Targeting Mitochondrial Dynamics in VEGFR-TKI Hypertension and Cardiotoxicity

Cardiovascular toxicity has emerged as one of the most pressing clinical challenges in the era of precision oncology. Among the expanding arsenal of targeted anticancer agents, vascular endothelial growth factor receptor tyrosine kinase inhibitors (VEGFR-TKIs) occupy a prominent position, offering meaningful survival advantages across multiple tumor types. However, the cardiovascular price of these therapeutic benefits is increasingly difficult to ignore. Hypertension, the most frequently encountered cardiovascular adverse event associated with VEGFR-TKI therapy, affects a substantial proportion of treated patients and can precipitate dose reductions, treatment discontinuation, or serious cardiovascular events.¹ The challenge facing oncologists and cardiologists alike is therefore not merely one of managing blood pressure (BP), but of understanding the biological mechanisms by which these agents perturb vascular homeostasis, and identifying intervention strategies that can mitigate cardiovascular toxicity without compromising antitumor efficacy. The endothelium occupies a central position in this pathophysiology. Under physiological conditions, the endothelium serves as a dynamic, metabolically active interface between the circulating blood and the underlying vascular smooth muscle, orchestrating vasodilation primarily through the production of nitric oxide (NO) via the PI3K-AKT-eNOS signaling cascade.² The binding of VEGF-A to VEGFR-2 constitutes a critical upstream stimulus for this pathway, and its pharmacological inhibition by VEGFR-TKIs predictably impairs NO bioavailability while simultaneously activating the vasoconstrictor endothelin-1 (ET-1) pathway. Mitochondria are dynamic organelles regulated by fusion proteins, including mitofusins 1 and 2 (MFN1/2) and optic atrophy protein 1 (OPA1), and fission proteins, including dynamin-related protein 1 (Drp1), fission protein 1 (Fis1), and mitochondrial fission factor (MFF). In endothelial cells, excessive Drp1-mediated mitochondrial fission promotes mitochondrial reactive oxygen species (mitoROS) production, impaired eNOS phosphorylation, reduced NO bioavailability, and apoptosis, thereby contributing to endothelial dysfunction. Drp1-mediated pathological fission has been implicated in essential hypertension,³ and pharmacological Drp1 inhibition with mitochondrial division inhibitor-1 (Mdivi-1) improves vascular function without impairing antitumor activity.5 Drp1 is negatively regulated by the mitochondria-localized E3 ubiquitin ligase MARCH5 (membrane-associated RING-CH finger,⁴ also known as MITOL), which promotes Drp1 degradation and limits excessive mitochondrial fission. It is within this multifaceted scientific landscape that the manuscript by Si and colleagues⁵ in this issue of Hypertension makes its contribution, offering a mechanistically detailed account of how apatinib, a VEGFR-2-selective TKI approved in China for advanced gastric cancer, induces hypertension through Drp1-mediated endothelial mitochondrial fission, regulated in part by the suppression of MARCH5 expression.

The study represents a meaningful mechanistic advance in the field of cardio-oncology, specifically in the understudied domain of TKI-associated vascular toxicity. The central finding, that apatinib suppresses MARCH5 expression in vascular endothelial cells, thereby reducing ubiquitin-dependent degradation of Drp1, permitting its accumulation and triggering excessive mitochondrial fission, endothelial dysfunction, and hypertension, is both biologically plausible and supported by a coherent and internally consistent experimental architecture (Figure 1). The translational relevance is bolstered by the demonstration that pharmacologically inhibiting of Drp1 with Mdivi-1 normalizes BP in apatinib-treated tumor-bearing nude mice without compromising the drugs antitumor efficacy, a finding with immediate therapeutic implications.⁵ These findings advance our mechanistic understanding beyond the canonical VEGF-NO axis and position mitochondrial dynamics and the ubiquitin-proteasome system as actionable targets in TKI-related hypertension.

Figure 1. Proposed mechanism of apatinib-induced hypertension mediated by the MARCH5–Drp1 mitochondrial fission axis.

Under physiological conditions, VEGF-A/VEGFR-2 signaling activates the PI3K/AKT/eNOS pathway, promoting nitric oxide (NO) production and endothelial-dependent vasodilation. Apatinib, a VEGFR-2 tyrosine kinase inhibitor (TKI), suppresses MARCH5 expression, thereby reducing ubiquitin-dependent degradation of dynamin-related protein 1 (Drp1) and promoting its accumulation. Increased Drp1 activity induces excessive mitochondrial fission and mitochondrial reactive oxygen species (mitoROS) generation, leading to impaired PI3K/AKT/eNOS signaling, reduced eNOS phosphorylation and NO bioavailability, endothelial dysfunction, vasoconstriction, and hypertension. Pharmacological inhibition of Drp1 with mitochondrial division inhibitor-1 (Mdivi-1) attenuates mitoROS production, restores endothelial signaling and vascular function, normalizes blood pressure, and preserves antitumor efficacy.

