The estrogen signaling pathway reprograms prostate cancer cell metabolism and supports proliferation and disease progression

Just as the androgen receptor (AR), the estrogen receptor α (ERα) is expressed in the prostate and is thought to influence prostate cancer (PCa) biology. Yet, the incomplete understanding of ERα functions in PCa hinders our ability to fully comprehend its clinical relevance and restricts the repurposing of estrogen-targeted therapies for the treatment of this disease. Using two human PCa tissue microarray cohorts, we first demonstrated that nuclear ERα expression was heterogeneous among patients, being only detected in half of tumors. Positive nuclear ERα levels were correlated with disease recurrence, progression to metastatic PCa, and patient survival. Using in vitro and in vivo models of the normal prostate and PCa, bulk and single-cell RNA-Seq analyses revealed that estrogens partially mimic the androgen transcriptional response and induce specific biological pathways linked to proliferation and metabolism. Bioenergetic flux assays and metabolomics confirmed the regulation of cancer metabolism by estrogens, supporting proliferation. Using cancer cell lines and patient-derived organoids, selective estrogen receptor modulators, a pure anti-estrogen, and genetic approaches impaired cancer cell proliferation and growth in an ERα-dependent manner. Overall, our study revealed that, when expressed, ERα functionally reprograms PCa metabolism, is associated with disease progression, and could be targeted for therapeutic purposes.

Isocitrate dehydrogenase 1 sustains a hybrid cytoplasmic-mitochondrial tricarboxylic acid cycle that can be targeted for therapeutic purposes in prostate cancer

The androgen receptor (AR) is an established orchestrator of cell metabolism in prostate cancer (PCa), notably by inducing an oxidative mitochondrial program. Intriguingly, AR regulates cytoplasmic isocitrate dehydrogenase 1 (IDH1), but not its mitochondrial counterparts IDH2 and IDH3. Here, we aimed to understand the functional role of IDH1 in PCa. Mouse models, in vitro human PCa cell lines, and human patient-derived organoids (PDOs) were used to study the expression and activity of IDH enzymes in the normal prostate and PCa. Genetic and pharmacological inhibition of IDH1 was then combined with extracellular flux analyses and gas chromatography-mass spectrometry for metabolomic analyses and cancer cell proliferation in vitro and in vivo. In PCa cells, more than 90% of the total IDH activity is mediated through IDH1 rather than its mitochondrial counterparts. This profile seems to originate from the specialized prostate metabolic program, as observed using mouse prostate and PDOs. Pharmacological and genetic inhibition of IDH1 impaired mitochondrial respiration, suggesting that this cytoplasmic enzyme contributes to the mitochondrial tricarboxylic acid cycle (TCA) in PCa. Mass spectrometry-based metabolomics confirmed this hypothesis, showing that inhibition of IDH1 impairs carbon flux into the TCA cycle. Consequently, inhibition of IDH1 decreased PCa cell proliferation in vitro and in vivo. These results demonstrate that PCa cells have a hybrid cytoplasmic-mitochondrial TCA cycle that depends on IDH1. This metabolic enzyme represents a metabolic vulnerability of PCa cells and a potential new therapeutic target.

Abstract 3700: Isocitrate dehydrogenase 1 sustains a hybrid cytoplasmic-mitochondrial tricarboxylic acid cycle in prostate cancer

Background: The androgen receptor (AR) is an established orchestrator of cell metabolism in prostate cancer (PCa), notably by inducing an oxidative mitochondrial program. Intriguingly, AR regulates cytoplasmic isocitrate dehydrogenase 1 (IDH1) but not its mitochondrial counterparts IDH2 and IDH3. Here, we aimed to understand the functional role of IDH1 in PCa.

Methods: Mouse models, in vitro human PCa cell lines, and human prostate organoids were used to study the expression and activity of IDH enzymes in the normal prostate and PCa. Genetic and pharmacological inhibition of IDH1 was then combined with extracellular flux analysis and gas chromatography-mass spectrometry for metabolomic analyses and cancer cell proliferation in vitro and in vivo.

Results: In PCa cells, more than 90% of the total IDH activity is mediated through IDH1 rather than its mitochondrial counterparts. This profile seems to originate from the specialized prostate metabolic program, as observed using mouse prostate and human patient-derived organoids. Pharmacological and genetic inhibition of IDH1 impaired mitochondrial respiration, suggesting that this cytoplasmic enzyme contributes to the mitochondrial tricarboxylic acid cycle (TCA) in PCa. Mass spectrometry-based metabolomics confirmed this hypothesis, showing that inhibition of IDH1 impairs carbon flux into the TCA cycle. Consequently, inhibition of IDH1 decreased PCa cell proliferation in vitro and in vivo.

Conclusions: These results demonstrate that PCa cells have a hybrid cytoplasmic-mitochondrial TCA cycle that depends on IDH1. This metabolic enzyme represents a metabolic vulnerability of PCa cells and a potential new therapeutic target.

Citation Format: Kevin Gonthier, Cindy Weidmann, Line Berthiaume, Cynthia Jobin, Aurélie Lacouture, Camille Lafront, Mario Harvey, Bertrand Neveu, Jérémy Loehr, Alain Bergeron, Yves Fradet, Louis Lacombe, Julie Riopel, Éva Latulippe, Chantal Atallah, Michael Shum, Jean-Philippe Lambert, Frédéric Pouliot, Martin Pelletier, Étienne Audet-Walsh. Isocitrate dehydrogenase 1 sustains a hybrid cytoplasmic-mitochondrial tricarboxylic acid cycle in prostate cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3700.

FACS-Free isolation and purification protocol of mouse prostate epithelial cells for organoid primary culture

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This protocol enables the generation of mouse prostate organoids without using flow cytometry, facilitating its implementation in most research laboratories.

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Usage of prostate organoids allows the study of complex in vivo phenotypes, beyond what can be done with immortalized cell lines.

The prostate is a gland that contributes to men's fertility. It is highly responsive to androgens and is often the site of carcinogenesis, as prostate cancer is the most frequent cancer in men in over a hundred countries. To study the normal prostate, few in vitro models exist, and most of them do not express the androgen receptor (AR). To overcome this issue, prostate epithelial cells can be grown in primary culture ex vivo in 2- and 3-dimensional culture (organoids). However, methods to purify these cells often require flow cytometry, thus necessitating specialized instruments and expertise. Herein, we present a detailed protocol for the harvest, purification, and primary culture of mouse prostate epithelial cells to grow prostate organoids ex vivo. This protocol does not require flow cytometry approaches, facilitating its implementation in most research laboratories, and organoids grown with this protocol are highly responsive to androgens. In summary, we present a new simple method that can be used to grow prostate organoids that recapitulate the androgen response of this gland in vivo.

Multiple metabolic pathways fuel the truncated tricarboxylic acid cycle of the prostate to sustain constant citrate production and secretion

Objective

The prostate is metabolically unique: it produces high levels of citrate for secretion via a truncated tricarboxylic acid (TCA) cycle to maintain male fertility. In prostate cancer (PCa), this phenotype is reprogrammed, making it an interesting therapeutic target. However, how the truncated prostate TCA cycle works is still not completely understood.

Methods

We optimized targeted metabolomics in mouse and human organoid models in ex vivo primary culture. We then used stable isotope tracer analyses to identify the pathways that fuel citrate synthesis.

Results

First, mouse and human organoids were shown to recapitulate the unique citrate-secretory program of the prostate, thus representing a novel model that reproduces this unusual metabolic profile. Using stable isotope tracer analysis, several key nutrients were shown to allow the completion of the prostate TCA cycle, revealing a much more complex metabolic profile than originally anticipated. Indeed, along with the known pathway of aspartate replenishing oxaloacetate, glutamine was shown to fuel citrate synthesis through both glutaminolysis and reductive carboxylation in a GLS1-dependent manner. In human organoids, aspartate entered the TCA cycle at the malate entry point, upstream of oxaloacetate. Our results demonstrate that the citrate-secretory phenotype of prostate organoids is supported by the known aspartate–oxaloacetate–citrate pathway, but also by at least three additional pathways: glutaminolysis, reductive carboxylation, and aspartate–malate conversion.

Conclusions

Our results add a significant new dimension to the prostate citrate-secretory phenotype, with at least four distinct pathways being involved in citrate synthesis. Better understanding this distinctive citrate metabolic program will have applications in both male fertility as well as in the development of novel targeted anti-metabolic therapies for PCa.

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Targeted metabolomics and stable isotope tracer analysis were optimized in mouse and human prostate organoids.

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Organoids recapitulate the unique citrate-secretory phenotype of the prostate.

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Glutamine fuels citrate synthesis for secretion by glutaminolysis and reductive carboxylation.

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Aspartate enters the TCA cycle at different entry points in mouse and human prostate organoids for citrate production.

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We revealed a much more complex TCA cycle in the prostate than originally anticipated.

