The relevance of microRNAs and circadian rhythms in drug safety

Drug-induced liver injury (DILI) is a serious adverse drug reaction (ADR) that is frequently encountered during drug development, representing a major cause of drug attrition. Furthermore, DILI is also a serious concern in the clinic, accounting for approximately half of all acute liver failure cases. Paracetamol overdose (acetaminophen; APAP) accounts for the majority of DILI-associated cases of ALF encountered in patients. The identification and development of novel biomarkers of DILI that are sensitive, specific, and rise early during hepatotoxicity are urgently required in the clinic and in the laboratory. Two liver-specific microRNAs (miRNAs) have recently been described that serve as sensitive and early markers of APAP-induced acute liver injury (APAP-induced ALI) in a mouse model. Together with the superior liver-enrichment of some liver-enriched miRNAs, these potential markers need to be assessed in patients for the clinical promise. Moreover, further work is warranted to test these potential markers in alternative pre-clinical models with other compounds to gain a better understanding regarding sensitivity of release, mechanism of release and circulatory kinetics. Furthermore, in separate work discussed in this thesis, the mammalian biological clock has been found to exert a powerful influence on the physiology of mammalian systems. This regulation hinges on the complex interplay between the clock genes and their products that oscillate over a twenty-four hour period and promote a diurnal variation in numerous output pathways. Emerging evidence suggests that the efficacy and toxicity of many drugs follow a diurnal rhythm and that this may be at least partly attributable to the clock-mediated regulation of drug targets and pathways of drug metabolism. APAP and FS represent two compounds that elicit hepatotoxicity in the mouse through two distinct mechanisms. Both APAP and FS are known to exhibit circadian variation in their toxicology and/or pharmacology. However, little is known about the molecular mechanisms that govern these differences in circadian variation. Two liver-enriched miRNAs (miR-122 and miR-192) were tested alongside serum ALT activity, the gold-standard marker of ALI, for sensitivity and time of release in a mouse model of APAP-induced ALI. At 2 hours after APAP administration, miR-122 (ΔΔCt 75.0, P=0.02) was significantly higher compared to controls (ΔΔCt 4.1) while ALT levels were in the normal range (21 U/L) indicating earlier release of miR-122. In a sensitivity study, miR-122 was not more sensitive than ALT at a 300 mg/kg dose of APAP compared to controls (mean values 300 mg/kg vs 0 mg/kg: ALT = 491 U/L vs 38.1 U/L; miR-122 = ΔΔCt 572.9 vs ΔΔCt 209.4). In patients, serum miR-122 and miR-192 were substantially higher in APAP-induced ALI patients, compared to healthy controls (median ΔΔCt miR-122: 1,265 versus 12.1, P 3 x ULN serum ALT activity) compared to those that did not (median ΔΔCt 3.48 vs ΔΔCt 0.16, P 1.3) compared to those that did not (ΔΔCt vs 3.48 vs ΔΔCt 0.17, P=0.0004). In contrast, presentation ALT levels were not different between patients who developed ALI iv compared to those that did not (median ALT = 21 U/L vs 19 U/L). In chronotoxicity studies, both APAP exhibited greater toxicity in the evening (mean ALT = 12785, 66% survival) compared to morning (mean ALT = 380, 100% survival) whereas FS showed greater toxicity after morning administration (mean ALT=561, 100% survival) compared to evening administration (mean ALT = 69.2, 100% survival). Circadian variation in APAP-induced ALI was associated with 38% lower (P=0.003) GSH levels and 20% higher (P=0.024) Cyp2e1 levels at 21:00h compared to 09:00. This work confirms that miR-122 is released earlier than ALT in a young mouse model of APAP-induced ALI. Furthermore, it is shown for the first time that circulating liver enriched miRNAs are higher in patients following an APAP overdose. Also, plasma miR-122 is raised at emergency room presentation when serum ALT activity is in the normal range. Further clinical development of blood-based miR-122 is warranted, this work suggests that miR-122 analysis at the point of hospital admission can predict risk of subsequent liver injury in patients. Finally, APAP and FS exhibit circadian variation in their toxicity in a mouse model associated with circadian variation with genes involved in drug metabolism and drug detoxification. Profiling of the hepatic proteome over the circadian phase is now warranted

Mechanistic biomarkers provide early and sensitive detection of acetaminophen-induced acute liver injury at first presentation to hospital

