Novel mechanism of C-reactive protein for enhancing mouse liver innate immunity

C-Reactive Protein: Pathophysiology, Diagnosis, False Test Results and a Novel Diagnostic Algorithm for Clinicians

The current literature provides a body of evidence on C-Reactive Protein (CRP) and its potential role in inflammation. However, most pieces of evidence are sparse and controversial. This critical state-of-the-art monography provides all the crucial data on the potential biochemical properties of the protein, along with further evidence on its potential pathobiology, both for its pentameric and monomeric forms, including information for its ligands as well as the possible function of autoantibodies against the protein. Furthermore, the current evidence on its potential utility as a biomarker of various diseases is presented, of all cardiovascular, respiratory, hepatobiliary, gastrointestinal, pancreatic, renal, gynecological, andrological, dental, oral, otorhinolaryngological, ophthalmological, dermatological, musculoskeletal, neurological, mental, splenic, thyroid conditions, as well as infections, autoimmune-supposed conditions and neoplasms, including other possible factors that have been linked with elevated concentrations of that protein. Moreover, data on molecular diagnostics on CRP are discussed, and possible etiologies of false test results are highlighted. Additionally, this review evaluates all current pieces of evidence on CRP and systemic inflammation, and highlights future goals. Finally, a novel diagnostic algorithm to carefully assess the CRP level for a precise diagnosis of a medical condition is illustrated.

Pioglitazone Modifies Kupffer Cell Function and Protects against Escherichia coli-Induced Bacteremia in Burned Mice

Infectious complications and subsequent sepsis in severely burned patients lead to high morbidity and mortality in response to uncontrolled innate immune responses mediated by macrophages. Peroxisome proliferator-activated receptor gamma (PPARγ) has anti-inflammatory activity and acts as a master regulator of macrophage polarization. In this study, we investigated whether the administration of a PPARγ agonist could modulate the Kupffer cell phenotype and thereby ameliorate the dysregulated innate response during post-burn bacterial infection. C57BL/6 mice were subjected to severe burns and randomized to receive either the PPARγ agonist, pioglitazone, or the vehicle control five days after injury, followed by the subsequent analysis of hepatic macrophages. Survival from the bacterial infection was monitored for seven days. Pioglitazone protected burned mice against bacterial infection. A single treatment with pioglitazone significantly enhanced phagocytosis, phagosome acidification, bacterial clearance, and reduction in inflammatory mediators in Kupffer cells. In conclusion, PPARγ activation by pioglitazone prevents clinical deterioration due to post-burn bacterial infection and improves survival. Our findings suggest that pioglitazone may be an effective therapeutic candidate for post-burn infectious complications.

The systemic-level repercussions of cancer-associated inflammation mediators produced in the tumor microenvironment

The tumor microenvironment is a dynamic, complex, and redundant network of interactions between tumor, immune, and stromal cells. In this intricate environment, cells communicate through membrane-membrane, ligand-receptor, exosome, soluble factors, and transporter interactions that govern cell fate. These interactions activate the diverse and superfluous signaling pathways involved in tumor promotion and progression and induce subtle changes in the functional activity of infiltrating immune cells. The immune response participates as a selective pressure in tumor development. In the early stages of tumor development, the immune response exerts anti-tumor activity, whereas during the advanced stages, the tumor establishes mechanisms to evade the immune response, eliciting a chronic inflammation process that shows a pro-tumor effect. The deregulated inflammatory state, in addition to acting locally, also triggers systemic inflammation that has repercussions in various organs and tissues that are distant from the tumor site, causing the emergence of various symptoms designated as paraneoplastic syndromes, which compromise the response to treatment, quality of life, and survival of cancer patients. Considering the tumor-host relationship as an integral and dynamic biological system, the chronic inflammation generated by the tumor is a communication mechanism among tissues and organs that is primarily orchestrated through different signals, such as cytokines, chemokines, growth factors, and exosomes, to provide the tumor with energetic components that allow it to continue proliferating. In this review, we aim to provide a succinct overview of the involvement of cancer-related inflammation at the local and systemic level throughout tumor development and the emergence of some paraneoplastic syndromes and their main clinical manifestations. In addition, the involvement of these signals throughout tumor development will be discussed based on the physiological/biological activities of innate and adaptive immune cells. These cellular interactions require a metabolic reprogramming program for the full activation of the various cells; thus, these requirements and the by-products released into the microenvironment will be considered. In addition, the systemic impact of cancer-related proinflammatory cytokines on the liver-as a critical organ that produces the leading inflammatory markers described to date-will be summarized. Finally, the contribution of cancer-related inflammation to the development of two paraneoplastic syndromes, myelopoiesis and cachexia, will be discussed.

The application of the Glasgow prognostic score to predict the survival in patients with metastatic pancreatic carcinoma

Objectives:

Thither is a more pressing effort to think about chemotherapy (CTx) in second-line and beyond in patients with metastatic pancreatic cancer (mPC). The current work aimed to evaluate the value of the Glasgow prognostic score (GPS) and modified Glasgow prognostic score (mGPS) to predict the survival in patients receiving second-line CTx protocol.

Material and Methods:

We retrospectively reviewed the patients’ medical files with mPC who received second-line CTx protocol between September 2013 and December 2017. The GPS/mGPS graded from 0 to 2 based on C-reactive protein and serum albumin.

Results:

One hundred and sixty-nine patients with mPC were eligible. Survival of patients with Score 0 (GPS/mGPS) was better than that of Score 1 (GPS/mGPS) or Score 2 (GPS/mGPS), which was statistically significant (P < 0.001). Of 78 patients who died, only 16 patients belonged to Score 0 (GPS/mGPS), compared to 30 patients belonged to Score 1 (GPS/mGPS) and 32 patients belonged to Score 2 (GPS/mGPS). Univariate analysis showed that high GPS/mGPS (P < 0.000) as well as poor Eastern Cooperative Oncology Group Performance Status (P < 0.000) and metastasis either to the liver (P < 0.01) or lung (P < 0.04) were linked with worse prognosis. A statistically significant association was detected between the two scores. Cohen’s Kappa coefficient (k) was 0.9, SD = 0.03; 95% CI (0.787–0.922; P < 0.001).

Conclusion:

Our data suggested that GPS/mGPS is an easy and applicable index that may be used in daily practice and may help in the prognostic stratification of mPC patients to avert overtreatment in frail patients and raise the best supportive treatment concept.

Inflammatory markers in postoperative cognitive dysfunction for patients undergoing total hip arthroplasty: a meta-analysis

BACKGROUND

Postoperative cognitive dysfunction (POCD) is a poorly understood disorder, very common even after total hip arthroplasty (THA). It is widely considered that inflammation response play a role in the pathogenesis of POCD.

AIMS

The aim of the present study was to investigate whether inflammation cytokine concentrations could serve as biomarkers for POCD in patients undergoing THA.

METHODS

A systematic search of databases was conducted to retrieve publications measuring circulating inflammatory markers of patients with and without POCD after THA. Inflammatory markers identified in more than two studies were pooled. The standardized mean difference (SMD) and the 95% confidence interval (95% CI) were calculated for each outcome. Fail-safe N statistics was calculated to estimate possible publication bias.

RESULTS

The pooled incidence rate of POCD after THA by combining 11 cohort studies was 31%. A total of five inflammatory markers, CRP, S-100B, IL-1β, IL-6 and TNF-α, were assessed. Significantly higher pre-operative CRP (P = 0.012) and S-100B (P < 0.0001) as well as post-operative CPR (P = 0.005) and IL-6 (P < 0.0001) at 6 h were found in POCD compared with non-POCD patients undergoing THA. Fail-safe N statistics revealed that these results are robust.

