Dupilumab in CRSwNP: Responder Analysis Using Clinically Meaningful Efficacy Outcome Thresholds.

OBJECTIVES/HYPOTHESIS: Dupilumab, a fully human monoclonal antibody that blocks the shared interleukin (IL)-4/IL-13 receptor component, significantly improved outcomes for patients with chronic rhinosinusitis with nasal polyps (CRSwNP) in the SINUS-24 and SINUS-52 studies. This post hoc analysis evaluated dupilumab's effect on patient-reported symptoms and objective outcome measures using thresholds of clinically meaningful within-patient change from baseline. METHODS: Patients with CRSwNP receiving subcutaneous dupilumab or placebo every 2 weeks in SINUS-24/SINUS-52 were analyzed. Patients recorded severity of nasal congestion (NC), loss of smell (LoS), and anterior/posterior rhinorrhea (each within range 0-3) daily. Total Symptom Score (TSS) was calculated as a composite severity score (0-9) for these symptoms. Objective measures included University of Pennsylvania Smell Identification Test (UPSIT; 0-40), nasal polyps score (NPS; 0-8), and Lund-Mackay computed tomography score (LMK-CT; 0-24). Thresholds of within-patient change in scores from baseline at weeks 24 and 52 considered clinically meaningful were ≥1.0 (NC, LoS), ≥3.0 (TSS), ≥8.0 (UPSIT), ≥1.0 (NPS), and ≥5.0 (LMK-CT). RESULTS: A total of 724 and 303 patients were included in the week 24 and 52 analyses, respectively. Responder rates were significantly higher with dupilumab versus placebo at week 24 for NC (64% vs. 24%), LoS (63% vs. 14%), TSS (62% vs. 15%), UPSIT (54% vs. 6%), NPS (63% vs. 14%), and LMK-CT (59% vs. 3%); all P < .0001. Results were consistent at week 52. CONCLUSION: Significantly greater proportions of dupilumab-treated patients with CRSwNP compared with placebo demonstrated clinically meaningful improvements in patient-reported sinonasal symptoms and objective outcomes. LEVEL OF EVIDENCE: 2 Laryngoscope, 132:259-264, 2022.

Expression and activity of the nucleotide-binding domains of the human ABCA1 transporter.

The aim of this study was the expression and production in Escherichia coli of the nucleotide-binding domains (NBDs) of the human ABCA1 transporter, in a soluble, non-denatured form. To increase the protein solubility, and avoid expression in E. coli inclusion bodies, we extended the length of the expressed NBD domains, to include proximal domains. The corresponding cDNA constructs were used to express the N-terminal His-tagged WT and mutant proteins, which were purified by Ni(2+)-affinity chromatography. Optimal expression of soluble proteins was obtained for constructs including the NBD, the downstream 80-residue domain, and about 20 upstream residues. The size homogeneity of WT and mutant NBDs was determined by Dynamic Light Scattering, and ATP-binding constants and ATPase activities were measured. The NBD1 and NBD2 domains bound ATP with comparable affinity. The ATPase activity of WT His-NBD1 was about three times higher than that of NBD2 and amounted to 5913 compared to 1979 nmol Pi/micromol NBD/min for WT His-NBD2. All engineered mutants had comparable ATPase activity to the corresponding WT protein. The optimisation of the length of the expressed proteins, based upon the boundary prediction of NBDs and neighbour domains, enables the expression and purification of soluble ABCA1 NBDs, with high ATPase activity. This approach should prove useful for the study of the structural and functional properties of the NBDs and other domains of the ABC transporters.

In-depth haplotype analysis of ABCA1 gene polymorphisms in relation to plasma ApoA1 levels and myocardial infarction.

