OAE Publishing Inc.

The Journal of Cardiovascular Aging

Published by OAE Publishing Inc. and International Academy of Cardiovascular Sciences
Online ISSN: 2768-5993
Discipline: Biochemistry, Genetics and Molecular, Medicine
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Aims and scope

To establish The Journal of Cardiovascular Aging as a premier, most desirable, and entirely transparent international platform for dissemination of the state-of-the-art basic, translational, and clinical studies in aging and cardiovascular disease. The journal aims to publish state-of-the-art scientific discoveries pertaining to the broad spectrum of cardiovascular consequences of aging. The Editors aim to provide timely, fair, and balanced considerations to all manuscripts submitted and seek the opinions of the external experts in prioritizing the meritorious manuscripts.

The Journal of Cardiovascular Aging aims to publish clinical, translational, and basic science discoveries that pertain to all aspects of aging and cardiovascular disease. All aspects of basic and clinical sciences relating to aging in the context of cardiovascular disease are considered to be within the scope of the journal. Examples include clinical trials, diet, treatment, genetics, epigenetics, genomics, stem cells, immunology, inflammation, cell cycle regulation, senescence, signaling pathways, and pharmacology, among others. The primary focus of the journal is to publish original research articles that provide novel insights into cardiovascular aging. Studies confirming and validating previous findings, whenever providing unequivocal findings, are also within the scope of the journal. Review manuscripts on topics of broad interest to the readership of the journal, Editorials, and Commentaries on timely and important topics will also be considered.



Recent publications
Sarcopenia is common in aging and in patients with heart failure (HF) who may experience worse outcomes. Patients with muscle wasting are more likely to experience falls and can have serious complications when undergoing cardiac procedures. While intensive nutritional support and exercise rehabilitation can help reverse some of these changes, they are often under-prescribed in a timely manner, and we have limited insights into who would benefit. Mechanistic links between gut microbial metabolites (GMM) have been identified and may contribute to adverse clinical outcomes in patients with cardio-renal diseases and aging. This review will examine the emerging evidence for the influence of the gut microbiome-derived metabolites and notable signaling pathways involved in both sarcopenia and HF, especially those linked to dietary intake and mitochondrial metabolism. This provides a unique opportunity to gain mechanistic and clinical insights into developing novel therapeutic strategies that target these GMM pathways or through tailored nutritional modulation to prevent progressive muscle wasting in elderly patients with heart failure.
Injected STEMIN and YAP5SA mmRNA induced nuclear replication in infarcted adult mouse hearts. (A) Schematic diagram of short-term (24 h) in vivo experiment. A combination of STEMIN and YAP5SA mmRNA was injected in five locations around the infarct in the left ventricle of inbred litter mates (100 days old). (B) Mouse IVIS bioluminescence images 24 h post-injection: (Left) mouse heart injected with 70 µg (50 µL) Luc mmRNA + 32 µL Lipofectamine MessengerMAX; and (Right) non-Luc control mouse heart injected with PBS (50 µL) + 32 µL Lipofectamine MessengerMAX. D-luciferin (150 mg/kg mouse body weight) injected via subcutaneous injection 4 h before light emission analysis to detect luciferase signal using an IVIS BioImager. (C) Images of DAPI and EdU staining of paraformaldehyde fixed left ventricle cardiac sections taken 24 h after five equal injections of STEMIN (50 µg in 38 µL) and YAP5SA (50 µg in 22 µL) with 33 µL Lipofectamine MessengerMAX around the infarct. The control group was injected with PBS (60 µL) and 33 µL Lipofectamine MessengerMAX. EdU (10 μg/g of mouse body weight) was injected via subcutaneous injection at 8 h prior to sacrifice. The intact heart was immediately washed and drained of blood cells, fixed in 4% paraformaldehyde, stored in 70% ethanol, and then embedded into paraffin for histological assessment. Each heart was cross-sectioned and EdU was detected by Click-iT EdU Cell Proliferation Kit (ThermoFisher). Note the overlapping images stained along three needle tracts for DAPI, EdU, Anti-SRF, and Anti-YAP. (D) Merged images of DAPI and EdU staining were first divided into 90 equal optical slices and then integrated density was measured, in which the same threshold was used for all the optical slices.
Injected STEMIN and YAP5SA mmRNA induced DAPI and Alpha EdU stained nuclei, but not in control infarcted adult mouse hearts. (A-C) An infarcted control heart injected with only Lipofectamine MessengerMAX and PBS. No DAPI and or alpha-EdU staining was observed along needle tract. (D-F) Another infarcted heart injected with STEMIN and YAP5SA mmRNA together with Lipofectamine MessengerMAX adjuvant. We observed overlapping DAPI and alpha-EdU staining, indicating strong nuclear myocyte proliferation. Arrows point to doublet nuclei.
Injected STEMIN and YAP5SA mmRNA induced cell replication and DNA replisome factors. (A) In a second injected heart, anti-phospho-histone H3 stain of a serial section was observed along two needle tracts marked by white arrows. Robust EdU stain overlap anti-pHH3 stains exactly in the same orientation and location. A key component of the DNA replisome was stained by anti-CLASPIN overlapped anti-pHH3 and Edu stains. Anti-NANOG stained NANOG was observed, but peaked levels were probably about 12 h earlier[15]. (B) In a third injected heart, anti-ORC2 (Origin recognition complex subunit 2) and anti-MCM2 showed the stained markers of the pre-initiation phase in early G1 stage induced in the injected hearts. Anti-ATR stained Ataxia telangiectasia and Rad3-related, an essential kinase that is active in S phase which overlapped other DNA replisome factors. Thus, STEMIN and YAP5SA mmRNA treatment fostered cell cycle entry by promoting DNA replication in the G1 phase.
Injections of the combination of STEMIN and YAP5SA mmRNA repaired infarcted adult mouse hearts in vivo. (A) Schematic diagram of long-term in vivo experiments in adult mice (100 days old) infarcted by LAD ligation. Five equal injections of STEMIN (50 µg in 38 µL) and YAP5SA (50 µg in 22 µL) with 33 µL Lipofectamine MessengerMAX around the cardiac infarct. In addition, Individual synthetic mmRNA were tested for their ability to restore cardiac function following infarctions. The control group was injected with PBS (60 µL) with 33 µL Lipofectamine MessengerMAX. Echo Doppler measurements were taken prior to infarction and one, two, and four weeks after mmRNA injections. (B) Cardiac function was graphed for Echo Doppler measurements of the infarcted controls (six mice) and the combination of STEMIN and YAP5SA mmRNA experimental group (four mice) from the same inbred liter. The EF declined greater for the control than the combination experimental group by the second and fourth weeks, and both were significantly different (P < 0.05, two-tailed, shown by *). EF of STEMIN or YAP5SA mmRNA individual injections into infarcted hearts failed to significantly improve cardiac EF above the control levels. STEMIN showed a slight trend upwards and YAP5SA was not better than the infarcted controls. (C) At the end of four weeks, the hearts were removed, sectioned, and stained with Picrosirius red. The infarct zone was marked as pink/red with the Picrosirius staining. (D) Infarct scar area and total area of myocardium were traced and measured by ImageJ. Infarcted size% = Picroirius red + scar area/total ventricular area. Measurements of the infarct zone taken from the combination of STEMIN and YAP5SA mmRNA experimental group injected treatment group (four hearts) compared to all controls (six hearts) showed significant reduction (P < 0.05, two-tailed, shown by *). STEMIN injections alone tended to reduce the size of the cardiac infarcts stained by Picrosirius red but were statistically insignificant. YAP5SA mmRNA was not better than STEMIN in cardiac repair.
