Inhibition of Ras signalling reduces neutrophil infiltration and tissue damage in severe acute pancreatitis

Immunodynamic axis of fibroblast-driven neutrophil infiltration in acute pancreatitis: NF-κB-HIF-1α-CXCL1

BACKGROUND

Acute pancreatitis (AP) is a sterile inflammation, and 10-20% of cases can progress to severe acute pancreatitis (SAP), which seriously threatens human life and health. Neutrophils and their extracellular traps (NETs) play an important role in the progression of AP. However, the immunodynamic factors between the excessive infiltration of neutrophils during the occurrence of AP have not been fully elucidated.

METHODS

Adult male C57BL/6 J mice were selected. An AP model was induced by cerulein, and a control group was set up. Single-cell sequencing technology was used to reveal the cell atlas of AP pancreatitis tissue. In vivo, the model mice were treated with anti-Ly6G antibody, DNase I, SC75741, PX-478, and SRT3109 respectively. In vitro, human pancreatic stellate cells were treated with hypoxia, H2O2, NAC, and JSH-2, and co-cultured with neutrophils in Transwell chambers. The severity of inflammation was evaluated, and the molecular mechanism by which fibroblasts exacerbate AP was revealed through techniques such as cell colony formation assay, cell migration assay, cell transfection, immunofluorescence, flow cytometry, Western blot, reverse-transcription quantitative polymerase chain reaction (RT-qPCR), and co-immunoprecipitation (co-IP).

RESULTS

The study showed that the elimination of neutrophils and NETs could significantly improve AP. Single-cell RNA sequencing (scRNA-seq) indicated that both neutrophils and fibroblasts in pancreatic tissue exhibited heterogeneity during AP. Among them, neutrophils highly expressed CXCR2, and fibroblasts highly expressed CXCL1. Further experimental results demonstrated that the infiltration of neutrophils in the early stage of AP was related to the activation of fibroblasts. The activation of fibroblasts depended on the nuclear factor kappa B (NF-κB) signaling pathway induced by hypoxia. NF-κB enhanced the activation of pancreatic stellate cells (PSCs) and the secretion of CXCL1 by directly promoting the transcription of HIF-1α and indirectly inhibiting PHD2, resulting in the accumulation of HIF-1α protein. The NF-κB-HIF-1α signal promoted the secretion of CXCL1 by fibroblasts through glycolysis and induced the infiltration of neutrophils. Finally, blocking the NF-κB-HIF-1α-CXCL1 signaling axis in vivo reduced the infiltration of neutrophils and improved AP.

CONCLUSIONS

This study, for the first time, demonstrated that activation of fibroblasts is one of the immunological driving factors for neutrophil infiltration and elucidated that glycolysis driven by the NF-κB-HIF-1α pathway is the intrinsic molecular mechanism by which fibroblasts secrete CXCL1 to chemotactically attract neutrophils. This finding provides a highly promising target for the treatment of AP.

The Important Role of p21-Activated Kinases in Pancreatic Exocrine Function

The p21-activated kinases (PAKs) are a conserved family of serine/threonine protein kinases, which are effectors for the Rho family GTPases, namely, Rac/Cdc42. PAKs are divided into two groups: group I (PAK1-3) and group II (PAK4-6). Both groups of PAKs have been well studied in apoptosis, protein synthesis, glucose homeostasis, growth (proliferation and survival) and cytoskeletal regulation, as well as in cell motility, proliferation and cycle control. However, little is known about the role of PAKs in the secretory tissues, including in exocrine tissue, such as the exocrine pancreas (except for islet function and pancreatic cancer growth). Recent studies have provided insights supporting the importance of PAKs in exocrine pancreas. This review summarizes the recent insights into the importance of PAKs in the exocrine pancreas by reviewing their presence and activation; the ability of GI hormones/neurotransmitters/GFs/post-receptor activators to activate them; the kinetics of their activation; the participation of exocrine-tissue PAKs in activating the main growth-signaling cascade; their roles in the stimulation of enzyme secretion; finally, their roles in pancreatitis. These insights suggest that PAKs could be more important in exocrine/secretory tissues than currently appreciated and that their roles should be explored in more detail in the future.

