Age-dependent increases in the oxidative damage of DNA, RNA, and their metabolites in normal and senescence-accelerated mice analyzed by LC-MS/MS: urinary 8-oxoguanosine as a novel biomarker of aging

Base excision repair and double strand break repair cooperate to modulate the formation of unrepaired double strand breaks in mouse brain

We lack the fundamental information needed to understand how DNA damage in the brain is generated and how it is controlled over a lifetime in the absence of replication check points. To address these questions, here, we integrate cell-type and region-specific features of DNA repair activity in the normal brain. The brain has the same repair proteins as other tissues, but normal, canonical repair activity is unequal and is characterized by high base excision repair (BER) and low double strand break repair (DSBR). The natural imbalance creates conditions where single strand breaks (SSBs) can convert to double strand breaks (DSBs) and reversibly switch between states in response to oxidation both in vivo and in vitro. Our data suggest that, in a normal background of repair, SSBs and DSBs are in an equilibrium which is pushed or pulled by metabolic state. Interconversion of SSB to DSBs provides a physiological check point, which would allow the formation of unrepaired DSBs for productive functions, but would also restrict them from exceeding tolerable limits.

Cardioprotective response and senescence in aged sEH null female mice exposed to LPS

Deterioration of physiological systems, like the cardiovascular system, occurs progressively with age impacting an individual's health and increasing susceptibility to injury and disease. Cellular senescence has an underlying role in age-related alterations and can be triggered by natural aging or prematurely by stressors such as the bacterial toxin lipopolysaccharide (LPS). The metabolism of polyunsaturated fatty acids by CYP450 enzymes produces numerous bioactive lipid mediators that can be further metabolized by soluble epoxide hydrolase (sEH) into diol metabolites, often with reduced biological effects. In our study, we observed age-related cardiac differences in female mice, where young mice demonstrated resistance to LPS injury, and genetic deletion or pharmacological inhibition of sEH using trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid attenuated LPS-induced cardiac dysfunction in aged female mice. Bulk RNA-sequencing analyses revealed transcriptomics differences in aged female hearts. The confirmatory analysis demonstrated changes to inflammatory and senescence gene markers such as Il-6, Mcp1, Il-1β, Nlrp3, p21, p16, SA-β-gal, and Gdf15 were attenuated in the hearts of aged female mice where sEH was deleted or inhibited. Collectively, these findings highlight the role of sEH in modulating the aging process of the heart, whereby targeting sEH is cardioprotective.NEW & NOTEWORTHY Soluble epoxide hydrolase (sEH) is an essential enzyme for converting epoxy fatty acids to their less bioactive diols. Our study suggests deletion or inhibition of sEH impacts the aging process in the hearts of female mice resulting in cardioprotection. Data indicate targeting sEH limits inflammation, preserves mitochondria, and alters cellular senescence in the aged female heart.

The intrinsic apoptotic pathway lies upstream of reactive species production in cortical neurons and age-related oxidative stress in the brain

A BAX- and mitochondria-dependent production of reactive oxygen species (ROS) and reactive species (reactive nitrogen species, RNS) lying downstream of these ROS occurs in apoptotic and nonapoptotic mouse sympathetic neurons and cerebellar granule cells in cell culture. These ROS have been shown to lie downstream of caspase 3 in mouse sympathetic neurons. Here we show that BAX is necessary for similar ROS production in apoptotic and nonapoptotic mouse cortical neurons in cell culture and that it also positively regulates oxidative stress in the brains of mice of different ages. Brains from mice with genetically reduced levels of mitochondrial superoxide dismutase 2 (SOD2) exhibited elevated levels of DNA strand breaks consistent with oxidative damage. Lipid peroxides were also elevated at some ages in comparison to the brains of wild type animals. BAX deletion in these mice reduced both brain DNA strand breaks and lipid peroxide levels to well below those of wild type animals. Deletion of caspase 3 greatly reduced age-augmented levels of brain oxidative stress markers including lipid peroxides, oxidized DNA, and nitrosylated proteins. These findings indicate that BAX contributes to ROS production in mouse cortical neurons, to oxidative stress their brains, and that this effect is likely mediated via caspase 3 activity.

Different Aspects of Aging in Migraine

Migraine is a common neurological disease displaying an unusual dependence on age. For most patients, the peak intensity of migraine headaches occurs in 20s and lasts until 40s, but then headache attacks become less intense, occur less frequently and the disease is more responsive to therapy. This relationship is valid in both females and males, although the prevalence of migraine in the former is 2-4 times greater than the latter. Recent concepts present migraine not only as a pathological event, but rather as a part of evolutionary adaptive response to protect organism against consequences of stress-induced brain energy deficit. However, these concepts do not fully explain that unusual dependence of migraine prevalence on age. Many aspects of aging, both molecular/cellular and social/cognitive, are interwound in migraine pathogenesis, but they neither explain why only some persons are affected by migraine, nor suggest any causal relationship. In this narrative/hypothesis review we present information on associations of migraine with chronological aging, brain aging, cellular senescence, stem cell exhaustion as well as social, cognitive, epigenetic, and metabolic aging. We also underline the role of oxidative stress in these associations. We hypothesize that migraine affects only individuals who have inborn, genetic/epigenetic, or acquired (traumas, shocks or complexes) migraine predispositions. These predispositions weakly depend on age and affected individuals are more prone to migraine triggers than others. Although the triggers can be related to many aspects of aging, social aging may play a particularly important role as the prevalence of its associated stress has a similar age-dependence as the prevalence of migraine. Moreover, social aging was shown to be associated with oxidative stress, important in many aspects of aging. In perspective, molecular mechanisms underlying social aging should be further explored and related to migraine with a closer association with migraine predisposition and difference in prevalence by sex.

Birth size and the serum level of biological age markers in men

Previous studies showed that intrauterine growth restrictions, resulting in smaller body size at birth, are associated with altered development and the risk of age-related diseases in adult life. Thus, prenatal development may predict aging trajectories in humans. The study aimed to verify if body size at birth is related to biological age in adult men. The study sample consisted of 159 healthy, non-smoking men with a mean age of 35.24 (SD 3.44) years. Birth weight and length were taken from medical records. The ponderal index at birth was calculated. Biological age was evaluated based on serum levels of s-Klotho, hsCRP, DHEA/S, and oxidative stress markers. Pregnancy age at birth, lifestyle, weight, cortisol, and testosterone levels were controlled. The results showed no relationship between birth size and s-Klotho, DHEA/S level, inflammation, or oxidative stress. Also, men born as small-for-gestational-age (N = 49) and men born as appropriate-for-gestational-age (N = 110) did not differ in terms of biological age markers levels. The results were similar when controlled for pregnancy week at birth, chronological age, BMI, testosterone, or cortisol level. The results suggest that there is no relationship between intrauterine growth and biomarkers of aging in men aged 30-45 years from the affluent population.

