A 3-(4-nitronaphthen-1-yl) amino-benzoate analog as a bifunctional AKR1C3 inhibitor and AR antagonist: Head to head comparison with other advanced AKR1C3 targeted therapeutics

Drugs used for the treatment of castration resistant prostate cancer (CRPC) include Abiraterone acetate (Zytiga®) and Enzalutamide (XTANDI®). However, these drugs provide clinical benefit in metastatic disease for only a brief period before drug resistance emerges. One mechanism of drug resistance involves the overexpression of type 5 17-β-hydroxysteroid dehydrogenase (aldo-keto reductase 1C3 or AKR1C3), a major enzyme responsible for the formation of intratumoral androgens that activate the androgen receptor (AR). 3-((4-Nitronaphthalen-1-yl)amino)benzoic acid 1 is a "first-in-class" AKR1C3 competitive inhibitor and AR antagonist. Compound 1 was compared in a battery of in vitro studies with structurally related N-naphthyl-aminobenzoates, and AKR1C3 targeted therapeutics e.g. GTx-560 and ASP9521, as well as with R-bicalutamide, enzalutamide and abiraterone acetate. Compound 1 was the only naphthyl derivative that was a selective AKR1C3 inhibitor and AR antagonist in direct competitive binding assays and in AR driven reporter gene assays. GTx-560 displayed weak activity as a direct AR antagonist but had high potency in the AR reporter gene assay consistent with its ability to inhibit the co-activator function of AKR1C3. By contrast ASP9521 did not act as either an AR antagonist or block AR reporter gene activity. Compound 1 was the only compound that showed comparable potency to inhibit AKR1C3 and act as a direct AR antagonist. Compound 1 blocked the formation of testosterone in LNCaP-AKR1C3 cells, and the expression of PSA driven by the AKR1C3 substrate (4-androstene-3,17-dione) and by an AR agonist, 5α-dihydrotestosterone consistent with its bifunctional role. Compound 1 blocked the nuclear translocation of the AR at similar concentrations to enzalutamide and caused disappearance of the AR from cell lysates. R-biaclutamide and enzalutamide inhibited AKR1C3 at concentrations 200x greater than compound 1, suggesting that its bifunctionality can be explained by a shared pharmacophore that can be optimized.

Human and murine steroid 5β-reductases (AKR1D1 and AKR1D4): insights into the role of the catalytic glutamic acid

Mammalian steroid 5β-reductases belong to the Aldo-Keto Reductase 1D sub-family and are essential for the formation of A-ring 5β-reduced steroids. Steroid 5β-reduction is required for the biosynthesis of bile-acids and the metabolism of all steroid hormones that contain a Δ⁴-3-ketosteroid functionally to yield the 5β-reduced metabolites. In mammalian AKR1D enzymes the conserved catalytic tetrad found in all AKRs (Y55, H117, K84 and D50) has changed in that the conserved H117 is replaced with a glutamic acid (E120). E120 may act as a "superacid" to facilitate enolization of the Δ⁴-ketosteroid. In addition, the absence of the bulky imidazole side chain of histidine in E120 permits the steroid to penetrate deeper into the active site so that hydride transfer can occur to the steroid C5 position. In murine steroid 5β-reductase AKR1D4, we find that there is a long-form, with an 18 amino-acid extension at the N-terminus (AKR1D4L) and a short-form (AKR1D4S), where the latter is recognized as AKR1D4 by the major data-bases. Both enzymes were purified to homogeneity and product profiling was performed. With progesterone and cortisol, AKR1D4L and AKR1D4S catalyzed smooth conversion to the 5β-dihydrosteroids. However, with Δ⁴-androstene-3,17-dione as substrate, a mixture of products was observed which included, 5β-androstane-3,17-dione (expected) but 3α-hydroxy-5β- androstan-17-one was also formed. The latter compound was distinguished from its isomeric 3β-hydroxy-5β-androstan-17-one by forming picolinic acid derivatives followed by LC-MS. These data show that AKR1D4L and AKR1D4S also act as 3α-hydroxysteroid dehydrogenases when presented with Δ⁴-androstene-3,17-dione and suggest that E120 alters the position the steroid to enable a correct trajectory for hydride transfer and may not act as a "superacid".

Potent and Highly Selective Aldo-Keto Reductase 1C3 (AKR1C3) Inhibitors Act as Chemotherapeutic Potentiators in Acute Myeloid Leukemia and T-Cell Acute Lymphoblastic Leukemia

Aldo-keto reductase 1C3 (AKR1C3) catalyzes the synthesis of 9α,11β-prostaglandin (PG) F_2α and PGF_2α prostanoids that sustain the growth of myeloid precursors in the bone marrow. The enzyme is overexpressed in acute myeloid leukemia (AML) and T-cell acute lymphoblastic leukemia (T-ALL). Moreover, AKR1C3 confers chemotherapeutic resistance to the anthracyclines: first-line agents for the treatment of leukemias. The highly homologous isoforms AKR1C1 and AKR1C2 inactivate 5α-dihydrotestosterone, and their inhibition would be undesirable. We report herein the identification of AKR1C3 inhibitors that demonstrate exquisite isoform selectivity for AKR1C3 over the other closely related isoforms to the order of >2800-fold. Biological evaluation of our isoform-selective inhibitors revealed a high degree of synergistic drug action in combination with the clinical leukemia therapeutics daunorubicin and cytarabine in in vitro cellular models of AML and primary patient-derived T-ALL cells. Our developed compounds exhibited >100-fold dose reduction index that results in complete resensitization of a daunorubicin-resistant AML cell line to the chemotherapeutic and >100-fold dose reduction of cytarabine in both AML cell lines and primary T-ALL cells.

