Linked 15-hydroxyprostaglandin Dehydrogenase Research Articles

Effect of 15-PGDH on the Proliferation and Migration of Human Gastric Cancer Cells

Objective: To investigate the effect of stable transfection with NAD+-linked 15-hydroxyprostaglandin dehydrogenase (15-PGDH) on the growth, proliferation and migration of gastric cancer cells. Methods: The levels of 15-PGDH in four kinds of gastric cancer cells with different differentiation rates were compared by RT-PCR measurements, and the poorly differentiated gastric cancer cells SGC7901 were chose to perform follow-up experiments. SGC7901 cells were transfected with recombinant plasmid pcDNA3/15-PGDH and empty plasmid pcDNA3 as a control by using lipofectamine 2000. Cells with steady expression capability were sorted out by G418. RT-PCR and Western blot were used to confirm the transfection and expression of 15-PGDH in SGC7901 cells. MTT, cell scratch assay, soft-agar colony formation assays were used to determine the proliferation, migration and cell clone formation activities of SGC7901 with stable transfection of 15-PGDH. Flow cytometry assay was used to examine the effect of 15-PGDH on cell cycle and apoptosis. RT-PCR was used to analyze the levels of cell cycle-related genes (p53, p21 and p16) and apoptosis-related genes (Survivin, BCL-2 and Caspase3). Results: Both recombinant plasmid pcDNA3/15-PGDH and empty vector plasmid pcDNA3 were successfully transfected into human gastric cancer SGC7901 cell line. Proliferation, migration and cell clone formation capabilities of pcDNA3/15-PGDH groups were significantly inhibited compared with other two control groups (P<0.05). Flow cytometry results demonstrated an increased fraction of sub-G1 phase and the increase of apoptotic cells for pcDNA3/15-PGDH groups compared with other two control groups (P<0.05). The levels of p16, p21 and p53 mRNA for pcDNA3/15-PGDH groups were higher than those in other two control groups (p<0.05). pcDNA3/15-PGDH groups exhibited a higher level of caspase3 mRNA but lower levels of survivin and BCL-2 mRNA in SGC7901 cells compared with other two control groups (P< 0.05). Conclusion: The gene transfection of 15-PGDH has negative effects on the growth, proliferation and migration of gastric cancer SGC7901 cells by inducing apoptosis and cell cycle arrest.

MiR-21 Targets 15-PGDH and Promotes Cholangiocarcinoma Growth

miRNAs are a group of small, noncoding RNAs that modulate the translation of genes by binding to specific target sites in the target mRNA. This study investigated the biologic function and molecular mechanism of miR-21 in human cholangiocarcinoma. In situ hybridization analysis of human cholangiocarcinoma specimens showed increased miR-21 in cholangiocarcinoma tissue compared with the noncancerous biliary epithelium. Lentiviral transduction of miR-21 enhanced human cholangiocarcinoma cell growth and clonogenic efficiency in vitro, whereas inhibition of miR-21 decreased these parameters. Overexpression of miR-21 also promoted cholangiocarcinoma growth using an in vivo xenograft model system. The NAD(+)-linked 15-hydroxyprostaglandin dehydrogenase (15-PGDH/HPGD), a key enzyme that converts the protumorigenic prostaglandin E2 (PGE2) to its biologically inactive metabolite, was identified as a direct target of miR-21 in cholangiocarcinoma cells. In parallel, cyclooxygenase-2 (COX2) overexpression and PGE2 treatment increased miR-21 levels and enhanced miR-21 promoter activity in human cholangiocarcinoma cells. Cholangiocarcinogenesis and tumor progression are regulated by a novel interplay between COX-2/PGE2 and miR-21 signaling, which converges at 15-PGDH.

Abstract 1179: 15-PGDH inhibits cholangiocarcinogenesis through the induction of TAp63

