Biochemistry and pathology of radical-mediated protein oxidation

Radical-mediated damage to proteins may be initiated by electron leakage, metal-ion-dependent reactions and autoxidation of lipids and sugars. The consequent protein oxidation is O2-dependent, and involves several propagating radicals, notably alkoxyl radicals. Its products include several categories of reactive species, and a range of stable products whose chemistry is currently being elucidated. Among the reactive products, protein hydroperoxides can generate further radical fluxes on reaction with transition-metal ions; protein-bound reductants (notably dopa) can reduce transition-metal ions and thereby facilitate their reaction with hydroperoxides; and aldehydes may participate in Schiff-base formation and other reactions. Cells can detoxify some of the reactive species, e.g. by reducing protein hydroperoxides to unreactive hydroxides. Oxidized proteins are often functionally inactive and their unfolding is associated with enhanced susceptibility to proteinases. Thus cells can generally remove oxidized proteins by proteolysis. However, certain oxidized proteins are poorly handled by cells, and together with possible alterations in the rate of production of oxidized proteins, this may contribute to the observed accumulation and damaging actions of oxidized proteins during aging and in pathologies such as diabetes, atherosclerosis and neurodegenerative diseases. Protein oxidation may also sometimes play controlling roles in cellular remodelling and cell growth. Proteins are also key targets in defensive cytolysis and in inflammatory self-damage. The possibility of selective protection against protein oxidation (antioxidation) is raised.

Stable markers of oxidant damage to proteins and their application in the study of human disease

The mechanisms of formation and the nature of the altered amino acid side chains formed on proteins subjected to oxidant attack are reviewed. The use of stable products of protein side chain oxidation as potential markers for assessing oxidative damage in vivo in humans is discussed. The methods developed in the authors laboratories are outlined, and the advantages and disadvantages of these techniques compared with other methodologies for assessing oxidative damage to proteins and other macromolecules. Evidence is presented to show that protein oxidation products are sensitive markers of oxidative damage, that the pattern of products detected may yield information as to the nature of the original oxidative insult, and that the levels of oxidized side-chains can, in certain circumstances, be much higher than those of other markers of oxidation such as lipid hydroperoxides.

Increased expression and cellular localization of inducible nitric oxide synthase and cyclooxygenase 2 in Helicobacter pylori gastritis

BACKGROUND & AIMS

Inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 are important regulators of mucosal inflammation and epithelial cell growth. To determine the role of iNOS and COX-2 in Helicobacter pylori-induced tissue injury, we compared their gene expression in H. pylori-induced gastritis with that in normal gastric mucosa and in non-H. pylori gastritis.

METHODS

In 43 patients, we assessed H. pylori infection status, histopathology, messenger RNA (mRNA) and protein expression, and cellular localization of iNOS and COX-2.

RESULTS

By reverse-transcription polymerase chain reaction (RT-PCR), antral iNOS and COX-2 mRNA expression was absent to low in normal mucosa (n = 10), significantly increased in H. pylori-negative gastritis (n = 13), and even more markedly increased in H. pylori-positive gastritis (n = 20). Increased iNOS and COX-2 levels were confirmed by Northern and Western blot analysis and were both greater in the gastric antrum than in the gastric body of infected patients. Immunohistochemistry also showed increased expression of both genes in H. pylori gastritis: iNOS protein was detected in epithelium, endothelium, and lamina propria inflammatory cells, and COX-2 protein localized to mononuclear and fibroblast cells in the lamina propria.

CONCLUSIONS

iNOS and COX-2 are induced in H. pylori-positive gastritis and thus may modulate the inflammation and alterations in epithelial cell growth that occur in this disease. Higher levels of iNOS and COX-2 in H. pylori-positive vs. -negative gastritis and in gastric antrum, where bacterial density is greatest, suggest that expression of these genes is a direct response to H. pylori infection.

A precision measurement of the mass of the top quark

The standard model of particle physics contains parameters--such as particle masses--whose origins are still unknown and which cannot be predicted, but whose values are constrained through their interactions. In particular, the masses of the top quark (M(t)) and W boson (M(W)) constrain the mass of the long-hypothesized, but thus far not observed, Higgs boson. A precise measurement of M(t) can therefore indicate where to look for the Higgs, and indeed whether the hypothesis of a standard model Higgs is consistent with experimental data. As top quarks are produced in pairs and decay in only about 10(-24) s into various final states, reconstructing their masses from their decay products is very challenging. Here we report a technique that extracts more information from each top-quark event and yields a greatly improved precision (of +/- 5.3 GeV/c2) when compared to previous measurements. When our new result is combined with our published measurement in a complementary decay mode and with the only other measurements available, the new world average for M(t) becomes 178.0 +/- 4.3 GeV/c2. As a result, the most likely Higgs mass increases from the experimentally excluded value of 96 to 117 GeV/c2, which is beyond current experimental sensitivity. The upper limit on the Higgs mass at the 95% confidence level is raised from 219 to 251 GeV/c2.

