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Original Articles

Long-term administration of salicylate enhances prestin expression in rat cochlea

, , , &
Pages 18-23 | Received 26 Nov 2008, Published online: 07 Jul 2009
 

Abstract

Salicylate, a common drug frequently used long term in the clinic, is well known for causing reversible hearing loss and tinnitus. Our previous study, however, demonstrated that chronic administration of salicylate progressively raised the amplitude of distortion product of otoacoustic emissions (DPOAEs), which are mainly caused by (outer hair cell) OHC electromotility. How salicylate affects OHC electromotility to cause this paradoxical increase remains unclear. One possibility is that it could affect prestin, which is a motor protein that contributes to the mechano-electrical properties of OHCs. In this experiment, we assessed the effect of acute and chronic salicylate treatment on prestin expression. Interestingly, after long-term salicylate injection (200 mg/kg, twice daily for 14 days), prestin gene and protein levels were up-regulated about twofold. These levels returned to baseline 14 days after treatment stopped. Acute injection of salicylate (single injection, 400 mg/kg) did not affect prestin levels. These data reveal that chronic salicylate administration markedly, but reversibly, increased prestin levels which may contribute to the enhanced DPOAE amplitudes we observed previously with similar salicylate treatment, which may be responsible for salicylate-induced tinnitus generation.

Abbreviations
Ct=

Threshold cycle

DPOAE=

Distortion product otoacoustic emission

OHC=

Outer hair cell

RT-PCR=

Real-time polymerase chain reaction

Abbreviations
Ct=

Threshold cycle

DPOAE=

Distortion product otoacoustic emission

OHC=

Outer hair cell

RT-PCR=

Real-time polymerase chain reaction

Sumario

El salicilato, una droga común frecuentemente usada en la clínica por periodos prolongados, es bien conocido por causar pérdida auditiva reversible y acúfeno. Nuestro estudio previo, sin embargo, demostró que la administración crónica de salicilatos elevó progresivamente la amplitud de las emisiones otoacústicas por productos de distorsión (DPOAE), que son principalmente causadas por (células ciliadas externas) la electromotilidad de la OHC. Continúa siendo poco clara la forma cómo afectan los salicilatos la electromotilidad de las OHC para causar este aumento paradójico. Una posibilidad es que afecte la prestina, que es la proteína motora que contribuye con las propiedades mecano-eléctricas de la OHC. En este experimento, evaluamos el efecto del tratamiento agudo y crónico con salicilatos sobre la expresión de la prestina. Interesantemente, luego de inyecciones a largo plazo de salicilato (200 mg/kg, dos veces al día por 14 días), el gen de la prestina y los niveles de proteína fueron sobre-regulados hasta el doble. Estos niveles volvieron al nivel basal 14 días después que el tratamiento fue detenido. La inyección aguda de salicilatos (inyección sola, 400 mg/kg) no afectaron los niveles de prestina. Estos datos revelan que la administración crónica de salicilatos aumenta marcada, aunque reversiblemente, los niveles de prestina, que pueden contribuir al aumento en las amplitudes de los DPOAE que observamos previamente con tratamiento similar con salicilatos, que pueden ser responsables de la generación de acúfenos inducidos por salicilatos.

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