An integrated approach to evaluate acetamiprid-induced oxidative damage to tRNA in human cells based on oxidized nucleotide and tRNA profiling

Acetamiprid is poisonous to mammals due to severe acetamiprid-induced oxidative stress that could cause mitochondrial dysfunctions, lipid and protein oxidation, inflammation, apoptosis, and DNA damage. Evidence has accumulated for the role of oxidative stress in changing structures and functions of transfer RNAs (tRNAs) by inducing tRNA cleavage, reprogramming tRNA modifications and impairing aminoacyl-tRNA synthetase editing sites. However, the impact of acetamiprid-induced oxidative stress on tRNA is still unknown. Here, we investigated the effects of acetamiprid on cell viability, reactive oxygen species (ROS) levels, DNA damage, cellular oxidized nucleotide concentrations, and oxidative damage to tRNA in HepG2 cells and LO2 cells. Acetamiprid can cause the significant increment of ROS and DNA oxidative damage. In this study, an integrated approach was established to simultaneously study the network of oxidized nucleotides and explore the tRNA oxidative damage after acetamiprid exposure. A simple and high-throughput liquid chromatography with tandem mass spectrometry (LC-MS/MS) method coupled with (trimethylsilyl)diazomethane (TMSD) derivatization was successfully developed to quantify 12 cellular oxidized nucleotides that cannot be detected using traditional detection methods because of the huge interferences from naturally abundant nucleotides. Meanwhile, the accumulation rate and the locating sites of 8-oxo-2, 7-dihydro-guanine (8-oxo-G) in tRNA were inspected using the established N-(tert-Butyldimethylsilyl)-N-methyl-trifluoroacetamide (MTBSTFA) labeling-based tRNA profiling method. After acetamiprid treatment, the increment of oxidized nucleoside triphosphates is smaller than that of their corresponding mono- and diphosphates, as well as the dephosphorylated nucleosides, on account of the existence of sanitization enzymes. Several tRNA fragments, CUC[m1A]Gp, CACGp, [Cm]C[m2G]p, and DDGp, are significantly downregulated in acetamiprid-treated HepG2 cells, while only [Cm]C[m2G]p in acetamiprid-treated LO2 cells. According to the profiling results, the significantly changed fragment CUC[m1A]Gp might be caused by the oxidation of guanine (G) to form 8-oxo-G at position 15 in human tRNAphe([Gm]AA), providing more information about the effect of oxidized nucleobases on tRNA's functions.

DNA damage-induced stalling of transcription drives aging through gene expression imbalance

Age-related changes in gene expression have long been examined to understand the biology of aging. The hallmarks of aging are biological processes known to be associated with aging, but whether there is a unifying driver of these attributes, is not well understood. With the advent of technology over the last few years, it is quite clear that aging leads to global decline in transcription. In this Perspective, we highlight a new study in Nature Genetics that aimed to determine why global transcription rate reduces with age and how this phenomenon is the driver that interconnects multiple hallmarks of aging. This study recognizes that age-related accumulation of DNA damage, particularly transcription-blocking lesions, stalls RNA polymerase. This phenomenon affects longer genes leading to a gradual loss of transcription and skewing the transcriptome. In order to design a successful aging intervention, future work will be needed to test how some promising therapies in pre-clinical trials target affect transcriptional rate.

Cellular mechanisms in brain aging: Focus on physiological and pathological aging

Aging is a natural phenomenon characterized by accumulation of cellular damage and debris. Oxidative stress, cellular senescence, sustained inflammation, and DNA damage are the main cellular processes characteristic of aging associated with morphological and functional decline. These effects tend to be more pronounced in tissues with high metabolic rates such as the brain, mainly in regions such as the prefrontal cortex, hippocampus, and amygdala. These regions are highly related to cognitive behavior, and therefore their atrophy usually leads to decline in processes such as memory and learning. These cognitive declines can occur in physiological aging and are exacerbated in pathological aging. In this article, we review the cellular processes that underlie the triggers of aging and how they relate to one another, causing the atrophy of nerve tissue that is typical of aging. The main topic of this review to determine the central factor that triggers all the cellular processes that lead to cellular aging and discriminate between normal and pathological aging. Finally, we review how the use of supplements with antioxidant and anti-inflammatory properties reduces the cognitive decline typical of aging, which reinforces the hypothesis of oxidative stress and cellular damage as contributors of physiological atrophy of aging. Moreover, cumulative evidence suggests their possible use as therapies, which improve the aging population's quality of life.

8-oxo-dGTP curbs tumor development via S phase arrest and AIF-mediated apoptosis

Oxidative stress can attack precursor nucleotides, resulting in nucleic acid damage in cells. It remains unclear how 8-oxo-dGTP and 8-oxoGTP, oxidized forms of dGTP and GTP, respectively, could affect DNA or RNA oxidation levels and tumor development. To address this, we intravenously administered 8-oxo-dGTP and 8-oxoGTP to wild-type and MTH1-knockout mice. 8-oxoGTP administration increased frequency of tumor incidence, which is more prominent in MTH1-knockout mice. However, 8-oxo-dGTP treatment rather reduced tumor development regardless of the mouse genotype. The tumor suppressive effects of 8-oxo-dGTP were further confirmed using xenograft and C57/6J-Apc^Min/Nju mouse models. Mechanistically, 8-oxo-dGTP increased the 8-oxo-dG contents in DNA and DNA strand breakage, induced cell cycle arrest in S phase and apoptosis mediated by AIF, eventually leading to reduced tumor incidence. These results suggest distinct roles of 8-oxo-dGTP and 8-oxoGTP in tumor development.

Urinary 8-oxoGuo as a potential novel evaluation index for patients with nephrotic syndrome

Urinary 8-oxo-7,8-dihydroguanosine (8-oxoGuo) and 8-oxo-7,8-dihydro-2'- deoxyguanosine (8-oxodGuo) are considered biomarkers of oxidative stress, and patients with nephrotic syndrome have been reported to have increased oxidative stress levels. In this study, we aimed to assess the value of 8-oxoGuo and 8-oxodGuo as novel biomarkers to evaluate the severity of nephrotic syndrome. In total, 107 patients with nephrotic syndrome and 116 healthy controls were recruited for this study. The concentrations of urinary 8-oxoGuo and 8-oxodGuo were measured using isotope-labeled liquid chromatography with tandem mass spectrometry. Urinary creatinine was used to regulate 8-oxoGuo and 8-oxodGuo concentrations. Urinary 8-oxoGuo and 8-oxoGuo/Cr levels in patients with nephrotic syndrome were significantly higher than those in healthy control participants. 8-oxoGuo/Cr showed a positive correlation with the 24 h urinary total protein (UTP) and UTP levels and negative correlations with serum total protein and albumin levels. After treatment, urinary 8-oxoGuo and 8-oxoGuo/Cr levels were significantly lower in the group with a low 24 h-UTP value (<3.5 g/d) than in the high value group. 8-oxoGuo can be used as a feasible and reliable biomarker for the assessment of nephrotic syndrome.HighlightsUrinary 8-oxoGuo level was significantly increased in patients with nephrotic syndrome.Urinary 8-oxoGuo level increased with an increase in plasma protein and a decrease in urine protein.Urinary 8-oxoGuo level decreased with nephrotic syndrome remission when urinary microalbumin showed no significant change.Urinary 8-oxoGuo level can be used as novel biomarkers of nephrotic syndrome.

Cellular senescence: the good, the bad and the unknown

Cellular senescence is a ubiquitous process with roles in tissue remodelling, including wound repair and embryogenesis. However, prolonged senescence can be maladaptive, leading to cancer development and age-related diseases. Cellular senescence involves cell-cycle arrest and the release of inflammatory cytokines with autocrine, paracrine and endocrine activities. Senescent cells also exhibit morphological alterations, including flattened cell bodies, vacuolization and granularity in the cytoplasm and abnormal organelles. Several biomarkers of cellular senescence have been identified, including SA-βgal, p16 and p21; however, few markers have high sensitivity and specificity. In addition to driving ageing, senescence of immune and parenchymal cells contributes to the development of a variety of diseases and metabolic disorders. In the kidney, senescence might have beneficial roles during development and recovery from injury, but can also contribute to the progression of acute kidney injury and chronic kidney disease. Therapies that target senescence, including senolytic and senomorphic drugs, stem cell therapies and other interventions, have been shown to extend lifespan and reduce tissue injury in various animal models. Early clinical trials confirm that senotherapeutic approaches could be beneficial in human disease. However, larger clinical trials are needed to translate these approaches to patient care.

