Sensory neurons promote immune homeostasis in the lung.

Cytokines employ downstream Janus kinases (JAKs) to promote chronic inflammatory diseases. JAK1-dependent type 2 cytokines drive allergic inflammation, and patients with JAK1 gain-of-function (GoF) variants develop atopic dermatitis (AD) and asthma. To explore tissue-specific functions, we inserted a human JAK1 GoF variant (JAK1GoF) into mice and observed the development of spontaneous AD-like skin disease but unexpected resistance to lung inflammation when JAK1GoF expression was restricted to the stroma. We identified a previously unrecognized role for JAK1 in vagal sensory neurons in suppressing airway inflammation. Additionally, expression of Calcb/CGRPß was dependent on JAK1 in the vagus nerve, and CGRPß suppressed group 2 innate lymphoid cell function and allergic airway inflammation. Our findings reveal evolutionarily conserved but distinct functions of JAK1 in sensory neurons across tissues. This biology raises the possibility that therapeutic JAK inhibitors may be further optimized for tissue-specific efficacy to enhance precision medicine in the future.

Mechanisms and Therapeutic Relevance of Neuro-immune Communication.

Active research at the frontiers of immunology and neuroscience has identified multiple points of interaction and communication between the immune system and the nervous system. Immune cell activation stimulates neuronal circuits that regulate innate and adaptive immunity. Molecular mechanistic insights into the inflammatory reflex and other neuro-immune interactions have greatly advanced our understanding of immunity and identified new therapeutic possibilities in inflammatory and autoimmune diseases. Recent successful clinical trials using bioelectronic devices that modulate the inflammatory reflex to significantly ameliorate rheumatoid arthritis and inflammatory bowel disease provide a path for using electrons as a therapeutic modality for targeting molecular mechanisms of immunity. Here, we review mechanisms of peripheral sensory neuronal function in response to immune challenges, the neural regulation of immunity and inflammation, and the therapeutic implications of those mechanistic insights.

Downregulation of mesenteric afferent sensitivity following long-term systemic treatment of vincristine in mice.

AIMS: Gastrointestinal paresthesia and dysmotility are common side effects of vincristine (VCR) chemotherapy, which have become one of the factors for dose reduction, therapy delay or discontinuation. However, the mechanism is not entirely clear, whether it is related to autonomic nerves injury remains unknown. Therefore, we aimed to study whether VCR-induced gastrointestinal toxicity is related to changes in mesenteric afferent activity. METHODS: The effects of a single VCR stimulation and long-term systemic VCR treatment on mesenteric afferent activity were investigated by directly recording mesenteric afferent discharge in vitro. RESULTS: Our results showed that a single VCR (0.001-1 µmol/L) stimulation obviously increased the spontaneous, chemically evoked and mechanically evoked discharge of jejunal and colonic mesenteric afferents. This kind of hypersensitivity of VCR could be blocked by capsazepine, a transient receptor potential vanilloid 1 (TRPV1) antagonist. For the mice treated with VCR (0.1 mg/kg/d, i.p.) for 14 days, the abdominal withdrawal reflex and writhing response scores were reduced. Meanwhile, the spontaneous discharge of colonic mesenteric afferents and the afferent response to VCR was downregulated, and the afferent sensitivity to chemical and mechanical stimulation was reduced. Moreover, the expression of TRPV1 in colon was decreased. CONCLUSIONS: These results suggest that the direct stimulation by VCR increases the mesenteric afferent sensitivity by activating TRPV1, which may be the reason of VCR-induced abdominal pain; the long-term systemic treatment of VCR decreases mesenteric afferent sensitivity by reducing TRPV1, which may be the reason of VCR-induced constipation.

Opioid-Induced Pronociceptive Signaling in the Gastrointestinal Tract Is Mediated by Delta-Opioid Receptor Signaling.

