SDF-1alpha up-regulates interleukin-6 through CXCR4, PI3K/Akt, ERK, and NF-kappaB-dependent pathway in microglia

Stromal cell-derived factor-1 (SDF-1), also known as CXCL12, and its receptor CXC chemokine receptor 4 (CXCR4) express in various kinds of cells in central nervous system. The SDF-1/CXCR4 signaling pathway is regulated by diverse biological effects. SDF-1 is up-regulated in the ischemic penumbra following stroke and has been known to be associated with the homing of bone marrow cells to injury. However, the effect of SDF-1alpha/CXCR4 on cytokine production in microglia is mostly unknown. Here, we demonstrated that SDF-1alpha enhanced IL-6 production in both primary cultured microglia and BV-2 microglia. We further investigated the signaling pathway involved in IL-6 production stimulated by SDF-1alpha in microglia. SDF-1alpha increased IL-6 production in both protein and mRNA levels. These effects were attenuated by ERK, phosphatidylinositol 3-kinase (PI3K), NF-kappaB inhibitors, and IkappaB protease inhibitor. Stimulation of microglia with SDF-1alpha also increased Akt and ERK1/2 phosphorylation. In addition, SDF-1alpha treatment also increased IkappaB kinase alpha/beta (IKK alpha/beta) phosphorylation, IkappaBalpha phosphorylation, IkappaBalpha degradation, p65 phosphorylation at Ser(276), translocation of p65 and p50 from cytosol to nucleus and kappaB-luciferase activity. Moreover, SDF-1alpha-mediated increase of kappaB-luciferase activity was inhibited by pre-transfection of DN-p85, DN-Akt or DN-ERK2. Increase of IKK alpha/beta phosphorylation and binding of p65 and p50 to the NF-kappaB element were both antagonized by PI3K and ERK inhibitors. Our results demonstrate a mechanism linking SDF-1alpha and IL-6, and provide additional support for the notion that SDF-1alpha plays a regulatory role in microglia activation.

Inhibitory effect of stevioside on calcium influx to produce antihypertension

Stevioside is a sweet-tasting glycoside occurring abundantly in the leaves of Stevia rebaudiana (Compositae). It has been used popularly in Japan and Brazil as a sugar substitute for decades. Previous study has shown that it lowered blood pressure in spontaneously hypertensive rats (SHRs) when administered intravenously. This study shows that intraperitoneal injection of stevioside 25 mg/kg also has antihypertensive effect in SHRs. In isolated aortic rings from normal rats, stevioside could dose-dependently relax the vasopressin-induced vasoconstriction in both the presence and absence of endothelium. However, stevioside had no effect on phenylephrine- and KCl-induced phasic vasoconstriction. In addition, stevioside lost its influence on vasopressin-induced vasoconstriction in Ca(2+)-free medium. The results indicate that stevioside caused vasorelaxation via an inhibition of Ca(2+) influx into the blood vessel. This phenomenon was further confirmed in cultured aortic smooth muscle cells (A7r5). Using 10(-5) M methylene blue for 15 min, stevioside could still relax 10(-8) M vasopressin-induced vasoconstriction in isolated rat aortic rings, showing that this vasorelaxation effect was not related to nitric oxide. The present data show that the vasorelexation effect of stevioside was mediated mainly through Ca(2+) influx inhibition.

Isosteviol acts on potassium channels to relax isolated aortic strips of Wistar rat

Isosteviol is a derivative of stevioside, a constituent of Stevia rebaudiana, which is commonly used as a noncaloric sugar substitute in Japan and Brazil. In the present study, the role of potassium channels in the vasodilator effect of isosteviol was investigated using potassium channel blockers on isosteviol-induced relaxation of isolated aortic rings prepared from Wistar rats. Isosteviol dose-dependently relaxed the vasopressin (10(-8) M)-induced vasoconstriction in isolated aortic rings with or without endothelium. However, in the presence of potassium chloride (3x10(-2) M), the vasodilator effect of isosteviol on arterial strips disappeared. Only the inhibitors specific for the ATP-sensitive potassium (K(ATP)) channel or small conductance calcium-activated potassium (SK(Ca)) channel inhibited the vasodilator effect of isosteviol in isolated aortic rings contracted with 10(-8) M vasopressin. Also; since the isosteviol-induced relaxation was unchanged by methylene blue, a role of nitric oxide and/or endothelium in the vasodilatation produced by isosteviol could be ruled out. The obtained results indicated that vasodilatation induced by isosteviol is related to the opening of SK(Ca) and K(ATP) channels.

