Smad3/HIF-2α Dual-Target PROTAC for the Treatment of Hypertensive Cardio-Renal Injury

Hypertension is one of the most common cardiovascular diseases worldwide. Long-term sustained hypertension can lead to multi-organ damage, particularly in the heart and kidneys. Although existing antihypertensive drugs can control blood pressure to some extent, pathological changes such as myocardial hypertrophy, ventricular remodeling, glomerulosclerosis, and renal interstitial fibrosis induced by hypertension may continue to progress even after blood pressure targets are met, ultimately leading to heart failure and chronic kidney disease. Currently, there is a lack of effective clinical strategies to directly delay or reverse the process of cardio-renal fibrosis. Therefore, in-depth research into its pathogenesis and the development of novel therapeutic strategies are of significant clinical importance. Studies have shown that tissue hypoxia and related fibrosis are core mechanisms, with the TGF-β/Smad3 signaling pathway and HIF-2α playing key roles. This study developed a novel dual-target small-molecule compound based on PROTAC technology, aiming to simultaneously degrade Smad3 and stabilize HIF-2α to synergistically inhibit the fibrosis process. The therapeutic potential of this compound was validated in animal and organoid models.

We established a hypertensive cardio-renal injury model in C57BL/6J mice using unilateral nephrectomy combined with continuous subcutaneous infusion of angiotensin II (Ang II). The animals were randomly divided into a sham group, a hypertension model group, and a PROTAC treatment group. The treatment group received daily subcutaneous injections of the Smad3/HIF-2α dual-target PROTAC compound, while the model group received an equal volume of solvent. During the experimental period, systolic blood pressure in the tail artery and cardiac function parameters (including ejection fraction EF% and fractional shortening FS%) were regularly monitored. At the endpoint of the experiment, serum was collected for creatinine and urea nitrogen measurements. Heart and kidney tissues were subjected to Masson's trichrome staining to evaluate collagen deposition and the degree of fibrosis. Additionally, we used human induced pluripotent stem cells (iPSCs) to differentiate into kidney organoids and applied TGF-β stimulation in vitro to simulate a fibrotic microenvironment. The anti-fibrotic effects of the PROTAC compound were further evaluated in this human tissue model, and changes in the expression of fibroblast activation markers (α-SMA) were analyzed using immunofluorescence.

Compared to the hypertension model group, the PROTAC treatment group showed a significant reduction in mean systolic blood pressure and marked improvement in cardiac function, specifically evidenced by significantly higher EF% and FS% (P < 0.05). In terms of renal function, serum creatinine and urea nitrogen levels were also significantly lower in the treatment group. Histopathological results revealed a significant reduction in collagen fiber deposition in the myocardial interstitium and renal tubulointerstitium of the treatment group, with a lower proportion of fibrotic area compared to the model group. In vitro experiments demonstrated that PROTAC treatment significantly inhibited TGF-β-induced fibroblast proliferation and the expression of extracellular matrix-related proteins in human kidney organoids.

The results of this study indicate that the Smad3/HIF-2α dual-target PROTAC small-molecule drug not only effectively reduces blood pressure in hypertensive model mice but also significantly improves their cardiac and renal functions while markedly alleviating fibrotic lesions in heart and kidney tissues. The mechanism of action may be related to the simultaneous inhibition of Smad3 phosphorylation and HIF-2α-mediated fibrotic signaling pathways. This study provides experimental evidence and conceptual direction for the development of novel anti-fibrotic therapeutic strategies targeting hypertensive organ damage.