Opioid tolerance (OT) leads to dose escalation and serious side effects, including opioid-induced hyperalgesia (OIH). We sought to better understand the mechanisms underlying this event in the gastrointestinal tract. Chronic in vivo administration of morphine by intraperitoneal injection in male C57BL/6 mice evoked tolerance and evidence of OIH in an assay of colonic afferent nerve mechanosensitivity; this was inhibited by the δ-opioid receptor (DOPr) antagonist naltrindole when intraperitoneally injected in previous morphine administration. Patch-clamp studies of DRG neurons following overnight incubation with high concentrations of morphine, the µ-opioid receptors (MOPr) agonist [D-Ala2, N-Me-Phe4, Gly5-ol]-Enkephalin (DAMGO) or the DOPr agonist [D-Ala2, D-Leu5]-Enkephalin evoked hyperexcitability. The pronociceptive actions of these opioids were blocked by the DOPr antagonist SDM25N but not the MOPr antagonist D-Pen-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 The hyperexcitability induced by DAMGO was reversed after a 1 h washout, but reapplication of low concentrations of DAMGO or [D-Ala2, D-Leu5]-Enkephalin restored the hyperexcitability, an effect mediated by protein kinase C. DOPr-dependent DRG neuron hyperexcitability was blocked by the endocytosis inhibitor Pitstop 2, and the weakly internalizing DOPr agonist ARM390 did not cause hyperexcitability. Bioluminescence resonance energy transfer studies in HEK cells showed no evidence of switching of G-protein signaling from Gi to a Gs pathway in response to either high concentrations or overnight incubation of opioids. Thus, chronic high-dose opioid exposure leads to opioid tolerance and features of OIH in the colon. This action is mediated by DOPr signaling and is dependent on receptor endocytosis and downstream protein kinase C signaling.SIGNIFICANCE STATEMENT Opioids are effective in the treatment of abdominal pain, but escalating doses can lead to opioid tolerance and potentially opioid-induced hyperalgesia. We found that δ-opioid receptor (DOPr) plays a central role in the development of opioid tolerance and opioid-induced hyperalgesia in colonic afferent nociceptors following prolonged exposure to high concentrations of MOPr or DOPr agonists. Furthermore, the role of DOPr was dependent on OPr internalization and activation of a protein kinase C signaling pathway. Thus, targeting DOPr or key components of the downstream signaling pathway could mitigate adverse side effects by opioids.

Cardiac sympathetic afferent ablation to prevent ventricular arrhythmia complicating acute myocardial infarction by inhibiting activated astrocytes.

Enhanced cardiac sympathetic afferent reflex (CSAR) contributes to ventricular arrhythmia (VA) after acute myocardial infarction (AMI). However, central regulation mechanisms remain unknown. The aim of this study was to investigate whether local cardiac sympathetic afferent ablation (LCSAA) could reduce VA by inhibiting activated astrocytes in the hypothalamus paraventricular (PVN) in an AMI rat model. The rats were randomly divided into AMI, AMI + BD (baroreceptor denervation), AMI + LCSAA and AMI + BD+ LCSAA groups. Before the generation of AMI, BD and (or) LCSAA were performed. At 24 h after AMI, the incidence and duration of VA in AMI + LCSAA group and AMI + BD + LCSAA group were significantly reduced than AMI group (P < 0.05). Furthermore, LCSAA significantly reduced GFAP (a marker for activated astrocytes) positive cells and their projections as well as the level of TNF-α and IL-6 in the PVN of AMI + LCSAA group and AMI + BD+ LCSAA group, along with the decrease of neuronal activation in PVN and sympathetic nerve activity (P < 0.05). but BD had no obvious difference between AMI + LCSAA and AMI + BD + LCSAA group (P > 0.05). Therefore, LCSAA could decrease sympathoexcitation and VA occurrence in AMI rats by inhibiting astrocyte and neuronal activation in the PVN. Our study demonstrates that activated astrocytes may play an important role on CSAR in AMI.

Role of PTHrP in attenuating transient pressure rises and associated afferent nerve activity of the rat bladder.

