Cyclosporin A does not increase the oxidative susceptibility of low density lipoprotein in vitro

Cyclosporin A and atherosclerosis--cellular pathways in atherogenesis

Cyclosporin A (CsA) is an immunosuppressant drug widely used in organ transplant recipients and people with autoimmune disorders. Long term treatment with CsA is associated with many side effects including hyperlipidemia and an increased risk of atherosclerosis. While its immunosuppressive effects are closely linked to its effects on T cell activation via the inhibition of the nuclear factor of activated T cells (NFAT) pathway, the precise mechanisms underlying its cardiovascular effects appear to involve multiple pathways additional to those relevant for immunosuppression. These include inhibition of calcineurin activity and intracellular cyclophilin peptidylprolyl isomerase and chaperone activities, inhibition of pro-inflammatory extracellular cyclophilin A, and NFAT-independent transcriptional effects. CsA demonstrates complex effects on lipoprotein metabolism and bile acid production, and affects endothelial cells, smooth muscle cells and macrophages, all of which are critical to the atherosclerotic process. Interpretation of the available data is hampered as many experimental models are used to study the effects of CsA in vivo and in vitro, leading to diverse and often contradictory findings. In this review we will describe the cellular mechanisms related to CsA-induced hyperlipidemia and atherosclerosis, with a focus on identifying pro-atherogenic pathways that are distinct from those relevant to its immunosuppressant effects. The potential of CsA analogues to avoid such sequelae will be discussed.

Oxidized LDL Accumulation in Experimental Renal Ischemia Reperfusion Injury Model

BACKGROUND/AIMS

The aim of this study was to identify oxidative damage of kidney during ischemia reperfusion injury (IRI) by evaluating changes in lipid peroxidation markers in tissue and blood by an experimental model. Oxidized LDL (ox-LDL) was used as an oxidative stress biomarker, whereas paraoxonase (PON-1) activity was used as an antioxidative biomarker.

METHODS

Sixty-three male Wistar rats were randomly assigned into three groups: renal IRI, sham, and control. In the renal IRI group, the right kidney was removed and the artery and vein of the left kidney were clamped for 90 minutes. The presence of ox-LDL in the kidney tissue sections was determined by using an immunofluorescent staining method.

RESULTS

The plasma ox-LDL levels did not increase significantly at the 24th hour following IRI, made a peak at the 48th hour, and declined at the 72nd hour. Accumulation of ox-LDL was detected in the kidney tissue on the 24th, 48th, and 72nd hours of the renal IRI. Serum PON-1 levels have peaked on the 24th hour and then declined.

CONCLUSION

This study demonstrates the accumulation of ox-LDL molecules in the renal tissues of the IRI model. Future strategies aimed to reduce the lipid peroxidation during the initial hours of renal IRI may be useful to prevent complications of ischemia.

Hyperlipidemia in Iranian liver transplant recipients: prevalence and risk factors

BACKGROUND

Hyperlipidemia is a metabolic complication after liver transplantation (LT). The aim of this study was to investigate the prevalence and risk factors for developing hyperlipidemia in patients who underwent LT in the Shiraz Organ Transplantation Center.

METHODS

Our patients were 170 liver recipients who underwent LT from 1994 to 2006 in the Organ Transplantation Center of the Shiraz University of Medical Sciences. To perform this study we administered questionnaires, including information about age, sex, body mass index (BMI), underlying liver disease, graft type, immunosuppressive medications, and serum levels of triglycerides and cholesterol, before and 6 months after LT. Serum triglyceride and cholesterol levels were considered elevated if they were >150 mg/dl and >250 mg/dl, respectively. Data were analyzed with SPSS software.

RESULTS

There were 108 male and 62 female patients, with a mean age of 31.4 +/- 13.3 years, and the mean duration of follow-up was 25.9 +/- 23.5 months. The average pretransplant serum triglyceride and cholesterol (mean of individual means) levels were 104.6 +/- 73.2 and 109.5 +/- 51.5 mg/dl, respectively, and the average posttransplant levels were 230.1 +/- 131 and 185 +/- 77 mg/dl, respectively. Six months after LT, 119 (70%) and 26 (15.3%) patients developed hypertriglyceridemia and hypercholesterolemia, respectively. Age, sex, BMI, and underlying liver disease were not predictors of hypertriglyceridemia or hypercholesterolemia (P > 0.05). Posttransplant hypertriglyceridemia was significantly more common in patients receiving tacrolimus than in those receiving cyclosporine (P = 0.040), but posttransplant hypercholesterolemia had no significant correlation with type of immune suppression (P > 0.05).

