Regulatory Cell Populations in Relapsing-Remitting Multiple Sclerosis (RRMS) Patients: Effect of Disease Activity and Treatment Regimens

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) of autoimmune etiology that results from an imbalance between CNS-specific T effector cells and peripheral suppressive mechanisms mediated by regulatory cells (RC). In this research, we collected blood samples from 83 relapsing remitting MS (RRMS) patients and 45 healthy persons (HC), to assess the sizes of their RC populations, including CD4⁺CD25^highFoxp3⁺ (nTregs), CD3⁺CD4⁺HLA⁻G⁺, CD3⁺CD8⁺CD28⁻, CD3⁺CD56⁺, and CD56^bright cells, and how RC are affected by disease activity (acute phase or remission) and types of treatment (methylprednisolone, interferon, or natalizumab). In addition, we isolated peripheral blood mononuclear cells (PBMC) and cultured them with peptides mapping to myelin antigens, to determine RC responsiveness to autoantigens. The results showed decreased levels of nTregs in patients in the acute phase ± methylprednisolone and in remission + natalizumab, but HC levels in patients in remission or receiving interferon. Patients + interferon had the highest levels of CD3⁺CD4⁺HLA⁻G⁺ and CD3⁺CD8⁺CD28⁻ RC, and patients in the acute phase + methylprednisolone the lowest. Patients in remission had the highest levels of CD3⁺CD56⁺, and patients in remission + natalizumab the highest levels of CD56^bright cells. Only nTregs responded to autoantigens in culture, regardless of disease activity or treatment. The highest suppressive activity was exhibited by nTregs from patients in remission. In conclusion, in RRMS disease activity and type of treatment affect different RC populations. nTregs respond to myelin antigens, indicating that it is possible to restore immunological tolerance through nTreg induction.     

Particle Transport and Deposition under High-Frequency Oscillatory Ventilation and Normal Breathing

The fluid mechanics of high-frequency oscillatory ventilation (HFOV) for gas transport in the pulmonary region of the human lungs have been thoroughly studied by different methods. The major concept of HFOV adaptation is to push gas into further generation of the bronchial tree, with adequate gas mixing and small tidal volume. However, particle transport and deposition under HFOV is a rarely studied case where different mechanisms, compared to the mechanisms of gas transport, may associate. The target of this study is to numerically compare the efficiency of particle drug deposition under HFOV to normal breathing (NB) and to further clarify the mechanisms of particle transport and deposition under oscillating flows. A fully Eulerian computational fluid particles dynamic (CFPD) model is used for studying the transport and deposition of several sizes of inertia particles, under different transient flow conditions, inside a single physiologically realistic bifurcation created by generations G3–G4 of the human lung. An insight into the particle dynamics under high-frequency oscillating flow fields is given and the results showed that the highly oscillating field (HFOV) displayed stronger secondary flows, thinner boundary layers, and strong counter flow that accumulate and deposit particles further than a lower frequency oscillatory field (NB).

Copyright 2014 American Association for Aerosol Research     

Economic model predictive control with time‐varying objective function for nonlinear process systems

Economic model predictive control (EMPC) is a control scheme that combines real‐time dynamic economic process optimization with the feedback properties of model predictive control (MPC) by replacing the quadratic cost function with a general economic cost function. Almost all the recent work on EMPC involves cost functions that are time invariant (do not explicitly account for time‐varying process economics). In the present work, we focus on the development of a Lyapunov‐based EMPC (LEMPC) scheme that is formulated with an explicitly time‐varying economic cost function. First, the formulation of the proposed two‐mode LEMPC is given. Second, closed‐loop stability is proven through a theoretical treatment. Last, we demonstrate through extensive closed‐loop simulations of a chemical process that the proposed LEMPC can achieve stability with time‐varying economic cost as well as improve economic performance of the process over a conventional MPC scheme. © 2013 American Institute of Chemical Engineers AIChE J 60: 507–519, 2014     

Assessment of the Validity and Reproducibility of a Novel Standardized Test Meal for the Study of Postprandial Triacylglycerol Concentrations

Lipotest^® is a standardized fat‐rich meal designed for use as a test meal during a fat tolerance test (FTT) for the study of postprandial triacylglycerol (TAG) concentrations. Herein we examined the precision and reproducibility of examination using Lipotest^® on postprandial TAG levels. A total of 26 healthy consenting subjects were examined twice after 8–10 h fasting with an interval of approximately 1 week apart. Blood samples were collected at baseline and 1, 2, 3, and 4 h after consumption of the test meal for measurement of plasma total TAG levels. We examined agreement, precision, and accuracy between the two visits using the Altman plots and correlation coefficient. Reproducibility was tested using the coefficient of variation (CV) and intraclass correlation coefficient (ICC). Moreover, the area under the curve (AUC) as a summary measure of the overall postprandial TAG levels was calculated. The agreement, precision (r ≥ 0.74, p < 0.001), and accuracy (≥0.99) between the measurements in plasma TAG during Lipotest^® testing in the two visits were high. In terms of reproducibility, the values of CV were 15.59–23.83% while those of ICC were ≥0.75. The values of the AUCs in the visits were not different (p = 0.87). A single measurement of plasma TAG levels at 4 h after Lipotest^® consumption depicted peak postprandial TAG concentration. A FTT using Lipotest^® as a standardized meal has good precision and reproducibility for the study of postprandial TAG levels in healthy individuals. A single determination of plasma TAG concentration at 4 h after Lipotest^® consumption captures peak postprandial TAG response.     