Hearts injected with a combination of STEMIN and YAP5SA revealed little if any staining for immune cells infiltrates. (A) Anti-F4/80 antibody recognizes the mouse F4/80 antigen, a 160 kD glycoprotein expressed by murine macrophages[20]. The secondary antibody (goat anti-rat Alexa Fluor 488) showed staining overlapped the infarcted ventricular wall of the control hearts. Anti-Ly6g stained a marker expressed predominantly on neutrophils[21]; in addition, a subset of eosinophils, differentiating pre-monocytes, and plasmacytoid dendritic cells showed staining in the infarcted heart. (B) Sectioned STEMIN and YAP5SA synthetic mmRNA treated infarcted hearts after four weeks did not reveal fibrotic scarring or staining with anti-F4/80 or anti-Ly6g.
Introduction: The adult heart lacks the regenerative capacity to self-repair. Serum response factor (SRF) is essential for heart organogenesis, sarcomerogenesis, and contractility. SRF interacts with co-factors, such as NKX2.5 and GATA4, required for cardiac specified gene activity. ETS factors such as ELK1 interact with SRF and drive cell replication. To weaken SRF interactions with NKX2.5 and GATA4, one mutant, SRF153(A3) named STEMIN, did not bind CArG boxes, yet induced stem cell factors such as NANOG and OCT4, cardiomyocyte dedifferentiation, and cell cycle reentry. The mutant YAP5SA of the Hippo pathway also promotes cardiomyocyte proliferation and growth. Methods and Results: Mice were pulsed one day later with alpha-EDU and then heart sections were DAPI stained. Replicating cells were identified by immuno-staining against members of the DNA replisome pathway that mark entry to S phase of the cell cycle. Echocardiography was used to determine cardiac function following infarcts and mRNA treatment. To monitor cardiac wall repair, microscopic analysis was performed, and the extent of myocardial fibrosis was analyzed for immune cell infiltration. Injections of STEMIN and YAP5SA mmRNA into the left ventricles of infarcted adult mice promoted a greater than 17-fold increase in the DAPI stained and alpha-EDU marked cardiomyocyte nuclei, within a day. We observed de novo expression of phospho-histone H3, ORC2, MCM2, and CLASPIN. Cardiac function was significantly improved by four weeks post-infarct, and fibrosis and immune cell infiltration were diminished in hearts treated with STEMIN and YAP5SA mmRNA than each alone. Conclusion: STEMIN and YAP5SA mmRNA improved cardiac function and myocardial fibrosis in left ventricles of infarcted adult mice. The combinatorial use of mmRNA encoding STEMIN and YAP5SA has the potential to become a powerful clinical strategy to treat human heart disease.
Introduction: Mutations in the LMNA gene, encoding Lamin A/C (LMNA), are established causes of dilated cardiomyopathy (DCM). The phenotype is typically characterized by progressive cardiac conduction defects, arrhythmias, heart failure, and premature death. DCM is primarily considered a disease of cardiac myocytes. However, LMNA is also expressed in other cardiac cell types, including fibroblasts. Aim: The purpose of the study was to determine the contribution of the fibroblasts to DCM caused by LMNA deficiency. Methods and Results: The Lmna gene was deleted by crossing the platelet-derived growth factor receptor α-Cre recombinase (Pdgfra-Cre) and floxed Lmna (LmnaF/F) mice. The LMNA protein was nearly absent in ~80% of the cardiac fibroblasts and ~25% of cardiac myocytes in the Pdgfra-Cre:LmnaF/F mice. The Pdgfra-Cre:LmnaF/F mice showed an early phenotype characterized by cardiac conduction defects, arrhythmias, cardiac dysfunction, myocardial fibrosis, apoptosis, and premature death within the first six weeks of life. The Pdgfra-Cre:LmnaWild type/F (LmnaW/F) mice also showed a similar but slowly evolving phenotype that was expressed within one year of age. RNA sequencing of LMNA-deficient and wild-type cardiac fibroblasts identified differential expression of ~410 genes, which predicted activation of the TP53 and TNFA/NFκB and suppression of the cell cycle pathways. In agreement with these findings, levels of phospho-H2AFX, ATM, phospho-TP53, and CDKN1A, markers of the DNA damage response (DDR) pathway, were increased in the Pdgfra-Cre:LmnaF/F mouse hearts. Moreover, expression of senescence-associated beta-galactosidase was induced and levels of the senescence-associated secretory phenotype (SASP) proteins TGFβ1, CTGF (CCN2), and LGLAS3 were increased as well as the transcript levels of additional genes encoding SASP proteins in the Pdgfra-Cre:LmnaF/F mouse hearts. Finally, expression of pH2AFX, a bonafide marker of the double-stranded DNA breaks, was increased in cardiac fibroblasts isolated from the Pdgfra-Cre:LmnaF/F mouse hearts. Conclusion: Deletion of the Lmna gene in fibroblasts partially recapitulates the phenotype of the LMNA-associated DCM, likely through induction of double-stranded DNA breaks, activation of the DDR pathway, and induction of expression of the SASP proteins. The findings indicate that the phenotype in the LMNA-associated DCM is the aggregate consequence of the LMNA deficiency in multiple cardiac cells, including cardiac fibroblasts. One sentence summary: Cardiac fibroblasts contribute to the pathogenesis of DCM - associated with LMNA deficiency through activation of the senescence-associated secretory phenotype.
Introduction: Aging is associated with sarcopenia, myocyte loss, and dysfunction. The problem is compounded as the adult heart lacks the regenerative capacity to self-repair. Serum response factor’s (SRF’s) dual activity is essential for cell replication and heart cell differentiation. SRF interacts with cofactors, such as NKX2-5 and GATA4, which give cardiac-specific gene activity, and ETS factors such as ELK1 drive cell replication. Recently, the mutant YAP-5SA of the Hippo pathway was implicated in cardiomyocyte proliferation and growth. Aim: We hypothesized that disruption of interactions of SRF with NKX2-5 and GATA4 would lead to dedifferentiation of cardiomyocytes to a proliferative stem cell state and complement YAP-5SA to generate undifferentiated cardiomyocytes in a more primitive replicative state. Methods and results: To weaken SRF interactions with NKX2-5 and GATA4, alanine scanning mutations were generated across the SRF N-terminus of the MADS-box. One SRF mutant, SRF153(A3), was tested along with the YAP-5SA mutant, as degradable synthetic modified mRNAs (mmRNAs), in rat primary cardiomyocytes. To measure cell replication, adult cardiomyocytes were pulsed with alpha-EdU and then DAPI stained, while gene activity was assayed by RNA sequencing. To measure chromatin remodeling, Transposon 5 was used in ATAC sequencing. We observed that single and triple alanine substitutions of mutants centering over SRF-Lys154 essentially blocked myocyte differentiation, and NKX2-5 and GATA4 failed to stabilize mutated SRF DNA binding. Instead, many stem cell factors including NANOG and OCT4 were induced. SRF153(A3) does not recognize SRF response elements per ATAC sequencing and consequently induces stem cell factors such as NANOG and OCT4, cardiomyocyte dedifferentiation, and cell cycle reentry. SRF153(A3) and YAP5SA mmRNA led to alpha-EDU incorporation in ~35% of the cardiomyocytes. DIAPH 3, a marker of the contractile ring during anaphase, appeared between and around replicated nuclei in three-month-old adult mouse cardiac myocytes. The combination of these synthetic mRNA increased nuclei replication with the expression of origin of replication genes, while genes associated with cardiomyocyte differentiation were down-regulated. ATAC sequencing revealed SRF153(A3) and YAP5SA mmRNA-induced chromatin remodeling of cell cycle, spindle, and growth factor genes by additive and synergistic activities. Conclusion: SRF153(A3) synthetic mmRNA and the mutant YAP-5SA mmRNA induced cardiomyocyte dedifferentiation, to nuclear replication in adult cardiac myocytes. The combinatorial use of mmRNA encoding SRF153(A3) and YAP-5SA has the potential to become a powerful clinical strategy for treating human heart disease.
