Interaction between adenosine and allergen or compound 48/80 on lung parenchymal strips from actively sensitized Brown Norway rats

No Gender Differences in Egocentric and Allocentric Environmental Transformation After Compensating for Male Advantage by Manipulating Familiarity

The present study has two-fold aims: to investigate whether gender differences persist even when more time is given to acquire spatial information; to assess the gender effect when the retrieval phase requires recalling the pathway from the same or a different reference perspective (egocentric or allocentric). Specifically, we analyse the performance of men and women while learning a path from a map or by observing an experimenter in a real environment. We then asked them to reproduce the learned path using the same reference system (map learning vs. map retrieval or real environment learning vs. real environment retrieval) or using a different reference system (map learning vs. real environment retrieval or vice versa). The results showed that gender differences were not present in the retrieval phase when women have the necessary time to acquire spatial information. Moreover, using the egocentric coordinates (both in the learning and retrieval phase) proved easier than the other conditions, whereas learning through allocentric coordinates and then retrieving the environmental information using egocentric coordinates proved to be the most difficult. Results showed that by manipulating familiarity, gender differences disappear, or are attenuated in all conditions.

Propofol Attenuates Small Intestinal Ischemia Reperfusion Injury through Inhibiting NADPH Oxidase Mediated Mast Cell Activation

Both oxidative stress and mast cell (MC) degranulation participate in the process of small intestinal ischemia reperfusion (IIR) injury, and oxidative stress induces MC degranulation. Propofol, an anesthetic with antioxidant property, can attenuate IIR injury. We postulated that propofol can protect against IIR injury by inhibiting oxidative stress subsequent from NADPH oxidase mediated MC activation. Cultured RBL-2H3 cells were pretreated with antioxidant N-acetylcysteine (NAC) or propofol and subjected to hydrogen peroxide (H2O2) stimulation without or with MC degranulator compound 48/80 (CP). H2O2 significantly increased cells degranulation, which was abolished by NAC or propofol. MC degranulation by CP further aggravated H2O2 induced cell degranulation of small intestinal epithelial cell, IEC-6 cells, stimulated by tryptase. Rats subjected to IIR showed significant increases in cellular injury and elevations of NADPH oxidase subunits p47(phox) and gp91(phox) protein expression, increases of the specific lipid peroxidation product 15-F2t-Isoprostane and interleukin-6, and reductions in superoxide dismutase activity with concomitant enhancements in tryptase and β-hexosaminidase. MC degranulation by CP further aggravated IIR injury. And all these changes were attenuated by NAC or propofol pretreatment, which also abrogated CP-mediated exacerbation of IIR injury. It is concluded that pretreatment of propofol confers protection against IIR injury by suppressing NADPH oxidase mediated MC activation.

The mechanism of sevoflurane preconditioning-induced protections against small intestinal ischemia reperfusion injury is independent of mast cell in rats

The study aimed to investigate whether sevoflurane preconditioning can protect against small intestinal ischemia reperfusion (IIR) injury and to explore whether mast cell (MC) is involved in the protections provided by sevoflurane preconditioning. Sprague-Dawley rats exposed to sevoflurane or treated with MC stabilizer cromolyn sodium (CS) were subjected to 75-minute superior mesenteric artery occlusion followed by 2-hour reperfusion in the presence or absence of MC degranulator compound 48/80 (CP). Small intestinal ischemia reperfusion resulted in severe intestinal injury as demonstrated by significant elevations in intestinal injury scores and p47^phox and gp91^phox, ICAM-1 protein expressions and malondialdehyde and IL-6 contents, and MPO activities as well as significant reductions in SOD activities, accompanied with concomitant increases in mast cell degranulation evidenced by significant increases in MC counts, tryptase expression, and β-hexosaminidase concentrations, and those alterations were further upregulated in the presence of CP. Sevoflurane preconditioning dramatically attenuated the previous IIR-induced alterations except MC counts, tryptase, and β-hexosaminidase which were significantly reduced by CS treatment. Furthermore, CP exacerbated IIR injury was abrogated by CS but not by sevoflurane preconditioning. The data collectively indicate that sevoflurane preconditioning confers protections against IIR injury, and MC is not involved in the protective process.

Role of sphingosine-1-phosphate (S1P) and the S1P(2) receptor in allergen-induced, mast cell-dependent contraction of rat lung parenchymal strips

Lung parenchymal strips isolated from ovalbumin-sensitized rats manifest a mast cell-dependent, biphasic contraction when challenged with allergen. The first phase is mediated by the release of preformed 5-HT while the second phase is dependent on de novo synthesis of leukotrienes. Sphingosine 1-phosphate (S1P) is a sphingolipid metabolite which is readily generated in mast cells and has been demonstrated to be an important regulator of allergen-induced mast cell activation. We have used the parenchymal strip to explore the role of sphingosine 1-phosphate and the S1P(2) receptor in the two components of the acute response to allergen. Lung parenchymal strips were prepared from Brown Norway rats actively sensitized to ovalbumin. The strips were set up in organ baths and contractile responses measured isometrically. The inhibitors of sphingosine kinase, D-erythro-NN-dimethylsphingosine (dimethylsphingosine) and 4-[4-(4-chloro-phenyl)-thiazol-2-ylamino]-phenol (SKI-II) inhibited concentration-dependently both phases of the contractile response induced by 0.1 microg ml(-1) ovalbumin. The effects were seen at concentrations similar to those which inhibit the purified enzyme and were selective in that neither the contractile response to adenosine nor that to 5-hydroxytryptamine was affected. JTE-013 (a selective S1P(2) receptor antagonist) also blocked the response to ovalbumin (0.1 microg ml(-1)). However, the concentrations of JTE-013 required (microM) were substantially higher than its affinity for the S1P(2) receptors (nM). However, when tested against a lower concentration of ovalbumin (0.03 microg ml(-1)), JTE-013 inhibited the response with nM potency. These data demonstrate the importance of S1P and the S1P(2) receptor as regulators of allergen-induced activation of mast cells in their natural environment in the rat lung.

