The role of corneal crystallins in the cellular defense mechanisms against oxidative stress

Human Aldehyde Dehydrogenases: A Superfamily of Similar Yet Different Proteins Highly Related to Cancer

The superfamily of human aldehyde dehydrogenases (hALDHs) consists of 19 isoenzymes which are critical for several physiological and biosynthetic processes and play a major role in the organism's detoxification via the NAD(P) dependent oxidation of numerous endogenous and exogenous aldehyde substrates to their corresponding carboxylic acids. Over the last decades, ALDHs have been the subject of several studies as it was revealed that their differential expression patterns in various cancer types are associated either with carcinogenesis or promotion of cell survival. Here, we attempt to provide a thorough review of hALDHs' diverse functions and 3D structures with particular emphasis on their role in cancer pathology and resistance to chemotherapy. We are especially interested in findings regarding the association of structural features and their changes with effects on enzymes' functionalities. Moreover, we provide an updated outline of the hALDHs inhibitors utilized in experimental or clinical settings for cancer therapy. Overall, this review aims to provide a better understanding of the impact of ALDHs in cancer pathology and therapy from a structural perspective.

Differential Responses of Retinal Neurons and Glia Revealed via Proteomic Analysis on Primary and Secondary Retinal Ganglion Cell Degeneration

To explore the temporal profile of retinal proteomes specific to primary and secondary retinal ganglion cell (RGC) loss. Unilateral partial optic nerve transection (pONT) was performed on the temporal side of the rat optic nerve. Temporal and nasal retinal samples were collected at 1, 4 and 8 weeks after pONT (n = 4 each) for non-biased profiling with a high-resolution hybrid quadrupole time-of-flight mass spectrometry running on label-free SWATHTM acquisition (SCIEX). An information-dependent acquisition ion library was generated using ProteinPilot 5.0 and OneOmics cloud bioinformatics. Combined proteome analysis detected 2531 proteins with a false discovery rate of <1%. Compared to the nasal retina, 10, 25 and 61 significantly regulated proteins were found in the temporal retina at 1, 4, and 8 weeks, respectively (p < 0.05, FC ≥ 1.4 or ≤0.7). Eight proteins (ALDH1A1, TRY10, GFAP, HBB-B1, ALB, CDC42, SNCG, NEFL) were differentially expressed for at least two time points. The expressions of ALDH1A1 and SNCG at nerve fibers were decreased along with axonal loss. Increased ALDH1A1 localization in the inner nuclear layer suggested stress response. Increased GFAP expression demonstrated regional reactivity of astrocytes and Muller cells. Meta-analysis of gene ontology showed a pronounced difference in endopeptidase and peptidase inhibitor activity. Temporal proteomic profiling demonstrates established and novel protein targets associated with RGC damage.

Crystallin Alpha-B Overexpression as a Possible Marker of Reactive Astrogliosis in Human Cerebral Contusions

The pathophysiology of traumatic brain injury (TBI) has not yet been fully elucidated. Crystallin alpha-B (CRYAB) is a molecular chaperone that apparently tries to stabilize the rapid thickening of the intermediate filaments of glial fibrillary acidic protein (GFAP) during the process of reactive astrogliosis in response to TBI. Previous analyses of the gene expression profile in human brain contusion tissue showed us an exacerbated CRYAB overexpression. Here, we used 3, 3’-diaminobenzidine (DAB) immunohistochemistry and immunofluorescence to verify CRYAB overexpression and to describe its expression and distribution in samples of contused cortical tissue derived from emergency decompressive surgery after severe TBI. The histological expression of CRYAB was mainly seen in subcortical white matter astrocytes of injured tissue. Most of the cells that overexpressed GFAP in the analyzed tissue also overexpressed CRYAB, a finding corroborated by the co-localization of the two markers. The only difference was the presence of a few pyramidal neurons that expressed CRYAB in layer V of the cerebral cortex. The selective vulnerability of layer V of the cerebral cortex during TBI could explain the expression of CRYAB in neurons of this cortical layer. Our results indicate a parallel behavior in the cellular expression of CRYAB and GFAP during the subacute response to TBI. These results lead us to postulate CRYAB as a possible marker of reactive astrogliosis in contused cortical tissue.

Bio-functionalized zinc oxide nanoparticles: Potential toxicity impact on freshwater fish Cyprinus carpio

There is a growing concern nowadays over the exposure of nanomaterials and their effects in aquatic life. In spite of reporting the changes in physiology, reproduction and behaviour in fish by different nanoparticles, the molecular events underlying in the aquatic bodies due to the toxicity of zinc oxide nanoparticles (ZnO NPs) are mainly unexplored. Therefore, the present study carried out an ex vivo exposure of ZnO NPs at various concentrations (0.382, 0.573 and 1.146 mg L^-1) in freshwater fish Cyprinus carpio to investigate the potential adverse effects. The results revealed that ZnO NPs exposure altered the haematological parameter and induces the reactive oxygen species (ROS) that leads to elevation of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidise (GPx), glutathione S-transferase (GST) and reduced glutathione (GSH) activity in C. carpio. Furthermore, histopathological analysis exhibited that the ZnO NPs caused lamellar fusion, aneurism, cytoplasmic vacuolation, nuclear alteration, necrotic muscle fiber and pyknotic nuclei in the gills, liver and muscles of C. carpio. ZnO NPs exposure significantly up-regulated the overlapping expressions of SOD1, CAT, GPx1a, GST-α, CYP1A, and Nrf-2 genes. A higher level of Zn bioaccumulation was observed in the following order: gill (35.03 ± 2.50 μg g^-1), liver (5.33 ± 0.73 μg g^-1) and muscle (2.30 ± 0.20 μg g^-1) at 1.146 mg L^-1 exposure of ZnO NPs. Hence, the current study indicated that the biogenic ZnO NPs generate toxicity in fishes by modifying the antioxidant defense mechanisms, histomorphology, and oxidative stress encoding genes.

Phenotypic and transcriptomic changes in the corneal epithelium following exposure to cigarette smoke

Cigarette smoke extract (CSE), a complex mixture of compounds, contributes to a range of eye diseases; however, the underlying pathophysiological responses to tobacco smoke remain ambiguous. The purpose of the present study was to evaluate the cigarette smoke-induced phenotypic and transcriptomic changes in the corneal epithelium with a view to elucidating the likely underlying mechanism. Accordingly, for the first time, we characterized the genome-wide effects of CSE on the corneal epithelium. The ocular surface of the mice in the experimental groups was exposed to CSE for 1 h per day for a period of one week, while mice in the control group were exposed to preservative-free artificial tears. Corneal fluorescein staining, in vivo confocal microscopy and scanning electron microscopy were performed to examine the corneal ultrastructure. Transcriptome sequencing and bioinformatics analysis were performed followed by RT-qPCR to validate gene expression changes. The results indicate that CSE exposure disrupted the structural integrity of the superficial epithelium, decreased the density of microvilli, and compromised the corneal epithelial barrier intactness. RNA-seq revealed 667 differentially expressed genes, and functional analysis highlighted the enhancement of several biological processes such as antioxidant activity and the response to oxidative stress. Moreover, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that glutathione metabolism and drug metabolism cytochrome P450 were the most relevant pathways contributing to the effects of CSE on the corneal epithelium. Protein-protein interaction (PPI) network analysis illustrated that GCLC, NQO1, and HMOX1 were the most relevant nodes. In conclusion, the present study indicates that CSE exposure induces changes in the phenotype and genotype of the corneal epithelium. The antioxidant response element is essential for counteracting the effects of cigarette smoke on this tissue layer. These results shed novel insights into how cigarette smoke damages this ocular surface.

