Transient Receptor Potential Vanilloid Research Articles

Conserved and Unique Mitochondrial Target Sequence of TRPV4 Can Independently Regulate Mitochondrial Functions.

Though mitochondria have their own genome and protein synthesis machineries, the majority of the mitochondrial proteins are actually encoded by the nuclear genome. Most of these mitochondrial proteins are imported into specific compartments of the mitochondria due to their mitochondrial target sequence (MTS). Unlike the nuclear target sequence, the MTS of most of the mitochondrial localized proteins remain poorly understood, mainly due to their variability, heterogeneity, unconventional modes of action, mitochondrial potential-dependent transport, and other complexities. Recently, we reported that transient receptor potential vanilloid subtype 4 (TRPV4), a thermosensitive cation channel, is physically located at the mitochondria. Here we characterize a small segment (AA 592-630) located at the TM4-loop4-TM5 segment of TRPV4 that acts as a novel MTS. The same region remains highly conserved in all vertebrates and contains a large number of point mutations each of which causes an diverse spectrum of diseases in human. Using confocal and super-resolution microscopy, we show that this MTS of TRPV4 or its mutants localizes to the mitochondria independently and also induces functional and quantitative changes in the mitochondria. By using conformal microscopy, we could detect the presence of the MTS region within the isolated mitochondria. These findings may be important to understand the complexity of MTS and TRPV4-induced channelopathies better.

Electroacupuncture Mitigates TRPV1 Overexpression in the Central Nervous System Associated with Fibromyalgia in Mice

Background: Fibromyalgia (FM) is characterized by chronic pain, significantly affecting the quality of life and functional capabilities of patients. In addition to pain, patients may experience insomnia, chronic fatigue, depression, anxiety, and headaches, further complicating their overall well-being. The Transient Receptor Potential Vanilloid 1 (TRPV1) receptor responds to various noxious stimuli and plays a key role in regulating pain sensitivity and inflammation. Thus, targeting TRPV1 may provide analgesic and anti-inflammatory benefits. This study investigates the efficacy of electroacupuncture (EA) in alleviating chronic pain in FM through TRPV1 and its downstream molecules in the central nervous system (CNS). Methods: To model FM, we subjected mice to intermittent cold stress (ICS) for three days. The study comprised five rodent groups: Control (CON), ICS, ICS + EA, ICS + Sham EA, and ICS + KO (TRPV1 knockout mice). Results: Our findings revealed that ICS induced allodynia and hyperalgesia in mice by day four, persisting until day 21. EA at 2 Hz and TRPV1 KO significantly decreased both mechanical and thermal hypersensitivity (Withdrawal—Day 14: 2.43 ± 0.19 g; Day 21: 5.88 ± 0.47 g, n = 6, p < 0.05; Latency—Day 14: 2.77 ± 0.22 s; Day 21: 5.85 ± 0.41 s, n = 6, p < 0.05). In contrast, sham EA did not produce significant effects. Additionally, TRPV1 and several pain-related proteins were significantly elevated in the thalamus, somatosensory cortex (SSC), medial prefrontal cortex (mPFC), hippocampus, hypothalamus, cerebellum regions V (CB V), VI (CB VI) and VII (CB VII) after the ICS model. Both EA at the ST36 acupoint and TRPV1 KO mice showed diminished overexpression of pain-related proteins, with the sham EA group showing no significant changes compared to the ICS group. Conclusions: Chronic widespread pain was reduced by EA and TRPV1 KO, with the effects of EA on the TRPV1 pain pathway clearly evident in the CNS after 21 days.

TRPV1 Promotes Periodontitis Tissue Inflammation and Oxidative Damage by Regulating STAT3 Signaling Pathway.

