Acute effect of β‐sitosterol on calcium uptake mediates anti‐inflammatory effect in murine activated neutrophils

Objectives To evaluate the effect of β‐sitosterol on ⁴⁵Ca²⁺ uptake in activated murine neutrophils, and upon myeloperoxidase and adenosine deaminase activity, and interleukin‐1β (IL‐1β) and tumour necrosis factor‐α (TNF‐α) levels, in carrageenan‐induced inflammation in the mouse air pouch model. Methods Dried Esenbeckia leiocarpa bark was macerated and extracted resulting in a crude hydroalcoholic extract (CHE) that was partitioned to obtain an alkaloid fraction. The alkaloid was then partitioned in polar and nonpolar subfractions. β‐Sitosterol was isolated from the nonpolar subfraction and identified by comparison with the literature. The effect of β‐sitosterol on ⁴⁵Ca²⁺ uptake in activated murine neutrophils, and upon myeloperoxidase and adenosine deaminase activity, IL‐1β and TNF‐α levels in carrageenan‐induced inflammation in mice were evaluated. Key findings β‐Sitosterol promoted a time‐ and dose‐dependent increase of the calcium uptake in activated neutrophils that was promptly reversed by nifedipine, BAPTA‐AM, LY294002, and colchicine. β‐Sitosterol inhibited myeloperoxidase and adenosine deaminase activity, and IL‐1β and TNF‐α levels. Conclusions β‐Sitosterol inhibited either myeloperoxidase and adenosine deaminase activity or IL‐1β and TNF‐α levels. This effect seemed to be mediated by the calcium uptake in activated neutrophils in a time‐ and concentration‐dependent manner through L‐type voltage dependent calcium channels, intracellular calcium, phosphoinositide kinase‐3, and microtubule modulation.     

Mechanism of the vasorelaxant effect induced by trans‐4‐methyl‐β‐nitrostyrene,a synthetic nitroderivative,in rat thoracic aorta

Mechanisms underlying the vasorelaxant effects of trans‐4‐methyl‐β‐nitrostyrene (T4MeN) were studied in rat aortic rings. In endothelium‐intact preparations, T4MeN fully and similarly relaxed contractions induced by phenylephrine (PHE) (IC₅₀ = 61.41 [35.40‐87.42] μmol/L) and KCl (IC₅₀ = 83.50 [56.63‐110.50] μmol/L). The vasorelaxant effect of T4MeN was unchanged by endothelium removal, pretreatment with L‐NAME, indomethacin, tetraethylammonium, ODQ or MDL‐12,330A. Under Ca²⁺‐free conditions, T4MeN significantly reduced with a similar potency: (i) phasic contractions induced by PHE, but not by caffeine; (ii) contractions due to CaCl₂ in aortic preparations stimulated with PHE (in the presence of verapamil) or high KCl; (iii) contractions evoked by the restoration of external Ca²⁺ levels after depletion of intracellular Ca²⁺ stores in the presence of thapsigargin. In contrast, T4MeN was more potent at inhibiting contractions evoked by the tyrosine phosphatase inhibitor, sodium orthovanadate, than those induced by the activator of PKC, phorbol‐12,13‐dibutyrate. These results suggest that T4MeN induces an endothelium‐ independent vasorelaxation that appears to occur intracellularly through the inhibition of contractions that are independent of Ca²⁺ influx from the extracellular milieu but involve phosphorylation of tyrosine residues.     

Involvement of L‐type Ca2+ channel and toll‐like receptor‐4 in nickel‐induced interleukin‐8 gene expression

The metal nickel (Ni²⁺) is found everywhere in our daily lives, including coins, costume jewelry, and even nuts and chocolates. Nickel poisoning can cause inflammatory reactions, respiratory diseases, and allergic contact dermatitis. To clarify the mechanism by which nickel induces mediators of inflammation, we used the human acute monocytic leukemia THP‐1 cell line as a model. Interleukin (IL)‐8 promoter activity as well as gene expression were tested by luciferase assay and real‐time polymerase chain reaction. The underlying mechanisms of nickel‐induced IL‐8 were investigated. We found that nickel induced IL‐8 gene expression via the L‐type Ca²⁺ channel, Toll‐like receptor‐4 (TRL‐4) and nuclear factor NF‐κB signal transduction pathways. Nickel activated NF‐κB expression through extracellular signal‐regulated kinase 1/2 phosphorylation and then increased IL‐8 expression. Thus, the L‐type Ca²⁺ channel and TRL‐4 play important roles in nickel‐induced inflammatory gene expressions. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 5–12, 2016.     