NAD⁺ metabolism in cells and its compartmentalization[99,103]. Human cells produce NAD⁺ through three major pathways: the Kynurenine pathway, Preiss-Handler pathway, and Salvage pathway. In the Kynurenine pathway, which is a de novo pathway, the precursor molecule, tryptophan (Trp), after entering the cells via the transporters SLC7A5 and SLC36A4, is converted to N-formyl kynurenine (FK) by the rate-limiting enzyme indoleamine 2,3- dioxygenase (IDO) or the rate-limiting enzyme tryptophan 2,3- dioxygenase (TDO) and then FK is converted to kynurenine. The kynurenine aminotransferases (KATs) convert kynurenine to kynurenic acid, further converted to quinaldic acid. In addition to this, kynurenine 3-monooxygenase (KMO) converts kynurenine to 3-hydroxykynurenine (3-HK), which is further transformed to 3- hydroxy anthranilic acid (3-HAA) by tryptophan 2,3- dioxygenase (KYNU). The 3-HAA gives rise to α- amino- β- carboxy muconate ε- semialdehyde (ACMS) by the enzyme 3-hydroxyanthranilic acid oxygenase (3HAO). Finally, ACMS is transformed to picolinic acid by α-amino-β-carboxy muconate-ε-semialdehyde decarboxylase (ACMSD) or quinolinic acid. In the Preiss-Handler pathway, the precursor molecule nicotinic acid (NA) first enters the cells via SLC5A8 or SLC22A3 transporters. It is then converted to nicotinic acid mononucleotide (NAMN) by the enzyme nicotinic acid phosphoribosyltransferase (NAPRT), which is then converted into nicotinic acid adenine dinucleotide (NAAD) by the enzymes called nicotinamide mononucleotide adenylyl transferases (NMNAT1, NMNAT2, and NMNAT3). Next, NAD⁺ synthase (NADS) transforms NAAD to NAD⁺. The NAD⁺ can be directly phosphorylated by NAD⁺ kinase (NADK) to produce NADP(H). In the Salvage pathway, the intracellular nicotinamide (NAM) is recycled back to NAD⁺ via the formation of nicotinamide mononucleotide (NMN) by intracellular nicotinamide phosphoribosyltransferase (iNAMPT). The NAM is the byproduct generated by the NAD⁺ consuming enzymes, sirtuins, poly (ADP- ribose) polymerases (PARPs), CD38, CD157, and SARM1. The Salvage pathway also uses nicotinamide riboside (NR) to produce the NMN via the enzyme nicotinamide riboside kinases 1 and 2 (NRK1 and NRK2). The cellular NAD⁺ level is balanced by biosynthesis and consumption in different subcellular compartments. For example, in the cytoplasm, the intracellular NAMPT (iNAMPT) converts NAM to NMN, further transformed to NAD⁺ by another cytoplasm-specific enzyme, NMNAT2. The NADH, generated from the NAD⁺ in the cytoplasm and utilized by Glycolysis, is transported to the mitochondria via the malate/aspartate shuttle. Via the electron transport chain (ETC), the NADH is oxidized to NAD⁺ by mitochondria specific complex I, while by tricarboxylic acid (TCA) cycle, the NAD⁺ is transformed to NADH. The mitochondrial SIRT 3, 4, 5 convert NAD⁺ to NAM. The NADH can enter the mitochondria via the glyceraldehyde 3- phosphate shuttle and results in reduced flavin adenine dinucleotide (FADH2), which is converted to the FADH mitochondrial complex II. The mitochondrial transporter SLC25A51 can also help the direct mitochondrial entry of NAD⁺. The nuclear NAD⁺ pool equilibrates with the cytosolic NAD⁺ pool by diffusion through the unidentified nuclear pore[99,103]. The nuclear enzymes SIRT 1, 6, 7, and PARPs, CD38, SARM1, consume NAD⁺ and regulate the NAD⁺ homeostasis in the nucleus.
The SASP is sustained by a positive feedback loop constituted by p90RSK-ERK5 S496[77]. In the cells exposed to chemoradiation, a sustained SASP is maintained for the long term via the positive feedback loop. (1) The chemoradiation induces the production of mitochondrial ROS (mtROS) in the mitochondria, which in turn (2) increases the p90RSK phosphorylation leading to ERK5 S496 phosphorylation, the decreased transcriptional activity of ERK5, and reduced NRF2 transcriptional activity. Consequently, the (3) level of cellular antioxidant is dropped, causing (4) telomeric DNA damage, (5) PARP activation, and leading to NAD⁺ depletion. (6) The NAD⁺ depletion causes mitochondrial dysfunction, along with severe ATP depletion, termed reversible mitochondrial (mt) stunning, which further (7) causes mtROS production and reactivates the same p90RSK-ERK5-NRF2 module, thus constituting a positive feedback loop. This figure was modified from the figure in reference[77].
Numerous studies have revealed the critical role of premature senescence induced by various cancer treatment modalities in the pathogenesis of aging-related diseases. Senescence-associated secretory phenotype (SASP) can be induced by telomere dysfunction. Telomeric DNA damage response induced by some cancer treatments can persist for months, possibly accounting for long-term sequelae of cancer treatments. Telomeric DNA damage-induced mitochondrial dysfunction and increased reactive oxygen species production are hallmarks of premature senescence. Recently, we reported that the nucleus-mitochondria positive feedback loop formed by p90 ribosomal S6 kinase (p90RSK) and phosphorylation of S496 on ERK5 (a unique member of the mitogen-activated protein kinase family that is not only a kinase but also a transcriptional co-activator) were vital signaling events that played crucial roles in linking mitochondrial dysfunction, nuclear telomere dysfunction, persistent SASP induction, and atherosclerosis. In this review, we will discuss the role of NAD+ depletion in instigating SASP and its downstream signaling and regulatory mechanisms that lead to the premature onset of atherosclerotic cardiovascular diseases in cancer survivors.
Post-translation modification of LMNA. (A) The LMNA gene, which is comprised of 12 exons, encodes the prelamin A/C protein, which undergoes farnesylation of the cysteine residue at the CaaX motif at the COOH terminus (amino acids CSIM), which is then cleaved by ZMPSTE24 or FACE1, leading to the removal of the SIM amino acids. This is followed by carboxylation of the cysteine residue by isoprenylcysteine carboxyl methyltransferase (ICMT). The carboxylated protein is cleaved at RSY^LLG recognition motif by the ZMPSTE24, resulting in the removal of the last 18 amino acids from the protein and producing the mature LMNA protein. (B) In the classic Hutchinson-Gilford Progeria Syndrome (HGPS), a C>T transition in exon 11 of the gene, while a synonymous variant, introduced a cryptic splicing site, which removes 150 nucleotides from the mRNA. Thus, the prelamin A/C protein has a deletion of 50 amino acids near the COOH terminal of the protein. The protein undergoes farnesylation, removal of the SIM amino acids at the COOH terminal, and carboxylation of the cysteine residue. However, because of the deletion of the 50 amino acids, the ZMPSTE24 recognition site is deleted, and consequently, the farnesylated/carboxylated mutant pre-LMNA referred to as progerin, accumulates in the nucleus.
