Arsenate‐induced apoptosis in murine embryonic maxillary mesenchymal cells via mitochondrial‐mediated oxidative injury

BACKGROUND : Arsenic is a ubiquitous element that is a potential carcinogen and teratogen and can cause adverse developmental outcomes. Arsenic exerts its toxic effects through the generation of reactive oxygen species (ROS) that include hydrogen peroxide (H₂O₂), superoxide‐derived hydroxyl ion, and peroxyl radicals. However, the molecular mechanisms by which arsenic induces cytotoxicity in murine embryonic maxillary mesenchymal (MEMM) cells are undefined. METHODS : MEMM cells in culture were treated with different concentrations of pentavalent sodium arsenate [As (V)] for 24 or 48 hr and various end points measured. RESULTS : Treatment of MEMM cells with the pentavalent form of inorganic arsenic resulted in caspase‐mediated apoptosis, accompanied by generation of ROS and disruption of mitochondrial membrane potential. Treatment with caspase inhibitors markedly blocked apoptosis. In addition, the free radical scavenger N‐acetylcysteine dramatically attenuated arsenic‐mediated ROS production and apoptosis, and exposure to arsenate increased Bax and decreased Bcl protein levels in MEMM cells. CONCLUSIONS : Taken together, these findings suggest that in MEMM cells arsenate‐mediated oxidative injury acts as an early and upstream initiator of the cell death cascade, triggering cytotoxicity, mitochondrial dysfunction, altered Bcl/Bax protein ratios, and activation of caspase‐9. Birth Defects Research (Part A), 2010. © 2009 Wiley‐Liss, Inc.     

Tumour necrosis factor alpha mediated apoptosis in murine macrophages by Salmonella enterica serovar Typhi under oxidative stress

Invasive Salmonella has been reported to induce apoptosis of macrophages as part of its infection process, which may allow it to avoid detection by the innate immune system. However, the induction of apoptosis under the different host environments remains to be examined, including the oxidative stress experienced by pathogens in the macrophage milieu. To simulate in vivo oxidative conditions, Salmonella enterica serovar Typhi was grown in the presence of hydrogen peroxide and its ability to induce apoptosis of murine macrophages was assessed. Analysis of data revealed that oxidative stressed S. Typhi caused apoptotic cell death in 51% of macrophages, whereas S. Typhi grown under normal conditions accounted for apoptotic cell death in only 32% of macrophages. A significant increase in the levels of oxidants and decrease in the antioxidant was also observed which correlated with the increased generation of tumour necrosis factor alpha, interleukin-1alpha and interleukin-6. These results suggest that tumour necrosis factor alpha in conjunction with other cytokines may induce apoptotic cell death through the up-regulation of lipid peroxidation and down-regulation of superoxide dismutase. This finding may help us to understand better the host-pathogen interactions and may be of clinical importance in the development of preventive intervention against infection.     

Changes in mitochondrial morphology induced by calcium or rotenone in primary astrocytes occur predominantly through ros‐mediated remodeling

Morphological changes in mitochondria have been primarily attributed to fission and fusion, while the more pliable transformations of mitochondria (remodeling, rounding, or stretching) have been largely overlooked. In this study, we quantify the contributions of fission and remodeling to changes in mitochondrial morphology induced by the Ca²⁺ ionophore 4Br‐A23187 and the metabolic toxin rotenone. We also examine the role of reactive oxygen species (ROS) in the regulation of mitochondrial remodeling. In agreement with our previous studies, mitochondrial remodeling, not fission, is the primary contributor to Ca²⁺‐mediated changes in mitochondrial morphology induced by 4Br‐A23187 in rat cortical astrocytes. Treatment with rotenone produced similar results. In both paradigms, remodeling was selectively blocked by antioxidants whereas fission was not, suggesting a ROS‐mediated mechanism for mitochondrial remodeling. In support of this hypothesis, inhibition of endogenous ROS by overnight incubation in antioxidants resulted in elongated reticular networks of mitochondria. Examination of inner and outer mitochondrial membranes revealed that they largely acted in concert during the remodeling process . While mitochondrial morphology is traditionally ascribed to a net output of fission and fusion processes, in this study we provide evidence that the acute pliability of mitochondria can be a dominant factor in determining their morphology. More importantly, our results suggest that the remodeling process is independently regulated through a ROS‐signaling mechanism.

