Hydrogen peroxide reduces lead-induced oxidative stress to mouse brain and liver

Chronic GPER1 Activation Protects Against Oxidative Stress-Induced Cardiomyoblast Death via Preservation of Mitochondrial Integrity and Deactivation of Mammalian Sterile-20-Like Kinase/Yes-Associated Protein Pathway

Introduction: Estrogen (17β-estradiol, E2) is well-known to induce cardioprotective effects against ischemia/reperfusion (I/R) injury. We recently reported that acute application of E2 at the onset of reperfusion in vivo induces cardioprotective effects against I/R injury via activation of its non-steroidal receptor, G protein-coupled estrogen receptor 1 (GPER1). Here, we investigated the impact and mechanism underlying chronic GPER1 activation in cultured H9c2 rat cardiomyoblasts. Methods: H9c2 rat cardiomyoblasts were cultured and pretreated with the cytotoxic agent H₂O₂ for 24 h and incubated in the presence of vehicle (control), GPER1 agonists E2 and G1, or GPER1 agonists supplemented with G15 (GPER1 antagonist) for 48 or 96 h. After treatment, cells were collected to measure the rate of cell death and viability using flow cytometry and Calcein AM assay or MTT assay, respectively. The resistance to opening of the mitochondrial permeability transition pore (mPTP), the mitochondrial membrane potential, and ATP production was assessed using fluorescence microscopy, and the mitochondrial structural integrity was observed with electron microscopy. The levels of the phosphorylation of mammalian sterile-20-like kinase (MST1) and yes-associated protein (YAP) were assessed by Western blot analysis in whole-cell lysate, while the expression levels of mitochondrial biogenesis genes, YAP target genes, and proapoptotic genes were measured by qRT-PCR. Results: We found that after H₂O₂ treatment, chronic E2/G1 treatment decreased cell death effect was associated with the prevention of the S phase of the cell cycle arrest compared to control. In the mitochondria, chronic E2/G1 activation treatment preserved the cristae morphology, and increased resistance to opening of mPTP, but with little change to mitochondrial fusion/fission. Additionally, chronic E2/G1 treatment predominantly reduced phosphorylation of MST1 and YAP, as well as increased MST1 and YAP protein levels. E2 treatment also upregulated the expression levels of TGF-β and PGC-1α mRNAs and downregulated PUMA and Bim mRNAs. Except for ATP production, all the E2 or G1 effects were prevented by the cotreatment with the GPER1 antagonist, G15. Conclusion: Together, these results indicate that chronic GPER1 activation with its agonists E2 or G1 treatment protects H9c2 cardiomyoblasts against oxidative stress-induced cell death and increases cell viability by preserving mitochondrial structure and function as well as delaying the opening of mPTP. These chronic GPER1 effects are associated with the deactivation of the non-canonical MST1/YAP mechanism that leads to genetic upregulation of cell growth genes (CTGF, CYR61, PGC-1α, and ANKRD1), and downregulation of proapoptotic genes (PUMA and Bim).

Dehydroepiandrosterone Prevents H2O2-Induced BRL-3A Cell Oxidative Damage through Activation of PI3K/Akt Pathways rather than MAPK Pathways

Dehydroepiandrosterone (DHEA) is a popular dietary supplement that has well-known benefits in animals and humans, but there is not enough information about the mechanisms underlying its effects. The present study aimed at investigating these mechanisms through in vitro experiments on the effects of DHEA on rat liver BRL-3A cells exposed to oxidative stress through H₂O₂. The findings showed that DHEA increased the antioxidant enzyme activity, decreased ROS generation, and inhibited apoptosis in H₂O₂-treated cells. These effects of DHEA were not observed when the cells were pretreated with known antagonists of sex hormones (Trilostane, Flutamide, or Fulvestrant). Furthermore, treatment with estradiol and testosterone did not have the same protective effects as DHEA. Thus, the beneficial effects of DHEA were associated with mechanisms that were independent of steroid hormone pathways. With regard to the mechanism underlying the antiapoptotic effect of DHEA, pretreatment with DHEA was found to induce a significant decrease in the protein expression of Bax and caspase-3 and a significant increase in the protein expression of PI3K and p-Akt in H₂O₂-treated BRL-3A cells. These effects of DHEA were abolished when the cells were pretreated with the PI3K inhibitor LY294002. No changes were observed on the p-ERK1/2, p-p38, and p-JNK protein levels in H₂O₂-induced BRL-3A cells pretreated with DHEA. In conclusion, our data demonstrate that DHEA protects BRL-3A cells against H₂O₂-induced oxidative stress and apoptosis through mechanisms that do not involve its biotransformation into steroid hormones or the activation of sex hormone receptors. Importantly, the protective effect of DHEA on BRL-3A cells was mainly associated with PI3K/Akt signaling pathways, rather than MAPK signaling pathways.

