ASCVD is a major cause of death and morbidity worldwide, with inflammation being a principal trigger for the development of atherosclerosis(27). This study highlights the crucial role of macrophage-derived JAML in the progression of atherosclerosis, demonstrating its significant upregulation in PBMCs from patients with CAD and in the plaques of ApoE−/− mice. Our findings show that JAML deletion reduces atherosclerotic plaques, whereas JAML overexpression promotes them. Mechanistically, JAML enhances the phosphorylation and nuclear translocation of PKM2, thereby activating NF-κB signaling and the NLRP3 inflammasome, accelerating atherosclerosis progression (Fig. 9). Collectively, these findings suggest that inhibiting JAML in macrophages could be an effective anti-inflammatory therapeutic strategy for atherosclerosis.
Additionally, this study provides substantial evidence that JAML regulates NLRP3 inflammasome activation in macrophages by modulating PKM2 phosphorylation, as beyond its role as a cell adhesion molecule, JAML participates in protein complexes crucial for signal transduction. Moreover, studies have shown that the intracellular domain of JAML activates downstream signaling pathways through direct binding with intracellular proteins(4, 5).
JAML plays a critical role in the pathophysiology of various diseases, and its dysfunction is linked to diabetic kidney disease, gastric cancer, and intestinal epithelial injury(12, 13, 28). In mouse models of diabetes, JAML induces lipid synthesis by altering the SIRT1-SREBP1 signaling pathway, leading to podocyte injury and albuminuria(11). High JAML expression is correlated with deep invasion, larger tumor size, and poor prognosis in cancerous tissues(14). In gastric cancer, JAML promotes cell proliferation and migration partially through the P38 signaling pathway, suggesting its potential as a therapeutic target in tumors. In this study, we observed that JAML expression is upregulated in macrophages within human and mouse atherosclerotic plaques. Consequently, using JAMLM−KO/ApoE−/− and JAMLM−KI/ApoE−/− mice, we elucidated the role of JAML in atherosclerosis, highlighting the significant contribution of macrophage-derived JAML to atherosclerotic progression. This research expands our understanding of the biological functions of JAML.
The NLRP3 inflammasome, an innate immune signaling complex, is a pivotal mediator of the IL-1 cytokine family in atherosclerosis(19, 29). Its activation contributes to vascular inflammation, a critical factor in atherosclerotic progression(19, 30). The activation of NLRP3 inflammasomes in macrophages involves two steps(17). First, priming occurs when microbial or endogenous signals promote NF-κB nuclear translocation to regulate the transcription and expression of NLRP3, pro-IL-1β, and pro-IL-18. The second step involves assembly, where ATP, pore-forming toxins, and reactive oxygen species facilitate the assembly and activation of the NLRP3 inflammasome, leading to the maturation and secretion of IL-1β and IL-18. The NF-κB signaling pathway is a classical pathway that activates the NLRP3 inflammasome(19). To our knowledge, this study is the first to demonstrate that JAML promotes NLRP3 inflammasome activation in macrophages.
One notable finding of this study is the interaction between JAML and PKM2 in macrophages. PKM2, one of the two isoforms of PKM, is associated with glycolysis and the Warburg effect. Emerging evidence indicates that PKM2 can function as a protein kinase to regulate gene transcription either alone or with other factors such as p65 (21, 31, 32). PKM2 phosphorylation at Tyr105 by tyrosine kinases, such as sarcoma kinase and hematopoietic cell kinase(33), promotes its nuclear translocation, where it interacts with p65 to form a functional complex, The PKM2/p65 complex, that activates the NF-κB signaling pathway, driving the expression of downstream genes(34, 35). Consistent with this role, our results showed that JAML deletion abolished LPS-induced PKM2 nuclear translocation and phosphorylation. Interestingly, JAML deficiency suppressed the interaction between PKM2 and p65 without affecting total PKM2 expression, indicating that JAML regulates PKM2 in macrophages.
In conclusion, our findings suggest that JAML activates the NF-κB signaling pathway through the regulation of PKM2 phosphorylation and nuclear translocation, leading to NLRP3 inflammasome activation and subsequent secretion of pro-inflammatory cytokine. Thus, JAML in macrophages plays a crucial role in regulating NLRP3 inflammasome activation during atherosclerosis and presents potential targets for anti-inflammatory therapeutics for this disease. Therefore, this work proves that JAML functions as a prognostic marker and has promising prospects in atherosclerosis treatment.