Activation of Signaling Pathways and Stress-Response
Genes in an Experimental Model of Retinal Detachment
David N. Zacks, Ying Han, Yong Zeng, and Anand Swaroop
PURPOSE. Despite the high metabolic demands of the neural
retina, its detachment from the retinal pigment epithelium
does not lead to immediate death for most of the cells. This
study was undertaken to test the hypothesis that intrinsic
protective mechanisms are activated in the neural retina during
early stages of retinal detachment.
METHODS. Retinal detachments were created in Brown Norway
rats by injection of 1% hyaluronic acid into the subretinal
space. Gene expression profiles of retinas detached for 24
hours were generated with a gene microarray (rat U34 GeneChips; Affymetrix, Santa Clara, CA) and compared to the profiles from control attached retinas in a robust multiarray protocol and false-discovery-rate analysis. Changes in individual,
differentially expressed genes were validated by quantitative
real-time polymerase chain reaction (qRT-PCR) analysis. Additional qRT-PCR and immunoblot analyses were performed for
additional selected genes.
RESULTS. Genome-wide expression profiling revealed 27 genes
that are differentially expressed in retinas detached for 24
hours. In silico analysis and functional clustering suggested
that most genes belonged to three signaling pathways: interleukin-6/STAT, transforming growth factor-␤/Smad, and aryl
hydrocarbon receptor oxidative stress response. Additional
analyses of selected genes from these pathways demonstrated
a time-dependent increase in their expression in detached
retinas.
CONCLUSIONS. Retinal detachment results in the early activation
of stress-response genes and specific signaling pathways. This
adaptive response may enable the photoreceptor cells to survive the acute phase of a retinal detachment, and it is the
breakdown of these protective mechanisms in chronic disease
that leads to the ultimate death of the cell. (Invest Ophthalmol
Vis Sci. 2006;47:1691–1695) DOI:10.1167/iovs.05-1209
R
etinal detachment is defined as the separation of the neurosensory retina from the underlying retinal pigment epithelium (RPE). It can result in severe vision loss, either directly
from the death of photoreceptor cells or because of alterations
in other retinal cell types (both neuronal and glial elements).1
It is expected that these changes are the direct consequence of
the altered microenvironment of the retina. Molecular path-
From the Kellogg Eye Center, University of Michigan, Ann Arbor,
Michigan.
Supported by National Eye Institute Grants K08-EY-14705,
EY011115 (administrative supplement), and EY07003 (core grant);
Research to Prevent Blindness, Inc; The Foundation Fighting Blindness;
the Herrick Foundation; and the Elmer and Sylvia Sramek Foundation.
Submitted for publication September 12, 2005; revised November
16 and December 5, 2005; accepted January 23, 2006.
Disclosure: D.N. Zacks, None; Y. Han, None; Y. Zeng, None; A.
Swaroop, None
The publication costs of this article were defrayed in part by page
charge payment. This article must therefore be marked “advertisement” in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Corresponding author: David N. Zacks, Kellogg Eye Center, University of Michigan, 1000 Wall Street, Ann Arbor, MI 48105;
davzacks@umich.edu.
Investigative Ophthalmology & Visual Science, April 2006, Vol. 47, No. 4
Copyright © Association for Research in Vision and Ophthalmology
ways implicated in photoreceptor death include the intrinsic
apoptosis pathway2,3 and the FAS/FAS-ligand–mediated pathway.4 However, the precise molecular mechanisms underlying
the adaptive cellular response and the pathways leading to
apoptotic cell death have not been clearly delineated.
Despite the high metabolic demand of the outer retina, its
detachment from the RPE does not induce a massive, synchronized, and/or immediate death of the photoreceptors. Studies
of experimental detachment in mice using cell counts and
markers of apoptosis (TUNEL staining) show that the rate of
death is relatively slow, with a peak of approximately 5% to
10% of cells exhibiting TUNEL-positive staining by 3 days after
detachment.5 Though measurable decreases in outer nuclear
layer thickness may occur in as little as 1 to 3 days after
detachment, a significant number of photoreceptors survive
for many days or even weeks.3,6,7 Outcome analyses of maculainvolving rhegmatogenous retinal detachments in humans
have shown that similar visual acuity results are obtained if
retinal reattachment is achieved anytime within 1 week after
the detachment occurs.8,9 Though these analyses are based on
a retrospective review of reattachment surgery outcomes and
are limited by the fact that they primarily measure visual acuity
and do not reflect more subtle aspects of visual function, such
as contrast sensitivity, they confirm that enough photoreceptors and other retinal elements survive the detached state to
allow for the presence of a clinical “window of opportunity”
for recovery of significant visual function after retinal reattachment.
