Biliary obstruction results in PD-1-dependent liver T cell dysfunction and acute inflammation mediated by Th17 cells and neutrophils

The gut microbiota-bile acid axis in cholestatic liver disease

Cholestatic liver diseases (CLD) are characterized by impaired normal bile flow, culminating in excessive accumulation of toxic bile acids. The majority of patients with CLD ultimately progress to liver cirrhosis and hepatic failure, necessitating liver transplantation due to the lack of effective treatment. Recent investigations have underscored the pivotal role of the gut microbiota-bile acid axis in the progression of hepatic fibrosis via various pathways. The obstruction of bile drainage can induce gut microbiota dysbiosis and disrupt the intestinal mucosal barrier, leading to bacteria translocation. The microbial translocation activates the immune response and promotes liver fibrosis progression. The identification of therapeutic targets for modulating the gut microbiota-bile acid axis represents a promising strategy to ameliorate or perhaps reverse liver fibrosis in CLD. This review focuses on the mechanisms in the gut microbiota-bile acids axis in CLD and highlights potential therapeutic targets, aiming to lay a foundation for innovative treatment approaches.

Cholestasis-induced phenotypic transformation of neutrophils contributes to immune escape of colorectal cancer liver metastasis

BACKGROUND

Cholestasis is a common yet severe complication that occurs during the advancement of liver metastasis. However, how cholestasis impacts the development, treatment, and tumor microenvironment (TME) of liver metastasis remains to be elucidated.

METHODS

Extrahepatic and intrahepatic cholestatic mouse models with liver metastasis were established to detect the differential expression levels of genes, infiltration of immune cells and change in bile acid-associated metabolites by using RNA-Sequencing, flowcytometry, and liquid chromatography and mass spectrometry. Western blot was applied to neutrophils under the stimulation of primary bile acids (BAs) in vitro to study the mechanism of phenotypic alteration. In vitro coculture of BA-treated neutrophils with CD8+ T cells were performed to study the immune-suppressive effect of phenotypic-altered neutrophils. Clinical samples collected from colorectal cancer patients with liver metastasis and cholestasis were applied to RNA-Seq.

RESULTS

Compared to non-cholestatic mice, the progression of liver metastasis of cholestatic mice was significantly accelerated, which was associated with increased neutrophil infiltration and T-cell exclusion. Both neutrophils and T cells expressed higher immunosuppressive markers in the cholestatic mouse model, further indicating that an immunosuppressive tumor microenvironment was induced during cholestasis. Although neutrophils deletion via anti-Ly6G antibody partially hindered liver metastasis progression, it reduced the overall survival of mice. Tauro-β-muricholic acid (Tβ-MCA) and Glycocholic acid (GCA), the two most abundant cholestasis-associated primary BAs, remarkably promoted the expression of Arg1 and iNOS on neutrophils via p38 MAPK signaling pathway. In addition, BAs-pretreated neutrophils significantly suppressed the activation and cytotoxic effects of CD8+ T cells, indicating that the immunosuppressive phenotype of neutrophils was directly induced by BAs. Importantly, targeting BA anabolism with Obeticholic acid (OCA) under cholestasis effectively suppressed liver metastasis progression, enhanced the efficacy of immune checkpoint blockade, and prolonged survival of mice.

CONCLUSIONS

Our study reveals the TME of cholestasis-associated liver metastasis and proposes a new strategy for such patients by targeting bile acid anabolism.

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

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

Short-term preoperative drainage is associated with improved postoperative outcomes compared to that of long-term biliary drainage in pancreatic surgery

Purpose

The treatment of choice for patients presenting with obstructive cholestasis due to periampullary carcinoma is oncologic resection without preoperative biliary drainage (PBD). However, resection without PBD becomes virtually impossible in patients with obstructive cholangitis or severely impaired liver cell function. The appropriate duration of drainage by PBD has not yet been defined for these patients.

Methods

A retrospective analysis was conducted on 170 patients scheduled for pancreatic resection following biliary drainage between January 2012 and June 2018 at the University Hospital Dresden in Germany. All patients were deemed eligible for inclusion, regardless of the underlying disease entity. The primary endpoint analysis was defined as the overall morbidity (according to the Clavien-Dindo classification). Secondary endpoints were the in-hospital mortality and malignancy adjusted overall and recurrence-free survival rates.

Results

A total of 170 patients were included, of which 45 (26.5%) and 125 (73.5%) were assigned to the short-term (< 4 weeks) and long-term (≥ 4 weeks) preoperative drainage groups, respectively.

