Deficient phospholipase C activity in blood polimorphonuclear neutrophils from patients with liver cirrhosis

Circulating neutrophil anti-pathogen dysfunction in cirrhosis

Neutrophils are the largest population of leucocytes and are among the first cells of the innate immune system to fight against intruding pathogens. In patients with cirrhosis, neutrophils exhibit altered functionality, including changes in phagocytic ability, bacterial killing, chemotaxis, degranulation, reactive oxygen species production and NET (neutrophil extracellular trap) formation. This results in their inability to mount an adequate antibacterial response and protect the individual from infection. Prognosis and survival in patients with cirrhosis are greatly influenced by the development of infectious complications. Multidrug-resistant bacterial infections in patients with cirrhosis are currently a growing problem worldwide; therefore, alternative methods for the prevention and treatment of bacterial infections in cirrhosis are urgently needed. The prevention and treatment of neutrophil dysfunction could be a potential way to protect patients from bacterial infections. However, the reasons for changes in neutrophil function in cirrhosis are still not completely understood, which limits the development of efficient therapeutic strategies. Both cellular and serum factors have been proposed to contribute to the functional impairment of neutrophils. Herein, we review the current knowledge on features and proposed causes of neutrophil dysfunction in cirrhosis, with a focus on current knowledge gaps and limitations, as well as opportunities for future investigations in this field.

The Mechanisms of Systemic Inflammatory and Immunosuppressive Acute-on-Chronic Liver Failure and Application Prospect of Single-Cell Sequencing

Acute-on-chronic liver failure (ACLF) is a complex clinical syndrome, and patients often have high short-term mortality. It occurs with intense systemic inflammation, often accompanied by a proinflammatory event (such as infection or alcoholic hepatitis), and is closely related to single or multiple organ failure. Liver inflammation begins when innate immune cells (such as Kupffer cells (KCs)) are activated by binding of pathogen-associated molecular patterns (PAMPs) from pathogenic microorganisms or damage-associated molecular patterns (DAMPs) of host origin to their pattern recognition receptors (PRRs). Activated KCs can secrete inflammatory factors as well as chemokines and recruit bone marrow-derived cells such as neutrophils and monocytes to the liver to enhance the inflammatory process. Bacterial translocation may contribute to ACLF when there are no obvious precipitating events. Immunometabolism plays an important role in the process (including mitochondrial dysfunction, amino acid metabolism, and lipid metabolism). The late stage of ACLF is mainly characterized by immunosuppression. In this process, the dysfunction of monocyte and macrophage is reflected in the downregulation of HLA-DR and upregulation of MER tyrosine kinase (MERTK), which weakens the antigen presentation function and reduces the secretion of inflammatory cytokines. We also describe the specific function of bacterial translocation and the gut-liver axis in the process of ACLF. Finally, we also describe the transcriptomics in HBV-ACLF and the recent progress of single-cell RNA sequencing as well as its potential application in the study of ACLF in the future, in order to gain a deeper understanding of ACLF in terms of single-cell gene expression.

Clostridioides difficile infection in liver cirrhosis patients: A population-based study in United States

BACKGROUND

Clostridioides (formerly Clostridium) difficile infection (CDI) is an increasingly frequent cause of morbidity and mortality in hospitalized patients. Multiple risk factors are documented in the literature that includes, but are not limited to, antibiotics use, advanced age, and gastric acid suppression. Several epidemiological studies have reported an increased incidence of CDI in advanced liver disease patients. Some have also demonstrated a higher prevalence of nosocomial infections in cirrhotic patients.

AIM

To use a large nationwide database, we sought to determine CDI’s risk among liver cirrhosis patients in the United States.

METHODS

We queried a commercial database (Explorys Inc^TM, Cleveland, OH, United States), and obtained an aggregate of electronic health record data from 26 major integrated United States healthcare systems comprising 360 hospitals in the United States from 2018 to 2021. Diagnoses were organized into the Systematized Nomenclature of Medicine Clinical Terms (SNOMED–CT) hierarchy. Statistical analysis for the multivariable model was performed using Statistical Package for Social Sciences (SPSS version 25, IBM Corp^TM). For all analyses, a two-sided P value of < 0.05 was considered statistically significant.