Parathyroid hormone-related protein (PTHrP) released from detrusor smooth muscle (DSM) as the bladder fills acts as an endogenous DSM relaxant to facilitate bladder storage function. Here, the effects of exogenous PTHrP on transient pressure rises (TPRs) in the bladder and associated afferent nerve activity during bladder filling were investigated. In anaesthetized rats, changes in the intravesical pressure were measured while the bladder was gradually filled with saline. Afferent nerve activity was simultaneously recorded from their centrally disconnected left pelvic nerves. In DSM strips, spontaneous and nerve-evoked contractions were isometrically recorded. The distribution of PTHrP receptors (PTHrPRs) in the bladder wall was also examined by fluorescence immunostaining. The bladders in which the contralateral pelvic nerve was also centrally disconnected developed nifedipine, an L-type voltage-dependent Ca2+ channel blocker-sensitive TPRs (< 3 mmHg). Intravenous administration of PTHrP suppressed these TPRs and associated bursts of afferent nerve activity. In the bladders with centrally connected contralateral pelvic nerves, atropine, a muscarinic receptor antagonist-sensitive large TPRs (> 3 mmHg) developed in the late filling phase. PTHrP diminished the large TPRs and corresponding surges of afferent nerve activity. In DSM strips, bath-applied PTHrP (10 nM) suppressed spontaneous phasic contractions, while less affecting nerve-evoked contractions. PTHrPRs were expressed in DSM cells but not in intramural nerve fibers. Thus, PTHrP appears to suppress bladder TPRs and associated afferent nerve activity even under the influence of low degree of parasympathetic neural input during storage phases. Endogenous PTHrP may indirectly attenuate afferent nerve activity by suppressing TPRs to facilitate urinary accommodation.

Contributions of afferent and sympathetic renal nerves to cystogenesis and arterial pressure regulation in a preclinical model of autosomal recessive polycystic kidney disease.

Polycystic kidney disease (PKD) is the most common inheritable cause of kidney failure, and the underlying mechanisms remain incompletely uncovered. Renal nerves contribute to hypertension and chronic kidney disease-frequent complications of PKD. There is limited evidence that renal nerves may contribute to cardiorenal dysfunction in PKD and no investigations of the role of sympathetic versus afferent nerves in PKD. Afferent renal nerve activity (ARNA) is elevated in models of renal disease and fibrosis. However, it remains unknown if this is true in PKD. We tested the hypothesis that ARNA is elevated in a preclinical model of autosomal recessive PKD and that targeted renal nerve ablation would attenuate cystogenesis and cardiorenal dysfunction. We tested this by performing total renal denervation (T-RDNx) or afferent renal denervation (A-RDNx) denervation in 4-wk-old male and female PCK rats and then quantified renal and cardiovascular responses 6 wk following treatment. Cystogenesis was attenuated with A-RDNx and T-RDNx versus sham controls, highlighting a crucial role for renal afferent nerves in cystogenesis. In contrast, blood pressure was improved with T-RDNx but not A-RDNx. Importantly, treatments produced similar results in both males and females. Direct renal afferent nerve recordings revealed that ARNA was twofold greater in PCK rats versus noncystic controls and was directly correlated with cystic severity. To our knowledge, we are the first to demonstrate that PCK rats have greater ARNA than noncystic, age-matched controls. The findings of this study support a novel and crucial role for renal afferent innervation in cystogenesis in the PCK rat.NEW & NOTEWORTHY This is the first study to dissect the contributions of renal sympathetic and afferent innervation in the PCK rat, a preclinical model of autosomal recessive polycystic kidney disease. We demonstrated that resting afferent renal nerve activity is greater in the PCK rat than noncystic controls and that basal afferent renal nerve activity is directly correlated with the extent of renal cystogenesis.

Protective effects of hydrogen sulfide pretreatment on cyclophosphamide-induced bladder dysfunction in rats via suppression of bladder afferent nerves.

