bims-nocaut Biomed News
on Non-canonical autophagy
Issue of 2023–09–24
two papers selected by
Quentin Frenger, University of Strasbourg
  1. Autophagy and LC3-associated phagocytosis contribute negatively to the killing capability of THP-1-derived macrophages against Candida albicans at the mid-stage.
  2. Role of inhibiting inflammation of LC3-associated phagocytosis in dry eye disease.
  1. Immunol Lett. 2023 Sep 15. pii: S0165-2478(23)00155-4. [Epub ahead of print]
    Autophagy and LC3-associated phagocytosis contribute negatively to the killing capability of THP-1-derived macrophages against Candida albicans at the mid-stage.
    Ding Li, Lin Wang, Zhihong Zhao, Changsen Bai, Xichuan Li.
      In innate immunity, macrophages play critical roles in defending against pathogens via the lysosomal degradation function of autophagy. Two distinct autophagy pathways have been identified in decades: canonical autophagy (referred to as autophagy) and LC3-associated phagocytosis (LAP). Since several conflicting findings about the anti-Candida capability of autophagy (or LAP) have been reported, they serve as the foe or friend for Candida survival is still unclearly. The current study showed that the fungicidal process of THP-1-derived macrophages (THP-1-MФ) against Candida albicans is divided into three stages as follows, the early stage (the first 12 h, increasing in the killing capability), the mid-stage (12-24 h, no change in killing capability), and the late stage (24-48 h, decreasing of the killing capability). Autophagic protein LC3B-II reached the peak in THP-1-MФ after 24 h inoculated either with C.albicans or whole glucan particles (WGP). Thus, both anti-Candida roles of autophagy and the LAP pathway have been detected at the mid-stage. For autophagy, after 24 h inoculation with C.albicans, ULK1 increased, but p-ATG13(s318) decreased obviously in THP-1-MФ, and the killing assay showed that autophagy is unhelpful for Candida killing capability. For the LAP pathway, Rubicon and ROS raised significantly in THP-1-MФ after 24 h inoculated with C.albicans; each inhibition would sharply cut down the LC3B-II accumulation, which indicated that LAP had been induced. However, mCherry-GFP-LC3 fluorescent assay exhibited that LAP phago-lysosomal fusion has been blocked, and Rubicon knockdown facilitated the Candida killing activity. These data indicated that autophagy presented as redundant to Candida defense, and LAP phago-lysosomal fusion obstruction impairs the Candida killing capability of THP-1-MФ at the mid-stage. That may explain the no change in Candida killing capability at the mid-stage.
    Keywords:  Autophagy; C. albicans; LAP; Macrophage; Mid-stage
    DOI:  https://doi.org/10.1016/j.imlet.2023.09.006
  2. Curr Eye Res. 2023 Sep 21. 1-13
    Role of inhibiting inflammation of LC3-associated phagocytosis in dry eye disease.
    Sasa Zhang, Xing Liu, Cui Li, Qian Wang, Shanshan Yang, Xudong Peng, Liting Hu, Guiqiu Zhao, Jing Lin.
       PURPOSE: To confirm the expression and investigate the role of LC3-associated phagocytosis (LAP) in dry eye disease (DED).
    METHODS: The DED model of mice was established by scopolamine subcutaneous injection in a low humidity environment chamber. Tear secretion test and corneal fluorescein sodium staining were used to evaluate the severity of DED. Expression levels of Rubicon, Microtubule associated protein light chain 3-II (LC3-II), Beclin-1 and autophagy related gene-7 (Atg-7) in corneas of mice with DED were tested by western blot. Cell Counting Kit-8 (CCK-8) assay was used to detect the effects of different concentrations of hypertonic solutions on the proliferation activity of human corneal epithelial cells (HCECs). The expression levels of Dectin-1, IL-6 and IL-1β in HCECs after stimulation with different concentrations of hypertonic solutions were tested. The expressions of Rubicon, LC3-II, Beclin-1 and ATG-7 in HCECs were detected by reverse transcription polymerase chain reaction (RT-PCR). After being pretreated with 10 μM si-Rubicon, the severity of the disease was documented by corneal fluorescein sodium staining. And the expression levels of IL-6 and IL-1β were also tested by RT-PCR.
    RESULTS: Compared with the normal control group, the corneal fluorescein sodium staining scores and tear secretion were significantly reduced. Rubicon, LC3-II, Beclin-1 and ATG-7 were significantly elevated. CCK-8 showed that the 400 and 450 mOsM hypertonic solutions did not affect the proliferation activity of HCECs. The expression of Dectin-1, IL-1β and IL-6 were elevated after stimulation with 450 mOsM solution. LC3-II, Rubicon, ATG-7 and Beclin-1 increased after stimulation with 450 mOsM hyperosmolar solution in HCECs. Corneal fluorescein staining showed that si-Rubicon increased the severity of DED in mice. Moreover, the mRNA expressions of inflammatory factors IL-1β and IL-6 in the cornea of mice were significantly increased.
    CONCLUSION: DED increased the expression of protein associated to LAP. LAP could play an anti-inflammatory effect in DED.
    Keywords:  LC3-associated phagocytosis; cornea; dry eye disease; hypertonic; inflammation
    DOI:  https://doi.org/10.1080/02713683.2023.2262169
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