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Cao J, Verma SK, Jaworski E, Mohan S, Nagasawa CK, Rayavara K, Sooter A, Miller SN, Holcomb RJ, Powell MJ, Ji P, Elrod ND, Yildirim E, Wagner EJ, Popov V, Garg NJ, Routh AL, Kuyumcu-Martinez MN. RBFOX2 is critical for maintaining alternative polyadenylation patterns and mitochondrial health in rat myoblasts. Cell Rep 2021; 37:109910. [PMID: 34731606 PMCID: PMC8600936 DOI: 10.1016/j.celrep.2021.109910] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 07/22/2021] [Accepted: 10/08/2021] [Indexed: 12/16/2022] Open
Abstract
RBFOX2, which has a well-established role in alternative splicing, is linked to heart diseases. However, it is unclear whether RBFOX2 has other roles in RNA processing that can influence gene expression in muscle cells, contributing to heart disease. Here, we employ both 3'-end and nanopore cDNA sequencing to reveal a previously unrecognized role for RBFOX2 in maintaining alternative polyadenylation (APA) signatures in myoblasts. RBFOX2-mediated APA modulates mRNA levels and/or isoform expression of a collection of genes, including contractile and mitochondrial genes. Depletion of RBFOX2 adversely affects mitochondrial health in myoblasts, correlating with disrupted APA of mitochondrial gene Slc25a4. Mechanistically, RBFOX2 regulation of Slc25a4 APA is mediated through consensus RBFOX2 binding motifs near the distal polyadenylation site, enforcing the use of the proximal polyadenylation site. In sum, our results unveil a role for RBFOX2 in fine-tuning expression of mitochondrial and contractile genes via APA in myoblasts relevant to heart diseases.
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Affiliation(s)
- Jun Cao
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Sunil K Verma
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Elizabeth Jaworski
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Stephanie Mohan
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Chloe K Nagasawa
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Kempaiah Rayavara
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Amanda Sooter
- School of Medicine, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Sierra N Miller
- Center for Addiction Research, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Richard J Holcomb
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Mason J Powell
- School of Medicine, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Ping Ji
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Nathan D Elrod
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Eda Yildirim
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27708, USA
| | - Eric J Wagner
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA; Sealy Centre for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Vsevolod Popov
- Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Nisha J Garg
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Andrew L Routh
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA; Sealy Centre for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Muge N Kuyumcu-Martinez
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA; Department of Neuroscience, Cell biology and Anatomy, University of Texas Medical Branch, Galveston, TX 77555, USA.
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Niu X, Zhang J, Ling C, Bai M, Peng Y, Sun S, Li Y, Zhang Z. Polysaccharide from Angelica sinensis protects H9c2 cells against oxidative injury and endoplasmic reticulum stress by activating the ATF6 pathway. J Int Med Res 2018. [PMID: 29517941 PMCID: PMC5991254 DOI: 10.1177/0300060518758863] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Objectives Angelica sinensis exerts various pharmacological effects, such as antioxidant and anti-apoptotic activity. This study aimed to investigate the active ingredients in A. sinensis with antioxidant properties and whether A. sinensis polysaccharide (ASP) protects H9c2 cells against oxidative and endoplasmic reticulum (ER) stress. Methods The ingredients of A. sinensis and their targets and related pathways were determined using web-based databases. Markers of oxidative stress, cell viability, apoptosis, and ER stress-related signalling pathways were measured in H9c2 cells treated with hydrogen peroxide (H2O2) and ASP. Results The ingredient–pathway–disease network showed that A. sinensis exerted protective effects against oxidative injury through its various active ingredients on regulation of multiple pathways. Subsequent experiments showed that ASP pretreatment significantly decreased H2O2-induced cytotoxicity and apoptosis in H9c2 cells. ASP pretreatment inhibited H2O2-induced reactive oxygen species generation, lactic dehydrogenase release, and malondialdehyde production. ASP exerted beneficial effects by inducing activating transcription factor 6 (ATF6) and increasing ATF6 target protein levels, which in turn attenuated ER stress and increased antioxidant activity. Conclusions Our findings indicate that ASP, a major water-soluble component of A. sinensis, exerts protective effects against H2O2-induced injury in H9c2 cells by activating the ATF6 pathway, thus ameliorating ER and oxidative stress.