MTH1 suppression enhances the stemness of MCF7 through upregulation of STAT3

MTH1 protein can sanitize the damaged (d)NTP pool and MTH1 inhibitors have been developed to impede the growth of rapidly proliferating tumor cells; however, the effect of MTH1 inhibition on breast cancer stemness has not been reported yet. Here, we constructed breast cancer cell lines with the stable depletion of MTH1. MTH1 suppression clearly increased the ratio of CD44⁺CD24^-/low subpopulations and promoted the formation of tumorspheres in MCF7 and T47D cells. RNA expression profiling, RT-qPCR and Western blotting showed the upregulation of master stem cell transcription factors Sox2, Oct4 and Nanog in MTH1 knockdown cells. GSEA suggested and Western blotting verified that MTH1 knockdown increased the expression of phosphorylated STAT3 (Tyr705). Furthermore, we indirectly demonstrated that the increased concentration of 8-oxo-dGTP and 8-oxo-GTP in MTH1-knockdown cells and exogenous 8-oxoGTP, rather than 8-oxo-dGTP, could significantly increase the phosphorylation of STAT3. In conclusion, this work indicates that MTH1 inhibition increased the proportion of breast cancer stem cells (BCSCs) and promoted stemness properties in MCF7 cells.

Role of a Urinary Biomarker in the Common Mechanism of Physical Performance and Cognitive Function

Introduction

Healthy aging is described as a process of developing and maintaining intrinsic abilities, including physical and cognitive functions. Although oxidative stress is a common mechanism shared by loss of muscle strength and dementia, its relationship with decreased physical performance and cognitive impairment remains unclear. We aimed to investigate the role of urinary 8-oxo-7, 8-dihydroguanosine (8-oxoGsn), a biomarker of oxidative damage to RNA, in physical and cognitive decline.

Methods

The study followed a cross-sectional design and recruited 40–94-year-old inhabitants of Beijing, China (471 men and 881 women). The physical performance of the participants was assessed using handgrip strength, walking speed, and the repeated chair stand test. The cognitive function was assessed using the Montreal Cognitive Assessment (MoCA) 5-min protocol. Urinary 8-oxoGsn levels were measured for all participants.

Results

Participants with high urinary 8-oxoGsn levels were more likely to have low grip strength, slow walking speed, poor performance in the repeated chair stand test, and low scores on the MoCA 5-min protocol (odds ratio [OR] 3.43, 95% confidence interval [CI]: 1.52–7.76; OR 1.71, 95% CI: 1.16–2.53; OR 2.06, 95% CI: 0.92–4.63; OR 1.75, 95% CI: 1.18–2.58), after adjusting for age, sex, smoking habits, alcohol consumption, hypertension, diabetes, cerebro-cardiovascular disease, and chronic kidney disease.

Conclusion

Elevated levels of oxidative stress are independently associated with cognitive and physical impairment. Thus, these results can help in the early identification and development of strategies for the prevention and treatment of intrinsic capacity decline.

Alzheimer's disease: a tale of two diseases?

Sporadic late-onset Alzheimer's disease (SLOAD) and familial early-onset Alzheimer's disease (FEOAD) associated with dominant mutations in APP, PSEN1 and PSEN2, are thought to represent a spectrum of the same disorder based on near identical behavioral and histopathological features. Hence, FEOAD transgenic mouse models have been used in past decades as a surrogate to study SLOAD pathogenic mechanisms and as the gold standard to validate drugs used in clinical trials. Unfortunately, such research has yielded little output in terms of therapeutics targeting the disease's development and progression. In this short review, we interrogate the widely accepted view of one, dimorphic disease through the prism of the Bmi1+/- mouse model and the distinct chromatin signatures observed between SLOAD and FEOAD brains.

Urinary 8-oxo-7,8-dihydroguanosine levels are elevated in HCV-infected patients

HCV patients are usually under substantial oxidative stress because of viral infection. A total of 177 patients with HCV infection and 198 age- and sex-matched healthy controls were enrolled in this study. We evaluated the urinary levels of 8-oxo-7, 8-dihydro-2'deoxyguanosine (8-oxodGuo) and 8-oxo-7, 8-dihydroguanosine (8-oxoGuo) in patients with HCV infection and explored the factors affecting the urinary 8-oxodGuo or 8-oxoGuo levels. Biomarkers of liver function, cancer, and inflammation were determined. Nonparametric correlations were used to evaluate the correlation between 8-oxoGuo or 8-oxodGuo and various laboratory biochemical indicators. Results showed that the levels of urinary 8-oxoGuo both in male and female patients with HCV infection were significantly higher than those in healthy controls (both p < 0.0001), while the urinary 8-oxodGuo levels only in male patients with HCV infection were significantly higher than those in healthy controls (p < 0.01). Urinary 8-oxoGuo was significantly associated with the white blood cell count, C-reactive protein level, and 8-oxodGuo level (p = 0.016, p = 0.003, and p = 0.000, respectively). Urinary 8-oxodGuo was significantly associated with the white blood cell count and 8-oxoGuo level (p = 0.018 and p = 0.000, respectively). A regression equation of urinary 8-oxoGuo or 8-oxodGuo was also established using the biomarkers in plasma. The results suggested that patients with a high C-reactive protein level are likely to have high urinary 8-oxoGuo levels as well, which may be useful for assessing the level of inflammation and oxidative stress in HCV patients.Supplemental data for this article is available online at https://doi.org/10.1080/15257770.2021.1961272 .

Coping with RNA damage with a focus on APE1, a BER enzyme at the crossroad between DNA damage repair and RNA processing/decay

Interest in RNA damage as a novel threat associated with several human pathologies is rapidly increasing. Knowledge on damaged RNA recognition, repair, processing and decay is still scanty. Interestingly, in the last few years, more and more evidence put a bridge between DNA damage repair enzymes and the RNA world. The Apurinic/apyrimidinic endodeoxyribonuclease 1 (APE1) was firstly identified as a crucial enzyme of the base excision repair (BER) pathway preserving genome stability toward non-distorting DNA lesion-induced damages. Later, an unsuspected role of APE1 in controlling gene expression was discovered and its pivotal involvement in several human pathologies, ranging from tumor progression to neurodegenerative diseases, has emerged. Recent novel findings indicate a role of APE1 in RNA metabolism, particularly in processing activities of damaged (abasic and oxidized) RNA and in the regulation of oncogenic microRNAs (miRNAs). Even though the role of miRNAs in human pathologies is well-known, the mechanisms underlying their quality control are still totally unexplored. A detailed knowledge of damaged RNA decay processes in human cells is crucial in order to understand the molecular processes involved in multiple pathologies. This cutting-edge perspective article will highlight these emerging aspects of damaged RNA processing and decay, focusing the attention on the involvement of APE1 in RNA world.

Metabolomics Signatures of Aging: Recent Advances

Metabolomics is the latest state-of-the-art omics technology that provides a comprehensive quantitative profile of metabolites. The metabolites are the cellular end products of metabolic reactions that explain the ultimate response to genomic, transcriptomic, proteomic, or environmental changes. Aging is a natural inevitable process characterized by a time-dependent decline of various physiological and metabolic functions and are dominated collectively by genetics, proteomics, metabolomics, environmental factors, diet, and lifestyle. The precise mechanism of the aging process is unclear, but the metabolomics has the potential to add significant insight by providing a detailed metabolite profile and altered metabolomic functions with age. Although the application of metabolomics to aging research is still relatively new, extensive attempts have been made to understand the biology of aging through a quantitative metabolite profile. This review summarises recent developments and up-to-date information on metabolomics studies in aging research with a major emphasis on aging biomarkers in less invasive biofluids. The importance of an integrative approach that combines multi-omics data to understand the complex aging process is discussed. Despite various innovations in metabolomics and metabolite associated with redox homeostasis, central energy pathways, lipid metabolism, and amino acid, a major challenge remains to provide conclusive aging biomarkers.

