Age-associated changes in oxidative damage and the activity of antioxidant enzymes in rats with inherited overgeneration of free radicals

Evolution Shapes the Gene Expression Response to Oxidative Stress

Reactive oxygen species (ROS) play a key role in cell physiology and function. ROS represents a potential source of damage for many macromolecules including DNA. It is thought that daily changes in oxidative stress levels were an important early factor driving evolution of the circadian clock which enables organisms to predict changes in ROS levels before they actually occur and thereby optimally coordinate survival strategies. It is clear that ROS, at relatively low levels, can serve as an important signaling molecule and also serves as a key regulator of gene expression. Therefore, the mechanisms that have evolved to survive or harness these effects of ROS are ancient evolutionary adaptations that are tightly interconnected with most aspects of cellular physiology. Our understanding of these mechanisms has been mainly based on studies using a relatively small group of genetic models. However, we know comparatively little about how these mechanisms are conserved or have adapted during evolution under different environmental conditions. In this review, we describe recent work that has revealed significant species-specific differences in the gene expression response to ROS by exploring diverse organisms. This evidence supports the notion that during evolution, rather than being highly conserved, there is inherent plasticity in the molecular mechanisms responding to oxidative stress.

Antihypertensive effects of fargesin in vitro and in vivo via attenuating oxidative stress and promoting nitric oxide release

Fargesin, a bioactive neolignan isolated from magnolia plants, is widely used in the treatment of managing rhinitis, inflammation, histamine, sinusitis, and headache. To provide more biological information about fargesin, we investigated the effects of fargesin on rat aortic rings and 2-kidney, 1-clip (2K1C) hypertensive rats. In vitro, fargesin caused concentration-dependent vasorelaxation in rat isolated aortic rings induced by KCl and norepinephrine. The effect was weakened by endothelium denudation and nitric oxide (NO) synthesis inhibition. In vivo, the evolution of systolic blood pressure (SBP) was followed by weekly measurements. Angiotensin II (Ang II) and endothelin (ET) levels, NO and nitric oxide synthase (NOS), and plasma and liver oxidative stress markers were determined at the end of the experimental period. After 5 weeks of fargesin treatment, we found that fargesin treatment reduced SBP, cardiac hypertrophy, and Ang II and ET levels of hypertensive rats. Increased NOS activity and NO level were observed in fargesin-treated rats. Normalisation of plasma MDA concentrations and improvement of the antioxidant defence system in plasma and liver accompanied the antihypertensive effect of fargesin. Taken together, these results provided substantial evidences that fargesin has antihypertensive effect in 2K1C hypertensive rats via inhibiting oxidative stress and promoting NO release.

G6PD protects from oxidative damage and improves healthspan in mice

Reactive oxygen species (ROS) are constantly generated by cells and ROS-derived damage contributes to ageing. Protection against oxidative damage largely relies on the reductive power of NAPDH, whose levels are mostly determined by the enzyme glucose-6-phosphate dehydrogenase (G6PD). Here, we report a transgenic mouse model with moderate overexpression of human G6PD under its endogenous promoter. Importantly, G6PD-Tg mice have higher levels of NADPH, lower levels of ROS-derived damage, and better protection from ageing-associated functional decline, including extended median lifespan in females. The G6PD transgene has no effect on tumour development, even after combining with various tumour-prone genetic alterations. We conclude that a modest increase in G6PD activity is beneficial for healthspan through increased NADPH levels and protection from the deleterious effects of ROS.

The enzyme G6PD generates the reductive metabolite NADPH, which has antioxidant effects, but has also been linked to tumour growth. Here the authors generate mice that modestly overexpress G6PD and report increased lifespan in females, and no negative effects on tumour formation in various genetic models.

Aqueous extract of dioscorea opposita thunb. normalizes the hypertension in 2K1C hypertensive rats

BACKGROUND

Dioscorea opposita Thunb. (Huai Shan Yao, DOT), a common staple food in China, has been used for more than 2000 years in traditional Chinese medicine (TCM) to treat different systemic diseases including hypertension. The objective of this study was to investigate the possible antihypertensive effects of the aqueous extract of (DOT) in renovascular hypertensive rats as well as the mechanism in reducing blood pressure.

METHODS

The two-kidney one-clip (2K1C) Goldblatt model of renovascular hypertension was used in Wistar rats. Rats with captopril, low-dose DOT and high-dose DOT treated 2K1C groups for 6 weeks. The blood pressure, cardiac mass index (heart weight/body weight), plasma level of angiotensin-II (Ang-II), endothelin-1(ET-1), superoxide dismutase (SOD) and malondialdehyde (MDA) were evaluated.

