Toll-like receptor 4 Asp299Gly polymorphism is associated with an increased risk of pancreatic necrotic infection in acute pancreatitis: a study in the Chinese population

The Role of TLR-4 and Galectin-3 Interaction in Acute Pancreatitis

Toll-like receptor-4 (TLR-4) is a member of evolutionarily conserved type I transmembrane proteins that can initiate sterile inflammatory cascade in the pancreas. Expression of TLR-4 is up-regulated in pancreatic tissue, as well as, on peripheral blood innate immune cells in human and experimental models of acute pancreatitis. TLR-4 plays important pro-inflammatory roles during development of acute pancreatitis: it recognize alarmins released from injured acinar cells and promotes activation and infiltration of innate immune cells after the premature and intraacinar activation of tripsinogen. Galectin-3 is β-galactoside-binding lectin that plays pro-inflammatory roles in a variety autoimmune diseases, acute bacterial infections and during tumorigenesis. It is reported that Galectin-3 is alarmin in experimental models of neuroinflammation and binds to TLR-4 promoting the pro-inflammatory phenotype of microglia. Also, in experimental model of acute pancreatitis Galectin-3 is colocalized with TLR-4 on innate inflammatory cells resulted in enhanced production of inflammatory cytokines, TNF-α and IL-1β, increased infiltration of pro-inflammatory N1 neutrophils, macrophages and dendritic cells and increased damage of pancreatic tissue. This review paper discusses the role of TLR-4/Gal-3 axis in the pathogenesis of acute pancreatitis.

Meta-analysis and field synopsis of genetic variants associated with the risk and severity of acute pancreatitis

Background

Genetic risk factors can provide insight into susceptibility for acute pancreatitis (AP) and disease progression towards (infected) necrotizing pancreatitis and persistent organ failure. The aim of the study was to undertake a systematic review of the genetic evidence for AP.

Methods

Online databases (MEDLINE, Embase, BIOSIS, Web of Science, Cochrane Library) were searched to 8 February 2018. Studies that reported on genetic associations with AP susceptibility, severity and/or complications were eligible for inclusion. Meta‐analyses were performed of variants that were reported by at least two data sources. Venice criteria and Bayesian false‐discovery probability were applied to assess credibility.

Results

Ninety‐six studies reporting on 181 variants in 79 genes were identified. In agreement with previous meta‐analyses, credible associations were established for SPINK1 (odds ratio (OR) 2·87, 95 per cent c.i. 1·89 to 4·34), IL1B (OR 1·23, 1·06 to 1·42) and IL6 (OR 1·64, 1·15 to 2·32) and disease risk. In addition, two novel credible single‐nucleotide polymorphisms were identified in Asian populations: ALDH2 (OR 0·48, 0·36 to 0·64) and IL18 (OR 1·47, 1·18 to 1·82). Associations of variants in TNF, GSTP1 and CXCL8 genes with disease severity were identified, but were of low credibility.

Conclusion

Genetic risk factors in genes related to trypsin activation and innate immunity appear to be associated with susceptibility to and severity of AP.

TLR4 Asp299Gly and Thr399Ile and TLR2 intron 2 microsatellite gene polymorphism in patients with acute biliary pancreatitis: Does it cause the disease?

OBJECTIVES

There has been coverage of Toll-like receptor 4 and Toll-like receptor 2 gene polymorphisms in inflammatory episodes in a number of studies. In view of the inflammatory nature of acute pancreatitis, we aimed to determine the predictive value of mutations in Asp299Gly and Thr399Ile of the Toll-like receptor 4 gene, and the intron 2 microsatellite polymorphism of the Toll-like receptor 2 gene on the occurrence of acute biliary pancreatitis.

MATERIAL AND METHODS

The study included 86 patients for the Toll-like receptor 4 Thr399Ile polymorphism, 100 patients for the Toll-like receptor 4 Asp299Gly polymorphism with acute biliary pancreatitis, and 101 healthy volunteers. At the same time, 93 patients and 92 healthy volunteers were included in the study to research the Toll-like receptor 2 intron 2 microsatellite polymorphism. Genotypes were determined using the restriction fragment length polymorphism analysis of PCR products and by an allele-specific PCR.

