Oligodendrocytes depend on MCL-1 to prevent spontaneous apoptosis and white matter degeneration

Neurologic disorders often disproportionately affect specific brain regions, and different apoptotic mechanisms may contribute to white matter pathology in leukodystrophies or gray matter pathology in poliodystrophies. We previously showed that neural progenitors that generate cerebellar gray matter depend on the anti-apoptotic protein BCL-xL. Conditional deletion of Bcl-xL in these progenitors produces spontaneous apoptosis and cerebellar hypoplasia, while similar conditional deletion of Mcl-1 produces no phenotype. Here we show that, in contrast, postnatal oligodendrocytes depend on MCL-1. We found that brain-wide Mcl-1 deletion caused apoptosis specifically in mature oligodendrocytes while sparing astrocytes and oligodendrocyte precursors, resulting in impaired myelination and progressive white matter degeneration. Disabling apoptosis through co-deletion of Bax or Bak rescued white matter degeneration, implicating the intrinsic apoptotic pathway in Mcl-1-dependence. Bax and Bak co-deletions rescued different aspects of the Mcl-1-deleted phenotype, demonstrating their discrete roles in white matter stability. MCL-1 protein abundance was reduced in eif2b5-mutant mouse model of the leukodystrophy vanishing white matter disease (VWMD), suggesting the potential for MCL-1 deficiency to contribute to clinical neurologic disease. Our data show that oligodendrocytes require MCL-1 to suppress apoptosis, implicate MCL-1 deficiency in white matter pathology, and suggest apoptosis inhibition as a leukodystrophy therapy.

Spontaneous apoptosis and BCL2 gene expression as predictors of early death and short overall survival in acute leukemia patients: a prospective, case cohort study

Background Spontaneous apoptosis and expression of MCL1, BCL2, and BCL-XL may be useful prognostic markers in acute leukemia patients. The purpose of this study is to examine the prognosis in adult leukemia patients based on spontaneous apoptosis and anti-apoptosis gene expressions in circulating leukocytes. Results Early, late, and total apoptosis were significantly increased in peripheral blood leukocytes from patients diagnosed with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) compared to controls and in cases of ALL versus AML (P < 0.001). Total apoptosis decreased significantly in AML and ALL patients who died early (ED); P = 0.001 and P = 0.002, respectively. Anti-apoptosis genes MCL1, BCL2, and BCL-XL were upregulated in 62.4%, 64.2%, and 62.4% of the acute leukemia patients, respectively. Among the AML patients, the up-regulation of BCL2 was paradoxically associated with increased apoptosis and low rates of ED. The expression levels of MCL1 and BCL-XL had no significant prognostic values; among patients diagnosed with non-acute promyelocytic leukemia (non-APL-AML), total spontaneous apoptosis, expression of BCL2, and performance status were independent predictors of overall survival (OS). Conclusion Total spontaneous apoptosis and BCL2 gene expression may be valuable independent markers for OS in patients with non-APL-AML. Moreover, in ALL patients decreased levels of spontaneous apoptosis were associated with ED, although this was not a significant predictor of OS.

CBIO-23. ANTIAPOPTOTIC Bcl-xL RESTRICTS APOPTOSIS IN SHH MEDULLOBLASTOMA AND PROMOTES PROGRESSION

Medulloblastomas in most patients are distinctively sensitive to radiation therapy, but the mechanisms that mediate this sensitivity are unclear. Current treatments still fail 20%-60% of patients with SHH medulloblastoma and can leave survivors with long-term neurocognitive and social deficits. Understanding the mechanisms driving the typical radiation-sensitivity may identify less-toxic therapeutic strategies and provide insight into treatment failure. We previously showed that radiation sensitivity depends on the intrinsic apoptotic pathway, mediated by pro-apoptotic BAX. In cerebellar granule neuron progenitors (CGNPs), the cell of origin for SHH medulloblastoma, BAX activity is directly inhibited by anti-apoptotic BCL-xL; Bcl-xL-deleted CGNPs undergo spontaneous apoptosis. To test the therapeutic potential of disrupting BCL-xL in medulloblastoma, we conditionally deleted Bcl-xL in mice genetically engineered to develop SHH medulloblastoma. Here, I show that Bcl-xL deletion slows SHH medulloblastoma growth and prolongs survival of medulloblastoma-bearing mice. Bcl-xL-deleted tumors initially showed increased rates of spontaneous apoptosis, but this effect waned over time, suggesting the emergence of BCL-xL-independent survival mechanisms. We also noted increased microglial infiltration in Bcl-xL-deleted medulloblastomas. We hypothesize that IGF1 produced by microglia in the tumor microenvironment may be contributing to tumor resistance by upregulating translation of MCL-1, an anti-apoptotic BCL-xL homolog. IGF1 is known to upregulate translation through the mTOR pathway, while anti-apoptotic MCL-1 protein abundance is dependent upon translation regulation. Our on-going studies are testing the efficacy of pharmacologically targeting BCL-xL in mice with medulloblastoma, in combination with targeting IGF1 signaling using mTORC1 inhibitors.