Surgical complications (Clavien-Dindo classification > 2) occurred in 80 (47.1%) patients, with significantly fewer complications observed in the short-term drainage group (31.1% vs. 52%; p = 0.02). We found that long-term preoperative drainage (unadjusted OR, 3.386; 95% CI, 1.507–7.606; p < 0.01) and periampullary carcinoma (unadjusted OR, 5.519; 95% CI, 1.722–17.685; p-value < 0.01) were independent risk factors for postoperative morbidity, based on the results of a multivariate regression model. The adjusted overall and recurrence-free survival did not differ between the groups (p = 0.12).

Conclusion

PBD in patients scheduled for pancreatic surgery is associated with substantial perioperative morbidity. Our results indicate that patients who have undergone PBD should be operated on within 4 weeks after drainage.

Programmed cell death 1 positive lymphocytes at palate tonsils in the elder patients with chronic tonsillitis

Circulating lymphocytes infiltrate into local foci at the inflammatory phase of acute wound healing for activation of the immune system and express an immune checkpoint protein programmed cell death 1 (PD-1) at the resolution phase for inactivation of the immune system. Conversely, the PD-1 expression was still found even on circulating lymphocytes of the elder patients with chronic tonsillitis at the palliative stage. Recently, an adhesion G protein coupled receptor 56 (GPR56) was reported to at least work as a proliferation factor for infiltrated lymphocytes into local foci at the resolution phase of acute wound healing. To preliminary examine a similar role of PD-1 and GPR56 at local foci at chronic inflammation, palate tonsils were prepared from small amounts of patients with chronic tonsillitis and tonsillar hypertrophy. A positive relationship of RNA expression might be observed between PD-1 and GPR56 in the elder patients with chronic tonsillitis. In regard to immunohistopathological findings, there were huge and small amounts of PD-1 and GPR56 expression at the marginal zone of lymphoid follicles of palate tonsils with chronic tonsillitis. Moreover, the positive relationship of RNA expression between PD-1 and GPR56 confirmed in large numbers of the elder patients with chronic tonsillitis. Probably, GPR56 participates in a supplement of PD-1⁺ lymphocytes to circulating bloods of the elder patients with chronic tonsillitis through a lymphocyte cell maintenance system at the marginal zone of the lymphoid follicles of palate tonsils.

An insight into the mechanism and molecular basis of dysfunctional immune response involved in cholestasis

Cholestasis is one of the most common clinical symptom of liver diseases. If patients do not receive effective treatment, cholestasis can evolve into liver fibrosis, cirrhosis and ultimately liver failure requiring liver transplantation. Currently, only ursodeoxycholic acid, obeticholic acid and bezafibrate are FDA-approved drugs, thereby requiring a breakthrough in new mechanisms and therapeutic development. Inflammation is one of the common complications of cholestasis. Hepatic accumulation of toxic hydrophobic bile acids is a highly immunogenic process involving both resident and immigrating immune cells. And the resulting inflammation may further aggravate hepatocyte injury. Though, great investigations have been made in the immune responses during cholestasis, the relationship between immune responses and cholestasis remains unclear. Moreover, scarce reviews summarize the immune responses during cholestasis and the efficacy of therapies on immune response. The main purpose of this paper is to review the existing literature on dysfunctional immune response during cholestasis and the effect of treatment on immune response which may provide an insight for researchers and drug development.

Hematological toxicities in immune checkpoint inhibitors: A pharmacovigilance study from 2014 to 2019

Immune checkpoint inhibitors (ICIs) have shown remarkable clinical effects in many cancer types. However, ICIs could also induce severe organ system toxicities, including those of the hematological system. The present study aimed to extensively characterize the hematological toxicities of ICIs immunotherapy. Data were extracted from the US Food and Drug Administration Adverse Event Reporting System (FAERS) database from January 1, 2014, to March 31, 2019. Disproportionality analysis, including information component (IC) and reporting odds ratio (ROR), was used to detect potential disproportionality signal. The lower boundary of the 95% confidence interval of IC (IC₀₂₅ ) exceeding zero or that of ROR (ROR₀₂₅ ) exceeding one was considered statistically significant for detecting disproportionality signal. A total of 29 294 335 records were extracted from the database, with 132 573 related to ICIs. Overall, hematological adverse events (AEs) were more frequently reported in ICIs (IC₀₂₅ : 0.81; ROR₀₂₅ : 1.80). On further analysis, hematological AEs were overreported in female patients (female vs male, ROR₀₂₅ : 1.04) and anti-CTLA-4 monotherapy groups (anti-CTLA-4 vs anti-PD-1, ROR₀₂₅ : 1.33) and polytherapy groups (polytherapy vs monotherapy, ROR: 1.20, ROR₀₂₅ : 1.11). Moreover, class-specific hematological AEs were also detected and differed in unique ICI regimens. Notably, disseminated intravascular coagulation had the highest proportion of death outcomes among the top 10 most frequently reported ICI-associated hematological AEs. Our study shows a high reporting frequency of hematological AEs induced by ICI monotherapy (especially by anti-CTLA-4 therapy) and reinforced by polytherapy. A spectrum of class-specific disproportionality signal was also detected; some were fatal and reported for the first time. The heterogeneous clinical spectrum of hematological toxicities, including the non-negligible proportion of death as reported outcome, are warranted to be reminded by clinicians. Early recognition and management of ICI-related hematological AEs are highly important and further studies are needed to confirm the results of our study.