RESULTS

The Toll-like receptor 4 Thr399Ile homozygotes mutant variants (p=0.005) and Toll-like receptor 2 MM genotype (p<0.001) were detected with a significantly higher frequency in patients with acute biliary pancreatitis than in the healthy blood donors.

CONCLUSION

The Toll-like receptor 4 Asp299Gly and Thr399Ile polymorphisms and the Toll-like receptor 2 intron 2 microsatellite polymorphism are statistically associated with ABP.

Genetic Polymorphisms: A Novel Perspective on Acute Pancreatitis

Acute pancreatitis (AP) is a complex disease that results in significant morbidity and mortality. For many decades, it has compelled researchers to explore the exact pathogenesis and the understanding of the pathogenesis of AP has progressed dramatically. Currently, premature trypsinogen activation and NF-κB activation for inflammation are two remarkable hypotheses for the mechanism of AP. Meanwhile, understanding of the influence of genetic polymorphisms has resulted in tremendous development in the understanding of the advancement of complex diseases. Now, genetic polymorphisms of AP have been noted gradually and many researchers devote themselves to this emerging area. In this review, we comprehensively describe genetic polymorphisms combined with the latest hypothesis of pathogenesis associated with AP.

Effects of ω-3 Fatty Acids on Toll-like Receptor 4 and Nuclear Factor κB p56 in the Pancreas of Rats With Severe Acute Pancreatitis

OBJECTIVES

The aims of this study were to determine the effects of ω-3 fatty acids (ω-3FAs) on the Toll-like receptor 4 (TLR4)/nuclear factor κB p56 (NF-κBp56) signaling pathway in the pancreas of rats with severe acute pancreatitis (SAP).

METHODS

Sixty-four Sprague-Dawley rats were randomly divided into 4 groups: the control, SAP-saline, SAP-soybean oil, and SAP-ω-FA groups. Severe acute pancreatitis was induced by the retrograde infusion of sodium taurocholate into the pancreatic duct. The expression of TLR4 and NF-κBp56 in the pancreas was evaluated by immunohistochemistry and Western blot analysis. The levels of the proinflammatory cytokines interleukin 6 and tumor necrosis factor α in the pancreas were measured by enzyme-linked immunosorbent assays.

RESULTS

Toll-like receptor 4, NF-κBp56, and inflammatory cytokine expression in the pancreas was increased significantly in the SAP group compared with that in the control group (P < 0.05), but was significantly decreased in the ω-3FA group compared with that in the soybean oil group at 24 and 48 hours (P < 0.05).

CONCLUSIONS

Our results suggest that during the initial stage of SAP ω-3FAs could efficiently lower the inflammatory response by activating the TLR4/NF-κBp56 signaling pathway.

Immunopathogenesis of pancreatitis

The conventional view of the pathogenesis of acute and chronic pancreatitis is that it is due to a genetic- or environment-based abnormality of intracellular acinar trypsinogen activation and thus to the induction of acinar cell injury that, in turn, sets in motion an intra-pancreatic inflammatory process. More recent studies, reviewed here, present strong evidence that while such trypsinogen activation is likely a necessary first step in the inflammatory cascade underlying pancreatitis, sustained pancreatic inflammation is dependent on damage-associated molecular patterns-mediated cytokine activation causing the translocation of commensal (gut) organisms into the circulation and their induction of innate immune responses in acinar cells. Quite unexpectedly, these recent studies reveal that the innate responses involve activation of responses by an innate factor, nucleotide-binding oligomerization domain 1 (NOD1), and that such NOD1 responses have a critical role in the activation/production of nuclear factor-kappa B and type I interferon. In addition, they reveal that chronic inflammation and its accompanying fibrosis are dependent on the generation of IL-33 by injured acinar cells and its downstream induction of T cells producing IL-13. These recent studies thus establish that pancreatitis is quite a unique form of inflammation and one susceptible to newer, more innovative therapy.