A phosphorylation of RIPK3 kinase initiates an intracellular apoptotic pathway that promotes prostaglandin2α-induced corpus luteum regression

Receptor-interacting serine/threonine-protein kinase 3 (RIPK3) normally signals to necroptosis by phosphorylating MLKL. We report here that when the cellular RIPK3 chaperone Hsp90/CDC37 level is low, RIPK3 also signals to apoptosis. The apoptotic function of RIPK3 requires phosphorylation of the serine 165/threonine 166 sites on its kinase activation loop, resulting in inactivation of RIPK3 kinase activity while gaining the ability to recruit RIPK1, FADD, and caspase-8 to form a cytosolic caspase-activating complex, thereby triggering apoptosis. We found that PGF2α induces RIPK3 expression in luteal granulosa cells in the ovary to cause luteal regression through this RIPK3-mediated apoptosis pathway. Mice carrying homozygous phosphorylation-resistant RIPK3 S165A/T166A knockin mutations failed to respond to PGF2α but retained pro-necroptotic function, whereas mice with phospho-mimicking S165D/T166E homozygous knock-in mutation underwent spontaneous apoptosis in multiple RIPK3-expressing tissues and died shortly after birth. Thus, RIPK3 signals to either necroptosis or apoptosis depending on its serine 165/threonine 166 phosphorylation status.

A phosphorylation of RIPK3 kinase initiates an intracellular apoptotic pathway that promotes corpus luteum regression

Receptor-interacting serine/threonine-protein kinase 3 (RIPK3) normally signals to necroptosis by phosphorylating MLKL. We report here that when the cellular RIPK3 chaperone Hsp90/CDC37 level is low, RIPK3 also signals to apoptosis. The apoptotic function of RIPK3 requires phosphorylation of the serine 165/threonine 166 sites on its kinase activation loop, resulting in inactivation of RIPK3 kinase activity while gaining the ability to recruit RIPK1, FADD, and caspase-8 to form a cytosolic caspase-activating complex, thereby triggering apoptosis. We found that PGF2α induces RIPK3 expression in luteal granulosa cells in the ovary to cause luteal regression through this RIPK3-mediated apoptosis pathway. Mice carrying homozygous phosphorylation-resistant RIPK3 S165A/T166A knockin mutations failed to respond to PGF2α but retained pro-necroptotic function, whereas mice with phospho-mimicking S165D/T166E homozygous knockin mutation underwent spontaneous apoptosis in multiple RIPK3-expressing tissues and died shortly after birth. Thus, RIPK3 signals to either necroptosis or apoptosis depending on its serine 165/threonine 166 phosphorylation status.

Influence of lithium chloride on neutrophil activation in the development of systemic inflammatory response syndrome in patients after on-pump cardiac surgery

