Stimulation of peripheral Kappa opioid receptors inhibits inflammatory hyperalgesia via activation of the PI3Kγ/AKT/nNOS/NO signaling pathway

Abstract Background In addition to their central effects, opioids cause peripheral analgesia. There is evidence showing that peripheral activation of kappa opioid receptors (KORs) inhibits inflammatory pain. Moreover, peripheral μ-opioid receptor (MOR) activation are able to direct block PGE2-induced ongoing hyperalgesia However, this effect was not tested for KOR selective activation. In the present study, the effect of the peripheral activation of KORs on PGE2-induced ongoing hyperalgesia was investigated. The mechanisms involved were also evaluated. Results Local (paw) administration of U50488 (a selective KOR agonist) directly blocked, PGE2-induced mechanical hyperalgesia in both rats and mice. This effect was reversed by treating animals with L-NMMA or N-propyl-L-arginine (a selective inhibitor of neuronal nitric oxide synthase, nNOS), suggesting involvement of the nNOS/NO pathway. U50488 peripheral effect was also dependent on stimulation of PI3Kγ/AKT because inhibitors of these kinases also reduced peripheral antinociception induced by U50488. Furthermore, U50488 lost its peripheral analgesic effect in PI3Kγ null mice. Observations made in vivo were confirmed after incubation of dorsal root ganglion cultured neurons with U50488 produced an increase in the activation of AKT as evaluated by western blot analyses of its phosphorylated form. Finally, immunofluorescence of DRG neurons revealed that KOR-expressing neurons also express PI3Kγ (≅ 43%). Conclusions The present study indicates that activation of peripheral KORs directly blocks inflammatory hyperalgesia through stimulation of the nNOS/NO signaling pathway which is probably stimulated by PI3Kγ/AKT signaling. This study extends a previously study of our group suggesting that PI3Kγ/AKT/nNOS/NO is an important analgesic pathway in primary nociceptive neurons.

Associations of the TNF-alpha -308 G/A, IL6 -174 G/C and AdipoQ 45 T/G polymorphisms with inflammatory and metabolic responses to lifestyle intervention in Brazilians at high cardiometabolic risk

Abstract Background Cytokines secreted by the adipose tissue influence inflammation and insulin sensitivity, and lead to metabolic disturbances. How certain single-nucleotide polymorphisms (SNPs) interfere on lifestyle interventions is unclear. We assessed associations of selected SNPs with changes induced by a lifestyle intervention. Methods This 9-month intervention on diet and physical activity included 180 Brazilians at high cardiometabolic risk, genotyped for the TNF-α -308 G/A, IL-6 -174 G/C and AdipoQ 45 T/G SNPs. Changes in metabolic and inflammatory variables were analyzed according to these SNPs. Individuals with at least one variant allele were grouped and compared with those with the reference genotype. Results In the entire sample (66.7% women; mean age 56.5 ± 11.6 years), intervention resulted in lower energy intake, higher physical activity, and improvement in anthropometry, plasma glucose, HOMA-IR, lipid profile and inflammatory markers, except for IL-6 concentrations. After intervention, only variant allele carriers of the TNF-α -308 G/A decreased plasma glucose, after adjusting for age and gender (OR 2.96, p = 0.025). Regarding the IL6 -174 G/C SNP, carriers of the variant allele had a better response of lipid profile and adiponectin concentration, but only the reference genotype group decreased plasma glucose. In contrast to individuals with the reference genotype, carriers of variant allele of AdipoQ 45 T/G SNP did not change plasma glucose, apolipoprotein B, HDL-c and adiponectin concentrations in response to intervention. Conclusion The TNFα -308 G/A SNP may predispose a better response of glucose metabolism to lifestyle intervention. The IL-6 -174 G/C SNP may confer a beneficial effect on lipid but not on glucose metabolism. Our findings reinforce unfavorable effects of the AdipoQ 45 T/G SNP in lipid profile and glucose metabolism after intervention in Brazilians at cardiometabolic risk. Further studies are needed to direct lifestyle intervention to subsets of individuals at cardiometabolic risk.

