Differential Protein Expression in Response to Varlitinib Treatment in Oral Cancer Cell Line: an In Vitro Therapeutic Approach

Epidermal growth factor receptor (EGFR) is the most frequently overexpressed receptor histologically exhibited by oral squamous cell carcinoma (OSCC) patients. Aberrated EGFR signaling may lead to recurrence and metastasis, thus laying the foundation of targeted therapy. Deactivating EGFR is likely to prevent downstream signaling thus resulting in apoptosis. Tyrosine kinase inhibitors (TKIs) have come into play to revert aggressiveness of OSCC. We exploited comparative proteomic analyses based on anti-EGFR potential of varlitinib, using cellular proteomes from treated and untreated groups of oral cancer cells to identify protein players functional during oral carcinogenesis. Following separation by two-dimensional electrophoresis, differentially expressed cellular proteins (varlitinib-treated and untreated cells) were analyzed and later identified using QTOF mass spectrometer. In silico analysis for protein-protein interaction was carried out using STRING. Six differentially expressed proteins were identified as binding immunoglobulin protein (BiP), heat shock protein 7 C (HSP7C), protein disulfide isomerase 1 A (PDIA1), vimentin (VIME), keratin type I cytoskeletal 14 (K1C14), and β-Actin (ACTB). Relative expression of five proteins was found to be downregulated upon varlitinib treatment, whereas only K1C14 was upregulated in treated cells compared to control. Protein network analysis depicts the interaction between BiP, PDIA1, VIME, etc. indicating their role in oral carcinogenesis. Oral cancer cells show proteome shift based on varlitinib treatment compared to corresponding controls. Our data suggest candidature of varlitinib as a potent therapeutic agent and BiP, PDIA1, HSP7C, VIME, and β-Actin as complementary/prognostic markers of OSCC.

Chemical Hypoxic Preconditioning Improves Survival and Proliferation of Mesenchymal Stem Cells

Increasing evidence has demonstrated that mesenchymal stem cells (MSCs) have been linked to tissue regeneration both in vitro and in vivo. However, poor engraftment and low survival rate of transplanted MSCs are still a major concern. It has been found that the proliferation, survival, and migration of MSCs are all increased by hypoxic preconditioning. However, the molecular mechanism through which hypoxic preconditioning enhances these beneficial properties of MSCs remains to be fully investigated. Therefore, the present study is aimed to investigate the mechanism by which hypoxic preconditioning enhances the survival of MSCs. We used proteomic analysis to explore the molecules that may contribute to the survival and proliferation of hypoxic preconditioned (HP) MSCs. The analysis revealed a higher expression of prelamin A/C (Lmna), glutamate dehydrogenase 1(Glud1), Actin, cytoplasmic 1(Actb), Alpha-enolase (Eno1), Glucose-6-phosphate 1-dehydrogenase (G6pd), Protein disulfide-isomerase A3 (Pdia3), Malate dehydrogenase (Mdh1), Peroxiredoxin-6 (Prdx6), Superoxide dismutase (Sod1), and Annexin A2 (Anxa2) in HP-MSCs. These proteins are possibly involved in cellular survival and proliferation through various cellular pathways. This research could aid in understanding the processes involved in hypoxic preconditioning of MSCs and designing of cell-based therapeutic strategies for tissue regeneration.

The structural characterization and bioactivity assessment of nonspecific lipid transfer protein 1 (nsLTP1) from caraway (Carum carvi) seeds

BACKGROUND

Carum carvi (caraway) of the Apiaceae family has been used in many cultures as a cooking spice and part of the folk medicine. Previous reports primarily focus on the medicinal properties of caraway seed essential oil and the whole seeds extract. However, no effort has been made to study caraway proteins and their potential pharmacological properties, including nonspecific lipid transfer protein (nsLTP), necessitating further research. The current study aimed to characterize nonspecific lipid transfer protein 1 (nsLTP1) from caraway seed, determine its three-dimensional structure, and analyze protein-ligand complex interactions through docking studies. We also evaluated nsLTP1 in vitro cytotoxic effect and antioxidant capacity. Additionally, nsLTP1 thermal- and pH- stability were investigated.

METHODS

Caraway nsLTP1 was purified using two-dimensional chromatography. The complete amino acid sequence of nsLTP1 was achieved by intact protein sequence for the first 20 residues and the overlapping digested peptides. The three-dimensional structure was predicted using MODELLER. Autodock Vina software was employed for docking fatty acids against caraway nsLTP1. Assessment of nsLTP1 cytotoxic activity was achieved by MTS assay, and the Trolox equivalent antioxidant capacity (TAC) was determined. Thermal and pH stability of the nsLTP1 was examined by circular dichroism (CD) spectroscopy.

RESULTS

Caraway nsLTP1 is composed of 91 residues and weighs 9652 Da. The three-dimensional structure of caraway nsLTP1 sequence was constructed based on searching known structures in the PDB. We chose nsLTP of Solanum melongena (PDB ID: 5TVI) as the modeling template with the highest identity among all other homologous proteins. Docking linolenic acid with caraway protein showed a maximum binding score of -3.6 kcal/mol. A preliminary screening of caraway nsLTP1 suppressed the proliferation of human breast cancer cell lines MDA-MB-231 and MCF-7 in a dose‑dependent manner with an IC₅₀ value of 52.93 and 44.76 μM, respectively. Also, nsLTP1 (41.4 μM) showed TAC up to 750.4 μM Trolox equivalent. Assessment of nsLTP1 demonstrated high thermal/pH stability.

CONCLUSION

To the best of our knowledge, this is the first study carried out on nsLTP1 from caraway seeds. We hereby report the sequence of nsLTP1 from caraway seeds and its possible interaction with respective fatty acids using in silico approach. Our data indicated that the protein had anticancer and antioxidant activities and was thermally stable.

Polymorphic Variants of ASS1 Gene Related to Arginine Metabolism and the Risk of HCC

BACKGROUND

Hepatocellular carcinoma is a primary liver cancer and 6th most common cancer globally. Inefficient diagnostic strategies and the limited availability of treatments are the foremost reasons. Variable factors directly impact the disease burden, among them, molecular alterations have been found to play a significant role. In liver, argininosuccinate synthase-1 is a center of arginine metabolism and rate limiting enzyme of urea cycle. It also triggers multiple mechanisms that lead to HCC pathogenesis.

OBJECTIVES

The aim of this study is to analyze the ASS1 gene expression, its polymorphic genotype and microsatellite instability among HCC patients from our Pakistani population.

