Globule leukocytes and mast cells in the rat trachea: their number, distribution, and response to compound 48/80 and dexamethasone

Correlations between clinical signs and corneal cytology in feline eosinophilic keratoconjunctivitis

Objective

To assess correlations between clinical and cytological features of feline eosinophilic keratoconjunctivitis at the time of cytological diagnosis.

Animals Studied

Fifteen client‐owned, domestic breed cats (18 eyes) examined between 2007 and 2019.

Procedures

An electronic search and medical record review of cats diagnosed with feline eosinophilic keratitis or keratoconjunctivitis (FEK) based on clinical examination findings and eosinophils detected on corneal cytology were conducted. Clinical severity was graded using a modified version of a previously validated semiquantitative preclinical ocular toxicology scoring (SPOTS) system. Clinical grades were assigned following review of clinical images and medical record descriptions, and cytological grades were assigned following review of archived corneal cytology slides. Correlations were analyzed for significance using Spearman's rank correlation coefficient.

Results

Higher total corneal scores correlated with higher total conjunctival scores, but not with total fluorescein scores. Small lymphocyte scores correlated negatively with scores for collagen degeneration or mineralization. Globule leukocytes, a unique cell type not previously described in ocular cytology, were identified in 4 of 18 cytological samples. Higher globule leukocyte scores were correlated with higher scores for mast cells or plasma cells. Specimens with lower eosinophil scores had higher globule leukocyte scores.

Conclusions

Large variability was detected in the cytological characteristics and clinical features of FEK‐affected cats. This is the first report of globule leukocytes being identified in ocular cytology from any species. The role of globule leukocytes in the etiopathogenesis and progression of FEK remains unknown and warrants further investigation.

Histamine-induced changes in rat tracheal goblet cell mucin store and mucosal edema

The pathology of chronic asthma in human and mouse is characterized by inflammation and remodeling of airway tissues. As a result of repeated inflammatory insults to the lower airways, smooth muscle thickening, mucin secretion and airway hyperreactivity may develop. In ovalbumin (OVA)-sensitized mice with repeated challenges with OVA to the lower airways, the trachea and bronchi are characterized by goblet cell hyperplasia and mucus hypersecretion from goblet cells. Previous study reports that intravenous (i.v.) application of a high dose of capsaicin releases tachykinin from capsaicin-sensitive nerves, producing acute plasma leakage and mucosal edema formation and causing depletion of mucin granules in goblet cells that results in a reduction in the number and size of Alcian blue (AB)-positive goblet cells in the rat trachea within a few minute after capsaicin application. Histamine is an important non-neural mediator of asthma from mast cells. The present study investigated whether i.v. application of a high dose of histamine (18 μmol/ml/kg) could result in these acute changes and the similar time-course changes in rat trachea. The tracheal whole mounts stained with chloroacetate esterase reagent and AB and tracheal methacrylate sections stained with AB and periodic acid-Schiff reagent were used for evaluation of histological and cellular changes. At 5 min after histamine application, mucosal leaky venules were numerous and subepithelial edema ratio (% of length of edema along the mucosal epithelial circumference of tracheal cross section) was found to be 48.2 ± 4.9, which was greater (P < 0.01) than saline-treated rats. But, the number of AB-positive goblet cells, 2,030 ± 170/mm(2) of mucosal surface epithelium, was similar to saline-treated group (P > 0.05). One day later, edema ratio remained large and the number of AB-positive goblet cells was 1,140 ± 150/mm(2) epithelium, reduced to half the number of the group at 5 min after histamine (P < 0.01). It is suggested that mucus hypersecretion occurred at this time point. At 3 or 5 days after histamine, edema ratio gradually decreased. The number of AB-positive goblet cells continued to remain small on day 3. On day 5 after histamine, the number of AB-positive goblet cells restored to the level of rat group at 5 min after histamine application. At 7 days after histamine, edema ratio returned to the level of saline-treated group. It is concluded that degranulation and thinning of tracheal goblet cells and mucus hypersecretion lagged behind histamine-induced acute plasma leakage and edema, and restoration of mucin store in goblet cells was associated with remission of mucosal edema.

Adenosine receptor antagonism suppresses functional and histological inflammatory changes in the rat urinary bladder

Cyclophosphamide (CYP) induces an interstitial cystitis-like inflammation. The resulting bladder dysfunction has been associated with increased release of adenosine-5'-triphosphate (ATP), structural bladder wall changes and contractile impairment. Due to the inflammatory modulatory effects of purines it was presently wondered if pre-treatment with P1 and P2 purinoceptor antagonists affect the CYP-induced alterations. Rats were pre-treated with saline or antagonists for five days, and 60 h before the in vitro functional examination the rats were administered either saline or CYP. Histological examination revealed CYP-induced bladder wall thickening largely depending on submucosal enlargement, mast cell invasion of the detrusor muscle, increase in muscarinic M5 receptor expression and macrophage migration inhibitory factor (MIF) occurrence in large parts of the urothelium. Functionally, methacholine- and ATP-evoked contractions were smaller in urinary bladders from CYP-treated rats. Pre-treatment with the P2 purinoceptor antagonist suramin and the P1A2B antagonist PSB1115 did not to any great extent affect the CYP-induced changes. The P1A1 antagonist DPCPX, however, abolished the difference of methacholine-evoked contractions between saline- and CYP-treated rats. ATP-evoked contractions were reduced in control after the DPCPX pre-treatment, but not in cystitis. The functional observations for DPCPX were supported by its suppression of CYP-induced submucosal thickening, muscarinic M5 receptor expression and, possibly, detrusor mast cell infiltration and the spread of urothelial MIF occurrence. Thus, P1A1 is an important pro-inflammatory receptor in the acute CYP-induced cystitis and a P1A1 blockade during the initial phase may suppress CYP-induced cystitis. P1A1 purinoceptors seem to regulate contractility in healthy and in inflamed rat urinary bladders.

