Malaria in pregnancy regulates P‐glycoprotein (P‐gp/Abcb1a) and ABCA1 efflux transporters in the Mouse Visceral Yolk Sac

Abstract

Malaria in pregnancy (MiP) induces intrauterine growth restriction (IUGR) and preterm labour (PTL). However, its effects on yolk sac morphology and function are largely unexplored. We hypothesized that MiP modifies yolk sac morphology and efflux transport potential by modulating ABC efflux transporters. C57BL/6 mice injected with Plasmodium berghei ANKA (5 × 105 infected erythrocytes) at gestational day (GD) 13.5 were subjected to yolk sac membrane harvesting at GD 18.5 for histology, qPCR and immunohistochemistry. MiP did not alter the volumetric proportion of the yolk sac's histological components. However, it increased levels of Abcb1a mRNA (encoding P‐glycoprotein) and macrophage migration inhibitory factor (Mif chemokine), while decreasing Abcg1 (P < 0.05); without altering Abca1, Abcb1b, Abcg2, Snat1, Snat2, interleukin (Il)‐1β and C‐C Motif chemokine ligand 2 (Ccl2). Transcripts of Il‐6, chemokine (C‐X‐C motif) ligand 1 (Cxcl1), Glut1 and Snat4 were not detectible. ABCA1, ABCG1, breast cancer resistance protein (BCRP) and P‐gp were primarily immunolocalized to the cell membranes and cytoplasm of endodermic epithelium but also in the mesothelium and in the endothelium of mesodermic blood vessels. Intensity of P‐gp labelling was stronger in both endodermic epithelium and mesothelium, whereas ABCA1 labelling increased in the endothelium of the mesodermic blood vessels. The presence of ABC transporters in the yolk sac wall suggests that this fetal membrane acts as an important protective gestational barrier. Changes in ABCA1 and P‐gp in MiP may alter the biodistribution of toxic substances, xenobiotics, nutrients and immunological factors within the fetal compartment and participate in the pathogenesis of malaria‐induced IUGR and PTL.

Breast cancer resistance protein (Bcrp/Abcg2) is selectively modulated by lipopolysaccharide (LPS) in the mouse yolk sac

“…Our data suggest that the placenta is capable of limiting the maternal pro-inflammatory transfer into the yolk sac, or alternatively the yolk sac is less capable of mounting a robust pro-inflammatory response to LPS infection. This is consistent with our previous findings that MiP induced a massive maternal and placental pro-inflammatory response, without activating a substantial yolk sac cytokine/chemokine output [ 10 , 23 ]. In this context, it is possible that other routes of LPS injection could have elicited a stronger pro-inflammatory response, since inoculation of LPS (1 mg/kg) directly into the amniotic cavity for 6 h induced fetal membrane upregulation of Il-1β , and Il-6 at GD15/16 in DBA/2 mice [ 35 ].…”

“…Previously, we have demonstrated that malaria in pregnancy (MiP), an important inducer of preterm labor, upregulated term yolk sac P-gp and Abca1 expression [ 23 ]. These previous results, together with those presented herein, indicate that different infective agents potentially disrupt yolk sac efflux transport potential via alterations in the expression of selected ABC efflux transport systems, which may alter the biodistribution, within the embryo/fetal compartment, of endogenous and exogenous substrates present in the extraembyonic coelom, in the uterine cavity and / or in the yolk sac circulation.…”

“…The volumetric proportion of the mouse visceral yolk sac from LPS-treated and control animals (n = 8/group) was assessed as previously described with modifications [ 23 , 24 ]. Briefly, after dissection from the amnion membrane, yolk sac specimens were included in buffered paraformaldehyde phosphate solution (4 %) for 24 h. Samples were then immersed in ethanol and xylene series and embedded in paraffin (Histopar, SP, Brazil).…”

“…Yolk sac samples were processed for immunohistochemical analysis as previously described [ 22 , 23 ]. Mouse placental sections (GD18.5) were concomitantly processed, as positive controls.…”

“…Quantification of intensity and area of immunolabeling in yolk sac components, endodermal epithelium, connective tissue, endothelium and mesothelium, were performed using a semi-quantitative scoring described previously [ 22 , 25 ], with modifications [ 22 , 23 ]. Immunolabeled area was scored as follows: 0) undetectable; 1) 1–25 %; 2) 26–50 %; 3) 51–75 %; and 4) 76–100 %.…”