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Caffeic acid phenethyl ester to inhibit posterior capsule opacification in rabbits
Caffeic acid phenethyl ester to inhibit posterior capsule opacification in rabbits Ibrahim F. Hepsen, MD, Huseyin Bayramlar, MD, Ahmet Gultek, PhD, Suleyman Ozen, MD, Fikret Tilgen, MD, Cem Evereklioglu, MD
ABSTRACT Purpose: To assess whether caffeic acid phenethyl ester (CAPE) prevents posterior capsule opacification (PCO) by suppressing the transformation of the lens epithelial cells. Setting: Departments of Ophthalmology, Chemistry, and Pathology, Turgut Ozal Medical Center, University of Inonu, Malatya, Turkey. Methods: Twenty pigmented island rabbits having phacoemulsification in their right eyes were randomized into two groups. In Group 1, 10 ~g/ml of CAPE was added to the anterior chamber irrigating solution and a 1% solution of CAPE was injected subconjunctivally for 3 weeks postoperatively. The irrigating solution in Group 2 (control) did not include CAPE. The development of PCO was assessed weekly and its density was graded by slitlamp biomicroscopy. Histologic analysis was performed 3 months after surgery. Results: Group 1 had clear capsules or minor PCO. Group 2 developed more severe PCO or complete opacification. The difference between the two groups was statistically significant (P = .04). Conclusion: These preliminary results indicate that CAPE is effective in suppressing
pea
in pigmented rabbits and may be beneficial in clinical use in humans
because it has no documented harmful effects on normal cells. J Cataract Refract Surg 1997; 23: 1572-1576
P
osterior capsule opacification (PCO) is a significant long-term complication and the most frequent cause of decreased visual acuity after extracapsular cataract extraction (ECCE) and intraocular lens (IOL) implantation. It results from the proliferation, migration, and metaplasia of residual lens epithelial cells (LECs).1 After ECCE, LECs become activated and transform into fibroblasts and myofibroblasts. z-7 From the Departments of Ophthalmology (Hepsen, Bayramlar, Tilgen, Evereklioglu), Chemistry (Gultek), and Pathology (Oun), Turgut Ozal Medical Center, University ofInonu, Malatya, Turkey. Reprint requests to Ibrahim E Hepsen, MD, Department of Ophthalmology, Turgut Ozal Medical Center, University of Inonu, 44280 Malatya, Turkey. 1572
Caffeic acid phenethyl ester (CAPE), the active component of the propolis produced by honeybees in their hives, selectively inhibits the growth of several virus-transformed and oncogene-transformed fibroblasts and carcinoma cell lines but not the normal cells. 8- 10 This study assessed whether intracameral and subconjunctival administration of CAPE suppresses LEC proliferation and transformation and thus prevents PCO in rabbits having phacoemulsification.
Materials and Methods Twenty pigmented island rabbits weighing 2.0 to 2.5 kg were randomly divided into two groups. Each
] CATARACT REFRACT SURG--VOL 23, DECEMBER 1997
CAFFEIC ACID PHENETHYL ESTER INHIBITION OF PCO
group comprised 10 eyes in 10 rabbits. In Group 1, CAPE (10 f,.Ig/mL) , synthesized using the technique described by Grunberger et al.,s was added to the anterior chamber irrigating solution of balanced salt solution (BSS® Plus). Group 2 eyes (controls) had surgery by the same technique but without CAPE in the irrigating solution. All the surgeries were performed by one surgeon (H.B.) skilled in phacoemulsification and familiar with the phaco machine used. The surgeon was masked as to the treatment group. The right eye in each animal was prepared for cataract surgery. The animals were anesthetized with ketamine hydrochloride (Ketalar®) 35 mg/kg and xylazine (Rompun®) 10 mg/kg given intramuscularly. Pupils were dilated with tropicamide 0.5% and phenylephrine hydrochloride 10%. After the ocular area was disinfected with povidone-iodine, the lids were retracted with a wire lid speculum. A clear corneal incision was made with a 3.2 mm keratome. A small, round anterior capsulorhexis was performed with a capsule forceps; its approximate diameter was 5.0 to 6.0 mm. A phacoemulsification tip (Performa, Ophthalmed) was inserted through the corneal wound, and the nucleus was removed by the chip and flip technique using an ultrasound power of 70%, aspiration flow rate of 16 to 20 minI cc, and