Paclitaxel mitigates structural alterations and cardiac conduction system defects in a mouse model of Hutchinson-Gilford progeria syndrome.

AIMS: Hutchinson-Gilford progeria syndrome (HGPS) is an ultrarare laminopathy caused by expression of progerin, a lamin A variant, also present at low levels in non-HGPS individuals. HGPS patients age and die prematurely, predominantly from cardiovascular complications. Progerin-induced cardiac repolarization defects have been described previously, although the underlying mechanisms are unknown. METHODS AND RESULTS: We conducted studies in heart tissue from progerin-expressing LmnaG609G/G609G (G609G) mice, including microscopy, intracellular calcium dynamics, patch-clamping, in vivo magnetic resonance imaging, and electrocardiography. G609G mouse cardiomyocytes showed tubulin-cytoskeleton disorganization, t-tubular system disruption, sarcomere shortening, altered excitation-contraction coupling, and reductions in ventricular thickening and cardiac index. G609G mice exhibited severe bradycardia, and significant alterations of atrio-ventricular conduction and repolarization. Most importantly, 50% of G609G mice had altered heart rate variability, and sinoatrial block, both significant signs of premature cardiac aging. G609G cardiomyocytes had electrophysiological alterations, which resulted in an elevated action potential plateau and early afterdepolarization bursting, reflecting slower sodium current inactivation and long Ca+2 transient duration, which may also help explain the mild QT prolongation in some HGPS patients. Chronic treatment with low-dose paclitaxel ameliorated structural and functional alterations in G609G hearts. CONCLUSIONS: Our results demonstrate that tubulin-cytoskeleton disorganization in progerin-expressing cardiomyocytes causes structural, cardiac conduction, and excitation-contraction coupling defects, all of which can be partially corrected by chronic treatment with low dose paclitaxel.

Reactive Species in Progeroid Syndromes and Aging-Related Processes.

Significance: Reactive species have been classically considered causative of age-related degenerative processes, but the scenario appears considerably more complex and to some extent counterintuitive than originally anticipated. The impact of reactive species in precocious aging syndromes is revealing new clues to understand and perhaps challenge the resulting degenerative processes. Recent Advances: Our understanding of reactive species has considerably evolved, including their hormetic effect (beneficial at a certain level, harmful beyond this level), the occurrence of diverse hormetic peaks in different cell types and organisms, and the extended type of reactive species that are relevant in biological processes. Our understanding of the impact of reactive species has also expanded from the dichotomic damaging/signaling role to modulation of gene expression. Critical Issues: These new concepts are affecting the study of aging and diseases where aging is greatly accelerated. We discuss how notions arising from the study of the underlying mechanisms of a progeroid disease, Cockayne syndrome, represent a paradigm shift that may shed a new light in understanding the role of reactive species in age-related degenerative processes. Future Issues: Future investigations urge to explore established and emerging notions to elucidate the multiple contributions of reactive species in degenerative processes linked to pathophysiological aging and their possible amelioration. Antioxid. Redox Signal. 37, 208-228.

Decreased vascular smooth muscle contractility in Hutchinson-Gilford Progeria Syndrome linked to defective smooth muscle myosin heavy chain expression.

Children with Hutchinson-Gilford Progeria Syndrome (HGPS) suffer from multiple cardiovascular pathologies due to the expression of progerin, a mutant form of the nuclear envelope protein Lamin A. Progerin expression has a dramatic effect on arterial smooth muscle cells (SMCs) and results in decreased viability and increased arterial stiffness. However, very little is known about how progerin affects SMC contractility. Here, we studied the LaminAG609G/G609G mouse model of HGPS and found reduced arterial contractility at an early age that correlates with a decrease in smooth muscle myosin heavy chain (SM-MHC) mRNA and protein expression. Traction force microscopy on isolated SMCs from these mice revealed reduced force generation compared to wild-type controls; this effect was phenocopied by depletion of SM-MHC in WT SMCs and overcome by ectopic expression of SM-MHC in HGPS SMCs. Arterial SM-MHC levels are also reduced with age in wild-type mice and humans, suggesting a common defect in arterial contractility in HGPS and normal aging.

Arterial stiffness and cardiac dysfunction in Hutchinson-Gilford Progeria Syndrome corrected by inhibition of lysyl oxidase.