Molecular mechanism and potential role of mitophagy in acute pancreatitis

Acute pancreatitis (AP) is a multifaceted inflammatory disorder stemming from the aberrant activation of trypsin within the pancreas. Despite the contribution of various factors to the pathogenesis of AP, such as trypsin activation, dysregulated increases in cytosolic Ca2+ levels, inflammatory cascade activation, and mitochondrial dysfunction, the precise molecular mechanisms underlying the disease are still not fully understood. Mitophagy, a cellular process that preserves mitochondrial homeostasis under stress, has emerged as a pivotal player in the context of AP. Research suggests that augmenting mitophagy can mitigate pancreatic injury by clearing away malfunctioning mitochondria. Elucidating the role of mitophagy in AP may pave the way for novel therapeutic strategies. This review article aims to synthesize the current research findings on mitophagy in AP and underscore its significance in the clinical management of the disorder.

Neutrophils in pancreatic ductal adenocarcinoma: bridging preclinical insights to clinical prospects for improved therapeutic strategies

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy characterized by a dismal five-year survival rate of less than 10%. Neutrophils are key components of the innate immune system, playing a pivotal role in the PDAC immune microenvironment.

AREAS COVERED

This review provides a comprehensive survey of the pivotal involvement of neutrophils in the tumorigenesis and progression of PDAC. Furthermore, it synthesizes preclinical and clinical explorations aimed at targeting neutrophils within the milieu of PDAC, subsequently proposing a conceptual framework to propel further inquiry focused on enhancing the therapeutic efficacy of PDAC through neutrophil-targeted strategies. PubMed and Web of Science databases were utilized for researching neutrophils in pancreatic cancer publications prior to 2024.

EXPERT OPINION

Neutrophils play roles in promoting tumor growth and metastasis in PDAC and are associated with poor prognosis. However, the heterogeneity and plasticity of neutrophils and their complex relationships with other immune cells and extracellular matrix also provide new insights for immunotherapy targeting neutrophils to achieve a better prognosis for PDAC.

Recent advances in the role of neutrophils and neutrophil extracellular traps in acute pancreatitis

Pancreatitis is an inflammatory disease, which is triggered by adverse events in acinar cells of the pancreas. After the initial injury, infiltration of neutrophils in pancreas is observed. In the initial stages of pancreatitis, the inflammation is sterile. It has been shown that the presence of neutrophils at the injury site can modulate the disease. Their depletion in experimental animal models of the acute pancreatitis has been shown to be protective. But information on mechanism of contribution to inflammation by neutrophils at the injury site is not clear. Once at injury site, activated neutrophils release azurophilic granules containing proteolytic enzymes and generate hypochlorous acid which is a strong microbicidal agent. Additionally, emerging evidence shows that neutrophil extracellular traps (NETs) are formed which consist of decondensed DNA decorated with histones, proteases and granular and cytosolic proteins. NETs are considered mechanical traps for microbes, but there is preliminary evidence to indicate that NETs, which constitute a special mechanism of the neutrophil defence system, play an adverse role in pancreatitis by contributing to the pancreatic inflammation and distant organ injury. This review presents the overall current information about neutrophils and their role including NETs in acute pancreatitis (AP). It also highlights current gaps in knowledge which should be explored to fully elucidate the role of neutrophils in AP and for therapeutic gains.