Cyclophosphamide (CYP), a broad-spectrum anticancer drug, causes serious side effects, such as haemorrhagic cystitis (HC). Hydrogen sulfide (H2S), an endogenous gasotransmitter, has physiological properties, including anti-inflammation, anti-oxidation, and neuromodulation. In this study, we investigated the effects of NaHS (H2S donor) pretreatment on bladder dysfunction in CYP-treated rats. Male Wistar rats were intraperitoneally pretreated with NaHS (3 or 10 µmol/kg) or vehicle once daily for 7 days before cystometry, and CYP (150 mg/kg) or saline was intraperitoneally administered 2 days before cystometry. After cystometry, the bladder tissues were collected for haematoxylin and eosin staining. In some rats, capsaicin (CAP), which can desensitise CAP-sensitive afferent nerves, was subcutaneously injected at 125 mg/kg 4 days before cystometry. CYP reduced intercontraction intervals (ICI) and bladder compliance (Comp) and increased the number of non-voiding contractions (NVCs) compared with the saline-treated control group. NaHS pretreatment dose-dependently improved the CYP-induced these changes. In bladder tissues, CYP increased histological scores of neutrophil infiltration, haemorrhage, and oedema, while NaHS had no effect on these CYP-induced changes. CAP showed a tendency to suppress CYP-induced changes in ICI. NaHS-induced improvement in CYP-induced changes in urodynamic parameters were not detected in CAP-treated rats. These findings suggest that NaHS pretreatment prevented bladder dysfunction in CYP-treated rats by suppressing CAP-sensitive bladder afferent nerves, but not by suppressing bladder inflammation. Therefore, H2S represents a new candidate as a protective drug for bladder dysfunction induced by HC, a side effect of CYP chemotherapy.

Hypersensitivity of bladder low threshold, wide dynamic range, afferent fibres following treatment with the chemotherapeutic drugs cyclophosphamide and ifosfamide.

The cytotoxic drugs cyclophosphamide (CPO) and ifosfamide (IFO) cause toxic urological effects due to the production of urinary metabolites that cause bladder inflammation. This study aimed to identify changes in the bladder afferent system following treatment with these drugs that might explain reported urological adverse effects. Intravesical pressure and afferent nerve activity were recorded during bladder distension and drug administration in isolated bladders from mice, 24 h after intraperitoneal treatment with cyclophosphamide (100 mg/kg), ifosphamide (200 mg/kg) or saline (control). In isolated bladders, total afferent nerve activity at maximum bladder distension was increased from 182 ± 13 imp/s in control animals, to 230 ± 14 imp/s in CPO-treated (p < 0.05) and 226 ± 17 imp/s in IFO-treated (p < 0.001) mice. Single fibre analysis revealed the increase resulted from an enhanced activity in low threshold, wide dynamic range fibres (23.3 ± 1.9 imp/s/fibre in controls to 31.5 ± 2.5 (p < 0.01) in CPO and 29.9 ± 2.0 imp/s/fibre (p < 0.05) in IFO treated). CPO treatment was accompanied by an increase in urinary frequency in vivo, but was not associated with increases in urothelial release of ATP or acetylcholine, bladder compliance or spontaneous muscle activity. Also, CPO-treatment did not affect afferent nerve responses or pressure responses to purinergic, muscarinic or nicotinic agonists. This is the first report of CPO and IFO-induced changes in specific populations of bladder afferents, namely an increase in low threshold, wide dynamic range fibres. These effects appear to be direct and not secondary to increases in smooth muscle activity or the release of urothelial mediators.

Increased α2δ-1-NMDA receptor coupling potentiates glutamatergic input to spinal dorsal horn neurons in chemotherapy-induced neuropathic pain.

Painful peripheral neuropathy is a severe and difficult-to-treat neurological complication associated with cancer chemotherapy. Although chemotherapeutic drugs such as paclitaxel are known to cause tonic activation of presynaptic NMDA receptors (NMDARs) to potentiate nociceptive input, the molecular mechanism involved in this effect is unclear. α2δ-1, commonly known as a voltage-activated calcium channel subunit, is a newly discovered NMDAR-interacting protein and plays a critical role in NMDAR-mediated synaptic plasticity. Here we show that paclitaxel treatment in rats increases the α2δ-1 expression level in the dorsal root ganglion and spinal cord and the mRNA levels of GluN1, GluN2A, and GluN2B in the spinal cord. Paclitaxel treatment also potentiates the α2δ-1-NMDAR interaction and synaptic trafficking in the spinal cord. Strikingly, inhibiting α2δ-1 trafficking with pregabalin, disrupting the α2δ-1-NMDAR interaction with an α2δ-1 C-terminus-interfering peptide, or α2δ-1 genetic ablation fully reverses paclitaxel treatment-induced presynaptic NMDAR-mediated glutamate release from primary afferent terminals to spinal dorsal horn neurons. In addition, intrathecal injection of pregabalin or α2δ-1 C-terminus-interfering peptide and α2δ-1 knockout in mice markedly attenuate paclitaxel-induced pain hypersensitivity. Our findings indicate that α2δ-1 is required for paclitaxel-induced tonic activation of presynaptic NMDARs at the spinal cord level. Targeting α2δ-1-bound NMDARs, not the physiological α2δ-1-free NMDARs, may be a new strategy for treating chemotherapy-induced neuropathic pain. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.