Abstract P5-02-01: A FACS-free purification method to study estrogen signaling, organoid formation, and metabolic reprogramming in mammary epithelial cells

Mammary epithelial cells (MECs) are known to have their metabolism reprogrammed following pregnancy to allow the increased energy requirements for lactation. The estrogen receptor α (ERα) is mainly associated with the regulation of biological pathways linked to mammary gland development but its influence on MECs metabolism is still unknown. Our hypothesis is that ERα reprograms cell metabolism in normal MECs, a phenomenon that would be reprogrammed during breast carcinogenesis. Few in vitro models are used to study MECs, and most of them do not express ERα. Primary MECs can be used to overcome this issue, but methods to purify these cells generally require flow cytometry and fluorescence-activated cell sorting (FACS), which require specialized instruments and expertise. Herein, we present in detail a FACS-free protocol for purification and primary culture of mouse MECs to study ERα metabolic functions using mass spectrometry (MS). Purified MECs from nulliparous mice remain differentiated for up to six days with >85% luminal epithelial cells in two-dimensional culture. When seeded in Matrigel, they form organoids that recapitulate the mammary gland morphology in vivo by developing lumens, contractile cells, and lobular structures. MECs express a functional ERα signaling pathway in both two- and three-dimensional cell culture, as shown at the mRNA and protein levels and by the phenotypic characterization. Extracellular metabolic flux analysis showed that estrogens induce a metabolic switch favouring aerobic glycolysis over mitochondrial respiration in MECs grown in two-dimensions, a phenomenon known as the Warburg effect. We also performed (MS)-based metabolomics in organoids. Estrogens altered the levels of metabolites from various pathways, including aerobic glycolysis, citric acid cycle, urea cycle, and amino acid metabolism, demonstrating that ERα reprograms cell metabolism in mammary organoids. To further understand this reprogramming, stable isotope tracer analysis in primary culture organoids are currently performed. In addition, pregnancy and breast-feeding are known to be protective against breast carcinogenesis. Consequently, we also performed MEC purification and organoid culture using mammary glands from multiparous mice. Intriguingly, organoid phenotypic characterization indicated a difference in organoid structures between MECs from nulliparous and multiparous mice. Furthermore, we observe significant differences in estrogenic response between both conditions, suggesting that pregnancy and/or lactation promotes the establishment of specific epigenetic marks that are preserved even ex vivo. Chromatin immunoprecipitation of specific histone marks and MS-based metabolic studies are ongoing to better understand the different responses of mammary organoids to estrogens between nulliparous and multiparous mice. Overall, we have optimized mouse MEC isolation and purification for two- and three-dimensional cultures and for MS-based metabolomics. We demonstrated that these organoids retain a functional ERα pathway over time and that ERα significantly reprograms multiple metabolic pathways. This model represents a valuable tool to study how estrogens modulate mammary gland biology, and particularly how these hormones reprogram metabolism during lactation and breast carcinogenesis.

Citation Format: Aurélie Lacouture, Cynthia Jobin, Alisson Clemenceau, Cindy Weidmann, Line Berthiaume, Dominic Bastien, Isabelle Laverdière, Martin Pelletier, Caroline Diorio, Francine Durocher, Étienne Audet-Walsh. A FACS-free purification method to study estrogen signaling, organoid formation, and metabolic reprogramming in mammary epithelial cells [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-02-01.

A FACS-Free Purification Method to Study Estrogen Signaling, Organoid Formation, and Metabolic Reprogramming in Mammary Epithelial Cells

Few in vitro models are used to study mammary epithelial cells (MECs), and most of these do not express the estrogen receptor α (ERα). Primary MECs can be used to overcome this issue, but methods to purify these cells generally require flow cytometry and fluorescence-activated cell sorting (FACS), which require specialized instruments and expertise. Herein, we present in detail a FACS-free protocol for purification and primary culture of mouse MECs. These MECs remain differentiated for up to six days with >85% luminal epithelial cells in two-dimensional culture. When seeded in Matrigel, they form organoids that recapitulate the mammary gland's morphology in vivo by developing lumens, contractile cells, and lobular structures. MECs express a functional ERα signaling pathway in both two- and three-dimensional cell culture, as shown at the mRNA and protein levels and by the phenotypic characterization. Extracellular metabolic flux analysis showed that estrogens induce a metabolic switch favoring aerobic glycolysis over mitochondrial respiration in MECs grown in two-dimensions, a phenomenon known as the Warburg effect. We also performed mass spectrometry (MS)-based metabolomics in organoids. Estrogens altered the levels of metabolites from various pathways, including aerobic glycolysis, citric acid cycle, urea cycle, and amino acid metabolism, demonstrating that ERα reprograms cell metabolism in mammary organoids. Overall, we have optimized mouse MEC isolation and purification for two- and three-dimensional cultures. This model represents a valuable tool to study how estrogens modulate mammary gland biology, and particularly how these hormones reprogram metabolism during lactation and breast carcinogenesis.

Implementing a routine flow cytometry assay for nucleated red blood cell counts in cord blood units

INTRODUCTION

As required by standards organizations, Héma-Québec Cord Blood Bank performs enumeration of nucleated red blood cells (NRBCs) in cord blood units (CBUs). This study presents the validation and implementation approaches developed to transfer the routine NRBC enumeration from the manual blood film method to a flow cytometric assay.

METHODS

The flow cytometry method was adapted from Tsuji (Cytometry, 37, 1999, 291). This assay was validated to assess the specificity, detection limit, repeatability, and reproducibility of the method, including interoperator and interlaboratory testing. Finally, postimplementation follow-up and adjustments were performed for CBU over a 7-month period.

RESULTS

Blood film and flow cytometry NRBC enumerations showed a strong correlation (n = 40; Pearson's r correlation = 0.90). Validation was successful as exemplified by the correlation in interlaboratory testing (n = 30; r = 0.98). During implementation, our routine laboratory analyses revealed that CBU with low NRBC content (≤2%), representing 26% of all CBU tested, resulted in 15% of repeated reading and/or staining and was the principal source of nonconformity. Small adjustments in the standard operating procedures (SOPs), including a fixed 200-event setting in the NRBC gate for the second reading of the replicates, have completely solved this issue.

CONCLUSION

Flow cytometric NRBC enumerations, now implemented in Héma-Québec Public Cord Blood Bank, is an improvement in the efficiency of our operations by integrating the count for NRBC into our flow cytometry platform.

Intestinal Microbiota in Inflammatory Bowel Disease and Carcinogenesis: Implication for Therapeutics

Trillions of bacteria inhabit our intestine, forming a community called the microbiota, whose contributions are essential to maintain host homeostasis. Disruption of this normal microbial-host communication network has deleterious consequences for the host and is associated with intestinal pathologies such as inflammatory bowel diseases (IBD) and colorectal cancer (CRC). Here we present key concepts and mechanisms by which bacteria may participate in intestinal pathology, and discuss possible means to therapeutically target the microbiome.

High purity galacto-oligosaccharides enhance specific Bifidobacterium species and their metabolic activity in the mouse gut microbiome

Prebiotics are selectively fermented ingredients that result in specific changes in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefit(s) upon the host health. The aim of this study was to evaluate the influence of a β(1-4)galacto-oligosaccharides (GOS) formulation consisting of 90% pure GOS (GOS90), on the composition and activity of the mouse gut microbiota. Germ-free mice were colonised with microbiota from four pathogen-free wt 129 mice donors (SPF), and stools were collected during a feeding trial in which GOS90 was delivered orally for 14 days. Pyrosequencing of 16S rDNA amplicons showed that Bifidobacterium and specific Lactobacillus, Bacteroides and Clostridiales were more prevalent in GOS90-fed mice after 14 days, although the prebiotic impact on Bifidobacterium varied among individual mice. Prebiotic feeding also resulted in decreased abundance of Bacteroidales, Helicobacter and Clostridium. High-throughput quantitative PCR showed an increased abundance of Bifidobacterium adolescentis, Bifidobacterium pseudocatenulatum, Bifidobacterium lactis and Bifidobacterium gallicum in the prebiotic-fed mice. Control female mice showed a higher diversity (phylogenetic diversity (PD) = 15.1 ± 3.4 in stools and PD = 13.0 ± 0.6 in intestinal contents) than control males (PD = 7.8 ± 1.6 in stool samples and PD = 9.5 ± 1.0 in intestinal contents). GOS90 did not modify inflammatory biomarkers (interleukin (IL)-6, IL-12, IL-1β, interferon gamma and tumour necrosis factor alpha). Decreased butyrate, acetate and lactate concentrations in stools of prebiotic fed mice suggested an increase in colonic absorption and reduced excretion. Overall, our results demonstrate that GOS90 is capable of modulating the intestinal microbiome resulting in expansion of the probiome (autochtonous commensal intestinal bacteria considered to have a beneficial influence on health).

Partial depletion of the proinflammatory monocyte population is neuroprotective in the myenteric plexus but not in the basal ganglia in a MPTP mouse model of Parkinson's disease

Parkinson's disease (PD) patients often suffer from gastrointestinal (GI) impairments that are associated with the alteration of dopaminergic (DAergic) neurons in the myenteric nervous system. Growing evidence suggests that inflammation originating from the gut may have a major impact in both the initiation and progression of PD. Here, we investigated the role of the innate immune response in neurodegeneration occurring in central nervous system (CNS) and enteric nervous system (ENS) in response to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a neurotoxin that produces Parkinsonism in both humans and animal models. We found a strong immune response in the gut of mice treated with MPTP, as demonstrated by the prominent presence of macrophages derived from CD115(+) CD11b(+) Ly6C(Hi) monocytes, known as M1 monocytes, and increased production of IL-1β and IL-6. Partial depletion of proinflammatory M1 monocytes through intravenous injections of clodronate-encapsulated liposome protects against MPTP-induced reduction of tyrosine hydroxylase (TH) expression in the ENS. In contrast, loss of striatal TH expression in the CNS after MPTP intoxication occurs regardless of partial monocyte depletion. Examination of brain tissue revealed that microglial activation, comprising the majority of the immune response in the CNS after MPTP injections is unaffected by M1 depletion. In vitro experiments revealed that MPTP and MPP(+) act directly on monocytes to elicit a proinflammatory response that is, in part, dependent on the MyD88/NF-κB signaling pathway resulting in nitrite and proinflammatory cytokine production. Taken together, our results demonstrate a critical role for proinflammatory M1 monocytes/macrophages in DAergic alterations occurring in the GI, but not in the brain, in the MPTP model of PD.

