Zimering Mark B
Medical Service, Veterans Affairs New Jersey Healthcare System, East Orange, New Jersey, USA.
Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ, USA.
Endocrinol Diabetes Metab J. 2023 Jun 15;7(2):1-12. doi: 10.31038/EDMJ.2023722.
Traumatic brain injury (TBI) was associated with increased plasma agonist autoantibodies targeting the serotonin 2A receptor. Repeated TBI exposure is associated with high risk for neurodegenerative and neuropsychiatric complications. Here we tested a hypothesis that repeated TBI is associated with plasma agonist autoantibodies targeting more than one kind of catecholamine G-protein coupled receptor.
Protein-A affinity chromatography was used to isolate the IgG fraction of plasma in forty-two middle-aged and older adults who had experienced one or more TBI exposures. The Ig (1/40 dilution=7.5 ug/mL) were tested for neurotoxicity in mouse neuroblastoma cells using an acute neurite retraction assay indicative of Gq11/IP3/Ca2+ and RhoA/Rho kinase signaling pathways' activation. Three different linear synthetic peptides corresponding to the second extracellular loop of the alpha 1A, alpha 2A or serotonin 2A receptors were used as target antigen in different enzyme-linked immunoassays. The second extracellular loop receptor peptides themselves (alpha 1A, alpha 2A) or a fragment (serotonin 2A) were tested for ability to prevent Ig-induced neurite retraction.
Patients who had experienced either repeated TBI (N=10) or a single TBI with a co-morbid autoimmune disease (N=5) were significantly more likely to harbor neurotoxic plasma autoantibodies targeting both alpha 1 adrenergic and serotonin 2A receptors vs. patients having only a single TBI. Ig-induced neurotoxicity was significantly prevented by co-incubation with either 850 nM prazosin (alpha 1 adrenergic receptor) and/or 500 nM M100907 (serotonin 2A receptor) antagonists. Alpha 1 adrenergic receptor and serotonin 2A receptor Ig immunoreactive level and titer were significantly increased in repeated TBI and single TBI/autoimmune patients (N=7-8) compared to age-matched TBI patients without neurotoxic plasma Ig (N=4). SN.8, a linear synthetic peptide corresponding to a conserved region of the second extracellular loop (ECL) of the serotonin 2A receptor completely prevented neurite retraction induced by repeated TBI plasma Ig. A repeated TBI patient harboring alpha adrenergic receptor AAB alone experienced prospective steep decline in cognitive function over two years.
Repeated TBI and TBI with associated autoimmunity harbored more than one kind of neurotoxic catecholaminergic agonist GPCR autoantibody each associated with high risk for steep rate of cognitive decline. Specific immunoassays using the second extracellular receptor loop as target antigen are needed to detect each specific different GPCR autoantibody. A fragment of the second ECL of the serotonin 2A receptor (SN.8) neutralized Ig-induced neurotoxicity in repeated TBI or TBI with associated systemic autoimmunity.
创伤性脑损伤（TBI）与靶向5-羟色胺2A受体的血浆激动剂自身抗体增加有关。反复暴露于TBI与神经退行性和神经精神并发症的高风险相关。在此，我们检验了一个假设，即反复TBI与靶向不止一种儿茶酚胺G蛋白偶联受体的血浆激动剂自身抗体有关。
采用蛋白A亲和层析法从42名经历过一次或多次TBI暴露的中老年人血浆中分离IgG组分。使用急性神经突回缩试验检测Ig（1/40稀释=7.5μg/mL）在小鼠神经母细胞瘤细胞中的神经毒性，该试验可指示Gq11/IP3/Ca2+和RhoA/Rho激酶信号通路的激活。在不同的酶联免疫分析中，使用三种分别对应于α1A、α2A或5-羟色胺2A受体第二细胞外环的不同线性合成肽作为靶抗原。测试第二细胞外环受体肽本身（α1A、α2A）或片段（5-羟色胺2A）预防Ig诱导的神经突回缩的能力。
与仅经历单次TBI的患者相比，经历反复TBI（N=10）或伴有共病自身免疫性疾病的单次TBI（N=5）的患者更有可能携带靶向α1肾上腺素能受体和5-羟色胺2A受体的神经毒性血浆自身抗体。与850 nM哌唑嗪（α1肾上腺素能受体）和/或500 nM M100907（5-羟色胺2A受体）拮抗剂共同孵育可显著预防Ig诱导的神经毒性。与年龄匹配的无神经毒性血浆Ig的TBI患者（N=4）相比，反复TBI和单次TBI/自身免疫患者（N=7-8）中α1肾上腺素能受体和5-羟色胺2A受体Ig免疫反应水平和滴度显著升高。SN.8是一种对应于5-羟色胺2A受体第二细胞外环（ECL）保守区域的线性合成肽，可完全预防反复TBI血浆Ig诱导的神经突回缩。一名仅携带α肾上腺素能受体AAB的反复TBI患者在两年内认知功能出现预期的急剧下降。
反复TBI和伴有自身免疫的TBI携带不止一种神经毒性儿茶酚胺能激动剂GPCR自身抗体，每种抗体都与认知功能急剧下降的高风险相关。需要使用第二细胞外受体环作为靶抗原的特异性免疫分析来检测每种特定的不同GPCR自身抗体。5-羟色胺2A受体第二ECL的一个片段（SN.8）可中和反复TBI或伴有全身性自身免疫的TBI中Ig诱导的神经毒性。
