Inhibition of collagenase breakdown of equine corneas by tetanus antitoxin, equine serum and acetylcysteine.

This research article investigates whether tetanus antitoxin, equine serum, and acetylcysteine can inhibit the degradation of equine cornea collagen by bacterial collagenase. This study suggests that these substances, currently used in the treatment of equine corneal ulcer, can reduce collagenase activity by an average of 50%.

Methods and Methodology

• The researchers used corneas sourced from 40 adult horses for the experiments.
• The corneas were treated with saline, bacterial collagenase in saline, and combinations of bacterial collagenase in saline with either equine tetanus antitoxin, equine serum, or acetylcysteine.
• These compounds were used at varied concentrations to observe differences in effects.
• The extent of collagen digestion was determined by examining the concentration of hydroxyproline present in the incubation media and/or deducing weight loss of the cornea post-treatment.

Results

• When the corneas were exposed to collagenase, a significant amount of hydroxyproline was released (43.1 +/- 2.3 microg/mL/100 mg cornea/5 h) and a reduction in cornea weight of up to 89% was witnessed.
• At their highest concentrations, the blood serum (200 microL/mL), tetanus antitoxin (120 units/mL), and acetylcysteine (20 mg/mL) were able to block about 50% of the collagenase activity.
• Purified albumin or globulin fractions of serum showed a similar effect, and the dilution of these inhibitors led to decreased corneal protection and linearly increasing corneal weight loss.

Conclusion

• The researchers concluded that tetanus antitoxin, equine serum, and acetylcysteine are equally effective at protecting corneas from collagenase digestion under in vitro conditions.
• Despite these promising results, the authors acknowledge the need for clinical trials to fully understand the relative therapeutic value of these substances when used for collagenase inhibition in an actual clinical scenario.