title: Bilirubin augments Ca2+load of developing bushy neurons by targeting specific subtype of voltage-gated calcium channels.
abstract: Neonatal brain is particularly vulnerable to pathological levels of bilirubin which elevates and overloads intracellular Ca2+, leading to neurotoxicity. However, how voltage-gated calcium channels (VGCCs) are functionally involved in excess calcium influx remains unknown. By performing voltage-clamp recordings from bushy cells in the ventral cochlear nucleus (VCN) in postnatal rat pups (P4-17), we found the total calcium current density was more than doubled over P4-17, but the relative weight of VGCC subtypes changed dramatically, being relatively equal among T, L, N, P/Q and R-type at P4-6 to predominantly L, N, R over T and P/Q at P15-17. Surprisingly, acute administration of bilirubin augmented the VGCC currents specifically mediated by high voltage-activated (HVA) P/Q-type calcium currents. This augment was attenuated by intracellular loading of Ca2+buffer EGTA or calmodulin inhibitory peptide. Our findings indicate that acute exposure to bilirubin increases VGCC currents, primarily by targeting P/Q-type calcium channels via Ca2+and calmodulin dependent mechanisms to overwhelm neurons with excessive Ca2+. Since P/Q-subtype calcium channels are more prominent in neonatal neurons (e.g. P4-6) than later stages, we suggest this subtype-specific enhancement of P/Q-type Ca2+currents likely contributes to the early neuronal vulnerability to hyperbilirubinemia in auditory and other brain regions.
authors.affiliation: Department of Otorhinolaryngology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, 200233, P. R. China.
authors.forename: Min
authors.initials: M
authors.lastname: Liang
authors.affiliation: Department of Otorhinolaryngology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, 200233, P. R. China.
authors.forename: Xin-Lu
authors.initials: XL
authors.lastname: Yin
authors.affiliation: Department of Otorhinolaryngology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, 200233, P. R. China.
authors.forename: Hai-Bo
authors.initials: HB
authors.lastname: Shi
authors.affiliation: Department of Otorhinolaryngology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, 200233, P. R. China.
authors.forename: Chun-Yan
authors.initials: CY
authors.lastname: Li
authors.affiliation: Department of Otorhinolaryngology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, 200233, P. R. China.
authors.forename: Xin-Yi
authors.initials: XY
authors.lastname: Li
authors.affiliation: Department of Otorhinolaryngology, West China Hospital, Sichuan University, No. 37, GuoXueXiang, Chengdu, 610041, P. R. China.
authors.forename: Ning-Ying
authors.initials: NY
authors.lastname: Song
authors.affiliation: Department of Otorhinolaryngology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, 200233, P. R. China.
authors.forename: Hao-Song
authors.initials: HS
authors.lastname: Shi
authors.affiliation: Department of Otorhinolaryngology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, 200233, P. R. China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Programs in Neurosciences & Mental Health, SickKids Research Institute and Department of Physiology, University of Toronto, Toronto, ON, M5G 1X8, Canada. luyang.wang@utoronto.ca.
authors.forename: Lu-Yang
authors.initials: LY
authors.lastname: Wang
authors.affiliation: Department of Otorhinolaryngology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, 200233, P. R. China. yinshankai@china.com.
authors.forename: Shan-Kai
authors.initials: SK
authors.lastname: Yin
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001663:Bilirubin / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002478:Cells, Cultured; D009474:Neurons / Q000187:drug effects* / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats
chemical_list: D015220:Calcium Channels; D001663:Bilirubin; D002118:Calcium