Combined treatment with statins and aminobisphosphonates extends longevity in a mouse model of human premature aging

Evaluating protein prenylation of human and viral CaaX sequences using a humanized yeast system

Prenylated proteins are prevalent in eukaryotic biology (∼1-2% of proteins) and are associated with human disease, including cancer, premature aging and infections. Prenylated proteins with a C-terminal CaaX sequence are targeted by CaaX-type prenyltransferases and proteases. To aid investigations of these enzymes and their targets, we developed Saccharomyces cerevisiae strains that express these human enzymes instead of their yeast counterparts. These strains were developed in part to explore human prenyltransferase specificity because of findings that yeast FTase has expanded specificity for sequences deviating from the CaaX consensus (i.e. atypical sequence and length). The humanized yeast strains displayed robust prenyltransferase activity against CaaX sequences derived from human and pathogen proteins containing typical and atypical CaaX sequences. The system also recapitulated prenylation of heterologously expressed human proteins (i.e. HRas and DNAJA2). These results reveal that substrate specificity is conserved for yeast and human farnesyltransferases but is less conserved for type I geranylgeranyltransferases. These yeast systems can be easily adapted for investigating the prenylomes of other organisms and are valuable new tools for helping define the human prenylome, which includes physiologically important proteins for which the CaaX modification status is unknown.

Effect of bisphosphonates and statins on the in vitro radiosensitivity of breast cancer cell lines

BACKGROUND

Early-stage breast cancer is usually treated with breast-conserving surgery followed by adjuvant radiation therapy. Acute skin toxicity is a common radiation-induced side effect experienced by many patients. Recently, a combination of bisphosphonates (zoledronic acid) and statins (pravastatin), or ZOPRA, was shown to radio-protect normal tissues by enhancing DNA double-strand breaks (DSB) repair mechanism. However, there are no studies assessing the effect of ZOPRA on cancerous cells. The purpose of this study is to characterize the in vitro effect of the zoledronic acid (ZO), pravastatin (PRA), and ZOPRA treatment on the molecular and cellular radiosensitivity of breast cancer cell lines.

MATERIALS

Two breast cancer cell lines, MDA MB 231 and MCF-7, were tested. Cells were treated with different concentrations of pravastatin (PRA), zoledronate (ZO), as well as their ZOPRA combination, before irradiation. Anti-γH2AX and anti-pATM immunofluorescence were performed to study DNA DSB repair kinetics. MTT assay was performed to assess cell proliferation and viability, and flow cytometry was performed to analyze the effect of the drugs on the cell cycle distribution. The clonogenic assay was used to assess cell survival.

RESULTS

ZO, PRA, and ZOPRA treatments were shown to increase the residual number of γH2AX foci for both cell lines. ZOPRA treatment was also shown to reduce the activity of the ATM kinase in MCF-7. ZOPRA induced a significant decrease in cell survival for both cell lines.

CONCLUSIONS

Our findings show that pretreatment with ZOPRA can decrease the radioresistance of breast cancer cells at the molecular and cellular levels. The fact that ZOPRA was previously shown to radioprotect normal tissues, makes it a good candidate to become a therapeutic window-widening drug.

Bisphosphonates as Radiopharmaceuticals: Spotlight on the Development and Clinical Use of DOTAZOL in Diagnostics and Palliative Radionuclide Therapy

Bisphosphonates are therapeutic agents that have been used for almost five decades in the treatment of various bone diseases, such as osteoporosis, Paget disease and prevention of osseous complications in cancer patients. In nuclear medicine, simple bisphosphonates such as 99mTc-radiolabelled oxidronate and medronate remain first-line bone scintigraphic imaging agents for both oncology and non-oncology indications. In line with the growing interest in theranostic molecules, bifunctional bisphosphonates bearing a chelating moiety capable of complexing a variety of radiometals were designed. Among them, DOTA-conjugated zoledronate (DOTAZOL) emerged as an ideal derivative for both PET imaging (when radiolabeled with 68Ga) and management of bone metastases from various types of cancer (when radiolabeled with 177Lu). In this context, this report provides an overview of the main medicinal chemistry aspects concerning bisphosphonates, discussing their roles in molecular oncology imaging and targeted radionuclide therapy with a particular focus on bifunctional bisphosphonates. Particular attention is also paid to the development of DOTAZOL, with emphasis on the radiochemistry and quality control aspects of its preparation, before outlining the preclinical and clinical data obtained so far with this radiopharmaceutical candidate.

Hutchinson-Gilford progeria syndrome: Cardiovascular manifestations and treatment

Hutchinson-Gilford progeria syndrome (HGPS), also known as hereditary progeria syndrome, is caused by mutations in the LMNA gene and the expression of progerin, which causes accelerated aging and premature death, with most patients dying of heart failure or other cardiovascular complications in their teens. HGPS patients are able to exhibit cardiovascular phenotypes similar to physiological aging, such as extensive atherosclerosis, smooth muscle cell loss, vascular lesions, and electrical and functional abnormalities of the heart. It also excludes the traditional risk causative factors of cardiovascular disease, making HGPS a new model for studying aging-related cardiovascular disease. Here, we analyzed the pathogenesis and pathophysiological characteristics of HGPS and the relationship between HGPS and cardiovascular disease, provided insight into the molecular mechanisms of cardiovascular disease pathogenesis in HGPS patients and treatment strategies for this disease. Moreover, we summarize the disease models used in HGPS studies to improve our understanding of the pathological mechanisms of cardiovascular aging in HGPS patients.

Chromatin: the old and young of it

Aging affects nearly all aspects of our cells, from our DNA to our proteins to how our cells handle stress and communicate with each other. Age-related chromatin changes are of particular interest because chromatin can dynamically respond to the cellular and organismal environment, and many modifications at chromatin are reversible. Changes at chromatin occur during aging, and evidence from model organisms suggests that chromatin factors could play a role in modulating the aging process itself, as altering proteins that work at chromatin often affect the lifespan of yeast, worms, flies, and mice. The field of chromatin and aging is rapidly expanding, and high-resolution genomics tools make it possible to survey the chromatin environment or track chromatin factors implicated in longevity with precision that was not previously possible. In this review, we discuss the state of chromatin and aging research. We include examples from yeast, Drosophila, mice, and humans, but we particularly focus on the commonly used aging model, the worm Caenorhabditis elegans, in which there are many examples of chromatin factors that modulate longevity. We include evidence of both age-related changes to chromatin and evidence of specific chromatin factors linked to longevity in core histones, nuclear architecture, chromatin remodeling, and histone modifications.

A Humanized Yeast System for Evaluating the Protein Prenylation of a Wide Range of Human and Viral CaaX Sequences

The C-terminal CaaX sequence (cysteine-aliphatic-aliphatic-any of several amino acids) is subject to isoprenylation on the conserved cysteine and is estimated to occur in 1-2% of proteins within yeast and human proteomes. Recently, non-canonical CaaX sequences in addition to shorter and longer length CaX and CaaaX sequences have been identified that can be prenylated. Much of the characterization of prenyltransferases has relied on the yeast system because of its genetic tractability and availability of reporter proteins, such as the a-factor mating pheromone, Ras GTPase, and Ydj1 Hsp40 chaperone. To compare the properties of yeast and human prenyltransferases, including the recently expanded target specificity of yeast farnesyltransferase, we have developed yeast strains that express human farnesyltransferase or geranylgeranyltransferase-I in lieu of their yeast counterparts. The humanized yeast strains display robust prenyltransferase activity that functionally replaces yeast prenyltransferase activity in a wide array of tests, including the prenylation of a wide variety of canonical and non-canonical human CaaX sequences, virus encoded CaaX sequences, non-canonical length sequences, and heterologously expressed human proteins HRas and DNAJA2. These results reveal highly overlapping substrate specificity for yeast and human farnesyltransferase, and mostly overlapping substrate specificity for GGTase-I. This yeast system is a valuable tool for further defining the prenylome of humans and other organisms, identifying proteins for which prenylation status has not yet been determined.

