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PubMed2002

Novel thalidomide analogues display anti-angiogenic activity independently of immunomodulatory effects.

The anti-tumour effects of thalidomide have been associated with its anti-angiogenic properties. Second generation thalidomide analogues are distinct compounds with enhanced therapeutic potential. Although these compounds are beginning to enter trials for the treatment of cancer there is very little information regarding the anti-angiogenic activity of these clinically relevant compounds. Furthermore, it is not known how the various immunomodulatory activities of these compounds relate to anti-angiogenic activity. In this study we assessed the anti-angiogenic activity of compounds from both IMiD and SelCID classes of analogues using a novel in vitro multicellular human assay system and the established rat aorta assay. Our results show that both the IMiDs and SelCIDs tested are significantly more potent than thalidomide. The anti-angiogenic potency of the analogues was not related to inhibition of endothelial cell proliferation, nor their TNF-alpha/PDE type 4 inhibitory properties. However, anti-migratory effects in vitro and inhibition of tumour growth in vivo was observed with the analogue IMiD-1 (clinically known as REVIMID). Our results show that anti-angiogenic activity spans both currently defined classes of thalidomide analogue and is not related to their previously described immunomodulatory properties. Identification of the differential effects of these compounds will enable targeting of such compounds into the appropriate clinical setting.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2004

Correlation between the fluorescent response of microfluidity probes and the water content and viscosity of ionic liquid and water mixtures.

Accurate data on transport properties such as viscosity are essential in plant and process design involving ionic liquids. In this study, we determined the absolute viscosity of the ionic liquid + water system at water mole fractions from 0 to 0.25 for three 1-alkyl-3-methylimidazolium ionic liquids: 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide and 1-ethyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide. In each case, the excimer to monomer ratio for 1,m-bis(1-pyrenyl)alkanes (m= 3 or 10) was found to increase linearly with the mole fraction of water. Of the probes studied only PRODAN and rhodamine 6G, both of which have the ability to participate in hydrogen bonding, exhibited Perrin hydrodynamic behavior in the lower viscosity bis(trifluoromethane sulfonyl)imides. As a result, these probes allow for the extrapolation of the absolute viscosity of the ionic liquid mixture from the experimental fluorescence steady-state polarization values.

Journal Article↗
PubMed1979

Hydrolysis of p-NN'-phenylenebismaleimide and its adducts with cysteine. Implications for cross-linking of proteins.

To understand the extent of the cross-linking of proteins by the bifunctional reagent p-NN'-phenylenebismaleimide, a quantitative study of competing reactions has been undertaken. The two reactive maleimide rings of the bismaleimide are hydrolysed in mildly alkaline aqueous solutions much more rapidly than is the single maleimide ring of the monofunctional analogue N-ethylmaleimide. The kinetics of hydrolysis are second-order, depending on both imide and hydroxyl ion concentration in the pH range 8-10. The hydrolysis of the first imide ring of the bismaleimide is more rapid than the second, with second-order rate constants of 1600 M-1 . s-1 and 500 M-1 . s-1 respectively, at 25 degrees C. The half-times for hydrolysis of the first and second imide rings at pH 9.0 are therefore only 43s and 140s. Because it renders the maleimide ring unreactive towards cysteine, this rapid hydrolysis can limit the extent of cross-linking of proteins by the bismaleimide.

Chemical Phenomena↗
PubMed1980

Modification and identification of glutamate residues at the arginine-recognition site in the catalytic subunit of adenosine 3' :5'-cyclic monophosphate-dependent protein kinase of rabbit skeletal muscle.