Palmitic acid-induced lipotoxicity and protection by (+)-catechin in rat cortical astrocytes

BACKGROUND

Astrocytes do not only maintain homeostasis of the extracellular milieu of the neurons, but also play an active role in modulating synaptic transmission. Palmitic acid (PA) is a saturated fatty acid which, when being excessive, is a significant risk factor for lipotoxicity. Activation of astrocytes by PA has been shown to cause neuronal inflammation and demyelination. However, direct damage by PA to astrocytes is relatively unexplored. The aim of this study was to identify the mechanism(s) of PA-induced cytotoxicity in rat cortical astrocytes and possible protection by (+)-catechin.

METHODS

Cytotoxicity and endoplasmic reticulum (ER) markers were assessed by MTT assay and Western blotting, respectively. Cytosolic Ca(2+) and mitochondrial membrane potential (MMP) were measured microfluorimetrically using fura-2 and rhodamine 123, respectively. Intracellular reactive oxygen species (ROS) production was assayed by the indicator 2'-7'-dichlorodihydrofluorescein diacetate.

RESULTS

Exposure of astrocytes to 100μM PA for 24h resulted in apoptotic cell death. Whilst PA-induced cell death appeared to be unrelated to ER stress and perturbation in cytosolic Ca(2+) signaling, it was likely a result of ROS production and subsequent MMP collapse, since ascorbic acid (anti-oxidant, 100μM) prevented PA-induced MMP collapse and cell death. Co-treatment of astrocytes with (+)-catechin (300μM), an anti-oxidant found abundantly in green tea, significantly prevented PA-induced ROS production, MMP collapse and cell death.

CONCLUSION

Our results suggest that PA-induced cytotoxicity in astrocytes may involve ROS generation and MMP collapse, which can be prevented by (+)-catechin.

The novel phloroglucinol derivative BFP induces apoptosis of glioma cancer through reactive oxygen species and endoplasmic reticulum stress pathways

Prenyl-phloroglucinol derivatives from hop plants have been shown to have anticancer activities. This study is the first to investigate the anticancer effects of the new phloroglucinol derivative (2,4-bis(4-fluorophenylacetyl)phloroglucinol; BFP). BFP induced cell death and anti-proliferation in three glioma, U251, U87 and C6 cells, but not in primary human astrocytes. BFP-induced concentration-dependently cell death in glioma cells was determined by MTT and SRB assay. Moreover, BFP-induced apoptotic cell death in glioma cells was measured by Hochest 33258 staining and fluorescence-activated cell sorter (FACS) of propidine iodine (PI) analysis. Treatment of U251 human glioma cells with BFP was also found to induce reactive oxygen species (ROS) generation, which was detected by a fluorescence dye used FACS analysis. Treatment of BFP also increased a number of signature endoplasmic reticulum (ER) stress markers glucose-regulated protein (GRP)-78, GRP-94, IRE1, phosphorylation of eukaryotic initiation factor-2α (eIF-2α) and up-regulation of CAAT/enhancer-binding protein homologous protein (CHOP). Moreover, treatment of BFP also increased the down-stream caspase activation, such as pro-caspase-7 and pro-caspase-12 degradation, suggesting the induction of ER stress. Furthermore, BFP also induced caspase-9 and caspase-3 activation as well as up-regulation of cleaved PARP expression. Treatment of antioxidants, or pre-transfection of cells with GRP78 or CHOP siRNA reduced BFP-mediated apoptotic-related protein expression. Taken together, the present study provides evidences to support that ROS generation, GRP78 and CHOP activation are mediating the BFP-induced human glioma cell apoptosis.

