A chemical probe to modulate human GID4 Pro/N-degron interactions

The C-terminal to LisH (CTLH) complex is a ubiquitin ligase complex that recognizes substrates with Pro/N-degrons via its substrate receptor Glucose-Induced Degradation 4 (GID4), but its function and substrates in humans remain unclear. Here, we report PFI-7, a potent, selective and cell-active chemical probe that antagonizes Pro/N-degron binding to human GID4. Use of PFI-7 in proximity-dependent biotinylation and quantitative proteomics enabled the identification of GID4 interactors and GID4-regulated proteins. GID4 interactors are enriched for nucleolar proteins, including the Pro/N-degron-containing RNA helicases DDX21 and DDX50. We also identified a distinct subset of proteins whose cellular levels are regulated by GID4 including HMGCS1, a Pro/N-degron-containing metabolic enzyme. These data reveal human GID4 Pro/N-degron targets regulated through a combination of degradative and nondegradative functions. Going forward, PFI-7 will be a valuable research tool for investigating CTLH complex biology and facilitating development of targeted protein degradation strategies that highjack CTLH E3 ligase activity.

Specific quinone reductase 2 inhibitors reduce metabolic burden and reverse Alzheimer's disease phenotype in mice

Biological aging can be described as accumulative, prolonged metabolic stress and is the major risk factor for cognitive decline and Alzheimer's disease (AD). Recently, we identified and described a quinone reductase 2 (QR2) pathway in the brain, in which QR2 acts as a removable memory constraint and metabolic buffer within neurons. QR2 becomes overexpressed with age, and it is possibly a novel contributing factor to age-related metabolic stress and cognitive deficit. We found that, in human cells, genetic removal of QR2 produced a shift in the proteome opposing that found in AD brains while simultaneously reducing oxidative stress. We therefore created highly specific QR2 inhibitors (QR2is) to enable evaluation of chronic QR2 inhibition as a means to reduce biological age-related metabolic stress and cognitive decline. QR2is replicated results obtained by genetic removal of QR2, while local QR2i microinjection improved hippocampal and cortical-dependent learning in rats and mice. Continuous consumption of QR2is in drinking water improved cognition and reduced pathology in the brains of AD-model mice (5xFAD), with a noticeable between-sex effect on treatment duration. These results demonstrate the importance of QR2 activity and pathway function in the healthy and neurodegenerative brain and what we believe to be the great therapeutic potential of QR2is as first-in-class drugs.

Anti-Extra Domain B Splice Variant of Fibronectin Antibody-Drug Conjugate Eliminates Tumors with Enhanced Efficacy When Combined with Checkpoint Blockade

Extra domain B splice variant of fibronectin (EDB+FN) is an extracellular matrix protein (ECM) deposited by tumor-associated fibroblasts, and is associated with tumor growth, angiogenesis, and invasion. We hypothesized that EDB+FN is a safe and abundant target for therapeutic intervention with an antibody-drug conjugate (ADC). We describe the generation, pharmacology, mechanism of action, and safety profile of an ADC specific for EDB+FN (EDB-ADC). EDB+FN is broadly expressed in the stroma of pancreatic, non-small cell lung (NSCLC), breast, ovarian, head and neck cancers, whereas restricted in normal tissues. In patient-derived xenograft (PDX), cell-line xenograft (CLX), and mouse syngeneic tumor models, EDB-ADC, conjugated to auristatin Aur0101 through site-specific technology, demonstrated potent antitumor growth inhibition. Increased phospho-histone H3, a pharmacodynamic biomarker of response, was observed in tumor cells distal to the target site of tumor ECM after EDB-ADC treatment. EDB-ADC potentiated infiltration of immune cells, including CD3+ T lymphocytes into the tumor, providing rationale for the combination of EDB-ADC with immune checkpoint therapy. EDB-ADC and anti-PD-L1 combination in a syngeneic breast tumor model led to enhanced antitumor activity with sustained tumor regressions. In nonclinical safety studies in nonhuman primates, EDB-ADC had a well-tolerated safety profile without signs of either on-target toxicity or the off-target effects typically observed with ADCs that are conjugated through conventional conjugation methods. These data highlight the potential for EDB-ADC to specifically target the tumor microenvironment, provide robust therapeutic benefits against multiple tumor types, and enhance activity antitumor in combination with checkpoint blockade.

