Role Of TRPV1 Research Articles

The Emerging Roles of TRPV4 in Cancer

The Emerging Roles of TRPV4 in Cancer

TRPV1 modulates morphine-induced conditioned place preference via p38 MAPK in the nucleus accumbens

Emerging evidence suggests that the transient receptor potential vanilloid type 1 channel (TRPV1) is a novel target for the treatment of drug addiction, such as cocaine and morphine. Previously we reported that TRPV1 inhibition reduced morphine reward in the dorsal striatum (DSt) of mice and morphine self-administration through a decrease in accumbal activity in rats. However, the role of TRPV1 on morphine-conditioned reward in addiction-related brain regions, such as the nucleus accumbens (NAc), has not been previously established. Here, we investigated the effects of TRPV1 on morphine conditioned place preference (CPP) and intracellular mechanisms of TRPV1 using Western blot analysis and immunohistochemistry (IHC) in morphine-administered mice. TRPV1 knockout mice did not exhibit morphine reward responses, and both i.p. and intra-NAc injections of SB366791, a selective TRPV1 antagonist, reduced morphine-induced CPP in wild-type mice. Furthermore, i.p. injection of SB203580, a selective p38 MAPK inhibitor, also dampened morphine-induced CPP. To determine the molecular mechanisms of the TRPV1/p38 MAPK pathway in morphine CPP, we investigated the expression of adenylyl cyclase type 1 (AC1) and phospho-p38 mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) in the NAc. Either SB366791 or SB203580 decreased the protein expression levels of phospho-p38 MAPK, phosphor-NF-κB, and AC1 in the NAc of morphine CPP mice. Taken together, our findings suggest that TRPV1 may modulate morphine-induced conditioned reward effects via the p38 MAPK signaling pathway in the NAc. Therefore, blockade of TRPV1 may provide a novel therapeutic approach for the prevention and treatment of opioid addiction.

TRPV4 calcium-permeable channel is a novel regulator of oxidized LDL-induced macrophage foam cell formation

Cardiovascular disease is the number one cause of death in United States, and atherosclerosis, a chronic inflammatory arterial disease, is the most dominant underlying pathology. Macrophages are thought to orchestrate atherosclerosis by generating lipid-laden foam cells and by secreting inflammatory mediators. Emerging data support a role for a mechanical factor, e.g., matrix stiffness, in regulation of macrophage function, vascular elasticity, and atherogenesis. However, the identity of the plasma membrane mechanosensor and the mechanisms by which pro-atherogenic signals are transduced/maintained are unknown. We have obtained evidence that TRPV4, an ion channel in the transient receptor potential vanilloid family and a known mechanosensor, is the likely mediator of oxidized low-density lipoprotein (oxLDL)-dependent macrophage foam cell formation, a critical process in atherogenesis. Specifically, we found that: i) genetic ablation of TRPV4 or pharmacologic inhibition of TRPV4 activity by a specific antagonist blocked oxLDL-induced macrophage foam cell formation, and ii) TRPV4 deficiency prevented pathophysiological range matrix stiffness or scratch-induced exacerbation of oxLDL-induced foam cell formation. Mechanistically, we found that: i) plasma membrane localization of TRPV4 was sensitized to the increasing level of matrix stiffness, ii) lack of foam cell formation in TRPV4 null cells was not due to lack of expression of CD36, a major receptor for oxLDL, and iii) TRPV4 channel activity regulated oxLDL uptake but not its binding on macrophages. Altogether, these findings identify a novel role for TRPV4 in regulating macrophage foam cell formation by modulating uptake of oxLDL. These findings suggest that therapeutic targeting of TRPV4 may provide a selective approach to the treatment of atherosclerosis.