Insights into Aldehyde Dehydrogenase Enzymes: A Structural Perspective

Aldehyde dehydrogenases engage in many cellular functions, however their dysfunction resulting in accumulation of their substrates can be cytotoxic. ALDHs are responsible for the NAD(P)-dependent oxidation of aldehydes to carboxylic acids, participating in detoxification, biosynthesis, antioxidant and regulatory functions. Severe diseases, including alcohol intolerance, cancer, cardiovascular and neurological diseases, were linked to dysfunctional ALDH enzymes, relating back to key enzyme structure. An in-depth understanding of the ALDH structure-function relationship and mechanism of action is key to the understanding of associated diseases. Principal structural features 1) cofactor binding domain, 2) active site and 3) oligomerization mechanism proved critical in maintaining ALDH normal activity. Emerging research based on the combination of structural, functional and biophysical studies of bacterial and eukaryotic ALDHs contributed to the appreciation of diversity within the superfamily. Herewith, we discuss these studies and provide our interpretation for a global understanding of ALDH structure and its purpose–including correct function and role in disease. Our analysis provides a synopsis of a common structure-function relationship to bridge the gap between the highly studied human ALDHs and lesser so prokaryotic models.

Proteomic insight on the polychlorinated biphenyl degrading mechanism of Pleurotus pulmonarius LBM 105

White-rot fungi are well known bioremediation agents capable of removing recalcitrant xenobiotics. However, the molecular mechanism involved in this process is not well understood. The aim of the present study was to compare the proteomic profiles of Pleurotus pulmonarius LBM 105 in presence and absence of a mixture of polychlorinated biphenyls. Cultures of the fungus were spiked with a mixture of Aroclors and cultivated for 28 days. This strain achieved a peak of PCBs-removal of 65.50 ± 8.09% after 21 days. The ecotoxicological assays showed a toxicity reduction of 46.47%. Based on these findings, a proteomic study was carried out and it was proven that the oxidative metabolism was highly affected. Two proteins that have a function at the transcriptional level and related to the oxidative metabolism, the glyceraldehyde-3-phosphate dehydrogenase and the basal transcription factor 3, presented an increase in their quantity in PCBs presence. Several oxidases and reductases were highly induced, presenting the short chain reductases, aldo/keto reductases, laccases and versatile peroxidases as the enzymes with the most notorious changes. These results indicate a complex response of the fungal metabolism towards these pollutants, which includes a transcriptional response to the oxidative stress and a modification of the intra- and extra-cellular enzymatic profile.

Antioxidant Defenses in the Human Eye: A Focus on Metallothioneins

The human eye, the highly specialized organ of vision, is greatly influenced by oxidants of endogenous and exogenous origin. Oxidative stress affects all structures of the human eye with special emphasis on the ocular surface, the lens, the retina and its retinal pigment epithelium, which are considered natural barriers of antioxidant protection, contributing to the onset and/or progression of eye diseases. These ocular structures contain a complex antioxidant defense system slightly different along the eye depending on cell tissue. In addition to widely studied enzymatic antioxidants, including superoxide dismutase, glutathione peroxidase, catalase, peroxiredoxins and selenoproteins, inter alia, metallothioneins (MTs) are considered antioxidant proteins of growing interest with further cell-mediated functions. This family of cysteine rich and low molecular mass proteins captures and neutralizes free radicals in a redox-dependent mechanism involving zinc binding and release. The state of the art of MTs, including the isoforms classification, the main functions described to date, the Zn-MT redox cycle as antioxidant defense system, and the antioxidant activity of Zn-MTs in the ocular surface, lens, retina and its retinal pigment epithelium, dependent on the number of occupied zinc-binding sites, will be comprehensively reviewed.

What Makes Cornea Immunologically Unique and Privileged? Mechanistic Clues from a High-Resolution Proteomic Landscape of the Human Cornea

Success rates of corneal transplantation are particularly high owing to its unique, innate immune privilege derived from a phenomenon known as Anterior Chamber-Associated Immune Deviation (ACAID). Of note, cornea is a transparent, avascular structure that acts as a barrier along with sclera to protect the eye and contributes to optical power. Molecular and systems biology mechanisms underlying ACAID and the immunologically unique and privileged status of cornea are not well known. We report here a global unbiased proteomic profiling of the human cornea and the identification of 4824 proteins, the largest catalog of human corneal proteins identified to date. Moreover, signaling pathway analysis revealed enrichment of spliceosome, phagosome, lysosome, and focal adhesion pathways, thereby demonstrating the protective functions of corneal proteins. We observed an enrichment of neutrophil-mediated immune response processes in the cornea as well as proteins belonging to the complement and ER-Phagosome pathways that are suggestive of active immune and inflammatory surveillance response. This study provides a key expression map of the corneal proteome repertoire that should enable future translational medicine studies on the pathological conditions of the cornea and the mechanisms by which cornea immunology are governed. Molecular mechanisms of corneal immune privilege have broad relevance to understand and anticipate graft rejection in the field of organ transplantation.

Light-induced stress as a primary evolutionary driver of eye origins

Eyes are quintessential complex traits and our understanding of their evolution guides models of trait evolution in general. A long-standing account of eye evolution argues natural selection favors morphological variations that allow increased functionality for sensing light. While certainly true in part, this focus on visual performance does not entirely explain why diffuse photosensitivity persists even after eyes evolve, or why eyes evolved many times, each time using similar building blocks. Here, we briefly review a vast literature indicating most genetic components of eyes historically responded to stress caused directly by light, including ultraviolet damage of DNA, oxidative stress, and production of aldehydes. We propose light-induced stress had a direct and prominent role in the evolution of eyes by bringing together genes to repair and prevent damage from light-stress, both before and during the evolution of eyes themselves. Stress-repair and stress-prevention genes were perhaps originally deployed as plastic responses to light and/or as beneficial mutations genetically driving expression where light was prominent. These stress-response genes sense, shield, and refract light but only as reactions to ongoing light stress. Once under regulatory-genetic control, they could be expressed before light stress appeared, evolve as a module, and be influenced by natural selection to increase functionality for sensing light, ultimately leading to complex eyes and behaviors. Recognizing the potentially prominent role of stress in eye evolution invites discussions of plasticity and assimilation and provides a hypothesis for why similar genes are repeatedly used in convergent eyes. Broadening the drivers of eye evolution encourages consideration of multi-faceted mechanisms of plasticity/assimilation and mutation/selection for complex novelties and innovations in general.

Mapping Keratoconus Molecular Substrates by Multiplexed High-Resolution Proteomics of Unpooled Corneas

Keratoconus (KCN) is a leading cause for cornea grafting worldwide. Keratoconus is a multifactorial disease that causes progressive thinning of the cornea and whose etiology is poorly understood. Several studies have used proteomics on patient tear fluids to identify potential biomarkers. However, proteome of the cornea itself has not been investigated fully. We report here new findings from a case-control study using multiplexed mass spectrometry (MS) on individual (unpooled) corneas to gain deeper insights into proteins and biomarkers relevant to keratoconus. We employed a high-pressure approach to extract total protein from individual corneas from five cases and five controls, followed by trypsin digestion and tandem mass tag (TMT) labeling. The MS-derived data were searched using the Human NCBI RefSeq protein database v92, with peptides and proteins filtered at 1% false discovery rate. A total of 3132 proteins were detected, of which 627 were altered significantly (p ≤ 0.05) in keratoconus corneas. The increases were overwhelmingly in the mTOR/PI3/AKT signal-mediated regulations of cell survival and proliferation, nonsense-mediated decay of transcripts, and proteasomal pathways. The decreases were in several extracellular matrix proteins and in many members of the complement system. Importantly, this multiplexed proteomic study of keratoconus corneas identified, to our knowledge, the largest number of corneal proteins. The novel findings include changes in pathways that regulate transcript stability, proteasomal degradation, and the complement system in corneas with keratoconus. These observations offer new prospects toward future discovery of novel molecular targets for diagnostic and therapeutic innovations for patients with keratoconus.

