Division of Cardiovascular Disease (P.U., S.T., A.P.S., Q.Z., H.L.), The University of Alabama at Birmingham.
Department of Radiation Oncology (J.C.A.), The University of Alabama at Birmingham.
Circ Res. 2022 Sep 16;131(7):620-636. doi: 10.1161/CIRCRESAHA.122.321431. Epub 2022 Sep 2.
Heart failure is the leading cause of mortality, morbidity, and health care expenditures worldwide. Numerous studies have implicated GSK-3 (glycogen synthase kinase-3) as a promising therapeutic target for cardiovascular diseases. GSK-3 isoforms seem to play overlapping, unique and even opposing functions in the heart. Previously, we have shown that of the 2 isoforms of GSK-3, cardiac fibroblast GSK-3β acts as a negative regulator of myocardial fibrosis in the ischemic heart. However, the role of cardiac fibroblast-GSK-3α in the pathogenesis of cardiac diseases is completely unknown.
To define the role of cardiac fibroblast-GSK-3α in myocardial fibrosis and heart failure, GSK-3α was deleted from fibroblasts or myofibroblasts with tamoxifen-inducible Tcf21- or Postn-promoter-driven Cre recombinase. Control and GSK-3α KO mice were subjected to cardiac injury and heart parameters were evaluated. The fibroblast kinome mapping was carried out to delineate molecular mechanism followed by in vivo and in vitro analysis.
Fibroblast-specific GSK-3α deletion restricted fibrotic remodeling and preserved function of the injured heart. We observed reductions in cell migration, collagen gel contraction, α-SMA protein levels, and expression of ECM genes in TGFβ1-treated KO fibroblasts, indicating that GSK-3α is required for myofibroblast transformation. Surprisingly, GSK-3α deletion did not affect SMAD3 activation, suggesting the profibrotic role of GSK-3α is SMAD3 independent. The molecular studies confirmed decreased ERK signaling in GSK-3α-KO CFs. Conversely, adenovirus-mediated expression of a constitutively active form of GSK-3α (Ad-GSK-3α) in fibroblasts increased ERK activation and expression of fibrogenic proteins. Importantly, this effect was abolished by ERK inhibition.
GSK-3α-mediated MEK-ERK activation is a critical profibrotic signaling circuit in the injured heart, which operates independently of the canonical TGF-β1-SMAD3 pathway. Therefore, strategies to inhibit the GSK-3α-MEK-ERK signaling circuit could prevent adverse fibrosis in diseased hearts.
心力衰竭是全球死亡、发病和医疗支出的主要原因。许多研究表明 GSK-3（糖原合酶激酶-3）是心血管疾病有前途的治疗靶点。GSK-3 同工型似乎在心脏中发挥重叠、独特甚至相反的功能。以前，我们已经表明，在 GSK-3 的 2 种同工型中，心肌成纤维细胞 GSK-3β 作为缺血性心脏心肌纤维化的负调节剂。然而，心肌成纤维细胞-GSK-3α 在心脏疾病发病机制中的作用尚完全未知。
为了确定心肌成纤维细胞-GSK-3α 在心肌纤维化和心力衰竭中的作用，使用他莫昔芬诱导的 Tcf21-或 Postn 启动子驱动的 Cre 重组酶从成纤维细胞或肌成纤维细胞中删除 GSK-3α。将对照和 GSK-3α KO 小鼠进行心脏损伤，并评估心脏参数。进行成纤维细胞激酶组映射以描绘后续的体内和体外分析的分子机制。
成纤维细胞特异性 GSK-3α 缺失限制了纤维化重塑并保留了受损心脏的功能。我们观察到在 TGFβ1 处理的 KO 成纤维细胞中，细胞迁移、胶原凝胶收缩、α-SMA 蛋白水平和 ECM 基因的表达减少，表明 GSK-3α 是肌成纤维细胞转化所必需的。令人惊讶的是，GSK-3α 缺失不影响 SMAD3 激活，表明 GSK-3α 的促纤维化作用不依赖于 SMAD3。分子研究证实 GSK-3α-KO CFs 中的 ERK 信号降低。相反，成纤维细胞中组成型激活形式的 GSK-3α（Ad-GSK-3α）的腺病毒表达增加了 ERK 激活和纤维原蛋白的表达。重要的是，这种作用被 ERK 抑制所消除。
GSK-3α 介导的 MEK-ERK 激活是受损心脏中关键的促纤维化信号通路，该通路独立于经典的 TGF-β1-SMAD3 途径。因此，抑制 GSK-3α-MEK-ERK 信号通路的策略可以防止患病心脏中的不良纤维化。
