Yishen-Qingli-Huoxue formula attenuates renal fibrosis by inhibiting indoxyl sulfate via AhR/snai1 signaling

BACKGROUND

Chronic kidney disease (CKD) is challenging to reverse and its treatment options are limited. Yishen-Qingli-Huoxue Formula (YQHF) is an effective treatment Chinese formula for CKD, as verified by clinical randomized controlled trial. However, the correlative YQHF therapeutic mechanisms are still unknown.

PURPOSE

The current study aimed to investigate the potential anti-renal fibrosis effects of YQHF as well as the underlying mechanism.

METHODS

After affirming the curative effects of YQHF on adenine-induced CKD rats, Masson staining, immunohistochemistry, and ELISA were used to assess the effects of YQHF on renal fibrosis. Subsequently, metabolomics and transcriptomics analyses were conducted to clarify the potential mechanisms. Furthermore, high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), molecular docking analysis and in vitro experiments were used to verify final mechanism of anti-fibrosis.

RESULTS

Our results demonstrated that YQHF could improve renal morphology, decrease blood urea nitrogen (BUN), serum creatinine (Scr), and increase body weight gain of model rats. Masson staining, immunohistochemistry of collagen I, fibronectin (FN), α-smooth muscle actin (α-SMA), vimentin and E-cadherin showed that YQHF delayed CKD progression by alleviating renal fibrosis, and the expression of fibrotic factors smoc2 and cdh11 were obviously suppressed by YQHF. Metabolomic and transcriptomic measures discovered that indoxyl sulfate might be a crucial factor inducing renal fibrosis, and the antagonistic effect of YQHF on renal fibrosis may be exerted via AhR/snai1 signaling. Subsequently, western blot and immunohistochemical experiments revealed YQHF indeed inhibited AhR/snai1 signaling in adenine-induced renal fibrosis of CKD rat, which confirmed previous results. In addition, molecular docking and in vitro experiments further supported this conclusion, in which astilbin, the main compound identified YQHF, was certified to exert a significant effect on AhR.

CONCLUSION

Our findings showed that YQHF can effectively treat CKD by antagonizing renal fibrosis, the potential mechanisms were relating with the regulation on AhR/snai1 signaling.

Phenolic Compounds from Mori Cortex Ameliorate Sodium Oleate-Induced Epithelial-Mesenchymal Transition and Fibrosis in NRK-52e Cells through CD36

Lipid deposition in the kidney can cause serious damage to the kidney, and there is an obvious epithelial–mesenchymal transition (EMT) and fibrosis in the late stage. To investigate the interventional effects and mechanisms of phenolic compounds from Mori Cortex on the EMT and fibrosis induced by sodium oleate-induced lipid deposition in renal tubular epithelial cells (NRK-52e cells), and the role played by CD36 in the adjustment process, NRK-52e cells induced by 200 μmol/L sodium oleate were given 10 μmoL/L moracin-P-2″-O-β-d-glucopyranoside (Y-1), moracin-P-3′-O-β-d-glucopyranoside (Y-2), moracin-P-3′-O-α-l-arabinopyranoside (Y-3), and moracin-P-3′-O-[β-glucopyranoside-(1→2)arabinopyranoside] (Y-4), and Oil Red O staining was used to detect lipid deposition. A Western blot was used to detect lipid deposition-related protein CD36, inflammation-related protein (p-NF-κB-P65, NF-κB-P65, IL-1β), oxidative stress-related protein (NOX1, Nrf2, Keap1), EMT-related proteins (CD31, α-SMA), and fibrosis-related proteins (TGF-β, ZEB1, Snail1). A qRT-PCR test detected inflammation, EMT, and fibrosis-related gene mRNA levels. The TNF-α levels were detected by ELISA, and the colorimetric method was used to detects SOD and MDA levels. The ROS was measured by flow cytometry. A high-content imaging analysis system was applied to observe EMT and fibrosis-related proteins. At the same time, the experiment silenced CD36 and compared the difference between before and after drug treatment, then used molecular docking technology to predict the potential binding site of the active compounds with CD36. The research results show that sodium oleate can induce lipid deposition, inflammation, oxidative stress, and fibrosis in NRK-52e cells. Y-1 and Y-2 could significantly ameliorate the damage caused by sodium oleate, and Y-2 had a better ameliorating effect, while there was no significant change in Y-3 or Y-4. The amelioration effect of Y-1 and Y-2 disappeared after silencing CD36. Molecular docking technology showed that the Y-1 and Y-2 had hydrogen bonds to CD36 and that, compared with Y-1, Y-2 requires less binding energy. In summary, moracin-P-2″-O-β-d-glucopyranoside and moracin-P-3′-O-β-d-glucopyranoside from Mori Cortex ameliorated lipid deposition, EMT, and fibrosis induced by sodium oleate in NRK-52e cells through CD36.

