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More MS news articles for May 2004

Kv1.3-blocking 5-phenylalkoxypsoralens: a new class of immunomodulators

Mol Pharmacol. 2004 Jun;65(6):1364-74
Vennekamp J, Wulff H, Beeton C, Calabresi PA, Grissmer S, Hansel W, Chandy KG.
Pharmaceutical Institute, University of Kiel, Germany.

The lymphocyte potassium channel Kv1.3 is widely regarded as a promising new target for immunosuppression.

To identify a potent small-molecule Kv1.3 blocker, we synthesized a series of 5-phenylalkoxypsoralens and tested them by whole-cell patch clamp.

The most potent compound of this series, 5-(4-phenylbutoxy)psoralen (Psora-4), blocked Kv1.3 in a use-dependent manner, with a Hill coefficient of 2 and an EC50 value of 3 nM, by preferentially binding to the C-type inactivated state of the channel.

Psora-4 is the most potent small-molecule Kv1.3 blocker known.

It exhibited 17- to 70-fold selectivity for Kv1.3 over closely related Kv1-family channels (Kv1.1, Kv1.2, Kv1.4, and Kv1.7) with the exception of Kv1.5 (EC50, 7.7 nM) and showed no effect on human ether-a-go-go-related channel, Kv3.1, the calcium-activated K+ channels (IKCa1, SK1-SK3, and BKCa), or the neuronal NaV1.2 channel.

In a test of in vivo toxicity in rats, Psora-4 did not display any signs of acute toxicity after five daily subcutaneous injections at 33 mg/kg body weight.

Psora-4 selectively suppressed the proliferation of human and rat myelin-specific effector memory T cells with EC50 values of 25 and 60 nM, respectively, without persistently suppressing peripheral blood naive and central memory T cells.

Because autoantigen-specific effector memory T cells contribute to the pathogenesis of T cell-mediated autoimmune diseases such as multiple sclerosis, Psora-4 and other Kv1.3 blockers may be useful as immunomodulators for the therapy of autoimmune disorders.