Oral 2-chlorodeoxyadenosine in psoriatic arthritis. A preliminary report

OBJECTIVE

To determine if weekly oral 2-chlorodeoxyadenosine (2-CdA) can induce selective lymphocytopenia, and reduce inflammation, in patients with refractory psoriatic arthritis.

METHODS

Seven patients with psoriatic arthritis were treated with oral 2-CdA at weekly dosages of 0.3 mg/kg to 0.45 mg/kg for 12 weeks, followed by monthly maintenance therapy. The patients were evaluated after 6 months.

RESULTS

The drug treatment produced selective lymphocytopenia, and reduced lymphocyte infiltration into involved skin. One patient did not complete 12 weeks of therapy because of perceived lack of efficacy. Four of the 6 remaining patients had improved joint disease, and 5 of 6 had improved psoriasis.

CONCLUSION

Weekly oral 2-CdA appears to be a well-tolerated regimen for the inducement of peripheral lymphocytopenia in patients with psoriatic arthritis. Larger-scale, controlled trials may be warranted.

The presence and binding characteristics of calmodulin in microsomal preparations enriched in sarcoplasmic reticulum from rabbit skeletal muscle

ATP-dependent oxalate facilitated calcium transport in sarcoplasmic reticulum (SR) preparations obtained from rabbit vastus lateralis muscle (fast skeletal muscle; Fsr) and soleus (slow skeletal muscle; Ssr) was determined. Addition of exogenous calmodulin did not stimulate calcium transport in either Fsr or Ssr preparations. Fsr and Ssr previously washed in 1 mM EGTA demonstrated a reduced capacity to transport Ca2+; the exogenous addition of calmodulin (0.24 microM) under these conditions, did not restore uptake activity but significantly decreased the steady-state level of Ca2+ uptake. Extracts of skeletal SR prepared by treatment with 0.2 mM EDTA and boiling produced significantly more stimulation of red cell Ca2+ATPase activity than extracts prepared by boiling alone. This stimulation of red cell Ca2+-ATPase was inhibited to a significant extent by 48/80, a known anti-calmodulin agent. Radioimmunoassay revealed that extracts prepared by boiling or EDTA-treatment followed by boiling contained considerable amounts of calmodulin. Washing with 1 mM EGTA, though, did not release any calmodulin from SR. These studies reveal that calmodulin is present in both Fsr and Ssr and can only be removed by harsh treatments. The role of calmodulin in skeletal muscle Ca2+-transport remains to be determined.

Ca2+-transport in skeletal muscle sarcoplasmic reticulum of the chronically diabetic rat

Ca2+-transport in fast skeletal muscle sarcoplasmic reticulum preparations was studied in experimentally-induced diabetic rats 90 days after treatment. A significant decrease in ATP-dependent oxalate facilitated Ca2+-uptake was observed in these animals at all free Ca2+ concentrations tested (0.1-2.0 microM). A concomitant elevation in the levels of both free carnitine and long-chain acylcarnitine was also found. These observations paralleled results obtained in diabetic rat heart sarcoplasmic reticulum preparations and suggest a generalized pathophysiological mechanism affecting muscle tissue function in the diabetic animal.

Depression of calcium transport in sarcoplasmic reticulum from diabetic rats: lack of involvement by specific regulatory mediators

Cardiac sarcoplasmic reticulum (SR) ATP-dependent Ca2+-uptake was found to be depressed in 4 month streptozotocin-induced diabetic rats. Calmodulin, cAMP-dependent protein kinase and K+ stimulated Ca2+-uptake to similar degrees in SR from both control diabetic rats. Long chain acylcarnitine (7 microM) decreased Ca2+-transport in control rats by 46% but only 26% in diabetic animals. The data suggests that the depression in cardiac SR Ca2+-uptake activity in diabetic rats is non-specific in origin and not a result of alterations in regulation of SR function.