Local secretion of complement C3 in the exocrine pancreas: ductal epithelial cells as a possible biosynthetic site

Colon-targeted complement C5a1 receptor inhibition using pH-sensitive nanoparticles ameliorates experimental colitis

BACKGROUND AND PURPOSE

The complement system is associated with inflammatory bowel disease (IBD) pathology. Complement activation induces C5a production, which signals through the C5a1 receptor (C5aR1) to drive inflammatory responses that may underlie IBD.

EXPERIMENTAL APPROACH

We examined mucosal biopsies from ulcerative colitis patients and identified C5a1 receptor up-regulated in active lesions, supporting the C5a1 receptor as a target for therapeutic intervention. Cyclic peptide C5a1 receptor antagonists such as PMX205 are orally efficacious in preclinical colitis models; however, their clinical application may be limited by rapid metabolism. We therefore encapsulated PMX205 within pH-sensitive polymers to target drug for colon delivery following oral administration.

KEY RESULTS

PMX205 nanoparticles were non-toxic and released bioactive PMX205 in simulated colon fluid. In vivo imaging of Cy5-labelled nanoparticles demonstrated rapid entry and persistence in the mouse colon for up to 48 h. Next, we utilised the dextran sodium sulphate-induced colitis model to examine efficacy of the C5a1 receptor-antagonist formulation. We show that oral administration of PMX205 nanoparticles every 2 days from symptom onset significantly mitigated weight loss, clinical illness, colon length reduction and epithelial damage to a similar degree as C5a1 receptor-/- mice. Notably, unformulated PMX205 was markedly less effective in this dosing regimen.

CONCLUSION AND IMPLICATIONS

This novel colon-targeted formulation therefore offers a potent therapeutic strategy for translating C5a1 receptor antagonists for IBD conditions such as ulcerative colitis.

Transcriptomic Module Discovery of Diarrhea-Predominant Irritable Bowel Syndrome: A Causal Network Inference Approach

Irritable bowel syndrome with diarrhea (IBS-D) is the most prevalent subtype of IBS, characterized by chronic gastrointestinal symptoms in the absence of identifiable pathological findings. This study aims to investigate the molecular mechanisms underlying IBS-D using transcriptomic data. By employing causal network inference methods, we identify key transcriptomic modules associated with IBS-D. Utilizing data from public databases and applying advanced computational techniques, we uncover potential biomarkers and therapeutic targets. Our analysis reveals significant molecular alterations that affect cellular functions, offering new insights into the complex pathophysiology of IBS-D. These findings enhance our understanding of the disease and may foster the development of more effective treatments.

Obesity Contributes to Inflammation in Patients with IBS via Complement Component 3 and C-Reactive Protein

Irritable Bowel Syndrome (IBS) is usually a lifelong state that disturbs the digestive system. IBS has been linked to low-grade inflammation and the release of inflammatory mediators into the bloodstream. This could be associated with the degree of obesity presented by patients with IBS. Reports imply that IBS is more frequent in obese patients than in the overall population, with a prevalence of up to 31%. Here, we evaluated the serum levels of immunological and inflammation molecules and their correlation with Body Mass Index in IBS patients and the healthy control (HC). Seventy-nine serum samples of the IBS patients and thirty-five of the HC group were analyzed to determine the levels of each molecule and compare them with their BMI. Serum levels of C3 and C4 were significantly increased in IBS patients. C3 and C4 levels were higher in IBS-M and IBS-D subtypes compared with the HC group. When patients were grouped by BMI, a positive correlation between serum C3 (r = 0.49, p < 0.0001) and CRP (r = 0.40, p < 0.001) levels was found. Our results show, for the first time, a correlation between immunological molecules and BMI in IBS patients, suggesting that the inflammatory nature of obesity could contribute to the development of the symptoms in IBS through the stimulation and release of proteins as complement components and CRP.

The Combination of Radiotherapy and Complement C3a Inhibition Potentiates Natural Killer cell Functions Against Pancreatic Cancer

Pancreatic cancer is one of the deadliest cancers, against which current immunotherapy strategies are not effective. Herein, we analyzed the immune cell composition of the tumor microenvironment of pancreatic cancer samples in The Cancer Genome Atlas and found that the presence of intratumoral NK cells correlates with survival. Subsequent analysis also indicated that NK cell exclusion from the microenvironment is found in a high percentage of clinical pancreatic cancers and in preclinical models of pancreatic cancer. Mechanistically, NK cell exclusion is regulated in part by complement C3a and its receptor signaling. Inhibition of the C3a receptor enhances NK cell infiltration in syngeneic mouse models of pancreatic cancer resulting in tumor growth delay. However, tumor growth inhibition mediated by NK cells is not sufficient alone for complete tumor regression, but is potentiated when combined with radiation therapy. Our findings indicate that although C3a inhibition is a promising approach to enhance NK cell-based immunotherapy against pancreatic cancer, its combination with radiation therapy hold greater therapeutic benefit.

