Effect of chemotherapy in tumor on coronary arteries: Mechanisms and management

Coronary artery disease (CAD) is an important contributor to the cardiovascular burden in cancer survivors. The development of coronary ischemia events, myocardial infarction, and heart failure has been associated with many conventional chemotherapeutic agents, new targeted therapies, and immunotherapy. The most frequent pathological manifestations of chemotherapy-mediated coronary damage include acute vasospasm, acute thrombosis, accelerated atherosclerosis development, and microvascular dysfunction. Potential screening techniques for CAD patients include baseline risk factor evaluation, polygenic risk factors, and coronary artery calcium scores. Determining the risk requires consideration of both the type of chemotherapy and the type of cancer being treated. Cardiology-oncology guidelines offer some suggestions for the care of coronary artery disease, which might involve medication, lifestyle changes, and coronary revascularization.

Multimodality imaging approach in a case of vascular toxicity caused by cabozantinib

Vascular toxicity caused by cancer treatment can present as vasospasm, arterial thrombosis, and accelerated atherosclerosis. We report a case of a 60-year-old man with metastatic renal cell carcinoma under cabozantinib treatment for 3 years who presented to the hospital with relapsing episodes of rest angina. Due to the presence of ST depression in the 12-lead electrocardiogram and elevated troponin, a non-ST-segment elevation myocardial infarction was suspected. The patient underwent invasive coronary angiography, which revealed extended coronary artery spasm, and it subsided totally after nitrate administration. One year later, the patient presented again at the cardio-oncology outpatient clinic, reporting relapsing episodes of angina during the previous month. Coronary computed tomography angiography was performed, and it revealed 2 subsequent 70%-99% stenosis in OM1. To our knowledge, this is the first case of a patient treated with cabozantinib presenting with coronary artery spasm and accelerated atherosclerosis, in which a multimodality imaging approach was followed.

Azithromycin induces neurotoxicity in zebrafish by interfering with the VEGF/Notch signaling pathway

Azithromycin (AZM) is a widely used antibiotic in both human and veterinary medicine, and its use has significantly increased during the COVID-19 pandemic. However, potential adverse effects of AZM on aquatic organisms have not been well studied. In this study, we explored the neurotoxicity of AZM in zebrafish and delved into its underlying mechanisms. Our results showed that AZM exposure resulted in a spectrum of detrimental effects in zebrafish, encompassing abnormal behaviors, damaged neuronal development, aberrant lateral line nervous system development, vascular malformations and perturbed expression of genes related to neural development. Moreover, we observed a concentration-dependent exacerbation of these neurotoxic manifestations with increasing AZM concentrations. Notably, AZM induced excessive cell apoptosis and oxidative stress damage. In addition, alterations in the expression levels of the genes involved in the VEGF/Notch signaling pathway were evident in AZM-exposed zebrafish. Consequently, we hypothesize that AZM may induce neurotoxicity by influencing the VEGF/Notch signaling pathway. To validate this hypothesis, we introduced a VEGF signaling inhibitor, axitinib, and a Notch signaling agonist, valproic acid, alongside AZM exposure. Remarkably, the administration of these rescue compounds significantly mitigated the neurotoxic effects induced by AZM. This dual verification provides compelling evidence that AZM indeed induces neurotoxicity during the early developmental stages of zebrafish, primarily through its interference with the VEGF/Notch pathway. Innovatively, our study reveals the molecular mechanism of AZM-induced neurotoxicity from the perspective of the close connection between blood vessels and nervous system. These findings provide new insights into the potential mechanisms underlying the neurotoxic effect of antibiotics and highlight the need for further investigation into the ecotoxicological effects of antibiotics on aquatic organisms and the potential risks to human health.

Antineoplastic drugs inducing cardiac and vascular toxicity - An update

With the improvement in cancer prognosis due to advances in antitumor therapeutic protocols and new targeted and immunotherapies, we are witnessing a growing increase in survival, however, at the same timeincrease in morbidity among cancer survivors as a consequences of the increased cardiovascular adverse effects of antineoplastic drugs. Common cardiovascular complications of antineoplastic therapies may include cardiac complications such as arrhythmias, myocardial ischemia, left ventricular dysfunction culminating in heart failure as well as vascular complications including arterial hypertension, thromboembolic events, and accelerated atherosclerosis. The toxicity results from the fact that these drugs not only target cancer cells but also affect normal cells within the cardiovascular system. In this article, we review the clinical features and main mechanisms implicated in antineoplastic drug-induced cardiovascular toxicity, including oxidative stress, inflammation, immunothrombosis and growth factors-induced signaling pathways.

Developmental toxicity of flufenacet including vascular, liver, and pancreas defects is mediated by apoptosis and alters the Mapk and PI3K/Akt signal transduction in zebrafish

Release of agrochemicals from agricultural fields could unintentionally harm organisms that not targeted by pesticides. Flufenacet is one of the oxyacetamide herbicide applied in cultivation fields of crops and this has a possibility of unintentional exposure to diverse ecosystems including streams and surface water. Despite these environmental risks, limited information regarding toxicity of flufenacet on vertebrates is available. This study is aimed to assess environmental hazards and underlying toxic mechanisms of flufenacet by using a zebrafish model. Mortality measurements and morphological observations after the treatment of flufenacet suggested developmental toxicity of flufenacet in zebrafish. In addition, its toxicity on specific organs was evaluated using transgenic fluorescent zebrafish embryo. Adverse effects of flufenacet on vascular and hepatopancreatic development were demonstrated using Tg(flk1:EGFP) and Tg(fabp10a:DsRed; ela3l:EGFP) respectively. To address intracellular actions of flufenacet in zebrafish, cellular responses including apoptosis, cell cycle modulation, and Mapk and Akt signaling pathway were verified in transcriptional and protein levels. These results demonstrated developmental toxicity of flufenacet using the zebrafish model, providing essential information for assessing its potential hazards on vertebrates that are not directly targeted by the pesticide and for elucidating molecular mechanisms.

Cocaine induces vascular smooth muscle cells proliferation via DRP1-mediated mitochondrial fission and PI3K/HIF-1α signaling

Long-term cocaine abuse is associated with cardiovascular and pulmonary vascular complications. The vascular toxicity of cocaine can lead to vascular remodeling characterized by excessive proliferation of vascular smooth muscle cells. Though hypoxia-inducible factor (HIF) signaling and mitochondrial fission have been suggested to play essential roles in the pathogenesis of hypoxia-induced vascular remodeling, pathogenetic mechanism for cocaine-related vascular remodeling remains to be elucidated. In this study, we explore the effect of cocaine on the proliferation of vascular smooth muscle cells by in vitro experiments. The findings indicated that the cocaine-induced vascular smooth muscle cell hyperproliferation is achieved by enhancing DRP1-mediated mitochondrial fission and activating PI3K/HIF-1α signaling. Current findings suggested that mitochondrial fission would play a pivotal role in cocaine-related vascular remodeling and would be helpful in understanding the vascular toxicity of cocaine.

