Referred Somatic Hyperalgesia Mediates Cardiac Regulation by the Activation of Sympathetic Nerves in a Rat Model of Myocardial Ischemia

Therapeutically Fine-Tuning Autonomic Nervous System to Treat Sepsis: A New Perspective on the Immunomodulatory Effects of Acupuncture

Recent studies have highlighted the immunomodulatory effects of acupuncture on sepsis and proposed novel non-pharmacological or bioelectronic approaches to managing inflammatory illnesses. Establishing rules for selectively activating sympathetic or vagal nerve-mediated anti-inflammatory pathways using acupuncture has valuable clinical applications. Over the years, studies have revealed the segmental modulatory role of acupuncture in regulating visceral function by targeting the autonomic nervous system (ANS). In this review, we aim to summarize recent findings on acupuncture in treating sepsis, focusing on the underlying ANS mechanism, as well as the rules of acupoint specificity, intensity, frequency, and other parameters utilized in these studies. Mechanistically, the immunomodulatory properties of the sympathetic nervous system have been highlighted. Furthermore, we explore the immunotherapeutic benefits of acupuncture in treating sepsis. A better understanding of the immunoregulatory mechanism of sympathetic nervous system may offer novel approaches for the development of therapeutics to treat or prevent a variety of inflammatory diseases.

Neuregulin4-ErbB4 signalling pathway is driven by electroacupuncture stimulation to remodel brown adipose tissue innervation

AIM

To show that electroacupuncture stimulation (ES) remodels sympathetic innervation in brown adipose tissue (BAT) via the bone morphogenic protein 8B (BMP8B)-neuregulin 4 (NRG4)-ErbB4 axis, with somatotopic dependence.

MATERIALS AND METHODS

We established a high-fat diet (HFD) model with C57BL/6J mice to measure the thermogenesis and metabolism of BAT. In addition, the sympathetic nerve activity (SNA) was measured with the electrophysiological technique, and the immunostaining of c-Fos was used to detect the central nervous system sources of sympathetic outflows. Finally, the key role of the BMP8B-NRG4-ErbB4 axis was verified by peripheral specific antagonism of ErbB4.

RESULTS

ES at the forelimb and abdomen regions significantly up-regulate SNA, whereas ES at the hindlimb region has a limited regulatory effect on SNA but still partially restores HFD-induced BAT dysfunction. Mechanistically, ES at the forelimb and abdomen regions driving catecholaminergic signals in brown adipocytes depends on neural activities projected from the ventromedial nucleus of the hypothalamus (VMH) to the spinal cord intermediolateral column (IML). Notably, the peripheral suppression of ErbB4 in BAT inhibits the thermogenesis and metabolic function of BAT, as well as significantly hindering the SNA activation and metabolic benefits induced by ES.

CONCLUSION

These results suggest that ES appears to be an effective approach for remodeling sympathetic innervation in BAT, which is closely related to neuronal activity in the VMH and the NRG4-ErbB4 signaling pathway.

Continuous peripheral electrical nerve stimulation improves cardiac function via autonomic nerve regulation in MI rats

BACKGROUND

Peripheral electrical nerve stimulation (PENS) reportedly improves cardiac function after myocardial ischemia (MI) by rebalancing the cardiac autonomic nervous system. The dynamic and continuous influence of PENS on autonomic and cardiac function based on cardiac self-repair is not well understood.

OBJECTIVES

This study aimed to explore the relationship between autonomic nervous balance and functional cardiac repair after MI and to clarify the optimal acupoint selection and time course for PENS.

METHODS

The activities of the superior cervical cardiac sympathetic nerve and vagus nerve were recorded to evaluate the autonomic tone directly. The pressure-volume loop system was used for left ventricular diastolic and systolic function. Noninvasive continuous electrocardiography and echocardiography were performed to analyze heart rate, heart rate variability, and left ventricular function. The effect of continuous PENS (cPENS) or instant PENS (iPENS) on autonomic and cardiac indications was tested.

