TRP channels in cardiac and intestinal fibrosis

The roles of TRPC6 in renal tubular disorders: a narrative review

The transient receptor potential canonical 6 (TRPC6) channel, a nonselective cation channel that allows the passage of Ca2+, plays an important role in renal diseases. TRPC6 is activated by Ca2+ influx, oxidative stress, and mechanical stress. Studies have shown that in addition to glomerular diseases, TRPC6 can contribute to renal tubular disorders, such as acute kidney injury, renal interstitial fibrosis, and renal cell carcinoma (RCC). However, the tubule-specific physiological functions of TRPC6 have not yet been elucidated. Its pathophysiological role in ischemia/reperfusion (I/R) injury is debatable. Thus, TRPC6 may have dual roles in I/R injury. TRPC6 induces renal fibrosis and immune cell infiltration in a unilateral ureteral obstruction (UUO) mouse model. Additionally, TRPC6 overexpression may modify G2 phase transition, thus altering the DNA damage checkpoint, which can cause genomic instability and RCC tumorigenesis and can control the proliferation of RCC cells. This review highlights the importance of TRPC6 in various conditions of the renal tubular system. To better understand certain renal disorders and ultimately identify new therapeutic targets to improve patient care, the pathophysiology of TRPC6 must be clarified.

The role and mechanism of vascular wall cell ion channels in vascular fibrosis remodeling

Fibrosis is usually the final pathological state of many chronic inflammatory diseases and may lead to organ malfunction. Excessive deposition of extracellular matrix (ECM) molecules is a characteristic of most fibrotic tissues. The blood vessel wall contains three layers of membrane structure, including the intima, which is composed of endothelial cells; the media, which is composed of smooth muscle cells; and the adventitia, which is formed by the interaction of connective tissue and fibroblasts. The occurrence and progression of vascular remodeling are closely associated with cardiovascular diseases, and vascular remodeling can alter the original structure and function of the blood vessel. Dysregulation of the composition of the extracellular matrix in blood vessels leads to the continuous advancement of vascular stiffening and fibrosis. Vascular fibrosis reaction leads to excessive deposition of the extracellular matrix in the vascular adventitia, reduces vessel compliance, and ultimately alters key aspects of vascular biomechanics. The pathogenesis of fibrosis in the vasculature and strategies for its reversal have become interesting and important challenges. Ion channels are widely expressed in the cardiovascular system; they regulate blood pressure, maintain cardiovascular function homeostasis, and play important roles in ion transport, cell differentiation, proliferation. In blood vessels, different types of ion channels in fibroblasts, smooth muscle cells and endothelial cells may be relevant mediators of the development of fibrosis in organs or tissues. This review discusses the known roles of ion channels in vascular fibrosis remodeling and discusses potential therapeutic targets for regulating remodeling and repair after vascular injury.

TRPM7 controls skin keratinocyte senescence by targeting intracellular calcium signaling

Cellular senescence is described as an irreversible cell cycle arrest for proliferating cells and is associated with the secretion of senescence associated secretory phenotype factors. It has been known to accumulate with age and is regarded as a key driver of aging-associated skin pathologies. However, the lack of markers of skin senescence and partially understood skin cellular senescence mechanisms has limited the exploration of skin aging and anti-skin aging strategies. Recently, intracellular calcium signaling has emerged as an important regulator of cellular senescence and aging. However, little is known about the modulation of skin cellular senescence by calcium-associated factors. Here, we found that the expression of calcium channel transient receptor potential melastatin 7 (TRPM7) is elevated during skin keratinocyte senescence and aging. Importantly, TRPM7 promotes skin keratinocyte senescence by triggering intracellular calcium transfer from the endoplasmic reticulum to the mitochondria; accumulation of mitochondrial calcium then induces a drop in mitochondrial membrane potential and reactive oxygen species production, leading to subsequent nuclear enlargement and DNA damage. Altogether, these findings indicate that TRPM7 controls skin keratinocyte senescence through regulating intracellular calcium signaling, and thus, shed light on novel strategies for anti-skin aging therapy.

Ca2+ Signaling in Cardiovascular Fibroblasts

Fibrogenesis is a physiological process required for wound healing and tissue repair. It is induced by activation of quiescent fibroblasts, which first proliferate and then change their phenotype into migratory, contractile myofibroblasts. Myofibroblasts secrete extracellular matrix proteins, such as collagen, to form a scar. Once the healing process is terminated, most myofibroblasts undergo apoptosis. However, in some tissues, such as the heart, myofibroblasts remain active and sensitive to neurohumoral factors and inflammatory mediators, which lead eventually to excessive organ fibrosis. Many cellular processes involved in fibroblast activation, including cell proliferation, protein secretion and cell contraction, are highly regulated by intracellular Ca2+ signals. This review summarizes current research on Ca2+ signaling pathways underlying fibroblast activation. We present receptor- and ion channel-mediated Ca2+ signaling pathways, discuss how localized Ca2+ signals of the cell nucleus may be involved in fibroblast activation and present Ca2+-sensitive transcription pathways relevant for fibroblast biology. When investigated, we highlight how the function of Ca2+-handling proteins changes during cardiac and pulmonary fibrosis. Many aspects of Ca2+ signaling remain unexplored in different types of cardiovascular fibroblasts in relation to pathologies, and a better understanding of Ca2+ signaling in fibroblasts will help to design targeted therapies against fibrosis.

Role of TRPC6 in apoptosis of skeletal muscle ischemia/reperfusion injury

BACKGROUND

Skeletal muscle ischaemia-reperfusion injury (IRI) is a prevalent condition encountered in clinical practice, characterised by muscular dystrophy. Owing to limited treatment options and poor prognosis, it can lead to movement impairments, tissue damage, and disability. This study aimed to determine and verify the influence of transient receptor potential canonical 6 (TRPC6) on skeletal muscle IRI, and to explore the role of TRPC6 in the occurrence of skeletal muscle IRI and the signal transduction pathways activated by TRPC6 to provide novel insights for the treatment and intervention of skeletal muscle IRI.

METHODS

In vivo ischaemia/reperfusion (I/R) and in vitro hypoxia/reoxygenation (H/R) models were established, and data were comprehensively analysed at histopathological, cellular, and molecular levels, along with the evaluation of the exercise capacity in mice.

RESULTS

By comparing TRPC6 knockout mice with wild-type mice, we found that TRPC6 knockout of TRPC6 could reduced skeletal muscle injury after I/R or H/R, of skeletal muscle, so as therebyto restoringe some exercise capacity inof mice. TRPC6 knockdown can reduced Ca2+ overload in cells, therebyo reducinge apoptosis. In additionAdditionally, we also found that TRPC6 functionsis not only a key ion channel involved in skeletal muscle I/R injury, but also can affects Ca2+ levels and then phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) signalling pathway. by knocking downTherefore, knockdown of TRPC6, so as to alleviated the injury inducedcaused by skeletal muscle I/R or and H/R.

CONCLUSIONS

These findingsdata indicate that the presence of TRPC6 exacerbatescan aggravate the injury of skeletal muscle injury after I/Rischemia/reperfusion, leading towhich not only causes Ca2+ overload and apoptosis., Additionally, it impairsbut also reduces the self- repair ability of cells by inhibiting the expression of the PI3K/Akt/mTOR signalling pathway. ETo exploringe the function and role of TRPC6 in skeletal muscle maycan presentprovide a novelew approachidea for the treatment of skeletal muscle ischemia/reperfusion injury.

The Role of TRP Channels in Sepsis and Colitis

To date, several members of the transient receptor potential (TRP) channels which provide a wide array of roles have been found in the gastrointestinal tract (GI). The goal of earlier research was to comprehend the intricate signaling cascades that contribute to TRP channel activation as well as how these receptors' activity affects other systems. Moreover, there is a large volume of published studies describing the role of TRP channels in a number of pathological disorders, including inflammatory bowel disease (IBD) and sepsis. Nevertheless, the generalizability of these results is subject to certain limitations. For instance, the study of IBD relies on various animal models and experimental methods, which are unable to precisely imitate the multifactorial chronic disease. The diverse pathophysiological mechanisms and unique susceptibility of animals may account for the inconsistency of the experimental data collected. The main purpose of this study was to conduct a comprehensive review and analysis of existing studies on transient receptor potential (TRP) channels implicating specific models of colitis and sepsis, with particular emphasis on their involvement in pathological disorders such as IBD and sepsis. Furthermore, the text endeavors to evaluate the generalizability of experimental findings, taking into consideration the limitations posed by animal models and experimental methodologies. Finally, we also provide an updated schematic of the most important and possible molecular signaling pathways associated with TRP channels in IBD and sepsis.