Periodontitis is a chronic disease affecting adult oral health. Transient receptor potential vanilloid 1 (TRPV1) expression is shown to upregulate in many inflammatory diseases. Nevertheless, its biological potential along with the molecular mechanism in periodontitis is unclear. Our study aimed to explore the biological role and underlying signaling pathway of TRPV1 in periodontitis. In the current research, human periodontal ligament stem cells (hPDLSCs) were stimulated by lipopolysaccharide (LPS) to induce inflammatory conditions invitro. Invivo, the periodontitis mouse model was built by ligating the gingival sulcus of male C57BL/6J mice. Thereafter, the proliferation, apoptosis, inflammation, and oxidative stress-related processes were assessed. We found that LPS induced apoptosis and inflammation in hPDLCs, along with oxidative stress, while simultaneously inhibiting hPDLC proliferation (p < 0.05). Notably, TRPV1 expression was elevated in LPS-treated hPDLSCs and gingival samples from patients with periodontitis. Interestingly, the increase in TRPV1 expression induced by Capsaicin, a TRPV1 agonist, inhibited cell proliferation while promoting LPS-stimulated apoptosis, inflammation, and oxidative stress in hPDLSCs (p < 0.01). In contrast, inhibition of TRPV1 expression using Capsazepine, a TRPV1 inhibitor, produced opposite effects (p < 0.01). Invivo experiments revealed that inhibition of TRPV1 attenuated ligation-induced periodontitis in mice, as evidenced by enhanced oxidative stress, inflammatory response, and elevated apoptosis (p < 0.01). Additionally, rescue assays indicated that TRPV1 promoted periodontitis-associated tissue inflammation and oxidative damage via activating the STAT3 signaling pathway (p < 0.01). Our study demonstrates that TRPV1 expression is high in periodontitis and facilitates periodontitis-associated tissue inflammation and oxidative damage by regulating STAT3 signaling pathway, which implies that TRPV1 may represent a new therapeutic target for periodontitis.

Targeting Dlat-Trpv3 pathway by hyperforin elicits non-canonical promotion of adipose thermogenesis as an effective anti-obesity strategy

IntroductionPromoting adipose thermogenesis is considered as a promising therapeutic intervention in obesity. However, endeavors to develop anti-obesity medications by targeting the canonical thermogenesis regulatory pathway, particularly β3-adrenergic receptor (β3-AR)-dependent mechanism, have failed due to the off-target effects of β3-AR agonists, exacerbating the risk of cardiovascular disease. Hyperforin (HPF), a natural compound extracted from the traditional herbal St. John’s Wort, binds to Dihydrolipoamide s-acetyltransferase (Dlat) and exerts effective anti-obesity properties through promoting adipose thermogenesis. ObjectivesThe objective of this study was to investigate the oral efficacy and pharmacokinetics profile of HPF, and explore the detailed mechanism by which Dlat modulates HPF-mediated adipose thermogenesis. MethodsTo assess the anti-obesity efficacy of orally administered HPF in vivo, Dlat heterozygous knockout (Dlat+/-) mice and wild-type (WT) mice, both fed a high-fat diet (HFD), underwent a validation process that involved the use of metabolic cages, NMR analysis, and infrared imaging. Sprague Dawley rats were employed to determine the pharmacokinetic parameters of HPF. Seahorse assays, JC-1 staining, qPCR, and immunoblotting were performed to evaluate cellular thermogenic efficacy of HPF and Dlat in vitro. ResultsOur study uncovered a non-canonical thermogenesis pathway involving Dlat, transient receptor potential vanilloid 3 (Trpv3, a calcium channel) and AMPK. Dlat interacted with Trpv3 to activate it, resulting in an increase in intracellular calcium (Ca2+) and the activation of Camkkβ. Camkkβ then stimulated AMPK, leading to elevated Ucp1 expression and initiating adipose thermogenesis. HPF promoted thermogenesis in adipose tissues through enhancing the Dlat-Trpv3 interaction independently of β3­AR, causing minimal cardiac side effects. Notably, HPF’s thermogenic effects were reduced in Dlat+/- mice. Moreover, HPF exerted favorable oral bioavailability, a relatively long half-life, and extensive distribution within adipose tissues. ConclusionIn summary, our study demonstrates that HPF targets a novel mechanism for promoting adipose thermogenesis and exhibits potent and safe anti-obesity efficacy.