Evidence for roles of radicals in protein oxidation in advanced human atherosclerotic plaque

Oxidative damage might be important in atherogenesis. Oxidized lipids are present at significant concentrations in advanced human plaque, although tissue antioxidants are mostly present at normal concentrations. Indirect evidence of protein modification (notably derivatization of lysine) or oxidation has been obtained by immunochemical methods; the specificities of these antibodies are unclear. Here we present chemical determinations of six protein-bound oxidation products: dopa, o-tyrosine, m-tyrosine, dityrosine, hydroxyleucine and hydroxyvaline, some of which reflect particularly oxy-radical-mediated reaction pathways, which seem to involve mainly the participation of transition- metal ions. We compared the relative abundance of these oxidation products in normal intima, and in human carotid plaque samples with that observed after radiolytically generated hydroxyl radical attack on BSA in vitro. The close similarities in relative abundances in the latter two circumstances indicate that hydroxyl radical damage might occur in plaque. The relatively higher level of dityrosine in plaque than that observed after radiolysis suggests the additional involvement of HOCl-mediated reactions in advanced plaque.

Protein hydroperoxides can give rise to reactive free radicals

Proteins damaged by free-radical-generating systems in the presence of oxygen yield relatively long-lived protein hydroperoxides. These hydroperoxides have been shown by e.p.r. spectroscopy to be readily degraded to reactive free radicals on reaction with iron(II) complexes. Comparison of the observed spectra with those obtained with free amino acid hydroperoxides had allowed identification of some of the protein-derived radical species (including a number of carbon-centred radicals, alkoxyl radicals and a species believed to be the CO2 radical anion) and the elucidation of novel fragmentation and rearrangement processes involving amino acid side chains. In particular, degradation of hydroperoxide functions on the side chain of glutamic acid is shown to result in decarboxylation at the side-chain carboxy group via the formation of the CO2 radical anion; the generation of an identical radical from hydroperoxide groups on proteins suggests that a similar process occurs with these molecules. In a number of cases these fragmentation and rearrangement reactions give rise to further reactive free radicals (R., O2-./HO2., CO2-.) which may act as chain-carrying species in protein oxidations. These studies suggest that protein hydroperoxides are capable of initiating further radical chain reactions both intra- and inter-molecularly, and provide information on some of the fundamental mechanisms of protein alteration and side-chain fragmentation.

Emerging roles of aerobic glycolysis in breast cancer

Altered aerobic glycolysis is a well-recognized characteristic of cancer cell energy metabolism, known as the Warburg effect. Even in the presence of abundant oxygen, a majority of tumor cells produce substantial amounts of energy through a high glycolytic metabolism, and breast cancer (BC) is no exception. Breast cancer continues to be the second leading cause of cancer-associated mortality in women worldwide. However, the precise role of aerobic glycolysis in the development of BC remains elusive. Therefore, the present review attempts to address the implication of key enzymes of the aerobic glycolytic pathway including hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK), glucose transporters (GLUTs), together with related signaling pathways including protein kinase B(PI3K/AKT), mammalian target of rapamycin (mTOR) and adenosine monophosphate-activated protein kinase (AMPK) and transcription factors (c-myc, p53 and HIF-1) in the research of BC. Thus, the review of aerobic glycolysis in BC may evoke novel ideas for the BC treatment.

Effects of basic fibroblast growth factor (bFGF) on early stages of tendon healing: a rat patellar tendon model

We studied the effects of basic fibroblast growth factor (bFGF) on cell proliferation, type III collagen expression, ultimate stress and the pyridinoline content in the early stages of healing in rat patellar tendon. 96 male Sprague Dawley rats were injected with increasing doses of basic fibroblast growth factor (bFGF) at 3 days after a "window defect" was induced in the mid-part of the patellar tendon. They were killed at 7 and 14 days after the injury. A dose-dependent increase in the number of proliferating cells and the level of expression of type III collagen was demonstrated at only 7 days post-injury. On the other hand, we found no effects of bFGF on ultimate stress and the pyridinoline content of healing tendons. Only time significantly affected both strength-associated parameters. We showed that in vivo supplementation with bFGF affected the initial events of healing such as cell proliferation and type III collagen expression.

