Pulmonary arterial hypertension (PAH) is characterized by increased lung vascular stiffness and impaired vessel relaxation, primarily due to reduced nitric oxide (NO) production in endothelial cells. Recent studies indicate that chloroquine, an autophagy inhibitor, may help lower pulmonary arterial pressure and enhance lung vascular function. This study investigates the mechanisms underlying the chloroquine-mediated restoration of NO bioavailability in endothelial cells derived from aortopulmonary shunt lambs, a relevant model for congenital heart defect (CHD)-associated PAH. We found that NO production was significantly reduced in shunt pulmonary artery endothelial cells (PAECs), attributable to decreased levels of tetrahydrobiopterin (BH₄) and diminished expression of GTP cyclohydrolase 1 (GCH1), despite a slight increase in endothelial nitric oxide synthase (eNOS) levels. Chloroquine robustly restored endothelial NO production, which correlated with increased BH₄ levels and restored GCH1 expression. The mechanistically upregulated carboxyl terminus of Hsp70-interacting protein (CHIP) in shunt PAECs is responsible for heightened GCH1 degradation, and chloroquine disrupted the assembly of the GCH1-HSP70-CHIP complex to preserve cellular GCH1. Similarly, another autophagy inhibitor, bafilomycin A1, demonstrated comparable effects. These findings suggest that autophagy inhibition can effectively enhance NO synthesis in endothelial cells experiencing depleted NO bioavailability, presenting a potential therapeutic strategy for managing PAH.

Infiltration of T cell acute lymphoblastic leukemia (T-ALL) into the meninges worsens prognosis, underscoring the need to understand mechanisms driving meningeal involvement. Here, we show that T-ALL cells expressing CXCR3 exploit normal T cell function to infiltrate the inflamed meninges. CXCR3 deletion hampered disease progression and extramedullary dissemination by reducing leukemic cell proliferation and migration. Conversely, forced expression of CXCR3 facilitated T-ALL trafficking to the meninges. We identified the ubiquitin-specific protease 7 as a key regulator of CXCR3 protein stability in T-ALL. Furthermore, we discovered elevated levels of CXCL10, a CXCR3 ligand, in the cerebrospinal fluid from patients with T-ALL and leukemia-bearing mice. Our studies demonstrate that meningeal stromal cells, specifically pericytes and fibroblasts, induce CXCL10 expression in response to leukemia and that loss of CXCL10 attenuated T-ALL influx into the meninges. Moreover, we report that leukemia-derived proinflammatory cytokines, TNF-α, IL-27, and IFN-γ, induced CXCL10 in the meningeal stroma. Pharmacological inhibition or deletion of CXCR3 or CXCL10 reduced T-ALL cell migration and adhesion to meningeal stromal cells. Finally, we reveal that CXCR3 and CXCL10 upregulated VLA-4/VCAM-1 signaling, promoting cell-cell adhesion and thus T-ALL retention in the meninges. Our findings highlight the pivotal role of CXCR3-CXCL10 signaling in T-ALL progression and meningeal colonization.