Adherence Affects Monocyte Innate Immune Function and Metabolic Reprogramming after Lipopolysaccharide Stimulation In Vitro

Abstract

Circulating nonadherent monocytes can migrate to extravascular sites by a process that involves adherence. Alterations in intracellular metabolism shape the immunological phenotype of phagocytes upon activation. To determine the effect of adherence on their metabolic and functional response human monocytes were stimulated with LPS under nonadherent and adherent conditions. Adherent monocytes (relative to nonadherent monocytes) produced less TNF and IL-1b (proinflammatory) and more IL-10 (antiinflammatory) upon LPS stimulation and had an increased capacity to phagocytose and produce reactive oxygen species. RNA sequencing analysis confirmed that adherence modified the LPS-induced response of monocytes, reducing expression of proinflammatory genes involved in TLR signaling and increasing induction of genes involved in pathogen elimination. Adherence resulted in an increased glycolytic response as indicated by lactate release, gene set enrichment, and [ 13 C]-glucose flux analysis. To determine the role of glycolysis in LPS-induced immune responses, this pathway was inhibited by glucose deprivation or the glucose analogue 2-deoxy-D-glucose (2DG). Although both interventions equally inhibited glycolysis, only 2DG influenced monocyte functions, inhibiting expression of genes involved in TLR signaling and pathogen elimination, as well as cytokine release. 2DG, but not glucose deprivation, reduced expression of genes involved in oxidative phosphorylation. Inhibition of oxidative phosphorylation affected TNF and IL-10 release in a similar way as 2DG. Collectively, these data suggest that adherence may modify the metabolic and immunological profile of monocytes and that inhibition of glycolysis and oxidative phosphorylation, but not inhibition of glycolysis alone, has a profound effect on immune functions of monocytes exposed to LPS.

Role of Myeloid Tet Methylcytosine Dioxygenase 2 in Pulmonary and Peritoneal Inflammation Induced by Lipopolysaccharide and Peritonitis Induced by Escherichia coli

“…Macrophages from both body sites showed increased Tet2 mRNA levels upon LPS exposure. To determine whether TET2 expression is regulated similarly in human cells, we made use of publicly available datasets derived from previous studies from our group [ 27 , 28 ]. Primary human monocytes, either adherent or non-adherent, stimulated with LPS demonstrated increased TET2 mRNA levels relative to monocytes cultured in medium only ( Figure 1 C; GSE161839) [ 27 ].…”

“…To determine whether TET2 expression is regulated similarly in human cells, we made use of publicly available datasets derived from previous studies from our group [ 27 , 28 ]. Primary human monocytes, either adherent or non-adherent, stimulated with LPS demonstrated increased TET2 mRNA levels relative to monocytes cultured in medium only ( Figure 1 C; GSE161839) [ 27 ]. Likewise, human AMs harvested after an in vivo bronchial LPS challenge in healthy subjects showed increased TET2 mRNA levels when compared with AMs obtained from the contralateral control lung administered with normal saline ( Figure 1 D, GSE40885) [ 28 ].…”

“…TET2 expression in human monocytes activated ex vivo with LPS was determined using RNAseq dataset GSE161839, derived from a study from our group [ 27 ]. The RNA was isolated from adherent and non-adherent human monocytes before or after 24 h of LPS (10 ng/mL) stimulation ( n = 6 for each condition) as described in detail [ 27 ]. TET2 expression was determined in human AMs using microarray data deposited in GSE40885, derived from a study from our group [ 28 ].…”

Comparative transcriptomic analysis of long noncoding RNAs in Leishmania-infected human macrophages

“…BAALC is a binder of MAP3K1 and KLF4, previously described in cancer as interacting with these molecules and inhibiting their functions ( Morita et al, 2015 ). MAP3K1 is involved in MAPK signaling in response to pro-inflammatory stimuli ( Otto et al, 2021 ). It can be directly targeted by miR-770, reducing the M2 polarization of macrophages ( Liu et al, 2021 ).…”

The Effect of Magnesium Sulfate on Lipopolysaccharide Tolerance in Human Monocytes

“…Phenotypes or activities of monocytes, such as cell adherence or proliferation, relates to innate immune function [9]. For example, adherence of monocytes to endothelial cells determines progress of atherosclerosis [10].…”