Deficiency of complement component 3 may be linked to the development of constipation in FVB/N-C3em1Hlee /Korl mice

Alterations in complement component 3 (C3) expression has been reported to be linked to several bowel diseases including Crohn's disease, inflammatory bowel disease, and ulcerative colitis; however, the association with constipation has never been investigated. In this study, we aimed to investigate the correlation between C3 regulation and constipation development using a C3 deficiency model. To achieve these, alterations in stool excretion, transverse colon histological structure, and mucin secretion were analyzed in FVB/N-C3em1Hlee /Korl (C3 knockout, C3 KO) mice with the deletion of 11 nucleotides in exon 2 of the C3 gene. The stool excretion parameters, gastrointestinal transit, and intestine length were remarkably decreased in C3 KO mice compared with wild-type (WT) mice, although there was no specific change in feeding behavior. Furthermore, C3 KO mice showed a decrease in mucosal and muscle layer thickness, alterations in crypt structure, irregular distribution of goblet cells, and an increase of mucin droplets in the transverse colon. Mucin secretion was suppressed, and they accumulated in the crypts of C3 KO mice. In addition, the constipation phenotypes detected during C3 deficiency were confirmed in FVB/N mice treated with C3 convertase inhibitor (rosmarinic acid (RA)). Similar phenotypes were observed with respect to stool excretion parameters, gastrointestinal transit, intestine length, alterations in crypt structure, and mucin secretion in RA-treated FVB/N mice. Therefore, the results of the present study provide the first scientific evidence that C3 deficiency may play an important role in the development of constipation phenotypes in C3 KO mice.

Complement opsonization of HIV affects primary infection of human colorectal mucosa and subsequent activation of T cells

HIV transmission via genital and colorectal mucosa are the most common routes of dissemination. Here, we explored the effects of free and complement-opsonized HIV on colorectal tissue. Initially, there was higher antiviral responses in the free HIV compared to complement-opsonized virus. The mucosal transcriptional response at 24 hr revealed the involvement of activated T cells, which was mirrored in cellular responses observed at 96 hr in isolated mucosal T cells. Further, HIV exposure led to skewing of T cell phenotypes predominantly to inflammatory CD4+ T cells, that is Th17 and Th1Th17 subsets. Of note, HIV exposure created an environment that altered the CD8+ T cell phenotype, for example expression of regulatory factors, especially when the virions were opsonized with complement factors. Our findings suggest that HIV-opsonization alters the activation and signaling pathways in the colorectal mucosa, which promotes viral establishment by creating an environment that stimulates mucosal T cell activation and inflammatory Th cells.

Podocytes Produce and Secrete Functional Complement C3 and Complement Factor H

Podocytes are an important part of the glomerular filtration barrier and the key player in the development of proteinuria, which is an early feature of complement mediated renal diseases. Complement factors are mainly liver-born and present in circulation. Nevertheless, there is a growing body of evidence for additional sites of complement protein synthesis, including various cell types in the kidney. We hypothesized that podocytes are able to produce complement components and contribute to the local balance of complement activation and regulation. To investigate the relevant balance between inhibiting and activating sides, our studies focused on complement factor H (CFH), an important complement regulator, and on C3, the early key component for complement activation. We characterized human cultured podocytes for the expression and secretion of activating and regulating complement factors, and analyzed the secretion pathway and functional activity. We studied glomerular CFH and C3 expression in puromycin aminonucleoside (PAN) -treated rats, a model for proteinuria, and the physiological mRNA-expression of both factors in murine kidneys. We found, that C3 and CFH were expressed in cultured podocytes and expression levels differed from those in cultivated glomerular endothelial cells. The process of secretion in podocytes was stimulated with interferon gamma and located in the Golgi apparatus. Cultured podocytes could initiate the complement cascade by the splitting of C3, which can be shown by the generation of C3a, a functional C3 split product. C3 contributed to external complement activation. Podocyte-secreted CFH, in conjunction with factor I, was able to split C3b. Podocytes derived from a patient with a CFH mutation displayed impaired cell surface complement regulation. CFH and C3 were synthesized in podocytes of healthy C57Bl/6-mice and were upregulated in podocytes of PAN treated rats. These data show that podocytes produce functionally active complement components, and could therefore influence the local glomerular complement activation and regulation. This modulating effect should therefore be considered in all diseases where glomerular complement activation occurs. Furthermore, our data indicate a potential novel role of podocytes in the innate immune system.

