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No longer considered to be exclusive to cellular developmental pathways, the Wnt family of secreted cysteine-rich glycosylated proteins has emerged as versatile targets for a variety of conditions that involve cardiovascular disease, aging, cancer, diabetes, neurodegeneration, and inflammation. In particular, modulation of Wnt signaling may fill a critical void for the treatment of disorders that impact upon both cellular survival and cellular longevity. Yet, in some scenarios, Wnt signaling can become the catalyst for disease development or promote cell senescence that can compromise clinical utility. This double edge sword in regards to the role of Wnt and its signaling pathways highlights the critical need to further elucidate the cellular mechanisms governed by Wnt in conjunction with the development of robust pharmacological ligands that may open new avenues for disease treatment. Here we discuss the influence of the Wnt pathway during cell survival, metabolism, and aging in order for one to gain a greater insight for the novel role of Wnt signaling as well as exemplify its unique cellular pathways that influence both normal physiology and disease.

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No longer considered exclusive for the function of the hematopoietic system, erythropoietin (EPO) is now considered as a viable agent to address central nervous system injury in a variety of cellular systems that involve neuronal, vascular, and inflammatory cells. Yet, it remains unclear whether the protective capacity of EPO may be effective for chronic neurodegenerative disorders such as Alzheimer's disease (AD) that involve beta-amyloid (Abeta) apoptotic injury to hippocampal neurons. We therefore investigated whether EPO could prevent both early and late apoptotic injury during Abeta exposure in primary hippocampal neurons and assessed potential cellular pathways responsible for this protection. Primary hippocampal neuronal injury was evaluated by trypan blue dye exclusion, DNA fragmentation, membrane phosphatidylserine (PS) exposure, and nuclear factor-kappaB (NF-kappaB) expression with subcellular translocation. We show that EPO, in a concentration specific manner, is able to prevent the loss of both apoptotic genomic DNA integrity and cellular membrane asymmetry during Abeta exposure. This blockade of Abeta generated neuronal apoptosis by EPO is both necessary and sufficient, since protection by EPO is completely abolished by co-treatment with an anti-EPO neutralizing antibody. Furthermore, neuroprotection by EPO is closely linked to the expression of NF-kappaB p65 by preventing the degradation of this protein by Abeta and fostering the subcellular translocation of NF-kappaB p65 from the cytoplasm to the nucleus to allow the initiation of an anti-apoptotic program. In addition, EPO intimately relies upon NF-kappaB p65 to promote neuronal survival, since gene silencing of NF-kappaB p65 by RNA interference removes the protective capacity of EPO during Abeta exposure. Our work illustrates that EPO is an effective entity at the neuronal cellular level against Abeta toxicity and requires the close modulation of the NF-kappaB p65 pathway, suggesting that either EPO or NF-kappaB may be used as future potential therapeutic strategies for the management of chronic neurodegenerative disorders, such as AD.

Nicotinamide, the amide form of niacin (vitamin B 3 ), is the precursor for the coenzyme β-nicotinamide adenine dinucleotide (NAD + ) and plays a significant role during the enhancement of cell survival as well as cell longevity. Yet, these abilities of nicotinamide appear to be diametrically opposed. Here we describe the development of nicotinamide as a novel agent that is critical for modulating cellular metabolism, plasticity, longevity, and inflammatory microglial function as well as for influencing cellular life span. The capacity of nicotinamide to govern not only intrinsic cellular integrity, but also extrinsic cellular inflammation rests with the modulation of a host of cellular targets that involve mitochondrial membrane potential, poly(ADP-ribose) polymerase, protein kinase B (Akt), Forkhead transcription factors, Bad, caspases, and microglial activation. Further knowledge acquired in regards to the ability of nicotinamide to foster cellular survival and regulate cellular lifespan should significantly promote the development of therapies against a host of disorders, such as aging, Alzheimer's disease, diabetes, cerebral ischemia, Parkinson's disease, and cancer. KeywordsAkt; Alzheimer's disease; apoptosis; caspases; diabetes; erythropoietin; Huntington's disease; microglia; NAD + ; Parkinson's disease; stroke; vitamin B 3 NICOTINAMIDE, NAD + PRECURSOR, AND CELLULAR METABOLISMAs the amide form of niacin or vitamin B 3 , nicotinamide is the precursor for the coenzyme β-nicotinamide adenine dinucleotide (NAD + ) and is essential for the synthesis of nicotinamide adenine dinucleotide phosphate (NADP + ) [1,2]. Nicotinamide and nicotinic acid can be obtained either through synthesis in the body or through a dietary source [3]. The predominant form of niacin in dietary plant sources is nicotinic acid that is rapidly absorbed through the gastrointestinal epithelium. Nicotinamide is formed through the conversion of nicotinic acid in the liver or through the hydrolysis of NAD + . Once nicotinamide is obtained in the body, it is utilized to synthesize NAD + [4].Nicotinamide through NAD + plays a critical physiological role in cellular metabolism and can be directly utilized by cells to synthesize NAD + [4]. Nicotinamide also participates in energy metabolism through the tricarboxylic acid cycle by utilizing NAD + in the mitochondrial respiratory electron transport chain for the production of ATP, DNA synthesis, and DNA repair *Address correspondence to this author at the Department of Neurology, 8C-1 UHC, Wayne State University School of Medicine, 4201 St. Antoine, Detroit, MI 48201, USA; Fax: 313-966-0486; E-mail: kmaiese@med.wayne.edu. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript [5][6][7]. Furthermore, nicotinamide can significantly increase NAD + levels in vulnerable regions of the ischemic brain, suggesting that nicotinamide may offer cytoprotection of injured tissue through the maintenance of NAD + levels [8]. Administration of nicotinamide can signif...

Initially described as a modulator of embryogenesis for a number of organ systems, Wnt1 has recently been linked to the development of several neurodegenerative disorders, none being of greater significance than Alzheimer's disease. We therefore examined the ability of Wnt1 to oversee vital pathways responsible for cell survival during β-amyloid (Aβ 1-42 )exposure. Here we show that Wnt1 is critical for protection in the SH-SY5Y neuronal cell line against genomic DNA degradation, membrane phosphatidylserine (PS) exposure, and microglial activation, since these neuroprotective attributes of Wnt1 are lost during gene silencing of Wnt1 protein expression. Intimately tied to Wnt1 protection is the presence and activation of Akt1. Pharmacological inhibition of the PI 3-K pathway or gene silencing of Akt1 expression can abrogate the protective capacity of Wnt1. Closely aligned with Wnt1 and Akt1 are the integrated canonical pathways of synthase kinase-3β (GSK-3β) and β-catenin. Through Akt1 dependent pathways, Wnt1 phosphorylates GSK-3β and maintains β-catenin integrity to insure its translocation from the cytoplasm to the nucleus to block apoptosis. Our work outlines a highly novel role for Wnt1 and its integration with Akt1, GSK-3β, and β-catenin to foster neuronal cell survival and repress inflammatory microglial activation that can identify new avenues of therapy against neurodegenerative disorders.