METHOD

Blood samples were collected from disease and healthy control individuals. Allele-Specific PCR was performed for SNP analysis. MSI of tri and tetra nucleotide repeats were analyzed by PCR. The differential expression of ASS1 gene was also investigated. Furthermore, the reactome database and STRING software were utilized for finding correlations between ASS1 gene with other associated gene/proteins.

RESULTS

The GG wild-type genotype was more prevailed in the disease group as compared to the control. Significant downregulation in ASS1 and NOS2 genes was observed. Bioinformatics analysis reveals the correlation between ASS1 polymorphism and HCC development appears to be linked with the EMT pathway and polyamine production. Furthermore, MSI significantly resided in the disease group. Results were analyzed statistically to calculate the significance of obtained results.

CONCLUSION

Study concludes that the insight of HCC mechanism through population-specific genetic mutations and altered gene expression of ASS1 might be helpful in early diagnostic and therapeutic purposes.

Novel Synergistic Combination of Pamidronate and Temozolomide for Breast Cancer Therapeutics

OBJECTIVE

Human breast cancer is among one major health concerns with high prevalence and mortality among women worldwide. Various cellular signaling pathways are implicated in carcinogenesis. One of the major pathways that affect the downstream cellular growth cascades is Mevalonate pathway (MVA). The inhibition of MVA is therapeutically beneficial for various cancers. Pamidronate (PAM) (MVA inhibitor), a nitrogen-containing bisphosphosphonate, is an antiresorptive FDAapproved drug. The objective of our study was to explore adjuvant therapy using a combination of PAM and an alkylating agent, Temozolomide (TMZ) against breast cancer.

METHODS

We have examined the differential gene and protein expression in response to the combination treatment strategy. For gene expression analysis RT-qPCR and for proteomic study, twodimensional gel electrophoresis and mass spectrometry techniques were utilized.

RESULTS

Combination treatment (PAM+TMZ) showed more pronounced cytotoxic effect as compared to single agent treatment. Our results indicate that MVA pathway regulatory genes (FDFT1, FDPS, KRAS) are significantly (p<0.05) downregulated in combination-treated breast cancer cells. The differential proteomic analysis showed lower expression of GFAP, PPA1 and TRIM68 proteins after synergistic treatment whereas, these proteins are found to be up-regulated in multiple cancers.

CONCLUSION

The present study reveals that a combination of PAM and TMZ produces an effective anti-cancerous effect on breast cancer cells. Therefore, this novel therapeutic regimen is likely to provide a better treatment strategy for breast cancer.

Prenatal diagnosis of maternal serum from mothers carrying β-thalassemic fetus

BACKGROUND

This study focuses on the discovery of protein biomarkers from the maternal serum of β-thalassemic trait mothers carrying the normal fetus and β-thalassemic major fetus.

METHODS

Serum samples from β-thalassemic trait mothers carrying major (N = 5) and normal fetuses (N = 5) were studied. The IVS1-5 thalassemia mutation was common among β-thalassemic trait mothers who were carrying a homozygous β-thalassemic fetus (IVS1-5/ IVS1-5 mutation) or a normal fetus (no mutation). We employed two-dimensional gel electrophoresis and mass spectrometry analysis to explore differentially expressed maternal serum proteins from thalassemia carrier couples with the same β-thalassemia mutation. Western blotting was performed for one of the identified proteins to validate our data.

RESULTS

Ten proteins were identified in the maternal serum of β-thalassemic trait mothers carrying the β-thalassemic major fetus and normal fetus. Among these, serotransferrin, haptoglobin, α-1 anti-trypsin, apo-lipoprotein A1, and the fibrinogen-β chain were found to be upregulated in mothers carrying major fetuses and are known to be associated with pregnancy-related disorders. The expression of α-1 anti-trypsin was validated through western blotting.

CONCLUSIONS

Proteins identified in the current study from maternal serum are reported to contribute to hereditary disorders. We suggest that these can serve as putative screening markers for non-invasive prenatal diagnosis in β-thalassemic pregnancies.

Antioxidant Activity and Oxidative Stress Status in Maternal Serum of β-thalassemic Mothers Carrying β-thalassemic Major and Normal Fetuses

Objectiveβ-thalassemia is a genetic disorder characterized by reduction or absence of β-globin chain with mutations in both copies (β-thalassemia major) or in one copy (β-thalassemia minor). Pregnancies in β- thalassemic carrier women are considered symptom free but have risk of inheriting β-thalassemic fetuses. Current study was designed to compare oxidative stress and antioxidants status in maternal serum from β-thalassemic minor mothers having β-thalassemic major and normal fetuses. Method: We investigated paraoxonase (PON1) and arylesterase (ARE) activities along with malondialdehyde (MDA) and reactive oxygen species (ROS) in maternal serum of β-thalassemic carrier women. Results: PON1 and ARE activities were found to be significantly decreased, whereas the concentration of MDA and ROS were significantly increased in β-thalassemic minor mothers with β-thalassemic major fetuses. Conclusion: The study concludes that redox imbalance in β-thalassemic trait mothers carrying thalassemic fetuses is higher than in mothers carrying normal fetuses.

Oxidative Stress Induced Cell Cycle Arrest: Potential Role of PRX-2 and GSTP-1 as Therapeutic Targets in Hepatocellular Carcinoma

BACKGROUND

The increasing incidence and mortality rate of HCC is a major concern, especially for developing countries of the world. Hence, extensive research is being carried out in order to explore new approaches for developing successful therapeutic strategies for HCC. The controversial role of oxidative stress in the prognosis and treatment of various diseases such as cancer has become the area of great interest and intrigue for many scientists throughout the world.

OBJECTIVE

We aim to investigate the role of induced oxidative stress on the suppression of HCC Huh-7 cancerous cells as therapeutic approach.

METHODS

Induction of oxidative stress via H2O2 treatment produced cell cytotoxicity in a dose dependent manner and also led to the over expression of GSTP-1 and PRX-2. The expression of GSTP-1 and PRX-2 was compared in HCC Huh-7 treated, untreated cells and normal hepatocytes using immunocytochemistry. Furthermore, the effects of oxidative stress on cell cycle arrest were also studied through flow cytometry.

RESULTS

Our study demonstrated the inhibition of cancer cell proliferation as a result of H2O2 induction by arresting the cell cycle at G2 phase.

CONCLUSION

The induction of oxidative stress could be a potential therapeutic approach for treating HCC in the future. GSTP-1 and PRX-2 can serve as substantial therapeutic targets for the treatment of HCC.

