Ss. Twining et al., CHANGES IN RAT CORNEAL MATRIX METALLOPROTEINASES AND SERINE PROTEINASES UNDER VITAMIN-A-DEFICIENCY, Current eye research, 16(2), 1997, pp. 158-165
Purpose. Vitamin A deficiency alters the transparency of the cornea du
e to epithelial cell keratinization and increases the susceptibility o
f the cornea to ulceration. The purpose of this study was to determine
the effect of vitamin A deficiency on rat corneal matrix metalloprote
inases and serine proteinases. Methods. Four dietary groups of male WA
G/RijMCW rats were prepared: (1) Vitamin A deficient rats were raised
on a casein-based retinoid deficient diet; (2) Retinol repleted rats w
ere raised on the retinoid deficient diet. On the eighty-sixth day on
this diet, the rats were fed retinyl palmitate and then given free acc
ess to the retinyl palmitate-supplemented control diet; (3) The weight
-matched, pair-fed rats were restricted in their intake of the retinyl
palmitate-supplemented diet so that their weight gain matched that of
the A- rats; (4) The non-restricted rats were given free access to th
e retinyl palmitate-supplemented diet. The animals were killed at the
late plateau stage for weight of the deficiency (102-106 days). Zymogr
aphy was used to study proteinases in the corneal extracts. Results. V
itamin A deficient and control rat corneas contain multiple matrix met
alloproteinases and serine proteinases. The matrix metalloproteinases
at 90/92 kDa (gelatinase B) and 66/63/57 kDa (gelatinase A) were signi
ficantly decreased in the corneas of the vitamin A deficient rats rela
tive to the control corneas. Corneas from the four groups of rats cont
ained 76, 45, 38, 28 and 22 kDa proteinases that cleaved casein. Only
the vitamin A deficient corneas contained a 50 kDa casein cleaving enz
yme. The 76, 45, 38 and 28 kDa serine proteinases were significantly l
ower in the vitamin A deficient corneas. The major 22 kDa enzyme was n
ot altered by the deficiency. All casein cleaving proteinases were inh
ibited by phenylmethylsulfonyl fluoride and chymostatin except for a m
inor 76 kDa band. The activity of this band was not altered by inhibit
ors for the other classes of proteinases, ethylenediaminetetraacetic a
cid, E-64 or pepstatin. The concentrations of the 61, 52 and 40 kDa pl
asminogen activators were not altered by the deficiency. Conclusions.
Alterations in corneal proteinases under vitamin A deficiency conditio
ns may be involved in the characteristic changes observed in the corne
a under vitamin A deficiency conditions: decreased exfoliation of epit
helial cells, increased levels of keratofibrils in the corneal keratoc
ytes, increased stromal keratocyte degradation and increased susceptib
ility towards ulceration.