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

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 lowand 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.

The Roles of the Secreted Phospholipase A2 Gene Family in Immunology

“…PLA2G2F selectively hydrolyzes DHA-containing plasmalogen-PE (P-PE) in skin-extracted phospholipids to yield DHA and plasmalogen-lysophosphatidylethanolamine (P-LPE) at a physiological concentration . PLA2G2F also hydrolyzes lipoprotein phospholipids to release PUFAs in vitro, which in turn prevent the in vitro growth of the malaria parasite (Plasmodium falciparum) in infected erythrocytes (Guillaume et al, 2015). However, the lipoproteinhydrolytic and antimalaria actions of PLA2G2F need to be confirmed in vivo.…”

“…With regard to polar head groups, PLA2G2A and other group II sPLA 2 s show preference for phosphatidylethanolamine (PE) over phosphatidylcholine (PC), while PLA2G10 is very active on PC, and these preferences can be partly explained in terms of crystal structure (Pan et al, 2002;Scott et al, 1991). With regard to sn-2 fatty acids, PLA2G1B, PLA2G2A, and PLA2G2E do not distinguish fatty acid species, PLA2G5 prefers fatty acids with a lower degree of unsaturation (eg, oleic acid (OA)), and PLA2G2D, PLA2G2F, PLA2G3, and PLA2G10 show preference for polyunsaturated fatty acids (PUFAs) such as arachidonic acid (AA) and docosahexaenoic acid (DHA) to various degrees (Chen & Dennis, 1998;Chen, Engle, Seilhamer, & Tischfield, 1994b;Cupillard, Koumanov, Mattei, Lazdunski, & Lambeau, 1997;Guillaume et al, 2015;Hanasaki et al, 1999;Miki et al, 2013;Mitsuishi, Masuda, Kudo, & Murakami, 2007;Murakami et al, 2003;Murase et al, 2016;Pruzanski et al, 2005;Sato et al, 2014;Yamamoto et al, 2015). Although the substrate specificity of sPLA 2 s differs according to the in vitro assay conditions employed, particularly when excess amounts of the enzymes are used, the overall tendency is recapitulated in several if not all in vivo systems, often with even more selective patterns of hydrolysis that may be affected by the phospholipid compositions of the target membranes.…”

Group IID, IIE, IIF and III secreted phospholipase A2s

“…The anti-malaria property of sPLA 2 s is dependent on their ability to release PUFAs relative to other fatty acids from lipoproteins, sPLA 2 -IIF being the most PUFA-selective sPLA 2 . Indeed, lipoprotein phospholipids are potently hydrolyzed, with marked PUFA preference, when treated with sPLA 2 -IIF in vitro [87,88] or in Pla2g2f-TG mice in vivo (Fig. 3C).…”

“…Recombinant sPLA 2 -IIF has a potent capacity to prevent malaria infection in vitro [87]. The anti-malaria property of sPLA 2 s is dependent on their ability to release PUFAs relative to other fatty acids from lipoproteins, sPLA 2 -IIF being the most PUFA-selective sPLA 2 .…”

What do secreted phospholipases A2 have to offer in combat against different viruses up to SARS-CoV-2?

“…Both endogenous and exogenous sPLA 2 s play direct and indirect roles in host defence against various types of bacteria, parasites and viruses [ [17] , [18] , [19] , [20] , [21] ]. For example, an early study showed that several snake and bee venom sPLA 2 s exhibit direct antiviral activity by blocking HIV-1 virus entry into host cells [ 21 ].…”