Oxidative stress-induced mitochondrial fragmentation and movement in skeletal muscle myoblasts

Abstract

Iqbal S, Hood DA. Oxidative stress-induced mitochondrial fragmentation and movement in skeletal muscle myoblasts. Am J Physiol Cell Physiol 306: C1176 -C1183, 2014. First published April 16, 2014; doi:10.1152/ajpcell.00017.2014.-Mitochondria are dynamic organelles, capable of altering their morphology and function. However, the mechanisms governing these changes have not been fully elucidated, particularly in muscle cells. We demonstrated that oxidative stress with H2O2 resulted in a 41% increase in fragmentation of the mitochondrial reticulum in myoblasts within 3 h of exposure, an effect that was preceded by a reduction in membrane potential. Using live cell imaging, we monitored mitochondrial motility and found that oxidative stress resulted in a 30% reduction in the average velocity of mitochondria. This was accompanied by parallel reductions in both organelle fission and fusion. The attenuation in mitochondrial movement was abolished by the addition of N-acetylcysteine. To investigate whether H2O2-induced fragmentation was mediated by dynaminrelated protein 1, we incubated cells with mDivi1, an inhibitor of dynamin-related protein 1 translocation to mitochondria. mDivi1 attenuated oxidative stress-induced mitochondrial fragmentation by 27%. Moreover, we demonstrated that exposure to H2O2 upregulated endoplasmic reticulum-unfolded protein response markers before the initiation of mitophagy signaling and the mitochondrial-unfolded protein response. These findings indicate that oxidative stress is a vital signaling mechanism in the regulation of mitochondrial morphology and motility. mitochondria; mitochondrial movement; oxidative stress; mitochondrial morphology MITOCHONDRIA ARE ESSENTIAL ORGANELLES for the life and death of eukaryotic cells. They play key roles in aerobic energy production, apoptosis, mitophagy, and cellular signaling. These versatile organelles were once thought to be static and rigid structures. More recently, mitochondria have been appreciated for their dynamic nature. They can change their distribution by moving along cytoskeletal tracks or change their overall morphology. The maintenance and appropriate networking of mitochondria within the cell is mediated by fusion and opposing fission processes. Fusion involves the mixing of mitochondrial material, whereas fission divides the organelle into smaller components. Disruptions in either of these opposing events can lead to developmental defects and disease (29), suggesting that the proper maintenance of mitochondrial morphology is critical for normal cell function.Mitochondrial fission is orchestrated, in part, by dynaminrelated protein 1 (Drp1) (4, 25), a protein that is a GTPase of the dynamin family. All dynamin members are structurally similar but functionally diverse GTP-binding proteins. Drp1 assists in mitochondrial fission by polymerizing into a ring-like structure around the organelle. The cross-bridging of the GTPase domains of adjacent Drp1 proteins results in GTP hydrolysis, constriction, and the ultimate severing of mitochon...

MitoNEET-dependent formation of intermitochondrial junctions

“…Mitochondrial fusion and fission is known to be affected by many physiological parameters. It has been reported previously that in cells exposed to an oxidative stress, the mitochondrial network is rapidly fragmented (14,15). In contrast, other types of stress, and in particular inhibition of protein synthesis by cycloheximide, result in a marked increase in mitochondrial connectivity (16).…”

Appoptosin interacts with mitochondrial outer-membrane fusion proteins and regulates mitochondrial morphology

“…Because the fusion activity of MFN1-MFN2 heterotypic oligomers is comparable to those of homo-oligomers of MFN1 or MFN2 (Detmer and Chan, 2007), overexpression of appoptosin might interfere with the fusion machinery by impairing the interaction between MFN1 and MFN2, thus leading to mitochondrial fragmentation. Interestingly, considerable efforts have been devoted to studying the fission machinery deficits in Alzheimer's disease, with a focus on DRP1, and findings show that excessive ROS increases DRP1 activity (Iqbal and Hood, 2014;Wu et al, 2011), that Aβ interacts with DRP1 and increases its activity (Manczak et al, 2011), that S-nitrosylation of DRP1 enhances its activity (Cho et al, 2009) and that phosphorylation of DRP1 at specific sites promotes its activity (Chang and Blackstone, 2007;Cribbs and Strack, 2007;Merrill et al, 2011;Meuer et al, 2007;Rambold et al, 2011;Rehman et al, 2012;Taguchi et al, 2007). In contrast, research on the fusion machinery during Alzheimer's disease is limited.…”

“…suggested to cause mitochondrial fragmentation by increasing the mitochondrial translocation of DRP1 (Iqbal and Hood, 2014;Wu et al, 2011). Herein, after transfection with appoptosin in HeLa cells, we treated cells with the ROS scavenger, N-acetyl-L-cysteine (NAC) ( Fig.…”

ENOS deficiency causes podocyte injury with mitochondrial abnormality

“…In turn, oxidative stress could modulate mitochondrial function and structure. Recently, Iqbal et al showed that hydrogen peroxide caused mitochondrial fragmentation in muscle cells, suggesting that mitochondrial structure can be modulated by oxidative stress [38,39]. Taken together, eNOS deficiency, mitochondrial fragmentation and oxidative stress could be closely linked each other and likely create vicious cycles.…”

“…A potential mechanism for mitochondrial dysfunction could be the mitochondrial fragmentation. Indeed, previous studies demonstrated that fragmented mitochondria induced oxidative stress [36] while oxidative stress is also able to induce mitochondrial fragmentation [38], suggesting the close relationships between oxidative stress and mitochondrial fragmentation. We next found that D-17 deletion, which is a marker of damaged mitochondrial DNA and associated with such pathological condition as aging [22], was more frequently induced in the eNOSKO mouse, indicating that the damaged mitochondrial DNA could also impair mitochondrial function in the eNOSKO mice.…”