汉防己甲素对兔眼毒性作用的初步研究

目的 运用描述性毒理学初步探讨汉防己甲素(tetrandrine,Tet)对兔眼的毒性作用.方法 健康新西兰大耳白兔30只,随机分为4组,1 g·L-1组、3 g·L-1组、9 g·L-1组及正常对照组,模拟临床连续用药3个月.进行急性眼刺激性实验,临床裂隙灯观察,A超测量角膜厚度,考马斯亮兰测房水蛋白浓度,角膜内皮细胞茜素红台盼兰联合染色及组织病理学和透射电镜检查.结果 1 g·L-1、3 g·L-1 Tet对眼均无刺激性;9 g·L-1 Tet有轻度刺激性.临床裂隙灯观察,1 g·L-1组眼前节正常,3 g·L-1、9 g·L-1组出现不同程度角膜水肿,9 g·L-1组出现明显炎症反应.1 g·L-1组与正常对照组比较,角膜厚度、房水蛋白含量、角膜内皮细胞活性率均无显著性差异(P>0.05);3 g·L-1、9 g·L-1组与正常对照组比较,角膜厚度、房水蛋白含量显著增加,内皮细胞活性率显著降低(P<0.05).组织病理及超微结构检查示:1 g·L-1组无病理及超微结构改变;3 g·L-1组可见角膜水肿,睫状体上皮水肿,晶状体上皮细胞胞核出现核沟;9 g·L-1组可见角膜上皮细胞、角膜细胞和内皮细胞水肿、变性、坏死,虹膜和睫状体上皮细胞水肿,晶状体上皮细胞胞质出现半透明空化区,线粒体肿胀.结论 Tet的浓度、用药时间与刺激性及毒性呈正相关,1 g·L-1浓度Tet对眼组织无刺激性、毒性,应可安全应用于眼部.     

Effect of permeation enhancers on beta-endorphin systemic uptake after topical application to the eye.

Solutions of human beta-endorphin were applied topically to the eyes of rabbits. Atrial blood was collected and plasma beta-endorphin was assayed using a Nichols Diagnostics radioimmunoassay kit. Levels peaked rapidly (within 10-20 min) at greater than 5 ng/ml with 1% beta-endorphin and no enhancer, and then returned to background within 2 h. When the permeation enhancers Brij-78 or BL-9 were added to the formulation applied topically, plasma levels were elevated above 30 ng/ml and remained elevated above 1 ng/ml over 1 h. Plasma levels were actually higher after topical application using either enhancer than after intravenous injection at the collection points of 45 min and later. The data suggest that topical application to the eyes can be an efficacious method of systemic delivery of peptide drugs.     

Corneal concentration and systemic absorption of cyclosporin-A following its topical application in the rabbit eye.

To ascertain the corneal storage and the possible systemic absorption of 2% cyclosporin-A (CsA) eyedrops, the authors studied, by RIA with monoclonal specific antibodies, the corneal and blood levels of the drug following its topical administration on healthy albino rabbit eyes. When topical CsA was administered following a low-dose application schedule [such as a single dose of 100 microliters every 12 h for 5 days (group 1)], CsA corneal levels of 260.8 +/- 59.8 ng/ml and blood levels of 55.67 +/- 24.4 ng/ml (expressed as means +/- SD) were achieved. These levels significantly increased to 1,111.27 +/- 449.4 ng/ml (p > 0.0001) and 88.66 +/- 59.7 ng/ml (p > 0.05), respectively, when a higher dosage was used [100 microliters every 6 h for 10 days (group 2)]. It is shown that a dose-dependent corneal concentration of CsA, due to a cumulative effect, is achieved in the intact rabbit cornea following topical application of the drug. Systemic absorption of CsA, although irregular, does exist. Therefore, when using topical 2% CsA as in this study, a systemic effect of the drug (especially in low weight animals) should be considered when analyzing the results of topical application.     

Systemic and intraocular uptake of spantide, a tachykinin antagonist, following topical application to the rabbit eye.

Previous observations have indicated that topical application to the rabbit eye of tachykinin antagonists, including spantide, effectively prevents the miosis and the disruption of the blood-aqueous barrier consequent to ocular injury. The present study shows that spantide is taken up into the rabbit eye following topical application. This was established by determination of spantide in the aqueous humor by radioimmunoassay. The concentrations reached in the aqueous humor were those that could be expected to block tachykinin receptors. The elimination of spantide from the aqueous humor was found to be slow. From HPLC analysis it seemed that spantide in the aqueous humor is degraded to smaller products, predominantly spantide 5-11. Some of the topically applied peptide appeared in the general circulation. Here the rate of elimination was rapid by comparison. Very small amounts of spantide appeared in the cerebrospinal fluid after intravenous injection.     