Glial cell activity is maintained during prolonged inflammatory challenge in rats

We evaluated the expression of glial fibrillary acidic protein (GFAP), glutamine synthetase (GS), ionized calcium binding adaptor protein-1 (Iba-1), and ferritin in rats after single or repeated lipopolysaccharide (LPS) treatment, which is known to induce endotoxin tolerance and glial activation. Male Wistar rats (200-250 g) received ip injections of LPS (100 µg/kg) or saline for 6 days: 6 saline (N = 5), 5 saline + 1 LPS (N = 6) and 6 LPS (N = 6). After the sixth injection, the rats were perfused and the brains were collected for immunohistochemistry. After a single LPS dose, the number of GFAP-positive cells increased in the hypothalamic arcuate nucleus (ARC; 1 LPS: 35.6 ± 1.4 vs control: 23.1 ± 2.5) and hippocampus (1 LPS: 165.0 ± 3.0 vs control: 137.5 ± 2.5), and interestingly, 6 LPS injections further increased GFAP expression in these regions (ARC = 52.5 ± 4.3; hippocampus = 182.2 ± 4.1). We found a higher GS expression only in the hippocampus of the 6 LPS injections group (56.6 ± 0.8 vs 46.7 ± 1.9). Ferritin-positive cells increased similarly in the hippocampus of rats treated with a single (49.2 ± 1.7 vs 28.1 ± 1.9) or repeated (47.6 ± 1.1 vs 28.1 ± 1.9) LPS dose. Single LPS enhanced Iba-1 in the paraventricular nucleus (PVN: 92.8 ± 4.1 vs 65.2 ± 2.2) and hippocampus (99.4 ± 4.4 vs 73.8 ± 2.1), but had no effect in the retrochiasmatic nucleus (RCA) and ARC. Interestingly, 6 LPS increased the Iba-1 expression in these hypothalamic and hippocampal regions (RCA: 57.8 ± 4.6 vs 36.6 ± 2.2; ARC: 62.4 ± 6.0 vs 37.0 ± 2.2; PVN: 100.7 ± 4.4 vs 65.2 ± 2.2; hippocampus: 123.0 ± 3.8 vs 73.8 ± 2.1). The results suggest that repeated LPS treatment stimulates the expression of glial activation markers, protecting neuronal activity during prolonged inflammatory challenges.

Oxidative stress and inflammatory response increase during coronary artery bypass grafting with extracorporeal circulation

INTRODUCTION: Thiobarbituric acid-reactive substance is a marker of oxidative stress and has cytotoxic and genotoxic actions. C- reactive protein is used to evaluate the acute phase of inflammatory response. OBJECTIVES: To assess the thiobarbituric acid-reactive substance and C-reactive protein levels during extracorporeal circulation in patients submitted to cardiopulmonary bypass. METHODS: Twenty-five consecutive surgical patients (16 men and nine women; mean age 61.2 ± 9.7 years) with severe coronary artery disease diagnosed by angiography scheduled for myocardial revascularization surgery with extracorporeal circulation were selected. Blood samples were collected immediately before initializing extracorporeal circulation, T0; in 10 minutes, T10; and in 30 minutes, T30. RESULTS: The thiobarbituric acid-reactive substance levels increased after extracorporeal circulation (P=0.001), with average values in T0=1.5 ± 0.07; in T10=5.54 ± 0.35; and in T30=3.36 ± 0.29 mmoles/mg of serum protein. The C-reactive protein levels in T0 were negative in all samples; in T10 average was 0.96 ± 0.7 mg/dl; and in T30 average was 0.99 ± 0.76 mg/dl. There were no significant differences between the dosages in T10 and T30 (P=0.83). CONCLUSIONS: C-reactive protein and thiobarbituric acid-reactive substance plasma levels progressively increased during extracorporeal circulation, with maximum values of thiobarbituric acid-reactive substance at 10 min and of Creactive protein at 30 min. It suggests that there are an inflammatory response and oxidative stress during extracorporeal circulation.

Increased fibroblast telomerase expression precedes myofibroblast α-smooth muscle actin expression in idiopathic pulmonary fibrosis

