Cardiac vanilloid receptor-1 afferent depletion enhances stellate ganglion neuronal activity and efferent sympathetic response to cardiac stress

Attenuation of immobilization stress-induced hypertension by temperature-controllable warm needle acupuncture in rats and the peripheral neural mechanisms

Introduction

We and others have shown that electrical stimulation of the PC-6 acupoint over the wrist relieves hypertension by stimulating afferent sensory nerve fibers and activating the central endogenous opioid system. Warm needle acupuncture has long been utilized to treat various diseases in clinics.

Methods

Here, we developed a temperature-controllable warm needle acupuncture instrument (WAI) and investigated the peripheral mechanism underlying the effect of warm needle acupuncture at PC-6 on hypertension in a rat model of immobilization stress-induced hypertension.

Results

Stimulation with our newly developed WAI and traditional warm needle acupuncture attenuated hypertension development. Such effects were reproduced by capsaicin (a TRPV1 agonist) injection into PC-6 or WAI stimulation at 48°C. In contrast, PC-6 pretreatment with the TRPV1 antagonist capsazepine blocked the antihypertensive effect of WAI stimulation at PC-6. WAI stimulation at PC-6 increased the number of dorsal root ganglia double-stained with TRPV1 and CGRP. QX-314 and capsaicin perineural injection into the median nerve for chemical ablation of small afferent nerve fibers (C-fibers) prevented the antihypertensive effect of WAI stimulation at PC-6. Additionally, PC-6 pretreatment with RTX ablated the antihypertensive effect of WAI stimulation.

Conclusion

These findings suggest that warm needle acupuncture at PC-6 activates C-fiber of median nerve and the peripheral TRPV1 receptors to attenuate the development of immobilization stress-induced hypertension in rats.

Metrics of high cofluctuation and entropy to describe control of cardiac function in the stellate ganglion

Stellate ganglia within the intrathoracic cardiac control system receive and integrate central, peripheral, and cardiopulmonary information to produce postganglionic cardiac sympathetic inputs. Pathological anatomical and structural remodeling occurs within the neurons of the stellate ganglion (SG) in the setting of heart failure (HF). A large proportion of SG neurons function as interneurons whose networking capabilities are largely unknown. Current therapies are limited to targeting sympathetic activity at the cardiac level or surgical interventions such as stellectomy, to treat HF. Future therapies that target the SG will require understanding of their networking capabilities to modify any pathological remodeling. We observe SG networking by examining cofluctuation and specificity of SG networked activity to cardiac cycle phases. We investigate network processing of cardiopulmonary transduction by SG neuronal populations in porcine with chronic pacing-induced HF and control subjects during extended in-vivo extracellular microelectrode recordings. We find that information processing and cardiac control in chronic HF by the SG, relative to controls, exhibits: (i) more frequent, short-lived, high magnitude cofluctuations, (ii) greater variation in neural specificity to cardiac cycles, and (iii) neural network activity and cardiac control linkage that depends on disease state and cofluctuation magnitude.

Proteomics Reveals Long-Term Alterations in Signaling and Metabolic Pathways Following Both Myocardial Infarction and Chemically Induced Denervation

Myocardial infraction (MI) is the principal risk factor for the onset of heart failure (HF). Investigations regarding the physiopathology of MI progression to HF have revealed the concerted engagement of other tissues, such as the autonomic nervous system and the medulla oblongata (MO), giving rise to systemic effects, important in the regulation of heart function. Cardiac sympathetic afferent denervation following application of resiniferatoxin (RTX) attenuates cardiac remodelling and restores cardiac function following MI. While the physiological responses are well documented in numerous species, the underlying molecular responses during the initiation and progression from MI to HF remains unclear. We obtained multi-tissue time course proteomics with a murine model of HF induced by MI in conjunction with RTX application. We isolated tissue sections from the left ventricle (LV), MO, cervical spinal cord and cervical vagal nerves at four time points over a 12-week study. Bioinformatic analyses consistently revealed a high statistical enrichment for metabolic pathways in all tissues and treatments, implicating a central role of mitochondria in the tissue-cellular response to both MI and RTX. In fact, the additional functional pathways found to be enriched in these tissues, involving the cytoskeleton, vesicles and signal transduction, could be downstream of responses initiated by mitochondria due to changes in neuronal pulse frequency after a shock such as MI or the modification of such frequency communication from the heart to the brain after RTX application. Development of future experiments, based on our proteomic results, should enable the dissection of more precise mechanisms whereby metabolic changes in neuronal and cardiac tissues can effectively ameliorate the negative physiological effects of MI via RTX application.