Abstract NAD+-linked 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is responsible for the catabolism of prostaglandins in a variety of cell types such as inflammation an dtumorigenesis. In this study we showed that forced overexpression of 15-PGDH in human cholangiocarcinoma cells (CCLP1) suppressed tumor cell growth, invasion and clonogenic formation capacity. In contrast, 15-PGDH knockdown in CCLP1 cells enhanced tumor cell growth, invasion and clonogenic formation. Flow cytometry analysis revealed that 15-PGDH overexpression induced cell cycle arrest at G1/S checkpoint. When implanted into SCID mice, 15-PGDH overexpressed CCLP1 cells formed smaller xenograft tumors, whereas 15-PGDH-depleted cells formed larger xenograft tumors when compared with each of the corresponding controls (p&amp;lt;0.01). In addition, intratumoral injection of an adenoviral vector expressing 15-PGDH (pAd-15-PGDH) significantly inhibited the growth of cholangiocarcinoima in SCID mice. Western blot analysis showed that 15-PGDH induced the expression of TAp63, a key tumor suppressive gene. Furthermore, 15-PGDH induced the phosphorylation of Smad2/3 and enhanced the interaction between p53 and pSmad2/3 in CCLP1 cells; the pSmad2/3 and p53 binding complex appeared to play a key role for the induction of TAp63 expression. Taken together, our data suggest that 15-PGDH inhibits cholangiocarcinoma growth and this effect is at least in part through pSmad2/3 and p53-mediated induction of TAp63. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1179. doi:1538-7445.AM2012-1179

Loss of 15-Hydroxyprostaglandin Dehydrogenase Expression Contributes to Bladder Cancer Progression

Prostaglandin E2, which is known to contribute to cancer progression, is inactivated by the catabolic enzyme, 15-hydroxyprostaglandin dehydrogenase (PGDH), which has tumor-suppressor activity in lung, colon, breast, and gastric cancers. Therefore, we evaluated the expression of PGDH in human bladder cancer tissue specimens and cell lines. Immunoperoxidase staining of bladder cancer tissues demonstrated that (1) PGDH is highly expressed by normal urothelial cells but (2) reduced in many low stage (Ta/Tis) bladder cancers, and (3) PGDH is completely lost in most invasive bladder cancers. Of eight cancer cell lines tested, only two relatively well-differentiated bladder cancer cell lines, RT4 and UM-UC9, expressed PGDH. Moreover, inhibition of PGDH expression in well-differentiated RT4 cells using small inhibitory RNA or short hairpin RNA resulted in a more aggressive phenotype with increased motility and anchorage-independent growth. Additionally, PGDH knockdown affected prostaglandin E2 signaling as measured by cAMP generation. These data indicate that loss of PGDH expression contributes to a more malignant bladder cancer phenotype and may be necessary for bladder cancer development and/or progression.

Experimental cancer therapy using restoration of NAD+-linked 15-hydroxyprostaglandin dehydrogenase expression

Preclinical and clinical evidence shows that cyclooxygenase-2 (Cox-2)-mediated prostaglandin E(2) (PGE(2)) overexpression plays an important role in tumor growth, metastasis, and immunosuppression. It has been shown that expression of NAD(+)-linked 15-hydroxyprostaglandin dehydrogenase (15-PGDH), a key enzyme responsible for PGE(2) inactivation, is suppressed in the majority of cancers, including breast and colon carcinoma. We have developed adenoviral vectors (Ad) encoding the 15-PGDH gene under control of the vascular endothelial growth factor receptor 1 (VEGFR1/flt-1; Adflt-PGDH) and the Cox-2 (Adcox-PGDH) promoters. The purpose of this study was to investigate cytotoxicity in vitro and therapeutic efficacy in vivo of 15-PGDH-mediated cancer therapy. The levels of PGE(2) and VEGF expression were correlated with PGE(2) receptor and Cox-2 and flt-1 expression in cancer cells. The in vitro study showed that Ad-mediated 15-PGDH expression significantly decreased proliferation and migration of cancer cells. Animal breast and colon tumor therapy studies showed that 15-PGDH gene therapy produced a significant delay in 2LMP and LS174T tumor growth. Combined therapy using 15-PGDH and anti-VEGF antibody (bevacizumab) significantly increased inhibition of growth of LS174T tumor xenografts in comparison with agents alone. These results suggest that 15-PGDH-mediated regulation of PGE(2) catabolism in the tumor microenvironment represents a novel approach for therapy of human breast and colon cancer.