Impairment of α1‐adrenoceptor‐mediated contractile activity in caudal arterial smooth muscle from Type 2 diabetic Goto‐Kakizaki rats

1. In the present study, we compared the responsiveness of de‐endothelialized caudal artery smooth muscle strips, isolated from Type 2 diabetic Goto‐Kakizaki (GK) and normal Wistar rats, to α₁‐adrenoceptor stimulation (cirazoline) and membrane depolarization (K⁺). 2. The contractile and myosin 20 kDa light chain (LC₂₀) phosphorylation responses to 0.3 μmol/L cirazoline of caudal artery strips isolated from 12‐week‐old GK rats were significantly reduced compared with those of age‐matched Wistar rats, whereas the contractile and LC₂₀ phosphorylation responses to 60 mmol/L K⁺ were unaltered. 3. Stimulation of fura 2‐AM‐loaded strips from GK rats with 0.3 μmol/L cirazoline induced a significantly smaller rise in [Ca²⁺]_i (by ～20%) compared with that in strips from Wistar rats, whereas comparable Ca²⁺ transients were evoked by K⁺ in both. 4. Using quantitative polymerase chain reaction, no significant differences were detected in the mRNA expression of α_1A‐, α_1B‐ and α_1D‐adrenoceptor subtypes between GK and Wistar rats. 5. Cirazoline (1 μmol/L)‐ and caffeine (20 mmol/L)‐induced contractions in the absence of extracellular Ca²⁺ were unaltered in GK rats, suggesting that the release of Ca²⁺ from the sarcoplasmic reticulum in response to cirazoline does not differ between GK and Wistar rats. 6. The results of the present study suggest that Ca²⁺ entry from the extracellular space via α₁‐adrenoceptor‐activated, Ca²⁺‐permeable channels, but not via membrane depolarization and voltage‐gated L‐type Ca²⁺ channels, is impaired in caudal artery smooth muscle of GK rats.     

Cellular calcium regulatory machinery of vasorelaxation elicited by petasin

1. The present study examined the cytosolic Ca²⁺ regulatory machinery involved in the vasorelaxation produced by petasin, a sesquiterpene isolated from Petasites formosanus. 2. Aortic rings isolated from Sprague‐Dawley rats were exposed to petasin (0.01–100 μmol/L) to elucidate its vascular effects on isometric contraction elicited by vasoconstrictors, as well as the contribution of the endothelium and Ca²⁺ to the responses observed. In addition, L‐type voltage‐dependent Ca²⁺ channel (VDCC) activity and [Ca²⁺]_i were determined in cultured vascular smooth muscle cells (VSMCs) from Sprague‐Dawley rats in the presence of 1–100 μmol/L petasin using whole‐cell patch‐clamp recording and the fluorescent probe fura‐2/AM. The effects of petasin on vascular responses were compared between aortic rings from spontaneously hypertensive rats (SHR) and normotensive Wistar‐Kyoto (WKY) rats. 3. Petasin reduced isometric contraction elicited by KCl or the L‐type Ca²⁺ channel opener BayK 8644 (IC₅₀ 3.0 ± 0.4 and 4.1 ± 1.1 μmol/L, respectively) in aortic rings isolated from Sprague‐Dawley rats, independent of the endothelium. In addition, petasin triggered a rightward shift in the concentration–response curve to KCl while reducing the maximal response by 82%. In Ca²⁺‐depleted and high K⁺‐depolarized aortic rings, 1–100 μmol/L petasin pretreatment attenuated the Ca²⁺‐induced contraction in a concentration‐dependent manner. 4. In cultured VSMCs, whole‐cell patch‐clamp recording revealed that petasin inhibited VDCC activity. Measurement of [Ca²⁺]_i using fura‐2/AM fluorescence indicated that petasin suppressed the KCl‐induced increase in [Ca²⁺]_i. However, receptor binding assays failed to identify any significant interaction between petasin and the dihydropyridine binding sites of the L‐type VDCC. 5. In aortic rings from SHR and WKY rats, petasin inhibited Ca²⁺‐induced contractions in Ca²⁺‐depleted and high K⁺‐depolarized solution with a more pronounced effect in rings from SHR. 6. Together, the results suggest that direct Ca²⁺ antagonism of L‐type VDCC in vascular smooth muscle may account, at least in part, for petasin‐induced vasorelaxation. The more pronounced effect of the sesquiterpene in blood vessels from SHR suggests its possible therapeutic potential in the mangement of hypertension.     