RESULTS

Sympathetic nerve activity and vagus nerve activity increased as compensatory self-regulation on days 7 and 14 post-MI, followed by an imbalance of autonomic tone and cardiac dysfunction on day 28. cPENS at acupoint PC6 maintained autonomic hyperexcitability, improved myocardial systolic and diastolic abilities, and reduced myocardial fibrosis on day 28 post-MI, whereas cPENS at acupoint ST36 had a limited effect. Both iPENS at PC6 and ST36 improved the autonomic and cardiac function of rats in the cPENS groups.

CONCLUSION

Rats showed autonomic fluctuations and cardiac dysfunction 28 days post-MI. cPENS produced sympathomimetic action to sustain cardiac self-compensation, but with acupoint specificity. On the basis of cPENS, iPENS evoked autonomic regulation and cardiac benefits without acupoint differentiation.

Electroacupuncture pretreatment mediates sympathetic nerves to alleviate myocardial ischemia-reperfusion injury via CRH neurons in the paraventricular nucleus of the hypothalamus

BACKGROUND

Myocardial ischemia-reperfusion can further exacerbate myocardial injury and increase the risk of death. Our previous research found that the paraventricular nucleus (PVN) of the hypothalamus plays a crucial role in the improvement of myocardial ischemia-reperfusion injury (MIRI) by electroacupuncture (EA) pretreatment, but its mechanism of action is still unclear. CRH neurons exhibit periodic concentrated expression in PVN, but further research is needed to determine whether they are involved in the improvement of MIRI by EA pretreatment. Meanwhile, numerous studies have shown that changes in sympathetic nervous system innervation and activity are associated with many heart diseases. This study aims to investigate whether EA pretreatment improves MIRI through sympathetic nervous system mediated by PVNCRH neurons.

METHODS

Integrated use of fiber-optic recording, chemical genetics and other methods to detect relevant indicators: ECG signals were acquired through Powerlab standard II leads, and LabChart 8 calculated heart rate, ST-segment offset, and heart rate variability (HRV); Left ventricular ejection fraction (LVEF), left ventricular short-axis shortening (LVFS), left ventricular end-systolic internal diameter (LVIDs) and interventricular septal thickness (IVSs) were measured by echocardiography; Myocardial infarct area (IA) and area at risk (AAR) were calculated by Evans-TTC staining. Pathological changes in cardiomyocytes were observed by HE staining; Changes in PVNCRH neuronal activity were recorded by fiber-optic photometry; Sympathetic nerve discharges were recorded for in vivo electrophysiology; NE and TH protein expression was assayed by Western blot.

RESULTS

Our data indicated that EA pretreatment can effectively alleviate MIRI. Meanwhile, we found that in the MIRI model, the number and activity of CRH neurons co labeled with c-Fos in the PVN area of the rat brain increased, and the frequency of sympathetic nerve discharge increased. EA pretreatment could reverse this change. In addition, the results of chemical genetics indicated that inhibiting PVNCRH neurons has a similar protective effect on MIRI as EA pretreatment, and the activation of PVNCRH neurons can counteract this protective effect.

CONCLUSION

EA pretreatment can inhibit PVNCRH neurons and improve MIRI by inhibiting sympathetic nerve, which offers fresh perspectives on the application of acupuncture in the management of cardiovascular disease.

Effects and mechanisms of acupuncture analgesia mediated by afferent nerves in acupoint microenvironments