Modulation of lncRNA links endothelial glycocalyx to vascular dysfunction of tyrosine kinase inhibitor

AIMS

Novel cancer therapies leading to increased survivorship of cancer patients have been negated by a concomitant rise in cancer therapies-related cardiovascular toxicities. Sunitinib, a first line multi-receptor tyrosine kinase inhibitor, has been reported to cause vascular dysfunction although the initiating mechanisms contributing to this side effect remain unknown. Long non-coding RNAs (lncRNAs) are emerging regulators of biological processes in endothelial cells (ECs); however, their roles in cancer therapies-related vascular toxicities remain underexplored.

METHODS AND RESULTS

We performed lncRNA expression profiling to identify potential lncRNAs that are dysregulated in human-induced pluripotent stem cell-derived ECs (iPSC-ECs) treated with sunitinib. We show that the lncRNA hyaluronan synthase 2 antisense 1 (HAS2-AS1) is significantly diminished in sunitinib-treated iPSC-ECs. Sunitinib was found to down-regulate HAS2-AS1 by an epigenetic mechanism involving hypermethylation. Depletion of HAS2-AS1 recapitulated sunitinib-induced detrimental effects on iPSC-ECs, whereas CRISPR-mediated activation of HAS2-AS1 reversed sunitinib-induced dysfunction. We confirmed that HAS2-AS1 stabilizes the expression of its sense gene HAS2 via an RNA/mRNA heteroduplex formation. Knockdown of HAS2-AS1 led to reduced synthesis of hyaluronic acid (HA) and up-regulation of ADAMTS5, an enzyme involved in extracellular matrix degradation, resulting in disruption of the endothelial glycocalyx which is critical for ECs. In vivo, sunitinib-treated mice showed reduced coronary flow reserve, accompanied by a reduction in Has2os and degradation of the endothelial glycocalyx. Finally, we identified that treatment with high molecular-weight HA can prevent the deleterious effects of sunitinib both in vitro and in vivo by preserving the endothelial glycocalyx.

CONCLUSIONS

Our findings highlight the importance of lncRNA-mediated regulation of the endothelial glycocalyx as an important determinant of sunitinib-induced vascular toxicity and reveal potential novel therapeutic avenues to attenuate sunitinib-induced vascular dysfunction.

Terbutryn causes developmental toxicity in zebrafish (Danio rerio) via apoptosis and major organ malformation in the early stages of embryogenesis

Terbutryn (2-(ethylamino)-4-(tert-butylamino)-6-(methylthio)-1,3,5-triazine) is a substituted symmetrical triazine herbicide used in agricultural fields to prevent undesired vegetation growth by inhibiting photosynthesis in target weeds. Although terbutryn has various benefits, long-term exposure, misuse, or abuse of terbutryn may cause non-target toxicity and severe ecosystem pollution. To provide a detailed description of the embryonic developmental toxicity of terbutryn, zebrafish (Danio rerio) were exposed to 2, 4, and 6 mg/L of terbutryn and the morphological changes, pathological abnormalities, and developmental endpoints were assessed relative to that of a solvent control. The results showed that terbutryn induces a loss of survivability, reduction in body and eye size, and edema in the yolk sac. Through fluorescence microscopy, blood vessels, motor neurons, and liver development were investigated using transgenic zebrafish models based on fluorescently tagged genes (fllk1:eGFP, olig2:dsRed, and L-fabp:dsRed). Furthermore, cell death by apoptosis in zebrafish caused by terbutryn exposure was evaluated via acridine orange staining, which is a selective fluorescent staining agent. To support the preceding results, gene expression alterations caused by terbutryn exposure in zebrafish larvae were assessed. The overall results indicate that exposure to terbutryn induces apoptosis and disrupts organ development. These embryonic developmental toxicity results suggest that terbutryn should be applied in the right areas at the appropriate rates, concentrations, and quantities.

Exposure to real-ambient particulate matter induced vascular hypertrophy through activation of PDGFRβ

BACKGROUND

Vascular toxicity induced by particulate matter (PM) exposure exacerbates the onset and development of cardiovascular diseases; however, its detailed mechanism remains unclear. Platelet-derived growth factor receptor β (PDGFRβ) acts as a mitogen for vascular smooth muscle cells (VSMCs) and is therefore essential for normal vasoformation. However, the potential effects of PDGFRβ on VSMCs in PM-induced vascular toxicity have not yet been elucidated.

METHODS

To reveal the potential roles of PDGFRβ signalling in vascular toxicity, individually ventilated cage (IVC)-based real-ambient PM exposure system mouse models and PDGFRβ overexpression mouse models were established in vivo, along with in vitro VSMCs models.

RESULTS

Vascular hypertrophy was observed following PM-induced PDGFRβ activation in C57/B6 mice, and the regulation of hypertrophy-related genes led to vascular wall thickening. Enhanced PDGFRβ expression in VSMCs aggravated PM-induced smooth muscle hypertrophy, which was attenuated by inhibiting the PDGFRβ and janus kinase 2 /signal transducer and activator of transcription 3 (JAK2/STAT3) pathways.

CONCLUSION

Our study identified the PDGFRβ gene as a potential biomarker of PM-induced vascular toxicity. PDGFRβ induced hypertrophic effects through the activation of the JAK2/STAT3 pathway, which may be a biological target for the vascular toxic effects caused by PM exposure.

Oxamyl exerts developmental toxic effects in zebrafish by disrupting the mitochondrial electron transport chain and modulating PI3K/Akt and p38 Mapk signaling

Oxamyl, a carbamate insecticide, is mainly used to control nematodes in the agricultural field. Although oxamyl is a widely used insecticide that is associated with ecological concerns, limited studies have examined the toxic effects of oxamyl on the developmental stage and the underlying mechanisms. In this study, the developmental toxicity of oxamyl was demonstrated using zebrafish, which is a representative model as it is associated with rapid embryogenesis and a toxic response similar to that of other vertebrates. The morphological alteration of zebrafish larvae was analyzed to confirm the sub-lethal toxicity of oxamyl. Analysis of transgenic zebrafish (olig2:dsRED and flk1:eGFP line) and mRNA levels of genes associated with individual organ development revealed that oxamyl exerted toxic effects on the development of neuron, notochord, and vascular system. Next, the adverse effect of oxamyl on the mitochondrial electron transport chain was examined. Treatment with oxamyl altered the PI3K/Akt signaling and p38 Mapk signaling pathways in zebrafish. Thus, this study elucidated the mechanisms underlying the developmental toxicity of oxamyl and provided information on the parameters to assess the developmental toxicity of other environmental contaminants.

