To understand why this matters, it helps to picture what actually goes wrong in pulmonary hypertension. In healthy pulmonary arteries, smooth muscle cells embedded in the vessel wall exist in a quiescent, contractile state, squeezing and relaxing in response to physiological signals. In pulmonary hypertension, these cells undergo what biologists call phenotypic switching: they abandon their contractile identity, revert to a synthetic, proliferative state, and begin dividing relentlessly while resisting apoptosis, the normal program of cell death. The result is thickening of the vessel wall, narrowing of the lumen, and a steady rise in pulmonary vascular resistance that eventually overloads the right ventricle of the heart. Current therapies, including prostacyclin analogues, endothelin receptor antagonists, and phosphodiesterase-5 inhibitors such as sildenafil, can dilate vessels and modestly improve symptoms, but none of them halts or reverses the remodeling process itself. This is precisely the gap that NFAT-targeting strategies hope to fill.

The NFAT family comprises five proteins, NFAT1 through NFAT5, each encoded by a separate gene. The classical members, NFAT1 through NFAT4, share a distinctive mode of regulation centered on calcium. When intracellular calcium concentrations rise, the calcium-binding protein calmodulin activates the phosphatase calcineurin, which strips phosphate groups from NFAT proteins and exposes nuclear localization sequences. The dephosphorylated transcription factors migrate into the nucleus, bind to specific DNA sequences, and switch on programs of gene expression. When calcium signaling subsides, kinases rephosphorylate NFAT and export it back to the cytoplasm, shutting the switch off. This elegant cycle, first characterized in immune cells in the late 1980s, has since been recognized in vascular smooth muscle, cardiac muscle, skeletal muscle, and endothelial cells, making NFAT a versatile integrator of calcium-dependent signals across many tissues.

In the pulmonary artery, the calcium connection is critical. Multiple upstream pathways converge to elevate calcium in pulmonary artery smooth muscle cells during the development of pulmonary hypertension. Hypoxia, the hallmark stimulus of the disease, increases the activity of store-operated calcium channels through proteins such as STIM1 and STIM2, and modulates transient receptor potential channels including TRPC6, TRPV1, and TRPV4. Vasoconstrictive and mitogenic agonists such as endothelin-1, platelet-derived growth factor, serotonin, and sphingosine-1-phosphate further amplify calcium entry. Each of these inputs has been shown to feed the calcineurin-NFAT axis. When Luo and colleagues surveyed this literature, they found a consistent pattern: whatever raises cytosolic calcium in these cells ultimately drives NFAT into the nucleus, where it activates genes that promote cell-cycle progression, migration, and survival.

The specific NFAT isoforms appear to play distinct roles. NFATC2, corresponding to NFAT2, has been implicated in cyclin A expression, a gene essential for DNA synthesis and cell division. Platelet-derived growth factor, a potent mitogen in pulmonary hypertension, drives proliferation and migration of pulmonary artery smooth muscle cells in part by regulating NFATC2. NFATC1, or NFAT3 in some nomenclature conventions, targets cyclin A as well in vascular smooth muscle and has been linked to the proliferative response in restenosis, a related vascular overgrowth process. NFATC3, however, has attracted particular attention in the pulmonary circulation. Studies in mice lacking functional NFATC3 showed that this isoform is required for chronic hypoxia-induced pulmonary hypertension in both adult and neonatal animals. NFATC3 mediates the up-regulation of alpha-actin during hypoxic remodeling, contributes to the expression of collagen type V, and regulates soluble guanylyl cyclase alpha-1, a key component of the nitric oxide signaling pathway that keeps vessels dilated. Its activation can be driven not only by calcium but also by redox changes, with increased superoxide and reduced hydrogen peroxide promoting NFATC3 activation in pulmonary arterial smooth muscle.