Blocking 5-LO pathway alleviates renal fibrosis by inhibiting the epithelial-mesenchymal transition

The enzyme 5-lipoxygenase (5-LO) converts arachidonic acid to leukotrienes, which mediate inflammation. The enzyme is known to contribute to organ fibrosis, but how it contributes to renal fibrosis is unclear. Here, we reported that fibrotic kidneys expressed high levels of 5-LO, and deleting the 5-LO gene mitigated renal fibrosis in mice subjected to unilateral ureteral obstruction (UUO), based on assays of collagen deposition, injury and inflammation. Mechanistically, the exogenous leukotrienes B₄ and C₄, the downstream products of 5-LO, could induce the epithelial-mesenchymal transition (EMT) in kidney epithelial cell cultures, based on assays of E-cadherin, vimentin and snail expression. Studies in UUO mice confirmed that 5-LO deletion inhibited the EMT in the obstructed kidney. More importantly, 5-LO inhibitor zileuton loaded in CREKA-Lip, which could target to fibrotic kidney, markedly attenuated UUO-induced renal fibrosis and injury by inhibiting the EMT in the obstructed kidney. Our results suggested that 5-LO activity may contribute to renal fibrosis by promoting renal EMT, implying that the enzyme may be a useful therapeutic target.

Microvasculature partial endothelial mesenchymal transition in early posttransplant biopsy with acute tubular necrosis identifies poor recovery renal allografts

Acute tubular necrosis (ATN), a frequent histopathological feature in the early post-renal transplant biopsy, affects long-term graft function. Appropriate markers to identify patients at risk of no or incomplete recovery after delayed graft function are lacking. In this study, we first included 41 renal transplant patients whose biopsy for cause during the first month after transplantation showed ATN lesions. Using partial microvasculature endothelial (fascin, vimentin) and tubular epithelial (vimentin) to mesenchymal transition markers, detected by immunohistochemistry, we found a significant association between partial endothelial to mesenchymal transition and poor graft function recovery (Spearman's rho = -0.55, P = .0005). Transforming growth factor-β1 was strongly expressed in these phenotypic changed endothelial cells. Extent of ATN was also correlated with short- and long-term graft dysfunction. However, the association of extensive ATN with long-term graft dysfunction (24 months posttransplant) was observed only in patients with partial endothelial to mesenchymal transition marker expression in their grafts (Spearman's rho = -0.64, P = .003), but not in those without. The association of partial endothelial to mesenchymal transition with worse renal graft outcome was confirmed on 34 other early biopsies with ATN from a second transplant center. Our results suggest that endothelial cell activation at the early phase of renal transplantation plays a detrimental role.

ZEB1 Mediates Fibrosis in Corneal Endothelial Mesenchymal Transition Through SP1 and SP3

Purpose

ZEB1 is induced during endothelial-mesenchymal transition (EnMT) in the cornea. Induction of SP1 and SP3 by ZEB1 along with identification of putative SP1 and SP3 binding sites in promoters of EnMT-associated gene lead us to investigate their roles in retrocorneal membrane formation in the corneal endothelium.

