The evaluation of the immunomodulating properties of ERA-63 a pharmaceutical with estrogenic activity

This paper describes studies performed with ERA-63 a low molecular weight pharmaceutical with intended immunomodulatory effects. Since this compound was also known to have estrogenic activity a non-conventional approach was taken in order to differentiate between estrogenic and non-estrogenic-induced immunomodulatory effects. EE was included not only for qualitative comparison (hazard identification) between immunomodulatory effects but also, in case of similar effects, to facilitate the extrapolation of the findings in the rat to anticipated effects in humans. After 28 days of treatment with dosages ranging from pharmacological up to clearly toxic levels for both compounds the immunotoxic potential was assessed by performing a T cell-dependent antibody response and a host resistance assay in rats. Selected ERA-63 dose levels (0.167-0.2, 1.67-2 and 16.7-20mg/kg) were expected to have comparable estrogenic activity to respective EE dose levels (0.05, 0.5 and 5mg/kg). General toxicity parameters reflecting estrogenic activity (i.e. decreased body- and organ weights of thymus and testis, and increased bilirubin and GGT levels) confirmed the comparable estrogenic activity for both compounds at the dose levels tested. Together with the comparable estrogen-related immune suppression (i.e. decreases in specific antibody responses and an increased susceptibility for Listeria monocytogenes infects) for both compounds, this indicates that available clinical data for EE facilitates the human risk assessment of ERA-63.

Coadministration of antigen and particles optimally stimulates the immune response in an intranasal administration model in mice

Some particulate matter is known to affect human health, yet the mechanism(s) by which it acts is largely unknown. One of the factors that may play a role in the immune- stimulating activity of particles is binding of allergen to particles. This may turn the particles into allergen carriers, resulting in antigen deposition within the altered inflammatory microenvironment created by the particles. We compared the efficacy of simultaneous versus separate administration of antigen and particles during sensitization in an intranasal exposure model in BALB/c mice. Sensitization consisted of three separate doses (10 microg) of TNP-OVA at Days 1, 2, and 3. Two hundred micrograms of carbon black particles (CBP) were administered either 1 day before sensitization (Day 0), 1 day after sensitization (Day 4), or during sensitization. The latter was performed either at Day 1 (200 microg) or at Days 1, 2, and 3 (67 microg/day). At Day 10 a challenge with 10 microg of TNP-OVA was performed, and at Day 15 the immune response was assessed. The total number of cells as well as antibody-forming cells (AFC) in lymph nodes draining the lung (peribronchial lymph nodes [PBLN]) were determined, and immunoglobulin levels in blood were assessed. Cell numbers of PBLN increased significantly in all particle-treated groups compared to controls. The number of TNP-specific IgG1-forming cells in the groups receiving particles during sensitization was significantly higher than control level. Only groups receiving particles during or before sensitization displayed significantly higher IgG1 levels than controls, in contrast to the group receiving particles after sensitization. Only in animals receiving three doses of 67 microg during sensitization did TNP-specific IgE increase significantly compared to controls. IgG2a did not show significant differences compared to controls, indicating that the response is predominantly Th2 mediated. These data indicate that coadministration of particles at all time points of antigen dosing is the most effective way to stimulate an immune response in our model compared to separate particle and antigen dosing. Also, administration shortly before antigen administration was effective in stimulating an immune response, suggesting that time-dependent processes are involved in immune-stimulating activity of particles, supporting the important role of the altered inflammatory microenvironment created by the particles.

Adjuvant activity of particulate pollutants in different mouse models

Particulate air pollutants may play a role in the increasing prevalence of respiratory allergy by acting as adjuvants for a T helper 2 (Th2) mediated immune response to common allergens. The immunomodulating capacity of well-defined polystyrene particles as well as different particles as present in our environment (diesel exhaust, carbon black, and silica particles) was investigated in different models. Polystyrene particles were injected intraperitoneally or installed intratracheally, while the environmentally relevant particles were injected subcutaneously. From these studies, it becomes clear that all particles exert an adjuvant effect on the immune response to the co-administered antigen. The particle core rather than attached chemical factors seems to be mainly responsible for this effect. The different particles, however, stimulate different types of immune responses, indicating that physicochemical properties of particles may be of importance in steering the response towards a T helper 1 (Th1) or a Th2-like response.

