Katherine Smith

Liver disease: Kupffer cells regulate the progression of ALD and NAFLD

The balance of classic proinflammatory M1 Kupffer cells and alternatively activated anti-inflammatory M2 Kupffer cells is important for the tight regulation of the development of liver injury in alcoholic liver disease (ALD) and NAFLD, new findings published in Hepatology have revealed.

Neurogastroenterology: Improving 3D imaging of the enteric nervous system

Imaging the enteric nervous system (ENS)—a complex multidimensional structure comprising dispersed neurites and fibers and structural components —is challenging. Shiue-Cheng Tang and colleagues now show that optical clearing could aid 3D visualization of the ENS. Conventional microtome-based 2D ENS imaging provides only a limited perspective of the neural network. To generate a comprehensive 3D view, Liu et al. imaged the human ileum using confocal microscopy after optical clearing. “Optical clearing reduces light scattering in the specimen, thus promoting photon penetration across the tissue to generate high-definition images,” explains Tang. Human ileal enteric nerve specimens were immunostained with marker PGP9.5 and immersed in optical-clearing solution before deep-tissue confocal microscopy; images were then processed for 3D image rendering and analysis. Fluorescence signal decay along the focal path in the human ileal wall was NEUROGASTROENTEROLOGY

Microbiota: Gut microbiota produce alcohol in patients with NASH

NASH has a poor prognosis. It currently accounts for 10% of liver transplantations conducted in the USA and is predicted to soon become the most common indication for liver transplantation. “Understanding the pathophysiology of NASH is therefore of crucial importance,” explains Lixin Zhu, corresponding author of a study published in Hepatology. “Histologically, NASH is indistinguishable from alcoholic liver disease, so we predicted that alcohol also has a role in NASH.” Previous data from this group revealed that global gene expression in livers from patients with NASH was distinct from that of healthy livers. Interestingly, although dietary alcohol intake was similar, the expression of all genes involved in alcohol metabolism was greater in NASH livers than healthy livers. “We concluded that the only possible source of alcohol in patients with NASH was the gut microbiome,” says Zhu. The aim of this study was simple: identify and quantitate the microbial species in the gut of obese patients with NASH, and compare them with those identified in the gut of obese patients without NASH and healthy individuals as controls. The investigators pyrosequenced 16S rRNA extracted from the gut MICROBIOTA

Biliary tract: GPC1 genetic risk further links Hedgehog signalling with pathogenesis of biliary atresia

“Biliary atresia is the most common identifiable cause of neonatal cholestasis and is the leading cause of liver transplantation in children,” states Randolph Matthews, corresponding author of a recent study investigating the pathogenesis of this disease. “Although advances have been made in our understanding of the mechanisms underlying the fibroinflammatory damage to the biliary tree that occurs in patients with this disorder, uncovering the cause of biliary atresia continues to be a major challenge,” he explains.

Pancreatic cancer: FASCINating insights into the metastatic nature of pancreatic cancer

FASCINating insights into the metastatic nature of pancreatic cancer Pancreatic ductal adenocarcinoma (PDAC)—the most common form of pancreatic cancer in humans—is highly invasive and metastatic and is associated with poor survival in patients. The actin-bundling protein fascin has previously been reported to be a biomarker of invasive and advanced PDAC, leading Professor Laura Machesky, Dr Ang Li and colleagues from the Beatson Institute for Cancer Research in Glasgow to investigate its potential role in the progression of pancreatic cancer. “No treatments currently exist for preventing metastasis in patients with pancreatic cancer, so we sought to explore whether fascin was an interesting target for blocking PDAC metastasis,” states Machesky. The team used a combination of in vitro and in vivo studies to demonstrate that fascin contributes to the metastatic nature of PDAC, and they also revealed underlying mechanisms that could explain how fascin promotes PDAC progression. As an initial step, the effect of fascin deficiency was determined in KPC mice, a well-documented mouse model of pancreatic cancer. KPC mice have some of the most commonly mutated oncogenes and tumour suppressor genes found in human PDAC. Pancreatic cancer in these mice also progresses from pancreatic intraepithelial neoplasia (PanIN) to PDAC and then metastasis, in a manner similar to the stages observed in human disease. “By studying KPC mice deficient in fascin [termed FKPC mice], we were able to determine how loss of fascin affects tumour spread from a primary pancreatic tumour that was genetically encoded,” explains Machesky. FKPC mice had increased survival times (from 132 days to 189 days, 43%), delayed onset of PDAC and reduced tumour burden when compared with control (KPC) mice. An unexpected finding for the authors of this study is that FKPC mice had similar levels of PDAC invasion into the bowel and peritoneum as KPC mice. However, as expected, the level of tumour metastasis (to the liver, among other organs) was lower in FKPC mice than in control mice. How could fascin promote pancreatic cancer metastasis? Fascin expression in KPC mice varied according to the stage of pancreatic cancer. Cells isolated from early stage PanINs were negative for fascin, but expression increased to 6% of cells taken from mice with PanIN stage 3 and to 100% in PDAC cells. Fascin was also shown to be expressed in vitro in PDAC cell lines and was found to be a direct target of the neural crest transcription factor slug, which regulates the epithelial– mesenchymal transition during tumour formation and is believed to be a key driver of tumour metastasis. Fascin localization was concentrated in filopodia (finger-like protrusions that have a role in cell invasion) in both PDAC cell lines and in cells isolated from mice. Fascin expression was essential for filopodia assembly and turnover, and it promoted the intercalation of filopodia into mesothelial cell layers, driving PDAC cell transmigration. The researchers then went on to correlate fascin expression levels with patient outcome. The majority of 122 resected PDAC samples from patients expressed fascin. Moreover, high fascin levels were associated with poor patient outcome, vascular invasion and a reduced time to recurrence. “One of our most significant findings is that loss of fascin seems to delay the onset of PDAC and reduce early tumour formation,” Machesky says. This point is echoed by Professor Anirban Maitra, an expert in the field from the MD Anderson Cancer Centre (USA) who was not involved in this study. “The role of fascin in this ‘early’ disease might be related to recent observations in mouse models of pancreatic cancer that metastatic programming (including the onset of epithelial–mesenchymal transition) occurs far earlier than previously believed,” he comments. “Although loss of fascin did not affect tumour invasion in mice, we saw a dramatic reduction in metastasis to the liver and diaphragm, indicating that fascin is potentially an interesting target against PDAC metastatic dissemination,” Machesky concludes. Indeed, the researchers have now formed a drug discovery collaboration with colleagues at the Beatson Institute to try to develop fascin inhibitors as antimetastatic agents. “As most patients with pancreatic cancer present with advanced disease, it might preclude the possibility of targeting fascin for its purported role in early disease,” Maitra cautions. “But, as the authors have elegantly shown, there is continued requirement of fascin for metastatic colonization, providing a window of therapeutic opportunity,” he adds.

