scholarly journals Inhibition of cAMP/PKA Pathway Protects Optic Nerve Head Astrocytes against Oxidative Stress by Akt/Bax Phosphorylation-Mediated Mfn1/2 Oligomerization

2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Won-Kyu Ju ◽  
Myoung Sup Shim ◽  
Keun-Young Kim ◽  
Tae Lim Park ◽  
Sangphil Ahn ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Optic Nerve ◽  
Protein Expression ◽  
Cell Viability ◽  
Optic Nerve Head ◽  
Mitochondrial Dynamics ◽  
Nerve Degeneration ◽  
Scanning Electron Microscopy Data ◽  
Pka Pathway ◽  
The Impact

Glaucoma is characterized by a progressive optic nerve degeneration and retinal ganglion cell loss, but the underlying biological basis for the accompanying neurodegeneration is not known. Accumulating evidence indicates that structural and functional abnormalities of astrocytes within the optic nerve head (ONH) have a role in glaucomatous neurodegeneration. Here, we investigate the impact of activation of cyclic adenosine 3′,5′-monophosphate (cAMP)/protein kinase A (PKA) pathway on mitochondrial dynamics of ONH astrocytes exposed to oxidative stress. ONH astrocytes showed a significant loss of astrocytic processes in the glial lamina of glaucomatous DBA/2J mice, accompanied by basement membrane thickening and collagen deposition in blood vessels and axonal degeneration. Serial block-face scanning electron microscopy data analysis demonstrated that numbers of total and branched mitochondria were significantly increased in ONH astrocytes, while mitochondrial length and volume density were significantly decreased. We found that hydrogen peroxide- (H2O2-) induced oxidative stress compromised not only mitochondrial bioenergetics by reducing the basal and maximal respiration but also balance of mitochondrial dynamics by decreasing dynamin-related protein 1 (Drp1) protein expression in rat ONH astrocytes. In contrast, elevated cAMP by dibutyryl-cAMP (dbcAMP) or isobutylmethylxanthine treatment significantly increased Drp1 protein expression in ONH astrocytes. Elevated cAMP exacerbated the impairment of mitochondrial dynamics and reduction of cell viability to oxidative stress in ONH astrocytes by decreasing optic atrophy type 1 (OPA1), and mitofusin (Mfn)1/2 protein expression. Following combined treatment with H2O2 and dbcAMP, PKA inhibition restored mitochondrial dynamics by increasing mitochondrial length and decreasing mitochondrial number, and this promoted cell viability in ONH astrocytes. Also, PKA inhibition significantly promoted Akt/Bax phosphorylation and Mfn1/2 oligomerization in ONH astrocytes. These results suggest that modulation of the cAMP/PKA signaling pathway may have therapeutic potential by activating Akt/Bax phosphorylation and promoting Mfn1/2 oligomerization in glaucomatous ONH astrocytes.

scholarly journals Differential Activation of Glioprotective Intracellular Signaling Pathways in Primary Optic Nerve Head Astrocytes after Treatment with Different Classes of Antioxidants

Antioxidants ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 324 ◽  
Author(s):  
Anita K. Ghosh ◽  
Vidhya R. Rao ◽  
Victoria J. Wisniewski ◽  
Alexandra D. Zigrossi ◽  
Jamie Floss ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Optic Nerve ◽  
Cell Viability ◽  
Optic Nerve Head ◽  
Intracellular Signaling ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Glaucomatous Optic Neuropathy ◽  
Related Factor ◽  
Expression Levels ◽  
Reactive Astrocytosis

Optic nerve head astrocytes are the specialized glia cells that provide structural and trophic support to the optic nerve head. In response to cellular injury, optic nerve head astrocytes undergo reactive astrocytosis, the process of cellular activation associated with cytoskeletal remodeling, increases in the rate of proliferation and motility, and the generation of Reactive Oxygen Species. Antioxidant intervention has previously been proposed as a therapeutic approach for glaucomatous optic neuropathy, however, little is known regarding the response of optic nerve head astrocytes to antioxidants under physiological versus pathological conditions. The goal of this study was to determine the effects of three different antioxidants, manganese (III) tetrakis (1-methyl-4-pyridyl) porphyrin (Mn-TM-2-PyP), resveratrol and xanthohumol in primary optic nerve head astrocytes. Effects on the expression of the master regulator nuclear factor erythroid 2-related factor 2 (Nrf2), the antioxidant enzyme, manganese-dependent superoxide dismutase 2 (SOD2), and the pro-oxidant enzyme, nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4), were determined by quantitative immunoblotting. Furthermore, efficacy in preventing chemically and reactive astrocytosis-induced increases in cellular oxidative stress was quantified using cell viability assays. The results were compared to the effects of the prototypic antioxidant, Trolox. Antioxidants elicited highly differential changes in the expression levels of Nrf2, SOD2, and NOX4. Notably, Mn-TM-2-PyP increased SOD2 expression eight-fold, while resveratrol increased Nrf2 expression three-fold. In contrast, xanthohumol exerted no statistically significant changes in expression levels. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) uptake and lactate dehydrogenase (LDH) release assays were performed to assess cell viability after chemically and reactive astrocytosis-induced oxidative stress. Mn-TM-2-PyP exerted the most potent glioprotection by fully preventing the loss of cell viability, whereas resveratrol and xanthohumol partially restored cell viability. Our data provide the first evidence for a well-developed antioxidant defense system in optic nerve head astrocytes, which can be pharmacologically targeted by different classes of antioxidants.