OBJECTIVE: This study sought to identify the relationship between fibroblast telomerase expression, myofibroblasts, and telomerase-mediated regulatory signals in idiopathic pulmonary fibrosis. METHODS: Thirty-four surgical lung biopsies, which had been obtained from patients with idiopathic pulmonary fibrosis and histologically classified as usual interstitial pneumonia, were examined. Immunohistochemistry was used to evaluate fibroblast telomerase expression, myofibroblast α-smooth muscle actin expression and the tissue expression of inter leu kin-4, transforming growth factor-β, and basic fibroblast growth factor. The point-counting technique was used to quantify the expression of these markers in unaffected, collapsed, mural fibrosis, and honeycombing areas. The results were correlated to patient survival. RESULTS: Fibroblast telomerase expression and basic fibroblast growth factor tissue expression were higher in collapsed areas, whereas myofibroblast expression and interleukine-4 tissue expression were higher in areas of mural fibrosis. Transforming growth factor-β expression was higher in collapsed, mural fibrosis and honeycombing areas in comparison to unaffected areas. Positive correlations were found between basic fibroblast growth factor tissue expression and fibroblast telomerase expression and between interleukin-4 tissue expression and myofibroblast α-smooth muscle actin expression. Negative correlations were observed between interleukin-4 expression and basic fibroblast growth factor tissue expression in areas of mural fibrosis. Myofibroblast α-smooth muscle actin expression and interleukin-4 tissue expression in areas of mural fibrosis were negatively associated with patient survival. CONCLUSION: Fibroblast telomerase expression is higher in areas of early remodeling in lung tissues demonstrating typical interstitial pneumonia, whereas myofibroblast α-smooth muscle actin expression predominates in areas of late remodeling. These events seem to be regulated by basic fibroblast growth factor and interleukin-4 tissue expression, respectively.

Pharmacokinetics of cyclosporin: a microemulsion in children with idiopathic nephrotic syndrome

OBJECTIVE: We present a prospective study of a microemulsion of cyclosporin to treat idiopathic nephrotic syndrome in ten children with normal renal function who presented cyclosporin trough levels between 50 and 150 ng/ml and achieved complete remission with cyclosporin. To compare the pharmacokinetic parameters of cyclosporin in idiopathic nephrotic syndrome during remission and relapse of the nephrotic state. METHOD: The pharmacokinetic profile of cyclosporin was evaluated with the 12-hour area under the timeconcentration curve (auc0-12) using seven time-point samples. This procedure was performed on each patient during remission and relapse with the same cyclosporin dose in mg/kg/day. The 12-hour area under the timeconcentration curve was calculated using the trapezoidal rule. All of the pharmacokinetic parameters and the resumed 4-hour area under the time-concentration curve were correlated with the 12-hour area under the timeconcentration curve. ClinicalTrials.gov:NCT01616446. RESULTS: There were no significant differences in any parameters of the pharmacokinetic of cyclosporin during remission and relapse, even when the data were normalized by dose. The best correlation with the 12-hour area under the time-concentration curve was the 4-hour area under the time-concentration curve on remission and relapse of the disease, followed by the 2-hour level after cyclosporin (c2) dosing in both disease states. CONCLUSIONS: These data indicate that the same parameters used for cyclosporin therapeutic monitoring estimated during the nephrotic state can also be used during remission. Larger controlled studies are needed to confirm these findings.

Guava pomace: a new source of anti-inflammatory and analgesic bioactives

Abstract Background Guava pomace is an example of the processing waste generated after the manufacturing process from the juice industry that could be a source of bioactives. Thus, the present investigation was carried out in order to evaluate the anti-inflammatory and antinociceptive potential and determinate the main phenolic compounds of a guava pomace extract (GPE). Methods The anti-inflammatory activity was evaluated by carrageenan, dextran, serotonin, histamine-induced paw edema and neutrophils migration in the peritoneal cavity models. Acetic acid-induced abdominal writhing and formalin test were performed to investigate the antinociceptive effects. In addition, the content of total phenolic and of individual phenolic compounds was determined by GC/MS. Results GPE showed anti-inflammatory activity by carrageenan, dextran, serotonin, histamine-induced paw edema and neutrophils migration in the peritoneal cavity models (p < 0.05). GPE also demonstrated antinociceptive activity by acetic acid-induced abdominal writhing and formalin test (p < 0.05). The total phenolic value was 3.40 ± 0.09 mg GAE/g and epicatechin, quercetin, myricetin, isovanilic and gallic acids were identified by GC/MS analysis. Conclusions The presence of bioactive phenolic compounds as well as important effects demonstrated in animal models suggest that guava pomace could be an interesting source of anti-inflammatory and analgesic substances.

