15-Hydroxyprostaglandin dehydrogenase can be induced by dexamethasone and other glucocorticoids at the therapeutic level in A549 human lung adenocarcinoma cells

Inhibition of Prostaglandin-Degrading Enzyme 15-PGDH Mitigates Acute Murine Lung Allograft Rejection

PURPOSE

Acute rejection is a frequent complication among lung transplant recipients and poses substantial therapeutic challenges. 15-hydroxyprostaglandin dehydrogenase (15-PGDH), an enzyme responsible for the inactivation of prostaglandin E2 (PGE2), has recently been implicated in inflammatory lung diseases. However, the role of 15-PGDH in lung transplantation rejection remains elusive. The present study was undertaken to examine the expression of 15-PGDH in rejected lung allografts and whether inhibition of 15-PGDH ameliorates acute lung allograft rejection.

METHODS

Orthotopic mouse lung transplantations were performed between donor and recipient mice of the same strain or allogeneic mismatched pairs. The expression of 15-PGDH in mouse lung grafts was measured. The efficacy of a selective 15-PGDH inhibitor (SW033291) in ameliorating acute rejection was assessed through histopathological examination, micro-CT imaging, and pulmonary function tests. Additionally, the mechanism underlying the effects of SW033291 treatment was explored using CD8+ T cells isolated from mouse lung allografts.

RESULTS

Increased 15-PGDH expression was observed in rejected allografts and allogeneic CD8+ T cells. Treatment with SW033291 led to an accumulation of PGE2, modulation of CD8+ T-cell responses and mitochondrial activity, and improved allograft function and survival.

CONCLUSION

Our study provides new insights into the role of 15-PGDH in acute lung rejection and highlights the therapeutic potential of inhibiting 15-PGDH for enhancing graft survival. The accumulation of PGE2 and modulation of CD8+ T-cell responses represent potential mechanisms underlying the benefits of 15-PGDH inhibition in this model. Our findings provide impetus for further exploring 15-PGDH as a target for improving lung transplantation outcomes.

Methylome and transcriptome profiling of giant cell arteritis monocytes reveals novel pathways involved in disease pathogenesis and molecular response to glucocorticoids

OBJECTIVES

Giant cell arteritis (GCA) is a complex systemic vasculitis mediated by the interplay between both genetic and epigenetic factors. Monocytes are crucial players of the inflammation occurring in GCA. Therefore, characterisation of the monocyte methylome and transcriptome in GCA would be helpful to better understand disease pathogenesis.

METHODS

We performed an integrated epigenome-and transcriptome-wide association study in CD14+ monocytes from 82 patients with GCA, cross-sectionally classified into three different clinical statuses (active, in remission with or without glucocorticoid (GC) treatment), and 31 healthy controls.

RESULTS

We identified a global methylation and gene expression dysregulation in GCA monocytes. Specifically, monocytes from active patients showed a more proinflammatory phenotype compared with healthy controls and patients in remission. In addition to inflammatory pathways known to be involved in active GCA, such as response to IL-6 and IL-1, we identified response to IL-11 as a new pathway potentially implicated in GCA. Furthermore, monocytes from patients in remission with treatment showed downregulation of genes involved in inflammatory processes as well as overexpression of GC receptor-target genes. Finally, we identified changes in DNA methylation correlating with alterations in expression levels of genes with a potential role in GCA pathogenesis, such as ITGA7 and CD63, as well as genes mediating the molecular response to GC, including FKBP5, ETS2, ZBTB16 and ADAMTS2.

CONCLUSION

Our results revealed profound alterations in the methylation and transcriptomic profiles of monocytes from GCA patients, uncovering novel genes and pathways involved in GCA pathogenesis and in the molecular response to GC treatment.

