Autoantibody Biomarkers for Basal Ganglia Encephalitis in Sydenham Chorea and Pediatric Autoimmune Neuropsychiatric Disorder Associated With Streptococcal Infections

Movement, behavioral, and neuropsychiatric disorders in children have been linked to infections and a group of anti-neuronal autoantibodies, implying dopamine receptor-mediated encephalitis within the basal ganglia. The purpose of this study was to determine if anti-neuronal biomarkers, when used as a group, confirmed the acute disease in Sydenham chorea (SC) and pediatric autoimmune neuropsychiatric disorder associated with streptococcal infections (PANDAS). IgG autoantibodies against four neuronal autoantigens (tubulin, lysoganglioside GM1, and dopamine receptors D1 and D2) were detected in SC sera (N=8), sera and/or cerebrospinal fluid (CSF) from two groups of PANDAS cases (N=25 first group and N=35 second group), sera from Tourette's syndrome (N=18), obsessive-compulsive disorder (N=25), attention deficit hyperactivity disorder (N=18), and healthy controls (N=28) by direct enzyme-linked immunosorbent assay (ELISA). IgG specific for neuronal autoantigens was significantly elevated during the acute symptomatic phase, and the activity of calcium/calmodulin-dependent protein kinase II (CaMKII) pathway was significantly elevated in human neuronal cells. Five assays confirmed the disease in SC and in two groups of children with PANDAS. In 35 acute onset PANDAS patients, 32 sera (91.4%) were positive for one or more of the anti-neuronal autoantibodies compared with 9 of 28 healthy controls (32.1%, p<0.0001). Importantly, CSF of 32 (91.4%) PANDAS patients had one or more detectable anti-neuronal autoantibody titers and CaMKII activation. Among healthy control subjects with elevated serum autoantibody titers for individual antigens, none (0%) were positively associated with elevated positive CaMKII activation, which was a striking contrast to the sera of PANDAS subjects, who had 76-89% positive association with elevated individual autoantibody titers and positive CaMKII activity. At 6 months follow-up, symptoms improved for more than 80% of PANDAS subjects, and serum autoantibody titers also significantly decreased. Results reported herein and previously published studies in our laboratory suggest the antibody biomarkers may be a useful adjunct to clinical diagnosis of SC, PANDAS, and related disorders and are the first known group of autoantibodies detecting dopamine receptor-mediated encephalitis in children.

Dopamine Deficiency Reduces Striatal Cholinergic Interneuron Function in Models of Parkinson's Disease

Motor and cognitive functions depend on the coordinated interactions between dopamine (DA) and acetylcholine (ACh) at striatal synapses. Increased ACh availability was assumed to accompany DA deficiency based on the outcome of pharmacological treatments and measurements in animals that were critically depleted of DA. Using Slc6a3^DTR/+ diphtheria-toxin-sensitive mice, we demonstrate that a progressive and L-dopa-responsive DA deficiency reduces ACh availability and the transcription of hyperpolarization-activated cation (HCN) channels that encode the spike timing of ACh-releasing tonically active striatal interneurons (ChIs). Although the production and release of ACh and DA are reduced, the preponderance of ACh over DA contributes to the motor deficit. The increase in striatal ACh relative to DA is heightened via D1-type DA receptors that activate ChIs in response to DA release from residual axons. These results suggest that stabilizing the expression of HCN channels may improve ACh-DA reciprocity and motor function in Parkinson's disease (PD). VIDEO ABSTRACT.

Elevated plasma concentrations of S100 calcium-binding protein B and tumor necrosis factor alpha in children with autism spectrum disorders

Objective:

To investigate plasma concentrations of S100B (a calcium-binding protein derived primarily from the glia) and inflammatory cytokines in children with autism and the relationship between S100B and cytokine concentrations.

Methods:

Plasma levels of S100B, tumor necrosis factor alpha (TNF-α), interferon gamma, interleukin (IL)-1β, IL-4, IL-6, IL-10, and IL-17A were measured in 40 unmedicated children with autism and 35 normally developing healthy children. The severity of autism was assessed using the Childhood Autism Rating Scale (CARS).

Results:

Concentrations of both S100B and TNF-α were higher in children with autism before and after adjusting for a priori-selected confounders (age, sex, and body mass index). S100B concentrations were higher in children with severe autism compared to children with mild-moderate autism. However, this association remained as a trend after adjusting for confounders. S100B concentrations correlated positively with TNF-α concentrations.

Conclusion:

Our findings showing an increase in peripheral concentrations of S100B and TNF-α provide limited support to the hypothesis about the roles of altered immune function and S100B in autism spectrum disorder (ASD). Studies of larger numbers of well-characterized individuals with ASD are needed to clarify the potential role of the immune system in the pathophysiology of this disorder.

Diagnostic and therapeutic potentials of exosomes in CNS diseases

A newly discovered cell-to-cell communication system involves small, membrane-enveloped nanovesicles, called exosomes. We describe here how these extracellular nanoparticles were discovered and how it became gradually apparent that they play fundamental roles in regulation of physiological functions and pathological processes. Exosomes enable intercellular communication by transporting genetic material, proteins and lipids to cells in their vicinity or at distant sites, and subsequently regulating functions of targeted cells. Relatively recent experiments indicate that exosomes are released also by CNS cells, including cortical and hippocampal neurons, glial cells, astrocytes and oligodendrocytes, and that exosomes have significant impact on pathophysiology of the brain. How it is decided what individual exosomes will carry to their targets is not understood, but it appears that the contents may represent "signature cargos" that are characteristic for various conditions. Exploration of such characteristics could result in discovery of novel diagnostic biomarkers. Exosomes are also promising as a vehicle for therapeutic delivery of micro RNA or other compounds. How to deliver exosomes to selected sites has been a tantalizing question. Recent experiments revealed that at least some exosomes carry antibodies on their surface, suggesting that it may be feasible to deliver exosomes to unique sites based on the recognition of antigens by those antibodies. This discovery implies that rather precise targeting of both natural and engineered exosomes may be feasible. This would reduce distribution volume of therapeutics, and consequently minimize their side effects. This article is part of a Special Issue entitled Neuroimmunology in Health And Disease.

Risperidone-related improvement of irritability in children with autism is not associated with changes in serum of epidermal growth factor and interleukin-13

Risperidone has been shown to improve serious behavioral problems in children with autism. Here we asked whether risperidone-associated improvement was related to changes in concentrations of inflammatory molecules in the serum of these subjects. Seven molecules were identified as worthy of further assessment by performing a pilot analysis of 31 inflammatory markers in 21 medication-free subjects with autism versus 15 healthy controls: epidermal growth factor (EGF), interferon-γ (IFN-γ), interleukin (IL)-13, IL-17, monocyte chemoattractant protein-1 (MCP-1), IL-1 and IL-1-receptor antagonist. Serum concentrations of these markers were then established in a different set of subjects that participated in a double-blind, clinical trial and an expanded group of healthy subjects. In the first analysis, samples obtained from subjects with autism at baseline visits were compared to visits after 8-week treatment with placebo (n=37) or risperidone (n=40). The cytokine concentrations remained stable over the 8-week period for both risperidone and placebo groups. In the second analysis, we explored further the differences between medication-free subjects with autism (n=77) and healthy controls (recruited independently; n=19). Serum levels of EGF were elevated in subjects with autism (median=103 pg/mL, n=75) in comparison to healthy controls (75 pg/mL, n=19; p<0.05), and levels of IL-13 were decreased in autism (median=0.8 pg/mL, n=77) in comparison to controls (9.8 pg/mL, n=19; p=0.0003). These changes did not correlate with standardized measures used for a diagnosis of autism. In summary, risperidone-induced clinical improvement in subjects with autism was not associated with changes in the serum inflammatory markers measured. Whether altered levels of EGF and IL-13 play a role in the pathogenesis or phenotype of autism requires further investigation.