vacuum of 100 to 120 mm Hg. Care was taken to irrigate and aspirate all cortical material. The corneal incision was closed with a single 10-0 nylon suture. Gentamicin and dexamethasone were injected subconjunctivally at the end of the surgery. Postoperatively, the eyes having surgery were treated with topical prednisolone acetate and tobramycin four times a day and atropine sulfate once a day for 3 weeks. A 1% solution of CAPE (0.4 cc) was also injected subconjunctivally every 3 days for 3 weeks in Group 1 eyes. The development of PCO was assessed weekly for 3 months by slitlamp biomicroscopy. One person (I.F.H.), masked as to treatment group, performed all slitlamp examinations. At the final examination, PCO was graded on a scale of 0 to 3: 0 = clear, no visible proliferative tissue on the peripheral or central posterior capsule; 1 = mild, proliferative tissue in peripheral area only; 2 = moderate, sparse proliferative tissue on both
the peripheral and central capsules; 3 = dense, diffuse and thick opacification on the entire capsule. The rabbits were killed and their eyes enucleated for histologic examination at the end of 3 months. One eye in Group 2 had a posterior capsule rupture during phacoemulsification, and one rabbit in each group died. Therefore, one eye in Group 1 and two in Group 2 were excluded from evaluation. The Mann-Whitney U-test was used for statistical analysis.
Results In four eyes in Group 1 and two in Group 2, the anterior capsulorhexis was unsuccessful but the posterior capsules were intact. Mean phacoemulsification time was 163.33 seconds ± 51.65 (SO) in Group 1 and 171.42 ± 63.88 seconds in Group 2. In Group 1, mean total irrigation time with the BSS Plus containing CAPE was 3.76 ± 1.37 minutes. One week postoperatively, the corneal area around the incision was relatively edematous in all eyes. Inflammatory membrane and a small cortical remnant in the anterior chamber were seen in three eyes in both groups. Posterior capsules were biomicroscopically clear in all eyes. Two weeks postoperatively, the anterior chambers and corneas were clear. At the slitlamp, the regenerating lens tissue was first seen as fern- or crystalline-shaped striae. The striae on the posterior capsule became more evident 3 weeks postoperatively. Biomicroscopic findings of the posterior capsule almost remained stable from 4 weeks to 3 months postoperatively.
., w
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.o
w
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_
"z DENSITY
OF
peo
Figure 1. (Hepsen) Formation of peo 3 months postoperatively.
J CATARACT REFRACT SURG-VOL 23, DECEMBER 1997
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CAFFEIC ACID PHENETHYL ESTER INHIBITION OF PCO
Figure 2. (Hepsen) Left: In this Group 2 eye with clinically graded dense pea, LEes have proliferated in the equatorial region (light micrograph; anterior lens surface is at the top) (hematoxylin and eosin x 100). Right: Light micrograph of the two layers of proliferative cells (cuboidal posteriorly and columnar anteriorly) on the central posterior capsule (anterior surface of posterior lens capsule is at the top) (hematoxylin and eosin x 200).
Figure 1 shows the results ofbiomicroscopic examination at the end of the third month. No eye in Group 1 developed dense PCO, although seven developed mild to moderate PCO. In Group 2, no eye had a clear capsule, and mild to moderate PCO was seen in six eyes. Although there was an overlap in the distribution of PCO density between the two groups (Figure 1), the difference was statistically significant (U = 16.0; P = .04). Histologic examination of the posterior capsule showed that the monolayers and multilayers of the regenerated LECs proliferated and migrated along the
Figure 3. (Hepsen) Light micrograph of a Group 1 eye clinically graded as having moderate pea shows a proliferated epithelial cell line with poor regenerative quality on the central posterior capsule surface (anterior surface of posterior lens capsule is at the top) (hematoxylin and eosin x 200). 1574
capsular surface toward the equatorial region and posterior capsule in eyes with PCO scores of 2 (moderate) and 3 (dense) (Figures 2 and 3). There was no proliferative activity on the posterior capsule surfaces and equatorial zones in the eyes clinically graded as clear (Figure 4).
