Brain-specific repression of AMPKα1 alleviates pathophysiology in Alzheimer’s model mice

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Abstract

AMP-activated protein kinase (AMPK) is a key regulator at the molecular level to maintain energy metabolism homeostasis. Mammalian AMPK is a heterotrimeric complex and its catalytic α subunit exists in two isoforms: AMPKα1 and AMPKα2. Recent studies suggest a role of AMPKα over-activation in AD-associated synaptic failure. However, whether AD-associated dementia can be improved by targeting AMPK remains unclear, and roles of AMPKα isoforms in AD pathophysiology are not understood. Here we showed distinct disruption of hippocampal AMPKα isoform expression patterns in post mortem human AD patients and AD model mice. We further investigated the effects of brain- and isoform-specific AMPKα repression on AD pathophysiology. We found that repression of AMPKα1 alleviated cognitive deficits and synaptic failure displayed in two separate lines of AD model mice. In contrast, AMPKα2 suppression did not alter AD pathophysiology. Using unbiased mass spectrometry-based proteomics analysis, we identified distinct patterns of protein expression associated with specific AMPKα isoform suppression in AD model mice. Further, AD-associated hyper-phosphorylation of eukaryotic elongation factor 2 (eEF2) was blunted with selective AMPKα1 inhibition. Our findings reveal isoform-specific roles of AMPKα in AD pathophysiology, thus providing insights into potential therapeutic strategy for AD and related dementia syndromes.

Authors

Helena R. Zimmermann, Wenzhong Yang, Nicole P. Kasica, Xueyan Zhou, Xin Wang, Brenna C. Beckelman, Jingyun Lee, Cristina M. Furdui, C. Dirk Keene, Tao Ma

Molecular cross-talk between Y5-receptor and neuropeptide Y drives liver cancer

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Abstract

Hepatocellular carcinoma (HCC) is clearly age-related and represents one of the deadliest cancer types worldwide. Due to globally increasing risk factors including metabolic disorders, the incidence rates of HCC are still rising. However, the molecular hallmarks of HCC remain poorly understood. Neuropeptide Y (NPY) and NPY-receptors represent a highly conserved, stress-activated system which is involved in diverse cancer-related hallmarks including aging and metabolic alterations, but its impact on liver cancer had been unclear. Here, we observed increased NPY5-receptor (Y5R) expression in HCC which correlated with tumor growth and survival. Furthermore, we found that its ligand NPY was secreted by peri-tumorous hepatocytes. Hepatocyte-derived NPY promoted HCC progression by Y5R-activation. Transforming growth factor beta 1 (TGFβ1) was identified as a regulator of NPY in hepatocytes and induced Y5R in invasive cancer cells. Moreover, NPY-conversion by dipeptidylpeptidase 4 (DPP4) augmented Y5R-activation and function in liver cancer. The TGFβ-NPY-Y5R-axis and DPP4 represent attractive therapeutic targets for controlling liver cancer progression.

Authors

Peter Dietrich, Laura Wormser, Valerie Fritz, Tatjana Seitz, Monica De Maria, Alexandra Schambony, Andreas E. Kremer, Claudia Günther, Timo Itzel, Wolfgang E. Thasler, Andreas Teufel, Jonel Trebicka, Arndt Hartmann, Markus F. Neurath, Stephan von Hörsten, Anja Bosserhoff, Claus Hellerbrand

BubR1 allelic effects drive phenotypic heterogeneity in mosaic-variegated aneuploidy progeria syndrome

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Abstract

Mosaic-variegated aneuploidy (MVA) syndrome is a rare childhood disorder characterized by biallelic BUBR1, CEP57, or TRIP13 aberrations; increased chromosome missegregation; and a broad spectrum of clinical features, including various cancers, congenital defects, and progeroid pathologies. To investigate the mechanisms underlying this disorder and its phenotypic heterogeneity, we mimicked the BUBR1L1012P mutation in mice (BubR1L1002P) and combined it with 2 other MVA variants, BUBR1X753 and BUBR1H, generating a truncated protein and low amounts of wild-type protein, respectively. Whereas BubR1X753/L1002P and BubR1H/X753 mice died prematurely, BubR1H/L1002P mice were viable and exhibited many MVA features, including cancer predisposition and various progeroid phenotypes, such as short lifespan, dwarfism, lipodystrophy, sarcopenia, and low cardiac stress tolerance. Strikingly, although these mice had a reduction in total BUBR1 and spectrum of MVA phenotypes similar to that of BubR1H/H mice, several progeroid pathologies were attenuated in severity, which in skeletal muscle coincided with reduced senescence-associated secretory phenotype complexity. Additionally, mice carrying monoallelic BubR1 mutations were prone to select MVA-related pathologies later in life, with predisposition to sarcopenia correlating with mTORC1 hyperactivity. Together, these data demonstrate that BUBR1 allelic effects beyond protein level and aneuploidy contribute to disease heterogeneity in both MVA patients and heterozygous carriers of MVA mutations.