Targeting Nuclear Receptors in Lung Cancer—Novel Therapeutic Prospects

Lung cancer, the second most commonly diagnosed cancer, is the major cause of fatalities worldwide for both men and women, with an estimated 2.2 million new incidences and 1.8 million deaths, according to GLOBOCAN 2020. Although various risk factors for lung cancer pathogenesis have been reported, controlling smoking alone has a significant value as a preventive measure. In spite of decades of extensive research, mechanistic cues and targets need to be profoundly explored to develop potential diagnostics, treatments, and reliable therapies for this disease. Nuclear receptors (NRs) function as transcription factors that control diverse biological processes such as cell growth, differentiation, development, and metabolism. The aberrant expression of NRs has been involved in a variety of disorders, including cancer. Deregulation of distinct NRs in lung cancer has been associated with numerous events, including mutations, epigenetic modifications, and different signaling cascades. Substantial efforts have been made to develop several small molecules as agonists or antagonists directed to target specific NRs for inhibiting tumor cell growth, migration, and invasion and inducing apoptosis in lung cancer, which makes NRs promising candidates for reliable lung cancer therapeutics. The current work focuses on the importance of various NRs in the development and progression of lung cancer and highlights the different small molecules (e.g., agonist or antagonist) that influence NR expression, with the goal of establishing them as viable therapeutics to combat lung cancer.

Robust COX-2-mediated prostaglandin response may drive arthralgia and bone destruction in patients with chronic inflammation post-chikungunya

Patients following infection by chikungunya virus (CHIKV) can suffer for months to years from arthralgia and arthritis. Interestingly, methotrexate (MTX) a major immune-regulatory drug has proved to be of clinical benefit. We have previously shown that CHIKV can persist in the joint of one patient 18 months post-infection and plausibly driving chronic joint inflammation but through ill-characterized mechanisms. We have pursued our investigations and report novel histological and in vitro data arguing for a plausible role of a COX-2-mediated inflammatory response post-CHIKV. In the joint, we found a robust COX-2 staining on endothelial cells, synovial fibroblasts and more prominently on multinucleated giant cells identified as CD11c+ osteoclasts known to be involved in bone destruction. The joint tissue was also strongly stained for CD3, CD8, CD45, CD14, CD68, CD31, CD34, MMP2, and VEGF (but not for NO synthase and two B cell markers). Dendritic cells were rarely detected. Primary human synovial fibroblasts were infected with CHIKV or stimulated either by the synthetic molecule polyriboinosinic:polyribocytidylic acid (PIC) to mimic chronic viral infection or cytokines. First, we found that PIC and CHIKV enhanced mRNA expression of COX-2. We further found that PIC but not CHIKV increased the mRNA levels of cPLA2α and of mPGES-1, two other central enzymes in PGE2 production. IFNβ upregulated cPLA2α and COX-2 transcription levels but failed to modulated mPGES-1 mRNA expression. Moreover, PIC, CHIKV and IFNβ decreased mRNA expression of the PGE2 degrading enzyme 15-PGDH. Interestingly, MTX failed to control the expression of all these enzymes. In sharp contrast, dexamethasone was able to control the capacity of pro-inflammatory cytokines, IL-1β as well as TNFα, to stimulate mRNA levels of cPLA2α, COX-2 and mPGES-1. These original data argue for a concerted action of CHIKV (including viral RNA) and cytokines plausibly released from recruited leukocytes to drive a major COX-2-mediated PGE2 proinflammatory responses to induce viral arthritis.

It is important to have a better understanding of the immuno-pathogenesis of Chikungunya virus (CHIKV) and particularly focusing on the chronic phase associated to arthralgia and arthritis. Benefiting from our prospective cohort studies, we herein provide novel in vivo data identifying for the first time the implication of COX-2 and several other enzymes involved in prostaglandin biosynthesis and the persistence of the virus on the joint. Prostaglandin has major activities in inflammation and joint destruction. In vitro, we have used a model of human synovial fibroblasts to decipher the regulatory mechanisms of prostaglandin biosynthesis pathway. We have made important observations showing that the virus itself as well as major inflammatory cytokines can dramatically control the expression of all enzymes involved in the metabolism of prostaglandin. Interestingly, pharmacological investigations further revealed that dexamethasone, but not methotrexate (currently used to treat patients with chikungunya) may be of clinical values.

Cortisol Regeneration in the Fetal Membranes, A Coincidental or Requisite Event in Human Parturition?

