Iterative liver injury results in progressive fibrosis disrupting hepatic architecture, regeneration potential, and liver function. Hepatic stellate cells (HSCs) are a major source of pathological ...matrix during fibrosis and are thought to be a functionally homogeneous population. Here, we use single-cell RNA sequencing to deconvolve the hepatic mesenchyme in healthy and fibrotic mouse liver, revealing spatial zonation of HSCs across the hepatic lobule. Furthermore, we show that HSCs partition into topographically diametric lobule regions, designated portal vein-associated HSCs (PaHSCs) and central vein-associated HSCs (CaHSCs). Importantly we uncover functional zonation, identifying CaHSCs as the dominant pathogenic collagen-producing cells in a mouse model of centrilobular fibrosis. Finally, we identify LPAR1 as a therapeutic target on collagen-producing CaHSCs, demonstrating that blockade of LPAR1 inhibits liver fibrosis in a rodent NASH model. Taken together, our work illustrates the power of single-cell transcriptomics to resolve the key collagen-producing cells driving liver fibrosis with high precision.
Display omitted
•scRNA-seq reveals spatial zonation of hepatic stellate cells (HSCs)•HSCs partition into topographically diametric lobule regions•Functional zonation of HSCs during centrilobular injury-induced fibrosis is uncovered•LPAR1 is a therapeutic target on pathological central vein-associated HSC
Dobie et al. use scRNA-seq to reveal spatial and functional zonation of hepatic stellate cells (HSCs) across the hepatic lobule, identifying central vein-associated HSCs as the dominant pathogenic collagen-producing cells during centrilobular injury-induced fibrosis. This illustrates the power of scRNA-seq to resolve the key collagen-producing cells driving liver fibrosis.
The risk of poor post-operative outcome and the benefits of surgical resection as a curative therapy require careful assessment by the clinical care team for patients with primary and secondary liver ...cancer. Advances in surgical techniques have improved patient outcomes but identifying which individual patients are at greatest risk of poor post-operative liver performance remains a challenge. Here we report results from a multicentre observational clinical trial (ClinicalTrials.gov NCT03213314) which aimed to inform personalised pre-operative risk assessment in liver cancer surgery by evaluating liver health using quantitative multiparametric magnetic resonance imaging (MRI). We combined estimation of future liver remnant (FLR) volume with corrected T1 (cT1) of the liver parenchyma as a representation of liver health in 143 patients prior to treatment. Patients with an elevated preoperative liver cT1, indicative of fibroinflammation, had a longer post-operative hospital stay compared to those with a cT1 within the normal range (6.5 vs 5 days; p = 0.0053). A composite score combining FLR and cT1 predicted poor liver performance in the 5 days immediately following surgery (AUROC = 0.78). Furthermore, this composite score correlated with the regenerative performance of the liver in the 3 months following resection. This study highlights the utility of quantitative MRI for identifying patients at increased risk of poor post-operative liver performance and a longer stay in hospital. This approach has the potential to inform the assessment of individualised patient risk as part of the clinical decision-making process for liver cancer surgery.
Acute kidney injury (AKI) following ischemia-reperfusion injury (IRI) has a high mortality and lacks specific therapies. Here, we report that mice lacking kynurenine 3-monooxygenase (KMO) activity ...(Kmo
mice) are protected against AKI after renal IRI. We show that KMO is highly expressed in the kidney and exerts major metabolic control over the biologically active kynurenine metabolites 3-hydroxykynurenine, kynurenic acid, and downstream metabolites. In experimental AKI induced by kidney IRI, Kmo
mice had preserved renal function, reduced renal tubular cell injury, and fewer infiltrating neutrophils compared with wild-type (Kmo
) control mice. Together, these data confirm that flux through KMO contributes to AKI after IRI, and supports the rationale for KMO inhibition as a therapeutic strategy to protect against AKI during critical illness.