Acetaminophen overdose is a common reason for hospital admission and the most frequent cause of hepatotoxicity in the Western world. Early identification would facilitate patient-individualized treatment strategies. We investigated the potential of a panel of novel biomarkers (with enhanced liver expression or linked to the mechanisms of toxicity) to identify patients with acetaminophen-induced acute liver injury (ALI) at first presentation to the hospital when currently used markers are within the normal range. In the first hospital presentation plasma sample from patients (n = 129), we measured microRNA-122 (miR-122; high liver specificity), high mobility group box-1 (HMGB1; marker of necrosis), full-length and caspase-cleaved keratin-18 (K18; markers of necrosis and apoptosis), and glutamate dehydrogenase (GLDH; marker of mitochondrial dysfunction). Receiver operator characteristic curve analysis and positive/negative predictive values were used to compare sensitivity to report liver injury versus alanine transaminase (ALT) and International Normalized Ratio (INR). In all patients, biomarkers at first presentation significantly correlated with peak ALT or INR. In patients presenting with normal ALT or INR, miR-122, HMGB1, and necrosis K18 identified the development of liver injury (n = 15) or not (n = 84) with a high degree of accuracy and significantly outperformed ALT, INR, and plasma acetaminophen concentration for the prediction of subsequent ALI (n = 11) compared with no ALI (n = 52) in patients presenting within 8 hours of overdose. Conclusion: Elevations in plasma miR-122, HMGB1, and necrosis K18 identified subsequent ALI development in patients on admission to the hospital, soon after acetaminophen overdose, and in patients with ALTs in the normal range. The application of such a biomarker panel could improve the speed of clinical decision-making, both in the treatment of ALI and the design/execution of patient-individualized treatment strategies

Insulin Production and Resistance in Different Models of Diet-Induced Obesity and Metabolic Syndrome

The role of the liver and the endocrine pancreas in development of hyperinsulinemia in different types of obesity remains unclear. Sedentary rats (160 g) were fed a low-fat-diet (LFD, chow 13% kcal fat), high-fat-diet (HFD, 35% fat), or HFD+ 30% ethanol+ 30% fructose (HF-EFr, 22% fat). Overnight-fasted rats were culled after one, four or eight weeks. Pancreatic and hepatic mRNAs were isolated for subsequent RT-PCR analysis. After eight weeks, body weights increased three-fold in the LFD group, 2.8-fold in the HFD group, and 2.4-fold in the HF-EFr (p < 0.01). HF-EFr-fed rats had the greatest liver weights and consumed less food during Weeks 4–8 (p < 0.05). Hepatic-triglyceride content increased progressively in all groups. At Week 8, HOMA-IR values, fasting serum glucose, C-peptide, and triglycerides levels were significantly increased in LFD-fed rats compared to that at earlier time points. The greatest plasma levels of glucose, triglycerides and leptin were observed in the HF-EFr at Week 8. Gene expression of pancreatic-insulin was significantly greater in the HFD and HF-EFr groups versus the LFD. Nevertheless, insulin: C-peptide ratios and HOMA-IR values were substantially higher in HF-EFr. Hepatic gene-expression of insulin-receptor-substrate-1/2 was downregulated in the HF-EFr. The expression of phospho-ERK-1/2 and inflammatory-mediators were greatest in the HF-EFr-fed rats. Chronic intake of both LFD and HFD induced obesity, MetS, and intrahepatic-fat accumulation. The hyperinsulinemia is the strongest in rats with the lowest body weights, but having the highest liver weights. This accompanies the strongest increase of pancreatic insulin production and the maximal decrease of hepatic insulin signaling, which is possibly secondary to hepatic fat deposition, inflammation and other factors

Alternatively activated macrophages promotes necrosis resolution following acute liver injury