Inflammation: Cause or consequence of chronic cholestatic liver injury

Cholestasis is a result of obstruction of the biliary tracts. It is a common cause of liver pathology after exposure to toxic xenobiotics and during numerous other liver diseases. Accumulation of bile acids in the liver is thought to be a major driver of liver injury during cholestasis and can lead to eventual liver fibrosis and cirrhosis. As such, current therapy in the field of chronic liver diseases with prominent cholestasis relies heavily on increasing choleresis to limit accumulation of bile acids. Many of these same diseases also present with autoimmunity before the onset of cholestasis though, indicating the inflammation may be an initiating component of the pathology. Moreover, cytotoxic inflammatory mediators accumulate during cholestasis and can propagate liver injury. Anti-inflammatory biologics and small molecules have largely failed clinical trials in these diseases though and as such, targeting inflammation as a means to address cholestatic liver injury remains debatable. The purpose of this review is to understand the different roles that inflammation can play during cholestatic liver injury and attempt to define how new therapeutic targets that limit or control inflammation may be beneficial for patients with chronic cholestatic liver disease.

The Inhibitory T Cell Receptors PD1 and 2B4 Are Differentially Regulated on CD4 and CD8 T Cells in a Mouse Model of Non-alcoholic Steatohepatitis

Infiltrating CD4 and CD8 T cells have been shown to worsen inflammatory liver damage in non-alcoholic steatohepatitis (NASH). Inhibitory T cell receptors such as the programmed cell death protein 1 (PD1) and the natural killer cell receptor 2B4 regulate the activity of CD4 and CD8 T cells and therefore play an important role in immune tolerance required in the liver. In this study, we investigated the expression profile of inhibitory T cell receptors on CD4 and CD8 T cells in a mouse model of NASH. Male B57BL/6J mice were fed a Western diet for 24 weeks. The expression levels of inhibitory receptors on the surface of intrahepatic and peripheral T cells were measured and correlated with markers of activation (CD107a, CD69, and CD44), metabolic disorder (serum triglycerides, serum cholesterol, γ-glutamyl transferase, hepatic triglycerides), inflammation (serum alanine aminotransferase and aspartate aminotransferase) and hepatic fibrosis (collagen 1A1, α-smooth muscle actin, hydroxyproline). Under Western diet, PD1 is exclusively upregulated on intrahepatic and peripheral CD8⁺ T cells, whereas the expression level on CD4 T cells is unaffected. In contrast, 2B4 is upregulated liver-specifically on both CD4 and CD8 T cells and unchanged on peripheral T cells. Upregulation of PD1 on CD8 T cells is restricted to CD8 effector memory T cells and correlates with lower levels of degranulation. Similarly, the inhibitory function of PD1 on intrahepatic CD4 T cells is shown by a lower CD69 and CD44 expression on PD1-positive CD4 T cells. In murine steatohepatitis, the upregulation of PD1 on CD8 T cells and 2B4 on CD4 and CD8 T cells potentially limits T cell-mediated liver damage. Therefore, these inhibitory T cell receptors could serve as promising targets of immune-modulatory NASH therapy.

Preventive effect of artemisinin extract against cholestasis induced via lithocholic acid exposure

Obstructive cholestasis characterized by biliary pressure increase leading to leakage of bile back that causes liver injury. The present study aims to evaluate the effects of artemisinin in obstructive cholestasis in mice. The present study was carried out on 40 adult healthy mice that were divided into 4 groups, 10 mice each; the negative control group didn’t receive any medication. The normal group was fed normally with 100 mg/kg of artemisinin extract orally. The cholestatic group fed on 1% lithocholic acid (LCA) mixed into control diet and cholestatic group co-treated with 100 mg/kg of artemisinin extract orally. Mice were treated for 1 month then killed at end of the experiment. A significant increase in alanine aminotransferase, aspartate aminotransferase, and total and direct bilirubin was detected in mice exposed to LCA toxicity. That increase was significantly reduced to normal values in mice co-treated with artemisinin. LCA toxicity causes multiple areas of necrosis of irregular distribution. However, artemisinin co-treatment showed normal hepatic architecture. Moreover, LCA causes down-regulation of hepatic mRNA expressions of a set of genes that are responsible for ATP binding cassette and anions permeability as ATP-binding cassette sub-family G member 8, organic anion-transporting polypeptide, and multidrug resistance-associated protein 2 genes that were ameliorated by artemisinin administration. Similarly, LCA toxicity significantly down-regulated hepatic mRNA expression of constitutive androstane receptor, OATP4, and farnesoid x receptor genes. However, artemisinin treatment showed a reasonable prevention. In conclusion, the current study strikingly revealed that artemisinin treatment can prevent severe hepatotoxicity and cholestasis that led via LCA exposure.

