Liver dysfunction and phosphatidylinositol-3-kinase signalling in early sepsis: experimental studies in rodent models of peritonitis

Safety and efficacy of Single-Pass Albumin Dialysis (SPAD), Prometheus, and Molecular Adsorbent Recycling System (MARS) liver haemodialysis vs. Standard Medical Therapy (SMT): meta-analysis and systematic review

Introduction

Because not all liver dysfunction patients are suitable for transplantations and there is a shortage of grafts, liver support therapies have gained interest. In this regard, extracorporeal albumin dialysis devices such as single-pass albumin dialysis (SPAD), Prometheus, and molecular adsorbent recycling system (MARS) have been valuable in supplementing standard medical therapy (SMT). However, the efficacy and safety of these devices is often questioned.Aim: We performed a systematic review to summarize the efficacy and safety of MARS, SPAD, and Prometheus as supportive treatments for liver dysfunction.

Material and methods

PubMed, Medline, Cochrane Library, Web of Science, and Google Scholar electronic databases were extensively searched for all randomized trials published in English. In addition, meta-analytic analyses were performed with Review Manager software, and Cochrane's risk of bias tool embedded in this software was used for bias assessment.

Results

Twelve trials including a total of 653 patients were eligible for inclusion. Subgroup analyses of data from these trials revealed that MARS and Prometheus were associated with significant removal of bilirubin (MD = -5.14 mg/dl; 95% CI: -7.26 - -3.02; p < 0.00001 and MD = -8.11 mg/dl; 95% CI: -12.40 - -3.82; p = 0.0002, respectively) but not bile acids and ammonia when compared to SMT. Furthermore, MARS was as effective as Prometheus and SPAD in the reduction of bilirubin (MD = 2.98 mg/dl; 95% CI: -4.26 - 10.22; p = 0.42 and MD = 0.67 mg/dl; 95% CI: -2.22 - 3.56; p = 0.65), bile acids (MD = -17.06 µmol/l; 95% CI: -64.33 - 30.20; p = 0.48 and MD = 16.21 µmol/l; 95% CI: -17.26 - 49.68; p = 0.34), and ammonia (MD = 26 µmol/l; 95% CI: -12.44 - 64.44; p = 0.18). In addition, MARS had a considerable effect in improving hepatic encephalopathy (HE) (RR = 1.54; 95% CI: 1.15-2.05; p = 0.004). However, neither MARS nor Prometheus had a mortality benefit compared to SMTRR (0.86; 95% CI: 0.71-1.03; p = 0.11 and RR = 0.87; 95% CI: 0.66-1.14; p = 0.31, respectively).

Conclusions

MARS, SPAD, and Prometheus, as liver support therapies, are equally effective in reducing albumin-bound and water-soluble substances. Moreover, MARS is associated with HE improvement. However, none of the therapies was associated with a significant reduction in mortality or adverse events.

Inflammatory liver diseases and susceptibility to sepsis

Patients with inflammatory liver diseases, particularly alcohol-associated liver disease and metabolic dysfunction-associated fatty liver disease (MAFLD), have higher incidence of infections and mortality rate due to sepsis. The current focus in the development of drugs for MAFLD is the resolution of non-alcoholic steatohepatitis and prevention of progression to cirrhosis. In patients with cirrhosis or alcoholic hepatitis, sepsis is a major cause of death. As the metabolic center and a key immune tissue, liver is the guardian, modifier, and target of sepsis. Septic patients with liver dysfunction have the highest mortality rate compared with other organ dysfunctions. In addition to maintaining metabolic homeostasis, the liver produces and secretes hepatokines and acute phase proteins (APPs) essential in tissue protection, immunomodulation, and coagulation. Inflammatory liver diseases cause profound metabolic disorder and impairment of energy metabolism, liver regeneration, and production/secretion of APPs and hepatokines. Herein, the author reviews the roles of (1) disorders in the metabolism of glucose, fatty acids, ketone bodies, and amino acids as well as the clearance of ammonia and lactate in the pathogenesis of inflammatory liver diseases and sepsis; (2) cytokines/chemokines in inflammatory liver diseases and sepsis; (3) APPs and hepatokines in the protection against tissue injury and infections; and (4) major nuclear receptors/signaling pathways underlying the metabolic disorders and tissue injuries as well as the major drug targets for inflammatory liver diseases and sepsis. Approaches that focus on the liver dysfunction and regeneration will not only treat inflammatory liver diseases but also prevent the development of severe infections and sepsis.

Acute-on-chronic liver failure - steps towards harmonization of the definition!

Acute-on-chronic liver failure (ACLF), usually precipitated by alcohol misuse or viral reactivation, is characterised by rapid onset and usually reversible liver failure. Various definitions of ACLF have been proposed and widely used across the globe, including those by APASL, COSSH, EASL-CLIF, Japanese experts, and NACSELD. Although all the definitions have several similarities and connote high short-term mortality, a clear and standardised definition is still lacking, hampering research in this key area. In this review, we discuss the similarities and differences among various definitions and propose steps to harmonise EASL-CLIF, APASL, NACSELD, Japanese, and Chinese definitions of ACLF.

Altered DNA methylation underlies monocyte dysregulation and immune exhaustion memory in sepsis

Monocytes can develop an exhausted memory state characterized by reduced differentiation, pathogenic inflammation, and immune suppression that drives immune dysregulation during sepsis. Chromatin alterations, notably via histone modifications, underlie innate immune memory, but the contribution of DNA methylation remains poorly understood. Using an ex vivo sepsis model, we show altered DNA methylation throughout the genome of exhausted monocytes, including genes implicated in immune dysregulation during sepsis and COVID-19 infection (e.g., Plac8). These changes are recapitulated in septic mice induced by cecal slurry injection. Methylation profiles developed in septic mice are maintained during ex vivo culture, supporting the involvement of DNA methylation in stable monocyte exhaustion memory. Methylome reprogramming is driven in part by Wnt signaling inhibition in exhausted monocytes and can be reversed with DNA methyltransferase inhibitors, Wnt agonists, or immune training molecules. Our study demonstrates the significance of altered DNA methylation in the maintenance of stable monocyte exhaustion memory.

Hemoadsorption Therapy for Critically Ill Patients with Acute Liver Dysfunction: A Meta-Analysis and Systematic Review

Critically ill patients are at risk of developing acute liver dysfunction as part of multiorgan failure sequelae. Clearing the blood from toxic liver-related metabolites and cytokines could prevent further organ damage. Despite the increasing use of hemoadsorption for this purpose, evidence of its efficacy is lacking. Therefore, we conducted this systematic review and meta-analysis to assess the evidence on clinical outcomes following hemoadsorption therapy. A systematic search conducted in six electronic databases (PROSPERO registration: CRD42022286213) yielded 30 eligible publications between 2011 and 2023, reporting the use of hemoadsorption for a total of 335 patients presenting with liver dysfunction related to acute critical illness. Of those, 26 are case presentations (n = 84), 3 are observational studies (n = 142), and 1 is a registry analysis (n = 109). Analysis of data from individual cases showed a significant reduction in levels of aspartate transaminase (p = 0.03) and vasopressor need (p = 0.03) and a tendency to lower levels of total bilirubin, alanine transaminase, C-reactive protein, and creatinine. Pooled data showed a significant reduction in total bilirubin (mean difference of -4.79 mg/dL (95% CI: -6.25; -3.33), p = 0.002). The use of hemoadsorption for critically ill patients with acute liver dysfunction or failure seems to be safe and yields a trend towards improved liver function after therapy, but more high-quality evidence is crucially needed.

Contribution of radixin and ezrin to the maintenance of hepatocytes' excretory function in health and disease

Background & aims

Excretory liver failure is frequently associated with poor prognosis in critically ill patients. It is characterized by the loss of canalicular membrane export pumps at the hepatocyte membrane. The membrane export pump Multidrug resistant-associated protein (MRP) 2 is pivotal in hepatocytes for brushed membrane morphology and transport of various metabolites. In addition, MRP2 anchoring proteins of the Ezrin/Radixin/Moesin (ERM) family are crucial for the correct MRP2 location, integration, and function in different tissues. In hepatocytes, altered ERM signaling is elementary for developing excretory liver failure.

Methods

Polarized human HepaRG cells, primary human hepatocytes, and hepatocyte-specific Ezrin knockout mice are employed to investigate ERM expression and function in health and the bile duct ligation model of obstructive cholestasis.

Results

ERM-scaffolding protein Ezrin has no relevant function in maintaining the canalicular structure in hepatocytes during health and disease.

