Modulation of release and pharmacokinetics from nanoscale lipid prodrugs of dexamethasone with variable linkage chemistry.

In an attempt to tune drug release and subsequent pharmacokinetics once administered intravenously, we have synthesized three lipid-drug conjugates (LDCs) of dexamethasone (DXM) each possessing a different lipid-drug chemical linkage: namely ester, carbamate and carbonate. These LDCs were thoroughly characterized before being turned into nanoscale particles by an emulsion-evaporation process using DSPE-PEG2000 (Distearoyl-sn-Glycero-3-Phosphoethanolamine-N-(methoxy(polyethylene glycol)-2000) as the only excipient. Spherical nanoparticles (NPs) of about 140-170 nm, with a negative zeta potential, were obtained for each LDC and exhibited good stability upon storage at 4 °C for 45 days with no recrystallization of LDCs observed. LDC encapsulation efficacy was above 95% for the three LDCs, leading to a LDC loading of about 90% and an equivalent DXM loading above 50%. Although the ester and carbonate NPs did not exhibit any toxicity up to an equivalent DXM concentration of 100 µg/mL, the carbamate LDC NPs appeared very toxic towards RAW 264.7 macrophages and were discarded. Both ester and carbonate LDC NPs were shown to exert anti-inflammatory activity on LPS-activated macrophages. DXM release from LDC NPs in murine plasma was faster from ester than from carbonate NPs. Finally, pharmacokinetics and biodistribution were conducted, showing a lower exposure to DXM from carbonate LDC NPs than from ester LDC NPs, correlated with the slower DXM release from carbonate LDC NPs. These results outline the need for extended studies to find the best prodrug system for extended drug release.

Genome Analysis of a Variant of Streptomyces coelicolor M145 with High Lipid Content and Poor Ability to Synthetize Antibiotics.

Streptomyces coelicolor M145 is a model strain extensively studied to elucidate the regulation of antibiotic biosynthesis in Streptomyces species. This strain abundantly produces the blue polyketide antibiotic, actinorhodin (ACT), and has a low lipid content. In a process designed to delete the gene encoding the isocitrate lyase (sco0982) of the glyoxylate cycle, an unexpected variant of S. coelicolor was obtained besides bona fide sco0982 deletion mutants. This variant produces 7- to 15-fold less ACT and has a 3-fold higher triacylglycerol and phosphatidylethanolamine content than the original strain. The genome of this variant was sequenced and revealed that 704 genes were deleted (9% of total number of genes) through deletions of various sizes accompanied by the massive loss of mobile genetic elements. Some deletions include genes whose absence could be related to the high total lipid content of this variant such as those encoding enzymes of the TCA and glyoxylate cycles, enzymes involved in nitrogen assimilation as well as enzymes belonging to some polyketide and possibly trehalose biosynthetic pathways. The characteristics of this deleted variant of S. coelicolor are consistent with the existence of the previously reported negative correlation existing between lipid content and antibiotic production in Streptomyces species.

In vitro Raman imaging of human macrophages: Impact of eicosapentaenoic acid on the hydrolysis of cholesterol esters in lipid droplets.

Atherosclerosis - a cardiovascular disease and the primary cause of morbidity and mortality in industrialized countries - is linked to the existence of atherosclerotic plaques characterized by cholesterol-laden macrophages called foam cells. In these cells, cholesterol esters associated with triglycerides form lipid droplets (LD). The only way to remove this excess cholesterol is to promote free cholesterol efflux from macrophages to specific acceptors. It has been shown recently that eicosapentaenoic acid (EPA) reduces efflux on cholesterol-loaded THP-1 macrophages in vitro due to decreased cholesterol esters hydrolysis. These in vitro observations could reflect EPA's difficulty in facilitating in vivo the antiatherogenic process of cholesterol efflux within advanced atherosclerotic plaques. This work aims to study in vitro the impact of EPA on cholesterol esters hydrolysis in the LD of human THP-1 macrophages using vibrational Raman microspectroscopy. For this, we used deuterated EPA and recorded spectral images at the cell scale after different hydrolysis times. RESULTS: showed that EPA is involved in forming triglycerides and phospholipids of LD. Hydrolysis kinetics slowed down after 24 h, triglycerides increased, and the intensity of the characteristic bands linked to deuteration decreased. The size of LD without hydrolysis (H0) is higher than that after 24 h (H1) or 48 h (H2) of hydrolysis. The size decrease is sharper when going from H0 to H1 than from H1 to H2. Principal component analysis illustrated data' projection according to the cellular compartment, the hydrolysis time, and the supplementation of the medium.

