Protective effect of grape seed extract against oxidative stress-induced cell death in a staurosporine-differentiated retinal ganglion cell line

OBJECTIVE

Grape seed extract (GSE) is a potent antioxidant. We examined the effect of GSE on oxidative stress-induced cell death in a transformed retinal ganglion cell line, RGC-5.

METHODS

Staurosporine-differentiated RGC-5 (ssdRGC-5) cells obtained by treating RGC-5 cells with 1 µM staurosporine were incubated with GSE for 2 h and then exposed to buthionine sulfoximine plus glutamate (B/G) for 24 h. Cell death was detected using the LIVE/DEAD viability assay and the type of cell death was evaluated using fluorescein isothiocyanate-conjugated Annexin-V/propidium iodide staining. To investigate the mechanism underlying cell death, we determined the caspase-3 activity and level of reactive oxygen species (ROS) formation.

RESULTS

Treatment of ssdRGC-5 cells with B/G increased intracellular ROS and induced apoptosis (not necrosis) with increasing caspase-3 activity. GSE rescued the ssdRGC-5 cells from oxidative stress-induced cell death by inhibiting both intracellular ROS production and caspase-3 activation.

CONCLUSION

GSE had a neuroprotective effect against oxidative stress-induced apoptotic death in ssdRGC-5 cells.

Onion (Allium cepa) extract attenuates brain edema

OBJECTIVE

This study investigated the potential beneficial effects of onion extract on brain ischemia-induced edema and blood-brain barrier (BBB) dysfunction. The possible underlying mechanisms are investigated, especially those linked to the antioxidant effects of the onion extract.

METHODS

Brain ischemia was induced by middle cerebral artery occlusion (MCAO) for 2 h followed by reperfusion in mice. Mice were treated intravenously with onion extract 30 min before MCAO. Brain edema and BBB hyperpermeability were evaluated by the measurement of the brain water content and Evans blue extravasation, respectively. The disruption of tight junction proteins was examined by immunohistochemical staining. The level of malondialdehyde was determined using the thiobarbituric acid method. The activities of glutathione peroxidase and catalase were determined by spectrophotometric assay.

RESULTS

Brain water content in the ischemic hemisphere was significantly reduced by treatment with onion extract. Onion extract also had a significant effect on both the decrease in Evans blue extravasation and the inhibition of zonula occludens-1 and occludin disruption caused by brain ischemia. In addition, onion extract significantly prevented brain ischemia-induced reduction in catalase and glutathione peroxidase activities and elevation of malondialdehyde level in the brain tissue.

CONCLUSION

The results from this study demonstrate that onion extract prevents brain edema, BBB hyperpermeability, and tight junction proteins disruption, possibly through its antioxidant effects in the mouse MCAO model. This study suggests that onion extract may be a beneficial nutrient for the prevention of BBB function during brain ischemia.

The Na+/H+ exchanger-1 inhibitor cariporide prevents glutamate-induced necrotic neuronal death by inhibiting mitochondrial Ca2+ overload

In the brain, Na+/H+ exchanger-1 (NHE-1) activation has a significant impact on ischemic injury, and, in recent studies, NHE-1 inhibition has been found to protect neurons from ischemic injury. This protective effect has been ascribed to the prevention of apoptosis, but neuronal cell death following ischemia is a consequence of both necrotic and apoptotic cell death. Here, we evaluated the ability of the potent NHE-1 inhibitor cariporide to prevent necrotic cell death in an in vitro model of excitotoxic neuronal death. Cariporide (100 nM) was found to reduce both glutamate-induced necrotic and apoptotic neuronal cell death. Ca2+ concentrations were observed to peak twice in cytosol and mitochondria in cultured neuronal cells after glutamate exposure, and cariporide was found to reduce the second Ca2+ concentration increase, but not the first. Furthermore, glutamate-mediated mitochondrial death pathways involving loss of mitochondrial membrane potential and reactive oxygen species (ROS) accumulation were found to be attenuated by cariporide. In addition, cariporide effectively prevented necrosis following exposure to glutamate and ameliorated the mitochondrial Ca2+ and ROS production increases implicated in necrotic cell death. These results suggest that NHE-1 participates in the necrotic cell death process and that its inhibition offers a means of preventing both necrosis and apoptosis.

Chrysophanol-8-O-glucoside, an anthraquinone derivative in rhubarb, has antiplatelet and anticoagulant activities

Rhubarb is a widely used traditional medicine and has been reported to elicit a number of biological effects including anti-inflammatory and antiplatelet effects. In the present study, we investigated the effects of anthraquinone derivatives isolated from rhubarb on platelet activity. Of four anthraquinone derivatives isolated from rhubarb examined, chrysophanol-8-O-glucoside (CP-8-O-glc) was found to have the most potent inhibitory effect on collagen- and thrombin-induced platelet aggregation. CP-8-O-glc-treated mice showed significantly prolonged bleeding times. Furthermore, CP-8-O-glc was found to have a significant inhibitory effect on rat platelet aggregation ex vivo and on thromboxane A(2) formation in vitro. In coagulation tests, CP-8-O-glc did not alter prothrombin time, and it prolonged the activated partial thromboplastin time. However, CP-8-O-glc only inhibited platelet phosphatidylserine exposure, but not exert direct inhibition on intrinsic factors. This study demonstrates the antiplatelet and anticoagulant effects of CP-8-O-glc and suggests that this compound might be of therapeutic benefit for the prevention of platelet-related cardiovascular diseases.

Antiplatelet effects of Cyperus rotundus and its component (+)-nootkatone

ETHNOPHARMACOLOGICAL RELEVANCE

Cyperus rotundus, a well-known oriental traditional medicine, has been reported to exhibit wide spectrum activity in biological systems including the circulatory system, however, little information is available on its antiplatelet activity. This study was undertaken to investigate the antiplatelet effects of Cyperus rotundus EtOH extract (CRE) and its constituent compounds.

MATERIALS AND METHODS

The antiplatelet activities of CRE and its eight constituent compounds were evaluated by examining their effects on rat platelet aggregations in vitro and ex vivo, and on mice tail bleeding times.

RESULTS

During the in vitro platelet aggregation study, CRE showed significant and concentration-dependent inhibitory effects on collagen-, thrombin-, and/or AA-induced platelet aggregation. Of its eight components, (+)-nootkatone was found to have the most potent inhibitory effect on collagen-, thrombin-, and AA-induced platelet aggregation. In addition, CRE- and (+)-nootkatone-treated mice exhibited significantly prolonged bleeding times. Furthermore, (+)-nootkatone had a significant inhibitory effect on rat platelet aggregation ex vivo.

CONCLUSIONS

This study demonstrates the antiplatelet effects of CRE and its active component (+)-nootkatone, and suggests that these agents might be of therapeutic benefit for the prevention of platelet-associated cardiovascular diseases.