DISCUSSION

The current evidence suggests that some of the inflammatory markers, including CRP, S-100B, and IL-6, were correlated with the occurrence of POCD after THA.

CONCLUSION

Monitor of inflammatory markers might help early diagnosis of POCD after THA and development of preventive strategies.

C-Reactive Protein Is an Indicator of the Immunosuppressive Microenvironment Fostered by Myeloid Cells in Hepatocellular Carcinoma

BACKGROUND

C-reactive protein (CRP) is a widely used marker of systemic inflammation and predicts poor clinical outcomes in patients with hepatocellular carcinoma (HCC); however, its significance in the local immune response at the tumor site is not clear.

METHODS

Serum CRP levels of 329 HCC patients were detected before resection. Paired paraffin-embedded tumor samples were used to quantify immune cell populations, such as CD11b+ myeloid cells, CD68+ macrophages (Mφs), CD15+ neutrophils, CD8+ T cells, and CD206+, CD204+, CD163+ and CD169+ Mφs, by immunohistochemistry. Enrichment scores for 34 types of immune cells based on transcriptome data from 24 HCC samples were calculated by xCell. Overall survival of patients was analyzed using the Kaplan-Meier method.

RESULTS

Serum CRP levels were correlated with liver functions and tumor stages in patients with HCC. The densities of CD68+ tumor-associated macrophages (TAMs) and CD15+ tumor-associated neutrophils (TANs) were significantly higher in patients with elevated serum CRP levels than in those with low CRP levels (both p < 0.0001). Further analysis of TAM subtypes revealed that serum CRP levels were associated with CD204+ and CD163+ Mφ densities (p < 0.0001 and p = 0.0003, respectively). Moreover, transcriptome data showed that CRP expression was associated with the expression of myeloid cell infiltration-related genes in HCC tumors. The combination of serum CRP with TAMs or TANs in both the nontumor and intratumor regions could represent a powerful criterion for predicting patient prognoses.

CONCLUSION

Serum CRP could serve as an indicator of an immunosuppressive TME in HCC, which could be of potential clinical application for treatment strategies targeting the TME.

Infections, Reactions of Natural Killer T Cells and Natural Killer Cells, and Kidney Injury

Natural killer T (NKT) cells and NK cells are representative innate immune cells that perform antitumor and antimicrobial functions. The involvement of these cells in various renal diseases, including acute kidney injury (AKI), has recently become evident. Murine NKT cells are activated and cause AKI in response to various stimuli, such as their specific ligand, cytokines, and bacterial components. Both renal vascular endothelial cell injury (via the perforin-mediated pathway) and tubular epithelial cell injury (via the tumor necrosis factor-alpha/Fas ligand pathway) are independently involved in the pathogenesis of AKI. NK cells complement the functions of NKT cells, thereby contributing to the development of infection-associated AKI. Human CD56⁺ T cells, which are a functional counterpart of murine NKT cells, as well as a subpopulation of CD56⁺ NK cells, strongly damage intrinsic renal cells in vitro upon their activation, possibly through mechanisms similar to those in mice. These cells are also thought to be involved in the acute exacerbation of pre-existing glomerulonephritis triggered by infection in humans, and their roles in sepsis-associated AKI are currently under investigation. In this review, we will provide an overview of the recent advances in the understanding of the association among infections, NKT and NK cells, and kidney injury, which is much more profound than previously considered. The important role of liver macrophages in the activation of NKT cells will also be introduced.

Biosynthesis of gold nanoparticles for the treatment of osteoarthritis alone or in combination with Diacerein® in a rat model

Gold (Au) compounds were used as an effective therapeutic agent for various inflammatory diseases; however, the use of Au compounds becomes limited because of its association with several side effects. Hence, gold nanoparticles (AuNPs) were developed as a new option for the medical proposes. However, the safety evaluation of gold nanoparticles (AuNPs) in osteoarthritis (OA) treatment remains vague. This study aimed to biosynthesize, characterize and evaluate the therapeutic effects of biosynthesized AuNPs and/or Diacerein^® (DIA) in experimental OA. OA was induced by a single injection of monosodium iodoacetate (3 mg/joint) in the intra-articular knee of female rats. Normal rats (N-rats) and OA-rats were treated orally for 5 weeks as follow: untreated N-rats; untreated OA-rats; N-rats received DIA (50 mg/kg b.w); N-rats received AuNPs (30 μg/kg b.w.); N-rats received AuNPs plus DIA; OA-rats received DIA; OA-rats received AuNPs, and OA-rats received AuNPs plus DIA. Blood, knee cartilage, liver and kidney samples were collected for biochemical and histological analysis. The synthesized AuNPs were nearly spherical with average size of 20 nm and zeta potential of 33 mV. AuNPs and DIA induced a significant improvement in serum inflammatory cytokines, biochemical parameters, estrogen level, hepatic and renal oxidative markers, hepatic DNA fragmentation, genomic template stability and cartilage joint histology of OA-rats. AuNPs were more effective than DIA and the combined treatment was more effective than the single treatment. It could be concluded that AuNPs are promising for the treatment of OA alone or in combination with DIA.

The Efficacy of Posttreatment with Synthetic C-Reactive Protein in Murine Bacterial Peritonitis via Activation of FcγRI-Expressing Kupffer Cells

Pretreatment with synthetic C-reactive protein (CRP), a functional CRP peptide, has the potential to augment macrophage phagocytosis by bacterial challenge. However, the posttreatment is clinically ideal. We investigated the efficacy of posttreatment with synthetic CRP on murine cecal ligation and puncture (CLP), focusing on liver macrophages. Mice received CLP, and 1 h later, synthetic CRP or saline was intraperitoneally administered. Posttreatment with synthetic CRP increased the murine survival after CLP. It reduced viable bacterial counts in the liver 24 h after CLP with an increase in the number of Kupffer cells but not monocyte-derived liver macrophages. Posttreatment with synthetic CRP increased the phagolytic activity of Kupffer cells against Escherichia coli (E. coli) as well as capsulated Klebsiella pneumoniae at 3 h after CLP. Synthetic CRP therapy augmented TNF production by E. coli-phagocytosing Kupffer cells, resulting in an increase in tissue TNF levels in the liver at 24 h. Kupffer cells substantially expressed FcγRI, which is a ligand of CRP, and their FcγRI expression was further increased after CLP. In contrast, synthetic CRP therapy affected neither the phagocytic function of monocyte-derived liver macrophages (showing a weak FcγRI expression) nor their TNF production. Depletion of Kupffer cells in mice inhibited these beneficial effects of synthetic CRP in CLP mice. Conclusion: Posttreatment with synthetic CRP effectively improves murine bacterial peritonitis via the activation of phagocytosis of FcγRI-expressing Kupffer cells.

Validation of the conventional Glasgow Prognostic Score and development of the improved Glasgow Prognostic Score in patients with stage 0-III colorectal cancer after curative resection

AIM

Many inflammation-nutrition scores, including the Glasgow Prognostic Score (GPS), have been reported as prognostic biomarkers in patients with colorectal cancer (CRC). We aimed to examine the predictive ability of the GPS and to improve the GPS.

METHODS

We included a total of 438 patients with stage 0-III CRC who underwent curative surgery from 2010 to 2013. They were divided into a training set comprising 221 patients and a validation set comprising 227 patients, according to the date of surgery. In the training set, the GPS was verified using a Cox regression model, and cut-off values for C-reactive protein (CRP) and albumin for relapse-free survival (RFS) were calculated using receiver operating characteristics (ROC) curves. The improved GPS (iGPS) was developed with additional optimal cut-off values. We also compared the iGPS with the conventional GPS in the validation set.

