In vitro systems toxicology-based assessment of the potential modified risk tobacco product CHTP 1.2 for vascular inflammation- and cytotoxicity-associated mechanisms promoting adhesion of monocytic cells to human coronary arterial endothelial cells

Human Umbilical Vein Endothelial Cells as a Versatile Cellular Model System in Diverse Experimental Paradigms: An Ultrastructural Perspective

Human umbilical vein endothelial cells (HUVECs) are primary cells isolated from the vein of an umbilical cord, extensively used in cardiovascular studies and medical research. These cells, retaining the characteristics of endothelial cells in vivo, serve as a valuable cellular model system for understanding vascular biology, endothelial dysfunction, pathophysiology of diseases such as atherosclerosis, and responses to different drugs or treatments. Transmission electron microscopy (TEM) has been a cornerstone in revealing the detailed architecture of multiple cellular model systems including HUVECs, allowing researchers to visualize subcellular organelles, membrane structures, and cytoskeletal elements. Among them, the endoplasmic reticulum, Golgi apparatus, mitochondria, and nucleus can be meticulously examined to recognize alterations indicative of cellular responses to various stimuli. Importantly, Weibel-Palade bodies are characteristic secretory organelles found in HUVECs, which can be easily distinguished in the TEM. These distinctive structures also dynamically react to different factors through regulated exocytosis, resulting in complete or selective release of their contents. This detailed review summarizes the ultrastructural features of HUVECs and highlights the utility of TEM as a pivotal tool for analyzing HUVECs in diverse research frameworks, contributing valuable insights into the comprehension of HUVEC behavior and enriching our knowledge into the complexity of vascular biology.

Optimisation of an in vitro human cardiovascular model on-a-chip for toxicological assessment of nicotine delivery products

Background

Smoking cigarettes is a cause of serious diseases in smokers, including cardiovascular disease. Through a pathway of endothelial dysfunction, lipid infiltration, macrophage recruitment and vascular remodeling, atherosclerosis is fundamental in the development of most cardiovascular diseases. There is an increasing number of next-generation products (NGP) which provide potentially reduced harm forms of nicotine delivery to adult smokers. This study aimed to optimise an in vitro cardiovascular model to assess such products. Human Coronary Artery Endothelial Cells (HCAECs) were cultured on an OrganoPlate®2-lane chip (Mimetas BV) combined with THP-1 monocytes under flow conditions.

Methods

An aqueous aerosol extract from the 1R6F reference cigarette was compared with two categories of NGP, (a heated tobacco product (HTP) and an electronic nicotine delivery system (ENDS)), to assess relative effects on select atherogenic endpoints (oxidative stress, monocyte adhesion, ICAM-1 expression, and inflammatory markers). Following exposure of THP-1 monocytes with the aqueous extracts, the resulting conditioned medium was then added to the HCAEC vessels.

Results

1R6F was consistently the most potent test article, eliciting observed responses at 4x lower concentrations than applied for both the HTP and ENDS. The HTP was more potent than the ENDS product across all endpoints, however, all test articles increased monocyte adhesion. ICAM-1 did not appear to be a main driver for monocyte adhesion, however, this could be due to replicate variability. Upon comparison to an extract-only control exposure, THP-1-medium pre-conditioning was an important mediator of the responses observed.

Conclusion

In conclusion, the data suggests that the NGP extracts, containing primary aerosol chemical constituents exhibit a marked reduction in biological activity in the early key events associated with atherogenesis when compared to a cigarette, adding to the weight of evidence for the tobacco harm reduction potential of such products.

Research progress and prospect on the safety of heated tobacco products

In recent years, Heated tobacco products (HTP) have gradually entered the market and become more and more popular with consumers because of their low risk (compared with traditional cigarette). With the increasing popularity and proportion of HTP in the international market, people pay more and more attention to the safety evaluation of HTP, but there is still a lack of systematic review of HTP safety research. In this review, the harmful components of HTP, multi-organ functional programming effects (including respiratory system, cardiovascular system, etc.), and mechanism of the effect generation (including oxidative stress, inflammatory response, etc.) were systematically reviewed, the safety effects of HTP and traditional cigarettes were compared in detail, and the shortcomings and future research directions in the field of HTP safety were discussed. In summary, this review conforms to the general trend of contemporary "tobacco and health", helps people to understand and evaluate HTP more systematically, and provides a strong theoretical support and literature basis for the tobacco industry to carry out HTP risk assessment and exposure improvement.

