Fig 1: Molecular mechanism diagram of the role of sinomenine in diabetic peripheral neuropathic pain by regulating prostaglandin-endoperoxide synthase 2 (PTGS2)-mediated the inositol-requiring enzyme 1 alpha (IRE1a)–X-box binding protein 1 (XBP1s) pathway. Sinomenine downregulates the expression of PTGS2 to inactivate the IRE1a–XBP1s signaling pathway, which inhibits microglial cell activation and the release of inflammatory factors, finally alleviating diabetic peripheral neuropathic pain. DPN, diabetic peripheral neuropathy; IL, interleukin; TNF-a, tumor necrosis factor-a.
Fig 2: Sinomenine inhibits the inositol-requiring enzyme 1 alpha (IRE1a)–X-box binding protein 1 (XBP1s) pathway activation by downregulating prostaglandin-endoperoxide synthase 2 (PTGS2) to relieve pain symptoms in diabetic peripheral neuropathic pain (DPNP) rats. (a) Detection of blood glucose level in DPNP rats. (b) Detection of bodyweight of DPNP rats. (c) Evaluation of the paw withdrawal threshold and paw withdrawal latency of rats before and after streptozotocin injection. (d) The expression of tumor necrosis factor-a (TNF-a), interleukin (IL)-1ß and IL-6 in rat spinal cord tissue measured by enzyme-linked immunosorbent assay. (e) Microglia cell activation in the spinal cord of rats measured by immunofluorescence (scale bar: 25 µm). (f) PTGS2 expression in the spinal cord of rats determined by quantitative reverse transcription polymerase chain reaction. (g) The expression of PTGS2, IRE1a and XBP1s in the spinal cord of rats measured by enzyme-linked immunosorbent assay. (h) PTGS2-positive cells in the spinal cord of DPNP rats measured using immunofluorescence (scale bar: 25 µm). *P < 0.05 versus the control group. n.s. indicates that the data between the two groups are not statistically significant (n = 10 in each group). DPN, diabetic peripheral neuropathy; NC, normal control; oe, overexpression; SI, sinomenine.
Fig 3: Sinomenine (SIN) in Sinomenium acutum might alleviate diabetic peripheral neuropathic pain by regulating inositol-requiring enzyme 1 alpha–X-box binding protein 1 pathway through prostaglandin-endoperoxide synthase 2 (PTGS2). (a) Protein–protein interaction network of candidate genes analyzed using String database. (b) Protein–protein interaction network constructed using Cytoscape. (c) Protein–protein interaction network of top 10 core genes screened out using Cytoscape. (d) Top 10 core genes scored using Cytoscape. (e) Bar chart of the expression of PTGS2 in GSE95849 microarray (n = 6 for the control and diabetic peripheral neuropathic pain groups, respectively). DPN, diabetic peripheral neuropathy. mRNA, messenger ribonucleic acid.
Fig 4: Sinomenine inhibits the inositol-requiring enzyme 1 alpha (IRE1a)–X-box binding protein 1 (XBP1s) pathway through prostaglandin-endoperoxide synthase 2 (PTGS2) to suppress the activation of spinal cord microglia and inflammatory response. (a) The expression of OX-42 was detected by immunofluorescence to identify the purity of the isolate (scale bar: 25 µm). (b) The transfection efficiency of PTGS2 in spinal cord microglia measured by quantitative reverse transcription polymerase chain reaction. (c) PTGS2 expression in rat spinal cord microglia determined by quantitative reverse transcription polymerase chain reaction. (d) The expression of PTGS2, IRE1a and XBP1s in rat spinal cord microglia measured by enzyme-linked immunosorbent assay. (e) The expression of tumor necrosis factor-a (TNF-a), interleukin (IL)-1ß and IL-6 in supernatants of rat spinal cord microglia measured using enzyme-linked immunosorbent assay. (f) The activation of rat spinal cord microglia determined by immunofluorescence (scale bar: 25 µm). *P < 0.05 versus the control group. n.s. indicates that the data between the two groups are not statistically significant. The cell experiments were repeated three times. HG, high glucose; NC, normal control; oe, overexpression; SI, sinomenine.
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