Angiogenesis-associated pathways play critical roles in neonatal sepsis outcomes.

Neonatal sepsis is a major cause of childhood mortality. Limited diagnostic tools and mechanistic insights have hampered our abilities to develop prophylactic or therapeutic interventions. Biomarkers in human neonatal sepsis have been repeatedly identified as associated with dysregulation of angiopoietin signaling and altered arachidonic acid metabolism. We here provide the mechanistic evidence in support of the relevance for these observations. Angiopoetin-1 (Ang-1), which promotes vascular integrity, was decreased in blood plasma of human and murine septic newborns. In preclinical models, administration of Ang-1 provided prophylactic protection from septic death. Arachidonic acid metabolism appears to be functionally connected to Ang-1 via reactive oxygen species (ROS) with a direct role of nitric oxide (NO). Strengthening this intersection via oral administration of arachidonic acid and/or the NO donor L-arginine provided prophylactic as well as therapeutic protection from septic death while also increasing plasma Ang-1 levels among septic newborns. Our data highlight that targeting angiogenesis-associated pathways with interventions that increase Ang-1 activity directly or indirectly through ROS/eNOS provide promising avenues to prevent and/or treat severe neonatal sepsis.

The bone marrow microenvironment of pre-B acute lymphoblastic leukemia at single-cell resolution.

The bone marrow microenvironment (BMM) plays a key role in leukemia progression, but its molecular complexity in pre-B cell acute lymphoblastic leukemia (B-ALL), the most common cancer in children, remains poorly understood. To gain further insight, we used single-cell RNA sequencing to characterize the kinetics of the murine BMM during B-ALL progression. Normal pro- and pre-B cells were found to be the most affected at the earliest stages of disease and this was associated with changes in expression of genes regulated by the AP1-transcription factor complex and regulatory factors NELFE, MYC and BCL11A. Granulocyte-macrophage progenitors show reduced expression of the tumor suppressor long non-coding RNA Neat1 and disruptions in the rate of transcription. Intercellular communication networks revealed monocyte-dendritic precursors to be consistently active during B-ALL progression, with enriched processes including cytokine-mediated signaling pathway, neutrophil-mediated immunity and regulation of cell migration and proliferation. In addition, we confirmed that the hematopoietic stem and progenitor cell compartment was perturbed during leukemogenesis. These findings extend our understanding of the complexity of changes and molecular interactions among the normal cells of the BMM during B-ALL progression.

Amsacrine Derivatives Selectively Inhibit Mycobacterial Topoisomerase I (TopA), Impair M. smegmatis Growth and Disturb Chromosome Replication.

Amsacrine, which inhibits eukaryotic type II topoisomerase via DNA intercalation and stabilization of the cleavable topoisomerase-DNA complex, promotes DNA damage and eventually cell death. Amsacrine has also been shown to inhibit structurally distinct bacterial type I topoisomerases (TopAs), including mycobacterial TopA, the only and essential topoisomerase I in Mycobacterium tuberculosis. Here, we describe the modifications of an amsacrine sulfonamide moiety that presumably interacts with mycobacterial TopA, which notably increased the enzyme inhibition and drug selectivity in vivo. To analyse the effects of amsacrine and its derivatives treatment on cell cycle, we used time-lapse fluorescence microscopy (TLMM) and fusion of the ß-subunit of DNA polymerase III with enhanced green fluorescence protein (DnaN-EGFP). We determined that treatment with amsacrine and its derivatives increased the number of DnaN-EGFP complexes and/or prolonged the time of chromosome replication and cell cycle notably. The analysis of TopA depletion strain confirmed that lowering TopA level results in similar disturbances of chromosome replication. In summary, since TopA is crucial for mycobacterial cell viability, the compounds targeting the enzyme disturbed the cell cycle and thus may constitute a new class of anti-tuberculosis drugs.

New therapeutic opportunities from dissecting the pre-B leukemia bone marrow microenvironment.

The microenvironments of leukemia and cancer are critical for multiple stages of malignancies, and they are an attractive therapeutic target. While skeletal abnormalities are commonly seen in children with acute lymphoblastic leukemia (ALL) prior to initiating osteotoxic therapy, little is known about the alterations to the bone marrow microenvironment during leukemogenesis. Therefore, in this study, we focused on the development of precursor-B cell ALL (pre-B ALL) in an immunocompetent BCR-ABL1+ model. Here we show that hematopoiesis was perturbed, B lymphopoiesis was impaired, collagen production was reduced, and the number of osteoblastic cells was decreased in the bone marrow microenvironment. As previously found in children with ALL, the leukemia-bearing mice exhibited severe bone loss during leukemogenesis. Leukemia cells produced high levels of receptor activator of nuclear factor κB ligand (RANKL), sufficient to cause osteoclast-mediated bone resorption. In vivo administration of zoledronic acid rescued leukemia-induced bone loss, reduced disease burden and prolonged survival in leukemia-bearing mice. Taken together, we provide evidence that targeting leukemia-induced bone loss is a therapeutic strategy for pre-B ALL.

[Searching for new antibiotics--inhibitors of bacterial chromosome replication]. / W poszukiwaniu nowych antybiotyków--inhibitory replikacji chromosomów bakteryjnych.

The excessive and often unreasonable use of antibacterial drugs leads to rise of antibioticresistant strains. To overcome this problem, new antibiotics are searched and the new drug targets are investigated. The proteins involved in replication of bacterial chromosomes seem to be promising candidates for drug targets since they are involved in crucial life pathways and are structurally and/or functionally different from the eukaryotic homologues. Within last few years, a large number of newly developed methods allowed to search among thousands of molecules for the ones that specifically inhibit DNA synthesis in the prokaryotic cell. In this review, we present some of these methods.

Topoisomerase I (TopA) is recruited to ParB complexes and is required for proper chromosome organization during Streptomyces coelicolor sporulation.

Streptomyces species are bacteria that resemble filamentous fungi in their hyphal mode of growth and sporulation. In Streptomyces coelicolor, the conversion of multigenomic aerial hyphae into chains of unigenomic spores requires synchronized septation accompanied by segregation of tens of chromosomes into prespore compartments. The chromosome segregation is dependent on ParB protein, which assembles into an array of nucleoprotein complexes in the aerial hyphae. Here, we report that nucleoprotein ParB complexes are bound in vitro and in vivo by topoisomerase I, TopA, which is the only topoisomerase I homolog found in S. coelicolor. TopA cannot be eliminated, and its depletion inhibits growth and blocks sporulation. Surprisingly, sporulation in the TopA-depleted strain could be partially restored by deletion of parB. Furthermore, the formation of regularly spaced ParB complexes, which is a prerequisite for proper chromosome segregation and septation during the development of aerial hyphae, has been found to depend on TopA. We hypothesize that TopA is recruited to ParB complexes during sporulation, and its activity is required to resolve segregating chromosomes.