Journal: bioRxiv
Article Title: Galectin-3 recruitment at the Mycobacterium tuberculosis -containing phagosome is critical in macrophage but dispensable in epithelial cells
doi: 10.64898/2026.06.04.730029
Figure Lengend Snippet: Galectin-3 recruitment to intracellular bacteria and associated cellular phenotypes during infection. THP-1 cells were grown in 384-well plates, infected with Mtb H37Rv pMRF1 (MOI = 1) or heat-killed (HK) H37Rv pMRF1 for 5 days and imaged by automated confocal microscopy. (A) Representative images of THP-1 (nucleus; blue) infected with H37Rv pMRF1 (yellow) over 5 days. Scale bar = 50 μm (20X). (B) Representative images of THP-1 infected with live and HK H37Rv pMRF1 (MOI = 1; yellow) and labelled by immunofluorescence for Galectin-3 (Gal3; red) at day 3 post-infection. (Left) The focused image highlights a live bacterium colocalized with a Gal3 spot, indicating phagosomal membrane damage, while (right) no colocalization of HK bacterium with Gal3 spot is shown. The magnified inset of bystander cells under conditions of infection with both live and HK bacteria show Gal3 spots, suggesting cellular damage. Scale bar = 50 μm (20X). (C, D, E, F, G) Quantitative image analysis of infected and bystander HPAEpiC cells infected with live and HK H37Rv pMRF1 and in non-infected conditions over 5 days. (C) Percentage of bacteria colocalizing with Gal3 spots. Live bacteria display significantly higher rate of colocalization with Gal3 than HK bacteria from day 1 post-infection (Mann-Whitney, P≤0.05). (D) Intracellular bacterial area (pixel²) per infected cells containing at least one bacterium that is positive for Gal3 (Gal3+, rupture) compared to cells infected with bacteria not colocalized with Gal3 spot (Gal3-, non-rupture). The cells exhibiting colocalization with Gal3 show significantly greater bacterial area from 1 day after infection (Wilcoxon test, P≤0.05). (E) Total cell number. No significant difference is detected on day 0, while cell numbers obtained for live-infection conditions and HK controls are significantly different from day 1 post-infection (One-way Anova, P≤0.05). (F) Percentage of infected and bystander Gal3-positive THP-1 cells for infection with live bacteria. Infected cells show significant higher rate of Gal3-positive cells than bystander cells (Paired t-test, P≤0.05). (G) Percentage of infected and bystander Gal3-positive THP-1 cells for infection with HK bacteria. Infected cells exhibit a significantly higher proportion of Gal3-positive cells up to the first day following infection, whereas no significant difference is observed from the day 2 (Paired t-test, P≤0.05). (H) Mean cellular Gal3 fluorescence intensity. Infected cells exhibit significantly reduced Gal3 intensity relative to bystanders from day 1 (Paired t-test, P≤0.05), whereas bystander and uninfected cells do not differ (Unpaired t-test). (I) Mean cellular Gal3 fluorescence intensity over time in infected and bystander cells obtained for infection with HK H37Rv pMRF1, and in uninfected controls. No significant differences (paired and unpaired t-test, P≤0.05).
Article Snippet: We analyzed Gal3 dynamics over a five-day infection course in THP-1 differentiated human macrophages with a virulent red fluorescent strain of Mtb (H37Rv) followed by immunostaining with an anti-Galectin 3 (Gal3) antibody and nuclear labeling with DAPI ( ).
Techniques: Bacteria, Infection, Confocal Microscopy, Immunofluorescence, Membrane, MANN-WHITNEY, Fluorescence