Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary Cumming School of Medicine, Calgary, Alberta, Canada.
Department of Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States.
Pharmacol Res. 2020 Nov;161:105222. doi: 10.1016/j.phrs.2020.105222. Epub 2020 Oct 3.
The estrogen-inducible protein Heat Shock Protein 27 (HSP27) as well as anti-HSP27 antibodies are elevated in healthy subjects compared to cardiovascular disease patients. Vaccination of ApoE mice with recombinant HSP25 (rHSP25, the murine ortholog), boosts anti- HSP25 levels and attenuates atherogenesis. As estrogens promote HSP27 synthesis, cellular release and blood levels, we hypothesize that menopause will result in loss of HSP27 atheroprotection. Hence, the rationale for this study is to compare the efficacy of rHSP25 vaccination vs. estradiol (E2) therapy for the prevention of post-menopausal atherogenesis.
ApoE mice subjected to ovariectomy (OVX) showed a 65 % increase atherosclerotic burden compared to sham mice after 5 weeks of a high fat diet. Relative to vaccination with rC1, a truncated HSP27 control peptide, atherogenesis was reduced by 5-weekly rHSP25 vaccinations (-43 %), a subcutaneous E2 slow release pellet (-52 %) or a combination thereof (-82 %). Plasma cholesterol levels declined in parallel with the reductions in atherogenesis, but relative to rC1/OVX mice plasma PCSK9 levels were 52 % higher in E2/OVX and 41 % lower in rHSP25/OVX mice (p < 0.0001 for both). Hepatic LDLR mRNA levels did not change with E2 treatment but increased markedly with rHSP25 vaccination. Conversely, hepatic PCSK9 mRNA increased 148 % with E2 treatment vs. rC1/OVX but did not change with rHSP25 vaccination. In human HepG2 hepatocytes E2 increased PCSK9 promoter activity 303 %, while the combination of [rHSP27 + PAb] decreased PCSK9 promoter activity by 64 %.
The reduction in post-OVX atherogenesis and cholesterol levels with rHSP25 vaccination is associated with increased LDLR but not PCSK9 expression. Surprisingly, E2 therapy attenuates atherogenesis and cholesterol levels post-OVX without altering LDLR but increases PCSK9 expression and promoter activity. This is the first documentation of increased PCSK9 expression with E2 therapy and raises questions about balancing physiological estrogenic / PCSK9 homeostasis and targeting PCSK9 in women - are there effects beyond cholesterol?
与心血管疾病患者相比，健康受试者体内的雌激素诱导蛋白热休克蛋白 27（HSP27）以及抗 HSP27 抗体水平升高。用重组 HSP25（rHSP25，鼠同源物）对 ApoE 小鼠进行疫苗接种可提高抗 HSP25 水平并减轻动脉粥样硬化形成。由于雌激素可促进 HSP27 的合成、细胞释放和血液水平，因此我们假设绝经会导致 HSP27 动脉粥样硬化保护作用丧失。因此，这项研究的原理是比较 rHSP25 疫苗接种与雌二醇（E2）疗法预防绝经后动脉粥样硬化形成的疗效。
与假手术小鼠相比，接受卵巢切除术（OVX）的 ApoE 小鼠在高脂肪饮食 5 周后动脉粥样硬化负担增加了 65%。与 rC1（截短 HSP27 对照肽）疫苗接种相比，5 周 rHSP25 疫苗接种可使动脉粥样硬化形成减少（-43%）、皮下雌二醇缓慢释放微球（-52%）或两者联合（-82%）。血浆胆固醇水平与动脉粥样硬化形成减少平行下降，但与 rC1/OVX 小鼠相比，E2/OVX 小鼠的血浆 PCSK9 水平高 52%，rHSP25/OVX 小鼠低 41%（两者均<0.0001）。E2 治疗并未改变肝 LDLR mRNA 水平，但明显增加了 rHSP25 疫苗接种的水平。相反，E2 治疗使肝 PCSK9 mRNA 增加了 148%，而 rC1/OVX 则增加了 148%，rHSP25 疫苗接种未改变。在 HepG2 人肝细胞中，E2 使 PCSK9 启动子活性增加了 303%，而[rHSP27+PAb]的组合则使 PCSK9 启动子活性降低了 64%。
rHSP25 疫苗接种减少了 OVX 后动脉粥样硬化形成和胆固醇水平，同时增加了 LDLR 但不增加 PCSK9 的表达。令人惊讶的是，E2 治疗可减轻 OVX 后动脉粥样硬化形成和胆固醇水平，而不改变 LDLR，但增加了 PCSK9 的表达和启动子活性。这是首次证明 E2 治疗可增加 PCSK9 的表达，并提出了关于平衡生理性雌激素/PCSK9 内稳态和靶向女性 PCSK9 的问题——是否存在除胆固醇以外的影响？
