Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0392674 (exhaustion)
 13,658 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of cytokines in regulation of hematopoietic stem cells (HSCs) remains poorly understood. Herein we demonstrate that thrombopoietin (THPO) and its receptor, MPL, are critically involved in postnatal steady-state HSC maintenance, reflected in a 150-fold reduction of HSCs in adult Thpo(-/-) mice. Further, whereas THPO and MPL proved not required for fetal HSC expansion, HSC expansion posttransplantation was highly MPL and THPO dependent. The distinct role of THPO in postnatal HSC maintenance is accompanied by accelerated HSC cell-cycle kinetics in Thpo(-/-) mice and reduced expression of the cyclin-dependent kinase inhibitors p57(Kip2) and p19(INK4D) as well as multiple Hox transcription factors. Although also predicted to be an HSC viability factor, BCL2 failed to rescue the HSC deficiency of Thpo(-/-) mice. Thus, THPO regulates posttransplantation HSC expansion as well as the maintenance of adult quiescent HSCs, of critical importance to avoid postnatal HSC exhaustion.
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PMID:Critical role of thrombopoietin in maintaining adult quiescent hematopoietic stem cells. 1837 99

BID, a BH3-only BCL2 family member, functions in apoptosis as well as the DNA-damage response. Our previous data demonstrated that BID is an ATM effector acting to induce cell-cycle arrest and inhibition of apoptosis following DNA damage. Here we show that ATM-mediated BID phosphorylation plays an unexpected role in maintaining the quiescence of haematopoietic stem cells (HSCs). Loss of BID phosphorylation leads to escape from quiescence of HSCs, resulting in exhaustion of the HSC pool and a marked reduction of HSC repopulating potential in vivo. We also demonstrate that BID phosphorylation plays a role in protecting HSCs from irradiation, and that regulating both quiescence and survival of HSCs depends on BID's ability to regulate oxidative stress. Moreover, loss of BID phosphorylation, ATM knockout or exposing mice to irradiation leads to an increase in mitochondrial BID, which correlates with an increase in mitochondrial oxidative stress. These results show that the ATM-BID pathway serves as a critical checkpoint for coupling HSC homeostasis and the DNA-damage stress response to enable long-term regenerative capacity.
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PMID:The ATM-BID pathway regulates quiescence and survival of haematopoietic stem cells. 2244 38

The female germ line in mammals is subjected to massive cell death that eliminates 60-85% of the germinal reserve by birth and continues from birth to adulthood until the exhaustion of the germinal pool. Germ cell demise occurs mainly through apoptosis by means of a biased expression in favour of pro-apoptotic members of the BCL2 gene family. By contrast, the South American plains vizcacha, Lagostomus maximus, exhibits sustained expression of the anti-apoptotic BCL2 gene throughout gestation and a low incidence of germ cell apoptosis. This led to the proposal that, in the absence of death mechanisms other than apoptosis, the female germ line should increase continuously from foetal life until after birth. In this study, we quantified all healthy germ cells and follicles in the ovaries of L. maximus from early foetal life to day 60 after birth using unbiased stereological methods and detected apoptosis by labelling with TUNEL assay. The healthy germ cell population increased continuously from early-developing ovary reaching a 50 times higher population number by the end of gestation. TUNEL-positive germ cells were <0.5% of the germ cell number, except at mid-gestation (3.62%). Mitotic proliferation, entrance into prophase I stage and primordial follicle formation occurred as overlapping processes from early pregnancy to birth. Germ cell number remained constant in early post-natal life, but a remnant population of non-follicular VASA- and PCNA-positive germ cells still persisted at post-natal day 60. L. maximus is the first mammal so far described in which female germ line develops in the absence of constitutive massive germ cell elimination.
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PMID:Quantification of healthy and atretic germ cells and follicles in the developing and post-natal ovary of the South American plains vizcacha, Lagostomus maximus: evidence of continuous rise of the germinal reserve. 2423 69

Functional differences between healthy progenitor and cancer initiating cells may provide unique opportunities for targeted therapy approaches. Hematopoietic stem cells are tightly controlled by a network of CDK inhibitors that govern proliferation and prevent stem cell exhaustion. Loss of Inca1 led to an increased number of short-term hematopoietic stem cells in older mice, but Inca1 seems largely dispensable for normal hematopoiesis. On the other hand, Inca1-deficiency enhanced cell cycling upon cytotoxic stress and accelerated bone marrow exhaustion. Moreover, AML1-ETO9a-induced proliferation was not sustained in Inca1-deficient cells in vivo. As a consequence, leukemia induction and leukemia maintenance were severely impaired in Inca1-/- bone marrow cells. The re-initiation of leukemia was also significantly inhibited in absence of Inca1-/- in MLL-AF9- and c-myc/BCL2-positive leukemia mouse models. These findings indicate distinct functional properties of Inca1 in normal hematopoietic cells compared to leukemia initiating cells. Such functional differences might be used to design specific therapy approaches in leukemia.
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PMID:Maintenance of leukemia-initiating cells is regulated by the CDK inhibitor Inca1. 2552 9

High-risk chronic lymphocytic leukemia (CLL) has been defined by clinical and/or genetic resistance (TP53 abnormalities) to treatment with chemoimmunotherapy (CIT). With the availability of pathway inhibitors (PIs), such as kinase inhibitors and BCL2 antagonists, the outlook of CIT-resistant patients has dramatically improved. Here, we propose a revision of the concept of high-risk CLL, driven by TP53 abnormalities and response to treatment with PI. CLL high-risk-I, CIT-resistant is defined by clinically CIT-resistant disease with TP53 aberrations, but fully responsive to PI. This category is largely the domain of PI-based therapy, and cellular therapy (ie, allogeneic hematopoietic cell transplantation) remains an option only in selected patients with low individual procedure-related risk. In CLL high-risk-II, CIT- and PI-resistant, characterized by increasing exhaustion of pharmacological treatment possibilities, cellular therapies (including chimeric antigen receptor-engineered T cells) should be considered in patients eligible for these procedures. Moreover, molecular and cellular therapies are not mutually exclusive and could be used synergistically to exploit their full potential.
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PMID:High-risk chronic lymphocytic leukemia in the era of pathway inhibitors: integrating molecular and cellular therapies. 2999 21

The mechanisms that regulate hematopoietic stem cell (HSC) regeneration after myelosuppressive injury are not well understood. Here, we showed that disruption of Notch signaling aggravated chemotherapy-induced myelosuppression in inducible genetic mice. Conversely, Notch activation correlated positively with clinical HSC engraftment. We used endothelial-targeted chimeric Notch ligand Delta-like 1 (D1R) to activate Notch signaling in hematopoietic stem/progenitor cells through micro-environmental cellular contact. Recombinant protein D1R contributed to the recovery of the HSC pool and sustained HSC vitality in response to various chemotherapeutic agents in vivo. Mechanistically, D1R treatment promoted HSC proliferation transiently, prevented HSC exhaustion, correlated with activation of the downstream phosphoinositide 3-kinase (PI3K)/extracellular-signal-regulated kinase (ERK)/BCL2 associated agonist of cell death (BAD) signaling axis during regeneration, and partially mediated upregulation of c-Myc in HSCs. These data reveal an unrecognized role for Notch signaling in promoting HSC repopulation after myelosuppressive chemotherapy and offer a new therapeutic approach to mitigate chemotherapy-induced injury.
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PMID:Notch signaling mitigates chemotherapy toxicity by accelerating hematopoietic stem cells proliferation via c-Myc. 3319 68