Immunomodulatory therapies for acute pancreatitis

It is currently difficult for conventional treatments of acute pancreatitis (AP), which primarily consist of anti-inflammatory therapies, to prevent the progression of AP or to improve its outcome. This may be because the occurrence and progression of AP, which involves various inflammatory cells and cytokines, includes a series of complex immune events. Considering the complex immune system alterations during the course of AP, it is necessary to monitor the indicators related to immune cells and inflammatory mediators and to develop more individualized interventions for AP patients using immunomodulatory therapy. This review discusses the recent advances in immunomodulatory therapies. It has been suggested that overactive inflammatory responses should be inhibited and excessive immunosuppression should be avoided in the early stages of AP. The optimal duration of anti-inflammatory therapy may be shorter than previously expected (< 24 h), and appropriate immunostimulatory therapies should be administered during the period from the 3^rd d to the 14^th d in the course of AP. A combination therapy of anti-inflammatory and immune-stimulating drugs would hopefully constitute an alternative to anti-inflammatory drug monotherapy. Additionally, the detection of the genotypes of critical inflammatory mediators may be useful for screening populations of AP patients at high risk of severe infections to enable the administration of early interventions to improve their prognosis.

Toll-like receptor 4 polymorphisms to determine acute pancreatitis susceptibility and severity: A meta-analysis

AIM: To investigate the correlation of toll-like receptor 4 (TLR4) gene Asp299Gly and Thr399Ile polymorphisms and acute pancreatitis (AP) risk and severity.

METHODS: To get a more precise estimation of the relationship, a comprehensive search was performed to examine all the eligible studies of TLR4 Asp299Gly and Thr399Ile polymorphisms and AP risk. The odds ratios with 95% confidence intervals were used to assess the strength of the association. Publication bias was analyzed by Begg’s funnel plots.

RESULTS: In total, six studies with 1255 cases and 998 controls were included in this meta-analysis. Totally, no significant associations were found between TLR4 Asp299Gly or Thr399Ile polymorphisms and AP risk using five models with high homogeneity (P > 0.05). Furthermore, stratification analysis by ethnicity or assay also found no significant association in these two polymorphisms (P > 0.05), and TLR4 Asp299Gly was not associated with AP severity (P > 0.05). In addition, no publication bias was found in these studies (P > 0.05).

CONCLUSION: Our current meta-analysis suggests that TLR4 Asp299Gly and Thr399Ile polymorphisms may not be risk factors to AP susceptibility.

Acquired immunity plays an important role in the development of murine experimental pancreatitis induced by alcohol and lipopolysaccharide

OBJECTIVE

Although chronic alcohol ingestion is the major cause of chronic pancreatitis, less than 10% of alcohol abusers develop this disease. To address this issue, we created a murine model of pancreatitis induced by alcohol and lipopolysaccharide (LPS) and analyzed its immune responses.

METHODS

C57BL/6 mice were administered 20% ethanol (AL) in their drinking water and then injected intraperitoneally with LPS twice weekly for 4 weeks. Severe combined immunodeficient mice were reconstituted with splenocytes, CD4 cells, or CD8 T cells isolated from wild-type mice and then treated similarly. The severity of pancreatitis was graded histologically, and serum cytokine levels were measured.

RESULTS

Ethanol alone did not cause pancreatitis. However, the administration of AL+LPS or LPS alone induced pancreatitis. The histological scores were higher in the mice treated with AL+LPS than in those treated with LPS. Serum levels of interleukin 1β, interferon-γ, and tumor necrosis factor α were elevated in the AL+LPS-treated mice. The severe combined immunodeficient mice developed pancreatitis only after their reconstitution with splenocytes, CD4 cells, or CD8 T cells.

CONCLUSIONS

Repeated stimulation of the innate immune system is necessary, but not sufficient, to cause pancreatitis. The participation of the acquired immune response is essential for the development of the disease.

