Pathogenic effects of inhibition of mTORC1/STAT3 axis facilitates Staphylococcus aureus-induced pyroptosis in human macrophages

Abstract

Background Pyroptosis is a recently identified pathway of caspase-mediated cell death in response to microbes, lipopolysaccharide, or chemotherapy in certain types of cells. However, the mechanism of how pyroptosis is regulated is not well-established. Methods Herein, the intracellular bacteria were detected by staining and laser confocal microscopy and TEM. Live/dead cell imaging assay was used to examine macrophage death. Western blot and immunohistochemical staining were used to examine the protein changes. IFA was used to identify typical budding vesicles of pyroptosis and the STAT3 nuclear localization. SEM was used to observe the morphological characteristics of pyroptosis. ELISA was used to detect the level of inflammatory cytokines. Pyroptosis was filmed in macrophages by LSCM. Results S. aureus was internalized by human macrophages. Intracellular S. aureus induced macrophage death. S. aureus invasion increased the expression of NLRP3, Caspase1 (Casp-1 p20) and the accumulation of GSDMD-NT, GSDMD-NT pore structures, and the release of IL-1β and IL-18 in macrophages. Macrophages pyroptosis induced by S. aureus can be abrogated by blockage of S. aureus phagocytosis. The pyroptosic effect by S. aureus infection was promoted by either rapamycin or Stattic, a specific inhibitor for mTORC1 or STAT3. Inhibition of mTORC1 or STAT3 induced pyroptosis. mTORC1 regulated the pyroptosic gene expression through governing the nuclear localization of STAT3. mTORC1/STAT3 axis may play a regulatory role in pyroptosis within macrophages. Conclusions S. aureus infection induces human macrophage pyroptosis, inhibition of mTORC1/STAT3 axis facilitates S. aureus-induced pyroptosis. mTORC1 and STAT3 are associated with pyroptosis. Our findings demonstrate a regulatory function of the mTORC1/STAT3 axis in macrophage pyroptosis, constituting a novel mechanism by which pyroptosis is regulated in macrophages.

Identification of Novel Pyroptosis-Related lncRNAs Associated with the Prognosis of Breast Cancer Through Interactive Analysis

“…mTORC1/STAT3 axis may play a moderating role in pyroptosis of macrophages. 30 As a hormone-sensitive disease, the response of breast cancer to androgen was associated with cancer progression. 31 Feng and their colleagues found that a high response rate of androgen in breast cancer could lead to cancer development and metastasis.…”

Monocarboxylate Transporter 4 Triggered Cell Pyroptosis to Aggravate Intestinal Inflammation in Inflammatory Bowel Disease

“…The current studies have shown that mTOR/STAT3 axis ( 33 ) and IKK-NF- κ B pathway ( 34 , 35 ), including IKK epsilon ( 36 ), played a critical role in regulating cell pyroptosis. In addition, a missense mutation of NLRP3 could lead to NLRP3 inflammasome activation causing cell pyroptosis ( 37 – 41 ), such as R779C increased NLRP3 inflammasome activation and pyroptosis in macrophages, which was mediated by enhanced deubiquitination of NLRP3 via binding with deubiquitinases BRCC3 and JOSD2 ( 41 ).…”

Metformin improves renal injury of MRL/lpr lupus-prone mice via the AMPK/STAT3 pathway

“… 24 STAT3 activation also enhances caspase-1 and successive production of mature IL-1β and IL-18, even triggering pyroptosis, another type of cell death. 26 27 Recent research indicates that RIPK3 is involved in activating the inflammasome. 28 29 …”

“…In addition to necroptosis, renal inflammation can be promoted through inflammasome activation in intrinsic renal cells and proinflammatory cells 24. STAT3 activation also enhances caspase-1 and successive production of mature IL-1β and IL-18, even triggering pyroptosis, another type of cell death 26 27. Recent research indicates that RIPK3 is involved in activating the inflammasome 28 29…”