PReS-FINAL-2177: Safety and lack of autoantibody production following influenza H1N1 vaccination in patients with juvenile idiopathic arthritis (JIA)

Introduction Vaccination is an effective tool against several infectious agents including influenza. In 2010, the Advisory Committee on Immunization Practices (ACIP) recommended influenza A H1N1/2009 immunization for high risk groups, including juvenile idiopathic arthritis (JIA) patients and more recently the EULAR task force reinforced the importance of vaccination in immunosuppressed pediatric rheumatologic patients. We have recently shown that Influenza A H1N1/2009 vaccination generated protective antibody production with short-term safety profile among 93 JIA patients, but the possible impact of the vaccine in autoimmune response in JIA have not been studied. Therefore, we aimed to assess the production of some autoantibodies generated following influenza H1N1 vaccination in JIA patients. Objectives To assess the autoimmune response and H1N1 serology following influenza H1N1 vaccination in patients with JIA. Methods Cepa A/California/7/2009 (NYMC X-179A) anti-H1N1 was used to vaccinate JIA patients: 1 dose of immunization was given to all participants and those <9yrs of age received a second booster 3 weeks apart. Sera were analyzed before and 3 weeks following complete vaccination. Serology against H1N1 virus was performed by hemagglutination inhibition antibody assay, rheumatoid factor (RF) by latex fixation test, antinuclear antibodies (ANA) by IIF, IgM and IgG anticardiolipin (aCL) by ELISA.Results Among 98 JIA patients that were vaccinated, 58 sera were available for this study. Mean age of 58 JIA patients was 23.9 ± 9.5 yrs, 38 were females and 20 males with mean disease duration of 14.7 ± 10.1 yrs. JIA subtypes were: 33 (57%) poliarticular, 10 (17%) oligoarticular, 6 (10%) systemic and 9 (16%) other. Sixteen patients were off drugs while 42 (72%) were under different pharmacotherapy: 32 (55%) were on 1 DMARD/IS, 10 (17%) on 2 DMARDs/IS, 19 (33%) antimalarials, 29 (50%) MTX, 8(14%) sulfasalazine, 6 (10%) anti-TNFs, 4 (7%) abatacept; no patient was using prednisone >0.5 mg/kg/d. Seroprotection rates against H1N1 influenza increased from 23 to 83% and seroconversion rates were achieved in 78% JIA. Prior to vaccination, 31(53.4%) JIA patients were ANA+, 6(10.3%) RF+, and 4 (7%) IgM + IgG aCL+. After complete H1N1 vaccination, positivity for ANA remained the same whereas 1 patient became negative for IgG aCL, and another for RF, IgM and IgG aCL. One (1.7%) patient turned low titer IgG aCL+. Conclusion Vaccination of JIA patients against pandemic influenza A (H1N1) generated successful protective antibody production without the induction of autoantibody production, except for 1 patient that became positive for low titer IgG aCL, supporting its safety.

PReS-FINAL-2170: Work disability in adult patients with juvenile idiopathic arthritis (JIA)

Introduction Approximately 20% JIA patients enters adulthood with clinically active disease and disabled, therefore work condition may be affected. Objectives To assess the prevalence of work disability among adult patients with JIA regularly attending a tertiary heumatology center and to determine possible associated risk factors. Methods This was a cross-sectional study that enrolled 43 JIA patients according to 2004 revised ILAR criteria. A questionnaire was developed in order to evaluate working status and labor activity: occupation, current/previous work, employment status and withdrawal rate were actively searched. Demographic data, JIA characteristics, clinical activity (DAS28>2.6), therapeutic intervention, comorbidities, physical activity, sedentarism (WHO definitions), functional class (1991 ACR criteria), HAQ and SF-36 were recorded. The prevalence of work disability was calculated using 95% confidence interval, and compared to all parameters; qualitative variables were analyzed using tests of association (chi-square test) and quantitative variables by Mann-Whitney or student test. Results Patients' mean age was 29+7.4 yrs (range 19-41) with mean JIA duration = 17.2+12.3 yrs (range 3-33); 63% were males and 37% females. JIA subtypes were 64% polyarticular, 11% oligoarticular, 9% systemic, 9% ERA, 2% extended oligoarticular, 2% psoriatic arthritis; 7% had uveitis. Serum RF was positive in 21% and ANA in 21%. The majority (72%, n = 31) of JIA patients were employed, whereas 28% (n = 12) were currently not working. In the latter group, 83% (10/12) were retired due to JIA related disability. Further analysis comparing those currently working vs. Those not working revealed similar age (25,3 yrs vs.29,5 yrs, p = 0,09). Although not significantly, most patients currently working had Poly onset JIA (22 vs. 6 p = 0,37), higher frequencies of good education level >12 yrs of school (31 vs.9, p = 0,38), functional class I (p = 0,96), practiced regular physical activity (9 vs. 0, p = 0,89), were singles (26 vs. 8, p = 0,15). Both groups had comparable HAQ and DAS 28 scores (0,62 vs. 0.59, p = 0,47 and 2,51 vs.2,07, p = 0,64) and similar arthroplasty rate (8 vs. 4, p = 0,427). Frequencies of hypertension (3 vs.1, p = 0,999), dyslipidemia (1 vs. 1, p = 0,125), diabetes (1 vs. 0 p = 0,999), depression (1 vs. 0, p = 0,999) and smokers (3 vs. 1, p = 0,99) were alike in both groups. Remarkably, employed patients had higher SF 36 mental health component (84.0 vs. 70.42, P = 0.01). Conclusion High prevalence of almost 1/3 work disability and of retirement due to disease related incapacity remain major problems for adult JIA individuals. We also identified worse mental health in employed patients indicating that further research is needed, in addition to intense affirmative disability actions in order to remove possible disabling barriers and to adapt restrictive environments for these patients. Moreover, enhanced strategies and policy for inclusion of JIA patients in the job market is urged.