Authors

Cynthia J. Sieben, Karthik B. Jeganathan, Grace G. Nelson, Ines Sturmlechner, Cheng Zhang, Willemijn H. van Deursen, Bjorn Bakker, Floris Foijer, Hu Li, Darren J. Baker, Jan M. van Deursen

Nox2 contributes to age-related oxidative damage to neurons and the cerebral vasculature

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Abstract

Oxidative stress plays an important role in aging-related neurodegeneration. This study used littermates of WT and Nox2-knockout (Nox2KO) mice plus endothelial cell–specific human Nox2 overexpression–transgenic (HuNox2Tg) mice to investigate Nox2-derived ROS in brain aging. Compared with young WT mice (3–4 months), aging WT mice (20–22 months) had obvious metabolic disorders and loss of locomotor activity. Aging WT brains had high levels of angiotensin II (Ang II) and ROS production; activation of ERK1/2, p53, and γH2AX; and losses of capillaries and neurons. However, these abnormalities were markedly reduced in aging Nox2KO brains. HuNox2Tg brains at middle age (11–12 months) already had high levels of ROS production and activation of stress signaling pathways similar to those found in aging WT brains. The mechanism of Ang II–induced endothelial Nox2 activation in capillary damage was examined using primary brain microvascular endothelial cells. The clinical significance of Nox2-derived ROS in aging-related loss of cerebral capillaries and neurons was investigated using postmortem midbrain tissues of young (25–38 years) and elderly (61–85 years) adults. In conclusion, Nox2 activation is an important mechanism in aging-related cerebral capillary rarefaction and reduced brain function, with the possibility of a key role for endothelial cells.

Authors

Lampson M. Fan, Li Geng, Sarah Cahill-Smith, Fangfei Liu, Gillian Douglas, Chris-Anne Mckenzie, Colin Smith, Gavin Brooks, Keith M. Channon, Jian-Mei Li

Endothelial progerin expression causes cardiovascular pathology through an impaired mechanoresponse

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Abstract

Hutchinson-Gilford progeria syndrome (HGPS) is a premature aging disorder characterized by accelerated cardiovascular disease with extensive fibrosis. It is caused by a mutation in LMNA leading to expression of truncated prelamin A (progerin) in the nucleus. To investigate the contribution of the endothelium to cardiovascular HGPS pathology, we generated an endothelium-specific HGPS mouse model with selective endothelial progerin expression. Transgenic mice develop interstitial myocardial and perivascular fibrosis and left ventricular hypertrophy associated with diastolic dysfunction and premature death. Endothelial cells show impaired shear stress response and reduced levels of endothelial nitric oxide synthase (eNOS) and NO. On the molecular level, progerin impairs nucleocytoskeletal coupling in endothelial cells through changes in mechanoresponsive components at the nuclear envelope, increased F-/G-actin ratios and deregulation of mechanoresponsive myocardin-related transcription factor-A (MRTFA). MRTFA binds to the Nos3 promoter reducing eNOS expression, thereby mediating a pro-fibrotic paracrine response in fibroblasts. MRTFA inhibition rescues eNOS levels and ameliorates the pro-fibrotic effect of endothelial cells in vitro. Although this murine model lacks the key anatomical feature of vascular smooth muscle cell loss seen in HGPS patients, our data show that progerin-induced impairment of mechanosignaling in endothelial cells contributes to excessive fibrosis and cardiovascular disease in HGPS patients.

