Effects of benzalkonium chloride on cell viability, inflammatory response, and oxidative stress of human alveolar epithelial cells cultured in a dynamic culture condition

Is it time to re-evaluate exposure risks to quaternary ammonium compounds as disinfectants?

•The use of quaternary ammonium compounds (QACs) as disinfectants has increased exponentially due to the COVID-19 pandemic.•There is, thus, a corresponding increase in human exposure to these compounds.•New studies reveal important human health concerns.•A re-evaluation of the use of these compounds is in order.•A change over to newer and safer products may bode well for the future.

Melatonin mediated tolerance to benzalkonium chloride phytotoxicity through improved growth, photochemical reactions, and antioxidant system in wild-type and snat2 mutant Arabidopsis lines

Melatonin (Mel) is a phytohormone that plays a crucial role in various plant processes, including stress response. Despite numerous studies on the role of Mel in stress resistance, its significance in plants exposed to benzalkonium chloride (BAC) pollution remains unexplored. BAC, a common antiseptic, poses a threat to terrestrial plants due to its widespread use and inefficient removal, leading to elevated concentrations in the environment. This study investigated the impact of BAC (0.5 mg L-1) pollution on wild-type Col-0 and snat2 knockout mutant Arabidopsis lines, revealing reduced growth, altered water relations, and gas exchange parameters. On the other hand, exogenous Mel (100 μM) treatments mitigated BAC-induced phytotoxicity and increased the growth rate by 1.8-fold in Col-0 and 2-fold in snat2 plants. snat2 mutant seedlings had a suppressed carbon assimilation rate (A) under normal conditions, but BAC contamination led to further A repression by 71% and 48% in Col-0 and snat2 leaves, respectively. However, Mel treatment on stressed plants was successful in improving Fv/Fm and increased the total photosynthesis efficiency by regulating photochemical reactions. Excessive H2O2 accumulation in the guard cells of plants exposed to BAC pollution was detected by confocal microscopy. Mel treatments triggered almost all antioxidant enzyme activities (except POX) in both Arabidopsis lines under stress. This enhanced antioxidant activity, facilitated by foliar Mel application, contributed to the alleviation of oxidative damage, regulation of photosynthesis reactions, and promotion of plant growth in Arabidopsis. In addition to corroborating results observed in many agricultural plants regarding the development of tolerance to environmental stresses, this study provides novel insights into the action mechanisms of Mel under the emerging pollutant benzalkonium chloride.

Risks of benzalkonium chlorides as emerging contaminants in the environment and possible control strategies from the perspective of ecopharmacovigilance

An unprecedented increase in the use of disinfection products triggered by the coronavirus disease 2019 (COVID-19) pandemic is resulting in aggravating environmental loads of disinfectants as emerging contaminants, which has been considered a cause for worldwide secondary disasters. This review analyzed the literature published in the last decade about occurrence, bioaccumulation, and possible environmental risks of benzalkonium chlorides (BKCs) as emerging contaminants. Results indicated that BKCs globally occurred in municipal wastewater, surface water, groundwater, reclaimed water, sludge, sediment, soil, roof runoff, and residential dust samples across 13 countries. The maximum residual levels of 30 mg/L and 421 μg/g were reported in water and solid environmental samples, respectively. Emerging evidences suggested possible bioaccumulation of BKCs in plants, even perhaps humans. Environmentally relevant concentrations of BKCs exert potential adverse impacts on aquatic and terrestrial species, including genotoxicity, respiratory toxicity, behavioural effects and neurotoxicity, endocrine disruption and reproductive impairment, phytotoxicity, etc. Given the intrinsic biocidal and preservative properties of disinfectants, the inductive effects of residual BKCs in environment in terms of resistance and imbalance of microorganisms have been paid special attention. Considering the similarities of disinfectants to pharmaceuticals, from the perspective of ecopharmacovigilance (EPV), a well-established strategy for pharmaceutical emerging contaminants, we use the control of BKC pollution as a case, and provide some recommendations for employing the EPV measures to manage environmental risks posed by disinfectant emerging contaminants.