Activation of NF-κB after chronic ethanol intake and haemorrhagic shock/resuscitation in mice

BACKGROUND AND PURPOSE

Chronic ethanol abuse and haemorrhagic shock are major causes of global mortality and, separately, induce profound hepato- and immune-toxic effects via activation of NF-κB. Here, we assessed the effects of chronic ethanol intake upon the pathophysiological derangements after haemorrhagic shock with subsequent resuscitation (H/R), with particular attention to the contribution of NF-κB.

EXPERIMENTAL APPROACH

Transgenic NF-κB(EGFP) mice, expressing the enhanced green fluorescent protein (EGFP) under the transcriptional control of NF-κB cis-elements were fed a Lieber-DeCarli diet containing ethanol (EtOH-diet) or an isocaloric control diet for 4 weeks and were then pairwise subjected to H/R. Liver tissues and peripheral blood were sampled at 2 or 24 h after H/R. Cytokines in blood and tissue and leukocyte activation (as CD11b expression) were measured, along with EGFP as a marker of NF-κB activation.

KEY RESULTS

The EtOH-diet increased mortality at 24 h after H/R and elevated liver injury, associated with an up-regulation of NF-κB-dependent genes and IL-6 release; it also increased production of NF-κB-driven intercellular adhesion molecule 1 (ICAM-1) and EGFP in liver tissue. At 2h after the H/R procedure in ethanol-fed mice we observed the highest proportion of NF-κB activated non-parenchymal cells and an NF-κB-dependent increase in polymorphonuclear leukocyte CD11b expression.

CONCLUSIONS AND IMPLICATIONS

The EtOH-diet exacerbated liver injury after H/R, accompanying an overwhelming hepatic and systemic immune response. Our findings contribute to evidence implicating NF-κB as a key player in the orchestration of the immune response in haemorrhagic shock patients with a history of chronic ethanol abuse.

Wound healing responses at the gastrointestinal epithelium: a close look at novel regulatory factors and investigative approaches

The gastrointestinal epithelium functions as an important physical barrier that separates the rich, diverse, and potentially immunogenic luminal content from the underlying mucosal immune system. In pathological situations such as inflammatory bowel disease, ischemic/hypoxic episodes and bacterial infection, insults to the intestinal epithelium threaten the integrity of the mucosal barrier and represent a huge challenge for the host. During episodes of epithelial injury and barrier breakdown, the host initiates a rapid wound healing response aimed at resealing the gap region and reestablishing homeostasis. This response named "restitution" involves migration of epithelial cells toward the injured regions, as well as epithelial cell proliferation until the gap is closed and the barrier function is reestablished. These biological processes are influenced by a variety of factors derived from the gastrointestinal microenvironment, including host epithelial and lamina propria cells, as well as the microbiota, and the dietary and non-dietary components present in the gastrointestinal lumen. In this manuscript, we will review both host signaling events and luminal factors that influence the wound healing response and have an impact on host homeostasis.

Limited effects of dietary curcumin on Th-1 driven colitis in IL-10 deficient mice suggest an IL-10-dependent mechanism of protection

Curcumin (diferulolylmethane) demonstrates profound anti-inflammatory effects in intestinal epithelial cells (IEC) and in immune cells in vitro and exhibits a protective role in rodent models of chemically induced colitis, with its presumed primary mechanism of action via inhibition of NF-kappaB. Although it has been demonstrated effective in reducing relapse rate in ulcerative colitis patients, curcumin's effectiveness in Crohn's disease (CD) or in Th-1/Th-17 mediated immune models of CD has not been evaluated. Therefore, we investigated the effects of dietary curcumin (0.1-1%) on the development of colitis, immune activation, and in vivo NF-kappaB activity in germ-free IL-10(-/-) or IL-10(-/-);NF-kappaB(EGFP) mice colonized with specific pathogen-free microflora. Proximal and distal colon morphology showed a mild protective effect of curcumin only at 0.1%. Colonic IFN-gamma and IL-12/23p40 mRNA expression followed similar pattern ( approximately 50% inhibition at 0.1%). Secretion of IL-12/23p40 and IFN-gamma by colonic explants and mesenteric lymph node cells was elevated in IL-10(-/-) mice and was not decreased by dietary curcumin. Surprisingly, activation of NF-kappaB in IL-10(-/-) mice (phospho-NF-kappaBp65) or in IL-10(-/-);NF-kappaB(EGFP) mice (whole organ or confocal imaging) was not noticeably inhibited by curcumin. Furthermore, we demonstrate that IL-10 and curcumin act synergistically to downregulate NF-kappaB activity in IEC and IL-12/23p40 production by splenocytes and dendritic cells. In conclusion, curcumin demonstrates limited effectiveness on Th-1 mediated colitis in IL-10(-/-) mice, with moderately improved colonic morphology, but with no significant effect on pathogenic T cell responses and in situ NF-kappaB activity. In vitro studies suggest that the protective effects of curcumin are IL-10 dependent.

Salvia miltiorrhiza water-soluble extract, but not its constituent salvianolic acid B, abrogates LPS-induced NF-kappaB signalling in intestinal epithelial cells

Herbal medicine has become an increasing popular therapeutic alternative among patients suffering from various inflammatory disorders. The Salvia miltiorrhizae water-soluble extract (SME) have been shown to possess antioxidant and anti-inflammatory properties in vitro. However, the mechanism of action and impact of SME on LPS-induced gene expression is still unknown. We report that SME significantly abrogated LPS-induced IkappaB phosphorylation/degradation, NF-kappaB transcriptional activity and ICAM-1 gene expression in rat IEC-18 cells. Chromatin immunoprecipitation assay demonstrated that LPS-induced RelA recruitment to the ICAM-1 gene promoter was inhibited by SME. Moreover, in vitro kinase assay showed that SME directly inhibits LPS induced IkappaB kinase (IKK) activity in IEC-18 cells. To investigate the physiological relevance of SME inhibitory activity on NF-kappaB signalling, we used small intestinal explants and primary intestinal epithelial cells derived from a transgenic mouse expressing the enhanced green fluorescent protein (EGFP) under the transcriptional control of NF-kappaB cis-elements (cis-NF-kappaB(EGFP)). SME significantly blocked LPS-induced EGFP expression and IkappaBalpha phosphorylation in intestinal explants and primary IECs, respectively. However, salvianolic acid B, an activate component of SME did not inhibit NF-kappaB transcriptional activity and IkappaB phosphorylation/degradation in IEC-18 cells. These results indicate that SME blocks LPS-induced NF-kappaB signalling pathway by targeting the IKK complex in intestinal epithelial cells. Modulation of bacterial product-mediated NF-kappaB signalling by natural plant extracts may represent an attractive strategy towards the prevention and treatment of intestinal inflammation.

Salvia miltiorrhiza water-soluble extract, but not its constituent salvianolic acid B, abrogates LPS-induced NF-kappaB signalling in intestinal epithelial cells

Herbal medicine has become an increasing popular therapeutic alternative among patients suffering from various inflammatory disorders. The Salvia miltiorrhizae water-soluble extract (SME) have been shown to possess antioxidant and anti-inflammatory properties in vitro. However, the mechanism of action and impact of SME on LPS-induced gene expression is still unknown. We report that SME significantly abrogated LPS-induced IkappaB phosphorylation/degradation, NF-kappaB transcriptional activity and ICAM-1 gene expression in rat IEC-18 cells. Chromatin immunoprecipitation assay demonstrated that LPS-induced RelA recruitment to the ICAM-1 gene promoter was inhibited by SME. Moreover, in vitro kinase assay showed that SME directly inhibits LPS induced IkappaB kinase (IKK) activity in IEC-18 cells. To investigate the physiological relevance of SME inhibitory activity on NF-kappaB signalling, we used small intestinal explants and primary intestinal epithelial cells derived from a transgenic mouse expressing the enhanced green fluorescent protein (EGFP) under the transcriptional control of NF-kappaB cis-elements (cis-NF-kappaB(EGFP)). SME significantly blocked LPS-induced EGFP expression and IkappaBalpha phosphorylation in intestinal explants and primary IECs, respectively. However, salvianolic acid B, an activate component of SME did not inhibit NF-kappaB transcriptional activity and IkappaB phosphorylation/degradation in IEC-18 cells. These results indicate that SME blocks LPS-induced NF-kappaB signalling pathway by targeting the IKK complex in intestinal epithelial cells. Modulation of bacterial product-mediated NF-kappaB signalling by natural plant extracts may represent an attractive strategy towards the prevention and treatment of intestinal inflammation.