965 - Role of TRPV4 in the Mechanosensitivity of Esophageal Myenteric Neurons

965 - Role of TRPV4 in the Mechanosensitivity of Esophageal Myenteric Neurons

OS 36-09 DEFICIENCY OF THERMOGENESIS AND HEAT SENSATION ACCELERATES OBESITY AND HIGH BLOOD PRESSURE

Objective: Obesity is global healthy problem. Uncoupling protein 1 (UCP1) mainly expresses on brown adipose tissue (BAT), uncouples energy substrate oxidation from mitochondrial ATP production and results in the loss of potential energy as heat. Transient receptor potential vanilloid subfamily, member 1 (TRPV1) is the heat-gated cation ion channel. The aim of this study was to investigate the in vivo role of TRPV1 and UCP1 co-action in obesity. Design and Method: We generated and characterized UCP1−/− mice lacking TRPV1 activity (TRPV1−/−/UCP1−/− mice). The core-body temperature and the locomotor activity were simultaneously measured by the telemetry system. The rate of mitochondrial respiration was measured using the Oxygraph-2k. Cytosol superoxide anion was determined by DHE and mitochondrial superoxide anion was measured by MitoSOX. The levels of ATP in primary cultured brown adipocytes were measured using a firefly luciferase-based ATP assay kit. Primary brown adipocytes were cultured and the fluorescence measurements of cells were made using a fluorescent plate reader. Results: TRPV1 and UCP1 double knockout would appear obesity in advance and more severe comparing with WT, TRPV1−/− and UCP1−/− mice. TRPV1 and UCP1 double knockout in mice reduced functional BAT generation to cause BAT white, and decreased lipolysis comparing with the other three groups. TRPV1−/−/UCP1−/− mice significantly decreased resting oxygen consumptions, heat production and locomotor activities. Mitochondrial respiratory function seriously disordered in BAT of TRPV1−/−/UCP1−/− mice. TRPV1 and UCP1 double knockout resulted in dramatically reduced Ca2+mito uptake in low [Ca2+]cyto that was coupled with H+mito extrusion, which affected ATP generation and oxidative stress in BAT mitochondria. TRPV1 knockout caused to a Ca2+mito uptake compensatory rise. Conclusions: The results of our genetic manipulation studies provide in vivo evidence for the pathogenesis of TRPV1 and UCP1 double knockout in mice caused obesity and offer a novel target to manipulate obesity and associated complications.

Mitogen-Activated Protein Kinase and Intracellular Polyamine Signaling Is Involved in TRPV1 Activation-Induced Cardiac Hypertrophy.

BackgroundThe transient receptor potential vanilloid type 1 (TRPV1) is expressed in the cardiovascular system, and increased TRPV1 expression has been associated with cardiac hypertrophy. Nevertheless, the role of TRPV1 in the pathogenesis of cardiac hypertrophy and the underlying molecular mechanisms remain unclear.Methods and ResultsIn cultured cardiomyocytes, activation of TRPV1 increased cell size and elevated expression of atrial natriuretic peptide mRNA and intracellular calcium level, which was reversed by TRPV1 antagonist capsazepine. Increased expression of phosphorylated calmodulin‐dependent protein kinase IIδ and mitogen‐activated protein kinases were found in TRPV1 agonist capsaicin‐treated cardiomyocytes. Selective inhibitor of calmodulin‐dependent protein kinase IIδ decreased phosphorylation of extracellular signal–regulated kinases and p38. Capsaicin induced an increase in expression of ornithine decarboxylase protein, which is the key enzyme in polyamine biosynthesis in cardiomyocytes. Nevertheless, there was no obvious change of ornithine decarboxylase expression in TRPV1 knockdown cells after capsaicin treatment, and specific inhibitors of calmodulin‐dependent protein kinase IIδ or p38 downregulated the capsaicin‐induced expression of ornithine decarboxylase. Capsazepine alleviated the increase in cross‐sectional area of cardiomyocytes and the ratio of heart weight to body weight and improved cardiac function, including left ventricular internal end‐diastolic and ‐systolic dimensions and ejection fraction and fractional shortening percentages, in mice treated with transverse aorta constriction. Capsazepine also reduced expression of ornithine decarboxylase and cardiac polyamine levels. Transverse aorta constriction induced increases in phosphorylated calmodulin‐dependent protein kinase IIδ and extracellular signal–regulated kinases, and p38 and Serca2a were attenuated by capsazepine treatment.ConclusionsThis study revealed that the mitogen‐activated protein kinase signaling pathway and intracellular polyamines are essential for TRPV1 activation–induced cardiac hypertrophy.