Characterization of Specific N-α-Acetyltransferase 50 (Naa50) Inhibitors Identified Using a DNA Encoded Library

Two novel compounds were identified as Naa50 binders/inhibitors using DNA-encoded technology screening. Biophysical and biochemical data as well as cocrystal structures were obtained for both compounds (3a and 4a) to understand their mechanism of action. These data were also used to rationalize the binding affinity differences observed between the two compounds and a MLGP peptide-containing substrate. Cellular target engagement experiments further confirm the Naa50 binding of 4a and demonstrate its selectivity toward related enzymes (Naa10 and Naa60). Additional analogs of inhibitor 4a were also evaluated to study the binding mode observed in the cocrystal structures.

Quick Building Blocks (QBB): An Innovative and Efficient Business Model To Speed Medicinal Chemistry Analog Synthesis

Many pharmaceutical companies have invested millions of dollars in establishing internal chemical stores to provide reliable access to large numbers of building blocks (BB) for the synthesis of new molecules, especially for the timely design and execution of parallel (library) synthesis. Recognizing budget and logistical limitations, we required a more economically scalable process to provide diverse BB. We disclose a novel business partnership that achieves the goals of just-in-time, economical access to commercial BB that increases chemical space coverage and accelerates the synthesis of new drug candidates. We believe that this model can be of benefit to companies of all sizes that are engaged in drug discovery by reducing cost, increasing diversity of analog molecules in a time-conscious manner, and reducing BB inventory. More efficient use of BB by customers may allow commercial vendors to devote a greater portion of their resources to preparing novel BB that increase chemical diversity as opposed to resynthesizing out-of-stock compounds that are inaccessible within company compound collections.

Identification and Profiling of a Selective and Brain Penetrant Radioligand for in Vivo Target Occupancy Measurement of Casein Kinase 1 (CK1) Inhibitors

To enable the clinical development of our CNS casein kinase 1 delta/epsilon (CK1δ/ε) inhibitor project, we investigated the possibility of developing a CNS positron emission tomography (PET) radioligand. For this effort, we focused our design and synthesis efforts on the initial CK1δ/ε inhibitor HTS hits with the goal of identifying a compound that would fulfill a set of recommended PET ligand criteria. We identified [³H]PF-5236216 (9) as a tool ligand that meets most of the key CNS PET attributes including high CNS MPO PET desirability score and kinase selectivity, CNS penetration, and low nonspecific binding. We further used [³H]-9 to determine the binding affinity for PF-670462, a literature CK1δ/ε inhibitor tool compound. Lastly, [³H]-9 was used to measure in vivo target occupancy (TO) of PF-670462 in mouse and correlated TO with CK1δ/ε in vivo pharmacology (circadian rhythm modulation).

Novel 3-fluoro-6-methoxyquinoline derivatives as inhibitors of bacterial DNA gyrase and topoisomerase IV

Novel (non-fluoroquinolone) inhibitors of bacterial type II topoisomerases (NBTIs) are an emerging class of antibacterial agents. We report an optimized series of cyclobutylaryl-substituted NBTIs. Compound 14 demonstrated excellent activity both in vitro (S. aureus MIC₉₀=0.125μg/mL) and in vivo (systemic and tissue infections). Enhanced inhibition of Topoisomerase IV correlated with improved activity in S. aureus strains with mutations conferring resistance to NBTIs. Compound 14 also displayed an improved hERG IC₅₀ of 85.9μM and a favorable profile in the anesthetized guinea pig model.

Optimization of Tubulysin Antibody-Drug Conjugates: A Case Study in Addressing ADC Metabolism

As part of our efforts to develop new classes of tubulin inhibitor payloads for antibody-drug conjugate (ADC) programs, we developed a tubulysin ADC that demonstrated excellent in vitro activity but suffered from rapid metabolism of a critical acetate ester. A two-pronged strategy was employed to address this metabolism. First, the hydrolytically labile ester was replaced by a carbamate functional group resulting in a more stable ADC that retained potency in cellular assays. Second, site-specific conjugation was employed in order to design ADCs with reduced metabolic liabilities. Using the later approach, we were able to identify a conjugate at the 334C position of the heavy chain that resulted in an ADC with considerably reduced metabolism and improved efficacy. The examples discussed herein provide one of the clearest demonstrations to-date that site of conjugation can play a critical role in addressing metabolic and PK liabilities of an ADC. Moreover, a clear correlation was identified between the hydrophobicity of an ADC and its susceptibility to metabolic enzymes. Importantly, this study demonstrates that traditional medicinal chemistry strategies can be effectively applied to ADC programs.

