Donor ABCB1 genetic polymorphisms influence epithelial-to-mesenchyme transition in tacrolimus-treated kidney recipients

Linagliptin Mitigates TGF-β1 Mediated Epithelial-Mesenchymal Transition in Tacrolimus-Induced Renal Interstitial Fibrosis via Smad/ERK/P38 and HIF-1α/LOXL2 Signaling Pathways

The dipeptidyl peptidase-4 (DPP-4) inhibitors, a novel anti-diabetic medication family, are renoprotective in diabetes, but a comparable benefit in chronic non-diabetic kidney diseases is still under investigation. This study aimed to elucidate the molecular mechanisms of linagliptin's (Lina) protective role in a rat model of chronic kidney injury caused by tacrolimus (TAC) independent of blood glucose levels. Thirty-two adult male Sprague Dawley rats were equally randomized into four groups and treated daily for 28 d as follows: The control group; received olive oil (1 mL/kg/d, subcutaneously), group 2; received Lina (5 mg/kg/d, orally), group 3; received TAC (1.5 mg/kg/d, subcutaneously), group 4; received TAC plus Lina concomitantly in doses as the same previous groups. Blood and urine samples were collected to investigate renal function indices and tubular injury markers. Additionally, signaling molecules, epithelial-mesenchymal transition (EMT), and fibrotic-related proteins in kidney tissue were assessed by enzyme-linked immunosorbent assay (ELISA) and Western blot analysis, immunohistochemical and histological examinations. Tacrolimus markedly induced renal injury and fibrosis as indicated by renal dysfunction, histological damage, and deposition of extracellular matrix (ECM) proteins. It also increased transforming growth factor β1 (TGF-β1), Smad4, p-extracellular signal-regulated kinase (ERK)1/2/ERK1/2, and p-P38/P38 mitogen-activated protein kinase (MAPK) protein levels. These alterations were markedly attenuated by the Lina administration. Moreover, Lina significantly inhibited EMT, evidenced by inhibiting Vimentin and α-smooth muscle actin (α-SMA) and elevating E-cadherin. Furthermore, Lina diminished hypoxia-related protein levels with a subsequent reduction in Snail and Twist expressions. We concluded that Lina may protect against TAC-induced interstitial fibrosis by modulating TGF-β1 mediated EMT via Smad-dependent and independent signaling pathways.

Tacrolimus induces a pro-fibrotic response in donor-derived human proximal tubule cells dependent on common variants of the CYP3A5 and ABCB1 genes

BACKGROUND

Common genetic variants of the enzymes and efflux pump involved in tacrolimus disposition have been associated with calcineurin inhibitor nephrotoxicity, but their importance is unclear because of the multifactorial background of renal fibrosis. This study explores the pro-fibrotic response of tacrolimus exposure in relation to the differential capacity for tacrolimus metabolism in proximal tubule cells (PTCs) with a variable (pharmaco)genetic background.

METHODS

PTCs were obtained from protocol allograft biopsies with different combinations of CYP3A5 and ABCB1 variants and were incubated with tacrolimus within the concentration range found in vivo. Gene and protein expression, CYP3A5 and P-glycoprotein function, and tacrolimus metabolites were measured in PTC. Connective tissue growth factor (CTGF) expression was assessed in protocol biopsies of kidney allograft recipients.

RESULTS

PTCs produce CTGF in response to escalating tacrolimus exposure, which is approximately 2-fold higher in cells with the CYP3A5*1 and ABCB1 TT combination in vitro. Increasing tacrolimus exposure results in relative higher generation of the main tacrolimus metabolite {13-O-desmethyl tacrolimus [M1]} in cells with this same genetic background. Protocol biopsies show a larger increase in in vivo CTGF tissue expression over time in TT vs. CC/CT but was not affected by the CYP3A5 genotype.

CONCLUSIONS

Tacrolimus exposure induces a pro-fibrotic response in a PTC model in function of the donor pharmacogenetic background associated with tacrolimus metabolism. This finding provides a mechanistic insight into the nephrotoxicity associated with tacrolimus treatment and offers opportunities for a tailored immunosuppressive treatment.