Mucin adsorbed by E. coli can affect neutrophil activation in vitro

Bacteria colonizing human intestine adhere to the gut mucosa and avoid the innate immune system. We previously demonstrated that Escherichia coli isolates can adsorb mucin from a diluted solution in vitro. Here, we evaluated the effect of mucin adsorption by E. coli cells on neutrophil activation in vitro. Activation was evaluated based on the detection of reactive oxygen species production by a chemiluminescent reaction (ChL), observation of morphological alterations in neutrophils and detection of exocytosis of myeloperoxidase and lactoferrin. We report that mucin adsorbed by cells of SharL1 isolate from Crohn's disease patient's inflamed ileum suppressed the potential for the activation of neutrophils in whole blood. Also, the binding of plasma complement proteins and immunoglobulins to the bacteria was reduced. Desialylated mucin, despite having the same adsorption efficiency to bacteria, had no effect on the blood ChL response. The effect of mucin suggests that it shields epitopes that interact with neutrophils and plasma proteins on the bacterial outer membrane. Potential candidates for these epitopes were identified among the proteins within the bacterial outer membrane fraction by 2D‐PAGE, fluorescent mucin binding on a blot and HPLC‐MS/MS. In vitro, the following proteins demonstrated mucin adsorption: outer membrane porins (OmpA, OmpC, OmpD and OmpF), adhesin OmpX, the membrane assembly factor OmpW, cobalamine transporter, ferrum uptake protein and the elongation factor Ef Tu‐1. In addition to their other functions, these proteins are known to be bacterial surface antigens. Therefore, the shielding of epitopes by mucin may affect the dynamics and intensity of an immune response.

The intestinal complement system in inflammatory bowel disease: Shaping intestinal barrier function

The complement system is part of innate sensor and effector systems such as the Toll-like receptors (TLRs). It recognizes and quickly systemically and/or locally respond to microbial-associated molecular patterns (MAMPs) with a tailored defense reaction. MAMP recognition by intestinal epithelial cells (IECs) and appropriate immune responses are of major importance for the maintenance of intestinal barrier function. Enterocytes highly express various complement components that are suggested to be pivotal for proper IEC function. Appropriate activation of the intestinal complement system seems to play an important role in the resolution of chronic intestinal inflammation, while over-activation and/or dysregulation may worsen intestinal inflammation. Mice deficient for single complement components suffer from enhanced intestinal inflammation mimicking the phenotype of patients with chronic inflammatory bowel disease (IBD) such as Crohn's disease (CD) or ulcerative colitis (UC). However, the mechanisms leading to complement expression in IECs seem to differ markedly between UC and CD patients. Hence, how IECs, intestinal bacteria and epithelial cell expressed complement components interact in the course of IBD still remains to be mostly elucidated to define potential unique patterns contributing to the distinct subtypes of intestinal inflammation observed in CD and UC.

C3aR and C5aR1 act as key regulators of human and mouse β-cell function

AIMS

Complement components 3 and 5 (C3 and C5) play essential roles in the complement system, generating C3a and C5a peptides that are best known as chemotactic and inflammatory factors. In this study we characterised islet expression of C3 and C5 complement components, and the impact of C3aR and C5aR1 activation on islet function and viability.

MATERIALS AND METHODS

Human and mouse islet mRNAs encoding key elements of the complement system were quantified by qPCR and distribution of C3 and C5 proteins was determined by immunohistochemistry. Activation of C3aR and C5aR1 was determined using DiscoverX beta-arrestin assays. Insulin secretion from human and mouse islets was measured by radioimmunoassay, and intracellular calcium ([Ca2+]i), ATP generation and apoptosis were assessed by standard techniques.

RESULTS

C3 and C5 proteins and C3aR and C5aR1 were expressed by human and mouse islets, and C3 and C5 were mainly localised to β- and α-cells. Conditioned media from islets exposed for 1 h to 5.5 and 20 mM glucose stimulated C3aR and C5aR1-driven beta-arrestin recruitment. Activation of C3aR and C5aR1 potentiated glucose-induced insulin secretion from human and mouse islets, increased [Ca2+]i and ATP generation, and protected islets against apoptosis induced by a pro-apoptotic cytokine cocktail or palmitate.

CONCLUSIONS

Our observations demonstrate a functional link between activation of components of the innate immune system and improved β-cell function, suggesting that low-level chronic inflammation may improve glucose homeostasis through direct effects on β-cells.

Regulation of epithelial cell expressed C3 in the intestine - Relevance for the pathophysiology of inflammatory bowel disease?

