Proteomic profile of the lens in a streptozotocin-induced diabetic rat model using shotgun proteomics

Abstract

Abstract. Streptozotocin (STZ)-induced diabetic rats (STZ rats) were used to investigate diabetic cataracts. In the current study, a shotgun liquid chromatography (LC)/mass spectrometry (MS)-based global proteomic analysis method was used to examine the mechanism of lens opacification as a result of hyperglycemia in STZ rats. The 6-week old Wistar rats were injected with STZ for 2 days (100 mg/kg/day, i.p.) and housed for 3 weeks. The plasma glucose levels were identified to be significantly higher when compared with the normal rats and insulin was not detected in the STZ rats. Furthermore, opacification of the cortical epithelium was observed in the lenses of STZ rats. A total of 235 proteins were identified in the lenses of the STZ rats and 229 in the lenses of the normal rats. A label-free semi-quantitative method, based on spectral counting, identified 52 proteins that were differentially expressed in the lenses of STZ rats compared with normal rats. In particular, superoxide dismutase, which is a critical antioxidant enzyme that detoxifies superoxide through redox cycling, was downregulated when analyzed by the semi-quantitative method. In addition, phosphorylated-p38, which is important in the signaling pathway involved in the oxidative stress response, was significantly increased in the lenses of STZ rats when compared with normal rats (P<0.05). Thus, the changes in protein expression were evaluated in the lenses of STZ rats using a shotgun LC/MS-based global proteomic analysis approach, and a decrease in antioxidant enzymes and an increase in oxidative stress were identified in the lenses of STZ rats. Further studies are required to examine the role of these proteins in the onset or progression of diabetic cataracts. IntroductionDiabetes mellitus is one of the most severe types of metabolic disorder in humans globally, and is characterized by insulin resistance and impaired insulin secretion (1). Long-term hyperglycemia in diabetics leads to many complications with tissues that require insulin for glucose entrance or with insulin-independent organs (2), and cataracts are one of the most common complications of exposure to uncontrolled chronic hyperglycemia in diabetes. It has been reported that the onset of cataracts in diabetic patients is 20 years earlier than in non-diabetic subjects (3).Activation of the polyol pathway (4), non-enzymatic glycation of lens proteins (5-8) and increased oxidative stress (9-13) were reported as pathogenetic mechanisms of diabetic cataracts. In the polyol pathway, the excess glucose changes to sorbitol via aldose reductase and the excessive accumulation of sorbitol in the crystalline lens produces a high osmotic gradient, and causes the collapse and liquefaction of lens fibers, resulting in cataract formation (14,15). Furthermore, enhanced osmotic stress leads to the production of reactive oxygen species (ROS) in the crystalline lens (16)(17)(18). In addition, sorbitol is metabolized to fructose. The fructose is metabolized into fructose-3-phospate and 3-deoxyglucosone (p...

A Proteomic Approach for Understanding the Mechanisms of Delayed Corneal Wound Healing in Diabetic Keratopathy Using Diabetic Model Rat

“…In particular, a shotgun liquid chromatography (LC)/mass spectrometry (MS)-based global proteomic analysis method is considered a useful technique [ 23 , 29 , 30 ]. As we reported previously, changes in protein expression levels in the lenses of streptozotocin-induced diabetic rat (STZ rats) were evaluated using this methodology, and revealed a decrease in superoxide dismutase in the lenses of STZ rats which contributed to the progression of diabetic cataracts [ 31 ]. The analysis may be used to elucidate the causal factor of diabetic keratopathy.…”

Probucol Slows the Progression of Cataracts in Streptozotocin-Induced Hyperglycemic Rats

“…Multiple mechanisms are involved in the pathogenesis of diabetic cataracts, such as activation of the polyol pathway [5][6][7][8], non-enzymatic glycosylation (glycation) of lens proteins [9,10], and accumulation of reactive oxygen species that ultimately induce oxidative stress injury [11][12][13][14]. These molecules and biochemical pathways may be targets for the treatment of diabetic cataracts [15][16][17][18].…”

Retinal proteomic evaluation of rats following streptozotocin‑injection using shotgun proteomics

“…next, we applied lc/MS-based proteomics analysis to elucidate factors and mechanisms of acute retinal dysfunction in STZ rats. although a quantitative value obtained using spectral counting may not be accurate, it reflects differences in expression and has been used in previous studies investigating novel diagnostic biomarkers and biological mechanisms (11,12,(31)(32)(33)(34)(35). a total of 88 proteins had >2-fold change in expression in the retinas of STZ rats, and we examined their roles in an analysis against four Go terms.…”

“…We previously used this methodology to evaluate changes in protein expression in the lens and cornea of STZ rats and found decreased superoxide dismutase. This decrease contributed to the progression of diabetic cataracts and overexpression of lumican, leading to delayed corneal wound healing in diabetic keratopathy-affected corneas (11,12).…”