Peroxisome proliferator-activated receptor-γ agonists prevent in vivo remodeling of human artery induced by alloreactive T cells

BACKGROUND

Ligands activating the transcription factor peroxisome proliferator-activated receptor-γ (PPARγ) have antiinflammatory effects. Vascular rejection induced by allogeneic T cells can be responsible for acute and chronic graft loss. Studies in rodents suggest that PPARγ agonists may inhibit graft vascular rejection, but human T-cell responses to allogeneic vascular cells differ from those in rodents, and the effects of PPARγ in human transplantation are unknown.

METHODS AND RESULTS

We tested the effects of PPARγ agonists on human vascular graft rejection using a model in which human artery is interposed into the abdominal aorta of immunodeficient mice, followed by adoptive transfer of allogeneic (to the artery donor) human peripheral blood mononuclear cells. Interferon-γ-dependent rejection ensues within 4 weeks, characterized by intimal thickening, T-cell infiltrates, and vascular cell activation, a response resembling clinical intimal arteritis. The PPARγ agonists 15-deoxy-prostaglandin-J(2), ciglitazone, and pioglitazone reduced intimal expansion, intimal infiltration of CD45RO(+) memory T cells, and plasma levels of inflammatory cytokines. The PPARγ antagonist GW9662 reversed the protective effects of PPARγ agonists, confirming the involvement of PPARγ-mediated pathways. In vitro, pioglitazone inhibited both alloantigen-induced proliferation and superantigen-induced transendothelial migration of memory T cells, indicating the potential mechanisms of PPARγ effects.

CONCLUSION

Our results suggest that PPARγ agonists inhibit allogeneic human memory T cell responses and may be useful for the treatment of vascular graft rejection.

Altered immunoglobulin profiles in children with Tourette syndrome

BACKGROUND

Post-infectious autoimmunity and immune deficiency have been implicated in the pathogenesis of Tourette syndrome (TS). We asked here whether B cell immunity of patients with TS differs from healthy subjects.

METHODS

In two independent cross-sectional samples, we compared serum levels of IgG1, IgG2, IgG3, IgG4, IgM, IgA, and IgE in 21 patients with TS from Yale University (17 males, 4 females, 8-16 years) versus 21 healthy controls (13 males, 8 females, 7-17 years); and in 53 patients with TS from Groningen University (45 males, 8 females, 6-18 years) versus 53 healthy controls (22 males, 31 females, 6-18 years), respectively. We also investigated correlations between Ig concentrations and symptom severity. In 13 additional patients (9 males, 4 females, age range 9-14), we established Ig profiles at time points before, during, and after symptom exacerbations.

RESULTS

IgG3 levels were significantly lower in Yale patients compared to healthy children (medians 0.28 versus 0.49 mg/ml, p=.04), while levels of IgG2, IgG4, and IgM in patients were lower at trend-level significance (p≤.10). Decreased IgG3 (medians 0.45 versus 0.52 mg/ml; p=.05) and IgM (medians 0.30 versus 0.38 mg/ml; p=.04) levels were replicated in the Groningen patients. Ig levels did not correlate with symptom severity. There was a trend-level elevation of IgG1 during symptom exacerbations (p=.09).

CONCLUSION

These pilot data indicate that at least some patients with TS have decreased serum IgG3, and possibly also IgM levels, though only few subjects had fully expressed Ig immunodeficiency. Whether these changes are related to TS pathogenesis needs to be investigated.

Streptococcal upper respiratory tract infections and exacerbations of tic and obsessive-compulsive symptoms: a prospective longitudinal study

OBJECTIVE

The objective of this blinded, prospective, longitudinal study was to determine whether new group A β hemolytic streptococcal (GABHS) infections are temporally associated with exacerbations of tic or obsessive-compulsive (OC) symptoms in children who met published criteria for pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS). A group of children with Tourette syndrome and/or OC disorder without a PANDAS history served as the comparison (non-PANDAS) group.

METHOD

Consecutive clinical ratings of tic and OC symptom severity were obtained for 31 PANDAS subjects and 53 non-PANDAS subjects. Clinical symptoms and laboratory values (throat cultures and streptococcal antibody titers) were evaluated at regular intervals during a 25-month period. Additional testing occurred at the time of any tic or OC symptom exacerbation. New GABHS infections were established by throat swab cultures and/or recent significant rise in streptococcal antibodies. Laboratory personnel were blinded to case or control status, clinical (exacerbation or not) condition, and clinical evaluators were blinded to the laboratory results.

RESULTS

No group differences were observed in the number of clinical exacerbations or the number of newly diagnosed GABHS infections. On only six occasions of a total of 51 (12%), a newly diagnosed GABHS infection was followed, within 2 months, by an exacerbation of tic and/or OC symptoms. In every instance, this association occurred in the non-PANDAS group.

CONCLUSIONS

This study provides no evidence for a temporal association between GABHS infections and tic/OC symptom exacerbations in children who meet the published PANDAS diagnostic criteria.

Elevated expression of MCP-1, IL-2 and PTPR-N in basal ganglia of Tourette syndrome cases

BACKGROUND

Post-infectious autoimmunity has been implicated in pathogenesis of Tourette's syndrome (TS) but no evidence of inflammation in central nervous system has been reported yet. We evaluated the expression of genes encoding selected inflammatory factors in post-mortem specimen of adult TS patients: interferon-γ (a cytokine released from CD8 and Thelper 1 CD4 subset of T lymphocytes), interleukin-2 (IL-2, a growth factor derived from T lymphocytes), interleukin-1 β (a cytokine involved in initiation of inflammation), monocyte chemotactic factor -1 (MCP-1, a marker of chronic inflammation) and CD45 (pan-leukocytic marker). For validation purposes, we determined expression of three genes that were previously reported to be elevated in post-mortem specimen of other TS cases: protein tyrosine phosphatase receptor-N (PTPR-N), PTPR-U and recoverin.

METHODS

Total RNA was isolated from formalin fixed brain tissue sections of basal ganglia area from four patients with TS and four control subjects, and real-time reverse transcription-polymerase chain reaction analysis was employed to quantitatively evaluate gene expression of the selected genes.

RESULTS

Significantly increased expression of MCP-1, IL-2 and PTPR-N was observed in TS cases (6.5-fold, 2.3-fold and 16.1-fold increase, respectively, p<0.05).

CONCLUSIONS

Elevated expression of MCP-1 and IL-2 supports the possibility of chronic inflammatory processes in the basal ganglia. Replication of elevated expression of PTPR-N in TS specimen suggests that pathway(s) involving this molecule may be important in TS pathogenesis.

Children with Tourette's syndrome may suffer immunoglobulin A dysgammaglobulinemia: preliminary report

BACKGROUND

Postinfectious autoimmunity has been implicated in Tourette's syndrome and obsessive-compulsive disorder (TS/OCD), whereas increased frequency of upper respiratory tract infections (URTI) in TS/OCD patients suggests immune deficiency. We hypothesized that antineuronal antibodies may be elevated in patients (reflecting autoimmune processes), and levels of total immunoglobulins (Igs) may be decreased (reflecting immune deficiency).

METHODS

We analyzed plasma of TS/OCD patients (n = 24) and healthy age- and sex-matched control subjects (n = 22) by enzyme-linked immunosorbent assay (ELISA) for the levels of total and specific IgG, IgM, and IgA against antigens previously identified in multiple sclerosis (myelin basic protein and myelin-associated glycoprotein) and Sydenham's chorea (ganglioside-GM1, lysoganglioside, and tubulin).