AKR1C3 Inhibitor KV-37 Exhibits Antineoplastic Effects and Potentiates Enzalutamide in Combination Therapy in Prostate Adenocarcinoma Cells

Aldo-keto reductase 1C3 (AKR1C3), also known as type 5 17 β-hydroxysteroid dehydrogenase, is responsible for intratumoral androgen biosynthesis, contributing to the development of castration-resistant prostate cancer (CRPC) and eventual chemotherapeutic failure. Significant upregulation of AKR1C3 is observed in CRPC patient samples and derived CRPC cell lines. As AKR1C3 is a downstream steroidogenic enzyme synthesizing intratumoral testosterone (T) and 5α-dihydrotestosterone (DHT), the enzyme represents a promising therapeutic target to manage CRPC and combat the emergence of resistance to clinically employed androgen deprivation therapy. Herein, we demonstrate the antineoplastic activity of a potent, isoform-selective and hydrolytically stable AKR1C3 inhibitor (E)-3-(4-(3-methylbut-2-en-1-yl)-3-(3-phenylpropanamido)phenyl)acrylic acid (KV-37), which reduces prostate cancer cell growth in vitro and in vivo and sensitizes CRPC cell lines (22Rv1 and LNCaP1C3) toward the antitumor effects of enzalutamide. Crucially, KV-37 does not induce toxicity in nonmalignant WPMY-1 prostate cells nor does it induce weight loss in mouse xenografts. Moreover, KV-37 reduces androgen receptor (AR) transactivation and prostate-specific antigen expression levels in CRPC cell lines indicative of a therapeutic effect in prostate cancer. Combination studies of KV-37 with enzalutamide reveal a very high degree of synergistic drug interaction that induces significant reduction in prostate cancer cell viability via apoptosis, resulting in >200-fold potentiation of enzalutamide action in drug-resistant 22Rv1 cells. These results demonstrate a promising therapeutic strategy for the treatment of drug-resistant CRPC that invariably develops in prostate cancer patients following initial treatment with AR antagonists such as enzalutamide. Mol Cancer Ther; 17(9); 1833-45. ©2018 AACR.

Testicular vs adrenal sources of hydroxy-androgens in prostate cancer

Neoadjuvant androgen deprivation therapy (NADT) is one strategy for the treatment of early-stage prostate cancer; however, the long-term outcomes of NADT with radical prostatectomy including biochemical failure-free survival are not promising. One proposed mechanism is incomplete androgen ablation. In this study, we aimed to evaluate the efficiency of serum hydroxy-androgen suppression in patients with localized high-risk prostate cancer under NADT (leuprolide acetate plus abiraterone acetate and prednisone) and interrogate the primary sources of circulating hydroxy-androgens using our recently described stable isotope dilution liquid chromatography mass spectrometric method. For the first time, three androgen diols including 5-androstene-3β,17β-diol (5-adiol), 5α-androstane-3α,17β-diol (3α-adiol), 5α-androstane-3β,17β-diol (3β-adiol), the glucuronide or sulfate conjugate of 5-adiol and 3α-adiol were measured and observed to be dramatically reduced after NADT. By comparing patients that took leuprolide acetate alone vs leuprolide acetate plus abiraterone acetate and prednisone, we were able to distinguish the primary sources of these androgens and their conjugates as being of either testicular or adrenal in origin. We find that testosterone, 5α-dihydrotestosterone (DHT), 3α-adiol and 3β-adiol were predominately of testicular origin. By contrast, dehydroepiandrosterone (DHEA), epi-androsterone (epi-AST) and their conjugates, 5-adiol sulfate and glucuronide were predominately of adrenal origin. Our findings also show that NADT failed to completely suppress DHEA-sulfate levels and that two unappreciated sources of intratumoral androgens that were not suppressed by leuprolide acetate alone were 5-adiol-sulfate and epi-AST-sulfate of adrenal origin.

