Single- and double-walled carbon nanotubes enhance atherosclerogenesis by promoting monocyte adhesion to endothelial cells and endothelial progenitor cell dysfunction

Developments in nanotechnology approaches for the treatment of solid tumors

Nanotechnology has revolutionized cancer therapy by introducing advanced drug delivery systems that enhance therapeutic efficacy while reducing adverse effects. By leveraging various nanoparticle platforms-including liposomes, polymeric nanoparticles, and inorganic nanoparticles-researchers have improved drug solubility, stability, and bioavailability. Additionally, new nanodevices are being engineered to respond to specific physiological conditions like temperature and pH variations, enabling controlled drug release and optimizing therapeutic outcomes. Beyond drug delivery, nanotechnology plays a crucial role in the theranostic field due to the functionalization of specific materials that combine tumor detection and targeted treatment features. This review analyzes the clinical impact of nanotechnology, spanning from early-phase trials to pivotal phase 3 studies that have obtained regulatory approval, while also offering a critical perspective on the preclinical domain and its translational potential for future human applications. Despite significant progress, greater attention must be placed on key challenges, such as biocompatibility barriers and the lack of regulatory standardization, to ensure the successful translation of nanomedicine into routine clinical practice.

Effects of engineered nanomaterials on the cardiovascular system

With the explosive development of nanotechnology, engineered nanomaterials are currently being used in various industries, including food and medicine. Concern about the health effects of nanomaterials has been raised, and available research indicates that the relative surface area of nanomaterials seems to correlate with the severity of their toxicity. With regard to engineered nanomaterials, the scope of their acute and chronic toxicities and their mechanisms are not fully understood. Studies suggest that exposure to certain nanomaterials can generate reactive oxidant species and enhance permeability of the phagolysosomal membrane, which leads to inflammasome activation, causing oxidative stress and inflammation. Since the latter 2 are implicated in the development of cardiovascular diseases, such as hypertension and atherosclerosis, it can be presumed that exposure to engineered nanomaterials could significantly impact cardiovascular function. In this review, I raise issues that should be considered in the assessment of the effects of engineered nanomaterials on cardiovascular function, and evaluate their cardiovascular toxicity as described in various in vitro and/or in vivo toxicological studies and industrial investigations.

Nonlinear proinflammatory effect of short-term PM2.5 exposure: A potential role of lipopolysaccharide

The association between PM2.5 (particulate matter ≤ 2.5 µm) short-term exposure and its health effect is non-linear from the epidemiological studies. And this nonlinearity is suggested to be related with the PM2.5 heterogeneity, however, the underlying biological mechanism is still unclear. Here, a total of 38 PM2.5 filters were collected continuously for three weeks in winter Beijing, with the ambient PM2.5 varying between 10 and 270 µg/m3. Human monocytes-derived macrophages (THP-1) were treated with PM2.5 water-soluble elutes at 10 µg/mL to investigate the PM2.5 short-term exposure effect from a proinflammatory perspective. The proinflammatory cytokine tumor necrosis factor (TNF) induced by the PM2.5 elutes at equal concentrations were unequal, showing the heterogeneity of PM2.5 proinflammatory potentials. Of the various chemical and biological components, lipopolysaccharide (LPS) showed a strong positive association with the TNF heterogeneity. However, some outliers were observed among the TNF-LPS association. Specifically, for PM2.5 from relatively clean air episodes, the higher LPS amount corresponded to relatively low TNF levels. And this phenomenon was also observed in the promotion tests by treating macrophages with PM2.5 elutes dosed with additional trace LPS. Gene expression analysis indicated the involvement of oxidative-stress related genes in the LPS signaling pathway. Therefore, a potential oxidative-stress-mediated suppression on the PM2.5-borne LPS proinflammatory effect was proposed to be accounted for the outliers. Overall, the results showed the differential role of LPS in the heterogeneity of PM2.5 proinflammatory effects from a component-based perspective. Future experimental studies are needed to elucidate the signaling pathway of LPS attached on PM2.5 from different air quality episodes.

