TRPV channels in tumor growth and progression. Adv Exp Med Biol. 2011;704:947-967. [PMID: 21290335 DOI: 10.1007/978-94-007-0265-3_49]

A pan-cancer study of ADAM9's immunological function and prognostic value particularly in liver cancer

A pan-cancer analysis summarizing the overall changes in mRNA and protein stability of ADM9, as well as its oncogenic function on immune cell line modulation and checkpoints within the tumor microenvironment (TME), is lacking, despite the fact that ADM9 up-regulation is correlated with the progression of many cancers. Therefore, in this study, we comprehensively analyzed the role of ADAM9 expression and its prognostic value in different cancers to fill this gap. Multiple bioinformatics databases such as Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx), and Clinical Proteomic Tumor Analysis Consortium (CPTAC) were used to evaluate the ADAM9 genetic alternation, phosphorylation, and methylation, and indicated highly positive correlated genes that might play a critical interaction with ADAM9 and their molecular function with GO analysis. We also evaluate the effect of higher ADAM9 with prominent immune modulatory genes and immune infiltration especially in liver cancer pathogenesis stimulates lower NK cell effector functions based on its role in MICA shedding and increasing the Tregs infiltration. Immunohistochemistry (IHC) staining from 90 pathologically verified samples proved the positive correlation between ADAM9 and tumor stages and proved the higher expression of ADAM9 correlated genes (SNX9, APP, TNF, CDH1, ITGAV, MAD2L2) in HCC pathogenesis. In conclusion, this pan-cancer study provides a comprehensive understanding of the prognostic value of ADAM9 in various tumors emphasizing its importance to be considered as an innovative treatment approach, especially in tumor immunity shortly.

TRPV3 facilitates lipolysis and attenuates diet-induced obesity via activation of the NRF2/FSP1 signaling axis

Transient receptor potential vanilloid (TRPV) ion channels play a crucial role in various cellular functions by regulating intracellular Ca2+ levels and have been extensively studied in the context of several metabolic diseases. However, the regulatory effects of TRPV3 in obesity and lipolysis are not well understood. In this study, utilizing a TRPV3 gain-of-function mouse model (TRPV3G568V/G568V), we assessed the metabolic phenotype of both TRPV3G568V/G568V mice and their control littermates, which were randomly assigned to either a 12-week high-fat diet or a control diet. We investigated the potential mechanisms underlying the role of TRPV3 in restraining obesity and promoting lipolysis both in vivo and in vitro. Our findings indicate that a high-fat diet led to significant obesity, characterized by increased epididymal and inguinal white adipose tissue weight and higher fat mass. However, the gain-of-function mutation in TRPV3 appeared to counteract these adverse effects by enhancing lipolysis in visceral fat through the upregulation of the major lipolytic enzyme, adipocyte triglyceride lipase (ATGL). In vitro experiments using carvacrol, a TRPV3 agonist, demonstrated the promotion of lipolysis and antioxidation in 3T3-L1 adipocytes after TRPV3 activation. Notably, carvacrol failed to stimulate Ca2+ influx, lipolysis, and antioxidation in 3T3-L1 adipocytes treated with BAPTA-AM, a cell-permeable calcium chelator. Our results revealed that TRPV3 activation induced the action of transcriptional factor nuclear factor erythroid 2-related factor 2 (NRF2), resulting in increased expression of ferroptosis suppressor protein 1 (FSP1) and superoxide dismutase2 (SOD2). Moreover, the inhibition of NRF2 impeded carvacrol-induced lipolysis and antioxidation in 3T3-L1 adipocytes, with downregulation of ATGL, FSP1, and SOD2. In summary, our study suggests that TRPV3 promotes visceral fat lipolysis and inhibits diet-induced obesity through the activation of the NRF2/FSP1 signaling axis. We propose that TRPV3 may be a potential therapeutic target in the treatment of obesity.

Transient receptor potential vanilloid-1 (TRPV1) channels act as suppressors of the growth of glioma

The aim of this study was to investigate the expression and function of the transient receptor potential vanilloid 1 (TRPV1) in glioma. We found that the expression of TRPV1 mRNA and protein were upregulated in glioma compared with normal brain by qPCR and western blot analysis. In order to investigate the function of TRPV1 in glioma, short hairpin RNA (shRNA) and the inhibitor of TRPV1 were used. In vitro, the activation of TRPV1 induced cell apoptosis with decreased migration capability and inhibited proliferation, which was abolished upon TRPV1 pharmacological inhibition and silencing. Mechanistically, TRPV1 modulated glioma proliferation through the protein kinase B (Akt) signaling pathway. More importantly, in immunodeficient (NOD-SCID) mouse xenograft models, tumor size was significantly increased when TRPV1 expression was disrupted by a shRNA knockdown approach in vivo. Altogether, our findings indicate that TRPV1 negatively controls glioma cell proliferation in an Akt-dependent manner, which suggests that targeting TRPV1 may be a potential therapeutic strategy for glioma.

Advances in TRPV6 inhibitors for tumors by targeted therapies: Macromolecular proteins, synthetic small molecule compounds, and natural compounds

TRPV6, a Ca2+-selective member of the transient receptor potential vanilloid (TRPV) family, plays a key role in extracellular calcium transport, calcium ion reuptake, and maintenance of a local low calcium environment. An increasing number of studies have shown that TRPV6 is involved in the regulation of various diseases. Notably, overexpression of TRPV6 is closely related to the occurrence of various cancers. Research confirmed that knocking down TRPV6 could effectively reduce the proliferation and invasiveness of tumors by mainly mediating the calcium signaling pathway. Hence, TRPV6 has become a promising new drug target for numerous tumor treatments. However, the development of TRPV6 inhibitors is still in the early stage, and the existing TRPV6 inhibitors have poor selectivity and off-target effects. In this review, we focus on summarizing and describing the structure characters, and mechanisms of existing TRPV6 inhibitors to provide new ideas and directions for the development of novel TRPV6 inhibitors.

A TRP to Pathological Angiogenesis and Vascular Normalization

Uncontrolled angiogenesis underlies various pathological conditions such as cancer, age-related macular degeneration (AMD), and proliferative diabetic retinopathy (PDR). Hence, targeting pathological angiogenesis has become a promising strategy for the treatment of cancer and neovascular ocular diseases. However, current pharmacological treatments that target VEGF signaling have met with limited success either due to acquiring resistance against anti-VEGF therapies with serious side effects including nephrotoxicity and cardiovascular-related adverse effects in cancer patients or retinal vasculitis and intraocular inflammation after intravitreal injection in patients with AMD or PDR. Therefore, there is an urgent need to develop novel strategies which can control multiple aspects of the pathological microenvironment and regulate the process of abnormal angiogenesis. To this end, vascular normalization has been proposed as an alternative for antiangiogenesis approach; however, these strategies still focus on targeting VEGF or FGF or PDGF which has shown adverse effects. In addition to these growth factors, calcium has been recently implicated as an important modulator of tumor angiogenesis. This article provides an overview on the role of major calcium channels in endothelium, TRP channels, with a special focus on TRPV4 and its downstream signaling pathways in the regulation of pathological angiogenesis and vascular normalization. We also highlight recent findings on the modulation of TRPV4 activity and endothelial phenotypic transformation by tumor microenvironment through Rho/YAP/VEGFR2 mechanotranscriptional pathways. Finally, we provide perspective on endothelial TRPV4 as a novel VEGF alternative therapeutic target for vascular normalization and improved therapy. © 2024 American Physiological Society. Compr Physiol 14:5389-5406, 2024.

The TRPV6 Calcium Channel and Its Relationship with Cancer

Transient receptor potential vanilloid-6 (TRPV6) is a cation channel belonging to the TRP superfamily, specifically the vanilloid subfamily, and is the sixth member of this subfamily. Its presence in the body is primarily limited to the skin, ovaries, kidney, testes, and digestive tract epithelium. The body maintains calcium homeostasis using the TRPV6 channel, which has a greater calcium selectivity than the other TRP channels. Several pieces of evidence suggest that it is upregulated in the advanced stages of thyroid, ovarian, breast, colon, and prostate cancers. The function of TRPV6 in regulating calcium signaling in cancer will be covered in this review, along with its potential applications as a cancer treatment target.