Sex-specific alterations of lipid metabolism in zebrafish exposed to polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) mixtures exerting environmental health risk. In mammals, PCBs have been shown to disrupt metabolic state, especially lipid metabolism, and energy balance, but their effects on lipid metabolism in fish are largely unknown. The zebrafish were selected as model and both male and female adult zebrafish were exposed to different concentrations of PCBs at gradient concentrations of 0.2, 2.0 and 20.0 μg/L for 6 weeks. PCB exposure did not affect survival, but a significant inhibition of growth was observed in the males after exposure to 20.0 μg/L. The lower concentrations of 0.2 and 2.0 μg/L increased hepatic lipid accumulation to a greater extent in male fish, but the higher concentration of 20.0 μg/L did not cause significant fat accumulation in either male or female fish. In males, the expression of genes related to lipogenesis and lipid catabolism was upregulated in a concentration-dependent manner in the liver and visceral mass without liver and gonad; the effects of exposure on lipid metabolism-related genes in female fish were less pronounced. PCB exposure did not induce significant oxidative stress, but did upregulate the expression of stress- and apoptosis-related genes, mostly in male fish. The low concentrations of PCBs (0.2 μg/L and 2.0 μg/L) exerted sex-specific effects on zebrafish lipid metabolism, and male fish were more sensitive to the exposure. This study provides new mechanistic insights into the complex interactions between PCBs, lipid metabolism, and sex in zebrafish, and may contribute to a future systematic assessment of the effects of PCBs on aquatic ecosystems.

Evolutionary Origins of Pax6 Control of Crystallin Genes

The birth of novel genes, including their cell-specific transcriptional control, is a major source of evolutionary innovation. The lens-preferred proteins, crystallins (vertebrates: α- and β/γ-crystallins), provide a gateway to study eye evolution. Diversity of crystallins was thought to originate from convergent evolution through multiple, independent formation of Pax6/PaxB-binding sites within the promoters of genes able to act as crystallins. Here, we propose that αB-crystallin arose from a duplication of small heat shock protein (Hspb1-like) gene accompanied by Pax6-site and heat shock element (HSE) formation, followed by another duplication to generate the αA-crystallin gene in which HSE was converted into another Pax6-binding site. The founding β/γ-crystallin gene arose from the ancestral Hspb1-like gene promoter inserted into a Ca2+-binding protein coding region, early in the cephalochordate/tunicate lineage. Likewise, an ancestral aldehyde dehydrogenase (Aldh) gene, through multiple gene duplications, expanded into a multigene family, with specific genes expressed in invertebrate lenses (Ω-crystallin/Aldh1a9) and both vertebrate lenses (η-crystallin/Aldh1a7 and Aldh3a1) and corneas (Aldh3a1). Collectively, the present data reconstruct the evolution of diverse crystallin gene families.

Mucosal-luminal interface proteomics reveals biomarkers of pediatric inflammatory bowel disease-associated colitis

OBJECTIVE

Improved biomarkers are an unmet clinical need for suspected inflammatory bowel disease (IBD). Need is greatest for children, since current biomarkers suffers from low specificity, particularly in this population; thus, invasive testing methods, with the accompanying risk of complications, are necessary. Additionally, current biomarkers do not delineate disease extent assessment for ulcerative colitis (UC), a factor involved in therapeutic decisions.

METHODS

Intestinal mucosal-luminal interface (MLI) aspirates from the ascending colon (AC) and descending colon (DC) were collected during diagnostic colonoscopy from treatment-naïve children. The MLI proteomes of 18 non-IBD and 42 IBD patients were analyzed by liquid chromatography mass spectrometry. Analyses of proteomic data generated protein panels distinguishing IBD from non-IBD and pancolitis from non-pancolitis (UC disease extent). Select protein biomarkers were evaluated in stool samples by enzyme-linked immunosorbent assay (n = 24).

RESULTS

A panel of four proteins discriminated active IBD from non-IBD (discovery cohort) with a sensitivity of 0.954 (95% confidence interval (CI): 0.772-0.999) and >0.999 (95% CI: 0.824-1.00) for the AC and DC, respectively, and a specificity of >0.999 (AC, 95% CI: 0.815-1.00; DC, 95% CI:0.692-1.00) for both the AC and DC. A separate panel of four proteins distinguished pancolitis from non-pancolitis in UC patients with sensitivity >0.999 (95% CI: 0.590-1.00) and specificity >0.999 (95% CI: 0.715-1.00). Catalase (p < 0.0001) and LTA4H (p = 0.0002) were elevated in IBD stool samples compared to non-IBD stool samples.

CONCLUSION

This study identified panels of proteins that have significantly different expression levels and contribute to accurate IBD diagnosis and disease extent characterization in children with UC. Biomarkers identified from the MLI demonstrate transferable results in stool samples.

Acute toxicity, bioconcentration, elimination and antioxidant effects of fluralaner in zebrafish, Danio rerio

Fluralaner is a novel isoxazoline insecticide which shows high insecticidal activity against parasitic, sanitary and agricultural pests, but there is little information about the effect of fluralaner on non-target organisms. This study reports the acute toxicity, bioconcentration, elimination and antioxidant response of fluralaner in zebrafish. All LC₅₀ values of fluralaner to zebrafish were higher than 10 mg L^-1 at 24, 48, 72 and 96 h. To study the bioconcentration and elimination, the zebrafish were exposed to sub-lethal concentrations of fluralaner (2.00 and 0.20 mg L^-1) for 15 d and then held 6 d in clean water. The results showed medium BCF of fluralaner with values of 12.06 (48 h) and 21.34 (144 h) after exposure to 2.00 and 0.20 mg L^-1 fluralaner, respectively. In the elimination process, a concentration of only 0.113 mg kg^-1 was found in zebrafish on the 6th day after removal to clean water. After exposure in 2.00 mg L^-1 fluralaner, the enzyme activities of SOD, CAT, and GST, GSH-PX, CarE and content of MDA were measured. Only CAT and CarE activities were significantly regulated and the others stayed at a stable level compared to the control group. Meanwhile, transcriptional expression of CYP1C2, CYP1D1, CYP11A were significantly down-regulated at 12 h exposed to 2.00 mg L^-1 of fluralaner. Except CYP1D1, others CYPs were up-regulated at different time during exposure periods. Fluralaner and its formulated product (BRAVECTO^®) are of low toxicity to zebrafish and are rapidly concentrated in zebrafish and eliminated after exposure in clean water. Antioxidant defense and metabolic systems were involved in the fluralaner-induced toxicity. Among them, the activities of CAT and CarE, and most mRNA expression level of CYPs showed fast response to the sub-lethal concentration of fluralaner, which could be used as a biomarker relevant to the toxicity.

Proteomic Analysis of Various Rat Ocular Tissues after Ischemia-Reperfusion Injury and Possible Relevance to Acute Glaucoma

Glaucoma is a group of eye diseases that can cause vision loss and optical nerve damage. To investigate the protein expression alterations in various intraocular tissues (i.e., the cornea, conjunctiva, uvea, retina, and sclera) during ischemia–reperfusion (IR) injury, this study performed a proteomic analysis to qualitatively investigate such alterations resulting from acute glaucoma. The IR injury model combined with the proteomic analysis approach of two-dimensional difference gel electrophoresis (2D-DIGE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to monitor the protein expression alterations in two groups of specimens (an IR injury group and a control group). The analysis results revealed 221 unique differentially expressed proteins of a total of 1481 proteins in the cornea between the two groups. In addition, 97 of 1206 conjunctival proteins, 90 of 1354 uveal proteins, 61 of 1180 scleral proteins, and 37 of 1204 retinal proteins were differentially expressed. These findings imply that different ocular tissues have different tolerances against IR injury. To sum up, this study utilized the acute glaucoma model combined with 2D-DIGE and MALDI-TOF MS to investigate the IR injury affected protein expression on various ocular tissues, and based on the ratio of protein expression alterations, the alterations in the ocular tissues were in the following order: the cornea, conjunctiva, uvea, sclera, and retina.

