Kv1.3-Blocking 5-Phenylalkoxypsoralens: A New Class of Immunomodulators

Abstract

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 EC 50 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 (EC 50 , 7.7 nM) and showed no effect on human ether-a-go-go-related channel, Kv3.1, the calcium-activated K ϩ channels (IKCa1, SK1-SK3, and BK Ca ), or the neuronal Na V 1.2 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 EC 50 values of 25 and 60 nM, respectively, without persistently suppressing peripheral blood naive and central memory T cells.

K+ Channel Expression during B Cell Differentiation: Implications for Immunomodulation and Autoimmunity

“…6). Similar results were obtained with Psora-4, the most potent small molecule inhibitor of Kv1.3 (31). Psora-4 suppressed the proliferation of IgD Ϫ CD27 ϩ memory B cells with an EC 50 of 250 nM (data not shown) but had no effect on the proliferation of IgD ϩ B cells at concentrations up to 1 M. These results indicate that Kv1.3 blockers preferentially suppress the proliferation of class-switched memory B cells, whereas IKCa1 blockers suppress the proliferation of naive and IgD ϩ CD27 ϩ B cells.…”

“…In proof-of-concept studies in rats, Kv1.3 blockers have been shown to ameliorate adoptive experimental autoimmune encephalomyelitis induced by myelin-specific memory T cells (16,70), a model for MS, and to prevent inflammatory bone resorption in experimental periodontal disease caused mainly by memory cells (81). Several small-molecule Kv1.3 inhibitors with nanomolar potency have been developed over the last decade (WIN-17317, CP-339818, U.K.-78,282, correolide, trans-N-propylcarbamoyloxy-PAC, sulfamidebenzamidoindanes, tetraphenylporphyrins, dichlorophenylpyrazolopyrimidines, chalcones, and Psora-4 (6,7,31,69,82,83)), and the continuing development of more selective and potent Kv1.3 blockers may make Kv1.3-based immunomodulation for autoimmune disorders a reality.…”

“…TRAM-34 and Psora-4 were synthesized as previously described by our group (30,31). Dendrotoxin-I and dendrotoxin-were purchased from Sigma-Aldrich (St. Louis, MO).…”

Kv1.3: a multifunctional channel with many pathological implications

“…Moreover, Psora-4, which displays no signs of toxicity after medium-term treatments, selectively suppresses the proliferation of human and rat myelin-specific effector memory T cells (EC 50 25 and 60 nM, respectively) without affecting peripheral blood naive and central memory T cells [19]. Unlike other Kv1.3 blockers [2], Psora-4 inhibits both Kv1.3 and Kv1.5 with similar potency (EC 50 = 3 nM and 7 nM, respectively) thereby, supporting the use of this drug to target the heterotetramer [19].…”

Ion channels and anti-cancer immunity

“…Some of these molecules were also developed on a natural template, e.g. the K þ channel blocking component of Ruta graveolens alkaloids, 5-methoxypsoralen was chemically modified to generate a series of Kv1.3 inhibitors including Psora-4 [61] and PAP-1 [62] with nanomolar affinity for Kv1.3 and good selectivity over other K þ channels. The therapeutic applications of PAP-1 for inhibiting specific immune reactions have also been shown in animal models of skin diseases [63].…”