Pharmacological Enhancement of Adult Hippocampal Neurogenesis Improves Behavioral Pattern Separation in Young and Aged Mice.

BACKGROUND: Impairments in behavioral pattern separation (BPS)-the ability to distinguish between similar contexts or experiences-contribute to memory interference and overgeneralization seen in many neuropsychiatric conditions, including depression, anxiety, PTSD, dementia, and age-related cognitive decline. While BPS relies on the dentate gyrus and is sensitive to changes in adult hippocampal neurogenesis (AHN), its significance as a pharmacological target has not been tested. METHODS: In this study, we applied a human neural stem cell high-throughput screening cascade to identify compounds that increase human neurogenesis. One compound with a favorable profile, RO6871135, was then tested in BPS in mice. RESULTS: Chronic treatment with RO6871135, 7.5 mg/kg increased AHN and improved BPS in a fear discrimination task in both young and aged mice. RO6871135 treatment also lowered innate anxiety-like behavior, which was more apparent in mice exposed to chronic corticosterone. Ablation of AHN by hippocampal irradiation supported a neurogenesis-dependent mechanism for RO6871135-induced improvements in BPS. To identify possible mechanisms of action, in vitro and in vivo kinase inhibition and chemical proteomics assays were performed. These tests indicated that RO6871135 inhibited CDK8, CDK11, CaMK2a, CaMK2b, MAP2K6, and GSK3b. An analog compound also demonstrated high affinity for CDK8, CaMK2a, and GSK3b. CONCLUSIONS: These studies demonstrate a method for empirical identification and preclinical testing of novel neurogenic compounds that can improve BPS, and points to possible novel mechanisms that can be interrogated for the development of new therapies to improve specific endophenotypes such as impaired BPS.

Impact of non-ionizable lipids and phase mixing methods on structural properties of lipid nanoparticle formulations.

Lipid nanoparticles (LNPs) have been widely investigated for nucleic acid therapeutic delivery, and demonstrated their potential in enabling new mRNA vaccines. LNPs are usually formulated with multi-lipid components and the composition variables may impact their structural properties. Here, we investigated the impact of helper lipids on physicochemical properties of LNPs using a Design of Experiments (DoE) definitive screening design. Phospholipid head group, degree of unsaturation, ratio to cholesterol as well as PEG-lipid content were varied and a series of 14 LNPs were prepared by microfluidic- and solvent-injection mixing. Solvent-injection mixing by a robotic liquid handler yielded 50-225 nm nanoparticles with highly ordered, ∼5 nm inter-lamellar spacing as measured by small angle X-ray scattering (SAXS) and confirmed by cryo-transmission electron microscopy (cryo-EM). In contrast, microfluidic mixing resulted in less ordered, notably smaller (50-75 nm) and more homogenous nanoparticles. Significant impacts of the stealth-lipid DSPE-PEG2000 on nanoparticle size, polydispersity and encapsulation efficiency of an oligonucleotide cargo were observed in LNPs produced by both methods, while varying the phospholipid type and content had only marginal effect on these physicochemical properties. These findings suggest that from a physicochemical perspective, the design space for combinations of helper lipids in LNPs may be considerably larger than anticipated based on the conservative formulation composition of the currently FDA-approved LNPs, thereby opening opportunities for screening and optimization of novel LNP formulations.

An Improved Impact Ratio for Identifying Critical Process Parameters in Pharmaceutical Manufacturing Processes.

The identification of critical process parameters in biologics and small molecule process development is a key element of quality by design. The objectivity and consistency of procedures to identify critical process parameters can be improved with the use of impact ratios. Impact ratios quantify a process parameter's practical effect on a critical quality attribute relative to the critical quality attribute's acceptance limits. If the impact ratio is large, i.e., exceeds a predefined impact ratio threshold, the recommendation is to classify the process parameter as a critical process parameter. This article introduces an improved and mathematically well-defined impact ratio. Benefits of this impact ratio are a consistent interpretation for many scenarios commonly encountered in practice, high suitability to automation, and the possibility of standardizing on a single impact ratio definition for pharmaceutical manufacturing.