The role of TRPV ion channels in adipocyte differentiation: What is the evidence?

Obesity is a complex disorder, and the incidence of obesity continues to rise at an alarming rate worldwide. In particular, the growing incidence of overweight and obesity in children is a major health concern. However, the underlying mechanisms of obesity remain unclear and the efficacy of several approaches for weight loss is limited. As an important calcium-permeable temperature-sensitive cation channel, transient receptor potential vanilloid (TRPV) ion channels directly participate in thermo-, mechano-, and chemosensory responses. Modulation of TRPV ion channel activity can alter the physiological function of the ion channel, leading to neurodegenerative diseases, chronic pain, cancer, and skin disorders. In recent years, increasing studies have demonstrated that TRPV ion channels are abundantly expressed in metabolic organs, including the liver, adipose tissue, skeletal muscle, pancreas, and central nervous system, which has been implicated in various metabolic diseases, including obesity and diabetes mellitus. In addition, as an important process for the pathophysiology of adipocyte metabolism, adipocyte differentiation plays a critical role in obesity. In this review, we focus on the role of TRPV ion channels in adipocyte differentiation to broaden the ideas for prevention and control strategies for obesity.

"ThermoTRP" Channel Expression in Cancers: Implications for Diagnosis and Prognosis (Practical Approach by a Pathologist)

Temperature-sensitive transient receptor potential (TRP) channels (so-called "thermoTRPs") are multifunctional signaling molecules with important roles in cell growth and differentiation. Several "thermoTRP" channels show altered expression in cancers, though it is unclear if this is a cause or consequence of the disease. Regardless of the underlying pathology, this altered expression may potentially be used for cancer diagnosis and prognostication. "ThermoTRP" expression may distinguish between benign and malignant lesions. For example, TRPV1 is expressed in benign gastric mucosa, but is absent in gastric adenocarcinoma. TRPV1 is also expressed both in normal urothelia and non-invasive papillary urothelial carcinoma, but no TRPV1 expression has been seen in invasive urothelial carcinoma. "ThermoTRP" expression can also be used to predict clinical outcomes. For instance, in prostate cancer, TRPM8 expression predicts aggressive behavior with early metastatic disease. Furthermore, TRPV1 expression can dissect a subset of pulmonary adenocarcinoma patients with bad prognosis and resistance to a number of commonly used chemotherapeutic agents. This review will explore the current state of this rapidly evolving field with special emphasis on immunostains that can already be added to the armoire of diagnostic pathologists.

Role of extrinsic physical cues in cancer progression

The tumor microenvironment (TME) is a complex system composed of many cell types and an extracellular matrix (ECM). During tumorigenesis, cancer cells constantly interact with cellular components, biochemical cues, and the ECM in the TME, all of which make the environment favorable for cancer growth. Emerging evidence has revealed the importance of substrate elasticity and biomechanical forces in tumor progression and metastasis. However, the mechanisms underlying the cell response to mechanical signals-such as extrinsic mechanical forces and forces generated within the TME-are still relatively unknown. Moreover, having a deeper understanding of the mechanisms by which cancer cells sense mechanical forces and transmit signals to the cytoplasm would substantially help develop effective strategies for cancer treatment. This review provides an overview of biomechanical forces in the TME and the intracellular signaling pathways activated by mechanical cues as well as highlights the role of mechanotransductive pathways through mechanosensors that detect the altering biomechanical forces in the TME. as an adjuvant for cancer immunotherapy.[BMB Reports 2023; 56(5): 287-295].

Transient receptor potential vanilloid type 4 (TRPV4) promotes tumorigenesis via NFAT4 activation in nasopharyngeal carcinoma

Transient receptor potential vanilloid type 4 (TRPV4) can function as an oncogene or tumor suppressor depending on the tumor types. However, little is known regarding the effect of TRPV4 in nasopharyngeal carcinoma (NPC), a highly prevalent malignancy in Southern China and Southeast Asia. We found that TRPV4 mRNA and protein levels were significantly upregulated in NPC tissues. In addition, activation of TRPV4 in NPC cell lines using GSK1016790A (100 nM) induced a Ca²⁺ influx, whereas pharmacological inhibition or gene knockdown of TRPV4 reduced the proliferation rates of NPC cells. TRPV4 knockdown also decreased the growth of tumor xenografts in vivo. Mechanistically, TRPV4-mediated tumorigenesis is dependent on the activation of Ca²⁺/calcineurin/calcineurin-nuclear factor of activated T cell 4 (NFAT4) signaling. Furthermore, NFAT4 protein level was overexpressed in NPC tissues and correlated positively with TRPV4. Taken together, TRPV4 promotes the malignant potential of NPC cells by activating NFAT4 signaling. Our findings highlight TRPV4-NFAT4 axis as a potential therapeutic target in NPC.

Transient receptor potential vanilloid subtype 1: A potential therapeutic target for fibrotic diseases

The transient receptor potential vanilloid subtype 1 (TRPV1), belonging to the TRPV channel family, is a non-selective, calcium-dependent, cation channel implicated in several pathophysiological processes. Collagen, an extracellular matrix component, can accumulate under pathological conditions and may lead to the destruction of tissue structure, organ dysfunction, and organ failure. Increasing evidence indicates that TRPV1 plays a role in the development and occurrence of fibrotic diseases, including myocardial, renal, pancreatic, and corneal fibrosis. However, the mechanism by which TRPV1 regulates fibrosis remains unclear. This review highlights the comprehensive role played by TRPV1 in regulating pro-fibrotic processes, the potential of TRPV1 as a therapeutic target in fibrotic diseases, as well as the different signaling pathways associated with TRPV1 and fibrosis.

TRPs in Ovarian Serous Cystadenocarcinoma: The Expression Patterns, Prognostic Roles, and Potential Therapeutic Targets

Ovarian cancer (usually ovarian serous cystadenocarcinoma, or OV) is the fifth leading cause of cancer-related deaths in women, with more than 184,000 deaths reported worldwide annually, and is a highly malignant carcinoma. However, the mechanism of etiology remains unclear. The lack of prognostic and diagnostic biomarkers is a main limitation for clinical diagnosis and treatment. The transient receptor potential (TRP) channels play essential roles in the occurrence and development of cancers which may have the potential as a therapeutic target for OV. In our study, we used bioinformatic methods to study the potential effect and function of the TRP family in patients with OV. Differential expression analysis showed that the expression of TRPC7, TRPV4, and other TRP family members was significantly different between tumor and normal tissues. Through survival analysis, we screened out that the high expression of TRPC7, TRPV4, and TRPM (2,4,8) was negatively correlated with the prognosis of patients. In contrast, the low expression of TRPM3 was negatively associated with the prognosis. Cox regression analysis further indicated that TRPV4 was OV’s most likely therapeutic target. Finally, we conducted mRNA expression analysis, functional enrichment analysis, and immune infiltration analysis to confirm that TRPV4 was the most convincing therapeutic target of OV.

Pan-cancer analyses reveal the genetic and pharmacogenomic landscape of transient receptor potential channels

Transient-receptor potential (TRP) channels comprise a diverse family of ion channels, which play important roles in regulation of intracellular calcium. Emerging evidence has revealed the critical roles of TRP channels in tumor development and progression. However, we still lack knowledge about the genetic and pharmacogenomics landscape of TRP genes across cancer types. Here, we comprehensively characterized the genetic and transcriptome alterations of TRP genes across >10,000 patients of 33 cancer types. We revealed prevalent somatic mutations and copy number variation in TRP genes. In particular, mutations located in transmembrane regions of TRP genes were likely to be deleterious mutations (p-values < 0.001). Genetic alterations were correlated with transcriptome dysregulation of TRP genes, and we found that TRPM2, TRPM8, and TPRA1 showed extent dysregulation in cancer. Patients with TRP gene alterations were with significantly higher hypoxia scores, tumor mutation burdens, tumor stages and grades, and poor survival. The alterations of TRP genes were significantly associated with the activity of cancer-related pathways. Moreover, we found that the expression of TRP genes were potentially useful for development of targeted therapies. Our study provided the landscape of genomic and transcriptomic alterations of TPRs across 33 cancer types, which is a comprehensive resource for guiding both mechanistic and therapeutic analyses of the roles of TRP genes in cancer. Identifying the TRP genes with extensive genetic alterations will directly contribute to cancer therapy in the context of predictive, preventive, and personalized medicine.

