Danhong injection improves neurological function in rats with ischemic stroke by enhancing neurogenesis and activating BDNF/AKT/CREB signaling pathway.

Danhong injection (DHI) is a traditional Chinese medicine injection that promotes blood circulation and removes blood stasis and has been widely used in the treatment of stroke. Many studies have focused on the mechanism of DHI in acute ischemic stroke (IS); however, few studies have thoroughly explored its role during recovery. In this study, we aimed to determine the effect of DHI on long-term neurological function recovery after cerebral ischemia and explored the related mechanisms. Middle cerebral artery occlusion (MCAO) was used to establish an IS model in rats. The efficacy of DHI was assessed using neurological severity scores, behaviors, cerebral infarction volume and histopathology. Immunofluorescence staining was performed to assess hippocampal neurogenesis. An in vitro oxygen-glucose deprivation/reoxygenation (OGD/R) cell model was constructed and western-blot analyses were performed to verify the underlying mechanisms. Our results showed that DHI treatment greatly reduced the infarct volume, promoted neurological recovery and reversed brain pathological changes. Furthermore, DHI promoted neurogenesis by increasing the migration and proliferation of neural stem cells, and enhancing synaptic plasticity. Moreover, we found that the pro-neurogenic effects of DHI were related to an increase in brain-derived neurotrophic factor (BDNF) expression and the activation of AKT/CREB, which were attenuated by ANA-12 and LY294002, the inhibitors of the BDNF receptor and PI3K. These results suggest that DHI improves neurological function by enhancing neurogenesis and activating the BDNF/AKT/CREB signaling pathways.

Metal ions stabilize a dimeric molten globule state between the open and closed forms of malic enzyme.

Malic enzyme is a tetrameric protein with double dimer quaternary structure. In 3-5 M urea, the pigeon cytosolic NADP(+)-dependent malic enzyme unfolded and aggregated into various forms with dimers as the basic unit. Under the same denaturing conditions but in the presence of 4 mM Mn(2+), the enzyme existed exclusively as a molten globule dimer in solution. Similar to pigeon enzyme (Chang, G. G., T. M. Huang, and T. C. Chang. 1988. Biochem. J. 254:123-130), the human mitochondrial NAD(+)-dependent malic enzyme also underwent a reversible tetramer-dimer-monomer quaternary structural change in an acidic pH environment, which resulted in a molten globule state that is also prone to aggregate. The aggregation of pigeon enzyme was attributable to Trp-572 side chain. Mutation of Trp-572 to Phe, His, Ile, Ser, or Ala abolished the protective effect of the metal ions. The cytosolic malic enzyme was completely digested within 2 h by trypsin. In the presence of Mn(2+), a specific cutting site in the Lys-352-Gly-Arg-354 region was able to generate a unique polypeptide with M(r) of 37 kDa, and this polypeptide was resistant to further digestion. These results indicate that, during the catalytic process of malic enzyme, binding metal ion induces a conformational change within the enzyme from the open form to an intermediate form, which upon binding of L-malate, transforms further into a catalytically competent closed form.