Methods

Expressions of SP1, SP3, and EnMT associated genes were analyzed by immunoblotting and semiquantitative reverse transcription polymerase chain reaction. Accell SMARTpool siRNAs targeting ZEB1, SP1, and SP3 were used for gene knockdown. SP1 and SP3 binding to promoters of EnMT associated genes was investigated by chromatin immunoprecipitation assay. Corneal endothelium in mice was surgically injured in vivo under direct visualization.

Results

Transient Fibroblast Growth Factor 2 stimulation increased the expression of both SP1 and SP3 in the human corneal endothelium ex vivo. ZEB1 siRNA knockdown inhibited FGF2-induced SP1 mRNA and protein but not the expression of SP3. FGF2-induced expression of EnMT-related genes, such as fibronectin, vimentin, and type I collagen, was reduced by both SP1 and SP3 siRNA knockdown, with inhibition of SP1 having a greater inhibitory effect than SP3. Additionally, although SP1 and SP3 proteins were found to bind together, SP1 and SP3 could bind to the same promoter binding sites of EnMT-related genes in the absence of the other. Moreover, siRNA knockdown of Zeb1 inhibited injury-dependent RCM formation in mouse corneal endothelium in vivo.

Conclusions

Zeb1, through SP1 and SP3, plays a central role in mesenchymal transition induced fibrosis in the corneal endothelium and suggests that Zeb1 could be targeted to inhibit anterior segment fibrosis.

Ursolic acid inhibits epithelial-mesenchymal transition in vitro and in vivo

CONTEXT

Ursolic acid (UA; 3β-hydroxy-urs-12-en-28-oic acid), one of the pentacyclic triterpenoids found in various plants and herbs, possesses some beneficial effects under pathological conditions, including combating hepatic fibrosis.

OBJECTIVE

This study investigates the effects of UA on renal tubulointerstitial fibrosis in vivo and in vitro.

MATERIALS AND METHODS

In vivo, 24 male C57BL6 mice were divided into four groups. Eighteen mice were subjected to unilateral ureteral obstruction (UUO) and the remaining six sham-operated mice served as control. UUO mice received either vehicle or UA (50 or 100 mg/kg) by gastric gavage for 6 days. In vitro, HK-2 cells were treated with 10 or 50 μM UA and 10 ng/mL recombinant human transforming growth factor-β1 (TGF-β1). The molecular mechanisms of fibrosis were investigated.

RESULTS

UUO induced marked interstitial collagen I and fibronectin deposition and epithelial-mesenchymal transition (EMT), as evidenced by increased α-smooth muscle actin (α-SMA) and decreased E-cadherin. However, UA treatment significantly reduced collagen I and fibronectin accumulation in the fibrotic kidney. UA treatment also decreased α-SMA and preserved E-cadherin in vivo. In vitro, TGF-β1-treated HK-2 cells demonstrated elevated α-SMA, snail1, slug, TGF-β1, and p-smad3, as well as diminished E-cadherin. UA pretreatment prevented E-cadherin loss and diminished α-SMA expression in HK-2 cells. UA downregulated mRNA expression of snail1 and slug. UA also lowered TGF-β1 protein expression and p-Smad3 in HK-2 cells.

CONCLUSIONS

UA attenuated renal tubulointerstitial fibrosis by inhibiting EMT, and such inhibition may be achieved by decreasing profibrotic factors. UA may be a novel therapeutic agent for renal fibrosis.

Renal tubular epithelial cells: the neglected mediator of tubulointerstitial fibrosis after injury

Renal fibrosis, especially tubulointerstitial fibrosis, is the inevitable outcome of all progressive chronic kidney diseases (CKDs) and exerts a great health burden worldwide. For a long time, interests in renal fibrosis have been concentrated on fibroblasts and myofibroblasts. However, in recent years, growing numbers of studies have focused on the role of tubular epithelial cells (TECs). TECs, rather than a victim or bystander, are probably a neglected mediator in renal fibrosis, responding to a variety of injuries. The maladaptive repair mechanisms of TECs may be the key point in this process. In this review, we will focus on the role of TECs in tubulointerstitial fibrosis. We will follow the fate of a tubular cell and depict the intracellular changes after injury. We will then discuss how the repair mechanism of tubular cells becomes maladaptive, and we will finally discuss the intercellular crosstalk in the interstitium that ultimately proceeds tubulointerstitial fibrosis.

