Interleukin-12/T cell stimulating factor,a cytokine with multiple effects on T helper type 1 (Th1) but not on Th2 cells

At least two subsets of CD4⁺ T helper cell lymphocytes termed T_h1 and T _h, 2 exist in the mouse and probably in humans. They are characterized by the secretion of different lymphokines and by their functional behavior. Dysregulated expansion of one or the other subset may be one reason for the development of certain diseases. Thus, it is of importance to define the signals involved in the differentiation and activation of the two T_h cell subsets. It is known and has been confirmed in this report that the cytokine interleukin (IL)-1 acts onT_h2 cells but not on T_h1 cells. We now report that a previously identified cytokine which was provisionally termed T cell stimulating factor is identical with IL-12 and exhibits a reciprocal behaviour to IL-1. IL-12 has several effects on T_h1 cells. It can induce the proliferation of certain T_h1 cells in combination with IL-2. Synthesis of interferon (IFN)-γ by T_h1 cells can be triggered by IL-2 plus IL-12. In contrast to the IFN-γ production observed after T cell receptor (TcR) CD3 stimulation of T_h1 cells with lectin Concanavalin A the IFN-γ production induced by IL-12+IL-2 is insensitive to the immunosuppressive drug cyclosporin A. Furthermore, IL-12 enhances the TcR/CD3-induced synthesis of IFN-γ of several T_h1 clones. Finally, IL-12 (+ IL-2) induces homotypic cell aggregation of T_h1 clones. This type of cell aggregation depends on the participation of LFA-1 and ICAM-1 molecules. In all activation systems with T_h1 cells no effect of IL-1 was demonstrable. In contrast, only IL-1 but not IL-12 served as a co-stimulatory signal for several T_h2 cell lines activated via the TcR/CD3 complex.     

Th17 cells promote pancreatic inflammation but only induce diabetes efficiently in lymphopenic hosts after conversion into Th1 cells

IDDM is characterized by leukocyte invasion to the pancreatic tissues followed by immune destruction of the islets. Despite the important function of Th17 cells in other autoimmune disease models, their function in IDDM is relatively unclear. In this study, we found association of elevated Th17 cytokine expression with diabetes in NOD mice. To understand the function of Th17 cells in IDDM, we differentiated islet‐reactive BDC2.5 TcR transgenic CD4⁺ cells in vitro into Th17 cells and transferred them into NOD.scid and neonate NOD mice. NOD.scid recipient mice developed rapid onset of diabetes with extensive insulitic lesions, whereas in newborn NOD mice, despite extensive insulitis, most recipient mice did not develop diabetes. Surprisingly, BDC2.5⁺ cells recovered from diabetic NOD.scid mice, in comparison with those from neonate NOD mice, showed predominant IFN‐γ over IL‐17 expression, indicating conversion of donor cells into Th1 cells. Moreover, diabetes progression in NOD.scid recipients was dependent on IFN‐γ while anti‐IL‐17 treatment reduced insulitic inflammation. These results indicate that islet‐reactive Th17 cells promote pancreatic inflammation, but only induce IDDM upon conversion into IFN‐γ producers.     

T1/ST2 expression on Th2 cells negatively regulates allergic pulmonary inflammation

The transmembrane form of T1/ST2 (ST2) is a specific marker on murine Th2 cells that have been generated in vitro, or isolated from sites of allergic type 2 inflammation. Despite the association of ST2 with Th2 cells, to date no obligate role for ST2 in type 2 responses in vivo has been described. We have specifically addressed the role of ST2 on T cells by generation of ST2(-/-) mice crossed with ovalbumin (OVA) T cell receptor-transgenic mice. OVA-specific ST2(-/-) cells had normal cytokine responses to T cell activation after in vitro Th2 differentiation, but OVA stimulation of IL-5 was increased. Transfer of OVA-specific ST2(-/-) Th2 cells into BALB/c mice caused exacerbated pulmonary inflammation with occluded airways, elevated airway hyper-responsiveness and increased susceptibility to methacholine challenge that was associated with mortalities of recipient mice. The increased pulmonary inflammation in OVA-specific ST2(-/-) Th2 cell recipients was associated with selective differences in pulmonary levels of Th2 cytokines compared with OVA-specific ST2(+) Th2 cell recipients. Recipients of OVA-specific ST2(-/-) Th2 cells had a significant increase in eosinophils and a significant reduction in F4/80(hi) macrophages in the lungs. This is the first demonstration of a role for ST2 expression on Th2 cells down-regulating pulmonary inflammation. These data have major implications for the targeting of ST2 as a therapy for allergic airway disorders.     

