Evolution of Biomarkers of Atherogenic Risk in Liver Transplantation Recipients.

BACKGROUND: Cardiovascular disease is a major contributing factor to long-term mortality after liver transplantation (LT). METHODS: This study evaluated the evolution of atherogenic risk in liver transplant recipients (LTRs). Thirty-six subjects were prospectively enrolled at 12 months and followed for 48 months after liver transplantation. Serum biomarkers of endothelial dysfunction (sICAM-1 and sVCAM-1), chronic inflammation (serum amyloid A), and oxidative stress (myeloperoxidase) were measured at 12 and 48 months after LT. Additionally, at 12 months all patients underwent a cardiac computed tomography (CT) scan and a coronary artery calcium score (CACS). RESULTS: The prevalence of risk factors of metabolic syndrome (MS) increased over the course of the study. The patients' sVCAM-1 and sICAM-1 increased from 1.82 ± 0.44 ng/mL to 9.10 ± 5.82 ng/mL (P < .001) and 0.23 ± 0.09 ng/mL to 2.7 ± 3.3 ng/mL, respectively from month 12 to 48. Serum myeloperoxidase increased from 0.09 ± 0.07 ng/mL to 3.46 ± 3.92 ng/mL (P < .001) over the course of the study. Serum amyloid A also increased from 21.4 ± 40.7 ng/mL at entry to 91.5 ± 143.6 ng/mL at end of study (P < .001). CONCLUSION: No association between these biomarkers and MS was noted. The cardiac CT revealed mild and moderate disease in 19% and 25% of the cohort, respectively. No association between serum biomarkers and CACS was noted. Serum biomarkers of atherogenic risk increase rapidly in LTRs and precede coronary plaques.

The Role of Acetylcholine in the Inflammatory Response in Animals Surviving Sepsis Induced by Cecal Ligation and Puncture.

The cholinergic anti-inflammatory pathway controls the inflammatory response and nonreflexive consciousness through bidirectional communication between the brain and immune system. Moreover, brain acetylcholinesterase activity may have a role in regulating the vagus nerve in this pathway. Thus, we analyzed the role of acetylcholine (ACh) in the inflammatory response 15 days after induction of sepsis by cecal ligation and puncture (CLP). Balb/c mice were pretreated with or without donepezil (5 mg/kg/day, orally) 7 days before CLP, and mice homozygous for vesicular ACh transporter (VAChT) knockdown (KD) were subjected to CLP. All animals were sacrificed 15 days after CLP, and the plasma, spleen, and hippocampus were collected. Characterization of splenic lymphocytes and cytokine levels in the plasma, spleen, and hippocampus was determined. Our results showed a splenomegaly in group CLP. The numbers of cytotoxic T cells, helper T cells, regulatory T cells, B cells, and Th17 cells differed between mice subjected to CLP and to sham operation in both untreated and donepezil-treated groups. In VAChT-KD mice, CLP resulted in decreased cytotoxic and helper T cells and increased in Th17 cells compared with the sham. Additionally, in VAChT-KD mice, the levels of pro-inflammatory cytokines, such as IL-1ß, IL-6, and TNF-α, were increased following CLP. Thus, we concluded that ACh affected the inflammatory response at 15 days after CLP since stimulation of cholinergic transmission increased the proliferation of lymphocytes, including regulatory T cells, in association with a lower inflammatory profile and VAChT-KD decreased the number of lymphocytes and increased inflammation.

Effects of hepatitis C virus on cardiovascular risk in infected patients: a comparative study.