Snail and kidney fibrosis

Snail family zinc finger 1 (SNAI1) is a transcription factor expressed during renal embryogenesis, and re-expressed in various settings of acute kidney injury (AKI). Subjected to tight regulation, SNAI1 controls major biological processes responsible for renal fibrogenesis, including mesenchymal reprogramming of tubular epithelial cells, shutdown of fatty acid metabolism, cell cycle arrest and inflammation of the microenvironment surrounding tubular epithelial cells. The present review describes in detail the interactions of SNAI1 with AKI-associated signalling pathways. We also discuss how this central factor has been iteratively (and promisingly) targeted in a number of animal models in order to prevent or slow down renal fibrogenesis.

CERA Attenuates Kidney Fibrogenesis in the db/db Mouse by Influencing the Renal Myofibroblast Generation

Tubulointerstitial fibrosis (TIF) is a pivotal pathophysiological process in patients with diabetic nephropathy (DN). Multiple profibrotic factors and cell types, including transforming growth factor beta 1 (TGF-β1) and interstitial myofibroblasts, respectively, are responsible for the accumulation of extracellular matrix in the kidney. Matrix-producing myofibroblasts can originate from different sources and different mechanisms are involved in the activation process of the myofibroblasts in the fibrotic kidney. In this study, 16-week-old db/db mice, a model for type 2 DN, were treated for two weeks with continuous erythropoietin receptor activator (CERA), a synthetic erythropoietin variant with possible non-hematopoietic, tissue-protective effects. Non-diabetic and diabetic mice treated with placebo were used as controls. The effects of CERA on tubulointerstitial fibrosis (TIF) as well as on the generation of the matrix-producing myofibroblasts were evaluated by morphological, immunohistochemical, and molecular biological methods. The placebo-treated diabetic mice showed significant signs of beginning renal TIF (shown by picrosirius red staining; increased connective tissue growth factor (CTGF), fibronectin and collagen I deposition; upregulated KIM1 expression) together with an increased number of interstitial myofibroblasts (shown by different mesenchymal markers), while kidneys from diabetic mice treated with CERA revealed less TIF and fewer myofibroblasts. The mechanisms, in which CERA acts as an anti-fibrotic agent/drug, seem to be multifaceted: first, CERA inhibits the generation of matrix-producing myofibroblasts and second, CERA increases the ability for tissue repair. Many of these CERA effects can be explained by the finding that CERA inhibits the renal expression of the cytokine TGF-β1.

Urinary mRNA analysis of biomarkers to epithelial mesenchymal transition of renal allograft

Renal allograft loss is most often a chronic process, irrespective of the mechanism at stake. In this prospective study, we studied the expression of epithelial to mesenchymal transition (EMT) markers vimentin and β-catenin by immunohistochemistry in the surveillance biopsy and measured the mRNA encoding vimentin (VIM), CD45, GAPDH and uroplakin 1a (UPK) by quantitative PCR in urinary cells in 75 renal transplant patients. The aim is to establish a simple screening test for chronic renal allograft dysfunction. We found that the value of the mRNA of vimentin and CD45 relative to the uroplakin 1a (UPK) mRNA is correlated with the score in vimentin immunostaining in routine biopsies. These biomarkers could be used as a noninvasive tool to monitor the renal graft fibrogenesis. This test could be used for early detection of fibrotic diseases of the kidney transplant.

Dimethylarginine Dimethylaminohydrolase 1 Deficiency Induces the Epithelial to Mesenchymal Transition in Renal Proximal Tubular Epithelial Cells and Exacerbates Kidney Damage in Aged and Diabetic Mice

AIMS

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, is mainly degraded by dimethylarginine dimethylaminohydrolase (DDAH). Emerging evidence suggests that plasma ADMA accumulation and DDAH1 activity/expression reduction are linked to chronic kidney disease (CKD) pathology, but the mechanisms remain largely unknown. Here, we examined the role of ADMA/DDAH1 in the epithelial-mesenchymal transition (EMT) of tubular epithelial cells (TECs), an important mechanism for the pathogenesis of renal fibrosis.