Mitogen-activated protein kinase signaling mediates opioid-induced presynaptic NMDA receptor activation and analgesic tolerance.

Opioid-induced hyperalgesia and analgesic tolerance can lead to dose escalation and inadequate pain treatment with µ-opioid receptor agonists. Opioids cause tonic activation of glutamate NMDA receptors (NMDARs) at primary afferent terminals, increasing nociceptive input. However, the signaling mechanisms responsible for opioid-induced activation of pre-synaptic NMDARs in the spinal dorsal horn remain unclear. In this study, we determined the role of MAPK signaling in opioid-induced pre-synaptic NMDAR activation caused by chronic morphine administration. Whole-cell recordings of excitatory post-synaptic currents (EPSCs) were performed on dorsal horn neurons in rat spinal cord slices. Chronic morphine administration markedly increased the frequency of miniature EPSCs, increased the amplitude of monosynaptic EPSCs evoked from the dorsal root, and reduced the paired-pulse ratio of evoked EPSCs. These changes were fully reversed by an NMDAR antagonist and normalized by inhibiting extracellular signal-regulated kinase 1/2 (ERK1/2), p38, or c-Jun N-terminal kinase (JNK). Furthermore, intrathecal injection of a selective ERK1/2, p38, or JNK inhibitor blocked pain hypersensitivity induced by chronic morphine treatment. These inhibitors also similarly attenuated a reduction in morphine's analgesic effect in rats. In addition, co-immunoprecipitation assays revealed that NMDARs formed a protein complex with ERK1/2, p38, and JNK in the spinal cord and that chronic morphine treatment increased physical interactions of NMDARs with these three MAPKs. Our findings suggest that opioid-induced hyperalgesia and analgesic tolerance are mediated by tonic activation of pre-synaptic NMDARs via three functionally interrelated MAPKs at the spinal cord level. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.

Afferent nerve fibres in the wall of the rat urinary bladder.

Structure and distribution of afferent nerve fibres in the rat bladder were studied by fluorescence microscopy after selective staining with antibodies against neuropeptide CGRP. Afferent fibres are very abundant (by comparison with other viscera) and interconnected in all bladder parts: muscle, urothelium, connective tissue, blood vessels, serosa. Their highest concentration is beneath the urothelium in equatorial and caudal regions, where they form a plexus, while individually maintaining a tree-like structure with innumerable branches running without preferential orientation. In cranial regions, mucosal afferent fibres become rare or absent. Abundant fibres are found in the detrusor, within each muscle bundle, with long strings of varicosities parallel to muscle cells. Afferent fibres, invariably varicose over hundreds of micrometres of their terminal parts and while still branching, comprise chains of hundreds of varicosities. Varicosities are irregular in size, frequency and separation, without specialised terminal structures around them, or within or around the fibre's ending. The possibility that varicosities are transduction points for sensory inputs is discussed, with the implication of a process taking place over considerable length in each branch of each fibre. Interconnectedness of afferent nerves of various bladder tissues, distribution of varicosities over hundreds of micrometres along axonal branches, absence of clear target structures for the fibres, apparent irregularity in the size and sequence of varicosities suggest an innervation that is not rigidly wired with distinct sensory pathways. In fact, the structural evidence suggests extensive afferent integration at the periphery, with wide distribution of source points and broad range of physical detectors.

