Effect of Calcineurin Inhibitors on Low-Density Lipoprotein Oxidation

Restoration of HMGCS2-mediated ketogenesis alleviates tacrolimus-induced hepatic lipid metabolism disorder

Tacrolimus, one of the macrolide calcineurin inhibitors, is the most frequently used immunosuppressant after transplantation. Long-term administration of tacrolimus leads to dyslipidemia and affects liver lipid metabolism. In this study, we investigated the mode of action and underlying mechanisms of this adverse reaction. Mice were administered tacrolimus (2.5 mg·kg-1·d-1, i.g.) for 10 weeks, then euthanized; the blood samples and liver tissues were collected for analyses. We showed that tacrolimus administration induced significant dyslipidemia and lipid deposition in mouse liver. Dyslipidemia was also observed in heart or kidney transplantation patients treated with tacrolimus. We demonstrated that tacrolimus did not directly induce de novo synthesis of fatty acids, but markedly decreased fatty acid oxidation (FAO) in AML12 cells. Furthermore, we showed that tacrolimus dramatically decreased the expression of HMGCS2, the rate-limiting enzyme of ketogenesis, with decreased ketogenesis in AML12 cells, which was responsible for lipid deposition in normal hepatocytes. Moreover, we revealed that tacrolimus inhibited forkhead box protein O1 (FoxO1) nuclear translocation by promoting FKBP51-FoxO1 complex formation, thus reducing FoxO1 binding to the HMGCS2 promoter and its transcription ability in AML12 cells. The loss of HMGCS2 induced by tacrolimus caused decreased ketogenesis and increased acetyl-CoA accumulation, which promoted mitochondrial protein acetylation, thereby resulting in FAO function inhibition. Liver-specific HMGCS2 overexpression via tail intravenous injection of AAV8-TBG-HMGCS2 construct reversed tacrolimus-induced mitochondrial protein acetylation and FAO inhibition, thus removing the lipid deposition in hepatocytes. Collectively, this study demonstrates a novel mechanism of liver lipid deposition and hyperlipidemia induced by long-term administration of tacrolimus, resulted from the loss of HMGCS2-mediated ketogenesis and subsequent FAO inhibition, providing an alternative target for reversing tacrolimus-induced adverse reaction.

Adverse Drug Events after Kidney Transplantation

Introduction: Kidney transplantation stands out as the optimal treatment for patients with end-stage kidney disease, provided they meet specific criteria for a secure outcome. With the exception of identical twin donor-recipient pairs, lifelong immunosuppression becomes imperative. Unfortunately, immunosuppressant drugs, particularly calcineurin inhibitors like tacrolimus, bring about adverse effects, including nephrotoxicity, diabetes mellitus, hypertension, infections, malignancy, leukopenia, anemia, thrombocytopenia, mouth ulcers, dyslipidemia, and wound complications. Since achieving tolerance is not feasible, patients are compelled to adhere to lifelong immunosuppressive therapies, often involving calcineurin inhibitors, alongside mycophenolic acid or mTOR inhibitors, with or without steroids. Area covered: Notably, these drugs, especially calcineurin inhibitors, possess narrow therapeutic windows, resulting in numerous drug-related side effects. This review focuses on the prevalent immunosuppressive drug-related side effects encountered in kidney transplant recipients, namely nephrotoxicity, post-transplant diabetes mellitus, leukopenia, anemia, dyslipidemia, mouth ulcers, hypertension, and viral reactivations (cytomegalovirus and BK virus). Additionally, other post-kidney-transplantation drugs such as valganciclovir may also contribute to adverse events such as leukopenia. For each side effect, we propose preventive measures and outline appropriate treatment strategies.

Cardiovascular effects of immunosuppression agents

Immunosuppressive medications are widely used to treat patients with neoplasms, autoimmune conditions and solid organ transplants. Key drug classes, namely calcineurin inhibitors, mammalian target of rapamycin (mTOR) inhibitors, and purine synthesis inhibitors, have direct effects on the structure and function of the heart and vascular system. In the heart, immunosuppressive agents modulate cardiac hypertrophy, mitochondrial function, and arrhythmia risk, while in vasculature, they influence vessel remodeling, circulating lipids, and blood pressure. The aim of this review is to present the preclinical and clinical literature examining the cardiovascular effects of immunosuppressive agents, with a specific focus on cyclosporine, tacrolimus, sirolimus, everolimus, mycophenolate, and azathioprine.

