500 q 2001 Blackwell Science Ltd Resveratrol, a natural dietary phytoalexin, possesses similar properties to hydroxyurea towards erythroid differentiation Christelle M. Rodrigue, 1 Nicole Arous, 1 Dora Bachir, 2 Juliette Smith-Ravin, 3 Paul-Henri Romeo, 1 Fre Âde Âric Galacteros 1,2 and Marie-Claude Garel 1 1 INSERM U474, Maternite  Port-Royal, ICGM Cochin, Paris, 2 Centre de la Dre Âpanocytose et des Thalasse Âmies, Ho Ãpital Henri Mondor AP±HP, Cre Âteil, France, and 3 Universite  des Antilles et de la Guyane, De Âpartement de Biologie Animale, Campus de Fouillole, Guadeloupe FWI) Received 7 August 2000; accepted for publication 8 January 2001 Summary. Resveratrol, a natural dietary polyphenol, has been postulated to be implicated in the cardioprotective effect of red wine and the low incidence of breast and prostate cancers among vegetarians and Orientals respec- tively. This compound inhibits ribonucleotide reductase as does hydroxyurea, the first therapeutic agent used in the treatment of sickle cell disease. Using the human erythro- leukaemic K562 cell line as an invitro model, we show here that 50 mmol/l of resveratrol induced a higher haemoglobin production sevenfold) in K562 cells than 500 mmol/l of hydroxyurea 3´5-fold). This erythroid differentiation was linked to a dose- and time-dependent inhibition of cell proliferation associated with an equivalent increased expression of p21 mRNA, but with a higher increased level of p21 protein sixfold) for cells treated with resveratrol than for those treated with hydroxyurea 1´5-fold). We also show that 50 mmol/l of resveratrol and 25 mmol/l of hydroxyurea induced variable but similar inhancements of fetal haemoglobin synthesis in cultured erythroid progeni- tors for the majority of the sickle cell patients studied. These inductions were linked to, but not correlated with, a variable decrease in erythroid burst-forming unit clone number. Taken together, these results show that resveratrol merits further investigations in sickle cell disease therapy. Keywords: K562 cells, erythroid differentiation, resveratrol, hydroxyurea, HbF. The 3, 5, 4 0 -trihydroxystilbene currently named resveratrol is a natural phytoalexin present in red wine and other constituents of the human diet Hain etal, 1990; Soleas etal, 1997). This polyphenol inhibits cyclooxygenase-1 activity and was implicated in chemopreventive action, which has been used to explain the low incidence of breast and prostate cancers among vegetarians and Orientals respec- tively Adlercreutz et al, 1995; Makela et al, 1995; Jang et al, 1997; Mgbonyebi et al, 1998; Carbo et al, 1999). Resveratrol is also a radical scavenger that prevents many heart disorders by inhibiting lipoprotein oxidation and platelet aggregation Frankel etal, 1993; Pace-Asciak etal, 1995; Jang etal, 1997; Rotondo etal, 1998). This molecule was associated with the low incidence of ischaemic heart disease observed in the French population, a phenomenon called the `French Paradox'. This was attributed to its presence in wine and to a moderate consumption of red wine Renaud & De Logeril, 1993; Soleas et al, 1997). Therefore, resveratrol seems to have a very broad range of biological properties Mizutani et al, 1998; Pendurthi et al, 1999), but little is known about the molecular basis of its activity. Recent studies have shown that resveratrol is a ribo- nucleotide reductase inhibitor Fontecave etal, 1998), much more effective than hydroxyurea HU), a molecule that has been used clinically against a variety of tumours. HU inhibits DNA synthesis and plays a role in cell growth inhibition associated with a reversible p53-independent induction of the cyclin-dependent kinase inhibitor CDKI) p21 Linke etal, 1996). HU is the first therapeutic agent for the treatment of sickle cell anaemia Charache etal, 1995), a haemoglobinopathy characterized by the polymerization of a mutated form of adult haemoglobin HbS) leading to erythrocyte sickling which plays an important part in the disease morbidity Bunn, 1997). Hydroxyurea has proven clinical benefit as it can increase fetal haemoglobin HbF) levels in the red cells of sickle cell patients inhibiting HbS polymer formation Platt etal, 1984; Charache etal, 1987; Steinberg etal, 1997; Maier-Redelsperger etal, 1998; Bunn, 1999). However, the increase in HbF is variable and some British Journal of Haematology , 2001, 113, 500±507 Correspondence: Dr Marie-Claude Garel, INSERM U474, Maternite  Port-Royal, 123 boulevard de Port-Royal, 75014 Paris, France. E-mail: garel@cochin.inserm.fr