Initial clinical experience with selective bladder denervation for refractory overactive bladder.

AIMS: To report the initial clinical experience with selective bladder denervation (SBD) of the trigone in women with refractory overactive bladder (OAB). METHODS: Females with refractory OAB underwent SBD of the bladder sub-trigone region. Patients were treated using a 10-s voltage-controlled radiofrequency (RF) algorithm (RF10) at study onset. The protocol was modified during the study after which point remaining patients received 60-s temperature-controlled RF (RF60). Patients were followed for 12 weeks and evaluated for adverse events and changes in OAB symptoms. Exploratory analyses on the influence of RF duration were performed. RESULTS: Among 63 patients, SBD resulted in statistically significant and clinically important improvements for most outcomes. Comparing RF10 (n = 34) to RF60 (n = 29), treatment benefit was greater with RF60 including mean reduction in urgency urinary incontinence (-2.5 vs -0.9; P < 0.01), urinary incontinence (-2.6 vs -0.8; P < 0.001), and total urgency and frequency score (-13 vs -7; P = 0.02); and improvements in symptom bother (-33 vs -18; P < 0.01) and quality of life (28 vs 16; P = 0.02) on the OAB questionnaire. The proportion of urgency urinary incontinence treatment responders (≥50% reduction in episodes) was 79% with RF60 and 31% with RF10. The frequency of device- or procedure-related adverse events was comparable in RF10 versus RF60 groups (14.7% vs 17.2%). CONCLUSIONS: This study demonstrated the feasibility of SBD in alleviating symptoms of refractory OAB. A 60-s RF algorithm using deeper ablations of the sub-trigonal tissues was more effective and comparably safe to a 10-s RF algorithm using more superficial ablations.

NKA enhances bladder-afferent mechanosensitivity via urothelial and detrusor activation.

Tachykinins are expressed within bladder-innervating sensory afferents and have been shown to generate detrusor contraction and trigger micturition. The release of tachykinins from these sensory afferents may also activate tachykinin receptors on the urothelium or sensory afferents directly. Here, we investigated the direct and indirect influence of tachykinins on mechanosensation by recording sensory signaling from the bladder during distension, urothelial transmitter release ex vivo, and direct responses to neurokinin A (NKA) on isolated mouse urothelial cells and bladder-innervating DRG neurons. Bath application of NKA induced concentration-dependent increases in bladder-afferent firing and intravesical pressure that were attenuated by nifedipine and by the NK2 receptor antagonist GR159897 (100 nM). Intravesical NKA significantly decreased bladder compliance but had no direct effect on mechanosensitivity to bladder distension (30 µl/min). GR159897 alone enhanced bladder compliance but had no effect on mechanosensation. Intravesical NKA enhanced both the amplitude and frequency of bladder micromotions during distension, which induced significant transient increases in afferent firing, and were abolished by GR159897. NKA increased intracellular calcium levels in primary urothelial cells but not bladder-innervating DRG neurons. Urothelial ATP release during bladder distention was unchanged in the presence of NKA, whereas acetylcholine levels were reduced. NKA-mediated activation of urothelial cells and enhancement of bladder micromotions are novel mechanisms for NK2 receptor-mediated modulation of bladder mechanosensation. These results suggest that NKA influences bladder afferent activity indirectly via changes in detrusor contraction and urothelial mediator release. Direct actions on sensory nerves are unlikely to contribute to the effects of NKA.