Symmetric signal transduction and negative allosteric modulation of heterodimeric mGlu1/5 receptors.

For a long time metabotropic glutamate receptors (mGluRs) were thought to regulate neuronal functions as obligatory homodimers. Recent reports, however, indicate the existence of heterodimers between group-II and -III mGluRs in the brain, which differ from the homodimers in their signal transduction and sensitivity to negative allosteric modulators (NAMs). Whether the group-I mGluRs, mGlu1 and mGlu5, form functional heterodimers in the brain is still a matter of debate. We now show that mGlu1 and mGlu5 co-purify from brain membranes and hippocampal tissue and co-localize in cultured hippocampal neurons. Complementation assays with mutants deficient in agonist-binding or G protein-coupling reveal that mGlu1/5 heterodimers are functional in heterologous cells and transfected cultured hippocampal neurons. In contrast to heterodimers between group-II and -III mGluRs, mGlu1/5 receptors exhibit a symmetric signal transduction, with both protomers activating G proteins to a similar extent. NAMs of either protomer in mGlu1/5 receptors partially inhibit signaling, showing that both protomers need to be able to reach an active conformation for full receptor activity. Complete heterodimer inhibition is observed when both protomers are locked in their inactive state by a NAM. In summary, our data show that mGlu1/5 heterodimers exhibit a symmetric signal transduction and thus intermediate signaling efficacy and kinetic properties. Our data support the existence of mGlu1/5 heterodimers in neurons and highlight differences in the signaling transduction of heterodimeric mGluRs that influence allosteric modulation.

A Risk Index and Data Display for Process Performance in the Pharmaceutical Industry.

We propose a new index and graphical display for quantifying and visualizing process performance in the pharmaceutical industry. These tools can provide management a comprehensive, high level overview of the process performance of a global manufacturing network suitable for risk ranking, by which is meant: identifying those processes at greatest risk of failing to meet specifications, and prioritizing resources to drive continuous process improvement. Our index, like others currently in use, compares the observed variation of CQAs-critical quality attributes-to their specifications. However, instead of relying on traditional data summaries such as means and standard deviations to characterize process results, the proposed index uses sample quantiles. Quantiles are more accurate and reliable when data are skewed or short-tailed as is often observed for pharmaceutical processes. Perhaps just as important, we communicate the results with a new visual display that accurately compares processes and sites. The display identifies instances when the summaries may mislead and the subject matter expert needs to "drill down" into manufacturing data to assure correct understanding.LAY ABSTRACT: The proposed risk index and graphical display enables high-risk processes to be identified, process improvements to be prioritized, resources to be efficiently allocated, and strategic planning for continuous process improvement to be evidence-based.

Binding to SMN2 pre-mRNA-protein complex elicits specificity for small molecule splicing modifiers.

Small molecule splicing modifiers have been previously described that target the general splicing machinery and thus have low specificity for individual genes. Several potent molecules correcting the splicing deficit of the SMN2 (survival of motor neuron 2) gene have been identified and these molecules are moving towards a potential therapy for spinal muscular atrophy (SMA). Here by using a combination of RNA splicing, transcription, and protein chemistry techniques, we show that these molecules directly bind to two distinct sites of the SMN2 pre-mRNA, thereby stabilizing a yet unidentified ribonucleoprotein (RNP) complex that is critical to the specificity of these small molecules for SMN2 over other genes. In addition to the therapeutic potential of these molecules for treatment of SMA, our work has wide-ranging implications in understanding how small molecules can interact with specific quaternary RNA structures.

Remodeling of plasma lipoproteins in patients with rheumatoid arthritis: Interleukin-6 receptor-alpha inhibition with tocilizumab.

