Electroacupuncture Inhibits the Activity of Astrocytes in Spinal Cord in Rats with Visceral Hypersensitivity by Inhibiting P2Y₁ Receptor‐Mediated MAPK/ERK Signaling Pathway

Abstract

Background. Irritable bowel syndrome (IBS) is a chronic functional bowel disease characterized by abdominal pain and changes in bowel habits in the absence of organic disease. Electroacupuncture (EA) has been shown to alleviate visceral hypersensitivity (VH) in IBS rat models by inhibiting the activation of astrocytes in the spinal cord. However, the underlying molecular mechanisms mediated by P2Y1 receptor of this effect of electroacupuncture remain unclear. Aim. To explore whether EA inhibits the activity of astrocytes in the spinal cord dorsal horn of rat with visceral hypersensitivity by inhibiting P2Y1 receptor and its downstream mitogen activated protein kinase/extracellular regulated kinase 1 (MAPK/ERK) pathway. Methods. Ten-day-old Sprague-Dawley (SD) male rats were given an intracolonic injection of 0.2 ml of 0.5% acetic acid (AA) to establish a visceral hypersensitivity model. EA was performed at Zusanli (ST 36) and Shangjuxu (ST 37) at 100 Hz for 1.05 s and 2 Hz for 2.85 s alternately, pulse width for 0.1 ms, 1 mA, 30 min/d, once a day, for 1 week. Cytokines IL-6, IL-1β, and TNF-α were analyzed by ELISA. The expressions of the P2Y1 receptor and pERK1/2 were analyzed by Western Blot and real-time PCR in the model and EA treated animals to explore the molecular mechanism of EA in inhibiting the activity of spinal cord dorsal horn (L6-S2 segment) astrocytes in rats with IBS visceral hypersensitivity. Results. EA significantly reduced the behavioral abdominal withdrawal reflex score (AWRs) of IBS rats with visceral hypersensitivity induced by AA. For comparison, intrathecal injection of astrocytes activity inhibitor fluorocitrate (FCA) also reduced visceral hypersensitivity in IBS rats. EA at Zusanli and Shangjuxu inhibited the mRNA and protein expression of the glial fibrillary acidic protein (GFAP) and in rat spinal cord and reduced the release of inflammatory cytokines IL-6, IL-1, and TNF-α from astrocytes. EA also inhibited acetic acid-induced expression of the P2Y1 receptor in the spinal cord. Adenosine 5′-[β-thio]diphosphate trilithium salt (ADP), a selective agonist of the P2Y1 receptor, reversed the inhibitory effect of EA on visceral hypersensitivity. ADP also overrode the downregulation of GFAP by EA. Conversely, MRS2179 (MRS), a selective antagonist of the P2Y1 receptor, inhibited visceral hypersensitivity suggesting that EA negatively regulated the P2Y1 receptor in astrocytes. Acetic acid also upregulated the expression of pERK1/2 protein and mRNA in the spinal cord of rats with visceral hypersensitivity, which was inhibited by EA and the inhibitory effect of EA on pERK1/2 was reversed by ADP. We also found that SCH772984 (SCH), an ERK1/2 inhibitor (10 μg, 10 μl), reduced the AWRs. Compared to the SCH group, AWR scores in SCH + EA group were decreased. The application of P2Y1 agonists failed to increase the AWR scores after the intrathecal injection of SCH. GFAP level in the spinal cord in the SCH group was significantly reduced when compared to the Model group. The GFAP expression was further reduced in the SCH + EA group. Conclusion. EA inhibited astrocyte activity in the spinal cord dorsal horn of rat with IBS visceral hypersensitivity by inhibiting the P2Y1 receptor and its downstream, PKC, and MAPK/ERK1/2 pathways.

Electroacupuncture Attenuates Post-Inflammatory IBS-Associated Visceral and Somatic Hypersensitivity and Correlates With the Regulatory Mechanism of Epac1–Piezo2 Axis

“…The analgesic effect of EA on visceral hypersensitivity has been extensively demonstrated (40)(41)(42)(43)(44), and the results of our study are consistent with this. EA reduced AWR scores and increased PWT, indicating that EA attenuated the visceral sensitization and peripheral mechanical hyperalgesia of PI-IBS.…”

Effects of Electroacupuncture on Alleviating Prostatodynia and Inflammation in Rats with Chronic Nonbacterial Prostatitis

“…that regard, studies have shown the ability of EA to regulate inflammatory substance release and glial cell activation in the spinal cord. [37][38][39] In the present study, immunohistochemistry showed that GFAP and Iba1 expressions in the L5-S2 segments were enhanced in the dorsal horn of the spinal cord among the model group rats. In contrast, EA treatment showed an inhibitory effect on the activation of two immune related cells in the spinal cord among the EA group rats.…”

Ulinastatin Exhibits Antinociception in Rat Models of Acute Somatic and Visceral Pain Through Inhibiting the Local and Central Inflammation

“…59 In addition to the local inflammation evoked by acetic acid, the role of spinal inflammatory reaction, including glial activation and pro-inflammatory cytokines release, in acetic acidinduced writhing response has also been reported. [60][61][62] Previous studies verified that both minocycline and fluorocitrate were able to markedly reduce acetic acid-induced acute visceral nociception. 62,63 In this point, we for the first time provided evidence that ulinastatin inhibited the activity of microglia and astrocytes in the spinal cord with visceral pain.…”

“…[60][61][62] Previous studies verified that both minocycline and fluorocitrate were able to markedly reduce acetic acid-induced acute visceral nociception. 62,63 In this point, we for the first time provided evidence that ulinastatin inhibited the activity of microglia and astrocytes in the spinal cord with visceral pain.…”