Differential modulation of T helper type 1 (Th1) and T helper type 2 (Th2) cytokine secretion by prostaglandin E2 critically depends on interleukin-2

Prostaglandin E₂ (PGE₂) favors T helper type 2 (Th2)-like cytokine secretion profiles in murine and human CD4⁺ T cells by inhibiting the production of the Th1-associated cytokines interleukin-2 (IL-2) and interferon-γ (IFN-γ) and up-regulating the production of the Th2-associated cytokines IL-4 and IL-5 in a dose-dependent way. However, the potent inhibition of IL-2 production by PGE₂ seems to be in contrast with the simultaneous up-regulation of IL-4 and IL-5 production, because the induction of these cytokines requires IL-2. We, therefore, investigated to which extent the net modulatory effect of PGE₂ is determined by the availability of IL-2. To this aim, we examined the effects of PGE₂ on the cytokine secretion profiles of a panel of human Th0 clones upon stimulation via different activation pathways, resulting either in high or low IL-2 production. The differential modulation of Th1 and Th2 cytokines by PGE₂ was observed only upon modes of stimulation resulting in high IL-2 production. When IL-2 production was low, PGE₂ inhibited the secretion of all four cytokines. These different modulation patterns were directly related to the IL-2 availability, because (i) neutralizing antibody to IL-2 abrogated the up-regulatory effect of PGE₂ on IL-4 and IL-5 secretion in experiments with high endogenous IL-2 levels, (ii) lack of differential cytokine modulation by PGE₂ in conditions with low levels of endogenous IL-2 could be restored with exogenous IL-2, and (iii) cell viability was comparable in all conditions. These results demonstrate that the net modulatory effect of PGE₂ on the cytokine secretion profile of T cells critically depends on the availability of IL-2. Since this parameter varies with the experimental conditions and the T cell population studied, this finding may explain why certain immune responses may be either up- or down-regulated by PGE₂ under different conditions.     

Components of diesel exhaust particles differentially affect Th1/Th2 response in a murine model of allergic airway inflammation

BACKGROUND: Diesel exhaust particles (DEP) can enhance various respiratory diseases. However, it is unclear as to which components in DEP are associated with the enhancement. We investigated the effects of DEP components on antigen-related airway inflammation, using residual carbonaceous nuclei of DEP after extraction (washed DEP), extracted organic chemicals (OC) in DEP (DEP-OC), and DEP-OC plus washed DEP (whole DEP) in the presence or absence of ovalbumin (OVA). METHODS: Male ICR mice were intratracheally administrated with OVA and/or DEP components. We examined the cellular profile of bronchoalveolar lavage (BAL) fluid, histological changes, lung expression of inflammatory molecules, and antigen-specific production of IgG1 in the serum. RESULTS: DEP-OC, rather than washed DEP, enhanced infiltration of inflammatory cells into BAL fluid, magnitude of airway inflammation, and proliferation of goblet cells in the airway epithelium in the presence of OVA, which was paralleled by the enhanced lung expression of eotaxin and IL-5 as well as the elevated concentration of OVA-specific IgG1. In contrast, washed DEP with OVA showed less change and increased the lung expression of IFN-gamma. The combination of whole DEP and OVA caused the most remarkable changes in the entire enhancement, which was also accompanied by the enhanced expression of IL-13 and macrophage inflammatory protein-1 alpha. CONCLUSION: DEP-OC, rather than washed DEP, exaggerated allergic airway inflammation through the enhancement of T-helper type 2 responses. The coexistence of OC with carbonaceous nuclei caused the most remarkable aggravation. DEP components might diversely affect various types of respiratory diseases, while whole DEP might mostly aggravate respiratory diseases.     

Obesity promotes prolonged ovalbumin‐induced airway inflammation modulating T helper type 1 (Th1), Th2 and Th17 immune responses in BALB/c mice