Dexamethasone-induced eosinopenia is associated with lower progesterone production in cattle

Eosinophilic cells accumulate in the capillaries of the bovine Graafian follicle shortly before ovulation and in the early developing corpus luteum (CL). Suppressing the migration of these eosinophilic cells by dexamethasone allowed us to evaluate their possible function in the CL development. Brown Swiss cows (n = 10) were randomly subdivided into two groups (n = 5). Every group was used once as control group and once as experimental group with two oestrous cycles between each treatment. Eighteen hours (h) after oestrus synchronization, dexamethasone or saline was given. Ovulation was induced 24 h later with gonadotropin-releasing hormone. Another injection of dexamethasone or saline was given 12 h later. Eosinophilic cells in the blood were counted daily until day 7 after the first dexamethasone injection. The collection of ovaries took place at days 1, 2 and 5. Gene expression, protein concentration and location of angiogenic factors, chemokines, insulin-like growth factor 1 (IGF1) and eosinophilic cells were studied. No eosinophilic cells were found in the CL of the treatment group. Blood progesterone decreased significantly in the dexamethasone group from day 8 to 17. The protein concentration of FGF2 increased significantly in CL tissue at day 2 and VEGFA decreased. Local IGF1 gene expression in the CL was not regulated. We assume from our data that the migration of eosinophilic cells into the early CL is not an essential, but an important stimulus for angiogenesis during early CL development in cattle.

Amphetamine modulates cellular recruitment and airway reactivity in a rat model of allergic lung inflammation

Asthma is characterized by pulmonary cellular infiltration, vascular exudation and airway hyperresponsiveness. Several drugs that modify central nervous system (CNS) activity can modulate the course of asthma. Amphetamine (AMPH) is a highly abused drug that presents potent stimulating effects on the CNS and has been shown to induce behavioral, biochemical and immunological effects. The purpose of this study was to investigate the effects of AMPH on pulmonary cellular influx, vascular permeability and airway reactivity. AMPH effects on adhesion molecule expression, IL-10 and IL-4 release and mast cell degranulation were also studied. Male Wistar rats were sensitized with ovalbumin (OVA) plus alum via subcutaneous injection. One week later, the rats received another injection of OVA-alum (booster). Two weeks after this booster, the rats were subjected to AMPH treatment 12 h prior to the OVA airway challenge. In rats treated with AMPH, the OVA challenge reduced cell recruitment into the lung, the vascular permeability and the cellular expression of ICAM-1 and Mac-1. Additionally, elevated levels of IL-10 and IL-4 were found in samples of lung explants from allergic rats. AMPH treatment, in comparison, increased IL-10 levels but reduced those of IL-4 in the lung explants. Moreover, the tracheal responsiveness to methacholine (MCh), as well as to an in vitro OVA challenge, was reduced by AMPH treatment, and levels of PCA titers were not modified by the drug. Our findings suggest that single AMPH treatment down-regulates several parameters of lung inflammation, such as cellular migration, vascular permeability and tracheal responsiveness. These results also indicate that AMPH actions on allergic lung inflammation include endothelium-leukocyte interaction mechanisms, cytokine release and mast cell degranulation.

Eosinophilic Inclusions in Rat Clara Cells and the Effect of an Inhaled Corticosteroid

Large eosinophilic cytoplasmic inclusions (ECIs) are occasionally seen in untreated rat Clara cells. Following inhalation exposure to a corticosteroid, the number of ECIs was increased. This is the first histopathological description of rat ECIs and attempted characterization by immunohistochemistry, in situ hybridization, and electron microscopy. ECIs were strongly positive for surfactant protein D (SP-D) and weakly positive for Clara cell specific protein (CCSP). Clara cell cytoplasm was positive for CCSP mRNA regardless of ECIs, but not within ECIs. Corticosteroid treatment and ECI presence did not affect the immunohistochemistry and in situ hybridization staining intensities. Electron microscopy revealed large intracytoplasmic granules with an irregular limiting membrane. The ECI number was microscopically quantified in rats from three-, six-, and twenty-four-month studies. The mean ECI counts in treated rats increased from three- to fifty-four-fold with a positive dose-related trend, when compared with vehicle controls. Although the mechanism is unclear, SP-D and to a lesser extent CCSP accumulate in the ECIs. As human bronchial epithelium does not appear to contain structures analogous to the ECI, it is suggested that the observation of an increased number of ECIs in the treated rats is not likely to be relevant for human clinical risk assessment.

Pulmonary neutrophil recruitment and bronchial reactivity in formaldehyde-exposed rats are modulated by mast cells and differentially by neuropeptides and nitric oxide

We have used a pharmacological approach to study the mechanisms underlying the rat lung injury and the airway reactivity changes induced by inhalation of formaldehyde (FA) (1% formalin solution, 90 min once a day, 4 days). The reactivity of isolated tracheae and intrapulmonary bronchi were assessed in dose-response curves to methacholine (MCh). Local and systemic inflammatory phenomena were evaluated in terms of leukocyte countings in bronchoalveolar lavage (BAL) fluid, blood, bone marrow lavage and spleen. Whereas the tracheal reactivity to MCh did not change, a significant bronchial hyporesponsiveness (BHR) was found after FA inhalation as compared with naive rats. Also, FA exposure significantly increased the total cell numbers in BAL, in peripheral blood and in the spleen, but did not modify the counts in bone marrow. Capsaicin hindered the increase of leukocyte number recovered in BAL fluid after FA exposure. Both compound 48/80 and indomethacin were able to prevent the lung neutrophil influx after FA, but indomethacin had no effect on that of mononuclear cells. Following FA inhalation, the treatment with sodium cromoglycate (SCG), but not with the nitric oxide (NO) synthase inhibitor L-NAME, significantly reduced the total cell number in BAL. Compound 48/80, L-NAME and SCG significantly prevented BHR to MCh after FA inhalation, whereas capsaicin was inactive in this regard. On the other hand, indomethacin exacerbated BHR. These data suggest that after FA inhalation, the resulting lung leukocyte influx and BHR may involve nitric oxide, airway sensory fibers and mast cell-derived mediators. The effect of NO seemed to be largely restricted to the bronchial tonus, whereas neuropeptides appeared to be linked to the inflammatory response, therefore indicating that the mechanisms responsible for the changes of airway responsiveness caused by FA may be separate from those underlying its inflammatory lung effects.