RESULTS

In HK-2 cells, DDAH1 expression was reduced by aldosterone treatment, and overexpression of DDAH1 significantly attenuated aldosterone-induced EMT. More interestingly, DDAH1 deficiency resulted in EMT-related changes in primary TECs via increasing oxidative stress, impairing adenosine monophosphate-activated kinase (AMPK) signaling, and downregulating of peroxiredoxin 5 (Prdx5). However, those effects could not be mimicked by increasing the ADMA concentration. After regular feeding for 24 months or inducing type 2 diabetes, Ddah1^-/- mice had higher serum creatinine levels than wild-type (WT) mice. In the kidneys of the aged or diabetic mice, loss of DDAH1 resulted in more interstitial fibrosis, more collagen deposition, and greater induction of EMT-related changes and oxidative stress than in the WT kidneys. Innovation and Conclusion: Our results provide the first direct evidence that the DDAH1 has a marked effect on kidney fibrosis and oxidative stress induced by aging or diabetes. Our findings suggest that strategies to increase DDAH1 activity in TECs may provide a novel approach to attenuate CKD development. Antioxid. Redox Signal. 27, 1347-1360.

Snail1 is positively correlated with atrial fibrosis in patients with atrial fibrillation and rheumatic heart disease

The present study investigated the association between Snail1 and atrial fibrosis in patients with atrial fibrillation (AF) and rheumatic heart disease (RHD) and to determine the possible mechanism underlying this interrelation. A total of 19 patients were included in the current study and were divided into two groups: A sinus rhythm (SR) group (n=9) and an AF group (n=10). All patients underwent heart valve replacement surgery, during which ~200 mg right atrium tissue was obtained. Hematoxylin and eosin and Masson's trichrome-stained sections were used to evaluate the morphological changes of cardiomyocytes and the level of fibrosis. Immunohistochemistry was applied to observe the location and expression of Snail1. Reverse transcription-quantitative polymerase chain reaction was used to measure Snail1 mRNA levels. Western blotting was used to determine changes in the expression of Snail1, as well as in the expression of proteins involved in the Wnt pathway, including Wnt1, Wnt 3a, Wnt8a, Wnt5a and Wnt11. Compared with the SR group, expanded cardiomyocytes and higher collagen deposition was detected in the atrial tissue of the AF group. The expression of Snail1 mRNA and protein was significantly higher in the AF group than in the SR group (P<0.05). Additionally, the expression of Wnt1, 3a and 8a in the canonical Wnt signaling pathway, and Wnt5a and 11 in the noncanonical Wnt signaling pathway were significantly increased in the AF group. Furthermore, the phosphorylation level of glycogen synthase kinase 3β (GSK3β) and the levels of β-catenin and GSK3β were significantly increased in the AF group compared with the SR group (P<0.05). Snail1 may be involved in the development and maintenance of atrial fibrosis in patients with atrial fibrillation and rheumatic heart disease and may be developed as a novel biomarker to evaluate myocardial fibrosis in the future. Additionally, the current study suggests that the Wnt signaling pathway may participate in the process of increased Snail1 expression and atrial fibrosis in patients with AF and RHD.

Tubular Cytoplasmic Expression of Zinc Finger Protein SNAI1 in Renal Transplant Biopsies: A Sign of Diseased Epithelial Phenotype?

