Biomarker analysis demonstrates a hypoxic environment in the castrated ratventral prostate gland

Within the first 24 h after castration of an adult male rat, the vascular s ystem of the ventral prostate gland undergoes a degenerative process that d rastically reduces blood flow to the tissue. Since the vascular degeneratio n precedes the loss of the prostatic epithelium (by apoptosis), we have pro posed that the onset of epithelial cell apoptosis in this tissue is caused by an ischemic/hypoxic environment resulting from the loss of blood flow. I n order to further evaluate the extent to which ischemia/hypoxia might be a factor in apoptosis of the prostate epithelium after castration, we analyz ed for biomarkers of cellular hypoxia in rat ventral prostates during the f irst 3 days following castration. Ventral prostate tissues removed from hyp oxyprobe-1-treated adult male rats (uncastrated controls; surgically castra ted for 24, 48 or 72 h, or sham-castrated for equivalent times) were direct ly analyzed for evidence of hypoxia by in situ immunohistochemical evaluati on of hypoxyprobe-1 adduct formation in the prostate cells. Protein extract s from these tissues were also tested for expression of the 120 kDa hypoxia -inducible factor-1-alpha (HIF-1-alpha) protein as well as for expression o f mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) proteins using a Western blot assay. The tyrosine phosphorylation status o f the latter signaling molecules was also evaluated by Western blotting usi ng anti-tyrosine phosphate antibodies. Our results showed that epithelial c ells of the rat ventral prostate stained positively for hypoxyprobe-1 adduc ts at all times after castration, whereas cells in control tissues were uns tained by this procedure. In addition, the prostatic expression of HIF-1-al pha protein was increased approximately 20-fold at 48 h after castration co mpared to control tissues. Finally, although prostatic MAPK and JNK protein expression was unaltered during the early period after castration, phospho rylation of the JUN kinase protein was significantly elevated, indicating t hat this stress-activated cellular signaling pathway becomes more active su bsequent to castration. These results support our proposal that early castr ation-induced degeneration and constriction of the vascular system of the r at ventral prostate gland leads to reduced oxygenation of prostatic epithel ial eel Is and the activation of hypoxic cellular signaling in these cells through upregulation of HIF-1-alpha expression and stimulation of the JUN k inase signaling pathway. J. Cell. Biochem. 81:437-444, 2001. (C) 2001 Wiley -Liss, Inc.