Evaluation of toxicity of polystyrene microplastics under realistic exposure levels in human vascular endothelial EA.hy926 cells

Microplastics (MPs) have emerged as a global concern, with a recent study being the first to detect them in the bloodstream of healthy people. However, precise information regarding the toxic effects of MPs on the human vascular system is currently lacking. In this study, we used human vascular endothelial EA. hy926 cells to examine the toxic potential of polystyrene MPs (PSMPs) under realistic blood concentrations. Our findings indicated that PSMPs can cause oxidative stress by reducing the expression of antioxidants, thereby leading to apoptotic cytotoxicity in EA. hy926 cells. Furthermore, the protective potential of heat shock proteins can be reduced by PSMPs. PSMP-induced apoptosis might also lower the expression of rho-associated protein kinase-1 and nuclear factor-κB expression, thus dampening LRR- and pyrin domain-containing protein 3 in EA. hy926 cells. Moreover, we observed that PSMPs induce vascular barrier dysfunction via the depletion of zonula occludens-1 protein. However, although protein expression of the nuclear hormone receptor 77 was inhibited, no significant increase in ectin-like oxidized low-density lipoprotein receptor-1 was noted in PSMP-treated EA. hy926 cells. These results demonstrate that exposure to PSMPs may not sufficiently increase the risk of developing atherosclerosis. Overall, our research signifies that exposure to realistic blood concentrations of PSMPs is associated with low atherosclerotic cardiovascular risk in humans.

Cancer Therapies and Vascular Toxicities

OPINION STATEMENT

Vascular events have become an important issue in the overall management of cancer patients. They usually result from a combination of (i) direct or indirect toxicity of anticancer treatments, (ii) a higher prevalence of cardiovascular risk factors in cancer patients, and (iii) prolonged exposure to treatments due to an increasing patient survival rate. In addition to conventional chemotherapies and radiotherapy, targeted therapies and immunotherapies have been developed which improve the prognosis of cancer patients but sometimes at the cost of vascular toxicity, which can lead to systemic or pulmonary hypertension and arterial/venous thromboembolic events. Endothelial dysfunction, a procoagulant state and metabolic disorders are the three main pathophysiological patterns leading to cancer treatment-related vascular toxicity. This issue is challenging because serious vascular adverse events can necessitate cancer treatment being put on hold or stopped, which could compromise patient survival. In addition to increasing the risk of thrombotic adverse events, cancer therapies may lead to an increased risk of bleeding, especially in treatments with vascular endothelial growth factor inhibitors. Therefore, we can define vasculo-oncology as a part of the cardio-oncology specialty; its aims are to predict, prevent, screen, and treat vascular toxicity related to cancer treatments. While the level of evidence is low regarding the management of vascular toxicity during cancer therapy, cardiologists and specialists in vascular diseases should closely collaborate with oncologists and hematologists to determine the optimal strategy for each patient.

A systematic comparison of the developmental vascular toxicity of bisphenol A and its alternatives in vivo and in vitro

Due to the potential toxicity of bisphenol A (BPA), several bisphenols (BPs), including bisphenol F (BPF), bisphenol S (BPS) and bisphenol AF (BPAF), have been gradually used as its main substitutes, and the levels of these alternatives in different environmental media have been constantly increasing. Although some previous studies have shown that bisphenol substitutes have similar or greater acute toxicity and estrogenic effects than BPA, comparative studies on the cardiovascular toxicity of BPs have not been evaluated. In this study, the developmental vascular toxicity of BPA and three predominant substitutes (BPF, BPS and BPAF) were evaluated using zebrafish embryos and human vascular endothelial cells (HUVECs). BP exposure at a sublethal concentration of 1/10 96 h median lethal concentration (96 h-LC₅₀) significantly hindered intersegmental vessel (ISV) growth, delayed common cardinal vein (CCV) remodeling and decreased subintestinal vessels (SIVs) in Tg (fli1:EGFP) zebrafish embryos. Meanwhile, the results of the endothelial tube formation assay showed that in vitro angiogenesis was inhibited by BP exposure. Mechanistically, BP exposure increased oxidative stress characterized by a significant decrease in superoxide dismutase (SOD) and catalase (CAT) activity, accompanied by increased levels of malondialdehyde (MDA) and reactive oxygen species (ROS) in both zebrafish and HUVECs. Therefore, the vascular toxicity and oxidative stress potency of the BPs were compared and evaluated, ranking as follows: BPAF > BPF > BPA > BPS. To the best of our knowledge, the present work, for the first time, systematically provides direct evidence for BPA and its alternatives on developmental vascular toxicity in vitro and in vivo. Therefore, these findings will provide insight into the rational and safe application of BPA substitutes.

Sdox, a H2S releasing anthracycline, with a safer profile than doxorubicin toward vasculature

Sdox is a synthetic H₂S-releasing doxorubicin (Dox) less cardiotoxic and more effective than Dox in pre-clinical, Dox-resistant tumour models. The well-known anthracycline vascular toxicity, however, might limit Sdox clinical use. This study aimed at evaluating Sdox vascular toxicity in vitro, using Dox as reference compound. Both vascular smooth muscle A7r5 and endothelial EA.hy926 cells were more sensitive to Dox than Sdox, although both drugs equally increased intracellular free radical levels. Sdox released H₂S in both cell lines. The H₂S scavenger hydroxocobalamin partially reverted Sdox-induced cytotoxicity in A7r5, but not in EA.hy926 cells, suggesting a role for H₂S in smooth muscle cell death. Markers of Sdox-induced apoptosis were significantly lower than, in A7r5 cells, and comparable to those of Dox in EA.hy926 cells. In A7r5 cells, Dox increased the activity of caspase 3, 8, and 9, Sdox affecting only that of caspase 3. Moreover, both drugs induced comparable DNA damage in A7r5 cells, while Sdox was less toxic than Dox in Ea.hy926 cells. In fresh aorta rings, only Dox weakly increased phenylephrine-induced contraction when endothelium was present. In rings cultured with both drugs for 7 days, Sdox blunted phenylephrine- and high K⁺-induced contractions though at a concentration 10-fold higher than that of Dox. In conclusion, Sdox may represent the prototype of an innovative anthracycline, effective against Dox-resistant tumours, displaying a more favourable vascular toxicity profile compared to the parent compound.

