Damage Associated Molecular Pattern Molecule-Induced microRNAs (DAMPmiRs) in Human Peripheral Blood Mononuclear Cells

Abstract

Endogenous damage associated molecular pattern molecules (DAMPs) released from necrotic, damaged or stressed cells are associated with an inflammatory response. Whether the microRNA (miR) expression signature of this response is different from that of a pathogen associated molecular pattern (PAMP)-stimulated inflammatory response is unknown. We report here that miR-34c and miR-214 are significantly expressed in fresh human peripheral blood mononuclear cells (PBMCs) exposed to DAMP-containing freeze-thaw lysates, or to conditioned media from serum-starved and glucose-deprived cells (p<6×10−4 and p<3.7×10−3), respectively. Interestingly, only miR-34c expression was differentially expressed in PBMCs exposed to freeze-thaw lysates or conditioned media from wildtype High Mobility Group B1 (HMGB1+/+) mouse embryonic fibroblast (MEF) cells, when compared to cultures exposed to lysates or conditioned media from HMGB1−/− MEFs. miR-155 expression in these cultures was negligible, but was significantly expressed in PBMCs stimulated with Lipopolysaccahride (LPS) or most other Toll-like receptor (TLR) ligands, making it the prototypic “PAMPmiR”. Exposure to a damaged human colorectal carcinoma cell line lysate (HCT116) similarly resulted in increased miR-34c and miR-214 levels. When PBMCs were pre-transfected with anti-miR-34c and then exposed to lysate, expression levels of IKKγ mRNA, a putative target of miR-34c, increased, while protein levels of IKKγ in cultures transfected with a pre-miR-34c were abrogated. Levels of miR-34c expression (as well as pro-inflammatory cytokines, IL-1β and TNFα) decreased when PBMC cultures were briefly pre-incubated with the K+ channel (inflammasome) inhibitor, glybenclamide, suggesting that inflammasome activation is upstream of miR-34c expression in response to DAMPs. Our findings demonstrate that a specific microRNA expression signature is associated with the inflammatory response to damaged/injured cells and carries implications for many acute and chronic inflammatory disorders.

Danger signalling during cancer cell death: origins, plasticity and regulation

“…A recent study revealed that exposure of leukocytes to DAMPs induces expression of miR-34c and miR-214 and downregulates miR-34a. 85 miR-34c is involved in silencing IKKg, an essential signalling molecule within NF-kB pathway, indicating that fine tuning of inflammatory pathways is extremely complex.…”

The Power of Negative Thinking: Which Cells Limit Tumor Immunity?

“…Indeed, it may be that damage-associated molecular pattern molecules (DAMP), released by the stressed or dying tumor could provoke tumor myeloid cells to upregulate microRNAs as we have shown, capable of limiting immunity (8). Alternatively enhanced resistance to immune effectors, possibly mediated by enhanced autophagy, might be directly regulated by cytokines or microRNAs released by tumors (9).…”

Pathogen-Induced Autophagy Signaling in Innate Immunity

“…Upon further injury of the cell, HMGB1 is released from dying cells to act in a paracrine manner to further induce autophagy [84,85]. miR-34c and miR-214 are significantly expressed in fresh human peripheral blood mononuclear cells exposed to DAMP-containing freeze-thaw lysates or to conditioned media from serum-starved and glucose-deprived cells [86]. miR-34c and miR-214 expression in human peripheral blood mononuclear cells is dependent on the presence of HMGB1 [86].…”

“…miR-34c and miR-214 are significantly expressed in fresh human peripheral blood mononuclear cells exposed to DAMP-containing freeze-thaw lysates or to conditioned media from serum-starved and glucose-deprived cells [86]. miR-34c and miR-214 expression in human peripheral blood mononuclear cells is dependent on the presence of HMGB1 [86]. Both HMGB1 and these miRs may play a common role in driving autophagy and the response to inflammation.…”