Comprehensive pulmonary toxicity assessment of cetylpyridinium chloride using A549 cells and Sprague-Dawley rats

The formation of lamellar body-like structures may be a trigger of cetylpyridinium chloride-induced cell death and inflammatory response

Cetylpyridinium chloride (CPC) is a quaternary ammonium compound used widely in health and personal care products. Meanwhile, due to its increasing use, its potential adverse health effects are emerging as a topic of public concern. In this study, we first administered CPC by pharyngeal aspiration to determine the survival level (the maximum concentration at which no death is observed) and then administered CPC to mice repeatedly for 28 days using the survival level as the highest concentration. CPC increased the total number of pulmonary cells secreting pro- and anti-inflammatory cytokines and chemokines. Infiltration of inflammatory cells, production of foamy alveolar macrophages, and chronic inflammatory lesions were found in the lung tissue of male and female mice exposed to the highest dose of CPC. We also investigated the toxicity mechanism using BEAS-2B cells isolated from normal human bronchial epithelium. At 6 h after exposure to CPC, the cells underwent non-apoptotic cell death, especially at concentrations greater than 2 μg/mL. The expression of the transferrin receptor was remarkably enhanced, and the expression of proteins that contribute to intracellular iron storage was inhibited. The expression of both mitochondrial SOD and catalase increased with CPC concentration, and PARP protein was cleaved, suggesting possible DNA damage. In addition, the internal structure of mitochondria was disrupted, and fusion between damaged organelles was observed in the cytoplasm. Most importantly, lamellar body-like structures and autophagosome-like vacuoles were found in CPC-treated cells, with enhanced expression of ABCA3 protein, a marker for lamellar body, and a docking score between ABCA3 protein and CPC was considered to be approximately -6.8969 kcal/mol. From these results, we propose that mitochondrial damage and iron depletion may contribute to CPC-induced non-apoptotic cell death and that pulmonary accumulation of cell debris may be closely associated with the inflammatory response. Furthermore, we hypothesize that the formation of lamellar body-like structures may be a trigger for CPC-induced cell death.

Antimicrobial cetylpyridinium chloride causes functional inhibition of mitochondria as potently as canonical mitotoxicants, nanostructural disruption of mitochondria, and mitochondrial Ca2+ efflux in living rodent and primary human cells

People are exposed to high concentrations of antibacterial agent cetylpyridinium chloride (CPC) via food and personal care products, despite little published information regarding CPC effects on eukaryotes. Here, we show that low-micromolar CPC exposure, which does not cause cell death, inhibits mitochondrial ATP production in primary human keratinocytes, mouse NIH-3T3 fibroblasts, and rat RBL-2H3 immune mast cells. ATP inhibition via CPC (EC50 1.7 μM) is nearly as potent as that caused by canonical mitotoxicant CCCP (EC50 1.2 μM). CPC inhibition of oxygen consumption rate (OCR) tracks with that of ATP: OCR is halved due to 1.75 μM CPC in RBL-2H3 cells and 1.25 μM in primary human keratinocytes. Mitochondrial [Ca2+] changes can cause mitochondrial dysfunction. Here we show that CPC causes mitochondrial Ca2+ efflux from mast cells via an ATP-inhibition mechanism. Using super-resolution microscopy (fluorescence photoactivation localization) in live cells, we have discovered that CPC causes mitochondrial nanostructural defects in live cells within 60 min, including the formation of spherical structures with donut-like cross section. This work reveals CPC as a mitotoxicant despite widespread use, highlighting the importance of further research into its toxicological safety.

Triclosan and its alternatives, especially chlorhexidine, modulate macrophage immune response with distinct modes of action

