Host Defense Peptide Piscidin and Yeast-Derived Glycolipid Exhibit Synergistic Antimicrobial Action through Concerted Interactions with Membranes

Developing new antimicrobials as alternatives to conventional antibiotics has become an urgent race to eradicate drug-resistant bacteria and to save human lives. Conventionally, antimicrobial molecules are studied independently even though they can be cosecreted in vivo. In this research, we investigate two classes of naturally derived antimicrobials: sophorolipid (SL) esters as modified yeast-derived glycolipid biosurfactants that feature high biocompatibility and low production cost; piscidins, which are host defense peptides (HDPs) from fish. While HDPs such as piscidins target the membrane of pathogens, and thus result in low incidence of resistance, SLs are not well understood on a mechanistic level. Here, we demonstrate that combining SL-hexyl ester (SL-HE) with subinhibitory concentration of piscidins 1 (P1) and 3 (P3) stimulates strong antimicrobial synergy, potentiating a promising therapeutic window. Permeabilization assays and biophysical studies employing circular dichroism, NMR, mass spectrometry, and X-ray diffraction are performed to investigate the mechanism underlying this powerful synergy. We reveal four key mechanistic features underlying the synergistic action: (1) P1/3 binds to SL-HE aggregates, becoming α-helical; (2) piscidin-glycolipid assemblies synergistically accumulate on membranes; (3) SL-HE used alone or bound to P1/3 associates with phospholipid bilayers where it induces defects; (4) piscidin-glycolipid complexes disrupt the bilayer structure more dramatically and differently than either compound alone, with phase separation occurring when both agents are present. Overall, dramatic enhancement in antimicrobial activity is associated with the use of two membrane-active agents, with the glycolipid playing the roles of prefolding the peptide, coordinating the delivery of both agents to bacterial surfaces, recruiting the peptide to the pathogenic membranes, and supporting membrane disruption by the peptide. Given that SLs are ubiquitously and safely used in consumer products, the SL/peptide formulation engineered and mechanistically characterized in this study could represent fertile ground to develop novel synergistic agents against drug-resistant bacteria.

Hydrophilic Interaction Liquid Chromatography at Subzero Temperature for Hydrogen-Deuterium Exchange Mass Spectrometry

Chromatographic separations at subzero temperature significantly improve the precision of back-exchange-corrected hydrogen-deuterium exchange mass spectrometry (HDX-MS) determinations. Our previously reported dual-enzyme HDX-MS analysis instrument used reversed phase liquid chromatography (RPLC) at -30 °C, but high backpressures limited flow rates and required materials and equipment rated for very high pressures. Here, we report the design and performance of a dual-enzyme HDX-MS analysis instrument comprising a RPLC trap column and a hydrophilic interaction liquid chromatography (HILIC) analytical column in a two-dimensional RPLC-HILIC configuration at subzero temperature. During operation at -30 °C, the HILIC column manifests greatly reduced backpressure, which enables faster analytical flow rates and the use of materials rated for lower maximum pressures. The average peptide eluted from a HILIC column during a 40 min gradient at -30 °C contained ≈13% more deuterium than peptides eluted from a tandem RPLC-RPLC apparatus using a conventional 8 min gradient at 0 °C. A subset of peptides eluted from the HILIC apparatus contained ≈24% more deuterium.

Particle Metrology Approach to Understanding How Storage Conditions Affect Long-Term Liposome Stability

Lipid nanoparticles are a generic type of nanomaterial with broad applicability in medicine as drug delivery vehicles. Liposomes are a subtype of lipid nanoparticles and, as a therapeutic platform, can be loaded with a genetic material or pharmaceutical agents for use as drug treatments. An open question for these types of lipid nanoparticles is what factor(s) affect the long-term stability of the particles. The stability of the particle is of great interest to understand and predict the effective shelf-life and storage requirements. In this report, we detail a one-year study of liposome stability as a function of lipid composition, buffer composition/pH, and storage temperature. This was done in aqueous solution without freezing. The effect of lipid composition is shown to be a critical factor when evaluating stability of the measured particle size and number concentration. Other factors (i.e., storage temperature and buffer pH/composition) were shown to be less critical but still have some effect. The stability of these particles informs formulation and optimal storage requirements and assists with future developmental planning of a NIST liposome-based reference material. This work also highlights the complex nature of long-term soft particle storage in biopharmaceutical applications.

Chromatography at -30 °C for Reduced Back-Exchange, Reduced Carryover, and Improved Dynamic Range for Hydrogen-Deuterium Exchange Mass Spectrometry

For hydrogen-deuterium exchange mass spectrometry (HDX-MS) to have an increased role in quality control of biopharmaceuticals, H for D back-exchange occurring during protein analyses should be minimized to promote greater reproducibility. Standard HDX-MS analysis systems that digest proteins and separate peptides at pH 2.7 and 0 °C can lose >30% of the deuterium marker within 15 min of sample injection. This report describes the architecture and performance of a dual-enzyme, HDX-MS instrument that conducts liquid chromatography (LC) separations at subzero temperature, thereby reducing back-exchange and supporting longer LC separations with improved chromatographic resolution. LC separations of perdeuterated, fully reduced, iodoacetamide-treated BSA protein digest standard peptides were performed at 0, -10, -20, and -30 °C in ethylene glycol (EG)/H₂O mixtures. Analyses conducted at -20 and -30 °C produced similar results. After subtracting for deuterium retained in arginine side chains, the average peptide eluted during a 40 min gradient contained ≈16% more deuterium than peptides eluted with a conventional 8 min gradient at 0 °C. A subset of peptides exhibited ≈26% more deuterium. Although chromatographic peaks shift with EG concentration and temperature, the apparatus elutes unbroadened LC peaks. Electrospray ion intensity does not decline with increasing EG fraction. To minimize bias from sample carryover, the fluidic circuits allow flush and backflush cleaning of all enzyme and LC columns. The system can perform LC separations and clean enzyme columns simultaneously. Temperature zones are controlled ±0.058 °C. The potential of increased sensitivity by mixing acetonitrile with the analytical column effluent was also examined.

Interlaboratory Studies Using the NISTmAb to Advance Biopharmaceutical Structural Analytics

Biopharmaceuticals such as monoclonal antibodies are required to be rigorously characterized using a wide range of analytical methods. Various material properties must be characterized and well controlled to assure that clinically relevant features and critical quality attributes are maintained. A thorough understanding of analytical method performance metrics, particularly emerging methods designed to address measurement gaps, is required to assure methods are appropriate for their intended use in assuring drug safety, stability, and functional activity. To this end, a series of interlaboratory studies have been conducted using NISTmAb, a biopharmaceutical-representative and publicly available monoclonal antibody test material, to report on state-of-the-art method performance, harmonize best practices, and inform on potential gaps in the analytical measurement infrastructure. Reported here is a summary of the study designs, results, and future perspectives revealed from these interlaboratory studies which focused on primary structure, post-translational modifications, and higher order structure measurements currently employed during biopharmaceutical development.