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

Afferent fibers expressing the vanilloid receptor 1 (VR1) channel have been implicated in cardiac nociception; however, their role in modulating reflex responses to cardiac stress is not well understood. We evaluated this role in Yorkshire pigs by percutaneous epicardial application of resiniferatoxin (RTX), a toxic activator of the VR1 channel, resulting in the depletion of cardiac VR1-expressing afferents. Hemodynamics, epicardial activation recovery intervals, and in vivo activity of stellate ganglion neurons (SGNs) were recorded in control and RTX-treated animals. Stressors included inferior vena cava or aortic occlusion and rapid right ventricular pacing (RVP) to induce dyssynchrony and ischemia. In the epicardium, stellate ganglia, and dorsal root ganglia, immunostaining for the VR1 channel, calcitonin gene-related peptide, and substance P was significantly diminished by RTX. RTX-treated animals exhibited higher basal systolic blood pressures and contractility than control animals. Reflex responses to epicardial bradykinin and capsaicin were mitigated by RTX. Cardiovascular reflex function, as assessed by inferior vena cava or aortic occlusion, was similar in RTX-treated versus control animals. RTX-treated animals exhibited resistance to hemodynamic collapse induced by RVP. Activation recovery interval shortening during RVP, a marker of cardiac sympathetic outflow, was greater in RTX-treated animals and exhibited significant delay in returning to baseline values after cessation of RVP. The basal firing rate of SGNs and firing rates in response to RVP were also greater in RTX-treated animals, as was the SGN network activity in response to cardiac stressors. These data suggest that elimination of cardiac nociceptive afferents reorganizes the central-peripheral nervous system interaction to enhance cardiac sympathetic outflow. NEW & NOTEWORTHY Our work demonstrates a role for cardiac vanilloid receptor-1-expressing afferents in reflex processing of cardiovascular stress. Current understanding suggests that elimination of vanilloid receptor-1 afferents would decrease reflex cardiac sympathetic outflow. We found, paradoxically, that sympathetic outflow to the heart is instead enhanced at baseline and during cardiac stress.

The effect of the electrophilic fatty acid nitro-oleic acid on TRP channel function in sensory neurons.

Nitro-oleic acid (NO2-OA) and related nitroalkenes are electrophilic fatty acid derivatives that are present in normal tissues at nanomolar concentrations and can increase significantly during inflammation. These substances can suppress multiple intracellular signaling pathways contributing to inflammation by reversible Michael addition reactions with nucleophilic residues such as cysteine and histidine leading to post-translational modification of proteins. NO2-OA also can influence inflammation and pain by acting on transient receptor potential (TRP) channels in primary sensory neurons. TRPV1, TRPA1 and TRPC can respond to electrophilic fatty acids because they have ankyrin-like repeats in their N terminus that are rich in cysteine residues that react with electrophiles and other thiol modifying species. NO2-OA acts on TRP channels to initially depolarize and induce firing in sensory neurons followed by desensitization and suppression of firing. In vivo experiments revealed that pretreatment with NO2-OA reduces nociceptive behavior evoked by local administration of a TRPA1 agonist (AITC) to the rat hind paw. These results raise the possibility that NO2-OA might be useful clinically to reduce neurogenic inflammation and certain types of painful sensations by desensitizing TRPA1 expressing nociceptive afferents.

Emerging studies of human visceral nociceptors.

Animal studies have led to significant advances in our understanding of pain mechanisms in the intestine that could lead to altered signaling in disorders such as irritable bowel syndrome. However, how these translate to the human afferent nervous system is unclear. Recent studies have demonstrated that it is possible to use a variety of techniques, including electrophysiological recordings, to begin to examine these concepts in humans. This mini-review examines these studies to explore how well animal studies translate to humans suffering from irritable bowel syndrome, highlights some of the advantages and technical limitations of these approaches, and identifies some priorities for future studies using human tissues.

Sensory function assessment of the human male lower urinary tract using current perception thresholds.