Highlights on the Role of KRAS Mutations in Reshaping the Microenvironment of Pancreatic Adenocarcinoma

The most frequent mutated oncogene family in the history of human cancer is the RAS gene family, including NRAS, HRAS, and, most importantly, KRAS. A hallmark of pancreatic cancer, recalcitrant cancer with a very low survival rate, is the prevalence of oncogenic mutations in the KRAS gene. Due to this fact, studying the function of KRAS and the impact of its mutations on the tumor microenvironment (TME) is a priority for understanding pancreatic cancer progression and designing novel therapeutic strategies for the treatment of the dismal disease. Despite some recent enlightening studies, there is still a wide gap in our knowledge regarding the impact of KRAS mutations on different components of the pancreatic TME. In this review, we will present an updated summary of mutant KRAS role in the initiation, progression, and modulation of the TME of pancreatic ductal adenocarcinoma (PDAC). This review will highlight the intriguing link between diabetes mellitus and PDAC, as well as vitamin D as an adjuvant effective therapy via TME modulation of PDAC. We will also discuss different ongoing clinical trials that use KRAS oncogene signaling network as therapeutic targets.

Systemic Immune-Inflammation Index for Predicting the Prognosis of Critically Ill Patients with Acute Pancreatitis

Background

Systemic immune-inflammation index (SII) has been identified as a prognostic biomarker in various diseases. However, its significance in acute pancreatitis (AP) has not been reported. Therefore, the main aim of this study was to determine the association of SII with clinical outcomes of AP patients, after adjusting for several confounders.

Methods

This retrospective cohort study was conducted using data retrieved from the Medical Information Mart for Intensive Care III database (MIMIC-III). The study only included patients diagnosed with AP. SII was calculated as the platelet counts x neutrophil counts/lymphocyte counts. Cox regression models were employed to assess the impact of SII on the 30- and 90-day mortality of AP patients. Subgroup analysis was carried out to explore the stability of the relationship between SII and AP mortality.

Results

A total of 513 patients were found to be eligible based on the inclusion and exclusion criteria. For 30-day all-cause mortality, in the model adjusted for multiple confounders, the HR (95% CI) for mid-SII group (SII: 75.6−104.2) and high-SII groups (SII: >104.2) were 1.29 (0.65, 2.56) and 2.57 (1.35, 4.88), respectively, compared to the low-SII group (SII: <75.5). A similar trend was observed for 90-day mortality. Subgroup analyses presented a stable relationship between SII and 30-day all-cause mortality of AP patients.

Conclusion

SII is a potentially useful prognostic biomarker for AP. However, prospective studies are needed to confirm this finding.

The Role of Pancreatic Infiltrating Innate Immune Cells in Acute Pancreatitis

Acute pancreatitis (AP) is a leading cause of gastrointestinal-related hospital admissions with significant morbidity and mortality. Although the underlying pathophysiology of AP is rather complex, which greatly limits the treatment options, more and more studies have revealed that infiltrating immune cells play a critical role in the pathogenesis of AP and determine disease severity. Thus, immunomodulatory therapy targeting immune cells and related inflammatory mediators is expected to be a novel treatment modality for AP which may improve the prognosis of patients. Cells of the innate immune system, including macrophages, neutrophils, dendritic cells, and mast cells, represent the majority of infiltrating cells during AP. In this review, an overview of different populations of innate immune cells and their role during AP will be discussed, with a special focus on neutrophils and macrophages.

