Increased Oxidized Protein Hydrolase Activity in Serum and Urine of Diabetic Rat Models

Abstract

Oxidative stress, caused by an imbalance between antioxidant activity and oxidant production within cells and plasma, is implicated in the pathogenesis of several diseases, including diabetes mellitus.1-3) Several mechanisms appear to be involved in the genesis of oxidative stress in diabetes mellitus, including glucose autoxidation, 4) protein glycation, 5) and the formation of advanced glycation end-products (AGEs). 6)As a consequence of oxidative stress, severe damage to proteins as well as DNA and lipids occurs.On the other hand, oxidized protein hydrolase (OPH) is a serine protease that preferentially degrades oxidized and glycated proteins rather than the corresponding unmodified proteins compared with other representative serine proteases, trypsin and chymotrypsin.7) The presence of OPH has been shown in a wide variety of biological samples, such as many different types of cells, tissues, and plasma.8) The purification 7) of OPH from human erythrocytes and several investigations [8][9][10][11][12][13] to elucidate its physiological function have been carried out by Kikugawa and his group. Based on a homology search regarding the amino acid sequence, OPH has subsequently been identified 9) as the same enzyme as acylpeptide hydrolase (ACPH) 14,15) or acylamino acid-releasing enzyme (AARE) (EC 3.4.19.1), which releases N-acylamino acids from N-acylpeptides; both a chymotrypsin-like endopeptidase activity originally demonstrated with OPH and an exopeptidase activity demonstrated with ACPH are shown to be shared by either OPH or ACPH.9,10) Even though long known, the physiological significance of ACPH has been insufficiently clarified. Recently, Fujino et al.11) demonstrated that OPH functions in the removal of aggregated erythrocyte membrane proteins induced by oxidative stress. Shimizu (a coauthor of this report) et al.12) demonstrated with COS-7 cell lines that OPH confers cellular resistance to oxidative stress, by eliminating cytotoxic denatured proteins produced through oxidation. They also showed with the cell lines that OPH and the proteasome coordinate in the clearance of oxidatively damaged proteins.13)The present study was undertaken to investigate whether or not OPH has a preventive or delaying role in the development and progression of diabetes mellitus. Using streptozotocin (STZ)-induced diabetic Wistar and Goto-Kakizaki (GK) rats as models of types 1 and 2 diabetes, respectively, we traced the changes in serum and urinary OPH activity with the pathological progress. This is the first report demonstrating enhanced OPH activity in diabetes mellitus in an animal study. Experimental Animals Eight-week-old male Wistar and GK rats (Japan Laboratory Animals, Tokyo) were used. Wistar rats were separated into two groups, each consisting of six rats: control and STZ groups. Type 1 diabetes mellitus was induced as previously described. 16,17) Briefly, a single injection of STZ (60 mg/kg body weight) dissolved in normal saline buffered with 0.1 M sodium citrate (pH 4.5) was carried out via the tail vein of ...

Differential Carbonylation of Proteins as a Function of in vivo Oxidative Stress

“…46 Moreover, the activity of oxidized protein hydrolase (OPH) in the serum of diabetic rats increased nearly in parallel to the increase of blood glucose levels. 47 In addition, oxidized proteins are ubiquitinated and form aggregates in the cytoplasm of pancreatic β cells that degrade through autophagy. 48 Diabetes induced OS in the retinal endothelial cells and up-regulated the ubiquitin proteasomal system in yet another study.…”

“…Previous reports indicated that there is an increase in proteolysis of some oxidized and glycated proteins in the plasma of diabetic patients, particularly in the case of methyl glyoxal adducts . Moreover, the activity of oxidized protein hydrolase (OPH) in the serum of diabetic rats increased nearly in parallel to the increase of blood glucose levels . In addition, oxidized proteins are ubiquitinated and form aggregates in the cytoplasm of pancreatic β cells that degrade through autophagy .…”

A novel class of bifunctional acylpeptide hydrolases – potential role in the antioxidant defense systems of the Antarctic fish Trematomus bernacchii

“…Among these, acylpeptide hydrolase (APEH), first identified as oxidized protein hydrolase [12][13][14], was recently hypothesized to participate in the degradation of oxidized and cytotoxic proteins [15][16][17]. For these reasons, APEH may represent a promising therapeutic target for a wide array of human diseases caused by the accumulation of damaged proteins [18,19].…”

Oxidized Substrates of APEH as a Tool to Study the Endoprotease Activity of the Enzyme

“…It is widely accepted that high ROS levels may have deleterious effects on macromolecules such as proteins and different proteolytic systems that operate in a number of different biochemical mechanisms aimed at tissue detoxification. In this context, recent studies assign to APEH (Acylaminoacyl Peptidase or acylamino-acid-releasing enzyme) a crucial role in these mechanisms, given its ability to process and degrade many protein substrates through both exo- and endopeptidase activity [ 2 , 3 , 4 , 5 , 6 , 7 , 8 ].…”