Protective effect of components isolated from Lindera erythrocarpa against oxidative stress-induced apoptosis of H9c2 cardiomyocytes

Eight compounds were isolated from the methanol fraction of Lindera erythrocarpa and assessed for their ability to protect H9c2 cardiomyocytes against oxidative stress-induced cell death. Three of the compounds significantly reduced the release of lactate dehydrogenase from H9c2 cardiomyocytes treated with buthionine-[S,R]-sulfoximine and reduced the uptake of propidium iodide by these cells. These effects were concentration-dependent. The three inhibitory compounds were identified as (-)-epicatechin, avicularin and quercitrin by spectroscopic techniques including one- and two-dimensional NMR and mass spectroscopy.

Differential regulation of proliferation and differentiation in neural precursor cells by the Jak pathway

Neuronal precursor cells (NPCs) are temporally regulated and have the ability to proliferate and differentiate into mature neurons, oligodendrocytes, and astrocytes in the presence of growth factors (GFs). In the present study, the role of the Jak pathway in brain development was investigated in NPCs derived from neurosphere cultures using Jak2 and Jak3 small interfering RNAs and specific inhibitors. Jak2 inhibition profoundly decreased NPC proliferation, preventing further differentiation into neurons and glial cells. However, Jak3 inhibition induced neuronal differentiation accompanied by neurite growth. This phenomenon was due to the Jak3 inhibition-mediated induction of neurogenin (Ngn)2 and NeuroD in NPCs. Jak3 inhibition induced NPCs to differentiate into scattered neurons and increased the expression of Tuj1, microtubule associated protein 2 (MAP2), Olig2, and neuroglial protein (NG)2, but decreased glial fibrillary acidic protein (GFAP) expression, with predominant neurogenesis/polydendrogenesis compared with astrogliogenesis. Therefore, Jak2 may be important for NPC proliferation and maintenance, whereas knocking-down of Jak3 signaling is essential for NPC differentiation into neurons and oligodendrocytes but does not lead to astrocyte differentiation. These results suggest that NPC proliferation and differentiation are differentially regulated by the Jak pathway.

Antitumor effect of novel small chemical inhibitors of Snail-p53 binding in K-Ras-mutated cancer cells

p53 is frequently mutated by genetic alternation or suppressed by various kinds of cellular signaling pathways in human cancers. Recently, we have revealed that p53 is suppressed and eliminated from cells by direct binding with oncogenic K-Ras-induced Snail. On the basis of the fact, we generated specific inhibitors against p53-Snail binding (GN25 and GN29). These chemicals can induce p53 expression and functions in K-Ras-mutated cells. However, it does not show cytotoxic effect on normal cells or K-Ras-wild-type cells. Moreover, GN25 can selectively activate wild-type p53 in p53(WT/MT) cancer cells. But single allelic mt p53 containing cell line, Panc-1, does not respond to our chemical. In vivo xenograft test also supports the antitumor effect of GN25 in K-Ras-mutated cell lines. These results suggest that our compounds are strong candidate for anticancer drug against K-Ras-initiated human cancers including pancreatic and lung cancers.

Role of CK1 in GSK3beta-mediated phosphorylation and degradation of snail

The epithelial to mesenchymal transition (EMT) that occurs during embryonic development has begun to attract attention as a potential mechanism for tumor cell metastasis. Snail is a well-known Zn-finger transcription factor that promotes EMT by repressing E-cadherin expression. It is known that Snail is phosphorylated by GSK3beta and degraded by beta-TrCP-mediated ubiquitination. Here we described another protein kinase, CK1, whose phosphorylation of Snail is required for the subsequent GSK3beta phosphorylation. Specific inhibition or depletion of CK1varepsilon inhibits the phosphorylation and degradation of Snail and promotes cell migration, suggesting a central role of CK1varepsilon in the EMT process. Furthermore, our study uncovered distinct roles and steps of Snail phosphorylation by CK1varepsilon and GSK3beta. Taken together, we identified CK1varepsilon as a new component of the Snail-mediated EMT process, providing insight into the mechanism of human cancer metastasis.

Hypoxic stress up-regulates the expression of Toll-like receptor 4 in macrophages via hypoxia-inducible factor

Toll-like receptors (TLRs) are germline-encoded innate immune receptors that recognize invading micro-organisms and induce immune and inflammatory responses. Deregulation of TLRs is known to be closely linked to various immune disorders and inflammatory diseases. Cells at sites of inflammation are exposed to hypoxic stress, which further aggravates inflammatory processes. We have examined if hypoxic stress modulates the TLR activity of macrophages. Hypoxia and CoCl(2) (a hypoxia mimetic) enhanced the expression of TLR4 messenger RNA and protein in macrophages (RAW264.7 cells), whereas the messenger RNA of other TLRs was not increased. To determine the underlying mechanism, we investigated the role of hypoxia-inducible factor 1 (HIF-1) in the regulation of TLR4 expression. Knockdown of HIF-1alpha expression by small interfering RNA inhibited hypoxia-induced and CoCl(2)-induced TLR4 expression in macrophages, while over-expression of HIF-1alpha potentiated TLR4 expression. Chromatin immunoprecipitation assays revealed that HIF-1alpha binds to the TLR4 promoter region under hypoxic conditions. In addition, deletion or mutation of a putative HIF-1-binding motif in the TLR4 promoter greatly attenuated HIF-1alpha-induced TLR4 promoter reporter expression. Up-regulation of TLR4 expression by hypoxic stress enhanced the response of macrophages to lipopolysaccharide, resulting in increased expression of cyclooxygenase-2, interleukin-6, regulated on activation normal T cell expressed and secreted, and interferon-inducible protein-10. These results demonstrate that TLR4 expression in macrophages is up-regulated via HIF-1 in response to hypoxic stress, suggesting that hypoxic stress at sites of inflammation enhances susceptibility to subsequent infection and inflammatory signals by up-regulating TLR4.

Pharmacokinetics of oltipraz in diabetic rats with liver cirrhosis

BACKGROUND AND PURPOSE

The incidence of diabetes mellitus is increased in patients with liver cirrhosis. Oltipraz is currently in trials to treat patients with liver fibrosis and cirrhosis induced by chronic hepatitis types B and C and is primarily metabolized via hepatic cytochrome P450 isozymes CYP1A1/2, 2B1/2, 2C11, 2D1 and 3A1/2 in rats. We have studied the influence of diabetes mellitus on pharmacokinetics of oltipraz and on expression of hepatic, CYP1A, 2B1/2, 2C11, 2D and 3A in rats with experimental liver cirrhosis.