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Affiliation(s)
- Xiaowei Niu
- 1 The First School of Clinical Medicine, Lanzhou University, Lanzhou, Gansu, China
| | | | - Chun Ling
- 3 The First People's Hospital of Chuzhou, Chuzhou, Anhui, China
| | - Ming Bai
- 4 Department of Cardiology, the First Hospital of Lanzhou University, Lanzhou, Gansu, China.,5 Gansu Key Laboratory of Cardiovascular Disease, Lanzhou, Gansu, China
| | - Yu Peng
- 4 Department of Cardiology, the First Hospital of Lanzhou University, Lanzhou, Gansu, China.,5 Gansu Key Laboratory of Cardiovascular Disease, Lanzhou, Gansu, China
| | - Shaobo Sun
- 6 Key Lab of Prevention and Treatment for Chronic Disease, Traditional Chinese Medicine of Gansu Province, Lanzhou, Gansu, China
| | - Yingdong Li
- 6 Key Lab of Prevention and Treatment for Chronic Disease, Traditional Chinese Medicine of Gansu Province, Lanzhou, Gansu, China
| | - Zheng Zhang
- 4 Department of Cardiology, the First Hospital of Lanzhou University, Lanzhou, Gansu, China.,5 Gansu Key Laboratory of Cardiovascular Disease, Lanzhou, Gansu, China
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Abstract
Small-conductance Ca2+-activated potassium (SK) channels are relative newcomers within the field of cardiac electrophysiology. In recent years, an increased focus has been given to these channels because they might constitute a relatively atrial-selective target. This review will give a general introduction to SK channels followed by their proposed function in the heart under normal and pathophysiological conditions. It is revealed how antiarrhythmic effects can be obtained by SK channel inhibition in a number of species in situations of atrial fibrillation. On the contrary, the beneficial effects of SK channel inhibition in situations of heart failure are questionable and still needs investigation. The understanding of cardiac SK channels is rapidly increasing these years, and it is hoped that this will clarify whether SK channel inhibition has potential as a new anti–atrial fibrillation principle.
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17Beta-Estradiol Inhibits Calcium-Activated Potassium Channel Expressions in Rat Whole Bladder. Int Neurourol J 2016; 20:18-25. [PMID: 27032553 PMCID: PMC4819160 DOI: 10.5213/inj.1630492.246] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 02/15/2016] [Indexed: 11/22/2022] Open
Abstract
Purpose: To investigate the effect of estrogen on the expression of calcium-activated potassium (KCa) channels in an overactive bladder rat model. To this end, mRNA and protein levels of KCa channel subtypes in the bladder of ovariectomized rats were measured by reverse transcription polymerase chain reaction and western blotting, respectively. Methods: Ten-week-old female Sprague-Dawley rats were divided randomly into 3 groups: sham-operated control group (n=11), ovariectomy group (n=11), and the group treated with estrogen after ovariectomy (n=12). Rats in the last group were subcutaneously injected with 17β-estradiol (50 μg/kg) every other day for 2 weeks, whereas rats in the other 2 groups received vehicle (soybean oil) alone. Two weeks after treatment, the whole bladder was excised for mRNA and protein measurements. Results: Protein levels of the large-conductance KCa (BK) channels in the ovariectomy group were 1.5 folds higher than those in the sham-operated control group. However, the protein levels of the other KCa channel subtypes did not change significantly upon bilateral ovariectomy. Treatment with 17β-estradiol after ovariectomy restored BK channel protein levels to the control value. In contrast, BK channel mRNA levels were not significantly affected by either ovariectomy alone or 17β-estradiol treatment. The small-conductance KCa type 3 channel (SK3) mRNA and protein levels decreased to 75% of control levels upon 17β-estradiol treatment. Conclusions: These results suggest that 17β-estradiol may influence urinary bladder function by modulating BK and SK3 channel expression.