Ca2+ store depletion and endoplasmic reticulum stress are involved in P2X7 receptor-mediated neurotoxicity in differentiated NG108-15 cells

P2X7 receptor (P2X7R) activation by extracellular ATP triggers influx of Na(+) and Ca(2+), cytosolic Ca(2+) overload and consequently cytotoxicity. Whether disturbances in endoplasmic reticulum (ER) Ca(2+) homeostasis and ER stress are involved in P2X7R-mediated cell death is unknown. In this study, a P2X7R agonist (BzATP) was used to activate P2X7R in differentiated NG108-15 neuronal cells. In a concentration-dependent manner, application of BzATP (10-100 µM) immediately raised cytosolic Ca(2+) concentration ([Ca(2+)]i) and caused cell death after a 24-h incubation. P2X7R activation for 2 h did not cause cell death but resulted in a sustained reduction in ER Ca2+ pool size, as evidenced by a diminished cyclopiazonic acid-induced Ca(2+) discharge (fura 2 assay) and a lower fluorescent signal in cells loaded with Mag-fura 2 (ER-specific Ca(2+)-fluorescent dye). Furthermore, P2X7R activation (2 h) led to the appearance of markers of ER stress [phosphorylated α subunit of eukaryotic initiation factor 2 (p-eIF2α) and C/EBP homologous protein (CHOP)] and apoptosis (cleaved caspase 3). Xestospongin C (XeC), an antagonist of inositol-1,4,5-trisphosphate (IP3) receptor (IP3R), strongly inhibited BzATP-triggered [Ca(2+)]i elevation, suggesting that the latter involved Ca(2+) release via IP3R. XeC pretreatment not only attenuated the reduction in Ca(2+) pool size in BzATP-treated cells, but also rescued cell death and prevented BzATP-induced appearance of ER stress and apoptotic markers. These novel observations suggest that P2X7R activation caused not only Ca(2+) overload, but also Ca(2+) release via IP3R, sustained Ca(2+) store depletion, ER stress and eventually apoptotic cell death.

Antihyperglycemic action of angiotensin II receptor antagonist, valsartan, in streptozotocin-induced diabetic rats

OBJECTIVES

In the present study, we use valsartan, a highly selective antagonist for angiotensin(1) (AT(1)) receptor subtype, to investigate the effect of AT(1) receptor on the plasma glucose metabolism in streptozotocin-induced diabetic rats (STZ-diabetic rats).

METHODS

The plasma glucose concentration was assessed by glucose oxidase method and plasma insulin was measured using enzyme-linked immunosorbent assay. Systolic blood pressure (SBP) was determined by the tail-cuff method. The intravenous glucose challenge test (IVGCT) was carried out to evaluate the effect of valsartan on the glucose utilization in vivo. The mRNA levels of the subtype 4 form of glucose transporter (GLUT4) in soleus muscle and phosphoenolpyruvate carboxykinase (PEPCK) in the liver were detected by Northern blotting analysis. Moreover, the protein levels of GLUT4 in isolated soleus muscle and hepatic PEPCK were investigated using Western blotting analysis.

RESULTS

A single intravenous injection of valsartan decreased the plasma glucose concentrations in a dose-dependent manner in STZ-diabetic rats. Plasma glucose-lowering action of valsartan also observed in normal rats although in a way not so effective as that in STZ-diabetic rats. Valsartan at the dose of 0.2 mg/kg that produced the maximal plasma glucose-lowering activity in STZ-diabetic rats is also effective to lower the SBP. However, oral treatment with nifedipine or nicorandil in STZ-diabetic rats at the dose sufficient to decrease SBP showed no change of plasma glucose. Otherwise, infusion of saralasin (10 microg/kg per min) into STZ-diabetic rats produced a plasma glucose-lowering activity similar to that by valsartan at 0.2 mg/kg. Moreover, valsartan (0.2 mg/kg) significantly attenuated the raise of plasma glucose induced by IVGCT in normal rats. Repeated intravenous administration of valsartan (0.2 mg/kg) in STZ-diabetic rats resulted in the lowering of plasma glucose after 3 days. The mRNA and protein levels of GLUT4 in the soleus muscle were increased after repeated intravenous administration of valsartan in STZ-diabetic rats for 3 days. Moreover, similar repeated treatment with valsartan reversed the elevated mRNA and protein levels of PEPCK in the liver of STZ-diabetic rats.