RESULTS

Total IgA was decreased in TS/OCD patients (median 115 mg/100 mL) compared with control subjects (141 mg/100 mL; p = .02). Specific IgA against all antigens, except tubulin were also decreased in the patients (MPB 0 vs. 13 [ELISA units [EU]; myelin-associated glycoprotein 29 vs. 44 EU, p = .04; ganglioside GM1 21 vs. 35 EU, p = .01; lysoganglioside 44 vs. 56 EU, p = .03; tubulin 44 vs. 44 EU, p = .8). The levels of total IgA and anti-myelin basic protein (MBP) IgA were significantly lower in the subgroup of pediatric autoimmune neuropsychiatric disorder associated with Streptococcus (PANDAS) cases (n = 10) than in non-PANDAS cases (n = 9; total IgA 98 mg/100 mL vs. 133 mg/mL, p = .03; anti-MBP IgA 1 vs. 6 EU, p = .03) or healthy control subjects (total IgA 141 mg/100 mL, p = .02; anti-MBP IgA 13 EU, p = .005).

CONCLUSIONS

At least some TS/OCD patients may suffer IgA dysgammaglobulinemia, possibly rendering the children more prone to URTI.

Comparison of human fetal liver, umbilical cord blood, and adult blood hematopoietic stem cell engraftment in NOD-scid/gammac-/-, Balb/c-Rag1-/-gammac-/-, and C.B-17-scid/bg immunodeficient mice

Immunodeficient mice bearing components of a human immune system present a novel approach for studying human immune responses. We investigated the number, phenotype, developmental kinetics, and function of developing human immune cells following transfer of CD34(+) hematopoietic stem cell (HSC) preparations originating from second trimester human fetal liver (HFL), umbilical cord blood (UCB), or granulocyte colony-stimulating factor-mobilized adult blood (G-CSF-AB) delivered via intrahepatic injection into sublethally irradiated neonatal NOD-scid/gammac(-/-), Balb/c-Rag1(-/-)gammac(-/-), and C.B-17-scid/bg mice. HFL and UCB HSC provided the greatest number and breadth of developing cells. NOD-scid/gammac(-/-) and Balb/c-Rag1(-/-)gammac(-/-) harbored human B and dendritic cells as well as human platelets in peripheral blood, whereas NOD-scid/gammac(-/-) mice harbored higher levels of human T cells. NOD-scid/gammac(-/-) mice engrafted with HFL CD34(+) HSC demonstrated human immunological competence evidenced by white pulp expansion and increases in total human immunoglobulin following immunization with T-dependent antigens and delayed-type hypersensitivity-infiltrating leukocytes in response to antigenic challenge. In conclusion, we describe an encouraging base system for studying human hematopoietic lineage development and function utilizing human HFL or UCB HSC-engrafted NOD-scid/gammac(-/-) mice that is well suited for future studies toward the development of a fully competent humanized mouse model.

Decreased numbers of regulatory T cells suggest impaired immune tolerance in children with tourette syndrome: a preliminary study

BACKGROUND

Post-streptococcal autoimmune inflammation of basal ganglia was suggested to be an etiological factor in some cases of Tourette syndrome (TS). Since regulatory T (T reg) cells play a major role in preventing autoimmunity, we hypothesized that a defect in T reg cells may be present in children with TS. We also postulated that group A beta hemolytic streptococcal infections could promote autoimmune responses by releasing exotoxins (streptococcal pyrogenic exotoxins [SPE]).

METHODS

We analyzed peripheral blood of TS patients and healthy age-matched control subjects by fluorescence-activated cell sorting (FACS) on multiple occasions and determined the numbers of CD4(+)CD25(+)CD69(-) T reg cells. Further, we quantified the number of CD4(+) and CD8(+) lymphocytes with regard to Vbeta chains to which SPEs are known to bind.

RESULTS

A significant decrease in T reg cells was observed in patients with moderate to severe TS symptoms compared with healthy age-matched control children. A decrease in T reg cell number was also noted during symptom exacerbations in five out of six patients. Further, we found a significant decrease in numbers of CD8(+)Vbeta18(+) T cells in moderate to severe TS patients.

CONCLUSIONS

These data support our hypothesis that at least some TS patients may have a decreased capacity to inhibit autoreactive lymphocytes through a deficit in T reg cells. Interactions of host T cell immunity and microbial factors may also contribute to the pathogenesis of TS.

Manganese treatment modulates the expression of peroxisome proliferator-activated receptors in astrocytoma and neuroblastoma cells

Peroxisome proliferator-activated receptors (PPARs) play roles in neural cells by regulating energy balance, cell proliferation and anti-oxidant responses although the molecular mechanisms underlying such roles are unclear. Chronic exposure to excess manganese (Mn) leads to neurotoxicity, although Mn-induced neurotoxic mechanisms have not been fully elucidated. We hypothesized Mn neurotoxicity differentially alters the expression of PPARs. We investigated the effects of manganese chloride treatment (0.01-4 mM) on protein expression of PPAR isoforms (alpha, beta, and gamma) in human astrocytoma (U87) and neuroblastoma (SK-N-SH) cells. The two cell types expressed the 3 PPAR isoforms differentially: their expression of the PPARs was altered by Mn-treatment. Furthermore, nuclear and cytosolic fractions derived from the 2 cell types, with and without Mn-treatment, exhibited marked differences in the protein content of PPARs. Our results constitute the first demonstration that the PPAR signaling pathway may assume pathophysiological importance in Mn neurotoxicity.

Increased serum levels of interleukin-12 and tumor necrosis factor-alpha in Tourette's syndrome

BACKGROUND

The hypothesis that common infections can modulate the onset and course of tic disorders and early-onset obsessive-compulsive disorder (OCD) in pediatric populations is longstanding. To date, most investigations have focused on the hypothesis of molecular mimicry and humoral immune responses. This study was carried out to investigate whether cytokines associated with the innate immune response or T cell activation were altered under baseline conditions and during periods of symptom exacerbation.

METHODS

Forty-six patients with Tourette's syndrome and/or early-onset OCD, aged 7-17 years, and 31 age-matched control subjects participated in a prospective longitudinal study. Ratings of clinical severity and serum were collected at regular intervals, and serum concentrations of 10 cytokines were measured repeatedly.

RESULTS

Interleukin-12 and tumor necrosis factor alpha concentrations at baseline were elevated in patients compared with control subjects. Both of these markers were further increased during periods of symptom exacerbation.

CONCLUSIONS

These findings suggest that symptom exacerbations are associated with an inflammatory process propagated by systemic and local cytokine synthesis that might involve the central nervous system. We conclude that, in the future, longitudinal studies of children with neuropsychiatric disorders should examine the involvement of innate and T cell immunity.

Airway hyper-reactivity mediated by B-1 cell immunoglobulin M antibody generating complement C5a at 1 day post-immunization in a murine hapten model of non-atopic asthma

Contact skin immunization of mice with reactive hapten antigen and subsequent airway challenge with the same hapten induces immediate airflow obstruction and subsequent airway hyper-reactivity (AHR) to methacholine challenge, which is dependent on B cells but not on T cells. This responsiveness to airway challenge with antigen is elicited as early as 1 day postimmunization and can be adoptively transferred to naïve recipients via 1-day immune cells. Responses are absent in 1-day immune B-cell-deficient JH(-/-) mice and B-1 B-cell-deficient xid male mice, as well as in recipients of 1-day immune cells depleted of cells with the B-1 cell phenotype (CD19(+) B220(+) CD5(+)). As B-1 cells produce immunoglobulin M (IgM), we sought and found significantly increased numbers of anti-hapten IgM-producing cells in the spleen and lymph nodes of 1-day immune wild-type mice, but not in xid mice. Then, we passively immunized naive mice with anti-hapten IgM monoclonal antibody and, following airway hapten challenge of the recipients, we showed both immediate airflow obstruction and AHR. In addition, AHR was absent in complement C5 and C5a receptor-deficient mice. In summary, this study of the very early elicited phase of a hapten asthma model suggests, for the first time, a role of B-1 cells in producing IgM to activate complement to rapidly mediate asthma airway reactivity only 1 day after immunization.

