The Mode of Action of Cyclosporin

Low-dose short-term cyclosporine versus etretinate in psoriasis: improvement of skin, nail, and joint involvement

BACKGROUND

High-dose cyclosporine therapy significantly alleviates psoriasis within 2 to 4 weeks but is associated with a high rate of side effects. Reports are conflicting on the frequency and promptness of relapse after discontinuation of cyclosporine therapy.

OBJECTIVE

Our purpose was to compare the efficacy and safety of low-dose cyclosporine with that of etretinate and the stability of remission after replacing cyclosporine therapy with topical anthralin during tapering of cyclosporine.

METHODS

In a multicenter study 210 patients with moderate to severe chronic plaque-type psoriasis were randomly assigned to treatment with cyclosporine or etretinate. The initial dosages were 2.5 mg/kg/day for cyclosporine and 0.5 mg/kg/day for etretinate, which could be individually adjusted to 5.0 and 0.75 mg/kg/day, respectively. After a treatment phase of 10 weeks (phase 1) patients receiving cyclosporine were again randomly assigned to a group in which cyclosporine was replaced by topical dithranol (anthralin), or to another group in which the drug was tapered during the next 12 weeks (phase 2). All patients treated with etretinate discontinued therapy after 10 weeks and used topical dithranol.

RESULTS

Mean Psoriasis Area and Severity Index decreased by 71% in the cyclosporine group and by 47% in the etretinate group during phase 1. After 10 weeks of treatment 47% of the patients treated with cyclosporine and 10% of those treated with etretinate showed a reduction of more than 80% in skin involvement. Sixty-four percent of the cyclosporine group and 48% of the etretinate group did not require an increase in the initial dosage, resulting in a mean daily dose of 3.0 and 0.53 mg/kg, respectively. There was significant alleviation of nail involvement and joint complaints in both groups. In phase 2 the increase in mean Psoriasis Area and Severity Index and the incidence of relapse were significantly higher in patients in whom cyclosporine was discontinued and replaced by dithranol than in patients in whom cyclosporine was tapered or who were pretreated with etretinate. During treatment four patients from the cyclosporine group and three patients of the etretinate group discontinued the study because of side effects.

CONCLUSION

Low-dose short-term cyclosporine therapy for psoriasis is, in comparison with etretinate, highly effective and well tolerated. Individually adjusted cyclosporine therapy allows the majority of patients to continue the low dosage of 2.5 mg/kg/day and still achieve a good clinical response. Remission can be better preserved by tapering the drug than by discontinuing treatment abruptly.

The use of a digitizer to measure area in dermatology

The accuracy and reproducibility of area measurements made with a computerized digitizer were studied. Known areas were measured varying the way in which the system was operated, altering the characteristics of the shapes being measured and varying the ways in which the image on the computer screen was formed. Accuracy and reproducibility were dependent on all these factors; altering the operating technique caused the mean measured area to vary from 76% to 124% of the actual area, with the greatest inaccuracies being produced by altering the computer screen image. The accuracy and reproducibility of results obtained using a digitizer are critically dependent on the way in which it is used.

The effect of indomethacin on anthralin inflammation

The effect of prostaglandin inhibition, using topical indomethacin, on anthralin inflammation was studied. Indomethacin gel and gel base were applied to opposite flexor forearm skin sites of 11 volunteers for 2 h and then washed off. Anthralin and UVB were then applied to the gel-treated skin and the anthralin- and UVB-induced erythema and oedema were measured at 2, 6, 24 and 48 h using Harpenden callipers and a reflectance erythrometer. Prostaglandin inhibition was demonstrated by a significant reduction of UVB erythema at the indomethacin-treated sites compared to the gel-base-treated sites. There was a small but significant reduction in anthralin erythema, but not oedema, at the indomethacin-treated sites compared to the gel-base sites. This study demonstrates that prostaglandins, and other inflammatory mediators because the inhibitory effect was small, are involved in anthralin inflammation.

Time-dependent inhibition of growth of human keratinocytes and fibroblasts by cyclosporin A: effect on keratinocytes at therapeutic blood levels

The effect of cyclosporin A (CyA) on the growth of cultured normal human keratinocytes and fibroblasts was studied. Tritiated thymidine incorporation per DNA content was used for short-term studies (1-2 days) and cell counting for longer term studies (up to 14 days). CyA caused a dose- and time-dependent inhibition of growth of both cell types. Keratinocytes (serum free, 70 microM Ca2+) were more sensitive to CyA than fibroblasts (10% serum). For keratinocytes, at 2 days growth was 61% and 6% of controls with 3 and 10 micrograms/ml CyA, respectively, at 4 days growth was 51% with 1 microgram/ml with complete inhibition at 10 micrograms/ml, and at 11 days growth was 58 and 39% with 0.1 and 1 micrograms/ml. For fibroblasts, at 4 days growth was 72 and 58% of controls with 10 and 30 micrograms/ml CyA, respectively, at 10 days growth was 76, 43 and 10% with 3, 10 and 30 micrograms/ml, and at 14 days growth was 41 and 11% with 3 and 10 micrograms/ml with complete inhibition with 30 micrograms/ml. For keratinocytes the effect of 24 h of CyA on growth was reversible. Growth of keratinocytes was inhibited by 10% delipidized serum, and 1% serum had a small stimulatory effect, but the action of CyA was unaltered. We conclude that increasing the duration of exposure to CyA increases the concentration-dependent growth inhibition. At therapeutic blood levels of CyA the growth of cultured keratinocytes but not fibroblasts is inhibited. The benefit of CyA in reducing the hyperproliferation of psoriasis may include a direct effect on keratinocytes.