Comparative study of the effects of cigarette smoke versus next-generation tobacco and nicotine product extracts on inflammatory biomarkers of human monocytes

Monocytes exhibiting a pro-inflammatory phenotype play a key role in adhesion and development of atherosclerotic plaques. As an alternative to smoking, next-generation tobacco and nicotine products (NGP) are now widely used. However, little is known about their pro-inflammatory effects on monocytes. We investigated cell viability, anti-oxidant and pro-inflammatory gene and protein expression in THP-1 monocytes after exposure to aqueous smoke extracts (AqE) of a heated tobacco product (HTP), an electronic cigarette (e-cig), a conventional cigarette (3R4F) and pure nicotine (nic). Treatment with 3R4F reduced cell viability in a dose-dependent manner, whereas exposure to alternative smoking products showed no difference to control. At the highest non-lethal dose of 3R4F (20%), the following notable mRNA expression changes were observed for 3R4F, HTP, and e-cig respectively, relative to control; HMOX1 (6-fold, < 2-fold, < 2-fold), NQO1 (3.5-fold, < 2-fold, < 2-fold), CCL2 (4-fold, 3.5-fold, 2.5-fold), IL1B (4-fold, 3-fold, < 2-fold), IL8 (5-fold, 2-fold, 2-fold), TNF (2-fold, 2-fold, < 2-fold) and ICAM1 was below the 2-fold threshold for all products. With respect to protein expression, IL1B (3-fold, < 2-fold, < 2-fold) and IL8 (3.5-fold, 2-fold, 2-fold) were elevated over the 2-fold threshold, whereas CCL2, TNF, and ICAM1 were below 2-fold expression for all products. At higher doses, greater inductions were observed with all extracts; however, NGP responses were typically lower than 3R4F. In conclusion, anti-oxidative and pro-inflammatory processes were activated by all products. NGPs overall showed lower responses relative to controls than THP-1 cells exposed to 3R4F AqE.

Human vasculature-on-a-chip with macrophage-mediated endothelial activation: The biological effect of aerosol from heated tobacco products on monocyte adhesion

Heated tobacco products (HTPs) are expected to have the potential to reduce risks of smoking-associated cardiovascular disease (CVD). However, mechanism-based investigations of the effect of HTPs on atherosclerosis remain insufficient and further studies under human-relevant situations are desired for deeper understanding of the reduced risk potential of HTPs. In this study, we first developed an in vitro model of monocyte adhesion by considering macrophage-derived proinflammatory cytokine-mediated endothelial activation using an organ-on-a-chip (OoC), which provided great opportunities to mimic major aspects of human physiology. Then biological activities of aerosol from three different types of HTPs in terms of monocyte adhesion were compared with that of cigarette smoke (CS). Our model showed that the effective concentration ranges of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were close to the actual condition in CVD pathogenesis. The model also showed that monocyte adhesion was less induced by each HTP aerosol than CS, which may be caused by less proinflammatory cytokine secretion. In summary, our vasculature-on-a-chip model assessed the difference in biological effects between cigarettes and HTPs, and suggested a reduced risk potential of HTPs for atherosclerosis.

Alpha-Lipoic Acid Modulates the Oxidative and Inflammatory Responses Induced by Traditional and Novel Tobacco Products in Human Liver Epithelial Cells

Smoking has been associated with NAFLD recently, thus might be a contributing factor for liver disease progression. In this study, we identified the modulative action of α-lipoic acid (α-LA), an organosulphur compound, towards heated tobacco product (HTP) and cigarette smoke extract (CSE)-induced oxidative stress and inflammation in human liver HepG2 cells. The cells were pre-treated with α-LA and exposed to tobacco extracts, and cytotoxicity, oxidative response (SOD, CAT activities and GSH, MDA levels), inflammation (nitrite, IL-6, AhR levels), and liver function (AST/ALT) were assessed. According to the results, a notable increase in oxidative response was observed with CSE, whereas GSH depletion and decreased SOD activity were the key toxicological events induced by HTP (p<0.05). The oxidative and inflammatory responses were ameliorated with α-LA treatment, particularly through GSH restoration and IL-6 modulation. To conclude, these findings on α-LA might contribute to the design of novel adjuvant therapies for people exposed to tobacco smoke.

The Frequency of Use and Harm Perception of Heated Tobacco Products (HTPs): The 2019 Cross-Sectional Survey among Medical Students from Poland

Heated tobacco products (HTPs) are devices for generating a nicotine aerosol by heating the tobacco sticks. This study aimed to assess (1) the prevalence of HTP and tobacco cigarette usage among medical students, (2) to characterize smoking habits and (3) to assess students’ awareness and opinions about HTPs. A cross-sectional survey on the frequency and attitudes toward cigarettes, e-cigarettes and HTP use was performed between 2019–2020 at the Medical University of Silesia in Katowice (Poland). The data were obtained from 1344 students aged 21.8 ± 1.9 years (response rate: 66.9%). Current traditional tobacco use was 13.2%, e-cigarettes use 3.5%, and HTP use 2.8% of students. Duration of use was shorter among HTPs users comparing to cigarette smokers (p < 0.001) although the number of tobacco sticks used daily was similar (p = 0.1). Almost 30% of respondents have ever tried HTPs. HTPs were considered safe by 5.3% of respondents (43.2% of HTP users vs. 3.9% of non-HTP users, p < 0.001). HTP users were more likely to report that heating tobacco is not addictive (odds ratio (OR) = 8.9, 95% confidence interval (CI): 1.8–45.8) and disagreed with a public ban on HTP use (OR = 4.9, 95%CI: 2.5–9.8). Among students, HTP use was less popular than cigarette smoking, but awareness of their presence is widespread.