Role of the ion channel, transient receptor potential cation channel subfamily V member 1 (TRPV1), in allergic asthma.

BackgroundAsthma prevalence has increased world-wide especially in children; thus there is a need to develop new therapies that are safe and effective especially for patients with severe/refractory asthma. CD4+ T cells are thought to play a central role in disease pathogenesis and associated symptoms. Recently, TRPV1 has been demonstrated to regulate the activation and inflammatory properties of CD4+ cells. The aim of these experiments was to demonstrate the importance of CD4+ T cells and the role of TRPV1 in an asthma model using a clinically ready TRPV1 inhibitor (XEN-D0501) and genetically modified (GM) animals.MethodsMice (wild type, CD4 −/− or TRPV1 −/−) and rats were sensitised with antigen (HDM or OVA) and subsequently topically challenged with the same antigen. Key features associated with an allergic asthma type phenotype were measured: lung function (airway hyperreactivity [AHR] and late asthmatic response [LAR]), allergic status (IgE levels) and airway inflammation.ResultsCD4+ T cells play a central role in both disease model systems with all the asthma-like features attenuated. Targeting TRPV1 using either GM mice or a pharmacological inhibitor tended to decrease IgE levels, airway inflammation and lung function changes.ConclusionOur data suggests the involvement of TRPV1 in allergic asthma and thus we feel this target merits further investigation.

AB259. TRPV1 receptor associated with detrusor overactivity induced by partial bladder outlet obstruction in rats

BackgroundTo investigate the role of TRPV1 in the pathological process of DO induced by partial bladder outlet obstruction (pBOO).MethodsIn 40 female Wistar rats, pBOO was achieved by partial urethral ligation and urodynamic analysis was taken to filter the DO rats six weeks later. Urinary bladder and dorsal root ganglia (DRG) were removed and RT-PCR, Western Blot and IHC were performed to investigate the expression and location of TRPV1 in control and DO rats. Effect of different concentrations of TRPV1 agonist, as well as TRPV1 antagonist, was also evaluated with isolated detrusor strips.ResultsForty female Wistar rats received pBOO surgery and 24 of them developed DO. Expression of TRPV1 mRNA and protein in urinary bladder and dorsal root ganglia (DRG) significantly increased in pBOO induced OAB rats. While that did not significantly change after de-urothelial treatment both in OAB and control rats. Immunohistochemistry observed linear TRPV1-reactive staining mainly in suburothlial and muscular layer. In isolated detrusor strips studies, the amplitude and frequency of contractions of DO tissues were significantly higher than that of control ones (P<0.05). Capsaicin significantly increased the amplitude but not frequency of detrusor intrinsic contractility and this effect was enhanced in OAB conditions. All changes induced by capsaicin were blocked by capsazepine pre-incubated.ConclusionsIn pBOO induced DO rats, over-expressed TRPV1 was involved in DO pathological process by directly sensitizing bladder afferent fibers or indirectly enhancing detrusor intrinsic properties.

Concurrent shear stress and chemical stimulation of mechano-sensitive cells by discontinuous dielectrophoresis.

Microfluidic platforms enable a variety of physical or chemical stimulation of single or multiple cells to be examined and monitored in real-time. To date, intracellular calcium signalling research is, however, predominantly focused on observing the response of cells to a single mode of stimulation; consequently, the sensitising/desensitising of cell responses under concurrent stimuli is not well studied. In this paper, we provide an extended Discontinuous Dielectrophoresis procedure to investigate the sensitising of chemical stimulation, over an extensive range of shear stress, up to 63 dyn/cm(2), which encompasses shear stresses experienced in the arterial and venus systems (10 to 60 dyn/cm(2)). Furthermore, the TRPV4-selective agonist GSK1016790A, a form of chemical stimulation, did not influence the ability of the cells' to remain immobilised under high levels of shear stress; thus, enabling us to investigate shear stress stimulation on agonism. Our experiments revealed that shear stress sensitises GSK1016790A-evoked intracellular calcium signalling of cells in a shear-stimulus dependent manner, as observed through a reduction in the cellular response time and an increase in the pharmacological efficacy. Consequently, suggesting that the role of TRPV4 may be underestimated in endothelial cells-which experience high levels of shear stress. This study highlights the importance of conducting studies at high levels of shear stress. Additionally, our approach will be valuable for examining the effect of high levels of shear on different cell types under different conditions, as presented here for agonist activation.