     

Cyclophilin A inhibits A549 cell oxidative stress and apoptosis by modulating the PI3K/Akt/mTOR signaling pathway

The excessive and inappropriate production of reactive oxygen species (ROS) can cause oxidative stress and is implicated in the pathogenesis of lung cancer. Cyclophilin A (CypA), a member of the immunophilin family, is secreted in response to ROS. To determine the role of CypA in oxidative stress injury, we investigated the role that CypA plays in human lung carcinoma (A549) cells. Here, we showed the protective effect of human recombinant CypA (hCypA) on hydrogen peroxide (H₂O₂)-induced oxidative damage in A549 cells, which play crucial roles in lung cancer. Our results demonstrated that hCypA substantially promoted cell viability, superoxide dismutase (SOD), glutathione (GSH), and GSH peroxidase (GSH-Px) activities, and attenuated ROS and malondialdehyde (MDA) production in H₂O₂-induced A549 cells. Compared with H₂O₂-induced A549 cells, Caspase-3 activity in hCypA-treated cells was significantly reduced. Using Western blotting, we showed that hCypA facilitated Bcl-2 expression and inhibited Bax, Caspase-3, Caspase-7, and PARP-1 expression. Furthermore, hCypA activates the PI3K/Akt/mTOR pathway in A549 cells in response to H₂O₂ stimulation. Additionally, peptidyl-prolyl isomerase activity was required for PI3K/Akt activation by CypA. The present study showed that CypA protected A549 cells from H₂O₂-induced oxidative injury and apoptosis by activating the PI3K/Akt/mTOR pathway. Thus, CypA might be a potential target for lung cancer therapy.     

Nicotine-induced memory impairment by increasing brain oxidative stress

Male Wistar rats were subjected to chronic nicotine treatment (0.3 mg/kg; 7 continuous days) and their memory performance was studied by means of Y-maze and multi-trial passive avoidance tasks. Nicotine significantly decreased spontaneous alternation in Y-maze task and step-through-latency in the multi-trial passive avoidance task, suggesting effects on both short-term memory and long-term memory, respectively. In addition, nicotine induced neuronal apoptosis, DNA fragmentation, reduced antioxidant enzymes activity, and increased production of lipid peroxidation and reactive oxygen species, suggesting pro-oxidant activity. Our results provide further support that nicotine-induced memory impairment is due to an increase in brain oxidative stress in rats.     

Autophagy: a cyto-protective mechanism which prevents primary human hepatocyte apoptosis during oxidative stress

The role of autophagy in the response of human hepatocytes to oxidative stress remains unknown. Understanding this process may have important implications for the understanding of basic liver epithelial cell biology and the responses of hepatocytes during liver disease. To address this we isolated primary hepatocytes from human liver tissue and exposed them ex vivo to hypoxia and hypoxia-reoxygenation (H-R). We showed that oxidative stress increased hepatocyte autophagy in a reactive oxygen species (ROS) and class III PtdIns3K-dependent manner. Specifically, mitochondrial ROS and NADPH oxidase were found to be key regulators of autophagy. Autophagy involved the upregulation of BECN1, LC3A, Atg7, Atg5 and Atg 12 during hypoxia and H-R. Autophagy was seen to occur within the mitochondria of the hepatocyte and inhibition of autophagy resulted in the lowering a mitochondrial membrane potential and onset of cell death. Autophagic responses were primarily observed in the large peri-venular (PV) hepatocyte subpopulation. Inhibition of autophagy, using 3-methyladenine, increased apoptosis during H-R. Specifically, PV human hepatocytes were more susceptible to apoptosis after inhibition of autophagy. These findings show for the first time that during oxidative stress autophagy serves as a cell survival mechanism for primary human hepatocytes.     

