Inhibition of Chemokine Receptor CCR2 and CCR5 Expression Contributes to Simvastatin-induced Attenuation of Cardiac Allograft Vasculopathy

Cardiac Allograft Vasculopathy: The Enduring Enemy of Cardiac Transplantation

Cardiac allograft vasculopathy remains a major limiting factor in the long-term survival of the heart transplant recipient. Our understanding of its pathogenesis is continuously evolving as advances in imaging modalities have allowed a direct window into the natural history of the disease. Innovation in diagnostic modalities has spurred the proliferation of prognostic tools and biomarkers. And in parallel, pharmacological advances have emerged that have helped ameliorate the disease's progressive course.

Hypercholesterolemia after conversion to sirolimus as primary immunosuppression and cardiac allograft vasculopathy in heart transplant recipients

BACKGROUND

Sirolimus (SRL) attenuates cardiac allograft vasculopathy (CAV) progression after heart transplantation (HT) but often results in hyperlipidemia. In this study we investigated the differential effects of SRL-based and calcineurin inhibitor (CNI)-based immunosuppression on CAV progression and clinical outcomes in HT recipients.

METHODS

CAV progression was assessed by coronary intravascular ultrasound (IVUS) as changes in volumetric measurements after correction to time between the first and last follow-up IVUS exams. CAV progression rate and CAV-associated events were compared between patients with mean follow-up low-density lipoprotein (LDL) <100 mg/dl (lower level or LL) and ≥100 mg/dl (higher level or HL) in the SRL and CNI groups.

RESULTS

We identified 227 patients on SRL (LL: 118; HL: 109) and 96 on CNI (LL: 56; HL: 40), with a median follow-up of 6.7 years. Clinical characteristics did not differ between the LL and HL groups and all patients were on statins. In the SRL arm, there were no significant differences in CAV progression rate and there were no differences in all-cause mortality and CAV-associated events between the LL and HL groups. In the CNI arm, the Δ change in plaque volume normalized to segment length and time of follow-up (PV/SL/year) (0.55 ± 0.53 vs 1.53 ± 2.32, p = 0.003) and Δ change in plaque index per year (defined as PV/vessel volume ratio) (3.1 ± 3.7% vs 6.3 ± 10.4%; p = 0.034) were significantly lower in the LL than the HL group. After adjusting for patient characteristics, HL was associated with higher rates of advanced CAV requiring coronary angioplasty (hazard ratio [HR] 3.0, 95% confidence interval [CI] 1.05 to 9.40, p = 0.040) and higher rates of all CAV-associated events (HR 2.2, 95% CI 1.10 to 4.54, p = 0.026) in these CNI-treated subjects.

CONCLUSION

Unlike CNI-based immunosuppression, the effects of SRL on attenuating CAV progression are independent of LDL cholesterol levels post-HT.

Combined treatment with simvastatin and rapamycin attenuates cardiac allograft rejection through the regulation of T helper 17 and regulatory T cells

Allograft rejection is an important issue post cardiac transplantation. In order to investigate the effect of combined treatment with simvastatin and rapamycin on allograft rejection, a cardiac transplantation rat model was employed in the present study. The survival time of rats following cardiac transplantation was recorded, while histopathological alterations were assessed by hematoxylin and eosin staining. The levels of transcription factors were measured by reverse transcription-quantitative polymerase chain reaction. In addition, the levels of CD4⁺ interleukin (IL)-17⁺ cells and CD4⁺ forkhead box P3 (FOXP3)⁺ cells in the allografts and CD4⁺ T cells and CD8⁺ T cells in the spleens were detected by flow cytometry. The results of the current study demonstrated that, following treatment with simvastatin and rapamycin, the survival time of model rats was prolonged, and the histopathological damage was attenuated. Treatment with simvastatin and rapamycin also led to decreased retinoic acid receptor-related orphan receptor γt (RORγt) level, increased FOXP3 level, reduced levels of CD4⁺IL-17⁺, CD4⁺ T and CD8⁺ T cells, and increased level of CD4⁺FOXP3⁺ cells. In conclusion, the current study observed that simvastatin and rapamycin performed a synergistic effect to reduce cardiac transplantation rejection. Thus, combined therapy of simvastatin and rapamycin may be a promising adjuvant therapy to reduce rejection post cardiac transplantation.

Monocyte chemoattractant protein 1-mediated migration of mesenchymal stem cells is a source of intimal hyperplasia

OBJECTIVE

Intimal hyperplasia is considered to be a healing response and is a major cause of vessel narrowing after injury, where migration of vascular progenitor cells contributes to pathological events, including transplant arteriosclerosis.

