Severity Of Acute Pancreatitis In Mice Research Articles

Emodin nanocapsules inhibit acute pancreatitis by regulating lipid metabolic reprogramming in macrophage polarization

BackgroundEmodin is a chemical compound found in traditional Chinese herbs. It possesses anti-inflammatory and many other pharmacological effects. Our previous study showed that emodin significantly alleviates the inflammation effect of severe acute pancreatitis (SAP). However, its poor solubility, high toxicity and limited pancreas retention time hinder its clinical application. PurposeWe aimed to prepare emodin nanocapsules with improved bioavailability to achieve the controlled release of emodin by targeting macrophages. Further, the mechanism of mannose-conjugated chitosan-coated lipid nanocapsules loaded with emodin (M-CS-E-LNC) in the treatment of SAP was explored. MethodsM-CS-E-LNC were prepared by the phase inversion method with slight modification. The expression of inflammation mediators and the anti-inflammation efficacy of M-CS-E-LNC were examined by ELISA, IHC and IF in macrophage cells and LPS-induced SAP mice. IVIS spectrum imaging and HPLC were applied to explore the controlled release of M-CS-E-LNC in the pancreas. LC-MS/MS was performed for lipidomics analysis of macrophages. Moreover, a vector-based short hairpin RNA (shRNA) method was used to silence CTP1 gene expression in macrophage cells. ResultsThe levels of inflammatory mediators in macrophages were markedly decreased after treatment with M-CS-E-LNC. The same anti-inflammation effects were detected in SAP mouse through the analysis of serum levels of amylase, TNF-α and IL-6. Importantly, M-CS-E-LNC allowed the emodin to selectively accumulate at pancreas and gastrointestinal tissues, thus exhibiting a targeted release. Mechanistically, the M-CS-E-LNC treatment group showed up-regulated expression of the carnitine palmitoyltransferase 1 (CPT1) protein which promoted intracellular long-chain fatty acid transport, thereby promoting the M2 phenotype polarization of macrophages. ConclusionM-CS-E-LNC exhibited significantly improved bioavailability and water solubility, which translated to greater therapeutic effects on macrophage polarization. Our findings also demonstrate, for the first time, that CPT1 may be a new therapeutic target for SAP treatment.

Melatonin ameliorates multiorgan injuries induced by severe acute pancreatitis in mice by regulating the Nrf2 signaling pathway

Severe acute pancreatitis (SAP) is a complicated inflammatory reaction that impacts the pancreas, often resulting in damage to numerous organs. This disorder encompasses a range of processes such as inflammation, oxidative stress, and pancreatitis. The hormone melatonin (MT) is primarily secreted by the pineal gland and plays a crucial role in mitigating inflammation, countering the harmful effects of free radicals, and regulating oxidative stress. The aim of this research was to investigate the potential protective impact and the underlying mechanism of melatonin in mice afflicted with SAP. The biochemical and histological assessments unequivocally demonstrated that melatonin effectively inhibited necrosis, infiltration, edema and cell death in pancreatic tissues, thereby suppressing acute pancreatitis. Notably, melatonin also alleviated the consequent harm to distant organs, notably the lungs, liver, and kidneys. Furthermore, both preventive and therapeutic administration of melatonin prompted nuclear factor E2-related factor 2 (Nrf2) activation followed by Nrf2 target gene expression. Nrf2 initiates the activation of antioxidant genes, thereby providing defense against oxidative stress. Conversely, Nrf2 reduction may contribute to impaired antioxidant protection in SAP. The beneficial impact of Nrf2 on antioxidants was absent in Nrf2-knockout mice, leading to the accumulation of LDH and exacerbation of cell death. This deterioration in both pancreatitis and injuries in distant organs intensified significantly. The results indicate that melatonin has an enhanced ability to protect against multiorgan damage caused by SAP, which is accomplished through the increase in Nrf2 expression. Additionally, Nrf2 initiates the activation of antioxidant genes that offer defense against cell death.

HP-MSCs attenuate severe acute pancreatitis in mice via inhibiting NLRP3 inflammasome-mediated acinar cell pyroptosis.

