The Hypoxic Transcriptome of the Retina: Identification of Factors with Potential Neuroprotective Activity

Thiersch, Markus; Raffelsberger, Wolfgang; Frigg, Enrico; Samardzija, Marijana; Blank, Patricia R.; Poch, Olivier; Grimm, Christian

doi:10.1007/978-0-387-74904-4_8

Cited by 6 publications

(5 citation statements)

References 27 publications

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“…During our differentiation protocol under hypoxic conditions, both genes were significantly upregulated when compared with normoxic conditions. This data suggest that hypoxia, through activation of HIF‐1α, decreasing apoptosis, and cytotoxicity, has influenced retinal differentiation [66, 67]. Although, the source of Vegfa could be RPE cells observed in retinal progenitors generated in hypoxic conditions [68] (data not shown), further investigation has to be performed to elucidate the origin of neuroprotective processes.…”

Section: Discussionmentioning

confidence: 99%

Hypoxia Increases the Yield of Photoreceptors Differentiating from Mouse Embryonic Stem Cells and Improves the Modeling of Retinogenesis In Vitro

et al. 2013

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Retinitis pigmentosa (RP), a genetically heterogeneous group of diseases together with age-related macular degeneration (AMD), are the leading causes of permanent blindness and are characterized by the progressive dysfunction and death of the light sensing photoreceptors of the retina. Due to the limited regeneration capacity of the mammalian retina, the scientific community has invested significantly in trying to obtain retinal progenitor cells from embryonic stem cells (ESC). These represent an unlimited source of retinal cells, but it has not yet been possible to achieve specific populations, such as photoreceptors, efficiently enough to allow them to be used safely in the future as cell therapy of RP or AMD. In this study, we generated a high yield of photoreceptors from directed differentiation of mouse ESC (mESC) by recapitulating crucial phases of retinal development. We present a new protocol of differentiation, involving hypoxia and taking into account extrinsic and intrinsic cues. These include niche-specific conditions as well as the manipulation of the signaling pathways involved in retinal development. Our results show that hypoxia promotes and improves the differentiation of mESC toward photorecep- Disclosure of potential conflicts of interest is found at the end of this article.

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Section: Discussionmentioning

confidence: 99%

Hypoxia Increases the Yield of Photoreceptors Differentiating from Mouse Embryonic Stem Cells and Improves the Modeling of Retinogenesis In Vitro

et al. 2013

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“…We have previously demonstrated that binding of adenosine to its receptors is a trigger for IPC (Li and Roth 1999) and that downstream signal transduction factors, including mitochondrial KATP channels (mKATP), protein kinase C (PKC), reactive O 2 species (ROS), nitric oxide synthase (NOS), PKC, and erythropoietin, are components of this neuroprotection(Junk et al 2002; Roth et al 2006; Dreixler et al 2008). More recently, microarray analysis of different paradigms of retinal preconditioning show a number of retinal genes undergoing changes in gene expression (Kamphuis et al 2007; Thiersch et al 2008). Activation of the Akt pathway may be one of the mechanisms involved in IPC protection.…”

Section: Discussionmentioning

confidence: 99%

The role of Akt/protein kinase B subtypes in retinal ischemic preconditioning

Dreixler

Hemmert

Shenoy

et al. 2009

Experimental Eye Research

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Purpose-Potent endogenous protection from ischemia can be induced in the retina by ischemic preconditioning (IPC). Protein kinase B/Akt is a cellular survival factor. We hypothesized that Akt was integral to IPC based upon differential effects of Akt subtypes.Methods-Rats were subjected to retinal ischemia after IPC or IPC-mimicking by the opening of mitochondrial KATP (mKATP) channels. The effects of blocking Akt using wortmannin, API-2, or small interfering RNA (siRNA) were examined. Electroretinography assessed functional recovery after ischemia, and TUNEL examined retinal ganglion cell apoptosis. We studied the relationship between Akt activation, and known initiators of IPC, including adenosine receptor stimulation and the opening of mKATP channels.Results-The PI-3 kinase inhibitor wortmannin 1 or 4 mg/kg (i.p.), the specific Akt inhibitor API-2, 5-500 μM in the vitreous, or intravitreal siRNA directed against Akt2 or -3, but not Akt1, significantly attenuated the neuroprotective effect of IPC. Interfering RNA against any of the three Akt subtypes significantly but time-dependently attenuated mKATP channel opening to mimic IPC. Adenosine A1 receptor blockade (DPCPX), A2a blockade (CSC), or the mKATP channel blocker 5-hydroxydecanoic acid significantly attenuated Akt activation after IPC. Interfering RNA directed against Akt subtypes prevented the ameliorative effect of IPC on post-ischemic apoptosis. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. (Roth et al. 1998;Zhang et al. 2002;Roth et al. 2006). Such protection offers a model for uncovering pathways and agents to treat retinal ischemia. Ischemic preconditioning (IPC) protects the rat retina against the deleterious effects of a severe ischemic event (Roth et al. 1998;Li et al. 2000;Li et al. 2003). Conclusions-All NIH Public AccessThe cytoplasmic proto-oncogene 57 kD serine/threonine protein kinase Akt (protein kinase B, PKB), is one of the most important kinases, and at the core of numerous and diverse physiological functions. It is activated by receptor tyrosine kinases, integrins, G-protein coupled receptors, and other stimuli, with over 100 reported non-redundant Akt substrates (Manning and Cantley 2007). The Akt pathway has been identified as a cellular survival signal in diverse neuronal cell types and in protection from oxidative stress (Chong et al. 2005). Akt phosphorylates Ser136 on Bad, thus interfering with mitochondrial cytochrome C release (Datta et al. 2000), and it inhibits caspase-9 by phosphorylating Ser196 (Cardone et al. 1998 Because of its involvement in cell survival, Akt is a logi...