Nongenotoxic ABCB1 activator tetraphenylphosphonium can contribute to doxorubicin resistance in MX-1 breast cancer cell line

Hyperactivation of ABC transporter ABCB1 and induction of epithelial–mesenchymal transition (EMT) are the most common mechanism of acquired cancer chemoresistance. This study describes possible mechanisms, that might contribute to upregulation of ABCB1 and synergistically boost the acquisition of doxorubicin (DOX) resistance in breast cancer MX-1 cell line. DOX resistance in MX-1 cell line was induced by a stepwise increase of drug concentration or by pretreatment of cells with an ABCB1 transporter activator tetraphenylphosphonium (TPP⁺) followed by DOX exposure. Transcriptome analysis of derived cells was performed by human gene expression microarrays and by quantitative PCR. Genetic and epigenetic mechanisms of ABCB1 regulation were evaluated by pyrosequencing and gene copy number variation analysis. Gradual activation of canonical EMT transcription factors with later activation of ABCB1 at the transcript level was observed in DOX-only treated cells, while TPP⁺ exposure induced considerable activation of ABCB1 at both, mRNA and protein level. The changes in ABCB1 mRNA and protein level were related to the promoter DNA hypomethylation and the increase in gene copy number. ABCB1-active cells were highly resistant to DOX and showed morphological and molecular features of EMT. The study suggests that nongenotoxic ABCB1 inducer can possibly accelerate development of DOX resistance.

Clinical Impact of the Adaptation of Initial Tacrolimus Dosing to the CYP3A5 Genotype After Kidney Transplantation: Systematic Review and Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

The aim of this systematic review and meta-analysis was to compare the clinical outcomes between genotype-guided and conventional tacrolimus doses in kidney transplantation patients.

MATERIALS AND METHODS

We performed a comprehensive literature search of the PubMed, EMBASE, and Cochrane databases from the date of inception to 26 February 2020. References of the retrieved articles were also reviewed and any further relevant studies were included. The search terms included 'tacrolimus', 'cytochrome P-450 CYP3A', 'polymorphism, genetic', 'genomics', 'genome', 'genotype', 'genes', 'alleles', and 'pharmacogenetics'.

RESULTS

Our study showed that the genotype-guided group included an increased proportion of patients with tacrolimus concentrations in the therapeutic range at steady state (risk ratio [RR] 1.40, 95% confidence interval [CI] 1.14-1.72, p = 0.001; high quality), with a trend for achieving therapeutic concentrations earlier compared with those in the conventional group. However, there was no statistical difference in the incidence of delayed graft function (RR 1.98, 95% CI 0.92-1.76, p = 0.12; moderate quality), incidence of acute rejection (RR 1.00, 95% CI 0.64-1.55, p = 1.00; moderate quality), incidence of graft survival censored for death (RR 1.02, 95% CI 0.98-1.06, p = 0.37; moderate quality), and incidence of adverse effects (AEs).

CONCLUSIONS

Although the genotype-guided group had a higher proportion of patients within the targeted concentration and less median time to achieve the therapeutic range, the clinical endpoints, including delayed graft function, acute rejection, graft survival censored for death, and AEs were similar in both groups. All in all, evidence suggested there was no utility in pharmacogenetics for tacrolimus based on the cytochrome P450 (CYP) 3A5 genotype. Studies with Chinese and African American populations are needed due to the frequency of genetic polymorphisms of CYP3A5. Furthermore, a dosing algorithm that includes demographic and clinical factors plus multiple genetic variants should be added for consideration, and may optimize early tacrolimus exposure.

Caveolin-1 rs4730751 single-nucleotide polymorphism may not influence kidney transplant allograft survival

Caveolin-1 is a protein (encoded by the CAV1 gene) supposedly harboring a protective effect against fibrosis. CAV1 rs4730751 single nucleotide polymorphism (SNP) AA genotype was initially associated with lower graft survival compared to non-AA. However, subsequent studies could not find the same effect. CAV1 rs4730751 SNP was investigated on 918 kidney donors. Multivariate Cox-model analyses were performed to evaluate risk factors for graft loss. Longitudinal changes on long-term estimated glomerular filtration rate (eGFRs) were evaluated with a linear mixed model. Histopathological findings from protocolled biopsies after 3 months post transplantation were also analyzed. Donor CAV1 rs4730751 genotyping proportions were 7.1% for AA, 41.6% for AC and 51.3% for CC. The AA genotype, compared to non-AA, was not associated with lower graft survival censored or not for death (multivariate analysis: HR = 1.23 [0.74–2.05] and HR = 1.27 [0.84–1.92]). Linear mixed model on long-term eGFRs revealed also no significant difference according to the genotype, yet we observed a trend. AA genotype was also not associated with a higher degree of fibrosis index on protocolled kidney biopsies at 3 months. To conclude, donor CAV1 rs4730751 SNP may impact on kidney transplantation outcomes, but this study could not confirm this hypothesis.

