Down-regulation of aquaporin 1 in rats with experimental acute necrotizing pancreatitis

Construction and validation of a rat model of acute necrotizing pancreatitis-associated intestinal injury

Acute pancreatitis (AP) is an acute inflammatory reaction of the pancreatic tissue, which involves auto-digestion, edema, hemorrhage, and necrosis. AP can be categorized into mild, moderately severe, and severe AP, with severe pancreatitis also referred to as acute necrotizing pancreatitis (ANP). ANP is characterized by the accumulation of necrotic material in the peritoneal cavity. This can result in intestinal injury. However, the mechanism of ANP-associated intestinal injury remains unclear. We established an ANP-associated intestinal injury rat model (ANP-IR model) by injecting pancreatitis-associated ascites fluid (PAAF) and necrotic pancreatic tissue at various proportions into the triangular area formed by the left renal artery and ureter. The feasibility of the ANP-IR model was verified by comparing the similar changes in indicators of intestinal inflammation and barrier function between the two rat models. In addition, we detected changes in apoptosis levels and YAP protein expression in the ileal tissues of rats in each group and validated them in vitro in rat epithelial crypt cells (IEC-6) to further explore the potential injury mechanisms of ANP-associated intestinal injury. We also collected clinical data from patients with ANP to validate the effects of PAAF and pancreatic necrosis on intestinal injury. Our findings offer a theoretical basis for restricting the buildup of peritoneal necrosis in individuals with ANP, thus promoting the restoration of intestinal function and enhancing treatment efficacy. The use of the ANP-IR model in further studies can help us better understand the mechanism and treatment of ANP-associated intestinal injury.NEW & NOTEWORTHY We constructed a rat model of acute necrotizing pancreatitis-associated intestinal injury and verified its feasibility. In addition, we identified the mechanism by which necrotic pancreatic tissue and pancreatitis-associated ascites fluid (PAAF) cause intestinal injury through the HIPPO signaling pathway.

Insights into the Function of Aquaporins in Gastrointestinal Fluid Absorption and Secretion in Health and Disease

Aquaporins (AQPs), transmembrane proteins permeable to water, are involved in gastrointestinal secretion. The secretory products of the glands are delivered either to some organ cavities for exocrine glands or to the bloodstream for endocrine glands. The main secretory glands being part of the gastrointestinal system are salivary glands, gastric glands, duodenal Brunner's gland, liver, bile ducts, gallbladder, intestinal goblet cells, exocrine and endocrine pancreas. Due to their expression in gastrointestinal exocrine and endocrine glands, AQPs fulfill important roles in the secretion of various fluids involved in food handling. This review summarizes the contribution of AQPs in physiological and pathophysiological stages related to gastrointestinal secretion.

The Mechanism of Lung and Intestinal Injury in Acute Pancreatitis: A Review

Acute pancreatitis (AP), as a common cause of clinical acute abdomen, often leads to multi-organ damage. In the process of severe AP, the lungs and intestines are the most easily affected organs aside the pancreas. These organ damages occur in succession. Notably, lung and intestinal injuries are closely linked. Damage to ML, which transports immune cells, intestinal fluid, chyle, and toxic components (including toxins, trypsin, and activated cytokines to the systemic circulation in AP) may be connected to AP. This process can lead to the pathological changes of hyperosmotic edema of the lung, an increase in alveolar fluid level, destruction of the intestinal mucosal structure, and impairment of intestinal mucosal permeability. The underlying mechanisms of the correlation between lung and intestinal injuries are inflammatory response, oxidative stress, and endocrine hormone secretion disorders. The main signaling pathways of lung and intestinal injuries are TNF-α, HMGB1-mediated inflammation amplification effect of NF-κB signal pathway, Nrf2/ARE oxidative stress response signaling pathway, and IL-6-mediated JAK2/STAT3 signaling pathway. These pathways exert anti-inflammatory response and anti-oxidative stress, inhibit cell proliferation, and promote apoptosis. The interaction is consistent with the traditional Chinese medicine theory of the lung being connected with the large intestine (fei yu da chang xiang biao li in Chinese). This review sought to explore intersecting mechanisms of lung and intestinal injuries in AP to develop new treatment strategies.

