In the present study, we aimed to determine whether ethanol extracts of Fructus Schisandrae (FS), the dried fruit of Schizandra chinensis Baillon, mitigates the development of dexamethasone-induced muscle atrophy. Adult SPF/VAT outbred CrljOri:CD1 (ICR) mice were either treated with dexamethasone to induce muscle atrophy. Some mice were treated with various concentrations of FS or oxymetholone, a 17α-alkylated anabolic-androgenic steroid. Muscle thickness and weight, calf muscle strength, and serum creatine and creatine kinase (CK) levels were then measured. The administration of FS attenuated the decrease in calf thickness, gastrocnemius muscle thickness, muscle strength and weight, fiber diameter and serum lactate dehydrogenase levels in the gastrocnemius muscle bundles which was induced by dexamethasone in a dose-dependent manner. Treatment with FS also prevented the dexamethasone-induced increase in serum creatine and creatine kinase levels, histopathological muscle fiber microvacuolation and fibrosis, and the immunoreactivity of muscle fibers for nitrotyrosine, 4-hydroxynonenal, inducible nitric oxide synthase and myostatin. In addition, the destruction of the gastrocnemius antioxidant defense system was also inhibited by the administration of FS in a dose-dependent manner. FS downregulated the mRNA expression of atrogin-1 and muscle RING-finger protein-1 (involved in muscle protein degradation), myostatin (a potent negative regulator of muscle growth) and sirtuin 1 (a representative inhibitor of muscle regeneration), but upregulated the mRNA expression of phosphatidylinositol 3-kinase, Akt1, adenosine A1 receptor and transient receptor potential cation channel subfamily V member 4, involved in muscle growth and the activation of protein synthesis. The overall effects of treatment with 500 mg/kg FS were comparable to those observed following treatment with 50 mg/kg oxymetholone. The results from the present study support the hypothesis that FS has a favorable ameliorating effect on muscle atrophy induced by dexamethasone, by exerting anti-inflammatory and antioxidant effects on muscle fibers, which may be due to an increase in protein synthesis and a decrease in protein degradation.

No abstract

DNA damage is implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). However, relationships between DNA damage accumulation, DNA damage response (DDR), and upper and lower motor neuron vulnerability in human ALS are unclear; furthermore, it is unknown whether epigenetic silencing of DNA repair pathways contributes to ALS pathogenesis. We tested the hypotheses that DNA damage accumulates in ALS motor neurons along with diminished DDR, and that DNA repair genes undergo hypermethylation. Human postmortem CNS tissue was obtained from ALS cases (N = 34) and age-matched controls without neurologic disease (N = 15). Compared to age-matched controls, abasic sites accumulated in genomic DNA of ALS motor cortex and laser capture microdissection-acquired spinal motor neurons but not in motor neuron mitochondrial DNA. By immunohistochemistry, DNA damage accumulated significantly in upper and lower motor neurons in ALS cases as single-stranded DNA and 8-hydroxy-deoxyguanosine (OHdG) compared to age-matched controls. Significant DDR was engaged in ALS motor neurons as evidenced by accumulation of c-Abl, nuclear BRCA1, and ATM activation. DNA damage and DDR were present in motor neurons at pre-attritional stages and throughout the somatodendritic attritional stages of neurodegeneration. Motor neurons with DNA damage were also positive for activated p53 and cleaved caspase-3. Gene-specific promoter DNA methylation pyrosequencing identified the DNA repair genes Ogg1, Apex1, Pnkp and Aptx as hypomethylated in ALS. In human induced-pluripotent stem cell (iPSC)-derived motor neurons with familial ALS SOD1 mutations, DNA repair capacity was similar to isogenic control motor neurons. Our results show that vulnerable neurons in human ALS accumulate DNA damage, and contrary to our hypothesis, strongly activate and mobilize response effectors and DNA repair genes. This DDR in ALS motor neurons involves recruitment of c-Abl and BRCA1 to the nucleus in vivo, and repair of DNA double-strand breaks in human ALS motor neurons with SOD1 mutations in cell culture.

Understanding midbrain dopamine (DA) neuron differentiation is of importance, because of physiological and clinical implications of this neuronal subtype. We show that prolonged membrane depolarization induced by KCl treatment promotes DA neuron differentiation from neural precursor cells (NPCs) derived from embryonic ventral midbrain (VM). Interestingly, the depolarization-induced increase of DA neuron yields was not abolished by L-type calcium channel blockers, along with no depolarizationmediated change of intracellular calcium level in the VMderived NPCs (VM-NPCs), suggesting that the depolarization effect is due to a calcium-independent mechanism. Experiments with labeled DA neuron progenitors indicate that membrane depolarization acts at the differentiation fate determination stage and promotes the expression of DA phenotype genes (tyrosine hydroxylase [TH] and DA transporter [DAT]). Recruitment of Nurr1, a transcription factor crucial for midbrain DA neuron development, to the promoter of TH gene was enhanced by depolarization, along with increases of histone 3 acetylation (H3Ac) and trimethylation of histone3 on lysine 4 (H3K4m3), and decreases of H3K9m3 and H3K27m3 in the consensus Nurr1 binding regions of TH promoter. Depolarization stimuli on differentiating VM-NPCs also induced dissociation of methyl CpG binding protein 2 and related repressor complex molecules (repressor element-1 silencing transcription factor corepressor and histone deacetylase 1) from the CpG sites of TH and DAT promoters. Based on these findings, we suggest that membrane depolarization promotes DA neuron differentiation by opening chromatin structures surrounding DA phenotype genes and inhibiting the binding of corepressors, thus allowing transcriptional activators such as Nurr1 to access DA neuron differentiation gene promoter regions.