The aim of the present study was to analyze in vivo the role of zinc finger protein SNAI1 (SNAI1) on renal fibrosis. Unilateral ureteral obstruction injury was induced in Snai1 knockout mice. Snai1 gene deletion was, however, only partial and could therefore not be correlated to reduced fibrosis. Expression of SNAI1 protein and epithelial-mesenchymal transformation markers was then assessed in human chronic allograft nephropathy biopsy specimens. Significant up-regulation of SNAI1 protein was detected within cytoplasm of proximal tubules localized, for some of them, near foci of fibrosis and tubular atrophy. No concomitant epithelial-mesenchymal transformation could, however, be demonstrated analyzing the expression of the fibroblast markers vimentin, α-smooth muscle actin, and S100A4. SNAI1 cytoplasmic up-regulation was particularly evident in biopsy specimens obtained from calcineurin inhibitor-treated patients, which might be because of, as suggested by in vitro experiments, a decrease of the proteasome chimotrypsin activity. Deeper analysis on chronic allograft nephropathy biopsy specimens suggested that SNAI1 cytoplasmic up-regulation was preceded by a transient increase of phosphorylated heat shock protein 27, p38 mitogen-activated protein kinase, and glycogen synthase kinase 3β. Concomitant down-regulation of the polyubuquitinylated conjugates was detected in SNAI1⁺ tubules. Altogether, these results might suggest that calcineurin inhibitor-induced tubular SNAI1 protein cytoplasmic accumulation, possibly because of impaired SNAI1 proteasomal degradation and nuclear translocation, might be a sign of a diseased profibrotic epithelial phenotype.

Partial Epithelial-to-Mesenchymal Transition and Other New Mechanisms of Kidney Fibrosis

Kidney fibrosis is the unavoidable consequence of chronic kidney disease irrespective of the primary underlying insult. It is a complex phenomenon governed by the interplay between different cellular components and intricate networks of signaling pathways, which together lead to loss of renal functionality and replacement of kidney parenchyma with scar tissue. An immense effort has recently been made to understand the molecular and cellular mechanisms leading to kidney fibrosis. The cellular protagonists of this process include myofibroblasts, tubular epithelial cells, endothelial cells, and immune cells. We discuss here the most recent findings, including partial epithelial-to-mesenchymal transition (EMT), in the initiation and progression of tissue fibrosis and chronic kidney disease (CKD). A deep understanding of these mechanisms will allow the development of effective therapies.

Is there any role of epithelial to mesenchymal transition in the pathogenesis of contrast nephropathy?

AIM

Contrast medium-induced nephropathy is one of the major complications of intravenous contrast medium use. But its pathogenesis is unclear. Epithelial mesenchymal transition (EMT) is defined as the transformation of the primer epithelial cells to mesenchymal cells. EMT in tubular cells might cause tubulointerstitial damage. In this study, we investigated whether or not EMT has a role in radiocontrast-induced nephropathy. Radiocontrast medium might be triggering reversible EMT via serum and glucocorticoid-regulated kinase 1 (SGK 1). We investigated the effect of different concentrations of the contrast agent iopromide on human proximal tubule cell (HK-2) culture by measuring the level of SGK1, snail family zinc finger 1 (SNAIL1), connective tissue growth factor (CTGF), and collagen type I alpha 1 (COL1A1).

METHODS

We conducted a scratch assay and qPCR. HK-2 cells were cultured in the petri dishes/flasks and starved with serum-free medium. The 40, 20, and 10 mg/mL doses of iopromide were administrated to cells. The scratches were photographed immediately and again at the 20th hour. The levels of gene expression of SGK1, SNAIL1, CTGF, and COL1A1 were measured using the real-time qPCR system at the end of the 24th hour.

RESULTS

Iopromide caused the breaking of intercellular connections, the disappearance of the cobblestone appearance of cells, and the migration of cells at the 20th hour in the scratch assay. It also increased the expression of SGK1, SNAIL1, CTGF, and COL1A1 genes.

CONCLUSION

Our study concluded that certain important markers of EMT increase in different concentrations of the contrast agent. High osmolality might trigger EMT. The relationship between contrast agent and EMT has not been defined before. Further in vivo and in vitro studies are required.

