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Age is a risk factor for hematologic malignancies. Attributes of the aging hematopoietic system include increased myelopoiesis, impaired adaptive immunity, and a functional decline of the hematopoietic stem cells (HSCs) that maintain hematopoiesis. Changes in the composition of diverse HSC subsets have been suggested to be responsible for age-related alterations, however, the underlying regulatory mechanisms are incompletely understood in the context of HSC heterogeneity. In this study, we investigated how distinct HSC subsets, separated by CD49b, functionally and molecularly change their behavior with age. We demonstrate that the lineage differentiation of both lymphoid-biased and myeloid-biased HSC subsets progressively shifts to a higher myeloid cellular output during aging. In parallel, we show that HSCs selectively undergo age-dependent gene expression and gene regulatory changes in a progressive manner, which is initiated already in the juvenile stage. Overall, our studies suggest that aging intrinsically alters both cellular and molecular properties of HSCs., QC 20240924

Although tyrosine kinase inhibitors (TKIs) are effective in treating chronic myeloid leukemia (CML), they often fail to eradicate the leukemia-initiating stem cells (LSCs), causing disease persistence and relapse. Evidence indicates that LSC persistence may be because of bone marrow (BM) niche protection; however, little is known about the underlying mechanisms. Herein, we molecularly and functionally characterize BM niches in patients with CML at diagnosis and reveal the altered niche composition and function in these patients. Long-term culture initiating cell assay showed that the mesenchymal stem cells from patients with CML displayed an enhanced supporting capacity for normal and CML BM CD34+CD38- cells. Molecularly, RNA sequencing detected dysregulated cytokine and growth factor expression in the BM cellular niches of patients with CML. Among them, CXCL14 was lost in the BM cellular niches in contrast to its expression in healthy BM. Restoring CXCL14 significantly inhibited CML LSC maintenance and enhanced their response to imatinib in vitro, and CML engraftment in vivo in NSG-SGM3 mice. Importantly, CXCL14 treatment dramatically inhibited CML engraftment in patient-derived xenografted NSG-SGM3 mice, even to a greater degree than imatinib, and this inhibition persisted in patients with suboptimal TKI response. Mechanistically, CXCL14 upregulated inflammatory cytokine signaling but downregulated mTOR signaling and oxidative phosphorylation in CML LSCs. Together, we have discovered a suppressive role of CXCL14 in CML LSC growth. CXCL14 might offer a treatment option targeting CML LSCs., Funding: Institute for Regenerative Medicine, Karolinska Institute Doctoral Edu-cation (KID) [2-1293/2014, 2021-00480]; Stiftelsen Clas Gro-schinskys Minnesfond [M16 50]; Knut and Alice Wallenberg Foundation [KAW 2020.0102]; Cancer Research KI; Incyte Biosciences Nordic; Blodcancerfonden; Nordic Cancer Union and Cancer Foundation Finland

eSSENCE

Tyrosine kinase inhibitors targeting the BCR-ABL oncoprotein in chronic myeloid leukemia (CML) are remarkably effective inducing deep molecular remission in most patients. However, they are less effective to eradicate the leukemic stem cells (LSC), resulting in disease persistence. Therefore, there is great need to develop novel therapeutic strategies to specifically target the LSC. In an experimental mouse CML model system, the leukotriene pathway, and specifically, the expression ALOX5, encoding 5-lipoxygenase (5-LO), has been reported as a critical regulator of the LSC. Based on these results, the 5-LO inhibitor zileuton has been introduced in clinical trials as a therapeutic option to target the LSC although its effect on primary human CML LSC has not been studied. We have here by using multiplex single cell PCR analyzed the expression of the mediators of the leukotriene pathway in bone marrow (BM) BCR-ABL(+)CD34(+)CD38(-) cells at diagnosis, and found low or undetectable expression of ALOX5. In line with this, zileuton did not exert significant overall growth inhibition in the long-term culture-initiating cell (LTC-IC) and colony (CFU-C) assays of BM CD34(+)CD38(-) cells from 7 CML patients. The majority of the single leukemic BCR-ABL(+)CD34(+)CD38(-) cells expressed cysteinyl leukotriene receptors CYSLTI and CYSLT2. However, montelukast, an inhibitor of CYSLTI, also failed to significantly suppress CFU-C and LTC-IC growth. These findings indicate that targeting ALOX5 or CYSLTI signaling with leukotriene antagonists, introduced into the clinical practice primarily as prophylaxis and treatment for asthma, may not be a promising pharmacological strategy to eradicate persisting LSC in CML patients. (C) 2017 The Author(s). Published by Elsevier Inc.