HDX-MS and MD Simulations Provide Evidence for Stabilization of the IgG1-FcγRIa (CD64a) Immune Complex Through Intermolecular Glycoprotein Bonds

Previous reports present different models for the stabilization of the Fc-FcγRI immune complex. Although accord exists on the importance of L235 in IgG1 and some hydrophobic contacts for complex stabilization, discord exists regarding the existence of stabilizing glycoprotein contacts between glycans of IgG1 and a conserved FG-loop (¹⁷¹MGKHRY¹⁷⁶) of FcγRIa. Complexes formed from the FcγRIa receptor and IgG1s containing biantennary glycans with N-acetylglucosamine, galactose, and α2,6-N-acetylneuraminic terminations were measured by hydrogen-deuterium exchange mass spectrometry (HDX-MS), classified for dissimilarity with Welch's ANOVA and Games-Howell post hoc procedures, and modeled with molecular dynamics (MD) simulations. For each glycoform of the IgG1-FcγRIa complex peptic peptides of Fab, Fc and FcγRIa report distinct H/D exchange rates. MD simulations corroborate the differences in the peptide deuterium content through calculation of the percent of time that transient glycan-peptide bonds exist. These results indicate that stability of IgG1-FcγRIa complexes correlate with the presence of intermolecular glycoprotein interactions between the IgG1 glycans and the ¹⁷³KHR¹⁷⁵ motif within the FG-loop of FcγRIa. The results also indicate that intramolecular glycan-protein bonds stabilize the Fc region in isolated and complexed IgG1. Moreover, HDX-MS data evince that the Fab domain has glycan-protein binding contacts within the IgG1-FcγRI complex.

Dataset from HDX-MS Studies of IgG1 Glycoforms and Their Interactions with the FcγRIa (CD64) Receptor

This document presents hydrogen-deuterium exchange mass spectrometry (HDX-MS) data from measurements of three purified IgG1 glycoform samples, predominantly G0F, G2F, and SAF, in isolation and in complexation with the high-affinity receptor, FcγRIa (CD64). The IgG1 antibody used in this study, aIL8hFc, is a murine-human chimeric IgG1, which inhibits IL-8 binding to human neutrophils.

Conformational gating, dynamics and allostery in human monoacylglycerol lipase

Inhibition of human Monoacylglycerol Lipase (hMGL) offers a novel approach for treating neurological diseases. The design of inhibitors, targeting active-inactive conformational transitions of the enzyme, can be aided by understanding the interplay between structure and dynamics. Here, we report the effects of mutations within the catalytic triad on structure, conformational gating and dynamics of hMGL by combining kinetics, NMR, and HDX-MS data with metadynamics simulations. We found that point mutations alter delicate conformational equilibria between active and inactive states. HDX-MS reveals regions of the hMGL that become substantially more dynamic upon substitution of catalytic acid Asp-239 by alanine. These regions, located far from the catalytic triad, include not only loops but also rigid α-helixes and β-strands, suggesting their involvement in allosteric regulation as channels for long-range signal transmission. The results identify the existence of a preorganized global communication network comprising of tertiary (residue-residue contacts) and quaternary (rigid-body contacts) networks that mediate robust, rapid intraprotein signal transmission. Catalytic Asp-239 controls hMGL allosteric communications and may be considered as an essential residue for the integration and transmission of information to enzymes' remote regions, in addition to its well-known role to facilitate Ser-122 activation. Our findings may assist in the identification of new druggable sites in hMGL.

Interlaboratory Comparison of Hydrogen-Deuterium Exchange Mass Spectrometry Measurements of the Fab Fragment of NISTmAb

Hydrogen-deuterium exchange mass spectrometry (HDX-MS) is an established, powerful tool for investigating protein-ligand interactions, protein folding, and protein dynamics. However, HDX-MS is still an emergent tool for quality control of biopharmaceuticals and for establishing dynamic similarity between a biosimilar and an innovator therapeutic. Because industry will conduct quality control and similarity measurements over a product lifetime and in multiple locations, an understanding of HDX-MS reproducibility is critical. To determine the reproducibility of continuous-labeling, bottom-up HDX-MS measurements, the present interlaboratory comparison project evaluated deuterium uptake data from the Fab fragment of NISTmAb reference material (PDB: 5K8A ) from 15 laboratories. Laboratories reported ∼89 800 centroid measurements for 430 proteolytic peptide sequences of the Fab fragment (∼78 900 centroids), giving ∼100% coverage, and ∼10 900 centroid measurements for 77 peptide sequences of the Fc fragment. Nearly half of peptide sequences are unique to the reporting laboratory, and only two sequences are reported by all laboratories. The majority of the laboratories (87%) exhibited centroid mass laboratory repeatability precisions of ⟨ s^Lab⟩ ≤ (0.15 ± 0.01) Da (1σ_x̅). All laboratories achieved ⟨s^Lab⟩ ≤ 0.4 Da. For immersions of protein at T_HDX = (3.6 to 25) °C and for D₂O exchange times of t_HDX = (30 s to 4 h) the reproducibility of back-exchange corrected, deuterium uptake measurements for the 15 laboratories is σ_{reproducibility}^{15 Laboratories}( t_HDX) = (9.0 ± 0.9) % (1σ). A nine laboratory cohort that immersed samples at T_HDX = 25 °C exhibited reproducibility of σ_{reproducibility}^25C cohort( t_HDX) = (6.5 ± 0.6) % for back-exchange corrected, deuterium uptake measurements.

Hydrogen-Deuterium Exchange Mass Spectrometry (HDX-MS) Centroid Data Measured between 3.6 °C and 25.4 °C for the Fab Fragment of NISTmAb

The spreadsheet file reported herein provides centroid data, descriptive of deuterium uptake, for the FabFragment of NISTmAb (PDB: 5K8A) reference material, as measured by the bottom-up hydrogen-deuterium exchange mass spectrometry (HDX-MS) method. The protein sample was incubated in deuterium-rich solutions under uniform pH and salt concentrations between 3.6 oC and 25.4 oC for seven intervals ranging over (0 to 14,400) s plus a ∞pseudo s control. The deuterium content of peptic peptide fragments were measured by mass spectrometry. These data were reported by fifteen laboratories, which conducted the measurements using orbitrap and Q-TOF mass spectrometers. The cohort reported ≈ 78,900 centroids for 430 proteolytic peptide sequences of the heavy and light chains of NISTmAb, providing nearly 100 % coverage. In addition, some groups reported ≈ 10,900 centroid measurements for 77 peptide sequences of the Fc fragment. The instrumentation and physical and chemical conditions under which these data were acquired are documented.

Automated Removal of Phospholipids from Membrane Proteins for H/D Exchange Mass Spectrometry Workflows

Membrane proteins are currently the most common targets for pharmaceuticals. However, characterization of their structural dynamics by hydrogen/deuterium exchange mass spectrometry (HDX-MS) is sparse due to insufficient automated methods to handle full-length membrane proteins in lipid bilayers. Additionally, membrane lipids used to mimic the membrane environment and to solubilize membrane proteins can impair chromatography performance and cause ion suppression in the mass spectrometer. The workflow discussed herein advances HDX-MS capabilities and other MS applications for membrane proteins by providing a fully automated method for HDX-MS analysis based on a phospholipid removal scheme compatible with robotic handling. Phospholipids were depleted from protein samples by the addition of zirconium oxide beads, which were subsequently removed by inline filtration using syringeless nanofilters. To demonstrate this method, single-pass transmembrane protein FcγRIIa (CD32a) expressed into liposomes was used. Successful depletion of phospholipids ensured optimal liquid-chromatography-mass-spectrometry performance, and measurement of peptides from the transmembrane domain of FcγRIIa indicated phospholipids associated with this region were either not present or did not shield the transmembrane domain from digestion by pepsin. Furthermore, amino acid sequence coverage provided by this method was suitable to enable future measurement of structural dynamics of ectodomain, transmembrane domain, and endodomain of FcγRIIa. Moreover, this method is the first to enable fully automated HDX-MS on full-length transmembrane proteins in lipid bilayers, a notable advancement to facilitate understanding of membrane proteins, development of pharmaceuticals, and characterization for regulatory agencies.