Insights into the toxicological effects of nanomaterials on atherosclerosis: mechanisms involved and influence factors

Atherosclerosis is one of the most common types of cardiovascular disease and is driven by lipid accumulation and chronic inflammation in the arteries, which leads to stenosis and thrombosis. Researchers have been working to design multifunctional nanomedicines with the ability to target, diagnose, and treat atherosclerosis, but recent studies have also identified that nanomaterials can cause atherosclerosis. Therefore, this review aims to outline the molecular mechanisms and physicochemical properties of nanomaterials that promote atherosclerosis. By analyzing the toxicological effects of nanomaterials on cells involved in the pathogenesis of atherosclerosis such as vascular endothelial cells, vascular smooth muscle cells and immune cells, we aim to provide new perspectives for the prevention and treatment of atherosclerosis, and raise awareness of nanotoxicology to advance the clinical translation and sustainable development of nanomaterials.

A comparative study of toxicity of graphdiyne and graphene oxide to human umbilical vein endothelial cells

The success of graphene oxide (GO) has attracted extensive research interests in developing novel 2D nanomaterials (NMs). Graphdiyne (GDY) is a new member of carbon-based 2D NMs possessing sp- and sp2 -hybridized carbon atoms. However, the toxicity of GDY is less investigated as GO. In this study, we compared the toxicity of GDY and GO with human umbilical vein endothelial cells (HUVECs). Exposure to up to 100-μg/ml GDY and GO induced cytotoxicity, but there was no statistically significant difference between GDY and GO. At noncytotoxic concentration, 25-μg/ml GDY or GO led to the internalization of NMs, typically in cytoplasm but not in nuclei. Only GO but not GDY significantly increased THP-1 adhesion onto NM-exposed HUVECs. Meanwhile, compared with GDY, GO more effectively promoted the release of soluble intracellular cell adhesion molecule-1 (sICAM-1), indicating the differential effects of GDY and GO on endothelial activation. Neither GDY nor GO induced intracellular superoxide. However, GO significantly promoted the expression of endoplasmic reticulum (ER) stress genes activating transcription factor 4 (ATF4) and X-box binding protein 1 spliced (XBP-1s), as well pyroptosis genes NLR family pyrin domain containing 3 (NLRP3) and gasdermin D (GSDMD), whereas GDY did not show this effect. The results suggested that GDY and GO could be internalized into HUVECs leading to cytotoxic effects. However, GO was more potent to activate endothelial activation probably due to the activation of ER stress and pyroptosis genes.

Comparison of multi-walled carbon nanotubes and halloysite nanotubes on lipid profiles in human umbilical vein endothelial cells

Tubular nanomaterials (NMs), such as multi-walled carbon nanotubes (MWCNTs) and halloysite nanotubes (HNTs), may be used in biomedicine, but previous studies showed that MWCNTs induced toxicity to endothelial cells (ECs). However, the influence of tubular NMs on EC lipid profiles has gained little attention, probably because ECs are not traditionally considered to be involved in regulating lipid homeostasis. This study compared the different effects of MWCNTs and HNTs on lipid profile changes in human umbilical vein ECs (HUVECs). The results showed that MWCNTs but not HNTs of the same mass concentrations induced cytotoxicity, ultrastuctural changes and intracellular thiol depletion. Meanwhile, only MWCNTs promoted lipid accumulation due to the induction of ER stress leading to up-regulation of fatty acid synthase (FASN). Interestingly, lipidomics results showed that the main lipid classes induced by MWCNTs but not HNTs were ceramide (Cer) and phosphatidylinositol (PI), with most of the lipid classes unaltered or even decreased after NM exposure. Then, extra Cer and PI were added to explore the implications of increase of these lipids. Adding Cer promoted the cytotoxicity of MWCNTs to HUVECs, indicating the lipotoxic role of Cer. Whereas adding PI partially increased intracellular NO and decreased interleukin-6 (IL-6) release due to MWCNT exposure, indicating the signaling role of PI. These results indicated novel roles of lipid dysfunction in NM-induced toxicity to ECs, even though ECs are not the professional cells for controlling lipid homeostasis.