Validation of Peripheral Neuromodulation Mechanisms of Icariin in Knee Osteoarthritis–Related Chronic Pain

ABSTRACTKnee osteoarthritis (KOA) is a chronic degenerative joint disease‐causing chronic pain and disability. Neuromodulation of subchondral bone affects KOA‐related pain and involves dorsal root ganglion (DRG). Our previous studies have demonstrated efficacy of icariin (ICA) in treating KOA, but neuromodulation mechanisms in peripheral nerves associated with the treatment of chronic pain in KOA remain unclear. This study aimed to investigate peripheral neuromodulation mechanisms of ICA in KOA‐related chronic pain: (1) assessing therapeutic effect of ICA in a rat model of KOA‐induced chronic pain; (2) investigating changes in pain‐related nerve fibres and transient receptor potential vanilloid Subfamily 1 (TRPV1) pathway in subchondral bone following ICA treatment; and (3) exploring expression of pain‐related Nogo‐A/TRPV1 pathway in DRG, thereby elucidating neurotransmission of pain. Experimental results confirmed the curative effect of ICA on KOA by relieving chronic pain and pathological changes. ICA also effectively reduced bone remodelling, the area of pain‐related positive nerve fibres and expression of TRPV1 in subchondral bone. Furthermore, ICA downregulated pain‐related Nogo‐A/TRPV1 pathway in the DRG. These findings provide new mechanistic insights into the therapeutic potential of ICA in relieving peripheral nervous system‐related chronic pain in KOA.

Liu-Shen-Wan inhibits PI3K/Akt and TRPV1 signaling alleviating bone cancer pain in rats

ABSTRACT Patients with advanced-stage cancers often suffer from severe pain caused by bone metastasis and destruction, for which effective treatment options are limited. Liu-Shen-Wan (LSW) is a widely recognized herbal formula utilized for pain relief. This study aims to elucidate the effects of LSW on bone cancer pain (BCP). In this study, the pharmacology of LSW on BCP was screened by network pharmacology. A BCP model was conducted using Walker 256 cells. Paw withdrawal threshold and paw withdrawal latency were employed as measures to assess the pain threshold in rats. The pathways and cell types of LSW against BCP were explored. Next, the impact of LSW on Walker 256 cells was evaluated, and UPLC-MS was utilized to identify the active ingredients of LSW. Furthermore, the effects of the key active ingredient, Bufalin, on the BCP rats were evaluated. There were 275 shared targets between LSW and BCP, which were enriched in neural tissue ligand-receptor interaction pathway. LSW increased pain threshold and decreased inflammatory cytokines levels in BCP rats by inhibiting PI3K/Akt and transient receptor potential vanilloid 1 (TRPV1) signaling through astrocytes and microglia. LY294002 further alleviated BCP in rats, while the effects were reversed after treatment with insulin-like growth factor 1 (IGF-1). Both LSW and its active ingredient Bufalin were shown to inhibit the viability and migration of Walker 256 cells and induce apoptosis. Bufalin appears to be the key active ingredient of LSW and exerts its pain-relieving effects by suppressing PI3K/Akt and TRPV1 signaling in BCP.

Bionanoparticles with In Situ Nitric Oxide Release for Precise Modulation of ER-TRPV1 Ion Channels in Multimodal Killing of Glioblastoma.

Glioblastoma (GBM) with highly immunosuppressive tumor microenvironment is a significant factor contributing to its treatment resistance and low survival rate. The activation of the transient receptor potential vanilloid 1 (TRPV1) ion channel, which is overexpressed on the endoplasmic reticulum (ER) of GBM cells, governs the control of multi-organelle stress pathway branches to inhibit GBM expansion. Precise modulation of ER-TRPV1 is considered an effective strategy for inhibition of GBM. As an effective intracellular and extracellular second messenger, nitric oxide (•NO) activates the TRPV1 ion channel through nitrosylation of cysteine residues. However, the short lifespan and limited effective range of •NO makes it challenging to achieve precise regulation of ER-TRPV1. Herein, a biomimetic upconversion nanoassembly (M-UCN-T) is constructed, which encapsulates an organic •NO donor and is coated with homologous tumor-targeting cell membrane and ER-targeting peptide. In response to near-infrared light and glutathione, M-UCN-T releases •NO in situ to activate the ER-TRPV1 ion channels. This study developed a •NO-targeted release nanoplatform with stepwise targeting functions, which allow for the precise modulation of ER-TPRV1 in GBM through in situ release of •NO. This approach induces multi-organelle stress signaling pathways, ultimately resulting in multi-modal killing of tumor cells.

