Spinal astrocytic EAATs mediate endothelin-1-induced breakthrough cancer pain in mice

BACKGROUND: Breakthrough cancer pain (BTcP) lacks representative animal models. The roles of spinal excitatory amino acid transporters (EAATs) in BTcP remain unclear. METHODS: We established a modified BTcP mouse model using lung cancer bone metastasis and endothelin-1 (ET-1) injections once daily on postoperative days 16-18, with validation through behavioral and electrophysiological assessments. Spinal EAAT1, EAAT2 and connexin 43 (Cx43) were investigated. Mice were administered intrathecal ceftriaxone (EAAT2 activator), Gap26 (gap junction blocker), or control agents. RESULTS: The BTcP model showed reduced pain thresholds and function, accompanied by decreased EAAT1/EAAT2 and increased phosphorylated C×43 (p-Cx43) in spinal astrocytes. Ceftriaxone reversed pain hypersensitivity, upregulated EAAT2, and reduced p-Cx43 without affecting EAAT1/total Cx43. Gap26 increased EAAT1/EAAT2, decreased Cx43/p-Cx43, and alleviated pain behaviors. CONCLUSION: This optimized ET-1 model provides a robust platform for BTcP research. Spinal EAATs, downregulation and C×43 activation, contribute to BTcP pathogenesis, and both are potential therapeutic targets of BTcP.