紫外线对培养兔晶体的氧化损伤及超微形态学研究

目的 探讨实验性兔晶体氧自由基损伤与白内障的发病机制。方法 利用近距离紫外线（ＵＶ）照射体外培养兔晶体,诱发氧自由基损伤。并同时观察超氧化物歧化酶（ＳＯＤ）的抗氧化作用。实验分为ＵＶ照射组、ＵＶ＋ＳＯＤ组及对照组,采用硫代巴比妥酸比色法分别检测三组晶体匀浆中脂质过氧化产物丙二醛含量,并通过透射电镜观察三组晶体上皮细胞的超微结构。结果 ＵＶ照射组兔晶体匀浆中的丙二醛含量明显增高。ＵＶ＋ＳＯＤ组（ＵＶ     

Effect of ultraviolet-B radiation on protein synthesis in cultured lens epithelial cells

Exposure of cultured rabbit lens epithelial cells to repetitive doses of UV-B radiation delays their growth and alters the synthesis of specific proteins. Irradiated cells on the shoulder of the survival curve exhibited a dose-dependent decrease in growth when subcultured in serum-supplemented medium. UV-B irradiation did not affect the subsequent attachment efficiency of the cells. Control and UV-B irradiated cells were incubated with [35S]methionine and the pattern of protein synthesis in the cells was analyzed by SDS-PAGE and autoradiography. Analysis of the labeled proteins from cells exposed to UV-B radiation showed the induction of a 32 kD polypeptide and the loss of a 26 kD polypeptide compared with controls. Analysis of the proteins released by the UV-B irradiated cells into the culture medium revealed the 50% loss of a 37 kD radiolabeled protein compared with controls. The alteration of protein synthesis in lens epithelial cells by UV-B radiation may contribute to cataract formation.     

Long-term lens organ culture system to determine age-related effects of UV irradiation on the eye lens

Aging of the eye lens represents the life-long accumulation of damage. Factors responsible for age-related cataract are unknown because medical evaluations of aged populations demonstrate a wide range of systemic diseases and medical disorders. There are some main suspected factors, which may contribute to accumulated age-related damage in the eye lens. (1) Diseases, such as diabetes, substantially increase the probability of cataract formation in the age group from 40 to 49, and double or triple this probability for ages 50 to 69. (2) Drugs, including systemic medications such as steroids. (3) Environmental factors, such as UV radiation, heat and electromagnetic radiation. Our study represents an effort to determine the effects of suspected cataractogenic factors on the eye lens. The experiments are performed using a unique long-term lens organ culture system of bovine lenses. In our system it is possible to give controlled amounts of insult and monitor changes in lens optical quality throughout the culture period of 8-15 days. The optical properties, monitored in association with biochemical analysis of lens epithelium, cortex and nuclear samples, help in determining the mechanisms of cataract formation. The present study investigates mechanisms by which UV-A radiation at 365 nm causes damage to the lens. It is believed that solar radiation is one of the major environmental factors involved in lens cataractogenesis. Bovine lenses were placed in our special culture cells for pre-incubation of 24 hr followed by irradiation of 29 or 33 J cm(-2). The lenses were maintained in the cells during irradiation. After irradiation, lens optical quality was monitored throughout the culture period and lens epithelium was taken for enzyme analysis. Using the culture system we learned that: (a) young lenses (less than one-year-old) are less sensitive to UV radiation than 3-year-old lenses; (b) the lenses have the ability to recover in organ culture conditions; (c) applying the insult in one step results in less damage than dividing the same insult in 4 steps with 24 hr interval between each one; and (d) the damage from UV is greater if the intervals between each irradiation stage are insufficient to permit full recovery.     

Light conductance in the ocular lens

The collimated beam of a He-Ne laser aimed tangentially at the equator of submerged bovine or rabbit ocular lenses enters the lens and travels in the surface of the lens. We suggest that the effect is the result of light conductance along the interface between the bulk of the lens (including the lens epithelium on the anterior surface) as the medium of higher refractive index and the capsule as a medium of lower refractive index. Light conductance can be demonstrated in isolated lenses as well as in intact eyes. It is very sensitive to alterations of the state of the lens and therefore it may offer a new method to study very early stages of lens damage and cataract formation.     

