Sawa Ran, Ogawa Manami, Suzuki Hana, Okimura Yasuhiko
Department of Nutrition and Food Science, Kobe Women's University Graduate School of Life Sciences, Kobe 654-8585, Japan.
Biomed Rep. 2025 Apr 7;22(6):93. doi: 10.3892/br.2025.1971. eCollection 2025 Jun.
Sestrin 2 (SESN2) is a conserved protein whose expression is upregulated under various cellular stresses including hepatic injury. In the injured liver, hepatic stellate cells (HSCs) become activated and produce collagen, contributing to fibrosis; however, SESN2 overexpression has been shown to suppress collagen synthesis. Amino acids are known to influence SESN2 expression; however, their specific effects remain unclear. In the present study, it was investigated whether specific amino acids regulate SESN2 expression and the function of quiescent RI-T HSCs, which are responsible for collagen production, using reverse transcription-quantitative PCR, western blotting, and cell proliferation assay. It was found that supplementation with asparagine (Asn) and proline (Pro) (AP), both non-essential amino acids, led to a complete reduction in and mRNA levels after 5 h of incubation. Additionally, AP partially reduced mRNA levels. However, knockdown of SESN2 or ATF4 resulted in a more substantial reduction in mRNA levels than the supplementation with AP. These results suggest that SESN2, which is induced by amino acid insufficiency, contributes to the upregulation of mRNA levels and that AP may increase mRNA levels through pathways independent of SESN2. The COL1A1-inducing effect of SESN2 contrasted with the inhibitory effect of SESN2 on activated HSCs. In long-term cultures, AP supplementation increased mRNA and protein levels, as well as RI-T cell proliferation, while and mRNA levels remained suppressed. These findings suggested that the absence of AP induces relative amino acid starvation, leading to increased ATF4/SESN2 expression. By contrast, long-term AP supplementation alleviated this stress, promoting cell proliferation and COL1A1 synthesis. The present results indicate that SESN2 function in quiescent HSCs may differ from its role in activated cells, providing new insights into its regulatory mechanisms in collagen production.
硒蛋白2（SESN2）是一种保守蛋白，其表达在包括肝损伤在内的各种细胞应激下会上调。在受损肝脏中，肝星状细胞（HSCs）被激活并产生胶原蛋白，导致肝纤维化；然而，已表明SESN2过表达可抑制胶原蛋白合成。已知氨基酸会影响SESN2表达；然而，它们的具体作用仍不清楚。在本研究中，使用逆转录定量PCR、蛋白质印迹和细胞增殖试验，研究了特定氨基酸是否调节SESN2表达以及负责胶原蛋白产生的静止RI-T HSCs的功能。发现补充非必需氨基酸天冬酰胺（Asn）和脯氨酸（Pro）（AP），在孵育5小时后导致 和 mRNA水平完全降低。此外，AP部分降低了 mRNA水平。然而，敲低SESN2或ATF4导致 mRNA水平的降低比补充AP更显著。这些结果表明，由氨基酸不足诱导的SESN2有助于 mRNA水平的上调，并且AP可能通过独立于SESN2的途径增加 mRNA水平。SESN2对COL1A1的诱导作用与SESN2对活化HSCs的抑制作用形成对比。在长期培养中，补充AP增加了 mRNA和蛋白质水平以及RI-T细胞增殖，而 和 mRNA水平仍然受到抑制。这些发现表明，缺乏AP会导致相对氨基酸饥饿，导致ATF4/SESN2表达增加。相比之下，长期补充AP减轻了这种应激，促进了细胞增殖和COL1A1合成。目前的结果表明，SESN2在静止HSCs中的功能可能与其在活化细胞中的作用不同，为其在胶原蛋白产生中的调节机制提供了新的见解。