RESULTS

DOT significantly reduced mean systolic and diastolic blood pressure after treatment. DOT also significantly increased plasma SOD activity but decreased plasma MDA concentration. Renal function was improved with captopril and DOT. DOT reduced plasma Ang-II activity and plasma ET concentration. They couldalso significantly reduce the left ventricular hypertrophy and cardiac mass index.

CONCLUSIONS

Our results suggest that DOT may have an antihypertensive effect on hypertension by inhibit ET-converting enzyme and antioxidant activity, which warrant further exploration.

Rat retinal transcriptome: effects of aging and AMD-like retinopathy

Pathogenesis of age-related macular degeneration (AMD), the leading cause of vision loss in the elderly, remains poorly understood due to the paucity of animal models that fully replicate the human disease. Recently, we showed that senescence-accelerated OXYS rats develop a retinopathy similar to human AMD. To identify alterations in response to normal aging and progression of AMD-like retinopathy, we compared gene expression profiles of retina from 3- and 18-mo-old OXYS and control Wistar rats by means of high-throughput RNA sequencing (RNA-Seq). We identified 160 and 146 age-regulated genes in Wistar and OXYS retinas, respectively. The majority of them are related to the immune system and extracellular matrix turnover. Only 24 age-regulated genes were common for the two strains, suggestive of different rates and mechanisms of aging. Over 600 genes showed significant differences in expression between the two strains. These genes are involved in disease-associated pathways such as immune response, inflammation, apoptosis, Ca ( 2+) homeostasis and oxidative stress. The altered expression for selected genes was confirmed by qRT-PCR analysis. To our knowledge, this study represents the first analysis of retinal transcriptome from young and old rats with biologic replicates generated by RNA-Seq technology. We can conclude that the development of AMD-like retinopathy in OXYS rats is associated with an imbalance in immune and inflammatory responses. Aging alters the expression profile of numerous genes in the retina, and the genetic background of OXYS rats has a profound impact on the development of AMD-like retinopathy.

Age-dependent guanine oxidation in DNA of different brain regions of Wistar rats and prematurely aging OXYS rats

BACKGROUND

Oxidative damage to the cell, including the formation of 8-oxoG, has been regarded as a significant factor in carcinogenesis and aging. An inbred prematurely aging rat strain (OXYS) is characterized by high sensitivity to oxidative stress, lipid peroxidation, protein oxidation, DNA rearrangements, and pathological conditions paralleling several human degenerative diseases including learning and memory deterioration.

METHODS

We have used monoclonal antibodies against a common pre-mutagenic base lesion 8-oxoguanine (8-oxoG) and 8-oxoguanine DNA glycosylase (OGG1) in combination with indirect immunofluorescence microscopy and image analysis to follow the relative amounts and distribution of 8-oxoG and OGG1 in various cells of different brain regions from OXYS and control Wistar rats.

RESULTS

It was shown that 8-oxoG increased with age in mature neurons, nestin- and glial fibrillary acidic protein (GFAP)-positive cells of hippocampus and frontal cortex in both strains of rats, with OXYS rats always displaying statistically significantly higher levels of oxidative DNA damage than Wistar rats. The relative content of 8-oxoG and OGG1 in nestin- and GFAP-positive cells was higher than in mature neurons in both Wistar and OXYS rats. However, there was no significant interstrain difference in the content of OGG1 for all types of cells and brain regions analyzed, and no difference in the relative content of 8-oxoG between different brain regions.

CONCLUSIONS

Oxidation of guanine may play an important role in the development of age-associated decrease in memory and learning capability of OXYS rats.

GENERAL SIGNIFICANCE

The findings are important for validation of the OXYS rat strain as a model of mammalian aging.

Initiation of 8-oxoguanine base excision repair within trinucleotide tandem repeats

Trinucleotide repeat expansion provides a molecular basis for several devastating neurodegenerative diseases. In particular, expansion of a CAG run in the human HTT gene causes Huntington's disease. One of the main reasons for triplet repeat expansion in somatic cells is base excision repair (BER), involving damaged base excision and repair DNA synthesis that may be accompanied by expansion of the repaired strand due to formation of noncanonical DNA structures. We have analyzed the kinetics of excision of a ubiquitously found oxidized purine base, 8-oxoguanine (oxoG), by DNA glycosylase OGG1 from the substrates containing a CAG run flanked by AT-rich sequences. The values of k(2) rate constant for the removal of oxoG from triplets in the middle of the run were higher than for oxoG at the flanks of the run. The value of k(3) rate constant dropped starting from the third CAG-triplet in the run and remained stable until the 3'-terminal triplet, where it decreased even more. In nuclear extracts, the profile of oxoG removal rate along the run resembled the profile of k(2) constant, suggesting that the reaction rate in the extracts is limited by base excision. The fully reconstituted BER was efficient with all substrates unless oxoG was near the 3'-flank of the run, interfering with the initiation of the repair. DNA polymerase β was able to perform a strand-displacement DNA synthesis, which may be important for CAG run expansion initiated by BER.

Effect of the proline-rich polypeptide complex/colostrinin™ on the enzymatic antioxidant system

Proline-rich polypeptide complex (PRP) and its constituent nonapeptide (NP) possess immunoregulatory and procognitive properties. PRP in the form of sublingually administered tablets called Colostrinin™ improves the outcome of patients with Alzheimer's disease (AD). Free radical-induced oxidative stress has been implicated in the pathogenesis of AD. It has been previously shown that PRP and NP inhibit overproduction of reactive oxygen species, nitric oxide and proinflammatory cytokines induced by lipopolysaccharide or PMA. Antioxidant defense includes both low molecular weight components and enzymatic systems including dismutases, catalase, glutathione reductase (GSSGR) and glutathione peroxidase (GSHPx). An early event during the development of AD is lipid and protein peroxidation. PRP and NP showed no modulatory effect on lipid peroxidation. A protective effect on protein oxidation was found only when high doses of NP were used. We have previously shown, in a model of human peripheral blood mononuclear cells, that PRP/NP affects activities of superoxide dismutase and NF-κB. In the present study with the use of the same cell model and whole blood cells we observed an activatory effect of PRP/NP on GSHPx and GSSGR activity but not catalase. The observed effect suggests that PRP/NP can act as a modulatory agent of the "first line" of antioxidant defense. It can be assumed therefore that PRP/Colostrinin by regulation of the early phase of the redox system does not reduce but rather prevents oxidative damage. This effect may shed some light on the beneficial effect of PRP/Colostrinin in AD patients.

Flow injection catalase activity measurement based on gold nanoparticles/carbon nanotubes modified glassy carbon electrode

Amperometric flow injection method of hydrogen peroxide analysis was developed based on catalase enzyme (CAT) immobilization on a glassy carbon electrode (GC) modified with electrochemically deposited gold nanoparticles on a multiwalled carbon nanotubes/chitosan film. The resulting biosensor was applied to detect hydrogen peroxide with a linear response range 1.0×10(-7)-2.5×10(-3)M with a correlation coefficient 0.998 and response time less than 10s. The optimum conditions of film deposition such as potential applied, deposition time and pH were tested and the flow injection conditions were optimized to be: flow rate of 3ml/min, sample volume 75μl and saline phosphate buffer of pH 6.89. Catalase enzyme activity was successfully determined in liver homogenate samples of rats, raised under controlled dietary plan, using a flow injection analysis system involving the developed biosensor simultaneously with spectrophotometric detection, which is the common method of enzymatic assay.

Increased susceptibility to liver fibrosis with age is correlated with an altered inflammatory response

It has been suggested that increasing age is correlated with an acceleration of the progression of liver fibrosis induced by various agents, such as hepatitis C virus or chronic alcohol consumption. However, the cellular and molecular changes underlying this predisposition are not entirely understood. In the context of an aging population, it becomes challenging to decipher the mechanisms responsible for this higher susceptibility of older individuals to this acquired liver disorder. To address this issue, we induced liver fibrosis by carbon tetrachloride (CCl(4)) chronic administration to 8-week- and 15-month-old mice. We confirmed that susceptibility to fibrosis development increased with age and showed that aging did not affect fibrosis resolution capacity. We then focused on the impairment of hepatocyte proliferation, oxidative stress, and inflammation as potential mechanisms accelerating the development of fibrosis in the elderly. We detected no inhibition of hepatocyte proliferation after CCl(4) injury in 15-month-old mice, whereas it was inhibited after a partial hepatectomy. Finally, we observed that, in a context in which liver oxidative stress was not differentially increased in both experimental groups, there was a higher recruitment of inflammatory cells, including mostly macrophages and lymphocytes, oriented toward a T helper 2 (T(H)2) response in older mice. Our data show that in conditions of equivalent levels of oxidative stress and maintained hepatocyte proliferative capacity, an increased inflammatory reaction mainly composed of CD4(+) lymphocytes and macrophages expressing T(H)2 cytokines is the main factor involved in the higher susceptibility to fibrosis with increasing age.

