Enhanced susceptibility of cyclin kinase inhibitor p21 knockout mice to high fat diet induced atherosclerosis

Unveiling the role of ABI3 and hub senescence-related genes in macrophage senescence for atherosclerotic plaque progression

BACKGROUND

Atherosclerosis, characterized by abnormal arterial lipid deposition, is an age-dependent inflammatory disease and contributes to elevated morbidity and mortality. Senescent foamy macrophages are considered to be deleterious at all stages of atherosclerosis, while the underlying mechanisms remain largely unknown. In this study, we aimed to explore the senescence-related genes in macrophages diagnosis for atherosclerotic plaque progression.

METHODS

The atherosclerosis-related datasets were retrieved from the Gene Expression Omnibus (GEO) database, and cellular senescence-associated genes were acquired from the CellAge database. R package Limma was used to screen out the differentially expressed senescence-related genes (DE-SRGs), and then three machine learning algorithms were applied to determine the hub DE-SRGs. Next, we established a nomogram model to further confirm the clinical significance of hub DE-SRGs. Finally, we validated the expression of hub SRG ABI3 by Sc-RNA seq analysis and explored the underlying mechanism of ABI3 in THP-1-derived macrophages and mouse atherosclerotic lesions.

RESULTS

A total of 15 DE-SRGs were identified in macrophage-rich plaques, with five hub DE-SRGs (ABI3, CAV1, NINJ1, Nox4 and YAP1) were further screened using three machine learning algorithms. Subsequently, a nomogram predictive model confirmed the high validity of the five hub DE-SRGs for evaluating atherosclerotic plaque progression. Further, the ABI3 expression was upregulated in macrophages of advanced plaques and senescent THP-1-derived macrophages, which was consistent with the bioinformatics analysis. ABI3 knockdown abolished macrophage senescence, and the NF-κB signaling pathway contributed to ABI3-mediated macrophage senescence.

CONCLUSION

We identified five cellular senescence-associated genes for atherogenesis progression and unveiled that ABI3 might promote macrophage senescence via activation of the NF-κB pathway in atherogenesis progression, which proposes new preventive and therapeutic strategies of senolytic agents for atherosclerosis.

DNA damage response signaling: A common link between cancer and cardiovascular diseases

DNA damage response (DDR) signaling ensures genomic and proteomic homeostasis to maintain a healthy genome. Dysregulation either in the form of down- or upregulation in the DDR pathways correlates with various pathophysiological states, including cancer and cardiovascular diseases (CVDs). Impaired DDR is studied as a signature mechanism for cancer; however, it also plays a role in ischemia-reperfusion injury (IRI), inflammation, cardiovascular function, and aging, demonstrating a complex and intriguing relationship between cancer and pathophysiology of CVDs. Accordingly, there are increasing number of reports indicating higher incidences of CVDs in cancer patients. In the present review, we thoroughly discuss (1) different DDR pathways, (2) the functional cross talk among different DDR mechanisms, (3) the role of DDR in cancer, (4) the commonalities and differences of DDR between cancer and CVDs, (5) the role of DDR in pathophysiology of CVDs, (6) interventional strategies for targeting genomic instability in CVDs, and (7) future perspective.

Association between atherogenic risk-modulating proteins and endothelium-dependent flow-mediated dilation in coronary artery disease patients

PURPOSE

Endothelial dysfunction is an early and integral event in the development of atherosclerosis and coronary artery disease (CAD). Reduced NO bioavailability, oxidative stress, vasoconstriction, inflammation and senescence are all implicated in endothelial dysfunction. However, there are limited data examining associations between these pathways and direct in vivo bioassay measures of endothelial function in CAD patients. This study aimed to examine the relationships between in vivo measures of vascular function and the expression of atherogenic risk-modulating proteins in endothelial cells (ECs) isolated from the radial artery of CAD patients.

METHODS

Fifty-six patients with established CAD underwent trans-radial catheterization. Prior to catheterization, radial artery vascular function was assessed using a) flow-mediated dilation (FMD), and b) exercise-induced dilation in response to handgrip (HE%). Freshly isolated ECs were obtained from the radial artery during catheterization and protein content of eNOS, NAD(P)H oxidase subunit NOX2, NFκB, ET-1 and the senescence markers p53, p21 and p16 were evaluated alongside nitrotyrosine abundance and eNOS Ser¹¹⁷⁷ phosphorylation.