Conclusions

Homeostasis of the canalicular pole in hepatocytes is maintained exclusively by Radixin but not Ezrin, and Radixin dysfunction promotes cholestasis.

The Role of Inflammation in Cholestatic Liver Injury

Cholestasis is a common clinical event in which bile formation and excretion are blocked, leading to retention of bile acids or bile salts; whether it occurs intra- or extrahepatically, primary or secondary, its pathogenesis is still unclear and is influenced by a combination of factors. In a variety of inflammatory and immune cells such as neutrophils, macrophages (intrahepatic macrophages are also known as Kupffer cells), mast cells, NK cells, and even T cells in humoral immunity and B cells in cellular immunity, inflammation can be a "second strike" against cholestatic liver injury. These cells, stimulated by a variety of factors such as bile acids, inflammatory chemokines, and complement, can be activated and accumulate in the cholestatic liver, and with the involvement of inflammatory mediators and modulation by cytokines, can lead to destruction of hepatocytes and bile duct epithelial cells and exacerbate (and occasionally retard) the progression of cholestatic liver disease. In this paper, we summarized the new research advances proposed so far regarding the relationship between inflammation and cholestasis, aiming to provide reference for researchers and clinicians in the field of cholestatic liver injury research.

Immunosuppressive effects of circulating bile acids in human endotoxemia and septic shock: patients with liver failure are at risk

BACKGROUND

Sepsis-induced immunosuppression is a frequent cause of opportunistic infections and death in critically ill patients. A better understanding of the underlying mechanisms is needed to develop targeted therapies. Circulating bile acids with immunosuppressive effects were recently identified in critically ill patients. These bile acids activate the monocyte G-protein coupled receptor TGR5, thereby inducing profound innate immune dysfunction. Whether these mechanisms contribute to immunosuppression and disease severity in sepsis is unknown. The aim of this study was to determine if immunosuppressive bile acids are present in endotoxemia and septic shock and, if so, which patients are particularly at risk.

METHODS

To induce experimental endotoxemia in humans, ten healthy volunteers received 2 ng/kg E. coli lipopolysaccharide (LPS). Circulating bile acids were profiled before and after LPS administration. Furthermore, 48 patients with early (shock onset within < 24 h) and severe septic shock (norepinephrine dose > 0.4 μg/kg/min) and 48 healthy age- and sex-matched controls were analyzed for circulating bile acids. To screen for immunosuppressive effects of circulating bile acids, the capability to induce TGR5 activation was computed for each individual bile acid profile by a recently published formula.

RESULTS

Although experimental endotoxemia as well as septic shock led to significant increases in total bile acids compared to controls, this increase was mild in most cases. By contrast, there was a marked and significant increase in circulating bile acids in septic shock patients with severe liver failure compared to healthy controls (61.8 µmol/L vs. 2.8 µmol/L, p = 0.0016). Circulating bile acids in these patients were capable to induce immunosuppression, as indicated by a significant increase in TGR5 activation by circulating bile acids (20.4% in severe liver failure vs. 2.8% in healthy controls, p = 0.0139).

CONCLUSIONS

Circulating bile acids capable of inducing immunosuppression are present in septic shock patients with severe liver failure. Future studies should examine whether modulation of bile acid metabolism can improve the clinical course and outcome of sepsis in these patients.

Altered DNA methylation underlies monocyte dysregulation and innate exhaustion memory in sepsis

Innate immune memory is the process by which pathogen exposure elicits cell-intrinsic states to alter the strength of future immune challenges. Such altered memory states drive monocyte dysregulation during sepsis, promoting pathogenic behavior characterized by pro-inflammatory, immunosuppressive gene expression in concert with emergency hematopoiesis. Epigenetic changes, notably in the form of histone modifications, have been shown to underlie innate immune memory, but the contribution of DNA methylation to this process remains poorly understood. Using an ex vivo sepsis model, we discovered broad changes in DNA methylation throughout the genome of exhausted monocytes, including at several genes previously implicated as major drivers of immune dysregulation during sepsis and Covid-19 infection (e.g. Plac8 ). Methylome alterations are driven in part by Wnt signaling inhibition in exhausted monocytes, and can be reversed through treatment with DNA methyltransferase inhibitors, Wnt agonists, or immune training molecules. Importantly, these changes are recapitulated in septic mice following cecal slurry injection, resulting in stable changes at critical immune genes that support the involvement of DNA methylation in acute and long-term monocyte dysregulation during sepsis.

The Gut Microbiota Contributes to Systemic Responses and Liver Injury in Gut-Derived Sepsis

The gut microbiota, as a major source of opportunistic pathogens, poses a great threat to systemic infection, whereas the role of the gut microbiota in sepsis is underestimated. Here, we aimed to explore the effects of different gut microbiota patterns (namely, enterotypes) in cecal ligation and puncture (CLP)-induced murine sepsis. To achieve this purpose, we built four kinds of enterotypes by exposing mice to different types of antibiotics (azithromycin, amoxicillin, metronidazole, and levofloxacin). The results showed that antibiotic exposure induced different enterotypes, which, in turn, led to varying levels of systemic inflammation in septic mice, with amoxicillin-associated enterotypes exhibiting the most severe inflammation, followed by metronidazole, azithromycin, and levofloxacin. Specifically, the amoxicillin-associated enterotype was characterized by an abundance of intestinal opportunistic pathogens, including Enterobacteriaceae, Sutterellaceae, and Morganellaceae. This enterotype played a significant role in promoting the pathogenic potential of the gut microbiota, ultimately contributing to the development of severe systemic inflammation. Furthermore, the amoxicillin-associated enterotype exaggerated the sepsis-related liver injury, as evidenced by higher levels of alanine aminotransferase, aspartate transaminase, and hepatic malondialdehyde. The results of the RNA sequencing and the fecal suspension intraperitoneal injection sepsis model indicated that the amoxicillin-associated enterotype provoked acute hepatic immune responses and led to more significant metabolic compensation in the event of sepsis. Collectively, we concluded that the gut microbiota was one crucial factor for heterogeneity in sepsis, where the modulated gut microbiota likely prevented or reduced the serious consequences of sepsis, at least in gut-derived sepsis.

Development and Recovery of Liver Injury in Piglets by Incremental Injection of LPS

This study aimed to explore the effects of the incremental injection of lipopolysaccharide (LPS) on liver histopathology, inflammation, oxidative status, and mitochondrial function in piglets. Forty healthy Duroc × Landrace × Yorkshire castrated boars (21 ± 2 days old, weight 6.84 ± 0.11 kg) were randomly assigned to five groups (n = 8) and then slaughtered on days 0 (group 0, without LPS injection), 1 (group 1), 5 (group 5), 9 (group 9), and 15 (group 15) of LPS injection, respectively. The results showed that, compared to the piglets without LPS injection, LPS injection caused liver injury in the early phase, as manifested by the increased activities of serum liver injury-related parameters (aspartate amino transferase, alanine aminotransferase, alkaline phosphatase, cholinesterase, and total bile acid) on day 1, and impaired liver morphology (disordered hepatic cell cord arrangement, dissolved and vacuolized hepatocytes, karyopycnosis, and inflammatory cell infiltration and congestion) on days 1 and 5. Meanwhile, LPS injection caused liver inflammation, oxidative stress, and mitochondrial dysfunction on days 1 and 5, as reflected by the upregulated mRNA expression of TNF-α, IL-6, IL-1β, TLR4, MyD88, and NF-κB; increased MPO and MDA content; and impaired mitochondrial morphology. However, these parameters were ameliorated in the later phase (days 9~15). Taken together, our data indicate that the incremental injection of the LPS-induced liver injury of piglets could be self-repaired.

Forsythiaside A alleviates Lipopolysacchrride-induced acute liver Injury through inhibiting endoplasmic reticulum stress and NLRP3 inflammasome activation

The liver is the primary site of inflammation caused by bacterial endotoxins in sepsis, and septic acute liver injury (SALI) is usually associated with poor outcomes in sepsis. Forsythiaside A (FTA), an active constituent of Forsythia suspensa, has been reported to have anti-inflammatory properties, antioxidant properties, and protective properties against neuroinflammation, sepsis, and edema.Therefore, the purpose of the present study was to examine FTA's potential effects on lipopolysaccharide (LPS)-induced SALI in mice.Our results indicated that pretreatment with FTA significantly attenuated aspartate aminotransferase (AST) and aminoleucine transferase (ALT) levels in plasma, ameliorated histopathological damage, inhibited hepatocyte apoptosis, diminished the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 in the liver from mice exposed to LPS. Furthermore, our data showed that the administration of LPS resulted in robust endoplasmic reticulum (ER) stress response, as evidenced by GRP78 upregulation, p-PERK activation, elF2α phosphorylation, and ATF4 and CHOP overexpression in the liver. This, in turn, led to nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3 (NLRP3) inflammasome activation, including the cleavage of caspase-1, secretion of IL-1β, and pyroptotic cell death in the liver specimens. Importantly, the ER stress response induced by the LPS challenge was blocked by FTA administration. Correspondingly, NLRP3 inflammasome activation was significantly ameliorated by the pretreatment with FTA. Thus, we demonstrated that FTA pretreatment could protect mice from LPS-induced SALI, and its protective effects were possibly mediated by inhibiting ER stress response and subsequent NLRP3 inflammasome activation.