Molecular mechanisms of survival and apoptosis in RAW 264.7 macrophages under oxidative stress

Organisms living in an aerobic environment are continuously exposed to reactive oxygen species (ROS). Apoptosis of cells can be induced by ROS and cells also develop negative feedback mechanisms to limit ROS induced cell death. In this study, RAW264.7 murine macrophage cells were treated with H₂O₂ and cDNA microarray technique was used to produce gene expression profiles. We found that H₂O₂ treatment caused up-regulation of stress, survival and apoptosis related genes, and down-regulation of growth and cell cycle promoting genes. Numerous genes of metabolism pathways showed special expression patterns under oxidative stress: glycolysis and lipid synthesis related genes were down-regulated whereas the genes of lipid catabolism and protein synthesis were up-regulated. We also identified several signaling molecules as ROS-responsive, including p53, Akt, NF- B, ERK, JNK, p38, PKC and INF- . They played important roles in the process of apoptosis or cell survival. Finally, an interactive pathway involved in cellular response to oxidative stress was proposed to provide some insight into the molecular events of apoptosis induced by ROS and the feedback mechanisms involved in cell survival.Y. Zhang and C.C. Fong contributed equally to this work.     

Protective effect of Homer 1a against hydrogen peroxide-induced oxidative stress in PC12 cells

Abstract

Oxidative stress-induced cell damage is involved in many neurological diseases. Homer protein, as an important scaffold protein at postsynaptic density, regulates synaptic structure and function. Here, we reported that hydrogen peroxide (H₂O₂) induced the expression of Homer 1a. Down-regulation of Homer 1a with a specific small interfering RNA (siRNA) exacerbated H₂O₂-induced cell injury. Up-regulation of Homer 1a by lentivirus transfection did not affect the anti-oxidant activity, but significantly reduced the reactive oxygen species (ROS) production and lipid peroxidation after H₂O₂-induced oxidative stress. Overexpression of Homer 1a attenuated the loss of mitochondrial membrane potential (MMP) and ATP production induced by H₂O₂, and subsequently inhibited mitochondrial dysfunction-induced cytochrome c release, increase of Bax/Bcl-2 ratio and caspase-9/caspase-3 activity. Furthermore, in the presence of BAPTA-AM, an intracellular free-calcium (Ca^{2 +}) chelator, overexpression of Homer 1a had no significant effects on H₂O₂-induced oxidative stress. These results suggest that Homer 1a has protective effects against H₂O₂-induced oxidative stress by reducing ROS accumulation and activation of mitochondrial apoptotic pathway, and these protective effects are dependent on the regulation of intracellular Ca^{2 +} homeostasis.     

Curcumin induced apoptosis is mediated through oxidative stress in mutated p53 and wild type p53 colon adenocarcinoma cell lines

Curcumin has anti‐oxidant, anti‐cancer and anti‐carcinogen property. Our laboratory had previously reported that, curcumin treatment induces reactive oxygen species (ROS) generation in HT‐29 cell line, an effect contradictory to its anti‐oxidant property. This study evaluates the role of p53 in curcumin mediated ROS generation and cell death. Curcumin induced ROS was determined by 2’,7’‐dichlorofluorescein and apoptosis by Hoechst33342/PI staining in HT‐29 and HCT‐116 cell lines. ROS generation occurs within 1 hour of 40 µM curcumin treatment and a reduction was observed by third hour in HCT‐116 insinuating p53 involvement. N‐acetyl cysteine (NAC) pre‐treatment effectively quenched ROS and inhibited membrane potential loss in HT‐29, but less effective in HCT‐116. Mitochondrial membrane potential loss is evident with 10 and 40 µM curcumin in HCT‐116 and at 40 µM curcumin in HT‐29. Total p53 protein level increase was observed by 24 hours in HCT‐116 upon NAC pre‐treatment. Our results indicate that curcumin induces ROS mediated cell death in colon adenocarcinoma cell lines and may be mediated via p53.     