The hydroxyl radical in lens nuclear cataractogenesis

Cataract is the major cause of blindness; the most common form is age-related, or senile, cataract. The reasons for the development of cataract are unknown. Here we demonstrate that nuclear cataract is associated with the extensive hydroxylation of protein-bound amino acid residues, which increases with the development of cataract by up to 15-fold in the case of DOPA. The relative abundance of the oxidized amino acids in lens protein (assessed per parent amino acid) is DOPA > o- and m-tyrosine > 3-hydroxyvaline, 5-hydroxyleucine > dityrosine. Nigrescent cataracts, in which the normally transparent lens becomes black and opaque, contain the highest level of hydroxylated amino acids yet observed in a biological tissue: for example, per 1000 parent amino acid residues, DOPA, 15; 3-hydroxyvaline, 0.3; compared with dityrosine, 0.05. The products include representatives of the hydroperoxide and DOPA pathways of protein oxidation, which can give rise to secondary reactive species, radical and otherwise. The observed relative abundance corresponds closely with that of products of hydroxyl radical or metal-dependent oxidation of isolated proteins, and not with the patterns resulting from hypochlorite or tyrosyl-radical oxidation. Although very little light in the 300-400-nm range passes the cornea and the filter compounds of the eye, we nevertheless also demonstrate that photoxidation of lens proteins with light of 310 nm, the part of the spectrum in which protein aromatic residues have residual absorbance, does not give rise to the hydroxylated aliphatic amino acids. Thus the post-translational modification of crystallins by hydroxyl radicals/Fenton systems seems to dominate their in vivo oxidation, and it could explain the known features of such nuclear cataractogenesis.

Structural characterization of the products of hydroxyl-radical damage to leucine and their detection on proteins

We have previously reported the formation of valine hydroperoxides and aldehydes from hydroxyl-radical attack on free valine and protein molecules. We have also demonstrated that the major degradation products of valine hydroperoxides by several biochemical and cellular systems are the corresponding hydroxides, and therefore proposed that hydroxyvalines may serve as useful in vivo markers for studying protein oxidation. Here we have undertaken the structural elucidation of the oxidation products of leucine, another amino acid which is very susceptible to peroxidation. Hydroxyl-radical (HO.) attack on l-leucine in the presence of oxygen, followed by NaBH4 reduction, gave rise to five major oxidation products which have been isolated and identified. On the basis of chemical and spectroscopic evidence, the five products have been identified as (2S)-gamma-hydroxyleucine, (2S,4S)-delta-hydroxyleucine, (2S,4R)-delta-hydroxyleucine, (2S,4R)-4-methylproline (trans-4-methyl-l-proline) and (2S,4S)-4-methylproline (cis-4-methyl-l-proline). The three hydroxyleucines have been confirmed to be the reduction products of the corresponding hydroperoxyleucines, while the two proline analogues are from reduction of their corresponding cyclic Schiff bases. By HPLC analysis using post-column o-phthaldialdehyde derivatization, we have detected hydroxyleucines in the hydrolysates of tripeptides and proteins which had been gamma-radiolysed and treated with NaBH4. Furthermore, we demonstrate the occurrence of the hydroxyleucines on proteins in physiological and pathological samples. Hydroxyleucines, like hydroxyvalines, may provide useful in vivo markers for studying protein oxidation. In the present study we also investigated the competition between leucine, valine and phenylalanine for HO., and proposed a possible radical-transfer process in such free-radical reactions.

Targeted methylation sequencing of plasma cell-free DNA for cancer detection and classification

Background

Targeted methylation sequencing of plasma cell-free DNA (cfDNA) has a potential to expand liquid biopsies to patients with tumors without detectable oncogenic alterations, which can be potentially useful in early diagnosis.

Patients and methods

We developed a comprehensive methylation sequencing assay targeting 9223 CpG sites consistently hypermethylated according to The Cancer Genome Atlas. Next, we carried out a clinical validation of our method using plasma cfDNA samples from 78 patients with advanced colorectal cancer, non-small-cell lung cancer (NSCLC), breast cancer or melanoma and compared results with patients' outcomes.