Chronic ablation of TRPV1-sensitive skeletal muscle afferents attenuates the muscle metaboreflex

Exercise intolerance is a hallmark symptom of cardiovascular disease and likely occurs via enhanced activation of muscle metaboreflex-induced vasoconstriction of the heart and active skeletal muscle which, thereby limits cardiac output and peripheral blood flow. Muscle metaboreflex vasoconstrictor responses occur via activation of metabolite-sensitive afferent fibers located in ischemic active skeletal muscle, some of which express transient receptor potential vanilloid 1 (TRPV1) cation channels. Local cardiac and intrathecal administration of an ultrapotent noncompetitive, dominant negative agonist resiniferatoxin (RTX) can ablate these TRPV1-sensitive afferents. This technique has been used to attenuate cardiac sympathetic afferents and nociceptive pain. We investigated whether intrathecal administration (L4-L6) of RTX (2 µg/kg) could chronically attenuate subsequent muscle metaboreflex responses elicited by reductions in hindlimb blood flow during mild exercise (3.2 km/h) in chronically instrumented conscious canines. RTX significantly attenuated metaboreflex-induced increases in mean arterial pressure (27 ± 5.0 mmHg vs. 6 ± 8.2 mmHg), cardiac output (1.40 ± 0.2 L/min vs. 0.28 ± 0.1 L/min), and stroke work (2.27 ± 0.2 L·mmHg vs. 1.01 ± 0.2 L·mmHg). Effects were maintained until 78 ± 14 days post-RTX at which point the efficacy of RTX injection was tested by intra-arterial administration of capsaicin (20 µg/kg). A significant reduction in the mean arterial pressure response (+45.7 ± 6.5 mmHg pre-RTX vs. +19.7 ± 3.1 mmHg post-RTX) was observed. We conclude that intrathecal administration of RTX can chronically attenuate the muscle metaboreflex and could potentially alleviate enhanced sympatho-activation observed in cardiovascular disease states.

A novel metric linking stellate ganglion neuronal population dynamics to cardiopulmonary physiology

Cardiopulmonary sympathetic control is exerted via stellate ganglia (SG); however, little is known about how neuronal firing patterns in the stellate ganglion relate to dynamic physiological function in the heart and lungs. We performed continuous extracellular recordings from SG neurons using multielectrode arrays in chloralose-anesthetized pigs (n = 6) for 8-9 h. Respiratory and left ventricular pressures (RP and LVP, respectively) and the electrocardiogram (ECG) were recorded concomitantly. Linkages between sampled spikes and LVP or RP were determined using a novel metric to evaluate specificity in neural activity for phases of the cardiac and pulmonary cycles during resting conditions and under various cardiopulmonary stressors. Firing frequency (mean 4.6 ± 1.2 Hz) varied spatially across the stellate ganglion, suggesting regional processing. The firing pattern of most neurons was synchronized with both cardiac (LVP) and pulmonary (RP) activity indicative of cardiopulmonary integration. Using the novel metric to determine cardiac phase specificity of neuronal activity, we found that spike density was highest during diastole and near-peak systole. This specificity was independent of the actual LVP or population firing frequency as revealed by perturbations to the LVP. The observed specificity was weaker for RP. Stellate ganglion neuronal populations exhibit cardiopulmonary integration and profound specificity toward the near-peak systolic phase of the cardiac cycle. This novel approach provides practically deployable tools to probe stellate ganglion function and its relationship to cardiopulmonary pathophysiology.NEW & NOTEWORTHY Activity of stellate ganglion neurons is often linking indirectly to cardiac function. Using novel approaches coupled with extended period of recordings in large animals, we link neuronal population dynamics to mechanical events occurring at near-peak systole. This metric can be deployed to probe stellate ganglion neuronal control of cardiopulmonary function in normal and disease states.