Evaluation of a high-throughput in vitro endothelial cell migration assay for the assessment of nicotine and tobacco delivery products

Endothelial cell migration is a critical process in the maintenance of healthy blood vessels. Impaired endothelial migration is reportedly associated with the development of cardiovascular diseases. Here, we report on the development of a 96-well in vitro endothelial migration assay for the purpose of comparative toxicological assessment of a novel THP relative to cigarette smoke, to be able to rapidly inform regulatory decision making. Uniform scratches were induced in confluent human umbilical vein endothelial cells using the 96-pin wound maker and exposed to 3R4F cigarette or THP aqueous extracts (AqE). Endothelial migration was recorded over 24 h, and the rate of wound closure calculated using mean relative wound density rather than migration rate as previously reported. This self-normalising parameter accounts for starting wound size, by comparing the density of the scratch to the outer region at each time-point. Furthermore, wound width acceptance criteria was defined to further increase the sensitivity of the assay. 3R4F and THP AqE samples were tested at comparable nicotine concentrations. 3R4F showed significant cytotoxicity and inhibition of wound healing whereas THP AqE did not show any response in either endpoint. This 96-well endothelial migration assay was suitably sensitive to distinguish combustible cigarette and THP test articles.

Optimization of aqueous aerosol extract (AqE) generation from e-cigarettes and tobacco heating products for in vitro cytotoxicity testing

Electronic cigarettes (e-cigarettes) and tobacco heating products (THPs) have reduced yields of toxicants and have recently emerged as a potentially safer alternative to combustible cigarettes. To understand if reduced toxicant exposure is associated with reductions in biological responses, there is a need for high-quality pre-clinical in vitro studies. Here, we investigated the cytotoxic response of human umbilical vein endothelial cells to conventional cigarette aqueous aerosol extracts (AqE) and highly concentrated AqEs from e-cigarettes (two generations of atomisers) and THPs (two variants). All AqE samples were generated by a standardized methodology and characterized for nicotine, propylene glycol and vegetable glycerol. The cigarette AqE caused a maximum 100 ± 0.00 % reduction in cell viability at 35 % dose (2.80 puffs) as opposed to 96.63 ± 2.73 % at 50 % (20 puffs) and 99.85 ± 0.23 % at 75 % (30 puffs) for the two THP variants (glo Bright Tobacco, glo Rich Tobacco), and 99.07 ± 1.61 % at the neat ePen2.0 e-cigarette (200 puffs). The AqE of the remaining e-cigarettes either resulted in an incomplete dose-response or did not elicit any response. The methods utilized were suitably sensitive to not only differentiate between cigarette, THP and e-cigarette aerosols but also to distinguish between products within each product category.

Comparing the preclinical risk profile of inhalable candidate and potential candidate modified risk tobacco products: A bridging use case

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Heated tobacco products tested for reduced exposure and reduced risk properties.

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Bridging opportunities for nonclinical results from two heated tobacco products.

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Similarly reduced impact on apical and molecular endpoints relative to cigarettes.

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Evidence evaluated along a “causal chain of events leading to disease” (CELSD).

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Representative assays along CELSD could support nonclinical substantial equivalence.

Cigarette smoking causes major preventable diseases, morbidity, and mortality worldwide. Smoking cessation and prevention of smoking initiation are the preferred means for reducing these risks. Less harmful tobacco products, termed modified-risk tobacco products (MRTP), are being developed as a potential alternative for current adult smokers who would otherwise continue smoking. According to a regulatory framework issued by the US Food and Drug Administration, a manufacturer must provide comprehensive scientific evidence that the product significantly reduces harm and the risk of tobacco-related diseases, in order to obtain marketing authorization for a new MRTP. For new tobacco products similar to an already approved predicate product, the FDA has foreseen a simplified procedure for assessing “substantial equivalence”. In this article, we present a use case that bridges the nonclinical evidence from previous studies demonstrating the relatively reduced harm potential of two heat-not-burn products based on different tobacco heating principles. The nonclinical evidence was collected along a “causal chain of events leading to disease” (CELSD) to systematically follow the consequences of reduced exposure to toxicants (relative to cigarette smoke) through increasing levels of biological complexity up to disease manifestation in animal models of human disease. This approach leverages the principles of systems biology and toxicology as a basis for further extrapolation to human studies. The experimental results demonstrate a similarly reduced impact of both products on apical and molecular endpoints, no novel effects not seen with cigarette smoke exposure, and an effect of switching from cigarettes to either MRTP that is comparable to that of complete smoking cessation. Ideally, a subset of representative assays from the presented sequence along the CELSD could be sufficient for predicting similarity or substantial equivalence in the nonclinical impact of novel products; this would require further validation, for which the present use case could serve as a starting point.

