Systolic pressure overload caused pulmonary oxidative stress, vessel remodeling and severe microvascular thrombosis...

Pulmonary thrombosis is a fatal complication observed in patients following severe trauma or pulmonary infections. Patients with existing heart failure (HF) are more susceptible to infection-induced lung thrombosis; however, the underlying mechanisms remain poorly understood. This study introduces a severe mouse pulmonary thrombosis model utilizing CD40 knockout (KO) mice following transverse aortic constriction (TAC)-induced HF. While CD40 KO was found to have no detectable effect on left ventricular (LV) structure or function in mice either after TAC or under control conditions, the CD40 KO mice developed profound pulmonary micro-thrombosis after TAC. CD40 deficiency also significantly exacerbated TAC-induced pulmonary leukocyte infiltration (such as total CD45⁺ cells, Mac2⁺ cells and CD3⁺ cells), ∼1.7-fold more pulmonary fibrosis, and pulmonary vessel remodeling, as well as the consequent right ventricular hypertrophy. Mechanistically, our findings indicate that CD40 KO significantly enhanced TAC-induced pulmonary oxidative stress and pulmonary vascular endothelial cell activation, as indicated by upregulated vascular cell adhesion molecule-1 (VCAM-1) and intercellular cell adhesion molecule-1 expression (ICAM-1). Moreover, CD40 KO and TAC synergistically augmented thrombin (49.1 ± 3.0 in CD40 KO TAC group vs 27.2 ± 4.8 in WT TAC group), collagen (51.4 ± 2.5 in CD40 KO TAC group vs 37.8 ± 2.4 in WT TAC group), and ADP-induced platelet aggregation (40.1 ± 2.1 in CD40 KO TAC group vs 31.0 ± 1.8 in WT TAC group) and blood clot contraction(0.92 ± 0.01 in CD40 KO TAC group vs 0.72 ± 0.03 in WT TAC group) in mice. Furthermore, mild but significant pulmonary micro-thrombosis and increased blood clot retraction (0.80 ± 0.02 in CD40 KO sham group vs 0.66 ± 0.02 in WT sham group) were also observed in CD40 KO mice under baseline (control) conditions. Collectively, these results demonstrate that the profound pulmonary micro-thrombosis observed in CD40 KO mice is the outcome of a synergistic effect involving an inherent platelet defect in CD40 KO mice, combined with HF-induced pulmonary endothelial oxidative stress, endothelial activation, and systemic platelet activation. This unique lung micro-thrombosis model may serve as a useful tool for investigating the mechanisms and therapeutic strategies for pulmonary micro-thrombosis, particularly under conditions of existing HF.