Acinar Cell Production of Leukotriene B4 Contributes to Development of Neurogenic Pancreatitis in Mice

Molecular mechanisms of pain in acute pancreatitis: recent basic research advances and therapeutic implications

Although severe abdominal pain is the main symptom of acute pancreatitis, its mechanisms are poorly understood. An emerging body of literature evidence indicates that neurogenic inflammation might play a major role in modulating the perception of pain from the pancreas. Neurogenic inflammation is the result of a crosstalk between injured pancreatic tissue and activated neurons, which leads to an auto-amplification loop between inflammation and pain during the progression of acute pancreatitis. In this review, we summarize recent findings on the role of neuropeptides, ion channels, and the endocannabinoid system in acute pancreatitis-related pain. We also highlight potential therapeutic strategies that could be applied for managing severe pain in this disease.

Membrane Lipid Derivatives: Roles of Arachidonic Acid and Its Metabolites in Pancreatic Physiology and Pathophysiology

One of the most important constituents of the cell membrane is arachidonic acid. Lipids forming part of the cellular membrane can be metabolized in a variety of cellular types of the body by a family of enzymes termed phospholipases: phospholipase A2, phospholipase C and phospholipase D. Phospholipase A2 is considered the most important enzyme type for the release of arachidonic acid. The latter is subsequently subjected to metabolization via different enzymes. Three enzymatic pathways, involving the enzymes cyclooxygenase, lipoxygenase and cytochrome P450, transform the lipid derivative into several bioactive compounds. Arachidonic acid itself plays a role as an intracellular signaling molecule. Additionally, its derivatives play critical roles in cell physiology and, moreover, are involved in the development of disease. Its metabolites comprise, predominantly, prostaglandins, thromboxanes, leukotrienes and hydroxyeicosatetraenoic acids. Their involvement in cellular responses leading to inflammation and/or cancer development is subject to intense study. This manuscript reviews the findings on the involvement of the membrane lipid derivative arachidonic acid and its metabolites in the development of pancreatitis, diabetes and/or pancreatic cancer.

Nicotinic stimulation of splenic T cells is protective in endoscopic retrograde cholangiopancreatography-induced acute pancreatitis in mice

It has previously been shown that current smoking is protective against endoscopic retrograde cholangiopancreatography (ERCP)-induced acute pancreatitis, but the mechanism of this effect was not identified. We tested the hypothesis that nicotine is the active factor in this protection in a mouse model of ERCP. Pretreatment with nicotine dose dependently inhibited acute pancreatitis caused by infusion of ERCP contrast solution into the main pancreatic duct in mice. 3-2,4-Dimethoxybenzylidene anabaseine (GTS-21), a specific partial agonist of the α7 nicotinic cholinergic receptor (α7nAChR), also protected the pancreas against ERCP-induced acute pancreatitis. The effects of GTS-21 were abolished by pretreatment with the nicotinic receptor antagonist mecamylamine. Surgical splenectomy performed 7 days before ERCP-induced pancreatitis blocked the protective effects of GTS-21. Intravenous injection of a crude preparation of total splenocytes prepared from mice pretreated with GTS-21 inhibited ERCP-induced pancreatitis; splenocytes from mice treated with vehicle had no effect. When T cells were removed from the crude GTS-21-treated splenocyte preparation by immunomagnetic separation, the remaining non-T-cell splenocytes did not protect against ERCP-induced acute pancreatitis. We conclude that nicotine protects against ERCP-induced acute pancreatitis and that splenic T cells are required for this effect. Stimulation of α7 nicotinic cholinergic receptors may protect against ERCP-induced acute pancreatitis and may also be a novel approach to therapeutic reversal of ongoing acute pancreatitis.NEW & NOTEWORTHY Epidemiological evidence indicated that acute smoking reduced the risk of endoscopic retrograde cholangiopancreatography (ERCP)-induced pancreatitis, but the mechanism has remained elusive. The current findings indicate the nicotine reduces the severity of ERCP-induced pancreatitis by stimulating a population of splenic T cells that exert a protective effect on the pancreas. These findings raise the possibility that nicotinic agonists might be useful in treating pancreatitis.

Role of Bile Acids and Bile Salts in Acute Pancreatitis: From the Experimental to Clinical Studies

ABSTRACT

Acute pancreatitis (AP) is one of the most common gastroenterological disorders leading to hospitalization. It has long been debated whether biliary AP, about 30% to 50% of all cases, is induced by bile acids (BAs) when they reach the pancreas via reflux or via the systemic blood circulation.Besides their classical function in digestion, BAs have become an attractive research target because of their recently discovered property as signaling molecules. The underlying mechanisms of BAs have been investigated in various studies. Bile acids are internalized into acinar cells through specific G-protein-coupled BA receptor 1 and various transporters. They can further act via different receptors: the farnesoid X, ryanodine, and inositol triphosphate receptor. Bile acids induce a sustained Ca2+ influx from the endoplasmic reticulum and release of Ca2+ from acidic stores into the cytosol of acinar cells. The overload of intracellular Ca2+ results in mitochondrial depolarization and subsequent acinar cell necrosis. In addition, BAs have a biphasic effect on pancreatic ductal cells. A more detailed characterization of the mechanisms through which BAs contribute to the disease pathogenesis and severity will greatly improve our understanding of the underlying pathophysiology and may allow for the development of therapeutic and preventive strategies for gallstone-inducedAP.

