stilbenes and Wallerian-Degeneration

Axonal degeneration is a central process in the pathogenesis of several neurodegenerative diseases. Understanding the molecular mechanisms that are involved in axonal degeneration is crucial to developing new therapies against diseases involving neuronal damage. Resveratrol is a putative SIRT1 activator that has been shown to delay neurodegenerative diseases, including Amyotrophic Lateral Sclerosis, Alzheimer, and Huntington's disease. However, the effect of resveratrol on axonal degeneration is still controversial. Using an in vitro model of Wallerian degeneration based on cultures of explants of the dorsal root ganglia (DRG), we showed that resveratrol produces a delay in axonal degeneration. Furthermore, the effect of resveratrol on Wallerian degeneration was lost when SIRT1 was pharmacologically inhibited. Interestingly, we found that knocking out Deleted in Breast Cancer-1 (DBC1), an endogenous SIRT1 inhibitor, restores the neuroprotective effect of resveratrol. However, resveratrol did not have an additive protective effect in DBC1 knockout-derived DRGs, suggesting that resveratrol and DBC1 are working through the same signaling pathway. We found biochemical evidence suggesting that resveratrol protects against Wallerian degeneration by promoting the dissociation of SIRT1 and DBC1 in cultured ganglia. Finally, we demonstrated that resveratrol can delay degeneration of crushed nerves in vivo. We propose that resveratrol protects against Wallerian degeneration by activating SIRT1 through dissociation from its inhibitor DBC1.

Topics: Analysis of Variance; Animals; Animals, Newborn; Antioxidants; Cells, Cultured; Disease Models, Animal; Ganglia, Spinal; Humans; In Vitro Techniques; Mice; NAD; Neurofilament Proteins; Neurons; Resveratrol; RNA-Binding Proteins; Sciatic Nerve; Sirtuin 1; Stilbenes; Time Factors; Transfection; Wallerian Degeneration

The slow Wallerian degeneration protein (Wld(S)), a fusion protein incorporating full-length nicotinamide mononucleotide adenylyltransferase 1 (Nmnat1), delays axon degeneration caused by injury, toxins and genetic mutation. Nmnat1 overexpression is reported to protect axons in vitro, but its effect in vivo and its potency remain unclear. We generated Nmnat1-overexpressing transgenic mice whose Nmnat activities closely match that of Wld(S) mice. Nmnat1 overexpression in five lines of transgenic mice failed to delay Wallerian degeneration in transected sciatic nerves in contrast to Wld(S) mice where nearly all axons were protected. Transected neurites in Nmnat1 transgenic dorsal root ganglion explant cultures also degenerated rapidly. The delay in vincristine-induced neurite degeneration following lentiviral overexpression of Nmnat1 was significantly less potent than for Wld(S), and lentiviral overexpressed enzyme-dead Wld(S) still displayed residual neurite protection. Thus, Nmnat1 is significantly weaker than Wld(S) at protecting axons against traumatic or toxic injury in vitro, and has no detectable effect in vivo. The full protective effect of Wld(S) requires more N-terminal sequences of the protein.

Topics: Animals; Axons; Mice; Mice, Inbred C57BL; Mice, Transgenic; NAD; Nerve Tissue Proteins; Nicotinamide-Nucleotide Adenylyltransferase; Point Mutation; Resveratrol; Sciatic Neuropathy; Stilbenes; Wallerian Degeneration

Resveratrol is a natural polyphenol having a wide range of biological and pharmacological activities. Here we have investigated the effect of resveratrol on neurodegeneration in cultured cerebellar granule cells from slow Wallerian degeneration (Wld(S)) mice, characteristic of substantial delay of degeneration in the distal stump of transected axons. Resveratrol diminished resistance of Wld(S) neurons to axonal degeneration induced by colchicine, a microtubule depolymerizing drug. Resveratrol also decreased the level of tubulin acetylation in Wld(S) neurons and their homogenates. This promoting effect on tubulin deacetylation was mimicked by NAD, suggesting the involvement of SIRT2, an NAD-dependent tubulin deacetylase. Indeed, resveratrol promoted tubulin deacetylation in the presence of GFP-SIRT2 but not GFP-SIRT2 N168A, a catalytically inactive mutant. Moreover, SIRT2 silencing restored the resistance to axonal degeneration in resveratrol-treated Wld(S) neurons. These results suggest that resveratrol abolishes the resistance of Wld(S) mice to axonal degeneration by enhancing SIRT2-mediated tubulin deacetylation.

Topics: Acetylation; Animals; Axons; Cells, Cultured; Drug Resistance; Enzyme Activation; Gene Expression Regulation, Enzymologic; Humans; Mice; Mice, Inbred C57BL; Mice, Transgenic; Microtubules; Resveratrol; RNA, Small Interfering; Sirtuin 2; Sirtuins; Stilbenes; Tubulin; Wallerian Degeneration

Axonal degeneration is an active program of self-destruction that is observed in many physiological and pathological settings. In Wallerian degeneration slow (wlds) mice, Wallerian degeneration in response to axonal injury is delayed because of a mutation that results in overexpression of a chimeric protein (Wlds) composed of the ubiquitin assembly protein Ufd2a and the nicotinamide adenine dinucleotide (NAD) biosynthetic enzyme Nmnat1. We demonstrate that increased Nmnat activity is responsible for the axon-sparing activity of the Wlds protein. Furthermore, we demonstrate that SIRT1, a mammalian ortholog of Sir2, is the downstream effector of increased Nmnat activity that leads to axonal protection. These findings suggest that novel therapeutic strategies directed at increasing the supply of NAD and/or Sir2 activation may be effective for treatment of diseases characterized by axonopathy and neurodegeneration.

Topics: 3T3 Cells; Animals; Axons; Axotomy; Benzamides; Cell Line; Cell Nucleus; Cell Survival; Cells, Cultured; Ganglia, Spinal; Humans; Lentivirus; Mice; Mutation; NAD; Naphthols; Nerve Tissue Proteins; Neuroprotective Agents; Nicotinamide-Nucleotide Adenylyltransferase; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Resveratrol; RNA, Small Interfering; Sirtuin 1; Sirtuins; Stilbenes; Ubiquitin-Protein Ligases; Vincristine; Wallerian Degeneration