Effect of cinnamtannin B‐1 on cholecystokinin‐8‐evoked responses in mouse pancreatic acinar cells

1. Cinnamtannin B‐1 is a naturally occurring A‐type proanthocyanidin that belongs to a class of polyphenols widely distributed throughout the plant kingdom and exhibiting anti‐oxidant properties. 2. In the present study, we examined the effects of cinnamtannin B‐1 on cholecystokinin octapeptide (CCK‐8)‐evoked Ca²⁺ mobilization, reactive oxygen species (ROS) production and amylase secretion in the exocrine pancreas. 3. Stimulation of cells with 1 nmol/L CCK‐8 led to a transient increase in the cytosolic free calcium concentration ([Ca²⁺]_c), followed by a decrease towards a value close to the prestimulation level. In the presence of 10 μmol/L cinnamtannin B‐1, stimulation of cells with CCK‐8 resulted in a smaller [Ca²⁺]_c peak response, a faster rate of decay of [Ca²⁺]_c and lower values for the steady state of [Ca²⁺]_c, compared with the effect of CCK‐8 alone. Cinnamtannin B‐1 decreased Ca²⁺ influx after depletion of intracellular stores by either CCK‐8 or thapsigargin (1 μmol/L). Conversely, CCK‐8 increased the fluorescence of 5‐(and‐6)‐chloromethyl‐2′,7′‐dichlorodihydrofluorescein diacetate acetyl ester (CM‐H₂DCFDA), reflecting an increase in oxidation. Cinnamtannin B‐1 reduced CCK‐8‐induced oxidation of CM‐H₂DCFDA. Cholecystokinin‐8 had a biphasic effect on amylase secretion, producing maximum at a concentration of 0.1 nmol/L and reducing secretion at higher concentrations. Pre‐incubation of cells with 10 μmol/L cinnamtannin B‐1 significantly attenuated the inhibition of enzyme secretion in response to high concentrations of CCK‐8 (i.e. >10^?10 mol/L). Finally, the anti‐oxidant protected acinar cells against CCK‐8‐induced cell death. 4. The beneficial effects of cinnamtannin B‐1 appear to be mediated by a reduction in intracellular Ca²⁺ overload, ROS production and intracellular accumulation of digestive enzymes, which is a common pathological precursor that mediates pancreatitis.     

Trimebutine maleate relaxes the isolated rat thoracic aorta: The role of nitric oxide and L‐type calcium channels