Reciprocal regulation of cyclooxygenase-2 and 15-hydroxyprostaglandin dehydrogenase expression in A549 human lung adenocarcinoma cells

Human lung adenocarcinoma cells, A549, possess the capacity of expressing both cyclooxygenase-2 (COX-2) and NAD+-linked 15-hydroxyprostaglandin dehydrogenase (15-PGDH). Resting cells express little COX-2 but significant levels of 15-PGDH. Interleukin (IL) 1beta, tumor necrosis factor-alpha (TNF-alpha) or phorbol ester [phorbol 12-myristate 13-acetate (PMA)] induced the expression of COX-2, as revealed by western blot analysis. Combination of PMA and IL-1beta or TNF-alpha induced synergistically the expression of COX-2. Interestingly, cytokines and cytokine plus PMA-induced expression of COX-2 were accompanied by a downregulation of 15-PGDH. This was evident from both the western blot analysis and activity assay of 15-PGDH. It appears that the higher the expression of COX-2 was induced, the lower the expression of 15-PGDH was found. This was further supported by the observation that overexpression of COX-2 but not COX-1 by adenovirus-mediated approach led to a decrease in 15-PGDH expression, indicating the specificity of COX-2. Furthermore, downregulation of the IL-1beta-induced expression of COX-2 by silencing RNA (siRNA) approach resulted in an increase in the expression of 15-PGDH by COX-2-siRNA but not by COX-1-siRNA, indicating that it was indeed the expression of COX-2 attenuating the expression of 15-PGDH. The IL-1beta-induced reduction of the expression of 15-PGDH was shown not to be mediated by COX-2-derived products since the presence of COX-2 inhibitors did not block the attenuation of the expression of 15-PGDH. Exogenous PGE2 also did not induce the reduction of the expression of 15-PGDH. However, overexpression of 15-PGDH by transfection with recombinant plasmid encoding 15-PGDH or adenovirus-mediated approach attenuated IL-1beta-induced expression of COX-2. On the contrary, downregulation of 15-PGDH expression by 15-PGDH-siRNA or 15-PGDH-antisense approach resulted in an increase in IL-1beta-induced expression of COX-2 but not that of COX-1. In fact, it was further observed that A549 clones expressing different degrees of 15-PGDH showed also different levels of COX-2 expression after IL-1beta induction. The levels of IL-1beta-induced COX-2 expression appeared to correlate inversely with those of 15-PGDH expression in the cells. These results support the contention that COX-2 and 15-PGDH are regulated reciprocally in A549 cells.

NAD+-Linked 15-Hydroxyprostaglandin Dehydrogenase: Structure and Biological Functions

NAD(+)-linked 15-hydroxyprostaglandin dehydrogenase (15-PGDH) catalyzes the oxidation of 15(S)-hydroxyl group of prostaglandins and lipoxins resulting in the formation of 15-keto metabolites which exhibit greatly reduced biological activities. Therefore, this enzyme has been considered the key enzyme responsible for the inactivation of prostaglandins and lipoxins. Both the cDNA and the genomic DNA of the 15-PGDH gene have been cloned. Structural characterization, transcriptional regulation and biological functions of this enzyme have been investigated. Molecular modeling corroborated with site-directed mutagenesis has identified key residues and domains involved in coenzyme and substrate binding. Catalytic mechanism has been proposed. Studies on the regulation of enzyme expression and activity by physiological and pharmacological agents have begun to uncover its significant roles in cancer, inflammation and reproduction. Apparently, 15-PGDH works with cyclooxygenase-2 to control the cellular levels of prostaglandins. Their reciprocal regulation within the same cells appears to determine the fate of the cells. Because of its ability to inactivate both prostaglandins and lipoxins of two opposite biological activities, the roles of 15-PGDH in cancer and inflammation are particularly intriguing and challenging. Future investigations in these areas are warranted.

NAD+-linked 15-hydroxyprostaglandin dehydrogenase (15-PGDH) behaves as a tumor suppressor in lung cancer.