The role of hepatitis C virus (HCV) in the pathogenesis of atherosclerosis and cardiovascular events is unclear. The aim of this study was to evaluate the direct effect of HCV on cardiovascular risk and correlate it with pro and anti-inflammatory cytokines in patients with HCV. HCV monoinfected patients, genotype 1, naive, non-obese (BMI<30) and non-diabetics were included and compared to controls (blood donors). Patients with prior diagnosis of cardiovascular diseases, hypertension, chronic renal failure, cancer and chronic use of lipid-lowering drugs or immunosuppressants were excluded. Age, BMI, systolic blood pressure (SBP) and diastolic (DBP), fasting glucose and lipid levels were determined. Serum cytokines (IL-6, IL-10 and TNF-α) and Framingham score were also evaluated. 62 HCV patients, 34 (54.8%) were males and none of them was smoking. The Framingham scores (median and 25th and 75th percentiles) were 12% (6.5-14%), showing an intermediate cardiovascular risk in patients with HCV. There was significant direct correlation between Framingham and total cholesterol (p=0.043) and DBP (p=0.007). HDL-C (p=0.002) was inversely correlated with the Framingham score. HCV patients had higher levels of proinflammatory cytokines (IL-6 and TNF-α) compared to controls (p<0.0001) and the relation of proinflammatory/anti-inflammatory TNF-α/IL10 and IL-6/IL10 were higher in HCV patients (p<0.01). The Framingham score was directly correlated to IL-6 and TNF-α, but differences were not statistically significant. Patients with HCV monoinfected, nonobese, naïve and non diabetic have an intermediate cardiovascular risk, as measured by the Framingham score and high levels of proinflammatory cytokines (IL-6 and TNF).

Immune cells and oxidative stress in the endotoxin tolerance mouse model

Sepsis is a systemic inflammatory response that can lead to tissue damage and death. In order to increase our understanding of sepsis, experimental models are needed that produce relevant immune and inflammatory responses during a septic event. We describe a lipopolysaccharide tolerance mouse model to characterize the cellular and molecular alterations of immune cells during sepsis. The model presents a typical lipopolysaccharide tolerance pattern in which tolerance is related to decreased production and secretion of cytokines after a subsequent exposure to a lethal dose of lipopolysaccharide. The initial lipopolysaccharide exposure also altered the expression patterns of cytokines and was followed by an 8- and a 1.5-fold increase in the T helper 1 and 2 cell subpopulations. Behavioral data indicate a decrease in spontaneous activity and an increase in body temperature following exposure to lipopolysaccharide. In contrast, tolerant animals maintained production of reactive oxygen species and nitric oxide when terminally challenged by cecal ligation and puncture (CLP). Survival study after CLP showed protection in tolerant compared to naive animals. Spleen mass increased in tolerant animals followed by increases of B lymphocytes and subpopulation Th1 cells. An increase in the number of stem cells was found in spleen and bone marrow. We also showed that administration of spleen or bone marrow cells from tolerant to naive animals transfers the acquired resistance status. In conclusion, lipopolysaccharide tolerance is a natural reprogramming of the immune system that increases the number of immune cells, particularly T helper 1 cells, and does not reduce oxidative stress.

Immune cells and oxidative stress in the endotoxin tolerance mouse model.

Sepsis is a systemic inflammatory response that can lead to tissue damage and death. In order to increase our understanding of sepsis, experimental models are needed that produce relevant immune and inflammatory responses during a septic event. We describe a lipopolysaccharide tolerance mouse model to characterize the cellular and molecular alterations of immune cells during sepsis. The model presents a typical lipopolysaccharide tolerance pattern in which tolerance is related to decreased production and secretion of cytokines after a subsequent exposure to a lethal dose of lipopolysaccharide. The initial lipopolysaccharide exposure also altered the expression patterns of cytokines and was followed by an 8- and a 1.5-fold increase in the T helper 1 and 2 cell subpopulations. Behavioral data indicate a decrease in spontaneous activity and an increase in body temperature following exposure to lipopolysaccharide. In contrast, tolerant animals maintained production of reactive oxygen species and nitric oxide when terminally challenged by cecal ligation and puncture (CLP). Survival study after CLP showed protection in tolerant compared to naive animals. Spleen mass increased in tolerant animals followed by increases of B lymphocytes and subpopulation Th1 cells. An increase in the number of stem cells was found in spleen and bone marrow. We also showed that administration of spleen or bone marrow cells from tolerant to naive animals transfers the acquired resistance status. In conclusion, lipopolysaccharide tolerance is a natural reprogramming of the immune system that increases the number of immune cells, particularly T helper 1 cells, and does not reduce oxidative stress.