Impact of TRP Channels on Extracellular Matrix Remodeling: Focus on TRPV4 and Collagen

Disturbed remodeling of the extracellular matrix (ECM) is frequently observed in several high-prevalence pathologies that include fibrotic diseases of organs such as the heart, lung, periodontium, liver, and the stiffening of the ECM surrounding invasive cancers. In many of these lesions, matrix remodeling mediated by fibroblasts is dysregulated, in part by alterations to the regulatory and effector systems that synthesize and degrade collagen, and by alterations to the functions of the integrin-based adhesions that normally mediate mechanical remodeling of collagen fibrils. Cell-matrix adhesions containing collagen-binding integrins are enriched with regulatory and effector systems that initiate localized remodeling of pericellular collagen fibrils to maintain ECM homeostasis. A large cadre of regulatory molecules is enriched in cell-matrix adhesions that affect ECM remodeling through synthesis, degradation, and contraction of collagen fibrils. One of these regulatory molecules is Transient Receptor Potential Vanilloid-type 4 (TRPV4), a mechanically sensitive, Ca2+-permeable plasma membrane channel that regulates collagen remodeling. The gating of Ca2+ across the plasma membrane by TRPV4 and the consequent generation of intracellular Ca2+ signals affect several processes that determine the structural and mechanical properties of collagen-rich ECM. These processes include the synthesis of new collagen fibrils, tractional remodeling by contractile forces, and collagenolysis. While the specific mechanisms by which TRPV4 contributes to matrix remodeling are not well-defined, it is known that TRPV4 is activated by mechanical forces transmitted through collagen adhesion receptors. Here, we consider how TRPV4 expression and function contribute to physiological and pathological collagen remodeling and are associated with collagen adhesions. Over the long-term, an improved understanding of how TRPV4 regulates collagen remodeling could pave the way for new approaches to manage fibrotic lesions.

Piezo channels in the intestinal tract

The intestine is the largest mechanosensitive organ in the human body whose epithelial cells, smooth muscle cells, neurons and enteroendocrine cells must sense and respond to various mechanical stimuli such as motility, distension, stretch and shear to regulate physiological processes including digestion, absorption, secretion, motility and immunity. Piezo channels are a newly discovered class of mechanosensitive ion channels consisting of two subtypes, Piezo1 and Piezo2. Piezo channels are widely expressed in the intestine and are involved in physiological and pathological processes. The present review summarizes the current research progress on the expression, function and regulation of Piezo channels in the intestine, with the aim of providing a reference for the future development of therapeutic strategies targeting Piezo channels.

The Dysfunction of Ca2+ Channels in Hereditary and Chronic Human Heart Diseases and Experimental Animal Models

Chronic heart diseases, such as coronary heart disease, heart failure, secondary arterial hypertension, and dilated and hypertrophic cardiomyopathies, are widespread and have a fairly high incidence of mortality and disability. Most of these diseases are characterized by cardiac arrhythmias, conduction, and contractility disorders. Additionally, interruption of the electrical activity of the heart, the appearance of extensive ectopic foci, and heart failure are all symptoms of a number of severe hereditary diseases. The molecular mechanisms leading to the development of heart diseases are associated with impaired permeability and excitability of cell membranes and are mainly caused by the dysfunction of cardiac Ca2+ channels. Over the past 50 years, more than 100 varieties of ion channels have been found in the cardiovascular cells. The relationship between the activity of these channels and cardiac pathology, as well as the general cellular biological function, has been intensively studied on several cell types and experimental animal models in vivo and in situ. In this review, I discuss the origin of genetic Ca2+ channelopathies of L- and T-type voltage-gated calcium channels in humans and the role of the non-genetic dysfunctions of Ca2+ channels of various types: L-, R-, and T-type voltage-gated calcium channels, RyR2, including Ca2+ permeable nonselective cation hyperpolarization-activated cyclic nucleotide-gated (HCN), and transient receptor potential (TRP) channels, in the development of cardiac pathology in humans, as well as various aspects of promising experimental studies of the dysfunctions of these channels performed on animal models or in vitro.

Novel approaches to target fibroblast mechanotransduction in fibroproliferative diseases

The ability of cells to sense and respond to changes in mechanical environment is vital in conditions of organ injury when the architecture of normal tissues is disturbed or lost. Among the various cellular players that respond to injury, fibroblasts take center stage in re-establishing tissue integrity by secreting and organizing extracellular matrix into stabilizing scar tissue. Activation, activity, survival, and death of scar-forming fibroblasts are tightly controlled by mechanical environment and proper mechanotransduction ensures that fibroblast activities cease after completion of the tissue repair process. Conversely, dysregulated mechanotransduction often results in fibroblast over-activation or persistence beyond the state of normal repair. The resulting pathological accumulation of extracellular matrix is called fibrosis, a condition that has been associated with over 40% of all deaths in the industrialized countries. Consequently, elements in fibroblast mechanotransduction are scrutinized for their suitability as anti-fibrotic therapeutic targets. We review the current knowledge on mechanically relevant factors in the fibroblast extracellular environment, cell-matrix and cell-cell adhesion structures, stretch-activated membrane channels, stress-regulated cytoskeletal structures, and co-transcription factors. We critically discuss the targetability of these elements in therapeutic approaches and their progress in pre-clinical and/or clinical trials to treat organ fibrosis.

Multilayer omics reveals the molecular mechanism of early infection of Clonorchis sinensis juvenile

BACKGROUND

Clonorchiasis remains a non-negligible global zoonosis, causing serious socioeconomic burdens in endemic areas. Clonorchis sinensis infection typically elicits Th1/Th2 mixed immune responses during the course of biliary injury and periductal fibrosis. However, the molecular mechanism by which C. sinensis juvenile initially infects the host remains poorly understood.

METHODS

The BALB/c mouse model was established to study early infection (within 7 days) with C. sinensis juveniles. Liver pathology staining and observation as well as determination of biochemical enzymes, blood routine and cytokines in blood were conducted. Furthermore, analysis of liver transcriptome, proteome and metabolome changes was performed using multi-omics techniques. Statistical analyses were performed using Student's t-test.

RESULTS

Histopathological analysis revealed that liver injury, characterized by collagen deposition and inflammatory cell infiltration, occurred as early as 24 h of infection. Blood indicators including ALT, AST, WBC, CRP and IL-6 indicated that both liver injury and systemic inflammation worsened as the infection progressed. Proteomic data showed that apoptosis and junction-related pathways were enriched within 3 days of infection, indicating the occurrence of liver injury. Furthermore, proteomic and transcriptomic analysis jointly verified that the detoxification and antioxidant defense system was activated by enrichment of glutathione metabolism and cytochrome P450-related pathways in response to acute liver injury. Proteomic-based GO analysis demonstrated that biological processes such as cell deformation, proliferation, migration and wound healing occurred in the liver during the early infection. Correspondingly, transcriptomic results showed significant enrichment of cell cycle pathway on day 3 and 7. In addition, the KEGG analysis of multi-omics data demonstrated that numerous pathways related to immunity, inflammation, tumorigenesis and metabolism were enriched in the liver. Besides, metabolomic screening identified several metabolites that could promote inflammation and hepatobiliary periductal fibrosis, such as CA7S.

CONCLUSIONS

This study revealed that acute inflammatory injury was rapidly triggered by initial infection by C. sinensis juveniles in the host, accompanied by the enrichment of detoxification, inflammation, fibrosis, tumor and metabolism-related pathways in the liver, which provides a new perspective for the early intervention and therapy of clonorchiasis.