It has been reported that two inducible prostaglandin synthetic enzymes, cylooxygenase-2 (COX-2) and microsomal PGE synthase, are over-expressed in non-small cell lung cancer (NSCLC). Using quantitative reverse transcription-polymerase chain reaction, we analyzed RNA levels of the key prostaglandin catabolic enzyme, NAD+-linked 15-hydroxyprostaglandin dehydrogenase (15-PGDH), in 19 pairs of NSCLC tumors and adjacent non-malignant tissue from the same patient. We found that 100% of tumor-tissue pairs showed at least a 2-fold decrease and 61% showed a 10-fold decrease. This suggests that the increased expression of COX-2 and PGE synthase in tumors may work in concert with the decreased expression of 15-PGDH to amplify an increase in tissue levels of proliferative PGE2. To further explore if 15-PGDH is related to tumorigenesis, athymic nude mice were injected with control A549 cells or cells transiently over-expressing wild-type or mutant 15-PGDH (Y151F). It was found that mice injected with control A549 cells or with cells expressing mutant enzyme produced tumors normally. However, mice injected with A549 cells expressing wild-type 15-PGDH had a significant decrease in tumor growth. Examining the effects of 15-PGDH expression on cellular changes in A549 cells, we found that over-expression of 15-PGDH induced apoptosis of A549 cells as evidenced by fragmentation of DNA, activation of pro-caspase 3, cleavage of poly(ADP-ribose) polymerase and decreased expression of Bcl-2. We also found that the expression of 15-PGDH was negatively related to that of pro-adhesive and invasive CD44. Furthermore, the expression of 15-PGDH was found to be stimulated by hyaluronidase. These results suggest that 15-PGDH may decrease the level of proliferative PGE2, induce apoptosis and function like a tumor suppressor.

Structure and function of human NAD(+)-linked 15-hydroxyprostaglandin dehydrogenase.

Prostaglandins are rapidly metabolized in the body. The primary route of metabolism is initiated by NAD+-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH) which catalyzes the reversible oxidation of 15(S)-hydroxyl group to a keto function resulting in a great loss of biological activities. 15-PGDH is therefore considered a key enzyme responsible for biological inactivation of prostaglandins. The enzyme is ubiquitously present in mammalian tissues. The first cDNA was cloned form human placenta and was found to have an open reading frame of 798 bp coding for 266 amino acids.’ The native enzyme is believed to be a dimer composed of identical subunits with a M.W. of 29 kDa. The enzyme utilizes a wide range of prostaglandins, lipoxins and hydroxy fatty acids as substrates and prefers NAD+ over NADP+ as a coenzyme.’ The enzyme is sensitive to sulfhydryl inhibitors indicating one or more cysteinyl residues are essential.’ The primary structure of 15-PGDH shows that it belongs to a superfamily of short chain dehydrogenases/reductases (SDR).3Sequence analysis indicates that an overall homology of 20% among SDRs with several conserved amino acid residues. Whether these conserved residues and cysteinyl residues are involved in catalytic activity and/or structural integrity remains to be determined. Most of these conserved residues reside in the first two thirds of the polypeptide chain suggesting that they might be involved in interacting with the common coenzyme NAD+. The C-terminal third shows little homology in sequences indicating that this segment appears to accommodate substrates of diversed structures.. This study is focused on using site-directed mutagenesis to examine the roles of several conserved and cysteinyl residues in catalytic activity and the involvement of C-terminal domain in enzyme and substrate interactions.

Induction of NAD+-Linked 15-Hydroxyprostaglandin Dehydrogenase Expression by Androgens in Human Prostate Cancer Cells

Prostate cancer cells are known to express cyclooxygenases (COXs) and synthesize prostaglandins. Catabolism of prostaglandins in these cells remains to be determined. Induction of NAD+-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH), a key metabolic inactivation enzyme, was investigated in androgen-sensitive LNCaP cells and in hormone-independent PC3 cells. 15-PGDH was found to be induced by dihydrotestosterone or testosterone in a time- and dose-dependent manner in LNCaP but not in PC3 cells as shown by activity assay and immunoblot analysis. However, prostaglandin synthetic enzymes, COX-1 and COX-2, were not found to be induced by androgens. Induction was also achieved by 17β-estradiol and progesterone, although to a lesser extent. Induction of 15-PGDH was not blocked by steroid receptor antagonist, RU 486, nor by antiandrogen, flutamide. However, induction was inhibited by tyrosine kinase inhibitor, genistein, and by ERK kinase inhibitor, PD 98059, but not by protein kinase C inhibitor, GF109203X. These results suggest that androgens induce 15-PGDH gene expression through an unconventional nongenomic pathway.