Arterial stiffening and cardiac dysfunction are hallmarks of premature aging in Hutchinson-Gilford Progeria Syndrome (HGPS), but the molecular regulators remain unknown. Here, we show that the LaminAG609G mouse model of HGPS recapitulates the premature arterial stiffening and early diastolic dysfunction seen in human HGPS. Lysyl oxidase (LOX) is up-regulated in the arteries of these mice, and treatment with the LOX inhibitor, ß-aminopropionitrile, improves arterial mechanics and cardiac function. Genome-wide and mechanistic analysis revealed reduced expression of the LOX-regulator, miR-145, in HGPS arteries, and forced expression of miR-145 restores normal LOX gene expression in HGPS smooth muscle cells. LOX abundance is also increased in the carotid arteries of aged wild-type mice, but its spatial expression differs from HGPS and its up-regulation is independent of changes in miR-145 abundance. Our results show that miR-145 is selectively misregulated in HGPS and that the consequent up-regulation of LOX is causal for premature arterial stiffening and cardiac dysfunction.

Hutchinson-Gilford Progeria Syndrome: An Overview of the Molecular Mechanism, Pathophysiology and Therapeutic Approach.

Lamin A/C encoded by the LMNA gene is an essential component for maintaining the nuclear structure. Mutation in the lamin A/C leads to a group of inherited disorders is known as laminopathies. In the human body, there are several mutations in the LMNA gene that have been identified. It can affect diverse organs or tissues or can be systemic, causing different diseases. In this review, we mainly focused on one of the most severe laminopathies, Hutchinson-Gilford progeria syndrome (HGPS). HGPS is an immensely uncommon, deadly, metameric ill-timed laminopathies caused by the abnormal splicing of the LMNA gene and production of an aberrant protein known as progerin. Here, we also presented the currently available data on the molecular mechanism, pathophysiology, available treatment, and future approaches to this deadly disease. Due to the production of progerin, an abnormal protein leads to an abnormality in nuclear structure, defects in DNA repair, shortening of telomere, and impairment in gene regulation which ultimately results in aging in the early stage of life. Now some treatment options are available for this disease, but a proper understanding of the molecular mechanism of this disease will help to develop a more appropriate treatment which makes it an emerging area of research.

Premature aging disorders: A clinical and genetic compendium.

Progeroid disorders make up a heterogeneous group of very rare hereditary diseases characterized by clinical signs that often mimic physiological aging in a premature manner. Apart from Hutchinson-Gilford progeria syndrome, one of the best-investigated progeroid disorders, a wide spectrum of other premature aging phenotypes exist, which differ significantly in their clinical presentation and molecular pathogenesis. Next-generation sequencing (NGS)-based approaches have made it feasible to determine the molecular diagnosis in the early stages of a disease. Nevertheless, a broad clinical knowledge on these disorders and their associated symptoms is still fundamental for a comprehensive patient management and for the interpretation of variants of unknown significance from NGS data sets. This review provides a detailed overview on characteristic clinical features and underlying molecular genetics of well-known as well as only recently identified premature aging disorders and also highlights novel findings towards future therapeutic options.

Mini-Review: molecular elucidations of hutchinson-gilford progeria syndrome: A hope for managing horrors of premature aging in children.

Hutchinson-Gilford Progeria syndrome (or Progeria) is an exceptionally rare genetic disorder in children. It is caused by a rare point mutation in the lamin gene. It encodes lamin A protein, resulting in the de-shaping of nuclear membrane. This altered structure of the nuclear membrane renders the nucleus unstable. The shortened lifespan of the nucleus makes the cell liable for rapid ageing. Children are healthy by appearance when they are born but the signs appear after 12-24 months of age. Cardiovascular system is greatly affected which became a reason for the death of most of the patients of progeria. Stiffened joints disturb the bone movements; and alopecia affects the appearance of the patient. Rate of occurrence of the disease is one per four hundred thousand of people, though both sexes are equally affected.

Premature Vascular Aging with Features of Plaque Vulnerability in an Atheroprone Mouse Model of Hutchinson-Gilford Progeria Syndrome with Ldlr Deficiency.