The asynchronous and delayed photoreceptor death in experimental retinal detachments, as well as the clinically recognized “window of opportunity” for reattachment of rhegmatogenous detachments, suggests the possibility that intrinsic
protective mechanisms may be activated in neural retina. Such
protective mechanisms may permit photoreceptor survival for
a period after detachment. Photoreceptor apoptosis and other
detachment-associated sequelae would result only when these
intrinsic protective mechanisms are overcome by the chronic
detachment. Relatively little is known about the types of protective, molecular pathways that become activated in the early,
postdetachment time frame. The purpose of this study was to
test the hypothesis that activation of intrinsic protective mechanisms occurs in early stages of retinal detachment.
METHODS
Experimental Retinal Detachment
All experiments were performed in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research and
the guidelines established by the University Committee on Care and
Use of Animals of the University of Michigan. Retinal detachments
were created in adult male Brown Norway rats (300 – 400 g), as previously described.3 Briefly, rats were anesthetized with a 50:50 mix of
ketamine (100 mg/mL) and xylazine (20 mg/mL), and pupils were
dilated with topical phenylephrine (2.5%) and tropicamide (1%). A
sclerotomy was created approximately 2 mm posterior to the limbus
with a 20-gauge microvitreoretinal blade (Walcott Scientific, Marmora,
NJ), with special caution taken to avoid damaging the lens. A Glaser
subretinal injector (32-gauge tip; BD Ophthalmic Systems, Sarasota, FL)
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Zacks et al.
connected to a syringe filled with 10 mg/mL sodium hyaluronate
(Healon; Pharmacia and Upjohn Co., Kalamazoo, MI) was introduced
through the sclerotomy into the vitreous cavity. The tip of the subretinal injector was introduced into the subretinal space through a peripheral retinotomy, and the sodium hyaluronate was slowly injected. In all
experiments, approximately one third to one half of the neurosensory
retina was detached from the underlying retinal pigment epithelium.
Detachments were made in the left eye, with the right eye serving as
the control. For control eyes, a sham surgery was performed in which
all procedures were completed except introduction of the subretinal
injector and creation of the detachment. In experimental eyes, only the
detached portion of the retina was harvested for analysis. All samples
were harvested 24 hours after the detachment.
Microarray and Statistical Analysis
Total RNA was extracted (TRIzol; Invitrogen, Carlsbad, CA) and purified (RNeasy Mini Kit; Qiagen, Valencia, CA). RNA quality was checked
by gel electrophoresis. The first strand of cDNA was synthesized with
10 ␮g of total RNA, 1 ␮L of T7-(dT)24 primer (100 picomoles/␮L;
Invitrogen) and a reverse transcriptase (Superscript II RNase H Reverse
Transcriptase kit; Invitrogen), as per the manufacturer’s instructions.
Second-strand cDNA synthesis was performed by adding the singlestrand cDNA solution DEPC-H2O (91 ␮L), 5⫻ second-strand buffer (30
␮L; Invitrogen), 10 mM dNTP mix (3 ␮L; Invitrogen), 10 U/␮L Escherichia coli DNA ligase (1 ␮L; Invitrogen), 10 U/␮L E. coli DNA polymerase I (4 ␮L; Invitrogen), and 2 U/␮L E. Coli RNase H (1 ␮L;
Invitrogen) and incubated at 16°C for 2 hours. T4 DNA polymerase (2
␮L; Invitrogen) was then added and the solution incubated in a 16°C
water bath for 5 minutes. The reaction was then stopped by adding 10
␮L of 0.5 M EDTA (Ambion, Austin, TX). The double-stranded cDNA
was purified with a pre-spin phase-lock gel (PLG) tube (VWR Scientific;
Chicago, IL) run for 30 seconds at 12,000g. Phenol-chloroform-isoamyl
alcohol (25:24:1; 162 ␮L; Invitrogen) was added to the cDNA, vortexed
briefly, and rerun through the PLG tubes for 2 minutes at 12,000g. The
aqueous phase was transferred to a fresh 1.5 mL tube, and diluted 2:1
with 7.5 M NH4OAc (Sigma-Aldrich, St. Louis, MO) and this mixture
diluted 1:2.5 with absolute ethanol. This mixture was vortexed thoroughly and centrifuged at room temperature for 20 minutes at 12,000g.