Inflammatory neurodegeneration induced by lipoteichoic acid from Staphylococcus aureus is mediated by glia activation, nitrosative and oxidative stress, and caspase activation

In this study we investigated the mechanisms of neuronal cell death induced by lipoteichoic acid (LTA) and muramyl dipeptide (MDP) from Gram-positive bacterial cell walls using primary cultures of rat cerebellum granule cells (CGCs) and rat cortical glial cells (astrocytes and microglia). LTA (+/- MDP) from Staphylococcus aureus induced a strong inflammatory response of both types of glial cells (release of interleukin-1beta, tumour necrosis factor-alpha and nitric oxide). The death of CGCs was caused by activated glia because in the absence of glia (treatment with 7.5 microm cytosine-d-arabinoside to inhibit non-neuronal cell proliferation) LTA + MDP did not cause significant cell death (less than 20%). In addition, staining with rhodamine-labelled LTA confirmed that LTA was bound only to microglia and astrocytes (not neurones). Neuronal cell death induced by LTA (+/- MDP)-activated glia was partially blocked by an inducible nitric oxide synthase inhibitor (1400 W; 100 microm), and completely blocked by a superoxide dismutase mimetic [manganese (III) tetrakis (4-benzoic acid)porphyrin chloride; 50 microm] and a peroxynitrite scavenger [5,10,15,20-tetrakis (4-sulfonatophenyl) porphyrinato iron (III); 100 microm] suggesting that nitric oxide and peroxynitrite contributed to LTA-induced cell death. Moreover, neuronal cell death was inhibited by selective inhibitors of caspase-3 (z-DEVD-fmk; 50 microm) and caspase-8 (z-Ile-Glu(O-Me)-Thr-Asp(O-Me) fluoromethyl ketone; 50 microm) indicating that they were involved in LTA-induced neuronal cell death.     

Cytoprotective effect of dieckol on human endothelial progenitor cells (hEPCs) from oxidative stress-induced apoptosis

Abstract

Although endothelial progenitor cells (EPCs) have been used to promote revascularization after peripheral or myocardial ischemia, excess amounts of reactive oxygen species (ROS) are often involved in senescence and apoptosis of EPCs, thereby causing defective neovascularization and reduced or failed recovery. Here, we examined the cytoprotective effect of Ecklonia cava-derived antioxidant dieckol (DK) on oxidative stress-induced apoptosis in EPCs to improve EPC bioactivity for vessel repair. Although H₂O₂ (10 ^{? 3} M) increased the intracellular ROS level in EPCs, DK (10ug/ml) pretreatment suppressed the H₂O₂-induced ROS increase and drastically reduced the ratios of apoptotic cells. H₂O₂-induced ROS increased the phosphorylation of p38 MAPK and JNK; this was inhibited by DK pretreatment. H₂O₂ treatment increased the phosphorylation of NF-κB, which was blocked by pretreatment with SB 203580, a p38 MAPK inhibitor, or SP 600125, a JNK inhibitor. H₂O₂ decreased the cellular levels of Bcl-2 and c-IAPs, cellular inhibitors of apoptosis proteins, but increased caspase-3 activation. However, all these effects were inhibited by pretreatment with DK. Injection of DK-mixed EPCs (DK + EPCs) into myocardial ischemic sites in vivo induced cellular proliferation and survival of cells at the ischemic sites and, thereby, enhanced the secretion of angiogenic cytokines at the ischemic sites. These results show that DK + EPC exhibit markedly enhanced anti-apoptotic and antioxidative capabilities, unlike that shown by EPCs alone; thus, they contribute to improved repair of ischemic myocardial injury through cell survival and angiogenic cytokine production.     

