Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark.
PLoS One. 2012;7(7):e40243. doi: 10.1371/journal.pone.0040243. Epub 2012 Jul 5.
The epidermal growth factor (EGF) receptors HER2 and HER4 and the ligands HB-EGF and NRG1 are crucial for heart development. The purpose of our study was to investigate the role of the complete EGF system in relation to hypoxia of the heart.
METHODOLOGY/PRINCIPAL FINDINGS: We examined the mRNA expression by real time PCR of the 4 receptors and 12 ligands from the EGF-system in paired normoxic and hypoxic biopsies isolated from human hearts during coronary artery bypass operation. Compared to normoxic biopsies, hypoxic samples showed down-regulation of HER2 (P = 0.0005) and NRG1 (both α (P = 0.02) and β (P = 0.03) isoforms). In contrast, HB-EGF (P = 0.0008), NRG2β (P = 0.01) and EGFR (P = 0.02) were up-regulated. As HER2 is essential for heart development and we find its expression reduced under hypoxia we investigated the effect of HER2 inhibition in hypoxic HL-1 cardiomyocytes by treatment with trastuzumab (20 nM). This resulted in inhibition of cardiomyocyte proliferation, but interestingly only in hypoxic cells. Co-treatment of HL-1 cells with HB-EGF (10 nM) but not with NRG-1 (5 ng/ml) rescued the cardiomyocytes from HER2 inhibition. HL-1 cardiomyocytes exposed to hypoxia revealed nuclear translocation of activated MAPK and the activity of this downstream signaling molecule was decreased by HER2 inhibition (20 nM trastuzumab), and re-established by HB-EGF (10 nM).
CONCLUSIONS/SIGNIFICANCE: Hypoxia in the human heart alters the expression of the EGF system. Mimicking the HER2 down-regulation seen in the human heart in cultured cardiomyocytes inhibited their proliferation under hypoxic conditions. Interestingly, HB-EGF is induced in the hypoxic human hearts, and rescues hypoxic cardiomyocytes from the effect of HER2 inhibition in the in vitro model. The results have implications for future treatment strategies of patients with ischemic heart disease.
表皮生长因子（EGF）受体 HER2 和 HER4 及其配体 HB-EGF 和 NRG1 对心脏发育至关重要。我们研究的目的是探讨完整的 EGF 系统在心脏缺氧中的作用。
方法/主要发现：我们通过实时 PCR 检查了在冠状动脉旁路手术中从人类心脏的正常氧合和缺氧活检中分离的 4 种受体和 12 种 EGF 系统配体的 mRNA 表达。与正常氧合活检相比，缺氧样本显示 HER2（P=0.0005）和 NRG1（α 同工型（P=0.02）和 β 同工型（P=0.03））下调。相反，HB-EGF（P=0.0008）、NRG2β（P=0.01）和 EGFR（P=0.02）上调。由于 HER2 对心脏发育至关重要，并且我们发现其在缺氧下的表达减少，因此我们通过用曲妥珠单抗（20 nM）处理来研究 HER2 抑制对缺氧 HL-1 心肌细胞的影响。这导致心肌细胞增殖受到抑制，但有趣的是仅在缺氧细胞中。将 HB-EGF（10 nM）而非 NRG-1（5 ng/ml）共同处理 HL-1 细胞可使心肌细胞免受 HER2 抑制的影响。暴露于缺氧的 HL-1 心肌细胞显示出激活的 MAPK 的核转位，并且这种下游信号分子的活性通过 HER2 抑制（20 nM 曲妥珠单抗）降低，并通过 HB-EGF（10 nM）重建。
结论/意义：人类心脏中的缺氧改变了 EGF 系统的表达。在培养的心肌细胞中模拟人类心脏中所见的 HER2 下调抑制了其在缺氧条件下的增殖。有趣的是，HB-EGF 在缺氧的人心目中被诱导，并在体外模型中使缺氧心肌细胞免受 HER2 抑制的影响。这些结果对缺血性心脏病患者的未来治疗策略具有重要意义。