Tissue Uptake Mechanisms Involved in the Clearance of Non-Protein Nanoparticles that Mimic LDL Composition: A Study with Knockout and Transgenic Mice

Lipid core nanoparticles (LDE) resembling LDL behave similarly to native LDL when injected in animals or subjects. In contact with plasma, LDE acquires apolipoproteins (apo) E, A‐I and C and bind to LDL receptors. LDE can be used to explore LDL metabolism or as a vehicle of drugs directed against tumoral or atherosclerotic sites. The aim was to investigate in knockout (KO) and transgenic mice the plasma clearance and tissue uptake of LDE labeled with ³H‐cholesteryl ether. LDE clearance was lower in LDLR KO and apoE KO mice than in wild type (WT) mice (p < 0.05). However, infusion of human apoE3 into the apoE KO mice increased LDE clearance. LDE clearance was higher in apoA‐I KO than in WT. In apoA‐I transgenic mice, LDE clearance was lower than in apoA‐I KO and than in apoA‐I KO infusion with human HDL. Infusion of human HDL into the apoA‐I KO mice resulted in higher LDE clearance than in the apoA‐I transgenic mice (p < 0.05). In apoA‐I KO and apoA‐I KO infused human HDL, the liver uptake was greater than in WT animals and apoA‐I transgenic animals (p < 0.05). LDE clearance was lower in apoE/A‐I KO than in WT. Infusion of human HDL increased LDE clearance in those double KO mice. No difference among the groups in LDE uptake by the tissues occurred. In conclusion, results support LDLR and apoE as the key players for LDE clearance, apoA‐I also influences those processes.     

Real‐time economic model predictive control of nonlinear process systems

Closed‐loop stability of nonlinear systems under real‐time Lyapunov‐based economic model predictive control (LEMPC) with potentially unknown and time‐varying computational delay is considered. To address guaranteed closed‐loop stability (in the sense of boundedness of the closed‐loop state in a compact state‐space set), an implementation strategy is proposed which features a triggered evaluation of the LEMPC optimization problem to compute an input trajectory over a finite‐time prediction horizon in advance. At each sampling period, stability conditions must be satisfied for the precomputed LEMPC control action to be applied to the closed‐loop system. If the stability conditions are not satisfied, a backup explicit stabilizing controller is applied over the sampling period. Closed‐loop stability under the real‐time LEMPC strategy is analyzed and specific stability conditions are derived. The real‐time LEMPC scheme is applied to a chemical process network example to demonstrate closed‐loop stability and closed‐loop economic performance improvement over that achieved for operation at the economically optimal steady state. © 2014 American Institute of Chemical Engineers AIChE J, 61: 555–571, 2015     

Immobilization of Lipid Substrates: Application on Phospholipase A2 Determination

The purpose of the study was to assess a fluorimetric assay for the determination of total phospholipase A₂ (PLA₂) activity in biological samples introducing the innovation of immobilized substrates on crosslinked polymeric membranes. The immobilized C₁₂‐NBD‐PtdCho, a fluorescent analogue of phosphatidylcholine, exhibited excellent stability for 3 months at 4 °C and was not desorbed in the aqueous reaction mixture during analysis. The limit of detection was 0.5 pmol FA (0.2 pg) and the linear part of the response curve extended from 1 up to 190 nmol FA/h/mL sample. The intra‐ and inter‐day relative standard deviations (%RSD), were ≤6 and ≤9 %, respectively. Statistical comparison with other fluorescent methods showed excellent correlation and agreement. Semiempirical calculations showed a fair amount of electrostatic interaction between the NBD‐labeled substrate and the crosslinked polyvinyl alcohol with the styryl pyridinium residues (PVA‐SbQ) material, from the plane of which, the sn‐2 acyl chain of the phospholipid stands out and is accessible by PLA₂. Atomic Force Microscopy revealed morphological alterations of the immobilized substrate after the reaction with PLA₂. Mass spectrometry showed that only C₁₂‐NBD‐FA, the PLA₂ hydrolysis product, was detected in the reaction mixture, indicating that PLA₂ recognizes PVA‐SbQ/C₁₂‐NBD‐PtdCho as a surface to perform catalysis.     

Increased Autotaxin Levels in Severe COVID-19, Correlating with IL-6 Levels,Endothelial Dysfunction Biomarkers,and Impaired Functions of Dendritic Cells

Autotaxin (ATX; ENPP2) is a secreted lysophospholipase D catalyzing the extracellular production of lysophosphatidic acid (LPA), a pleiotropic signaling phospholipid. Genetic and pharmacologic studies have previously established a pathologic role for ATX and LPA signaling in pulmonary injury, inflammation, and fibrosis. Here, increased ENPP2 mRNA levels were detected in immune cells from nasopharyngeal swab samples of COVID-19 patients, and increased ATX serum levels were found in severe COVID-19 patients. ATX serum levels correlated with the corresponding increased serum levels of IL-6 and endothelial damage biomarkers, suggesting an interplay of the ATX/LPA axis with hyperinflammation and the associated vascular dysfunction in COVID-19. Accordingly, dexamethasone (Dex) treatment of mechanically ventilated patients reduced ATX levels, as shown in two independent cohorts, indicating that the therapeutic benefits of Dex include the suppression of ATX. Moreover, large scale analysis of multiple single cell RNA sequencing datasets revealed the expression landscape of ENPP2 in COVID-19 and further suggested a role for ATX in the homeostasis of dendritic cells, which exhibit both numerical and functional deficits in COVID-19. Therefore, ATX has likely a multifunctional role in COVID-19 pathogenesis, suggesting that its pharmacological targeting might represent an additional therapeutic option, both during and after hospitalization.