Role of vanilloid receptors in the capsaicin-mediated induction of iNOS in PC12 cells

The Role of the Activation of the TRPV1 Receptor and of Nitric Oxide in Changes in Endothelial and Cardiac Function and Biomarker Levels in Hypertensive Rats

The purpose of the present study was to analyze the actions of transient receptor potential vanilloid type 1 (TRPV1) agonist capsaicin (CS) and of its antagonist capsazepine (CZ), on cardiac function as well as endothelial biomarkers and some parameters related with nitric oxide (NO) release in L-NG-nitroarginine methyl ester (L-NAME)-induced hypertensive rats. NO has been implicated in the pathophysiology of systemic arterial hypertension (SAHT). We analyzed the levels of nitric oxide (NO), tetrahydrobiopterin (BH4), malondialdehyde (MDA), total antioxidant capacity (TAC), cyclic guanosin monophosphate (cGMP), phosphodiesterase-3 (PDE-3), and the expression of endothelial nitric oxide synthase (eNOS), guanosine triphosphate cyclohydrolase 1 (GTPCH-1), protein kinase B (AKT), and TRPV1 in serum and cardiac tissue of normotensive (118±3 mmHg) and hypertensive (H) rats (165 ± 4 mmHg). Cardiac mechanical performance (CMP) was calculated and NO was quantified in the coronary effluent in the Langendorff isolated heart model. In hypertensive rats capsaicin increased the levels of NO, BH4, cGMP, and TAC, and reduced PDE-3 and MDA. Expressions of eNOS, GTPCH-1, and TRPV1 were increased, while AKT was decreased. Capsazepine diminished these effects. In the hypertensive heart, CMP improved with the CS treatment. In conclusion, the activation of TRPV1 in H rats may be an alternative mechanism for the improvement of cardiac function and systemic levels of biomarkers related to the bioavailability of NO.

Pantoprazole Induces Mitochondrial Apoptosis and Attenuates NF-κB Signaling in Glioma Cells

Gastric H⁺/K⁺-ATPase or vacuolar-ATPases (V-ATPases) are critical for the cancer cells survival and growth in the ischemic microenvironment by extruding protons from the cell. The drugs which inhibit V-ATPases are known as proton pump inhibitors (PPIs). In the present study, we aimed to evaluate the anticancer efficacy of pantoprazole (PPZ) and its consequences on NF-κB signaling in glioma cells. We have used MTT and clonogenic assay to show PPZ effect on glioma cell growth. Propidium iodide and rhodamine 123 staining were performed to demonstrate cell cycle arrest and mitochondrial depolarization. TUNEL staining was used to evidence apoptosis after PPZ treatment. Immunoblotting and immunofluorescence microscopy were performed to depict protein levels and localization, respectively. Luciferase assay was performed to confirm NF-κB suppression by PPZ. Our results revealed PPZ treatment inhibits cell viability or growth and induced cell death in a dose- and time-dependent manner. PPZ exposure arrested G0/G1 cyclic phase and increased TUNEL positivity, caspase-3 and PARP cleavage with altered pro and anti-apoptotic proteins. PPZ also induced ROS levels and depolarized mitochondria (Δψm) with increased cytosolic cytochrome c level. Further, PPZ suppressed TNF-α stimulated NF-κB signaling by repressing p65 nuclear translocation. NF-κB luciferase reporter assays revealed significant inhibition of NF-κB gene upon PPZ treatment. PPZ exposure also reduced the expression of NF-κB-associated genes, such as cyclin-D1, iNOS, and COX-2, which indicate NF-κB inhibition. Altogether, the present study disclosed that PPZ exerts mitochondrial apoptosis and attenuates NF-κB signaling suggesting PPZ can be an effective and safe anticancer drug for glioma.