The pellet was washed twice with 0.5 mL of 80% ethanol. After it was
air dried, the pellet was resuspended in RNase-free water and quantified by gel electrophoresis.
Biotin-labeled complementary RNA (cRNA) was synthesized with
an RNA transcript labeling kit (BioArray High Yield RNA kit; Enzo Life
Sciences, Farmingdale, NY) according to the manufacturer’s instructions. Product was purified and quantified as indicated above. Fragmentation of the cRNA was performed with a kit (GeneChip Sample
Cleanup Module Kit; Affymetrix, Inc., Santa Clara, CA).
Fragmented cRNA was hybridized to the Rat U34 GeneChip (Affymetrix, Inc.), according to the manufacturer’s instructions. After
hybridization, the chips were run through a fluidics station and
scanned through a spectrophotometer (both from Affymetrix).
We then subjected the microarray data to a robust multiarray
analysis protocol10 and false-discovery-rate analysis,11 as previously
described.12,13 This allowed probe level background adjustments and
quantile normalization and assigned log-transformed perfect-match values to each gene. Genes were then categorized as having significant
changes in transcript abundance with a false-discovery rate set at less
than or equal to 50% (i.e., the probability that an identified gene is
actually differentially expressed is 50%).
Quantitative Real-Time Polymerase Chain
Reaction Analysis
Quantitative real-time polymerase chain reaction (qRT-PCR) was performed as previously described,4 with rat hypoxanthine phosphoribosyl transferase (rHPRT) used for internal normalization. All primers
were designed to span intron– exon boundaries. Samples lacking reverse transcriptase or cDNA template served as the negative control.
IOVS, April 2006, Vol. 47, No. 4
For each primer set, qRT-PCR was performed on samples derived from
three different animals and repeated three times per sample. The
average change in expression (x-fold) relative to the rHPRT transcript
level was calculated.
Immunoblot Analysis
Western blot analyses were performed on detached retinas from experimental eyes and attached retinas from control eyes, as previously
described.4 Antibodies against the following proteins were used:
STAT-1 (Axxora, LLC, San Diego, CA), STAT-3 (Affinity BioReagents,
Golden, CO), CNTF (Abcam, Inc., Cambridge, MA), and TGF␤-1 (R&D
Systems, Inc, Minneapolis, MN). Equal loading was verified by ponceau
S staining and densitometry analysis of a nonspecific band present
across all lanes.
RESULTS
To determine the cellular response to a 24-hour detachment,
we generated gene expression profiles with the rat U34 GeneChip (Affymetrix, Inc.). Four independent samples, each containing two detached retinas, were compared to the attached
retinas of the contralateral eyes. After normalization and statistical analysis, we identified 27 genes that exhibited a significant
change in expression in the detached versus the attached
retinas (Table 1). An additional 10 expressed sequence tags
(ESTs) were identified but not analyzed further with qRT-PCR.
Of the 27 known genes, 23 showed higher and 4 showed lower
expression in the detached retinas. For each of these genes, the
modulation of transcription was confirmed by qRT-PCR (Table
1). The direction of transcriptional alteration was confirmed
for 25 (93%) of the 27 genes.
In silico analysis revealed that 10 of the differentially expressed and validated genes are transcription factors. Of these,
nine exhibited higher and only one (nerve growth factor induced gene B) lower expression in the detached retina. Other
genes encoded proteins involved in receptor-mediated apoptosis, ion channels, transport or binding proteins, cytokine, and
growth factor receptors and cofactors. Enhanced expression of
genes involved in receptor-mediated apoptosis is consistent
with our previous results showing a time-dependent increase
in the transcript level of FAS-pathway intermediates.4
Functional clustering of the differentially expressed genes
based on known association with specific stress-response signaling pathways suggests the increased transcription of genes
belonging to three families of stress-response pathways. These
are the interleukin-6/STAT pathway, transforming growth factor-␤/Smad pathway, and aryl hydrocarbon receptor (Ahr) oxidative stress response pathway. We predicted that additional
components of these stress-response pathways may be transcriptionally altered at later time points. To test this, we performed quantitative real-time PCR and immunoblot analysis on
select components of these pathways in retinas detached for
3 and 7 days as described in the following sections (Table 2,
Fig. 1).