A fish perspective on SARS-CoV-2: Toxicity of benzalkonium chloride on Danio rerio

SARS-CoV-2 outbreak led to an increased marketing of disinfectants, creating a potential environmental problem. For instance, pre-pandemic environmental levels of the disinfectant benzalkonium chloride (BAC) ranging from 0.5 to 5 mgL-1 in effluents were expected to further increase threatening aquatic life. Our aim was to characterize potential adverse effects after an acute exposure of zebrafish to different concentrations of BAC. An increase in the overall swimming activity, thigmotaxis behavior, and erratic movements were observed. An increase in CYP1A1 and catalase activities, but inhibitions of CY1A2, GSTs and GPx activities were also noticed. BAC is metabolized by CYP1A1, increasing the production of H2O2, thereby activating the antioxidant enzyme CAT. Data also showed an increase of AChE activity. Our study highlights adverse embryonic, behavioral, and metabolic effects of noteworthy environmental significance, especially considering that the use and release of BAC is most likely to increase in a near future.

The study of the cytotoxic effect of disinfectants

The toxicity of individual disinfectants has been studied in vitro using human cell cultures (HT-29 (epithelial-like cells of colon adenocarcinoma), HEK 293 (human embryonic kidney cells)) to create a model for assessing the toxicity of residual amounts of disinfectants that can enter milk for a person. Standard tests have been used to assess cell viability and amount: methyl tetrazolium (MTT) test, neutral red cell staining (NRP), and sulforhodamine B (SRB) test. Disinfectants have a dose- and time-dependent cytotoxic effect on human cell cultures. IC50avg (concentration of the drug that suppresses a certain cell function by 50%) of disinfectants based on the effect on cell cultures (average value) is Biodez – 117.29 ±14 μl/l, Blanidas – 389.25 ±20.83 μl/l, Virkon-S – 343.04 ±28.04 μl/l, Neochlor  – 473.82 ±30.16 μl/l, Phan – 56.71 ±7.05 μl/l, Chlorination – 343.28 ±27.26 μl/l, Chlorinated lime – 117.35 ±9.44 μl/l. Mean toxic doses for cell cultures are lower than the mean lethal dose (based on literature data) for rats and mice by gastric administration. The novelty is that determining the cytotoxicity of disinfectants in vitro using human cell cultures can significantly reduce the number of animals for establishing LD50 during the registration procedure of new agents, making it possible to make preliminary conclusions about the toxicity of substances at the stage of chemical screening, preliminary hygienic regulation, identify target organs of toxic influence.

Pharmaceutical excipients with potential to cause adverse effects in paediatric nasal medicines

Some pharmaceutical excipients may cause adverse reactions, excipient-related interactions and/or contraindications. Due to the unique characteristics of the paediatric population, adverse effects may occur to substances generally thought safe. The proportion of topical nasal medicines approved for paediatric use and the prevalence and labelling of excipients with known effect (EKE) in these products were compared in Serbia as a non-EU country and Croatia and Slovenia as EU countries. The study was designed as a post-authorization safety study and safety of excipients was considered in accordance with recommendations of the European Medicines Agency (EMA). More than 90% of topical nasal medicines registered in the three countries were approved for paediatric use and more than half of these paediatric medicines contained EKE that may cause adverse effects. Benzalkonium chloride was found in 52.38%, 55.81% and 59.09% of these products in Serbia, Croatia and Slovenia, respectively. Propylene glycol, benzyl alcohol, ethanol, methyl paraben, propyl paraben and boric acid were also present in a few analysed preparations. A significant number of EKE labelling deficiencies were detected in all three countries, hindering healthcare professionals' access to information needed for adequate patient counselling. A revision of the nasal paediatric medicines' PLs and SmPCs is recommended.