Early delayed-type hypersensitivity eosinophil infiltrates depend on T helper 2 cytokines and interferon-gamma via CXCR3 chemokines

We investigated the role of T helper (Th)1- and Th2-type cytokines in delayed-type hypersensitivity to soluble protein antigens elicited early postimmunization. Mice were sensitized by intradermal injection without adjuvants, or subcutaneously with complete Freund's adjuvant, and subsequently ear challenged intradermally. As soon as day 3, antigen-specific eosinophil-rich responses were elicited in wild-type mice, but not in T-cell receptor-alpha-/- mice without adjuvant. Draining lymph node T cells stimulated with antigen secreted interleukin (IL)-4, IL-5 and interferon-gamma (IFN-gamma). IFN-gamma-dependent specific immunoglobulin G (IgG)2a and IL-4-dependent IgG1 were also generated. Delayed-type hypersensitivity ear swelling and local eosinophil recruitment were decreased in IL-5-/-, IL-4-/- and signal transducer and activator of transcription-6 (STAT-6)-/- mice, and with anti-IL-4 treatment of wild-type mice, suggesting Th2 mechanisms. Interestingly, responses were also decreased in IFN-gamma-/- mice, and IFN-gamma protein and the IFN-gamma-inducible CXC chemokine, IP-10, were present in 24-hr ear tissue extracts, suggesting Th1 effects. Finally, ear swelling, total histology and eosinophils were decreased in mice deficient in CXCR3, the chemokine receptor for IP-10. These results suggest that both a Th2-like (IL-5, IL-4 and STAT-6) and a Th1-like (IFN-gamma, IP-10, CXCR3) pathway contribute to eosinophil recruitment in early delayed-type hypersensitivity.

B-1 B Cells Mediate Required Early T Cell Recruitment to Elicit Protein-Induced Delayed-Type Hypersensitivity

We define the initiation of elicited delayed-type hypersensitivity (DTH) as a series of processes leading to local extravascular recruitment of effector T cells. Responses thus have two sequential phases: 1) 2-h peaking initiation required for subsequent recruitment of T cells, and 2) the late classical 24-h component mediated by the recruited T cells. We analyzed DTH initiation to protein Ags induced by intradermal immunization without adjuvants. Ag-spceific initiating cells are present by 1 day in spleen and lymph nodes. Their phenotypes, determined by depletion of cell transfers by mAb and complement, are CD5(+), CD19(+), CD22(+), B220(+), Thy1(+), and Mac1(+), suggesting that they are B-1 B cells. DTH initiation is absent in micro MT B cell and xid B-1 cell deficient mice, is impaired in mice unable to secrete IgM, and is reconstituted with 1 day immune serum, suggesting that early B-1 cell-derived IgM is responsible. Study of complement C5a receptor-deficient mice, anti-C5 mAb neutralization, or mast cell deficiency suggests that DTH initiation depends on complement and mast cells. ELISPOT assay confirmed production of Ag-specific IgM Abs at days 1 and 4 in wild-type mice, but not in B-1 cell-deficient xid mice. We conclude that rapidly activated B-1 cells produce specific IgM Abs which, after local secondary skin challenge, form Ag-Ab complexes that activate complement to generate C5a. This stimulates C5a receptors on mast cells to release vasoactive substances, leading to endothelial activation for the 2-h DTH-initiating response, allowing local recruitment of DTH-effector T cells.

B cell-dependent T cell responses: IgM antibodies are required to elicit contact sensitivity

Contact sensitivity (CS) is a classic example of in vivo T cell immunity in which skin sensitization with reactive hapten leads to immunized T cells, which are then recruited locally to mediate antigen-specific inflammation after subsequent skin challenge. We have previously shown that T cell recruitment in CS is triggered by local activation of complement, which generates C5a that triggers C5a receptors most likely on mast cells. Here, we show that B-1 cell-derived antihapten IgM antibodies generated within 1 day (d) of immunization combine with local challenge antigen to activate complement to recruit the T cells. These findings overturn three widely accepted immune response paradigms by showing that (a) specific IgM antibodies are required to initiate CS, which is a classical model of T cell immunity thought exclusively due to T cells, (b) CS priming induces production of specific IgM antibodies within 1 d, although primary antibody responses typically begin by day 4, and (c) B-1 cells produce the 1-d IgM response to CS priming, although these cells generally are thought to be nonresponsive to antigenic stimulation. Coupled with previous evidence, our findings indicate that the elicitation of CS is initiated by rapidly formed IgM antibodies. The IgM and challenge antigen likely form local complexes that activate complement, generating C5a, leading to local vascular activation to recruit the antigen-primed effector T cells that mediate the CS response.

Subunits of IgM reconstitute defective contact sensitivity in B-1 cell-deficient xid mice: kappa light chains recruit T cells independent of complement

The elicitation of contact sensitivity (CS) to local skin challenge with the hapten trinitrophenyl (TNP) chloride requires an early process that is necessary for local recruitment of CS-effector T cells. This is called CS initiation and is due to the B-1 subset of B cells activated at immunization to produce circulating IgM Ab. At challenge, the IgM binds hapten Ag in a complex that locally activates C to generate C5a that aids in T cell recruitment. In this study, we present evidence that CS initiation is indeed mediated by C-activating classic IgM anti-TNP pentamer. We further demonstrate the involvement of IgM subunits derived either from hybridomas or from lymphoid cells of actively immunized mice. Thus, reduced and alkylated anti-TNP IgM also initiates CS, likely due to generated H chain-L chain dimers, as does a mixture of separated H and L chains that still could weakly bind hapten, but could not activate C. Remarkably, anti-TNP kappa L chains alone mediated CS initiation that was C-independent, but was dependent on mast cells. Thus, B-1 cell-mediated CS initiation required for T cell recruitment is due to activation of C by specific IgM pentamer, and also subunits of IgM, while kappa L chains act via another C-independent but mast cell-dependent pathway.

Early local generation of C5a initiates the elicitation of contact sensitivity by leading to early T cell recruitment

We have shown previously that an early complement C5-dependent cascade is required to recruit T cells to elicit 24-h contact sensitivity (CS) responses. In this paper, we have characterized molecular events of this early required cascade by biochemically analyzing extracts of mouse ears undergoing elicitation of CS. Chemotactic activity was found after local Ag challenge, in CS ear extracts early (by 1 h), in CS ear extracts late (through 24 h), in previously immunized mice, but not in ears of vehicle-immunized or non-immune-challenged mice. The early chemotactic activity at 2 h was likely caused by C5a, because it was neutralized in vitro by anti-C5a Ab, was inactive on C5aR-deficient (C5aR-/-) macrophages, and was absent in C5-deficient mice. The activity was present in T cell-deficient mice, but elaboration was Ag-specific. This T cell-independent, Ag-specific elaboration of C5a early in CS ear responses likely led to T cell recruitment, because subsequent local IFN-gamma mRNA and protein expression, as markers of T cell arrival and activation, began by 4 h after Ag challenge. In contrast to early C5a chemotactic activity, late chemotactic activity 24 h after Ag challenge was unaffected by anti-C5, was active on C5aR-/- macrophages, was T cell-dependent, and by ELISA appeared largely due to chemokines (macrophage-inflammatory protein-1alpha and -1beta, IFN-gamma-inducible protein-10, and monocyte chemoattractant protein-1). Importantly, early generation of C5a was required for T cell recruitment because C5aR-/- mice had absent 24-h CS. Taken together, these findings indicate an important linkage of C5a as a component of early activated innate immunity that is required for later elicitation of acquired T cell immunity, probably by facilitating the initial recruitment of T cells into the Ag-challenged local site in CS responses.