Since European regulators restricted the use of bacteriocidic triclosan (TCS), alternatives for TCS are emerging. Recently, TCS has been shown to reprogram immune metabolism, trigger the NLRP3 inflammasome, and subsequently the release of IL-1β in human macrophages, but data on substitutes is scarce. Hence, we aimed to examine the effects of TCS compared to its alternatives at the molecular level in human macrophages. LPS-stimulated THP-1 macrophages were exposed to TCS or its substitutes, including benzalkonium chloride, benzethonium chloride, chloroxylenol, chlorhexidine (CHX) and cetylpyridinium chloride, with the inhibitory concentration (IC10-value) of cell viability to decipher their mode of action. TCS induced the release of the pro-inflammatory cytokine TNF and high level of IL-1β, suggesting the activation of the NLRP3-inflammasome, which was confirmed by non-apparent IL-1β under the NLRP3-inhibitor MCC950 treatment d. While IL-6 release was reduced in all treatments, the alternative CHX completely abolished the release of all investigated cytokines. To unravel the underlying molecular mechanisms, we used untargeted LC-MS/MS-based proteomics. TCS and CHX showed the strongest cellular response at the protein and signalling pathway level, whereby pathways related to metabolism, translation, cellular stress and migration were mainly affected but to different proposed modes of action. TCS inhibited mitochondrial electron transfer and affected phagocytosis. In contrast, in CHX-treated cells, the translation was arrested due to stress conditions, resulting in the formation of stress granules. Mitochondrial (e.g. ATP5F1D, ATP5PB, UQCRQ) and ribosomal (e.g. RPL10, RPL35, RPS23) proteins were revealed as putative key drivers. Furthermore, we have demonstrated the formation of podosomes by CHX, potentially involved in ECM degradation. Our results exhibit modulation of the immune response in macrophages by TCS and its substitutes and illuminated underlying molecular effects. These results illustrate critical processes involved in the modulation of macrophages' immune response by TCS and its alternatives, providing information essential for hazard assessment.

Inhibitory Effects of Shikonin Dispersion, an Extract of Lithospermum erythrorhizon Encapsulated in β-1,3-1,6 Glucan, on Streptococcus mutans and Non-Mutans Streptococci

Shikonin is extracted from the roots of Lithospermum erythrorhizon, and shikonin extracts have been shown to have inhibitory effects on several bacteria. However, shikonin extracts are difficult to formulate because of their poor water solubility. In the present study, we prepared a shikonin dispersion, which was solubilized by the inclusion of β-1,3-1,6 glucan, and analysed the inhibitory effects of this dispersion on Streptococcus mutans and non-mutans streptococci. The shikonin dispersion showed pronounced anti-S. mutans activity, and inhibited growth of and biofilm formation by this bacterium. The shikonin dispersion also showed antimicrobial and antiproliferative effects against non-mutans streptococci. In addition, a clinical trial was conducted in which 20 subjects were asked to brush their teeth for 1 week using either shikonin dispersion-containing or non-containing toothpaste, respectively. The shikonin-containing toothpaste decreased the number of S. mutans in the oral cavity, while no such effect was observed after the use of the shikonin-free toothpaste. These results suggest that shikonin dispersion has an inhibitory effect on S. mutans and non-mutans streptococci, and toothpaste containing shikonin dispersion may be effective in preventing dental caries.

Effect of Commercial Children's Mouthrinses and Toothpastes on the Viability of Neonatal Human Melanocytes: An In Vitro Study

In this study, we examined the cytotoxic effects of six commercial children's mouthrinses (designated as #1, #2, #3, #4, #5, and #6) and four commercial children's toothpastes (designated as #1, #2, #3, and #4) on primary human neonatal melanocytes that were used as a representative model for oral melanocytes. Mouthrinses diluted directly with culture medium (1:2, 1:5, 1:10, 1:100, and 1:1000) were added to monolayers of melanocytes for 2 min, followed by 24 h recovery, after which MTS cytotoxicity assay was conducted. The extracts of each toothpaste were prepared (50% w/v), diluted in culture medium (1:2, 1:5, 1:10, 1:50, 1:100, and 1:1000), and added to cell monolayers for 2 min (standard brushing time), followed by an analysis of cell viability after 24 h. Results showed that all mouthrinses except mouthrinse #4 showed significantly greater loss of cell viability, ascribed to cetylpyridinium chloride (CPC) that induced significant cytotoxicity to melanocytes (IC50 = 54.33 µM). In the case of toothpastes, the examination of cellular morphology showed that a 2 min exposure to all toothpaste extracts induced a concentration-dependent decline in cell viability, pronounced in toothpaste containing sodium lauryl sulfate (SLS) detergent. Further results suggested SLS to be the critical driver of cytotoxicity (IC50 = 317.73 µM). It is noteworthy that toothpaste #1 exhibited much lower levels of cytotoxicity compared to the other three toothpastes containing SLS. Taken together, these findings suggest that the melanocytotoxicity of children's mouthrinse (#4) and toothpaste (#1) is comparatively low. To the best of our knowledge, this is the first study to examine the impact of children's toothpastes and mouthrinses on neonatal primary human melanocytes. Future studies to investigate these findings in a realistic scenario replicating oral cavity conditions of the presence of microbiota, pellicle layer and saliva, and other cell types are warranted.

