Immediate and delayed potentiating effects of tumor necrosis factor-α on TRPV1 sensitivity of rat vagal pulmonary sensory neurons

Huang

Lan

et al. 2020

IJMS

Self Cite

Airway exposure to 1,3-β-D-glucan (β-glucan), an essential component of the cell wall of several pathogenic fungi, causes various adverse responses, such as pulmonary inflammation and airway hypersensitivity. The former response has been intensively investigated; however, the mechanism underlying β-glucan-induced airway hypersensitivity is unknown. Capsaicin-sensitive lung vagal (CSLV) afferents are very chemosensitive and stimulated by various insults to the lungs. Activation of CSLV afferents triggers several airway reflexes, such as cough. Furthermore, the sensitization of these afferents is known to contribute to the airway hypersensitivity during pulmonary inflammation. This study was carried out to determine whether β-glucan induces airway hypersensitivity and the role of the CSLV neurons in this hypersensitivity. Our results showed that the intratracheal instillation of β-glucan caused not only a distinctly irregular pattern in baseline breathing, but also induced a marked enhancement in the pulmonary chemoreflex responses to capsaicin in anesthetized, spontaneously breathing rats. The potentiating effect of β-glucan was found 45 min later and persisted at 90 min. However, β-glucan no longer caused the irregular baseline breathing and the potentiating of pulmonary chemoreflex responses after treatment with perineural capsaicin treatment that blocked the conduction of CSLV fibers. Besides, the potentiating effect of β-glucan on pulmonary chemoreflex responses was significantly attenuated by N-acetyl-L-cysteine (a ROS scavenger), HC-030031 (a TRPA1 antagonist), and Laminarin (a Dectin-1 antagonist). A combination of Laminarin and HC-030031 further reduced the β-glucan-induced effect. Indeed, our fiber activity results showed that the baseline fiber activity and the sensitivity of CSLV afferents were markedly elevated by β-glucan instillation, with a similar timeframe in anesthetized, artificially ventilated rats. Moreover, this effect was reduced by treatment with HC-030031. In isolated rat CSLV neurons, the β-glucan perfusion caused a similar pattern of potentiating effects on capsaicin-induced Ca2+ transients, and β-glucan-induced sensitization was abolished by Laminarin pretreatment. Furthermore, the immunofluorescence results showed that there was a co-localization of TRPV1 and Dectin-1 expression in the DiI-labeled lung vagal neurons. These results suggest that CSLV afferents play a vital role in the airway hypersensitivity elicited by airway exposure to β-glucan. The TRPA1 and Dectin-1 receptors appear to be primarily responsible for generating β-glucan-induced airway hypersensitivity.

Section: Methodsmentioning

confidence: 99%

“…The methodology of isolation and culture of nodose and jugular ganglion neurons was described in detail in our previous studies [ 58 , 59 , 60 ]. At 7–11 days, the DiI-labeled SD rats were anesthetized with 5% isoflurane and decapitated.…”

Section: Methodsmentioning

confidence: 99%

Involvement of Capsaicin-Sensitive Lung Vagal Neurons and TRPA1 Receptors in Airway Hypersensitivity Induced by 1,3-β-D-Glucan in Anesthetized Rats

Huang

Lan

et al. 2020

IJMS

Self Cite

“…However, another study reported a lack of potentiating effect of TNF on rat vagal sensory neuron rapid transient current mediated by ASICs but a significant increase of the slow sustained current mediated by TRPV1 through a COX2-dependant mechanism (Hsu et al, 2017). Differences in the experimental conditions (origin of the neurons and culture conditions, TNF concentration, perfusion time) could explain these different results.…”

Section: Native Proton-gated Currents Of Sensory Neurons Are Stronglymentioning

confidence: 97%

C-Jun N-terminal kinase post-translational regulation of pain-related Acid-Sensing Ion Channels 1b and 3

