Influence of FK506 on experimental atherosclerosis in cholesterol-fed rabbits

The effect of hyperlipidemia on bone graft regeneration of peri-implantal created defects in rabbits

Aim

It is reported that hyperlipidemia affects quality and density of bone and adversely affects wound healing. The effect of hyperlipidemia on implant osseointegration and peri-implant defect regeneration has not been fully explained. The purpose of this study was to examine the effects of hyperlipidemia on the healing potential of the materials used for peri-implant bone regeneration and implant stability.

Materials and methods

Twelve male, New Zealand rabbits were used in this study. Half of the rabbits were fed a 2% cholesterol diet for 8 weeks to induce hypercholesterolemia. Peri-implant defects (7 mm diameter) were created in the tibias of rabbits and placed implants (3.3 mm in diameter). This study was conducted as a split-mouth design. Animals were randomly divided into two groups: (1) hypercholesterol+autogenous graft group and hypercholesterol+xenograft group (n = 6), and (2) autogenous graft and xenograft groups as controls (n = 6). At 8 weeks after surgery, the rabbits were euthanized. During implant surgery and at 8 weeks, implant stability was measured with resonance frequency analysis (RFA values). Bone-to-implant contact (BIC) was analyzed via histomorphometric analysis.

Results

Hyperlipidemic groups showed significantly lower BIC values than those of the control groups at 8 weeks (p < 0.05). According to baseline RFA readings, there was no significant difference between control and hyperlipidemic groups (p ˃ 0.05). The hypercholesterol+autogenous graft group had significantly lower RFA readings and BIC values than the hypercholesterol+xenograft group at 8 weeks (p < 0.05).

Conclusion

Within the limitations of this study, it was found that hyperlipidemia may negatively affect the implant stability especially in the autogenous group and also, may decrease peri-implant bone regeneration. However, further studies are necessary to confirm these results more.

Sphingomyelin synthase 2 over-expression induces expression of aortic inflammatory biomarkers and decreases circulating EPCs in ApoE KO mice

AIMS

This study sought to assess the effect of sphingomyelin synthase 2 (SMS2) over-expression on plaque component and endothelial dysfunction in atherosclerosis.

MAIN METHODS

We generated recombinant adenovirus vectors containing human SMS2 cDNA (AdV-SMS2) or control gene GFP cDNA (AdV-GFP). Both AdVs were injected (i.v.) into ApoE KO mice to establish SMS2 over-expressing and control mice models, respectively. The mice were fed a high fat diet for 30 days. We then examined their plasma lipid levels, expression levels of aortic inflammatory biomarkers critical for the plaque's stability, and numbers of peripheral endothelial progenitor cells (EPC).

KEY FINDINGS

Compared with the control mice, SMS2 over-expression had significantly (1) increased aortic matrix metalloproteinase-2 (MMP-2), monocyte chemoattractant protein-1 (MCP-1), tissue factor (TF) and cyclooxygenase-2 (COX-2) mRNA levels (1.9-fold, 2.2-fold, 2.6-fold and 3.2-fold, respectively, P<0.01) and protein levels (2.2-fold, 1.9-fold, 1.9-fold and 2.1-fold, respectively, P<0.01); (2) increased MMP-2, COX-2 in situ expression in aortic root (2.6-fold and 2.3-fold, respectively, P<0.01); (3) decreased aortic COX-1 mRNA levels (65%, P<0.01) and protein levels (64%, P<0.01); and (4) decreased CD34/KDR-positive cells (33%, P<0.01), circulating angiogenic cells (CACs) (50%, P<0.05), and colony forming units (CFUs) (40%, P<0.05) in circulation.

SIGNIFICANCE

SMS2 over-expression was probably associated with increased expression of aortic inflammatory biomarkers, as well as decreased numbers of CD34/KDR-positive cells, CACs and CFUs in circulation. Therefore, SMS2 over-expression might correlate with endothelial dysfunction and aggravate atherosclerotic plaque instability in ApoE KO mice.

