Loss of Mir146b with aging contributes to inflammation and mitochondrial dysfunction in thioglycollate-elicited peritoneal macrophages

Macrophages undergo programmatic changes with age leading to altered cytokine polarization and immune dysfunction, shifting these critical immune cells from protective sentinels to disease promoters. The molecular mechanisms underlying macrophage inflammaging are poorly understood. Using an unbiased RNA-seq approach, we identified Mir146b as a microRNA whose expression progressively and unidirectionally declined with age in thioglycollate-elicited murine macrophages. Mir146b deficiency led to altered macrophage cytokine expression and reduced mitochondrial metabolic activity, two hallmarks of cellular aging. Single cell RNA sequencing identified patterns of altered inflammation and interferon gamma signaling in Mir146b deficient macrophages. Identification of Mir146b as a potential regulator of macrophage aging provides novel insights into immune dysfunction associated with aging.

O9 M1 macrophages evoke an increase in PIGR expression in MDA-MB468 breast cancer cells through interlukin-1β

Introduction The polymeric immunoglobulin receptor (PIGR) is a transmembrane protein, which transports polymeric immunoglobulin (pIg) across the epithelial cells. High expression of PIGR in breast cancer has been reported to associate with increased 5-year survival rate. In this study, the factors in tumour microenvironment which affected PIGR expression in breast cancer cell lines, were investigated. Method M1, M2 macrophage conditioned media (CM) and recombinant human cytokines were used to determine factors which increased PIGR expression in breast cancer cells. The level of PIGR expression in the cells and secreted PIGR free secretory component (SC) were evaluated by real time quantitative polymerase chain reaction and Western blotting. Results M1 macrophage CM induced a striking dose dependent increase in PIGR mRNA expression in MDA-MB468 cells, up to 20-fold in 100% CM. Interferon gamma (IFNγ) and interleukin (IL)-1β also increased PIGR expression in MDA-MB468 cells. However, IL-1β was demonstrated to increase in M1 macrophages, while IFNγ was not. The role of IL-1β secreted from M1 macrophages in increasing expression of PIGR was confirmed by IL-1 receptor blockade, indicating that IL-1β was the M1 macrophage cytokine that enhanced PIGR expression in breast cancer cells. Conclusions IL-1β was the M1 macrophage cytokine which enhanced PIGR expression in breast cancer cells. IFNγ was also shown to increase PIGR expression in the present study. These imply that elevated PIGR expression in breast cancer in vivo may reflect the polarization state of tumour associated immune cells. Take-home Message IL-1β secreted from M1 macrophage enhances PIGR expression in breast cancer cells. The elevated PIGR expression in breast cancer in vivo may reflect the polarization state of tumour associated immune cells.

Macrophage cytokine responses to commensal Gram-positive Lactobacillus salivarius strains are TLR2-independent and Myd88-dependent

The mechanisms through which cells of the host innate immune system distinguish commensal bacteria from pathogens are currently unclear. Toll-like receptors (TLRs) are a class of pattern recognition receptors (PRRs) expressed by host cells which recognize microbe-associated molecular patterns (MAMPs) common to both commensal and pathogenic bacteria. Of the different TLRs, TLR2/6 recognize bacterial lipopeptides and trigger cytokines responses, especially to Gram-positive and Gram-negative pathogens. We report here that TLR2 is dispensable for triggering macrophage cytokine responses to different strains of the Gram-positive commensal bacterial species Lactobacillus salivarius. The L. salivarius UCC118 strain strongly upregulated expression of the PRRs, Mincle (Clec4e), TLR1 and TLR2 in macrophages while downregulating other TLR pathways. Cytokine responses triggered by L. salivarius UCC118 were predominantly TLR2-independent but MyD88-dependent. However, macrophage cytokine responses triggered by another Gram-positive commensal bacteria, Bifidobacterium breve UCC2003 were predominantly TLR2-dependent. Thus, we report a differential requirement for TLR2-dependency in triggering macrophage cytokine responses to different commensal Gram-positive bacteria. Furthermore, TNF-α responses to the TLR2 ligand FSL-1 and L. salivarius UCC118 were partially Mincle-dependent suggesting that PRR pathways such as Mincle contribute to the recognition of MAMPs on distinct Gram-positive commensal bacteria. Ultimately, integration of signals from these different PRR pathways and other MyD88-dependent pathways may determine immune responses to commensal bacteria at the host-microbe interface.

M2 macrophage-secreted Slit3 intensifies sympathetic nerve function in adipose tissue and enhances thermogenesis: A long-term cold adaption way

Beiging of white adipose tissue (WAT) is capable of adaptive thermogenesis and dissipating energy. The beiging processes have been associated with the increase of anti-inflammatory M2 macrophages, however the function of M2 macrophage on beiging and the underlying mechanism are not fully understood. Here we identified a macrophage cytokine Slit3 by analyzing the transcriptome of M2 macrophages collected with FACS in inguinal WAT (iWAT) of mice after cold exposure. Once released from macrophages, Slit3 bound to the ROBO1 receptor on sympathetic neuron and activated tyrosine hydrolase (TH) through PKA and CaMKⅡ signaling, and thus stimulated norepinephrine (NE) synthesis and release. NE acts on adipocytes and stimulate thermogenesis. Adoptive transfer of Slit3-overexpressing M2 macrophages to iWAT depot acquired local adipocytes with beiging phenotype and enhanced thermogenesis. In addition, mice bearing the myeloid inactivation of Slit3 were cold intolerant and gained more weight due to the lowered metabolic rate. Collectively, we demonstrate Slit3 is a macrophage cytokine and promotes beiging and thermogenesis through intensifying the sympathetic nerve function. As the expanded M2 macrophages are integral cell population in adipose tissue, the macrophage-Slit3-sympathetic neuron-adipocyte axis assures the long-term cold adaption.