Schisandra chinensis (Turcz.) Baill, a traditional Chinese medicine with significant nourishing functions, has a regulatory effect on the cardiovascular system, digestive system, central nervous system, and endocrine and immune systems. It can protect the cardiovascular system, improve immunity, and has anti-oxidant and anti-aging properties. This study aimed to identify the chisandra chinensis components that increased NAD+ levels, by using spectrum-effect analysis and experimental validations. First, the quality of the S. chinensis extract was analyzed by HPLC-MS. The extract of S. chinensis increased the NAD+ levels of HUVECs during oxygen and glucose deprivation injury, and protected HUVEC s from injury from superoxide dismutase (SOD) and aging. The relationships of spectral effects were studied by partial least square regression. Coupled with target cell extraction, the material basis for increasing NAD+ levels in S. chinensis was obtained. The pharmacological activity of S. chinensis was verified at the cellular level. The related enzymes of the NAD+ synthesis and decomposition pathways were identified, showing that S. chinensis increased the level of NAD+ by increasing the activity of related enzymes in the synthesis pathways of NMNAT1, NMNAT2, NMNAT3, and NAMPT, but had no effect on the decomposition pathway. Finally, four constituents were confirmed, in vitro, to be the basis of S. chinensis -induced increases in the levels of NAD+. The EC 50 values of the four constituents were also determined.
Nicotinamide adenine dinucleotide (NAD) is a coenzyme found in all living cells and mediates multiple cellular signaling pathways. In the present study, a 35% decrease of cellular NAD level is achieved by stable expression of the N-terminal truncated CD38, a NAD hydrolase. CD38-expressing (CD38(+)) cells have the lower growth rate and are more susceptive to oxidative stress than the wild type cells and empty vector-transfected (CD38(−)) cells. Quantitative proteomic analysis shows that 178 proteins are down-regulated in CD38(+) cells, which involve in diverse cellular processes including glycolysis, RNA processing and protein synthesis, antioxidant, and DNA repair. Down regulation of six selected proteins is confirmed by Western blotting. However, down-regulation of mRNA expressions of genes associated with glycolysis, antioxidant, and DNA repair is less significant than the corresponding change in protein expression, suggesting the low NAD level impairs the protein translational machinery in CD38(+) cells. Down-regulation of antioxidant protein and DNA-repair protein expression contributes to the susceptibility of CD38(+) cells to oxidative stress. Taken together, these results demonstrate that CD38(+) cells are a useful model to study effects of the cellular NAD levels on cellular processes and establish a new linker between cellular NAD levels and oxidative stress.
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