PURPOSE: Rheumatoid arthritis (RA) is associated with increased cardiovascular risk, mediated in part by elevated circulating interleukin-6 levels and proinflammatory changes in plasma lipoproteins. We hypothesized that RA patients acquire inflammation-induced modifications to the protein cargo of circulating lipoproteins that may be reversed by tocilizumab, an interleukin-6 receptor-alpha inhibitor. EXPERIMENTAL DESIGN: Size-exclusion chromatography and reverse-phase protein arrays using 29 antibodies against 26 proteins were applied at baseline and after tocilizumab treatment to analyze the distributions of apolipoproteins, enzymes, lipid transfer proteins, and other associated proteins in plasma lipoprotein fractions from 20 women with RA. RESULTS: A 30% reduction in high-density lipoprotein (HDL)-associated serum amyloid A4 and complement C4 occurred with tocilizumab. Levels of C-reactive protein, associated or comigrating with HDL and low-density lipoprotein (LDL) peaks, were reduced on treatment by approximately 80% and 24%, respectively. Reductions in lipoprotein-associated phospholipase A2, lipoprotein (a), and cholesteryl ester transfer protein in the LDL fraction suggest reductions in LDL-associated proatherogenic factors. Elevations in very low-density lipoprotein (VLDL) enriched with apolipoprotein E were equally observed. CONCLUSIONS AND CLINICAL RELEVANCE: Tocilizumab treatment led to reductions in proinflammatory components and proatherogenic proteins associated with HDL. Whether changes in the proteome of VLDL, LDL, and HDL induced by anti-inflammatory tocilizumab treatment in RA patients modify cardiovascular disease risk requires further investigation.

Factors Governing the Precision of Subvisible Particle Measurement Methods - A Case Study with a Low-Concentration Therapeutic Protein Product in a Prefilled Syringe.

PURPOSE: The current study was performed to assess the precision of the principal subvisible particle measurement methods available today. Special attention was given to identifying the sources of error and the factors governing analytical performance. METHODS: The performance of individual techniques was evaluated using a commercial biologic drug product in a prefilled syringe container. In control experiments, latex spheres were used as standards and instrument calibration suspensions. RESULTS: The results reported in this manuscript clearly demonstrated that the particle measurement techniques operating in the submicrometer range have much lower precision than the micrometer size-range methods. It was established that the main factor governing the relatively poor precision of submicrometer methods in general and inherently, is their low sampling volume and the corresponding large extrapolation factors for calculating final results. CONCLUSIONS: The variety of new methods for submicrometer particle analysis may in the future support product characterization; however, the performance of the existing methods does not yet allow for their use in routine practice and quality control.

Quantification of HER2 by Targeted Mass Spectrometry in Formalin-Fixed Paraffin-Embedded (FFPE) Breast Cancer Tissues.

The ability to accurately quantify proteins in formalin-fixed paraffin-embedded tissues using targeted mass spectrometry opens exciting perspectives for biomarker discovery. We have developed and evaluated a selectedreaction monitoring assay for the human receptor tyrosine-protein kinase erbB-2 (HER2) in formalin-fixed paraffin-embedded breast tumors. Peptide candidates were identified using an untargeted mass spectrometry approach in relevant cell lines. A multiplexed assay was developed for the six best candidate peptides and evaluated for linearity, precision and lower limit of quantification. Results showed a linear response over a calibration range of 0.012 to 100 fmol on column (R(2): 0.99-1.00).The lower limit of quantification was 0.155 fmol on column for all peptides evaluated. The six HER2 peptides were quantified by selected reaction monitoring in a cohort of 40 archival formalin-fixed paraffin-embedded tumor tissues from women with invasive breast carcinomas, which showed different levels of HER2 gene amplification as assessed by standard methods used in clinical pathology. The amounts of the six HER2 peptides were highly and significantly correlated with each other, indicating that peptide levels can be used as surrogates of protein amounts in formalin-fixed paraffin-embedded tissues. After normalization for sample size, selected reaction monitoring peptide measurements were able to correctly predict 90% of cases based on HER2 amplification as defined by the American Society of Clinical Oncology and College of American Pathologists. In conclusion, the developed assay showed good analytical performance and a high agreement with immunohistochemistry and fluorescence in situ hybridization data. This study demonstrated that selected reaction monitoring allows to accurately quantify protein expression in formalin-fixed paraffin-embedded tissues and represents therefore a powerful approach for biomarker discovery studies. The untargeted mass spectrometry data is available via ProteomeXchange whereas the quantification data by selected reaction monitoring is available on the Panorama Public website.