Цель исследования - изучение in vitro действия хлорида лития на активность нейтрофилов человека при действии сывороток пациентов с синдромом системного воспалительного ответа, развившемся после операций на сердце с искусственным кровообращением. Методика. Исследование проводили in vitro на нейтрофилах, выделенных из крови 6 здоровых доноров. Нейтрофилы активировали при помощи сыворотки пациентов с синдромом системного воспалительного ответа (ССВО), перенесших операции на сердце с искусственным кровообращением (ИК). Активность нейтрофилов оценивали с использованием флуоресцентных антител к маркерам дегрануляции CD11b и CD66b. Уровень апоптоза и некроза нейтрофилов оценивали через 22 ч после выделения из крови здоровых доноров; количественная оценка была проведена с использованием аннексина V и иодистого пропидия на проточном цитофлуориметре. Интактные и активированные нейтрофилы обрабатывали раствором хлорида лития в концентрациях 0,3; 3,0 и 9,0 мМ. Результаты. Инкубация нейтрофилов с сывороткой крови пациентов с ССВО после операций на сердце с ИК увеличивала экспрессию CD11b в 1,5 раза и экспрессию CD66b в 1,4 раза в сравнении с экспрессией на интактных нейтрофилах. Инкубация нейтрофилов с сывороткой крови пациентов с ССВО и раствором хлорида лития в концентрациях 3,0 и 9,0 мМ приводило к статистически значимому снижению уровня экспрессии CD11b CD66b на поверхности нейтрофилов в сравнении с активированными контрольными. Установлено, что хлорид лития в концентрациях 3,0 и 9,0 мМ возвращал уровни экспрессии CD11b и CD66b на активированных нейтрофилах к уровню экспрессии на интактных нейтрофилах. В концентрации 0,3 мМ хлорид лития, используемый при инкубации с активированными нейтрофилами, не вызывал значимого снижения экспрессии CD11b и CD66b относительно контрольных активированных нейтрофилов. Экспрессия CD11b и CD66b на активированных нейтрофилах при их инкубации с хлоридом лития в концентрации 0,3 мМ была значимо выше относительно экспрессии данных молекул на интактных нейтрофилах. Сыворотка пациентов с развившемся ССВО снижала спонтанный апоптоз нейтрофилов, а раствор хлорида лития в концентрации 3,0 или 9,0 мМ, добавленный в среду инкубации, увеличивал способность нейтрофилов к спонтанному апоптозу. Заключение. Хлорид лития оказывал противовоспалительный эффект снижал дегрануляцию и активацию нйтрофилов посредством уменьшения уровня экспрессии молекул CD11b и CD66b на поверхности нейтрофилов, которые предварительно были активированы сыворотками пациентов с ССВО. В концентрации 3,0 мМ и выше хлорид лития индуцировал спонтанный апоптоз нейтрофилов, активированных сыворотками пациентов с ССВО после операций на сердце с ИК. The aim of this work was to study the anti-inflammatory effect of lithium chloride on human neutrophils in vitro under the action of the serum of patients with systemic inflammatory response syndrome (SIRS), which developed after on-pump cardiac surgery. Methods. The study was performed on neutrophils isolated from the blood of five healthy donors, which was activated using serum from patients with SIRS. Neutrophil activity was assessed using fluorescent antibodies to CD11b and CD66b degranulation markers. The level of apoptosis and necrosis of human neutrophils was evaluated 22 hours after isolation. Quantification was performed using annexin V and propidium iodide on a flow cytometer. Intact and activated neutrophils were treated with 0.3, 3.0 аnd 9.0 mM lithium chlorides. Results. Incubation of neutrophils with the blood serum of patients with SIRS after on-pump cardiac surgery increased the expression of CD11b by 1.5 times and the expression of CD66b by 1.4 times compared to expression on intact neutrophils. Incubation of neutrophils with blood serum of patients with SIRS and 3.0 and 9.0 mM lithium chloride solutions led to a statistically significant decrease in the level of expression of CD11b CD66b on the surface of neutrophils in comparison with control activated neutrophils. It was found that 3.0 and 9.0 mM lithium chloride solutions returned the expression levels of CD11b and CD66b on activated neutrophils to the expression level on intact neutrophils. 0.3 mM of lithium chloride, used during incubation with activated neutrophils, did not cause a significant decrease in the expression of CD11b and CD66b relative to control activated neutrophils. The expression of CD11b and CD66b on activated neutrophils during their incubation with 0.3 mM of lithium chloride was significantly higher relative to the expression of these molecules on intact neutrophils. The serum of patients with advanced SIRS decreased the ability of neutrophils to spontaneous apoptosis. 3.0 or 9.0 mM lithium chloride solutions added to the incubation medium increased the ability of neutrophils to spontaneous apoptosis. Conclusion. Lithium chloride reduced the degranulation and activation of neutrophils by reducing the expression level of CD11b and CD66b molecules on the surface of neutrophils that were previously activated by the serum of patients with SIRS. This effect determines the anti-inflammatory influence of lithium chloride. Lithium chloride at 3.0 mM and higher induced spontaneous apoptosis of neutrophils activated by the serum of patients with SIRS after on-pump cardiac surgery.

