Ascorbic acid improves postischemic vasodilatation impaired by infusion of soybean oil into canine iliac artery

Lipid Emulsion to Treat Acute Poisonings: Mechanisms of Action, Indications, and Controversies

Biodetoxification using intravenous lipid emulsion (ILE) in acute poisoning is of growing interest. As well as for local anesthetics, ILE is currently used to reverse toxicity caused by a broad-spectrum of lipophilic drugs. Both pharmacokinetic and pharmacodynamic mechanisms have been postulated to explain its possible benefits, mainly combining a scavenging effect called "lipid sink" and cardiotonic activity. Additional mechanisms based on ILE-attributed vasoactive and cytoprotective properties are still under investigation. Here, we present a narrative review on lipid resuscitation, focusing on the recent literature with advances in understanding ILE-attributed mechanisms of action and evaluating the evidence supporting ILE administration that enabled the international recommendations. Many practical aspects are still controversial, including the optimal dose, the optimal administration timing, and the optimal duration of infusion for clinical efficacy, as well as the threshold dose for adverse effects. Present evidence supports the use of ILE as first-line therapy to reverse local anesthetic-related systemic toxicity and as adjunct therapy in lipophilic non-local anesthetic drug overdoses refractory to well-established antidotes and supportive care. However, the level of evidence is low to very low, as for most other commonly used antidotes. Our review presents the internationally accepted recommendations according to the clinical poisoning scenario and provides the precautions of use to optimize the expected efficacy of ILE and limit the inconveniences of its futile administration. Based on their absorptive properties, the next generation of scavenging agents is additionally presented. Although emerging research shows great potential, several challenges need to be overcome before parenteral detoxifying agents could be considered as an established treatment for severe poisonings.

Lipid Emulsions Containing Medium Chain Triacylglycerols Blunt Bradykinin-Induced Endothelium-Dependent Relaxation in Porcine Coronary Artery Rings

Lipid emulsions for parenteral nutrition are used to provide calories and essential fatty acids for patients. They have been associated with hypertriglyceridemia, hypercholesterolemia, and metabolic stress, which may promote the development of endothelial dysfunction in patients. The aim of the present study was to determine whether five different industrial lipid emulsions may affect the endothelial function of coronary arteries. Porcine coronary artery rings were incubated with lipid emulsions 0.5, 1, or 2% (v/v) for 30 min before the determination of vascular reactivity in organ chambers and the level of oxidative stress using electron paramagnetic resonance. Incubation of coronary artery rings with either Lipidem^®, Medialipid^® containing long- and medium-chain triacylglycerols (LCT/MCT), or SMOFlipid^® containing LCT, MCT, omega-9, and -3, significantly reduced the bradykinin-induced endothelium-dependent relaxation, affecting both the nitric oxide (NO) and endothelium-dependent hyperpolarization (EDH) components, whereas, Intralipid^® containing LCT (soybean oil) and ClinOleic^® containing LCT (soybean and olive oil) did not have such an effect. The endothelial dysfunction induced by Lipidem^® was significantly improved by indomethacin, a cyclooxygenase (COX) inhibitor, inhibitors of oxidative stress (N-acetylcysteine, superoxide dismutase, catalase) and transition metal chelating agents (neocuproine, tetrathiomolybdate, deferoxamine and L-histidine). Lipidem^® significantly increased the arterial level of oxidative stress. The present findings indicate that lipid emulsions containing LCT/MCT induce endothelial dysfunction in coronary artery rings by blunting both NO- and EDH-mediated relaxations. The Lipidem^®-induced endothelial dysfunction is associated with increased vascular oxidative stress and the formation of COX-derived vasoconstrictor prostanoids.

Postprandial lipids accelerate and redirect nitric oxide consumption in plasma

Nitric oxide (NO) and O2 are both three-to four-fold more soluble in biological lipids than in aqueous solutions. Their higher concentration within plasma lipids accelerates NO autoxidation to an extent that may be of importance to overall NO bioactivity. This study was undertaken to test the hypothesis that increased plasma lipids after a high-fat meal appreciably accelerate NO metabolism and alter the byproducts formed. We found that plasma collected from subjects after consumption of a single high-fat meal had a higher capacity for NO consumption and consumed NO more rapidly compared to fasting plasma. This increased NO consumption showed a direct correlation with plasma triglyceride concentrations (p = 0.006). The accelerated NO consumption in postprandial plasma was reversed by removal of the lipids from the plasma, was mimicked by the addition of hydrophobic micelles to aqueous buffer, and could not be explained by the presence of either free hemoglobin or ceruloplasmin. The products of NO consumption were shifted in postprandial plasma, with 55% more nitrite (n = 12, p = 0.002) but 50% less SNO (n = 12, p = 0.03) production compared to matched fasted plasma. Modeling calculations indicated that NO autoxidation was accelerated by about 48-fold in the presence of plasma lipids. We conclude that postprandial triglyceride-rich lipoproteins exert a significant influence on NO metabolism in plasma.