Radiotherapy for age related macular degeneration causes transient lens transparency changes

AIM: Evaluation of potential side effects of photon radiotherapy on the transparency of the lens. METHODS: The anterior segments of 14 phakic eyes from patients suffering from subfoveal neovascularisation as a result of age related macular degeneration (AMD) were documented by Scheimpflug photography (Topcon SL-45, Kodak Tmax 400) before the start of radiotherapy as well as 6 and 12 months afterwards. All negatives were evaluated by microdensitometry, and peak heights for distinct layers of the lens were used for statistical comparison. External beam radiotherapy (6 MeV photons) consisted of a total dose of 20 Gy, delivered as 10 fractions of 2 Gy. RESULTS: Six and 12 months following irradiation statistical comparison of the ratios in density change of lenses from irradiated versus non-irradiated fellow eyes revealed statistically significant (p相似文献   

Induction of ultraviolet cataracts in vitro: prevention by pyruvate.

Ultraviolet (UV) radiation is one of the important cataract risk factors. The present studies examined the hypothesis that this effect is due to the UV penetration through the cornea and subsequent induction of a photochemical generation of reactive species of oxygen (ROS) in the aqueous and lens. The hypothesis was ascertained by rat lens organ culture studies conducted under UV (365 nm), with media containing micromolar levels of riboflavin, with and without pyruvate, the latter acting as an ROS scavenger. The implication of ROS in the UV-induced damage was confirmed by measurements of peroxide generation. Damage to the lens was assessed physiologically by measuring the decrease in its active transport of rubidium ions. Biochemically, it was assessed by measuring the lowering of adenosine triphosphate and glutathione. The incorporation of pyruvate in the medium protected the lens against these deleterious effects. That the beneficial effect of pyruvate is attributable to its ROS-scavenging property was proven by the peroxide depletion in its presence, commensurate with its own utilization in parallel. A protective effect of this keto acid against UV-induced tissue damage has been shown for the first time, suggesting its clinical usefulness against UV irradiation-induced pathologies. Hence, further studies on the possible protective effects of such alpha-keto acids against UV damage are in progress.     

紫外线辐射致白内障发生的研究现状

长期慢性的紫外线(UV)辐射被认为是老年性白内障形成的重要原因。皮质型和混合型白内障的发生与UV辐射关系密切。大量的流行病学研究表明,导致皮质型白内障发生的10%～30%相对危险因素可以归结于射线辐射。UV辐射,特别是UVB是皮质型白内障发生的重要危险因素。晶状体上皮细胞是晶状体代谢最活跃的部位,也是UV作用的重要靶组织。晶状体上皮细胞的过度凋亡以及晶状体蛋白损伤与白内障的发生、发展密切相关。     

小窝蛋白-1mRNA在紫外线诱导的大鼠白内障的晶状体中的表达及意义

目的研究紫外线照射对小窝蛋白-1mRNA在大鼠晶状体中的表达量的影响。方法50只大鼠的晶状体随机分为A组（对照组25只）,B组（UV照射组25只）于MEM培养液中培养8h。实验组：紫外线照射晶状体30min后,加入MEM培养液,于37℃下,置5％C02培养箱中培养,分别在加入培养液后〈1h、6h、12h、24h、48h时,应用荧光realtimelit-PCR技术检测晶状体中小窝蛋白-1的表达量,对照组不照射,与同等条件下用同样的方法检测小窝蛋白-1的表达量。结果紫外线照射30min后,测得的小窝蛋白-1mRNA表达水平随着时间的延长有逐渐下降的趋势（P〈0．05）。结论紫外线照射对鼠晶状体上皮细胞产生影响,并导致细胞小窝蛋白-1表达量减少,小窝蛋白-1的减少在氧化性白内障的发生中有一定作用,小窝蛋白-1在晶状体上皮细胞膜上的表达减少。推测小窝蛋白-1对维持白内障晶状体透明具有保护意义。     

Morphological and cell volume changes in the rat lens during the formation of radiation cataracts