Tissue-selective mast cell reconstitution and differential lung gene expression in mast cell-deficient Kit(W-sh)/Kit(W-sh) sash mice

BACKGROUND

Mast cell-deficient Kit(W)/Kit(W-v) mice are an important resource for studying mast cell functions in vivo. However, because they are compound heterozygotes in a mixed genetic background and are infertile, they cannot be crossed easily with other mice.

OBJECTIVE

To overcome this limitation, we explored the use of Kit(W-sh)/Kit(W-sh) mice for studying mast cell biology in vivo.

RESULTS

These mice are in a C57BL/6 background, are fertile and can be bred directly with other genetically modified mice. Ten-week-old Kit(W-sh)/Kit(W-sh) are profoundly mast cell-deficient. No mast cells are detected in any major organ, including the lung. Gene microarrays detect differential expression of just seven of 16,463 genes in lungs of Kit(W-sh)/Kit(W-sh) mice compared with wild-type mice, indicating that resting mast cells regulate expression of a small set of genes in the normal lung. Injecting 10(7) bone marrow-derived mast cells (BMMC) into tail veins of Kit(W-sh)/Kit(W-sh) mice reconstitutes mast cell populations in lung, stomach, liver, inguinal lymph nodes, and spleen, but not in the tongue, trachea or skin. Injection of BMMC into ear dermis or peritoneum reconstitutes mast cells locally in these tissues. When splenectomized Kit(W-sh)/Kit(W-sh) mice are intravenously injected with BMMC, mast cells circulate longer and are found more often in the liver and inguinal lymph nodes, indicating that the spleen acts as a reservoir for mast cells following injection and limits migration to some tissues.

CONCLUSION

In summary, these findings show that mast cell-deficient Kit(W-sh)/Kit(W-sh) mice possess unique attributes that favour their use for studying mast cell functions in vivo.

Mechanisms Involved in the Enhancement of Allergic Airways Neutrophil Influx by Permanent C-Fiber Degeneration in Rats

This study was undertaken to clarify the mechanisms by which C-fiber degeneration at neonatal stages exacerbates the inflammatory responses of rat airways. Rats were treated with capsaicin at neonatal stages and immunized with ovalbumin (OVA) at adult ages. Challenge of capsaicin-pretreated rats with OVA promoted a higher influx of neutrophils in bronchoalveolar lavage (BAL) fluid compared with the vehicle group. No significant differences were found for the other cell types. The increased adhesion of N-formyl-methionyl-leucyl-phenylalanine (fMLP; 0.1 microM)- and phorbol myristate acetate (PMA; 1 microM)-treated neutrophils to fibronectin-coated wells did not differ among vehicle- and capsaicin-pretreated rats. Additionally, fMLP (10 microM), platelet-activating factor (0.1 microM), and substance P (50 microM) induced a significant neutrophil chemotaxis, but no differences were found among vehicle and capsaicin groups. Increased levels of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-10, and leukotriene B4 in BAL fluid as well as higher expression of cytokine-induced neutrophil chemoattractant (CINC)-3 in lung homogenates were detected in the capsaicin group compared with vehicle group. In the capsaicin group, chronic treatment with compound 48/80 restored the TNF-alpha levels to control values and prevented the neutrophil influx in BAL fluid. The enhanced production of TNF-alpha, superoxide anion, and nitrite by isolated alveolar macrophages in response to lipopolysaccharide (3 microg/ml), PMA (10 nM), and/or zymosan (100 particles/cell) did not differ between vehicle- and capsaicin-pretreated rats. In conclusion, chronic neuropeptide depletion promoted by neonatal capsaicin treatment up-regulates airways mast cells, which upon activation by antigen at adult ages, release large amounts of cytokines such as TNF-alpha and CINC-3 that accounts for the massive airways neutrophil infiltration.

Differential regulation of the release of tumor necrosis factor-alpha and of eicosanoids by mast cells in rat airways after antigen challenge

BACKGROUND: Rat trachea display a differential topographical distribution of connective tissue mast cells (CTMC) and mucosal mast cells (MMC) that may imply regional differences in the release of allergic mediators such as tumor necrosis factor-alpha (TNF-alpha) and eicosanoids. AIM: To evaluate the role of CTMC and MMC for release of TNF-alpha and eicosanoids after allergenic challenge in distinct segments of rat trachea. MATERIALS AND METHODS: Proximal trachea (PT) and distal trachea (DT) from ovalbumin (OVA)-sensitized rats, treated or not with compound 48/80 (48/80) or dexamethasone, were incubated in culture medium. After OVA challenge, aliquots were collected to study release of TNF-alpha and eicosanoids. RESULTS: Release of TNF-alpha by PT upon OVA challenge peaked at 90 min and decayed at 6 and 24 h. Release from DT peaked at 30-90 min and decayed 6 and 24 h later. When CTMC were depleted with 48/80, OVA challenge exacerbated the TNF-alpha release by PT at all time intervals, while DT exacerbated TNF-alpha levels 6 and 24 h later only. Dexamethasone reduced TNF-alpha production after 90 min of OVA challenge in PT and at 3 and 6h in DT. OVA challenge increased prostaglandin D2) in DT and leukotriene B4 in both segments but did not modify prostaglandin E2 and leukotriene C4 release. CONCLUSION: OVA challenge induces TNF-alpha release from MMC, which is negatively regulated by CTMC. The profile of TNF-alpha and eicosanoids depends on the time after OVA challenge and of the tracheal segment considered.