Lipid Readjustment in Yarrowia lipolytica Odd-Chain Fatty Acids Producing Strains.

Yarrowia lipolytica is a promising oleaginous yeast for producing unusual lipids, such as odd-chain fatty acids (OCFA). Their diverse applications and low natural production make OCFA particularly interesting. In recent studies, inhibiting the catabolic pathway of precursor, boosting precursor pools, and optimizing substrate combination greatly improved the production of OCFA in Y. lipolytica. We explored the lipid readjustment of OCFA in engineered Y. lipolytica strains. NPLC-Corona-CAD® evidenced a time-dependent overproduction of free fatty acids, diglycerides, and phosphatidylcholine (PC) in obese LP compared to obese L. Phosphatidylethanolamine (PE) and phosphatidylinositol, largely overproduced in obese LP at 72 h compared to obese L, vanished at 216 h. The fatty acyls (FAs) composition of glycero- and glycerophospholipids was determined by NPLC-APPI+-HRMS from in-source generated monoacylglycerol-like fragment ions. C18:1 and C17:1 were predominant acylglycerols in obese L and obese LP, respectively. Phosphatidic acid, PE, and PC exhibited similar FAs composition but differed in their molecular species distributions. Cardiolipin (CL) is known to contain mostly C18:2 FAs corresponding to the composition in obese L, 50% of C18:2, and 35% of C18:1. In obese LP, both FAs dropped to drop to 20%, and C17:1 were predominant, reaching 55%. We hypothesize that CL-modified composition in obese LPs may alter mitochondrial function and limit lipid production.

Rapid assessment of fatty acyls chains of phospholipids and plasmalogens by atmospheric pressure chemical ionization in positive mode and high-resolution mass spectrometry using in-source generated monoacylglycerol like fragments intensities.

We recently published a new concept using monoacylglycerol-like fragments [MG+H-H2O]+ (ions B) produced in-source by atmospheric pressure photoionization in positive mode and high-resolution mass spectrometry for the determination of the fatty acyl (FA) composition of triacylglycerols (TGs) from plant oils. This study extends the concept to the phospholipids (PLs) category and shows that the APCI+ source can also be used. Moreover, the coupling with NP-LC allows to simultaneously analyze different PLs classes in the same sample. We compared the relative intensities of the ions B produced in-source to the % composition of FAs determined by GC-FID. In the case of PLs from natural extracts composed exclusively of diacyl-PLs, the relative intensities of ions B are close to the % of the FAs obtained by GC-FID. This approach is not directly useable for extracts containing plasmalogens (P-PLs). For these PLs, acidic hydrolysis by HCl fumes allows hydrolyzing selectively vinyl ether functions to form lyso-PLs. The analysis of hydrolyzed extracts makes it possible to obtain the composition of P-PLs FAs thanks to the lyso-PLs thus formed, while the diacyl-PLs composition remains unchanged. Unlike GC-FID FAs determination, this approach allows a distinction between the diacyl-PLs and P-PLs FAs composition. We also found that the ion B intensities were consistent among the PL classes (PG, PE, PA, PI, CL, PS and PC) and lyso- forms (LPE and LPC). In the case of the diacyl-PLs extracts analyzed, no statistically significant differences were found between the PLs FAs compositions calculated from ion B intensities and the corresponding GC-FID data. A weighting coefficient was applied to correct ion B intensities issued from polyunsaturated FAs with three or more double bonds. The fatty alkenyls composition of P-PLs could also be calculated from the % intensities of specific ions.