Alcohol exacerbates LPS-induced fibrosis in subclinical acute pancreatitis

The role of pancreatic acinar cells in initiating fibrogenic responses during the early stages of alcoholic acute pancreatitis has not been evaluated. We investigated the ability of injured acinar cells to generate pancreatic fibrosis in acute pancreatitis. Rats were fed either an ethanol-containing or control diet over 14 weeks and euthanized 3 or 24 hours after a single lipopolysaccharide injection. Profibrotic transforming growth factor-β of acinar cells and pancreatic fibrosis were assessed by immunofluorescence, histological characteristics, and electron microscopy. Human pancreatic tissues were also evaluated. Periacinar cell fibrosis and collagen were exacerbated 24 hours after endotoxemia in alcohol-fed rats. Alcohol exposure exacerbated acinar cell-specific production of transforming growth factor β in response to lipopolysaccharide in vivo and in acinar cell-like AR42J cells in vitro. Although a morphological examination showed no visible signs of necrosis, early pancreatic fibrosis can be initiated by little or no pancreatic necrosis. Transforming growth factor β was also significantly increased in human acinar cells from patients with acute/recurrent pancreatitis compared with chronic pancreatitis tissue. Alcohol exacerbates lipopolysaccharide-induced pancreatic fibrosis during the early onset of mild, subclinical, acute pancreatitis. We suggest that multiple, subclinical, acute pancreatitis episodes can accumulate in fibrosis during the development of chronic pancreatitis, even if there is no history of acute pancreatitis.

Role of immune cells and immune-based therapies in pancreatitis and pancreatic ductal adenocarcinoma

Immune cells are important in the pathogenesis of acute pancreatitis and determine disease severity. Results from cytokine-based clinical trials for acute pancreatitis have been disappointing, so strategies that target and alter the behavior of infiltrating immune cells require consideration. Recurrent acute pancreatitis can progress to chronic pancreatitis, which is a well-described risk factor for pancreatic ductal adenocarcinoma (PDA). However, most patients with chronic pancreatitis do not develop PDA, and most patients with PDA do not have a history of pancreatitis. Interestingly, chronic pancreatitis and PDA tissues have similarities in their desmoplasia and inflammatory infiltrates, indicating overlapping inflammatory responses. Further studies are needed to determine the differences and similarities of these responses, improve our understanding of PDA pathogenesis, and develop specific immune-based therapies. Immune cells in PDA produce immunosuppressive signals that allow tumors to evade the immune response. Unlike single therapeutic agent studies that block immunosuppressive mechanisms, studies of combination therapies that include therapeutic vaccines have provided promising results.

Sensing of commensal organisms by the intracellular sensor NOD1 mediates experimental pancreatitis

The intracellular sensor NOD1 has important host-defense functions relating to a variety of pathogens. Here, we showed that this molecule also participates in the induction of a noninfectious pancreatitis via its response to commensal organisms. Pancreatitis induced by high-dose cerulein (a cholecystokinin receptor agonist) administration depends on NOD1 stimulation by gut microflora. To analyze this NOD1 activity, we induced pancreatitis by simultaneous administration of a low dose of cerulein (that does not itself induce pancreatitis) and FK156, an activator of NOD1 that mimics the effect of gut bacteria that have breached the mucosal barrier. The pancreatitis was dependent on acinar cell production of the chemokine MCP-1 and the intrapancreatic influx of CCR2(+) inflammatory cells. Moreover, MCP-1 production involved activation of the transcription factors NF-κB and STAT3, each requiring complementary NOD1 and cerulein signaling. These studies indicate that gut commensals enable noninfectious pancreatic inflammation via NOD1 signaling in pancreatic acinar cells.

Lack of the Toll-Like Receptor 4 Gene Polymorphisms Asp299Gly and Thr399ile in a Chinese Population

The toll-like receptor 4 (TLR4), predominantly known for its role as an important mediator of immune reactions, is expressed in atherosclerotic lesions. Atherosclerosis resulting in cerebral or carotid arterial stenosis/occlusion plays the most important role in the occurrence of cerebral infarction (CI), and thus TLR4 polymorphisms may influence formation of atherosclerosis and the development of CI. This study was aimed to detect two commonly reported Asp299Gly and Thr399Ile polymorphisms in TLR4 gene in Hunan Han Chinese and their possible relationship with CI. By using the method of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), the polymorphisms TLR4, Asp299Gly and Thr399Ile, were determined in 366 CI patients and 200 controls from Changsha area of Hunan Province. Carotid intima-media thickness (CIMT) also was detected by Bmode ultrasonography. Our results suggested both the TLR4, Asp299Gly and Thr399Ile, genetic polymorphisms were not observed in all subjects from Hunan Changsha. Therefore, we speculate they might not be an important factor in the development of CI in the Chinese.

TRAF6 as the key adaptor of TLR4 signaling pathway is involved in acute pancreatitis

OBJECTIVES

To study the potential role of tumor necrosis factor receptor-associated factor 6 (TRAF6) as the key adaptor of the toll-like receptor 4 (TLR4) signaling pathway in acute pancreatitis (AP) in mice.

