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Rationale: Stroke is a leading cause of adult disability worldwide, but no drug provides functional recovery during the repair phase. Accumulating evidence demonstrates that environmental enrichment (EE) promotes stroke recovery by enhancing network excitability. However, the complexities of utilizing EE in a clinical setting limit its translation. Methods: We used multifaceted approaches combining electrophysiology, chemogenetics, optogenetics, and floxed mice in a mouse photothrombotic stroke model to reveal the key target of EE-mediated stroke recovery. Results: EE reduced tonic gamma-aminobutyric acid (GABA) inhibition and facilitated phasic GABA inhibition in the peri-infarct cortex, thereby promoting network excitability and stroke recovery. These beneficial effects depended on GAT-1, a GABA transporter regulating both tonic and phasic GABA signaling, as EE positively regulated GAT-1 expression, trafficking, and function. Furthermore, GAT-1 was necessary for EE-induced network plasticity, including structural neuroplasticity, input synaptic strengthening in the peri-infarct cortex, output synaptic strengthening in the corticospinal tract, and sprouting of uninjured corticospinal axons across the midline into the territory of denervated spinal cord, and functional recovery from stroke. Moreover, restoration of GAT-1 function in the peri-infarct cortex by its overexpression showed similar beneficial effects on stroke recovery as EE exposure. Conclusion: GAT-1 is a key molecular substrate of the effects of EE on network excitability and consequent stroke recovery and can serve as a novel therapeutic target for stroke treatment during the repair phase.

Environmental enrichment (EE) is a generally accepted strategy to promote stroke recovery and its beneficial effect is positively correlated with neuroplasticity. However, the mechanisms underlying it remain elusive. Histone deacetylase 2 (HDAC2), a negative regulator of neuroplasticity, is up-regulated after stroke. Thus, we hypothesized that HDAC2 may participate in EE-mediated stroke recovery. In this study, focal stroke was induced by photothrombosis in male mice exposing to EE or standard housing (SH) conditions. Recombinant virus vectors, including Ad-HDAC2-Flag, AAV-CAG-EGFP-Cre, LV-shHDAC2, or their controls were microinjected into the motor cortex at 3 days before stroke. Grid-walking and cylinder tasks were conducted to assess motor function. Western blot and immunostaining were used to uncover the mechanisms underlying EE-mediated stroke recovery. We found that EE exposure reversed stroke-induced HDAC2 up-regulation, implicating HDAC2 in EE-mediated functional recovery. Importantly, EE-dependent stroke recovery was counteracted by over-expressing HDAC2, and HDAC2 knockdown promoted functional recovery from stroke to the similar extent as EE exposure. Moreover, the knockdown of HDAC2 epigenetically enhanced expressions of neurotrophins and neuroplasticity-related proteins, with similar effects as EE, and consequently, whole brain and corticospinal tract (CST) rewiring. Together, our findings indicate that HDAC2 is critical for EE-dependent functional restoration. Precisely targeting HDAC2 may mimic EE and serve as a novel therapeutic strategy for stroke recovery.

A filamentous fungi strain, Aspergillus niger, producing β-glucosidase was screened to transform geniposide in traditional Chinese medicine Gardenia jasminoides into genipin. The conversion rate of gardenia hydrolyzed by β-glucosidase which had been extracted from fermentation broth of A. niger could reach 15 % at the enzyme concentration of 5 %, enzyme digestion time of 40 min, temperature at 50 °C. On the other hand, genipin was achieved with the method of microbial cell transformation. The optimum conversion conditions by cells were: β-glucosidase activity dose 10.12 U/mL at a fermentation time of 96 h, rotation speed of 180 r/min, medium capacity of 50 mL and gardenia concentration of 10 %. By HPLC analysis, the maximum conversion efficiency of 22 % was achieved. By this way, conversion efficiency was increased by 7 % and the extraction process was saved compared with enzymatic hydrolysis method.