Transplantation/immunology
Protective Effects of Atorvastatin on Chronic Allograft Nephropathy in Rats

https://doi.org/10.1016/j.jss.2006.12.557Get rights and content

Objective

Chronic allograft nephropathy (CAN) is the leading cause of late kidney allograft loss. Recent studies have suggested that atorvastatin (ATO) may interact with the acute inflammatory process in the renal interstitium and suppress the proliferation of mesangial cells. We hypothesized that ATO could also inhibit the chronic inflammatory process and prevent the progression of CAN.

Materials and methods

Fisher (F344) kidneys were orthotopically transplanted into Lewis rat recipients. Lewis-to-Lewis rat kidney transplantation was served as the syngeneic control (Syn group). Allograft recipients were randomized and treated with cyclosporine A alone (Allo group) or in combination with ATO (15 or 30 mg/kg/d intrgastric, respectively, the low dose treatment group/high dose treatment group [LT/HT] groups). Renal function and the urine protein excretion were analyzed. Animals were sacrificed 20 weeks posttransplantation for histological and immunohistochemical studies, as well as analysis of mRNA levels of cytokines and chemokines.

Results

Renal function progressively deteriorated and substantial proteinuria developed in the Allo group compared with the Syn group. ATO-treated rats had significantly higher creatinine clearance rate and less amount of proteinuria. Histological examination revealed obvious features of CAN in the Allo group, whereas LT/HT groups demonstrated minimal glomerulosclerosis, interstitial fibrosis, intimal thickening, and tubular atrophy. The numbers of infiltrating mononuclear cells (ED1+, CD8+, and CD68+) decreased markedly, and the intragraft expression of transforming growth factor β1 (TGF-β1) and collagen III were also significantly attenuated in the LT/HT groups, as compared with the Allo group. The mRNA levels of proinflammatory cytokines (interleukin-2, interferon-γ, interleukin-10), chemokines (RANTES, MCP-1), and profibrotic genes (TGF-β1, collagen III) were significantly down-regulated in ATO-treated rats.

Conclusion

Atorvastatin showed excellent favorable effects on blocking renal inflammation and fibrosis, and thus, efficiently inhibited the development and progression of CAN, which might improve the long-term survival rate of renal allografts.

Introduction

Despite the enormous advancement of immunosuppressive therapy and a significant improvement in short-term graft survival rate after kidney transplantation, chronic allograft nephropathy (CAN) still remains one of the leading causes of renal allograft loss and also a great challenge to clinicians, which is characterized by chronic progressive deterioration of graft function and is associated with glomerulosclerosis, tubular atrophy, interstitial fibrosis, and intimal thickening of transplant arterioles [1, 2]. The pathogenesis of CAN is complex, multifactorial, and incompletely understood. Its etiology includes both immunological and nonimmunological factors relating to donor and recipient. Numerous proinflammatory and profibrotic mediators including interleukin (IL)-2, interferon (INF)-γ, IL-10, chemokines, transforming growth factor (TGF)-β, and extracellular matrix (ECM) component collagen III, etc, have been demonstrated to be involved in the pathogenesis and progression of chronic inflammation and the repair process in CAN [3]. Among them, TGF-β1 plays a key role in regulating matrix synthesis and renal resident cells phenotype and its physiological and pathological functions were documented in various renal diseases [4, 5].

Due to their favorable effects on lipid levels and cardiovascular outcome, 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) have been commonly used after kidney transplantation. Recent studies have demonstrated that statins have pleiotropic effects unrelated to lipid levels including reduced inflammation, improved endothelial function, and improved insulin sensitivity [6, 7, 8]. Since mevalonate is the precursor of many nonsteroidal compounds, inhibiting HMG-CoA by statins may produce these pleiotropic effects besides its lipid-lowing function [9, 10]. In an experimental model of cyclosporine A nephrotoxicity, Li et al. reported the inhibitory effects of pravastatin on macrophage infiltration and interstitial fibrosis [11]. In addition, statin therapy resulted in the down-regulation of TGF-β inducible gene h3, which is associated with reduced endothelial nitric oxide synthesis [5]. However, studies about whether and how the family of statins could play a role in inhibiting the development of CAN in animal models are not fully explored yet.

In our previous study, we have shown the close relationship between renal inflammation and tubulointerstitial damage and fibrosis [12, 13]. We found that atorvastatin (ATO) (Fig. 1) could dramatically attenuate lymphocyte cellular infiltration and the expression of osteopontin in renal allografts in the early stage after kidney transplantation in a rat model [13]. Therefore, in the current study, we wanted to investigate whether atorvastatin could also prevent the development and progression of CAN. Taking the advantage of a classical rat model of kidney transplantation, we applied a nontoxic high dose and a routinely used low dose of ATO immediately after kidney transplantation. Allogeneic kidney transplantation without ATO treatment and syngeneic kidney transplantation were used as controls. Twenty weeks of screening were performed to investigate the therapeutic effects of ATO on the renal graft function, urine protein excretion, graft fibrosis, cell infiltration, and the expression of various inflammatory cytokines and chemokines.

Section snippets

Animals, Surgery, and Treatment

All rats were fed with standard chow and water ad libitum and were provided by the experimental animal center in Nanjing Medical University. Kidneys of inbred male Fisher rats (F344, RT11v1) (200–250 g) were transplanted into male Lewis rats (LEW, RT11) (200–250 g). The surgical procedure was performed as described by Fisher and modified by Xu et al. [14, 15]. Briefly, rats were anesthetized by 0.3% barbital sodium 30 mg/kg body weight intraperitoneally. After intravenous heparinization (300

General Conditions and Renal Allograft Function

The basic parameters in the four groups did not differ much before the transplantation, as shown in Table 2. All rats receiving kidney transplantation in this study survived for more than 20 weeks and the mean body weight generally increased during the observation, among which rats with syngeneic kidney transplantation gained the most amount of weight (P < 0.05). ATO treatment significantly reduced the level of serum total cholesterol level (P < 0.05), but did not affect total triglyceride

Discussion

CAN has been recognized as the main cause of renal allograft failure following the first year post kidney transplantation [20]. Both immunological and nonimmunological factors play roles in the development and progression of CAN. Immunological factors include acute rejection, degree of HLA mismatch, and inadequate immunosuppression. Nonimmunological factors contain delayed graft function, ischemia-reperfusion injury, nephrotoxicity of calcineurin inhibitors, hyperfiltration, hypertension, and

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