Synthesis, metal ion binding, and biological evaluation of new anticancer 2-(2'-hydroxyphenyl)benzoxazole analogs of UK-1

UK-1 is a bis(benzoxazole) natural product displaying activity against a wide range of human cancer cell lines. A simplified analog of UK-1, 4-carbomethoxy-2-(2'-hydroxyphenyl)benzoxazole, was previously found to be almost as active as UK-1 against cancer cell lines, and similar to the natural product, formed complexes with a variety of metal ions such as Mg2+ and Zn2+. A series of 4-substituted-2-(2'-hydroxyphenyl)benzoxazole analogs of this 'minimal pharmacophore' of UK-1 were prepared. The anti-cancer activity of these analogs was examined in breast and lung cancer cell lines. Spectrophotometric titrations in methanol were carried out in order to assess the ability of UK-1 and these analogs to coordinate with Mg2+ and Cu2+ ions. Although none of the new analogs were more cytotoxic than 4-carbomethoxy-2-(2'-hydroxyphenyl)benzoxazole, some analogs were identified that display similar cytotoxicity to this simplified UK-1 analog with improved water solubility. UK-1 and all of these new analogs bind Cu2+ ions better than Mg2+ ions, and the nature of the 4-substituent is important for the Mg2+ ion binding ability of these 2-(2'-hydroxyphenyl)benzoxazoles. Previous studies of a limited number of UK-1 analogs demonstrated a correlation between Mg2+ ion binding ability and cytotoxicity; however, within this series of 4-substituted-2-(2'-hydroxyphenyl)benzoxazoles the variations in cytotoxicity do not correlate with either Mg2+ or Cu2+ ion binding ability. These results, together with recent ESI-MS studies of Cu2+-mediated DNA binding by UK-1 and analogs, indicate that UK-1 and analogs may exert their cytotoxic effects by interaction with Cu2+ or other transition metal ions, rather than Mg2+, and that metal ion-mediated DNA binding, rather than metal ion binding affinity, is important for the cytotoxic effect of these compounds. The potential role of Cu2+ ions in the cytotoxic action of UK-1 is further supported by the observation that UK-1 in the presence of Cu2+ displays enhanced cytotoxicity to MCF-7 and A549 cells when compared to UK-1 alone.     

UK-1 and structural analogs are potent inhibitors of hepatitis C virus replication

The bacterial natural product UK-1 and several structural analogs inhibit replication of the hepatitis C virus in the replicon assay, with IC₅₀ values as low as 0.50 μM. The NS3 helicase has been identified as a possible target of inhibition for several of these compounds, while the remaining inhibitors act via an undetermined mechanism. Gel shift assays suggest that helicase inhibition is a direct result of inhibitor–enzyme binding as opposed to direct RNA binding, and the ATPase activity of NS3 is not affected. The syntheses and biological results are presented herein.     

UK-69,578, a novel inhibitor of EC 3.4.24.11 which increases endogenous ANF levels and is natriuretic and diuretic

A search for potent inhibitors of EC 3.4.24.11, an enzyme which is found most abundantly in the kidney and which degrades atrial natriuretic factor, has led to the identification of UK-69,578. Structure-activity studies starting from substituted N-carboxymethyl dipeptide inhibitors resulted in the introduction of a cyclo-alkane P1' residue and in the replacement of the aza-link between P1 and P1' residues by a methylene group, with a net ten-fold potency gain. UK-69,578 increases endogenous ANF levels and produces natriuretic and diuretic responses intravenously in mice.     