A comparative study on the anti-inflammatory effects of single oral doses of naproxen and its hydrogen sulfide (H2S)-releasing derivative ATB-346 in rats with carrageenan-induced synovitis

Abstract Background Non-steroidal antiinflammatory drugs (NSAIDs) are the most commonly prescribed agents for arthritic patients, although gastric effects limit their long-term use. Considering the reported gastric safety of hydrogen sulfide (H2S)-releasing NSAIDs, in addition to the anti-inflammatory effects of H2S administration to rats with synovitis, we decided to evaluate the effects of the H2S-releasing naproxen derivative ATB-346 in this animal model. Methods Male Wistar rats were anesthetized with inhalatory halothane and pre-treated with equimolar oral doses of either naproxen (0.3, 1, 3 or 10 mg/kg) or ATB-346 (0.48, 1.6, 4.8, or 16 mg/kg) 30 min before the i.art. injection of 7.5 mg of carrageenan (CGN) into the right knee joint cavity. Joint swelling and pain score were assessed after 1, 3 and 5 h, and tactile allodynia after 2 and 4 h. After the last measurement, the joint cavity lavages were performed for counting of the recruited leukocytes. The drugs (at the highest doses) were also tested for their gastric effects by evaluating macroscopical damage score and neutrophil recruitment (measured as myeloperoxidase – MPO activity) in the stomachs 5 h after administration of the drugs. In addition, the serum naproxen pharmacokinetic profiles of both compounds, administered at the highest equimolar doses, were obtained during the first 6 h after dosing. Results At the two highest tested doses, both naproxen and ATB-346 reduced edema and pain score (measured 3 and 5 h after CGN; P < 0.001). Tactile allodynia was similarly inhibited by ~45% 4 h after CGN by both naproxen (at 1, 3 and 10 mg/kg) and ATB-346 (at 1.6 and 4.8 mg/kg; P < 0.001), as well as leukocyte infiltration. Naproxen (but not ATB-346) induced significant gastric damage and, despite the increased gastric MPO activity by ~130% in the naproxen-, but not in the ATB-346-treated rats, this effect was of no statistical significance. Conclusion The presence of a H2S-releasing moiety in the ATB-346 structure does not impair the antiinflammatory activity of the parent compound in rats with CGN-induced synovitis. In addition, released H2S may account for the absence of deleterious gastric effects, thus making of ATB-346 a potentially useful therapeutic alternative to traditional naproxen for treatment of patients with arthritis.

Beneficial effects of Anadenanthera colubrina (Vell.) Brenan extract on the inflammatory and nociceptive responses in rodent models

Ethnopharmacological relevance:Anadenantheracolubrina (Vell.) Brenan,popularlyknownas “angico”, is a plantthathasbeenwidelyusedinfolkmedicineduetoitsanti-inflammatory property.Toevaluatethe pharmacological activitiesofthisplant,studieswereperformedonitsantinociceptiveandanti- inflammatoryproperties. Materials andmethods: The AEof Anadenantheracolubrina, madefromthebark,wasusedinrodentsvia oral route(p.o.),at100,200,and400mg/kginclassicalmodelsofnociception(aceticacid-induced writhing andhot-platetest)andinflammation evokedbycarrageenan(e.g.,pawedema,peritonitis,and synovitis). Results: The aceticacid-inducedabdominalwrithesinmiceweresignificantly reduced(Po0.001)by oral treatmentwiththeextract(100,200,and400mg/kg),buttheextractdidnotsignificantly increase the latencyinthenociceptivehot-platetest. Anadenantheracolubrina aqueousextractreduced significantly theedemaand,besides,diminishedthemieloperoxidaseactivity(200and400mg/kg, Po0.01).Thecarrageenan-inducedperitonitiswassignificantly reduced(Po0.05) bytheaqueous extractat100,200,and400mg/kg.Theaqueousextract(200mg/kg)reducesthesynovialleukocyte infiltration oncarrageenan-inducedsynovitisinrats(Po0.01),butfailedtosignificantly affectjoint swelling andimpairedmobility. Conclusions: Weshowforthe first timethattheanti-inflammatory andperipheralantinociceptive activities of Anadenantheracolubrina are consistent,atleastinpart,withtheuseofthisplantinpopular medicine practices.