Analysis of the Effect of the TRPC4/TRPC5 Blocker, ML204, in Sucrose-Induced Metabolic Imbalance

Sugar-induced metabolic imbalances are a major health problem since an excessive consumption of saccharides has been linked to greater obesity rates at a global level. Sucrose, a disaccharide composed of 50% glucose and 50% fructose, is commonly used in the food industry and found in a range of fast, restaurant, and processed foods. Herein, we investigated the effects of a TRPC4/TRPC5 blocker, ML204, in the metabolic imbalances triggered by early exposure to sucrose-enriched diet in mice. TRPC4 and TRPC5 belong to the family of non-selective Ca+2 channels known as transient receptor potential channels. High-sucrose (HS)-fed animals with hyperglycaemia and dyslipidaemia, were accompanied by increased body mass index. mesenteric adipose tissue accumulation with larger diameter cells and hepatic steatosis in comparison to those fed normal diet. HS mice also exhibited enhanced adipose, liver, and pancreas TNFα and VEGF levels. ML204 exacerbated hyperglycaemia, dyslipidaemia, fat tissue deposition, hepatic steatosis, and adipose tissue and liver TNFα in HS-fed mice. Normal mice treated with the blocker had greater hepatic steatosis and adipose tissue cell numbers/diameter than those receiving vehicle, but showed no significant changes in tissue inflammation, glucose, and lipid levels. The results indicate that TRPC4/TRPC5 protect against the metabolic imbalances caused by HS ingestion.

Humanized NSG Mouse Models as a Preclinical Tool for Translational Research in Inflammatory Bowel Diseases

The development of animal models reflecting the pathologies of ulcerative colitis (UC) and Crohn's disease (CD) remains a major challenge. The NOD/SCID/IL2rγnull (NSG) mouse strain, which is immune-compromised, tolerates the engraftment of human peripheral blood mononuclear cells (PBMC) derived from patients with UC (NSG-UC) or CD (NSG-CD). This offers the opportunity to examine the impact of individual immunological background on the development of pathophysiological manifestations. When challenged with ethanol, NSG-UC mice exhibited a strong pro-inflammatory response, including the development of edemas, influx of human T cells, B cells and monocytes into the mucosa and submucosa, and elevated expression of the inflammatory markers CRP and CCL-7. Fibrotic alterations were characterized by an influx of fibroblasts and a thickening of the muscularis mucosae. In contrast, the development of pathological manifestations in NSG-CD mice developed without challenge and was signified by extensive collagen deposition between the muscularis propria and muscularis mucosae, as observed in the areas of strictures in CD patients. Vimentin-expressing fibroblasts supplanting colonic crypts and elevated expression of HGF and TGFß corroborated the remodeling phenotype. In summary, the NSG-UC and NSG-CD models partially reflect these human diseases and are powerful tools to examine the mechanism underlying the inflammatory processes in UC and CD.

Cellular mechanotransduction in health and diseases: from molecular mechanism to therapeutic targets

Cellular mechanotransduction, a critical regulator of numerous biological processes, is the conversion from mechanical signals to biochemical signals regarding cell activities and metabolism. Typical mechanical cues in organisms include hydrostatic pressure, fluid shear stress, tensile force, extracellular matrix stiffness or tissue elasticity, and extracellular fluid viscosity. Mechanotransduction has been expected to trigger multiple biological processes, such as embryonic development, tissue repair and regeneration. However, prolonged excessive mechanical stimulation can result in pathological processes, such as multi-organ fibrosis, tumorigenesis, and cancer immunotherapy resistance. Although the associations between mechanical cues and normal tissue homeostasis or diseases have been identified, the regulatory mechanisms among different mechanical cues are not yet comprehensively illustrated, and no effective therapies are currently available targeting mechanical cue-related signaling. This review systematically summarizes the characteristics and regulatory mechanisms of typical mechanical cues in normal conditions and diseases with the updated evidence. The key effectors responding to mechanical stimulations are listed, such as Piezo channels, integrins, Yes-associated protein (YAP) /transcriptional coactivator with PDZ-binding motif (TAZ), and transient receptor potential vanilloid 4 (TRPV4). We also reviewed the key signaling pathways, therapeutic targets and cutting-edge clinical applications of diseases related to mechanical cues.

TRPA1 deficiency attenuates cardiac fibrosis via regulating GRK5/NFAT signaling in diabetic rats

BACKGROUND

Transient receptor potential ankyrin 1 (TRPA1) has been linked to the development of various cardiovascular diseases, but its role in diabetic cardiomyopathy is not well understood. This study aimed to investigate the protective effects of TRPA1 deficiency on diabetic cardiomyopathy in rats with streptozotocin-induced diabetes and in neonatal rat cardiac fibroblasts (CFs) exposed to high glucose (HG).

METHODS

Cardiac TRPA1 expression levels were measured in diabetic rats. Cardiac function, remodeling, and fibrosis were analyzed in Sprague-Dawley (SD) rats and TRPA1-deficient rats with diabetic cardiomyopathy. In vitro, fibrosis was measured in CFs exposed to HG. Additionally, 1,8-cineole, a natural inhibitor of TRPA1, was used to treat SD rats with diabetic cardiomyopathy.

RESULTS

TRPA1 expression was increased in the heart tissue of diabetic rats and in CFs treated with HG. TRPA1 deficiency significantly improved cardiac function in diabetic rats, as evidenced by improved echocardiography and reduced cardiac hypertrophy and fibrosis. In vitro, TRPA1 deficiency suppressed the transformation of HG-induced CFs into myofibroblasts. The cardioprotective effect of TRPA1 deficiency was found to inhibit cardiac fibrosis by regulating GRK5/NFAT signaling. Furthermore, inhibition of GRK5/NFAT signaling abolished the promotion of CF transformation into myofibroblasts by TRPA1 activation. Inhibition of TRPA1 activation by 1,8-cineole reduced cardiac dysfunction and remodeling in diabetic rats by regulating GRK5/NFAT signaling.

CONCLUSIONS

TRPA1 deficiency reduced cardiac fibrosis in diabetic rats and inhibited HG-induced CF activation in vitro by regulating GRK5/NFAT signaling. The TRPA1 inhibitor 1,8-cineole may serve as a novel therapeutic agent for the treatment of diabetic cardiomyopathy.

Pathophysiological Roles of the TRPV4 Channel in the Heart

The transient receptor potential vanilloid 4 (TRPV4) channel is a non-selective cation channel that is mostly permeable to calcium (Ca²⁺), which participates in intracellular Ca²⁺ handling in cardiac cells. It is widely expressed through the body and is activated by a large spectrum of physicochemical stimuli, conferring it a role in a variety of sensorial and physiological functions. Within the cardiovascular system, TRPV4 expression is reported in cardiomyocytes, endothelial cells (ECs) and smooth muscle cells (SMCs), where it modulates mitochondrial activity, Ca²⁺ homeostasis, cardiomyocytes electrical activity and contractility, cardiac embryonic development and fibroblast proliferation, as well as vascular permeability, dilatation and constriction. On the other hand, TRPV4 channels participate in several cardiac pathological processes such as the development of cardiac fibrosis, hypertrophy, ischemia-reperfusion injuries, heart failure, myocardial infarction and arrhythmia. In this manuscript, we provide an overview of TRPV4 channel implications in cardiac physiology and discuss the potential of the TRPV4 channel as a therapeutic target against cardiovascular diseases.

TRPC6 promotes daunorubicin-induced mitochondrial fission and cell death in rat cardiomyocytes with the involvement of ERK1/2-DRP1 activation

Daunorubicin (DNR-) induced cardiotoxicity seriously restricts its clinical application. Transient receptor potential cation channel subfamily C member 6 (TRPC6) is involved in multiple cardiovascular physiological and pathophysiological processes. However, the role of TRPC6 anthracycline-induced cardiotoxicity (AIC) remains unclear. Mitochondrial fragmentation greatly promotes AIC. TRPC6-mediated ERK1/2 activation has been shown to favor mitochondrial fission in dentate granule cells. The aim of the present study was to elucidate the effects of TRPC6 on daunorubicin- induced cardiotoxicity and identify the mechanisms associated with mitochondrial dynamics. The sparkling results showed that TRPC6 was upregulated in models in vitro and in vivo. TRPC6 knockdown protected cardiomyocytes from DNR-induced cell apoptosis and death. DNR largely facilitated mitochondrial fission, boosted mitochondrial membrane potential collapse and damaged debilitated mitochondrial respiratory function in H9c2 cells，these effects were accompanied by TRPC6 upregulation. siTRPC6 effectively inhibited these mitochondrial adverse aspects showing a positive unexposed effect on mitochondrial morphology and function. Concomitantly, ERK1/2-DRP1 which is related to mitochondrial fission was significantly activated with amplified phosphorylated forms in DNR-treated H9c2 cells. siTRPC6 effectively suppressedERK1/2-DPR1 over activation, hinting at a potential correlation between TRPC6 and ERK1/2-DRP1 by which mitochondrial dynamics are possibly modulated in AIC. TRPC6 knockdown also raised the Bcl-2/Bax ratio, which may help to block mitochondrial fragmentation-related functional impairment and apoptotic signaling. These findings suggested an essential role of TRPC6 in AIC by intensifying mitochondrial fission and cell death via ERK1/2-DPR1, which could be a potential therapeutic target for AIC.

