Babafemi Adenuga

Anti-Plasmodial Activity of Aroylhydrazone and Thiosemicarbazone Iron Chelators: Effect on Erythrocyte Membrane Integrity, Parasite Development and the Intracellular Labile Iron Pool

Iron chelators inhibit the growth of the malaria parasite, Plasmodium falciparum, in culture and in animal and human studies. We previously reported the anti-plasmodial activity of the chelators, 2-hydroxy-1-naphthylaldehyde isonicotinoyl hydrazone (311), 2-hydroxy-1-naphthylaldehyde 4-methyl-3-thiosemicarbazone (N4mT), and 2-hydroxy-1-naphthylaldehyde 4-phenyl-3-thiosemicarbazone (N4pT). In fact, these ligands showed greater growth inhibition of chloroquine-sensitive (3D7) and chloroquine-resistant (7G8) strains of P. falciparum in culture compared to desferrioxamine (DFO). The present study examined the effects of 311, N4mT and N4pT on erythrocyte membrane integrity and asexual parasite development. While the characteristic biconcave disk shape of the erythrocytes was unaffected, the chelators caused very slight hemolysis at IC50 values that inhibited parasite growth. The chelators 311, N4mT and N4pT affected all stages of the intra-erythrocytic development cycle (IDC) of P. falciparum in culture. However, while these ligands primarily affected the ring-stage, DFO inhibited primarily trophozoite and schizont-stages. Ring, trophozoite and schizont-stages of the IDC were inhibited by significantly lower concentrations of 311, N4mT, and N4pT (IC50=4.45±1.70, 10.30±4.40, and 3.64±2.00μM, respectively) than DFO (IC50=23.43±3.40μM). Complexation of 311, N4mT and N4pT with iron reduced their anti-plasmodial activity. Estimation of the intracellular labile iron pool (LIP) in erythrocytes showed that the chelation efficacy of 311, N4mT and N4pT corresponded to their anti-plasmodial activities, suggesting that the LIP may be a potential source of non-heme iron for parasite metabolism within the erythrocyte. This study has implications for malaria chemotherapy that specifically disrupts parasite iron utilization.

Place of birth, cancer beliefs and being current with colon cancer screening among US adults

Background Historically, studies suggested that immigrants acquire the risk of colorectal cancer (CRC) as US-born persons within the same generation. CRC risk of immigrants is largely unknown in this era of cancer screening and widespread immigration. We investigated the association of place of birth and cancer beliefs with uptake of CRC screening. Methods The 2007 Health Information National Trends Survey was used and 4,299 respondents (weighted population size=81,896,392) who were 50 years and older (3,960 US-born and 339 foreign-born) were identified. We defined being current with CRC screening guidelines as the use of fecal occult blood test within 1 year, sigmoidoscopy within 5 years, or colonoscopy within 10 years. We compared being up-to-date with CRC screening among foreign-born versus US-born respondents. Logistic regression models were used to calculate odds ratios (OR) and 95% confidence intervals (CI). Results Overall, 2,594 (63.3%) US-born and 208 (52.8%) foreign-born respondents were current with CRC screening. Foreign-born respondents were less current in unadjusted model (OR 0.65; 95% CI: 0.50-0.85) but became non-statistically significant after adjustment (OR 0.79; 95% CI: 0.51-1.24). Respondents who believed that screening finds cancer when it is easy to treat (OR 2.85; 95% CI: 1.44-3.61), those who believed that cancer can be cured when detected early (OR 1.56; 95% CI: 1.20-2.00), and those who worry about getting cancer (OR 1.34; 95% CI: 1.10-1.61) were likely to be current with CRC screening. However, respondents with fatalistic beliefs were borderline less likely to be current (OR 0.82; 95% CI: 0.65-1.04). Conclusion There is a need to improve education on CRC screening, particularly among foreign-born adults.

Plasmodium falciparum: Activity of artemisinin against Plasmodium falciparum cultured in sickle trait hemoglobin AS and normal hemoglobin AA red blood cells

The presence of sickle hemoglobin causes accumulation of hemoglobin degradative products that favor oxidative reaction in erythrocytes. Artemisinin derivatives exert antiparasite effects through oxidative reactions within infected erythrocytes. Using [(3)H]-hypoxanthine incorporation, we therefore did an in vitro comparison of IC(50) values for artemisinin in Plasmodium falciparum-infected erythrocytes from sickle cell trait (AS) and normal (AA) individuals. IC(50) values for chloroquine served as control. Without drugs, parasite growth was similar in AA and AS erythrocytes. Gender, age and blood group of donors had no significant effects on parasite growth. IC(50) value for artemisinin was 27+/-14nM in AS (N=22) compared to 24+/-9nM (N=27) in AA erythrocytes (P=0.4). IC(50) values for chloroquine were also similar in AA (22+/-8nM) and AS (20+/-11nM) erythrocytes. These results show no evidence of elevated artemisinin activity on P. falciparum in AS erythrocytes in vitro.