Aorticorenal ganglion as a novel target for renal neuromodulation

BACKGROUND

Clinical trials for renal artery (RA) ablation have shown limited efficacy.

OBJECTIVE

The purpose of this study was to investigate whether the aorticorenal ganglion (ARG) can be targeted for renal denervation.

METHODS

Twenty-eight pigs were studied under isoflurane or alpha-chloralose to examine hemodynamic responses and catecholamine release in response to RA or ARG stimulation. To assess the efficacy of ARG ablation, we randomized 16 pigs to either sham, RA, or ARG ablation, followed by occlusion of the left anterior descending coronary artery (LAD). Hemodynamic responses, cardiac electrophysiological parameters, and arrhythmias/sudden cardiac death were assessed following LAD occlusion. Absent hemodynamic responses to stimulation confirmed ARG or RA ablation. In vivo stellate ganglion neural activity was recorded to assess cardiac sympathetic signaling. Cadaveric dissections were performed to localize the ARG in humans for comparison to swine.

RESULTS

The ARG is a purely sympathetic ganglion with cholinergic inputs and pass-through sensory afferent fibers. Compared to RA stimulation, ARG stimulation yielded greater hemodynamic responses during alpha-chloralose anesthesia. However, neither site yielded significant responses under isoflurane. Radiofrequency ablation of the ARG eliminated responses to both RA and ARG stimulation, whereas RA ablation did not eliminate responses to ARG stimulation. Ablation of the ARG did not impact the kidneys or adrenal glands. Compared to control and RA ablation, ARG ablation was protective against ventricular arrhythmias and sudden death. Human and swine ARG are similarly located in the aorticorenal region.

CONCLUSION

Our findings indicate that the ARG may be a novel target for renal neuromodulation. Further studies are warranted to validate these findings.

Cardiac afferent signaling partially underlies premature ventricular contraction-induced cardiomyopathy

BACKGROUND

The mechanisms underlying premature ventricular contraction (PVC)-induced cardiomyopathy (PIC) remain unknown. Transient receptor potential vanilloid-1 (TRPV1) afferent fibers are implicated in the reflex processing of cardiac stress.

OBJECTIVE

The purpose of this study was to determine whether cardiac TRPV1 afferent signaling promote PIC.

METHODS

A PIC swine model (50% PVC burden) was created via an implanted pacemaker. We selectively depleted cardiac TRPV1 afferent fibers using percutaneous epicardial application of resiniferatoxin (RTX). Animals were randomized to PVC only (n = 11), PVC+RTX (n = 11), or control (n = 6). We examined early-stage (4 weeks after implantation; n = 5) and late-stage PIC (8 weeks after implantation; n = 6). At terminal experimentation, animals underwent echocardiography, serum sampling, and physiological and autonomic reflex testing.

RESULTS

Depletion of cardiac TRPV1 afferents by RTX treatment was confirmed by absent sensory fibers and absent functional responses to TRPV1 activators. Left ventricular ejection fraction was worse in late-stage than early-stage PIC (P <.01). At 4 weeks (early stage), left ventricular ejection fraction was higher in PVC+RTX vs PVC animals (51.7% ± 1.6% vs 45.0% ± 2.1%; P = .030), whereas no significant difference between PVC and PVC+RTX was observed at 8 weeks (late stage). Histologic studies demonstrated reduced fibrosis in PVC+RTX vs PVC alone at 4 weeks (2.27% ± 0.14% vs 3.01% ± 0.21%; P = .020), suggesting that RTX mitigated profibrotic pathways induced by persistent PVCs.

CONCLUSION

TRPV1 afferent depletion alleviates left ventricular dysfunction in early- but not late-stage PIC. This temporal effect suggests that multiple pathways promote PIC, of which TRPV1 afferents are a part.

Cardiac sensory afferents modulate susceptibility to anxio-depressive behaviour in a mouse model of chronic heart failure

AIM

Impairments in cerebral structure and cognitive performance in chronic heart failure (CHF) are critical components of its comorbidity spectrum. Autonomic afferents that arise from cardiac sensory fibres show enhanced activity with CHF. Desensitization of these fibres by local application of resiniferatoxin (RTX) during myocardial infarction (MI) is known to prevent cardiac hypertrophy, sympathetic hyperactivity and CHF. Whether these afferents mediate cerebral allostasis is unknown.