Solvent-mediated analgesia via the suppression of water permeation through TRPV1 ion channels.

Activation of the ion channel transient receptor potential vanilloid 1 (TRPV1), which is integral to pain perception, leads to an expansion of channel width, facilitating the passage of cations and large organic molecules. However, the permeability of TRPV1 channels to water remains uncertain, owing to a lack of suitable tools to study water dynamics. Here, using upconversion nanophosphors to discriminate between H2O and D2O, by monitoring water permeability across activated TRPV1 at the single-cell and single-molecule levels, and by combining single-channel current measurements with molecular dynamics simulations, we show that water molecules flow through TRPV1 and reveal a direct connection between water migration, cation flow and TRPV1 functionality. We also show in mouse models of acute or chronic inflammatory pain that the administration of deuterated water suppresses TRPV1 activity, interrupts the transmission of pain signals and mitigates pain without impacting other neurological responses. Solvent-mediated analgesia may inspire alternative options for pain management.

Antibody selection and automated quantification of TRPV1 immunofluorescence on human skin

Assessing localization of the transient receptor potential vanilloid-1 (TRPV1) in skin nerve fibers is crucial for understanding its role in peripheral neuropathy and pain. However, information on the specificity and sensitivity of TRPV1 antibodies used for immunofluorescence (IF) on human skin is currently lacking. To find a reliable TRPV1 antibody and IF protocol, we explored antibody candidates from different manufacturers, used rat DRG sections and human skin samples for screening and human TRPV1-expressing HEK293 cells for further validation. Final specificity assessment was done on human skin samples. Additionally, we developed two automated image analysis methods: a Python-based deep-learning approach and a Fiji-based machine-learning approach. These methods involve training a model or classifier for nerve fibers based on pre-annotations and utilize a nerve fiber mask to filter and count TRPV1 immunoreactive puncta and TRPV1 fluorescence intensity on nerve fibers. Both automated analysis methods effectively distinguished TRPV1 signals on nerve fibers from those in keratinocytes, demonstrating high reliability as evidenced by excellent intraclass correlation coefficient (ICC) values exceeding 0.75. This method holds the potential to uncover alterations in TRPV1 associated with neuropathic pain conditions, using a minimally invasive approach.

Microneedle patches incorporating zinc-doped mesoporous silica nanoparticles loaded with betamethasone dipropionate for psoriasis treatment

Treating psoriasis presents a major clinical challenge because of the limitations associated with traditional topical glucocorticoid therapy. This study introduced a drug delivery system utilizing zinc-doped mesoporous silica nanoparticle (Zn-MSN) and microneedle (MN), designed to enhance drug utilization for prolonged anti-inflammatory and anti-itch effects. The MN system facilitated the transdermal delivery of betamethasone dipropionate (BD), allowing its slow release. The BD@Zn-MSN-MN system promoted the polarization of macrophages towards the anti-inflammatory M2 phenotype, achieving superior anti-inflammatory effects compared to the clinically used BD cream. Additionally, this study demonstrated that BD@Zn-MSN-MN could further alleviate itching in psoriasis-afflicted mice by decreasing the excitability of the transient receptor potential vanilloid V1 (TRPV1) ion channel positive neurons and reducing the release of calcitonin gene-related peptide (CGRP) in the dorsal root ganglion (DRG). These findings offer new insights and effective therapeutic options for the future design of transdermal drug delivery for psoriasis.

Mechanosensitive release of ATP in the urinary bladder mucosa.