Effects of endotoxin and allergen alone and in combination on the sensitivity of the rat airways to adenosine

1 The airways of patients with asthma are hyperresponsive to adenosine. The phenomenon can be mimicked in the actively sensitized Brown Norway rat by exposure to allergen or lipopolysaccharide (LPS). We wondered whether combined treatment with allergen and endotoxin would result in additive effects or synergism with respect to increasing the sensitivity of the airways of the Brown Norway rat to adenosine. 2 Animals actively sensitized to ovalbumin and challenged intratracheally with allergen or endotoxin manifested increased bronchoconstrictor responses to adenosine. A combination of ovalbumin and endotoxin also increased the response to adenosine but the effects were at best additive. 3 Changes in the response to adenosine were selective as responses to 5-hydroxytryptamine were unaltered following ovalbumin or LPS either alone or in combination. 4 Thus, endotoxin and allergen acting together could play a role in up-regulating the response of the human asthmatic airway to adenosine. However, our data suggest that the interaction would be additive rather than synergistic.

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.

Activation of connective tissue-type and mucosal-type mast cells in compound 48/80-induced airway response

The pathology of non-immunological airway contraction is not well understood. To define the activation of different phenotypes of mast cells, a rat non-immunological asthmatic model was prepared. Airway contraction in rats was measured by an unrestrained whole-body plethysmographic system following a 10-min inhalation challenge with a 5% solution of compound 48/80. Histamine, leukotrein C(4) (LTC(4)) and tumor necrosis factor (TNF)-alpha levels in bronchoalveolar lavage fluid, as well as tissue histamine content were quantified. Mast cells and eosinophils were detected by histology. Both the early and late phase of airway responses were induced by inhalation of compound 48/80. Histamine and TNF-alpha levels increased significantly 30 min after challenge, but no increases were detected at either 8 or 24 h after challenge. A high LTC(4) level was detected in 30 min and 8 h after challenge. Tissue histamine content decreased at 30 min after challenge and returned to the unstimulated level by 8 h. Connective tissue mast cells in rat trachea showed a degranulation response. Along with the increase in numbers of mucosal mast cells, rat mast cell protease II at both mRNA and protein levels in the trachea epithelial layer was also increased significantly at 30 min after challenge. We conclude that compound 48/80 inhalation causes both the early and late phase of airway contraction in rats. Mast cell degranulation is responsible for the early phase of airway response, which subsequently triggers the late phase of airway response.

The receptor mechanism mediating the contractile response to adenosine on lung parenchymal strips from actively sensitised, allergen-challenged Brown Norway rats

Parenchymal strips prepared from lungs removed from actively sensitised Brown Norway rats challenged with allergen show hyperresponsiveness to adenosine. The response is mast cell mediated and a preliminary pharmacological analysis suggested the involvement of a receptor (or receptors) that could not be classified as any of the known adenosine receptor subtypes. We present a further analysis of the response. Male Brown Norway (BN) rats, actively sensitised to ovalbumin (OA), were challenged intratracheally with OA and killed 3 h later to provide parenchymal strip preparations. The augmented contractile responses to adenosine were partially blocked by the 5-HT receptor antagonist, methysergide, or the A(1) receptor antagonist, DPCPX, and abolished in the presence of both antagonists. Responses to high concentrations of the A(1) receptor agonist, CPA were, like those to adenosine, augmented on tissues from allergen-challenged animals and blocked by a combination of methysergide and DPCPX. The A(3) receptor agonist, Cl-IB-MECA, did not contract the tissue, but partially blocked the response to adenosine. A combination of Cl-IB-MECA and methysergide induced a similar degree of blockade to that seen with either drug given alone. Combination of Cl-IB-MECA and/or methysergide with DPCPX abolished the response to adenosine. The effects of the A(3) receptor agonist, inosine, were augmented on tissues from allergen-challenged animals and markedly inhibited by disodium cromoglycate, methysergide or Cl-IB-MECA. Responses to adenosine were abolished when parenchymal strips were taken from rats pretreated 48 h previously with pertussis toxin. 8-SPT, CGS 15943, XAC, MRS 1754, DPCPX and theophylline, at concentrations which inhibit the A(1) A(2A) and/or A(2B) receptors but have negligible affinity for the rat A(3) receptor, inhibited responses to adenosine, but high concentrations were required and blockade was incomplete. MRS 1523 and MRS 1191, which are antagonists at the rat A(3) receptor, had no effect on the response to adenosine. The present results support and clarify our earlier conclusion that an atypical receptor mechanism mediates contraction of the parenchymal strip prepared from the lungs of actively sensitised BN rats challenged with allergen to adenosine. The response arises from a combined effect of adenosine on the A(1) receptor and a receptor with similarities to the A(3) receptor, but where Cl-IB-MECA behaves as an antagonist and MRS 1523 and MRS 1191 are inactive at concentrations that substantially exceed their affinities for the rat A(3) receptor.