Spontaneous remission of edema and regranulation of goblet cells in rat tracheae after capsaicin-induced acute inflammation

Previous studies have investigated the short-term effect of capsaicin on edema formation and goblet-cell secretion in the trachea. The present study sought to investigate the long-term effect of a high dose of capsaicin (90 micro g/ml/kg), administered intravenously, on changes in the formation of endothelial gaps among venular endothelial cells, mucosal tissue edema and the secretory activity of goblet cells, including the number and size of goblet cells, and the mucus score and secretory ratio of goblet-cell mucus secretion in the trachea of rats. The tracheal whole mounts with silver staining, those stained with chloroacetate esterase reagent and Alcian blue and tracheal tissue sections stained with Alcian blue and periodic acid-Schiff reagent were used for evaluation. Formation of endothelial gaps occurred a few min after administration of capsaicin, and gaps almost closed within 12 min after capsaicin injection. Five min after capsaicin, the leaky blood vessels were numerous and the subepithelial edema ratio (% of length of edema along the inner circumference of tracheal cross section) was found to be 57.8+/-3.0% ( n=6). The number of Alcian blue-positive goblet cells (1,090+/-220 per mm(2) of mucosal surface) was reduced to half the number of goblet cells in the vehicle-treated rats (2,200+/-230). The mucus score of goblet cell secretion was not changed. The secretory ratio was greatly increased. One day after capsaicin, the edema ratio remained large and the number of Alcian blue-positive goblet cells was also small. The mucus score was also not changed. The secretory ratio was still large. On day 3, the edema ratio remained large, but the number of Alcian blue-positive goblet cells was increased to the level of the controls. The mucus score and secretory ratio returned to the control level. On day 5, the edema ratio was greatly decreased, but it was still significantly larger than that of the controls. The mucus score and secretory ratio remained at the baseline level. Seven days after capsaicin, the edema ratio was similar to the controls. The number of goblet cells was even larger than controls. It is concluded that capsaicin-induced acute inflammation in the rat trachea involves formation of endothelial gaps, extensive plasma extravasation and edema formation, and depletion of goblet-cell secretory granules. Spontaneous gradual remission of edema was accompanied by regranulation of goblet cells with gradual mucogenesis for several days.

Pharmacological modulation of allergic inflammation in the rat airways and association with mast cell heterogeneity

Administration of ovalbumin by aerosol to sensitised rats produced a rapid (15 min) protein exudation in different airway tissues, as determined by Evans blue staining. This was associated with marked mast cell degranulation determined by histological examination, with there being no difference between mucosal and connective tissue mast cells. A 5-day administration regimen with compound 48/80 selectively depleted connective tissue mast cell (positive to berberine staining) without modifying ovalbumin-induced plasma protein extravasation. Treatment of rats with dexamethasone (1 mg/kg, -12 h) or nor-dihydroguaiaretic acid (30 mg/kg i.p., -30 min) significantly reduced ovalbumin-induced protein extravasation and preserved mucosal mast cell morphology. Indomethacin (4 mg/kg i.v., -30 min) exerted no effect on either parameter. In conclusion, we propose the mucosal mast cell as a target cell responsible at least partly for the inhibitory actions of known anti-inflammatory drugs. We suggest an involvement of endogenous leukotriene(s), but not prostanoid(s), in mucosal mast cell activation/degranulation.

Do mucosal mast cells contribute to the immediate asthma response?

In rat trachea, two types of mast cells have been identified, connective tissue mast cells (CTMCs) and mucosal mast cells (MMCs). We previously reported that CTMCs play an important role in tracheal contraction in vitro via 5-hydroxytryptamine (5-HT) release in a rat model. In this study, we investigated whether MMCs also play a role in tracheal contraction by employing mast cell-deficient (Ws/Ws) rats and their congenic (+/+) rats. Rats were actively sensitized with ovalbumin and challenged with it 2 weeks later. To exclude the influence of CTMCs, rats were pretreated for 7 days with compound 48/80 injected i.p. in increasing doses. Histological study confirmed that degranulation occurred in CTMCs, but MMCs still remained. Histamine levels in trachea decreased to 9.31% of control levels. Ovalbumin-specific IgE production showed a time-dependent increase in both Ws/Ws and +/+ rats after sensitization with no significantly different values between the two groups. Ovalbumin challenge caused contraction of the trachea in sensitized control (+/+) rats, but not in sensitized Ws/Ws and compound 48/80-pretreated +/+ rats. Ketanserin inhibited the contraction, but leukotriene antagonist ONO-1078 did not, indicating that the contraction was due to 5-HT, whereas leukotriene, a mediator specific derived from MMCs, has no significant effect. The results suggest that MMCs has minimal, if any, contribution to tracheal contraction and might have another function. Furthermore, Ws/Ws and the congenic rats provide a good model for studying the role of mast cells in the immunologic response in airways.