Modification of glycolysis affects cell sensitivity to apoptosis induced by oxidative stress and mediated by mitochondria

The effect of alteration of the glycolytic pathway on cell damage induced by oxidative stress was investigated with dihydrofolate reductase-deficient Chinese hamster ovary (CHO) cells that either overexpress cytosolic glycerol-3-phosphate dehydrogenase (CHO/cGPDH cells) or are depleted of the A subunit of lactate dehydrogenase as a result of anti-sense RNA expression (CHO/anti-LDH cells). The extent of oxidative phosphorylation in CHO/anti-LDH and CHO/cGPDH cells was increased and decreased, respectively, relative to that in parental CHO cells, as revealed by measurement of the intracellular content of ATP, the rate of cellular O(2) consumption, the mitochondrial membrane potential (DeltaPsi(m)), and the generation of reactive oxygen species. The sensitivity of these cell lines to cell death induced by the exogenous oxidant tert-butyl hydroperoxide decreased according to the rank order CHO/anti-LDH>CHO>CHO/cGPDH. Exogenous pyruvate markedly increased the sensitivity of CHO/cGPDH cells to oxidant-induced death. The differences among the three cell lines in susceptibility to oxidant-induced death were reflected in the proportion of oxidant-treated cells with a subdiploid DNA content, with a collapsed DeltaPsi(m), and with cytochrome c in the cytosol, indicating that death was mediated by apoptosis. These results demonstrate that the influx of respiratory substrate into mitochondria is an important determinant of cell sensitivity to oxidant-induced apoptosis.     

Impact of oxidative stress in aged mouse oocytes on calcium oscillations at fertilization

In vivo post-ovulatory aging of oocytes significantly affects the development of oocytes and embryos. Also, oocyte aging alters the regulation of the intracellular calcium concentration, thus affecting Ca(2+) oscillations in fertilized oocytes. Because reactive oxygen species (ROS) are known to significantly perturb Ca(2+) homeostasis mainly through direct effects on the machinery involved in intracellular Ca(2+) storage, we hypothesized that the poor development of aged oocytes that may have been exposed to oxidative stress for a prolonged time might arise from impaired Ca(2+)-oscillation-dependent signaling. The fertilization rates of aged oocytes and of fresh oocytes treated with 100 microM hydrogen peroxide (H(2)O(2)) for 10 min were significantly lower than that of fresh oocytes. Comparing within the fertilized oocytes, blastocyst formation was decreased while embryo fragmentation was increased similarly in the aged and H(2)O(2)-treated fresh oocytes. The frequency of Ca(2+) oscillations was significantly increased whereas the amplitude of individual Ca(2+) transients was lowered in the aged and H(2)O(2)-treated fresh oocytes. The rates of rise and decline in individual Ca(2+) transients were decreased in these oocytes, indicating impaired Ca(2+) handling. When lipid peroxidation was assessed using 4,4-difluoro-5-(4-phenyl-1,3-buttadienyl)-4-bora-3a, 4a-diaza-s-indacene-3-undecanoic acid (C11-BODIPY) in unfertilized oocytes placed in a 5% CO(2) in air atmosphere, the green fluorescence (indicating lipid peroxidation) increased faster in the aged oocytes than in the fresh oocytes. Furthermore, the green fluorescence in the aged oocytes was already approximately 20 times higher than that in the fresh oocytes at the beginning of the measurements. These findings support the idea that Ca(2+) oscillations play a key role in the development of fertilized aged oocytes.     