Severe acute pancreatitis (SAP) is a serious gastrointestinal disease that is facilitated by pancreatic acinar cell death. The protective role of human placental mesenchymal stem cells (hP-MSCs) in SAP has been demonstrated in our previous studies. However, the underlying mechanisms of this therapy remain unclear. Herein, we investigated the regularity of acinar cell pyroptosis during SAP and investigated whether the protective effect of hP-MSCs was associated with the inhibition of acinar cell pyroptosis. A mouse model of SAP was established by the retrograde injection of sodium taurocholate (NaTC) solution in the pancreatic duct. For the hP-MSCs group, hP-MSCs were injected via the tail vein and were monitored in vivo. Transmission electron microscopy (TEM) was used to observe the pyroptosis-associated ultramorphology of acinar cells. Immunofluorescence and Western blotting were subsequently used to assess the localization and expression of pyroptosis-associated proteins in acinar cells. Systemic inflammation and local injury-associated parameters were evaluated. Acinar cell pyroptosis was observed during SAP, and the expression of pyroptosis-associated proteins initially increased, peaked at 24h, and subsequently showed a decreasing trend. hP-MSCs effectively attenuated systemic inflammation and local injury in the SAP model mice. Importantly, hP-MSCs decreased the expression of pyroptosis-associated proteins and the activity of the NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome in acinar cells. Our study demonstrates the regularity and important role of acinar cell pyroptosis during SAP. hP-MSCs attenuate inflammation and inhibit acinar cell pyroptosis via suppressing NLRP3 inflammasome activation, thereby exerting a protective effect against SAP.

NLRC4-mediated pyroptosis was involved in coagulation disorders of acute pancreatitis.

Acute pancreatitis (AP) is a potentially lethal acute disease highly involved in coagulation disorders. Pyroptosis has been reported to exacerbate coagulation disorders, yet this implication has not been illustrated completely in AP. RNA sequencing data of peripheral blood of AP patients were downloaded from the Gene Expression Omnibus database. Gene set variation analysis and single sample gene set enrichment analysis were used to calculate the enrichment score of coagulation-related signatures and pyroptosis. Spearman and Pearson correlation analysis was used for correlation analysis. Peripheral blood samples and related clinical parameters were collected from patients with AP and healthy individuals. A severe AP (SAP) model of mice was established using caerulein and lipopolysaccharide. Enzyme-linked immunosorbent assay, chemiluminescence immunoassay and immunohistochemical analysis were employed to detect the level of coagulation indicators and pyroptosis markers in serum and pancreas tissues. Additionally, we evaluated the effect of pyroptosis inhibition and NLRC4 silence on the function of human umbilical vein endothelial cells (HUVECs). Coagulation disorders were significantly positively correlated to the severity of AP, and they could be a predictor for AP severity. Further analyses indicated that six genes-DOCK9, GATA3, FCER1G, NLRC4, C1QB and C1QC-may be involved in coagulation disorders of AP. Among them, NLRC4 was positively related to pyroptosis that had a positive association with most coagulation-related signatures. Data from patients showed that NLRC4 and other pyroptosis markers, including IL-1β, IL-18, caspase1 and GSDMD, were significant correlation to AP severity. In addition, NLRC4 was positively associated with coagulation indicators in AP patients. Data from mice showed that NLRC4 was increased in the pancreas tissues of SAP mice. Treatment with a pyroptosis inhibitor effectively alleviated SAP and coagulation disorders in mice. Finally, inhibiting pyroptosis or silencing NLRC4 could relieve endothelial dysfunction in HUVECs. NLRC4-mediated pyroptosis damages the function of endothelial cells and thereby exacerbates coagulation disorders of AP. Inhibiting pyroptosis could improve coagulation function and alleviate AP.

High expression of P-selectin induces neutrophil extracellular traps via the PSGL-1/Syk/Ca2+/PAD4 pathway to exacerbate acute pancreatitis.