METHODS

Acute pancreatitis was induced by 7 intraperitoneal injections of cerulein in TLR4-deficient (TLR4-Def) and TLR4 wild-type (TLR4-WT) mice. Inflammatory severity was scored and evaluated based on pathological study. TRAF6 expression was determined by reverse transcriptase polymerase chain reaction, Western blot, and immunohistochemistry.

RESULTS

Acute pancreatitis was successfully induced in both mice strains, but the inflammatory progression was different. In TLR4-Def mice, pancreatic inflammation was blunt and mild first, then became increasingly intensive and peaked at the later stage, whereas in the TLR4-WT mice, the response was fast initiated and peaked at the early stage of AP, then alleviated gradually. TRAF6 expression in TLR4-Def mice was significantly higher than that in the TLR4-WT mice. Immunohistochemistry located TRAF6 expressed mainly in the pancreatic acinar cells.

CONCLUSIONS

The TLR4-TRAF6 signaling pathway is critically involved in AP. Other signaling pathways beyond TLR4 may participate in the pancreatic inflammatory process via TRAF6. As a convergence point of the TLR4-dependent and the TLR4-independent signaling pathways, TRAF6 plays an important role in AP.

Microsatellite polymorphism in intron 2 of human Toll-like receptor 2 gene is associated with susceptibility to acute pancreatitis in Japan

This study evaluated the association of the polymorphisms in the Toll-like receptor (TLR)2 and TLR4 genes with acute pancreatitis (AP) in Japan. The numbers of guanine-thymine [(GT)n] repeats in intron 2 of the TLR2 gene were counted in 202 unrelated patients with AP (80 with severe and 122 with mild disease) and in 286 healthy controls, using polymerase chain reaction and Genescan analysis. The alleles were divided into three subclasses: (GT)16 or less as the S allele; between (GT)17 and (GT)22 as the M allele; and (GT)23 or more as the L allele. Asp299Gly and Thr399Ile polymorphisms in the TLR4 gene were examined by polymerase chain reaction-restriction fragment length polymorphism analysis. Patients with AP had more S alleles (p < 0.001; odds ratio = 2.37; 95% confidence interval = 1.78-3.17) and fewer M alleles (p < 0.001; odds ratio = 0.40; 95% confidence interval 0.31-0.52) than did healthy controls. Genotypes SS and SL were more common, whereas MM and ML were less common in patients with AP. In subgroup analyses, the genotypes including S alleles were more common in patients with severe AP than in controls. No Asp299Gly and Thr399Ile polymorphisms were detected. In conclusion, microsatellite polymorphism in intron 2 of the TLR2 gene was associated with susceptibility to AP and its severity in Japan.

Molecular basis for pancreatitis

PURPOSE OF REVIEW

This timely review will focus on clinical and basic science studies that have greatly advanced our knowledge of the molecular mechanisms of both acute pancreatitis and chronic pancreatitis over the last year.

RECENT FINDINGS

Animal models of both severe acute pancreatitis and chronic pancreatitis have recently been developed. Several unexpected protective mechanisms, mediated by the protease activated receptor 2 and heat shock protein 70, have been described. A genetic study suggested that polymorphisms in toll-like receptor-4 might affect the risk of developing infections in acute pancreatitis. Studies of chronic pancreatitis have shown that specific neural receptors, transient receptor potential vanilloid subtype 1, mediate pain responses in a model of chronic pancreatitis. The pancreatic zymogen, chymotrypsin C, can degrade pathologically activated trypsin in the acinar cell. Inactivating mutations in chymotrypsin C have been reported to predispose to the development of chronic pancreatitis, especially in those who are prone to alcohol abuse.

SUMMARY

The implications of the last year's findings are widespread. Improved animal models of acute pancreatitis and chronic pancreatitis will be critical for performing pilot studies of therapy. A greater understanding of genetic factors and pain responses could lead to potential treatments. This review will first discuss issues related to acute pancreatitis, and then conclude with studies most relevant to chronic disease.