Mannosylation of budesonide palmitate nanoprodrugs for improved macrophage targeting.

In a strategy to improve macrophage targeting of glucocorticoids (GCs) for anti-inflammatory therapy, a so-called nanoprodrug of budesonide palmitate decorated by mannose moieties was designed. The synthesis of budesonide palmitate (BP) was obtained by esterification and mannosylated lipid (DSPE-PEG-Man) by reacting 1,2-Distearoyl-sn-Glycero-3-Phosphoethanolamine (DSPE)-polyethylene glycol-amine and α-D-mannopyranosylphenyl isothiocyanate (MPITC). Nanoparticles were formulated by emulsion-evaporation and different ratios of mannosylated lipid were introduced in the formulation of BP nanoprodrugs. Using up to 75% of DSPE-PEG-man (75/25) led to 200 nm particles with a polydispersity index below 0.2, a negative zeta potential ranging from -10 to -30 mV, and one-month stability at 4 °C. The encapsulation efficiency of BP approached 100% proving that the prodrug was associated with the particles, leading to a final BP loading of 50-to 60% (w/w). The lectin agglutination test confirmed the availability of mannose on the nanoprodrug surface. Nanoprodrug uptake by RAW 264.7 macrophages was observed by confocal microscopy and flow cytometry. After 24 and 48 h of incubation, a significantly greater internalization of mannosylated nanoparticles as compared to PEGylated nanoparticles was achieved. The mannose receptor-mediated uptake was confirmed by a mannan inhibition study. After LPS-induced inflammation, the anti-inflammatory effect of mannosylated nanoparticles was assessed. After 48 h of incubation, cytokines (MCP-1 and TNFα) were reduced demonstrating that the functionalization of nanoprodrugs is possible and efficient.

Rapid assessment of triacylglycerol fatty acyls composition by LC-APPI+-HRMS using monoacylglycerol like fragments intensities.

We present a new analytical approach for the analysis of triacylglycerol fatty acyls distribution by normal phase liquid chromatography (NPLC) coupled with APPI+-HRMS. The NPLC method used allows the separation of more than 30 classes of lipids. The energy of the APPI+ source enables the formation of low-intensity ions B fragments ([RC = O+74]+ <3%), characteristic of lipids with a glycerol esterified by one or more fatty acyls. We found the relative intensities of ions B were close to the fatty acyl distribution. To establish the proof of concept, we decided to focus on the triacylglycerols (TGs) class, the major component of plant oils. By either NPLC or FIA, the TGs class appeared as a single peak. In our experimental conditions, ions B are always present in the mass spectra of TGs and each ion B is specific to a fatty acyl group. The Orbitrap mass spectrometer featured high enough resolution and accuracy to identify ions B and distinguish them from other TG fragment ions. A further adjustment of the fatty acyls relative quantities calculation from ions B intensities was computed using weighting coefficients of ions B response. The methodology was developed and validated using plant oils characterized by a GC-FID reference method. NPLC-APPI+-HRMS method offers the advantage of analyzing the fatty acyl composition of complex lipid extracts without the need for sample preparation.

Investigation of stationary phases performance for eicosanoids profiling in RP-HPLC.