Toward an Early Diagnosis for Alzheimer's Disease Based on the Perinuclear Localization of the ATM Protein

Alzheimer's disease (AD) is the most common neurodegenerative dementia, for which the molecular origins, genetic predisposition and therapeutic approach are still debated. In the 1980s, cells from AD patients were reported to be sensitive to ionizing radiation. In order to examine the molecular basis of this radiosensitivity, the ATM-dependent DNA double-strand breaks (DSB) signaling and repair were investigated by applying an approach based on the radiation-induced ataxia telangiectasia-mutated (ATM) protein nucleoshuttling (RIANS) model. Early after irradiation, all ten AD fibroblast cell lines tested showed impaired DSB recognition and delayed RIANS. AD fibroblasts specifically showed spontaneous perinuclear localization of phosphorylated ATM (pATM) forms. To our knowledge, such observation has never been reported before, and by considering the role of the ATM kinase in the stress response, it may introduce a novel interpretation of accelerated aging. Our data and a mathematical approach through a brand-new model suggest that, in response to a progressive and cumulative stress, cytoplasmic ATM monomers phosphorylate the APOE protein (pAPOE) close to the nuclear membrane and aggregate around the nucleus, preventing their entry in the nucleus and thus the recognition and repair of spontaneous DSB, which contributes to the aging process. Our findings suggest that pATM and/or pAPOE may serve as biomarkers for an early reliable diagnosis of AD on any fibroblast sample.

In vitro and in vivo effects of zoledronic acid on senescence and senescence-associated secretory phenotype markers

In addition to reducing fracture risk, zoledronic acid has been found in some studies to decrease mortality in humans and extend lifespan and healthspan in animals. Because senescent cells accumulate with aging and contribute to multiple co-morbidities, the non-skeletal actions of zoledronic acid could be due to senolytic (killing of senescent cells) or senomorphic (inhibition of the secretion of the senescence-associated secretory phenotype [SASP]) actions. To test this, we first performed in vitro senescence assays using human lung fibroblasts and DNA repair-deficient mouse embryonic fibroblasts, which demonstrated that zoledronic acid killed senescent cells with minimal effects on non-senescent cells. Next, in aged mice treated with zoledronic acid or vehicle for 8 weeks, zoledronic acid significantly reduced circulating SASP factors, including CCL7, IL-1β, TNFRSF1A, and TGFβ1 and improved grip strength. Analysis of publicly available RNAseq data from CD115+ (CSF1R/c-fms+) pre-osteoclastic cells isolated from mice treated with zoledronic acid demonstrated a significant downregulation of senescence/SASP genes (SenMayo). To establish that these cells are potential senolytic/senomorphic targets of zoledronic acid, we used single cell proteomic analysis (cytometry by time of flight [CyTOF]) and demonstrated that zoledronic acid significantly reduced the number of pre-osteoclastic (CD115+/CD3e-/Ly6G-/CD45R-) cells and decreased protein levels of p16, p21, and SASP markers in these cells without affecting other immune cell populations. Collectively, our findings demonstrate that zoledronic acid has senolytic effects in vitro and modulates senescence/SASP biomarkers in vivo. These data point to the need for additional studies testing zoledronic acid and/or other bisphosphonate derivatives for senotherapeutic efficacy.

Refracture risk and all-cause mortality after vertebral fragility fractures: Anti-osteoporotic medications matter

BACKGROUND

Osteoporotic vertebral fractures may predict the future occurrence of fractures and increase mortality. Treating underlying osteoporosis may prevent second fractures. However, whether anti-osteoporotic treatment can reduce the mortality rate is not clear. The aim of this population study was to identify the degree of decreased mortality following the use of anti-osteoporotic medication after vertebral fractures.

METHODS

We identified patients who had newly diagnosed osteoporosis and vertebral fractures from 2009 to 2019 using the Taiwan National Health Insurance Research Database (NHIRD). We used national death registration data to determine the overall mortality rate.

RESULTS

There were 59,926 patients with osteoporotic vertebral fractures included in this study. After excluding patients with short-term mortality, patients who had previously received anti-osteoporotic medications had a lower refracture rate as well as a lower mortality risk (hazard ratio (HR): 0.84, 95% confidence interval (CI): 0.81-0.88). Patients receiving treatment for more than 3 years had a much lower mortality risk (HR: 0.53, 95% CI: 0.50-0.57). Patients who used oral bisphosphonates (alendronate and risedronate, HR: 0.95, 95% CI: 0.90-1.00), intravenous zoledronic acid (HR: 0.83, 95% CI: 0.74-0.93), and subcutaneous denosumab injections (HR: 0.71, 95% CI: 0.65-0.77) had lower mortality rates than patients without further treatment after vertebral fractures.

CONCLUSION

In addition to fracture prevention, anti-osteoporotic treatments for patients with vertebral fractures were associated with a reduction in mortality. A longer duration of treatment and the use of long-acting drugs was also associated with lower mortality.

Molecular Influence of the ATM Protein in the Treatment of Human Cells with Different Radioprotective Drugs: Comparisons between Antioxidative and Pro-Episkevic Strategies

The radiation protection strategy with chemical agents has long been based on an antioxidative approach consisting in reducing the number of radical oxygen and nitrogen species responsible for the formation of the radiation-induced (RI) DNA damage, notably the DNA double-strand breaks (DSB), whose subset participates in the RI lethal effect as unrepairable damage. Conversely, a DSB repair-stimulating strategy that may be called the “pro-episkevic” approach (from the ancient Greek episkeve, meaning repair) can be proposed. The pro-episkevic approach directly derives from a mechanistic model based on the RI nucleoshuttling of the ATM protein (RIANS) and contributes to increase the number of DSB managed by NHEJ, the most predominant DSB repair and signaling pathway in mammalians. Here, three radioresistant and three radiosensitive human fibroblast cell lines were pretreated with antioxidative agents (N-acetylcysteine or amifostine) or to two pro-episkevic agents (zoledronate or pravastatin or both (ZOPRA)) before X-ray irradiation. The fate of the RI DSB was analyzed by using γH2AX and pATM immunofluorescence. While amifostine pretreatment appeared to be the most efficient antioxidative process, ZOPRA shows the most powerful radiation protection, suggesting that the pro-episkevic strategy may be an alternative to the antioxidative one. Additional investigations are needed to develop some new drugs that may elicit both antioxidative and pro-episkevic properties and to quantify the radiation protection action of both types of drugs applied concomitantly.

In vitro and in vivo effects of zoledronate on senescence and senescence-associated secretory phenotype markers

In addition to reducing fracture risk, zoledronate has been found in some studies to decrease mortality in humans and extend lifespan and healthspan in animals. Because senescent cells accumulate with aging and contribute to multiple co-morbidities, the non-skeletal actions of zoledronate could be due to senolytic (killing of senescent cells) or senomorphic (inhibition of the secretion of the senescence-associated secretory phenotype [SASP]) actions. To test this, we first performed in vitro senescence assays using human lung fibroblasts and DNA repair-deficient mouse embryonic fibroblasts, which demonstrated that zoledronate killed senescent cells with minimal effects on non-senescent cells. Next, in aged mice treated with zoledronate or vehicle for 8 weeks, zoledronate significantly reduced circulating SASP factors, including CCL7, IL-1β, TNFRSF1A, and TGFβ1 and improved grip strength. Analysis of publicly available RNAseq data from CD115+ (CSF1R/c-fms+) pre-osteoclastic cells isolated from mice treated with zoledronate demonstrated a significant downregulation of senescence/SASP genes (SenMayo). To establish that these cells are potential senolytic/senomorphic targets of zoledronate, we used single cell proteomic analysis (cytometry by time of flight [CyTOF]) and demonstrated that zoledronate significantly reduced the number of pre-osteoclastic (CD115+/CD3e-/Ly6G-/CD45R-) cells and decreased protein levels of p16, p21, and SASP markers in these cells without affecting other immune cell populations. Collectively, our findings demonstrate that zoledronate has senolytic effects in vitro and modulates senescence/SASP biomarkers in vivo . These data point to the need for additional studies testing zoledronate and/or other bisphosphonate derivatives for senotherapeutic efficacy.