Design, Synthesis, and Cytotoxic Evaluation of Novel Tubulysin Analogues as ADC Payloads

The tubulysin class of natural products has attracted much attention from the medicinal chemistry community due to its potent cytotoxicity against a wide range of human cancer cell lines, including significant activity in multidrug-resistant carcinoma models. As a result of their potency, the tubulysins have become an important tool for use in targeted therapy, being widely pursued as payloads in the development of novel small molecule drug conjugates (SMDCs) and antibody-drug conjugates (ADCs). A structure-based and parallel medicinal chemistry approach was applied to the synthesis of novel tubulysin analogues. These efforts led to the discovery of a number of novel and potent cytotoxic tubulysin analogues, providing a framework for our simultaneous report, which highlights the discovery of tubulysin-based ADCs, including use of site-specific conjugation to address in vivo stability of the C-11 acetate functionality.

Natural Product Splicing Inhibitors: A New Class of Antibody-Drug Conjugate (ADC) Payloads

There is a considerable ongoing work to identify new cytotoxic payloads that are appropriate for antibody-based delivery, acting via mechanisms beyond DNA damage and microtubule disruption, highlighting their importance to the field of cancer therapeutics. New modes of action will allow a more diverse set of tumor types to be targeted and will allow for possible mechanisms to evade the drug resistance that will invariably develop to existing payloads. Spliceosome inhibitors are known to be potent antiproliferative agents capable of targeting both actively dividing and quiescent cells. A series of thailanstatin-antibody conjugates were prepared in order to evaluate their potential utility in the treatment of cancer. After exploring a variety of linkers, we found that the most potent antibody-drug conjugates (ADCs) were derived from direct conjugation of the carboxylic acid-containing payload to surface lysines of the antibody (a "linker-less" conjugate). Activity of these lysine conjugates was correlated to drug-loading, a feature not typically observed for other payload classes. The thailanstatin-conjugates were potent in high target expressing cells, including multidrug-resistant lines, and inactive in nontarget expressing cells. Moreover, these ADCs were shown to promote altered splicing products in N87 cells in vitro, consistent with their putative mechanism of action. In addition, the exposure of the ADCs was sufficient to result in excellent potency in a gastric cancer xenograft model at doses as low as 1.5 mg/kg that was superior to the clinically approved ADC T-DM1. The results presented herein therefore open the door to further exploring splicing inhibition as a potential new mode-of-action for novel ADCs.

Design of Pyridopyrazine-1,6-dione γ-Secretase Modulators that Align Potency, MDR Efflux Ratio, and Metabolic Stability

Herein we describe the design and synthesis of a series of pyridopyrazine-1,6-dione γ-secretase modulators (GSMs) for Alzheimer's disease (AD) that achieve good alignment of potency, metabolic stability, and low MDR efflux ratios, while also maintaining favorable physicochemical properties. Specifically, incorporation of fluorine enabled design of metabolically less liable lipophilic alkyl substituents to increase potency without compromising the sp(3)-character. The lead compound 21 (PF-06442609) displayed a favorable rodent pharmacokinetic profile, and robust reductions of brain Aβ42 and Aβ40 were observed in a guinea pig time-course experiment.

Discovery of cytotoxic dolastatin 10 analogues with N-terminal modifications

Auristatins, synthetic analogues of the antineoplastic natural product Dolastatin 10, are ultrapotent cytotoxic microtubule inhibitors that are clinically used as payloads in antibody-drug conjugates (ADCs). The design and synthesis of several new auristatin analogues with N-terminal modifications that include amino acids with α,α-disubstituted carbon atoms are described, including the discovery of our lead auristatin, PF-06380101. This modification of the peptide structure is unprecedented and led to analogues with excellent potencies in tumor cell proliferation assays and differential ADME properties when compared to other synthetic auristatin analogues that are used in the preparation of ADCs. In addition, auristatin cocrystal structures with tubulin are being presented that allow for the detailed examination of their binding modes. A surprising finding is that all analyzed analogues have a cis-configuration at the Val-Dil amide bond in their functionally relevant tubulin bound state, whereas in solution this bond is exclusively in the trans-configuration. This remarkable observation shines light onto the preferred binding mode of auristatins and serves as a valuable tool for structure-based drug design.

β-Cell dysfunction in chronic pancreatitis

Chronic pancreatitis (CP) is a progressive inflammatory disease characterized by irreversible destruction of pancreatic secretory parenchyma, fibrosis, exocrine atrophy, and endocrine insufficiency leading to diabetes. Secondary diabetes occurring in CP subsequent to destruction of pancreatic β-cells is distinct, since it involves β-cell dysfunction amidst an inflammatory milieu. Even though considerable knowledge is available on the pathophysiology and clinical management of CP, relatively much less is known about the molecular events leading to β-cell dysfunction. Investigators have demonstrated that altered morphology, reduced β-cell mass, and β-cell numbers result in endocrine insufficiency. However, recent reports and our observations suggest that β-cell dysfunction develops in the early stages of CP while clinical diabetes manifests later, when there is profound fibrosis. In the early stages, altered internal milieu and physiology arising due to inflammation and release of cytokines might lead to deranged signaling pathways and islet dysfunction. Subsequently, development of fibrosis causes islet destruction. This suggests that endocrine deficiency in CP is multifactorial. Although the role of transcription factors (Pdx-1, MafA, NeuroD) on β-cell functions is understood, alterations in internal milieu of pancreatic tissue that affects β-cell functions in CP has not been elucidated. In this review, we summarize the factors that have an effect on islet functions. Understanding molecular events of β-cell dysfunction in CP can lead to the development of targeted preventive and therapeutic modalities.