Transcriptional and post-translational changes in the brain of mice deficient in cholesterol removal mediated by cytochrome P450 46A1 (CYP46A1)

Cytochrome P450 46A1 (CYP46A1) converts cholesterol to 24-hydroxycholesterol and thereby controls the major pathways of cholesterol removal from the brain. Cyp46a1-/- mice have a reduction in the rate of cholesterol biosynthesis in the brain and significant impairments to memory and learning. To gain insights into the mechanisms underlying Cyp46a1-/- phenotype, we used Cyp46a1-/- mice and quantified their brain sterol levels and the expression of the genes pertinent to cholesterol homeostasis. We also compared the Cyp46a1-/- and wild type brains for protein phosphorylation and ubiquitination. The data obtained enable the following inferences. First, there seems to be a compensatory upregulation in the Cyp46a1-/- brain of the pathways of cholesterol storage and CYP46A1-independent removal. Second, transcriptional regulation of the brain cholesterol biosynthesis via sterol regulatory element binding transcription factors is not significantly activated in the Cyp46a1-/- brain to explain a compensatory decrease in cholesterol biosynthesis. Third, some of the liver X receptor target genes (Abca1) are paradoxically upregulated in the Cyp46a1-/- brain, possibly due to a reduced activation of the small GTPases RAB8, CDC42, and RAC as a result of a reduced phosphorylation of RAB3IP and PAK1. Fourth, the phosphorylation of many other proteins (a total of 146) is altered in the Cyp46a1-/- brain, including microtubule associated and neurofilament proteins (the MAP and NEF families) along with proteins related to synaptic vesicles and synaptic neurotransmission (e.g., SLCs, SHANKs, and BSN). Fifth, the extent of protein ubiquitination is increased in the Cyp46a1-/- brain, and the affected proteins pertain to ubiquitination (UBE2N), cognition (STX1B and ATP1A2), cytoskeleton function (TUBA1A and YWHAZ), and energy production (ATP1A2 and ALDOA). The present study demonstrates the diverse potential effects of CYP46A1 deficiency on brain functions and identifies important proteins that could be affected by this deficiency.

Assessment of Extracellular Vesicles Purity Using Proteomic Standards

The increasing interest in extracellular vesicles (EVs) research is fueled by reports indicating their unique role in intercellular communication and potential connection to the development of common human diseases. The unique role assumes unique protein and nucleic acid cargo. Unfortunately, accurate analysis of EVs cargo faces a challenge of EVs isolation. Generally used isolation techniques do not separate different subtypes of EVs and even more, poorly separate EVs from non-EVs contaminants. Further development of EVs isolation protocols urgently needs a quantitative method of EVs purity assessment. We report here that multiple reaction monitoring assay using internal standards carrying peptides for quantification of EVs and non-EVs proteins is a suitable approach to assess purity of EVs preparations. As a first step in potential standardization of EVs isolation, we have evaluated polymer-based precipitation techniques and compared them to traditional ultracentrifugation protocol.

In vitro cytochrome P450 46A1 (CYP46A1) activation by neuroactive compounds

Cytochrome P450 46A1 (CYP46A1, cholesterol 24-hydroxylase) is the enzyme responsible for the majority of cholesterol elimination from the brain. Previously, we found that the anti-HIV drug efavirenz (EFV) can pharmacologically activate CYP46A1 in mice. Herein, we investigated whether CYP46A1 could also be activated by endogenous compounds, including major neurotransmitters. In vitro experiments with purified recombinant CYP46A1 indicated that CYP46A1 is activated by l-glutamate (l-Glu), l-aspartate, γ-aminobutyric acid, and acetylcholine, with l-Glu eliciting the highest increase (3-fold) in CYP46A1-mediated cholesterol 24-hydroxylation. We also found that l-Glu and other activating neurotransmitters bind to the same site on the CYP46A1 surface, which differs from the EFV-binding site. The other principal differences between EFV and l-Glu in CYP46A1 activation include an apparent lack of l-Glu binding to the P450 active site and different pathways of signal transduction from the allosteric site to the active site. EFV and l-Glu similarly increased the CYP46A1 k_cat, the rate of the "fast" phase of the enzyme reduction by the redox partner NADPH-cytochrome P450 oxidoreductase, and the amount of P450 reduced. Spectral titrations with cholesterol, in the presence of EFV or l-Glu, suggest that water displacement from the heme iron can be affected in activator-bound CYP46A1. Moreover, EFV and l-Glu synergistically activated CYP46A1. Collectively, our in vitro data, along with those from previous cell culture and in vivo studies by others, suggest that l-Glu-induced CYP46A1 activation is of physiological relevance.

Conformational Changes in Active and Inactive States of Human PP2Cα Characterized by Hydrogen/Deuterium Exchange-Mass Spectrometry

PPM serine/threonine protein phosphatases function in signaling pathways and require millimolar concentrations of Mn²⁺ or Mg²⁺ ions for activity. Whereas the crystal structure of human PP2Cα displayed two tightly bound Mn²⁺ ions in the active site, recent investigations of PPM phosphatases have characterized the binding of a third, catalytically essential metal ion. The binding of the third Mg²⁺ to PP2Cα was reported to have millimolar affinity and to be entropically driven, suggesting it may be structurally and catalytically important. Here, we report the use of hydrogen/deuterium exchange-mass spectrometry and molecular dynamics to characterize conformational changes in PP2Cα between the active and inactive states. In the presence of millimolar concentrations of Mg²⁺, metal-coordinating residues in the PP2Cα active site are maintained in a more rigid state over the catalytically relevant time scale of 30-300 s. Submillimolar Mg²⁺ concentrations or introduction of the D146A mutation increased the conformational mobility in the Flap subdomain and in buttressing helices α1 and α2. Residues 192-200, located in the Flap subdomain, exhibited the greatest interplay between effects of Mg²⁺ concentration and the D146A mutation. Molecular dynamics simulations suggest that the presence of the third metal ion and the D146A mutation each produce distinct conformational realignments in the Flap subdomain. These observations suggest that the binding of Mg²⁺ to the D146/D239 binding site stabilizes the conformation of the active site and the Flap subdomain.

