ABSTRACT
[This corrects the article DOI: 10.1155/2019/8060962.].
ABSTRACT
The inducible activation system is valuable for investigating spatiotemporal roles of molecules. A chemically inducible activation system for Fas (CD95/APO-1), which works efficiently to induce apoptosis and leads non-apoptotic pathways, has not yet been developed. Here, we engineered a rapamycin-induced dimerization system of Fas consisting of FKBP and FRB proteins. Treatment of rapamycin specifically induces cellular apoptosis. In neurons and cells with high c-FLIP expression, rapamycin-induced Fas activation triggered the activation of the non-apoptotic pathway components instead of cell death. Intracranial delivery of the system could be utilized to induce apoptosis of tumor cells upon rapamycin treatment. Our results demonstrate a novel inducible Fas activation system which operates with high efficiency and temporal precision in vitro and in vivo promising a potential therapeutic strategy.
Subject(s)
Protein Engineering/methods , Sirolimus/pharmacology , Tacrolimus Binding Protein 1A/metabolism , Tacrolimus Binding Proteins/metabolism , fas Receptor/metabolism , Animals , Apoptosis/drug effects , Apoptosis/genetics , Brain Neoplasms/drug therapy , Brain Neoplasms/pathology , Cells, Cultured , Female , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , HeLa Cells , Humans , Mice, Inbred C57BL , Neurons/metabolism , Pregnancy , Rats, Sprague-Dawley , Tacrolimus Binding Protein 1A/genetics , Xenograft Model Antitumor Assays , fas Receptor/geneticsABSTRACT
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.
Subject(s)
Astrocytes/metabolism , Cyclic AMP-Dependent Protein Kinases/metabolism , GTP Phosphohydrolases/metabolism , Glaucoma/metabolism , Membrane Proteins/metabolism , Mitochondrial Proteins/metabolism , Optic Nerve/metabolism , Oxidative Stress , Protein Multimerization , Signal Transduction , bcl-2-Associated X Protein/metabolism , Animals , Astrocytes/pathology , Female , Glaucoma/pathology , Mice , Optic Nerve/pathology , Rats , Rats, Sprague-DawleyABSTRACT
Coenzyme Q10 (CoQ10) protects retinal ganglion cells (RGCs) in experimental retinal ischemia and glaucoma by scavenging reactive oxygen species. We tested whether a diet supplemented with ubiquinol, the reduced form of CoQ10, promotes RGC survival and blocks the apoptotic pathway in ischemic mouse retina induced by acute high intraocular pressure (IOP) elevation. Ubiquinol (1%) treatment significantly promoted RGC survival at 2 weeks after ischemia/reperfusion. The ubiquinol treatment significantly blocked activation of astroglial and microglial cells in the ischemic retina at 2 weeks. While the ubiquinol treatment significantly decreased active Bax protein expression in the ischemic retina, phosphorylation of Bad at serine 112 and Bcl-xL protein expression were preserved in the ubiquinol-treated ischemic retina at 12â¯h. Consistently, the ubiquinol treatment prevented apoptotic cell death by blocking caspase-3 cleavage. These results suggest that the ubiquinol enhances RGC survival by modulating the Bax/Bad/Bcl-xL-mediated apoptotic pathway in the ischemic retina. Ubiquinol has therapeutic potential for ameliorating elevated IOP-induced ischemic retinal degeneration.
Subject(s)
Antioxidants/pharmacology , Gene Expression Regulation/drug effects , Reperfusion Injury/drug therapy , Retinal Degeneration/prevention & control , Retinal Ganglion Cells/drug effects , Ubiquinone/analogs & derivatives , Animals , Apoptosis , Astrocytes/drug effects , Astrocytes/metabolism , Astrocytes/pathology , Caspase 3/genetics , Caspase 3/metabolism , Cell Survival/drug effects , Disease Models, Animal , Female , Intraocular Pressure , Mice , Mice, Inbred C57BL , Microglia/drug effects , Microglia/metabolism , Microglia/pathology , Oxidative Stress/drug effects , Phosphorylation/drug effects , Reactive Oxygen Species/antagonists & inhibitors , Reactive Oxygen Species/metabolism , Reperfusion Injury/genetics , Reperfusion Injury/metabolism , Reperfusion Injury/pathology , Retinal Degeneration/genetics , Retinal Degeneration/metabolism , Retinal Degeneration/pathology , Retinal Ganglion Cells/metabolism , Retinal Ganglion Cells/pathology , Signal Transduction , Ubiquinone/pharmacology , bcl-2-Associated X Protein/genetics , bcl-2-Associated X Protein/metabolism , bcl-Associated Death Protein/genetics , bcl-Associated Death Protein/metabolism , bcl-X Protein/genetics , bcl-X Protein/metabolismABSTRACT
Optineurin (OPTN) mutations are linked to glaucoma pathology and E50K mutation shows massive cell death in photoreceptor cells and retinal ganglion cells. However, little is known about E50K-mediated mitochondrial dysfunction in photoreceptor cell degeneration. We here show that overexpression of E50K expression triggered BDNF deficiency, leading to Bax activation in RGC-5â¯cells. BDNF deficiency induced mitochondrial dysfunction by decreasing mitochondrial maximal respiration and reducing intracellular ATP level in RGC-5â¯cells. However, BDNF deficiency did not alter mitochondrial dynamics. Also, BDNF deficiency resulted in LC3-mediated mitophagosome formation in RGC-5â¯cells. These results strongly suggest that E50K-mediated BDNF deficiency plays a critical role in compromised mitochondrial function in glaucomatous photoreceptor cell degeneration.