Application of the bicyclo[1.1.1]pentane motif as a nonclassical phenyl ring bioisostere in the design of a potent and orally active γ-secretase inhibitor

Replacement of the central, para-substituted fluorophenyl ring in the γ-secretase inhibitor 1 (BMS-708,163) with the bicyclo[1.1.1]pentane motif led to the discovery of compound 3, an equipotent enzyme inhibitor with significant improvements in passive permeability and aqueous solubility. The modified biopharmaceutical properties of 3 translated into excellent oral absorption characteristics (~4-fold ↑ C(max) and AUC values relative to 1) in a mouse model of γ-secretase inhibition. In addition, SAR studies into other fluorophenyl replacements indicate the intrinsic advantages of the bicyclo[1.1.1]pentane moiety over conventional phenyl ring replacements with respect to achieving an optimal balance of properties (e.g., γ-secretase inhibition, aqueous solubility/permeability, in vitro metabolic stability). Overall, this work enhances the scope of the [1.1.1]-bicycle beyond that of a mere "spacer" unit and presents a compelling case for its broader application as a phenyl group replacement in scenarios where the aromatic ring count impacts physicochemical parameters and overall drug-likeness.

Design and synthesis of dihydrobenzofuran amides as orally bioavailable, centrally active γ-secretase modulators

We report the discovery and optimization of a novel series of dihydrobenzofuran amides as γ-secretase modulators (GSMs). Strategies for aligning in vitro potency with drug-like physicochemical properties and good microsomal stability while avoiding P-gp mediated efflux are discussed. Lead compounds such as 35 and 43 have moderate to good in vitro potency and excellent selectivity against Notch. Good oral bioavailability was achieved as well as robust brain Aβ42 lowering activity at 100 mg/kg po dose.

Interferon γ and glycemic status in diabetes associated with chronic pancreatitis

BACKGROUND/AIMS

Although the role of cytokines in the etiopathology of chronic pancreatitis (CP) is well recognized, information on pancreatic tissue cytokines in CP with/without associated diabetes is unavailable. The aim of the present study was to identify the differences in pancreatic cytokines and observe their correlations with the glycemic status in CP.

METHODS

Pancreata were obtained from CP patients (n = 44), with/without associated diabetes and non-diabetic control subjects (n= 20). Patients with CP were classified into two groups after ascertaining their diabetic status. Pancreatic cytokines (IL 1β, IL 6, IL 8, IL 10, IL 12P70, TNF α, IFN γ) were analyzed by flow cytometer. The influence of individual and cocktail of cytokines on glucose stimulated insulin release (GSIR) was examined by challenging the islets from control subjects.

RESULTS

The pancreatic IFN γ levels in diabetic and non diabetic CP patients were significantly higher in comparison to controls. The glucose stimulated insulin release (GSIR) in response to high glucose concentration in control islets, islets from non-diabetic and diabetic CP patients was 8.2, 5.67 and 3.15 μU × 10(-3)/min/islet equivalent respectively. IFN γ resulted in 82.35% decrease in GSIR from the control islet cells at a concentration of >20 pg/ml which was reversed by epigallocatechin-3-gallate (EGCG).

CONCLUSION

These results suggest that IFN γ among other cytokines, play a major role in β-cell dysfunction associated with CP.

Quantitative pharmacokinetic/pharmacodynamic analyses suggest that the 129/SVE mouse is a suitable preclinical pharmacology model for identifying small-molecule γ-secretase inhibitors

