Competitive Flow Research Articles

Lateral Flow Immunoassay Based on Quantum-Dot Nanobeads for Detection of Chloramphenicol in Aquatic Products.

Quantum dot nanobeads (QBs) were used as signal source to develop competitive lateral flow immunoassay (LFIA) for the detection of chloramphenicol (CAP). The quantitative detection of CAP was achieved by calculating the total color difference (∆E) values of the test line (T line) using the images of test strips. QB-based LFIA (QBs-LFIA) allowed the effective dynamic linear detection of CAP in the range of 0.1-1.5 ng/mL. The limit of detection (LOD) was 3.0 ng/mL, which was 50 and 667 times lower than those achieved for two different brands of colloidal gold kits. The recoveries of CAP during real-sample detection were 82.82-104.91% at spiked levels of 0.1, 0.7, and 1.5 ng/mL. These results indicate that the developed QBs-LFIA facilitates the sensitive detection of CAP.

Decorated DNA-Based Scaffolds as Lateral Flow Biosensors.

Here we develop Lateral Flow Assays (LFAs) that employ as functional elements DNA-based structures decorated with reporter tags and recognition elements. We have rationally re-engineered tile-based DNA tubular structures that can act as scaffolds and can be decorated with recognition elements of different nature (i.e. antigens, aptamers or proteins) and with orthogonal fluorescent dyes. As a proof-of-principle we have developed sandwich and competitive multiplex lateral flow platforms for the detection of several targets, ranging from small molecules (digoxigenin, Dig and dinitrophenol, DNP), to antibodies (Anti-Dig, Anti-DNP and Anti-MUC1/EGFR bispecific antibodies) and proteins (thrombin). Coupling the advantages of functional DNA-based scaffolds together with the simplicity of LFAs, our approach offers the opportunity to detect a wide range of targets with nanomolar sensitivity and high specificity.

Decorated DNA‐Based Scaffolds as Lateral Flow Biosensors

AbstractHere we develop Lateral Flow Assays (LFAs) that employ as functional elements DNA‐based structures decorated with reporter tags and recognition elements. We have rationally re‐engineered tile‐based DNA tubular structures that can act as scaffolds and can be decorated with recognition elements of different nature (i.e. antigens, aptamers or proteins) and with orthogonal fluorescent dyes. As a proof‐of‐principle we have developed sandwich and competitive multiplex lateral flow platforms for the detection of several targets, ranging from small molecules (digoxigenin, Dig and dinitrophenol, DNP), to antibodies (Anti‐Dig, Anti‐DNP and Anti‐MUC1/EGFR bispecific antibodies) and proteins (thrombin). Coupling the advantages of functional DNA‐based scaffolds together with the simplicity of LFAs, our approach offers the opportunity to detect a wide range of targets with nanomolar sensitivity and high specificity.

No-Touch Saphenous Vein as Y-Composite vs Aortocoronary Graft: Early Outcome Analysis

BackgroundA randomized controlled trial was designed to compare 1-year morphologic changes of the no-touch saphenous vein (SV) as a Y-composite graft (composite group) vs an aortocoronary graft (aorta group) in coronary artery bypass grafting. This study evaluated early clinical and angiographic outcomes as a preliminary analysis. MethodsThe primary end point of the trial was the intima-media thickness measured by intravascular ultrasound at 1-year angiographic follow-up. Patients were screened to enroll 25 patients in each group based on a superiority design. Early postoperative clinical and angiographic outcomes were compared between the 2 groups. ResultsThe numbers of distal anastomoses per SV graft were 2.7 ± 1.1 and 2.6 ± 0.8 in the composite and aorta groups, respectively. There was no operative death, and postoperative complications in the 2 groups did not significantly differ. All patients underwent early postoperative graft angiography at a median of 1 (interquartile range, 1-1) day after operation. Early angiographic patency rates were 98.9% (93/94 anastomoses) and 100% (90/90 anastomoses) in the composite and aorta groups, respectively. There was no distal anastomosis showing competitive flow in the aorta group, whereas 3 anastomoses with competitive flow were found in the composite group. All 3 anastomoses with competitive flow were SV grafts that were anastomosed to the right coronary artery territory with moderate stenosis. ConclusionsEarly clinical outcomes and angiographic graft patency rates were not significantly different with use of no-touch SV as a Y-composite graft or an aortocoronary graft.