Clinical and epidemiological studies indicate that obesity affects the development and phenotype of asthma by inducing inflammatory mechanisms in addition to eosinophilic inflammation. The aim of this study was to assess the effect of obesity on allergic airway inflammation and T helper type 2 (Th2) immune responses using an experimental model of asthma in BALB/c mice. Mice fed a high‐fat diet (HFD) for 10 weeks were sensitized and challenged with ovalbumin (OVA), and analyses were performed at 24 and 48 h after the last OVA challenge. Obesity induced an increase of inducible nitric oxide synthase (iNOS)‐expressing macrophages and neutrophils which peaked at 48 h after the last OVA challenge, and was associated with higher levels of interleukin (IL)‐4, IL‐9, IL‐17A, leptin and interferon (IFN)‐γ in the lungs. Higher goblet cell hyperplasia was associated with elevated mast cell influx into the lungs and trachea in the obese allergic mice. In contrast, early eosinophil influx and lower levels of IL‐25, thymic stromal lymphopoietin (TSLP), CCL11 and OVA‐specific immunoglobulin (IgE) were observed in the obese allergic mice in comparison to non‐obese allergic mice. Moreover, obese mice showed higher numbers of mast cells regardless of OVA challenge. These results indicate that obesity affects allergic airway inflammation through mechanisms involving mast cell influx and the release of TSLP and IL‐25, which favoured a delayed immune response with an exacerbated Th1, Th2 and Th17 profile. In this scenario, an intense mixed inflammatory granulocyte influx, classically activated macrophage accumulation and intense mucus production may contribute to a refractory therapeutic response and exacerbate asthma severity.     

Small molecule CXCR3 antagonist NIBR2130 has only a limited impact on type 1 diabetes in a virus-induced mouse model

CXCL10 is one of the key chemokines involved in trafficking of autoaggressive T cells to the islets of Langerhans during the autoimmune destruction of beta cells in type 1 diabetes (T1D). Blockade of CXCL10 or genetic deletion of its receptor CXCR3 results in a reduction of T1D in animal models. As an alternative to the use of neutralizing monoclonal antibodies to CXCL10 or CXCR3 we evaluated the small molecule CXCR3 antagonist NIBR2130 in a virus-induced mouse model for T1D. We found that the overall frequency of T1D was not reduced in mice administered with NIBR2130. An initial slight delay of diabetes onset was not stable over time, because the mice turned diabetic upon removal of the antagonist. Accordingly, no significant differences were found in the islet infiltration rate and the frequency and activity of islet antigen-specific T cells between protected mice administered with NIBR2130 and control mice. Our data indicate that in contrast to direct inhibition of CXCL10, blockade of CXCR3 with the small molecule antagonist NIBR2130 has no impact on trafficking and/or activation of autoaggressive T cells and is not sufficient to prevent T1D.     

Regulation of ST2L expression on T helper (Th) type 2 cells

T1/ST2L, an IL-1 receptor homologue, is selectively expressed on murine Th2 cells and specific anti-ST2L antibodies can profoundly modulate the Th1/Th2 balance in vivo. Naive CD4+ T cells do not express ST2L but do so on activation with specific antigen in the presence of IL-4 or when stimulated with low doses of antigen in the absence of exogenously added IL-4. Similarly enhanced ST2L expression occurred after stimulation of Th2 cells with antigen or the mitogen ConA in the presence of APC. Restimulation of Th2 cells in the presence of IFN-gamma led to a decreased expression of ST2L to below basal levels. Conversely, Th2 cells cultured with IL-4 led to increased ST2L expression. The reduced expression of ST2L in response to high doses of antigen is also reversed by the neutralization of IFN-gamma. Using an ST2L promoter/luciferase reporter gene construct, we show that the distal but not proximal ST2L promoter is responsible for specific gene expression in Th2 cells. IL-4 enhances, whereas IFN-gamma suppresses ST2L expression via direct modulation of the distal promoter of the ST2L gene. These data provide a mechanistic explanation for the selective expression of ST2L on Th2 cells.     

Cytotoxic T lymphocyte antigen 4 immunoglobulin modified dendritic cells attenuate allergic airway inflammation and hyperresponsiveness by regulating the development of T helper type 1 (Th1)/Th2 and Th2/regulatory T cell subsets in a murine model of asthma