EXPERIMENTAL APPROACH

Oltipraz was given intravenously (10 mg x kg(-1)) or orally (30 mg x kg(-1)) to rats with liver cirrhosis induced by N-dimethylnitrosamine (LC rats) or with diabetes, induced by streptozotocin (DM rats) or to rats with both liver cirrhosis and diabetes (LCD rats) and to control rats, and pharmacokinetic variables measured. Protein expression of hepatic CYP1A, 2B1/2, 2C11, 2D and 3A was measured using Western blot analysis.

KEY RESULTS

After i.v. or p.o. administration of oltipraz to LC and DM rats, the AUC was significantly greater and smaller, respectively, than that in control rats. In LCD rats, the AUC was that of LC and DM rats (partially restored towards control rats). Compared with control rats, the protein expression of hepatic CYP1A increased, that of CYP2C11 and 3A decreased, but that of CYP2B1/2 and 2D was not altered in LCD rats.

CONCLUSIONS AND IMPLICATIONS

In rats with diabetes and liver cirrhosis, the AUC of oltipraz was partially restored towards that of control rats.

Methanolic extract of onion (Allium cepa) attenuates ischemia/hypoxia-induced apoptosis in cardiomyocytes via antioxidant effect

BACKGROUND

Although there is growing awareness of the beneficial potential of onion intake to lower the risk of cardiovascular disease, there is little information about the effect of onion on ischemic heart injury, one of the most common cardiovascular diseases.

AIM OF THE STUDY

This study investigates the effect of the methanol-soluble extract of onion on ischemic injury in heart-derived H9c2 cells in vitro and in rat hearts in vivo. The underlying mechanism is also investigated.

METHODS

To evaluate the effect of onion on ischemia-induced cell death, LDH release and TUNEL-positivity were assessed in H9c2 cells, and the infarct size was measured in a myocardial infarct model. To investigate the mechanism of the cardioprotection by onion, the reactive oxygen species (ROS) level and the mitochondrial membrane potential (DeltaPsi(m)) were measured using an imaging technique; the caspase-3 activity was assayed, and Western blotting was performed to examine cytochrome c release in H9c2 cells.

RESULTS

The methanolic extract of onion had a preventive effect on ischemia/hypoxia-induced apoptotic death in H9c2 cells in vitro and in rat heart in vivo. The onion extract (0.05 g/ml) inhibited the elevation of the ROS, mitochondrial membrane depolarization, cytochrome c release and caspase-3 activation during hypoxia in H9c2 cells. In the in vivo rat myocardial infarction model, onion extract (10 g/kg) significantly reduced the infarct size, the apoptotic cell death of the heart and the plasma MDA level.

CONCLUSION

In conclusion, the results of this study suggest that the methanolic extract of onion attenuates ischemia/hypoxia-induced apoptosis in heart-derived H9c2 cells in vitro and in rat hearts in vivo, through, at least in part, an antioxidant effect.

Antimicrobial effect of water-soluble muscadine seed extracts on Escherichia coli O157:H7

Water-soluble extracts were prepared from purple (cultivar Ison) and bronze (cultivar Carlos) muscadine seeds with or without heating. The Ison extracts had strong antimicrobial activity against a cocktail of three strains of Escherichia coli O157: H7. This extract had higher acidity (pH 3.39 to 3.43), total phenolics (2.21 to 3.49 mg/ml), tartaric acid (5.6 to 10.7 mg/ml), tannic acid (5.7 to 8.1 mg/ml), and gallic acid (0.33 to 0.59 mg/ml) than did the Carlos extracts. Heat treatment on both extracts increased antimicrobial activity, possibly because of increased acidity, tartaric acid, total phenolics, and individual phenolics. Heating of Ison extracts increased ellagic acid up to 83%. Up to 10.7 mg/ml tartaric acid alone was not as effective against E. coli O157:H7 as were water-soluble seed extracts. This finding suggests the involvement of other factors, such as tannic and gallic acids, in inactivation of this pathogen. Water-soluble muscadine seed extracts may be useful for incorporation into juice and other beverage products as natural preservatives.

Cyclooxygenase-2 expression in human thyroid disease

OBJECTIVES

Cyclooxygenase (COX)-2, which is the inducible form of the COX enzyme for prostaglandin synthesis and a key mediator of epithelial cell growth, has been shown to be up-regulated in gastrointestinal cancers. Additionally, regular intake of other non-steroidal anti-inflammatory drugs (NSAID) is known to decrease the incidence of these cancers. Therefore, the goals of the present study were to determine the possible involvement of COX-2 in human thyroid diseases.

METHODS

We used immunohistochemical staining and Western blot analysis to characterize the expression of COX-2 proteins in thyroid tissues from 64 patients with thyroiditis, benign tumors, and malignant tumors with or without metastasis. Immunoreactivity scores were calculated by multiplication of the determined grades.

RESULTS

COX-2 proteins were not expressed in normal thyroid tissues. However, each type of tumor tissue showed intense bands of COX-2 protein expression in Western blot analyses, and the immunoreactivity scores were 7.67+/-1.17 (SD) for thyroiditis, 7.87+/-0.9 for benign tumors, 7.53+/-1.53 for follicular cancer, 7.63+/-1.11 for papillary cancer without metastasis, and 7.17+/-1.55 for papillary cancer with metastasis. No significant differences were found in the levels of COX-2 expression between different tumor tissue types.

CONCLUSION

No significant correlations were observed between clinical and/or pathological characteristics of thyroid tumors and the intensity of COX-2 protein expression. In addition, we found no difference in COX-2 protein expression between thyroiditis and thyroid tumors. Thus, up-regulation of COX-2 protein synthesis in human thyroid diseases does not appear to be of clinical significance.

Pharmacodynamic characteristics and cardioprotective effects of new NHE1 inhibitors

Inhibitors of Na(+)/H(+) exchanger (NHE) 1 have been shown to exert protective effects on various myocardial injuries. In this study, we characterized the pharmacodynamic properties of new guanidine NHE1 inhibitors (cariporide, sabiporide, KR-32511, KR-32570, and KR-33028) to analyze their myocardial protective effects. Although NHE1 is the major NHE isoform in cardiomyocytes, IC(50)values of these chemicals tested in rat cardiomyocytes were significantly different from those in PS120/hNHE1 cells where human NHE1 is heterologously expressed. In rat cardiomyocytes, KR-32570 and KR-33028 exhibited the highest potencies and their IC(50)values were 7+/-2 nM and 9+/-3 nM, respectively. The IC(50)values of all the chemicals tested on rat submandibular gland NHE2 were in the micromolar range, and they showed no inhibitory effects on hNHE3 and epithelial Na(+) channels up to 30 microM, suggesting a high selectivity toward NHE1. Sabiporide and KR-32570 exhibited slow dissociation kinetics with NHE1 inhibition persisting even after rinsing-out. When the cytoprotective effects of chemicals against hypoxic damage of rat cardiomyocytes were examined, the order of potency was KR-32570>or=KR-33028>sabiporide>cariporide>KR-32511. This order was exactly the same as that for the NHE1 inhibition in rat cardiomyocytes and did not correlate with any other properties, including the slow dissociation kinetics. Taken together, these results suggest that KR-32570 and KR-33028 are potent candidates for cardioprotective agents, and that the IC(50) in the target organ is the most critical factor governing the cytoprotective effects of NHE1 inhibitors.

