Targeting endothelial SMAD4 ameliorates endothelial dysfunction in hypertensive mice

Objective: Endothelial dysfunction is a key contributor to hypertension, and dysregulation of TGF-β/BMP signaling pathways exacerbates vascular pathogenesis. However, the precise role of SMAD4 in the development of vascular inflammation and dysfunction in hypertension remains poorly understood.
Methods: Tie2-Cre/ERT2 system was used to generate an endothelial-specific Smad4 knockout mouse. Hypertension was induced by infusion of angiotensin II (Ang II) via implanting an osmotic pump subcutaneously. Endothelium-dependent relaxations (EDRs) of various blood vessels were assessed using a wire myograph system. Gene expression in vivo and in vitro was evaluated through RNA-seq, qPCR, immunofluorescence staining, and western blotting. Nitric oxide (NO) and reactive oxygen species (ROS) production were measured using fluorescent probes under confocal microscopy.
Results: EC-Smad4 KO mice showed a significant reduction in Ang II-induced blood pressure elevation compared to control EC-Smad4 WT mice. EDRs in the aorta, mesenteric, and carotid arteries were markedly improved in EC-Smad4 KO mice. In the aortic endothelium, excess ROS generation and VCAM1 expression induced by Ang II were suppressed in EC-Smad4 KO mice. SMAD4 knockdown also led to diminished phosphorylation of p38 MAPK in response to Ang II, increased phosphorylated eNOS (p-eNOS) at Ser1177. Additionally, Smad4 downregulation resulted in reduced mRNA and protein levels of GRP78, ATF6, and PERK, key markers of tunicamycin-induced endoplasmic reticulum (ER) stress.
Conclusion: Smad4 signaling is a critical mediator of endothelial dysfunction and vascular inflammation in hypertension. Endothelial-specific deletion of Smad4 ameliorates vascular dysfunction by reducing oxidative stress, suppressing ER stress, and alleviating vascular inflammation.
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