Cyclodextrins in eye drop formulations: enhanced topical delivery of corticosteroids to the eye

Cyclodextrins are cylindrical oligosaccharides with a lipophilic central cavity and hydrophilic outer surface. They can form water-soluble complexes with lipophilic drugs, which 'hide' in the cavity. Cyclodextrins can be used to form aqueous eye drop solutions with lipophilic drugs, such as steroids and some carbonic anhydrase inhibitors. The cyclodextrins increase the water solubility of the drug, enhance drug absorption into the eye, improve aqueous stability and reduce local irritation. Cyclodextrins are useful excipients in eye drop formulations of various drugs, including steroids of any kind, carbonic anhydrase inhibitors, pilocarpine, cyclosporins, etc. Their use in ophthalmology has already begun and is likely to expand the selection of drugs available as eye drops. In this paper we review the properties of cyclodextrins and their application in eye drop formulations, of which their use in the formulation of dexamethasone eye drops is an example. Cyclodextrins have been used to formulate eye drops containing corticosteroids, such as dexamethasone, with levels of concentration and ocular absorption which, according to human and animal studies, are many times those seen with presently available formulations. Cyclodextrin-based dexamethasone eye drops are well tolerated in the eye and seem to provide a higher degree of bioavailability and clinical efficiency than the steroid eye drop formulations presently available. Such formulations offer the possibility of once per day application of corticosteroid eye drops after eye surgery, and more intensive topical steroid treatment in severe inflammation. While cyclodextrins have been known for more than a century, their use in ophthalmology is just starting. Cyclodextrins are useful excipients in eye drop formulations for a variety of lipophilic drugs. They will facilitate eye drop formulations for drugs that otherwise might not be available for topical use, while improving absorption and stability and decreasing local irritation.     

眼科局部用药的毒性反应分析

临床工作中可遇到长期使用或滥用眼药水后导致的眼部毒性反应,如引起眼部不适,泪膜不稳定,结膜炎[1],结膜上皮细胞的调亡,角膜表面损伤等。其中较常见的是使用抗生素和抗青光眼药后,本文就这一常见的临床现象从其药物毒性的表现,以及分析其最可能的原因和提出一些可行的解决方法等方面进行综述,以期对临床工作有所帮助。     

Ultrastructural and immunohistochemical study on the effect of topical cyclosporin A in the rabbit eye

The effect of topically administered cyclosporin A (CyA) was evaluated in this experimental study by means of transmission and scanning electron microscopy, and immunohistochemistry. CyA dissolved in sterile olive oil was injected in the retrobulbar area and in the subconjunctival space, or administered as eyedrops in both non-grafted and corneal xenografted rabbit eyes. The vehicle rather than the drug was thought to be responsible for the inflammatory reaction observed in the conjunctiva of the injected eyes as well as for the surface epithelial defects developing in the cornea of the topically administered eyes. CyA was found to be effective in prolonging the survival of the xenografts after 1 month follow-up. The immunohistochemistry indirectly demonstrated the CyA effectiveness in impairing the T-cell function, and this is, to our knowledge, the first documented report on this subject. We conclude that another type of vehicle for the drug has to be introduced and that the administration of CyA as eyedrops is the best route to provide fast diffusion and to avoid adverse side effects.     

Distribution of a steroid antagonist in the eye following topical administration

The distribution of a steroid antagonist, RU486, that is known to reduce rabbit intraocular pressure has been examined in the eye. On an equal tissue weight basis, the corneal epithelium is the site of maximal absorption followed by conjunctival tissues (bulbar and palpebral) and the rest of the cornea. Aqueous humor concentrations of drug vary between 5 X 10(-6) and 5 X 10(-8) at 1 and 24 hours, respectively: these concentrations have been shown by others to inhibit dexamethasone binding to rat thymocytes, and are sufficient to act as an antagonist at steroid receptors in the eye. Multiple drop administration for 10 days (3 drops per day) revealed no accumulation in the treated eye, but did show the presence of drug in the untreated contralateral eye that could explain the contralateral pharmacological effect seen on intraocular pressure after several days of treatment.     

拷贝数变异及其在眼病分子遗传学研究中的应用

拷贝数变异(CNV)是人类基因组内大于1kb的DNA片段拷贝数的异常变化,它广泛存在于正常个体,可能是人类表型变异的重要原因之一,是研究包括眼病在内的人类疾病的热点.目前认为CNV的形成机制可能是非等位基因同源性重组和非同源末端连接等所致.本文对CNV的多态性与表型变异、形成机制、检测方法及其在青光眼、白内障、虹膜发育不良、葡萄膜黑色素瘤、X-连锁眼白化病等眼病分子遗传学中的应用进行综述.     

