Corrigendum: c-Jun amino terminal kinase signaling promotes aristolochic acid-induced acute kidney injury.

[This corrects the article DOI: 10.3389/fphys.2021.599114.].

Cyclophilin D Promotes Acute, but Not Chronic, Kidney Injury in a Mouse Model of Aristolochic Acid Toxicity.

The plant-derived toxin, aristolochic acid (AA), is the cause of Chinese Herb Nephropathy and Balkan Nephropathy. Ingestion of high dose AA induces acute kidney injury, while chronic low dose ingestion leads to progressive kidney disease. Ingested AA is taken up by tubular epithelial cells of the kidney, leading to DNA damage and cell death. Cyclophilin D (CypD) participates in mitochondrial-dependent cell death, but whether this mechanism operates in acute or chronic AA-induced kidney injury is unknown. We addressed this question by exposing CypD-/- and wild type (WT) mice to acute high dose, or chronic low dose, AA. Administration of 5 mg/kg AA to WT mice induced acute kidney injury 3 days later, characterised by loss of kidney function, tubular cell damage and death, and neutrophil infiltration. All of these parameters were significantly reduced in CypD-/- mice. Chronic low dose (2 mg/kg AA) administration in WT mice resulted in chronic kidney disease with impaired renal function and renal fibrosis by day 28. However, CypD-/- mice were not protected from AA-induced chronic kidney disease. In conclusion, CypD facilitates AA-induced acute kidney damage, but CypD does not contribute to the transition of acute kidney injury to chronic kidney disease during ongoing AA exposure.

c-Jun Amino Terminal Kinase Signaling Promotes Aristolochic Acid-Induced Acute Kidney Injury.

Aristolochic acid (AA) is a toxin that induces DNA damage in tubular epithelial cells of the kidney and is the cause of Balkan Nephropathy and Chinese Herb Nephropathy. In cultured tubular epithelial cells, AA induces a pro-fibrotic response via the c-Jun amino terminal kinase (JNK) signaling pathway. This study investigated the in vivo role of JNK signaling with a JNK inhibitor (CC-930) in mouse models of acute high dose AA-induced kidney injury (day 3) and renal fibrosis induced by chronic low dose AA exposure (day 22). CC-930 treatment inhibited JNK signaling and protected from acute AA-induced renal function impairment and severe tubular cell damage on day 3, with reduced macrophage infiltration and expression of pro-inflammatory molecules. In the chronic model, CC-930 treatment inhibited JNK signaling but did not affect AA-induced renal function impairment, tubular cell damage including the DNA damage response and induction of senescence, or renal fibrosis; despite a reduction in the macrophage pro-inflammatory response. In conclusion, JNK signaling contributes to acute high dose AA-induced tubular cell damage, presumably via an oxidative stress-dependent mechanism, but is not involved in tubular atrophy and senescence that promote chronic kidney disease caused by ongoing DNA damage in chronic low dose AA exposure.

Initial mycophenolate dose in tacrolimus treated renal transplant recipients, a cohort study comparing leukopaenia, rejection and long-term graft function.

The evidence supporting an initial mycophenolate mofetil (MMF) dose of 2 g daily in tacrolimus-treated renal transplant recipients is limited. In a non-contemporaneous single-centre cohort study we compared the incidence of leukopaenia, rejection and graft dysfunction in patients initiated on MMF 1.5 g and 2 g daily. Baseline characteristics and tacrolimus trough levels were similar by MMF group. MMF doses became equivalent between groups by 12-months post-transplant, driven by dose reductions in the 2 g group. Leukopaenia occurred in 42.4% of patients by 12-months post-transplant. MMF 2 g was associated with a 1.80-fold increased risk of leukopaenia compared to 1.5 g. Rejection occurred in 44.8% of patients by 12-months post-transplantation. MMF 2 g was associated with half the risk of rejection relative to MMF 1.5 g. Over the first 7-years post-transplantation there was no difference in renal function between groups. Additionally, the development of leukopaenia or rejection did not result in reduced renal function at 7-years post-transplant. Leukopaenia was not associated with an increased incidence of serious infections or rejection. This study demonstrates the initial MMF dose has implications for the incidence of leukopaenia and rejection. Since neither dose produced superior long-term graft function, clinical equipoise remains regarding the optimal initial mycophenolate dose in tacrolimus-treated renal transplant recipients.

Cyclophilin A Promotes Inflammation in Acute Kidney Injury but Not in Renal Fibrosis.