Trimebutine maleate (TMB), a widely prescribed drug for functional gastrointestinal disorders, has been reported to regulate smooth muscle contractility by modulating multiple ion channel activities in the gastrointestinal tract. However, its action on isolated aorta has not yet been reported. The aim of the present study was to evaluate in vitro vasorelaxant properties and the underlying pharmacological mechanisms of TMB in isolated rat thoracic aortic rings. Vascular activity experiments were performed on thoracic aorta isolated from Sprague‐Dawley rats in vitro, including endothelium‐intact and endothelium‐denuded aortic rings. TMB (10^?10‐10^?5 mol/L) induced relaxation in endothelium‐intact aortic rings precontracted by phenylephrine with a potency similar to that of carbachol. TMB‐induced relaxation was not altered by glibenclamide and atropine in endothelium‐intact aortic rings. However, L‐NAME and endothelium denudation significantly reduced but not completely reversed the vasorelaxant effect of TMB. Also, TMB‐induced relaxation wasn't affected by diclofenac in endothelium‐intact aortic rings. TMB at 10^?5 mol/L significantly reduced the CaCl₂‐induced contractions in endothelium‐intact aortic rings stimulated with KCl, but not stimulated with phenylephrine under Ca²⁺free conditions. Moreover, TMB at 10^?5 mol/L effectively attenuated Bay‐K8644‐induced contractions in aortic rings. These results suggest that TMB‐induced relaxation was mediated by both endothelium‐dependent and endothelium‐independent manner in isolated rat thoracic aorta. The mechanism of TMB‐induced relaxation at low concentrations is partially related to NO‐ and endothelium‐dependent but unrelated to prostanoids formation. However, inhibition of Ca²⁺ influx through voltage‐operated calcium channels and L‐type Ca²⁺channel blocking effect appears to be involved in the mechanism of vasorelaxant effect of TMB at high concentrations.     

Hypertonic saline inhibits airway smooth muscle contraction by inhibiting Ca2+ sensitization

The effects of hypertonic solution on airway smooth muscle (ASM) contraction and the underlying mechanisms are largely unknown. We found that hypertonic saline (HS) inhibited acetylcholine (ACh)‐induced contraction of ASM from the mouse trachea and human bronchi. In single mouse ASM cells (ASMCs), ACh induced an increase in intracellular Ca²⁺ that was further enhanced by 5% NaCl, indicating that the HS‐induced inhibition of ASM contraction was not mediated by a decrease in cytosolic Ca²⁺. The Rho‐associated kinase (ROCK) inhibitor Y‐27632 relaxed ACh‐induced precontraction of mouse tracheal rings. However, such inhibition was not observed after the relaxation induced by 5% NaCl. Moreover, the incubation of mouse tracheal rings with 5% NaCl decreased ACh‐induced phosphorylation of myosin light chain 20 and myosin phosphatase target subunit 1. These data indicate that HS inhibits the contraction of ASM by inhibiting Ca²⁺ sensitization, not by decreasing intracellular Ca²⁺.     

Lead Induces Endothelium‐ and Ca2+‐Independent Contraction in Rat Aortic Rings

Abstract: The contractile effect of lead on rat aortic rings was examined. Lead (0.1–3.1 mM) elicited concentration‐dependent but endothelium‐independent contractions, which were unaffected by prazosin (1 μM). The contractile effects of lead were similar when the aortic rings were bathed either in the absence or presence of external Ca²⁺. Lanthanum (1 mM) but not verapamil (1 μM) inhibited the lead contractions; hence non‐L‐calcium channels are involved in such effect. In addition, lead induced contractions on aortic rings incubated in Ca²⁺‐free EGTA‐containing solution for 70 min., an experimental condition in which intracellular Ca²⁺‐stores are depleted. Finally, the contractile effect of lead was not modified by calphostin C (an inhibitor of protein kinase C). In conclusion, the present results suggest that in rat aorta, the lead‐induced contraction is independent of extra‐ and intracellular calcium stores. In addition, the effect of lead is independent of either catecholamines or protein kinase C. It is likely that in rat aorta, lead enters into the smooth muscle cells through non‐L‐calcium channels, and when acting like calcium on the contractile machinery it produces contraction. The differences observed between our results and those obtained by other authors may indicate that the mechanism of the contractile effect of lead varies among the different blood vessels.     

