Palmitoylated COX-2Cys555 reprogrammed mitochondrial metabolism in pyroptotic inflammatory injury in patients with post-acute COVID-19 syndrome

Abstract

Introduction: The complex interplay between protein palmitoylation, mitochondrial dynamics, and inflammatory responses plays a pivotal role in respiratory diseases. One significant feature of post-acute coronavirus disease 2019 (COVID-19) syndrome (PACS) is the occurrence of a storm of inflammatory cytokines related to the NOD-like receptor protein 3 (NLRP3). However, the specific mechanisms via which palmitoylation affects mitochondrial function and its impact on the NLRP3 inflammasome under pathological respiratory conditions remain to be elucidated.

Objective: This study aimed to investigate how protein palmitoylation influences inflammatory responses and mitochondrial dynamics in respiratory diseases, such as those induced by the SARS-CoV-2 spike S protein in PACS, thereby providing a therapeutic target for inflammatory lung injury.

Methods: In vivo experiments were conducted using AdV5-pADM-CMV-COVID-19-S (AdV5-S) nasal drip-treated C57BL/6 mice to assess NLRP3 inflammasome activation and inflammatory response. In vitro experiments were performed using pCMV-S-transfected human lung epithelial BEAS-2B cells to analyze the effects of DHHC5-mediated palmitoylation of cyclooxygenase-2 (COX-2) at cysteine 555 (COX-2^Cys555) on mitochondrial metabolism and NLRP3 inflammasome activation.

Results: Palmitoylation of COX-2^Cys555 enhanced its interaction with hexokinase 2 (HK2) to regulate mitochondrial metabolic reprogramming, leading to NLRP3 inflammasome activation and pyroptosis. Pharmacological and genetic suppression of palmitoylation diminished the mitochondrial localization of palmitoylated COX-2 and its interaction with HK2, thereby reducing mitochondrial metabolic reprogramming. Furthermore, genetic intervention targeting DHHC5 (shDhhc5) alleviated NLRP3 activation and pyroptosis, mitigating the chronic inflammatory damage associated with PACS.

Conclusion: This study highlights the regulatory role of COX-2^Cys555 palmitoylation in mitochondrial metabolism and lung inflammatory injury, and suggests potential therapeutic targets to combat respiratory pathogenesis linked to palmitoylated COX-2.

Keywords: COX-2 palmitoylation; Lung inflammatory injury; Mitochondrial metabolic reprogramming; NLRP3 inflammasome activation; Post-acute COVID-19 syndrome (PACS); SARS-CoV-2 spike protein.