Lysophosphatidic Acid Induces Thrombogenic Activity Through Phosphatidylserine Exposure and Procoagulant Microvesicle Generation in Human Erythrocytes

OBJECTIVE

Although erythrocytes have been suggested to play a role in blood clotting, mediated through phosphatidylserine (PS) exposure and/or PS-bearing microvesicle generation, an endogenous substance that triggers the membrane alterations leading to a procoagulant activity in erythrocytes has not been reported. We now demonstrated that lysophosphatidic acid (LPA), an important lipid mediator in various pathophysiological processes, induces PS exposure and procoagulant microvesicle generation in erythrocytes, which represent a biological significance resulting in induction of thrombogenic activity.

METHODS AND RESULTS

In human erythrocytes, LPA treatment resulted in PS exposure on remnant cells and PS-bearing microvesicle generation in a concentration-dependent manner. Consistent with the microvesicle generation, scanning electron microscopic study revealed that LPA treatment induced surface changes, alteration of normal discocytic shape into echinocytes followed by spherocytes. Surprisingly, chelation of intracellular calcium did not affect LPA-induced PS exposure and microvesicle generation. On the other hand, protein kinase C (PKC) inhibitors significantly reduced PS exposure and microvesicle generation induced by LPA, reflecting the role of calcium-independent PKC. Activation of PKC was confirmed by Western blot analysis showing translocation of calcium-independent isoform, PKCzeta, to erythrocyte membrane. The activity of flippase, which is important in the maintenance of membrane asymmetry, was also inhibited by LPA. Furthermore, LPA-exposed erythrocytes actually potentiated the thrombin generation as determined by prothrombinase assay and accelerated the coagulation process initiated by recombinant human tissue factor in plasma. The adherence of erythrocytes to endothelial cells, another important feature of thrombogenic process, was also stimulated by LPA treatment.

CONCLUSIONS

These results suggested that LPA-exposed erythrocytes could make an important contribution to thrombosis mediated through PS exposure and procoagulant microvesicle generation.

COX-2 is associated with cadmium-induced ICAM-1 expression in cerebrovascular endothelial cells

In order to get insight into the mechanism of cadmium (Cd)-induced brain injury, we investigated the effects of Cd on the induction of COX-2 and ICAM-1 in bEnd.3 mouse brain endothelial cells (EC). Cd stimulated PGE(2) release in a time and dose dependent manner, which was accompanied by increase of COX-2 expression. The thiol-reducing antioxidant N-acetylcyteine attenuated Cd-induced PGE(2) production and COX-2 expression. Cd increased phosphorylation of p38 MAPK, but not of JNK and ERK1/2. A blockade of p38 MAPK pathway abrogated Cd-induced COX-2 expression and PGE(2) production. Cd-induced ICAM-1 expression and leukocyte-EC adhesion were diminished by non-steroidal anti-inflammatory drugs such as indomethacin and NS-398, which was reversed by addition of PGE(2). Together, these data suggest that Cd induces COX-2 expression through the activation of p38 MAPK, an oxidative stress-sensitive cellular signaling molecule, and induction of COX-2 is associated with ICAM-1 expression in brain endothelial cells following Cd exposure.

[Synthesis of reactivators of phosphorylated acetylcholinesterase of bis-pyridiniumdialdoxime type with a 3-oxapentane connecting chain and their testing in vitro on a model of the enzyme inhibited by chlorpyrifos and methylchlorpyrifos]

Insecticides (e.g., parathion, chlorpyrifos, methylchlorpyrifos) and nerve agents (e.g.. soman, sarin, tabun, VX) belong to the group of organophosphates. They are able to irreversibly inhibit the enzyme acetylcholinesterase (AChE). Three new reactivators with a 3-oxapentane connecting chain were prepared. The ability of the new compounds to reactivate AChE inhibited by pesticides was tested in vitro and compared to known oxime 10(-3) M which is unfortunately not applicable to in vivo experiments. All tested compounds are practically ineffective for methylchlorpyrifos-inhibited AChE at the physiological concentration (10(-5) M). On the other hand, the known reactivators surpass new substances in the case of chlorpyrifos-inhibited AChE at both concentrations.

Inhibitory effect of select nitrocompounds on growth and survivability of Listeria monocytogenes in vitro

We report the effects of 2-nitro-1-propanol (2NPOH), 2-nitroethanol (2NEOH), and nitroethane (NE) on growth and survivability of Listeria monocytogenes. In all cases, inhibition was greatest with 2NPOH and least with NE. For example, specific growth rates of L. monocytogenes strain 18 declined (P < 0.05) 76, 60, and 29% from controls during aerobic culture at 37 degrees C in brain heart infusion broth containing 10 mM 2NPOH, 2NEOH, or NE, respectively. Mean specific growth rate for the controls incubated likewise without added nitrocompound was 0.62 +/- 0.02 h(-1). Specific growth rates of L. monocytogenes Scott A decreased (P < 0.05) 67, 45, and 11%, respectively, from controls (0.67 +/- 0.02 h(-1)) when cultured similarly. Specific growth rates for L. monocytogenes strain 18 incubated similarly except at 30 degrees C were reduced (P < 0.05) 76, 60, and 30%, respectively, and were reduced (P < 0.05) 78, 23, and 23% during anaerobic culture at 30 degrees C in brain heart infusion broth containing 15 mM 2NPOH, 2NEOH, or NE (control rates ranged from 0.37 +/- 0.07 to 0.74 +/- 0.05 h(-1)). Survivability of L. monocytogenes strain 18 was reduced (P < 0.05) during aerobic storage (4 months at 4 degrees C) in brain heart infusion broth containing 2NPOH or 2NEOH (by 7.8 and 1.9 log units, respectively) but not NE. The inhibitory effect of 2NPOH was approximately 20% greater during growth at pH 7.0 than at pH 5.6 or 8.0. These results demonstrate the differential inhibitory activity of 2NPOH, 2NEOH, and NE against L. monocytogenes in vitro.

