Distinct roles of resident and nonresident macrophages in nonischemic cardiomyopathy.

Nonischemic cardiomyopathy (NICM) resulting from long-standing hypertension, valvular disease, and genetic mutations is a major cause of heart failure worldwide. Recent observations suggest that myeloid cells can impact cardiac function, but the role of tissue-intrinsic vs. tissue-extrinsic myeloid cells in NICM remains poorly understood. Here, we show that cardiac resident macrophage proliferation occurs within the first week following pressure overload hypertrophy (POH; a model of heart failure) and is requisite for the heart's adaptive response. Mechanistically, we identify Kruppel-like factor 4 (KLF4) as a key transcription factor that regulates cardiac resident macrophage proliferation and angiogenic activities. Finally, we show that blood-borne macrophages recruited in late-phase POH are detrimental, and that blockade of their infiltration improves myocardial angiogenesis and preserves cardiac function. These observations demonstrate previously unappreciated temporal and spatial roles for resident and nonresident macrophages in the development of heart failure.

CCN3 Regulates Macrophage Foam Cell Formation and Atherosclerosis.

Recent studies implicate the Cyr61, CTGF, Nov (CCN) matricellular signaling protein family as emerging players in vascular biology, with NOV (alias CCN3) as an important regulator of vascular homeostasis. Herein, we examined the role of CCN3 in the pathogenesis of atherosclerosis. In response to a 15-week high-fat diet feeding, CCN3-deficient mice on the atherosclerosis-prone Apoe-/- background developed increased aortic lipid-rich plaques compared to control Apoe-/- mice, a result that was observed in the absence of alterations in plasma lipid content. To address the cellular contributor(s) responsible for the atherosclerotic phenotype, we performed bone marrow transplantation experiments. Transplantation of Apoe; Ccn3 double-knockout bone marrow into Apoe-/- mice resulted in an increase of atherosclerotic plaque burden, whereas transplantation of Apoe-/- marrow to Apoe; Ccn3 double-knockout mice caused a reduction of atherosclerosis. These results indicate that CCN3 deficiency, specifically in the bone marrow, plays a major role in the development of atherosclerosis. Mechanistically, cell-based studies in isolated peritoneal macrophages demonstrated that CCN3 deficiency leads to an increase of lipid uptake and foam cell formation, an effect potentially attributed to the increased expression of scavenger receptors CD36 and SRA1, key factors involved in lipoprotein uptake. These results suggest that bone marrow-derived CCN3 is an essential regulator of atherosclerosis and point to a novel role of CCN3 in modulating lipid accumulation within macrophages.

Bcl2 overexpression rescues the hematopoietic stem cell defects in Ku70-deficient mice by restoration of quiescence.

DNA repair is essential for hematopoietic stem cell (HSC) maintenance. Ku70 is a key component of the nonhomologous end-joining pathway, which is the major pathway for DNA double-strand break repair. We find that HSCs from Ku70-deficient mice are severely defective in self-renewal, competitive repopulation, and bone marrow (BM) hematopoietic niche occupancy and that loss of quiescence results in a dramatic defect in the maintenance of Ku70-deficient HSCs. Interestingly, although overexpression of Bcl2 does not rescue the severe combined immunodeficiency phenotype in Ku70-deficient mice, overexpression of Bcl2 in Ku70-deficient HSCs almost completely rescued the impaired HSC quiescence, repopulation, and BM hematopoietic niche occupancy capacities. Together, our data indicate that the HSC maintenance defect of Ku70-deficient mice is due to the loss of HSC quiescent populations, whereas overexpression of Bcl2 rescues the HSC defect in Ku70-deficient mice by restoration of quiescence. Our study uncovers a novel role of Bcl2 in HSC quiescence regulation.

Testing the dimensional structure of DSM-5 posttraumatic stress disorder symptoms in a nonclinical trauma-exposed adolescent sample.