AIMS: To evaluate the feasibility and reliability of current perception threshold (CPT) measurement for sensory assessment of distinct locations in the male lower urinary tract (LUT). METHODS: Twelve male subjects (>18 years) without LUT symptoms or medical comorbidities were eligible. CPTs were determined twice (interval: 7-20 days) at the bladder dome, trigone and the proximal, membranous, and distal urethra. Square wave electrical stimulation of 3 Hz/0.2 ms and 0.5 Hz/1 ms was applied using a transurethral 8F catheter placed under fluoroscopic control. Bladder volume was kept constant (60 mL) using a second 10F catheter. Repetitive measurements and reliability were assessed by analysis of variance (ANOVA) and intraclass correlation coefficient (ICC). RESULTS: The ANOVA revealed significant main effects for stimulation site (P = 0.008) and type of stimulation (P < 0.001) with lower CPTs for 0.5 Hz/1 ms compared to 3 Hz/0.2 ms. There was no significant effect for visit number (P = 0.061). CPTs were higher for bladder dome than for proximal (0.5 Hz/1 ms: P = 0.022; 3 Hz/0.2 ms: P = 0.022) and distal urethra (0.5 Hz/1 ms: P = 0.026; 3 Hz/0.2 ms: P = 0.030). Reliability of CPT measurements was excellent to good (ICC = 0.67-0.96) except for the bladder dome (5 Hz/1 ms: ICC = 0.45; 3 Hz/0.2 ms: ICC = 0.20) and distal urethra (3 Hz/0.2 ms: ICC = 0.57). CONCLUSIONS: CPTs can be reliably detected at different LUT locations. However, alert and compliant subjects are essential. CPTs of LUT may become a complementary assessment method providing information on responsiveness and sensitivity of afferent LUT nerves. This is especially relevant for urethral afferents, which are not covered by standard urodynamic investigations. Neurourol. Urodynam. 36:469-473, 2017. © 2016 Wiley Periodicals, Inc.

Renal Afferents.

PURPOSE OF REVIEW: The etiology of hypertension, a critical public health issue affecting one in three US adults, involves the integration of the actions of multiple organ systems, including the renal sympathetic nerves. The renal sympathetic nerves, which are comprised of both afferent (sensory input) and efferent (sympathetic outflow) arms, have emerged as a major potential therapeutic target to treat hypertension and disease states exhibiting excess renal sympathetic activity. RECENT FINDINGS: This review highlights recent advances in both clinical and basic science that have provided new insight into the distribution, function, and reinnervation of the renal sympathetic nerves, with a focus on the renal afferent nerves, in hypertension and hypertension-evoked disease states including salt-sensitive hypertension, obesity-induced hypertension, and chronic kidney disease. Increased understanding of the differential role of the renal afferent versus efferent nerves in the pathophysiology of hypertension has the potential to identify novel targets and refine therapeutic interventions designed to treat hypertension.

Capsaicin treatment reduces nasal hyperreactivity and transient receptor potential cation channel subfamily V, receptor 1 (TRPV1) overexpression in patients with idiopathic rhinitis.

BACKGROUND: Idiopathic rhinitis (IR) is a prevalent condition for which capsaicin nasal spray is the most effective treatment. However, the mechanisms underlying IR and the therapeutic action of capsaicin remain unknown. OBJECTIVE: We sought to investigate the molecular and cellular bases of IR and the therapeutic action of capsaicin. METHODS: Fourteen patients with IR and 12 healthy control subjects (HCs) were treated with intranasal capsaicin. The therapeutic effect was assessed in patients with IR by using visual analog scale and therapeutic response evaluation scores, and nasal hyperreactivity was evaluated by means of cold dry air provocation. Nasal samples served to measure the levels of neuromediators and expression of chemosensory cation channels, protein gene product 9.5 (PGP 9.5), and the mast cell marker c-kit. The effects of capsaicin were also tested in vitro on human nasal epithelial cells and mast cells. RESULTS: Patients with IR had higher baseline transient receptor potential cation channel subfamily V, receptor 1 (TRPV1) expression in the nasal mucosa and higher concentrations of substance P (SP) in nasal secretions than HCs. Symptomatic relief was observed in 11 of 14 patients with IR after capsaicin treatment. Expression of TRPV1; transient receptor potential cation channel subfamily M, receptor 8 (TRPM8); and PGP 9.5 was only reduced in patients with IR after capsaicin treatment. Capsaicin did not alter c-KIT expression or nasal epithelial morphology in patients with IR and HCs nor did it induce apoptosis or necrosis in cultured human nasal epithelial cells and mast cells. CONCLUSION: IR features an overexpression of TRPV1 in the nasal mucosa and increased SP levels in nasal secretions. Capsaicin exerts its therapeutic action by ablating the TRPV1-SP nociceptive signaling pathway in the nasal mucosa.