Beyond the direct calcium route, the review highlights how NFAT sits at the downstream end of several signaling cascades already implicated in pulmonary hypertension. The STAT3/PIM-1/NFAT pathway, well known for its role in cancer cell survival, is constitutively activated in pulmonary arterial hypertension, and the nuclear receptor Nur77 suppresses smooth muscle cell proliferation by inhibiting this very axis. The kinase DYRK1A, which phosphorylates NFAT and promotes its export from the nucleus, emerged as a protective brake; inhibiting DYRK1A in experimental models actually worsened remodeling through the STAT3/PIM-1/NFAT pathway, whereas pharmacological approaches that restrain NFAT activation attenuated vascular remodeling. MicroRNAs add another layer of control: microRNA-124 suppresses NFAT transactivation by targeting multiple genes and inhibits smooth muscle cell proliferation, microRNA-204 is down-regulated in pulmonary hypertension with consequences for NFAT-driven proliferation, and microRNA-153 induces apoptosis by targeting NFATC3, improving vascular remodeling in experimental disease.

Crucially, the therapeutic implications have already been tested in animal models. The landmark demonstration came from a 2007 study showing that the nuclear factor of activated T cells in pulmonary arterial hypertension can be therapeutically targeted, establishing proof of principle that blocking NFAT activation could reverse established disease in rodents. Cyclosporin A and tacrolimus, calcineurin inhibitors used clinically as immunosuppressants in transplantation, inhibit the NFAT pathway and have been shown to attenuate hypoxia-induced pulmonary hypertension and right ventricular hypertrophy in animal studies, with case reports describing responses in patients with pulmonary arterial hypertension secondary to inflammatory conditions. Sildenafil, already approved for pulmonary arterial hypertension, was found to inhibit calcineurin/NFATC2-mediated cyclin A expression in pulmonary artery smooth muscle cells, suggesting that part of its clinical benefit may derive from previously unappreciated effects on this transcriptional pathway. Other agents with NFAT-modulating activity include docosahexaenoic acid, which inhibits hypoxia-induced phenotype switching by blocking NFATC1 signaling; dehydroepiandrosterone, which restores right ventricular structure and function in severe experimental disease; and plumbagin and parp1-modulating compounds that act through microRNA-dependent mechanisms upstream of NFAT.

The review is candid about what remains unknown. NFAT5, the most ancient family member, is fundamentally different from its relatives: it is constitutively nuclear, does not cooperate with FOS and JUN, and is regulated not by calcium but by osmotic and mechanical stress. Recent work shows that NFAT5 is indispensable for a balanced adaptive transcriptional response of lung endothelial cells to hypoxia, and that arterial wall stress controls NFAT5 activity in vascular smooth muscle, where specific isoforms govern biomechanical stress responses and flow- and pressure-induced arterial remodeling in mice. Whether NFAT5 acts as a friend or foe in pulmonary hypertension, protecting endothelial resilience or contributing to maladaptive remodeling, is a question the authors flag as unresolved. They also note broader limitations: much of the evidence comes from rodent models such as monocrotaline and Sugen/hypoxia systems, whose fidelity to human disease is imperfect, and isoform-specific functions in human pulmonary artery smooth muscle cells remain incompletely mapped.

Nevertheless, the synthesis carries a clear message for the field. The convergence of calcium overload, redox signaling, growth factor stimulation, and inflammatory cytokines on the NFAT transcription factors suggests that these proteins act as a bottleneck through which multiple pathological inputs funnel into a single proliferative output. Targeting that bottleneck, whether with existing calcineurin inhibitors repurposed for vascular disease, with isoform-selective inhibitors that spare the immune system, or with microRNA-based approaches that tune NFAT activity with greater precision, offers a route toward therapies that address vascular remodeling rather than merely dilating vessels. As the global burden of pulmonary arterial hypertension continues to grow according to recent Global Burden of Disease analyses, and as guidelines from the European Society of Cardiology and European Respiratory Society emphasize the unmet need for antiremodeling treatments, the NFAT pathway stands out as one of the most mechanistically grounded and therapeutically actionable targets on the horizon.