The Pleiotropic Role of Extracellular ATP in Myocardial Remodelling

Myocardial remodelling is a molecular, cellular, and interstitial adaptation of the heart in response to altered environmental demands. The heart undergoes reversible physiological remodelling in response to changes in mechanical loading or irreversible pathological remodelling induced by neurohumoral factors and chronic stress, leading to heart failure. Adenosine triphosphate (ATP) is one of the potent mediators in cardiovascular signalling that act on the ligand-gated (P2X) and G-protein-coupled (P2Y) purinoceptors via the autocrine or paracrine manners. These activations mediate numerous intracellular communications by modulating the production of other messengers, including calcium, growth factors, cytokines, and nitric oxide. ATP is known to play a pleiotropic role in cardiovascular pathophysiology, making it a reliable biomarker for cardiac protection. This review outlines the sources of ATP released under physiological and pathological stress and its cell-specific mechanism of action. We further highlight a series of cardiovascular cell-to-cell communications of extracellular ATP signalling cascades in cardiac remodelling, which can be seen in hypertension, ischemia/reperfusion injury, fibrosis, hypertrophy, and atrophy. Finally, we summarize current pharmacological intervention using the ATP network as a target for cardiac protection. A better understanding of ATP communication in myocardial remodelling could be worthwhile for future drug development and repurposing and the management of cardiovascular diseases.

The Role of Myofibroblasts in Physiological and Pathological Tissue Repair

Myofibroblasts are the construction workers of wound healing and repair damaged tissues by producing and organizing collagen/extracellular matrix (ECM) into scar tissue. Scar tissue effectively and quickly restores the mechanical integrity of lost tissue architecture but comes at the price of lost tissue functionality. Fibrotic diseases caused by excessive or persistent myofibroblast activity can lead to organ failure. This review defines myofibroblast terminology, phenotypic characteristics, and functions. We will focus on the central role of the cell, ECM, and tissue mechanics in regulating tissue repair by controlling myofibroblast action. Additionally, we will discuss how therapies based on mechanical intervention potentially ameliorate wound healing outcomes. Although myofibroblast physiology and pathology affect all organs, we will emphasize cutaneous wound healing and hypertrophic scarring as paradigms for normal tissue repair versus fibrosis. A central message of this review is that myofibroblasts can be activated from multiple cell sources, varying with local environment and type of injury, to either restore tissue integrity and organ function or create an inappropriate mechanical environment.

TRPA1 participation in behavioral impairment induced by chronic corticosterone administration

RATIONALE

Major depressive disorder (MDD) is one of the most diagnosed mental disorders. Despite this, its pathophysiology remains poorly understood. In this context, basic research aims to unravel the pathophysiological mechanisms of MDD as well as investigate new targets and substances with therapeutic potential. Transient receptor potential ankyrin 1 (TRPA1) is a transmembrane channel considered a sensor for inflammation and oxidative stress. Importantly, both inflammation and oxidative stress have been suggested as participants in the pathophysiology of MDD. However, the potential participation of TRPA1 in depressive disorder remains poorly investigated.

OBJECTIVE

To investigate the involvement of the TRPA1 channel in the behavioral changes induced by chronic corticosterone administration (CCA) in male mice.

METHODS

Swiss male mice were exposed to 21 days of CCA protocol and then treated with HC-030031 or A-967079, TRPA1 antagonists. Behavioral tests, analyzes of oxidative parameters and TRPA1 immunocontent were performed in the prefrontal cortex (PFC) and hippocampus (HIP).

RESULTS

CCA induced despair-like behavior in mice accompanied by an increase in the levels of hydrogen peroxide (H₂O₂), a TRPA1 agonist, which was reversed by TRPA1 antagonists and ketamine (positive control). In addition, CCA protocol reduced the immunocontent of this channel in the HIP and showed a tendency to increase the TRPA1 protein expression in the PFC.

CONCLUSION

Our work suggests that TRPA1 channel appears crucial to mediate the behavioral impairment induced by CCA in male Swiss mice.

Inhibition of TRPC6 suppressed TGFβ-induced fibroblast-myofibroblast transdifferentiation in renal interstitial NRK-49F cells

Renal fibrosis is a global health concern with limited curative treatment. Canonical transient receptor potential channel 6 (TRPC6), a nonselective cation channel, has been shown to regulate the renal fibrosis in murine models. However, the molecular mechanism is unclear. Fibroblast-myofibroblast transdifferentiation is one of the critical steps in the progression of renal fibrosis. In the present study, we demonstrate that transforming growth factor (TGF)-β1 exposure significantly increases the TRPC6 expression in renal interstitial fibroblast NRK-49F cells. Pharmacological inhibition of TRPC6 and knockdown of Trpc6 by siRNA alleviate TGF-β1-increased expression levels of α-smooth muscle actin (α-SMA) and collagen I, two key markers of myofibroblasts. Although direct activation of TRPC6 by 1-oleoyl-2-acetyl-sn-glycerol (OAG) does not affect the expression of α-SMA and collagen I, OAG potentiates TGF-β1-induced fibroblast-myofibroblast transdifferentiation. Further study demonstrates that TGF-β1 exposure increases the phosphorylation level of p38 and Yes-associated protein (YAP) translocation into the nuclei. Inhibition of p38 and YAP decreases TGF-β1-enhanced TRPC6 and α-SMA expression. In conclusion, we demonstrate that TRPC6 is a key regulator of TGF-β1-induced fibroblast-myofibroblast transdifferentiation and provides the mechanism of how TGF-β1 exposure regulates TRPC6 expression in NRK-49F fibroblasts.

Emerging role of transient receptor potential (TRP) ion channels in cardiac fibroblast pathophysiology

Cardiac fibroblasts make up a major proportion of non-excitable cells in the heart and contribute to the cardiac structural integrity and maintenance of the extracellular matrix. During myocardial injury, fibroblasts can be activated to trans-differentiate into myofibroblasts, which secrete extracellular matrix components as part of healing, but may also induce cardiac fibrosis and pathological cardiac structural and electrical remodeling. The mechanisms regulating such cellular processes still require clarification, but the identification of transient receptor potential (TRP) channels in cardiac fibroblasts could provide further insights into the fibroblast-related pathophysiology. TRP proteins belong to a diverse superfamily, with subgroups such as the canonical (TRPC), vanilloid (TRPV), melastatin (TRPM), ankyrin (TRPA), polycystin (TRPP), and mucolipin (TRPML). Several TRP proteins form non-selective channels that are permeable to cations like Na+ and Ca2+ and are activated by various chemical and physical stimuli. This review highlights the role of TRP channels in cardiac fibroblasts and the possible underlying signaling mechanisms. Changes in the expression or activity of TRPs such as TRPCs, TRPVs, TRPMs, and TRPA channels modulate cardiac fibroblasts and myofibroblasts, especially under pathological conditions. Such TRPs contribute to cardiac fibroblast proliferation and differentiation as well as to disease conditions such as cardiac fibrosis, atrial fibrillation, and fibroblast metal toxicity. Thus, TRP channels in fibroblasts represent potential drug targets in cardiac disease.