Multi-Omics Analysis of the Prognosis and Biological Function for TRPV Channel Family in Clear Cell Renal Cell Carcinoma

Background

The transient receptor potential vanilloid (TRPV) channels family, TRPV1-6, has been identified to profoundly affect a wide spectrum of pathological processes in various cancers. However, the biological function and prognostic value of TRPVs in clear cell renal cell carcinoma (ccRCC) are still largely unknown.

Methods

We obtained the gene expression data and clinical information of 539 ccRCC patients from The Cancer Genome Atlas (TCGA) database. A series of databases were used for data processing and visualization, including GEPIA, GeneMANIA, MethSurv, GSCA, TIMER, and starBase databases.

Results

The mRNA expression of TRPV2/3 was upregulated while the expression of TRPV5/6 was downregulated in ccRCC tumor tissues. TRPV family members in ccRCC were rarely mutated (nearly 7 frequencies). The ROC curve showed that TRPV2/5/6 had a high diagnostic ability in discriminating ccRCC from the control samples (AUC>0.9). Higher levels of TRPV3 expression were associated with poor prognosis of ccRCC patients, while higher expression of TRPV4 was associated with favorable prognosis. The expression of TRPV3 in normal and ccRCC tissues was validated by Immunohistochemistry, and its expression was remarkably related to high histologic grade and advanced stage. Besides, TRPV3 exhibit a reduction of DNA methylation level with tumor progression, and 12 CpGs of TRPV3 were associated with a significant prognosis. In addition, TRPV3 expression was significantly associated with the accumulation of several tumor-infiltrating immune cells, especially regulatory T cells. Furthermore, high levels of TRPV3 induced the expression of immune checkpoints such as LAG3, CTLA4, PDCD1, and TIGIT. Finally, we predicted a key SNHG3/AL513497.1-miR-10b-5p-TRPV3 axis linking to carcinogenesis and progression of ccRCC.

Conclusion

Our study may uncover TRPV channels–associated molecular mechanisms involved in the tumorigenesis and progression of ccRCC. TRPV family members might be diagnosed and prognostic markers and potential therapeutic targets for ccRCC patients.

Down-regulation of TRPV6 Is Associated With Adverse Prognosis in Hepatocellular Carcinoma Treated With Curative Resection

BACKGROUND/AIM

Transient receptor potential vanilloid 6 (TRPV6), an endothelial Ca2+-selective entry channel, is expressed in various cancer types, and a selective TRPV6 inhibitor is currently being investigated in a clinical trial. However, TRPV6 expression in hepatocellular carcinoma (HCC) has not been reported.

MATERIALS AND METHODS

We evaluated TRPV6 expression in 219 cases of HCC and analyzed its association with clinicopathological parameters and prognostic significance. TRPV6 mRNA expression was compared between HCC and non-tumor liver tissues using various public datasets, and its prognostic effect was examined in The Cancer Genome Atlas (TCGA) cohort.

RESULTS

Low TRPV6 expression was found in 37.4% of patients, which was significantly associated with adverse histologic features, and patients with low TRPV6 expression had shorter recurrence-free and disease-free survival. TRPV6 mRNA expression was consistently lower in HCC compared to non-tumor liver samples in public datasets, at the whole tissue level as well as single-cell level. Patients with low TRPV6 expression in the TCGA cohort had shorter progression-free survival.

CONCLUSION

TRPV6 expression is down-regulated in HCCs and associated with a poor prognosis. TRPV6 may be a prognostic biomarker in HCC.

TRPV Protein Family-From Mechanosensing to Cancer Invasion

Biophysical cues from the cellular microenvironment are detected by mechanosensitive machineries that translate physical signals into biochemical signaling cascades. At the crossroads of extracellular space and cell interior are located several ion channel families, including TRP family proteins, that are triggered by mechanical stimuli and drive intracellular signaling pathways through spatio-temporally controlled Ca2+-influx. Mechanosensitive Ca2+-channels, therefore, act as critical components in the rapid transmission of physical signals into biologically compatible information to impact crucial processes during development, morphogenesis and regeneration. Given the mechanosensitive nature of many of the TRP family channels, they must also respond to the biophysical changes along the development of several pathophysiological conditions and have also been linked to cancer progression. In this review, we will focus on the TRPV, vanilloid family of TRP proteins, and their connection to cancer progression through their mechanosensitive nature.

Infrared neural stimulation at different wavelengths and pulse shapes

Neural stimulation with infrared radiation has been explored for brain tissue, peripheral nerves, and cranial nerves including the auditory nerve. Initial experiments were conducted at wavelengths between λ = 1850 and λ = 2140 nm and the radiant energy was delivered with square pulses. Water absorption of the infrared radiation at λ = 1860 nm is similar to absorption at wavelengths between λ = 1310 and λ = 1600 nm, which are in the radiation wavelength range used for the communication industry. Technology for those wavelengths has already been developed and miniaturized and is readily available. The possibility of the infrared light to evoke compound action potentials (CAP) in the cochlea at λ = 1,375, λ = 1,460, and λ = 1550 nm was explored and compared to that of λ = 1860 nm in guinea pigs. Furthermore, rise and fall times of the 100 μs long pulses were changed and four basic pulse shapes (square, triangular, ramp-up, and ramp-down) were explored in their ability to evoke a CAP. In animals with pure tone threshold averages (PTAs) above 70 dB SPL, the results show that the favorable wavelength is λ = 1460 nm to reach threshold for stimulation and λ = 1375 nm or λ = 1460 nm for obtaining maximum amplitude. The most favorable pulse shape is either ramp-up or triangular.

Mutations in calmodulin-binding domains of TRPV4/6 channels confer invasive properties to colon adenocarcinoma cells

Transient receptor potential (TRP) channels form a family of polymodal cation channels gated by thermal, mechanical, or chemical stimuli, with many of them involved in the control of proliferation, apoptosis, or cell cycle. From an evolutionary point of view, TRP family is characterized by high conservation of duplicated genes originating from whole-genome duplication at the onset of vertebrates. The conservation of such “ohnolog” genes is theoretically linked to an increased probability of generating phenotypes deleterious for the organism upon gene mutation. We aimed to test experimentally the hypothesis that TRP mutations, in particular gain-of-function, could be involved in the generation of deleterious phenotypes involved in cancer, such as gain of invasiveness. Indeed, a number of TRP channels have been linked to cancer progression, and exhibit changes in expression levels in various types of cancers. However, TRP mutations in cancer have been poorly documented. We focused on 2 TRPV family members, TRPV4 and TRPV6, and studied the effect of putative gain-of-function mutations on invasiveness properties. TRPV channels have a C-terminal calmodulin-binding domain (CaMBD) that has important functions for regulating protein function, through different mechanisms depending on the channel (channel inactivation/potentiation, cytoskeleton regulation). We studied the effect of mutations mimicking constitutive phosphorylation in TRPV4 and TRPV6 CaMBDs: TRPV4 S823D, S824D and T813D, TRPV6 S691D, S692D and T702. We found that most of these mutants induced a strong gain of invasiveness of colon adenocarcinoma SW480 cells, both for TRPV4 and TRPV6. While increased invasion with TRPV6 S692D and T702D mutants was correlated to increased mutant channel activity, it was not the case for TRPV4 mutants, suggesting different mechanisms with the same global effect of gain in deleterious phenotype. This highlights the potential importance to search for TRP mutations involved in cancer.