Differential effects of memory enhancing and impairing doses of methylphenidate on serotonin metabolism and 5-HT1A, GABA, glutamate receptor expression in the rat prefrontal cortex

Methylphenidate (MPD), a psychostimulant, is a prescription medicine for treating attention deficit hyperactivity disorder (ADHD). Previously we have shown that moderate doses of MPD enhanced learning and memory while higher doses impaired it. To understand neurochemical mechanisms and receptors involved in memory enhancing and impairing effects of MPD, the present study concerns the effects of these doses of MPD on serotonin, 5-HT1A, GABA, and NMDA receptor mRNA expression in the prefrontal cortex (PFC). We found that low doses (2.5 mg/kg) of MPD improved performance in the water-maze test but higher doses (5 mg/kg) impaired memory retention. Animals showing improved performance had high 5-HT metabolism in the PFC while these levels were not affected in the group treated with higher MPD doses and exhibiting impaired memory. There was downregulation of 5-HT1A receptors in the PFC of rats treated with higher dose MPD, which didn't occur in low dose of MPD treated animals. Further, a decrease in GABA_Areceptor mRNA expression occurred in low doses of MPD treated animals and GluN2A expression was reduced in higher doses of MPD treated animals. The findings suggest that memory enhancing doses of MPD increase 5-HT and reduce GABA_A receptor mRNA expression in the PFC to release excitatory glutamate neurons from the inhibitory influence of GABA. Conversely, higher dose of MPD downregulates 5-HT1A receptor mRNA expression to enhance inhibitory GABA influence on glutamate neurons and impair cognitive performance. The findings show an important role of 5-HT1A heteroreceptors in the PFC for improving therapeutic use of MPD and developing novel cognitive enhancers.

Serum HSP90-Alpha and Oral Squamous Cell Carcinoma : A Prospective Biomarker

AIM

Current study aims to perform differential protein expression analysis of serum samples from Oral squamous cell carcinoma (OSCC) patients and healthy controls in search of potential diagnostic and/or prognostic biomarker(s).

OBJECTIVE

OSCC is diagnosed late, resulting in poor survival and high mortality. Identification of non-invasive prognostic biomarker is of utmost importance for early diagnosis and proper management of the disease; hence we used proteomic approach to identify potential biomarkers from serum.

METHODS

Serum samples (OSCC n=45 and control n=30) were depleted and proteins were separated using 2-D gel electrophoresis followed by identification by mass spectrometric analysis. Gene expression analysis of identified proteins in malignant and normal tissue was also performed to complement proteomics studies.

RESULTS

Among differentially expressed proteins, a noteworthy observation was up regulation of Heat shock protein alpha (HSP90α) from serum of oral cancer patients. We also observed elevated levels of Haptoglobin (HP) along with down regulation of Type II keratin cytoskeletal 1(KRT1) and serum Albumin (ALB) in oral cancer patients. Gene expression studies of identified proteins in malignant and normal tissue revealed a similar pattern with the exception of KRT1. We believe that elevated levels of serum HSP90 alpha might be used as a potential biomarker.

CONCLUSION

Our findings suggest the contribution of HSP90 alpha and other identified proteins in oral pathology as pro/anti apoptotic modulators, thus they are being considered as predictive biomarkers.

Evaluation of anti-EGFR potential of quinazoline derivatives using molecular docking: An in silico approach

Overexpression of epidermal growth factor receptor (EGFR) is commonly reported in epithelial malignancies such as oral squamous cell carcinoma. Inhibition of EGFR is, therefore, considered a potential therapeutic strategy. Among various anti-EGFR drugs, quinazoline-based tyrosine kinase inhibitors (TKIs) have gained increasing attention. Present study focused to investigate anti-EGFR potential of quinazoline-based compounds using in silico approach. Two widely used docking programs GOLD and AutoDock Vina were used for the study. Four drugs were docked on the X-ray crystallographic EGFR structure (1XKK). GOLD and AutoDock Vina produced results in terms of fitness score and binding affinity, respectively. GOLD prioritized varlitinib and AutoDock Vina preferred imatinib over other drugs. To reach the consensus from both software, all four drugs coupled with EGFR were studied rigorously. GOLD demonstrated varlitinib to be the best inhibitor with highest fitness score of 109, whereas AutoDock Vina revealed imatinib as the potent ligand with least binding energy of -10.9 kcal/mol. Most stable hydrogen bonds observed by GOLD and maximum number of hydrophobic contacts along with strong ionic interaction exhibited by varlitinib through both software have led us to conclude varlitinib as the most potent EGFR inhibitor in the studied group.

Integrated Cheminformatics-Molecular Docking Approach to Drug Discovery Against Viruses

BACKGROUND

In the current study, we present an integrated in silico cheminformaticsmolecular docking approach to screen and test potential therapeutic compounds against viruses. Fluoroquinolones have been shown to inhibit HCV replication by targeting HCV NS3-helicase. Based on this observation, we hypothesized that natural analogs of fluoroquinolones will have similar or superior inhibitory potential while having potentially fewer adverse effects.

METHODS

To screen for natural analogs of fluoroquinolones, we devised an integrated in silico Cheminformatics-Molecular Docking approach. We used 17 fluoroquinolones as bait reference, to screen large databases of natural analogs. 10399 natural compounds and their derivatives were retrieved from the databases. From these compounds, molecules bearing physicochemical similarities with fluoroquinolones were analyzed using a cheminformatics-docking approach.

RESULTS

From the 10399 compounds screened using our cheminformatics approach, only 20 compounds were found to share physicochemical similarities with fluoroquinolones, while the remaining 10379 compounds were physiochemically different from fluoroquinolones. Molecular docking analysis showed 32 amino acids in the HCV NS3 active site that were most frequently targeted by fluoroquinolones and their natural analogues, indicating a functional similarity between the two groups of compounds.

CONCLUSION

This study describes a speedy and inexpensive approach to complement drug discovery and design against viral agents. The in silico analyses we used here can be employed to shortlist promising compounds/putative drugs that can be further tested in wet-lab.