Authors

Selma Osmanagic-Myers, Attila Kiss, Christina Manakanatas, Ouafa Hamza, Franziska Sedlmayer, Petra L. Szabo, Irmgard Fischer, Petra Fichtinger, Bruno K. Podesser, Maria Eriksson, Roland Foisner

Tuberous sclerosis complex–mediated mTORC1 overactivation promotes age-related hearing loss

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Abstract

The underlying molecular mechanisms of age-related hearing loss (ARHL) in humans and many strains of mice have not been fully characterized. This common age-related disorder is assumed to be closely associated with oxidative stress. Here, we demonstrate that mTORC1 signaling is highly and specifically activated in the cochlear neurosensory epithelium (NSE) in aging mice, and rapamycin injection prevents ARHL. To further examine the specific role of mTORC1 signaling in ARHL, we generated murine models with NSE-specific deletions of Raptor or Tsc1, regulators of mTORC1 signaling. Raptor-cKO mice developed hearing loss considerably more slowly than WT littermates. Conversely, Tsc1 loss led to the early-onset death of cochlear hair cells and consequently accelerated hearing loss. Tsc1-cKO cochleae showed features of oxidative stress and impaired antioxidant defenses. Treatment with rapamycin and the antioxidant N-acetylcysteine rescued Tsc1-cKO hair cells from injury in vivo. In addition, we identified the peroxisome as the initial signaling organelle involved in the regulation of mTORC1 signaling in cochlear hair cells. In summary, our findings identify overactive mTORC1 signaling as one of the critical causes of ARHL and suggest that reduction of mTORC1 activity in cochlear hair cells may be a potential strategy to prevent ARHL.

Authors

Xiaolong Fu, Xiaoyang Sun, Linqing Zhang, Yecheng Jin, Renjie Chai, Lili Yang, Aizhen Zhang, Xiangguo Liu, Xiaochun Bai, Jianfeng Li, Haibo Wang, Jiangang Gao

Short telomere syndromes cause a primary T cell immunodeficiency

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Abstract

The mechanisms that drive T cell aging are not understood. We report children and adult telomerase mutation carriers with short telomere length (TL) develop a T cell immunodeficiency that can manifest in the absence of bone marrow failure and causes life-threatening opportunistic infections. Mutation carriers shared T cell aging phenotypes seen in adults five decades older including depleted naïve T cells, increased apoptosis, and restricted T cell repertoire. T cell receptor excision circles (TRECs) were also undetectable or low, suggesting newborn screening may identify individuals with germline telomere maintenance defects. Telomerase null mice with short TL showed defects throughout T cell development including increased apoptosis of stimulated thymocytes, their intra-thymic precursors, in addition to depleted hematopoietic reserves. When we examined the transcriptional programs of T cells from telomerase mutation carriers, we found they diverged from older adults with normal TL. Short telomere T cells up-regulated DNA damage and intrinsic apoptosis pathways, while older adult T cells up-regulated extrinsic apoptosis pathways and PD-1 expression. T cells from mice with short TL also showed an active DNA damage response, in contrast to old wild-type mice, despite their shared propensity to apoptosis. Our data suggest there are telomere length-dependent and telomere length-independent mechanisms that differentially contribute to distinct molecular programs of T cell apoptosis with aging.

Authors

Christa L. Wagner, Vidya Sagar Hanumanthu, C. Conover Talbot Jr., Roshini S. Abraham, David Hamm, Dustin L. Gable, Christopher G. Kanakry, Carolyn D. Applegate, Janet Siliciano, J. Brooks Jackson, Stephen V. Desiderio, Jonathan K. Alder, Leo Luznik, Mary Armanios

Dysfunction of the MDM2/p53 axis is linked to premature aging

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Abstract

The tumor suppressor p53, a master regulator of the cellular response to stress, is tightly regulated by the E3 ubiquitin ligase MDM2 via an autoregulatory feedback loop. In addition to its well-established role in tumorigenesis, p53 has also been associated with aging in mice. Several mouse models with aberrantly increased p53 activity display signs of premature aging. However, the relationship between dysfunction of the MDM2/p53 axis and human aging remains elusive. Here, we have identified an antiterminating homozygous germline mutation in MDM2 in a patient affected by a segmental progeroid syndrome. We show that this mutation abrogates MDM2 activity, thereby resulting in enhanced levels and stability of p53. Analysis of the patient’s primary cells, genome-edited cells, and in vitro and in vivo analyses confirmed the MDM2 mutation’s aberrant regulation of p53 activity. Functional data from a zebrafish model further demonstrated that mutant Mdm2 was unable to rescue a p53-induced apoptotic phenotype. Altogether, our findings indicate that mutant MDM2 is a likely driver of the observed segmental form of progeria.