Recent advances in nanomaterials for therapy and diagnosis for atherosclerosis

Atherosclerosis is a chronic inflammatory disease driven by lipid accumulation in arteries, leading to narrowing and thrombosis. It affects the heart, brain, and peripheral vessels and is the leading cause of mortality in the United States. Researchers have strived to design nanomaterials of various functions, ranging from non-invasive imaging contrast agents, targeted therapeutic delivery systems to multifunctional nanoagents able to target, diagnose, and treat atherosclerosis. Therefore, this review aims to summarize recent progress (2017-now) in the development of nanomaterials and their applications to improve atherosclerosis diagnosis and therapy during the preclinical and clinical stages of the disease.

Proteomic identification of the proteins related to cigarette smoke-induced cardiac hypertrophy in spontaneously hypertensive rats

Smoking increases the risk of cardiovascular diseases. The present study was designed to determine the effects of 2-month exposure to cigarette smoke (CS) on proteins in the left ventricles of spontaneously hypertensive rats (SHR) and to identify the molecular targets associated with the pathogenesis/progression of CS-induced cardiac hypertrophy. SHR and Wistar Kyoto rats (WKY) were exposed to CS at low (2 puffs/min for 40 min) or high dose (2 puffs/min for 120 min), 5 days a week for 2 months. Using the two-dimensional fluorescence difference gel electrophoresis combined with MALDI-TOF/TOF tandem mass spectrometry, we compared differences in the expression levels of proteins in the whole left ventricles induced by long-term smoking. High-dose CS mainly caused cardiac hypertrophy in SHR, but not WKY, but no change in blood pressure. Proteomic analysis identified 30 protein spots with significant alterations, with 14 up-regulated and 16 down-regulated proteins in the left ventricles of CS-exposed SHR, compared with control SHR. Among these proteins, two members of the heat shock proteins (HSP70 and HSP20) showed significant up-regulation in the left ventricles of CS high-dose SHR, and the results were confirmed by western blot analysis. Our findings suggested that HSPs play an important role in regulation of CS-induced cardiac hypertrophy.

Susceptibility Factors in Chronic Lung Inflammatory Responses to Engineered Nanomaterials

Engineered nanomaterials (ENMs) are products of the emerging nanotechnology industry and many different types of ENMs have been shown to cause chronic inflammation in the lungs of rodents after inhalation exposure, suggesting a risk to human health. Due to the increasing demand and use of ENMs in a variety of products, a careful evaluation of the risks to human health is urgently needed. An assessment of the immunotoxicity of ENMs should consider susceptibility factors including sex, pre-existing diseases, deficiency of specific genes encoding proteins involved in the innate or adaptive immune response, and co-exposures to other chemicals. This review will address evidence from experimental animal models that highlights some important issues of susceptibility to chronic lung inflammation and systemic immune dysfunction after pulmonary exposure to ENMs.

Evaluation of toxicity of halloysite nanotubes and multi-walled carbon nanotubes to endothelial cells in vitro and blood vessels in vivo

Nanomaterials (NMs) with tubular structures, such as halloysite nanotubes (HNTs), have potential applications in biomedicine. Although the biocompatibility of HNTs has been investigated before, the toxicity of HNTs to blood vessels is rarely systemically evaluated. Herein, we compared the toxicity of HNTs and multi-walled carbon nanotubes (MWCNTs) to human umbilical vein endothelial cells (HUVECs) in vitro and blood vessels of mice in vivo. HUVECs internalized HNTs and MWCNTs, but the uptake of HNTs was not obviously changed by clathrin inhibitor. Exposure to NMs decreased cellular viability, activated apoptotic proteins and up-regulated adhesion molecules, including soluble vascular cell adhesion molecule 1 (sVCAM-1) and VCAM-1. As the mechanisms, NMs decreased NO levels, eNOS mRNA and eNOS/p-eNOS proteins. Meanwhile, NMs promoted intracellular ROS and autophagy dysfunction, shown as decreased protein levels of LC3, beclin-1 and ATG5. The eNOS regulator Kruppel-like factor 4 (KLF4) was inhibited, but another eNOS regulator KLF4 was surprisingly up-regulated. Under in vivo conditions, ICR mice intravenously injected with NMs (50 μg/mouse, once a day for 5 days) showed an increased percentage of neutrophils, monocytes and basophils. Meanwhile, autophagy dysfunction, eNOS uncoupling, activation of apoptotic proteins and alteration of KLF proteins were also observed in mouse aortas. All of the toxic effects were more pronounced for MWCNTs in comparison with HNTs based on the same mass concentrations. Our results may provide novel insights about the toxicity of NMs with tubular structures to blood vessels. Considering the toxicological data reported here, HNTs are probably safer nanocarriers compared with MWCNTs.