Cytochrome P450 27A1 Deficiency and Regional Differences in Brain Sterol Metabolism Cause Preferential Cholestanol Accumulation in the Cerebellum

Cytochrome P450 27A1 (CYP27A1 or sterol 27-hydroxylase) is a ubiquitous, multifunctional enzyme catalyzing regio- and stereospecific hydroxylation of different sterols. In humans, complete CYP27A1 deficiency leads to cerebrotendinous xanthomatosis or nodule formation in tendons and brain (preferentially in the cerebellum) rich in cholesterol and cholestanol, the 5α-saturated analog of cholesterol. In Cyp27a1^-/- mice, xanthomas are not formed, despite a significant cholestanol increase in the brain and cerebellum. The mechanism behind cholestanol production has been clarified, yet little is known about its metabolism, except that CYP27A1 might metabolize cholestanol. It also is unclear why CYP27A1 deficiency results in preferential cholestanol accumulation in the cerebellum. We hypothesized that cholestanol might be metabolized by CYP46A1, the principal cholesterol 24-hydroxylase in the brain. We quantified sterols along with CYP27A1 and CYP46A1 in mouse models (Cyp27a1^-/-, Cyp46a1^-/-, Cyp27a1^-/-Cyp46a1^-/-, and two wild type strains) and human brain specimens. In vitro experiments with purified P450s were conducted as well. We demonstrate that CYP46A1 is involved in cholestanol removal from the brain and that several factors contribute to the preferential increase in cholestanol in the cerebellum arising from CYP27A1 deficiency. These factors include (i) low cerebellar abundance of CYP46A1 and high cerebellar abundance of CYP27A1, the lack of which probably selectively increases the cerebellar cholestanol production; (ii) spatial separation in the cerebellum of cholesterol/cholestanol-metabolizing P450s from a pool of metabolically available cholestanol; and (iii) weak cerebellar regulation of cholesterol biosynthesis. We identified a new physiological role of CYP46A1, an important brain enzyme and cytochrome P450 that could be activated pharmacologically.

A new approach to quantification of mAb aggregates using peptide affinity probes

Using mAbs as therapeutic molecules is complicated by the propensity of mAbs to aggregate at elevated concentrations, which can lead to a variety of adverse events in treatment. Here, we describe a proof-of-concept for new methodology to detect and quantify mAb aggregation. Assay development included using an aggregated mAb as bait for screening of phage display peptide library and identifying those peptides with random sequence which can recognize mAb aggregates. Once identified, the selected peptides can be used for developing quantitative methods to assess mAb aggregation. Results indicate that a peptide binding method coupled with mass spectrometric detection of bound peptide can quantify mAb aggregation and potentially be useful for monitoring aggregation propensity of therapeutic protein candidates.

Mapping of the Allosteric Site in Cholesterol Hydroxylase CYP46A1 for Efavirenz, a Drug That Stimulates Enzyme Activity

Cytochrome P450 46A1 (CYP46A1) is a microsomal enzyme and cholesterol 24-hydroxylase that controls cholesterol elimination from the brain. This P450 is also a potential target for Alzheimer disease because it can be activated pharmacologically by some marketed drugs, as exemplified by efavirenz, the anti-HIV medication. Previously, we suggested that pharmaceuticals activate CYP46A1 allosterically through binding to a site on the cytosolic protein surface, which is different from the enzyme active site facing the membrane. Here we identified this allosteric site for efavirenz on CYP46A1 by using a combination of hydrogen-deuterium exchange coupled to MS, computational modeling, site-directed mutagenesis, and analysis of the CYP46A1 crystal structure. We also mapped the binding region for the CYP46A1 redox partner oxidoreductase and found that the allosteric and redox partner binding sites share a common border. On the basis of the data obtained, we propose the mechanism of CYP46A1 allostery and the pathway for the signal transmission from the P450 allosteric site to the active site.

Quantification of Borrelia burgdorferi Membrane Proteins in Human Serum: A New Concept for Detection of Bacterial Infection

The Borrelia burgdorferi spirochete is the causative agent of Lyme disease, the most common tick-borne disease in the United States. The low abundance of bacterial proteins in human serum during infection imposes a challenge for early proteomic detection of Lyme disease. To address this challenge, we propose to detect membrane proteins released from bacteria due to disruption of their plasma membrane triggered by the innate immune system. These membrane proteins can be separated from the bulk of serum proteins by high-speed centrifugation causing substantial sample enrichment prior to targeted protein quantification using multiple reaction monitoring mass spectrometry. This new approach was first applied to detection of B. burgdorferi membrane proteins supplemented in human serum. Our results indicated that detection of B. burgdorferi membrane proteins, which are ≈10(7) lower in abundance than major serum proteins, is feasible. Therefore, quantitative analysis was also carried out for serum samples from three patients with acute Lyme disease. We were able to demonstrate the detection of ospA, the major B. burgdorferi lipoprotein at the level of 4.0 fmol of ospA/mg of serum protein. The results confirm the concept and suggest that the proposed approach can be expanded to detect other bacterial infections in humans, particularly where existing diagnostics are unreliable.

Histone post-translational modifications in frontal cortex from human donors with Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the sixth leading cause of death and the most costly disease in the US. Despite the enormous impact of AD, there are no treatments that delay onset or stop disease progression currently on the market. This is partly due to the complexity of the disease and the largely unknown pathogenesis of sporadic AD, which accounts for the vast majority of cases. Epigenetics has been implicated as a critical component to AD pathology and a potential "hot spot" for treatments. Histone post-translational modifications (PTMs) are a key element in epigenetic regulation of gene expression and are known to be associated with the pathology of numerous diseases. Investigation of histone PTMs can help elucidate AD pathology and identify targets for therapies.

RESULTS

A multiple reaction monitoring mass spectrometry assay was used to measure changes in abundance of several histone PTMs in frontal cortex from human donors affected with AD (n = 6) and age-matched, normal donors (n = 6). Of the changes observed, notable decreases in methylation of H2B residue K108 by 25 % and H4 residue R55 by 35 % were measured and are likely associated with hydrogen bonding networks important for nucleosome stability. Additionally, a 91 % increase in ubiquitination of K120 on H2B was measured as well as an apparent loss in acetylation of the region near the N-terminus of H4. Our method of quantification was also determined to be precise and robust, signifying measured changes were representative of true biological differences between donors and sample groups.

CONCLUSION

We are the first to report changes in methylation of H2B K108, methylation of H4 R55, and ubiquitination of H2B K120 in frontal cortex from human donors with AD. These notable PTM changes may be of great importance in elucidating the epigenetic mechanism of AD as it relates to disease pathology. Beyond the structural and functional impacts of the changes we have measured, the sites of altered PTMs may be used to identify enzymes responsible for their modulation, which could be used as prospective drug targets for highly specific AD therapies.

Histone H3 Ser57 and Thr58 phosphorylation in the brain of 5XFAD mice

Alzheimer's disease has been shown to have a global reduction in gene expression, called an epigenetic blockade, which may be regulated by histone post-translational modifications. Histone H3 has been shown to be highly regulated by phosphorylation. We, therefore, chose H3 for investigation of phosphorylation of the core sites serine-57 (S57) and threonine-58 (T58). Hemispheres of brains from a mouse model of rapid amyloid deposition (5XFAD) were used for measurement of S57 and T58 phosphorylation. Multiple reaction monitoring (MRM) was used to measure the level of phosphorylation, which was normalized to a non-modified "housekeeping" peptide of H3. S57 phosphorylation was decreased by 40%, T58 phosphorylation was decreased by 45%, and doubly phosphorylated S57pT58p was decreased by 30% in 5XFAD brain in comparison to C57BL/6J age- and sex-matched wild type controls. Amyloid-β (Aβ) and amyloid precursor protein were also measured to confirm that 5XFAD mice produced high levels of Aβ. Decreased phosphorylation of these sites in close proximity to DNA may lead to stabilization of DNA-histone interactions and a condensed chromatin state, consistent with the epigenetic blockade associated with AD. Our findings of H3 sites S57 and T58 exhibiting lower levels of phosphorylation in 5XFAD model compared to wild type control implicate these sites in the epigenetic blockade in neurodegeneration pathology.