Alzheimer's disease (AD) poses a serious public health threat to the United States. Disease-modifying drugs slowing AD progression are in urgent need, but they are still unavailable. According to the amyloid cascade hypothesis, inhibition of β- or γ-secretase, key enzymes for the production of amyloid β (Aβ), may be viable mechanisms for the treatment of AD. For the discovery of γ-secretase inhibitors (GSIs), the APP-overexpressing Tg2576 mouse has been the preclinical model of choice, in part because of the ease of detection of Aβ species in its brain, plasma, and cerebrospinal fluid (CSF). Some biological observations and practical considerations, however, argue against the use of the Tg2576 mouse. We reasoned that an animal model would be suitable for GSI discovery if the pharmacokinetic (PK)/pharmacodynamic (PD) relationship of a compound for Aβ lowering in this model is predictive of that in human. In this study, we assessed whether the background 129/SVE strain is a suitable preclinical pharmacology model for identifying new GSIs by evaluating the translatability of the intrinsic PK/PD relationships for brain and CSF Aβ across the Tg2576 and 129/SVE mouse and human. Using semimechanistically based PK/PD modeling, our analyses indicated that the intrinsic PK/PD relationship for brain Aβx-42 and CSF Aβx-40 in the 129/SVE mouse is indicative of that for human CSF Aβ. This result, in conjunction with practical considerations, strongly suggests that the 129/SVE mouse is a suitable model for GSI discovery. Concurrently, the necessity and utilities of PK/PD modeling for rational interpretation of Aβ data are established.

Discovery of CP-690,550: a potent and selective Janus kinase (JAK) inhibitor for the treatment of autoimmune diseases and organ transplant rejection

There is a critical need for safer and more convenient treatments for organ transplant rejection and autoimmune disorders such as rheumatoid arthritis. Janus tyrosine kinases (JAK1, JAK3) are expressed in lymphoid cells and are involved in the signaling of multiple cytokines important for various T cell functions. Blockade of the JAK1/JAK3-STAT pathway with a small molecule was anticipated to provide therapeutic immunosuppression/immunomodulation. The Pfizer compound library was screened against the catalytic domain of JAK3 resulting in the identification of a pyrrolopyrimidine-based series of inhibitors represented by CP-352,664 (2a). Synthetic analogues of 2a were screened against the JAK enzymes and evaluated in an IL-2 induced T cell blast proliferation assay. Select compounds were evaluated in rodent efficacy models of allograft rejection and destructive inflammatory arthritis. Optimization within this chemical series led to identification of CP-690,550 1, a potential first-in-class JAK inhibitor for treatment of autoimmune diseases and organ transplant rejection.

Design of selective, ATP-competitive inhibitors of Akt

This paper describes the design and synthesis of novel, ATP-competitive Akt inhibitors from an elaborated 3-aminopyrrolidine scaffold. Key findings include the discovery of an initial lead that was modestly selective and medicinal chemistry optimization of that lead to provide more selective analogues. Analysis of the data suggested that highly lipophilic analogues would likely suffer from poor overall properties. Central to the discussion is the concept of optimization of lipophilic efficiency and the ability to balance overall druglike propeties with the careful control of lipophilicity in the lead series. Discovery of the nonracemic amide series and subsequent modification produced an advanced analogue that performed well in advanced preclinical assays, including xenograft tumor growth inhibition studies, and this analogue was nominated for clinical development.

Cell Wall Composition of Neurospora crassa Under Conditions of Copper Toxicity

The mycelia of Neurospora crassa grown in the presence of high concentrations of copper were blue in color, but only on a medium containing inorganic nitrate and phosphate as the nitrogen and phosphate sources, respectively. The cell wall isolate of the blue mycelia contained large amounts (12%) of copper and higher amounts of chitosan, phosphate, and amino groups, with a 42% decrease in the chitin content. Although all the glucosamine of the cell wall of control cultures could be released within 6 h of hydrolysis with acid, that of the blue mycelium required prolonged hydrolysis for 24 h. On removal of copper, the cell wall of the blue mycelium could quantitatively bind again to copper as well as to zinc. Although zinc binding was fivefold greater, copper alone was preferentially bound from a mixture of the two metal ions. Supplementation of iron along with copper in the culture medium resulted in the disappearance of the blue color of the mycelium and restoration of normal growth and composition of the cell wall, probably by limiting the uptake of copper from the medium. The possibility of the cell wall being a specific site of lesion in copper toxicity in the mold is discussed.

Structural comparison of chromosomal and exogenous dihydrofolate reductase from Staphylococcus aureus in complex with the potent inhibitor trimethoprim