BACKGROUND: The current study investigated the underlying dimensionality of DSM-5 posttraumatic stress disorder (PTSD) symptoms in a trauma-exposed Chinese adolescent sample using a confirmatory factor analytic (CFA) alternative model approach. METHODS: The sample consisted of 559 students (242 females and 314 males) ranging in age from 12 to 18 years (M = 15.8, SD = 1.3). Participants completed the PTSD Checklist for DSM-5, the Major Depression Disorder and Panic Disorder subscales of the Revised Children's Anxiety and Depression Scale, and the Aggressive Behavior subscale of the Youth Self-Report. RESULTS: Confirmatory factor analytic results indicated that a seven-factor model comprised of intrusion, avoidance, negative affect, anhedonia, externalizing behavior, anxious arousal, and dysphoric arousal factors emerged as the best-fitting model. Further analyses showed that the external measures of psychopathological variables including major depressive disorder, panic disorder, and aggressive behavior were differentially associated with the resultant factors. CONCLUSIONS: These findings support and extend previous findings for the newly refined seven-factor hybrid model, and carry clinical and research implications for trauma-related psychopathology.

Exonuclease 1 is a critical mediator of survival during DNA double strand break repair in nonquiescent hematopoietic stem and progenitor cells.

Hematopoietic stem cell (HSC) populations require DNA repair pathways to maintain their long-term survival and reconstitution capabilities, but mediators of these processes are still being elucidated. Exonuclease 1 (Exo1) participates in homologous recombination (HR) and Exo1 loss results in impaired 5' HR end resection. We use cultured Exo1(mut) fibroblasts and bone marrow to demonstrate that loss of Exo1 function results in defective HR in cycling cells. Conversely, in Exo1(mut) mice HR is not required for maintenance of quiescent HSCs at steady state, confirming the steady state HSC reliance on nonhomologous end joining (NHEJ). Exo1(mut) mice sustained serial repopulation, displayed no defect in competitive repopulation or niche occupancy, and exhibited no increased sensitivity to whole body ionizing radiation. However, when Exo1(mut) HSCs were pushed into cell cycle in vivo with 5-fluorouracil or poly IC, the hematopoietic population became hypersensitive to IR, resulting in HSC defects and animal death. We propose Exo1-mediated HR is dispensable for stem cell function in quiescent HSC, whereas it is essential to HSC response to DNA damage processing after cell cycle entry, and its loss is not compensated by intact NHEJ. In HSCs, the maintenance of stem cell function after DNA damage is dependent on the DNA repair capacity, segregated by active versus quiescent points in cell cycle.

An intrinsic BM hematopoietic niche occupancy defect of HSC in scid mice facilitates exogenous HSC engraftment.

Although scid mice have been widely used for human HSC engraftment studies, the function of HSCs of scid mice has not been characterized. We hypothesized that the DNA repair defect of scid mice results in a stem cell defect that facilitates HSC engraftment. scid BM cells showed severely impaired repopulation potentials in the competitive repopulation assay. To assess the BM hematopoietic niche occupancy ability of scid HSC, WT BM cells were transplanted into scid mice without any conditioning and observed to achieve long-term engraftment. Furthermore, the defects of scid HSCs are independent of their inability to perform lymphopoiesis because a similar defect in hematopoietic niche occupancy was not observed with Rag1(-/-) recipients. These results demonstrate that scid HSCs are impaired in maintenance within the niche, which may explain the nature of the conducive marrow niche environment of scid mice for xenotransplantation.

Impact of age, antiretroviral therapy, and cancer on epigenetic aging in people living with HIV.

BACKGROUND: Premature aging has been identified as a global risk factor for cancer. Causes of premature aging are multifactorial, including inflammation, infection, chronic stress, and lifestyle factors. METHOD: We evaluated whether premature aging in people living with HIV (PLWH) was associated with antiretroviral therapy (ART) or the diagnosis of cancer. We used well-established DNA methylation patterns to assess premature aging, using Horvath et al., in individuals with HIV located in Cleveland, Ohio and compared these to standardized datasets of US historical blood samples. Some of the PLWH developed cancer over time. RESULTS: We found that DNA methylation analysis identified accelerated aging in PLWH whereas ART therapy mitigated the advancement of DNA methylation age. A variety of cancers were observed in this population, but a cancer diagnosis was not significantly associated with more advanced DNA methylation age. CONCLUSION: We find that the age acceleration detected in PLWH is mitigated by ART therapy and is not further accelerated by a diagnosis of cancer.

Assessing psychological resilience: translation and validation of the Chinese version of the resilience evaluation scale (RES).

