Slooter, Charlotte D.; van den Brand, Floris F.; Lleo, Anna; Liberal, Rodrigo; de Boer, Ynto S. Author Information

We have read with great interest the Letter to the Editor from Shen and colleagues and appreciate all their comments. First, we acknowledge that our study has not fully exploited NLRP3 inflammasome differences between macrophages and hepatocytes. A possible explanation is that adaptor molecule apoptosis-associated speck-like protein containing a CARD (ASC) specks in hepatocytes could activate caspase-8 instead of caspase-1, as previously demonstrated in bone marrow–derived macrophages.1 Furthermore, because of the increased abundance of bone marrow–derived monocytes and neutrophils in the liver in alcoholic hepatitis, ex-ASC specks would amplify inflammation even if restricted to innate immune cells and independent of hepatocytes. We agree that evaluating the effect of ASC specks derived from NLRP3-deficient macrophages on inflammation activation in both macrophages and hepatocytes could strengthen our findings. However, it was demonstrated that MCC950 selectively inhibits NLRP3 by directly interacting with this sensor, preventing NLRP3 oligomerization and activation.2 Moreover, studies have shown that NLRP3 knockouts THP-1 cells do not form ASC-specks.3 Second, we agree that assessing ex-ASC specks oligomerization could clarify the difference between macrophage and hepatocyte-derived ASC specks. We would like to respectfully point out that we could not be aware of the articles on the degree of ASC oligomerization published in 2023 because our manuscript was accepted in December 2022. Finally, regarding the contribution of other tissues to the release of ex-ASC specks to circulation in our model, previous studies showed that NLRP3 expression is low in hepatocytes but high in macrophages and KCs.4 Furthermore, 20%–35% of hepatic nonparenchymal liver cells are macrophages, which account for 80%–90% of total host macrophages.5 Therefore, we speculate that the inhibition of NLRP3 will have a huge impact on the release of ASC specks by the liver, inhibiting systemic and hepatic inflammation. We previously demonstrated that the absence of NLRP3 decreases alcohol-induced liver damage. Nonetheless, alcohol-induced ex-ASC formation in tissues other than the liver remains to be explored. In summary, we believe that our study elegantly demonstrates the role of ex-ASC specks in sustained inflammation in AH and encourages further studies on the role ex-ASC specks in AH.

1Division of Gastroenterology and Liver Diseases, University of Southern California Keck School of Medicine, Los Angeles, CA 2Institute for Addiction Science, University of Southern California, Los Angeles, CA 3Department of Population and Public Health Sciences, University of Southern California Keck School of Medicine, Los Angeles, CA Correspondence Brian P. Lee, University of Southern California, Division of Gastrointestinal and Liver Diseases. Email: [email protected]