The effects of aqueous extract of vaccinium arctostaphylos leaves on blood pressure in renal hypertensive rats

BACKGROUND

The leaves of Vaccinium arctostaphylos (Qare qat) is advocated for the treatment of hypertension in Iran' folk medicine. The objective of was to examine the possible hypotensive activity of aqueous extract of Vaccinium arctostaphylos leaves in rat model of two-kidney, one-clip hypertension.

METHODS

Rats were subjected to sham operation of the placement of Plexiglass clip on left renal arteries. Four weeks later, renal artery clipped rats were given intravenous injection of normal saline or the extract at 10, 25, or 75 mg/kg, and mean blood pressure and heart rate were measured before and 20, 40 and 60 minutes after vehicle or drug administration.

RESULTS

Compared to sham group, renal artery clipped groups had a significantly higher mean blood pressure, heart and right kidney weights, lower left kidney weight and significantly indifferent heart rate. Compared to vehicle treatment, the extract at 75 mg/kg, but not at 10 or 25 mg/kg, did reduce the mean blood pressure at 20, 40 and 60 minutes after administration without changing the heart rate.

CONCLUSION

The findings showed that at a higher dose the extract did have hypotensive activity without changing the heart rate. The exact hypotensive mechanism remains to be investigated.

Age- and tissue-specific changes in mitochondrial and nuclear DNA base excision repair activity in mice: Susceptibility of skeletal muscles to oxidative injury

In this study, we investigated age- and tissue-dependent changes in the DNA base excision repair (BER) of oxidative lesions in mitochondrial and nuclear extracts by measuring single-nucleotide (SN)- and long-patch (LP)-BER activities in five tissues isolated from 4-, 10- and 20-month-old mice. Age-dependent SN-BER and LP-BER activity was increased in the mitochondria of liver, kidney and heart, but generally decreased in skeletal muscles. In contrast, no significant changes in repair activity were observed in nuclear extracts of the same tissues, except for quadriceps, where the SN-BER activity was higher in the old animals. Moreover, the BER activities in both the nucleus and the mitochondria were significantly lower in skeletal muscles compared to liver or kidney of the same mice. The protein level of three antioxidant enzymes, Mn and Cu/Zn superoxide dismutases (SOD) and catalase, was also significantly lower in skeletal muscle compared to liver or kidney. In addition, we found higher levels of protein carbonylation in the mitochondria of skeletal muscle relative to other tissues. Thus, it appears likely that mouse skeletal muscle is highly susceptible to oxidative stress due to deficiency in both repair of oxidative DNA damage and antioxidant enzymes, contributing to age-dependent muscle loss.

Dietary calcium and dairy modulation of oxidative stress and mortality in aP2-agouti and wild-type mice

Oxidative and inflammatory stress have been implicated as major contributors to the aging process. Dietary Ca reduced both factors in short-term interventions, while milk exerted a greater effect than supplemental Ca. In this work, we examined the effects of life-long supplemental and dairy calcium on lifespan and life-span related biomarkers in aP2-agouti transgenic (model of diet-induced obesity) and wild-type mice fed obesigenic diets until their death. These data demonstrate that dairy Ca exerts sustained effects resulting in attenuated adiposity, protection against age-related muscle loss and reduction of oxidative and inflammatory stress in both mouse strains. Although these effects did not alter maximum lifespan, they did suppress early mortality in wild-type mice, but not in aP2-agouti transgenic mice.

[New promising antioxidants based on 2,6-dimethylphenol]

Three new sulfur-containing derivatives of 2,6-dimethylphenol were synthesized. Their antioxidative activity, mutagenicity, and genotoxicity were examined by bacterial tests and by calculating the dominant lethal mutations in murine embryonic cells. It was shown that all the compounds synthesized have a marked antioxidative effect and no genotoxic or mutagenic properties. One of the antioxidants, 4-(3-dodecylthiopropyl)-2,6-dimethylphenol, increases the survival of cells of both the wild-type Escherichia coli strain and bacterial strains defective in the genes of repair enzymes and has a more distinct antioxidative effect than the classic antioxidants alpha-tocopherol and trolox, increasing the survival of cells devoid of repair enzymes.

