Wang Hong-Qian, Kong Er-Liang, Zhang Xia, Meng Xiao-Yan, Zhang Jin-Min, Yu Wei-Feng, Wu Fei-Xiang
Department of Critical Care Medicine, Shanghai Eastern Hepatobiliary Surgery Hospital, Naval Medical University, Shanghai, 200438, China.
Department of Anesthesiology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, 250021, China.
Cell Biol Toxicol. 2021 Oct;37(5):679-693. doi: 10.1007/s10565-021-09602-3. Epub 2021 Mar 31.
Neonatal jaundice is a common symptom that occurs in neonates during the first month of their life and is generally divided into physiological and pathological subtypes. In serious cases, pathological neonatal jaundice frequently shows complications including seizures, cerebral palsy, and kernicterus. However, due to the unclear pathogenesis of pathological neonatal jaundice, effective drugs for this disease remain unsatisfied. In the present study, we first estimated the protective effects of folic acid (FA) on phenylhydrazine (PHA) or homocysteine (Hcy)-injected neonatal rats (2-3 days aged). Intriguingly, we found that FA significantly decreased the elevated total bilirubin (TBIL) and direct bilirubin (DBIL) concentration, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) activity in PHA- or Hcy-injected rats, indicating that FA improves liver functions. Meanwhile, our results also showed that the plasma Hcy level and N-homocysteinylation (N-Hcy) modification of albumin were significantly elevated in the jaundice rats, which were obviously reversed after FA administration. Furthermore, we identified a novel N-Hcy modification site K of human serum albumin (HSA) using LC-MS/MS, and the mutagenesis assay in HEK293 further validated these observations. Besides, we demonstrated that the N-Hcy modification of albumin functionally inhibits the bilirubin-binding ability of albumin without altering its protein level both in vitro and in vivo. Altogether, we highlight a mechanism that FA reduces the plasma Hcy level and thereby enhance the bilirubin-binding ability of albumin, which may provide a novel therapeutic strategy for the treatment of pathological neonatal jaundice.
新生儿黄疸是新生儿出生后第一个月内出现的常见症状，通常分为生理性和病理性亚型。在严重情况下，病理性新生儿黄疸常伴有惊厥、脑瘫和核黄疸等并发症。然而，由于病理性新生儿黄疸的发病机制尚不清楚，针对该疾病的有效药物仍不尽人意。在本研究中，我们首先评估了叶酸（FA）对注射苯肼（PHA）或同型半胱氨酸（Hcy）的新生大鼠（2 - 3日龄）的保护作用。有趣的是，我们发现FA显著降低了注射PHA或Hcy的大鼠中升高的总胆红素（TBIL）和直接胆红素（DBIL）浓度、丙氨酸转氨酶（ALT）、天冬氨酸转氨酶（AST）和碱性磷酸酶（ALP）活性，表明FA改善了肝功能。同时，我们的结果还显示黄疸大鼠的血浆Hcy水平和白蛋白的N - 同型半胱氨酸化（N - Hcy）修饰显著升高，FA给药后明显逆转。此外，我们使用液相色谱 - 串联质谱（LC - MS/MS）鉴定了人血清白蛋白（HSA）的一个新的N - Hcy修饰位点K，并且在HEK293细胞中的诱变试验进一步验证了这些观察结果。此外，我们证明白蛋白的N - Hcy修饰在体外和体内均在不改变其蛋白质水平的情况下功能性地抑制白蛋白与胆红素的结合能力。总之，我们揭示了一种机制，即FA降低血浆Hcy水平，从而增强白蛋白与胆红素的结合能力，这可能为病理性新生儿黄疸的治疗提供一种新的治疗策略。