Systemic inflammation, which results from the massive release of proinflammatory molecules into the circulatory system, is a major risk factor for severe illness, but the precise mechanisms ...underlying its control are not fully understood. We observed that prostaglandin E₂ (PGE₂), through its receptor EP4, is down-regulated in human systemic inflammatory disease. Mice with reduced PGE₂ synthesis develop systemic inflammation, associated with translocation of gut bacteria, which can be prevented by treatment with EP4 agonists. Mechanistically, we demonstrate that PGE₂-EP4 signaling acts directly on type 3 innate lymphoid cells (ILCs), promoting their homeostasis and driving them to produce interleukin-22 (IL-22). Disruption of the ILC–IL-22 axis impairs PGE₂-mediated inhibition of systemic inflammation. Hence, the ILC–IL-22 axis is essential in protecting against gut barrier dysfunction, enabling PGE₂-EP4 signaling to impede systemic inflammation.
The most hazardous complication to pancreatic surgery is the development of a post-operative pancreatic fistula (POPF). Appropriate understanding of the underlying pathophysiology, risk factors and ...perioperative mechanisms may allow for better management and use of preventive measures.
Systematic literature search using the English PubMed literature up to April 2019, with emphasis on the past 5 years.
Several risk scores have been developed but none are perfect in predicting POPF risk. A conceptual framework of factors that contribute to the pathophysiology of pancreatic fistulae is still developing but incomplete. Recognized factors include those related to the patient, the pathology and the perioperative care. Interventions such as use of drains, stents and various drugs to mediate risk is still debated. Emerging data suggest that both the microbiome and the inflammation in the post-operative phase may play important roles in risk for POPF. Available risk scores allow for stratification of risk and mitigation strategies tailored to reduce this. However, accurate estimation of risk remains a challenge and mechanisms are only partially understood.
The pathophysiology of POPF remains poorly understood. Current models only partially explain risks or associated mechanisms. Novel areas of investigation need to be explored for better prediction.
OBJECTIVE:Acute Pancreatitis (AP) is sudden onset pancreas inflammation that causes systemic injury with a wide and markedly heterogeneous range of clinical consequences. Here, we hypothesized that ...this observed clinical diversity corresponds to diversity in molecular subtypes that can be identified in clinical and multiomics data.
SUMMARY BACKGROUND DATA:Observational cohort study. n = 57 for the discovery cohort (clinical, transcriptomics, proteomics, and metabolomics data) and n = 312 for the validation cohort (clinical and metabolomics data).
METHODS:We integrated coincident transcriptomics, proteomics, and metabolomics data at serial time points between admission to hospital and up to 48 hours after recruitment from a cohort of patients presenting with acute pancreatitis. We systematically evaluated 4 different metrics for patient similarity using unbiased mathematical, biological, and clinical measures of internal and external validity.We next compared the AP molecular endotypes with previous descriptions of endotypes in a critically ill population with acute respiratory distress syndrome (ARDS).
RESULTS:Our results identify 4 distinct and stable AP molecular endotypes. We validated our findings in a second independent cohort of patients with AP.We observed that 2 endotypes in AP recapitulate disease endotypes previously reported in ARDS.
CONCLUSIONS:Our results show that molecular endotypes exist in AP and reflect biological patterns that are also present in ARDS, suggesting that generalizable patterns exist in diverse presentations of critical illness.
Kynurenine monooxygenase (KMO) blockade protects against multiple organ failure caused by acute pancreatitis (AP), but the link between KMO and systemic inflammation has eluded discovery until now. ...Here, we show that the KMO product 3-hydroxykynurenine primes innate immune signaling to exacerbate systemic inflammation during experimental AP. We find a tissue-specific role for KMO, where mice lacking Kmo solely in hepatocytes have elevated plasma 3-hydroxykynurenine levels that prime inflammatory gene transcription. 3-Hydroxykynurenine synergizes with interleukin-1β to cause cellular apoptosis. Critically, mice with elevated 3-hydroxykynurenine succumb fatally earlier and more readily to experimental AP. Therapeutically, blockade with the highly selective KMO inhibitor GSK898 rescues the phenotype, reducing 3-hydroxykynurenine and protecting against critical illness and death. Together, our findings establish KMO and 3-hydroxykynurenine as regulators of inflammation and the innate immune response to sterile inflammation. During critical illness, excess morbidity and death from multiple organ failure can be rescued by systemic KMO blockade.