Single or multiple arterial grafting to design a coronary bypass: a retrospective study

Aim. To compare the efficiency of single arterial grafting (SAG) and multiple arterial grafting (MAG) at coronary artery bypass graft (CABG) surgery in the long term.Material and Methods. To assess the angiographic outcomes, we evaluated the patency of 323 bypasses at 102 angiograms obtained during coronary angiography performed > 10 years post-CABG surgery.Results. Out of 323 analyzed bypasses, 230 (71.2%) showed physiological functioning, whereas stenosis, occlusions, and other coronary artery alterations were found in 93 (28.8%) bypasses. The most common cause for the failure of anastomoses was competitive flow (most frequently registered in the anastomoses between left internal thoracic artery and left anterior descending artery, left internal thoracic artery and diagonal branches of left anterior descending artery, right internal thoracic artery and left anterior descending artery, and between right internal thoracic artery and right coronary artery), poor distal bed (most frequently revealed in the anastomosis between left internal thoracic artery and obtuse marginal artery, saphenous vein and diagonal branches of left anterior descending artery, saphenous vein and obtuse marginal artery, and between saphenous vein and right coronary artery), progression of atherosclerosis in combination with poor distal bed (most frequently detected in the anastomosis between right internal thoracic artery and obtuse marginal artery), and combination of poor distal bed, competitive flow, and graft degeneration (most frequently found in the anastomoses between radial artery and obtuse marginal artery and between radial artery and right coronary artery). In 5 (5.4%) cases, the cause of coronary bypass dysfunction was unclear.Conclusion. The main causes for the coronary bypass failure included competitive flow (in case with multiple arterial grafting) and poor distal bed (in case with single arterial grafting).

A surface-enhanced Raman scattering-based competitive lateral flow assay for on-orbit rapid detection of bone loss biomarker CTX I

The complexity of space environment will lead to a series of health problems, especially the bone loss caused by weightlessness is one of the key medical problems limiting long-term manned space flight. However, the size and energy constraints of the aircraft make conventional bone loss detection methods impractical. Hence, it is necessary to establish on-orbit bone loss detection methods to ensure the health of astronauts. As one of NASA's recommended methods, the lateral flow assay (LFA) would be an ideal tool to solve this problem. Herein, a surface-enhanced Raman based molecular probe was designed and integrated with LFA to detect carboxy-terminal cross-linked telopeptides of type I collagen (CTX I) with high sensitivity and specificity, and the limit of detection was 232 pg/mL. This method was not interference by the serum matrix or other targets, and the storage life of LFA was up to 6 months at 4 °C. Compared with the method previously reported, SERS-based LFA was an ideal detection method with simple operation, convenient and time saving. It is also expected to be chosen as a potential analytical tool to detect bone loss for long-term on-orbit, and guarantee the health of astronauts.

Preoperative angiography-derived fractional flow reserve may predict coronary artery bypass grafting occlusion and disease progression.

Graft occlusion after coronary artery bypass grafting (CABG) has been associated with competitive flow of native coronary arteries. To assess with coronary computed tomography angiography (CCTA) graft occlusion and coronary artery disease (CAD) progression of native vessels after CABG and their relationship with angiography-derived vessel fractional flow reserve (vFFR) performed before surgery. Between 2006 and 2018, serial vFFR analyses were obtained before CABG in each major native coronary vessel from two institutions. All patients underwent follow-up CCTA. In 171 consecutive patients, serial preoperative angiograms were suitable for vFFR analysis of 298 grafted and 59 nongrafted vessels. Median time between CABG and CCTA was 2.1 years. Preoperative vFFR was assessed in 131 left anterior descending artery (LAD), 132 left circumflex artery (LCX) and 94 right coronary aretry (RCA) and was less than 0.80 in 255 of 298 bypassed vessels. Graft occlusion was observed at CCTA in 28 of 298 grafts. The median preoperative vFFR value of native coronaries was higher in occluded compared with patent grafts (0.75 vs. 0.60, P < 0.001) and was associated with graft. The best vFFR cut-off to predict graft occlusion was 0.67. Progression of CAD was higher in grafted than in nongrafted vessels (89.6 vs. 47.5%, P < 0.001). Pre-CABG vFFR predicted disease progression of grafted native vessels (AUC = 0.83). Preoperative vFFR derived from invasive coronary angiography was able to predict graft occlusion and CAD progression of grafted coronary arteries.