Diesel exhaust, carbon black, and silica particles display distinct Th1/Th2 modulating activity

Certain particulate air pollutants may play an important role in the increasing prevalence of respiratory allergy by stimulating T helper 2 cell (Th2)-mediated immune responses to common antigens. The study described here examined different particles, diesel exhaust particles (DEP), carbon black particles (CBP), and silica particles (SIP) for their immunomodulating capacity in both primary and secondary immune responses in female BALB/C mice. The primary response was studied after subcutaneous injection of 1 mg of particle together with 10 microgram of reporter antigen TNP-OVA (2,4,6-trinitrophenyl coupled to ovalbumin) into the hind paw. Interferon-gamma (IFN-gamma) and interleukin 4 (IL-4) production was assessed in the popliteal lymph node (PLN) at Day 2 and Day 5 after injection by flow cytometry and ELISA. The number of IL-4-containing CD4(+) T cells increased between Day 2 and Day 5 in DEP- and CBP-exposed mice, in contrast to SIP-treated animals. IL-4 production by cultured PLN cells was also significantly increased for DEP- and CBP-treated animals. The secondary response was studied in different organs after an intranasal challenge with TNP-OVA (50 microgram), which was given 4 weeks after the initial subcutaneous injection. Five days after challenge the number of antibody-forming cells (AFCs) was assessed in peribronchial lymph nodes (PBLN), spleen, bone marrow, and PLN, and antibody levels were determined in weekly obtained blood samples. It appeared that all particles acted as adjuvant, but the different particles stimulated distinct types of immune responses to TNP-OVA. DEP-treated animals show high IgG1 and IgE levels in serum and high IgG1 and IgE-forming AFC numbers in PBLN, bone marrow, and spleen. CBP-treated animals show even higher IgG1 and IgE levels and AFC numbers, and in addition display IgG2a production. SIP-injected animals display predominantly IgG2a responses. It is concluded that DEP are able to skew the immune response toward the T helper 2 (Th2) side, whereas SIP stimulate a Th1 response and CBP have a mixed activity, stimulating both Th1 and Th2 responses in this model.

Altered pattern of connexin40 distribution in persistent atrial fibrillation in the goat

INTRODUCTION

Since altered expression of gap junction proteins (connexins) in diseased myocardial tissue may lead to abnormal electrical coupling between cardiomyocytes and hence contribute to arrhythmogenesis, the expression of connexin(Cx)40 and Cx43 was studied in atrial appendage from goats in sinus rhythm (SR) and persistent atrial fibrillation (AF).

METHODS AND RESULTS

Biopsies were taken from the left and right atrial appendages from goats in SR or after pacing-induced persistent AF. Analyses of Cx40 and Cx43 mRNA and protein levels, using quantitative (competitive) polymerase chain reaction and western blotting, respectively, revealed no significant changes in the overall expression of Cx40 and Cx43 as a result of persistent AF. At the cellular level, immunohistochemistry and confocal laser scanning microscopy showed a homogeneous distribution of either connexin in atrial sections taken during SR. After induction of AF, the distribution of Cx43 gap junctions was unchanged whereas the Cx40 pattern showed marked inhomogeneities with small areas (0.15 to 0.6 mm in diameter, 25% of section surface area) of low-density Cx40 located between larger areas of normal (unchanged) Cx40 density. Activation mapping (244 electrodes, spatial resolution 2.25 mm) of the right atrial wall did not reveal changes in atrial conduction velocity.

CONCLUSION

Pacing-induced persistent AF in the goat gave rise to changes in the spatial organization of Cx40 gap junctions. Although the overall conduction velocity appeared not to have changed, microheterogeneities in conduction due to the local redistribution of Cx40 gap junctions might have contributed to the initiation and maintenance of AF.