Synopsis on cellular senescence and apoptosis

Potential role of ergothioneine rich mushroom as anti-aging candidate through elimination of neuronal senescent cells

Oxidative stress can upset the antioxidant balance and cause accelerated aging including neurodegenerative diseases and decline in physiological function. Therefore, an antioxidant-rich diet plays a crucial role in healthy aging. This study aimed to identify and quantify mushrooms with the highest ergothioneine content through HPLC analysis and evaluate their anti-aging potential as a natural antioxidant and antisenescence in HT22 cells. Among the 14 evaluated mushroom species, Lentinula edodes (LE), shiitake mushroom contains the highest ergothioneine content and hence was used for the in-vitro studies. The cells were preincubated with ethanolic extract of ergothioneine-rich mushroom and the equimolar concentration of EGT on t-BHP-induced senescence HT22 cells. The extract was analyzed for its free radical scavenging properties using DPPH and ABTS methods. Then, the neuroprotective effect was conducted by measuring the cell viability using MTT. Senescence-associated markers and ROS staining were also analyzed. Our results revealed that a low dose of t-BHP reduces cell viability and induces senescence in HT22 cells as determined through β-galactosidase staining and expressions of P16INK4a, P21CIPL which are the markers of cellular senescence. However, the pretreatment with ethanolic extract of LE for 8 h significantly improved the cell viability, reversed the t-BHP-induced cellular senescence in the neuronal cells, and reduced the reactive oxygen species visualized through DCFH-DA staining. These results suggest that ergothioneine-rich mushroom is a potential candidate for anti-aging exploration through the elimination of senescent cells.

Novel Strategy in Searching for Natural Compounds with Anti-Aging and Rejuvenating Potential

We suggest a novel approach for searching natural compounds with anti-aging and rejuvenation potential using cell cultures, with a high potential for the further in vivo applications. The present paper discusses ways of defining age for cell populations with large numbers of cells and suggests a method of assessing how young or old a cell population is based on a cell age profile approach. This approach uses experimental distributions of the cells over the cell cycle stages, acquired using flow cytometry. This paper discusses how such a profile should evolve under homeostatic maintenance of cell numbers in the proliferation niches. We describe promising results from experiments on a commercial substance claiming rejuvenating and anti-aging activity acting upon the cultures of human mononuclear cells and dermal fibroblasts. The chosen substance promotes a shift towards larger proportion of cells in synthesis and proliferation stages, and increases cell culture longevity. Further, we describe promising in vivo testing results of a selected food supplement. Based on the described concept of cell age profile and available test results, a strategy to search for natural compounds with regenerative, anti-aging and rejuvenation potential is suggested and proposed for wider and thorough testing. Proposed methodology of age assessment is rather generic and can be used for quantitative assessment of the anti-aging and rejuvenation potential of different interventions. Further research aimed at the tests of the suggested strategy using more substances and different interventions, and the thorough studies of molecular mechanisms related to the action of the substance used for testing the suggested search methodology, are needed.

Gut Microbiota-Derived Trimethylamine N-Oxide Contributes to Abdominal Aortic Aneurysm Through Inflammatory and Apoptotic Mechanisms

BACKGROUND

Large-scale human and mechanistic mouse studies indicate a strong relationship between the microbiome-dependent metabolite trimethylamine N-oxide (TMAO) and several cardiometabolic diseases. This study aims to investigate the role of TMAO in the pathogenesis of abdominal aortic aneurysm (AAA) and target its parent microbes as a potential pharmacological intervention.

METHODS

TMAO and choline metabolites were examined in plasma samples, with associated clinical data, from 2 independent patient cohorts (N=2129 total). Mice were fed a high-choline diet and underwent 2 murine AAA models, angiotensin II infusion in low-density lipoprotein receptor-deficient (Ldlr-/-) mice or topical porcine pancreatic elastase in C57BL/6J mice. Gut microbial production of TMAO was inhibited through broad-spectrum antibiotics, targeted inhibition of the gut microbial choline TMA lyase (CutC/D) with fluoromethylcholine, or the use of mice genetically deficient in flavin monooxygenase 3 (Fmo3-/-). Finally, RNA sequencing of in vitro human vascular smooth muscle cells and in vivo mouse aortas was used to investigate how TMAO affects AAA.