T helper type 2 (Th2) and regulatory T cells (T(reg) ) have been postulated to have critical roles in the pathogenesis of allergic asthma. Cytotoxic T lymphocyte antigen 4 immunoglobulin (CTLA4Ig) gene-modified dendritic cells (DC-CTLA4Ig) have the potential to reduce Th2 cells and induce T(reg) cells. In the present study, we evaluated the therapeutic effects and potential mechanisms of the adoptive transfer of DC-CTLA4Ig into mice in an experimental model of asthma. BALB/c mice were sensitized with ovalbumin (OVA) and challenged with aerosolized OVA for 7 days. Just prior to the first challenge, DC-CTLA4Ig, DCs or DCs infected with DC-green fluorescent protein (GFP) were injected intravenously into mice. The administration of DC-CTLA4Ig reduced airway hyperresponsiveness, relieved asthmatic airway inflammation and decreased the numbers of esosinophils in the BALF in OVA-sensitized/challenged mice. In addition, DC-CTLA4Ig altered the balance of Th1/Th2 cytokine production in the lungs with increased interferon (IFN)-γ levels and decreased interleukin (IL)-4 levels, decreased the percentage of Th2 and increased both the percentage of Th1 and T(reg) cells in the lungs of OVA-sensitized/challenged mice. This research demonstrates that DC-CTL4Ig reduces airway hyperresponsiveness effectively and prevents airway inflammation in OVA-sensitized/challenged mice, which is due most probably to attenuated secretion of Th2 cytokines and increased secretion of Th1 cytokines in the local airway, and the correction of the pulmonary imbalance between Th1/Th2 cells and Th2/T(reg) cells.     

T helper 2 (Th2) but not Th1 clones co-stimulate resting T cells in the presence of anti-CD3 monoclonal antibody

We have investigated the effects of monoclonal antibody (mAb) to the CD3 epsilon protein on interactions between small, resting T cells and antigen-specific T helper clones. Highly purified, splenic T cells lacking identifiable accessory cells do not proliferate in a thymidine uptake assay to anti-CD3 mAb, Con A, rIL-2, rIL-4, or irradiated T helper clones (both Th1 and Th2). However, the responding T cells proliferate significantly to the combined stimulus of Th2 clones and anti-CD3 antibody. Only the Th2, not the Th1, subpopulation of T helper cells has the ability to induce a T cell response. The Th2 cell-dependent activation of small resting T cells does not require the external cross-linkage of the anti-CD3 mAb via Fc receptor expressing cells or the secretion of lymphokines from the Th2 helper clones, but it is inhibitable by anti-LFA 1 antibody. Thus, Th2 clones provide a co-stimulatory signal which in conjunction with anti-CD3 mAb causes resting T cell proliferation in the absence of conventional accessory cells.     

A dominant role for chemoattractant receptor-homologous molecule expressed on T helper type 2 (Th2) cells (CRTH2) in mediating chemotaxis of CRTH2+ CD4+ Th2 lymphocytes in response to mast cell supernatants

Human cultured mast cells, immunologically activated with immunoglobuin E (IgE)/anti-IgE, released a factor(s) that promoted chemotaxis of human CRTH2+ CD4+ T helper type 2 (Th2) lymphocytes. Mast cell supernatants collected at 20 min, 1 hr, 2 hr and 4 hr after activation caused a concentration-dependent increase in the migration of Th2 cells. The effect of submaximal dilutions of mast-cell-conditioned media was inhibited in a dose-dependent manner by ramatroban (IC50 = 96 nm), a dual antagonist of both the thromboxane-like prostanoid (TP) receptor and the chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2), but not by the selective TP antagonist SQ29548, implicating CRTH2 in mediating the chemotactic response of these Th2 cells. The effect of mast-cell-conditioned media was mimicked by prostaglandin D2 (PGD2) and this eicosanoid was detected in the conditioned media from activated mast cells in concentrations sufficient to account for the activity of the mast cell supernatants. Treatment of the mast cells with the cyclo-oxygenase inhibitor diclofenac (10 microm) inhibited both the production of PGD2 and the CRTH2+ CD4+ Th2-stimulatory activity, while addition of exogenous PGD2 to conditioned media from diclofenac-treated mast cells restored the ability of the supernatants to promote chemotaxis of these Th2 cells. The degree of inhibition caused by diclofenac treatment of the mast cells was concordant with the degree of inhibition of chemotactic responses afforded by CRTH2 blockade. These data suggest that PGD2, or closely related metabolites of arachidonic acid, produced from mast cells may play a central role in the activation of CRTH2+ CD4+ Th2 lymphocytes through a CRTH2-dependent mechanism.     