RESULTS

FMD was positively associated with eNOS Ser¹¹⁷⁷ phosphorylation (r = 0.290, P = 0.037), and protein content of p21 (r = 0.307, P = 0.027) and p16 (r = 0.426, P = 0.002). No associations were found between FMD and markers of oxidative stress, vasoconstriction or inflammation. In contrast to FMD, HE% was not associated with any of the EC proteins.

CONCLUSION

These data revealed a difference in the regulation of endothelium-dependent vasodilation measured in vivo between patients with CAD compared to previously reported data in subjects without a clinical diagnosis, suggesting that eNOS Ser¹¹⁷⁷ phosphorylation may be the key to maintain vasodilation in CAD patients.

Single or combined ablation of peripheral serotonin and p21 limit adipose tissue expansion and metabolic alterations in early adulthood in mice fed a normocaloric diet

Identifying the fundamental molecular factors that drive weight gain even in the absence of hypercaloric food intake, is crucial to enable development of novel treatments for the global pandemic of obesity. Here we investigated both adipose tissue-specific and systemic events that underlie the physiological weight gain occurring during early adulthood in mice fed a normocaloric diet. In addition, we used three different genetic models to identify molecular factors that promote physiological weight gain during normocaloric and hypercaloric diets. We demonstrated that normal physiological weight gain was accompanied by an increase in adipose tissue mass and the presence of cellular and metabolic signatures typically found during obesity, including adipocyte hypertrophy, macrophage recruitment into visceral fat and perturbed glucose metabolism. At the molecular level, this was associated with an increase in adipose tissue tryptophan hydroxylase 1 (Tph1) transcripts, the key enzyme responsible for the synthesis of peripheral serotonin. Genetic inactivation of Tph1 was sufficient to limit adipose tissue expansion and associated metabolic alterations. Mechanistically, we discovered that Tph1 inactivation resulted in down-regulation of cyclin-dependent kinase inhibitor p21Waf1/Cip1 expression. Single or double ablation of Tph1 and p21 were equally effective in preventing adipocyte expansion and systemic perturbation of glucose metabolism, upon both normocaloric and hypercaloric diets. Our results suggest that serotonin and p21 act as a central molecular determinant of weight gain and associated metabolic alterations, and highlights the potential of targeting these molecules as a pharmacologic approach to prevent the development of obesity.

Microtubule affinity regulating kinase 4: A promising target in the pathogenesis of atherosclerosis

Microtubule affinity regulating kinase 4 (MARK4), an important member of the serine/threonine kinase family, regulates the phosphorylation of microtubule-associated proteins and thus modulates microtubule dynamics. In human atherosclerotic lesions, the expression of MARK4 is significantly increased. Recently, accumulating evidence suggests that MARK4 exerts a proatherogenic effect via regulation of lipid metabolism (cholesterol, fatty acid, and triglyceride), inflammation, cell cycle progression and proliferation, insulin signaling, and glucose homeostasis, white adipocyte browning, and oxidative stress. In this review, we summarize the latest findings regarding the role of MARK4 in the pathogenesis of atherosclerosis to provide a rationale for future investigation and therapeutic intervention.

Long-Term Effects of Very Low Dose Particle Radiation on Gene Expression in the Heart: Degenerative Disease Risks