Aging and Bone Metabolism

Changes in bone architecture and metabolism with aging increase the likelihood of osteoporosis and fracture. Age-onset osteoporosis is multifactorial, with contributory extrinsic and intrinsic factors including certain medical problems, specific prescription drugs, estrogen loss, secondary hyperparathyroidism, microenvironmental and cellular alterations in bone tissue, and mechanical unloading or immobilization. At the histological level, there are changes in trabecular and cortical bone as well as marrow cellularity, lineage switching of mesenchymal stem cells to an adipogenic fate, inadequate transduction of signals during skeletal loading, and predisposition toward senescent cell accumulation with production of a senescence-associated secretory phenotype. Cumulatively, these changes result in bone remodeling abnormalities that over time cause net bone loss typically seen in older adults. Age-related osteoporosis is a geriatric syndrome due to the multiple etiologies that converge upon the skeleton to produce the ultimate phenotypic changes that manifest as bone fragility. Bone tissue is dynamic but with tendencies toward poor osteoblastic bone formation and relative osteoclastic bone resorption with aging. Interactions with other aging physiologic systems, such as muscle, may also confer detrimental effects on the aging skeleton. Conversely, individuals who maintain their BMD experience a lower risk of fractures, disability, and mortality, suggesting that this phenotype may be a marker of successful aging. © 2023 American Physiological Society. Compr Physiol 13:4355-4386, 2023.

The Nuclear Envelope in Ageing and Progeria

Development from embryo to adult, organismal homeostasis and ageing are consecutive processes that rely on several functions of the nuclear envelope (NE). The NE compartmentalises the eukaryotic cells and provides physical stability to the genetic material in the nucleus. It provides spatiotemporal regulation of gene expression by controlling nuclear import and hence access of transcription factors to target genes as well as organisation of the genome into open and closed compartments. In addition, positioning of chromatin relative to the NE is important for DNA replication and repair and thereby also for genome stability. We discuss here the relevance of the NE in two classes of age-related human diseases. Firstly, we focus on the progeria syndromes Hutchinson-Gilford (HGPS) and Nestor-Guillermo (NGPS), which are caused by mutations in the LMNA and BANF1 genes, respectively. Both genes encode ubiquitously expressed components of the nuclear lamina that underlines the nuclear membranes. HGPS and NGPS patients manifest symptoms of accelerated ageing and cells from affected individuals show similar defects as cells from healthy old donors, including signs of increased DNA damage and epigenetic alternations. Secondly, we describe how several age-related neurodegenerative diseases, such as amyotrophic lateral sclerosis and Huntington's disease, are related with defects in nucleocytoplasmic transport. A common feature of this class of diseases is the accumulation of nuclear pore proteins and other transport factors in inclusions. Importantly, genetic manipulations of the nucleocytoplasmic transport machinery can alleviate disease-related phenotypes in cell and animal models, paving the way for potential therapeutic interventions.

The Normal, the Radiosensitive, and the Ataxic in the Era of Precision Radiotherapy: A Narrative Review

(1) Background: radiotherapy is a cornerstone of cancer treatment. When delivering a tumoricidal dose, the risk of severe late toxicities is usually kept below 5% using dose-volume constraints. However, individual radiation sensitivity (iRS) is responsible (with other technical factors) for unexpected toxicities after exposure to a dose that induces no toxicity in the general population. Diagnosing iRS before radiotherapy could avoid unnecessary toxicities in patients with a grossly normal phenotype. Thus, we reviewed iRS diagnostic data and their impact on decision-making processes and the RT workflow; (2) Methods: following a description of radiation toxicities, we conducted a critical review of the current state of the knowledge on individual determinants of cellular/tissue radiation; (3) Results: tremendous advances in technology now allow minimally-invasive genomic, epigenetic and functional testing and a better understanding of iRS. Ongoing large translational studies implement various tests and enriched NTCP models designed to improve the prediction of toxicities. iRS testing could better support informed radiotherapy decisions for individuals with a normal phenotype who experience unusual toxicities. Ethics of medical decisions with an accurate prediction of personalized radiotherapy's risk/benefits and its health economics impact are at stake; (4) Conclusions: iRS testing represents a critical unmet need to design personalized radiotherapy protocols relying on extended NTCP models integrating iRS.

Quantification of Farnesylated Progerin in Hutchinson-Gilford Progeria Patient Cells by Mass Spectrometry

Hutchinson-Gilford progeria syndrome (HGPS) is a rare fatal disorder characterized by premature aging and death at a median age of 14.5 years. The most common cause of HGPS (affecting circa 90% of patients) is a de novo heterozygous synonymous single-base substitution (c.1824C>T; p.G608G) in the LMNA gene that results in the accumulation of progerin, an aberrant form of lamin A that, unlike mature lamin A, remains permanently farnesylated. The ratio of progerin to mature lamin A correlates with disease severity in HGPS patients, and can be used to assess the effectiveness of therapies aimed at lessening aberrant splicing or progerin farnesylation. We recently showed that the endogenous content of lamin A and progerin can be measured by mass spectrometry (MS), providing an alternative to immunological methods, which lack the necessary specificity and quantitative accuracy. Here, we present the first non-immunological method that reliably quantifies the levels of wild-type lamin A and farnesylated progerin in cells from HGPS patients. This method, which is based on a targeted MS approach and the use of isotope-labeled internal standards, could be applied in ongoing clinical trials evaluating the efficacy of drugs that inhibit progerin farnesylation.

Status of treatment strategies for Hutchinson-Gilford progeria syndrome with a focus on prelamin: A posttranslational modification

Hutchinson-Gilford progeria syndrome (HGPS) is a rare genetic disorder characterized by premature ageing and early death at a mean age of 14.7 years. At the molecular level, HGPS is caused by a de novo heterozygous mutation in LMNA, the gene encoding A-type lamins (mainly lamin A and C) and nuclear proteins, which have important cellular functions related to structure of the nuclear envelope. The LMNA mutation leads to the synthesis of a truncated prelamin A protein (called progerin), which cannot undergo normal processing to mature lamin A. In normal cells, prelamin A processing involves four posttranslational processing steps catalysed by four different enzymes. In HGPS cells, progerin accumulates as a farnesylated and methylated intermediate in the nuclear envelope where it is toxic and causes nuclear shape abnormalities and senescence. Numerous efforts have been made to target and reduce the toxicity of progerin, eliminate its synthesis and enhance its degradation, but as of today, only the use of farnesyltransferase inhibitors is approved for clinical use in HGPS patients. Here, we review the main current strategies that are being evaluated for treating HGPS, and we focus on efforts to target the posttranslational processing of progerin.

Hutchinson-Gilford Progeria Syndrome: A Literature Review

Hutchinson-Gilford progeria syndrome (HGPS) is a premature aging condition that involves genetic mutations, resulting in debilitating phenotypic features. The present state of knowledge on the molecular pathways that contribute to the pathophysiology of HGPS and the techniques being tested in vitro and in vivo to combat progerin toxicity have been discussed here. Nuclear morphological abnormalities, dysregulated gene expression, DNA repair deficiencies, telomere shortening, and genomic instability are all caused by progerin accumulation, all of which impair cellular proliferative capability. In addition, HGPS cells and preclinical animal models have revealed new information about the disease's molecular and cellular pathways and putative mechanisms involved in normal aging. This article has discussed the understanding of the molecular pathways by which progerin expression leads to HGPS and how the advanced therapy options for HGPS patients can help us understand and treat the condition.

The Impact of Various Anti-Osteoporosis Drugs on All-Cause Mortality After Hip Fractures: A Nationwide Population Study

Anti-osteoporosis treatment following hip fractures may reduce the overall mortality rate. However, the effects of different drugs on mortality is still unclear. This population-based cohort study aimed to identify the degree of reduced mortality after various anti-osteoporosis regimens following hip fracture surgery. We conducted this cohort study to identify patients with newly diagnosed osteoporosis and hip fractures from 2009 to 2017 using the Taiwan National Health Insurance Research Database (NHIRD). The subsequent use of anti-osteoporosis medication following hip fracture surgery was collected and analyzed. National death registration records were retrieved to determine mortality. A total of 45,226 new cases of osteoporotic hip fracture were identified. Compared with patients who did not receive further treatment, patients who had ever used oral bisphosphonates (alendronate and risedronate, hazard ratio [HR] 0.81; 95% confidence interval [CI], 0.78-0.84), ibandronate (HR 0.76; 95% CI, 0.67-0.86), zoledronic acid (HR 0.70; 95% CI, 0.64-0.76), and denosumab (HR 0.64; 95% CI, 0.60-0.68) showed lower all-cause mortality rates. Patients treated with bisphosphonates had a lower mortality risk than those treated with selective estrogen receptor modulators (HR 0.81; 95% CI, 0.75-0.87). Patients treated with zoledronic acid showed a lower mortality risk than those treated with oral bisphosphonates (HR 0.89; 95% CI, 0.82-0.97). However, patients receiving denosumab and zoledronic acid did not show a significant difference in mortality (HR 0.94; 95% CI, 0.85-1.03). Different anti-osteoporosis treatments for postsurgical patients were associated with different levels of decline in mortality. Generally, longer durations of drug use were associated with lower mortality. © 2022 American Society for Bone and Mineral Research (ASBMR).

