Increase In Intracellular Free Ca2 Research Articles

Combination of amino acid/dipeptide with ligustrazine-betulinic acid as antitumor agents

The lead compound TBA, 3β-Hydroxy-lup-20(29)-ene-28-oic acid-3, 5, 6-trimethylpyrazin-2-methyl ester, which exhibited promising antitumor activity and induced tumor cell apoptosis in various cancer cell lines, had previously been reported. Moreover, reports have revealed that the introduction of amino acid to betulinic acid could improve selective cytotoxicity as well as water solubility. Thus, a series of novel TBA amino acid and dipeptide derivatives were designed, synthesized and screened for selective cytotoxic activity against five cancer cell lines (HepG2, HT-29, Hela, BCG-823 and A549) and the not malignant cell line MDCK by standard MTT assay. Most of the tested TBA-amino acid and dipeptide analogues showed stronger anti-proliferative activity against all tested tumor cell lines than TBA. Among them, BA-25 exhibited the greatest cytotoxic activity on tumor cell lines (mean IC50 = 2.31 ± 0.78 μM), that was twofold than the positive drug cisplatin (DDP), while it showed lower cytotoxicity on MDCK cell line than DDP. Further cell apoptosis analyses indicated BA-25-induced apoptosis was associated with loss of mitochondrial membrane potential and increase of intracellular free Ca2+ concentration.

Changes in the expression of the type 2 diabetes-associated gene VPS13C in the β-cell are associated with glucose intolerance in humans and mice.

Single nucleotide polymorphisms (SNPs) close to the VPS13C, C2CD4A and C2CD4B genes on chromosome 15q are associated with impaired fasting glucose and increased risk of type 2 diabetes. eQTL analysis revealed an association between possession of risk (C) alleles at a previously implicated causal SNP, rs7163757, and lowered VPS13C and C2CD4A levels in islets from female (n = 40, P < 0.041) but not from male subjects. Explored using promoter-reporter assays in β-cells and other cell lines, the risk variant at rs7163757 lowered enhancer activity. Mice deleted for Vps13c selectively in the β-cell were generated by crossing animals bearing a floxed allele at exon 1 to mice expressing Cre recombinase under Ins1 promoter control (Ins1Cre). Whereas Vps13cfl/fl:Ins1Cre (βVps13cKO) mice displayed normal weight gain compared with control littermates, deletion of Vps13c had little effect on glucose tolerance. Pancreatic histology revealed no significant change in β-cell mass in KO mice vs. controls, and glucose-stimulated insulin secretion from isolated islets was not altered in vitro between control and βVps13cKO mice. However, a tendency was observed in female null mice for lower insulin levels and β-cell function (HOMA-B) in vivo. Furthermore, glucose-stimulated increases in intracellular free Ca2+ were significantly increased in islets from female KO mice, suggesting impaired Ca2+ sensitivity of the secretory machinery. The present data thus provide evidence for a limited role for changes in VPS13C expression in conferring altered disease risk at this locus, particularly in females, and suggest that C2CD4A may also be involved.

Involvement of Ion Channels in Endothelin-1-induced Signalling in Human Prostate Cancer Cells

Objective: Endothelin-1 (ET-1), a potent vasoconstrictor secreted primarily by endothelial and various epithelial cancer cells has been implicated in prostate cancer progression and the ET axis has been suggested to represent a novel and exciting target in the treatment of prostate cancer (PCa). ET-1, acting primarily through the endothelin receptors (ETRs) is integrally involved in multiple facets of PCa progression, including cell growth, inhibition of apoptosis, angiogenesis and development of bone metastases. ET-1 and ETRs are expressed in PCa tissues and their expression is modulated during the evolution of these cancers. The purpose of the present work was to study the effects of ET-1 on proliferation of human PCa cells PC-3 and the mechanisms by which the activation of ETRs may promote the PCa cells growth. Methods: Prostate cancer cell lines and primary cultured epithelial cells from prostate cancer, RT-PCR and calcium imaging techniques were used to study the expression and functionality of the Endothelin receptors and involvement of ion channels in the effects of ET-1 in prostate cancer cells. Results: We show for the first time that the application of ET-1 induces a dose-dependent cell proliferation and an increase in intracellular free Ca2+ concentrations ([Ca2+]i) via a mobilisation of the internal calcium stores and by a capacitative calcium entry (CCE). These effects of ET-1 were completely abolished by BQ123, a selective ETAR antagonist, but not by BQ788, a selective ETBR antagonist. By use of pharmacological inhibitors and siRNA targeting calcium-activated (IKCa1 and BKCa) potassium channels and calcium channels (TRPC1, TRPV6, Orai1), we showed that these ion channels play an important role in calcium entry and cell proliferation induced by ET-1 in PCa cells. Conclusion: These results suggest that these ions channels evidenced here might constitute potential targets to block the ET axis in human prostate cancers.