Function and therapeutic potential of transient receptor potential ankyrin 1 in fibrosis

The transient receptor potential (TRP) protein superfamily is a special group of cation channels expressed in different cell types and signaling pathways. In this review, we focus on TRPA1 (transient receptor potential ankyrin 1), an ion channel in this family that exists in the cell membrane and shows a different function from other TRP channels. TRPA1 usually has a special activation effect that can induce cation ions, especially calcium ions, to flow into activated cells. In this paper, we review the role of TRPA1 in fibroblasts. To clarify the relationship between fibroblasts and TRPA1, we have also paid special attention to the interactions between TRPA1 and inflammatory factors leading to fibroblast activation. TRPA1 has different functions in the fibrosis process in different organs, and there have also been interesting discussions of the mechanism of TRPA1 in fibroblasts. Therefore, this review aims to describe the function of TRP channels in controlling fibrosis through fibroblasts in different organ inflammatory and immune-mediated diseases. We attempt to prove that TRPA1 is a target for fibrosis. In fact, some clinical trials have already proven that TRPA1 is a potential adjuvant therapy for treating fibrosis.

Ion channels as a therapeutic target for renal fibrosis

Renal ion channel transport and electrolyte disturbances play an important role in the process of functional impairment and fibrosis in the kidney. It is well known that there are limited effective drugs for the treatment of renal fibrosis, and since a large number of ion channels are involved in the renal fibrosis process, understanding the mechanisms of ion channel transport and the complex network of signaling cascades between them is essential to identify potential therapeutic approaches to slow down renal fibrosis. This review summarizes the current work of ion channels in renal fibrosis. We pay close attention to the effect of cystic fibrosis transmembrane conductance regulator (CFTR), transmembrane Member 16A (TMEM16A) and other Cl− channel mediated signaling pathways and ion concentrations on fibrosis, as well as the various complex mechanisms for the action of Ca2+ handling channels including Ca2+-release-activated Ca2+ channel (CRAC), purinergic receptor, and transient receptor potential (TRP) channels. Furthermore, we also focus on the contribution of Na+ transport such as epithelial sodium channel (ENaC), Na+, K+-ATPase, Na+-H+ exchangers, and K+ channels like Ca2+-activated K+ channels, voltage-dependent K+ channel, ATP-sensitive K+ channels on renal fibrosis. Proposed potential therapeutic approaches through further dissection of these mechanisms may provide new therapeutic opportunities to reduce the burden of chronic kidney disease.

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.

Transient Receptor Potential Vanilloid-1 (TRPV1) Alleviates Hepatic Fibrosis via TGF-β Signaling

Hepatic fibrosis is a major global health problem and considered a leading cause of liver-related morbidity and mortality worldwide. Although previous studies have suggested that transient receptor potential vanilloid-1 (TRPV1) is protective against cardiac and renal fibrosis, its functional role in hepatic fibrosis has remained elusive. Herein, we characterize the effects of TRPV1 on carbon tetrachloride- (CCl4-) induced mice, in vitro transforming growth factor-β- (TGF-β-) treated hepatic stellate cells (HSCs), and human fibrosis specimens. Finally, our results demonstrated the significant TRPV1 downregulation in human liver fibrosis tissues. Knocking out TRPV1 significantly increased the expression of various hepatic fibrosis markers, while the expression of these biomarkers declined markedly in capsaicin-activated mice. Moreover, our study revealed that knocking down TRPV1 would enhance the promotive effect of TGF-β on HSC proliferation, cell cycle, cell apoptosis, and ECM expression. Also, such promotive effect can be partially reversible by capsaicin, an exogenous activator of TRPV1. Collectively, the obtained data suggest that TRPV1 may alleviate CCl4-induced hepatic fibrosis and attenuate the effect of TGF-β on HSC activation, proliferation, and apoptosis, which overall implies that targeting TRPV1 channel activity may be an effective therapeutic strategy for treating hepatic fibrosis.

Focusing on Mechanoregulation Axis in Fibrosis: Sensing, Transduction and Effecting

Fibrosis, a pathologic process featured by the excessive deposition of connective tissue components, can affect virtually every organ and has no satisfactory therapy yet. Fibrotic diseases are often associated with organ dysfunction which leads to high morbidity and mortality. Biomechanical stmuli and the corresponding cellular response havebeen identified in fibrogenesis, as the fibrotic remodeling could be seen as the incapacity to reestablish mechanical homeostasis: along with extracellular matrix accumulating, the physical property became more “stiff” and could in turn induce fibrosis. In this review, we provide a comprehensive overview of mechanoregulation in fibrosis, from initialing cellular mechanosensing to intracellular mechanotransduction and processing, and ends up in mechanoeffecting. Our contents are not limited to the cellular mechanism, but further expand to the disorders involved and current clinical trials, providing an insight into the disease and hopefully inspiring new approaches for the treatment of tissue fibrosis.

Revisiting fibrosis in inflammatory bowel disease: the gut thickens

Intestinal fibrosis, which is usually the consequence of chronic inflammation, is a common complication of inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis. In the past few years, substantial advances have been made in the areas of pathogenesis, diagnosis and management of intestinal fibrosis. Of particular interest have been inflammation-independent mechanisms behind the gut fibrotic process, genetic and environmental risk factors (such as the role of the microbiota), and the generation of new in vitro and in vivo systems to study fibrogenesis in the gut. A huge amount of work has also been done in the area of biomarkers to predict or detect intestinal fibrosis, including novel cross-sectional imaging techniques. In parallel, researchers are embarking on developing and validating clinical trial end points and protocols to test novel antifibrotic agents, although no antifibrotic therapies are currently available. This Review presents the state of the art on the most recently identified pathogenic mechanisms of this serious IBD-related complication, focusing on possible targets of antifibrotic therapies, management strategies, and factors that might predict fibrosis progression or response to treatment.

PACS2-TRPV1 axis is required for ER-mitochondrial tethering during ER stress and lung fibrosis

Endoplasmic reticulum (ER) and mitochondria (mito) play a vital role in alveolar type II cell (AEC2) homeostasis and are both stressed in patients with idiopathic pulmonary fibrosis (IPF). Up to now, no data are available with regard to ER–mito cross talk and tethering under conditions of IPF. We here demonstrate that ER–mitochondrial tethering is reduced upon experimental ER stress in vitro and in the IPF AECII ex vivo, and this is—at least in part—due to decreased phosphofurin acidic cluster sorting protein 2 (PACS-2, also called PACS2) protein levels. PACS2 levels are influenced by its interaction with the transient receptor potential cation channel subfamily V member 1 (TRPV1) and can be experimentally modified by the TRPV1-modulating drug capsaicin (CPS). Employing alveolar epithelial cells with overexpression of the terminal ER stress signaling factor Chop or the IPF-associated surfactant protein C mutation (SPC^Δexon4) in vitro, we observed a restoration of PACS2 levels upon treatment with CPS. Similarly, treatment of precision cut lung slices from IPF patients with CPS ex vivo forwarded similar effects. Importantly, in all models such kind of intervention also greatly reduced the extent of alveolar epithelial apoptosis. We therefore conclude that therapeutic targeting of the PACS2–TRPV1 axis represents an interesting novel, epithelial-protective approach in IPF.

Distribution and Assembly of TRP Ion Channels

In the last several decades, a large family of ion channels have been identified and studied intensively as cellular sensors for diverse physical and/or chemical stimuli. Named transient receptor potential (TRP) channels, they play critical roles in various aspects of cellular physiology. A large number of human hereditary diseases are found to be linked to TRP channel mutations, and their dysregulations lead to acute or chronical health problems. As TRP channels are named and categorized mostly based on sequence homology rather than functional similarities, they exhibit substantial functional diversity. Rapid advances in TRP channel study have been made in recent years and reported in a vast body of literature; a summary of the latest advancements becomes necessary. This chapter offers an overview of current understandings of TRP channel distribution and subunit assembly.

Transcription Factors Involved in the Development and Prognosis of Cardiac Remodeling

To compensate increasing workload, heart must work harder with structural changes, indicated by increasing size and changing shape, causing cardiac remodeling. However, pathological and unlimited compensated cardiac remodeling will ultimately lead to decompensation and heart failure. In the past decade, numerous studies have explored many signaling pathways involved in cardiac remodeling, but the complete mechanism of cardiac remodeling is still unrecognized, which hinders effective treatment and drug development. As gene transcriptional regulators, transcription factors control multiple cellular activities and play a critical role in cardiac remodeling. This review summarizes the regulation of fetal gene reprogramming, energy metabolism, apoptosis, autophagy in cardiomyocytes and myofibroblast activation of cardiac fibroblasts by transcription factors, with an emphasis on their potential roles in the development and prognosis of cardiac remodeling.

