intervention with 1% GOS. Moreover, HDM sensitization and challenge resulted in significantly enhanced concentrations of IL-6, CCL17, IL-33, CCL5 and IL-13 in lung tissue. Both dietary intervention with 1% GOS or budesonide treatment significantly decreased the HDM-induced increased concentrations of CCL5 and IL-13 in lung tissue, while budesonide also reduced the HDM-enhanced concentrations of IL-6 and CCL17 in lung tissue.

Conclusion

Not only did dietary intervention with 1% GOS during sensitization and challenge prevent the induction of airway eosinophilia and Th2-related cytokine and chemokine concentrations in the lung equally effective as budesonide treatment, it also prevented AHR development in HDM-allergic mice. GOS might be useful for the prevention and/or treatment of symptoms in asthmatic disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0171-0) contains supplementary material, which is available to authorized users.     

Diet-induced obesity causes innate airway hyperresponsiveness to methacholine and enhances ozone-induced pulmonary inflammation.

We previously reported that genetically obese mice exhibit innate airway hyperresponsiveness (AHR) and enhanced ozone (O(3))-induced pulmonary inflammation. Such genetic deficiencies in mice are rare in humans, and they may not be representative of human obesity. Thus the purpose of this study was to determine the pulmonary phenotype of mice with diet-induced obesity (DIO), which more closely mimics the cause of human obesity. Therefore, wild-type C57BL/6 mice were reared from the time of weaning until at least 30 wk of age on diets in which either 10 or 60% of the calories are derived from fat in the form of lard. Body mass was approximately 40% greater in mice fed 60 vs. 10% fat diets. Baseline airway responsiveness to intravenous methacholine, measured by forced oscillation, was greater in mice fed 60 vs. 10% fat diets. We also examined lung permeability and inflammation after exposure to room air or O(3) (2 parts/million for 3 h), an asthma trigger. Four hours after the exposure ended, O(3)-induced increases in bronchoalveolar lavage fluid protein, interleukin-6, KC, macrophage inflammatory protein-2, interferon-gamma-inducible protein-10, and eotaxin were greater in mice fed 60 vs. 10% fat diets. Innate AHR and augmented responses to O(3) were not observed in mice raised from weaning until 20-22 wk of age on a 60% fat diet. These results indicate that mice with DIO exhibit innate AHR and enhanced O(3)-induced pulmonary inflammation, similar to genetically obese mice. However, mice with DIO must remain obese for an extended period of time before this pulmonary phenotype is observed.     

Disruption of group IVA cytosolic phospholipase A(2) attenuates myocardial ischemia-reperfusion injury partly through inhibition of TNF-α-mediated pathway

Group IVA cytosolic phospholipase A(2) (cPLA(2)α), which preferentially cleaves arachidonic acid from phospholipids, plays a role in apoptosis and tissue injury. Downstream signals in response to tumor necrosis factor (TNF)-α, a mediator of myocardial ischemia-reperfusion (I/R) injury, involve cPLA(2)α activation. This study examined the potential role of cPLA(2)α and its mechanistic link with TNF-α in myocardial I/R injury using cPLA(2)α knockout (cPLA(2)α(-/-)) mice. Myocardial I/R was created with 10-wk-old male mice by 1 h ligation of the left anterior descending coronary artery, followed by 24 h of reperfusion. As a result, compared with wild-type (cPLA(2)α(+/+)) mice, cPLA(2)α(-/-) mice had a 47% decrease in myocardial infarct size, preservation of echocardiographic left ventricle (LV) function (%fractional shortening: 14 vs. 21%, respectively), and lower content of leukotriene B(4) and thromboxane B(2) (62 and 50% lower, respectively) in the ischemic myocardium after I/R. Treatment with the TNF-α inhibitor (soluble TNF receptor II/IgG1 Fc fusion protein, sTNFR:Fc) decreased myocardial I/R injury and LV dysfunction in cPLA(2)α(+/+) mice but not cPLA(2)α(-/-) mice. sTNFR:Fc also suppressed cPLA(2)α phosphorylation in the ischemic myocardium after I/R of cPLA(2)α(+/+) mice. Similarly, sTNFR:Fc exerted protective effects against hypoxia-reoxygenation (H/R)-induced injury in the cultured cardiomyocytes from cPLA(2)α(+/+) mice but not cPLA(2)α(-/-) cardiomyocytes. H/R and TNF-α induced cPLA(2)α phosphorylation in cPLA(2)α(+/+) cardiomyocytes, which was reversible by sTNFR:Fc. In cPLA(2)α(-/-) cardiomyocytes, TNF-α induced apoptosis and release of arachidonic acid to a lesser extent than in cPLA(2)α(+/+) cardiomyocytes. In conclusion, disruption of cPLA(2)α attenuates myocardial I/R injury partly through inhibition of TNF-α-mediated pathways.     

