Groundbreaking in Circulation (IF 41.3): Zhang Mei, Dai Shen & Liu Fengming’s team from Shandong University uncovers a novel regulatory mechanism of vascular remodeling in pulmonary hypertension

Pulmonary hypertension (PH) is a progressive, life-threatening disease characterized mainly by pulmonary vascular remodeling, in which endothelial dysfunction plays a crucial role. However, the molecular factors driving this pathological process remain incompletely understood. Previous studies, through proteomic analysis of hypoxia-treated human pulmonary artery endothelial cells, identified serine hydroxymethyltransferase 2 (SHMT2) as a potential target in PH, yet its role in disease pathogenesis and the underlying mechanisms remained unclear. On June 10, 2026, the team of Professor Zhang Mei at Qilu Hospital of Shandong University, together with the teams of Dai Shen and Liu Fengming at the School of Basic Medical Sciences of Shandong University, jointly published the research paper "Endothelial SHMT2 Drives Pulmonary Vascular Remodeling Through Noncanonical Pathway in Pulmonary Hypertension" in Circulation (IF 41.3). The study systematically reveals a novel mechanism by which endothelial SHMT2 drives pulmonary vascular remodeling in PH through a noncanonical pathway, and identifies the small-molecule inhibitor Namodenoson, providing a brand-new strategy for PH therapy.

WZBIO Support - AAV, Adenovirus and Plasmid
(SHMT2, RhoB and their truncated mutant plasmids)

SHMT2 protein expression is significantly increased in lung tissue of AAV9-ICAM2-Shmt2-treated mice

SHMT2 protein expression is significantly reduced in lung tissue of AAV9-Shmt2-shRNA-treated rats

Research Results

1. SHMT2 is a potential therapeutic target in PH

Through experiments, the research team identified SHMT2 as a potential therapeutic target in PH that correlates with disease severity and is specifically upregulated in endothelial cells. Endothelial cell-specific knockout of Shmt2 significantly attenuated the PH phenotype in hypoxia-exposed mice. The team then constructed AAV9-Shmt2 overexpression virus driven by the ICAM2 endothelial promoter; flow sorting confirmed a significant increase in SHMT2 protein expression in CD45^-CD31⁺ endothelial cells, and immunofluorescence staining showed that GFP was mainly expressed in vascular endothelium, with minimal off-target expression in the lung and other major organs. After exposure to hypoxia, compared with AAV9-ICAM2-Ctrl-treated mice, AAV9-ICAM2-Shmt2-treated mice exhibited a more severe PH phenotype, including elevated right ventricular systolic pressure (RVSP), RV hypertrophy, and aggravated muscularization of small pulmonary arteries. To further evaluate the protective effect of EC-specific Shmt2 silencing on PH, the team administered AAV9-Shmt2-shRNA to rats 2 weeks before monocrotaline (MCT) injection. On day 21 after MCT injection, compared with control rats, AAV9-Shmt2-shRNA-treated rats showed significantly attenuated increases in mean pulmonary arterial pressure and RVSP associated with PH, a significant decrease in right ventricular hypertrophy index, reduced pulmonary arterial medial thickness, and a decreased proportion of muscularized small pulmonary arteries. Consistent therapeutic effects were also obtained when AAV9-Shmt2-shRNA intervention was given in the SuHx-induced rat PH model.

EC-specific inhibition of Shmt2 delays the development of PH in MCT- or SuHx-induced rat PH models

2. SHMT2 promotes hypoxia-induced endothelial barrier dysfunction and PH progression by upregulating RhoB

The research team performed proteomic analysis on hPAECs with SHMT2 silenced under hypoxia and found that differentially expressed proteins were significantly enriched in phenotypes such as stress fiber assembly and endothelial barrier establishment. Further investigation revealed that SHMT2 promotes the proliferation of hypoxic ECs through the one-carbon metabolic pathway; however, the regulation of endothelial permeability is independent of its enzymatic activity, a conclusion also confirmed by overexpression experiments with the SHMT2 enzyme-dead mutant (K95Q/K280Q). SHMT2α is a cytosolic isoform of SHMT2 that lacks the mitochondrial targeting sequence and localizes to the cytoplasm; previous studies suggested that it has non-enzymatic functions. The research team used adenovirus and AAV9 viral vectors to mediate in vitro and in vivo overexpression of SHMT2α respectively, and the results confirmed that SHMT2 participates in hypoxia-induced endothelial barrier dysfunction mainly through a non-metabolic mechanism. Proteomic analysis identified RhoB as a candidate mediator of SHMT2-induced endothelial barrier dysfunction, and in in vitro experiments, knockdown of RhoB blocked stress fiber formation and hyperpermeability caused by SHMT2α overexpression. Endothelium-specific overexpression of RhoB via AAV9-ICAM2-RhoB-GFP in Shmt2^ECKO mice reversed the protective effect of Shmt2 knockout, manifested as rebound increases in RVSP, Fulton index and the degree of pulmonary vascular muscularization, while transmission electron microscopy and Evans blue assays indicated disruption of endothelial tight junctions and increased permeability, thereby confirming that RhoB is a key downstream mediator of SHMT2-induced endothelial barrier dysfunction. Further investigation revealed that SHMT2, by participating in the BRISC deubiquitinase complex, inhibits K63-linked ubiquitination of RhoB, thereby preventing its degradation via the lysosomal pathway and enhancing RhoB protein stability.

RhoB mediates SHMT2-related endothelial barrier dysfunction and pulmonary hypertension

3. Namodenoson is an inhibitor of the noncanonical function of SHMT2

Based on the crystal structure of the SHMT2-BRISC complex, the research team conducted molecular docking-based virtual screening of more than 100,000 small-molecule compounds; 200 candidate molecules were obtained in the primary screen, which was narrowed to 27 based on druggability and clinical application background, and Namodenoson was ultimately identified. At the in vitro cell level, it was demonstrated that Namodenoson can directly block the protein binding between SHMT2 and RhoB, inhibit SHMT2-BRISC complex-mediated deubiquitination of RhoB, and downregulate RhoB protein levels; at the same time, it reverses the endothelial injury phenotype without interfering with the metabolic function of SHMT2. In both SuHx and MCT rat PH models, Namodenoson administration significantly improved pulmonary hypertension, right ventricular hypertrophy and pulmonary vascular remodeling, indicating that it exerts protective effects against PH in rodent models and holds potential for both prevention and treatment of PH. Mechanistically, Namodenoson ameliorates PH by targeting the SHMT2-RhoB axis.

Screening of Namodenoson, a small-molecule inhibitor of the noncanonical function of SHMT2, and its therapeutic potential in PH

Conclusion

This study identifies SHMT2 as a key regulator of pulmonary artery endothelial dysfunction in PH, revealing a noncanonical function of SHMT2, namely promoting endothelial hyperpermeability by enhancing the deubiquitination of RhoB in PAECs. In addition, Namodenoson was identified as an effective inhibitor targeting this noncanonical pathway, thereby exerting protective effects in PH. Taken together, these findings suggest that targeting SHMT2 may represent a promising therapeutic strategy for PH.