Background & Aim Following acetaminophen (APAP) overdose, acute liver injury (ALI) can occur in patients that present too late for N-acetylcysteine treatment, potentially leading to acute liver failure, systemic inflammation, and death. Macrophages influence the progression and resolution of ALI due to their innate immunological function and paracrine activity. Syngeneic primary bone marrow-derived macrophages (BMDMs) were tested as a cell-based therapy in a mouse model of APAP-induced ALI (APAP-ALI). Methods Several phenotypically distinct BMDM populations were delivered intravenously to APAP-ALI mice when hepatic necrosis was established, and then evaluated based on their effects on injury, inflammation, immunity, and regeneration. In vivo phagocytosis assays were used to interrogate the phenotype and function of alternatively activated BMDMs (AAMs) post-injection. Finally, primary human AAMs sourced from healthy volunteers were evaluated in immunocompetent APAP-ALI mice. Results BMDMs rapidly localised to the liver and spleen within 4 h of administration. Injection of AAMs specifically reduced hepatocellular necrosis, HMGB1 translocation, and infiltrating neutrophils following APAP-ALI. AAM delivery also stimulated proliferation in hepatocytes and endothelium, and reduced levels of several circulating proinflammatory cytokines within 24 h. AAMs displayed a high phagocytic activity both in vitro and in injured liver tissue post-injection. Crosstalk with the host innate immune system was demonstrated by reduced infiltrating host Ly6Chi macrophages in AAM-treated mice. Importantly, therapeutic efficacy was partially recapitulated using clinical-grade primary human AAMs in immunocompetent APAP-ALI mice, underscoring the translational potential of these findings. Conclusion We identify that AAMs have value as a cell-based therapy in an experimental model of APAP-ALI. Human AAMs warrant further evaluation as a potential cell-based therapy for APAP overdose patients with established liver injury. Lay summary After an overdose of acetaminophen (paracetamol), some patients present to hospital too late for the current antidote (N-acetylcysteine) to be effective. We tested whether macrophages, an injury-responsive leukocyte that can scavenge dead/dying cells, could serve as a cell-based therapy in an experimental model of acetaminophen overdose. Injection of alternatively activated macrophages rapidly reduced liver injury and reduced several mediators of inflammation. Macrophages show promise to serve as a potential cell-based therapy for acute liver injury

Human umbilical cord perivascular cells improve human pancreatic islet transplant function by increasing vascularization

Islet transplantation is an efficacious therapy for type 1 diabetes; however, islets from multiple donor pancreata are required, and a gradual attrition in transplant function is seen. Here, we manufactured human umbilical cord perivascular mesenchymal stromal cells (HUCPVCs) to Good Manufacturing Practice (GMP) standards. HUCPVCs showed a stable phenotype while undergoing rapid ex vivo expansion at passage 2 (p2) to passage 4 (p4) and produced proregenerative factors, strongly suppressing T cell responses in the resting state and in response to inflammation. Transplanting an islet equivalent (IEQ):HUCPVC ratio of 1:30 under the kidney capsule in diabetic NSG mice demonstrated the fastest return to normoglycemia by 3 days after transplant: Superior glycemic control was seen at both early (2.7 weeks) and later stages (7, 12, and 16 weeks) versus ratios of 1:0, 1:10, and 1:50, respectively. Syngeneic islet transplantation in immunocompetent mice using the clinically relevant hepatic portal route with a marginal islet mass showed that mice transplanted with an IEQ:HUCPVC ratio of 1:150 had superior glycemic control versus ratios of 1:0, 1:90, and 1:210 up to 6 weeks after transplant. Immunodeficient mice transplanted with human islets (IEQ:HUCPVC ratio of 1:150) exhibited better glycemic control for 7 weeks after transplant versus islet transplant alone, and islets transplanted via the hepatic portal vein in an allogeneic mouse model using a curative islet mass demonstrated delayed rejection of islets when cotransplanted with HUCPVCs (IEQ:HUCPVC ratio of 1:150). The immunosuppressive and proregenerative properties of HUCPVCs demonstrated long-term positive effects on graft function in vivo, indicating that they may improve long-term human islet allotransplantation outcomes

TWEAK/Fn14 signalling promotes cholangiocarcinoma niche formation and progression.

Background & Aims: Cholangiocarcinoma (CCA) is a cancer of the hepatic bile ducts that is rarely resectable and is associated with poor prognosis. Tumour necrosis factor-like weak inducer of apoptosis (TWEAK) is known to signal via its receptor fibroblast growth factor-inducible 14 (Fn14) and induce cholangiocyte and myofibroblast proliferation in liver injury. We aimed to characterise its role in CCA. Methods: The expression of the TWEAK ligand and Fn14 receptor was assessed immunohistochemically and by bulk RNA and single cell transcriptomics of human liver tissue. Spatiotemporal dynamics of pathway regulation were comprehensively analysed in rat and mouse models of thioacetamide (TAA)-mediated CCA. Flow cytometry, qPCR and proteomic analyses of CCA cell lines and conditioned medium experiments with primary macrophages were performed to evaluate the downstream functions of TWEAK/Fn14. In vivo pathway manipulation was assessed via TWEAK overexpression in NICD/AKT-induced CCA or genetic Fn14 knockout during TAA-mediated carcinogenesis. Results: Our data reveal TWEAK and Fn14 overexpression in multiple human CCA cohorts, and Fn14 upregulation in early TAA-induced carcinogenesis. TWEAK regulated the secretion of factors from CC-SW-1 and SNU-1079 CCA cells, inducing polarisation of proinflammatory CD206+ macrophages. Pharmacological blocking of the TWEAK downstream target chemokine monocyte chemoattractant protein 1 (MCP-1 or CCL2) significantly reduced CCA xenograft growth, while TWEAK overexpression drove cancer-associated fibroblast proliferation and collagen deposition in the tumour niche. Genetic Fn14 ablation significantly reduced inflammatory, fibrogenic and ductular responses during carcinogenic TAA-mediated injury. Conclusion: These novel data provide evidence for the action of TWEAK/Fn14 on macrophage recruitment and phenotype, and cancer-associated fibroblast proliferation in CCA. Targeting TWEAK/Fn14 and its downstream signals may provide a means to inhibit CCA niche development and tumour growth. Lay summary: Cholangiocarcinoma is an aggressive, chemotherapy-resistant liver cancer. Interactions between tumour cells and cells that form a supportive environment for the tumour to grow are a source of this aggressiveness and resistance to chemotherapy. Herein, we describe interactions between tumour cells and their supportive environment via a chemical messenger, TWEAK and its receptor Fn14. TWEAK/Fn14 alters the recruitment and type of immune cells in tumours, increases the growth of cancer-associated fibroblasts in the tumour environment, and is a potential target to reduce tumour formation