Structural characterization and in vitro lipid binding studies of non-specific lipid transfer protein 1 (nsLTP1) from fennel (Foeniculum vulgare) seeds

Non-specific lipid transfer proteins (nsLTPs) are cationic proteins involved in intracellular lipid shuttling in growth and reproduction, as well as in defense against pathogenic microbes. Even though the primary and spatial structures of some nsLTPs from different plants indicate their similar features, they exhibit distinct lipid-binding specificities signifying their various biological roles that dictate further structural study. The present study determined the complete amino acid sequence, in silico 3D structure modeling, and the antiproliferative activity of nsLTP1 from fennel (Foeniculum vulgare) seeds. Fennel is a member of the family Umbelliferae (Apiaceae) native to southern Europe and the Mediterranean region. It is used as a spice medicine and fresh vegetable. Fennel nsLTP1 was purified using the combination of gel filtration and reverse-phase high-performance liquid chromatography (RP-HPLC). Its homogeneity was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry. The purified nsLTP1 was treated with 4-vinyl pyridine, and the modified protein was then digested with trypsin. The complete amino acid sequence of nsLTP1 established by intact protein sequence up to 28 residues, overlapping tryptic peptides, and cyanogen bromide (CNBr) peptides. Hence, it is confirmed that fennel nsLTP1 is a 9433 Da single polypeptide chain consisting of 91 amino acids with eight conserved cysteines. Moreover, the 3D structure is predicted to have four α-helices interlinked by three loops and a long C-terminal tail. The lipid-binding property of fennel nsLTP1 is examined in vitro using fluorescent 2-p-toluidinonaphthalene-6-sulfonate (TNS) and validated using a molecular docking study with AutoDock Vina. Both of the binding studies confirmed the order of binding efficiency among the four studied fatty acids linoleic acid > linolenic acid > Stearic acid > Palmitic acid. A preliminary screening of fennel nsLTP1 suppressed the growth of MCF-7 human breast cancer cells in a dose-dependent manner with an IC50 value of 6.98 µM after 48 h treatment.

Therapeutic effect of hydrogen peroxide via altered expression of glutathione S-transferase and peroxiredoxin-2 in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) has a high incidence and mortality that epitomizes one of the prominent causes of cancer-related death globally. Novel therapeutic approaches are therefore required. Reactive oxygen species (ROS) are necessary for maintaining cell cycle. Although ROS is involved in HCC progression, hydrogen peroxide (H₂O₂) has anti-proliferative effect on HCC.

METHOD

HCC Huh-7 cells were cultured and incubated with various concentrations of H₂O₂. Paraoxonase activity, levels of malondialdehyde, glutathione and protein oxidation were measured in treated and untreated Huh-7 cells. Furthermore, untreated and treated Huh-7 cells were subjected to two dimensional gel electrophoresis and identified protein spots which were differentially expressed by LC-MS/MS analysis. qRT-PCR was performed to validate the identified proteins.

RESULTS

H₂O₂ depleted glutathione (GSH) with the concomitant up-regulation of GSTP1 and Prx2. H₂O₂ also increased malondialdehyde and protein oxidation, decreased the activity of paraoxonase in Huh-7 cells.

CONCLUSION

H₂O₂ could be used as a novel therapeutic agent that might be beneficial in inducing cell cytotoxicity and hence suppress HCC proliferation.

Varlitinib Mediates Its Activity Through Down Regulating MAPK/EGFR Pathway in Oral Cancer

Background:

Oral Squamous Cell Carcinoma (OSCC) is a major sub-type of oral cancer that shares 90% proportion of oral cavity cancers. It is declared as the sixth most frequent cancer among all cancer types throughout the world. Higher morbidity in Asian countries is reported due to frequent use of Smokeless Tobacco (SLT) products besides exposure to other risk factors. Hyperactivation of epidermal growth factor receptors is a molecular event in many solid tumors including oral cancer making them potential therapeutic targets.

Objective:

Current study was designed to explore the effect of varlitinib, a pan-HER inhibitor, on oral cancer cell line. We investigated key regulatory genes in downstream pathway in response to drug treatment. Furthermore, we also examined expression profile of these genes in malignant and healthy oral tissue.

Method:

Gene expression pattern in drug treated and untreated cancer cell line along with OSCC tumor samples (n=45) and adjacent normal tissues was studied using real time PCR.

Results:

In response to varlitinib treatment, significant suppression of oncogenes (IGF1R, MAPK1, SFN and CDK2) was observed. Interestingly, mRNA expression level of CDKN1A and Akt1 was found to be the opposite of what was expected. In case of malignant tissue, over expression of oncogenes (IGF1R, Akt1, MAPK1, SFN and CDK2) with simultaneous down expression of tumor suppressor genes (Tp53 and CDKN1A) was noted. STRING analysis indicated a strong association among differentially expressed genes suggesting their combined role in carcinogenesis.

Conclusion:

In summary, our results indicate that varlitinib can be considered as a potential therapeutic agent in oral cancer due to its antitumor potential.

Identification of Differentially Expressed Proteins from Smokeless Tobacco Addicted Patients Suffering from Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is the eight most common malignancy worldwide with an incidence rate of 40% in south-east Asia. Lack of effective diagnostic tools at early stage and disease recurrence despite extensive treatments are main reasons for high mortality and low survival rates. The aim of current study was to identify differentially expressed proteins to explore potential candidate biomarkers having diagnostic significance. We performed comparative proteomic analysis of paired protein samples (cancerous buccal mucosa and adjacent normal tissue) from OSCC patients using a combination of two dimensional gel electrophoresis and Mass spectrometric analysis. On the basis of spot intensity, seventeen proteins were found to be consistently differentially expressed among most of the samples which were identified through mass spectrometry. For validation of identified proteins, expression level of stratifin was determined using immuno-histochemistry and Western blot analysis. All identified proteins were analyzed by STRING to explore their interaction. Among uniquely identified proteins in this study, at least two candidate markers (Ig Kappa chain C region and Isoform 2 of fructose bisphosphate aldolase A) were found to be novel with respect to OSCC which can be explored further. Results presented in current study are likely to contribute in understanding the involvement of these molecules in carcinogenesis apart from their plausible role as diagnostic/prognostic markers.

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.

Pharmacoproteomics Profiling of Plasma From β-Thalassemia Patients in Response to Hydroxyurea Treatment

β-Thalassemia is a genetic disorder caused by defects in the β-globin gene resulting in the absence or reduced synthesis of adult hemoglobin (HbA). Hydroxyurea is an effective drug to increase fetal γ-globin (HbF) expression, replacing the missing adult β-globin. The mechanism of HbF induction by hydroxyurea and improvement in clinical symptoms are still poorly understood. In the present study we performed comparative analysis of plasma proteome in pre- and post-hydroxyurea-treated β-thalassemia major transfusion-dependent children (n = 10, mean age = 3.2 years) as well as responders versus nonresponders to hydroxyurea treatment. Plasma was collected before and after 6 months of hydroxyurea treatment, with patients subcategorized on the basis of their response to hydroxyurea. Among 400 identified proteins using a label-free quantitative proteomics approach, 28 proteins were found to be significantly different in pre- versus post-hydroxyurea-treated groups, with transferrin receptor protein-1 being most downregulated and hemopexin and haptoglobin the most upregulated proteins after treatment. In responder versus nonresponder comparison, 26 proteins were found to be differentially expressed, with carbonic anhydrase 1, hemoglobin subunit γ-1, and peroxiredoxin-2 showing the significant changes. The mechanism of hydroxyurea treatment in β-thalassemia patients appears to be complex, requiring a large sample size and a longer period of treatment to reveal its details.