Sodium-glucose cotransporter type 2 inhibitors prevent ponatinib-induced endothelial senescence and disfunction: A potential rescue strategy

BACKGROUND

Ponatinib (PON), a third-generation tyrosine kinase inhibitor (TKI), has proven cardiovascular toxicity, with no known preventing agents usable to limit such side effect. Sodium-glucose cotransporter type 2 (SGLT2) inhibitors are a new class of glucose-lowering agents, featuring favorable cardiac and vascular effects.

AIMS

We assessed the effects of the SGLT2 inhibitors empagliflozin (EMPA) and dapagliflozin (DAPA) on human aortic endothelial cells (HAECs) and underlying vasculo-protective mechanisms in an in vitro model of PON-induced endothelial toxicity.

METHODS AND RESULTS

We exposed HAECs to PON or vehicle (DMSO) in the presence or absence of EMPA (100 and 500 nmol/L) or dapagliflozin (DAPA) for 0-48 h exposure times. Compared with vehicle, incubations of HAECs with PON significantly reduced cell viability (0.56 ± 0.11 vs 0.23 ± 0.05 absorbance units, p < 0.01), increased the number of senescent cells at β-gal-assay (PON 9 ± 4 vs basal DMSO 3 ± 1 β-Gal⁺ cells/field, p < 0.01), decreased tubulization in Matrigel (PON PON: 6 ± 1 vs basal DMSO 12 ± 1 tubuli number/field, p < 0.05) with a non-statistically significant trend of PON to decrease the number of autophagic cells at immunofluorescence assay and flow cytometry. EMPA reverted the effects of PON on cell viability (E 500 + PON 0.24 ± 0.05 vs PON 0.56 ± 0.11 absorbance units, p < 0.01) and induced autophagy (E 500 7 ± 4.3 vs basal DMSO 2.6 ± 2.3 mean fluorescence vs PON 2.6 ± 2.4 mean fluorescence, p < 0.05). EMPA and DAPA also reversed the effects of PON on cell senescence (E 500 + PON 4 ± 1 and DAPA 100 4 ± 2 vs PON 9 ± 4 β-Gal⁺ cells/field, p < 0.01) and improved cell tubulization (E 500 + PON 21 ± 3 vs PON 6 ± 1 tubuli number/field, p < 0.05; DAPA 100 + PON 16 ± 2 vs PON 6 ± 1 tubuli number/field, p < 0.05).

CONCLUSION

EMPA and DAPA attenuate the vasculo-toxic effect exerted by PON by reverting endothelial cell senescence and dysfunction. These findings support the design of clinical studies exploring the vasculo-protective effects of EMPA or DAPA on PON-induced vascular toxicity.

Cisplatin, environmental metals, and cardiovascular disease: an urgent need to understand underlying mechanisms

Significantly increased risks of cardiovascular disease occur in testicular cancer survivors given cisplatin-based chemotherapy. The postulated mechanism of platinum-based chemotherapy’s vascular toxicity has been thought secondary to its different early- and late- effects on vascular injury, endothelial dysfunction, and induction of a hypercoagulable state. We highlight for the first time the similarities between platinum-associated vascular adverse events and the vascular toxicity associated with other xenobiotic-metal contaminants. The vascular toxicity seen in large epidemiologic studies of testicular cancer survivors may in part be similar and mechanistically linked to the risk seen in environmental heavy metal contaminants linked to cardiovascular disease. Future research should be directed to better understand the magnitude of the adverse cardiovascular effects of platinum and to elucidate the underlying mechanisms of action.

A mixture of chloromethylisothiazolinone and methylisothiazolinone impairs rat vascular smooth muscle by depleting thiols and thereby elevating cytosolic Zn2+ and generating reactive oxygen species

Chloromethylisothiazolinone (CMIT) and methylisothiazolinone (MIT) are biocidal preservatives and the active ingredients in Kathon CG, which contains ca. 1.5% mixture of CMIT and MIT at a ratio of 3:1 (CMIT/MIT). CMIT/MIT was misused as humidifier disinfectant products, which caused serious health problems in Korea. Here, the vascular effects of CMIT/MIT were investigated to evaluate claims of putative cardiovascular toxicity observed in humidifier disinfectant users. CMIT/MIT did not affect the basal tension of the rat thoracic aorta up to 2.5 μg/mL in myograph experiments. Instead, pretreatment with CMIT/MIT impaired phenylephrine- or 5-hydroxytryptamine-induced vasoconstriction in a range of 0.5-2.5 μg/mL, which was largely irreversible and not recovered by washing out the CMIT/MIT. Similarly, the application of CMIT/MIT to pre-contracted aorta caused a gradual loss of tension. In primary cultured vascular smooth muscle cells (VSMCs), CMIT/MIT caused thiol depletion, which in turn led to cytosolic Zn²⁺ elevation and reactive oxygen species (ROS) formation. CMIT/MIT-induced shrinkage, detachment, and lysis of VSMCs depending on the concentration and the treatment time. All events induced by CMIT/MIT were prevented by a thiol donor N-acetylcysteine (NAC). Cytolysis could be inhibited by a Zn²⁺ chelator TPEN and a superoxide scavenger TEMPOL, whereas they did not affect shrinkage and detachment. In accordance with these results, CMIT/MIT-exposed aortas exhibited dissociation and collapse of tissue in histology analysis. Taken together, CMIT/MIT causes functional impairment and tissue damage to blood vessels by depleting thiol and thereby elevating cytosolic Zn²⁺ and generating ROS. Therefore, exposure to CMIT/MIT in consumer products may be a risk factor for cardiovascular disorders.