Perspectives of TRPV1 Function on the Neurogenesis and Neural Plasticity.

The development of new strategies to renew and repair neuronal networks using neural plasticity induced by stem cell graft could enable new therapies to cure diseases that were considered lethal until now. In adequate microenvironment a neuronal progenitor must receive molecular signal of a specific cellular context to determine fate, differentiation, and location. TRPV1, a nonselective calcium channel, is expressed in neurogenic regions of the brain like the subgranular zone of the hippocampal dentate gyrus and the telencephalic subventricular zone, being valuable for neural differentiation and neural plasticity. Current data show that TRPV1 is involved in several neuronal functions as cytoskeleton dynamics, cell migration, survival, and regeneration of injured neurons, incorporating several stimuli in neurogenesis and network integration. The function of TRPV1 in the brain is under intensive investigation, due to multiple places where it has been detected and its sensitivity for different chemical and physical agonists, and a new role of TRPV1 in brain function is now emerging as a molecular tool for survival and control of neural stem cells.

Role of TRPV1 in thermoregulation

Role of TRPV1 in thermoregulation

Alcohol and high fat induced chronic pancreatitis: TRPV4 antagonist reduces hypersensitivity

The pathogenesis of pain in chronic pancreatitis is poorly understood, and its treatment can be a major clinical challenge. Surgical and other invasive methods have variable outcomes that can be unsatisfactory. Therefore, there is a great need for further discovery of the pathogenesis of pancreatitis pain and new therapeutic targets. Human and animal studies indicate a critical role for oxidative stress and activation of transient receptor potential (TRP) cation channel subfamily members TRPV1 and TRPA1 on pancreatic nociceptors in sensitization mechanisms that result in pain. However, the in vivo role of transient receptor potential cation channel subfamily V member 4 (TRPV4) in chronic pancreatitis needs further evaluation. The present study characterized a rat alcohol/high fat diet (AHF)-induced chronic pancreatitis model with hypersensitivity, fibrotic pathology, and fat vacuolization consistent with the clinical syndrome. The rats with AHF-induced pancreatitis develop referred visceral pain-like behaviors, i.e. decreased hindpaw mechanical thresholds and shortened abdominal and hindpaw withdrawal latency to heat. In this study, oxidative stress was characterized as well as the role of TRPV4 in chronic visceral hypersensitivity. Lipid peroxidase and oxidative stress were indicated by increased plasma thiobarbituric acid reactive substances (TBARS) and diminished pancreatic manganese superoxide dismutase (MnSOD). The secondary sensitization associated with AHF-induced pancreatitis was effectively alleviated by the TRPV4 antagonist, HC 067047. Similarity of the results to those with the peripherally restricted μ-opiate receptor agonist, loperamide, suggested TRPV4 channel activated peripheral sensitization. This study using a reliable model that provides pre-clinical correlates of human chronic pancreatitis provides further evidence that TRPV4 channel is a potential therapeutic target for treatment of pancreatitis pain.

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.

Abstract P230: Glucagon-like Peptide-1-induced Increases in Afferent Renal Nerve Activity and Renal Sodium Excretion: Role of Trpv1