Near-infrared stimulation of the auditory nerve: A decade of progress toward an optical cochlear implant

OBJECTIVES

We provide an appraisal of recent research on stimulation of the auditory system with light. In particular, we discuss direct infrared stimulation and ongoing controversies regarding the feasibility of this modality. We also discuss advancements and barriers to the development of an optical cochlear implant.

METHODS

This is a review article that covers relevant animal studies.

RESULTS

The auditory system has been stimulated with infrared light, and in a much more spatially selective manner than with electrical stimulation. However, there are experiments from other labs that have not been able to reproduce these results. This has resulted in an ongoing controversy regarding the feasibility of infrared stimulation, and the reasons for these experimental differences still require explanation. The neural response characteristics also appear to be much different than with electrical stimulation. The electrical stimulation paradigms used for modern cochlear implants do not apply well to optical stimulation and new coding strategies are under development. Stimulation with infrared light brings the risk of heat accumulation in the tissue at high pulse repetition rates, so optimal pulse shapes and combined optical/electrical stimulation are being investigated to mitigate this. Optogenetics is another promising technique, which makes neurons more sensitive to light stimulation by inserting light sensitive ion channels via viral vectors. Challenges of optogenetics include the expression of light sensitive channels in sufficient density in the target neurons, and the risk of damaging neurons by the expression of a foreign protein.

CONCLUSION

Optical stimulation of the nervous system is a promising new field, and there has been progress toward the development of a cochlear implant that takes advantage of the benefits of optical stimulation. There are barriers, and controversies, but so far none that seem intractable.

LEVEL OF EVIDENCE

NA (animal studies and basic research).

Expression of transient receptor potential vanilloid genes and proteins in diabetic rat heart

Cardiac complications are leading causes of death in diabetic patients. Imbalance of Ca²⁺ homeostasis is a hallmark of cardiac dysfunction in diabetes, while TRPV channels are non-selective for cations and are permeable to Ca²⁺. Our aim was to evaluate the expression levels of TRPV1, TRPV2, TRPV3, TRPV4, TRPV5, and TRPV6 genes and proteins in cardiac tissue at 3 days and 4, 8, and 12 weeks after induction of diabetes. Sprague-Dawley rats were assigned to control and DM groups. DM was induced by intraperitoneal injection of streptozotocin (60 mg/kg). The expression levels of TRPV genes were analyzed by the quantitative reverse transcription polymerase chain reaction, and TRPV proteins were determined by western blotting. Compared to controls, the expression levels of TRPV2, TRPV3, and TRPV6 in diabetic myocardium did not change, while TRPV1 decreased at 4, 8, and 12 weeks, TRPV4 was upregulated at 3 days and 4, 8, and 12 weeks, TRPV5 mRNA increased at 8 and 12 weeks, and TRPV5 protein increased at 4, 8, and 12 weeks. Our findings showed that TRPV1, TRPV4, and TRPV5 are associated with the diabetic heart.

TRPV2: A Cancer Biomarker and Potential Therapeutic Target

The Transient Receptor Potential Vanilloid type-2 (TRPV2) channel exhibits oncogenicity in different types of cancers. TRPV2 is implicated in signaling pathways that mediate cell survival, proliferation, and metastasis. In leukemia and bladder cancer, the oncogenic activity of TRPV2 was linked to alteration of its expression profile. In multiple myeloma patients, TRPV2 overexpression correlated with bone tissue damage and poor prognosis. In prostate cancer, TRPV2 overexpression was associated with the castration-resistant phenotype and metastasis. Loss or inactivation of TRPV2 promoted glioblastoma cell proliferation and increased resistance to CD95-induced apoptotic cell death. TRPV2 overexpression was associated with high relapse-free survival in triple-negative breast cancer, whereas the opposite was found in patients with esophageal squamous cell carcinoma or gastric cancer. Another link was found between TRPV2 expression and either drug-induced cytotoxicity or stemness of liver cancer. Overall, these findings validate TRPV2 as a prime candidate for cancer biomarker and future therapeutic target.

Emerging role of transient receptor potential (TRP) channels in cancer progression

Transient receptor potential (TRP) channels comprise a diverse family of ion channels, the majority of which are calcium permeable and show sophisticated regulatory patterns in response to various environmental cues. Early studies led to the recognition of TRP channels as environmental and chemical sensors. Later studies revealed that TRP channels mediated the regulation of intracellular calcium. Mutations in TRP channel genes result in abnormal regulation of TRP channel function or expression, and interfere with normal spatial and temporal patterns of intracellular local Ca2+ distribution. The resulting dysregulation of multiple downstream effectors, depending on Ca2+ homeostasis, is associated with hallmarks of cancer pathophysiology, including enhanced proliferation, survival and invasion of cancer cells. These findings indicate that TRP channels affect multiple events that control cellular fate and play a key role in cancer progression. This review discusses the accumulating evidence supporting the role of TRP channels in tumorigenesis, with emphasis on prostate cancer. [BMB Reports 2020; 53(3): 125-132].

The pharmacological basis for application of cannabidiol in cancer chemotherapy

Chemotherapy is one of the therapeutic approaches for cancer treatment and has demonstrated great success with the introduction of selectively acting molecules against specific biomarkers of some types of tumors. Despite this success there is a large unmet need for novel therapies that provide effective control on the progression of advanced or drug-resistant cancer diseases. In this review, we briefly summarized our knowledge of cannabinoids and the endocannabinoid system, as possible agents for cancer therapy. We analyzed the anticancer properties and mechanism of action of cannabidiol (CBD), the main non-psychoactive cannabinoid received from hemp of Cannabis plant. Despite of data for pleiotropic effects of CBD, we here present the results for the efficacy of CBD in the modulation of different stages of cancer development. The analysis of the anticancer properties of CBD is made in relation to the proposed or newly discovered molecular targets of action. Thereafter, we consider the specific effects of CBD on primary tumors, their invasiveness and metastases, whether the influence on identified tumor markers in different types of tumors reflect the therapeutic potential of CBD. The studies reviewed herein indicate that CBD elicit activity through the cannabinoid receptor dependent and independent pathways. The processes such as ceramide production, ER-stress, autophagy and apoptosis, angiogenesis and matrix remodeling also appear to regulate the anticancer activity of CBD. So, the pharmacological basis for therapeutic application of CBD is constructed on the scientific data for its antitumor activity, extensively provided studies in vitro and in vivo in animal tumor models, and available data on the safety profile of clinically approved CBD products. We also try to reduce the deficits of our understanding in relation of pharmacological synergistic interactions of CBD with cytostatic drugs, where data remains limited. It is recognized that more studies for defining the specific molecular and signaling mechanisms of anticancer action of cannabinoids, particularly CBD, requires further evaluation. We believe that the therapeutic advantages of CBD are associated not only with its non-psychoactive behavior, but also are related to its influence on the important biochemical pathways and signal molecules, defining the genome instability and specific changes of the malignant tumor cells.

pH sensing in skin tumors: Methods to study the involvement of GPCRs, acid-sensing ion channels and transient receptor potential vanilloid channels

Solid tumors exhibit an inversed pH gradient with increased intracellular pH (pH_i ) and decreased extracellular pH (pH_e ). This inside-out pH gradient is generated via sodium/hydrogen antiporter 1, vacuolar-type H + ATPases, monocarboxylate transporters, (bi)carbonate (co)transporters and carboanhydrases. Our knowledge on how pH_e -signals are sensed and what the respective receptors induce inside cells is scarce. Some pH-sensitive receptors (GPR4, GPR65/TDAG8, GPR68/OGR1, GPR132/G2A, possibly GPR31 and GPR151) and ion channels (acid-sensing ion channels ASICs, transient receptor potential vanilloid receptors TRPVs) transduce signals inside cells. As little is known on the expression and function of these pH sensors, we used immunostainings to study tissue samples from common and rare skin cancers. Our current and future work is directed towards investigating the impact of all the pH-sensing receptors in different skin tumors using cell culture techniques with selective knockdown/knockout (siRNA/CRISPR-Cas9). To study cell migration and proliferation, novel impedance-based wound healing assays have been developed and are used. The field of pH sensing in tumors and wounds holds great promise for the development of pH-targeting therapies, either against pH regulators or sensors to inhibit cell proliferation and migration.