Eicosanoids - oxidative derivatives from arachidonic acid - represent biologically active lipid mediators in inflammatory processes. Different analytical methods treat eicosanoid analysis. Among which, reverse phase liquid chromatography figures as the appropriate method for eicosanoid profiling. RP-HPLC for eicosanoid analysis is often conducted on C18 columns. Some studies focused on profiling one family of eicosanoids; others considered all eicosanoid families. In both cases, co-elution remained a major issue and detection in mass spectrometry partially resolves this problem. In fact, the mass transitions used to monitor eicosanoid species are not specific enough and many isobars can be listed. For this, optimizing the RP-HPLC separation remains important. Based on the parameter Fs - deriving from the hydrophobic-subtraction model - and radar plots, we chose columns with different selectivities. The hydrophobic-subtraction model guided our interpretation of molecular interactions between eicosanoids and stationary phases. We founded our approach for selectivity optimization on peak capacity per minute and time needed values. Herein, we screened seven stationary phases and evaluated their chromatographic performances in RP-HPLC. Stationary phases presented different chemistry, type of silica, length, and particle size. Superficially porous particle columns registered better chromatographic profiles than classical stationary phases; and columns with embedded polar group did not serve our purpose. The stationary phase Accucore C30 - even being the least retentive - revealed the best selectivity and efficiency, and recorded the shorter duration for eicosanoid analysis.

Impact of Phosphate Availability on Membrane Lipid Content of the Model Strains, Streptomyces lividans and Streptomyces coelicolor.

In this issue we demonstrated that the phospholipid content of Streptomyces lividans varies greatly with Pi availability being was much lower in Pi limitation than in Pi proficiency whereas that of Streptomyces coelicolor varied little with Pi availability. In contrast the content in phosphate free ornithine lipids was enhanced in both strains in condition of phosphate limitation. Ornithine lipids biosynthesis starts with the N-acylation of ornithine to form lyso-ornithine that is then O-acylated to yield ornithine lipid. The operon sco1222-23 was proposed to be involved in the conversion of specific amino acids into ornithine in condition of phosphate limitation whereas the sco0921-20 operon encoding N- and O-acyltransferase, respectively, was shown to be involved in the biosynthesis of these lipids. The expression of these two operons was shown to be under the positive control of the two components system PhoR/PhoP and thus induced in phosphate limitation. The expression of phoR/phoP being weak in S. coelicolor, the poor expression of these operons resulted into a fivefold lower ornithine lipids content in this strain compared to S. lividans. In the deletion mutant of the sco0921-20 operon of S. lividans, lyso-ornithine and ornithine lipids were barely detectable and TAG content was enhanced. The complementation of this mutant by the sco0921-20 operon or by sco0920 alone restored ornithine lipids and TAG content to wild type level and was correlated with a twofold increase in the cardiolipin content. This suggested that SCO0920 bears, besides its broad O-acyltransferase activity, an N-acyltransferase activity and this was confirmed by the detection of lyso-ornithine in this strain. In contrast, the complementation of the mutant by sco0921 alone had no impact on ornithine lipids, TAG nor cardiolipin content but was correlated with a high lyso-ornithine content. This confirmed that SCO0921 is a strict N-acyltransferase. However, interestingly, the over-expression of the sco0921-20 operon or of sco0921 alone in S. coelicolor, led to an almost total disappearance of phosphatidylinositol that was correlated with an enhanced DAG and TAG content. This suggested that SCO0921 also acts as a phospholipase C, degrading phosphatidylinositol to indirectly supply of phosphate in condition of phosphate limitation.

New Nanoparticle Formulation for Cyclosporin A: In Vitro Assessment.

Cyclosporin A (CsA) is a molecule with well-known immunosuppressive properties. As it also acts on the opening of mitochondrial permeability transition pore (mPTP), CsA has been evaluated for ischemic heart diseases (IHD). However, its distribution throughout the body and its physicochemical characteristics strongly limit the use of CsA for intravenous administration. In this context, nanoparticles (NPs) have emerged as an opportunity to circumvent the above-mentioned limitations. We have developed in our laboratory an innovative nanoformulation based on the covalent bond between squalene (Sq) and cyclosporin A to avoid burst release phenomena and increase drug loading. After a thorough characterization of the bioconjugate, we proceeded with a nanoprecipitation in aqueous medium in order to obtain SqCsA NPs of well-defined size. The SqCsA NPs were further characterized using dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryoTEM), and high-performance liquid chromatography (HPLC), and their cytotoxicity was evaluated. As the goal is to employ them for IHD, we evaluated the cardioprotective capacity on two cardiac cell lines. A strong cardioprotective effect was observed on cardiomyoblasts subjected to experimental hypoxia/reoxygenation. Further research is needed in order to understand the mechanisms of action of SqCsA NPs in cells. This new formulation of CsA could pave the way for possible medical application.