DNA damage response in aging. The genome is not only affected by the mutations but also by various endogenous, such as reactive oxygen species, and exogenous, such as ultraviolet light, resulting in various forms of DNA damage, most notably double-stranded DNA breaks (DSBs). The red color staining depicts the cardia myocyte LMNA protein, which resides in the inner nuclear membrane close to the chromatin. LMNA is involved in induction as well as repair of the DSBs and has a crucial role in nuclear membrane integrity. In the presence of LMNA mutations or deficiency, DSBs are increased and released into the cytoplasm, which is then sensed by the cyclic GMP-AMP synthase (CGAS) followed by activation of stimulator of interferon genes protein 1 (STING1) and TANK binding kinase 1 (TBK1). STING1 activates the nuclear factor kappa B (NFκB) components p65 and p50, whereas TBK1 phosphorylates interferon regulatory factor 3 (IFR3) which translocates into the nucleus and induces the expression of pro-inflammatory genes. Several proteins are recruited to the site of the DSBs, including the ataxia-telangiectasia mutated (ATM), which phosphorylates H2 histone family member X (H2AFX) and the tumor suppressor protein 53 (TP53). Activated TP53 translocates into the nucleus and induces the expression of genes involved in senescence-associated secretory phenotype (SASP), which collectively mediates molecular and cellular phenotypes of aging such as cell cycle arrest, senescence, fibrosis, apoptosis, and others.
Aging is an archetypical complex process influenced by genetic and environmental factors. Genetic variants impart a gradient of effect sizes, albeit the effect sizes seem to be skewed toward those with small effect sizes. On one end of the spectrum are the rare monogenic premature aging syndromes, such as Hutchinson Gilford Progeria Syndrome, whereby single nucleotide changes lead to rapidly progressive premature aging. On the end of the spectrum is the complex, slowly progressive process of living to an arbitrary-defined old age, i.e., longevity. Whereas the genetic basis of rare premature aging syndromes has been elucidated, only a small fraction of the genetic determinants of longevity and life span, time from birth to death, have been identified. The latter point to the complexity of the process and involvement of myriad of genetic and non-genetic factors and hence, the diluted effect of each determinant on longevity. The genetic discoveries point to the involvement of the DNA damage and activation of the DNA damage response pathway, particularly in the premature aging syndromes. Likewise, the insulin/insulin-like growth factor 1/mTOR/FOXO pathways have emerged as major regulators of life span. A notable fraction of the genetic variants that are associated with life span is also associated with age-related cardiovascular diseases, such as coronary artery disease and dyslipidemia, which places cardiovascular aging at the core of human life span. The clinical impact of the discoveries pertains to the identification of the pathways that are involved in life span, which might serve as targets of interventions to prevent, slow, and even possibly reverse aging.
(A, B) Effects on Lifespan of mTOR, protein synthesis and dietary restriction on catabolic and anabolic energy metabolism. (C) The integrated stress response (ISR) involves activation of GCN2, a kinase that is activated upon nutrient deprivation, phosphorylates eIF2a, which inhibits most mRNA translation, but allows translation of a few mRNAs, such as that encoding ATF4. (D) ATF4 is a transcription factor that (E) induces numerous stress-response genes required for cells to adjust to decreased nutrient availability. (F) Inhibition of mTOR, which then decreases translation, or inhibition of translation direction with protein synthesis inhibitors, such as cycloheximide, decreases proteotoxic stress in C. elegans, leading to lifespan extension. (G) Statzer et al.[4] showed a new, non-canonical mechanism of increasing ATF4 translation that does not require eIF2a phosphorylation. (H) One of the genes Statzer et al.[4] found to be induced by ATF4 in C. elegans is CTH-2, which catalyzes the formation of H2S. (I) Among the new findings reported by Statzer et al.[4] are that ATF4 induced by inhibiting mTOR or translation induces CTH-2, which increases H2S and lifespan extension; (J) H2S contributes to persulfication of cysteine thiols on proteins, which affects their structures and functions in protective ways.
The molecular determinants of lifespan can be examined in animal models with the long-term objective of applying what is learned to the development of strategies to enhance longevity in humans. Here, we comment on a recent publication examining the molecular mechanisms that determine lifespan in worms, Caenorhabditis elegans (C. elegans), where it was shown that inhibiting protein synthesis increased levels of the transcription factor, ATF4. Gene expression analyses showed that ATF4 increased the expression of genes responsible for the formation of the gas, hydrogen sulfide (H2S). Further examination showed that H2S increased longevity in C. elegans by modifying proteins in ways that stabilize their structures and enhance their functions. H2S has been shown to improve cardiovascular performance in mouse models of heart disease, and clinical trials are underway to test the effects of H2S on cardiovascular health in humans. These findings support the concept that nutrient deprivation, which slows protein synthesis and leads to ATF4-mediated H2S production, may extend lifespan by improving the function of the cardiovascular system and other systems that influence longevity in humans.
MEOX1 is a master regulator of fibroblast activation and cardiac fibrosis. Alexanian et al.[2] identified MEOX1 as a key regulator of fibroblast activation in the heart. TAC induces cardiac remodeling and fibrosis, which results in chromatin remodeling and BET protein binding to MEOX1 enhancer elements and transcriptional activation of MEOX1. Treatment with the small molecule BET inhibitor, JQ1, disengages BET proteins from the MEOX1 enhancer and prevents downstream engagement of MEOX1 target genes implicated in fibroblast activation and ECM deposition including Ctgf and Postn. BET: Bromodomain and extra terminal domain protein. TAC: Transverse aortic constriction; Meox1: mesenchyme homeobox 1; Postn: periostin; Ctgf: connective tissue growth factor. Figures created with BioRender.com.
Fibroblast activation is a hallmark feature of pathological remodeling of the heart and represents an attractive target for therapeutic intervention. Pharmacological inhibition of chromatin remodeling enzymes reduces cardiac fibrosis, but the underlying transcriptional regulatory mechanisms remain poorly understood. Using single-cell genomics to profile alterations in the transcriptional and chromatin landscape during stress-induced cardiac remodeling, Alexanian et al. discovered a critical role for Mesenchyme Homeobox 1 in the regulation of myofibroblast activation and cardiac fibrosis. We briefly review these important findings and comment on the significance of their work.
The (well-justified) emphasis on innovation and significance tends to favor publication and funding of improbable observations with impressive positive results. Typically, surprising findings that challenge existing concepts and support a mechanism with a low pre-study probability, are perceived as novel, and are more likely to be published in high-impact journals. Moreover, interventional studies are considered “highly significant” when strongly positive effects are found. Studies perceived as highly innovative and/or highly significant (red arrows) are selectively published, and are also more likely to attract funding. Moreover, these competitive advantages of high innovation/high-significance findings exert pressures on success-driven investigators that may generate additional investigator-dependent intentional or non-intentional bias. In contrast, findings supporting more plausible, high-probability concepts, or interventions producing modest or negative effects are considered much less exciting, have a lower chance of publication in high-impact journals, and may not attract research funding. These patterns in publication priority, research funding and dissemination of study results paint a biased perspective of a field, disproportionately rewarding improbable observations that report high-magnitude effects.