The fetal membranes are equipped with high capacity of cortisol regeneration through the reductase activity of 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1). The expression of 11β-HSD1 in the fetal membranes is under the feedforward induction by cortisol, which is potentiated by proinflammatory cytokines. As a result, the abundance of 11β-HSD1 increases with gestational age and furthermore at parturition with an escalation of cortisol concentration in the fetal membranes. Accumulated cortisol takes parts in a number of crucial events pertinent to the onset of labor in the fetal membranes, including extracellular matrix (ECM) remodeling and stimulation of prostaglandin output. Cortisol remodels the ECM through multiple approaches including induction of collagen I, III, and IV degradation, as well as inhibition of their cross-linking. These effects of cortisol are executed through activation of the autophagy, proteasome, and matrix metalloprotease 7 pathways, as well as inhibition of the expression of cross-linking enzyme lysyl oxidase in mesenchymal cells of the membranes. With regard to prostaglandin output, cortisol not only increases prostaglandin E2 and F2α syntheses through induction of their synthesizing enzymes such as cytosolic phospholipase A2, cyclooxygenase 2, and carbonyl reductase 1 in the amnion, but also decreases their degradation through inhibition of their metabolizing enzyme 15-hydroxyprostaglandin dehydrogenase in the chorion. Taking all together, data accumulated so far denote that the feedforward cortisol regeneration by 11β-HSD1 in the fetal membranes is a requisite event in the onset of parturition, and the effects of cortisol on prostaglandin synthesis and ECM remodeling may be enhanced by proinflammatory cytokines in chorioamnionitis.

15-hydroxyprostaglandin dehydrogenase is upregulated by hydroxychloroquine in rheumatoid arthritis fibroblast-like synoviocytes

15-Hydroxyprostaglandin dehydrogenase (HPGD) is the key enzyme responsible for the metabolic inactivation of prostaglandin E2 (PGE₂) catabolism. PGE₂ is one of the predominant catabolic factors involved in rheumatoid arthritis (RA). However, the expression and regulation of HPGD in RA fibroblast-like synoviocyte (FLS) remain to be elucidated. Disease-modifying anti-rheumatic drugs (DMARDs) are the most important anti-arthritic drugs, which reduce the effect of joint injury. The aim of the present study was to assess the expression of HPGD in RA tissues and cells, and normal synovial tissues and cells. The effect of the most popular DMARDs, hydroxychloroquine, on the expression of HPGD in RA-FLS was also investigated. Western blotting and immuno-histochemical analysis demonstrated that the expression levels of HPGD in human synovium were lower in RA synovium compared with the normal and OA synovium. In RA-FLS, the expression of HPGD was increased following treatment with several DMARDs, including sulfasalazine, methotrexate, and hydroxychloroquine. Hydroxychloroquine (10 µM) treatment induced the phosphorylation of ERK, SAPK/JNK and p38. Hydroxychloroquine induced a decrease in the release of PGE₂, which was restored by mitogen-activated protein (MAP) kinase pathway inhibitors. Hydroxychloroquine may therefore, affect the pathogenesis of RA through the MAP kinase pathway by regulating the expression of HPGD.

Inverse expression of prostaglandin E2-related enzymes highlights differences between diverticulitis and inflammatory bowel disease

BACKGROUND

Prostaglandin E2 (PGE2) is the dominant prostaglandin in the colon and is associated with colonic inflammation. PGE2 levels are regulated not only by cyclooxygenases (COX-1 and COX-2) but also by 15-hydroxyprostaglandin dehydrogenase (15-PGDH), the major PGE2-degrading enzyme. Information about the involvement of 15-PGDH in colonic inflammation is sparse.

AIM

We thus aimed to determine the gene expression and immunoreactivity (IR) of COX-1, COX-2, and 15-PGDH in colonic mucosa from patients with diverse inflammatory disorders: ulcerative colitis (UC), Crohn's disease (CD), and acute diverticular disease (DD).

