Temporal modulation of host aerobic glycolysis determines the outcome of M. marinum infection

Abstract

24Macrophages are the first-line host defense where the invading Mycobacterium 25 tuberculosis (Mtb) encounters. It has been recently reported that host aerobic glycolysis 26 was elevated post the infection by a couple of virulent mycobacterial species. However, 27 whether this metabolic transition is required for host defense against intracellular 28 pathogens and the underlying mechanisms remain to be further investigated. By 29 analyzing carbon metabolism, we found that macrophages infected by M. marinum, a 30 surrogate mycobacterial specie to Mtb, showed a strong elevation of glycolysis. Next, 31 three glycolysis inhibitors were examined for their ability to inhibit mycobacterial 32 proliferation inside RAW264.7, a murine macrophage-like cell line. Among them, a 33 glucose analog, 2-deoxyglucose (2-DG) displayed a protective effect on assisting host 34 to resist mycobacterial infection, which was further validated in zebrafish-infection 35 model. The phagocytosis of M. marinum was significantly decreased in macrophages 36 pre-treated with 2-DG at concentrations of 0.5 and 1 mM, at which no inhibitory effect 37 was posed on M. marinum growth in vitro. Moreover, 2-DG pre-treatment exerted a 38 significant protective effect on zebrafish larvae to limit the proliferation of M. marinum, 39 and such effect was correlated to tumor necrosis factor alpha (TNF-α). On the contrary, 40 the 2-DG treatment post infection did not restrain proliferation of M. marinum in WT 41 zebrafish, and even accelerated bacterial replication in TNF-α -/zebrafish. Together, 42 modulation of glycolysis prior to infection boosts host immunity against M. marinum 43 infection, indicating a potential intervention strategy to control mycobacterial infection.44 3 45 46 Author Summary 47As an intracellular pathogen, Mtb exploits multiple strategies to invade and hijack 48 macrophages for its own advantages. Accordingly, recent investigations have shown 49 that Mtb infection is accompanied with an alteration of host glucose metabolism. 50Macrophage and zebrafish infection models of M. marinum, facilitating our 51 understanding towards mycobacterial pathogenesis, were applied in this study. We 52 found that the pre-treatment of macrophages with a glucose analog, 2-DG, inhibited 53 aerobic glycolysis and made host cells more inert to phagocytose the bud. In infected 54 zebrafish larvae, bacterial load inside host pretreated with 2-DG remains at a 55 significantly lower level compared to the untreated group. These findings imply that 56 the modulation of host glycolysis regulates the fate of M. marinum infection, and 57 indicate a promising metabolic target in TB intervention. 4 58 Introduction 59 Tuberculosis (TB), a serious chronic infectious disease caused by Mycobacterium 60 tuberculosis (Mtb), is still a major threaten to public health worldwide. The interaction 61 between Mtb and macrophages was initiated with phagocytosis [1]. Downstream cell 62 defense events will then be switched on, including phagosome maturation, acidification, 63 th...