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. 2022 Jul 5:2022:5113473.
doi: 10.1155/2022/5113473. eCollection 2022.

Effects of Electroacupuncture on Gastrointestinal Motility Function, Pain, and Inflammation via Transient Receptor Potential Vanilloid 1 in a Rat Model after Colonic Anastomoses

Xuelai Zhong  1 , Zhaodi Zhang  1 , Jiaying Li  1 , Dandan Liu  1 , Chao Ma  2 , Guonian Wang  3
Affiliations

Effects of Electroacupuncture on Gastrointestinal Motility Function, Pain, and Inflammation via Transient Receptor Potential Vanilloid 1 in a Rat Model after Colonic Anastomoses

Xuelai Zhong et al. Dis Markers. .

Abstract

Background: Complications after colon surgery are a major obstacle to postoperative recovery. The purpose of this study was to investigate the effect of electroacupuncture (EA) at Zusanli (ST36) on gastrointestinal motility in rats after colonic anastomosis and the mechanism of transient receptor potential vanillin 1 (TRPV1) channel in regulating gastrointestinal motility, pain, and inflammation.

Methods: The rats were randomly divided into six groups, including the control, model, EA, sham-EA, capsaicin, and capsaicin+EA groups, with preoperative capsaicin pretreatment and EA treatment at ST36 acupoint after surgery. Rats were treated using EA at ST36 or sham acupoints after surgery for 5 days. Capsaicin was intraperitoneally injected into rats 3 hours before surgery. Gastrointestinal motility was assessed by measuring the gastric residue, small intestinal propulsion in vivo, contractile tension, and frequency of isolated muscle strips in vitro. The mechanical withdrawal threshold (MWT) of abdominal incision skin and spontaneous nociceptive scores were observed and recorded in rats after colon anastomosis. The expressions of TRPV1, substance P (SP), neurokinin 1 (NK1) receptor, nuclear factor kappa-B (NF-κB), interleukin- (IL-) 6, L-1β, and tumor necrosis factor- (TNF-) α were determined.

Results: Compared with the model group, electroacupuncture at ST36 point could significantly reduce the residual rate of stomach in rats after operation and increase the propulsive force of the small intestine and the contraction tension of the isolated smooth muscle. Electroacupuncture also increased postoperative day 3 MWT values and decreased postoperative spontaneous nociception scores. In addition, electroacupuncture treatment downregulated the expressions of IL-6, IL-1β, TNF-α, TRPV1, NF-κB, SP, and NK1 receptors in the colon tissue of rats after colonic anastomosis.

Conclusions: Our study showed that electroacupuncture at ST36 acupoint could improve gastrointestinal motility in rats after colonic anastomosis and relieve intestinal inflammation and pain. The mechanism may be to inhibit the activation of NF-κB and SP/NK1 receptor signaling pathways by inhibiting TRPV1.

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Conflict of interest statement

No potential conflicts of interest were disclosed.