Quantitative ADME proteomics - CYP and UGT enzymes in the Beagle dog liver and intestine.

PURPOSE: Beagle dogs are used to study oral pharmacokinetics and guide development of drug formulations for human use. Since mechanistic insight into species differences is needed to translate findings in this species to human, abundances of cytochrome P450 (CYP) and uridine diphosphate glucuronosyltransferase (UGT) drug metabolizing enzymes have been quantified in dog liver and intestine. METHODS: Abundances of enzymes were measured in Beagle dog intestine and liver using selected reaction monitoring mass spectrometry. RESULTS: Seven and two CYPs were present in the liver and intestine, respectively. CYP3A12 was the most abundant CYP in both tissues. Seven UGT enzymes were quantified in the liver and seven in the intestine although UGT1A11 and UGT1A9 were present only in the intestine and UGT1A7 and UGT2B31 were found only in the liver. UGT1A11 and UGT1A2 were the most abundant UGTs in the intestine and UGT2B31 was the most abundant UGT in the liver. Summed abundance of UGT enzymes was similar to the sum of CYP enzymes in the liver whereas intestinal UGTs were up to four times more abundant than CYPs. The estimated coefficients of variation of abundance estimates in the livers of 14 donors were separated into biological and technical components which ranged from 14 to 49% and 20 to 39%, respectively. CONCLUSIONS: Abundances of canine CYP enzymes in liver and intestine have been confirmed in a larger number of dogs and UGT abundances have been quantified for the first time. The biological variability in hepatic CYPs and UGTs has also been estimated.

A novel immuno-competitive capture mass spectrometry strategy for protein-protein interaction profiling reveals that LATS kinases regulate HCV replication through NS5A phosphorylation.

Mapping protein-protein interactions is essential to fully characterize the biological function of a protein and improve our understanding of diseases. Affinity purification coupled to mass spectrometry (AP-MS) using selective antibodies against a target protein has been commonly applied to study protein complexes. However, one major limitation is a lack of specificity as a substantial part of the proposed binders is due to nonspecific interactions. Here, we describe an innovative immuno-competitive capture mass spectrometry (ICC-MS) method to allow systematic investigation of protein-protein interactions. ICC-MS markedly increases the specificity of classical immunoprecipitation (IP) by introducing a competition step between free and capturing antibody prior to IP. Instead of comparing only one experimental sample with a control, the methodology generates a 12-concentration antibody competition profile. Label-free quantitation followed by a robust statistical analysis of the data is then used to extract the cellular interactome of a protein of interest and to filter out background proteins. We applied this new approach to specifically map the interactome of hepatitis C virus (HCV) nonstructural protein 5A (NS5A) in a cellular HCV replication system and uncovered eight new NS5A-interacting protein candidates along with two previously validated binding partners. Follow-up biological validation experiments revealed that large tumor suppressor homolog 1 and 2 (LATS1 and LATS2, respectively), two closely related human protein kinases, are novel host kinases responsible for NS5A phosphorylation at a highly conserved position required for optimal HCV genome replication. These results are the first illustration of the value of ICC-MS for the analysis of endogenous protein complexes to identify biologically relevant protein-protein interactions with high specificity.

Automated sample preparation platform for mass spectrometry-based plasma proteomics and biomarker discovery.