STAT6 deficiency in a mouse model of allergen-induced airways inflammation abolishes eosinophilia but induces infiltration of CD8+ T cells

BACKGROUND: The TH2-type cytokines have been reported to contribute to the asthmatic response. STAT6 has an essential role in IL-4 signalling and in production of TH2 cytokines from T cells and is involved in IgE and IgG1 responses after nematode infections, indicating that STAT6 has an important role in allergic diseases. OBJECTIVE: In this study we investigated the effects of STAT6 deficiency on allergen-induced airways inflammation in mice. METHODS: Both ovalbumin (OVA)-sensitized STAT6 deficient (STAT6-/-) mice and wild-type C57BL/6 mice were challenged with aerosolized OVA. Changes in inflammatory cell infiltration and cytokine levels in lung tissue as well as serum immunoglobulin levels were analysed in OVA-challenged STAT6-/- and wild-type mice. RESULTS: The eosinophilia and lung damage normally resulting from aeroallergen challenge were not seen in STAT6-/- mice. Expression of TH2 cytokines (IL-4 and IL-5) in the lung tissue as well as IgE and IgG1 responses after OVA challenge were profoundly reduced in STAT6-/- mice, whereas expression of IFNgamma was the same in STAT6-/- mice and wild-type mice after OVA challenge. Immunocytochemical analysis of T cells showed the infiltration of CD4+ T cells but not CD8+ T cells increased into the lung of wild-type mice after OVA challenge. However, the OVA-exposed STAT6-/- mice demonstrated the infiltration of both CD4+ T cells and CD8+ T cells with a significant increase in percentage and total number of CD8+ T cells compared with OVA-exposed wild-type mice. CONCLUSION: These results indicate that factors which signal through STAT6 are important regulators of eosinophilia of allergic airway inflammation, regulating TH2-type cytokine production both in CD4+ T cells and CD8+ T cells.     

Jagged1-expressing adenovirus-infected dendritic cells induce expansion of Foxp3+ regulatory T cells and alleviate T helper type 2-mediated allergic asthma in mice

Dendritic cells (DCs) are professional antigen-presenting cells that play a key role in directing T-cell responses. Regulatory T (Treg) cells possess an immunosuppressive ability to inhibit effector T-cell responses, and Notch ligand Jagged1 (Jag1) is implicated in Treg cell differentiation. In this study, we evaluated whether bone marrow-derived DCs genetically engineered to express Jag1 (Jag1-DCs) would affect the maturation and function of DCs in vitro and further investigated the immunoregulatory ability of Jag1-DCs to manipulate T helper type 2 (Th2) -mediated allergic asthma in mice. We produced Jag1-DCs by adenoviral transduction. Overexpression of Jag1 by ovalbumin (OVA) -stimulated Jag1-DCs exhibited increased expression of programmed cell death ligand 1 (PD-L1) and OX40L molecules. Subsequently, co-culture of these OVA-pulsed Jag1-DCs with allogeneic or syngeneic CD4⁺ T cells promoted the generation of Foxp3⁺ Treg cells, and blocking PD-L1 using specific antibodies partially reduced Treg cell expansion. Furthermore, adoptive transfer of OVA-pulsed Jag1-DCs to mice with OVA-induced asthma reduced allergen-specific immunoglobulin E production, airway hyperresponsiveness, airway inflammation, and secretion of Th2-type cytokines (interleukin-4, interleukin-5, and interleukin-13). Notably, an increased number of Foxp3⁺ Treg cells associated with enhanced levels of transforming growth factor-β production was observed in Jag1-DC-treated mice. These data indicate that transgenic expression of Jag1 by DCs promotes induction of Foxp3⁺ Treg cells, which ameliorated Th2-mediated allergic asthma in mice. Our study supports an attractive strategy to artificially generate immunoregulatory DCs and provides a novel approach for manipulating Th2 cell-driven deleterious immune diseases.     

Long-chain polyunsaturated fatty acids are consumed during allergic inflammation and affect T helper type 1 (Th1)- and Th2-mediated hypersensitivity differently

Studies have shown that atopic individuals have decreased serum levels of n‐3 fatty acids. Indicating these compounds may have a protective effect against allergic reaction and/or are consumed during inflammation. This study investigated whether fish (n‐3) or sunflower (n‐6) oil supplementation affected T helper type 1 (Th1)‐ and Th2‐mediated hypersensitivity in the skin and airways, respectively, and whether the fatty acid serum profile changed during the inflammatory response. Mice were fed regular chow, chow + 10% fish oil or chow + 10% sunflower oil. Mice were immunized with ovalbumin (OVA) resolved in Th1 or Th2 adjuvant. For Th1 hypersensitivity, mice were challenged with OVA in the footpad. Footpad swelling, OVA‐induced lymphocyte proliferation and cytokine production in the draining lymph node were evaluated. In the airway hypersensitivity model (Th2), mice were challenged intranasally with OVA and the resulting serum immunoglobulin (Ig)E and eosinophilic lung infiltration were measured. In the Th1 model, OVA‐specific T cells proliferated less and produced less interferon (IFN)‐γ, tumour necrosis factor (TNF) and interleukin (IL)‐6 in fish oil‐fed mice versus controls. Footpad swelling was reduced marginally. In contrast, mice fed fish oil in the Th2 model produced more OVA‐specific IgE and had slightly higher proportions of eosinophils in lung infiltrate. A significant fall in serum levels of long‐chain n‐3 fatty acids accompanied challenge and Th2‐mediated inflammation in Th2 model. Fish oil supplementation affects Th1 and Th2 immune responses conversely; significant consumption of n‐3 fatty acids occurs during Th2‐driven inflammation. The latter observation may explain the association between Th2‐mediated inflammation and low serum levels of n‐3 fatty acids.     