Potential Metabolic Activation of a Representative C4-Alkylated Polycyclic Aromatic Hydrocarbon Retene (1-Methyl-7-isopropyl-phenanthrene) Associated with the Deepwater Horizon Oil Spill in Human Hepatoma (HepG2) Cells

Exposure to petrogenic polycyclic aromatic hydrocarbons (PPAHs) in the food chain is the major human health hazard associated with the Deepwater Horizon oil spill. C4-Phenanthrenes are representative PPAHs present in the crude oil and could contaminate the seafood. We describe the metabolism of a C4-phenanthrene regioisomer retene (1-methyl-7-isopropyl-phenanthrene) in human HepG2 cells as a model for metabolism in human hepatocytes. Retene because of its sites of alkylation cannot be metabolized to a diol-epoxide. The structures of the metabolites were identified by HPLC-UV-fluorescence detection and LC-MS/MS. O-Monosulfonated-retene-catechols were discovered as signature metabolites of the ortho-quinone pathway of PAH activation catalyzed by aldo-keto reductases. We also found evidence for the formation of bis-ortho-quinones where the two dicarbonyl groups were present on different rings of retene. The identification of O-monosulfonated-retene-catechol and O-bismethyl-O-monoglucuronosyl-retene-bis-catechol supports metabolic activation of retene by P450 and aldo-keto reductase isozymes followed by metabolic detoxification of the ortho-quinone through interception of redox cycling by catechol-O-methyltransferase, uridine 5'-diphospho-glucuronosyltransferase, and sulfotransferase isozymes. We propose that catechol conjugates could be used as biomarkers of human exposure to retene resulting from oil spills.

Simultaneous quantitation of nine hydroxy-androgens and their conjugates in human serum by stable isotope dilution liquid chromatography electrospray ionization tandem mass spectrometry

Castration resistant prostate cancer (CRPC), the fatal form of prostate cancer, remains androgen dependent despite castrate levels of circulating testosterone (T) and 5α-dihydrotestosterone (DHT). To investigate mechanisms by which the tumor can synthesize its own androgens and develop resistance to abiraterone acetate and enzalutamide, methods to measure a complete androgen profile are imperative. Here, we report the development and validation of a stable isotope dilution liquid chromatography electrospray ionization tandem mass spectrometric (SID-LC-ESI-MS/MS) method to quantify nine human hydroxy-androgens as picolinates, simultaneously with requisite specificity and sensitivity. In the established method, the fragmentation patterns of all nine hydroxy-androgen picolinates were identified, and [13C3]-5α-androstane-3α, 17β-diol and [13C3]-5α-androstane-3β, 17β-diol used as internal standards were synthesized enzymatically. Intra-day and inter-day precision and accuracy corresponds to the U.S. Food and Drug Administration Criteria for Bioanalytical Method Validation. The lower limit of quantitation (LLOQ) of nine hydroxy-androgens is 1.0pg to 2.5pg on column. Diols which have been infrequently measured: 5-androstene-3β, 17β-diol and 5α-androstane-3α, 17β-diol can be determined in serum at values as low as 1.0pg on column. The method also permits the quantitation of conjugated hydroxy-androgens following enzymatic digestion. While direct detection of steroid conjugates by electrospray-ionization tandem mass spectrometry has advantages the detection of unconjugated and conjugated steroids would require separate methods for each set of analytes. Our method was applied to pooled serum from male and female donors to provide reference values for both unconjugated and conjugated hydroxy-androgens. This method will allow us to interrogate the involvement of the conversion of 5-androstene-3β, 17β-diol to T, the backdoor pathway involving the conversion of 5α-androstane-3α, 17β-diol to DHT and the inactivation of DHT to 5α-androstane-3β, 17β-diol in advanced prostate cancer.

Discovery of (R)-2-(6-Methoxynaphthalen-2-yl)butanoic Acid as a Potent and Selective Aldo-keto Reductase 1C3 Inhibitor

Type 5 17β-hydroxysteroid dehydrogenase, aldo-keto reductase 1C3 (AKR1C3) converts Δ(4)-androstene-3,17-dione and 5α-androstane-3,17-dione to testosterone (T) and 5α-dihydrotestosterone, respectively, in castration resistant prostate cancer (CRPC). In CRPC, AKR1C3 is implicated in drug resistance, and enzalutamide drug resistance can be surmounted by indomethacin a potent inhibitor of AKR1C3. We examined a series of naproxen analogues and find that (R)-2-(6-methoxynaphthalen-2-yl)butanoic acid (in which the methyl group of R-naproxen was replaced by an ethyl group) acts as a potent AKR1C3 inhibitor that displays selectivity for AKR1C3 over other AKR1C enzymes. This compound was devoid of inhibitory activity on COX isozymes and blocked AKR1C3 mediated production of T and induction of PSA in LNCaP-AKR1C3 cells as a model of a CRPC cell line. R-Profens are substrate selective COX-2 inhibitors and block the oxygenation of endocannabinoids and in the context of advanced prostate cancer R-profens could inhibit intratumoral androgen synthesis and act as analgesics for metastatic disease.