Pharmacological profile of KR-33028, a highly selective inhibitor of Na+/H+ exchanger

We evaluated the cardioprotective effects of 4-cyano (benzo[b]thiophene-2-carbonyl)guanidine (KR-33028), a recently developed inhibitor of the Na+/H+ exchanger (NHE), on hypoxia-induced H9c2 cell death and on perfused rat hearts subjected to ischemia/reperfusion. KR-33028 inhibited in a concentration-dependent manner the recovery from acidosis induced by an NH4Cl prepulse in PS120 fibroblast cells expressing the human NHE-1 isoform (IC50: 2.59 microM). Treatment with KR-33028 (1-10 microM) significantly decreased hypoxia-induced necrotic cell death and apoptotic cell death in H9c2 cells. KR-33028 significantly inhibited hypoxia-induced increases in cytosolic and mitochondrial Ca2+ level and cytochrome c release, and recovered hypoxia-induced Delta psi(m) reduction. In the perfused rat hearts subjected to 30 min of ischemia and 30 min of reperfusion, KR-33028 (1-10 microM) improved cardiac contractility, decreased lactate dehydrogenase release, and increased content of tissue ATP, creatine phosphate and glycogen in a concentration-dependent manner. In addition, KR-33028 did not produce significant acute or subacute toxicity in the rats at doses tested. Our results suggest that a novel NHE-1 inhibitor KR-33028 possesses potent cardioprotective effects with minimal toxicity and that the effects may be mediated by inhibition of intracellular Ca2+ overload and mitochondrial cell death pathway.

Protective effect of KR-31378 on oxidative stress in cardiac myocytes

In this study, we investigated whether a novel anti-ischemic KATP opener KR-31378 [(2S,3S,4R)-N"-cyano-N-(6-amino-3,4-dihydro-3-hydroxy-2-methly-2-dimethoxymethly-2H-benzopyran-4-yl)-N'-benzylguanidine] has protective effect against oxidative stress-induced death in heart-derived H9c2 cells. Cell death was induced by BSO, butionine sulfoximine, which inhibits GSH synthesis and subsequently increases reactive oxygen species (ROS) level. Cell death was quantitatively determined by measuring lactate dehydrogenase (LDH) activity and stained by Hoechst 33258. BSO-induced ROS production and mitochondrial membrane potential (MMP) were measured using 2',7'-dichlorofluorescein diacetate oxidation and rhodamine 123, respectively. Both the LDH release and the ROS elevation induced by treatment of H9c2 cells with 10 mM BSO, were significantly decreased by KR-31378. These protective effect and antioxidant effect of KR-31378 appeared to be independent on KATP channel opening. Cells exposed to BSO showed an early reduction in MMP, and this reduction in MMP was significantly reversed by treatment with KR-31378. Caspase-3 activity in BSO treated H9c2 cells was remarkably increased, and this increased caspase-3 activity was significantly reversed by KR-31378. In conclusion, our results suggest that KR-31378 can produce cardioprotective effect against oxidative stress-induced cell death through antioxidant mechanism.

KR-32570, a novel Na+/H+ exchanger-1 inhibitor, attenuates hypoxia-induced cell death through inhibition of intracellular Ca2+ overload and mitochondrial death pathway in H9c2 cells

A novel Na+/H+ exchanger-1 (NHE-1) inhibitor [5-(2-methoxy-5-chloro-5-phenyl)furan-2-ylcarbonyl]guanidine (KR-32570) has been previously demonstrated to elicit cardioprotective effect against ischemic injury in rat heart. In the present study, we examined the effects of KR-32570 on cell death induced by hypoxic insult in heart-derived H9c2 cells. Treatment with KR-32570 (1-10 microM) significantly reduced hypoxia-induced necrotic cell death (lactate dehydrogenase release) and apoptotic cell death (TUNEL-positivity, caspase-3 activity). KR-32570 also decreased the cytosolic and mitochondrial Ca2+ overload induced by hypoxia. Inhibition of mitochondrial Ca2+ overload by ruthenium red mimicked the anti-apoptotic effect of KR-32570. In addition, KR-32570 significantly recovered the large reduction in mitochondrial membrane potential (delta psi(m)) and cytochrome c release induced by hypoxia. Taken together, our results suggest that a new NHE-1 inhibitor KR-32570 elicits potent cardioprotective effects in H9c2 cells, and its effects may be mediated by inhibition of intracellular Ca2+ overload and mitochondrial death pathway during hypoxia.

Arachidonic acid induces neuronal death through lipoxygenase and cytochrome P450 rather than cyclooxygenase

Arachidonic acid (AA) is released from membrane phospholipids during normal and pathologic processes such as neurodegeneration. AA is metabolized via lipoxygenase (LOX)-, cyclooxygenase (COX)-, and cytochrome P450 (CYP450)-catalyzed pathways. We investigated the relative contributions of these pathways in AA-induced neuronal death. Exposure of cultured cortical neurons to AA (50 microM) yielded significantly apoptotic neuronal death, which was attenuated greatly by LOX inhibitors (nordihydroguaiaretic acid, AA861, and baicalein), or CYP450 inhibitors (SKF525A and metyrapone), rather than COX inhibitors (indomethacin and NS398). AA (10 microM)-induced neurotoxicity was prevented by all kinds of inhibitors. Compared, the neurotoxic effects of three pathway metabolites, 12-hydroxyeicosatetraenoic acid (12-HETE), a major LOX metabolite, induced a significant neurotoxicity. AA also produced reactive oxygen species within 30 min, which was reduced by all inhibitors tested, including COX inhibitors, and AA neurotoxicity was abolished by the antioxidant Trolox. AA treatment also depleted glutathione levels; this depletion was reduced by the LOX or CYP450 inhibitors rather than by the COX inhibitors. Taken together, our data suggested that the LOX pathway likely plays a major role in AA-induced neuronal death with the modification of intracellular free radical levels.

Effects of sabiporide, a specific Na+/H+ exchanger inhibitor, on neuronal cell death and brain ischemia

We investigated the effects of an Na(+)/H(+) exchanger inhibitor, sabiporide, on excitotoxicity in cultured neuronal cells and in vivo. Sabiporide attenuated glutamate- or NMDA (N-methyl-d-aspartic acid)-induced neuronal cell death. Sabiporide also reduced glutamate or NMDA-induced increase in [Ca(2+)](i). In in vivo brain ischemia model, sabiporide produced protective effects, decreasing the infarct size and edema volume. Our results suggest that sabiporide elicits neuroprotective effect both in vitro and in vivo.

Activation of protein kinase C-delta attenuates kainate-induced cell death of cortical neurons

We investigated the role of individual protein kinase C (PKC) isoforms during kainate toxicity in cortical neurons. Treatment with 50 microM kainate induced isoform-specific activation of PKC-delta according to the translocation from the soluble to the particulate fraction, while it caused remarkable decreases in PKC alpha, beta, epsilon and zeta in both fractions. Kainate-induced neuronal death was significantly increased by pharmacological inhibition of PKC-delta with rottlerin, suggesting a protective role of PKC-delta against kainate toxicity. A PKC activator phorbol 12-myristate 13-acetate remarkably attenuated the kainate-induced neuronal death. Although phorbol 12-myristate 13-acetate activates PKC-epsilon and PKC-delta, the protective effect of phorbol 12-myristate 13-acetate was almost completely abolished by rottlerin, but not by epsilonV1-2. These results suggest that activation of PKC-delta attenuates the kainate-induced cell death of cortical neurons.

