Cancer cells isolated from malignant pleural and peritoneal effusions inhibit phospholipase A2 activity in human polymorphonuclear leukocytes

Regulatory role of cytosolic phospholipase A2alpha in NADPH oxidase activity and in inducible nitric oxide synthase induction by aggregated Abeta1-42 in microglia

In Alzheimer's disease, extracellular deposits of amyloid beta(1-42) (Abeta(1-42)) may induce activation of microglial cells by releasing proinflammatory factors that contribute to the neurodegeneration process. Since the activation of cytosolic phospholipase A(2)alpha (cPLA(2)alpha) has been reported in inflammatory conditions, its role in primary rat microglial cell activated by aggregated Abeta(1-42) was elucidated. The results of the present study show that activation of microglia by 5 microM aggregated Abeta(1-42) (as evident by the amoeboid morphology and increased CD68 immunofluorescence reactivity) caused an immediate activation of cPLA(2)alpha, measured by its phosphorylated form and its specific activity, followed by a gradual elevation of its expression and activity during 24 h. Inhibition of cPLA(2)alpha expression and activity by the presence of 1 microM specific antisense resulted in a significant decrease in NADPH oxidase activity that releases superoxides, PGE(2) formation, iNOS expression, and NO production, indicating a major role for cPLA(2)alpha in the regulation of these inflammatory processes. NADPH oxidase activity, which is under cPLA(2)alpha regulation, was found to upregulate cPLA(2)alpha and COX-2 protein expression through the redox-sensitive NFkappaB activation as evident by its phosphorylation on Ser-536, resulting in increased PGE(2) formation. The secreted PGE(2) induced the synthesis of iNOS and the production of NO through the PKA-CREB pathway. Taken together, our results suggest that the response of cPLA(2)alpha to aggregated Abeta(1-42) is probably a key player in the oxidative stress present in AD, regulating potent oxidative agents: the production of superoxides by NADPH oxidase and NO formation by iNOS.

[Secreted phospholipases A2 (sPLA2): friends or foes? Are they actors in antibacterial and anti-HIV resistance?]

In this paper the authors update on the deletereous or beneficial roles of human and animal secretory phospholipases A2 (sPLA2). Although human sPLA2-IIA (inflammatory) was initially thought as a foe because its pathogenic implication in sepsis, multiorganic failure or other related syndromes, recent data indicates its role in in the antiinfectious host resistance. Thus, sPLA2-IIA exhibits potent bactericidal activities against gram-negative and gram-positive (in this case, together with other endogenous inflammatory factors) bacteria. Surprisingly, human sPLA-IIA does not show in vitro anti-human immunodeficiency virus (HIV) activity, whilst several sPLA2-IA isolated from bee and serpent venons do it: this is the case for crotoxin, a sPLA2-IA isolated from the venon of Crotalus durissus terrificus (sPLA2-Cdt). The mechanism for the in vitro anti-HIV activity of sPLA2-Cdt (inhibition of Gag p24) appears to be related to the ability of the drug to desestabilize ancorage (heparans) and fusion (cholesterol) receptors on HIV target cells.