Involvement of Neural Transient Receptor Potential Channels in Peripheral Inflammation

Transient receptor potential (TRP) channels are a superfamily of non-selective cation channels that act as polymodal sensors in many tissues throughout mammalian organisms. In the context of ion channels, they are unique for their broad diversity of activation mechanisms and their cation selectivity. TRP channels are involved in a diverse range of physiological processes including chemical sensing, nociception, and mediating cytokine release. They also play an important role in the regulation of inflammation through sensory function and the release of neuropeptides. In this review, we discuss the functional contribution of a subset of TRP channels (TRPV1, TRPV4, TRPM3, TRPM8, and TRPA1) that are involved in the body’s immune responses, particularly in relation to inflammation. We focus on these five TRP channels because, in addition to being expressed in many somatic cell types, these channels are also expressed on peripheral ganglia and nerves that innervate visceral organs and tissues throughout the body. Activation of these neural TRP channels enables crosstalk between neurons, immune cells, and epithelial cells to regulate a wide range of inflammatory actions. TRP channels act either through direct effects on cation levels or through indirect modulation of intracellular pathways to trigger pro- or anti-inflammatory mechanisms, depending on the inflammatory disease context. The expression of TRP channels on both neural and immune cells has made them an attractive drug target in diseases involving inflammation. Future work in this domain will likely yield important new pathways and therapies for the treatment of a broad range of disorders including colitis, dermatitis, sepsis, asthma, and pain.

Extracellular release of ATP promotes systemic inflammation during acute pancreatitis

In the current study, we explored the role of extracellular ATP (eATP) in promoting systemic inflammation during development of acute pancreatitis (AP). Release of extracellular (e)ATP was evaluated in plasma and bronchoalveolar lavage fluid (BALF) of mice with experimental acute pancreatitis (AP). Prophylactic intervention using apyrase or suramin was used to understand the role and contribution of eATP in pancreatitis-associated systemic injury. AP of varying severity was induced in C57BL/6 mice using 1-day or 2-day caerulein, caerulein + LPS and l-arginine models. eATP was measured in plasma and BALF. Mice were treated with suramin or apyrase in the caerulein and l-arginine models of AP. Plasma cytokines, lung, and pancreatic myeloperoxidase, and morphometric analysis of pancreatic and lung histology, were used to assess the severity of pancreatitis. Plasma eATP and purinergic 2 (P2) receptors in the pancreas and lungs were significantly elevated in the experimental models of AP. Blocking the effect of eATP by suramin led to reduced levels of plasma IL-6 and TNFα as well as reduced lung, and pancreatic injury. Neutralizing eATP with apyrase reduced systemic injury but did not ameliorate local injury. The results of this study support the role of eATP and P2 receptors in promoting systemic inflammation during AP. Modulating purinergic signaling during AP can be an important therapeutic strategy in controlling systemic inflammation and, thus, systemic inflammatory response syndrome during AP.NEW & NOTEWORTHY Released ATP from injured cells promotes systemic inflammation in acute pancreatitis.

The Role of Transient Receptor Potential Vanilloid 1 in Common Diseases of the Digestive Tract and the Cardiovascular and Respiratory System

Transient receptor potential vanilloid subtype 1 (TRPV1), a member of the transient receptor potential vanilloid (TRPV) channel family, is a nonselective cation channel that is widely expressed in sensory nerve fibers and nonneuronal cells, including certain vascular endothelial cells and smooth muscle cells. The activation of TRPV1 may be involved in the regulation of various physiological functions, such as the release of inflammatory mediators in the body, gastrointestinal motility function, and temperature regulation. In recent years, a large number of studies have revealed that TRPV1 plays an important role in the physiological and pathological conditions of the digestive system, cardiovascular system, and respiratory system, but there is no systematic report on TRPV1. The objective of this review is to explain the function and effects of TRPV1 on specific diseases, such as irritable bowel syndrome, hypertension, and asthma, and to further investigate the intrinsic relationship between the expression and function of TRPV1 in those diseases to find new therapeutic targets for the cure of related diseases.

Animal Models: Challenges and Opportunities to Determine Optimal Experimental Models of Pancreatitis and Pancreatic Cancer

At the 2018 PancreasFest meeting, experts participating in basic research met to discuss the plethora of available animal models for studying exocrine pancreatic disease. In particular, the discussion focused on the challenges currently facing the field and potential solutions. That meeting culminated in this review, which describes the advantages and limitations of both common and infrequently used models of exocrine pancreatic disease, namely, pancreatitis and exocrine pancreatic cancer. The objective is to provide a comprehensive description of the available models but also to provide investigators with guidance in the application of these models to investigate both environmental and genetic contributions to exocrine pancreatic disease. The content covers both nongenic and genetically engineered models across multiple species (large and small). Recommendations for choosing the appropriate model as well as how to conduct and present results are provided.