Increased transient receptor potential canonical 3 activity is involved in the pathogenesis of detrusor overactivity by dynamic interaction with Na+/Ca2+ exchanger 1

Transient receptor potential canonical 3 (TRPC3) is a nonselective cation channel, and its dysfunction is the basis of many clinical diseases. However, little is known about its possible role in the bladder. The purpose of this study was to explore the function and mechanism of TRPC3 in partial bladder outlet obstruction (PBOO)-induced detrusor overactivity (DO). We studied 31 adult female rats with DO induced by PBOO (the DO group) and 40 sham-operated rats (the control group). Here we report that the expression of TRPC3 in the bladder of DO rats increased significantly. Furthermore, PYR10, which can selectively inhibit the TRPC3 channel, significantly reduced bladder excitability in DO and control rats, but the decrease of the bladder excitability of DO rats was more obvious. PYR10 significantly reduced the intracellular calcium concentration in smooth muscle cells (SMCs) in DO and control rats. Finally, Na+/Ca2+ exchanger 1 (NCX1) colocalizes with TRPC3 and affects its expression and function. Collectively, these results indicate that TRPC3 plays an important role in the pathogenesis of DO through a synergistic effect with NCX1. TRPC3 and NCX1 may be new therapeutic targets for DO.

TRPC3, but not TRPC1, as a good therapeutic target for standalone or complementary treatment of DMD

Background

Duchenne muscular dystrophy (DMD) is an X-linked inherited disease caused by mutations in the gene encoding dystrophin that leads to a severe and ultimately life limiting muscle-wasting condition. Recombinant adeno-associated vector (rAAV)-based gene therapy is promising, but the size of the full-length dystrophin cDNA exceeds the packaging capacity of a rAAV. Alternative or complementary strategies that could treat DMD patients are thus needed. Intracellular calcium overload due to a sarcolemma permeability to calcium (SPCa) increase is an early and critical step of the DMD pathogenesis. We assessed herein whether TRPC1 and TRPC3 calcium channels may be involved in skeletal muscle SPCa alterations and could represent therapeutic targets to treat DMD.

Methods

All experiments were conducted in the DMD^mdx rat, an animal model that closely reproduces the human DMD disease. We measured the cytosolic calcium concentration ([Ca²⁺]_c) and SPCa in EDL (Extensor Digitorum Longus) muscle fibers from age-matched WT and DMD^mdx rats of 1.5 to 7 months old. TRPC1 and TRPC3 expressions were measured in the EDL muscles at both the mRNA and protein levels, by RT-qPCR, western blot and immunocytofluorescence analysis.

Results

As expected from the malignant hyperthermia like episodes observed in several DMD^mdx rats, calcium homeostasis alterations were confirmed by measurements of early increases in [Ca²⁺]_c and SPCa in muscle fibers. TRPC3 and TRPC1 protein levels were increased in DMD^mdx rats. This was observed as soon as 1.5 months of age for TRPC3 but only at 7 months of age for TRPC1. A slight but reliable shift of the TRPC3 apparent molecular weight was observed in DMD^mdx rat muscles. Intracellular localization of both channels was not altered. We thus focused our attention on TRPC3. Application of Pyr10, a specific inhibitor of TRPC3, abolished the differences between SPCa values measured in WT and DMD^mdx. Finally, we showed that a rAAV-microdystrophin based treatment induced a high microdystrophin expression but only partial prevention of calcium homeostasis alterations, skeletal muscle force and TRPC3 protein increase.

Conclusions

All together our results show that correcting TRPC3 channel expression and/or activity appear to be a promising approach as a single or as a rAAV-based complementary therapy to treat DMD.

Transient Receptor Potential Channels in the Epithelial-to-Mesenchymal Transition

The epithelial-to-mesenchymal transition (EMT) is a strictly regulated process that is indispensable for normal development, but it can result in fibrosis and cancer progression. It encompasses a complete alteration of the cellular transcriptomic profile, promoting the expression of genes involved in cellular migration, invasion and proliferation. Extracellular signaling factors driving the EMT process require secondary messengers to convey their effects to their targets. Due to its remarkable properties, calcium represents an ideal candidate to translate molecular messages from receptor to effector. Therefore, calcium-permeable ion channels that facilitate the influx of extracellular calcium into the cytosol can exert major influences on cellular phenotype. Transient receptor potential (TRP) channels represent a superfamily of non-selective cation channels that decode physical and chemical stimuli into cellular behavior. Their role as cellular sensors renders them interesting proteins to study in the context of phenotypic transitions, such as EMT. In this review, we elaborate on the current knowledge regarding TRP channel expression and activity in cellular phenotype and EMT.

Mutation of the TRPM3 cation channel underlies progressive cataract development and lens calcification associated with pro-fibrotic and immune cell responses

Transient-receptor-potential cation channel, subfamily M, member 3 (TRPM3) serves as a polymodal calcium sensor in diverse mammalian cell-types. Mutation of the human TRPM3 gene (TRPM3) has been linked with inherited forms of early-onset cataract with or without other eye abnormalities. Here, we have characterized the ocular phenotypes of germline "knock-in" mice that harbor a human cataract-associated isoleucine-to-methionine mutation (p.I65M) in TRPM3 (Trpm3-mutant) compared with germline "knock-out" mice that functionally lack TRPM3 (Trpm3-null). Despite strong expression of Trpm3 in lens epithelial cells, neither heterozygous (Trpm3^+/- ) nor homozygous (Trpm3^-/- ) Trpm3-null mice developed cataract; however, the latter exhibited a mild impairment of lens growth. In contrast, homozygous Trpm3-M/M mutants developed severe, progressive, anterior pyramid-like cataract with microphthalmia, whereas heterozygous Trpm3-I/M and hemizygous Trpm3-M/- mutants developed anterior pyramidal cataract with delayed onset and progression-consistent with a semi-dominant lens phenotype. Histochemical staining revealed abnormal accumulation of calcium phosphate-like deposits and collagen fibrils in Trpm3-mutant lenses and immunoblotting detected increased αII-spectrin cleavage products consistent with calpain hyper-activation. Immunofluorescent confocal microscopy of Trpm3-M/M mutant lenses revealed fiber cell membrane degeneration that was accompanied by accumulation of alpha-smooth muscle actin positive (α-SMA+ve) myofibroblast-like cells and macrosialin positive (CD68+ve) macrophage-like cells. Collectively, our mouse model data support an ocular disease association for TRPM3 in humans and suggest that (1) Trpm3 deficiency impaired lens growth but not lens transparency and (2) Trpm3 dysfunction resulted in progressive lens degeneration and calcification coupled with pro-fibrotic (α-SMA+ve) and immune (CD68+ve) cell responses.

Channelling the Force to Reprogram the Matrix: Mechanosensitive Ion Channels in Cardiac Fibroblasts

Cardiac fibroblasts (CF) play a pivotal role in preserving myocardial function and integrity of the heart tissue after injury, but also contribute to future susceptibility to heart failure. CF sense changes to the cardiac environment through chemical and mechanical cues that trigger changes in cellular function. In recent years, mechanosensitive ion channels have been implicated as key modulators of a range of CF functions that are important to fibrotic cardiac remodelling, including cell proliferation, myofibroblast differentiation, extracellular matrix turnover and paracrine signalling. To date, seven mechanosensitive ion channels are known to be functional in CF: the cation non-selective channels TRPC6, TRPM7, TRPV1, TRPV4 and Piezo1, and the potassium-selective channels TREK-1 and KATP. This review will outline current knowledge of these mechanosensitive ion channels in CF, discuss evidence of the mechanosensitivity of each channel, and detail the role that each channel plays in cardiac remodelling. By better understanding the role of mechanosensitive ion channels in CF, it is hoped that therapies may be developed for reducing pathological cardiac remodelling.