In the past few decades, the use of acupuncture analgesia in clinical practice has increased worldwide. This is due to its various benefits, including natural alleviation of pain without causing various adverse effects associated with non-steroidal anti-inflammatory drugs (NSAID) and opioids. The acupoint represents the initial site of acupuncture stimulation, where diverse types of nerve fibers located at the acupoint hold significant roles in the generation and transmission of acupuncture-related information. In this study, we analyzed the patterns and mechanisms of acupuncture analgesic mediated by acupoint afferent fibers, and found that acupuncture stimulates acupoints which rapidly and directly induces activation of high-density primary afferent fibers under the acupoints, including myelinated A fibers and unmyelinated C fibers. During acupuncture stimulation at the muscle layer, the analgesic effects can be induced by stimulation of A fiber threshold intensity. At the skin layer, the analgesic effects can only be produced by stimulation of C fiber threshold intensity. Electroacupuncture (EA) activates A fibers, while manual acupuncture (MA) activates both A and C fibers. Furthermore, acupuncture alters acupoint microenvironments, which positively modulates afferent fibers, enhancing the transmission of analgesic signals. In addition to local activation and conduction at acupoints, nerve fibers mediate the transmission of acupuncture information to pain centers. In the spinal cord, acupuncture activates neurons by inducing afferent fiber depolarization, modulating pain gating, inhibiting long-term potentiation (LTP) of the spinal dorsal horn and wide dynamic range (WDR) neuronal activities. At higher nerve centers, acupuncture inhibits neuronal activation in pain-related brain regions. In summary, acupuncture inhibits pain signal transmission at peripheral and central systems by activating different patterns of afferent fibers located on various layers of acupoints. This study provides ideas for enhancing the precise application and clinical translation of acupuncture.

A New Target of Electroacupuncture Pretreatment Mediated Sympathetic Nervous to Improve MIRI: Glutamatergic Neurons in Fastigial Nucleus of the Cerebellum

Ischemic heart disease is a fatal cardiovascular disease that irreversibly impairs the function of the heart, followed by reperfusion leading to a further increase in infarct size. Clinically, we call it myocardial ischemia-reperfusion injury (MIRI). A growing number of clinical observations and experimental studies have found electroacupuncture (EA) to be effective in alleviating MIRI. This study attempts to investigate whether glutamatergic neurons in fastigial nucleus (FN) of the cerebellum are involved in EA pretreatment to alleviate MIRI via sympathetic nerves, and the potential mechanisms of EA pretreatment process. A MIRI model was established by ligating the coronary artery of the left anterior descending branch of the heart for 30 minutes, followed by 2 hours of reperfusion. Multichannel physiological recordings, electrocardiogram, cardiac ultrasound, chemical genetics, enzyme-linked immunosorbent assay and immunofluorescence staining methods were combined to demonstrate that EA pretreatment inhibited neuronal firing and c-Fos expression in FN of the cerebellum and reduced cardiac sympathetic firing. Meanwhile, EA pretreatment significantly reduced cardiac ejection fraction (EF), shortening fraction (SF), percentage infarct area, decreased myocardial norepinephrine (NE), creatine kinase isoenzyme MB (CK-MB) concentrations, and improved MIRI-induced myocardial tissue morphology. The results were similar to the inhibition of glutamatergic neurons in FN. However, the activation of glutamatergic neurons in FN diminished the aforementioned effects of EA pretreatment. This study revealed that glutamatergic neurons in FN of the cerebellum is involved in EA pretreatment mediated sympathetic nervous and may be a potential mediator for improving MIRI.

Efficacy and safety of community-based moxibustion for primary hypertension: A randomized controlled trial with patient preference arms

Moxibustion has been shown to have a potential antihypertensive effect, but its applicability for the primary care of hypertension is unclear. The authors conducted a multicenter randomized controlled trial (RCT) with patient preference arms to investigate the effect, safety, cost-effectiveness, and compliance of moxibustion in community patients with hypertension. Patients with primary hypertension were enrolled from seven communities randomly or nonrandomly assigned to receive self-administered moxibustion + the original hypertensive regimen or the original hypertensive regimen alone for 6 months. The authors mainly evaluated the effects of moxibustion on hypertensive outcomes and adverse events. As a result, a total of 160 and 240 patients were recruited into the randomized and nonrandomized arms, respectively, with 87.5% completing the follow-up. At month 6, there was a significantly greater reduction in systolic blood pressure (SBP) (difference: -10.57 mmHg), a higher proportion of responders (82.2% vs. 53.7%; odds ratio 4.00), and better improvements in hypertensive symptoms and quality of life (QoL) in the moxibustion group than in the control group in the randomized population, but there was no significant between-group difference in diastolic blood pressure (DBP). The nonrandomized findings showed the same effect direction for all outcomes, except for DBP. All moxibustion-related adverse events were mild. In conclusion, moxibustion can reduce SBP and improve hypertensive symptoms and QoL in community patients with hypertension, with good safety and low cost, although its effect on DBP remains uncertain. The findings suggest that moxibustion may be an appropriate technique for community primary care of hypertension.

