M. bovis PPD Enhances Respiratory Bioenergetics of Human vs. Bovine Macrophages

The role of macrophage (MO) cellular metabolism and reprogramming during TB infection is of great interest due to the influence of Mycobacterium spp. on MO bioenergetics. Recent studies have shown that M. tuberculosis induces a TLR2-dependent shift towards aerobic glycolysis and metabolic reprogramming, comparable to the established LPS induced pro-inflammatory M1 MO polarisation. Distinct differences in the metabolic profile of murine and human MO indicates species-specific differences in bioenergetics. So far, studies examining the metabolic potential of cattle are lacking, thus the basic bioenergetics of bovine and human MO were explored in response to a variety of innate immune stimuli. Cellular energy metabolism kinetics were measured concurrently for both species on a Seahorse XFe96 platform to generate bioenergetic profiles for the response to the bona-fide TLR2 and TLR4 ligands, FSL-1 and LPS respectively. Despite previous reports of species-specific differences in TLR signalling and cytokine production between human and bovine MO, we observed similar respiratory profiles for both species. Basal respiration remained constant between stimulated MO and controls, whereas addition of TLR ligands induced increased glycolysis. In contrast to MO stimulation with M. tuberculosis PPD, another TLR2 ligand, M. bovis PPD treatment significantly enhanced basal respiration rates and glycolysis only in human MO. Respiratory profiling further revealed significant elevation of ATP-linked OCR and maximal respiration suggesting a strong OXPHOS activation upon M. bovis PPD stimulation in human MO. Our results provide an exploratory set of data elucidating the basic respiratory profile of bovine vs. human MO that will not only lay the foundation for future studies to investigate host-tropism of the M. tuberculosis complex but may explain inflammatory differences observed for other zoonotic diseases. HighlightsO_LISimilar baseline respiratory profiles for human and bovine macrophages C_LIO_LIM. bovis PPD treatment altered metabolic profile only in human MO C_LIO_LIStrong OXPHOS activation upon M. bovis PPD stimulation only in human MO C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=134 SRC="FIGDIR/small/582730v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@e833fborg.highwire.dtl.DTLVardef@acdda6org.highwire.dtl.DTLVardef@10bcbfforg.highwire.dtl.DTLVardef@17ddf31_HPS_FORMAT_FIGEXP M_FIG Created with BioRender (www.biorender.com) by A. Gibson C_FIG