DEVELOPMENT OF AZATHIOPRINE-BASED TREATMENT REGIMEN FOR PATIENTS WITH STEROID RESISTANT PEMPHIGUS BASED ON ASSESSMENT OF MOLECULAR MECHANISMS AT THE POST-RECEPTOR LEVEL

Background: Autoimmune pemphigus is the most severe skin and mucous membranes disorders with production of IgG autoantibodies to desmogleins 1 and 3. Administration of systemic corticosteroids may help to abrogate active signs of pemphigus. However, some patients do not give an adequate response to systemic glucocorticosteroid monotherapy, as well as to their combination with immune suppressants and cytostatic agents. Aim: To develop an azathioprine-based treatment regimen for patients with autoimmune pemphigus resistant to steroids. Materials and methods: At the first step of development of a treatment regimen for patients with steroid-resistant pemphigus we analyzed retrospectively a clinical database on 23 patients who had been treated from 2000 to 2014 and whose treatment regimen included azathioprine, in addition to systemic glucocorticosteroids. At the second step, from 2013 to 2015, we assessed and treated with the azathioprine-based regimen 24 patients with autoimmune pemphigus, 14  of them being steroid resistant and 10, steroid sensitive (control group). To assess molecular mechanisms of steroid resistance at the post-receptor level (effect of prednisolone on incorporation of ³Н-uridine into lymphocyte mRNA, changes of intracellular levels of nuclear transcription factor NF-κB) we used a  real-time polymerase chain reaction, radioisotope method and liquid scintillation radiometry. Results: At the first step, we developed an azathioprine-based treatment regimen for patients with steroid resistant autoimmune pemphigus. Initial dose of azathioprine was 150 mg daily. After achievement of response, the dose was decreased to 100 mg daily. When the dose of systemic glucocorticosteroids was decreased to 20  mg daily, the dose of azathioprine was decreased to 50 mg daily, thereafter steroid resistant patients were taking azathioprine at a dose of 50 mg daily from 3  months to 2.5  years. Investigation of molecular mechanisms at the second step of the study showed that in 28%  of steroid resistant patients there was a decreased incorporation of ³Н-uridine into lymphocyte mRNA under prednisolone treatment with an increase in synthesis of total mRNA in lymphocytes (range, from 68.67 to 78.35%, р < 0.05). Compared to the control group, in all steroid resistant patients (n = 14), an increased NF-κB gene expression in lymphocytes was found (range, from 65.39 to 86.17%  and from 88.8  to 98.61%, respectively, р < 0.05). The combination therapy with systemic glucocorticosteroids and azathioprine in steroid resistant patients resulted in a  decrease in intracellular NF-κB gene expression (p < 0.01), which underlies the steroid-sparing effect of azathioprine. Conclusion: We demonstrated a statistically significant suppression of NF-κB gene expression in the cases of its high baseline levels before combination therapy in patients with autoimmune pemphigus. The steroid-sparing effect of azathioprine allows for its effective use in steroid-resistant pemphigus.