Pulmonary inflammation and cellular responses following exposure to benzalkonium chloride: Potential impact of disrupted pulmonary surfactant homeostasis

Benzalkonium chloride (BKC) is a prototypical quaternary ammonium disinfectant. Previously, we suggested a no lethal dose level (0.005%) and an LD50 range (0.5-0.05%) of BKC following a single pharyngeal aspiration. Herein, we exposed BKC repeatedly by pharyngeal aspiration for 14 days (0.005 and 0.01%, female mice, total five times with interval of two days, 5 mice/group) and 28 days (0, 0.001, 0.005, and 0.01%, male and female mice, weekly, 16 mice/sex/group). Death following 14 days-repeated exposure did not occur. Meanwhile, chronic pathological lesions were observed in the lung tissues of mice exposed to BKC for 28 days. The total number of bronchial alveolar lavage cells increased, and pulmonary homeostasis of immunologic messenger molecules was disturbed. Following, we investigated BKC-induced cellular responses using human bronchial epithelial cells. The cytotoxicity increased rapidly with concentration. Lysosomal volume, NO production, and lipid peroxidation increased in BKC-treated cells, whereas intracellular ROS level decreased accompanying structural and functional damage of mitochondria. We also found that BKC affected the expression level of immune response, DNA damage, and amino acid biosynthesis-related molecules. More interestingly, lamellar body- and autophagosome-like structures were notably observed in cells exposed to BKC, and necrotic and apoptotic cell death were identified accompanying cell accumulation in the G2/M phase. Therefore, we suggest that repeated respiratory exposure of BKC causes pulmonary inflammation and lung tissue damage and that dead and damaged cells may contribute to the inflammatory response. In addition, the formation process of lamellar body-like structures may function as a key toxicity mechanism.

Topical effect of benzalkonium bromide on wound healing and potential cellular and molecular mechanisms

Benzalkonium bromide (BB) has been widely used as a skin antiseptic for wound management. However, BB had proinflammation and reactive oxygen species (ROS) induction effect, making its role in wound healing complex and unclear. A rat full-thickness skin defect wound model was established. The effects of BB, povidone iodine (PVP-I), chlorhexidine gluconate (CHG), and normal saline (NS) on wound healing and infection control were then evaluated based on wound healing rate (WHr) and bacterial killing. The wound tissues were sectioned for histopathological evaluation and nuclear factor E2 related factor 2 (Nrf2) expression determination. The ROS production, Nrf2 activation, and heme oxygenase 1 (HO-1) expression of the HaCat cells and the cytotoxicity treated with BB were further explored. Compared with NS, PVP-I, and CHG, BB showed the best wound infection control efficiency while delayed wound healing with the WHr of 91.42 ± 5.12% at day 20. The wound tissue of the BB group showed many inflammatory cells but few granulation tissue and capillaries and no obvious collagen deposition, resulting in the lowest histopathological scores of 4.17 ± 0.75 for BB group. BB showed higher cytotoxicity on HaCat cells with the lowest IC25, IC50, and IC75 of 1.90, 4.16, and 9.09 g/mL compared with PVP-I and CHG. TUNEL staining evaluated the cytotoxicity of BB on wound tissue, which indicates the high apoptosis index BB group (5.05 ± 1.77). Compared with PVP-I and CHG, BB induced much more cell apoptosis. The results of flow cytometry and fluorescence staining showed that PVP-I, CHG, and BB induced ROS production in a concentration-dependent manner and cells treated with BB had the highest ROS production at the same inhibition concentration. The cells and the wound tissues treated with BB showed highest Nrf2 activation and HO-1 expression than PVP-I and CHG. BB was highly efficient in wound infection control while delayed wound healing. The prolonged and strengthened inflammation and the raised ROS production originating from BB administration may contribute to delayed wound healing.