Cellular model systems to study cardiovascular injury from chemotherapy

In spite of all the efforts for generating efficient pharmacological treatment options for cancer patients, the unwanted side effect of these substances on the cardiovascular system is becoming a major issue for cancer survivors. The fast pacing oncology field necessitate the quest for more accurate and reliable preclinical screenings. hiPSCs derived cardiomyocytes, endothelial and vascular smooth muscle cells provide unlimited source of physiologically relevant cells that could be used in the screening platforms. Cells derived from hiPSCs can measure drug induced alterations to different aspect of the heart including electrophysiology, contractility and structure. In this review, we will give an overview of the different in vivo and in vitro preclinical drug safety screenings. In following sections, we will focus on hiPSCs derived cardiomyocytes, endothelial and vascular smooth muscle cells and present the current knowledge of the application of these cells in unicellular cardiotoxicity assays. In the final part, we will focus on cardiac organoids as multi cell type platform and their role in cardiotoxicity screening of the chemotherapeutic drugs.

In vitro vascular toxicity assessment of NitDOX, a novel NO-releasing doxorubicin

The conjugation of doxorubicin (DOX) with nitric oxide (NO)-releasing groups gave rise to novel anthracyclines, such as nitrooxy-DOX (NitDOX), capable to overcome multidrug resistance. The widely described anthracycline cardiovascular toxicity, however, might limit their clinical use. This study aimed to investigate NitDOX-induced effects, as potential hazard, on vascular smooth muscle A7r5 and endothelial EA.hy926 cell viability, on the mechanical activity of freshly and cultured rat aorta rings, as well as on Ca_v1.2 channels of A7r5 cells. DOX was used as a reference compound. Although an increase in intracellular radicals and a reduction in mitochondrial potential occurred upon treatment with both drugs, A7r5 and EA.hy926 cells proved to be more sensitive to DOX than to NitDOX. Both compounds promoted comparable effects in A7r5 cells, whereas NitDOX was less active than DOX in inducing DNA damage and in eliciting apoptotic-mediated cell death revealed as an increase in sub-diploid-, DAPI- and annexin V-positive- EA.hy926 cell percentage. Moreover, in EA.hy926 cells, NitDOX doubled basal NO content, while preincubation with the NO-scavenger PTIO increased NitDOX-induced cytotoxicity. DOX exhibited a negligible contracturing effect in endothelium-intact rings, while NitDOX induced a significant ODQ-sensible, vasodilation in endothelium-denuded rings. In arteries cultured with both drugs for 7 days, NitDOX prevented either phenylephrine- or KCl-induced contraction at a concentration 10-fold higher than that of DOX. These results demonstrate that NitDOX displays a more favourable vascular toxicity profile than DOX. Taking into account its greater efficacy against drug-resistant cells, NitDOX is worth of further investigations in preclinical and clinical settings.

Vehicular Particulate Matter (PM) Characteristics Impact Vascular Outcomes Following Inhalation

Roadside proximity and exposure to mixed vehicular emissions (MVE) have been linked to adverse pulmonary and vascular outcomes. However, because of the complex nature of the contribution of particulate matter (PM) versus gases, it is difficult to decipher the precise causative factors regarding PM and the copollutant gaseous fraction. To this end, C57BL/6 and apolipoprotein E knockout mice (ApoE-/-) were exposed to either filtered air (FA), fine particulate (FP), FP+gases (FP+G), ultrafine particulate (UFP), or UFP+gases (UFP+G). Two different timeframes were employed: 1-day (acute) or 30-day (subchronic) exposures. Examined biological endpoints included aortic vasoreactivity, aortic lesion quantification, and aortic mRNA expression. Impairments in vasorelaxation were observed following acute exposure to FP+G in C57BL/6 animals and FP, UFP, and UFP+G in ApoE-/- animals. These effects were completely abrogated or markedly reduced following subchronic exposure. Aortic lesion quantification in ApoE-/- animals indicated a significant increase in atheroma size in the UFP-, FP-, and FP+G-exposed groups. Additionally, ApoE-/- mice demonstrated a significant fold increase in TNFα expression following FP+G exposure and ET-1 following UFP exposure. Interestingly, C57BL/6 aortic gene expression varied widely across exposure groups. TNFα decreased significantly following FP exposure and CCL-5 decreased in the UFP-, FP-, and FP+G-exposed groups. Conversely, ET-1, CCL-2, and CXCL-1 were all significantly upregulated in the FP+G group. These findings suggest that gas-particle interactions may play a role in vascular toxicity, but the contribution of surface area is not clear.

Human In Vitro Models for Assessing the Genomic Basis of Chemotherapy-Induced Cardiovascular Toxicity

Chemotherapy-induced cardiovascular toxicity (CICT) is a well-established risk for cancer survivors and causes diseases such as heart failure, arrhythmia, vascular dysfunction, and atherosclerosis. As our knowledge of the precise cardiovascular risks of each chemotherapy agent has improved, it has become clear that genomics is one of the most influential predictors of which patients will experience cardiovascular toxicity. Most recently, GWAS-led, top-down approaches have identified novel genetic variants and their related genes that are statistically related to CICT. Importantly, the advent of human-induced pluripotent stem cell (hiPSC) models provides a system to experimentally test the effect of these genomic findings in vitro, query the underlying mechanisms, and develop novel strategies to mitigate the cardiovascular toxicity liabilities due to these mechanisms. Here we review the cardiovascular toxicities of chemotherapy drugs, discuss how these can be modeled in vitro, and suggest how these models can be used to validate genetic variants that predispose patients to these effects.

SSeCKS/Gravin/AKAP12 Inhibits PKCζ-Mediated Reduction of ERK5 Transactivation to Prevent Endotoxin-Induced Vascular dysfunction

SSeCKS/Gravin/AKAP12 is a protein kinase C (PKC) substrate that inhibits the activity of PKC through binding with it. SSeCKS is expressed in vascular endothelial cells (ECs). The atypical PKC isoform ζ (PKCζ) is a pathologic mediator of endothelial dysfunction. However, the functional significance of SSeCKS/PKCζ dimerization in the vascular endothelium remains poorly understood. Given this background, we investigated the effects of SSeCKS on endothelial dysfunction and elucidated the possible mechanism involved. Vascular endothelial dysfunction and inflammatory changes were induced by treatment with bacterial endotoxin lipopolysaccharide (LPS, a vascular endothelial toxicity inducer). LPS can increase the level of SSeCKS. However, we also found that depletion of SSeCKS aggravated the LPS-induced vascular endothelial dysfunction, upregulated pro-inflammatory proteins and phosphorylation level of PKCζ, increased ROS formation, decreased extracellular-signal-regulated kinase 5 (ERK5) transcriptional activity, and reduced eNOS expression. Further examination revealed that depletion of SSeCKS increased PKCζ/ERK5 dimerization. These findings provide preliminary evidence that the expression of SSeCKS induced by LPS, as a negative feedback mechanism, has the potential to improve endothelium-dependent relaxation in vascular disease conditions by inhibiting PKCζ-mediated reduction of ERK5 transactivation.