The lack of compound 48/80-induced contraction in isolated trachea of mast cell-deficient Ws/Ws rats in vitro: the role of connective tissue mast cells

In the rat trachea, two types of mast cells have been identified, connective tissue mast cells and mucosal mast cells. Their different characteristics may account for their different biological functions. The role of connective tissue mast cells in tracheal contraction as one feature of the immediate reaction of asthma was studied in vitro in isolated trachea, using tissue derived from mast cell-deficient (Ws/Ws) rats, heterozygous (Ws/+) rats and control (+/+) rats, and compound 48/80 as a potent inducer of mast cell degranulation. The contractile response of tracheas from the three types of rats was also studied upon exposure to the following spasmogens: histamine, 5-hydroxytryptamine (5-HT), and carbachol. Histamine content in tissues reflected the differing mast cell numbers in strips from the three rat types. It was found that carbachol and 5-HT elicited tracheal contraction in a similar manner in strips from the three types of rats. Histamine had no contractile effect. Compound 48/80, at a dose of 25 microg/ml, elicited contraction in tracheas from both control (+/+) and heterozygous (Ws/+), but not in trachea from Ws/Ws rats. Compound 48/80-induced contractions in tracheas from +/+ rats were inhibited by 0.1 microM ketanserin and 0.1 microM nedocromil, but not by 0.1 microM mepyramine. Enzyme histochemistry confirmed that the degranulation occurred in connective tissue mast cells, but not in mucosal mast cells. We concluded that connective tissue mast cells play an important role in rat tracheal contraction via 5-HT release induced by compound 48/80. In addition, the specific mast cell-deficient (Ws/Ws) rats provide a good tool for studying the roles of mast cells in airway system.

Eosinophilic gastroenterocolitis in iron lactate-overloaded rats

Eosinophilic gastroenterocolitis with peripheral eosinophilia was induced in rats fed a diet containing 2.5% or 5.0% iron lactate for 3 mo. Additional findings consistent with iron overload were also observed. Microscopically, the lesions consisted of eosinophilic infiltrations in the mucosa and submucosa along the whole length of the gastrointestinal tracts, increased surface area of the gastric mucosal propria covered with mucous cells, and increased apoptotic bodies in the gastric glandular neck of rats in the 2.5% and 5.0% groups. An increased number of intraepithelial globule leukocytes in the gastric and intestinal lamina propria was also observed in the 5.0% group. Globule leukocytes in the gastric mucosa contained obviously enlarged granules in their cytoplasm in these rats. The granules of the globule leukocytes were positive for rat mast cell protease II, suggesting the mastocyte origin of these cells. Although severe infiltration of eosinophils and globule leukocytes suggested a type-1 hypersensitivity reaction, other features such as an increasing vascular permeability were not detected. Serum IgE levels in the 5.0% and control groups were < 3 ng/ml. Final body weights of male and female rats of the 5.0% group were suppressed to 70% and 90%, respectively, of those of the control rats, whereas food consumption was comparable to that of the control group. The morphologic characteristics of the gastrointestinal lesions and peripheral eosinophilia induced in rats fed iron lactate were very similar to those in some cases of eosinophilic gastroenterocolitis in humans and other animals.

Endothelial gaps and adherent leukocytes in allergen-induced early- and late-phase plasma leakage in rat airways

Exposure of sensitized individuals to antigen can induce allergic responses in the respiratory tract, manifested by early and late phases of vasodilatation, plasma leakage, leukocyte influx, and bronchoconstriction. Similar responses can occur in the skin, eye, and gastrointestinal tract. The early-phase response involves mast cell mediators and the late-phase response is leukocyte dependent, but the mechanism of leakage is not understood. We sought to identify the leaky blood vessels, to determine whether these vessels contained endothelial gaps, and to analyze the relationship of the gaps to adherent leukocytes, using biotinylated lectins or silver nitrate to stain the cells in situ and Monastral blue as a tracer to quantify plasma leakage. Most of the leakage occurred in postcapillary venules (< 40-microns diameter), whereas most of the leukocyte migration (predominantly neutrophils) occurred in collecting venules. Capillaries and arterioles did not leak. Endothelial gaps were found in the leaky venules, both by silver nitrate staining and by scanning electron microscopy, and 94% of the gaps were distinct from sites of leukocyte adhesion or migration. We conclude that endothelial gaps contribute to both early and late phases of plasma leakage induced by antigen, but most leakage occurs upstream to sites of leukocyte adhesion.

Contractile responses of proximal and distal trachea segments isolated from rats subjected to immunological stimulation: role of connective tissue mast cells

1. Anaphylaxis-induced contractions of proximal and distal tracheal segments isolated from 14-day ovalbumin (OA)-sensitized rats were studied. 2. OA-induced contractions in distal segments were significantly greater than those observed in proximal segments. 3. Pretreatment of the rats with compound 48/80 or with sodium cromoglycate (SCG) aerosolization significantly reduced OA-induced contractions of trachea distal segments, whereas the contractions of proximal segments were reduced only by compound 48/80. 4. Mepacrine reduced and indomethacin increased the OA-induced contractions in all tracheal segments. Nor-dihydroguaiaretic acid increased the OA-induced contractions in distal tracheal segments, whereas dazoxiben inhibited the contractions in these same segments; neither of these drugs had any effect on the contractions in proximal tracheal segments. 5. The depletion of connective tissue mast cells and subsequent in vitro treatment with indomethacin increased the OA-induced contractions in both segments. 6. We conclude that the contractions of tracheal muscle from OA-sensitized rats depends on the topographic and anatomical origin of the airway tissue. 7. Mediators released by connective tissue mast cells in proximal and distal segments play a pivotal role in this response and may account for variations in the intensity of contraction seen after the addition of OA.

