Neuroprotectin D1 (NPD1) is a stereoselective mediator derived from the omega-3 essential
fatty acid docosahexaenoic acid (DHA) with potent inflammatory resolving and neuroprotective bioactivity. NPD1 reduces Aβ42
peptide release from aging human brain cells and is severely depleted in
Alzheimer's disease (AD) brain. Here we further characterize the mechanism of NPD1's neurogenic actions using 3xTg-AD mouse models and human neuronal-glial (HNG) cells in primary culture, either challenged with Aβ42 oligomeric
peptide, or transfected with
beta amyloid precursor
protein (βAPP)(sw) (Swedish double mutation APP695(sw), K595N-M596L). We also show that NPD1 downregulates Aβ42-triggered expression of the pro-inflammatory
enzyme cyclooxygenase-2 (COX-2) and of B-94 (a TNF-α-inducible pro-inflammatory
element) and apoptosis in HNG cells. Moreover, NPD1 suppresses Aβ42
peptide shedding by down-regulating β-secretase-1 (BACE1) while activating the α-
secretase ADAM10 and up-regulating sAPPα, thus shifting the cleavage of βAPP
holoenzyme from an amyloidogenic into the non-amyloidogenic pathway. Use of the
thiazolidinedione peroxisome proliferator-activated receptor gamma (PPARγ) agonist
rosiglitazone, the irreversible PPARγ antagonist
GW9662, and overexpressing PPARγ suggests that the NPD1-mediated down-regulation of BACE1 and Aβ42
peptide release is PPARγ-dependent. In conclusion, NPD1 bioactivity potently down regulates inflammatory signaling, amyloidogenic APP cleavage and apoptosis, underscoring the potential of this
lipid mediator to rescue human brain cells in early stages of neurodegenerations.