Cell-interactive alginate hydrogels for bone tissue engineering

There is significant interest in the development of injectable carriers for cell transplantation to engineer bony tissues. In this study, we hypothesized that adhesion ligands covalently coupled to hydrogel carriers would allow one to control pre-osteoblast cell attachment, proliferation, and differentiation. Modification of alginate with an RGD-containing peptide promoted osteoblast adhesion and spreading, whereas minimal cell adhesion was observed on unmodified hydrogels. Raising the adhesion ligand density increased osteoblast proliferation, and a minimum ligand density (1.5-15 femtomoles/cm2) was needed to elicit this effect. MC3T3-E1 cells demonstrated increased osteoblast differentiation with the peptide-modified hydrogels, as confirmed by the up-regulation of bone-specific differentiation markers. Further, transplantation of primary rat calvarial osteoblasts revealed statistically significant increases of in vivo bone formation at 16 and 24 weeks with G4RGDY-modified alginate compared with unmodified alginate. These findings demonstrate that biomaterials may be designed to control bone development from transplanted cells.

Degradation of partially oxidized alginate and its potential application for tissue engineering

Alginate has been widely used in a variety of biomedical applications including drug delivery and cell transplantation. However, alginate itself has a very slow degradation rate, and its gels degrade in an uncontrollable manner, releasing high molecular weight strands that may have difficulty being cleared from the body. We hypothesized that the periodate oxidation of alginate, which cleaves the carbon-carbon bond of the cis-diol group in the uronate residue and alters the chain conformation, would result in promoting the hydrolysis of alginate in aqueous solutions. Alginate, oxidized to a low extent (approximately 5%), degraded with a rate depending on the pH and temperature of the solution. This polymer was still capable of being ionically cross-linked with calcium ions to form gels, which degraded within 9 days in PBS solution. Finally, the use of these degradable alginate-derived hydrogels greatly improved cartilage-like tissue formation in vivo, as compared to alginate hydrogels.

Treatment of head and neck melanoma, lentigo maligna subtype: a practical surgical technique

Melanoma with the lentigo maligna histological pattern often provides a significant and difficult challenge to the head and neck surgeon. The lentigo maligna subtype is the most common type of melanoma on the head and neck. This potentially lethal form of cancer is associated with greater nonvisual lesional extension that is often not clinically apparent. Failure to excise the entire lesion results in a higher risk of local recurrence and a poorer prognosis. The staged excision technique described herein results in histological interpretation of 100% of the peripheral margins using formalin-fixed vertical sections. Definitive local excision and soft tissue reconstruction are performed in a subsequent stage, with an assurance that 100% of the peripheral margins have been evaluated and interpreted as free of disease.

Studies of the interactions between melatonin and 2 Hz, 0.3 mT PEMF on the proliferation and invasion of human breast cancer cells

Interactions between the hormone melatonin at pharmacological concentrations (10(-3) M) and 2 Hz, 0.3 mT pulsed electromagnetic fields (PEMF) on the proliferation and invasion of human breast cancer cells were studied in vitro. Three types of human breast cancer cells were used in this study: MDA-MB-435, MDA-MB-231, and MCF-7. Results showed that cellular growth of MDA-MB-231 cells, which were reported to be lowly metastatic, and MCF-7 cells, which were reported to be nonmetastatic, were both significantly reduced by melatonin regardless of the presence of the field. Results also showed that MDA-MB-435 and MDA-MB-231 cells were invasive, with MDA-MB-231 cells being more invasive than the MDA-MB-435 cells for both unexposed and experimental-PEMF groups. In addition, invasion studies showed that MCF-7 cells were not invasive and that melatonin did not have any effects on the invasion of these cells, with or without the PEMF. It is also suggested that since metastasis requires growth and invasion into tissue, anti-invasion agents can be used in conjunction with melatonin to prevent formation of secondary metastases. The overall studies suggest that PEMF at 2 Hz, 0.3 mT does not influence cancer metastasis; while having clinical merit in the healing of soft tissue injury, this field has shown no influence on cancer cells as 60 Hz power line fields have.

Cognitive versus behavior therapy in the group treatment of obsessive-compulsive disorder

This study examined the effects of cognitive-behavior therapy (CBT) compared with traditional behavior therapy (exposure and response prevention [ERP]) in the group treatment of obsessive-compulsive disorder. Of the 76 participants who started treatment, 38 were wait-listed for 3 months before treatment to assess possible course effects. Both treatments were superior to the control condition in symptom reduction, with ERP being marginally more effective than CBT by end of treatment and again at 3-month follow-up. In terms of clinically significant improvement, treatment groups were equivalent on the conclusion of treatment, but 3 months later significantly more ERP participants met criteria for recovered status. Only 1 of 7 belief measures changed with treatment improvement, and the extent of this cognitive change was similar between CBT and ERP groups. Discussion includes consideration of optimal formats for the delivery of different types of treatment.

Detection of biotin in individual sea urchin oocytes using a bioluminescence binding assay

The ability to detect biomolecules in single cells is important in order to fully understand the processes by which many biochemical events occur. To that end, we have developed a bioluminescence binding assay capable of measuring the intracellular biotin content of individual cells. The assay depends on competition between an aequorin-biotin conjugate (AEQ-biotin) and free biotin within the oocytes for binding sites on the protein avidin. The assay is performed by microinjecting each component into the oocytes and following the resulting bioluminescence within the oocyte upon triggering of aequorin. Results obtained using sea urchin oocytes show that the assay performed within the cells behaves in a manner consistent with assay theory. Using the assay, the individual biotin content of the oocytes is an average of approximately 20 amol. To our knowledge, this is the first reported multicomponent binding assay to be performed inside an intact single cell.

Controlled growth factor release from synthetic extracellular matrices

Polymeric matrices can be used to grow new tissues and organs, and the delivery of growth factors from these matrices is one method to regenerate tissues. A problem with engineering tissues that exist in a mechanically dynamic environment, such as bone, muscle and blood vessels, is that most drug delivery systems have been designed to operate under static conditions. We thought that polymeric matrices, which release growth factors in response to mechanical signals, might provide a new approach to guide tissue formation in mechanically stressed environments. Critical design features for this type of system include the ability to undergo repeated deformation, and a reversible binding of the protein growth factors to polymeric matrices to allow for responses to repeated stimuli. Here we report a model delivery system that can respond to mechanical signalling and upregulate the release of a growth factor to promote blood vessel formation. This approach may find a number of applications, including regeneration and engineering of new tissues and more general drug-delivery applications.

