Impairment of the transcriptional responses to oxidative stress in the heart of aged C57BL/6 mice

Propolis supplementation attenuates the negative effects of oxidative stress induced by paraquat injection on productive performance and immune function in turkey poults

Paraquat (PQ) is used as a herbicide in agriculture and causes oxidative and inflammatory damage to animal tissues. The current study was conducted to investigate the positive effects of dietary propolis (PR), as a potent naturally produced antioxidant, on growth performance and immune function of turkey poults exposed to oxidative stress induced by PQ injection. Native male turkey poults (n = 120, 49-d-old) were randomly assigned into 4 groups: poults received a basal diet with a daily subcutaneous PQ injection of 5 mg/kg BW for 7 consecutive days (PQ group), an experimental diet containing 1 g/kg PR with a daily subcutaneous PQ injection for 7 days (PR+PQ group), or received the experimental PR diet with a daily subcutaneous injection of 0.5 mL sterile saline for 7 days (PR group); while the control poults received a basal diet with a daily subcutaneous saline injection for 7 consecutive days (C group). The productive performance in the PQ group showed a significant (P < 0.05) reduction in the weight gain (WG) and feed intake (FI), and impaired feed conversion ratio (FCR). Propolis supplementation in the PR+PQ group significantly ameliorated the PQ effects on WG and FCR. Turkey poults of the PQ and PR+PQ groups had a significant augmentation in the blood malondialdehyde (MDA), tumor necrosis factor-α (TNFα), and corticosterone levels, and in contrast, a significant reduction in the triiodothyronine (T₃), when compared to the C group. While propolis significantly reduced the MDA and corticosterone, and increased the T₃ levels in the PR+PQ group compared to the PQ group. Furthermore, the dietary PR supplementation significantly limited the PQ-suppressive effects on cell- and humoral-mediated immunity and lymphocyte proliferation of turkey poults. In addition, propolis supplementation in the PR and PR+PQ groups markedly reversed the PQ-induced DNA fragmentation and heat shock protein 70 (Hsp70) over-expression in blood cells. It can be concluded that PR could improve turkey immunity and performance, particularly under inflammation and oxidative stress induced by PQ exposure.

MicroRNA-206 Protects against Myocardial Ischaemia-Reperfusion Injury in Rats by Targeting Gadd45β

MicroRNAs are widely involved in the pathogenesis of cardiovascular diseases through regulating gene expression via translational inhibition or degradation of their target mRNAs. Recent studies have indicated a critical role of microRNA-206 in myocardial ischaemia-reperfusion (I/R) injury. However, the function of miR-206 in myocardial I/R injury is currently unclear. The present study was aimed to identify the specific role of miR-206 in myocardial I/R injury and explore the underlying molecular mechanism. Our results revealed that the expression level of miR-206 was significantly decreased both in rat I/R group and H9c2 cells subjected to hypoxia/reoxygenation (H/R) compared with the corresponding control. Overexpression of miR-206 observably decreased infarct size and inhibited the cardiomyocyte apoptosis induced by I/R injury. Furthermore, bioinformatics analysis, luciferase activity and western blot assay proved that Gadd45β (growth arrest DNA damage-inducible gene 45β) was a direct target gene of miR-206. In addition, the expression of pro-apoptotic-related genes, such as p53, Bax and cleaved caspase3, was decreased in association with the down-regulation of Gadd45β. In summary, this study demonstrates that miR-206 could protect against myocardial I/R injury by targeting Gadd45β.