Excessive neutrophil extracellular traps (NETs) is involved in the progression of acute pancreatitis (AP) but the mechanisms controlling NETs formation in AP are not fully understood. Therefore, our study sought to investigate the mechanism of the highly expressed P-selectin stimulating the formation of NETs in AP. NETs formation was detected by flow cytometry, immunofluorescence staining, and cf-DNA and MPO-DNA complexes were measured as biomarkers of NETs formation. Neutrophils treated with P-selectin and pharmacological inhibitors were examined by western blot, immunofluorescence staining and flow cytometry. Mouse model of AP was established by caerulein and the effect of inhibiting P-selectin by PSI-697 on the level of NETs and PAD4 in pancreatic tissue was observed. The severity of AP was evaluated by histopathological score and the detection of serum amylase and lipase. Patients with AP had elevated levels of NETs and P-selectin compared with healthy volunteers. Stimulation of P-selectin up-regulated the expression of PSGL-1, increased the phosphorylation of Syk, mediated intracellular calcium signal and led to the activation and expression of PAD4, which modulated NETs formation in neutrophils. Pretreament with PSI-697 blunted NETs formation and PAD4 expression in the pancreatic tissue, and ameliorated the severity of AP in mice. Taken together, these results suggest that P-selectin induces NETs through PSGL-1 and its downstream Syk/Ca2+/PAD4 signaling pathway, and that targeting this pathway might be a promising strategy for the treatment of AP.

HDAC3 improves intestinal function of mice by regulating cGAS-Sting pathway of intestinal glial cells

It is found that HDAC3 may be a potential therapeutic target for intestinal related diseases. At present, the role and mechanism of HDAC3 in the pathogenesis of severe acute pancreatitis (SAP) have not been reported, which needs to be further explored. The SAP mouse model was established and the expression of HDAC3 was detected by immunohistochemistry. H&E staining showed the intestinal pathological state of SAP mice. The expression of HDAC3 was measured by real-time quantitative PCR (RT qPCR) and Western blot. Apoptosis kit was used to determine cell apoptosis rate. The level of inflammatory factors was detected by ELISA kits. The expressions of HDAC3, cGAS and Sting were significantly increased in SAP patients and SAP mice. Silencing HDAC3 promoted the proliferation and adhesion of intestinal glial cells and inhibited the inflammation and apoptosis of intestinal epithelial cells. In addition, silencing HDAC3 inhibited oxidative stress in intestinal epithelial cells. Furthermore, silencing HDAC3 inhibited the activation of cGAS-Sting pathway in intestinal glial cells. More importantly, silencing HDAC3 alleviates intestinal barrier function in SAP mice. HDAC3 inhibition improves acute pancreatitis in mice by regulating cGAS-Sting pathway of intestinal glial cells.

Fenbufen Alleviates Severe Acute Pancreatitis by Suppressing Caspase-1/Caspase-11-mediated Pyroptosis in Mice.

In the present study, we aimed to investigate the effects of Fenbufen treatment on the SAP model induced by caerulein and lipopolysaccharide. Severe acute pancreatitis (SAP) is an extremely dangerous disease with high mortality, which is associated with inflammatory response and acinar cell death. The caspase family plays an important role in cell death, such as caspase-1 and caspase-11 in pyroptosis. In recent years, caspases have been shown to be a novel pharmacological target of Fenbufen. Effects of Fenbufen on pancreatic tissue damage and serum levels of lipase and amylase in SAP in mice; Effect of Fenbufen on caspase-1 pathway in SAP in mice; Effect of Fenbufen on caspase-1/caspase-11-mediated pyroptosis of PACs in SAP in mice; Effect of Fenbufen on isolated PACs and caspase-1/caspase-11-mediated pyroptosis in vitro. In vivo, eighteen female C57BL/6 mice were randomly divided into 3 groups: the NC group, the SAP group, and the Fenbufen +SAP group with 6 mice in each group. The SAP model was induced by intraperitoneal injection of caerulein and lipopolysaccharide. The pathological changes in pancreatic and the serum levels of lipase and amylase and the relative gene and protein expressions in each group were compared. In vitro, pancreatic acinar cells were assigned to 5 groups: medium group, SAP group, Fenbufen 100μM group, Fenbufen 200μM group, and Fenbufen 400μM group. The cell damage and the relative gene and protein expressions in each group were evaluated. Our results showed that Fenbufen ameliorated the severity of SAP and decreased the serum levels of lipase and amylase. Meanwhile, the in vivo and in vitro data demonstrated that Fenbufen inhibited the activation of caspase-1 and caspase-11, decreasing the levels of IL-1β, IL-18, and GSDMD. In in vitro experiments, we found that by inhibiting the activation of caspase-1 and caspase-11, Fenbufen significantly reduced lactate dehydrogenase (LDH) excretion by acinar cells. In general, our data showed that Fenbufen could protect the pancreatic acinar cell from injury by inhibiting pyroptosis.