Effects of polyphenols and lipids from Pennisetum glaucum grains on T-cell activation: modulation of Ca(2+) and ERK1/ERK2 signaling.

BackgroundPearl millet (PM), i.e., Pennisetum glaucum, is widely grown in Africa and known for its anti-oxidant and anti-hyperlipidemic properties.MethodsThe P. glaucum grains were obtained from the region of Ouled Aïssa (South of Algeria). We assessed the effects of phenolic compounds and lipids, extracted from seeds of P. glaucum, on rat lymphocyte proliferation, activated by phorbol 12-myristate 13-acetate and ionomycin. In order to explore signaling pathway, triggered by these compounds, we assessed interleukin-2 (IL-2) mRNA expression and extracellular signal-regulated kinase-1/2 (ERK1/ERK2) phosphorylation. Finally, we determined increases in free intracellular Ca2+ concentrations, [Ca2+]i, by employing Fura-2/AM in rat lymphocytes.ResultsThe composition of P. glaucum grains in polyphenols was estimated to be 1660 µg gallic acid equivalents (GAE)/g. Lipids represented 4.5 %, and more than 72% of the fatty acids belonged to unsaturated family. Our investigation showed that both lipid and phenolic compounds inhibited mitogen-induced T-cell proliferation. Compared with phenolic compounds, lipids exerted weaker effects on ERK-1/ERK2 phosphorylation and Ca2+ signaling in mitogen-activated T-cells.ConclusionWe conclude that the immunomodulatory effects of P. glaucum could be contributed by its phenolic and lipid contents.

Sensitization of H2O2-induced TRPM2 activation and subsequent interleukin-8 (CXCL8) production by intracellular Fe2+ in human monocytic U937 cells

Transient receptor potential melastatin 2 (TRPM2) is an oxidative stress-sensitive Ca2+-permeable channel. In monocytes/macrophages, H2O2-induced TRPM2 activation causes cell death and/or production of chemokines that aggravate inflammatory diseases. However, relatively high concentrations of H2O2 are required for activation of TRPM2 channels in vitro. Thus, in the present study, factors that sensitize TRPM2 channels to H2O2 were identified and subsequent physiological responses were examined in U937 human monocytes. Temperature increase from 30°C to 37°C enhanced H2O2-induced TRPM2-mediated increase in intracellular free Ca2+ ([Ca2+]i) in TRPM2-expressing HEK 293 cells (TRPM2/HEK cells). The H2O2-induced TRPM2 activation enhanced by the higher temperature was dramatically sensitized by intracellular Fe2+-accumulation following pretreatment with FeSO4. Thus intracellular Fe2+-accumulation sensitizes H2O2-induced TRPM2 activation at around body temperature. Moreover, intracellular Fe2+-accumulation increased poly(ADP-ribose) levels in nuclei by H2O2 treatment, and the sensitization of H2O2-induced TRPM2 activation were almost completely blocked by poly(ADP-ribose) polymerase inhibitors, suggesting that intracellular Fe2+-accumulation enhances H2O2-induced TRPM2 activation by increase of ADP-ribose production through poly(ADP-ribose) polymerase pathway. Similarly, pretreatment with FeSO4 stimulated H2O2-induced TRPM2 activation at 37°C in U937 cells and enhanced H2O2-induced ERK phosphorylation and interleukin-8 (CXCL8) production. Although the addition of H2O2 to cells under conditions of intracellular Fe2+-accumulation caused cell death, concentration of H2O2 required for CXCL8 production was lower than that resulting in cell death. These results indicate that intracellular Fe2+-accumulation sensitizes TRPM2 channels to H2O2 and subsequently produces CXCL8 at around body temperature. It is possible that sensitization of H2O2-induced TRPM2 channels by Fe2+ may implicated in hemorrhagic brain injury via aggravation of inflammation, since Fe2+ is released by heme degradation under intracerebral hemorrhage.

A Series of New Ligustrazine-Triterpenes Derivatives as Anti-Tumor Agents: Design, Synthesis, and Biological Evaluation.

