Cre-GFP Adeno-associated virus(AAV Serotype 8)

Oxaliplatin-induced chronic painful neuropathy is the most common dose-limiting adverse event that negatively affects the quality of life of cancer patients. Here, researchers found that intraperitoneal injection of 4 mg/kg oxaliplatin for five consecutive days significantly upregulated the expression of CXC motif ligand 12 (CXCL12) in dorsal root ganglia, while intrathecal injection of anti-CXCL12 neutralizing antibody or CXCL12 siRNA attenuated oxaliplatin-induced mechanical allodynia and thermal hyperalgesia. Signal transducer and activator of transcription 3 (STAT3) was also found to be activated in dorsal root ganglia, and inhibition of STAT3 with S3I-201 or injection of AAV8-Cre-GFP into STAT3^flox/flox mice prevented the upregulation of CXCL12 expression and chronic pain in dorsal root ganglia after oxaliplatin treatment. Double-labeled fluorescent immunohistochemistry results also showed that p-STAT3 was mainly localized in CXCL12-positive cells in dorsal root ganglia. Furthermore, the results of chromatin immunoprecipitation assays showed that p-STAT3 might be required for oxaliplatin-induced CXCL12 upregulation by directly binding to a specific location in the CXCL12 gene promoter. These findings suggest that upregulation of CXCL12 via TNF-α/IL-1β-dependent STAT3 activation contributes to oxaliplatin-induced chronic pain.

The study showed that the expression of p-STAT3 in dorsal root ganglion (DRG) increased significantly at 5, 7, and 10 days after oxaliplatin treatment (Figure 1a). The behavioral study results showed that continuous intrathecal injection of S3I-201 could alleviate oxaliplatin-induced mechanical hyperalgesia and thermal hyperalgesia (Figure 1b and c). To further confirm the role of p-STAT3 in DRG in the pathogenesis of oxaliplatin-induced chronic pain, recombinant Adeno-associated virus Serotype 8 encoding Cre and GFP (AAV8-Cre-GFP) was intrathecally injected into the subarachnoid space of the L4-L6 spinal cord of STAT3^flox/flox mice. Control mice were injected with AAV8 encoding GFP (AAV8-GFP). Twenty-one days after virus injection, marked green fluorescence in the restricted DRG suggested a high efficiency of transfection (Figure 1d). qPCR and Western blot analysis showed that the expression of STAT3 mRNA (Figure 1e) and protein (Figure 1f) in DRG was significantly reduced on day 21 after AAV8-Cre-GFP injection into STAT3^flox/flox mice. Importantly, mechanical allodynia and thermal hyperalgesia were significantly improved in STAT3^flox/flox mice injected with AAV8-Cre-GFP after oxaliplatin treatment compared with STAT3^flox/flox mice injected with AAV8-GFP (Figure 1g and h). Taken together, these results suggest that STAT3 activation in DRG is one of the causes of oxaliplatin-induced chronic pain.

Figure 1. Activated STAT3 in the DRG-mediated chronic pain induced by oxaliplatin. (Li Y Y, et al., 2017)