Publication: Ethanol enhances thymocyte apoptosis and autophagy in macrophages of rat thymi
Authors
Betsuyaku, Tsubasa ; Eid, Nabil ; Ito, Yuko ; Tanaka, Yoshihisa ; Otsuki, Yoshinori ; Kondo, Yoichi
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Publisher
Universidad de Murcia. Departamento de Biología Celular e Histología
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DOI
DOI: 10.14670/HH-11-861
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info:eu-repo/semantics/article
Description
Abstract
Tingible body macrophages (TBMs) play
essential roles in the phagocytosis of apoptotic
lymphocytes, specifically under exposure to various
stressors. Although excessive ethanol consumption may
enhance thymocyte apoptosis, reports investigating the
autophagic response of the thymus to ethanol toxicity are
still lacking. We investigated apoptosis and autophagy in
thymi of an animal model of binge ethanol exposure.
Adult male Wistar rats were injected intraperitoneally
either with 5 g/kg ethanol or phosphate buffer saline (for
the control group) and sacrificed 0, 3, 6 and 24 hours
after injection. Light and transmission electron
microscopy (TEM) studies revealed enhanced formation
of TBMs phagocytosing many apoptotic thymocytes in
the thymic cortex of the ethanol-treated rats (ETRs), and
this formation was particularly marked at 24 h. The
macrophages showed signs of activation under TEM and
immunofluorescence double labeling with RM4 (a
macrophage marker) and iNOS. Additionally, in
comparison to the control group, autophagy was
enhanced in ETR thymic TBMs as evidenced
ultrastructurally by accumulation of autophagic
vacuoles, immunohistochemical increases in LC3
puncta, Western blot analysis of the latter protein, and
colocalization of LC3 and RM4 in immunofluorescence
double labeling. Immunoelectron microscopy also
revealed LC3-labeled autophagic vacuoles and apoptotic
cell phagosomes in ETR TBMs, suggesting the
possibility of LC3-related phagocytosis. This was
confirmed by enhanced colocalization of LC3 with
lysosomal cathepsins in double labeling. These results
indicate that enhanced autophagy in ETR thymic TBMs
is not only a cytoprotective mechanism but could also be
involved in the clearance of apoptotic thymocytes, thus
preventing autoimmune reactions and suppressing
inflammatory response.
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