The urinary bladder mucosa (urothelium and suburothelium/lamina propria) functions as a barrier between the content of the urine and the underlying bladder tissue. The bladder mucosa is also a mechanosensitive tissue that releases signaling molecules that affect functions of cells in the bladder wall interconnecting the mucosa with the detrusor muscle and the CNS. Adenosine 5'-triphosphate (ATP) is a primary mechanotransduction signal that is released from cells in the bladder mucosa in response to bladder wall distention and activates cell membrane-localized P2X and P2Y purine receptors on urothelial cells, sensory and efferent neurons, interstitial cells, and detrusor smooth muscle cells. The amounts of ATP at active receptor sites depend significantly on the amounts of extracellularly released ATP. Spontaneous and distention-induced release of ATP appear to be under differential control. This review is focused on mechanisms underlying urothelial release of ATP in response to mechanical stimulation. First, we present a brief overview of studies that report mechanosensitive ATP release in bladder cells or tissues. Then, we discuss experimental evidence for mechanosensitive release of urothelial ATP by vesicular and non-vesicular mechanisms and roles of the stretch-activated channels PIEZO channels, transient receptor potential vanilloid type 4, and pannexin 1. This is followed by brief discussion of possible involvement of calcium homeostasis modulator 1, acid-sensing channels, and connexins in the release of urothelial ATP. We conclude with brief discussion of limitations of current research and of needs for further studies to increase our understanding of mechanotransduction in the bladder wall and of purinergic regulation of bladder function.

The expression of contextual fear conditioning involves the dorsal hippocampus TRPV1 receptor interacting with the NMDA/NO/cGMP signalling pathway.

The dorsal hippocampus (dHIP) is pivotal for learning, memory, and defensive responses. Transient receptor potential vanilloid type 1 (TRPV1) receptors in the dHIP modulate contextual fear conditioning by triggering a cascade involving glutamate release, nitric oxide (NO) formation and cyclic guanosine monophosphate (cGMP) production. The present study investigated the involvement of dHIP TRPV1 receptors and their interaction with the glutamate/NO/cGMP signalling pathway in modulating the expression of contextual fear conditioning (CFC). Male Wistar rats were submitted to an aversive contextual conditioning session and, 48 h later, were re-introduced to the same aversive environment where the freezing response and autonomic activity (evidenced by increased arterial pressure and heart rate and a decrease in tail temperature) were measured. The results demonstrated that the TRPV1 antagonist 6-I-CPS in dHIP reduced the expression of CFC, whereas the agonist capsaicin had the opposite effect. Furthermore, dHIP pre-treatment with an NMDA receptor antagonist (AP7), neuronal NO synthase inhibitor (N-propyl-L-arginine), NO scavenger (c-PTIO) or guanylate cyclase inhibitor (ODQ) attenuated capsaicin-induced increases in CFC. Finally, we observed that re-exposure to the aversive chamber increased dHIP NO levels in conditioned animals compared with a non-conditioned group, which was prevented by the administration of the TRPV1 antagonist, 6-I-CPS. Our study revealed that TRPV1 receptors in the dHIP play a crucial role in modulating contextual fear expression by acting through the NMDA receptor/NO/cGMP signalling pathway, providing important insights into the underlying mechanisms and potential therapeutic avenues associated with these pathways.

Palmitoylation by ZDHHC4 inhibits TRPV1-mediated nociception.

Transient receptor potential vanilloid 1 (TRPV1) is a capsaicin-sensitive ion channel implicated in pain sensation. While TRPV1 potentiation in hyperalgesia development has been extensively investigated, its functional decline during pain relief remains largely unexplored. Here, by molecular, electrophysiological and in vivo evidence, we reveal that S-palmitoylation fine-tunes TRPV1 function by promoting its degradation via the lysosome pathway thereby facilitating inflammatory pain relief. The palmitoyl acyltransferase ZDHHC4 is identified to physically interact with TRPV1 and to catalyze S-palmitoylation at the cysteine residues C157, C362, C390, and C715 of the channel. Furthermore, we show that TRPV1 palmitoylation is counterbalanced by the depalmitoylase acyl-protein thioesterase 1 (APT1), thereby reinstating pain sensation. These findings provide important mechanistic insights into the relief phase of inflammatory pain.