Exposure of ELF-EMF and RF-EMF Increase the Rate of Glucose Transport and TCA Cycle in Budding Yeast

In this study, we investigated the transcriptional response to 50 Hz extremely low frequency electromagnetic field (ELF-EMF) and 2.0 GHz radio frequency electromagnetic field (RF-EMF) exposure by Illumina sequencing technology using budding yeast as the model organism. The transcription levels of 28 genes were upregulated and those of four genes were downregulated under ELF-EMF exposure, while the transcription levels of 29 genes were upregulated and those of 24 genes were downregulated under RF-EMF exposure. After validation by reverse transcription quantitative polymerase chain reaction (RT-qPCR), a concordant direction of change both in differential gene expression (DGE) and RT-qPCR was demonstrated for nine genes under ELF-EMF exposure and for 10 genes under RF-EMF exposure. The RT-qPCR results revealed that ELF-EMF and RF-EMF exposure can upregulate the expression of genes involved in glucose transportation and the tricarboxylic acid (TCA) cycle, but not the glycolysis pathway. Energy metabolism is closely related with the cell response to environmental stress including EMF exposure. Our findings may throw light on the mechanism underlying the biological effects of EMF.

Profenofos induced biochemical alterations and in silico modelling of hatching enzyme, ZHE1 in zebrafish (Danio rerio) embryos

The current study was aimed to investigate the oxidative stress response in zebrafish embryos exposed to sub-lethal (LC10) and lethal (LC50) concentrations of profenofos for 96-h and in silico modelling of zebrafish hatching enzyme, ZHE1 to explain the delayed hatching. Embryos exposed to profenofos under semi-static conditions significantly diminished glutathione (GSH), superoxide dismutase (SOD) and glutathione reductase (GR) levels, but increased the activities of catalase (CAT) and glutathione S-transferase (GST) concomitantly with marked elevation in malondialdehyde (MDA) content in whole-body homogenate of the treated groups compared with control. In addition, stress protein Hsp70 expression and DNA damage were significantly increased in a concentration- dependent manner compared with controls. From the computational docking studies of ZHE1 with profenofos revealed that profenofos is binding to three amino acids, histidine 99, histidine 109 and arginine 182 at the active site of the enzyme through hydrogen bonding which may lead to inhibition of hatching.

Developmental toxicity, oxidative stress, and related gene expression induced by dioxin-like PCB 126 in zebrafish (Danio rerio)

3,3',4,4',5-Pentachlorobiphenyl (PCB126) cause multiple adverse effects in organisms including animals and humans. Although PCB toxicities are linked to oxidative damage in rodents, the mechanism in early life stages of zebrafish is not clear. To explore the developmental toxicity mechanism of PCB126, three paradigms (toxicological phenotypes, biochemical changes, and molecular changes) were studied in 3-h postfertilization (hpf) zebrafish (Danio rerio) embryos exposed to different PCB126 concentrations (0, 16, 32, 64, and 128 μg/L) until 168 hpf. Developmental malformations, including pericardial and yolk sac edema, impaired lower jaw growth, spinal curvature, head edema and failure to inflate the swim bladder were observed, some as early as 72 hpf. Mortality was not apparent in early stages but significantly increased in a dose-dependent manner from 144 hpf onward. A dose-dependent significant increase in malformation rate was observed from 72 hpf onward with up to 100% at 132 hpf in embryos exposed to 128 μg/L of PCB126. Higher doses of PCB126 significantly decreased the copper-zinc superoxide dismutase (CuZn-Sod), catalase (Cat), and glutathione peroxidase (Gpx) enzyme activities at 96, 132 hpf, but markedly declined from thereafter. PCB126 at 128 μg/L significantly increased the malondialdehyde content at 72, 96, and 132 hpf. The transcriptional gene expression of antioxidant enzymes Cat and Gpx was upregulated in embryos exposed to 64 μg/L of PCB126 at 24 and 96 hpf. Sod1 messenger RNA (mRNA) was low in embryos exposed to 32 μg/L at 72 and 96 hpf but was induced in embryos exposed to 64 and 128 μg/L doses at 132 hpf. Collectively, the results suggest oxidative stress as a major factor in the induction of multiple developmental abnormalities in early life stages of zebrafish exposed to PCB126. However, the relationship between the antioxidant enzyme activity and the mRNA expression was not clear and the potential reasons for this are discussed.

Up-Regulation of ENO1 by HIF-1α in Retinal Pigment Epithelial Cells after Hypoxic Challenge Is Not Involved in the Regulation of VEGF Secretion

Purpose

Alpha-enolase (ENO1), a major glycolytic enzyme, is reported to be over-expressed in various cancer tissues. It has been demonstrated to be regulated by the Hypoxia-inducible factor 1-α (HIF-1α), a crucial transcriptional factor implicated in tumor progression and cancer angiogenesis. Choroidal neovascularization (CNV), which is a leading cause of severe vision loss caused by newly formed blood vessels in the choroid, is also engendered by hypoxic stress. In this report, we investigated the expression of ENO1 and the effects of its down-regulation upon cobalt (II) chloride-induced hypoxia in retinal pigment epithelial cells, identified as the primary source of ocular angiogenic factors.

Methods

HIF-1α-diminished retinal pigment epithelial cells were generated by small interfering RNA (siRNA) technology in ARPE-19 cells, a human retinal pigment epithelial cell line. Both normal and HIF-1α-diminished ARPE-19 cells were then subjected to hypoxic challenge using cobalt (II) chloride (CoCl₂) or anaerobic chamber. The relation between ENO1 expression and vascular endothelial growth factor (VEGF) secretion by retinal pigment epithelial cells were examined. Protein levels of HIF-1α and ENO1 were analyzed using Western Blot, while VEGF secretion was essayed by enzyme-linked immunosorbent assay (ELISA). Cytotoxicity after hypoxia was detected by Lactate Dehydrogenase (LDH) Assay.

Results

Upon 24 hr of CoCl₂-induced hypoxia, the expression levels of ENO1 and VEGF were increased along with HIF-1α in ARPE-19 cells, both of which can in turn be down-regulated by HIF-1α siRNA application. However, knockdown of ENO1 alone or together with HIF-1α did not help suppress VEGF secretion in hypoxic ARPE-19 cells.

Conclusion

ENO1 was demonstrated to be up-regulated by HIF-1α in retinal pigment epithelial cells in response to hypoxia, without influencing VEGF secretion.

The structural and optical properties of type III human collagen biosynthetic corneal substitutes

The structural and optical properties of clinically biocompatible, cell-free hydrogels comprised of synthetically cross-linked and moulded recombinant human collagen type III (RHCIII) with and without the incorporation of 2-methacryloyloxyethyl phosphorylcholine (MPC) were assessed using transmission electron microscopy (TEM), X-ray scattering, spectroscopy and refractometry. These findings were examined alongside similarly obtained data from 21 human donor corneas. TEM demonstrated the presence of loosely bundled aggregates of fine collagen filaments within both RHCIII and RHCIII-MPC implants, which X-ray scattering showed to lack D-banding and be preferentially aligned in a uniaxial orientation throughout. This arrangement differs from the predominantly biaxial alignment of collagen fibrils that exists in the human cornea. By virtue of their high water content (90%), very fine collagen filaments (2–9 nm) and lack of cells, the collagen hydrogels were found to transmit almost all incident light in the visible spectrum. They also transmitted a large proportion of UV light compared to the cornea which acts as an effective UV filter. Patients implanted with these hydrogels should be cautious about UV exposure prior to regrowth of the epithelium and in-growth of corneal cells into the implants.