The Prognostic Value of Preoperative Neutrophil-to-Lymphocyte Ratio in Resected Patients with Pancreatic Adenocarcinoma

PURPOSE

This research aims to analyze neutrophil-to-lymphocyte ratio (NLR) for resectable pancreatic ductal adenocarcinoma (PDAC) patients and reveal its predictive value.

METHODS

We enrolled 389 pancreatic adenocarcinoma patients who had undergone curative surgery between January 1, 2008 and August 15, 2015 in Jiangsu Provincial People's Hospital, and they were followed up until December 20, 2016. Among them, 219 patients had definite recurrence record in our hospital. The appropriate cutoff value for the NLR was obtained from X-tile software. The association between qualitative variables and NLR was analyzed by Chi-square test or Fisher's exact test, and for quantitative values, the association was analyzed by independent Student's t test. Additionally, survival analysis was performed by Kaplan-Meier plots. Independent prognostic factors were found according to Cox regression analysis.

RESULTS

Based on univariate analysis, the elevated preoperative NLR had an important influence on the decreased recurrence-free survival (RFS) (8.2 vs. 14.9 months) and overall survival (OS) (13.7 vs. 22 months), and this result also counted in the multivariate analysis. Regarding OS, both patients with or without postoperative chemotherapy can obtain benefits from low NLR according to subgroup analysis. Stage I and II pancreatic adenocarcinoma patients can get longer OS and RFS from low NLR, while patients with stage III cancer cannot. Regarding recurrence site, high NLR level was also related to distant metastasis (P = 0.02).

CONCLUSION

Preoperative NLR level could be a useful prognostic indication for resectable pancreatic adenocarcinoma patients.

Safety and efficacy of n-3 fatty acid-based parenteral nutrition in patients with obstructive jaundice: a propensity-matched study

Background

It is reported that lipid emulsion enriched in n-3 fatty acids (FAs) helps us to improve postoperative recovery for surgical patients with biliary tract disease. Its role for postoperative patients with obstructive jaundice is as yet unclear. The object of this study was to evaluate the safety and efficacy of n-3 fatty acid-based parenteral nutrition (PN) for patients with obstructive jaundice following surgical procedures.

Methods

Data were collected from patients with obstructive jaundice who received PN, including n-3 PUFA-enriched lipid emulsions and standard non-enriched lipid emulsions (e.g., soybean oil). We then calculated a propensity score, the probability of receiving different PN, by the propensity score matched (PSM) method. After matching, we compared isonitrogenous total PN with 20% Structolipid and 10% n-3 fatty acid (Omegaven, Fresenius-Kabi, Germany) (treatment group) to Structolipid alone (control group) for 5 days postoperatively, in the absence of enteral nutrition.

Results

Before the propensity score matching, there were 226 patients enrolled. After propensity score stratification, 108 cases remained, and all covariates were balanced. Among matched patients with PN, patients in the control group were at a higher risk for long-term jaundice recovery (12.9 ± 8.5 VS 16.4 ± 7.9 P = 0.029), lower velocity of reduction in jaundice (P = 0.045), and lower pre-albumin (P = 0.002). No significant difference as found in terms of comorbidities, white blood cell (WBC), albumin and other aspects.

Conclusion

PN with n-3 PUFA-enriched lipid emulsions was safe and effective in accelerating jaundice recovery for patients after surgical procedures. This trial was registered at clinicaltrials.gov as NCT03376945.

Reprogramming of pro-inflammatory human macrophages to an anti-inflammatory phenotype by bile acids

Cholestasis is caused by autoimmune reactions, drug-induced hepatotoxicity, viral infections of the liver and the obstruction of bile ducts by tumours or gallstones. Cholestatic conditions are associated with impaired innate and adaptive immunity, including alterations of the cellular functions of monocytes, macrophages, NK cells and T-cells. Bile acids act as signalling molecules, affecting lipopolysaccharide (LPS)-induced cytokine expression in primary human macrophages. The present manuscript investigates the impact of bile acids, such as taurolithocholic acid (TLC), on the transcriptome of human macrophages in the presence or absence of LPS. While TLC itself has almost no effect on gene expression under control conditions, this compound modulates the expression of 202 out of 865 transcripts in the presence of LPS. Interestingly, pathway analysis revealed that TLC specifically supressed the expression of genes involved in mediating pro-inflammatory effects, phagocytosis, interactions with pathogens and autophagy as well as the recruitment of immune cells, such as NK cells, neutrophils and T cells. These data indicate a broad influence of bile acids on inflammatory responses and immune functions in macrophages. These findings may contribute to the clinical observation that patients with cholestasis present a lack of response to bacterial or viral infections.

