Cytokeratin-18 is a sensitive biomarker of alanine transaminase increase in a placebo-controlled, randomized, crossover trial of therapeutic paracetamol dosing (PATH-BP biomarker substudy).

Drug-induced liver injury (DILI) is a challenge in clinical medicine and drug development. Highly sensitive novel biomarkers have been identified for detecting DILI following a paracetamol overdose. The study objective was to evaluate biomarker performance in a 14-day trial of therapeutic dose paracetamol. The PATH-BP trial was a double-blind, placebo-controlled, crossover study. Individuals (n = 110) were randomized to receive 1 g paracetamol 4× daily or matched placebo for 2 weeks followed by a 2-week washout before crossing over to the alternate treatment. Blood was collected on days 0 (baseline), 4, 7, and 14 in both arms. Alanine transaminase (ALT) activity was measured in all patients. MicroRNA-122 (miR-122), cytokeratin-18 (K18), and glutamate dehydrogenase (GLDH) were measured in patients who had an elevated ALT on paracetamol treatment (≥50% from baseline). ALT increased in 49 individuals (45%). All 3 biomarkers were increased at the time of peak ALT (K18 paracetamol arm: 18.9 ± 9.7 ng/ml, placebo arm: 11.1 ± 5.4 ng/ml, ROC-AUC = 0.80, 95% CI 0.71-0.89; miR-122: 15.1 ± 12.9fM V 4.9 ± 4.7fM, ROC-AUC = 0.83, 0.75-0.91; and GLDH: 24.6 ± 31.1U/l V 12.0 ± 11.8U/l, ROC-AUC = 0.66, 0.49-0.83). All biomarkers were correlated with ALT (K18 r = 0.68, miR-122 r = 0.67, GLDH r = 0.60). To assess sensitivity, biomarker performance was analyzed on the visit preceding peak ALT (mean 3 days earlier). K18 identified the subsequent ALT increase (K18 ROC-AUC = 0.70, 0.59-0.80; miR-122 ROC-AUC = 0.60, 0.49-0.72, ALT ROC-AUC = 0.59, 0.48-0.70; GLDH ROC-AUC = 0.70, 0.50-0.90). Variability was lowest for ALT and K18. In conclusion, K18 was more sensitive than ALT, miR-122, or GLDH and has potential significant utility in the early identification of DILI in trials and clinical practice.

Circulating argonaute-bound microRNA-126 reports vascular dysfunction and treatment response in acute and chronic kidney disease.

Vascular and kidney dysfunction commonly co-exist. There is a need for biomarkers of vascular health. Circulating microRNAs are biomarkers; miR-126 is endothelial cell-enriched. We measured circulating miR-126 in rats with nephrotoxic nephritis (NTN) and humans with acute endothelial and renal injury (vasculitis associated with autoantibodies to neutrophil cytoplasm antigens (ANCAs)). We compared these findings to those from patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD) and explored the relationship between miR-126 and vascular dysfunction. In NTN, miR-126 was reduced. In ANCA vasculitis (N = 70), pre-treatment miR-126 was reduced compared to health (N = 60) (88-fold). miR-126 increased 3.4-fold post-treatment but remained lower than in health (∼26-fold). Argonaute 2-bound miR-126 increased with ANCA vasculitis treatment. miR-126 did not differ between CKD (N = 30) and health but its concentration correlated with endothelial dysfunction. miR-126 was reduced in ESRD (N = 15) (∼350 fold). miR-126 may be a marker of vascular inflammation and could aid decision-making.

Vasopressin Regulates Extracellular Vesicle Uptake by Kidney Collecting Duct Cells.

Extracellular vesicles (ECVs) facilitate intercellular communication along the nephron, with the potential to change the function of the recipient cell. However, it is not known whether this is a regulated process analogous to other signaling systems. We investigated the potential hormonal regulation of ECV transfer and report that desmopressin, a vasopressin analogue, stimulated the uptake of fluorescently loaded ECVs into a kidney collecting duct cell line (mCCDC11) and into primary cells. Exposure of mCCDC11 cells to ECVs isolated from cells overexpressing microRNA-503 led to downregulated expression of microRNA-503 target genes, but only in the presence of desmopressin. Mechanistically, ECV entry into mCCDC11 cells required cAMP production, was reduced by inhibiting dynamin, and was selective for ECVs from kidney tubular cells. In vivo, we measured the urinary excretion and tissue uptake of fluorescently loaded ECVs delivered systemically to mice before and after administration of the vasopressin V2 receptor antagonist tolvaptan. In control-treated mice, we recovered 2.5% of administered ECVs in the urine; tolvaptan increased recovery five-fold and reduced ECV deposition in kidney tissue. Furthermore, in a patient with central diabetes insipidus, desmopressin reduced the excretion of ECVs derived from glomerular and proximal tubular cells. These data are consistent with vasopressin-regulated uptake of ECVs in vivo We conclude that ECV uptake is a specific and regulated process. Physiologically, ECVs are a new mechanism of intercellular communication; therapeutically, ECVs may be a vehicle by which RNA therapy could be targeted to specific cells for the treatment of kidney disease.