Regional protein levels of cytosolic phospholipase A2 and cyclooxygenase-2 in Rhesus monkey brain as a function of age.

Limited evidence suggests that brain cytosolic phospholipase A(2) (cPLA(2)), which selectively releases arachidonic acid (AA) from membrane phospholipids, and cyclooxygenase-2 (COX-2), the rate-limiting enzyme for AA metabolism to prostanoids, change as a function of normal aging. In this study, we examined the protein levels of cPLA(2) and COX-2 enzymes in hippocampus, frontal pole and cerebellum from young (2-5 years old), middle-aged (8-11 years old) and old (23 years old) male and female Rhesus monkeys. In the cerebellum, cPLA(2) protein level was higher in the young brain as compared to levels seen at both middle-aged and old. Similarly, in the frontal pole, the young brain showed a higher level of COX-2 protein as compared to the levels seen at both older ages. For both, once an animal reached 8-11 years of age the levels appeared to remain relatively constant over the next decade. Immunohistochemistry of COX-2 protein within the brain demonstrated no significant change in the localization to neurons within the frontal pole. Qualitatively, a greater number of neurons were positively stained for COX-2 in the young brain than in the aged brain. Based on the previous reports of localization of cPLA(2) and COX-2 at post-synaptic sites in neurons results from the current study suggest that the elevated protein levels of the two enzymes seen in the younger brain is related to the greater potential for synaptic plasticity across multiple neurons as a function of age and that cPLA(2) and COX-2 may be considered as post-synaptic markers.