Targeting neutrophil extracellular traps in severe acute pancreatitis treatment

Severe acute pancreatitis (SAP) is a critical abdominal disease associated with high death rates. A systemic inflammatory response promotes disease progression, resulting in multiple organ dysfunction. The functions of neutrophils in the pathology of SAP have been presumed traditionally to be activation of chemokine and cytokine cascades accompanying the inflammatory process. Recently, since their discovery, a new type of antimicrobial mechanism, neutrophil extracellular traps (NETs), and their role in SAP, has attracted widespread attention from the scientific community. Significantly different from phagocytosis and degranulation, NETs kill extracellular microorganisms by releasing DNA fibers decorated with granular proteins. In addition to their strong antimicrobial functions, NETs participate in the pathophysiological process of many noninfectious diseases. In SAP, NETs injure normal tissues under inflammatory stress, which is associated with the activation of inflammatory cells, to cause an inflammatory cascade, and SAP products also trigger NET formation. Thus, due to the interaction between NET generation and SAP, a treatment targeting NETs might become a key point in SAP therapy. In this review, we summarize the mechanism of NETs in protecting the host from pathogen invasion, the stimulus that triggers NET formation, organ injury associated with SAP involving NETs, methods to interrupt the harmful effects of NETs, and different therapeutic strategies to preserve the organ function of patients with SAP by targeting NETs.

Both knock-down and overexpression of Rap2a small GTPase in macrophages result in impairment of NF-κB activity and inflammatory gene expression

Small Ras GTPases are key molecules that regulate a variety of cellular responses in different cell types. Rap1 plays important functions in the regulation of macrophage biology during inflammation triggered by toll-like receptors (TLRs). However, despite sharing a relatively high degree of similarity with Rap1, no studies concerning Rap2 in macrophages and innate immunity have been reported yet. In this work, we show that either way alterations in the levels of Rap2a hampers proper macrophages response to TLR stimulation. Rap2a is activated by LPS in macrophages, and although putative activator TLR-inducible Ras guanine exchange factor RasGEF1b was sufficient to induce, it was not fully required for Rap2a activation. Silencing of Rap2a impaired LPS-induced production of IL-6 cytokine and KC/Cxcl1 chemokine, and also NF-κB activity as measured by reporter gene studies. Surprisingly, overexpression of Rap2a did also lead to marked inhibition of NF-κB activation induced by LPS, Pam3CSK4 and downstream TLR signaling molecules. We also found that Rap2a can inhibit the LPS-induced phosphorylation of the NF-κB subunit p65 at serine 536. Collectively, our data suggest that expression levels of Rap2a in macrophages might be tightly regulated to avoid unbalanced immune response. Our results implicate Rap2a in TLR-mediated responses by contributing to balanced NF-κB activity status in macrophages.

Frontline Science: TNF-α and GM-CSF1 priming augments the role of SOS1/2 in driving activation of Ras, PI3K-γ, and neutrophil proinflammatory responses

Circulating neutrophils are, by necessity, quiescent and relatively unresponsive to acute stimuli. In regions of inflammation, mediators can prime neutrophils to react to acute stimuli with stronger proinflammatory, pathogen-killing responses. In neutrophils G protein-coupled receptor (GPCR)-driven proinflammatory responses, such as reactive oxygen species (ROS) formation and accumulation of the key intracellular messenger phosphatidylinositol (3,4,5)-trisphosphate (PIP₃ ), are highly dependent on PI3K-γ, a Ras-GTP, and Gβγ coincidence detector. In unprimed cells, the major GPCR-triggered activator of Ras is the Ras guanine nucleotide exchange factor (GEF), Ras guanine nucleotide releasing protein 4 (RasGRP4). Although priming is known to increase GPCR-PIP₃ signaling, the mechanisms underlying this augmentation remain unclear. We used genetically modified mice to address the role of the 2 RasGEFs, RasGRP4 and son of sevenless (SOS)1/2, in neutrophil priming. We found that following GM-CSF/TNFα priming, RasGRP4 had only a minor role in the enhanced responses. In contrast, SOS1/2 acquired a substantial role in ROS formation, PIP₃ accumulation, and ERK activation in primed cells. These results suggest that SOS1/2 signaling plays a key role in determining the responsiveness of neutrophils in regions of inflammation.