Results

Median methylation scores in plasma cfDNA samples from patients on therapy were lower than from patients off therapy (4.74 versus 85.29; P = 0.001). Of 68 plasma samples from patients off therapy, methylation scores detected the presence of cancer in 57 (83.8%), and methylation-based signatures accurately classified the underlying cancer type in 45 (78.9%) of these. Methylation scores were most accurate in detecting colorectal cancer (96.3%), followed by breast cancer (91.7%), melanoma (81.8%) and NSCLC (61.1%), and most accurate in classifying the underlying cancer type in colorectal cancer (88.5%), followed by NSCLC (81.8%), breast cancer (72.7%) and melanoma (55.6%). Low methylation scores versus high were associated with longer survival (10.4 versus 4.4 months, P < 0.001) and longer time-to-treatment failure (2.8 versus 1.6 months, P = 0.016).

Conclusions

Comprehensive targeted methylation sequencing of 9223 CpG sites in plasma cfDNA from patients with common advanced cancers detects the presence of cancer and underlying cancer type with high accuracy. Methylation scores in plasma cfDNA correspond with treatment outcomes.

Reactions of hypochlorous acid with tyrosine and peptidyl-tyrosyl residues give dichlorinated and aldehydic products in addition to 3-chlorotyrosine

The toxicity of hypochlorous acid (HOCl) generated from activated neutrophils has been associated with several pathological processes such as atherosclerosis. Formation of 3-chlorotyrosine (Cl-Tyr) has been used as a marker for assessing the involvement of HOCl in such processes. In this study, we aimed to investigate the formation of Cl-Tyr from reaction of HOCl with tyrosine (both free and peptide-bound) and the fate of Cl-Tyr under such conditions. Tyrosine, N-acetyltyrosine, bovine serum albumin, and human low density lipoproteins were incubated with a range of reagent hypochlorite concentrations for varying periods in 10 mM phosphate buffer (pH 7.4) at 22 degrees C. The reaction products, and several biological samples, were hydrolyzed (in the case of proteins), isolated, and purified by high pressure liquid chromatography and characterized or quantitated by mass spectrometry and NMR. A significant amount of 3,5-dichlorotyrosine (diCl-Tyr) was obtained from the bovine serum albumin, low density lipoprotein, and some biological samples, in addition to Cl-Tyr, indicating that Cl-Tyr competes effectively for HOCl even when tyrosine is present in great excess. Cl-Tyr and diCl-Tyr were also formed from free tyrosine but then reacted further with HOCl. This finding differs from a claim in the literature that Cl-Tyr was not formed in such a system. The further reaction products of Cl-Tyr and diCl-Tyr with HOCl were elucidated as their corresponding mono- and dichlorinated 4-hydroxyphenylacetaldehydes. These results indicate the importance of assessing other products of HOCl action in addition to Cl-Tyr.

Immunoglobulin E antibodies from pancreatic cancer patients mediate antibody-dependent cell-mediated cytotoxicity against pancreatic cancer cells

In addition to allergy and parasitic infections, immunoglobulin E (IgE) has been shown recently to possess anti-viral and anti-cancer effects. We investigated serum levels of IgE, its low-affinity receptor, soluble CD23 (sCD23) in patients with pancreatic cancer and the effect of IgE against pancreatic cancer cells. Twelve patients were evaluated for pancreatic cancer by imaging and confirmed by biopsy. Fifteen healthy volunteers served as controls. Serum Igs (IgG, IgM, IgA, IgE) and sCD23 levels were determined (enzyme-linked immunosorbent assay, nephelometry) and the presence of cancer-specific IgE was assessed (fluorescence microscopy, Western blot). IgE anti-cancer activity was determined by antibody-dependent cell-mediated cytotoxicity (ADCC). Serum levels of IgE and sCD23 were elevated significantly in patients with pancreatic cancer versus controls, whereas no differences were observed in other Ig isotypes (IgG, IgM, IgA). Flow cytometry and immunofluorescence microscopy demonstrated similar presence of IgG and IgE pancreatic cancer Igs. However, Western blot analysis indicated differences in IgG and IgE antigen-specific antibodies; IgE antibody recognized a 50 kD protein. ADCC studies demonstrated that serum and purified IgE-mediated cytotoxicity against pancreatic cancer cells, effects which were reversed with anti-IgE neutralizing antibody and IgE depletion (immunoaffinity); greater cytotoxicity was observed in patient serum when compared with healthy controls. These data suggest that IgE and sCD23 may serve as useful biomarkers for patients with pancreatic cancer and may be important in the immune response to this disease in that IgE-directed therapy may help to direct treatment.