Immunomorphologic studies of mast cell heterogeneity, location, and distribution in the rat conjunctiva

Mast cells are crucial components of immediate and some delayed-type hypersensitivity reactions. They play a pivotal role in allergic conjunctivitis and other immunoinflammatory disorders of the ocular surface, yet little is known of their distribution and heterogeneity in the conjunctiva of potential animal models, such as the rat. In this study, mast cell types were investigated in histologic sections and corneal-conjunctival-lid whole mounts by using toluidine blue, alcian blue-safranin, and immunohistochemical staining methods (anti-rat mast cell proteinase [RMCP] antibodies). Quantitative analyses were performed on corneal-conjunctival-lid whole mounts by using the optical dissector procedure to obtain the density of mast cells per unit volume in different regions of the conjunctiva. Single and double immunohistochemical analyses revealed that the mast cells in the conjunctiva of the limbus, fornices, and lid margin were strongly RMCP I+, suggesting that they were of the connective tissue phenotype. Mast cells containing the mucosal mast cell proteinase RMCP II were not present in the normal conjunctiva. Histochemical analysis revealed that the maturity of the connective tissue mast cells, as assessed by the presence or absence of safranin (heparin)-positive granules in their cytoplasm varied in different regions. In the lid margin 60% to 78% of the mast cells were solely alcian blue-positive, whereas in the fornices 68% to 78% were safranin-positive. In the limbus the predominant type of mast cell was either safranin-positive or contained mixed granules. Mast cell densities were greatest close to the lid margin (10,000 to 12,000 cells/mm3), followed by the limbus (3400 to 4800 cells/mm3) and were rare in the remainder of the conjunctiva (500 to 1000 cells/mm3), with the exception of the region around the nictitating membrane. This study of rat conjunctival mast cells provides essential baseline data for future studies of the role of mast cells in models of allergic conjunctivitis.

Multiple mechanisms for the effects of capsaicin, bradykinin and nicotine on CGRP release from tracheal afferent nerves: role of prostaglandins, sympathetic nerves and mast cells

Application of capsaicin (CAP), bradykinin (BK) or nicotine (NIC) to intraluminally perfused rat tracheas induced an increase in calcitonin gene-related peptide (CGRP) levels in the perfusates. Depletion of sensory afferent CGRP with systemic CAP pretreatment resulted in a significant reduction of CGRP release evoked by CAP, BK or NIC. Chemical destruction of sympathetic nerve fibres by systemic pretreatment with 6-hydroxydopamine reduced CGRP release evoked by NIC, but did not alter the release produced by CAP or BK. Elimination of the tracheal mast cell population by pretreatment with compound 48/80 did not alter the effects of CAP, BK or NIC. CGRP release evoked by BK and NIC, but not CAP, was diminished by indomethacin, suggesting that cyclooxygenase products mediate the actions of BK and NIC. Prostaglandins, PGE1, PGE2, PGF2 alpha and PGI2, displayed stimulatory effects on CGRP release in the trachea. There are evidently multiple mechanisms mediating CGRP release from sensory terminals in rat trachea. It appears that CAP exerts a direct action on sensory nerves, while the effects of BK and NIC are mediated by PG synthesis. Sympathetic activation may be involved in NIC, but not BK, induced PG-mediated CGRP release.

Fasting or dexamethasone treatment reduce protease content in rat lung mast cells and modulation of histamine synthesis by H3 receptors

The sensitivity of mast cells to H3-receptor modulation was studied in rat lung under various hormonal conditions. The heterogeneity of mast cell sub-populations in rat lung was assessed by the tissue content of rat mast cell protease I (RMCP I) and rat mast cell protease II (RMCP II). After 24 h fasting, concentrations of RMCP I were unchanged whereas the concentration of RMCP II was significantly reduced by 49%. The [3H]histamine (HA) synthesis was concomitantly decreased by 35%. In addition, the modulation of [3H]HA synthesis by the H3 receptor agonist, (R)alpha-methylHA and by the antagonist, thioperamide, observed in control rats, was lost in fasted rats. Single and repeated administrations of dexamethasone did not influence RMCPI concentrations, but decreased the concentrations of RMCP II with a parallel decrease in [3H]HA synthesis. The inhibitory effect of (R)alpha-methylHA on [3H]HA synthesis was also reduced. These results suggest that a subpopulation of RMCP II-containing mast cells, very sensitive to environmental factors, could be the mast cells synthesizing HA in an H3-receptor-dependent manner.

Developmental changes in intestinal globule leukocytes of normal rats

The changes in the number, distribution, and ultrastructure of globule leukocytes (GL) during postnatal development were investigated in the intestinal epithelium of non-infected healthy rats. Intestinal GL were abundant in normal newborn rats even in the absence of infection. They subsequently decreased markedly to the adult level by the fourth week. Ultrastructurally, morphological variations suggesting maturation of the cells were observed in the GL during development. These changes could be noted neither in the mucosal mast cells (MMC) nor in the granular intra-epithelial lymphocytes. Morphological differences between GL and other cells were evident in adult animals. Most notably, paracrystalline structures were found exclusively in the granules of the GL. Immunohistochemically, both the GL and MMC were stained with anti-serotonin, but not with anti-IgE. Degranulation of GL in developing rats was caused by repeated intraperitoneal administration of dexamethasone. Neither GL nor MMC were affected by compound 48/80. These results indicate that (1) the GL and MMC are derived from a common ancestral cell toward the end of embryonic development, (2) the immature GL migrate from the lamina propria into the epithelium to differentiate, mature, and proliferate, and (3) the immature GL have specific functions during the neonatal period.

