The involvement of matrix metalloproteinases 2 and 9 in rat retinal ischemia.
BACKGROUND
The involvement of matrix metalloproteinases (MMPs) in ischemic tissue damage and remodeling has been reported by many investigators. Our study was designed to investigate the involvement of MMPs and of tissue inhibitors of metalloproteinases (TIMPs) in rat retinal ischemic injury, the effect of nitric oxide synthase (NOS) inhibitors on MMPs' activity in this model and whether minocycline (an MMP inhibitor) is protective in retinal ischemia.


METHODS
Ninety-four rats were used in the study. Ischemia was induced by 90 min elevation of intraocular pressure. MMPs' activities and the effect of NOS inhibitors [aminoguanidine (AG) or N-nitro-L-arginine (NNA)] and minocycline on MMPs' activities were assessed by zymography and TIMPs expression by Western analysis. Morphological damage was quantified by morphometry of hematoxylin and eosin-stained retinal sections.


RESULTS
Retinal extracts exhibited activities of proMMP-9 and proMMP-2. The activity of proMMP-9 increased immediately post ischemia (PI) and peaked to 4.6 times that of normal untreated controls in ischemic retinas and to 2.6 times that of controls in retinas of fellow sham-treated eyes at 24 h PI. The relative amount of TIMP-1 increased to 1.9-fold following ischemia and 2.5-fold in fellow sham-treated eyes at 24 h PI. ProMMP-2 activity increased more than two-fold immediately, at 24 h and at 48 h PI in ischemic retinas, and insignificantly in fellow sham-treated eyes. Treatment with 25 mg/kg AG or NNA caused a non-significant increase in proMMP-9 activity at 24 h PI (3.7- and 2.9-fold, respectively, p>0.6). There was no effect of AG or NNA on the activity of proMMP-2. Minocycline significantly attenuated the retinal ischemic damage, primarily by partially preserving ganglion cells and the inner plexiform layer. Minocyline (0.5 mg/ml or 5 mg/ml) inhibited MMPs' activities in ischemic retinal extracts in vitro.


CONCLUSIONS
MMPs participated in morphological ischemic damage to rat retina. Treatment with minocycline dramatically attenuated damage to the retina.
Mathalone
Nurit
N
Department of Ophthalmology, Carmel Medical Center, 7 Michal Street, Haifa, 34362, Israel.
Lahat
Nitza
N
Rahat
Michal A
MA
Bahar-Shany
Keren
K
Oron
Yoram
Y
Geyer
Orna
O
D000818:Animals; D015153:Blotting, Western; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000627:therapeutic use; D006146:Guanidines / Q000627:therapeutic use; D007511:Ischemia / Q000201:enzymology* / Q000473:pathology / Q000517:prevention & control; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D061965:Matrix Metalloproteinase Inhibitors; D008911:Minocycline / Q000627:therapeutic use; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000627:therapeutic use; D051381:Rats; D017207:Rats, Sprague-Dawley; D012164:Retinal Diseases / Q000201:enzymology* / Q000473:pathology / Q000517:prevention & control; D012171:Retinal Vessels; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism
D004791:Enzyme Inhibitors; D006146:Guanidines; D061965:Matrix Metalloproteinase Inhibitors; D019715:Tissue Inhibitor of Metalloproteinase-1; D019335:Nitroarginine; D019001:Nitric Oxide Synthase; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D008911:Minocycline; C004479:pimagedine