METHODS

RNA from human colonic mucosa was extracted and assessed for gene expression by real-time PCR. Intact colon sections were processed for immunohistochemistry with immunostaining of the mucosal areas quantified using ImageJ.

RESULTS

In colonic mucosa of both UC and CD, COX-2 mRNA and COX-2-IR were significantly increased, whereas 15-PGDH mRNA and 15-PGDH-IR were significantly reduced. In macroscopically undamaged acute DD mucosa, the opposite findings were seen: for both gene expression and immunoreactivity, there was a significant downregulation of COX-2 and upregulation of 15-PGDH. COX-1 mRNA and COX-1-IR remained unchanged in all diseases.

CONCLUSIONS

Our study for the first time demonstrated differential expression of the PGE2-related enzymes COX-2 and 15-PGDH in colonic mucosa from UC, CD, and acute DD. The reduction of 15-PGDH in IBD provides an additional mechanism for PGE2 increase in IBD. With respect to DD, alterations of PGE2-related enzymes suggest that a low PGE2 level may precede the onset of inflammation, thus providing new insight into the pathogenesis of DD.

Comparison of the effects of betamethasone and dexamethasone on surfactant protein A mRNA expression in human lung cells

OBJECTIVE

While prenatal administration of synthetic corticosteroids stimulates both fetal lung development and expression of pulmonary surfactant, the specific effects may depend on the corticosteroid formulation used. We compared the dose-dependent effects of various concentrations of two synthetic corticosteroids, betamethasone and dexamethasone, on steady state levels of surfactant protein A (SP-A) mRNA in human lung cells.

METHODS

Cultured human NCI-H441 bronchoalveolar epithelial cells were exposed to varying concentrations of betamethasone or dexamethasone (10^-7 to 10^-12 M) for 48 h alone or in combination with dibutyryl cAMP (1 mM), which augments surfactant protein gene expression. RNA was harvested and SP-A mRNA levels were quantified by real-time quantitative reverse transcriptase polymerase chain reaction analysis. Results were compared using the Kruskal-Wallis test.

RESULTS

A dose-dependent modification in SP-A mRNA levels was demonstrated with both dexamethasone and betamethasone. Cells treated with cAMP expressed higher levels of SP-A mRNA than untreated cells. A biphasic curve in the SP-A mRNA response to corticosteroids was elicited only in the presence of cAMP: at lower concentrations (10^-10 through 10^-12 M), SP-A mRNA levels were upregulated, whereas at higher concentrations (10^-7 and 10^-8 M), SP-A mRNA levels were reduced. Dexamethasone was more effective than betamethasone in inducing these changes.

CONCLUSIONS

Our results support a biphasic effect on SP-A mRNA levels after exposure to corticosteroids in combination with cAMP. At higher corticosteroid concentrations, betamethasone is less inhibitory than dexamethasone on SP-A mRNA.

Regulation of 15-hydroxyprostaglandin dehydrogenase expression in hepatocellular carcinoma

Cyclooxygenase-2 (COX-2), a rate limiting step in arachidonic acid cascade, plays a key role in the biosynthesis of prostaglandin E2 (PGE2) upon inflammatory stimuli, growth factors, hormones and other cellular stresses. Overproduction of PGE2 stimulates proliferation of various cancer cells, confers resistance to apoptosis and favors metastasis and angiogenesis. The steady-state level of PGE2 is maintained by interplay between the biosynthetic pathway including COX and PGE2 synthases and the catabolic pathways involving nicotinamide adenine dinucleotide (NAD(+))-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH). 15-PGDH is a crucial enzyme responsible for the biological inactivation of PGE2. Adult hepatocytes fail to induce COX-2 expression regardless of the pro-inflammatory factors used. COX-2 is induced in hepatocytes after partial hepatectomy (PH), in animal models of cirrhosis, in human hepatoma cell lines, in human HCC and after HBV and HCV infection. However, no data are available regarding 15-PGDH expression in HCC. Our results show that 15-PGDH is downregulated in human hepatoma cells with a high COX-2 expression, in chemical and genetic murine models of HCC and in human HCC biopsies. Moreover, 15-PGDH expression is suppressed by EGF (epidermal growth factor) and HGF (hepatocyte growth factor) mainly involving PI3K (phosphatidylinositol-3-kinase), ERK (extracellular signal-regulated kinase) and p38MAPK (mitogen-activated protein kinase) activation. Conversely, ectopic expression of 15-PGDH induces apoptosis in hepatoma cells and decreases the growth of hepatoma cells in nude mice whereas the silencing of 15-PGDH increases the tumor formation. These data suggest a potential therapeutic application of 15-PGDH in HCC.