Drugs inhibiting the renin - angiotensin system

There are several approaches for interfering with the renin-angiotensin system. Antibodies against renin angiotensins I and II (AI and AII) have not been consistently successful in the past, probably because of nonspecific effects; however, recent purification of renin now makes this approach more promising. Renin inhibitors include pepstatin and analogs, lipids and phospholipids, and renin-substrate analogs. Pepstatin and analogs are the most potent and specific but they are not orally active. The phospholipids are the most effective in vivo but their specificity is yet to be established. No renin-substrate analogs have been developed that have biologically significant effects. Some of the most potent and specific agents available for interfering with the renin-angiotensin system are the AII-receptor antagonists. While these compounds effectively prevent the actions of AII, they suffer from several severe deficiencies: partial agonist activity, short duration of action, and lack of oral activity. The recent development of angiotensin-converting enzyme ACE) inhibitors that are orally active has provided the greatest degree of clinical success for inhibitors of the renin-angiotensin system and, consequently, the impetus to develop still better compounds. Captopril (SQ 14,225) is the prototype ACE inhibitor, being highly potent and specific with no other demonstrated pharmacological activity. Captopril is effective in all forms of human and animal models of hypertension except mineralocorticoid hypertension, which requires concomitant diuretic therapy. Because ACE is the same enzyme as kininase II, the enzyme that degrades kinins, the possibility exists that kinins are involved in the cardiovascular action of captopril, although this prospect is unlikely.     

Inhibition of HIV-1 integration protein by aurintricarboxylic acid monomers, monomer analogs, and polymer fractions.

Several aurintricarboxylic acid (ATA) monomers, monomer analogs, and polymer fractions have been tested as inhibitors of HIV-1 integration protein (IN). Both of the ATA monomers and all of the ATA polymer fractions inhibited a selective DNA cleavage reaction catalyzed by IN. The ATA monomer analogs were inactive or had low activity. The activities of the substances as inhibitors of HIV IN correlated in a positive way with their activities as inhibitors of the cytopathic effect of HIV-1 in CEM and HIV-2 in MT4 cells. These results suggest that inhibition of HIV IN may contribute to the antiviral activity of the ATA monomers and monomer analogs in cell culture.     

Selective urokinase-type plasminogen activator (uPA) inhibitors. Part 3: 1-isoquinolinylguanidines

A series of 1-isoquinolinylguanidines are shown to be potent inhibitors of uPA with selectivity over tPA and plasmin. Potency is enhanced by the presence of a 4-halo and a 7-aryl substituent, particularly when substituted by a 3-carboxylic acid group. Compound 13j (UK-356,202) combines excellent potency and selectivity, and has been selected as a candidate for clinical evaluation.     

Comparative genome analysis of the high pathogenicity Salmonella Typhimurium strain UK-1

Salmonella enterica serovar Typhimurium, a gram-negative facultative rod-shaped bacterium causing salmonellosis and foodborne disease, is one of the most common isolated Salmonella serovars in both developed and developing nations. Several S. Typhimurium genomes have been completed and many more genome-sequencing projects are underway. Comparative genome analysis of the multiple strains leads to a better understanding of the evolution of S. Typhimurium and its pathogenesis. S. Typhimurium strain UK-1 (belongs to phage type 1) is highly virulent when orally administered to mice and chickens and efficiently colonizes lymphoid tissues of these species. These characteristics make this strain a good choice for use in vaccine development. In fact, UK-1 has been used as the parent strain for a number of nonrecombinant and recombinant vaccine strains, including several commercial vaccines for poultry. In this study, we conducted a thorough comparative genome analysis of the UK-1 strain with other S. Typhimurium strains and examined the phenotypic impact of several genomic differences. Whole genomic comparison highlights an extremely close relationship between the UK-1 strain and other S. Typhimurium strains; however, many interesting genetic and genomic variations specific to UK-1 were explored. In particular, the deletion of a UK-1-specific gene that is highly similar to the gene encoding the T3SS effector protein NleC exhibited a significant decrease in oral virulence in BALB/c mice. The complete genetic complements in UK-1, especially those elements that contribute to virulence or aid in determining the diversity within bacterial species, provide key information in evaluating the functional characterization of important genetic determinants and for development of vaccines.     

Structure-activity relationships, and drug metabolism and pharmacokinetic properties for indazole piperazine and indazole piperidine inhibitors of ROCK-II

ROCK has been implicated in many diseases ranging from glaucoma to spinal cord injury and is therefore an important target for therapeutic intervention. In this study, we have designed a series of 1-(4-(1H-indazol-5-yl)piperazin-1-yl)-2-hydroxy(or 2-amino) analogs and a series of 1-(4-(1H-indazol-5-yl amino)piperidin-1-yl)-2-hydroxy(or 2-amino) inhibitors of ROCK-II. SR-1459 has IC(50)=13nM versus ROCK-II while the IC(50)s for SR-715 and SR-899 are 80nM and 100nM, respectively. Many of these inhibitors, especially the 2-amino substituted analogs for both series, are modest/potent CYP3A4 inhibitors as well. However, a few of these inhibitors (SR-715 and SR-899) show strong selectivity for ROCK-II over CYP3A4, but the overall potency of the 2-amino analogs (SR-1459) on CYP3A4 and the high clearance and volume of distribution of these compounds makes the in vivo utility of these analogs undesirable.     