Developmental exposure to BDE-99 hinders cerebrovascular growth and disturbs vascular barrier formation in zebrafish larvae

Polybrominated diphenyl ethers (PBDEs) are distributed throughout the environment. Despite a moratorium on their use, concentrations of PBDEs in the atmosphere and in residential environments remain high due to their persistence. The environmental health risks remain concerning and one of the major adverse effects is neurodevelopmental toxicity. However, the early response and effects of PBDEs exposure on the developing brain remain unknown. In the present study, we investigated the impacts of 2,2',4,4',5-pentabrominated diphenyl ether (BDE-99) on vascular growth and vascular barrier function with an emphasis on cerebral blood vessels, in the early life stages, using a zebrafish model. No general toxicity was observed in exposing zebrafish larvae to 0-0.5 μM BDE-99 at 72 hpf. BDE-99 exposure resulted in neither general toxicity nor pronounced developmental impairment in somatic blood vessels, including intersegmental vessels (ISV) and common cardinal veins (CCV). Meanwhile, both 0.05 μM and 0.5 μM of BDE-99 reduced cerebrovascular density as well as down-regulation of VEGFA and VEGFR2 in the head. In addition, BDE-99 exposure increased vascular leakage, both in cerebral and truncal vasculature at 72 hpf. The accentuated vascular permeability was observed in the head. The mRNA levels of genes encoding tight junction molecules decreased in the BDE-99-exposed larvae, and more robust reductions in Cldn5, Zo1 and Jam were detected in the head than in the trunk. Moreover, proinflammatory factors including TNF-α, IL-1β and ICAM-1 were induced, and the expression of neurodevelopment-related genes was suppressed in the head following BDE-99 exposure. Taken together, these results reveal that developmental exposure to BDE-99 impedes cerebrovascular growth and disturbs vascular barrier formation. The cerebral vasculature in developing zebrafish, a more sensitive target for BDE-99, may be a promising tool for the assessment of the early neurodevelopmental effects due to PBDEs exposure.

l-arginine alleviates doxorubicin-induced endothelium-dependent dysfunction by promoting nitric oxide generation and inhibiting apoptosis

BACKGROUND/AIMS

Patients with doxorubicin (Dox) treatment have a high risk of developing vascular toxicity with an unknown mechanism. l-arginine is a substrate for nitric oxide (NO). The decreased level of arginine-NO metabolite in Dox-treated cancer patients was associated with increased level of vascular damage, which promoted us to investigate the mechanism of Dox-induced vascular dysfunction and verify whether l-arginine supplement could alleviate this vasculotoxic effect.

METHOD

Within a mouse model of Dox injection (5 mg/kg i.p., 2 or 4 weeks), we measured vascular relaxation, blood pressure, vascular NO generation, apoptosis, and oxidative stress. We tested the efficacy of l-arginine (1.5 mg/g/day, 4 weeks) on Dox-induced vascular relaxation, blood pressure, vascular NO generation, apoptosis, as well as oxidative stress.

RESULTS

Dox induced endothelium-dependent vascular dysfunction, which was associated with increased reactive oxidative stress (ROS) production and reduced NO generation in the vessel. ROS was required for Dox-induced apoptosis of both smooth muscle cells and endothelial cells. Dox treatment in mice increased blood pressure, but had no effect on vascular inflammation and fibrosis. L-aringine restored Dox-induced vascular dysfunction via enhancing vascular NO production and alleviating ROS-mediated apoptosis.

CONCLUSION

We for the first time demonstrated l-arginine was effectively in suppressing Dox-induced vascular dysfunction, by attenuating vascular NO release and apoptosis. Our results provide a therapeutic target or a circulating marker for assessing vascular dysfunction which response to Dox treatment, and advance our understanding of the mechanisms of Dox-induced vascular dysfunction.

Exposure to tris(1,3-dichloro-2-propyl) phosphate (TDCPP) induces vascular toxicity through Nrf2-VEGF pathway in zebrafish and human umbilical vein endothelial cells

The growing production and extensive use of organophosphate flame retardants (OPFRs) have led to an increase in their environmental distribution and human exposure. Developmental toxicity is a major concern of OPFRs' adverse health effects. However, the impact of OPFRs exposure on vascular development and the toxicity pathway for developmental defects are poorly understood. In this study, we investigated the effects of exposure to tris(1,3-dichloro-2-propyl) phosphate (TDCPP), a frequently detected OPFR, on early vascular development, and the possible role of nuclear factor erythroid 2-related factor (Nrf2)-dependent angiogenic pathway in TDCPP's vascular toxicity. TDCPP exposure at 300 and 500 μg/L impeded the growth of intersegmental vessels (ISV), a type of microvessels, as early as 30 hpf. Consistently, a similar pattern of decreased extension and remodeling of common cardinal vein (CCV), a typical macrovessel, was observed in zebrafish at 48 hpf and 72 hpf. Developing vasculature in zebrafish was more sensitive than general developmental parameters to TDCPP exposure. The expression of genes related to VEGF signaling pathway dose-dependently decreased in TDCPP-treated larvae. In in vitro experiments using human umbilical vein endothelial cells (HUVECs), the increased cell proliferation induced by VEGF was suppressed by TDCPP exposure in a dose-dependent fashion. In addition, we found a repression of Nrf2 expression and activity in TDCPP-treated larvae and HUVECs. Strikingly, the application of CDDO-Im, a potent Nrf2 activator, enhanced VEGF and protected against defective vascular development in zebrafish. Our results reveal that vascular impairment is a sensitive index for early exposure to TDCPP, which could be considered in the environmental risk assessment of OPFRs. The identification of Nrf2-mediating VEGF pathway provides new insight into the adverse outcome pathway (AOP) of OPFRs.

