HSP90alpha, HSP90beta, and p53 expression following in vitro hyperthermia exposure in gestation day 10 rat embryos

The studies presented here are aimed at understanding the expression of p53, HSP90alpha, and HSP90beta in gestation day (GD) 10 CD rat embryos. GD 10 rat embryos were exposed in vitro to 37 degrees C or 42 degrees C for 15 min, then cultured at 37 degrees C for 0.5, 1, 3, or 5 h. Immunohistochemistry was performed on formalin-fixed, paraffin embedded, sectioned embryos for p53, HSP90alpha, or HSP90beta expression. p53 expression was minimal in control embryos but was induced with heat exposure. Maximum expression of p53 was observed in rostral tissues, e.g., the optic vesicle, rostral neuroepithelium, and mature (rostral) somites 3 and 5 h after heat exposure. Expression of p53 in the caudal region, such as in mid and caudal neuroepithelium, immature (caudal) somites, and presomitic mesoderm, was moderate compared to rostral areas. No p53 expression was observed in the heart under any condition. The rostral-caudal gradient of p53 expression was not observed for HSP90alpha expression. HSP90alpha was induced in heat-exposed embryos beginning at 1 h, predominantly in neural tube and optic vesicle. Moderate but increased expression was observed in the somites of heat-exposed embryos at 3 and 5 h. Expression of p53 was primarily nuclear while HSP90alpha expression was mostly cytoplasmic. No clear association was observed between heat-induced HSP90alpha and p53 expression. HSP90beta was expressed extensively in control and heat-exposed embryos. Results indicate that heat induces p53 and HSP90alpha expression, but not HSP90beta expression, and that HSP90alpha induction is not likely to be involved in p53 regulation in mammalian embryos.