CEBPB promotes gastrointestinal motility dysfunction after severe acute pancreatitis via the MALAT1/CIRBP/ERK axis.

Severe acute pancreatitis (SAP) is a kind of reversible inflammatory process of the exocrine pancreas with gastrointestinal motility dysfunction involved. Studies have highlighted the role of long noncoding RNA metastasis associated lung adenocarcinoma transcript 1 (MALAT1) in AP. However, the mechanism underlying its role in the gastrointestinal motility dysfunction remains undefined. Hence, we explored the regulatory role of MALAT1 in gastrointestinal motility dysfunction following SAP. Then, the expression of CCAAT/enhancer-binding protein beta (CEBPB), MALAT1 and cold-inducible RNA binding protein (CIRBP) was detected in plasma of SAP patients and pancreatic and intestinal tissues of SAP mouse models with their correlation analyzed also. Additionally, the effect of MALAT1 on the pancreatic and intestinal injury, expression of inflammatory factors and the ERK pathway-related genes as well as gastrointestinal motility dysfunction was assessed using ectopic expression and depletion experiments. CEBPB, MALAT1 and CIRBP were highly expressed in plasma of SAP patients and pancreatic and intestinal tissues of SAP mice. Further analysis showed that knockdown of MALAT1 could alleviate pancreatic and intestinal injury, reduce inflammation, and prevent gastrointestinal motility dysfunction in SAP mice. The transcription factor CEBPB could bind to the promoter region of MALAT1, thus activating the transcription of MALAT1. MALAT1 interacted with CIRBP and inhibited the degradation of CIRBP, leading to activated extracellular signal-regulated kinase (ERK) pathway and the resultant gastrointestinal motility dysfunction. In conclusion, CEBPB exhibits a promoting activity towards gastrointestinal motility dysfunction in SAP by pumping up MALAT1 expression and activating the CIRBP-dependent ERK pathway.

MLKL signaling regulates macrophage polarization in acute pancreatitis through CXCL10

Acute pancreatitis (AP) is a disease characterized by local and systemic inflammation with an increasing incidence worldwide. Receptor-interacting serine/threonine protein kinase 3 (RIPK3), mixed-lineage kinase domain-like protein (MLKL), and innate immune cell macrophages have been reported to be involved in the pathogenesis of AP. However, the mechanisms by which RIPK3 and MLKL regulate pancreatic injury, as well as the interactions between injured pancreatic acinar cells and infiltrating macrophages in AP, remain poorly defined. In the present study, experimental pancreatitis was induced in C57BL/6J, Ripk3-/- and Mlkl-/- mice by cerulein plus lipopolysaccharide in vivo, and primary pancreatic acinar cells were also isolated to uncover cellular mechanisms during cerulein stimulation in vitro. The results showed that MLKL and its phosphorylated protein p-MLKL were upregulated in the pancreas of the mouse AP model and cerulein-treated pancreatic acinar cells, independent of its canonical upstream molecule Ripk3, and appeared to function in a cell death-independent manner. Knockout of Mlkl attenuated AP in mice by reducing the polarization of pancreatic macrophages toward the M1 phenotype, and this protective effect was partly achieved by reducing the secretion of CXCL10 from pancreatic acinar cells, whereas knockout of Ripk3 did not. In vitro neutralization of CXCL10 impaired the pro-M1 ability of the conditioned medium of cerulein-treated pancreatic acinar cells, whereas in vivo neutralization of CXCL10 reduced the polarization of pancreatic macrophages toward M1 and the severity of AP in mice. These findings suggested that targeting the MLKL-CXCL10-macrophage axis might be a promising strategy for the treatment of AP.