Potential Effects of Immunosuppression on Oxidative Stress and Atherosclerosis in Kidney Transplant Recipients

Chronic kidney disease is a public health problem that, depending on the country, affects approximately 8-13% of the population, involving both males and females of all ages. Renal replacement therapy remains one of the most costly procedures. It is assumed that one of the factors influencing the course of chronic kidney disease might be oxidative stress. It is believed that the main mediators of oxidative stress are reactive oxygen species (ROS). Transiently increased concentrations of ROS play a significant role in maintaining an organism's homeostasis, as they are part of the redox-related signaling, and in the immune defense system, as they are produced in high amounts in inflammation. Systemic oxidative stress can significantly contribute to endothelial dysfunction along with exaggeration of atherosclerosis and development of cardiovascular disease, the leading cause of mortality in patients with kidney disease. Moreover, the progression of chronic kidney disease is strictly associated with the atherosclerotic process. Transplantation is the optimal method for renal replacement therapy. It improves better quality of life and prolongs survival compared with hemodialysis and peritoneal dialysis; however, even a successful transplantation does not correct the abnormalities found in chronic kidney disease. As transplantation reduces the concentration of uremic toxins, which are a factor of inflammation per se, both the procedure itself and the subsequent immunosuppressive treatment may be a factor that increases oxidative stress and hence vascular sclerosis and atherosclerotic cardiovascular disease. In the current work, we review the effect of several risk factors in kidney transplant recipients as well as immunosuppressive therapy on oxidative stress.

The circFASN/miR-33a pathway participates in tacrolimus-induced dysregulation of hepatic triglyceride homeostasis

Dyslipidemia exhibits a high incidence after liver transplantation, in which tacrolimus, a widely used immunosuppressant, plays a fundamental role. MicroRNAs and related circRNAs represent a class of noncoding RNAs that have been recognized as important regulators of genes associated with lipid metabolism. However, their transcriptional activities and functional mechanisms in tacrolimus-related dyslipidemia remain unclear. In this study, we observed that tacrolimus could induce triglyceride accumulation in hepatocytes by stimulating sterol response element-binding proteins (SREBPs) and miR-33a. Our in silico and experimental analyses identified miR-33a as a direct target of circFASN. Tacrolimus could downregulate circFASN and result in elevated miR-33a in vivo and in vitro. Overexpression of circFASN or silencing of miR-33a decreased the promoting effects of tacrolimus on triglyceride accumulation. Clinically, the incidence of dyslipidemia in liver transplant recipients with elevated serum miR-33a after liver transplantation was higher than that in patients without elevated serum miR-33a (46.3% vs. 18.8% p = 0.012, n = 73). Our results showed that the circFASN/miR-33a regulatory system plays a distinct role in tacrolimus-induced disruption of lipid homeostasis. MiR-33a is likely a risk factor for tacrolimus-related dyslipidemia, providing a potential therapeutic target to combat tacrolimus-induced dyslipidemia after liver transplantation.

Trained immunity in organ transplantation

Consistent induction of donor-specific unresponsiveness in the absence of continuous immunosuppressive therapy and toxic effects remains a difficult task in clinical organ transplantation. Transplant immunologists have developed numerous experimental treatments that target antigen-presentation (signal 1), costimulation (signal 2), and cytokine production (signal 3) to establish transplantation tolerance. While promising results have been obtained using therapeutic approaches that predominantly target the adaptive immune response, the long-term graft survival rates remain suboptimal. This suggests the existence of unrecognized allograft rejection mechanisms that contribute to organ failure. We postulate that trained immunity stimulatory pathways are critical to the immune response that mediates graft loss. Trained immunity is a recently discovered functional program of the innate immune system, which is characterized by nonpermanent epigenetic and metabolic reprogramming of macrophages. Since trained macrophages upregulate costimulatory molecules (signal 2) and produce pro-inflammatory cytokines (signal 3), they contribute to potent graft reactive immune responses and organ transplant rejection. In this review, we summarize the detrimental effects of trained immunity in the context of organ transplantation and describe pathways that induce macrophage training associated with graft rejection.

