Acute cerebral ischemia-induced down-regulation of Sirt3 protein expression contributes to neuronal injury via damaging mitochondrial function / 生理学报

This study was aimed to determine the effect of acute cerebral ischemia on the protein expression level of silent mating type information regulator 2 homolog 3 (Sirt3) in the neurons and clarify the pathological role of Sirt3 in acute cerebral ischemia. The mice with middle cerebral artery occlusion (MCAO) and primary cultured rat hippocampal neurons with oxygen glucose deprivation (OGD) were used as acute cerebral ischemia models in vivo and in vitro, respectively. Sirt3 overexpression was induced in rat hippocampal neurons by lentivirus transfection. Western blot was utilized to measure the changes in Sirt3 protein expression level. CCK8 assay was used to detect cell viability. Immunofluorescent staining was used to detect mitochondrial function. Transmission electron microscope was used to detect mitochondrial autophagy. The results showed that, compared with the normoxia group, hippocampal neurons from OGD1 h/reoxygenation 2 h (R2 h) and OGD1 h/R12 h groups exhibited down-regulated Sirt3 protein expression levels. Compared with contralateral normal brain tissue, the ipsilateral penumbra region from MCAO1 h/reperfusion 24 h (R24 h) and MCAO1 h/R72 h groups exhibited down-regulated Sirt3 protein expression levels, while there was no significant difference between the Sirt3 protein levels on both sides of sham group. OGD1 h/R12 h treatment damaged mitochondrial function, activated mitochondrial autophagy and reduced cell viability in hippocampal neurons, whereas Sirt3 over-expression attenuated the above damage effects of OGD1 h/R12 h treatment. These results suggest that acute cerebral ischemia results in a decrease in Sirt3 protein level. Sirt3 overexpression can alleviate acute cerebral ischemia-induced neural injuries by improving the mitochondrial function. The current study sheds light on a novel strategy against neural injuries caused by acute cerebral ischemia.

Cloning and heterologous expression of sansanmycin biosynthetic gene cluster in Streptomyces coelicolor / 药学学报

Sansanmycins (SSs), produced by Streptomyces sp. SS, belong to uridyl peptide antibiotics which exhibit a good inhibitory effect on Mycobacterium tuberculosis and Pseudomonas aeruginosa. They share a unique chemical scaffold with a 4',5'-enamide-3'-deoxyuridine attached to DABA (N-methyl-2,3-diaminobutyryl) which was located in the peptide chain through peptide bond. In order to study the function of related genes and to employ synthetic biology to gain new SS derivatives, we obtained a complete SS biosynthetic gene cluster and heterologously expressed it in Streptomyces coelicolor M1146, M1152 and M1154. Fermentation broth of the recombinant strains were detected using HPLC and HPLC-MS/MS, and the result showed that SS-A was successfully produced in the three strains, and its production level in S. coelicolor M1154 was similar to the original wild type strain. In addition, a potential SS analogue named as SS-1154 was discovered from the fermentation broth of S. coelicolor M1154.