Translational failures are often due to the contrasting characteristics of animal model investigations and of interventional therapeutic studies in human patients. Animal model studies are excellent tools for testing a hypothesis on the role of a cellular mechanism, or of a specific molecular signal in the pathophysiology of disease. To achieve these goals, animal model investigations are designed to minimize variability by using standardized protocols that control the impact of comorbid conditions, genetic differences or environmental conditions. These studies provide valuable information on cell biological mechanisms and have potential implications for organ function, but are of much more limited value in predicting the outcome of a similar intervention in the clinical context. In complex multifactorial human diseases, patient populations exhibit remarkable pathophysiologic heterogeneity. Moreover, differences in age, gender, genetic substrate, the presence or absence of concomitant diseases, treatment with other agents, environmental conditions, may directly affect cellular responses, affecting clinical outcomes. No animal model can recapitulate the pathophysiologic heterogeneity of human disease. Thus, animal model investigations should optimally be used for cell biological dissection, and not for the prediction of therapeutic outcomes. Moreover, in the clinical context, stratification of patients with complex clinical syndromes (such as heart failure, or chronic renal insufficiency) to pathophysiologically distinct subpopulations with well-defined molecular perturbations may improve the chances for successful translation.
The development of novel therapies based on understanding the pathophysiologic basis of disease is a major goal of biomedical research. Despite an explosion in new knowledge on the molecular mechanisms of disease derived from animal model investigations, translation into effective treatment for human patients has been disappointingly slow. Several fundamental problems may explain the translational failures. First, the emphasis on novel and highly significant findings selectively rewards implausible, low-probability observations and high-magnitude effects, providing a biased perspective of the pathophysiology of disease that underappreciates the complexity and redundancy of biological systems. Second, even when a sound targetable mechanism is identified, animal models cannot recapitulate the pathophysiologic heterogeneity of the human disease, and are poor predictors of therapeutic success. Third, traditional classifications of most complex diseases are based primarily on clinical criteria and do not reflect the diverse pathophysiologic mechanisms that may be involved. The development of a flexible and dynamic conceptual paradigm that takes into account the totality of the evidence on the mechanisms of disease, and pathophysiologic stratification of patients to identify subpopulations with distinct pathogenetic mechanisms, are crucial for the development of new therapeutics.
Sex-specific cardiac aging in male and female with respect to changes in major sex hormones testosterone and estrogen. While aging is characterized by ventricular hypertrophy, fibrosis, and changes in ventricular function, several mechanisms are more pronounced in the male heart compared to female. For example, the aged male heart demonstrates eccentric remodeling, systolic dysfunction, and lower adrenergic sensitivity as opposed to aged female heart, which demonstrates diastolic dysfunction and concentric remodeling. While some of these changes likely coincide with temporal changes in sex hormones, others are likely regulated by non-hormonal changes, or occur via different temporal patterns in the male and female heart.
Fibrosis in the male and female heart across the life course. Collagen accumulation was assessed by picro-sirius red in LV in mice from 4 distinct age groups: juvenile (Juv; 4 weeks), adult (4-6 months), middle-aged (12 months), and aged (18 months) mice of both sexes. Quantification of fibrosis demonstrates that fibrotic content increases earlier in life for males, while females show relatively delayed fibrosis later in life. (A) Representative images; (B) quantification of fibrosis content in male and female samples. In male LV, fibrotic content was significantly higher in adult, while in female, fibrosis was not significantly elevated until middle age. n = 3/group; (C) expression of pro- and anti-fibrosis genes occurs in a sex-dependent manner with aging. Blue: male; pink/red: female.
Aging promotes structural and functional remodeling of the heart, even in the absence of external factors. There is growing clinical and experimental evidence supporting the existence of sex-specific patterns of cardiac aging, and in some cases, these sex differences emerge early in life. Despite efforts to identify sex-specific differences in cardiac aging, understanding how these differences are established and regulated remains limited. In addition to contributing to sex differences in age-related heart disease, sex differences also appear to underlie differential responses to cardiac stress such as adrenergic activation. Identifying the underlying mechanisms of sex-specific differences may facilitate the characterization of underlying heart disease phenotypes, with the ultimate goal of utilizing sex-specific therapeutic approaches for cardiac disease. The purpose of this review is to discuss the mechanisms and implications of sex-specific cardiac aging, how these changes render the heart more susceptible to disease, and how we can target age- and sex-specific differences to advance therapies for both male and female patients.
Glycoprotein nonmetastatic melanoma protein B (GPNMB) as a vaccine target for senolysis. Suda et al.[10] utilized RNAseq data on senescent cells to uncover GPNMB as a transmembrane protein disproportionately upregulated in senescent endothelial cells. GPNMB-based vaccination protected mice against vascular plaque burden, and extended lifespan in an accelerated aging model characterized by vascular pathology. Pink cells represent healthy cells; grey cells represent senescent cells; yellow icons represent GPNMB protein that accumulates on aged and senescent endothelial cells; white outlined cells represent eliminated senescent cells from senolytic vaccination.
Senescent cell accumulation is increasingly associated with a number of age-related cardiovascular diseases. Now, a new manuscript in Nature Aging suggests that a novel vaccine-based strategy might provide a targeted method to eliminate the senescent cell population.
Introduction: Aging is associated with cardiac myocyte loss, sarcopenia, and cardiac dysfunction. Adult cardiac myocytes are postmitotic cells with an insufficient proliferative capacity to compensate for myocyte loss. The canonical WNT (cWNT) pathway is involved in the regulation of cell cycle reentry in various cell types. The effects of the cWNT pathway on the expression of genes involved in cell cycle reentry in the postmitotic cardiac myocytes are unknown. Aim: The aim of the study was to identify genes whose expression is regulated by the β-catenin, the indispensable component to the cWNT signaling, in the postmitotic myocytes. Methods and results: Cardiac myocyte-specific tamoxifen-inducible MerCreMer (Myh6-Mcm) mice were used to delete the floxed exon 3 or exons 8 to 13 of the Ctnnb1 gene to induce gain-of-function (GoF) or loss-of-function (LoF) the β-catenin, respectively. Deletion of exon 3 leads to the expression of a stable β-catenin. In contrast, deletion of exons 8-13 leads to the expression of transcriptionally inactive truncated β-catenin, which is typically degraded. GoF or LoF of the β-catenin was verified by reverse transcription-polymerase chain reaction (RT-PCR), immunoblotting, and immunofluorescence. Myocyte transcripts were analyzed by RNA-Sequencing (RNA-Seq) at 4 weeks of age. The GoF of β-catenin was associated with differential expression of ~1700 genes, whereas its LoF altered expression of ~400 genes. The differentially expressed genes in the GoF myocytes were enriched in pathways regulating the cell cycle, including karyokinesis and cytokinesis, whereas the LoF was associated with increased expression of genes involved in mitochondrial oxidative phosphorylation. These findings were validated by RT-PCR in independent samples. Short-term GoF nor LoF of β-catenin did not affect the number of cardiac myocytes, cardiac function, myocardial fibrosis, myocardial apoptosis, or adipogenesis at 4 weeks of age. Conclusion: Activation of the β-catenin of the cWNT pathway in postmitotic myocytes leads to cell cycle reentry and expression of genes involved in cytokinesis without leading to an increase in the number of myocytes. In contrast, suppression of the β-catenin modestly increases the expression of genes involved in oxidative phosphorylation. The findings provide insights into the role of β-catenin of the cWNT pathway in the regulation of cell cycle reentry and oxidative phosphorylation in the postmitotic cardiac myocytes.
Pulse Doppler showing transmitral (A and B) and pulmonary venous (C and D) flow: (A) Mitral inflow pattern E > A in a young, healthy individual; (B) mitral inflow pattern E < A noted in an elderly healthy individual; (C) pulmonary venous flow S < D in a young, healthy individual; and (D) pulmonary venous flow S > D in an elderly, healthy individual. E: Early diastolic transmitral flow velocity; A: late diastolic transmitral flow velocity; S: systolic velocity; D: diastolic velocity.