Immune dysregulation and RNA N6-methyladenosine modification in sepsis

Sepsis is defined as life-threatening organ dysfunction caused by the host immune dysregulation to infection. It is a highly heterogeneous syndrome with complex pathophysiological mechanisms. The host immune response to sepsis can be divided into hyper-inflammatory and immune-suppressive phases which could exist simultaneously. In the initial stage, systemic immune response is activated after exposure to pathogens. Both innate and adaptive immune cells undergo epigenomic, transcriptomic, and functional reprogramming, resulting in systemic and persistent inflammatory responses. Following the hyper-inflammatory phase, the body is in a state of continuous immunosuppression, which is related to immune cell apoptosis, metabolic failure, and epigenetic reprogramming. Immunosuppression leads to increased susceptibility to secondary infections in patients with sepsis. RNA N6-Methyladenosine (m6A) has been recognized as an indispensable epitranscriptomic modification involved in both physiological and pathological processes. Recent studies suggest that m6A could reprogram both innate and adaptive immune cells through posttranscriptional regulation of RNA metabolism. Dysregulated m6A modifications contribute to the pathogenesis of immune-related diseases. In this review, we summarize immune cell changes and the potential role of m6A modification in sepsis. This article is categorized under: RNA in Disease and Development > RNA in Disease RNA Processing > RNA Editing and Modification.

A reduced glycine-to-taurine ratio of conjugated serum bile acids signifies an adaptive mechanism and is an early marker of outcome in acute respiratory distress syndrome

The accumulation of Bile Acids (BA) in serum is a common finding in critically ill patients and has been found in patients with Acute Respiratory Distress Syndrome (ARDS), where liver and biliary function could be essentially affected by the underlying disease process and subsequent therapeutic measures. We hypothesized that the glycine-to-taurine conjugation ratio (G/T-ratio) is predictive of outcome in ARDS patients and would support our previously published hypothesis that the BA profile reflects a (mal-) adaptive response of bile acid production when suffering from a disease or syndrome such as ARDS. In 70 patients with ARDS, we determined conjugated BA fractions from protein precipitated serum samples using a LC-MS/MS method and calculated the G/T-ratios, which were then compared with a healthy control group. In patients with ARDS, the G/T-ratio was markedly lower compared to the control group, due to an increase in taurine-conjugated BA. The G/T ratio was lowest on the day of diagnosis and increased steadily during the following days (control = 3.80 (2.28-4.44); day 0 = 1.79 (1.31-3.86); day 3 = 2.91 (1.71-5.68); day 5 = 2.28 (1.25-7.85), significant increases were found between day 0 and day 3 (p = 0.019) and between day 0 and day 5 (p = 0.031). G/T-ratio was significantly correlated with SAPS II score on day 0 (p = 0.009) and day 3 (p = 0.036) and with survival (p = 0.006). Regarding survival, the receiver-operator characteristic revealed an area-under-the-curve of 0.713 (CI 0.578-0.848), the Youden index revealed a G/T-ratio cut-off level of 2.835 (sensitivity 78.4%, specificity 63.2%). Our findings further support our previously published hypothesis that alterations in BA profiles represent adaptive mechanisms in states of severe disease. Our current study adds the finding of an increase in taurine-conjugated BA expressed by a decrease in the G/T-ratio of conjugated BA in serum. The G/T-ratio on day 3 using a threshold G/T-ratio of 2.8 was even associated with survival (p = 0.006); these results are yet to be confirmed by subsequent studies.

Proteomic changes associated with racial background and sepsis survival outcomes

Intra-abdominal infection is a common cause of sepsis, and intra-abdominal sepsis leads to ∼156 000 U.S. deaths annually. African American/Black adults have higher incidence and mortality rates from sepsis compared to Non-Hispanic White adults. A limited number of studies have traced survival outcomes to molecular changes; however, these studies primarily only included Non-Hispanic White adults. Our goal is to better understand molecular changes that may contribute to differences in sepsis survival in African American/Black and Non-Hispanic White adults with primary intra-abdominal infection. We employed discovery-based plasma proteomics of patient samples from the Protocolized Care for Early Septic Shock (ProCESS) cohort (N = 107). We identified 49 proteins involved in the acute phase response and complement system whose expression levels are associated with both survival outcome and racial background. Additionally, 82 proteins differentially-expressed in survivors were specific to African American/Black or Non-Hispanic White patients, suggesting molecular-level heterogeneity in sepsis patients in key inflammatory pathways. A smaller, robust set of 19 proteins were in common in African American/Black and Non-Hispanic White survivors and may represent potential universal molecular changes in sepsis. Overall, this study identifies molecular factors that may contribute to differences in survival outcomes in African American/Black patients that are not fully explained by socioeconomic or other non-biological factors.

FABP5 Deficiency Impaired Macrophage Inflammation by Regulating AMPK/NF-κB Signaling Pathway

Fatty acid binding protein 5 (FABP5) is mainly involved in the uptake, transport, and metabolism of fatty acid in the cytoplasm, and its role in immune cells has been recognized in recent years. However, the role of FABP5 in macrophage inflammation and its underlying mechanisms were not fully addressed. In our study, the acute liver injury and sepsis mouse models were induced by i.p. injection of LPS and cecal contents, respectively. Oleic acid (0.6 g/kg) was injected four times by intragastric administration every week, and this lasted for 1 wk before the LPS or cecal content challenge. We found that myeloid-specific deletion of FABP5 mitigated LPS-induced acute liver injury with reduced mortality of mice, histological liver damage, alanine aminotransferase, and proinflammatory factor levels. Metabolic analysis showed that FABP5 deletion increased the intracellular unsaturated fatty acids, especially oleic acid, in LPS-induced macrophages. The addition of oleic acid also decreased LPS-stimulated macrophage inflammation in vitro and reduced acute liver injury in LPS-induced or cecal content-induced sepsis mice. RNA-sequencing and molecular mechanism studies showed that FABP5 deletion or oleic acid supplementation increased the AMP/ATP ratio and AMP-activated protein kinase (AMPK) activation and inhibited the NF-κB pathway during the inflammatory response to LPS stimulation of macrophages. Inhibiting AMPK activation or expression by chemical or genetic approaches significantly rescued the decreased NF-κB signaling pathway and inflammatory response in LPS-treated FABP5-knockout macrophages. Our present study indicated that inhibiting FABP5 or supplementation of oleic acid might be used for the treatment of sepsis-caused acute liver injury.

USP9x promotes CD8 + T-cell dysfunction in association with autophagy inhibition in septic liver injury

Sepsis is a life-threatening condition manifested by concurrent inflammation and immunosuppression. Ubiquitin-specific peptidase 9, X-linked (USP9x), is a USP domain-containing deubiquitinase which is required in T-cell development. In the present study, we investigate whether USP9x plays a role in hepatic CD8 ⁺ T-cell dysfunction in septic mice. We find that CD8 ⁺ T cells are decreased in the blood of septic patients with liver injury compared with those without liver injury, the CD4/CD8 ratio is increased, and the levels of cytolytic factors, granzyme B and perforin are downregulated. The number of hepatic CD8 ⁺ T cells and USP9x expression are both increased 24 h after cecal ligation and puncture-induced sepsis in a mouse model, a pattern similar to liver injury. The mechanism involves promotion of CD8 ⁺ T-cell dysfunction by USP9x associated with suppression of cell cytolytic activity via autophagy inhibition, which is reversed by the USP9x inhibitor WP1130. In the in vivo studies, autophagy is significantly increased in hepatic CD8 ⁺ T cells of septic mice with conditional knockout of mammalian target of rapamycin. This study shows that USP9x has the potential to be used as a therapeutic target in septic liver injury.