Display omitted
•KMO activity primes innate immune and inflammatory gene transcription through 3HK production•3HK synergizes with interleukin-1β to cause cell apoptosis•Therapeutic KMO blockade rescues fatal inflammation in experimental acute pancreatitis
Hayes et al. characterize a metabolic link between 3-hydroxykynurenine generated by KMO activity and priming of innate immune gene transcription during systemic inflammation. Therapeutic blockade using the highly specific KMO inhibitor GSK898 rescues the phenotype and protects against excess morbidity and death from multiple organ failure in experimental acute pancreatitis.
Circadian rhythms are responsible for governing various physiological processes, including hormone secretion, immune responses, metabolism, and the sleep/wake cycle. In critical illnesses such as ...acute pancreatitis (AP), circadian rhythms can become dysregulated due to disease. Evidence suggests that time of onset of disease, coupled with peripheral inflammation brought about by AP will impact on the circadian rhythms generated in the central pacemaker and peripheral tissues. Cells of the innate and adaptive immune system are governed by circadian rhythms and the diurnal pattern of expression can be disrupted during disease. Peak circadian immune cell release and gene expression can coincide with AP onset, that may increase pancreatic injury, tissue damage and the potential for systemic inflammation and multiple organ failure to develop. Here, we provide an overview of the role of circadian rhythms in AP and the underpinning inflammatory mechanisms to contextualise ongoing research into the chronobiology and chronotherapeutics of AP.
Display omitted
Kynurenine-3-monooxygenase (KMO) is a key FAD-dependent enzyme of tryptophan metabolism. In animal models, KMO inhibition has shown benefit in neurodegenerative diseases such as Huntington's and ...Alzheimer's. Most recently it has been identified as a target for acute pancreatitis multiple organ dysfunction syndrome (AP-MODS); a devastating inflammatory condition with a mortality rate in excess of 20%. Here we report and dissect the molecular mechanism of action of three classes of KMO inhibitors with differentiated binding modes and kinetics. Two novel inhibitor classes trap the catalytic flavin in a previously unobserved tilting conformation. This correlates with picomolar affinities, increased residence times and an absence of the peroxide production seen with previous substrate site inhibitors. These structural and mechanistic insights culminated in GSK065(C1) and GSK366(C2), molecules suitable for preclinical evaluation. Moreover, revising the repertoire of flavin dynamics in this enzyme class offers exciting new opportunities for inhibitor design.
The aim of treatment in congenital adrenal hyperplasia is to suppress excess adrenal androgens while achieving physiological glucocorticoid replacement. However, current glucocorticoid replacement ...regimes are inadequate because doses sufficient to suppress excess androgens almost invariably induce adverse metabolic effects. Although both cortisol and corticosterone are glucocorticoids that circulate in human plasma, any physiological role for corticosterone has been neglected. In the brain, the adenosine 5'-triphosphate-binding cassette transporter ABCB1 exports cortisol but not corticosterone. Conversely, ABCC1 exports corticosterone but not cortisol. We show that ABCC1, but not ABCB1, is expressed in human adipose and that ABCC1 inhibition increases intracellular corticosterone, but not cortisol, and induces glucocorticoid-responsive gene transcription in human adipocytes. Both C57Bl/6 mice treated with the ABCC1 inhibitor probenecid and FVB mice with deletion of Abcc1 accumulated more corticosterone than cortisol in adipose after adrenalectomy and corticosteroid infusion. This accumulation was sufficient to increase glucocorticoid-responsive adipose transcript expression. In human adipose tissue, tissue corticosterone concentrations were consistently low, and ABCC1 mRNA was up-regulated in obesity. To test the hypothesis that corticosterone effectively suppresses adrenocorticotropic hormone (ACTH) without the metabolic adverse effects of cortisol, we infused cortisol or corticosterone in patients with Addison's disease. ACTH suppression was similar, but subcutaneous adipose transcripts of glucocorticoid-responsive genes were higher after infusion with cortisol rather than with corticosterone. These data indicate that corticosterone may be a metabolically favorable alternative to cortisol for glucocorticoid replacement therapy when ACTH suppression is desirable, as in congenital adrenal hyperplasia, and justify development of a pharmaceutical preparation.
PDF