Upregulation of transient receptor potential melastatin 4 (TRPM4) in ventricular fibroblasts from heart failure patients

The transient receptor potential melastatin 4 (TRPM4) is a Ca2+-activated nonselective monovalent cation channel belonging to the TRP channel superfamily. TRPM4 is widely expressed in various tissues and most abundantly expressed in the heart. TRPM4 plays a critical role in cardiac conduction. Patients carrying a gain-of-function or loss-of-function mutation of TRPM4 display impaired cardiac conduction. Knockout or over-expression of TRPM4 in mice recapitulates conduction defects in patients. Moreover, recent studies have indicated that TRPM4 plays a role in hypertrophy and heart failure. Whereas the role of TRPM4 mediated by cardiac myocytes has been well investigated, little is known about TRPM4 and its role in cardiac fibroblasts. Here we show that in human left ventricular fibroblasts, TRPM4 exhibits typical Ca2+-activation characteristics, linear current-voltage (I-V) relation, and monovalent permeability. TRPM4 currents recorded in fibroblasts from heart failure patients (HF) are more than 2-fold bigger than those from control individuals (CTL). The enhanced functional TRPM4 in HF is not resulted from changed channel properties, as TRPM4 currents from both HF and CTL fibroblasts demonstrate similar sensitivity to intracellular calcium activation and extracellular 9-phenanthrol (9-phen) blockade. Consistent with enhanced TRPM4 activity, the protein level of TRPM4 is about 2-fold higher in HF than that of CTL hearts. Moreover, TRPM4 current in CTL fibroblasts is increased after 24 hours of TGFβ1 treatment, implying that TRPM4 in vivo may be upregulated by fibrogenesis promotor TGFβ1. The upregulated TRPM4 in HF fibroblasts suggests that TRPM4 may play a role in cardiac fibrogenesis under various pathological conditions.

Transient receptor potential (TRP) channels in human colorectal cancer: evidence and perspectives

Colorectal cancer (CRC) is one of the leading causes of death in the civilized world. Transient receptor potential channels (TRPs) are a heterogeneous family of cation channels that play an important role in gastrointestinal physiology. TRPs have been linked with carcinogenesis in the colon and their role as potential therapeutic targets and prognostic biomarkers is under investigation.

Lithium Reduces Migration and Collagen Synthesis Activity in Human Cardiac Fibroblasts by Inhibiting Store-Operated Ca2+ Entry

Cardiac fibrosis plays a vital role in the pathogenesis of heart failure. Fibroblast activity is enhanced by increases in store-operated Ca²⁺ entry (SOCE) and calcium release-activated calcium channel protein 1 (Orai1) levels. Lithium regulates SOCE; however, whether therapeutic concentrations of lithium can be used to inhibit cardiac fibrogenesis is unknown. Migration and proliferation assays, Western blotting, real-time reverse-transcription polymerase chain reaction analysis, and calcium fluorescence imaging were performed in human cardiac fibroblasts treated with or without LiCl at 1.0 mM (i.e., therapeutic peak level) or 0.1 mM (i.e., therapeutic trough level) for 24 h. Results showed that LiCl (0.1 mM, but not 1.0 mM) inhibited the migration and collagen synthesis ability of cardiac fibroblasts. Additionally, thapsigargin-induced SOCE was reduced in fibroblasts treated with LiCl (0.1 mM). The expression level of Orai1 was lower in LiCl (0.1 mM)-treated fibroblasts relative to the fibroblasts without LiCl treatment. Fibroblasts treated with a combination of LiCl (0.1 mM) and 2-APB (10 μM, an Orai1 inhibitor) demonstrated similar migration and collagen synthesis abilities as those in LiCl (0.1 mM)-treated fibroblasts. Altogether, lithium at therapeutic trough levels reduced the migration and collagen synthesis abilities of human cardiac fibroblasts by inhibiting SOCE and Orai1 expression.

Mechanosensing dysregulation in the fibroblast: A hallmark of the aging heart

The myofibroblast is a specialized fibroblast that expresses α-smooth muscle actin (α-SMA) and participates in wound contraction and fibrosis. The fibroblast to myofibroblast transition depends on chemical and mechanical signals. A fibroblast senses the changes in the environment (extracellular matrix (ECM)) and transduces these changes to the cytoskeleton and the nucleus, resulting in activation or inhibition of α-SMA transcription in a process called mechanosensing. A stiff matrix greatly facilitates the transition from fibroblast to myofibroblast, and although the aging heart is much stiffer than the young one, the aging fibroblast has difficulties in transitioning into the contractile phenotype. This suggests that the events occurring downstream of the matrix, such as activation or changes in expression levels of various proteins participating in mechanotransduction can negatively alter the ability of the aging fibroblast to become a myofibroblast. In this review, we will discuss in detail the changes in ECM, receptors (integrin or non-integrin), focal adhesions, cytoskeleton, and transcription factors involved in mechanosensing that occur with aging.

TRPM4 non-selective cation channel in human atrial fibroblast growth

Cardiac fibroblasts play an important role in cardiac matrix turnover and are involved in cardiac fibrosis development. Ca²⁺ is a driving belt in this phenomenon. This study evaluates the functional expression and contribution of the Ca²⁺-activated channel TRPM4 in atrial fibroblast phenotype. Molecular and electrophysiological investigations were conducted in human atrial fibroblasts in primary culture and in atrial fibroblasts obtained from wild-type and transgenic mice with disrupted Trpm4 gene (Trpm4^-/-). A typical TRPM4 current was recorded on human cells (equal selectivity for Na⁺ and K⁺, activation by internal Ca²⁺, voltage sensitivity, conductance of 23.2 pS, inhibition by 9-phenanthrol (IC₅₀ = 6.1 × 10^-6 mol L^-1)). Its detection rate was 13% on patches at days 2-4 in culture but raised to 100% on patches at day 28. By the same time, a cell growth was observed. This growth was smaller when cells were maintained in the presence of 9-phenanthrol. Similar cell growth was measured on wild-type mice atrial fibroblasts during culture. However, this growth was minimized on Trpm4^-/- mice fibroblasts compared to control animals. In addition, the expression of alpha smooth muscle actin increased during culture of atrial fibroblasts from wild-type mice. This was not observed in Trpm4^-/- mice fibroblasts. It is concluded that TRPM4 participates in fibroblast growth and could thus be involved in cardiac fibrosis.

Transient Receptor Potential Channels and Inflammatory Bowel Disease

The transient receptor potential (TRP) cation channels are present in abundance across the gastrointestinal (GI) tract, serving as detectors for a variety of stimuli and secondary transducers for G-protein coupled receptors. The activation of TRP channels triggers neurogenic inflammation with related neuropeptides and initiates immune reactions by extra-neuronally regulating immune cells, contributing to the GI homeostasis. However, under pathological conditions, such as inflammatory bowel disease (IBD), TRP channels are involved in intestinal inflammation. An increasing number of human and animal studies have indicated that TRP channels are correlated to the visceral hypersensitivity (VHS) and immune pathogenesis in IBD, leading to an exacerbation or amelioration of the VHS or intestinal inflammation. Thus, TRP channels are a promising target for novel therapeutic methods for IBD. In this review, we comprehensively summarize the functions of TRP channels, especially their potential roles in immunity and IBD. Additionally, we discuss the contradictory findings of prior studies and offer new insights with regard to future research.