Transcriptional Signatures of Aging

Genome-wide studies of aging have identified subsets of genes that show age-related changes in expression. Although the types of genes that are age regulated vary among different tissues and organisms, some patterns emerge from these large data sets. First, aging is associated with a broad induction of stress response pathways, although the specific genes and pathways involved differ depending on cell type and species. In contrast, a wide variety of functional classes of genes are downregulated with age, often including tissue-specific genes. Although the upregulation of age-regulated genes is likely to be governed by stress-responsive transcription factors, questions remain as to why particular genes are susceptible to age-related transcriptional decline. Here, we discuss recent findings showing that splicing is misregulated with age. While defects in splicing could lead to changes in protein isoform levels, they could also impact gene expression through nonsense-mediated decay of intron-retained transcripts. The discovery that splicing is misregulated with age suggests that other aspects of gene expression, such as transcription elongation, termination, and polyadenylation, must also be considered as potential mechanisms for age-related changes in transcript levels. Moreover, the considerable variation between genome-wide aging expression studies indicates that there is a critical need to analyze the transcriptional signatures of aging in single-cell types rather than whole tissues. Since age-associated decreases in gene expression could contribute to a progressive decline in cellular function, understanding the mechanisms that determine the aging transcriptome provides a potential target to extend healthy cellular lifespan.

Role of MAPK-mediated endoplasmic reticulum stress signaling in the heart during aging in senescence-accelerated prone mice

Heart failure is typically related to aging as there is a definite relationship between age-related changes in the heart and the pathogenesis of heart failure. We have previously reported the involvement of p38 mitogen-activated protein kinase protein in cardiac function using animal models of heart failure. To further understand its relationship with aging-induced heart failure, we have compared its expression in the hearts of senescence accelerated-prone (SAMP8) mice and their control (SAMR1) with normal aging behavior. We have identified its activation along with reduced expression of 14-3-3η protein in SAMP8 mice hearts than in SAMR1 mice. To reveal the downstream signaling, we have measured the endoplasmic reticulum stress marker proteins along with some inflammatory and apoptosis markers and identified a significant increase in SAMP8 mice hearts than that of SAMR1. In addition, we have performed comet assay and revealed a significant DNA damage in the cardiomyocytes of SAMP8 mice when compared with SAMR1 mice. All these results demonstrate the role of 14-3-3η protein and the downstream mitogen-activated protein kinase-mediated endoplasmic reticulum stress, and apoptosis and DNA damage in aging-induced cardiac malfunction in SAMP8 mice. Thus targeting this signaling might be effective in treating age-related cardiac dysfunction. © 2016 BioFactors, 42(4):368-375, 2016.

Aging and Autophagy in the Heart

The aging population is increasing in developed countries. Because the incidence of cardiac disease increases dramatically with age, it is important to understand the molecular mechanisms through which the heart becomes either more or less susceptible to stress. Cardiac aging is characterized by the presence of hypertrophy, fibrosis, and accumulation of misfolded proteins and dysfunctional mitochondria. Macroautophagy (hereafter referred to as autophagy) is a lysosome-dependent bulk degradation mechanism that is essential for intracellular protein and organelle quality control. Autophagy and autophagic flux are generally decreased in aging hearts, and murine autophagy loss-of-function models develop exacerbated cardiac dysfunction that is accompanied by the accumulation of misfolded proteins and dysfunctional organelles. On the contrary, stimulation of autophagy generally improves cardiac function in mouse models of protein aggregation by removing accumulated misfolded proteins, dysfunctional mitochondria, and damaged DNA, thereby improving the overall cellular environment and alleviating aging-associated pathology in the heart. Increasing lines of evidence suggest that autophagy is required for many mechanisms that mediate lifespan extension, such as caloric restriction, in various organisms. These results raise the exciting possibility that autophagy may play an important role in combating the adverse effects of aging in the heart. In this review, we discuss the role of autophagy in the heart during aging, how autophagy alleviates age-dependent changes in the heart, and how the level of autophagy in the aging heart can be restored.