Glucagon-like peptide 1 (GLP-1), an incretin hormone that has clinically been used to treat type 2 diabetic patients, may cause diuresis and natriuresis. However, the mechanism of GLP-1 effects on the kidney is largely unknown. We test the hypothesis that GLP-1 increases afferent renal nerve activity (ARNA) and renal sodium excretion by activation of the transient receptor potential vanilloid 1 (TRPV1) channels expressed in afferent renal nerves innervating the kidney. Exendin-4 (Ex4, 3*10-7M), a GLP-1 receptor agonist perfused into the left renal pelvis, increased ipsilateral ARNA in wild type (WT) mice when compared to TRPV1-null mutant (TRPV1–/–) mice (ARNA % integrated activity, WT:160±22 vs TRPV1-/-: 109±5, p&lt;0.05). Ex4-induced increases in ARNA in WT mice were abolished by capsazepine, a selective antagonist of TRPV1, or by RP67580, a selective antagonist of the neurokinin 1 (NK1) receptor, but not by calcitonin-gene related peptide (CGRP)8-37, a selective antagonist of the CGRP receptor pre-perfused into the renal pelvis. Ex4 increased substance P (SP) and CGRP release from the renal pelvis isolated from WT but not TRPV1-/- mice. Ex4-induced increases in SP and CGRP in WT mice were prevented by Ex9-39, a GLP-1 receptor antagonist, 2,5-dideoxyadenosine, an adenylate cyclase inhibitor (ACI), and brefeldin A (BFA), an EPAC inhibitor, or attenuated by bisindolylmaleimide I (BIM) , a PKC inhibitor, and H89, a PKA inhibitor. Wortmannin (Wort), a PI3K inhibitor, had no effect on Ex4-induced SP or CGRP release. Acute Ex4 treatment (3ug/kg, i.p.) increased renal sodium excretion in both strains with greater degree of increases in WT compared to TRPV1-/- mice (increased % rate, WT: 160±36 vs. TRPV1-/-: 82±7, p&lt;0.05). Thus, our data show that Ex4 increases ARNA, renal SP and CGRP release, and urinary sodium excretion in WT mice, and these functions of Ex4 are impaired in TRPV1-/- mice. These data indicate that Ex4-induced enhancement of ARNA and natriuresis attributes to, at least in part, activation of TRPV1-positive afferent nerves possibly via stimulating the GLP-1R/cAMP-PKA/PKC-TRPV1/SP pathway.

Possible role of TRPV-1 and AQPs in the regulation of trophoblast cell volume

Tryptophan hydroxylase-2 (Tph2) is the rate limiting enzyme of serotonin synthesis in the brain. The functional (C1473G) polymorphism in the mouse Tph2 gene affecting the enzymatic activity was suspected to be involved in behavioral actions of ethanol (EtOH). Congenic B6–1473C (C/C) and B6–1473G (G/G) lines bred from C57BL/6 mice were not different in EtOH-induced sleep time and hypothermia. B6–1473C mice displayed increased EtOH preference on the second and third days compared to that of the first day, but no differences in this parameter was found across genotypes. Both lines demonstrated the same responsiveness to hypothermic and hypnotic effect of acute EtOH treatment after repeated alcohol exposure. However, acute EtOH administration led to reduction of locomotor activity in B6–1473C, but not in B6–1473G animals and to increase of time spent in the center of open-field arena in B6–1473G, but not in B6–1473C mice. Thus, the present study indicates the involvement of C1473G polymorphism in mTph2 gene in the regulation of EtOH-induced effects on locomotor activity and anxiety-like behavior in mice.

Role of trpv1 (transient receptor potential v1 channel) in piperine induced hyperalgesia: a preliminary study

Background: The inflammatory disease is associated with chronic pain and hypersensitivity to noxious stimuli in form of hyperalgesia. Transient receptor potential vanilloid type-1 (TRPV1) activated by various inflammatory mediators; plays a key role in occurrence of hyperalgesia. Piperine is the primary pungent alkaloid of Piper nigrum. Piperine has common binding site with capsaicin (TRPV1 agonist) on TRPV1 and it has more efficacy for activation of TRPV1 than capsaicin. Objective: The purpose of the study was to investigate the role of TRPV1 in piperine induced hyperalgesia in diabetic mice. Methods: Diabetes mellitus was induced in mice using streptozotocin (STZ). Nociception was measured by three types of thermal nociceptive tests (Hot plate method, radient heat tail-flick method and tail immersion test). Pilot study (using 2.5, 5, 10 and 50 mg kg-1 piperine, i.p.) was carried out and 5 mg kg-1 piperine is used as optimum dose for further study. Capsaicin, capsazepine and piperine were administered to their respected groups and nociceptive threshold was noted on day 4, 7 and 10 in all groups. Results: Piperine showed a significant decrease in nociceptive threshold as compared to diabetic control group, while there was a significant increase in reaction time, tail flick latency and tail withdrawal latency, in the animals pre-treated with capsazepine before piperine administration as compare to only piperine treated diabetic group. Conclusion: Activation of TRPV1 might be one of the possible mechanisms of Piperine induced hyperalgesia. Keywords: Capsaicin, Capsazepine, Hyperalgesia, Nociceptive Threshold, Piperine, TRPV1.