Bis‐(3‐hydroxyphenyl) diselenide inhibits LPS‐stimulated iNOS and COX‐2 expression in RAW 264.7 macrophage cells through the NF‐kB inactivation

Objectives Previously, we reported that diaryl diselenide compounds have strong inhibitory effects on lipopolysaccharide (LPS)‐induced nitric oxide (NO) production in macrophages. In this study, we investigated the molecular mechanisms underlying NO suppression and prostaglandin E₂ (PGE₂) production by diaryl diselenide compounds, bis‐(2‐hydroxyphenyl) diselenide (DSE‐A), bis‐(3‐hydroxyphenyl) diselenide (DSE‐B), bis‐(4‐hydroxyphenyl) diselenide (DSE‐C), dipyridyl diselenide (DSE‐D) and diphenyl diselenide (DSE‐E). Methods The effect of these compounds on NO suppression and PGE₂ production was investigated in RAW 264.7 macrophages. Key findings Our data indicate that of the above, DSE‐B most potently inhibits NO and PGE₂ production, and that it also significantly reduces the releases of tumour necrosis factor (TNF)‐α, interleukin(IL)‐1β and IL‐6. Consistent with these observations, DSE‐B also reduced the protein levels of inducible NO synthase (iNOS) and cyclooxygenase‐2 (COX‐2), and the mRNA levels of iNOS, COX‐2, TNF‐α, IL‐1β and IL‐6. Furthermore, DSE‐B inhibited LPS‐induced nuclear factor‐κB (NF‐κB) activation, which was associated with the prevention of the inhibitor κB‐α (IκB‐α) degradation and a subsequent reduction in nuclear p65 protein levels. Conclusions Taken together, our data suggest that the anti‐inflammatory properties of DSE‐B are due to reduction in the expression of iNOS, COX‐2, TNF‐α, IL‐1β and IL‐6 through the down‐regulation of NF‐κB binding activity.     

Changes in the contractile responses to carbachol and in the inhibitory effects of verapamil and nitrendipine on isolated smooth muscle preparations from rats subchronically exposed to Co2+ and Ni2+

Male Wistar rats were exposed to subtoxic doses of Co²⁺ or Ni²⁺, receiving Co(NO₃)₂ or NiSO₄ with drinking water for 30 days. No significant differences in the body weight and no visible changes in the behaviour of the controls and experimental animals were established. Cumulative concentration-effect curves for carbachol were obtained in ileum and trachea isolated from control and Co²⁺- or Ni²⁺-treated rats. The effect of the Ca²⁺ antagonists on the carbachol-induced contractions was studied by adding increasing concentrations of verapamil or nitrendipine to the bath solution 20 min prior to carbachol. The results showed that exposure of rats to subtoxic doses of Co(NO₃)₂ or NiSO₄ altered the contractile responses to carbachol. The changes in the pD₂ values and the shift to the left of the concentration-effect curves suggest a higher sensitivity to carbachol in preparations from the ileum of Co²⁺- or Ni²⁺-exposed rats. The tracheal strips isolated from control and heavy metal-treated rats showed a less potent sensitiveness to carbachol as compared to the ileal segments. An opposite tendency for decreased cholinergic reactivity was observed in tracheal strips from Co²⁺- and Ni²⁺-treated animals. The inhibitory effect of the Ca²⁺-antagonists on the contractility of ileal preparations from Co²⁺-treated rats increased at all concentrations of verapamil and at the highest concentration of nitrendipine, but decreased at lower concentrations of nitrendipine. The effect of verapamil on the preparations from Ni²⁺-exposed rats was unchanged or even decreased at higher verapamil concentrations. The inhibitory effect of nitrendipine on preparations from Ni²⁺-exposed rats decreased at the lowest concentration but increased at the highest concentration of the blocker. In Co²⁺- or Ni²⁺-treated tracheal preparations verapamil inhibited the contractions induced by low and medium concentrations of carbachol but increased the maximal contractile responses to high concentrations of carbachol.     