Discussion Posterior capsule opacification is a common postoperative complication of ECCE with IOL implantation. If visual acuity is markedly reduced, a neo-
Figure 4. (Hepsen) No epithelial cell proliferation was seen in the equatorial region of lens capsule in this Group 1 eye clinically graded as clear (light micrograph; anterior lens surface at the top) (hematoxylin and eosin x 200).
J CATARACT REFRACT SURG-VOL 23, DECEMBER 1997
CAFFEIC ACID PHENETHYL ESTER INHIBITION OF PCO
dymium:YAG laser capsulotomy may be necessary. Various pharmacologic agents (antimetabolites), including 5-fluorouracil,11 mitomycin,12 methotrexate, 13 daunomycin,14 and colchicine,15 have been used experimentally with the aim of irreversibly damaging residual LECs and thus preventing PCO.1 Propolis, a natural hive product produced by honeybees, has strong antimicrobial,I6-19 anti-inflammatory, 17,20,21 antioxidant,22-24 and antineoplastic activity.8,10,25,26 Flavanoids and CAPE, the two active components of propolis extract, may be responsible for most of these biologic activities. 22 ,23 It has been shown that CAPE is a selective growth suppressor with differential cytotoxic effects on virus- and oncogene-transformed rat and human fibroblasts and several cancer cell lines at the stage of progression of the transformed state, but not on the normal rat and human fibroblasts. 8- 1O Chiao et al. 9 found that CAPE blocked cell proliferation in nontumorogenic rat embryo fibroblasts and caused cell death by inducing apoptosis in adenovirustransformed fibroblasts. They suggested that CAPEassociated growth inhibition might be related to the effect on oxidative processes induced by mitogenic stimuli. These observations support the concept that the transformed phenotype is specifically sensitive to CAPE.27 We hypothesized that CAPE would effectively inhibit PCO by its antiproliferative and cytotoxic effects on transformed LECs. To our knowledge, this is the first study to adapt these effects of CAPE in an attempt to prevent PCO by damaging the residual LECs as they begin to transform into fibroblasts. Postoperatively, the regenerative activity of residual LECs begins within days in the rabbit,28 and the intraoperative use of CAPE alone may not be sufficient to prevent it. Therefore, to provide additional antiproliferative effect on residual LECs postoperatively, subconjunctival injections of CAPE were given. In this study, we investigated the preventive effect of CAPE on PCO and found it effective in reducing PCO after phacoemulsification in pigmented rabbits. Our preliminary results are encouraging. We believe that better results can be obtained by determining the optimal application route and adjusting the dosage. In addition, CAPE may be beneficial in humans as it has no known harmful effects on normal, nonproliferative cells.
References 1. Apple OJ, Solomon KD, Tetz MR, et al. Posterior capsule opacification. Surv Ophthalmol 1992; 37:73116 2. Hara T, Azuma N, Chiba K, et al. Anterior capsular opacification after endocapsular cataract surgery. Ophthalmic Surg 1992; 23:94-98 3. Zhu ZR. Pathogenesis of posterior capsular opacification after extracapsular cataract extraction. Chung-Hua Yen Ko Tsa Chih 1990; 26:298-300 4. Ishibashi T, Araki H, Sugai S, et al. Histopathologic study of anterior capsule opacification in pseudophakic eyes. Nippon Ganka Zasshi 1993; 97:460-466 5. Kappelhof JP, Vrensen GF. The pathology of aftercataract; a minireview. Acta Ophthalmol Suppl 1992; 205:13-24 6. McDonnell PJ, Stark WJ, Green WR. Posterior capsule opacification: a specular microscopic study. Ophthalmology 1984; 91:853-856 7. McDonnell pJ, Zarbin MA, Green WR. Posterior capsule opacification in pseudophakic eyes. Ophthalmology 1983; 90:1548-1553 8. Grunberger 0, Banerjee R, Eisinger K, et al. Preferential cytotoxicity on tumor cells by caffeic acid phenethyl ester isolated from propolis. Experientia 1988; 44:230232 9. Chiao