We could clearly demonstrate that in both mutants there is no response to cellular stress i.e. induction of inducible nitric oxide synthase (iNos2) of the human host once modification of eIF-5A is interrupted by silencing of either parasitic DHS or eIF-5A. However, nitric oxide synthase is induced 20-fold after infection with the wild type P. berghei ANKA strain in comparison to the shRNA mutants

P #176 (DHS) and P #18 (EIF5A) with a 18-fold and 20-fold lowered formation of nitric oxide. These findings do not only prove a link between the hypusine pathway and iNos production but also broaden our understanding of the CM Selleckchem BIIB057 malaria pathology and implicate alternative strategies for therapy. Similar results have been obtained in DHS heterozygous knockout mice with attenuated cytokine signalling as evidenced KU55933 mw by reduced nitric oxide synthase production [31]. Malaria patients often present with hypoargininemia [32], and metabolomic studies of Plasmodium ��-Nicotinamide purchase falciparum during its 48 h intraerythrocytic life cycle reveal nearly complete depletion of L-arginine levels. Nitric oxide synthase is induced by arginine and catalyzes the reaction to nitric oxide (NO) and urea. However, in cerebral malaria there is a lack of nitric oxide due to the presence

of parasite-specific arginase which leads to a depletion of arginine and subsequent downregulation of host-specific nitric oxide synthase. This may allow the parasite to evade a NO-dependent immune response in the host since NO is deleterious to parasite

proliferation [33]. During Plasmodium berghei ANKA infection in mice exogenous nitric oxide decreases brain vascular inflammation, leakage and venular resistance [17, 18] and protects against cerebral malaria. Finally, the crystal structure of Plasmodium arginase has been resolved recently and indicates a low complexity region [33] which is largely disordered and its deletion does not significantly compromise enzyme activity. Moreover, disruption of P. falciparum arginase led to an apparent reduction in liver stage infection. Conclusions Although it has been previously suggested that RNAi is not functional in Plasmodium, a putative, Vorinostat solubility dmso non-canonical RNAi pathway might exist in malaria parasites. In vivo knockdown of eIF-5A and DHS by expression of shRNAs after infection in a rodent model decreased parasitemia intermittently in the development of cerebral malaria. The data are similar to the related but non-lethal phenotype P. berghei ANKA NK 65. These results might be of further interest to study the function of hypusine modification with respect to malaria infection and therapy. Materials and methods Ethics statement All animal experiments were performed under FELASA category B and GV-SOLAS standards. Animal experiments were approved by German authorities (Regierungspräsidium Karlsruhe, Germany).