Tissue Doppler images showing mitral annular early (e’) and late (a’) diastolic velocities in healthy young and elderly subjects. (A) Septal e’ in young, healthy individual is higher than septal e’ velocity in an elderly healthy individual (B). In comparison, a’ velocity is higher in the older subject. (C) Lateral e’ in young, healthy individual is higher than lateral e’ velocity in an elderly healthy individual (D). In comparison, a’ velocity is higher in the older subject.
Overview of age related changes in cardiac structure and function. LV: Left ventricle; LA: left atrium; RV: right ventricle; LVEF: left ventricular ejection fraction; PASP: pulmonary artery systolic pressure.
Aging is associated with progressive changes in cardiac structure and function. The prevalence of cardiovascular risk factors and disease also increases profoundly with advancing age. Therefore, understanding the spectrum of physiological changes in the aging heart is crucial for the identification and risk stratification of cardiovascular disease. In this review, we discuss echocardiographic features of age-related cardiac remodeling.
The hallmarks of cellular senescence. Cellular senescence can be defined as the irreversible growth arrest that occurs when the cells encounter a stressor. Senescent cells differ from other nondividing (quiescent, terminally differentiated) cells in several ways, although no single feature of the senescent phenotype is exclusively specific. The hallmarks of senescent cells include an essentially irreversible growth arrest; expression of senescence associated (SA)-β gal activity and p16INK4a; robust secretion of numerous growth factors, cytokines, proteases, and other proteins (SASP); and nuclear foci containing damaged DNA. SASP: Senescence associated secretory proteins; TERT: telomerase reverse transcriptase.
Ischemic heart disease and heart failure (HF) remain the leading causes of death worldwide. The inability of the adult heart to regenerate itself following ischemic injury and subsequent scar formation may explain the poor prognosis in these patients, especially when necrosis is extensive and leads to severe left ventricular dysfunction. Under physiological conditions, the crosstalk between cardiomyocytes and cardiac interstitial/vascular cells plays a pivotal role in cardiac processes by limiting ischemic damage or promoting repair processes, such as angiogenesis, regulation of cardiac metabolism, and the release of soluble paracrine or endocrine factors. Cardiovascular risk factors are the main cause of accelerated senescence of cardiomyocytes and cardiac stromal cells (CSCs), causing the loss of their cardioprotective and repairing functions. CSCs are supportive cells found in the heart. Among these, the pericytes/mural cells have the propensity to differentiate, under appropriate stimuli in vitro, into adipocytes, smooth muscle cells, osteoblasts, and chondroblasts, as well as other cell types. They contribute to normal cardiac function and have an antifibrotic effect after ischemia. Diabetes represents a condition of accelerated senescence. Among the new pharmacological armamentarium with hypoglycemic effect, gliflozins have been shown to reduce the incidence of HF and re-hospitalization, probably through the anti-remodeling and anti-senescent effect on the heart, regardless of diabetes. Therefore, either reducing the senescence of CSC or removing senescent cells from the infarcted heart could represent future antisenescence strategies capable of preventing the deterioration of heart function leading to HF.
Effects of tamoxifen (TAM) injection and expression of the MerCreMer (MCM) transgene protein on cardiac myocyte transcripts. (A) Levels of the transgene (Mcm) transcripts detected by RT-PCR of the ligand binding domain of the estrogen receptor (Esr1), showing markedly increased levels in the TAM injected Myh6-Mcm relative to wild type (WT) mouse myocytes. (B) Heart/body weight ratio showing no difference between the two groups. (C) Principal component analysis (PCA) of the cardiac myocyte transcripts showing distinct separation of the transcripts of myocytes isolated from the WT and Myh6-Mcm mice. (D) Volcano plot of transcripts identifying the differentially expressed genes (DEGs). The up-regulated genes are shown in red, the downregulated ones in blue, and those unchanged in black. (E) Heat map of the DEGs, showing distinct genotype-dependent categorization. (F) Pearson correlation plot showing a significant correlation in the changes in the transcript levels of 85 genes between the WT and Myh6-Mcm myocytes, as detected by RNA-sequencing (RNA-Seq) and reverse transcription-polymerase chain reaction (RT-PCR) methods in independent samples. Changes between the genotypes are presented as fold change (Log2). (G) Heat map of the transcript levels of selected genes in the WT and Myh6-Mcm myocytes as quantified by the RNA-Seq and RT-PCR in independent samples.
Predicted changes in the regulators of gene expression and biological pathways. (A) Panel A illustrated the transcriptional regulators (TRs), which are predicted to be activated or suppressed based on the number of differentially expressed genes (DEGs). The latter is depicted next to each TR. Red indicated predicted activation and blue predicted suppression. A Z score of < -2 and greater > 2 is considered significant. (B) The list of the biological pathways obtained from the overrepresentation (OR) analysis of the upregulated genes is depicted in the graph, along with the number of DEGs that overlaps with the genes in that pathway. (C) The list of biological pathways was obtained from the OR analysis of the downregulated genes in the Myh6-Mcm myocytes. The number of the DEGs that overlap with the genes in each pathway is listed next to each pathway. (D) Circos plot depicting the predicted activated biological pathways and contribution of the genes to the dysregulated pathways. (E) Gene set enrichment analysis (GSEA) showing enrichment of the genes in the interferon alpha pathway in the Myh6-Mcm myocytes.
Histological evaluation of the myocardium in the Myh6-Mcm mice injected with tamoxifen (TAM) at 4 weeks of age. (A) Picrosirius red-stained thin myocardial sections in the wild type and Myh6-Mcm (injected with TAM) mice at 4 weeks of age, showing no evidence of myocardial fibrosis. (B) Quantitative data of myocardial fibrosis presented as collagen volume fraction (CVF) in the experimental groups. (C) Assessment of apoptosis by the transferase deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) assay in the myocardial sections from the wild type and Myh6-Mcm (injected with TAM) mice, showing rare cells stained for TUNEL in green. Nuclei are stained with 4′,6-diamidino-2-phenylindole (DAPI) and shown in blue color. (D) Quantitative data showing the percentage of nuclei stained for TUNEL in each experimental group. (E) Immunofluorescence panel showing thin myocardial sections stained for phospho-the histone protein family member X (H2AFX) in the wild type and Myh6-Mcm (injected with TAM) mice, showing scattered positive cells. (F) Quantitative data showing the percent of phospho-H2AFX stained nuclei in the experimental groups. (G) Immunoblot analysis of cardiac myocyte protein extracts of wild type and Myh6-Mcm (injected with TAM) mice detecting phospho-H2AFX and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) [Supplementary Figure 1]. (H) Quantitative analysis of immunoblots detecting the phospho-H2AFX protein levels normalized to the GAPDH protein levels.
Gene expression and myocardial histology in 6 months old wild type and Myh6-Mcm mice. (A) Transcript levels of a dozen genes analyzed by reverse transcription-polymerase chain reaction 6 months after induction of activation of the MerCreMer protein upon injection of tamoxifen for 5 consecutive days at 2 weeks of age. Transcript levels of Esr1, representing the transgene, remained significantly elevated at 6 months of age. Transcript levels of Abhd1 and Armcx4 were also modestly reduced. (B) Picrosirius red-stained thin myocardial sections in the 6 months old wild type and Myh6-Mcm (injected with tamoxifen) mice, showing no evidence of myocardial fibrosis. (C) Quantitative data of myocardial fibrosis presented as CVF. (D) Myocardial panels from 6 months old mice stained for the TUNEL assay. Rare nuclei stained for the TUNEL (green) were detected. Nuclei are shown in blue upon DAPI staining. (E) Quantitative data showing the percentage of nuclei stained for TUNEL. CVF: Collagen volume fraction; TUNEL: transferase deoxyuridine triphosphate (dUTP) nick end labeling.