Compared to low doses of gamma irradiation (γ-IR), high-charge-and-energy (HZE) particle IR may have different biological response thresholds in cardiac tissue at lower doses, and these effects may be IR type and dose dependent. Three- to four-month-old female CB6F1/Hsd mice were exposed once to one of four different doses of the following types of radiation: γ-IR ¹³⁷Cs (40-160 cGy, 0.662 MeV), ¹⁴Si-IR (4-32 cGy, 260 MeV/n), or ²²Ti-IR (3-26 cGy, 1 GeV/n). At 16 months post-exposure, animals were sacrificed and hearts were harvested and archived as part of the NASA Space Radiation Tissue Sharing Forum. These heart tissue samples were used in our study for RNA isolation and microarray hybridization. Functional annotation of twofold up/down differentially expressed genes (DEGs) and bioinformatics analyses revealed the following: (i) there were no clear lower IR thresholds for HZE- or γ-IR; (ii) there were 12 common DEGs across all 3 IR types; (iii) these 12 overlapping genes predicted various degrees of cardiovascular, pulmonary, and metabolic diseases, cancer, and aging; and (iv) these 12 genes revealed an exclusive non-linear DEG pattern in ¹⁴Si- and ²²Ti-IR-exposed hearts, whereas two-thirds of γ-IR-exposed hearts revealed a linear pattern of DEGs. Thus, our study may provide experimental evidence of excess relative risk (ERR) quantification of low/very low doses of full-body space-type IR-associated degenerative disease development.

Time-dependent replicative senescence vs. disturbed flow-induced pre-mature aging in atherosclerosis

Accumulation of senescent cells has a causative role in the pathology of age-related disorders including atherosclerosis (AS) and cardiovascular diseases (CVDs). However, the concept of senescence is now drastically changing, and the new concept of senescence-associated reprogramming/stemness has emerged, suggesting that senescence is not merely related to “cell cycle arrest” or halting various cellular functions. It is well known that disturbed flow (D-flow) accelerates pre-mature aging and plays a significant role in the development of AS. We will discuss in this review that pre-mature aging induced by D-flow is not comparable to time-dependent aging, particularly with a focus on the possible involvement of senescence-associated secretory phenotype (SASP) in senescence-associated reprogramming/stemness, or increasing cell numbers. We will also present our outlook of nicotinamide adenine dinucleotides (NAD)⁺ deficiency-induced mitochondrial reactive oxygen species (mtROS) in evoking SASP by activating DNA damage response (DDR). MtROS plays a key role in developing cross-talk between nuclear-mitochondria, SASP, and ultimately atherosclerosis formation. Although senescence induced by time and various stress factors is a classical concept, we wish that the readers will see the undergoing Copernican-like change in this concept, as well as to recognize the significant contrast between pre-mature aging induced by D-flow and time-dependent aging.

The Role of Protein SUMOylation in the Pathogenesis of Atherosclerosis

Atherosclerosis is a progressive, inflammatory cardiovascular disorder characterized by the development of lipid-filled plaques within arteries. Endothelial cell dysfunction in the walls of blood vessels results in an increase in vascular permeability, alteration of the components of the extracellular matrix, and retention of LDL in the sub-endothelial space, thereby accelerating plaque formation. Epigenetic modification by SUMOylation can influence the surface interactions of target proteins and affect cellular functionality, thereby regulating multiple cellular processes. Small ubiquitin-like modifier (SUMO) can modulate NFκB and other proteins such as p53, KLF, and ERK5, which have critical roles in atherogenesis. Furthermore, SUMO regulates leukocyte recruitment and cytokine release and the expression of adherence molecules. In this review, we discuss the regulation by SUMO and SUMOylation modifications of proteins and pathways involved in atherosclerosis.

Senescent cells in the development of cardiometabolic disease

PURPOSE OF REVIEW

Senescent cells have recently been identified as key players in the development of metabolic dysfunction. In this review, we will highlight recent developments in this field and discuss the concept of targeting these cells to prevent or treat cardiometabolic diseases.

RECENT FINDINGS

Evidence is accumulating that cellular senescence contributes to adipose tissue dysfunction, presumably through induction of low-grade inflammation and inhibition of adipogenic differentiation leading to insulin resistance and dyslipidaemia. Senescent cells modulate their surroundings through their bioactive secretome and only a relatively small number of senescent cells is sufficient to cause persistent physical dysfunction even in young mice. Proof-of-principle studies showed that selective elimination of senescent cells can prevent or delay the development of cardiometabolic diseases in mice.

SUMMARY

The metabolic consequences of senescent cell accumulation in various tissues are now unravelling and point to new therapeutic opportunities for the treatment of cardiometabolic diseases.