Adrenal sympathetic nerve mediated the anti-inflammatory effect of electroacupuncture at ST25 acupoint in a rat model of sepsis

Acupuncture plays a vital anti-inflammatory action in sepsis by activating autonomic nerve anti-inflammatory pathways, such as sympathoadrenal medullary pathway, but the mechanism remains unclear. This study aims to explore the optimum parameter of electroacupuncture (EA) stimulation in regulating the sympathoadrenal medullary pathway and evaluate EA's anti-inflammatory effect on sepsis. To determine the optimum parameter of EA at homotopic acupoint on adrenal sympathetic activity, the left adrenal sympathetic nerve firing rate evoked by different intensities of single shock electrical stimulation (ES) at ST25 in healthy male Sprague-Dawley rats were evaluated by in vivo electrophysiological recording, and the levels of norepinephrine (NE) and its metabolites normetanephrine (NMN) were also examined using mass spectrometry. To verify the role of EA at ST25 in sepsis, the rats were given an intraperitoneal injection of lipopolysaccharide (LPS) to induce sepsis model, and survival rate, clinical score, and the level of interleukin (IL)-6, IL-1β, and IL-10 were evaluated after EA application. We observed that 3 mA is the optimal intensity for activating adrenal sympathetic nerve, which significantly elevated the level of NE in the peripheral blood. For LPS-treated rats, EA at the ST25 apparently increased the survival rate and improved the clinical score compared to the control group. Furthermore, 3 mA EA at ST25 significantly decreased pro-inflammatory cytokines IL-6 and IL-1β and upregulated anti-inflammatory cytokine IL-10 compared to the LPS-treated group. Overall, our data suggested that 3 mA is the optimal EA intensity at ST25 to activate the sympathoadrenal medullary pathway and exert an anti-inflammatory effect in sepsis.

Modulating activity of PVN neurons prevents atrial fibrillation induced circulation dysfunction by electroacupuncture at BL15

BACKGROUND

Circulation dysfunction is a major contributing factor to thrombosis in patients with atrial fibrillation (AF) for which effective interventions are lacking. Growing evidence indicates that regulating the paraventricular nucleus (PVN), an autonomic control center, could offer a novel strategy for treating cardiovascular and circulatory diseases. Concurrently, electroacupuncture (EA) at Xinshu (BL15), a form of peripheral nerve stimulation, has shown efficacy in treating several cardiovascular conditions, although its specific mechanism remains unclear. This study aimed to assess the impact of EA at BL15 on circulatory dysfunction in a rat AF model and investigate the pivotal role of PVN neuronal activity.

METHODS

To mimic the onset of AF, male SD rats received tail intravenous injection of ACh-CaCl2 and were then subjected to EA at BL15, sham EA, or EA at Shenshu (BL23). Macro- and micro-circulation function were evaluated using in vivo ultrasound imaging and laser doppler testing, respectively. Vasomotricity was assessed by measuring dimension changes during vascular relaxation and contraction. Vascular endothelial function was measured using myograph, and the activation of the autonomic nerve system was evaluated through nerve activity signals. Additionally, chemogenetic manipulation was used to block PVN neuronal activation to further elucidate the role of PVN activation in the prevention of AF-induced blood circulation dysfunction through EA treatment.

RESULTS

Our data demonstrate that EA at BL15, but not BL23 or sham EA, effectively prevented AF-induced macro- and micro-circulation dysfunction. Furthermore, EA at BL15 restored AF-induced vasomotricity impairment. Additionally, EA treatment prevented abnormal activation of the autonomic nerve system induced by AF, although it did not address vascular endothelial dysfunction. Importantly, excessive activation of PVN neurons negated the protective effects of EA treatment on AF-induced circulation dysfunction in rats.

CONCLUSION

These results indicate that EA treatment at BL15 modulates PVN neuronal activity and provides protection against AF-induced circulatory dysfunction.

