Tat-NOL3 protects against hippocampal neuronal cell death induced by oxidative stress through the regulation of apoptotic pathways.

Oxidative stress-induced apoptosis is associated with neuronal cell death and ischemia. The NOL3 [nucleolar protein 3 (apoptosis repressor with CARD domain)] protein protects against oxidative stress-induced cell death. However, the protective mechanism responsible for this effect as well as the effects of NOL3 against oxidative stress in ischemia remain unclear. Thus, we examined the protective effects of NOL3 protein on hydrogen peroxide (H2O2)-induced oxidative stress and the mechanism responsible for these effects in hippocampal neuronal HT22 cells and in an animal model of forebrain ischemia using Tat-fused NOL3 protein (Tat-NOL3). Purified Tat-NOL3 protein transduced into the H2O2-exposed HT22 cells and inhibited the production of reactive oxygen species (ROS), DNA fragmentation and reduced mitochondrial membrane potential (ΔΨm). In addition, Tat-NOL3 prevented neuronal cell death through the regulation of apoptotic signaling pathways including Bax, Bcl-2, caspase-2, -3 and -8, PARP and p53. In addition, Tat-NOL3 protein transduced into the animal brains and significantly protected against neuronal cell death in the CA1 region of the hippocampus by regulating the activation of microglia and astrocytes. Taken together, these findings demonstrate that Tat-NOL3 protein protects against oxidative stress-induced neuronal cell death by regulating oxidative stress and by acting as an anti-apoptotic protein. Thus, we suggest that Tat-NOL3 represents a potential therapeutic agent for protection against ischemic brain injury.

Silk peptides inhibit adipocyte differentiation through modulation of the Notch pathway in C3H10T1/2 cells.

Silk protein is a biocompatible material that has been used in many biotechnological applications and exhibits body fat-lowering effects. Recent studies have shown that silk peptides increase expression of osteogenic markers in osteoblast-like cells. Because osteogenic and adipogenic differentiation from common mesenchymal progenitor cells are inverse processes and often regulated reciprocally, we hypothesized that silk peptides might suppress adipocyte differentiation. We therefore endeavored to evaluate the effects of silk peptides on adipocyte differentiation in C3H10T1/2 cells. We find that silk peptides inhibit lipid accumulation and morphological differentiation in these cells. Molecular studies show that silk peptides block expression of adipocyte-specific genes such as peroxisome proliferator-activated receptor γ and its targets, including aP2, Cd36, CCAAT enhancer binding proteinα. Silk peptides appear to inhibit adipogenesis by suppression of the Notch pathway, repressing the Notch target genes Hes-1 and Hey-1. In addition, these peptides inhibit endogenous Notch activation, as shown by a reduction in generation of Notch intracellular domain. N-[N-(3.5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butylester, compound E, and WPE-III-31C, which are all known Notch signaling inhibitors, block adipocyte differentiation to an extent similar to silk peptides. Together, our data demonstrate that silk peptides can modulate adipocyte differentiation through inhibition of the Notch signaling and further suggest potential future strategies for treating obesity and its related metabolic diseases.