The Role of Lamins in the Nucleoplasmic Reticulum, a Pleiomorphic Organelle That Enhances Nucleo-Cytoplasmic Interplay

Invaginations of the nuclear membrane occur in different shapes, sizes, and compositions. Part of these pleiomorphic invaginations make up the nucleoplasmic reticulum (NR), while others are merely nuclear folds. We define the NR as tubular invaginations consisting of either both the inner and outer nuclear membrane, or only the inner nuclear membrane. Specifically, invaginations of both the inner and outer nuclear membrane are also called type II NR, while those of only the inner nuclear membrane are defined as type I NR. The formation and structure of the NR is determined by proteins associated to the nuclear membrane, which induce a high membrane curvature leading to tubular invaginations. Here we review and discuss the current knowledge of nuclear invaginations and the NR in particular. An increase in tubular invaginations of the nuclear envelope is associated with several pathologies, such as laminopathies, cancer, (reversible) heart failure, and Alzheimer’s disease. Furthermore, viruses can induce both type I and II NR. In laminopathies, the amount of A-type lamins throughout the nucleus is generally decreased or the organization of lamins or lamin-associated proteins is disturbed. Also, lamin overexpression or modulation of lamin farnesylation status impacts NR formation, confirming the importance of lamin processing in NR formation. Virus infections reorganize the nuclear lamina via (de)phosphorylation of lamins, leading to an uneven thickness of the nuclear lamina and in turn lobulation of the nuclear membrane and the formation of invaginations of the inner nuclear membrane. Since most studies on the NR have been performed with cell cultures, we present additional proof for the existence of these structures in vivo, focusing on a variety of differentiated cardiovascular and hematopoietic cells. Furthermore, we substantiate the knowledge of the lamin composition of the NR by super-resolution images of the lamin A/C and B1 organization. Finally, we further highlight the essential role of lamins in NR formation by demonstrating that (over)expression of lamins can induce aberrant NR structures.

Progeria-a Rare Genetic Condition with Accelerated Ageing Process

Progeria is a rare genetic disease which is characterised by accelerated ageing and reduced life span. There are differing types of progeria, but the classic type is Hutchinson-Gilford progeria syndrome (HGPS). Within a year of birth, people suffering from it start showing several features such as very low weight, scleroderma, osteoporosis and loss of hair. Their life expectancy is highly reduced and the average life span is around 14.6 years. Research is going on to understand the genetic and molecular level causes of this disease. Apart from that, several studies are also going on to discover therapeutic techniques and drugs to treat this disease but the success rate is very low. To gain a better understanding about research developments of progeria more experimental models, drugs and molecular technologies are under trial. Different important aspects and recent developments in epidemiology, genetic causes, symptoms, diagnosis and treatment options of progeria are discussed in this review.

Abolishing the prelamin A ZMPSTE24 cleavage site leads to progeroid phenotypes with near-normal longevity in mice

The zinc metalloprotease ZMPSTE24 removes the last 15 amino acids of prelamin A, including a farnesylated cysteine, to produce mature lamin A. The premature aging disorder Hutchinson–Gilford progeria syndrome is caused by a permanently farnesylated prelamin A variant lacking the ZMPSTE24 cleavage site. ZMPSTE24 loss of function leads to the accumulation of farnesylated prelamin A and causes progeroid disorders. Some studies have implicated prelamin A in physiological aging. We describe mice with an amino acid substitution in prelamin A that blocks the ZMPSTE24-catalyzed cleavage. These mice develop progeroid phenotypes but, in contrast to those modeling Hutchinson–Gilford progeria syndrome or ZMPSTE24 deficiency, have near-normal lifespans, thus providing a model to study the effects of farnesylated prelamin A during aging.

Prelamin A is a farnesylated precursor of lamin A, a nuclear lamina protein. Accumulation of the farnesylated prelamin A variant progerin, with an internal deletion including its processing site, causes Hutchinson–Gilford progeria syndrome. Loss-of-function mutations in ZMPSTE24, which encodes the prelamin A processing enzyme, lead to accumulation of full-length farnesylated prelamin A and cause related progeroid disorders. Some data suggest that prelamin A also accumulates with physiological aging. Zmpste24^−/− mice die young, at ∼20 wk. Because ZMPSTE24 has functions in addition to prelamin A processing, we generated a mouse model to examine effects solely due to the presence of permanently farnesylated prelamin A. These mice have an L648R amino acid substitution in prelamin A that blocks ZMPSTE24-catalyzed processing to lamin A. The Lmna^L648R/L648R mice express only prelamin and no mature protein. Notably, nearly all survive to 65 to 70 wk, with ∼40% of male and 75% of female Lmna^L648R/L648R mice having near-normal lifespans of 90 wk (almost 2 y). Starting at ∼10 wk of age, Lmna^L648R/L648R mice of both sexes have lower body masses than controls. By ∼20 to 30 wk of age, they exhibit detectable cranial, mandibular, and dental defects similar to those observed in Zmpste24^−/− mice and have decreased vertebral bone density compared to age- and sex-matched controls. Cultured embryonic fibroblasts from Lmna^L648R/L648R mice have aberrant nuclear morphology that is reversible by treatment with a protein farnesyltransferase inhibitor. These novel mice provide a model to study the effects of farnesylated prelamin A during physiological aging.

Usher Syndrome Belongs to the Genetic Diseases Associated with Radiosensitivity: Influence of the ATM Protein Kinase

Usher syndrome (USH) is a rare autosomal recessive disease characterized by the combination of hearing loss, visual impairment due to retinitis pigmentosa, and in some cases vestibular dysfunctions. Studies published in the 1980s reported that USH is associated with cellular radiosensitivity. However, the molecular basis of this particular phenotype has not yet been documented. The aim of this study was therefore to document the radiosensitivity of USH1—a subset of USH—by examining the radiation-induced nucleo-shuttling of ATM (RIANS), as well as the functionality of the repair and signaling pathways of the DNA double-strand breaks (DSBs) in three skin fibroblasts derived from USH1 patients. The clonogenic cell survival, the micronuclei, the nuclear foci formed by the phosphorylated forms of the X variant of the H2A histone (ɣH2AX), the phosphorylated forms of the ATM protein (pATM), and the meiotic recombination 11 nuclease (MRE11) were used as cellular and molecular endpoints. The interaction between the ATM and USH1 proteins was also examined by proximity ligation assay. The results showed that USH1 fibroblasts were associated with moderate but significant radiosensitivity, high yield of micronuclei, and impaired DSB recognition but normal DSB repair, likely caused by a delayed RIANS, suggesting a possible sequestration of ATM by some USH1 proteins overexpressed in the cytoplasm. To our knowledge, this report is the first radiobiological characterization of cells from USH1 patients at both molecular and cellular scales.

Molecular Pathology of Laminopathies

The nuclear envelope is composed of the nuclear membranes, nuclear lamina, and nuclear pore complexes. Laminopathies are diseases caused by mutations in genes encoding protein components of the lamina and these other nuclear envelope substructures. Mutations in the single gene encoding lamin A and C, which are expressed in most differentiated somatic cells, cause diseases affecting striated muscle, adipose tissue, peripheral nerve, and multiple systems with features of accelerated aging. Mutations in genes encoding other nuclear envelope proteins also cause an array of diseases that selectively affect different tissues or organs. In some instances, the molecular and cellular consequences of laminopathy-causing mutations are known. However, even when these are understood, mechanisms explaining specific tissue or organ pathology remain enigmatic. Current mechanistic hypotheses focus on how alterations in the nuclear envelope may affect gene expression, including via the regulation of signaling pathways, or cellular mechanics, including responses to mechanical stress.