Effects of Acidification and Alkalinization on the Lipid Emulsion-Mediated Reversal of Toxic Dose Levobupivacaine-Induced Vasodilation in the Isolated Rat Aorta

The goal of this in vitro study was to examine the effects of pre-acidification and pre-akalinization on the lipid emulsion-mediated reversal of toxic dose levobupivacaine-induced vasodilation in isolated rat aorta. Isolated aortic rings with and without the nitric oxide synthase inhibitor N(ω)-nitro-L-arginine methyl ester (L-NAME) were exposed to four types of Krebs solution (pH 7.0, 7.2, 7.4, and 7.6), followed by the addition of 60 mM potassium chloride. When the toxic dose of levobupivacaine (3 × 10(-4) M) produced a stable and sustained vasodilation in the isolated aortic rings that were precontracted with 60 mM potassium chloride, increasing lipid emulsion concentrations (SMOFlipid(®): 0.24, 0.48, 0.95 and 1.39%) were added to generate concentration-response curves. The effects of mild pre-acidification alone and mild pre-acidification in combination with a lipid emulsion on endothelial nitric oxide synthase (eNOS) phosphorylation in human umbilical vein endothelial cells were investigated by Western blotting. Mild pre-acidification caused by the pH 7.2 Krebs solution enhanced the lipid emulsion-mediated reversal of levobupivacaine-induced vasodilation in isolated endothelium-intact aortic rings, whereas mild pre-acidification caused by the pH 7.2 Krebs solution did not significantly alter the lipid emulsion-mediated reversal of the levobupivacaine-induced vasodilation in isolated endothelium-denuded aortic rings or endothelium-intact aortic rings with L-NAME. A lipid emulsion attenuated the increased eNOS phosphorylation induced by the pH 7.2 Krebs solution. Taken together, these results suggest that mild pre-acidification enhances the lipid emulsion-mediated reversal of toxic dose levobupivacaine-induced vasodilation in the endothelium-intact aorta via the inhibition of nitric oxide.

Lipid Emulsion Attenuates Acetylcholine-Induced Relaxation in Isolated Rat Aorta

We investigated the effect of Lipofundin MCT/LCT and Intralipid on acetylcholine-induced nitric oxide- (NO-) mediated relaxation in rat aorta to determine which lipid emulsion (LE) is more potent in terms of inhibition of NO-induced relaxation. Dose-response curves of responses induced by acetylcholine, the calcium ionophore A23187, and sodium nitroprusside were generated using isolated rat aorta with or without LE. The effect of Lipofundin MCT/LCT on acetylcholine-induced endothelial nitric oxide synthase (eNOS) phosphorylation in human umbilical vein endothelial cells (HUVECs) was investigated using western blotting. Lipofundin MCT/LCT (0.1 and 0.2%) attenuated acetylcholine-induced relaxation in endothelium-intact aorta with or without tiron, whereas 0.2% Intralipid only inhibited relaxation. Lipofundin MCT/LCT inhibited relaxation induced by the calcium ionophore A23187 and sodium nitroprusside in endothelium-intact aorta, but Lipofundin MCT/LCT had no effect on sodium nitroprusside-induced relaxation in the endothelium-denuded aorta. Combined pretreatment with l-arginine plus Lipofundin MCT/LCT increased acetylcholine-induced maximal relaxation in endothelium-intact aorta compared with Lipofundin MCT/LCT alone. l-Arginine attenuated Lipofundin MCT/LCT-mediated inhibition of acetylcholine-induced eNOS phosphorylation in HUVECs. Taken together, Lipofundin MCT/LCT attenuated acetylcholine-induced NO-mediated relaxation via an inhibitory effect on the endothelium including eNOS, which is proximal to activation of guanylyl cyclase.