Impact of 60-GHz millimeter waves on stress and pain-related protein expression in differentiating neuron-like cells

Millimeter waves (MMW) will be increasingly used for future wireless telecommunications. Previous studies on skin keratinocytes showed that MMW could impact the mRNA expression of Transient Receptor Potential cation channel subfamily Vanilloid, member 2 (TRPV2). Here, we investigated the effect of MMW exposure on this marker, as well as on other membrane receptors such as Transient Receptor Potential cation channel subfamily Vanilloid, member 1 (TRPV1) and purinergic receptor P2X, ligand-gated ion channel, 3 (P2 × 3). We exposed the Neuroscreen-1 cell line (a PC12 subclone), in order to evaluate if acute MMW exposures could impact expression of these membrane receptors at the protein level. Proteotoxic stress-related chaperone protein Heat Shock Protein 70 (HSP70) expression level was also assessed. We used an original high-content screening approach, based on fluorescence microscopy, to allow cell-by-cell analysis and to detect any cell sub-population responding to exposure. Immunocytochemistry was done after 24 h MMW exposure of cells at 60.4 GHz, with an incident power density of 10 mW/cm(2) . Our results showed no impact of MMW exposure on protein expressions of HSP70, TRPV1, TRPV2, and P2 × 3. Moreover, no specific cell sub-populations were found to express one of the studied markers at a different level, compared to the rest of the cell populations. However, a slight insignificant increase in HSP70 expression and an increase in protein expression variability within cell population were observed in exposed cells, but controls showed that this was related to thermal effect. Bioelectromagnetics. 37:444-454, 2016. © 2016 Wiley Periodicals, Inc.

Sensory dysfunction of bladder mucosa and bladder oversensitivity in a rat model of metabolic syndrome

Purpose

To study the role of sensory dysfunction of bladder mucosa in bladder oversensitivity of rats with metabolic syndrome.

Materials and Methods

Female Wistar rats were fed a fructose-rich diet (60%) or a normal diet for 3 months. Based on cystometry, the fructose-fed rats (FFRs) were divided into a group with normal detrusor function or detrusor overactivity (DO). Acidic adenosine triphosphate (ATP) solution (5mM, pH 3.3) was used to elicit reflex micturition. Cystometric parameters were evaluated before and after drug administration. Functional proteins of the bladder mucosa were assessed by western blotting.

Results

Compared to the controls, intravesical acidic ATP solution instillation induced a significant increase in provoked phasic contractions in both FFR groups and a significant decrease in the mean functional bladder capacity of group DO. Pretreatment with capsaicin for C-fiber desentization, intravesical liposome for mucosal protection, or intravenous pyridoxal 5-phosphate 6-azophenyl-2′,4′-disulfonic acid for antagonized purinergic receptors can interfere with the urodynamic effects of intravesical ATP in FFRs and controls. Over-expression of TRPV1, P2X₃, and iNOS proteins, and down-regulation of eNOS proteins were observed in the bladder mucosa of both fructose-fed groups.

Conclusions

Alterations of sensory receptors and enzymes in the bladder mucosa, including over-expression of TRPV1, P2X₃, and iNOS proteins, can precipitate the emergence of bladder phasic contractions and oversensitivity through the activation of C-afferents during acidic ATP solution stimulation in FFRs. The down-regulation of eNOS protein in the bladder mucosa of FFRs may lead to a failure to suppress bladder oversensitivity and phasic contractions. Sensory dysfunction of bladder mucosa and DO causing by metabolic syndrome are easier to elicit bladder oversensitivity to certain urothelium stimuli.

Mimosine-induced apoptosis in C6 glioma cells requires the release of mitochondria-derived reactive oxygen species and p38, JNK activation

Growth-inhibitory effects of mimosine, a plant amino acid, on rat C6 glioma cells were analyzed. Mimosine markedly inhibited proliferation and induced apoptosis of C6 glioma cells in a dose- and time-dependent manner. Mimosine-mediated apoptosis was accompanied by promoting reactive oxygen species (ROS) generation in mitochondria, and by decreased mitochondrial membrane potential (Δψ), and release of cytochrome c from mitochondria, followed by caspase 3 activation. Furthermore, mimosine increased the phosphorylation level of c-Jun-N-terminal protein kinase and p38, which was the downstream effect of ROS accumulation. Mimosine was confirmed to show profound effects on apoptosis of C6 glioma cells by ROS-regulated mitochondria pathway, and these results bear on the hypothesized potential for mimosine as promising agents in the treatment of malignant gliomas.