Effects of immunomodulatory drugs on plasma inflammatory markers in a rabbit model of atherosclerosis

Atherosclerosis is a chronic disease of the arterial wall where both innate and adaptive immuno-inflammatory mechanisms are involved. Inflammatory cytokines are implicated in the development and progression of atherosclerotic lesions. Immunomodulatory therapies have been proposed for the treatment of atherosclerosis. Therefore, the aim of this study was to investigate the systemic anti-inflammatory and immunomodulatory effects of atorvastatin, cyclosporine A (CsA), and tacrolimus (FK506) on plasma inflammatory markers in atherosclerotic rabbits. Male New Zealand rabbits were randomized into five groups each of 12 animals. Standard diet-fed group served as control, and the cholesterol-fed group received a diet supplemented with 1% cholesterol alone, cholesterol + atorvastatin, cholesterol + FK506, and cholesterol + CsA. Serum levels of lipid profile parameters (triglycerides, cholesterol, and high-density lipoprotein) were measured using colorimetric methods. Serum levels of C-reactive protein (CRP), interleukin-6 (Il-6), and interferon-gamma (INF-γ) were measured in all studied groups using ELISA techniques. Our results revealed a significant decrease (p < 0.001) in the serum levels of lipid profile parameters, CRP, Il-6, and INF-γ in atorvastatin-treated group compared with the cholesterol-fed group. On the other hand, a non-significant difference was observed for the same parameters in either FK506- or CsA-treated groups compared with the cholesterol-fed group. In conclusion, atorvastatin has a systemic anti-inflammatory role that far surpassed the cholesterol reduction effect alone. FK506 or CsA failed to suppress elevated plasma inflammatory markers. Thus, low doses of these two immunomodulating drugs could not have generalized systemic anti-inflammatory or immunosuppressive effects.

Improved outcome with immunosuppressive monotherapy after renal transplantation in Schimke-immuno-osseous dysplasia

SIOD is a multisystem disorder caused by a mutant chromatin remodelling protein. The main clinical findings are spondyloepiphyseal dysplasia with disproportionate growth restriction, defective cellular immunity, and steroid-resistant nephrotic syndrome secondary to biopsy proven FSGS leading to ESRF. Concerning ESRF, kidney transplantation is the therapy of choice since FSGS does not recur in the graft. However, with respect to the underlying immune disorder and the increased susceptibility to life threatening infections, the question of the optimal immunosuppressive therapy after renal transplantation remains unresolved. Under conventional immunosuppressive regimens some SIOD patients have developed severe disseminated cutaneous papilloma virus infections or EBV associated lymphoproliferative disease. We present several cases of children with SIOD (four of five had SMARCAL1 mutations) and monotherapy maintenance immunosuppression after renal transplantation and compare them with 13 patients from the SIOD registry. We have found that post-renal transplantation immunosuppressive monotherapy results in a good outcome with a reduced number of severe infections. Due to the underlying immunodeficiency in SIOD, limited immunosuppression may be possible without increasing the risk of acute or chronic rejection.

Immunization for atherosclerosis

This review summarizes experimental findings that highlight the complex roles of the immune system in atherogenesis. Immune activation can have either proatherogenic or atheroprotective effects. Immune-modulation therapy via an active or passive immunization strategy aims to exploit the atheroprotective aspects of the immune system to modulate atherosclerosis. Several experimental studies have demonstrated that such an approach is feasible and effective, raising the tantalizing possibility that an atheroprotective vaccine can be developed for clinical testing. Several potential immunogens have been identified and tested for their atheroprotective efficacy with variable results. Although several questions such as choice of optimal antigens, choice of most effective adjuvants, the optimal route of administration, durability of effects, and safety remain to be answered, we believe that a vaccine-based approach to manage atherosclerotic cardiovascular disease is a potentially viable paradigm.

Therapeutic potential of VIVIT, a selective peptide inhibitor of nuclear factor of activated T cells, in cardiovascular disorders

Cardiovascular disease is the major cause of death in industrialized nations. Targeted intervention in calcineurin, a calmodulin-dependent, calcium-activated phosphatase and its substrate, nuclear factor of activated T cells (NFAT), was demonstrated to be effective in the treatment of cardiovascular diseases. Although effective in the disruption of calcineurin phosphatase activity, cyclosporin A (CsA) and FK506 also resulted in undesired side effects and toxicity, prompting the discovery of VIVIT, a novel peptide inhibitor. VIVIT selectively and potently inhibits calcineurin/NFAT interaction, but does not compromise calcineurin phosphatase activity and non-NFAT-mediated signaling. VIVIT displays a favorable therapeutic profile as a potential drug candidate and constitutes a useful tool in exploring calcineurin-NFAT functionality. This review describes the development of VIVIT peptide as a selective NFAT inhibitor and its application as a therapeutic agent in cardiovascular disorders including cardiac hypertrophy, restenosis, atherosclerosis, and angiogenesis.

