Mycobacterium vaccae NCTC 11659, a Soil-Derived Bacterium with Stress Resilience Properties, Modulates the Proinflammatory Effects of LPS in Macrophages

Abstract

Inflammatory conditions, including allergic asthma and conditions in which chronic low-grade inflammation is a risk factor, such as stress-related psychiatric disorders, are prevalent and are a significant cause of disability worldwide. Novel approaches for the prevention and treatment of these disorders are needed. One approach is the use of immunoregulatory microorganisms, such as Mycobacterium vaccae NCTC 11659, which have anti-inflammatory, immunoregulatory, and stress-resilience properties. However, little is known about how M. vaccae NCTC 11659 affects specific immune cell targets, including monocytes, which can traffic to peripheral organs and the central nervous system and differentiate into monocyte-derived macrophages that, in turn, can drive inflammation and neuroinflammation. In this study, we investigated the effects of M. vaccae NCTC 11659 and subsequent lipopolysaccharide (LPS) challenge on gene expression in human monocyte-derived macrophages. THP-1 monocytes were differentiated into macrophages, exposed to M. vaccae NCTC 11659 (0, 10, 30, 100, 300 µg/mL), then, 24 h later, challenged with LPS (0, 0.5, 2.5, 250 ng/mL), and assessed for gene expression 24 h following challenge with LPS. Exposure to M. vaccae NCTC 11659 prior to challenge with higher concentrations of LPS (250 ng/mL) polarized human monocyte-derived macrophages with decreased IL12A, IL12B, and IL23A expression relative to IL10 and TGFB1 mRNA expression. These data identify human monocyte-derived macrophages as a direct target of M. vaccae NCTC 11659 and support the development of M. vaccae NCTC 11659 as a potential intervention to prevent stress-induced inflammation and neuroinflammation implicated in the etiology and pathophysiology of inflammatory conditions and stress-related psychiatric disorders.

Effects of Mycobacterium vaccae NCTC 11659 and Lipopolysaccharide Challenge on Polarization of Murine BV-2 Microglial Cells

“…Studies using M. vaccae NCTC 11659 in vivo have shown that, in the absence of subsequent stress exposure or LPS challenge, M. vaccae NCTC 11659 has an adjuvant-like effect, e.g., increasing bronchopulmonary Il1b , Il6 , and Tnf mRNA expression 12 h to 3 days following intratracheal administration [ 25 ] and resulting in a persistent increase in the secretion of IL-6 from mesenteric lymph node cells stimulated with an anti-CD3 antibody in vitro [ 11 ] or a persistent increase in hippocampal Il6 mRNA expression [ 20 ]. Likewise, in vitro studies have revealed that the treatment of human THP-1-derived-macrophages with M. vaccae NCTC 11659 increases the expression of genes involved in proinflammatory signaling, including Il1b , Ccl2 , and numerous other canonical inflammatory markers [ 19 ] (Holbrook et al, 2023). In the present study, 48 h following the exposure of BV-2 cells to 100 µg/mL M. vaccae NCTC 11659, 5 of the 248 endogenous genes in the CodeSet (i.e., 2%) were differentially expressed ( p < 0.05 and fold change either less than –1.5 or greater than 1.5) within the CMV groups between M. vaccae NCTC 11659 conditions (i.e., 100 µg/mL M. vaccae NCTC 11659/CMV vs. BBS/CMV) ( Figure 3 A).…”

“…Previous studies have demonstrated that 250 ng/mL LPS ( Escherichia coli 0111:B4) potently induces inflammation in BV-2 microglial cells and human THP-1-derived macrophages [ 19 , 21 , 28 ]. Twenty-four hours following the exposure of BV-2 cells to 250 ng/mL LPS, relative to CMV control conditions, 71 of the 248 endogenous inflammation-related genes in the CodeSet (i.e., 28.6%) were differentially expressed, as assessed by a moderated t -test (i.e., satisfied the criteria of p < 0.05 and fold change either less than –1.5 or greater than 1.5) (i.e., BBS/250 ng/mL LPS vs. BBS/CMV) ( Figure 3 B).…”

“…Previous studies have shown that 100 µg/0.1 mL M. vaccae NCTC 11659, given by s.c. injection once a week for three weeks, can attenuate the stress-induced exaggeration of inflammatory hippocampal gene expression [ 20 ]. In THP-1-derived macrophages, pretreatment with 300 µg/mL M. vaccae NCTC 11659 24 h prior to LPS exposure, relative to the BBS/LPS condition, increases the expression of a number of genes involved in anti-inflammatory signaling, including Il10 , Il10rb , Tgfb2 , Tgfbr1 , and Mrc1 , and decreases the expression of genes encoding proinflammatory cytokines, such as Il12b [ 19 ]. In the present study, among cells exposed to LPS-challenge conditions, exposure to 100 µg/mL M. vaccae NCTC 11659 relative to the BBS control condition (i.e., 100 µg/mL M. vaccae NCTC 11659/250 ng/mL LPS vs. BBS/250 ng/mL LPS) led to the differential expression of 3 of the 248 genes in the CodeSet (i.e., 1.2%) ( p < 0.05 and fold change either less than –1.5 or greater than 1.5) when assessed 48 h following exposure to M. vaccae NCTC 11659 ( Figure 3 C).…”

“…The overall effects of M. vaccae NCTC 11659 in enhancing inflammatory responses induced by LPS in microglia are distinct from the effects of M. vaccae NCTC 11659 on peripheral immune cells. Previous studies have shown that human THP-1-derived macrophages respond to exposure to M. vaccae NCTC 11659 with attenuated LPS-induced decreases in Il10 : Il12b , Il10 : Il23a , Tgfb1 : Il12b , and Tgfb1 : Il23a mRNA expression ratios [ 19 ].…”

“…Therefore, we set out to determine the effects of M. vaccae NCTC 11659, relative to vehicle control conditions, applied directly to murine BV-2 microglial cells when followed, 24 h later, by an immune challenge with LPS or vehicle control conditions. For a detailed description of the history of the development of M. vaccae NCTC 11659 used here, see [ 19 ]. For a description of the alternative designations and different preparations and production processes of M. vaccae NCTC 11659 used in clinical trials or preclinical studies, see [ 20 ].…”