RESUMO
Cav3.2 T-type Ca2+ channels are expressed in the primary afferents and play a pronociceptive role. The activity of Cav3.2 is enhanced by H2S, a gasotransmitter, and suppressed by ascorbic acid (vitamin C) through metal-catalyzed oxidation of the Zn2+-binding His191 in Cav3.2. Since rodents, but not humans, are capable of synthesizing ascorbic acid, the present study examined the role of ascorbic acid in nociceptive processing, using the mice lacking GNL/SMP30, an enzyme essential for ascorbic acid biosynthesis. Intraplantar and intracolonic administration of NaHS, an H2S donor, caused somatic allodynia and referred hyperalgesia, respectively, and repeated treatment with paclitaxel produced neuropathic allodynia in wild-type mice, all of which were suppressed by ascorbic acid or T-type Ca2+ channel blockers. Dietary ascorbic acid restriction caused dramatic decreases in plasma and tissue ascorbic acid levels in GNL/SMP30-knockout, but not wild-type, mice. The ascorbic acid restriction enhanced the somatic and visceral hypersensitivity following intraplantar and intracolonic NaHS, respectively, and paclitaxel-induced neuropathy in GNL/SMP30-knockout mice, while it had no such effect in wild-type mice. Together, our data unveil the critical role of ascorbic acid in regulating somatic and visceral pain sensitivity and support accumulating clinical evidence for the usefulness of ascorbic acid in pain management.
Assuntos
Deficiência de Ácido Ascórbico/metabolismo , Ácido Ascórbico/metabolismo , Proteínas de Ligação ao Cálcio/genética , Hiperalgesia/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/genética , Dor Visceral/metabolismo , Animais , Deficiência de Ácido Ascórbico/complicações , Deficiência de Ácido Ascórbico/genética , Canais de Cálcio Tipo T/metabolismo , Proteínas de Ligação ao Cálcio/metabolismo , Hiperalgesia/etiologia , Hiperalgesia/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Limiar da Dor , Dor Visceral/etiologia , Dor Visceral/genéticaRESUMO
Early myocardial reperfusion is an effective therapy but ischemia/reperfusion (I/R) causes lethal myocardial injury. The aging heart was reported to show greater cardiac damage after I/R injury than that observed in young hearts. Senescence marker protein 30 (SMP30), whose expression decreases with age, plays a role in reducing oxidative stress and apoptosis. However, the impact of SMP30 on myocardial I/R injury remains to be determined. In this study, the left anterior descending coronary artery was occluded for 30 min, followed by reperfusion in wild-type (WT) and SMP30 knockout (KO) mice. After I/R, cardiomyocyte apoptosis and the ratio of infarct area/area at risk were higher, left ventricular fractional shortening was lower, and reactive oxygen species (ROS) generation was enhanced in SMP30 KO mice. Moreover, the previously increased phosphorylation of GSK-3ß and Akt was lower in SMP30 KO mice than in WT mice. In cardiomyocytes, silencing of SMP30 expression attenuated Akt and GSK-3ß phosphorylation, and increased Bax to Bcl-2 ratio and cardiomyocyte apoptosis induced by hydrogen peroxide. These results suggested that SMP30 deficiency augments myocardial I/R injury through ROS generation and attenuation of Akt activation.