RESULTS

There were a total of 19387760 patients in the database who were above 20 years of age between the years 2018-2021. Of those, 133400 were diagnosed with liver cirrhosis. The prevalence of CDI amongst the liver cirrhosis population was 134.93 per 100.000 vs 19.06 per 100.000 in non-cirrhotic patients (P < 0.0001). The multivariate analysis model uncovered that cirrhotic patients were more likely to develop CDI (OR: 1.857; 95%CI: 1.665-2.113, P < 0.0001) compared to those without any prior history of liver cirrhosis.

CONCLUSION

In this large database study, we uncovered that cirrhotic patients have a significantly higher CDI prevalence than those without cirrhosis. Liver cirrhosis may be an independent risk factor for CDI. Further prospective studies are needed to clarify this possible risk association that may lead to the implementation of screening methods in this high-risk population.

The multifactorial mechanisms of bacterial infection in decompensated cirrhosis

Infections, due to a dysfunctional immune response, pose a great risk to patients with decompensated cirrhosis and herald the beginning of the terminal phase of this disease. Infections typically result from breaches in innate immune barriers and inadequate clearance by immune cells. This leads to bacterial and bacterial product translocation to the systemic circulation, which is already primed by ongoing hepatic inflammation in patients with cirrhosis, who are particularly prone to developing organ failure in the presence of an infection. Early identification of bacterial infection, along with the prompt use of appropriate antibiotics, have reduced the mortality associated with certain infections in patients with decompensated cirrhosis. Judicious use of antibiotic therapy remains imperative given the emergence of multidrug-resistant infections in the cirrhotic population. Important research over the last few years has identified molecular targets on immune cells that may enhance their function, and theoretically prevent infections. Clinical trials are ongoing to delineate the beneficial effects of targeted molecules from their off-target effects. Herein, we review the mechanisms that predispose patients with cirrhosis to bacterial infections, the clinical implications of infections and potential targets for the prevention or treatment of infections in this vulnerable population.

The Clinical Impact of Cirrhosis on the Hospital Outcomes of Patients Admitted With Influenza Infection: Propensity Score Matched Analysis of 2011-2017 US Hospital Data

BACKGROUND/OBJECTIVES

Patients with cirrhosis have liver-related immune dysfunction that potentially predisposes the patients to increased influenza infection risk. Our study evaluates this cross-sectional relationship using a national registry of hospital patients.

METHODS

This study included the 2011-2017 National Inpatient Sample database. From this, respiratory influenza cases were isolated and stratified using the presence of cirrhosis into a cirrhosis-present study cohort and cirrhosis-absent controls; propensity score matching method was used to match the controls to the study cohort (cirrhosis-present) using a 1:1 matching ratio. The endpoints included mortality, length of stay, hospitalization costs, and influenza-related complications.

RESULTS

Following the match, there were 2,040 with cirrhosis and matched 2,040 without cirrhosis admitted with respiratory influenza infection. Compared to the controls, cirrhosis patients had higher in-hospital mortality (7.79 vs 3.43% p < 0.001, OR 2.38 95% CI 1.78-3.17), longer length of stay (7.25 vs 6.52 d p < 0.001), higher hospitalization costs ($70,009 vs $65,035 p < 0.001), and were more likely be discharged to a skilled nursing facility and home healthcare (vs routine home discharges). In terms of influenza-related complications, the cirrhosis cohort had higher rates of sepsis (29.8 vs 22% p < 0.001, OR 1.51 95% CI 1.31-1.74). In the multivariate regression analysis, cirrhosis was associated with higher mortality (p < 0.001, aOR 2.31 95% CI 1.59-3.35) and length of stay (p = 0.018, aOR 1.03 95% CI 1.01-1.06). In subgroup analysis of patients with decompensated (n = 597) versus compensated cirrhosis (n = 1443), those with decompensated cirrhosis had higher rates of in-hospital mortality (12.7 vs 5.75% p < 0.001, OR 2.39 95% CI 1.72-3.32), length of stay (8.85 vs 6.59 d p < 0.001), and hospitalization costs ($92,858 vs $60,556 p < 0.001). In the multivariate analysis, decompensated cirrhosis was associated with increased mortality (p < 0.001, aOR 2.86 95% CI 1.90-4.32).

CONCLUSION

This study shows the presence of cirrhosis to result in higher hospital mortality and postinfluenza complications in patients with influenza infection.