High-fat diets promote colon orthotopic transplantation tumor metastasis in BALB/c mice

High-fat diets (HFDs) are a risk factor for colorectal cancer. The present study investigated whether HFDs increase colon cancer metastasis in BALB/c mice. A total of 40 BALB/c mice were divided into four groups, including the tumor, tumor-HFD, HFD and control groups. After 3 weeks, the tumor weights and metastases were observed. The serum levels of triglyceride, total cholesterol, lapin, interleukin-6 (IL-6) and tumor necrosis factor were analyzed using ELISA. The CD34, vascular endothelial growth factor (VEGF) and angiotensin 2 (ANG2) protein and mRNA levels in tumor tissues were analyzed with immunohistochemistry and reverse transcription-polymerase chain reaction. The metastasis frequency increased in the tumor-HFD group. However, there was no difference in the mean tumor weight between the tumor-HFD and tumor groups. The serum cholesterol levels were increased in the tumor-HFD and HFD groups compared with the control group. The levels of serum IL-6 and tumor necrosis factor-α were increased in the tumor-HFD group compared with other groups. The CD34 protein level, and VEGF protein and mRNA levels were increased in the tumor-HFD group compared with the tumor group. No difference was identified between the ANG2 protein and mRNA levels in of the two groups. It was concluded that HFD increased the serum level of cholesterol and cytokines, and potentially induced tumor angiogenesis, promoting transplanted orthotopic colon tumor metastasis in BALB/c mice.

Senescent cells: a therapeutic target for cardiovascular disease

Cellular senescence, a major tumor-suppressive cell fate, has emerged from humble beginnings as an in vitro phenomenon into recognition as a fundamental mechanism of aging. In the process, senescent cells have attracted attention as a therapeutic target for age-related diseases, including cardiovascular disease (CVD), the leading cause of morbidity and mortality in the elderly. Given the aging global population and the inadequacy of current medical management, attenuating the health care burden of CVD would be transformative to clinical practice. Here, we review the evidence that cellular senescence drives CVD in a bimodal fashion by both priming the aged cardiovascular system for disease and driving established disease forward. Hence, the growing field of senotherapy (neutralizing senescent cells for therapeutic benefit) is poised to contribute to both prevention and treatment of CVD.

MicroRNA-296: a promising target in the pathogenesis of atherosclerosis?

Atherosclerosis has been recognized as an inflammatory disease involving the vascular wall. MicroRNAs are a group of small noncoding RNAs to regulate gene expression at the transcriptional level through mRNA degradation or translation repression. Recent studies suggest that miR-296 may play crucial roles in the regulation of angiogenesis, inflammatory response, cholesterol metabolism, hypertension, cellular proliferation and apoptosis. In this review, we primarily discussed the molecular targets of miR-296 involved in the development of atherosclerosis, which may provide a basis for future investigation and a better understanding of the biological functions of miR-296 in atherosclerosis.

Senescent cells: an emerging target for diseases of ageing

Chronological age represents the single greatest risk factor for human disease. One plausible explanation for this correlation is that mechanisms that drive ageing might also promote age-related diseases. Cellular senescence, which is a permanent state of cell cycle arrest induced by cellular stress, has recently emerged as a fundamental ageing mechanism that also contributes to diseases of late life, including cancer, atherosclerosis and osteoarthritis. Therapeutic strategies that safely interfere with the detrimental effects of cellular senescence, such as the selective elimination of senescent cells (SNCs) or the disruption of the SNC secretome, are gaining significant attention, with several programmes now nearing human clinical studies.

Different transcriptional profiling between senescent and non-senescent human coronary artery endothelial cells (HCAECs) by Omeprazole and Lansoprazole treatment