Toxicity of Carbon Nanotubes as Anti-Tumor Drug Carriers

Nanoparticle drug formulations have enormous application prospects owing to achievement of targeted and sustained release drug delivery, improvement in drug solubility and reduction of adverse drug reactions. Recently, a variety of efficient drug nanometer carriers have been developed, among which carbon nanotubes (CNT) have been increasingly utilized in the field of cancer therapy. However, these nanotubes exert various toxic effects on the body due to their unique physical and chemical properties. CNT-induced toxicity is related to surface modification, degree of aggregation in vivo, and nanoparticle concentration. This review has focused on the potential toxic effects of CNTs utilized as anti-tumor drug carriers. The main modes by which CNTs enter target sites, the toxicity expressive types and the factors affecting toxicity are discussed.

Pharmacological and toxicological aspects of carbon nanotubes (CNTs) to vascular system: A review

Carbon nanotubes (CNTs) are novel carbon based nanomaterials (NMs) that could be used in many areas ranging from electronics to biotechnology. The present review summarized pharmacological and toxicological aspects of CNTs to vascular systems, because the vascular systems are important targets for CNTs during manufacturing process, daily contact and biomedical uses. Functionalized CNTs could be used as novel nanoplateforms to regulate angiogenesis for cancer therapy, as well as nanocarriers to cross blood brain barrier (BBB), one of the major obstacles to prevent the entering of therapeutic substances into brains. However, it has also been shown that inhalational or intravenous contact with CNTs might induce adverse vascular effects, such as progression of atherosclerotic plaque, vasomotor dysfunction, and changes of blood pressure and/or heart rate in laboratory animals, although currently there are only limited reports obtained from CNT-exposed human beings and the results are inconclusive. The mechanisms associated with the vascular toxicity of CNTs remain poorly understood, and it appears that multiple signaling pathways are likely to be involved. The toxicity of CNTs to vascular systems might be reduced by controlling the physicochemical properties of CNTs, particularly lengths, diameters and surface chemistry. At present, the beneficial and adverse effects of CNTs to vascular systems are still largely unknown and require further extensive studies.

The toxicity of multi-walled carbon nanotubes (MWCNTs) to human endothelial cells: The influence of diameters of MWCNTs

The biological applications of multi-walled carbon nanotubes (MWCNTs) may lead to their exposure to human blood vessels, but the influence of their physicochemical properties on toxicity to endothelial cells is incompletely known. Here, human umbilical vein endothelial cells (HUVECs) were exposed to three commercially available MWCNTs, namely XFM4, XFM22, and XFM34 (diameters XFM4 < XFM22 < XFM34), to understand the possible role of their diameter on toxicity. Based on the same mass concentration, XFM4 induced significantly higher level of cytotoxicity than the other two MWCNTs, and HUVECs internalized more XFM4. Cytokine release, monocyte adhesion, and intracellular reactive oxygen species levels were significantly induced only after XFM4 treatment. The exposure to XFM4 significantly reduced the expression of autophagic genes autophagy-related 7 (ATG7), autophagy-related 12 (ATG12), and beclin 1 (BECN1) and increased the expression of endoplasmic reticulum (ER) stress genes DNA damage inducible transcript 3 (DDIT3) and X-box binding protein 1 spliced (XBP-1s). Moreover, the modulation of autophagy-ER stress by chemicals resulted in a significant increase in the cytotoxicity of XFM4 but had minimal impact on the cytotoxicity of XFM34. These data indicate that the diameter of MWCNTs may influence their toxicity to HUVECs, probably through autophagy dysfunction and ER stress.