Evaluation of Serum Oxidized Low-Density Lipoprotein in Renal Transplant Recipients and Hemodialysis Patients and Relation With Involved Variables

OBJECTIVES

Disturbances in metabolism of lipo-proteins and oxidative modification of low-density lipoprotein contribute to cardiovascular disease and development of oxidative stress in patients under renal replacement therapy (hemodialysis and renal transplant). This study was designed to compare oxidized low-density lipoprotein levels and lipid profiles in renal transplant recipients and hemo-dialysis patients.

MATERIALS AND METHODS

We investigated the concentration of oxidized low-density lipoprotein in hemodialysis (n = 38) and renal transplant (n = 59) patients who had no active inflammatory disease, liver disease, or malignancy, and results were compared to a control group (n = 30).

RESULTS

Renal transplant recipients had hypercholesterolemia, hypertriglyceridemia, and increased oxidized low-density lipoprotein levels (P = .019) compared with the control group. Hemodialysis patients had moderate hypertriglyceridemia (not significant), hypercholesterolemia, decrease in high-density lipoprotein, and increase in oxidized low-density lipoprotein levels (P < .0001) compared with the control group. In the renal transplant group, oxidized low-density lipoprotein level had a negative correlation with the duration after transplant (r = -0.407; P = .026), positive association with cyclosporine level (r = 0.288; P = .04), and negative correlation with high-density lipoprotein level (r = -.30; P = .05); oxidized low-density lipo-protein/high-density lipoprotein ratio also had a positive correlation with cyclosporine level (r = 0.309; P = .027) and negative correlation with high-density lipoprotein level (r = -0.72; P < .001) in the renal transplant group and high-density lipoprotein in the hemodialysis group (r = -0.87; P < .001). Multiple stepwise regression analyses showed that oxidized low-density lipoprotein only was associated with cyclosporine level (R2 = 0.155; β=0.393; P = .024).

CONCLUSIONS

History of cardiovascular disease is the most important factor associated with end-stage renal disease, and high oxidized low-density lipoprotein level, oxidized low-density lipo-protein/high-density lipoprotein ratio, and high-density lipoprotein level may affect cardiovascular disease.

Effects of calcineurin inhibitors on paraoxonase and arylesterase activity after a kidney transplant

OBJECTIVES

Cardiovascular disease is a common cause of morbidity and mortality in patients with chronic kidney failure, before and after a kidney transplant. Oxidation of lipoproteins that contain apolipoprotein B may contribute to the initiation of atherosclerosis. Paraoxonase may prevent cardiovascular disease. We compared the effects of different calcineurin inhibitors on risk factors for cardiovascular disease in kidney transplant recipients.

MATERIALS AND METHODS

In 16 kidney transplant recipients, treatment included tacrolimus in 8 patients and cyclosporine in 8 patients. Hemoglobin, glucose, renal function, lipid parameters, high-sensitivity C-reactive protein, homocysteine, malondialdehyde, paraoxonase activity, and arylesterase activity were measured before transplant and at 1, 6, and 12 months after the transplant.

RESULTS

The levels of homocysteine and malondialdehyde did not change significantly in patients who received either tacrolimus or cyclosporine. The high-sensitivity C-reactive protein was decreased (tacrolimus group, 1 mo) and increased (cyclosporine group, 6 and 12 mo) after the kidney transplant. Paraoxonase activity was increased (tacrolimus group, 1 mo). Arylesterase activity was increased (tacrolimus group, 1, 6, and 12 mo; cyclosporine group, 1 and 6 mo). The percentage of change in arylesterase activity was higher at 12 months in the tacrolimus than in the cyclosporine group.

CONCLUSIONS

Tacrolimus may be more effective than cyclosporine in improving risk factors for cardiovascular disease after kidney transplant.

Changes in oxidative stress in renal graft patients receiving calcineurin inhibitors: cyclosporine versus tacrolimus

OBJECTIVES

The effects of calcineurin inhibitors on oxidative stress after renal transplant are obscure. This study sought to investigate the changes in plasma oxidative stress and lipid levels in patients receiving cyclosporine or tacrolimus before and after renal transplant for 6 months.

MATERIALS AND METHODS

Twenty-one patients and 15 healthy controls were involved in our study. Twelve of the patients were treated with cyclosporine and 9 were treated with tacrolimus. Plasma malondialdehyde, nitrite/nitrate, vitamin C, vitamin E, and plasma glutathione levels, as well as total cholesterol and triglyceride levels, were evaluated before and after transplant for 6 months.

