Homocysteinemia is inversely correlated with platelet count and directly correlated with sE- and sP-selectin levels in females homozygous for C677T methylenetetrahydrofolate reductase MAURO RONGIOLETTI 1 , MAURO BALDASSINI 1 , FABRIZIO PAPA 1 , ETTORE CAPOLUONGO 4 , BIANCA ROCCA 3 , RAIMONDO DE CRISTOFARO 3 , GIUSEPPINA SALVATI 1 , GIOVANNI LARCIPRETE 2 , ANNALISA STROPPOLO 4 , PIERO ANTONIO ANGELUCCI 2 , ELIO CIRESE 2 , & FRANCO AMEGLIO 1 1 Laboratory of Clinical Pathology, General Hospital ‘S. Giovanni Calibita’, FBF/AFAR, Rome, Italy, 2 Divisione di Ginecologia e Ostetricia, General Hospital ‘S. Giovanni Calibita’, FBF/AFAR, Rome, Italy, 3 Servizio Malattie Emorragiche e Trombotiche, Universita’ Cattolica Sacro Cuore, Rome, Italy, and 4 Istituto di Biochimica e Biochimica Clinica, Universita’ Cattolica Sacro Cuore, Rome, Italy (Received 11 September 2004; accepted 14 October 2004) Abstract Plasma homocysteine levels depend in part on the molecular nature of the methylenetetrahydrofolate reductase (MTHFR) and on blood folate intake. Little has been reported on platelet counts in the presence of hyperhomocysteinemia and MTHFR polymorphisms, with the exception of delayed platelet recovery in homozygous MTHFR C677T subjects after treatment with methotrexate for ovarian cancer. The aim of this investigation was to evaluate the possibility of a link between the platelet count and plasma homocysteine levels in different MTHFR variants in 165 female patients. Determinations of plasma homocysteine levels were by ELISA and of MTHFR polymorphisms (A1298C and C677T) were by inverse hybridization. Serum P- and E-selectin concentrations were obtained by ELISA. An inverse correlation (R ¼0.88, P < 0.001) was observed between blood platelet counts and plasma homocysteine levels in the women homozygous for MTHFR C677T. This correlation did not depend on pregnancy or other variables reported. Serum concentrations of sE- and sP-selectin, markers of endothelial and platelet activation, were significantly and positively correlated with homocysteine levels. These findings suggest that homocysteine affects platelet numbers in women with MTHFR C677T possibly consequent to endothelial and platelet activation. Keywords: Homocysteine, platelets, MTHFR, sP-selectin, sE-selectin Introduction Hyperhomocysteinemia has been described in patients with the methylenetetrahydrofolate reduc- tase (MTHFR) C677T. This type of variant molecule cannot remethylate homocysteine to methionine [1,2]. In the presence of folates, the C677T mutation is more stable and functionally more efficient [3,4]. Homocysteine has been reported to be able to activate platelets through inhibition of NO [5–8]. In addition, homocysteine may damage endothelia that release platelet activating cytokines [9–12]. In turn, folate is able to reduce platelet aggregation and therefore platelets may be conditioned by low folate levels, high homocysteine levels and by activated endothelial cells [9–14]. Since the C677T variant of MTHFR has been associated with thrombophilic states, effects on platelets may be relevant [12,15–20]. Surprisingly, very few data have been reported concerning platelets and MTHFR polymorphisms. One exception regards the greater toxicity observed in patients with ovarian cancer treated with metho- trexate [21]. In fact, in patients homozygous for MTHFR C677T, the platelet counts lowered by this therapy showed prolonged periods of time to recover as compared with other patients. The aim of this investigation was to evaluate a possible link between the platelet count and MTHFR type. This report shows that in female patients homo- zygous for C677T MTHFR, platelets counts are inversely correlated to homocysteine levels, while the other mutations do not present this type of correlation. The homozygous group also presents increased concentrations of serum E- and P-selectins, Correspondence: Franco Ameglio, Md,PHD, Laboratory of Clinical Pathology, General Hospital ‘S. Giovanni Calibita’, Fatebenefratelli/AFAR, Isola Tiberina 39, Rome, Italy. Tel: 39-6-6837367. Fax: 39-6-6879345. E-mail: francoameglio@hotmail.com Platelets, May/June 2005; 16(3/4): 185–190 ISSN 0953–7104 print/ISSN 1369–1635 online ß 2005 Taylor & Francis Group Ltd DOI: 10.1080/09537100400020187