Subject of Research: The role of NFAT transcription factors in pulmonary artery smooth muscle cell proliferation and pulmonary vascular remodeling in pulmonary hypertension

Article Title: The critical role of NFAT transcription factors in pulmonary arterial remodeling and pulmonary hypertension: from PASMC proliferation to therapeutic targeting

Article References: Luo, J., Liu, J., Zhang, H., Xin, B., & Ha, X. (2026). The critical role of NFAT transcription factors in pulmonary arterial remodeling and pulmonary hypertension: from PASMC proliferation to therapeutic targeting. Molecular Biology Reports, 53(1), Article 1696. https://doi.org/10.1007/s11033-026-12810-x

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12810-x

Keywords: pulmonary hypertension, NFAT transcription factors, pulmonary artery smooth muscle cells, vascular remodeling, calcineurin signaling, calcium signaling, phenotypic switching, NFATC3, therapeutic targeting, microRNAs, cyclosporin A, pulmonary vascular disease

Hypoxic pulmonary hypertension develops when the lungs are deprived of adequate oxygen over long periods, as occurs at high altitude or in chronic lung disease. The low-oxygen environment provokes an aggressive remodeling of the small pulmonary arteries: the muscular walls thicken, cells proliferate excessively, and the vessel lumens narrow, driving up resistance to blood flow. The right side of the heart, forced to pump against this rising resistance, experiences elevated pressure and eventually fails. Current treatments dilate vessels or target a handful of known signaling pathways, but they do not reverse the structural remodeling itself, which is why investigators continue to search for the molecular switches that govern it.

SCAMP3 belongs to a family of proteins embedded in the membranes of secretory carriers, the intracellular vesicles that shuttle material between cellular compartments. Although its day job involves membrane trafficking, SCAMP3 has recently attracted attention in cancer biology, where studies have linked it to the proliferation and migration of triple-negative breast cancer cells through modulation of AKT, ERK, and STAT3 signaling, and to tumor progression via a c-MYC–β-catenin–SQSTM1 axis. Elevated SCAMP3 expression has also been documented in pancreatic adenocarcinoma. What remained unknown was whether this trafficking protein plays any role in the vascular smooth muscle cells whose runaway growth defines pulmonary hypertension.

To find out, the team led by Peng Ye, Le Zhu, and corresponding authors Juan Zhang and Xiaomin Jiang turned to a well-established mouse model. Fifty mice were randomly divided into five groups of ten: a blank control group, a group exposed to hypoxia to induce pulmonary hypertension, a group receiving a non-targeting small interfering RNA as a negative control, a group treated with siRNA against SCAMP3, and a combined group receiving siRNA against both SCAMP3 and WWP1. The researchers then measured right ventricular systolic pressure, the Fulton index—the ratio of right ventricle weight to left ventricle plus septum weight, a standard gauge of right heart hypertrophy—and pulmonary function, while hematoxylin-eosin staining revealed the architecture of the pulmonary vessels.

The results were striking. Compared with normoxic animals, mice in the hypoxia group showed significantly increased SCAMP3 expression, both at the message and protein levels, alongside the expected rises in right ventricular systolic pressure and Fulton index and clear signs of vascular remodeling. In parallel experiments on human pulmonary artery smooth muscle cells grown under low-oxygen conditions, hypoxia again raised SCAMP3 protein and increased cell proliferation as measured by OD450 values in proliferation assays, while apoptosis rates fell and WWP1 protein levels dropped. In other words, the hypoxic environment simultaneously boosted the pro-growth trafficking protein and suppressed the ubiquitin ligase that would normally restrain growth.

Silencing SCAMP3 reversed this picture. In the hypoxia plus si-SCAMP3 group, SCAMP3 expression fell, proliferation of the pulmonary artery smooth muscle cells declined, and apoptosis rose significantly, with WWP1 protein expression climbing in step. In the living animals, knocking down SCAMP3 eased the hemodynamic and structural consequences of hypoxia: right ventricular systolic pressure and the Fulton index dropped, and the remodeling indexes calculated from stained vessel sections improved. The findings suggest that SCAMP3 acts as a brake release on the abnormal growth of vascular smooth muscle cells, and that removing it restores a healthier balance between cell division and cell death in the remodeled pulmonary arteries.