Treatment of osteoporosis after hip fracture is associated with lower all-cause mortality: A nationwide population study

PURPOSE

Mortality after osteoporotic hip fractures is high. Postoperative care is as important as surgery itself to prevent a second fracture and improve outcomes, and the effect of anti-osteoporosis treatment after hip fractures on overall mortality is controversial. This nationwide population study aimed to determine whether anti-osteoporosis treatment might reduce overall mortality after hip fracture surgery.

METHODS

We conducted this cohort study using the National Health Insurance Research Database (NHIRD) of Taiwan to identify patients admitted for surgery due to hip fractures from 2008 to 2018. The subsequent use and duration of anti-osteoporotic medication and other parameters were analyzed, and national death registration records were retrieved to investigate mortality.

RESULTS

A total of 59,943 patients admitted for hip fracture surgery were identified. The 22,494 patients (37.5%) who received anti-osteoporotic medication showed a lower all-cause mortality rate compared with the 37,449 patients (62.5%) who did not receive further treatment (hazard ratio (HR): 0.69, 95% confidence interval (CI): 0.67-0.70, p < 0.0001). Patients who received anti-osteoporotic medication for more than 1, 2, and 3 years exhibited propotional reductions in all-cause mortality (HR & 95%CI: 0.57 (0.54-0.60), 0.42 (0.38-0.46), and 0.29 (0.26-0.33) respectively).

CONCLUSION

Anti-osteoporosis treatment was associated with lower all-cause mortality after hip fracture surgery. A longer duration of treatment was also associated with lower mortality. Postoperative treatment for osteoporosis is crucial for patients with hip fracture.

Case report: Focal segmental glomerulosclerosis in a pediatric atypical progeroid syndrome

Atypical progeroid syndrome (APS) is a rare type of progeroid syndrome mainly caused by heterozygous missense mutations in the LMNA (MIM 150330) gene. APS has heterogeneous clinical manifestations, and its kidney manifestations, particularly in children, are rarely documented. Here, we report the first pediatric case of APS with focal segmental glomerulosclerosis (FSGS). A 10-year-old boy with progeroid features was referred to the nephrology clinic because of hyperuricemia. He had dark skin, protruding eyes, and beaked nose and was very thin, suggesting lipodystrophy. He had been treated for recurrent urinary tract infection during infancy, and liver biopsy for persisting hepatitis showed steatohepatitis. He also had hypertrophic cardiomyopathy (HCMP) with mitral and tricuspid valve regurgitation. Genetic studies were performed considering his multisystem symptoms, and he was diagnosed as having APS according to exome sequencing findings (c.898G > C, p.Asp300His of LMNA). During the first visit to the nephrology clinic, he had minimal proteinuria (urine protein/creatinine ratio of 0.23 mg/mg), which worsened during follow-up. In three years, his urine protein/creatinine ratio and N-acetyl-b-D-glucosaminidase/creatinine ratio increased to 1.52 and 18.7, respectively. The kidney biopsy result was consistent with findings of FSGS, peri-hilar type, showing segmental sclerosis of 1 (5%) glomerulus out of 21 glomeruli. An angiotensin receptor blocker was added to manage his proteinuria. This is the first pediatric report of FSGS in an APS patient with confirmed LMNA defect, who manifested progeroid features, lipodystrophy, HCMP with heart valve dysfunction, and steatohepatitis. Our case suggests that screening for proteinuric nephropathy is essential for managing APS patients since childhood.

Disruption of FDPS/Rac1 axis radiosensitizes pancreatic ductal adenocarcinoma by attenuating DNA damage response and immunosuppressive signalling

Background

Radiation therapy (RT) has a suboptimal effect in patients with pancreatic ductal adenocarcinoma (PDAC) due to intrinsic and acquired radioresistance (RR). Comprehensive bioinformatics and microarray analysis revealed that cholesterol biosynthesis (CBS) is involved in the RR of PDAC. We now tested the inhibition of the CBS pathway enzyme, farnesyl diphosphate synthase (FDPS), by zoledronic acid (Zol) to enhance radiation and activate immune cells.

Methods

We investigated the role of FDPS in PDAC RR using the following methods: in vitro cell-based assay, immunohistochemistry, immunofluorescence, immunoblot, cell-based cholesterol assay, RNA sequencing, tumouroids (KPC-murine and PDAC patient-derived), orthotopic models, and PDAC patient's clinical study.

Findings

FDPS overexpression in PDAC tissues and cells (P < 0.01 and P < 0.05) is associated with poor RT response and survival (P = 0.024). CRISPR/Cas9 and pharmacological inhibition (Zol) of FDPS in human and mouse syngeneic PDAC cells in conjunction with RT conferred higher PDAC radiosensitivity in vitro (P < 0.05, P < 0.01, and P < 0.001) and in vivo (P < 0.05). Interestingly, murine (P = 0.01) and human (P = 0.0159) tumouroids treated with Zol+RT showed a significant growth reduction. Mechanistically, RNA-Seq analysis of the PDAC xenografts and patients-PBMCs revealed that Zol exerts radiosensitization by affecting Rac1 and Rho prenylation, thereby modulating DNA damage and radiation response signalling along with improved systemic immune cells activation. An ongoing phase I/II trial (NCT03073785) showed improved failure-free survival (FFS), enhanced immune cell activation, and decreased microenvironment-related genes upon Zol+RT treatment.

Interpretation

Our findings suggest that FDPS is a novel radiosensitization target for PDAC therapy. This study also provides a rationale to utilize Zol as a potential radiosensitizer and as an immunomodulator in PDAC and other cancers.

Funding

National Institutes of Health (P50, P01, and R01).

Individual Response to Radiation of Individuals with Neurofibromatosis Type I: Role of the ATM Protein and Influence of Statins and Bisphosphonates

Neurofibromatosis type 1 (NF1) is a disease characterized by high occurrence of benign and malignant brain tumours and caused by mutations of the neurofibromin protein. While there is an increasing evidence that NF1 is associated with radiosensitivity and radiosusceptibility, few studies have dealt with the molecular and cellular radiation response of cells from individuals with NF1. Here, we examined the ATM-dependent signalling and repair pathways of the DNA double-strand breaks (DSB), the key-damage induced by ionizing radiation, in skin fibroblast cell lines from 43 individuals with NF1. Ten minutes after X-rays irradiation, quiescent NF1 fibroblasts showed abnormally low rate of recognized DSB reflected by a low yield of nuclear foci formed by phosphorylated H2AX histones. Irradiated NF1 fibroblasts also presented a delayed radiation-induced nucleoshuttling of the ATM kinase (RIANS), potentially due to a specific binding of ATM to the mutated neurofibromin in cytoplasm. Lastly, NF1 fibroblasts showed abnormally high MRE11 nuclease activity suggesting a high genomic instability after irradiation. A combination of bisphosphonates and statins complemented these impairments by accelerating the RIANS, increasing the yield of recognized DSB and reducing genomic instability. Data from NF1 fibroblasts exposed to radiation in radiotherapy and CT scan conditions confirmed that NF1 belongs to the group of syndromes associated with radiosensitivity and radiosusceptibility.

Preclinical Advances of Therapies for Laminopathies

Laminopathies are a group of rare disorders due to mutation in LMNA gene. Depending on the mutation, they may affect striated muscles, adipose tissues, nerves or are multisystemic with various accelerated ageing syndromes. Although the diverse pathomechanisms responsible for laminopathies are not fully understood, several therapeutic approaches have been evaluated in patient cells or animal models, ranging from gene therapies to cell and drug therapies. This review is focused on these therapies with a strong focus on striated muscle laminopathies and premature ageing syndromes.