Farnesyl thiosalicylic acid prevents iNOS induction triggered by lipopolysaccharide via suppression of iNOS mRNA transcription in murine macrophages

Inducible nitric oxide synthase (iNOS) is a molecule critical for the development of inflammation-associated disorders. Its induction should be tightly controlled in order to maintain cellular homeostasis. Upon lipopolysaccharide (LPS) stimulation, iNOS, in most settings, is induced by the activation of inhibitor of κB-α (IκB-α)-nuclear factor κB (NF-κB) signaling. Farnesyl thiosalicylic acid (FTS), a synthetic small molecule that is considered to detach Ras from the inner cell membrane, has been shown to exhibit numerous anti-inflammatory functions. However, it remains unclear whether and how it affects iNOS induction in macrophages. The present study addressed this issue in cultured macrophages and endotoxemic mice. Results showed that FTS pretreatment significantly prevented LPS-induced increases in iNOS protein and mRNA expression levels in murine cultured macrophages, which were confirmed in organs in vivo from endotoxemic mice, such as the liver and lung. Mechanistic studies revealed that FTS pretreatment did not affect IκB-α degradation and NF-κB activation in LPS-treated macrophages. The nuclear transport of the active NF-κB was also not affected by FTS. But FTS pretreatment reduced the binding of NF-κB to its DNA elements, and reduced NF-κB bindings to iNOS promoter inside LPS-treated macrophages. Finally, our results showed that FST pretreatment increased mouse survival rate compared to LPS alone treatment. Taken together, these results indicate that FTS attenuates iNOS induction in macrophages likely through inhibition of iNOS mRNA transcription, providing further insight into the molecular mechanism of action of FTS in inflammatory disorder therapy.

Value of neutrophil to lymphocyte ratio combined with red blood cell distribution width for predicting severity of acute pancreatitis

AIM

To explore the value of neutrophil to lymphocyte ratio (NLR) combined with red blood cell distribution width (RDW) for predicting the severity of acute pancreatitis (AP).

METHODS

The clinical data of 120 patients with AP were retrospectively analyzed in this study. The patients were assigned to three groups: mild AP (MAP) group, moderately severe AP (MSAP) group, and severe AP (SAP) group. The clinical indexes (NLR and RDW) of the three groups of patients were measured at 24 h after hospitalization. All of these data were compared among the groups, and between dead patients and surviving cases. The receiver operator characteristic curves (ROCs) of NLR, RDW, and NLR plus RDW were plotted to assess their value in predicting the prognosis of AP.

RESULTS

With the increase of the severity of AP, the value of NLR increased significantly (P < 0.05). There was no significant difference in RDW between the MAP and MSAP groups (P > 0.05). The RDW value of the SAP group was significantly different from those of the MAP and MSAP groups (P < 0.05). The values of NLR and RDW in the death group were significantly higher than those in the survival group (P < 0.05). The area under the curve of NLR in predicting AP severity was 0.794, which was significantly higher than that of RDW (0.745; P < 0.05). The area under the NLR + RDW curve was 0.876 (sensitivity, 0.795; specificity, 0.852), which was significantly higher than that of NLR and RDW alone (P < 0.05).

CONCLUSION

NLR and RDW are both related to the severity of AP, and the combination of the two indexes can improve the sensitivity and specificity of predicting the severity of AP.

miR-425 regulates inflammatory cytokine production in CD4+ T cells via N-Ras upregulation in primary biliary cholangitis

BACKGROUND & AIMS

Primary biliary cholangitis (PBC) is an autoimmune liver disease of unknown pathogenesis. Consequently, therapeutic targets for PBC have yet to be identified. CD4⁺ T cells play a pivotal role in immunological dysfunction observed in PBC, and therefore, microRNA (miRNA) and mRNA expression were analysed in CD4⁺ T cells, to investigate PBC pathogenesis and identify novel therapeutic targets.

METHODS

Integral miRNA and mRNA analysis of 14 PBC patients and ten healthy controls was carried out using microarray and quantitative real-time polymerase chain reaction (qRT-PCR), with gene set enrichment analysis. The functional analyses of miRNA were then assessed using reporter and miRNA-overexpression assays.