Recent evidence suggests that high dose and/or long term use of proton pump inhibitors (PPIs) may increase the risk of adverse cardiovascular events in older patients, but mechanisms underlying these detrimental effects are not known. Taking into account that the senescent endothelial cells have been implicated in the genesis or promotion of age-related cardiovascular disease, we hypothesized an active role of PPIs in senescent cells. The aim of this study is to investigate the changes in gene expression occurring in senescent and non-senescent human coronary artery endothelial cells (HCAECs) following Omeprazole (OPZ) or Lansoprazole (LPZ) treatment. Here, we show that atherogenic response is among the most regulated processes in PPI-treated HCAECs. PPIs induced down-regulation of anti-atherogenic chemokines (CXCL11, CXCL12 and CX3CL1) in senescent but not in non-senescent cells, while the same chemokines were up-regulated in untreated senescent cells. These findings support the hypothesis that up-regulated anti-atherogenic chemokines may represent a defensive mechanism against atherosclerosis during cellular senescence, and suggest that PPIs could activate pro-atherogenic pathways by changing the secretory phenotype of senescent HCAECs. Moreover, the genes coding for fatty acid binding protein 4 (FABP4) and piezo-type mechanosensitive ion channel component 2 (PIEZO2) were modulated by PPIs treatment with respect to untreated cells. In conclusions, our results show that long-term and high dose use of PPI could change the secretory phenotype of senescent cells, suggesting one of the potential mechanisms by which use of PPI can increase adverse outcomes in older subjects.

Senescent intimal foam cells are deleterious at all stages of atherosclerosis

Advanced atherosclerotic lesions contain senescent cells, but the role of these cells in atherogenesis remains unclear. Using transgenic and pharmacological approaches to eliminate senescent cells in atherosclerosis-prone low-density lipoprotein receptor-deficient (Ldlr^-/-) mice, we show that these cells are detrimental throughout disease pathogenesis. We find that foamy macrophages with senescence markers accumulate in the subendothelial space at the onset of atherosclerosis, where they drive pathology by increasing expression of key atherogenic and inflammatory cytokines and chemokines. In advanced lesions, senescent cells promote features of plaque instability, including elastic fiber degradation and fibrous cap thinning, by heightening metalloprotease production. Together, these results demonstrate that senescent cells are key drivers of atheroma formation and maturation and suggest that selective clearance of these cells by senolytic agents holds promise for the treatment of atherosclerosis.

Cellular senescence in aging and age-related disease: from mechanisms to therapy

Cellular senescence, a process that imposes permanent proliferative arrest on cells in response to various stressors, has emerged as a potentially important contributor to aging and age-related disease, and it is an attractive target for therapeutic exploitation. A wealth of information about senescence in cultured cells has been acquired over the past half century; however, senescence in living organisms is poorly understood, largely because of technical limitations relating to the identification and characterization of senescent cells in tissues and organs. Furthermore, newly recognized beneficial signaling functions of senescence suggest that indiscriminately targeting senescent cells or modulating their secretome for anti-aging therapy may have negative consequences. Here we discuss current progress and challenges in understanding the stressors that induce senescence in vivo, the cell types that are prone to senesce, and the autocrine and paracrine properties of senescent cells in the contexts of aging and age-related diseases as well as disease therapy.

The emerging role of senescent cells in tissue homeostasis and pathophysiology

Cellular senescence is a state of permanent growth arrest and is thought to play a pivotal role in tumor suppression. Cellular senescence may play an important role in tumor suppression, wound healing, and protection against tissue fibrosis in physiological conditions in vivo. However, accumulating evidence that senescent cells may have harmful effects in vivo and may contribute to tissue remodeling, organismal aging, and many age-related diseases also exists. Cellular senescence can be induced by various intrinsic and extrinsic factors. Both p53/p21 and p16/RB pathways are important for irreversible growth arrest in senescent cells. Senescent cells secret numerous biologically active factors. This specific secretion phenotype by senescent cells may largely contribute to physiological and pathological consequences in organisms. Here I review the molecular basis of cell cycle arrest and the specific secretion phenotype in cellular senescence. I also summarize the current knowledge of the role of cellular senescence in vivo in physiological and pathological settings.

The COP9 signalosome and vascular function: intriguing possibilities?