C, Carothers AM, Grunberger 0, et al. Apoptosis and altered redox state induced by caffeic acid phenethyl ester (CAPE) in transformed rat fibroblast cells. Cancer Res 1995; 55:3576-3583 10. Su ZZ, Lin J, Grunberger 0, Fisher PB. Growth suppression and toxicity induced by caffeic acid phenethyl ester (CAPE) in type 5 adenovirus-transformed rat embryo cells correlate directly with transformation progression. Cancer Res 1994; 54:1865-1870 11. Ruiz JM, Medrano M, Alio JL. Inhibition of posterior capsule opacification by 5-fluorouracil in rabbits. Ophthalmic Res 1990; 22:201-208 12. Haus CM, Galand AL. Mitomycin against posterior capsular opacification: an experimental study in rabbits. Br J OphthalmoI1996; 80:1087-1091 13. Hansen TJ, Tyndall R, SolI DB. Methotrexateanticollagen conjugate inhibits in vitro lens cell outgrowth. Invest Ophthalmol Vis Sci 1987; 28:12061209 14. Weller M, Wiedemann P, Fischbach R, et al. Evaluation of daunomycin toxicity on lens epithelium in vitro. Int Ophthalmol1988; 12:127-130 15. Legler UF, Apple OJ, Assia EI, et al. Inhibition of posterior capsule opacification. The effect of colchicine in a sustained drug delivery system. J Cataract Refract Surg 1993; 19:462-470 16. Focht J, Hansen SH, Nielsen JV, et al. Bactericidal effect of propolis in vitro against agents causing upper respira-
J CATARACT REFRACT SURG-VOL 23, DECEMBER 1997
1575
CAFFEIC ACID PHENETHYL ESTER INHIBITION OF PCO
17.
18.
19.
20.
21.
22.
1576
tory tract infections. Arzneimittelforschung 1993; 43:921-923 Dobrowolski Jw, Vohora SB, Sharma K, et al. Antibacterial, antifungal, antiamoebic, antiinflammatory and antipyretic studies on propolis bee products. J Ethnopharmacol 1991; 35:77-82 Amoros M, Lurton E, Boustie J, et al. Comparison of the anti-herpes simplex virus activities of propolis and 3-methyl-but-2-enyl caffeate. J Nat Prod 1994; 57:644647 Amoros M, Sauvager F, Girre L, Cormier M. In-vitro antiviral activity of propolis. Apidologie 1992; 23:231240 Khayyal MT, el-Ghazaly MA, el-Khatib AS. Mechanisms involved in the antiinflammatory effect of propolis extract. Drugs Exp Clin Res 1993; 19:197-203 Strehl E, Volpert R, Elstner EF. Biochemical activities of propolis-extracts. III. Inhibition of dihydrofolate reductase. Z Naturforsch [C] 1994; 49:39-43 Krol W, Czuba Z, Scheller S, et al. Anti-oxidant property of ethanolic extract of propolis (EEP) as evaluated by inhibiting the chemiluminescence oxidation of luminol. Biochem Int 1990; 21:593-597
23. Sud'ina GF, Mirzoeva OK, Pushkareva MA, et al. Caffeic acid phenethyl ester as a lipoxygenase inhibitor with antioxidant properties. FEBS Lett 1993; 329:2124 24. Pascual C, Gonzalez R, Torricella RG. Scavenging action of propolis extract against oxygen radicals. J Ethnopharmacol 1994; 41:9-13 25. Scheller S, Krol W, Swiacik J, et al. Antitumoral property of ethanolic extract of propolis in mice-bearing Ehrlich carcinoma, as compared to bleomycin. Z Naturforsch [C] 1989; 44:1063-1065 26. Frenkel K, Wei H, Bhimani R, et al. Inhibition of tumor promoter-mediated processes in mouse skin and bovine lens by caffeic acid phenethyl ester. Cancer Res 1993; 53:1255-1261 27. Guarini L, Su ZZ, Zucker S, et al. Growth inhibition and modulation of antigenic phenotype in human melanoma and glioblastoma multiforme cells by caffeic acid phenethyl ester (CAPE). Cell Mol BioI 1992; 38:513-527; erratum p 615 28. Gwon AE, Gruber LJ, Mundwiler KE. A histologic study of lens regeneration in aphakic rabbits. Invest Ophthalmol Vis Sci 1990; 31:540-547
J CATARACT REFRACT SURG-VOL 23. DECEMBER 1997