DNA Double-Strand Breaks Induced in Human Cells by Twelve Metallic Species: Quantitative Inter-Comparisons and Influence of the ATM Protein

Despite a considerable amount of data, the molecular and cellular bases of the toxicity due to metal exposure remain unknown. Recent mechanistic models from radiobiology have emerged, pointing out that the radiation-induced nucleo-shuttling of the ATM protein (RIANS) initiates the recognition and the repair of DNA double-strand breaks (DSB) and the final response to genotoxic stress. In order to document the role of ATM-dependent DSB repair and signalling after metal exposure, we applied twelve different metal species representing nine elements (Al, Cu, Zn Ni, Pd, Cd, Pb, Cr, and Fe) to human skin, mammary, and brain cells. Our findings suggest that metals may directly or indirectly induce DSB at a rate that depends on the metal properties and concentration, and tissue type. At specific metal concentration ranges, the nucleo-shuttling of ATM can be delayed which impairs DSB recognition and repair and contributes to toxicity and carcinogenicity. Interestingly, as observed after low doses of ionizing radiation, some phenomena equivalent to the biological response observed at high metal concentrations may occur at lower concentrations. A general mechanistic model of the biological response to metal exposure based on the nucleo-shuttling of ATM is proposed to describe the metal-induced stress response and to define quantitative endpoints for toxicity and carcinogenicity.

Hutchinson-Gilford Progeria Syndrome (Hgps) And Application Of Gene Therapy Based Crispr/Cas Technology As A Promising Innovative Treatment Approach

BACKGROUND

Hutchinson-Gilford progeria syndrome (HGPS) also known as progeria of childhood or progeria is a rare, rapid, autosomal dominant genetic disorder characterized by premature aging which occurs shortly after birth. HGPS occurs as a result of de novo point mutation in the gene recognized as LMNA gene that encodes two proteins Lamin A protein and Lamin C protein which are the structural components of the nuclear envelope. Mutations in the gene trigger abnormal splicing and induce internal deletion of 50 amino acids leading to the development of a truncated form of Lamin A protein known as Progerin. Progerin generation can be considered as the crucial step in HGPS since the protein is highly toxic to human cells, permanently farnesylated, and exhibits variation in several biochemical and structural properties within the individual. HGPS also produces complications such as skin alterations, growth failure, atherosclerosis, hair and fat loss, and bone and joint diseases. We have also revised all relevant patents relating to Hutchinson-gilford progeria syndrome and its therapy in the current article.

METHOD

The goal of the present review article is to provide information about Hutchinson-Gilford progeria syndrome (HGPS) and the use of CRISPR/Cas technology as a promising treatment approach in the treatment of the disease. The review also discusses about different pharmacological and non-pharmacological methods of treatment currently used for HGPS.

RESULTS

The main limitation associated with progeria is the lack of a definitive cure. The existing treatment modality provides only symptomatic relief. Therefore, it is high time to develop a therapeutic method that hastens premature aging in such patients.

CONCLUSION

CRISPR/Cas technology is a novel gene-editing tool that allows genome editing at specific loci, and is found to be a promising therapeutic approach for the treatment of genetic disorders such as HGPS where dominant-negative mutations take place.

Isoprenylcysteine Carboxylmethyltransferase-Based Therapy for Hutchinson-Gilford Progeria Syndrome

Hutchinson-Gilford progeria syndrome (HGPS, progeria) is a rare genetic disease characterized by premature aging and death in childhood for which there were no approved drugs for its treatment until last November, when lonafarnib obtained long-sought FDA approval. However, the benefits of lonafarnib in patients are limited, highlighting the need for new therapeutic strategies. Here, we validate the enzyme isoprenylcysteine carboxylmethyltransferase (ICMT) as a new therapeutic target for progeria with the development of a new series of potent inhibitors of this enzyme that exhibit an excellent antiprogeroid profile. Among them, compound UCM-13207 significantly improved the main hallmarks of progeria. Specifically, treatment of fibroblasts from progeroid mice with UCM-13207 delocalized progerin from the nuclear membrane, diminished its total protein levels, resulting in decreased DNA damage, and increased cellular viability. Importantly, these effects were also observed in patient-derived cells. Using the Lmna ^G609G/G609G progeroid mouse model, UCM-13207 showed an excellent in vivo efficacy by increasing body weight, enhancing grip strength, extending lifespan by 20%, and decreasing tissue senescence in multiple organs. Furthermore, UCM-13207 treatment led to an improvement of key cardiovascular hallmarks such as reduced progerin levels in aortic and endocardial tissue and increased number of vascular smooth muscle cells (VSMCs). The beneficial effects go well beyond the effects induced by other therapeutic strategies previously reported in the field, thus supporting the use of UCM-13207 as a new treatment for progeria.

Small-Molecule Therapeutic Perspectives for the Treatment of Progeria

Hutchinson-Gilford progeria syndrome (HGPS), or progeria, is an extremely rare disorder that belongs to the class of laminopathies, diseases characterized by alterations in the genes that encode for the lamin proteins or for their associated interacting proteins. In particular, progeria is caused by a point mutation in the gene that codifies for the lamin A gene. This mutation ultimately leads to the biosynthesis of a mutated version of lamin A called progerin, which accumulates abnormally in the nuclear lamina. This accumulation elicits several alterations at the nuclear, cellular, and tissue levels that are phenotypically reflected in a systemic disorder with important alterations, mainly in the cardiovascular system, bones, skin, and overall growth, which results in premature death at an average age of 14.5 years. In 2020, lonafarnib became the first (and only) FDA approved drug for treating progeria. In this context, the present review focuses on the different therapeutic strategies currently under development, with special attention to the new small molecules described in recent years, which may represent the upcoming first-in-class drugs with new mechanisms of action endowed with effectiveness not only to treat but also to cure progeria.

Human Radiosensitivity and Radiosusceptibility: What Are the Differences?

The individual response to ionizing radiation (IR) raises a number of medical, scientific, and societal issues. While the term "radiosensitivity" was used by the pioneers at the beginning of the 20st century to describe only the radiation-induced adverse tissue reactions related to cell death, a confusion emerged in the literature from the 1930s, as "radiosensitivity" was indifferently used to describe the toxic, cancerous, or aging effect of IR. In parallel, the predisposition to radiation-induced adverse tissue reactions (radiosensitivity), notably observed after radiotherapy appears to be caused by different mechanisms than those linked to predisposition to radiation-induced cancer (radiosusceptibility). This review aims to document these differences in order to better estimate the different radiation-induced risks. It reveals that there are very few syndromes associated with the loss of biological functions involved directly in DNA damage recognition and repair as their role is absolutely necessary for cell viability. By contrast, some cytoplasmic proteins whose functions are independent of genome surveillance may also act as phosphorylation substrates of the ATM protein to regulate the molecular response to IR. The role of the ATM protein may help classify the genetic syndromes associated with radiosensitivity and/or radiosusceptibility.

Zoledronate extends healthspan and survival via the mevalonate pathway in a FOXO-dependent manner

Over recent decades, increased longevity has not been paralleled by extended healthspan, resulting in more years spent with multiple diseases in older age. As such, interventions to improve healthspan are urgently required. Zoledronate is a nitrogen containing bisphosphonate, which inhibits the farnesyl pyrophosphate synthase (FPPS) enzyme, central to the mevalonate pathway. It is already used clinically to prevent fractures in osteoporotic patients, who have been reported to derive unexpected and unexplained survival benefits. Using Drosophila as a model we determined the effects of Zoledronate on lifespan, parameters of healthspan (climbing ability and intestinal dysplasia) and the ability to confer resistance to oxidative stress using a combination of genetically manipulated Drosophila strains and Western blotting. Our study shows that Zoledronate extended lifespan, improved climbing activity and reduced intestinal epithelial dysplasia and permeability with age. Mechanistic studies showed that Zoledronate conferred resistance to oxidative stress and reduced accumulation of X-ray-induced DNA damage via inhibition of FPPS. Moreover, Zoledronate was associated with inhibition of pAKT in the mTOR pathway downstream of the mevalonate pathway and required dFOXO for its action, both molecules associated with increased longevity. Taken together, our work indicates that Zoledronate, a drug already widely used to prevent osteoporosis and dosed only once a year, modulates important mechanisms of ageing. Its repurposing holds great promise as a treatment to improve healthspan.