Selective AKR1C3 Inhibitors Potentiate Chemotherapeutic Activity in Multiple Acute Myeloid Leukemia (AML) Cell Lines

We report the design, synthesis, and evaluation of potent and selective inhibitors of aldo-keto reductase 1C3 (AKR1C3), an important enzyme in the regulatory pathway controlling proliferation, differentiation, and apoptosis in myeloid cells. Combination treatment with the nontoxic AKR1C3 inhibitors and etoposide or daunorubicin in acute myeloid leukemia cell lines, elicits a potent adjuvant effect, potentiating the cytotoxicity of etoposide by up to 6.25-fold and the cytotoxicity of daunorubicin by >10-fold. The results validate AKR1C3 inhibition as a common adjuvant target across multiple AML subtypes. These compounds in coadministration with chemotherapeutics in clinical use enhance therapeutic index and may avail chemotherapy as a treatment option to the pediatric and geriatric population currently unable to tolerate the side effects of cancer drug regimens.

Pentafluorosulfanyl-containing flufenamic acid analogs: Syntheses, properties and biological activities

Pentafluorosulfanyl-containing analogs of flufenamic acid have been synthesized in high yields. Computationally, pKa, LogP and LogD values have been determined. Initial bioactivity studies reveal effects as ion channel modulators and inhibitory activities on aldo-keto reductase 1C3 (AKR1C3) as well as COX-1 and COX-2.

Abstract 4580A: Metabolic activation of 3-nitrobenzanthrone by human aldo-keto reductases (AKR1C1-AKR1C4)

In 2012, the International Agency for Research on Cancer (IARC) classified diesel exhaust as a Group 1 carcinogen due to sufficient evidence that exposure is associated with increased risk for lung cancer in humans. However, only a subset of individuals exposed to diesel exhaust develops cancer, indicating the need to identify the genes involved in metabolic activation of these compounds and their genetic variants. Nitro-polycyclic aromatic hydrocarbons (NO2-PAH) are a major component of diesel exhaust and require metabolic activation to exert their carcinogenic activity. A representative NO2-PAH, 3-nitrobenzanthrone (3-NBA), is metabolically activated to 3-aminobenzanthrone (3-ABA) via a 6-electron nitroreduction catalyzed by NQO1 and POR. The reaction leads to the formation of 3-aminobenzanthrone (3-ABA) derived DNA adducts which promote G to T transversions. Building upon previous data that shows human aldo-keto reductase 1C3 (AKR1C3) contains nitroreductase activity towards chemotherapeutic agents (Guise, C.P., Abbattista, M.R., et al., Cancer Res, 70(4), 2010), we chose to examine the nitroreductase activity of AKR1C1-AKR1C4 towards NO2-PAH. We have demonstrated here for the first time that AKR1C enzymes catalyze the nitroreduction of 3-NBA to 3-ABA. We monitored reactions with reverse phase HPLC coupled to in-line photo-diode-array detection (PDA) and fluorescence detection (FLD) to quantify 3-NBA and 3-ABA levels. Fluorescence and UV spectroscopy were used to validate the identity of the compounds. This method was adapted for discontinuous enzymatic assays to measure steady state kinetic parameters for the nitoreductase activity of AKR1C1-AKR1C4 and NQO1. Results indicate that the NQO1 catalyzed reduction of 3-NBA has a higher specific activity, but the combined specific activities of AKR1C catalyzed reduction may play a more significant role in the overall production of 3-ABA. These results suggest that the relative expression of NQO1 and AKR1C enzymes will determine their respective contribution to 3-NBA reduction, especially since all the aforementioned enzymes are inducible by the Nrf2-Keap1 system. This work is supported by P30E513508 and RO1 CA39504 to TMP.

Citation Format: Jessica R. Murray, Meng Huang, Tianzhu Zang, Volker M. Arlt, Heinz H. Schmeiser, Trevor M. Penning. Metabolic activation of 3-nitrobenzanthrone by human aldo-keto reductases (AKR1C1-AKR1C4). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4580A. doi:10.1158/1538-7445.AM2015-4580A

Screening baccharin analogs as selective inhibitors against type 5 17β-hydroxysteroid dehydrogenase (AKR1C3)

Aldo-keto reductase 1C3 (AKR1C3), also known as type 5 17β-hydroxysteroid dehydrogenase, is a downstream steroidogenic enzyme and converts androgen precursors to the potent androgen receptor ligands: testosterone and 5α-dihydrotestosterone. Studies have shown that AKR1C3 is involved in the development of castration resistant prostate cancer (CRPC) and that it is a rational drug target for the treatment of CRPC. Baccharin, a component of Brazilian propolis, has been observed to exhibit a high inhibitory potency and selectivity for AKR1C3 over other AKR1C isoforms and is a promising lead compound for developing more potent and selective inhibitors. Here, we report the screening of fifteen baccharin analogs as selective inhibitors against AKR1C3 versus AKR1C2 (type 3 3α-hydroxysteroid dehydrogenase). Among these analogs, the inhibitory activity and selectivity of thirteen compounds were evaluated for the first time. The substitution of the 4-dihydrocinnamoyloxy group of baccharin by an acetate group displayed nanomolar inhibitory potency (IC50: 440 nM) and a 102-fold selectivity over AKR1C2. By contrast, when the cinnamic acid group of baccharin was esterified, there was a dramatic decrease in potency and selectivity for AKR1C3 in comparison to baccharin. Low or sub-micromolar inhibition was observed when the 3-prenyl group of baccharin was removed, and the selectivity over AKR1C2 was low. Although unsubstituted baccharin was still the most potent (IC50: 100 nM) and selective inhibitor for AKR1C3, these data provide structure-activity relationships required for the optimization of new baccharin analogs. They suggest that the carboxylate group on cinnamic acid, the prenyl group, and either retention of 4-dihydrocinnamoyloxy group or acetate substituent on cinnamic acid are important to maintain the high potency and selectivity for AKR1C3.

Reprogramming the fate of human glioma cells to impede brain tumor development

Malignant gliomas, the most common solid tumors in the central nervous system, are essentially incurable due to their rapid growth and very invasive nature. One potential approach to eradicating glioma cells is to force these cells to undergo terminal differentiation and, in the process, to irreversible postmitotic arrest. Here, we show that neurogenin 2 (NGN2, also known as NEUROG2) synergizes with sex-determining region Y-box 11 (SOX11) to very efficiently convert human glioma cells to terminally differentiated neuron-like cells in both cell culture and adult mouse brains. These cells exhibit neuronal morphology, marker expression, and electrophysiological properties. The conversion process is accompanied by cell cycle exit, which dramatically inhibits glioma cell proliferation and tumor development after orthotopic transplantation. Most importantly, intracranial injection of NGN2- and SOX11-expressing virus into the tumor mass also curtails glioma growth and significantly improves survival of tumor-bearing mice. Taken together, this study shows a simple and highly efficient strategy for reprogramming malignant glioma cells into postmitotic cells, which might be a promising therapeutic approach for brain tumors.

Decreased glutathione and elevated hair mercury levels are associated with nutritional deficiency-based autism in Oman

Genetic, nutrition, and environmental factors have each been implicated as sources of risk for autism. Oxidative stress, including low plasma levels of the antioxidant glutathione, has been reported by numerous autism studies, which can disrupt methylation-dependent epigenetic regulation of gene expression with neurodevelopmental consequences. We investigated the status of redox and methylation metabolites, as well as the level of protein homocysteinylation and hair mercury levels, in autistic and neurotypical control Omani children, who were previously shown to exhibit significant nutritional deficiencies in serum folate and vitamin B12. The serum level of glutathione in autistic subjects was significantly below control levels, while levels of homocysteine and S-adenosylhomocysteine were elevated, indicative of oxidative stress and decreased methionine synthase activity. Autistic males had lower glutathione and higher homocysteine levels than females, while homocysteinylation of serum proteins was increased in autistic males but not females. Mercury levels were markedly elevated in the hair of autistic subjects vs. control subjects, consistent with the importance of glutathione for its elimination. Thus, autism in Oman is associated with decreased antioxidant resources and decreased methylation capacity, in conjunction with elevated hair levels of mercury.

Discovery of undefined protein cross-linking chemistry: a comprehensive methodology utilizing 18O-labeling and mass spectrometry

Characterization of protein cross-linking, particularly without prior knowledge of the chemical nature and site of cross-linking, poses a significant challenge, because of their intrinsic structural complexity and the lack of a comprehensive analytical approach. Toward this end, we have developed a generally applicable workflow-XChem-Finder-that involves four stages: (1) detection of cross-linked peptides via (18)O-labeling at C-termini; (2) determination of the putative partial sequences of each cross-linked peptide pair using a fragment ion mass database search against known protein sequences coupled with a de novo sequence tag search; (3) extension to full sequences based on protease specificity, the unique combination of mass, and other constraints; and (4) deduction of cross-linking chemistry and site. The mass difference between the sum of two putative full-length peptides and the cross-linked peptide provides the formulas (elemental composition analysis) for the functional groups involved in each cross-linking. Combined with sequence restraint from MS/MS data, plausible cross-linking chemistry and site were inferred, and ultimately confirmed, by matching with all data. Applying our approach to a stressed IgG2 antibody, 10 cross-linked peptides were discovered and found to be connected via thioethers originating from disulfides at locations that had not been previously recognized. Furthermore, once the cross-link chemistry was revealed, a targeted cross-link search yielded 4 additional cross-linked peptides that all contain the C-terminus of the light chain.

Enzyme-catalyzed transfer of a ketone group from an S-adenosylmethionine analogue: a tool for the functional analysis of methyltransferases

S-adenosylmethionine (AdoMet or SAM)-dependent methyltransferases belong to a large and diverse family of group-transfer enzymes that perform vital biological functions on a host of substrates. Despite the progress in genomics, structural proteomics, and computational biology, functional annotation of methyltransferases remains a challenge. Herein, we report the synthesis and activity of a new AdoMet analogue functionalized with a ketone group. Using catechol O-methyltransferase (COMT, EC 2.1.1.6) and thiopurine S-methyltransferase (TPMT, EC 2.1.1.67) as model enzymes, this robust and readily accessible analogue displays kinetic parameters that are comparable to AdoMet and exhibits multiple turnovers with enzyme. More importantly, this AdoMet surrogate displays the same substrate specificity as the natural methyl donor. Incorporation of the ketone group allows for subsequent modification via bio-orthogonal labeling strategies and sensitive detection of the tagged ketone products. Hence, this AdoMet analogue expands the toolbox available to interrogate the biochemical functions of methyltransferases.