Evaluation of Resting Serum Bile Acid Concentrations in Dogs with Sepsis

Recent studies in the human literature suggest that serum bile acid concentrations could be an early predictor of short-term survival in critically ill patients. However, there is no available information in the veterinary literature regarding serum bile acid concentrations in dogs with sepsis. We aimed to evaluate if resting serum bile acid concentrations differ between septic and non-septic dogs. This was a retrospective observational study, of medical records at a single referral center over a twelve-year period. Twenty-six client-owned dogs diagnosed with sepsis were identified. Twenty-one dogs presenting with a non-hepatobiliary systemic disease and twenty-nine dogs admitted for an elective orthopedic procedure, considered otherwise healthy, were selected as control groups. Resting serum bile acid concentrations were significantly higher in the septic compared to the non-septic groups (ill control and orthopedic control groups). However, when assessing bile acid concentrations between groups individually, no difference was identified between the septic and the orthopedic control group. These results should be interpreted cautiously.

Critical care hepatology: definitions, incidence, prognosis and role of liver failure in critically ill patients

Organ dysfunction or overt failure is a commonplace event in the critically ill affecting up to 70% of patients during their stay in the ICU. The outcome depends on the resolution of impaired organ function, while a domino-like deterioration of organs other than the primarily affected ones paves the way for increased mortality. “Acute Liver Failure” was defined in the 1970s as a rare and potentially reversible severe liver injury in the absence of prior liver disease with hepatic encephalopathy occurring within 8 weeks. Dysfunction of the liver in general reflects a critical event in “Multiple Organ Dysfunction Syndrome” due to immunologic, regulatory and metabolic functions of liver parenchymal and non-parenchymal cells. Dysregulation of the inflammatory response, persistent microcirculatory (hypoxic) impairment or drug-induced liver injury are leading problems that result in “secondary liver failure,” i.e., acquired liver injury without underlying liver disease or deterioration of preexisting (chronic) liver disease (“Acute-on-Chronic Liver Failure”). Conventional laboratory markers, such as transaminases or bilirubin, are limited to provide insight into the complex facets of metabolic and immunologic liver dysfunction. Furthermore, inhomogeneous definitions of these entities lead to widely ranging estimates of incidence. In the present work, we review the different definitions to improve the understanding of liver dysfunction as a perpetrator (and therapeutic target) of multiple organ dysfunction syndrome in critical care.

Graphic Abstract

Immunomodulation by Hemoadsorption—Changes in Hepatic Biotransformation Capacity in Sepsis and Septic Shock: A Prospective Study

Background: Sepsis is often associated with liver dysfunction, which is an indicator of poor outcomes. Specific diagnostic tools that detect hepatic dysfunction in its early stages are scarce. So far, the immune modulatory effects of hemoadsorption with CytoSorb^® on liver function are unclear. Method: We assessed the hepatic function by using the dynamic LiMAx^® test and biochemical parameters in 21 patients with sepsis or septic shock receiving CytoSorb^® in a prospective, observational study. Points of measurement: T₁: diagnosis of sepsis or septic shock; T₂ and T₃: 24 h and 48 h after the start of CytoSorb^®; T₄: 24 h after termination of CytoSorb^®. Results: The hepatic biotransformation capacity measured by LiMAx^® was severely impaired in up to 95 % of patients. Despite a rapid shock reversal under CytoSorb^®, a significant improvement in LiMAx^® values appeared from T₃ to T₄. This decline and recovery of liver function were not reflected by common parameters of hepatic metabolism that remained mostly within the normal range. Conclusions: Hepatic dysfunction can effectively and safely be diagnosed with LiMAx^® in ventilated ICU patients under CytoSorb^®. Various static liver parameters are of limited use since they do not adequately reflect hepatic dysfunction and impaired hepatic metabolism.

Early Diagnosis and Prevention of Infections in Cirrhosis

Strategies to prevent infection and improve outcomes in patients with cirrhosis. HAV, hepatitis A virus; HBV, hepatitis B virus; COVID-19, novel coronavirus disease 2019; NSBB, nonselective β-blocker; PPI, proton pump inhibitors.Cirrhosis is a risk factor for infections. Majority of hospital admissions in patients with cirrhosis are due to infections. Sepsis is an immunological response to an infectious process that leads to end-organ dysfunction and death. Preventing infections may avoid the downstream complications, and early diagnosis of infections may improve the outcomes. In this review, we discuss the pathogenesis, diagnosis, and biomarkers of infection; the incremental preventive strategies for infections and sepsi; and the consequent organ failures in cirrhosis. Strategies for primary prevention include reducing gut translocation by selective intestinal decontamination, avoiding unnecessary proton pump inhibitors' use, appropriate use of β-blockers, and vaccinations for viral diseases including novel coronavirus disease 2019. Secondary prevention includes early diagnosis and a timely and judicious use of antibiotics to prevent organ dysfunction. Organ failure support constitutes tertiary intervention in cirrhosis. In conclusion, infections in cirrhosis are potentially preventable with appropriate care strategies to then enable improved outcomes.

The liver in sepsis: molecular mechanism of liver failure and their potential for clinical translation

Liver failure is a life-threatening complication of infections restricting the host's response to infection. The pivotal role of the liver in metabolic, synthetic, and immunological pathways enforces limits the host's ability to control the immune response appropriately, making it vulnerable to ineffective pathogen resistance and tissue damage. Deregulated networks of liver diseases are gradually uncovered by high-throughput, single-cell resolved OMICS technologies visualizing an astonishing diversity of cell types and regulatory interaction driving tolerogenic signaling in health and inflammation in disease. Therefore, this review elucidates the effects of the dysregulated host response on the liver, consequences for the immune response, and possible avenues for personalized therapeutics.

Role of bile acids and their receptors in gastrointestinal and hepatic pathophysiology

Bile acids (BAs) can regulate their own metabolism and transport as well as other key aspects of metabolic homeostasis via dedicated (nuclear and G protein-coupled) receptors. Disrupted BA transport and homeostasis results in the development of cholestatic disorders and contributes to a wide range of liver diseases, including nonalcoholic fatty liver disease and hepatocellular and cholangiocellular carcinoma. Furthermore, impaired BA homeostasis can also affect the intestine, contributing to the pathogenesis of irritable bowel syndrome, inflammatory bowel disease, and colorectal and oesophageal cancer. Here, we provide a summary of the role of BAs and their disrupted homeostasis in the development of gastrointestinal and hepatic disorders and present novel insights on how targeting BA pathways might contribute to novel treatment strategies for these disorders.

Automated multicolor mesoscopic imaging for the 3-dimensional reconstruction of fluorescent biomarker distribution in large tissue specimens

Research in translational medicine often requires high-resolution characterization techniques to visualize or quantify the fluorescent probes. For example, drug delivery systems contain fluorescent molecules enabling in vitro and in vivo tracing to determine biodistribution or plasma disappearance. Albeit fluorescence imaging systems with sufficient resolution exist, the sample preparation is typically too complex to image a whole organism of the size of a mouse. This article established a mesoscopic imaging technique utilizing a commercially available cryo-microtome and an in-house built episcopic imaging add-on to perform imaging during serial sectioning. Here we demonstrate that our automated red, green, blue (RGB) and fluorescence mesoscope can generate sequential block-face and 3-dimensional anatomical images at variable thickness with high quality of 6 µm × 6 µm pixel size. In addition, this mesoscope features a numerical aperture of 0.10 and a field-of-view of up to 21.6 mm × 27 mm × 25 mm (width, height, depth).

Glaucocalyxin a protect liver function via inhibiting platelet over-activation during sepsis

BACKGROUND

Rabdosia japonica (Burm. f.) var. glaucocalyx (Maxim.) is a perennial herb, and is traditionally used as folk medicine for treating inflammatory diseases and cancer. Gaucocalyxin A (GLA) is an ent‑kaurane diterpenoid that is isolated from the aerial parts of R. japonica (Burm. f.) var. glaucocalyx (Maxim.). In a recent study, we found that GLA protects against acute liver dysfunction induced by Escherichia coli, which is likely related to its anti-inflammatory effects. However, the mechanism by which GLA protects liver injury during sepsis is unknown.

AIM

To evaluate the anti-inflammatory function of GLA and its regulatory effect on platelet function.

METHOD

An in vivo model of sepsis was established by inoculating mice with E. coli. Live function and platelet activation were evaluated through standard assays. The levels of pro-inflammatory factors were measured through ELISA and qRT-PCR.

RESULTS

GLA alleviated liver dysfunction in the mouse model of sepsis. GLA-treated mice displayed lower complement activation and liver dysfunction after E. coli infection. GLA alleviated the decrease in peripheral platelet counts by inhibiting their clearance by Kupffer cells in liver. Furthermore, GLA inhibited platelet activation through the RIP1/RIP3/AKT pathway and downregulated C3aR expression on the platelets, thereby inhibiting liver injury and dysfunction due to excessive complement activation.