Background: The Resilience Evaluation Scale (RES) is a novel and freely available measure of psychological resilience (factored into self-confidence and self-efficacy). To date, psychometric properties were evaluated in Dutch and American samples, but not yet in a Chinese sample. Objective: We aimed to validate the RES in a Chinese sample by examining its factor structure, reliability, and construct validity. Methods: The RES was translated into Chinese following a cross-cultural translation and adaptation procedure. Self-report questionnaires including the RES, exposure to potentially traumatic events (PTE's), the PTSD checklist for DSM-5 (PCL-5), and scales for conceptually related constructs of psychological resilience were then administered via an online survey. Results: In total, 484 Chinese adults (females, 66.9%; age: 27.33 ± 6.86 years) participated. Parallel analysis results suggested a one-factor structure for the Chinese RES. The Chinese RES demonstrated good internal consistency (Cronbach's alpha = 0.88). Construct validity was demonstrated through significant associations with hypothesised related constructs and through a relation with lower levels of PTSD among the PTE-exposed subsample (n = 116) via the mediating role of avoidant coping strategies, i.e. behavioural disengagement and self-blame. Conclusion: Our results suggest that the RES is a reliable and valid assessment of psychological resilience to use in Chinese, in addition to its Dutch and English versions. The RES could potentially be adopted to measure psychological resilience in cross-cultural contexts.

Antecedentes: La Escala de Evaluación de la Resiliencia (RES en su sigla en inglés) es una medida nueva y disponible de forma gratuita de la resiliencia psicológica (conformada por los factores de autoconfianza y autoeficacia). A la fecha, las propiedades psicométricas fueron evaluadas en muestras danesas y americanas, pero no en una muestra china todavía.Objetivo: Buscamos validar la RES en una muestra china evaluando su estructura factorial, confiabilidad, y validez de constructo.Métodos: La RES fue traducida al chino siguiendo un procedimiento de traducción y adaptación intercultural. Se administraron en una encuesta en línea los cuestionarios de autoinforme incluyendo la RES, exposición a eventos potencialmente traumáticos (PTE's en su sigla en inglés), y la lista de chequeo del TEPT para el DSM-5 (PCL-5 en su sigla en inglés), y las escalas de constructos conceptualmente relacionados a la resiliencia psicológica.Resultados: En total, participaron 484 adultos chinos (mujeres, 66.9%; edad: 27.33 ± 6.86 años). Los resultados de los análisis paralelos sugirieron una estructura de un factor para la RES china. La RES china demostró una buena consistencia interna (alfa de Cronbach = 0.88). La validez de constructo fue demostrada a través de asociaciones significativas con los constructos hipotéticamente relacionades y a través de una relación con niveles más bajo de TEPT en la sub-muestra expuesta a PTEs (n = 116) por medio del rol mediador de los mecanismos de afrontamiento evitativos, es decir, desconexión conductual y autoculpa.Conclusión: Nuestros resultados sugieren que la RES es una evaluación fiable y valida de resiliencia psicológica para usar en chino, en adición a sus versiones danesa e inglesa. La RES podría potencialmente ser adaptada para medir la resiliencia psicológica en contextos interculturales.

Mental health responses to COVID-19 around the world.

Background: The mental health impact of the COVID-19 crisis may differ from previously studied stressful events in terms of psychological reactions, specific risk factors, and symptom severity across geographic regions worldwide. Objective: To assess the impact of COVID-19 on a wide range of mental health symptoms, to identify relevant risk factors, to identify the effect of COVID-19 country impact on mental health, and to evaluate regional differences in psychological responses to COVID-19 compared to other stressful events. Method: 7034 respondents (74% female) participated in the worldwide Global Psychotrauma Screen - Cross-Cultural responses to COVID-19 study (GPS-CCC), reporting on mental health symptoms related to COVID-19 (n = 1838) or other stressful events (n = 5196) from April to November 2020. Results: Events related to COVID-19 were associated with more mental health symptoms compared to other stressful events, especially symptoms of PTSD, anxiety, depression, insomnia, and dissociation. Lack of social support, psychiatric history, childhood trauma, additional stressful events in the past month, and low resilience predicted more mental health problems for COVID-19 and other stressful events. Higher COVID-19 country impact was associated with increased mental health impact of both COVID-19 and other stressful events. Analysis of differences across geographic regions revealed that in Latin America more mental health symptoms were reported for COVID-19 related events versus other stressful events, while the opposite pattern was seen in North America. Conclusions: The mental health impact of COVID-19-related stressors covers a wide range of symptoms and is more severe than that of other stressful events. This difference was especially apparent in Latin America. The findings underscore the need for global screening for a wide range of mental health problems as part of a public health approach, allowing for targeted prevention and intervention programs.

