Protective effect of heat shock protein 70 against oxidative stresses in human corneal fibroblasts

The Role of Heat Shock Protein 70 (HSP70) in the Pathogenesis of Ocular Diseases-Current Literature Review

Heat shock proteins (HSPs) have been attracting the attention of researchers for many years. HSPs are a family of ubiquitous, well-characterised proteins that are generally regarded as protective multifunctional molecules that are expressed in response to different types of cell stress. Their activity in many organs has been reported, including the heart, brain, and retina. By acting as chaperone proteins, HSPs help to refold denatured proteins. Moreover, HSPs elicit inhibitory activity in apoptotic pathways and inflammation. Heat shock proteins were originally classified into several subfamilies, including the HSP70 family. The aim of this paper is to systematise information from the available literature about the presence of HSP70 in the human eye and its role in the pathogenesis of ocular diseases. HSP70 has been identified in the cornea, lens, and retina of a normal eye. The increased expression and synthesis of HSP70 induced by cell stress has also been demonstrated in eyes with pathologies such as glaucoma, eye cancers, cataracts, scarring of the cornea, ocular toxpoplasmosis, PEX, AMD, RPE, and diabetic retinopathy. Most of the studies cited in this paper confirm the protective role of HSP70. However, little is known about these molecules in the human eye and their role in the pathogenesis of eye diseases. Therefore, understanding the role of HSP70 in the pathophysiology of injuries to the cornea, lens, and retina is essential for the development of new therapies aimed at limiting and/or reversing the processes that cause damage to the eye.

Genomics of corneal wound healing: a review of the literature

Corneal wound healing is a complex process: its mechanisms and the underlying genetic control are not fully understood. It involves the integrated actions of multiple growth factors, cytokines and proteases produced by epithelial cells, stromal keratocytes, inflammatory cells and lacrimal gland cells. Following an epithelial insult, multiple cytokines are released triggering a cascade of events that leads to repair the epithelial defect and remodelling of the stroma to minimize the loss of transparency and function. In this review, we examine the literature surrounding the genomics of corneal wound healing with respect to the following topics: epithelial and stromal wound healing (including inhibition); corneal neovascularisation; the role of corneal nerves in wound healing; the endothelium; the role of aquaporins and aptamers. We also examine the effect of ectasia on corneal wound healing with regard to keratoconus and following corneal surgery. A better understanding of the cellular and molecular changes that occur during repair of corneal wounds will provide the opportunity to design treatments that selectively modulate key phases of the healing process resulting in scars that more closely resemble normal corneal architecture.

Heat shock proteins in the human eye

Heat shock proteins (Hsps) are believed to primarily protect and maintain cell viability under stressful conditions such as those occurring during thermal and oxidative challenges chiefly by refolding and stabilizing proteins. Hsps are found throughout the various tissues of the eye where they are thought to confer protection from disease states such as cataract, glaucoma, and cancer. This minireview summarizes the placement, properties, and roles of Hsps in the eye and aims to provide a better comprehension of their function and involvement in ocular disease pathogenesis.

Toxic potential of municipal solid waste leachates in transgenic Drosophila melanogaster (hsp70-lacZ): hsp70 as a marker of cellular damage

Municipal solid wastes (MSWs) are one of the major sources of environmental pollution. Leachates from these wastes might contaminate the water sources and affect quality of environment. The study was carried out to determine the possible toxic effects of leachates from MSW in transgenic Drosophila melanogaster (hsp70-lacZ). Third instar larvae exposed to 1.0-3.0% of these leachates at different time intervals were examined for hsp70 expression, oxidative stress enzyme activities, proteotoxicity, tissue damage along with effect on emergence and reproduction. Maximum hsp70 expression was observed in the larvae exposed to highly acidic leachates. Overwhelming of hsp70 expression in the exposed larvae caused a concomitant decline in total protein content and a significant elevation in oxidative stress enzymes and lipid peroxidation (LPO) product. The leachates caused a significant delay in emergence of flies and affected the reproductive performance of the flies at the tested concentrations. The present study highlights the toxic potential of MSW leachates and the advantage of Drosophila as a model to evaluate the impact of leachates at organismal and cellular levels, also advocating Hsp70 as the first tier indicator of toxicity.