Drug-induced immunomodulation to affect the development and progression of atherosclerosis: a new opportunity?

Inflammation and cytokine pathways are crucial for the development and progression of atherosclerotic lesions. In this review, the hypothesis that immunomodulatory drugs provide a possible therapeutic modality for cardiovascular disease is evaluated. Therefore, after a short overview of the specific inflammatory pathways involved in atherosclerosis, literature on the effect of several immunomodulatory drugs, such as nonsteroidal anti-inflammatory drugs, specific cyclooxygenase inhibitors and immunosuppressive drugs, used currently in the prevention of rejection after organ transplant, on the development and progression of atherosclerosis is reviewed. In addition, the pleiotropic immunomodulatory effect of two established cardiovascular drugs (angiotensin-converting enzyme inhibitors and statins) is discussed.

Low-dose FK506 blocks collar-induced atherosclerotic plaque development and stabilizes plaques in ApoE-/- mice

Since atherosclerosis is a chronic inflammatory disease, we tested the hypothesis that the immunosuppressive drug FK506 would attenuate the development of atherosclerosis using a mouse model of collar-induced atherosclerosis. ApoE-/- mice were treated for 4 weeks with the immunosuppressive drug FK506 (0.05 mg/kg/day), yielding sustained blood levels (approximately 0.2 ng/mL) without systemic side effects. Atherosclerotic plaque development of FK506-treated mice was significantly reduced (63%) while plaque cell density was increased (52%) compared to controls. Importantly, FK506 also blocked progression of pre-existing atherosclerotic plaques. Plaque area of pre-existing plaques was 35% reduced by FK506. Cell density (35%) and collagen content (51%) were significantly increased, whereas necrotic core content was decreased (42%), indicating a more stable plaque morphology. Similar results were found during spontaneous atherosclerotic plaque development in ApoE-/- mice (treatment 17-25 weeks of age). Flow-cytometric analysis showed no peripheral effects on blood cell count or T-cell activation after FK506-treatment. In vitro, FK506 decreased vascular smooth muscle cell (VSMC) apoptosis and inhibited nuclear factor of activated T cells (NFAT)-luciferase reporter activity at concentrations in the range of the in vivo concentration. Low-dose FK506 inhibits collar-induced atherosclerotic plaque development and progression and induces more stable plaque phenotypes in ApoE-/- mice without any peripheral side effects.

MYCOPHENOLATE MOFETIL PREVENTS TRANSPLANT ARTERIOSCLEROSIS BY DIRECT INHIBITION OF VASCULAR SMOOTH MUSCLE CELL PROLIFERATION1

BACKGROUND.: Transplant arteriosclerosis is one of the main features of chronic graft failure in organ transplantation. In this article, the authors investigate mechanisms of mycophenolate mofetil (MMF) on prevention of transplant arteriosclerosis in a rat aortic allograft model.

METHODS

Orthotopic rat abdominal aortic transplantation was performed from Brown Norway (RT1) to Lewis (RT1) rats. The recipients were divided into three oral treatment groups: (1). vehicle; (2). MMF40 (40 mg/kg); and (3). MMF20 (20 mg/kg). The authors histologically and immunohistochemically evaluated neointima formation; infiltration of macrophages and T cells; and expression of endothelin (ET)-1, platelet-derived growth factor (PDGF)-B, PDGF receptor-beta (Rbeta), transforming growth factor (TGF) beta 1, and osteopontin (OPN). Using cultured rat vascular smooth muscle cells (VSMC), effects of mycophenolic acid (MPA) on ET-1-induced proliferation and ERK1/2 activation were also examined in vitro.