Biological fate of amino acid, peptide and protein hydroperoxides

In the course of searching for a suitable marker for studying protein oxidation, we have successfully elucidated the structures of three valine hydroperoxides, i.e. beta-hydroperoxyvaline, (2S,3S)-gamma-hydroperoxyvaline and (2S,3R)-gamma-hydroperoxyvaline, which are novel products of protein oxidation. The corresponding valine hydroxides were obtained by sodium borohydride reduction [Fu, Hick, Sheil and Dean (1995) Free Rad. Biol. Med. 19, 281-292]. We hypothesized that valine hydroxides might be the major biological degradation products of valine hydroperoxides and, as such, could be useful markers for the study of protein oxidation in vivo. The aim of this study was to investigate the fate of valine hydroperoxide in selected biological systems by the use of chemiluminescence detection of hydroperoxides and HPLC analysis of O-phthaldialdehyde derivatives of amino acid residues. The degradation of hydroperoxides present on gamma-radiolysed solutions of valine, Pro-Val-Gly, or BSA occurred in the presence of: (1) transition metals (Fe2+, Fe3+, or Cu2+), (2) the detoxifying enzyme GSH peroxidase, (3) human plasma, and (4) J774 mouse monocyte macrophage cells. The major degradation product of valine hydroperoxide recovered in each case was found to be a valine hydroxide. These results suggest that valine hydroxide (derived from the hydroperoxide) may well be a useful in vivo marker for studying protein damage under oxidative stress.

The Saccharomyces cerevisiae TCM62 gene encodes a chaperone necessary for the assembly of the mitochondrial succinate dehydrogenase (complex II)

The assembly of the mitochondrial respiratory chain is mediated by a large number of helper proteins. To better understand the biogenesis of the yeast succinate dehydrogenase (SDH), we searched for assembly-defective mutants. SDH is encoded by the SDH1, SDH2, SDH3, and SDH4 genes. The holoenzyme is composed of two domains. The membrane extrinsic domain, consisting of Sdh1p and Sdh2p, contains a covalent FAD cofactor and three iron-sulfur clusters. The membrane intrinsic domain, consisting of Sdh3p and Sdh4p, is proposed to bind two molecules of ubiquinone and one heme. We isolated one mutant that is respiration-deficient with a specific loss of SDH oxidase activity. SDH is not assembled in this mutant. The complementing gene, TCM62 (also known as SCYBR044C), does not encode an SDH subunit and is not essential for cell viability. It encodes a mitochondrial membrane protein of 64,211 Da. The Tcm62p sequence is 17.3% identical to yeast hsp60, a molecular chaperone. The Tcm62p amino terminus is in the mitochondrial matrix, whereas the carboxyl terminus is accessible from the intermembrane space. Tcm62p forms a complex containing at least three SDH subunits. We propose that Tcm62p functions as a chaperone in the assembly of yeast SDH.

Structural identification of valine hydroperoxides and hydroxides on radical-damaged amino acid, peptide, and protein molecules

We have previously demonstrated the formation of two reactive moieties on proteins during free radical attack: hydroperoxides, and 3,4-dihydroxyphenylalanine (DOPA). Here we have undertaken the structural elucidation of the hydroperoxides of valine, the amino acid which is most susceptible to peroxidation. Exposure of L-valine to free radicals generated by radiolysis in an oxygen-saturated system produced three valine hydroperoxides. Upon treatment with sodium borohydride these were reduced to their corresponding hydroxides, which can be separated and purified by high performance liquid chromatography (HPLC). Based on spectroscopic data from high resolution chemical ionization (CI) mass spectrometry (MS), electrospray (ES) MS, electron impact (EI) MS, proton (1H) nuclear magnetic resonance (NMR) and carbon-13 (13C) NMR studies, the three valine hydroxides have been identified as beta-hydroxyvaline [(2S)-2-amino-3-hydroxy-3-methyl-butanoic acid], (2S,3S)-gamma-hydroxyvaline [(2S,3S)-2-amino-3-hydroxymethyl-butanoic acid], and (2S,3R)-gamma-hydroxyvaline [(2S,3R)-2-amino-3-hydroxymethyl-butanoic acid]. HPLC analysis of O-phthaldialdehyde (OPA) derivatives of the hydroxyvalines provides a sensitive and accurate method for quantitative measurement. This method enabled hydroxyvalines to be detected in the hydrolysates of a tripeptide (glutamyl-valinyl-phenylalanine) and a protein (bovine serum albumin) that had been gamma-radiolysed and treated with sodium borohydride. Hydroxyvaline may be useful as a marker in studying protein oxidation in some biological systems under oxidative stress.