A rapid in vivo zebrafish model to elucidate oxidative stress-mediated PCB126-induced apoptosis and developmental toxicity

Dioxin-like 3,3',4,4',5-pentachlorobiphenyl (PCB126) is one of the most potent and widespread environmental pollutants. Although PCB126-induced toxicity is related to the aryl hydrocarbon receptor pathway, there is still no study that has constructed an in vivo visual model to clarify the role of the Nrf2/ARE signaling pathway in the oxidative stress mechanism of PCB126-induced toxicity. In the present study, an in vivo zebrafish model of nrf2a fused to enhanced green fluorescent protein (nrf2a-eGFP) was constructed. The zebrafish embryos microinjected with nrf2a-eGFP (72h postfertilization) were exposed to various concentrations of PCB126 (0, 25, 50, 100, 200μg/L) or 30mMN-acetylcysteine (NAC)+200μg/L PCB126. After 72h exposure, PCB126 significantly increased the malformation rates and induced eGFP expression in a dose-dependent manner in several zebrafish tissue types. The distribution of eGFP fluorescence coincided with developmental deformity sites. NAC pretreatment effectively counteracted PCB126-induced developmental toxicity including heart rate, pericardial edema, and body length. The highest PCB126 dose, 200μg/L, produced marked apoptosis in the eye, gill, and trunk detected by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. At 48 and 72h exposure, 200μg/L PCB126 affected glutathione metabolism as evidenced by decreased glutathione and increased glutathione disulfide concentrations, indicative of oxidative stress. These effects were also counteracted by NAC pretreatment. Furthermore, the Nrf2-regulated genes gclc, gpx, gstp1, and hmox1 were significantly induced at 24, 48, and 72h at the highest PCB126 exposures but not in the NAC-pretreated group. In addition, a significant increase in ROS generation was detected in zebrafish larvae at 72h PCB126 exposure, which might offer a link for future mechanistic studies. Collectively, these data suggest that PCB126-induced developmental toxicity and apoptosis in the nrf2a-eGFP-injected zebrafish model are due to oxidative stress mediated by disruption to glutathione metabolism and changes in Nrf2-regulated gene expression.

Study on the Protective Effect of a New Manganese Superoxide Dismutase on the Microvilli of Rabbit Eyes Exposed to UV Radiation

We present a study on the protective effects against UV radiation of a gel formulation containing a new recombinant form of manganese superoxide dismutase on the conjunctiva and corneal epithelia of rabbit eyes. The integrity of the microvilli of both ocular tissues has been considered as an indicator of the health of the tissues. Samples, collected by impression cytology technique, were added of 80 µL of a gel formulation containing superoxide dismutase (2.0 µg/mL) and irradiated with UV rays for 30 minutes and were evaluated with scanning electron microscopy. Wilcoxon test was used to verify the possible occurrence of statistically significant differences between damage for treated and nontreated tissues. Application of gel produces a significant reduction of damage by UV irradiation of ocular epithelia; both epithelia present a significant reduction of damaged microvilli number if treated with the superoxide dismutase gel formulation: the p values (differences between damage found for treated and nontreated both ocular tissues) for conjunctiva and cornea samples were p ≪ 0.01 and p ≪ 0.0001, respectively, at confidence level of 95%. The administration of this gel formulation before UV exposure plays a considerable protective role in ocular tissues of rabbit eye with a significant reduction of the damage.

Time and Demand are Two Critical Dimensions of Immunometabolism: The Process of Macrophage Activation and the Pentose Phosphate Pathway

A process is a function of time; in immunometabolism, this is reflected by the stepwise adaptation of metabolism to sustain the bio-energetic demand of an immune-response in its various states and shades. This perspective article starts by presenting an early attempt to investigate the physiology of inflammation, in order to illustrate one of the basic concepts of immunometabolism, wherein an adapted metabolism of infiltrating immune cells affects tissue function and inflammation. We then focus on the process of macrophage activation and aim to delineate the factor time within the current molecular context of metabolic-rewiring important for adapting primary carbohydrate metabolism. In the last section, we will provide information on how the pentose phosphate pathway may be of importance to provide both nucleotide precursors and redox-equivalents, and speculate how carbon-scrambling events in the non-oxidative pentose phosphate pathway might be regulated within cells by demand. We conclude that the adapted metabolism of inflammation is specific in respect to the effector-function and appears as a well-orchestrated event, dynamic by nature, and based on a functional interplay of signaling- and metabolic-pathways.

Identification of active retinaldehyde dehydrogenase isoforms in the postnatal human eye

BACKGROUND/OBJECTIVES

Retinaldehyde dehydrogenase 2 (RALDH2) has been implicated in regulating all-trans-retinoic acid (atRA) synthesis in response to visual signals in animal models of myopia. To explore the potential role of retinaldehyde dehydrogenase (RALDH) enzymes and atRA in human postnatal ocular growth, RALDH activity, along with the distribution of RALDH1, RALDH2, and RALDH3 in the postnatal eye was determined.

METHODOLOGY

Retina, retinal pigment epithelium (RPE), choroid, and sclera were isolated from donor human eyes. RALDH catalytic activity was measured in tissue homogenates using an in vitro atRA synthesis assay together with HPLC quantification of synthesized atRA. Homogenates were compared by western blotting for RALDH1, RALDH2, and RALDH3 protein. Immunohistochemistry was used to determine RALDH1 and RALDH2 localization in posterior fundal layers of the human eye.

PRINCIPAL FINDINGS

In the postnatal human eye, RALDH catalytic activity was detected in the choroid (6.84 ± 1.20 pmol/hr/ug), RPE (5.46 ± 1.18 pmol/hr/ug), and retina (4.21 ± 1.55 pmol/hr/ug), indicating the presence of active RALDH enzymes in these tissues. RALDH2 was most abundant in the choroid and RPE, in moderate abundance in the retina, and in relatively low abundance in sclera. RALDH1 was most abundant in the choroid, in moderate abundance in the sclera, and substantially reduced in the retina and RPE. RALDH3 was undetectable in human ocular fundal tissues. In the choroid, RALDH1 and RALDH2 localized to slender cells in the stroma, some of which were closely associated with blood vessels.

CONCLUSIONS/SIGNIFICANCE

Results of this study demonstrated that: 1) Catalytically active RALDH is present in postnatal human retina, RPE, and choroid, 2) RALDH1 and RALDH2 isoforms are present in these ocular tissues, and 3) RALDH1 and RALDH2 are relatively abundant in the choroid and/or RPE. Taken together, these results suggest that RALDH1 and 2 may play a role in the regulation of postnatal ocular growth in humans through the synthesis of atRA.

Antioxidant activity stimulated by ultraviolet radiation in the nervous system of a crustacean

Ultraviolet (UV) radiation can produce biological damage, principally oxidative stress, by increasing the production of reactive oxygen species (ROS). This study evaluated biochemical impairments related to the oxidative stress induced by UVA, UVB and UVA+UVB (solar simulator-SIM) in environmental doses, during five consecutive days of exposure, in the brain and eyestalk of the crab Ucides cordatus. We evaluated these regions by sampling on the 1st, 3rd and 5th days of UV exposure for lipid peroxidation (LPO), antioxidant capacity against the peroxyl radical (ACAP), and the activities of catalase (CAT), glutathione peroxidase (GPX) and glutathione-S-transferase (GST). Immunohistochemical and immunoblotting assays were performed for anti-activated-caspase 3 in the brains. After the first day of exposure, LPO increased in the eyestalks and brains of the UV-exposed animals; ACAP, and CAT, GPX and GST activities also increased in the brains. On the third day, the LPO values in the eyestalk remained high in the UV-exposed groups, while ACAP decreased in the brain and eyestalk and CAT activity remained high in all irradiated groups in both regions. On the fifth day, LPO decreased in the eyestalk and brain of the UV-exposed groups. These results may have been a consequence of the antioxidant defense system (ADS) activity, since CAT activity was high in both regions, ACAP was high in the eyestalks of the SIM group, and GPX activity remained high in the eyestalks of the UVA and UVB groups. Immunohistochemical assays and immunoblotting showed that there was apoptosis in the brains of the UV-exposed crabs. In conclusion, environmental doses of UV can cause oxidative damage to the CNS cells, including apoptosis.