CONCLUSION

GLA can inhibit platelet activation by reducing surface expression of C3aR, which protect the liver from injury induced by excessive complement activation. GLA is a novel therapeutic agent for controlling sepsis-related liver dysfunction.

Pathophysiology of sepsis‐induced cholestasis: A review

Sepsis is a critical condition resulting from the excessive activation of the inflammatory/immune system in response to an infection, with high mortality if treatment is not administered promptly. One of the many possible complications of sepsis is liver dysfunction with consequent cholestasis. The aim of this paper is to review the main mechanisms involved in the development of cholestasis in sepsis. Cholestasis in a septic patient must raise the suspicion that it is the consequence of the septic condition and limit the laborious attempts of finding a hepatic or biliary disease. Prompt antibiotic administration when sepsis is suspected is essential and may improve liver enzymes. Cholestasis is a syndrome with a variety of etiologies, among which sepsis is frequently overlooked, despite a number of studies and case reports in the literature demonstrating not only the association between sepsis and cholestasis but also the role of cholestasis as a prognostic factor for sepsis‐induced death.

Paeoniflorin ameliorates lipopolysaccharide-induced acute liver injury by inhibiting oxidative stress and inflammation via SIRT1/FOXO1a/SOD2 signaling in rats

Acute liver injury (ALI) is a poor prognosis and high mortality complication of sepsis. Paeoniflorin (PF) has remarkable anti-inflammatory effects in different disease models. Here, we explored the protective effect and underlying molecular mechanisms of PF against lipopolysaccharide (LPS)-induced ALI. Sprague-Dawley rats received intraperitoneal (i.p.) injection of PF for 7 days, 1 h after the last administration, and rats were injected i.p. 10 mg/kg LPS. PF improved liver structure and function, reduced hepatic reactive oxygen species (ROS) and methane dicarboxylic aldehyde (MDA) levels, and increased superoxide dismutase (SOD) activity. Western blot analysis suggested that PF significantly inhibited expression of inflammatory cytokines (TNF-α, IL-1β, and IL-18) and inhibited activation of the NLRP3 inflammasome. PF or mitochondrial ROS scavenger (mito-TEMPO) significantly improved liver mitochondrial function by scavenging mitochondrial ROS (mROS), restoring mitochondrial membrane potential loss and increasing level of ATP and enzyme activity of complex I and III. In addition, PF increased expression of sirtuin-1 (SIRT1), forkhead box O1 (FOXO1a) and manganese superoxide dismutase (SOD2), and increased FOXO1a nuclear retention. However, the inhibitor of SIRT1 (EX527) abolished the protective effect of PF. Taken together, PF promotes mROS clearance to inhibit mitochondrial damage and activation of the NLRP3 inflammasome via SIRT1/FOXO1a/SOD2 signaling.

The Emerging Role of Ferroptosis in Sepsis

Ferroptosis is a novel form of cell death characterized by the iron-dependent accumulation of lipid peroxides and is different from other types of cell death. The mechanisms of ferroptosis are discussed in the review, including System Xc-, Glutathione Peroxidase 4 pathway, Ferroptosis Suppressor Protein 1 and Dihydroorotate Dehydrogenase pathway. Ferroptosis is associated with the occurrence of various diseases, including sepsis. Research in recent years has displayed that ferroptosis is involved in sepsis occurrence and development. Iron chelators can inhibit the development of sepsis and improve the survival rate of septic mice. The ferroptotic cells can release damage-associated molecular patterns and lipid peroxidation, which further mediate inflammatory responses. Ferroptosis inhibitors can resist sepsis-induced multiple organ dysfunction and inflammation. Finally, we reviewed ferroptosis, an iron-dependent form of cell death that is different from other types of cell death in biochemistry, morphology, and major regulatory mechanisms, which is involved in multiple organ injuries caused by sepsis. Exploring the relationship between sepsis and ferroptosis may yield new treatment targets for sepsis.

Catabolism in Critical Illness

OBJECTIVES

Ongoing risk of death and poor functional outcomes are important consequences of prolonged critical illness. Characterizing the catabolic phenotype of prolonged critical illness could illuminate biological processes and inform strategies to attenuate catabolism. We aimed to examine if urea-to-creatinine ratio, a catabolic signature of prolonged critical illness, was associated with mortality after the first week of ICU stay.

DESIGN

Reanalysis of multicenter randomized trial of glutamine supplementation in critical illness (REducing Deaths due to OXidative Stress [REDOXS]).

SETTING

Multiple adult ICUs.

PATIENTS

Adult patients admitted to ICU with two or more organ failures related to their acute illness and surviving to day 7.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The association between time-varying urea-to-creatinine ratio and 30-day mortality was tested using Bayesian joint models adjusted for prespecified-covariates (age, kidney replacement therapy, baseline Sequential Organ Failure Assessment, dietary protein [g/kg/d], kidney dysfunction, and glutamine-randomization). From 1,021 patients surviving to day 7, 166 (16.3%) died by day 30. After adjustment in a joint model, a higher time-varying urea-to-creatinine ratio was associated with increased mortality (hazard ratio [HR], 2.15; 95% credible interval, 1.66-2.82, for a two-fold greater urea-to-creatinine ratio). This association persisted throughout the 30-day follow-up. Mediation analysis was performed to explore urea-to-creatinine ratio as a mediator-variable for the increased risk of death reported in REDOXS when randomized to glutamine, an exogenous nitrogen load. Urea-to-creatinine ratio closest to day 7 was estimated to mediate the risk of death associated with randomization to glutamine supplementation (HR, 1.20; 95% CI, 1.04-1.38; p = 0.014), with no evidence of a direct effect of glutamine (HR, 0.90; 95% CI, 0.62-1.30; p = 0.566).

CONCLUSIONS

The catabolic phenotype measured by increased urea-to-creatinine ratio is associated with increased risk of death during prolonged ICU stay and signals the deleterious effects of glutamine administration in the REDOXS study. Urea-to-creatinine ratio is a promising catabolic signature and potential interventional target.

Dynamic changes of serum metabolites associated with infection and severity of patients with acute hepatitis E infection

Dynamic changes in metabolites may affect liver disease progression, and provide new methods for predicting liver damage. We used ultra-performance liquid chromatography-mass spectroscopy to assess serum metabolites in healthy controls (HC), and patients with acute hepatitis E (AHE) or hepatitis E virus acute liver failure (HEV-ALF). The principal component analysis, partial least squares discriminant analysis, and discriminant analysis of orthogonal projections to latent structures models illustrated significant differences in the metabolite components between AHE patients and HCs, or between HEV-ALF and AHE patients. In pathway enrichment analysis, we further identified two altered pathways, including linoleic acid metabolism and phenylalanine, tyrosine, and tryptophan biosynthesis, when comparing AHE patients with HCs. Linoleic acid metabolism and porphyrin and chlorophyll metabolism pathways were significantly different in HEV-ALF when compared with AHE patients. The discriminative performances of differential metabolites showed that taurocholic acid, glycocholic acid, glycochenodeoxycholate-3-sulfate, and docosahexaenoic acid could be used to distinguish HEV-ALF from AHE patients. The serum levels of glycocholic acid, taurocholic acid, deoxycholic acid glycine conjugate, and docosahexaenoic acid were associated with the prognosis of HEV-ALF patients. Dynamic changes in serum metabolites were associated with AHE infection and severity. The identified metabolites can be used to diagnose and predict the prognosis of HEV-ALF.

The Many Roles of Cholesterol in Sepsis: A Review

RATIONALE

The biological functions of cholesterol are diverse, ranging from cell membrane integrity and signalling, immunity, to the synthesis of steroid and sex hormones, Vitamin D, bile acids and oxysterols. Multiple studies have demonstrated hypocholesterolemia in sepsis, the degree of which is an excellent prognosticator of poor outcomes. However, the clinical significance of hypocholesterolemia has been largely unrecognized.

OBJECTIVES/METHODS

We undertook a detailed review of the biological roles of cholesterol, the impact of sepsis, its reliability as a prognosticator in sepsis, and the potential utility of cholesterol as a treatment.

MEASUREMENTS AND MAIN RESULTS

Sepsis affects cholesterol synthesis, transport and metabolism. This likely impacts upon its biological functions including immunity, hormone and vitamin production, and cell membrane receptor sensitivity. Early preclinical studies show promise for cholesterol as a pleiotropic therapeutic agent.

CONCLUSIONS

Hypocholesterolemia is a frequent condition in sepsis and an important early prognosticator. Low plasma levels are associated with wider changes in cholesterol metabolism and its functional roles, and these appear to play a significant role in sepsis pathophysiology. The therapeutic impact of cholesterol elevation warrants further investigation.

