Iron accumulation and oxidative stress are hallmarks of retinas from patients with
age-related macular degeneration (AMD). We have previously demonstrated that
iron-overloaded retinas are a good in vitro model for the study of
retinal degeneration during
iron-induced oxidative stress. In this model we have previously characterized the role of cytosolic
phospholipase A2 (cPLA2) and
calcium-independent
isoform (iPLA2). The aim of the present study was to analyze the implications of Group V secretory PLA2 (
sPLA2), another member of PLA2 family, in
cyclooxygenase (COX)-2 and
nuclear factor kappa B (NF-κB) regulation. We found that
sPLA2 is localized in cytosolic fraction in an
iron concentration-dependent manner. By immunoprecipitation (IP) assays we also demonstrated an increased association between
Group V sPLA2 and COX-2 in retinas exposed to
iron overload. However, COX-2 activity in IP assays was observed to decrease in spite of the increased
protein levels observed. p65 (RelA) NF-κB levels were increased in nuclear fractions from retinas exposed to
iron. In the presence of ATK (cPLA2 inhibitor) and
YM 26734 (
sPLA2 inhibitor), the nuclear localization of both p65 and p50 NF-κB subunits was restored to control levels in retinas exposed to
iron-induced oxidative stress. Membrane repair mechanisms were also analyzed by studying the participation of
acyltransferases in
phospholipid remodeling during
retinal oxidation stress. Acidic
phospholipids, such as
phosphatidylinositol (PI) and
phosphatidylserine (PS), were observed to show an inhibited acylation profile in retinas exposed to
iron while
phosphatidylethanolamine (PE) showed the opposite. The use of PLA2 inhibitors demonstrated that PS is actively deacylated during
iron-induced oxidative stress. Results from the present study suggest that
Group V sPLA2 has multiple intracellular targets during
iron-induced
retinal degeneration and that the specific role of
sPLA2 could be related to inflammatory responses by its participation in NF-κB and COX-2 regulation.