Mutation analysis and prenatal diagnosis of a family with congenital contractural arachnodactyly

BACKGROUND

Congenital contractural arachnodactyly (CCA) is a rare autosomal dominant condition caused by mutations in the fibrillin 2 gene (FBN2). The primary clinical symptoms of CCA include multiple flexion contractures, arachnodactyly, dolichostenomelia, scoliosis, abnormal pinnae, muscular hypoplasia, and crumpled ears.

METHODS

We used whole-exome sequencing technology to examine an arthrogryposis multiplex congenita and used Sanger sequencing technology to genetically confirm its family.

RESULTS

FBN2 c.3344A>T(p.D1115V) was identified in this family with CCA in a pedigree. Prenatal diagnosis and counseling were carried out simultaneously to avoid the birth of the sick fetus.

CONCLUSION

The study is on FBN2 variant in CCA, which potentially having implications for genetic counseling and clinical management, our study may provide new insights into the cause and diagnosis of CCA.

Systemic RNA oxidation can be used as a biomarker of infection in challenged with Vibrio parahaemolyticus

More and more evidence support the concept that RNA oxidation plays a substantial role in the progress of multiple diseases; however, only a few studies have reported RNA oxidation caused by microbial pathogens. Urinary 8-oxo-7,8-dihydroguanosine (8-oxo-Gsn) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dGsn), which are broadly used as indicators of oxidative damage of RNA and DNA, were analyzed in this study to determine which can be used as a biomarker of infection in challenged with Vibrio parahaemolyticus (V. parahaemolyticus). In this work, 24 specific-pathogen-free (SPF) male SD rats were randomly divided into two groups: an infection group and a phosphate-buffered saline (PBS) control group. Our results proved that 8-oxo-Gsn rather than 8-oxo-dGsn was significantly increased after challenged with V. parahaemolyticus in urine and tissue samples of SD rats compared with the PBS control group. Simultaneously, white blood cells (WBCs) counts, intestinal inflammation and inflammatory factors (including CRP, IL-6, IL-1β, TNF-α, IL-10, and IL-17A) were also increased sharply. Which has more clinical value is that the trend of urinary 8-oxo-Gsn was consistent with WBCs, intestinal inflammation and all kinds of inflammatory factors. More importantly is that urinary 8-oxo-Gsn of infection group was positively correlated with WBCs and various inflammatory cytokines. In a word, our results demonstrated that as a systemic RNA oxidation biomarker, we hope 8-oxo-Gsn can be used as a biomarker of the severity of microbial pathogens infection, rather than a specific biomarker of microbial pathogens infection.

Short-term biological variation and Reference change values of urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine and 8-oxo-7,8-dihydroguanosine

AIM

The DNA and RNA oxidative damage products urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-odGsn) and 8-oxo-7,8-dihydroguanosine (8-oGsn) have potential use in clinical practice. However, biological variation (BV) and reference change values (RCVs) have not been established. The aim of this study was to establish the short-term between-subject BV(CV_G )_, within-subject BV(CV_I ), and RCVs for urinary 8-odGsn and 8-oGsn.

METHODS

First-morning midstream urine specimens were collected from 20 apparently healthy subjects(ten males and ten females) on five consecutive days. 8-odGsn and 8-oGsn were measured using LC-MS/MS, while urine creatinine (U-Cr) was also measured to correct their results. A two-level nested ANOVA was used to estimate the CV_I and CV_G. RESULTS: The values of CV_G for 8-odGsn, 8-odGsn/U-Cr, 8-oGsn, and 8-oGsn/U-Cr were 31.2%, 39.6%, 35.3%, and 28.8%, respectively, while CV_I for them were 40.5%, 9.0%, 33.5%, and 12.1%, respectively. The RCVs for 8-odGsn, 8-odGsn/U-Cr, 8-oGsn, and 8-oGsn/U-Cr were 112.5%, 26.7%, 93.7%, and 36.5%, respectively.

CONCLUSION

BV and RCVs were firstly established for 8-oxo-dGsn and 8-oGsn, and can be used in clinical practice.

The Significance of 8-oxoGsn in Aging-Related Diseases

Aging is a common risk factor for the occurrence and development of many diseases, such as Parkinson’s disease, Alzheimer’s disease, diabetes, hypertension, atherosclerosis and coronary heart disease, and cancer, among others, and is a key problem threatening the health and life expectancy of the elderly. Oxidative damage is an important mechanism involved in aging. The latest discovery pertaining to oxidative damage is that 8-oxoGsn (8-oxo-7,8-dihydroguanosine), an oxidative damage product of RNA, can represent the level of oxidative stress. The significance of RNA oxidative damage to aging has not been fully explained, but the relationship between the accumulation of 8-oxoGsn, a marker of RNA oxidative damage, and the occurrence of diseases has been confirmed in many aging-related diseases. Studying the aging mechanism, monitoring the aging level of the body and exploring the corresponding countermeasures are of great significance for achieving healthy aging and promoting public health and social development. This article reviews the progress of research on 8-oxoGsn in aging-related diseases.

The intrinsic apoptotic pathway lies upstream of oxidative stress in multiple organs

Oxidative stress increases with age in multiple organ systems and is implicated in the development of age-related pathologies in them. Studies from our laboratory show that the intrinsic pathway proapoptotic proteins BAX and caspase-3 (CASP3) lie upstream of mitochondrial production of oxidative stress-inducing reactive species (RS) such as reactive oxygen and reactive nitrogen species (ROS and RNS) in apoptotic and nonapoptotic neurons in cell culture. Our objective in this study was to determine if these findings could be generalized to the development of oxidative stress in nonneuronal tissues in vivo. We first investigated the effect of genetic deletion of Bax on DNA damage in the liver, heart and kidneys of female mice of increasing ages (5, 14, 22 months). The organs of the aged mice showed increased oxidative DNA strand breaks compared to young animals (5 month). Ablation of Bax greatly reduced this damage. We next assessed lipid peroxidation, DNA oxidation, and protein tyrosine nitration to determine whether Casp3 deletion reduces oxidative stress in the hearts, livers, and kidneys of 12-month-old female mice. Lipid peroxides and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels were much lower in organs from mice with depleted Casp3 than in those of wild type animals. Nitration of protein tyrosine residues, caused by RNS, was also significantly suppressed in the tissues of Casp3 null mice compared to those in wild type mice. Our findings indicate that BAX and CASP3 have a vital role in the generation of oxidative stress in organs of aged mice.

Increased Transglutaminase 2 Expression and Activity in Rodent Models of Obesity/Metabolic Syndrome and Aging

Diastolic dysfunction of the heart and decreased compliance of the vasculature and lungs (i.e., increased organ tissue stiffness) are known features of obesity and the metabolic syndrome. Similarly, cardiac diastolic dysfunction is associated with aging. Elevation of the enzyme transglutaminase 2 (TG2) leads to protein cross-linking and enhanced collagen synthesis and participates as a candidate pathway for development of tissue stiffness. With these observations in mind we hypothesized that TG2 may be elevated in tissues of a rat model of obesity/metabolic syndrome (the ZSF 1 rat) and a mouse model of aging, i.e., the senescent SAMP8 mouse. In the experiments reported here, TG2 expression and activity were found for the first time to be spontaneously elevated in organs from both the ZSF1 rat and the SAMP8 mouse. These observations are consistent with a hypothesis that a TG2-related pathway may participate in the known tissue stiffness associated with cardiac diastolic dysfunction in these two rodent models. The potential TG2 pathway needs better correlation with physiologic dysfunction and may eventually provide novel therapeutic insights to improve tissue compliance.

