Background: Both Tetramethylpyrazine (TMPZ) and Astragaloside IV (AGS-IV) can ameliorate neuronal apoptosis and neuroinflammation in CNS diseases. This study revolves around the underlying mechanism of TMPZ and AGS-IV in spinal cord injury (SCI)-associated neuropathic pain (NP).
Materials and methods: An in-vivo NP model was constructed in Sprague-Dawley (SD) rats via SCI. qRT-PCR was employed to detect OIP5-AS1 and miR-34a. The paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) of the rats were evaluated. Neuronal apoptosis in the spinal cord of rats was examined by Nissl staining and TUNEL staining. The interactions between OIP5-AS1 and miR-34a as well as miR-34a and Sirt1 were investigated through dual luciferase assay and RIP assay. The protein expressions of Bad, Bax, Caspase-3, iNOS, COX2, NF-κB, and Sirt1 were examined by western blot.
Results: TMPZ and AGS-IV combination relieved behavioral symptoms of neuropathic pain in the SCI rat model, enhanced the levels of OIP5-AS1 and Sirt1, and lowered the profile of miR-34a. OIP5-AS1 downregulation weakened the neuroprotective function of TMPZ and AGS-IV in SCI rats and reversed their anti-inflammatory and anti-apoptotic effects on LPS-elicited primary spinal cord neurons. miR-34a was identified as a target of OIP5-AS1. Upregulated miR-34a partly abated the protective functions of TMPZ and AGS-IV in primary spinal cord neurons. Additionally, miR-34a targeted and repressed Sirt1, thus activating the NF-κB pathway and inflammatory reactions. Sirt1 inhibition reduced the protective effects mediated by OIP5-AS1.
Conclusion: TMPZ and AGS-IV ameliorate SCI-elicited NP via the OIP5-AS1/miR-34a/Sirt1/NF-κB pathway.
Keywords: Astragaloside IV; OIP5-AS1; Sirt1; Spinal cord injury; Tetramethylpyrazine; miR-34a.
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