Zinc-Iron Rechargeable Flow Battery with High Energy Density

In current research, electrochemical energy storage systems have gaining interest because they constitute an essential element in the development of sustainable energy technologies [1,2]. Among them, rechargeable flow batteries (RFBs) are one of the most promising technologies for the integration in grid-connected electricity, especially if combined with unpredictable and intermittent renewable energy sources, due to their high efficiency, power/energy independent sizing and room temperature operation [3]. At the moment, among all RFBs systems, the most investigated and advanced technology is the vanadium based RFB, characterized by an energy efficiency equal to 80% and energy density ranging 15-45 Wh/l [4]. However, nowadays the main bulk of research is focused on finding an economically convenient and technically competitive flow battery chemistry, able to ensure long lifetime and high energy efficiency [5,6]. In this study, a zinc-iron RFBs based on sulfate and sulfamate electrolytes will be presented, discussing the achievement of a charge density in the range 30-70 Wh/l. The combination of high energy efficiency of the Zn-Fe RFB with its ability to withstand a large number of charge/discharge cycles and the low cost, makes this battery system suitable for energy storage applications. Alotto, M. Guarnieri, and F. Moro. Renewable and Sustainable Energy Reviews 29 (2014): 325-335. Weber, M.M. Mench, J.P. Meyers, P.N. Ross, J.T. Gostick and Q. Liu. Journal of Applied Electrochemistry (2011), 41(10), 1137. Kear, A.A Shah, and F.C. Walsh. International journal of energy research, (2012), 36(11), 1105-1120. Ding, H. Zhang, X. Li, T. Liu, and F. Xing. The Journal of Physical Chemistry Letters, (2013), 4(8), 1281-1294. C- Xie, Y. Duan, W. Xu, H. Zhang, and X Li. Angewandte Chemie International Edition, (2017) 56 (47), 14953-14957. Selverston, R. F. Savinell, and J. S. Wainright. Journal of The Electrochemical Society 164, (2017): A1069-A1075.

Competitive ratiometric fluorescent lateral flow immunoassay based on dual emission signal for sensitive detection of chlorothalonil

In this study, we develop a competitive ratiometric fluorescent lateral flow immunoassay (CRF-LFIA) based on dual emission fluorescence signal, which has great advantage in visual and quantitative detection of Chlorothalonil (CTN). Red-emitted fluorescent magnetic nanobeads (FMNBs) and green-emitted aggregation-induced emission fluorescent microsphere (AIEFM) are synthesized and conjugated to antibodies and antigens respectively, resulting in competitive binding with the analyte. The ratiometric fluorescence signal which comes from the overlap of these two fluorescence emissions. FMNBs probes also provide immunomagnetic separation (IMS) to enrich the analysts and resist complex matrix effects. This strip generates a visually discernible yellow-to-green fluorescence color change in the presence of CTN (2 ng/mL), which could be incisively observed by naked eye. Moreover, the limit of detection (LOD) reached 0.152 ng/mL by measurement of color (Red-Green-Blue, RGB) signals. Method validation shows a good correlation between CRF-LFIA and LC-MS/MS.

Introduction of multilayered quantum dot nanobeads into competitive lateral flow assays for ultrasensitive and quantitative monitoring of pesticides in complex samples.

A competitive fluorescent lateral flow assay (CFLFA) is proposed for direct, ultrasensitive, quantitative detection of common pesticides imidacloprid (IMI) and carbendazim (CBZ) in complex food samples by using silica-core multilayered quantum dot nanobeads (SiO2-MQB) as liquid fluorescent tags. The SiO2-MQB nanostructure comprises a 200-nm SiO2 core and a shell of hundreds of carboxylated QDs (excitation/emission maxima ~365/631 nm), and can generate better stability, superior dispersibility, and higher luminescence than traditional fluorescent beads, greatly improving the sensitivity of current LFA methods for pesticides. Moreover, using liquid SiO2-MQB directly instead of via the conjugate pad both simplifies the structure of LFA system and improves the efficiency of immunobinding reactions between nanotags and the targets. Applying these methods, the established CFLFA realized the stable and accurate detection of IMI and CBZ in 12 min, with detection limits down to 1.94 and 14.79 pg/mL, respectively. The SiO2-MQB-CFLFA is practicable for application to real food samples (corn, apple, cucumber, and cabbage), and undoubtedly a promising and low-cost tool for on-site monitoring of trace pesticide residues.