Chemical methods for the detection of protein N-homocysteinylation via selective reactions with aldehydes

Elevated blood levels of homocysteine (Hcy), hyperhomocysteinemia or homocystinuria, have been associated with various diseases and conditions. Homocysteine thiolactone (Hcy TL) is a metabolite of Hcy and reacts with amine groups in proteins to form stable amides, homocystamides, or N-homocysteinylated proteins. It has been proposed that protein N-homocysteinylation contributes to the cytotoxicity of elevated Hcy. Due to its heterogeneity and relatively low abundance, detection of this posttranslational modification remains challenging. On the other hand, the gamma-aminothiol group in homocystamides imparts different chemical reactivities than the native proteins. Under mildly acidic conditions, gamma-aminothiols irreversibly and stoichiometrically react with aldehydes to form stable 1,3-thiazines, whereas the reversible Schiff base formation between aldehydes and amino groups in native proteins is markedly disfavored due to protonation of amines. As such, we have developed highly selective chemical methods to derivatize N-homocysteinylated proteins with various aldehyde tags, thereby facilitating the subsequent analyses. For instance, fluorescent or biotin tagging coupled with gel electrophoresis permits quantification and global profiling of complex biological samples, such as hemoglobin and plasma from rat, mouse and human; affinity enrichment with aldehyde resins drastically reduces sample complexity. In addition, different reactivities of lysine residues in hemoglobin toward Hcy TL were observed.

A naturally occurring brominated furanone covalently modifies and inactivates LuxS

Halogenated furanones, a group of natural products initially isolated from marine red algae, are known to inhibit bacterial biofilm formation, swarming, and quorum sensing. However, their molecular targets and the precise mode of action remain elusive. Herein, we show that a naturally occurring brominated furanone covalently modifies and inactivates LuxS (S-ribosylhomocysteine lyase, EC 4.4.1.21), the enzyme which produces autoinducer-2 (AI-2).

Chemo-enzymatic detection of protein isoaspartate using protein isoaspartate methyltransferase and hydrazine trapping

Isoaspartate formation is a ubiquitous post-translation modification arising from spontaneous asparagine deamidation or aspartate isomerization. The formation of isoaspartate inserts a methylene group into the protein backbone, generating a "kink", and may drastically alter protein structure and function, thereby playing critical roles in a myriad of biological processes, human diseases, and protein pharmaceutical development. Herein, we report a chemo-enzymatic detection method for the isoaspartate protein, which in particular allows the affinity enrichment of isoaspartate-containing proteins. In the initial step, protein isoaspartate methyltransferase selectively converts isoaspartates into the corresponding methyl esters. Subsequently, the labile methyl ester is trapped by strong nucleophiles in aqueous solutions, such as hydrazines to form hydrazides. The stable hydrazide products can be analyzed by standard proteomic techniques, such as matrix-assisted laser desorption ionization and electrospray ionization mass spectrometry. Furthermore, the chemical trapping step allows us to introduce several tagging strategies for product identification and quantification, such as UV-vis and fluorescence detection through a dansyl derivative. Most significantly, the hydrazide product can be enriched by affinity chromatography using aldehyde resins, thus drastically reducing sample complexity. Our method hence represents the first technique for the affinity enrichment of isoaspartyl proteins and should be amendable to the systematic and comprehensive characterization of isoaspartate, particularly in complex systems.

A fused selenium-containing protein with both GPx and SOD activities

As a safeguard against oxidative stress, the balance between the main antioxidant enzymes including superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) was believed to be more important than any single one, for example, dual-functional SOD/CAT enzyme has been proved to have better antioxidant ability than either single enzyme. By combining traditional fusion protein technology with amino acid auxotrophic expression system, we generated a bifunctional enzyme with both GPx and SOD activities. It displayed better antioxidant ability than GPx or SOD. Such dual-functional enzymes could facilitate further studies of the cooperation of GPx and SOD and generation of better therapeutic agents.

Menstrual cycle lengths and bone mineral density: a cross-sectional, population-based study in rural Chinese women ages 30-49 years

INTRODUCTION

The menstrual cycle involves periodic fluctuations in estrogen and progesterone levels. Longer cycles have been associated with longer follicular phase, delayed estrogen peak and a lower mean oestradiol level of the entire cycle.