Insights and perspectives on calcium channel functions in the cockpit of cancerous space invaders

Development of metastasis causes the most serious clinical consequences of cancer and is responsible for over 90 % of cancer-related deaths. Hence, a better understanding of the mechanisms that drive metastasis formation appears critical for drug development designed to prevent the spread of cancer and related mortality. Metastasis dissemination is a multistep process supported by the increased motility and invasiveness capacities of tumor cells. To succeed in overcoming the mechanical constraints imposed by the basement membrane and surrounding tissues, cancer cells reorganize their focal adhesions or extend acto-adhesive cellular protrusions, called invadosomes, that can both contact the extracellular matrix and tune its degradation through metalloprotease activity. Over the last decade, accumulating evidence has demonstrated that altered Ca²⁺ channel activities and/or expression promote tumor cell-specific phenotypic changes, such as exacerbated migration and invasion capacities, leading to metastasis formation. While several studies have addressed the molecular basis of Ca²⁺ channel-dependent cancer cell migration, we are still far from having a comprehensive vision of the Ca²⁺ channel-regulated mechanisms of migration/invasion. This is especially true regarding the specific context of invadosome-driven invasion. This review aims to provide an overview of the current evidence supporting a central role for Ca²⁺ channel-dependent signaling in the regulation of these dynamic degradative structures. It will present available data on the few Ca²⁺ channels that have been studied in that specific context and discuss some potential interesting actors that have not been fully explored yet.

Exploring the Therapeutic Potential of Membrane Transport Proteins: Focus on Cancer and Chemoresistance

Improving the therapeutic efficacy of conventional anticancer drugs represents the best hope for cancer treatment. However, the shortage of druggable targets and the increasing development of anticancer drug resistance remain significant problems. Recently, membrane transport proteins have emerged as novel therapeutic targets for cancer treatment. These proteins are essential for a plethora of cell functions ranging from cell homeostasis to clinical drug toxicity. Furthermore, their association with carcinogenesis and chemoresistance has opened new vistas for pharmacology-based cancer research. This review provides a comprehensive update of our current knowledge on the functional expression profile of membrane transport proteins in cancer and chemoresistant tumours that may form the basis for new cancer treatment strategies.

TRPV6 as A Target for Cancer Therapy

Two decades ago a class of ion channels, hitherto unsuspected, was discovered. In mammals these Transient Receptor Potential channels (TRPs) have not only expanded in number (to 26 functional channels) but also expanded the view of our interface with the physical and chemical environment. Some are heat and cold sensors while others monitor endogenous and/or exogenous chemical signals. Some TRP channels monitor osmotic potential, and others measure cell movement, stretching, and fluid flow. Many TRP channels are major players in nociception and integration of pain signals. One member of the vanilloid sub-family of channels is TRPV6. This channel is highly selective for divalent cations, particularly calcium, and plays a part in general whole-body calcium homeostasis, capturing calcium in the gut from the diet. TRPV6 can be greatly elevated in a number of cancers deriving from epithelia and considerable study has been made of its role in the cancer phenotype where calcium control is dysfunctional. This review compiles and updates recent published work on TRPV6 as a promising drug target in a number of cancers including those afflicting breast, ovarian, prostate and pancreatic tissues.

Calcium Signaling and the Regulation of Chemosensitivity in Cancer Cells: Role of the Transient Receptor Potential Channels

Cancer cells acquire the ability to modify the calcium signaling network by altering the expression and functions of cation channels, pumps or transporters. Calcium signaling pathways are involved in proliferation, angiogenesis, invasion, immune evasion, disruption of cell death pathways, ECM remodelling, epithelial-mesenchymal transition (EMT) and drug resistance. Among cation channels, a pivotal role is played by the Transient Receptor Potential non-selective cation-permeable receptors localized in plasma membrane, endoplasmic reticulum, mitochondria and lysosomes. Several findings indicate that the dysregulation in calcium signaling induced by TRP channels is responsible for cancer growth, metastasis and chemoresistance. Drug resistance represents a major limitation in the application of current therapeutic regimens and several efforts are spent to overcome it. Here we describe the ability of Transient Receptor Potential Channels to modify, by altering the intracellular calcium influx, the cancer cell sensitivity to chemotherapeutic drugs.

Evaluation of cationic channel TRPV2 as a novel biomarker and therapeutic target in Leukemia-Implications concerning the resolution of pulmonary inflammation

Patients treated during leukemia face the risk of complications including pulmonary dysfunction that may result from infiltration of leukemic blast cells (LBCs) into lung parenchyma and interstitium. In LBCs, we demonstrated that transient receptor potential vanilloid type 2 channel (TRPV2), reputed for its role in inflammatory processes, exhibited oncogenic activity associated with alteration of its molecular expression profile. TRPV2 was overexpressed in LBCs compared to normal human peripheral blood mononuclear cells (PBMCs). Additionally, functional full length isoform and nonfunctional short form pore-less variant of TRPV2 protein were up-regulated and down-regulated respectively in LBCs. However, the opposite was found in PBMCs. TRPV2 silencing or pharmacological targeting by Tranilast (TL) or SKF96365 (SKF) triggered caspace-mediated apoptosis and cell cycle arrest. TL and SKF inhibited chemotactic peptide fMLP-induced response linked to TRPV2 Ca²⁺ activity, and down-regulated expression of surface marker CD38 involved in leukemia and lung airway inflammation. Challenging lung airway epithelial cells (AECs) with LBCs decreased (by more than 50%) transepithelial resistance (TER) denoting barrier function alteration. Importantly, TL prevented such loss in TER. Therefore, TRPV2 merits further exploration as a pharmacodynamic biomarker for leukemia patients (with pulmonary inflammation) who might be suitable for a novel [adjuvant] therapeutic strategy based on TL.

Cannabis sativa L. and Nonpsychoactive Cannabinoids: Their Chemistry and Role against Oxidative Stress, Inflammation, and Cancer

In the last decades, a lot of attention has been paid to the compounds present in medicinal Cannabis sativa L., such as Δ⁹-tetrahydrocannabinol (Δ⁹-THC) and cannabidiol (CBD), and their effects on inflammation and cancer-related pain. The National Cancer Institute (NCI) currently recognizes medicinal C. sativa as an effective treatment for providing relief in a number of symptoms associated with cancer, including pain, loss of appetite, nausea and vomiting, and anxiety. Several studies have described CBD as a multitarget molecule, acting as an adaptogen, and as a modulator, in different ways, depending on the type and location of disequilibrium both in the brain and in the body, mainly interacting with specific receptor proteins CB₁ and CB₂. CBD is present in both medicinal and fibre-type C. sativa plants, but, unlike Δ⁹-THC, it is completely nonpsychoactive. Fibre-type C. sativa (hemp) differs from medicinal C. sativa, since it contains only few levels of Δ⁹-THC and high levels of CBD and related nonpsychoactive compounds. In recent years, a number of preclinical researches have been focused on the role of CBD as an anticancer molecule, suggesting CBD (and CBD-like molecules present in the hemp extract) as a possible candidate for future clinical trials. CBD has been found to possess antioxidant activity in many studies, thus suggesting a possible role in the prevention of both neurodegenerative and cardiovascular diseases. In animal models, CBD has been shown to inhibit the progression of several cancer types. Moreover, it has been found that coadministration of CBD and Δ⁹-THC, followed by radiation therapy, causes an increase of autophagy and apoptosis in cancer cells. In addition, CBD is able to inhibit cell proliferation and to increase apoptosis in different types of cancer models. These activities seem to involve also alternative pathways, such as the interactions with TRPV and GRP55 receptor complexes. Moreover, the finding that the acidic precursor of CBD (cannabidiolic acid, CBDA) is able to inhibit the migration of breast cancer cells and to downregulate the proto-oncogene c-fos and the cyclooxygenase-2 (COX-2) highlights the possibility that CBDA might act on a common pathway of inflammation and cancer mechanisms, which might be responsible for its anticancer activity. In the light of all these findings, in this review we explore the effects and the molecular mechanisms of CBD on inflammation and cancer processes, highlighting also the role of minor cannabinoids and noncannabinoids constituents of Δ⁹-THC deprived hemp.