Role of TRPV1 and ASIC3 in formalin-induced secondary allodynia and hyperalgesia

BackgroundIn the present study we determined the role of transient receptor potential V1 channel (TRPV1) and acid-sensing ion channel 3 (ASIC3) in chronic nociception. Methods1% formalin was used to produce long-lasting secondary allodynia and hyperalgesia in rats. Western blot was used to determine TRPV1 and ASIC3 expression in dorsal root ganglia. ResultsPeripheral ipsilateral, but not contralateral, pre-treatment (−10min) with the TRPV1 receptor antagonists capsazepine (0.03–0.3μM/paw) and A-784168 (0.01–1μM/paw) prevented 1% formalin-induced secondary mechanical allodynia and hyperalgesia in the ipsilateral and contralateral paws. Likewise, peripheral ipsilateral, but not contralateral, pre-treatment with the non-selective and selective ASIC3 blocker benzamil (0.1–10μM/paw) and APETx2 (0.02–2μM/paw), respectively, prevented 1% formalin-induced secondary mechanical allodynia and hyperalgesia in both paws. Peripheral ipsilateral post-treatment (day 6 after formalin injection) with capsazepine (0.03–0.3μM/paw) and A-784168 (0.01–1μM/paw) reversed 1% formalin-induced secondary mechanical allodynia and hyperalgesia in both paws. In addition, peripheral ipsilateral post-treatment with benzamil (0.1–10μM/paw) and APETx2 (0.02–2μM/paw), respectively, reversed 1% formalin-induced secondary mechanical allodynia and hyperalgesia in both paws. TRPV1 and ASIC3 proteins were expressed in dorsal root ganglion in normal conditions, and 1% formalin injection increased expression of both proteins in this location at 1 and 6 days compared to naive rats. ConclusionsData suggest that TRPV1 and ASIC3 participate in the development and maintenance of long-lasting secondary allodynia and hyperalgesia induced by formalin in rats. The use of TRPV1 and ASIC3 antagonists by peripheral administration could prove useful to treat chronic pain.

α,β-Unsaturated aldehyde crotonaldehyde triggers cardiomyocyte contractile dysfunction: Role of TRPV1 and mitochondrial function

Recent evidence has suggested that cigarette smoking is associated with an increased prevalence of heart diseases. Given that cigarette smoking triggers proinflammatory response via stimulation of the capsaicin-sensitive transient receptor potential cation channel TRPV1, this study was designed to evaluate the effect of an essential α,β-unsaturated aldehyde from cigarette smoke crotonaldehyde on myocardial function and the underlying mechanism with a focus on TRPV1 and mitochondria. Cardiomyocyte mechanical and intracellular Ca2+ properties were evaluated including peak shortening (PS), maximal velocity of shortening/relengthening (±dL/dt), time-to-PS (TPS), time-to-90% relengthening (TR90), fura-2 fluorescence intensity (FFI), intracellular Ca2+ decay and SERCA activity. Apoptosis and TRPV1 were evaluated using Western blot analysis. Production of reactive oxygen species (ROS) and DNA damage were measured using the intracellular fluoroprobe 5-(6)-chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate and 8-hydroxy-2′-deoxyguanosine (8-OHdG), respectively. Our data revealed that crotonaldehyde interrupted cardiomyocyte contractile and intracellular Ca2+ property including depressed PS, ±dL/dt, ΔFFI and SERCA activity, as well as prolonged TR90 and intracellular Ca2+ decay. Crotonaldehyde exposure increased TRPV1 and NADPH oxidase levels, promoted apoptosis, mitochondrial injury (decreased aconitase activity, PGC-1α and UCP-2) as well as production of ROS and 8-OHdG. Interestingly, crotonaldehyde-induced cardiac defect was obliterated by the ROS scavenger glutathione and the TRPV1 inhibitor capsazepine. Capsazepine (not glutathione) ablated crotonaldehyde-induced mitochondrial damage. Capsazepine, glutathione and the NADPH inhibitor apocynin negated crotonaldehyde-induced ROS accumulation. Our data suggest a role of crotonaldehyde compromises cardiomyocyte mechanical function possibly through a TRPV1- and mitochondria-dependent oxidative stress mechanism.