Targeting of human fibroblast growth factor receptor 2 by a novel specific nanobody

Inhibition of FGFR2 signaling is promising in targeted therapy of FGFR2-related tumors. In this study, anti-FGFR2 nanobodies (Nbs) were isolated through screening of an immune camelid phage display library. Four rounds of biopanning were carried out with commercial human FGFR2 antigen and enrichment was assessed by ELISA and phage titration. The gene of Nb was sub-cloned into the expression vector, and the recombinant vector was transformed into Escherichia coli WK6 cells. The recombinant protein was purified using Ni–NTA affinity chromatography. The anti-FGFR2 Nb (C13) was characterized by SDS-PAGE, western blotting, competitive inhibition ELISA, flow cytometry, MTT, and migration assay. C13 Nb recognized FGFR2 with high specificity and no cross-reactivity was observed with other tested antigens. The affinity of C13 Nb was calculated to be 1.5 × 10−9 M. Results of cytotoxicity showed that C13 Nb (10 µg/ml) inhibited 85% of the proliferation of T-47D cells (p < 0.001). In addition, C13 inhibited the migration of 68% of T-47D toward the source of the growth factor (p < 0.01). The flow cytometry showed that C13 Nb bound to the surface of FGFR2+ cells, T-47D cell line (96%). Results indicate the potential of anti-FGFR2 Nb for targeted therapy of FGFR2-overexpressing tumors after complementary investigations.

Aptamer-based diagnosis of various SARS-CoV2 strains isolated from clinical specimens

The emergence of the SARS-CoV-2 virus, an unknown strain of coronavirus, has resulted in severe acute respiratory syndrome with high mortality rates worldwide. Due to the possibility of asymptomatic carriers, late diagnosis of infected individuals can lead to uncontrollable transmission of the disease, making early and accurate detection crucial in controlling the spread of the virus. In this study we identified high-binding-affinity aptamers targeting various strains of the SARS-CoV2 (COVID-19) virus, using the GO-Cell-SELEX (Graphene Oxide- Systematic Evolution of Ligands by Exponential Enrichment) strategy. A total of 96 aptamers were developed through 11 rounds of GO-Cell-SELEX from a random 40 nucleotide single-strand DNA (ssDNA) aptamer library. Using the surface plasmon resonance (SPR) method, the dissociation constant (Kd) values of all aptamers were calculated and two aptamers 52 and 91 with Kd 50 and 61 were selected for enzyme-linked apta-sorbent assay (ELASA). Aptamer 91 could detect various strains of the virus in above 97% of clinical samples obtained from nasopharyngeal swaps (NPS) specimens kept in viral transport media (VTM), confirmed by real-time PCR assay at COVID-19 Reference Diagnostic Laboratory of Iran, Pasture Institute. Aptamer 52 could detect the SARS-CoV2 virus in a competitive lateral flow assay (LFA) to be considered for a future designed kit. These two simple, specific, and sensitive tests can be used in combination for rapid and early diagnosis of various strains of the COVID-19 virus. Our results suggest that these two discovered aptamers present an opportunity for developing a new rapid aptamer-based coronavirus diagnostic kit.

Enhanced Lateral Flow Immunoassay with Double Competition and Two Kinds of Nanoparticles Conjugates for Control of Insecticide Imidacloprid in Honey.

Finding optimal conditions for competitive lateral flow immunoassay is a controversial task. The content of specific antibodies labeled by nanoparticles should be simultaneously high to reach intense signals and low to register an influence on the signals for minimal concentrations of the target analyte. We propose to use two kinds of complexes of gold nanoparticles in the assay, with antigen-protein conjugates and with specific antibodies. The first complex interacts both with immobilized antibodies in the test zone and with antibodies on the surface of the second complex. In this assay, the coloration is enhanced by the binding of two-colored preparations in the test zone, whereas the antigen in the sample inhibits both the binding of the first conjugate with the immobilized antibodies and with the second conjugate. This approach is realized for the detection of insecticide imidacloprid (IMD), an important toxic contaminant connected with the recent global death of bees. The proposed technique expands the working range of the assay, that is, in accordance with its theoretical analysis. The reliable change of coloration intensity is achieved for a 2.3-times-lower concentration of the analyte. The limit of IMD detection is 0.13 ng/mL for tested solutions and 1.2 µg/kg for initial honey samples. The combination of two conjugates doubles the coloration in the absence of the analyte. The developed lateral flow immunoassay is applicable for five-fold-diluted honey samples without extraction, does not require additional stages (all reagents are pre-applied to the test strip), and is implemented in 10 min.