Endothelial cell injury is involved in atherosclerosis and lupus symptoms in gld.apoE- / - mice

AIM

Cardiovascular complications related to atherosclerosis are major causes of morbidity and mortality in patients with systemic lupus erythematosus (SLE). However, the underlying mechanisms are not fully understood. Endothelial dysfunction has been identified as having involvement in pathogenesis of cardiovascular diseases and SLE. This study aims to evaluate endothelial cell injury in mice with the combination of lupus and atherosclerosis.

METHODS

The mouse model of accelerated atherosclerosis in lupus (gld.apoE^{- / -} mouse) was generated from apolipoprotein E-deficient (apoE^{- / -} ) and Fasl^gld C57BL/6 mice. The lupus-like autoimmunity and atherosclerotic lesions were evaluated. The endothelial cell injury was determined.

RESULTS

The results showed that the double-mutant gld.apoE^{- / -} mice were generated. Spleens from 5-month-old gld.apoE^{- / -} mice were significantly enlarged compared with wild-type mice (WT mice). The gld.apoE^{- / -} mice produced high levels of total immunoglobulin G (IgG) and IgM and showed marked increase of IgG and C3 deposits in the glomeruli. The gld.apoE^{- / -} mice displayed a pattern of glomerulonephritis typically found in SLE. The gld.apoE^{- / -} mice have high levels of serum creatinine. The total cholesterol, low-density lipoprotein cholesterol and triglycerides were significantly increased, while high-density lipoprotein cholesterol decreased in the double-mutant mice. The circulating endothelial progenitor cells were significantly decreased. The serum levels of thrombomodulin and vascular cell adhesion molecule-1 were significantly elevated in gld.apoE^{- / -} mice. The gld.apoE^{- / -} mice simultaneously exhibited SLE and atherosclerosis characteristics.

CONCLUSION

Our findings indicated that endothelial cell injury might be a biomarker for evaluating risks of cardiovascular disease in SLE and targeting endothelial cell dysfunction might prevent and treat atherosclerosis in SLE.

The Yin and Yang of carbon nanomaterials in atherosclerosis

With unique characteristics such as high surface area, capacity of various functionalization, low weight, high conductivity, thermal and chemical stability, and free radical scavenging, carbon nanomaterials (CNMs) such as carbon nanotubes (CNTs), fullerene, graphene (oxide), carbon nanohorns (CNHs), and their derivatives have increasingly been utilized in nanomedicine and biomedicine. On the one hand, owing to ever-increasing applications of CNMs in technological and industrial fields as well as presence of combustion-derived CNMs in the ambient air, the skepticism has risen over the adverse effects of CNMs on human being. The influences of CNMs on cardiovascular system and cardiovascular diseases (CVDs) such as atherosclerosis, of which consequences are ischemic heart disease and ischemic stroke, as the main causes of death, is of paramount importance. In this regard, several studies have been devoted to specify the biomedical applications and cardiovascular toxicity of CNMs. Therefore, the aim of this review is to specify the roles and applications of various CNMs in atherosclerosis, and also identify the key role playing parameters in cardiovascular toxicity of CNMs so as to be a clue for prospective deployment of CNMs.

Cytotoxicity, cytokine release and ER stress-autophagy gene expression in endothelial cells and alveolar-endothelial co-culture exposed to pristine and carboxylated multi-walled carbon nanotubes

Recently we found that direct exposure of human umbilical vein endothelial cells (HUVECs) to multi-walled carbon nanotubes (MWCNTs) might induce toxicological responses through the modulation of ER stress gene expression, but whether this signal could be transferred from other cells to endothelial cells (ECs) is unknown. This study investigated the toxicity of pristine and carboxylated MWCNTs to HUVECs and alveolar-endothelial co-culture, the later of which could mimic the possible signaling communications between ECs and MWCNT exposed alveolar cells. The results showed that direct contact with high levels of MWCNTs induced cytotoxicity and modulated expression of genes associated with ER stress (HSPA5, DDIT3 and XBP-1s) and autophagy (BECN1 and ATG12) both in A549-THP-1 macrophages cultured in the upper chambers as well as HUVECs. However, most of these responses were minimal or negligible in HUVECs cultured in the lower chambers. Moreover, significantly increased cytokine release (interleukin-6 and soluble vascular cell adhesion molecule-1) was only observed in MWCNT exposed HUVECs (p < 0.01) but not HUVECs cultured in the lower chambers (p > 0.05). The minimal or even absent response was likely due to relatively low translocation of MWCNTs from upper chambers to lower chambers, whereas A549-macrophages cultured in the upper chambers internalized large amount MWCNTs. The results indicated that ER stress-autophagy signaling might not be able to transfer from alveolar cells to endothelial cells unless sufficient MWCNTs are translocated.