Cajaninstilbene acid protects corticosterone-induced injury in PC12 cells by inhibiting oxidative and endoplasmic reticulum stress-mediated apoptosis

It has been reported that high corticosterone level could damage the normal hippocampal neurons both in vitro and in vivo. Furthermore, high concentration of corticosterone induced impair in PC12 cells has been widely used as in vitro model to screen neuroprotective agents. Cajaninstilbene acid (CSA), a natural stilbene isolated from Cajanus cajan leaves, has various activities. In present study, we investigated the effect of CSA on corticosterone-induced cell apoptosis and explored its possible signaling pathways in PC12 cells. We demonstrated that pretreatment with CSA at the concentrations of 1-8 μmol/L remarkably reduced the cytotoxicity induced by 200 μmol/L of corticosterone in PC12 cells by MTT, and further confirmed the neuroprotection by Hoechst 33342 and PI double staining and lactate dehydrogenase release (LDH) assay at the concentration of 8 μmol/L. Moreover, the cytoprotection of CSA was proved to be associated with the homeostasis of intracellular Ca(2+), relieving corticosterone-induced oxidative stress by decreasing the contents of ROS and malondialdehyde (MDA), increasing the activities of superoxide dismutase (SOD) and catalase (CAT), and the stabilization of ER stress via down-regulating the expression of ER chaperone protein glucose-regulated protein 78 (GRP78), ER stress associated transcription factor C/EBP homologous protein (CHOP/GADD153), and the X box-binding protein-1 (XBP-1), as well as the expression of ER stress-specific protein caspase-12 and its downstream protein caspase-9. Considering all the findings, it is suggested that the neuroprotective activity of CSA against the impairment induced by corticosterone in PC12 cells was through the inhibition of oxidative stress and ER stress-mediated pathway.

Focus on molecular events in the anterior chamber leading to glaucoma

Primary open-angle glaucoma is a multifactorial disease that affects the retinal ganglion cells, but currently its therapy is to lower the eye pressure. This indicates a definite involvement of the trabecular meshwork, key region in the pathogenesis of glaucoma. This is the first target of glaucoma, and its functional complexity is a real challenge to search. Its functions are those to allow the outflow of aqueous humor and not the reflux. This article describes the morphological and functional changes that happen in anterior chamber. The "primus movens" is oxidative stress that affects trabecular meshwork, particularly its endothelial cells. In these develops a real mitochondriopaty. This leads to functional impotence, the trabecular meshwork altering both motility and cytoarchitecture. Its cells die by apoptosis, losing barrier functions and altering the aqueous humor outflow. All the morphological alterations occur that can be observed under a microscope. Intraocular pressure rises and the malfunctioning trabecular meshwork endotelial cells express proteins that completely alter the aqueous humor. This is a liquid whose functional proteomics complies with the conditions of the trabecular meshwork. Indeed, in glaucoma, it is possible detect the presence of proteins which testify to what occurs in the anterior chamber. There are six classes of proteins which confirm the vascular endothelium nature of the anterior chamber and are the result of the morphofunctional trabecular meshwork decay. It is possible that, all or in part, these proteins can be used as a signal to the posterior pole.

A proteomics approach to the identification of plasma biomarkers for latent tuberculosis infection

A proteomic analysis was performed to screen the potential latent tuberculosis infection (LTBI) biomarkers. A training set of spectra was used to generate diagnostic models, and a blind testing set was used to determine the accuracy of the models. Candidate peptides were identified using nano-liquid chromatography-electrospray ionization–tandem mass spectrometry. Based on the training set results, 3 diagnostic models recognized LTBI subjects with good cross-validation accuracy. In the blind testing set, LTBI subjects could be identified with sensitivities and specificities of 85.20% to 88.90% and 85.7% to 100%, respectively. Additionally, 14 potential LTBI biomarkers were identified, and all proteins were identified for the first time through proteomics in the plasma of healthy, latently infected individuals. In all, proteomic pattern analyses can increase the accuracy of LTBI diagnosis, and the data presented here provide novel insights into potential mechanisms involved in LTBI.

Mechanisms for PDGF, a serum cytokine, stimulating loss of corneal keratocyte crystallins

PURPOSE

As corneal stromal cells (keratocytes) become activated before transition to the fibroblastic repair phenotype in response to injury (in situ) or serum (in culture), the corneal crystallins, transketolase (TKT) and aldehyde dehydrogenase (ALDH1A1), are lost. The authors previously showed that the serum cytokine platelet-derived growth factor-BB (PDGF), but not transforming growth factor beta2 (TGF-beta2), stimulates TKT loss. The goal of this study was to further define the molecular mechanisms for PDGF-stimulated loss of crystallins to elucidate the pathway for keratocyte activation.

METHODS

Freshly isolated rabbit corneal keratocytes were plated in serum-free medium with or without PDGF and/or specific inhibitors of the PDGF-relevant signal pathway components, PDGF receptor, PI3K/AKT, or ras-initiated MAPK proteins. Intracellular TKT protein levels were quantified by immunoblotting. Ubiquitinated TKT levels were assessed by immunoprecipitation, and TKT messenger RNA (mRNA) levels were quantified by quantitative reverse transcription-polymerase chain reaction.

RESULTS

PDGF treatment at the same time as inhibition of PDGF receptor, Akt, JNK, and ubiquitin-proteasome pathway prevented PDGF-induced TKT protein loss. In contrast, treatment with PDGF did not affect TKT mRNA levels.

CONCLUSIONS

The results suggest that PDGF-stimulated TKT loss is mediated through cross talk between PI3K-independent Akt and JNK. This signaling pathway leads to the degradation of existing TKT protein but does not compromise the accumulation of TKT mRNA. Therefore, cells retain the potential to reaccumulate TKT protein that is enabled by PDGF removal. These findings suggest that targeting PDGF signaling could improve repair outcomes after surgical procedures in the cornea.

9-cis retinoic acid is the ALDH1A1 product that stimulates melanogenesis

Aldehyde dehydrogenase 1A1 (ALDH1A1), an enzyme that catalyses the conversion of lipid aldehydes to lipid carboxylic acids, plays pleiotropic roles in UV-radiation resistance, melanogenesis and stem cell maintenance. In this study, a combination of RNAi and pharmacologic approaches were used to determine which ALDH1A1 substrates and products regulate melanogenesis. Initial studies revealed that neither the UV-induced lipid aldehyde 4-hydroxy-2-nonenal nor the ALDH1A1 product all-trans retinoic acid appreciably induced melanogenesis. In contrast, both the ALDH1A1 substrate 9-cis retinal and its corresponding product 9-cis retinoic acid potently induced the accumulation of MITF mRNA, Tyrosinase mRNA and melanin. ALDH1A1 depletion inhibited the ability of 9-cis retinal but not 9-cis retinoic acid to stimulate melanogenesis, indicating that ALDH1A1 regulates melanogenesis by catalysing the conversion of 9-cis retinal to 9-cis retinoic acid. The addition of potent ALDH1A inhibitors (cyanamide or Angeli's salt) suppressed Tyrosinase and MITF mRNA accumulation in vitro and also melanin accumulation in skin equivalents, suggesting that 9-cis retinoids regulate melanogenesis in the intact epidermis. Taken together, these studies not only identify cyanamide as a potential novel treatment for hyperpigmentary disorders, but also identify 9-cis retinoic acid as a pigment stimulatory agent that may have clinical utility in the treatment of hypopigmentary disorders, such as vitiligo.