481 Troubleshooting the Bypass: Intraoperative Management of Initially Failed Anastomosis in Cerebral Extracranial – Intracranial Direct Revascularization Surgery

INTRODUCTION: Direct cerebral revascularization is considered one the most technically challenging operations in neurosurgery. Technical errors are often not identified during the completion of the anastomosis. Initial assessment and management at this moment can determine the success of the entire case, making re-circulation one of the most stressful moments in the procedure. METHODS: A retrospective analysis of direct bypass cases based on operative reports and available videos, were studied in detai. A case was defined as an “initially failed bypass”, irrespective of its final result, if after removal of the temporary clips, the bypass was not patent, or significant leak was encountered. RESULTS: 138 cases were included (109 being STA-MCA) done for flow replacement (n = 49), or for flow augmentation (n = 89). 45 initially failed anastomosis, out of which 37 were the result of a technical error encounterd. Causes were clot(n = 10), vessel kinking(n = 5), spasm(n = 6), inappropriate donor(n = 3) or recipient(n = 2), competitive flow(n = 6) or a leak(n = 5). 31/37 cases were troubleshooted successfully resulting in a working bypass. Rescue maneuvers included: Partial re-opening of the suture line and irrigation for clot, graft repositioning for kinking, papaverine-vessel massage for spasm, and partial vessel cut at the donor site for anastomosis inspection. In “local” lack of demand, a new anastomosis was done by the same donor. 30-days follow-up showed similar rates of patency between successfully troubleshooted patients and the rest of the patients (82% vs 85%, p = 0.35). CONCLUSIONS: A comprehensive approach detailing technical “corrections”, describing maneuvers and the sequence of actions done in order to “revive” the bypass, as well as their prevalence, was not previously well described. In this study we present 3 of initial failure types: a leak, acute occlusion or delayed occlusion, presenting an algorithm for intra-operative management in these cases.

Electrohydrodynamic air amplifier for low-energy airflow generation—An experimental proof-of-concept

With electrohydrodynamics (EHD), we can propel air in a low-energy fashion. EHD airflow, or ionic wind, arises when a high voltage gradient is applied to a set of electrodes. The air ionizes between electrodes via corona discharge and accelerates in an electric field, exchanging momentum with the surrounding air. While the ionization process is energy-efficient, reaching competitive flow rates remains challenging from a high-voltage engineering perspective. To increase EHD-generated flow rates, this study experimentally investigates a novel concept called EHD air amplification. The concept uses ionic wind as bleed flow to induce a more significant bulk flow by the air-amplifying Coanda effect. Due to the complex interactions between EHD and dielectric structures for air amplification, the conceptual EHD air amplifier device is designed stage-wise, starting with a simple emitter-collector electrode configuration. First, regular EHD flow was studied in a 150 × 150 × 500 mm3 channel. Then, a dielectric material was added to determine its influence on the electric field. The impact of a converging nozzle on the EHD-generated airflow was subsequently studied. Lastly, the converged nozzle airflow was used to create a bleed flow on a plate to facilitate air amplification of the surrounding air. We show the proof-of-concept for an EHD air amplification system. After a voltage threshold of 14 kV, amplified airstreams up to an amplification factor of 3 were measured. Maximum airflow rates of about 15 m3 h−1 were obtained shortly before electric breakdown at 22 kV. Compared to regular EHD, we achieved a higher aerodynamic performance for the same electric energy invested. The flow rate to electric power ratio increased to 66% in EHD air amplification compared to regular EHD. The proposed EHD air amplifier operates at atmospheric pressure. It lays the groundwork for further optimization studies to position EHD air amplification as a low-energy, low-maintenance, motor- and noiseless airflow generation technology.

Assessment of verdinexor as a canine P-glycoprotein substrate.