Leukocytes, Systemic Inflammation and Immunopathology in Acute-on-Chronic Liver Failure

Acute-on-chronic liver failure (ACLF) is a complex syndrome that develops in patients with cirrhosis and is characterized by acute decompensation, organ failure(s) and high short-term mortality. ACLF frequently occurs in close temporal relationship to a precipitating event, such as acute alcoholic, drug-induced or viral hepatitis or bacterial infection and, in cases without precipitating events, probably related to intestinal translocation of bacterial products. Dysbalanced immune function is central to its pathogenesis and outcome with an initial excessive systemic inflammatory response that drives organ failure and mortality. This hyperinflammatory state ultimately impairs the host defensive mechanisms of immune cells, rendering ACLF patients immunocompromised and more vulnerable to secondary infections, and therefore to higher organ dysfunction and mortality. In this review, we describe the prevailing characteristics of the hyperinflammatory state in patients with acutely decompensated cirrhosis developing ACLF, with special emphasis on cells of the innate immune system (i.e., monocytes and neutrophils), their triggers (pathogen- and damage-associated molecular patterns [PAMPs and DAMPs]), their effector molecules (cytokines, chemokines, growth factors and bioactive lipid mediators) and the consequences on tissue immunopathology. In addition, this review includes a chapter discussing new emerging therapies based on the modulation of leukocyte function by the administration of pleiotropic proteins such as albumin, Toll-like receptor 4 antagonists, interleukin-22 or stem cell therapy. Finally, the importance of finding an appropriate intervention that reduces inflammation without inducing immunosuppression is highlighted as one of the main therapeutic challenges in cirrhosis.

Innate immune cells in cirrhosis

Cirrhosis is a multisystemic disease wherein inflammatory responses originating from advanced liver disease and its sequelae affect distant compartments. Patients with cirrhosis are susceptible to bacterial infections, which may precipitate acute decompensation and acute-on-chronic liver failure, both of which are associated with high short-term mortality. Innate immune cells are an essential first line of defence against pathogens. Activation of liver macrophages (Kupffer cells) and resident mastocytes generate proinflammatory and vaso-permeating mediators that induce accumulation of neutrophils, lymphocytes, eosinophils and monocytes in the liver, and promote tissue damage. During cirrhosis progression, damage- and pathogen-associated molecular patterns activate immune cells and promote development of systemic inflammatory responses which may involve different tissues and compartments. The antibacterial function of circulating neutrophils and monocytes is gradually and severely impaired as cirrhosis worsens, contributing to disease progression. The mechanisms underlying impaired antimicrobial responses are complex and incompletely understood. This review focuses on the continuous and distinct perturbations arising in innate immune cells during cirrhosis, including their impact on disease progression, as well as reviewing potential therapeutic targets.

Review of Defective NADPH Oxidase Activity and Myeloperoxidase Release in Neutrophils From Patients With Cirrhosis

Patients with decompensated cirrhosis are highly susceptible to develop bacterial infections and these can trigger multiorgan failure associated with high in-hospital mortality. Neutrophils from patients with decompensated cirrhosis exhibit marked alterations that may explain the susceptibility of these patients to develop bacterial infections. These neutrophil alterations include marked defects in intracellular signaling pathways involving serine/threonine kinases such as protein kinase B (AKT), p38-mitogen-activated protein kinase (MAPK), and the MAP kinases1/2; activation of the NADPH oxidase complex; myeloperoxidase (MPO) release; and bactericidal activity of neutrophils stimulated by the bacterial peptide formyl-Methionine-Leucine-Phenylalanine (fMLF). Impaired activity of the NADPH oxidase 2 (NOX2) complex is also related to reduced levels of expression of its major components through post-transcriptional mechanisms. In addition, the catalytic NOX2 component gp91 ^phox is subject to degradation by elastase highly present in patients' plasma. A defect in the protein kinase B (AKT) and p38 MAPK-mediated signaling pathways may explain the decrease in phosphorylation of p47 ^phox (an important component of the NADPH oxidase complex) and MPO release, in response to neutrophil stimulation by fMLF. Most of these alterations are reversible ex vivo with TLR7/8 agonists (CL097, R848), raising the possibility that these agonists might be used in the future to restore neutrophil antibacterial functions in patients with cirrhosis.