RNAi Silencing of IL‐1β and TNF‐α in the Treatment of Post‐traumatic Arthritis in Rabbits

Post‐traumatic arthritis is a secondary complication to severe joint trauma. With the disease progression, it may eventually lead to osteoarthritis in patients whose age is considerably younger than patients with traditional bone arthritis. The main objective of this study was to explore the feasibility of using lentiviral‐mediated RNA interference silencing of IL‐1β and TNF‐α to treat post‐traumatic arthritis in rabbits. About 48 New Zealand rabbits underwent bilateral knee joint surgery to stimulate traumatic arthritis. They were then randomly divided into four groups of 12 rabbits each. The histopathology of the cartilage was observed, and the changes were assessed by Mankin scoring. ELISA was used to detect the expression of IL‐1β and TNF‐α in the synovial fluid. (i) Compared with the control group, the transfection and co‐transfected groups displayed reduced cartilage damage and speed of degeneration. The co‐transfected group showed the greatest alleviation of symptoms. The Mankin score was statistically different (p < 0.01). (ii) Compared with the control group, the expression of IL‐1β or TNF‐α was reduced in the respective transfection groups (p < 0.01 in both groups) and IL‐1β and TNF‐α were reduced in the co‐transfected group (p < 0.01). The co‐transfected group showed the lowest expression of the three experimental groups of both IL‐1β and TNF‐α (p < 0.01). Lentivirus‐mediated RNA interference can knock down the expression of IL‐1β and TNF‐α in joint fluids and, in a synergistic effect when two siRNAs are co‐transfected, ease cartilage degeneration.     

Effect of the Anti‐Breast Cancer Drug Tamoxifen on Ca2+ Movement in Human Osteosarcoma Cells

Abstract:The anti‐breast cancer drug tamoxifen has recently been shown to cause an increase in [Ca²⁺]_i in renal tubular cells, breast cells and bladder cells. Because tamoxifen is known to interact with oestrogens leading to modulation of bone metabolism, the present study was aimed at exploring whether tamoxifen could alter Ca²⁺ signaling in human osteoblast‐like MG63 cells. Cytosolic free Ca²⁺ levels were recorded by using the Ca²⁺‐sensitive dye fura‐2. Tamoxifen induced a sustained [Ca²⁺]_i increase at concentrations above 1 μM with an EC₅₀ of 8 μM. Removal of extracellular Ca²⁺ reduced the response by 40%, suggesting that tamoxifen induced both Ca²⁺ influx and store Ca²⁺ release. Tamoxifen‐induced Ca²⁺ influx was confirmed as tamoxifen caused Mn²⁺ influx‐induced quench of fura‐2 fluorescence. In Ca²⁺‐free medium, pretreatment with 10 μM tamoxifen abolished the [Ca²⁺]_i increase induced by 1 μM thapsigargin (an endoplasmic reticulum Ca²⁺ pump inhibitor), and by 2 μM carbonylcyanide m‐chlorophenylhydrazone (a mitochondrial uncoupler). Conversely, pretreatment with thapsigargin and carbonylcyanide m‐chlorophenylhydrazone only reduced 64% of tamoxifen‐induced [Ca²⁺]_i increases. Addition of 2 μM U73122 to inhibit phospholipase C activity abolished the [Ca²⁺]_i increase induced by 1 μM histamine, a phospholipase C‐dependent Ca²⁺ mobilizer, without affecting 10 μM tamoxifen‐induced Ca²⁺ release. The [Ca²⁺]_i increase induced by 10 μM tamoxifen was not altered by 10 μM of nifedipine, verapamil and diltiazem. Together, the data show that tamoxifen induced a lasting increase in [Ca²⁺]_i in human osteoblast‐like cells by causing Ca²⁺ influx and releasing Ca²⁺ from multiple stores in a phospholipase C‐independent manner.     

