LYSOSOMAL CYSTEINE PROTEASES AND DISTURBANCES OF THEIR REGULATION IN ATHEROSCLEROSIS (Invited Lecture)



Tatiana A. Korolenko, Ph.D., Institute of Physiology and Basic Medicine, Novosibirsk, Russia

Objectives. Hyperlipidaemia increases the risk of myocardial infarction and stroke.
Background. The poloxamer 407 (P-407)-induced hyperlipidemic mouse model represents a convenient, inexpensive, and well-documented mouse model with which to study cardiovascular heart disease arising from dyslipidemia and atherosclerosis. Methods. Mice were administered P-407, a well-documented general lipase inhibitor, for 1 month as an i.p. injection at a dose of 300 mg/kg twice per week. The specific activities of cathepsin B (EC 3.4.22.1) and cathepsin L (EC 3.4.22.15) were determined according to Barrett and Kirschke (1981). The expression of lysosomal acid lipase (LAL), a lipase inhibited by P-407, was quantified using RT-qPCR.
Results. Similar to humans, the onset of atherosclerosis in P-407-treated mice was characterized by a steady increase in serum low-density, intermediate-density and very-low-density lipoprotein (VLDL) fractions, as well as VLDL subfractions.
P-407-treated mice revealed significant hyperlipidemia, moderately elevated blood pressure, general lipidosis in liver cells, increased cysteine protease activity in heart tissue, and contractile-type changes in cardiomyocytes. The specific activity of cathepsin B in liver tissue increased modestly 24 h after stopping P-407 treatment for 1 month.
The specific activity of cathepsin B and cathepsin L in heart tissue remained significantly (p < 0.01) elevated relative to control for as long as 24 h after the last dose of P-407 and returned to normal (control) values by day 4 following discontinuation of P-407 treatment.
Conclusion. We demonstrated that an increase in the activity of cathepsins B and L in heart tissue was positively correlated with morphological changes observed in contractile-type cardiomyocytes.