Murine cytomegalovirus infection alters Th1/Th2 cytokine expression, decreases airway eosinophilia, and enhances mucus production in allergic airway disease.

Concomitant infection of murine CMV (MCMV), an opportunistic respiratory pathogen, altered Th1/Th2 cytokine expression, decreased bronchoalveolar lavage (BAL) fluid eosinophilia, and increased mucus production in a murine model of OVA-induced allergic airway disease. Although no change in the total number of leukocytes infiltrating the lung was observed between challenged and MCMV/challenged mice, the cellular profile differed dramatically. After 10 days of OVA-aerosol challenge, eosinophils comprised 64% of the total leukocyte population in BAL fluid from challenged mice compared with 11% in MCMV/challenged mice. Lymphocytes increased from 11% in challenged mice to 30% in MCMV/challenged mice, and this increase corresponded with an increase in the ratio of CD8(+) to CD4(+)TCRalphabeta lymphocytes. The decline in BAL fluid eosinophilia was associated with a change in local Th1/Th2 cytokine profiles. Enhanced levels of IL-4, IL-5, IL-10, and IL-13 were detected in lung tissue from challenged mice by RNase protection assays. In contrast, MCMV/challenged mice transiently expressed elevated levels of IFN-gamma and IL-10 mRNAs, as well as decreased levels of IL-4, IL-5, and IL-13 mRNAs. Elevated levels of IFN-gamma and reduced levels of IL-5 were also demonstrated in BAL fluid from MCMV/challenged mice. Histological evaluation of lung sections revealed extensive mucus plugging and epithelial cell hypertrophy/hyperplasia only in MCMV/challenged mice. Interestingly, the development of airway hyperresponsiveness was observed in challenged mice, not MCMV/challenged mice. Thus, MCMV infection can modulate allergic airway inflammation, and these findings suggest that enhanced mucus production may occur independently of BAL fluid eosinophilia.

Proinflammatory roles of T-cell receptor (TCR)gammadelta and TCRalphabeta lymphocytes in a murine model of asthma.

The role of lymphocytes bearing alphabeta or gammadelta T-cell receptors (TCRs) was assessed during the acute allergic response in a mouse model of asthma. The inflammatory immune response to ovalbumin (OVA) was characterized in wild-type C57BL/6J mice and congenic TCRbeta(-/-) and TCRdelta(-/-) mice by evaluation of airway eosinophilia, histopathology, serum immunoglobulin (Ig)E levels, and in vivo airway responsiveness to methacholine. OVA-challenged wild-type mice demonstrated marked pulmonary inflammation, evidenced by airway eosinophilia (68 +/- 7 x 10(4) cells), peribronchial lympho-plasmocytic infiltration, and elevated serum IgE (4.9 +/- 0.6 microg/ml). These responses were markedly attenuated in TCRdelta(-/-) animals (5.0 +/- 1.0 x 10(4) eosinophils and 1.6 +/- 0. 3 microg/ml IgE) and were completely absent in TCRbeta(-/-) mice (< 1 x 10(3) eosinophils and 0.38 +/- 0.21 microg/ml IgE). Similar results were observed in mice treated with anti-TCRgammadelta or anti-TCRalphabeta monoclonal antibodies. Airway responsiveness to aerosolized methacholine was also reduced in challenged TCRdelta(-/-) animals relative to challenged wild-type mice. These results demonstrate that acute allergic airway responses are dependent upon intact TCRalphabeta and TCRgammadelta lymphocyte function and that TCRgammadelta cells promote acute airway sensitization.

Shifts in lung lymphocyte profiles correlate with the sequential development of acute allergic and chronic tolerant stages in a murine asthma model.

T lymphocytes have a central regulatory role in the pathogenesis of asthma. We delineated the participation of lymphocytes in the acute allergic and chronic tolerant stages of a murine model of asthma by characterizing the various subsets of lymphocytes in bronchoalveolar lavage and lung tissue associated with these responses. Acute (10-day) aerosol challenge of immunized C57BL/6J mice with ovalbumin resulted in airway eosinophilia, histological evidence of peribronchial and perivascular airway inflammation, clusters of B cells and TCRgammadelta cells in lung tissue, increased serum IgE levels, and airway hyperresponsiveness to methacholine. In mice subjected to chronic (6-week) aerosol challenge with ovalbumin, airway inflammation and serum IgE levels were significantly attenuated and airway hyperresponsiveness was absent. The marked increases in lung B and T cell populations seen in the acute stage were also significantly reduced in the chronic stage of this model. Thus, acute ovalbumin challenge resulted in airway sensitization characteristic of asthma, whereas chronic ovalbumin challenge elicited a suppressed or tolerant state. The transition from antigenic sensitization to tolerance was accompanied by shifts in lymphocyte profiles in the lung and bronchoalveolar lavage fluid.

Methacholine-induced pulmonary gas trapping in guinea pigs, hamsters, mice, and rats.

Postmortem pulmonary gas trapping was investigated as an index of in vivo airway obstruction following methacholine inhalation in four different rodent species. Male guinea pigs (Hartley), hamsters (golden Syrian), mice (A/J, BALB/c, and ICR), and rats (Brown-Norway, Fischer 344, Lewis, and Sprague-Dawley) were exposed to aerosols of methacholine or sodium chloride. Maximum excised lung gas volumes (ELGV) of methacholine-exposed guinea pigs, hamsters, mice, and rats were 2.3-8.7 times those of sodium chloride-treated animals. Mean ELGV values of sodium chloride-exposed animals ranged from 1.50 +/- 0.20 ml/kg for guinea pigs to 2.75 +/- 0.20 ml/kg for Brown-Norway rats. Although all species responded to methacholine, guinea pigs were the most responsive, with approximately 1.6 microgram/kg of inhaled methacholine needed to increase ELGV to 200% of control. Compared with guinea pigs, hamsters, mice, and rats were 11- to 1,395-fold less responsive. Although hamsters, mice, and rats are less sensitive than guinea pigs to the airway-obstructive effects of methacholine, pulmonary gas trapping appears useful as a measure of airway responses in these species.