Targeted delivery of a phosphoinositide 3-kinase γ inhibitor to restore organ function in sepsis

Jaundice, the clinical hallmark of infection-associated liver dysfunction, reflects altered membrane organization of the canalicular pole of hepatocytes and portends poor outcomes. Mice lacking phosphoinositide 3-kinase-γ (PI3Kγ) are protected against membrane disintegration and hepatic excretory dysfunction. However, they exhibit a severe immune defect that hinders neutrophil recruitment to sites of infection. To exploit the therapeutic potential of PI3Kγ inhibition in sepsis, a targeted approach to deliver drugs to hepatic parenchymal cells without compromising other cells, in particular immune cells, seems warranted. Here, we demonstrate that nanocarriers functionalized through DY-635, a fluorescent polymethine dye, and a ligand of organic anion transporters can selectively deliver therapeutics to hepatic parenchymal cells. Applying this strategy to a murine model of sepsis, we observed the PI3Kγ-dependent restoration of biliary canalicular architecture, maintained excretory liver function, and improved survival without impairing host defense mechanisms. This strategy carries the potential to expand targeted nanomedicines to disease entities with systemic inflammation and concomitantly impaired barrier functionality.

Oxidative Stress and Localization Status of Hepatocellular Transporters: Impact on Bile Secretion and Role of Signaling Pathways

Significance: Most hepatopathies are primarily or secondarily cholestatic in nature. Oxidative stress (OS) is a frequent trait among them, and impairs the machinery to generate bile by triggering endocytic internalization of hepatocellular transporters, thus causing cholestasis. This is critical, since it leads to accelerated transporter degradation, which could explain the common post-transcriptional downregulation of transporter expression in human cholestatic diseases. Recent Advances: The mechanisms involved in OS-induced hepatocellular transporter internalization are being revealed. Filamentous actin (F-actin) cytoskeleton disorganization and/or detachment of crosslinking actin proteins that afford transporter stability have been characterized as causal factors. Activation of redox-sensitive signaling pathways leading to changes in phosphorylation status of these structures is involved, including Ca²⁺-mediated activation of "classical" and "novel" protein kinase C (PKC) isoforms or redox-signaling cascades downstream of NADPH oxidase. Critical Issues: Despite the well-known occurrence of hepatocellular transporter internalization in human hepatopathies, the cholestatic implications of this phenomenon have been overlooked. Accordingly, no specific treatment has been established in the clinical practice for its prevention/reversion. Future Directions: We need to improve our knowledge on the pro-oxidant triggering factors and the multiple signaling pathways that mediate this oxidative injury in each cholestatic hepatopathy, so as to envisage tailor-made therapeutic strategies for each case. Meanwhile, administration of antioxidants or heme oxygenase-1 induction to elevate the hepatocellular levels of the endogenous scavenger bilirubin are promising alternatives that need to be re-evaluated and implemented. They may complement current treatments in cholestasis aimed to enhance transcriptional carrier expression, by providing membrane stability to the newly synthesized carriers. Antioxid. Redox Signal. 35, 808-831.

Neuropeptide W Attenuates Oxidative Multi-Organ Injury in Rats Induced with Intra-Abdominal Sepsis

Sepsis leads to systemic hypotension, disturbed perfusion, inflammation, and tissue toxicity in vital organs. Neuropeptide W (NPW) has modulatory effects in the control of blood pressure and inflammatory processes, implicating a potential beneficial effect against sepsis-induced oxidative damage. Under anesthesia, male Sprague Dawley rats underwent cecal ligation and puncture. Immediately after surgery, either saline or TNF-alpha inhibitor (etanercept; 1 mg/kg) antibiotic (ceftriaxon; 10 mg/kg) combination or NPW (0.1, 1, or 3 μg/kg) was given subcutaneously, and injections were repeated on the 12th and 24th h. The sham-operated control group was treated with saline at the same time points. All rats were euthanized on the 25th h of surgery. Sepsis resulted in oxidative damage of the brain, heart, lung, liver, and kidney. Elevations in blood urea nitrogen and alkaline phosphatase, showing renal and hepatic dysfunction, were not evident when septic rats were treated with NPW. NPW reduced serum levels of C-reactive protein, corticosterone, and interleukin-6, while histopathologically verified tissue damage in all the studied tissues was ameliorated. NPW treatment suppressed lipid peroxidation in the heart, lung, and brain, and the depleted antioxidant GSH levels of the brain and heart were replenished by NPW. Moreover, sepsis-related neutrophil recruitment to the liver and lung was also suppressed by NPW. Although the survival rate of the rats was not significantly prolonged by NPW, most of these improvements in systemic and local inflammatory events were comparable with those reached by the etanercept and antibiotic combination, suggesting the therapeutic impact of NPW during the acute period of sepsis.

Persistent hyperammonia and altered concentrations of urea cycle metabolites in a 5-day swine experiment of sepsis

We measured plasma and cerebrospinal fluid (CSF) metabolite concentrations in a 5-day porcine sepsis model of fecal peritonitis. The objectives were: (i) to verify whether the expected pathways that had emerged in previous studies pertain only to the early inflammatory response or persist for the subsequent days; (ii) to identify metabolic derangements that arise later; (iii) to verify whether CSF metabolite concentrations were altered and if these alterations were similar to those in the blood or delayed. We observed an early response to inflammation and cytokine storms with alterations in lipid and glucose metabolism. The arginine/asymmetric dimethylarginine (ADMA) and phenylalanine/tyrosine balances changed 24 h after resuscitation in plasma, and later in CSF. There was a rise in ammonia concentration, with altered concentrations of metabolites in the urea cycle. Whether persistent derangement of these pathways have a role not only on short-term outcomes but also on longer-term comorbidities, such as septic encephalopathy, should be addressed in further studies.

A metabolomic endotype of bioenergetic dysfunction predicts mortality in critically ill patients with acute respiratory failure

Acute respiratory failure (ARF) requiring mechanical ventilation, a complicating factor in sepsis and other disorders, is associated with high morbidity and mortality. Despite its severity and prevalence, treatment options are limited. In light of accumulating evidence that mitochondrial abnormalities are common in ARF, here we applied broad spectrum quantitative and semiquantitative metabolomic analyses of serum from ARF patients to detect bioenergetic dysfunction and determine its association with survival. Plasma samples from surviving and non-surviving patients (N = 15/group) were taken at day 1 and day 3 after admission to the medical intensive care unit and, in survivors, at hospital discharge. Significant differences between survivors and non-survivors (ANOVA, 5% FDR) include bioenergetically relevant intermediates of redox cofactors nicotinamide adenine dinucleotide (NAD) and NAD phosphate (NADP), increased acyl-carnitines, bile acids, and decreased acyl-glycerophosphocholines. Many metabolites associated with poor outcomes are substrates of NAD(P)-dependent enzymatic processes, while alterations in NAD cofactors rely on bioavailability of dietary B-vitamins thiamine, riboflavin and pyridoxine. Changes in the efficiency of the nicotinamide-derived cofactors' biosynthetic pathways also associate with alterations in glutathione-dependent drug metabolism characterized by substantial differences observed in the acetaminophen metabolome. Based on these findings, a four-feature model developed with semi-quantitative and quantitative metabolomic results predicted patient outcomes with high accuracy (AUROC = 0.91). Collectively, this metabolomic endotype points to a close association between mitochondrial and bioenergetic dysfunction and mortality in human ARF, thus pointing to new pharmacologic targets to reduce mortality in this condition.

Dichloroacetate reverses sepsis-induced hepatic metabolic dysfunction

Metabolic reprogramming between resistance and tolerance occurs within the immune system in response to sepsis. While metabolic tissues such as the liver are subjected to damage during sepsis, how their metabolic and energy reprogramming ensures survival is unclear. Employing comprehensive metabolomic, lipidomic, and transcriptional profiling in a mouse model of sepsis, we show that hepatocyte lipid metabolism, mitochondrial tricarboxylic acid (TCA) energetics, and redox balance are significantly reprogrammed after cecal ligation and puncture (CLP). We identify increases in TCA cycle metabolites citrate, cis-aconitate, and itaconate with reduced fumarate and triglyceride accumulation in septic hepatocytes. Transcriptomic analysis of liver tissue supports and extends the hepatocyte findings. Strikingly, the administration of the pyruvate dehydrogenase kinase (PDK) inhibitor dichloroacetate reverses dysregulated hepatocyte metabolism and mitochondrial dysfunction. In summary, our data indicate that sepsis promotes hepatic metabolic dysfunction and that targeting the mitochondrial PDC/PDK energy homeostat rebalances transcriptional and metabolic manifestations of sepsis within the liver.