Immune checkpoint inhibition: prospects for prevention and therapy of hepatocellular carcinoma

The global prevalence of liver cancer is rapidly rising, mostly as a result of the amplified incidence rates of viral hepatitis, alcohol abuse and obesity in recent decades. Treatment options for liver cancer are remarkably limited with sorafenib being the gold standard for advanced, unresectable hepatocellular carcinoma but offering extremely limited improvement of survival time. The immune system is now recognised as a key regulator of cancer development through its ability to protect against infection and chronic inflammation, which promote cancer development, and eliminate tumour cells when present. However, the tolerogenic nature of the liver means that the immune response to infection, chronic inflammation and tumour cells within the hepatic environment is usually ineffective. Here we review the roles that immune cells and cytokines have in the development of the most common primary liver cancer, hepatocellular carcinoma (HCC). We then examine how the immune system may be subverted throughout the stages of HCC development, particularly with respect to immune inhibitory molecules, also known as immune checkpoints, such as programmed cell death protein-1, programmed cell death 1 ligand 1 and cytotoxic T lymphocyte antigen 4, which have become therapeutic targets. Finally, we assess preclinical and clinical studies where immune checkpoint inhibitors have been used to modify disease during the carcinogenic process. In conclusion, inhibitory molecule-based immunotherapy for HCC is in its infancy and further detailed research in relevant in vivo models is required before its full potential can be realised.

Dietary and metabolic modulators of hepatic immunity

The liver is the central metabolic organ of the organism and is thus constantly exposed to gut-derived dietary and microbial antigens. The liver maintains homoeostatic tolerance to these mostly harmless antigens. However, the liver also functions as a barrier organ to harmful pathogens and is thus permissive to liver inflammation. The regulation of the delicate balance between liver tolerance and liver inflammation is of vital importance for the organism. In recent years, a general role for dietary components and metabolites as immune mediators has been emerging. However, although the liver is exposed to a great deal of metabolic mediators, surprisingly, little is known about their actual role in the regulation of hepatic immune responses. Here, we will explore the possible impacts of metabolic mediators for homoeostatic and pathological immunity in the liver, by highlighting selected examples of metabolic immune regulation in the liver.

Mechanisms of bile acid mediated inflammation in the liver

Bile acids are synthesized in the liver and are the major component in bile. Impaired bile flow leads to cholestasis that is characterized by elevated levels of bile acid in the liver and serum, followed by hepatocyte and biliary injury. Although the causes of cholestasis have been extensively studied, the molecular mechanisms as to how bile acids initiate liver injury remain controversial. In this chapter, we summarize recent advances in the pathogenesis of bile acid induced liver injury. These include bile acid signaling pathways in hepatocytes as well as the response of cholangiocytes and innate immune cells in the liver in both patients with cholestasis and cholestatic animal models. We focus on how bile acids trigger the production of molecular mediators of neutrophil recruitment and the role of the inflammatory response in this pathological process. These advances point to a number of novel targets where drugs might be judged to be effective therapies for cholestatic liver injury.

Mechanisms of bile acid mediated inflammation in the liver

Bile acids are synthesized in the liver and are the major component in bile. Impaired bile flow leads to cholestasis that is characterized by elevated levels of bile acid in the liver and serum, followed by hepatocyte and biliary injury. Although the causes of cholestasis have been extensively studied, the molecular mechanisms as to how bile acids initiate liver injury remain controversial. In this chapter, we summarize recent advances in the pathogenesis of bile acid induced liver injury. These include bile acid signaling pathways in hepatocytes as well as the response of cholangiocytes and innate immune cells in the liver in both patients with cholestasis and cholestatic animal models. We focus on how bile acids trigger the production of molecular mediators of neutrophil recruitment and the role of the inflammatory response in this pathological process. These advances point to a number of novel targets where drugs might be judged to be effective therapies for cholestatic liver injury.

The impact of sterile inflammation in acute liver injury

BACKGROUND

The liver has a number of functions in innate immunity. These functions predispose the liver to innate immune-mediated liver injury when inflammation goes unchecked. Significant progress has been made in the last 25 years on sterile inflammatory liver injury in a number of models; however, a great deal of controversy and many questions about the nature of sterile inflammation still exist.

AIM

The goal of this article is to review sterile inflammatory liver injury using both a basic approach to what constitutes the inflammatory injury, and through examination of current models of liver injury and inflammation. This information will be tied to human patient conditions when appropriate.