Urinary markers of oxidative stress respond to infection and late-life in wild chimpanzees

Oxidative stress (OS) plays a marked role in aging and results from a variety of stressors, making it a powerful measure of health and a way to examine costs associated with life history investments within and across species. However, few urinary OS markers have been examined under field conditions, particularly in primates, and their utility to non-invasively monitor the costs of acute stressors versus the long-term damage associated with aging is poorly understood. In this study, we examined variation in 5 urinary markers of oxidative damage and protection under 5 validation paradigms for 37 wild, chimpanzees living in the Kibale National Park, Uganda. We used 924 urine samples to examine responses to acute immune challenge (respiratory illness or severe wounding), as well as mixed-longitudinal and intra-individual variation with age. DNA damage (8-OHdG) correlated positively with all other markers of damage (F-isoprostanes, MDA-TBARS, and neopterin) but did not correlate with protection (total antioxidant capacity). Within individuals, all markers of damage responded to at least one if not both types of acute infection. While OS is expected to increase with age, this was not generally true in chimpanzees. However, significant changes in oxidative damage were detected within past-prime individuals and those close to death. Our results indicate that OS can be measured using field-collected urine and integrates short- and long-term aspects of health. They further suggest that more data are needed from long-lived, wild animals to illuminate if common age-related increases in inflammation and OS damage are typical or recently aberrant in humans.

Role of RNA Oxidation in Neurodegenerative Diseases

In the history of nucleic acid research, DNA has always been the main research focus. After the sketch of the human genome was completed in 2000, RNA has been started to gain more attention due to its abundancies in the cell and its essential role in cellular physiology and pathologies. Recent studies have shown that RNAs are susceptible to oxidative damage and oxidized RNA is able to break the RNA strand, and affect the protein synthesis, which can lead to cell degradation and cell death. Studies have shown that RNA oxidation is one of the early events in the formation and development of neurodegenerative disorders, including Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis. However, its molecular mechanism, as well as its impact on these diseases, are still unclear. In this article, we review the different types of RNA oxidative damage and the neurodegenerative diseases that are reported to be associated with RNA oxidative damage. In addition, we discuss recent findings on the association between RNA oxidative damage and the development of neurodegenerative diseases, which will have great significance for the development of novel strategies for the prevention and treatment of these diseases.

Urinary 8-oxo-7,8-dihydroguanosine as a potential biomarker of frailty for elderly patients with cardiovascular disease

The diagnosis of frailty is usually subjective, which calls for objective biomarkers in clinical medicine. 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGsn) and 8-oxo-7, 8-dihydroguanosine (8-oxoGsn) in urine are two aging biomarkers that have not been explored deeply in cases of frailty. A total of 508 elderly patients with cardiovascular disease (mean age 75.0 ± 6.5 years, 50.8% males) were enrolled consecutively. Frailty was assessed by the Fried phenotype (robust: 0 score; pre-frail: 1-2 scores; frail: 3-5 scores). The concentrations of 8-oxoGsn and 8-oxodGsn in urine were measured by improved ultra-high-performance liquid chromatography-mass spectrometry (UPLC-MS/MS). Urinary creatinine (Cre) was tested to correct the 8-oxoGsn and 8-oxodGsn levels. According to the Fried phenotype score, the proportions of robust, pre-frail, and frail subjects were 20.5% (104/508), 53.9% (274/508), and 25.6% (130/508), respectively. The urinary 8-oxoGsn/Cre (P < 0.001) differed significantly among these 3 groups, but the urinary 8-oxodGsn/Cre (P = 0.600) showed no marked difference. Univariate and multivariate logistic regression showed that the age (odds ratio [OR] = 1.090, P < 0.001), systolic blood pressure (OR = 0.981, P = 0.008), 8-oxoGsn/Cre (OR = 1.203, P = 0.007), hemoglobin (OR = 0.980, P = 0.007), and sodium (OR = 0.915, P = 0.044) were independently associated with frailty. The sensitivity and specificity to identify frailty were 53.08% and 71.96%, respectively, for 8-oxoGsn/Cre at the optimal cut-off value of 3.879 μmol/mol according to the maximal Youden index. Urinary 8-oxoGsn, as a recognized biomarker of RNA oxidation, is independently associated with frailty in elderly patients with cardiovascular disease. However, the urinary 8-oxodGsn shows no obvious correlation with frailty. To obtain a better diagnostic performance for frailty, more biomarkers from different pathophysiological pathways should be explored in the future.

A potential urinary biomarker to determine frailty status among older adults

BACKGROUND

Association of oxidative stress biomarkers with aging and several age-related diseases is well documented. However, the possible role of these factors on frailty status in older adults has not been extensively studied.

OBJECTIVE

To evaluate whether urinary 8-oxo-7,8-dihydroguanosine (8-oxo-Gsn), a biomarker of RNA oxidative damage, was independently associated with frailty.

METHODS

In this cross-sectional analysis, frailty phenotype was assessed among 230 participants living in a senior community. Participants received a comprehensive geriatric assessment. Serum high-sensitivity C-reactive protein (hsCRP), white blood cell count (WBC), urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine, and 8-oxo-Gsn were measured.

RESULTS

Participants' mean age was 83.9 ± 4.4 years. In total, 33 % were frail, 45 % were pre-frail, and 22 % were non-frail. Urinary 8-oxo-Gsn, serum hsCRP, and WBC were significantly higher in the frail group than in the non-frail and pre-frail groups (p-values < 0.05). Adjusting for age, sex, and Charlson comorbidity index, statistically significant positive associations with frailty were observed for urinary 8-oxo-Gsn (odds ratio [OR]: 1.70, 95 % confidence interval [CI]: 0.264-0.732) and hsCRP (OR: 1.337, 95 % CI: 0.089-0.412). Urinary 8-oxo-Gsn of 3.175 μmol/mol had the optimal predictive value for frailty, with an area under the receiver operating characteristic curve (AUC) of 0.72 (95 % CI: 0.649-0.788). The prediction probability combining urinary 8-oxo-Gsn and a simple question evaluating exhaustion had the optimal predictive value for frailty, with an AUC of 0.90 (p < 0.001, 95 % CI: 0.85-0.95).

CONCLUSION

Urinary 8-oxo-Gsn level was independently associated with frailty. This urinary biomarker may be a promising indicator of frailty.

On the epigenetic role of guanosine oxidation

Chemical modifications of DNA and RNA regulate genome functions or trigger mutagenesis resulting in aging or cancer. Oxidations of macromolecules, including DNA, are common reactions in biological systems and often part of regulatory circuits rather than accidental events. DNA alterations are particularly relevant since the unique role of nuclear and mitochondrial genome is coding enduring and inheritable information. Therefore, an alteration in DNA may represent a relevant problem given its transmission to daughter cells. At the same time, the regulation of gene expression allows cells to continuously adapt to the environmental changes that occur throughout the life of the organism to ultimately maintain cellular homeostasis. Here we review the multiple ways that lead to DNA oxidation and the regulation of mechanisms activated by cells to repair this damage. Moreover, we present the recent evidence suggesting that DNA damage caused by physiological metabolism acts as epigenetic signal for regulation of gene expression. In particular, the predisposition of guanine to oxidation might reflect an adaptation to improve the genome plasticity to redox changes.

Urinary bisphenol analogues concentrations and biomarkers of oxidative DNA and RNA damage in Chinese school children in East China: A repeated measures study

The associations between bisphenol analogues (BPs) exposure and oxidative damage was explored in this 3-year longitudinal study of 275 school children in East China. Nine BPs in first morning urine samples were measured to assess BPs exposure, and 8-hydroxydeoxyguanosine (8-OHdG) and 8-oxo-7,8-dihydroguanosine (8-OHG) were measured as biomarkers of oxidative DNA and RNA damage. Linear mixed model (LMM) was used for repeated measures analysis. School children were mainly exposed to BPA, BPS, BPF, and BPAF (detection frequencies: 97.9%, 42.2%, 13.3%, and 12.8%) with median concentrations of 1.55, 0.355, 0.236 and 0.238 μg g^-1_Cre, respectively. An interquartile range (IQR) increase in urinary BPA was significantly associated with 12.9% (95% CI: 6.1%, 19.6%) increase in 8-OHdG and 19.4% (95% CI: 11.7%, 27.1%) increase in 8-OHG, and for total of BPs (the sum of BPA, BPS, BPF, and BPAF), they were 17.4% (95% CI: 8.9%, 26.0%) for 8-OHdG and 25.9% (95% CI: 16.1%, 35.7%) for 8-OHG, respectively. BPS was positively associated with 8-OHG, but not with 8-OHdG. The study found positive associations of urinary levels of BPA and total BPs with 8-OHdG and 8-OHG and indicated that BPs exposure might cause oxidative RNA damage.

The mechanism of RNA oxidation involved in the development of heart failure

Heart failure (HF) has become a global public health problem due to its unclear pathogenesis. Our previous studies have found that RNA oxidation is associated with the occurrence and development of a variety of chronic diseases in the elderly, but whether RNA oxidation is related to the pathogenesis of HF remains unclear. Male Dahl salt-sensitive rats (DSSR) were divided into 8% NaCl groups and 0.3% NaCl groups. The blood pressure of DSSR, HE staining of cardiac tissue, cardiac function index of colour Doppler echocardiography and plasma N-terminal probrain Natriuretic Peptide (NT-ProBNP) were used to evaluate the model making. The levels of 8-hydroxyguanosine (8-oxoGsn) and 8-hydroxydeoxyguanosine (8-oxodGsn) in myocardium and urine of DSSR were determined by high-performance liquid chromatography-mass spectrometry (LC-MS/MS). The expression of ERK-MAPK pathway and MTH1 was detected by Western blot (WB). Rats in the 8% NaCl group developed heart failure symptoms such as increased blood pressure, myocardial hypertrophy, decreased diastolic function, and increased plasma NT-ProBNP. The content of 8-oxoGsn in urine and heart tissue also increased, which was positively correlated with the related indicators of heart failure. This process is also accompanied by the sequential activation of ERK-MAPK pathway molecules and the increase of MTH1. The mechanism of RNA oxidation and inhibition is related to the occurrence and development of HF, which may be involved through ERK-MAPK pathway.

Nuclear Genomic Instability and Aging

The nuclear genome decays as organisms age. Numerous studies demonstrate that the burden of several classes of DNA lesions is greater in older mammals than in young mammals. More challenging is proving this is a cause rather than a consequence of aging. The DNA damage theory of aging, which argues that genomic instability plays a causal role in aging, has recently gained momentum. Support for this theory stems partly from progeroid syndromes in which inherited defects in DNA repair increase the burden of DNA damage leading to accelerated aging of one or more organs. Additionally, growing evidence shows that DNA damage accrual triggers cellular senescence and metabolic changes that promote a decline in tissue function and increased susceptibility to age-related diseases. Here, we examine multiple lines of evidence correlating nuclear DNA damage with aging. We then consider how, mechanistically, nuclear genotoxic stress could promote aging. We conclude that the evidence, in toto, supports a role for DNA damage as a nidus of aging.

An Ecologist’s Guide to Mitochondrial DNA Mutations and Senescence

Longevity plays a key role in the fitness of organisms, so understanding the processes that underlie variance in senescence has long been a focus of ecologists and evolutionary biologists. For decades, the performance and ultimate decline of mitochondria have been implicated in the demise of somatic tissue, but exactly why mitochondrial function declines as individual’s age has remained elusive. A possible source of decline that has been of intense debate is mutations to the mitochondrial DNA. There are two primary sources of such mutations: oxidative damage, which is widely discussed by ecologists interested in aging, and mitochondrial replication error, which is less familiar to most ecologists. The goal of this review is to introduce ecologists and evolutionary biologists to the concept of mitochondrial replication error and to review the current status of research on the relative importance of replication error in senescence. We conclude by detailing some of the gaps in our knowledge that currently make it difficult to deduce the relative importance of replication error in wild populations and encourage organismal biologists to consider this variable both when interpreting their results and as viable measure to include in their studies.

Classification and Temporal Variability in Urinary 8-oxodG and 8-oxoGuo: Analysis by UHPLC-MS/MS

Oxidative stress damage has been found to be associated with exposure of children to environmental pollutants, but there are few data on the variability of urinary oxidative stress biomarkers and the accuracy of biomarker concentration classification. We performed a longitudinal study in Chinese school-aged children to investigate the variability of urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanosine (8-oxoGuo) concentrations and the ability of a single first morning urine sample to assess accuracy and sensitivity of biomarkers concentration classification. After adjusting for both creatinine and specific gravity, we characterized the distribution and reproducibility of repeated measurement of 8-oxodG and 8-oxoGuo by using intraclass correlation coefficients (ICCs) derived from linear mixed model and performed surrogate category analyses to determine whether a single spot sample could accurately classify 8-oxodG and 8-oxoGuo levels. Results indicated that the geometric mean (GM) concentrations of 8-oxodG and 8-oxoGuo were 3.865 ng/mL and 5.725 ng/mL, respectively. High variability of 8-oxodG and 8-oxoGuo was observed in the single spot first morning urine sample (ICC = 0.25 and 0.18, respectively). Three repeated urinary specimens achieved sensitivity of 0.87 for 8-oxodG and 0.83 for 8-oxoGuo in low tertile and sensitivity of 0.78 in high tertile. But classification in medium tertile was less accurate for both 8-oxodG and 8-oxoGuo. In conclusion, high variability of urinary 8-oxodG and 8-oxoGuo levels results in repeated samplings needed for accurate classification.

Mitochondrial DNA Damage Does Not Determine C. elegans Lifespan

The mitochondrial free radical theory of aging (mFRTA) proposes that accumulation of oxidative damage to macromolecules in mitochondria is a causative mechanism for aging. Accumulation of mitochondrial DNA (mtDNA) damage may be of particular interest in this context. While there is evidence for age-dependent accumulation of mtDNA damage, there have been only a limited number of investigations into mtDNA damage as a determinant of longevity. This lack of quantitative data regarding mtDNA damage is predominantly due to a lack of reliable assays to measure mtDNA damage. Here, we report adaptation of a quantitative real-time polymerase chain reaction (qRT-PCR) assay for the detection of sequence-specific mtDNA damage in C. elegans and apply this method to investigate the role of mtDNA damage in the aging of nematodes. We compare damage levels in old and young animals and also between wild-type animals and long-lived mutant strains or strains with modifications in ROS detoxification or production rates. We confirm an age-dependent increase in mtDNA damage levels in C. elegans but found that there is no simple relationship between mtDNA damage and lifespan. MtDNA damage levels were high in some mutants with long lifespan (and vice versa). We next investigated mtDNA damage, lifespan and healthspan effects in nematode subjected to exogenously elevated damage (UV- or γ-radiation induced). We, again, observed a complex relationship between damage and lifespan in such animals. Despite causing a significant elevation in mtDNA damage, γ-radiation did not shorten the lifespan of nematodes at any of the doses tested. When mtDNA damage levels were elevated significantly using UV-radiation, nematodes did suffer from shorter lifespan at the higher end of exposure tested. However, surprisingly, we also found hormetic lifespan and healthspan benefits in nematodes treated with intermediate doses of UV-radiation, despite the fact that mtDNA damage in these animals was also significantly elevated. Our results suggest that within a wide physiological range, the level of mtDNA damage does not control lifespan in C. elegans.

Higher Number of Night Shifts Associates with Good Perception of Work Capacity and Optimal Lung Function but Correlates with Increased Oxidative Damage and Telomere Attrition

Sleep deprivation and the consequent circadian clock disruption has become an emergent health question being associated with premature aging and earlier chronic diseases onset. Night-shift work leads to circadian clock misalignment, which is linked to several age-related diseases. However, mechanisms of this association are not well understood. Aim of this study is to explore in night-shift workers early indicators of oxidative stress response and biological aging [oxidized/methylated DNA bases and leukocytes telomere length (LTL)] and late indicators of functional aging [lung function measurements (FEV1 and FVC)] in relation to personal evaluation of work capacity, measured by work ability index (WAI). One hundred fifty-five hospital workers were studied within the framework of a cross-sectional study. We collected physiological, pathological, and occupational history including pack-years, alcohol consumption, physical activity, and night shifts, together with blood and urine samples. Relationships were appraised by univariate and multivariate ordered-logistic regression models. We found that workers with good and excellent WAI present higher FEV1 (p< 0.01) and number of night-work shifts (p<0.05), but they reveal higher urinary levels of 8-oxoGua (p<0.01) and shorter LTL (p<0.05). We confirmed that higher work ability was prevalent among chronological younger workers (p<0.05), who have also a significant reduced number of diseases, particularly chronic (p<0.01) and musculoskeletal diseases (p<0.01). The new findings which stem from our work are that subjects with the highest work ability perception may have more demanding and burdensome tasks; they in fact present the highest number of night-shift work and produce unbalanced oxidative stress response that might induce premature aging.

Oxidative DNA Damage-Mediated Genomic Heterogeneity Is Regulated by NKX3.1 in Prostate Cancer

The 8-hydroxy-2'-deoxyguanosine (8-OHdG) damages are base damages induced by reactive oxygen species. We aimed to investigate the role of Androgen Receptor and NKX3.1 in 8-OHdG formation and repair activation by quantitating the DNA damage using Aklides.NUK system. The data demonstrated that the loss of NKX3.1 resulted in increased oxidative DNA damage and its overexpression contributes to the removal of menadione-induced 8-OHdG damage even under oxidative stress conditions. Moreover, 8-oxoguanine DNA glycosylase-1 (OGG1) expression level positively correlates to NKX3.1 expression. Also in this study, first time a reliable cell-based quantitation method for 8-OHdG damages is reported and used for data collection.

The Naked Mole Rat: A Unique Example of Positive Oxidative Stress

The oxidative stress theory of aging, linking reactive oxygen species (ROS) to aging, has been accepted for more than 60 years, and numerous studies have associated ROS with various age-related diseases. A more precise version of the theory specifies that mitochondrial oxidative stress is a direct cause of aging. The naked mole rat, a unique animal with exceptional longevity (32 years in captivity), appears to be an ideal model to study successful aging and the role of ROS in this process. Several studies in the naked mole rat have shown that these animals exhibit a remarkable resistance to oxidative stress. At low concentrations, ROS serve as second messengers, and these important intracellular signalling functions are crucial for the regulation of cellular processes. In this review, we examine the literature on ROS and their functions as signal transducers. We focus specifically on the longest-lived rodent, the naked mole rat, which is a perfect example of the paradox of living an exceptionally long life with slow aging despite high levels of oxidative damage from a young age.

Oxidative DNA and RNA damage and their prognostic values during Salmonella enteritidis-induced intestinal infection in rats

Emerging evidence suggests that microbial pathogens may induce oxidative stress in infected hosts. The aim of the present study was to investigate the relationship between changes in oxidative stress and intestinal infection with and without antibiotic treatment in animal models. Sprague-Dawley (SD) rats were divided into three groups: rats infected with Salmonella enterica serovar Enteritidis (S. enteritidis), rats infected with S. enteritidis followed by norfloxacin treatment, and the control group. To evaluate oxidative stress changes, levels of 8-oxo-7,8-dihydroguanosine (8-oxo-Gsn) and 8-oxo-7,8-dihydro-2-deoxyguanosine (8-oxo-dGsn), which represented oxidative damage to RNA and DNA, respectively, were analysed in urine and tissue samples. In urine, the level of 8-oxo-Gsn increased significantly after oral exposure to S. enteritidis (p ≤ 0.001) and returned to baseline after recovery. Notably, norfloxacin treatment decreased the level of 8-oxo-Gsn in urine significantly (p = 0.001). Changes of 8-oxo-Gsn measured in tissues from the small intestine, colon, liver and spleen were consistent with 8-oxo-Gsn measured in urine. Our study suggested that 8-oxo-Gsn in urine may serve as a highly sensitive biomarker for evaluating the severity of S. enteritidis infection and the effectiveness of antibiotic treatment against infection.

Transcriptional mutagenesis mediated by 8-oxoG induces translational errors in mammalian cells

Reactive oxygen species formed within the mammalian cell can produce 8-oxo-7,8-dihydroguanine (8-oxoG) in mRNA, which can cause base mispairing during gene expression. Here we found that administration of 8-oxoGTP in MTH1-knockdown cells results in increased 8-oxoG content in mRNA. Under this condition, an amber mutation of the reporter luciferase is suppressed. Using second-generation sequencing techniques, we found that U-to-G changes at preassigned sites of the luciferase transcript increased when 8-oxoGTP was supplied. In addition, an increased level of 8-oxoG content in RNA induced the accumulation of aggregable amyloid β peptides in cells expressing amyloid precursor protein. Our findings indicate that 8-oxoG accumulation in mRNA can alter protein synthesis in mammalian cells. Further work is required to assess the significance of these findings under normal physiological conditions.

Effects of two lichen acids isolated from Pseudevernia furfuracea (L.) Zopf in cultured human lymphocytes

The present study aims at assessing the efficacies of olivetoric acid (OA) and physodic acid (PA) isolated from Pseudevernia furfuracea (L.) Zopf (Parmeliaceae) in human lymphocytes (HLs) in vitro. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and lactate dehydrogenase assays were performed to establish cytotoxicity in HLs. Besides, oxidative stress and genotoxicity were monitored by estimating the changes of total oxidative stress (TOS) and 8-hydroxy-2′-deoxyguanosine (8-OH-dG) levels, respectively, in HLs. At the same time, OA- and PA-induced total antioxidant capacity (TAC) levels in HLs were determined. Although especially low concentrations of OA (IC50=109.94 mg/L) and PA (IC50=665.49 mg/L) did not show cytotoxic effect at high levels in HLs, it was revealed that cytotoxicity was significantly (p<0.05) associated with oxidative stress and genotoxicity via correlation analysis. While TOS level in HLs did not statistically (p>0.05) increase in the presence of all treatments (0.5–100 mg/L) of PA, TAC level was increased by PA applications in certain concentrations (0.5–10 mg/L). Overall, the obtained data indicate that OA and especially PA as lichen compounds that do not cause oxidative stress can be a new resource of therapeutics as recognized in the present study with their high antioxidant features.

Urinary 8-oxo-7,8-dihydroguanosine as a Potential Biomarker of Aging

Background: A molecular biomarker of physiologic age, as opposed to chronologic age, is needed in clinical medicine. 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGsn) and 8-oxo-7, 8-dihydroguanosine (8-oxoGsn) are two promising aging biomarkers.

Methods: A total of 1,228 healthy Chinese residents (613 males and 615 females) 2–90 years of age were randomly selected. Spot urine samples were collected, and the concentrations of 8-oxodGsn and 8-oxoGsn were measured using ultra-high-performance liquid chromatography with a triple quadrupole mass spectrometer (UPLC-MS/MS). Method validation, including accuracy, precision, linearity and quantification limit, was performed. The relationship between oxidized guanosine and age/gender was evaluated.

Results: 8-oxodGsn and 8-oxoGsn were eluted at 1.61 and 1.30 min, respectively. The calibration curve was linear in the range of 0.2–500 ng/ml for both analytes. The lowest limit of quantification (LLOQ) was 0.2 ng/ml for 8-oxodGsn and 0.1 ng/ml for 8-oxoGsn. There was an age-dependent increase in the biomarkers from the 21- to 30-year-old group to the 81- to 90-year-old group in both genders. In the subjects older than 61 years of age, the levels of 8-oxodGsn as well as 8-oxoGsn in urine were much higher in females than in males. The content of 8-oxoGsn correlated more closely with age and was higher (approximately 2-fold) than that of 8-oxodGsn for a given individual.