Bone Aging, Cellular Senescence, and Osteoporosis

Changes in aging bone that lead to osteoporosis are mediated at multiple levels, including hormonal alterations, skeletal unloading, and accumulation of senescent cells. This pathological interplay is superimposed upon medical conditions, potentially bone-wasting medications, modifiable and unmodifiable personal risk factors, and genetic predisposition that accelerate bone loss with aging. In this study, the focus is on bone hemostasis and its dysregulation with aging. The major physiological changes with aging in bone and the role of cellular senescence in contributing to age-related osteoporosis are summarized. The aspects of bone aging are reviewed including remodeling deficits, uncoupling phenomena, inducers of cellular senescence related to bone aging, roles of the senescence-associated secretory phenotype, radiation-induced bone loss as a model for bone aging, and the accumulation of senescent cells in the bone microenvironment as a predominant mechanism for age-related osteoporosis. The study also addresses the rationale and potential for therapeutic interventions based on the clearance of senescent cells or suppression of the senescence-associated secretory phenotype. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Key Enzymes for the Mevalonate Pathway in the Cardiovascular System

ABSTRACT

Isoprenylation is an important post-transcriptional modification of small GTPases required for their activation and function. Isoprenoids, including farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate, are indispensable for isoprenylation by serving as donors of a prenyl moiety to small G proteins. In the human body, isoprenoids are mainly generated by the mevalonate pathway (also known as the cholesterol-synthesis pathway). The hydroxymethylglutaryl coenzyme A reductase catalyzes the first rate-limiting steps of the mevalonate pathway, and its inhibitor (statins) are widely used as lipid-lowering agents. In addition, the FPP synthase is also of critical importance for the regulation of the isoprenoids production, for which the inhibitor is mainly used in the treatment of osteoporosis. Synthetic FPP can be further used to generate geranylgeranyl pyrophosphate and cholesterol. Recent studies suggest a role for isoprenoids in the genesis and development of cardiovascular disorders, such as pathological cardiac hypertrophy, fibrosis, endothelial dysfunction, and fibrotic responses of smooth-muscle cells. Furthermore, statins and FPP synthase inhibitors have also been applied for the management of heart failure and other cardiovascular diseases rather than their clinical use for hyperlipidemia or bone diseases. In this review, we focus on the function of several critical enzymes, including hydroxymethylglutaryl coenzyme A reductase, FPP synthase, farnesyltransferase, and geranylgeranyltransferase in the mevalonate pathway which are involved in regulating the generation of isoprenoids and isoprenylation of small GTPases, and their pathophysiological role in the cardiovascular system. Moreover, we summarize recent research into applications of statins and the FPP synthase inhibitors to treat cardiovascular diseases, rather than for their traditional indications respectively.

Nuclear organization and regulation of the differentiated state

Regulation of the differentiated identity requires active and continued supervision. Inability to maintain the differentiated state is a hallmark of aging and aging-related disease. To maintain cellular identity, a network of nuclear regulators is devoted to silencing previous and non-relevant gene programs. This network involves transcription factors, epigenetic regulators, and the localization of silent genes to heterochromatin. Together, identity supervisors mold and maintain the unique nuclear environment of the differentiated cell. This review describes recent discoveries regarding mechanisms and regulators that supervise the differentiated identity and protect from de-differentiation, tumorigenesis, and attenuate forced somatic cell reprograming. The review focuses on mechanisms involved in H3K9me3-decorated heterochromatin and the importance of nuclear lamins in cell identity. We outline how the biophysical properties of these factors are involved in self-compartmentalization of heterochromatin and cell identity. Finally, we discuss the relevance of these regulators to aging and age-related disease.

A 13-Year-Old Boy from Thailand with Hutchinson-Gilford Progeria Syndrome with Coronary Artery and Aortic Calcification and Non-ST-Segment Elevation Myocardial Infarction (NSTEMI)

Patient: Male, 13-year-old

Final Diagnosis: Hutchinson-Gilford progeria syndrome with coronary artery and aortic calcification and non-ST-segment elevation myocardial infarction

Symptoms: Chest discomfort

Medication: —

Clinical Procedure: —

Specialty: Cardiology

First radiobiological characterization of the McCune-Albright syndrome: influence of the ATM protein and effect of statins + bisphosphonates treatment

PURPOSE

MacCune-Albright syndrome (MAS) is a rare autosomal dominant osteo-hormonal disorder. MAS is characterized by a severe form of polyostotic fibrous dysplasia, 'café-au-lait' pigmentation of the skin and multiple endocrinopathies. MAS was shown to be caused by mosaic missense somatic mutations in the GNAS gene coding for the alpha-subunit of the stimulatory G-protein. MAS is also associated with radiation-induced malignant tumors, like osteosarcoma, fibrosarcoma and chondrosarcoma but their origin remains misunderstood. In parallel, bisphosphonates treatment was shown to improve the MAS patients' outcome, notably by increasing bone density but, again, the molecular mechanisms supporting these observations remain misunderstood.

MATERIALS AND METHODS

Here, by using fibroblast and osteoblast cell lines derived from 2 MAS patients, the major radiobiological features of MAS were investigated. Notably, the clonogenic cell survival, the micronuclei and the γH2AX, pATM and MRE11 immunofluorescence assays were applied to MAS cells.

RESULTS

It appears that cells from the 2 MAS patients are associated with a moderate but significant radiosensitivity, a delayed radiation-induced nucleoshuttling of the ATM kinase likely caused by its sequestration in cytoplasm, suggesting impaired DNA double-strand breaks (DSB) repair and signaling in both fibroblasts and osteoblasts. Such delay may be partially corrected by using bisphosphonates combined with statins, which renders cells more radioresistant.

CONCLUSIONS

Our findings represent the first radiobiological characterization of fibroblasts and osteoblasts providing from MAS patients. Although the number of studied cases is reduced, our findings suggest that the MAS cells tested belong to the group of syndromes associated with moderate but significant radiosensitivity. Further investigations are however required to secure the clinical transfer of the combination of bisphosphonates and statins, to reduce the disease progression and to better evaluate the potential risks linked to radiation exposure.

Progerinin, an optimized progerin-lamin A binding inhibitor, ameliorates premature senescence phenotypes of Hutchinson-Gilford progeria syndrome

Previous work has revealed that progerin-lamin A binding inhibitor (JH4) can ameliorate pathological features of Hutchinson-Gilford progeria syndrome (HGPS) such as nuclear deformation, growth suppression in patient’s cells, and very short life span in an in vivo mouse model. Despite its favorable effects, JH4 is rapidly eliminated in in vivo pharmacokinetic (PK) analysis. Thus, we improved its property through chemical modification and obtained an optimized drug candidate, Progerinin (SLC-D011). This chemical can extend the life span of Lmna^G609G/G609G mouse for about 10 weeks and increase its body weight. Progerinin can also extend the life span of Lmna^G609G/+ mouse for about 14 weeks via oral administration, whereas treatment with lonafarnib (farnesyl-transferase inhibitor) can only extend the life span of Lmna^G609G/+ mouse for about two weeks. In addition, progerinin can induce histological and physiological improvement in Lmna^G609G/+ mouse. These results indicate that progerinin is a strong drug candidate for HGPS.

Kang, Park and colleagues develop and demonstrate the effects of a new drug candidate for treatment of Hutchinson-Gilford progeria syndrome pathologies. Progerinin extends the life span of mice used to model this disease and induces histological and physiological improvements.

Bisphosphonates in veterinary medicine: The new horizon for use

Bisphosphonates (BPs) are characterized by their ability to bind strongly to bone mineral and inhibit bone resorption. However, BPs exert a wide range of pharmacological activities beyond the inhibition of bone resorption, including the inhibition of cancer cell metastases and angiogenesis and the inhibition of proliferation and apoptosis in vitro. Additionally, the inhibition of matrix metalloproteinase activity, altered cytokine and growth factor expression, as well as reductions in parameters of pain have also been reported. In humans, clinical BP use has transformed the treatment of post-menopausal osteoporosis, rare bone diseases such as osteogenesis imperfecta, as well as multiple myeloma and metastatic breast and prostate cancer, albeit not without infrequent but significant adverse events. Despite the well-characterized health benefits of BP use in humans, the evidence-base for the therapeutic efficacy of BPs in veterinary medicine is, by comparison, limited. Notwithstanding, BPs are used widely in small animal veterinary practice for the medical management of hyperparathyroidism, idiopathic hypercalcemia in cats, as well as for the palliative care of bone tumors which are common in dogs, and in particular, primary bone tumors such as osteosarcoma. Palliative BP treatment has also recently increased in veterinary oncology to alleviate tumor-associated bone pain. In equine veterinary practice, non-nitrogen-containing BPs are FDA-approved to control clinical signs associated with navicular syndrome in adult horses. However, there are growing concerns regarding the off-label use of BPs in juvenile horses. Here we discuss the current understanding of the strengths, weaknesses and current controversies surrounding BP use in veterinary medicine to highlight the future utility of these potentially beneficial drugs.