It has been proposed that the active centre of cyclic AMP-dependent protein kinase contains an arginine-recognition site, which is considered to be essential for the function of the catalytic subunit of the kinase [Matsuo, Huang & Huang (1978) Biochem. J.173, 441-447]. The catalytic subunit can be inactivated by 3-(3-dimethylaminopropyl)-1-ethylcarbodi-imide and glycine ethyl ester at pH6.5. The enzyme can be protected from inactivation by preincubation with histone, a protein substrate of the enzyme. On the other hand, ATP, which also serves as a protein kinase substrate, does not afford protection. Polyarginine, a competitive inhibitor of protein kinase, which is known from kinetic studies to interact specifically with the arginine-recognition site, partially protects the catalytic subunit from inactivation by 3-(3-dimethylaminopropyl)-1-ethylcarbodi-imide. These results lead to the conclusion that the site of modification by carbodi-imide/glycine ethyl ester is most likely located at the arginine-recognition site of the active centre. A value of 1.7+/-0.2 (mean+/-s.d.) mol of carboxy groups per mol of catalytic subunit has been obtained for the number of essential carboxy groups for the function of protein kinase; a complete chemical modification of these essential carboxy groups results in total loss of catalytic activity. Finally, we have identified the essential carboxy group in the catalytic subunit of cyclic AMP-dependent protein kinase as being derived from glutamate residues. This is achieved by a three-step procedure involving an extensive proteolytic digestion of the [1-(14)C]glycine ethyl ester-modified enzyme and two successive high-voltage electrophoreses of the hydrolysate. It is concluded that 1.7mol of glutamyl carboxy groups per mol of catalytic subunit may be considered a component of the arginine-recognition site in the active centre of cyclic AMP-dependent protein kinase.

Amino Acids↗
PubMed1982

Association of fibronectin with carboxy-group-modified proteins in vitro.

Treatment of human immunoglobulin G, albumin and fibronectin with water-soluble carbodi-imide at pH4.75 in the presence of glycine ethyl ester resulted in an avid binding of (125)I-labelled native fibrinectin to the modified proteins. Succinoylation, reduction and alkylation or heat-denaturation had no such effect. In affinity chromatography under physiological conditions, serum was depleted of fibronectin when run through columns of the carbodi-imide-treated proteins coupled to agarose. Fractions eluted from such columns with urea were enriched in fibronectin. The binding of radiolabelled fibronectin to the carbodi-imide-treated proteins was inhibited by unlabelled fibronectin in relatively low concentrations, but also by albumin in higher concentrations. Heat-denatured albumin inhibited at concentrations approx. 10-30 times lower than native albumin. The binding reaction had a pH optimum of 6-8. It was inhibited at high ionic strength and in the presence of urea. Anionic detergents inhibited at millimolar concentrations, but non-ionic detergents did not inhibit the binding reaction. The results were interpreted as showing that: (1) fibronectin is capable of binding to itself, to immunoglobulin G and to albumin after a reduction of the negative surface charge of these proteins, and may have a general ability to bind such modified proteins; (2) this binding can take place under physiological conditions; (3) carboxy-group-modified proteins selectively bind fibronectin from serum. This novel binding phenomenon could be important in terms of the opsonin function of circulatory fibronectin. We propose that fibronectin may recognize modified (denatured) proteins and mediate their uptake by the reticuloendothelial system.

Cations, Divalent↗
PubMed1990

Essential carboxy groups in xylanase A.

An endo-1,4-beta-xylanase of Schizophyllum commune was purified to homogeneity through a modified procedure employing DEAE-Sepharose CL-6B and gel-filtration chromatography on Sephadex G-50. The role of carboxy groups in the catalytic mechanism was delineated through chemical modification studies. The water-soluble carbodi-imide 1-(4-azonia-4,4-dimethylpentyl)-3-ethylcarbodi-imide iodide (EAC) inactivated the xylanase rapidly and completely in a pseudo-first-order process. Other carbodi-imides and Woodward's Reagent K were less effective in decreasing enzymic activity. Significant protection of the enzyme against EAC inactivation was provided by a mixture of neutral xylo-oligomers. The pH-dependence of the EAC inactivation revealed the presence of a critical ionizable group with a pKa value of 6.6 in the active site of the xylanase. Treatment of the enzyme with diethyl pyrocarbonate resulted in modification of all three histidine residues in the enzyme with 100% retention of original enzymic activity. Titration of the enzyme with 5,5-dithiobis-(2-nitrobenzoic acid) and treatment with iodoacetimide and p-chloromercuribenzoate indicated the absence of free/reactive thiol groups. Reaction of the xylanase with tetranitromethane did not result in a significant activity loss as a result of modification of tyrosine residues.

Basidiomycota↗
PubMed1993

Infrared analysis of peptide succinimide derivatives.