Novel preharvest strategies involving the use of experimental chlorate preparations and nitro-based compounds to prevent colonization of food-producing animals by foodborne pathogens

Foodborne diseases caused by enterohemorrhagic Escherichia coli, Salmonella, and Campylobacter species are of public health and economic significance. Shedding of these pathogens during production and slaughter are risks for contamination of products for human consumption. Consequently, strategies are sought to prevent or reduce the carriage of these pathogens in food animals before slaughter. Experimental products containing chlorate salts have been proven efficacious in reducing concentrations of E. coli and Salmonella Typhimurium in the gut of cattle, sheep, swine, and poultry when administered as feed or water additives. Mechanistically, chlorate selectively targets bacteria expressing respiratory nitrate reductase activity, such as most members of the family Enterobacteriaceae, as this enzyme catalyzes the reduction of chlorate to lethal chlorite. Most beneficial gut bacteria lack respiratory nitrate reductase activity, and thus the technology appears compatible with many bacteria exhibiting competitive exclusion capabilities. More recently, select nitrocompounds have been investigated as potential feed additives, and although these nitrocompounds significantly reduce pathogens on their own, evidence indicates that they may most effectively be used to complement the bactericidal activity of chlorate. A particularly attractive aspect of the nitrocompound technology is that, as potent inhibitors of ruminal methanogenesis, they may allow producers the opportunity to recoup costs associated with their use. At present, neither chlorate nor the nitrocompounds have been approved as feed additives by the US Food and Drug Administration, and consequently they are not yet available for commercial use.

Role of PKC-delta during hypoxia in heart-derived H9c2 cells

In the present study, we investigated the role of protein kinase C (PKC) isoforms during hypoxia in heart-derived H9c2 cells. Hypoxia caused a rapid translocation of PKC-delta from soluble to particulate fraction and a downregulation of PKC-epsilon and PKC-zeta, whereas PKC-alpha and PKC-beta I remained unaltered. When H9c2 cells were pretreated with PKC-delta inhibitor rottlerin (3 microM), hypoxia-induced apoptotic and necrotic cell death were significantly increased. Hypoxic insult also caused an activation of extracellular signal-regulated protein kinase (ERK) and p38 MAPK with no change in c-Jun NH(2)-terminal protein kinase (JNK) phosphorylation. Hypoxia-induced cell death was increased by treatment with ERK1/2 inhibitor U0126 (10 microM), but attenuated by p38 MAPK inhibitor SB202190 (10 microM). Treatment with rottlerin completely blocked the hypoxia-induced ERK phosphorylation, whereas it significantly increased p38 MAPK phosphorylation. The hypoxia-induced translocation of PKC-delta was not altered by U0126 and/or SB202190. From these results, it is suggested that hypoxia causes a rapid translocation of PKC-delta and subsequently ERK activation and p38 inactivation, rendering H9c2 cells resistant to hypoxia-induced cell death.

Neuroprotection by fructose-1,6-bisphosphate involves ROS alterations via p38 MAPK/ERK

Fructose-1,6-bisphosphate (FBP) is a glucose metabolism intermediate that shows a neuroprotective action in animal models of ischemia and other injuries. The intracellular mechanism of FBP on neuroprotection has not been previously defined. Here, we examined whether FBP has a neuroprotective effect against excitotoxicity, and whether it affects the production of reactive oxygen species (ROS), which are involved in the MAPK pathway in cortical neurons. FBP prevented neuronal death in a dose-dependent manner following 24 h of treatment with the excitotoxin, NMDA. After 8 h of NMDA treatment, we observed FBP-induced inhibition of the production of intracellular ROS, and at the earlier time FBP suppressed NMDA-induced p-p38 and p-ERK expression. In addition, MAPK inhibitors reduced NMDA-induced excitotoxicity and also ROS production. Taken together, our results suggest that the neuroprotective effects of FBP could be explained by down-regulation of free radical production through the p38MAPK/ERK pathway.

Identification of caspase-independent PKCepsilon-JNK/p38 MAPK signaling module in response to metabolic inhibition in H9c2 cells

To understand the molecular mechanism of ischemia-induced cardiac myocyte cell death, H9c2 cells were studied by chemical hypoxia (CH), using metabolic inhibition buffer. CH suppressed the activities of caspase-3, -8, and -9. c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK) were activated, whereas extracellular regulated kinase (ERK) was inactivated. Only protein kinase Cepsilon (PKCepsilon) among PKC isotypes was translocated to the membrane fraction implying its activation. Moreover, the administration of PKCepsilon inhibitor suppressed the phosphorylations of JNK/p38 MAPK and reduced CH-induced cell death. An administration of JNK/p38 MAPK inhibitors also decreased CH-induced cell deaths, implying JNK/p38 MAPK's causative roles in the deaths. Collectively, this study identified a novel caspase-independent PKCepsilon-JNK/p38 MAPK signaling module induced by CH in cardiac myocytes. Our data show that the PKCepsilon-JNK/p38 MAPK signaling module contributes to CH-induced H9c2 cell death. This contrasts with previous notions, i.e., PKCepsilon's protective effect against ischemic death. Thus our data suggest that PKCepsilon can mediate alternative signals, i.e., beneficiary or deleterious signals, depending on the cell type, intensity, and/or type of injury.

KR-31378, a novel benzopyran analog, attenuates hypoxia-induced cell death via mitochondrial KATP channel and protein kinase C-ɛ in heart-derived H9c2 cells

A novel compound KR-31378 [(2S,3S,4R)-N''-cyano-N-(6-amino-3,4-dihydro-3-hydroxy-2-methly-2-dimethoxy-methly-2H-benzo-pyran-4-yl)-N-benzylguanidine] has been demonstrated as an anti-ischemic agent in rat heart and brain. Here, we report the effects of this compound on hypoxia-induced cell death and possible signaling pathways in heart-derived H9c2 cells. Treatment with KR-31378 (3-30 microM) 1 h before and during hypoxia significantly reduced hypoxia-induced cell death in a concentration-dependent manner. In addition, increase in hypoxia-induced transferase UTP nick end labeling (TUNEL)-positive cells was reduced by KR-31378, suggesting its antiapoptotic potential in H9c2 cells. The protective effect conferred by KR-31378 (10 microM) was abolished by cotreatment with 5-hydroxydecanoate (5HD), a specific blocker of the mitochondrial KATP (mtKATP) channel, but not by HMR-1883 (1-[[5-[2-(5-chloro-o-anisamido)ethyl]-methoxyphenyl]sulfonyl]-3-methylthiourea), a specific blocker of the sarcolemmal KATP channel. We observed that the treatment with KR-31378 could increase the expression of protein kinase C (PKC)-epsilon protein, but not other PKC isotypes (-alpha, -beta, -delta, -zeta), in the particulate fraction. This increased level of PKC-epsilon was sustained during the hypoxic period up to 8 h. In addition, our results showed that treatment with KR-31378 induced the expression of PKC-epsilon mRNA as early as 15 min after the treatment. A specific inhibitor for PKC-epsilon isoform, epsilonV1-2, completely blocked the protective effect of KR-31378 against hypoxia-induced cell death. In conclusion, our results suggest that KR-31378 can protect cultured H9c2 cells from hypoxia-induced death via the mtKATP channel and PKC-epsilon.

