Dual-lipid metabolomics revealed the communication of MTB or MB with Bovine alveolar macrophages in lipid metabolisms

M. tuberculosis(MTB) and M. bovis(MB) of the Mycobacterium tuberculosis complex (MTBC) are the causative agents of the notorious infectious disease tuberculosis(TB) in a range of mammals, including cattle and human. The lipid composition of MTB/MB performed imperative function as invading host macrophage. In the present study, a dual-lipid metabolomics were used to elucidate the differences in lipid composition of MTB and MB and the different responses in lipid metabolisms of bovine alveolar macrophage challenged by MTB/MB. The lipid metabolomics of MTB and MB indicated that there were significant differences in lipid composition of both bacteria that the level of various lipids belonged to Glycerophospholipids, Sterol Lipids, Fatty Acyls and Polyketides exhibited differences between MTB and MB. Meanwhile, both MTB and MB with different lipid composition could invoked different responses in lipid metabolisms of the host macrophage. MTB infection mainly induced the increase in content of Polyketides and Glycerophospholipids in macrophages, whereas MB infection induced the level of Glycerophospholipids and Sterol Lipids of macrophages. Furthermore, we identified TAG 13:0-18:5-18:5 of MTB and PC(16:1(9E)/0:0), PI(20:2(11Z,14Z)/22:6(4Z,7Z,10Z,13Z,16Z,19Z)), 4,6-Decadiyn-1-ol isovalerate and LacCer(d18:1/24:1(15Z)) of MB caused the different variations in lipid metabolisms of macrophage following MTB/MB attacks, respectively. Finally, we proposed MTB and MB with different lipid compositions could successfully colonize in macrophage by different mechanisms that MTB could promote the formation of foam cells of macrophage for its colonization and development, while MB mainly through suppressing the macrophage autophagy to escape the immune responses of host.

The bovine alveolar macrophage DNA methylome is resilient to infection with Mycobacterium bovis

DNA methylation is pivotal in orchestrating gene expression patterns in various mammalian biological processes. Perturbation of the bovine alveolar macrophage (bAM) transcriptome, due to Mycobacterium bovis (M. bovis) infection, has been well documented; however, the impact of this intracellular pathogen on the bAM epigenome has not been determined. Here, whole genome bisulfite sequencing (WGBS) was used to assess the effect of M. bovis infection on the bAM DNA methylome. The methylomes of bAM infected with M. bovis were compared to those of non-infected bAM 24 hours post-infection (hpi). No differences in DNA methylation (CpG or non-CpG) were observed. Analysis of DNA methylation at proximal promoter regions uncovered >250 genes harbouring intermediately methylated (IM) promoters (average methylation of 33–66%). Gene ontology analysis, focusing on genes with low, intermediate or highly methylated promoters, revealed that genes with IM promoters were enriched for immune-related GO categories; this enrichment was not observed for genes in the high or low methylation groups. Targeted analysis of genes in the IM category confirmed the WGBS observation. This study is the first in cattle examining genome-wide DNA methylation at single nucleotide resolution in an important bovine cellular host-pathogen interaction model, providing evidence for IM promoter methylation in bAM.