Restricted replication of primary HIV-1 isolates using both CCR5 and CXCR4 in Th2 but not in Th1 CD4(+) T cells

We have previously reported that CCR5-dependent human immunodeficiency virus type-1 (HIV-1; R5), but not CXCR4-restricted (X4) virus, efficiently replicates in T helper cell type 1 (Th1), Th2, or Th0 polyclonal T cells obtained from human umbilical cord blood (CB lines). The X4 virus restriction was env-dependent but did not occur at the level of viral entry. Here, we describe that in contrast to these monotropic HIVs, primary HIV-1 isolates capable of using CCR5 or CXCR4 indifferently for entry (i.e., R5X4 viruses) efficiently replicated in Th2 but not in Th1 CB lines. Although Th1 cells secreted significantly higher amounts of the three CCR5-binding chemokines in comparison with Th2 cells, this restriction was not explained by a defective infection of Th1 cells. Interferon-gamma (IFN-gamma) down-regulated CCR5 in Th1 cells and inhibited, whereas interleukin-4 (IL-4) up-regulated CXCR4 and enhanced the spreading of R5 and R5X4 viruses in polarized CB lines. However, both cytokines did not rescue the replication of X4 and dualtropic viruses in both types of CB lines or in Th1 cells, respectively, whereas addition of anti-IL-4- or anti-IFN-gamma-neutralizing antibodies did not activate virus expression. These findings together suggest the existence of post-entry restriction pathways influenced by gp120 Env/chemokine coreceptor interaction that may significantly contribute to the superior capacity of R5 and R5X4 HIV-1 strains to spread in vivo in comparison to X4 monotropic viruses.     

Role of angiotensin II type 1 (AT1) and type 2 (AT2) receptors in airway reactivity and inflammation in an allergic mouse model of asthma

Objective: Angiotensin II (Ang II) exerts its effects through two G-protein coupled receptors: angiotensin II type 1 receptors (AT1) and type 2 receptors (AT2). Both these receptor subtypes are poorly understood in asthma. In this study, we investigated effects of AT1 receptor antagonist losartan, novel AT2 receptor agonist novokinin and AT2 receptor antagonist PD 123319 in a mouse model of asthma.

Methods: Mice were divided into control (CON) and allergen sensitized (SEN) groups. SEN was sensitized with ovalbumin (OVA) on days 1 and 6 (30?μg; i.p.), followed by 5% OVA aerosol challenge (days 11–13). Treatments included (a) losartan (SEN?+?LOS; 20?mg/kg i.p., day 14), (b) novokinin (SEN?+?NOV; 0.3?mg/kg i.p., day 14), and (c) PD 123319 (SEN?+?PD; 5?mg/kg i.p., day 14). Experiments for airway responsiveness, bronchoalveolar lavage, and tracheal ring reactivity using isolated organ bath were performed.

Results: Airway responsiveness to methacholine (MCh) (48?mg/mL) was significantly higher in SEN (563.71?±?40% vs. 294.3?±?123.84 in CON). This response was potentiated in SEN?+?PD group (757?±?30%; p?<?.05 compared to SEN). SEN?+?LOS (247.61?±?86.85%) and SEN?+?NOV (352?±?11%) had significantly lower response compared to SEN. SEN?+?LOS (26.22?±?0.29%) and SEN?+?NOV (46.20?±?0.76%) treatment significantly (p?<?.001) attenuated total cell count and eosinophils compared to SEN group (69.38?±?1.5%), while SEN?+?PD (73.04?±?0.69%) had highest number of eosinophils. Tracheal response to MCh was significantly higher in SEN group compared to controls, and this response was significantly lowered with the losartan and novokinin treatments.

Conclusions: These data suggest that AT1 and AT2 receptors have opposite effects in modulating airway hyperresponsiveness and inflammation in asthma.