A series of novel ligustrazine-triterpenes derivatives was designed, synthesized and screened for their cytotoxicity against five cancer cell lines (Bel-7402, HepG2, HT-29, Hela, and MCF-7) and Madin-Darby canine kidney (MDCK). Current study suggested that most of the ligustrazine-triterpenes conjunctions showed better cytotoxicity than the starting materials. In particular, compound 4a exhibited better cytotoxic activity (IC50 < 5.23 μM) against Bel-7402, HT-29, MCF-7, Hela, and HepG2 than the standard anticancer drug cisplatin (DDP). The cytotoxicity selectivity detection revealed that 4a exhibited low cytotoxicity (IC50 > 20 μM) towards MDCK cells. A combination of fluorescence staining observation and flow cytometric analysis indicated that 4a could induce HepG2 cell apoptosis. Further studies suggested that 4a-induced apoptosis is mediated through depolarization of the mitochondrial membrane potential and increase of intracellular free Ca2+ concentration. In addition, the structure-activity relationships of these derivatives were briefly discussed.

Glucose-Dependent Insulin Secretion in Pancreatic β-Cell Islets from Male Rats Requires Ca2+ Release via ROS-Stimulated Ryanodine Receptors.

Glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells requires an increase in intracellular free Ca2+ concentration ([Ca2+]). Glucose uptake into β-cells promotes Ca2+ influx and reactive oxygen species (ROS) generation. In other cell types, Ca2+ and ROS jointly induce Ca2+ release mediated by ryanodine receptor (RyR) channels. Therefore, we explored here if RyR-mediated Ca2+ release contributes to GSIS in β-cell islets isolated from male rats. Stimulatory glucose increased islet insulin secretion, and promoted ROS generation in islets and dissociated β-cells. Conventional PCR assays and immunostaining confirmed that β-cells express RyR2, the cardiac RyR isoform. Extended incubation of β-cell islets with inhibitory ryanodine suppressed GSIS; so did the antioxidant N-acetyl cysteine (NAC), which also decreased insulin secretion induced by glucose plus caffeine. Inhibitory ryanodine or NAC did not affect insulin secretion induced by glucose plus carbachol, which engages inositol 1,4,5-trisphosphate receptors. Incubation of islets with H2O2 in basal glucose increased insulin secretion 2-fold. Inhibitory ryanodine significantly decreased H2O2-stimulated insulin secretion and prevented the 4.5-fold increase of cytoplasmic [Ca2+] produced by incubation of dissociated β-cells with H2O2. Addition of stimulatory glucose or H2O2 (in basal glucose) to β-cells disaggregated from islets increased RyR2 S-glutathionylation to similar levels, measured by a proximity ligation assay; in contrast, NAC significantly reduced the RyR2 S-glutathionylation increase produced by stimulatory glucose. We propose that RyR2-mediated Ca2+ release, induced by the concomitant increases in [Ca2+] and ROS produced by stimulatory glucose, is an essential step in GSIS.

Anti-oxidation and Antiapoptotic Effects of Chondroitin Sulfate on 6-Hydroxydopamine-Induced Injury Through the Up-Regulation of Nrf2 and Inhibition of Mitochondria-Mediated Pathway.

The purpose of the study was to investigate the protective effect and molecular mechanism of chondroitin sulfate (CS) against 6-hydroxydopamine (6-OHDA) induced toxicity in the human neuroblastoma cell line SH-SY5Y. The results showed that CS could protect SH-SY5Y cells against 6-OHDA-induced injury. The subsequent mechanism study showed that the anti-oxidation of CS may partly be mediated through inhibiting the intracellular reactive oxygen species overproduction, recovering the reduction of nuclear NF-E2-related factor-2 (Nrf2) expression and the reduction of antioxidants activity induced by 6-OHDA. Furthermore, CS pretreatment significantly attenuated 6-OHDA-induced cell apoptosis and nuclear condensation. 6-OHDA-induced dysfunctions, including the decrease of mitochondrial membrane potential (ΔΨm), increase of intracellular free Ca(2+), imbalance of Bcl-2/Bax ratio, release of Cyt-c from the mitochondria and activation of caspase-3 and caspase-9 were attenuated by CS pretreatment, which demonstrated that CS suppressed 6-OHDA-induced apoptosis in SH-SY5Y cells possibly through mitochondria protection. These results suggest that CS exhibits anti-oxidation through the up-regulation of Nrf2 along with endogenous antioxidant, and reduces apoptosis via inhibiting the mitochondrial pathway to protect SH-SY5Y cells damaged by 6-OHDA.