Piezo1 is a mechanically activated ion channel and mediates pressure induced pancreatitis

Merely touching the pancreas can lead to premature zymogen activation and pancreatitis but the mechanism is not completely understood. Here we demonstrate that pancreatic acinar cells express the mechanoreceptor Piezo1 and application of pressure within the gland produces pancreatitis. To determine if this effect is through Piezo1 activation, we induce pancreatitis by intrapancreatic duct instillation of the Piezo1 agonist Yoda1. Pancreatitis induced by pressure within the gland is prevented by a Piezo1 antagonist. In pancreatic acinar cells, Yoda1 stimulates calcium influx and induces calcium-dependent pancreatic injury. Finally, selective acinar cell-specific genetic deletion of Piezo1 protects mice against pressure-induced pancreatitis. Thus, activation of Piezo1 in pancreatic acinar cells is a mechanism for pancreatitis and may explain why pancreatitis develops following pressure on the gland as in abdominal trauma, pancreatic duct obstruction, pancreatography, or pancreatic surgery. Piezo1 blockade may prevent pancreatitis when manipulation of the gland is anticipated.

Manipulation of the pancreas during surgery can induce acute pancreatitis due to zymogen activation. Here the authors show that the mechanoreceptor Piezo1 is activated by pressure and its activation leads to calcium dependent pancreatic injury whereas its inhibition is protective against pancreatitis.

Substance P-regulated leukotriene B4 production promotes acute pancreatitis-associated lung injury through neutrophil reverse migration

Leukotriene B4 (LTB4) is a potent chemoattractant and inflammatory mediator involved in multiple inflammatory diseases. Substance P (SP) has been reported to promote production of LTB4 in itch-associated response in vivo and in some immune cells in vitro. Here, we investigated the role of LTB4 in acute pancreatitis (AP), AP-associated acute lung injury (ALI) and the related mechanisms of LTB4 production in AP. In vivo, murine AP model was induced by caerulein and lipopolysaccharide or L-arginine. The levels of LTB4 and its specific receptor BLT1 were markedly upregulated in both AP models. Blockade of BLT1 by LY293111 attenuated the severity of AP, decreased neutrophil reverse transendothelial cell migration (rTEM) into the circulation and alleviated the severity of ALI. In vitro, treatment of pancreatic acinar cells with SP increased LTB4 production. Furthermore, SP treatment increased phosphorylation of protein kinase C (PKC) α and mitogen activated protein kinases (MAPKs), including extracellular signal-regulated kinase (ERK), p-38 MAPK and c-Jun NH2-terminal kinase (JNK). Finally, blockade of neurokinin-1 receptor by CP96345 significantly attenuated the severity of AP and decreased the level of LTB4 when compared to AP group. In summary, these results show that SP regulates the production of LTB4 via PKCα/MAPK pathway, which further promotes AP-associated ALI through neutrophil rTEM.

Leukotriene B4 induces EMT and vimentin expression in PANC-1 pancreatic cancer cells: Involvement of BLT2 via ERK2 activation

Leukotriene B₄ (LTB₄) is a leukocyte chemoattractant and plays a major role controlling inflammatory responses including pancreatitis. LTB₄ is known to be correlated with cancer progression. LTB₄ induces keratin phosphorylation and reorganization by activating extracellular regulated kinase (ERK) in PANC-1 pancreatic cancer cell lines. However, the role of LTB₄ in epithelial mesenchymal transition (EMT) and vimentin expression in pancreatic cancer cells is unknown. We examined whether LTB₄ induces EMT and vimentin expression by Western blot, si-RNA, and RT-PCR. LTB₄ induced morphological change, decreased E-cadherin expression and increased N-cadherin and vimentin expression. LTB4 increased migration and invasion of PANC-1 cancer cells. LTB₄ dose-dependently upregulated expression of vimentin in PANC-1 cancer cells. LTB₄-induced vimentin expression was suppressed by LY255283 (BLT2 antagonist). Comp A, a BLT2 agonist, further increased vimentin expression. Gene silencing of BLT2 suppressed LTB₄-or Comp A-induced vimentin expression in PANC-1 cells. The MEK inhibitor, PD98059 suppressed Comp A-induced vimentin expression. Comp A or transfection of plasmid containing BLT2 cDNA (pC_BLT2) activated ERK, and BLT2 gene silencing suppressed Comp A-induced ERK activation. ERK2 siRNA abrogated Comp A-induced vimentin expression and ERK2 overexpression enhanced vimentin expression. One of well-known cause of ras mutation, cigarette smoke extracts increased BLT2 expression in PANC-1 cancer cells. Taken together, these results suggest that BLT2 is involved in LTB₄-induced vimentin expression through ERK2 in PANC-1 cells.