CONCLUSIONS

These results suggest that the plasma glucose-lowering activity of AT(1) receptor antagonism was associated with an increase in the glucose utilization in peripheral tissue and/or a reduction in hepatic gluconeogenesis in the absence of insulin.

Tetramethylpyrazine protects mice against thioacetamide-induced acute hepatotoxicity

In this study, the intraperitoneal administration of 1 mg/kg thioacetamide (TAA) produced hepatotoxicity in mice. The increase in serum SGOT and SGPT produced at 24 h by this regimen was decreased in a dose-dependent manner by coadministration of tetramethylpyrazine (TMP; 10, 25 and 50 mg/kg). A rise in serum interleukin-2 was similarly prevented. Increased concentrations of malondialdehyde (MDA) generated in vitro in liver homogenates prepared from TAA-treated mice were decreased by TMP treatments. The increase in MDA produced by TAA was also prevented by in vitro addition of TMP to liver homogenates. These results suggest that part of the hepatocellular injury induced by TAA is mediated by oxidative stress caused by the action of cytokines through lipid peroxidation. TMP appears to act by preventing lipid peroxidation.

Protection by hot water extract of Panax notoginseng on chronic ethanol-induced hepatotoxicity

The purpose of this study was to investigate the antioxidant effects of a hot water extract of Panax notoginseng (PNG) against chronic ethanol-induced hepatotoxicity. Fifty mice were divided into fi ve equal groups with 10 in each group. Group 1 (control) received saline, whereas group 2 received ethanol (70%, 0.1 mL, p.o.) once daily for 4 weeks, which induced hepatotoxicity, manifested biochemically by a significant elevation of serum enzyme activities, such as SGOT and SGPT. Hepatotoxicity was further evidenced by a significant increase in the hepatic lipid peroxidation measured. Groups 3-5 were administered a hot water extract of PNG at doses of 10, 25 and 50 mg/kg 2 weeks after initiating oral administration of ethanol, for a further 2 weeks. PNG ameliorated the rise in serum sGOT and sGPT induced by chronic ethanol administration. The mice were killed after PNG administration. In a separate study, PNG inhibited the lipid peroxidation in the mouse liver homogenate induced by ethanol in a dose-dependent manner. The findings indicate that PNG is an efficient cytoprotective agent against chronic ethanol-induced hepatotoxicity, possibly through inhibition of the production of oxygen-free radicals that cause lipid peroxidation.

Antioxidant activity ofGanoderma lucidum in acute ethanol-induced heart toxicity

The hot water extract of the mushroom Ganoderma lucidum was shown to have antioxidative effect against heart toxicity. Investigations into the mechanisms of action, level of lipid peroxidation level in vivo, and superoxide scavenging activity were also conducted. The mice were divided into six groups with ten animals in each group. Ganoderma lucidum, at doses of 10, 25 and 50 mg/kg (p.o.) was administered. Superoxide anions were assayed by UV spectrophotometer using the cytochrome C reduction method. The results of this study showed that Ganoderma lucidum exhibited a dose-dependent antioxidative effect on lipid peroxidation and superoxide scavenging activity in mouse heart homogenate. Additionally, this result indicated that heart damage induced by ethanol shows a higher malonic dialdehyde level compared with heart homogenate treated with Ganoderma lucidum. It is concluded that the antioxidative activity may therefore contribute to the cardioprotective effect of Ganoderma lucidum, and may therefore protect the heart from superoxide induced damage.

