Up-Regulation of Soluble Axl and Mer Receptor Tyrosine Kinases Negatively Correlates with Gas6 in Established Multiple Sclerosis Lesions

Multiple sclerosis is a disease that is characterized by inflammation, demyelination, and axonal damage; it ultimately forms gliotic scars and lesions that severely compromise the function of the central nervous system. Evidence has shown previously that altered growth factor receptor signaling contributes to lesion formation, impedes recovery, and plays a role in disease progression. Growth arrest-specific protein 6 (Gas6), the ligand for the TAM receptor tyrosine kinase family, consisting of Tyro3, Axl, and Mer, is important for cell growth, survival, and clearance of debris. In this study, we show that levels of membrane-bound Mer (205 kd), soluble Mer (∼150 kd), and soluble Axl (80 kd) were all significantly elevated in homogenates from established multiple sclerosis lesions comprised of both chronic active and chronic silent lesions. Whereas in normal tissue Gas6 positively correlated with soluble Axl and Mer, there was a negative correlation between Gas6 and soluble Axl and Mer in established multiple sclerosis lesions. In addition, increased levels of soluble Axl and Mer were associated with increased levels of mature ADAM17, mature ADAM10, and Furin, proteins that are associated with Axl and Mer solubilization. Soluble Axl and Mer are both known to act as decoy receptors and block Gas6 binding to membrane-bound receptors. These data suggest that in multiple sclerosis lesions, dysregulation of protective Gas6 receptor signaling may prolong lesion activity.Multiple sclerosis (MS) is a debilitating white matter disease of the central nervous system (CNS). Although much of the evidence from animal models and MS suggests it to be an autoimmune disorder mediated by TH-1 type T cells,¹ other possible causes include genetic and environmental factors, antibody-dependent cytotoxicity, and bacterial and viral infections that may mediate altered protein expression resulting in inflammation, axonal and oligodendrocyte damage, demyelination and CNS scarring.² Growth and survival factors that protect against axonal and oligodendrocyte damage or loss, and dampen the inflammatory response are actively being pursued for MS therapy.^2,3,4,5,6 One growth factor associated with oligodendrocyte maturation, survival and dampening the immune response is growth-arrest specific protein 6 (Gas6). Gas6 is a secreted protein that is widely expressed in the central and peripheral nervous systems by endothelial cells and neurons, and is involved in numerous physiological and pathological functions including cell growth, survival and apoptosis.^{7,8,9,10,11,12} Gas6 binds and activates the TAM family of receptor tyrosine kinases consisting of Tyro3 (Rse/Dtk/Sky), Axl (Ufo), and Mer (Eyk).^{8,11,13,14,15} Many cell types express all three receptors and receptor activation can result from homophilic and heterophilic interactions.^16,17 Axl contains the major and minor Gas6 binding groove. Only the minor groove is conserved in Tyro3 and Mer and as a result, response to Gas6 is mediated in a concentration-dependent manner; Gas6 binding affinity is Axl>Tyro3>Mer.¹⁸We previously reported mRNA expression of Axl, Tyro3, and Mer receptors on human fetal oligodendrocytes and the ability of Gas6 to promote oligodendrocyte survival in vitro by activating Axl, resulting in Axl directly and indirectly recruiting phosphatidylinositol 3 kinase and activating the Akt pathway.^19,20 Moreover, we have shown that Gas6/Axl signaling through the Akt pathway can protect oligodendrocytes from tumor necrosis factor α (TNFα)-induced apoptosis.²¹ Down-regulation or deletion of Axl, even in the presence of Gas6, results in loss of protection against TNFα.²²During the relapse phase of relapsing-remitting MS, serum TNFα levels and TNFα mRNA are elevated.^23,24 TNFα is one of the major cytokines expressed in MS lesions.²⁵ TNFα is cleaved to its mature, soluble, secretable form by the matrix metalloproteinase (MMP) TNFα converting enzyme, also known as ADAM17.^26,27,28 MMPs, including ADAM17 and ADAM10 are involved in normal processes such as wound repair and tissue remodeling and are associated with disease states, including MS.^{29,30,31,32,33,34,35,36} Expression of ADAM17 is observed in acute and chronic active MS lesions, primarily in perivascular cuffs and cells morphologically resembling lymphocytes.³⁷ ADAM17 up-regulation in cerebrospinal fluid of MS patients is associated with inflammation and increased soluble TNFα.^37,38 ADAM10 is constitutively expressed on astrocytes in normal appearing white matter and on astrocytes and perivascular macrophages in MS lesions.^38,39,40,41 ADAM10 cleaves Axl, and ADAM17 cleaves Axl and Mer. Cleaved forms of receptors can result in internalization of the receptor and transport off the membrane for recycling. Cleavage can also result in shortened, soluble forms that act as a decoy to regulate the level of a growth factor at the membrane.^41,42Soluble forms of Axl and Mer can reduce the number of viable receptors for Gas6 binding and act as a decoy by sequestering Gas6 extracellularly; potentially a normal mechanism of receptor activation regulation.^40,41 During inflammation, soluble Mer has been reported to inhibit macrophage clearance of apoptotic cells.^41,43 Also, soluble Axl blocked the protective effect of membrane-bound Axl by inhibiting Gas6 induced tyrosine phosphorylation of Axl.⁴⁴ The binding of Gas6 to TAM receptors acts as an inhibitor of inflammation by inhibiting Toll-like receptor and cytokine receptor cascades.⁴⁴ Up-regulation of Axl and its subsequent interaction with interferon α and β receptors results in the expression of cytokine and Toll-like receptor inhibitors.^44,45 Thus, loss of Gas6 signaling, along with dysregulation of the balance between Gas6, Axl and Mer by increased extracellular levels of soluble Axl and Mer, might detrimentally impact the nervous system, especially in established (chronic active and chronic silent) lesions associated with MS. Chronic active MS lesions are characterized by ongoing demyelination, astrogliosis, macrophage and lymphocyte infiltration, astroglial hypertrophy, and oligodendrocyte hyperplasia.⁴⁶ Chronic silent MS lesions are characterized by the absence of actively infiltrating and inflammatory cells, oligodendrocyte loss and no evidence of ongoing demyelination.^46,47,48In this study, we investigated in chronic active and chronic silent MS lesions whether increased expression of soluble Axl and Mer was associated with increased expression of the MMPs ADAM17 and ADAM10, similar to previous studies that showed an association between increased ADAM17 and ADAM10 with TNFα in the CNS of MS patients.^37,38 We also investigated whether in lesions increased soluble Axl and Mer was associated with decreased Gas6, resulting in loss of the beneficial effects from activating membrane-bound Axl and Mer receptors.     

