Teratogen-induced activation of ERK, JNK, and p38 MAP kinases in early postimplantation murine embryos

Background: Although many teratogens are known to activate apoptotic pathwa ys culminating in abnormal development, little is known about how the embry o transduces a teratogenic exposure into specific responses. Signal recepti on and transduction are regulated by a number of signal transduction pathwa ys, including the extracellular signal-regulated protein kinases (ERKs), c- Jun N-terminal kinases (JNKs) and the stress-activated protein kinase, p38. Methods: To analyze the effects of teratogens on MAP kinases, we used whole embryo culture, Western blot analyses, and antibodies recognizing inactive or active MAP kinases, or both. Results: We show that heat shock (HS) induces a rapid, strong, but transien t activation of ERK, JNK, and p38 with maximal activation occurring within 30 min of the heat shock. By contrast, cyclophosphamide (CP) and staurospor ine (ST) failed to activate ERK or JNK during the time period studied (7.5 hr). ST and CP did induce a low but reproducible activation of p38 beginnin g at around 3 hr and 5 hr, respectively, after the initiation of exposure. Previous work has shown that heat shock induces elevated cell death in the embryo, primarily in the developing neuroepithelium, but not in the embryon ic heart. Thus, we also compared the activation of these three MAP kinase p athways in heads. hearts, and trunks isolated from day 9 embryos exposed to 43 degrees C for 15 min. The results show that ERK, JNK, and p38 are activ ated in heads, hearts, and trunks. Conclusions: Our results show that day 9 embryos do activate MAP kinase sig naling pathways in response to teratogenic exposures; however, activation o f a particular pathway does not appear to be required for teratogen-induced apoptosis. (C) 2000 Wiley-Liss, Inc.