RESUMEN
Since 6-prenylnaringenin (6-PNG) was recently identified as a novel T-type calcium channel blocker with the IC50 value around 1⯵M, a series of flavanone derivatives were designed, synthesized and subsequently evaluated for T-channel-blocking activity in HEK293 cells transfected with Cav3.2â¯T-type channels using a patch-clamp technique. As a result, several new flavanones blocked Cav3.2-dependent T-currents more potently than 6-PNG. In the synthesized compounds, 6-(3-ethylpent-2-enyl)-5,7-dihydroxy-2-(2-hydroxyphenyl)chroman-4-one 8j, 6-(3-ethylpent-2-enyl)-5,7-dihydroxy-2-(4-hydroxyphenyl)chroman-4-one 11b, 6-(2-cyclopentylideneethyl)-5,7-dihydroxy-2-(4-hydroxyphenyl)chroman-4-one 11d, and 6-(2-Cyclopentylethyl)-5,7-dihydroxy-2-(4-hydroxyphenyl)chroman-4-one 12c were more potent blocker than 6-PNG with the IC50 value of 0.39, 0.26, 0.46, and 0.50⯵M, respectively. Among the above four derivatives, the compound 8j provided the best result in the in vivo experiments; i.e. systemic administration of 8j at the minimum dose completely restored neuropathic pain induced by partial sciatic nerve ligation in mice.
Asunto(s)
Analgésicos/síntesis química , Bloqueadores de los Canales de Calcio/síntesis química , Canales de Calcio Tipo T/química , Diseño de Fármacos , Flavonoides/química , Potenciales de Acción/efectos de los fármacos , Analgésicos/farmacología , Analgésicos/uso terapéutico , Animales , Bloqueadores de los Canales de Calcio/farmacología , Bloqueadores de los Canales de Calcio/uso terapéutico , Canales de Calcio Tipo T/metabolismo , Modelos Animales de Enfermedad , Flavonoides/farmacología , Flavonoides/uso terapéutico , Células HEK293 , Humanos , Concentración 50 Inhibidora , Masculino , Ratones , Neuralgia/tratamiento farmacológico , Técnicas de Placa-Clamp , Relación Estructura-ActividadRESUMEN
Since Cav3.2â¯T-type Ca2+ channels (T-channels) expressed in the primary afferents and CNS contribute to intractable pain, we explored T-channel-blocking components in distinct herbal extracts using a whole-cell patch-clamp technique in HEK293â¯cells stably expressing Cav3.2 or Cav3.1, and purified and identified sophoraflavanone G (SG) as an active compound from SOPHORAE RADIX (SR). Interestingly, hop-derived SG analogues, (2S)-6-prenylnaringenin (6-PNG) and (2S)-8-PNG, but not naringenin, also blocked T-channels; IC50 (µM) of SG, (2S)-6-PNG and (2S)-8-PNG was 0.68-0.75 for Cav3.2 and 0.99-1.41 for Cav3.1. (2S)-6-PNG and (2S)-8-PNG, but not SG, exhibited reversible inhibition. The racemic (2R/S)-6-PNG as well as (2S)-6-PNG potently blocked Cav3.2, but exhibited minor effect on high-voltage-activated Ca2+ channels and voltage-gated Na+ channels in differentiated NG108-15â¯cells. In mice, the mechanical allodynia following intraplantar (i.pl.) administration of an H2S donor was abolished by oral or i.p. SR extract and by i.pl. SG, (2S)-6-PNG or (2S)-8-PNG, but not naringenin. Intraperitoneal (2R/S)-6-PNG strongly suppressed visceral pain and spinal ERK phosphorylation following intracolonic administration of an H2S donor in mice. (2R/S)-6-PNG, administered i.pl. or i.p., suppressed the neuropathic allodynia induced by partial sciatic nerve ligation or oxaliplatin, an anti-cancer agent, in mice. (2R/S)-6-PNG had little or no effect on open-field behavior, motor performance or cardiovascular function in mice, and on the contractility of isolated rat aorta. (2R/S)-6-PNG, but not SG, was detectable in the brain after their i.p. administration in mice. Our data suggest that 6-PNG, a hop component, blocks T-channels, and alleviates neuropathic and visceral pain with little side effects.