Inherited 18q23 duplication in a fetus with multiple congenital anomalies

We report on a fetus with multiple congenital anomalies including atypical lissencephaly, corpus callosum agenesis, cerebellar hypoplasia, cleft palate, ventricular septal defect, and hypoplastic aortic arch. The initial routine chromosome study failed to detect any abnormality. Subtelomeres analysis by MLPA identified an 18q23 duplication inherited from its healthy father. We describe the anomalies identified and discuss diagnosis and the causability of this telomeric duplication.     

With complements: C3 inhibition in the clinic

C3 is a key complement protein, located at the nexus of all complement activation pathways. Extracellular, tissue, cell-derived, and intracellular C3 plays critical roles in the immune response that is dysregulated in many diseases, making it an attractive therapeutic target. However, challenges such as very high concentration in blood, increased acute expression, and the elevated risk of infections have historically posed significant challenges in the development of C3-targeted therapeutics. This is further complicated because C3 activation fragments and their receptors trigger a complex network of downstream effects; therefore, a clear understanding of these is needed to provide context for a better understanding of the mechanism of action (MoA) of C3 inhibitors, such as pegcetacoplan. Because of C3's differential upstream position to C5 in the complement cascade, there are mechanistic differences between pegcetacoplan and eculizumab that determine their efficacy in patients with paroxysmal nocturnal hemoglobinuria. In this review, we compare the MoA of pegcetacoplan and eculizumab in paroxysmal nocturnal hemoglobinuria and discuss the complement-mediated disease that might be amenable to C3 inhibition. We further discuss the current state and outlook for C3-targeted therapeutics and provide our perspective on which diseases might be the next success stories in the C3 therapeutics journey.     

1p36 deletion syndrome: Review and mapping with further characterization of the phenotype,a new cohort of 86 patients