In vitro neurotoxicity evaluation of piperazine designer drugs in differentiated human neuroblastoma SH‐SY5Y cells

Abuse of synthetic drugs is widespread worldwide. Studies indicate that piperazine designer drugs act as substrates at dopaminergic and serotonergic receptors and/or transporters in the brain. This work aimed to investigate the cytotoxicity of N-benzylpiperazine, 1-(3-trifluoromethylphenyl)piperazine, 1-(4-methoxyphenyl)piperazine and 1-(3,4-methylenedioxybenzyl)piperazine in the differentiated human neuroblastoma SH-SY5Y cell line. Cytotoxicity was evaluated after 24 h incubations through the MTT reduction and neutral red uptake assays. Oxidative stress (reactive oxygen and nitrogen species production and glutathione content) and energetic (ATP content) parameters, as well as intracellular Ca(2+), mitochondrial membrane potential, DNA damage (comet assay) and cell death mode were also evaluated. Complete cytotoxicity curves were obtained after 24 h incubations with each drug. A significant decrease in intracellular total glutathione content was noted for all the tested drugs. All drugs caused a significant increase of intracellular free Ca(2+) levels, accompanied by mitochondrial hyperpolarization. However, ATP levels remained unchanged. The investigation of cell death mode revealed a predominance of early apoptotic cells. No genotoxicity was found in the comet assay. Among the tested drugs, 1-(3-trifluoromethylphenyl)piperazine was the most cytotoxic. Overall, piperazine designer drugs are potentially neurotoxic, supporting concerns on risks associated with the abuse of these drugs.

Activation of endogenously expressed ion channels by active complement in the retinal pigment epithelium.

Defective regulation of the alternative pathway of the complement system is believed to contribute to damage of retinal pigment epithelial (RPE) cells in age-related macular degeneration. Thus we investigated the effect of complement activation on the RPE cell membrane by analyzing changes in membrane conductance via patch-clamp techniques and Ca(2+) imaging. Exposure of human ARPE-19 cells to complement-sufficient normal human serum (NHS) (25 %) resulted in a biphasic increase in intracellular free Ca(2+) ([Ca(2+)]i); an initial peak followed by sustained Ca(2+) increase. C5- or C7-depleted sera did not fully reproduce the signal generated by NHS. The initial peak of the Ca(2+) response was reduced by sarcoplasmic Ca(2+)-ATPase inhibitor thapsigargin, L-type channel blockers (R)-(+)-BayK8644 and isradipine, transient-receptor-potential (TRP) channel blocker ruthenium-red and ryanodine receptor blocker dantrolene. The sustained phase was carried by CaV1.3 L-type channels via tyrosine-phosphorylation. Changes in [Ca(2+)]I were accompanied by an abrupt hyperpolarization, resulting from a transient increase in membrane conductance, which was absent under extracellular Ca(2+)- or K(+)-free conditions and blocked by (R)-(+)-BayK8644 or paxilline, a maxiK channel inhibitor. Single-channel recordings confirmed the contribution of maxiK channels. Primary porcine RPE cells responded to NHS in a comparable manner. Pre-incubation with NHS reduced H2O2-induced cell death. In summary, in a concerted manner, C3a, C5a and sC5b-9 increased [Ca(2+)]i by ryanodine-receptor-dependent activation of L-type channels in addition to maxi-K channels and TRP channels absent from any insertion of a lytic pore.

Abstract 16460: Enhanced Trpc Channel-Mediated Ca2+ Influx in the Cells With Phospholipase C-δ1 Overexpression