Trace Elements and Paraoxonase-1 Activity in Lower Extremity Artery Disease

Oxidative stress and inflammation are candidate mechanisms to explain the potential role of exposure to metals and reduced activity of paraoxonase-1 (PON1) in age-related diseases. Both may be risk factors contributing to atherosclerosis. In the present study, inductively coupled mass spectrometry was used to explore multiple trace elements, while in-house methods were employed to measure PON1-related variables in patients with lower extremity artery disease (LEAD). Healthy controls were matched for sex, age, body weight, and relevant genotype variants. Serum concentrations of As, Ba, Cu, and Sr were higher in patients than those in controls, with a strong predictive ability to discriminate between groups. Differences in serum Pb, Cd, and Zn were negligible. Serum Cu increased when the disease was more severe, but a negative trend was noted for serum As, B, Ba, and Zn. The only variable associated with ankle-brachial index was serum Zn. Serum PON1 activity was significantly lower in LEAD patients. When the ability of serum trace elements to modulate PON1 activity was explored, the analysis revealed a unique association with serum Zn. The current results strongly suggest that Zn may have a protective effect in non-coronary atherosclerosis and indicate that this element may exert its anti-inflammatory and antioxidant functions through interactions with PON1 activity. These findings deserve confirmation and further research. In particular, the periodic evaluation of serum trace elements and the prescription of Zn supplements are easy measures to implement and that can improve the treatment of patients with LEAD.

Waterborne exposure to low concentrations of BDE-47 impedes early vascular development in zebrafish embryos/larvae

Polybrominated diphenyl ethers (PBDEs) are persistent flame retardants ubiquitously existing in various environment matrices. In spite of a recent reduction in use according to the phase-out policy, high levels of PBDEs are still found in both environmental and biological samples due to their persistent property and large-scale production over a long history. Developmental toxicity is a major health concern of PBDEs. However, the impact of PBDE exposure on vascular development remains poorly understood. In this study, we investigated the effect of low concentrations of 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47), a predominant PBDE congener, in environmental matrices and biota, on early vascular development using zebrafish. Zebrafish embryos were continuously exposed to waterborne BDE-47 at 0.06, 0.2, 0.6 μM starting from 2 h post-fertilization (hpf). Fluorescent images of vasculatures in Tg(kdrl:eGFP) zebrafish were acquired using a confocal microscope. The results indicated that BDE-47 exposure had no effect on hatching rate, survival, body weight, body length or heart rate in the early stage within 72 hpf, whereas zebrafish exposed to BDE-47 exhibited impairments in the growth of multiple types of blood vessels. The percentage of completed intersegmental vessels (ISV) at 30 hpf decreased in embryos treated with BDE-47 in a dose-dependent fashion. BDE-47 exposure led to a slight decrease in the growth of common cardinal vein (CCV), while dramatically hindered CCV remodeling process reflected by the larger CCV area and wider ventral diameter. BDE-47 exposure significantly reduced sub-intestinal vessels (SIV) area as well as the vascularized yolk area in zebrafish larvae at 72 hpf. In addition, the expression of genes related to vascular growth and remodeling was markedly suppressed in BDE-47-exposed zebrafish. These findings demonstrate the adverse effects of BDE-47 on early vascular development, and confirm the vascular toxicity of PBDEs in vivo. The results indicate that developing vasculature in zebrafish is sensitive to BDE-47 exposure, and may serve as a powerful tool for the assessment of early exposure to PBDEs.

Investigation on vascular cytotoxicity and extravascular transport of cationic polymer nanoparticles using perfusable 3D microvessel model

Vascular networks are the first sites exposed to cationic polymer nanoparticles (NPs) administered intravenously, and thus function as a barrier for NPs reaching the target organ. While cationic polymer NPs have been intensively studied as non-viral delivery systems, their biological effects in human microvessels have been poorly investigated due to a lack of appropriate in vitro systems. Here, we employed a three-dimensional microvessel on a chip, which accurately models in vivo conditions. An open and perfused microvessel surrounded by pericytes was shown to reproduce the important features of living vasculature, including barrier function and biomarkers. Using this microvessel chip, we observed contraction of the microvascular lumen induced by perfused polyethylenimine (PEI)/DNA NPs. We demonstrated that the oxidative stress present when microvessels were exposed to PEI NPs led to rearrangement of microtubules resulting in microvessel contraction. Furthermore, the transcytotic behavior of PEI NPs was analyzed in the microvessel by monitoring the escape of PEI NPs from the microvascular lumen into the perivascular region, which was not possible in two-dimensional culture systems. With our new understanding of the different behaviors of cationic polymer NPs depending on their transcytotic route, we suggest that caveolae-mediated transcytosis is a powerful route for efficient extravascular transport.

STATEMENT OF SIGNIFICANCE

Microvascular networks are not only biological system constituting largest surface area in the body and but also first site exposed to nanoparticle in vivo. While cationic polymer NPs have been intensively studied as non-viral delivery systems, its biological effects in human microvessel have been poorly investigated due to lack of appropriate in vitro systems. Here, we microengineered an open and perfused 3D pericyte incorporated microvessel model which possesses same morphological characteristic of in vivo. Using the microengineered model, this study represents the first report of transcytotic behavior of NPs in 3D microvessel, and its effect on extravasation efficiency. Our study lays the groundwork for the integration of innovative technologies to examine blood vessel-nanoparticle interaction, which a critical but ill-defined phenomenon.

The use of the tyrosine kinase inhibitor Nilotinib in Spondyloarthritis: does targeting inflammatory pathways with a treatment lead to vascular toxicity?

Spondylarthritis (SpA) is an inflammatory rheumatic disease associated with increased incidence of major adverse cardiovascular events (MACEs). Recently, Paramarta et al. proposed the use of the tyrosine kinase inhibitor Nilotinib in Spondyloarthritis to target certain inflammatory pathways. However, Nilotinib, which is highly effective for the treatment of patients with chronic myeloid leukaemia (CML), is also associated with an increased risk of MACEs. The authors suggest that Nilotinib may be effective in peripheral SpA by modulating inflammation, but not in axial SpA. Considering the vascular toxicity of Nilotinib and the acceleration of atherosclerosis in SpA patients, we suggest taking MACEs as an end-point in future trials.

Assessment of pazopanib-related hypertension, cardiac dysfunction and identification of clinical risk factors for their development

BACKGROUND

Antineoplastic therapy with the tyrosine kinase inhibitor pazopanib in patients with advanced/metastatic renal cell carcinoma (mRCC) has been associated with hypertension (HTN), cardiomyopathy, and cardiac dysrhythmias. We therefore assessed the cardiovascular (CV) risk with pazopanib in a clinical setting.

METHODS

Medical records of 35 antineoplastic-naïve mRCC patients newly started on pazopanib were retrospectively reviewed at a single academic medical center. Assessment of the hypertensive response and adverse cardiac events associated with pazopanib was the primary objective. Outcomes were defined using the National Cancer Institute's Common Terminology Criteria for Adverse Events v4.0. Potential clinical risk factors were investigated with univariate and multivariable logistic regression.

