RESUMO
BACKGROUND: Phytochemicals are a large group of plant-derived compounds that have a broad range of pharmacological effects. Some of these effects are derived from their action on transport proteins, including ion channels. The present study investigates the effects of the phytochemicals genistein and capsaicin on voltage-gated potassium Kv2.1 channels. METHODS: The whole-cell patch clamp technique was used to explore the regulation of Kv2.1 channels expressed in HEK293 cells by genistein and capsaicin. RESULTS: Both phytochemicals had a profound effect on the gating properties of Kv2.1 channels; the voltage dependence of activation and inactivation was shifted to hyperpolarized potentials, the closed-state inactivation was accelerated, and the recovery from inactivation was delayed. Moreover, genistein and capsaicin inhibited Kv2.1 currents in a concentration dependent manner. CONCLUSION: This study effectively demonstrated the inhibitory effects of genistein and capsaicin on Kv2.1 channels. As Kv2.1 channels play a prominent role in glucose-stimulated insulin secretion, our findings contribute to our understanding of the putative mechanism by which these phytochemicals exert their reported hypoglycemic effects.
Assuntos
Capsaicina/farmacologia , Genisteína/farmacologia , Canais de Potássio Shab/antagonistas & inibidores , Capsaicina/administração & dosagem , Relação Dose-Resposta a Droga , Genisteína/administração & dosagem , Células HEK293 , Humanos , Hipoglicemiantes/administração & dosagem , Hipoglicemiantes/farmacologia , Técnicas de Patch-Clamp , Bloqueadores dos Canais de Potássio/administração & dosagem , Bloqueadores dos Canais de Potássio/farmacologia , Canais de Potássio Shab/metabolismoRESUMO
The voltage-gated potassium channel Kv1.3 is a novel target for immunomodulation of autoreactive effector memory T cells, which play a major role in the pathogenesis of autoimmune diseases. In this study, the Ts6 and Ts15 toxins isolated from Tityus serrulatus (Ts) were investigated for their immunosuppressant roles on CD4(+) cell subsets: naive, effector (TEF ), central memory (TCM) and effector memory (TEM). The electrophysiological assays confirmed that both toxins were able to block Kv1.3 channels. Interestingly, an extended Kv channel screening shows that Ts15 blocks Kv2.1 channels. Ts6 and Ts15 significantly inhibit the proliferation of TEM cells and interferon-γ production; however, Ts15 also inhibits other CD4(+) cell subsets (naive, TEF and TCM). Based on the Ts15 inhibitory effect of proliferation of all CD4(+) cell subsets, and based on its blocking effect on Kv2.1, we investigated the Kv2.1 expression in T cells. The assays showed that CD4(+) and CD8(+) cells express the Kv2.1 channels mainly extracellularly with TCM cells expressing the highest number of Kv2.1 channels. We also provide in vivo experimental evidence to the protective effect of Ts6 and Ts15 on delayed-type hypersensitivity reaction. Altogether, this study presents the immunosuppressive behaviour of Ts6 and Ts15 toxins, indicating that these toxins could be promising candidates for autoimmune disease therapy. Moreover, this is the first report illustrating the involvement of a novel K(+) channel subtype, Kv2.1, and its distribution in T-cell subsets.
Assuntos
Imunossupressores/farmacologia , Bloqueadores dos Canais de Potássio/farmacologia , Canais de Potássio de Abertura Dependente da Tensão da Membrana/antagonistas & inibidores , Venenos de Escorpião/farmacologia , Linfócitos T/efeitos dos fármacos , Animais , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Feminino , Hipersensibilidade Tardia/imunologia , Hipersensibilidade Tardia/metabolismo , Hipersensibilidade Tardia/prevenção & controle , Canal de Potássio Kv1.3/antagonistas & inibidores , Canal de Potássio Kv1.3/metabolismo , Ativação Linfocitária/efeitos dos fármacos , Masculino , Potenciais da Membrana , Camundongos Endogâmicos BALB C , Canais de Potássio de Abertura Dependente da Tensão da Membrana/genética , Canais de Potássio de Abertura Dependente da Tensão da Membrana/metabolismo , Soroalbumina Bovina , Canais de Potássio Shab/antagonistas & inibidores , Canais de Potássio Shab/metabolismo , Linfócitos T/imunologia , Linfócitos T/metabolismo , Xenopus laevisRESUMO
BACKGROUND: The aim of the present study was to assess the effects of curcumin on the voltage-dependent Kv2.1 potassium channel. METHODS: The whole-cell patch-clamp technique was used to explore the regulation of Kv2.1 channels expressed in HEK293 cells by curcumin. RESULTS: Curcumin reduced the Kv2.1 currents; the inhibition occurred with a slow time course and was partially reversible. Curcumin did not alter the kinetics and voltage dependence of activation; however, the kinetics of open- and closed-state inactivation was accelerated by curcumin along with a hyperpolarizing shift in the voltage dependence of inactivation. Curcumin inhibition of Kv2.1 current was not use-dependent. CONCLUSIONS: Overall, our data suggest that curcumin inhibits Kv2.1 channels by modulating the inactivation gating, which would be expected to impact cellular physiology.