Background: We recently showed that ergometrine induces coronary spasm in the mice with enhanced phospholipase C (PLC)-δ1 activity, which was detected in patients with coronary spasm (Circulation 2012), and PLC-mediated Ca2+ entry is involved in the genesis of coronary spams. We examined the role of enhanced PLC-δ1 in extracellular Ca2+ entry and its underlying mechanisms in human embryonic kidney (HEK)-293 cells and human coronary arteries smooth muscle cells (CASMC). Methods and Results: The cells were stimulated with acetylcholine (ACh) in a extracellular Ca2+-free condition, and the increase in intracellular free Ca2+ concentration ([Ca2+]i) after addition of extracellular Ca2+ was defined as Ca2+ influx. [Ca2+]i was measured by fura-2. In HEK-293 cells, ACh-induced Ca2+ influx (nM ) was 21±2 in the control and 52±6 in the cells with PLC-δ1 overexpression (p&lt;0.05). ACh-induced Ca2+ influx in the cells with PLC-δ1 overexpression was suppressed by nifedipine in a dose-dependent manner but was partially by 36±13% at 10-5M (p&lt;0.05), thereby even after treatment with nifedipine at 10-5M, ACh-induced Ca2+ influx was increased by 2.9±0.1 times by enhanced PLC-δ1 compared with the control (p&lt;0.05). To clarify the role of diacylglycerol (DAG) in Ca2+ influx, the effect of blockers for DAG-activated transient receptor potential (TRPC) channel was examined. ACh-induced Ca2+ influx in the cells with PLC-δ1 overexpression was suppressed by 2-APB, an inhibitor of non-selective cation channel TRPC, in a dose-dependent manner, and was almost completely blocked by 89±12% at 10-4M (p&lt;0.05). While TRPC3 siRNA did not affect ACh-induced Ca2+ influx (59±27 vs 75±23 nM, p=ns), TRPC6 siRNA suppressed Ca2+ influx to 37±28 nM (p&lt;0.05). In human CASMC, ACh-induced Ca2+ influx was 41±11 in the control and 64±15 in the cells with PLC-δ1 overexpression (p&lt;0.05). Like HEK-293 cells, pretreatment with nifedipine partially suppressed Ca2+ influx, whereas either 2-APB or TRPC6 siRNA almost completely blocked it. Conclusion: ACh-induced Ca2+ influx, mediated by both voltage-gated Ca2+ channels and non-selective cation channels TRPC6, is enhanced by PLC-δ1 overexpression. Inhibition of TRPC may be effective in enhanced PLC-δ1-mediated coronary spasm.

P67 Effects of hydrogen sulphide on Ca2+ signalling in endothelial and smooth muscle cells

In the vascular system, ATP-sensitive K + -channels are a major target for H 2 S but recently evidence has accumulated that Na + - and Ca 2+ -permeable channels as well as intracellular Ca 2+ stores are also modulated by H 2 S. In this study we investigated the effect of H 2 S on Ca 2+ signalling on cultured endothelial and smooth muscle cells. Experiments were performed with endothelial cells isolated from porcine aorta (PAECs) and smooth muscle cells (SMCs) isolated from rat aorta and trachea. Activity of endothelial nitric oxide synthase (eNOS) was determined as conversion of incorporated L-[ 3 H]-arginine into L-[ 3 H]-citrulline. The intracellular free Ca 2+ concentration was measured with FURA-2. Incubation of PAECs with the H 2 S donors NaHS and GYY4137 markedly diminished both the release of Ca 2+ from intracellular stores and Ca 2+ entry elicited by receptor agonists such as ATP and histamine. As a consequence, the stimulatory effect of these agonists on NO formation was strongly diminished. In contrast to its inhibitory effect on ATP-induced Ca 2+ release and entry, H 2 S stimulated Ca 2+ influx from the extracellular space, but the resulting increase in intracellular free Ca 2+ concentration was not sufficient to affect endothelial NO formation. Inhibition of Ca 2+ release by H 2 S was not a peculiarity of endothelial cells but also occured in smooth muscle cells. Interestingly, similar to H 2 S, thiol-reducing agents such as DTT also inhibited ATP-induced store-operated Ca 2+ release in PAECs.

The role of canonical transient receptor potential channels in seizure and excitotoxicity.

Canonical transient receptor potential (TRPC) channels are a family of polymodal cation channels with some degree of Ca2+ permeability. Although initially thought to be channels mediating store-operated Ca2+ influx, TRPC channels can be activated by stimulation of Gq-coupled G-protein coupled receptors, or by an increase in intracellular free Ca2+ concentration. Thus, activation of TRPC channels could be a common downstream event of many signaling pathways that contribute to seizure and excitotoxicity, such as N-methyl-D-aspartate (NMDA) receptor-mediated Ca2+ influx, or metabotropic glutamate receptor activation. Recent studies with genetic ablation of various TRPC family members have demonstrated that TRPC channels, in particular heteromeric TRPC1/4 channels and homomeric TRPC5 channels, play a critical role in both pilocarpine-induced acute seizures and neuronal cell death. However, exact underlying mechanisms remain to be fully elucidated, and selective TRPC modulators and antibodies with better specificity are urgently needed for future research.