Interference of a short-term exposure to nitrogen dioxide with allergic airways responses to allergenic challenges in BALB/c mice

Nitrogen dioxide (NO(2)) is a common indoor and outdoor air pollutant whose role in the induction of asthma is unclear. We investigated the effects of NO(2) on the development of asthma-like responses to allergenic challenge in BALB/c mice. Ovalbumin (OVA)-immunized mice were intranasally challenged with OVA or saline solution just before starting a 3 h exposure to 5 or 20 ppm NO(2) or air. Twenty parts per million of NO(2) induced a significant increase of bronchopulmonary hyperreactivity in OVA-challenged mice and of permeability according to the fibronectin content of the bronchoalveolar lavage fluid (BALF) 24 h after exposure, as compared with air or 5 ppm NO(2). Eosinophilia (cell counts in the BALF and eosinophil peroxidase of lung tissue) was detected at 24 and 72 h with similar levels for air and 20 ppm NO(2), whereas a marked reduction was unexpectedly observed for 5 ppm NO(2). At 24 h, interleukin-5 in the BALF was markedly reduced at 5 ppm compared with 20 ppm NO(2) and was also more intense for 20 ppm NO(2) than for the air group. In contrast to specific IgG1 titers, anti-OVA IgE titers and interleukin-4 in the BALF were not affected by NO(2) exposure. Irrespective of the concentration of NO(2), OVA-challenged mice did not develop late mucosal metaplasia compared with those exposed to OVA-air. These results indicate that a short exposure to NO(2) can exacerbate or inhibit some features of the development of allergic disease in mice and may depend on the concentration of pollutant.     

Involvement of phosphoinositide 3-kinases in neutrophil activation and the development of acute lung injury.

Activated neutrophils contribute to the development and severity of acute lung injury (ALI). Phosphoinositide 3-kinases (PI3-K) and the downstream serine/threonine kinase Akt/protein kinase B have a central role in modulating neutrophil function, including respiratory burst, chemotaxis, and apoptosis. In the present study, we found that exposure of neutrophils to endotoxin resulted in phosphorylation of Akt, activation of NF-kappaB, and expression of the proinflammatory cytokines IL-1beta and TNF-alpha through PI3-K-dependent pathways. In vivo, endotoxin administration to mice resulted in activation of PI3-K and Akt in neutrophils that accumulated in the lungs. The severity of endotoxemia-induced ALI was significantly diminished in mice lacking the p110gamma catalytic subunit of PI3-K. In PI3-Kgamma(-/-) mice, lung edema, neutrophil recruitment, nuclear translocation of NF-kappaB, and pulmonary levels of IL-1beta and TNF-alpha were significantly lower after endotoxemia as compared with PI3-Kgamma(+/+) controls. Among neutrophils that did accumulate in the lungs of the PI3-Kgamma(-/-) mice after endotoxin administration, activation of NF-kappaB and expression of proinflammatory cytokines was diminished compared with levels present in lung neutrophils from PI3-Kgamma(+/+) mice. These results show that PI3-K, and particularly PI3-Kgamma, occupies a central position in regulating endotoxin-induced neutrophil activation, including that involved in ALI.     

Tyk2-signaling plays an important role in host defense against Escherichia coli through IL-23-induced IL-17 production by gammadelta T cells

Tyrosine kinase 2 (Tyk2), a member of the JAK-signal transducer family, is involved in intracellular signaling triggered by various cytokines, including IL-23. We have recently reported that resident gammadelta T cells in the peritoneal cavity of naive mice produced IL-17 in response to IL-23. In this study, we examined importance of Tyk2-mediated signaling in the IL-17 production by gammadelta T cells using Tyk2 deficient (-/-) mice. Gammadelta T cells in the peritoneal cavity of Tyk2(-/-) mice displayed effecter/memory phenotypes and TCR V repertoire similar to those in Tyk2(+/+) mice and produced comparable level of IL-17 to those in Tyk2(+/+) mice in response to PMA and ionomycin, indicating normal differentiation to IL-17-producing effectors in the absence of Tyk2-signaling. However, gammadelta T cells in Tyk2(-/-) mice produced less amount of IL-17 in response to IL-23 in vitro than those in Tyk2(+/+) mice. Similarly, gammadelta T cells in the peritoneal cavity of Tyk2(-/-) mice showed severely impaired IL-17 production after an i.p. infection with E. coli despite comparable level of IL-23 production to Tyk2(+/+) mice. As a consequence, Tyk2(-/-) mice showed a reduced infiltration of neutrophils and severely impaired bacterial clearance after Escherichia coli infection. These results indicate that Tyk2-signaling is critical for IL-23-induced IL-17 production by gammadelta T cells, which is involved in the first line of host defense by controlling neutrophil-mediated immune responses.     

