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Cyclosporin A exacerbates mercuric chloride-induced vasculitis in the brown Norway rat
F J Qasim1, P W Mathieson, S Thiru
1Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, United Kingdom.
Background:
Administration of mercuric chloride (HgCl2) to the Brown Norway (BN) rat induces a necrotizing leukocytoclastic vasculitis (most marked in the gut) and anti-myeloperoxidase (anti-MPO) antibodies. The development of autoimmunity in the BN rat is a T cell-dependent phenomenon, and there is evidence that the induction of autoantibodies and tissue injury is a Th2-driven process. Cyclosporin A (CyA) is an anti-T cell agent with a dose-dependent differential effect on Th cell subsets that can ameliorate or enhance autoimmune responses. In the BN it can suppress HgCl2-induced autoantibody production, but the effect on tissue injury has not been previously examined.
Experimental Design:
We have studied the effect of CyA given "early" (Days 1-10, concurrently with the HgCl2) or "late" (Days 11-14) on tissue injury and autoantibody response. Serial blood samples were taken for anti-glomerular basement membrane, anti-MPO, and IgE antibody levels. Necropsies were performed on animals killed on Day 15. The presence and extent of vasculitis was scored macroscopically and histologically. Controls were incorporated to assess the effect of vehicle and of CyA alone.
Results:
CyA given early delayed the rise in anti-MPO and anti-glomerular basement membrane levels and ameliorated tissue injury, whereas CyA given late, although suppressing the rise in anti-MPO and anti-glomerular basement membrane antibodies, caused a marked exacerbation of vasculitis.
Conclusions:
The effect of CyA depends on the timing of treatment with respect to HgCl2. Anti-MPO antibodies are not of primary importance in the pathogenesis of tissue injury. The late effect may be due to a direct toxic effect on the endothelium or to loss of a protective T cell subset. These observations have implications for the use of CyA in the treatment of systemic vasculitis in humans.
Insights
Cyclosporin A (CyA) timing impacts mercuric chloride-induced vasculitis in rats. Early CyA treatment ameliorates injury, while late treatment exacerbates it, suggesting timing is crucial for managing autoimmune diseases.
Area of Science:
- Immunology
- Toxicology
- Pharmacology
Background:
- Mercuric chloride (HgCl2) in Brown Norway rats causes vasculitis and anti-myeloperoxidase (anti-MPO) antibodies.
- Autoimmunity development is T cell-dependent and potentially Th2-driven.
- Cyclosporin A (CyA) modulates T cell subsets and autoimmune responses.
Purpose of the Study:
- To investigate the effect of early versus late CyA administration on HgCl2-induced vasculitis and autoantibody production.
- To determine the role of anti-MPO antibodies in the pathogenesis of tissue injury.
Main Methods:
- Rats received HgCl2 with either early (Days 1-10) or late (Days 11-14) CyA treatment.
- Antibody levels (anti-GBM, anti-MPO, IgE) were monitored via serial blood samples.
- Vasculitis severity was assessed macroscopically and histologically at Day 15.
Main Results:
- Early CyA delayed autoantibody rise and ameliorated tissue injury.
- Late CyA suppressed autoantibodies but markedly exacerbated vasculitis.
- Controls confirmed vehicle and CyA alone had no significant effects.
Conclusions:
- The therapeutic effect of CyA is critically dependent on treatment timing relative to HgCl2 exposure.
- Anti-MPO antibodies are not the primary drivers of HgCl2-induced tissue injury.
- Late CyA's exacerbation may involve direct endothelial toxicity or loss of protective T cells, with implications for human vasculitis treatment.