Objective was to clarify the etiology and pathogenesis of
systemic lupus erythematosus (SLE).
Drug-induced lupus (DIL) and SLE are both found in humans, are exacerbated by the same viruses or drugs, and they are both more common in slow acetylators. Thus, DIL can be used as a model for SLE and the Adhami equation of DIL can be applied to SLE.
Polyamines are the only possible link between the viral and
amine hypotheses of SLE pathogenesis. Based on the Adhami equation,
polyamines can explain the actual annual incidence of SLE in the general population.
Putrescine is a very weak SLE-causing agent, while
spermine and
spermidine contribute equally in triggering SLE. The positively charged
polyamines bind to negatively charged internucleosomal
DNA and change its conformation from B (non-immunogenic) to Z (immunogenic). This is the major contribution of
polyamines in triggering SLE. The other effects of
polyamines are only secondary. Apoptosis is a necessary step in SLE pathogenesis, because it causes the internucleosomal fragmentation of
DNA and exposes
Z-DNA to the immune system (due to cell death). The next step is the production of
anti-DNA antibodies, followed by other SLE phenomena.
Polyamines not only cause SLE, but they are also important in sustaining the disease. Other endogenous and exogenous
amines have additive effects with
polyamines and may contribute in exacerbating SLE. When SLE is in the active phase,
polyamine levels are higher as compared to remissions. Fluctuations in
polyamine levels due to diet, metabolic factors,
infections, intestinal flora, etc. or the presence of other
amines may explain the course of SLE, characterized by remissions and exacerbations.
Acetylcysteine is a
drug that can be completely metabolized to acetyl groups. As such, this
drug is proposed as the ideal acetyl donor for the acetylation of
polyamines and other SLE-triggering compounds. Clinical trials will be necessary to test the role of
acetylcysteine in the etiologic treatment of SLE.
CONCLUSIONS: Changes in DNA conformation by
polyamines are the first step in SLE pathogenesis. Many genetic and environmental factors may increase or decrease the effects or levels of
polyamines, causing SLE exacerbations or remissions. Viruses and other infectious agents may cause SLE by producing
polyamines or by increasing the levels of endogenous
polyamines. The major
autoimmune diseases are characterized by remissions and exacerbations and not by a continuously progressive course, as commonly believed. Consequently, they are not sustained by internal vicious cycles, but by the initial triggering agent(s). While the conventional treatment of autoimmune disorders is important in minimizing tissue damage, the neutralization of their etiology may be important in curing and preventing autoimmunity.