Adhesion of nonmetastatic and highly metastatic breast cancer cells to endothelial cells exposed to shear stress

The mechanical stimulus of shear stress has to date been neglected when studying the adhesion of cancer cells to the endothelium. Confluent monolayers of endothelial cells were subjected to either 4 or 15 hours of arterial shear stress. Adhesion of nonmetastatic (MCF-7) and highly metastatic (MDA-MB-435) human breast cancer cells was then quantified using a detachment assay carried out inside the parallel plate flow chamber. Four hours of shear stress exposure had no effect on adhesion. However, 15 hours of shear stress exposure led to marked changes in the ability of the endothelial monolayer to bind human breast cancer cells. An increase in adhesive strength was observed for nonmetastatic MCF-7 cells, while a decrease in adhesive strength was observed for highly metastatic MDA-MB-435 cells. Hence, endothelial shear stress stimulation does influence the adhesion of cancer cells to the endothelium and can have different effects on the adhesion of cancer cells with different metastatic potentials. Furthermore, adhesion of nonmetastatic and highly metastatic human breast cancer cells may be controlled by two different endothelial cell adhesion molecules that are differentially regulated by shear stress. Immunohistochemistry confirmed that shear stress did in fact differentially regulate endothelial cell adhesion molecule expression.

Development of binding assays in microfabricated picoliter vials: an assay for biotin

A homogeneous binding assay for the detection of biotin in picoliter vials was developed using the photoprotein aequorin as the label. The binding assay was based on the competition of free biotin with biotinylated aequorin (AEQ-biotin) for avidin. A sequential protocol was used, and modification of the assay to reduce the number of steps was examined. Results showed that detection limits on the order of 10(-14) mol of biotin were possible. Reducing the number of steps provided similar detection limits but only if the amount of avidin used was decreased. These binding assays based on picoliter volumes have potential applications in a variety of fields, including microanalysis and single-cell analysis, where the amount of sample is limited. In addition, these assays are suitable for the high-throughput screening of biopharmaceuticals.

Role of metastatic potential in the adhesion of human breast cancer cells to endothelial monolayers

To gain further insight into the process of metastasis, adhesion to endothelial monolayers was compared for a nonmetastatic and a highly metastatic human breast cancer cell line. The parallel plate flow chamber was employed to quantify adhesion using an attachment assay. This assay was carried out at several physiological shear stresses both with and without endothelial TNF-alpha stimulation. At a venular shear stress of 1 dyne cm-2, the nonmetastatic cell line was more adhesive to stimulated endothelial monolayers, while no differences could be noted for resting monolayers. At a lower shear stress of 0.25 dynes cm-2, the highly metastatic cell line was more adhesive to stimulated endothelial monolayers, while the nonmetastatic cell line was more adhesive to resting monolayers. Thus, metastatic potential correlated with attachment only at low shear stresses and following endothelial stimulation. These results emphasize the importance of studying cancer cell adhesion under multiple physiological flow conditions. Furthermore, these results indicate that adhesion of these two cell lines may be controlled by two different mechanisms. Antibody blocking experiments of adhesion molecules on the endothelial cells confirmed that adhesion of the nonmetastatic cell line was mediated by E-selectin expressed on the endothelial cells and adhesion of the highly metastatic cell line was mediated by both E-selectin and VCAM-1 expressed on the endothelial cells.

Controlled layer-by-layer immobilization of horseradish peroxidase

Horseradish peroxidase (HRP) was biotinylated with biotinamidocaproate N-hydroxysuccinimide ester (BcapNHS) in a controlled manner to obtain biotinylated horseradish peroxidase (Bcap-HRP) with two biotin moieties per enzyme molecule. Avidin-mediated immobilization of HRP was achieved by first coupling avidin on carboxy-derivatized polystyrene beads using a carbodiimide, followed by the attachment of the disubstituted biotinylated horseradish peroxidase from one of the two biotin moieties through the avidin-biotin interaction (controlled immobilization). Another layer of avidin can be attached to the second biotin on Bcap-HRP, which can serve as a protein linker with additional Bcap-HRP, leading to a layer-by-layer protein assembly of the enzyme. Horseradish peroxidase was also immobilized directly on carboxy-derivatized polystyrene beads by carbodiimide chemistry (conventional method). The reaction kinetics of the native horseradish peroxidase, immobilized horseradish peroxidase (conventional method), controlled immobilized biotinylated horseradish peroxidase on avidin-coated beads, and biotinylated horseradish peroxidase crosslinked to avidin-coated polystyrene beads were all compared. It was observed that in solution the biotinylated horseradish peroxidase retained 81% of the unconjugated enzyme's activity. Also, in solution, horseradish peroxidase and Bcap-HRP were inhibited by high concentrations of the substrate hydrogen peroxide. The controlled immobilized horseradish peroxidase could tolerate much higher concentrations of hydrogen peroxide and, thus, it demonstrates reduced substrate inhibition. Because of this, the activity of controlled immobilized horseradish peroxidase was higher than the activity of Bcap-HRP in solution. It is shown that a layer-by-layer assembly of the immobilized enzyme yields HRP of higher activity per unit surface area of the immobilization support compared to conventionally immobilized enzyme.

Comparative evaluation of culture and PCR for the detection and determination of persistence of bacterial strains and DNAs in the Chinchilla laniger model of otitis media

This study was designed to determine the persistence of culturable bacteria versus DNA in the presence of a middle ear effusion in a chinchilla model of otitis media. Cohorts of animals were either infected with an ampicillin-resistant Haemophilus influenzae strain or injected with a tripartite inoculum consisting of freeze-thawed Streptococcus pneumoniae; pasteurized Moraxella catarrhalis; and DNA from H influenzae. The H influenzae-infected animals displayed culture positivity and polymerase chain reaction positivity through day 35. In the chinchillas infected with the low-copy number inocula of S pneumoniae, DNA was not detectable after day 1 from the co-inoculated pasteurized M catarrhalis bacteria or the purified H influenzae DNA; however, amplifiable DNA from the live low-copy number bacteria persisted through day 21 even though they were not culture-positive past day 3. These results demonstrate that DNA, and DNA from intact but nonviable bacteria, does not persist in an amplifiable form for more than a day in the presence of an effusion; however, live bacteria, while not culturable, persist in a viable state for weeks.

Detecting biomolecules in picoliter vials using aequorin bioluminescence

The quantitative determination of proteins in picoliter-volume vials is described. The assay is based on the bioluminescence of the photoprotein aequorin along with photon-counting detection. Using this approach, avidin can be detected at femtomole levels by taking advantage of its inhibitory effect on the bioluminescence signal generated by biotinylated recombinant aequorin. The picoliter vials were fabricated on glass substrates using a laser ablation technique. Parameters that affect the reproducibility of the assay such as the fabrication and calibration of the pipets, the fabrication of the vials, and the composition of the assay solutions were studied.