ABSTRACT Purpose: To assess whether caffeic acid phenethyl ester (CAPE) prevents posterior capsule opacification (PCO) by suppressing the transformation of the lens epithelial cells. Setting: Departments of Ophthalmology, Chemistry, and Pathology, Turgut Ozal Medical Center, University of Inonu, Malatya, Turkey. Methods: Twenty pigmented island rabbits having phacoemulsification in their right eyes were randomized into two groups. In Group 1, 10 ~g/ml of CAPE was added to the anterior chamber irrigating solution and a 1% solution of CAPE was injected subconjunctivally for 3 weeks postoperatively. The irrigating solution in Group 2 (control) did not include CAPE. The development of PCO was assessed weekly and its density was graded by slitlamp biomicroscopy. Histologic analysis was performed 3 months after surgery. Results: Group 1 had clear capsules or minor PCO. Group 2 developed more severe PCO or complete opacification. The difference between the two groups was statistically significant (P = .04). Conclusion: These preliminary results indicate that CAPE is effective in suppressing
pea
in pigmented rabbits and may be beneficial in clinical use in humans
because it has no documented harmful effects on normal cells. J Cataract Refract Surg 1997; 23: 1572-1576
P
osterior capsule opacification (PCO) is a significant long-term complication and the most frequent cause of decreased visual acuity after extracapsular cataract extraction (ECCE) and intraocular lens (IOL) implantation. It results from the proliferation, migration, and metaplasia of residual lens epithelial cells (LECs).1 After ECCE, LECs become activated and transform into fibroblasts and myofibroblasts. z-7 From the Departments of Ophthalmology (Hepsen, Bayramlar, Tilgen, Evereklioglu), Chemistry (Gultek), and Pathology (Oun), Turgut Ozal Medical Center, University ofInonu, Malatya, Turkey. Reprint requests to Ibrahim E Hepsen, MD, Department of Ophthalmology, Turgut Ozal Medical Center, University of Inonu, 44280 Malatya, Turkey. 1572
Caffeic acid phenethyl ester (CAPE), the active component of the propolis produced by honeybees in their hives, selectively inhibits the growth of several virus-transformed and oncogene-transformed fibroblasts and carcinoma cell lines but not the normal cells. 8- 10 This study assessed whether intracameral and subconjunctival administration of CAPE suppresses LEC proliferation and transformation and thus prevents PCO in rabbits having phacoemulsification.
Materials and Methods Twenty pigmented island rabbits weighing 2.0 to 2.5 kg were randomly divided into two groups. Each
] CATARACT REFRACT SURG--VOL 23, DECEMBER 1997
CAFFEIC ACID PHENETHYL ESTER INHIBITION OF PCO
group comprised 10 eyes in 10 rabbits. In Group 1, CAPE (10 f,.Ig/mL) , synthesized using the technique described by Grunberger et al.,s was added to the anterior chamber irrigating solution of balanced salt solution (BSS® Plus). Group 2 eyes (controls) had surgery by the same technique but without CAPE in the irrigating solution. All the surgeries were performed by one surgeon (H.B.) skilled in phacoemulsification and familiar with the phaco machine used. The surgeon was masked as to the treatment group. The right eye in each animal was prepared for cataract surgery. The animals were anesthetized with ketamine hydrochloride (Ketalar®) 35 mg/kg and xylazine (Rompun®) 10 mg/kg given intramuscularly. Pupils were dilated with tropicamide 0.5% and phenylephrine hydrochloride 10%. After the ocular area was disinfected with povidone-iodine, the lids were retracted with a wire lid speculum. A clear corneal incision was made with a 3.2 mm keratome. A small, round anterior capsulorhexis was performed with a capsule forceps; its approximate diameter was 5.0 to 6.0 mm. A phacoemulsification tip (Performa, Ophthalmed) was inserted through the corneal wound, and the nucleus was removed by the chip and flip technique using an ultrasound power of 70%, aspiration flow rate of 16 to 20 minI cc, and vacuum of 100 to 120 mm Hg. Care was taken to irrigate and aspirate all cortical material. The corneal incision was closed with a single 10-0 nylon suture. Gentamicin and dexamethasone were injected subconjunctivally at the end of the surgery. Postoperatively, the eyes having surgery were treated with topical