Blockage of TRPV4 Downregulates the Nuclear Factor-Kappa B Signaling Pathway to Inhibit Inflammatory Responses and Neuronal Death in Mice with Pilocarpine-Induced Status Epilepticus

TRPV4 Blockage Inhibits the Neurogenesis in the Adult Hippocampal Dentate Gyrus Following Pilocarpine‑Induced Status Epilepticus

Aberrant neurogenesis in the adult hippocampal dentate gyrus (DG) contributes to synapse remodeling during temporal lobe epilepsy (TLE). Transient receptor potential vanilloid 4 (TRPV4) is involved in the pathogenesis of TLE. Activation of TRPV4 can modulate neurogenesis in the adult hippocampal DG. The present study examined whether TRPV4 is responsible for the aberrant neurogenesis in the adult hippocampal DG during TLE. Herein, administration of a TRPV4-specific antagonist, HC-067047, attenuated the enhanced neural stem cell proliferation in the adult hippocampal DG in mice following pilocarpine‑induced status epilepticus (PISE). HC-067047 reduced the heightened hippocampal protein levels of cyclin-dependent kinase (CDK) 2, CDK6, cyclin E1, cyclin A2, and phosphorylated retinoblastoma (p-Rb) observed following PISE. Meanwhile, HC-067047 inhibited the extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (p38 MAPK) pathways that were enhanced and responsible for the increased proliferation of stem cells and higher levels of CDKs, cyclins, and p-Rb protein. HC-067047 reduced the 28-day-old BrdU+ cells but increased the ratio of 28-day-old BrdU+ cells to 1-day-old BrdU+ cells, indicating that TRPV4 blockage reduced the number but increased the survival rate of newborn cells following PISE. Finally, HC-067047 increased the Akt signaling that was inhibited and responsible for the decreased survival rate of newborn cells following PISE. It is concluded that TRPV4 blockage inhibits stem cell proliferation in the hippocampal DG following PISE, likely through inhibiting ERK1/2 and p38 MAPK signaling to decrease cell cycle-related protein expression, and increases newborn cell survival rate likely through increasing phosphoinositide 3 kinase-Akt signaling.

TRPV4 Channel in Neurological Disease: from Molecular Mechanisms to Therapeutic Potential

Transient Receptor Potential Vanilloid 4 (TRPV4) is a non-selective cation channel with pivotal roles in various physiological processes, including osmosensitivity, mechanosensation, neuronal development, vascular tone regulation, and bone homeostasis in human bodies. Recent studies have made significant progress in understanding the structure and functional role of TRPV4, shedding light on its involvement in pathological processes, particularly in the realm of neurological diseases. Here, we aim to provide a comprehensive exploration of the multifaceted contributions of TRPV4 to neurological diseases, spanning its intricate molecular mechanisms to its potential as a target for therapeutic interventions. We delve into the structural and functional attributes of TRPV4, scrutinize its expression profile, and elucidate the possible mechanisms through which it participates in the pathogenesis of neurological disorders. Furthermore, we discussed recent years' progress in therapeutic strategies aimed at harnessing TRPV4 for the treatment of these diseases. These insights will provide a basis for understanding and designing modality-specific pharmacological agents to treat TRPV4-associated disorders.

Lasmiditan ameliorates serotonergic itch in mice: Possible involvement of 5-HT1F receptors

Previously, some allergic conditions involving pruritus have been linked to migraine, raising the possibility that migraine and itching may be governed by similar underlying mechanisms. We aimed to investigate the efficacy of Lasmiditan, a highly selective agonist of the 5-hydroxytryptamine 1F (5-HT1F) receptor and a recently approved medication for the treatment of migraine headaches, in ameliorating serotonergic itching. Forty animals were employed in the present study (n = 40). Eight animals were randomly assigned to each of the following study groups (n = 8, in each group): (1) "Normal Saline": This group was given intradermal injections of normal saline (2) "5-HT": The animals were injected with intradermal 5-HT, which was used to induce itching. (3) "Lasmiditan 0.3", "Lasmiditan 1", and "Lasmiditan 3" groups: injected with 5-HT as well as intraperitoneal Lasmiditan at different dose levels (0.3, 1, and 3 mg/kg, respectively). Scratching behavior was recorded for 60 min, and the skin tissue of three mice was sampled at the end of the behavioral experiment to assess the levels of TLR-4, IL-31, 5-HT1F receptor, CGRP & TRPV4. In the present study, we found that Lasmiditan when administered at 1 mg/kg effectively reduced serotonin-induced itching compared to the "5-HT" group (P < 0.0001). Following the administration of Lasmiditan (1 mg/kg), the expression levels of the 5-HT1F receptor significantly increased (P < 0.01). Further, the levels of TLR-4, IL-31, CGRP & TRPV4 were substantially reduced upon the administration of Lasmiditan (1 mg/kg). We found that Lasmiditan is effective in reducing serotonergic itch in mice through its interaction with the 5-HT1F receptor in the skin tissue of mice.

Transient receptor potential channels in dental inflammation and pain perception: A comprehensive review

Transient Receptor Potential (TRP) channels are a family of ion channels that play pivotal roles in various physiological processes, including sensory transduction, temperature regulation, and inflammation. In the context of dentistry, recent research has highlighted the involvement of TRP channels in mediating sensory responses and inflammation in dental tissues and temporo-mandibular joint (TMJ) structure. TRP channels have emerged as major contributors in the development of inflammatory conditions and pain affecting the oral cavity and related structures, such as periodontitis, dental erosion cause hypersensitivity, pulpitis, and TMJ disorders. These inflammatory conditions notably contribute to oral health challenges, often leading to sharp pain, dull aches, and compromised functionality. Pharmacological interventions and emerging strategies aimed at modulating TRP channel activity are critically evaluated. The therapeutic potential of targeting TRP channels in the management within dental practice is a focal point of view to alleviate pain and inflammation. In conclusion, this comprehensive review provides a valuable synthesis of current knowledge regarding the involvement of TRP channels in inflammatory conditions of dentistry underscoring the potential of TRP channels as promising targets for therapeutic intervention, and then paving the way for innovative strategies to address the complexities of inflammatory dental conditions.