RESULTS

The high GPS (GPS: 1-2) was correlated with RFS and overall survival (OS) in the training set. Cut-off values of CRP and albumin for RFS were 1.6 and 3.9, and we modified the GPS accordingly, adding the cut-off values of 2 and 3.9 to CRP and albumin, respectively. In the validation set, a high iGPS was an independent prognostic factor for RFS (hazard ratio [HR]: 2.273; 95% confidence interval [CI]: 1.212-4.364; P = .011), although the conventional GPS was not.

CONCLUSION

The iGPS was a more accurate prognostic predictor for patients with stage 0-III CRC.

Exosomes from Placenta-Derived Mesenchymal Stem Cells Are Involved in Liver Regeneration in Hepatic Failure Induced by Bile Duct Ligation

Although the liver has a regenerative capacity, hepatic failure is a severe and irreversible chronic disease. Placenta-derived mesenchymal stem cells (PD-MSCs) have distinctive features, such as recycling of the placenta waste after birth, ease of accessibility, abundant cell numbers, and strong immunosuppressive properties. Previously, we reported that PD-MSCs can regenerate the liver in hepatic failure through antifibrotic and autophagic mechanisms. Many reports have investigated whether exosomes, which are formed by the budding of vesicular bodies and are emitted into the blood, from stem cells have therapeutic potential in various diseases. C-reactive protein (CRP) is produced in hepatocytes and secreted via vessels. Therefore, the objectives of this study were to compare the expression of CRP in exosomes of a hepatic failure rat model (bile duct ligation, BDL) and to evaluate the therapeutic effect by their correlation between CRP and angiogenesis depending on PD-MSC transplantation. The exosomes were analyzed in a BDL rat model with transplantation of PD-MSCs through LC-MS analysis and precipitation solution. The exosomes, CRP, and factors related to these molecules were evaluated and quantified in exosomes as well as investigated by real-time PCR, Western blot, and immunofluorescence (IF) in vivo and in vitro. CRP was present in exosomes from serum of a rat model and increased by PD-MSC transplantation. In the exosomes, CRP upregulated the factors related to the Wnt signaling pathway and angiogenesis in the BDL rat liver-transplanted PD-MSCs. Also, CRP regulated the Wnt pathway and vascularization in rat hepatocytes by interacting with endothelial cells. Therefore, our findings indicate that CRP in exosomes excreted by PD-MSCs functions in angiogenesis via the Wnt signaling pathway.

Reduction of inflammation in chronic pancreatitis using a soy bread intervention: A feasibility study

INTRODUCTION

Chronic pancreatitis is a chronic inflammatory disease, which progresses to fibrosis. Currently there are no interventions to delay or stop the progression to irreversible organ damage. In this study, we assessed the tolerability and feasibility of administering soy bread to reduce circulating inflammatory mediators.

METHODS

Subjects with chronic pancreatitis diagnosed using the American Pancreatic Association diagnostic guidelines were enrolled. During the dose escalation (DE) phase, subjects received one week of soy bread based using a 3 + 3 dose-escalation design, which was then followed by a maximally tolerated dose (MTD) phase with four weeks of intervention. Dose-limiting toxicities (DLTs) were monitored. Plasma cytokine levels were measured using a Meso Scale Discovery multiplex assay kit. Isoflavonoid excretion in 24-h urine collection was used to measure soy bread compliance.

RESULTS

Nine subjects completed the DE phase, and one subject completed the MTD phase without any DLTs at a maximum dosage of three slices (99 mg of isoflavones) per day. Reported compliance to soy bread intervention was 98%, and this was confirmed with urinary isoflavones and their metabolites detected in all subjects. There was a significant decline in the TNF-α level during the DE phase (2.667 vs 2.382 pg/mL, p = 0.039); other levels were similar.

CONCLUSIONS

In this feasibility study, there was excellent compliance with a short-term intervention using soy bread in chronic pancreatitis. Reduction was seen in at least one pro-inflammatory cytokine with short-term intervention. Larger cohorts and longer interventions with soy are warranted to assess the efficacy of reducing pro-inflammatory mediators of disease.

The Cross-Talk Between Gut Microbiota and Lungs in Common Lung Diseases

Emerging findings indicate there is a vital cross-talk between gut microbiota and the lungs, which is known as gut-lung axis. The gut disturbances in lung diseases including allergy, asthma, chronic obstructive pulmonary disease, cystic fibrosis and lung cancer were observed by extensive studies. Investigating how gut microbiota impact other distant organs is of great interest in recent years. Although it has not been fully understood whether the disturbance is the cause or effect of lung diseases, alterations in the gut microbial species and metabolites have been linked to changes in immune responses and inflammation as well as the disease development in the lungs. In this article, we systemically review the role and mechanisms underlying the changes in the constituent of gut microbiota and metabolites in lung diseases. In particular, the roles of gut-lung axis in mediating immune responses and reshaping inflammation are highlighted. Furthermore, we discuss the potential of strategies to manipulate the gut microbiota and metabolites as the therapeutic approach for lung diseases.

C-Reactive Protein Promotes Inflammation through FcγR-Induced Glycolytic Reprogramming of Human Macrophages

C-reactive protein (CRP) is an acute-phase protein produced in high quantities by the liver in response to infection and during chronic inflammatory disorders. Although CRP is known to facilitate the clearance of cell debris and bacteria by phagocytic cells, the role of CRP in additional immunological functions is less clear. This study shows that complexed CRP (phosphocholine [PC]:CRP) (formed by binding of CRP to PC moieties), but not soluble CRP, synergized with specific TLRs to posttranscriptionally amplify TNF, IL-1β, and IL-23 production by human inflammatory macrophages. We identified FcγRI and IIa as the main receptors responsible for initiating PC:CRP-induced inflammation. In addition, we identified the underlying mechanism, which depended on signaling through kinases Syk, PI3K, and AKT2, as well as glycolytic reprogramming. These data indicate that in humans, CRP is not only a marker but also a driver of inflammation by human macrophages. Therefore, although providing host defense against bacteria, PC:CRP-induced inflammation may also exacerbate pathology in the context of disorders such as atherosclerosis.

Pioglitazone improves phagocytic activity of liver recruited macrophages in elderly mice possibly by promoting glucose catabolism

Recent studies have revealed that the immunological function of leukocytes is dependent on their cellular metabolism, and some researchers have advocated the beneficial effects of pioglitazone against sepsis in young mice, although bacterial infections are more prevalent in elderly hosts. Here, we investigated pioglitazone’s preventative effect against sepsis induced by intravenous injection of a lethal dose of Escherichia coli in elderly mice (50–60 wk old) and examined its immunological and metabolic effects on liver leukocytes. Pioglitazone improved bacterial elimination in the peripheral blood, lowered serum pro-inflammatory cytokines (TNF-α, IL-12, IFN-γ), and prevented septic death. It also enhanced bacterial elimination in the liver, by increasing the phagocytic and bactericidal activities of liver F4/80+CD11b+ recruited macrophages (Mφ), their CD206 expression and reactive oxygen species production. Quantitative PCR revealed that pioglitazone treatment enhanced gene expression of rate-limiting enzymes for glycolysis in hepatic CD11b+ cells (including neutrophils and recruited Mφ), and their improved phagocytic and bactericidal activities were abolished by glycolysis inhibiting reagents. These findings present the possibility that pioglitazone strengthens the phagocytic and bactericidal activities of liver recruited Mφ and that these immunological activities are closely associated with their glucose catabolism.

High-throughput proteomic profiling of the fish liver following bacterial infection

Background

High-throughput proteomics was used to determine the role of the fish liver in defense responses to bacterial infection. This was done using a rainbow trout (Oncorhynchus mykiss) model following infection with Aeromonas salmonicida, the causative agent of furunculosis. The vertebrate liver has multifaceted functions in innate immunity, metabolism, and growth; we hypothesize this tissue serves a dual role in supporting host defense in parallel to metabolic adjustments that promote effective immune function. While past studies have reported mRNA responses to A. salmonicida in salmonids, the impact of bacterial infection on the liver proteome remains uncharacterized in fish.