The mechanistic twist came from the double-knockdown group. When the researchers silenced WWP1 alongside SCAMP3, the benefits of SCAMP3 knockdown were partially undone: SCAMP3 expression crept back up, proliferation resumed, apoptosis declined, and WWP1 protein fell. This partial rescue implies that WWP1 sits downstream of SCAMP3 in the pathway, and that the protective effect of removing SCAMP3 depends at least in part on allowing WWP1 to accumulate. WWP1, a WW domain-containing E3 ubiquitin ligase, is known to tag other proteins for degradation and to regulate signaling cascades such as transforming growth factor-beta, and it has previously been implicated in cardiac hypertrophy, where targeting WWP1 prevented pathological heart muscle growth by destabilizing DVL2 through inhibition of K27-linked ubiquitination.

The statistical rigor of the study lends weight to its conclusions. All comparisons between the hypoxia group and the normoxia group, between the hypoxia plus si-SCAMP3 group and the hypoxia group, and between the double-knockdown group and the single SCAMP3 knockdown group reached significance at P less than 0.05. The animal work was approved by the Institutional Animal Care and Use Committee of Nanjing First Hospital and conducted in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals, with efforts made to minimize animal suffering. The study was funded by the National Natural Science Foundation of China and the Nanjing Health Science and Technology Development Special Fund Project, and the authors declared no conflicts of interest.

For the field, the study adds SCAMP3 to a growing roster of trafficking and ubiquitination proteins implicated in pulmonary vascular disease, a list that includes recent work on ErbB3 in endothelial dysfunction, BRCC3 regulation of ALK2 in vascular smooth muscle, and endothelial fIS1 deSUMOylation. What distinguishes the new findings is the proposed SCAMP3–WWP1 axis, which links membrane trafficking to the ubiquitin-proteasome machinery that decides the fate of growth-regulating proteins. If future work confirms the interaction at the molecular level—for example by identifying which substrates WWP1 tags when SCAMP3 is depleted—the pathway could yield drug targets capable of not just dilating vessels but reversing the wall thickening that makes pulmonary hypertension so lethal.

The caveats are real. The double knockdown only partially restored the disease phenotype, suggesting that other pathways downstream of SCAMP3 remain to be discovered, and the experiments were confined to mice and cultured cells rather than human tissue. The authors note that all original data are available upon reasonable request, which should help other laboratories test the mechanism independently. Still, the core message is clear and potentially consequential: a protein once regarded as a mundane component of the cellular shipping system appears to help orchestrate the vascular remodeling that underlies hypoxic pulmonary hypertension, and dialing it down—perhaps through RNA-based therapeutics or small molecules that stabilize WWP1—may one day offer patients a way to halt, or even reverse, the structural damage that current drugs cannot touch.

Subject of Research: The role of SCAMP3 knockdown and the E3 ubiquitin ligase WWP1 in attenuating hypoxic pulmonary hypertension and pulmonary vascular remodeling.

Article Title: Secretory Carrier Membrane Protein 3 Knockdown Attenuates Hypoxic Pulmonary Hypertension Potentially Involving WW Domain-Containing E3 Ubiquitin Protein Ligase 1

Article References: Ye, P., Zhu, L., Chu, P., Wang, D., Luo, J., Zhang, J., & Jiang, X. (2026). Secretory Carrier Membrane Protein 3 Knockdown Attenuates Hypoxic Pulmonary Hypertension Potentially Involving WW Domain-Containing E3 Ubiquitin Protein Ligase 1. Biochemical Genetics. https://doi.org/10.1007/s10528-026-11446-7

Image Credits: AI Generated

DOI: 10.1007/s10528-026-11446-7

Keywords: SCAMP3, WWP1, hypoxic pulmonary hypertension, pulmonary vascular remodeling, pulmonary artery smooth muscle cells, E3 ubiquitin ligase, apoptosis, cell proliferation, right ventricular systolic pressure, Fulton index, hypoxia, Biochemical Genetics