RESULTS

The integral analysis of miRNA and mRNA identified four significantly downregulated miRNAs (miR-181a, -181b, -374b, and -425) related to the T cell receptor (TCR) signalling pathway in CD4⁺ T cells of PBC. N-Ras, a regulator of the TCR signalling pathway, was found to be targeted by all four identified miRNAs. In addition, in vitro assays confirmed that decreased miR-425 strongly induced inflammatory cytokines (interleukin [IL]-2 and interferon [IFN]-γ) via N-Ras upregulation in the TCR signalling pathway.

CONCLUSION

The decreased expression of four miRNAs that dysregulate TCR signalling in PBC CD4⁺ T cells was identified. miR-425 was demonstrated as an inflammatory regulator of PBC via N-Ras upregulation. Therefore, the restoration of decreased miR-425 or the suppression of N-Ras may be a promising immunotherapeutic strategy against PBC.

LAY SUMMARY

Primary biliary cholangitis (PBC) is an autoimmune liver disease, but the causes are unknown. MicroRNAs are molecules known to regulate biological signals. In this study, four microRNAs were identified as being decreased in PBC patients, leading to activation of T cell receptor signalling pathways, involved in inflammation. One particular target, N-Ras, could be an attractive and novel immunotherapeutic option for PBC.

TRANSCRIPT PROFILING

Microarray data are deposited in GEO (GEO accession: GSE93172).

The cornerstone K-RAS mutation in pancreatic adenocarcinoma: From cell signaling network, target genes, biological processes to therapeutic targeting

RAS belongs to the super family of small G proteins and plays crucial roles in signal transduction from membrane receptors in the cell. Mutations of K-RAS oncogene lead to an accumulation of GTP-bound proteins that maintains an active conformation. In the pancreatic ductal adenocarcinoma (PDAC), one of the most deadly cancers in occidental countries, mutations of the K-RAS oncogene are nearly systematic (>90%). Moreover, K-RAS mutation is the earliest genetic alteration occurring during pancreatic carcinogenetic sequence. In this review, we discuss the central role of K-RAS mutations and their tremendous diversity of biological properties by the interconnected regulation of signaling pathways (MAPKs, NF-κB, PI3K, Ral…). In pancreatic ductal adenocarcinoma, transcriptome analysis and preclinical animal models showed that K-RAS mutation alters biological behavior of PDAC cells (promoting proliferation, migration and invasion, evading growth suppressors, regulating mucin pattern, and miRNA expression). K-RAS also impacts tumor microenvironment and PDAC metabolism reprogramming. Finally we discuss therapeutic targeting strategies of K-RAS that have been developed without significant clinical success so far. As K-RAS is considered as the undruggable target, targeting its multiple effectors and target genes should be considered as potential alternatives.

Therapeutic implications of innate immune system in acute pancreatitis

INTRODUCTION

Acute pancreatitis (AP) is an inflammatory disorder of the pancreas encompassing a cascade of cellular and molecular events. It starts from premature activation of zymogens with the involvement of innate immune system to a potential systemic inflammatory response and multiple organ failure. Leukocytes are the major cell population that participate in the propagation of the disease. Current understanding of the course of AP is still far from complete, limiting treatment options mostly to conservative supportive care. Emerging evidence has pointed to modulation of the immune system for strategic therapeutic development, by mitigating the inflammatory response and severity of AP. In the current review, we have focused on the role of innate immunity in the condition and highlighted therapeutics targeting it for treatment of this challenging disease.

AREAS COVERED

The current review has aimed to elaborate in-depth understanding of specific roles of innate immune cells, derived mediators and inflammatory pathways that are involved in AP. Summarizing the recent therapeutics and approaches applied experimentally that target immune responses to attenuate AP.

EXPERT OPINION

The current state of knowledge on AP, limitations of presently available therapeutic approaches and the promise of therapeutic implications of innate immune system in AP are discussed.