Vandegriff Kim D, Malavalli Ashok, Lohman Jeff, Young Mark A, Terraneo Laura, Virgili Eleonora, Bianciardi Paola, Caretti Anna, Samaja Michele
Sangart, Inc., San Diego, California.
Transfusion. 2014 Aug;54(8):2045-54. doi: 10.1111/trf.12643. Epub 2014 Mar 28.
Extracellular hemoglobin (Hb)-based oxygen carriers (HBOCs) are under extensive consideration as oxygen therapeutics. Their effects on cellular mechanisms related to apoptosis are of particular interest, because the onset of proapoptotic pathways may give rise to tissue damage.
The objective was to assess whether the properties of the Hb that replaces blood during an isovolemic hemodilution would modulate apoptotic-response mechanisms in rat brain and whether such signaling favors cytoprotection or damage. We exposed rats to exchange transfusion (ET; 50% blood volume and isovolemic replacement with Hextend [negative colloid control], MP4OX [PEGylated HBOC with high oxygen affinity], and ααHb [αα-cross-linked HBOC with low oxygen affinity; n=4-6/group]). Sham rats acted as control. Animals were euthanized at 2, 6, and 12 hours after ET; brain tissue was harvested and processed for analysis.
In MP4OX animals, the number of neurons that overexpressed the hypoxia-inducible factor (HIF)-1α was higher than in ααHb, particularly at the early time points. In addition, MP4OX was associated with greater phosphorylation of protein kinase B (Akt), a well-known cytoprotective factor. Indeed, the degree of apoptosis, measured as terminal deoxynucleotidyl transferase-positive neurons and caspase-3 cleavage, ranked in order of MP4OX < Hextend < ααHb.
Even though both HBOCs showed increased levels of HIF-1α compared to shams or Hextend-treated animals, differences in signaling events resulted in very different outcomes for the two HBOCs. ααHb-treated brain tissue showed significant neuronal damage, measured as apoptosis. This was in stark contrast to the protection seen with MP4OX, apparently due to recruitment of Akt and neuronal specific HIF-1α pathways.
基于细胞外血红蛋白（Hb）的氧载体（HBOCs）作为氧治疗剂正在受到广泛关注。它们对与细胞凋亡相关的细胞机制的影响尤其令人感兴趣，因为促凋亡途径的启动可能导致组织损伤。
目的是评估在等容血液稀释过程中替代血液的Hb特性是否会调节大鼠脑内的凋亡反应机制，以及这种信号传导是否有利于细胞保护或损伤。我们将大鼠暴露于换血（ET；50%血容量，用Hextend[阴性胶体对照]、MP4OX[具有高氧亲和力的聚乙二醇化HBOC]和ααHb[具有低氧亲和力的αα交联HBOC]进行等容替代；每组n = 4 - 6）。假手术大鼠作为对照。在ET后2、6和12小时对动物实施安乐死；收集脑组织并进行分析处理。
在MP4OX处理的动物中，过表达缺氧诱导因子（HIF）-1α的神经元数量高于ααHb处理的动物，尤其是在早期时间点。此外，MP4OX与蛋白激酶B（Akt）的磷酸化增加有关，Akt是一种著名 的细胞保护因子。实际上，以末端脱氧核苷酸转移酶阳性神经元和半胱天冬酶-3裂解来衡量的凋亡程度，按MP4OX＜Hextend＜ααHb的顺序排列。
尽管与假手术组或Hextend处理的动物相比，两种HBOCs均显示HIF-1α水平升高，但信号传导事件的差异导致两种HBOCs产生非常不同的结果。以凋亡衡量，ααHb处理的脑组织显示出明显的神经元损伤。这与MP4OX所观察到的保护作用形成鲜明对比，显然这是由于Akt和神经元特异性HIF-1α途径的激活所致。