Cognitive restructuring in the treatment of social phobia. Efficacy and mode of action

Cognitive restructuring (CR) is commonly used to treat social phobia, although its contribution to treatment efficacy has not been established. CR requires the person to think about and discuss feared social events with his or her therapist and thus entails some degree of exposure to social stimuli. CR also is thought to enhance the efficacy of therapeutic exposure exercises (EXP). Four predictions were tested based on this model: Relative to a control intervention matched for the exposure inherent in CR, CR is more effective in (1) reducing social phobia, (2) reducing negative social cognitions, (3) increasing positive cognitions, and (4) enhancing the effects of subsequent EXP. People with generalized social phobia (N = 60) were randomly assigned to CR followed by EXP or to a control intervention followed by EXP. Support was found for predictions 1 to 3, but not 4.

Calibration of micropipets using the bioluminescent protein aequorin

A new method for calibrating micropipets and determining accurate injection volumes using a pressure-based injector has been developed. This method employs the bioluminescent protein aequorin and can be used to determine injection volumes as small as 3 pL. The calibration plots are linear over at least 3 orders of magnitude. In contrast to conventional micropipet calibration methods that employ fluorescent molecules, the present method produces small background signals.

Determination of the extent of protein biotinylation by fluorescence binding assay

A method was developed to determine the total amount of biotin present in biotinylated protein conjugates. Conjugates of bovine serum albumin, alkaline phosphatase, and horseradish peroxidase were used in this case study. The extent of biotinylation was determined by complete acid hydrolysis or by enzymatic digestion using proteinase K to release biotin from the biotinylated proteins, followed by sensitive detection of biotin using a coupled HPLC-binding assay system. This detection system is based on the enhancement of the fluorescence of streptavidin-FITC by biotin. The extent of biotinylation determined by this method was compared with the values obtained by a conventional colorimetric method that is based on the displacement of the dye 4-hydroxyazobenzene-2-carboxylic acid (HABA) from the binding sites of avidin. It was found that, because the described method determines the amount of liberated biotin after hydrolysis, it does not suffer from steric hindrance problems associated with the ability of biotin on a protein surface to displace HABA from avidin. Therefore, this method can provide a more accurate determination of the extent of biotinylation. It was also determined that the acid hydrolysis of the biotinylated protein was more effective in releasing the conjugated biotin compared to enzymatic digestion by proteinase K.

Empirical analysis of factors in depressive cognition: the cognitive triad inventory

The purpose of this study was to examine the factor analytic evidence for the three components of Beck's cognitive triad (view of self, world, and future). Two hundred sixty college undergraduates participated in the study. Factor analytic results indicated that the three scales of the CTI generate five factors, which represent positively phrased "future" items, negatively phrased "future" items, positively phrased "world" items, negatively phrased "world" items, and positively phrased "self" items. The negatively phrased "self" items were distributed among the negatively phrased "world" and negatively phrased "future" factors. These findings partially support the utility of categorizing depressogenic cognitions into three constructs (self, world, and future) and also the notion that different cognitive operations or response styles may be elicited from positive vs. negative items.

Preincubation of endotoxin with monoclonal anti-lipid A (E5), but not in vivo treatment, inhibits circulatory dysfunction

Monoclonal antibodies (mAb) directed against the toxic lipid A portion of lipopolysaccharide (LPS) have been shown to bind lipid A in vitro, but clinical trials of such mAbs have yielded mixed results. In 53 rats instrumented for macrocirculatory and cremaster muscle microcirculatory measurements, we examined whether E5, a murine-derived anti-lipid A mAb, could inhibit LPS-induced circulatory dysfunction when incubated with LPS in vitro or given separately in vivo prior to LPS administration. Compared with Control rats (Group I), rats infused with 10 mg/kg Escherichia coli LPS (Group II) displayed marked decreases in arterial pressure and cardiac output and marked decreases in erythrocyte velocity in second, third, and fourth order skeletal muscle arterioles. Infusion of 2 mg/kg E5 90 min prior to LPS infusion (Group III) did not improve cardiovascular performance. In contrast, incubation of LPS with either 2 mg/kg (Group IV) or 10 mg/kg (Group V) E5 prior to infusion significantly attenuated LPS-induced changes in both macrocirculatory and microcirculatory function. Further investigation of the disparity between the in vitro and in vivo neutralizing capacity of anti-lipid A mAbs may aid interpretation of the variable clinical results achieved with these preparations.

Research methods for investigating causal relations between SLE disease variables and psychiatric symptomatology

People with systemic lupus erythematosus (SLE) frequently experience psychiatric problems. Some researchers and clinicians presume that these psychiatric problems are a direct manifestation of the disease, while others suggest that psychosocial and environmental factors have greater etiological significance. The majority of the studies addressing these issues in patients with SLE are too methodologically limited to make confident conclusions regarding etiology. More methodologically sound research in this area is needed. This article describes some of the limitations in past research in the areas of sampling, measurement, research design, data analyses and data presentation. Suggestions for improved methodology in future research are offered.

Molecular analysis of bacterial pathogens in otitis media with effusion

OBJECTIVE

To determine if the polymerase chain reaction (PCR) can detect bacterial DNA in pediatric middle ear effusions that are sterile by standard cultural methods.

DESIGN

Single-center, blinded, comparative study of diagnostic assays. The PCR-based detection systems for Moraxella catarrhalis, Haemophilus influenzae, and Streptococcus pneumoniae were designed and validated using a battery of DNAs obtained from cultured bacteria. Chronic middle ear effusion specimens were collected and comparatively analyzed by culture and the PCR.

SETTING

Tertiary care pediatric hospital.

PATIENTS

A total of 97 middle ear effusions were collected from pediatric outpatients at Children's Hospital of Pittsburgh (Pa) during myringotomy and tube placement for chronic otitis media with effusion (duration > 3 months). All patients had failed multiple courses of antimicrobial therapy and were diagnosed by a combination of validated otoscopy and tympanograms.

MAIN OUTCOME MEASURE

Differences in the percentage of positive test results between PCR-based assays and culture for M catarrhalis, H influenzae, and S pneumoniae.

RESULTS

Of the 97 specimens of otitis media with effusion, 28 (28.9%) tested positive by both culture and PCR for M catarrhalis, H influenzae, or S pneumoniae. An additional 47 specimens (48%) were PCR positive/culture negative for these three bacterial species. Thus, 75 (77.3%) of the 97 specimens tested PCR positive for one or more of the three test organisms. The minimum number of bacterial genomic equivalents present in the average culture-negative ear was estimated to be greater than 10(4) based on dilutional experiments.

CONCLUSIONS

The PCR-based assay systems can detect the presence of bacterial DNA in a significant percentage of culturally sterile middle ear effusions. While this finding is not proof of an active bacterial infectious process, the large number of bacterial genomic equivalents present in the ears is suggestive of an active process.

Combination therapy with zidovudine prevents selection of human immunodeficiency virus type 1 variants expressing high-level resistance to L-697,661, a nonnucleoside reverse transcriptase inhibitor

L-697,661 is a human immunodeficiency virus type 1 (HIV-1)-specific nonnucleoside reverse transcriptase (RT) inhibitor. Its tolerability and activity in combination with zidovudine were evaluated in a 48-week double-blind study. One hundred nineteen zidovudine-naive HIV-1-infected patients with CD4 cell counts of 200-500/mm3 received either combination therapy, L-697,661 alone, or zidovudine alone. Activity was assessed by CD4 cell count changes. Selection for L-697,661-resistant virus was monitored by susceptibility testing of RT expressed by circulating viral RNA. Therapy was generally well tolerated. All groups receiving zidovudine exhibited transient increases in CD4 cell counts, while the L-697,661 monotherapy group showed a significant decline and yielded RT > 100-fold resistant to L-697,661 and associated with substitutions at RT residue 181. The RT from patients receiving combination therapy was maximally 15-fold less susceptible to L-697,661. Hence, cotreatment with zidovudine prevents selection of HIV-1 variants that are highly resistant to L-697,661 in patients naive to both compounds.