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Montoya TI, Acevedo JF, Smith B, Keller PW, Sailors JL, Tang L, Word RA, Wai CY. Myogenic stem cell-laden hydrogel scaffold in wound healing of the disrupted external anal sphincter. Int Urogynecol J 2015; 26:893-904. [PMID: 25644049 DOI: 10.1007/s00192-014-2620-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 12/22/2014] [Indexed: 01/30/2023]
Abstract
OBJECTIVE To evaluate the effect of myogenic stem cell-laden hydrogel scaffold on contractile function and histomorphology of the external anal sphincter (EAS) after transection without repair. METHODS Eighty female rats underwent anal sphincter transection without repair. After 2 weeks, animals were injected at the transection site with: nothing (non-repaired control, NRC group); a polyethylene glycol-based hydrogel matrix scaffold combined with phosphate-buffered saline (PBS/hydrogel group); a hydrogel matrix scaffold combined with myogenic stem cells (stem cell/hydrogel group): or type I collagen (collagen) group. 4 (n = 40) or 12 (n = 40) weeks later, the anal sphincter complexes were dissected out and analyzed for contractile function, disruption, and striated muscle volume. Time-matched unoperated controls (UOC) were utilized for each of the two time points (n = 20). RESULTS After 4 weeks, maximal electrical field-stimulated (EFS) contractions were significantly decreased in all four non-repaired treatment groups compared with UOC. However, EFS-stimulated contractions, tetanic force generation, and twitch tension were improved in non-repaired EAS injected with stem cell/hydrogel group relative to the NRC, PBS/hydrogel, or collagen groups. NRC and sphincters injected with PBS/hydrogel deteriorated further by 12 weeks, while those receiving stem cell/hydrogel maintained improved contractile function at varying frequencies and voltages. Striated muscle volume increased from 4 to 12 weeks for PBS/hydrogel and stem cell/hydrogel animals. At 12 weeks, stem cell/hydrogel animals had greater sphincter striated muscle volumes compared with all other treatment groups. CONCLUSION In this animal model, sustained improvement of contractile responses in non-repaired EAS treated with biogel scaffold and myogenic stem cells suggests that a biologically compatible matrix may facilitate stem cell survival, differentiation, or function leading to recovery of contractile function even after persistent disruption.
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Affiliation(s)
- T Ignacio Montoya
- Division of Female Pelvic Medicine and Reconstructive Surgery, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390-9032, USA
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Schmitt N, Grunnet M, Olesen SP. Cardiac potassium channel subtypes: new roles in repolarization and arrhythmia. Physiol Rev 2014; 94:609-53. [PMID: 24692356 DOI: 10.1152/physrev.00022.2013] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K+ channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K+ channels drive the late repolarization of the ventricle with some redundancy, and in atria this repolarization reserve is supplemented by the fairly atrial-specific KV1.5, Kir3, KCa, and K2P channels. The role of the latter two subtypes in atria is currently being clarified, and several findings indicate that they could constitute targets for new pharmacological treatment of atrial fibrillation. The interplay between the different K+ channel subtypes in both atria and ventricle is dynamic, and a significant up- and downregulation occurs in disease states such as atrial fibrillation or heart failure. The underlying posttranscriptional and posttranslational remodeling of the individual K+ channels changes their activity and significance relative to each other, and they must be viewed together to understand their role in keeping a stable heart rhythm, also under menacing conditions like attacks of reentry arrhythmia.
