Malaria, the disease caused by
Plasmodium infection, is endemic to poverty in so-called underdeveloped countries.
Plasmodium falciparum, the main infectious
Plasmodium species in sub-Saharan countries, can trigger the development of severe malaria, including cerebral malaria, a neurological
syndrome that claims the lives of more than one million children (<5 years old) per year. Attempts to eradicate
Plasmodium infection, and in particular its lethal outcomes, have so far been unsuccessful. Using well-established rodent models of
malaria infection, we found that survival of a
Plasmodium-infected host is strictly dependent on the host’s ability to up-regulate the expression of heme oxygenase-1 (HO-1 encoded
by the gene
Hmox1). HO-1 is a stress-responsive enzyme that catabolizes free heme into biliverdin, via a reaction that releases Fe and generates
the gas carbon monoxide (CO). Generation of CO through heme catabolism by HO-1 prevents the onset of cerebral malaria. The
protective effect of CO is mediated via its binding to cell-free hemoglobin (Hb) released from infected red blood cells during
the blood stage of
Plasmodium infection. Binding of CO to cell-free Hb prevents heme release and thus generation of free heme, which we found to play a
central role in the pathogenesis of cerebral malaria. We will address hereby how defense mechanisms that prevent the deleterious
effects of free heme, including the expression of HO-1, impact on the pathologic outcome of
Plasmodium infection and how these may be used therapeutically to suppress its lethal outcomes.
Keywords
Plasmodium
- Malaria - Heme - Heme oxygenase-1 - Carbon monoxide - Inflammation