Our research is focused on studies on oxidative stress and ageing in the yeast Saccharomyces cerevisiae. Glycolytic enzymes, chaperones and Cu,Zn-superoxide dismutase were identified by us [1] and other groups as major proteins oxidized in H2O2-treated cells. Aiming at characterizing the molecular mechanisms involved in cell recovery after oxidative stress, we have shown that the Pep4p vacuolar protease plays a key role in the turnover of oxidized proteins. Moreover, our studies indicate that Pep4p is induced and plays a homeostatic function during chronological ageing [4]. We are currently working on two main lines of research that aim to: (i) characterize the role of sphingolipid-mediated signal transduction in oxidative stress resistance and chronological life span; (ii) characterize in vivo the protective effects of natural antioxidants.

Sphingolipid metabolites, including ceramide, sphingosine and sphingosine-1-phosphate, are bioactive compounds regulating several biological processes, including cell cycle arrest, proliferation, apoptosis and cell senescence. Many stress stimuli increase the levels of ceramide and sphingosine, leading to growth arrest and apoptosis. In contrast, sphingosine-1-phosphate suppresses apoptosis. The ratio between S1P and sphingosine/ceramide is, therefore, a major factor that determines cell fate. This "sphingolipid rheostat" is often dysregulated in many diseases. Thus, targeting sphingolipid metabolism may be of potential therapeutic relevance. Changes in sphingolipid metabolism have been linked to oxidative stress resistance and life span. The neutral sphingomyelinase nSMase2 is considered a major candidate for mediating ceramide-signalling during stress responses and ageing. We have recently shown that Isc1p, the yeast orthologue of nSMase2, plays a key role in oxidative stress resistance and chronological lifespan, modulating redox homeostasis, iron levels and apoptosis [6]. Our current interest aims to get insights into the role of Isc1p in the regulation of iron uptake and signalling cascades that may govern programmed cell death.

Studies using yeast and other model organisms have shown that aged cells contain increased levels of oxidative stress markers [2,3]. Natural antioxidants are, therefore, potential therapeutic agents during ageing and in diseases associated with oxidative stress. Plant polyphenols have long been recognized to act as antioxidants. Quercetin is the most common flavonol in the diet and its properties has been extensively studied in vitro. Using yeast cells as an eukaryotic model organism, we have shown that quercetin increases oxidative stress resistance and chronological life span by scavenging free radicals, maintaining the redox homeostasis, and preventing oxidative damages [5]. We are currently screening for other natural antioxidants with putative in vivo protective effects and investigating whether these compounds exert their effects through modulation of cell signaling pathways.

[1] Costa V, Amorim MA, Quintanilha A and Moradas-Ferreira P (2002) “Hydrogen peroxide-induced carbonylation of key metabolic enzymes in Saccharomyces cerevisiae: the involvement of the oxidative stress response regulators Yap1 and Skn7”. Free Rad Biol Med, 33, 1507-1515.

[2] Harris N, Costa V, MacLean M, Mollapour M, Moradas-Ferreira P and Piper PW (2003) “Mn-Sod overexpression extends the yeast chronological (G0) life span, but acts independently of Sir2p histone deacetylase to shorten the replicative life span of dividing cells” Free Rad Biol Med 34, 1599-1606.

[3] Harris N, Bachler M, Costa V, Mollapour M, Moradas-Ferreira P and Piper PW (2005) “Overexpressed Sod1p acts either to reduce or to increase the lifespans and stress resistance of yeast, depending on whether it is Cu2+-deficient or an active Cu,Zn-superoxide dismutase” Aging Cell 4, 41-52.

[4] Marques M, Mojzita D, Amorim MA, Almeida T, Hohmann S, Moradas-Ferreira P and Costa V (2006) "The Pep4p vacuolar proteinase contributes to the turnover of oxidised proteins but PEP4 overexpression is not sufficient to increase chronological lifespan in Saccharomyces cerevisiae” Microbiol 152, 3595-3605.

[5] Belinha I, Amorim MA, Rodrigues P, de Freitas V, Moradas-Ferreira P, Mateus N and Costa V (2007) "Quercetin increases oxidative stress resistance and longevity in Saccharomyces cerevisiae” J Agric Food Chem 55, 2446-2451.

[6] Almeida T, Marques M, Mojzita D, Amorim MA, Silva RD, Almeida B, Rodrigues P, Ludovico P, Hohmann S, Moradas-Ferreira P, Côrte-Real M, and Costa V. (2008) “Isc1p plays a key role in hydrogen peroxide resistance and chronological lifespan through modulation of iron levels and apoptosis”. Mol Biol Cell 19, 865-876.