Dihydrofolate reductase (DHFR) is the enzyme responsible for the NADPH-dependent reduction of 5,6-dihydrofolate to 5,6,7,8-tetrahydrofolate, an essential cofactor in the synthesis of purines, thymidylate, methionine, and other key metabolites. Because of its importance in multiple cellular functions, DHFR has been the subject of much research targeting the enzyme with anticancer, antibacterial, and antimicrobial agents. Clinically used compounds targeting DHFR include methotrexate for the treatment of cancer and diaminopyrimidines (DAPs) such as trimethoprim (TMP) for the treatment of bacterial infections. DAP inhibitors of DHFR have been used clinically for >30 years and resistance to these agents has become widespread. Methicillin-resistant Staphylococcus aureus (MRSA), the causative agent of many serious nosocomial and community acquired infections, and other gram-positive organisms can show resistance to DAPs through mutation of the chromosomal gene or acquisition of an alternative DHFR termed "S1 DHFR." To develop new therapies for health threats such as MRSA, it is important to understand the molecular basis of DAP resistance. Here, we report the crystal structure of the wild-type chromosomal DHFR from S. aureus in complex with NADPH and TMP. We have also solved the structure of the exogenous, TMP resistant S1 DHFR, apo and in complex with TMP. The structural and thermodynamic data point to important molecular differences between the two enzymes that lead to dramatically reduced affinity of DAPs to S1 DHFR. These differences in enzyme binding affinity translate into reduced antibacterial activity against strains of S. aureus that express S1 DHFR.

Pyrimidine benzamide-based thrombopoietin receptor agonists

A series of pyrimidine benzamide-based thrombopoietin receptor agonists is described. The lead molecule contains a 2-amino-5-unsubstituted thiazole, a group that has been associated with idiosyncratic toxicity. The potential for metabolic oxidation at C-5 of the thiazole, the likely source of toxic metabolites, was removed by substitution at C-5 or by replacing the thiazole with a thiadiazole. Potency in the series was improved by modifying the substituents on the pyrimidine and/or on the thiazole or thiadiazole pendant aryl ring. In vivo examination revealed that compounds from the series are not highly bioavailable. This is attributed to low solubility and poor permeability.

Influence of extremely low frequency magnetic fields on Ca2+ signaling and NMDA receptor functions in rat hippocampus

Extremely low frequency (ELF<300Hz) electromagnetic fields affect several neuronal activities including memory. Because ELF magnetic fields cause altered Ca(2+) homeostasis in neural tissues, we examined their influence on Ca(2+) signaling enzymes in hippocampus and related them with NMDA receptor functions. Hippocampal regions were obtained from brains of 21-day-old rats that were exposed for 90 days to 50Hz magnetic fields at 50 and 100 microT intensities. In comparison to controls, ELF exposure caused increased intracellular Ca(2+) levels concomitant with increased activities of Ca(2+)-dependent protein kinase C (PKC), cAMP-dependent protein kinase and calcineurin as well as decreased activity of Ca(2+)-calmodulin-dependent protein kinase in hippocampal regions. Simultaneous ligand-binding studies revealed decreased binding to N-methyl-D-aspartic acid (NMDA) receptors. The combined results suggest that perturbed neuronal functions caused by ELF exposure may involve altered Ca(2+) signaling events contributing to aberrant NMDA receptor activities.

Biochemical analysis of oxidative stress in the production of aflatoxin and its precursor intermediates

The relevance of oxidative stress in the production of aflatoxin and its precursors was examined in different mutants of Aspergillus parasiticus, which produce aflatoxin or its precursor intermediates, and compared with results obtained from a non-toxigenic strain. In comparison to the non-toxigenic strain (SRRC 255), an aflatoxin producing strain (NRRL 2999) or mutants that accumulate aflatoxin precursors such as norsolorinic acid (by SRRC 162) or versicolorin (by NRRL 6196) or O-methyl sterigmatocystin (by SRRC 2043) had greater oxygen requirements and higher contents of reactive oxygen species. These changes were in the graded order of NRRL 2999 > SRRC 2043 > NRRL 6196 > SRRC 162 > SRRC 255, indicating incremental accumulation of reactive oxygen species, being least in the non-toxigenic strain and increasing progressively during the ternary steps of aflatoxin formation. Oxidative stress in these strains was evident by increased activities of xanthine oxidase and free radical scavenging enzymes (superoxide dismutase and glutathione peroxidase) as compared to the non-toxigenic strain (SRRC 255). Culturing the toxigenic strain in presence of 0.1-10 muM H(2)O(2 )in the medium resulted in enhanced aflatoxin production, which could be related to dose-dependent increase in [(14)C]-acetate incorporation into aflatoxin B(1) and increased acetyl CoA carboxylase activity. The combined results suggest that formation of secondary metabolites such as aflatoxin and its precursors by A. parasiticus may occur as a compensatory response to reactive oxygen species accumulation.

