N-acylethanolamine acid amidase inhibition reduces SARS-CoV-2 infection in Human Precision cut-lung slices and downregulates NF-κB signalling
Authors: Rocca Veronica La , Filipponi Carolina , Diesendorf Viktoria , Carli Alessandro De , Sciandrone Giulia , Nottoli Silvia , Plicanti Erika , Fonnesu Rossella , Iacono Elena , Mengozzi Alessandro , Masi Stefano , Lenzi Paola , Fornai Francesco , Sewald Katherina , Obernolte Helena , Bodem Jochen , Freer Giulia , Pistello Mauro , Lai Michele 
Published: July 2024

Like other positive-sense RNA viruses, SARS-CoV-2 manipulates host lipid metabolism to facilitate its replication by enhancing lipogenesis and lipid droplet formation. In doing so, SARS-CoV-2 infection perturbs bioactive lipid levels associated with the inflammatory response. One of these, Palmitoylethanolamide (PEA) is suppressed during SARS-CoV-2 infection since it activates the Peroxisome Proliferator-Activated Receptor-α (PPAR-α), a transcription factor that suppresses the nuclear factor-B (NF-κB), which is mandatory to sustain SARS-CoV-2 replication. PEA levels are regulated by N-acylethanolamine acid amidase (NAAA), a lysosomal enzyme responsible for catalysing the breakdown of PEA. We hypothesized that NAAA inhibition might interfere with SARS-CoV-2 replication since it will lead PEA to accumulate, activating PPAR-α and, consequently, suppressing NF-κB.

Our results reveal that genetic or chemical ablation of NAAA significantly suppresses SARS-CoV-2 replication by three log10in human-derived precision-cut lung slices. Therefore, we investigated whether inhibiting NAAA could influence NF-κB activation through the activation of PPAR-α. We observed PPAR-α increased expression in NAAA-/-cells, while PPAR-α expression remained low in infected parental cells. As expected, the elevated PPAR-α expression correlated with a parallel reduction in NF-κB activation when NAAA is ablated. These findings underscore NAAA as an essential host factor for SARS-CoV-2 replication and propose a potential mechanism of action rooted in the attenuation of NF-κB activation during viral replication.

Author summary

Over the past three years, COVID-19 has claimed nearly 7 million lives worldwide, prompting extensive efforts to find effective treatments. While RNA-based vaccines have been developed rapidly, they alone have not completely halted the spread of the virus, making the search for antiviral therapies crucial. One promising approach targets the anti-inflammatory lipid PEA, which has shown some success in COVID-19 clinical trials. PEA is quickly degraded by the enzyme NAAA. Researchers have found that inhibiting NAAA can enhance and prolong PEA anti-inflammatory effects. NAAA inhibitors have already shown effectiveness in reducing chronic pain and lung inflammation in animal models and have also been effective against Zika virus replication. Our research focused on testing the NAAA inhibitor ARN726 against SARS-CoV-2. In human lung cells and lung tissue samples, ARN726 significantly reduced SARS-CoV-2 replication and inflammation. We discovered that this inhibition suppresses the NF-κB pathway, which the virus uses to fuel its replication and sustain Cytokine storm. Overall, our findings suggest that NAAA inhibitors like ARN726 could be repurposed to combat COVID-19 and potentially other coronaviruses, offering a novel and effective antiviral strategy.