Chromosome 1p36 deletion syndrome (1p36DS) is one of the most common terminal deletion syndromes (incidence between 1/5000 and 1/10,000 live births in the American population), due to a heterozygous deletion of part of the short arm of chromosome 1. The 1p36DS is characterized by typical craniofacial features, developmental delay/intellectual disability, hypotonia, epilepsy, cardiomyopathy/congenital heart defect, brain abnormalities, hearing loss, eyes/vision problem, and short stature. The aim of our study was to (1) evaluate the incidence of the 1p36DS in the French population compared to 22q11.2 deletion syndrome and trisomy 21; (2) review the postnatal phenotype related to microarray data, compared to previously publish prenatal data. Thanks to a collaboration with the ACLF (Association des Cytogénéticiens de Langue Française), we have collected data of 86 patients constituting, to the best of our knowledge, the second-largest cohort of 1p36DS patients in the literature. We estimated an average of at least 10 cases per year in France. 1p36DS seems to be much less frequent than 22q11.2 deletion syndrome and trisomy 21. Patients presented mainly dysmorphism, microcephaly, developmental delay/intellectual disability, hypotonia, epilepsy, brain malformations, behavioral disorders, cardiomyopathy, or cardiovascular malformations and, pre and/or postnatal growth retardation. Cardiac abnormalities, brain malformations, and epilepsy were more frequent in distal deletions, whereas microcephaly was more common in proximal deletions. Mapping and genotype–phenotype correlation allowed us to identify four critical regions responsible for intellectual disability. This study highlights some phenotypic variability, according to the deletion position, and helps to refine the phenotype of 1p36DS, allowing improved management and follow-up of patients.     

Safety and immunogenicity of adjuvanted recombinant subunit herpes zoster vaccine in lung transplant recipients

Lung transplant recipients are at high risk for herpes zoster and preventive measures are a significant unmet need. We investigated the safety and immunogenicity of two doses of a recombinant zoster vaccine (RZV) in lung transplant recipients (≥50 years). We enrolled 50 patients of which 49 received at least one vaccine dose. Anti-glycoprotein E (gE) antibody levels (n = 43) increased significantly compared to baseline (median optical density [OD] 1.96; interquartile range [IQR]: 1.17–2.89) after the first (median OD 3.41, IQR 2.54–3.81, p < .0001) and second vaccine dose (median OD 3.63, IQR 3.39–3.86, p < .0001). gE-specific polyfunctional CD4+ T cell frequencies (n = 38) also increased from baseline (median 85 per 10⁶ CD4+ T cells; IQR: 46–180) to the first (median 128 per 10⁶ CD4+ T cells; IQR: 82–353; p = .023) and after the second dose (median 361 per 10⁶ CD4+ T cells; IQR: 146–848; p < .0001). Tenderness (83.0%; 95%CI: 69.2–92.4%) and redness (31.9%; 95%CI: 19.1–47.1%) at injection site were common. One rejection episode within 3 weeks of vaccination was observed. This is the first study demonstrating that RZV was safe and elicited significant humoral and cell-mediated immunity in lung transplant recipients. RZV is a new option for the prevention of shingles in this population.     

Multi‐scale network regression for brain‐phenotype associations

Brain networks are increasingly characterized at different scales, including summary statistics, community connectivity, and individual edges. While research relating brain networks to behavioral measurements has yielded many insights into brain‐phenotype relationships, common analytical approaches only consider network information at a single scale. Here, we designed, implemented, and deployed Multi‐Scale Network Regression (MSNR), a penalized multivariate approach for modeling brain networks that explicitly respects both edge‐ and community‐level information by assuming a low rank and sparse structure, both encouraging less complex and more interpretable modeling. Capitalizing on a large neuroimaging cohort (n = 1, 051) , we demonstrate that MSNR recapitulates interpretable and statistically significant connectivity patterns associated with brain development, sex differences, and motion‐related artifacts. Compared to single‐scale methods, MSNR achieves a balance between prediction performance and model complexity, with improved interpretability. Together, by jointly exploiting both edge‐ and community‐level information, MSNR has the potential to yield novel insights into brain‐behavior relationships.     

The proteome microenvironment determines the protective effect of preconditioning in cisplatin-induced acute kidney injury

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Automated measurement of lymph nodes: a phantom study

The purpose of this study was to assess the accuracy of automated nodal quantification in a phantom. MDCT of a phantom with 17 synthetic lymph nodes of different sizes (diameter 6.0–30.0 mm) was performed at varying tube currents, reconstruction kernels and slice thicknesses. RECIST diameter and volume were measured using an automated software tool. Results were compared with the reference diameter and volume by calculating the absolute percentage error (APE). Degree of agreement between software and reference measurements was evaluated by computing corresponding concordance correlation coefficients (CCC). Under varying tube currents the mean APE (CCC) varied between 5.18% and 10.12% (0.95–0.99) for RECIST diameter and between 7.22% and 16.21% (0.94–1.00) for the volume. At different reconstruction kernels the mean APE values ranged between 7.20% and 7.55% (0.99) (RECIST) and between 8.96% and 14.42% (1.00) (volume). With different slice thicknesses the mean APE values differed from 5.81% to 9.20% (0.97–0.99) (RECIST) and from 8.16% to 22.66% (0.99–1.00) (volume). Regarding RECIST criteria and volume, automated evaluation of lymph nodes in a phantom demonstrated a high accuracy under varying MDCT parameters.