Isosteviol as a potassium channel opener to lower intracellular calcium concentrations in cultured aortic smooth muscle cells

Isosteviol is a derivative of stevioside, a constituent of Stevia rebaudiana, and is commonly used as a non-caloric sugar substitute in Japan and Brazil. The present study attempted to elucidate the role of potassium (K (+)) channels in the action of isosteviol on intracellular calcium concentrations ([Ca (2+)]i) in cultured vascular smooth muscle (A7r5) cells using the Ca (2+)-sensitive dye Fura-2 as an indicator. The increase of [Ca (2+)]i in A7r5 cells produced by vasopressin (1 micromol/L) or phenylephrine (1 micromol/L) was attenuated by isosteviol from 0.01 micromol/L to 10 micromol/L. The attenuation by isosteviol of the vasopressin- and phenylephrine-induced increase in [Ca (2+)]i was inhibited by glibenclamide, apamin and 4-aminopyridine but not by charybdotoxin. Furthermore, the inhibitory action of isosteviol on [Ca (2+)]i was blocked when A7r5 cells co-treated with glibenclamide and apamin in conjunction with 4-aminopyridine were present. Therefore, not only did the ATP-sensitive potassium (K (ATP)) channel affect the action of isosteviol on [Ca (2+)]i modulation in A7r5 cells, but also those on the small conductance calcium-activated potassium (SK (Ca)) channels and voltage-gated (Kv) channels. However, the blockers of large-conductance Ca (2+)-activated potassium channels failed to modify the inhibitory action of isosteviol on [Ca (2+)]i. The obtained results indicated that a decrease of [Ca (2+)]i in A7r5 cells by isosteviol is mainly mediated by the selective opening of K (ATP) channel or/and SK (Ca) channel. Alteration in the Kv channel also plays a critical role in the inhibitory action of isosteviol.

Antiproliferative effect of isosteviol on angiotensin-II-treated rat aortic smooth muscle cells

Isosteviol is a derivative of stevioside, a constituent of Stevia rebaudiana, which is commonly used as a noncaloric sugar substitute in Japan and Brazil. The aims of this study were to examine whether isosteviol alters angiotensin-II-induced cell proliferation in rat aortic smooth muscle cells. Cultured rat aortic smooth muscle cells were preincubated with isosteviol, then stimulated with angiotensin II, after which [(3)H]thymidine incorporation and endothelin-1 secretion were examined. Isosteviol (1-100 micromol/l) inhibits angiotensin-II-induced DNA synthesis and endothelin-1 secretion. Measurements of 2'7'-dichlorofluorescin diacetate, a redox-sensitive fluorescent dye, showed an isosteviol-mediated inhibition of intracellular reactive oxygen species generated by the effects of angiotensin II. The inductive properties of angiotensin II on extracellular signal-regulated kinase (ERK) phosphorylation were found reversed with isosteviol and antioxidants such as N-acetylcysteine. In summary, we speculate that isosteviol inhibits angiotensin-II-induced cell proliferation and endothelin-1 secretion via attenuation of reactive oxygen species generation. Thus, this study provides important insights that may contribute to the effects of isosteviol on the cardiovascular system.

Effect of tetramethylpyrazine on potassium channels to lower calcium concentration in cultured aortic smooth muscle cells

1. Tetramethylpyrazine (TMP) is one of the active principles contained in Ligusticum chuanxiong Hort. (Umbelliferae), a herb that has been used widely in China to treat vascular disorders. 2. In an attempt to elucidate the possible mechanisms of action of TMP, the effect of TMP on intracellular calcium concentrations ([Ca2+]i) was investigated in cultured vascular smooth muscle (A7r5) cells using the Ca(2+)-sensitive dye Fura-2 as an indicator. 3. The increase in [Ca2+]i in A7r5 cells produced by vasopressin (1 micromol/L) or phenylephrine (1 micromol/L) was attenuated by TMP in a concentration-dependent manner. Only inhibitors specific to ATP-sensitive potassium (KATP) channels or small conductance calcium-activated potassium (SKCa) channels attenuated the action of TMP (10 micromol/L) on [Ca2+]i. However, blockers of other K+ channels failed to modify the inhibitory action of TMP (10 micromol/L) on [Ca2+]i. 4. The action of TMP on membrane potential in A7r5 cells was monitored by the fluorescence of bisoxonol. Tetramethylpyrazine caused a concentration-dependent inhibition of changes in membrane potential elicited by KCl (20 mmol/L) or phenylephrine (1 micro mol/L), an effect that was totally reversed by glibenclamide (100 micromol/L) and apamin (100 nmol/L) in combination. 5. The results obtained indicate that the decrease in [Ca2+]i in A7r5 cells produced by TMP is mediated mainly by opening of KATP and/or SKCa channels.