Salidroside protects against caerulein with the LPS-induced severe acute pancreatitis through suppression of oxidative stress and inflammation in mice

• Salidroside attenuated caerulein with LPS-induced pancreatic injury in a mouse model of SAP. • Salidroside significantly ameliorated oxidative stress and inflammation responses in the pancreas of SAP mice. • Depletion of Nrf2 weakened the therapeutic effect of salidroside and reduced the anti-oxidative stress and anti-inflammatory effects in salidroside treated SAP mice. • Molecular mechanism studies showed that salidroside mediated anti-oxidant stress and anti-inflammatory responses in SAP mice partially through the Nrf2/NF-κB p65 pathway. Severe acute pancreatitis (SAP) is a fatal inflammation with no effective treatment. Salidroside, a monomer isolated from the traditional Chinese medicine Rhodiola, has been shown cytoprotective roles in many inflammation-related diseases. However, whether salidroside plays a protective role in an acute inflammation like SAP in mice is unknown. In this study, we aimed to investigate the molecular mechanism underlying the pancreatic protection of salidroside. The results showed that salidroside attenuated caerulein with the LPS-induced pancreatic injury in a mouse model of SAP. Also, we found that salidroside ameliorated oxidative stress and inflammation responses in SAP mice. Furthermore, SAP mice treated with salidroside were associated with higher phosphorylation levels of Nrf2 and less nuclear accumulation of NF-κB p65. We further found that depletion of Nrf2 weakened the protective effect of salidroside in SAP mice. Collectively, salidroside mediated anti-oxidant stress and anti-inflammation in SAP mice partially through the Nrf2/NF-κB p65 pathway.

Tetrahedral Framework Nucleic Acids Can Alleviate Taurocholate-Induced Severe Acute Pancreatitis and Its Subsequent Multiorgan Injury in Mice.

Severe acute pancreatitis (SAP) is an inflammatory disease of the pancreas accompanied by tissue injury and necrosis. It not only affects the pancreas but also triggers a systemic inflammatory response that leads to multiorgan failure or even death. Moreover, there is no effective treatment currently that can reverse the disease progression. In this study, tetrahedral framework nucleic acids (tFNAs) were utilized to treat SAP in mice for the first time and proved to be effective in suppressing inflammation and preventing pathological cell death. Serum levels of pancreatitis-related biomarkers witnessed significant changes after tFNAs treatment. Reduction in the expression of certain cytokines involved in local and systemic inflammatory response were observed, together with alteration in proteins related to cell death and apoptosis. Collectively, our results demonstrate that tFNAs could both alleviate SAP and its subsequent multiorgan injury in mice, thus offering a novel and effective option to deal with SAP in the future.

Treatment of Severe Acute Pancreatitis and Related Lung Injury by Targeting Gasdermin D-Mediated Pyroptosis.

The functional relevance and effects of the pyroptosis executioner gasdermin D (GSDMD) on severe acute pancreatitis (SAP)-associated lung injury are unclear. We established caerulein-induced mouse models of SAP-associated lung injury, which showed that GSDMD-mediated pyroptosis was activated in both pancreatic and lung tissues. Compared with Gsdmd wild-type SAP mouse models, Gsdmd knockout (Gsdmd–/–) ameliorated SAP-induced pancreas and related lung injury. Additionally, we investigated the effects of disulfiram on the treatment of SAP. Disulfiram is a Food and Drug Administration (FDA)-approved anti-alcoholism drug, which is reported as an effective pyroptosis inhibitor by either directly covalently modifying GSDMD or indirectly inhibiting the cleavage of GSDMD via inactivating Nod-like receptor protein 3 inflammasome. We demonstrated that disulfiram inhibited the cleavage of GSDMD, alleviated caerulein-induced SAP and related lung injury, and decreased the expression levels of proinflammatory cytokines (IL-1β and IL-18). Collectively, these findings disclosed the role of GSDMD-mediated pyroptosis in SAP and the potential application of disulfiram in the treatment of SAP.

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

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. 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 6h after SAP-induction with taurocholate. The control group received saline or the same number of SSEA-3(-)-non-Muse MSCs. 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 72h. 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 18h than that in the non-Muse MSCs and control groups. Intravenous injection of human Muse cells was suggested to be effective for attenuating edema, inflammation and apoptosis in the acute phase of SAP.