Valproic acid (VPA) is an anticonvulsant used to treat bipolar disorder, a psychiatric disease associated with disturbances in circadian rhythmicity. Little is known about how VPA affects circadian rhythms. The authors cultured tissues containing the master brain pacemaker for circadian rhythmicity, the suprachiasmatic nuclei (SCN), and skin fibroblasts from transgenic PERIOD2::LUCIFERASE (PER2::LUC) mice and studied the effect of VPA on the circadian PER2::LUC rhythm by measuring bioluminescence. VPA (1 mM) significantly phase advanced the PER2::LUC rhythm when applied at a time point corresponding to the lowest (trough, similar to ZT 0) PER2::LUC expression but phase delayed the PER2::LUC rhythm when the drug was administered at the time of highest (peak, similar to ZT 12) protein expression. In addition, it significantly increased the overall amplitude of PER2::LUC oscillations at time points at or close to ZT 12 but had no effect on period. Real-time PCR analyses on mouse and human fibroblasts revealed that expressions of other clock genes were increased after 2 h treatment with VPA. Because VPA is known to inhibit histone deacetylation, the authors treated cultures with an established histone deacetylation inhibitor, trichostatin A (TSA; 20 ng/mL), to compare the effect of VPA and TSA on molecular rhythmicity. They found that TSA had similar effects on the PER2::LUC rhythm as VPA. Furthermore, VPA and TSA significantly increased acetylation on histone H3 but in comparison little on histone H4. Lithium is another commonly used treatment for bipolar disorder. Therefore, the authors also studied the impact of lithium chloride (LiCl; 10 mM) on the PER2::LUC rhythm. LiCl delayed the phase, but in contrast to VPA and TSA, LiCl lengthened the PER2::LUC period and had no effect on histone acetylation. These results demonstrate that VPA can delay or advance the phase, as well as increase the amplitude, of the PERIOD2::LUCIFERASE rhythm depending on the circadian time of

Although short–term alcohol drinking causes euphoric and stress relieving effects, alcohol abuse is a major risk factor for neurobehavioural, liver and muscle injury as well as reduced host defence with enhanced susceptibility to bacterial infections. Although such reductions also suggest potential use as an anti-inflammatory drug, well known side effects of ethanol limits its clinical use. Instead, an ethanol derivate, ethyl pyruvate (EtP), might serve as an alternative; it is not associated with cerebral intoxica-tion, prolongs survival in a septic shock model and acts rapidly. Endothelial and epithelial cells, the former at the interface between blood and tissues and the latter facing various bodily surfaces, are among the first cells to become ex-posed to ethanol following ingestion. In this thesis I explored their reactions to ethanol and EtP in the setting of an acute inflammatory reaction, e.g. after challenge with LPS, IL-1, TNFalpha or LTB4 mimicking, for instance, sepsis. In paper I, we observed that ethanol attenuated LPS triggered human umbilical vein endothelial cells (HUVEC) to release chemokines and myeloid growth factors such as IL-8, G-CSF, GM-CSF and SCF. Furthermore, exposure to ethanol reduced the adhe-siveness of HUVEC for neutrophils, effects that were possibly linked to the reduced activation of the transcription factor NF-kappaB. In paper II, we report that ethanol impaired G-CSF and IL-8 release from lung epithelial cells (EpC, A549) elicited by IL-1beta or TNFalpha. Moreover, we found that ethanol interfered with translocation from cytosol to nucleus as well as gene activation of the p65 components of NF-kappaB, important for activation of many genes controlling pro-inflammatory systems. In paper III, we compared effects of ethanol and EtP on LPS, IL-1beta or TNFalpha stimu-lated reactions in and between neutrophils, HUVEC and EpC. EtP was several folds more potent than ethanol in decreasing cytokine release, surface expression of adhesion