Evidence for the Contribution of the Hemozoin Synthesis Pathway of the Murine Plasmodium yoelii to the Resistance to Artemisinin-Related Drugs

Plasmodium falciparum malaria is a major global health problem, causing approximately 780,000 deaths each year. In response to the spreading of P. falciparum drug resistance, WHO recommended in 2001 to use artemisinin derivatives in combination with a partner drug (called ACT) as first-line treatment for uncomplicated falciparum malaria, and most malaria-endemic countries have since changed their treatment policies accordingly. Currently, ACT are often the last treatments that can effectively and rapidly cure P. falciparum infections permitting to significantly decrease the mortality and the morbidity due to malaria. However, alarming signs of emerging resistance to artemisinin derivatives along the Thai-Cambodian border are of major concern. Through long-term in vivo pressures, we have been able to select a murine malaria model resistant to artemisinins. We demonstrated that the resistance of Plasmodium to artemisinin-based compounds depends on alterations of heme metabolism and on a loss of hemozoin formation linked to the down-expression of the recently identified Heme Detoxification Protein (HDP). These artemisinins resistant strains could be able to detoxify the free heme by an alternative catabolism pathway involving glutathione (GSH)-mediation. Finally, we confirmed that artemisinins act also like quinolines against Plasmodium via hemozoin production inhibition. The work proposed here described the mechanism of action of this class of molecules and the resistance to artemisinins of this model. These results should help both to reinforce the artemisinins activity and avoid emergence and spread of endoperoxides resistance by focusing in adequate drug partners design. Such considerations appear crucial in the current context of early artemisinin resistance in Asia

Untangling Amyloid-beta, Tau, and Metals in Alzheimer's Disease

Protein misfolding and metal ion dyshomeostasis are believed to underlie numerous neurodegenerative diseases, including Alzheimer's disease (AD). The pathological hallmark of AD is accumulation of misfolded amyloid-?? (A??) peptides and hyperphosphorylated tau (ptau) proteins in the brain. Since AD etiology remains unclear, several hypotheses have emerged to elucidate its pathological pathways. The amyloid cascade hypothesis, a leading hypothesis for AD development, advocates A?? as the principal culprit. Additionally, evidence suggests that tau may contribute to AD pathology. A?? and tau have also been shown to impact each other's pathology either directly or indirectly. Furthermore, metal ion dyshomeostasis is associated with these misfolded proteins. Metal interactions with A?? and tau/ptau also influence their aggregation properties and neurotoxicity. Herein, we present current understanding on the roles of A??, tau, and metal ions, placing equal emphasis on each of these proposed features, as well as their inter-relationships in AD pathogenesis.close341