JAK-STAT signaling maintains homeostasis in T cells and macrophages.

Immune cells need to sustain a state of constant alertness over a lifetime. Yet, little is known about the regulatory processes that control the fluent and fragile balance that is called homeostasis. Here we demonstrate that JAK-STAT signaling, beyond its role in immune responses, is a major regulator of immune cell homeostasis. We investigated JAK-STAT-mediated transcription and chromatin accessibility across 12 mouse models, including knockouts of all STAT transcription factors and of the TYK2 kinase. Baseline JAK-STAT signaling was detected in CD8+ T cells and macrophages of unperturbed mice-but abrogated in the knockouts and in unstimulated immune cells deprived of their normal tissue context. We observed diverse gene-regulatory programs, including effects of STAT2 and IRF9 that were independent of STAT1. In summary, our large-scale dataset and integrative analysis of JAK-STAT mutant and wild-type mice uncovered a crucial role of JAK-STAT signaling in unstimulated immune cells, where it contributes to a poised epigenetic and transcriptional state and helps prepare these cells for rapid response to immune stimuli.

Kinase-inactivated CDK6 preserves the long-term functionality of adult hematopoietic stem cells.

ABSTRACT: Hematopoietic stem cells (HSCs) are characterized by the ability to self-renew and to replenish the hematopoietic system. The cell-cycle kinase cyclin-dependent kinase 6 (CDK6) regulates transcription, whereby it has both kinase-dependent and kinase-independent functions. Herein, we describe the complex role of CDK6, balancing quiescence, proliferation, self-renewal, and differentiation in activated HSCs. Mouse HSCs expressing kinase-inactivated CDK6 show enhanced long-term repopulation and homing, whereas HSCs lacking CDK6 have impaired functionality. The transcriptomes of basal and serially transplanted HSCs expressing kinase-inactivated CDK6 exhibit an expression pattern dominated by HSC quiescence and self-renewal, supporting a concept, in which myc-associated zinc finger protein (MAZ) and nuclear transcription factor Y subunit alpha (NFY-A) are critical CDK6 interactors. Pharmacologic kinase inhibition with a clinically used CDK4/6 inhibitor in murine and human HSCs validated our findings and resulted in increased repopulation capability and enhanced stemness. Our findings highlight a kinase-independent role of CDK6 in long-term HSC functionality. CDK6 kinase inhibition represents a possible strategy to improve HSC fitness.

Relevance of dedicated multiple sclerosis serum biomarkers in predicting contrast enhancement with gadolinium: Results from the REDUCE-GAD trial.

BACKGROUND: The presence of contrast enhancement (CE) on magnetic resonance imaging (MRI) is one of the principal criteria for diagnosis and disease activity of multiple sclerosis (MS). Therefore, MS patients are frequently exposed to contrast agents, which may cause deposition in the brain, restricting its use in repeat examinations. Thus, serum biomarkers may be valuable as surrogate parameters to evaluate MS activity. METHODS: REDUCE-GAD was a prospective, multicentric, biobanking study to determine whether established serum markers (neurofilament light chain [NfL], glial fibrillary acidic protein [GFAP], tau protein, ubiquitin-carboxyl-terminal-hydrolase (UCH-L1), S100B and matrix-metalloproteinase 9 [MMP9]) are predictive of CE-positive MRI lesions. Blood samples were obtained from patients undergoing MRI 5 days before or after collection. RESULTS: Patients (N = 102) from four different centers with confirmed MS or related disorders were included; n = 57 (55.9%) showed CE on MRI versus n = 45 (44.1%) without CE. Only higher NfL values indicated CE (odds ratio [OR] 1.05; 95% CI 1.0-1.09) and were correlated with number (ρ = 0.47; p < 0.001) and diameter of CE lesions (ρ = 0.58; p < 0.001). Nfl Z-scores improved diagnostic accuracy (OR 1.52; 95% CI 1.06-2.18). Receiver operator characteristic analysis revealed a reasonable cut-off value for NfL at 14.1 pg/mL (sensitivity 49.1%; specificity 82.2%; positive predictive value 77.8%; negative predictive value 56.0%). NfL ≥59.2 pg/mL was exclusively observed in patients with CE. CONCLUSIONS: Evaluation of several possible serum biomarkers for CE in MS patients provided the most robust results for NfL, particularly as Z-scores. Following further evaluation, biomarkers may help stratify the application of contrast agents for brain imaging in MS patients.