Interleukin 11 expression in the normal canine eye

OBJECTIVES

The purpose of this study was to characterize the expression of interleukin-11 (IL-11), a cytokine with anti-inflammatory, cytoprotective, and immune-modulating characteristics, in the canine eye.

PROCEDURES

Normal canine eyes were collected from clinically healthy dogs that had been euthanized for reasons unrelated to this study. The distribution of IL-11 expression in the different ocular layers was evaluated by immunofluorescence (eight eyes). Expression levels were quantified (based on fluorescence intensity) using pixel density analysis. Primary cell cultures were derived from all three corneal cell layers. IL-11 mRNA expression was assessed in these cultures using quantitative RT-PCR before and after treatment with TGF-β1, a known inducer of IL-11 expression. IL-11 protein expression was also assessed in the media of these cells by Western blot analysis.

RESULTS

IL-11 protein was detected in the corneal epithelium, keratocytes, and the corneal endothelium of the normal canine eyes examined using immunofluorescence. Baseline IL-11 mRNA expression was noted in the corneal epithelium, fibroblasts, and endothelium using quantitative RT-PCR. Treatment of canine corneal cell lines with TGF-β1 resulted in statistically significant increases in IL-11 expression in the corneal epithelium, endothelial and fibroblast cell lines with strongest induction noted in the fibroblasts and endothelium.

CONCLUSION

This is the first description of IL-11 expression in the canine eye. The protein and mRNA appear to be constitutively present throughout all layers of the cornea and are increased by TGF-β1, a cytokine important in ocular inflammation and disease.

Aldehyde dehydrogenases: from eye crystallins to metabolic disease and cancer stem cells

The aldehyde dehydrogenase (ALDH) superfamily is composed of nicotinamide adenine dinucleotide (phosphate) (NAD(P)(+))-dependent enzymes that catalyze the oxidation of aldehydes to their corresponding carboxylic acids. To date, 24 ALDH gene families have been identified in the eukaryotic genome. In addition to aldehyde metabolizing capacity, ALDHs have additional catalytic (e.g. esterase and reductase) and non-catalytic activities. The latter include functioning as structural elements in the eye (crystallins) and as binding molecules to endobiotics and xenobiotics. Mutations in human ALDH genes and subsequent inborn errors in aldehyde metabolism are the molecular basis of several diseases. Most recently ALDH polymorphisms have been associated with gout and osteoporosis. Aldehyde dehydrogenase enzymes also play important roles in embryogenesis and development, neurotransmission, oxidative stress and cancer. This article serves as a comprehensive review of the current state of knowledge regarding the ALDH superfamily and the contribution of ALDHs to various physiological and pathophysiological processes.

Environmental light and endogenous antioxidants as the main determinants of non-cancer ocular diseases

The human eye is constantly exposed to sunlight and artificial lighting. Exogenous sources of reactive oxygen species (ROS) such as UV light, visible light, ionizing radiation, chemotherapeutics, and environmental toxins contribute to oxidative damage in ocular tissues. Long-term exposure to these insults places the aging eye at considerable risk for pathological consequences of oxidative stress. Furthermore, in eye tissues, mitochondria are an important endogenous source of ROS. Over time, all ocular structures, from the tear film to the retina, undergo oxidative stress, and therefore, the antioxidant defenses of each tissue assume the role of a safeguard against degenerative ocular pathologies. The ocular surface and cornea protect the other ocular tissues and are significantly exposed to oxidative stress of environmental origin. Overwhelming of antioxidant defenses in these tissues clinically manifests as pathologies including pterygium, corneal dystrophies, and endothelial Fuch's dystrophy. The crystalline lens is highly susceptible to oxidative damage in aging because its cells and their intracellular proteins are not turned over or replaced, thus providing the basis for cataractogenesis. The trabecular meshwork, which is the anterior chamber tissue devoted to aqueous humor drainage, has a particular susceptibility to mitochondrial oxidative injury that affects its endothelium and leads to an intraocular pressure increase that marks the beginning of glaucoma. Photo-oxidative stress can cause acute or chronic retinal damage. The pathogenesis of age-related macular degeneration involves oxidative stress and death of the retinal pigment epithelium followed by death of the overlying photoreceptors. Accordingly, converging evidence indicates that mutagenic mechanisms of environmental and endogenous sources play a fundamental pathogenic role in degenerative eye diseases.

The human crystallin gene families

Crystallins are the abundant, long-lived proteins of the eye lens. The major human crystallins belong to two different superfamilies: the small heat-shock proteins (α-crystallins) and the βγ-crystallins. During evolution, other proteins have sometimes been recruited as crystallins to modify the properties of the lens. In the developing human lens, the enzyme betaine-homocysteine methyltransferase serves such a role. Evolutionary modification has also resulted in loss of expression of some human crystallin genes or of specific splice forms. Crystallin organization is essential for lens transparency and mutations; even minor changes to surface residues can cause cataract and loss of vision.

Impact of organ culturing on metabolic profile of human corneas: preliminary results

PURPOSE

It is suggested that the quality of corneal graft may depend on modifications that appear in the tissue during culturing. The aim of this study was to investigate the differences in the metabolic profile between cultured and noncultured human corneas.

METHODS

Corneas from 12 donors were obtained post-mortem and cultured for 6-20 days. Control corneas were obtained from four patients with malignant melanoma of the chorioidea and were kept frozen at -80 °C until analysed. The metabolic profiles of the samples were investigated using high-resolution, magic angle spinning (1) H nuclear magnetic resonance spectroscopy and special software for: (i) analysis of complex mixtures, (ii) principal component analysis and (iii) specialized statistical analysis.

RESULTS

Twenty metabolites were detected and assigned in the corneas. Significant differences in metabolic profiles between cultured and noncultured corneas were revealed. It was also shown in samples kept in culture for 9-14 days that the levels of (i) alanine, formate, lactate and (ii) acetate, alanine, arginine, lactate were elevated in comparison with the samples kept for <9 and more than 14 days, respectively.

CONCLUSIONS

Corneal culturing affects the metabolic profile of the tissue. The increases in the levels of some metabolites within the second week of culturing likely result from variations in tissue metabolic or enzymatic activity caused by changed (organ culture) environment. As the mechanisms responsible for these changes are not clear, further research is indicated.

Ocular aldehyde dehydrogenases: protection against ultraviolet damage and maintenance of transparency for vision

Aldehyde dehydrogenase (ALDH) enzymes catalyze the NAD(P)(+)-dependent oxidation of a wide variety of endogenous and exogenous aldehydes to their corresponding acids. Some members of the ALDH superfamily of enzymes are abundantly expressed in the mammalian cornea and lens in a taxon-specific manner. Considered to be corneal and lens crystallins, they confer protective and transparent properties upon these ocular tissues. ALDH3A1 is highly expressed in the cornea of most mammals, with the exception of rabbit that expresses exclusively ALDH1A1 in the cornea. ALDH1A1 is present in both the cornea and lens of several animal species. As a result of their catalytic and non-catalytic functions, ALDH3A1 and ALDH1A1 proteins protect inner ocular tissues from ultraviolet radiation and reactive oxygen-induced damage. In addition, these corneal crystallins contribute to cellular transparency in corneal stromal keratocytes, supporting a structural role of these ALDH proteins. A putative regulatory function of ALDH3A1 on corneal cell proliferation has also been proposed. Finally, the three retinaldehyde dehydrogenases cooperatively mediate retinoic acid signaling during the eye development.