Intravenous injection of human multilineage-differentiating stress-enduring cells alleviates mouse severe acute pancreatitis without immunosuppressants

INTRODUCTION

We examined the effect of intravenously injected human multilineage-differentiating stress-enduring (Muse) cells, non-tumorigenic endogenous reparative stem cells already used in clinical trials, on a severe acute pancreatitis (SAP) mouse model without immunosuppressants.

METHODS

Human Muse cells (1.0 × 105 cells) collected from mesenchymal stem cells (MSCs) as SSEA-3(+) were injected into a C57BL/6 mouse model via the jugular vein 6 h after SAP-induction with taurocholate. The control group received saline or the same number of SSEA-3(-)-non-Muse MSCs.

RESULTS

Edematous parameters, F4/80(+) macrophage infiltration and terminal deoxynucleotidyl transferase dUTP nick-end labeling positivity was the lowest and the number of proliferating endogenous pancreatic progenitors (CK18(+)/Ki67(+) cells) the highest in the Muse group among the three groups, with statistical significance, at 72 h. An enzyme-linked immunosorbent assay and quantitative polymerase chain reaction demonstrated that in vitro production of VEGF, HGF, IGF-1, and MMP-2, which are relevant to tissue protection, anti-inflammation, and anti-fibrosis, were higher in Muse cells than in non-Muse MSCs, particularly when cells were cultured in SAP mouse serum. Consistently, the pancreas of animals in the Muse group contained higher amounts of those factors according to Western blotting at 18 h than that in the non-Muse MSCs and control groups.

CONCLUSIONS

Intravenous injection of human Muse cells was suggested to be effective for attenuating edema, inflammation and apoptosis in the acute phase of SAP.

The regulatory roles of aquaporins in the digestive system

Aquaporins (AQPs) are highly conserved small transmembrane proteins, which are responsible for the water transport across the cell membrane. AQPs are abundantly expressed in numerous types of cells such as epithelial and endothelial cells. The expression of AQP-1, -3, -4, -5, -8 and -9 were found in the digestive system, where these six AQP isoforms serve essential roles including mediating the transmembrane water transport and regulating the secretion of gastrointestinal (GI) fluids, consequently facilitating the digestion and absorption of GI contents. In addition, the expression levels of AQPs are controlled by various factors, and AQPs can stimulate numerous signaling pathways; however, aberrant expression of AQPs in the GI tracts are associated with the initiation and development of numerous diseases. Thus, this review provides an overview of the expression and functions of AQPs in the digestive system.

Current status of diagnosis and Mesenchymal stem cells therapy for acute pancreatitis

Acute pancreatitis (AP) is an acute gastrointestinal disorder that is the most common and requiring emergency hospitalization. Its incidence is increasing worldwide, thus increasing the burden of medical services. Approximately 20% of the patients develop moderate to severe necrotizing pancreatitis associated with pancreatic or peri-pancreatic tissue necrosis and multiple organ failure. There are many reports about the anti-inflammatory effect of mesenchymal stem cells (MSCs) on pancreatitis and the repair of tissue damage. MSCs cells come from a wide range of sources, autologous MSCs come from bone marrow and allogeneic MSCs such as umbilical cord blood MSCs, placenta-derived MSCs, etc. The wide source is not only an advantage of MSCs but also a disadvantage of MSCs. Because of different cell sources and different methods of collection and preparation, it is impossible to establish a unified standard method for evaluation of efficacy. The biggest advantage of iMSCs is that it can be prepared by a standardized process, and can be prepared on a large scale, which makes it easier to commercialize. This paper reviews the present status of diagnosis and progress of MSCs therapy for AP.