The role of D-GADD45 in oxidative, thermal and genotoxic stress resistance

There is a relationship between various cellular stress factors and aging. In earlier studies, we demonstrated that overexpression of the D-GADD45 gene increases the life span of Drosophila melanogaster. In this study, we investigate the relationship between D-GADD45 activity and resistance to oxidative, genotoxic and thermal stresses as well as starvation. In most cases, flies with constitutive and conditional D-GADD45 overexpression in the nervous system were more stress-resistant than ones without overexpression. At the same time, most of the studied stress factors increased D-GADD45 expression in the wild-type strain. The lifespan-extending effect of D-GADD45 overexpression was also retained after exposure to chronic and acute gamma-irradiation, with doses of 40 сGy and 30 Gy, respectively. However, knocking out D-GADD45 resulted in a significant reduction in lifespan, lack of radiation hormesis and radioadaptive response. A dramatic decrease in the spontaneous level of D-GADD45 expression was observed in the nervous system as age progressed, which may be one of the causes of the age-related deterioration of organismal stress resistance. Thus, D-GADD45 expression is activated by most of the studied stress factors, and D-GADD45 overexpression resulted in an increase of stress resistance.

Gadd45 proteins: relevance to aging, longevity and age-related pathologies

The Gadd45 proteins have been intensively studied, in view of their important role in key cellular processes. Indeed, the Gadd45 proteins stand at the crossroad of the cell fates by controlling the balance between cell (DNA) repair, eliminating (apoptosis) or preventing the expansion of potentially dangerous cells (cell cycle arrest, cellular senescence), and maintaining the stem cell pool. However, the biogerontological aspects have not thus far received sufficient attention. Here we analyzed the pathways and modes of action by which Gadd45 members are involved in aging, longevity and age-related diseases. Because of their pleiotropic action, a decreased inducibility of Gadd45 members may have far-reaching consequences including genome instability, accumulation of DNA damage, and disorders in cellular homeostasis - all of which may eventually contribute to the aging process and age-related disorders (promotion of tumorigenesis, immune disorders, insulin resistance and reduced responsiveness to stress). Most recently, the dGadd45 gene has been identified as a longevity regulator in Drosophila. Although further wide-scale research is warranted, it is becoming increasingly clear that Gadd45s are highly relevant to aging, age-related diseases (ARDs) and to the control of life span, suggesting them as potential therapeutic targets in ARDs and pro-longevity interventions.

Sirtuin-3 (Sirt3) regulates skeletal muscle metabolism and insulin signaling via altered mitochondrial oxidation and reactive oxygen species production

Sirt3 is a member of the sirtuin family of protein deacetylases that is localized in mitochondria and regulates mitochondrial function. Sirt3 expression in skeletal muscle is decreased in models of type 1 and type 2 diabetes and regulated by feeding, fasting, and caloric restriction. Sirt3 knockout mice exhibit decreased oxygen consumption and develop oxidative stress in skeletal muscle, leading to JNK activation and impaired insulin signaling. This effect is mimicked by knockdown of Sirt3 in cultured myoblasts, which exhibit reduced mitochondrial oxidation, increased reactive oxygen species, activation of JNK, increased serine and decreased tyrosine phosphorylation of IRS-1, and decreased insulin signaling. Thus, Sirt3 plays an important role in diabetes through regulation of mitochondrial oxidation, reactive oxygen species production, and insulin resistance in skeletal muscle.

Apolipoprotein D alters the early transcriptional response to oxidative stress in the adult cerebellum

The lipocalin Apolipoprotein D (ApoD), known to protect the nervous system against oxidative stress (OS) in model organisms, is up-regulated early in the mouse brain in response to the ROS generator paraquat. However, the processes triggered by this up-regulation have not been explored. We present here a study of the effect of ApoD on the early transcriptional changes upon OS in the mouse cerebellum using microarray profiling. ApoD-KO and transgenic mice over-expressing ApoD in neurons are compared to wild-type controls. In control conditions, ApoD affects the transcriptional profile of neuron and oligodendrocyte-specific genes involved in neuronal excitability, synaptic function, and myelin homeostasis. When challenged with paraquat, the absence of ApoD modifies the response of genes mainly related to OS management and myelination. Interestingly, the over-expression of ApoD in neurons almost completely abolishes the early transcriptional response to OS. We independently evaluate the expression of protein kinase Cδ, a gene up-regulated by OS only in the ApoD-KO cerebellum, and find it over-expressed in cultured ApoD-KO primary astrocytes, which points to a role for ApoD in astrocyte-microglia signaling. Our results support the hypothesis that ApoD is necessary for a proper response of the nervous system against physiological and pathological OS.

Distinct mechanisms of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrimidine resistance revealed by transcriptome mapping in mouse striatum

The etiology of idiopathic Parkinson's disease is thought to involve interplay between environmental factors and predisposing genetic traits, although the identification of genetic risk factors remain elusive. The neurotoxicant, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrimidine (MPTP) produces parkinsonian-like symptoms and pathology in mice and humans. As sensitivity to MPTP is genetically determined in mice this provides an opportunity to identify genes and biological mechanisms that modify the response to an exogenous agent that produces a Parkinson's disease-like condition. MPTP primarily targets dopaminergic nerve terminals in the striatum and elicits changes in striatal gene expression. Therefore, we used Affymetrix and qRT-PCR technology to characterize temporal mRNA changes in striatum in response to MPTP in genetically MPTP-sensitive, C57BL/6J, and MPTP-resistant Swiss Webster and BCL2-associated X protein (Bax)-/- mice. We identified three phases of mRNA expression changes composed of largely distinct gene sets. An early response (5 h) occurred in all strains of mice and multiple brain regions. In contrast, intermediate (24 h) and late (72 h) phases were striatum specific and much reduced in Swiss Webster, indicating these genes contribute and/or are responsive to MPTP-induced pathology. However, Bax-/- mice have robust intermediate responses. We propose a model in which the acute entry of MPP+ into dopaminergic nerve terminals damages them but is insufficient per se to kill the neurons. Rather, we suggest that the compromised nerve terminals elicit longer lasting transcriptional responses in surrounding cells involving production of molecules that feedback on the terminals to cause additional damage that results in cell death. In Swiss Webster, resistance lies upstream in the cascade of events triggered by MPTP and uncouples the acute events elicited by MPTP from the damaging secondary responses. In contrast, in Bax-/- mice resistance lies downstream in the cascade and suggests enhanced tolerance to the secondary insult rather than its attenuation.

AGEMAP: a gene expression database for aging in mice

We present the AGEMAP (Atlas of Gene Expression in Mouse Aging Project) gene expression database, which is a resource that catalogs changes in gene expression as a function of age in mice. The AGEMAP database includes expression changes for 8,932 genes in 16 tissues as a function of age. We found great heterogeneity in the amount of transcriptional changes with age in different tissues. Some tissues displayed large transcriptional differences in old mice, suggesting that these tissues may contribute strongly to organismal decline. Other tissues showed few or no changes in expression with age, indicating strong levels of homeostasis throughout life. Based on the pattern of age-related transcriptional changes, we found that tissues could be classified into one of three aging processes: (1) a pattern common to neural tissues, (2) a pattern for vascular tissues, and (3) a pattern for steroid-responsive tissues. We observed that different tissues age in a coordinated fashion in individual mice, such that certain mice exhibit rapid aging, whereas others exhibit slow aging for multiple tissues. Finally, we compared the transcriptional profiles for aging in mice to those from humans, flies, and worms. We found that genes involved in the electron transport chain show common age regulation in all four species, indicating that these genes may be exceptionally good markers of aging. However, we saw no overall correlation of age regulation between mice and humans, suggesting that aging processes in mice and humans may be fundamentally different.

Impaired p38 MAPK/HSP27 signaling underlies aging-related failure in opioid-mediated cardioprotection

Cardioprotection and preconditioning mediated via G-protein-coupled receptors may be lost or impaired with advancing age, limiting ischemic tolerance and the ability to pharmacologically protect older hearts from ischemic injury. Our preliminary findings indicated a loss of delta-opioid receptor-mediated protection in aged vs. young mouse hearts, which may involve alterations in protective kinase signaling. In the present study, we tested the hypothesis that aging-related loss of opioid-triggered cardioprotection involves failure to activate p38 MAPK and its distal signaling targets. Langendorff-perfused hearts from young (10-14 weeks) or aged (24-26 months) C57 mice underwent 25-min ischemia and 45-min reperfusion in the presence or absence of 1 micromol/l DPDPE (delta-opioid agonist) or 1 micromol/l anisomycin (activator of p38 MAPK), and functional recovery and protein activation/phosphorylation were assessed. Contractile recovery was similar in untreated young and aged hearts (50+/-2% and 53+/-5%, respectively), and was enhanced by DPDPE in young hearts only (67+/-3%). Immunoblot analysis revealed that DPDPE comparably activated or phosphorylated GRK2, Akt, ERK1/2 and p70S6 kinase in young and aged hearts, whereas aging abrogated the stimulatory effects of DPDPE on p38 MAPK and HSP27. Treatment with anisomycin elicited comparable activation of p38 MAPK and HSP27 in both young and aged hearts, coupled with a pronounced and equivalent cardioprotection in the two groups (73+/-3% and 77+/-2%, respectively), an effect abolished by the p38 MAPK inhibitor, SB203580. These data indicate that aging-related loss of delta-opioid-mediated cardioprotection involves failure to activate p38 MAPK and HSP27. Direct targeting of this pathway elicits comparable protection in both age groups.

Age-related loss of the DNA repair response following exposure to oxidative stress

Young (4- to 6-month-old) and aged (24- to 28-month-old) mice were exposed to 2-nitropropane (2-NP), a DNA oxidizing agent, and the ability to induce DNA polymerase beta (beta-pol) and AP endonuclease (APE) was determined. In contrast to the inducibility of these gene products in response to oxidative damage in young mice, aged mice showed a lack of inducibility of beta-pol and APE. APE protein level and endonuclease activity were both reduced 40% (p<.01) in response to 2-NP. Accordingly, the accumulation of DNA repair intermediates in response to 2-NP differed with age. Young animals accumulated 3'OH-containing DNA strand breaks, whereas the aged animals did not. A role for p53 in the difference in DNA damage response with age is suggested by the observation that the accumulation of p53 protein in response to DNA damage in young animals was absent in the aged animals. Our results are consistent with a reduced ability to process DNA damage with age.

Oxidative stress in leukocytes from young prematurely aging mice is reversed by supplementation with biscuits rich in antioxidants

Aging is associated with a progressive dysregulation of immune responses as a result of increased oxidative stress. Therefore, we have assessed the oxidative stress status of peritoneal leukocytes from young prematurely aging mice (PAM) as compared with non-prematurely aging mice (NPAM), as well as the effects on this oxidative stress of a dietary supplementation with biscuits rich in antioxidants (vitamin C, vitamin E, beta-carotenes, zinc and selenium). We found that, in the peritoneal leukocytes, the levels of several parameters of oxidation such as extracellular superoxide anion (O(2)(-)), Prostaglandin E(2) (PGE(2)), nitric oxide, oxidized glutathione (GSSG) and lipid peroxidation (malondialdehyde, MDA) were higher in PAM as compared with NPAM, whereas the antioxidant defences such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) activities, as well as reduced glutathione (GSH) levels, were decreased. Consequently, young PAM showed an oxidative stress in their leukocytes, which is characteristic of mice of an older chronological age. Antioxidant diet supplementation was able to restore redox homeostasis, increasing the antioxidant and decreasing the oxidant levels. Accordingly, supplementation with adequate levels of antioxidants, from an early age, could be useful to preserve health, especially in prematurely aging populations.

Expression profiling in the aging brain: a perspective

To evaluate molecular events associated with the aging process in animal models and human tissues, microarray analysis is performed at the regional and cellular levels to define transcriptional patterns or mosaics that may lead to better understanding of the mechanism(s) that drive senescence. In this review, we outline the experimental and analytical issues associated with high-throughput genomic analyses in aging brain and other tissues for a comprehensive evaluation of the current state of microarray analysis in aging paradigms. Ultimately, the goal of these studies is to apply functional genomics and proteomics approaches to aging research to develop new tools to assess age in cell- and tissue-specific manners in order to develop aging biomarkers for pharmacotherapeutic interventions and disease prevention.