Correlation among antioxidant, antimicrobial, hemolytic, and antiproliferative properties of Leiothrix spiralis leaves extract

The biological activities of a plant extract depend on a complex sum of individual properties including the antioxidant activity. Several biological activities protect against the harmful action of reactive oxygen species (ROS), and here we focused our attention on the relationship between the biological activities tested and the antioxidant properties. In this study, the total flavonoid content as well as the antioxidant, antimicrobial, hemolytic and cytotoxicity activities of the methanolic extract of Leitothrix spiralis leaves were evaluated. The extract showed a total flavonoid content of 19.26% and the chemical characterization by HPLC-PAD confirmed the presence of flavonoids as the major secondary metabolite compounds. Significant antioxidant activity (IC₅₀ = 1.743 μg/mL ± 0.063) was demonstrated and was effective against Gram-negative organisms and all Candida strains tested, and showed an ability to inhibit hyphal formation. Non-hemolytic and antiproliferative activity could be demonstrated.

Molecular mechanisms of ALDH3A1-mediated cellular protection against 4-hydroxy-2-nonenal

Evidence suggests that aldehydic molecules generated during lipid peroxidation (LPO) are causally involved in most pathophysiological processes associated with oxidative stress. 4-Hydroxy-2-nonenal (4-HNE), the LPO-derived product, is believed to be responsible for much of the cytotoxicity. To counteract the adverse effects of this aldehyde, many tissues have evolved cellular defense mechanisms, which include the aldehyde dehydrogenases (ALDHs). Our laboratory has previously characterized the tissue distribution and metabolic functions of ALDHs, including ALDH3A1, and demonstrated that these enzymes may play a significant role in protecting cells against 4-HNE. To further characterize the role of ALDH3A1 in the oxidative stress response, a rabbit corneal keratocyte cell line (TRK43) was stably transfected to overexpress human ALDH3A1. These cells were studied after treatment with 4-HNE to determine their abilities to: (a) maintain cell viability, (b) metabolize 4-HNE and its glutathione conjugate, (c) prevent 4-HNE-protein adduct formation, (d) prevent apoptosis, (e) maintain glutathione homeostasis, and (f) preserve proteasome function. The results demonstrated a protective role for ALDH3A1 against 4-HNE. Cell viability assays, morphological evaluations, and Western blot analyses of 4-HNE-adducted proteins revealed that ALDH3A1 expression protected cells from the adverse effects of 4-HNE. Based on the present results, it is apparent that ALDH3A1 provides exceptional protection from the adverse effects of pathophysiological concentrations of 4-HNE such as may occur during periods of oxidative stress.

αA-crystallin in the pathogenesis and intervention of experimental murine corneal neovascularization

This study was to determine the potential roles of lens crystallins in the pathogenesis of corneal neovascularization (CorNV) and implications in therapy of CorNV-related diseases. Suture- or chemical burn-induced CorNV in different strains of mice were used. Changes of gene expression patterns were analyzed by microarray, and the results of interesting genes were confirmed by real-time quantitative PCR and Western blot. Mice deficient in αA-crystallin gene were used to evaluate the role of αA-crystallin in the development of CorNV. In some animals, exogenous αA-crystallin proteins were injected around time of CorNV induction. CorNV was assessed by slit-lamp, flat-mounts and histology. In BALB/C mice, the expression of α-, β-, and γ-crystallins were up-regulated at day 5 and returned to baseline level at day 10 of suture-induced CorNV, but remained up-regulated from day 6 to day 14 of chemical burn-induced CorNV. In chemical burn-induced CorNV in C57BL/6J mice, however, they were down-regulated at day 6. Corneal crystallins were down-regulated in both CorNV models at all time points in both BALB/c and C57BL/6J mice. Comparison of CorNV development in αA-crystallin-deficient mice and that in wild-type mice revealed no significant difference. Subconjunctival injection of αA-crystallin significantly attenuated suture-induced CorNV, and the inhibitory activity might be implemented by the increased expression of soluble VEGFR-1. In conclusion, the expression patterns of lens crystallins were time- and strain-dependent but different from that of corneal crystallins in mouse CorNV models. Exogenous αA-crystallin protein attenuated CorNV, potentially by increasing the expression of soluble VEGFR-1.

Myofibroblast differentiation modulates keratocyte crystallin protein expression, concentration, and cellular light scattering

PURPOSE

The purpose of this study was to determine whether myofibroblast differentiation altered keratocyte crystallin protein concentration and increased cellular light scattering.

METHODS

Serum-free cultured rabbit corneal keratocytes and TGFβ (5 ng/mL) induced myofibroblasts were harvested and counted and protein/RNA extracted. Expression of myofibroblast and keratocyte markers was determined by real-time PCR and Western blot analysis. The cell volume of calcein AM-loaded keratocytes and myofibroblasts was determined by using nonlinear optical microscopy. Cellular light scattering of transformed myofibroblasts expressing human keratocyte crystallins was measured by reflectance confocal microscopy.

RESULTS

Differentiated myofibroblasts showed a significant decrease in RNA levels for the keratocyte markers ALDH1A1, lumican, and keratocan and a significant increase in the myofibroblast marker α-smooth muscle actin. Volumetric and protein measurements showed that myofibroblast differentiation significantly increased cytoplasmic volume (293%; P < 0.001) and water-soluble and -insoluble protein content per cell (respectively, 442% and 431%; P < 0.002) compared to keratocytes. Western blot analysis showed that the level of ALDH1A1 protein per cell was similar between myofibroblasts and keratocytes, but was substantially reduced as a percentage of total water-soluble protein. Light scattering measurements showed that induced expression of corneal crystallins significantly decreased light scattering.

CONCLUSIONS

These data suggest that myofibroblast differentiation leads to a marked increase in cell volume and dilution of corneal crystallins associated with an increase in cellular light scattering.

Differential response of lens crystallins and corneal crystallins in degenerative corneas

Corneal degenerations, occurring either spontaneously or as a complication to other diseases, cause vision problems by endangering corneal transparency. Our past cornea research projects involving mice revealed that some recruited mice presented corneal problems similar to human corneal degeneration. The present study examines the histology of diseased mice corneas, including ultrastructure. Genome-wide microarray and proteomic methods were utilized to screen for molecular changes in the diseased corneas. It was found that abnormalities affected mainly anterior layers of the corneas. The most often observed histological abnormalities included neoplasm or detachment of the epithelial layer, erosion or breakage of Bowman membranes, blood vessel formation, and bleeding in the stroma. Microarray assay showed that among the 46 up-regulated probes in diseased corneas, 13 were for lens crystallins. However, all corneal crystallins genes remained unchanged. αA-crystallin was among the proteins that showed the greatest increase in diseased corneas, as detected by gel electrophoresis. We propose that lens crystallins, rather than corneal crystallins, are involved in the pathological process of corneal degeneration. Further study along these lines would provide insight into the mechanism of corneal transparency.

Impact of diabetes on alpha-crystallins and other heat shock proteins in the eye

Diabetes and its related complications represent a major growing health concern and economic burden worldwide. Ocular manifestations of diabetes include cataractogenesis and retinopathy, the latter being the leading cause of blindness in the working-age population. Despite numerous studies and recent progress, the exact pathophysiology of the disease remains to be fully elucidated and development of new and improved therapeutic strategies for this chronic condition are greatly needed. Heat shock proteins (Hsps) are highly conserved families of proteins, which are generally regarded as protective molecules that play a wide variety of roles and can be expressed in response to different types of cellular stresses. In recent years, numerous studies have reported their implication in various ocular diseases including diabetic retinopathy. The present review focuses on the potential implication of Hsps in ocular diabetic complications and discusses their specific mechanisms of regulation with respect to their expression, functions and alteration during diabetes. The review will conclude by examining the potential of Hsps as therapeutic agents or targets for the treatment of diabetic retinopathy.