Purine nucleotides reduce superoxide production by nitric oxide synthase in a murine sepsis model

Sepsis involves a systemic inflammatory response of multiple endogenous mediators, resulting in many of the injurious and sometimes fatal physiological symptoms of the disease. This systemic activation leads to a compromised vascular response and endothelial dysfunction. Purine nucleotides interact with purinoceptors and initiate a variety of physiological processes that play an important role in maintaining cardiovascular function. The purpose of the present study was to investigate the effects of ATP on vascular function in a lipopolysaccharide (LPS) model of sepsis. LPS induced a significant increase in aortic superoxide production 16 h after injection. Addition of ATP to the organ bath incubation solution reduced superoxide production by the aortas of endotoxemic animals. Reactive Blue, an antagonist of the P2Y receptor, blocked the effect of ATP on superoxide production, and the nonselective P2Y agonist MeSATP inhibited superoxide production. Nitric oxide synthase (NOS) inhibition by L-NAME blocked vascular relaxation and reduced superoxide production in LPS-treated animals. In the presence of L-NAME there was no ATP effect on superoxide production. A vascular reactivity study showed that ATP increased maximal relaxation in LPS-treated animals compared to controls. The presence of ATP induced increases in Akt and endothelial NOS phosphorylated proteins in the aorta of septic animals. ATP reduces superoxide release resulting in an improved vasorelaxant response. Sepsis may uncouple NOS to produce superoxide. We showed that ATP through Akt pathway phosphorylated endothelial NOS and “re-couples” NOS function.

Purine nucleotides reduce superoxide production by nitric oxide synthase in a murine sepsis model.

Sepsis involves a systemic inflammatory response of multiple endogenous mediators, resulting in many of the injurious and sometimes fatal physiological symptoms of the disease. This systemic activation leads to a compromised vascular response and endothelial dysfunction. Purine nucleotides interact with purinoceptors and initiate a variety of physiological processes that play an important role in maintaining cardiovascular function. The purpose of the present study was to investigate the effects of ATP on vascular function in a lipopolysaccharide (LPS) model of sepsis. LPS induced a significant increase in aortic superoxide production 16 h after injection. Addition of ATP to the organ bath incubation solution reduced superoxide production by the aortas of endotoxemic animals. Reactive Blue, an antagonist of the P2Y receptor, blocked the effect of ATP on superoxide production, and the nonselective P2Y agonist MeSATP inhibited superoxide production. Nitric oxide synthase (NOS) inhibition by L-NAME blocked vascular relaxation and reduced superoxide production in LPS-treated animals. In the presence of L-NAME there was no ATP effect on superoxide production. A vascular reactivity study showed that ATP increased maximal relaxation in LPS-treated animals compared to controls. The presence of ATP induced increases in Akt and endothelial NOS phosphorylated proteins in the aorta of septic animals. ATP reduces superoxide release resulting in an improved vasorelaxant response. Sepsis may uncouple NOS to produce superoxide. We showed that ATP through Akt pathway phosphorylated endothelial NOS and "re-couples" NOS function.

Liver mitochondrial dysfunction and oxidative stress in the pathogenesis of experimental nonalcoholic fatty liver disease.

Oxidative stress and hepatic mitochondria play a role in the pathogenesis of nonalcoholic fatty liver disease. The aim of the present study was to evaluate the role of hepatic mitochondrial dysfunction and oxidative stress in the pathogenesis of the disease. Fatty liver was induced in Wistar rats with a choline-deficient diet (CD; N = 7) or a high-fat diet enriched with PUFAs-omega-3 (H; N = 7) for 4 weeks. The control group (N = 7) was fed a standard diet. Liver mitochondrial oxidation and phosphorylation were measured polarographically and oxidative stress was estimated on the basis of malondialdehyde and glutathione concentrations. Moderate macrovacuolar liver steatosis was observed in the CD group and mild liver steatosis was observed in the periportal area in the H group. There was an increase in the oxygen consumption rate by liver mitochondria in respiratory state 4 (S4) and a decrease in respiratory control rate (RCR) in the CD group (S4: 32.70 +/- 3.35; RCR: 2.55 +/- 0.15 ng atoms of O2 min-1 mg protein-1) when compared to the H and control groups (S4: 23.09 +/- 1.53, 17.04 +/- 2.03, RCR: 3.15 +/- 0.15, 3.68 +/- 0.15 ng atoms of O2 min-1 mg protein-1, respectively), P < 0.05. Hepatic lipoperoxide concentrations were significantly increased and the concentration of reduced glutathione was significantly reduced in the CD group. A choline-deficient diet causes moderate steatosis with disruption of liver mitochondrial function and increased oxidative stress. These data suggest that lipid peroxidation products can impair the flow of electrons along the respiratory chain, causing overreduction of respiratory chain components and enhanced mitochondrial reactive oxygen species. These findings are important in the pathogenesis of nonalcoholic fatty liver disease.