Toll-like receptor 4 mediates ozone-induced murine lung hyperpermeability via inducible nitric oxide synthase

We tested the hypotheses that 1) inducible nitric oxide synthase (iNOS) mediates ozone (O3)-induced lung hyperpermeability and 2) mRNA levels of the gene for iNOS (Nos2) are modulated by Toll-like receptor 4 (Tlr4) during O3 exposure. Pretreatment of O3-susceptible C57BL/6J mice with a specific inhibitor of total NOS (N(G)-monomethyl-L-arginine) significantly decreased the mean lavageable protein concentration (a marker of lung permeability) induced by O3 (0.3 parts/million for 72 h) compared with vehicle control mice. Furthermore, lavageable protein in C57BL/B6 mice with targeted disruption of Nos2 [Nos2(-/-)] was 50% less than the protein in wild-type [Nos2(+/+)] mice after O3. To determine whether Tlr4 modulates Nos2 mRNA levels, we studied C3H/HeJ (HeJ) and C3H/HeOuJ mice that differ only at a missense mutation in Tlr4 that confers resistance to O3-induced lung hyperpermeability in the HeJ strain. Nos2 and Tlr4 mRNA levels were significantly reduced and correlated in resistant HeJ mice after O3 relative to those in susceptible C3H/HeOuJ mice. Together, the results are consistent with an important role for iNOS in O3-induced lung hyperpermeability and suggest that Nos2 mRNA levels are mediated through Tlr4.     

Acute ozone-induced change in airway permeability: role of infiltrating leukocytes.

The role of infiltrating polymorphonuclear leukocytes (PMNs) in acute lung injury and inflammation is still controversial. In inbred mice, acute ozone (O3) exposure induces airway inflammation that is characterized by a maximal influx of lavageable PMNs 6 h after exposure and a maximal increase in lung permeability 24 h after O3. We tested the hypothesis that O3-induced change in airway epithelial permeability of O3-susceptible C57BL/6J mice is due to infiltrating PMNs. Male mice (6-8 wk) were treated with a nonsteroidal anti-inflammatory drug (indomethacin), a chemotactic inhibitor (colchicine), or an immunosuppressant (cyclophosphamide) to deplete or inhibit PMNs from infiltrating the airways. After drug or vehicle treatment, mice were exposed for 3 h to 2 ppm O3 or filtered air, and pulmonary inflammation was assessed by inflammatory cell counts and total protein content (a marker of airway permeability) in bronchoalveolar lavage (BAL) fluid. Filtered air exposure did not affect the parameters of pulmonary inflammation at any time after exposure. Compared with vehicle controls, each of the drug treatments resulted in significant reduction of PMN influx 6 and 24 h after O3. However, total BAL protein content was not attenuated significantly by the three treatments at either 6 or 24 h postexposure. Results of these experiments suggest that the influx of PMNs and the change in total BAL protein are not mutually dependent events in this model and suggest that infiltrating PMNs do not play a major role in acute O3-induced changes in permeability of the murine lung.     

Airway responses to chronic ozone exposure are partially mediated through mast cells.

Airways inflammation and epithelial injury induced by chronic ozone (O(3)) in genetically mast cell-deficient mice (Kit(W)/Kit(W-v)) were compared with those in mast cell-sufficient mice (+/+) and Kit(W)/Kit(W-v) mice repleted of mast cells (Kit(W)/Kit(W-v)-BMT). Mice were exposed to 0.26 ppm O(3) 8 h/day, 5 days/wk, for 1-90 days. Background was 0.06 ppm O(3). Age-matched mice were exposed to filtered air for O(3) controls. Reversibility of lesions was evaluated 35 days after exposure. Compared with Kit(W)/Kit(W-v), O(3) caused greater increases in lavageable macrophages, epithelial cells, and polymorphonuclear leukocytes in +/+ and Kit(W)/Kit(W-v)-BMT mice. O(3) also caused lung hyperpermeability, but the genotypic groups were not different. Cells and permeability returned to air control levels after O(3). O(3) induced lung cell proliferation only in +/+ and Kit(W)/Kit(W-v)-BMT mice; proliferation remained elevated or increased in +/+ and Kit(W)/Kit(W-v)-BMT mice after O(3). Greater O(3)-induced cell proliferation was found in nasal epithelium of +/+ and Kit(W)/Kit(W-v)-BMT mice compared with Kit(W)/Kit(W-v) mice. Results are consistent with the hypothesis that mast cells affect airway responses induced by chronic O(3) exposure.