scholarly journals The Impact of Intraocular Pressure Elevation on Optic Nerve Head and Choroidal Blood Flow

2018 ◽  
Vol 59 (8) ◽  
pp. 3488 ◽  
Author(s):  
Naoki Kiyota ◽  
Yukihiro Shiga ◽  
Kohei Ichinohasama ◽  
Masayuki Yasuda ◽  
Naoko Aizawa ◽  
...  
Keyword(s):  
Blood Flow ◽  
Intraocular Pressure ◽  
Optic Nerve ◽  
Optic Nerve Head ◽  
Choroidal Blood Flow ◽  
Pressure Elevation ◽  
Intraocular Pressure Elevation ◽  
The Impact

scholarly journals Elevated intracellular cAMP exacerbates vulnerability to oxidative stress in optic nerve head astrocytes

2018 ◽  
Vol 9 (3) ◽  
Author(s):  
Myoung Sup Shim ◽  
Keun-Young Kim ◽  
Jung Hyun Bu ◽  
Hye Seung Nam ◽  
Seung Won Jeong ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Optic Nerve ◽  
Optic Nerve Head ◽  
Intracellular Camp

scholarly journals Cytochrome c oxidase III as a mechanism for apoptosis in heart failure following myocardial infarction

2009 ◽  
Vol 297 (4) ◽  
pp. C928-C934 ◽  
Author(s):  
Changgong Wu ◽  
Lin Yan ◽  
Christophe Depre ◽  
Sunil K. Dhar ◽  
You-Tang Shen ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Myocardial Infarction ◽  
Heart Failure ◽  
Cytochrome C ◽  
Protein Expression ◽  
Cell Viability ◽  
Cytochrome C Oxidase ◽  
Mitochondrial Gene

Cytochrome c oxidase (COX) is composed of 13 subunits, of which COX I, II, and III are encoded by a mitochondrial gene. COX I and II function as the main catalytic components, but the function of COX III is unclear. Because myocardial ischemia affects mitochondrial oxidative metabolism, we hypothesized that COX activity and expression would be affected during postischemic cardiomyopathy. This hypothesis was tested in a monkey model following myocardial infarction (MI) and subsequent pacing-induced heart failure (HF). In this model, COX I protein expression was decreased threefold after MI and fourfold after HF ( P < 0.05 vs. sham), whereas COX II expression remained unchanged. COX III protein expression increased 5-fold after MI and further increased 10-fold after HF compared with sham ( P < 0.05 vs. sham). The physiological impact of COX III regulation was examined in vitro. Overexpression of COX III in mitochondria of HL-1 cells resulted in an 80% decrease in COX I, 60% decrease in global COX activity, 60% decrease in cell viability, and threefold increase in apoptosis ( P < 0.05). Oxidative stress induced by H2O2 significantly ( P < 0.05) increased COX III expression. H2O2 decreased cell viability by 47 ± 3% upon overexpression of COX III, but only by 12 ± 5% in control conditions ( P < 0.05). We conclude that ischemic stress in vivo and oxidative stress in vitro lead to upregulation of COX III, followed by downregulation of COX I expression, impaired COX oxidative activity, and increased apoptosis. Therefore, upregulation of COX III may contribute to the increased susceptibility to apoptosis following MI and subsequent HF.

scholarly journals Plate reader-based cell viability assays for glioprotection using primary rat optic nerve head astrocytes

2015 ◽  
Vol 138 ◽  
pp. 159-166 ◽  
Author(s):  
Simon Kaja ◽  
Andrew J. Payne ◽  
Yuliya Naumchuk ◽  
Deborah Levy ◽  
Danish H. Zaidi ◽  
...  
Keyword(s):  
Optic Nerve ◽  
Cell Viability ◽  
Optic Nerve Head ◽  
Plate Reader

scholarly journals Elevated hydrostatic pressure activates sodium/hydrogen exchanger-1 in rat optic nerve head astrocytes

