SDF-1/CXCL12 modulates mitochondrial respiration of immature blood cells in a bi-phasic manner

SDF-1/CXCL12 is a potent chemokine required for the homing and engraftment of hematopoietic stem and progenitor cells. Previous data from our group has shown that in an SDF-1/CXCL12 transgenic mouse model, lineage(-) Sca-1(+) c-Kit(+) (LSK) bone marrow cells have reduced mitochondrial membrane potential versus wild-type. These results suggested that SDF-1/CXCL12 may function to keep mitochondrial respiration low in immature blood cells in the bone marrow. Low mitochondrial metabolism helps to maintain low levels of reactive oxygen species (ROS), which can influence differentiation. To test whether SDF-1/CXCL12 regulates mitochondrial metabolism, we employed the human leukemia cell line HL-60, that expresses high levels of the SDF-1/CXCL12 receptor, CXCR4, as a model of hematopoietic progenitor cells in vitro. We treated HL-60 cells with SDF-1/CXCL12 for 2 and 24h. Oxygen consumption rates (OCR), mitochondrial-associated ATP production, mitochondrial mass, and mitochondrial membrane potential of HL-60 cells were significantly reduced at 2h and increased at 24h as compared to untreated control cells. These biphasic effects of SDF-1/CXCL12 were reproduced with lineage negative primary mouse bone marrow cells, suggesting a novel function of SDF-1/CXCL12 in modulating mitochondrial respiration by regulating mitochondrial oxidative phosphorylation, ATP production and mitochondrial content

Role of STAT3 and SDF-1/CXCL 12 in mitochondrial function in hematopoietic stem and progenitor cells

Indiana University-Purdue University Indianapolis (IUPUI)Mitochondria are the major ATP producing source within cells. There is increasing data supporting a direct involvement of mitochondria and mitochondrial function in regulating stem cell pluripotency. Mitochondria have also been shown to be important for hematopoietic stem and progenitor cell function. Hematopoietic stem cells have lower numbers of mitochondria (mass), lower mitochondrial membrane potential, and lower ATP levels as compared to other blood cell types. Mitochondria play an important role in hematopoietic stem and progenitor cells, thus we investigated the role of the chemokine, SDF-1/CXCL12, in mitochondrial function in hematopoietic stem and progenitor cells using an SDF-1/CXCL12 transgenic mouse model. We found increased mitochondrial mass is linked to CD34 surface expression in hematopoietic stem and progenitor cells, suggesting that mitochondrial biogenesis is linked to loss of pluripotency. Interestingly these hematopoietic progenitor cells have low mitochondrial membrane potential and these mitochondrial become active prior to leaving the progenitor cell compartment. We also tested the ability of SDF-1/CXL12 to modulate mitochondrial function in vitro by treating the human leukemia cell line, HL-60, and primary mouse lineage- bone marrow cells with SDF-1/CXCL12. We found significantly reduced mitochondrial function at two hours while mitochondrial function was significantly increased at 24 hours. This suggests that SDF1/CXCL12 regulates mitochondrial function in a biphasic manner in a model of hematopoietic progenitors and immature blood cells. This suggests SDF1/CXCL12 may play a role in regulating mitochondrial function in hematopoiesis. We also investigated STAT3 in hematopoietic stem and progenitor cells. Mitochondrial STAT3 plays an essential role in regulating mitochondrial function. By using a knockout (Stat3-/-) mouse model we found that Stat3-/- hematopoietic progenitor cells had reduced colony forming ability, slower cell cycling status, and loss of proliferation in response to multi-cytokine synergy. We also found mitochondrial dysfunction in Stat3-/- hematopoietic stem and progenitor cells. Our results suggest an essential role for mitochondria in HSC function and a novel role for SDF-1/CXCL12 and STAT3 in regulating mitochondrial function in hematopoietic stem and progenitor cells

SIRT1 positively regulates autophagy and mitochondria function in embryonic stem cells under oxidative stress

SIRT1, an NAD-dependent deacetylase, plays a role in regulation of autophagy. SIRT1 increases mitochondrial function and reduces oxidative stress, and has been linked to age-related reactive oxygen species (ROS) generation, which is highly dependent on mitochondrial metabolism. H2O2 induces oxidative stress and autophagic cell death through interference with Beclin 1 and the mTOR signaling pathways. We evaluated connections between SIRT1 activity and induction of autophagy in murine (m) and human (h) embryonic stem cells (ESCs) upon ROS challenge. Exogenous H2 O2 (1 mM) induced apoptosis and autophagy in wild-type (WT) and Sirt1-/- mESCs. High concentrations of H2O2 (1 mM) induced more apoptosis in Sirt1-/-, than in WT mESCs. However, addition of 3-methyladenine, a widely used autophagy inhibitor, in combination with H2O2 induced more cell death in WT than in Sirt1-/- mESCs. Decreased induction of autophagy in Sirt1-/- mESCs was demonstrated by decreased conversion of LC3-I to LC3-II, lowered expression of Beclin-1, and decreased LC3 punctae and LysoTracker staining. H2O2 induced autophagy with loss of mitochondrial membrane potential and disruption of mitochondrial dynamics in Sirt1-/- mESCs. Increased phosphorylation of P70/85-S6 kinase and ribosomal S6 was noted in Sirt1-/- mESCs, suggesting that SIRT1 regulates the mTOR pathway. Consistent with effects in mESCs, inhibition of SIRT1 using Lentivirus-mediated SIRT1 shRNA in hESCs demonstrated that knockdown of SIRT1 decreased H2O2-induced autophagy. This suggests a role for SIRT1 in regulating autophagy and mitochondria function in ESCs upon oxidative stress, effects mediated at least in part by the class III PI3K/Beclin 1 and mTOR pathways

Modeling Sitagliptin Effect on Dipeptidyl Peptidase 4 (DPP4) Activity in Adults with Hematological Malignancies After Umbilical Cord Blood (UCB) Hematopoietic Cell Transplant (HCT)

Background and Objectives— Dipeptidyl peptidase-4 (DPP4) inhibition is a potential strategy to increase the engraftment rate of hematopoietic stem/progenitor cells. A recent clinical trial using sitagliptin, a DPP4 inhibitor approved for type 2 diabetes mellitus, has shown to be a promising approach in adults with hematological malignancies after umbilical cord blood (UCB) hematopoietic cell transplant (HCT). Based on data from this clinical trial, a semi-mechanistic model was developed to simultaneously describe DPP4 activity after multiple doses of sitagliptin in subjects with hematological malignancies after a single-unit UCB HCT. Methods— The clinical study included 24 patients that received myeloablative conditioning followed by 4 oral sitagliptin 600mg with single-unit UCB HCT. Using a nonlinear mixed effects approach, a semi-mechanistic pharmacokinetic/pharmacodynamic model was developed to describe DPP4 activity from this trial data using NONMEM 7.2. The model was used to drive Monte-Carlo simulations to probe various dosage schedules and the attendant DPP4 response. Results— The disposition of sitagliptin in plasma was best described by a 2-compartment model. The relationship between sitagliptin concentration and DPP4 activity was best described by an indirect response model with a negative feedback loop. Simulations showed that twice a day or three times a day dosage schedules were superior to once daily schedule for maximal DPP4 inhibition at the lowest sitagliptin exposure. Conclusion— This study provides the first pharmacokinetic/pharmacodynamic model of sitagliptin in the context of HCT, and provides a valuable tool for exploration of optimal dosing regimens, critical for improving time to engraftment in patients after UCB HCT

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe