Differences in phospholipase A2 activity between males and females and Asian Indians and Caucasians

There is epidemiological evidence that chronic inflammatory diseases occur more frequently in female than in male subjects and prevail differently in various ethnic populations. Phospholipase A₂ (PLA₂) (group II) plays a key role in many inflammatory reactions by releasing free arachidonic acid, which is a prerequisite for the production of proinflammatory lipid mediators. We therefore, measured PLA₂ activity in plasma, serum, leucocytes and lymphocytes in 20 female and 20 male subjects, 10 of each group being of Asian Indian and of Caucasian origin respectively. When PLA₂ activity was measured in crude plasma and serum no dependency from gender and ethnicity was observed. Following acid extraction and heating, PLA₂ activity in plasma was higher in Caucasians (27.8 ± 2.2 nmol L^?1 mg ^?1 protein 60 min^?1) than in Asian Indians (17.9 ± 2.5 nmol L^?1 mg^?1 protein 60 min^?1) (P < 0.005) and higher in females (28.5 ± 2.6 nmol L^?1 mg^?1 protein 60 min^?1) than in males (17.3 ± 2.0 nmol L^?1 mg^?1 protein 60 min^?1) (P < 0.001). Similar differences were observed when only Asian Indian or Caucasian females were compared with their corresponding males. Contrary to plasma, in which the specific activity of PLA₂ increased following acid extraction and heating, the activity was completely abrogated in serum after extraction and heating. Lymphocytes exhibited lower activities of PLA₂ than neutrophils in all four groups of subjects investigated. Females had a tendency towards higher PLA₂ activity in both lymphocytes and neutrophils than males. In conclusion the present investigation revealed an ethnic- and sex-dependent basal activity of PLA₂, a key enzyme in the pathogenesis of chronic inflammatory diseases.