Clin Exp Otorhinolaryngol.  2014 Mar;7(1):1-6.

Expression Profile of Fas-Fas Ligand in Spiral Ganglion Cells During Apoptosis

• Gu TW
• Bae WY
• Park HT
• Lee JH
• Kang MY
• Jeong SW
• Shin YK

Abstract

OBJECTIVES
To examine the expression profile of Fas-Fas ligand (FasL) during glutamate (Glu)-induced spiral ganglion cell (SGC) apoptosis.
METHODS
Cultured SGCs were treated with 10-mM, 25-mM, and 50-mM concentrations of Glu and incubated for 24 or 48 hours. The expression intensity of FasL, Fas, caspase 3, and morphology of single SGC were evaluated using immunofluorescence staining.
RESULTS
In semiquantitative analysis of the Glu-treated SGC, FasL, and caspase 3 expression intensity were increased with concentration- and time-dependent manner. Fas expression intensity did not change with different concentration at 48 hours. In morphologic analysis of the Glu-treated SGC, number of apoptotic cells were increased with concentration- and time-dependent manner.
CONCLUSION
FasL was expressed in apoptotic SGCs, suggesting that the Fas-FasL signaling pathway may be involved in the Glu-induced apoptosis of dissociated SGCs.

Keyword

Spiral ganglion cell; Glutamate; Apoptosis; Fas ligand; Caspase 3

MeSH Terms

Apoptosis*
Caspase 3
Fas Ligand Protein
Fluorescent Antibody Technique
Glutamic Acid
Spiral Ganglion*
Caspase 3
Fas Ligand Protein
Glutamic Acid

Figure

• 

  Fig. 1 Confocal microscopic images of cultured spiral ganglion cells (SGCs) in control and Glutamate (Glu)-treated group at 24 hours. Non-apoptotic SGCs were showed in control group. Typical apoptotic SGCs showed nucleus condensation or fragmentation at Hoechst staining in the treatment groups. Expression of Fas ligand (FasL) in apoptotic SGCs increased in a dose-dependent manner. FasL increased on cell body, especially around nucleus. Neurites were disappeared and cell body was not elliptical shape with neurofilament staining. Cont, control; Glu 10, 10 mM Glu; Glu 25, Glu 25 mM; Glu 50, 50 mM Glu; NF, neurofilament; red scale bar, 10 µm (×200).

• 

  Fig. 2 Assessment of cell death. The ratio of apoptotic cells increased significantly in a dose-dependent manner in Glutamate (Glu)-treated spiral ganglion cells (SGCs) at 24 hours (P<0.05). At 48 hours after Glu treatment, the ratio of apoptotic SGCs increased significantly in each treatment group compared with controls (P<0.001). Cont, control group; Glu 10, glutamate 10 mM; Glu 25, glutamate 25 mM; Glu 50, glutamate 50 mM; number of field in each group, 10. *P<0.05. **P<0.001.

• 

  Fig. 3 Schematic figure for the conclusion. Excessive noise, ototoxic drugs and cochlear ischemia lead to excessive and nonphysiological release of Glutamate (Glu) into synaptic cleft. It leads to induce spiral ganglion cell (SGC) apoptosis and the Fas-Fas ligand signaling pathway is involved in the Glu-induced apoptosis of SGCs.

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