Plasticity-Enhancing Effects of Levodopa Treatment after Stroke

Dopaminergic treatment in combination with rehabilitative training enhances long-term recovery after stroke. However, the underlying mechanisms on structural plasticity are unknown. Here, we show an increased dopaminergic innervation of the ischemic territory during the first week after stroke induced in Wistar rats subjected to transient occlusion of the middle cerebral artery (tMCAO) for 120 min. This response was also found in rats subjected to permanent focal ischemia induced by photothrombosis (PT) and mice subjected to PT or tMCAO. Dopaminergic branches were detected in the infarct core of mice and rats in both stroke models. In addition, the Nogo A pathway was significantly downregulated in rats treated with levodopa (LD) compared to vehicle-treated animals subjected to tMCAO. Specifically, the number of Nogo A positive oligodendrocytes as well as the levels of Nogo A and the Nogo A receptor were significantly downregulated in the peri-infarct area of LD-treated animals, while the number of Oligodendrocyte transcription factor 2 positive cells increased in this region after treatment. In addition, we observed lower protein levels of Growth Associated Protein 43 in the peri-infarct area compared to sham-operated animals without treatment effect. The results provide the first evidence of the plasticity-promoting actions of dopaminergic treatment following stroke.

Endothelial Progenitor Cell Transplantation Attenuated Synaptic Loss by Enhancing CR3 Dependent Microglial Phagocytosis in Mice

Background: Endothelial progenitor cell (EPC) transplantation has been shown to have therapeutic effects in cerebral ischemia. However, whether the therapeutic effect of EPCs is a result of the modulation of microglia activity remain elusive. Methods: Adult male mice (n=184) underwent 90 minute-middle cerebral artery occlusion and EPCs were transplanted into the peri-infarct region immediately after the surgery. Microglia migration and phagocytosis were evaluated in the ischemic brain in vivo and underwent oxygen-glucose-deprivation culture condition in vitro. Complement receptor 3 was examined in ischemic brain and cultured primary microglia. Complement receptor 3 agonist leukadherin-1 was intraperitoneally injected to mice immediately after ischemia to imitate the EPC effect. Expression of synapse remodeling related synaptophysin and PSD-95 proteins was detected in the EPC and leukadherin-1 treated mice, separately. Results: EPC transplantation increased the number of microglia in the peri-infarct region of the brain at 3 days after focal ischemia (p<0.05). The ability of phagocytizing apoptotic cells of microglia was higher in EPCs transplanted group at 3 days after ischemia compared to the controls (p<0.05). In vitro study showed that cultured microglia displayed a higher migration (p<0.05) and phagocytosis ability (p<0.05) under the stimulation of EPC conditioned medium or cultured EPCs compared to the controls. Complement receptor 3 expression in the ischemic mouse brain with EPC transplantation (p<0.05), and primary microglia treated by EPC conditioned medium or cultured EPCs was up-regulated (p<0.05). Leukadherin-1 reduced brain atrophy volume at 14 days (p<0.05) and ameliorated neurological deficiency during 14 days after cerebral ischemia (p<0.05). Both EPC transplantation and leukadherin-1 injection increased synaptophysin (p<0.05) and PSD-95 expressions (p<0.05) at 14 days after focal ischemia. Conclusion: We concluded that EPC transplantation promoted regulating complement receptor 3 mediated microglial phagocytosis at acute phase, and subsequently benefited for attenuating synaptic loss at the recovery phase of ischemic stroke, which provided a novel therapeutic mechanism of EPC for cerebral ischemia.

THE COMBINED USE OF PROPARGYLGLYCINE AND L-CYSTEINE PREVENTS OXIDATIVE AND NITROSATIVE STRESS IN CARDIAC TISSUES IN FOCAL CEREBRAL ISCHEMIA-REPERFUSION

Cerebral ischemia is a neurogenerative disoder that leads to partial or general paralysis and subsequent disability. The development of oxidative-nitrosative stress on the background of insufficient production of nitric oxide (NO) and hydrogen sulfide (H2S) are the main reasons behind the pathogenesis of focal ischemia-reperfusion and cerebrocardial syndrome. We studied the combined use of propargylglycine and L-cysteine as drugs that prevent oxidative and nitrosative stress and are activators of gasotransmitters - NO and H2S in the heart tissues of rats with focal ischemia. It was shown that focal ischemiareperfusion was accompanied by a significant increase in the heart of rats calcium-independent inducible synthesis of NO (iNOS) and an increase in markers of oxidative stress (superoxide anion radical, hydroxyl radical, diene conjugates) NO-synthase (cNOS). This caused disruption of nitric oxide synthesis due to the uncoupling state of cNOS in the rat heart. The use of a combination of DL-proparlgylglycine (11.31 mg/ kg) and L-cysteine (112.1 mg / kg) 40 min before the modeling of focal ischemia significantly reduced the activity of iNOS and the content of markers of oxidative metabolism in the heart of adult rats and increased the constitutive synthesis of NO, which led to restoration of the cNOS incoupling. We observed activation of endogenous synthesis of H2S, which interacts closely with the nitric oxide system and is a powerful antioxidant. It should also be noted an increase in animal survival after 24 h by 25%. Thus, the combined use of propargylglycine and Lcysteine in rats prevented disruption of NO and H2S synthesis in cardiac tissues in ishemia-reperfusion due to a slowing of the development of oxidative stress, which helped to restore cNOS coupling.