Fig. 5: Lactate downregulates VE–cadherin and increases vascular permeability. | Nature Communications

Fig. 5: Lactate downregulates VE–cadherin and increases vascular permeability.

From: Lactate released by inflammatory bone marrow neutrophils induces their mobilization via endothelial GPR81 signaling

Fig. 5

a Levels of BM Evans Blue Dye (EBD) absorbance per femur at 620 nm in WT mice treated with PBS or lactate (n = 5). b Representative fluorescence images of Endomucin (green), GPR81 (red; RFP), and nuclei (blue; DAPI) in the femoral diaphysis of GRP81-RFP reporter mice; yellow indicates Endomucin+ GPR81+ sinusoidal BM endothelial cells. Representative images out of four independent experiments are shown. Scale bar indicates 20 μm. c PB neutrophils frequency following 4 h post administration of GPR81 agonist in WT mice (n = 7, PBS; n = 6, GPR81 agonist). ***p(0.0002). d–f Levels of BM EBD absorbance following GPR81 agonist treatment to WT mice (d, n = 6, PBS; n = 4, GPR81 agonist; ***p(0.0009)), after lactate or LPS injection to WT vs. GPR81−/− mice (e, n = 5, WT + PBS or lactate; n = 3, WT + LPS; n = 3, GPR81−/− + PBS; n = 4, GPR81−/− + lactate; n = 3, GPR81−/− + LPS) and following neutrophil depletion and exposure to LPS and lactate in WT mice (f, n = 5, PBS; n = 3, LPS; n = 5, α-Ly6G Abs + LPS; n = 3, α-Ly6G Abs + LPS + lactate). g Quantitative analysis and representative flow cytometry histogram plot of surface VE–cadherin expression on sBMEC 30 min post injection of lactate or LPS to WT vs. GPR81−/− mice (WT; n = 5, PBS or LPS; n = 6, lactate; GPR81−/−; n = 6, PBS; n = 5, lactate; n = 4, LPS). h Quantitative analysis and representative flow cytometry density plots for PB neutrophils following administration of blocking anti-VE–cadherin antibodies to WT vs. GPR81−/− mice (n = 4 per group). i, j Levels of BM EBD absorbance and neutrophil frequency in PB following treatment with lactate alone or with Epac1 agonist (i, n = 4 per group; j, n = 5 per group). i **p(PBS vs. lactate) = 0.0018; ***p(lactate vs. lactate+Epac1 agonist) = 0.0009; j **p(PBS vs. lactate) = 0.0013; ***p(lactate vs. lactate+Epac1 agonist) = 0.0008. k A scheme depicting lactate mode of action controlling BM vascular permeability via GPR81 signaling. Data are represented as mean ± SEM from 4 to 5 independent experiments. **p < 0.01; ***p < 0.001; ****p < 0.0001, Student’s two-tailed unpaired t test (a, c, d), one-way ANOVA with Tukey’s post hoc test (f, i, j) or two-way ANOVA with Tukey’s post hoc test (e, g, h). See also Supplementary Fig. 6.

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