Susceptibility to cyclosporin A-induced autoimmunity: strain differences in relation to autoregulatory T cells

Sympathetic neurotransmission in spleens from aging Brown-Norway rats subjected to reduced sympathetic tone

Senescence of innate and adaptive responses and low-grade inflammation (inflammaging) hallmarks normal aging, which increases vulnerability to infectious diseases, autoimmunity and cancer. In normal aging, sympathetic dysregulation contributes to the dysregulation of innate and adaptive immunity and inflammaging. Sympathetic innervation of immune cells in secondary immune organs regulates immune responses. Previously in Fischer 344 (F344) rats, we reported an age-related increase in sympathetic tone and sympathetic dysfunction in beta-adrenergic receptor (AR) signaling of splenic lymphocytes that contributes to immune senescence, although the responsible mechanisms remains unexplored. In this study, we extend our previous findings using the much longer-lived Brown-Norway (BN) rats, whose behavior and immune response profile differ strikingly from F344 rats. Here, we investigated whether increased sympathetic nerve activity (SNA) in the aging spleen contributes to age-related sympathetic neuropathy and altered neurotransmission in splenic lymphocytes in BN rats. Fifteen-month male BN rats received 0, 0.5 or 1.5 μg/kg/day rilmenidine intraperitoneally for 90 days to lower sympathetic tone. Untreated young and age-matched rats controlled for effects of age. We found that elevated SNA in the aging BN rat spleen does not contribute significantly to sympathetic neuropathy or the aging-induced impairment of canonical β-AR signal transduction. Despite the rilmenidine-induced increase in β-AR expression, splenocyte c-AMP production was comparable with age-matched controls, thus dampening nerve activity had no effect on receptor coupling to adenylate cyclase. Understanding how aging affects neuroimmune regulation in healthy aging rodent models may eventually lead to strategies that improve health in aging populations vulnerable to immunosenescence and low-grade systemic inflammation.

Drug-induced lupus erythematosus: incidence, management and prevention

The generation of autoantibodies and autoimmune diseases such as systemic lupus erythematosus has been associated with the use of certain drugs in humans. Early reports suggested that procainamide and hydralazine were associated with the highest risk of developing lupus, quinidine with a moderate risk and all other drugs were considered low or very low risk. More recently, drug-induced lupus has been associated with the use of the newer biological modulators such as tumour necrosis factor (TNF)-α inhibitors and interferons. The clinical features and laboratory findings of TNFα inhibitor-induced lupus are different from that of traditional drug-induced lupus or idiopathic lupus, and standardized criteria for the diagnosis of drug-induced lupus have not been established. The mechanism(s) responsible for the development of drug-induced lupus may vary depending on the drug or even on the patient. Besides lupus, other autoimmune diseases have been associated with drugs or toxins. Diagnosis of drug-induced lupus requires identification of a temporal relationship between drug administration and symptom development, and in traditional drug-induced lupus there must be no pre-existing lupus. Resolution of symptoms generally occurs after cessation of the drug. In this review, we will discuss those drugs that are more commonly associated with drug-induced lupus, with an emphasis on the new biologicals and the difficulty of making the diagnosis of drug-induced lupus against a backdrop of the autoimmune diseases that these drugs are used to treat. Stimulation of the immune system by these drugs to cause autoimmunity may in fact be associated with an increased effectiveness in treating the pathology for which they are prescribed, leading to the dilemma of deciding which is worse, the original disease or the adverse effect of the drug. Optimistically, one must hope that ongoing research in drug development and in pharmacogenetics will help to treat patients with the maximum effectiveness while minimizing side effects. Vigilance and early diagnosis are critical. The purpose of this review is to summarize the most recent developments in our understanding of the incidence, pathogenesis, diagnosis and treatment of drug-induced lupus.

Risk of autoimmune disease: challenges for immunotoxicity testing

Autoimmunity represents a potentially diverse and complex category among the range of adverse outcomes for detection with immunotoxicity testing. For this reason, the risk of autoimmune disease is discussed in this overview chapter with additional mention among the later specific protocol chapters. Improvements in clinical diagnostic capabilities and disease recognition have led to a more accurate picture of the extent of autoimmune diseases across different human populations. While the risk of any single autoimmune disease remains modest when compared with that of lung or heart disease, the cumulative prevalence of autoimmune diseases is both significant and increasing. Autoimmune diseases are usually viewed in the context of the damaged tissue or organ (e.g., as a thyroid, gastrointestinal, cardiovascular or neurological disease). But improved recognition that underlying immune dysfunction can connect the risks for these as well as other diseases is critical for optimizing risk assessment. Since autoimmune diseases are chronic in nature with many first appearing in children or in young adults, these diseases exert a serious impact on both health care costs and quality of life. This chapter provides a discussion of the issues that should be considered with immunotoxicity testing for risk of autoimmunity.