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Stacey MW, Sabuncu AC, Beskok A. Dielectric characterization of costal cartilage chondrocytes. Biochim Biophys Acta Gen Subj 2013; 1840:146-52. [PMID: 24016606 DOI: 10.1016/j.bbagen.2013.08.031] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2013] [Revised: 07/24/2013] [Accepted: 08/29/2013] [Indexed: 11/18/2022]
Abstract
BACKGROUND Chondrocytes respond to biomechanical and bioelectrochemical stimuli by secreting appropriate extracellular matrix proteins that enable the tissue to withstand the large forces it experiences. Although biomechanical aspects of cartilage are well described, little is known of the bioelectrochemical responses. The focus of this study is to identify bioelectrical characteristics of human costal cartilage cells using dielectric spectroscopy. METHODS Dielectric spectroscopy allows non-invasive probing of biological cells. An in house computer program is developed to extract dielectric properties of human costal cartilage cells from raw cell suspension impedance data measured by a microfluidic device. The dielectric properties of chondrocytes are compared with other cell types in order to comparatively assess the electrical nature of chondrocytes. RESULTS The results suggest that electrical cell membrane characteristics of chondrocyte cells are close to cardiomyoblast cells, cells known to possess an array of active ion channels. The blocking effect of the non-specific ion channel blocker gadolinium is tested on chondrocytes with a significant reduction in both membrane capacitance and conductance. CONCLUSIONS We have utilized a microfluidic chamber to mimic biomechanical events through changes in bioelectrochemistry and described the dielectric properties of chondrocytes to be closer to cells derived from electrically excitably tissues. GENERAL SIGNIFICANCE The study describes dielectric characterization of human costal chondrocyte cells using physical tools, where results and methodology can be used to identify potential anomalies in bioelectrochemical responses that may lead to cartilage disorders.
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Affiliation(s)
- Michael W Stacey
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA
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Absi M, Oso H, Khattab M. The effect of streptozotocin-induced diabetes on the EDHF-type relaxation and cardiac function in rats. J Adv Res 2012; 4:375-83. [PMID: 25685443 PMCID: PMC4293870 DOI: 10.1016/j.jare.2012.07.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Revised: 07/11/2012] [Accepted: 07/13/2012] [Indexed: 11/19/2022] Open
Abstract
The endothelium-derived hyperpolarizing factor (EDHF) response is a critical for the functioning of small blood vessels. We investigated the effect of streptozotocin-induced diabetes on the EDHF response and its possible role in the regulation of cardiac function. The vasorelaxant response to ACh- or NS309- (direct opener endothelial small- (SKCa)- and intermediate-conductance (IKCa) calcium-activated potassium channels; main components of EDHF response) were measured in pressurized mesenteric arteries (diameter 300–350 μm). The response to 1 μM ACh was reduced in diabetes (84.8 ± 2.8% control vs 22.5 ± 5.8% diabetics; n ⩾ 8; P < 0.001). NS309 (1 μM) relaxations were also decreased in diabetic arteries (78.5 ± 8.7% control vs 32.1 ± 5.8% diabetics; n ⩾ 5; P < 0.001). SKCa and IKCa-mediated EDHF relaxations in response ACh or NS309 were also significantly reduced by diabetes. Ruthenium red, RuR, a blocker of TRP channels, strongly depress the response to ACh and NS309 in control and diabetic arteries. RuR decreased SKCa and IKCa-mediated EDHF vasodilatation in response to NS309 but not to ACh. An elevation in systolic blood pressure was observed in diabetic animals. ECG recording of control hearts showed shortening of PR interval. RuR reduced PR interval and R wave amplitude in diabetic hearts. In conclusion, the reduced EDHF-type relaxations in STZ-induced diabetes is due impairment of KCa channels function. TRP channels possibly contribute to EDHF vasodilatation via direct opening of endothelial KCa. It is possible that EDHF and TRP channels contribute to the regulation of cardiac function and therefore can be considered as therapeutic targets to improve cardiovascular complications of diabetes.
