Reactive Nitrogen Intermediate (RNI) Levels Inside and Outside Plasmodium Infected Red Blood Cells in Murine Malaria

Abstract

Abstract

Malaria is one of the most important parasitic diseases in the world. In addition to numerous cytokines, nitric oxide (NO) is thought to be an important mediator and critical signaling molecule of malaria pathology and a target for novel drug therapy. This study has investigated the involvement of reactive nitrogen intermediates (RNI) in murine malaria, P. berghei parasitized and uninfected red blood cells (PRBC, URBC), in order to evaluate the actual level of RNI relating to intracellular and extracellular activities of Plasmodium.

In PRBC, nitrite reacts with Hb to form toxic nitrosothiol-Hb, met-Hb and hydrogen peroxide. NO may be the precursor of chemical species that are even more toxic, such as peroxinitrite or hydroxyl radicals. The RNI levels are measured in plasma as the surrounding medium for PRBC, however, understanding the quantitative level of NO production inside the PRBC seems to be important to elucidating the mechanism of parasite penetration into the RBC.

The objective of this study was to measure RNI levels in both inside and outside the RBC during infection with Plasmodium as an intracellular parasite. It is suggested that NO or RNI is critical for intracellular parasites such as plasmodia. This experiment was carried out in two parts; in part A, the RNI levels were measured inside the PRBC and URBC of the host, and in part B, it was studied in plasma as an extracellular level of NO production. The results showed that the amounts of RNI levels inside the RBC were low at the baseline detection of Griess microassay (GMA). However, the RNI levels in the plasma of the malarial (47.7 ± 9.1 μM) and control groups (26.8 ± 2.1 μM) showed a significant difference (n = 5, P < 0.05). The exact mechanism(s) by which NO acts during malaria infection is not fully understood and requires more investigation.

Keywords : nitric oxide, RNI, malaria, Plasmodium, RBC, hemoglobin