In order to establish parameters to identify imide derivatives formed during in vitro aging of aspartyl-alanyl-containing proteins, a dipeptide and a tetrapeptide containing this sequence were acidified and heated in vacuo. The formation of succinimide derivatives could be confirmed by FTIR and Raman spectroscopy. Hereto, earlier assignments of succinimide vibrations had to be revised. FTIR absorbance spectra of the succinimide, derived from H-Asp-Ala-OH, in the solid state give five bands between 1700 and 1800 cm-1. In this case, owing to Fermi resonance, the anti-symmetric imide carbonyl stretching vibration gives rise to an apparent doublet, centered around 1715 cm-1. The symmetric stretching mode is found at 1793 cm-1. The other bands are assigned to carboxylic acid stretching modes (1728 cm-1; COOH dimer and 1751 cm-1: COOH monomer). Fermi resonance does not occur in succinimide derivatives occurring in larger peptides. As a consequence, the imide bands of the succinimide, generated from H-Val-Asp-Ala-Gly-OH, are observed at 1716 and 1791 cm-1 (anti-symmetric and symmetric stretching modes, respectively).

Amino Acid Sequence↗
PubMed2005

Inhibition of ribonucleotide reductase reduces neointimal formation following balloon injury.

Percutaneous transluminal coronary angioplasty (PTCA) has greatly benefited patients with occluded coronary arteries, but its benefits have been undermined by a high incidence of restenosis. The introduction of coronary stents has significantly improved the short and long term outcome but restenosis still occurs in approximately 15 to 30% of patients within 6 months. Research efforts are now being directed toward combination stenting and drug delivery. Among the therapeutic targets being pursued are agents that can impede smooth muscle cell migration and proliferation, as these processes are critical components of restenosis injury. We propose that inhibiting the conversion of ribonucleotides to deoxyribonucleotides will impede cell proliferation and, as such, limit the degree of restenosis. Therefore, we tested whether the potent ribonucleotide reductase inhibitors Didox (3,4-dihydroxybenzohydraxamic acid) and Imidate (ethyl-3,4,5-hydroxybenzimidate) can limit the neointimal proliferation associated with restenosis using a rat carotid model of balloon dilatation injury. Results demonstrated that both Didox and Imidate significantly reduced intimal thickening, resulting in a 71 and 62% decrease in the intima/media ratio, respectively. Similar efficacy was seen with the commercially available ribonucleotide reductase inhibitor hydroxyurea, demonstrating the importance of this enzyme in vascular remodeling. Results from cell proliferation studies suggest that the mechanism of protection is inhibition of smooth muscle cell (SMC) proliferation. In addition, Didox and Imidate (100 microM) are potent inhibitors of SMC migration, which may also contribute to their vascular protective effects. These results suggest that inhibition of ribonucleotide reductase may provide a potent strategy to prevent post-PTCA restenosis.

Animals↗
PubMed1997

Mitindomide is a catalytic inhibitor of DNA topoisomerase II that acts at the bisdioxopiperazine binding site.

The antitumor drug mitindomide (NSC 284356) was shown to inhibit the decatenation activity of human and Chinese hamster ovary (CHO) topoisomerase II [DNA topoisomerase (ATP-hydrolyzing), EC 5.99.1.1]. Mitindomide did not induce the formation of topoisomerase II-DNA covalent cleavable complexes in CHO cells. These results taken together indicate that mitindomide is a catalytic/noncleavable complex-forming-type inhibitor of topoisomerase II. The growth inhibitory effects of mitindomide and dexrazoxane toward a sensitive parent CHO cell line and the dexrazoxane-resistant DZR cell line, which is highly (500-fold) resistant to the bisdioxopiperazine dexrazoxane, were measured. The DZR cell line was shown to be 30-fold cross-resistant to mitindomide. Mitindomide, like dexrazoxane, was shown to inhibit cleavable complex formation by the topoisomerase II poison etoposide. The attenuated inhibition of etoposide-induced cleavable complexes in DZR compared with CHO cells was, likewise, very similar for dexrazoxane and mitindomide. Together these results suggest that mitindomide acts at the same site on topoisomerase II as does dexrazoxane and other bisdioxopiperazines. Various molecular parameters obtained by molecular modeling were compared for mitindomide and dexrazoxane. Mitindomide, which is conformationally very rigid, has highly coplanar imide rings, as does dexrazoxane in the solid state. Other molecular parameters, such as the imide nitrogen-to-imide nitrogen bond distances, and polar and nonpolar surface areas were also very similar. Thus, it is concluded that mitindomide exerts its antitumor effects through its inhibition of topoisomerase II by binding to the bisdioxopiperazine binding site.