Galangin ameliorates severe acute pancreatitis in mice by activating the nuclear factor E2-related factor 2/heme oxygenase 1 pathway

Acute pancreatitis (AP) is a common serious acute condition of the digestive system that remains a clinical challenge. Severe acute pancreatitis (SAP) in particular is characterized by high morbidity and mortality. The present study was designed to investigate the protective effect of Galangin (Gal), a natural flavonol obtained from lesser galangal, on L-arginine-induced SAP in mice and in AR42J cells. Amylase and lipase activities were measured and the histopathology of the pancreas, lung, and kidney was evaluated. Inflammation and oxidative stress were assessed using ELISA, western blotting, RT-PCR, and immunohistochemistry. Gal was shown to reduce proinflammatory cytokine production and reactive oxygen species (ROS) generation in vivo and in vitro. L-arginine treatment reduced the expression of components of the nuclear factor E2-related factor 2 (Nrf2) signaling pathway and the downstream protein heme oxygenase-1 (HO-1) in mice, whereas Gal increased their expression. Furthermore, the Nrf2/HO-1 pathway inhibitor brusatol prevented the anti-inflammatory and antioxidant effects of Gal in mice with SAP. Taken together, our results imply that Gal has protective effects in L-arginine-induced SAP that are induced by the upregulation of the Nrf2/HO-1 pathway, which has anti-inflammatory and antioxidant effects. Thus, Gal may represent a promising treatment for SAP.

CCR2+ monocytes, not neutrophils, are responsible for lung and kidney damage during severe acute pancreatitis in mice

CCR2+ monocytes, not neutrophils, are responsible for lung and kidney damage during severe acute pancreatitis in mice

Mechanism of gasdermin D on intestinal injury in severe acute pancreatitis by mediating pyroptosis

To investigate the function of gasdermin D (GSDMD) in intestinal damage of mice with severe acute pancreatitis (SAP). The healthy C57BL/6 mice were divided into four groups randomly, including normal saline (NS) group, small interfering RNA (siRNA)-NS group, SAP model group and siRNA-SAP group, with 6 mice in each group. The SAP mouse model was reproduced by intraperitoneal injection of caerulein 50 μg/kg combined with lipopolysaccharide (LPS) 10 mg/kg; the NS group was given the same amount of NS; in the siRNA-SAP group and siRNA-NS group, siRNA 50 mg/kg was injected through the tail vein three times before modeling or injection of NS. The blood of mice eyeball in each group was taken 12 hours after modeling, and serum interleukins (IL-1β, IL-18) levels were detected by enzyme linked immunosorbent assay (ELISA). The mice were sacrificed to observe the general changes in abdominal cavity, the pancreas and ileum tissues were taken to observe the pathological changes under a light microscope. The expression of long-chain non-coding RNA uc.173 (lnc uc.173) was detected by reverse transcription-polymerase chain reaction (RT-PCR). Immunohistochemical method was used to detect the expression of tight junction proteins zonula occluden-1 (ZO-1) and Occludin in intestinal mucosal epithelial cells. Western blotting was used to detect the GSDMD protein expression level in the intestinal tissue. The serum levels of IL-1β and IL-18 in the SAP model group were significantly higher than those in the NS group and the siRNA-NS group [IL-1β (ng/L): 146.66±1.40 vs. 44.48±5.76, 81.49±10.75, IL-18 (ng/L): 950.47±177.09 vs. 115.43±16.40, 84.84±21.90, all P < 0.05]; and the levels of IL-1β and IL-18 in the siRNA-SAP group were significantly lower than those in the SAP model group [IL-1β (ng/L): 116.26±15.54 vs. 146.66±1.40, IL-18 (ng/L): 689.96±126.08 vs. 950.47±177.09, both P < 0.05]. General observation showed that there were no obvious abnormalities in the abdominal cavity of the mice in the NS and siRNA-NS groups; the mice in the SAP model group and the siRNA-SAP group had different degrees of edema and congestion in the intestine; compared with the SAP model group, the abnormalities in the siRNA-SAP group was significantly reduced. Under light microscope, there were no obvious changes in the pancreas and intestinal mucosa in the NS group and the siRNA-NS group; the pancreatic tissue of the SAP model group and the siRNA-SAP group had different degrees of edema, inflammatory cell infiltration, and lobular structure damage, and the intestinal mucosa was damaged to a certain degree, and the villi were broken to varying degrees, but the damage in the siRNA-SAP group was lighter. The results of RT-PCR showed that the expression of lnc uc.173 in the intestinal tissues of the model SAP group was significantly lower than that of the NS group and the siRNA-NS group (2-ΔΔCt: 0.26±0.12 vs. 1.01±0.37, 0.67±0.32, both P < 0.05), while the expression of lnc uc.173 in the siRNA-SAP group was significantly higher than that in the SAP model group (2-ΔΔCt: 0.60±0.39 vs. 0.26±0.12, P < 0.05). Immunohistochemistry showed that ZO-1 and Occludin proteins in the NS group were distributed along the epithelial cells of the intestinal mucosa, showing a strong expression; ZO-1 and Occludin expressions were significantly reduced in the SAP model group and siRNA-SAP group, but the expressions in the siRNA-SAP group was higher than that in the SAP model group. Western blotting showed that the expression level of GSDMD protein in the intestinal tissues of the SAP model group was significantly higher than that of the NS group and the siRNA-NS group [GSDMD protein (GSDMD-N/β-actin): 1.99±0.46 vs. 1, 1.00±0.78, both P < 0.05]. Compared with the SAP model group, the expression of GSDMD protein in the siRNA-SAP group was significantly decreased [GSDMD protein (GSDMD-N/β-actin): 1.42±0.42 vs. 1.99±0.46, P < 0.05]. The systemic inflammatory response and intestinal mucosal barrier damage of SAP mice may be related to the increase of GSDMD expression in intestinal tissues. GSDMD mediates cell pyrolysis to promote the release of inflammatory factors, cause intestinal injury, and down-regulate the expression of intestinal epithelial cell tight junction proteins such as ZO-1 and Occludin, resulting in intestinal mucosal damage.