RESULTS

Before the transplant, patients had higher malondialdehyde and plasma glutathione levels than did healthy controls (3.76 ± 0.79 nmol/mL vs 3.21 ± 0.57 nmol/mL; P < .05, and 66.6 ± 23.2 μmol/L vs 43.3 ± 26.9 μmol/L; P < .05). In the overall group of patients, a significant increase in malondialdehyde levels was detected 3 and 6 months after transplant (3.76 ± 0.79 nmol/mL vs 4.38 ± 0.87 nmol/mL in the third month; P = .02; and 3.76 ± 0.79 nmol/mL vs 4.28 ± 0.69 nmol/mL in the sixth month; P = .04). A significant reduction in plasma glutathione levels 1 month after transplant and nitrite/nitrate levels 6 months after transplant was found. No changes in vitamin C and vitamin E levels were detected before and after transplant. After 3 and 6 months of transplant, cyclosporine-treated patients had higher levels of total cholesterol and triglycerides when compared with tacrolimus-treated patients.

CONCLUSIONS

An enhancement in plasma malondialdehyde levels was found after transplant at 6-month follow-up. However, no significant change in vitamin C, vitamin E, nitrite/nitrate levels between patients and controls was recorded. Although both calcineurin inhibitors showed similar effects on oxidative stress, cyclosporine-treated patients had higher levels of total cholesterol and triglycerides.

Stabilization of oxidative stress 1 year after kidney transplantation: effect of calcineurin immunosuppressives

Kidney transplantation (KT) is one of the best treatments for patients with chronic renal disease. It leads to improved kidney function, but the oxidative stress (OS) is only partially eliminated after KT. This study evaluated the effect of KT on outcomes, such as (a) specific kidney functions, (b) metabolic parameters, as well as (c) OS-related markers in 70 patients (46 males, 24 females; mean age = 54 ± 11) before and 1 year after KT. Post KT, the patients were divided into two groups: those receiving only cyclosporine A (N = 36) and those receiving only tacrolimus (N = 34). Improved kidney function (creatinine, urea, and glomerular filtration rate) and biochemical and hematological parameters were found 1 year after KT. OS-related markers (total antioxidant capacity, advanced oxidation protein, and lipid peroxidation products) decreased, but glutathione level increased after KT. Alterations in superoxide dismutase and catalase activities were also found. Glutathione peroxidase levels were unchanged. The level of oxidized low-density lipoprotein was surprisingly, not significantly increased. There was no significant difference between calcineurin inhibitors in any of the measured parameters. Improved renal function after KT is linked to reduction in OS but independent of immunosuppressive therapy.

Quantitative proteomic analysis of cyclosporine-induced toxicity in a human kidney cell line and comparison with tacrolimus

The calcineurin-inhibitors (CNIs) cyclosporine (CsA) and tacrolimus (TAC) remain the pillars of modern immunosuppression regimens used in solid organ transplantation. Nephrotoxicity is an adverse effect that limits their successful use. The precise molecular mechanisms underlying this nephrotoxicity remain unclear. Using SILAC together with LC-MALDI-TOF/TOF, we investigated the CNIs-induced proteomic perturbations in renal cells. Among the 495 proteins quantifiable in both forward and reverse SILAC, 69 displayed CsA-induced perturbations: proteins involved in ER-stress/protein folding, apoptosis, metabolism/transport or cytoskeleton pathways were up-regulated, while cyclophilin B as well as nuclear and RNA-processing proteins were down-regulated. Co-administration of CsA with the antioxidant N-acetylcysteine significantly decreased lipid peroxidation and also partially corrected the CsA-induced unfolded protein response. TAC toxicity profile was apparently different from that of CsA, especially without perturbation of cyclophilins A and B, up-regulation of ER-chaperones nor down-regulation of a number of nuclear proteins. These results provide a new insight and are consistent with recent data regarding the molecular mechanisms of CNIs-induced nephrotoxicity. Our findings offer new directions for future research aiming to identify specific biomarkers of CsA nephrotoxicity.