Cyclophilin A (CypA) is a highly abundant protein in the cytoplasm of most mammalian cells. Beyond its homeostatic role in protein folding, CypA is a Damage-Associated Molecular Pattern which can promote inflammation during tissue injury. However, the role of CypA in kidney disease is largely unknown. This study investigates the contribution of CypA in two different types of kidney injury: acute tubular necrosis and progressive interstitial fibrosis. CypA (Ppia) gene deficient and wild type (WT) littermate controls underwent bilateral renal ischaemia/reperfusion injury (IRI) and were killed 24h later or underwent left unilateral ureteric obstruction (UUO) and were killed 7 days later. In the IRI model, CypA-/- mice showed substantial protection against the loss of renal function and from tubular cell damage and death. This was attributed to a significant reduction in neutrophil and macrophage infiltration since CypA-/- tubular cells were not protected from oxidant-induced cell death in vitro. In the UUO model, CypA-/- mice were not protected from leukocyte infiltration or renal interstitial fibrosis. In conclusion, CypA promotes inflammation and acute kidney injury in renal IRI, but does not contribute to inflammation or interstitial fibrosis in a model of progressive kidney fibrosis.

Cyclophilin Inhibition Protects Against Experimental Acute Kidney Injury and Renal Interstitial Fibrosis.

Cyclophilins have important homeostatic roles, but following tissue injury, cyclophilin A (CypA) can promote leukocyte recruitment and inflammation, while CypD can facilitate mitochondrial-dependent cell death. This study investigated the therapeutic potential of a selective cyclophilin inhibitor (GS-642362), which does not block calcineurin function, in mouse models of tubular cell necrosis and renal fibrosis. Mice underwent bilateral renal ischemia/reperfusion injury (IRI) and were killed 24 h later: treatment with 10 or 30 mg/kg/BID GS-642362 (or vehicle) began 1 h before surgery. In the second model, mice underwent unilateral ureteric obstruction (UUO) surgery and were killed 7 days later; treatment with 10 or 30 mg/kg/BID GS-642362 (or vehicle) began 1 h before surgery. GS-642362 treatment gave a profound and dose-dependent protection from acute renal failure in the IRI model. This protection was associated with reduced tubular cell death, including a dramatic reduction in neutrophil infiltration. In the UUO model, GS-642362 treatment significantly reduced tubular cell death, macrophage infiltration, and renal fibrosis. This protective effect was independent of the upregulation of IL-2 and activation of the stress-activated protein kinases (p38 and JNK). In conclusion, GS-642362 was effective in suppressing both acute kidney injury and renal fibrosis. These findings support further investigation of cyclophilin blockade in other types of acute and chronic kidney disease.

Accuracy and Utility of Estimating Lean Body Mass and Nutritional Status in Patients with Chronic Kidney Disease on Long-Term Hemodialysis Using Anthropometric Skinfold Thickness Measurements.

Malnutrition is common in patients on hemodialysis (prevalence of 30% to 50%) and is associated with higher mortality. Lean body mass (LBM) assessment is an accurate way of assessing nutritional status. The dual-energy X-ray absorptiometry (DEXA) scan is a reliable method in assessing body compositions and LBM; however, it is expensive and largely inaccessible. Anthropometric skinfold thickness measurement (ASFM) is useful in assessing LBM. It is cheaper and accessible, but underutilized clinically. The subjective global score (SGA) is a well-established method of assessing nutritional status. All three methods of assessing nutritional status were compared. In this pilot observational study, there was a significant correlation between LBM% estimated by DEXA and ASFM (mean difference -1.46% [95% CI -4.09 to 1.18]; LOA -14.0 to 11.1). Nutritional status by SGA could only detect those severely malnourished when using LBM% by ASFM as comparison. Our study demonstrated that ASFM is a useful method of assessing LBM and nutritional status, which can be easily utilized clinically.

Renal transplant ultrasound: The nephrologist's perspective.

One of the principal roles of a nephrologist is to closely monitor renal transplant allograft function and promptly evaluate any dysfunction. Renal transplant sonography has a major role in this assessment process given its ability to easily define renal transplant anatomy and surrounding structures. Abnormalities can be extrarenal or involve vascular, parenchymal and urological components of the graft and these can acutely or chronically influence graft function and survival. Procedural guidance as is required during allograft biopsy, as well as routine surveillance and screening for post transplant complications such as malignancy are also important applications of ultrasound in the management of renal transplant recipients. This article outlines key ultrasound findings and applications in renal transplantation from the clinician's perspective.