A new paradigm of T cell allergy: requirement for the B-1 cell subset

BACKGROUND

We have uncovered a role for B-1-B-cell-produced IgM antibody, in the initiation of contact sensitivity (CS) in mice. CS and delayed-type hypersensitivity (DTH) involve recruitment of T cells to the tissues, to be activated by antigen-presenting cells (APC), and then make cytokines. Little is known about low recruitment is initiated. In CS, soon after immunization, the unique B-1 cell subset, responsible for the formation of most IgM, is activated to produce antigen (Ag)-specific IgM for export to tissues. IgM forms complexes with challenge Ag, activating the classical complement (C) pathway, generating C5a, to activate endothelium directly, or indirectly via C5a receptors (R) on mast cells and platelets, that release vasoactive amines (serotonin) and cytokines (TNF-alpha). These act together to induce vasodilatation, vascular permeability and expression of endothelial adhesion molecules to promote optimal T cell recruitment.

METHODS AND RESULTS

New findings that established this pathway include: (1) absent CS response in C-deficient, or C-inhibited mice; (2) local generation of C5a in CS tissue extracts; (3) absent CS in C5aR-/- mice; (4) decreased CS in B cell and B-1-cell-deficient mice, and (5) reconstitution of CS by transfer of B-1 cells, or hapten-specific IgM.

CONCLUSION

These findings indicate that the B-1 subset producing Ag-specific IgM is required early in CS to activate C, to induce vasoactive mediators that initiate local T recruitment.

Relationship between systemic blood pressure, airway blood flow and plasma exudation in guinea-pig

Plasma exudation in the airways is mainly dependent on microvascular permeability of the tracheobronchial circulation and may be affected by local blood flow. Aortic blood pressure provides the major inflow pressure to tracheobronchial circulation. Therefore, systemically administered vasoconstrictors, in doses enough to increase systemic blood pressure, may theoretically increase the blood flow in the tracheobronchial circulation by enhancing inflow pressure. Consequently, this may influence plasma exudation induced by inflammatory mediators in the airways. To test this hypothesis, we used guinea-pigs to study: (1) the effects of i.v. vasoconstrictors (methoxamine and angiotensin II) on blood flow in the tracheal mucosa and in the leg skeletal muscle (Laser-Doppler flowmetry); (2) the effects of i.v. vasoconstrictors on plasma exudation induced by tracheal administration of the inflammatory mediator bradykinin (150 nmol). We found that i.v. methoxamine and angiotensin II significantly increase tracheal mucosa blood flow and systemic blood pressure. The increase in tracheal mucosa blood flow was, in the case of angiotensin II, found to be significantly related to the increase in systemic blood pressure. In separate experiments, pre-treatment with i.v. methoxamine and angiotensin II significantly potentiates Evan's Blue dye exudation induced by bradykinin in the trachea and main bronchi. We conclude that i.v. methoxamine and angiotensin II potentiate bradykinin-induced plasma exudation in the guinea-pig airways, possibly by increasing the local blood flow. The increase in the local blood flow is most likely induced by enhanced systemic blood pressure (inflow pressure), owing to a redistribution of the total body blood flow.

Contraction of human airway smooth muscle by endothelin-1 and IRL 1620: effect of bosentan

We have examined whether 4-tert-butyl-N-[6-(2-hydroxy-ethoxy)-2,2'-bipyrimidin-4-yl]-benzen esulfonamide (bosentan; endothelin ET(A/B) receptor antagonist) and (R)2-[(R)-2-[(S)-2-[[1-(hexahydro-1H-azepinyl)]carbonyl] amino-4-methylpentanoil]amino-3-[3-(1-methyl-1H-indoyl)]prop ionyl]amino-3-(2-pyridyl) propionic acid (FR 139317; endothelin ET(A) receptor antagonist) inhibit contractions of human airway smooth muscle induced by endothelin-1 or Suc-[Glu9,Ala(11,15)]enthothelin-1-(8-21) (IRL 1620; endothelin ET(B) receptor agonist). Endothelin-1 and IRL 1620 were equipotent. Bosentan and FR 139317 (each 10 microM) produced a small shift in response curves to endothelin-1 (1.6- and 1.5-fold, respectively). However, bosentan was more potent against contractions elicited by IRL 1620 (10 microM, 11.2-fold shift) suggesting that these agonists exhibit different kinetic interactions with endothelin receptors or implying an interaction with a novel endothelin ET(B) receptor subtype in human airways.

8-Epi-PGF2alpha induces airflow obstruction and airway plasma exudation in vivo

8-Epi-prostaglandin F2alpha (8-epi-PGF2alpha) is an F2-isoprostane formed mainly via noncyclooxygenase pathways in vivo. We investigated whether 8-epi-PGF2alpha has any effect on airflow obstruction and plasma exudation in vivo. Airflow obstruction was quantified by measuring lung resistance (RL) in anesthetized and ventilated guinea pigs, and plasma exudation was quantified by the Evans Blue dye method (20 mg/kg intravenously). Intratracheal instillation of 8-epi-PGF2alpha (1 nmol or 10 nmol) caused dose-related increases in RL. Furthermore, the higher dose of 8-epi-PGF2alpha produced Evans Blue dye extravasation in main bronchi and intrapulmonary airways. A prostanoid TP-receptor antagonist, BAY u3405 (1 mg/kg intravenously), abolished the airway effects of 8-epi-PGF2alpha (10 nmol). A thromboxane A2 (TxA2) synthase inhibitor, OKY-406 (30 mg/kg intravenously), significantly attenuated these effects of 8-epi-PGF2alpha (10 nmol). The level of TxB2, a stable TxA2 metabolite, increased in bronchoalveolar lavage fluid (BALF) after 8-epi-PGF2alpha instillation. We conclude that 8-epi-PGF2alpha causes airflow obstruction and plasma exudation in vivo. This effect may be mediated primarily via prostanoid TP-receptors, and a secondary generation of TxA2 may be involved in part of the airway responses in 8-epi-PGF2alpha in the guinea pig.

U46619 (a thromboxane A2 mimetic) induces airflow obstruction and airway plasma extravasation in the guinea pig: the role of histamine, cyclooxygenase metabolites, leukotrienes and PAF

The aim of the present study was to characterize the airway effects of U46619, a stable thromboxane A2 mimetic, instilled into the trachea of guinea pigs in vivo, and to investigate the role of different mediators in these effects. The airflow obstruction was evaluated by measurement of airway insufflation pressure (P1) and plasma extravasation by quantification of Evans Blue dye (EBD) in airways. U46619, given as a single dose to each animal (1 pmol-10 nmol), caused a dose-dependent increase in P1 and extravasation of EBD. The threshold dose required to induce an increase in P1 was 30 times lower than the threshold dose necessary to evoke EBD extravasation. The role of inflammatory mediators was studied when 10 pmol (inducing only the increase in P1) or 10 nmol (inducing the increase in both P1 and EBD extravasation) of U46619 was administered. The effects of both doses of U46619 were abolished by ICI192,605, an antagonist of prostanoid receptor for thromboxane A2 (0.5 mg/kg i.v.). The airflow obstruction induced by 10 nmol of U46619 was potentiated by indomethacin, a cyclo-oxygenase inhibitor (10 mg/kg i.v.). EBD extravasation induced by 10 nmol U46619 was attenuated by BW70C (6 mg/kg i.v.), a selective 5-lipoxygenase inhibitor, by ICI198,615 (0.5 microgram/kg i.v.), a leukotriene D4/E4 receptor antagonist and by WEB2086 (1 mg/kg i.v.) a platelet-activating factor receptor antagonist. Pyrilamine (2 mg/kg i.v.), a histamine H1 receptor antagonist, did not have any influence on U46619-induced airway effects. We conclude that U46619 possesses a higher potency in the induction of airflow obstruction than in the induction of plasma extravasation and that U46619-induced plasma extravasation may be partly mediated via leukotrienes and platelet-activating factor.