11β-Hydroxysteroid Dehydrogenase Type II is a Potential Target for Prevention of Colorectal Tumorigenesis

Colorectal cancer (CRC) is a leading cause of cancer death, yet primary prevention remains the best approach to reducing overall morbidity and mortality. There is a clear molecular link between cyclooxygenase-2 (COX-2)-derived prostaglandin E₂ (PGE₂) production and CRC progression. Although selective COX-2 inhibitors as well as non-steroidal anti-inflammatory drugs (NSAIDs) reduce the number and sizes of colonic adenomas, increased cardiovascular risks of selective COX-2 inhibitors and increased gastrointestinal side-effects of NSAIDs limit their use in chemoprevention of CRC. Glucocorticoids induce apoptosis and are endogenous, potent COX-2 inhibitors. Glucocorticoids have been used for the treatment of hematologic malignancies, but not for solid tumors due to adverse side-effects such as immunosuppression and osteoporosis. In tissues, glucocorticoid actions are down-regulated by t y p e 2 1 1 β-hydroxysteroid dehydrogenase (11βHSD2), and inhibition of 11βHSD2 activity will elevate intracellular active glucocorticoid to levels that effectively suppress COX-2 expression. Both COX-2 and 11βHSD2 increase in Apc^+/min mouse intestinal adenomas and human colonic adenomas and either pharmacologic or genetic 11βHSD2 inhibition leads to decreases in COX-2-mediated PGE₂ production in tumors and prevents adenoma formation, tumor growth, and metastasis. 11βHSD2 inhibition may represent a novel approach for CRC chemoprevention by increasing tumor cell intracellular glucocorticoid activity, which in turn inhibits tumor growth by suppressing the COX-2-derived PGE₂ pathway, as well as other pathways, without potential side-effects relating to chronic application of COX-2 inhibitors, NSAIDs and glucocorticoids.

Limited effect of anti-rheumatic treatment on 15-prostaglandin dehydrogenase in rheumatoid arthritis synovial tissue

Introduction

Rheumatoid arthritis (RA) is a chronic inflammatory disease in which prostaglandin E₂ (PGE₂) displays an important pathogenic role. The enzymes involved in its synthesis are highly expressed in the inflamed synovium, while little is known about 15- prostaglandin dehydrogenase (15-PGDH) that metabolizes PGE₂. Here we aimed to evaluate the localization of 15-PGDH in the synovial tissue of healthy individuals or patients with inflammatory arthritis and determine the influence of common RA therapy on its expression.

Methods

Synovial tissue specimens from healthy individuals, psoriatic arthritis, ostheoarthritis and RA patients were immunohistochemically stained to describe the expression pattern of 15-PGDH. In addition, the degree of enzyme staining was evaluated by computer analysis on stained synovial biopsies from two groups of RA patients, before and after RA specific treatment with either intra-articular glucocorticoids or oral methotrexate therapy. Prostaglandins derived from the cyclooxygenase (COX) pathway were determined by liquid-chromatography mass spectrometry in supernatants from interleukin (IL) 1β-activated fibroblast-like synoviocytes (FLS) treated with methotrexate.

Results

15-PGDH was present in healthy and inflamed synovial tissue, mainly in lining macrophages, fibroblasts and vessels. Intra-articular glucocorticoids showed a trend towards reduced 15-PGDH expression in RA synovium (p = 0.08) while methotrexate treatment left the PGE₂ pathway unaltered both in biopsies ex vivo and in cultured FLS.