Presence of dopa and amino acid hydroperoxides in proteins modified with advanced glycation end products (AGEs): amino acid oxidation products as a possible source of oxidative stress induced by AGE proteins

Glycation and subsequent Maillard or browning reactions of glycated proteins, leading to the formation of advanced glycation end products (AGEs), are involved in the chemical modification of proteins during normal aging and have been implicated in the pathogenesis of diabetic complications. Oxidative conditions accelerate the browning of proteins by glucose, and AGE proteins also induce oxidative stress responses in cells bearing AGE receptors. These observations have led to the hypothesis that glycation-induced pathology results from a cycle of oxidative stress, increased chemical modification of proteins via the Maillard reaction, and further AGE-dependent oxidative stress. Here we show that the preparation of AGE-collagen by incubation with glucose under oxidative conditions in vitro leads not only to glycation and formation of the glycoxidation product Nepsilon-(carboxymethyl)lysine (CML), but also to the formation of amino acid oxidation products on protein, including m-tyrosine, dityrosine, dopa, and valine and leucine hydroperoxides. The formation of both CML and amino acid oxidation products was prevented by anaerobic, anti-oxidative conditions. Amino acid oxidation products were also formed when glycated collagen, prepared under anti-oxidative conditions, was allowed to incubate under aerobic conditions that led to the formation of CML. These experiments demonstrate that amino acid oxidation products are formed in proteins during glycoxidation reactions and suggest that reactive oxygen species formed by redox cycling of dopa or by the metal-catalysed decomposition of amino acid hydroperoxides, rather than by redox activity or reactive oxygen production by AGEs on protein, might contribute to the induction of oxidative stress by AGE proteins.

First-in-human study of pbi-05204, an oleander-derived inhibitor of akt, fgf-2, nf-κΒ and p70s6k, in patients with advanced solid tumors

BACKGROUND

PBI-05204, a Nerium oleander extract (NOE) containing the cardiac glycoside oleandrin, inhibits the α-3 subunit of Na-K ATPase, as well as FGF-2 export, Akt and p70S6K, hence attenuating mTOR activity. This first-in-human study determined the safety, pharmacokinetics (PK) and pharmacodynamics (PD) of PBI-05204 in patients with advanced cancer. Methods Forty-six patients received PBI-05204 by mouth for 21 of 28 days (3 + 3 trial design). Dose was escalated 100% using an accelerated titration design until grade 2 toxicity was observed. Plasma PK and mTOR effector (p70S6K and pS6) protein expressions were evaluated. Results Dose-limiting toxicities (grade 3 proteinuria, fatigue) were observed at dose level 8 (0.3383 mg/kg/day). Common possible drug-related adverse were fatigue (26 patients, 56.5%), nausea (19 patients, 41.3%) and diarrhea (15 patients, 32.6 %). Electrocardiogram monitoring revealed grade 1 atrioventricular block (N = 10 patients) and grade 2 supraventricular tachycardia (N = 1). The MTD was DL7 (0.2255 mg/kg) where no toxicity of grade ≥ 3 was observed in seven patients treated. Seven patients (15%) had stable disease > 4 months. Mean peak oleandrin concentrations up to 2 ng/mL were achieved, with area under the curves 6.6 to 25.5 μg/L*hr and a half-life range of 5-13 h. There was an average 10% and 35% reduction in the phosphorylation of Akt and pS6 in PBMC samples in 36 and 32 patients, respectively, tested between predose and 21 days of treatment. Conclusions PBI-05204 was well tolerated in heavily pretreated patients with advanced solid tumors. The recommended Phase II dose is 0.2255 mg/kg/day.

Phenylbutyrate-induced G1 arrest and apoptosis in myeloid leukemia cells: structure-function analysis

The aromatic fatty acid phenylbutyrate (PB) induces cytostasis, differentiation, and apoptosis in primary myeloid leukemic cells at clinically achievable concentrations. In the present study, we have investigated the structural and cellular basis for PB-induced cytostasis, using the ML-1 human myeloid leukemia cell line as a model system. PB induced a dose-dependent increase in cells in G1 with a corresponding decrease in cells in S-phase of the cell cycle. At comparable doses, PB induced expression of CD11b, indicating myeloid differentiation. At higher doses, the drug induced apoptosis. The antitumor activity was independent of the aromatic ring, as butyric acid (BA) was of equal or greater potency at producing these biological changes. In contrast, shortening of the fatty acid carbon chain length, as demonstrated with phenylacetate (PA), significantly diminished drug potency. Consistent with their effects on cell cycle, PB and BA, but not PA, induced the cyclin-dependent kinase inhibitor, p21(WAF1/CIP1), and led to the appearance of hypophosphorylated Rb, suggesting a role for p21(WAF1/CIP1) in PB-induced cytostasis. Therefore, it appears that the fatty acid moiety of PB, rather than its aromatic ring, is critical for its activity in myeloid leukemic cells. These data provide a potential mechanistic basis for the increased potency of PB over PA previously demonstrated in primary leukemic samples, and support the further clinical development of PB in the treatment of hematologic malignancies.