Circulating Bile Acids in Liver Failure Activate TGR5 and Induce Monocyte Dysfunction

BACKGROUND & AIMS

Retention of bile acids in the blood is a hallmark of liver failure. Recent studies have shown that increased serum bile acid levels correlate with bacterial infection and increased mortality. However, the mechanisms by which circulating bile acids influence patient outcomes still are elusive.

METHODS

Serum bile acid profiles in 33 critically ill patients with liver failure and their effects on Takeda G-protein-coupled receptor 5 (TGR5), an immunomodulatory receptor that is highly expressed in monocytes, were analyzed using tandem mass spectrometry, novel highly sensitive TGR5 bioluminescence resonance energy transfer using nanoluciferase (NanoBRET, Promega Corp, Madison, WI) technology, and in vitro assays with human monocytes.

RESULTS

Twenty-two patients (67%) had serum bile acids that led to distinct TGR5 activation. These TGR5-activating serum bile acids severely compromised monocyte function. The release of proinflammatory cytokines (eg, tumor necrosis factor α or interleukin 6) in response to bacterial challenge was reduced significantly if monocytes were incubated with TGR5-activating serum bile acids from patients with liver failure. By contrast, serum bile acids from healthy volunteers did not influence cytokine release. Monocytes that did not express TGR5 were protected from the bile acid effects. TGR5-activating serum bile acids were a risk factor for a fatal outcome in patients with liver failure, independent of disease severity.

CONCLUSIONS

Depending on their composition and quantity, serum bile acids in liver failure activate TGR5. TGR5 activation leads to monocyte dysfunction and correlates with mortality, independent of disease activity. This indicates an active role of TGR5 in liver failure. Therefore, TGR5 and bile acid metabolism might be promising targets for the treatment of immune dysfunction in liver failure.

Paeonol derivative-6 attenuates inflammation by activating ZEB2 in acute liver injury

Paeonol is a natural phenolic compound and isolated as an active ingredient from Moutan Cortex. Paeonol derivative-6 (DPF-6) is a derivative of paeonol improved in water solubility and bioavailability. Previous studies have reported that paeonol possesses a variety of pharmacological activities, such as antioxidant and anti-inflammatory properties. Moreover, we have previously verified that DPF-6 has anti-inflammatory effects. However, the role and fundamental mechanism of DPF-6 in acute liver injury (ALI) was still unclear. In this study, we indicated that DPF-6 inhibited inflammation and the expression of TNF-α, IL-6 and IL-1β in liver tissues and LPS-mediated L-02 cells, concomitant with the upregulated expression of ZEB2. More importantly, it was demonstrated that overexpression of ZEB2 inhibited the expression level of TNF-α, IL-6 and IL-1β in LPS-mediated L-02 cells. In contrast, knockdown of ZEB2 increased the expression level of TNF-α, IL-6 and IL-1β in LPS-mediated L-02 cells. Further studies showed that ZEB2 inhibited the inflammation cytokine secretion via JNK signaling pathway in L-02 cells. Taken together, all the above results indicate that DPF-6 increased the expression of ZEB2, consequently inhibited inflammation cytokine secretion through JNK signaling pathway, which may be utilized as a potential anti-inflammation monomeric compound in the treatment of ALI.

Gadolinium Chloride Inhibits the Production of Liver Interleukin-27 and Mitigates Liver Injury in the CLP Mouse Model

BACKGROUND

Liver macrophages play an important regulatory role in the inflammatory response of liver injury after severe infection. Interleukin- (IL-) 27 is an inflammatory cytokine that plays an important role in diseases caused by bacterial infection. However, the relationship between IL-27 and liver macrophages in liver injury after severe infection is not yet clear.

METHODS

A cecal ligation puncture (CLP) model was established in wild-type (WT) and IL-27 receptor- (WSX-1-) deficient (IL-27r-/-) mice, and recombinant IL-27 and gadolinium chloride (GdCl3) were injected into WT mice in the designated groups. The serum and liver IL-27, IL-6, tumor necrosis factor alpha (TNF-α), and IL-1β expression levels were evaluated by ELISA, quantitative PCR, or Western blotting; serum ALT and AST were detected by detection kits; and the severity of liver damage was evaluated by hematoxylin and eosin staining and the TUNEL assay of the liver tissue from the different groups. Liver macrophage polarization was evaluated by immunofluorescence. In addition, the polarization of peritoneal macrophage was evaluated by flow cytometry.

RESULTS

The serum and liver IL-27 expression levels were elevated in WT mice after CLP-induced severe infection, which were consistent with the changes in HE scores in the liver tissue. The levels of serum ALT, AST, liver IL-6, TNF-α, and IL-1β mRNA and liver pathological injury scores were further increased when pretreated with recombinant IL-27 in WT mice, but these levels were decreased in IL-27r-/- mice after CLP-induced severe infection compared to WT mice. In WT mice pretreated with GdCl3, liver pathological scores, serum ALT and AST, TUNEL-positive cell proportion from liver tissues, liver IL-27 expression, and the liver macrophages M1 polarization proportion decreased after CLP; however, the serum IL-27, IL-6, TNF-α, and IL-1β levels and the pathological lung and kidney scores were not significantly changed. When supplemented with exogenous IL-27, the liver pathological scores, serum ALT, AST, TUNEL-positive cell proportion of liver tissues, liver IL-27 expression, and the liver macrophage M1 polarization proportion increased. The in vitro, IL-27 expression increased in peritoneal macrophages when stimulated with LPS. Recombinant IL-27 together with LPS promoted the elevations in IL-6, TNF-α, and IL-1β levels in supernatant and the M1 polarization of peritoneal macrophages.

CONCLUSION

IL-27 is an important cytokine in the inflammatory response to liver injury after severe infection. The reduction of liver injury by gadolinium chloride in severe infection mice models may relate to the inhibition of liver IL-27 production. These changes may be mainly related to the decrease of liver macrophages M1 polarization. IL-27 may have a positive feedback on these macrophages.

Keep Your Friends Close, but Your Enemies Closer: Role of Acid Sphingomyelinase During Infection and Host Response

Breakdown of the inert and constitutive membrane building block sphingomyelin to the highly active lipid mediator ceramide by extracellularly active acid sphingomyelinase is tightly regulated during stress response and opens the gate for invading pathogens, triggering the immune response, development of remote organ failure, and tissue repair following severe infection. How do one enzyme and one mediator manage all of these affairs? Under physiological conditions, the enzyme is located in the lysosomes and takes part in the noiseless metabolism of sphingolipids, but following stress the protein is secreted into circulation. When secreted, acid sphingomyelinase (ASM) is able to hydrolyze sphingomyelin present at the outer leaflet of membranes to ceramide. Its generation troubles the biophysical context of cellular membranes resulting in functional assembly and reorganization of proteins and receptors, also embedded in highly conserved response mechanisms. As a consequence of cellular signaling, not only induction of cell death but also proliferation, differentiation, and fibrogenesis are affected. Here, we discuss the current state of the art on both the impact and function of the enzyme during host response and damage control. Also, the potential role of lysosomotropic agents as functional inhibitors of this upstream alarming cascade is highlighted.

Targeting Complement C5a Receptor 1 for the Treatment of Immunosuppression in Sepsis

Complement factor C5a was originally identified as a powerful promoter of inflammation through activation of the C5a receptor 1 (C5ar1). Recent evidence suggests involvement of C5a not only in pro- but also in anti-inflammatory signaling. The present study aims to unveil the role of C5ar1 as potential therapeutic target in a murine sepsis model. Our study discloses a significantly increased survival in models of mild to moderate but not severe sepsis of C5ar1-deficient mice. The decreased mortality of C5ar1-deficient mice is accompanied by improved pathogen clearance and largely preserved liver function. C5ar1-deficient mice exhibited a significantly increased production of the pro-inflammatory mediator interferon-γ (IFN-γ) and a decreased production of the anti-inflammatory cytokine interleukin-10 (IL-10). Together, these data uncover C5a signaling as a mediator of immunosuppressive processes during sepsis and describe the C5ar1 and related changes of the IFN-γ to IL-10 ratio as markers for the immunological (dys)function accompanying sepsis.