MicroRNAs as Potential Mediators for Cigarette Smoking Induced Atherosclerosis

Smoking increases the risk of atherosclerosis-related events, such as myocardial infarction and ischemic stroke. Recent studies have examined the expression levels of altered microRNAs (miRNAs) in various diseases. The profiles of tissue miRNAs can be potentially used in diagnosis or prognosis. However, there are limited studies on miRNAs following exposure to cigarette smoke (CS). The present study was designed to dissect the effects and cellular/molecular mechanisms of CS-induced atherosclerogenesis. Apolipoprotein E knockout (ApoE KO) mice were exposed to CS for five days a week for two months at low (two puffs/min for 40 min/day) or high dose (two puffs/min for 120 min/day). We measured the area of atherosclerotic plaques in the aorta, representing the expression of miRNAs after the exposure period. Two-month exposure to the high dose of CS significantly increased the plaque area in aortic arch, and significantly upregulated the expression of atherosclerotic markers (VCAM-1, ICAM-1, MCP1, p22phox, and gp91phox). Exposure to the high dose of CS also significantly upregulated the miRNA-155 level in the aortic tissues of ApoE KO mice. Moreover, the expression level of miR-126 tended to be downregulated and that of miR-21 tended to be upregulated in ApoE KO mice exposed to the high dose of CS, albeit statistically insignificant. The results suggest that CS induces atherosclerosis through increased vascular inflammation and NADPH oxidase expression and also emphasize the importance of miRNAs in the pathogenesis of CS-induced atherosclerosis. Our findings provide evidence for miRNAs as potential mediators of inflammation and atherosclerosis induced by CS.

Internalization, cytotoxicity, oxidative stress and inflammation of multi-walled carbon nanotubes in human endothelial cells: influence of pre-incubation with bovine serum albumin

When entering circulation, multi-walled carbon nanotubes (MWCNTs) will inevitably adsorb proteins, which can consequently influence their toxicity to cells lining human blood vessels. In this study, we investigated the influence of pre-incubation with bovine serum albumin (BSA) on internalization, cytotoxicity, oxidative stress and inflammation induced by pristine/carboxylated MWCNTs to human umbilical vein endothelial cells (HUVECs). Atomic force microscopy (AFM) indicated the adsorption of proteins onto the surface of MWCNTs, which consequently increased the diameter. Pre-incubation with BSA did not obviously influence the hydrodynamic sizes, but decreased the zeta potential of MWCNTs. Transmission electron microscopy (TEM) indicated the internalization of both types of MWCNTs into HUVECs, whereas pre-incubation with BSA appeared to enhance the internalization. MWCNT exposure induced cytotoxicity and oxidative stress, as well as a modest inflammatory response shown as an increased THP-1 adhesion to HUVECs, but not release of interleukin 6 (IL-6) or tumor necrosis factor (TNFα). Exposure to MWCNTs pre-incubated with BSA induced less cytotoxicity to HUVECs, associated with increased intracellular glutathione (GSH). However, MWCNTs induced IL-6 and TNFα release, as well as THP-1 adhesion to HUVECs, were enhanced after pre-incubation with BSA. In summary, these data indicated that pre-incubation with BSA could enhance the internalization of MWCNTs to HUVECs, which consequently reduces the cytotoxicity and oxidative stress, but enhances the inflammatory response of MWCNTs. The reduced cytotoxicity and oxidative stress, and enhanced inflammatory responses are likely due to a combined effect of BSA and MWCNTs, which suggests that when assessing the biological effects of MWCNTs in circulation, it is necessary to consider the interactions between MWCNTs and serum proteins.