RESULTS

In the vehicle group, marked neointima formation was observed, with massive macrophages and T-cell infiltration in neointima, media, and adventitia. Marked expression of ET-1, PDGF-B, PDGFR-beta, TGFbeta1, and OPN were also observed in neointima. In the MMF40 and MMF20 groups, neointima formation was halted, but macrophages and T cells were infiltrated in the adventitia and adhered to the endothelium. In the MMF40 group, medial infiltration by macrophages and T cells and intimal expression of ET-1, PDGF-B, PDGFR-beta, TGFbeta1, and OPN was inhibited compared with the vehicle and MMF20 groups. Furthermore, MPA inhibited ET-1-induced VSMC proliferation but failed to inhibit its ERK1/2 activation.

CONCLUSIONS

MMF treatment might have preventive potential in transplant patients with chronic vasculopathy through inhibition of VSMC proliferation.

Cyclosporin A enhances interleukin-8 expression by inducing activator protein-1 in human aortic smooth muscle cells

OBJECTIVE

Cyclosporin A (CsA) and tacrolimus (FK506) are widely used as immunosuppressants. However, their use has been hampered by various adverse effects, such as acceleration of atherosclerosis. Interleukin (IL)-8, a chemotactic cytokine, plays an important role in pathogenesis of atherosclerosis. We thus investigated whether synthesis of IL-8 from primary human aortic smooth muscle cells is influenced by CsA and FK506.

METHODS AND RESULTS

Northern blot analysis revealed that CsA increased IL-8 mRNA level and enhanced its increase by epidermal growth factor or tumor necrosis factor-alpha. In contrast, FK506 had no effect on the mRNA level. IL-8 accumulation in culture media was also increased by CsA. Stability of IL-8 mRNA was not affected by CsA, whereas luciferase reporter gene assay using the human IL-8 promoter revealed that CsA significantly augmented the promoter activity. Electrophoretic mobility shift assay showed that binding activity of activator protein (AP)-1 was increased by CsA, and introduction of a mutation into the AP-1 site in the promoter abolished its CsA-dependent activation. The increased AP-1 binding activity was accompanied by c-Fos synthesis.

CONCLUSIONS

CsA stimulates synthesis of IL-8 via activation of AP-1 in human aortic smooth muscle cells, providing a novel aspect of biological effects of CsA on the cells.

Mycophenolate mofetil significantly reduces leukocyte graft infiltration after heterotopic cardiac transplantation in a rat model: comparative study with cyclosporine and FK 506

BACKGROUND

The purpose of the study was to evaluate the effects of cyclosporine (CsA), FK 506 and mycophenolate mofetil (MMF) on graft-infiltrating leukocytes (CD4, CD8, CD11a, CD18) after cardiac transplantation in rats.

METHODS

Three hundred forty animals were transplanted and randomly divided into 4 groups: CsA, 3 mg/kg/d (n = 74); MMF, 40 mg/kg/d (n = 96); FK 506, 0.3 mg/kg/d (n = 96); and a control group receiving no immunosuppressive therapy (n = 74). Three or 4 animals from each group were killed at intervals of 1 to 4 days up to Day 60. Immunohistochemistry was performed using monoclonal antibodies (MAb) against CD4, CD8, CD11a and CD18. Positively stained cells were analyzed in the perivascular space (PVS) of intra- and epicardial arteries. Statistical analysis was performed using area-under-the-curve assessment with an extended t-test.

RESULTS

CsA and FK 506 reduced the presence graft-infiltrating leukocytes (CD4, CD8, CD11a, CD18) in the PVS of intra- and epicardial arteries when compared with control animals. MMF therapy resulted in a further significant reduction in infiltrating leukocytes when compared with the 2 calcineurin inhibitors. MMF had a faster onset of action than the calcineurin inhibitors. CsA and FK 506 required 12 to 20 additional days to achieve the reducing effect of graft infiltration seen in MMF-treated animals.

CONCLUSION

MMF possesses potent infiltration-blocking properties and its application leads to a greater reduction of cellular infiltration in the course of transplant rejection when compared with calcineurin inhibitors.