ATF6 aggravates acinar cell apoptosis and injury by regulating p53/AIFM2 transcription in Severe Acute Pancreatitis

Background: There is no curative therapy for severe acute pancreatitis (SAP) due to poor understanding of its molecular mechanisms. Endoplasmic reticulum (ER) stress is involved in SAP and increased expression of ATF6 has been detected in SAP patients. Here, we aimed to investigate the role of ATF6 in a preclinical SAP mouse model and characterize its regulatory mechanism.Methods: Pancreatic tissues of healthy and SAP patients were collected during surgery. Humanized PRSS1 transgenic mice were treated with caerulein to mimic the SAP development, which was crossed to an ATF6 knockout mouse line, and pancreatic tissues from the resulting pups were screened by proteomics. Adenovirus-mediated delivery to the pancreas of SAP mice was used for shRNA-based knockdown or overexpression. The potential functions and mechanisms of ATF6 were clarified by immunofluorescence, immunoelectron microscopy, Western blotting, qRT-PCR, ChIP-qPCR and luciferase reporter assay.Results: Increased expression of ATF6 was associated with elevated apoptosis, ER and mitochondrial disorder in pancreatic tissues from SAP patients and PRSS1 mice. Knockout of ATF6 in SAP mice attenuated acinar injury, apoptosis and ER disorder. AIFM2, known as a p53 target gene, was identified as a downstream regulatory partner of ATF6, whose expression was increased in SAP. Functionally, AIFM2 could reestablish the pathological disorder in SAP tissues in the absence of ATF6. p53 expression was also increased in SAP mice, which was downregulated by ATF6 knockout. p53 knockout significantly suppressed acinar apoptosis and injury in SAP model. Mechanistically, ATF6 promoted AIFM2 transcription by binding to p53 and AIFM2 promoters.Conclusion: These results reveal that ATF6/p53/AIFM2 pathway plays a critical role in acinar apoptosis during SAP progression, highlighting novel therapeutic target molecules for SAP.

The mechanism of Toll-like receptor 4 pathway in lung injury induced by severe acute pancreatitis in mice