The Inhibition of Antibiotic Production in Streptomyces coelicolor Over-Expressing the TetR Regulator SCO3201 IS Correlated With Changes in the Lipidome of the Strain.

In condition of over-expression, SCO3201, a regulator of the TetR family was previously shown to strongly inhibit antibiotic production and morphological differentiation in Streptomyces coelicolor M145. In order to elucidate the molecular processes underlying this interesting, but poorly understood phenomenon, a comparative analysis of the lipidomes and transcriptomes of the strain over-expressing sco3201 and of the control strain containing the empty plasmid, was carried out. This study revealed that the strain over-expressing sco3201 had a higher triacylglycerol content and a lower phospholipids content than the control strain. This was correlated with up- and down- regulation of some genes involved in fatty acids biosynthesis (fab) and degradation (fad) respectively, indicating a direct or indirect control of the expression of these genes by SCO3201. In some instances, indirect control might involve TetR regulators, whose encoding genes present in close vicinity of genes involved in lipid metabolism, were shown to be differentially expressed in the two strains. Direct interaction of purified His6-SCO3201 with the promoter regions of four of such TetR regulators encoding genes (sco0116, sco0430, sco4167, and sco6792) was demonstrated. Furthermore, fasR (sco2386), encoding the activator of the main fatty acid biosynthetic operon, sco2386-sco2390, has been shown to be an illegitimate positive regulatory target of SCO3201. Altogether our data demonstrated that the sco3201 over-expressing strain accumulates TAG and suggested that degradation of fatty acids was reduced in this strain. This is expected to result into a reduced acetyl-CoA availability that would impair antibiotic biosynthesis either directly or indirectly.

Negative Correlation between Lipid Content and Antibiotic Activity in Streptomyces: General Rule and Exceptions.

Streptomycetes are well known antibiotic producers and are among the rare prokaryotes able to store carbon as lipids. Previous comparative studies of the weak antibiotic producer Streptomyces lividans with its ppk mutant and with Streptomyces coelicolor, which both produce antibiotics, suggested the existence of a negative correlation between total lipid content and the ability to produce antibiotics. To determine whether such a negative correlation can be generalized to other Streptomyces species, fifty-four strains were picked randomly and grown on modified R2YE medium, limited in phosphate, with glucose or glycerol as the main carbon source. The total lipid content and antibiotic activity against Micrococcus luteus were assessed for each strain. This study revealed that the ability to accumulate lipids was not evenly distributed among strains and that glycerol was more lipogenic than glucose and had a negative impact on antibiotic biosynthesis. Furthermore, a statistically significant negative Pearson correlation between lipid content and antibiotic activity could be established for most strains, but a few strains escape this general law. These exceptions are likely due to limits and biases linked to the type of test used to determine antibiotic activity, which relies exclusively on Micrococcus luteus sensitivity. They are characterized either by high lipid content and high antibiotic activity or by low lipid content and undetectable antibiotic activity against Micrococcus luteus. Lastly, the comparative genomic analysis of two strains with contrasting lipid content, and both named Streptomyces antibioticus (DSM 41,481 and DSM 40,868, which we found to be phylogenetically related to Streptomyces lavenduligriseus), indicated that some genetic differences in various pathways related to the generation/consumption of acetylCoA could be responsible for such a difference.

Hybrid Lipid Polymer Nanoparticles for Combined Chemo- and Photodynamic Therapy.