Estradiol-17beta protects against hypoxia-induced hepatocyte injury through ER-mediated upregulation of Bcl-2 as well as ER-independent antioxidant effects

Although many previous studies have suggested that estrogen functions as a cytoprotective agent under oxidative stress conditions, the underlying mechanism by which this effect is exerted remains to be elucidated. This study assessed the effects of estradiol-17beta (E(2)) (10(-8) M) on hypoxia-induced cell injury and its related signaling in primary cultured chicken hepatocytes. Hypoxic conditions were found to augment the level of DNA damage and to reduce cell viability and the level of [(3)H]-thymidine incorporation, and these phenomena were prevented through treatment with E(2). Hypoxia also increased caspase-3 expression, but showed no evidence of an influence on the expression of Bcl-2. However, E(2) induced an increase in the level of Bcl-2 expression under hypoxic conditions and reduced the level of caspase-3 expression. The effects of E(2) on Bcl-2 and caspase expression were blocked by ICI 182780 (E(2) receptor (ER) antagonist, 10(-7) M). In addition, hypoxia resulted in an increase in the intracellular reactive oxygen species (ROS) generated. These effects were blocked by E(2), but not by E(2)-BSA and ICI 182780. Hypoxia also activated p38 mitogen-activated protein kinase (MAPK), c-JUN N-terminal kinase/stress-activated protein kinase (JNK/SAPK) and nuclear factor-kappaB (NF-kappaB). These effects were blocked by E(2), but not by ICI 182780. The inhibition of p38 MAPK and JNK/SAPK blocked NF-kappaB activation. In conclusion, E(2) was found to protect against hypoxia-induced cell injury in chicken hepatocytes through ER-mediated upregulation of Bcl-2 expression and through reducing the activity of ROS-dependent p38 MAPK, JNK/SAPK and NF-kappaB.

Omega-3 fatty acids and antioxidants in neurological and psychiatric diseases: an overview

RATIONALE

Omega-3 fatty acids are known to play a role in nervous system activity, cognitive development, memory-related learning, neuroplasticity of nerve membranes, synaptogenesis and synaptic transmission. The brain is considered abnormally sensitive to oxidative damage, and aging is considered one of the most significant risk factors for degenerative neurological disorders. Recently, clinical trials of several neurodegenerative diseases have increasingly targeted the evaluation of the effectiveness of various antioxidants.

OBJECTIVES

The effects of omega-3 fatty acids and antioxidants on the anatomic and functional central nervous system development and their possible therapeutical use in some neurological and psychiatric pathologies are evaluated.

RESULTS

A number of critical trials have confirmed the benefits of dietary supplementation with omega-3 fatty acids not only in several psychiatric conditions, but also in inflammatory and autoimmune and neurodegenerative diseases. Many evidences indicate that antioxidants are also essential in maintaining a correct neurophysiology.

CONCLUSIONS

Omega-3 fatty acids could be useful in the prevention of different pathologies, such as cardiovascular, psychiatric, neurological, dermatological and rheumatological disorders. A number of studies suggest that antioxidants can prevent the oxidation of various macromolecules such as DNA, proteins, and lipids. The ideal use of antioxidants should be a prophylactic and continue treatment before aging.

Oxidation of guanine in liver and lung DNA of prematurely aging OXYS rats

Immunofluorescence assay was applied for determination of 8-oxoguanine (8-oxoG) in DNA. The 8-oxoG content in liver and lung DNA of 2- and 18-month-old Wistar rats was compared with that of prematurely aging OXYS rats. It was shown that for rats of both strains, 8-oxoG content in lung DNA compared with liver DNA was 1.7-2.0-fold and 1.3-1.7-fold higher for 2- and 18-month-old rats, respectively. However, the degree of oxidative damage in liver DNA of OXYS rats was 2.4- (p < 0.01) and 1.5-fold (p < 0.05) higher for 2- and 18-month-old animals, respectively, than that in liver DNA of Wistar rats. Oxidation of guanine in lung DNA of OXYS rats was 2- (p < 0.01) and 1.7-fold (p < 0.05) higher for 2- and 18-month-old animals, respectively, than that in lung DNA of Wistar rats. The data indicate that elevated DNA oxidative damage in various organs of OXYS rats may be an important factor of accelerated aging and progression of age-related diseases--cataract, macular dystrophy, hypertension, osteoporosis, cognitive and behavioral dysfunctions, and also lung and liver pathologies.