CHOP links endoplasmic reticulum stress to NF-κB activation in the pathogenesis of nonalcoholic steatohepatitis

Free fatty acid induction of inflammation and cell death is an important feature of nonalcoholic steatohepatitis (NASH) and has been associated with disruption of the endoplasmic reticulum and activation of the Unfolded Protein Response (UPR). Following chronic UPR activation, the transcription factor CHOP (GADD153/DDIT3) triggers cell death; however, the mechanisms linking the UPR or CHOP to hepatoceullular injury and inflammation in the pathogenesis of NASH are not well understood. Using HepG2 and primary human hepatocytes, we found that CHOP induces cell death and inflammatory responses following saturated free fatty acid exposure by activating NF-κB through a pathway involving IRAK2 expression, resulting in secretion of cytokines IL-8 and TNFα directly from hepatocytes. TNFα facilitates hepatocyte death upon exposure to saturated free fatty acids and secretion of both IL-8 and TNFα contribute to inflammation. Interestingly, CHOP/NF-κB signaling is not conserved in primary rodent hepatocytes. Our studies suggest that CHOP plays a vital role in the pathophysiology of NASH through induction of secreted factors that trigger inflammation and hepatocellular death via a signaling pathway specific to human hepatocytes

Multifocal Gastric Ulcers Caused by Diffuse Large B Cell Lymphoma in a Patient With Significant Weight Loss

Primary gastrointestinal (GI) lymphoma is a heterogeneous disease with varied clinical presentations. The stomach is the most common GI site and accounts for 70% to 75% of GI lymphomas. We present a patient with gastric diffuse large B cell lymphoma (DLBCL) who presented with significant weight loss, early satiety, and multifocal ulcerated gastric lesions. Esophagoduodenoscopy should be performed in patients presenting with warning symptoms as in our case. Diagnosis is usually made by endoscopic biopsies. Multiple treatment modalities including surgery, radiotherapy, and chemotherapy have been used. Advancements in endoscopic and pathologic technology decrease turnaround time for diagnosis and treatment initiation, thus reducing the need for surgery. Health care providers should maintain a high level of suspicion and consider gastric DLBCL as part of the differential diagnosis, especially in those with warning symptoms such as weight loss and early satiety with abnormal endoscopic findings

Individuals with Primary Sclerosing Cholangitis Have Elevated Levels of Biomarkers for Apoptosis but Not Necrosis

BACKGROUND AND AIM: Hepatocyte apoptosis or necrosis from accumulation of bile salts may play an important role in the disease progression of primary sclerosing cholangitis (PSC). The aim of the current study was to measure serum markers of hepatocyte apoptosis (cytokeratin-18 fragments--K18) and necrosis (high-mobility group protein B1--HMGB1) in adults with PSC and examine the relationship with disease severity. METHODS: We measured serum levels of K18 and HMGB1 in well-phenotyped PSC (N = 37) and 39 control subjects (N = 39). Severity of PSC was assessed biochemically, histologically, and PSC Mayo risk score. Quantification of hepatocyte apoptosis was performed using TUNEL assay. RESULTS: The mean age of the study cohort was 49.7 ± 13.3 years and comprised of 67% men and 93% Caucasian. Serum K18 levels were significantly higher in the PSC patients compared to control (217.4 ± 78.1 vs. 157.0 ± 58.2 U/L, p = 0.001). However, HMGB1 levels were not different between the two groups (5.38 ± 2.99 vs. 6.28 ± 2.85 ng/mL, p = 0.15). Within the PSC group, K18 levels significantly correlated with AST (r = 0.5, p = 0.002), alkaline phosphatase (r = 0.5, p = 0.001), total bilirubin (r = 0.61, p ≤ 0.001), and albumin (r = -0.4, p = 0.02). Serum K18 levels also correlated with the level of apoptosis present on the liver biopsy (r = 0.8, p ≤ 0.001) and Mayo risk score (r = 0.4, p = 0.015). CONCLUSION: Serum K18 but not HMGB1 levels were increased in PSC and associated with severity of underlying liver disease and the degree of hepatocyte apoptosis

Function of inhibitor of Bruton's tyrosine kinase isoform α (IBTKα) in nonalcoholic steatohepatitis links autophagy and the unfolded protein response

Nonalcoholic fatty liver disease (steatosis) is the most prevalent liver disease in the Western world. One of the advanced pathologies is nonalcoholic steatohepatitis (NASH), which is associated with induction of the unfolded protein response (UPR) and disruption of autophagic flux. However, the mechanisms by which these processes contribute to the pathogenesis of human diseases are unclear. Herein, we identify the α isoform of the inhibitor of Bruton's tyrosine kinase (IBTKα) as a member of the UPR, whose expression is preferentially translated during endoplasmic reticulum (ER) stress. We found that IBTKα is located in the ER and associates with proteins LC3b, SEC16A, and SEC31A and plays a previously unrecognized role in phagophore initiation from ER exit sites. Depletion of IBTKα helps prevent accumulation of autophagosome intermediates stemming from exposure to saturated free fatty acids and rescues hepatocytes from death. Of note, induction of IBTKα and the UPR, along with inhibition of autophagic flux, was associated with progression from steatosis to NASH in liver biopsies. These results indicate a function for IBTKα in NASH that links autophagy with activation of the UPR

A role for miR-296 in the regulation of lipoapoptosis by targeting PUMA.

