ATF2 maintains a subset of neural progenitors through CBF1/Notch independent Hes-1 expression and synergistically activates the expression of Hes-1 in Notch-dependent neural progenitors.

Hes-1 and Hes-5 are downstream effectors of Notch signaling that are known to be involved in different aspects of neural stem cell proliferation and differentiation. Evidence has emerged that Hes-1 expression can be regulated by alternate signaling pathways independent of canonical Notch/CBF1 interaction. This context-dependent differential regulation of Hes-1 expression in neural progenitor gains a lot of importance as it would help in its exponential expansion without the requirement of interaction from neighboring cells during development. Here, we have clearly demonstrated the existence of a population of neural progenitors with Notch/CBF1-independent Hes-1 expression in vitro. Further analysis demonstrated the role of FGF2 in activating Hes-1 expression through the direct binding of ATF2, a JNK downstream target, on Hes-1 promoter. This raises the possibility for the existence of two distinct populations of neural progenitors - one maintained by Hes-1 expression exclusively through Notch-independent mechanism and the other mediating Hes-1 expression through both canonical Notch and FGF2-ATF2 pathway. This alternative pathway will insure a constant expression of Hes-1 even in the absence of canonical Notch intracellular domain-mediated signaling, thereby maintaining a pool of proliferating neural progenitors required during development.

In vitro differentiation of retinal ganglion-like cells from embryonic stem cell derived neural progenitors.

ES cells have been reported to serve as an excellent source for obtaining various specialized cell types and could be used in cell replacement therapy. Here, we demonstrate the potential of ES cells to differentiate along retinal ganglion cell (RGC) lineage. FGF2-induced ES cell derived neural progenitors (ES-NPs) were able to generate RGC-like cells in vitro upon differentiation. These cells expressed RGC regulators and markers such as, Ath5, Brn3b, RPF-1, Thy-1 and Islet-1, confirming their potential to differentiate into RGCs. The generation of RGCs from ES-NPs was enhanced with the exposure of FGF2 and Sonic hedgehog (Shh), although Shh treatment alone did not affect RGC differentiation significantly. ES-NPs, after exposure to FGF2, were capable of integrating and differentiating into RGCs in vivo upon transplantation. Thus, our study suggests that ES cells can serve an excellent renewable source for generating RGCs that can be used to treat neurodegenerative diseases like glaucoma.

Curcumin treatment alleviates the effects of glutathione depletion in vitro and in vivo: therapeutic implications for Parkinson's disease explained via in silico studies.

Oxidative stress has been implicated in the degeneration of dopaminergic neurons in the substantia nigra (SN) of Parkinson's disease (PD) patients. An important biochemical feature of presymptomatic PD is a significant depletion of the thiol antioxidant glutathione (GSH) in these neurons resulting in oxidative stress, mitochondrial dysfunction, and ultimately cell death. We have earlier demonstrated that curcumin, a natural polyphenol obtained from turmeric, protects against peroxynitrite-mediated mitochondrial dysfunction both in vitro and in vivo. Here we report that treatment of dopaminergic neuronal cells and mice with curcumin restores depletion of GSH levels, protects against protein oxidation, and preserves mitochondrial complex I activity which normally is impaired due to GSH loss. Using systems biology and dynamic modeling we have explained the mechanism of curcumin action in a model of mitochondrial dysfunction linked to GSH metabolism that corroborates the major findings of our experimental work. These data suggest that curcumin has potential therapeutic value for neurodegenerative diseases involving GSH depletion-mediated oxidative stress.

Mitochondrial complex I inhibition in Parkinson's disease: how can curcumin protect mitochondria?

Selective damage of mitochondrial complex I within the dopaminergic neurons of the substantia nigra is the central event during Parkinson disease. Peroxynitrite is one of the important free radicals probably mediating complex I damage. Peroxynitrite inhibits brain complex I mainly by 3-nitrotyrosine and nitrosothiol formation, but how these modifications alter the structure-function relation of complex I is unclear. Curcumin pretreatment protects brain mitochondria against peroxynitrite in vitro by direct detoxification and prevention of 3-nitrotyrosine formation and in vivo by elevation of total cellular glutathione levels. These results suggest a potential therapeutic role for curcumin against nitrosative stress in neurological disorders.