Novel poly(ADP-ribose) polymerase-1 inhibitors

Synthesis and activity of a series of 4-thiazol-yl substituted analogs of novel pyrrolocarbazole 1 as poly(ADP-ribose) polymerase-1 (PARP-1) inhibitors have been disclosed.     

Complete genome sequence of the universal killer Salmonella enterica Serovar Typhimurium UK-1 (ATCC 68169)

The Salmonella enterica serovar Typhimurium strain UK-1 exhibits the highest invasion and virulence attributes among the most frequently studied strains. S. Typhimurium UK-1 has been used as the foundation for developing recombinant vaccines and has been used extensively on virulence and colonization studies in chickens and mice. We describe here the complete genome sequence of S. Typhimurium UK-1. Comparative genomics of Salmonella Typhimurium will provide insight into factors that determine virulence and invasion.     

Synthesis of C-ring-modified blebbistatin derivatives and evaluation of their myosin II ATPase inhibitory potency

(S)-Blebbistatin is a micromolar myosin II ATPase inhibitor that is extensively used in research. In search of analogs with improved potency, we have synthesized for the first time C-ring modified analogs. We introduced hydroxymethyl or allyloxymethyl functionalities in search of additional favorable interactions and a more optimal filling of the binding pocket. Unfortunately, the resulting compounds did not significantly inhibit the ATPase activity of rabbit skeletal-muscle myosin II. This and earlier reports suggest that rational design of potent myosin II inhibitors based on the architecture of the blebbistatin binding pocket is an ineffective strategy.     

Inflammation,oxidative stress and renin angiotensin system in atherosclerosis

Atherosclerosis is a chronic inflammatory disease associated with cardiovascular dysfunction including myocardial infarction, unstable angina, sudden cardiac death, stroke and peripheral thromboses. It has been predicted that atherosclerosis will be the primary cause of death in the world by 2020. Atherogenesis is initiated by endothelial injury due to oxidative stress associated with cardiovascular risk factors including diabetes mellitus, hypertension, cigarette smoking, dyslipidemia, obesity, and metabolic syndrome. The impairment of the endothelium associated with cardiovascular risk factors creates an imbalance between vasodilating and vasoconstricting factors, in particular, an increase in angiotensin Ⅱ(Ang Ⅱ) and a decrease in nitric oxide. The renin-angiotensin system(RAS), and its primary mediator Ang Ⅱ, also have a direct influence on the progression of the atherosclerotic process via effects on endothelial function, inflammation, fibrinolytic balance, and plaque stability. Anti-inflammatory agents [statins, secretory phospholipase A2 inhibitor, lipoprotein-associated phospholipase A2 inhibitor, 5-lipoxygenase activating protein, chemokine motif ligand-2, C-C chemokine motif receptor 2 pathway inhibitors, methotrexate, IL-1 pathway inhibitor and RAS inhibitors(angiotensin-converting enzyme inhibitors)], Ang Ⅱ receptor blockers and ranin inhibitors may slow inflammatory processes and disease progression. Several studies in human using anti-inflammatory agents and RAS inhibitors revealed vascular benefits and reduced progression of coronary atherosclerosis in patients with stable angina pectoris; decreased vascular inflammatory markers, improved common carotid intima-media thickness and plaque volume in patients with diagnosed atherosclerosis. Recent preclinical studies have demonstrated therapeutic efficacy of vitamin D analogs paricalcitol in Apo E-deficient atherosclerotic mice.     