Glycogenolysis and purinergic signaling.

Both ATP and glutamate are on one hand essential metabolites in brain and on the other serve a signaling function as transmitters. However, there is the major difference that the flux in the pathway producing transmitter glutamate is comparable to the rate of glucose metabolism in brain, whereas that producing transmitter ATP is orders of magnitude smaller than the metabolic turnover between ATP and ADP. Moreover, de novo glutamate production occurs exclusively in astrocytes, whereas transmitter ATP is produced both in neurons and astrocytes. This chapter deals only with ATP and exclusively with its formation and release in astrocytes, and it focuses on potential associations with glycogenolysis, which is known to be indispensable for the synthesis of glutamate. Glycogenolysis is dependent upon an increase in free intracellular Ca(2+) concentration (Ca(2+)]i). It can be further stimulated by cAMP, but in contrast to widespread beliefs, cAMP can on its own not induce glycogenolysis. Astrocytes generate ATP from accumulated adenosine, and this process does not seem to require glycogenolysis. A minor amount of the generated ATP is utilized as a transmitter, and its synthesis requires the presence of the mainly intracellular nucleoside transporter ENT3. Many transmitters as well as extracellular K(+) concentrations high enough to open the voltage-sensitive L-channels for Ca(2+) cause a release of transmitter ATP from astrocytes. Adenosine and ATP induce release of ATP by action at several different purinergic receptors. The release evoked by transmitters or elevated K(+) concentrations is abolished by DAB, an inhibitor of glycogenolysis.

Intracellular Calcium Attenuates Persistent Current Conducted by Mutant Human Cardiac Sodium Channels in Long-QT Syndrome

Mutation in the cardiac voltage-gated sodium channel NaV1.5 can cause congenital long-QT syndrome type 3 (LQT3). Most NaV1.5 mutations associated with LQT3 promote a mode of sodium channel gating in which some channels fail to inactivate, contributing to sustained or persistent sodium current (INa,P), which is directly responsible for delayed repolarization and prolongation of the QT interval. LQT3 patients have highest risk of arrhythmia during sleep or during periods of slow heart rate. During exercise (high heart rate), there is an increase in the steady-state intracellular free calcium (Ca) concentration. We hypothesized that higher levels of intracellular Ca may act in some way to lower arrhythmia risk in LQT3 subjects. We tested this idea by examining the effects of varying intracellular Ca concentrations on the level of INa,P in cells expressing a typical LQT3 mutation, delKPQ. We found that elevated intracellular Ca concentration significantly reduced INa,P conducted by delKPQ channels but not wild-type channels. INa,P measured 200-ms after the peak transient current (expressed as % of peak current) for mutant channels was 2.6±0.4% in low Ca and 0.6±0.1% in high Ca (p<0.001). This attenuation of INa,P in delKPQ expressing cells by Ca remained in the presence of KN-93 indicating it was not due to CaM kinase II activation (2.2±0.2% in low Ca and 0.9±0.3% in high Ca; p<0.001). We conclude that intracellular Ca contributes to the regulation of INa,P conducted by a LQT3 mutant and propose that, during excitation-contraction coupling, the increase of intracellular free Ca may contribute to suppression of mutant channel current and protect cells from delayed repolarization. These findings help explain the increased arrhythmia risk in LQT3 during slow heart rate.

The K+ Channel KCa3.1 as a Novel Target for Idiopathic Pulmonary Fibrosis

BackgroundIdiopathic pulmonary fibrosis (IPF) is a common, progressive and invariably lethal interstitial lung disease with no effective therapy. We hypothesised that KCa3.1 K+ channel-dependent cell processes contribute to IPF pathophysiology. MethodsKCa3.1 expression in primary human lung myofibroblasts was examined using RT-PCR, western blot, immunofluorescence and patch-clamp electrophysiology. The role of KCa3.1 channels in myofibroblast proliferation, wound healing, collagen secretion and contraction was examined using two specific and distinct KCa3.1 blockers (TRAM-34 and ICA-17043 [Senicapoc]). ResultsBoth healthy non fibrotic control and IPF-derived human lung myofibroblasts expressed KCa3.1 channel mRNA and protein. KCa3.1 ion currents were elicited more frequently and were larger in IPF-derived myofibroblasts compared to controls. KCa3.1 currents were increased in myofibroblasts by TGFβ1 and basic FGF. KCa3.1 was expressed strongly in IPF tissue. KCa3.1 pharmacological blockade attenuated human myofibroblast proliferation, wound healing, collagen secretion and contractility in vitro, and this was associated with inhibition of TGFβ1-dependent increases in intracellular free Ca2+.ConclusionsKCa3.1 activity promotes pro-fibrotic human lung myofibroblast function. Blocking KCa3.1 may offer a novel approach to treating IPF with the potential for rapid translation to the clinic.