Mechanical loading inhibits cartilage inflammatory signalling via an HDAC6 and IFT-dependent mechanism regulating primary cilia elongation

OBJECTIVE

Physiological mechanical loading reduces inflammatory signalling in numerous cell types including articular chondrocytes however the mechanism responsible remains unclear. This study investigates the role of chondrocyte primary cilia and associated intraflagellar transport (IFT) in the mechanical regulation of interleukin-1β (IL-1β) signalling.

DESIGN

Isolated chondrocytes and cartilage explants were subjected to cyclic mechanical loading in the presence and absence of the cytokine IL-1β. Nitric oxide (NO) and prostaglandin E₂ (PGE₂) release were used to monitor IL-1β signalling whilst Sulphated glycosaminoglycan (sGAG) release provided measurement of cartilage degradation. Measurements were made of HDAC6 activity and tubulin polymerisation and acetylation. Effects on primary cilia were monitored by confocal and super resolution microscopy. Involvement of IFT was analysed using ORPK cells with hypomorphic mutation of IFT88.

RESULTS

Mechanical loading suppressed NO and PGE₂ release and prevented cartilage degradation. Loading activated HDAC6 and disrupted tubulin acetylation and cilia elongation induced by IL-1β. HDAC6 inhibition with tubacin blocked the anti-inflammatory effects of loading and restored tubulin acetylation and cilia elongation. Hypomorphic mutation of IFT88 reduced IL-1β signalling and abolished the anti-inflammatory effects of loading indicating the mechanism is IFT-dependent. Loading reduced the pool of non-polymerised tubulin which was replicated by taxol which also mimicked the anti-inflammatory effects of mechanical loading and prevented cilia elongation.

CONCLUSIONS

This study reveals that mechanical loading suppresses inflammatory signalling, partially dependent on IFT, by activation of HDAC6 and post transcriptional modulation of tubulin.

Phase I study of pazopanib and vorinostat: a therapeutic approach for inhibiting mutant p53-mediated angiogenesis and facilitating mutant p53 degradation

BACKGROUND

We carried out a phase I trial of the vascular endothelial growth factor inhibitor pazopanib and the histone deacetylase inhibitor vorinostat to determine the safety and efficacy. Because these agents are known to target factors activated by TP53 mutation and facilitate mutant p53 degradation, a subgroup analysis may be interesting in patients with TP53 mutant malignancies.

PATIENTS AND METHODS

Patients with advanced solid tumors (n = 78) were enrolled following a 3 + 3 design, with dose expansion for those with responsive tumors. Hotspot TP53 mutations were tested when tumor specimens were available.

RESULTS

Adverse events of ≥grade 3 included thrombocytopenia, neutropenia, fatigue, hypertension, diarrhea and vomiting. Overall, the treatment produced stable disease for at least 6 months or partial response (SD ≥6 months/PR) in 19% of the patients, median progression-free survival (PFS) of 2.2 months, and median overall survival (OS) of 8.9 months. In patients with detected hotspot TP53 mutant advanced solid tumors (n = 11), the treatment led to a 45% rate of SD ≥6 months/PR (1 PR and 3 SD ≥6 months), median PFS of 3.5 months, and median OS of 12.7 months, compared favorably with the results for patients with undetected hotspot TP53 mutations (n = 25): 16% (1 PR and 3 SD ≥6 months, P = 0.096), 2.0 months (P = 0.042), and 7.4 months (P = 0.1), respectively.

CONCLUSION

The recommended phase II dosage was oral pazopanib at 600 mg daily plus oral vorinostat at 300 mg daily. The preliminary evidence supports further evaluation of the combination in cancer patients with mutated TP53, especially in those with metastatic sarcoma or metastatic colorectal cancer.

CLINICAL TRIAL REGISTRATION

www.clinicaltrials.gov, NCT01339871.

The attentional effects of peripheral cueing as revealed by two event-related potential studies

OBJECTIVE

The mechanism of visual spatial attention elicited by peripheral cueing was investigated in two studies.

METHOD

Event-related potentials (ERPs) were recorded when the subjects were performing a spatial frequency discrimination task and a location discrimination task. Stimuli were randomly flashed in the left or right visual field. Prior to each stimulus a peripheral cue was presented with a validity of 75%.