Results

Rainbow trout were injected with A. salmonicida or PBS (control) and liver extracted 48 h later for analysis on a hybrid quadrupole-Orbitrap mass spectrometer. A label-free method was used for protein abundance profiling, which revealed a strong innate immune response along with evidence to support parallel rewiring of metabolic and growth systems. 3076 proteins were initially identified against all proteins (n = 71,293 RefSeq proteins) annotated in a single high-quality rainbow trout reference genome, of which 2433 were maintained for analysis post-quality filtering. Among the 2433 proteins, 109 showed significant differential abundance following A. salmonicida challenge, including many upregulated complement system and acute phase response proteins, in addition to molecules with putative functions that may support metabolic re-adjustments. We also identified novel expansions in the complement system due to gene and whole genome duplication events in salmonid evolutionary history, including eight C3 proteins showing differential changes in abundance.

Conclusions

This study provides the first high-throughput proteomic examination of the fish liver in response to bacterial challenge, revealing novel markers for the host defense response, and evidence of metabolic remodeling in conjunction with activation of innate immunity.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5092-0) contains supplementary material, which is available to authorized users.

Role of C-Reactive Protein at Sites of Inflammation and Infection

C-reactive protein (CRP) is an acute inflammatory protein that increases up to 1,000-fold at sites of infection or inflammation. CRP is produced as a homopentameric protein, termed native CRP (nCRP), which can irreversibly dissociate at sites of inflammation and infection into five separate monomers, termed monomeric CRP (mCRP). CRP is synthesized primarily in liver hepatocytes but also by smooth muscle cells, macrophages, endothelial cells, lymphocytes, and adipocytes. Evidence suggests that estrogen in the form of hormone replacement therapy influences CRP levels in the elderly. Having been traditionally utilized as a marker of infection and cardiovascular events, there is now growing evidence that CRP plays important roles in inflammatory processes and host responses to infection including the complement pathway, apoptosis, phagocytosis, nitric oxide (NO) release, and the production of cytokines, particularly interleukin-6 and tumor necrosis factor-α. Unlike more recent publications, the findings of early work on CRP can seem somewhat unclear and at times conflicting since it was often not specified which particular CRP isoform was measured or utilized in experiments and whether responses attributed to nCRP were in fact possibly due to dissociation into mCRP or lipopolysaccharide contamination. In addition, since antibodies for mCRP are not commercially available, few laboratories are able to conduct studies investigating the mCRP isoform. Despite these issues and the fact that most CRP research to date has focused on vascular disorders, there is mounting evidence that CRP isoforms have distinct biological properties, with nCRP often exhibiting more anti-inflammatory activities compared to mCRP. The nCRP isoform activates the classical complement pathway, induces phagocytosis, and promotes apoptosis. On the other hand, mCRP promotes the chemotaxis and recruitment of circulating leukocytes to areas of inflammation and can delay apoptosis. The nCRP and mCRP isoforms work in opposing directions to inhibit and induce NO production, respectively. In terms of pro-inflammatory cytokine production, mCRP increases interleukin-8 and monocyte chemoattractant protein-1 production, whereas nCRP has no detectable effect on their levels. Further studies are needed to expand on these emerging findings and to fully characterize the differential roles that each CRP isoform plays at sites of local inflammation and infection.

Kupffer cell-derived TNF-α promotes hepatocytes to produce CXCL1 and mobilize neutrophils in response to necrotic cells

The damage-associated molecular pattern molecules (DAMPs) released by necrotic cells can trigger inflammatory response, which will facilitate the clearance of these dead cells. Neutrophil mobilization is a very important step for the dead cell clearance, however the detailed mechanisms for DAMPs induce neutrophil mobilization remains largely elusive. In this study, by using a necrotic cell-induced neutrophil mobilization mice model, we found that both neutrophil number and percentage rapidly (as early as 30 min) increased with necrotic cells but not live cell treatment. CXCL1 was rapidly increased in the serum and was responsible for the neutrophil mobilization when treated with necrotic cells. We further demonstrated that the hepatocytes in the liver were the main source of CXCL1 production in response to necrotic cells challenge. However, the hepatocytes did not express CXCL1 when incubating with necrotic cells alone. When Kupffer cells were ablated, the increased CXCL1 levels as well as neutrophil mobilization were abolished with necrotic cells challenge. Moreover, we clarified Kupffer cells-derived TNF-α activates the NF-κB pathway in hepatocytes and promote hepatocytes to express CXCL1. In summary, we showed that the liver is the main source for necrotic cell-induced CXCL1 production and neutrophil mobilization. Kupffer cells in the liver sense DAMPs and release TNF-α to activate the NF-κB pathway in hepatocytes. The interaction between Kupffer cells and hepatocytes is critical for CXCL1 production.

Immune-mediated liver injury of the cancer therapeutic antibody catumaxomab targeting EpCAM, CD3 and Fcγ receptors

The immunotherapeutic catumaxomab targets EpCAM positive cancers and is approved for the treatment of peritoneal carcinomatosis. To assess the safety of intravenous applications a phase 1 clinical trial was initiated. Treatment of EpCAM positive tumor patients with catumaxomab caused dose dependent hepatitis as evidenced by significant elevations in serum alanine- and aspartate aminotransferases, bilirubin, γGT and induction of the acute phase C-reactive protein (CRP) and the cytokines IL6 and IL8. The first patient receiving 10μg catumaxomab experienced fatal acute liver failure which led to the termination of the study. Immmunopathology revealed catumaxomab to bind via its Fc-fragment to FcγR-positive Kupffer cells to stimulate CRP, chemokine and cytokine release. The observed CD3+T-cell margination at activated hepatic macrophages exacerbated T-cell mediated cytotoxicity. Strikingly, the combined Kupffer/T-cell responses against liver cells did not require hepatocytes to be EpCAM-positive. Catumaxomab's off-target activity involved T-cell mediated lysis of the granzyme B cell death pathway and the molecular interaction of hepatic sinusoidal macrophages with T-cells induced cytolytic hepatitis. Although the bile ducts were surrounded by densely packed lymphocytes these rarely infiltrated the ducts to suggest an intrahepatic cholestasis as the cause of hyperbilirubinaemia. Lastly, evidence for the programming of memory T-cells was observed with one patient that succumbed to his cancer six weeks after the last catumaxomab infusion. In conclusion, our study exemplifies off-target hepatotoxicity with molecularly targeted therapy and highlights the complexities in the clinical development of immunotherapeutic antibodies.

Liver immunotolerance and hepatocellular carcinoma: Patho-physiological mechanisms and therapeutic perspectives

At the moment of the diagnosis of hepatocellular carcinoma (HCC), 70% of patients have only access to palliative treatments, with very few therapeutic options. Liver immunology is very specific, and liver immunotolerance is particularly developed because of the constant and massive influx of antigens. Deregulation of hepatic immunotolerance is implicated in chronic liver diseases development and particularly in liver carcinogenesis. For these reasons, HCC may be an excellent candidate for anticancer immunotherapies such as immune checkpoint inhibitors targeting CTLA-4 and PD-L1/PD-1. Nonetheless, because of the specific immune environment of the liver and the frequent association of HCC with hepatocellular insufficiency, the safety and the efficacy of these new treatments have to be properly studied in this situation. Thus, multiple phase II and III studies are in progress studying immune checkpoint inhibitor monotherapies, combination of different immunotherapies or local strategies such as transarterial chemoembolization combined with immune checkpoint inhibitors. Currently, only the final results of the tremelimumab phase II and the Nivolumab phase I/II study (CheckMate-040) are available. The latter is promising but need to be confirmed by the ongoing phase III studies to confirm the place of immunotherapy in the treatment of HCC. With many new molecular targets and therapeutic combination, immunotherapy represents a new hope in treating HCC patients although serious evaluation is still needed to confirm its interest.