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Affiliation(s)
- Mais Absi
- Pharmacology and Toxicology Department, Faculty of Pharmacy, Aleppo University, Syria
- Corresponding author. Present address: Faculty of Life Sciences, The University of Manchester, A.1025 Michael Smith Building, Manchester M13 9PT, UK. Tel.: +44 161 2751500; fax: +44 161 2755600.
| | - Hani Oso
- Pharmacology and Toxicology Department, Faculty of Pharmacy, Aleppo University, Syria
| | - Marwan Khattab
- Faculty of Sciences, Zoology Department, Aleppo University, Syria
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Nattel S. Calcium-activated potassium current: a novel ion channel candidate in atrial fibrillation. J Physiol 2009; 587:1385-6. [PMID: 19336611 DOI: 10.1113/jphysiol.2009.170621] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Affiliation(s)
- Stanley Nattel
- Department of Medicine and Research Center, Montreal Heart Institute and Université de Montréal, Quebec, Canada.
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Shi R, Huang CC, Aronstam RS, Ercal N, Martin A, Huang YW. N-acetylcysteine amide decreases oxidative stress but not cell death induced by doxorubicin in H9c2 cardiomyocytes. BMC Pharmacol 2009; 9:7. [PMID: 19368719 PMCID: PMC2670828 DOI: 10.1186/1471-2210-9-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2008] [Accepted: 04/15/2009] [Indexed: 03/03/2023] Open
Abstract
Background While doxorubicin (DOX) is widely used in cancer chemotherapy, long-term severe cardiotoxicity limits its use. This is the first report of the chemoprotective efficacy of a relatively new thiol antioxidant, N-acetylcysteine amide (NACA), on DOX-induced cell death in cardiomyocytes. We hypothesized that NACA would protect H9c2 cardiomyocytes from DOX-induced toxicity by reducing oxidative stress. Accordingly, we determined the ability of NACA to mitigate the cytotoxicity of DOX in H9c2 cells and correlated these effects with the production of indicators of oxidative stress. Results DOX at 5 μM induced cardiotoxicity while 1) increasing the generation of reactive oxygen species (ROS), 2) decreasing levels and activities of antioxidants and antioxidant enzymes (catalase, glutathione peroxidase, glutathione reductase) and 3) increasing lipid peroxidation. NACA at 750 μM substantially reduced the levels of ROS and lipid peroxidation, as well as increased both GSH level and GSH/GSSG ratio. However, treating H9c2 cells with NACA did little to protect H9c2 cells from DOX-induced cell death. Conclusion Although NACA effectively reduced oxidative stress in DOX-treated H9c2 cells, it had minimal effects on DOX-induced cell death. NACA prevented oxidative stress by elevation of GSH and CYS, reduction of ROS and lipid peroxidation, and restoration of antioxidant enzyme activities. Further studies to identify oxidative stress-independent pathways that lead to DOX-induced cell death in H9c2 are warranted.
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Affiliation(s)
- Rong Shi
- Department of Chemistry, Missouri University of Science and Technology, 400 W. 11st Street, 142 Schrenk Hall, Rolla, MO 65409, USA.
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N-acetylcysteine amide decreases oxidative stress but not cell death induced by doxorubicin in H9c2 cardiomyocytes. BMC Pharmacol 2009. [PMID: 19368719 DOI: 10.1186/1471-2210-9-7, 10.1186/1472-6904-9-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND While doxorubicin (DOX) is widely used in cancer chemotherapy, long-term severe cardiotoxicity limits its use. This is the first report of the chemoprotective efficacy of a relatively new thiol antioxidant, N-acetylcysteine amide (NACA), on DOX-induced cell death in cardiomyocytes. We hypothesized that NACA would protect H9c2 cardiomyocytes from DOX-induced toxicity by reducing oxidative stress. Accordingly, we determined the ability of NACA to mitigate the cytotoxicity of DOX in H9c2 cells and correlated these effects with the production of indicators of oxidative stress. RESULTS DOX at 5 microM induced cardiotoxicity while 1) increasing the generation of reactive oxygen species (ROS), 2) decreasing levels and activities of antioxidants and antioxidant enzymes (catalase, glutathione peroxidase, glutathione reductase) and 3) increasing lipid peroxidation. NACA at 750 microM substantially reduced the levels of ROS and lipid peroxidation, as well as increased both GSH level and GSH/GSSG ratio. However, treating H9c2 cells with NACA did little to protect H9c2 cells from DOX-induced cell death. CONCLUSION Although NACA effectively reduced oxidative stress in DOX-treated H9c2 cells, it had minimal effects on DOX-induced cell death. NACA prevented oxidative stress by elevation of GSH and CYS, reduction of ROS and lipid peroxidation, and restoration of antioxidant enzyme activities. Further studies to identify oxidative stress-independent pathways that lead to DOX-induced cell death in H9c2 are warranted.