Antecedentes: El impacto de la crisis por la COVID-19 sobre la salud mental podría diferir de otros eventos estresantes estudiados con anterioridad en relación con reacciones psicológicas, factores de riesgo específicos y severidad de síntomas en diferentes regiones geográficas alrededor del mundo. Objetivo: Evaluar el impacto de la COVID-19 sobre una amplia variedad de síntomas de salud mental, identificar los factores de riesgo relevantes, identificar el efecto que el impacto de la COVID-19 sobre un país ejerce, a su vez, sobre la salud mental, y evaluar las diferencias regionales en las respuestas psicológicas a la COVID-19 comparadas con otros eventos estresantes. Método: 7034 encuestados (74 % mujeres) participaron en el Mapeo Global de Psicotrauma ­ Estudio de Respuestas Transculturales frente a la COVID-19(GPS­CCC, por sus siglas en ingles), reportando síntomas de salud mental relacionados a la COVID-19 (n = 1838) u otros eventos estresantes (n = 5196) de abril a noviembre del 2020. Resultados: Los eventos relacionados a la COVID-19 se asociaron con un mayor número de síntomas de salud mental comparados con otros eventos estresantes, especialmente con síntomas del trastorno de estrés postraumático, ansiedad, depresión, insomnio, y disociación. La falta de apoyo social, los antecedentes psiquiátricos, el trauma infantil, los eventos estresantes adicionales ocurridos en el último mes y una baja resiliencia predijeron tener mayores problemas de salud mental por la COVID-19 y otros eventos estresantes. Un impacto más alto ejercido por la COVID-19 sobre un país se asoció, a su vez, con un mayor impacto sobre la salud mental, tanto por la COVID-19 como por otros eventos estresantes. Un análisis de las diferencias entre regiones geográficas reveló que en Latinoamérica se reportaron más síntomas de salud mental asociados a eventos relacionados con la COVID-19 en comparación con otros eventos estresantes, mientras que se observó un patrón opuesto en América del Norte. Conclusiones: El impacto de los estresores asociados a la COVID-19 sobre la salud mental abarca un amplio rango de síntomas y es más severo que otros eventos estresantes. Esta diferencia fue especialmente evidente en Latinoamérica. Estos hallazgos enfatizan la necesidad de un tamizaje global para detectar una amplia gama de problemas de salud mental como parte de un enfoque de salud pública, permitiendo programas específicos de prevención e intervención.

Symptom networks of COVID-19-related versus other potentially traumatic events in a global sample.

The potential mental health consequences of the coronavirus disease 2019 (COVID-19) pandemic are widely acknowledged; however, limited research exists regarding the nature and patterns of stress responses to COVID-19-related potentially traumatic events (PTEs) and the convergence/divergence with responses to other (non-COVID-19-related) PTEs. Network analysis can provide a useful method for evaluating and comparing these symptom structures. The present study includes 7034 participants from 86 countries who reported on mental health symptoms associated with either a COVID-19-related PTE (n = 1838) or other PTE (n = 5196). Using network analysis, we compared the centrality and connections of symptoms within and between each group. Overall, results show that the COVID-19-related network includes transdiagnostic symptom associations similar to networks tied to PTEs unrelated to the pandemic. Findings provide evidence for a shared centrality of depression across networks and theoretically consistent connections between symptoms. Network differences included stronger connections between avoidance-derealization and hypervigilance-depression in the COVID-19 network. Present findings support the conceptualization of psychological responses to pandemic-related PTEs as a network of highly interconnected symptoms and support the use of a transdiagnostic approach to the assessment and treatment of mental health challenges related to the COVID-19 pandemic.

Cortisol awakening response over the course of humanitarian aid deployment: a prospective cohort study.

