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Activation of pannexin-1 mediates triglyceride-induced macrophage cell death.

ABSTRACT: The accumulation of triglycerides (TGs) in macrophages induces cell death, a risk factor in the pathogenesis of atherosclerosis. We had previously reported that TG-induced macrophage death is triggered by caspase-1 and -2, therefore we investigated the mechanism underlying this phenomenon. We found that potassium efflux is increased in TG-treated THP-1 macrophages and that the inhibition of potassium efflux blocks TG-induced cell death as well as caspase-1 and -2 activation. Furthermore, reducing ATP concentration (known to induce potassium efflux), restored cell viability and caspase-1 and -2 activity. The activation of pannexin-1 (a channel that releases ATP), was increased after TG treatment in THP-1 macrophages. Inhibition of pannexin-1 activity using its inhibitor, probenecid, recovered cell viability and blocked the activation of caspase-1 and -2 in TG-treated macrophages. These results suggest that TG-induced THP-1 macrophage cell death is induced via pannexin- 1 activation, which increases extracellular ATP, leading to an increase in potassium efflux. [BMB Reports 2020; 53(11): 588-593].

SUBMITTER: Jung BC

PROVIDER: S-EPMC7704223 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Activation of pannexin-1 mediates triglyceride-induced macrophage cell death.

Jung Byung Chul BC Kim Sung Hoon SH Lim Jaewon J Kim Yoon Suk YS

BMB reports 20201101 11

The accumulation of triglycerides (TGs) in macrophages induces cell death, a risk factor in the pathogenesis of atherosclerosis. We had previously reported that TG-induced macrophage death is triggered by caspase-1 and -2, therefore we investigated the mechanism underlying this phenomenon. We found that potassium efflux is increased in TG-treated THP-1 macrophages and that the inhibition of potassium efflux blocks TG-induced cell death as well as caspase-1 and -2 activation. Furthermore, reducin ...[more]

PMID: 33050989

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Project description:OBJECTIVE:Alternative activation (M2) of adipose tissue resident macrophage (ATM) inhibits obesity-induced metabolic inflammation. The underlying mechanisms remain unclear. Recent studies have shown that dysregulated lipid homeostasis caused by increased lipolysis in white adipose tissue (WAT) in the obese state is a trigger of inflammatory responses. We investigated the role of M2 macrophages in lipotoxicity-induced inflammation. METHODS:We used microarray experiments to profile macrophage gene expression regulated by two M2 inducers, interleukin-4 (Il-4), and peroxisome proliferator-activated receptor delta/gamma (Ppar?/Ppar?) agonists. Functional validation studies were performed in bone marrow-derived macrophages and mice deprived of the signal transducer and activator of transcription 6 gene (Stat6; downstream effector of Il-4) or Ppar?/Ppar? genes (downstream effectors of Stat6). Palmitic acid (PA) and ?-adrenergic agonist were employed to induce macrophage lipid loading in vitro and in vivo, respectively. RESULTS:Profiling of genes regulated by Il-4 or Ppar?/Ppar? agonists reveals that alternative activation promotes the cell survival program, while inhibiting that of inflammation-related cell death. Deletion of Stat6 or Ppar?/Ppar? increases the susceptibility of macrophages to PA-induced cell death. NLR family pyrin domain containing 3 (Nlrp3) inflammasome activation by PA in the presence of lipopolysaccharide is also increased in Stat6-/- macrophages and to a lesser extent, in Ppar?/?-/- macrophages. In concert, ?-adrenergic agonist-induced lipolysis results in higher levels of cell death and inflammatory markers in ATMs derived from myeloid-specific Ppar?/?-/- or Stat6-/- mice. CONCLUSIONS:Our data suggest that ATM cell death is closely linked to metabolic inflammation. Within WAT where concentrations of free fatty acids fluctuate, M2 polarization regulated by the Stat6-Ppar axis enhances ATM's tolerance to lipid-mediated stress, thereby maintaining the homeostatic state.

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Activation of pannexin-1 mediates triglyceride-induced macrophage cell death.

Publications

Activation of pannexin-1 mediates triglyceride-induced macrophage cell death.

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