The identification of novel biomarkers from human plasma remains a critical need in order to develop and monitor drug therapies for nearly all disease areas. The discovery of novel plasma biomarkers is, however, significantly hampered by the complexity and dynamic range of proteins within plasma, as well as the inherent variability in composition from patient to patient. In addition, it is widely accepted that most soluble plasma biomarkers for diseases such as cancer will be represented by tissue leakage products, circulating in plasma at low levels. It is therefore necessary to find approaches with the prerequisite level of sensitivity in such a complex biological matrix. Strategies for fractionating the plasma proteome have been suggested, but improvements in sensitivity are often negated by the resultant process variability. Here we describe an approach using multidimensional chromatography and on-line protein derivatization, which allows for higher sensitivity, whilst minimizing the process variability. In order to evaluate this automated process fully, we demonstrate three levels of processing and compare sensitivity, throughput and reproducibility. We demonstrate that high sensitivity analysis of the human plasma proteome is possible down to the low ng/mL or even high pg/mL level with a high degree of technical reproducibility.

Development of a 5-plex SILAC method tuned for the quantitation of tyrosine phosphorylation dynamics.

The propagation of phosphorylation downstream of receptor tyrosine kinases is a key dynamic cellular event involved in signal transduction, which is often deregulated in disease states such as cancer. Probing phosphorylation dynamics is therefore crucial for understanding receptor tyrosine kinases' function and finding ways to inhibit their effects. MS methods combined with metabolic labeling such as stable isotope labeling with amino acids in cell culture (SILAC) have already proven successful in deciphering temporal phosphotyrosine perturbations. However, they are limited in terms of multiplexing, and they also are time consuming, because several experiments need to be performed separately. Here, we introduce an innovative approach based on 5-plex SILAC that allows monitoring of phosphotyrosine signaling perturbations induced by a drug treatment in one single experiment. Using this new labeling strategy specifically tailored for phosphotyrosines, it was possible to generate the time profiles for 318 unique phosphopeptides belonging to 215 proteins from an erlotinib-treated breast cancer cell line model. Hierarchical clustering of the time profiles followed by pathway enrichment analysis highlighted epidermal growth factor receptor (EGFR or ErbB1) and ErbB2 signaling as the major pathways affected by erlotinib, thereby validating the method. Moreover, based on the similarity of its time profile to those of other proteins in the ErbB pathways, the phosphorylation at Tyr453 of protein FAM59A, a recently described adaptor of EGFR, was confirmed as tightly involved in the signaling cascade. The present investigation also demonstrates the remote effect of EGFR inhibition on ErbB3 phosphorylation sites such as Tyr1289 and Tyr1328, as well as a potential feedback effect on Tyr877 of ErbB2. Overall, the 5-plex SILAC is a straightforward approach that extends sample multiplexing and builds up the arsenal of methods for tyrosine phosphorylation dynamics.

Multiple protein analysis of formalin-fixed and paraffin-embedded tissue samples with reverse phase protein arrays.

Reverse-phase protein arrays (RPPAs) have become an important tool for the sensitive and high-throughput detection of proteins from minute amounts of lysates from cell lines and cryopreserved tissue. The current standard method for tissue preservation in almost all hospitals worldwide is formalin fixation and paraffin embedding, and it would be highly desirable if RPPA could also be applied to formalin-fixed and paraffin embedded (FFPE) tissue. We investigated whether the analysis of FFPE tissue lysates with RPPA would result in biologically meaningful data in two independent studies. In the first study on breast cancer samples, we assessed whether a human epidermal growth factor receptor (HER) 2 score based on immunohistochemistry (IHC) could be reproduced with RPPA. The results showed very good concordance between the IHC and RPPA classifications of HER2 expression. In the second study, we profiled FFPE tumor specimens from patients with adenocarcinoma and squamous cell carcinoma in order to find new markers for differentiating these two subtypes of non-small cell lung cancer. p21-activated kinase 2 could be identified as a new differentiation marker for squamous cell carcinoma. Overall, the results demonstrate the technical feasibility and the merits of RPPA for protein expression profiling in FFPE tissue lysates.

Quantitative chemical proteomics profiling differentiates erlotinib from gefitinib in EGFR wild-type non-small cell lung carcinoma cell lines.

