Low phosphoinositide-specific phospholipase C activity and expression of phospholipase C beta(1) protein in the prefrontal cortex of teenage suicide subjects

Objective: The enzyme phosphoinositide-specific phospholipase C (PI-PLC) is a component of the phosphoinositide signal transduction system. Other comp onents of this system have been found to be abnormal in adults and adolesce nts who have committed suicide, and so the authors examined whether PI-PLC activity and protein expression of PLC isozymes are abnormal in postmortem brains of teenage suicide subjects. Method: PI-PLC activity and protein exp ression of the PLC beta(1), delta(1), and gamma(1) isozymes were examined i n Brodmann's areas 8 and 9 of postmortem brains obtained from 18 teenage su icide subjects and 18 matched comparison subjects. PI-PLC activity was dete rmined by enzymatic assay, and protein expression of the PLC isozymes was d etermined by the Western blot technique. Results: Compared with the normal subjects, the teenage suicide subjects had significantly lower PI-PLC activ ity and immunolabeling of the specific PLC beta(1) isozyme in both membrane and cytosol fractions of Brodmann's areas 8 and 9 combined (prefrontal cor tex). There was also a significant correlation between PI-PLC activity and protein levels of the PLC beta(1) isozyme in the brains of the teenage suic ide subjects. There was no significant difference in PI-PLC activity or lev el of PLC beta(1) protein between the suicide subjects with a history of me ntal disorders and those with no history of mental disorders; however, both groups had significantly lower PI-PLC activity and expression of PLC beta( 1) protein than the normal subjects. Conclusions: Low PI-PLC activity and e xpressed levels of the PLC beta(1) isozyme in postmortem brains of suicide subjects may have clinical relevance in the pathophysiology of suicidal beh avior.