Background: Internationally deployed humanitarian aid (HA) workers are routinely confronted with potentially traumatic stressors. However, it remains unknown whether HA deployment and related traumatic stress are associated with long-term changes in hypothalamic-pituitary-adrenal (HPA) axis function. Therefore, we investigated whether cortisol awakening response (CAR) decreased upon deployment and whether this was moderated by previous and recent trauma exposure and parallel changes in symptom severity and perceived social support. Methods: In this prospective study, n = 86 HA workers (68% females) completed questionnaires regarding trauma exposure, posttraumatic stress disorder (PTSD), anxiety and depressive symptoms and perceived social support, as well as salivary cortisol assessments at awakening and 30 minutes post-awakening at before, early and 3-6 months post-deployment. Results: Linear mixed models showed significantly decreased CAR (b(SE) = -.036(.011), p = .002) and awakening cortisol over time (b(SE) = -.007(.003), p = .014). The extent of awakening cortisol change was significantly moderated by interactions between previous and recent trauma exposure. Also, a steeper awakening cortisol decrease was significantly associated with higher mean anxiety and PTSD symptoms across assessments. No significant effects were found for social support. Conclusions: We observed attenuated CAR and awakening cortisol upon HA deployment, with a dose-response effect between trauma exposure before and during the recent deployment on awakening cortisol. Awakening cortisol change was associated with PTSD and anxiety symptom levels across assessments. Our findings support the need for organizational awareness that work-related exposures may have long-lasting biological effects. Further research assessing symptoms and biological measures in parallel is needed to translate current findings into guidelines on the individual level.

Antecedentes: Los trabajadores de la ayuda humanitaria desplegados internacionalmente (HA) se enfrentan rutinariamente a estresores potencialmente traumáticos. Sin embargo, aún se desconoce si el despliegue de la HA y el estrés traumático relacionado están asociados con cambios a largo plazo en la función del eje hipotalámico-pituitaria-suprarrenal (HPA). Por lo tanto, investigamos si la respuesta del cortisol al despertar (CAR, en sus siglas en inglés) disminuyó en el momento del despliegue y si esto fue moderado por una anterior o reciente exposición a un trauma y los cambios paralelos en la gravedad de los síntomas y el apoyo social percibido.Métodos: En este estudio prospectivo, x = 86 trabajadores de la HA (68% mujeres) completaron cuestionarios sobre la exposición al trauma, el trastorno de estrés postraumático (TEPT), la ansiedad y los síntomas depresivos y el apoyo social percibido, así como evaluaciones del cortisol salival al despertar y 30 minutos después del despertar, antes, durante y 3-6 meses después del despliegue.Resultados: Los modelos lineales mixtos mostraron una disminución significativa de la CAR (b(SE) = −.036(.011), p = .002) y del cortisol al despertar, en el transcurso del tiempo (b(SE) = −.007(.003), p = .014). El grado de cambio en el cortisol al despertar fue significativamente moderado por las interacciones entre la exposición anterior y reciente al trauma. Además, una disminución más pronunciada del cortisol al despertar se asoció significativamente con una mayor media de ansiedad y síntomas de TEPT en todas las evaluaciones. No se encontraron efectos significativos en cuanto al apoyo social.Conclusiones: Observamos CAR atenuado y cortisol al despertar en el despliegue de HA, con un efecto dosis-respuesta en el cortisol al despertar, entre la exposición al trauma antes y durante el reciente despliegue. El cambio de cortisol al despertar se asoció con el TEPT y los niveles de síntomas de ansiedad en todas las evaluaciones. Nuestros hallazgos apoyan la necesidad de la conciencia organizacional de que las exposiciones relacionadas con el trabajo pueden tener efectos biológicos duraderos. Se necesitan más investigaciones que evalúen los síntomas y las medidas biológicas en paralelo para traducir los hallazgos actuales en directrices a nivel individual.

Myeloid Krüppel-like factor 2 is a critical regulator of metabolic inflammation.

