Effects of low-density lipoprotein docosahexaenoic acid nanoparticles on cancer stem cells isolated from human hepatoma cell lines.

Docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid with anti-cancer properties. Recently, DHA packaged within low-density lipoprotein (LDL) nanoparticles (LDL-DHA) was demonstrated to be effective in a murine model of hepatocellular carcinoma (HCC). Cancer stem cells (CSCs) are a subpopulation of tumor cells that are resistant to most cancer therapies and thereby, contribute to tumor recurrences. To determine whether LDL-DHA is effective against CSCs derived from human HCC cell lines and tumor bearing rats. Epithelial cellular adhesion molecule positive and CD133 negative (EpCAM+CD133-) CSCs were isolated from HuH-7 and HepG2 human HCC lines and exposed to varying concentrations (1-60 µM) of LDL-DHA nanoparticles for 0-72 h. HCC tumor bearing rats were treated with 2 mg/kg LDL-DHA nanoparticles for 3 days. Regardless of the cell line employed, LDL-DHA nanoparticles achieved 70-100% killing of EpCAM+CD133- CSCs at a concentration of 40 µM after 48 h of exposure while DHA and LDL alone had minimal or no cytotoxic effects. Similar results were obtained with LDL-DHA nanoparticle treatment of EpCAM-CD133- adult cancer cells (ACCs). In keeping with these findings were similar levels of low density lipoprotein receptor expression and LDL-DHA nanoparticle induced lipid peroxidation activity and reactive oxygen species in the CSC and ACC populations. However, differences in sensitivity to LDL-DHA treatment were observed in vivo experiments where LDL-DHA nanoparticle treated tumors had a higher percent of surviving CSCs relative to ACCs. Further research on LDL-DHA nanoparticle therapy for human HCC is warranted.

[Prevalence of HIV infection among pregnant women. A study in rural Africa]. / Prévalence de l'infection par le VIH chez les femmes enceintes. Etude en milieu rural africain.

BACKGROUND: The goal of the study is to assess the prevalence and risk factors of HIV in pregnant women in the North-East rural area of the Democratic Republic of Congo. METHODS: We undertook an exploratory study on women attending the antenatal care during the study period (from December 2002 to December 2004) in the referral General hospital of the health catchments' area of Oicha (DRC). Women with gestational age equal or above 36 weeks were included in the study. After a first test using rapid test Abbott Determine locally, a second crossing check was performed in the referral HIV laboratory in Liege (Belgium). RESULTS: Among 5016 participants tested, 94 were positive (prevalence of 1.9% [CI95% 1.5-2.5]). Following factors predict a risk of being positive among participants: the statute of displacement (OR: 5.77; IC95%: 3.59-9.29); widowhood and divorces (OR: 4.47; IC95%: 1.47-13.60); mobility related to the profession of the husband (OR: 4.00; IC95%: 2.36-6,75); living the countryside (OR: 1.67; IC95%: 1.06-2.62; p: 0.0258).

Heteromultimeric Kv1.2-Kv1.5 channels underlie 4-aminopyridine-sensitive delayed rectifier K(+) current of rabbit vascular myocytes.

The molecular identity of vascular delayed rectifier K(+) channels (K(DR)) is poorly characterized. Inhibition by 4-aminopyridine (4-AP) of K(DR) of rabbit portal vein (RPV) myocytes was studied by patch clamp and compared with that of channels composed of Kv1.5 and/or Kv1.2 subunits cloned from the RPV and expressed in mammalian cells. 4-AP block of K(DR) was pulse-frequency dependent, required channel activation, and was associated with a positive shift in voltage dependence of activation. 4-AP caused a voltage-dependent reduction in mean open time of K(DR). Relief of 4-AP block of whole cell currents during washout required channel activation and was unaffected by voltage. Homotetrameric Kv1.5 channels did not exhibit the shift in voltage dependence of activation exhibited by the native channels. In contrast, Kv1.2 channels displayed a shift in voltage dependence of activation, and this characteristic was also evident during 4-AP treatment when Kv1.2 was coexpressed with Kv1.5 or coupled to Kv1.5 in a tandem construct to produce heterotetrameric [Kv1.5/Kv1.2](2) channels. K(DR) currents were not sensitive to charybdotoxin, which blocks homotetrameric Kv1.2 channels. The findings of this study (1) indicate that vascular K(DR) are inhibited by 4-AP via an open-state block mechanism and trapping of the drug within the pore on channel closure and (2) provide novel evidence based on a comparison of functional characteristics that indicate the dominant form of vascular K(DR) channel complex in RPV involves the heteromultimeric association of Kv1.2 and Kv1.5 subunits.

