Transient Receptor Potential Vanilloid 4 Regulation of Adenosine Triphosphate Release by the Adenosine Triphosphate Transporter Vesicular Nucleotide Transporter, a Novel Therapeutic Target for Gastrointestinal Baroreception and Chronic Inflammation

Influence of extracellular ATP on mammalian sperm physiology

In addition to its central role in cellular metabolism, adenosine 5'-triphosphate (ATP) is an important extracellular signalling molecule involved in various physiological processes. In reproduction, extracellular ATP participates in both autocrine and paracrine paths regulating gametogenesis, gamete maturation and fertilisation. This review focusses on how extracellular ATP modulates sperm physiology with emphasis on the mammalian acrosome reaction. The presence of extracellular ATP in the reproductive tract is primarily determined by the ion channels and transporters that influence its movement within the cells comprising the tract. The main targets of extracellular ATP in spermatozoa are its own transporters, particularly species-specific sperm purinergic receptors. We also discuss notable phenotypes from knock-out mouse models and human Mendelian inheritance related to ATP release mechanisms, along with immunological, proteomic, and functional observations regarding sperm purinergic receptors and their involvement in sperm signalling.

TRPV4 Regulates the Macrophage Metabolic Response to Limit Sepsis-induced Lung Injury

Sepsis is a systemic inflammatory response that requires effective macrophage metabolic functions to resolve ongoing inflammation. Previous work showed that the mechanosensitive cation channel, transient receptor potential vanilloid 4 (TRPV4), mediates macrophage phagocytosis and cytokine production in response to lung infection. Here, we show that TRPV4 regulates glycolysis in a stiffness-dependent manner by augmenting macrophage glucose uptake by GLUT1. In addition, TRPV4 is required for LPS-induced phagolysosome maturation in a GLUT1-dependent manner. In a cecal slurry mouse model of sepsis, TRPV4 regulates sepsis-induced glycolysis as measured by BAL fluid (BALF) lactate and sepsis-induced lung injury as measured by BALF total protein and lung compliance. TRPV4 is necessary for bacterial clearance in the peritoneum to limit sepsis-induced lung injury. It is interesting that BALF lactate is increased in patients with sepsis compared with healthy control participants, supporting the relevance of lung cell glycolysis to human sepsis. These data show that macrophage TRPV4 is required for glucose uptake through GLUT1 for effective phagolysosome maturation to limit sepsis-induced lung injury. Our work presents TRPV4 as a potential target to protect the lung from injury in sepsis.

Involvement of the Transient Receptor Channels in Preclinical Models of Musculoskeletal Pain

BACKGROUND

Musculoskeletal pain is a condition that affects bones, muscles, and tendons and is present in various diseases and/or clinical conditions. This type of pain represents a growing problem with enormous socioeconomic impacts, highlighting the importance of developing treatments tailored to the patient's needs. TRP is a large family of non-selective cation channels involved in pain perception. Vanilloid (TRPV1 and TRPV4), ankyrin (TRPA1), and melastatin (TRPM8) are involved in physiological functions, including nociception, mediation of neuropeptide release, heat/cold sensing, and mechanical sensation.

OBJECTIVE

In this context, we provide an updated view of the most studied preclinical models of muscle hyperalgesia and the role of transient receptor potential (TRP) in these models.

METHODS

This review describes preclinical models of muscle hyperalgesia induced by intramuscular administration of algogenic substances and/or induction of muscle damage by physical exercise in the masseter, gastrocnemius, and tibial muscles.

RESULTS

The participation of TRPV1, TRPA1, and TRPV4 in different models of musculoskeletal pain was evaluated using pharmacological and genetic tools. All the studies detected the antinociceptive effect of respective antagonists or reduced nociception in knockout mice.

CONCLUSION

Hence, TRPV1, TRPV4, and TRPA1 blockers could potentially be utilized in the future for inducing analgesia in muscle hypersensitivity pathologies.

SLC17A9 as a prognostic biomarker correlated with immune infiltrates in human non-small cell lung cancer

The vesicular nucleotide transporter (SLC17A9) has been overexpressed in various cancers. Nonetheless, little is known about its influence on non-small cell lung cancer (NSCLC), including human lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC). Integrative bioinformatics analysis was performed to investigate the prognostic significance and underlying mechanisms of SLC17A9 in patients with NSCLC. Here, we found that SLC17A9 up-regulation was significantly correlated with overall survival in LUAD and LUSC (P < 0.05). Gene set enrichment analysis and protein-protein interaction results revealed that SLC17A9 up-regulation was linked to metabolic process, the hallmark of MYC targets, DNA repair, coagulation and complement. SLC17A9 expression was negatively associated with overall survival and positively related to most LUSC immune cells and immunoinhibitor (20/23), particularly immuno A2aR, PD-1, and CTLA-4 (P < 0.001). High SLC17A9 was associated with infiltrating levels of B cells, CD4+ T cells, M1 macrophages, and T cell exhaustion checkpoints such as PD-1, CTLA4, and LAG3 in LUAD. Moreover, Real-time PCR, MTS assay, EdU assay, ATP production assays and cell cycle analysis were performed to validate SLC17A9 knockdown in LUAD cells. SLC17A9 knockdown significantly inhibited cell proliferation and ATP levels by affecting P2X1, Cytochrome C, and STAT3 expression in lung cancer cells. In conclusion, the present study suggested that SLC17A9 could potentially serve as a prognostic biomarker and correlated with immune infiltrates in LUAD and LUSC.