CONCLUSIONS

Hyperlipidemia was common after LT, and hypertriglyceridemia was more common than hypercholesterolemia. Among all risk factors, tacrolimus therapy was correlated with development of hypertriglyceridemia after LT.

Antioxidant and anti-inflammatory activities of N-acetyldopamine dimers from Periostracum Cicadae

A known N-acetyldopamine dimer, (2R,3S)-2-(3',4'-dihydroxyphenyl)-3-acetylamino-7-(N-acetyl-2''-aminoethyl)-1,4-benzodioxane (1) and a new N-acetyldopamine dimer, (2R,3S)-2-(3',4'-dihydroxyphenyl)-3-acetylamino-7-(N-acetyl-2''-aminoethylene)-1,4-benzodioxane (2) were isolated from the methanolic extracts of Periostracum Cicadae. Compounds 1 and 2 inhibited the Cu2+ -mediated, 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH)-mediated, and 3-morpholinosydnonimine (SIN)-1-mediated LDL oxidation in the thiobarbituric acid-reactive substances (TBARS) assay. The antioxidant activities of 1 and 2 were tested with respect to other parameters, such as lag time of conjugated diene formation, relative electrophoretic mobility (REM), and apoB-100 fragmentation on copper-mediated LDL-oxidation. Compounds 1 and 2 also showed 1,1-diphenyl-2-picrylhydrasyl (DPPH) radical scavenging activity. Compound 2 was more efficient than compound 1 at inhibiting the reactive oxygen species (ROS) generation, nitric oxide (NO) production, and nuclear factor-kappaB (NF-kappaB) activity as well as the expression of pro-inflammatory molecules such as inducible nitric oxide synthase (iNOS), interleukin (IL)-6, tumor necrosis factor (TNF)-alpha, and cyclooxygenase (COX)-2 in LPS-induced RAW264.7 cells.

Antioxidant activities of abietane diterpenoids isolated from Torreya nucifera leaves

Investigation on antioxidant compounds from the ethanolic extracts of Torreya nucifera leaves resulted in the isolation of abietane diterpenoids, a known 18-methylesterferruginol (1) and a new 18-dimethoxyferruginol (2). The structures of compounds 1 and 2 were elucidated on the basis of their spectroscopic analyses. Compounds 1 and 2 inhibited the Cu2+-mediated, 2,2'-azobis(2-amidinopropane)hydrochloride-mediated and 3-morpholinosydnonimine-1-mediated low-density lipoprotein (LDL) oxidation in the thiobarbituric acid-reactive substances assay as well as the macrophage-mediated LDL oxidation. Compounds 1 and 2 exhibited the potent antioxidant activities in the conjugated diene production, relative electrophoretic mobility, and apoB-100 fragmentation on copper-mediated LDL oxidation. Compound 1 also suppressed nitric oxide production and inducible nitric oxide synthase expression in lipopolysaccharide-stimulated RAW264.7 cells.

Antioxidant Effects of Quinoline Alkaloids and 2,4-Di-tert-butylphenol Isolated from Scolopendra subspinipes

The oxidized low-density lipoprotein (ox-LDL) plays a critical role at the early stages of atherosclerosis. Thus, the prevention of LDL-oxidation by antioxidants may arrest the progression of atherosclerosis. Two quinoline alkaloids, 3,8-dihydroxyquinoline (1) and 2,8-dihydroxy-3,4-dimethoxyquinoline (3), and 2,4-di-tert-butylphenol (2) were isolated from the dried body of Scolopendra subspinipes. Compounds 1-3 exhibited antioxidant activities on copper-mediated (1: IC50=2.6 microM, 2: IC50=8.2 microM, 3: IC50=63.0 microM), AAPH-mediated oxidation (1: IC50=3.9 microM, 2: IC50=9.9 microM, 3: IC50=71.8 microM), and SIN-1-mediated oxidation (1: 70%, 2: 52%, 3: 29% at 5.0 microM) in the TBARS assay. The antioxidant activities of compounds 1-3 were tested with respect to other parameters, such as the lag time of conjugated diene fromation, relative electrophoretic mobility (REM) of ox-LDL, and apoB-100 fragmentation on copper-mediated LDL-oxidation. In addition, compounds 1-3 showed 1,1-diphenyl-2-picrylhydrasyl (DPPH) radical scavenging activity and compound 1 also exhibited metal chelating activity.