Hutchinson-Gilford progeria syndrome (HGPS) is among the most devastating of the laminopathies, rare genetic diseases caused by mutations in genes encoding nuclear lamina proteins. HGPS patients age prematurely and die in adolescence, typically of atherosclerosis-associated complications. The mechanisms of HGPS-related atherosclerosis are not fully understood due to the scarcity of patient-derived samples and the availability of only one atheroprone mouse model of the disease. Here, we generated a new atherosusceptible model of HGPS by crossing progeroid LmnaG609G/G609G mice, which carry a disease-causing mutation in the Lmna gene, with Ldlr-/- mice, a commonly used preclinical atherosclerosis model. Ldlr-/-LmnaG609G/G609G mice aged prematurely and had reduced body weight and survival. Compared with control mice, Ldlr-/-LmnaG609G/G609G mouse aortas showed a higher atherosclerosis burden and structural abnormalities typical of HGPS patients, including vascular smooth muscle cell depletion in the media, adventitial thickening, and elastin structure alterations. Atheromas of Ldlr-/-LmnaG609G/G609G mice had features of unstable plaques, including the presence of erythrocytes and iron deposits and reduced smooth muscle cell and collagen content. Ldlr-/-LmnaG609G/G609G mice faithfully recapitulate vascular features found in patients and thus provide a new tool for studying the mechanisms of HGPS-related atherosclerosis and for testing therapies.

Identification of common cardiometabolic alterations and deregulated pathways in mouse and pig models of aging.

Aging is the main risk factor for cardiovascular and metabolic diseases, which have become a global concern as the world population ages. These diseases and the aging process are exacerbated in Hutchinson-Gilford progeria syndrome (HGPS or progeria). Here, we evaluated the cardiometabolic disease in animal models of premature and normal aging with the aim of identifying alterations that are shared or specific to each condition. Despite differences in body composition and metabolic markers, prematurely and normally aging mice developed heart failure and similar cardiac electrical abnormalities. High-throughput proteomics of the hearts of progeric and normally aged mice revealed altered protein oxidation and glycation, as well as dysregulated pathways regulating energy metabolism, proteostasis, gene expression, and cardiac muscle contraction. These results were corroborated in the hearts of progeric pigs, underscoring the translational potential of our findings, which could help in the design of strategies to prevent or slow age-related cardiometabolic disease.

Ultrasonic Characteristics of Cardiovascular Changes in Children with Hutchinson-Gilford Progeria Syndrome: A Comparative Study with Normal Children and Aging People.

BACKGROUND: The cardiovascular characteristics of children with Hutchinson-Gilford progeria syndrome (HGPS) remain unclear. The present study is aimed at evaluating the cardiovascular changes with ultrasound examination in children with HGPS and compared these with those in normal children and older people. METHODS: Seven HGPS children, 21 age-matched healthy children, and 14 older healthy volunteers were evaluated by three-dimensional echocardiography (including strain analysis) and carotid elasticity examination with the echo-tracking technique. RESULTS: Children with HGPS had higher left ventricular ejection fraction (LVEF) and global longitudinal strain, when compared to older healthy volunteers (P < 0.05). However, these parameters were not significantly different, when compared to those in healthy children. Furthermore, children with HGPS had lower average peak times in the left ventricle, when compared with the other two groups. For the structure of the carotid artery detected by ultrasound, the abnormality rates were similar between children with HGPS and older healthy volunteers (83.3% vs. 71.4%). The elastic parameters, elastic modulus, stiffness parameter, and pulsed wave transmittal velocity of children with HGPS were lower, when compared to those in older healthy volunteers (P < 0.05), while they were higher with arterial compliance (P > 0.05). Furthermore, no significant difference existed among the vascular elastic parameters between HGPS and normal children. CONCLUSION: HGPS children had impaired left ventricular (LV) synchrony, when compared to normal children, although the difference in LVEF was not statistically significant. Furthermore, the structural abnormality of the carotid artery in HGPS children was similar to that in older people, although the index of elasticity appears to be more favorable. These results suggest that the cardiovascular system in HGPS children differs from natural aging.

Vascular Smooth Muscle Cell-Specific Progerin Expression Provokes Contractile Impairment in a Mouse Model of Hutchinson-Gilford Progeria Syndrome that Is Ameliorated by Nitrite Treatment.

Cardiovascular disease (CVD) is the main cause of death worldwide, and aging is its leading risk factor. Aging is much accelerated in Hutchinson-Gilford progeria syndrome (HGPS), an ultra-rare genetic disorder provoked by the ubiquitous expression of a mutant protein called progerin. HGPS patients die in their teens, primarily due to cardiovascular complications. The primary causes of age-associated CVD are endothelial dysfunction and dysregulated vascular tone; however, their contribution to progerin-induced CVD remains poorly characterized. In the present study, we found that progeroid LmnaG609G/G609G mice with ubiquitous progerin expression show both endothelial dysfunction and severe contractile impairment. To assess the relative contribution of specific vascular cell types to these anomalies, we examined LmnaLCS/LCSTie2Cretg/+ and LmnaLCS/LCSSm22αCretg/+ mice, which express progerin specifically in endothelial cells (ECs) and vascular smooth muscle cells (VSMCs), respectively. Whereas vessel contraction was impaired in mice with VSMC-specific progerin expression, we observed no endothelial dysfunction in mice with progerin expression restricted to VSMCs or ECs. Vascular tone regulation in progeroid mice was ameliorated by dietary sodium nitrite supplementation. Our results identify VSMCs as the main cell type causing contractile impairment in a mouse model of HGPS that is ameliorated by nitrite treatment.

