SIDS and Sleep Apnoea Laboratory, Department of Medicine, Sydney Medical School, University of Sydney, Room 206, Blackburn Building, D06, Sydney, NSW, Australia.
BOSCH Institute of Biomedical Research, University of Sydney, Sydney, NSW, Australia.
Mol Neurobiol. 2017 Nov;54(9):7171-7185. doi: 10.1007/s12035-016-0234-3. Epub 2016 Oct 29.
We previously demonstrated that sudden infant death syndrome (SIDS) infants have decreased orexin immunoreactivity within the hypothalamus and pons compared to non-SIDS infants. In this study, we examined multiple mechanisms that may promote loss of orexin expression including programmed cell death, impaired maturation/structural stability, neuroinflammation and impaired unfolding protein response (UPR). Immunofluorescent and immunohistochemical staining for a number of markers was performed in the tuberal hypothalamus and pons of infants (1-10 months) who died from SIDS (n = 27) compared to age- and sex-matched non-SIDS infants (n = 19). The markers included orexin A (OxA), dynorphin (Dyn), cleaved caspase 3 (CC3), cleaved caspase 9 (CC9), glial fibrillary acid protein (GFAP), tubulin beta chain 3 (TUBB3), myelin basic protein (MBP), interleukin 1β (IL-1β), terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL), c-fos and the UPR activation markers: phosphorylated protein kinase RNA-like endoplasmic reticulum kinase (pPERK), and activating transcription factor 4 (ATF4). It was hypothesised that pPERK and ATF4 would be upregulated in Ox neurons in SIDS compared to non-SIDS. Within the hypothalamus, OxA and Dyn co-localised with a 20 % decrease in expression in SIDS infants (P = 0.001). pPERK and ATF4 expression in OxA neurons were increased by 35 % (P = 0.001) and 15 % (P = 0.001) respectively, with linear relationships between the decreased OxA/Dyn expression and the percentages of co-localised pPERK/OxA and ATF4/OxA evident (P = 0.01, P = 0.01). No differences in co-localisation with CC9, CC3, TUNEL or c-fos, nor expression of MBP, TUBB3, IL-1β and GFAP, were observed in the hypothalamus. In the pons, there were 40 % and 20 % increases in pPERK expression in the locus coeruleus (P = 0.001) and dorsal raphe (P = 0.022) respectively; ATF4 expression was not changed. The findings that decreased orexin levels in SIDS infants may be associated with an accumulation of pPERK suggest decreased orexin translation. As pPERK may inhibit multiple neuronal groups in the pons in SIDS infants, it could also indicate that a common pathway promotes loss of protein expression and impaired functionality of multiple brainstem neuronal groups.
我们之前的研究表明，与非 SIDS 婴儿相比，婴儿猝死综合征 (SIDS) 婴儿的下丘脑和脑桥中食欲素免疫反应降低。在这项研究中，我们研究了多种可能导致食欲素表达丧失的机制，包括程序性细胞死亡、成熟/结构稳定性受损、神经炎症和未折叠蛋白反应 (UPR) 受损。对死于 SIDS (n = 27) 的 1-10 个月婴儿的下丘脑结节和脑桥进行了多种标记物的免疫荧光和免疫组织化学染色，与年龄和性别匹配的非 SIDS 婴儿 (n = 19) 进行了比较。标记物包括食欲素 A (OxA)、强啡肽 (Dyn)、半胱天冬酶 3 切割 (CC3)、半胱天冬酶 9 切割 (CC9)、胶质纤维酸性蛋白 (GFAP)、微管β链 3 (TUBB3)、髓鞘碱性蛋白 (MBP)、白细胞介素 1β (IL-1β)、末端脱氧核苷酸转移酶 dUTP 缺口末端标记 (TUNEL)、c-fos 和 UPR 激活标记物：磷酸化蛋白激酶 RNA 样内质网激酶 (pPERK) 和激活转录因子 4 (ATF4)。假设 pPERK 和 ATF4 在 Ox 神经元中的表达在 SIDS 中比非 SIDS 中上调。在下丘脑中，OxA 和 Dyn 与表达减少 20%相关 (P = 0.001)。在 OxA 神经元中，pPERK 和 ATF4 的表达分别增加了 35% (P = 0.001) 和 15% (P = 0.001)，OxA/Dyn 表达减少与 pPERK/OxA 和 ATF4/OxA 共定位的百分比之间存在线性关系 (P = 0.01，P = 0.01)。在下丘脑中，没有观察到与 CC9、CC3、TUNEL 或 c-fos 的共定位或 MBP、TUBB3、IL-1β 和 GFAP 的表达差异。在脑桥上，蓝斑核 (P = 0.001) 和中缝背核 (P = 0.022) 中 pPERK 的表达分别增加了 40%和 20%；ATF4 的表达没有变化。SIDS 婴儿中食欲素水平降低与 pPERK 的积累有关，这表明食欲素翻译减少。由于 pPERK 可能抑制 SIDS 婴儿脑桥中的多个神经元群，这也表明共同的途径促进了多个脑干神经元群的蛋白质表达减少和功能受损。