Substantial evidence implicates crosstalk between metabolic tissues and the immune system in the inception and progression of obesity. However, molecular regulators that orchestrate metaflammation both centrally and peripherally remains incompletely understood. Here, we identify myeloid Krüppel-like factor 2 (KLF2) as an essential regulator of obesity and its sequelae. In mice and humans, consumption of a fatty diet downregulates myeloid KLF2 levels. Under basal conditions, myeloid-specific KLF2 knockout mice (K2KO) exhibit increased feeding and weight gain. High-fat diet (HFD) feeding further exacerbates the K2KO metabolic disease phenotype. Mechanistically, loss of myeloid KLF2 increases metaflammation in peripheral and central tissues. A combination of pair-feeding, bone marrow-transplant, and microglial ablation implicate central and peripheral contributions to K2KO-induced metabolic dysfunction observed. Finally, overexpression of myeloid KLF2 protects mice from HFD-induced obesity and insulin resistance. Together, these data establish myeloid KLF2 as a nodal regulator of central and peripheral metabolic inflammation in homeostasis and disease.

Loss of Uracil DNA Glycosylase Selectively Resensitizes p53-Mutant and -Deficient Cells to 5-FdU.

Thymidylate synthase (TS) inhibitors including fluoropyrimidines [e.g., 5-Fluorouracil (5-FU) and 5-Fluorodeoxyuridine (5-FdU, floxuridine)] and antifolates (e.g., pemetrexed) are widely used against solid tumors. Previously, we reported that shRNA-mediated knockdown (KD) of uracil DNA glycosylase (UDG) sensitized cancer cells to 5-FdU. Because p53 has also been shown as a critical determinant of the sensitivity to TS inhibitors, we further interrogated 5-FdU cytotoxicity after UDG depletion with regard to p53 status. By analyzing a panel of human cancer cells with known p53 status, it was determined that p53-mutated or -deficient cells are highly resistant to 5-FdU. UDG depletion resensitizes 5-FdU in p53-mutant and -deficient cells, whereas p53 wild-type (WT) cells are not affected under similar conditions. Utilizing paired HCT116 p53 WT and p53 knockout (KO) cells, it was shown that loss of p53 improves cell survival after 5-FdU, and UDG depletion only significantly sensitizes p53 KO cells. This sensitization can also be recapitulated by UDG depletion in cells with p53 KD by shRNAs. In addition, sensitization is also observed with pemetrexed in p53 KO cells, but not with 5-FU, most likely due to RNA incorporation. Importantly, in p53 WT cells, the apoptosis pathway induced by 5-FdU is activated independent of UDG status. However, in p53 KO cells, apoptosis is compromised in UDG-expressing cells, but dramatically elevated in UDG-depleted cells. Collectively, these results provide evidence that loss of UDG catalyzes significant cell death signals only in cancer cells mutant or deficient in p53.Implications: This study reveals that UDG depletion restores sensitivity to TS inhibitors and has chemotherapeutic potential in the context of mutant or deficient p53. Mol Cancer Res; 16(2); 212-21. ©2017 AACR.

Turning wounds into wisdom: Posttraumatic growth over the course of two types of trauma-focused psychotherapy in patients with PTSD.

BACKGROUND: Treatment studies in PTSD patients have mostly focused on adverse psychopathological outcomes whereas positive outcomes have received less attention. Objectives of this study were to investigate posttraumatic growth in response to two different psychotherapies, to examine the relationship between symptom improvement and growth, and to determine if posttraumatic growth predicted treatment response. METHODS: Outpatients diagnosed with PTSD after various types of trauma (n = 116) participated in a randomized controlled trial that compared Brief Eclectic Psychotherapy for PTSD (BEP) and Eye Movement Desensitization and Reprocessing therapy (EMDR). Posttraumatic growth was assessed pre- and post-treatment. PTSD severity was measured weekly. RESULTS: Posttraumatic growth scores significantly increased after trauma-focused psychotherapy, as well as scores in the subdomains personal strength, new possibilities, relating to others, and appreciation of life. Greater self-reported and clinician-rated PTSD decline was significantly related to greater increase in posttraumatic growth. No changes were found between treatment conditions, except for a stronger correlation between PTSD symptom decrease and increase in relating to others in BEP as compared to EMDR. No predictive effects were found. LIMITATIONS: We were unable to control for time effects because for ethical reasons, no control group not receiving treatment was included, and the stability of the changes could not be determined. CONCLUSIONS: Findings indicate that increases in posttraumatic growth accompany symptom decline in EMDR and BEP, and that these changes occur independent of whether the treatment specifically addresses posttraumatic growth as therapeutic process. Further research is encouraged to disentangle the contribution of therapeutic elements to growth.