Markers of Endothelial-to-Mesenchymal Transition: Evidence for Antibody-Endothelium Interaction during Antibody-Mediated Rejection in Kidney Recipients

Antibody-mediated rejection (ABMR) is a leading cause of allograft loss. Treatment efficacy depends on accurate diagnosis at an early stage. However, sensitive and reliable markers of antibody-endothelium interaction during ABMR are not available for routine use. Using immunohistochemistry, we retrospectively studied the diagnostic value of three markers of endothelial-to-mesenchymal transition (EndMT), fascin1, vimentin, and heat shock protein 47, for ABMR in 53 renal transplant biopsy specimens, including 20 ABMR specimens, 24 cell-mediated rejection specimens, and nine normal grafts. We validated our results in an independent set of 74 unselected biopsy specimens. Endothelial cells of the peritubular capillaries in grafts with ABMR expressed fascin1, vimentin, and heat shock protein 47 strongly, whereas those from normal renal grafts did not. The level of EndMT marker expression was significantly associated with current ABMR criteria, including capillaritis, glomerulitis, peritubular capillary C4d deposition, and donor-specific antibodies. These markers allowed us to identify C4d-negative ABMR and to predict late occurrence of disease. EndMT markers were more specific than capillaritis for the diagnosis and prognosis of ABMR and predicted late (up to 4 years after biopsy) renal graft dysfunction and proteinuria. In the independent set of 74 renal graft biopsy specimens, the EndMT markers for the diagnosis of ABMR had a sensitivity of 100% and a specificity of 85%. Fascin1 expression in peritubular capillaries was also induced in a rat model of ABMR. In conclusion, EndMT markers are a sensitive and reliable diagnostic tool for detecting endothelial activation during ABMR and predicting late loss of allograft function.

Drug-induced nephrotoxicity: clinical impact and preclinical in vitro models

The kidney is a major target for drug-induced toxicity. Drug-induced nephrotoxicity remains a major problem in the clinical setting, where the use of nephrotoxic drugs is often unavoidable. This leads frequently to acute kidney injury, and current problems are discussed. One strategy to avoid such problems would be the development of drugs with decreased nephrotoxic potential. However, the prediction of nephrotoxicity during preclinical drug development is difficult and nephrotoxicity is typically detected only late. Also, the nephrotoxic potential of newly approved drugs is often underestimated. Regulatory approved or validated in vitro models for the prediction of nephrotoxicity are currently not available. Here, we will review current approaches on the development of such models. This includes a discussion of three-dimensional and microfluidic models and recently developed stem cell based approaches. Most in vitro models have been tested with a limited number of compounds and are of unclear predictivity. However, some studies have tested larger numbers of compounds and the predictivity of the respective in vitro model had been determined. The results showed that high predictivity can be obtained by using primary or stem cell derived human renal cells in combination with appropriate end points.

Progression of pulse pressure in kidney recipients durably exposed to CsA is a risk factor for epithelial phenotypic changes: an ancillary study of the CONCEPT trial

In this ancillary study of the CONCEPT trial, we studied the role of CsA withdrawal at 3 months (3M) post-transplant on the intensity of epithelial phenotypic changes (EPC, an early marker for kidney fibrogenesis) on the 12 M surveillance biopsy. Although conversion from CsA to sirolimus (SRL) at 3M was reported to have improved mean graft function at 12 M, it did not reduce the score of EPC (1.73 ± 1.15 in the SRL group vs. 1.87 ± 1 in the CsA group, P = 0.61). Acute rejection, which had occurred twice more frequently in SRL-converted patients included here, was associated with 12 M EPC. Interestingly, we observed that the patients durably exposed to CsA and who developed 12 M EPC had a significant progression of blood pulse pressure (pp) from 1 to 6M post-transplantation (Δpp = +12.3 mmHg, P = 0.0035). Pulse pressure at 4, 6, and 9 M and pp progression from 1 to 6M were significantly associated with the development of EPC at 12 M in renal grafts. Logistic regression analysis revealed that a high 6M pp (≥ 60 mmHg) was an independent risk factor for 12 M EPC with an odds ratio of 2.25 per additional 10 mmHg pp (95%CI: 1.14-4.4, P = 0.02) after adjustment with recipient's and donor's age, acute rejection incidence and immunosuppressive regimen. A post hoc analysis of the data collected in the whole population CONCEPT study revealed that pp was significantly higher at 6 months in patients maintained on CsA and that at this time point pp correlated negatively with GFR at 1 year.