Propofol produces preventive analgesia via GluN2B-containing NMDA Receptor/ERK1/2 Signaling Pathway in a rat model of inflammatory pain

Abstract

Propofol, an intravenous anesthetic, has been shown to offer superior analgesic effect clinically. Whether propofol has preventive analgesic property remains unexplored. The present study investigated the antinociceptive effect of propofol and underlying molecular and cellular mechanisms via pre-emptive administration in a formalin-induced inflammatory pain model in rats. Male adult Sprague–Dawley rats were randomly allocated into four groups: naïve (Group Naïve), formalin injection only (Group Formalin), and formalin injection at 30 min (Group P-30 min) or 2 h (Group P-2 h) after intravenous infusion of propofol (0.6 mg kg−1 min−1) for 1 h. Nociceptive responses and protein expression of phosphorylated- or pan-GluN2B, ERK1/2, p38 mitogen-activated protein kinase, and c-Jun N-terminal kinase in the spinal dorsal horn were evaluated. Alteration of intracellular Ca2+ concentration induced by N-methyl-D-aspartate (NMDA) receptor agonists with or without pre-treatment of propofol was measured using fluorometry in SH-SY5Y cells while neuronal activation in the spinal dorsal horn by immunofluorescence. Pre-emptive propofol reduced pain with a delayed response to formalin and a reduction in hypersensitivity that lasted at least for 2 h. The formalin-induced activation of spinal GluN2B and ERK1/2 but not p38 or c-Jun N-terminal kinase was also diminished by propofol treatment. Preconditioning treatment with 3 µM and 10 µM of propofol inhibited Ca2+ influx mediated through NMDA receptors in SH-SY5Y cells. Propofol also reduced the neuronal expression of c-Fos and p-ERK induced by formalin. This study shows that pre-emptive administration of propofol produces preventive analgesic effects on inflammatory pain through regulating neuronal GluN2B-containing NMDA receptor and ERK1/2 pathway in the spinal dorsal horn.

Bradykinin-induced cell migration and COX-2 production mediated by the bradykinin B1 receptor in glioma cells

Bradykinin is produced and acts at the site of injury and inflammation. Recent reports have also shown that bradykinin selectively modulates blood-tumor barrier permeability. However, the molecular mechanisms and pathologic roles underlying bradykinin-induced glioma migration remain unclear. Glioma is the most common primary adult brain tumor, with a poor prognosis because of the ease with which tumor cells spread to other regions of the brain. In this study, we found that bradykinin increases the cell migration and expression of cyclo-oxygenase-2 (COX-2) in glioma cells. Bradykinin-mediated migration was attenuated by the selective COX-2 inhibitor NS-398. Moreover, increased motility of glioma cells and expression of COX-2 were mimicked by a bradykinin B1 receptor (B1R) agonist and markedly inhibited by a B1R antagonist. Bradykinin-mediated migration was attenuated by phosphoinositide 3-kinase (PI-3 kinase)/AKT inhibitors LY 294002 and wortmannin. Bradykinin stimulation also increased the phosphorylation of the p85 subunit of PI-3 kinase and serine 473 of AKT. Treatment of bradykinin with AP-1 inhibitors Tanshinone IIA and curcumin also reduced COX-2 expression and glioma cell migration. Moreover, treatment of bradykinin also induced phosphorylation of c-Jun in glioma cells. AP-1 promoter analysis in the luciferase reporter construct showed that bradykinin increased AP-1 transcription activity and was inhibited by LY 294002 and wortmannin. One mechanism underlying bradykinin-directed migration is transcriptional up-regulation of COX-2 and activation of the B1R receptor, PI-3 kinase, AKT, c-Jun, and AP-1 pathways.