The Cre-LoxP technology, including the tamoxifen (TAM) inducible MerCreMer (MCM), is increasingly used to delineate gene function, understand the disease mechanisms, and test therapeutic interventions. We set to determine the effects of TAM-MCM on cardiac myocyte transcriptome. Expression of the MCM was induced specifically in cardiac myocytes upon injection of TAM to myosin heavy chain 6-MCM (Myh6-Mcm) mice for 5 consecutive days. Cardiac function, myocardial histology, and gene expression (RNA-sequencing) were analyzed 2 weeks after TAM injection. A total of 346 protein coding genes (168 up- and 178 down-regulated) were differentially expressed. Transcript levels of 85 genes, analyzed by a reverse transcription-polymerase chain reaction in independent samples, correlated with changes in the RNA-sequencing data. The differentially expressed genes were modestly enriched for genes involved in the interferon response and the tumor protein 53 (TP53) pathways. The changes in gene expression were relatively small and mostly transient and had no discernible effects on cardiac function, myocardial fibrosis, and apoptosis or induction of double-stranded DNA breaks. Thus, TAM-inducible activation of MCM alters cardiac myocytes gene expression, provoking modest and transient interferon and DNA damage responses without exerting other discernible phenotypic effects. Thus, the effects of TAM-MCM on gene expression should be considered in discerning the bona fide changes that result from the targeting of the gene of interest.
Introduction: Cardiovascular disease and myocardial infarction are leading causes of morbidity and mortality in aged populations. Mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) are under evaluation as a therapeutic option for the treatment of myocardial infarction. Aim: This study aimed to develop a large-scale manufacturing procedure to harvest clinical-grade EVs required for the translation of EVs to the clinic. Methods and results: We compared the efficiency of large scale MSC-derived EV production and characterized EV miRNA cargo using the Quantum bioreactor with either fetal bovine serum or human platelet lysate (PLT)-containing expansion media. We tested the potency of the EV products in a murine model of acute myocardial infarction. Our results demonstrate an advantage of the Quantum bioreactor as a large-scale platform for EV production using PLT media; however, both media produced EVs with similar effects in vivo. The systemic delivery of EV products improved cardiac function following myocardial infarctions as indicated by a significant improvement in ejection fraction as well as parameters of cardiac performance, afterload, contractility and lusitropy. Conclusion: These findings have important implications for scale-up strategies of EVs and will facilitate clinical trials for their clinical evaluation.
Regression for White adults (A) and Black adults (B). Bland-Altman plots for estimated pulse velocity (ePWV V1) vs. carotid-femoral pulse wave velocity (cfPWV) for White adults (C) and Black adults (D). cfPWV: Carotid-femoral pulse wave velocity; ePWV: estimated pulse wave velocity; V1: ePWV equation version 1; V2: ePWV equation version 2.
Introduction: Aortic stiffness offers important insight into vascular aging and cardiovascular disease (CVD) risk. The referent measure of aortic stiffness is carotid-femoral pulse wave velocity (cfPWV). cfPWV can be estimated (ePWV) from age and mean arterial pressure. Few studies have directly compared the association of ePWV to measured cfPWV, particularly in non-White adults. Moreover, whether ePWV and cfPWV correlate similarly with CVD risk remains unexplored. Aim: (1) To estimate the strength of the agreement between ePWV and cfPWV in both Black and White older adults; and (2) to compare the associations of ePWV and cfPWV with CVD risk factors and determine whether these associations were consistent across races. Methods and Results: We evaluated 4478 [75.2 (SD 5.0) years] Black and White older adults in the Atherosclerosis Risk in Communities (ARIC) Study. cfPWV was measured using an automated pulse waveform analyzer. ePWV was derived from an equation based on age and mean arterial pressure. Association and agreement between the two measurements were determined using Pearson’s correlation coefficient (r), standard error of estimate (SEE), and Bland-Altman analysis. Associations between traditional risk factors with ePWV and cfPWV were evaluated using linear mixed regression models. We observed weak correlations between ePWV and cfPWV within White adults (r = 0.36) and Black adults (r = 0.31). The mean bias for Bland-Altman analysis was low at -0.17 m/s (95%CI: -0.25 to -0.09). However, the inspection of the Bland-Altman plots indicated systematic bias (P < 0.001), which was consistent across race strata. The SEE, or typical absolute error, was 2.8 m/s suggesting high variability across measures. In models adjusted for sex, prevalent diabetes, the number of prevalent cardiovascular diseases, and medication count, both cfPWV and ePWV were positively associated with heart rate, triglycerides, and fasting glucose, and negatively associated with body mass index (BMI) and smoking status in White adults (P < 0.05). cfPWV and ePWV were not associated with heart rate, triglycerides, and fasting glucose in Black adults, while both measures were negatively associated with BMI in Black adults. Conclusions: Findings suggest a weak association between ePWV and cfPWV in older White and Black adults from ARIC. There were similar weak associations between CVD risk factors with ePWV and cfPWV in White adults with subtle differences in associations in Black adults. One sentence summary: Estimated pulse wave velocity is weakly associated with measured carotid-femoral pulse wave velocity in older Black and White adults in ARIC.
  • Chandrika CanugoviChandrika Canugovi
  • Mark D. StevensonMark D. Stevenson
  • Aleksandr E. VendrovAleksandr E. Vendrov
  • [...]
  • Nageswara R. MadamanchiNageswara R. Madamanchi
Introduction: Low aerobic exercise capacity is an independent risk factor for cardiovascular disease (CVD) and a predictor of premature death. In combination with aging, low aerobic capacity lowers the threshold for CVD. Aim: Since low aerobic capacity and aging have been linked to mitochondrial oxidative stress and dysfunction, we investigated whether aged Low-Capacity Runner (LCR) rats (27 months) had vascular dysfunction compared to High-Capacity Runner (HCR) rats. Methods and Results: A significant decrease in aortic eNOS levels and vasodilation as well as an increase in aortic collagen and stiffness were observed in aged LCR rats compared to age and sex-matched HCR rats. There was a correlation between age-related vascular dysfunction and increased levels of ROS and DNA damage in aortas of LCR rats. Moreover, mitochondrial oxygen consumption, membrane potential, ATP levels, and mitophagy were lower in VSMCs of aged LCR rats. VSMCs from older LCR rats showed AIM2 inflammasome activation. VSMCs of young (4 months old) LCR rats treated with purified mitochondrial damage-associated molecular patterns (DAMP) recapitulated an inflammasome activation phenotype similar to that seen in aged rat VSMCs. Rapamycin, a potent immunosuppressant, induced mitophagy, stimulated electron transport chain activity, reduced inflammasome activity, mitochondrial ROS and DAMP levels in VSMCs from aged LCR rats. MitoTEMPO, a mitochondrial ROS scavenger, was similarly effective on VSMCs from aged rats. Conclusion: The findings suggest that impaired mitophagy and inflammasome activation in the vasculature under conditions of low aerobic exercise capacity during aging results in arterial dysfunction and aortic stiffness. In older adults with reduced aerobic capacity, mitochondrial antioxidants, mitophagy induction, and inflammasome inhibition may be effective therapeutic strategies for enhancing vascular health.
Cardiac aging is accompanied by progressive loss of cellular function, leading to impaired heart function and heart failure. There is an urgent need for efficient strategies to combat this age-related cardiac dysfunction. A growing number of events suggest that age-related cardiac diseases are tightly related to metabolic imbalance. This review summarizes recent findings concerning metabolic changes during cardiac aging and highlights the therapeutic approaches that target metabolic pathways in cardiac aging.
