In Vitro Anti-Plasmodium falciparum Properties of the Full Set of Human Secreted Phospholipases A 2

Abstract

ABSTRACT We have previously shown that secreted phospholipases A 2 (sPLA 2 s) from animal venoms inhibit the in vitro development of Plasmodium falciparum , the agent of malaria. In addition, the inflammatory-type human group IIA (hGIIA) sPLA 2 circulates at high levels in the serum of malaria patients. However, the role of the different human sPLA 2 s in host defense against P. falciparum has not been investigated. We show here that 4 out of 10 human sPLA 2 s, namely, hGX, hGIIF, hGIII, and hGV, exhibit potent in vitro anti- Plasmodium properties with half-maximal inhibitory concentrations (IC 50 s) of 2.9 ± 2.4, 10.7 ± 2.1, 16.5 ± 9.7, and 94.2 ± 41.9 nM, respectively. Other human sPLA2s, including hGIIA, are inactive. The inhibition is dependent on sPLA 2 catalytic activity and primarily due to hydrolysis of plasma lipoproteins from the parasite culture. Accordingly, purified lipoproteins that have been prehydrolyzed by hGX, hGIIF, hGIII, and hGV are more toxic to P. falciparum than native lipoproteins. However, the total enzymatic activities of human sPLA 2 s on purified lipoproteins or plasma did not reflect their inhibitory activities on P. falciparum . For instance, hGIIF is 9-fold more toxic than hGV but releases a lower quantity of nonesterified fatty acids (NEFAs). Lipidomic analyses of released NEFAs from lipoproteins demonstrate that sPLA 2 s with anti- Plasmodium properties are those that release polyunsaturated fatty acids (PUFAs), with hGIIF being the most selective enzyme. NEFAs purified from lipoproteins hydrolyzed by hGIIF were more potent at inhibiting P. falciparum than those from hGV, and PUFA-enriched liposomes hydrolyzed by sPLA 2 s were highly toxic, demonstrating the critical role of PUFAs. The selectivity of sPLA 2 s toward low- and high-density (LDL and HDL, respectively) lipoproteins and their ability to directly attack parasitized erythrocytes further explain their anti- Plasmodium activity. Together, our findings indicate that 4 human sPLA 2 s are active against P. falciparum in vitro and pave the way to future investigations on their in vivo contribution in malaria pathophysiology.