Role of immunocompetent cells in nonimmune renal diseases

Renal infiltration with macrophages and monocytes is a well-recognized feature of not only immune, but also nonimmune kidney disease. This review focuses on the investigations that have shown accumulation of immunocompetent cells in experimental models of acute and chronic ischemia, protein overload, hypercholesterolemia, renal ablation, obstructive uropathy, polycystic kidney disease, diabetes, aging, murine hypertension, and nephrotoxicity. We examine the mechanisms of infiltration of immunocompetent cells and their participation in the self-perpetuating cycle of activation of the angiotensin system, generation of reactive oxygen species, and further recruitment of monocytes and lymphocytes. We also discuss the possibility of antigen-dependent and antigen-independent mechanisms of immune cell activation in these animal models. Finally, we review the recent studies in which suppression of cellular immunity with mycophenolate mofetil has proven beneficial in attenuating or preventing the progression of renal functional and histologic damage in experimental conditions of nonimmune nature.

Effect of Saireitoh on rabbit smooth muscle cell proliferation and experimental atherosclerosis

Saireitoh is a traditional Chinese medicine that is often given to patients with nephrotic syndrome or glomerulonephritis. Studies have reported that Saireitoh stimulates intrinsic steroid secretion in rats and suppresses the proliferation of fibroblasts in vitro. We examined the effects of Saireitoh on vascular smooth muscle cell proliferation and migration in vitro and experimental atherosclerosis in vivo. Saireitoh rabbit serum obtained from New Zealand White rabbits which were given a diet containing 2% Saireitoh for 3 days significantly inhibited [3H]-thymidine incorporation by smooth muscle cells, which were isolated from thoracic aorta explants of rabbits. The addition of 10% Saireitoh rabbit serum to a culture medium containing smooth muscle cells inhibited DNA synthesis by 50% as compared with a control culture to which 10% normal rabbit serum was added. We also found that the number of smooth muscle cells in the culture containing Saireitoh rabbit serum was decreased. When PDGF was used as a chemoattractant, we demonstrated that Saireitoh rabbit serum slightly inhibits the migration of smooth muscle cells. In in vivo experiments, Saireitoh did not suppress the development of atherosclerosis but tended to reduce the damage. We concluded that although Saireitoh inhibited the proliferation of smooth muscle cells, the effect of prevention on the development of atherosclerosis is weak in the in vivo condition.

Mycophenolate mofetil treatment reduces cholesterol-induced atherosclerosis in the rabbit

Immunosuppressive therapy has been shown to either improve or, more frequently, enhance the development of atherosclerosis. We tested the effect of mycophenolate mofetil (MMF), an inhibitor of nucleotide synthesis widely used in transplant therapy, in diet-induced atherosclerosis in the rabbit. Two groups (n=10 each) of New Zealand White (NZW) rabbits were fed a 1% cholesterol diet for 12 weeks. One group received MMF (CHOL+MMF group) by gastric gavage (30 mg/kg daily) and the other group (CHOL) received the same volume of saline by the same route. There were no differences in the serum cholesterol (mean values > or =30 mmol/l in both groups after 2 weeks) or in the triglyceride, blood sugar, total protein, and albumin serum levels and weight gain in both groups of animals. The cholesterol-fed untreated rabbits had atherosclerotic plaques covering 43.9.1+/-SD 16.40% of their thoracic aorta and 41.9+/-22. 59% of their abdominal aorta, while the MMF treated group had 18. 5+/-7.17% and 17.7+/-9.71%, respectively (P<0.01). The cholesterol content of the aorta (mg/g) in the cholesterol-fed untreated group was 4.61+/-SD 1.21 in the thoracic aorta and 4.54+/-2.07 in the abdominal aorta, whereas the MMF treated group had and 2.83+/-0.84 and 2.77+/-1.44, respectively (P<0.01). Infiltrating macrophages (RAM 11 positive cells/100 nuclei) in the intimal layer of the aorta were 58.4+/-SD26.16 in the CHOL group and 8.5+/-5.51 in the CHOL+MMF group: (P<0.001). CD18 positive cells/100 nuclei were 27.4+/-17.6 in the CHOL group and 5.3+/-3.82 in the CHOL+MMF group (P<0.01), and the intima/media ratio was 0.66+/-0.11 in the CHOL group and 0. 30+/-0.09 in the MMF treated rabbits (P<0.001). MMF also reduced proliferating smooth muscle cells (HHF35 positive) infiltrating between the macrophages. These results indicate that MMF ameliorates importantly the atherogenic potential of a high cholesterol diet and this effect is associated with a reduction in macrophage and foam cell infiltration and smooth muscle cell proliferation and infiltration. Since chronic treatment with this drug is given routinely in various clinical conditions with relatively minor side effects, consideration may be given to its use as adjuvant therapy in atherosclerotic cardiovascular disease.