In vivo Lipopolysaccharide Tolerance Recruits CD11b+ Macrophages to the Liver with Enhanced Bactericidal Activity and Low Tumor Necrosis Factor-Releasing Capability, Resulting in Drastic Resistance to Lethal Septicemia

OBJECTIVES

In vivo lipopolysaccharide (LPS) tolerance on bacterial infection was investigated, focusing on liver macrophages.

METHODS

LPS tolerance was induced by intraperitoneal injections with 5 μg/kg of LPS for 3 consecutive days, and then mice were intravenously infected with Escherichia coli.

RESULTS

All LPS-primed mice survived lethal bacterial infection. Drastic enhancement of bactericidal activity of liver macrophages strongly contributed to bacterial clearance. Although LPS-primed mice produced substantial amounts of tumor necrosis factor (TNF) inside the liver, TNF efflux into the systemic circulation was markedly suppressed. These mice showed a dramatic increase in CD11b+ monocyte- derived macrophages in the liver. The CD11b+ macrophages that increased in LPS-primed mice were those with strong phagocytic/bactericidal activity and an upregulated expression of Fcγ receptor I, but the subfraction with a potent TNF-producing capacity and poor phagocytic activity diminished. The adoptive transfer of CD11b+ macrophages from LPS-primed mice to control mice increased survival after bacterial infection and reduced the elevation of plasma TNF. LPS priming did not affect the CD68+ resident Kupffer cells, and CD68+ Kupffer cell-depleted mice still exhibited LPS tolerance with strong resistance to bacteremia.

CONCLUSIONS

LPS tolerance recruits CD11b+ macrophages to the liver with enhanced bactericidal activity, which plays a central role in resistance to lethal bacteremia.

An Agent-Based Model of a Hepatic Inflammatory Response to Salmonella: A Computational Study under a Large Set of Experimental Data

We present an agent-based model (ABM) to simulate a hepatic inflammatory response (HIR) in a mouse infected by Salmonella that sometimes progressed to problematic proportions, known as "sepsis". Based on over 200 published studies, this ABM describes interactions among 21 cells or cytokines and incorporates 226 experimental data sets and/or data estimates from those reports to simulate a mouse HIR in silico. Our simulated results reproduced dynamic patterns of HIR reported in the literature. As shown in vivo, our model also demonstrated that sepsis was highly related to the initial Salmonella dose and the presence of components of the adaptive immune system. We determined that high mobility group box-1, C-reactive protein, and the interleukin-10: tumor necrosis factor-α ratio, and CD4+ T cell: CD8+ T cell ratio, all recognized as biomarkers during HIR, significantly correlated with outcomes of HIR. During therapy-directed silico simulations, our results demonstrated that anti-agent intervention impacted the survival rates of septic individuals in a time-dependent manner. By specifying the infected species, source of infection, and site of infection, this ABM enabled us to reproduce the kinetics of several essential indicators during a HIR, observe distinct dynamic patterns that are manifested during HIR, and allowed us to test proposed therapy-directed treatments. Although limitation still exists, this ABM is a step forward because it links underlying biological processes to computational simulation and was validated through a series of comparisons between the simulated results and experimental studies.

The Gut-Liver-Lung Axis. Modulation of the Innate Immune Response and Its Possible Role in Chronic Obstructive Pulmonary Disease

Evidence from epidemiological studies suggests that a diet high in fiber is associated with better lung function and reduced risk of chronic obstructive pulmonary disease (COPD). The mechanism for this benefit remains unknown, but, as fiber is not absorbed by the gut, this finding suggests that the gut may play an active role in pathogenic pathways underlying COPD. There is a growing awareness that aberrant activity of the innate immune system, characterized by increased neutrophil and macrophage activation, may contribute to the development or progression of COPD. Innate immunity is modulated in large part by the liver, where hepatic cells function in immune surveillance of the portal circulation, as well as providing a rich source of systemic inflammatory cytokines and immune mediators (notably, IL-6 and C-reactive protein). We believe that the beneficial effect of dietary fiber on lung function is through modulation of innate immunity and subsequent attenuation of the pulmonary response to inflammatory stimuli, most apparent in current or former smokers. We propose that the "gut-liver-lung axis" may play a modifying role in the pathogenesis of COPD. In this review, we summarize lines of evidence that include animal models, large prospective observational studies, and clinical trials, supporting the hypothesis that the gut-liver-lung axis plays an integral part in the pathogenic mechanisms underlying the pathogenesis of COPD.

Burn-Evoked Reactive Oxygen Species Immediately After Injury are Crucial to Restore the Neutrophil Function Against Postburn Infection in Mice

Although reactive oxygen species (ROS) basically play beneficial roles to maintain host homeostasis against external disturbance/stress including infection, excessive ROS generation by activated neutrophils can sometimes cause organ damage. We investigated the role of burn-induced ROS generation in the injured hosts, focusing on postburn infection. C57BL/6 mice received a 20% full-thickness burn injury. In these mice, the burn-induced ROS generation was inhibited during and immediately after injury by pretreatment with superoxide dismutase (at 1 h before and immediately before injury), or the subsequent ROS production was inhibited posttreatment with superoxide dismutase (at 1 and 2 h after injury), which could not scavenge the ROS produced immediately after injury. As expected, inhibition of ROS production during/immediately after injury reduced the burn-induced pulmonary damage at 6 h, whereas inhibition of the subsequent ROS production did not lead to any improvements. Burn injury rendered the mice susceptible to bacterial infection at 5 days after injury and impaired bactericidal activity of neutrophils. Nevertheless, inhibition of the ROS production during/immediately after injury did not improve the burn-induced susceptibility to infection or the neutrophil dysfunction. Interestingly, inhibition of the subsequent ROS production potently restored the neutrophil functions and hematopoietic function of the bone marrow myelocytes, thereby improving the postburn infection. Thus, although the inhibition of burn-evoked ROS generation is effective against burn-induced organ injury, it may be ineffective against postburn infection. Preservation of the immediate burn-evoked ROS production, but the inhibition of subsequent ROS production, may be crucial to protect against postburn infection.

Liver immunology and its role in inflammation and homeostasis

The human liver is usually perceived as a non-immunological organ engaged primarily in metabolic, nutrient storage and detoxification activities. However, we now know that the healthy liver is also a site of complex immunological activity mediated by a diverse immune cell repertoire as well as non-hematopoietic cell populations. In the non-diseased liver, metabolic and tissue remodeling functions require elements of inflammation. This inflammation, in combination with regular exposure to dietary and microbial products, creates the potential for excessive immune activation. In this complex microenvironment, the hepatic immune system tolerates harmless molecules while at the same time remaining alert to possible infectious agents, malignant cells or tissue damage. Upon appropriate immune activation to challenge by pathogens or tissue damage, mechanisms to resolve inflammation are essential to maintain liver homeostasis. Failure to clear 'dangerous' stimuli or regulate appropriately activated immune mechanisms leads to pathological inflammation and disrupted tissue homeostasis characterized by the progressive development of fibrosis, cirrhosis and eventual liver failure. Hepatic inflammatory mechanisms therefore have a spectrum of roles in the healthy adult liver; they are essential to maintain tissue and organ homeostasis and, when dysregulated, are key drivers of the liver pathology associated with chronic infection, autoimmunity and malignancy. In this review, we explore the changing perception of inflammation and inflammatory mediators in normal liver homeostasis and propose targeting of liver-specific immune regulation pathways as a therapeutic approach to treat liver disease.