Aquaporins Involvement in Pancreas Physiology and in Pancreatic Diseases

Aquaporins are a family of transmembrane proteins permeable to water. In mammals, they are subdivided into classical aquaporins that are permeable to water; aquaglyceroporins that are permeable to water, glycerol and urea; peroxiporins that facilitate the diffusion of H2O2 through cell membranes; and so called unorthodox aquaporins. Aquaporins ensure important physiological functions in both exocrine and endocrine pancreas. Indeed, they are involved in pancreatic fluid secretion and insulin secretion. Modification of aquaporin expression and/or subcellular localization may be involved in the pathogenesis of pancreatic insufficiencies, diabetes and pancreatic cancer. Aquaporins may represent useful drug targets for the treatment of pathophysiological conditions affecting pancreatic function, and/or diagnostic/predictive biomarker for pancreatic cancer. This review summarizes the current knowledge related to the involvement of aquaporins in the pancreas physiology and physiopathology.

Free Total Rhubarb Anthraquinones Protect Intestinal Injury via Regulation of the Intestinal Immune Response in a Rat Model of Severe Acute Pancreatitis

Intestinal mucosal immune barrier dysfunction plays a key role in the pathogenesis of severe acute pancreatitis (SAP). Rhubarb is a commonly used traditional Chinese medicine as a laxative in China. It markedly protects pancreatic acinar cells from trypsin-induced injury in rats. Free total rhubarb anthraquinones (FTRAs) isolated and extracted from rhubarb display the beneficial effects of antibacteria, anti-inflammation, antivirus, and anticancer. The principal aim of the present study was to investigate the effects of FTRAs on the protection of intestinal injury and modification of the intestinal barrier function through regulation of intestinal immune function in rats with SAP. We established a rat model of SAP by injecting 3.5% sodium taurocholate (STC, 350 mg/kg) into the biliopancreatic duct via retrograde injection and treated the rats with FTRAs (36 or 72 mg/kg) or normal saline (control) immediately and 12 h after STC injection. Then, we evaluated the protective effect of FTRAs on intestinal injury by pathological analysis and determined the levels of endotoxin (ET), interleukin 1β (IL-1β), tumor necrosis factor α (TNF-α), nitric oxide (NO), myeloperoxidase (MPO), capillary permeability, nucleotide-binding oligomerization domain-like receptors 3 (NLRP3), apoptosis-associated speck-like protein containing a CARD domain (ASC), casepase-1, secretary immunoglobulin A (SIgA), regulatory T cells (Tregs), and the ratio of Th1/Th2 in the blood and/or small intestinal tissues or mesenteric lymph node (MLN) cells. Moreover, the chemical profile of FTRAs was analyzed by HPLC-UV chromatogram. The results showed that FTRAs significantly protected intestinal damage and decreased the levels of ET, IL-1β, TNF-α, and NO in the blood and TNF-α, IL-1β, and protein extravasation in the intestinal tissues in SAP rats. Furthermore, FTRAs significantly decreased the expressions of NLRP3, ASC, and caspase-1, the number of Tregs and the ratio of Th1/Th2, while significantly increased the expression of SIgA in the intestinal tissues and/or MLN cells in SAP rats. Our results indicate that FTRAs could protect intestinal injury and improve intestinal mucosal barrier function through regulating immune function of SAP rats. Therefore, FTRAs may have the potential to be developed as the novel agent for the treatment of SAP clinically.

Effect of mesenchymal stem cells on small intestinal injury in a rat model of acute necrotizing pancreatitis

BACKGROUND

Acute necrotizing pancreatitis (ANP) is often complicated by multiple organ failure. The small intestine is frequently damaged during ANP. Capillary leakage in multiple organs during ANP is one of the most important causes of multiple organ dysfunction. Damage to the capillary endothelial barrier and impaired water transportation could lead to capillary leakage in ANP.

METHODS

Sprague-Dawley (SD) rats were randomized into a control group, the ANP group, the culture media-treated group, or the bone marrow-derived mesenchymal stem cell (BMSC)-treated group (30 rats in each group). Ten rats in each group were sacrificed at 6, 12, and 24 h after induction of experimental models. Serum, ascites, pancreatic, and small intestinal samples were collected. The levels of serum and ascites albumin and amylases were measured, pancreatic histology was assessed, and the connection changes between vessel endothelial cells were evaluated using scanning electron microscopy (SEM). Capillary leakage in small intestinal tissue was observed visually by tracking fluorescein isothiocyanate (FITC)-albumin, and was measured by the Evans blue extravasation method. The location and expression of aquaporin 1 (AQP1) in the small intestine was analyzed using immunohistochemistry, real-time polymerase chain reaction (PCR), and Western blot.