Conclusions

Early methotrexate therapy has little influence on the expression of 15-PGDH and on any of the PGE₂ synthesizing enzymes or COX-derived metabolites. Thus therapeutic strategies involving blocking induced PGE₂ synthesis may find a rationale in additionally reducing local inflammatory mediators.

Prostaglandin catabolic enzymes as tumor suppressors

15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is a key prostaglandin catabolic enzyme catalyzing the oxidation and inactivation of prostaglandin E(2) (PGE(2)) synthesized from the cyclooxygenase (COX) pathway. Accumulating evidence indicates that 15-PGDH may function as a tumor suppressor antagonizing the action of COX-2 oncogene. 15-PGDH has been found to be down-regulated contributing to elevated levels of PGE(2) in most tumors. The expression of 15-PGDH and COX-2 appears to be regulated reciprocally in cancer cells. Down-regulation of 15-PGDH in tumors is due, in part, to transcriptional repression and epigenetic silencing. Numerous agents have been found to up-regulate 15-PGDH by down-regulation of transcriptional repressors and by attenuation of the turnover of the enzyme. Up-regulation of 15-PGDH may provide a viable approach to cancer chemoprevention. Further catabolism of 15-keto-prostaglandin E(2) is catalyzed by 15-keto-prostaglandin-∆(13)-reductase (13-PGR), which also exhibits LTB(4)-12-hydroxydehydrogenase (LTB(4)-12-DH) activity. 13-PGR/LTB(4)-12-DH behaves as a tumor suppressor as well. This review summarizes current knowledge of the expression and function of 15-PGDH and 13-PGR/LTB(4)-12-DH in lung and other tissues during tumor progression. Future directions of research on these prostaglandin catabolic enzymes as tumor suppressors are also discussed.

15-Hydroxyprostaglandin dehydrogenase as a novel molecular target for cancer chemoprevention and therapy

Cyclooxygenase-2 (COX-2), a rate-limiting enzyme in arachidonic acid cascade, plays a key role in the biosynthesis of prostaglandin E(2) (PGE(2)) upon inflammatory insults. Overproduction of PGE(2) stimulates proliferation of various cancer cells, confers resistance to apoptosis of cancerous or transformed cells, and accelerates metastasis and angiogenesis. Excess PGE(2) undergoes metabolic inactivation which is catalyzed by NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH). In this context, 15-PGDH has been speculated as a physiological antagonist of COX-2 and a tumor suppressor. Thus, overexpression of 15-PGDH has been known to protect against experimentally induced carcinogenesis and renders the cancerous or transformed cells susceptible to apoptosis by counteracting oncogenic action of PGE(2). In contrast, silence of 15-PGDH is observed in some cancer cells, which is associated with epigenetic modification, such as DNA methylation and histone deacetylation, in the promoter region of 15-PGDH. A variety of compounds capable of inducing the expression of 15-PGDH have been reported, which include the histone deacetylase inhibitors, nonsteroidal anti-inflammatory drugs, and peroxisome proliferator-activated receptor-gamma agonists. Therefore, 15-PGDH may be considered as a novel molecular target for cancer chemoprevention and therapy. This review highlights the role of 15-PGDH in carcinogenesis and its regulation.

Interleukin-4 up-regulates 15-hydroxyprostaglandin dehydrogenase (15-PGDH) in human lung cancer cells

