Oxidative and nitrosative stress is increasingly associated with the pathology of neurodegeneration and aging. The molecular mechanisms underlying oxidative/nitrosative stress-induced neuronal damage are emerging and appear to involve a mode of death in which mitogen-activated protein kinase (MAPK) signaling pathways are strongly implicated. Thus, attention is turning towards the modulation of intracellular signaling as a therapeutic approach against neurodegeneration. Both endogenous and dietary agents have been suggested as potent modulators of intracellular signal transduction, e.g. nitric oxide and flavonoids, respectively. This review addresses recent findings on the biological effects of flavonoids and nitric oxide in neurodegeneration and aims to elucidate the rationale for their prospective use as modulators of cellular signal transduction. © 2002 Elsevier Science Inc. All rights reserved.Keywords: Apoptosis; Oxidative stress; Neuron; Flavonoids; MAP kinase; JNK; ERK; Epicatechin; Nitric oxide; Mitochondria; Redox status; Polyphenols Abbreviations: AKT, serine/threonine kinase (also known as protein kinase B); AP-1, activator protein-1; Apaf-1, apoptosis protease activating factor-1; ASK1, apoptosis signal-regulating kinase-1; Bad, Bcl-2/BclX Lassociated death promoting protein; Bax, pro-apoptotic protein of the Bcl-2 family; Bcl-2, B-cell lymphoma 2: protein with anti-apoptotic properties; BclX L , long form of Bclx: anti-apoptotic protein of the Bcl-2 family; Caspase, cysteinyl aspartic acid-protease; c-Jun, mammalian equivalent of Jun: part of the AP-1 transcription complex; CREB, cAMP response element binding protein; DIABLO/smac, mitochondria-related pro-apoptotic protein: inhibits XIAP; ERK1/2, extracellular signal-related kinase; Fas, CD95: member of the TNF receptor family; GSHST, glutathione Stransferase; JNK, c-Jun amino-terminal kinase; MAPK, mitogen-activated protein kinase; MAPKK, MAPK kinase; MAPKKK, MAPKK kinase; MEK1/2, ERK1/2-specific MAPKK; MKK4/7, JNK-specific MAPKK; MSK1, mitogen-and stress-activated kinase-1; NF-B, nuclear factor of immunoglobulin k locus in B-cells; ONOO − , peroxynitrite anion; p53, pro-apoptotic tumor suppressor gene product; PI3-kinase, phosphoinositol 3-kinase; Ras, small G-protein; RNS, reactive nitrogen species; ROS, reactive oxygen species; RSK, pp90 ribosomal S6 kinase; SAPK, stressactivated protein kinase; XIAP, X-linked inhibitor of apoptosis: inhibits the activation of caspase-9