P22 Effect of hydrogen sulfide on Ca2+ signaling in endothelial and smooth muscle cells

Endothelial cells are active participants in inflammatory processes. They are involved in diverse activities including the regulation of leucocyte extravasation, angiogenesis, cytokine production, protease and extracellular matrix synthesis, vasodilation, etc. The small gaseous molecule hydrogen sulfide (H 2 S) is involved in a variety of physiological processes like vascular relaxation, angiogenesis, neurotransmission and inflammation. In the vascular system, ATP-sensitive K + -channels are a major target for H 2 S but over the last few years evidence has accumulated that Na + - and Ca 2+ -permeable channels as well as intracellular Ca 2+ stores are also modulated by H 2 S. In the present study we investigated the effect of H 2 S on Ca 2+ signaling in cultured endothelial and smooth muscle cells with special emphasis given to the role of H 2 S in modulating Ca 2+ entry as well as receptor-mediated release of Ca 2+ from intracellular stores. Experiments were performed with human microvascular endothelial cells (HMEC-1), endothelial cells isolated from porcine aorta, and smooth muscle cells isolated from rat aorta and rat trachea. Mobilization of intracellular Ca 2+ and Ca 2+ entry was monitored by measuring the intracellular free Ca 2+ concentration with FURA-2 in the absence and presence extracellular Ca 2+ , respectively. Activity of endothelial nitric oxide synthase (eNOS) in intact cells was determined as conversion of incorporated l -[ 3 H]-arginine into l -[ 3 H]-citrulline. Incubation of human and porcine endothelial cells with the H 2 S-donor NaHS (100 μM, 10–45 min) markedly diminished the release of Ca 2+ from intracellular stores elicited by receptor agonists such as ATP or histamine. As a consequence, the stimulatory effect of these agonists on endothelial NO formation was strongly diminished, whereas the response to the Ca 2+ ionophore A23187 was barely affected. In contrast to its inhibitory effect on Ca 2+ release, NaHS stimulated Ca 2+ influx from the extracellular space, but the resulting increase in intracellular free Ca 2+ concentration was not sufficient to affect endothelial NO formation. In smooth muscle cells isolated from rat aorta or rat trachea NaHS also blocked receptor-mediated release of Ca 2+ from intracellular stores but in contrast to the results obtained with endothelial cells, no stimulatory effect of NaHS on Ca 2+ entry was observed. H 2 S inhibits the stimulatory effect of Ca 2+ mobilizing agonists on endothelial NO formation by attenuating the release of Ca 2+ from intracellular stores. Inhibition of Ca 2+ release by H 2 S is not a peculiarity of endothelial cells but also occurs in vascular and tracheal smooth muscle cells. These hitherto undescribed effects may be in part responsible for the beneficial effects of H 2 S in sulfur bath therapy.

PPARγ agonists upregulate sphingosine 1-phosphate (S1P) receptor 1 expression, which in turn reduces S1P-induced [Ca2 +]i increases in renal mesangial cells

We previously identified peroxisome proliferator-activated receptor gamma (PPARγ) agonists (thiazolidinediones, TZDs) as modulators of the sphingolipid metabolism in renal mesangial cells. TZDs upregulated sphingosine kinase 1 (SK-1) and increased the formation of intracellular sphingosine 1-phosphate (S1P), which in turn reduced the expression of pro-fibrotic connective tissue growth factor. Since S1P also acts as extracellular ligand at specific S1P receptors (S1PR, S1P1–5), we investigated here the effect of TZDs on S1PR expression in mesangial cells and evaluated the functional consequences by measuring S1P-induced increases in intracellular free Ca2+ concentration ([Ca2+]i). Treatment with two different TZDs, troglitazone and rosiglitazone, enhanced S1P1 mRNA and protein expression in rat mesangial cells, whereas S1P2–5 expression levels were not altered. Upregulation of S1P1 mRNA upon TZD treatment was also detected in human mesangial cells and mouse glomeruli. PPARγ antagonism and promoter studies revealed that the TZD-dependent S1P1 mRNA induction involved a functional PPAR response element in the S1P1 promoter. Pharmacological approaches disclosed that S1P-induced [Ca2+]i increases in rat mesangial cells were predominantly mediated by S1P2 and S1P3. Interestingly, the transcriptional upregulation of S1P1 by TZDs resulted in a reduction of S1P-induced [Ca2+]i increases, which was reversed by the S1P1/3 antagonist VPC-23019, the protein kinase C (PKC) inhibitor PKC-412, and by S1P1 siRNA. These data suggest that PPARγ-dependent upregulation of S1P1 leads to an inhibition of S1P-induced Ca2+ signaling in a PKC-dependent manner. Overall, these results reveal that TZDs not only modulate intracellular S1P levels but also regulate S1PR signaling by increasing S1P1 expression in mesangial cells.