Earlier studies in our laboratory showed that 24 hr after X-irradiation, epithelial cells of early postnatal rat lenses increased in volume. Three days after X-irradiation, the underlying lens fibers increased in volume. This finding suggested a correlation between damage to epithelial cell volume regulation and subsequent fiber cell swelling. To test this hypothesis 4-week-old rat lenses were three-dimensionally reconstructed to determine average cell volumes of specific lens regions and wet weights of whole lenses were measured during radiation cataract formation. In addition, the differentiation of epithelial cells into lens fibers was monitored by autoradiography. Four-week-old Sprague-Dawley rats were injected with [3H]-thymidine and, 24 hr later, their eyes were irradiated with either 400 or 1200 rad. Lenses were examined with a slit lamp and cataracts were graded on a scale of 1+ to 4+. Animals were killed 24 hr and 3, 5, 15 and 30 weeks after exposure. Lenses were serially sectioned at 0.75 micron and epithelial, equatorial and cortical fiber cell volumes were determined. Rats exposed to 400 or 1200 rad developed 0.5-1.5+ or 2.5-3.0+ cataracts, respectively, 10-16 weeks after X-irradiation. Epithelial and equatorial cells of both groups did not significantly increase in volume during this period. Three weeks after irradiation with 1200 rad cortical fibers were disorganized and had increased volume. By 5 and 15 weeks, cortical fibers had more normal cell volumes, although their morphology remained grossly altered. Cortical fiber volume of lenses irradiated with 400 rad were not significantly different from control lenses throughout the experimental period. By 15 weeks lenses irradiated with 400 rad showed subtle changes in morphology. Wet weight determinations indicated that the localized increase in cortical fiber volume did not result in an increase in the wet weight of the entire lens. Autoradiography showed that affected fibers had been epithelial cells at the time of X-irradiation. These results provide additional evidence that disturbances in fiber differentiation are involved with cataract formation, but do not support the initial hypothesis that a disturbance in epithelial cell volume regulation leads to fiber cell swelling. Earlier results suggesting defects in lens epithelial volume regulation in radiation cataract formation may have been complicated by ocular inflammation.     

近紫外线对培养兔晶状体损伤作用的研究

目的 观察近紫外照射下体外培养的兔昌状体超微形态学变化，以探讨光氧化作用下白内障的发生发展机理。方法 利用近紫外线混合光源距体外培养４８ｈ的兔晶状体５０ｃｍ处，照射１０ｍｉｎ，与对照组比较，观察其上皮细胞超微结构的变化。结果 近紫外线照射后，实验组晶状体上皮细胞的核染色质凝结，细胞膜性结构破坏、消失，甚至细胞死亡。对照组无变化。结论 短时间、近距离、高强度的近紫外线照射，对晶状体上皮细胞有明显损伤作用。     

Cataracts and avionic radiations.

Nine cases of hertzian radiation cataracts are reported among personnel working in operational aviation environments, where they were irradiated repeatedly at subliminal non-thermal field intensities. The resultant ocular pathology evolved insidiously and slowly over a period of years in a similar way to other forms of radiational injury. By the time of consultation examination, all had progressed to a relatively late state, exhibiting not only capsular cataract but also vesiculation and opacification of the proximal subcapsular lens substance. In addition to the ocular dangers of chronic exposure to nonionising radiation reference is made to the nonthermal effect or the radiation effect per se, as this could relate to general health--for example, as a possible previously unsuspected aetiological or contributory factor in many other disease processes.     

Ascorbic acid and the eye lens

Exposure of mice to hyperbaric oxygen leads to an inhibition of the mitotic activity in the germinative epithelium of the lens. This is followed by an eventual development of cataracts. Cataracts have also been observed in human beings treated with hyperbaric oxygen for different afflictions. The lens damage and cataract formation appears to be due to in situ generation of active radicals and other active species of oxygen. These oxygen derivatives may also contribute to the multifactorial process of senile cataract formation in human beings. This hypothesis is based on in vitro experiments with rat lenses cultured in medium generating oxygen radicals, the generation of the radicals being accomplished either photochemically or enzymatically. The ability of the lens to transport rubidium and amino acids from such a medium is adversely affected. This is a recognized index of the damage to the tissue physiology. Scavengers of active oxygen species have been found to protect against this damage. Ascorbate, present in concentrations similar to that in the primate aqueous and lens, is also protective. The studies, therefore, point to an antioxidant and perhaps an anti-cataract effect of ascorbate. Pyruvate is another agent useful in this regard.     

Cataracts induced by microwave and ionizing radiation

Microwaves most commonly cause anterior and/or posterior subcapsular lenticular opacities in experimental animals and, as shown in epidemiologic studies and case reports, in human subjects. The formation of cataracts seems to be related directly to the power of the microwave and the duration of exposure. The mechanism of cataractogenesis includes deformation of heat-labile enzymes, such as glutathione peroxide, that ordinarily protect lens cell proteins and membrane lipids from oxidative damage. Oxidation of protein sulfhydryl groups and the formation of high-molecular-weight aggregates cause local variations in the orderly structure of the lens cells. An alternative mechanism is thermoelastic expansion through which pressure waves in the aqueous humor cause direct physical damage to the lens cells. Cataracts induced by ionizing radiation (e.g., X-rays and gamma rays) usually are observed in the posterior region of the lens, often in the form of a posterior subcapsular cataract. Increasing the dose of ionizing radiation causes increasing opacification of the lens, which appears after a decreasing latency period. Like cataract formation by microwaves, cataractogenesis induced by ionizing radiation is associated with damage to the lens cell membrane. Another possible mechanism is damage to lens cell DNA, with decreases in the production of protective enzymes and in sulfur-sulfur bond formation, and with altered protein concentrations. Until further definitive conclusions about the mechanisms of microwaves and ionizing radiation induced cataracts are reached, and alternative protective measures are found, one can only recommend mechanical shielding from these radiations to minimize the possibility of development of radiation-induced cataracts.     