Hepatocytes: a key cell type for innate immunity

Hepatocytes, the major parenchymal cells in the liver, play pivotal roles in metabolism, detoxification, and protein synthesis. Hepatocytes also activate innate immunity against invading microorganisms by secreting innate immunity proteins. These proteins include bactericidal proteins that directly kill bacteria, opsonins that assist in the phagocytosis of foreign bacteria, iron-sequestering proteins that block iron uptake by bacteria, several soluble factors that regulate lipopolysaccharide signaling, and the coagulation factor fibrinogen that activates innate immunity. In this review, we summarize the wide variety of innate immunity proteins produced by hepatocytes and discuss liver-enriched transcription factors (e.g. hepatocyte nuclear factors and CCAAT/enhancer-binding proteins), pro-inflammatory mediators (e.g. interleukin (IL)-6, IL-22, IL-1β and tumor necrosis factor-α), and downstream signaling pathways (e.g. signal transducer and activator of transcription factor 3 and nuclear factor-κB) that regulate the expression of these innate immunity proteins. We also briefly discuss the dysregulation of these innate immunity proteins in chronic liver disease, which may contribute to an increased susceptibility to bacterial infection in patients with cirrhosis.

The effect of synthetic C-reactive protein on the in vitro immune response of human PBMCs stimulated with bacterial reagents

Synthetic C-reactive protein (CRP) rescues mice from lethal endotoxin shock or bacterial infection by suppressing tumor necrosis factor (TNF-α), but in turn, enhances Kupffer cell phagocytic activity. We herein assessed the influence of CRP in human peripheral blood mononuclear cells (PBMCs). When human PBMCs were stimulated in vitro with penicillin-treated Streptococcus pyogenes, bacterial DNA motifs and lipopolysaccharide with or without synthetic CRP, CRP suppressed the production of TNF-α and IL-12, but not that of IFN-γ. This was also the case for the in vitro Shwartzman reaction induced in PBMCs. CRP also decreased high-mobility group box 1 production from macrophages, which is crucial in the later phase of endotoxin/septic shock. However, CRP upregulated the perforin expression by CD56⁺ NK cells and increased their antitumor cytotoxicity. CRP may thus be a potent immunomodulatory factor in the human immune system, suggesting its therapeutic potential for use against human septic shock.

Liver immunology

The liver is the largest organ in the body and is generally regarded by nonimmunologists as having little or no lymphoid function. However, such is far from accurate. This review highlights the importance of the liver as a lymphoid organ. Firstly, we discuss experimental data surrounding the role of liver as a lymphoid organ. The liver facilitates tolerance rather than immunoreactivity, which protects the host from antigenic overload of dietary components and drugs derived from the gut and it is instrumental to fetal immune tolerance. Loss of liver tolerance leads to autoaggressive phenomena, which if not controlled by regulatory lymphoid populations, may lead to the induction of autoimmune liver diseases. Liver-related lymphoid subpopulations also act as critical antigen-presenting cells. The study of the immunological properties of liver and delineation of the microenvironment of the intrahepatic milieu in normal and diseased livers provides a platform to understand the hierarchy of a series of detrimental events that lead to immune-mediated destruction of the liver and the rejection of liver allografts. The majority of emphasis within this review will be on the normal mononuclear cell composition of the liver. However, within this context, we will discuss selected, but not all, immune-mediated liver disease and attempt to place these data in the context of human autoimmunity.

Serum acute phase reactants hallmark healthy individuals at risk for acetaminophen-induced liver injury

Background

Acetaminophen (APAP) is a commonly used analgesic. However, its use is associated with drug-induced liver injury (DILI). It is a prominent cause of acute liver failure, with APAP hepatotoxicity far exceeding other causes of acute liver failure in the United States. In order to improve its safe use this study aimed to identify individuals at risk for DILI prior to drug treatment by searching for non-genetic serum markers in healthy subjects susceptible to APAP-induced liver injury (AILI).

Methods

Healthy volunteers (n = 36) received either placebo or acetaminophen at the maximum daily dose of 4 g for 7 days. Blood samples were taken prior to and after APAP treatment. Serum proteomic profiling was done by 2D SDS-PAGE and matrix-assisted laser desorption/ionization-time of flight-mass spectrometry. Additionally, the proteins C-reactive protein, haptoglobin and hemopexin were studied by quantitative immunoassays.

Results

One-third of study subjects presented more than four-fold increased alanine transaminase activity to evidence liver injury, while serum proteomics informed on 20 proteins as significantly regulated. These function primarily in acute phase and immune response. Pre-treatment associations included C-reactive protein, haptoglobin isoforms and retinol binding protein being up to six-fold higher in AILI susceptible individuals, whereas alpha1-antitrypsin, serum amyloid A, kininogen and transtyretin were regulated by nearly five-fold in AILI responders. When compared with published findings for steatohepatitis and cases of hepatocellular, cholestatic and mixed DILI, 10 proteins were identified as uniquely associated with risk for AILI, including plasminogen. Notably, this zymogen facilitates macrophage chemotactic migration and inflammatory response as reported for plasminogen-deficient mice shown to be resistant to APAP hepatotoxicity. Finally, analysis of a publicly available database of gene expression profiles of cultures of human hepatocytes treated with drugs labeled as no- (n = 8), low- (n = 45) or most-DILI-concern (n = 39) confirmed regulation of the identified biomarkers to demonstrate utility in predicting risk for liver injury.

Conclusions

The significant regulation of acute phase reactants points to an important link between AILI and the immune system. Monitoring of serum acute phase reactants prior to drug treatment may contribute to prevention and management of AILI, and may also be of utility for other drugs with known liver liabilities.

Glucocorticoid receptor-dependent immunomodulatory effect of ursodeoxycholic acid on liver lymphocytes in mice

Although ursodeoxycholic acid (UDCA) has long been used for patients with chronic cholestatic liver diseases, particularly primary biliary cirrhosis, it may modulate the host immune response. This study investigated the effect of UDCA feeding on experimental hepatitis, endotoxin shock, and bacterial infection in mice. C57BL/6 mice were fed a diet supplemented with or without 0.3% (wt/vol) UDCA for 4 wk. UDCA improved hepatocyte injury and survival in concanavalin-A (Con-A)-induced hepatitis by suppressing IFN-γ production by liver mononuclear cells (MNC), especially NK and NKT cells. UDCA also increased survival after lipopolysaccharide (LPS)-challenge; however, it increased mortality of mice following Escherichia coli infection due to the worsening of infection. UDCA-fed mice showed suppressed serum IL-18 levels and production of IL-18 from liver Kupffer cells, which together with IL-12 potently induce IFN-γ production. However, unlike normal mice, exogenous IL-18 pretreatment did not increase the serum IFN-γ levels after E. coli, LPS, or Con-A challenge in the UDCA-fed mice. Interestingly, however, glucocorticoid receptor (GR) expression was significantly upregulated in the liver MNC of the UDCA-fed mice but not in their whole liver tissue homogenates. Silencing GR in the liver MNC abrogated the suppressive effect of UDCA on LPS- or Con-A-induced IFN-γ production. Furthermore, RU486, a GR antagonist, restored the serum IFN-γ level in UDCA-fed mice after E. coli, LPS, or Con-A challenge. Taken together, these results suggest that IFN-γ-reducing immunomodulatory property of UDCA is mediated by elevated GR in the liver lymphocytes in an IL-12/18-independent manner.