Effect of two lipid emulsions on reversing high-dose levobupivacaine-induced reduced vasoconstriction in the rat aortas

The goals of this study were to determine which lipid emulsion (Intralipid(®) and Lipofundin MCT/LCT(®)) is more effective in reversing high-dose levobupivacaine-induced reduced vasoconstriction in isolated rat aortas and to examine the associated cellular mechanisms with a particular focus on the endothelium. Two lipid emulsion concentration-response curves were generated using high-dose levobupivacaine-induced reduced vasoconstriction and vasodilation of isolated aortas pretreated with or without 60 mM KCl. Endothelial nitric oxide synthase (eNOS) and caveolin-1 phosphorylation were measured in rat aortic tissue treated with levobupivacaine in the presence or absence of lipid emulsion. Dichlorofluorescein oxidation, a measure of reactive oxygen species production, was measured in lipid emulsion-treated human umbilical vein endothelial cells. In levobupivacaine (0.3 mM)-induced reduced vasoconstriction of isolated aorta, the magnitude of the Intralipid(®)- and Lipofundin MCT/LCT(®)-mediated reversal was not significantly different. Lipid emulsion reversal of levobupivacaine-induced reduced vasoconstriction was greater in endothelium-intact aortas than in endothelium-denuded aortas. The two lipid emulsions similarly inhibited levobupivacaine-induced eNOS phosphorylation in aortic tissue. Pretreatment with both lipid emulsions increased dichlorofluorescein oxidation. Both Intralipid(®) and Lipofundin MCT/LCT(®) are equally effective for vascular tone recovery from high-dose levobupivacaine-induced reduced vasoconstriction. This reversal is mediated partially by decreasing nitric oxide bioavailability.

Systemic blockage of nitric oxide synthase by L-NAME increases left ventricular systolic pressure, which is not augmented further by Intralipid®

Intravenous lipid emulsions (LEs) are effective in the treatment of toxicity associated with various drugs such as local anesthetics and other lipid soluble agents. The goals of this study were to examine the effect of LE on left ventricular hemodynamic variables and systemic blood pressure in an in vivo rat model, and to determine the associated cellular mechanism with a particular focus on nitric oxide. Two LEs (Intralipid^® 20% and Lipofundin^® MCT/LCT 20%) or normal saline were administered intravenously in an in vivo rat model following induction of anesthesia by intramuscular injection of tiletamine/zolazepam and xylazine. Left ventricular systolic pressure (LVSP), blood pressure, heart rate, maximum rate of intraventricular pressure increase, and maximum rate of intraventricular pressure decrease were measured before and after intravenous administration of various doses of LEs or normal saline to an in vivo rat with or without pretreatment with the non-specific nitric oxide synthase inhibitor N^ω-nitro-L-arginine-methyl ester (L-NAME). Administration of Intralipid^® (3 and 10 ml/kg) increased LVSP and decreased heart rate. Pretreatment with L-NAME (10 mg/kg) increased LSVP and decreased heart rate, whereas subsequent treatment with Intralipid^® did not significantly alter LVSP. Intralipid^® (10 ml/kg) increased mean blood pressure and decreased heart rate. The increase in LVSP induced by Lipofundin^® MCT/LCT was greater than that induced by Intralipid^®. Intralipid^® (1%) did not significantly alter nitric oxide donor sodium nitroprusside-induced relaxation in endothelium-denuded rat aorta. Taken together, systemic blockage of nitric oxide synthase by L-NAME increases LVSP, which is not augmented further by intralipid^®.

Phosphorylation of GSK-3β mediates intralipid-induced cardioprotection against ischemia/reperfusion injury

BACKGROUND

Intralipid (Sigma, St. Louis, MO), a brand name for the first safe fat emulsion for human use, has been shown to be cardioprotective. However, the mechanism of this protection is not known. The authors investigated the molecular mechanism(s) of Intralipid-induced cardioprotection against ischemia/reperfusion injury, particularly the role of glycogen synthase kinase-3β (GSK-3β) and mitochondrial permeability transition pore in this protective action.

METHODS

In vivo rat hearts or isolated Langendorff-perfused mouse hearts were subjected to ischemia followed by reperfusion with Intralipid (1% in ex vivo and one bolus of 20% in in vivo) or vehicle. The hemodynamic function, infarct size, threshold for the opening of mitochondrial permeability transition pore, and phosphorylation levels of protein kinase B (Akt)/extracellular signal regulating kinase (ERK)/GSK-3β were measured.

RESULTS

Administration of Intralipid at the onset of reperfusion resulted in approximately 70% reduction in infarct size in the in vivo rat model. Intralipid also significantly improved functional recovery of isolated Langendorff-perfused mouse hearts as the rate pressure product was increased from 2,999 ± 863 mmHg*beats/min in the control group to 13,676 ± 611 mmHg*beats/min (mean±SEM) and the infarct size was markedly smaller (18.3 ± 2.4% vs. 54.8 ± 2.9% in the control group, P < 0.01). The Intralipid-induced cardioprotection was fully abolished by LY294002, a specific inhibitor of PI3K, but only partially by PD98059, a specific ERK inhibitor. Intralipid also increased the phosphorylation levels of Akt/ERK1/glycogen synthase kinase-3β by eightfold, threefold, and ninefold, respectively. The opening of mitochondrial permeability transition pore was inhibited by Intralipid because calcium retention capacity was higher in the Intralipid group (274.3 ± 8.4 nM/mg vs. 168.6 ± 9.6 nM/mg in the control group).