Saturated free fatty acids (FFA) induce hepatocyte lipoapoptosis, a key mediator of liver injury in nonalcoholic fatty liver disease (NAFLD). Lipoapoptosis involves the upregulation of the BH3-only protein PUMA, a potent pro-apoptotic protein. Given that dysregulation of hepatic microRNA expression has been observed in NAFLD, we examined the role of miRNA in regulating PUMA expression during lipotoxicity. By in silico analysis, we identified two putative binding sites for miR-296-5p within the 3\u27 untranslated region (UTR) of PUMA mRNA. Enforced miR-296-5p levels efficiently reduced PUMA protein expression in Huh-7 cells, while antagonism of miR-296-5p function increased PUMA cellular levels. Reporter gene assays identified PUMA 3\u27UTR as a direct target of miR-296-5p. The saturated FFA, palmitate, repressed miR-296-5p expression; and Huh-7 cells were sensitized to palmitate-induced lipotoxicity by antagonism of miR-296-5p function using a targeted locked nucleic acid (LNA). Finally, miR-296-5p was reduced in liver samples from nonalcoholic steatohepatitis (NASH) patients compared with patients with simple steatosis (SS) or controls. Also miR-296-5p levels inversely varied with PUMA mRNA levels in human liver specimens. Our results implicate miR-296-5p in the regulation of PUMA expression during hepatic lipoapoptosis. We speculate that enhancement of miR-296-5p expression may represent a novel approach to minimize apoptotic damage in human fatty liver diseases

TRAIL mediates liver injury by the innate immune system in the bile duct-ligated mouse.

The contribution of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a death ligand expressed by cells of the innate immune system, to cholestatic liver injury has not been explored. Our aim was to ascertain if TRAIL contributes to liver injury in the bile duct-ligated (BDL) mouse. C57/BL6 wild-type (wt), TRAIL heterozygote (TRAIL(+/-)), and TRAIL knockout (TRAIL(-/-)) mice were used for these studies. Liver injury and fibrosis were examined 7 and 14 days after BDL, respectively. Hepatic TRAIL messenger RNA (mRNA) was 6-fold greater in BDL animals versus sham-operated wt animals (P \u3c 0.01). The increased hepatic TRAIL expression was accompanied by an increase in liver accumulation of natural killer 1.1 (NK 1.1)-positive NK and natural killer T (NKT) cells, the predominant cell types expressing TRAIL. Depletion of NK 1.1-positive cells reduced hepatic TRAIL mRNA expression and serum alanine aminotransferase (ALT) values. Consistent with a role for NK/NKT cells in this model of liver injury, stress ligands necessary for their recognition of target cells were also up-regulated in hepatocytes following BDL. Compared to sham-operated wt mice, BDL mice displayed a 13-fold increase in terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and an 11-fold increase in caspase 3/7-positive hepatocytes (P \u3c 0.01). The number of TUNEL and caspase 3/7-positive cells was reduced by \u3e80% in BDL TRAIL knockout animals (P \u3c 0.05). Likewise, liver histology, number of bile infarcts, serum ALT values, hepatic fibrosis, and animal survival were also improved in BDL TRAIL(-/-) animals as compared to wt animals. Conclusion: These observations support a pivotal role for TRAIL in cholestatic liver injury mediated by NK 1.1-positive NK/NKT cells

Liver injury and fibrosis induced by dietary challenge in the ossabaw miniature Swine

BACKGROUND: Ossabaw miniature swine when fed a diet high in fructose, saturated fat and cholesterol (NASH diet) develop metabolic syndrome and nonalcoholic steatohepatitis (NASH) characterized by liver injury and fibrosis. This study was conducted to further characterize the development of NASH in this large animal model. METHODS: Ossabaw swine were fed standard chow (control group; n = 6) or NASH diet (n = 6) for 24 weeks. Blood and liver tissue were collected and liver histology were characterized at 0, 8, 16 and 24 weeks of dietary intervention. Hepatic apoptosis and lipid levels were assessed at week 24. RESULTS: The NASH diet group developed metabolic syndrome and progressive histologic features of NASH including: (a) hepatocyte ballooning at 8 weeks which progressed to extensive ballooning (>90% hepatocytes), (b) hepatic fibrosis at week 16, which progressed to moderate fibrosis, and (c) Kupffer cell accumulation with vacuolization at 8 weeks which progressed through week 24. The NASH diet group showed increased hepatocyte apoptosis that correlated with hepatic total and free cholesterol and free fatty acids, but not esterified cholesterol or triglycerides. CONCLUSIONS: This report further characterizes the progression of diet-induced NASH in the Ossabaw swine model. In Ossabaw swine fed the NASH diet: (a) hepatocyte injury and fibrosis can occur without macrovesicular steatosis or excess triglyceride accumulation; (b) hepatocyte ballooning generally precedes the development of fibrosis; (c) there is increased hepatocyte apoptosis, and it is correlated more significantly with hepatic free cholesterol than hepatic free fatty acids and had no correlation with hepatic triglycerides

Liver Lipid Quantification in NASH and Control Swine at Week 24.

<p>Quantification of lipid species in livers of NASH and control group swine at Week 24 of dietary intervention. Shown is the mean ± standard deviation.</p><p>Liver Lipid Quantification in NASH and Control Swine at Week 24.</p