Do drug transporter (ABCB1) SNPs and P-glycoprotein function influence cyclosporine and macrolides exposure in renal transplant patients? Results of the pharmacogenomic substudy within the symphony study

The function of the efflux pump P-glycoprotein (Pgp) and ABCB1 single nucleotide polymorphisms (SNPs) should be considered as important tools to deepen knowledge of drug nephrotoxicity and disposition mechanisms. The aim of this study is to investigate the association of C3435T, G2677T, C1236T, and T129C ABCB1 SNPs with Pgp activity and exposure to different immunosuppressive drugs in renal transplant patients. Patients included in the Symphony Pharmacogenomic substudy were genotyped for ABCB1 SNPs. According to the design, patients were randomized into four immunosuppressive regimens: low and standard dose of cyclosporine (n = 30), tacrolimus (n = 13), and sirolimus (n = 23) concomitantly with mycophenolate and steroids. Pgp activity was evaluated in PBMC using the Rhodamine 123 efflux assay. TT carrier patients on C3435T, G2677T, and C1236T SNPs (Pgp-low pumpers) showed lower Pgp activity than noncarriers. Pgp-high pumpers treated with cyclosporine showed lower values of Pgp function than macrolides. There was a negative correlation between cyclosporine AUC and Pgp activity at 3 months. Results did not show any correlation between tacrolimus and sirolimus AUC and Pgp activity at 3 months. We found an important role of the ABCB1 SNPs Pgp function in CD3+ peripheral blood lymphocytes from renal transplant recipients. Pgp activity was influenced by cyclosporine but not macrolides exposure

Morphometric analysis of glomerular hypertrophy and kidney fibrosis.

<p>Panel A. Representative images from histological sections stained with Sirius red: Sham Group (A), Control Group (B) and Everolimus Group (C) (magnification 200×). Panel B. Glomerular area (media and SD) and frequency distribution diagram of glomerular area. Panel C. Mesangial fibrosis area (mean and SD) and frequency distribution diagram of mesangial fibrosis area in the three groups. Panel D. Tubulointerstitial fibrosis area (mean and SD) and frequency distribution diagram of tubulointerstitial fibrosis area in the three groups. * p<0.05 vs sham group and †p<0.05 vs control group.</p

Immunohistochemistry: fibrosis, cell proliferation and inflamation.

<p>Representative results from the different groups are shown: Sham Group (A,D,G,J), Control Group (B,E,H,K) and Everolimus Group (C,F,I,L). PAS tinction (A,B,C) (magnification 200×), Immunohistochemistry for α smooth muscle actin (200×) (D,E, F), Glomerular and tubulointerstitial proliferating cell nuclear antigen (PCNA) immunostaining (200×) (G,H,I) and anti CD68 (400×) (J,K,L). Sections were counterstained with eosin.</p

Western blot and protein abundance ratio for pAkt/tAkt and pERK/tERK.

<p>A) Inmunoblotting analysis for Total Akt 1–2 and phospho-Akt (Ser473); B) Densitometric analysis of pAkt/total Akt: SG (n = 7), CG (n = 5) and EveG (n = 6); C) Inmunoblotting analysis for ERK 1/2 and p-ERK (E-4), D) Densitometric analysis of pERK/total ERK. SG (n = 7), CG (n = 5) and EveG (n = 6). * p<0.05 vs sham group.</p

Weight, blood pressure, renal function, proteinuria and microalbuminuria from animals at week 8 of treatment.

<p>Weight, blood pressure, renal function, proteinuria and microalbuminuria from animals at week 8 of treatment.</p

Histological and immunohistochemistry semiquantitative analysis.

<p>Histological and immunohistochemistry semiquantitative analysis.</p

mRNA expression for Akt, mTOR and TGF β.

<p>Relative mRNA expression levels of Akt, mTOR and TGF β were assessed by real time quantitative reverse transcriptase-PCR in remnant kidneys of SG (n = 7), CG (n = 5) and EveG (n = 7). *p<0.05 vs sham, **p<0.05 vs CG.</p

Delayed mTOR inhibition with low dose of everolimus reduces TGFβ expression, attenuates proteinuria and renal damage in the renal mass reduction model

The immunosuppressive mammalian target of rapamycin (mTOR) inhibitors are widely used in solid organ transplantation, but their effect on kidney disease progression is controversial. mTOR has emerged as one of the main pathways regulating cell growth, proliferation, differentiation, migration, and survival. The aim of this study was to analyze the effects of delayed inhibition of mTOR pathway with low dose of everolimus on progression of renal disease and TGFβ expression in the 5/6 nephrectomy model in Wistar rats