The Cation Channel TRPV4 Regulates Epithelial Barrier Responses to Lipopolysaccharides

TRPV4 is a calcium-permeable non-selective cation channel belonging to the vanilloid subfamily of Transient Receptor Potential proteins. This channel has a rather ubiquitous expression in epithelial cells (skin, airways, endothelium and urothelium), and it is known to be sensitive to a wide variety of physical and chemical stimuli, including heat, arachidonic acid metabolites and synthetic α-phorbol derivatives. We have found that lipopolysaccharide (LPS), an outer membrane component of Gram-negative bacteria, activates TRPV4 in HEK293T cells, independently of the renowned TLR4 pathway. Interestingly, conical LPS from E.coli induced larger TRPV4 response than cylindrical LPS from S. minnesota. Considering the role of TRPV4 in mechanosensation we hypothesized that TRPV4 senses the disturbances induced by insertion of LPS in the plasma membrane. By measuring membrane fluidity using fluorescence probes, we found that conically-shaped LPS from E. coli, but not cylindrical LPS from S. minnesota, causes a membrane phase shift towards gel-like state. This suggests that LPS structural differences are important in its ability to induce mechanical alterations in the membrane. We also found that LPS activates native TRPV4 in the human bronchial epithelial cell line 16HBE. Acute stimulation of TRPV4 in monolayer cultures of 16HBE cells induced a rapid increase of the transepithelial electrical resistance. Additionally, LPS-mediated TRPV4 activation increased colocalization of ZO-1 and Occludin in the plasma membrane. Altogether, these data suggest that LPS induces a TRPV4-dependent reorganization of tight junction proteins, leading to an increase in barrier function. We propose that TRPV4 participates in the orchestration of the innate immune response to the challenge with bacterial endotoxins.

Retracted: α,β‐Unsaturated aldehyde pollutant acrolein suppresses cardiomyocyte contractile function: Role of TRPV1 and oxidative stress

Air pollution is associated with an increased prevalence of heart disease and is known to trigger a proinflammatory response via stimulation of transient receptor potential vanilloid cation channels (TRPV1, also known as the capsaicin receptor). This study was designed to examine the effect of acrolein, an essential α,β-unsaturated aldehyde pollutant, on myocardial contractile function and the underlying mechanism involved with a focus on TRPV1 and oxidative stress. Cardiomyocyte mechanical and intracellular Ca(2+) properties were evaluated using an IonOptix MyoCam® system including peak shortening (PS), maximal velocity of shortening/relengthening (± dL/dt), time-to-PS (TPS), time-to-90% relengthening (TR90 ), fura-2 fluorescence intensity (FFI) and intracellular Ca(2+) decay. Changes in apoptosis and TRPV1 were evaluated using Western blot analysis. The degree of oxidative stress was assessed using the ratio between reduced and oxidized glutathione. Results obtained revealed that exposure of cardiomyocytes to acrolein acutely compromised contractile and intracellular Ca(2+) properties including depressed PS, ± dL/dt and ΔFFI, as well as prolonged TR90 and intracellular Ca(2+) decay. In addition, acrolein exposure upregulated TRPV1 associated with an increase in both apoptosis and oxidative stress. However, the acrolein-induced cardiomyocyte contractile and intracellular Ca(2+) anomalies, as well as apoptosis (as evidenced by Bcl-2, Bax, FasL, Caspase-3 and -8), were negated by the reactive oxygen species (ROS) scavenger glutathione or the TRPV1 antagonist capsazepine. Collectively these data suggest that the α,β-unsaturated aldehyde pollutant acrolein may play a role in the pathogenesis and sequelae of air pollution-induced heart disease via a TRPV1- and oxidative stress-dependent mechanism.