OBJECTIVE: By regulating the cellular cholesterol efflux from peripheral cells to high-density lipoprotein, the ABCA1 protein is suspected to play a key role in lipid homeostasis and atherosclerosis. Twenty-six polymorphisms of the ABCA1 gene were genotyped and tested for association with plasma levels of ApoA1 and myocardial infarction (MI) in the ECTIM study. METHODS AND RESULTS: In addition to single-locus analysis, a systematic exploration of all possible haplotype effects was performed, with this exploration being performed on a minimal set of "tag" polymorphisms that define the haplotype structure of the gene. Two polymorphisms were associated with plasma levels of ApoA1, 1 in the promoter (C-564T) and 1 in the coding (R1587K) regions, whereas only 1 polymorphism (R219K) was associated with the risk of MI. However, no haplotype effect was detected on ApoA1 variability or on the risk of MI. CONCLUSIONS: ABCA1 gene polymorphisms but not haplotypes are involved in the variability of plasma ApoA1 and the susceptibility to coronary artery disease.

Characterization of the ABCA transporter subfamily: identification of prokaryotic and eukaryotic members, phylogeny and topology.

An alignment of the mammalian ABCA transporters enabled the identification of sequence segments, specific to the ABCA subfamily, which were used as queries to search for eukaryotic and prokaryotic homologues. Thirty-seven eukaryotic half and full-length transporters were found, and a close relationship with prokaryotic subfamily 7 transporters was detected. Each half of the ABCA full-transporters is predicted to comprise a membrane-spanning domain (MSD) composed of six helices and a large extracellular loop, followed by a nucleotide-binding domain (NBD) and a conserved cytoplasmic 80-residue sequence, which might have a regulatory function. The topology predicted for the ABCA transporters was compared to the crystal structures of the MsbA and BtuCD bacterial transporters. The alignment of the MSD and NBD domains provided an estimate of the degree of residue conservation in the cytoplasmic, extracellular and transmembrane domains of the ABCA transporter subfamily. The phylogenic tree of eukaryotic ABCA transporters based upon the NBD sequences, consists of three major clades, corresponding to the half-transporter single NBDs and to the full-transporter NBDls and NBD2s. A phylogenic tree of prokaryotic transporters and the eukaryotic ABCA transporters confirmed the evolutionary relationship between prokaryotic subfamily 7 transporters and eukaryotic ABCA half and full-transporters.

Distinct sites on ABCA1 control distinct steps required for cellular release of phospholipids.

The loss of ABCA1 function leads to Tangier dyslipidemia in humans and to a Tangier-like phenotype in mice, by impairing the transformation of nascent apolipoproteins into mature HDL particles. Mechanistically this ensues from the inability of cells to release membrane lipids and cholesterol. Whereas the ability of ABCA1 to promote phospholipid effluxes, surface binding of apolipoproteins and outward flip of membrane lipids has been documented, the relationship between this series of ABCA1-dependent events is still elusive. Here we provide evidence that i) lipid effluxes require both flip of membrane lipids and binding of apolipoproteins to the cell surface, ii) apolipoprotein A-I binding depends on structural determinants on ABCA1, and iii) phospholipid effluxes can be modulated by engineered mutations on the structural determinants identified on ABCA1.

The ABCA1 transporter functions on the basolateral surface of hepatocytes.

ABCA1 on the cell surface and in endosomes plays an essential role in the cell-mediated lipidation of apoA-I to form nascent HDL. Our previous studies of transgenic mice overexpressing ABCA1 suggested that ABCA1 in the liver plays a major role in regulating plasma HDL levels. The site of function of ABCA1 in the polarized hepatocyte was currently assessed by expression of an adenoviral construct encoding a human ABCA1-GFP fusion protein in the polarized hepatocyte-like WIF-B cell line. Consistent with localization of ABCA1 at the basolateral (vascular) cell surface, expression of ABCA1-GFP stimulated apoA-I mediated efflux of WIF-B cell cholesterol into the culture medium. Confocal fluorescence microscopy revealed that ABCA1-GFP was expressed solely on the basolateral surface and associated endocytic vesicles. These findings suggest an important role for hepatocyte basolateral membrane ABCA1 in the regulation of the levels of intracellular hepatic cholesterol, as well as plasma HDL.