Electroacupuncture alleviates neuropathic pain in a rat model of CCD via suppressing P2X3 expression in dorsal root ganglia

BackgroundSciatica and low back pain are prevalent clinical types of neuropathic pain that significantly impair patients' quality of life. Conventional therapies often lack effectiveness, making these conditions challenging to treat. Electroacupuncture (EA) is an effective physiotherapy for pain relief. Prior research has demonstrated a relationship between the frequency of neuropathic pain and the analgesic impact of EA stimulation. This work aimed to assess the analgesic effects of EA in a rat model of chronic compression of the dorsal root ganglion (CCD) and to understand the underlying processes.MethodsWe established a rat CCD model to simulate sciatica and low back pain. EA was applied to rats with CCD at various frequencies (2 Hz, 100 Hz, and 2/100 Hz). The paw withdrawal threshold (PWT) was measured to assess analgesic effects. Additionally, protein levels of the purinergic receptor P2X3 (P2X3) and the expression of nociceptive neuronal markers were analyzed using immunohistochemistry and western blot (WB) techniques. The study also measured levels of proinflammatory cytokines TNF-α and IL-1β in the dorsal root ganglion (DRG). The involvement of P2X3 receptors was further investigated using the P2X3 agonist, α,β-methylene ATP (α,β-meATP).ResultsCCD rats developed pronounced mechanical allodynia. EA stimulation at all tested frequencies produced analgesic effects, with 2/100 Hz showing superior efficacy compared to 2 Hz and 100 Hz. The expression of P2X3 was increased in ipsilateral DRG of CCD model rats. P2X3 were co-labeled with isolectin B4 (IB4) and transient receptor potential vanilloid (TRPV1), indicating their role in nociception. 2/100 Hz EA treatment significantly reduced mechanical allodynia and inhibited the overexpression of P2X3, TRPV1, substance P (SP), and calcitonin gene-related peptide (CGRP) in the ipsilateral DRG of CCD model rats. Additionally, EA reduced the levels of proinflammatory cytokines TNF-α and IL-1β in the ipsilateral DRG, indicating an anti-inflammatory effect. The P2X3 agonist α,β-me ATP attenuated the analgesic effect of 2/100 Hz EA in CCD rats. The WB and immunofluorescence results consistently demonstrated P2X3 inhibition contributed to the analgesic effects of 2/100 Hz EA on CCD-induced neuropathic pain.ConclusionsOur findings suggest that 2/100 Hz EA alleviates neuropathic pain in rats by inhibiting the upregulation of P2X3 receptors in the ipsilateral DRG. This study backs up EA as a viable treatment option for sciatica and low back pain in clinical settings.

TRPV4-mediated Mechanotransduction Regulates the Differentiation of Valvular Interstitial Cells to Myofibroblasts: Implications for Aortic Stenosis.

As aortic valve stenosis (AVS) progresses, the valve tissue also stiffens. This increase in tissue stiffness causes the valvular interstitial cells (VICs) to transform into myofibroblasts in response. VIC-to-myofibroblast differentiation is critically involved in the development of AVS. Herein, we investigated the role of mechanosensitive Ca 2+ -permeant transient receptor potential vanilloid 4 (Trpv4) channels in matrix stiffness- and transforming growth factor β1 (TGFβ1)-induced VIC-myofibroblast activation. We confirmed Trpv4 functionality in primary mouse wild-type VICs compared to Trpv4 null VICs using live Ca 2+ influx detection during application of its selective agonist and antagonist. Using physiologically relevant hydrogels of varying stiffness that respectively mimic healthy or diseased aortic valve tissue stiffness, we found that genetic ablation of Trpv4 blocked matrix stiffness- and TGFβ1-induced VIC-myofibroblast activation as determined by changes in morphology, alterations of expression of α-smooth muscle actin, and modulations of F-actin generation. Our results showed that N-terminal residues 30-130 in Trpv4 were crucial for cellular force generation and VIC-myofibroblast activation, while deletion of residues 1-30 had no noticeable negative effect on these processes. Collectively, these data suggest a differential regulatory role for Trpv4 in stiffness/TGFβ1-induced VIC-myofibroblast activation. Our data further showed that Trpv4 regulates stiffness/TGFβ1-induced PI3K-AKT activity that is required for VIC-myofibroblast differentiation and cellular force generation, suggesting a mechanism by which Trpv4 activity regulates VIC-myofibroblast activation. Altogether, these data identify a novel role for Trpv4 mechanotransduction in regulating VIC-myofibroblast activation, implicating Trpv4 as a potential therapeutic target to slow and/or reverse AVS development.