UV-mediated cataractogenesis: A radical perspective

A number of epidemiologic and experimental studies indirectly support the idea that solar ultraviolet radiation may be cataractogenic. However, the physical and cellular processes which might be involved in such cataractogenesis are by no means clear. Because a major consequence of the UV irradiation of oxygenated organic matter is the production of activated oxygen species, the involvement of oxidants has been suspected to be of importance. However, because the lens may normally exist in an hypoxic or even anoxic environment, the extent of availability of oxygen for such reactions is presently unknown. So also are the possible mechanisms through which putative UV damage of the lens might eventuate in cataract. In addition to possible rapid and direct lethal damage to lens epithelium, possible cumulative damage to both lenticular DNA and proteins may occur. Furthermore, UV radiation has the potential to photolytically destroy light-sensitive nutrients and to generate damaging oxidants through interaction with ferruginous compounds. Given that Nature has probably provided the lens with substantial protective devices to ward off damaging effects of UV light, it is still an open question as to whether solar radiation contributes to cataract formation and, if so, by what mechanisms.     

实验性电离辐射白内障及其微量元素研究

采用20Gy~(60)Coγ射线一次性照射新西兰幼兔双眼,动态观察了兔眼电离辐射损伤后的全身反应及眼部改变,着重探讨电离辐射白内障的形态特点、房水性状及房水、晶体、玻璃体、虹膜睫状体和血清的微量元素变化。结果表明,照射后第11周实验组动物全部发生典型的辐射性白内障,且晶体和血清处于明显的低锌高铜状态,房水锌铜显著降低,玻璃体和虹膜睫状体的锌铜显著增高。作者提出电离辐射白内障时晶体锌铜反向代谢途径假说。     

UV-mediated cataractogenesis: A radical perspective

A number of epidemiologic and experimental studies indirectly support the idea that solar ultraviolet radiation may be cataractogenic. However, the physical and cellular processes which might be involved in such cataractogenesis are by no means clear. Because a major consequence of the UV irradiation of oxygenated organic matter is the production of activated oxygen species, the involvement of oxidants has been suspected to be of importance. However, because the lens may normally exist in an hypoxic or even anoxic environment, the extent of availability of oxygen for such reactions is presently unknown. So also are the possible mechanisms through which putative UV damage of the lens might eventuate in cataract. In addition to possible rapid and direct lethal damage to lens epithelium, possible cumulative damage to both lenticular DNA and proteins may occur. Furthermore, UV radiation has the potential to photolytically destroy light-sensitive nutrients and to generate damaging oxidants through interaction with ferruginous compounds. Given that Nature has probably provided the lens with substantial protective devices to ward off damaging effects of UV light, it is still an open question as to whether solar radiation contributes to cataract formation and, if so, by what mechanisms.     

Nerve growth factor (NGF) and lenses: effects of NGF in an in vitro rat model of cataract

Background The aims of this study are to investigate the presence and production of nerve growth factor (NGF) in the rat lens in basal conditions and to evaluate, in vitro, the role of NGF in a model of xylose-induced cataract.Methods Rat lenses were dissected and the expression of NGF, NGF mRNA and high-affinity NGF-receptor (TrkA) was evaluated by immunohistochemistry, immunoenzymatic assay (ELISA) and in-situ hybridization (ISH) techniques. To investigate the role of NGF in cataract formation we used an in vitro model of sugar-induced cataract by culturing rat lenses for 48 h in Eagle's minimum essential medium (MEM) supplemented with xylose. To evaluate the potential protective effect of NGF on xylose-induced cataract formation, exogenous NGF at different concentrations or antibodies neutralizing endogenous NGF (NGF-Ab) or aspecific antibodies were added to xylose-cultured lenses, and the following cataract-related parameters were evaluated and compared to xylose-treated lenses. Cataract formation was evaluated using three different parameters: staging of the cataract by lens photography, quantification of lens transparency in terms of gray level medium (GLM) and evaluation of the hydration percentage (H%) of the lens. To investigate the role of endogenous NGF in cataract onset, NGF levels were evaluated and compared in lenses cultured in xylose supplemented medium versus lenses cultured in control culture medium.Results The epithelium from fresh rat lenses expresses NGF-receptor, NGF protein and NGF-mRNA. NGF levels in fresh lens were 54.0±24.5 pg/g as quantified by ELISA. Xylose-cultured lenses develop cataract changes, including a decrease of GLM and an increase in hydration percentage, associated with a decrease in NGF levels when compared to lenses cultured in the control culture medium. The addition of NGF to xylose-cultured lenses reduces cataract formation, increasing GLM and decreasing the hydration percentage as compared to xylose-treated lenses. On the other hand, the addition of NGF-Ab induces an increase in cataract formation and lens hydration.Conclusions This study demonstrates that rat lens epithelium expresses and synthesizes NGF. Moreover, immunohistochemistry shows that lens epithelial cells also express the NGF receptor. Although the functional significance of TrkA on lens epithelium is at present not clear, the expression of NGF and its high-affinity receptor on the same cells together with our experimental results suggest that NGF is involved in supporting trophism and/or the function of the lens epithelium.     