Disorders of vascular function contribute importantly to cardiovascular disease which represents a substantial cause of morbidity and mortality worldwide. An emerging paradigm in the study of cardiovascular diseases is that protein ubiquitination and turnover represent key pathological mechanisms. Our understanding of these processes in the vasculature is growing but remains incomplete. Since protein ubiquitination and turnover can represent a terminal event in the life of a given protein, entry into these pathways must be highly regulated. However, at present understanding of these regulatory mechanisms, particularly in the vasculature, is fragmentary. The COP9 (constitutive photomorphogenic mutant 9) signalosome (CSN) is a heteromeric protein complex implicated in the control of protein degradation. The CSN participates critically in the control of Cullin Ring Ligases (CRLs), at least in part via the detachment of a small protein, Nedd8 (deneddylation). CRLs are one of the largest groups of ubiquitin ligases, which represent the most selective control point for protein ubiquitination. Thus, the CSN by virtue of its ability to control the CRLs ubiquitin ligase activity is ideally positioned to effect selective modulation of protein turnover. This review surveys currently available data regarding the potential role of the CSN in control of vascular function. Data potentially linking the CSN to control of regulatory proteins involved in vascular smooth muscle proliferation and to vascular smooth muscle contraction are presented with the intent of providing potentially intriguing possibilities for future investigation.

SIRT1-mediated epigenetic downregulation of plasminogen activator inhibitor-1 prevents vascular endothelial replicative senescence

The inactivation of plasminogen activator inhibitor-1 (PAI-1) has been shown to exert beneficial effects in age-related vascular diseases. Limited information is available on the molecular mechanisms regarding the negatively regulated expression of PAI-1 in the vascular system. In this study, we observed an inverse correlation between SIRT1, a class III histone deacetylase, and PAI-1 expression in human atherosclerotic plaques and the aortas of old mice, suggesting that internal negative regulation exists between SIRT1 and PAI-1. SIRT1 overexpression reversed the increased PAI-1 expression in senescent human umbilical vein endothelial cells (HUVECs) and aortas of old mice, accompanied by decreased SA-β-gal activity in vitro and improved endothelial function and reduced arterial stiffness in vivo. Moreover, the SIRT1-mediated inhibition of PAI-1 expression exerted an antisenescence effect in HUVECs. Furthermore, we demonstrated that SIRT1 is able to bind to the PAI-1 promoter, resulting in a decrease in the acetylation of histone H4 lysine 16 (H4K16) on the PAI-1 promoter region. Thus, our findings suggest that the SIRT1-mediated epigenetic inhibition of PAI-1 expression exerts a protective effect in vascular endothelial senescence.

Cellular senescence: from physiology to pathology

Recent discoveries are redefining our view of cellular senescence as a trigger of tissue remodelling that acts during normal embryonic development and upon tissue damage. To achieve this, senescent cells arrest their own proliferation, recruit phagocytic immune cells and promote tissue renewal. This sequence of events - senescence, followed by clearance and then regeneration - may not be efficiently completed in aged tissues or in pathological contexts, thereby resulting in the accumulation of senescent cells. Increasing evidence indicates that both pro-senescent therapies and antisenescent therapies can be beneficial. In cancer and during active tissue repair, pro-senescent therapies contribute to minimize the damage by limiting proliferation and fibrosis, respectively. Conversely, antisenescent therapies may help to eliminate accumulated senescent cells and to recover tissue function.

Fatty acids regulate endothelial lipase and inflammatory markers in macrophages and in mouse aorta: a role for PPARγ

OBJECTIVE

Macrophage endothelial lipase (EL) is associated with increased atherosclerosis and inflammation. Because of their anti-inflammatory properties we hypothesized that n-3 fatty acids, in contrast to saturated fatty acids, would lower macrophages and arterial EL and inflammatory markers.

METHODS AND RESULTS

Murine J774 and peritoneal macrophages were incubated with eicosapentaenoic acid or palmitic acid in the presence or absence of lipopolysaccaride (LPS). LPS increased EL mRNA and protein. Palmitic acid alone or with LPS dose-dependently increased EL mRNA and protein. In contrast, eicosapentaenoic acid dose-dependently abrogated effects of LPS or palmitic acid on increasing EL expression. EL expression closely linked to peroxisome proliferator activated receptor (PPAR)γ expression. Eicosapentaenoic acid blocked rosiglitazone (a PPARγ agonist)-mediated EL activation and GW9662 (a PPARγ antagonist)-blocked palmitic acid-mediated EL stimulation. Eicosapentaenoic acid alone or with LPS blunted LPS-mediated stimulation of macrophage proinflammatory interleukin-6, interleukin-12p40, and toll-like receptor-4 mRNA and increased anti-inflammatory interleukin-10 and mannose receptor mRNA. In vivo studies in low density lipoprotein receptor knockout mice showed that high saturated fat rich diets, but not n-3 diets, increased arterial EL, PPARγ, and proinflammatory cytokine mRNA.

