肺纤维化早期脂多糖诱导HDAC-FoxO3a相互作用启动肺成纤维细胞增殖-凋亡失衡的表观遗传学调控机制

Aberrant aggregation and activation of lung fibroblast (LF) is the precondition of pulmonary fibrosis. The inactivation of Forkhead Box O3a (FoxO3a) can inhibit the expression of p27 and caveolin-1 (Cav-1), thus cause the imbalance of accelerated proliferation and suppressed apoptosis, which result in LF aberrant aggregation. However, the mechanism remains enigmatic. Our previous research reveals that LPS could induce LF proliferation via activating histone deacetylase (HDAC), which could interact with FoxO3a by binding to it. Therefore, we hypothesize that LPS can activate HDAC, which can inhibit the activation of FoxO3a via binding to it, thus suppress the expression of p27 and Cav-1, as a result of the histone deacetylation at the gene promoter region, leading to LF proliferation-apoptosis imbalance and lung fibrosis. In this study, we explore the epigenetic regulatory mechanism of LPS-induced LF proliferation-apoptosis imbalance in vitro under the condition of three-dimensional polymerized collagen matrices, and aim to clarify the effects LPS-induced HDAC-FoxO3a interaction plays on p27 and Cav-1 gene transcription and LF proliferation-apoptosis imbalance. We will also attempt to prevent LF proliferation-apoptosis imbalance and lung fibrosis through interfering with the interaction between HDAC and FoxO3a. This study is expected to complete the mechanism of LPS-induced pulmonary fibrosis from the perspective of synergistic interaction between bio-macromolecules regulating cell cycle and lay the foundation for prevention and control of pulmonary fibrosis.

肺成纤维细胞（LF）异常聚集活化是肺纤维化发生的前提。FoxO3a失活可抑制p27及Cav-1表达，加速LF增殖并抑制凋亡，引起增殖-凋亡失衡，促进LF异常聚集，但机制未明。我们发现LPS能活化HDAC促进LF增殖，而HDAC可直接结合FoxO3a产生相互作用。我们推测LPS可活化HDAC，后者可结合FoxO3a使之失活，并引起基因转录启动区组蛋白去乙酰化而抑制p27和Cav-1表达，形成LF增殖-凋亡失衡和肺纤维化。本课题利用三维培养环境下LF增殖-凋亡失衡模型，研究LPS诱导LF增殖-凋亡失衡的表观遗传调控机制，重点明确LPS促进HDAC-FoxO3a直接互作对p27和Cav-1基因转录及LF增殖-凋亡失衡的作用，并通过干预HDAC或FoxO3a而抑制LF增殖-凋亡失衡及肺纤维化过程。本课题有望从生物大分子间直接互作对细胞周期调控的角度完善LPS诱导肺纤维化的机制，为该病防治奠定基础。

脂多糖（LPS）刺激肺成纤维细胞（LF）引起细胞异常增殖及凋亡抑制所致的增殖-凋亡失衡过程是LPS诱导肺成纤维细胞异常积聚、活化并引起肺纤维化的重要前提和关键环节，对其相关机制进行研究具有重要意义。本课题重点研究LPS诱导LF增殖-凋亡失衡的机制， 通过抑制或过表达FoxO3a对p27和Cav-1表达的影响，明确FoxO3a/p27信号通路、FoxO3a/Cav-1信号通路在LF增殖-凋亡失衡的作用。研究发现：LPS刺激肺成纤维细胞可促进细胞增殖和凋亡减少，引起增殖-凋亡失衡，促进LF异常聚集，同时伴有FoxO3a失活、p27表达的下降。过表达FoxO3a能逆转LPS对肺成纤维细胞p27蛋白的抑制作用，同时可抑转LPS诱导的肺成纤维细胞增殖。增强FoxO3a活性（吉非替尼）可抑转LPS介导的FoxO3a失活、p27蛋白下调和肺成纤维细胞增殖过程。敲减FoxO3a能增强LPS对肺成纤维细胞p27蛋白的抑制作用。综上所述，本课题研究证实LPS诱导FoxO3a失活通过抑制p27表达而促进肺成纤维细胞增殖，是肺成纤维细胞增殖及细胞异常聚集的关键环节，对FoxO3a和p27表达及活化进行有效调控有望成为抑制肺成纤维细胞在肺纤维化早期异常积聚的理想靶点，有望为脓毒症相关性肺纤维化的临床治疗提供一种治疗策略。