The complement system not only plays a critical role in efficient detection and clearance of bacteria, but also in intestinal immune homeostasis as mice deficient for key complement components display enhanced intestinal inflammation upon experimental colitis. Because underlying molecular mechanisms for this observation are unclear, we investigated the crosstalk between intestinal epithelial cells (IEC), bacteria and the complement system in the course of chronic colitis. Surprisingly, mouse intestinal epithelial cell lines constitutively express high mRNA levels of complement component 3 (C3), Toll-like receptor 2 (Tlr2) and Tlr4. Stimulation of these cells with lipopolysaccharide (LPS), but not with flagellin, LD-muramyldipeptide or peptidoglycan, triggered increased C3 expression, secretion and activation. Stimulation of the C3aR on these cell lines with C3a resulted in an increase of LPS-triggered pro-inflammatory response. Tissue biopsies from C57BL/6J mice revealed higher expression of C3, Tlr1, Tlr2 and Tlr4 in colonic primary IECs (pIECs) compared to ileal pIECs, while in germ-free mice no differences in C3 protein expression was observed. In DSS-induced chronic colitis mouse models, C3 mRNA expression was upregulated in colonic biopsies and ileal pIECs with elevated C3 protein in the lamina propria, IECs and the mucus. Notably, increased C3b opsonization of mucosa-attached bacteria and decreased fecal full-length C3 protein was observed in DSS-treated compared to untreated mice. Of significant interest, non-inflamed and inflamed colonic biopsy samples from CD but not UC patients displayed exacerbated C3 expression compared to controls. These findings suggest that a novel TLR4-C3 axis could control the intestinal immune response during chronic colitis.

Protective Role of Complement C3 Against Cytokine-Mediated β-Cell Apoptosis

Type 1 diabetes is a chronic autoimmune disease characterized by pancreatic islet inflammation and β-cell destruction by proinflammatory cytokines and other mediators. Based on RNA sequencing and protein-protein interaction analyses of human islets exposed to proinflammatory cytokines, we identified complement C3 as a hub for some of the effects of cytokines. The proinflammatory cytokines interleukin-1β plus interferon-γ increase C3 expression in rodent and human pancreatic β-cells, and C3 is detected by histology in and around the islets of diabetic patients. Surprisingly, C3 silencing exacerbates apoptosis under both basal condition and following exposure to cytokines, and it increases chemokine expression upon cytokine treatment. C3 exerts its prosurvival effects via AKT activation and c-Jun N-terminal kinase inhibition. Exogenously added C3 also protects against cytokine-induced β-cell death and partially rescues the deleterious effects of inhibition of endogenous C3. These data suggest that locally produced C3 is an important prosurvival mechanism in pancreatic β-cells under a proinflammatory assault.

Human Secretory IgM Antibodies Activate Human Complement and Offer Protection at Mucosal Surface

IgM molecules circulate in serum as large polymers, mainly pentamers, which can be transported by the poly-Ig receptor (pIgR) across epithelial cells to mucosal surfaces and released as secretory IgM (SIgM). The mucosal SIgM molecules have non-covalently attached secretory component (SC), which is the extracellular part of pIgR which is cleaved from the epithelial cell membrane. Serum IgM antibodies do not contain SC and have previously been shown to make a conformational change from 'a star' to a 'staple' conformation upon reaction with antigens on a cell surface, enabling them to activate complement. However, it is not clear whether SIgM similarly can induce complement activation. To clarify this issue, we constructed recombinant chimeric (mouse/human) IgM antibodies against hapten 5-iodo-4-hydroxy-3-nitro-phenacetyl (NIP) and in addition studied polyclonal IgM formed after immunization with a meningococcal group B vaccine. The monoclonal and polyclonal IgM molecules were purified by affinity chromatography on a column containing human SC in order to isolate joining-chain (J-chain) containing IgM, followed by addition of excess amounts of soluble SC to create SIgM (IgM J+ SC+). These SIgM preparations were tested for complement activation ability and shown to be nearly as active as the parental IgM J+ molecules. Thus, SIgM may offer protection against pathogens at mucosal surface by complement-mediated cell lysis or by phagocytosis mediated by complement receptors present on effector cells on mucosa.

Do antimicrobial peptides and complement collaborate in the intestinal mucosa?

It is well understood that multiple antimicrobial peptides (AMPs) are constitutively deployed by the epithelium to bolster the innate defenses along the entire length of the intestines. In addition to this constitutive/homeostatic production, AMPs may be inducible and levels changed during disease. In contrast to this level of knowledge on AMP sources and roles in the intestines, our understanding of the complement cascade in the healthy and diseased intestines is rudimentary. Epithelial cells make many complement proteins and there is compelling evidence that complement becomes activated in the lumen. With the common goal of defending the host against microbes, the opportunities for cross-talk between these two processes is great, both in terms of actions on the target microbes but also on regulating the synthesis and secretion of the alternate family of molecules. This possibility is beginning to become apparent with the finding that colonic epithelial cells possess anaphylatoxin receptors. There still remains much to be learned about the possible points of collaboration between AMPs and complement, for example, whether there is reciprocal control over expression in the intestinal mucosa in homeostasis and restoring the balance following infection and inflammation.