Although both erlotinib and gefitinib target the EGF receptor (EGFR), erlotinib is effective in patients with EGFR wild-type or mutated tumors, whereas gefitinib is only beneficial for patients with activating mutations. To determine whether these differences in clinical outcomes can be attributed to their respective protein interaction profiles, a label-free, quantitative chemical proteomics study was conducted. Using this method, 24 proteins were highlighted in the binding profiles of erlotinib and gefitinib. Unlike gefinitib, erlotinib displaced the ternary complex formed by integrin-linked kinase (ILK), α-parvin, and PINCH (IPP). The docking of erlotinib in the three-dimensional structure of ILK showed that erlotinib has the ability to bind to the ATP-binding site, whereas gefitinib is unlikely to bind with high affinity. As the IPP complex has been shown to be involved in epithelial-to-mesenchymal transition (EMT) and erlotinib sensitivity has been correlated with EMT status, we used a cellular model of inducible transition and observed that erlotinib prevented EMT in a more efficient way than gefitinib by acting on E-cadherin expression as well as on IPP levels. A retrospective analysis of the MERIT trial indicated that, besides a high level of E-cadherin, a low level of ILK could be linked to clinical benefit with erlotinib. In conclusion, we propose that, in an EGFR wild-type context, erlotinib may have a complementary mode of action by inhibiting IPP complex activities, resulting in the slowing down of the metastatic process of epithelial tumors.

Determination of free desmosine in human plasma and its application in two experimental medicine studies.

Elastin is one of the major extracellular matrix proteins associated with connective tissue. Its degradation leads to the liberation of the unique amino acids desmosine and isodesmosine. These have shown utility as biomarkers of elastin breakdown for disease progression, patient stratification, and drug efficacy. So far, the quantitation of desmosines in plasma is hampered by complex sample preparation. Here we demonstrate an improved and simplified procedure for detecting both free and total desmosines. The method is based on spiking with a deuterium-labeled desmosine standard, ethanol precipitation, propionylation, high-performance liquid chromatography (HPLC) separation, and selected reaction monitoring (SRM) mass spectrometry. The performance of the assay is illustrated by comparing the levels of free and total desmosines in normal healthy plasma and those from patients diagnosed with chronic obstructive pulmonary disease (COPD). A conserved ratio of 1:3 for free to total desmosine was found. The determination of free desmosine has higher accuracy than that of total desmosine; therefore, it is the method of choice when plasma volume is limiting. Finally, we show that the plasma desmosine concentration correlates with age and body mass index.

Qualitative improvement and quantitative assessment of N-terminomics.

Proteolysis represents one of the most tightly controlled physiological processes, as proteases create events that will typically commit pathways in an irreversible manner. Despite their implication in nearly all biological systems, our understanding of the role of proteases in disease pathology is often limited. Several approaches to studying proteolytic activity as it relates to biology, pathophysiology, and drug therapy have been published, including the recently described terminal amine isotopic labeling of substrates (TAILS) strategy by Kleifeld and colleagues. Here, we investigate TAILS as a methodology based on targeted enrichment and mass spectrometric detection of endogenous N-terminal peptides from clinically relevant biological samples and its potential to provide quantitative information on proteolysis and elucidation of the protease cleavage sites. While optimizing the most current protocol, by switching to a streamlined one-tube format and simplifying the reagents' removal steps, we demonstrate the advantages over previously published methods and provide solutions to some of the technical challenges presented in the Kleifeld publication. We also identify some of the current and unresolved limitations. We use human plasma as a model system to provide data, which illustrates some of the key analytical parameters of the modified TAILS procedure, including specificity, sensitivity, quantitative precision, and accuracy.

Mass spectrometry-based quantification of CYP enzymes to establish in vitro/in vivo scaling factors for intestinal and hepatic metabolism in beagle dog.