Liver mitochondrial dysfunction and oxidative stress in the pathogenesis of experimental nonalcoholic fatty liver disease

Oxidative stress and hepatic mitochondria play a role in the pathogenesis of nonalcoholic fatty liver disease. The aim of the present study was to evaluate the role of hepatic mitochondrial dysfunction and oxidative stress in the pathogenesis of the disease. Fatty liver was induced in Wistar rats with a choline-deficient diet (CD; N = 7) or a high-fat diet enriched with PUFAs-omega-3 (H; N = 7) for 4 weeks. The control group (N = 7) was fed a standard diet. Liver mitochondrial oxidation and phosphorylation were measured polarographically and oxidative stress was estimated on the basis of malondialdehyde and glutathione concentrations. Moderate macrovacuolar liver steatosis was observed in the CD group and mild liver steatosis was observed in the periportal area in the H group. There was an increase in the oxygen consumption rate by liver mitochondria in respiratory state 4 (S4) and a decrease in respiratory control rate (RCR) in the CD group (S4: 32.70 ± 3.35; RCR: 2.55 ± 0.15 ng atoms of O2 min-1 mg protein-1) when compared to the H and control groups (S4: 23.09 ± 1.53, 17.04 ± 2.03, RCR: 3.15 ± 0.15, 3.68 ± 0.15 ng atoms of O2 min-1 mg protein-1, respectively), P < 0.05. Hepatic lipoperoxide concentrations were significantly increased and the concentration of reduced glutathione was significantly reduced in the CD group. A choline-deficient diet causes moderate steatosis with disruption of liver mitochondrial function and increased oxidative stress. These data suggest that lipid peroxidation products can impair the flow of electrons along the respiratory chain, causing overreduction of respiratory chain components and enhanced mitochondrial reactive oxygen species. These findings are important in the pathogenesis of nonalcoholic fatty liver disease.

The effect of chronic nitric oxide inhibition on vascular reactivity and blood pressure in pregnant rats.

CONTEXT: The exact mechanism involved in changes in blood pressure and peripheral vascular resistance during pregnancy is unknown. OBJECTIVE: To evaluate the importance of endothelium-derived relaxing factor (EDRF) and its main component, nitric oxide, in blood pressure and vascular reactivity in pregnant rats. DESIGN: Clinical trial in experimentation animals. SETTING: University laboratory of Pharmacology. SAMPLE: Female Wistar rats with normal blood pressure, weight (152 to 227 grams) and age (90 to 116 days). INTERVENTION: The rats were divided in to four groups: pregnant rats treated with L-NAME (13 rats); pregnant control rats (8 rats); virgin rats treated with L-NAME (10 rats); virgin control rats (12 rats). The vascular preparations and caudal blood pressure were obtained at the end of pregnancy, or after the administration of L-NAME in virgin rats. MAIN MEASUREMENTS: The caudal blood pressure and the vascular response to acetylcholine in pre-contracted aortic rings, both with and without endothelium, and the effect of nitric oxide inhibition, Nw-L-nitro-arginine methyl-ester (L-NAME), in pregnant and virgin rats. The L-NAME was administered in the drinking water over a 10-day period. RESULTS: The blood pressure decreased in pregnancy. Aortic rings of pregnant rats were more sensitive to acetylcholine than those of virgin rats. After L-NAME treatment, the blood pressure increased and relaxation was blocked in both groups. The fetal-placental unit weight of the L-NAME group was lower than that of the control group. CONCLUSION: Acetylcholine-induced vasorelaxation sensitivity was greater in pregnant rats and that blood pressure increased after L-NAME administration while the acetylcholine-induced vasorelaxation response was blocked.

Nonspecific blockade of vascular free radical signals by methylated arginine analogues.