Pharmaceutical agent cetylpyridinium chloride inhibits immune mast cell function by interfering with calcium mobilization

Cetylpyridinium chloride (CPC) is an antimicrobial used in numerous personal care and janitorial products and food for human consumption at millimolar concentrations. Minimal information exists on the eukaryotic toxicology of CPC. We have investigated the effects of CPC on signal transduction of the immune cell type mast cells. Here, we show that CPC inhibits the mast cell function degranulation with antigen dose-dependence and at non-cytotoxic doses ∼1000-fold lower than concentrations in consumer products. Previously we showed that CPC disrupts phosphatidylinositol 4,5-bisphosphate, a signaling lipid critical for store-operated Ca2+ entry (SOCE), which mediates degranulation. Our results indicate that CPC inhibits antigen-stimulated SOCE: CPC restricts Ca2+ efflux from endoplasmic reticulum, reduces Ca2+ uptake into mitochondria, and dampens Ca2+ flow through plasma membrane channels. While inhibition of Ca2+ channel function can be caused by alteration of plasma membrane potential (PMP) and cytosolic pH, CPC does not affect PMP or pH. Inhibition of SOCE is known to depress microtubule polymerization, and here we show that CPC indeed dose-dependently shuts down formation of microtubule tracks. In vitro data reveal that CPC inhibition of microtubules is not due to direct CPC interference with tubulin. In summary, CPC is a signaling toxicant that targets Ca2+ mobilization.

Pharmaceutical agent cetylpyridinium chloride inhibits immune mast cell function by interfering with calcium mobilization

Cetylpyridinium chloride (CPC) is an antimicrobial used in numerous personal care and janitorial products and food for human consumption at millimolar concentrations. Minimal information exists on the eukaryotic toxicology of CPC. We have investigated the effects of CPC on signal transduction of the immune cell type mast cells. Here, we show that CPC inhibits the mast cell function degranulation with antigen dose-dependence and at non-cytotoxic doses ∼1000-fold lower than concentrations in consumer products. Previously we showed that CPC disrupts phosphatidylinositol 4,5-bisphosphate, a signaling lipid critical for store-operated Ca 2+ entry (SOCE), which mediates degranulation. Our results indicate that CPC inhibits antigen-stimulated SOCE: CPC restricts Ca 2+ efflux from endoplasmic reticulum, reduces Ca 2+ uptake into mitochondria, and dampens Ca 2+ flow through plasma membrane channels. While inhibition of Ca 2+ channel function can be caused by alteration of plasma membrane potential (PMP) and cytosolic pH, CPC does not affect PMP or pH. Inhibition of SOCE is known to depress microtubule polymerization, and here we show that CPC indeed dose-dependently shuts down formation of microtubule tracks. In vitro data reveal that CPC inhibition of microtubules is not due to direct CPC interference with tubulin. In summary, CPC is a signaling toxicant that targets Ca 2+ mobilization.

Novel Keto-Alkyl-Pyridinium Antifungal Molecules Active in Models of In Vivo Candida albicans Vascular Catheter Infection and Ex Vivo Candida auris Skin Colonization

New antifungal therapies are needed for both systemic, invasive infections in addition to superficial infections of mucosal and skin surfaces as well as biofilms associated with medical devices. The resistance of biofilm and biofilm-like growth phases of fungi contributes to the poor efficacy of systemic therapies to nonsystemic infections. Here, we describe the identification and characterization of a novel keto-alkyl-pyridinium scaffold with broad spectrum activity (2 to 16 μg/mL) against medically important yeasts and molds, including clinical isolates resistant to azoles and/or echinocandins. Furthermore, these keto-alkyl-pyridinium agents retain substantial activity against biofilm phase yeast and have direct activity against hyphal A. fumigatus. Although their toxicity precludes use in systemic infections, we found that the keto-alkyl-pyridinium molecules reduce Candida albicans fungal burden in a rat model of vascular catheter infection and reduce Candida auris colonization in a porcine ex vivo model. These initial preclinical data suggest that molecules of this class may warrant further study and development for nonsystemic applications.