Animals↗
PubMed1982

Effect of imidazole on the recovery from bilateral ureteral obstruction in dogs.

The effects of indomethacin (INDO) and imidazole (IMID) on postobstructed kidney functions were evaluated in dogs after 24 h of bilateral ureteral obstruction (BUO). In vehicle-treated dogs 1 h after release of BUO, clearances of inulin and PAH (Cin and Cpah) were 37 and 26%, respectively, of the preobstruction values. Fractional sodium excretion (FEna) increased from 0.5 +/- 0.1 to 2.9 +/- 0.6. Urine osmolality (Uosmol) increased by 55 +/- 9 mosmol/kg H2O in response to 50 mU of aqueous vasopressin. In INDO-treated dogs, Cin and Cpah were 39 and 21%, respectively, of the preobstruction values. FEna increased from 0.7 +/- 0.2 to 4.0 +/- 0.9. Uosmol increased by 91 +/- 19 mosmol/kg H2O in response to vasopressin. This lack of beneficial effects of INDO may reflect its cancelling effect on prostaglandins' and thromboxanes' (TX) effects on the renal hemodynamics of the postobstructed kidney. To further assess the roles of TX in the postobstructed kidney, IMID, and inhibitor of TX synthesis, was given before the release of obstruction. In this group of dogs, the Cin of the postobstructed kidney did not differ from the preobstruction value. CC pah was 45% of the preobstruction value, a level significantly higher than in either vehicle- or INDO-treated dogs. FEna wa 1.5 +/- 0.2 before and 3.5 +/- 2.3 after obstruction. Uosmol increased by 187 +/- 51 mosmol/kg H2O after vasopressin, a level significantly higher than in vehicle-treated dogs. The present study suggests that IMID improves Cin, Cpah, FEna, and concentrating ability of the postobstructed kidney. TX may be responsible for the persistent reductions of Cin and Cpah in the postobstructed kidney.

Animals↗
PubMedDate not supplied

Thalidomide and its derivatives: new promise for multiple myeloma.

BACKGROUND: The combination of melphalan and prednisone has been accepted as standard treatment for multiple myeloma (MM) because most studies demonstrate only minimal survival benefit of combination chemotherapy regimens when compared with melphalan and prednisone. Despite modest gains with more intensive myeloablative regimens for certain subgroups, myeloma remains incurable. In 1999, investigators at the University of Arkansas reported the promising results of a phase II study of thalidomide in patients with resistant MM. Since then various trials of thalidomide alone, and in combination, have been tested in patients with resistant, and more recently, untreated MM. In addition, preliminary results of phase I studies of the immunomodulatory derivatives (IMiDs) of thalidomide have recently been reported. METHODS: The author reviewed and reports the results of clinical trials of thalidomide and the IMiDs, as well as the pharmacology, mechanism of action, and toxicity of these agents. RESULTS: Thalidomide has demonstrated significant activity in both resistant and previously untreated multiple myeloma. Combination therapy with dexamethasone increases response rate, even in patients previously resistant to both drugs given as single agents, indicating probable synergy. More recent studies of thalidomide-dexamethasone in previously untreated patients are encouraging. IMiD-3 is active in resistant myeloma and has a toxicity profile different from that of thalidomide. CONCLUSIONS: Many studies have confirmed the activity of thalidomide in MM, as well as more responses with dexamethasone. Newer thalidomide derivatives with reduced toxicity are promising. Thalidomide-dexamethasone may now represent the treatment of choice for previously untreated patients. Further studies with these and other novel agents early in the course of myeloma, followed by rational programs of dose intensification, may improve complete remission rates and the frequency of long-term control.

Antineoplastic Agents↗
PubMed2003

Treatment of plasma cell dyscrasias with thalidomide and its derivatives.