8-Epi-PGF2 alpha, a novel noncyclooxygenase-derived prostaglandin, constricts airways in vitro

8-Epi-prostaglandin F2 alpha (8-epi-PGF2 alpha) is an F2-isoprostane formed via a noncyclooxygenase pathway. We investigated whether 8-epi-PGF2 alpha has any effects on isolated guinea-pig and human airway smooth-muscle tone, and characterized the receptor involved in these effects. Cumulative concentration responses to 8-epi-PGF2 alpha in the absence or presence of prostanoid TP- and EP1-receptors antagonists (ICI 192, 605 and AH 6809, respectively) were compared with the responses to U46619 (a thromboxane A2 mimetic) and PGF2 alpha. 8-epi-PGF2 alpha contracted airway smooth muscle with a rank order of potency of U46619 > PGF alpha > 8-epi-PGF2 alpha for guinea pig and U46619 > 8-epi-PGF2 alpha > PGF2 alpha for human smooth muscle. ICI 192,605 inhibited guinea-pig tracheal contraction produced by U46619 (pA2 = 10.0) with a similar potency to its inhibition of the contraction induced by 8-epi-PGF2 alpha (apparent pKB = 10.2, 10.3), but not that induced by PGF2 alpha (apparent pKB = 6.6). AH 6809 inhibited contraction induced by PGF2 alpha (pA2 = 6.6) with a greater potency than contraction induced by U46619 (apparent pKB = 5.1, 5.2) or 8-epi-PGF2 alpha (apparent pKB = 5.3). In human airways, ICI 192,605 inhibited contraction induced by U46619 and 8-epi-PGF2 alpha with apparent pKB values of 9.5 and 9.4, respectively, and AH 6809 inhibited contraction induced by 8-epi-PGF2 alpha with apparent pKB values of 5.7 and 5.4. We conclude that 8-epi-PGF2 alpha contracts human and guinea-pig airways via prostanoid TP receptors. However, if 8-epi-PGF2 alpha is formed in asthma, its production, unlike that of other prostanoids, would not be inhibited by cyclooxygenase inhibitors.

Airway responses following intradermal sensitization to different types of allergens: ovalbumin, trimellitic anhydride and Dermatophagoides farinae

Sensitization of guinea pigs by intradermal injections of the occupational allergen trimellitic anhydride (TMA) in oily vehicle has been shown to be very reproducible. We studied the effect of intradermal sensitization with ovalbumin (OA) in oily vehicle on immune and airway responses in guinea pigs. We also compared airway responses to trimellitic anhydride or Dermatophagoides farinae (DF; mite) with those to OA in guinea pigs intradermally sensitized to respective allergens. Three to four weeks after sensitization, the animals were challenged with intratracheal instillation of these allergens. Intradermal injections with OA developed dose-dependently specific IgG1 antibodies to OA demonstrated by ELISA. In animals sensitized with different doses of OA in corn oil vehicle, a challenge with OA induced a reversely dose-dependent airflow obstruction and airway plasma exudation. In contrast, animals sensitized with OA in saline vehicle had dose-dependent airway responses to OA. Challenge with OA caused an immediate peak and subsequently persistent airflow obstruction, whereas this response to either TMA guinea pig serum albumin or Df was slowly progressive in animals sensitized to respective allergens. The animals sensitized to TMA or Df may show a different profile of airway responses following the challenge compared to OA. Intradermal sensitization may be a valuable method of sensitization for the development of an animal model of airway allergy to different types of allergens, including chemicals or mites.

Bradykinin-induced release of thromboxane B2 into bronchoalveolar lavage fluid of guinea pigs: relationship to airflow obstruction

The aim of this study was to evaluate the role of thromboxane A2 in bradykinin-induced airflow obstruction in guinea pig in vivo. Airway insufflation pressure (Pi) was measured to assess airflow obstruction and the thromboxane B2 (a stable metabolite of thromboxane A2) concentration in bronchoalveolar lavage fluid was determined by radioimmunoassay. The animals were pretreated with propranolol (1 mg/kg i.v.) and suxamethonium (5 mg i.v.) prior to bradykinin administration. Bradykinin instillation into the trachea (300 nmol) induced a Pi increase (47.5 +/- 8.3 cm H2O versus 23.8 +/- 1.5 in sham) and significant thromboxane B2 release into bronchoalveolar lavage fluid (79 +/- 19 pg/ml versus 19 +/- 6 in sham). A thromboxane synthase inhibitor (OKY-046, 30 mg/kg i.v.; ((E-E)-3-[p(1H-imidazole-1-yl-methyl) phenyl]-2-propenoic acid hydrochloride mono-hydrate)) or a thromboxane A2 receptor antagonist (ICI192,605, 0.5 mg/kg i.v.; (4-(Z)-6-(2-o-chloro-phenyl-4-o-hydroxyphenyl-1,3-dioxan-cis-5-yl) hexenoic acid)) reduced the Pi increase evoked by bradykinin (38.7 +/- 3.8 and 40.6 +/- 3.8 cm H2O, respectively). OKY-046 abolished the thromboxane B2 release. A platelet-activating factor receptor antagonist, WEB2086 (1 mg/kg i.v.; (3-[4-(chlorophenyl)-9-methyl-6H-thienol [3,2-f][1,2,4]trizolo-[4,3-a][1,4] diazepin-2-yl]1-4-(4-morpholinyl)-1-propanon) did not significantly affect any measured parameter. We conclude that, in guinea pigs, bradykinin-induced airway effects are associated with a local thromboxane A2 release.

Effect of maturation on airway plasma exudation induced by eicosanoids in guinea pig

Airway reactivity to bronchoconstrictor mediators changes with age. We studied the effects of maturational change on airway responses induced by a thromboxane A2 mimetic, U-46619 (2, 6 and 20 nmol/kg; i.v.), leukotriene D4 (0.6 and 2 nmol/kg; i.v.) or vehicle (0.9% NaCl; i.v.) in immature (196 +/- 3 g: 2 weeks) and adult guinea pigs (512 +/- 5 g: 11 weeks). In the same animals, we measured both lung resistance (RL) to monitor airflow obstruction and extravasation of Evans Blue dye (20 mg/kg) to quantify airway plasma exudation. For a comparison, changes in RL in response to acetylcholine (5, 15 and 50 nmol/kg; i.v.) were also examined in both age groups. The order of potency to induce an increase in RL did not change with age (leukotriene D4 > U-46619 > acetylcholine). In immature animals, the peak RL after U-46619 (2, 6 and 20 nmol/kg; P < 0.05, P < 0.005 and P < 0.01, respectively) and leukotriene D4 (2 nmol/kg; P < 0.01) was significantly higher than in adult animals. U-46619 and leukotriene D4 produced significant extravasation of Evans Blue dye in both immature and adult animals. The order of potency to induce extravasated dye also did not change with age (leukotriene D4 > U-46619). The amount of extravasation of Evans Blue dye after U-46619 (6 and 20 nmol/kg) and leukotriene D4 (0.6 and 2 nmol/kg) was significantly smaller in immature animals than adults at all airway levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of eicosanoids in airflow obstruction and airway plasma exudation induced by trimellitic anhydride-conjugate in guinea-pigs 3 and 8 weeks after sensitization