Overexpression of FGF-2 increases cardiac myocyte viability after injury in isolated mouse hearts.

We generated transgenic (TG) mice overexpressing fibroblast growth factor (FGF)-2 protein (22- to 34-fold) in the heart. Chronic FGF-2 overexpression revealed no significant effect on heart weight-to-body weight ratio or expression of cardiac differentiation markers. There was, however, a significant 20% increase in capillary density. Although there was no change in FGF receptor-1 expression, relative levels of phosphorylated c-Jun NH(2)-terminal kinase and p38 kinase as well as of membrane-associated protein kinase C (PKC)-alpha and total PKC-epsilon were increased in FGF-2-TG mouse hearts. An isolated mouse heart model of ischemia-reperfusion injury was used to assess the potential of increased endogenous FGF-2 for cardioprotection. A significant 34-45% increase in myocyte viability, reflected in a decrease in lactate dehydrogenase released into the perfusate, was observed in FGF-2 overexpressing mice and non-TG mice treated exogenously with FGF-2. In conclusion, FGF-2 overexpression causes augmentation of signal transduction pathways and increased resistance to ischemic injury. Thus, stimulation of endogenous FGF-2 expression offers a potential mechanism to enhance cardioprotection.

Protein kinase C inhibits delayed rectifier K+ current in rabbit vascular smooth muscle cells.

The effect of protein kinase C (PKC) activation on 4-aminopyridine (4-AP)-sensitive delayed rectifier current (IdK) was studied in isolated rabbit portal vein smooth muscle cells by use of standard whole cell voltage clamp. The effects of the phorbol ester, 4 beta-phorbol 12,13-dibutyrate (PdBu, 100 nM) and diacylglycerol analogues, 1,2-dioctanoyl-sn-glycerol (1,2-diC8, 10 microM) and 1,3-dioctanoyl-sn-glycerol (1,3-diC8, 10 microM), on macroscopic whole cell IdK were assessed in myocytes dialyzed with 10 mM 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) and 5 mM ATP (20-22 degrees C). Activation of PKC by 1,2-diC8 or PdBu caused a decline in IdK that was reversed with washout of drug. 1,2-diC8 had no effect on outward current present after exposure to 4-AP (20 mM). The inactive analogue, 1,3-diC8, did not affect IdK, but subsequent exposure to the active analogue, 1,2-diC8, caused a marked depression of the current. The inhibition of IdK by 1,2-diC8 was significantly reduced by intracellular dialysis with the inhibitors of PKC, chelerythrine (50 microM) and calphostin C (1 microM). Substitution of extracellular Ca2+ with Mg2+ in the presence of 10 mM intracellular BAPTA did not affect the suppression of IdK by 1,2-diC8, indicating the involvement of a Ca(2+)-independent isoform of PKC. This study suggests a novel signal transduction mechanism for inhibition of 4-AP-sensitive IdK involving a phosphotransferase reaction catalyzed by PKC in vascular smooth muscle myocytes.

Modulation of cardiac performance by amiloride and several selected derivatives of amiloride.