The complement system in inflammatory bowel disease

Complement is well appreciated to be a potent innate immune defense against microbes and is important in the housekeeping act of removal of apoptotic and effete cells. It is also understood that hyperactivation of complement, or the lack of regulators, may underlie chronic inflammatory diseases. A pipeline of products to intervene in complement activation, some already in clinical use, is being studied in various chronic inflammatory diseases. To date, the role of complement in inflammatory bowel disease has not received a lot of research interest. Novel genetically modified laboratory animals and experiments using antagonists to complement effector molecules have kindled important research observations implicating the complement system in inflammatory bowel disease pathogenesis. We review the evidence base for the role and potential therapeutic manipulation of the complement cascade in inflammatory bowel disease.

Profiling the potential tumor markers of pancreatic ductal adenocarcinoma using 2D-DIGE and MALDI-TOF-MS: up-regulation of Complement C3 and alpha-2-HS-glycoprotein

BACKGROUND/AIMS

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease with an increasing incidence worldwide. Due to lack of early diagnosis and poor prognosis, it is rather critical to improve the early diagnosis of PDAC. A comparative proteomic method was used to analyze serum proteins to find a new potential specific marker.

METHODS

Comparative analysis of the pancreatic peripheral blood protein profiling from 40 pancreatic cancer patients, 10 pancreatic benign tumor patients, 10 chronic pancreatitis patients and 40 cancer-free controls. The samples were carried out by 2D-differential gel electrophoresis (2D-DIGE) and differentially expressed proteins were identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). Two up-regulated proteins were further validation by real time RT-PCR, Western blot analysis and Immunohistochemistry (IHC).

RESULTS

We identified fourteen differently expressed proteins in PDAC group compared with cancer-free control group, including 9 up-regulation and 5 down-regulation proteins. Increased Complement C3 and alpha-2-HS-glycoprotein (AHSG) were further confirmed by real time RT-PCR, Western blot analysis and IHC. The expressions of Complement C3 and AHSG were higher in PDAC than that in other groups.

CONCLUSIONS

These results suggest that Complement C3 and AHSG might be the potential tumor markers in PDAC screening and diagnosis. The finding of inflammation mediated factor Complement C3 revealed that inflammation might be closely related with the occurrence and development process of PDAC.

Neutralization of complement component C5 ameliorates the development of dextran sulfate sodium (DSS)-colitis in mice

The complement system is a potent effector of innate immunity. To elucidate the pathophysiological role of the complement system in inflammatory bowel disease, we evaluated the effects of anti-C5 antibodies on the development of dextran sulfate sodium-induced colitis in mice. Dextran sulfate sodium-colitis was induced in BALB/c mice with intraperitoneal administrations of anti-C5 antibodies (1 mg/body [DOSAGE ERROR CORRECTED]) every 48 h. Tissue samples were evaluated by standard histological procedures. The mucosal mRNA expression of the inflammatory cytokines was analyzed by real-time PCR. Body weight loss in the mice was completely blocked by the administration of anti-C5 antibody. The disease activity index was significantly lower in the anti-C5 antibody-treated mice than the dextran sulfate sodium mice. The colonic weight/length ratio, histological colitis score and mucosal myeloperoxidase activity were significantly lower in the anti-C5 antibody-treated mice than the dextran sodium sulfate mice. The administration of the anti-C5 antibody significantly reduced the mucosal expression of mRNAs for tumor necrosis factor-α, interleukin-1β and interleukin-6. In conclusion, the complement system plays a role in the development of dextran sodium sulfate-induced experimental colitis.

Role of Kupffer cells in the infection of biliary tract

Acute infection of biliary tract was a frequent severe case in hepatobiliary surgery and also a common cause of sepsis, multiple organ system failure (MOSF) and even death. The biliary system could suppress infection through physical, chemical and immune mechanisms. Kupffer cell (KC) is an important ingredient of the monocyte-phagocyte system and also a natural barrier against the infection of biliary tract, thus plays an important role both in the development and prevention of biliary tract infection. How to regulate the function of Kupffer cells and prevent multiple organ system failure in biliary duct infection are the most important problems to be solved.

The relative importance of local and systemic complement production in ischaemia, transplantation and other pathologies

Besides a critical role in innate host defence, complement activation contributes to inflammatory and immunological responses in a number of pathological conditions. Many tissues outside the liver (the primary source of complement) synthesise a variety of complement proteins, either constitutively or response to noxious stimuli. The significance of this local synthesis of complement has become clearer as a result of functional studies. It revealed that local production not only contributes to the systemic pool of complement but also influences local tissue injury and provides a link with the antigen-specific immune response. Extravascular production of complement seems particularly important at locations with poor access to circulating components and at sites of tissue stress responses, notably portals of entry of invasive microbes, such as interstitial spaces and renal tubular epithelial surfaces. Understanding the relative importance of local and systemic complement production at such locations could help to explain the differential involvement of complement in organ-specific pathology and inform the design of complement-based therapy. Here, we will describe the lessons we have learned over the last decade about the local synthesis of complement and its association with inflammatory and immunological diseases, placing emphasis on the role of local synthesis of complement in organ transplantation.