Nonylphenol‐induced cytosolic Ca2+ elevation and death in renal tubular cells

Nonylphenol is an environmental endocrine disrupter. The effect of nonylphenol on intracellular free Ca²⁺ levels ([Ca²⁺]_i) and viability in Madin‐Darby canine kidney (MDCK) cells was explored. Nonylphenol increased [Ca²⁺]_i in a concentration‐dependent manner (EC₅₀～0.8 μM). Nonylphenol‐induced Mn²⁺ entry demonstrated Ca²⁺ influx and removal of extracellular Ca²⁺ partly decreased the [Ca²⁺]_i rise. The [Ca²⁺]_i rise was inhibited by the protein kinase C activator, phorbol 13‐myristate acetate (PMA) but not by L‐type Ca²⁺ channel blockers. In Ca²⁺‐free medium, nonylphenol‐induced [Ca²⁺]_i rise was partly inhibited by pretreatment with 1 μM thapsigargin (an endoplasmic reticulum Ca²⁺ pump inhibitor). Conversely, nonylphenol pretreatment abolished thapsigargin‐induced Ca²⁺ release. Nonylphenol‐induced Ca²⁺ release was unaltered by inhibition of phospholipase C. At concentrations of 5–100 μM, nonylphenol killed cells in a concentration‐dependent manner. The cytotoxic effect of 100 μM nonylphenol was not affected by preventing [Ca²⁺]_i rises with BAPTA/AM. Collectively, this study shows that nonylphenol induced [Ca²⁺]_i increase in MDCK cells via evoking Ca²⁺ entry through protein kinase C‐regulated Ca²⁺ channels, and releasing Ca²⁺ from endoplasmic reticulum and other stores in a phospholipase C‐independent manner. Nonylphenol also killed cells in a Ca²⁺‐independent fashion. Drug Dev Res, 2009. © 2009 Wiley‐Liss, Inc.     

VCP746, a novel A1 adenosine receptor biased agonist,reduces hypertrophy in a rat neonatal cardiac myocyte model

VCP746 is a novel A₁ adenosine receptor (A₁AR) biased agonist previously shown to be cytoprotective with no effect on heart rate. The aim of this study was to investigate the potential anti‐hypertrophic effect of VCP746 in neonatal rat cardiac myocytes (NCM). NCM hypertrophy was stimulated with interleukin (IL)‐1β (10 ng/mL), tumour necrosis factor (TNF)‐α (10 ng/mL) or Ang II (100 nmol/L) and was assessed by ³H‐leucine incorporation assay. VCP746 significantly inhibited IL‐1β‐, TNF‐α‐ and Ang II‐stimulated NCM hypertrophy as determined by ³H‐leucine incorporation. The anti‐hypertrophic effect of VCP746 was also more potent than that of the prototypical A₁AR agonist, N⁶‐cyclopentyladenosine (CPA). Further investigation with the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) cell viability assay showed that neither CPA nor VCP746 had any effect on cell viability, confirming that the reduction in ³H‐leucine incorporation mediated by CPA and VCP746 was not due to a reduction in cell viability. IL‐1β, TNF‐α and Ang II were also shown to increase the mRNA expression of hypertrophy biomarkers, ANP, β‐MHC and α‐SKA in NCM. Treatment with VCP746 at concentrations as low as 1 nmol/L suppressed mRNA expression of ANP, β‐MHC and α‐SKA stimulated by IL‐1β, TNF‐α or Ang II, demonstrating the broad mechanistic basis of the potent anti‐hypertrophic effect of VCP746. This study has shown that the novel A₁AR agonist, VCP746, is able to attenuate cardiac myocyte hypertrophy. As such, VCP746 is potentially useful as a pharmacological agent in attenuating cardiac remodelling, especially in the post‐myocardial infarction setting, given its previously established cytoprotective properties.     