Prevention of isoproterenol-induced cardiac hypertrophy by eugenol, an antioxidant

Recent reports on the involvement of calcineurin in cardiac hypertrophy and its susceptibility to free radicals, prompted us to examine possible beneficial effects of dietary antioxidants in this regard. In continuation of initialin vitro studies revealing eugenol to be a potent calcineurin inhibitor, we investigated its ability to reverse isoproterenol-induced cardiac hypertrophy in rats. Intraperitoneal administration of isoproterenol (1 mg/kg body wt/day for 10 days) induced cardiac hypertrophy with increased heart weight and enhanced apoptosis of myocytes concomitant with accumulation of reactive oxygen species, decreased glutathione contents, increased activities of calcineurin and protein kinase C in ventricular tissue. Administering eugenol for 3 days (1 mg/kg body wt/twice a day), followed by combined administration of isoproterenol and eugenol resulted in significant reversal of cardiac hypertrophy and restoration of above changes. These results suggest that eugenol, a natural antioxidant of dietary origin, may offer potential benefits in the management of cardiac hypertrophy.

Potent pyrimidinetrione-based inhibitors of MMP-13 with enhanced selectivity over MMP-14

Through the use of computational modeling, a series of pyrimidinetrione-based inhibitors of MMP-13 was designed based on a lead inhibitor identified through file screening. Incorporation of a biaryl ether moiety at the C-5 position of the pyrimidinetrione ring resulted in a dramatic enhancement of MMP-13 potency. Protein crystallography revealed that this moiety binds in the S(1)(') pocket of the enzyme. Optimization of the C-4 substituent of the terminal aromatic ring led to incorporation of selectivity versus MMP-14 (MT-1 MMP). Structure activity relationships of the biaryl ether substituent are presented as is pharmacokinetic data for a compound that meets our in vitro potency and selectivity goals.

Serum calcineurin activity in relation to oxidative stress and glycemic control in type II diabetes mellitus

OBJECTIVES

In view of the well-recognized prevalence of oxidative stress in diabetes mellitus and the susceptibility of calcineurin (Ca(2+)-calmodulin dependent protein phosphatase 2 B) to free radicals, calcineurin was assayed in the sera of type II diabetic patients.

DESIGN AND METHODS

Serum contents of thiobarbituric acid reactive substances, calcineurin and calmodulin, as well as activities of calcineurin and superoxide dismutase were measured in 81 diabetic patients and compared with age-matched controls.

RESULTS

Oxidative stress in diabetic subjects was evidenced by increased thiobarbituric acid reactive substances, decreased superoxide dismutase activity concomitant with decreased calcineurin activity in sera. The observed decrease in calcineurin activity had a reciprocal correlation with fasting blood sugar, thiobarbituric acid reactive substances, and glycosylated hemoglobin.

CONCLUSION

The inverse correlation observed between serum calcineurin activity and glycosylated hemoglobin levels suggests that an assay of serum calcineurin activity may be useful in simultaneous assessment of oxidative stress and glycemic control in type II diabetes mellitus.

Copper alone, but not oxidative stress, induces copper–metallothionein gene inNeurospora crassa

Two metal response elements, flanking an antioxidant response element, were identified in regions upstream (-3730 bp) to copper metallothionein (CuMT) gene of Neurospora crassa. Presence of copper in culture media, but not of pro-oxidants like H2O2 or menadione, induced CuMT gene expression that could not be completely abolished by antioxidants such as N-acetyl cysteine and ascorbic acid. Gel shift assays revealed the ability of nuclear extracts from copper induced cultures to bind PCR-amplified metal response or antioxidant response elements. Similar observations could not be made with cultures exposed either to pro-oxidants or antioxidants. These results differentiate between CuMT gene induction by copper from antioxidant functions associated with the identified upstream elements.

Biological effects of power frequency magnetic fields: Neurochemical and toxicological changes in developing chick embryos

BACKGROUND: There are several reports that indicate a linkage between exposure to power frequency (50 - 60 Hz) magnetic fields with abnormalities in the early embryonic development of the chicken. The present study was designed to understand whether power frequency electromagnetic fields could act as an environmental insult and invoke any neurochemical or toxicological changes in developing chick embryo model. METHODS: Fertilized chicken eggs were subjected to continuous exposure to magnetic fields (50 Hz) of varying intensities (5, 50 or 100 microT) for a period of up to 15 days. The embryos were taken out of the eggs on day 5, day 10 and day 15. Neurochemical (norepinephrine and 5-hydroxytryptamine) and amino acid (tyrosine, glutamine and tryptophan) contents were measured, along with an assay of the enzyme glutamine synthetase in the brain. Preliminary toxicological investigations were carried out based on aminotransferases (AST and ALT) and lactate dehydrogenase activities in the whole embryo as well as in the liver. RESULTS: The study revealed that there was a significant increase (p < 0.01 and p < 0.001) in the level of norepinephrine accompanied by a significant decrease (p < 0.01 and p < 0.001) in the tyrosine content in the brain on day 15 following exposure to 5, 50 and 100 microT magnetic fields. There was a significant increase (p < 0.001) in glutamine synthetase activity resulting in the significantly enhanced (p < 0.001) level of glutamine in the brain on day 15 (for 100 microT only). The possible mechanisms for these alterations are discussed. Further, magnetic fields had no effect on the levels of tryptophan and 5-hydroxytryptamine in the brain. Similarly, there was no effect on the activity of either aminotransferases or lactate dehydrogenase in the whole embryo or liver due to magnetic field exposure. CONCLUSIONS: Based on these studies we conclude that magnetic field-induced changes in norepinephrine levels might help explain alterations in the circadian rhythm, observed during magnetic field stress. Also, the enhanced level of glutamine can act as a contributing factor for developmental abnormalities.