Metabolic Dysfunction in Hutchinson-Gilford Progeria Syndrome.

Hutchinson-Gilford Progeria Syndrome (HGPS) is a segmental premature aging disease causing patient death by early teenage years from cardiovascular dysfunction. Although HGPS does not totally recapitulate normal aging, it does harbor many similarities to the normal aging process, with patients also developing cardiovascular disease, alopecia, bone and joint abnormalities, and adipose changes. It is unsurprising, then, that as physicians and scientists have searched for treatments for HGPS, they have targeted many pathways known to be involved in normal aging, including inflammation, DNA damage, epigenetic changes, and stem cell exhaustion. Although less studied at a mechanistic level, severe metabolic problems are observed in HGPS patients. Interestingly, new research in animal models of HGPS has demonstrated impressive lifespan improvements secondary to metabolic interventions. As such, further understanding metabolism, its contribution to HGPS, and its therapeutic potential has far-reaching ramifications for this disease still lacking a robust treatment strategy.

Understanding the role of the cytoprotective transcription factor nuclear factor erythroid 2-related factor 2-lessons from evolution, the animal kingdom and rare progeroid syndromes.

The cytoprotective transcriptor factor nuclear factor erythroid 2- related factor 2 (NRF2) is part of a complex regulatory network that responds to environmental cues. To better understand its role in a cluster of inflammatory and pro-oxidative burden of lifestyle diseases that accumulate with age, lessons can be learned from evolution, the animal kingdom and progeroid syndromes. When levels of oxygen increased in the atmosphere, mammals required ways to protect themselves from the metabolic toxicity that arose from the production of reactive oxygen species. The evolutionary origin of the NRF2-Kelch-like ECH-associated protein 1 (KEAP1) signalling pathway from primitive origins has been a prerequisite for a successful life on earth, with checkpoints in antioxidant gene expression, inflammation, detoxification and protein homoeostasis. Examples from the animal kingdom suggest that superior antioxidant defense mechanisms with enhanced NRF2 expression have been developed during evolution to protect animals during extreme environmental conditions, such as deep sea diving, hibernation and habitual hypoxia. The NRF2-KEAP1 signalling pathway is repressed in progeroid (accelerated ageing) syndromes and a cluster of burden of lifestyle disorders that accumulate with age. Compelling links exist between tissue hypoxia, senescence and a repressed NRF2 system. Effects of interventions that activate NRF2, including nutrients, and more potent (semi)synthetic NRF2 agonists on clinical outcomes are of major interest. Given the broad-ranging actions of NRF2, we need to better understand the mechanisms of activation, biological function and regulation of NRF2 and its inhibitor, KEAP1, in different clinical conditions to ensure that modulation of this thiol-based system will not result in major adverse effects. Lessons from evolution, the animal kingdom and conditions of accelerated ageing clarify a major role of a controlled NRF2-KEAP1 system in healthy ageing and well-being.

Progerin in muscle leads to thermogenic and metabolic defects via impaired calcium homeostasis.

Mutations in lamin A (LMNA) are responsible for a variety of human dystrophic and metabolic diseases. Here, we created a mouse model in which progerin, the lamin A mutant protein that causes Hutchinson-Gilford progeria syndrome (HGPS), can be inducibly overexpressed. Muscle-specific overexpression of progerin was sufficient to induce muscular dystrophy and alter whole-body energy expenditure, leading to premature death. Intriguingly, sarcolipin (Sln), an endoplasmic reticulum (ER)-associated protein involved in heat production, is upregulated in progerin-expressing and Lmna knockout (Lmna-/- ) skeletal muscle. The depletion of Sln accelerated the early death of Lmna-/- mice. An examination at the molecular level revealed that progerin recruits Sln and Calnexin to the nuclear periphery. Furthermore, progerin-expressing myoblasts presented enhanced store-operated Ca2+ entry, as well as increased co-localization of STIM1 and ORAI1. These findings suggest that progerin dysregulates calcium homeostasis through an interaction with a subset of ER-associated proteins, resulting in thermogenic and metabolic abnormalities.