The experimental platform employed is methodologically rigorous and multi-layered. In vitro studies in human umbilical vein endothelial cells (HUVECs) were complemented by in vivo experiments in a subcutaneous gastric cancer xenograft model in nude mice, and proteomics analysis was deployed to identify differentially expressed proteins in the thoracic aorta, including the discovery of MARCH5 downregulation. The correlation between the mitochondrial circularity index and systolic and diastolic BP provides a meaningful association linking mitochondrial fragmentation to the hypertensive phenotype in vivo. The mechanistic validation of the MARCH5-Drp1 axis through siRNA knockdown and overexpression experiments, combined with ubiquitination assays, constitutes warrants particular attention from the research community.

The discovery that MARCH5 regulates Drp1 in this context connects to a broader and rapidly evolving literature on E3 ubiquitin ligases in mitochondrial homeostasis. Foundational work by Karbowski and colleagues established that the mitochondrial E3 ubiquitin ligase MARCH5 is required for Drp1-dependent mitochondrial division,⁶ and subsequent studies have elaborated on its role in regulating not only mitochondrial morphology but also apoptosis and endothelial function. Of particular relevance, MARCH5 has been shown to restore endothelial cell function against ischemic and hypoxic injury via the Akt/eNOS pathway,⁷ establishing an endothelial-protective role for this ligase that the current study now extends to the cardio-oncology setting. The proteomics-driven identification of MARCH5 as the single overlapping gene between E3 ligases detected in the aortic tissue and those predicted by the UbiBrowser 2.0 system to ubiquitinate Drp1⁵ is methodologically innovative, although the reliance on a computational prediction tool to establish substrate relationships introduces an inherent limitation that the authors wisely address with experimental validation.

The functional role of Drp1 in cardiovascular disease has been extensively documented. Swimming exercise has been shown to alleviate endothelial mitochondrial fragmentation by inhibiting Drp1 to improve vascular function in hypertension,⁸ while epigenetic dysregulation of Drp1 binding partners has been proven to promote mitochondrial fission in pulmonary arterial hypertension.⁹ These findings reinforce the centrality of Drp1 in vascular disease pathophysiology and lend mechanistic coherence to the current results. The observation that the pathological mitochondrial fission induced by apatinib is asymmetric rather than physiological symmetric fission is particularly noteworthy, as it aligns with seminal work by Kleele and collaborators¹⁰ demonstrating that distinct fission signatures predict whether mitochondria undergo degradation or biogenesis, suggesting that apatinib-induced fission is predominantly a degradative, pathological process rather than a homeostatic one.

The finding that mitoROS mediates, at least in part, the downstream impairment of PI3K/AKT/eNOS signaling⁵ is congruent with established redox biology. Oxidative stress is a well-recognized driver of endothelial dysfunction, capable of uncoupling eNOS and reducing NO bioavailability through multiple biochemical mechanisms, including direct oxidation of the eNOS cofactor tetrahydrobiopterin and S-glutathionylation of eNOS itself. The use of MitoTEMPO, a mitochondria-targeted superoxide scavenger, to partially rescue eNOS phosphorylation provides mechanistic evidence that mitoROS generated by excessive fission is functionally relevant. This finding suggests that mitochondria-targeted antioxidant strategies may complement Drp1 inhibition as cardioprotective interventions during VEGFR-TKI therapy.

The pan-cancer analysis constitutes another strategically important component. The demonstration that DNM1L (the gene encoding Drp1) and MARCHF5 are both significantly upregulated in gastric adenocarcinoma and multiple other gastrointestinal cancers, and that their expression correlates positively with tumor proliferative characteristics and DNA replication but not with angiogenesis, is a crucial observation.⁵ It provides a biological rationale for why inhibiting Drp1, rather than upregulating MARCH5, is the more therapeutically viable strategy: MARCH5 upregulation in the tumor context could inadvertently promote cancer cell survival by restraining the pro-apoptotic effects of mitochondrial fission in tumor cells. By contrast, Drp1 inhibition with Mdivi-1 appears to act in a complementary manner to apatinib, reducing hypertension without blunting, and possibly even augmenting, antitumor activity.

