Histone deacetylase inhibition prevents cell death induced by loss of tricellular tight junction proteins in temperature-sensitive mouse cochlear cells

Abstract

Tricellular tight junctions (tTJs) are specialized structures that occur where the corners of three cells meet to seal adjacent intercellular space. The molecular components of tTJs include tricellulin (TRIC) and lipolysis-stimulated lipoprotein receptor (LSR) which recruits TRIC, are required for normal hearing. Although loss of TRIC causes hearing loss with degeneration of cochlear cells, the detailed mechanisms remains unclear. In the present study, by using temperature-sensitive mouse cochlear cells, US/VOT-E36 cell line, we investigated the changes of TRIC and LSR during cochlear cell differentiation and the effects of histone deacetylase (HDAC) inhibitors against cell degeneration induced by loss of TRIC and LSR. During cell differentiation induced by the temperature change, expression of TRIC and LSR were clearly induced. Treatment with metformin enhanced expression TRIC and LSR via AMPK during cell differentiation. Loss of TRIC and LSR by the siRNAs induced cell death in differentiated cells. Treatment with HDAC inhibitors trichostatin A and HDAC6 inhibitor prevented the cell death induced by loss of TRIC and LSR. Collectively, these findings suggest that both tTJ proteins TRIC and LSR have crucial roles for the differentiated cochlear cell survival, and that HDAC inhibitors may be potential therapeutic agents to prevent hearing loss.

Metformin Reduces the Risk of Hearing Loss: A Retrospective Cohort Study

“…18 Another study using the temperature-sensitive mouse cochlear cells (US/VOT-E36 cell line) showed that metformin enhanced the expression of tricellulin and lipolysis-stimulated lipoprotein receptor (proteins required for normal hearing) during cell differentiation via 5′-adenosine monophosphate-activated protein kinase. 19 Animal studies also support the potential benefit of metformin in preventing hearing loss. [20][21][22][23][24][25][26] In humans, 1 previous observational study conducted in Taiwan by Chen et al 27 showed a beneficial effect of metformin on the risk of sudden deafness.…”

“…Cellular studies suggested that metformin, via limiting the production of reactive oxygen species, might attenuate the toxic effects in auditory cell lines (HEI‐OC1 cells) treated with gentamicin 17 and cisplatin 18 . Another study using the temperature‐sensitive mouse cochlear cells (US/VOT‐E36 cell line) showed that metformin enhanced the expression of tricellulin and lipolysis‐stimulated lipoprotein receptor (proteins required for normal hearing) during cell differentiation via 5′‐adenosine monophosphate‐activated protein kinase 19 . Animal studies also support the potential benefit of metformin in preventing hearing loss 20‐26 …”

Rho-kinase and PKCα Inhibition Induces Primary Cilia Elongation and Alters the Behavior of Undifferentiated and Differentiated Temperature-sensitive Mouse Cochlear Cells

“…1). 28 The cells were cultured in minimum essential medium (Nacalai Tesque, Inc., Kyoto, Japan) supplemented with 10% fetal bovine serum (FBS; Invitrogen, Carlsbad, CA), 100 µg/ml streptomycin, and 50 µg/ml amphotericin B. The cells were plated on 60-mm culture dishes (Corning Glass Works, Corning, NY) coated with rat-tail collagen (500 µg dried tendon/ml in 0.1% acetic acid) and incubated in a humidified atmosphere with 5% CO 2 at 33C.…”