Calcitonin gene-related peptide in secretory granules of serous cells in the rat tracheal epithelium

The tracheal epithelium of pathogen-free rats consists mainly of serous-type secretory cells, ciliated cells, basal cells, and a few neuroendocrine cells. Mucus-containing goblet cells are rare. Calcitonin gene-related peptide (CGRP) is known to exist in the neuroendocrine cells and in sensory nerves of the tracheal mucosa and is released into the airway lumen by sensory nerve stimulation. In this study, we determined whether epithelial serous cells are another source of CGRP. Tracheas of adult male specific pathogen-free F344 rats were immunostained by an avidin-biotin technique either as whole mounts or as cryostat sections using two different polyclonal primary antibodies to rat CGRP. Some specimens were stained for CGRP-like immunofluorescence and examined with a confocal microscope. CGRP immunoreactivity was present in granules of serous cells throughout the trachea. In whole mounts, the stained cells were most abundant between the cartilaginous rings, especially in the rostral trachea, where they constituted 56% of the epithelial cells in contact with the tracheal lumen. Serous cells were easily distinguished from neuroendocrine cells and nerve fibers with CGRP immunoreactivity. In evidence that the CGRP immunoreactivity was specific, the staining of serous cells was abolished by omitting the primary antibody and by absorption with 10 micrograms/ml CGRP. Antibodies to substance P, vasoactive intestinal polypeptide, and tyrosine hydroxylase did not stain epithelial serous cells. An antibody to protein gene product 9.5 labeled neuroendocrine cells, but not serous cells. Injection of capsaicin (150 micrograms/kg intravenously), a substance known to degranulate epithelial serous cells, reduced the staining of the serous cells for CGRP.(ABSTRACT TRUNCATED AT 250 WORDS)

Postnatal maturation of mast cell subpopulations in the rat respiratory tract

The distribution and enumeration of mast cell subpopulations within the respiratory tract of a high- and low-Ige responder rat strain was determined during postnatal development. Mast cells were identified in adjacent sections by the alcian blue (AB)/safranin (SAF) staining sequence, or using immunoperoxidase to detect the rat mast cell proteinases I (RMCPI) or II (RMCPII). At birth both mucosal mast cells (MMC) and connective tissue mast cells (CTMC) were represented in very low numbers at distinct locations throughout the respiratory tract. The total number of mast cells increased with age. MMC (AB+/RMCPII+ mast cells) were the predominant phenotype in the epithelium and lamina propria of the trachea and the major conducting airways of the lung in all age groups. In contrast, CTMC (AB+/RPMCPI+ and SAF+/RMCPI+ mast cells) predominated in the submucosa of the trachea and major conducting airways as well as in the parenchyma and visceral pleura of the peripheral lung. Both phenotypes co-exist in similar proportions in peribronchial adventitial tissue and adventitia surrounding large blood vessels in neonates as well as adults. In rats the tracheal epithelium is densely populated by MMC from around the time of weaning (3 weeks) and a small but generalized increase in the number of MMC at all sites within the respiratory tract is noted from this time. This increase in MMC frequency in tissue sections with increasing age is mirrored by the levels of circulating serum RMCPII. The number of bone marrow-derived MMC also increased with increasing age prior to weaning, with a significant drop (P less than 0.01) at 4 weeks of age before returning to the peak numbers in 3-week-old rats. The high-IgE responder Brown Norwegian (BN) rat strain constitutively produces significantly more IgE than the low-IgE responder White albino Glaxo (WAG) strain (P less than 0.001) at all ages studied. In contrast, only minor differences between the number and distribution of mast cells in the two strains were observed.

Studies on the density, distribution, and surface phenotype of intraepithelial class II major histocompatibility complex antigen (Ia)-bearing dendritic cells (DC) in the conducting airways

Conventional immunohistochemical analysis of airway intraepithelial class II major histocompatibility complex (Ia) expression demonstrates a morphologically heterogeneous pattern of staining, suggestive of the presence of a mixed population of endogenous antigen presenting cells. Employing a novel tissue sectioning technique in conjunction with optimal surface antigen fixation, we now demonstrate that virtually all intraepithelial Ia staining throughout the respiratory tree in the normal rat, can be accounted for by a network of cells with classical dendritic cell (DC) morphology. The density of DC varies from 600-800 per mm2 epithelial surface in the large airways, to 75 per mm2 in the epithelium of the small airways of the peripheral lung. All the airway DC costain for CD4, with low-moderate expression of a variety of other leukocyte surface markers. Both chronic (eosinophilic) inflammation and acute (neutrophilic) inflammation, caused respectively by inhalation of chemical irritants in dust or aerosolised bacterial lipopolysaccharide (LPS), are shown to be accompanied by increased intraepithelial DC density in the large airways (in the order of 50%) and up to threefold increased expression of activation markers, including the beta chain of CD11/18. The kinetics of the changes in the DC network in response to LPS mirrored those of the transient neutrophil influx, suggesting that airway intraepithelial DC constitute a dynamic population which is rapidly upregulated in response to local inflammation. These findings have important theoretical implications for research on T cell activation in the context of allergic and infectious diseases in the respiratory tract.

Macrophage engulfment of mucosal mast cells in rats treated with dexamethasone

The effects of corticosteroid treatment on mucosal mast cells in rat jejunal mucosa were examined. Rats previously infected with Nippostrongylus brasiliensis received a single IP injection of 1 mg dexamethasone. Three hours later, one third of mucosal mast cells demonstrated minor granular changes (fusion or peripheral clear zones) by electron microscopy. At 7 hours, by light microscopy, the majority of mucosal mast cells appeared abnormal with clustering of granules. By electron microscopy, 151 of 233 (65%) mucosal mast cells had been engulfed by enlarged macrophages and were in various stages of degeneration inside large phagosomes. By 24 hours, the number of mucosal mast cells had decreased to less than 10% of the initial number with parallel decreases in tissue rat mast cell protease II and histamine levels. Serum levels of rat mast cell protease II did not increase, and intestinal morphology was invariably normal with no evidence of inflammatory changes up to and including 24 hours. Observations were similar in uninfected animals. In contrast, in rats undergoing antigen-induced anaphylaxis, a significant elevation of serum rat mast cell protease II level was evident at 3 and 7 hours, and macrophage engulfment of mucosal mast cells was never seen, although tissue edema, enterocyte loss, and hemorrhage were observed. It is concluded that dexamethasone treatment results in macrophage engulfment and destruction of mucosal mast cells that occurs without granular mediator release and local inflammatory effects.