Distinct development and functions of resident and recruited liver Kupffer cells/macrophages

Although mouse liver F4/80(+) Kupffer cells consist of cytokine-producing CD11b(+) cells and phagocytic CD68(+) cells, an undefined CD11b(-) CD68(-) subset (30%) also exists. We herein demonstrate a more fundamental classification by adding CD32 (FcγRII), which covers most liver F4/80(+) cells and the distinct functions of them. Among the F4/80(+) cells, 50%, 40%, and 30% of cells were CD32(+), CD68(+), and CD11b(+), respectively, and one-half of the CD68(+) cells coexpressed CD32. CD68(+) and CD32(+) cells, but not CD11b(+) cells, expressed a phagocytosis-related CRIg. Gy (6) irradiation depleted liver CD11b(+) cells and those in the spleen, bone marrow, and peripheral blood but not liver CD32/CD68(+) cells. Transfer of bone marrow cells into the irradiated mice reconstituted liver CD11b(+) cells. Conversely, clodronate pretreatment depleted only liver CD32/CD68(+) cells but not liver CD11b(+) cells and peripheral blood or spleen CD11b(+) monocytes/macrophages. Moreover, the CD32(+) cells might be precursors of CD68(+) cells, as a large proportion of CD32(+) cells expressed the c-kit (CD117), and CD34 and CD32(+) cells acquired CD68 immediately after bacteria administration. CD32/CD68(+) cells, but not CD11b(+) cells, expressed resident macrophage-specific MerTK and CD64 (FcγRI). Challenge with Staphylococcus aureus or liver metastatic EL-4 tumor cells indicated that the CD68(+) subset is engaged in systemic bactericidal activity, whereas the CD11b(+) subset is pivotal for liver antitumor immunity. Human liver CD14(+) Kupffer cells could also be classified into three similar subsets. These results suggest that liver CD68(+) Kupffer cells and CD11b(+) Kupffer cells/macrophages are developmentally and functionally distinct subsets.

Activation of CD11b+ Kupffer cells/macrophages as a common cause for exacerbation of TNF/Fas-ligand-dependent hepatitis in hypercholesterolemic mice

We have reported that the mouse hepatic injury induced by either α-galactosylceramide (α-GalCer) or bacterial DNA motifs (CpG-ODN) is mediated by the TNF/NKT cell/Fas-ligand (FasL) pathway. In addition, F4/80(+) Kupffer cells can be subclassified into CD68(+) subset with a phagocytosing capacity and CD11b(+) subset with a TNF-producing capacity. CD11b(+) subset increase if mice are fed high-fat and cholesterol diet (HFCD). The present study examined how a HFCD affects the function of NKT cells and F4/80(+) CD11b(+) subset and these hepatitis models. After the C57BL/6 mice received a HFCD, high-cholesterol diet (HCD), high-fat diet (HFD) and control diet (CD) for four weeks, the HFCD mice increased surface CD1d and intracellular TLR-9 expression by the CD11b(+) population compared to CD mice. Hepatic injury induced either by α-GalCer or CpG-ODN was more severe in HCD and HFCD mice compared to CD mice, which was in proportion to the serum TNF levels. In addition, liver cholesterol levels but not serum cholesterol levels nor liver triglyceride levels were involved in the aggravation of hepatitis. The FasL expression of NKT cells induced by both reagents was upregulated in HFCD mice. Furthermore, the liver mononuclear cells and purified F4/80(+) CD11b(+) subset from HFCD mice stimulated with either reagent in vitro produced a larger amount of TNF than did those from CD mice. Intracellular TNF production in F4/80(+) CD11b(+) cells was confirmed. The increased number of F4/80(+) CD11b(+) Kupffer cells/macrophages by HFCD and their enhanced TNF production thus play a pivotal role in TNF/NKT cell/FasL dependent hepatic injury.

The immunologic outcome of enhanced function of mouse liver lymphocytes and Kupffer cells by high-fat and high-cholesterol diet

Dietary lipids/cholesterol may modulate liver immune function. We have recently found that mouse F4/80 Kupffer cells are classified into phagocytic CD68 Kupffer cells and cytokine-producing CD11b Kupffer cells. We here investigate how a high-fat and/or high-cholesterol diet affects innate immune liver mononuclear cells. For 4 weeks, C57BL/6 mice were fed a high-fat and high-cholesterol diet (HFCD), a high-cholesterol diet (HCD), a high-fat diet (HFD), or a control diet (CD). High-fat and high-cholesterol diet and HCD increased liver cholesterol levels; serum cholesterol levels increased in HFCD and HFD mice but not in HCD mice. The increased proportion of natural killer (NK) cells, downregulated NK1.1 expression of natural killer T cells, and enhanced CD69 and IL-12 receptor β mRNA expression of liver lymphocytes indicate the activation of them by HFCD. IL-12 production from Kupffer cells and interferon γ production from NK/natural killer T cells activated by LPS and/or IL-12 both increased. IL-12 pretreatment more effectively improved the survival of HFCD mice relative to the survival of CD mice upon injections of liver metastatic EL-4 cells. In contrast, HFCD mouse survival decreased after LPS injection and generalized Shwartzman reaction. Consistently in HFCD mice, Toll-like receptor 4 mRNA expression of whole Kupffer cells was upregulated, and CD11b Kupffer cells proportionally increased. Although the proportion of CD68 Kupffer cells decreased in HFCD mice, phagocytic activity of them was enhanced. Mice fed with HCD rather than those fed with HFD showed features closer to HFCD mice. Thus, enhanced function of mouse liver mononuclear cells is likely dependent on the liver cholesterol level, rather than the liver triglyceride level.

High susceptibility to lipopolysaccharide-induced lethal shock in encephalomyocarditis virus-infected mice

Secondary bacterial infection in humans is one of the pathological conditions requiring clinical attention. In this study, we examined the effect of lipopolysaccharide (LPS) on encephalomyocarditis virus (EMCV) infected mice. All mice inoculated with EMCV at 5 days before LPS challenge died within 24 h. LPS-induced TNF-α mRNA expression was significantly increased in the brain and heart at 5 days after EMCV infection. CD11b⁺/TLR4⁺ cell population in the heart was remarkably elevated at 5 days after EMCV infection, and sorted CD11b⁺ cells at 5 days after EMCV infection produced a large amount of TNF-α on LPS stimulation in vivo and in vitro. In conclusion, we found that the infiltration of CD11b⁺ cells into infected organs is involved in the subsequent LPS-induced lethal shock in viral encephalomyocarditis. This new experimental model can help define the mechanism by which secondary bacterial infection causes a lethal shock in viral encephalomyocarditis.

Antitumor immunity produced by the liver Kupffer cells, NK cells, NKT cells, and CD8 CD122 T cells

Mouse and human livers contain innate immune leukocytes, NK cells, NKT cells, and macrophage-lineage Kupffer cells. Various bacterial components, including Toll-like receptor (TLR) ligands and an NKT cell ligand (α-galactocylceramide), activate liver Kupffer cells, which produce IL-1, IL-6, IL-12, and TNF. IL-12 activates hepatic NK cells and NKT cells to produce IFN-γ, which further activates hepatic T cells, in turn activating phagocytosis and cytokine production by Kupffer cells in a positive feedback loop. These immunological events are essentially evoked to protect the host from bacterial and viral infections; however, these events also contribute to antitumor and antimetastatic immunity in the liver by activated liver NK cells and NKT cells. Bystander CD8⁺CD122⁺ T cells, and tumor-specific memory CD8⁺T cells, are also induced in the liver by α-galactocylceramide. Furthermore, adoptive transfer experiments have revealed that activated liver lymphocytes may migrate to other organs to inhibit tumor growth, such as the lungs and kidneys. The immunological mechanism underlying the development of hepatocellular carcinoma in cirrhotic livers in hepatitis C patients and liver innate immunity as a double-edged sword (hepatocyte injury/regeneration, septic shock, autoimmune disease, etc.) are also discussed.