Toll receptor 4 Asp299Gly polymorphism and its association with preterm birth and premature rupture of membranes in a South American population

Preterm birth (PTB) is a worldwide health problem and remains the leading cause of perinatal morbidity and mortality. Systemic and local intrauterine infections have been implicated in the pathogenesis of preterm labor and delivery. Common pathways between PTB, premature rupture of ovular membranes (PROM) and altered molecular routes of inflammation have been proposed. There is evidence to support a genetic component in these conditions. Lipopolysaccharide (LPS), a component of the cell wall of Gram-negative bacteria, is thought to play a key role in eliciting an inflammatory response. LPS is recognized by proteins of the innate immune system, including Toll-like receptor 4 (TLR4). Individuals from some European countries carrying the variant alleles resulting in an amino acid substitution (Asp299Gly) are at increased risk of Gram-negative infections and premature birth. The objective of this study was to determine if preterm newborns have different allele frequency of the Asp299Gly TLR4 variant from healthy term neonates in Uruguay. The impact of PROM was also examined. There was an increase in the risk for fetuses carrying the Asp299Gly substitution in TLR4 of being severely premature (<33 weeks) and to present PROM at the same time.

TLR and MBL gene polymorphisms in severe acute pancreatitis

BACKGROUND AND OBJECTIVE

Mannose-binding lectin (MBL) and toll-like receptor (TLR)-4 gene polymorphisms have been implicated in inflammatory episodes in a number of studies. In view of the inflammatory nature of acute pancreatitis, we aimed to determine the predictive value of two point mutations in the promoter region at position -550 (H/L variants) and -221 (X/Y variants) of the MBL2 gene, and the Asp299Gly and 119C>A polymorphisms of the TLR4 gene on the occurrence of severe acute pancreatitis (SAP).

METHODS

The study included 132 patients with SAP, 106 with mild acute pancreatitis (MAP), and 121 healthy volunteers. Genotypes were determined using restriction fragment length polymorphism analysis of PCR products and by allele-specific PCR.

RESULTS

No significant difference in genotype frequency was noted between the patients with acute pancreatitis and controls for any of the gene loci studied. The distributions of the HY/HY, HY/LY, LY/LY, and LY/LX genotypes of MBL2 gene promoter and 119C>A genotype of the TLR4 gene were similar in patients with mild or severe acute pancreatitis. HY/LX genotype frequency was significantly higher in patients with SAP compared with MAP (26% vs 14%; p = 0.028).

CONCLUSION

Results indicate that the MBL2 HY/LX genotype plays an important role in the determination of disease severity to acute pancreatitis.

Role of Toll-like receptors in the development of sepsis

The outcome of sepsis and septic shock has not significantly improved in recent decades despite the development of numerous drugs and supportive care therapies. To reduce sepsis-related mortality, a better understanding of molecular mechanism(s) associated with the development of sepsis and sepsis-related organ injury is essential. There is increasing evidence that Toll-like receptors (TLRs) play a key role in the mediation of systemic responses to invading pathogens during sepsis. However, the role of TLRs in the development of sepsis and in sepsis-related organ injury remains debatable. In this review, we focus on the biological significance of TLRs during sepsis. Medline was searched for pertinent publications relating to TLRs, with emphasis on their clinical and pathophysiological importance in sepsis. In addition, a summary of the authors' own experimental data from this field was set in the context of current knowledge regarding TLRs. In both animal models and human sepsis, TLRs are highly expressed on monocytes/macrophages, and this TLR expression may not simply be a ligand-specific response in such an environment. The fact that TLR signaling enables TLRs to recognize harmful mediators induced by invading pathogens may be associated with a positive feedback loop for the inflammatory response among different cell populations. This mechanism(s) may contribute to the organ dysfunction and mortality that occurs in sepsis. A better understanding of TLR biology may unveil novel therapeutic approaches for sepsis.

The effect of toll-like receptors and toll-like receptor genetics in human disease

Toll-like receptors (TLRs) enable innate immune recognition of endogenous and exogenous prototypic ligands. They also orchestrate innate and adaptive immune response to infection, inflammation, and tissue injury. Given their significance in the immune response, it is not surprising that genetic variations of TLRs can affect their function and by extension affect the response of the organism to environmental stimuli. The genetics of TLRs provides important insights in gene-environment interactions in health and disease, and it may enable scientists to assess patients' susceptibility to diseases or predict their response to treatments.