Targeting AXL overcomes resistance to docetaxel therapy in advanced prostate cancer

Resistance to docetaxel is a major clinical problem in advanced prostate cancer. The overexpression of AXL receptor tyrosine kinase (AXL) has been correlated with chemotherapeutic drug resistance. However, the role of AXL expression in docetaxel resistance in prostate cancer is yet unclear. In this study, we demonstrate that AXL is overexpressed and activated independent of Gas6 in docetaxel-resistant prostate cancer cells (PC3-DR and DU145-DR). Moreover, we show that forced overexpression of AXL in PC3 and DU145 cells is sufficient to induce resistance to docetaxel in these cell lines. Notably, genetic or pharmacologic inhibition of AXL in the resistant models suppressed cell proliferation, migration, invasion, and tumor growth, and these effects were significantly augmented when AXL inhibition was combined with docetaxel treatment. Mechanistically, we found that AXL inhibition led to reversion of the epithelial-mesenchymal transition (EMT) phenotype and decreased the expression of ATP-binding cassette B1 (ABCB1). Overall, our results identify AXL as an important mediator of docetaxel resistance in prostate cancer. We propose that AXL-targeted therapy, in combination with docetaxel, has the potential to improve the response to docetaxel therapy and reduce resistance induced by prolonged docetaxel therapy in prostate cancer.

The influence of living donor SHROOM3 and ABCB1 genetic variants on renal function after kidney transplantation

OBJECTIVE

A genome-wide association study has identified several gene polymorphisms associated with loss of renal function. The effect of these variants on renal function in kidney transplant recipients receiving immunosuppressive treatment is unknown.

MATERIALS AND METHODS

A cohort of 189 kidney transplant recipients and their living donors were recruited from West China Hospital of Sichuan University, on whom we assessed the association of five single nucleotide polymorphisms with renal function after kidney transplantation.

RESULTS

Glomerular filtration rate estimated by serum creatinine was significantly higher in recipients carrying allograft with the A allele at rs17319721 in SHROOM3 (shroom family member 3) than those in the group with the GG genotype from month 1 to month 6 after transplantation (P=0.020). Covariate adjustment analysis showed that the variant at rs17319721 in SHROOM3 was an independent risk factor for renal dysfunction after the first month after transplantation (P=0.022). The estimated glomerular filtration rate was the lowest in recipients with allograft carrying both the A allele at rs17319721 in SHROOM3 and the CC genotype at rs1045642 in ABCB1 (P<0.05).

CONCLUSION

The genetic variants in SHROOM3 and ABCB1 in donors were associated closely with renal function after kidney transplantation.

Kidney Fibrosis: Origins and Interventions

All causes of renal allograft injury, when severe and/or sustained, can result in chronic histological damage of which interstitial fibrosis and tubular atrophy are dominant features. Unless a specific disease process can be identified, what drives interstitial fibrosis and tubular atrophy progression in individual patients is often unclear. In general, clinicopathological factors known to predict and drive allograft fibrosis include graft quality, inflammation (whether "nonspecific" or related to a specific diagnosis), infections, such as polyomavirus-associated nephropathy, calcineurin inhibitors (CNI), and genetic factors. The incidence and severity of chronic histological damage have decreased substantially over the last 3 decades, but it is difficult to disentangle what effects individual innovations (eg, better matching and preservation techniques, lower CNI dosing, BK viremia screening) may have had. There is little evidence that CNI-sparing/minimization strategies, steroid minimization or renin-angiotensin-aldosterone system blockade result in better preservation of intermediate-term histology. Treatment of subclinical rejections has only proven beneficial to histological and functional outcome in studies in which the rate of subclinical rejection in the first 3 months was greater than 10% to 15%. Potential novel antifibrotic strategies include antagonists of transforming growth factor-β, connective tissue growth factor, several tyrosine kinase ligands (epidermal growth factor, platelet-derived growth factor, vascular endothelial growth factor), endothelin and inhibitors of chemotaxis. Although many of these drugs are mainly being developed and marketed for oncological indications and diseases, such as idiopathic pulmonary fibrosis, a number may hold promise in the treatment of diabetic nephropathy, which could eventually lead to applications in renal transplantation.

Protective effects of tacrolimus on podocytes in early diabetic nephropathy in rats

