Inflammatory cytokines mediate thoracic aortic aneurysm formation via plasma metabolites: A two-step Mendelian randomization and single cell sequencing-based investigation

Thoracic aortic aneurysm (TAA) is a life-threatening condition characterized by pathological dilation of the aorta. While inflammatory responses have been implicated in TAA pathogenesis, the causal relationships remain elusive. This study aimed to elucidate potential causal associations between inflammatory cytokines, plasma metabolites, and TAA risk using Mendelian randomization (MR) analysis. We conducted bidirectional two-sample MR analysis utilizing genome-wide association study data from 91 inflammatory cytokines (n = 14,824), 1400 plasma metabolites (n = 8299), and TAA (n = 385,857). The inverse-variance weighted method served as the primary analytical approach, with comprehensive sensitivity analyses performed to assess pleiotropy and heterogeneity. Two-step MR analysis was employed to explore potential mediating roles of plasma metabolites. Single-cell sequencing analysis was utilized to detect cell type enrichment and elucidate cellular functions of identified cytokines. Additionally, we conducted an analysis to identify druggable proteins as potential therapeutic targets for TAA. MR analysis revealed that genetically-determined increases in C-X-C motif chemokine 10 (CXCL10) (odds ratios OR = 1.149, 95% confidence interval CI: 1.009–1.309, P = .037) and fibroblast growth factor 5 (OR = 1.101, 95% CI: 1.013–1.196, P = .024) were associated with elevated TAA risk. Conversely, C-C motif chemokine 20 (CCL20) (OR = 0.870, 95% CI: 0.759–0.996, P = .043) and CD40L receptor (CD40) (OR = 0.906, 95% CI: 0.827–0.992, P = .033) demonstrated inverse associations with TAA risk. Two-step MR analysis identified potential mediating metabolites: the phosphate to linoleoyl-arachidonoyl-glycerol ratio for CXCL10, thyroxine and X-24585 for FGF-5, and the creatine to carnitine ratio for CCL20. Single-cell sequencing analysis revealed enrichment of these cytokines in specific cell types and pathways relevant to TAA pathogenesis. Drug–gene interaction analysis identified CXCL10, CCL20, and CD40 as potential targets for treatment of TAA. This study provides robust genetic evidence supporting causal relationships between specific inflammatory cytokines and TAA risk, with plasma metabolites potentially mediating these effects. CXCL10 and FGF-5 were identified as potential risk factors, while CCL20 and CD40 may confer protective effects. These findings offer novel insights into TAA pathogenesis and suggest potential targets for intervention. Further research is warranted to elucidate the underlying mechanisms and validate these results across diverse populations.