Treadmill training improves neurological deficits and suppresses neuronal apoptosis in cerebral ischemic stroke rats

Rehabilitation training is believed to be beneficial to patients with stroke, but its molecular mechanism is still unclear. Rat models of cerebral ischemic stroke were established by middle cerebral artery occlusion/reperfusion, and then received treadmill training of different intensities, twice a day for 30 minutes for 1 week. Low-intensity training was conducted at 5 m/min, with a 10-minute running, 10-minute rest, and 10-minute running cycle. In the moderate-intensity training, the intensity gradually increased from 5 m/min to 10 m/min in 5 minutes, with the same rest cycle as above. In high-intensity training, the intensity gradually increased from 5 m/min to 25 m/min in 5 minutes, with the same rest cycle as above. The Bederson scale was used to evaluate the improvement of motor function. Infarct volume was detected using 2,3,5-triphenyltetrazolium chloride staining. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining was applied to detect the apoptosis of nerve cells in brain tissue. Western blot assay was employed to analyze the activation of cyclic adenosine monophosphate (cAMP)/protein kinase A and Akt/glycogen synthase kinase-3β signaling pathways in rat brain tissue. All training intensities reduced the neurological deficit score, infarct volume, and apoptosis in nerve cells in brain tissue of stroke rats. Training intensities activated the cAMP/protein kinase A and Akt/glycogen synthase kinase-3 beta signaling pathways. This activation was more obvious with higher training intensities. These changes were reversed by intracerebroventricular injection of protein kinase A inhibitor Rp-cAMP. Our findings indicate that the neuroprotective effect of rehabilitation training is achieved via activation of the cAMP/protein kinase A and Akt/glycogen synthase kinase-3 beta signaling pathways. This study was approved by the Ethics Committee of Animal Experimentation in Shanghai No. 8 People’s Hospital, China.

Defective cerebellar response to mitogenic Hedgehog signaling in Down [corrected] syndrome mice

Trisomy 21 is the cause of Down [corrected] syndrome (DS) which is characterized by a number of phenotypes, including a brain which is small and hypocellular compared to that of euploid individuals. The cerebellum is disproportionately reduced. Ts65Dn mice are trisomic for orthologs of about half of the genes on human chromosome 21 and provide a genetic model for DS. These mice display a number of developmental anomalies analogous to those in DS, including a small cerebellum with a significantly decreased number of both granule and Purkinje cell neurons. Here we trace the origin of the granule cell deficit to precursors in early postnatal development, which show a substantially reduced mitogenic response to Hedgehog protein signaling. Purified cultures of trisomic granule cell precursors show a reduced but dose-dependent response to the Sonic hedgehog protein signal in vitro, demonstrating that this is a cell-autonomous deficit. Systemic treatment of newborn trisomic mice with a small molecule agonist of Hedgehog pathway activity increases mitosis and restores granule cell precursor populations in vivo. These results demonstrate a basis for and a potential therapeutic approach to a fundamental aspect of CNS pathology in DS.

Impaired megakaryopoiesis and behavioral defects in mafG-null mutant mice

The small Maf proteins (MafG, MafK, and MafF), which serve as heterodimeric partner molecules of CNC family proteins for binding in vitro to MARE sites, have been implicated in the regulation of both transcription and chromatin structure, but there is no current evidence that the proteins fulfill these functions in vivo. To elucidate possible contributions of the small Maf proteins to gene regulation, we have ablated the mafG and mafK genes in mice by replacing their entire coding sequences with the Escherichia coli lacZ gene. mafG homozygous mutant animals exhibit impaired platelet formation accompanied by megakaryocyte proliferation, as well as behavioral abnormalities, whereas mafK-null mutant mice are phenotypically normal. Characterization of the mafG and mafK embryonic expression patterns show that their developmental programs are distinct and intersecting, but not entirely overlapping. These results provide direct evidence that the small Maf transcription factors are vital participants in embryonic development and cellular differentiation.