Methylated arginine analogues are often used as probes of the effect of nitric oxide; however, their specificity is unclear and seems to be frequently overestimated. This study analyzed the effects of NG-methyl-L-arginine (L-NMMA) on the endothelium-dependent release of vascular superoxide radicals triggered by increased flow. Plasma ascorbyl radical signals measured by direct electron paramagnetic resonance spectroscopy in 25 rabbits increased by 3.8 +/- 0.7 nmol/l vs baseline (28.7 +/- 1.4 nmol/l, P < 0.001) in response to papaverine-induced flow increases of 121 +/- 12%. In contrast, after similar papaverine-induced flow increases simultaneously with L-NMMA infusions, ascorbyl levels were not significantly changed compared to baseline. Similar results were obtained in isolated rabbit aortas perfused ex vivo with the spin trap alpha-phenyl-N-tert-butylnitrone (N = 22). However, in both preparations, this complete blockade was not reversed by co-infusion of excess L-arginine and was also obtained by N-methyl-D-arginine, thus indicating that it is not related to nitric oxide synthase. L-arginine alone was ineffective, as previously demonstrated for NG-methyl-L-arginine ester (L-NAME). In vitro, neither L-arginine nor its analogues scavenged superoxide radicals. This nonspecific activity of methylated arginine analogues underscores the need for careful controls in order to assess nitric oxide effects, particularly those related to interactions with active oxygen species.

Nonspecific blockade of vascular free radical signals by methylated arginine analogues

Methylated arginine analogues are often used as probes of the effect of nitric oxide; however, their specificity is unclear and seems to be frequently overestimated. This study analyzed the effects of N G -methyl-L-arginine (L-NMMA) on the endothelium-dependent release of vascular superoxide radicals triggered by increased flow. Plasma ascorbyl radical signals measured by direct electron paramagnetic resonance spectroscopy in 25 rabbits increased by 3.8 ñ 0.7 nmol/l vs baseline (28.7 ñ 1.4 nmol/l, P<0.001) in response to papaverine-induced flow increases of 121 ñ 12 por cento. In contrast, after similar papaverine-induced flow increases simultaneously with L-NMMA infusions, ascorbyl levels were not significantly changed compared to baseline. Similar results were obtained in isolated rabbit aortas perfused ex vivo with the spin trap Ó-phenyl-N- tert -butylnitrone (N = 22). However, in both preparations, this complete blockade was not reversed by co-infusion of excess L-arginine and was also obtained by N-methyl-D-arginine, thus indicating that it is not related to nitric oxide synthase. L-arginine alone was ineffective, as previously demonstrated for N G -methyl-L-arginine ester (L-NAME). In vitro , neither L-arginine nor its analogues scavenged superoxide radicals. This nonspecific activity of methylated arginine analogues underscores the need for careful controls in order to assess nitric oxide effects, particularly those related to interactions with active oxygen species

Sex-related differences in the response of spontaneously hypertensive rats to angiotensin-converting enzyme inhibitor.

We have compared the endothelium-dependent responses of thoracic aortic rings obtained from age-matched male and female SHR in order to explore gender differences in the effectiveness of antihypertensive drug therapy in correcting the endothelial dysfunction found in these animals. For this, concentration-effect curves to acetylcholine and sodium nitroprusside were obtained using aortic rings with and without endothelium isolated from male and female rats which had or had not been pre-treated with enalapril for 72 h (acute) or 15 d (chronic). The maximal responses achieved and the EC50s were determined. The blood pressure of male and female spontaneously hypertensive rats (SHR) decreased to normal levels within 72 h of initiating treatment with enalapril and remained normal during the remainder of the treatment period (15 d). However, enalapril was not effective in restoring a normal blood pressure in all of the male and female SHR. Female SHR were more responsive to enalapril after both acute and chronic treatment (70% of the females and 45% of the males became normotensive). Enalapril corrected the decreased response to acetylcholine in male but not in female SHR. An increased sensitivity to sodium nitroprusside, an endothelium-independent vasodilator, was observed after acute or chronic treatment with enalapril in aortic rings with endothelium from male SHR. Indomethacin restored the decreased response to acetylcholine in aortic rings from enalapril-treated females and potentiated the response to acetylcholine in aortic rings from treated male SHR. We conclude that: a) there are significant differences in the responses of male and female SHR to enalapril, b) the imbalance in endothelium-dependent relaxing and contracting factors in SHR is corrected by enalapril in male but not in female SHR, c) correction of the endothelial dysfunction probably occurs independently of the normalization of blood pressure levels and appears to be gender-dependent.

