UV‐A‐related alterations of young and adult lens water‐insoluble α‐crystallin, plasma membranous and cytoskeletal proteins

Abstract

The damaging effects of UV-A irradiation on lens waterinsoluble a-crystallin, plasma membranous and cytoskeletal proteins derived from bovine lenses were studied. Young and adult bovine lenses were kept viable for 2 months in organ culture. After 24 h of incubation they were irradiated, and analyses of the proteins by one-dimensional and two-dimensional gel electrophoresis followed by Western blotting were carried out at several time intervals. RNA isolation, PCR and Northern blotting were also performed. We identified age-related changes in water-insoluble a-crystallin, the major membrane protein MP26 and the cytoskeletal proteins vimentin, phakinin and actin between control and UV-irradiated lenses. It appeared that adult lenses are more susceptible to UV light than young lenses, and protein modification occurred more frequently in adult lenses. UV-A irradiation affects not only the cytoskeletal structure, as deduced by the abnormal arrangement of actin in the fiber cells, but also leads to degradation of actin mRNA. Furthermore, analysis of the expression of hsp25 and hsp70 revealed some alteration in the protein pattern of adult lenses. We suggest that degradation of the cytoskeletal proteins following irradiation is due to, at least in part, the decreased protective ability of heat shock proteins upon aging.Keywords: a-crystallin; cytoskeletal proteins; lens aging; plasma membrane; UV-A irradiation.UV-A light (300±400 nm) penetrates the cornea and is maximally absorbed by the eye lens [1]. The human lens contains low molecular mass compounds which absorb maximally at < 365 nm [2] At this specific wavelength the lens is susceptible to irradiation. Experiments in organ culture of bovine lenses showed a relationship between UV-A radiation at 365 nm and subsequent lens opacity. It has been shown that epithelial enzymes of bovine lenses (ATPase, hexokinase, catalase and glucose-6-phosphate dehydrogenase), which are involved in metabolism and the defense mechanism against oxidation, are affected by UV-light [3,4]. Transglutaminase, which is a calciumdependent acyltransferase, may be involved in the mechanism by which UV-A causes damage to the eye lens [5]. The small heat shock protein aB-crystallin [6,7] and hsp25 [8] are substrates for the latter enzyme. We recently demonstrated that modifications, aggregation and reduced chaperone-like activity of water-soluble a-crystallin obtained from UV-A irradiated adult bovine lenses [9] affect lens transparency. This process may accumulate during aging.In this study we addressed the question of whether plasma membranous and cytoskeletal proteins from the water-insoluble fraction of young and adult bovine eye lenses are affected differently by UV-A radiation. The plasma membrane±cytoskeleton complex participates in the maintenance of lens shape, and both structures associate with lens crystallins [10]. We restricted our study to cytoskeletal proteins such as vimentin, phakinin (CP49), b-actin and the major lens membrane protein (MP26) which may be modified as a consequenc...

Ultraviolet radiation (UV) induces f-action rearrangement and cell death in the A549 human lung cancer cell line

“…We showed that UVinduced morphological changes were associated with actin cytoskeleton reorganization and characterized, at least in part by the disruption of actin stress fibres and cell-cell adhesions. Several other studies also revealed that UV radiation induced the actin cytoskeleton reorganization leading to the destruction of cell adherence and consequently to cell death [10,18,19]. In addition, we noticed that F-actin was presented in the form of dense ring-like structures surrounding the nuclei of cells with apoptotic-like phenotype.…”

Changes in gravitational force cause changes in gene expression in the lens of developing zebrafish

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“…During development, hsp70 plays an essential role in lens formation (Evans et al, 2005). Later, when lens proteins such as crystallins play a role in the maintenance of lens cell transparency, Hsp70 is thought to protect the lens proteins from aggregation caused by environmental stresses such as heat and cold shock, ultraviolet-A (UV-A) irradiation, and oxidative stress (de Jong et al, 1986;Weinreb et al, 2001;Bagchi et al, 2002;Banh et al, 2003). Recent studies with cultured cells also demonstrated that microgravity exposure changed the expression level of hsp70 (Carlsson et al, 2003;Kumei et al, 2003).…”

UVA Light In vivo Reaches the Nucleus of the Guinea Pig Lens and Produces Deleterious, Oxidative Effects

“…An investigation conducted with Chinese hamster ®broblasts (Banrud et al, 1999) found that while biologically-relevant uences of UVA were able to disintegrate actin ®laments in the cells, even lethal¯uences of UVB light had no effect on the proteins. Studies with cultured lenses have also indicated distinct damaging effects of UVA light on cytoskeletal proteins (Rafferty et al, 1993;Zigman et al, 1996;Weinreb et al, 2001); however, these studies investigated only damage to proteins present in the lens epithelium and cortex. The¯uences of UVA light used in the cultured lens work were at least 5±10 times higher than ours, which may be why the previous investigators were able to induce UVA damage in the epithelium and cortex, whereas we could not.…”