Mycophenolate mofetil treatment reduces atherosclerosis in the cholesterol-fed rabbit

Immune/inflammatory responses of arterial vessel wall constituents to lipid metabolic disturbances have been postulated to contribute to the pathogenesis of atherosclerosis. Mycophenolate mofetil (MMF), an antiproliferative agent used in clinical transplantation, has been shown to inhibit smooth muscle cell (SMC) proliferation and decrease the recruitment of monocytes into sites of chronic inflammation. This study was conducted to determine the effect of MMF on atherosclerotic plaque development after cholesterol-induced injury. New Zealand white rabbits were fed a high-cholesterol diet containing 0.5% cholesterol and 8% peanut oil. The experimental group (n = 10) was given MMF (80 mg/kg/day subcutaneously); the control group (n = 10) received placebo injections. The aortas were harvested at 12 weeks for immunohistochemical analyses. SMCs were identified by reactivity with a monoclonal antibody (mAb) to alpha smooth muscle actin. Monocytes/macrophages were detected with mAb RAM 11. Cross-sectional areas of the media and neointima were measured using computer-assisted image analysis. The density of SMCs and macrophage/foam cells within the neointima was calculated by dividing the number of cells by the area of the plaque. Total cholesterol, triglyceride, high density lipoprotein, and low density lipoprotein were significantly increased compared with levels before the initiation of a high-cholesterol diet, but there were no significant differences between the MMF-treated and untreated groups. Neointimal area in aortic tissue sections of the MMF-treated group (0.586 +/- 0.602 mm(2)) was significantly lower when compared with that in control animals (1.082 +/- 0.621 mm(2)) (P < 0.05). The densities of neointimal SMCs and monocytes/macrophages in the control group were 778 +/- 293 and 341 +/- 90 cells/mm(2), respectively. MMF treatment significantly reduced the number of neointimal SMCs (506 +/- 185 cells/mm(2)) (P < 0.05). The number of monocytes/macrophages was also reduced after MMF treatment (260 +/- 124 cells/mm(2)) but not significantly. Our results demonstrate that the administration of MMF significantly reduced neointimal SMC accumulation and plaque development in a hypercholesterolemic model of atherosclerosis.

Oxysterols: modulators of cholesterol metabolism and other processes

Oxygenated derivatives of cholesterol (oxysterols) present a remarkably diverse profile of biological activities, including effects on sphingolipid metabolism, platelet aggregation, apoptosis, and protein prenylation. The most notable oxysterol activities center around the regulation of cholesterol homeostasis, which appears to be controlled in part by a complex series of interactions of oxysterol ligands with various receptors, such as the oxysterol binding protein, the cellular nucleic acid binding protein, the sterol regulatory element binding protein, the LXR nuclear orphan receptors, and the low-density lipoprotein receptor. Identification of the endogenous oxysterol ligands and elucidation of their enzymatic origins are topics of active investigation. Except for 24, 25-epoxysterols, most oxysterols arise from cholesterol by autoxidation or by specific microsomal or mitochondrial oxidations, usually involving cytochrome P-450 species. Oxysterols are variously metabolized to esters, bile acids, steroid hormones, cholesterol, or other sterols through pathways that may differ according to the type of cell and mode of experimentation (in vitro, in vivo, cell culture). Reliable measurements of oxysterol levels and activities are hampered by low physiological concentrations (approximately 0.01-0.1 microM plasma) relative to cholesterol (approximately 5,000 microM) and by the susceptibility of cholesterol to autoxidation, which produces artifactual oxysterols that may also have potent activities. Reports describing the occurrence and levels of oxysterols in plasma, low-density lipoproteins, various tissues, and food products include many unrealistic data resulting from inattention to autoxidation and to limitations of the analytical methodology. Because of the widespread lack of appreciation for the technical difficulties involved in oxysterol research, a rigorous evaluation of the chromatographic and spectroscopic methods used in the isolation, characterization, and quantitation of oxysterols has been included. This review comprises a detailed and critical assessment of current knowledge regarding the formation, occurrence, metabolism, regulatory properties, and other activities of oxysterols in mammalian systems.