Exposure to harmful and potentially harmful constituents decreased in smokers switching to Carbon-Heated Tobacco Product

BACKGROUND

"Heat-not-burn" tobacco products are designed to heat processed tobacco instead of combusting it, thus significantly reducing the formation of harmful and potentially harmful constituents (HPHCs) found in cigarette smoke, and ultimately reducing the risk of smoking-related diseases. The Carbon-Heated Tobacco Product (CHTP), a heat-not-burn tobacco product similar in appearance and use ritual to cigarettes, has been developed for smokers who would otherwise continue smoking as an alternative to cigarettes. To evaluate reduced risk of harm potential of CHTP, it is critical to quantify exposure to HPHCs and consequent biological pathway disturbances involved in disease onset in smokers who switch to CHTP.

METHODS

In this 2-arm, parallel-group study, adult healthy smokers, not willing to quit, were randomized to switch to CHTP 1.2 (n = 80) or to continue using cigarettes (n = 40) for 5 days in confinement followed by 85 days in an ambulatory setting. Endpoints included biomarkers of exposure (BoExp) to HPHCs, and to nicotine, urinary excretion of mutagenic constituents (Ames assay), CYP1A2 activity, biomarkers of effect, and safety.

RESULTS

In switchers to CHTP, BoExp were 40%-95% lower compared to smokers after 5 days of product use, with sustained reductions (36%-93%) observed on Day 90. Urine mutagenicity and CYP1A2 activity were also lower in the CHTP group. Exposure to nicotine was higher in the CHTP group at Day 5, but was similar between the two groups at Day 90. Favorable changes in some biomarkers of effect were observed in the CHTP group showing reductions in white blood cell count, soluble intracellular adhesion molecule-1, and 11-dehydro-thromboxane B2, respectively, indicative of reduced inflammation, endothelial dysfunction, and platelet activation.

CONCLUSIONS

Switching from cigarettes to CHTP resulted in significantly reduced exposure to HPHCs and was associated with observed improvements in some biomarkers of effect representative of pathomechanistic pathways underlying the development of smoking-related diseases.

Anthocyanins and metabolites resolve TNF-α-mediated production of E-selectin and adhesion of monocytes to endothelial cells

This study investigated the capacity of an anthocyanin-rich fraction (ACN-RF) from blueberry, single anthocyanins (cyanidin, delphinidin and malvidin-3-glucoside; Cy, Dp and Mv-3-glc) and related metabolites (protocatechuic, gallic and syringic acid; PrA, GA and SA) to resolve an inflammation-driven adhesion of monocytes (THP-1) on endothelial cell (HUVECs) and secretion of cell adhesion molecules E-selectin and vascular cell adhesion molecule 1 (VCAM-1). The adhesion of THP-1 to HUVECs was induced by tumour necrosis factor α (TNF-α, 100 ng mL^-1). Subsequently, ACN-RF, single ACNs and metabolites (from 0.01 to 10 μg mL^-1) were incubated for 24 h. The adhesion was measured in a fluorescence spectrophotometer. E-selectin and VCAM-1 were quantified by ELISA. No toxicological effects were observed for the compounds and the doses tested. ACN-RF and Mv-3-glc reducedTHP-1 adhesion at all the concentrations with the maximum effect at 10 μg/ml (-60.2% for ACNs and-33.9% for Mv-3-glc). Cy-3-glc decreased the adhesion by about 41.8% at 10 μg mL^-1, while PrA and GA reduced the adhesion of THP-1 to HUVECs both at 1 and at 10 μg mL^-1 (-29.5% and -44.3% for PrA, respectively, and -18.0%and -59.3% for GA, respectively). At the same concentrations a significant reduction of E-selectin, but notVCAM-1 levels, was documented. No effect was observed following Dp-3-glc and SA supplementation. Overall, ACNs and metabolites seem to resolve, in a dose-dependent manner, the inflammation-driven adhesion of THP-1 to HUVECs by decreasing E-selectin concentrations. Interestingly, Mv-3-glc was active at physiologically relevant concentrations.