Phosphoinositide-specific phospholipase C in normal human liver and in alcohol abuse

The phosphoinositide (PI) signal transduction pathway participates in liver metabolism. Abnormal activity or expression of PI-specific phospholipase C (PLC) enzymes has been described in different liver diseases. We resume the role of the PI metabolism in liver and PLC abnormalities in different liver diseases. Moreover, we present the results of PLC analyses in a normal human liver and an alcohol-damaged liver. PLC enzymes and the expression of the corresponding genes in liver biopsies from individuals deceased for complications of the alcoholic liver disease (ALD) at different stages compared with normal controls (deceased individuals with histologically normal livers without alcohol addiction anamnesis) were analyzed by using immunohistochemistry and molecular biology techniques. The expression panel of PLCs was described in normal and alcohol abuse liver. Our observations suggest that the regulation of PLC expression might be due to posttranscriptional events and that alcohol affects the epigenetic control of PLC expression belonging to PI signaling. We also describe the alternate expression of PLCB1 and PLCH1 genes in liver. Our results corroborate literature data suggesting that PLC enzymes are differently expressed in normal versus pathological liver, playing a role in the histopathogenesis of liver tissue damage. The expression and/or localization of selected PLC isoforms is especially affected in alcohol-related liver tissue histopathology. Our present observations confirm that the modulation of protein synthesis plays a role in the regulation of PLC enzymes. We also suggest that this modulation might act at the transcription level. Further studies are required to investigate related epigenetic mechanisms.

Causes and Consequences of Innate Immune Dysfunction in Cirrhosis

Liver cirrhosis is an increasing health burden and public health concern. Regardless of etiology, patients with cirrhosis are at risk of a range of life-threatening complications, including the development of infections, which are associated with high morbidity and mortality and frequent hospital admissions. The term Cirrhosis-Associated Immune Dysfunction (CAID) refers to a dynamic spectrum of immunological perturbations that develop in patients with cirrhosis, which are intimately linked to the underlying liver disease, and negatively correlated with prognosis. At the two extremes of the CAID spectrum are systemic inflammation, which can exacerbate clinical manifestations of cirrhosis such as hemodynamic derangement and kidney injury; and immunodeficiency, which contributes to the high rate of infection in patients with decompensated cirrhosis. Innate immune cells, in particular monocytes/macrophages and neutrophils, are pivotal effector and target cells in CAID. This review focuses on the pathophysiological mechanisms leading to impaired innate immune function in cirrhosis. Knowledge of the phenotypic manifestation and pathophysiological mechanisms of cirrhosis associated immunosuppression may lead to immune targeted therapies to reduce susceptibility to infection in patients with cirrhosis, and better biomarkers for risk stratification, and assessment of efficacy of novel immunotherapies.

NADPH oxidase depletion in neutrophils from patients with cirrhosis and restoration via toll-like receptor 7/8 activation

OBJECTIVE

Cirrhosis downregulates phagocyte oxidant production via their antibacterial superoxide-generating system, NADPH oxidase (NOX2) and increases patients' susceptibility to infection and mortality rate. To explore novel biochemical parameters that explain susceptibility to infections, we investigated the expression of NOX2 and partners in neutrophils of patients with severe alcoholic cirrhosis and have provided a novel approach to restore superoxide production capacity in patients' neutrophils and blood.

DESIGN

Neutrophils were isolated from patients with decompensated alcoholic cirrhosis. NOX2 activity was assessed after stimulation of purified neutrophils or whole blood with the bacterial-derived peptide fMet-Leu-Phe. The expression of NOX2 and partners was studied by western blot analysis, flow cytometry and reverse transcription-PCR.

RESULTS

The impaired superoxide production by patients' neutrophils was associated with a severe deficient expression of the NADPH oxidase catalytic core flavocytochrome-b558 (gp91 ^phox /NOX2 and p22 ^phox ), its cytosolic partner p47 ^phox but not p67 ^phox . NOX2 expression decreased rapidly by protein degradation involving elastase released during degranulation of healthy neutrophils stimulated with fMet-Leu-Phe, or highly present in patients' plasma. Interestingly, the deficient superoxide production was reversed by treatment of patients' neutrophils and whole blood with toll-like receptor 7/8 (TLR7/8) agonists. This treatment stimulated a rapid NOX2 transcription and translation through a process involving mammalian target of rapamycin (mTOR) whose expression was also deficient in patients' neutrophils. NOX2 expression was also increased by the TLR4 agonist lipopolysaccharide but with only a modest improvement of reactive oxygen species production.