Zinc pyrithione ameliorates colitis in mice by interacting on intestinal epithelial TRPA1 and TRPV4 channels

AIMS

Although zinc pyrithione (ZPT) has been studied as topical antimicrobial and cosmetic consumer products, little is known about its pharmacological actions in gastrointestinal (GI) health and inflammation. Our aims were to investigate the effects of ZPT on transient receptor potential (TRP) channels and Ca2+ signaling in intestinal epithelial cells (IECs) and its therapeutic potential for colitis.

MAIN METHODS

Digital Ca2+ imaging and patch-clamp electrophysiology were performed on human colonic epithelial cells (HCoEpiC) and rat small intestinal epithelial cells (IEC-6). The transcription levels of proinflammatory cytokines such as IL-1β were detected by RTq-PCR. Dextran sulfate sodium (DSS) was used to induce colitis in mice.

KEY FINDINGS

ZPT dose-dependently induced Ca2+ signaling and membrane currents in IECs, which were attenuated by selective blockers of transient receptor potential ankyrin 1 (TRPA1) and transient receptor potential vanilloid 4 (TRPV4) channels, respectively. Interestingly, Ca2+ entry via TRPA1 channels inhibited the activity of TRPV4 channels in HCoEpiC, but not vice versa. ZPT significantly promoted migration of IECs by activating TRPA1 and TRPV4 channels. ZPT reversed lipopolysaccharides (LPS)-induced changes in mRNA expression of TRPA1 and TRPV4. Moreover, ZPT decreased mRNA levels of pro-inflammatory factors promoted by LPS in HCoEpiC, which were restored by selective TRPA1 blocker. In whole animal studies in vivo, ZPT significantly ameliorated DSS-induced body weight loss, colon shortening and increases in stool score, serum calprotectin and lactic acid (LD) in mouse model of colitis.

SIGNIFICANCE

ZPT exerts anti-colitic action likely by anti-inflammation and pro-mucosal healing through TRP channels in IECs. The present study not only expands pharmacology spectrum of ZPT in GI tract, but also repurposes it to a potential drug for colitis therapy.

Inflammation-induced TRPV4 channels exacerbate blood-brain barrier dysfunction in multiple sclerosis

BACKGROUND

Blood-brain barrier (BBB) dysfunction and immune cell migration into the central nervous system (CNS) are pathogenic drivers of multiple sclerosis (MS). Ways to reinstate BBB function and subsequently limit neuroinflammation present promising strategies to restrict disease progression. However, to date, the molecular players directing BBB impairment in MS remain poorly understood. One suggested candidate to impact BBB function is the transient receptor potential vanilloid-type 4 ion channel (TRPV4), but its specific role in MS pathogenesis remains unclear. Here, we investigated the role of TRPV4 in BBB dysfunction in MS.

MAIN TEXT

In human post-mortem MS brain tissue, we observed a region-specific increase in endothelial TRPV4 expression around mixed active/inactive lesions, which coincided with perivascular microglia enrichment in the same area. Using in vitro models, we identified that microglia-derived tumor necrosis factor-α (TNFα) induced brain endothelial TRPV4 expression. Also, we found that TRPV4 levels influenced brain endothelial barrier formation via expression of the brain endothelial tight junction molecule claudin-5. In contrast, during an inflammatory insult, TRPV4 promoted a pathological endothelial molecular signature, as evidenced by enhanced expression of inflammatory mediators and cell adhesion molecules. Moreover, TRPV4 activity mediated T cell extravasation across the brain endothelium.

CONCLUSION

Collectively, our findings suggest a novel role for endothelial TRPV4 in MS, in which enhanced expression contributes to MS pathogenesis by driving BBB dysfunction and immune cell migration.

TRP (transient receptor potential) ion channel family: structures, biological functions and therapeutic interventions for diseases

Transient receptor potential (TRP) channels are sensors for a variety of cellular and environmental signals. Mammals express a total of 28 different TRP channel proteins, which can be divided into seven subfamilies based on amino acid sequence homology: TRPA (Ankyrin), TRPC (Canonical), TRPM (Melastatin), TRPML (Mucolipin), TRPN (NO-mechano-potential, NOMP), TRPP (Polycystin), TRPV (Vanilloid). They are a class of ion channels found in numerous tissues and cell types and are permeable to a wide range of cations such as Ca²⁺, Mg²⁺, Na⁺, K⁺, and others. TRP channels are responsible for various sensory responses including heat, cold, pain, stress, vision and taste and can be activated by a number of stimuli. Their predominantly location on the cell surface, their interaction with numerous physiological signaling pathways, and the unique crystal structure of TRP channels make TRPs attractive drug targets and implicate them in the treatment of a wide range of diseases. Here, we review the history of TRP channel discovery, summarize the structures and functions of the TRP ion channel family, and highlight the current understanding of the role of TRP channels in the pathogenesis of human disease. Most importantly, we describe TRP channel-related drug discovery, therapeutic interventions for diseases and the limitations of targeting TRP channels in potential clinical applications.