Screening of dietary antioxidants against mitochondria-mediated oxidative stress by visualization of intracellular redox state

Mitochondrial impairment and the resulting generation of reactive oxygen species (ROS) have been associated with aging and its related pathological conditions. Recently, dietary antioxidants have gained significant attention as potential preventive and therapeutic agents against ROS-generated aging and pathological conditions. We previously demonstrated that food-derived antioxidants prevented intracellular oxidative stress under proteasome inhibition conditions, which was attributed to mitochondrial dysfunction and ROS generation, followed by cell death. Here, we further screened dietary antioxidants for their activity as redox modulators by visualization of the redox state using Redoxfluor, a fluorescent protein redox probe. Direct alleviation of ROS by antioxidants, but not induction of antioxidative enzymes, prevented mitochondria-mediated intracellular oxidation. The effective antioxidants scavenged mitochondrial ROS and suppressed cell death. Our study indicates that redox visualization under mitochondria-mediated oxidative stress is useful for screening potential antioxidants to counteract mitochondrial dysfunction, which has been implicated in aging and the pathogenesis of aging-related diseases.     

Exosomes derived from RPE cells under oxidative stress mediate inflammation and apoptosis of normal RPE cells through Apaf1/caspase-9 axis

This study aims to explore the effects of exosomes, secreted by retinal pigment epithelial (RPE) cells under oxidative stress (OS), on apoptosis and inflammation of normal RPE cells. Exosomes secreted by normal RPE cells (named as exo) and rotenone (2.5 µmol/L) stimulated RPE cells (named as rot-exo) were isolated and extracted by multi-step differential centrifugation for morphology observation under a transmission electron microscopy. pcDNA3.1a, pcDNA3.1a-Apaf1, and p3xFlag-CMV-caspase-9 plasmids were constructed and transfected into ARPE-19 cells. Exosomes secreted by ARPE-19 cells were injected into the vitreous body of rats to verify the effect of Apaf1 and caspase-9 on cell apoptosis and inflammation. Co-immunoprecipitation was applied to clarify the interaction of Apaf1 with caspase-9. Exosomes secreted by rotenone stimulated ARPE-19 cells could induce cell apoptosis, oxidative injury, and inflammation in ARPE-19 cells. Exosomes secreted under OS can damage retinal functions of rats and have upregulated expression of Apaf1. Overexpression of Apaf1 in exosomes secreted under OS can cause the inhibition of cell proliferation, the increase of cell apoptosis and elicitation of inflammatory response in ARPE-19 cells. Exosomes derived from ARPE-19 cells under OS regulate Apaf1 expression to increase cell apoptosis and to induce oxidative injury and inflammatory response through a caspase-9 apoptotic pathway.     

Extending life span by increasing oxidative stress

Various nutritional, behavioral, and pharmacological interventions have been previously shown to extend life span in diverse model organisms, including Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, mice, and rats, as well as possibly monkeys and humans. This review aims to summarize published evidence that several longevity-promoting interventions may converge by causing an activation of mitochondrial oxygen consumption to promote increased formation of reactive oxygen species (ROS). These serve as molecular signals to exert downstream effects to ultimately induce endogenous defense mechanisms culminating in increased stress resistance and longevity, an adaptive response more specifically named mitochondrial hormesis or mitohormesis. Consistently, we here summarize findings that antioxidant supplements that prevent these ROS signals interfere with the health-promoting and life-span-extending capabilities of calorie restriction and physical exercise. Taken together and consistent with ample published evidence, the findings summarized here question Harman's Free Radical Theory of Aging and rather suggest that ROS act as essential signaling molecules to promote metabolic health and longevity.     

The mechanisms of oxidative DNA damage and apoptosis induced by norsalsolinol, an endogenous tetrahydroisoquinoline derivative associated with Parkinson's disease