Decay-Accelerating Factor Deficiency Increases Susceptibility to Dextran Sulfate Sodium-Induced Colitis: Role for Complement in Inflammatory Bowel Disease

Decay-accelerating factor (DAF or CD55) is expressed on colonic epithelial cells but its function in the mucosa is unknown. In humans, a proportion of DAF-deficient (Cromer INAB) patients develop inflammatory bowel disease (IBD). To evaluate how DAF deficiency may contribute to gut inflammation and thus could play a role in IBD pathogenesis, we compared the severity of dextran sulfate sodium-induced colitis in Daf1 gene-targeted and control mice. Seven days after consuming 3% dextran sulfate sodium in their drinking water, Daf1(-/-) mice suffered markedly greater weight loss (-24.7 +/- 7.5% vs -14.2% +/- 4.9%), exhibited uniformly bloody diarrhea as compared with soft stool in control mice, developed shortened colons, and had larger spleens. Histological examination of distal colons showed massively increased neutrophilic and mononuclear cell infiltration, greater epithelial cell destruction, and increased ulcerations. Cytokine production in organ cultures of colonic explants showed increased levels of IL-12 and IL-6. Fourteen days after switching back to regular water, in contrast to the Daf1(+/+) controls which showed little stool abnormality, all Daf1(-/-) mice continued to have diarrhea. Organ culture cytokine measurements at this time point, i.e., the end of the recovery phase, showed markedly increased levels of IL-10 (6-fold), IL-12 (4-fold), and IL-6 (2-fold), as well as TNF-alpha (>10-fold) compared with the controls. Our findings argue that, as shown for IL-10 in IL-10(-/-) mice and IL-2 in IL-2(-/-) mice, DAF control of complement additionally is important in regulating gut homeostasis and consequently its activity may participate in protecting against IBD.

Intestinal trefoil factor induces decay-accelerating factor expression and enhances the protective activities against complement activation in intestinal epithelial cells

Mucosal damage induces a massive influx of serum complement components into the lumen. The epithelium produces a number of factors that can potentially ameliorate injury including intestinal trefoil factor (ITF), a small protease-resistant peptide produced and secreted onto the mucosal surface by goblet cells, and decay-accelerating factor (DAF), a protein produced by columnar epithelium which protects the host tissue from autologous complement injury. However, coordination of these intrinsic defensive products has not been delineated. DAF protein and mRNA expression were evaluated by immunoblotting and Northern blotting, respectively. NF-kappaB-DNA binding activity and DAF promoter activity were assessed by an electrophoretic gel mobility shift assay and a reporter gene luciferase assay, respectively. ITF induced a dose- and time-dependent increase in DAF protein and mRNA expression in human (HT-29 and T84) and rat (IEC-6) intestinal epithelial cells. In differentiated T84 cells grown on cell culture inserts, basolateral stimulation with ITF strongly enhanced DAF expression, but apical stimulation had no effects. The C3 deposition induced by complement activation was significantly blocked by the treatment with ITF. In HT-29 cells, ITF increased the stability of DAF mRNA. ITF also enhanced the promoter activity of the DAF gene via NF-kappaB motif and induced activation of NF-kappaB-DNA binding activity. ITF promotes protection of epithelial cells from complement activation via up-regulation of DAF expression, contributing to a robust mucosal defense.

Ligation of the Fas antigen stimulates chemokine secretion in pancreatic cancer cell line PANC-1

BACKGROUND AND AIM

The role of chemokines in the process of immune cell infiltration into pancreatic cancer tissue has been reported. In this study, we investigated the induction of chemokines (interleukin (IL)-8 and monocyte chemoattractant protein (MCP)-1) by Fas antigen (Ag)-stimulation in a human pancreatic cancer cell line, PANC-1.

METHODS

The chemokine secretion was evaluated by using an ELISA and a northern blot, and the activation of nuclear factor-kappa B (NF-kappa B) was assessed by using an electrophoretic gel mobility shift assay (EMSA).

RESULTS

The Fas antigen (Ag) stimulation clearly induced an increase in IL-8 and MCP-1 secretion in PANC-1 cells. This effect was also observed at the mRNA level. The induction of chemokine secretion by Fas Ag stimulation required de novo gene expression and protein synthesis. The pretreatment with interferon (IFN)-gamma markedly enhanced the effects of Fas Ag stimulation; IFN-gamma pretreatment and Fas Ag stimulation synergistically induced not only apoptosis but also IL-8 and MCP-1 secretion. Flow cytometric analysis demonstrated that IFN-gamma significantly enhanced Fas Ag expression. In addition, Fas Ag stimulation actually evoked NF-kappa B activation in this cell line.