APPROACH AND RESULTS

In this study, we used a rat aortic-allograft model to identify the predominant cell types associated with transplant arteriosclerosis and to identify factors important in their recruitment into the graft. Transplantation of labeled adventitial tissues allowed us to identify the adventitia as a major source of cells migrating to the intima. RNA microarrays revealed a potential role for monocyte chemoattractant protein 1 (MCP-1), stromal cell-derived factor 1, regulated on activation, normal T cell expressed and secreted, and interferon-inducible protein 10 in the induced vasculopathy. MCP-1 induced migration of adventitial fibroblast cells. CCR2, the receptor for MCP-1, was coexpressed with CD90, CD44, NG2, or sca-1 on mesenchymal stem cells. In vivo experiments using MCP-1-deficient and CCR2-deficient mice confirmed an important role of MCP-1 in the formation of intimal hyperplasia in a mouse model of vascular injury.

CONCLUSIONS

The adventitia is a potentially important cellular source that contributes to intimal hyperplasia, and MCP-1 is a potent chemokine for the recruitment of adventitial vascular progenitor cells to intimal lesions.

Suppression of cardiac allograft vasculopathy in mice by inhibition of CC-motif chemokine receptor 5

Cardiac allograft vasculopathy (CAV) is the leading cause of late morbidity and mortality in heart-transplant patients. Increasing evidences support the important role of chemokines and their receptors in transplant immunology. Chemokine-chemokine receptor interaction and subsequent recruitment of T-lymphocytes to the graft are early events in the development of chronic rejection of transplanted hearts. In this study, we first inhibited CC-motif chemokine receptor 5 (CCR5) expression by using lentiviral-mediated gene transfer of an anti-CCR5 siRNA, which introduced through CD34(+) hematopoietic stem/progenitor cell transplantation. Stably marked lymphocytes expressing siRNA and consistent downregulation of CCR5 expression were detected. Our results showed that survival was significantly prolonged in CCR5 knock-down mice and donor hearts from siRNA-treated mice developed markedly less CAV. Infiltration of CD4(+) and CD8(+) T-lymphocytes into transplanted hearts was also markedly decreased. These findings suggest that CCR5 plays an important role in CAV development and inhibition of this chemokine could improve long-term survival after cardiac transplantation.

Role of CCL2/MCP-1 in islet transplantation

High levels of donor-derived CCL2 have been associated with poor islet allograft outcome in patients with type 1 diabetes. The aim of our work was to determine whether CCL2 secreted by the islet has independent proinflammatory effects that influence engraftment and graft acceptance. Both in mice and humans CCL2 is significantly positively associated with other cytokines/chemokines, in particular with the highly released "proinflammatory" IL-6 and CXCL8 or CXCL1. Transplantation of CCL2-/- islets into syngenic recipients did not improve the transplant function. Transplantation of islets into CCL2-/- syngenic recipients led to a significant improvement of transplant function and partial abrogation of local hepatic inflammation. When evaluated in human islets CCL2 release was strongly related to the immediate local inflammatory response in the liver and impacted short-term human islet function dependently by the induced inflammatory response and independently by the immunosuppressive therapy. The data showed that islet CCL2 release is a sign of "inflamed" islets without having a direct role in graft failure. On the other hand, a causal effect for developing detrimental proinflammatory conditions after transplant was proved for recipient CCL2. Strategies to selectively decrease recipient, but not donor, CCL2 release may increase the success of islet transplantation.

CCR5 blockade in combination with rapamycin prolongs cardiac allograft survival in mice

Both chemokine receptor 5 (CCR5) blockade and rapamycin (rapa) are effective in modulating transplant immunity and led to prolonged allograft survival, yet a great many grafts were ultimately lost to acute rejection. In this study we examined the inhibition of CCR5 in combination with the treatment with rapa in cardiac transplantation. Fully major histocompatibility complex-mismatched murine cardiac allograft models were randomized to five groups. They were administered with anti-CCR5 antibody or control antibody and rapa or phosphate-buffered saline (PBS), respectively. An additional group was treated with anti-CCR5 antibody, rapa and anti-CD25 antibody. Allograft rejection was investigated by flow cytometric analyses and enzyme-linked immunospot assay. Allografts treated with anti-CCR5 antibody plus rapa showed significantly prolonged survival (83 +/- 3 days, P < 0.001) compared with control antibody plus PBS-treated allografts (6 +/- 1 days). Treatment with anti-CCR5 monoclonal antibody (mAb) plus rapa inhibited significantly the progression of chronic rejction. Further analysis of donor hearts in the anti-CCR5 antibody plus rapa-treated group demonstrated increased infiltration of CD4(+)CD25(+)forkhead box P3(+) regulatory T cells, and depletion of CD25(+) cells resulted in acute rejection of allografts in 18 +/- 1 day. CCR5 blockade in combination with rapa is effective in preventing acute and chronic rejection in a robust murine model. This effect is mediated by CD25(+) T cell recruitment and control of T lymphocyte proliferation.