Vemurafenib impairs the repair of ultraviolet radiation-induced DNA damage.

Targeted therapy with the BRAF inhibitors vemurafenib and dabrafenib is an effective treatment regimen in patients with advanced melanoma carrying the BRAF V600E mutation. A common side effect is an enhanced rate of nonmelanoma skin cancer (NMSC). BRAF inhibition leads to a paradoxical enhanced MAPK signalling in BRAF wild-type cells, which might in part be responsible for the enhanced NMSC burden. It is known that disturbances of DNA repair result in an increased rate of NMSC. In the present study, it was investigated whether BRAF inhibitors might interfere with the repair of ultraviolet radiation-induced DNA damage in vitro. Epidermal keratinocytes of 11 Caucasian donors were treated with vemurafenib or dabrafenib and, 24 h later, exposed to ultraviolet A. DNA damage and repair capacity were analysed using south-western slot blot detecting cyclobutane pyrimidine dimers. Using PCR and DNA sequencing, RAS mutations and human papilloma virus genes were investigated. RNA expression was determined using a Gene Expression Chip and qRT-PCR. In 36% of keratinocytes, vemurafenib hampers the repair of ultraviolet A-induced DNA damage. No changes in DNA repair were observed with dabrafenib, indicating a possible substance-specific effect of vemurafenib. In none of the keratinocytes, pre-existing RAS mutations or human papilloma virus-associated DNA sequences were detected. The expression of the interferon-related damage resistance signature is decreased upon vemurafenib treatment in 36% of donors. The enhanced rate of NMSC in patients treated with vemurafenib might be partly related to a vemurafenib-driven impaired capacity for DNA repair.

Fake news? Biotin interference in thyroid immunoassays.

We report on a 47 year old male patient with multiple sclerosis (MS) presenting in our outpatient neurology clinic in Frankfurt/Main for therapy evaluation. Before change of treatment laboratory investigations were performed. Thyroid function tests (TFTs) with a streptavidin/biotin based immunoassay revealed severe hyperthyroidism with positive thyroid autoantibodies suggestive for Graves' disease. Clinical presentation and thyroid sonography were unremarkable. Due to the discordance between clinical presentation and TFTs, we repeated medical history, in which the patient reported taking high-doses of biotin (300 mg/day) for MS. Recent studies with patients suffering from primary and secondary progressive MS, indicated promising effects of high-dose biotin on MS-related disability. In immunoassays relaying on streptavidin-biotin interaction, biotin intake can cause falsely high or low results. Two weeks after withdrawing biotin, biotin/streptavidin dependant assays showed no longer the biochemical picture of severe hyperthyroidism. Biotin intake should be paused for at least two to five days prior to the use of biotin/streptavidin dependant assays. Alternatively, non-biotin/streptavidin dependant assays (radioimmunoassay, gas chromatography-mass spectrometry/liquid chromatography-mass spectrometry) may be used.

Detecting depression in Alzheimer's disease: evaluation of four different scales.

Depression is a frequent condition in Alzheimer's disease (AD). The prevalence of depressive symptoms depends on the severity of dementia and the instruments used. Our aim was to assess the prevalence of depression dependent on the severity of dementia by four different scales: The 15-point Geriatric Depression Scale (GDS), the Montgomery and Asperg Depression Scale (MADRS), the Cornell Scale for Depression in Dementia (CSDD) and the Nurses Observation Scale for Geriatric Patients (NOSGER). The study population consisted of 316 patients with Alzheimer's disease from a psychiatric out-patients memory-clinic, which was divided into two groups: mild AD (Mini-Mental Status Examination (MMSE) > or = 18) and moderate to severe AD (MMSE <18). Additionally, internal consistency and correlation of these scales were calculated. Prevalence of depression ranged between 27.5 and 53.4% in mild AD and between 36.3 and 68.4% in moderate to severe AD. Internal consistency was good in all scales (Cronbach's alpha .63-.85). For MADRS and CSDD it was independent of the stage of AD, while in GDS and NOSGER internal consistency decreased with severity of dementia. Correlation between the scales was better in mild AD than moderate to severe AD; the best results were obtained for the correlation between CSDD and MADRS in both groups. We conclude that in our study population CSDD and MADRS were the most consistent tools for detecting depression in AD independently of the severity of dementia.