Retinoblastoma is a malignant tumor of the retina in infants. Conventional therapies are associated to severe side effects and some of them induce secondary tumors. Photodynamic therapy (PDT) thus appears as a promising alternative as it is nonmutagenic and generates minimal side effects. The effectiveness of PDT requires the accumulation of a photosensitizer (PS) in the tumor. However, most porphyrins are hydrophobic and aggregate in aqueous medium. Their incorporation into a nanocarrier may improve their delivery to the cell cytoplasm. In this work, we designed biodegradable liponanoparticles (LNPs) consisting of a poly(d,l)-lactide (PDLLA) nanoparticle coated with a phospholipid (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1,2-dioleoyl-3-trimethylammonium-propane) bilayer. An anticancer drug, beta-lapachone (ß-Lap) and a PS, m-THPC, were co-encapsulated for combined chemo- and PDT because it has been suggested that they may have a synergistic effect based on the activation of ß-Lap by PDT-induced over-expression of the enzyme NQO1. Using dynamic light scattering measurements, cryogenic transmission electron microscopy, and fluorescence confocal microscopy, we selected the appropriate conditions for the encapsulation of the compounds. LNPs were internalized in retinoblastoma cells within few hours. No obvious synergistic effect related to the activation of ß-Lap by PDT was observed. Conversely, the LNPs were cytotoxic at lower doses of the two encapsulated compounds as compared to the single therapies. Analysis of the combinatorial treatment showed that PDT and chemotherapy had an additive effect on the viability of retinoblastoma cells.

Nanoscale Lipophilic Prodrugs of Dexamethasone with Enhanced Pharmacokinetics.

The encapsulation of glucocorticoids, such as dexamethasone, in nanoparticles (NPs) faces two main issues: a low drug loading and the destabilization of the nanoparticle suspension due to drug crystallization. Here, we successfully formulated a prodrug of dexamethasone, dexamethasone palmitate (DXP), into nanoparticles stabilized by the sole presence of distearoyl- sn-glycero-3-phosphoethanolamine- N-[methoxy(poly(ethylene glycol))-2000] (DSPE-PEG2000). Two formulation processes, nanoprecipitation and emulsion-evaporation, allowed the formation of stable nanoparticles. By adjusting the drug/lipid ratio and the DXP concentration, nanoparticles of DXP (DXP-NPs) with a size between 130 and 300 nm can be obtained. Owing to the presence of DSPE-PEG2000, a high drug entrapment efficiency of 98% w/w was reached for both processes, corresponding to a very high equivalent dexamethasone drug loading of around 50% w/w in the absence of crystallization upon storage at 4 °C. The anti-inflammatory activity of DXP-NPs was preserved when incubated with macrophages activated with lipopolysaccharide. Pharmacokinetics parameters were evaluated after intravenous (IV) injection of DXP-NPs to healthy mice. The release of DXM from DXP-NPs in plasma was clearly controlled up to 18 h compared with the free drug, which was rapidly eliminated from plasma after administration. In conclusion, a novel type of nanoparticle combining the advantages of prodrugs and nanoparticles was designed, easy to produce with a high loading efficiency and leading to modified pharmacokinetics and tissue distribution after IV administration.

Investigation of lipid modifications in J774 macrophages by vibrational spectroscopies after eicosapentaenoic acid membrane incorporation in unloaded and cholesterol-loaded cells.

Atherosclerosis is an inflammatory disease of the arterial wall caused by the formation of an atheroma plaque in the vessel wall. The uptake of modified LDL lipoproteins by sub-endothelial macrophages induces the latter's transformation into foam cells, which is the key step of atheroma plaque formation. The modifications of neutral lipids caused by foam cells formation are marked by the appearance of lipid droplets. Polyunsaturated fatty acids (PUFAs) incorporation into membrane phospholipids (PL) modifies their composition, which may influence membrane protein functions. The incorporation of eicosapentaenoic acid (EPA) reduces the anti-atherogenic ABCA1 (ATP Binding Cassette transporter A1) pathway and induces PLs modifications. In order to study lipids directly in the cell environment, a comparative study is conducted by vibrational spectroscopies on murine macrophages J774, loaded or not with cholesterol, which were enriched or not with eicosapentaenoic acid (EPA). The study enabled to identify changes in the spectral signature after cells enrichment with fatty acid (FA) relying only on chemometric analysis without deuterium labelling. Results highlighted spectral changes in the regions attributed to lipids associated to triglycerides, phospholipids and cholesterol in both Raman and IR.