prednisolone acetate and tobramycin four times a day and atropine sulfate once a day for 3 weeks. A 1% solution of CAPE (0.4 cc) was also injected subconjunctivally every 3 days for 3 weeks in Group 1 eyes. The development of PCO was assessed weekly for 3 months by slitlamp biomicroscopy. One person (I.F.H.), masked as to treatment group, performed all slitlamp examinations. At the final examination, PCO was graded on a scale of 0 to 3: 0 = clear, no visible proliferative tissue on the peripheral or central posterior capsule; 1 = mild, proliferative tissue in peripheral area only; 2 = moderate, sparse proliferative tissue on both
the peripheral and central capsules; 3 = dense, diffuse and thick opacification on the entire capsule. The rabbits were killed and their eyes enucleated for histologic examination at the end of 3 months. One eye in Group 2 had a posterior capsule rupture during phacoemulsification, and one rabbit in each group died. Therefore, one eye in Group 1 and two in Group 2 were excluded from evaluation. The Mann-Whitney U-test was used for statistical analysis.
Results In four eyes in Group 1 and two in Group 2, the anterior capsulorhexis was unsuccessful but the posterior capsules were intact. Mean phacoemulsification time was 163.33 seconds ± 51.65 (SO) in Group 1 and 171.42 ± 63.88 seconds in Group 2. In Group 1, mean total irrigation time with the BSS Plus containing CAPE was 3.76 ± 1.37 minutes. One week postoperatively, the corneal area around the incision was relatively edematous in all eyes. Inflammatory membrane and a small cortical remnant in the anterior chamber were seen in three eyes in both groups. Posterior capsules were biomicroscopically clear in all eyes. Two weeks postoperatively, the anterior chambers and corneas were clear. At the slitlamp, the regenerating lens tissue was first seen as fern- or crystalline-shaped striae. The striae on the posterior capsule became more evident 3 weeks postoperatively. Biomicroscopic findings of the posterior capsule almost remained stable from 4 weeks to 3 months postoperatively.
., w
>- "
.o
w
.. w
m :IE
_
"z DENSITY
OF
peo
Figure 1. (Hepsen) Formation of peo 3 months postoperatively.
J CATARACT REFRACT SURG-VOL 23, DECEMBER 1997
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CAFFEIC ACID PHENETHYL ESTER INHIBITION OF PCO
Figure 2. (Hepsen) Left: In this Group 2 eye with clinically graded dense pea, LEes have proliferated in the equatorial region (light micrograph; anterior lens surface is at the top) (hematoxylin and eosin x 100). Right: Light micrograph of the two layers of proliferative cells (cuboidal posteriorly and columnar anteriorly) on the central posterior capsule (anterior surface of posterior lens capsule is at the top) (hematoxylin and eosin x 200).
Figure 1 shows the results ofbiomicroscopic examination at the end of the third month. No eye in Group 1 developed dense PCO, although seven developed mild to moderate PCO. In Group 2, no eye had a clear capsule, and mild to moderate PCO was seen in six eyes. Although there was an overlap in the distribution of PCO density between the two groups (Figure 1), the difference was statistically significant (U = 16.0; P = .04). Histologic examination of the posterior capsule showed that the monolayers and multilayers of the regenerated LECs proliferated and migrated along the
Figure 3. (Hepsen) Light micrograph of a Group 1 eye clinically graded as having moderate pea shows a proliferated epithelial cell line with poor regenerative quality on the central posterior capsule surface (anterior surface of posterior lens capsule is at the top) (hematoxylin and eosin x 200). 1574
capsular surface toward the equatorial region and posterior capsule in eyes with PCO scores of 2 (moderate) and 3 (dense) (Figures 2 and 3). There was no proliferative activity on the posterior capsule surfaces and equatorial zones in the eyes clinically graded as clear (Figure 4).