Sympathetic-Sensory Coupling as a Potential Mechanism for Acupoints Sensitization

A series of studies have demonstrated acupoint sensitization, in which acupoints can be activated in combination with sensory hypersensitivity and functional plasticity during visceral disorders. However, the mechanisms of acupoint sensitization remain unclear. Neuroanatomy evidence showed nociceptors innervated in acupoints contribute to the mechanism of acupoint sensitization. Increasing studies suggested sympathetic nerve plays a key role in modulating sensory transmission by sprouting or coupling with sensory neuron/nociceptor in the peripheral, forming the functional structure of the sympathetic-sensory coupling. Notably, the sensory inputs of the disease-induced sensitized acupoint contribute to the homeostatic regulation and also involve in delivering therapeutic information under acupuncture, hence, the role of sprouted sympathetic in acupoint function should be given attention. We herein reviewed the current knowledge of sympathetic and its sprouting in pain modulation, then discussed and highlighted the potential value of sympathetic-sensory coupling in acupoint functional plasticity.

Glutamatergic neurons in lateral hypothalamus play a vital role in acupuncture preconditioning to alleviate MIRI

Myocardial ischemia-reperfusion injury (MIRI) has high morbidity and mortality worldwide. Increasing evidence has shown that electroacupuncture (EA) plays a critical role in alleviating MIRI. The aim of this study is to investigate whether glutamatergic neurons in the lateral hypothalamus (LH) have vital effect on MIRI as well as the underlying mechanism during the EA pretreatment. The MIRI model was established by ligating the left anterior descending (LAD) coronary artery for 30 min followed by reperfusion for 2 h. Chemogenetics, electrocardiogram (ECG) recording, ELISA, multichannel physiology recording, and immunofluorescence staining methods were combined to demonstrate that firing frequencies of neurons in the LH and expression of c-Fos decreased by EA pretreatment. Meanwhile, EA preconditioning significantly reduced the percentage of infarct size and the levels of cardiac troponin I (cTnI) and creatine kinase isoenzymes (CK-MB) were similar to inhibition of glutamatergic neurons in LH, also attenuated morphology of myocardial tissue was induced by MIRI. However, activation of glutamatergic neurons in LH weakened the above effects of EA pretreatment.NEW & NOTEWORTHY This study demonstrates that EA preconditioning can attenuate myocardial injury for MIRI, which is similar to inhibition of glutamatergic neurons in LH. However, chemical activation of glutamatergic neurons in LH attenuates the protective effect of EA pretreatment. These findings help better understand the mechanisms of EA to regulate cardiac function.

Restoring the Autonomic Balance in an Atrial Fibrillation Rat Model by Electroacupuncture at the Neiguan Point

OBJECTIVES

Autonomic nervous activity imbalance plays an important role in atrial fibrillation (AF). AF can be treated by acupuncture at the Neiguan point (PC6), but the mechanism remains elusive. Here, we investigated autonomic nervous system activity in electroacupuncture (EA) at PC6 in a rat AF model.

MATERIAL AND METHODS

In this study, we established a rat AF model via tail vein injection with ACh-CaCl2 for ten consecutive days with or without EA at PC6. AF inducibility and heart rate variability (HRV) were assessed by electrocardiogram. Next, we completed in vivo recording of the activity of cervical sympathetic and vagal nerves, respectively. Finally, the activities of brain regions related to autonomic nerve regulation were assessed by c-Fos immunofluorescence and multichannel recording.

RESULTS

EA at PC6 decreased AF inducibility and prevented changes in HRV caused by ACh-CaCl2 injection. Meanwhile, EA at PC6 reversed the increased sympathetic and decreased vagal nerve activity in AF rats. Furthermore, EA treatment downregulated increased c-Fos expression in brain regions, including paraventricular nucleus, rostral ventrolateral medulla, and dorsal motor nucleus of the vagus in AF, while c-Fos expression in nucleus ambiguus was upregulated with EA.

CONCLUSION

The protective effect of EA at PC6 on AF is associated with balance between sympathetic and vagal nerve activities.