Induction of apoptosis in the vestibule of guinea pigs after middle ear inoculation with lipopolysaccharide (LPS)

Objective: During the process of apoptosis, double-stranded DNA is broken into single-stranded DNA (ssDNA) by the action of caspases and caspase activated deoxyribonuclease (CAD). We immunohistochemically examined the apoptotic changes induced by endotoxin in the vestibule of guinea pigs. Methods: Lipopolysaccharide (LPS) (5 mg/ml, 0.2 ml), a bacterial endotoxin, was transtympanically injected into the middle ear. 48 h after injection of LPS, animals were sacrificed by intracardiac perfusion of fixative. The temporal bones were then removed and immunohistochemically stained for ssDNA, CAD and caspase 3. Results: ssDNA was detected after 48 h in the dark cell area of the LPS group, not in the sensory epithelium. CAD was observed both in the dark cell area and the sensory epithelium. Caspase 3 was also detected both in the dark cell area and the sensory epithelium. Conclusion: Our findings suggest that apoptosis is involved in the dysfunction of the vestibule under inflammatory conditions.