Discussion Posterior capsule opacification is a common postoperative complication of ECCE with IOL implantation. If visual acuity is markedly reduced, a neo-
Figure 4. (Hepsen) No epithelial cell proliferation was seen in the equatorial region of lens capsule in this Group 1 eye clinically graded as clear (light micrograph; anterior lens surface at the top) (hematoxylin and eosin x 200).
J CATARACT REFRACT SURG-VOL 23, DECEMBER 1997
CAFFEIC ACID PHENETHYL ESTER INHIBITION OF PCO
dymium:YAG laser capsulotomy may be necessary. Various pharmacologic agents (antimetabolites), including 5-fluorouracil,11 mitomycin,12 methotrexate, 13 daunomycin,14 and colchicine,15 have been used experimentally with the aim of irreversibly damaging residual LECs and thus preventing PCO.1 Propolis, a natural hive product produced by honeybees, has strong antimicrobial,I6-19 anti-inflammatory, 17,20,21 antioxidant,22-24 and antineoplastic activity.8,10,25,26 Flavanoids and CAPE, the two active components of propolis extract, may be responsible for most of these biologic activities. 22 ,23 It has been shown that CAPE is a selective growth suppressor with differential cytotoxic effects on virus- and oncogene-transformed rat and human fibroblasts and several cancer cell lines at the stage of progression of the transformed state, but not on the normal rat and human fibroblasts. 8- 1O Chiao et al. 9 found that CAPE blocked cell proliferation in nontumorogenic rat embryo fibroblasts and caused cell death by inducing apoptosis in adenovirustransformed fibroblasts. They suggested that CAPEassociated growth inhibition might be related to the effect on oxidative processes induced by mitogenic stimuli. These observations support the concept that the transformed phenotype is specifically sensitive to CAPE.27 We hypothesized that CAPE would effectively inhibit PCO by its antiproliferative and cytotoxic effects on transformed LECs. To our knowledge, this is the first study to adapt these effects of CAPE in an attempt to prevent PCO by damaging the residual LECs as they begin to transform into fibroblasts. Postoperatively, the regenerative activity of residual LECs begins within days in the rabbit,28 and the intraoperative use of CAPE alone may not be sufficient to prevent it. Therefore, to provide additional antiproliferative effect on residual LECs postoperatively, subconjunctival injections of CAPE were given. In this study, we investigated the preventive effect of CAPE on PCO and found it effective in reducing PCO after phacoemulsification in pigmented rabbits. Our preliminary results are encouraging. We believe that better results can be obtained by determining the optimal application route and adjusting the dosage. In addition, CAPE may be beneficial in humans as it has no known harmful effects on normal, nonproliferative cells.
References 1. Apple OJ, Solomon KD, Tetz MR, et al. Posterior capsule opacification. Surv Ophthalmol 1992; 37:73116 2. Hara T, Azuma N, Chiba K, et al. Anterior capsular opacification after endocapsular cataract surgery. Ophthalmic Surg 1992; 23:94-98 3. Zhu ZR. Pathogenesis of posterior capsular opacification after extracapsular cataract extraction. Chung-Hua Yen Ko Tsa Chih 1990; 26:298-300 4. Ishibashi T, Araki H, Sugai S, et al. Histopathologic study of anterior capsule opacification in pseudophakic eyes. Nippon Ganka Zasshi 1993; 97:460-466 5. Kappelhof JP, Vrensen GF. The pathology of aftercataract; a minireview. Acta Ophthalmol Suppl 1992; 205:13-24 6. McDonnell PJ, Stark WJ, Green WR. Posterior capsule opacification: a specular microscopic study. Ophthalmology 1984; 91:853-856 7. McDonnell pJ, Zarbin MA, Green WR. Posterior capsule opacification in pseudophakic eyes. Ophthalmology 1983; 90:1548-1553 8. Grunberger 