RESULTS

Elevated TMAO was associated with increased AAA incidence and growth in both patient cohorts studied. Dietary choline supplementation augmented plasma TMAO and aortic diameter in both mouse models of AAA, which was suppressed with poorly absorbed oral broad-spectrum antibiotics. Treatment with fluoromethylcholine ablated TMAO production, attenuated choline-augmented aneurysm initiation, and halted progression of an established aneurysm model. In addition, Fmo3-/- mice had reduced plasma TMAO and aortic diameters and were protected from AAA rupture compared with wild-type mice. RNA sequencing and functional analyses revealed choline supplementation in mice or TMAO treatment of human vascular smooth muscle cells-augmented gene pathways associated with the endoplasmic reticulum stress response, specifically the endoplasmic reticulum stress kinase PERK.

CONCLUSIONS

These results define a role for gut microbiota-generated TMAO in AAA formation through upregulation of endoplasmic reticulum stress-related pathways in the aortic wall. In addition, inhibition of microbiome-derived TMAO may serve as a novel therapeutic approach for AAA treatment where none currently exist.

Pathophysiology of venous ulceration

Our understanding of the pathophysiologic process of venous ulceration has dramatically increased during the past two decades because of dedicated, venous-specific basic science research. Currently, the mechanisms regulating venous ulceration are a combination of macroscopic and microscopic pathologic processes. Macroscopic alterations refer to pathologic processes related to varicose vein formation, vein wall architecture, and cellular abnormalities that impair venous function. These processes are primarily caused by genetic factors that lead to the destruction of normal vein wall architecture and venous hypertension. Venous hypertension causes a chronic inflammatory response that over time can cause venous ulceration. The inciting inflammatory injury is chronic extravasation of macromolecules and red blood cell degradation products and iron overload. Chronic inflammation causes white blood cell extravasation into the dermis with secretion of numerous proinflammatory cytokines. These cytokines transform the phenotype of fibroblasts to a contractile phenotype that increases tension in the dermis. In addition, iron overload keeps macrophages in an M1 phenotype, which leads to tissue destruction instead of dermal repair. Current surgical and medical therapies are primarily directed at eliminating venous hypertension and promoting venous ulcer wound healing. Despite advances in our understanding of venous ulcer formation and healing, ulcers still take an average of 6 months to heal, and ulcer recurrence rates at 5 years are >58%. To improve the care of patients with venous ulcers, we need to further our understanding of the underlying pathologic events that lead to ulcer formation, prevent healing, and decrease ulcer-free recurrence intervals.

Is there a role for placental senescence in the genesis of obstetric complications and fetal growth restriction?

The placenta ages as pregnancy advances, yet its continued function is required for a successful pregnancy outcome. Placental aging is a physiological phenomenon; however, there are some placentas that show signs of aging earlier than others. Premature placental senescence and aging are implicated in a number of adverse pregnancy outcomes, including fetal growth restriction, preeclampsia, spontaneous preterm birth, and intrauterine fetal death. Here we discuss cellular senescence, a state of terminal proliferation arrest, and how senescence is regulated. We also explore the role of physiological placental senescence and how aberrant placental senescence alters placental function, contributing to the pathophysiology of fetal growth restriction, preeclampsia, spontaneous preterm labor/birth, and unexplained fetal death.

Oxidative stress, placental ageing-related pathologies and adverse pregnancy outcomes

Oxidative stress (OS), an imbalance between free radical generation and antioxidant defence, is recognized as a key factor in the pathogenesis of adverse pregnancy outcomes. Although OS is a common future of normal pregnancy, persistent, overwhelming OS leads to consumption and decline of antioxidants, affecting placental antioxidant capacity and reducing systems. The accumulation of OS causes damage to lipids, proteins and DNA in the placental tissue that induces a form of accelerated ageing. Premature ageing of the placenta is associated with placental insufficiency that prevents the organ meeting the needs of the foetus, and as a consequence, the viability of the foetus is compromised. This review summarizes the literature regarding the role of OS and premature placental ageing in the pathophysiology of pregnancy complications.

Ionizing irradiation inhibits keloid fibroblast cell proliferation and induces premature cellular senescence

Keloids are one of the common refractory conditions in dermatology and aesthetic plastic surgery. The most effective treatment is superficial radiotherapy followed by surgical removal. The rate of recurrence is strongly associated with the total dose of ionizing irradiation, and the underlying mechanism remains unclear. In this study, we used primary keloid fibroblasts (KFb) isolated from patient samples to investigate the effects of X-ray radiation on cell proliferation, cell toxicity and cell cycle, as detected by CCK-8 assay kit and flow cytometer. In addition, we examined senescence-associated β-galactosidase activity and the associated gene expression using real-time polymerase chain reaction and western blot in KFb exposed to X-ray radiation. X-ray radiation inhibited cell proliferation and induced cell senescence in KFb in a dose-dependent manner. Inhibition of cell proliferation and induction of cellular senescence were mediated by interruption of the cell cycle with an extended G0/G1 phase. Furthermore, the expressions of senescence-associated genes p21, p16 and p27 were upregulated both at mRNA and protein levels in KFb exposed to X-ray radiation. Taken together, our data indicate that X-ray radiation may prevent the recurrence of keloids by controlling fibroblast proliferation, arresting the cell cycle and inducing premature cellular senescence.

