The NAD+ precursor NMN activates dSarm to trigger axon degeneration in Drosophila.

Axon degeneration contributes to the disruption of neuronal circuit function in diseased and injured nervous systems. Severed axons degenerate following the activation of an evolutionarily conserved signaling pathway, which culminates in the activation of SARM1 in mammals to execute the pathological depletion of the metabolite NAD+. SARM1 NADase activity is activated by the NAD+ precursor nicotinamide mononucleotide (NMN). In mammals, keeping NMN levels low potently preserves axons after injury. However, it remains unclear whether NMN is also a key mediator of axon degeneration and dSarm activation in flies. Here, we demonstrate that lowering NMN levels in Drosophila through the expression of a newly generated prokaryotic NMN-Deamidase (NMN-D) preserves severed axons for months and keeps them circuit-integrated for weeks. NMN-D alters the NAD+ metabolic flux by lowering NMN, while NAD+ remains unchanged in vivo. Increased NMN synthesis by the expression of mouse nicotinamide phosphoribosyltransferase (mNAMPT) leads to faster axon degeneration after injury. We also show that NMN-induced activation of dSarm mediates axon degeneration in vivo. Finally, NMN-D delays neurodegeneration caused by loss of the sole NMN-consuming and NAD+-synthesizing enzyme dNmnat. Our results reveal a critical role for NMN in neurodegeneration in the fly, which extends beyond axonal injury. The potent neuroprotection by reducing NMN levels is similar to the interference with other essential mediators of axon degeneration in Drosophila.

Bisphenol A and its analogs exhibit different apoptotic potential in peripheral blood mononuclear cells (in vitro study).

There are only a few studies that have assessed the effect of bisphenol A (BPA) on human blood cells and no study has been conducted to analyze the impact of BPA analogs on human leucocytes. In this study, we have investigated the effect of BPA and its analogs like bisphenol F (BPF), bisphenol S (BPS) and bisphenol AF (BPAF) on apoptosis induction in human peripheral blood mononuclear cells (PBMCs). In order to clarify the mechanism of bisphenols-induced programmed cell death, changes in various signaling molecules of this process have been assessed. We observed an increase in cytosolic calcium ions (Ca(2+)) level and reduction of transmembrane mitochondrial potential (ΔΨm) in PBMCs incubated with all compounds examined, and particularly BPA and BPAF. All compounds studied changed PBMCs membrane permeability, activated caspase-8, -9, -3 and induced PARP-1 cleavage and chromatin condensation, which confirmed that they were capable of inducing apoptosis both via intrinsic and extrinsic pathway. Moreover, we have found that modus operandi of bisphenols studied was different. We noticed that BPAF and BPS caused mainly necrotic and apoptotic changes, respectively, whereas BPA induced comparable apoptotic and necrotic effects in the incubated cells.