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“…Events underlying IPC neuroprotection are under intense study (Ettaiche et al 2001; Nonaka et al 2001; Sakamoto et al 2001; Toprak et al 2002; Kamphuis et al 2007a; Thiersch et al 2008; Zhu et al 2008). Mechanisms uncovered to date include altered expression of a variety of genes (Kamphuis et al 2007b), attenuation of apoptosis (Zhang et al 2002), and involvement of adenosine (Li and Roth 1999), HIF-1α (Zhu et al 2007), erythropoietin (Dreixler et al 2009b), and protein kinases including Akt, PKC, and p38 (Dreixler et al 2009a; Dreixler et al 2009b; Dreixler et al 2009c).…”

Section: Introductionmentioning

confidence: 99%

Post-ischemic conditioning in the rat retina is dependent upon ischemia duration and is not additive with ischemic pre-conditioning

Dreixler

Shaikh

Alexander

et al. 2010

Experimental Eye Research

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Ischemic pre-conditioning (IPC) provides neuroprotection in the rat retina from the damaging effects of severe ischemia. Recently, neuroprotection by retinal ischemic post-conditioning (Post-C), i.e., transient ischemia after more lengthy, damaging ischemia, was described, but its mechanisms are not yet known. One possible explanation of the effectiveness of Post-C is that it augments intrinsic neuroprotective mechanisms initiated during ischemia. Increasing duration of the damaging ischemic insult may therefore impact the effectiveness of Post-C. IPC, in contrast, sets in motion a series of neuroprotective events prior to the onset of ischemia. Thus, IPC and Post-C may operate by differing mechanisms. Accordingly, we examined the effect of retinal ischemic duration on post-ischemic outcome in vivo in rats after adding Post-C, and the impact of combining pre- and post-conditioning. Recovery after ischemia performed 24 h after IPC, or after Post-C performed 5 min after ischemia ended, was assessed functionally (electroretinography) and histologically at 7 days after ischemia. Durations of ischemia of 45 and 55 min were studied. Since recovery with IPC or Post-C alone, with 55 min of ischemia, did not achieve the same degree of effect (i.e., not complete recovery) exhibited in our previous studies of IPC using a different ischemia model, we also combined IPC and Post-C to test the hypothesis of the possible additive effects of the IPC and Post-C. We found that the recovery after Post-C was enhanced to a greater degree when ischemia was of longer duration. Post-C led to greater post-ischemic recovery compared to IPC. Both IPC and Post-C also attenuated structural damage to the retina. Contrary to our hypothesis, IPC and Post-C did not combine to enhance recovery after ischemia. In earlier studies, IPC attenuated post-ischemic apoptosis. To begin to examine the mechanism of Post-C, we studied its impact on apoptosis following ischemia. We examined apoptosis by determining the percentage of TUNEL-positive cells at 24 h after ischemia. Post-C attenuated apoptosis, but when combined with IPC, TUNEL was similar in the combined group to that of ischemia alone. We also examined the role of the recruitment of an inflammatory response in ischemia and Post-C. We found that inflammatory markers increased by ischemia were not altered by Post-C. We conclude that Post-C effectiveness depends upon the duration of ischemia; Post-C is not additive with IPC, and Post-C functions, in part, by preventing apoptotic damage to the inner retina. Post-C has considerable promise for clinical translation to eye diseases that cause blindness by ischemia.

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The Hypoxic Transcriptome of the Retina: Identification of Factors with Potential Neuroprotective Activity

Cited by 6 publications

References 27 publications

Hypoxia Increases the Yield of Photoreceptors Differentiating from Mouse Embryonic Stem Cells and Improves the Modeling of Retinogenesis In Vitro

Hypoxia Increases the Yield of Photoreceptors Differentiating from Mouse Embryonic Stem Cells and Improves the Modeling of Retinogenesis In Vitro

The role of Akt/protein kinase B subtypes in retinal ischemic preconditioning

Post-ischemic conditioning in the rat retina is dependent upon ischemia duration and is not additive with ischemic pre-conditioning

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