Ocular distribution of antioxidant enzyme paraoxonase & its alteration in cataractous lens & diabetic retina

Increased oxidative stress biomarkers in central serous chorioretinopathy

Current data suggest that oxidative stress may play an important role in the occurrence of acute central serous chorioretinopathy (CSC), as chorioretinal integrity may be affected by disruption of the patient's metabolic redox balance, indicating the need for biomarkers. In addition to oxidative stress, high-density lipoprotein (HDL) dysfunction due to dyslipidemia can also lead to many types of physical discomfort. However, little is known about the pathophysiology of the disease resulting from oxidative stress and HDL dysfunction in CSC. The aim of this study was to investigate whether serum oxidative stress and HDL functionality markers have an impact on CSC disease. The case series of this study included 33 consecutive patients with treatment-naïve acute CSC. Thirty-five healthy volunteers of similar age were included in this study as non-CSC controls. Serum samples of the participants were taken and routine lipid values, serum Total Antioxidant Status (TAS), Total Oxidant Status (TOS), Oxidized Low Density Lipoprotein (ox-LDL), and Paraoxonase (PON1) levels were measured quantitatively. Serum oxidative stress index (OSI) was then calculated. Serum Ox-LDL, TOS and OSI levels in the acute CSC group, consisting of patients who had never been treated before and had no other disease, were statistically significantly higher than the control group. Conversely, serum PON1 and TAS levels were lower in CSC than in the control group. The relationship between CSC and deterioration in serum redox balance and decrease in PON1 activity, an important marker of HDL functionality, was demonstrated for the first time through this study. According to the literature, serum levels of these biomarkers, which identify acute/chronic inflammation and oxidative stress, have not been measured before in CSC disease. Finally, it is conceivable that redox balance and HDL functionality may be important in the diagnosis and treatment of the acute phase of CSC.

MS/MS in silico subtraction-based proteomic profiling as an approach to facilitate disease gene discovery: application to lens development and cataract

While the bioinformatics resource-tool iSyTE (integrated Systems Tool for Eye gene discovery) effectively identifies human cataract-associated genes, it is currently based on just transcriptome data, and thus, it is necessary to include protein-level information to gain greater confidence in gene prioritization. Here, we expand iSyTE through development of a novel proteome-based resource on the lens and demonstrate its utility in cataract gene discovery. We applied high-throughput tandem mass spectrometry (MS/MS) to generate a global protein expression profile of mouse lens at embryonic day (E)14.5, which identified 2371 lens-expressed proteins. A major challenge of high-throughput expression profiling is identification of high-priority candidates among the thousands of expressed proteins. To address this problem, we generated new MS/MS proteome data on mouse whole embryonic body (WB). WB proteome was then used as a reference dataset for performing "in silico WB-subtraction" comparative analysis with the lens proteome, which effectively identified 422 proteins with lens-enriched expression at ≥ 2.5 average spectral counts, ≥ 2.0 fold enrichment (FDR < 0.01) cut-off. These top 20% candidates represent a rich pool of high-priority proteins in the lens including known human cataract-linked genes and many new potential regulators of lens development and homeostasis. This rich information is made publicly accessible through iSyTE (https://research.bioinformatics.udel.edu/iSyTE/), which enables user-friendly visualization of promising candidates, thus making iSyTE a comprehensive tool for cataract gene discovery.

Association of PON2 and PON3 polymorphism with risk of developing cataract

Purpose

Paraoxonases (PON) are calcium bound enzymes offering protection against oxidative stress by working as endogenous free-radical scavenging molecules. Oxidative stress has been implicated in pathophysiology of many diseases including cataract. Lens opacity is an age related disorder which is a principal cause of blindness in Pakistani population. Relationship of PON2 and PON3 polymorphism with genetic predisposition for incidence of cataract has not been investigated till date. Objective of the current study was to explore possible association between PON2 and PON3 polymorphism with incidence of cataract in local population.

Methods

Our study design comprised of fifty-one cataractous and fifty-nine healthy individuals. Identification of single nucleotide polymorphism (SNP) at positions (C311S and G148A) for PON2 and C133A for PON3 was conducted using restriction fragment length polymorphism (RFLP).

Results

Statistical analysis revealed significant association of PON2 G148 allele with incidence of cataract. GG allele was found to be higher in cataract patients as compared to control (p < 0.001) suggesting distribution of PON2 G148A genotype and allele frequency is linked with cataractogenesis. There was no noticeable association between PON2 C311S and PON3 C133A. Significant difference was observed in distribution of 311CS/148A combined genotype with highest frequency in control individuals (88.89%), while 311S/148G combined genotypes showed the highest frequencies among the cataract patients (71.42%).

Conclusion

Our data suggests mutation at G148A might be related with incidence of cataract in studied population.