Occurrence of mast cells in relation to the distribution of nerve fibers in the rat larynx

The distribution of mast cells in the rat larynx was studied at a light microscopic level in relation to nerve fibers showing substance P (SP)- and calcitonin gene-related peptide (CGRP)-like immunoreactivity (-LI) and ultrastructurally in relation to unmyelinated nerve fibers. Connective tissue mast cells (CTMC), demonstrated by staining for avidin-peroxidase and immunohistochemical staining for 5-hydroxytryptamine (5-HT), were localized in the lamina propria. Alcian blue and toluidine blue revealed mast cells in the epithelium and the lamina propria. The mast cells showed similar regional differences in their distribution as fibers showing SP- and CGRP-LI. A large or moderate number of cells was found on the laryngeal side of the epiglottis, in the ventral recess and in the aryepiglottic folds. No mast cells were found in the vocal cords. In addition, a large number of cells showing 5-HT-LI were observed in the subglottic epithelium but not in the supraglottic and the glottic epithelia. Ultrastructurally and by use of SP- and CGRP-immunohistochemistry, nerve fibers were sometimes observed close to the mast cells. These findings may be of importance in the understanding of laryngeal pathophysiological events.

Glucocorticoids inhibit neurogenic plasma extravasation and prevent virus-potentiated extravasation in the rat trachea

Capsaicin increases the permeability of blood vessels in the rat tracheal mucosa through a mechanism involving the release of tachykinins from sensory nerves. This capsaicin-induced increase in vascular permeability is potentiated by viral infections of the respiratory tract. The present study was done to determine whether this "neurogenic plasma extravasation" can be inhibited by glucocorticoids, to learn the time course of this inhibition, and to determine whether glucocorticoids can prevent the potentiating effect of viral respiratory infections on neurogenic plasma extravasation. Groups of pathogen-free F344 rats were treated with dexamethasone for 2 or 8 h (4 mg/kg i.p.) or 48 or 120 h (0.5-4 mg/kg per d i.p.). Another group of rats was treated with dexamethasone for 120 h following the intranasal inoculation of Sendai virus. The magnitude of plasma extravasation produced by capsaicin or substance P was assessed after this treatment by using Monastral blue pigment and Evans blue dye as intravascular tracers. We found that dexamethasone reduced, in a dose-dependent fashion, the magnitude of plasma extravasation produced in the rat trachea by capsaicin and substance P. Significant inhibition was produced by a dose of dexamethasone as small as 0.5 mg/kg i.p. The effect of dexamethasone had a latency of several hours and reached a maximum after 2 d of treatment. Furthermore, dexamethasone prevented the potentiation of neurogenic plasma extravasation usually present after 5 d of Sendai virus respiratory infection.

Tracheal parasympathetic neurons of rat, mouse and guinea pig: partial expression of noradrenergic phenotype and lack of innervation from noradrenergic nerve fibres

Noradrenergic nerves were studied in whole-mount preparations of the rat, mouse and guinea pig trachea by means of glyoxylic acid-induced catecholamine fluorescence and dopamine beta-hydroxylase immunoreactivity. In an effort to raise tissue levels of catecholamines, some specimens were also treated with the monoamine oxidase inhibitor pargyline, and with L-DOPA, a precursor of noradrenaline. Noradrenergic nerve fibres were detected around blood vessels, within the tracheal smooth muscle and in the mucosa, but never around or in the proximity of neurons of the tracheal ganglia, even after amine precursor loading. These parasympathetic ganglion cells did not show catecholamine fluorescence under control conditions. In the rat and mouse, but not in the guinea pig, some tracheal neurones were dopamine beta-hydroxylase immunoreactive and showed uptake and metabolism of amine precursors, thus expressing aspects of the catecholaminergic phenotype.

Changes in epithelial secretory cells and potentiation of neurogenic inflammation in the trachea of rats with respiratory tract infections

In rats respiratory tract infections due to Sendai virus and coronavirus usually are transient, but they can have long-lasting consequences when accompanied by Mycoplasma pulmonis infections. Morphological alterations in the tracheal epithelium and a potentiation of the inflammatory response evoked by sensory nerve stimulation ("neurogenic inflammation") are evident nine weeks after the infections begin, but the extent to which these changes are present at earlier times is not known. In the present study we characterized these abnormalities in the epithelium and determined the extent to which they are present 3 and 6 weeks after the infections begin. We also determined the magnitude of the potentiation of neurogenic inflammation at these times, whether the potentiation can be reversed by glucocorticoids, and whether a proliferation of blood vessels contributes to the abnormally large amount of plasma extravasation associated with this potentiation. To this end, we studied Long-Evans rats that acquired these viral and mycoplasmal infections from other rats. We found that the tracheal epithelium of the infected rats had ten times as many Alcian blue-PAS positive mucous cells as did that of pathogen-free rats; but it contained none of the serous cells typical of pathogen-free rats, so the total number of secretory cells was not increased. In addition, the epithelium of the infected rats had three times the number of ciliated cells and had only a third of the number of globule leukocytes. In response to an injection of capsaicin (150 micrograms/kg i.v.), the tracheas of the infected rats developed an abnormally large amount of extravasation of two tracers, Evans blue dye and Monastral blue pigment, and had an abnormally large number of Monastral blue-labeled venules, particularly in regions of mucosa overlying the cartilaginous rings. This abnormally large amount of extravasation was blocked by dexamethasone (1 mg/day i.p. for 5 days). We conclude that M. pulmonis infections, exacerbated at the outset by viral infections, result within three weeks in the transformation of epithelial serous cells into mucous cells, the proliferation of ciliated cells, and the depletion of globule leukocytes. They also cause a proliferation of mediator-sensitive blood vessels in the airway mucosa, which is likely to contribute to the potentiation of neurogenic inflammation that accompanies these infections.