Murine models of accelerated aging and musculoskeletal disease.

The primary risk factor for most musculoskeletal diseases, including osteoarthritis, osteoporosis and sarcopenia, is aging. To treat the diverse types of musculoskeletal diseases and pathologies, targeting their root cause, the aging process itself, has the potential to slow or prevent multiple age-related musculoskeletal conditions simultaneously. However, the development of approaches to delay onset of age related diseases, including musculoskeletal pathologies, has been slowed by the relatively long lifespan of rodent models of aging. Thus, to expedite the development of therapeutic approaches for age-related musculoskeletal disease, the implementation of mouse models of accelerated musculoskeletal aging are of great utility. Currently there are multiple genetically diverse mouse models that mirror certain aspects of normal human and mouse aging. Here, we provide a review of some of the most relevant murine models of accelerated aging that mimic many aspects of natural musculoskeletal aging, highlighting their relative strengths and weaknesses. Importantly, these murine models of accelerated aging recapitulate phenotypes of musculoskeletal age-related decline observed in humans.

Imbalanced nucleocytoskeletal connections create common polarity defects in progeria and physiological aging.

Studies of the accelerated aging disorder Hutchinson-Gilford progeria syndrome (HGPS) can potentially reveal cellular defects associated with physiological aging. HGPS results from expression and abnormal nuclear envelope association of a farnesylated, truncated variant of prelamin A called "progerin." We surveyed the diffusional mobilities of nuclear membrane proteins to identify proximal effects of progerin expression. The mobilities of three proteins-SUN2, nesprin-2G, and emerin-were reduced in fibroblasts from children with HGPS compared with those in normal fibroblasts. These proteins function together in nuclear movement and centrosome orientation in fibroblasts polarizing for migration. Both processes were impaired in fibroblasts from children with HGPS and in NIH 3T3 fibroblasts expressing progerin, but were restored by inhibiting protein farnesylation. Progerin affected both the coupling of the nucleus to actin cables and the oriented flow of the cables necessary for nuclear movement and centrosome orientation. Progerin overexpression increased levels of SUN1, which couples the nucleus to microtubules through nesprin-2G and dynein, and microtubule association with the nucleus. Reducing microtubule-nuclear connections through SUN1 depletion or dynein inhibition rescued the polarity defects. Nuclear movement and centrosome orientation were also defective in fibroblasts from normal individuals over 60 y, and both defects were rescued by reducing the increased level of SUN1 in these cells or inhibiting dynein. Our results identify imbalanced nuclear engagement of the cytoskeleton (microtubules: high; actin filaments: low) as the basis for intrinsic cell polarity defects in HGPS and physiological aging and suggest that rebalancing the connections can ameliorate the defects.

A tyrosine kinase-activating variant Asn666Ser in PDGFRB causes a progeria-like condition in the severe end of Penttinen syndrome.

Missense variants located to the "molecular brake" in the tyrosine kinase hinge region of platelet-derived growth factor receptor-ß, encoded by PFGFRB, can cause Penttinen-type (Val665Ala) and Penttinen-like (Asn666His) premature ageing syndromes, as well as infantile myofibromatosis (Asn666Lys and Pro660Thr). We have found the same de novo PDGFRB c.1997A>G p.(Asn666Ser) variants in two patients with lipodystrophy, acro-osteolysis and severely reduced vision due to corneal neovascularisation, reminiscent of a severe form of Penttinen syndrome with more pronounced connective tissue destruction. In line with this phenotype, patient skin fibroblasts were prone to apoptosis. Both in patient fibroblasts and stably transduced HeLa and HEK293 cells, autophosphorylation of PDGFRß was observed, as well as increased phosphorylation of downstream signalling proteins such as STAT1, PLCγ1, PTPN11/SHP2-Tyr580 and AKT. Phosphorylation of MAPK3 (ERK1) and PTPN11/SHP2-Tyr542 appeared unaffected. This suggests that this missense change not only weakens tyrosine kinase autoinhibition, but also influences substrate binding, as both PTPN11 tyrosines (Tyr542 and Tyr580) usually are phosphorylated upon PDGFR activation. Imatinib was a strong inhibitor of phosphorylation of all these targets, suggesting an option for precision medicine based treatment.