The impact of bisphosphonates on mortality and cardiovascular risk among osteoporosis patients after cardiovascular disease

BACKGROUND/PURPOSE

Bisphosphonates (BPs) impact on the survival and cardiovascular safety of osteoporosis patients after acute coronary syndrome (ACS) or acute ischemic stroke (AIS) was evaluated.

METHODS

A nationwide epidemiological study was conducted using the Taiwan National Health Insurance Research Database from 2000 to 2010. From the 1456 osteoporosis patients with previous ACS or AIS, mortality and cardiovascular safety was compared between 464 patients who used BPs and 464 patients who did not. Primary outcomes included all-cause mortality, and major adverse cardiovascular events.

RESULTS

The BPs group had a lower risk of all-cause mortality than the control group after the 8-year follow-up (HR, 0.64; 95% CI, 0.46-0.88; P = 0.006). The risks of myocardial infarction, ischemic stroke, cardiovascular death, hospitalization for heart failure or other causes of mortality were similar across groups. However, there was a higher risk of hospitalization for atrial fibrillation in the BPs group than the control group (HR, 1.76; 95% CI, 1.26-2.46; P = 0.001).

CONCLUSION

Among osteoporosis patients after ACS or AIS, BPs use was associated with a reduced risk of all-cause mortality. However, patients with previous cardiovascular disease who received BP treatment should be careful about the risk of atrial fibrillation.

Repurposing drugs to fight aging: The difficult path from bench to bedside

The steady rise in life expectancy occurred across all developed countries during the last century. This demographic trend is, however, not accompanied by the same healthspan extension. This is since aging is the main risk factor for all age-associated pathological conditions. Therefore, slowing the rate of aging is suggested to be more efficient in preventing or delaying age-related diseases than treat them one by one, which is the common approach in a current pharmacological disease-oriented paradigm. To date, a variety of medications designed to treat particular pathological conditions have been shown to exhibit pro-longevity effects in different experimental models. Among them, there are many commonly used prescription and over-the-counter pharmaceuticals such as metformin, rapamycin, aspirin, statins, melatonin, vitamin antioxidants, etc. All of them are being increasingly investigated in preclinical and clinical trials with the aim of determine whether they have potential for extension of human healthspan. The results from these trials are frequently inconclusive and fall short of initial expectations, suggesting that innovative research ideas and additional translational steps are required to overcome obstacles for implementation of such approaches in clinical practice. In this review, recent advances and challenges in the field of repurposing widely used conventional pharmaceuticals to target the aging process are summarized and discussed.

Bisphosphonates and lifespan

Bisphosphonates are first line agents used to treat osteoporosis and reduce fracture rate. They bind to areas of exposed calcium in the skeleton and cause osteoclast apoptosis, thereby leading to a reduction in remodelling rates. They are also used to decrease skeletal complications of some cancers including a reduction in bone metastases. Following the landmark randomised controlled trial of zoledronate post hip fracture (HORIZON) in which an unexpected survival benefit was found, there has been increasing interest in their potential ability to increase lifespan. This review will consider the clinical evidence for their effect on mortality in both the osteoporosis and non-osteoporosis settings, the latter including studies in intensive care, cancer and cardiovascular disease. Where evidence exists, this review will briefly discuss some of the postulated mechanisms for this survival benefit.

Aging and Chronic Liver Disease

Aging increases the incidence of chronic liver disease (CLD), worsens its prognosis, and represents the predominant risk factor for its development at all different stages. The hepatic sinusoid, which is fundamental for maintaining liver homeostasis, is composed by hepatocytes, liver sinusoidal endothelial cells, hepatic stellate cells, and hepatic macrophages. During CLD progression, hepatic cells suffer deregulations in their phenotype, which ultimately lead to disease development. The effects of aging on the hepatic sinusoid phenotype and function are not well understood, nevertheless, studies performed in experimental models of liver diseases and aging demonstrate alterations in all hepatic sinusoidal cells. This review provides an updated description of age-related changes in the hepatic sinusoid and discusses the implications for CLD development and treatment. Lastly, we propose aging as a novel therapeutic target to treat liver diseases and summarize the most promising therapies to prevent or improve CLD and extend healthspan.

Extra-skeletal effects of bisphosphonates

Bisphosphonates (BPs) are pyrophosphate analogues widely used in diseases related to bone loss and increased bone turnover. Their high affinity for bone hydroxyapatite makes them ideal agents for bone diseases, while preventing them from reaching other cells and tissues. Data of the last decade, however, have demonstrated extra-skeletal tissue deposition and a variety of non-skeletal effects have been recently recognized. As such, BPs have been shown to exert anti-tumor, immunomodulatory, anti-inflammatory and anti-diabetic effects. In addition, new delivery systems (liposomes, nanoparticles, hydrogels) are being developed in an effort to expand BPs clinical application to extra-skeletal tissues and enhance their overall therapeutic spectrum and effectiveness. In the present review, we outline current data on extra-skeletal actions of bisphosphonates and attempt to unravel the underlying pathophysiological mechanisms.

Fibroblasts from Retinoblastoma Patients Show Radiosensitivity Linked to Abnormal Localization of the ATM Protein

PURPOSE/AIM OF THE STUDY

Retinoblastoma (Rb) is a rare form of pediatric cancer that develops from retina cells. Bilateral and some unilateral forms of Rb are associated with heterozygous germline mutations of the (retinoblastoma 1) RB1 gene. RB1 mutations are also associated with a significant risk of secondary malignancy like head and neck tumors. Hence, to date, even if Rb patients are less subjected to radiotherapy to treat their primary ocular tumors, their healthy tissues may be exposed to significant doses of ionizing radiation during the treatment against their secondary malignancies with a significant risk of adverse tissue reactions (radiosensitivity) and/or radiation-induced cancer (radiosusceptibility). However, the biological role of the Rb protein in response to radiation remains misunderstood. Since the ataxia telangiectasia mutated (ATM) protein is a key protein of radiation response and since untransformed skin fibroblasts are a current model to quantify cellular radiosensitivity, we investigated here for the first time the functionality of the ATM-dependent signaling and repair pathway of the radiation-induced DNA double-strand breaks (DSB) in irradiated skin fibroblasts derived from Rb patients.

MATERIALS AND METHODS

The major biomarkers of the DSB repair and signaling, namely clonogenic cell survival, micronuclei, nuclear foci of the phosphorylated forms of the X variant of the H2A histone (γH2AX), the phosphorylated forms of the ATM protein (pATM) and the meiotic recombination 11 nuclease (MRE11) were assessed in untransformed skin fibroblasts derived from three Rb patients.

RESULTS

Skin fibroblasts from Rb patients showed significant cellular radiosensitivity, incomplete DSB recognition, delay in the ATM nucleo-shuttling and exacerbated MRE11 nuclease activity. Treatment with statin and bisphosphonates led to significant complementation of these impairments.

CONCLUSIONS

Our findings strongly suggest the involvement of the ATM kinase in the radiosensitivity/radiosusceptibility phenotype observed in Rb cases.

Vulnerability of progeroid smooth muscle cells to biomechanical forces is mediated by MMP13

Hutchinson-Gilford Progeria Syndrome (HGPS) is a premature aging disease in children that leads to early death. Smooth muscle cells (SMCs) are the most affected cells in HGPS individuals, although the reason for such vulnerability remains poorly understood. In this work, we develop a microfluidic chip formed by HGPS-SMCs generated from induced pluripotent stem cells (iPSCs), to study their vulnerability to flow shear stress. HGPS-iPSC SMCs cultured under arterial flow conditions detach from the chip after a few days of culture; this process is mediated by the upregulation of metalloprotease 13 (MMP13). Importantly, double-mutant LmnaG609G/G609GMmp13-/- mice or LmnaG609G/G609GMmp13+/+ mice treated with a MMP inhibitor show lower SMC loss in the aortic arch than controls. MMP13 upregulation appears to be mediated, at least in part, by the upregulation of glycocalyx. Our HGPS-SMCs chip represents a platform for developing treatments for HGPS individuals that may complement previous pre-clinical and clinical treatments.