Two for one: Viral helicases as an ideal target for HIV and HCV co-infection

Helicase enzyme is responsible for the unwinding of complementary nucleic acid strands, which is one of the preliminary steps in DNA replication. They are crucial for replication of an organism, including viruses. HCV and HIV are two clinically significant pathogens, responsible for millions of infections and deaths worldwide. Due to similar transmission routes, these viruses can establish co-infection in an individual. Individually, these infections are difficult to treat, however, in case of co-infection, the treatment becomes more difficult. Additionally, these viruses accumulate mutation in response to drug therapy that renders the treatment ineffective. HCV and HIV both encode enzyme containing helicase activity. The viral-encoded helicase plays a significant role in HIV and HCV life cycle. Here we propose viral helicases as an ideal single-hit target that can inhibit HIV and HCV co-infection. We also hypothesize that search for natural analogs sharing basic ring structure with a class of helicase inhibitors called fluoroquinolones can yield natural agents with superior antiviral (anti-helicase) activity with lower toxicity index. The fluoroquinolones and their analogs are currently not part of any antiviral regimens. Our proposal is to include fluoroquinolones-derived natural analogs as a conjugate therapy along with main regimens available against HCV and HIV co-infection.

Alendronate and FTI-277 combination as a possible therapeutic approach for hepatocellular carcinoma: An in vitro study

BACKGROUND

An important product of mevalonate pathway is downstream synthesis of isoprenoid units that has long been implicated in development and progression of tumor. It has been speculated that inhibition of protein prenylation might be therapeutically beneficial. The objective of current study was to evaluate antitumor potential of a novel therapeutic combination of mevalonate pathway inhibitors, FTI-277 and alendronate. We also examined differentially expressed proteins in response to treatment using proteomics approach.

METHODS

Huh-7 cells were incubated with different concentrations of FTI-277 alone and in combination with alendronate. Differential protein and gene expression was examined through two dimensional gel electrophoresis and real-time quantitative polymerase chain reaction (qPCR), respectively. Proteins were identified using tandem mass spectrometry analysis.

RESULTS

Treatment of hepatocellular carcinoma (HCC) cell line with FTI-277 alone showed cell death in a time and dose dependent manner while in combination with alendronate, a synergistic apoptotic effect at 24 h was observed. Proteomic studies on the 20 µmol/L FTI-277 and 5 µmol/L alendronate +20 µmol/L FTI-277 treated cells revealed altered expression of different proteins including peroxiredoxin 2 (Prx2), glutathione S transferase 1 (GSTP1), Rho GTPase activating protein (RhoGAP), triosephosphate isomerase (TPI), and heat shock protein 60 (HSP60). Down-regulated expression of Prx2 and GSTP1 in treated cells was also confirmed by real-time qPCR analysis.

CONCLUSIONS

Combined treatment of FTI-277 and alendronate on Huh-7 HCC cells showed cell death suggesting their anticancer potential. Such treatment approaches are likely to offer new therapeutic strategies.

Simian Virus 40 Large T Antigen as a Model to Test the Efficacy of Flouroquinolones against Viral Helicases

Simian virus 40 large T-antigen (SV40 LT-Ag) is a 708 amino acid nuclear phosphoprotein. Among many functions of LT-Ag is its ability to perform as an ATPase-helicase, catalyzing the unwinding of viral genome during replication. The LT-Ag has been employed in the studies of helicase structure and function, and has served as a model helicase for the screening of antiviral drugs that target viral helicase. In this study, using in vitro enzyme assays and in silico computer modeling, we screened a batch of 18 fluoroquinolones to assess their potential as antivirals by virtue of their inhibition of the LT-Ag helicase. We found all fluoroquinolones to be inhibitory to the helicase activity of LT-Ag. In our docking analysis, most of these tested drugs showed similarity in their interactions with LT-Ag. Our study shows the potential of fluoroquinolones as antiviral drugs and of SV40 LT-Ag as a model protein for screening drugs against viral helicases.

Differential hemoglobin A sequestration between hemodialysis modalities

This report evaluates plasma protein patterns, dialysates and protein analysis of used dialysis membranes from the same patient under hemodialysis in three separate modalities, using high-flux membranes in concentration-driven transport (HD), convection-driven hemofiltration (HF) and combined hemodialfiltration (HDF). The plasma protein changes induced by each of the three dialysis modalities showed small differences in proteins identified towards our previous plasma analyses of chronic kidney disease (CKD) patients. The used dialysate peptide concentrations likewise exhibited small differences among the modalities and varied in the same relative order as the plasma changes, with protein losses in the order HD>HDF>HF. The membrane protein deposits allowed quantification of the relative Hb removal ratios as ~1.7 for HD and ~1.2 for HDF vs. ~1.0 for HF. Hence, plasma protein alterations, dialysate peptide contents and membrane Hb deposits all identify HD as the modality with the most extensive filtration results and exemplifies the accessibility of protein analysis of used membrane filters for evaluation of dialysis efficiencies.

New anthrarobin acyl derivatives as butyrylcholinesterase inhibitors: synthesis, in vitro and in silico studies

To treat Alzheimer's disease (AD), the available candidates are effective only against mild AD or have side effects. So, a study was planned to synthesis new candidates that may have good potential to treat AD. A series of new anthrarobin acyl derivatives (2–8) were synthesized by the reaction of anthrarobin (1) and acetic anhydride/acyl chlorides. The product were characterized by ¹H NMR and EI-MS, and evaluated for butyrylcholinesterase (BuChE) inhibition activity. Compounds 5 and 4 showed notable BuChE inhibitory potential with IC₅₀ 5.3 ± 1.23 and 17.2 ± 0.47 μM, respectively when compared with the standard eserine (IC₅₀ 7.8 ± 0.27 μM), compound 5 showed potent BuChE inhibition potential than the standard eserine. The active compounds 5 and 4 have acyl groups at 2-OH and 10-OH positions which may be responsible for inhibitory potential as this orientation is absent in other products. In silico studies of 5 and 4 products revealed the high inhibitory potential due to stable binding of ligand with the BuChE active sites with docking energy score −18.8779 kcal/mol and −23.1159 kcal/mol, respectively. Subsequently, compound 5 that have potent BuChE inhibitory activity could be the potential candidate for drug development for Alzheimer’s disease.