Vascular free radical release. Ex vivo and in vivo evidence for a flow-dependent endothelial mechanism.

Mechanisms underlying production of vascular free radicals are unclear. We hypothesized that changes in blood flow might serve as a physiological stimulus for endothelial free radical release. Intact isolated aortas from 45 rabbits were perfused with the spin trap alpha-phenyl-N-tert-butylnitrone (PBN, 20 mmol/L) and formed radical adducts detected by electron paramagnetic resonance spectroscopy (EPR). Sequential perfusion at 2, 7.5, and 12 mL/min changed cumulative vascular PBN radical adduct yields, respectively, from 3.2 +/- 0.9 to 4.1 +/- 0.7 (P < .05) and 7.0 +/- 1.5 (P < .005) pmol/mg with endothelium and from 3.6 +/- 1.6 to 3.8 +/- 1.4 and 2.2 +/- 0.8 pmol/mg without endothelium (P = NS). In endothelialized aortas, superoxide dismutase (SOD) completely blocked flow-induced free radical production, whereas inactivated SOD, indomethacin, and the nitric oxide synthetase antagonist nitro-L-arginine methyl ester (L-NAME) had no effect; relaxations to acetylcholine remained unchanged with higher flows. To assess the role of flow on in vivo radical production, femoral arterial plasma levels of the ascorbyl radical, a stable ascorbate oxidation product, were measured by direct EPR in 56 other rabbits. Ascorbyl levels were assessed at baseline (30.2 +/- 0.7 nmol/L) and at peak-induced iliac flow changes. Flow increases from 25% to 100% due to saline injections through an extracorporeal aortic loop induced significant dose-dependent increases in ascorbyl levels (n = 5). In addition, after papaverine bolus injections, flow increased by 114 +/- 8% versus baseline, and ascorbyl levels increased by 5.4 +/- 0.7 nmol/L (n = 31, P < .001); similar results occurred with adenosine, isoproterenol, or hyperemia after 30-second occlusions (P < .05, n = 4 or 5 in each group). Active SOD completely blocked papaverine-induced ascorbyl radical increase, despite preserved flow response (delta ascorbyl = 0.02 +/- 1.6 nmol/L, P = NS); inactivated SOD, catalase, indomethacin, and L-NAME had no effect. Blood flow decreases of 65% to 100% due to phenylephrine or 60-second balloon occlusions were accompanied by an average decrease of 4.4 nmol/L (P < .05) in ascorbyl levels. No change in ascorbyl signal was observed when rabbit blood alone was submitted to in vitro flow increases through a tubing circuit. Thus, increases in blood flow trigger vascular free radical generation; such a response seems to involve endothelium-derived superoxide radicals unrelated to cyclooxygenase or nitric oxide synthetase activities. This mechanism may contribute to explain vascular free radical generation in physiological or pathological circumstances.

Comparison of the effect of endothelin on microvessels and macrovessels in Goldblatt II and deoxycorticosterone acetate-salt hypertensive rats.

The response to endothelin, a novel 21-amino acid peptide, is investigated in isolated aortas with and without endothelium and in mesenteric microvessels in vivo-in situ, in Goldblatt II (GII) and deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Median effective concentrations and maximal responses to endothelin did not differ in aortas with endothelium isolated from GII, DOCA-salt hypertensive, and control rats. After removal of the endothelium, the potentiation of the aorta responses to endothelin was of the same magnitude in hypertensive and control rats. A closed-circuit television system was used to observe the microvascular bed of the exteriorized mesentery of anesthetized GII, DOCA-salt hypertensive, and control rats. The time necessary to induce a vasoconstrictor response was determined after the topical application of endothelin. Vessel diameters at rest and after endothelin application were also estimated. At the microcirculatory level, a greater reactivity to endothelin was observed in both hypertensive rat groups, whereas higher sensitivity to endothelin was recorded in the GII hypertensive microvessel preparations alone. It is suggested that the increased response to endothelin observed in hypertensive rats might be due to abnormal sensitivity or reactivity of the microvessels of these rats reflecting an alteration of the contractile sequence possibly at the plasma membrane level, or due to both. Endothelial dysfunction at the microcirculatory level, however, cannot be dismissed.