RESULTS

The subjects responded faster to valid trials than to invalid trials. The earliest visual ERP component, C1, was not modulated by the cue validity, suggesting that visual spatial attention elicited by peripheral cueing does not involve striate cortex. Valid trials elicited larger contralateral P1 but a smaller contralateral N1 than invalid trials. The early onsets of these attentional effects show that spatial attention affects stimulus processing at early sensory/perceptual stages. The latencies of contralateral P1 and contralateral N1 were shorter for invalid trials, however. The ipsilateral N1 was enhanced by valid trials in the spatial frequency discrimination task but was not in the location discrimination task, whereas the contralateral N1 was larger for invalid trials than for valid trials in both tasks.

CONCLUSION

The results indicate that involuntary allocation of attention involves different mechanisms from voluntary allocation of attention.

Pyronaridine: A new antimalarial drug

The worldwide spread of strains of Plasmodium falciparum that are resistant to chloroquine has highlighted the urgent need for new antimalarial drugs, particularly in less developed tropical countries. However, in the current economic climate the pharmaceutical giants in the developed world are withdrawing from tropical disease research. Consequently, the following article from Fu Sui and Xiao Shuhuo is of particular interest, not only because it summarizes work on on alternative antimalarial drug that is efficacious against multiply resistant Plasmodium but also because this drug has been developed primarily from Chinese research efforts, the results of which have largely only been published in the Chinese scientific literature. The drug under scrutiny is pyronaridine, and is the product of 30 years of chemistry that began with the mepacrine nucleus. This nucleus was selected as the starting point in the search for a chloroquine alternative because the various derivatives synthesized were active against chloroquine-resistant parasites. However, mepacrine itself also needed replacing as it is too toxic for mass use. After synthesizing and screening a huge series of substitutions, the addition of an amodiaquine side-chain to this nucleus was found to give the greatest activity for fewest adverse effects. Being aware of the rapid selection of pyronaridine-resistant Plasmodium strains that occurs in the laboratory, the Chinese efforts have also investigated the use of drug combinations to circumvent or delay the development of drug resistance. In addition to the triple combination described here, pyronaridine and primaquine combinations are under trial against both P. vivax and P. falciparum. Pyronaridine is a highly active blood schizonticide like chloroquine and amodiaquine. It has already undergone extensive trials in humans against both P. falciparum and P. vivax. However, nothing is known of its mode of action, nor the basis for the development of resistance and although it is active against chloroquine-resistant strains of parasite, paradoxically, pyronaridine-resistant Plasmodium is resistant to chloroquine.

Deficient iNOS in inflammatory bowel disease intestinal microvascular endothelial cells results in increased leukocyte adhesion

Microvascular endothelial cells play a key role in inflammation by undergoing activation and recruiting circulating immune cells into tissues and foci of inflammation, an early and rate-limiting step in the inflammatory process. We have previously [Binion et al., Gastroenterology112:1898-1907, 1997] shown that human intestinal microvascular endothelial cells (HIMEC) isolated from surgically resected inflammatory bowel disease (IBD) patient tissue demonstrate significantly increased leukocyte binding in vitro compared to normal HIMEC. Our studies [Binion et al., Am. J. Physiol.275 (Gastrointest. Liver Physiol. 38):G592-G603, 1998] have also demonstrated that nitric oxide (NO) production by inducible nitric oxide synthase (iNOS) normally plays a key role in downregulating HIMEC activation and leukocyte adhesion. Using primary cultures of HIMEC derived from normal and IBD patient tissues, we sought to determine whether alterations in iNOS-derived NO production underlies leukocyte hyperadhesion in IBD. Both nonselective (N(G)-monomethyl-L-arginine) and specific (N-Iminoethyl-L-lysine) inhibitors of iNOS significantly increased leukocyte binding by normal HIMEC activated with cytokines and lipopolysaccharide (LPS), but had no effect on leukocyte adhesion by similarly activated IBD HIMEC. When compared to normal HIMEC, IBD endothelial cells had significantly decreased levels of iNOS mRNA, protein, and NO production following activation. Addition of exogenous NO by co-culture with normal HIMEC or by pharmacologic delivery with the long-acting NO donor detaNONOate restored a normal leukocyte binding pattern in the IBD HIMEC. These data suggest that loss of iNOS expression is a feature of chronically inflamed microvascular endothelial cells, which leads to enhanced leukocyte binding, potentially contributing to chronic, destructive inflammation in IBD.