Antigen-induced airway hyperresponsiveness is associated with airway tissue NEP hypoactivity in rats

Cocaine sensitization does not alter SP effects on locomotion or excitatory synaptic transmission in the NAc of rats

Substance P (SP) and cocaine employ similar mechanisms to modify excitatory synaptic transmission in the nucleus accumbens (NAc), a region implicated in substance abuse. Here we explored, using NAc slices, whether SP effects on these synaptic responses were altered in rats that have been sensitized to cocaine and whether SP could mimic cocaine in triggering increased locomotion in sensitized rats. Intraperitoneal (IP) injection of naïve rats with cocaine (15 mg/kg) caused increased locomotion by 408.5 ± 85.9% (n = 5) which further increased by 733.1 ± 157.8% (n = 5) following a week of cocaine sensitization. A similar challenge with 10 mg/kg of SP after cocaine sensitization did not produce significant changes in locomotion (170.6 ± 61.0%; n = 4). In contrast to cocaine, IP injection of rats with SP or SP(5-11) (10-100 mg/kg) with or without phosphoramidon did not elicit changes in locomotion. In electrophysiological studies, both cocaine and SP depressed evoked NMDA and non-NMDA receptor-mediated excitatory synaptic currents (EPSCs) in slices obtained from naïve rats. In slices derived from cocaine-sensitized rats, cocaine but not SP produced a more profound decrease in non-NMDA compared to NMDA responses. Similar to that in naïve rats, cocaine's effect on the EPSCs in these sensitized rats occluded those of SP. Thus, although SP and cocaine may employ similar mechanisms to depress EPSCs in the NAc, IP injection of SP does not mimic cocaine-induced hyperlocomotion indicating that not all of cocaine's effects are mimicked by SP. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.

Increase in the expression of matrix metalloproteinase-12 in the airways of rats with allergic bronchial asthma

Although an involvement of matrix metalloproteinase (MMP)-12 in the development of chronic obstructive pulmonary disease (COPD) and airway inflammation has been suggested, its detailed role in the airways is not well known now. In the present study, the changes in the expression and localization of MMP-12 in airways of repeatedly antigen-challenged rats were investigated to show an association of MMP-12 with allergic bronchial asthma. Rats sensitized by dinitrophenylated Ascaris antigen were 3 times repeatedly challenged with aerosolized antigen solution to induce an asthmatic reaction. Twenty-four hours after the last antigen challenge, marked airway inflammation and bronchial smooth muscle hyperresponsiveness were observed. In this animal model of allergic bronchial asthma, a significant increase in the expression/activity of MMP-12 was found: the peak was observed at 12 h after the last antigen challenge. Furthermore, mRNA expression of MMP-12 was also increased at the early phase (1-3 h) after the last antigen challenge. Immunohistochemical studies revealed that MMP-12 was mainly expressed in airway epithelia and alveolar macrophages. These findings suggest that MMP-12 is upregulated after the induction of asthmatic reaction. MMP-12 might be a new target for the therapy against allergic bronchial asthma.

Functional characterization and biomarker identification in the Brown Norway model of allergic airway inflammation

1. The antigen-induced inflammatory response in the Brown Norway rat is a model commonly used to assess the impact of novel compounds on airway eosinophilia. A detailed functional, cellular and molecular characterization of this model has not yet been performed within a single study. This information together with the temporal changes in this phenomenon should be known before this model can be used, with confidence, to elucidate the mechanisms of action of novel anti-inflammatory drugs. 2. Antigen challenge caused an accumulation of eosinophils in lung tissue 24 h after challenge. Accumulation of CD2(+) T cells was not apparent until after 72 h. 3. Interestingly, mRNA for the Th2 type cytokines interleukin (IL)-4, IL-5 and IL-13 and eotaxin were elevated in lung tissue after challenge and the expression of IL-13 and eotaxin protein increased at around 8-12 h. The temporal changes in both the biomarker production and the functional responses are important factors to consider in protocol design prior to initiating a compound screening program. 4. A neutralising antibody (R73) against alphabeta-TCR caused a significant reduction in T cell numbers accompanied by a significant suppression of eosinophil accumulation. 5. Airway hyperreactivity (AHR) was not apparent in this specific Brown Norway model in sensitized animals after a single or multiple challenges although eosinophil influx was seen in the same animals. 6. In conclusion, this is a convenient pre-clinical model (incorporating the measurement of biomarkers and functional responses) for screening novel small molecule inhibitors and/or biotherapeutics targeted against T cell/eosinophil infiltration/activation.

Gq protein level increases concurrently with antigen-induced airway hyperresponsiveness in rats

In the present study, bronchial Gq protein level of the airway hyperresponsive rats was determined by using immunoblot analysis. In the airway hyperresponsive rats that were sensitized and repeatedly antigen challenged, the in vitro bronchial responsiveness to acetylcholine was significantly enhanced as compared with that in the sensitized control group. Moreover, the bronchial contraction induced by 10 microM AlF(4)(-) (generated by 10 microM AlCl(3) plus 10 mM NaF) was significantly elevated after repeated antigen challenge (0.44+/-0.13 and 1.09+/-0.09 g tension in the control and airway hyperresponsive groups, respectively; P<0.01). In both groups, immunoblotting with the antibody against G alpha q gave a single 42 kD band. The G alpha q protein levels in the airway hyperresponsive group (0.58+/-0.12) estimated by G alpha q/beta-actin ratio was significantly greater than those in the control group (0.30+/-0.10; P<0.05). These findings suggest that the increase in G alpha q protein level may be involved in the pathogenesis of antigen-induced airway hyperresponsiveness in rats.

Abnormal modulation of cholinergic neurotransmission by opioid in hyperresponsive bronchus of rats

1. The electrical field stimulation (EFS)-induced bronchoconstriction in vitro in rats challenged by DNP-Ascaris antigen was significantly greater than that in normal rats. 2. Morphine inhibited the EFS-induced bronchoconstriction in normal rats. Whereas the inhibition of EFS-induced bronchoconstriction by the opioid was little, if any, in the DNP-Ascaris-challenged rats. 3. These findings suggest that dysfunction of presynaptic inhibitory modulation through the opioid receptor may take place in the airways of DNP-Ascaris-challenged rats.