Maternal administration of melatonin prevents spatial learning and memory deficits induced by developmental ethanol and lead co-exposure

Melatonin is a radical scavenger with the ability to remove reactive oxidant species. There is report that co-exposure to lead and ethanol during developmental stages induces learning and memory deficits and oxidative stress. Here, we studied the effect of melatonin, with strong antioxidant properties, on memory deficits induced by lead and ethanol co-exposure and oxidative stress in hippocampus. Pregnant rats in lead and ethanol co-exposure group received lead acetate of 0.2% in distilled drinking water and ethanol (4g/kg) by oral gavages once daily from the 5th day of gestation until weaning. Rats received 10mg/kg melatonin by oral gavages. On postnatal days (PD) 30, rats trained with six trials per day for 6 consecutive days in the water maze. On day 37, a probe test was done and oxidative stress markers in the hippocampus were evaluated. Results demonstrated lead and ethanol co-exposed rats exhibited higher escape latency during training trials and reduced time spent in target quadrant, higher escape location latency in probe trial test and had significantly higher malondialdehyde (MDA) levels, significantly lower superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities in the hippocampus. Melatonin treatment could improve memory deficits, antioxidants activity and reduced MDA levels in the hippocampus. We conclude, co-exposure to lead and ethanol impair memory and melatonin can prevent from it by oxidative stress modulation.

The combined effects of developmental lead and ethanol exposure on hippocampus dependent spatial learning and memory in rats: Role of oxidative stress

Either developmental lead or ethanol exposure can impair learning and memory via induction of oxidative stress, which results in neuronal damage. we examined the effect of combined exposure with lead and ethanol on spatial learning and memory in offspring and oxidative stress in hippocampus. Rats were exposed to lead (0.2% in drinking water) or ethanol (4 g/kg) either individually or in combination in 5th day gestation through weaning. On postnatal days (PD) 30, rats were trained with six trials per day for 6 consecutive days in the water maze. On day 37, a probe test was done. Also, oxidative stress markers in the hippocampus were also evaluated. Results demonstrated that lead + ethanol co-exposed rats exhibited higher escape latency during training trials and reduced time spent in target quadrant, higher escape location latency and average proximity in probe trial test. There was significant decrease in superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities and increase of malondialdehyde (MDA) levels in hippocampus of animals co-exposed to lead and ethanol compared with their individual exposures. We suggest that maternal consumption of ethanol during lead exposure has pronounced detrimental effects on memory, which may be mediated by oxidative stress.

Iron-ascorbate-mediated lipid peroxidation causes epigenetic changes in the antioxidant defense in intestinal epithelial cells: impact on inflammation

Introduction

The gastrointestinal tract is frequently exposed to noxious stimuli that may cause oxidative stress, inflammation and injury. Intraluminal pro-oxidants from ingested nutrients especially iron salts and ascorbic acid frequently consumed together, can lead to catalytic formation of oxygen-derived free radicals that ultimately overwhelm the cellular antioxidant defense and lead to cell damage.

Hypothesis

Since the mechanisms remain sketchy, efforts have been exerted to evaluate the role of epigenetics in modulating components of endogenous enzymatic antioxidants in the intestine. To this end, Caco-2/15 cells were exposed to the iron-ascorbate oxygen radical-generating system.