DNA Damage Caused by Ionizing Radiation in Embryonic Diploid Fibroblasts WI-38 Induces Both Apoptosis and Senescence

Cellular response to ionizing radiation-induced damage depends on the cell type and the ability to repair DNA damage. Some types of cells undergo apoptosis, whereas others induce a permanent cell cycle arrest and do not proliferate. Our study demonstrates two types of response of embryonic diploid fibroblasts WI-38 to ionizing radiation. In the WI-38 cells p53 is activated, protein p21 increases, but the cells are arrested in G2 phase of cell cycle. Some of the cells die by apoptosis, but in remaining viable cells p16 increases, senescence associated DNA-damage foci occur, and senescence-associated beta-galactosidase activity increases, which indicate stress-induced premature senescence.

Cellular Senescence - its role in cancer and the response to ionizing radiation

Cellular senescence is a normal biological process that is initiated in response to a range of intrinsic and extrinsic factors that functions to remove irreparable damage and therefore potentially harmful cells, from the proliferative pool. Senescence can therefore be thought of in beneficial terms as a tumour suppressor. In contrast to this, there is a growing body of evidence suggesting that senescence is also associated with the disruption of the tissue microenvironment and development of a pro-oncogenic environment, principally via the secretion of senescence-associated pro-inflammatory factors. The fraction of cells in a senescent state is known to increase with cellular age and from exposure to various stressors including ionising radiation therefore, the implications of the detrimental effects of the senescent phenotype are important to understand within the context of the increasing human exposure to ionising radiation. This review will discuss what is currently understood about senescence, highlighting possible associations between senescence and cancer and, how exposure to ionising radiation may modify this.

Chromosome 9p21 variant predicts mortality after coronary artery bypass graft surgery

BACKGROUND

Recent genome-wide association studies have identified several chromosome 9p21 single nucleotide polymorphisms associated with coronary artery disease and myocardial infarction in nonsurgical populations. We have recently demonstrated an independent association between these 9p21 variants and perioperative myocardial injury after isolated primary coronary artery bypass graft (CABG) surgery. This study investigated the association of a 9p21 variant with mortality in patients after CABG surgery and its prognostic value to improve the EuroSCORE.

METHODS AND RESULTS

In a 2-center, prospective, observational study of 846 white primary CABG surgery patients, we genotyped rs10116277, the 9p21 variant with the strongest association to perioperative myocardial injury in our cohort. To estimate the utility of rs10116277 for predicting all-cause mortality within 5 years after surgery, a Cox proportional hazard model was constructed to estimate the hazard ratios (HR) and 95% confidence intervals (CI) while adjusting for demographics and clinical covariates. The homozygote minor allele of rs10116277 was associated with significantly increased risk of all-cause mortality even after adjusting for other clinical predictors of mortality in a Cox proportional hazards model (HR, 1.7; 95% CI, 1.1-2.7; P=0.026). Addition of rs10116277 to the logistic EuroSCORE also significantly improved model prediction for mortality (HR, 1.82; 95% CI, 1.15-2.88; P=0.01).

CONCLUSIONS

The 9p21 variant rs10116277 is independently associated with all-cause mortality after primary CABG surgery in whites and significantly improves the predictive value of the logistic EuroSCORE. Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifier: NCT00281164.

Common genetic variants on chromosome 9p21 predict perioperative myocardial injury after coronary artery bypass graft surgery

OBJECTIVE

Approximately 10% of patients undergoing cardiac surgery have perioperative myocardial injury. A recent genome-wide association study identified an association between myocardial infarction in nonsurgical populations and common genetic variants on chromosome 9p21. We hypothesized that these variants are also associated with perioperative myocardial injury after isolated primary coronary artery bypass graft surgery.

METHODS

In a prospective observational study of 846 Caucasian patients undergoing primary coronary bypass surgery at 2 US centers, we genotyped 61 linkage-disequilibrium tagging single nucleotide polymorphisms, encompassing 436 kbp of the 9p21 region. A multivariable logistic model was used to adjust for previously identified clinical covariates of perioperative myocardial injury. Perioperative myocardial injury was defined as a postoperative day 1 cardiac troponin I in the top 10th percentile (>9.13 microg/L) of the cohort. Multiple testing of single nucleotide polymorphisms was corrected for with family-wise errors.