MMR Deficiency Does Not Sensitize or Compromise the Function of Hematopoietic Stem Cells to Low and High LET Radiation.

One of the major health concerns on long-duration space missions will be radiation exposure to the astronauts. Outside the earth's magnetosphere, astronauts will be exposed to galactic cosmic rays (GCR) and solar particle events that are principally composed of protons and He, Ca, O, Ne, Si, Ca, and Fe nuclei. Protons are by far the most common species, but the higher atomic number particles are thought to be more damaging to biological systems. Evaluation and amelioration of risks from GCR exposure will be important for deep space travel. The hematopoietic system is one of the most radiation-sensitive organ systems, and is highly dependent on functional DNA repair pathways for survival. Recent results from our group have demonstrated an acquired deficiency in mismatch repair (MMR) in human hematopoietic stem cells (HSCs) with age due to functional loss of the MLH1 protein, suggesting an additional risk to astronauts who may have significant numbers of MMR deficient HSCs at the time of space travel. In the present study, we investigated the effects gamma radiation, proton radiation, and 56 Fe radiation on HSC function in Mlh1+/+ and Mlh1-/- marrow from mice in a variety of assays and have determined that while cosmic radiation is a major risk to the hematopoietic system, there is no dependence on MMR capacity. Stem Cells Translational Medicine 2018;7:513-520.

Mismatch repair deficient hematopoietic stem cells are preleukemic stem cells.

Whereas transformation events in hematopoietic malignancies may occur at different developmental stages, the initial mutation originates in hematopoietic stem cells (HSCs), creating a preleukemic stem cell (PLSC). Subsequent mutations at either stem cell or progenitor cell levels transform the PLSC into lymphoma/leukemia initiating cells (LIC). Thymic lymphomas have been thought to develop from developing thymocytes. T cell progenitors are generated from HSCs in the bone marrow (BM), but maturation and proliferation of T cells as well as T-lymphomagenesis depends on both regulatory mechanisms and microenvironment within the thymus. We studied PLSC linked to thymic lymphomas. In this study, we use MSH2-/- mice as a model to investigate the existence of PLSC and the evolution of PLSC to LIC. Following BM transplantation, we found that MSH2-/- BM cells from young mice are able to fully reconstitute multiple hematopoietic lineages of lethally irradiated wild-type recipients. However, all recipients developed thymic lymphomas within three and four months post transplantation. Transplantation of different fractions of BM cells or thymocytes from young health MSH2-/- mice showed that an HSC enriched fraction always reconstituted hematopoiesis followed by lymphoma development. In addition, lymphomas did not occur in thymectomized recipients of MSH2-/- BM. These results suggest that HSCs with DNA repair defects such as MSH2-/- are PLSCs because they retain hematopoietic function, but also carry an obligate lymphomagenic potential within their T-cell progeny that is dependent on the thymic microenvironment.

Inhibition of uracil DNA glycosylase sensitizes cancer cells to 5-fluorodeoxyuridine through replication fork collapse-induced DNA damage.

5-fluorodeoxyuridine (5-FdU, floxuridine) is active against multiple cancers through the inhibition of thymidylate synthase, which consequently introduces uracil and 5-FU incorporation into the genome. Uracil DNA glycosylase (UDG) is one of the main enzymes responsible for the removal of uracil and 5-FU. However, how exactly UDG mediates cellular sensitivity to 5-FdU, and if so whether it is through its ability to remove uracil and 5-FU have not been well characterized. In this study, we report that UDG depletion led to incorporation of uracil and 5-FU in DNA following 5-FdU treatment and significantly enhanced 5-FdU's cytotoxicity in cancer cell lines. Co-treatment, but not post-treatment with thymidine prevented cell death of UDG depleted cells by 5-FdU, indicating that the enhanced cytotoxicity is due to the retention of uracil and 5-FU in genomic DNA in the absence of UDG. Furthermore, UDG depleted cells were arrested at late G1 and early S phase by 5-FdU, followed by accumulation of sub-G1 population indicating cell death. Mechanistically, 5-FdU dramatically reduced DNA replication speed in UDG depleted cells. UDG depletion also greatly enhanced DNA damage as shown by γH2AX foci formation. Notably, the increased γH2AX foci formation was not suppressed by caspase inhibitor treatment, suggesting that DNA damage precedes cell death induced by 5-FdU. Together, these data provide novel mechanistic insights into the roles of UDG in DNA replication, damage repair, and cell death in response to 5-FdU and suggest that UDG is a target for improving the anticancer effect of this agent.