Inhibitory activity of 2-nitropropanol against select food-borne pathogens in vitro*

AIMS

To test the inhibitory activity of 2-nitro-1-propanol (2NPOH) against Salmonella Typhimurium, Escherichia coli O157:H7 and Enterococcus faecalis.

METHODS AND RESULTS

Specific growth rates (h(-1)) of S. Typhimurium, E. coli O157:H7 and Ent. faecalis were determined during culture in tryptic soya broth (TSB) supplemented with 0-10 mm 2NPOH. Growth rates were inhibited by 2NPOH, with nearly complete inhibition observed with 10 mm. Studies with S. Typhimurium revealed that its survivability during culture in TSB containing 5 or 10 mm 2NPOH was lower (P < 0.05) under aerobic than anaerobic conditions. The survivability of Salmonella during anaerobic culture in TSB containing 2.5 mm 2NPOH was less at pH 5.6 than at pH 7.0 and 8.0. No Salmonella survived anaerobic incubation in TSB supplemented with 10 mm 2NPOH regardless of pH. When incubated in suspensions of freshly collected populations of ruminal and faecal bacteria, Salmonella concentrations were lower (P < 0.05) in suspensions containing 10 mm 2NPOH than in suspensions containing no 2NPOH.

CONCLUSIONS

2NPOH inhibited S. Typhimurium, E. coli O157:H7 and Ent. faecalis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Results suggest that 2NPOH may be a useful antimicrobial supplement to reduce carriage of certain food-borne pathogens in food animals.

Cadmium stimulates the expression of ICAM-1 via NF-kappaB activation in cerebrovascular endothelial cells

Cadmium (Cd), a ubiquitous heavy metal, has been shown to accumulate in the central nervous system, especially outside of the blood-brain barrier (BBB), suggesting a potential toxicity to nervous tissue. Thus, we investigated the effect of Cd on intercellular adhesion molecule-1 (ICAM-1) expression, as an indicator of BBB injury, in mouse brain microvessel endothelial cells (bEnd.3 cells). The treatment with Cd increased the expression of ICAM-1 at the levels of protein and mRNA, and these increases were almost completely inhibited by a specific NF-kappaB inhibitor SN50. The treatment with Cd induced the translocation of NF-kappaB from cytosolic to membrane fraction and increased DNA binding activity of NF-kappaB, and this NF-kappaB activation was inhibited by SN50. Interestingly, Cd did not trigger the degradation of IkappaBalpha, suggesting that Cd-induced ICAM-1 expression is mediated through IkappaBalpha degradation-independent pathway. Instead, tyrosine phosphorylation of IkappaBalpha was significantly elevated by Cd treatment, and this elevation was blocked by genistein, a protein tyrosine kinase inhibitor. In summary, the present results suggest that Cd stimulates the expression of ICAM-1 in bEnd.3 cells, via NF-kappaB activation that is mediated by the tyrosine phosphorylation of IkappaBalpha.

Role for PKC-ε in neuronal death induced by oxidative stress

We investigated which isoforms of PKCs can be modulated and what their roles are during l-buthionine-S,R-sulfoximine (BSO)-induced neuronal death. We observed the isoform specific translocation of PKC-epsilon from the soluble fraction to the particulate in cortical neurons treated with 10 mM BSO. The translocation of PKC-epsilon by BSO was blocked by antioxidant trolox, suggesting the PKC-epsilon as a downstream of reactive oxygen species (ROS) elevated by BSO. Trolox inhibited the ROS elevation and the neuronal death in BSO-treated cortical cells. The BSO-induced neuronal death was remarkably inhibited by both the pharmacological inhibition of PKC-epsilon with epsilonV1-2 and the functional blockade for PKC-epsilon through overexpression of PKC-epsilon V1 region, suggesting the detrimental role of PKC-epsilon. These results suggest that PKC-epsilon is the major PKC isoform involved in the pathways triggered by ROS, leading to neuronal death in BSO-treated cortical neurons.

Effect of Drinking-Water Administration of Experimental Chlorate Ion Preparations on Salmonella enterica serovar Typhimurium Colonization in Weaned and Finished Pigs

Foodborne disease caused by Salmonella is of public health and economic significance. In order to assess the practical effectiveness of a new intervention strategy, experimental chlorate preparations (ECP) were administered via the drinking water to weaned and finished pigs that had been orally challenged the previous day with 10(9)-10(10) colony-forming units of Salmonella serovar Typhimurium. After 24 or 36 h ad libitum access to 0X, 1X or 2X ECP treatment (where X is the concentration estimated to deliver a minimal daily effective dose), the pigs were euthanized and gut contents and lymph tissue collected at necropsy were cultured for the challenge Salmonella. Drinking water administration of ECP effectively reduced (p < 0.05) caecal Salmonella concentrations and, with the weaned pigs, tended (p < or = 0.10) to reduce rectal Salmonella concentrations. No negative effects of ECP treatment on water intake and animal wellbeing were observed and only marginal effects on gut fermentation characteristics occurred. The bactericidal effect of administering ECP in drinking water was relatively rapid, with reductions in caecal Salmonella concentrations occurring within 24 h. These results suggest that ECP administered to pigs just days before slaughter may reduce gut concentrations of Salmonella; however, the impacts of such reductions on slaughter hygiene have yet to be determined.

Alterations in hepatic metabolism of sulfur-containing amino acids induced by ethanol in rats

Alterations in hepatic metabolism of S-amino acids were monitored over one week in male rats treated with a single dose of ethanol (3 g/kg, ip). Methionine and S-adenosylhomocysteine concentrations were increased rapidly, but S-adenosylmethionine, cysteine, and glutathione (GSH) decreased following ethanol administration. Activities of methionine adenosyltransferase, cystathionine gamma-lyase and cystathionine beta-synthase were all inhibited. gamma-Glutamylcysteine synthetase activity was increased from t = 8 hr, but GSH level did not return to control for 24 hr. Hepatic hypotaurine and taurine levels were elevated immediately, but reduced below control in 18 hr. Changes in serum and urinary taurine levels were consistent with results observed in liver. Cysteine dioxygenase activity was increased rapidly, but declined from t = 24 hr. The results show that a single dose of ethanol induces profound changes in hepatic S-amino acid metabolism, some of which persist for several days. Ethanol not only inhibits the cysteine synthesis but suppresses the cysteine availability further by enhancing its irreversible catabolism to taurine, which would play a significant role in the depletion of hepatic GSH.