Trimellitic anhydride (TMA) is a low molecular weight chemical which can cause occupational asthma. We studied the role of eicosanoids in airway responses to TMA at different times after sensitization in actively sensitized guinea-pigs. Sensitization was performed by two intradermal injections of free TMA (0.1 ml of 0.3% TMA in corn oil). At 3 and 8 weeks after sensitization, the guinea-pigs were anaesthetized and challenged with intratracheal instillation of 0.5% TMA conjugated to guinea-pig serum albumin (TMA-GPSA; 50 microliters). Lung resistance (RL) was measured to assess airflow obstruction, and the tissue content of Evans Blue dye was measured to assess airway plasma exudation. Intratracheal instillation of TMA-GPSA induced a slowly progressing increase in RL, reaching a peak at approximately 3.5 min after the challenge (6.0 +/- 2.0 cm H2O/ml/s in the 3-week group and 3.8 +/- 0.6 in the 8-week group). Pretreatment before challenge with pyrilamine (anti-histamine: 2 mg/kg, intravenously) slowed the onset of the increase in RL following challenge with TMA-GPSA, and significantly attenuated the peak response. A combination of pyrilamine and ICI-192,605 (thromboxane receptor antagonist; 0.5 mg/kg, intravenously) completely abolished the increase in RL in both week groups. A combination of pyrilamine and ICI-198,615 (leukotriene C4/D4/E4 receptor antagonist: 0.5 mg/kg, intravenously) did not further attenuate the increase in RL compared with pretreatment with pyrilamine alone, but the induced Evans Blue dye extravasation was completely inhibited in the 3-week group, whereas a remaining extravasation was observed in the 8-week group.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment with cyclosporin A during sensitization with trimellitic anhydride attenuates the airway responses to allergen challenge three weeks later

The present studies examined the effects of oral treatment with cyclosporin A, betamethasone or azelastine administered over the time of sensitization with trimellitic anhydride on allergen-induced airway responses, compared to those of control animals given corn oil alone. Drugs were given for 8 days. The animals were sensitized with trimellitic anhydride (0.1 ml of 0.3% w/v) in corn oil given intradermally on days 4 and 5 of drug treatment. Three to four weeks after sensitization with free trimellitic anhydride, the animals were anesthetized, tracheostomized and challenged with trimellitic anhydride conjugated to guinea pig serum albumin (trimellitic anhydride-guinea pig serum albumin; 0.5%; 50 microliters) instilled via the airway route. In the same animal, we measured both lung resistance (RL) to monitor airflow obstruction, and extravasation of Evans Blue dye (20 mg/kg) to quantify airway plasma exudation. In control animals, instillation of trimellitic anhydride-guinea pig serum albumin into the tracheal lumen caused a slowly progressing increase in RL over the observation period (6 min), in addition to extravasation of Evans Blue dye at all airway levels. In animals treated with 50 mg/kg of cyclosporin A, both the allergen-induced increase in RL and extravasation of Evans Blue dye in intrapulmonary airways were significantly attenuated. However, neither betamethasone nor azelastine significantly affected these responses. We conclude that cyclosporin A may influence the immune system in the guinea pig during the induction of allergy, thus leading to attenuation of allergen-induced airway obstruction at later time points.

Bradykinin-induced airflow obstruction and airway plasma exudation: effects of drugs that inhibit acetylcholine, thromboxane A2 or leukotrienes

1. The mechanisms behind bradykinin-induced effects in the airways are considered to be largely indirect. The role of cholinergic nerves and eicosanoids, and their relationship in these mechanisms were investigated in guinea-pigs. 2. The role of cholinergic nerves was studied in animals given atropine (1 mg kg-1, i.v.), hexamethonium (2 mg kg-1, i.v.), or vagotomized. To study the role of eicosanoids, animals were pretreated with a thromboxane A2 (TxA2) receptor antagonist (ICI 192,605; 10(-6) mol kg-1, i.v.) or with a leukotriene (LT) receptor C4/D4/E4 antagonist (ICI 198,615; 10(-6) mol kg-1, i.v.). 3. After pretreatment with a drug, bradykinin (150 nmol) was instilled into the tracheal lumen. We measured both airway insufflation pressure (Pi), to assess airway narrowing, and the content of Evans blue dye in airway tissue, to assess plasma exudation. 4. Bradykinin instillation into the trachea caused an increase in Pi and extravasation of Evans blue dye. The increase in Pi was significantly attenuated by atropine or the TxA2 receptor antagonist, but not by hexamethonium, vagotomy or the LT receptor antagonist. 5. The bradykinin-induced exudation of Evans blue dye was significantly attenuated in the intrapulmonary airways by the TxA2 receptor antagonist, but not by atropine, hexamethonium, cervical vagotomy or the LT receptor antagonist. 6. A thromboxane-mimetic U-46619 (20 nmol kg-1, i.v. or 10 nmol intratracheally), caused both an increase in Pi and extravasation of Evans blue dye at all airway levels. Atropine pretreatment slightly attenuated the peak Pi after the intratracheal administration of U-46619, but not after i.v. administration. 7. We conclude that peripheral cholinergic nerves are involved in bradykinin-induced airflow obstruction but not plasma exudation, and that TxA2 is involved in both airflow obstruction and airway plasma exudation induced by bradykinin given via the airway route. TxA2-induced airflow obstruction is mediated only to a minor degree, via the release of acetylcholine in the airways.

Airway allergy to trimellitic anhydride in guinea pigs: different time courses of IgG1 titer and airway responses to allergen challenge

BACKGROUND

Trimellitic anhydride (TMA) is a low molecular weight chemical that may cause occupational asthma in human beings. The objectives of this study were to determine the time course of immune and airway responses to TMA in guinea pigs and to relate the immunologic response to the immediate responses in lung resistance (RL) and plasma exudation induced by allergen challenge.

METHODS

We studied the effects of time course after sensitization on airway response to TMA in guinea pigs actively sensitized to free TMA, given by intradermal injection (0.1 ml of 0.3% TMA in corn oil). During weeks 1, 2, 3, 5, and 8 after sensitization, anesthetized animals were challenged with TMA conjugated to guinea pig serum albumin (TMA-GPSA), instilled via the airway route. Nonsensitized animals were challenged with the same amount of conjugate 4 weeks after intradermal injection of corn oil only. In the same animal, we measured both RL to monitor airflow obstruction and extravasation of Evans blue dye (20 mg/kg) to quantify airway plasma exudation.

RESULTS

Instillation of TMA-GPSA (0.5%; 50 microliters) into the tracheal lumen caused a significant increase in RL, reaching a maximum at 2.5 minutes after the instillation in the 1-week group (9.0 +/- 5.9 cm H2O/ml/sec) and between 5 and 6 minutes in the 2-, 3-, 5-, and 8-week groups (9.4 +/- 4.8, 12.7 +/- 5.5, 3.7 +/- 1.1, and 1.7 +/- 0.2 cm H2O/ml/sec, respectively). The maximal increase in RL after the challenge in nonsensitized animals was 0.39 +/- 0.05 cm H2O/ml/sec. TMA-GPSA also produced significant extravasation of Evans blue dye at all airway levels in the sensitized groups, and the amount of dye in the peripheral airways was significantly greater than that in the trachea. Furthermore, the level of Evans blue dye in airway tissue increased with the time after sensitization, up to the latest time point tested (8 weeks). Specific IgG1 antibodies to TMA-GPSA demonstrated by ELISA were detected in all animals in the 3-, 5-, and 8-week groups, with maximal levels 5 weeks after sensitization. Specific IgG1 titers to TMA-GPSA significantly correlated with the level of Evans blue dye induced by challenge with TMA-GPSA but not with the increase in RL.