Complementary LC-MS/MS Proteomic Analysis of Uremic Plasma Proteins

OBJECTIVE

To complement an earlier analysis of protein alterations in plasma from uremic versus healthy subjects by addition of further LC-MS/MS analysis to the previously used MALDI-TOF mass analyses.

METHODOLOGY

Sequence identifications of tryptic peptides from SDS gel electrophoretic fractions of immunodepleted and HPLC-fractionated plasma was performed from seven chronic kidney disease stage 5 patients (age 55 ± 14 years, glomerular filtration rate 6.9 ±2.9 mL/minute/1.73 m2) and from seven matched controls.

RESULTS

About twice as many proteins were increased in uremic plasma as the previously identified. The identifications included proteins that consistently complement the two identification patterns regarding separate subunits from the same protein complex.

CONCLUSION

Mass spectrometric analysis is applicable to complex plasma proteomes in clinical settings. The LC-MS/MS technique, based on individual peptide sequence analyses, gives increased identifications and also demonstrates feasibility of this technique in clinical practice.

Q192R paraoxonase1 polymorphism is a risk factor for cataract in Pakistani population

Cataract, the lens opacity, is among major causes of blindness in Pakistani population. In recent past, oxidative stress is suggested to play crucial role in loss of transparency. Along with other antioxidants, Paraoxonase 1 (PON1) has also shown decreased activity in patients suffering from cataract. The aim of current study was to examine the possible association of PON polymorphism with predisposition of cataract formation in local population. The study was conducted on 51 cataract patients and 50 control subjects considering all ethical issues. DNA was extracted from whole blood and PON1 polymorphism was identified using tetra primer ARMS-PCR method for both positions L55M and Q192R. Tetra primer ARMS-PCR results revealed that association between L55M polymorphism and cataract was insignificant while 192R genotype PON1 frequency was higher among the people suffering from cataract (78.4%) as compared to control subjects (56%), (odds ratio=2.857, confidence interval=1.197-6.820). Hence, R allele is likely to be a risk factor for cataract with allele frequency (82.3%) and (odds ratio=4.552, confidence interval=1.716-12.073, p-value=0.002). PON1 Q192R polymorphism is likely to be a risk factor for cataract development in Pakistani population while PON1 L55M was not found to be associated with cataract.

Effects of 5'-azacytidine and alendronate on a hepatocellular carcinoma cell line: a proteomics perspective

Hepatocellular carcinoma (HCC) is the third leading cause of cancer related deaths around the world. Due to late diagnosis and development of drug resistance in patients suffering from HCC, development of more effective therapeutic strategies is inevitable. The aim of this study was to evaluate the combined apoptotic effect of 5'-Azacytidine (5'-AzaC) and alendronate (ALN) on Huh-7 HCC cell line and to explore differential expression at genomics and proteomics level. Incubation of HCC cell line with 5'-AzaC alone showed cell death in a time and dose dependent manner while in combination with ALN, increased cytotoxicity was observed. Up-regulation of CASP7(Caspase7) and LZTS1 (leucine zipper, putative tumor suppressor 1) and down-regulation of DNMT1(DNA (cytosine-5-)-methyltransferase 1) was noted in treated cells. Proteomic studies on the treated cells revealed altered expression of different proteins including peroxiredoxin 2 (Prx2), Annexin 5 (Anx5), Rho GTPase activating protein (RhoGAP), Nuclear factor-kappa B (NF-kB), tumor necrosis factor alpha-induced protein (TNF), triosephosphate isomerase (TPI), Glutathione S transferase (GSTP1) and Heat shock protein60 (HSP60). Our study demonstrated the cytotoxic effect of 5'-AzaC and ALN drug combination on Huh-7 HCC cells suggesting such combinations may be explored as a possible therapeutic approach. Current study revealed that Huh-7 HCC cells are sensitive to 5'-AzaC and ALN drug combination and such combination approaches could lead to the development of new therapeutic strategies. Furthermore, we also report the expression of Anx5 exclusively in untreated cancerous cell line indicating the possibility of being used as a potential therapeutic target and biomarker.

Docking studies of antidepressants against single crystal structure of tryptophan 2, 3-dioxygenase using Molegro Virtual Docker software

Tryptophan 2, 3-dioxygenase (TDO) a heme containing enzyme found in mammalian liver is responsible for tryptophan (Trp) catabolism. Trp is an essential amino acid that is degraded in to N-formylkynurenine by the action of TDO. The protein ligand interaction plays a significant role in structural based drug designing. The current study illustrates the binding of established antidepressants (ADs) against TDO enzyme using in-silico docking studies. For this purpose, Fluoxetine, Paroxetine, Sertraline, Fluvoxamine, Seproxetine, Citalopram, Moclobamide, Hyperforin and Amoxepine were selected. In-silico docking studies were carried out using Molegro Virtual Docker (MVD) software. Docking results show that all ADs fit well in the active site of TDO moreover Hyperforin and Paroxetine exhibited high docking scores of -152.484k cal/mol and -139.706k cal/mol, respectively. It is concluded that Hyperforin and Paroxetine are possible lead molecules because of their high docking scores as compared to other ADs examined. Therefore, these two ADs stand as potent inhibitors of TDO enzyme.

Measurement of serum paraoxonase activity and MDA concentrations in patients suffering with oral squamous cell carcinoma

BACKGROUND

Oxidative stress is associated with many diseases including cancer. Oral squamous cell carcinoma (OSCC) is a prevalent cancer involving oral cavity. We evaluate the activity of paraoxonase 1 (PON1) in serum samples of subjects suffering from OSCC along with malondialdehyde (MDA) levels, a marker for oxidative stress. Antioxidant status in OSCC may reflect the role of oxidative imbalance in the disease.

METHODS

Forty-five patients suffering with OSCC and 30 healthy controls were selected for the study. Serum paraoxonase (PON) and arylesterase (ARE) activities were measured in subjects suffering from OSCC and their healthy counterparts. To examine the status of lipid peroxidation, MDA concentrations were estimated and a correlation was determined between PON activities and MDA concentrations. MDA expression in cancer and normal adjacent tissue was studied through immunohistochemical (IHC) analysis. Total reactive oxygen species (ROS) level was determined in serum from normal and diseased subjects. Our results revealed that both PON and ARE activities of PON1 were significantly decreased in OSCC patients. Serum MDA concentrations were inversely correlated to PON activity. Immunohistochemical analysis showed a higher expression of MDA in cancerous tissue. Total ROS levels were found to be significantly elevated in cancer subjects.

CONCLUSIONS

Along with other antioxidants, PON levels may act as an indicator of oxidative stress in cancer.