0, Banerjee R, Eisinger K, et al. Preferential cytotoxicity on tumor cells by caffeic acid phenethyl ester isolated from propolis. Experientia 1988; 44:230232 9. Chiao C, Carothers AM, Grunberger 0, et al. Apoptosis and altered redox state induced by caffeic acid phenethyl ester (CAPE) in transformed rat fibroblast cells. Cancer Res 1995; 55:3576-3583 10. Su ZZ, Lin J, Grunberger 0, Fisher PB. Growth suppression and toxicity induced by caffeic acid phenethyl ester (CAPE) in type 5 adenovirus-transformed rat embryo cells correlate directly with transformation progression. Cancer Res 1994; 54:1865-1870 11. Ruiz JM, Medrano M, Alio JL. Inhibition of posterior capsule opacification by 5-fluorouracil in rabbits. Ophthalmic Res 1990; 22:201-208 12. Haus CM, Galand AL. Mitomycin against posterior capsular opacification: an experimental study in rabbits. Br J OphthalmoI1996; 80:1087-1091 13. Hansen TJ, Tyndall R, SolI DB. Methotrexateanticollagen conjugate inhibits in vitro lens cell outgrowth. Invest Ophthalmol Vis Sci 1987; 28:12061209 14. Weller M, Wiedemann P, Fischbach R, et al. Evaluation of daunomycin toxicity on lens epithelium in vitro. Int Ophthalmol1988; 12:127-130 15. Legler UF, Apple OJ, Assia EI, et al. Inhibition of posterior capsule opacification. The effect of colchicine in a sustained drug delivery system. J Cataract Refract Surg 1993; 19:462-470 16. Focht J, Hansen SH, Nielsen JV, et al. Bactericidal effect of propolis in vitro against agents causing upper respira-
J CATARACT REFRACT SURG-VOL 23, DECEMBER 1997
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CAFFEIC ACID PHENETHYL ESTER INHIBITION OF PCO
17.
18.
19.
20.
21.
22.
1576
tory tract infections. Arzneimittelforschung 1993; 43:921-923 Dobrowolski Jw, Vohora SB, Sharma K, et al. Antibacterial, antifungal, antiamoebic, antiinflammatory and antipyretic studies on propolis bee products. J Ethnopharmacol 1991; 35:77-82 Amoros M, Lurton E, Boustie J, et al. Comparison of the anti-herpes simplex virus activities of propolis and 3-methyl-but-2-enyl caffeate. J Nat Prod 1994; 57:644647 Amoros M, Sauvager F, Girre L, Cormier M. In-vitro antiviral activity of propolis. Apidologie 1992; 23:231240 Khayyal MT, el-Ghazaly MA, el-Khatib AS. Mechanisms involved in the antiinflammatory effect of propolis extract. Drugs Exp Clin Res 1993; 19:197-203 Strehl E, Volpert R, Elstner EF. Biochemical activities of propolis-extracts. III. Inhibition of dihydrofolate reductase. Z Naturforsch [C] 1994; 49:39-43 Krol W, Czuba Z, Scheller S, et al. Anti-oxidant property of ethanolic extract of propolis (EEP) as evaluated by inhibiting the chemiluminescence oxidation of luminol. Biochem Int 1990; 21:593-597
23. Sud'ina GF, Mirzoeva OK, Pushkareva MA, et al. Caffeic acid phenethyl ester as a lipoxygenase inhibitor with antioxidant properties. FEBS Lett 1993; 329:2124 24. Pascual C, Gonzalez R, Torricella RG. Scavenging action of propolis extract against oxygen radicals. J Ethnopharmacol 1994; 41:9-13 25. Scheller S, Krol W, Swiacik J, et al. Antitumoral property of ethanolic extract of propolis in mice-bearing Ehrlich carcinoma, as compared to bleomycin. Z Naturforsch [C] 1989; 44:1063-1065 26. Frenkel K, Wei H, Bhimani R, et al. Inhibition of tumor promoter-mediated processes in mouse skin and bovine lens by caffeic acid phenethyl ester. Cancer Res 1993; 53:1255-1261 27. Guarini L, Su ZZ, Zucker S, et al. Growth inhibition and modulation of antigenic phenotype in human melanoma and glioblastoma multiforme cells by caffeic acid phenethyl ester (CAPE). Cell Mol BioI 1992; 38:513-527; erratum p 615 28. Gwon AE, Gruber LJ, Mundwiler KE. A histologic study of lens regeneration in aphakic rabbits. Invest Ophthalmol Vis Sci 1990; 31:540-547
J CATARACT REFRACT SURG-VOL 23. DECEMBER 1997