Dexamethasone palmitate nanoparticles: An efficient treatment for rheumatoid arthritis.

Rheumatoid arthritis (RA) is a prevalent autoimmune disease characterized by joint inflammation, bone and cartilage erosion. The use of glucocorticoids in the treatment of RA is hampered by significant side effects induced by their unfavorable pharmacokinetics. Delivering glucocorticoids by means of nanotechnologies is promising but the encapsulation of highly crystalline and poorly water-soluble drugs results in poor loading and low stability. We report here the design of 130 nm nanoparticles made of solely dexamethasone palmitate, stabilized by polyethylene glycol-linked phospholipids displaying a negative zeta potential (-55 mV), high entrapment efficiency and stability over 21 days under storage at 4 °C. X ray diffraction showed no crystallization of the drug. When incubated in serum, nanoparticles released free dexamethasone which explains the in vitro anti-inflammatory effect on LPS-activated RAW 264.7 macrophages. Moreover, we demonstrate in a murine collagen-induced arthritis model the improved therapeutic efficacy of these nanoparticles. Their passive accumulation in arthritic joints leads to disease remission and recovery of the joint structure at a dose of 1 mg/kg dexamethasone, without any adverse effects. Dexamethasone palmitate nanoparticles are promising in the treatment of inflammation in rheumatoid arthritis with a very significant difference occurring at the late stage of inflammation allowing to prevent the progression of the disease.

Optimization of classification and regression analysis of four monoclonal antibodies from Raman spectra using collaborative machine learning approach.

The use of monoclonal antibodies (mAbs) constitutes one of the most important strategies to treat patients suffering from cancers such as hematological malignancies and solid tumors. These antibodies are prescribed by the physician and prepared by hospital pharmacists. An analytical control enables the quality of the preparations to be ensured. The aim of this study was to explore the development of a rapid analytical method for quality control. The method used four mAbs (Infliximab, Bevacizumab, Rituximab and Ramucirumab) at various concentrations and was based on recording Raman data and coupling them to a traditional chemometric and machine learning approach for data analysis. Compared to conventional linear approach, prediction errors are reduced with a data-driven approach using statistical machine learning methods. In the latter, preprocessing and predictive models are jointly optimized. An additional original aspect of the work involved on submitting the problem to a collaborative data challenge platform called Rapid Analytics and Model Prototyping (RAMP). This allowed using solutions from about 300 data scientists in collaborative work. Using machine learning, the prediction of the four mAbs samples was considerably improved. The best predictive model showed a combined error of 2.4% versus 14.6% using linear approach. The concentration and classification errors were 5.8% and 0.7%, only three spectra were misclassified over the 429 spectra of the test set. This large improvement obtained with machine learning techniques was uniform for all molecules but maximal for Bevacizumab with an 88.3% reduction on combined errors (2.1% versus 17.9%).

Rapid analysis of glutamate, glutamine and GABA in mice frontal cortex microdialysis samples using HPLC coupled to electrospray tandem mass spectrometry.