Regulation of TNF-Related Apoptosis-Inducing Ligand-Mediated Death-Signal Pathway in Human β Cells by Fas-Associated Death Domain and Nuclear Factor κB

Transfectants of human CM and NES2Y beta cell lines and primary islets transfected by FADD-DN (dominant-negative form of Fas-associated death domain), a mutant of FADD and/or a superrepressor of nuclear factor kappaB (NF-kappaB) (AdIkappaB(SA)2), were examined for their susceptibility to the TRAIL (TNF-related apoptosis-inducing ligand)-induced death signal pathway, compared with controls, wild-type cells, and vector transfectants in caspase fluorescence, Western blot, electrophoretic mobility shift, apoptosis, and cytotoxicity assays. FADD-DN inhibited caspase-8 activation induced by TRAIL in the transfectants of CM and NES2Y cells. TRAIL-induced apoptosis and cytotoxicity to the FADD-DN transfectants were decreased in comparison to those responses in controls (CM, p < 0.01 and p < 0.01; NES2Y, p < 0.05, and p < 0.02, respectively). When CM, NES2Y, and primary islet cells were transfected by AdIkappaB(SA)2, TRAIL-induced IkappaB degradation and nuclear translocation of NF-kappaB p50/p65 were blocked. TRAIL-induced apoptosis and cytotoxicity to AdIkappaB(SA)2 transfectants of these cells were also reduced (CM, p < 0.02 and p < 0.02; NES2Y, p < 0.01 and p < 0.01, respectively, and islet p < 0.01 for cytotoxicity). Finally, cytotoxicity induced by TRAIL in CM and NES2Y cells transfected with both FADD-DN and AdIkappaB(SA)2 was reduced, compared with that observed in these cells transfected with either FADD-DN alone or AdIkappaB(SA)2 alone, suggesting that FADD and NF-kappaB have synergistic proapoptotic regulatory effects on the susceptibility of beta cell lines and islet cells to TRAIL-induced destruction.

Loss of E-cadherin leads to upregulation of NFkappaB activity in malignant melanoma

Malignant transformation of melanocytes frequently coincides with loss of E-cadherin expression. Here, we show that loss of E-cadherin leads to induction of nuclear factor kappa B (NFkappaB) activity in melanoma cell lines. Melanoma cells show constitutively active NFkappaB, whereas no activity is found in primary melanocytes. After re-expression of E-cadherin in melanoma cells, strong downregulation of NFkappaB activity was found. Consistently, NFkappaB activity was induced in primary human melanocytes after inhibition of E-cadherin activity by functionally blocking anti-E-cadherin antibodies. Interestingly, re-expression of E-cadherin-blocked p38 MAPK activity and the p38 MAPK inhibitors SB203580 and SB202190 almost completely prevented NFkappaB activation in melanoma cells. Furthermore, cytoplasmatic beta-catenin induced p38 and NFkappaB activation in malignant melanoma. To our knowledge, this is the first report suggesting a correlation between E-cadherin and NFkappaB activity in melanocytes and melanoma cells. In summary, we conclude that loss of E-cadherin and cytoplasmatic beta-catenin induces p38-mediated NFkappaB activation, potentially revealing an important mechanism of tumorigenesis in malignant melanomas.

NF-kappaB inducing kinase activates NF-kappaB transcriptional activity independently of IkappaB kinase gamma through a p38 MAPK-dependent RelA phosphorylation pathway

Molecular and biochemical analysis indicates that nuclear transcription factor kappaB (NF-kappaB)-inducing kinase (NIK) mediates IKK activation and NF-kappaB transcriptional activity. However, gene deletion studies suggest that NIK triggers gene expression without affecting IkappaBalpha degradation and NF-kappaB DNA binding activity. In order to investigate the role of NIK in NF-kappaB transcriptional activity, we used mouse embryonic fibroblasts (MEF) derived from wild-type (wt) and IkappaB kinase gamma (IKKgamma) gene deficient (IKKgamma(-/-)) mice. We report that although TNF-induced NF-kappaB transcriptional activity is abolished in IKKgamma(-/-) cells, adenoviral gene delivery of NIK (Ad5NIK) still enhanced transcriptional activity and IL-6 mRNA accumulation. Moreover, NIK targets the transactivation function of NF-kappaB through stimulation of the transactivation domain (TAD) of RelA (S536) in IKKgamma(-/-) cells. Interestingly, Ad5NIK, but not TNF, induces RelA S536 and p38 mitogen-activated protein kinase (MAPK) phosphorylation in IKKgamma(-/-) cells. Functional analysis demonstrated that Ad5NIK-induced NF-kappaB transcriptional activity, IL-6 mRNA expression and RelA phosphorylation are inhibited by the p38 inhibitor SB203580, suggesting a role for this MAPK in NIK signaling to NF-kappaB. These data demonstrate for the first time the presence of an IKKgamma-independent NIK/p38 MAPK-dependent signaling pathway that activates NF-kappaB and induces pro-inflammatory gene expression through RelA phosphorylation.

Differential effect of immune cells on non-pathogenic Gram-negative bacteria-induced nuclear factor-kappaB activation and pro-inflammatory gene expression in intestinal epithelial cells

We have previously shown that non-pathogenic Gram negative bacteria induce RelA phosphorylation, nuclear factor (NF)-kappaB transcriptional activity and pro-inflammatory gene expression in intestinal epithelial cells (IEC) in vivo and in vitro. In this study, we investigated the molecular mechanism of immune-epithelial cell cross-talk on Gram-negative enteric bacteria-induced NF-kappaB signalling and pro-inflammatory gene expression in IEC using HT-29/MTX as well as CaCO-2 transwell cultures Interestingly, while differentiated HT-29/MTX cells are unresponsive to non-pathogenic Gram negative bacterial stimulation, interleukin-8 (IL-8) mRNA accumulation is strongly induced in Escherichia coli- but not Bacteroides vulgatus-stimulated IEC cocultured with peripheral blood (PBMC) and lamina propria mononuclear cells (LPMC). The presence of PBMC triggered both E. coli- and B. vulgatus-induced mRNA expression of the Toll-like receptor-4 accessory protein MD-2 as well as endogenous IkappaBalpha phosphorylation, demonstrating similar capabilities of these bacteria to induce proximal NF-kappaB signalling. However, B. vulgatus failed to trigger IkappaBalpha degradation and NF-kappaB transcriptional activity in the presence of PBMC. Interestingly, B. vulgatus- and E. coli-derived lipopolysaccharide-induced similar IL-8 mRNA expression in epithelial cells after basolateral stimulation of HT-29/PBMC cocultures. Although luminal enteric bacteria have adjuvant and antigenic properties in chronic intestinal inflammation, PBMC from patients with active ulcerative colitis and Crohn's disease differentially trigger epithelial cell activation in response to E. coli and E. coli-derived LPS. In conclusion, this study provides evidence for a differential regulation of non-pathogenic Gram-negative bacteria-induced NF-kappaB signalling and IL-8 gene expression in IEC cocultured with immune cells and suggests the presence of mechanisms that assure hyporesponsiveness of the intestinal epithelium to certain commensally enteric bacteria.

Differential effects of deoxycholic acid and taurodeoxycholic acid on NF-kappa B signal transduction and IL-8 gene expression in colonic epithelial cells

Several effects of bile acids (BAs) on colonic epithelial cells (CECs) have been described, including induction of proliferation and apoptosis. Some of these effects are mediated through activation of the NF-kappa B transcriptional system. In this study, we investigated the molecular mechanisms underlying the BA-induced gene expression in CECs. The human CEC line HT-29 and primary human CECs were treated with dilutions of salts of deoxycholic acid (DCA) and taurodeoxycholic acid (TDCA). NF-kappa B binding activity was analyzed with EMSA, RelA translocation with immunofluorescence, and I kappa B alpha- and RelA-phosphorylation with Western blot analysis. IL-8 mRNA and protein expression were assessed by quantitative PCR and ELISA. Functional impact of NF-kappa B activation was determined by blocking the proteasome activity with MG132 or by preventing IKK activity with a dominant-negative IKK beta delivered by adenoviral dominant-negative (dn) IKK beta (Ad5dnIKK beta). DCA and TDCA induced IL-8 expression in a dose- and time-dependent manner. It is interesting that DCA but not TDCA induced I kappa B alpha-phosphorylation, RelA translocation, and NF-kappa B binding activity. Accordingly, the proteasome inhibitor MG132 blocked DCA- but not TDCA-induced IL-8 gene expression. In contrast, TDCA-induced IL-8 gene expression correlated with enhanced RelA phosphorylation, which was blocked by Ad5dnIKK beta. Our data suggest that DCA-induced signal transduction mainly utilized the I kappa B degradation and RelA nuclear translocation pathway, whereas TDCA primarily induced IL-8 gene expression through RelA phosphorylation. These differences may have implications for the understanding of the pathophysiology of inflammation and carcinogenesis in the gut.