Photoaffinity labeling of human placental NAD(+)-linked 15-hydroxyprostaglandin dehydrogenase with [alpha-32P]2N3NAD+. Identification of a peptide in the adenine ring binding domain

Oxidation of many prostaglandins at C-15 results in the formation of 15-keto metabolites, which have reduced biological activity. This reaction is catalyzed by NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase. Using the photoaffinity analog of NAD+, [alpha-32P]nicotinamide-2-azidoadenine dinucleotide, we have identified a peptide in the adenine ring binding domain of the NAD+ binding site of 15-hydroxyprostaglandin dehydrogenase. The specificity of photolabeling was demonstrated by saturation and protection experiments. Saturation of photolabeling was observed at approximately 45-50 microM with an apparent Kd of 8-10 microM. Approximately 90% of photolabeling could be protected by 200 microM NAD+ when the protein was photolyzed in the presence of 10 microM probe. The photolabeled protein was digested with Staphylococcus aureus V8 or chymotrypsin, and the photolabeled peptides were purified by either boronate affinity chromatography or Fe+3 chelate chromatography followed by reverse phase HPLC. The photolabeled peptide region was identified to be Val32-Glu40.

Three-dimensional model of NAD +-dependent 15-hydroxyprostaglandin dehydrogenase and relationships to the NADP +-dependent enzyme (carbonyl reductase)

Modelling the amino acid sequence of NAD +-linked 15-hydroxyprostaglandin dehydrogenase into the three-dimensional structure of 3α/20β-hydroxysteroid dehydrogenase shows that these two enzymes, as well as the NADP +-linked prostaglandin dehydrogenase (identical to carbonyl reductase) have similar conformations, in spite of very limited sequence identity (23–28%). Conservation of tertiary structures is greatest over the first two thirds of the polypeptide chains, where the typical NAD + binding fold is retained, including the five first β-strands, with only two short deletions or insertions up to residue 147. The remaining thirds of each of the prostaglandin dehydrogenases have significantly different architecture, including insertions that may contribute to enzyme specificity, and, except for an additional helix (αG), are difficult to model. Active site relationships can be evaluated and subunit interactions predicted, suggesting that the αE + αF two-helix surface constitutes the major subunit interacting area, forming a dimeric unit in the oligomeric enzymes.

Purification and structural characterization of placental NAD+-linked 15-hydroxyprostaglandin dehydrogenase. The primary structure reveals the enzyme to belong to the short-chain alcohol dehydrogenase family

Human placental NAD(+)-linked 15-hydroxyprostaglandin dehydrogenase was purified to homogeneity according to a five-step method, with chromatography on DEAE-Sepharose, Blue Sepharose, and Mono-Q FPLC as principal steps. Final yield was 23% and purification about 13,000-fold, with a specific activity of 24,000 milliunits/mg. The subunit molecular weight is about 29,000 as determined by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, and the native protein molecular weight is about 54,000 as estimated by Sephadex G-100 chromatography, establishing the enzyme to be a dimer of similar-sized protein chains. The subunit N-terminal residue is methionine, and the alpha-amino group is free. The complete primary structure was determined by peptide analysis, based essentially on four different proteolytic treatments (Lys-specific protease, Glu-specific protease, Asp-specific protease, and CNBr). The protein chain is composed of 266 residues, with C-terminal glutamine. A microheterogeneity was detected at position 217, with both Cys and Tyr, in about equal amounts, from a preparation starting with a single placenta. No other subunit heterogeneities were detected. The protein is clearly but distantly related to insect alcohol dehydrogenases, characterized bacterial dehydrogenases of sugar metabolism, and bacterial and eukaryotic steroid dehydrogenases. Together, these results establish that placental 15-hydroxyprostaglandin dehydrogenase is a member of the short-chain nonmetalloenzyme alcohol dehydrogenase protein family. The protein has four cysteine residues (five with the positional microheterogeneity), but there is no evidence for functional importance of any of these residues.(ABSTRACT TRUNCATED AT 250 WORDS)

Inactivation of pulmonary NAD +-dependent 15-hydroxyprostaglandin dehydrogenase by acrolein

Acrolein, a highly reactive aldehyde found in cigarette smoke, was shown to induce time-dependent inactivation of NAD +-linked 15-hydroxyprostaglandin dehydrogenase from porcine lung. The inactivation process followed pseudo-first-order kinetics and was irreversible. Inactivation by acrolein can be prevented by prior incubation of the enzyme with GSH but not by subsequent addition of GSH during assay. Inactivation can be also protected fully by prior incubation of the enzyme with NAD +, but only partially with prostaglandin E 1. The results suggest that acrolein alkylates the enzyme at the coenzyme binding site and inactivates the enzyme. Inactivation of pulmonary NAD +-linked 15-hydroxyprostaglandin dehydrogenase by acrolein may alter cellular and circulating thromboxane/prostacyclin ratios and subsequently disturb vascular homeostasis and augment inflammatory and anaphylactic responses in smokers.