Human CD133-positive hematopoietic progenitor cells enhance the malignancy of breast cancer cells

Background Human CD133+ hematopoietic progenitor cells (HPCs) are a specific subset of cells that can regulate tumor malignancy. However, the mechanism by which CD133+ HPCs affect the malignancy of human breast cancer has not been reported. Methods CD133+ HPCs were isolated and purified from human umbilical cord blood (UCB). We used in vitro culture of MCF-7 and MDA-MB-231 cell lines, and MCF-7 and MDA-MB-231 cells in nude mice to evaluate whether CD133+ HPCs affected the apoptosis, proliferation, invasion and epithelial mesenchymal transition EMT of breast cancer cells. Results Co-culture with CD133+ HPCs, but not UCB CD133- cells, promoted the proliferation of human breast cancer MCF-7 and MDA-MB-231 cells, accompanied by reducing in vitro spontaneous apoptosis. Co-administration of these two lines with CD133+ HPCs significantly enhanced the growth of implanted breast cancer in vivo. Furthermore, co-culture with CD133+ HPCs, enhanced the invasion of breast cancer cells, N-cadherin and Vimentin expression, but reduced E-cadherin expression in breast cancer cells. Conclusions Our study demonstrated that CD133+ HPCs enhance the malignancy of breast cancer cells by attenuating spontaneous apoptosis and promoting the process of epithelial mesenchymal transition. These findings may provide new insights into the role of human CD133+ HPCs in breast cancer pathogenesis. Therefore, CD133+ HPCs may be a new therapeutic target for inhibiting the progression of breast cancer.

Human CD133-positive hematopoietic progenitor cells enhance the malignancy of breast cancer cells

Background: Human CD133+ hematopoietic progenitor cells (HPCs) are a specific subset of cells that can regulate tumor malignancy. However, the mechanism by which CD133+ HPCs affect the malignancy of human breast cancer has not been reported. Methods: CD133+ HPCs were isolated and purified from human umbilical cord blood (UCB) .We used in vitro culture of MCF-7 and MDA-MB-231 cell lines, and MCF-7 and MDA-MB-231 cells in nude mice to evaluate whether CD133+ HPCs affected the apoptosis, proliferation, invasion and epithelial mesenchymal transition EMT of breast cancer cells. Results: Co-culture with CD133+ HPCs, but not UCB CD133- cells, promoted the proliferation of human breast cancer MCF-7 and MDA-MB-231 cells, accompanied by reducing in vitro spontaneous apoptosis. Co-administration of these two lines with CD133+ HPCs significantly enhanced the growth of implanted breast cancer in vivo. Furthermore, co-culture with CD133+ HPCs, enhanced the invasion of breast cancer cells, N-cadherin and Vimentin expression, but reduced E-cadherin expression in breast cancer cells. Conclusions: Our study demonstrated that CD133+ HPCs enhance the malignancy of breast cancer cells by attenuating spontaneous apoptosis and promoting the process of epithelial mesenchymal transition. These findings may provide new insights into the role of human CD133+ HPCs in breast cancer pathogenesis. Therefore, CD133+ HPCs may be a new therapeutic target for inhibiting the progression of breast cancer.

Human CD133-positive hematopoietic progenitor cells enhance the malignancy of breast cancer cells

Background: Human CD133+ hematopoietic progenitor cells (HPCs) are a specific subset of cells that can regulate tumor malignancy. However, the mechanism by which CD133+ HPCs affect the malignancy of human breast cancer has not been reported. Methods: CD133+ HPCs were isolated and purified from human umbilical cord blood (UCB) .We used in vitro culture of MCF-7 and MDA-MB-231 cell lines, and MCF-7 and MDA-MB-231 cells in nude mice to evaluate whether CD133+ HPCs affected the apoptosis, proliferation, invasion and epithelial mesenchymal transition EMT of breast cancer cells. Results: Co-culture with CD133+ HPCs, but not UCB CD133- cells, promoted the proliferation of human breast cancer MCF-7 and MDA-MB-231 cells, accompanied by reducing in vitro spontaneous apoptosis. Co-administration of these two lines with CD133+ HPCs significantly enhanced the growth of implanted breast cancer in vivo. Furthermore, co-culture with CD133+ HPCs, enhanced the invasion of breast cancer cells, N-cadherin and Vimentin expression, but reduced E-cadherin expression in breast cancer cells. Conclusions: Our study demonstrated that CD133+ HPCs enhance the malignancy of breast cancer cells by attenuating spontaneous apoptosis and promoting the process of epithelial mesenchymal transition. These findings may provide new insights into the role of human CD133+ HPCs in breast cancer pathogenesis. Therefore, CD133+ HPCs may be a new therapeutic target for inhibiting the progression of breast cancer.