2009 ◽  
Vol 297 (1) ◽  
pp. C111-C120 ◽  
Author(s):  
Amritlal Mandal ◽  
Mohammad Shahidullah ◽  
Nicholas A. Delamere ◽  
Marcos A. Terán
Keyword(s):  
Optic Nerve ◽  
Hydrostatic Pressure ◽  
Protein Expression ◽  
Optic Nerve Head ◽  
Elevated Hydrostatic Pressure ◽  
Cultured Astrocytes ◽  
Sodium Hydrogen Exchanger ◽  
Recovery From Acidification ◽  
Nhe1 Activity

Optic nerve head astrocytes become abnormal in eyes that have elevated intraocular pressure, and cultured astrocytes display altered protein expression after being subjected for ≥1 days to elevated hydrostatic pressure. Here we show that 2-h elevated hydrostatic pressure (15 or 30 mmHg) causes phosphorylation of ERK1/2, ribosomal S6 protein kinase (p90RSK), and Na/H exchanger (NHE)1 in cultured rat optic nerve head astrocytes as judged by Western blot analysis. The MEK/ERK inhibitor U0126 abolished phosphorylation of NHE1 and p90RSK as well as ERK1/2. To examine NHE1 activity, cytoplasmic pH (pHi) was measured with BCECF and, in some experiments, cells were acidified by 5-min exposure to 20 mM ammonium chloride. Although baseline pHi was unaltered, the rate of pHi recovery from acidification was fourfold higher in pressure-treated astrocytes. In the presence of either U0126 or dimethylamiloride (DMA), an NHE inhibitor, hydrostatic pressure did not change the rate of pHi recovery. The findings are consistent with NHE1 activation due to phosphorylation of ERK1/2, p90RSK, and NHE1 that occurs in response to hydrostatic pressure. These responses may precede long-term changes of protein expression known to occur in pressure-stressed astrocytes.

scholarly journals Zingiberensis Newsaponin Inhibits the Malignant Progression of Hepatocellular Carcinoma via Suppressing Autophagy Moderated by the AKR1C1-Mediated JAK2/STAT3 Pathway

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Keqing He ◽  
Xing Liu ◽  
Shiping Cheng ◽  
Pingsheng Zhou
Keyword(s):  
Oxidative Stress ◽  
Hepatocellular Carcinoma ◽  
Protein Expression ◽  
Cell Viability ◽  
Underlying Mechanism ◽  
Anticancer Effect ◽  
Stat3 Pathway ◽  
Stress Markers ◽  
And Migration ◽  
Hcc Cells

Objective. Saponins are a group of compounds from various plants, which exhibit an anticancer activity. This study aimed to explore the anticancer effect of zingiberensis newsaponin (ZnS) against hepatocellular carcinoma (HCC) and the underlying mechanism involving autophagy. Methods. HCC cells (Huh7 and SMMC7721) were treated with ZnS and/or 3-MA. The cell viability, migration, and apoptosis were determined using CCK-8 assay, transwell assay, and flow cytometry, respectively. The levels of oxidative stress markers (ROS, SOD, and MDA) were measured by ELISA assay. Autophagy was monitored using MDC assay, immunofluorescence staining, and transmission electron microscopy. The relative protein expression of LC3II/LC3I, P62, AKR1C1, p-JAK2, p-STAT3, JAK2, and STAT3 was determined using Western blot. Results. ZnS or 3-MA inhibited the cell viability and migration, and it promoted cell apoptosis and oxidative stress in HCC. MDC-positive cells and autophagosomes were reduced by ZnS or 3-MA treatment. The expression of autophagy-related proteins LC3 (LC3II/LC3I) and P62 was, respectively, downregulated and upregulated after ZnS or 3-MA treatment. In addition, ZnS or 3-MA suppressed the protein expression of AKR1C1, p-JAK2, and p-STAT3 in HCC cells. Furthermore, the above phenomena were evidently enhanced by ZnS combined 3-MA treatment. AKR1C1 overexpression weakened the effect of ZnS on inhibiting the expression of AKR1C1, p-JAK2, and p-STAT3. Conclusion. ZnS exerts an anticancer effect on HCC via inhibiting autophagy moderated by the AKR1C1-mediated JAK2/STAT3 pathway. ZnS and 3-MA exert a synergistic effect on inhibiting HCC.

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