Objective To investigate mechanism of Toll-like receptor 4 (TLR4) pathway in lung injury of severe acute pancreatitis (SAP). Methods The SAP model were induced in TLR4-/-and TLR4+ /+ mice and were randomly divided into group A: TLR4+ /+ group, B: TLR4+ /+ -SAP group, C: TLR4-/-group and D: TLR4-/--SAP group. The interleukins (IL)-6, tumor necrosis factor-α (TNF-α), IL-1β, IL-8 concentration of serum were detected by enzyme-linked immunoabsorbent assay; pathological changes of pancreas and lung were observed by hematoxylin-eosin; T helper cell 17 (Th17) and regulatory T cell (Treg) cells were detected by flow cytometry; mRNA expression of IL-17, forkhead box P3 (Foxp3), receptor-γt (RORγt) were detected by real-time polymerase chain reaction, p-signal transducer and activators of transcription (STAT)-3 and nuclear factor-κB (NF-κB) protein were detected by Western blotting. Results Compared with A and C group, serum IL-6, TNF-α, IL-1β and IL-8 concentrations were significantly increased in group B (P<0.05); Th17/Treg cells were significantly increased (P<0.05); levels of IL-17, Foxp3 and RORγt mRNA were significantly increased (P<0.05); expression of p-STAT-3 or NF-κB in B and D group were significantly higher than those in group A and group C. Compared with TLR4+ /+ -SAP group, concentration of cytokines in TLR4-/--SAP group was significantly lower than that of group (P<0.05) and levels of IL-17, Foxp3, RORγt, Th17 and Treg cells, levels of p-STAT-3 and NF-κB protein were significantly lower (P<0.01). Conclusion Blocking TLR4 pathway can reduce inflammation and lung injury in SAP. Key words: Severe acute pancreatitis; Toll-like receptor 4; T helper cell 17; Regulatory T cells; Inflammation

Protective effects of HTD4010, a Reg3α/PAP-derived peptide, in mouse model of acute pancreatitis via toll-like receptor 4 pathway

Acute pancreatitis (AP) is one of the most common digestive tract diseases, but effective drug therapy is still lack. Regenerating gene protein 3α (Reg3α) administration significantly reduced the severity of AP in mice. HTD4010 is a new 15 amino acid long synthetic peptide and its biological activities are similar to Reg3α. This study aimed to explore whether HTD4010 could protect pancreatic acinar cells against necrosis and decrease the inflammatory response in AP, and thus to explore underlying mechanisms. It was shown that administration of HTD4010 alleviated significantly the severity of biliary AP (BAP), characterized as less degree of pancreatic histological damage and acinar cell injury (both apoptosis and necroptosis), lower levels of serum amylase and pro-inflammatory cytokines. Moreover, HTD4010 down-regulated the expression of toll-like receptor 4 (TLR4) protein, and TLR4 deficiency eliminated the protective effect of HTD4010 on BAP in mice. In conclusion, these results showed that HTD4010 could alleviate the severity of pancreatitis, reduce the acinar cells necrosis and inflammatory response possibly by TLR4 signaling pathway in AP.

TSG-6 secreted by human adipose tissue-derived mesenchymal stem cells ameliorates severe acute pancreatitis via ER stress downregulation in mice

BackgroundThrough recent studies, the onset of acute pancreatitis in pancreatic acinar cells (PACs) and the regulatory role of PACs in severe acute pancreatitis (SAP) have been revealed. During the early stages of pancreatitis, the endoplasmic reticulum (ER) in PACs undergoes significant changes, including swelling and vacuolization. In response to an increase in the extracellular stress in ER, PACs lose their functions, leading to cell apoptosis and inflammation response. The beneficial effects of human adipose tissue-derived mesenchymal stem cells (hAT-MSCs) on SAP have been well documented in previous studies. However, the underlying mechanism of their action remains controversial.MethodsIn this study, the therapeutic effects of intraperitoneally administered hAT-MSCs in a caerulein (50 μg/kg)- and lipopolysaccharide (LPS) (10 mg/kg)-co-induced SAP mouse model were evaluated. Inflammatory response and ER stress were measured in pancreatic tissue samples, and the beneficial effects were evaluated through quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blot, and immunofluorescence analysis.ResultsInflammatory response and ER stress were ameliorated following hAT-MSC injection, and the beneficial effects were observed in the absence of significant engraftment of hAT-MSCs. hAT-MSCs transfected with siRNA-targeting tumour necrosis factor-α-induced gene/protein 6 (TSG-6) were unable to inhibit ER stress and inflammation. In addition, TSG-6 from hAT-MSCs significantly suppressed ER stress-induced apoptosis and nuclear factor kappa B (NF-κB) activity in SAP model mice.ConclusionsTSG-6 secreted by hAT-MSCs protects PACs in SAP model mice via the inhibition of ER stress, as well as inflammatory responses. This study has revealed a new area for ER stress-targeted therapy in SAP patients.Graphical abstract