Effect of Calcineurin Inhibitors on Low-Density Lipoprotein Oxidation

INTRODUCTION

Low-density lipoprotein (LDL) oxidation is considered a key factor in the biological processes that trigger and accelerate atherosclerosis. Reported data suggest that tacrolimus improves the lipid profile in renal transplant recipients.

OBJECTIVE

The objective of this study was to analyze the effect of converting from cyclosporine to tacrolimus on lipoprotein oxidation in renal transplant recipients.

METHODS

We studied a group of 12 recipients (6 men and 6 women of mean age 55 +/- 11 years) treated with a cyclosporine-mycophenolate mofetil (MMF)-prednisone combination that was converted to tacrolimus-MMF-prednisone because of gingival hyperplasia. The LDL fraction was isolated by density-gradient ultracentrifugation. Oxidative stress was studied before converting (baseline) and at 6 and 12 weeks, thereafter by in vivo oxidation analysis of LDL, a direct assay of oxidized LDL (oxLDL) and oxLDL autoantibodies (Ab-oxLDL) using enzyme-immunoassay techniques. We measured total cholesterol (TC), triglyceride, LDL-cholesterol, high-density lipoprotein (HDL)-cholesterol, ApoA1, ApoB, and Lp(a) levels.

RESULTS

The change to tacrolimus resulted in significant decreases in TC levels, 213 +/- 30 (B) versus 185 +/- 27 (12s) (P < .01); LDL, 129 +/- 24 (B) versus 104 +/- 14 (12s) (P = .002); and ApoB 98 +/- 15 (B) versus 85 +/- 10 (12s) (P < .01). HDL levels significantly increased (45 +/- 10 vs 48 +/- 10 [12s]; P = .018), whereas oxLDL concentrations decreased significantly after conversion (B) (55.42 +/- 10.61 vs 12s 45.76 +/- 10.21; P < .01). Converting to tacrolimus produced a nonsignificant decrease in Ab-oxLDL (baseline 204.88 +/- 134.49 vs 12s 179.51 +/- 143.54). A correlation was observed between LDL and oxLDL (r = 65, P = .02 [B] and r = 0.7, P = .01 [12s]) but not between oxLDL levels and Ab-oxLDL concentration (r = -0.05, P = .87 [3] and r = -0.1, P = .77 [12s]).

CONCLUSIONS

In renal transplantation, tacrolimus therapy was associated with a better lipid profile and lower in vivo LDL oxidation when compared with cyclosporine treatment.

Insulin resistance, LDL particle size, and LDL susceptibility to oxidation in pediatric kidney and liver recipients

BACKGROUND

Dyslipidemia is common after solid organ transplantation. We have described hypertriglyceridemia in about 50% of our pediatric kidney, and in about 30% of our liver recipients. The aim of the present study was to find out whether this post-transplantation hypertriglyceridemia after pediatric solid organ transplantation is associated with insulin resistance and the occurrence of small, dense low-density lipoprotein (LDL).

METHODS

Fifty kidney and 25 liver recipients (aged 4 to 18 years) on triple immunosuppression, and 181 control children participated in the study for an average of 5.3 and 6.4 years after kidney and liver transplantation (range 1 to 11 years), respectively. Homeostasis model assessments for insulin resistance (HOMA) were calculated and fasting lipoprotein lipid profile, apolipoprotein A-I and B concentrations, LDL particle diameter, and indices of LDL susceptibility to copper-induced oxidation determined.

RESULTS

Kidney patients had significantly higher serum total, high-density, and low-density lipoprotein cholesterol, triglyceride, apolipoprotein A-I and B concentrations than liver patients or control subjects (P < 0.003 for all). HOMA indices higher than the 95th percentile of Canadian normal children were seen in 50.0% of kidney (of liver 41.2%) recipients younger than 11 years, and in 27.3% of older recipients (of liver 37.5%). Smaller sized LDL or LDL of increased oxidizability was not more frequent in patients than in control children.