IL-4, an anti-inflammatory cytokine, was found to stimulate 15-PGDH activity in A549 and other lung cancer cells. Increase in 15-PGDH activity was due to increased transcription and decreased protein turnover of 15-PGDH. MMP-9 was shown to result in decreased levels of 15-PGDH in A549 cells. IL-4 induced down-regulation of MMP-9 mRNA and up-regulation of TIMP-1, an inhibitor of MMP-9. These data suggest that IL-4-induced down-regulation of MMP-9 activity may contribute to up-regulation of 15-PGDH in A549 cells. The role of JAK-STAT6 in IL-4-induced 15-PGDH expression was examined by using inhibitors. Inhibitors of JAKs, kaempferol and JAK inhibitor I, attenuated IL-4-stimulated STAT6 phosphorylation and 15-PGDH activity in a comparable concentration-dependent manner. Furthermore, JAK inhibitor I blocked IL-4-induced down-regulation of MMP-9 mRNA and up-regulation of TIMP-1 but not IL-4-stimulated up-regulation of 15-PGDH mRNA. These results indicate that JAK-STAT6 participated in IL-4-induced up-regulation of 15-PGDH through inhibition of MMP-9-mediated degradation. The roles of other signaling kinases in IL-4-induced 15-PGDH expression were also examined by using various inhibitors. Inhibitors of various MAPKs, PI-3K and PKC attenuated significantly IL-4-stimulated 15-PGDH activity indicating that MAPKs, PI-3K/Akt and PKC pathways participated in IL-4-induced up-regulation of 15-PGDH. Our results indicate that IL-4 up-regulates 15-PGDH by increased gene transcription and decreased protein turnover and the up-regulation can be mediated by JAK-STAT6 as well as MAPKs, PI-3K/Akt and PKC pathways.

Inhibition of 11beta-hydroxysteroid dehydrogenase type II selectively blocks the tumor COX-2 pathway and suppresses colon carcinogenesis in mice and humans

Colorectal cancer (CRC) is a leading cause of cancer death, yet primary prevention remains the best approach to reducing overall morbidity and mortality. Studies have shown that COX-2-derived PGE2 promotes CRC progression, and both nonselective COX inhibitors (NSAIDs) and selective COX-2 inhibitors (such as glucocorticoids) reduce the number and size of colonic adenomas. However, increased gastrointestinal side effects of NSAIDs and increased cardiovascular risks of selective COX-2 inhibitors limit their use in chemoprevention of CRC. We found that expression of 11beta-hydroxysteroid dehydrogenase type II (11betaHSD2), which converts active glucocorticoids to inactive keto-forms, increased in human colonic and Apc+/min mouse intestinal adenomas and correlated with increased COX-2 expression and activity. Furthermore, pharmacologic inhibition or gene silencing of 11betaHSD2 inhibited COX-2-mediated PGE2 production in tumors and prevented adenoma formation, tumor growth, and metastasis in mice. Inhibition of 11betaHSD2 did not reduce systemic prostacyclin production or accelerate atherosclerosis in mice, thereby avoiding the major cardiovascular side effects seen with systemic COX-2 inhibitors. Therefore, 11betaHSD2 inhibition represents what we believe to be a novel approach for CRC chemoprevention and therapy by increasing tumor glucocorticoid activity, which in turn selectively blocks local COX-2 activity.

Influence of dexamethasone on protease-activated receptor 2-mediated responses in the airways

Stimulants of protease-activated receptor (PAR)(2) promote the generation of the bronchoprotective prostanoid prostaglandin (PG) E(2) by airway epithelial cells. In contrast, glucocorticoids reduce the levels of PGE(2) in airway epithelial cell cultures by concomitantly inhibiting pathways required for PGE(2) synthesis and facilitating pathways involved in PGE(2) inactivation. The aim of this study was to determine whether glucocorticoids inhibited PAR(2)-mediated, PGE(2)-dependent responses in epithelial cell cultures, in intact airway preparations, and in whole animals. In cultures of A549 cells, a PAR(2)-activating peptide SLI-GRL-NH(2) produced concentration and time-dependent increases in PGE(2) levels, which were significantly enhanced after exposure to lipopolysaccharide (LPS). However, SLIGRL-NH(2)-induced increases in PGE(2) levels were abolished by pretreatment of cells with the glucocorticoid, dexamethasone. In mouse isolated tracheal preparations, SLIGRL-NH(2) and PGE(2) induced concentration-dependent relaxation responses that were unaffected by dexamethasone, irrespective of whether dexamethasone exposure occurred in vitro or in vivo. Intranasal administration of LPS produced a pronounced increase in the numbers of neutrophils recovered from the bronchoalveolar lavage fluid of BALB/c mice. Numbers of recovered neutrophils were 40 to 60% lower in mice that received f-LIGRL-NH(2) (PAR(2)-activating peptide, 30 microg intranasally), PGE(2) (10 mugintranasally), or dexamethasone (1 mg/kg i.p.). In the combined presence of dexamethasone and f-LIGRL-NH(2) or dexamethasone and PGE(2), the number of neutrophils was suppressed further (80-83% lower). Thus, although dexamethasone abolished PAR(2)-mediated generation of PGE(2) in A549 cells, neither the smooth muscle relaxant nor the anti-inflammatory effects of PAR(2)-activating peptides (and PGE(2)) were diminished by in vitro or in vivo exposure to dexamethasone.