PURPOSE: In 1999, investigators reported promising results of a phase II study of thalidomide in patients with resistant multiple myeloma (MM). Since then, various trials of thalidomide alone and in combination with other agents have been tested in patients with resistant and, more recently, untreated MM. In addition, preliminary results of phase I studies of the immunomodulatory derivatives (IMiDs) of thalidomide have been recently reported. DESIGN: We reviewed and report the results of clinical trials of thalidomide and the IMiDs, as well as the pharmacology, mechanism of action, and toxicity of these agents. RESULTS: Thalidomide has demonstrated significant activity in both resistant and previously untreated multiple myeloma. Combination therapy with dexamethasone increases response rate, even in patients previously resistant to both drugs given as single agents. More recent studies of thalidomide with dexamethasone in previously untreated patients are highly encouraging. The addition of chemotherapy to thalidomide and dexamethasone may further increase response rates, but its effect on patient survival has not been clarified. Preliminary results of trials of IMiD-3 indicate that this agent is active in resistant myeloma and has a toxicity profile different from that of thalidomide. CONCLUSION: Many studies have confirmed the activity of thalidomide in MM, as well as an improved response with dexamethasone. Newer thalidomide derivatives with reduced toxicity (neuropathy, teratogenicity) are also promising. Thalidomide with dexamethasone may now represent the treatment of choice for previously untreated patients. Further studies with these and other novel agents early in the course of myeloma may improve complete remission rates and frequency of long-term control.

Adjuvants, Immunologic↗
PubMed2004

Immunomodulation of multiple myeloma.

Multiple myeloma is a multi-process disease, and these different processes are responsible for the reduced sensitivity to chemotherapy and radiotherapy, hence the relapse and refractory nature of multiple myeloma. Emphasis is now placed on the hypothesis that myeloma cell growth, inhibition of apoptosis and drug resistance are dependent on immunomodulatory cytokines such as IL-6 and pro-angiogenic factors such as VEGF. In addition to its anti-angiogenic effects, the immunomodulatory properties of thalidomide make it a possible therapy for patients with advanced multiple myeloma. This has lead to the clinical development of a number of immunomodulatory thalidomide analogues (IMiDs) which are more potent and have less side effects than the parent drug, thalidomide. In the August 15(th) issue of Journal of Clinical Oncology, Schey SA et al. suggested that an IMiD (CC-4047) maybe efficacious due to T-cell co-stimulation, and safe in patients with relapsed or refractory multiple myeloma. This article demonstrates a supporting role for IMiDs as immunomodulatory adjuvant therapy.

Angiogenesis Inhibitors↗
PubMed1991

Isolation and characterization of a succinimide variant of methionyl human growth hormone.

Deamidation of asparagine and glutamine residues, isomerization of aspartic acid side chains, and racemization of the L- to the D-form of the amino acids are common spontaneous chemical reactions known to occur in proteins. Previous studies have implicated succinimides as intermediates in these reactions; however, the evidence has been indirect. Our results demonstrate, for the first time, the presence of a succinimide intermediate in an intact protein. The succinimide (cyclic imide) variant was isolated from thermally stressed recombinant methionyl human growth hormone (hGH) by high performance anion-exchange chromatography, further purified by reversed-phase high performance liquid chromatography, and analyzed by tryptic mapping. A later eluting tryptic peptide, compared with the native T12 peptide (residues 128-134, Leu-Glu-Asp-Gly-Ser-Pro-Arg), was analyzed by mass spectrometry (MS). This variant had a protonated molecular mass of 755.3 atomic mass units (u), as compared with 773.3 u for the native T12 peptide. A difference of 18 u, a loss of water, is consistent with the formation of a succinimide intermediate at Asp-130 of methionyl hGH. MS/MS analysis of the cyclic imide-containing peptide verified that the modification occurred at Asp-130. A difference of 18 u was also observed for the intact cyclic imide methionyl hGH variant (22,238 u), as measured by electrospray mass spectrometry, compared with native methionyl hGH (22,256 u).

Amino Acid Sequence↗
PubMed1987

Protein carboxyl methyltransferase facilitates conversion of atypical L-isoaspartyl peptides to normal L-aspartyl peptides.