CONCLUSIONS

Postischemic treatment with Intralipid inhibits the opening of mitochondiral permeability transition pore and protects the heart through glycogen synthase kinase-3β via PI3K/Akt/ERK pathways.

Endothelial function and early atherosclerotic changes

Endothelial dysfunction, including impaired vasomotor disturbance, abnormal coagulation, and increased vascular proliferation, is closely associated with the development of atherosclerosis and precedes the clinical manifestations of atherosclerosis. The impairment of endothelium-dependent vasodilation, which is chiefly attributed to decreased endothelial nitric oxide (NO) bioavailability, represents the functional characteristic of endothelial dysfunction and a early key step in the occurrence of atherosclerotic complications. An impairment of endothelial vasodilation is attributed to decreased NO production, deficiency of substrate or cofactor availability, and increased NO inactivation, and is not confined to a certain artery such as the coronary artery, but rather represents a systemic disorder that also affects peripheral vascular beds. Noninvasive endothelial function tests using extremities are a new popular method for the detection of endothelial NO bioavailability. The assessment of endothelial function detected before established atherosclerosis may be a more important risk factor to predict future atherosclerotic diseases compared with conventional risk factors such as hypertension and hyperlipidemia.

Influence of parenteral fat emulsion Intralipos and citric acid on blood viscosity and erythrocyte morphology in vitro

In most studies fat emulsion had been administered by enteral route. Recently a parenteral soybean-oil emulsion has been developed. In this study we assessed the effects of a parenteral soybean-oil emulsion (Intralipos) and citric acid on blood rheology and erythrocyte morphology in vitro. Porcine blood was incubated in vitro with increasing concentrations of fat emulsion Intralipos and citric acid at 37 degrees C for 1h. Viscosity of plasma and whole blood was measured using a FASCO-2050 digital viscometer. Red blood cell morphology was examined by light microscopy. The viscosity of whole blood represented an ascending dose-dependence for different Intralipos concentrations at high shear rate of 90 and 225 s(-1), however, it decreased with citric acid concentrations. On the other hand, the whole blood viscosity also declined with citric acid concentrations in presence of 30% Intralipos (v/v), and there is a minimal viscosity at 0.67% citric acid (v/v). There are some thorns on the blood membrane at 40% Intralipos as compared with control (no Intralipos addition), which indicates the Intralipos compound may affect blood cell membranes, and resulted in whole blood viscosity increase. We concluded that the intravenous soybean-oil preparation Intralipos interacts with the erythrocyte membrane, and citric acid could alleviate the whole blood viscosity.

Development, advances and applications of diagnostic ultrasound in animals

Ultrasound has many industrial applications but it was first introduced as a medical diagnostic aid in the 1940s with its first veterinary application, the detection of ovine pregnancy, being reported in 1966. Since then, improvements in equipment quality combined with an increased awareness of the benefits of ultrasound as an imaging technique have led to its widespread use in the veterinary field. Recent advances in computer technology have significantly influenced equipment design and the miniaturization of transducers allows intra-operative and intra-vascular applications. Software advances have improved the ability to manipulate and process data, leading to an increased amount of information being obtained from each examination and the advent of 'remote diagnosis'. Ultrasound guided interventional techniques can now be used for diagnostic or therapeutic purposes. Many of these developments have been introduced by equipment manufacturers but have found specific applications in the veterinary field. Ultrasound is currently employed in a very diverse range of situations, not just as a diagnostic tool in the routine clinical workup of a range of species, but also for disease screening, conservation projects, commercial services, herd management and clinical research.

Influence of ascorbic acid on BUN, creatinine, resistive index in canine renal ischemia-reperfusion injury

Renal ischemia as a course of renal transplantation is a common cause of renal dysfunction as renal failure. The purpose of this study was to investigate the influence of ascorbic acid on blood urea nitrogen (BUN), creatinine (Cr) and resistive index (RI) for dog models with renal ischemia-reperfusion (I/R) injury. Renal ischemia was induced on 6 Beagle dogs. The left kidney was exposed to normothermic ischemia for a short period at 30 min followed by reperfusion. On the blood Cr level and RI, there was no significant difference comparing both groups. 14 days after I/R injury a significant reduction on the blood BUN level was observed in the vehicle group (34.06 mg/dl) compared to that of ischemia induced treated group (10.3mg/dl) (p < 0.05). In conclusion, administration of ascorbic acid for renal ischemic-reperfusion injury had influence on blood BUN level, but it was not revealed the influence on blood Cr and RI.