Butyrate modulates intestinal epithelial cell-mediated neutrophil migration

Butyrate, a short-chain fatty acid released by colonic bacteria and administered therapeutically in inflammatory bowel diseases, exerts immunomodulatory properties. The aim of the study was to determine the functional consequences of butyrate exposure on the proinflammatory responsiveness of human intestinal epithelial cells (IEC). IL-8 promoter activity in IEC pretreated with butyrate then exposed to proinflammatory stimuli was assayed by transfection of luciferase constructs. IL-8 secretion was determined by ELISA and neutrophil migration by flow cytometry. Receptor mRNA was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR). Butyrate modulated proinflammatory IL-8 secretion differentially in Caco-2 and HT-29 cells on the transcriptional level. Pointing to the potentially underlying mechanism of increased IL-1 beta-stimulated IL-8 secretion in HT-29 cells, butyrate up-regulated IL-1RI mRNA but not IL-1RII. Butyrate pretreatment of IEC lines stimulated by IL-1 beta modulated neutrophil migration significantly: reduction towards Caco-2 and enhancement towards HT-29/p cells. Pharmacological inhibition of protein tyrosine phosphatases or treatment with mesalamine or sulphasalazine diminished IL-1 beta-stimulated IL-8 secretion by butyrate-exposed HT-29 cells substantially. Immunomodulatory effects of butyrate on IEC are functionally relevant for neutrophil migration. Pharmacological inhibition of enhanced IL-1 beta-mediated IL-8 secretion in a subpopulation of IEC may improve the clinical efficacy of butyrate.

Inhibition of cytokine-induced NF-kappaB activation by adenovirus-mediated expression of a NF-kappaB super-repressor prevents beta-cell apoptosis

Cytokine-induced beta-cell death is an important event in the pathogenesis of type 1 diabetes. The transcription factor nuclear factor-kappaB (NF-kappaB) is activated by interleukin-1beta (IL-1beta), and its activity promotes the expression of several beta-cell genes, including pro- and anti-apoptotic genes. To elucidate the role of cytokine (IL-1beta + gamma-interferon [IFN-gamma])-induced expression of NF-kappaB in beta-cell apoptosis, rat beta-cells were infected with the recombinant adenovirus AdIkappaB((SA)2), which contained a nondegradable mutant form of inhibitory kappaB (IkappaB((SA)2), with S32A and S36A) that locks NF-kappaB in a cytosolic protein complex, preventing its nuclear action. Expression of IkappaB((SA)2) inhibited cytokine-stimulated nuclear translocation and DNA-binding of NF-kappaB. Cytokine-induced gene expression of several NF-kappaB targets, namely inducible nitric oxide synthase, Fas, and manganese superoxide dismutase, was prevented by AdIkappaB((SA)2), as established by reverse transcriptase-polymerase chain reaction, protein blot, and measurement of nitrite in the medium. Finally, beta-cell survival after IL-1beta + IFN-gamma treatment was significantly improved by IkappaB((SA)2) expression, mostly through inhibition of the apoptotic pathway. Based on these findings, we conclude that NF-kappaB activation, under in vitro conditions, has primarily a pro-apoptotic function in beta-cells.

Cryptosporidium parvum activates nuclear factor kappaB in biliary epithelia preventing epithelial cell apoptosis

BACKGROUND & AIMS

Our previous studies have shown that Cryptosporidium parvum induces biliary epithelial cell apoptosis in vivo and causes apoptosis in bystander uninfected biliary epithelia in vitro. We analyzed C. parvum-induced nuclear factor kappa B (NF-kappaB) activation in human biliary epithelial cells and assessed its relevance to epithelial cell apoptosis.

METHODS

In vitro models of cryptosporidial infection using a human biliary epithelial cell line were used to assay C. parvum- induced NF-kappaB activation and associated apoptosis.

RESULTS

Degradation of I(kappa)B and nuclear translocation of the NF-kappaB family of proteins (p65 and p50) were observed in the biliary epithelial cell cultures directly exposed to the parasite. Activation of NF-kappaB was found only in directly infected cells (but not in bystander uninfected cells). A time-dependent secretion of a known NF-kappaB gene product, interleukin 8, from infected cell cultures was detected. C. parvum-induced biliary epithelial cell apoptosis was limited to bystander uninfected cells. In contrast, inhibition of NF-kappaB activation resulted in apoptosis in directly infected cells and significantly enhanced C. parvum-induced apoptosis in bystander uninfected cells.

CONCLUSIONS

These observations support the concept that, while C. parvum triggers host cell apoptosis in bystander uninfected biliary epithelial cells, which may limit spread of the infection, it directly activates the NF-kappaB/I(kappa)B system in infected biliary epithelia thus protecting infected cells from death and facilitating parasite survival and propagation.

Regulatory role of phosphatidylinositol 3-kinase on TNF-alpha-induced cyclooxygenase 2 expression in colonic epithelial cells

BACKGROUND AND AIMS

Cyclooxygenase (COX)-2 is up-regulated in most colonic cancers and in inflammatory bowel disease in which tumor necrosis factor (TNF)-alpha is believed to play a central role. There has been recent speculation on the activation of phosphatidylinositol 3-kinase (PI 3-kinase) by TNF-alpha and its role in the regulation of genes controlled by NF-kappaB. We investigated the regulatory role of PI 3-kinase on COX-2 expression in colonic epithelial cells.

METHODS

In HT-29 and Caco-2 colonic epithelial cells, COX-2 expression was induced by either TNF-alpha or interleukin (IL)-1alpha as observed by Northern and Western analyses. COX-2 activity was assessed by measuring prostaglandin E(2) (PGE2) production by enzyme-linked immunosorbent assay. NF-kappaB binding activity was assessed by electrophoretic mobility shift assay. PI 3-kinase activity was measured by quantifying the accumulation of PI 3-kinase-dependent D-3 lipid products by high-performance liquid chromatography.

RESULTS

The PI 3-kinase inhibitor wortmannin up-regulated induced COX-2 expression in a concentration-dependent manner in both HT-29 and Caco-2 cells. An alternative PI 3-kinase inhibitor, LY294002, caused up-regulation of induced COX-2 messenger RNA (mRNA) in HT-29 cells at concentrations of < or =1 micromol/L. IL-4 and IL-13, which are known to activate PI 3-kinase, down-regulated HT-29 COX-2 mRNA, protein, and PGE2 production. NF-kappaB binding activity was unaltered by PI 3-kinase inhibition in HT-29 cells, in which TNF-alpha was shown to activate PI 3-kinase directly.

CONCLUSIONS

COX-2 is negatively regulated by PI 3-kinase; we propose that the inhibitory effect of IL-4 and IL-13 is mediated via a PI 3-kinase-dependent pathway. This mechanism does not appear to involve NF-kappaB because PI 3-kinase inhibition did not alter NF-kappaB binding activity. TNF-alpha can activate PI 3-kinase directly in addition to inducing COX-2.

Prolonged survival in hereditary surfactant protein B (SP-B) deficiency associated with a novel splicing mutation

Hereditary surfactant protein B (SP-B) deficiency has been lethal in the first year of life without lung transplantation. We tested the hypothesis that SP-B gene mutations may result in milder phenotypes by investigating the mechanisms for lung disease in two children with less severe symptoms than have been previously observed in SP-B deficiency. Immunostaining patterns for pulmonary surfactant proteins were consistent with SP-B deficiency in both children. DNA sequence analysis indicated that both children were homozygous for a mutation in exon 5 that created an alternative splice site. Reverse transcriptase PCR and sequence analysis confirmed use of this splice site, which resulted in a frameshift and a premature termination codon in exon 7. The predominant reverse transcriptase PCR product, however, lacked exon 7, which restored the reading frame but would not allow translation of the exons that encode mature SP-B. Western blot analysis detected reduced amounts of mature SP-B as well as an aberrant SP-B proprotein that corresponded to the size expected from translation of the abnormal transcript. We conclude that a novel splicing mutation was the cause of lung disease in these children and that hereditary SP-B deficiency can be the cause of lung disease in older children.

Cellular differentiation causes a selective down-regulation of interleukin (IL)-1beta-mediated NF-kappaB activation and IL-8 gene expression in intestinal epithelial cells

Interleukin (IL)-1beta signals through various adapter proteins and kinases that lead to activation of numerous downstream targets, including the transcription factors including NF-kappaB. In this study, we analyzed and characterized the effect of the differentiation of intestinal epithelial cells on IL-1beta-mediated NF-kappaB activation and IL-8 gene expression. We report that IL-8 mRNA accumulation and protein secretion were down-regulated in IL-1beta- and lipopolysaccharide-stimulated differentiated HT-29 cells (HT-29/MTX, where MTX is methotrexate) compared with undifferentiated cells (HT-29/p), whereas no differential effects were found following tumor necrosis factor (TNF)-alpha or phorbol myristate acetate stimulation. Cross-linking and affinity binding studies reveal that IL-1beta exclusively binds the type I receptor (IL-1RI) and not IL-1RII in both HT-29/p and HT-29/MTX cells. IL-1beta-mediated IkappaB kinase and c-Jun N-terminal kinase (JNK) activity were both diminished in differentiated HT-29 cells. DNA binding activity in differentiated HT-29 cells relative to HT-29/p cells was strongly reduced following IL-1beta exposure but not after TNF-alpha stimulation. The proximal IL-1 signaling molecule IL-1 receptor-associated kinase was not degraded in IL-1beta-stimulated HT-29 cells, in contrast to Caco-2 cells. kappaB-luciferase reporter gene activity was 16-fold higher following TNF receptor-associated factor-6 transfection after IL-1beta stimulation in HT-29/MTX cells. We conclude that cellular differentiation of HT-29 cells selectively impairs the IL-1beta signaling pathway inhibiting both NF-kappaB and JNK activity in response to IL-1beta. This relative unresponsiveness to IL-1beta may represent an important regulatory mechanism of differentiated intestinal epithelial cells.