RELEVANCE FOR PATIENTS

Inflammation is one of the most critical factors for managing in-patient liver disease in a number of scenarios. More information is needed for both scientists and clinicians to develop rational treatments.

Improved survival after induction of sepsis by cecal slurry in PD-1 knockout murine neonates

BACKGROUND

Sepsis and the ensuing immune dysfunction continue to be major contributors to neonatal morbidity and mortality. Neonatal sepsis also is associated with profound immune dysfunction. We have recently identified a role for a family of coinhibitory molecules that are altered in murine sepsis and in critically ill adult patients, which may be a target for development of novel therapies. There is, however, a paucity of data pertaining to the role of coinhibitory checkpoint proteins in the control and modulation of neonatal sepsis.

METHODS

The cecal slurry model consists of harvesting the cecal content of an adult, wild-type, male mouse and combining it with 5% dextrose to create a cecal slurry with a concentration of 80 mg/mL (LD₇₀ at 7 days). Neonatal mice (5-7 days of age) underwent intraperitoneal injection of the cecal slurry or 0.9% saline for the sham procedure. Wild-type (C57BL/6) or PD-1^-/- mice were used; a 7-day survival study was undertaken. Cytometric bead array was used for cytokine expression. Blood and peritoneal fluid was cultured for bacterial burden. Flow cytometry was used to assess the peritoneal cavity cell populations.

RESULTS

There was no mortality after the sham procedure in either wild-type or PD-1^-/- pups. PD-1 markedly affected sepsis survival with significantly improved survival in the PD-1^-/- pups (40% vs 80%; P < .01). This survival improvement was not associated with any difference in bacterial clearance. The bacterial burden was equivalent between wild-type and PD-1^-/- pups at 24 hours after cecal slurry. However, PD-1^-/- pups did display an increased circulating cytokine response to the cecal slurry compared with wild type, with increased expression of IL-6, IL-10, and TNF-α levels. Within the peritoneal cavity, sepsis induced an influx of neutrophils, a finding that was increased in PD-1^-/- pups. Although the T-cell response was unaffected by PD-1, it was noted that cecal slurry induced a loss of peritoneal B cells in WT, while the peritoneal B-cell population was preserved in PD-1^-/- pups.

CONCLUSION

Our data suggest that the checkpoint protein, PD-1, plays an important role in controlling the immune response to sepsis in the neonate, ultimately affecting sepsis-related mortality in this neonatal murine model of sepsis. Akin to adult studies, these data further emphasize the potential therapeutic target for PD-1 across a spectrum of septic patients.

Murine model of long-term obstructive jaundice

BACKGROUND

With the recent emergence of conjugated bile acids as signaling molecules in cancer, a murine model of obstructive jaundice by cholestasis with long-term survival is in need. Here, we investigated the characteristics of three murine models of obstructive jaundice.

METHODS

C57BL/6J mice were used for total ligation of the common bile duct (tCL), partial common bile duct ligation (pCL), and ligation of left and median hepatic bile duct with gallbladder removal (LMHL) models. Survival was assessed by Kaplan-Meier method. Fibrotic change was determined by Masson-Trichrome staining and Collagen expression.

RESULTS

Overall, 70% (7 of 10) of tCL mice died by day 7, whereas majority 67% (10 of 15) of pCL mice survived with loss of jaundice. A total of 19% (3 of 16) of LMHL mice died; however, jaundice continued beyond day 14, with survival of more than a month. Compensatory enlargement of the right lobe was observed in both pCL and LMHL models. The pCL model demonstrated acute inflammation due to obstructive jaundice 3 d after ligation but jaundice rapidly decreased by day 7. The LHML group developed portal hypertension and severe fibrosis by day 14 in addition to prolonged jaundice.

CONCLUSIONS

The standard tCL model is too unstable with high mortality for long-term studies. pCL may be an appropriate model for acute inflammation with obstructive jaundice, but long-term survivors are no longer jaundiced. The LHML model was identified to be the most feasible model to study the effect of long-term obstructive jaundice.

The Inflammatory Cytokine IL-21 is Expressed by Splenic Neutrophils in Response to Transplantation of Allogeneic Cells