A comparative study on the anti-inflammatory effects of single oral doses of naproxen and its hydrogen sulfide (H2S)-releasing derivative ATB-346 in rats with carrageenan-induced synovitis

BACKGROUND: Non-steroidal antiinflammatory drugs (NSAIDs) are the most commonly prescribed agents for arthritic patients, although gastric effects limit their long-term use. Considering the reported gastric safety of hydrogen sulfide (H2S)-releasing NSAIDs, in addition to the anti-inflammatory effects of H2S administration to rats with synovitis, we decided to evaluate the effects of the H2S-releasing naproxen derivative ATB-346 in this animal model. METHODS: Male Wistar rats were anesthetized with inhalatory halothane and pre-treated with equimolar oral doses of either naproxen (0.3, 1, 3 or 10 mg/kg) or ATB-346 (0.48, 1.6, 4.8, or 16 mg/kg) 30 min before the i.art. injection of 7.5 mg of carrageenan (CGN) into the right knee joint cavity. Joint swelling and pain score were assessed after 1, 3 and 5 h, and tactile allodynia after 2 and 4 h. After the last measurement, the joint cavity lavages were performed for counting of the recruited leukocytes. The drugs (at the highest doses) were also tested for their gastric effects by evaluating macroscopical damage score and neutrophil recruitment (measured as myeloperoxidase - MPO activity) in the stomachs 5 h after administration of the drugs. In addition, the serum naproxen pharmacokinetic profiles of both compounds, administered at the highest equimolar doses, were obtained during the first 6 h after dosing. RESULTS: At the two highest tested doses, both naproxen and ATB-346 reduced edema and pain score (measured 3 and 5 h after CGN; P < 0.001). Tactile allodynia was similarly inhibited by ~45% 4 h after CGN by both naproxen (at 1, 3 and 10 mg/kg) and ATB-346 (at 1.6 and 4.8 mg/kg; P < 0.001), as well as leukocyte infiltration. Naproxen (but not ATB-346) induced significant gastric damage and, despite the increased gastric MPO activity by ~130% in the naproxen-, but not in the ATB-346-treated rats, this effect was of no statistical significance. CONCLUSION: The presence of a H2S-releasing moiety in the ATB-346 structure does not impair the antiinflammatory activity of the parent compound in rats with CGN-induced synovitis. In addition, released H2S may account for the absence of deleterious gastric effects, thus making of ATB-346 a potentially useful therapeutic alternative to traditional naproxen for treatment of patients with arthritis.

Role of M2 muscarinic receptor in the airway response to methacholine of mice selected for minimal or maximal acute inflammatory response

Airway smooth muscle constriction induced by cholinergic agonists such as methacholine (MCh), which is typically increased in asthmatic patients, is regulated mainly by muscle muscarinic M3 receptors and negatively by vagal muscarinic M2 receptors. Here we evaluated basal (intrinsic) and allergen-induced (extrinsic) airway responses to MCh. We used two mouse lines selected to respond maximally (AIRmax) or minimally (AIRmin) to innate inflammatory stimuli. We found that in basal condition AIRmin mice responded more vigorously to MCh than AIRmax. Treatment with a specific M2 antagonist increased airway response of AIRmax but not of AIRmin mice. The expression of M2 receptors in the lung was significantly lower in AIRmin compared to AIRmax animals. AIRmax mice developed a more intense allergic inflammation than AIRmin, and both allergic mouse lines increased airway responses to MCh. However, gallamine treatment of allergic groups did not affect the responses to MCh. Our results confirm that low or dysfunctional M2 receptor activity is associated with increased airway responsiveness to MCh and that this trait was inherited during the selective breeding of AIRmin mice and was acquired by AIRmax mice during allergic lung inflammation