The I kappa B/NF-kappa B system: a key determinant of mucosalinflammation and protection

The ubiquitous transcription factor NF-kappa B is a central regulator of the transcriptional activation of a number of genes involved in cell adhesion, immune and proinflammatory responses, apoptosis, differentiation, and growth. Induction of these genes in intestinal epithelial cells (IECs) by activated NF-kappa B profoundly influences mucosal inflammation and repair. NF-kappa B activation requires the removal of I kappa B from NF-kappa B by inducible proteolysis, which liberates this transcription factor for migration to the nucleus, where it binds to kappa B-regulatory elements and induces transcription. I kappa B alpha degradation is incomplete and delayed in IECs, resulting in buffered responses to luminal stimuli. The stimulatory environment partially determines whether the effect of NF-kappa B is protective or deleterious for the host. kappa B-dependent proinflammatory gene expression, particularly chemokines, major histocompatibility complex class II antigens, and adhesion molecules may be extremely important in early protective responses to mucosal pathogens but, when dysregulated, could lead to the development of chronic inflammation, as seen in inflammatory bowel diseases. The key role of NF-kappa B in regulating expression of a number of proinflammatory genes makes this protein an attractive target for selective therapeutic intervention.

Curcumin blocks cytokine-mediated NF-kappa B activation and proinflammatory gene expression by inhibiting inhibitory factor I-kappa B kinase activity

NF-kappa B plays a critical role in the transcriptional regulation of proinflammatory gene expression in various cells. Cytokine-mediated activation of NF-kappa B requires activation of various kinases, which ultimately leads to the phosphorylation and degradation of I kappa B, the NF-kappa B cytoplasmic inhibitor. The food derivative curcumin has been shown to inhibit NF-kappa B activity in some cell types. In this report we investigate the mechanism of action of curcumin on cytokine-induced proinflammatory gene expression using intestinal epithelial cells (IEC). Curcumin inhibited IL-1 beta-mediated ICAM-1 and IL-8 gene expression in IEC-6, HT-29, and Caco-2 cells. Cytokine-induced NF-kappa B DNA binding activity, RelA nuclear translocation, I kappa B alpha degradation, I kappa B serine 32 phosphorylation, and I kappa B kinase (IKK) activity were blocked by curcumin treatment. Wound-induced p38 phosphorylation was not inhibited by curcumin treatment. In addition, mitogen-activated protein kinase/ERK kinase kinase-1-induced IL-8 gene expression and 12-O-tetraphorbol 12-myristate 13-acetate-responsive element-driven luciferase expression were inhibited by curcumin. However, I kappa B alpha degradation induced by ectopically expressed NF-kappa B-inducing kinase or IKK was not inhibited by curcumin treatment. Therefore, curcumin blocks a signal upstream of NF-kappa B-inducing kinase and IKK. We conclude that curcumin potently inhibits cytokine-mediated NF-kappa B activation by blocking a signal leading to IKK activity.

TNF receptor-associated factor-2 is involved in both IL-1 beta and TNF-alpha signaling cascades leading to NF-kappa B activation and IL-8 expression in human intestinal epithelial cells

Cytokine signaling involves the participation of many adaptor proteins, including the docking protein TNF receptor-associated factor-2 (TRAF-2), which is believed to transmit the TNF-alpha signal through both the I kappa B/NF-kappa B and c-Jun N-terminal kinase (JNK)/stress-related protein kinase (SAPK) pathways. The physiological role of TRAF proteins in cytokine signaling in intestinal epithelial cells (IEC) is unknown. We characterized the effect of a dominant-negative TRAF-2 delivered by an adenoviral vector (Ad5dnTRAF-2) on the cytokine signaling cascade in several IEC and also investigated whether inhibiting the TRAF-2-transmitting signal blocked TNF-alpha-induced NF-kappa B and IL-8 gene expression. A high efficacy and level of Ad5dnTRAF-2 gene transfer were obtained in IEC using a multiplicity of infection of 50. Ad5dnTRAF-2 expression prevented TNF-alpha-induced, but not IL-1 beta-induced, I kappa B alpha degradation and NF-kappa B activation in NIH-3T3 and IEC-6 cells. TNF-alpha-induced JNK activation was also inhibited in Ad5dnTRAF-2-infected HT-29 cells. Induction of IL-8 gene expression by TNF-alpha was partially inhibited in Ad5dnTRAF-2-transfected HT-29, but not in control Ad5LacZ-infected, cells. Surprisingly, IL-1 beta-mediated IL-8 gene expression was also inhibited in HT-29 cells as measured by Northern blot and ELISA. We concluded that TRAF-2 is partially involved in TNF-alpha-mediated signaling through I kappa B/NF-kappa B in IEC. In addition, our data suggest that TRAF-2 is involved in IL-1 beta signaling in HT-29 cells. Manipulation of cytokine signaling pathways represents a new approach for inhibiting proinflammatory gene expression in IEC.

Molecular and cellular biology of the small intestine

The crypt-villus axis is composed of a dynamic cell population in perpetual change from a crypt proliferative and undifferentiated stage to a mature villus stage. The migration of crypt cells is accompanied by cellular differentiation that leads to morphological and functional changes. In addition to this intrinsic gene program, intestinal epithelial cells respond to extrinsic signals by producing various molecules. Using different experimental approaches, recent studies have further characterized intestinal epithelial-cell biology and provided evidence of their polyvalent and important role in gut homeostasis.

Suppression of NF-kappaB-dependent proinflammatory gene expression in human RPE cells by a proteasome inhibitor

PURPOSE

To determine whether nuclear transcription factor-kappaB (NF-kappaB) is activated in human retinal pigment epithelial (hRPE) cells in response to interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), or interferon-gamma (IFN-gamma) alone or in combination and if so, whether expression of proinflammatory genes induced by these agents can be blocked by a proteasome inhibitor, MG-132, which inhibits the degradation of I kappaB, an NF-kappaB inhibitor, thereby preventing nuclear translocation of NF-kappaB.

METHODS

Cultured hRPE were pretreated for 60 minutes with medium alone or medium containing the proteasome inhibitor MG-132 (20 microM) and then exposed to TNF-alpha (1.1 x 10(3) U/ml), IL-1beta (5 U/ml), or IFN-gamma (7.5 x 10(3) U/ml) alone or in combination (TII). Nuclear translocation of NF-kappaB was determined by fluorescence staining of the NF-kappaB Rel A (p65) subunit. Cytoplasmic I kappaB protein was measured by western blot analysis. Nuclear extract binding to kappaB DNA motifs was measured by electrophoretic mobility shift assay and antibody supershift assay. Steady state mRNA expression of the chemokines melanoma growth stimulating activity (MGSA)/gro-alpha, regulated on activation normal T-cell expression and secreted (RANTES), and monocyte chemoattractant protein (MCP-1), the cytokines IL-1beta and macrophage colony stimulating factor (M-CSF) and intercellular adhesion molecule-1 (ICAM-1) was evaluated by semiquantitative reverse transcription-polymerase chain reaction. Chemokine and cytokine protein secretion was measured by enzyme-linked immunosorbent assay. Cell-surface ICAM-1 expression was determined by flow cytometry.

RESULTS

TNF-alpha, IL-1beta, and TII but not IFN-gamma alone caused degradation of I kappaB, Rel A nuclear translocation, and increased NF-kappaB DNA binding activity, effects that were blocked by pretreatment with MG-132. MG-132 suppressed MGSA/gro-alpha, RANTES, MCP-1, IL-1beta, M-CSF, and ICAM-1 mRNA expression and secreted RANTES, MCP-1, and M-CSF protein, and cell-surface ICAM-1 that were induced by IL-1beta, TNF-alpha, and TII.

CONCLUSIONS

TNF-alpha, IL-1beta, and TII induce expression of proinflammatory cytokines and ICAM-1 in hRPE cells through an NF-kappaB-dependent signal transduction pathway. This effect is blocked by MG-132, a proteasome inhibitor that prevents I kappaB degradation. Inhibition of NF-kappaB may be a useful strategy to treat proliferative vitreoretinopathy and uveitis, ocular diseases initiated and perpetuated by cytokine activation.

Differential expression of interleukin 1 receptor antagonist isoforms in human intestinal epithelial cells

BACKGROUND & AIMS

Regulatory cytokines mediate intestinal epithelial cell (IEC) participation in mucosal immune responses. The aim of this study was to investigate the expression of secretory and intracellular isoforms of interleukin 1 receptor antagonist (IL-1Ra) in human primary IECs and carcinoma-derived cell lines.

METHODS

Primary IECs were isolated from patients with Crohn's disease or ulcerative colitis and from normal controls. Isoform-specific IL-1Ra messenger RNA (mRNA) and protein were assessed by reverse-transcription polymerase chain reaction and Western blot analysis. Expression during cellular differentiation was determined by in situ immunohistochemistry on sequentially released, native IECs and in vitro differentiated cell lines. Intracellular IL-1Ra I function was analyzed by permanent transfection of Caco-2 cells.

RESULTS

Intracellular IL-1Ra I protein accumulated in surface IECs with extension to the crypts during inflammation. Secretory IL-1Ra and intracellular IL-1Ra II mRNA, but not the corresponding protein, was detected. Transcription of intracellular IL-1Ra I mRNA was significantly up-regulated with inflammation and in vitro by phorbol myristate acetate and interleukin 1beta. In vitro differentiated cells had higher constitutive intracellular IL-1Ra I protein content. Intracellular IL-1Ra I expression in Caco-2 cells decreased IL-1beta-stimulated interleukin 8 secretion.