Lack of toxicity of a topical recombinant interferon alpha

We evaluated the potential ocular surface toxicity of a recombinant interferon-alpha (IFN alpha) preparation on rabbit eyes. Topical application of this interferon (1 x 10(6) U/day in each eye) for 6 weeks produced no discernible conjunctival or corneal abnormalities on clinical, histopathologic, or ultrastructural evaluations. We believe that this recombinant IFN alpha preparation is not toxic to the ocular surface of rabbits.     

Pharmacological effects of topical timolol in the rabbit eye

The ability of timolol to act as a beta-adrenergic antagonist in the cornea and in the iris--ciliary body of albino rabbits is reported. In vitro, timolol potently blocks the isoproterenol-stimulated synthesis of cAMP. In the iris-ciliary body, the apparent inhibition constant (K1) for timolol is 0.6 nM, indicating that timolol is approximately seven times more potent than propranolol. Topical timolol (0.5% and 4%) rapidly inhibits the beta-adrenergic--stimulated synthesis of cAMP in both corneal and iris--ciliary body tissues. Within 3 hr, however, the iris--ciliary body tissue regains its ability to produce large amounts of cAMP when challenged in vitro with isoproterenol. The washout of timolol from corneal tissue is more protracted. Intraocular pressure measurements by anterior chamber cannulation of anesthetized rabbits indicate that topical timolol (0.5% and 4%) has no significant influence on intraocular pressure. These concentrations of timolol significantly decrease heart rate but do not affect femoral arterial blood pressure. Because of the marked potency of timolol clinically, we conclude that the effects of the drug in the rabbit do not completely account for its therapeutic efficacy in humans, which must depend on more complex pharmacological actions.     

Pharmacokinetic of topical cyclosporin A in the rabbit eye

3H labelled cyclosporin A (CS-A) eye drops (2% in castor oil) were applied in rabbits. When a single drop of 10 microliters was given CS-A reached a maximal concentration of 900-1400 ng/ml in the cornea 6 hr after application and then slowly decreased. A substantial level of 600-900 ng/ml was still present after 48 hr. When corneas were analysed for their cellular compartments, 67% of CS-A was found in the epithelium, 25% in the stroma (probably in keratocytes), and 8% in the endothelium. In corneas denervated by circular keratotomy, slightly reduced concentrations were found after surgery, the reduction was not therapeutically significant. Using the HPLC method a significant corneal metabolism of CS-A could be excluded. Scleral concentrations of CS-A as high as 180 ng/ml were found. Concentrations of CS-A in aqueous humor, lens, vitreous body and uvea/retina were below the therapeutic range.     

Effect of topical chemical irritation on the blood-aqueous barrier of the rat eye

The effect of topical neutral formaldehyde on the blood-aqueous barrier of the rat was studied. Thirty minutes after irritation, the protein concentration of the aqueous humour had increased from the control value of 1.95 +/- 0.25 to 2.95 +/- 0.45 mg/ml (p less than 0.05). Extravasation of Evans blue dye from the iris vessels after irritation could be demonstrated by fluorescence microscope. These changes could be eliminated by prior denervation of the trigeminal sensory nerve. The present work demonstrates that the eye of the rat responds to topical chemical irritation. This response is dependent on sensory innervation.     

氢气的细胞保护作用及其在眼病的应用研究

氢气的还原性能及其医学价值近期引发人们重视.氢气可特异性中和羟自由基和过氧亚硝基阴离子,发挥选择性抗氧化作用.氢气的抗炎症特性可能与多种信号通路相关,它可抑制肿瘤坏死因子-α、促分裂原活化蛋白激酶家族和核因子-κB信号通路来减少炎性介质释放以及炎症细胞趋化,发挥抗炎症作用.氧化应激和炎症反应是多数眼病的共有致病机制,其中氧自由基、炎症因子是介导细胞损伤的重要介质.氢气浓度为0.6 mM的富氢盐水持续点眼或腹腔注射治疗可有效抑制实验动物眼部组织氧化水平,改善缺血再灌注损伤、兴奋性毒性以及糖尿病所致的视网膜退行性改变,抑制碱烧伤导致的角膜新生血管化.氢气治疗作用及其分子机制的深入研究有望为眼病治疗带来新的希望.     

关注滴眼剂的眼表毒性

滥用滴眼剂所致的眼表毒性常被忽视。其临床表现多为非特异性,易与其他原因引起的眼表疾病相混淆。不同滴眼剂所致眼表毒性的发病机制不尽相同。临床眼科医师应关注滴眼剂对眼表的毒性作用,并预防和治疗滴眼剂对眼表的毒性损害。