CONCLUSION

Impairment of neutrophil oxidants production in alcoholic cirrhosis is associated with NOX2 degradation and deficient mTOR-dependent translational machinery. The NOX2 depletion can be reversed via TRL7/8 activation and might be used to restore antimicrobial responses of immunocompromised patients.

Sepsis in alcohol-related liver disease

Alcohol-related liver disease (ALD) remains the most important cause of death due to alcohol. Infections, particularly bacterial infections, are one of the most frequent and severe complications of advanced ALDs, such as alcoholic cirrhosis and severe alcoholic hepatitis (sAH). The specific mechanisms responsible for this altered host defence are yet to be deciphered. The aim of the present study is to review the current knowledge of infectious complications in ALD and its pathophysiological mechanisms, distinguishing the role of alcohol consumption and the contribution of different forms of ALD. To date, corticosteroids are the only treatment with proven efficacy in sAH, but their impact on the occurrence of infections remains controversial. The combination of an altered host defence and corticosteroid treatment in sAH has been suggested as a cause of opportunistic fungal and viral infections. A high level of suspicion with systematic screening and prompt, adequate treatment are warranted to improve outcomes in these patients. Prophylactic or preemptive strategies in this high-risk population might be a preferable option, because of the high short-term mortality rate despite adequate therapies. However, these strategies should be assessed in well-designed trials before clinical implementation.

Impaired intracellular signaling, myeloperoxidase release and bactericidal activity of neutrophils from patients with alcoholic cirrhosis

BACKGROUND & AIMS

Myeloperoxidase exocytosis and production of hydrogen peroxide via the neutrophil superoxide-generating nicotinamide adenine dinucleotide phosphate (NADPH) oxidase contribute to efficient elimination of bacteria. Cirrhosis impairs immune functions and increases susceptibility to bacterial infection. We recently showed that neutrophils from patients with decompensated alcoholic cirrhosis exhibit a severe impairment of formylpeptide receptor (fPR)-mediated intracellular signaling and superoxide production. Here, we performed ex vivo studies with these patients' neutrophils to further investigate myeloperoxidase release, bactericidal capacity and signaling events following fPR stimulation by the formylpeptide formyl-met-leu-phe (fMLP).

METHODS

Myeloperoxidase release was studied by measuring extracellular myeloperoxidase activity. Activation of signaling effectors was studied by Western blot and their respective contribution to myeloperoxidase release studied using pharmacological antagonists.

RESULTS

fMLP-induced myeloperoxidase release was strongly impaired in patients' neutrophils whereas the intracellular myeloperoxidase stock was unaltered. The fMLP-induced phosphorylation of major signaling effectors, AKT, ERK1/2 and p38-MAP-Kinases, was also strongly deficient despite a similar expression of signaling effectors or fPR. However, based on effector inhibition in healthy neutrophils, AKT and p38-MAPK but not ERK1/2 upregulated fMLP-induced myeloperoxidase exocytosis. Interestingly, patients' neutrophils exhibited a defective bactericidal capacity that was reversed ex vivo by the TLR7/8 agonist CL097, through potentiation of the fMLP-induced AKT/p38-MAPK signaling axis and myeloperoxidase release.

CONCLUSIONS

We provide first evidence that neutrophils from patients with decompensated alcoholic cirrhosis exhibit a deficient AKT/p38-MAPK signaling, myeloperoxidase release and bactericidal activity, which can be reversed via TLR7/8 activation. These defects, together with the previously described severe deficient superoxide production, may increase cirrhotic patients' susceptibility to bacterial infections.

Bacterial infections in cirrhosis: A critical review and practical guidance

Bacterial infection is common and accounts for major morbidity and mortality in cirrhosis. Patients with cirrhosis are immunocompromised and increased susceptibility to develop spontaneous bacterial infections, hospital-acquired infections, and a variety of infections from uncommon pathogens. Once infection develops, the excessive response of pro-inflammatory cytokines on a pre-existing hemodynamic dysfunction in cirrhosis further predispose the development of serious complications such as shock, acute-on-chronic liver failure, renal failure, and death. Spontaneous bacterial peritonitis and bacteremia are common in patients with advanced cirrhosis, and are important prognostic landmarks in the natural history of cirrhosis. Notably, the incidence of infections from resistant bacteria has increased significantly in healthcare-associated settings. Serum biomarkers such as procalcitonin may help to improve the diagnosis of bacterial infection. Preventive measures (e.g., avoidance, antibiotic prophylaxis, and vaccination), early recognition, and proper management are required in order to minimize morbidity and mortality of infections in cirrhosis.

