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Alpha 1-antichymotrypsin is present in and synthesized by the cornea
S S Twining1, T Fukuchi, B Y Yue
1Department of Biochemistry, Medical College of Wisconsin, Milwaukee 53226.
Insights
The human cornea synthesizes alpha 1-antichymotrypsin, a proteinase inhibitor, in all its layers. This local production allows the cornea to manage degradation independently of the vascular system.
Area of Science:
- Ophthalmology
- Biochemistry
- Protease Inhibitor Research
Background:
- Alpha 1-antichymotrypsin is a key proteinase inhibitor.
- Its presence and synthesis in the human cornea were previously unconfirmed.
Purpose of the Study:
- To investigate the presence, localization, and synthesis of alpha 1-antichymotrypsin in the human cornea.
- To determine the cornea's capacity for local protease degradation control.
Main Methods:
- Immunolocalization in corneal sections.
- Western blot and immunodot blot analysis of separated corneal layers.
- Organ culture and metabolic labeling of intact cornea.
Main Results:
- Alpha 1-antichymotrypsin was detected in epithelial, stromal, and endothelial layers.
- Quantified levels: 1.3 µg/cornea (epithelial), 22.8 µg/cornea (stromal), 0.17 µg/cornea (endothelial).
- The cornea synthesizes both mature (64 kDa) and a smaller (50 kDa) form of the inhibitor.
Conclusions:
- The human cornea synthesizes alpha 1-antichymotrypsin locally.
- This local synthesis enables the cornea to regulate degradation processes.
- Corneal independence from the vascular system for this inhibitor supply is established.
Abstract:
The proteinase inhibitor alpha 1-antichymotrypsin is present in the epithelial, stromal and endothelial layers of the human cornea. This was determined by immunolocalization in corneal sections and by Western blot analysis of extracts from the three separated layers. The inhibitor was quantified in the extracts by immunodot blot analysis. The levels observed were 1.3 +/- 0.3 microgram/cornea for the epithelial layer, 22.8 +/- 3.8 micrograms/cornea for the stromal layer and an average of 0.17 micrograms/cornea for the endothelial layer. alpha 1-Antichymotrypsin is being synthesized by the cornea. Metabolically labeled inhibitor was immunoprecipitated from the three layers following organ culture of the intact cornea. Two major forms were detected. These were the native, mature 64 kDa form and a 50 kDa form which is either a degradation product or an incompletely glycosylated form. These results indicate that the cornea has the ability to locally control degradation through synthesis of this inhibitor. Local synthesis of this inhibitor releases the cornea from total dependance upon the vascular system for its supply of alpha 1-antichymotrypsin.