RESULTS

Pazopanib-induced HTN was observed in 57% of patients. Median maximal systolic blood pressure (SBP) during pazopanib treatment was 167.5 mmHg with median time to event of 24.5 days. New-onset HTN occurred in 6/14 (43%) patients. Baseline SBP > 130 mmHg (odds ratio [OR]: 5.32; 95% confidence interval [CI]: 0.94-29.99; p = 0.058) and ACEi/ARB use (OR: 4.88; 95% CI: 1.05 22.84; p = 0.044) were risk factors for pazopanib-induced HTN. When HTN was excluded, 34% of patients developed a CV adverse event. Age ≥ 60 years (OR: 8.72; 95% CI: 0.74-513.26; p = 0.105) trended towards being a predictor for a non-HTN CV adverse event.

CONCLUSIONS

Our findings suggest that pazopanib has a broad CV toxicity profile in treatment-naïve mRCC patients headlined by a rapid and striking hypertensive response. More intensive BP control prior to starting pazopanib and standardization of CV surveillance particularly in older patients may optimize oncologic care while minimizing CV risk.

Anticancer therapy-induced vascular toxicity: VEGF inhibition and beyond

Cardiotoxicity induced by chemotherapeutic agents and radiotherapy is a growing problem. In recent years, an increasing number of new drugs with targeted action have been designed. These molecules, such as monoclonal antibodies and tyrosine kinase inhibitors, can cause different type of toxicities compared to traditional chemotherapy. However, they can also cause cardiac complications such as heart failure, arterial hypertension, QT interval prolongation and arrhythmias. Currently, a field of intense research is the vascular toxicity induced by new biologic drugs, particularly those which inhibit vascular endothelial growth factor (VEGF) and its receptor (VEGF-R) and other tyrosine kinases. In this review, we aim at focusing on the problem of vascular toxicity induced by new targeted therapies, chemotherapy and radiotherapy, and describe the main mechanisms and emphasizing the importance of early diagnosis of vascular damage, in order to prevent clinical complications.

Long-Term Follow-Up of Chemotherapy-Induced Ovarian Failure in Young Breast Cancer Patients: The Role of Vascular Toxicity

BACKGROUND

We previously reported that chemotherapy-induced ovarian toxicity may result from acute vascular insult, demonstrated by decreased ovarian blood flow and diminished post-treatment anti-Müllerian hormone (AMH) levels. In the present study, we report the continuous prospective evaluation of ovarian function in that cohort.

METHODS

Patients (aged <43 years) with localized breast cancer were evaluated by transvaginal ultrasound prior to initiation of chemotherapy, immediately at treatment completion, and at 6 and 12 months after treatment cessation. Doppler flow velocity indices of the ovarian vasculature (resistance index [RI], pulsatility index [PI]) were visualized. Hormone markers of ovarian reserve were assessed at the same time points.

RESULTS

Twenty patients were enrolled in the study. Median age was 34 ± 5.24 years. Ovarian blood flow was significantly reduced immediately following chemotherapy (both RI and PI; p = .01). These parameters were partially recovered at later points of assessment (6 and 12 months after treatment); patients aged <35 years significantly regained ovarian blood flow compared with patients aged >35 years (p < .05). AMH dropped dramatically in all patients following treatment (p < .001) and recovered in only 10 patients. Hormone markers of ovarian reserve shortly after chemotherapy depicted a postmenopausal profile for most patients, accompanied by related symptoms. Follicle-stimulating hormone (FSH) levels recovered in 14 of 20 patients and significantly returned to the premenopausal range in patients aged <35 years (p = .04); 10 of 20 resumed menses at 12 months. The pattern of vascular impairment was lessened in patients treated with a trastuzumab-based protocol, although results did not reach statistical significance (p = .068).

CONCLUSION

Continuous prospective evaluation of ovarian vasculature and function in a cohort of young patients during and after chemotherapy indicated that ovarian toxicity may derive from acute vascular insult. Age may affect whether patients regain ovarian function, whereas recovery of blood flow and premenopausal FSH levels at later assessment was notable in patients aged <35 years.

IMPLICATIONS FOR PRACTICE

This study explored the role of vascular toxicity in mediating ovarian impairment and recovery following chemotherapy. Continuous prospective evaluation of ovarian vasculature and function in a cohort of young patients during and after chemotherapy indicated that ovarian toxicity may derive from acute vascular insult. Future studies are warranted to further characterize patterns of vascular toxicity of various chemotherapies in clinical practice and to assess the role of chemotherapy-induced vascular toxicity for specific end organs such as the ovary with systemic vascular effect. Elucidating the cause of impairment may facilitate development of measures to minimize vascular toxicity and consequences of acute vascular insult.

Manipulation of the HIF-Vegf pathway rescues methyl tert-butyl ether (MTBE)-induced vascular lesions

Methyl tert-butyl ether (MTBE) has been shown to be specifically anti-angiogenic in piscine and mammalian model systems at concentrations that appear non-toxic in other organ systems. The mechanism by which MTBE targets developing vascular structures is unknown. A global transcriptome analysis of zebrafish embryos developmentally exposed to 0.00625-5mM MTBE suggested that hypoxia inducible factor (HIF)-regulated pathways were affected. HIF-driven angiogenesis via vascular endothelial growth factor (vegf) is essential to the developing vasculature of an embryo. Three rescue studies were designed to rescue MTBE-induced vascular lesions: pooled blood in the common cardinal vein (CCV), cranial hemorrhages (CH), and abnormal intersegmental vessels (ISV), and test the hypothesis that MTBE toxicity was HIF-Vegf dependent. First, zebrafish vegf-a over-expression via plasmid injection, resulted in significantly fewer CH and ISV lesions, 46 and 35% respectively, in embryos exposed to 10mM MTBE. Then HIF degradation was inhibited in two ways. Chemical rescue by N-oxaloylglycine significantly reduced CCV and CH lesions by 30 and 32% in 10mM exposed embryos, and ISV lesions were reduced 24% in 5mM exposed zebrafish. Finally, a morpholino designed to knock-down ubiquitin associated von Hippel-Lindau protein, significantly reduced CCV lesions by 35% in 10mM exposed embryos. In addition, expression of some angiogenesis related genes altered by MTBE exposure were rescued. These studies demonstrated that MTBE vascular toxicity is mediated by a down regulation of HIF-Vegf driven angiogenesis. The selective toxicity of MTBE toward developing vasculature makes it a potentially useful chemical in the designing of new drugs or in elucidating roles for specific angiogenic proteins in future studies of vascular development.