Interleukin-6 Pathway
Among the genes detected on the microarray, three (11%)
correspond to interleukin-6 (IL-6), signal transducer and activator of transcription-1 (STAT-1), and nuclear factor IL-6 (NFIL6). IL-6 exerts its effect through the binding of ␣- and ␤-receptors. The latter is also known as gp130.14 IL-6 first binds the
IL-6␣-receptor, and this complex binds to a homodimer consisting of two IL-6␤-receptors, resulting in the intracellular
activation of one or more of the five members of the STAT
family of transcription factors. We performed qRT-PCR to detect the transcriptional activation of IL-6, IL-6␣-receptor, IL-6␤-
IOVS, April 2006, Vol. 47, No. 4
Signaling Pathways and Stress Response Genes in Retinal Detachments
TGF-␤ Pathway
TABLE 1. Results of Gene Microarray and qRT-PCR Analyses for
Retinal Detachments of 24-Hour Duration
Gene Name
Transcription factors
Aryl hydrocarbon receptor
Polyomavirus enhancer binding protein
(PEBP2␤)
Interferon regulatory factor 1
Activating transcription factor 3
JunB
Signal transducer and activator of
transcription 1 (STAT 1)
NF-E2-related factor 2
Nuclear factor interleukin 6 (NF-IL6)
Nerve growth factor-induced gene (NGFI)
Kruppel-associated box (KRAB)-zinc
finger protein 2
Apoptosis intermediates
Tumor necrosis factor ␣
Caspase 3
Transporters/membrane channels
Solute carrier family 11, member 2
Solute carrier family 20, member 2
Retinol-binding protein 4
Receptors/Cofactors
Interleukin 6 signal transducer
Latent TGF␤ binding protein (LTBP)-3
Integrin-associated protein
Membrane proteins
MHC class I antigen
MHC class Ib antigen
RT1 class I gene
Synuclein
Drosophila disc-large tumor suppressor
homologue (synapse-associated protein)
Intracellular enzymes
Guanine nucleotide binding protein ␤-4
Protein tyrosine phosphatase, non–
receptor-type 1
Paracrine agents
Endothelin-2
Structural proteins
Stathmin-1
1693
Chip
PCR
3.04
3.65
2.19
2.54
5.05
3.38
2.10
3.81
30.93
5.85
8.40
2.57
2.53
0.41
18.83
5.32
10.50
0.60
2.32
1.82
3.59
3.15
12.75
4.68
3.30
2.48
2.82
2.63
1.84
2.46
2.75
0.30
2.60
2.70
1.01
3.44
2.78
2.71
2.70
2.43
9.73
8.45
5.35
1.78
2.86
2.69
0.36
6.74
2.64
4.98
5.72
14.98
0.45
0.90
Data are x-fold change.
receptor, and STAT1 through -5. Retinas were analyzed at 3 and
7 days after detachment.
All the components of the IL-6 pathway tested showed
increased expression during retinal detachment. The STAT-1
gene demonstrated the largest increase, with an over 80-fold
change in transcript levels by 7 days after detachment. IL-6,
itself, also had an increased expression, with an almost 20- and
30-fold increase at 3 and 7 days after detachment, respectively.
Of the genes selected for immunoblot analysis, there was a
corresponding time-dependent increase in the protein level.
The growth factor CNTF (ciliary neurotrophic factor) belongs to the IL-6-like family of cytokines and uses a signal
transduction pathway similar to that of IL-6, with activation of
STAT transcription factors.14 CNTF transcript levels were increased approximately eightfold in detached retinas. Western
blot analysis showed that there was also an increase in the level
of the CNTF protein. Similar to IL-6, CNTF also binds to an
␣-receptor, but this complex then binds to a heterodimer,
composed of one gp130 subunit and one LIF (leukemia inhibitory factor) receptor subunit.14 In our model, the LIF receptor
was marginally upregulated by only approximately 1.6-fold in
both 3- and 7-day detachments (data not shown).
One of the genes that showed downregulation on the microarray was the latent TGF-␤ binding protein-3 (LTBP-3). LTBP-3
plays a role in sequestering extracellular TGF-␤, thus preventing it from binding its receptor. A decrease in LTBP-3 would
effectively result in an increased level of free TGF-␤ available
for receptor binding. We sought to determine whether the
decrease in LTBP-3 coincides with an actual increase in TGF-␤
itself and/or its downstream signal transducers. Transcript levels for TGF-␤1 and TGF-␤3 were elevated by up to 40- and
50-fold by day 7 after detachment, respectively; but TGF-␤2
showed only modest transcriptional upregulation. Protein expression was tested and confirmed for TGF-␤1. After TGF binds
to its surface receptor, the intracellular cascade is propagated
through the Smad family of transcription cofactors.15 Within
this set of genes, Smads3, -5, and -8 showed the highest levels
of increased transcription, albeit only approximately 2.3 to 2.5
times that present in the attached retinas.