Amiloride and its derivatives (benzamil, dichlorobenzamil, 5-(N,N-dimethyl)-amiloride, 5-(N-ethyl-N-isopropyl)-amiloride, (N,N-hexamethylene)- amiloride and 5-(N-methyl-N-isobutyl)-amiloride) are commonly used as selective blockers of Na+/Ca++ exchange or Na+/H+ exchange. Very little information is currently available regarding their effects on cardiac performance. It was observed that addition of amiloride or any of the selected derivatives to the coronary perfusate of the right ventricular wall produced a potent depressive effect on peak developed tension and the rates of tension generation and dissipation. The concentrations at which this occurred are those that are commonly used in ischemia or hypoxia studies. Significantly, the depressive action of the drugs increased with the perfusion duration and never achieved a stable level. An initial, transient positive inotropic effect was observed with some of the drugs. If the drug concentration and perfusion time was limited, the effects were reversible. All of the drugs except amiloride produced extra systoles. The drugs were capable of blocking Ca++ transients in isolated cardiomyocytes but had little effect on intracellular pH. The drugs lengthened the action potential duration and decreased the action potential amplitude and upstroke velocity. Their effects on cardiac performance may involve a complex inhibition of Ca++ influx and K+ efflux in addition to a stimulation of a nonselective cation current. It is concluded that amiloride and its analogs have striking effects on cardiac performance which may be unrelated to their capacity to inhibit Na+/Ca++ or Na+/H+ exchange. In summary, the use of these drugs is not normally recommended in cell or tissue perfusion experiments because of their nonselectivity. However, if the drug concentration and perfusion time is controlled carefully, interpretable data may be obtained in some cases.

ATP-regulated K+ channels protect the myocardium against ischemia/reperfusion damage.

The role of ATP-regulated K+ channels in protecting the myocardium against ischemia/reperfusion damage was explored using glibenclamide and pinacidil to block and activate the channels, respectively. Electrical and mechanical activity of arterially perfused guinea pig right ventricular walls was recorded simultaneously via an intracellular microelectrode and a force transducer. The preparations were subjected to either 1) 20 minutes of no-flow ischemia with or without glibenclamide (1 and 10 microM) followed by reperfusion, or 2) 30 minutes of no-flow ischemia with or without pinacidil (1 and 10 microM) followed by reperfusion. No-flow ischemia for 20 minutes produced changes in electrical and mechanical activity that were completely reversed on reperfusion; resting membrane potential declined by 13 +/- 1.2 mV, action potential duration at 90% repolarization (APD90) decreased by 62%, and developed tension fell by greater than 95%, but resting tension did not change significantly. Glibenclamide (10 microM) had no effect on activity during normal perfusion, but during ischemia, resting membrane potential fell slightly further (17 +/- 1.8 mV) and APD90 declined by only 24%. Developed tension declined more slowly and to a lesser extent, but resting tension rose significantly between 10 and 20 minutes of ischemia. Reperfusion of glibenclamide-treated tissues elicited arrhythmias (extrasystoles and tachycardia), and the preparations failed to recover mechanical function. Glibenclamide at 1 microM produced qualitatively similar effects, albeit less severe. After 30 minutes of no-flow ischemia in untreated tissues, resting tension increased by approximately 130% during the no-flow period. Reperfusion caused arrhythmias (extrasystoles, tachyarrhythmias, and fibrillation) and failed to restore resting or developed tension to preischemic levels. Pinacidil at 1 microM did not affect electrical or contractile function, but at 10 microM it had a negative inotropic effect, decreasing APD90 and developed tension by 5% and 18%, respectively. Both concentrations of the drug caused a faster and greater decline in APD90 during the no-flow period. Resting tension did not change during 30 minutes of no-flow ischemia in the presence of pinacidil, and reperfusion led to 85% and complete recovery of electrical and mechanical activity at 1 and 10 microM, respectively. The data indicate that glibenclamide enhances whereas pinacidil reduces myocardial damage caused by ischemia/reperfusion. The results are consistent with the hypothesis that activation of ATP-regulated K+ channels during ischemia is an important adaptive mechanism for protecting the myocardium when blood flow to the tissue is compromised.