Intracellular nicotinamide adenine dinucleotide promotes TNF-induced necroptosis in a sirtuin-dependent manner

Abstract

Cellular necrosis has long been regarded as an incidental and uncontrolled form of cell death. However, a regulated form of cell death termed necroptosis has been identified recently. Necroptosis can be induced by extracellular cytokines, pathogens and several pharmacological compounds, which share the property of triggering the formation of a RIPK3-containing molecular complex supporting cell death. Of interest, most ligands known to induce necroptosis (including notably TNF and FASL) can also promote apoptosis, and the mechanisms regulating the decision of cells to commit to one form of cell death or the other are still poorly defined. We demonstrate herein that intracellular nicotinamide adenine dinucleotide (NAD + ) has an important role in supporting cell progression to necroptosis. Using a panel of pharmacological and genetic approaches, we show that intracellular NAD + promotes necroptosis of the L929 cell line in response to TNF. Use of a pan-sirtuin inhibitor and shRNA-mediated protein knockdown led us to uncover a role for the NAD + -dependent family of sirtuins, and in particular for SIRT2 and SIRT5, in the regulation of the necroptotic cell death program. Thus, and in contrast to a generally held view, intracellular NAD + does not represent a universal pro-survival factor, but rather acts as a key metabolite regulating the choice of cell demise in response to both intrinsic and extrinsic factors. + as a substrate in a number of regulatory processes has shed a new light on its role in cell physiology. Indeed, NAD + represents a substrate for a wide range of enzymes including cADP-ribose synthases, poly (ADP-ribose) polymerases (PARPs) and the sirtuin family of NAD + -dependent deacylases (SIRTs). In marked contrast to its role in energy metabolism, the involvement of NAD + in these enzymatic reactions is based on its ability to function as a donor of ADP-ribose, a reaction that, if sustained, can lead to the depletion of the intracellular NAD + pool. 1-5The pro-survival role of NAD + has been particularly well described in cells exposed to genotoxic/oxidative stress. In response to DNA damage, PARP1, the founding and most abundant member of the PARP family, binds to DNA strand breaks and initiates a repair response by catalyzing the posttranslational modification of several nuclear proteins, including itself. This protective response is characterized by the transfer of successive units of the ADP-ribose moiety (up to 200 units) from NAD + to other proteins, compromising therefore both energy production (slowing the rate of glycolysis, electron transport and ATP formation) and activity of other NAD + -dependent enzymes through NAD + depletion. 6,7 Moreover, PARP1-synthesized PAR polymers can be degraded into free oligomers, known to translocate to the mitochondria where they can trigger the release of AIF from mitochondria to the nucleus. [8][9][10][11] The precise molecular steps linking PARP1 activation to this form of stress-induced cell death, termed parthanatos, have not been fully elucidated, and...

By inhibiting Ras/Raf/ERK and MMP-9, knockdown of EpCAM inhibits breast cancer cell growth and metastasis

“…We also found that higher EpCAM expression was correlated with high Ki67 expression and low p53 expression. It is well known that p53 is the tumor suppressor and has many mechanisms of anticancer function, and plays a role in apoptosis, genomic stability, and inhibition of angiogenesis [ 17 , 18 ]. Ki-67 is a tumor marker that is found in growing, dividing cells.…”

An Overview of Pathways of Regulated Necrosis in Acute Kidney Injury

“…42 Interestingly, contrary to the role for depletion of NAD þ in parthanatos, under certain pathophysiological circumstances, NAD þ via the sirtuins (SIRT)2 and to a lesser extent SIRT5 results in deacetylation of RIPK1, which stabilizes the RIPK1-RIPK3-MLKL necrosome. 43,44 These findings indicate that the NAD þ -SIRT2/5 axis can be an alternative link mediating necroptotic cell death in case PARP-1 does not deplete NAD þ . 40,44 To clarify the realtive contribution of parthanatos and MPT-RN in models of AKI, it would be interesting to investigate Parp1/Ppif double-knockout mice and combination therapies that contain both PARP-1 inhibitors and cyclosporine A or sanglifehrin A.…”

“…43,44 These findings indicate that the NAD þ -SIRT2/5 axis can be an alternative link mediating necroptotic cell death in case PARP-1 does not deplete NAD þ . 40,44 To clarify the realtive contribution of parthanatos and MPT-RN in models of AKI, it would be interesting to investigate Parp1/Ppif double-knockout mice and combination therapies that contain both PARP-1 inhibitors and cyclosporine A or sanglifehrin A.…”

<p>Effects of Nicotinamide on Cervical Cancer-Derived Fibroblasts: Evidence for Therapeutic Potential</p>

“…14 NAD + is henceforth, also known as a universal pro-survival factor, which plays a vital role in protecting the cell against extrinsic and intrinsic risk factors. 15 NAM, as a backbone of phosphorylated NAD+ (i.e., NADP+), is also known to participate in the synthesis of fatty acids and thereby maintains the oxidative balance in the cells. 16 In consent to its central role on several intracellular pathways in the cell, the potential therapeutic role of NAM has been well documented in the literature.…”