The Modulation of NADPH Oxidase Activity in Human Neutrophils by Moroccan Strains of Leishmania major and Leishmania tropica Is Not Associated with p47phox Phosphorylation

Abstract

Polymorphonuclear neutrophils (PMNs) are the first phagocyte recruited and infected by Leishmania. They synthetize superoxide anions (O2−) under the control of the NADPH oxidase complex. In Morocco, Leishmania major and L. tropica are the main species responsible for cutaneous leishmaniasis (CL). The impact of these parasites on human PMN functions is still unclear. We evaluated the in vitro capacity of primary Moroccan strains of L. major and L. tropica to modulate PMN O2− production and p47phox phosphorylation status of the NADPH oxidase complex. PMNs were isolated from healthy blood donors, and their infection rate was measured by microscopy. O2− production was measured by superoxide dismutase–inhibitable reduction of cytochrome C. P47phox phosphorylation was analyzed by Western blot using specific antibodies against Ser328 and Ser345 sites. Whereas we did not observe any difference in PMN infectivity rate, our results indicated that only L. tropica promastigotes inhibited both fMLF- and PMA-mediated O2− production independently of p47phox phosphorylation. Leishmania soluble antigens (SLAs) from both species significantly inhibited O2− induced by fMLF or PMA. However, they only decreased PMA-induced p47phox phosphorylation. L. major and L. tropica modulated differently O2− production by human PMNs independently of p47phox phosphorylation. The inhibition of ROS production by L. tropica could be a mechanism of its survival within PMNs that might explain the reported chronic pathogenicity of L. tropica CL.

Leishmania infantum Infection of Primary Human Myeloid Cells

“…Several reports have proposed that PMNs are more prone to die when infected with L. braziliensis [49], L. infantum or L. major [50], whereas others have proposed that L. major mediates parasite survival [51]. Thus, human PMN activation and function are dependent on the parasite strain used [11,52,53]. Whereas at higher doses, this population, CD14 bright CD16 brigh , disappeared, at lower quantities (1.10 6 parasites), this population persisted and was infected.…”

“…Thus, sCD14 could be in competition for PAMPs in binding limiting inflammation [55,57]. It was reported in some studies that increasing levels of sCD14 was correlated with severity [11,58] and was associated with the outcome of VL [54]. In this sense, parasites could, by an unknown mechanism, promote the release of sCD14 and thus decrease the inflammatory response by inhibiting macrophage activation [59,60].…”

“…PMNs may act as a Trojan horse, silently transmitting parasites to infiltrate mononuclear cells [4,5,[7][8][9][10]. Furthermore, Leishmania hijack host machinery to survive and multiply into host cells [11,12]. Of importance, the parasite has also been detected in the peripheral blood of patients with cutaneous or visceral leishmaniasis [13,14].…”