Carnosine Ameliorates Lens Protein Turbidity Formations by Inhibiting Calpain Proteolysis and Ultraviolet C-Induced Degradation

Abstract

Carnosine (CAR) is an endogenous peptide and present in lens, but there is little evidence for its effectiveness in calpain-induced proteolysis inhibition and its differential effects toward different wavelengths of ultraviolet (UV) irradiation. This study aimed to develop three in vitro cataract models to compare the mechanisms underlying the protective activities of CAR. Crude crystallins extracted from porcine lenses were used for antiproteolysis assays, and purified γ-crystallins were used for anti-UV assays. The turbidity in those in vitro models mimics cataract formation and was assayed by measuring optical density (OD) at 405 nm. The effectiveness of CAR on calpain-induced proteolysis was studied at 37 and 58 °C. Patterns of proteins were then analyzed by SDS-PAGE. The turbidity was reduced significantly (p<0.05) at 60 min measurements with the increased concentration of CAR (10-300 mM). SDS-PAGE showed that the decreased intensities at both ∼28 and ∼30 kDa protein bands in heat-enhanced assays were ameliorated by CAR at ≥10 mM concentrations. In UV-B studies, CAR (200, 300 mM) reduced the turbidity of γ-crystallin significantly (p<0.05) at 6 h observations. The turbidity of samples containing γ-crystallins was ameliorated while incubated with CAR (100, 300 mM) significantly (p<0.05) following 4 h of exposure to UV-C. SDS-PAGE showed that the presence of CAR reduced UV-B-induced aggregation of γ-crystallins at ∼44 kDa and resulted in less loss of γ-crystallin following UV-C exposure. The result of modeling also suggests that CAR acts as an inhibitor of calpain. In conclusion, CAR protects lens proteins more readily by inhibiting proteolysis and UV-C-induced degradation than aggregation induced by UV-B irradiation.

Anticataractogenesis Mechanisms of Curcumin and a Comparison of Its Degradation Products: An in Vitro Study

“…The protective effects of Cur or other tested compounds were assayed via an in vitro anticataract screening system in which lens protein turbidity was induced by either sodium selenite or calcium ions. Porcine lenses were decapsulated and homogenized in lens buffer as described in our previously study. , After centrifuging at 16060 g for 30 min, the supernatant was collected, and the protein concentration was determined using the Bradford method (Bio-Rad Laboratories, USA). Lens proteins with buffer only were used as a control.…”

CELF1 promotes matrix metalloproteinases gene expression at transcriptional level in lens epithelial cells

“…Posterior capsule opacification (PCO), which is also known as secondary cataract, was characterized by cellular migration onto the posterior lens capsule, coupling with deposition of abnormal extracellular matrix and capsular wrinkling, all of which could lead to opacification of lens and ultimately cataract [35]. In addition, proteolysis is another typical characteristic in cataract formation [36][37][38]. Wang et al proposed that elevated proteolysis resulted from S129R mutation might induce pathology since significant decline of functional proteins changed the protein-protein interaction network [39].…”

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