The unbearable lightness of bone marrow homeostasis

The anatomical and functional dimensions of bone marrow topography have been at the forefront of modern bone and immunological research for many years and remain a source of complexity and perplexity due to the multitude of microhabitats within this microenvironment. In fact, research has uncovered fascinating functional aspects of bone marrow residents, and the bone marrow niche has been identified as the foremost reservoir of a variety of cells including hematopoietic, skeletal and endothelial stem/progenitor cells. The physical interactions of the marrow residents, combined with the release of cytokines and growth factors, organize well-defined operative compartments, which preserve bone and immune cell homeostasis. In a simplistic view, both the hematopoietic and bone marrow stromal (mesenchymal) stem/progenitor cell populations dwell at the interface between the endosteum and the bone marrow area (endosteal niche) and in the perivascular space (vascular niche). Indeed, the tantalizing hypothesis of bone marrow regulatory dependency on these niches is supported by current research insofar as the increase in the number of osteoblasts results in a concomitant increase in the hematopoietic population, indicating that the osteoblasts and the endosteal niche are key components of HSC maintenance. On the other hand, impaired function of the vascular niche compromises the endosteal niche's ability to support hematopoiesis. These fascinating discoveries indicate that there are strong ties between bone marrow inhabitants within the confines of the bone marrow itself. When these ties fail, niche-niche communication suffers and results in reduced bone formation, enfeebled hematopoiesis and unrestrained HSC migration through blood circulation. This study focused on the extraordinary homeostatic equilibrium and function of both bone and immune cells within the spatially defined microenvironment of bone marrow. But how important is the anatomically outlined scenery in which the bone marrow entity supports and hosts the hematopoietic elements

A Splicing Mutation in the Novel Mitochondrial Protein DNAJC11 Causes Motor Neuron Pathology Associated with Cristae Disorganization, and Lymphoid Abnormalities in Mice

Mitochondrial structure and function is emerging as a major contributor to neuromuscular disease, highlighting the need for the complete elucidation of the underlying molecular and pathophysiological mechanisms. Following a forward genetics approach with N-ethyl-N-nitrosourea (ENU)-mediated random mutagenesis, we identified a novel mouse model of autosomal recessive neuromuscular disease caused by a splice-site hypomorphic mutation in a novel gene of unknown function, DnaJC11. Recent findings have demonstrated that DNAJC11 protein co-immunoprecipitates with proteins of the mitochondrial contact site (MICOS) complex involved in the formation of mitochondrial cristae and cristae junctions. Homozygous mutant mice developed locomotion defects, muscle weakness, spasticity, limb tremor, leucopenia, thymic and splenic hypoplasia, general wasting and early lethality. Neuropathological analysis showed severe vacuolation of the motor neurons in the spinal cord, originating from dilatations of the endoplasmic reticulum and notably from mitochondria that had lost their proper inner membrane organization. The causal role of the identified mutation in DnaJC11 was verified in rescue experiments by overexpressing the human ortholog. The full length 63 kDa isoform of human DNAJC11 was shown to localize in the periphery of the mitochondrial outer membrane whereas putative additional isoforms displayed differential submitochondrial localization. Moreover, we showed that DNAJC11 is assembled in a high molecular weight complex, similarly to mitofilin and that downregulation of mitofilin or SAM50 affected the levels of DNAJC11 in HeLa cells. Our findings provide the first mouse mutant for a putative MICOS protein and establish a link between DNAJC11 and neuromuscular diseases

MDR-involved human glutathione transferases (hGSTs) are targets for inhibition by 2,2'-dihydroxybenzophenones and N-carbonyl analogues

Over expression of human GSTA1-1 in tumour cells is part of MDR mechanisms. Substituted 2-hydroxybenzophenones are ubiquitous in naturally occurring and synthetic compounds, exhibiting important biological activities. 2,2’-Dihydroxybenzophenones and N-carbonyl analogues, structurally, are ringopened forms of xanthone analogues which we reported recently as hGSTA1-1 inhibitors. The present study combined GST inhibition screening, in silico molecular docking and enzyme inhibition kinetics, revealing four analogues with strong inhibitory potency (IC50 = 0.18-1.8 μM) and modest cytotoxic activity for Caco2 cell line (LC50 = 35 to > 400 μM), thus being useful as lead structures for the design of new inhibitors against hGSTs

Dexamethasone Administration in Mice Leads to Less Body Weight Gain over Time, Lower Serum Glucose, and Higher Insulin Levels Independently of NRF2.

