Characterization of β-secretase inhibitory extracts from sea cucumber (Stichopus japonicus) hydrolysis with their cellular level mechanism in SH-SY5Y cells

Alzheimer's disease (AD) is the main type of dementia found in the elderly population. The prevention of beta-amyloid (A beta) production by inhibiting beta-secretase, which is required for A beta generation, is the major focus of research in AD therapeutics. In this study, enzymatic extracts obtained from sea cucumber (Stichopus japonicus) hydrolysis were investigated for beta-secretase inhibitory activities. Sea cucumber hydrolysates were prepared using various enzymes (Alcalase, alpha-chymotrypsin, Neutrase, papain, pepsin, and trypsin). Trypsin hydrolysate (IC50, 93.59 +/- 0.68 mu g/ml) with the highest beta-secretase inhibitory activity was separated into crude polysaccharide (TCP) and protein (TP) by ethanol precipitation. TCP (IC50, 16.13 +/- 1.15 mu g/ml) exhibited higher beta-secretase inhibitory activity than trypsin hydrolysate and TP (IC50, 563.50 +/- 25.18 mu g/ml). Total sugar content in TCP was 11.58 +/- 0.32 g/100 g. Major monosaccharides present in S. japonicus were arabinose, fucose, galactose, mannose and ramnose at 1.76 mg/g, 11.98 mg/g, 1.33 mg/g and 0.1 mg/g, respectively. Sulfate and uronic acid contents were 5.69 +/- 0.15 g/100 g and 0.49 +/- 0.01 g/100 g. Cytotoxicity of TCP different concentrations were tested in SH-SY5Y cells using MTT assay. Treated concentrations at 1, 5, 10, 30, 50, and 100 mu g/ml concentrations were not toxic at cellular level. Further, quantitative protein expression reduction of BACE, sAPP beta, beta-amyloid, p-JNK, and p-p38 in SH-SY5Y cells were confirmed by Western blot analysis. Therefore, results of this study suggest the potential application of S. japonicus in food and biomedicine industries.

Automated summary

This study focused on investigating the beta-secretase inhibitory activities of enzymatic extracts obtained from sea cucumber hydrolysis. The results showed that TCP exhibited higher inhibitory activity and was non-toxic at cellular levels, suggesting the potential application of sea cucumber in food and biomedicine industries.