In vivo studies on the effect of UV-radiation on the eye lens in animals

Ultraviolet light is a non-ionizing radiation that induces photochemical reactions in the tissue. Its spectral A and B ranges are partially absorbed by the cornea and/or lens thus causing damage on the cellular, cell physiological and molecular level. UV-A does not seem to damage the cornea permanently and its effects in the lens have a very prolonged latency period. Typical reactions of the cornea are oedema, punctate keratitis (photoelectric keratitis) and neovascularization. In the lens all reactions that could be evidenced, were located in the epithelium and in the outer cortical fiber cells.In vivo UV-A induces swelling and slight vacuolation of the anterior suture system, but apart from these transient effects, only very limited permanent damage could be demonstrated. UV-B induces the formation of an anterior subcapsular cataract, starting also with vacuolation of the suture system. These morphological characteristics can be visualized at the slitlamp microscope. Histologically, sutural irregularities (UV-A) and epithelial hyperplasia with capsular multiplication (UV-B) as well as desintegration of the anterior suture system could be observed. Patho-physiologically, a reduction of lens fresh weight (UV-B) as well as changes of the equilibrium of reduced and oxidized glutathione (GSH/GSSG) could be demonstrated. On the protein-biochemical level, changes in the ratio of water-soluble versus water-insoluble protein could be evidenced, as well as effects on specific crystallin fractions, namelyα-crystallin. In addition, the appearance of a newly synthetized 31 kDa protein could be demonstrated in UV-B irradiated mice.     

DNA damage in lens epithelium of cataract patients in vivo and ex vivo

Purpose: DNA damage has been described in the human cataractous lens epithelium, and oxidative stress generated by UV radiation and endogenous metabolic processes has been suggested to play a significant role in the pathogenesis of cataract. In this study, the aim was to explore the quality and relative quantity of DNA damage in lens epithelium of cataract patients in vivo and after incubation in a cell culture system. Methods: Capsulotomy specimens were analysed, before and after 1 week of ex vivo cultivation, using the comet assay to measure DNA strand breaks, oxidized purine and pyrimidine bases and UV‐induced cyclobutane pyrimidine dimers. Results: DNA strand breaks were barely detectable, oxidized pyrimidines and pyrimidine dimers were present at low levels, whereas there was a relatively high level of oxidized purines, which further increased after cultivation. Conclusion: The observed levels of oxidized purines in cataractous lens epithelium may support a theory consistent with light damage and oxidative stress as mediators of molecular damage to the human lens epithelium. Damage commonly associated with UV‐B irradiation was relatively low. The levels of oxidized purines increased further in a commonly used culture system. This is of interest considering the importance and versatility of ex vivo systems in studies exploring the pathogenesis of cataract.     

Cataractogenesis after Repeat Laser in situ Keratomileusis

There has been the unsubstantiated clinical impression that laser refractive surgery accelerates cataract development along with solid experimental data about the cataractogenic effects of excimer laser treatment. We present the first documented case of significant cataract formation in a young myope after repeat excimer laser ablation necessitating phacoemulsification with a posterior chamber implant. Proposed explanations include focusing of the ablation wave on the posterior capsule (acoustic wave lens epithelial damage), photooxidative stress of the lens (ultraviolet and inflammatory oxidative stress), and corticosteroid-induced cataract (lens toxicity).Key Words: Photorefractive keratectomy, Excimer laser, Cataract, Cataractogenesis, Ultraviolet radiation, Oxidative stress, Refractive surgery complication