Gal-3 (Galectin-3) and KCa3.1 Mediate Heterogeneous Cell Coupling and Myocardial Fibrogenesis Driven by βAR (β-Adrenoceptor) Activation

Heart failure is associated with sympatho-βAR (β-adrenoceptor) activation and cardiac fibrosis. Gal-3 (galectin-3) and K_Ca3.1 channels that are upregulated in diverse cells of diseased heart are implicated in mediating myocardial inflammation and fibrosis. It remains unclear whether Gal-3 interacts with K_Ca3.1 leading to cardiac fibrosis in the setting of βAR activation. We tested the effect of K_Ca3.1 blocker TRAM-34 on cardiac fibrosis and inflammation in cardiac-restricted β₂-TG (β₂AR overexpressed transgenic) mice and determined K_Ca3.1 expression in β₂-TG×Gal-3^-/- mouse hearts. Mechanisms of K_Ca3.1 in mediating Gal-3 induced fibroblast activation were studied ex vivo. Expression of Gal-3 and K_Ca3.1 was elevated in β₂-TG hearts. Gal-3 gene deletion in β₂-TG mice decreased K_Ca3.1 expression in inflammatory cells but not in fibroblasts. Treatment of β₂-TG mice with TRAM-34 for 1 or 2 months significantly ameliorated cardiac inflammation and fibrosis and reduced Gal-3 level. In cultured fibroblasts, Gal-3 upregulated K_Ca3.1 expression and channel currents with enhanced membrane potential and Ca²⁺ entry through TRPV4 (transient receptor potential V4) and TRPC6 (transient receptor potential C6) channels leading to fibroblast activation. In conclusion, βAR stimulation promotes Gal-3 production that upregulates K_Ca3.1 channels in noncardiomyocyte cells and activates K_Ca3.1 channels in fibroblasts leading to hyperpolarization of membrane potential and Ca²⁺ entry via TRP channels. Gal-3-K_Ca3.1 signaling mobilizes diverse cells facilitating regional inflammation and fibroblast activation and hence myocardial fibrosis.

The Pivotal Role of TRP Channels in Homeostasis and Diseases throughout the Gastrointestinal Tract

The transient receptor potential (TRP) channels superfamily are a large group of proteins that play crucial roles in cellular processes. For example, these cation channels act as sensors in the detection and transduction of stimuli of temperature, small molecules, voltage, pH, and mechanical constrains. Over the past decades, different members of the TRP channels have been identified in the human gastrointestinal (GI) tract playing multiple modulatory roles. Noteworthy, TRPs support critical functions related to the taste perception, mechanosensation, and pain. They also participate in the modulation of motility and secretions of the human gut. Last but not least, altered expression or activity and mutations in the TRP genes are often related to a wide range of disorders of the gut epithelium, including inflammatory bowel disease, fibrosis, visceral hyperalgesia, irritable bowel syndrome, and colorectal cancer. TRP channels could therefore be promising drug targets for the treatment of GI malignancies. This review aims at providing a comprehensive picture of the most recent advances highlighting the expression and function of TRP channels in the GI tract, and secondly, the description of the potential roles of TRPs in relevant disorders is discussed reporting our standpoint on GI tract–TRP channels interactions.

Transmembrane insertases and N-glycosylation critically determine synthesis, trafficking, and activity of the nonselective cation channel TRPC6

Transient receptor potential cation channel subfamily C member 6 (TRPC6) is a widely expressed ion channel. Gain-of-function mutations in the human TRPC6 channel cause autosomal-dominant focal segmental glomerulosclerosis, but the molecular components involved in disease development remain unclear. Here, we found that overexpression of gain-of-function TRPC6 channel variants is cytotoxic in cultured cells. Exploiting this phenotype in a genome-wide CRISPR/Cas screen for genes whose inactivation rescues cells from TRPC6-associated cytotoxicity, we identified several proteins essential for TRPC6 protein expression, including the endoplasmic reticulum (ER) membrane protein complex transmembrane insertase. We also identified transmembrane protein 208 (TMEM208), a putative component of a signal recognition particle-independent (SND) ER protein-targeting pathway, as being necessary for expression of TRPC6 and several other ion channels and transporters. TRPC6 expression was also diminished by loss of the previously uncharacterized WD repeat domain 83 opposite strand (WDR83OS), which interacted with both TRPC6 and TMEM208. Additionally enriched among the screen hits were genes involved in N-linked protein glycosylation. Deletion of the mannosyl (α-1,3-)-glycoprotein β-1,2-N-acetylglucosaminyltransferase (MGAT1), necessary for the generation of complex N-linked glycans, abrogated TRPC6 gain-of-function variant-mediated Ca2+ influx and extracellular signal-regulated kinase activation in HEK cells, but failed to diminish cytotoxicity in cultured podocytes. However, mutating the two TRPC6 N-glycosylation sites abrogated the cytotoxicity of mutant TRPC6 and reduced its surface expression. These results expand the targets of TMEM208-mediated ER translocation to include multipass transmembrane proteins and suggest that TRPC6 N-glycosylation plays multiple roles in modulating channel trafficking and activity.

Pathophysiological Role and Drug Modulation of Calcium Transport in Ocular Surface Cells

The ocular surface structure and extraocular accessory organs constitute the ocular surface system, which includes the cornea, conjunctiva, eyelids, lacrimal organs, and lacrimal passages. This system is composed of, and stabilized by, the corneal epithelium, conjunctival cells, conjunctival goblet cells, lacrimal acinar cells and Tenon's fibroblasts, all of which maintain the healthy eyeball surface system. Ocular surface diseases are commonly referred to corneal and conjunctival disease and external ocular disease, resulting from damage to the ocular surface structure. A growing body of evidence has indicated that abnormal activation of the KCa3.1 channel and Ca2+/ calmodulin-dependent kinase initiates ocular injury. Signaling pathways downstream of the irregular Ca2+ influx induce cell progression and migration, and impair tight junctions, epithelial transport and secretory function. In this overview, we summarize the current knowledge regarding ocular surface disease in terms of physical and pathological alteration of the ocular system. We dissect in-depth, the mechanisms underlying disease progression, and we describe the current calcium transport therapeutics and the obstacles that remain to be solved. Finally, we summarize how to integrate the research results into clinical practice in the future.

TRPA1 Promotes Cardiac Myofibroblast Transdifferentiation after Myocardial Infarction Injury via the Calcineurin-NFAT-DYRK1A Signaling Pathway

Cardiac fibroblasts (CFs) are a critical cell population responsible for myocardial extracellular matrix homeostasis. After stimulation by myocardial infarction (MI), CFs transdifferentiate into cardiac myofibroblasts (CMFs) and play a fundamental role in the fibrotic healing response. Transient receptor potential ankyrin 1 (TRPA1) channels are cationic ion channels with a high fractional Ca²⁺ current, and they are known to influence cardiac function after MI injury; however, the molecular mechanisms regulating CMF transdifferentiation remain poorly understood. TRPA1 knockout mice, their wild-type littermates, and mice pretreated with the TRPA1 agonist cinnamaldehyde (CA) were subjected to MI injury and monitored for survival, cardiac function, and fibrotic remodeling. TRPA1 can drive myofibroblast transdifferentiation initiated 1 week after MI injury. In addition, we explored the underlying mechanisms via in vitro experiments through gene transfection alone or in combination with inhibitor treatment. TRPA1 overexpression fully activated CMF transformation, while CFs lacking TRPA1 were refractory to transforming growth factor β- (TGF-β-) induced transdifferentiation. TGF-β enhanced TRPA1 expression, which promoted the Ca²⁺-responsive activation of calcineurin (CaN). Moreover, dual-specificity tyrosine-regulated kinase-1a (DYRK1A) regulated CaN-mediated NFAT nuclear translocation and TRPA1-dependent transdifferentiation. These findings suggest a potential therapeutic role for TRPA1 in the regulation of CMF transdifferentiation in response to MI injury and indicate a comprehensive pathway driving CMF formation in conjunction with TGF-β, Ca²⁺ influx, CaN, NFATc3, and DYRK1A.

TRP Channels: Current Perspectives in the Adverse Cardiac Remodeling

Calcium is an important second messenger required not only for the excitation-contraction coupling of the heart but also critical for the activation of cell signaling pathways involved in the adverse cardiac remodeling and consequently for the heart failure. Sustained neurohumoral activation, pressure-overload, or myocardial injury can cause pathologic hypertrophic growth of the heart followed by interstitial fibrosis. The consequent heart’s structural and molecular adaptation might elevate the risk of developing heart failure and malignant arrhythmia. Compelling evidences have demonstrated that Ca²⁺ entry through TRP channels might play pivotal roles in cardiac function and pathology. TRP proteins are classified into six subfamilies: TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPA (ankyrin), TRPML (mucolipin), and TRPP (polycystin), which are activated by numerous physical and/or chemical stimuli. TRP channels participate to the handling of the intracellular Ca²⁺ concentration in cardiac myocytes and are mediators of different cardiovascular alterations. This review provides an overview of the current knowledge of TRP proteins implication in the pathologic process of some frequent cardiac diseases associated with the adverse cardiac remodeling such as cardiac hypertrophy, fibrosis, and conduction alteration.