TRPV channels in tumor growth and progression

Transient receptor potential (TRP) channels affect several physiological and pathological processes. In particular, TRP channels have been recently involved in the triggering of enhanced proliferation, aberrant differentiation, and resistance to apoptotic cell death leading to the uncontrolled tumor invasion. About thirty TRPs have been identified to date, and are classified in seven different families: TRPC (Canonical), TRPV (Vanilloid), TRPM (Melastatin), TRPML (Mucolipin), TRPP (Polycystin), and TRPA (Ankyrin transmembrane protein) and TRPN (NomPC-like). Among these channel families, the TRPC, TRPM, and TRPV families have been mainly correlated with malignant growth and progression. The aim of this review is to summarize data reported so far on the expression and the functional role of TRPV channels during cancer growth and progression. TRPV channels have been found to regulate cancer cell proliferation, apoptosis, angiogenesis, migration and invasion during tumor progression, and depending on the stage of the cancer, up- and down-regulation of TRPV mRNA and protein expression have been reported. These changes may have cancer promoting effects by increasing the expression of constitutively active TRPV channels in the plasma membrane of cancer cells by enhancing Ca(2+)-dependent proliferative response; in addition, an altered expression of TRPV channels may also offer a survival advantage, such as resistance of cancer cells to apoptotic-induced cell death. However, recently, a role of TRPV gene mutations in cancer development, and a relationship between the expression of specific TRPV gene single nucleotide polymorphisms and increased cancer risk have been reported. We are only at the beginning, a more deep studies on the physiopathology role of TRPV channels are required to understand the functional activity of these channels in cancer, to assess which TRPV proteins are associated with the development and progression of cancer and to develop further knowledge of TRPV proteins as valuable diagnostic and/or prognostic markers, as well as targets for pharmaceutical intervention and targeting in cancer.

Oncogenic TRP channels

Ion channels and notably TRP channels play a crucial role in a variety of physiological functions and in addition these channels have been also shown associated with several diseases including cancer. The process of cancer initiation and progression involves the altered expression of one or more of TRP proteins, depending on the nature of the cancer. The most clearly described role in pathogenesis has been evidenced for TRPM8, TRPV6 and TRPM1 channels. The increased expression of some other channels, such as TRPV1, TRPC1, TRPC6, TRPM4, and TRPM5 has also been demonstrated in some cancers. Further investigations are required to precise the role of TRP channels in cancer development and/or progression and to specifically develop further knowledge of TRP proteins as discriminative markers and prospective targets for pharmaceutical intervention in treating cancer.

Zhangfei, a novel regulator of the human nerve growth factor receptor, trkA

The replication of herpes simplex virus (HSV) in epithelial cells, and during reactivation from latency in sensory neurons, depends on a ubiquitous cellular protein called host cell factor (HCF). The HSV transactivator, VP16, which initiates the viral replicative cycle, binds HCF as do some other cellular proteins. Of these, the neuronal transcription factor Zhangfei suppresses the ability of VP16 to initiate the replicative cycle. It also suppresses Luman, another cellular transcription factor that binds HCF. Interactions of nerve growth factor (NGF) and its receptor tropomyosin-related kinase (trkA) appear to be critical for maintaining HSV latency. Because the neuronal transcription factor Brn3a, which regulates trkA expression, has a motif for binding HCF, we investigated if Zhangfei had an effect on its activity. We found that Brn3a required HCF for activating the trkA promoter and Zhangfei suppressed its activity in non-neuronal cells. However, in neuron-like NGF-differentiated PC12 cells, both Brn3a and Zhangfei activated the trkA promoter and induced the expression of endogenous trkA. In addition, capsaicin, a stressor, which activates HSV in in vitro models of latency, decreased levels of Zhangfei and trkA transcripts in NGF-differentiated PC12 cells.