Enhancement of neutrophil function by interleukin-18 therapy protects burn-injured mice from methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) infection is a grave concern in burn-injured patients. We investigated the efficacy of interleukin-18 (IL-18) treatment in postburn MRSA infection. Alternate-day injections of IL-18 into burn-injured C57BL/6 mice significantly increased their survival after MRSA infection and after methicillin-sensitive S. aureus infection. Although IL-18 treatment of burn-injured mice augmented natural IgM production before MRSA infection and gamma interferon (IFN-γ) production after MRSA infection, neither IgM nor IFN-γ significantly contributed to the improvement in mouse survival. IL-18 treatment increased/restored the serum tumor necrosis factor (TNF), IL-17, IL-23, granulocyte colony-stimulating factor (G-CSF), and macrophage inflammatory protein (MIP-2) levels, as well as the neutrophil count, after MRSA infection of burn-injured mice; it also improved impaired neutrophil functions, phagocytic activity, production of reactive oxygen species, and MRSA-killing activity. However, IL-18 treatment was ineffective against MRSA infection in both burn- and sham-injured neutropenic mice. Enhancement of neutrophil functions by IL-18 was also observed in vitro. Furthermore, when neutrophils from IL-18-treated burn-injured mice were adoptively transferred into nontreated burn-injured mice 2 days after MRSA challenge, survival of the recipient mice increased. NOD-SCID mice that have functionally intact neutrophils and macrophages (but not T, B, or NK cells) were substantially resistant to MRSA infection. IL-18 treatment increased the survival of NOD-SCID mice after burn injury and MRSA infection. An adoptive transfer of neutrophils using NOD-SCID mice also showed a beneficial effect of IL-18-activated neutrophils, similar to that seen in C57BL/6 mice. Thus, although neutrophil functions were impaired in burn-injured mice, IL-18 therapy markedly activated neutrophil functions, thereby increasing survival from postburn MRSA infection.

Antigen-presenting cell function in the tolerogenic liver environment

The demands that are imposed on the liver as a result of its function as a metabolic organ that extracts nutrients and clears gut-derived microbial products from the blood are met by a unique microanatomical and immunological environment. The inherent tolerogenicity of the liver and its role in the regulation of innate and adaptive immunity are mediated by parenchymal and non-parenchymal antigen-presenting cells (APCs), cell-autonomous molecular pathways and locally produced factors. Here, we review the central role of liver APCs in the regulation of hepatic immune function and also consider how recent insights may be applied in strategies to target liver tolerance for disease therapy.

Characterization of two F4/80-positive Kupffer cell subsets by their function and phenotype in mice

BACKGROUND & AIMS

Liver Kupffer cells have been suggested to be heterogeneous macrophage lineage cells. We explored this possibility by classifying the mouse Kupffer cells into subpopulations and characterizing them by their phenotype and function.

METHODS

Liver mononuclear cells (MNCs) from C57BL/6 mice were isolated and their phenotypes and functions were analyzed. The effects of clodronate liposomes and gadolinium chloride (GdCl(3)) on Kupffer cells were also investigated.

RESULTS

Approximately 25% of liver MNCs were F4/80(+) Kupffer cells. Of these, 46% were CD11b(-)CD68(+), 22% were CD11b(+)CD68(-), and 6% were CD11b(+)CD68(+). CD68(+) cells showed potent phagocytic activity and reactive oxygen species (ROS) production capacity after lipopolysaccharide (LPS) stimulation, whereas CD11b(+) cells did not. CD11b(+) cells showed a strong capacity for the production of cytokines (TNF and IL-12), which was much less prominent in CD68(+) cells. At 24h after LPS or Escherichia coli injection into mice, the proportions of CD11b(+)CD68(-) and CD11b(+)CD68(+) cells increased but that of CD11b(-)CD68(+) cells decreased. The increase in CD11b(+)CD68(+) cells appeared to be derived from the CD11b(+)CD68(-) subset. Although the CD11b(+) cells augmented phagocytic activity after LPS injection, they did not increase ROS production, suggesting their weak lytic activity. Injection of clodronate or GdCl(3) into mice depleted the CD68(+) cells but increased CD11b(+) cells proportionally because CD68(+) cells may phagocytose these toxic reagents and undergo apoptosis. GdCl(3)-treated mice also consistently increased serum TNF after LPS challenge.

CONCLUSIONS

Two F4/80(+) Kupffer cell subsets may exist, a CD68(+) subset with phagocytic activity and a CD11b(+) subset with cytokine-producing capacity.

Immunosuppression in the livers of mice with obstructive jaundice participates in their susceptibility to bacterial infection and tumor metastasis

Although patients with obstructive jaundice are susceptible to bacterial infections and cancers, the mechanisms remain to be elucidated. In the present study, liver mononuclear cells (MNCs) of bile duct-ligated (BDL) mice were immunologically assessed. Liver natural killer T cells were greatly decreased within 24 h after BDL. Upon injection of Escherichia coli (E. coli; 10 colony-forming units) at 7 days after the procedure, all BDL mice had died, but no sham mice died. Consistently, an overgrowth of E. coli was seen in the livers of BDL mice. Although the serum IL-12 and IL-18 levels after E. coli challenge in BDL mice were higher than those in sham mice, the IFN-gamma level was greatly suppressed. However, exogenous IFN-gamma injection significantly increased BDL mouse survival after E. coli challenge. Furthermore, liver MNC of BDL mice exhibited a lower cytotoxic activity against tumors, and BDL mice intravenously injected with liver metastatic EL-4 cells showed markedly increased EL-4 metastases. The total bile acids, as well as the bile acid fractions, increased in the sera and liver. IFN-gamma production by liver MNC from normal mice stimulated with LPS in vitro was inhibited by the addition of bile acids, whereas, conversely, the production of IL-12 and IL-18 increased. In conclusion, liver natural killer T cells were diminished in BDL mice, and the function of liver MNC (IFN-gamma production) was also impaired presumably due to increased bile acids. This may partly explain the increased susceptibility of BDL mice to bacterial infections and tumor metastasis.

Cardiac dysfunction induced by experimental myocardial infarction impairs the host defense response to bacterial infection in mice because of reduced phagocytosis of Kupffer cells

OBJECTIVE

This study was undertaken to investigate the effects of cardiac dysfunction induced by experimental myocardial infarction on the host defense response to bacterial infection and the role of Kupffer cells in mediating this response.

METHODS

Myocardial infarction was induced in C57BL/6 mice by ligation of the left anterior descending coronary artery. Mice were challenged with Escherichia coli intravenously 1, 5, and 14 days after myocardial infarction or sham operation. Thereafter, the cytokine production and the function of their Kupffer cells were assessed.

RESULTS

Mice with myocardial infarction showed remarkable cardiac dysfunction and had a significantly lower survival than sham mice after bacterial challenge at 5 days after surgery; bacterial challenge at 1 or 14 days after surgery resulted in no difference in survival between myocardial infarction and sham mice. The phagocytic activity of Kupffer cells, assessed by fluorescein isothiocyanate microspheres, remarkably decreased in mice with myocardial infarction 5 days after surgery. Serum peaks of tumor necrosis factor and interferon-gamma after bacterial challenge were also suppressed in mice with myocardial infarction at 5 days. Production of these cytokines and immunoglobulin-M from liver mononuclear cells was also impaired in mice with myocardial infarction. Enhancement of the phagocytic activity of Kupffer cells by C-reactive protein significantly improved survival after infection in mice with myocardial infarction, although neither interleukin-18 nor immunoglobulin-M treatment improved survival.

CONCLUSIONS

Cardiac dysfunction induced by myocardial infarction renders mice susceptible to bacterial infection and increases mortality because of a reduced ability of Kupffer cells to clear infectious bacteria. C-reactive protein-enhanced phagocytic activity of Kupffer cells may improve the poor prognosis after bacterial infection in mice with myocardial infarction.