Evolutionary journey of the Gc protein (vitamin D-binding protein) across vertebrates

With so many diverse functions such as transporter of vitamin D metabolites and fatty acids, actin scavenger and macrophage activating factor, Gc must have been one of the most conserved proteins in animal kingdom. Our objective was to investigate the evolution of Gc by analyzing its differences at protein level. Using BLAST (Basic Local Alignment Search Tool) searches, Gc amino acid sequences were analyzed for homology. Clustal W2 and Jalview were used for multiple sequence alignment analysis, phylogenetic tree by PhyML 3.0 while Batch Web CD-Search Tool was used for identification for conserved domains within protein sequences. Gc protein percent identity between human and rabbit was 83%, which decreased to 81% with cow, 78% with mouse, 76% with rat, 51% with chicken, 41% with frog and 28% with zebrafish. Phylogram showed that rat Gc was the most diverged, while chicken Gc was the most conserved protein. Analysis also indicated high homology among mammals (human, rabbit, cow, rat, and mouse). Gc is a highly conserved protein in chicken and zebrafish. However, the distance from ancestral protein gradually increased in amphibian (frog) and mammals (human, rabbit, cow, rat, and mouse). Human Gc and rabbit Gc appear to be recently evolved proteins. There appears to be an interesting evolutionary pattern- chicken Gc has the least distance from the ancestral protein, while rat Gc is the most diverged. There is no vertebrate devoid of Gc which is suggestive of its important role in vitamin D metabolism in vertebrates.

Use of the SYBR Green dye for measuring helicase activity

Here we describe a non-radioactive assay that exploits the fluorescent dye SYBR Green to measure the helicase enzyme activity. SYBR Green I emits fluorescence upon intercalation with double-stranded DNA or RNA. The fluorescence is lost proportionally as the nucleic acid is converted to single strands by a helicase, and this decrease in fluorescence intensity can be used to measure the activity of the helicase enzyme. The reaction was prepared by mixing a double-stranded substrate with the helicase enzyme, buffer, ATP and SYBR Green I. After completion, the reaction was terminated by EDTA and fluorescence was measured. Using this technique, a linear increase in substrate release was observed with increasing time and helicase concentrations. The assay described here is speedy, efficient and economical; it holds promise for use in large-scale screening of drugs that target helicases.

Osmotic stress induced oxidative damage: possible mechanism of cataract formation in diabetes

Chronic hyperglycemia causes increased level of reactive oxygen species which is thought to be involved in the pathogenesis of diabetes associated complications including cataract. In diabetic cataractous lens, over production of free radicals and decreased capacity of antioxidant defense system are the major contributors to oxidative damage by polyol pathway and advanced glycation end products. The current study focused on analysis of factors associated with osmotic imbalance and oxidative stress in aging and diabetic human cataractous lenses. We examined activities of polyol pathway enzymes, G6PD and glutathione system in lenses from subjects suffering from cataract due to aging and diabetes. We observed elevated activities of aldose reductase and sorbitol dehydrogenase while G6PD and glutathione system enzyme activities were found to be lower in cataractous subjects suffering from diabetes. The findings from the current study support the premise that osmotic imbalance, AGEs formation and oxidative stress contribute synergistically to the development of lens opacity in hyperglycemia.

Distribution of biological databases over low-bandwidth networks

Databases are integral part of bioinformatics and need to be accessed most frequently, thus downloading and updating them on a regular basis is very critical. The establishment of bioinformatics research facility is a challenge for developing countries as they suffer from inherent low-bandwidth and unreliable internet connections. Therefore, the identification of techniques supporting download and automatic synchronization of large biological database at low bandwidth is of utmost importance. In current study, two protocols (FTP and Bit Torrent) were evaluated and the utility of a BitTorren based peer-to-peer (btP2P) file distribution model for automatic synchronization and distribution of large dataset at our facility in Pakistan have been discussed.

Advanced glycation end products in diabetic and non-diabetic human subjects suffering from cataract

Advanced glycation end products (AGEs) play a pivotal role in loss of lens transparency, i.e., cataract. AGEs formation occurs as a result of sequential glycation and oxidation reaction between reducing sugars and protein. AGEs production takes place throughout the normal aging process but its accumulation is found to be more rapid in diabetic patients. In this study, we quantified AGEs and N-(carboxyethyl) lysine (CEL) in human cataractous lenses from non-diabetic (n=50) and diabetic patients (n=50) using ELISA. We observed significantly higher (p<0.001) levels of lens AGEs and CEL in diabetic patients with cataract as compared with their respective controls. The presence of AGEs and CEL was also determined by western blotting and immuno-histochemical analysis. Furthermore, isolated β-crystallin from cataractous lenses of non-diabetic and diabetic patients was incubated with different sugars to evaluate the extent of glycation in a time dependent manner. Our data indicated more pronounced glycation in patients suffering from diabetes as compared to non-diabetics subjects demonstrating the need to focus on developing normoglycemic approaches. Such studies may provide an insight in developing therapeutic strategies and may have clinical implications.

Expression and activity of paraoxonase 1 in human cataractous lens tissue

Paraoxonase 1 (PON1) is a high-density lipoprotein-associated enzyme that is believed to be involved in the protection against oxidative stress. There is evidence that paraoxonase activity is reduced in patients with diabetes and cataract. In the current study, we analyzed mRNA expression of PON1 as well as other members of the paraoxonase family, PON2 and PON3, in human cataractous lens samples. Our results indicate that only PON1 is expressed at the gene and protein levels in human lens tissues. We quantified MDA levels and measured PON1 (paraoxonase/arylesterase) enzymatic activities in subjects suffering from cataract due to aging and diabetes. Decreased PON1 activity was more pronounced in diabetic patients (p< 0.001) compared to senile subjects, which may be due to glycation and increased oxidative insult. To examine the structural alterations that occur in response to glycation, we constructed a three-dimensional model of PON1 and its glycated variant. Glycation at Lys70 and Lys75 is predicted to cause hindrance in binding of substrate to the active site of the enzyme.

Antioxidant markers in human senile and diabetic cataractous lenses

OBJECTIVE

To determine the role of free radicals and antioxidant enzymes in patients suffering from cataract due to aging and diabetes.

DESIGN

Experimental study.

PLACE AND DURATION OF STUDY

Department of Biochemistry, University of Karachi from December 2004 to May 2005.

PATIENTS AND METHODS

The study was conducted on 80 cataract patients. Lens and plasma samples from senile and diabetic subjects suffering from cataract were analyzed and activity of Cu, Zn-superoxide dismutase (Cu, Zn-SOD) was measured using xanthine oxidase system. Catalase (CAT) activity was estimated. Levels of malondialdehyde (MDA) was measured by thiobarbituric acid reaction. Student's t- test was employed for analysis of results.