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Sardão VA, Oliveira PJ, Holy J, Oliveira CR, Wallace KB. Vital imaging of H9c2 myoblasts exposed to tert-butylhydroperoxide--characterization of morphological features of cell death. BMC Cell Biol 2007; 8:11. [PMID: 17362523 PMCID: PMC1831770 DOI: 10.1186/1471-2121-8-11] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Accepted: 03/16/2007] [Indexed: 11/10/2022] Open
Abstract
Background When exposed to oxidative conditions, cells suffer not only biochemical alterations, but also morphologic changes. Oxidative stress is a condition induced by some pro-oxidant compounds, such as by tert-butylhydroperoxide (tBHP) and can also be induced in vivo by ischemia/reperfusion conditions, which is very common in cardiac tissue. The cell line H9c2 has been used as an in vitro cellular model for both skeletal and cardiac muscle. Understanding how these cells respond to oxidative agents may furnish novel insights into how cardiac and skeletal tissues respond to oxidative stress conditions. The objective of this work was to characterize, through vital imaging, morphological alterations and the appearance of apoptotic hallmarks, with a special focus on mitochondrial changes, upon exposure of H9c2 cells to tBHP. Results When exposed to tBHP, an increase in intracellular oxidative stress was detected in H9c2 cells by epifluorescence microscopy, which was accompanied by an increase in cell death that was prevented by the antioxidants Trolox and N-acetylcysteine. Several morphological alterations characteristic of apoptosis were noted, including changes in nuclear morphology, translocation of phosphatidylserine to the outer leaflet of the cell membrane, and cell blebbing. An increase in the exposure period or in tBHP concentration resulted in a clear loss of membrane integrity, which is characteristic of necrosis. Changes in mitochondrial morphology, consisting of a transition from long filaments to small and round fragments, were also detected in H9c2 cells after treatment with tBHP. Bax aggregates near mitochondrial networks were formed after short periods of incubation. Conclusion Vital imaging of alterations in cell morphology is a useful method to characterize cellular responses to oxidative stress. In the present work, we report two distinct patterns of morphological alterations in H9c2 cells exposed to tBHP, a pro-oxidant agent frequently used as model to induce oxidative stress. In particular, dynamic changes in mitochondrial networks could be visualized, which appear to be centrally involved in how these cells respond to oxidative stress. The data also indicate that the cause of H9c2 cell death following tBHP exposure is increased intracellular oxidative stress.