Synthesis and evaluation of anticancer benzoxazoles and benzimidazoles related to UK-1

UK-1 is a structurally unique bis(benzoxazole) natural product isolated from a strain of Streptomyces. UK-1 has been reported to possess anticancer activity but no activity against bacteria, yeast, or fungi. Previous work has also demonstrated the ability of UK-1 to bind a variety of di- and tri-valent metal ions, particularly Mg²⁺ ions, and to form complexes with double-stranded DNA in the presence of Mg²⁺ ions. Here we report the activity of UK-1 against a wide range of human cancer cell lines. UK-1 displays a wide spectrum of potent anticancer activity against leukemia, lymphoma, and certain solid tumor-derived cell lines, with IC₅₀ values as low as 20 nM, but is inactive against Staphylococcus aureus, a methicillin-resistant strain of S. aureus, or Pseudomonas aeruginosa. A series of analogues of the bis(benzoxazole) natural product UK-1 in which the carbomethoxy-substituted benzoxazole ring of the natural product was modified were prepared and evaluated for their anticancer and antibacterial properties. An analogue of UK-1 in which the carbomethoxy-substituted benzoxazole ring was replaced with a carbomethoxy-substituted benzimidazole ring was inactive against human cancer cell lines and the two strains of S. aureus. In contrast, a simplified analogue in which the carbomethoxy-substituted benzoxazole ring was replaced with a carbomethoxy group was almost as active as UK-1 against the four cancer cell lines examined but lacked activity against S. aureus. Metal ion binding studies of these analogues demonstrate that they both bind Zn²⁺ and Ca²⁺ ions about as well as UK-1. The non-cytotoxic benzimidazole UK-1 analogue binds Mg²⁺ ions 50-fold weaker than UK-1, whereas the simple benzoxazole analogue binds Mg²⁺ ions nearly as well as UK-1. These results support a role of Mg²⁺ ion binding in the selective cytotoxicity of UK-1 and provide a minimal pharmacophore for the selective cytotoxic activity of the natural product.     

Circular dichroism and nuclear magnetic resonance spectroscopic analysis of immunogenic gluten peptides and their analogs

Celiac Sprue, or gluten-sensitive enteropathy, is an inheritable human disease of the small intestine that is triggered by the dietary intake of gluten. Recently, several Pro- and Gln-rich peptide sequences (most notably PQPQLPY and analogs) have been identified from gluten with potent immunogenic activity toward CD4(+) T cells from small intestinal biopsies of Celiac Sprue patients. These peptides have three unusual properties. First, they are relatively stable toward further proteolysis by gastric, pancreatic, and intestinal enzymes. Second, they are recognized and deamidated by human tissue transglutaminase (tTGase) with high selectivity. Third, tTGase-catalyzed deamidation enhances their affinity for HLA-DQ2, the disease-specific class II major histocompatibility complex heterodimer. In an attempt to seek a mechanistic explanation for these properties, we undertook secondary structural studies on PQPQLPY and its analogs. Circular dichroism studies on a series of monomeric and dimeric analogs revealed a strong polyproline II helical propensity in a subset of them. Two-dimensional nuclear magnetic resonance spectroscopic analysis confirmed a polyproline II conformation of PQPQLPY, and was also used to elucidate the secondary structure of the most helical variant, (D-P)QPQLPY. Remarkably, a strong correlation was observed between polyproline II content of naturally occurring gluten peptides and the specificity of human tTGase toward these substrates. Analogs with up to two D-amino acid residues retained both polyproline II helical content and transglutaminase affinity. Since the Michaelis constant (K(m)) is the principal determinant of tTGase specificity for naturally occurring gluten peptides and their analogs, our results suggest that the tTGase binding site may have a preference for polyproline II helical substrates. If so, these insights could be exploited for the design of selective small molecule inhibitors of this pharmacologically important enzyme.     

Sulfamides as novel histone deacetylase inhibitors

The sulfamide moiety has been utilized to design novel HDAC inhibitors. The potency and selectivity of these inhibitors were influenced both by the nature of the scaffold, and the capping group. Linear long-chain-based analogs were primarily HDAC6-selective, while analogs based on the lysine scaffold resulted in potent HDAC1 and HDAC6 inhibitors.     

Tachyphylactic properties of angiotensin II analogs with bulky and hydrophobic substituents at the N-terminus.