METHODS

CHF was induced by myocardial infarction. To evaluate if cardiac afferents contribute to cerebral allostasis, RTX was acutely applied to the pericardial space in controls (RTX) and in MI treated animals (MI/RTX). Subjects were then evaluated in a series of behavioural tests recapitulating different symptoms of depressive disorders. Proteomics of the frontal cortices (FC) was performed to identify contributing proteins and pathways responsible for behavioural allostasis.

RESULTS

Desensitization of cardiac afferents relieves hallmarks of an anxio/depressive-like state in mice. Unique protein signatures and regulatory pathways in FCs isolated from each treatment reveal the degree of complexity inherent in the FC response to stresses originating in the heart. While cortices from the combined treatment (MI/RTX) did not retain protein signatures from the individual treatment groups, all three groups suffer dysregulation in circadian entrainment.

CONCLUSION

CHF is comorbid with an anxio/depressive-like state and ablation of cardiac afferents relieves the despair phenotype. The strikingly different proteomic profiles observed in FCs suggest that MI and RTX lead to unique brain-signalling patterns and that the combined treatment, potentially through destructive interference mechanisms, most closely resembles controls.

Capsaicin: Plants of the Genus Capsicum and Positive Effect of Oriental Spice on Skin Health

BACKGROUND

Capsaicin, the main pungent ingredient in hot chili peppers, causes excitation of small sensory neurons. It also provides the basic pungent flavor in Capsicum fruits.

SUMMARY

Capsaicin plays a vital role as an agonist for the TRPV1 (transient receptor potential cation channel, subfamily V, member 1) receptor. TRPV1 is essential for the reduction of oxidative stress, pain sensations, and inflammation. Therefore, it has many pros related to health issue. Activation and positive impact of TRPV1 via capsaicin has been studied in various dermatological conditions and in other skin-related issues. Past studies documented that capsaicin plays a vital role in the prevention of atopic dermatitis as well as psoriasis. Moreover, TRPV1 is also very important for skin health because it acts as a capsaicin receptor. It is found in nociceptive nerve fibers and nonneural structures. It prompts the release of a compound that is involved in communicating pain between the spinal cord nerves and other parts of the body. Key Messages: Here, we summarize the growing evidence for the beneficial role of capsaicin and TRPV1 and how they help in the relief of skin diseases such as inflammation, permeation, dysfunction, atopic dermatitis, and psoriasis and in pain amplification syndrome.

Cardiac TRPV1 afferent signaling promotes arrhythmogenic ventricular remodeling after myocardial infarction

Chronic sympathoexcitation is implicated in ventricular arrhythmogenesis (VAs) following myocardial infarction (MI), but the critical neural pathways involved are not well understood. Cardiac adrenergic function is partly regulated by sympathetic afferent reflexes, transduced by spinal afferent fibers expressing the transient receptor potential cation subfamily V member 1 (TRPV1) channel. The role of chronic TRPV1 afferent signaling in VAs is not known. We hypothesized that persistent TRPV1 afferent neurotransmission promotes VAs after MI. Using epicardial resiniferatoxin (RTX) to deplete cardiac TRPV1-expressing fibers, we dissected the role of this neural circuit in VAs after chronic MI in a porcine model. We examined the underlying mechanisms using molecular approaches, IHC, in vitro and in vivo cardiac electrophysiology, and simultaneous cardioneural mapping. Epicardial RTX depleted cardiac TRPV1 afferent fibers and abolished functional responses to TRPV1 agonists. Ventricular tachycardia/fibrillation (VT/VF) was readily inducible in MI subjects by programmed electrical stimulation or cesium chloride administration; however, TRPV1 afferent depletion prevented VT/VF induced by either method. Mechanistically, TRPV1 afferent depletion did not alter cardiomyocyte action potentials and calcium transients, the expression of ion channels, or calcium handling proteins. However, it attenuated fibrosis and mitigated electrical instability in the scar border zone. In vivo recordings of cardiovascular-related stellate ganglion neurons (SGNs) revealed that MI enhances SGN function and disrupts integrated neural processing. Depleting TRPV1 afferents normalized these processes. Taken together, these data indicate that, after MI, TRPV1 afferent-induced adrenergic dysfunction promotes fibrosis and adverse cardiac remodeling, and it worsens border zone electrical heterogeneity, resulting in electrically unstable ventricular myocardium. We propose targeting TRPV1-expressing afferent to reduce VT/VF following MI.