The aim of the present study was to investigate the protective effect of tacrolimus on early podocyte damage in rats with diabetic nephropathy (DN). A total of 38 normal male Sprague‑Dawley rats were randomly divided into four groups: Normal control group (group N; n=8), DN group (n=10), tacrolimus (FK506) treatment group (group F; n=10), benazepril (Lotensin) treatment group (group L; n=10). The rats in groups DN, F and L were administered with streptozotocin (STZ; 60 mg/kg) by intraperitoneal injection to establish the diabetic rat model. After 4 weeks, the diabetic rat model was established, and rats in the different groups were administered intragrastically with the respective drugs. Blood glucose (BS), body weight (BW) and 24‑h urine protein were detected every 4 weeks, serum creatinine (SCr), blood urea nitrogen (BUN) and kidney weight/body weight (KW/BW) were measured at the end of the 8 weeks of drug treatment. Renal pathological changes were observed under a light microscope and electron microscope. Expression of nephrin, which is a podocyte‑specific marker, was detected using western blot analysis. The results showed that the levels of SCr, BUN, KW/BW and 24‑h urine protein in groups D, F and L were significantly higher, compared with those in group N (P<0.05). No significant differences were found between groups F and L for the above indicators, with the exception of BS. However, all indices were significantly lower, compared with those in group DN (P<0.05). Renal pathological expression was normal in group N under light microscopy. There were significant increases in the glomerular volume, proliferative mesangial cells, width of the mesangial area and thickness of the basement membrane in group DN, however, all the above pathological characteristics were reduced in groups F and L, compared with group DN (P<0.05). No significant difference was found between groups F and L. A widened glomerular basement membrane, and disorder, widening and fusion of podocyte processes were observed under the electron microscope in group DN, however, these were reduced in groups F and L, compared with group DN (P<0.05). The results of the western blot analysis showed that the expression of nephrin decreased by 60.1% in group DN, compared with group N, and significant recovery in the expression of nephrin was observed in groups F and L (P<0.05). Tacrolimus reduced urinary protein and slowed the progression of DN, partially by recovering the protein expression of nephrin in the renal tissue of diabetic rats, and maintaining the integrity of the structure and function of podocytes.

Long-Term Clinical Impact of Adaptation of Initial Tacrolimus Dosing to CYP3A5 Genotype

Pretransplantation adaptation of the daily dose of tacrolimus to CYP3A5 genotype is associated with improved achievement of target trough concentration (C0 ), but whether this improvement affects clinical outcomes is unknown. In the present study, we have evaluated the long-term clinical impact of the adaptation of initial tacrolimus dosing according to CYP3A5 genotype: The transplantation outcomes of the 236 kidney transplant recipients included in the Tactique study were retrospectively investigated over a period of more than 5 years. In the Tactique study, patients were randomly assigned to receive tacrolimus at either a fixed dosage or a dosage determined by their genotype, and the primary efficacy end point was the proportion of patients for whom tacrolimus C0 was within target range (10-15 ng/mL) at day 10. Our results indicate that the incidence of biopsy-proven acute rejection and graft survival were similar between the control and the adapted tacrolimus dose groups, as well as between the patients who achieve the tacrolimus C0 target ranges earlier. Patients' death, cancer, cardiovascular events, and infections were also similar, and renal function did not change. We conclude that optimization of initial tacrolimus dose using pharmacogenetic testing does not improve clinical outcomes.

Pharmacogenetic aspects of the use of tacrolimus in renal transplantation: recent developments and ethnic considerations

INTRODUCTION

Tacrolimus (Tac) is effective in preventing acute rejection but has considerable toxicity and inter-individual variability in pharmacokinetics and pharmacodynamics. Part of this is explained by polymorphisms in genes encoding Tac-metabolizing enzymes and transporters. A better understanding of Tac pharmacokinetics and pharmacodynamics may help to minimize different outcomes amongst transplant recipients by personalizing immunosuppression.

AREAS COVERED

The pharmacogenetic contribution of Tac metabolism will be examined, with a focus on recent discoveries, new developments and ethnic considerations.

EXPERT OPINION

The strongest and most consistent association in pharmacogenetics is between the CYP3A5 genotype and Tac dose requirement, with CYP3A5 expressers having a ~ 40-50% higher dose requirement compared to non-expressers. Two recent randomized-controlled clinical trials using CYP3A5 genotype, however, did not show a decrease in acute rejections nor reduced toxicity. CYP3A4*22, CYP3A4*26, and POR*28 are also associated with Tac dose requirements and may be included to provide the expected improvement of Tac therapy. Studies focusing on the intracellular drug concentrations and on calcineurin inhibitor-induced nephrotoxicity also seem promising. For all studies, however, the ethnic prevalence of genotypes should be taken into account, as this may significantly impact the effect of pre-emptive genotyping.

Donor ABCB1 3435 C>T genetic polymorphisms influence early renal function in kidney transplant recipients treated with tacrolimus

AIM

Determine the effect of genetic variants of donors and recipients on early renal function and tacrolimus pharmacokinetics in kidney transplant recipients.

PATIENTS & METHODS

We measured CYP3A5 (6986A>G), ABCB1 (3435C>T, 2677G>T/A, 1236C>T) genetic polymorphisms in 120 renal transplant recipients and donors by high-resolution melting curve analysis. The renal function and tacrolimus trough concentrations were analyzed.

RESULTS

The genotype of CYP3A5 (6986A>G) in recipients showed strong influence on tacrolimus pharmacokinetics. The ABCB1 3435 CC genotype in donor was significantly associated with lower estimated glomerular filtration in recipients within 1 month (p < 0.05) and correlated with delayed creatinine recovery (p = 0.007).

CONCLUSIONS

ABCB1 3435 CC genotype in donor influences early renal function and creatinine recovery in tacrolimus-treated kidney transplant recipients.