Epigenetic Loss of MLH1 Expression in Normal Human Hematopoietic Stem Cell Clones is Defined by the Promoter CpG Methylation Pattern Observed by High-Throughput Methylation Specific Sequencing.

Normal human hematopoietic stem and progenitor cells (HPC) lose expression of MLH1, an important mismatch repair (MMR) pathway gene, with age. Loss of MMR leads to replication dependent mutational events and microsatellite instability observed in secondary acute myelogenous leukemia and other hematologic malignancies. Epigenetic CpG methylation upstream of the MLH1 promoter is a contributing factor to acquired loss of MLH1 expression in tumors of the epithelia and proximal mucosa. Using single molecule high-throughput bisulfite sequencing we have characterized the CpG methylation landscape from -938 to -337 bp upstream of the MLH1 transcriptional start site (position +0), from 30 hematopoietic colony forming cell clones (CFC) either expressing or not expressing MLH1. We identify a correlation between MLH1 promoter methylation and loss of MLH1 expression. Additionally, using the CpG site methylation frequencies obtained in this study we were able to generate a classification algorithm capable of sorting the expressing and non-expressing CFC. Thus, as has been previously described for many tumor cell types, we report for the first time a correlation between the loss of MLH1 expression and increased MLH1 promoter methylation in CFC derived from CD34+ selected hematopoietic stem and progenitor cells.

Matricellular protein CCN3 mitigates abdominal aortic aneurysm.

Abdominal aortic aneurysm (AAA) is a major cause of morbidity and mortality; however, the mechanisms that are involved in disease initiation and progression are incompletely understood. Extracellular matrix proteins play an integral role in modulating vascular homeostasis in health and disease. Here, we determined that the expression of the matricellular protein CCN3 is strongly reduced in rodent AAA models, including angiotensin II-induced AAA and elastase perfusion-stimulated AAA. CCN3 levels were also reduced in human AAA biopsies compared with those in controls. In murine models of induced AAA, germline deletion of Ccn3 resulted in severe phenotypes characterized by elastin fragmentation, vessel dilation, vascular inflammation, dissection, heightened ROS generation, and smooth muscle cell loss. Conversely, overexpression of CCN3 mitigated both elastase- and angiotensin II-induced AAA formation in mice. BM transplantation experiments suggested that the AAA phenotype of CCN3-deficient mice is intrinsic to the vasculature, as AAA was not exacerbated in WT animals that received CCN3-deficient BM and WT BM did not reduce AAA severity in CCN3-deficient mice. Genetic and pharmacological approaches implicated the ERK1/2 pathway as a critical regulator of CCN3-dependent AAA development. Together, these results demonstrate that CCN3 is a nodal regulator in AAA biology and identify CCN3 as a potential therapeutic target for vascular disease.

Assessing the underlying dimensionality of DSM-5 PTSD symptoms in Chinese adolescents surviving the 2008 Wenchuan earthquake.

By analyzing data yielded from a sample of Chinese adolescents surviving a high-intensity earthquake, this study investigated the underlying dimensionality of DSM-5 PTSD symptoms. The sample included 743 traumatized middle school students (396 females and 332 males) aged 11-17 years (mean=13.6, SD=1.0). Results of confirmatory factor analysis showed that an intercorrelated seven-factor model comprised of intrusion, avoidance, negative affect, anhedonia, externalizing behaviors, anxious arousal, and dysphoric arousal factors provided a significant better representation of DSM-5 PTSD symptoms than other alternative models. Further analyses indicated that external measures of major depression disorder and panic disorder symptoms displayed unique associations with four PTSD factors. The findings provide further support for the newly proposed seven-factor model of DSM-5 PTSD symptoms, add to very limited empirical knowledge on the latent structure of DSM-5 PTSD symptoms among adolescents, and carry implications for further refinement of the current classifications of PTSD symptoms and further clinical practice and research on posttraumatic stress symptomatology.