We have previously reported that GR-1 neutrophil/monocytes rose dramatically in the spleen, peaked by day 7 and declined through day 14. This period corresponded to the peak of acute Graft-Versus-Host Disease (aGVHD) in BALB/c mice transplanted with allogeneic donor cells. We now asked: what cytokines did these splenic neutrophil/monocytes express on day 7 and 14 post transplant? BALB/c mice were transplanted with allogeneic B6 or syngeneic BALB/c donor cells. Long term survival was recorded through day 31. Other groups were sacrificed on days 3, 5, 7, 14, 21 and 31 days post transplant to record the total number of cells in the spleens and their phenotypes. Neutrophils were isolated from the spleens of mice transplanted with B6 and BALB/c cells on days 7 and 14. Daily body weight demonstrated a transient drop in the syngeneic transplants on day 2 but a much greater drop with its nadir at day 7 and never fully recovering through 31 days. CD8/CD4 T lymphocytes peaked in the spleen on day 5 and were followed on day 7 by GR-I cells in all of the allogeneic transplants. In syngeneic transplants this early rise in lymphocytes did not occur and GR-1 cells peaked on day 14. Highly purified neutrophils were isolated in two separate experiments from the spleens on days 7 and 14 post transplant. In both experiments day 7 allogeneic neutrophils expressed significantly elevated levels of Interleukin-21 (IL-21) mRNA whereas the day 7 and 14 syngeneic cells expressed lower but significant levels of TNFα. Intracellular IL-21 was demonstrated in the allogeneic neutrophils on day 7 before and after in vitro stimulation. In conclusion Purified neutrophils isolated from the spleen on day 7, the early peak of allogeneic transplantation a GVHD, express high levels of IL-21 message and intracellular IL-21.

Immunology in the liver--from homeostasis to disease

The liver is a central immunological organ with a high exposure to circulating antigens and endotoxins from the gut microbiota, particularly enriched for innate immune cells (macrophages, innate lymphoid cells, mucosal-associated invariant T (MAIT) cells). In homeostasis, many mechanisms ensure suppression of immune responses, resulting in tolerance. Tolerance is also relevant for chronic persistence of hepatotropic viruses or allograft acceptance after liver transplantation. The liver can rapidly activate immunity in response to infections or tissue damage. Depending on the underlying liver disease, such as viral hepatitis, cholestasis or NASH, different triggers mediate immune-cell activation. Conserved mechanisms such as molecular danger patterns (alarmins), Toll-like receptor signalling or inflammasome activation initiate inflammatory responses in the liver. The inflammatory activation of hepatic stellate and Kupffer cells results in the chemokine-mediated infiltration of neutrophils, monocytes, natural killer (NK) and natural killer T (NKT) cells. The ultimate outcome of the intrahepatic immune response (for example, fibrosis or resolution) depends on the functional diversity of macrophages and dendritic cells, but also on the balance between pro-inflammatory and anti-inflammatory T-cell populations. As reviewed here, tremendous progress has helped to understand the fine-tuning of immune responses in the liver from homeostasis to disease, indicating promising targets for future therapies in acute and chronic liver diseases.

Interleukin 17, Produced by γδ T Cells, Contributes to Hepatic Inflammation in a Mouse Model of Biliary Atresia and Is Increased in Livers of Patients

BACKGROUND & AIMS

Biliary atresia (BA) is a rare disease in infants, with unknown mechanisms of pathogenesis. It is characterized by hepatobiliary inflammatory, progressive destruction of the biliary system leading to liver fibrosis, and deterioration of liver function. Interleukin (IL) 17A promotes inflammatory and autoimmune processes. We studied the role of IL17A and cells that produce this cytokine in a mouse model of BA and in hepatic biopsy samples from infants with BA.

METHODS

We obtained peripheral blood and liver tissue specimens from 20 patients with BA, collected at the time of Kasai portoenterostomy, along with liver biopsies from infants without BA (controls). The tissue samples were analyzed by reverse transcription quantitative polymerase chain reaction (PCR), in situ PCR, and flow cytometry analyses. BA was induced in balb/cAnNCrl mice by rhesus rotavirus infection; uninfected mice were used as controls. Liver tissues were collected from mice and analyzed histologically and by reverse transcriptase PCR; leukocytes were isolated, stimulated, and analyzed by flow cytometry and PCR analyses. Some mice were given 3 intraperitoneal injections of a monoclonal antibody against IL17 or an isotype antibody (control).

RESULTS

Livers from rhesus rota virus-infected mice with BA had 7-fold more Il17a messenger RNA than control mice (P = .02). γδ T cells were the exclusive source of IL17; no T-helper 17 cells were detected in livers of mice with BA. The increased number of IL17a-positive γδ T cells liver tissues of mice with BA was associated with increased levels of IL17A, IL17F, retinoid-orphan-receptor C, C-C chemokine receptor 6, and the IL23 receptor. Mice that were developing BA and given antibodies against IL17 had lower levels of liver inflammation and mean serum levels of bilirubin than mice receiving control antibodies (191 μmol/L vs 78 μmol/L, P = .002). Liver tissues from patients with BA had 4.6-fold higher levels of IL17 messenger RNA than control liver tissues (P = .02).

CONCLUSIONS

In livers of mice with BA, γδ T cells produce IL17, which is required for inflammation and destruction of the biliary system. IL17 is up-regulated in liver tissues from patients with BA, compared with controls, and might serve as a therapeutic target.