Physiological and Pathological Significance of Esophageal TRP Channels: Special Focus on TRPV4 in Esophageal Epithelial Cells

Transient receptor potential vanilloid 4 (TRPV4) is a non-selective cation channel that is broadly expressed in different human tissues, including the digestive system, where it acts as a molecular sensor and a transducer that regulates a variety of functional activities. Despite the extensive research to determine the role of this channel in the physiology and pathophysiology of different organs, the unique morphological and functional features of TRPV4 in the esophagus remain largely unknown. Ten years ago, TRPV4 was shown to be highly expressed in esophageal epithelial cells where its activation induces Ca²⁺-dependent ATP release, which, in turn, mediates several functions, ranging from mechanosensation to wound healing. This review summarizes the research progress on TRPV4, and focuses on the functional expression of TRPV4 in esophageal epithelium and its possible role in different esophageal diseases that would support TRPV4 as a candidate target for future therapeutic approaches to treat patients with these conditions.

The Cutting Edge Research of Functional Gastrointestinal Disorders in Japan: Review on JGA Core Symposium 2018-2020

Highly impacted articles on functional gastrointestinal (GI) disorders research presented at the core symposium held in the Japanese Gastroenterological Association (JGA) annual meeting 2018-2020 are selected and summarized. Regarding visceral hypersensitivity and sensor in GI tracts, transient receptor potential vanilloid 4 ion channel and acid-sensitive ion channel were candidates for hypersensitivity in GI tracts. ATP release from vesicular nucleotide transporter may be a key pathway to sensitize the nerve endings. Regarding inflammation and mucosal immune responses, patients infected with H. pylori having Ser70 type single nucleotide polymorphism of NapA gene was associated with H. pylori-related dyspepsia via gastric dysmotility. Gastric histology infected with Ser70 type NapA was shown severe infiltration of neutrophils into intramuscular layer. Macrophages, mast cells, and neutrophils are infiltrated in the colon of irritable bowel syndrome (IBS) patients and the locally produced IL-1β upregulated brain-derived neurotrophic factor (BDNF) in enteric glia cells. BDNF can also stimulate nerve endings and might be linked to pain in the colon. Dysbiosis in the composition of commensal bacteria communities is associated with the pathogenesis of various diseases including IBS and gut-brain interaction. The investigation on the mucosa-associated microbiota (MAM) is essential for understanding the interactions. The α-diversity and β-diversity of MAM indices are significantly different among IBS-D, IBS-C, and controls, and the different diversity might contribute to the pathophysiology of IBS. As research works on psychosocial factors show, maternal separation animal model was used and it is early life stress. The stress had induced colonic hyper-contraction, gastric hypersensitivity, and delayed emptying. The precise molecular mechanisms are still under investigations.

Purinergic P2 Receptors: Novel Mediators of Mechanotransduction

Mechanosensing and mechanotransduction are vital processes in mechanobiology and play critical roles in regulating cellular behavior and fate. There is increasing evidence that purinergic P2 receptors, members of the purinergic family, play a crucial role in cellular mechanotransduction. Thus, information on the specific mechanism of P2 receptor-mediated mechanotransduction would be valuable. In this review, we focus on purinergic P2 receptor signaling pathways and describe in detail the interaction of P2 receptors with other mechanosensitive molecules, including transient receptor potential channels, integrins, caveolae-associated proteins and hemichannels. In addition, we review the activation of purinergic P2 receptors and the role of various P2 receptors in the regulation of various pathophysiological processes induced by mechanical stimuli.

Physiopathological roles of vesicular nucleotide transporter (VNUT), an essential component for vesicular ATP release

Vesicular nucleotide transporter (VNUT) is the last identified member of the SLC17 organic anion transporter family, which plays a central role in vesicular storage in ATP-secreting cells. The discovery of VNUT demonstrated that, despite having been neglected for a long time, vesicular ATP release represents a major pathway for purinergic chemical transmission, which had been mainly attributed to ATP permeation channels. This article summarizes recent advances in our understanding of the mechanism of VNUT and its physiopathological roles as well as the development of inhibitors. Regulating the activity and/or the expression of VNUT represents a new and promising therapeutic strategy for the treatment of multiple diseases.

P2X7 receptor antagonist recovers ileum myenteric neurons after experimental ulcerative colitis

BACKGROUND

The P2X7 receptor is expressed by enteric neurons and enteric glial cells. Studies have demonstrated that administration of a P2X7 receptor antagonist, brilliant blue G (BBG), prevents neuronal loss.

AIM

To report the effects of BBG in ileum enteric neurons immunoreactive (ir) following experimental ulcerative colitis in Rattus norvegicus albinus.

METHODS

2,4,6-trinitrobenzene sulfonic acid (TNBS group, n = 5) was injected into the distal colon. BBG (50 mg/kg, BBG group, n = 5) or vehicle (sham group, n = 5) was given subcutaneously 1 h after TNBS. The animals were euthanized after 24 h, and the ileum was removed. Immunohistochemistry was performed on the myenteric plexus to evaluate immunoreactivity for P2X7 receptor, neuronal nitric oxide synthase (nNOS), choline acetyltransferase (ChAT), HuC/D and glial fibrillary acidic protein.

RESULTS

The numbers of nNOS-, ChAT-, HuC/D-ir neurons and glial fibrillary acidic protein-ir glial cells were decreased in the TNBS group and recovered in the BBG group. The neuronal profile area (μm²) demonstrated that nNOS-ir neurons decreased in the TNBS group and recovered in the BBG group. There were no differences in the profile areas of ChAT- and HuC/D-ir neurons.

CONCLUSION

Our data conclude that ileum myenteric neurons and glial cells were affected by ulcerative colitis and that treatment with BBG had a neuroprotective effect. Thus, these results demonstrate that the P2X7 receptor may be an important target in therapeutic strategies.