de Castro e Paula Luiz Augusto, Hansen Peter J
Department of Animal Sciences, University of Florida, Gainesville, Florida 32611-0910, USA.
Mol Reprod Dev. 2008 Jun;75(6):1063-70. doi: 10.1002/mrd.20841.
Ceramide is a second messenger induced by various cellular insults that plays a regulatory role in apoptosis. The objective of the present study was to determine whether ceramide signaling can occur in the preimplantation embryo by testing (1) effects of ceramide on development, cytokinesis, and apoptosis and (2) whether heat shock, which can induce apoptosis in embryos, causes activation of neutral or acidic sphingomyelinases responsible for generation of ceramide. Treatment of embryos > or =16 cells collected at Day 5 after insemination with 50 microM C(2)-ceramide increased caspase-9 activity and the proportion of blastomeres undergoing apoptosis but did not increase caspase-8 activity. Induction of apoptosis was more extensive when culture with ceramide was for 24 hr than for 9 hr. Ceramide also reduced the proportion of embryos that developed to the blastocyst stage when exposure was for 24 hr. At the two-cell stage, a period in development when apoptosis responses are blocked, culture of embryos with ceramide did not increase caspase-9 activity or the proportion of blastomeres that were apoptotic. However, culture with ceramide for 24 hr reduced cell proliferation and caused an increase in multinucleated cells because of inhibition of cytokinesis. Exposure of Day 5 embryos to a heat shock of 41 degrees C for 15 hr increased neutral sphingomyelinase activity but did not change acid sphingomyelinase activity. In conclusion, ceramide can regulate embryo development and apoptosis in a time and stage-of-development dependent manner and ceramide generation can be activated by cellular insult. Thus, the ceramide signaling pathway is present in the preimplantation embryo.
神经酰胺是由各种细胞损伤诱导产生的第二信使，在细胞凋亡中起调节作用。本研究的目的是通过测试（1）神经酰胺对发育、胞质分裂和细胞凋亡的影响，以及（2）能诱导胚胎细胞凋亡的热休克是否会激活负责生成神经酰胺的中性或酸性鞘磷脂酶，来确定神经酰胺信号是否能在植入前胚胎中发生。用50微摩尔/升的C2-神经酰胺处理授精后第5天收集的≥16细胞期胚胎，可增加半胱天冬酶-9的活性以及发生凋亡的卵裂球比例，但不会增加半胱天冬酶-8的活性。当与神经酰胺一起培养24小时时，诱导的细胞凋亡比培养9小时更为广泛。当暴露24小时时，神经酰胺还会降低发育至囊胚阶段的胚胎比例。在二细胞期，即细胞凋亡反应受阻的发育阶段，用神经酰胺培养胚胎不会增加半胱天冬酶-9的活性或凋亡卵裂球的比例。然而，用神经酰胺培养24小时会减少细胞增殖，并由于胞质分裂受到抑制而导致多核细胞增加。将第5天的胚胎暴露于41摄氏度的热休克中15小时，会增加中性鞘磷脂酶的活性，但不会改变酸性鞘磷脂酶的活性。总之，神经酰胺可以以时间和发育阶段依赖的方式调节胚胎发育和细胞凋亡，并且细胞损伤可以激活神经酰胺的生成。因此，神经酰胺信号通路存在于植入前胚胎中。