CONCLUSION

Our results indicate that Fas Ag stimulation can induce chemokine secretion in PANC-1 cells, suggesting the contribution of Fas stimulation to the accumulation of immune cells in pancreatic cancer tissue.

The expression of chemokine genes correlates with nuclear factor-kappaB activation in human pancreatic cancer cell lines

Chemokines may regulate the process of immune cell infiltration that is often found in pancreatic cancer. In this study, we investigated the secretion of the chemokines [interleukin (IL)-8, monocyte chemoattractant protein (MCP)-1, and RANTES (regulated on activation, normal T cell expressed and secreted)] in human pancreatic cancer cell lines. The chemokine secretion in three pancreatic cancer cell lines (PANC-1, MIA PaCa-2, and BxPC-3) was evaluated by enzyme-linked immunosorbent assay (ELISA) and Northern blot, and the activation of nuclear factor-kappaB (NF-kappaB) and NF-IL6 was assessed by an electrophoretic gel mobility shift assay (EMSA). Without any stimulation, IL-8 secretion was detected in all cell lines, and MCP-1 secretion was detected in PANC-1 and MIA PaCa-2 cells. However, RANTES secretion was not detected in all cells. The addition of IL-1beta and tumor necrosis factor (TNF)-alpha strongly enhanced IL-8, MCP-1, and RANTES secretion; these responses were observed at the mRNA level as well as at the protein level. IL-1beta and TNF-alpha induced a rapid activation of nuclear factor (NF)-kappaB in PANC-1 cells, and the increase in chemokine mRNA expression correlated with NF-kappaB activation. The activation of NF-IL6 was modest. A blockade of NF-kappaB activation by TPCK markedly reduced the IL-1beta- and TNF-alpha-induced chemokine gene expression. Our findings indicate that chemokines are produced by pancreatic cancer cells, and suggest that these factors may contribute to the accumulation of tumor-associated immune cells. In addition, the transcriptional activation of chemokine genes in pancreatic cancer cells may be closely associated with NF-kappaB activation.

Transforming growth factor-beta1 acts as a potent inhibitor of complement C3 biosynthesis in human pancreatic cancer cell lines

In this study, we attempted to determine how transforming growth factor (TGF)-beta1 affects complement C3 secretion in the pancreatic cancer cell lines PANC-1 and BxPC-3. We also compared the responses in C3 secretion with those in interleukin (IL)-8 secretion. The C3 and IL-8 expression was evaluated at the protein and messenger RNA (mRNA) levels. The activation of nuclear factor-kappaB (NF-kappaB) was assessed by an electrophoretic gel mobility shift assay (EMSA). IL-1beta and tumor necrosis factor (TNF)-alpha both induced a marked increase in C3 and IL-8 secretion. However, TGF-beta1 potently decreased the IL-1beta- and TNF-alpha-induced C3 secretion, whereas the IL-8 secretion was weakly but significantly enhanced. These responses were also observed at the mRNA level. In PANC-1 cells, IL-1beta and TNF-alpha induced a rapid activation of nuclear factor (NF)-kappaB, and TGF-beta1 enhanced this activation slightly. The induction of Fos protein has been reported to be required for the inhibitory action of TGF-beta1, and the translocation of Fos protein into the nucleus was associated with TGF-beta1 stimulation in PANC-1 cells. Our results suggest that TGF-beta1 may act as a potent inhibitor of C3 secretion in pancreatic cancer cell lines under inflammatory conditions. This action of TGF-beta1 did not correlate with NF-kappaB activation, but associated with the translocation of Fos protein into the nucleus.

Local complement genes expression in the mammary gland: effect of gestation and inflammation

Complement components in breast milk may enhance the local immune response in the gut of infants. In this study, we investigated the expression of complement genes in the mammary gland and attempted to determine possible regulatory mechanisms. We have studied the expression of C3, C4, factor B, and HLA-DRalpha mRNA by in situ hybridization in gestational mammary gland specimens and compared these findings to those in breast tissue affected with an inflammatory process, lactating adenoma or idiopathic gynecomastia. In normal resting breast, only C4 mRNA was noted in some ductal epithelium. In gestational mammary gland, there was a diffuse expression of C4, C3, and factor B mRNA in the epithelial cells of the acini. A similar pattern of complement gene expression was found in localized areas of an infectious inflammatory process. In addition, in the inflammatory specimens, there was also expression of C3 mRNA in infiltrating macrophages (CD 68 positive cells). In gynecomastia, C4 mRNA was noted in ductal epithelium, and there was a marked increased expression of C3 mRNA in the proliferating epithelium of the lactating adenoma. HLA-DRalpha was observed only in macrophages involved in the inflammatory response. Our findings, which reflect the hormonal and inflammatory events in vivo, provide new insights as to in situ complement gene expression.

