AAV9-CAG-Cre

The development and maintenance of chronic pain involve the reorganization of spinal nocioceptive circuits. The mechanistic target of rapamycin complex 2 (mTORC2), a central signalling hub that modulates both actin-dependent structural changes and mechanistic target of rapamycin complex 1 (mTORC1)-dependent mRNA translation, plays key roles in hippocampal synaptic plasticity and memory formation. Here, researchers show that pharmacological activation of spinal mTORC2 induces pain hypersensitivity, whereas inhibition of mTORC2 alleviates inflammation and neuropathic pain by downregulating the mTORC2-defining component Rictor. Cell type-specific deletion of Rictor shows that selective inhibition of mTORC2 in a subset of excitatory neurons impairs spinal synaptic potentiation and alleviates inflammation-induced mechanical and thermal hypersensitivity and nerve injury-induced heat hyperalgesia. Ablation of mTORC2 in inhibitory interneurons significantly attenuates nerve injury-induced mechanical hypersensitivity.

Here, researchers injected AAV expressing Cre recombinase under the universal CAG promoter into the lumbar segment of the spinal dorsal horn parenchyma of Rictorf/f mice to downregulate Rictor locally (Figure 1A). Viral injection downregulated Rictor protein levels and inhibited mTORC2 activity (reduced p-Akt) in the lumbar spinal dorsal horn of Rictorf/f mice (Figure 1B). Compared with control animals (wild-type mice injected with AAV9-CAG-Cre), Rictorf/f animals injected with AAV9-CAG-Cre showed relief of mechanical and thermal hypersensitivity and spontaneous pain induced by inflammation (Figure 1C-E), as well as nerve injury-induced mechanical allodynia and spontaneous pain (Figure 1F and G). To investigate the role of spinal mTORC2 after the development of neuropathic pain, AAV9-CAG-Cre was injected into the lumbar spinal dorsal horn of Rictorf/f animals 4 weeks after spared nerve injury (SNI) (Figure 1H). Downregulation of mTORC2 at 4 weeks post-injury alleviated mechanical allodynia 3 and 4 weeks later (7 and 8 weeks after SNI), suggesting its therapeutic potential in reducing established pain hypersensitivity (Figure 1I). These results suggest that mTORC2 is activated in the spinal cord following peripheral inflammation and nerve injury and that inhibition of mTORC2 can reduce pain hypersensitivity.

Figure 1. Local viral downregulation of Rictor and impairment of mechanistic target of rapamycin complex 2 (mTORC2) activity attenuates inflammatory and neuropathic pain. (Wong C, et al., 2024)