Neuroprotective effects of intravitreal mesenchymal stem cell transplantation in experimental glaucoma

Purpose. Retrograde neurotrophic factor transport blockade has been implicated in the pathophysiology of glaucoma. Stem cell transplantation appears to ameliorate some neurodegenerative conditions in the brain and spinal cord, in part by neurotrophic factor secretion. The present study was conducted to determine whether local or systemic bone marrow-derived mesenchymal stem cell (MSC) transplantation can confer neuroprotection in a rat model of laser-induced ocular hypertensive glaucoma. Methods. MSCs were isolated from the bone marrow of adult wild-type and transgenic rats that ubiquitously express green fluorescent protein. MSCs were transplanted intravitreally 1 week before, or intravenously on the day of, ocular hypertension induction by laser photocoagulation of the trabecular meshwork. Ocular MSC localization and integration were determined by immunohistochemistry. Optic nerve damage was quantified by counting axons within optic nerve cross-sections 4 weeks after laser treatment. Results. After intravitreal transplantation, MSCs survived for at least 5 weeks. Cells were found mainly in the vitreous cavity, though a small proportion of discrete cells migrated into the host retina. Intravitreal MSC transplantation resulted in a statistically significant increase in overall RGC axon survival and a significant decrease in the rate of RGC axon loss normalized to cumulative intraocular pressure exposure. After intravenous transplantation, MSCs did not migrate to the injured eye. Intravenous transplantation had no effect on optic nerve damage. Conclusions. Local, but not systemic, transplantation of MSCs was neuroprotective in a rat glaucoma model. Autologous intravitreal transplantation of MSCs should be investigated further as a potential neuroprotective therapy for glaucoma.

Cyclosporin-A inhibits ERK phosphorylation in B cells by modulating the binding of Raf protein to Bcl2

Extracellular signal-related kinase (ERK) signaling is regulated by sequential phosphorylation of upstream kinases including Raf. We report herein that ERK phosphorylation is inhibited by a short incubation with Cyclosporin-A (CsA) in anti-IgM activated Daudi B cells. As Bcl2, through its BH4 domain, was previously shown to bind both Calcineurin (Can) and Raf proteins, we hypothesized that CsA inhibited Can binding to Bcl2 allowing the latter to bind more Raf at the mitochondria thereby diverting it from activating the ERK cascade. In support of this less Bcl2 coprecipitated with Can heterodimer in total lysates of cells treated with CsA as compared to controls. In parallel, Raf1 was augmented in both the mitochondrial fractions of cells treated with CsA and in Bcl2 immunoprecipitates under CsA. Finally, introduction of a Bcl2 BH4 domain into Daudi cells augmented ERK phosphorylation in unstimulated cells and this augmentation was unsensitive to CsA. We therefore suggest that CsA indirectly inhibited ERK activation through sequestration of Raf1, at the mitochondria.

Developmental immunotoxicity investigations in the SD rat following pre- and post-natal exposure to cyclosporin

BACKGROUND

The development and function of the immune system was assessed in juvenile SD rats following pre- or post-natal exposure to cyclosporin. The main objective was to assess the feasibility of the methods available for the detection of adverse effects on the development of the immune system for use in the safety assessment of medicines.

METHODS

In a pre-natal experiment, 15 pregnant rats were given 10 mg/kg/day of cyclosporin by gavage from day 6 of gestation until 4 days after parturition. A control group received olive oil. In a post-natal experiment, the pups from 35 litters were given 10 mg/kg/day of cyclosporin by gavage from 4 to 28 days of age. Half of the pups in each litter were given water and acted as controls. Immune endpoints were determined in the pups in both experiments from two to 10 weeks of age, including: lymphocyte subsets, serum immunoglobulin titres, serum autoantibodies, primary antibody response to sheep red blood cells (SRBC), delayed-type hypersensitivity response, humoral response to keyhole limpet haemocyanin, spleen cellularity, immune organ weights, and histopathology.