Therapeutic targets for cholestatic liver injury

INTRODUCTION

Cholestasis is a reduction in bile flow that occurs during numerous pathologies. Blockage of the biliary tracts results in hepatic accumulation of bile acids or their conjugate bile salts. The molecular mechanisms behind liver injury associated with cholestasis are extensively studied, but not well understood. Multiple models of obstructive cholestasis result in a significant inflammatory infiltrate at the sites of necrosis that characterize the injury.

AREAS COVERED

This review will focus on direct bile acid toxicity during cholestasis, bile acid signaling processes and on the development and continuation of inflammation during cholestasis, with a focus on novel proposed molecular mediators of neutrophil recruitment. While significant progress has been made on these molecular mechanisms, a continued focus on how cholestasis and the innate immune system interact is necessary to discover targetable therapeutics that might protect the liver while leaving global immunity intact.

EXPERT OPINION

While bile acid toxicity likely occurs in humans and other mammals when toxic bile acids accumulate, persistent inflammation is likely responsible for continued liver injury during obstructive cholestasis. Targeting molecular mediators of inflammation may help prevent liver injury during acute cholestasis both in murine models and human patients.

Dendritic Cells Regulate Treg-Th17 Axis in Obstructive Phase of Bile Duct Injury in Murine Biliary Atresia

Several cell types are considered to be effector cells in bile duct injury in rhesus rotavirus (RRV)-induced experimental biliary atresia (BA). Here, we identified an increased T helper 17 (Th17) cell population in a BA mode. By depleting the Th17 cells, the BA symptoms (onset of jaundice, acholic stools and retarded growth) were attenuated and the survival rate was improved. Furthermore, we found that in mice with BA, the percentage of CD4⁺CD25^highFoxp3⁺ T regulatory (Treg) cells decreased along with the increased percentage of Th17 cells. However, the absolute numbers of Treg and Th17 cells were both increased in liver of RRV-injected mice compared to saline-injected mice. The proportion of Th17 cells at 7 days post-infection was decreased if Treg cells isolated from normal adult mice, but not Treg cells from the livers of mice with BA, were intraperitoneally transferred on day 5 of life. In vitro experiments also showed that Treg cells from mice with BA had a diminished suppressive effect on Th17 cell generation. To determine the mechanisms, we investigated the production of cytokines in the liver. The level of IL-6, which has been shown to be abundantly secreted by activated dendritic cells (DCs), was remarkably elevated. Importantly, in a Treg/Th17 cell suppression assay, IL-6 was demonstrated to paralyze the Treg cells’ suppressive effect on Th17 cells and eventually the unrestrained increase of Th17 cells contributed to bile duct injury. In conclusion, the DC-regulated Treg-Th17 axis, probably in conjunction with other effector T cells, aggravates progressive inflammatory injury at the time of ductal obstruction.

Lithocholic acid feeding results in direct hepato-toxicity independent of neutrophil function in mice

Lithocholic acid (LCA) supplementation in the diet results in intrahepatic cholestasis and bile infarcts. Previously we showed that an innate immune response is critical for cholestatic liver injury in the bile duct ligated mice. Thus, the purpose of this study was to investigate the role of neutrophils in the mechanism of liver injury caused by feeding mice a diet containing LCA. C57BL/6 mice were given control or 1% LCA containing diet for 24-96 h and then examined for parameters of hepatotoxicity. Plasma ALT levels were significantly increased by 48 h after LCA feeding, which correlated with both neutrophil recruitment to the liver and upregulation of numerous pro-inflammatory genes. The injury was confirmed by histology. Deficiency in intercellular adhesion molecule-1 (ICAM-1) expression or inhibition of neutrophil function failed to protect against the injury. Bile acid levels were quantified in plasma and bile of LCA-fed mice after 48 and 96 h. Only the observed biliary levels of taurochenodeoxycholic acid and potentially tauro-LCA caused direct cytotoxicity in mouse hepatocytes. These data support the conclusion that neutrophil recruitment occurs after the onset of bile acid-induced necrosis in LCA-fed animals, and is not a primary mechanism of cell death when cholestasis occurs through accumulation of hydrophobic bile acids.

Immunotherapy for solid tumors--a review for surgeons

Immunotherapy has evolved considerably in the last decade and is becoming an integral component of the armamentarium for the treatment of patients with advanced solid tumors. It is important for clinicians, especially surgeons, to understand the basic principles of novel immunotherapies and the immune system. This review summarizes the evolution of the most relevant immunotherapies, their mechanisms of action, the data supporting their clinical use, and integration of immunotherapy into multidisciplinary management of solid tumors. This review should serve as a primer for clinicians and surgeons to understand the rapidly evolving field of immunotherapy.