N-Acylethanolamine Acid Amidase Inhibition Reduces SARS-CoV-2 Infection in Human Precision Cut-Lung Slices and Downregulates NF-KBB Signalling.

SARS-CoV-2, like other positive-sense RNA viruses, manipulates host lipid metabolism to facilitate its replication by enhancing lipogenesis and lipid droplet formation. This infection disrupts bioactive lipid levels associated with the inflammatory response by increasing nuclear factor-κB (NF-κB) transcription. Recent findings have shown that NF-κB activation is essential for sustaining SARS-CoV-2 replication. Therefore, we proposed that counteracting NF-κB-driven pro-inflammatory lipid production could be accomplished by enhancing an anti-inflammatory, lipolytic pathway. Our goal was to increase levels of Palmitoylethanolamide (PEA), the main activator of the Peroxisome Proliferator-Activated Receptor-α (PPAR-α), a transcription factor that suppresses lipogenesis and NF-κB transcription. PEA levels are mainly regulated by N-acylethanolamine acid amidase (NAAA), a lysosomal enzyme that breaks down PEA. We hypothesized that inhibiting NAAA might interfere with SARS-CoV-2 replication by allowing PEA to accumulate, thereby activating PPAR-α and suppressing NF-κB. Our results show that genetic or chemical ablation of NAAA significantly suppresses SARS-CoV-2 replication ex-vivo by 3 log10 in human-derived precision-cut lung slices. We investigated whether inhibiting NAAA could block NF-κB activation by steering its opposite PPAR-α mediated pathway. We observed increased PPAR-α expression in NAAA KO cells, while PPAR-α expression remained low in infected untreated cells. Elevated PPAR-α expression correlated with reduced NF-κB activation when NAAA is ablated. These findings highlight NAAA as an essential host factor for SARS-CoV-2 replication and propose a mechanism that reduces both replication and inflammation by targeting NF-κB during Coronaviridae replication.