Induction of mesenchymal stem cells leads to HSP72 synthesis and higher resistance to oxidative stress

The phenomenon of neuronal transdifferentiation performed on bone marrow mesenchymal stem cells (MSCs) has been criticized by recent studies indicating that acquired neuron-like morphology of induced MSCs is caused by cellular stress. Therefore, to test this hypothesis we have investigated whether exposure of rat MSCs (rMSCs) to chemical inducer 2 mM beta-mercaptoethanol (BME) for 1-3 h followed by 24 h incubation leads to HSP72 synthesis, thus suggesting higher resistance of rMSCs to oxidative damage. Present data from immunohistochemistry clearly indicate development of time-dependent sub-cellular HSP72 distribution, initially seen in nuclei at 1 h followed by its translocation to surrounding central cytoplasm and processes at 2-3 h after BME stimulation. Western blot (WB) analysis confirmed the expression of HSP72 protein in induced rMSCs at both stimulation periods. Furthermore, preconditioned rMSCs with BME for 1 h expressing HSP72 positivity at 24 h showed higher resistance (78 +/- 10% of survival cells) to oxidative stress caused by 1 mM H(2)O(2) when compared to those preconditioned for 3 h (59 +/- 8% of survival cells) or control-unconditioned rMSCs exposed to the same stressor conditions (56 +/- 6% of survival cells). Thus, the cellular protection was lost if the duration of BME preconditioning was increased as far as possible (3 h) (while still remaining sub-lethal). This suggests that exposure of rMSCs to the optimal concentration of BME (2 mM) during optimal induction period (1 h) mediate their protection and increases resistance to oxidative injury, while over crossing these limits is in-effective. In addition, our findings confirm that cultured rMSCs remain competent to be preconditioned by BME, through a pathway that may increase the antioxidant balance or involve activation of HSP72 protein induced tolerance.

Dithiocarbamate fungicide thiram detection: comparison of bioluminescent and fluorescent whole-cell bioassays based on hsp22 stress promoter induction

Detection of toxic substances interfering with endocrine system is one of the major preoccupations of the European community. A whole-cell bioassay for pollution detection based on stress induction has been designed. Well characterized toxicants, cadmium chloride and thiram (a dithiocarbamate fungicide), were used to optimize the detection conditions such as time-course conditions, cell line and reporter gene to be used. HeLa cells containing the firefly luciferase (luc) reporter gene under the control of the Drosophila melanogaster hsp22 promoter were compared to liver cells (HepG2) containing the same stress gene promoter fused either to the luc or the EGFP (Enhanced-Green Fluorescent Protein) gene. The sensitivity of the obtained bioassay was found to be enhanced by the concomitant use of liver cells and EGFP reporter gene. The detection limits of the toxicants were then lowered from 1 to 0.1 microM and from 1 to 0.01 microM for CdCl(2) and thiram, respectively.

Hazardous effect of organophosphate compound, dichlorvos in transgenic Drosophila melanogaster (hsp70-lacZ): Induction of hsp70, anti-oxidant enzymes and inhibition of acetylcholinesterase

We tested a working hypothesis that stress genes and anti-oxidant enzyme machinery are induced by the organophosphate compound dichlorvos in a non-target organism. Third instar larvae of Drosophila melanogaster transgenic for hsp70 were exposed to 0.1 to 100.0 ppb dichlorvos and 5.0 mM CuSO(4) (an inducer of oxidative stress and stress genes) and hsp70, and activities of acetylcholinesterase (AchE), superoxide dismutase (SOD), catalase (CAT) and lipid peroxidation (LPO) product were measured. The study was further extended to examine tissue damage, if any, under such conditions. A concentration- and time-dependent increase in hsp70 and anti-oxidant enzymes was observed in the exposed organism as compared to control. A comparison of stress gene expression with SOD, CAT activities and LPO product under similar experimental conditions revealed that induction of hsp70 precedes the anti-oxidant enzyme activities in the exposed organism. Further, concomitant with a significant inhibition of AChE activity, significant induction of hsp70 was observed following chemical exposure. Mild tissue damage was observed in the larvae exposed to 10.0 ppb dichlorvos for 48 h when hsp70 expression reaches plateau. Dichlorvos at 0.1 ppb dietary concentration did not evoke significant hsp70 expression, anti-oxidant enzymes and LPO and AchE inhibition in the exposed organism, and thereby, was found to be non-hazardous to D. melanogaster. Conversely, 1.0 ppb of the test chemical stimulated a significant induction of hsp70 and anti-oxidant enzymes and significant inhibition of AchE; hence this concentration of test chemical was hazardous to the organism. The present study suggests that (a) both stress genes and anti-oxidant enzymes are stimulated as indices of cellular defense against xenobiotic hazard in D. melanogaster with hsp70 being proposed as first-tier bio-indicator of cellular hazard, (b) 0.1 ppb of the test chemical may be regarded as No Observed Adverse Effect Level (NOAEL), and 1.0 ppb dichlorvos as Low Observed Adverse Effect Level (LOAEL).