Pathophysiological mechanisms of liver injury in COVID-19

The recent outbreak of coronavirus disease 2019 (COVID-19), caused by the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has resulted in a world-wide pandemic. Disseminated lung injury with the development of acute respiratory distress syndrome (ARDS) is the main cause of mortality in COVID-19. Although liver failure does not seem to occur in the absence of pre-existing liver disease, hepatic involvement in COVID-19 may correlate with overall disease severity and serve as a prognostic factor for the development of ARDS. The spectrum of liver injury in COVID-19 may range from direct infection by SARS-CoV-2, indirect involvement by systemic inflammation, hypoxic changes, iatrogenic causes such as drugs and ventilation to exacerbation of underlying liver disease. This concise review discusses the potential pathophysiological mechanisms for SARS-CoV-2 hepatic tropism as well as acute and possibly long-term liver injury in COVID-19.

Pathophysiological mechanisms of liver injury in COVID-19

The recent outbreak of coronavirus disease 2019 (COVID-19), caused by the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has resulted in a world-wide pandemic. Disseminated lung injury with the development of acute respiratory distress syndrome (ARDS) is the main cause of mortality in COVID-19. Although liver failure does not seem to occur in the absence of pre-existing liver disease, hepatic involvement in COVID-19 may correlate with overall disease severity and serve as a prognostic factor for the development of ARDS. The spectrum of liver injury in COVID-19 may range from direct infection by SARS-CoV-2, indirect involvement by systemic inflammation, hypoxic changes, iatrogenic causes such as drugs and ventilation to exacerbation of underlying liver disease. This concise review discusses the potential pathophysiological mechanisms for SARS-CoV-2 hepatic tropism as well as acute and possibly long-term liver injury in COVID-19.

Prostaglandin F2α receptor antagonist attenuates LPS-induced systemic inflammatory response in mice

Although it is known that prostaglandin (PG) F_2α level is elevated in the plasma of patients with sepsis, the roles of PGF_2α is still unknown. We aimed to clarify the roles of PGF_2α in the regulation of lipopolysaccharide (LPS)-induced systemic inflammation. At 24 hours after LPS administration, neutrophil infiltration in peritoneal cavity, the mRNA expression of pro-inflammatory cytokines such as tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and macrophage inflammatory protein-2, and tissue damages in lung, liver, and kidney were all increased. Inhibition of FP receptors significantly decreased LPS-induced neutrophil infiltration and lowered the mRNA expression of the pro-inflammatory cytokines. At 6 hour after LPS administration, the level of anti-inflammatory cytokine, IL-10 in peritoneal lavage fluid was higher than that in naïve mice. Inhibition of FP receptors in these mice increased IL-10 level further. Stimulation of isolated peritoneal neutrophils by LPS increased the gene expression of IL-10, which was further increased by AL8810 treatment. Administration of an anti-IL-10 antibody antagonized the AL8810-decreased mRNA expression of pro-inflammatory cytokines and tissue damages. These results indicate that inhibition of FP receptors by AL8810 attenuated LPS-induced systemic inflammation in mice via enhanced IL-10 production.

Serum irisin levels are decreased in patients with sepsis, and exogenous irisin suppresses ferroptosis in the liver of septic mice

BACKGROUND

Sepsis remains a major health issue without an effective therapy. Ferroptosis, an iron-dependent programmed cell death, has been proposed to be related to the pathogenesis of sepsis. Irisin, a myokine released during exercise, improves mitochondrial function under various conditions. Ferroptosis is closely related to mitochondrial function. However, the role of irisin in sepsis-induced ferroptosis and mitochondrial dysfunction in the liver remained unknown. Thus, we hypothesize that irisin treatment suppresses ferroptosis and improves mitochondrial function in sepsis.

METHODS

To study this, we first explored the role of serum irisin levels in patients with sepsis, and then determined the effect of irisin administration on ferroptosis and mitochondrial function in the liver of septic mice.

RESULTS

Serum irisin levels were decreased and negatively correlated with the APACHE II scores in patients with sepsis. In mice subjected to cecal ligation and puncture (CLP), exogenous irisin administration suppressed ferroptosis, inhibited inflammatory response, decreased reactive oxygen species (ROS) production, restored abnormal mitochondrial morphology, and increased mtDNA copy number and adenosine triphosphate (ATP) content. The effect of irisin on ferroptosis was confirmed in LPS-treated hepatocytes and CLP-induced septic mice. Inhibition of glutathione peroxidase 4 (GPX4), a central regulator of ferroptosis, reduced irisin's protective effects in LPS-treated hepatocytes and CLP-induced septic mice, while blocking the irisin receptor with RGD peptide or Echistain decreased irisin-induced GPX4 expression.

CONCLUSIONS

Serum irisin levels are decreased and negatively correlated with disease severity in patients with sepsis, and irisin treatment suppresses ferroptosis and restores mitochondrial function in experimental sepsis. Irisin may offer therapeutic potential in the management of sepsis.

LncRNA XIST silencing protects against sepsis-induced acute liver injury via inhibition of BRD4 expression

Sepsis is recognized as the acute systemic inflammatory response to severe infection. It is main cause of multiple organ system dysfunction and even organ failure. Long non-coding RNA X inactivate-specific transcript (XIST) is implicated in multiple inflammatory diseases. The aim of present work was to investigate the precise mechanism of XIST underlying sepsis-induced acute liver injury. Rats were underwent cecal ligation and puncture (CLP) to establish sepsis-induced the animal models of acute liver injury. Hematoxylin and eosin (H&E) staining was performed to observe pathological alterations. Corresponding commercial assay kits were employed to analyze the levels of inflammatory cytokines and oxidative stress. Western blot and reverse transcriptional quantitative PCR (RT-qPCR) were performed to determine the expression of proteins and target genes. Finally, TUNEL and CCK-8 assays were performed to test apoptosis rate and cell viability, respectively. In our study, XIST and BRD4 were highly expressed in serum of patients with sepsis-induced acute liver injury. XIST knockdown ameliorated sepsis-induced acute liver injury and inhibited inflammation, oxidative stress, and cell apoptosis in sepsis-induced acute liver injury rats. Interestingly, XIST knockdown downregulated the expression of BRD4, and BRD4 overexpression abolished the impacts of XIST knockdown on inflammation, oxidative stress, and apoptosis of that LPS-induced Kupffer cells. We conclude that lncRNA XIST silencing protects against sepsis-induced acute liver injury via inhibition of the BRD4 expression. Therefore, XIST may be a biomarker for sepsis diagnosis and treatment.

Reduced Mrp2 surface availability as PI3Kγ-mediated hepatocytic dysfunction reflecting a hallmark of cholestasis in sepsis

Sepsis-associated liver dysfunction manifesting as cholestasis is common during multiple organ failure. Three hepatocytic dysfunctions are considered as major hallmarks of cholestasis in sepsis: impairments of microvilli covering canalicular membranes, disruptions of tight junctions sealing bile-collecting canaliculae and disruptions of Mrp2-mediated hepatobiliary transport. PI3Kγ loss-of-function was suggested as beneficial in early sepsis. Yet, the PI3Kγ-regulated cellular processes in hepatocytes remained largely unclear. We analysed all three sepsis hallmarks for responsiveness to massive PI3K/Akt signalling and PI3Kγ loss-of-function, respectively. Surprisingly, neither microvilli nor tight junctions were strongly modulated, as shown by electron microscopical studies of mouse liver samples. Instead, quantitative electron microscopy proved that solely Mrp2 surface availability, i.e. the third hallmark, responded strongly to PI3K/Akt signalling. Mrp2 plasma membrane levels were massively reduced upon PI3K/Akt signalling. Importantly, Mrp2 levels at the plasma membrane of PI3Kγ KO hepatocytes remained unaffected upon PI3K/Akt signalling stimulation. The effect explicitly relied on PI3Kγ's enzymatic ability, as shown by PI3Kγ kinase-dead mice. Keeping the surface availability of the biliary transporter Mrp2 therefore is a cell biological process that may underlie the observation that PI3Kγ loss-of-function protects from hepatic excretory dysfunction during early sepsis and Mrp2 should thus take center stage in pharmacological interventions.

The challenge of recognising sepsis: Future nanotechnology solutions

The urgent need to start anti-infective therapeutic interventions in suspected sepsis, and the lack of specific time-critical diagnostic information often lead to the widespread administration of broad-spectrum antimicrobial therapies, increasing the risk of unwanted patient harms and contributing to rising pathogen antimicrobial resistance. Nanotechnology, which involves engineering at the nanoscale, allows for the bespoke development of diagnostic solutions with multi-functionality and high sensitivity that has the potential to help provide time-critical information to make more accurate diagnoses and treatment decisions for sepsis. Nanotechnologies also have the potential to improve upon the current strategies used for novel biomarker discovery. Here we describe some of the current limitations to identifying sepsis and explore the potential role for nanotechnology solutions.