15-hydroxyprostaglandin dehydrogenase (15-PGDH) and lung cancer

15-hydroxyprostaglandin dehydrogenase (15-PGDH) catalyzes NAD(+)-linked oxidation of 15 (S)-hydroxyl group of prostaglandins and lipoxins and is the key enzyme responsible for the biological inactivation of these eicosanoids. The enzyme was found to be under-expressed as opposed to cyclooxygenase-2 (COX-2) being over-expressed in lung and other tumors. A549 human lung adenocarcinoma cells were used as a model system to study the role of 15-PGDH in lung tumorigenesis. Up-regulation of COX-2 expression by pro-inflammatory cytokines in A549 cells was accompanied by a down-regulation of 15-PGDH expression. Over-expression of COX-2 but not COX-1 by adenoviral-mediated approach also attenuated 15-PGDH expression. Similarly, over-expression of 15-PGDH by the same strategy inhibited IL-1beta-induced COX-2 expression. It appears that the expression of COX-2 and 15-PGDH is regulated reciprocally. Adenoviral-mediated transient over-expression of 15-PGDH in A549 cells resulted in apoptosis. Xenograft studies in nude mice also showed tumor suppression with cells transiently over-expressing 15-PGDH. However, cells stably over-expressing 15-PGDH generated tumors faster than those control cells. Examination of different clones of A549 cells stably expressing different levels of 15-PGDH indicated that the levels of 15-PGDH expression correlated positively with those of mesenchymal markers, and negatively with those of epithelial markers. It appears that the stable expression of 15-PGDH induces epithelial-mesenchymal transition (EMT) which may account for the tumor promotion in xenograft studies. A number of anti-cancer agents, such as transforming growth factor-beta1 (TGF-beta1), glucocorticoids and some histone deacetylase inhibitors were found to induce 15-PGDH expression. These results suggest that tumor suppressive action of these agents may, in part, be related to their ability to induce 15-PGDH expression.

Histone deacetylase inhibitors and transforming growth factor-beta induce 15-hydroxyprostaglandin dehydrogenase expression in human lung adenocarcinoma cells

Histone deacetylase (HDAC) inhibitors have been actively exploited as potential anticancer agents. To identify gene targets of HDAC inhibitors, we found that HDAC inhibitors such as sodium butyrate, scriptaid, apicidin and oxamflatin induced the expression of 15-hydroxyprostaglandin dehydrogenase (15-PGDH), a potential cyclooxygenase-2 (COX-2) antagonist and tumor suppressor, in a time and concentration dependent manner in A549 and H1435 lung adenocarcinoma cells. Detailed analyses indicated that HDAC inhibitors activated the 15-PGDH promoter-luciferase reporter construct in transfected A549 cells. A representative HDAC inhibitor, scriptaid, and its negative structural analog control, nullscript, were further evaluated at the chromatin level. Scriptaid but not nullscript induced a significant accumulation of acetylated histones H3 and H4 which were associated with the 15-PGDH promoter as determined by chromatin immunoprecipitation assay. Transforming growth factor-beta1 (TGF-beta1) also induced the expression of 15-PGDH in a time and concentration dependent manner in A549 and H1435 cells. Induction of 15-PGDH expression by TGF-beta1 was synergistically stimulated by the addition of Wnt3A which was inactive by itself. However, combination of TGF-beta and an HDAC inhibitor, scriptaid, only resulted in an additive effect. Together, our results indicate that 15-PGDH is one of the target genes that HDAC inhibitors and TGF-beta may induce to exhibit tumor suppressive effects.