Acupuncture at the muscle layer of the PC6 acupoint improved cardiac function and reduced myocardial ischemia in rats with acute myocardial infarction by upregulating TRPV1 expression through local muscle contraction.
Does acupuncture at the PC6 acupoint improve cardiac function and reduce myocardial ischemia in a rat model of acute myocardial infarction?
Acupuncture at the PC6 acupoint improves cardiac function in a rat model of AMI, mediated by local muscle contraction and TRPV1 activation.
Abstract Background The acupoint is the initial response site to acupuncture stimulation, and changes in the acupoint affect the subsequent therapeutic effects of acupuncture. However, the mechanism of acupuncture from this initial site has not yet been clarified. Based on an experimental model of acupuncture at Neiguan (PC6) for intervening in acute myocardial infarction (AMI), this study aimed to 1) investigate whether acupuncture-induced local muscle contraction at the PC6 acupoint mediates the therapeutic effect of acupuncture, and 2) explore the initiation mechanism of acupuncture’s effect from the perspective of transient receptor potential vanilloid 1 (TRPV1). Methods Sprague–Dawley (SD) rats were used to establish the AMI model via ligation of the left anterior descending coronary artery (LAD). 1.To identify the key tissue layer mediating acupuncture efficacy: SD rats were randomly divided into the Sham group, AMI group, AMI + acupuncture at muscle-layer (ACU-M) group, and AMI + acupuncture at subcutaneous-layer (ACU-S) group. Cardiac function was evaluated using a small animal ultrasound imaging system; myocardial ischemic area was measured via 2,3,5-triphenyltetrazolium chloride (TTC) staining, and serum norepinephrine (NE) levels were detected using an enzyme-linked immunosorbent assay (ELISA) kit. 2.To verify the role of muscle contraction: Another cohort of SD rats was randomly divided into the Sham + Vehicle (0.9% sodium chloride, NaCl) group, AMI + Vehicle group, AMI + Vehicle + acupuncture group and AMI + succinylcholine chloride (Scc, muscle relaxant) + acupuncture group. Acupuncture was performed post-AMI modeling, with the same efficacy indexes as above. Additionally, PC6 tissue and C5–T1 segmental dorsal root ganglia (DRG) were collected from each group. Immunofluorescence (IF) staining and western blot (WB) analysis were used to detect TRPV1 expression in the acupoint muscle layer and TRPV1-positive neuron activation in DRGs. 3. To clarify the role of TRPV1: a TRPV1 inhibitor was microinjected into the PC6 muscle layer before acupuncture; changes in TRPV1 (acupoint/DRGs), cardiac function, myocardial ischemic area, and serum NE were measured to evaluate the relationship between acupuncture effect and TRPV1. Results Both the acupuncture at muscle and subcutaneous layer improved cardiac function, reduced the area of myocardial ischemia, and lowered serum NE levels in AMI rats, however the modulatory effect of acupuncture at muscle layer was more pronounced in AMI rats. PC6 injection of Scc followed by acupuncture reversed the modulatory effect of acupuncture on AMI rats. WB and IF results both showed that compared with the AMI group, TRPV1-positive area of the muscle layer in the acupoint area, protein expression as well as activated TRPV1-positive neurons in the DRG were significantly increased, while with the use of Scc followed by acupuncture, TRPV1-positive expression in the muscle layer of the acupoint area as well as activated TRPV1-positive neurons in the DRG were significantly decreased. Muscle injection of TRPV1 inhibitors followed by acupuncture significantly reduced TRPV1-positive expression in the muscle layer of the acupoint area as well as activated TRPV1-positive neurons in the DRG compared with the muscle injection of vehicle group, and also suppressed the improvement of cardiac function and myocardial ischemic area in rats with AMI by acupuncture. Conclusion The muscle layer at the PC6 acupoint is the primary tissue mediating the therapeutic effect of acupuncture for AMI. Acupuncture-induced muscle contraction at the acupoint serves as a key link in this effect: it upregulates TRPV1 expression in the acupoint muscle layer and activates TRPV1 ion channels in C5–T1 DRGs. Microinjection of a TRPV1 inhibitor into the acupoint muscle layer reverses acupuncture’s cardioprotective effect in AMI rats, confirming that TRPV1 in the acupoint muscle layer is a critical mediator initiating the acupuncture effect.
Liu et al. (Wed,) conducted a other in Acute myocardial infarction (AMI). Acupuncture at the PC6 acupoint (muscle layer) vs. No acupuncture, subcutaneous acupuncture, or vehicle/inhibitor injection was evaluated on Cardiac function (LVEF, LVFS) and myocardial ischemic area. Acupuncture at the muscle layer of the PC6 acupoint improved cardiac function and reduced myocardial ischemia in rats with acute myocardial infarction by upregulating TRPV1 expression through local muscle contraction.