In vivo measurement of multiple neurotransmitters is highly interesting but remains challenging in the field of neuroscience. GABA and l-glutamic acid are the major inhibitory and excitatory neurotransmitters, respectively, in the central nervous system, and their changes are related to a variety of diseases such as anxiety and major depressive disorder. This study described a simple method allowing the simultaneous LC-MS/MS quantification of l-glutamic acid, glutamine and GABA. Analytes were acquired from samples of the prefrontal cortex by microdialysis technique in freely moving mice. The chromatographic separation was performed by hydrophilic interaction liquid chromatography (HILIC) with a core-shell ammonium-sulfonic acid modified silica column using a gradient elution with mobile phases consisting of a 25 mM pH 3.5 ammonium formate buffer and acetonitrile. The detection of l-glutamic acid, glutamine and GABA, as well as the internal standards [d6]-GABA and [d5]-glutamate was performed on a triple quadrupole mass spectrometer in positive electrospray ionization and multiple reaction monitoring mode. The limit of quantification was 0.63 ng/ml for GABA, 1.25 ng/ml for l-glutamic acid and 3.15 ng/ml for glutamine, and the intra-day and inter-day accuracy and precision have been assessed for the three analytes. Therefore, the physiological relevance of the method was successfully applied for the determination of basal extracellular levels and potassium-evoked release of these neuroactive substances in the prefrontal cortex in adult awake C57BL/6 mice.

Optimization of normal phase chromatographic conditions for lipid analysis and comparison of associated detection techniques.

One important challenge in lipid class analysis is to develop a method suitable or, at least adaptable, for a vast diversity of samples. In the current study, an improved normal-phase liquid chromatography (NPLC) method allowed analyzing the lipid classes present in mammalian, vegetable as well as microorganism (yeast and bacteria) lipid samples. The method effectively separated 30 lipid classes or subclasses with a special focus on medium polarity lipids. The separation was carried out with bare silica stationary phase and was coupled to evaporative light scattering detection (ELSD), charged aerosol detection (Corona-CAD®) and mass spectrometry. Solutions are provided to circumvent technical issues (such as pumping solvents of low viscosity, solvent purity, rinsing step). The influence of mobile phase composition and addition of ionic modifiers on the chromatographic behavior of particular lipid classes is documented. A comparison between ELSD and Corona-CAD® confirmed the interest of this later detector for samples with a wide range of concentration of different lipids. Three common atmospheric pressure ionization interfaces were used for coupling the NPLC separation to a LTQ Velos Pro® mass spectrometer. The comparison of the chromatographic profiles showed that atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) are both suitable to detect the different lipid classes whereas APPI allows a better sensitivity for lipids at low-concentration.

Eicosapentaenoic acid membrane incorporation impairs cholesterol efflux from cholesterol-loaded human macrophages by reducing the cholesteryl ester mobilization from lipid droplets.

A diet containing a high n-3/n-6 polyunsaturated fatty acids (PUFA) ratio has cardioprotective properties. PUFAs incorporation into membranes influences the function of membrane proteins. We investigated the impact of the membrane incorporation of PUFAs, especially eicosapentaenoic acid (EPA) (C20:5 n-3), on the anti-atherogenic cholesterol efflux pathways. We used cholesteryl esters (CE)-loaded human monocyte-derived macrophages (HMDM) to mimic foam cells exposed to the FAs for a long period of time to ensure their incorporation into cellular membranes. Phospholipid fraction of EPA cells exhibited high levels of EPA and its elongation product docosapentaenoic acid (DPA) (C22:5 n-3), which was associated with a decreased level of arachidonic acid (AA) (C20:4 n-6). EPA 70µM reduced ABCA1-mediated cholesterol efflux to apolipoprotein (apo) AI by 30% without any alteration in ABCA1 expression. The other tested PUFAs, DPA, docosahexaenoic acid (DHA) (C22:6 n-3), and AA, were also able to reduce ABCA1 functionality while the monounsaturated oleic FA slightly decreased efflux and the saturated palmitic FA had no impact. Moreover, EPA also reduced cholesterol efflux to HDL mediated by the Cla-1 and ABCG1 pathways. EPA incorporation did not hinder efflux in free cholesterol-loaded HMDM and did not promote esterification of cholesterol. Conversely, EPA reduced the neutral hydrolysis of cytoplasmic CE by 24%. The reduced CE hydrolysis was likely attributed to the increase in cellular TG contents and/or the decrease in apo E secretion after EPA treatment. In conclusion, EPA membrane incorporation reduces cholesterol efflux in human foam cells by reducing the cholesteryl ester mobilization from lipid droplets.