Effects of basic fibroblast growth factor on neuron death and learning disability

血小板因子4（PF 4）对肝素具有强亲和力，已显示抑制碱性成纤维细胞生长因子（bFGF）与细胞表面受体的结合，并在某些外周组织中抵消bFGF的生物学活性。在本发明的体外[^<125>I] bFGF结合实验中，[^<125>I] bFGF与受体的亲和力显示在缺血海马中比在正常海马中更高，并且PF 4一致地抑制所指示的bFGF与沙鼠海马的细胞膜的结合。为了研究缺血沙土鼠脑内内源性bFGF和/或bFGF受体可能激活的体内功能，我们通过渗透性微型泵向左侧脑室持续输注PF 4。当在3分钟缺血损伤后3天内开始输注PF 4时，它显著增强了海马CA 1区缺血诱导的学习障碍和缺血性神经元丢失，如以下结果所示： ...更多信息 f步下被动回避任务和随后的组织学检查。脑室内注入PF 4对沙土鼠的学习能力和CA 1区神经元数目没有影响。bFGF-中和抗体，当连续输注在脑室，也表现出神经毒性作用，在缺血，但不是完整的沙鼠。bFGF与肝素共输注，但不是单独的bFGF，挽救了大量的缺血性神经元，这些神经元在没有输注肝素化bFGF的情况下注定要退化，并且它防止了缺血诱导的学习障碍。在PF 4治疗前输注bFGF几乎完全消除了PF 4对缺血海马CA 1区的神经毒性作用。这些结果提示：（1）bFGF受体拮抗剂PF_4和bFGF中和抗体对缺血海马有神经毒性作用，（2）肝素对bFGF维持神经营养活性是必不可少的，（3）在PF_4治疗前灌注bFGF占据了缺血神经元细胞表面bFGF的结合位点，（4）bFGF中和抗体对缺血海马神经元细胞具有神经毒性作用。和（4）稍后输注PF 4，即使其部分阻断随后bFGF与受体的结合，也不再能抑制有利于神经元存活的bFGF介导的细胞内信号转导。因此，本研究表明内源性bFGF在缺血神经元的存活和功能恢复中起关键作用。在本研究中，肝素化bFGF的神经保护作用也与其他生长因子，细胞因子和药物，如白细胞介素6，血小板源性生长因子，β-雌二醇，TEI-7165，β-Rb 1，表皮生长因子，促红细胞生成素和白细胞介素3进行了比较。少

Platelet factor 4(PF4), which has a potent affinity for hparin, has shown to inhibit the binding of basic fibroblast growth factor (bFGF) to the cell surface receptor and to counteract the biological activities of bFGF in certain peripheral tissues. In the present in vitro [^<125>I] bFGF binding experiments, the affinity of [^<125>I] bFGF with the receptor was shown to be higher in the ischemic hippocampus than in the normal hippocampus and PF4 consistently inhibited the binding of indicated bFGF to cell membranes of the gerbil hippocampus. To investigate the in vivo function of endogenous bFGF and/or bFGF receptor possibly activated in the ischemic gerbil brain, we infused PF4 continuously into the left lateral ventricle through an osmotic minipump. When PF4 infusion was started within three days after a 3-min ischemic insult, it significantly enhanced ischemia-induced learning disability and ischemic neuronal loss in the CA1 region of the hippocampus, as demonstrated by the results o … More f a step-down passive avoidance task and by subsequent histological examinations. Infusion of PF4 into the cerebral ventricle of intact gerbils did not affect leaning ability or CA1 neuron number. bFGF-neutralizing antibody, when infused continuously in the cerebral ventricle, also exhibited a neurotoxic effect in ischemic but not intact gerbils. bFGF co-infused with heparin, but not bFGF alone, rescued a significant number of ischemic neurons which were destined to degenerate without the infusion of heparinized bFGF, and it prevented ischemia-induced learning disability. bFGF infusion prior to PF4 treatment abolished almost completely the neurotoxic effect of PF4 on the ischemic hippocampal CA1 region. These findings suggest that (1) PF4 as a putative bFGF receptor antagonist exerts a neurotoxic effect on the ischemic hippocampus and so does bFGF-neutralizing antibody ; (2) heparin is indispensible for bFGF to retain neurotrophic activity ; (3) bFGF infused before PF4 treatment occupies the binding sites of bFGF on the cell surfaces of ischemic neurons ; and (4) the later infusion of PF4, even though it blockes, partially, the subsequent binding of bFGF to the receptor, can no longer suppress the bFGF-mediated intracellular signal transduction in favor of neuronal survival. Thus, the present study indicates a pivotal role of endogenous bFGF in the survival and functional recovery of ischemic neurons. In the present study, the neuroprotective effect of heparinized bFGF was also compared with those of other growth factors, cytokines and drugs such as interleukin 6, platelet-derived growth factor, beta-estradiol, TEI-7165, ginsenoside Rb1, epidermal growth factor, erythropoietin and interleukin 3. Less