METHODS

We hypothesized that prolonged menstrual cycle length is associated with decreased bone mineral density (BMD) in a population of pre- and perimenopausal women. This population-based cross-sectional study was conducted in rural Anhui province, China. It includes 4,771 women, aged 30 to 49 years, who did not smoke or drink alcohol, and did not use oral contraceptives or breastfeed during the previous year. Dual-energy X-ray absorptionometry (DEXA) BMD measurements were taken at four skeletal sites: whole body, total hip, femoral neck and lumbar spine. Menstrual cycle characteristics (polymenorrhea, short normal, long normal, oligomenorrhea, 90-day amenorrhea, irregular cycle) in the prior year were assessed by questionnaire.

RESULTS

Prolonged menstrual cycle was consistently associated with decreased BMD at whole body, total hip, and femoral neck in both age 30-39, and age 40-49 stratum (p(trend)<0.05). Prolonged menstrual cycle was also associated with decreased lumbar spine BMD for women aged 40-49 (p(trend)<0.05). Among women with normal cycles aged 30-39, menstrual cycle length in the previous year was inversely associated with whole-body BMD (p<0.05). Women with 90-day amenorrhea had significantly lower mean total hip and femoral neck BMD relative to women with short normal cycles in the 30-39 age group; and had significantly lower whole body and total hip BMD relative to short normal cycles in the 40-49 age group. BMD in polymenorrheic women did not differ from BMD in women with short normal cycles at any of the skeletal sites.

CONCLUSIONS

We conclude that prolonged menstrual cycle length is associated with decreased BMD in pre- and perimenopausal women in this population.

Serum DDT, age at menarche, and abnormal menstrual cycle length

BACKGROUND

Although dichlorodiphenyl trichloroethane (DDT) exposure is known to affect human endocrine function, few previous studies have investigated the effects of DDT exposure on age at menarche or menstrual cycle length.

METHODS

A cross sectional study was conducted to study the effects of DDT exposure on age at menarche and menstrual cycle length among 466 newly married, nulliparous female Chinese textile workers aged 20-34 years enrolled between 1996 and 1998. Serum was analysed for DDT and its major metabolites. Multivariate linear regression was used to estimate DDT exposure effects on age at menarche and multivariate logistic regression was used to estimate DDT exposure effects on odds of experiencing short or long cycles.

RESULTS

Relative to those in the lowest DDT quartile, the adjusted mean age at menarche was younger in those in the fourth quartile (-1.11 years). Modeled as a continuous variable, a 10 ng/g increase in serum DDT concentration was associated with an adjusted reduction in age at menarche of 0.20 years. Relative to those in the lowest DDT quartile, odds of any short cycle (<21 days) in the previous year were higher for those in the fourth quartile (odds ratio = 2.78; 95% CI 1.07 to 7.14). There were no associations between serum DDT concentrations and odds of experiencing a long cycle (>40 days).

CONCLUSION

Results suggest that DDT exposure was associated with earlier age at menarche and increased risk of experiencing a shortened menstrual cycle.

Kinetic studies on the glutathione peroxidase activity of selenium-containing glutathione transferase

Selenium-containing glutathione transferase (seleno-GST) was generated by biologically incorporating selenocysteine into the active site of glutathione transferase (GST) from a blowfly Lucilia cuprina (Diptera: Calliphoridae). Seleno-GST mimicked the antioxidant enzyme glutathione peroxidase (GPx) and catalyzed the reduction of structurally different hydroperoxides by glutathione. Kinetic investigations reveal a ping-pong kinetic mechanism in analogy with that of the natural GPx cycle as opposed to the sequential one of the wild type GST. This difference of the mechanisms might result from the intrinsic chemical properties of the incorporated residue selenocysteine, and the selenium-dependent mechanism is suggested to contribute to enhancement of the enzymatic efficiency.

Protection of Mitochondrial Integrity From Oxidative Stress by Selenium-Containing Glutathione Transferase

The antioxidant activity of a novel artificial glutathione peroxidase-like enzyme, selenium-containing glutathione 5-transferase from Lucilia cuprina (seleno-LuGST1-1), was studied by using a ferrous sulfate/ascorbate-induced mitochondrial damage model system. Swelling of mitochondria, lipid peroxidation, and cytochrome-c oxidase activity were selected to evaluate the preservation of mitochondrial integrity in this system. Seleno-LuGST1-1 could effectively protect the mitochondria against oxidative damage in a dose-dependent manner and exhibited both higher catalytic activity and greater antioxidant ability than the classic mimic, 2-phenyl-1,2-benziososelenazol-3(2H)-one (Ebselen). This novel artificial biocatalyst therefore may have great potential for pharmacologic application in the treatment of reactive oxygen species-related diseases.

Stress and dysmenorrhoea: a population based prospective study

BACKGROUND

Dysmenorrhoea is the most common gynaecological disorder in women of reproductive age. Despite the association between stress and pregnancy outcomes, few studies have examined the possible link between stress and dysmenorrhoea.

