Silybin B exerts protective effect on cisplatin-induced neurotoxicity by alleviating DNA damage and apoptosis.

ETHNOPHARMACOLOGICAL RELEVANCE: Silybum marianum is a traditional Chinese medicine that has been used for treating liver disease. Silybin consisting of silybin A and silybin B, is a member of Silybum marianum, and exerts a therapeutic effect on many diseases. However, the protective effect of silybin on cisplatin-induced neurotoxicity and the stereoisomer contributing to the effect remain unknown. AIM OF THE STUDY: The present study aimed to study the effect of silybin on cisplatin-induced neuronal injury, compare the difference of protective effect between silybin A and silybin B, and the potential mechanism. MATERIALS AND METHODS: High performance liquid chromatography (HPLC) was used to separate silybin A and silybin B. X-ray crystallographic analysis in combination with experimental and calculated ECD were performed to identify the structure of silybin A and silybin B. The toxicity of the silybin or cisplatin against murine hippocampal neuronal HT22 cells was determined through MTT assay. The cell cycle and cell apoptosis were measured by PI staining and Annexin V-FITC/PI staining, respectively, and then subjected to flow cytometry. Western blot analysis was conducted to quantify the expression of proteins related to apoptosis and DNA damage. Immunofluorescence was used to evaluate the expression of DNA damage marker. In vivo experiment, the behavioral analysis was determined through pole test, swimming test and Morris water maze test. The index of superoxide dismutase (SOD), reduced glutathione (GSH), total antioxidant capacity (T-AOC) and lipid peroxidation (LPO) were examined to evaluate the antioxidant capacity in mice brain. Nissl staining and Tunel assay were used to detect the neuronal viability and apoptosis in hippocampus. RESULTS: We successfully separated and identified silybin A and silybin B. We found both silybin A and silybin B alleviated cisplatin-induced apoptosis and cell cycle arrest in HT22 cells, and silybin B was more effective. We chose silybin B for further mechanism investigation, and found silybin B alleviated DNA damage by enhancing phosphorylation of ATR and decreasing expression of γ-H2AX. In the in vivo experiment, we observed that silybin B markedly improved the behavioral abnormalities in cisplatin-treated mice, reduced LPO level while increased SOD, GSH and T-AOC in mice brain tissue. Nissl staining and Tunel assay showed that silybin B alleviated cisplatin-induced hippocampal damage. CONCLUSIONS: These results suggest that silybin B might serve as a promising drug candidate in mitigating cisplatin-induced neural injury in the brain and thereby improving the chemotherapeutic outcomes.

Protective Effect of Penetratin Analogue-Tagged SOD1 on Cisplatin-Induced Nephrotoxicity through Inhibiting Oxidative Stress and JNK/p38 MAPK Signaling Pathway.

Copper/zinc superoxide dismutase (SOD1) can clear cisplatin- (CP-) induced excessive reactive oxygen species (ROS), but exogenous SOD1 cannot enter cells because of its low biomembrane permeability. Cell-penetrating peptides (CPPs) can rapidly cross plasma membranes. This study is aimed at identifying an efficient and stable CPP-SOD1 and investigating its effects on CP-induced nephrotoxicity. We recombined SOD1 with 14 different CPPs and purified them using an NTA-Ni2+ column. In in vitro experiments, CPPs-SOD1 cell membrane penetration ability and JNK/p38 MAPK signaling pathway were evaluated using Western blotting. ROS production, mitochondrial membrane potential (MMP), and cell apoptosis were determined using flow cytometry and immunofluorescence staining in VERO and HK-2 cells. For in vivo experiments, mice were administered PSF-SOD1 for 2 h before cotreatment with a single CP injection for an additional 4 days. Blood and kidney samples were collected for renal function assessment (creatinine, urea nitrogen, histopathology, TUNEL assay, and JNK/p38 MAPK signaling pathway). Compared with TAT-SOD1, we found that PSF-SOD1 is more efficient at crossing the cell membrane and is stable after transduction into cells. Pretreatment with PSF-SOD1 inhibited CP-induced apoptosis, ROS generation, and JNK/p38 MAPK activation and restored CP-induced MMP loss in VERO and HK-2 kidney cells. Treatment of mice with PSF-SOD1 inhibited CP-induced serum creatinine, blood urea nitrogen elevation, and JNK/p38 MAPK activation. H&E staining and TUNEL assay indicated that kidney tissue damage was alleviated following PSF-SOD1 pretreatment. Overall, PSF-SOD1 ameliorated CP-induced renal damage by partially reducing oxidative stress and cell apoptosis by regulating JNK/p38 MAPK signaling pathway and might be a better cytoprotective agent than TAT-SOD1.

Soluble Expression, One-Step Purification and Characterization of Recombinant Human Growth Hormone Fused with ompA3 in Escherichia coli.

BACKGROUND: Human growth hormone (hGH) is the first recombinant protein approved for the treatment of human growth hormone deficiency. However, expression in inclusion bodies and low expression levels are enormous challenges for heterologous expression of hGH in Escherichia coli. OBJECTIVE: To increase the soluble expression of recombinant hGH with correct folding in E. coli. METHODS: We constructed a new recombinant expression plasmid containing the coding sequence of the outer membrane protein A (ompA3) which was used for the expression in Transetta (DE3) E. coli. In order to simplify the purification process and cleavage of recombinant proteins, the fusion sequence should contain hexahistidine-tag (His6) and enterokinase recognition sites (D4K). The effect of different expression conditions on recombinant hGH expression was optimized in flask cultivations. Furthermore, the periplasmic solution containing soluble hGH was purified by Ni-NTA affinity chromatography. Circular dichroism (CD), western blot and mass spectrometry analyses were used to characterize the protein. Moreover, the growth-promoting effect of the purified hGH was also evaluated by cell proliferation assay. RESULTS: High-level expression (800 µg/mL) was achieved by induction with 0.5 mM IPTG at 30°C for 10 hours. The purity of hGH was over 90%. The immunological activity, secondary structure and molecular weight of the purified hGH were consistent with native hGH. The purified hGH was found to promote the growth of MC3T3-E1 cells, and was found to show the highest activity at a concentration of 100 ng/mL. CONCLUSION: Our research provides a feasible and convenient method for the soluble expression of recombinant hGH in E. coli, and may lay a foundation for the production and application of hGH in the industry.