Spinal astrocytic activation contributes to mechanical allodynia in a mouse model of type 2 diabetes

Diabetic neuropathic pain (DNP) plays a major role in decreased life quality of type 2 diabetes patients, however, the molecular mechanisms underlying DNP remain unclear. Emerging research implicates the participation of spinal glial cells in some neuropathic pain models. However, it remains unknown whether spinal glial cells are activated under type 2 diabetic conditions and whether they contribute to diabetes-induced neuropathic pain. In the present study, using a db/db type 2 diabetes mouse model that displayed obvious mechanical allodynia, we found that spinal astrocyte but not microglia was dramatically activated. The mechanical allodynia was significantly attenuated by intrathecally administrated l-α-aminoadipate (astrocytic specific inhibitor) whereas minocycline (microglial specific inhibitor) did not have any effect on mechanical allodynia, which indicated that spinal astrocytic activation contributed to allodynia in db/db mice. Further study aimed to identify the detailed mechanism of astrocyte-incudced allodynia in db/db mice. Results showed that spinal activated astrocytes dramatically increased interleukin (IL)-1β expression which may induce N-methyl-d-aspartic acid receptor (NMDAR) phosphorylation in spinal dorsal horn neurons to enhance pain transmission. Together, these results suggest that spinal activated astrocytes may be a crucial component of mechanical allodynia in type 2 diabetes and “Astrocyte-IL-1β-NMDAR-Neuron” pathway may be the detailed mechanism of astrocyte-incudced allodynia. Thus, inhibiting astrocytic activation in the spinal dorsal horn may represent a novel therapeutic strategy for treating DNP.

Research Highlights
► Mechanical allodynia occurred in type 2 diabetic mice.
► Mechanical allodynia was induced by spinal astrocytic activation.
► Spinal astrocytic activation depended on diabetes-induced oxidative stress.
► Spinal astrocytes dramatically increased the expression of IL-1β.
► IL-1β induces NMDA receptor phosphorylation in spinal dorsal horn neurons.