RESULTS

Significant difference (p<0.001) was found in activity of Cu, Zn-SOD in cataract lenses from diabetic patients as compared to senile subjects, CAT activities was also lower (p<0.001) in lenses from diabetic cataract patients when compared to lenses from senile cataractous subjects. Lens MDA levels were significantly higher (p<0.001) in cataract lenses from diabetic patients than in senile subjects. Plasma MDA levels were lowest (p<0.001) in controls as compared to senile and diabetic cataractous patients.

CONCLUSION

Results of present study suggest that increased production of high levels of free oxygen species is linked to glucose oxidation and non-enzymatic glycation of proteins. Furthermore, elevated glucose levels might be involved in the insufficiency of antioxidant enzymatic activity and in the progression of lipid peroxidation.

Assessment of paraoxonase activity and lipid peroxidation levels in diabetic and senile subjects suffering from cataract

OBJECTIVES

The purpose of this study was to evaluate antioxidant effect of paraoxonase 1 activity and malondialdehyde (MDA) levels as a marker of oxidative stress in patients suffering from cataract due to diabetes and aging.

DESIGN AND METHODS

One hundred cataract patients (senile and diabetic) and age- and sex-matched controls were studied. Paraoxonase 1 and arylesterase activities in plasma samples were measured using paraoxon and phenylacetate as substrates, respectively. The magnitude of lipid peroxidation was established by measuring plasma MDA and oxidized low-density lipoprotein (ox LDL) levels. One-way ANOVA was employed for analysis of results.

RESULTS

We observed significantly lower plasma paraoxonase and arylesterase activities in senile and diabetic cataractous patients as compared to respective controls (p<0.001). Plasma MDA and ox LDL levels were found to be higher in patients suffering from cataract (p<0.001).

CONCLUSIONS

The results of present study suggest that the observed decrease in PON1 activity may be due to increase in oxidative stress. It can be concluded that lower paraoxonase activity could contribute to the higher risk of cataract formation.

Homology modeling of rho-crystallin from bullfrog (Rana catesbeiana) lens

rho-Crystallins are major protein component found in the eye lenses of frogs of the genus Rana. Structural analysis has indicated that frog rho-crystallins belong to aldo-keto reductase superfamily (AKRs) which include aldehyde and aldose reductases, prostaglandin F synthase and several detoxification enzymes. Members of AKRs catalyze the oxidation-reduction reaction over a range of substrates using NAD(P)(H) as a cofactor. In spite of higher structural similarity with AKRs and cofactor binding affinity, the rho-crystallins were found to be catalytically inactive. This study presents comparative or homology modeling of rho-crystallin from bullfrog (Rana catesbeiana) in presence and absence of cofactor NADP and a competitive inhibitor, testosterone. The predicted models are explored to examine the catalytic cleft, cofactor binding affinity characteristics and substrate binding pocket.

alpha-Crystallin chaperone function in diabetic rat and human lenses

This study focussed on the effect of diabetes on the chaperone function of alpha-crystallin. The authors relied on diabetic rats with a wide range of plasma glucose levels and non-diabetic control rats to establish a possible relationship between severity of diabetes and alpha-crystallin chaperone activity. In addition, 52-56 and 63-69 year-old diabetic and non-diabetic human lenses were used to show whether diabetes affects alpha-crystallin chaperone activity in human lenses. Correlation between plasma glucose levels and loss of chaperone activity of the alphaL-crystallin fraction in diabetic rats indicated good correlation. The glycemic threshold, reported before for cataract development in diabetic rats, seems to be valid for the chaperone activity loss as well. Analysis of the human lens alphaL-crystallin showed lower chaperone activity in all the diabetic lenses than in the age-matched control lenses. In the 63-69 age group, the loss in chaperone activity due to diabetes was significantly larger than in the 52-56 age group suggesting a dominant effect of duration of diabetes.

Advanced glycation end products in human senile and diabetic cataractous lenses

The authors prepared water-soluble (WSF), urea-soluble (USF), alkali-soluble (ASF), sonicated (SF), sonicated insoluble (SIF) and membrane (MF) fractions of lens proteins from human senile and diabetic cataractous lenses and age-matched clear lenses. Levels of advanced glycation end products (AGEs) including carboxymethyl lysine (CML), a glycoxidation product, were determined by both non-competitive and competitive enzyme-linked immunosorbent assay (ELISA). Distribution of AGEs in the various protein fractions was ascertained by SDS-PAGE and Western blotting. An overall increase in the levels of AGEs in diabetic cataractous lenses as compared to senile cataractous lenses and clear lenses has been observed. ASF and SF, both of which originated from the urea-insoluble fraction, showed the highest levels of AGEs. However, no clear-cut differences in CML levels were seen among clear lenses and senile and diabetic cataractous lenses. AGEs were found to be distributed mostly in the high molecular aggregates in all the fractions. These data suggest that AGEs contribute to protein aggregation and subsequent insolubilization.

Three-dimensional model and quaternary structure of the human eye lens protein gamma S-crystallin based on beta- and gamma-crystallin X-ray coordinates and ultracentrifugation

A 3-dimensional model of the human eye lens protein gamma S-crystallin has been constructed using comparative modeling approaches encoded in the program COMPOSER on the basis of the 3-dimensional structure of gamma-crystallin and beta-crystallin. The model is biased toward the monomeric gamma B-crystallin, which is more similar in sequence. Bovine gamma S-crystallin was shown to be monomeric by analytical ultracentrifugation without any tendency to form assemblies up to concentrations in the millimolar range. The connecting peptide between domains was therefore built assuming an intramolecular association as in the monomeric gamma-crystallins. Because the linker has 1 extra residue compared with gamma B and beta B2, the conformation of the connecting peptide was constructed by using a fragment from a protein database. gamma S-crystallin differs from gamma B-crystallin mainly in the interface region between domains. The charged residues are generally paired, although in a different way from both beta- and gamma-crystallins, and may contribute to the different roles of these proteins in the lens.

Primary structure of beta s-crystallin from human lens

The complete primary structure of beta s-crystallin from human lens is reported. The sequence was elucidated by automatic Edman degradation of tryptic and CNBr peptides. The blocked N-terminal dipeptide was identified by fast-atom-bombardment mass spectroscopy. The sequence comparison with other members of crystallin family reveals a closer relationship to human gamma-crystallin (53% identity) than with beta A3/A1 crystallin (37% identity). The structure, evolutionary characteristics and role of beta s-crystallin in lens are discussed.