Changes in the Density of Nitrergic Neurons in the Hippocampus of Rats Following Kainic Acid and Melatonin Administration

Nitric oxide (NO) may play a role in the pathophysiology of excitotoxicity. It is also possible that increase in Ca²⁺ overload and NO-mediated events are involved in neuronal loss during excitotoxicity. Using nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry, we have investigated the effects of melatonin on NADPH-d positive hippocampal neurons after kainic acid (KA) induced excitotoxicity in female rats of Wistar strain. Cytosolic Ca²⁺ (free calcium) in all the respective experimental groups was also studied. Kainic acid was administered, with a single dose of 10 mg/kg/bw (body weight) to the animals. KA treated rats were given melatonin at a dose of 20 mg/kg/bw (for 14 day). On the last day of treatment, animals were transcardially perfused with 4 % paraformaldehyde under deep thiopental anaesthesia. Cryostat sections (20 microm) were cut and stained for NADPH-d positive neurons. KA exposed animals showed a significantly increased number of NADPH-d positive neurons in the dorsal and ventral blade of the dentate gyrus (DG), hilus, CA1 and CA3 area of hippocampus, with a parallel increase in intracellular free Ca²⁺ ion concentration, as compared to the control group. KA + melatonin-treated animal groups showed reduced number of NADPH-d positive neurons in DG, hilus, CA1 and CA3 areas and a decline in cytosolic Ca²⁺ concentration, as compared to KA treated group. Our study suggests that the enhanced levels of cytosolic Ca²⁺ and nitric oxide (NO) play an important role in kainate induced excitotoxicity. Inhibition of NO production may be another means whereby melatonin can reduce oxidative damage and seems to play important role in neuroprotection.

Molecular cloning of a plasma membrane Ca2 + ATPase (PMCA) from Y-organs of the blue crab (Callinectes sapidus), and determination of spatial and temporal patterns of PMCA gene expression

Existing data indicate that a stage-specific increase in intracellular free Ca2+ stimulates ecdysteroid production by crustacean molting glands (Y-organs). The concentration of Ca2+ in cytosol is controlled mainly by proteins intrinsic to the plasma membrane and to the membranes of organelles. Several families of proteins are involved, including Ca2+ channels, Ca2+ pumps (ATPases), and Ca2+ exchangers. The family of Ca2+ pumps includes plasma membrane calcium ATPases (PMCAs). As a step toward understanding the involvement of calcium signaling in regulation of ecdysteroidogenesis, we used a PCR-based cloning strategy (RT-PCR followed by 3′- and 5′-RACE) to clone from Y-organs of the blue crab (Callinectes sapidus) a cDNA encoding a putative PMCA. The 4292base pair (bp) cDNA includes a 3510bp open reading frame encoding a 1170-residue protein (Cas-PMCA). The conceptually translated protein has a relative molecular mass of 128.8×103 and contains all signature domains of an authentic PMCA, including ten transmembrane domains and a calmodulin binding site. The predicted membrane topography of Cas-PMCA is as expected for an authentic PMCA protein. A phylogenetic analysis of nonredundant amino acid sequences of PMCA proteins from different species showed Cas-PMCA clusters with other arthropod PMCA proteins. An assessment of tissue distribution showed the Cas-PMCA transcript to be broadly distributed in both neural and non-neural tissues. Studies using quantitative real-time PCR revealed stage-specific changes in Cas-PMCA abundance during the molting cycle, with peak expression occurring during premolt stage D2, a pattern consistent with the hypothesis that Cas-PMCA functions to maintain cellular Ca2+ homeostasis in Y-organs.