RESULTS

The outcomes showed that the level of serum and ascites amylase is elevated. Conversely, the level of serum albumin is decreased while ascites albumin is elevated. There is damage to pancreatic tissue, and the small intestinal capillary endothelial barrier was aggravated. Furthermore, the expression of AQP1 was reduced significantly after induced ANP. Following treatment with MSCs, the elevation of amylase and the decrease of serum albumin were inhibited, the damage to pancreatic tissue and the level of small intestinal capillary leakage was alleviated, and the downregulation of AQP1 was reversed.

CONCLUSIONS

In conclusion, MSC therapy could alleviate small intestinal injury in rats with ANP, the mechanism of which might be related to reduction of damage to the small intestinal capillary endothelial barrier, and increased expression of AQP1 in the small intestine.

Aquaporins in Cardiovascular System

Recent studies have shown that some aquaporins (AQPs ), including AQP1, AQP4, AQP7 and AQP9, are expressed in endothelial cells, vascular smooth muscle cells and heart of cardiovascular system. These AQPs are involved in the cardiovascular function and in pathological process of related diseases, such as cerebral ischemia , congestion heart failure , hypertension and angiogenesis. Therefore, it is important to understand the accurate association between AQPs and cardiovascular system, which may provide novel approaches to prevent and treat related diseases. Here we will discuss the expression and physiological function of AQPs in cardiovascular system and summarize recent researches on AQPs related cardiovascular diseases.

Effect of mesenchymal stem cells on renal injury in rats with severe acute pancreatitis

The aim of this study was to preliminarily investigate the effect of bone marrow mesenchymal stem cells (MSCs) on structural change of capillary endothelial barrier and expression variation of aquaporin 1 (AQP1) in kidney at the onset of renal injury caused by severe acute pancreatitis (SAP). Ninety male Sprague-Dawley (SD) rats were divided into the control group, the SAP group in which animals received induction of SAP and the MSCs-treated group in which SAP-induced animals were injected with MSCs. They were further subdivided according to the time point that the animals were killed; 6 h, 12 h and 24 h after the closure of the incision, serum, pancreatic and renal samples were collected, respectively. The level of serum amylase (AMY), creatinine (Cr) and blood urea nitrogen (BUN) were analysed, the change of pancreatic histology was assessed, the structural change of the renal interstitial capillaries was evaluated using the transmission electron microscope (TEM) and the location and expression of AQP1 in kidney were analysed using immunohistochemistry, quantitative polymerase chain reaction and Western blot. The outcomes showed that the level of serum AMY, Cr, BUN elevated, the damage of pancreatic tissue and renal capillary endothelial barrier was aggravated and the expression of AQP1 was reduced significantly after induced pancreatitis. But after treatments with MSCs, the elevation of AMY, Cr and BUN was inhibited, the damage of pancreatic tissue and renal interstitial capillary barrier was alleviated and the down-regulation of AQP1 was reversed. In summary, the MSCs therapy could alleviate renal injury in rats with SAP, the mechanism of which might be related to reduction of the damage to renal interstitial capillary endothelial barrier, and up-expression of AQP1 in kidney.

Models of acute and chronic pancreatitis

Animal models of acute and chronic pancreatitis have been created to examine mechanisms of pathogenesis, test therapeutic interventions, and study the influence of inflammation on the development of pancreatic cancer. In vitro models can be used to study early stage, short-term processes that involve acinar cell responses. Rodent models reproducibly develop mild or severe disease. One of the most commonly used pancreatitis models is created by administration of supraphysiologic concentrations of caerulein, an ortholog of cholecystokinin. Induction of chronic pancreatitis with factors thought to have a role in human disease, such as combinations of lipopolysaccharide and chronic ethanol feeding, might be relevant to human disease. Models of autoimmune chronic pancreatitis have also been developed. Most models, particularly of chronic pancreatitis, require further characterization to determine which features of human disease they include.