TNF and type 2 diabetes mellitus: In T2DM rats, the upregulation of purinergic signaling promotes the activation of SGCs, increases tumor necrosis factor-alpha (TNF-α) release from SGCs, and enhances the excitability of dorsal root ganglion (DRG) neurons, which brings about the pain sensitivity (Liu et al., 2016; Gonçalves et al., 2018) (Figure 1).