Verkest

Diochot

Lingueglia

et al. 2021

Preprint

Neuronal proton-gated Acid-Sensing Ion Channels (ASICs) participate in the detection of tissue acidosis, a phenomenon often encountered in painful pathological diseases. Such conditions often involve in parallel the activation of various signaling pathways such as the Mitogen Activated Protein Kinases (MAPKs) that ultimately leads to phenotype modifications of sensory neurons. Here, we identify one member of the MAPKs, c-Jun N-terminal Kinase (JNK), as a new post-translational positive regulator of ASIC channels in rodent sensory neurons. Recombinant H+-induced ASIC currents in HEK293 cells are potently inhibited within minutes by the JNK inhibitor SP600125 in a subunit and species dependent manner, targeting both rat and human ASIC1b and ASIC3 subunits but only mouse ASIC1b subunit. The regulation by JNK of recombinant ASIC1b- and ASIC3-containing channels (homomers and heteromers) is lost upon mutation of a putative phosphorylation site within the intracellular N- and the C-terminal domain of the ASIC1b and ASIC3 subunit, respectively. Moreover, short-term JNK activation regulates the activity of native ASIC1b- and ASIC3-containing channels in rodent sensory neurons and is involved in the rapid potentiation of ASIC activity by the proinflammatory cytokine TNFα. Local JNK activation in vivo in mice induces a short-term potentiation of the acid-induced cutaneous pain in inflammatory conditions that is partially blocked by the ASIC1-specific inhibitor mambalgin-1. Collectively, our data identify pain-related channels as novel physiological JNK substrates in nociceptive neurons, and propose JNK-dependent phosphorylation as a fast post-translational mechanism of regulation of sensory neuron-expressed ASIC1b- and ASIC3-containing channels that may contribute to peripheral sensitization and pain hypersensitivity.

“…Isolation and identification of vagal pulmonary sensory neurones. Sensory neurones innervating the lungs and airways of young Sprague Dawley rats at 4-7 weeks of age (Charles River) were identified by retrograde labelling with the fluorescent tracer 1,1 -dioctadecyl-3,3,3 ,3 -tetramethylindocarbocyanine perchlorate (DiI); this procedure was performed when the rats were anaesthetized by inhalation of vaporized isoflurane (2% in O 2 ) through a nose cone, as described in detail in our previous study (Hsu et al 2017). Seven to 10 days later, rats were anaesthetized by inhalation of an overdose of isoflurane (5% in O 2 ) and then decapitated immediately.…”

Section: Study 2: Effect Of So 2 On the Intracellular Ca 2+ Transientmentioning

confidence: 99%

Mechanisms underlying the stimulatory effect of inhaled sulfur dioxide on vagal bronchopulmonary C‐fibres

Hsu

The Journal of Physiology

et al. 2020

Self Cite

Key points Brief inhalation of SO2 of concentration >500 p.p.m. triggered a pronounced stimulatory effect on vagal bronchopulmonary C‐fibres in anaesthetized rats. This stimulatory effect was drastically diminished by a pretreatment with NaHCO3 that raised the baseline arterial pH, suggesting a possible involvement of acidification of airway fluid and/or tissue generated by inhaled SO2. The stimulation was completely abolished by pretreatment with antagonists of both acid‐sensing ion channels and transient receptor potential vanilloid type‐1 receptors, indicating that this effect was caused by acid activation of these cation channels expressed in airway sensory nerves. This conclusion was further supported by the results obtained from studies in isolated rat vagal bronchopulmonary sensory neurones and also in the cough response to SO2 inhalation challenge in awake mice. These results provide new insight into the underlying mechanism of harmful irritant effects in the respiratory tract caused by accidental exposure to a high concentration of SO2. Abstract Inhalation of sulfur dioxide (SO2) triggers coughs and reflex bronchoconstriction, and stimulation of vagal bronchopulmonary C‐fibres is primarily responsible. However, the mechanism underlying this stimulatory effect is not yet fully understood. In this study, we tested the hypothesis that the C‐fibre stimulation was caused by SO2‐induced local tissue acidosis in the lung and airways. Single‐unit activities of bronchopulmonary C‐fibres in response to inhalation challenges of SO2 (500–1500 p.p.m., 10 breaths) were measured in anaesthetized rats. Inhalation of SO2 reproducibly induced a pronounced and sustained stimulation (lasting for 15–60 s) of pulmonary C‐fibres in a concentration‐dependent manner. This stimulatory effect was significantly attenuated by an increase in arterial pH generated by infusion of sodium bicarbonate (NaHCO3), and completely abrogated by a combined pretreatment with amiloride (an antagonist of acid‐sensing ion channels, ASICs) and AMG8910 (a selective antagonist of the transient receptor potential vanilloid type‐1 receptor, TRPV1). Furthermore, in isolated rat vagal pulmonary sensory neurones, perfusion of an aqueous solution of SO2 evoked a transient increase in the intracellular Ca2+ concentration; this response was also markedly diminished by a pretreatment with amiloride and AMG8910. In addition, inhalation of SO2 consistently evoked coughs in awake mice; responses were significantly smaller in TRPV1−/− mice than in wild‐type mice, and almost completely abolished after a pretreatment with amiloride in TRPV1−/− mice. These results suggested that the stimulatory effect of inhaled SO2 on bronchopulmonary C‐fibres was generated by acidification of fluid and/or tissue in the lung and airways, which activated both ASICs and TRPV1 expressed in these sensory nerves.