Neutrophil dysfunction in patients with liver cirrhosis

Liver cirrhosis is the final stage of chronic liver disease of any causes, in which the defensive reaction to infections is reducing. Patients with liver cirrhosis are at an increased risk of infections, sepsis and death. Neutrophils are an essential component of the innate immune response and the first line of defense to resist all kinds of detrimental factor, and participate in specific immunity. Immune dysfunction in cirrhosis is associated with neutrophil dysfunction. This paper reviews the neutrophil dysfunction and its pathogenesis in liver cirrhosis.

Cirrhosis-associated immune dysfunction: distinctive features and clinical relevance

The term cirrhosis-associated immune dysfunction refers to the main syndromic abnormalities of immune function, immunodeficiency and systemic inflammation that are present in cirrhosis. The course of advanced cirrhosis, regardless of its aetiology, is complicated by cirrhosis-associated immune dysfunction and this constitutes the pathophysiological hallmark of an increased susceptibility to bacterial infection, distinctive of the disease. Cirrhosis impairs the homeostatic role of the liver in the systemic immune response. Damage to the reticulo-endothelial system compromises the immune surveillance function of the organ and the reduced hepatic synthesis of proteins, involved in innate immunity and pattern recognition, hinders the bactericidal ability of phagocytic cells. Systemic inflammation, in form of activated circulating immune cells and increased serum levels of pro-inflammatory cytokines, is the result of persistent episodic activation of circulating immune cells from damage-associated molecular patterns, released from necrotic liver cells and, as cirrhosis progresses, from pathogen-associated molecular patterns, released from the leaky gut. Cirrhosis-associated immune dysfunction phenotypes switch from predominantly "pro-inflammatory" to predominantly "immunodeficient" in patients with stable ascitic cirrhosis and in patients with severely decompensated cirrhosis and extra-hepatic organ failure (e.g. acute-on-chronic liver failure), respectively. These cirrhosis-associated immune dysfunction phenotypes represent the extremes of a spectrum of reversible dynamic events that take place during the course of cirrhosis. Systemic inflammation can affect the functions of tissue somatic cells and modify the clinical manifestation of cirrhosis. The best characterized example is the contribution of systemic inflammation to the haemodynamic derangement of cirrhosis, which correlates negatively with prognosis.

Immune dysfunction in cirrhosis

Innate and adaptive immune dysfunction, also referred to as cirrhosis-associated immune dysfunction syndrome, is a major component of cirrhosis, and plays a pivotal role in the pathogenesis of both the acute and chronic worsening of liver function. During the evolution of the disease, acute decompensation events associated with organ failure(s), so-called acute-on chronic liver failure, and chronic decompensation with progression of liver fibrosis and also development of disease specific complications, comprise distinct clinical entities with different immunopathology mechanisms. Enhanced bacterial translocation associated with systemic endotoxemia and increased occurrence of systemic bacterial infections have substantial impacts on both clinical situations. Acute and chronic exposure to bacteria and/or their products, however, can result in variable clinical consequences. The immune status of patients is not constant during the illness; consequently, alterations of the balance between pro- and anti-inflammatory processes result in very different dynamic courses. In this review we give a detailed overview of acquired immune dysfunction and its consequences for cirrhosis. We demonstrate the substantial influence of inherited innate immune dysfunction on acute and chronic inflammatory processes in cirrhosis caused by the pre-existing acquired immune dysfunction with limited compensatory mechanisms. Moreover, we highlight the current facts and future perspectives of how the assessment of immune dysfunction can assist clinicians in everyday practical decision-making when establishing treatment and care strategies for the patients with end-stage liver disease. Early and efficient recognition of inappropriate performance of the immune system is essential for overcoming complications, delaying progression and reducing mortality.