Effects of sodium chlorate on toxin production by Escherichia coli O157:H7

Chlorate kills E. coli O157:H7 and has been proposed as a feed additive to be included in cattle rations immediately prior to slaughter to reduce E. coli O157: H7 populations in the gut. Antibiotic usage is not recommended in cases of E. coil O157:H7-induced hemorrhagic colitis because some antibiotics stimulate increased toxin production. This study was undertaken to determine if chlorate treatment affected toxin production. Pure cultures of E. coil O157:H7 were treated with 1/4 MIC of antibiotics (ampicillin, tetracycline, ceftiofur, gentamicin, monensin, tylosin, penicillin, ciprofloxacin, and novobiocin); toxin production was significantly increased by some antibiotics, but not by chlorate. Studies with mixed fecal bacteria demonstrated that chlorate killed E. coli O157:H7, but again did not stimulate toxin production. Chlorate appears to be an effective method to reduce shiga toxin-producing E. coil (STEC) populations in food animals, but additional studies are warranted before it is used to control infections.

Antimicrobial Resistance and Serotype Prevalence of Salmonella Isolated from Dairy Cattle in the Southwestern United States

Mature dairy cattle were sampled over a 2-year period (2001-2002) on six farms in New Mexico and Texas. Fecal samples (n = 1560) were collected via rectal palpation and cultured for Salmonella, and one isolate from each positive sample was serotyped. Three isolates of each serotype, with the exception of Salmonella Newport (n = 12), were examined for susceptibility to 17 antimicrobial agents. Twenty-two different serotypes were identified from a total of 393 Salmonella isolates. Montevideo was the predominant serotype (27%) followed by Mbandaka (15%), Senftenberg (11.4%), Newport (6.4%), Anatum (4.8%), and Give (4.8%). Salmonella Typhimurium and Dublin, two frequently reported serotypes, accounted for only 1% of the observed serotypes in this study. Sixty-four percent of the serotypes were susceptible to all 17 antimicrobials, 14% were resistant to a single agent, and 22% were multiresistant (2-11 types of resistance). All isolates tested were susceptible to amikacin, apramycin, imipenem, ceftriaxone, nalidixic acid, and ciprofloxacin. The most frequent types of resistance were to sulfamethoxazole, tetracycline, streptomycin, kanamycin, chloramphenicol, and ampicillin (ranging from 8.9 to 22.4%). Serotypes demonstrating multiple resistance included Dublin and Give (resistant to three or more antibiotics), Typhimurium (resistant to five antibiotics), and Newport (four and two isolates resistant to six and nine antibiotics, respectively). Class 1 integrons were present in only two Salmonella Dublin isolates and one Salmonella Newport isolate. The most prevalent resistance patterns observed in this study were toward antimicrobial agents commonly used in cattle, while all Salmonella isolates were susceptible to ceftriaxone and ciprofloxacin, antibiotics used in human medicine.

Isoform-specific induction of PKC-epsilon by high glucose protects heart-derived H9c2 cells against hypoxic injury

We investigated which PKC isoforms are involved in high glucose-induced protection against hypoxic injury. Treatment for 48 h with high glucose (22 mM) markedly increased the expression of PKC- epsilon in the particulate fraction (213+/-22.1% of the control) but had no effect on other types of PKC isoforms, suggesting that the high glucose-induced increase in PKC expression is isoform-specific. The mRNA level for PKC- epsilon was also substantially increased, reaching its peak after 4h of high glucose treatment. The high glucose increased PKC-epsilon activity in the particulate fraction up to 183+/-32.2% of the control. During hypoxia, the amount of PKC-epsilon in the particulate fraction was remarkably diminished in the low glucose-treated cells, but remained at a higher level in high glucose-treated cells. The treatment with epsilon V1-2 (10 microM), a specific inhibitor of PKC epsilon, abolished the protective effect of high glucose against hypoxia. These results suggest that isoform-specific induction of PKC-epsilon is involved in high glucose-induced protection against hypoxic injury in heart-derived H9c2 cells.

Ionophores: their use as ruminant growth promotants and impact on food safety

Ionophores (such as monensin, lasalocid, laidlomycin, salinomycin and narasin) are antimicrobial compounds that are commonly fed to ruminant animals to improve feed efficiency. These antimicrobials specifically target the ruminal bacterial population and alter the microbial ecology of the intestinal microbial consortium, resulting in increased carbon and nitrogen retention by the animal, increasing production efficiency. Ionophores transport ions across cell membranes of susceptible bacteria, dissipating ion gradients and uncoupling energy expenditures from growth, killing these bacteria. Not all bacteria are susceptible to ionophores, and several species have been shown to develop several mechanisms of ionophore resistance. The prophylactic use of antimicrobials as growth promotants in food animals has fallen under greater scrutiny due to fears of the spread of antibiotic resistance. Because of the complexity and high degree of specificity of ionophore resistance, it appears that ionophores do not contribute to the development of antibiotic resistance to important human drugs. Therefore it appears that ionophores will continue to play a significant role in improving the efficiency of animal production in the future.

KR-31466, a benzopyranylindol analog, attenuates hypoxic injury through mitochondrial K(ATP) channel and protein kinase C activation in heart-derived H9c2 cells

In the present study, we investigated whether a novel benzopyranylindol analogue, KR-31466 (KR466) (1-[(2S,3R,4S)-3,4-dihydro-2-dimethoxymethyl-3-hydroxy-2-methyl-6-nitro-2H-1-benzopyran-4-yl]-1H-indole-2-carboxylic acid ethyl ester) can attenuate hypoxic injury in heart-derived H9c2 cells and, if so, whether the protective effect of KR466 is mediated through mitochondrial ATP-sensitive potassium (mtK(ATP)) opening. The treatment of H9c2 cells with KR466 (3 - 30 microM) significantly reduced hypoxia-induced cell death in a concentration-dependent manner, as shown by lactate dehydrogenase release and propidium iodide-uptake. In addition, KR466 (10 microM) significantly reduced the increase in hypoxia-induced TUNEL-positive cells, suggesting its anti-apoptotic potential in H9c2 cells. The protective effects of KR466 were abolished by 5-hydroxydecanoate, a specific blocker of the mtK(ATP) channel, suggesting the involvement of the mtK(ATP) channel in the protective effect of KR466. A specific inhibitor of protein kinase C (PKC), chelerythrine (3 microM), significantly attenuated the protective effect of KR466 against hypoxia-induced cardiac cell death. In conclusion, our results suggest that KR466 can protect H9c2 cells from hypoxia-induced death through mtK(ATP) channel opening and PKC activation.