Dietary ascorbic acid restriction in GNL/SMP30-knockout mice unveils the role of ascorbic acid in regulation of somatic and visceral pain sensitivity.

Ca_v3.2 T-type Ca²⁺ channels are expressed in the primary afferents and play a pronociceptive role. The activity of Ca_v3.2 is enhanced by H₂S, a gasotransmitter, and suppressed by ascorbic acid (vitamin C) through metal-catalyzed oxidation of the Zn²⁺-binding His¹⁹¹ in Ca_v3.2. 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.

KEYWORDS: {{ getKeywords(articleDetailText.words) }}