Glucocorticoids are used widely on a long-term basis in autoimmune and inflammatory diseases. Their adverse effects include the development of hyperglycemia and osteoporosis, whose molecular mechanisms have been only partially studied in preclinical models. Both these glucocorticoid-induced pathologies have been shown to be mediated at least in part by oxidative stress. The transcription factor nuclear erythroid factor 2-like 2 (NRF2) is a central regulator of antioxidant and cytoprotective responses. Thus, we hypothesized that NRF2 may play a role in glucocorticoid-induced metabolic disease and osteoporosis. To this end, WT and Nrf2 knockout (Nrf2KO) mice of both genders were treated with 2 mg/kg dexamethasone or vehicle 3 times per week for 13 weeks. Dexamethasone treatment led to less weight gain during the treatment period without affecting food consumption, as well as to lower glucose levels and high insulin levels compared to vehicle-treated mice. Dexamethasone also reduced cortical bone volume and density. All these effects of dexamethasone were similar between male and female mice, as well as between WT and Nrf2KO mice. Hepatic NRF2 signaling and gluconeogenic gene expression were not affected by dexamethasone. A 2-day dexamethasone treatment was also sufficient to increase insulin levels without affecting body weight and glucose levels. Hence, dexamethasone induces hyperinsulinemia, which potentially leads to decreased glucose levels, as well as osteoporosis, both independently of NRF2

Designer Xanthone An Inhibitor Scaffold for MDR-Involved Human Glutathione Transferase Isoenzyme A1-1

Glutathione transferases (GSTs) are cell detoxifiers involved in multiple drug resistance (MDR), hampering the effectiveness of certain anticancer drugs. To our knowledge, this is the first report on well-defined synthetic xanthones as GST inhibitors. Screening 18 xanthones revealed three derivatives bearing a bromomethyl and a methyl group (7) or two bromomethyl groups (8) or an aldehyde group (17), with high inhibition potency (>85%), manifested by low IC50 values (7: 1.59 ± 0.25 μM, 8: 5.30 ± 0.30 μM, and 17: 8.56 ± 0.14 μM) and a competitive modality of inhibition versus CDNB (Ki(7) = 0.76 ± 0.18 and Ki(17) = 1.69 ± 0.08 μM). Of them, derivative 17 readily inhibited hGSTA1-1 in colon cancer cell lysate (IC50 = 10.54 ± 2.41 μM). Furthermore, all three derivatives were cytotoxic to Caco-2 intact cells, with 17 being the least cytotoxic (LC50 = 151.3 ± 16.3 μM). The xanthone scaffold may be regarded as a pharmacophore for hGSTA1-1 and the three derivatives, especially 17, as potent precursors for the synthesis of new inhibitors and conjugate prodrugs for human GSTs

2,20-Dihydroxybenzophenones and their carbonyl N-analogues as inhibitor scaffolds for MDR-involved human glutathione transferase isoenzyme A1-1

The MDR-involved human GSTA1-1, an important isoenzyme overexpressed in several tumors leading to chemotherapeutic-resistant tumour cells, has been targeted by 2,2′-dihydroxybenzophenones and some of their carbonyl N-analogues, as its potential inhibitors. A structure-based library of the latter was built-up by a nucleophilic cleavage of suitably substituted xanthones to 2,2′-dihydroxy-benzophenones (5–9) and subsequent formation of their N-derivatives (oximes 11–13 and N-acyl hydrazones 14–16). Screening against hGSTA1-1 led to benzophenones 6 and 8, and hydrazones 14 and 16, having the highest inhibition potency (IC50 values in the range 0.18 ± 0.02 to 1.77 ± 0.10 μM). Enzyme inhibition kinetics, molecular modeling and docking studies showed that they interact primarily at the CDNB-binding catalytic site of the enzyme. In addition, the results from cytotoxicity studies with human colon adenocarcinoma cells showed low LC50 values for benzophenone 6 and its N-acyl hydrazone analogue 14 (31.4 ± 0.4 μM and 87 ± 1.9 μM, respectively), in addition to the strong enzyme inhibition profile (IC50(6) = 1,77 ± 0.10 μM; IC50(14) = 0.33 ± 0.05 μM). These structures may serve as leads for the design of new potent mono- and bi-functional inhibitors and pro-drugs against human GTSs

MUGEN mouse database; Animal models of human immunological diseases

The MUGEN mouse database (MMdb) (www.mugen-noe.org/database/) is a database of murine models of immune processes and immunological diseases. Its aim is to share and publicize information on mouse strain characteristics and availability from participating institutions. MMdb's basic classification of models is based on three major research application categories: Models of Human Disease, Models of Immune Processes and Transgenic Tools. Data on mutant strains includes detailed information on affected gene(s), mutant allele(s) and genetic background (DNA origin, gene targeted, host and backcross strain background). Each gene/transgene index also includes IDs and direct links to Ensembl, ArrayExpress, EURExpress and NCBI's Entrez Gene database. Phenotypic description is standardized and hierarchically structured, based on MGI's mammalian phenotypic ontology terms. Availability (e.g. live mice, cryopreserved embryos, sperm and ES cells) is clearly indicated, along with handling and genotyping details (in the form of documents or hyperlinks) and all relevant contact information (including EMMA and Jax/IMSR hyperlinks where available). MMdb's design offers a user-friendly query interface and provides instant access to the list of mutant strains and genes. Database access is free of charge and there are no registration requirements for data querying