Gossypol stimulates opening of a Ca2+‐ and Na+‐permeable but Ni2+‐ and Co2+‐impermeable pore in bEND.3 endothelial cells

Gossypol, a polyphenolic dialdehyde toxin isolated from cotton seed, has anti‐cancer properties and has recently shown some success in the treatment of glioma. Its effects on brain neurons and blood vessels are poorly understood. In this work we examined the effects of gossypol on cytosolic Ca²⁺ concentration ([Ca²⁺]_i) of mouse brain bEND.3 endothelial cells. Cell viability tests revealed that after 3 hour and 18 hour exposures, 10 µmol/L gossypol caused 23% and 65% cell death, respectively; 3 µmol/L gossypol caused no and 21% cell death, respectively. [Ca²⁺]_i was raised concentration‐dependently by 1‐10 µmol/L gossypol. We then explored the Ca²⁺ signalling triggered by 3 µmol/L gossypol, which inflicted minimal toxicity: the Ca²⁺ signal was composed largely of Ca²⁺ influx and to a small extent, intracellular Ca²⁺ release. Such Ca²⁺ influx was much larger than store‐operated Ca²⁺ influx triggered by maximal Ca²⁺ pool depletion. The Ca²⁺ influx triggered by 3 and 10 µmol/L gossypol caused NO release and cell death, respectively. Gossypol also triggered influx of Mn²⁺ and Na⁺, but not Ni²⁺ and Co²⁺. Gossypol‐triggered Ca²⁺ signal was inhibited only by 14% and 37% by 100 µmol/L La³⁺ and 10 µmol/L nimodipine, respectively; and not suppressed at all by 5 mmol/L Ni²⁺. Gossypol‐triggered Ca²⁺ signal was suppressed by 78% by 30 µmol/L ruthenium red, suggesting gossypol may act on TRPV channels. Our results suggest gossypol triggered opening of a non‐selective cation pore, possibly a member of the TRPV family.     

Vasorelaxation induced by methyl cinnamate,the major constituent of the essential oil of Ocimum micranthum,in rat isolated aorta

The aim of the present study was to investigate the vascular effects of the E‐isomer of methyl cinnamate (E‐MC) in rat isolated aortic rings and the putative mechanisms underlying these effects. At 1–3000 μmol/L, E‐MC concentration‐dependently relaxed endothelium‐intact aortic preparations that had been precontracted with phenylephrine (PHE; 1 μmol/L), with an IC₅₀ value (geometric mean) of 877.6 μmol/L (95% confidence interval (CI) 784.1–982.2 μmol/L). These vasorelaxant effects of E‐MC remained unchanged after removal of the vascular endothelium (IC₅₀ 725.5 μmol/L; 95% CI 546.4–963.6 μmol/L) and pretreatment with 100 μmol/L N^G‐nitro‐l ‐arginine methyl ester (IC₅₀ 749.0 μmol/L; 95% CI 557.8–1005.7 μmol/L) or 10 μmol/L 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (IC₅₀ 837.2 μmol/L; 95% CI 511.4–1370.5 μmol/L). Over the concentration range 1–3000 μmol/L, E‐MC relaxed K⁺‐induced contractions in mesenteric artery preparations (IC₅₀ 314.5 μmol/L; 95% CI 141.9–697.0 μmol/L) with greater potency than in aortic preparations (IC₅₀ 1144.7 μmol/L; 95% CI 823.2–1591.9 μmol/L). In the presence of a saturating contractile concentration of K⁺ (150 mmol/L) in Ca²⁺‐containing medium combined with 3 μmol/L PHE, 1000 μmol/L E‐MC only partially reversed the contractile response. In contrast, under similar conditions, E‐MC nearly fully relaxed PHE‐induced contractions in aortic rings in a Ba²⁺‐containing medium. In preparations that were maintained under Ca²⁺‐free conditions, 600 and 1000 μmol/L E‐MC significantly reduced the contractions induced by exogenous Ca²⁺ or Ba²⁺ in KCl‐precontracted preparations, but not in PHE‐precontracted preparations (in the presence of 1 μmol/L verapamil). In addition, E‐MC (1–3000 μmol/L) concentration‐dependently relaxed the contractions induced by 2 mmol/L sodium orthovanadate. Based on these observations, E‐MC‐induced endothelium‐independent vasorelaxant effects appear to be preferentially mediated by inhibition of plasmalemmal Ca²⁺ influx through voltage‐dependent Ca²⁺ channels. However, the involvement of a myogenic mechanism in the effects of E‐MC is also possible.