Therapy: Probiotics do not reduce antibiotic-associated or Clostridium difficile diarrhoea in older hospitalized patients

Therapy: Probiotics do not reduce antibiotic-associated or Clostridium difficile diarrhoea in older hospitalized patients

Gastric cancer: new biologic therapy effective as second-line treatment in gastric cancer.

Ramucirumab—a monoclonal antibody that targets vascular endothelial growth factor receptor-2 (VEGFR-2)—has now been shown to prolong survival in patients with advanced gastric cancer whose cancer has progressed after first-line chemoradiotherapy, according to findings now published in The Lancet. Charles Fuchs and colleagues from the REGARD (ramucirumab monotherapy for previously treated advanced gastric or gastro-oesophageal junction adenocarcinoma) trial conducted a phase III study including 355 patients with advanced gastric or gastro-oesophageal junction adenocarcinoma from 29 countries worldwide. Only patients whose cancer progressed after first-line chemoradiotherapy were included in the study. Patients were randomly assigned to receive either ramucirumab (n = 238) or placebo (n = 117) at 8 mg/kg intravenously once every 2 weeks. The median overall survival was significantly greater in the ramucirumab GASTRIC CANCER

Neurogastroenterology: Colonic motor neurotransmission—is β-NAD + in control?

Normal gastrointestinal motility relies upon effective neural control, which is provided by inhibitory and excitatory motor neurons. Inhibitory neural regulation is mediated by the release of at least two neurotransmitters—nitric oxide and a purine—from intrinsic inhibitory motor neurons with cell bodies in the myenteric plexus; the purine responsible for mediating these inhibitory responses has, however, remained controversial. Findings published in Neurogastroenterology & Motility now indicate that β-nicotinamide adenine dinucleotide (β-NAD+) serves as the purinergic inhibitory neurotransmitter. Findings from previous reports had suggested that both ATP and β-NAD+ act as purinergic inhibitory neurotransmitters in the colon. “The methodological approach used in many of these studies, however, did not enable the sites of purine release to be effectively distinguished,” explains one of the authors from the study, Kenton Sanders. Here, the researchers used high-performance liquid chromatography to specifically analyse which purines were released after stimulation of the receptors expressed on motor neurons in the myenteric plexus of both mice and primates. Ganglionic stimulation yielded release of the purines ATP and β-NAD+ from the tunica muscularis of the monkey and NEUROGASTROENTEROLOGY

Microbiota: Manipulating the microbiota could affect colorectal cancer development.

“The gut microbiome is linked to various physiological functions associated with colon cancer,” explain Patrick Schloss, Grace Chen and Joseph Zackular, authors of a recent study published in mBio. “We wanted to determine whether changes in the gut microbiome are actively driving tumorigenesis or just a collateral effect of this process,” they add. To answer this question, the researchers used a mouse model of inflammationassociated colorectal cancer. Nextgeneration sequencing of the 16S rRNA gene was used to show how changes in the gut microbial community were associated with the development of tumours. Tumour-bearing mice had enrichment of Bacteroides, Odoribacter and Akkermansia genera and decreases of Prevotellaceae and Porphyromonadaceae family members when compared with healthy mice. Germ-free mice were then colonized with microbiota from either healthy or tumour-bearing mice. An increased MICROBIOTA

Neurogastroenterology: ICC act as pacemakers to control segmentation motor activity in the gut

Neurogastroenterology: ICC act as pacemakers to control segmentation motor activity in the gut