Several methodological limitations warrant candid appraisal. The use of immunodeficient nude mice is an acknowledged constraint, as the absence of an intact immune system prevents evaluation of immune-mediated vascular effects and precludes in vivo gene knockdown via adenoviral vectors. The authors compensate for this with detailed in vitro mechanistic studies, but the translational fidelity of the model relative to the human clinical situation remains uncertain. The exclusive use of male mice, while justified by the authors on grounds of hormonal stability and consistent with common practice in xenograft oncology, limits the generalizability of findings to female patients, a clinically relevant concern given that estrogen exerts cardioprotective effects and may modulate mitochondrial dynamics in ways not captured here. Furthermore, the study does not address the upstream mechanism by which apatinib suppresses MARCH5 expression: direct effects on MARCH5 transcription or translation, VEGFR-2-dependent signaling, or off-target kinase inhibition? Finally, the exclusive focus on acute functional endpoints means that the long-term structural vascular consequences of sustained Drp1 hyperactivation, including potential contributions to arterial remodeling, stiffness, and fibrosis, are not characterized, an important limitation for a drug used chronically in cancer patients.

The therapeutic implications of this work extend beyond apatinib. Hypertension is a class effect of VEGFR-TKIs, observed with sunitinib, sorafenib, pazopanib, axitinib, and other agents, and the VEGFR inhibition-independent mitochondrial mechanisms identified here may operate across this drug class. The identification of a druggable mitochondrial fission checkpoint that can be targeted without compromising antitumor efficacy opens a new therapeutic avenue. Mdivi-1, while a valuable experimental tool, has pharmacokinetic limitations that currently preclude direct clinical application, and future studies should explore more clinically translatable Drp1 inhibitors or delivery strategies. Additionally, MARCH5 itself merits exploration as a potential endogenous cardioprotective target; strategies to selectively upregulate its expression in vascular tissue while avoiding pro-tumorigenic effects in the gastrointestinal setting represent a challenging but worthwhile research objective. An important unresolved question is whether VEGFR2 inhibition and Drp1/mitoROS-mediated endothelial dysfunction regulate distinct downstream endothelial programs. While apatinib directly suppresses VEGFR2-dependent PI3K-AKT signaling required for angiogenesis, excessive Drp1 activation may preferentially amplify oxidative stress-mediated impairment of eNOS coupling and vascular tone regulation. This potentially non-overlapping regulatory relationship could explain why Drp1 inhibition restores endothelial function and BP control without attenuating the antiangiogenic efficacy of VEGFR2 blockade, and warrants further mechanistic investigation.

In conclusion, Si and colleagues⁵ have produced a mechanistically substantive study that meaningfully advances our understanding of VEGFR-TKI-induced hypertension. By implicating the MARCH5-Drp1-mitochondrial fission axis as a critical mediator of apatinib-induced endothelial dysfunction and hypertension, and by demonstrating that Drp1 inhibition can alleviate hypertension without compromising antitumor efficacy, the study provides both a new mechanistic framework and a potentially actionable therapeutic strategy. The integration of proteomics discovery, rigorous in vitro mechanistic validation, and in vivo tumor-bearing mouse experimentation reflects a well-designed translational study. Future work addressing the upstream regulation of MARCH5 by apatinib, the generalizability of these findings to other VEGFR-TKIs and to female subjects, and the long-term vascular structural consequences of Drp1 hyperactivation will be essential to fully realize the translational potential of these observations. As the field of cardio-oncology matures, studies such as this one that move beyond symptomatic management toward mechanism-based cardioprotection will be increasingly indispensable in enabling patients to receive the full benefit of life-prolonging targeted therapies without unacceptable cardiovascular harm. Beyond cardio-oncology, these findings further support the emerging concept that pathological Drp1-mediated mitochondrial fission may represent a broader therapeutic target in hypertension itself. Future studies should determine whether selective modulation of mitochondrial dynamics can improve endothelial dysfunction and BP control in non-tumor models of essential or metabolic hypertension.

Nonstandard Abbreviations and Acronyms

BP

blood pressure

Drp1

dynamin-related protein 1

eNOS

endothelial nitric oxide synthase

ET-1

endothelin-1

Fis1

fission protein 1

MARCH5

membrane-associated RING-CH finger 5

Mdivi-1

mitochondrial division inhibitor-1

MFN1/2

mitofusins 1 and 2

MITOL

mitochondrial ubiquitin ligase

NO

nitric oxide

OPA1

optic atrophy protein 1

PI3K

phosphoinositide 3-kinase

ROS

reactive oxygen species

TKI

tyrosine kinase inhibitor

VEGF

vascular endothelial growth factor