RESULTS

Prior myocardial infarction and longer cardiopulmonary bypass time were significant independent predictors of perioperative myocardial injury. Levels of postoperative cardiac troponin I were incrementally increased for each additional copy of the risk alleles of 3 single nucleotide polymorphisms: rs10116277, rs6475606, and rs2383207. Adjusted additive odds ratios ranged between 1.64 and 1.79 (asymptotic P value between 3.7 x 10(-3) and 6 x 10(-4)) and remained significantly associated with perioperative myocardial injury even after accounting for clinical covariates including severity of coronary disease, and multiple comparisons.

CONCLUSIONS

We have now demonstrated that common genetic variants in the same 9p21 locus, previously known to be associated with myocardial infarction in nonsurgical populations, are also associated with perioperative myocardial injury after coronary artery bypass grafting. Further investigation is warranted to elucidate functional mechanisms.

Pathomolecular effects of homocysteine on the aging process: A new theory of aging

Homocysteine has been associated with the most common age-related diseases but never associated with the acceleration of the aging process. This theoretical paper will try to demonstrate the pro-aging effects of homocysteine at the molecular, cellular, and organ level. High homocysteine levels in homocystinuria are associated with premature disease of the cardiovascular, skeletal, neurological, and other systems. These observations are similar to those noted in the aging process and should be considered as a progeroid syndrome. There is enough scientific evidence to support that homocysteine accelerates the aging process at the cellular and at the organism level. Most importantly, decreasing homocysteine levels by dietary or pharmacological interventions could prolong maximum life span in humans and/or delay the onset of the most common age-related diseases.

Maggots and wound healing: an investigation of the effects of secretions from Lucilia sericata larvae upon the migration of human dermal fibroblasts over a fibronectin-coated surface

Lucilia sericata larvae, or greenbottle fly maggots, placed within chronic wounds have been observed to remove necrotic tissue and infection. They are also believed to actively promote granulation tissue formation. Interactions between fibroblasts and the surrounding extracellular matrix play a crucial role in tissue formation, influencing fibroblast proliferation, migration, and tissue remodeling. For example, the strength of cell adhesion to surfaces coated with extracellular matrix influences cell motility. L. sericata larval excretory/secretory products having previously been shown to modify fibroblast adhesion to collagen and particularly fibronectin, it was hypothesized that these products would alter fibroblast migration. This was investigated using a two-dimensional in vitro wound assay, time-lapse digital photography, enzyme class-specific substrates and inhibitors, and gel electrophoresis. Results showed that L. sericata excretory/secretory products promoted fibroblast migration upon a fibronectin-coated surface. This was related to the degradation of fibronectin by serine proteinases within maggot excretion/secretions. The presence of a metalloproteinase activity may also have played a role. Thus, a possible mechanism by which maggots enhance tissue formation within wounds may be via the promotion of fibroblast motility, providing for a wider distribution of viable fibroblasts.

Differential responsiveness of early- and late-passage endothelial cells to shear stress

BACKGROUND

The incidence of vascular disease increases with age. Because atherosclerosis and neointimal hyperplasia colocalize in areas of disturbed shear stress, the effects of orbital shear stress (SS) on endothelial cell proliferation, protein kinase B (Akt) activation, and functional activity were analyzed using a senescence model.

METHODS

Early- (p3 to 7) and late- (p28 to 32) passage bovine aortic endothelial cells were exposed to orbital SS (210 rpm) or static conditions (0 to 5 days). Cell proliferation was directly counted and confirmed with proliferating cell nuclear antigen reactivity. Phosphorylated and total Akt were assessed with Western blotting. Endothelial cell-induced smooth muscle cell migration was assessed with a Boyden chamber.

RESULTS

Late-passage endothelial cells demonstrated no increase in orbital SS stimulated proliferation compared with early-passage cells (P = .42). Late-passage endothelial cells demonstrated decreased Akt phosphorylation in response to SS compared with early passage cells (n = 6, P = .01). Late-passage cells induced 26% less smooth muscle cell migration than early-passage cells (n = 3, P = .03).

CONCLUSIONS

Late-passage endothelial cells demonstrate decreased proliferation, Akt phosphorylation, and secretion of smooth muscle cell chemoattractants in response to orbital SS compared with early passage cells. These results suggest that late-passage endothelial cells respond to SS differently than early-passage cells and confirm the utility of the in vitro senescence model.