Exosome signalling in the kidney

Urine contains exosomes originating from the circulation and all cells lining the urinary tract. Exosomes are a route of inter-cellular communication along the nephron potentially able to transfer of protein and/or RNA. It is not known whether this is a regulated process analogous to other cell-to-cell signalling systems. The aims of this study were to develop nanoparticle tracking analysis (NTA) as a technique to quantify exosomes in urine. Secondly, the hormonal regulation of exosome uptake in vitro and in vivo was investigated. Thirdly, exosome excretion in a central diabetes insipidus (DI) patient and a patient group after radiocontrast exposure was measured to investigate exosome excretion along the kidney in injury. Using the fluorescent capabilities of NTA, urinary exosomes were quantified in urine samples. NTA was able to detect changes in aquaporin 2 levels in vitro and in vivo. Storage conditions for human urinary exosomes were also optimised using NTA. A kidney cortical collecting duct cell line (CCDs) was used to model regulation of exosome uptake in vitro. CCDs were stimulated with desmopressin, a vasopressin analogue, and uptake of fluorescently-loaded or microRNA-loaded exosomes was measured. Desmopressin stimulated exosome uptake into collecting duct cells via V2 receptor stimulation. Intra-cellular uptake of exosomes was confirmed by microRNA specific mRNA down-regulation. Mechanistically, exosome uptake in response to desmopressin required cyclic AMP production, was mediated by clathrin-dependent endocytosis and was selective for exosomes from kidney tubular cells. In mice, fluorescently-loaded exosomes were systemically injected before and after administration of the V2 antagonist, tolvaptan, and urinary exosome excretion was measured. Basally, 2.5% of injected exosomes were recovered in urine; tolvaptan treatment resulted in a 5-fold increase. By combining antibodies to nephron segment-specific proteins with NTA we measured human urinary exosome excretion in central diabetes insipidus (DI) and after radiocontrast exposure (n=37). In DI, desmopressin reduced the excretion of exosomes derived from upstream glomerular and proximal tubule cells. In patients exposed to radiocontrast, urinary exosomes from the glomerulus were positively correlated with the tubular injury markers KIM- 1 and NGAL. These findings therefore show that tubular exosome uptake is a specific, hormonally regulated process that is reduced with injury. Physiologically, exosomes are a mechanism of inter-cellular communication; therapeutically, exosomes represent a novel vehicle by which RNA therapy could be targeted for the treatment of kidney disease

Hypoxia shapes the immune landscape in lung injury and promotes the persistence of inflammation

Hypoxemia is a defining feature of acute respiratory distress syndrome (ARDS), an often-fatal complication of pulmonary or systemic inflammation, yet the resulting tissue hypoxia, and its impact on immune responses, is often neglected. In the present study, we have shown that ARDS patients were hypoxemic and monocytopenic within the first 48 h of ventilation. Monocytopenia was also observed in mouse models of hypoxic acute lung injury, in which hypoxemia drove the suppression of type I interferon signaling in the bone marrow. This impaired monopoiesis resulted in reduced accumulation of monocyte-derived macrophages and enhanced neutrophil-mediated inflammation in the lung. Administration of colony-stimulating factor 1 in mice with hypoxic lung injury rescued the monocytopenia, altered the phenotype of circulating monocytes, increased monocyte-derived macrophages in the lung and limited injury. Thus, tissue hypoxia altered the dynamics of the immune response to the detriment of the host and interventions to address the aberrant response offer new therapeutic strategies for ARDS