Ahr Oxidative Stress-Response Pathway
The final pathway extracted from the microarray analysis for
further confirmation was the Ahr–mediated response to oxidative stress. The Ahr was first identified as being essential in the
mediation of cellular responses to dioxin exposure and has
subsequently been shown to help in cellular adaptation to
oxidative stress.16 In a normal cell, the Ahr is localized to the
cytoplasm. The release of oxidative reactive species can result
in their binding to Ahr. This complex then translocates to the
nucleus where the activated Ahr can perform its function as a
transcription factor. The Ahr receptor, when activated, results
in the transcription of a “gene battery” consisting of five genes,
whose products are important in mediating the cellular response to the oxidative stress. These genes are cytochrome
TABLE 2. Increase in Transcript Level in the Detached Retina
Compared with That in the Attached Retina for Components of
Stress-Response Pathways
Component
Interleukin-6/STAT pathway
Interleukin-6
Interleukin-6␣ receptor
Interleukin-6␤ receptor (gp130)
CNTF
STAT1
STAT2
STAT3
STAT4
STAT5
Transforming growth factor-␤ pathway
Transforming growth factor-␤1
Transforming growth factor-␤2
Transforming growth factor-␤3
Smad1
Smad2
Smad3
Smad4
Smad5
Smad7
Smad8
Aryl hydrocarbon receptor-oxidative stress
response genes
Cytochrome P450
NAD(P)H:quinone oxidoreductase 1
Aldehyde dehydrogenase 3
UDP-glucuronosyltransferase
Glutathione transferase
Data are x-fold change.
3 Days
7 Days
22.6
8.2
4.1
7.8
14.6
1.6
2.5
14.7
1.0
35.9
6.5
7.6
9.0
87.1
13.9
5.3
6.9
1.5
4.0
4.9
6.7
1.8
1.5
2.3
1.3
1.4
1.3
1.8
38.7
1.0
53.2
1.3
1.3
2.6
1.4
2.3
1.4
2.3
6.3
14.6
18.6
11.4
5.5
17.1
9.1
6.2
3.4
6.2
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Zacks et al.
FIGURE 1. Western blot analysis for select genes with detachmentinduced increases in transcript levels. For each gene, there was a
time-dependent increase in transcript level that had an associated
increase in protein level. Lane 1: 3-day attached retina; lane 2: 3-day
detached retina; lane 3: 7-day attached retina; and lane 4: 7-day
detached retina.
P-450, NAD(P)H:quinone-oxidoreductase, aldehyde dehydrogenase 3, UDP:glucuronosyl-transferase, and glutathione transferase.
At the 24-hour time point, our microarray and qRT-PCR
analyses showed a threefold upregulation of the Ahr in the
detached retina. We predicted that increased transcription of
the individual components of the Ahr “gene battery” would be
detected in 3- and 7-day-old detachments, and this prediction
was confirmed with qRT-PCR. For some of these genes, the
transcript levels peaked at 3 days, but for some, the elevated
levels persisted up to the 7-day time point.
DISCUSSION
Separation of the retina from its source of nutritional and
metabolic support can exist in a variety of diseases such as
retinal detachment, diabetic retinopathy, and macular degeneration. Despite the recent advances in the treatment of these
diseases, the associated damage to the neurosensory retina can
limit the final visual outcome. Understanding the molecular
responses of the retina to detachment provides a logical entry
point for the development of targeted therapeutics for photoreceptor survival and improving visual outcomes. In the
present study, we demonstrated for the first time the activation
of signaling pathways, particularly those that control transcription, as a primary mechanism by which the retina responds to
the severe trauma of detachment. This study forms the basis for
defining the specific molecular mechanisms by which the complex array of detachment-induced changes in retinal cell arrangement, structure, and survival are initiated.