The adverse vascular effects of multi-walled carbon nanotubes (MWCNTs) to human vein endothelial cells (HUVECs) in vitro: role of length of MWCNTs

BACKGROUND

Increasing evidences indicate that exposure to multi-walled carbon nanotubes (MWCNTs) could induce adverse vascular effects, but the role of length of MWCNTs in determining the toxic effects is less studied. This study investigated the adverse effects of two well-characterized MWCNTs to human umbilical vein endothelial cells (HUVECs).

METHODS

The internalization and localization of MWCNTs in HUVECs were examined by using transmission electron microscopy (TEM). The cytotoxicity of MWCNTs to HUVECs was assessed by water soluble tetrazolium-8 (WST-8), lactate dehydrogenase (LDH) and neutral red uptake assays. Oxidative stress was indicated by the measurement of intracellular glutathione (GSH) and reactive oxygen species (ROS). ELISA was used to determine the release of inflammatory cytokines. THP-1 monocyte adhesion to HUVECs was also measured. To indicate the activation of endoplasmic reticulum (ER) stress, the expression of ddit3 and xbp-1s was measured by RT-PCR, and BiP protein level was measured by Western blot.

RESULTS

Transmission electron microscopy observation indicates the internalization of MWCNTs into HUVECs, with a localization in nuclei and mitochondria. The longer MWCNTs induced a higher level of cytotoxicity to HUVECs compared with the shorter ones. Neither of MWCNTs significantly promoted intracellular ROS, but the longer MWCNTs caused a higher depletion of GSH. Exposure to both types of MWCNTs significantly promoted THP-1 adhesion to HUVECs, accompanying with a significant increase of release of interleukin-6 (IL-6) but not tumor necrosis factor α (TNFα), soluble ICAM-1 (sICAM-1) or soluble VCAM-1 (sVCAM-1). Moreover, THP-1 adhesion and release of IL-6 and sVCAM-1 induced by the longer MWCNTs were significantly higher compared with the responses induced by the shorter ones. The biomarker of ER stress, ddit3 expression, but not xbp-1s expression or BiP protein level, was significantly induced by the exposure of longer MWCNTs.

CONCLUSIONS

Combined, these results indicated length dependent toxic effects of MWCNTs to HUVECs in vitro, which might be associated with oxidative stress and activation of ER stress.

Thrombospondin-1 mediates multi-walled carbon nanotube induced impairment of arteriolar dilation

Pulmonary exposure to multi-walled carbon nanotubes (MWCNT) has been shown to disrupt endothelium-dependent arteriolar dilation in the peripheral microcirculation. The molecular mechanisms behind these arteriolar disruptions have yet to be fully elucidated. The secreted matricellular matrix protein thrombospondin-1 (TSP-1) is capable of moderating arteriolar vasodilation by inhibiting soluble guanylate cyclase activity. We hypothesized that TSP-1 may be a link between nanomaterial exposure and observed peripheral microvascular dysfunction. To test this hypothesis, wild-type C57B6J (WT) and TSP-1 knockout (KO) mice were exposed via lung aspiration to 50 μg MWCNT or a Sham dispersion medium control. Following exposure (24 h), arteriolar characteristics and reactivity were measured in the gluteus maximus muscle using intravital microscopy (IVM) coupled with microiontophoretic delivery of acetylcholine (ACh) or sodium nitroprusside (SNP). In WT mice exposed to MWCNT, skeletal muscle TSP-1 protein increased > fivefold compared to Sham exposed, and exhibited a 39% and 47% decrease in endothelium-dependent and -independent vasodilation, respectively. In contrast, TSP-1 protein was not increased following MWCNT exposure in KO mice and exhibited no loss in dilatory capacity. Microvascular leukocyte-endothelium interactions were measured by assessing leukocyte adhesion and rolling activity in third order venules. The WT + MWCNT group demonstrated 223% higher leukocyte rolling compared to the WT + Sham controls. TSP-1 KO animals exposed to MWCNT showed no differences from the WT + Sham control. These data provide evidence that TSP-1 is likely a central mediator of the systemic microvascular dysfunction that follows pulmonary MWCNT exposure.