Figures

Figure 1
Figure 1
Effects of EA treatment on gastrointestinal motility in rats after colonic anastomosis. (a) Time to the first defecation. All groups were measured by receiving a red-carbon-containing suspension after surgery. (b and c) The gastric residual and intestine propulsion rates were determined in vivo using a black semisolid nutrient paste. (d) Contractile activates of isolated muscle strips. (e and f) The amplitude and frequency of the contractile response by isolated muscle strips. (n = 8; ∗P < 0.05 and∗∗P < 0.01 versus control; #P < 0.05 and##P < 0.01 versus model; one-way ANOVA followed by Tukey post hoc test).
Figure 2
Figure 2
Effects of EA treatment on postoperative pain and inflammation in rats after colonic anastomosis. (a) Changes in the MWT of skin around abdominal incision before and from day 1 to day 5 after surgery in each group in experiment 1. (b) The nociceptive scores of rats before operation (baseline) and at 3 h (T1), 6 h (T2), 12 h (T3), 24 h (T4), 36 h (T5), and 48 h (T6) after surgery in each group in experiment 1. (n = 8; ∗P < 0.05 versus the respective baseline in each group; #P < 0.05 versus the corresponding value in the control group; ΔP < 0.05 versus the corresponding value in the model group. The MWT and nociceptive scores were analyzed by two-way ANOVA followed by Bonferroni's post hoc test.) (c–e) The expressions of inflammatory cytokines in colon tissues, including IL-6, IL-1β and TNF-α, were detected by ELISA. (n = 8; ∗∗P < 0.01 versus control; ##P < 0.01 versus model; one-way ANOVA followed by Tukey's post hoc test).
Figure 3
Figure 3
Effects of EA treatment on the expression of TRPV1 in rats after colonic anastomosis. (a) Immunohistochemical staining for TRPV1 in colon tissues (×400, scale bar = 50 μm). (b) The mean density of TRPV1 positive staining in colon tissues. (c) The expression of TRPV1 mRNA in colon tissues of rats in each group was detected by quantitative real-time PCR. (n = 8; ∗∗P < 0.01 versus control; ##P < 0.01 versus model; one-way ANOVA followed by Tukey's post hoc test).
Figure 4
Figure 4
Effects of EA treatment on the SP/NK1 receptor binding and NF-κB expression in rats after colonic anastomosis. (a) SP levels in the colon tissues were calculated using ELISA kits. (b) The expression of NK1 receptor mRNA in colon tissues of rats in each group was detected by quantitative real-time PCR. (c) Immunohistochemical staining for NK1 receptor in intestinal tissues (×400, scale bar = 50 μm). (d) The mean density of NK1 receptor-positive staining in colon tissues. (e) NF-κB (p65) protein expression in colon tissues of rats in each group was detected by western blot. (n = 8; ∗P < 0.05 and∗∗P < 0.01 versus control; #P < 0.05 versus model; one-way ANOVA followed by Tukey's post hoc test).
Figure 5
Figure 5
TRPV1 and NF-κB were colocalized in colon tissues. (a) Immunofluorescence images of colon tissue sections of rats in each group. TRPV1-positive immunoreaction is shown in green, NF-κB-positive immunoreaction is shown in red, and nuclear nucleus staining with DAPI is shown in blue. Merge images show a superimposed image of triple markers. Magnification: ×400; scale bar = 50 μm. (b) Quantitative expressions of TRPV1 and NF-κB in tissue sections of different groups and statistical analysis. (n = 8; ∗∗P < 0.01 versus control; ##P < 0.01 versus model; one-way ANOVA followed by Tukey's post hoc test).
Figure 6
Figure 6
Effects of EA TRPV1 agonist on the expression of NF-κB in rats after colonic anastomosis. (a and b) Rats were pretreated with capsaicin (TRPV1 agonist) before colon anastomosis. The expressions of TPRV1 mRNA and protein in colon tissues were detected in each group. (n = 8; ∗∗P < 0.01 versus model; independent sample t-test.) (c) Immunofluorescence images of colon tissue sections of rats in each group. NF-κB-positive immunoreaction showed red, and DAPI staining showed blue nuclei. Magnification: ×400; scale bar = 50 μm. (d) Quantitative expression of NF-κB in tissue sections of different groups and statistical analysis. (e) NF-κB (p65) protein expression in colon tissues of rats in each group was detected by western blot assay. (n = 8; ∗P < 0.05 and∗∗P < 0.01 versus model; #P < 0.05 and##P < 0.01 versus EA; one-way ANOVA followed by Tukey's post hoc test).
Figure 7
Figure 7
Effects of EA TRPV1 agonist on postoperative pain and inflammation in rats after colonic anastomosis. (a) Changes in the MWT of skin around abdominal incision before and from day 1 to day 5 after surgery in each group. (b) The nociceptive scores of rats before operation (Baseline) and at 3 h (T1), 6 h (T2), 12 h (T3), 24 h (T4), 36 h (T5), and 48 h (T6) after surgery in each group. (n = 8; ∗P < 0.05 versus the respective baseline in each group; #P < 0.05 versus the corresponding value in the model group; ΔP < 0.05 versus the corresponding value in the EA group. The MWT and nociceptive scores were analyzed by two-way ANOVA followed by Bonferroni's post hoc test.) (c–f) The expressions of inflammatory cytokines in colon tissues, including IL-6, IL-1β, and TNF-α, were detected by ELISA. (∗P < 0.05 and∗∗P < 0.01 versus control; ##P < 0.01 versus EA; one-way ANOVA followed by Tukey's post hoc test).
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