Association between moderately oxidized low-density lipoprotein and high-density lipoprotein particle subclass distribution in hemodialyzed and post-renal transplant patients

Disturbances in the metabolism of lipoprotein profiles and oxidative stress in hemodialyzed (HD) and post-renal transplant (Tx) patients are proatherogenic, but elevated concentrations of plasma high-density lipoprotein (HDL) reduce the risk of cardiovascular disease. We investigated the concentrations of lipid, lipoprotein, HDL particle, oxidized low-density lipoprotein (ox-LDL) and anti-ox-LDL, and paraoxonase-1 (PON-1) activity in HD (n=33) and Tx (n=71) patients who were non-smokers without active inflammatory disease, liver disease, diabetes, or malignancy. HD patients had moderate hypertriglyceridemia, normocholesterolemia, low HDL-C, apolipoprotein A-I (apoA-I) and HDL particle concentrations as well as PON-1 activity, and increased ox-LDL and anti-ox-LDL levels. Tx patients had hypertriglyceridemia, hypercholesterolemia, moderately decreased HDL-C and HDL particle concentrations and PON-1 activity, and moderately increased ox-LDL and anti-ox-LDL levels as compared to the reference, but ox-LDL and anti-ox-LDL levels and PON-1 activity were more disturbed in HD patients. However, in both patient groups, lipid and lipoprotein ratios (total cholesterol (TC)/HDL-C, LDL-C/HDL-C, triglyceride (TG)/HDL-C, HDL-C/non-HDL-C, apoA-I/apoB, HDL-C/apoA-I, TG/HDL) were atherogenic. The Spearman's rank coefficient test showed that the concentration of ox-LDL correlated positively with HDL particle level (R=0.363, P=0.004), and negatively with TC (R=-0.306, P=0.012), LDL-C (R=-0.283, P=0.020), and non-HDL-C (R=-0.263, P=0.030) levels in Tx patients. Multiple stepwise forward regression analysis in Tx patients demonstrated that ox-LDL concentration, as an independent variable, was associated significantly positively with HDL particle level. The results indicated that ox-LDL and decreased PON-1 activity in Tx patients may give rise to more mildly-oxidized HDLs, which are less stable, easily undergo metabolic remodeling, generate a greater number of smaller pre-β-HDL particles, and thus accelerate reverse cholesterol transport, which may be beneficial for Tx patients. Further studies are necessary to confirm this.

Oxidative stress and 'monocyte reprogramming' after kidney transplant: a longitudinal study

Uremia has been implicated in increased oxidative stress (OS) and decreased monocyte HLA-DR expression in chronic kidney disease (CKD) patients. Thus, one would expect normalization of these parameters after successful kidney transplant (KTx). Our aim was to describe patterns of OS and HLA-DR expression after KTx and to explore the effect of renal function and different immunosuppression regimens. 30 KTx patients (20 male; 48 +/- 11 years) were enrolled and compared with 20 healthy controls. We measured advanced oxidation protein products (AOPP) and the percentage of monocytes expressing HLA-DR (%DR+) before (preKTx) and after KTx (on days 2, 30, 90, 180 and after 1 year). Compared to controls, patients had a higher preKTx AOPP (152.6 vs. 69.3 micromol/l; p < 0.001). AOPP decreased at 48 h after KTx, achieving values similar to controls. Thereafter, it increased again and remained significantly higher compared to controls, returning to preKTx levels at 90 days. Prior to KTx there was a trend for lower %DR+ in KTx patients compared to controls (96 vs. 98%; NS). Following KTx, patients had a lower %DR+ in the 1st month; then it gradually returned to preKTx levels during the 1st year; at no time did it reach a value similar to controls. Cyclosporine (CyA)-treated patients had a significantly higher AOPP (161.5 vs. 99.5 micromol/l; p = 0.03) and a lower %DR+ (91.7 vs. 96.4; p < 0.05) at 30 days than patients on tacrolimus (FK). Patients on mycophenolate mofetil (MMF) showed a low AOPP (106.9 vs. 168.1 micromol/l; p = 0.05) and a high %DR+ (96.7 vs. 88.2%; p = 0.001) than those on everolimus. After 3 months, CyA-treated patients had a non-significant increase in AOPP levels, whereas those on FK showed a decrease (p < 0.05) as did those treated with MMF (p < 0.05). Successful KTx reduced but did not normalize AOPP, suggesting ongoing OS, perhaps due to persistent mild renal dysfunction and the effects of immunosuppression. HLA-DR expression remained low after KTx, which may be a possible contributing factor to infectious complications after transplantation. Immunosuppressive agents appear to have diverse effects on OS and HLA-DR expression.

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.