Inhibition of mammalian target of rapamycin aggravates the respiratory burst defect of neutrophils from decompensated patients with cirrhosis

Cirrhosis is commonly accompanied by impaired defense functions of polymorphonuclear leucocytes (PMNs), increased patient susceptibility to infections, and hepatocellular carcinoma (HCC). PMN antimicrobial activity is dependent on a massive production of reactive oxygen species (ROS) by nicotinamide adenine dinucleotide phosphate (NADPH) 2 (NADPH oxidase 2; NOX2), termed respiratory burst (RB). Rapamycin, an antagonist of mammalian target of rapamycin (mTOR), may be used in the treatment of HCC and in transplanted patients. However, the effect of mTOR inhibition on the PMN RB of patients with cirrhosis remains unexplored and was studied here using the bacterial peptide, formyl-Met-Leu-Phe (fMLP), as an RB inducer. fMLP-induced RB of PMN from patients with decompensated alcoholic cirrhosis was strongly impaired (30%-35% of control) as a result of intracellular signaling alterations. Blocking mTOR activation (phospho-S2448-mTOR) with rapamycin further aggravated the RB defect. Rapamycin also inhibited the RB of healthy PMNs, which was associated with impaired phosphorylation of the NOX2 component, p47phox (phox: phagocyte oxidase), on its mitogen-activated protein kinase (MAPK) site (S345) as well as a preferential inhibition of p38-MAPK relative to p44/42-MAPK. However, rapamycin did not alter the fMLP-induced membrane association of p47phox and p38-MAPK in patients' PMNs, but did prevent their phosphorylation at the membranes. The mTOR contribution to fMLP-induced RB, phosphorylation of p47phox and p38-MAPK was further confirmed by mTOR knockdown in HL-60 cells. Finally, rapamycin impaired PMN bactericidal activity, but not bacterial uptake.

CONCLUSION

mTOR significantly up-regulates the PMN RB of patients with cirrhosis by p38-MAPK activation. Consequently, mTOR inhibition by rapamycin dramatically aggravates their PMN RB defect, which may increase patients' susceptibility to infection. Thus, concerns should be raised about the use of rapamycin in immuno-depressed patients.

Immune dysfunction and infections in patients with cirrhosis

Patients with cirrhosis are immunocompromised and susceptible to infections. Although detection and treatment of spontaneous bacterial peritonitis (SBP) have improved, overall survival rates have not increased greatly in recent decades-infection still increases mortality 4-fold among patients with cirrhosis. Hospitalized patients with cirrhosis have the highest risk of developing infections, especially patients with gastrointestinal (GI) hemorrhage. Bacterial infections occur in 32% to 34% of patients with cirrhosis who are admitted to the hospital and 45% of patients with GI hemorrhage. These rates are much higher than the overall rate of infection in hospitalized patients (5%-7%). The most common are SBP (25% of infections), urinary tract infection (20%), and pneumonia (15%). Bacterial overgrowth and translocation from the GI tract are important steps in the pathogenesis of SBP and bacteremia-these processes increase levels of endotoxins and cytokines that induce the inflammatory response and can lead to septic shock, multiorgan dysfunction, and death. A number of other bacterial and fungal pathogens are more common and virulent in patients with cirrhosis than in the overall population. We review the pathogenesis of infections in these patients, along with diagnostic and management strategies.

Bacterial infection-related morbidity and mortality in cirrhosis

OBJECTIVES

Bacterial infections are acknowledged causes of morbidity and mortality in cirrhotic patients; yet, apart from spontaneous bacterial peritonitis, other infection issues have been understudied. We evaluated the existing medical data on infectious risks and related preventive and treatment data for cirrhotic patients.

METHODS

Medical literature search through MEDLINE, using a variety of keywords focused on: (a) immunodeficiency parameters of cirrhosis and attempts at therapeutic reversal, (b) relative incidence of various focal infections and implications for prevention, and (c) specific pathogens posing a risk in cirrhosis and availability of preventive strategies.

RESULTS

Immunodeficiency in cirrhosis is multifactorial and might not be reversed by isolated interventions. Epidemiologic data on the incidence of specific infections and risk factors are scarce, only Child-Pugh stage C being a common denominator. A variety of common, such as Staphylococcus aureus, Streptococcus pneumoniae, and Mycobacterium tuberculosis, as well as uncommon pathogens possess significant risks in cirrhosis. Certain aspects of these risks remain though unrecognized.

CONCLUSIONS

To better understand the overall burden of bacterial infections on cirrhotic patients' survival, more data on preventive efficacy of pneumococcal vaccination, on the overall burden of tuberculosis, and the relative incidence of specific infections as endocarditis are warranted.