The Beast of Beauty: Environmental and Health Concerns of Toxic Components in Cosmetics

Cosmetic products are used in large quantities across the world. An increasing number of chemical compounds are being added to the formulation of cosmetic products as additives, fragrances, preservatives, stabilizers, surfactants, dye and shine to potentiate their quality, property and shelf life. Owing to their widespread use, active residues of cosmetic products are continuously introduced into the environment in several ways. Many of these chemicals are bioactive and are characterized by potential bioaccumulation ability and environmental persistence, thus exerting a major risk to humans and the health of ecosystems. Hence, the indiscriminate consumption of cosmetics may present a looming issue with significant adverse impacts on public health. This review intends to spotlight a current overview of toxic ingredients used in formulating cosmetics such as parabens, triclosan, benzalkonium chloride, 1,4-dioxane, plastic microbeads, formaldehyde, diazolidinyl urea, imidazolidinyl urea, sunscreen elements (organic and inorganic UV filters) and trace metals. Specific focus is given to illustrate the biological risks of these substances on human health and aquatic system in terms of genotoxicity, cytotoxicity, neurotoxicity mutagenicity, and estrogenicity. In addition to conclusive remarks, future directions are also suggested.

Mitochondrial Dysfunctions May Be One of the Major Causative Factors Underlying Detrimental Effects of Benzalkonium Chloride

Benzalkonium chloride (BAC) is currently the most commonly used antimicrobial preservative in ophthalmic solutions, nasal sprays, and cosmetics. However, a large number of clinical and experimental investigations showed that the topical administration of BAC-containing eye drops could cause a variety of ocular surface changes, from ocular discomfort to potential risk for future glaucoma surgery. BAC-containing albuterol may increase the risk of albuterol-related systemic adverse effects. BAC, commonly present in personal care products, in cosmetic products can induce irritation and dose-dependent changes in the cell morphology. The cationic nature of BAC (it is a quaternary ammonium) suggests that one of the major targets of BAC in the cell may be mitochondria, the only intracellular compartment charged negatively. However, the influence of BAC on mitochondria has not been clearly understood. Here, the effects of BAC on energy parameters of rat liver mitochondria as well as on yeast cells were examined. BAC, being a "weaker" uncoupler, potently inhibited respiration in state 3, diminished the mitochondrial membrane potential, caused opening of the Ca2+/Pi-dependent pore, blocked ATP synthesis, and promoted H₂O₂ production by mitochondria. BAC triggered oxidative stress and mitochondrial fragmentation in yeast cells. BAC-induced oxidative stress in mitochondria and yeast cells was almost totally prevented by the mitochondria-targeted antioxidant SkQ1; the protective effect of SkQ1 on mitochondrial fragmentation was only partial. Collectively, these data showed that BAC acts adversely on cell bioenergetics (especially on ATP synthesis) and mitochondrial dynamics and that its prooxidant effect can be partially prevented by the mitochondria-targeted antioxidant SkQ1.

Acute toxicity of benzalkonium chloride in Balb/c mice following intratracheal instillation and oral administration

Benzalkonium chloride is a cationic surfactant widely used as a disinfectant, preservative, and sanitizer in many public places as well as domestically. The purpose of this study is to compare the acute toxicity of lethal doses (LDx) and the target organs after intratracheal instillation and oral ingestion by mice, which is a preliminary test prior to the repeated dose toxicity test. When Balb/c mice were treated with a single dose of benzalkonium chloride via oral administration, LD50 was 241.7 mg/kg. However, it was comparatively decreased to 8.5 mg/kg following intratracheal treatment, which suggests that lung may be the main target of toxicity. Although the histopathology showed inflammatory responses in the lung after intratracheal instillation, it still did not confirm that the inflammatory responses were the key factors inducing death in the treated animal. Acute and fatal mechanisms such as bronchoconstriction or neurotoxicity associated with benzalkonium chloride exposure should be further investigated.