Conclusions: 8-oxodGsn and 8-oxoGsn can be easily measured by UPLC-MS/MS. Urinary 8-oxoGsn may be a potential biomarker to determine a person's physiologic age and identify individuals at high risk of developing age-associated disease.

Increased oxidative damage of RNA in liver injury caused by hepatitis B virus (HBV) infection

To evaluate the urinary levels of 8-oxo-7,8-dihydro-2'deoxyguanosine (8-oxo-dGsn) and 8-oxo-7,8-dihydroguanosine (8-oxo-Gsn) in liver injury patients with hepatitis B virus (HBV) infection and to explore the relationship between urinary 8-oxo-dGsn or 8-oxo-Gsn and degree of liver damage. We enrolled 138 liver injury patients with HBV infection and 169 age- and sex-matched healthy controls in this study. A sensitive and accurate isotope-diluted liquid chromatograph mass spectrometer/mass spectrometer (LC-MS/MS) method was used to measure the urinary levels of 8-oxo-Gsn and 8-oxo-dGsn. Simultaneously, pathological analysis of liver biopsy tissues was carried out, and immunohistochemistry was carried out for 8-oxo-Guo, 8-oxo-dGuo and MTH1 protein in some liver injury tissues. We analysed the correlation between the degrees of inflammation and fibrosis and levels of 8-oxo-Gsn and 8-oxo-dGsn. We also analysed the levels of urinary 8-oxo-Gsn and 8-oxo-dGsn with clinical data of HBeAg, HBsAg, and HBV genotype and detected the levels of plasma aspartate aminotransferase, alanine aminotransferase (AST), platelet, alkaline phosphatase, prothrombin time (PT) and HBV DNA, and calculated the aspartate amino transferase-to-platelet ratio index (APRI) score. Nonparametric correlations were used to evaluate the correlation between 8-oxo-Gsn, 8-oxo-dGsn or APRI and various laboratory biochemical indicators. Results showed that the levels of urinary 8-oxo-Gsn and 8-oxo-dGsn in patients with liver injury were significantly higher than those of healthy controls (both p < .001). Urinary 8-oxo-Gsn was significantly associated with AST, APRI and PT (p = .013, p = .026 and p = .049). The receiver operating characteristic curves of 8-oxo-Gsn were 0.696 (0.632-0.759) and 0.731 (0.672-0.790) for inflammatory activity and fibrosis, respectively. Patients with higher levels of urinary 8-oxo-Gsn are more likely to have a high degree of fibrosis and urinary 8-oxo-Gsn may have a great potential in assessing liver fibrosis.

MutT-related proteins are novel progression and prognostic markers for colorectal cancer

Background

MutT-related proteins, including MTH1, MTH2, MTH3 and NUDT5, can effectively degrade 8-oxoGua-containing nucleotides. The MTH1 expression is elevated in many types of human tumors and MTH1 overexpression correlates with the tumor pathological stage and poor prognosis. However, the expression of other MutT-related proteins in human cancers remains unknown. The present study systematically investigated the expression of MTH1, MTH2, MTH3 and NUDT5 in human colorectal cancer to establish its clinical significance.

Methods

Amounts of MutT-related mRNA and protein in CRC cell lines were assessed by qRT-PCR and Western blotting, respectively. Furthermore, the MutT-related protein expression was evaluated by immunohistochemical staining of tissue microarrays containing 87 paired CRC tissues and by Western blotting of 44 CRC tissue samples. Finally, the effect of knockdown of MutT-related proteins on CRC cell proliferation was investigated.

Results

The expression of MTH1, MTH2, MTH3 and NUDT5 was significantly higher in CRC cells and CRC tissues than normal cells and tissues, and this phenomenon was significantly associated with AJCC stage and lymph node metastasis of CRC specimens. CRC patients with high expression of MTH1, MTH2 or NUDT5 had an extremely poor overall survival after surgical resection. Notably, NUDT5 was an independent prognostic factor of CRC patients. We found that knockdown of MutT-related proteins inhibited CRC cell proliferation.

Conclusions

We showed for the first time that MutT-related proteins play an important role in CRC progression and prognosis. Further investigations are needed to elucidate the role of these proteins in CRC progression and their potential use for therapeutic targets.

Increased Oxidative Damage of RNA in Early-Stage Nephropathy in db/db Mice

To evaluate RNA oxidation in the early stage of diabetic nephropathy, we applied an accurate method based on isotope dilution high-performance liquid chromatography-triple quadruple mass spectrometry to analyze the oxidatively generated guanine nucleosides in renal tissue and urine from db/db mice of different ages. We further investigated the relationship between these oxidative stress markers, microalbumin excretion, and histological changes. We found that the levels of 8-oxo-7,8-dihydroguanosine (8-oxoGuo) and 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo) were increased in the urine and renal tissue of db/db mice and db/db mice with early symptoms of diabetic nephropathy suffered from more extensive oxidative damage than lean littermate control db/m mice. Importantly, in contrast to the findings in db/m mice, the 8-oxoGuo levels in the urine and renal tissue of db/db mice were higher than those of 8-oxodGuo at four weeks. These results indicate that RNA oxidation is more apparent than DNA oxidation in the early stage of diabetic nephropathy. RNA oxidation may provide new insight into the pathogenesis of diabetic nephropathy, and urinary 8-oxoGuo may represent a novel, noninvasive, and easily detected biomarker of diabetic kidney diseases if further study could clarify its source and confirm these results in a large population study.

Levels of 8-oxo-dGsn and 8-oxo-Gsn in random urine are consistent with 24 h urine in healthy subjects and patients with renal disease

Oxidatively generated damage to nucleic acids may play an important role in the pathophysiological processes of a variety of diseases. 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dGsn) and 8-oxo-7,8-dihydroguanosine (8-oxo-Gsn) are oxidatively generated products of DNA and RNA, respectively. Our previous studies have suggested that the amounts of 8-oxo-dGsn and 8-oxo-Gsn in urine were considerably higher than other body fluid or tissue. The aim of this study was to investigate whether 8-oxo-dGsn and 8-oxo-Gsn levels in random urine samples are consistent with those in 24 h urine samples in healthy subjects and patients with renal disease. A total of 16 healthy subjects and 104 renal disease patients were enrolled in this study, and their random and 24 h urine samples were collected. The levels of urinary 8-oxo-dGsn and 8-oxo-Gsn were quantified by LC-MS/MS and corrected by creatinine. Regardless of healthy subjects or renal disease patients, the levels of oxidised nucleosides in random urine samples were consistent with 24 h urine samples. Regardless of the age bracket, there is no significant difference between random samples and 24 h urine samples. In conclusion, 8-oxo-dGsn and 8-oxo-Gsn levels in random urine samples could replace those in 24 h urine samples, and were considered as the representative of the level of systemic oxidative stress for the whole day.

Signaling Networks Determining Life Span

The health of an organism is orchestrated by a multitude of molecular and biochemical networks responsible for ensuring homeostasis within cells and tissues. However, upon aging, a progressive failure in the maintenance of this homeostatic balance occurs in response to a variety of endogenous and environmental stresses, allowing the accumulation of damage, the physiological decline of individual tissues, and susceptibility to diseases. What are the molecular and cellular signaling events that control the aging process and how can this knowledge help design therapeutic strategies to combat age-associated diseases? Here we provide a comprehensive overview of the evolutionarily conserved biological processes that alter the rate of aging and discuss their link to disease prevention and the extension of healthy life span.