Suppression of voltage-gated Na(+) channels and neuronal excitability by imperatorin

Imperatorin is a naturally occurring furocoumarin compound isolated from plants such as Angelica archangelica and Cnidium monnieri. It has multiple pharmacological effects including anticonvulsant effects. Here we determined the effects of imperatorin on voltage-gated Na(+) channels (VGSC) using whole-cell patch clamp techniques in differentiated neuronal NG108-15 cells. We showed that imperatorin inhibited VGSC; such inhibition did not show state-dependence. Imperatorin caused a left shift in the steady-state inactivation curve without affecting activation gating. The inhibition of VGSC by imperatorin displayed a mild frequency-dependence. Imperatorin was also shown to inhibit VGSC and action potential amplitude without affecting voltage-gated K(+) channels in rat hippocampal CA1 neurons. In conclusion, our results suggest that imperatorin dampens neuronal excitability by inhibiting VGSC.

Propofol depresses angiotensin II-induced cell proliferation in rat cardiac fibroblasts

BACKGROUND

Propofol may have beneficial effects on the prevention of angiotensin II (Ang II)-induced cardiac fibroblast proliferation via its antioxidative properties. The authors hypothesized that propofol may alter Ang II-induced cell proliferation and aimed to identify the putative underlying signaling pathways in rat cardiac fibroblasts.

METHODS

Cultured rat cardiac fibroblasts were pretreated with propofol then stimulated with Ang II; cell proliferation and endothelin-1 gene expression were examined. The effect of propofol on Ang II-induced nicotinamide adenine dinucleotide phosphate-oxidase activity, reactive oxygen species formation, extracellular signal-regulated kinase phosphorylation, and activator protein 1-mediated reporter activity were also examined. The effect of propofol on nitric oxide production and protein kinase B and endothelial nitric oxide synthase phosphorylations were also tested to elucidate the intracellular mechanism of propofol in proliferation.

RESULTS

Ang II (100 nm) increased cell proliferation and endothelin-1 expression, which were partially inhibited by propofol (10 or 30 microm). Propofol also inhibited Ang II-increased nicotinamide adenine dinucleotide phosphate-oxidase activity, reactive oxygen species formation, extracellular signal-regulated kinase phosphorylation, and activator protein 1-mediated reporter activity. Propofol was also found to increase nitric oxide generation and protein kinase B and nitric oxide synthase phosphorylations. Nitric oxide synthase inhibitor (N-nitro-L-arginine methylester) and the short interfering RNA transfection for protein kinase B or endothelial nitric oxide synthase markedly attenuated the inhibitory effect of propofol on Ang II-induced cell proliferation.

CONCLUSIONS

The authors' results suggest that propofol prevents cardiac fibroblast proliferation by interfering with the generation of reactive oxygen species and involves the activation of the protein kinase B-endothelial nitric oxide synthase-nitric oxide pathway.

Osthol is a use-dependent blocker of voltage-gated Na+ channels in mouse neuroblastoma N2A cells

Osthol, a Chinese herbal compound, has been shown to possess vasorelaxant and neuroprotective properties. Not much is known about the effects of osthol on ionic channels, activities of which are implicated in vasorelaxation and neuroprotection. In this work we report that osthol could inhibit voltage-gated Na (+) currents with state-dependence in mouse neuroblastoma N2A cells (IC (50) = 12.3 microM and 31.5 microM at holding potentials of - 70 mV and - 100 mV, respectively). Current blockade was equally effective in both extracellular and intracellular application of osthol. Osthol (18 microM) did not significantly affect the kinetics and voltage-dependence of Na (+) channel activation, but left-shifted the steady-state inactivation curve (V (1/2) = - 60.5 mV and - 78.7 mV in the absence and presence of osthol, respectively). Osthol also mildly but significantly retarded channel recovery from inactivation (recovery time constant = 19.9 ms and 35.6 ms in the absence and presence of osthol, respectively). In addition, osthol blocked Na (+) currents in a frequency-dependent fashion: blockades of 17 %, 34 % and 49 % when currents were triggered at 0.33 Hz, 1 Hz and 3.33 Hz, respectively. Taken together, our results therefore suggest that osthol blocked voltage-gated Na (+) channels intracellularly with state- and frequency-dependence.