Detachment of transformed cells. Role of CD44 variants

A parallel-plate flow chamber was used to quantify the detachment of normal cloned rat embryo fibroblasts (CREF) fibroblasts, ras-transformed CREF fibroblasts (CREF T24), and CREF T24 fibroblasts transfected with a Krev/RAP1A suppressor gene (HK B1) from a confluent monolayer of normal CREF fibroblasts to determine if the expression patterns of CD44 variants (mol wt 110 and 140 kDa) corresponded with detachment properties and metastatic potential. In the detachment assay, known shear stresses ranging from 20-24 dyn/cm2 were applied to the adherent cells and the number of cells detached from the monolayer after 180 s was determined. Results showed that cellular expression of CD44 variants correlated with the metastatic potential of the cells and with the cells' ability to detach from a monolayer of normal cells. Western blot analysis showed a low level of expression of the CD44 variants in the normal cell line, CREF, and the lowly metastatic cell line, HK B1. Detachment studies showed a low percentage of detachment of both of these cell lines from a normal cell monolayer. Tumor-derived (HK B1-T) and lung nodule-derived (HK B1-M) cell lines were established and both formed tumors and metastasis with reduced latency periods as compared to HK B1, but still showed a markedly delayed latency period compared to the highly metastatic cell line, CREF T24. Both of these cell lines showed a higher expression of the CD44 variants as compared to CREF and HK B1, and detached easier than CREF and HK B1. CREF T24 showed a much higher level of expression of the variants and had a higher percentage detachment than all other cell lines. To further test the role of the CD44 variants in the ability of the cells to detach from the normal monolayer, CREF cells were transfected with a DNA construct that constitutively expresses the CD44 variants and the detachment properties of three randomly selected clones were studied. Clones 2 and 3 showed a low level of expression of the CD44 variants after transfection and detached from the normal monolayer similar to CREF. Clone 1 showed a high level of expression of the CD44 variants and the detachment of these cells was significantly higher than CREF. From these results, it is concluded that in the five cell lines studied, expression of the CD44 variants play a significant role in the ability of the cells to detach from a monolayer of normal cells. It is hypothesized that this detachment may be an important component of a cell's ability to metastasize.

Effect of lipopolysaccharide, leukocytes, and monoclonal anti-lipid A antibodies on erythrocyte membrane elastance

The micropipette aspiration technique was used to quantify membrane deformability of individual red blood cells (RBCs) before and after exposing whole blood and blood free of leukocytes to lipopolysaccharide (LPS). The ability of an anti-lipid A monoclonal antibody (E5) to inhibit the effects of LPS was also investigated. In the LPS/whole blood studies, a significant increase in elasticity modulus was observed following incubation with LPS. An increase in elasticity modulus indicates a decrease in RBC membrane deformability. The effect depended on the incubation time but was not concentration-dependent in the range studied (25, 40, or 170 micrograms/mL). When incubating blood free of leukocytes with LPS, the elasticity moduli of erythrocytes did not change. Results also showed that preincubation of the LPS with E5 prior to incubation with whole blood partially inhibited the effect of LPS, suggesting a possible mechanism of the beneficial actions of monoclonal antibodies in septic shock.

Effect of lipopolysaccharide on the physical conformation of the erythrocyte cytoskeletal proteins

Red blood cell deformability is important for effective circulation in the capillaries. It is known that red cell deformability is significantly reduced during septic shock. Surface to volume ratio, physical effects of the cytoskeletal proteins and the fluidity of lipid bilayer are some of the important intrinsic factors that regulate this mechanical function. Alterations in the physical conformation of cytoskeletal proteins in septic conditions could significantly alter their function. In this study, erythrocytes in whole blood were treated with lipopolysaccharide, the outer covering of Gram-negative bacteria released during Gram-negative sepsis. Electron paramagnetic resonance spectroscopy in conjunction with a protein-specific maleimide nitroxide spin label covalently bound to cytoskeletal proteins was used to investigate the resulting changes occurring in the physical state of cytoskeletal proteins in isolated membranes. Treatment of red blood cells with a lipopolysaccharide concentration as low as 40 micrograms/mL of blood solution for 90 minutes showed a significant decrease in the relevant EPR parameter (p < 0.01) of the spin label bound to subsequently isolated membranes, suggestive of a decreased segmental motion of the spin label and an increase in cytoskeletal protein-protein interactions. These results suggest a marked conformational alteration in the cytoskeletal proteins induced by the lipopolysaccharide and may explain, in part, the marked reduction in red blood cell deformability during septic shock. Bacterial lipopolysaccharide does not exert most of its effects on the host directly, but rather elicits the production of host factors that leads to complex septic shock. Leukocytes, endothelial tissue and many other cells release these mediators. Leukocytes are thought to be a particularly important source of such mediators, including cytokines (tumor necrosis factor, interleukins, etc.), oxygen free radicals, proteases, and hydrolyses. In order to characterize the possible mechanism by which the lipopolysaccharide acts on the physical state of the erythrocyte cytoskeleton, erythrocytes void of leukocytes and plasma were treated with lipopolysaccharide. The relevant EPR parameter showed no significant change over the control value. These results indicate that the leukocytes and their factors are responsible for the rearrangements seen in the cytoskeletal proteins of the erythrocyte membrane.

Effect of endotoxin on lipid order and motion in erythrocyte membranes

Electron paramagnetic resonance employing a lipid-specific spin label has been used to investigate the molecular effects of endotoxin on the physical state of bilayer lipids in rat erythrocyte membranes. When added at a concentration as low as 40 micrograms/ml to whole blood (plasma plus leukocytes present), decreased membrane lipid motion was found in subsequently washed and spin-labeled intact erythrocytes (P < 0.02). However, if endotoxin were added to washed, plasma plus leukocyte-free intact erythrocytes, no change in the motion of the spin label was found, suggesting that plasma-soluble substances and/or leukocytes are required to produce the change in the physical state of lipids. The decreased lipid motion found in these studies is discussed with reference to the known decreased deformability of endotoxin-treated red cells and to the pathogenesis of sepsis.

The etiology of psychiatric symptoms in patients with systemic lupus erythematosus

The purpose of this review was to explore the probable etiologies of psychiatric problems in patients with SLE. Although instances of psychosis generally are attributed to disease pathophysiology, the precise mechanism for this problem remains speculative. The etiology of non-psychotic psychiatric complaints is even less clear. Overall, it is likely that psychiatric complaints in patients with SLE are attributable to numerous factors including acquired brain dysfunction, organ system dysfunction, iatrogenic effects of corticosteroid treatment, learning history, psychosocial stressors, and current coping strategies. Additional research is needed to explore the bi-directional, synergistic, and dynamic interactions among diverse physiological and psychological variables as they impact an individual's psychiatric status.