CONCLUSIONS

Native human IECs and certain cell lines constitutively express intracellular IL-1Ra type I, which is up-regulated by inflammation, inflammatory stimuli, and cellular differentiation. Constitutive expression of this anti-inflammatory cytokine may contribute to mucosal protection.

Specific NF-kappaB blockade selectively inhibits tumour necrosis factor-alpha-induced COX-2 but not constitutive COX-1 gene expression in HT-29 cells

Cyclo-oxygenase (COX) is the key regulatory enzyme of the prostaglandin/eicosanoid pathway. While COX-1 is mostly constitutively expressed, the COX-2 isoform is inducible by proinflammatory cytokines. We used an adenoviral vector containing an NF-kappaB super-repressor (Ad5IkappaB) to investigate the role of NF-kappaB in tumour necrosis factor-alpha (TNF-alpha)-mediated COX-2 gene expression in a colonic epithelial cell line. COX-1 mRNA and protein were constitutively expressed in uninfected, control Ad5LacZ- or Ad5IkappaB-infected HT-29 cells with no apparent change following TNF-alpha exposure. COX-2 mRNA and protein expression was undetectable in unstimulated cells but was strongly up-regulated after TNF-alpha stimulation in uninfected and Ad5LacZ-infected HT-29 cells. This induction was prevented in Ad5IkappaB cells. TNF-alpha increased prostaglandin E2 production by 20-fold in Ad5LacZ-infected HT-29 cells compared with uninfected cells and was significantly inhibited in Ad5IkappaB-infected cells in agreement with the COX-2 mRNA findings. We conclude that NF-kappaB activation is critical in mediating COX-2, but not COX-1 gene expression in HT-29 cells. Selective inhibition of COX-2 expression with the NF-kappaB super-repressor may be useful in distinguishing the role of inducible versus constitutive prostaglandins in intestinal function and provides greater specificity than pharmacological inhibitors.

Cytokines induce NF-kappaB in activated but not in quiescent rat hepatic stellate cells

The hepatic stellate cell (HSC), after a fibrogenic stimulus, is transformed from a quiescent to an activated phenotype, including the induction of responsiveness to a variety of agonists. We investigated the activation of nuclear factor-kappaB (NF-kappaB) and the expression of the NF-kappaB-responsive genes intercellular adhesion molecule 1 (ICAM-1) and macrophage inflammatory protein-2 (MIP-2) in freshly isolated and culture-activated HSC by tumor necrosis factor-alpha (TNF-alpha) or interleukin-1beta. Inhibitor-kappaB was rapidly (<15 min) degraded, and NF-kappaB activity was induced in culture-activated but not in freshly isolated HSC after cytokine stimulation. After 30 min of stimulation, immunofluorescence revealed that the NF-kappaB p65 subunit was predominantly found in the nuclei of activated HSC compared with the cytoplasmic localization in unstimulated cells. No nuclear translocation appeared in freshly isolated HSC after stimulation, despite the presence of functional TNF-alpha receptors. NF-kappaB nuclear translocation appeared first partially after 4-5 days and completely after 9 days in culture. Consistent with this time course TNF-alpha induced the mRNA of the NF-kappaB-dependent genes ICAM-1 and MIP-2 in activated but not in quiescent HSC. Therefore, cytokines induce NF-kappaB activity and ICAM-1 and MIP-2 mRNAs in activated but not in quiescent HSC, through a postreceptor mechanism of regulation.

Mediation by NF-kappa B of cytokine induced expression of intercellular adhesion molecule 1 (ICAM-1) in an intestinal epithelial cell line, a process blocked by proteasome inhibitors

BACKGROUND/AIMS

The gene promoter for the intercellular adhesion molecule ICAM-1 possesses binding sites for several transcriptional factors, including nuclear factor kappa B (NF-kappa B). The role of NF-kappa B in ICAM-1 gene regulation was therefore examined by using different proteasome inhibitors in tumour necrosis factor alpha (TNF-alpha) stimulated IEC-6 rat intestinal epithelial cells.

METHODS

ICAM-1 expression was analysed by enzyme linked immunosorbent assay (ELISA), reverse transcriptase polymerase chain reaction, and immunohistochemistry. Steady state levels of cytoplasmic I kappa B protein were evaluated by western blot, and nuclear translocation of NF-kappa B was determined by electrophoretic mobility shift assay and immunofluorescence staining. Cell adhesion was assayed by measuring the binding of fluorescence labelled MOLT-4 cells.

RESULTS

TNF-alpha induced ICAM-1 mRNA and protein expression in IEC-6 cells, which was followed by increased adhesion of MOLT-4 lymphocytes. Blocking TNF-alpha induced I kappa B alpha degradation with proteasome inhibitors reduced TNF-alpha induced NF-kappa B activation and ICAM-1 gene induction and notably decreased MOLT-4 cell adhesion without affecting Jun N-terminal kinase (JNK/SAPK) activity or de novo protein synthesis.

CONCLUSION

TNF-alpha induction of ICAM-1 expression is mediated by the transcription factor NF-kappa B and can be inhibited by blocking I kappa B alpha degradation. Thus the I kappa B/NF-kappa B system is a promising target for pharmacological modulation of the expression of adhesion molecules and other inflammatory genes in the intestine.

Inhibition of NFkappaB in activated rat hepatic stellate cells by proteasome inhibitors and an IkappaB super-repressor

The hepatic stellate cell (HSC), following a fibrogenic stimulus, is transformed from a quiescent to an activated cell. Cytokines induce NFkappaB activity in activated but not in quiescent HSCs with subsequent expression of NFkappaB-responsive genes, such as intercellular adhesion molecule (ICAM)-1 and interleukin (IL)-6. We investigated the effect of proteasome inhibitors and an IkappaB super-repressor on the cytokine mediated activation of NFkappaB, ICAM-1, and IL-6 in activated HSCs. Culture-activated HSCs were stimulated with IL-1beta or tumor necrosis factor alpha (TNFalpha) in the presence or absence of proteasome inhibitors, ALLN or MG-132, or after infection with an adenovirus expressing the IkappaB super-repressor (Ad5IkappaB) or beta-galactosidase (Ad5LacZ) as a control. NFkappaB activity was evaluated by immunofluorescence and by electrophoretic mobility shift assay. The steady state level of cytoplasmic IkappaB protein was measured by Western Blot. ICAM-1 and IL-6 expression was measured by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbant assay. Proteasome inhibitors, which block the degradation of IkappaB, and the Ad5IkappaB, which provides an exogenous nondegradable IkappaB, block the stimulation of NFkappaB activity by TNFalpha and IL-1beta in activated HSCs. These reagents block the subsequent nuclear translocation of p65 NFkappaB and induction of ICAM-1 and IL-6 by cytokines. The specificities of the proteasome inhibitors and the IkappaB super-repressor are demonstrated by their failure to block c-Jun N-terminal kinase induction by cytokines. Cytokine-induced stimulation of NFkappaB, ICAM-1, and IL-6 is blocked by proteasome inhibitors and Ad5IkappaB in activated HSCs. Inhibition of IkappaBalpha degradation is a potential target for anti-inflammatory therapy in the liver and might influence the activation process of HSCs following fibrotic stimuli.

Inhibition of proinflammatory molecule production by adenovirus-mediated expression of a nuclear factor kappaB super-repressor in human intestinal epithelial cells

NF-kappaB plays a major role in the transcriptional regulation of many proinflammatory genes in multiple cell lineages, including intestinal epithelial cells (IEC). Activation of NF-kappaB requires both phosphorylation and degradation of its natural cytoplasmic inhibitor, IkappaB. We tested whether a super-repressor of NF-kappaB activity, which is a mutated nondegradable IkappaB alpha resistant to phosphorylation and degradation, could be delivered into IEC using an adenoviral vector (Ad5 IkappaB) and determined the antiinflammatory potential of this inhibitor following different stimuli. We showed for the first time that recombinant adenovirus efficiently infected (>80%) transformed as well as primary IEC. Cytoplasmic levels of the NF-kappaB super-repressor protein were more than 50-fold higher than those of endogenous IkappaB, and this mutated IkappaB was resistant to IL-1beta-induced degradation. Immunofluorescent RelA nuclear staining was strongly inhibited in Ad5 IkappaB-infected IEC compared with control Ad5LacZ and NF-kappaB, but not AP-1 binding activity, was reduced by more than 70% as measured by electrophoretic mobility shift assay (EMSA). Induction of inducible nitric-oxide synthase (iNOS), IL-1beta, and IL-8 genes by IL-1beta, TNF-alpha, or PMA was blocked in Ad5 IkappaB-infected cells but not in Ad5 LacZ controls as assayed by RT-PCR and ELISA. In addition, IL-1beta-induced IL-8 secretion was totally inhibited by Ad5 IkappaB in primary colonic IEC. We conclude that an adenoviral vector efficiently transfers a nondegradable IkappaB in both transformed and native IEC. The strong inhibition of NF-kappaB activity and the resulting down-regulation of multiple proinflammatory molecules by Ad5 IkappaB suggests an exciting approach for in vivo intestinal gene therapy and illustrates the key role of NF-kappaB in transcriptional regulation of the inflammatory phenotype of IEC.