PURPOSE: Physiologically based models, when verified in pre-clinical species, optimally predict human pharmacokinetics. However, modeling of intestinal metabolism has been a gap. To establish in vitro/in vivo scaling factors for metabolism, the expression and activity of CYP enzymes were characterized in the intestine and liver of beagle dog. METHODS: Microsomal protein abundance in dog tissues was determined using testosterone-6ß-hydroxylation and 7-hydroxycoumarin-glucuronidation as markers for microsomal protein recovery. Expressions of 7 CYP enzymes were estimated based on quantification of proteotypic tryptic peptides using multiple reaction monitoring mass spectrometry. CYP3A12 and CYP2B11 activity was evaluated using selective marker reactions. RESULTS: The geometric mean of total microsomal protein was 51 mg/g in liver and 13 mg/cm in intestine, without significant differences between intestinal segments. CYP3A12, followed by CYP2B11, were the most abundant CYP enzymes in intestine. Abundance and activity were higher in liver than intestine and declined from small intestine to colon. CONCLUSIONS: CYP expression in dog liver and intestine was characterized, providing a basis for in vitro/in vivo scaling of intestinal and hepatic metabolism.

Deletion of UDP-glucose pyrophosphorylase reveals a UDP-glucose independent UDP-galactose salvage pathway in Leishmania major.

The nucleotide sugar UDP-galactose (UDP-Gal) is essential for the biosynthesis of several abundant glycoconjugates forming the surface glycocalyx of the protozoan parasite Leishmania major. Current data suggest that UDP-Gal could arise de novo by epimerization of UDP-glucose (UDP-Glc) or by a salvage pathway involving phosphorylation of Gal and the action of UDP-glucose:alpha-D-galactose-1-phosphate uridylyltransferase as described by Leloir. Since both pathways require UDP-Glc, inactivation of the UDP-glucose pyrophosphorylase (UGP) catalyzing activation of glucose-1 phosphate to UDP-Glc was expected to deprive parasites of UDP-Gal required for Leishmania glycocalyx formation. Targeted deletion of the gene encoding UGP, however, only partially affected the synthesis of the Gal-rich phosphoglycans. Moreover, no alteration in the abundant Gal-containing glycoinositolphospholipids was found in the deletion mutant. Consistent with these findings, the virulence of the UGP-deficient mutant was only modestly affected. These data suggest that Leishmania elaborates a UDP-Glc independent salvage pathway for UDP-Gal biosynthesis.

In vivo profiling of DPP4 inhibitors reveals alterations in collagen metabolism and accumulation of an amyloid peptide in rat plasma.

Dipeptidyl peptidase 4 (DPP4) inhibitors represent a novel class of oral anti-hyperglycemic agents. The complete pharmacological profile of these protease inhibitors remains unclear. In order to gain deeper insight into the in vivo effects caused by DPP4 inhibition, two different DPP4 inhibitors (vildagliptin and AB192) were analyzed using differential peptide display. Wistar rats were treated with the DPP4 inhibitors (0.3mgkg(-1); 1mgkg(-1) or 3mgkg(-1) body weight) and DPP4 activity was measured before and at the end of the experiment. One hour after compound administration, blood plasma samples were collected to generate peptide displays and to subsequently identify differentially regulated peptides. A dose-dependent decrease in blood plasma DPP4 activity was measured for both inhibitors. DPP4 inhibition influenced collagen metabolism leading to depletion of collagen derived peptides (e.g. collagen alpha 1 (III) 521-554) and accumulation of related N-terminally extended collagen derived peptides (e.g. collagen alpha 1 (III) 519-554). Furthermore, the intact amyloid rat BRI (1-23) peptide was detected in plasma following in vivo DPP4 inhibition. DPP4 catalyzed cleavage kinetics of the BRI peptide were determined in vitro. The k(cat) and K(m) for cleavage by DPP4 were 5.2s(-1) and 14microM, respectively, resulting in a specificity constant k(cat)/K(m) of 0.36 x 10(6)s(-1)M(-1). Our results demonstrate that differential peptide analysis can be applied to monitor action of DPP4 inhibition in blood plasma. For the first time effects on basal collagen metabolism following DPP4 inhibition in vivo were demonstrated and the BRI amyloid peptide was identified as a novel DPP4 substrate.