The P-glycoprotein (P-gp) substrate status of antineoplastic drugs intended for veterinary patients is an important characteristic to define for two reasons. First, neoplastic cells expressing P-gp can actively efflux drugs that are P-gp substrates curtailing their efficacy. Second, antineoplastic drugs tend to have a narrow therapeutic index. Antineoplastic drugs that are P-gp substrates can cause severe adverse reactions in animals with P-gp dysfunction such as dogs with ABCB1-1Δ and cats with ABCB11930_1931del TC. Animals with P-gp dysfunction experience greater overall exposure to P-gp substrate drugs due to mechanisms such as increased intestinal absorption, decreased biliary clearance and greater central nervous system penetration compared with animals with normal P-gp function. Accordingly, knowing the P-gp substrate status of antineoplastic drugs is an important safety consideration prior to use in canine or feline cancer patients. This study used a cell line overexpressing canine P-gp to assess the P-gp substrate status of verdinexor. Based on both a cytotoxicity assay and a competitive flow cytometry assay verdinexor is not a substrate for canine P-gp.

Numerical study of heat transfer for gravity-driven binary size particle flow around circular tube

As the primary working medium in moving bed heat exchangers, solid bulk materials are composed of multiple size particles. To clarify the effect of particle size distribution (PSD) on heat transfer, the discrete element method (DEM) is used to study the flow and heat transfer of binary size particle flow around a circular tube. The heat transfer model for multiple size particles is developed and coupled with DEM method. The particle flow characteristics with PSD width are analyzed in detail. The results show that particle size segregation, competitive flow and flow instability are the unique characteristics of binary size particle flow around a tube. Wider PSD will enhance these characteristics and have a positive effect on particle renewal in the stagnation zone, which could decrease the local heat resistance. The total heat transfer coefficient between particle flow and tube wall increases at most by 9.73% as PSD is wider. • Binary size particle flow around a circular tube is studied with DEM method. • Binary size particle flow can form local particle size segregation around tube. • Binary size particles can decrease the stagnation zone above the tube. • A wider binary particle size distribution can increase the flow instability. • A wider binary particle size distribution can enhance heat transfer performance.

459 PREOPERATIVE ANGIOGRAPHY-DERIVED FRACTIONAL FLOW RESERVE MAY PREDICT BYPASS GRAFT OCCLUSION AND DISEASE PROGRESSION AT MID-TERM FOLLOW-UP

Abstract Background Coronary artery bypass grafting (CABG) is the most common revascularization mode for patients with multivessel coronary artery disease (CAD). Despite substantial improvements in the outcome of patients undergoing CABG surgery, graft occlusion remains a weakness of this procedure and has been associated with competitive flow of native coronary arteries. Our study aims to assess graft occlusion and the progression of CAD in native vessels after CABG surgery at follow-up with coronary CT angiography (CCTA), and their relationship with angiography-derived vessel-fractional flow reserve (vFFR) performed before surgery. Methods We retrospectively selected patients from two European institutions, treated with CABG between January 2006 and December 2018, who underwent follow-up with CCTA. All patients had a preoperative angiogram performed before CABG. Results In 171 consecutive patients, serial preoperative angiograms were suitable for vFFR analysis of 298 grafted and 59 non-grafted vessels. Table 1 shows clinical and main procedural characteristics. Preoperative vFFR was assessed in 131 left anterior descending arteries (LAD), 132 left circumflex arteries (LCX) and 94 right coronary arteries (RCA) and was &amp;lt;0.80 in 255 of 298 bypassed vessels. Graft occlusion was observed at CCTA in 28 of 298 grafts. The median preoperative vFFR value of native coronaries was higher in occluded compared to patent grafts (0.75 vs. 0.60, p&amp;lt;0.001) (Figure 1) and was associated with graft type. The best vFFR cut-off to predict graft occlusion was 0.67. The functional CAD progression was higher in grafted compared to non-grafted vessels (89.6% vs 47.5% p &amp;lt; 0.001) and pre-CABG vFFR predicted disease progression of grafted native vessels (AUC=0.83) (Figure 2). Conclusions Preoperative vFFR derived from invasive coronary angiography was able to predict graft occlusion and CAD progression of grafted coronary arteries.