Results

Fe/Asc induced a significant increase in lipid peroxidation as reflected by the elevated formation of malondialdehyde along with the alteration of antioxidant defense as evidenced by raised superoxide dismutase 2 (SOD2) and diminished glutathione peroxidase (GPx) activities and genes. Consequently, there was an up-regulation of inflammatory processes illustrated by the activation of NF-κB transcription factor, the higher production of interleukin-6 and cycloxygenase-2 as well as the decrease of IκB. Assessment of promoter’s methylation revealed decreased levels for SOD2 and increased degree for GPx2. On the other hand, pre-incubation of Caco-2/15 cells with 5-Aza-2′-deoxycytidine, a demethylating agent, or Trolox antioxidant normalized the activities of SOD2 and GPx, reduced lipid peroxidation and prevented inflammation.

Conclusion

Redox and inflammatory modifications in response to Fe/Asc -mediated lipid peroxidation may implicate epigenetic methylation.

Prenatal and lactational lead exposure enhanced oxidative stress and altered apoptosis status in offspring rats' hippocampus

Oxidative stress and apoptosis facilitation in the developing central nervous system (CNS) have been inferred as two mechanisms related to lead's neurotoxicity, and excessive reactive oxygen species (ROS) can promote oxidative stress and apoptosis facilitation. Few studies systematically investigated the potential relationship among oxidative stress, ROS generation, and apoptosis facilitation after lead exposure in earlier life as a whole. To better understand the adverse effect on the developing central nervous system (CNS) after lead exposure during pregnancy and lactation, the indexes of oxidative stress, apoptosis status, and Bax and Bcl-2 expression of offspring rats' hippocampus were determined. Pregnant rats were randomly divided into four groups and given free access to drinking water which contained 0 %, 0.05 %, 0.1 %, and 0.2 % Pb(AC)(2) respectively from gestation day 0 to postnatal day 21 (PND21). Results showed that ROS and malondialdehyde level of either PND7 or PND21 pups' hippocampus were significantly raised; reduced glutathione level and superoxide dismutase activity were obviously decreased following the increase of blood and brain lead level. Similar to apoptotic indexes, Bax/Bcl-2 ratio increased after 0.1 % and 0.2 % Pb(AC)(2) exposure, especially for the pups on PND7. Comparing with cortex, the hippocampus seemed much more sensitive to damage induced by lead. We concluded that the disruption of pro-oxidant and antioxidant balance and apoptosis facilitation could be associated with the mechanisms of neurotoxicity after lead exposure in earlier life.

Central N-acetylcysteine effects on baroreflex in juvenile spontaneously hypertensive rats

In this study, we evaluated the acute effects of central NAC administration on baroreflex in juvenile SHR and Wistar Kyoto (WKY) rats. Male SHR and WKY rats (8-10 weeks old) were implanted with a stainless steel guide cannula into the fourth cerebral ventricle (4th V). The femoral artery and vein were cannulated for mean arterial pressure (MAP) and heart rate (HR) measurement and drug infusion, respectively. After basal MAP and HR recordings, the baroreflex was tested with a pressor dose of phenylephrine (PHE, 8 μg/kg, bolus) and a depressor dose of sodium nitroprusside (SNP, 50 μg/kg, bolus). Baroreflex was evaluated before, 5, 15, 30 and 60 minutes after NAC injection into the 4th V. Vehicle treatment did not change baroreflex responses in WKY and SHR. Central NAC slightly but significantly increased basal HR at 15 minutes and significantly reduced PHE-induced increase in MAP 30 and 60 minutes after NAC injection (p < 0.05) in WKY rats. In relation to SHR, NAC decreased HR range 15 and 30 minutes after its administration. In conclusion, acute NAC into the 4th V does not improve baroreflex in juvenile SHR.

Dual role of vitamin C utilization in NO2-induced oxidative stress in lung tissues of mice

Earlier studies with in vitro models have revealed that application of vitamin C can act as a primary NO(2) absorption substrate to contribute to NO(2)-induced cellular injury. In the present study, we showed that the pharmacological application of vitamin C had dual role in lungs of mice exposed to NO(2), with an exacerbated oxidative stress occurring at low concentrations, as indicated by excessive reactive oxygen species production and lipid peroxidation. However, at high concentrations, vitamin C functioned as an antioxidant removing reactive oxygen species and maintaining a reducing status in cells, alleviating NO(2)-induced oxidative toxicity.