GLP-1 and its derived peptides mediate pain relief through direct TRPV1 inhibition without affecting thermoregulation

Hormonal regulation during food ingestion and its association with pain prompted the investigation of the impact of glucagon-like peptide-1 (GLP-1) on transient receptor potential vanilloid 1 (TRPV1). Both endogenous and synthetic GLP-1, as well as a GLP-1R antagonist, exendin 9–39, reduced heat sensitivity in naïve mice. GLP-1-derived peptides (liraglutide, exendin-4, and exendin 9–39) effectively inhibited capsaicin (CAP)-induced currents and calcium responses in cultured sensory neurons and TRPV1-expressing cell lines. Notably, exendin 9–39 alleviated CAP-induced acute pain, as well as chronic pain induced by complete Freund’s adjuvant (CFA) and spared nerve injury (SNI), in mice without causing hyperthermia associated with other TRPV1 inhibitors. Electrophysiological analyses revealed that exendin 9–39 binds to the extracellular side of TRPV1, functioning as a noncompetitive inhibitor of CAP. Exendin 9–39 did not affect proton-induced TRPV1 activation, suggesting its selective antagonism. Among the exendin 9–39 fragments, exendin 20–29 specifically binds to TRPV1, alleviating pain in both acute and chronic pain models without interfering with GLP-1R function. Our study revealed a novel role for GLP-1 and its derivatives in pain relief, suggesting exendin 20–29 as a promising therapeutic candidate.

Osteopontin Regulates AQP4 Expression by TRPV4 Activation in Müller Cells: Implications for Retinal Homeostasis.

During the intense neuronal activity in the retina, Müller cells are exposed to a hypotonic environment and activate a regulatory volume decrease (RVD) response, which depends on Aquaporin-4 (AQP4) and the calcium channel Transient Receptor Potential Vanilloid 4 (TRPV4). It was reported that Osteopontin (OPN), a cytokine and component of the extracellular matrix (ECM), may modulate the RVD of Müller cells. In other cell types, OPN participates in cell survival and migration, which Müller cells undergo to maintain retinal homeostasis. Therefore, the aim of this work was to study the putative crosstalk of OPN with AQP4 and/or TRPV4 in the main functions of Müller cells: RVD, morphology maintenance and migration. We used a human Müller cell line (MIO-M1) exposed to OPN and evaluated cell volume and osmotic permeability (Pf) during an osmotic swelling, AQP4 expression, cell morphology and migration. We observed that OPN induced a reduced Pf and RVD by downregulating AQP4 expression, which was prevented by TRPV4 inhibition. OPN also induced significant changes in cell morphology with an increased number of cytoplasmic projections. Finally, OPN reduced the migration of Müller cells, being this effect dependent on TRPV4. We propose that OPN affects water permeability and cell volume regulation of Müller cells by activating TRPV4 to reduce AQP4 expression. This represents a novel mechanism of regulation of water permeability by the ECM in Müller cells. Additionally, OPN-induced changes in morphology and migration of Müller cells may have an impact on retinal physiology.

MiR-203 modulates pregnant myometrium contractility via transient receptor potential vanilloid 4 channel expression.

