Abstract
N-acylethanolamines (NAE, also called ethanolamides) are significant lipid signaling molecules with anti-inflammatory, pain-relieving, cell-protective, and anticancer properties. Here, we present the use of a hitherto unreported group of Delta 3-NAE and also some Delta 4- and Delta 5-NAE, in in vitro and in vivo assays to gain a better understanding of their structure-bioactivity relationships. We have developed an efficient synthetic method to rapidly produce novel unlabeled and C-13-labeled Delta 3-NAE (NAE-18:5n-3, NAE-18:4n-6) and Delta 4-NAE (NAE-22:5n-6). The new NAE with shorter carbon backbone structures confers greater neuroprotection than their longer carbon backbone counterparts, including anandamide (Delta 5-NAE-20:4n-6) in a focal ischemia mouse model of stroke. This study highlights structure-dependent protective effects of new NAE following focal ischemia, in which some of the new NAE, administered intranasally, lead to significantly reduced infarct volume and improved recovery of limb use. The relative affinity of the new NAE toward cannabinoid receptors was assessed against anandamide, NAE-22:6n-3 and NAE-20:5n-3, which are known cannabinoid receptor ligands with high-binding constants. Among the newly synthesized NAE, Delta 4-NAE-22:5n-6 shows the greatest relative affinity to cannabinoid receptors hCB(1) and hCB(2), and inhibition of cyclic adenosine monophosphate activity through hCB(2) compared to anandamide.