AIMS AND METHODS

Using a population based cohort of Chinese women, the independent effect of women's perceived stress in the preceding menstrual cycle on the incidence of dysmenorrhoea in the subsequent cycle was investigated prospectively. The analysis included 1160 prospectively observed menstrual cycles from 388 healthy, nulliparous, newly married women who intended to conceive. The perception of stress and the occurrence of dysmenorrhoea in each menstrual cycle were determined from daily diaries recorded by the women.

RESULTS

After adjustment for important covariates, the risk of dysmenorrhoea was more than twice as great among women with high stress compared to those with low stress in the preceding cycle (OR = 2.4; 95% CI 1.4 to 4.3). The risk of dysmenorrhoea was greatest among women with both high stress and a history of dysmenorrhoea compared to women with low stress and no history of dysmenorrhoea (OR = 10.4, 95% CI 4.9 to 22.3). Stress in the follicular phase of the preceding cycles had a stronger association with dysmenorrhoea than stress in the luteal phase of the preceding cycles.

CONCLUSION

This study shows a significant association between stress and the incidence of dysmenorrhoea, which is even stronger among women with a history of dysmenorrhoea.

HIV-1 and Ebola virus encode small peptide motifs that recruit Tsg101 to sites of particle assembly to facilitate egress

Retroviral Gag proteins encode sequences, termed late domains, which facilitate the final stages of particle budding from the plasma membrane. We report here that interactions between Tsg101, a factor involved in endosomal protein sorting, and short peptide motifs in the HIV-1 Gag late domain and Ebola virus matrix (EbVp40) proteins are essential for efficient egress of HIV-1 virions and Ebola virus-like particles. EbVp40 recruits Tsg101 to sites of particle assembly and a short, EbVp40-derived Tsg101-binding peptide sequence can functionally substitute for the HIV-1 Gag late domain. Notably, recruitment of Tsg101 to assembling virions restores budding competence to a late-domain-defective HIV-1 in the complete absence of viral late domain. These studies define an essential virus-host interaction that is conserved in two unrelated viruses. Because the Tsg101 is recruited by small, conserved viral sequence motifs, agents that mimic these structures are potential inhibitors of the replication of these lethal human pathogens.

[Expression of COX-2 in prostatic cancer and benign prostatic hyperplasia]

OBJECTIVE

To investigate the expression of COX-2 in and benign prostatic hyperplasia and prostate cancer and its clinical implications.

METHODS

Forty-two patients with and benign prostatic hyperplasia and 16 with prostate cancer were studied by immunohischemistry and western blot.

RESULTS

Immunohischemiscal study showed positive results in 15 of the 16 patients and 11 of the 42 patients. Western blot showed that the expression of COX-2 was higher in prostate cancer than in and benign prostatic hyperplasia tissues(P < 0.01).

CONCLUSION

Overexpression of COX-2 in prostate cancer may be related to the staging of prostate cancer.

Expression of beta-catenin in renal cell carcinoma

OBJECTIVE

To investigate the expression of beta-catenin and its mRNA in renal cell carcinoma.

METHODS

Twenty-six cases with renal cell carcinoma (RCC) were studied by immunohistochemistry, Western blot and RT-PCR.

RESULTS

We found the expression of beta-catenis is higher in cancer tissues than in normal kidney tissues and the level of beta-catenin is associated with the tumor stage. Its expression in tumor of pT3 and pT4 is obviously higher than pT1 and pT2 (P < 0.01). That is to say, there was an overexpression of beta-catenin protein in RCC and its level was related to the tumor stage, but the expression of beta-catenin mRNA had no difference between tumor tissue and normal tissue.

CONCLUSION

beta-catenin may be related to the occurrence and progress of RCC.

[Expression of T cell factor 4 in renal cell carcinoma]

OBJECTIVE

To investigate of the transduction of Wnt/Frizzled pathway in nuclei and the function of TCF4 (T Cell Factor) in renal cell carcinoma.

METHODS

TCF4 mRNA are tested through RT-PCR and Northern Blot in renal cancer tissue and renal cancer cell strain (GRC-I).

RESULTS

It has been certificated that TCF4 are expressed in renal cell carcinoma, at the same time, there are some different splice of TCF4 in renal cancer. A new 300bp mutant gene are found.

CONCLUSION

TCF4, an important molecular of Wnt/Frizzled pathway, takes part in the formation and progression of renal cell carcinoma, different splice of TCF4 is one of the mechanism.

[Beta-catenin and its mRNA in renal cell carcinoma]

OBJECTIVES

To investigate the role of beta-catenin in renal cell carcinoma.

METHODS

The expression of beta-catenin in 26 cases of renal cell carcinoma was studied by LSAB immunohistochemistry, Western blotting and RT-PCR.

RESULTS

The expression of beta-catenin was higher in cancer tissues than in normal kidney tissues in 25 cases and the level of beta-catenin was associated with tumor stage. The expression was obviously higher in pT3 and pT4 than in pT1 and pT2 (P < 0.01). The expression of its mRNA was not higher in tumor cells than in normal cells. Beta-catenin was expressed mainly in cytoplasm.

CONCLUSIONS

Beta-catenin might be related to the occurrence and development of kidney tumor.