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Affiliation(s)
- Vilma A Sardão
- Center for Neurosciences and Cellular Biology, University of Coimbra, Coimbra, Portugal
| | - Paulo J Oliveira
- Center for Neurosciences and Cellular Biology, University of Coimbra, Coimbra, Portugal
| | - Jon Holy
- Department of Anatomy, Microbiology and Pathology, University of Minnesota-Medical School, Duluth, USA
| | - Catarina R Oliveira
- Center for Neurosciences and Cellular Biology, University of Coimbra, Coimbra, Portugal
| | - Kendall B Wallace
- Department of Biochemistry and Molecular Biology, University of Minnesota-Medical Medical School, Duluth, USA
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Barfod ET, Moore AL, Lidofsky SD. Cloning and functional expression of a liver isoform of the small conductance Ca2+-activated K+ channel SK3. Am J Physiol Cell Physiol 2001; 280:C836-42. [PMID: 11245600 DOI: 10.1152/ajpcell.2001.280.4.c836] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Small conductance Ca2+-activated K+ (SK) channels have been cloned from mammalian brain, but little is known about the molecular characteristics of SK channels in nonexcitable tissues. Here, we report the isolation from rat liver of an isoform of SK3. The sequence of the rat liver isoform differs from rat brain SK3 in five amino acid residues in the NH3 terminus, where it more closely resembles human brain SK3. SK3 immunoreactivity was detectable in hepatocytes in rat liver and in HTC rat hepatoma cells. Human embryonic kidney (HEK-293) cells transfected with liver SK3 expressed 10 pS K+ channels that were Ca2+ dependent (EC(50) 630 nM) and were blocked by the SK channel inhibitor apamin (IC(50) 0.6 nM); whole cell SK3 currents inactivated at membrane potentials more positive than -40 mV. Notably, the Ca2+ dependence, apamin sensitivity, and voltage-dependent inactivation of SK3 are strikingly similar to the properties of hepatocellular and biliary epithelial SK channels evoked by metabolic stress. These observations raise the possibility that SK3 channels influence membrane K+ permeability in hepatobiliary cells during liver injury.
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Affiliation(s)
- E T Barfod
- Department of Medicine, University of Vermont, Burlington, VT 05405, USA
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Sejersted OM, Sjøgaard G. Dynamics and consequences of potassium shifts in skeletal muscle and heart during exercise. Physiol Rev 2000; 80:1411-81. [PMID: 11015618 DOI: 10.1152/physrev.2000.80.4.1411] [Citation(s) in RCA: 350] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Since it became clear that K(+) shifts with exercise are extensive and can cause more than a doubling of the extracellular [K(+)] ([K(+)](s)) as reviewed here, it has been suggested that these shifts may cause fatigue through the effect on muscle excitability and action potentials (AP). The cause of the K(+) shifts is a transient or long-lasting mismatch between outward repolarizing K(+) currents and K(+) influx carried by the Na(+)-K(+) pump. Several factors modify the effect of raised [K(+)](s) during exercise on membrane potential (E(m)) and force production. 1) Membrane conductance to K(+) is variable and controlled by various K(+) channels. Low relative K(+) conductance will reduce the contribution of [K(+)](s) to the E(m). In addition, high Cl(-) conductance may stabilize the E(m) during brief periods of large K(+) shifts. 2) The Na(+)-K(+) pump contributes with a hyperpolarizing current. 3) Cell swelling accompanies muscle contractions especially in fast-twitch muscle, although little in the heart. This will contribute considerably to the lowering of intracellular [K(+)] ([K(+)](c)) and will attenuate the exercise-induced rise of intracellular [Na(+)] ([Na(+)](c)). 4) The rise of [Na(+)](c) is sufficient to activate the Na(+)-K(+) pump to completely compensate increased K(+) release in the heart, yet not in skeletal muscle. In skeletal muscle there is strong evidence for control of pump activity not only through hormones, but through a hitherto unidentified mechanism. 5) Ionic shifts within the skeletal muscle t tubules and in the heart in extracellular clefts may markedly affect excitation-contraction coupling. 6) Age and state of training together with nutritional state modify muscle K(+) content and the abundance of Na(+)-K(+) pumps. We conclude that despite modifying factors coming into play during muscle activity, the K(+) shifts with high-intensity exercise may contribute substantially to fatigue in skeletal muscle, whereas in the heart, except during ischemia, the K(+) balance is controlled much more effectively.
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Affiliation(s)
- O M Sejersted
- Institute for Experimental Medical Research, University of Oslo, Ullevaal Hospital, Oslo, Norway.
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