TRP channels as potential targets for antischistosomals

Ion channels are membrane protein complexes that underlie electrical excitability in cells, allowing ions to diffuse through cell membranes in a regulated fashion. They are essential for normal functioning of the neuromusculature and other tissues. Ion channels are also validated targets for many current anthelmintics, yet the properties of only a small subset of ion channels in parasitic helminths have been explored in any detail. Transient receptor potential (TRP) channels comprise a widely diverse superfamily of ion channels with important roles in sensory signaling, regulation of ion homeostasis, organellar trafficking, and other functions. There are several subtypes of TRP channels, including TRPA1 and TRPV1 channels, both of which are involved in, among other functions, sensory, nociceptive, and inflammatory signaling in mammals. Several lines of evidence indicate that TRPA1-like channels in schistosomes exhibit pharmacological sensitivities that differ from their mammalian counterparts and that may signify unique physiological properties as well. Thus, in addition to responding to TRPA1 modulators, schistosome TRPA1-like channels also respond to compounds that in other organisms modulate TRPV1 channels. Notably, TRPV channel genes are not found in schistosome genomes. Here, we review the evidence leading to these conclusions and examine potential implications. We also discuss recent results showing that praziquantel, the current drug of choice against schistosomiasis, selectively targets host TRP channels in addition to its likely primary targets in the parasite. The results we discuss add weight to the notion that schistosome TRP channels are worthy of investigation as candidate therapeutic targets.

Inhibition of Transient Receptor Potential Vanilloid 6 channel, elevated in human ovarian cancers, reduces tumour growth in a xenograft model

Background: Transient Receptor Potential Vanilloid 6 (TRPV6), a non-voltage gated calcium channel, is implicated in malignancies and correlates with Gleason scores in prostate cancer and with poor prognosis in breast cancer. Data on the TRPV6 status of ovarian malignancies has not received significant attention. The effect of inhibiting TRPV6 activity on ovarian tumour growth has never been reported.

Methods: We quantified TRPV6 mRNA and protein in biopsies of five types of ovarian cancer at different stages and grades by quantitative PCR and immunohistochemistry respectively. We verified the presence of TRPV6 in SKOV-3 cells and xenografts by Western Blotting. NOD/SCID mice bearing xenografted ovarian tumours derived from SKOV-3 were treated daily with TRPV6-antagonistic peptides (SOR-C13 and SOR-C27) at 400, 600 and 800 mg/kg delivered intraperitoneally (i.p.) over 12 days. Data from qPCR and tumour growth experiments were compared with a Student's t-test. Immunohistochemical ranking of staining were compared with Kruskall-Wallace one-way ANOVA and Dunn's Multiple Comparison post-test.

Results: TRPV6 mRNA and protein are significantly elevated at all stages and grades of 5 ovarian cancer types over normal tissue. Overall qPCR log2 values (n, mean, ± SEM) for mRNA in tumour (n = 165, 5.06 ± 0.16) were greater (p < 0.05) than normal tissues (n = 26, 0.45 ± 0.41). All stages and grades included in the biopsy arrays were significantly greater than normal tissues. Immunohistochemical staining of TRPV6 was ranked >2 (faint in most cells) in 80.5% of tumours (123) while 92% of normal tissues (23) ranked ≤ 2. Daily i.p. injection with SOR-C13 (400, 600 and 800 mg/kg) over 12 days inhibits tumour growth (59%) at the highest dose compared to non-treated controls. SOR-C27 at 800 mg/kg SOR-C27 inhibited tumour growth 55% after 12 days. Results of daily and intermittent dosing (Days 1, 2, 3 and 8, 9, 10) with SOR-C13 were indistinguishable.

Conclusion: TRPV6 mRNA and protein are elevated in biopsies of ovarian cancers compared to normal tissue. Inhibition of TRPV6 activity significantly reduces ovarian tumour growth providing evidence that TRPV6 is a feasible oncology target in ovarian cancers.

Transient receptor potential vanilloid-type 2 targeting on stemness in liver cancer

The malignant phenotype of the cells resulting from human liver cancer is driven by liver cancer stem-like cells (LCSLCs). Transient Receptor Potential Vanilloid-type 2 channel (TRPV2) contributes to the progression of different tumor types, including liver cancer. In the current study, the TRPV2 expression levels give rise to the effect on stemness in liver cancer cell lines. TRPV2 knockdown in HepG2 cells enhanced spheroid and colony formation, and expression levels of CD133, CD44 and ALDH1 whereas the opposite effects were observed in TRPV2 enforced expression in SMMC-7721 cells. Furthermore, TRPV2 overexpression restored inhibition of spheroid and colony formation, and stem cell markers expression in HepG2 cells with TRPV2 silencing. The addition of the TRPV2 agonist probenecid and the TRPV2 antagonist tranilast suppressed and/or increased in vitro spheroid and colony formation, and stem cell marker expression of LCSLCs and/or liver cancer cell lines, respectively. Notably, probenecid and tranilast significantly inhibited or promoted tumor growth of HepG2 xenografts in the severe combined immunodeficiency (SCID) mouse model, respectively. TRPV2 expression at protein levels revealed converse correlation with those of CD133 and CD44 in human hepatocellular carcinoma (HCC) tissue. Collectively, the data demonstrate that TRPV2 exert effects on stemness of liver cancer and is a potential target in the treatment of human liver cancer patients.

The Role of TRP Channels in the Metastatic Cascade

A dysregulated cellular Ca2+ homeostasis is involved in multiple pathologies including cancer. Changes in Ca2+ signaling caused by altered fluxes through ion channels and transporters (the transportome) are involved in all steps of the metastatic cascade. Cancer cells thereby "re-program" and "misuse" the cellular transportome to regulate proliferation, apoptosis, metabolism, growth factor signaling, migration and invasion. Cancer cells use their transportome to cope with diverse environmental challenges during the metastatic cascade, like hypoxic, acidic and mechanical cues. Hence, ion channels and transporters are key modulators of cancer progression. This review focuses on the role of transient receptor potential (TRP) channels in the metastatic cascade. After briefly introducing the role of the transportome in cancer, we discuss TRP channel functions in cancer cell migration. We highlight the role of TRP channels in sensing and transmitting cues from the tumor microenvironment and discuss their role in cancer cell invasion. We identify open questions concerning the role of TRP channels in circulating tumor cells and in the processes of intra- and extravasation of tumor cells. We emphasize the importance of TRP channels in different steps of cancer metastasis and propose cancer-specific TRP channel blockade as a therapeutic option in cancer treatment.

Pharmacological inhibition of TRPV4 channel suppresses malignant biological behavior of hepatocellular carcinoma via modulation of ERK signaling pathway

TRPV4 (transient receptor potential vanilloid 4), a member of the TRP superfamily, has been reported to correlate with several different forms of cancers. However, the role of TRPV4 in human hepatocellular carcinoma (HCC) remains unclear. The present study demonstrated that elevated expression of TRPV4 was shown in HCC tumor tissues when compared with paired non-tumoral livers both in protein and mRNA levels. Furthermore, the enhanced expression of TRPV4 was highly associated with histological grade (P = 0.036) and the number of tumors (P = 0.045). Pharmacological inhibition of TRPV4 channels in HCC cells with the specific antagonist HC-067047 suppressed cell proliferation, induced apoptosis and decreased the migration capability by attenuating the epithelial-mesenchymal transition (EMT) process in vitro. The p-ERK expression was apparently repressed after treatment with the TRPV4 antagonist, further blockade of the ERK pathway with U0126 could significantly aggravate HCC cells apoptosis. In NOD-SCID mouse xenograft models, intraperitoneal injection of HC-067047 could obviously suppress tumor growth and induce apoptosis in vivo. Together, our studies showed that the antitumor effects caused by TRPV4 channel inhibition in HCC cell lines might be attributed to the suppression of EMT process and inactivation of p-ERK which induced subsequent cell apoptosis. Thus, pharmacological inhibition of TRPV4 channel may be an option for HCC treatment.

