Mechanism of the JAK2/STAT3-CAV-1-NR2B signaling pathway in painful diabetic neuropathy.

PURPOSE: The aim of the present study was to further elucidate the role of JAK2/STAT3-CAV-1-NR2B on painful diabetic neuropathy. METHODS: In vivo, the mechanical withdrawal threshold and thermal withdrawal latency were measured to evaluate neuropathic pain behaviors (n= 8), while western blot (n= 5) and an immunofluorescence double staining experiment (n= 6) were performed to understand the molecular mechanism. In vitro, the individual culture of BV2 mouse microglia cell lines, the co-culture of BV2 mouse microglia cell lines and PC12 rat neuron cell lines, and western blot analysis were performed to understand the molecular mechanism between microglia and neurons. RESULTS: The expression of p-JAK2, p-STAT3, t-CAV-1, and p-NR2B was upregulated in the dorsal horn of DNP rats throughout the experiment. Through the immunofluorescence double staining experiment, it was found that p-STAT3 was mainly expressed in activated microglia, and this condition can be stably maintained for approximately 2 weeks after the establishment of the DNP model. The intrathecal injection of JAK2 inhibitor AG490 can relieve the abnormal expression of p-JAK2, p-STAT3, t-CAV-1, and p-NR2B, and relieve pain. The remission of AG490 began on the third day, and it could be stably sustained for 14 days. In vitro high-glucose induced the activation of p-STAT3 in microglia, thereby upregulating the expression of p-CAV-1 and p-NR2B in neurons in the co-culture system. JAK2 inhibitor AG490 can alleviate the abnormal expression of these proteins in the JAK2/STAT3-CAV-1-NR2B signaling pathway in vitro. CONCLUSIONS: Microglial JAK2/STAT3 signaling probably contributes to neuropathic pain by activating the CAV-1-NR2B pathway.

[The mechanism of RvD1 alleviates type 2 diabetic neuropathic pain by influencing microglia polarization in rats].

OBJECTIVE: To study the relationship between microglia polarization in the spinal dorsal horn and type 2 diabetic neuropathic pain (DNP). And explore the mechanism of RvD1 alleviating type 2 diabetic neuropathic pain. METHODS: Type 2 diabetes mellitus (T2DM) rats came from the male SD rats which were fed by high-fat and high-sucrose diet and given intraperitoneal streptozotocin(STZ), then detected fa sting blood glucose level, the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL), which was to prepare the type 2 DNP model rats. And they were randomly divided into 3 groups:type 2 DNP group (group D), type 2 DNP and RvD1 group (group R), type 2 DNP and solvent control group (group S), 36 rats in each group. After being given STZ 14 days, the rats of group D, R, S were placed a catheter in subarachnoid cavity. Three days later, the RvD1 10µl (10 ng/µl) and 100% ethanol 10µl were injected into subarach-noid cavity through the catheter once a day for 14 consecutive days. Another 36 normal rats were served as normal control group (group N) and were fed with common forage. MWT and TWL were measured at 1, 3, 7, 14 days after Subarachnoid injection, then the nine rats'spinal cord of the lumbar segment 4~6 were removed to detect the expression of inducible nitric oxide synthase(iNOS) and arginase 1(Arg1) by Western blot, the marker of microglia M1 and M2 polarization. RESULTS: Compared with group N, MWT was decreased significantly and TWL was shortened, the expression of Arg1 was down-regulated and the expression of iNOS was up-regulated in spinal dorsal horn at the 1, 3, 7, 14 days in groups D and S (P < 0.05). Compared with group D, MWT was significantly increased and TWL was prolonged, the expression of Arg1 was up-regulated and the expression of iNOS was down-regulated in spinal dorsal horn at the 7, 14 days in group R (P < 0.05). There was no significant difference in the MWT, TWL and expression of Arg1 and iNOS between D and S groups. CONCLUSIONS: RvD1 promotes mi-croglia toward M2 polarization and alleviates type 2 diabetic neuropathic pain in rats.