Corneal Endothelial Abnormalities Associated With Thalidomide Toxicity

Thalidomide and its analogues: A review of the potential for immunomodulation of fibrosis diseases and opthalmopathy

The US Food and Drug Administration approved thalidomide and its analogues for the treatment of erythema nodosum leprosum, in spite of the notoriety of reports of severe birth defects in the middle of the last century. As immunomodulatory drugs, thalidomide and its analogues have been used to effectively treat various diseases. In the present review, preclinical data about the effects of thalidomide and its analogues on the immune system are integrated, including the effects of cytokines on transdifferentiation, the anti-inflammatory effect, immune cell function regulation and angiogenesis. The present review also investigates the latest developments of thalidomide as a therapeutic option for the treatment of idiopathic pulmonary fibrosis, skin fibrosis, and ophthalmopathies.

Thalidomide attenuates nitric oxide mediated angiogenesis by blocking migration of endothelial cells

BACKGROUND

Thalidomide is an immunomodulatory agent, which arrests angiogenesis. The mechanism of anti-angiogenic activity of thalidomide is not fully understood. As nitric oxide is involved in angiogenesis, we speculate a cross-talk between thalidomide and nitric oxide signaling pathway to define angiogenesis. The aim of present study is to understand the mechanistic aspects of thalidomide-mediated attenuation of angiogenesis induced by nitric oxide at the cellular level.

METHODS

To study the cellular mechanism of thalidomide-mediated blocking of angiogenesis triggered by nitric oxide, we used two endothelial cell based models: 1) wound healing and 2) tube formation using ECV 304, an endothelial cell line. These cell-based models reflect pro-angiogenic events in vivo. We also studied the effects of thalidomide on nitric oxide mediated egg yolk angiogenesis. Thalidomide could block the formation of blood vessels both in absence and presence of nitric oxide. Thalidomide effects on migration of, and actin polymerization in, ECV 304 cells were studied at the single cell level using live cell imaging techniques and probes to detect nitric oxide.

RESULTS

Results demonstrate that thalidomide blocks nitric oxide-mediated angiogenesis in egg yolk model and also reduces the number of tubes formed in endothelial cell monolayers. We also observed that thalidomide arrests wound healing in presence and absence of nitric oxide in a dose-dependent fashion. Additionally, thalidomide promotes actin polymerization and antagonizes the formation of membrane extensions triggered by nitric oxide in endothelial cells. Experiments targeting single tube structure with thalidomide, followed by nitric oxide treatment, show that the tube structures are insensitive to thalidomide and nitric oxide. These observations suggest that thalidomide interferes with nitric oxide-induced migration of endothelial cells at the initial phase of angiogenesis before cells co-ordinate themselves to form organized tubes in endothelial cells and thereby inhibits angiogenesis.

CONCLUSION

Thalidomide exerts inhibitory effects on nitric oxide-mediated angiogenesis by altering sub-cellular actin polymerization pattern, which leads to inhibition of endothelial cell migration.

Cataract surgery in Fuchs?? dystrophy

PURPOSE OF REVIEW

Corneal decompensation after cataract surgery can occur in patients with Fuchs' endothelial dystrophy. This paper reviews the pathogenesis of corneal edema in Fuchs' dystrophy, the preoperative and perioperative risk factors for corneal endothelial cell loss during cataract surgery, and indications for cataract surgery alone or cataract surgery combined with keratoplasty for patients with visually significant cataracts and Fuchs' dystrophy.

RECENT FINDINGS

Accelerated loss of corneal endothelial cells in Fuchs' dystrophy is multifactorial, with apoptosis and altered gene regulation of aquaporin proteins playing a role. Preoperative factors contributing to decreased endothelial cell count include age, sex, diabetes, a history of ocular trauma or inflammation, and contact lens wear. Intra-operative measures shown to protect endothelial cells include the use of the soft-shell viscoelastic technique for very dense cataracts, efficient cataract removal techniques (phaco-chop, use of oscillatory handpiece), and surgery by an experienced surgeon. A triple procedure should be performed with preoperative corneal epithelial decompensation and considered with preoperative pachymetry greater than 640 mum. Otherwise, it is reasonable to attempt cataract surgery alone with proper patient education.

SUMMARY

Fuchs' dystrophy is a progressive disorder. Cataract surgery in the setting of Fuchs' dystrophy can be performed successfully, especially when the surgeon is aware of the preoperative and intraoperative factors that affect the number of functioning endothelial cells. All patients should be aware of the progressive nature of this disease and the possibility of keratoplasty at some point in their lifetime.