Increase in enzyme activities of prostaglandin biosynthesis and catabolism by acute ureteral ligation in rat kidney

Acute ureteral obstruction increased cyclooxygenase, thromboxane and prostacyclin synthases and NAD +-linked 15-hydroxyprostaglandin dehydrogenase activities in rat kidney. Significant increase in prostaglandin biosynthetic and catabolic activities may mediate some pathological consequences found in obstructive nephropathy.

Pulmonary NAD +-linked 15-hydroxyprostaglandin dehydrogenase activity is decreased by cigarette smoking

Male rats were exposed to freshly generated cigarette smoke once daily for 4 to 13 weeks. Inhalation of smoke was verified by elevated level of carboxyhemoglobin. NAD +-dependent 15-hydroxyprostaglandin dehydrogenase activity, the key enzyme responsible for biological inactivation of prostaglandins, was found to decrease in lung but not in kidney or stomach following cigarette smoke exposure. The consequence of impaired pulmonary metobolism of prostaglandins and thromboxane may result in alteration of vascular homeostasis and subsequently lead to cardiovascular disorders commonly found in smokers.

Inhibition of 15-hydroxyprostaglandin dehydrogenase by antiallergic agents

Some antiallergic agents having protective action agaist anaphylaxis were found to inhibit NAD+-linked 15-hydroxyprostaglandin dehydrogenase partially purified from guinea pig lung. The concentrations required to inhibit the enzyme by 50% were 3.0 μM for baicalein, 9.8 μM for xanoxic acid and 350μM for disodium cromoglycate. The inhibitory effects of these compounds on 15-hydroxyprostaglandin dehydrogenase were greater than on cAMP phosphodiesterase activity in the same tissue. Inhibitory effects of flavonoids other than baicalein were also investigated.

Early steps in prostaglandin metabolism in the human placenta

The activities of the enzymes catalyzing the early steps in prostaglandin metabolism (the nicotinamide adenine dinucleotide [NAD]-linked 15-hydroxyprostaglandin dehydrogenase, the nicotinamide adenine dinucleotide phosphate [NADP]-linked 15-hydroxyprostaglandin dehydrogenase, and the 15-ketoprostaglandin Δ 13 reductase) were measured in homogenates of term placenta. The NAD-linked enzyme possesses the highest activity of the three. The NADP-linked enzyme has much lower activity and probably acts physiologically as a 9-ketoprostaglandin reductase rather than as a 15-hydroxyprostaglandin dehydrogenase. Placental homogenates contain a low-molecular-weight, heat-stable inhibitor of the NADP-linked enzyme. The reaction catalyzed by the 15-ketoprostaglandin Δ 13 reductase is the rate-limiting step. Analysis of the activity of these enzymes has shown that there is no significant relationship between them; furthermore, whether the placentas are from spontaneous single or twin deliveries, induced deliveries, or cesarean sections (in labor or not in labor) does not have a significant effect on the activity of the NAD- or NADP-linked dehydrogenases.

Inhibition of 15-hydroxyprostaglandin dehydrogenase by antiallergic agents

Some antiallergic agents having protective action against anaphylaxis were found to inhibit NAD +-linked 15-hydroxyprostaglandin dehydrogenase partially purified from guinea pig lung. The concentrations required to inhibit the enzyme by 50% were 3.0 μM for baicalein, 9.8 μM for xanoxic acid and 350 μM for disodium cromoglycate. The inhibitory effects of these compounds on 15-hydroxyprostaglandin dehydrogenase were greater than on cAMP phosphodiesterase activity in the same tissue. Inhibitory effects of flavonoids other than baicalein were also investigated.

Studies on 15-Hydroxyprostaglandin Dehydrogenase with Various Prostaglandin Analogues

The NAD+-linked 15-hydroxyprostaglandin dehydrogenase (PGDH) of swine lung was purified to a high specific activity by affinity chromatographies on prostaglandin (PG)-and NAD+-Sepharose. The affinities of the enzyme for various synthetic analogues of PGA, E, F, and I and their inhibitory effects on the enzymatic reaction were examined. The modification of the alkyl side chain of PG, particularly at C-15 or C-16, reduced the affinity of the enzyme for these PG analogues. Furthermore, 14-methyl-13,14-dihydro-PGE1 and 16-cyclopentyl-omega-trinor-15-epi-PGE2 were potent inhibitors of PGDH.