Differential effects of cell density on 5-lipoxygenase (5-LO), five-lipoxygenase-activating protein (FLAP) and interleukin-1 beta (IL-1 beta) expression in human neutrophils

We have analyzed the effect of cellular density of 5-Lipoxygenase (5-LO), 5-lipoxygenase-activating protein (FLAP) and interleukin-1 beta (IL-1 beta) gene expression in neutrophils from healthy subjects under culture conditions of low and high cell density. By using RT-PCR techniques, we have found that 5-LO mRNA accumulation decreased in cells cultured at high density, while FLAP mRNA is not affected. De novo 5-LO synthesis, as well as steady-state levels, were reduced in cells maintained at high density. In contrast, the high density conditions lead to the induction of IL-1 beta gene at the RNA and protein levels as measured by RT-PCR and by immunoprecipitation. These results suggest that cellular density plays a role in gene modulation when neutrophils are accumulating at an inflammatory site since neutrophils obtained from the synovial fluid of patients with RA exhibit a protein synthesis profile similar to that observed in peripheral blood neutrophils cultured at high density.

Evidence for altered regulation of I kappa B alpha degradation in human colonic epithelial cells

The nuclear factor kappaB (NF-kappaB) regulates the transcription of genes bearing the kappaB consensus motif. Transmigration of NF-kappaB from the cytoplasm to the nucleus is regulated by the IkappaB family of inhibitory NF-kappaB-binding proteins. Dissociation of the NF-kappaB-IkappaB complex requires both phosphorylation and degradation of IkappaBs. We demonstrate that IL-1beta induces complete IkappaB alpha degradation in Caco-2 cell lines but not in HT-29, T84, SW-480 transformed cell lines, or native colonic epithelial cells. A similar lack of IkappaB alpha degradation in HT-29 cells followed TNF-alpha and bacterial polymer stimulation. IL-1beta stimulated NF-kappaB nuclear translocation and NF-kappaB-dependent IL-1beta and IL-8 expression in both Caco-2 and HT-29 cells as assayed by electrophoretic mobility shift assay, immunofluorescence, kappaB-luciferase transfection, reverse transcriptase-PCR analysis and ELISA. In HT-29 cells stimulated with IL-1beta, IkappaB alpha was phosphorylated and when cycloheximide blocked new protein synthesis, IkappaB alpha was partially degraded. NF-kappaB cytoplasmic to nuclear transmigration was incomplete and preceded IkappaB alpha degradation in 9T-29 cells, in contrast to complete coordinated NF-kappaB nuclear translocation and IkappaB alpha degradation in Caco-2 cells. Greater sensitivity of HT-29 cells to a calpain inhibitor, as measured by IL-8 secretion, suggested enhanced resistance to IkappaB alpha proteolysis. These data show that IL-1beta induces NF-kappaB activity and expression of NF-kappaB-dependent genes in colonic epithelial cells and suggest altered regulation of IkappaB alpha degradation compared with other cell lineages, which may result in their increased responsiveness to therapeutic blockade.

Evidence for altered regulation of I kappa B alpha degradation in human colonic epithelial cells

The nuclear factor kappaB (NF-kappaB) regulates the transcription of genes bearing the kappaB consensus motif. Transmigration of NF-kappaB from the cytoplasm to the nucleus is regulated by the IkappaB family of inhibitory NF-kappaB-binding proteins. Dissociation of the NF-kappaB-IkappaB complex requires both phosphorylation and degradation of IkappaBs. We demonstrate that IL-1beta induces complete IkappaB alpha degradation in Caco-2 cell lines but not in HT-29, T84, SW-480 transformed cell lines, or native colonic epithelial cells. A similar lack of IkappaB alpha degradation in HT-29 cells followed TNF-alpha and bacterial polymer stimulation. IL-1beta stimulated NF-kappaB nuclear translocation and NF-kappaB-dependent IL-1beta and IL-8 expression in both Caco-2 and HT-29 cells as assayed by electrophoretic mobility shift assay, immunofluorescence, kappaB-luciferase transfection, reverse transcriptase-PCR analysis and ELISA. In HT-29 cells stimulated with IL-1beta, IkappaB alpha was phosphorylated and when cycloheximide blocked new protein synthesis, IkappaB alpha was partially degraded. NF-kappaB cytoplasmic to nuclear transmigration was incomplete and preceded IkappaB alpha degradation in 9T-29 cells, in contrast to complete coordinated NF-kappaB nuclear translocation and IkappaB alpha degradation in Caco-2 cells. Greater sensitivity of HT-29 cells to a calpain inhibitor, as measured by IL-8 secretion, suggested enhanced resistance to IkappaB alpha proteolysis. These data show that IL-1beta induces NF-kappaB activity and expression of NF-kappaB-dependent genes in colonic epithelial cells and suggest altered regulation of IkappaB alpha degradation compared with other cell lineages, which may result in their increased responsiveness to therapeutic blockade.

Five-year changes in airflow obstruction and airway responsiveness in mild to moderate asthma

We documented changes in airflow obstruction and airway responsiveness to histamine after a period of 5 +/- 1 y in 40 subjects with mild to moderate asthma, 14 men and 26 women, aged 20-68 y (mean: 43.6 y). Asthma had to be stable at both evaluations. Each subject answered a respiratory questionnaire and expiratory flows and airway responsiveness to histamine were measured. No significant difference was found between the sub-groups based on atopic status and medication use for mean 5-y changes in FEV1 or PC20. However, although severity of asthma was similar in both groups, the number of subjects who significantly increased their FEV1 or PC20 at 5 y tended to be higher in the group using corticosteroids regularly (> 9 months/y): FEV1: 35.7%, PC20: 42.9% compared to those using them intermittently (< 3 months/y): FEV1: 23.3%, PC20: 35.3% (p > 0.05). This difference was related to recent (< 6 months) use of inhaled corticosteroids. On the other hand, the number of subjects with a significant reduction in FEV1 or PC20 after 5 y was lower when inhaled corticosteroids were used regularly: FEV1: 14.3%; PC20: 28.6%, compared to intermittently: FEV1: 41.2%; PC20: 41.2%, although this difference was not statistically significant. Changes in FEV1 or PC20 at 5 y were not correlated with the duration of asthma, the number of months on inhaled corticosteroids, or age at the time of diagnosis. Airway responsiveness was most often improved in atopics compared to non-atopics. In conclusion, overall 5-y changes in FEV1 or PC20 in our group of subjects were minimally influenced by the duration of the asthma and age at the time of diagnosis. The number of subjects with improved airway responsiveness was higher among atopics and after regular use of inhaled corticosteroids. Further prospective studies should be done on the long-term influence of regular vs. intermittent use of inhaled corticosteroids on the natural history of asthma.

Differential synthesis of 5-lipoxygenase in peripheral blood and synovial fluid neutrophils in rheumatoid arthritis

In order to investigate 5-lipoxygenase enzyme regulation in neutrophils during an inflammatory reaction, we studied 5-lipoxygenase mRNA levels, as well as de novo enzyme synthesis, in resting and activated neutrophils isolated from normal individuals and patients with rheumatoid arthritis. The approach used was to analyze these activities in resting peripheral blood neutrophils of normal individuals on the one hand and in peripheral blood and matched synovial fluid neutrophils isolated from patients with rheumatoid arthritis on the other hand. Our first observation was that resting peripheral blood neutrophils of either normal individuals or patients show detectable levels of 5-lipoxygenase mRNA and are able to synthesize the enzyme de novo. Our second observation was that inflammatory activated neutrophils from synovial fluid reveal lower 5-lipoxygenase mRNA levels and enzyme synthesis than do the patient-matched peripheral blood cells. This is in spite of the fact that, for other proteins, synovial fluid neutrophils are equally or more active than their peripheral blood counterparts. We conclude that peripheral blood neutrophils are capable of synthesizing the enzyme, thus ensuring the turnover of the protein. Furthermore, complex regulatory mechanisms appear to take place in response to inflammation as it occurs in synovial fluids of patients with rheumatoid arthritis, leading to decreased mRNA levels and enzyme synthesis. Possible mechanisms of regulation are discussed and are presently under investigation.

Differential synthesis of 5-lipoxygenase in peripheral blood and synovial fluid neutrophils in rheumatoid arthritis

In order to investigate 5-lipoxygenase enzyme regulation in neutrophils during an inflammatory reaction, we studied 5-lipoxygenase mRNA levels, as well as de novo enzyme synthesis, in resting and activated neutrophils isolated from normal individuals and patients with rheumatoid arthritis. The approach used was to analyze these activities in resting peripheral blood neutrophils of normal individuals on the one hand and in peripheral blood and matched synovial fluid neutrophils isolated from patients with rheumatoid arthritis on the other hand. Our first observation was that resting peripheral blood neutrophils of either normal individuals or patients show detectable levels of 5-lipoxygenase mRNA and are able to synthesize the enzyme de novo. Our second observation was that inflammatory activated neutrophils from synovial fluid reveal lower 5-lipoxygenase mRNA levels and enzyme synthesis than do the patient-matched peripheral blood cells. This is in spite of the fact that, for other proteins, synovial fluid neutrophils are equally or more active than their peripheral blood counterparts. We conclude that peripheral blood neutrophils are capable of synthesizing the enzyme, thus ensuring the turnover of the protein. Furthermore, complex regulatory mechanisms appear to take place in response to inflammation as it occurs in synovial fluids of patients with rheumatoid arthritis, leading to decreased mRNA levels and enzyme synthesis. Possible mechanisms of regulation are discussed and are presently under investigation.