Negative regulation of MMPs by MNK is more specific than PI3K/AKT/mTORC1 signalling.

<p>Global analysis of MMP, cytokine, chemokine and growth factors secretion from macrophages at 72h by Luminex array demonstrates that MNK inhibition augments MMP-1, MMP-3 and MMP-10 secretion significantly, but conversely suppresses TH₁, TH₂ and chemokine secretion. Median values normalised to Mtb values of an experiment performed in triplicate are shown, and are representative of an experiment performed on two occasions.</p

The PI3K and MNK pathways converge at the level of eIF4E phosphorylation.

<p><b>A.</b> Inhibition of eIF4F complex formation significantly suppresses MMP-1 secretion from Mtb-infected macrophages at 72h. <b>B.</b> Insulin, a PI3K pathway activator, increases macrophage eIF4E phosphorylation, while LY294002 abrogates phosphorylation. Mtb infection does not change basal eIF4E phosphorylation levels, but either MNK or PI3K/PD-1 inhibition suppresses eIF4E phosphorylation at 90 mins. A: representative data from an experiment performed in 2 donors in triplicate, B: performed on three occasions in different donors. Mean and standard deviation shown and p values are by Student’s t-test.</p

Mtb inhibits negative regulatory pathways in macrophages.

<p>Mtb upregulates MMP-1 via the MAPK pathways, whilst concurrently inducing microRNAs that target the negative regulatory pathways that limit MMP-1 expression, leading to excessive protease production and tissue destruction.</p

PI3Kδ expression is suppressed in human TB granulomas and infected macrophages.

<p><b>A, B.</b> Immunohistochemistry analysis of normal human lung tissue demonstrates that alveolar macrophages express both CD68 and PI3Kδ. <b>C, D</b>. Within human lung TB granulomas, CD68 is widely expressed, but no PI3Kδ immunoreactivity is observed. <b>E, F.</b> Both epithelioid macrophages and multinucleate giant cells around TB granulomas express CD68, but neither express PI3Kδ. <b>G.</b> In primary macrophages, Mtb infection significantly upregulates MMP-1 expression at 24h, whilst (<b>H</b>) concurrently suppresses <i>PIK3CD</i> mRNA accumulation. Immunohistochemistry images are representative of six donors with histopathologically confirmed TB who had lung biopsies as part of their routine clinical care. Scale bars: A, B, E, F: 100μm, C, D: 500 μm. Cellular experiments were performed in triplicate and are representative of at least three donors. P values are t-test comparisons.</p