The development of age-related cardiovascular (CV) dysfunction increases the risk of CV disease as well as other chronic age-associated disorders, including chronic kidney disease, and Alzheimer’s disease and related dementias. Major manifestations of age-associated CV dysfunction that increase disease risk are vascular dysfunction, primarily vascular endothelial dysfunction and arterial stiffening, and elevated systolic blood pressure. Declines in nitric oxide bioavailability secondary to increased oxidative stress and inflammation are established mechanisms of CV dysfunction with aging. Moreover, fundamental mechanisms of aging, termed the “hallmarks of aging” extend to the CV system and, as such, may be considered “hallmarks of CV aging”. These mechanisms represent viable therapeutic targets for treating CV dysfunction with aging. Healthy lifestyle behaviors, such as regular aerobic exercise and certain dietary patterns, are considered “first-line” strategies to prevent and/or treat age-associated CV dysfunction. Despite the well-established benefits of these strategies, many older adults do not meet the recommended guidelines for exercise or consume a healthy diet. Therefore, it is important to establish alternative and/or complementary evidence-based approaches to prevent or reverse age-related CV dysfunction. Targeting fundamental mechanisms of CV aging with interventions such as time-efficient exercise training, food-derived molecules, termed nutraceuticals, or select synthetic pharmacological agents represents a promising approach. In the present review, we will highlight emerging topics in the field of healthy CV aging with a specific focus on how exercise, nutrition/dietary patterns, nutraceuticals and select synthetic pharmacological compounds may promote healthy CV aging, in part, by targeting the hallmarks of CV aging.
Introduction: Postoperative atrial fibrillation (POAF), characterized as AF that arises 1-3 days after surgery, occurs after 30%-40% of cardiac and 10%-20% of non-cardiac surgeries, and is thought to arise due to transient surgery-induced triggers acting on a preexisting vulnerable atrial substrate often associated with inflammation and autonomic nervous system dysfunction. Current experimental studies often rely on human atrial tissue samples, collected during surgery prior to arrhythmia development, or animal models such as sterile pericarditis and atriotomy, which have not been robustly characterized. Aim: To characterize the demographic, electrophysiologic, and inflammatory properties of a POAF mouse model. Methods and Results: A total of 131 wild-type C57BL/6J mice were included in this study. A total of 86 (65.6%) mice underwent cardiothoracic surgery (THOR), which consisted of bi-atrial pericardiectomy with 20 s of aortic cross-clamping; 45 (34.3%) mice underwent a sham procedure consisting of dissection down to but not into the thoracic cavity. Intracardiac pacing, performed 72 h after surgery, was used to assess AF inducibility. THOR mice showed greater AF inducibility (38.4%) compared to Sham mice (17.8%, P = 0.027). Stratifying the cohort by tertiles of age showed that the greatest risk of POAF after THOR compared to Sham occurred in the 12-19-week age group. Stratifying by sex showed that cardiothoracic (CT) surgery increased POAF risk in females but had no significant effect in males. Quantitative polymerase chain reaction of atrial samples revealed upregulation of transforming growth factor beta 1 (TGF-β1) and interleukin 6 (IL6) and 18 (IL18) expression in THOR compared to Sham mice. Conclusion: Here, we demonstrate that the increased POAF risk associated with CT surgery is most pronounced in female and 12-19-week-old mice, and that the expression of inflammatory cytokines is upregulated in the atria of THOR mice prone to inducible AF. One sentence summary: We developed a mouse model of POAF that replicates key features of this condition in humans in terms of incidence and inflammatory indices. We demonstrated that female mice have a greater POAF risk than males, highlighting the importance of considering biological sex in future POAF mouse studies.
Identification of factors that lead to the severe clinical course of COVID-19 is crucial for timely allocation of resources. The purpose of this study was to evaluate possible sex differences in cardiac injury associated with HLA-C*04:01. High sensitivity troponin T on admission (hs-TnTa) and maximum high sensitivity troponin T (hs-TnTmax) were used to assess for cardiac injury in patients with COVID-19 (n = 435). We tested for the association of elevated hs-TnT with HLA-C* 04:01 and evaluated for potential sex-specific differences. An association between hs-TnTa and the severity of clinical course was identified. In addition, our study revealed that hs-TnTmax was higher in men who were carriers of HLA-C*04:01 compared to men without the risk allele. Male carriers of HLA-C*04:01 with COVID-19 developed higher hs-TnTmax, suggesting a larger extent of cardiac injury. This association suggests the presence of different pathomechanisms in COVID-19 based on sex.
Severe systemic inflammation in COVID-19 patients can lead to dysfunction of multiple organs, including the heart. Using an ex vivo cardiac organoid system, Mills et al discovered that inhibitors of the chromatin reader protein, bromodomain-containing protein 4, protect cardiomyocytes from COVID-associated "cytokine storm". We briefly review these important findings and highlight the translational significance of the work.
S-nitrosylation modifies a majority of proteins related to aging and longevity. Of 651 plasma proteins identified as significantly associated with age (either over-or under-represented in aged individuals)[16], 404 are known to be S-nitrosylated. Notable examples are displayed in the table to the right. A new addition, GSK-3β, has been identified by Salerno et al.[1] in this issue.
S-nitrosoglutathione reductase (GSNOR) is a denitrosylase enzyme responsible for reverting protein S-nitrosylation (SNO). In this issue, Salerno et al. [1] provide evidence that GSNOR deficiency - and thus elevated protein S-nitrosylation - accelerates cardiomyocyte differentiation and maturation of induced pluripotent stem cells (iPSCs). GSNOR inhibition (GSNOR-/- iPSCs) expedites the epithelial-mesenchymal transition (EMT) and promotes cardiomyocyte progenitor cell proliferation, differentiation, and migration. These findings are consistent with emerging roles for protein S-nitrosylation in developmental biology (including cardiomyocyte development), aging/longevity, and cancer.
A scheme representing GSK-3β mediated cardiac senescence through inhibition of ULK-1 directed autophagy. Under basal conditions, phosphorylation of ULK1 at S913 by GSK-3β promotes autophagy. During aging, phosphorylation of GSK-3β at S9 prevents activation of ULK1, leading to inhibition of autophagy and stimulation of cardiac aging processes, including hypertrophy, fibrosis, apoptosis, and cardiac dysfunction.
Cardiac senescence is the progressive decline in cardiac performance resulting from decline in age related structural and metabolic processes. Aging cardiac myocytes exhibit alterations in fatty acid and glucose oxidation metabolism, activation of innate immune signaling, enhanced fibrosis, mitochondrial dysfunction, endoplasmic reticulum stress, DNA damage, senescence-associated secreting phenotype and impaired autophagy. GSK-3β is an upstream regulator of autophagy through its interaction with ULK1 which regulates the initiation step of autophagy and formation of the autophagosme. Herein, we highlight a novel putative molecular mechanism that functionally links cardiac senescence, hypertrophy and autophagy regulation. Ser9 phosphorylation of GSK-3β is critical for promoting cardiac senescence via reduction in ULK1 phosphorylation at Ser913 and inhibition of autophagy.
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Melis Olcum Uzan
  • University of Texas Health Science Center at Houston
Zhongming Zhao
  • University of Texas Health Science Center at Houston
Siyang Fan
  • Beijing Fuwai Hospital
Kenneth Walsh
  • University of Virginia
Priyatansh Gurha
  • University of Texas Health Science Center at Houston