Shenfu Injection attenuates rat myocardial hypertrophy by up-regulating miR-19a-3p expression

Shenfu Injection (SFI) is a classical Chinese medicine used to treat heart failure. Our previous study demonstrated that miRNAs underwent changes in rats with myocardial hypertrophy induced by abdominal aortic constriction. Interestingly, there was a significant change in miR-19a-3p, whose target gene is known to be associated with MEF2 signaling. However, whether and how SFI regulates miR-19a-3p in the treatment of myocardial hypertrophy has not been investigated. The purpose of the present study was to investigate the regulatory effect of SFI on miR-19a-3p in MEF2 signaling in the rat hypertrophic myocardium. We found that the miR-19a-3p expression level was significantly decreased in the hypertrophic myocardium, and MEF2A was the target gene of miR-19a-3p. The protein expressions of MEF2A, β-MHC, BNP and TRPC1 were significantly increased in hypertrophic cardiomyocytes. MiR-19a-3p was up-regulated after SFI treatment, and the protein expressions of these genes were significantly decreased. In addition, miR-19a-3p over-expression in hypertrophic cardiomyocytes could decrease MEF2A mRNA and protein expressions, and anti-miR-19a-3p showed the opposite result. Our study provided substantial evidence that miR-19a-3p played a functional role in MEF2 signaling in myocardial hypertrophy. SFI attenuated cardiomyocyte hypertrophy probably through up-regulating or maintaining the miR-19a-3p levels and regulating the MEF2 signaling pathway.

Overexpression of transient receptor potential mucolipin-2 ion channels in gliomas: role in tumor growth and progression

The Transient Receptor Potential (TRP) superfamily consists of cation-selective and non-selective ion channels playing an important role both in sensory physiology and in physiopathology in several complex diseases including cancers. Among TRP family, the mucolipin (TRPML1, −2, and −3) channels represent a distinct subfamily of endosome/lysosome Ca²⁺ channel proteins. Loss-of-function mutations in human TRPML-1 gene cause a neurodegenerative disease, Mucolipidosis Type IV, whereas at present no pathology has been associated to human TRPML-2 channels.

Herein we found that human TRPML-2 is expressed both in normal astrocytes and neural stem/progenitor cells. By quantitative RT-PCR, western blot, cytofluorimetric and immunohistochemistry analysis we also demonstrated that TRPML-2 mRNA and protein are expressed at different levels in glioma tissues and high-grade glioma cell lines of astrocytic origin. TRPML-2 mRNA and protein levels increased with the pathological grade, starting from pylocitic astrocytoma (grade I) to glioblastoma (grade IV). Moreover, by RNA interference, we demonstrated a role played by TRPML-2 in survival and proliferation of glioma cell lines. In fact, knock-down of TRPML-2 inhibited the viability, altered the cell cycle, reduced the proliferation and induced apoptotic cell death in glioma cell lines. The DNA damage and apoptosis induced by TRPML-2 loss increased Ser139 H2AX phosphorylation and induced caspase-3 activation; furthermore, knock-down of TRPML-2 in T98 and U251 glioma cell lines completely abrogated Akt and Erk1/2 phosphorylation, as compared to untreated cells.

Overall, the high TRPML-2 expression in glioma cells resulted in increased survival and proliferation signaling, suggesting a pro-tumorigenic role played by TRPML-2 in glioma progression.

Peptide therapeutics from venom: Current status and potential

Peptides are recognized as being highly selective, potent and relatively safe as potential therapeutics. Peptides isolated from the venom of different animals satisfy most of these criteria with the possible exception of safety, but when isolated as single compounds and used at appropriate concentrations, venom-derived peptides can become useful drugs. Although the number of venom-derived peptides that have successfully progressed to the clinic is currently limited, the prospects for venom-derived peptides look very optimistic. As proteomic and transcriptomic approaches continue to identify new sequences, the potential of venom-derived peptides to find applications as therapeutics, cosmetics and insecticides grows accordingly.

TRPV4 plays a role in breast cancer cell migration via Ca2+-dependent activation of AKT and downregulation of E-cadherin cell cortex protein

TRPV4 belongs to the 'Transient Receptor Potential' (TRP) superfamily. It has been identified to profoundly affect a variety of physiological processes, including nociception, heat sensation and inflammation. Unlike other TRP superfamily channels, its role in cancers are unknown until recently when we reported TRPV4 to be required for cancer cell softness that may promote breast cancer cell extravasation and metastasis. Here, we elucidated the molecular mechanisms mediated by TRPV4 in the metastatic breast cancer cells. TRPV4-mediated signaling was demonstrated to involve Ca²⁺-dependent activation of AKT and downregulation of E-cadherin expression, which was abolished upon TRPV4 silencing. Functionally, TRPV4-enhanced breast caner cell transendothelial migration requires AKT activity while a combination of transcriptional and post-translational regulation contributed to the TRPV4-mediated E-cadherin downregulation. Finally, mass spectrometry analysis revealed that TRPV4 is required for the expression of a network of secreted proteins involved in extracellular matrix remodeling. In conclusion, TRPV4 may regulate breast cancer metastasis by regulating cell softness through the Ca²⁺-dependent AKT-E-cadherin signaling axis and regulation of the expression of extracellular proteins.

Constitutive calcium entry and cancer: updated views and insights

Tight control of basal cytosolic Ca²⁺ concentration is essential for cell survival and to fine-tune Ca²⁺-dependent cell functions. A way to control this basal cytosolic Ca²⁺ concentration is to regulate membrane Ca²⁺ channels including store-operated Ca²⁺ channels and secondary messenger-operated channels linked to G-protein-coupled or tyrosine kinase receptor activation. Orai, with or without its reticular STIM partner and Transient Receptor Potential (TRP) proteins, were considered to be the main Ca²⁺ channels involved. It is well accepted that, in response to cell stimulation, opening of these Ca²⁺ channels contributes to Ca²⁺ entry and the transient increase in cytosolic Ca²⁺ concentration involved in intracellular signaling. However, in various experimental conditions, Ca²⁺ entry and/or Ca²⁺ currents can be recorded at rest, without application of any experimental stimulation. This led to the proposition that some plasma membrane Ca²⁺ channels are already open/activated in basal condition, contributing therefore to constitutive Ca²⁺ entry. This article focuses on direct and indirect observations supporting constitutive activity of channels belonging to the Orai and TRP families and on the mechanisms underlying their basal/constitutive activities.

Pressure in the Cochlea During Infrared Irradiation

OBJECTIVE

The purpose of the study is to demonstrate laser-evoked pressure waves in small confined volumes such as the cochlea.

METHODS

Custom-fabricated pressure probes were used to determine the pressure in front of the optical fiber in a small dish and patch pipettes to measure temperature changes. Pressure probes were inserted into scala tympani (ST) or vestibuli during laser stimulation. With a sensitive microphone the pressure was measured in the outer ear canal.

RESULTS

Heating was spatially confined. The heat relaxation time was 35 ms. During laser stimulation in the cochlea at 17 μJ/pulse, the pressure in the outer ear canal (EC) was 43.5 dB (re 20 μPa). The corresponding intracochlear pressure was calculated to be about 78.5 dB (re 20 μPa) using the middle ear reverse transfer function of -35 dB. At 164 μJ/pulse, the pressure in the EC was on average 63 dB (re 20 μPa) and the intracochlear pressure was estimated to be 98 dB (re 20 μPa), which is similar to the value obtained with the pressure probe, 100 dB (re 20 μPa). Side-emitting optical fibers were used to steer the beam path. The pressure values were independent of the orientation of the beam path. Evoked compound action potentials of the auditory nerve were maximum when spiral ganglion neurons were in the beam path.

CONCLUSION

Pressure waves are generated during infrared laser stimulation. The intracochlear pressure was independent from the orientation of the beam path.