CONCLUSIONS

n-3 fatty acids, in contrast to saturated fatty acids, decrease EL in parallel with modulating pro- and anti-inflammatory markers, and these effects on EL link to PPARγ.

Is cellular senescence important in pediatric kidney disease?

Somatic cellular senescence (SCS) describes the limited ability of cells to divide. Normally, SCS is associated with physiological aging, but evidence suggests that it may play a role in disease progression, even in young patients. Stressors such as acute injury or chronic inflammation may induce SCS, which in turn exhausts organ regenerative potential. This review summarizes what is known about SCS in the kidney with aging and disease. As most patients with chronic kidney disease (CKD) also develop cardiovascular complications, a second focus of this review deals with the role of SCS in cardiovascular disease. Also, as SCS seems to accelerate CKD and cardiovascular disease progression, developing strategies for new treatment options that overcome SCS or protect a patient from it represents an exciting challenge.

Dual use of amphiphilic macromolecules as cholesterol efflux triggers and inhibitors of macrophage athero-inflammation

Activated vascular wall macrophages can rapidly internalize modified lipoproteins and escalate the growth of atherosclerotic plaques. This article proposes a biomaterials-based therapeutic intervention for depletion of non-regulated cholesterol accumulation and inhibition of inflammation of macrophages. Macromolecules with high scavenger receptor (SR)-binding activity were investigated for SR-mediated delivery of agonists to cholesterol-trafficking nuclear liver-X receptors. From a diverse feature space of a family of amphiphilic macromolecules of linear and aromatic mucic acid backbones modified with varied aliphatic chains and conjugated with differentially branched poly(ethylene glycol), a key molecule (carboxyl-terminated, C12-derivatized, linear mucic acid backbone) was selected for its ability to preferentially bind scavenger receptor A (SR-A) as the key target. At a basal level, this macromolecule suppressed the pro-inflammatory signaling of activated THP-1 macrophages while competitively lowering oxLDL uptake in vitro through scavenger receptor SRA-1 targeting. To further deplete intracellular cholesterol, the core macromolecule structure was exploited to solubilize a hydrophobic small molecule agonist for nuclear Liver-X Receptors, which regulate the efflux of intracellular cholesterol. The macromolecule-encapsulated agonist system was found to reduce oxLDL accumulation by 88% in vitro in comparison to controls. in vivo studies were designed to release the macromolecules (with or without encapsulated agonist) to injured carotid arteries within Sprague Dawley rats fed a high fat diet, conditions that yield enhanced cholesterol accumulation and macrophage recruitment. The macromolecules lowered intimal levels of accumulated cholesterol (50% for macromolecule alone; 70% for macromolecule-encapsulated agonist) and inhibited macrophage retention (92% for macromolecule; 96% for macromolecule-encapsulated agonist; 4 days) relative to non-treated controls. Thus, this study highlights the promise of designing bioactive macromolecule therapeutics based on scavenger receptor targeting, for potential management of vascular arterial disease.

Control of cell proliferation in atherosclerosis: insights from animal models and human studies

Excessive hyperplastic cell growth within occlusive vascular lesions has been recognized as a key component of the inflammatory response associated with atherosclerosis, restenosis post-angioplasty, and graft atherosclerosis after coronary artery bypass. Understanding the molecular mechanisms that regulate arterial cell proliferation is therefore essential for the development of new tools for the treatment of these diseases. Mammalian cell proliferation is controlled by a large number of proteins that modulate the mitotic cell cycle, including cyclin-dependent kinases, cyclins, and tumour suppressors. The purpose of this review is to summarize current knowledge about the role of these cell cycle regulators in the development of native and graft atherosclerosis that has arisen from animal studies, histological examination of specimens from human patients, and genetic studies.