Role of MCP-1 in cardiovascular disease: molecular mechanisms and clinical implications

Many of the major diseases, including cardiovascular disease, are widely recognized as inflammatory diseases. MCP-1 (monocyte chemotactic protein-1) plays a critical role in the development of cardiovascular diseases. MCP-1, by its chemotactic activity, causes diapedesis of monocytes from the lumen to the subendothelial space where they become foam cells, initiating fatty streak formation that leads to atherosclerotic plaque formation. Inflammatory macrophages probably play a role in plaque rupture and the resulting ischaemic episode as well as restenosis after angioplasty. There is strong evidence that MCP-1 plays a major role in myocarditis, ischaemia/reperfusion injury in the heart and in transplant rejection. MCP-1 also plays a role in cardiac repair and manifests protective effects under certain conditions. Such protective effects may be due to the induction of protective ER (endoplasmic reticulum) stress chaperones by MCP-1. Under sustained ER stress caused by chronic exposure to MCP-1, the protection would break down resulting in the development of heart failure. MCP-1 is also involved in ischaemic angiogenesis. The recent advances in our understanding of the molecular mechanisms that might be involved in the roles that MCP-1 plays in cardiovascular disease are reviewed. The gene expression changes induced by the signalling events triggered by MCP-1 binding to its receptor include the induction of a novel zinc-finger protein called MCPIP (MCP-1-induced protein), which plays critical roles in the development of the pathophysiology caused by MCP-1 production. The role of the MCP-1/CCR2 (CC chemokine receptor 2) system in diabetes, which is a major risk factor for cardiovascular diseases, is also reviewed briefly. MCP-1/CCR2- and/or MCPIP-targeted therapeutic approaches to intervene in inflammatory diseases, including cardiovascular diseases, may be feasible.

RETRACTED: Chronic cardiac allograft rejection in mice is alleviated by inhibition of CCR5 in combination with cyclosporine A

The chemokine receptor CCR5 plays important roles in acute allograft rejection. In this study, we examined the inhibition of CCR5 in combination with the treatment with cyclosporine A (CsA) in chronic rejection in cardiac transplantation. Forty-five transplant recipients were randomized to three groups. Recipients in group A were treated with anti-CCR5 mAb and CsA, mice in group B were given anti-CCR5 mAb alone, and animals in group C were administered with only CsA. On day 45 after transplantation, the allografts were harvested and examined by immunohistologic technique and PT-PCR methods. Allografts treated with anti-CCR5 mAb and CsA showed significantly prolonged survival (44.73 ± 0.258 days, P < 0.01) as compared with CsA-treated group (37.00 ± 2.04 days). Treatment with anti-CCR5 mAb plus CsA significantly inhibited the progression of cardiac allograft vasculopathy. Our findings demonstrated that anti-CCR5 mAb in combination with CsA can prolong the survival of allograft through their cardio-protective and immunomodulative properties. Thus, combined administration of anti-CCR5 mAb and CsA may become a new therapeutic approach for the prevention of cardiac graft failure that has not been obviated by conventional immunosuppressive agents.

High levels of donor CCL2/MCP-1 predict graft-related complications and poor graft survival after kidney-pancreas transplantation

In this study we analyzed the role of CCL2, a member of the chemokine family, in early graft damage. Using simultaneous kidney-pancreas transplantation (SPK) as a model, we showed that brain death significantly increases circulating CCL2 levels in humans. We found that in such situations, high donor CCL2 levels (measured before organ recovery and at the onset of cold preservation) correlate with increased postreperfusion release of CCL2 by both the graft and recipient throughout the week following transplantation (n = 28). In a retrospective study of 77 SPK recipients, we found a significant negative association between high donor levels of CCL2 and graft survival. Decreased survival in these patients is related to early posttransplant complications, including a higher incidence of pancreas thrombosis and delayed kidney function. Taken together our data indicate that high CCL2 levels in the donor serum predict both an increase in graft/recipient CCL2 production and poor graft survival. This suggests that the severity of the inflammatory response induced by brain death influences the posttransplant inflammatory response, independent of subsequent ischemia and reperfusion.