Deciphering the SP1/ADAM10/DRP1 Axis in Hypoxia Pulmonary Hypertension

Study Background and Research Question

Hypoxia pulmonary hypertension (HPH) is a severe vascular complication arising primarily from chronic obstructive pulmonary disease (COPD) and diffuse pulmonary lung diseases such as idiopathic pulmonary fibrosis and combined pulmonary fibrosis and emphysema. The pathological hallmark of HPH involves persistent elevation of mean pulmonary artery pressure, which frequently leads to right heart failure and reduced survival rates. Despite its prevalence and clinical burden, current treatments for HPH remain limited in efficacy, necessitating deeper mechanistic insights to identify new therapeutic targets.

Emergent research has highlighted the pivotal role of intercellular communication between pulmonary artery endothelial cells (ECs) and smooth muscle cells (SMCs) in driving vascular remodeling, a key process in HPH progression. While extracellular vesicles and soluble mediators have been implicated, the molecular axes governing these interactions under hypoxic stress are not fully defined. The reference study (Li et al., 2025) investigates whether the SP1/ADAM10/DRP1 axis serves as a mechanistic bridge linking ECs and SMCs during hypoxia-induced pulmonary vascular remodeling.

Key Innovation from the Reference Study

The central innovation of this work is the identification of a sequential signaling axis—SP1 transcription factor regulating ADAM10 expression in ECs, with ADAM10 modulating DRP1-driven mitochondrial dynamics in SMCs. This axis is demonstrated to mediate the pro-proliferative and anti-apoptotic effects of hypoxic ECs on adjacent SMCs, thereby driving pathological vascular remodeling in HPH. The study also delineates the involvement of the PI3K/AKT/mTOR pathway downstream of ADAM10, expanding the mechanistic framework for EC-SMC crosstalk in hypoxic environments.

Methods and Experimental Design Insights

The research employed an integrated strategy combining in vivo, in vitro, and bioinformatic approaches. Key methodological elements include:

• Hypoxia-exposed rat models to mirror clinical HPH and assess ADAM10 expression dynamics in lung tissue.
• Primary cultures of rat pulmonary artery ECs and SMCs, with ECs subjected to hypoxic conditions to generate conditioned media reflective of their secretory phenotype.
• Genetic manipulation: ADAM10 knockdown and overexpression in ECs to dissect functional contributions to SMC phenotype.
• Protein and gene expression analysis (Western blot, qPCR) for ADAM10, DRP1, PI3K, AKT, and mTOR.
• Cell proliferation and apoptosis assays to quantify SMC responses to conditioned media under various experimental conditions.
• Bioinformatic prediction (JASPAR database) and validation of SP1 as a transcriptional regulator of ADAM10.
• Pharmacological intervention using Mdivi-1 (a selective DRP1 inhibitor) and LY294002 (a PI3K inhibitor) to evaluate pathway specificity.

Core Findings and Why They Matter

The study establishes several mechanistic links central to HPH pathogenesis:

• ADAM10 upregulation in hypoxia: Both in rat lung tissue and cultured ECs, hypoxia led to increased ADAM10 expression. ECs under hypoxic stress secreted elevated ADAM10, influencing the microenvironment.
• Conditioned medium effects: SMCs exposed to conditioned media from hypoxic ECs exhibited enhanced proliferation and resistance to apoptosis, reflecting a shift to a pro-remodeling phenotype. Conversely, knockdown of ADAM10 in ECs blunted these effects, indicating its pivotal role in EC–SMC communication.
• DRP1 and PI3K/AKT/mTOR pathway involvement: SMCs treated with media from ADAM10-deficient ECs showed reduced protein levels of DRP1, PI3K, AKT, and mTOR. This suggests that ADAM10 acts upstream of both mitochondrial fission and growth signaling pathways in SMCs.
• Intervention with pathway inhibitors: Application of Mdivi-1 (targeting DRP1) or LY294002 (targeting PI3K) to SMCs cultured with conditioned medium from ADAM10-overexpressing ECs reduced proliferation and promoted apoptosis, confirming the functional significance of these pathways in the observed phenotypic changes.
• SP1 as a transcriptional regulator: Bioinformatic analysis and experimental validation identified SP1 as a driver of ADAM10 upregulation in hypoxic ECs. Downregulation of SP1 decreased ADAM10 expression, linking hypoxic signaling to the initial step of this axis.

Together, these findings provide a detailed molecular roadmap from hypoxic stress in ECs, through SP1-driven ADAM10 secretion, to downstream activation of mitochondrial dynamics and growth pathways in SMCs. This axis offers new intervention points for modulating vascular remodeling in HPH, potentially improving disease outcomes where current therapies fall short (Li et al., 2025).

Comparison with Existing Internal Articles

The mechanistic insights from this study align with broader literature on mitochondrial dynamics and their role in vascular and metabolic diseases. Internal resources such as "Mdivi-1: Selective DRP1 Inhibitor for Mitochondrial Dynamics Research" and "Chronic Intermittent Hypoxia, Apoptosis, and Microbiome: Mdivi-1 Insights" provide additional context for the use of DRP1 inhibitors in dissecting mitochondrial outer membrane permeabilization and cell fate decisions under hypoxic or metabolic stress. Notably, these articles corroborate the utility of Mdivi-1 in apoptosis assays and mitochondrial fission research, supporting its application in studies like the reference work.

This study's focus on pulmonary hypertension extends the domain of Mdivi-1 and DRP1 research, previously centered on neuroprotection or metabolic disease, into vascular remodeling—a cross-domain bridge of significant translational interest.

Limitations and Transferability

While the study offers compelling mechanistic data, several limitations warrant consideration. First, although the rat model and primary cell systems provide physiological relevance, interspecies differences may affect translatability to human HPH. Second, while the role of ADAM10 and DRP1 is well-supported, the involvement of other extracellular vesicle cargoes or parallel signaling pathways was not exhaustively explored. Finally, while pharmacological inhibition with Mdivi-1 and LY294002 confirmed pathway relevance, off-target effects remain a theoretical concern in complex cellular environments.

Despite these limitations, the identification of the SP1/ADAM10/DRP1 axis provides a robust framework for future translational studies, including those utilizing human-derived cells or in vivo models of other vascular diseases.

Protocol Parameters

• Hypoxia induction in rats: Typically 10% O₂ for 3–4 weeks to model chronic hypoxic stress relevant to pulmonary hypertension.
• ADAM10 knockdown in ECs: Lentiviral shRNA transduction, validated by qPCR and Western blot, 48–72 h prior to conditioned medium collection.
• Conditioned medium preparation: ECs cultured under hypoxia; supernatant collected after 24–48 h and filtered before addition to SMCs.
• Mdivi-1 treatment for DRP1 inhibition: 50 μM in cell-based assays, as supported by product documentation; DMSO vehicle control recommended.
• Apoptosis assay: Commonly annexin V/PI staining, performed 24 h after SMC exposure to conditioned medium and/or inhibitors.

Research Support Resources

For laboratories seeking to interrogate mitochondrial dynamics or test the impact of DRP1 inhibition in vascular remodeling models, Mdivi-1 (SKU A4472) is a validated, selective DRP1 inhibitor widely used in the field. Its application in cell-permeable formats, as described in both this study and internal reviews, supports robust and reproducible workflows in apoptosis and mitochondrial function assays. Researchers can refer to APExBIO for detailed usage guidelines and product specifications tailored to both in vitro and in vivo experimental designs.