The NLRC4 Inflammasome Drives Myelodysplastic Syndrome By Linking Epigenetic Reprogramming and Innate Immune Signaling

Introduction Myelodysplastic syndromes (MDS) are a heterogeneous group of hematopoietic stem cell (HSC) malignancies characterized by dysplastic and ineffective hematopoiesis. Despite emerging evidence that chronic inflammation contributes to the development of MDS, the mechanisms underlying the dysregulation of innate immune and inflammatory signaling pathways in hematopoietic stem and progenitor cells (HSPCs) remain poorly characterized. We have used multiple MDS mouse models to identify a tumor suppressive role for the EP300 epigenetic histone acetyltransferase enzyme in the progression of MDS to AML. Based on the gene expression changes we observed, we have used one specific mouse model, that lacks Tet2 expression, to define the role that chronic inflammation plays in promoting MDS development and the mechanisms involved. Methods We have conducted a series of in vitro, in vivo, and in silico experiments using Tet2-deficient mice, and chronic, low-dose LPS treatment to model chronic inflammation. Cytokine array immunoassays were performed to evaluate the inflammatory response of WT or Tet2-deficient mice to LPS treatment. Chimeric mice transplanted with bone marrow (BM) cells isolated from LPS or vehicle (PBS) treated WT or Tet2-deficient mice were monitored for the development of MDS and survival. Serial competitive bone marrow transplantation assays and flow cytometry profiling were used to determine the competitive advantage of LPS or PBS-treated BM cells, and their differentiation. Bioinformatic analyses of RNA sequencing (RNA-seq) results from our mouse model were performed to characterize the transcriptional profiling and identify novel innate immune pathways. Colony-forming unit (CFU) and qPCR assays were used to evaluate HSPC proliferative capacity, self-renewal, and gene expression changes. Results We find that mice lacking Tet2 develop a hyper-inflammatory status, marked by the expression of a number of pro-inflammatory cytokines, such as Il-1b and Il-6, which are further fueled by LPS-induced chronic inflammation. Chimeric mice transplanted with BM cells isolated from LPS-treated Tet2-deficient mice exhibit a significantly shorter life span and early onset of MDS phenotypes, including dysplastic hematopoiesis and thrombocytopenia, compared to age-matched chimeric mice transplanted with BM cells isolated from PBS-treated Tet2-deficient mice or LPS-treated WT mice. Chronic inflammation promotes the self-renewal and myeloid differentiation of Tet2-deficient HSPCs in the short term; however, it accelerates HSC exhaustion in the long run. Transcription profiling and subsequent bioinformatic analyses identify functional clusters in LPS-treated Tet2-deficient HSPCs, including genes involved in the regulation of epigenetics, immunity, metabolism, and cell cycle. Detailed inspection of the most highly differentially expressed genes reveals that many genes in the Nlrc4 inflammasome pathway are upregulated in LPS-treated Tet2-deficient HSPCs. We validate changes in the expression of these genes by qPCR, and then show that deleting Nlrc4 suppresses the colony formation of Tet2-deficient HSPCs in vitro. Ongoing work focuses on evaluating the effects of deleting Nlrc4 or blocking Nlrc4 function using a small molecule inhibitor on MDS development in vivo. Conclusions The combinatory role of intrinsic and extrinsic factors drives the development of MDS in this Tet2-deficient MDS mouse model. It is likely that different genetic mutations generate unique sensitivity to certain signaling pathways, and we demonstrate the epigenetic rewiring and activation of the Nlrc4 inflammasome pathway as a mechanistic basis for the inflammatory component of MDS [or clonal hematopoiesis of indeterminate potential (CHIP)] pathogenesis in Tet2-deficient cells. Our work has the potential to provide novel targeting opportunities in MDS management and confirm the importance of different components of inflammasome signaling in MDS.

Auction design for capacity allocation in the petroleum pipeline under fair opening

Auction is a dominant way to allocate transport capacities for the aim of profit, fairness, and transparency. Previous related work focuses on the natural gas pipeline and cannot be applied to the petroleum pipeline for its special technique of transporting multiple batches. This paper designs a bi-level model for capacity auction of the petroleum pipeline, which facilitates fair competition and free flow of petroleum products in market. The upper-level model simulates the decision-making process of pipeline company, and the lower-level one determines if shippers bid up prices for capacities somewhere. A real-world pipeline is taken as a case to explore the impact of different auction designs and proration on capacity allocation. New shippers obtain all the nominations of 18,700 m3 by auction but lost the capacities of 3,523 m3 by proration. Compared to proration, auction leads to a profit growth of 181,545 CNY and 150,019 CNY to pipeline company and new shippers respectively but a decrease of 4,586 CNY to regular shippers. Different orders of offering price lead to different outcomes regarding fairness and revenue. Letting new shippers offer price first is suggested as a base to design auction for capacity allocation since it generates a reduction of 0.2% to regular shippers but an increase of over 12% to others.