Enhancing tetrandrine cytotoxicity in human lung carcinoma A549 cells by suppressing mitochondrial ATP production

ATP depletion induced by inhibiting glycolysis or mitochondrial ATP production has been demonstrated to cause cancer cell death. Whether ATP depletion can enhance the efficacy and potency of anti-cancer effects of herbal compounds is so far unknown. We examined the enhancing effect of ATP depletion on anti-cancer actions of tetrandrine (TET) in human lung carcinoma A549 cells. A 24-h incubation of A549 cells with tetrandrine caused a concentration-dependent cytotoxic effect (LC50 = 66.1 μM). Co-incubation with 20 mM 2-deoxyglucose (2-DG, glycolysis inhibitor) caused only a very slight enhancement of tetrandrine cytotoxicity. By contrast, inhibiting mitochondrial ATP production with oligomycin (10 μM, ATP synthase inhibitor) and FCCP (30 μM, uncoupling agent) (thus, oligo-FCCP) on its own caused only slight cell cytotoxicity but strongly potentiated tetrandrine cytotoxicity (tetrandrine LC50 = 15.6 μM). The stronger enhancing effect of oligo-FCCP than 2-DG on TET toxicity did not result from more severe overall ATP depletion, since both treatments caused a similar ATP level suppression. Neither oligo-FCCP nor 2-DG synergized with tetrandrine in decreasing mitochondrial membrane potential. TET on its own triggered reactive oxygen species (ROS) production, and oligo-FCCP, but not 2-DG, potentiated TET in causing ROS production. Taken together, our results suggest that inhibiting ATP production from mitochondria, but not from glycolysis, appears to be a very effective means in augmenting TET-triggered ROS production and hence toxicity in A549 cells.

Perturbation of Akt Signaling, Mitochondrial Potential, and ADP/ATP Ratio in Acidosis-Challenged Rat Cortical Astrocytes

Cells switch to anaerobic glycolysis when there is a lack of oxygen during brain ischemia. Extracellular pH thus drops and such acidosis causes neuronal cell death. The fate of astrocytes, mechanical, and functional partners of neurons, in acidosis is less studied. In this report, we investigated the signaling in acidosis-challenged rat cortical astrocytes and whether these signals were related to mitochondrial dysfunction and cell death. Exposure to acidic pH (6.8, 6.0) caused Ca²⁺ release and influx, p38 MAPK activation, and Akt inhibition. Mitochondrial membrane potential was hyperpolarized after astrocytes were exposed to acidic pH as soon as 1 h and lasted for 24 h. Such mitochondrial hyperpolarization was prevented by SC79 (an Akt activator) but not by SB203580 (a p38 inhibitor) nor by cytosolic Ca²⁺ chelation by BAPTA, suggesting that only the perturbation in Akt signaling was causally related to mitochondrial hyperpolarization. SC79, SB203580, and BAPTA did not prevent acidic pH-induced cell death. Acidic pH suppressed ROS production, thus ruling out the role of ROS in cytotoxicity. Interestingly, pH 6.8 caused an increase in ADP/ATP ratio and apoptosis; pH 6.0 caused a further increase in ADP/ATP ratio and necrosis. Therefore, astrocyte cell death in acidosis did not result from mitochondrial potential collapse; in case of acidosis at pH 6.0, necrosis might partly result from mitochondrial hyperpolarization and subsequent suppressed ATP production. J. Cell. Biochem. 118: 1108-1117, 2017. © 2016 Wiley Periodicals, Inc.