Preterm labor is the leading cause of neonatal death and major morbidity but remains a poorly understood process with no effective tocolytic therapies. Recent work has identified the transient receptor potential vanilloid 4 (TRPV4) channel, a membrane calcium channel upregulated in uterine smooth muscle through gestation, as integral in the transition from quiescence to contraction in the gravid uterus. The present study builds upon these findings and investigates regulation of the TRPV4 channel during pregnancy in the murine and human uterus by micro-RNA 203 (miR-203). We find a progressive decrease in miR-203 expression during gestation, accompanied by a reciprocal increase in TRPV4 mRNA and protein expression. In human uterine smooth muscle cells (UtSMC), miR-203 overexpression reduces, and si-RNA-mediated silencing increases, TRPV4 expression. Studies using murine UtSMC demonstrate that miR-203 expression modulates TRPV4-mediated cytosolic calcium entry and contractility. Consistent with these findings, the response to pharmacologic TRVP4 agonists is increased in myometrial tissue from miRNA203 -/- mice compared to control mice. Moreover, we demonstrate that miR-203 binds specifically on the promoter region of TRPV4 to decrease expression. In murine inflammatory models of preterm labor, miR-203 overexpression prolongs pregnancy. Estradiol (E2) decreases miR-203 and increases TRPV4 expression, providing a potential physiologic link for the unique reciprocal relationship in UtSMC. Taken together, these findings provide evidence that miR-203 modulates uterine contractility during pregnancy via negative regulation of TRPV4. These findings support the hypothesis that targeting miR-203 holds the promise of an entirely novel approach to prevent prematurity and treat preterm labor.

Mild photothermal activation of TRPV1 pathway for enhanced calcium ion overload therapy of hepatocellular carcinoma

Transient receptor potential vanilloid 1 (TRPV1) pathway can result in the disruption of intracellular calcium ion (Ca2+) homeostasis, but how to effectively control the process of Ca2+ overload needs to be addressed for tumor treatment. Herein, we developed a mild photothermal activation of TRPV1 pathway strategy for enhanced Ca2+ overload therapy of hepatocellular carcinoma, in which the multifunctional nanoparticle (CNQ) loading with CaCO3, a novel polycyclic conjugated small molecule (2Br-NDIA) and quercetin (Qu) as the core for the efficient mild photothermal therapy (PTT). The photothermal property of CNQ can specifically activate the TRPV1 channel, which leads to mitochondrial Ca2+ overloading and the disruption of intracellular Ca2+ homeostasis. This CNQ-mediated activation of the TRPV1 channel by mild PTT provides an emerging paradigm for enhancing mitochondrial Ca2+ overload therapy and dismantling tumor self-defense, safely expanding cancer therapies for highly refractory tumors.

Upregulation of NGF/TrkA-Related Proteins in Dorsal Root Ganglion of Paclitaxel-Induced Peripheral Neuropathy Animal Model.

Paclitaxel (PTX) can induce chemotherapy-induced peripheral neuropathy (CIPN) as a side effect. The aim of this study was to understand the neurochemical changes induced by NGF/TrkA signaling in PTX-induced neuropathic pain. The PTX-induced CIPN mouse model was evaluated using nerve conduction velocity (NCV) and behavioral tests. Protein expression in mouse DRG was observed by Western blotting and immunohistochemistry. Nerve growth factor (NGF), IL-6, and IL-1β mRNA levels were determined using qRT-PCR by isolating total RNA from whole blood. PTX showed low amplitude and high latency values in NCV in mice, and induced cold allodynia and thermal hyperalgesia in behavioral assessment. Activating transcription factor 3 (ATF3) and MAPK pathway related proteins (ERK1/2), tropomyosin receptor kinase A (TrkA), calcitonin gene related peptide (CGRP) and transient receptor potential vanilloid 1 (TRPV1) were upregulated 7th and 14th days after 2 mg/kg and 10 mg/kg of PTX administration. Protein kinase C (PKC) was upregulated 7th days after 10 mg/kg PTX treatment and 14th days after 2 mg/kg and 10 mg/kg PTX administration. NGF, IL-6, and IL-1β fold change values also showed a time- and dose-dependent increase. Taken together, our findings may improve our understanding of the nociceptive symptoms associated with PTX-induced neuropathic pain and lead to the development of new treatments for peripheral neuropathy.