Effect of bronchoconstrictive aerosols on pulmonary gas trapping in the A/J mouse.

We exposed A/J mice to several challenge aerosols and measured gas trapped within excised lungs by quantitating their buoyancy in saline (Archimedes' principle). The temporal stability of the excised lung gas volume (ELGV) measurement was also examined. ELGV increased in a dose proportional manner with increasing concentrations of methacholine and reached a maximum of 338 +/- 33% above vehicle-exposed controls. The A/J mice were 100 times more responsive to aerosol methacholine compared to hyporesponsive C3H/HeJ mice. Aerosol challenges of U-46619, a thromboxane A2 mimetic, and serotonin resulted in a 40% and 135% increase in ELGV's versus their controls, respectively. ELGV's were not increased after aerosols of leukotriene C4, histamine, substance P, N-formyl-methionyl-leucyl-phenyl-alanine and platelet activating factor. Both normal (filtered air-exposed) and hyperinflated (methacholine-exposed) excised lungs lost about 10% of their initial volume by 30 min and 40-65% of initial volume by 4 h. Occlusion of the trachea in either group did not affect the total gas lost, suggesting that majority of the gas loss was via transpleural diffusion. We conclude that determination of ELGV in mice, when performed soon after challenge testing, is a simple, rapid and reliable estimate of airway obstruction.

Pulmonary actions of the neurokinin1-specific agonist [Sar9,Met(O2)11]-substance P.

We examined the relationship between airway obstruction and plasma extravasation produced by the intravenous administration of the selective NK1 receptor agonist [Sar9, Met(O2)11]-substance P(SP). Conscious guinea-pigs were injected with Evans' blue dye followed by intravenous [Sar9,Met(O2)11]-SP. Animals were killed 3 min later and airway obstruction, determined via excised lung gas volumes, and plasma extravasation in the trachea, mainstem bronchi and intrapulmonary airways quantitated. Maximal plasma protein extravasation occurred at a dose about 30 times less than that required to elicit airway obstruction. Neither the neutral endopeptidase (NEP) inhibitor, thiorphan, or the angiotensin-converting enzyme (ACE) inhibitor, captopril, altered the extravasation response to [Sar9,Met(O2)11]-SP. However, thiorphan alone or combined with captopril produced a small but significant potentiation of the airway obstructive response. The marked difference between pulmonary gas trapping and Evans' blue extravasation responses suggest that [Sar9,Met(O2)11]-SP-induced airway obstruction is not secondary to increased pulmonary edema.

Chronic physical activity alters hepatobiliary excretory function in rats.

Recent studies have indicated that exercise causes alterations in the biotransformation of some xenobiotics and the clearances of antipyrine and [14C]aminopyrine. The present study has investigated whether chronic voluntary physical activity alters hepatobiliary excretory function by comparing the clearance and biliary excretion of model substrates for each of four carrier-mediated transport systems (anion, uncharged, bile acid and cation; n = 8 for each chemical in each group) in active and inactive female rats. The active rats had access to running wheels and voluntarily ran 11.2 +/- 0.68 km/day. The active rats were fed ad libitum, and ate 37% more food than weight-matched, restricted-fed sedentary control rats. Basal bile flow was 34% higher in active rats than in inactive rats, and excretion of bile acids, cholesterol and phospholipid were also increased. The biliary excretion and biliary clearance of the anion, indocyanine green, were elevated in active rats, although total clearance and serum concentrations were not different due to decreased non-biliary clearance. Serum elimination and total clearance of the uncharged substrate, ouabain, were elevated in the active rats, due entirely to increased nonbiliary clearance. Total clearance of the bile acid, taurocholate, was higher in active rats due to an increased biliary clearance. In contrast, there were no differences in either the biliary excretion or clearances of the cation, procainamide ethobromide, between the two groups of rats. Finally, no differences in volume of distribution or elimination half-life were noted between inactive and active rats for any of the substrates.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic physical activity: hepatic hypertrophy and increased total biotransformation enzyme activity.

Does chronic voluntary physical activity alter hepatic or intestinal capacities for xenobiotic biotransformation? This question was investigated by comparing biotransformation enzyme activities in liver and small intestine of active and sedentary rats. Male rats allowed unlimited access to a running wheel and fed ad lib. for 6 weeks were weight-matched to sedentary controls; the active rats ate 22% more food than the sedentary rats (P less than 0.05). Active rats ran 2.8 +/- 0.6 miles/day. Liver weights were higher in the active rats (11.2 +/- 0.2 vs 9.8 +/- 0.2 g; P less than 0.05), as were total liver protein, and liver microsomal and cytosolic protein (P less than 0.05). As a result of liver hypertrophy, the active rats showed higher total liver activity of several biotransformation enzymes, including 2-naphthol sulfotransferase, styrene oxide hydrolase, benzphetamine N-demethylase, ethacrynic acid glutathione S-transferase and morphine UDP-glucuronosyltransferase (P less than 0.05). In contrast, there was no detectable difference in total liver N-acetyltransferase activity toward p-aminobenzoic acid, 2-naphthylamine, and 2-amino-fluorene as well as, relative hepatic enzyme activity (expressed per g liver or per mg protein) and total and relative intestinal enzyme activity. We conclude that chronic voluntary physical activity, accompanied by an increased food intake, results in liver hypertrophy and potentially increases total hepatic capacity to biotransform certain xenobiotic chemicals.