CONCLUSIONS

Intradermal sensitization to free TMA induces specific airway allergy for a long period after sensitization. Specific IgG1 antibodies to allergen may influence allergen-induced plasma exudation rather than the airflow obstruction in this animal model of TMA-induced asthma.

Leukotriene D4- and prostaglandin F2 alpha-induced airflow obstruction and airway plasma exudation in guinea-pig: role of thromboxane and its receptor

1. We studied the effects of a thromboxane A2 receptor (TP receptor) antagonist, ICI-192,605 (0.5 mg kg-1, i.v.) and a selective thromboxane (Tx) synthetase inhibitor, OKY-046 (30 mg kg-1, i.v.), on airway responses induced by leukotriene D4 (LTD4; 0.2 nmol) or prostaglandin F2 alpha (PGF2 alpha; 20 nmol) instilled via the airways route to anaesthetized guinea-pigs. For a comparison, airway responses to a TxA2-mimetic, U-46619 (0.02 nmol) were also studied. We measured both lung resistance (RL) to monitor airflow obstruction, and extravasation of Evans Blue dye to quantify airway plasma exudation. 2. Instilled LTD4 into the tracheal lumen induced an immediate peak and subsequently persistent increase in RL and produced a large amount of extravasation of Evans Blue dye at all airway levels. Both ICI-192,605 and OKY-046 significantly attenuated the persistent increase in RL following the immediate response and reduced LTD4-induced extravasation of Evans Blue dye in the trachea and proximal intrapulmonary airway. Instilled LTD4 produced significant increases in immunoreactive TxB2 in bronchoalveolar lavage fluid obtained 1.5 min after instillation of LTD4. 3. Instilled PGF2 alpha into the tracheal lumen induced an immediate increase in RL which peaked at approximately 15 s. We also observed a delayed sustained increase in RL, reaching a second peak at approximately 4 min. PGF2 alpha produced small but significant increases in the amount of Evans Blue dye at all airway levels. As with PGF2 alpha, instillation of U-46619 produced a biphasic increase in RL and extravasation of Evans Blue dye. The potency of PGF2a, in inducing these airway responses was about 1000 times less than U-46619. ICI-192,605 abolished both the immediate and the delayed increase in RL after PGF2a, and also blocked PGF2a,-induced extravasation of Evans Blue dye. However, OKY-046 had no inhibitory effects on these responses.4. We conclude that airflow obstruction and airway plasma exudation induced by instilled LTD4 is, in part, mediated via TxA2 generation and subsequent activation of TP-receptors. On the other hand,instilled PGF2a, while inducing similar responses, does so primarily by direct activation of TP receptors,rather than via TxA2 generation.

Role of arachidonic acid metabolites in airway responses induced by trimellitic anhydride in actively sensitized guinea pigs

We studied the role of arachidonic acid metabolites, histamine, and 5-HT in airway responses to trimellitic anhydride (TMA) in actively sensitized guinea pigs. Sensitization was produced by two intradermal injections of free TMA (0.1 ml of 0.3% TMA in corn oil). After 21 to 28 days, guinea pigs were anesthetized and challenged with intratracheal instillation of 0.5% TMA conjugated to guinea pig serum albumin (TMA-GPSA; 50 microliters). Lung resistance (RL) was measured to assess airflow obstruction, and the tissue content of Evans blue dye was measured to assess airway plasma exudation. Before challenge, sensitized animals were pretreated intravenously with inhibitors of different mediators: pyrilamine (antihistamine: 2 mg/kg, indomethacin (cyclooxygenase inhibitor: 10 mg/kg), OKY-046 (thromboxane synthetase inhibitor: 30 mg/kg), ICI-198,615 (leukotriene receptor antagonist: 10(-6) mol/kg), ketanserin (5-HT2 receptor antagonist: 1 mg/kg), or azelastine ("antiallergic agent": 1 mg/kg). Intratracheal instillation of TMA-GPSA induced a slowly progressing increase in RL and produced extravasation of Evans blue dye at all airway levels in sensitized animals. Pyrilamine and azelastine abolished the increase in RL induced by TMA-GPSA until 2.5 min after the challenge. Indomethacin and OKY-046 significantly attenuated the increase in RL 3 min after the challenge. ICI-198,615 and ketanserin did not significantly affect the increase in RL. Extravasation of Evans blue dye induced by TMA-GPSA was decreased by pyrilamine, azelastine and ICI-198,615 in main bronchi and intrapulmonary airways. Indomethacin, OKY-046 and ketanserin did not significantly affect the extravasation of dye into the airway tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Bradykinin-induced airway responses in guinea pig: effects of inhibition of cyclooxygenase and thromboxane synthetase

We studied the effects of indomethacin (10 mg/kg i.v.), a cyclooxygenase inhibitor, and OKY-046 (1, 10 and 30 mg/kg i.v.), a selective thromboxane synthetase inhibitor, on airflow obstruction and airway plasma exudation induced by bradykinin (150 nmol) instilled by the airway route to anesthetized guinea pigs. To do this, we studied changes in lung resistance (RL) and extravasation of Evans Blue dye respectively. Instilled bradykinin produced an immediate and marked increase in RL which peaked at approximately 30 s. We also observed a delayed increase in RL, reaching a second peak at approximately 3 min. Bradykinin produced airway plasma exudation at all airway levels, measured as extravasation of Evans Blue dye. Indomethacin significantly inhibited both the immediate and the delayed increase in RL after bradykinin. OKY-046 had a similar significant and dose-dependent inhibitory effect on these responses. In addition, both drugs inhibited bradykinin-induced Evans blue dye extravasation in intrapulmonary airways. Bradykinin instilled by the airway route significantly decreased systemic blood pressure but this effect was not altered in animals pretreated with either indomethacin or OKY-046. We conclude that the bronchoconstrictor response and airway plasma exudation induced by instilled-bradykinin may be mediated in part via thromboxane A2 generation.

Thyroxine treatment increases the hypoxic pulmonary vasoconstriction in isolated lungs from thyroidectomized rats

The possibility that changes in energy metabolism are involved in oxygen sensing during hypoxic pulmonary vasoconstriction was tested indirectly by measurement of hypoxic-pressor reactivity in lungs isolated from rats with low and high levels of plasma thyroxine. In the first study, male rats were treated for one week after thyroidectomy with 50 micrograms (n = 6) or 100 micrograms (n = 6) thyroxine per 100 g body weight (b.w.) daily or with solvent (n = 6). The lungs were isolated and perfused at constant flow with salt-albumin solution. They were ventilated with air +5% CO2 in a humid chamber at 38 degrees C. The dose-pressor response to hypoxia and angiotensin II were measured. In the second study, thyroidectomized male rats were treated similarly with 100 micrograms thyroxine (n = 7) or solvent (n = 6) and isolated lungs were perfused with homologous blood obtained from thyroidectomized blood donors treated in the same manner. Then the dose-pressor responses to hypoxia and K+ were elicited. The hypoxic-pressor responses were bigger in thyroxine than in solvent-treated rats. The response to angiotensin II and K+ was not affected by thyroxine treatment. The results are consistent with the idea that hypoxic-pressor reactivity varies directly with the metabolic rate of lung tissue.