Cardiac Afferent Denervation Abolishes Ganglionated Plexi and Sympathetic Responses to Apnea: Implications for Atrial Fibrillation

Background The autonomic nervous system response to apnea and its mechanistic connection to atrial fibrillation (AF) are unclear. We hypothesize that sensory neurons within the ganglionated plexi (GP) play a role. We aimed to delineate the autonomic response to apnea and to test the effects of ablation of cardiac sensory neurons with resiniferatoxin (RTX), a neurotoxic TRPV1 (transient receptor potential vanilloid 1) agonist. Methods Sixteen dogs were anesthetized and ventilated. Apnea was induced by stopping ventilation until oxygen saturations decreased to 80%. Nerve recordings from bilateral vagal nerves, left stellate ganglion, and anterior right GP were obtained before and during apnea, before and after RTX injection in the anterior right GP (protocol 1, n=7). Atrial effective refractory period and AF inducibility on single extrastimulation were assessed before and during apnea, and before and after intrapericardial RTX administration (protocol 2, n=9). GPs underwent immunohistochemical staining for TRPV1. Results Apnea increased anterior right GP activity, followed by clustered crescendo vagal bursts synchronized with heart rate and blood pressure oscillations. On further oxygen desaturation, a tonic increase in stellate ganglion activity and blood pressure ensued. Apnea-induced effective refractory period shortening from 110.20±31.3 ms to 90.6±29.1 ms ( P<0.001), and AF induction in 9/9 dogs versus 0/9 at baseline. After RTX administration, increases in GP and stellate ganglion activity and blood pressure during apnea were abolished, effective refractory period increased to 126.7±26.9 ms ( P=0.0001), and AF was not induced. Vagal bursts remained unchanged. GP cells showed cytoplasmic microvacuolization and apoptosis. Conclusions Apnea increases GP activity, followed by vagal bursts and tonic stellate ganglion firing. RTX decreases sympathetic and GP nerve activity, abolishes apnea's electrophysiological response, and AF inducibility. Sensory neurons play a role in apnea-induced AF.

Focal selective chemo-ablation of spinal cardiac afferent nerve by resiniferatoxin protects the heart from pressure overload-induced hypertrophy

Resiniferatoxin (RTX), a selective transient receptor potential vanilloid 1 (TRPV1) receptor agonist, can eliminate TRPV1+ primary sensory afferents and blunt cardiac sympathetic afferent reflex for a relatively long period. The present study determined the effects of intrathecal RTX administration on transverse aortic constriction (TAC)-induced cardiac dysfunction and cardiac remodeling in rats. Five days before TAC, RTX (2 μg/10 μl) was injected intrathecally into the T2/T3 interspace of rats. Cardiac sympathetic nerve activities (CSNAs) and cardiac structure and function were determined eight weeks after TAC. Intrathecal RTX administration abolished TRPV1 expression in the dorsal horn and reduced over-activated CSNA in the TAC rat model. Hemodynamic analysis revealed that RTX reduced left ventricular end-diastolic pressure, indicating the improvement of cardiac compliance. Histologic analysis, real-time reverse transcription-polymerase chain reaction, and Western blots showed that RTX prevented TAC-induced cardiac hypertrophy, cardiac fibrosis, and cardiac apoptosis and reduced the expression of apoptotic proteins and myocardial mRNAs. In conclusion, these results demonstrate that focal chemo-ablation of TRPV1+ afferents in the spinal cord protects the heart from pressure overload-induced cardiac remodeling and cardiac dysfunction, which suggest a novel promising therapeutic method for cardiac hypertrophy and diastolic dysfunction.