RNA interference-mediated knock-down of transient receptor potential vanilloid 1 prevents forepaw inflammatory hyperalgesia in rat

Transient receptor potential vanilloid (TRPV)1 is a ligand-gated cation channel expressed by primary sensory neurons, including those in the dorsal root ganglia (DRG). TRPV1 plays an essential role in development of inflammatory thermal hyperalgesia after tissue injury and its expression in rat lumbar DRG is increased after hindpaw inflammation. However, the identity of factors mediating forepaw inflammatory hyperalgesia has remained elusive. Here, we examined behavioral responses to noxious thermal stimuli after forepaw inflammation in rats and found that inflammation induced by intraplantar injection of complete Freund's adjuvant significantly reduced hot-plate latency (HPL) at 50 degrees C. TRPV1 expression levels in the ipsilateral cervical DRG were also elevated after forepaw inflammation. By contrast, HPL at 56 degrees C was not shortened after forepaw inflammation and expression of TRPV2, a TRPV1 homolog, in the DRG was not increased. Paratracheal injection of short interfering RNA targeting TRPV1 blocked TRPV1 up-regulation in cervical DRG and abolished inflammation-mediated HPL reductions seen at 50 degrees C. However, thermal hyperalgesia previously established by inflammation was not reversed by short interfering RNA injection. These results indicate that: (i) enhanced TRPV1 expression in cervical DRG is closely associated with development of inflammatory thermal hyperalgesia in the forepaw after tissue injury and (ii) RNA interference targeting TRPV1 prevents inflammatory thermal hyperalgesia after forepaw injuries but does not ameliorate it when already established in a rat model of nociceptive pain representing upper limb injury in humans.

Study of correlation between lead-induced cytotoxicity and nitric oxide production in PC12 cells

Despite reduction in its exposure, lead remains a major health problem. The primary target of lead toxicity is the central nervous system. The cellular, intracellular and molecular mechanisms of lead neurotoxicity are numerous, such as induction of apoptosis and interfering with Ca2+ dependent enzyme like nitric oxide synthase (NOS). To investigate the cytotoxic effect of lead on rat pheochromocytoma (PC12) cells, as a suitable model for neuroscience study, and possible correlation between lead toxicity and nitric oxide (NO) production, this study was performed. The current results showed that lead could induce cytotoxicity as well as NO production in a dose dependent manner in PC12 cells after 24h. The cytotoxicity was positively correlated with increased NOx (nitrite and nitrate) production in these cells. L-NAME, a NOS inhibitor, treatment (2.5 mM) could reverse this cytotoxicity. It can be concluded that lead-induced cytotoxicity in PC12 cells could partly be mediated by higher NO production.

Involvement of peroxynitrite in capsaicin-induced apoptosis of C6 glioma cells

Capsaicin induces apoptosis in some types of cells, but its mechanism remains obscure. In this study, peroxynitrite, a powerful oxidant generated from the reaction of superoxide and nitric oxide (NO) in biological system, was demonstrated to be responsible for capsaicin-mediated apoptosis in C6 glioma cells. Capsaicin-induced apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, and also identified by Annexin V staining and comet assay. Capsazepine and ruthenium red, the vanilloid receptor 1 (VR1/TPRV1) antagonists, did not inhibit capsaicin-induced apoptosis. Exposure to capsaicin not only promoted the generation of superoxide and iNOS, but also markedly suppressed the expression of SODs. Nitrite and nitrate, the NO metabolites accumulated in the medium, and the nitrotyrosine was also increased in proteins of C6 glioma cells exposed to capsaicin. Pretreatment of cells with 4 microM ebselen (a peroxynitrite scavenger) showed effective inhibitory effect on the capsaicin-induced apoptosis. These results suggest that peroxynitrite can act as a potential mediator in the capsaicin-induced apoptosis in C6 glioma cells.