Prolonged incubation of L-isoaspartate-containing forms of lactate dehydrogenase (231-242), sperm activating peptide, and adrenocorticotropin (22-27) at 37 degrees C, pH 7.4, with S-adenosyl-L-methionine and protein carboxyl methyltransferase from bovine brain leads to extensive conversion of the atypical isopeptide bond to a normal peptide bond. For the lactate dehydrogenase-related peptide, conversion was 80% complete after 24 h. For the other two peptides, conversion reached a level of approximately 65% after 48 h. The mechanism of conversion involves (i) rapid enzymatic methylation of the alpha-carboxyl of the L-iso-Asp residue; (ii) nonenzymatic demethylation resulting in formation of an L-aspartyl cyclic imide; and (iii) a slow, nonenzymatic hydrolysis of the cyclic imide to form a mixture of 15-25% normal L-Asp peptide and 75-85% L-iso-Asp peptide. The regenerated L-iso-Asp peptide is remethylated and the cycle is repeated. The extent of conversion is limited by a competing side reaction wherein the L-imide slowly racemizes, leading to the formation of mainly D-iso-Asp peptide, which is not a substrate for the methyltransferase. The ability of protein carboxyl methyltransferase to initiate conversion of L-iso-Asp residues to normal L-Asp suggests a possible role for this enzyme in facilitating the repair or degradation of deamidated proteins in vivo.

Amino Acid Sequence↗
PubMed1987

Imidazole and indomethacin improve hepatic perfusion in sepsis.

Visceral microcirculatory insufficiency has been demonstrated in sepsis despite a hyperdynamic systemic circulation. This study examines the effect of the cyclo-oxygenase inhibitor indomethacin and the thromboxane synthetase inhibitor imidazole on septic hemodynamics and visceral perfusion in a septic rat model of cecal ligation and puncture. Animals received either indomethacin (INDO), imidazole (IMID), or saline intramuscularly at t = 0, 6, and 12 hr of peritonitis. Thermodilution cardiac output, mean arterial pressure, heart rate, hematocrit, effective hepatic blood flow, effective renal plasma flow, and arterial and mixed venous blood gases were determined at 15 hr. Both INDO and IMID improved effective hepatic blood flow in the septic animals to virtually sham, nonseptic levels without significantly altering systemic hemodynamics. This study suggests that the reduction in hepatic perfusion in sepsis may be mediated by thromboxane, the synthesis of which is suppressed by both INDO and IMID.

Animals↗
PubMed1986

Antagonism of imidazole-induced shaking in the rat: a behavioural tool predictive of antidyskinetic activity?

In rats the intraperitoneal injection of imidazole (IMID) induced shaking behaviour, the effect appearing to be age- and sex-linked; younger animals responded less vigorously than older animals, while females always exhibited a significantly weaker response than males of the same age. After ovariectomy, however, the number of shakes of the two sexes was very similar. A number of drugs were examined for their antagonism of this highly reproducible syndrome. IMID-shakes were antagonized by reserpine, clonidine, high doses of B-HT 920, propranolol, haloperidol, morphine and diazepam, were not affected by apomorphine, (+)3-PPP, physostigmine, naloxone or methysergide, and were potentiated by sulpiride and scopolamine. The results are considered in the light of the possible neurochemical mechanisms underlying the IMID-syndrome; the suggested usefulness of this test for the study of human dyskinetic movements is disputed.

Aging↗
PubMed1991

Clefts as receptor and enzyme analogues.

Synthetic receptors for small biological targets have become a popular research topic in molecular recognition. This paper discusses the optimal functional group complements and the scaffolds that are ideal for such purposes. Specifically, remote steric barriers are used to control the conformation of (that is, to preorganize) hosts derived from acridine skeletons, triaryl benzenes and related systems. These structures separate entropic effects from enthalpic effects and show that entropy is an important contributor to high affinity. In a comparative study lactams are shown to be superior to imides in their capacity for self-association. Imides are shown to have higher affinity than lactams for adenine derivatives because of the presence of an unconventional hydrogen bond. Finally, preorganization in the context of chemical catalysis is demonstrated in two systems, one involving hemiacetal cleavage and a second involving a self-replicating system.

Chemical Phenomena↗