Overexpression of IL-4 alters the homeostasis in the skin.

IL-4 has been implicated to play an important role in the pathogenesis of many inflammatory diseases including skin diseases such as atopic dermatitis. Because it is not clear which pathologic features of atopic dermatitis are dependent on IL-4, we assessed the consequences of IL-4 overexpression in the skin, using transgenic mice overexpressing IL-4 ubiquitously. Although transgenic mice display no clinical signs of skin inflammation, IL-4 induced a wide spectrum of pathologies including an increased number of mast cells and Langerhans cells in dermis and epidermis, respectively, focal deposition of collagen and a considerably reduced adipocyte layer in the dermis as well as an increased mitotic activity of keratinocytes, reflected in acanthosis and hyperkeratosis. The increase in Langerhans cell number may be explained in part by the substantially reduced Langerhans cell emigration from the epidermis in transgenic mice. The molecular mechanism behind this phenomenon remains to be clarified. Under in vitro culture conditions, Langerhans cells from transgenic mice undergo a maturation process similar to that of Langerhans cells from control mice, and their immunostimulatory capacity is also comparable. In contrast, transgenic Langerhans cells are superior to control Langerhans cells in their antigen-processing capacity. We conclude that the overexpression of IL-4 in the skin is, by itself, not sufficient for the induction of a full-blown atopic dermatitis phenotype, but several changes seen in the skin of transgenic mice mirror the cardinal pathologic manifestations of this disease.

Internalization via plasmalemmal vesicles: a route for antidesmoplakin autoantibodies into cultured human keratinocytes.

Recently, autoantibodies to desmoplakin I and II have been identified in a subset of patients with a severe form of erythema multiforme. These autoantibodies recognize a specific peptide sequence at the carboxy terminal domain of desmoplakin I and II responsible for interaction with keratin filaments. Desmoplakins are major constitutive proteins of the inner dense desmosomal plaque of keratinocytes and are entirely localized within the cells. With the assumption of pathogenecity for circulating autoantibodies, the question arose how antidesmoplakin autoantibodies enter keratinocytes. Utilizing immunhistochemical procedures for cell motility and time kinetic studies at the light- and electron-microscopic level, we found that autoantibodies are bound at the cell surface of cultured human keratinocytes, internalized via plasmalemmal vesicles, and are found consecutively within tubulovesicular structures inside the cells. At the same time, a fraction of antibodies can be detected at the inner dense desmosomal plaques. Immunogold labeling reveals internalization of autoantibodies in small non-coated plasmalemmal vesicles positive for caveolin. These observations indicate that vesicular transport may represent a relevant biological mechanism for antidesmoplakin autoantibodies to enter keratinocytes and allow access to their corresponding antigenic target in vivo.

Depression in Alzheimer's disease might be associated with apolipoprotein E epsilon 4 allele frequency in women but not in men.

The association between depression and apolipoprotein E (apoE) was investigated in 137 out-patients with Alzheimer's disease. An ICD-10 diagnosis of depression was found in 21.1% of all patients. There was a good correlation between clinicians' diagnoses and blinded rating by the Montgomery-Asberg Depression Rating Scale (r = 0.70). In male patients, apoE 3/3 was detected in 34.1%, 3/4 in 38.6%, 4/4 in 13.6%, 2/4 in 6.8% and 2/3 in 6.8% of cases. In female patients, apoE 3/3 was detected in 35.5%, 3/4 in 45.2%, 4/4 in 12.8%, 2/4 in 3.2% and 2/3 in 3.2% of cases. When analyzing the variance of gene dosage effect, the frequency of the apoE epsilon 4 allele was significantly increased in depressed women but not in men. This effect remained stable in stepwise regression analysis when depression as the dependent variable was tested against the independent variables age, age of onset, duration of disease, cognitive status and years of school education.