RESULTS

Pre-natal exposure caused no effects on immune function. Post-natal exposure caused immune depression during the treatment period and a persistent impairment of the immune system characterised by lymphoid hyperplasia in the spleen and a reduced primary antibody response to SRBC at 10 weeks of age.

CONCLUSIONS

These results demonstrate the importance of a post-treatment follow-up period in developmental immunotoxicity studies, in order to distinguish between the transient effects of immune modulation and the persistent consequences of developmental toxicity.

Influence of PMN leukocyte-mediated pancreatic damage on the systemic immune response in severe acute pancreatitis in rats

The outcome of severe acute pancreatitis is determined by the development of the systemic inflammatory response and subsequent multiorgan dysfunction. Using the taurocholate-induced model of acute pancreatitis in rats, we investigated the relationship between early polymorphonuclear (PMN)-mediated pancreatic tissue damage and the systemic inflammatory response. The respiratory burst of PMN leukocytes was increased in animals with acute pancreatitis and was reduced by anti-ICAM-1 antibody and oxygen radical scavenger treatment after 24 hr. In acute pancreatitis a reduced number of peripheral helper T cells was evident, most likely due to L-selectin-mediated increased lymphocyte homing. After 24 hr the CD45RC(high)/CD45RC(low) ratio of helper T cells, a critical factor in T cell-mediated disease was increased due to a reduction of regulatory CD45RC(low) cells. Only the treatment with anti-ICAM-1 mAb affected these changes, indicating that immunological changes in necrotizing pancreatitis are only in part affected by early PMN leukocyte-mediated pancreatic damage.

CD4+ T cells prevent skin autoimmunity during chronic autologous graft-versus-host-disease

CD4 regulatory cells have been postulated to prevent autologous graft-vs.-host disease (GVHD). In order to test this hypothesis, we used BALB/c mice, a strain known to be resistant to autologous GVHD, which had received autologous stem cell transplantation (ASCT) and cyclosporine A (CsA). As expected, ASCT/CsA-treated BALB/c mice did not develop any sign of acute or chronic GVHD. However, depletion of CD4 T cells induced a skin disease with clinical and histological features of alopecia areata (AA), a CD8 T-cell-mediated human autoimmune skin disease. The hair loss in mice developing AA was associated with the infiltration of the skin by activated CD8 T cells. Analysis of the T-cell recovery in ASCT- and ASCT/CsA-treated mice showed that CsA induced an increase in the number of CD4+ 25+ T cells, suggesting that the lack of GVHD in ASCT/CsA treated-mice could be related to the expansion of this CD4 T-cell subset. Collectively these data show that CD4 T cells comprise regulatory cells controlling the onset of autologous GVHD and suggest that the naturally occurring CD4+ 25+ subset may be responsible for this effect.

A modified model of graft-versus-host-induced systemic sclerosis (scleroderma) exhibits all major aspects of the human disease

OBJECTIVE

Diffuse systemic sclerosis (SSc; scleroderma) is a debilitating disease characterized by excessive dermal fibrosis with later progression to internal organs. In addition to the fibrotic component, major aspects of the disease include vascular or circulatory involvement and immune dysregulation evidenced by inflammatory cells in affected tissues and production of autoantibodies. Many animal models resembling this disease have been studied, including genetic models in mice and chickens, challenge with chemicals such as bleomycin or vinyl chloride to induce fibrosis, and models of graft-versus-host (GVH)-induced disease using certain strains of mice with differences in minor histocompatibility loci. The present studies were undertaken to determine if alteration of the induction of GVH-induced scleroderma could result in a model that more fully represented the human condition.

METHODS

Disease was induced by injection of spleen cells from B10.D2 mice into BALB/c mice deficient in mature T and B cells (recombination-activating gene 2 targeted). Dermal thickening, collagen deposition, vasoconstriction, and parameters of immunity were analyzed.

RESULTS

Similar to the human disease, this modified GVH model of SSc demonstrated evidence of dermal thickening, particularly in the extremities, progressive fibrosis of internal organs, vasoconstriction and altered expression of vascularity markers in skin and internal organs, early immune activation, inflammation in skin and internal organs, and autoantibody generation.

CONCLUSION

This modified model of GVH-induced SSc exhibits all major components of human disease and is likely to contribute to better understanding of the disease mechanisms and, ultimately, improved treatments for patients.

Cyclosporin A-induced autoimmunity in the rat: central versus peripheral tollerance

No abstract available