IOVS, April 2006, Vol. 47, No. 4
We have used gene profiling and qRT-PCR technology to
develop and validate expression changes at an early stage (24
hours) of retinal detachment. Based on this transcriptional
profile, we identified three stress-response pathways for further investigation. We demonstrated the time-dependent increase in transcript levels as well as increased protein translation for multiple components of these three prototypical
pathways. These cytokine, growth factor, and stress response
pathways all have a known precedent for their role in cellular
response to injury. Their upregulation in our experimental
model of retinal detachment suggests that they contribute to
the intraretinal response to this particular form of injury.
IL-6 is a cytokine that can play an important role in regulating cell death.17,18 On binding to its receptor, IL-6 induces the
activation of the STAT family of transcription factors. These
transcription factors have been associated with photoreceptor
differentiation19,20 as well as retinal survival to ischemia–reperfusion injury.21 CNTF, also upregulated in our system, has been
shown to be neuroprotective of photoreceptors in experimental models of retinal degenerations.20 CNTF uses the same
receptor-mediated activation of the STAT transcription factors.
Our results show the transcriptional and translational upregulation of the IL-6/STAT pathway as well as of CNTF, suggesting
that elements within the retina itself produce the very factors
that might allow for its own survival after detachment. This is
consistent with the previous report of fibroblast growth factor
receptor 1 and STAT3 activation in detached feline retinas.22
Similarly, TGF-␤ is upregulated in our experimental system.
On the gene microarray analysis, we detected a downregulation of the protein latent TGF-␤ binding protein 3 (LTBP-3).
LTBP-3 is an extracellular protein involved in the sequestration
of TGF-␤. The downregulation of the sequestering protein,
coupled with the increased transcription and translation of
TGF-␤ itself, suggests a resultant net increase in the extracellular concentration of this growth factor. It has been shown
that TGF-␤ immunostaining is increased in Müller cells of
detached retinas.23 Our results suggest that this is due in part
to an increased level of TGF-␤ transcription. TGF-␤ may have a
beneficial effect on photoreceptor survival,24 but it has also
been shown to play a role in detachment-induced retinal pigment epithelial (RPE) cell dedifferentiation,25 as well as to
contribute to glial proliferation in the proliferative vitreoretinopathy that occurs after retinal detachment.23 TGF-␤-induced
RPE cell dedifferentiation occurs through the Smad3 pathway
intermediate.25 In our system, Smad3, -5, and -8 exhibited the
greatest amount of upregulation compared with other Smad
genes, consistent with their possible involvement in postdetachment TGF-␤-mediated signaling. TGF-␤ may also exert an
antiapoptotic effect in detached retinas through the transcription factor PEBP-2, which is a known regulator of the Bcl-2
apoptosis gene.26 PEBP-2 levels are known to increase in response to TGF-␤,27 and we detected and confirmed increased
PEBP-2 transcript levels with our microarray analysis and qRTPCR.
The final pathway revealed by microarray and further expanded on with qRT-PCR is the Ahr pathway. The Ahr was first
described as being important in cellular response to dioxin
exposure.16 On stimulation, the Ahr induces the transcription
of a set of five genes, known as the aryl hydrocarbon gene
battery. This gene battery codes for oxidative stress response
proteins, including cytochrome P450, NAD(P)H:quinone oxidoreductase, aldehyde dehydrogenase 3, UDP glucuronosyltransferase, and glutathione transferase. The Ahr is known to
respond to increased levels of retinoic acid and synthetic retinoids, suggesting that it may play a role in mitigating the
oxidative stress retinal detachment may create due to alteration
and interference in the normal metabolism of the retinal chromophore. We also validated an increase in the transcript levels
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Signaling Pathways and Stress Response Genes in Retinal Detachments
of the gene encoding for retinol binding protein type 4. This is
consistent with the hypothesis that the retina is responding to
the altered chromophore metabolism.
Of interest was that some of the aryl hydrocarbon gene
battery members exhibited lower transcript levels at 7 days
after detachment compared with 3 days after detachment. This
corresponds to the marked increase in TGF-␤ transcript at day
7. The Ahr can act as a negative regulator of the TGF-␤ transcription.28,29 The significance of this relationship in retinal
detachment remains to be determined, but our data indicate a
possible cross-talk between these upregulated pathways.
The three stress-response pathways we describe in this
work require further delineation in terms of their specific role
in postdetachment photoreceptor survival. Elucidation of
downstream targets for these transcription factors and signaling proteins will permit a better understanding of photoreceptor survival and retinal reorganization (including neurosensory,
glial, and vascular components of the retina) which is necessary for the targeted development of therapeutic interventions
and for preserving retinal structure to improve visual outcomes
after retinal detachment.
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