The Urokinase Receptor (uPAR) Facilitates Clearance of Borrelia burgdorferi
Figure 5
The course of Lyme borreliosis in uPAR knock-out mice on a B. burgdorferi susceptible mixed C57BL/6×C3H/HeN genetic background.
(A) Urokinase receptor deficient mice on the mixed genetic background also display higher B. burgdorferi numbers compared to WT littermate controls. C57BL/6 mice were backcrossed twice to a C3H/HeN background. We intercrossed F2 mice and used the homozygous and nullizygous offspring (F2 homozygous uPAR deficient C57BL/6×C3H/HeN mice and WT littermate controls) for our experiments. Mice were inoculated with B. burgdorferi or sham and sacrificed two weeks post infection, DNA was extracted from the indicated tissues and samples were subjected to quantitative Borrelia flab and mouse β-actin PCR. B. burgdorferi numbers are depicted as described in Figure 2. Six to eight mice per group were used. (B) Urokinase receptor deficient leukocytes from mice on the mixed genetic background are not as capable of phagocytosing B. burgdorferi as are granulocytes from WT littermate controls. Phagocytosis assays with whole blood were performed as described in Figure 2. Six to eight mice per group were used. (C, D and E) Peak carditis in these uPAR −/− mice (D) is more severe compared to carditis in WT littermate controls (C). Mice were inoculated with B. burgdorferi and sacrificed two weeks post infection. Pictures of hematoxylin and eosin stained sagittal sections depict representative sections. Carditis was scored as described in Figure 4 within the same session (E). Six to eight mice per group were used. (F and G) The main cell involved in murine Lyme carditis is the macrophage. Representative pictures of F4/80 stained sagittal sections of hearts from B. burgdorferi infected uPAR deficient mice (G) and WT littermate controls (F). (H) More severe inflammation in B. burgdorferi infected uPAR deficient animals (n = 7) compared to WT littermate controls (n = 7) as measured by multiplex ligation-dependent probe amplification (MPLA). MLPA was performed on RNA obtained from half of sagittally dissected hearts from B. burgdorferi or sham inoculated mice. Depicted are mRNA expression of TNF-α, CCL3, TLR2, CD14, IL1-β, IRAK3, ICAM1 and TBP (housekeeping gene [66]). Other genes included in the assay were IL6, IL10, INF-γ, TFPI, F3, PROCR, SERPINE1P, PLAT, PLAUR, TLR4, TLR9 LY96, IRAK1, F2R, NFKB1a, NOS3, ITGA5,B2M, ITGAV, ITGAB3, TFRC, HIF1A, MMP2 and HP. Bars represent the mean±SEM. A p-value<0.05 was considered statistically significant. * indicating p<0,05; ** p<0,01.