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Title: The roles of cyclic adenosine monophosphate (cAMP) and apolipoprotein A1 (ApoA1) in avian eye growth -a proteomic approach
Authors: Chun, Ka-man
Degree: Ph.D.
Issue Date: 2010
Abstract: The prevalence of myopia, as well as high myopia, in some Asian countries has been increasing in recent decades. High myopia is one of the leading causes of visual impairments due to its associated sight threatening conditions, such as retinal detachment and glaucoma. At present, the underlying mechanism of the development of myopia is still unclear. The origin of myopia signals is thought to reside in the retina which will initiate biochemical changes and accelerate eye growth. Profiling the retinal proteomes of myopic chick may help to capture such changes in terms of protein expressions during myopic growth. The current study employed two-dimensional fluorescence difference gel electrophoresis (2-D DIGE) to profile the retinal proteins in lens-induced myopia (LIM) and form deprivation myopia (FDM). With the aid of a nano-liquid chromatography coupled tandem mass spectrometry (LC-MS/MS), a number of differentially expressed retinal proteins related to myopic growth were identified. In eyes with three days of LIM, phosphoglycerate mutase 1 (brain) (PGAM) was up-regulated whereas apolipoprotein A1 (ApoA1) was decreased in expressions in myopic retinas. In terms of differentially expressed retinal proteins in three days of FDM by diffusers, there were six protein spots showing alternation in expressions. Only two of them were successfully identified. Up-regulation of destrin and down regulation of ApoA1 was shown in three days of FDM retinas by diffusers. Besides, there was also up-regulation of destrin after three days of myopia induced by occluders. After seven days of LIM and FDM, only six protein spots showed differential expressions and three of them were successfully identified. They belonged to destrin and PGAM that were both up-regulated in myopic retinas. Since ApoA1 was the common protein spot found to be down-regulated consistently after three days of LIM and FDM, the role of ApoA1 in the development of myopia was further studied.
Intravitreal injections of nicotinic acid and bezafibrate, which could increase ApoA1 protein expression, were tested for their efficacies in reducing LIM. Nicotinic acid (60mM) was effective in reducing vitreous chamber depth and increasing the retinal ApoA1 expressions in LIM. Localizations of retinal ApoA1 after LIM and lens-induced hyperopia (LIH) were carried out using immunohistochemistry. ApoA1 was more evident in the photoreceptor layer of myopic retina. In hyperopic eyes, ApoA1 was mainly located in inner limiting membrane and RPE. This is the first report showing differences in immunoreactivity of retinal ApoA1 in LIM and LIH. Since cyclic adenosine monophosphate (cAMP) is one of the modulators of ApoA1 expression, the effect of cAMP on myopia development was explored. Intravitreal injection of cAMP (1mM) analog was found to inhibit refractive errors and elongation of vitreous chamber depth in LIM. There was also an increase in retinal ApoA1 expression with intravitreal injection of cAMP. The results indicated cAMP may affect myopia development through ApoA1 expression. In the last part of this study, the level of retinal cAMP under LIM and LIH was measured using enzyme immunoassay. There was no change in retinal cAMP in myopic eyes but the retinal cAMP level was raised significantly in LIH. Concurrently, the expression of retinal ApoA1 was also increased in LIH. The data suggested that cAMP may play a significant role in the cascade of reactions leading to produce the "STOP" signal in eye growth. In conclusion, the present study profiled the changes in protein expressions in myopic retinas using 2-D DIGE. The data suggested that cAMP may modulate ApoA1 expression in chick retina and together they play an important and inhibitory role in the eye growth and development of myopia.
Subjects: Hong Kong Polytechnic University -- Dissertations
Adenylic acid
Contact lenses -- Complications
Enzyme-linked immunosorbent assay
Pages: xxi, 187 p. : ill. (some col.) ; 31 cm.
Appears in Collections:Thesis

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