Prevention of organ allograft rejection by a specific Janus kinase 3 inhibitor

Because of its requirement for signaling by multiple cytokines, Janus kinase 3 (JAK3) is an excellent target for clinical immunosuppression. We report the development of a specific, orally active inhibitor of JAK3, CP-690,550, that significantly prolonged survival in a murine model of heart transplantation and in cynomolgus monkeys receiving kidney transplants. CP-690,550 treatment was not associated with hypertension, hyperlipidemia, or lymphoproliferative disease. On the basis of these preclinical results, we believe JAK3 blockade by CP-690,550 has potential for therapeutically desirable immunosuppression in human organ transplantation and in other clinical settings.

Calcineurin activity as an indicator of oxidative stress in normal islet cells and insulinoma cells

A comparative study was conducted to evaluate calcineurin activity in normal pancreatic beta cells and insulinoma cells in relation to their oxidative state. In comparison to normal islets, insulinoma cells had enhanced oxidative stress as evidenced by increased content of thiobarbituric acid reactive substances. In addition, diminished activity of calcineurin in insulinoma cells was concomitant with decreased content of reduced glutathione and glutathione peroxidase activity signifying diminished antioxidant status in these cells. Culturing insulinoma cells in presence of the calcineurin inhibitor cyclosporin A resulted in further decrease of calcineurin activity with restoration of glutathione peroxidase but without restoration of reduced glutathione levels. These results indicate that an estimate of oxidative stress in pancreatic islets and insulinoma cells can be obtained by assaying calcineurin activity.

Clinical significance of serum calcineurin in acute leukemia

BACKGROUND

Calcineurin is involved in T-lymphocyte activation as well as in the maturation of hematopoietic cells. Identification of this predominantly intracellular phosphatase and of calmodulin (CaM) in human sera warranted their assessment in different types of acute leukemias.

METHODS

Phosphatase activity of calcineurin (CaN) was assayed, involving the measurement of trifluoperazine-sensitive neutral phosphatase, in sera of leukemic patients before and after treatment. Calcineurin and calmodulin contents were also determined by ELISA employing monoclonal antibodies specific to the proteins.

RESULTS

The activity of calcineurin was decreased by 75% and 85% in sera of patients diagnosed either for acute lymphoid leukemia and acute myeloid leukemia, respectively, without apparent changes in calmodulin or calcineurin contents under both these conditions. In addition, the decreased calcineurin activity in acute myeloid leukemia was restored to levels comparable to non-leukemic individuals upon treatment. This was not observed in cases of acute lymphoid leukemia.

CONCLUSIONS

These results suggest diagnostic utility in the measurement of serum calcineurin activity in acute leukemia. Restoration of normal calcineurin activity in patients undergoing treatment for acute myeloid leukemia may provide a means to monitor patient response to the prescribed therapeutic regimen.

Oxidative stress as a prerequisite for aflatoxin production by Aspergillus parasiticus

The relevance of free radical generation and oxidative stress with regard to aflatoxin production was examined by comparing the oxygen requirement and antioxidant status of a toxigenic strain of Aspergillus parasiticus with that of a nontoxigenic strain at early (trophophase) and late logarithmic (idiophase) growth phases. In comparison to the nontoxigenic strain, wherein the oxygen requirements were relatively unaltered at various growth phases, the toxigenic strain exhibited greater oxygen requirements at trophophase coinciding with onset of aflatoxin production. The activities of antioxidant enzymes such as xanthine oxidase, superoxide dismutase, and glutathione peroxidase and the mycelial contents of thiobarbituric acid-reactive substances as well as of reduced glutathione were all enhanced during the progression of toxigenic strain from trophophase to idiophase. The combined results suggest that aflatoxin production by the toxigenic strain may be a consequence of increased oxidative stress leading to enhanced lipid peroxidation and free radical generation.