Molecular characterization of complement components (C3, C4, and factor B) in human saliva

A molecular analysis of complement components (C3, C4, and factor B) in human saliva was performed by SDS-PAGE and immunoblotting. Complement C3 was detected as a molecule composed of a 115-kDa alpha-chain linked to a 70-kDa beta chain by disulfide bonds, and C3 levels ranged from 0.52 to 15.0 micrograms/ml (n = 15). C4 was detected as a triple-chain molecule (98-kDa alpha chain, 73-kDa beta chain, and 33-kDa gamma chain) linked by disulfide bonds, and C4 levels ranged from 0.086 to 4.8 micrograms/ml. Factor B was detected as a 100-kDa single chain, and factor B levels ranged from 0.042 to 0.62/microgram/ml. The sizes and subunit structures of the complement components in human saliva were compatible with those reported in human serum. The results of a hemolytic assay indicated that the complement molecules in human saliva were functionally active. These complement components may participate in the local immune and inflammatory responses in the oral cavity.

Biosynthesis and secretion of MHC class III gene products (complement C4 and factor B) in the exocrine pancreas

We recently found that complement C3 is locally synthesized and secreted into the exocrine pancreas. In the present study, we attempted to demonstrate the secretion of complement C4 and factor B in the exocrine pancreas. In five samples of pancreatic fluid, both C4 and factor B proteins were detected by enzyme-linked immunosorbent assay (ELISA). Immunoblot analysis revealed the C4 and factor B molecules in pancreatic fluid to be identical with these molecules in serum. Reverse transcriptase (RT)-polymerase chain reaction (PCR) analysis in pancreatic carcinoma cell lines suggested ductal epithelial cells to be the local production sites of these proteins in the pancreas. The secretion of C4 and factor B in ductal cell lines (PANC-1 and MIA PaCa-2) was independently regulated by interleukin (IL)-1 beta, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma; C4 secretion was induced by IFN-gamma, whereas factor B secretion was induced by IL-1 beta, TNF-alpha, or IFN-gamma. These observations indicate that: (a) complement C4 and factor B are secreted into the exocrine pancreas, (b) ductal epithelial cells appear to be the site of C4 and factor B biosynthesis, and (c) local secretion of C4 and factor B in the pancreas is differentially regulated by IL-1 beta, TNF-alpha, and IFN-gamma.

Characterization of complement C3, C4, and factor B molecules in human bile

We performed molecular analysis of complement components (C3, C4, and factor B) in human bile by sodium dodecyl sulfate-polyarylamide gel electrophoresis (SDS-PAGE) and immunoblotting. Complement C3 was detected as a molecule composed of a 115-kDa alpha-chain linked to a 70-kDa beta-chain by disulfide bonds, and C3 levels ranged from 45 to 650 micrograms/ml (n = 15). C4 was detected as a triple chain (98-kDa alpha-chain, 73-kDa beta-chain, and 33-kDa gamma-chain) molecule linked by disulfide bonds, and C4 levels ranged from 2.5 to 60 micrograms/ml. Factor B, a component of the alternative pathway, was also detected, as an intact form. Factor B levels ranged from 0.3 to 8.0 micrograms/ml. The sizes and subunit structures of complement components in human bile were compatible with those reported in human serum. The results of a hemolytic assay indicated that complement molecules in human bile were functionally active. These molecules may participate in local immune and inflammatory responses in the biliary tract.

Tumour necrosis factor-alpha up-regulates decay-accelerating factor gene expression in human intestinal epithelial cells

The increased expression of decay-accelerating factor (DAF) has been detected in intestinal epithelial cells at the inflamed mucosa. In this study, we examined the effects of tumour necrosis factor (TNF)-alpha on DAF expression in three intestinal epithelial cell lines. DAF mRNA expression was evaluated by Northern blot analysis, and DAF protein expression was analysed by biotin labelling and immunoprecipitation. TNF-alpha induced a marked increase in DAF mRNA and protein expression in HT-29, T84 and Caco-2 cells. In HT-29 cells, the effects of TNF-a on DAF mRNA accumulation were observed in a dose-dependent manner; DAF mRNA accumulation reached a maximum at 3-6 hr, and then gradually decreased. These effects of TNF-alpha required de novo protein synthesis. Messenger RNA stability studies suggested that TNF-alpha partially regulated DAF gene expression by a posttranscriptional mechanism. Moreover, the combination of TNF-alpha and interleukin (IL)-4 induced an additive increase in DAF mRNA accumulation in HT-29 and T84 cells. In human intestinal epithelial cells, TNF-alpha acts as a potent inducer of DAF mRNA expression, indicating an important role for TNF-alpha in the regulation of DAF expression at the inflamed mucosa.