Tetrahydroisoquinoline (TIQ) derivatives are putative neurotoxins that may contribute to the degeneration of dopaminergic neurons in Parkinson's disease. One TIQ, norsalsolinol (NorSAL), is present in dopamine-rich areas of human brain, including the substantia nigra. Here, we demonstrate that NorSAL reduces cell viability and induces apoptosis via cytochrome c release and caspase 3 activation in SH-SY5Y human neuroblastoma cells. Cytochrome c release, caspase 3 activation, and apoptosis induction were all inhibited by the antioxidant N -acetylcysteine. Thus, reactive oxygen species (ROS) contribute to apoptosis induced by NorSAL. Treatment with NorSAL also increased levels of oxidative damage to DNA, a stimulus for apoptosis, in SH-SY5Y. To clarify the mechanism of intracellular DNA damage, we examined the DNA damage caused by NorSAL using ³²P-5'-end-labeled isolated DNA fragments. NorSAL induced DNA damage in the presence of Cu(II). Catalase and bathocuproine, a Cu(I) chelator, inhibited this DNA damage, suggesting that ROS such as the Cu(I)-hydroperoxo complex derived from the reaction of H₂O₂ with Cu(I), promote DNA damage by NorSAL. In summary, NorSAL-generated ROS induced oxidative DNA damage, which led to caspase-dependent apoptosis in neuronal cells.     

Oxidative stress-induced apoptosis in dividing fibroblasts involves activation of p38 MAP kinase and over-expression of Bax: resistance of quiescent cells to oxidative stress

Oxidative stress has been postulated to be involved in aging and age-related degenerative diseases. Cell death as a result of oxidative stress plays an important role in the age related diseases. Using human diploid fibroblasts (HDF) as model to study the mechanism of cell death induced by oxidative stress, a condition was standardized to induce apoptosis in the early passage sub-confluent HDFs by a brief exposure of cells to 250 M hydrogen peroxide. It was observed that p38 MAP kinase (MAPK) was activated soon after the treatment followed by over-expression of Bax protein in cells undergoing apoptosis. An interesting finding of the present study is that the confluent, quiescent HDFs were resistant to cell death under identical condition of oxidative stress. The contact-inhibited quiescent HDFs exhibited increased glutathione level following H₂O₂-treatment, did not activate p38 MAP kinase, or over-express Bax, and were resistant to cell death. These findings indicated that there was a correlation between the cell cycle and sensitivity to oxidative stress. This is the first report to our knowledge that describes a relationship between the quiescence state and anti-oxidative defense. Furthermore, our results also suggest that the p38MAPK activation-Bax expression pathway might be involved in apoptosis induced by oxidative stress.     

活性氧、钙和心力衰竭

活性氧信号和钙信号广泛存在于机体内,两者相互作用,共同参与调节机体多种生理功能及病理过程。本文对这两个信号系统之间的相互作用及相关机制、在心力衰竭过程中的作用及可能的临床应用前景进行了综述。     

Baicalin protects human skin fibroblasts from ultraviolet A radiation-induced oxidative damage and apoptosis

Reactive oxygen species (ROS) are an important factor in the development of skin photodamage after ultraviolet A (UVA) radiation. A flavonoid antioxidant, baicalin, can selectively neutralize super-oxide anion (O₂^?) while having no significant effect on ^?OH. Fibroblasts are a key component of skin dermis. In the present study, we investigated the protective effects of baicalin on human skin fibroblasts (HSFs) under UVA induced oxidative stress. Fluorescence microscopy and flow cytometry were used to assay the intracellular O₂^?, NO, ROS concentrations and the mitochondrial membrane potential. Cell viability was determined using the Cell Counting Kit-8 (CCK-8). The concentrations of cellular MDA, SOD, GSH, T-AOC, and 8-oxo-dG were also measured. Cellular apoptosis was measured by flow cytometry and caspase-3 detection. The results revealed that UVA radiation could cause oxidative stress and apoptosis in HSFs. Interestingly, the use of baicalin after UVA radiation signi?cantly reduced the level of intracellular O₂^?, NO, and ROS, stabilized the mitochondrial membrane potential, and attenuated production of MDA and 8-oxo-dG. These ef?ciently enhanced the antioxidative defense system and protected the HSFs from subsequent oxidative stress damage and apoptosis. In other words, baicalin decreased the excessive generation of intracellular ROS and NO, and elevated the cellular antioxidative defense, which eventually mitigate the UVA-induced apoptosis. Based on our results, baicalin may have applications in the treatment of skin photodamage caused by UVA irradiation.