The novel angiotensin-I-converting enzyme inhibitory peptides from Scomber japonicus muscle protein hydrolysates: QSAR-based screening, molecular docking, kinetic and stability studies.

Food-derived angiotensin-converting enzyme-inhibitory (ACE-I) peptides have attracted extensive attention. Herein, the ACE-I peptides from Scomber japonicus muscle hydrolysates were screened, and their mechanisms of action and inhibition stability were explored. The quantitative structure-activity relationship (QSAR) model based on 5z-scale metrics was developed to rapidly screen for ACE-I peptides. Two novel potential ACE-I peptides (LTPFT, PLITT) were predicted through this model coupled with in silico screening, of which PLITT had the highest activity (IC50: 48.73 ± 7.59 µM). PLITT inhibited ACE activity with a mixture of non-competitive and competitive mechanisms, and this inhibition mainly contributed to the hydrogen bonding based on molecular docking study. PLITT is stable under high temperatures, pH, glucose, and NaCl. The zinc ions (Zn2+) and copper ions (Cu2+) enhanced ACE-I activity. The study suggests that the QSAR model is effective in rapidly screening for ACE-I inhibitors, and PLITT can be supplemented in foods to lower blood pressure.

Structure-immunomodulatory activity relationships of dietary polysaccharides.

Polysaccharides are usually composed of more than ten monosaccharide units, which are connected by linear or branched glycosidic bonds. The immunomodulatory effect of natural polysaccharides is one of the most important bioactive function. In this review, molecular weight, monosaccharide (including galactose, mannose, rhamnogalacturonan-I arabinogalactan and uronic acid), functional groups (namely sulfate, selenium, and acetyl groups), types of glycoside bond connection (including ß-1,3-D-glucosyl, α-1,4-D-glucosyl, ß-1,4-D-glucosyl, α-1,6-D-glucosyl, ß-1,4-D-mannosyl, and ß-1,4-D-Xylopyranosyl), conformation and the branching degrees are systematically identified as their contribution to the immunostimulatory activity of polysaccharides. At present, studies on the structure-activity relationships of polysaccharides are limited due to their low purity and high heterogeneity. However, it is an important step in providing useful guidance for dietary supplements with polysaccharides. The chemical structures and the process of immune responses induced are necessary to be discussed. Polysaccharides may bind with the cell surface receptors to modulate immune responses. This review mainly discusses the structure-activity relationship of dietary polysaccharides.

Huai Qi Huang-induced Apoptosis via Down-regulating PRKCH and Inhibiting RAF/MEK/ERK Pathway in Ph+ Leukemia Cells.

Imatinib mesylate (IM) is the first-line treatment for Philadelphia (Ph) chromosomal positive leukemia by inhibiting phosphorylation of substrates via binding to the ABL kinase domain. Because of the drug resistance, side effects and the high cost of IM, it is necessary to find anti-cancer drugs with relatively low toxicity and cost, and enhanced efficacy, such as traditional Chinese medicines (TCMs). As one of TCMs, Huai Qi Huang (HQH) was chosen to treat BV173 and K562 cells. Various concentrations of HQH were added to cells for 24-72 h. Co-treatment of HQH and trametinib, an MEK inhibitor, was used to verify the synergistic effects on cell viability and apoptosis. Knockdown and overexpression of mitogen-activated protein kinase kinase 4 (MEK4) were implemented to demonstrate the role of MEK in cell apoptosis. Cell viability and apoptosis were measured by cell counting kit-8 assay (CCK8) and flow cytometry, respectively. Western blotting and real-time quantitative PCR (RT-qPCR) were used to assess protein and mRNA expression levels, respectively. The results showed that HQH inhibited survival and promoted apoptosis of BV173 and K562 cells in a dose-dependent manner, accompanied with down-regulation of PRKCH mRNA as well as CRAF, MEK4, phospho-ERK (pERK) and BCL2 proteins, and up-regulation of cleaved caspase3 protein. Co-treatment of HQH and trametinib had a synergistic effect on inhibiting survival and promoting apoptosis. MEK4 knockdown increased apoptosis, and had a synergistic effect with HQH. In contrast, MEK4 overexpression decreased apoptosis, and had the opposite effect with HQH. Collectively, the results of this study may identify a therapeutic mechanism of HQH on promoting apoptosis, and provide a potential option for treatment of Ph+ leukemia.