Authors

Davor Lessel, Danyi Wu, Carlos Trujillo, Thomas Ramezani, Ivana Lessel, Mohammad K. Alwasiyah, Bidisha Saha, Fuki M. Hisama, Katrin Rading, Ingrid Goebel, Petra Schütz, Günter Speit, Josef Högel, Holger Thiele, Gudrun Nürnberg, Peter Nürnberg, Matthias Hammerschmidt, Yan Zhu, David R. Tong, Chen Katz, George M. Martin, Junko Oshima, Carol Prives, Christian Kubisch

FOXP1 controls mesenchymal stem cell commitment and senescence during skeletal aging

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Abstract

A hallmark of aged mesenchymal stem/progenitor cells (MSCs) in bone marrow is the pivot of differentiation potency from osteoblast to adipocyte coupled with a decrease in self-renewal capacity. However, how these cellular events are orchestrated in the aging progress is not fully understood. In this study, we have used molecular and genetic approaches to investigate the role of forkhead box P1 (FOXP1) in transcriptional control of MSC senescence. In bone marrow MSCs, FOXP1 expression levels declined with age in an inverse manner with those of the senescence marker p16^INK4A. Conditional depletion of Foxp1 in bone marrow MSCs led to premature aging characteristics, including increased bone marrow adiposity, decreased bone mass, and impaired MSC self-renewal capacity in mice. At the molecular level, FOXP1 regulated cell-fate choice of MSCs through interactions with the CEBPβ/δ complex and recombination signal binding protein for immunoglobulin κ J region (RBPjκ), key modulators of adipogenesis and osteogenesis, respectively. Loss of p16^INK4A in Foxp1-deficient MSCs partially rescued the defects in replication capacity and bone mass accrual. Promoter occupancy analyses revealed that FOXP1 directly represses transcription of p16^INK4A. These results indicate that FOXP1 attenuates MSC senescence by orchestrating their cell-fate switch while maintaining their replicative capacity in a dose- and age-dependent manner.

Authors

Hanjun Li, Pei Liu, Shuqin Xu, Yinghua Li, Joseph D. Dekker, Baojie Li, Ying Fan, Zhenlin Zhang, Yang Hong, Gong Yang, Tingting Tang, Yongxin Ren, Haley O. Tucker, Zhengju Yao, Xizhi Guo

Somatic mutations in telomerase promoter counterbalance germline loss-of-function mutations

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Abstract

Germline coding mutations in different telomere-related genes have been linked to autosomal-dominant familial pulmonary fibrosis. Individuals with these inherited mutations demonstrate incomplete penetrance of clinical phenotypes affecting the lung, blood, liver, skin, and other organs. Here, we describe the somatic acquisition of promoter mutations in telomerase reverse transcriptase (TERT) in blood leukocytes of approximately 5% of individuals with inherited loss-of-function coding mutations in TERT or poly(A)-specific ribonuclease (PARN), another gene linked to telomerase function. While these promoter mutations were initially identified as oncogenic drivers of cancer, individuals expressing the mutations have no history of cancer. Neither promoter mutation was found in population-based cohorts of similar or advanced age. The TERT promoter mutations were found more frequently in cis with the WT allele than was the TERT coding sequence mutation. EBV-transformed lymphoblastoid B cell lines (LCLs) derived from subjects with TERT promoter mutations showed increased telomerase expression and activity compared with cell lines from family members with identical coding mutations. TERT promoter mutations resulted in an increased proliferation of LCLs and demonstrated positive selection over time. The persistence and recurrence of noncoding gain-of-function mutations in these cases suggests that telomerase activation is not only safely tolerated but also advantageous for clonal expansion.

Authors

Lindley Maryoung, Yangbo Yue, Ashley Young, Chad A. Newton, Cindy Barba, Nicolai S. C. van Oers, Richard C. Wang, Christine Kim Garcia