Tachyphylaxis, defined as the acute loss of response of some smooth muscles upon repeated stimulations with angiotensin II (Ang II), has been shown to be dependent mainly on the N-terminal region of the ligand. To further study the structural requirements for the induction of tachyphylaxis we have synthesized Ang II analogs containing the bulky and very lipophilic substituents 9-fluorenylmethyloxycarbonyl (Fmoc) and 9-fluorenylmethyl ester (OFm) at the alpha-amino (Nalpha-Fmoc-Ang II) or the beta-carboxyl ([Asp(OFm)1]-Ang II) groups of the Asp1 residue, respectively. In binding assays with Chinese hamster ovary cells transfected with the AT1 Ang II receptor, Nalpha-Fmoc-Ang II bound with high affinity, whereas [Asp(OFm)1]-Ang II showed lower affinity. In biological assays, these two analogs were full agonists and showed 30 and 3%, respectively, of the Ang II potency in contracting the guinea-pig ileum smooth muscle. The two analogs induced tachyphylaxis, in spite of the lack of a free amino group in Nalpha-Fmoc-Ang II. Thus, analogs with Fmoc- or OFm-type groups coupled to the Asp1 residue, whether at the amino or carboxyl functions, induce tachyphylaxis through an unreported mechanism. Based in these findings and those available from the literature, an alternate molecular interaction mode between Ang II N-terminal portion and the AT1 receptor is proposed to explain the tachyphylactic phenomenon.     

Studies on the mechanism of adenosylcobalamin-dependent ribonucleotide reduction by the use of analogs of the coenzyme.

A series of 17 analogs of 5'-deoxy-5'-adenosylcobalamin(adenosylcobalamin) have been synthesized with modifications in the base or ribose moiety of the nucleoside ligand. These analogs have been examined for their effects on reactions catalyzed by the ribonucleotide reductase of Lactobacillus leichmannii. All the analogs are inhibitors of ATP reduction in the presence of adenosylcobalamin as coenzyme, and hence all are bound to the catalytic site. Only the 3-beta-D-ribofuranosyladenine analog (isoadenosylcobalamin) showed substantial activity as a coenzyme in ATP reduction, giving a rate of 59% of that obtained with the adenosylcobalamin. Lesser rates of reduction were obtained with nebularyl-, 2'-deoxyadenosyl-, tubercidyl-, isopropylideneadenosyl-, L-adenosyl-, and ara-adenosylcobalamin, coenzyme activity decreasing in that order. Other analogs showed no significant coenzyme activity. The rate of hydrogen exchange into water from the 5'-methylene group of the nucleoside ligand appeared to parallel the coenzyme activity in those analogs examined, but only the four cobalamins with highest coenzyme activity (adenosyl, isoadenosyl, nebularyl, 2'-deoxyadenosyl) gave detectable amounts of "active coenzyme B12," THe rapidly formed paramagnetic intermediate of ribonucleotide reduction. The enzyme system produced the slowly formed paramagnetic species characterized by a doublet EPR spectrum only with adenosyl- and isoadenosylcobalamin. By contrast the enzymic degradation of analogs to cob(II)alamin and 5'-deoxynucleoside occurred not only with those analogs active as coenzymes and in the exchange reaction but also with a number of coenzymically inactive analogs, and the rate of degradation was unrelated to the rate of ribonucleotide reduction for those analogs with coenzyme activity.     

Structure-activity relationships of semisynthetic mumbaistatin analogs

Mumbaistatin (1), a new anthraquinone natural product, is one of the most potent known inhibitors of hepatic glucose-6-phosphate translocase, an important target for the treatment of type II diabetes. Its availability, however, has been limited due to its extremely low yield from the natural source. Starting from DMAC (5, 3,8-dihydroxyanthraquinone-2-carboxylic acid), a structurally related polyketide product of engineered biosynthesis, we developed a facile semisynthetic method that afforded a variety of mumbaistatin analogs within five steps. This work was facilitated by the initial development of a DMAC overproduction system. In addition to reinforcing the biological significance of the anthraquinone moiety of mumbaistatin, several semisynthetic analogs were found to have low micromolar potency against the translocase in vitro. Two of them were also active in glucose release assays from primary hepatocytes. The synergistic combination of biosynthesis and synthesis is a promising avenue for the discovery of new bioactive substances.