CONCLUSION

Pediatric kidney recipients had significantly higher lipid and insulin concentrations than healthy control children. Combined hyperlipidemia and features of the dysmetabolic syndrome were common in children after kidney and liver transplantation. However, no small, dense LDL, or LDL prone to oxidation was seen in either group.

Effect of immunosuppressive agents on long-term survival of renal transplant recipients: focus on the cardiovascular risk

In the control of acute rejection, attention is being focused more and more on the long-term adverse effects of the immunosuppressive agents used. Since cardiovascular disease is the main cause of death in renal transplant recipients, optimal control of cardiovascular risk factors is essential in the long-term management of these patients. Unfortunately, several commonly used immunosuppressive drugs interfere with the cardiovascular system. In this review, the cardiovascular adverse effects of the immunosuppressive agents currently used for maintenance immunosuppression are thoroughly discussed. Optimising immunosuppression means finding a balance between efficacy and safety. Corticosteroids induce endothelial dysfunction, hypertension, hyperlipidaemia and diabetes mellitus, and impair fibrinolysis. The use of corticosteroids in transplant recipients is undesirable, not only because of their cardiovascular effects, but also because they induce such adverse effects as osteoporosis, obesity, and atrophy of the skin and vessel wall. Calcineurin inhibitors are the most powerful agents for maintenance immunosuppression. The calcineurin inhibitor ciclosporin (cyclosporine) not only induces these same adverse effects as corticosteroids but is also nephrotoxic. Tacrolimus has a more favourable cardiovascular risk profile than ciclosporin and is also less nephrotoxic. It has little or no effect on blood pressure and serum lipids; however, its diabetogenic effect is more prominent in the period immediately following transplantation, although at maintenance dosages, the diabetogenic effect appears to be comparable to that of ciclosporin. The diabetogenic effect of tacrolimus can be managed by reducing the dose of tacrolimus and early corticosteroid withdrawal. The effect of tacrolimus on endothelial function has not been completely elucidated. The proliferation inhibitors azathioprine and mycophenolate mofetil (MMF) have little effect on the cardiovascular system. Yet, indirectly, by inducing anaemia, they may lead to left ventricular hypertrophy. MMF is an attractive alternative to azathioprine because of its higher potency and possibly lower risk of malignancies. Sirolimus also induces anaemia, but may be promising because of its antiproliferative features. Whether the hyperlipidaemia induced by sirolimus counteracts its beneficial effects is, as yet, unknown. It may be combined with MMF, however, initial attempts resulted in severe mouth ulcers.

Studies of LDL particle size and susceptibility to oxidation and association with glucose metabolism in children after heart transplantation

BACKGROUND

Increased concentrations of serum triglyceride and low-density lipoprotein (LDL) cholesterol are common after heart transplantation (HTx). These abnormalities may promote transplant vascular disease and atherosclerosis, especially if LDL is small, dense, and oxidized. There have been no previous studies of LDL particle size and LDL susceptibility to oxidation in children after HTx.

METHODS

Twenty-three HTx recipients (aged 3-19 years) who received triple-drug immunosuppression therapy after HTx and 181 controls within the same age range participated in the study. Total, high-density lipoprotein, and LDL-cholesterol concentrations; triglyceride concentration, and glucose and insulin concentrations during oral glucose tolerance tests were determined an average of 3 years after HTx (range, 1-7 years). Moreover, we determined serum lipoprotein (a) concentration, apolipoprotein E phenotype, LDL particle size, and indices of LDL susceptibility to copper-induced oxidation in 12 HTx recipients.

RESULTS

We found hypertriglyceridemia in 56.5% and hyperinsulinemia in 30.4% of patients. Triglyceride concentration and body mass index were associated significantly with insulin concentration (p < 0.008 for both). Low-density lipoprotein particle size, LDL susceptibility to in vitro oxidation, and lipoprotein (a) concentrations did not differ significantly between HTx patients and controls. Low-density lipoprotein particle size was associated inversely with cyclosporine through level (Neoral, r = -0.59, p = 0.045), whereas weight-adjusted dosage of cyclosporine correlated positively with longer lag time of LDL oxidation (r = 0.69, p = 0.013).

CONCLUSIONS

Hypertriglyceridemia and hyperinsulinemia were common in children receiving triple-drug immunosuppression therapy after HTx. Increased cyclosporine through concentration was associated with small LDL particle size but did not increase LDL susceptibility to oxidation.