SIGNIFICANCE

Neural responses required the spiral ganglion neurons to be directly irradiated.

TRP channels in schistosomes

Praziquantel (PZQ) is effectively the only drug currently available for treatment and control of schistosomiasis, a disease affecting hundreds of millions of people worldwide. Many anthelmintics, likely including PZQ, target ion channels, membrane protein complexes essential for normal functioning of the neuromusculature and other tissues. Despite this fact, only a few classes of parasitic helminth ion channels have been assessed for their pharmacological properties or for their roles in parasite physiology. One such overlooked group of ion channels is the transient receptor potential (TRP) channel superfamily. TRP channels share a common core structure, but are widely diverse in their activation mechanisms and ion selectivity. They are critical to transducing sensory signals, responding to a wide range of external stimuli. They are also involved in other functions, such as regulating intracellular calcium and organellar ion homeostasis and trafficking. Here, we review current literature on parasitic helminth TRP channels, focusing on those in schistosomes. We discuss the likely roles of these channels in sensory and locomotor activity, including the possible significance of a class of TRP channels (TRPV) that is absent in schistosomes. We also focus on evidence indicating that at least one schistosome TRP channel (SmTRPA) has atypical, TRPV1-like pharmacological sensitivities that could potentially be exploited for future therapeutic targeting.

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We provide an overview of transient receptor potential (TRP) channels in schistosomes and other parasitic helminths.

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TRP channels are important for sensory signaling, ion homeostasis, organellar trafficking, and a host of other functions.

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Very little work has been done on TRP channels in parasitic helminths.

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TRPV channels, found throughout the Metazoa, appear not to be present in parasitic platyhelminths.

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TRP channels in schistosomes appear to have atypical pharmacology, perhaps an entrée for therapeutic targeting.

TRPV4 Regulates Breast Cancer Cell Extravasation, Stiffness and Actin Cortex

Metastasis is a significant health issue. The standard mode of care is combination of chemotherapy and targeted therapeutics but the 5-year survival rate remains low. New/better drug targets that can improve outcomes of patients with metastatic disease are needed. Metastasis is a complex process, with each step conferred by a set of genetic aberrations. Mapping the molecular changes associated with metastasis improves our understanding of the etiology of this disease and contributes to the pipeline of targeted therapeutics. Here, phosphoproteomics of a xenograft-derived in vitro model comprising 4 isogenic cell lines with increasing metastatic potential implicated Transient Receptor Potential Vanilloid subtype 4 in breast cancer metastasis. TRPV4 mRNA levels in breast, gastric and ovarian cancers correlated with poor clinical outcomes, suggesting a wide role of TRPV4 in human epithelial cancers. TRPV4 was shown to be required for breast cancer cell invasion and transendothelial migration but not growth/proliferation. Knockdown of Trpv4 significantly reduced the number of metastatic nodules in mouse xenografts leaving the size unaffected. Overexpression of TRPV4 promoted breast cancer cell softness, blebbing, and actin reorganization. The findings provide new insights into the role of TRPV4 in cancer extravasation putatively by reducing cell rigidity through controlling the cytoskeleton at the cell cortex.

TRPV1 channel as a target for cancer therapy using CNT-based drug delivery systems

Carbon nanotubes are being considered for the design of drug delivery systems (DDSs) due to their capacity to internalize molecules and control their release. However, for cellular uptake of drugs, this approach requires an active translocation pathway or a channel to transport the drug into the cell. To address this issue, it is suggested to use TRPV1 ion channels as a potential target for drug release by nano-DDSs since these channels are overexpressed in cancer cells and allow the permeation of large cationic molecules. Considering these facts, this work presents three studies using molecular dynamics simulations of a human TRPV1 (hTRPV1) channel built here. The purpose of these simulations is to study the interaction between a single-wall carbon nanotube (SWCNT) and hTRPV1, and the diffusion of doxorubicin (DOX) across hTRPV1 and across a POPC lipid membrane. The first study shows an attractive potential between the SWCNT surface and hTRPV1, tilting the adsorbed SWCNT. The second study shows low diffusion probability of DOX across the open hTRPV1 due to a high free energy barrier. Although, the potential energy between DOX and hTRPV1 reveals an attractive interaction while DOX is inside hTRPV1. These results suggest that if the channel is dilated, then DOX diffusion could occur. The third study shows a lower free energy barrier for DOX across the lipid membrane than for DOX across hTRPV1. Taking into account the results obtained, it is feasible to design novel nano-DDSs based on SWCNTs to accomplish controlled drug release into cells using as translocation pathway, the hTRPV1 ion channel.

Novel role of TRPV2 in promoting the cytotoxicity of H2O2-mediated oxidative stress in human hepatoma cells

Oxidative stress is important for the initiation and progression of cancers, which confers the cells with a survival advantage by inducing oxidative adaption and drug resistance. Therefore, developing strategies to promote oxidative stress-induced cytotoxicity could be important for cancer therapy. Herein, we found that H2O2-mediated oxidative stress increases TRPV2 expression in human hepatoma (HepG2 and Huh-7) cells. This occurred at the mRNA and protein levels in a dose-dependent manner. The significance of TRPV2 in promoting H2O2-induced cell death was demonstrated in gain and loss of function studies with overexpression and knockdown of TRPV2, respectively. Mechanistically, H2O2-induced cell death involves inhibition of pro-survival signaling proteins (Akt, Nrf2) and activation of pro-death signaling proteins (p38, JNK1). Overexpression of TRPV2 in H2O2-treated hepatoma cells aggravates the inhibition of Akt and Nrf2, while it enhances the activation of p38 and JNK1 at the early stage of cell death. Interestingly, increased expression of TRPV2 in HepG2 cells improved the efficacy of stress-associated chemicals to induce cell death. Our findings suggest that TRPV2 acts as an important enhancer for H2O2-induced cytotoxicity. This process occurred by the inhibition of Akt and Nrf2 as well as the early activation of p38 and JNK1. These findings have important implications for inhibition of oxidative adaption and drug resistance.

Danger- and pathogen-associated molecular patterns recognition by pattern-recognition receptors and ion channels of the transient receptor potential family triggers the inflammasome activation in immune cells and sensory neurons

An increasing number of studies show that the activation of the innate immune system and inflammatory mechanisms play an important role in the pathogenesis of numerous diseases. The innate immune system is present in almost all multicellular organisms and its activation occurs in response to pathogens or tissue injury via pattern-recognition receptors (PRRs) that recognize pathogen-associated molecular patterns (PAMPs) or danger-associated molecular patterns (DAMPs). Intracellular pathways, linking immune and inflammatory response to ion channel expression and function, have been recently identified. Among ion channels, the transient receptor potential (TRP) channels are a major family of non-selective cation-permeable channels that function as polymodal cellular sensors involved in many physiological and pathological processes.

In this review, we summarize current knowledge of interactions between immune cells and PRRs and ion channels of TRP families with PAMPs and DAMPs to provide new insights into the pathogenesis of inflammatory diseases. TRP channels have been found to interfere with innate immunity via both nuclear factor-kB and procaspase-1 activation to generate the mature caspase-1 that cleaves pro-interleukin-1β cytokine into the mature interleukin-1β.

Sensory neurons are also adapted to recognize dangers by virtue of their sensitivity to intense mechanical, thermal and irritant chemical stimuli. As immune cells, they possess many of the same molecular recognition pathways for danger. Thus, they express PRRs including Toll-like receptors 3, 4, 7, and 9, and stimulation by Toll-like receptor ligands leads to induction of inward currents and sensitization in TRPs. In addition, the expression of inflammasomes in neurons and the involvement of TRPs in central nervous system diseases strongly support a role of TRPs in inflammasome-mediated neurodegenerative pathologies. This field is still at its beginning and further studies may be required.

Overall, these studies highlight the therapeutic potential of targeting the inflammasomes in proinflammatory, autoinflammatory and metabolic disorders associated with undesirable activation of the inflammasome by using specific TRP antagonists, anti-human TRP monoclonal antibody or different molecules able to abrogate the TRP channel-mediated inflammatory signals.