Design, Physical Characterizations, and Biocompatibility of Cationic Solid Lipid Nanoparticles in HCT-116 and 16-HBE Cells: A Preliminary Study

In this study, pEGFP-LUC was used as a model plasmid and three distinct cationic lipids (dioleyloxy-propyl-trimethylammonium chloride [DOTMA], dioleoyl trimethylammonium propane [DOTAP], and cetylpyridinium chloride [CPC]) were tested along with PEG 5000, as a nonionic surfactant, to prepare glyceryl monostearate (GMS)-based cationic solid lipid nanoparticles (cSLNs). Both the type and quantity of surfactant had an impact on the physicochemical characteristics of the cSLNs. Thermal analysis of the greater part of the endothermic peaks of the cSLNs revealed they were noticeably different from the individual pure compounds based on their zeta potential (ZP ranging from +17 to +56 mV) and particle size (PS ranging from 185 to 244 nm). The addition of cationic surfactants was required to produce nanoparticles (NPs) with a positive surface charge. This suggested that the surfactants and extensive entanglement of the lipid matrix GMS provided support for the behavioral diversity of the cSLNs and their capacity to interface with the plasmid DNA. Additionally, hemolytic assays were used to show that the cSLNs were biocompatible with the human colon cancer HCT-116 and human bronchial epithelial 16-HBE cell lines. The DOTMA 6-based cSLN was selected as the lead cSLN for further ex vivo and in vivo investigations. Taken together, these new findings might provide some guidance in selecting surfactants to prepare extremely efficient and non-toxic cSLN-based therapeutic delivery systems (e.g., gene therapy).

Cumulative antitumor effect of bismuth lipophilic nanoparticles and cetylpyridinium chloride in inhibiting the growth of lung cancer

OBJECTIVE

To determine the combined antitumor effect of bismuth lipophilic nanoparticles (BisBAL NP) and cetylpyridinium chloride (CPC) on human lung tumor cells.

MATERIAL AND METHODS

The human lung tumor cells A549 were exposed to 1-100 µM BisBAL NP or CPC, either separately or in a 1:1 combination. Cell viability was measured with the PrestoBlue assay, the LIVE/DEAD assay, and fluorescence microscopy. The integrity and morphology of cellular microtubules were analyzed by immunofluorescence.

RESULTS

A 24-h exposure to 1 µM solutions reduced A549 growth with 21.5% for BisBAL NP, 70.5% for CPC, and 92.4% for the combination (p < 0.0001), while a 50 µM BisBAL NP/CPC mixture inhibited cell growth with 99% (p < 0.0001). BisBAL NP-curcumin conjugates were internalized within 30 min of exposure and could be traced within the nucleus of tumor cells within 2 h. BisBAL NP, but not CPC, interfered with microtubule organization, thus interrupting cell replication, similar to the action mechanism of docetaxel.

CONCLUSION

The growth inhibition of A549 human tumor cells by BisBAL NP and CPC was cumulative as of 1 µM. The BisBAL NP/CPC combination may constitute an innovative and cost-effective alternative for treating human lung cancer.

Quaternary ammonium compounds in hypersensitivity reactions

Quaternary ammonium compounds (QAC) are commonly used disinfectants, antiseptics, preservatives, and detergents due to their antibacterial property and represent the first used biocides before phenolic or nitrogen products. Their common structure consists of one or more quaternary ammonium bound with four lateral substituents. Their amphiphilic structure allows them to intercalate into microorganism surfaces which induces an unstable and porous membrane that explains their antimicrobial activity towards bacteria, fungi, and viruses. QAC are thus found in many areas, such as household products, medicines, hygiene products, cosmetics, agriculture, or industrial products but are also used in medical practice as disinfectants and antiseptics and in health care facilities where they are used for cleaning floors and walls. QAC exposure has already been involved in occupational asthma in healthcare workers or professional cleaners by many authors. They also have been suggested to play a role in contact dermatitis (CD) and urticaria in workers using cosmetics such as hairdressers or healthcare workers, inciting reglementary agencies to make recommendations regarding those products. However, distinguishing the irritant or sensitizing properties of chemicals is complex and as a result, the sensitizing property of QAC is still controverted. Moreover, the precise mechanisms underlying the possible sensitization effect are still under investigation, and to date, only a few studies have documented an immunological mechanism. Besides, QAC have been suggested to be responsible for neuromuscular blocking agents (NMBA) sensitization by cross-reactivity. This hypothesis is supported by a higher prevalence of quaternary ammonium (QA)-specific IgE in the professionally exposed populations, such as hairdressers, cleaners, or healthcare workers, suggesting that the sensitization happens with structurally similar compounds present in the environment. This review summarizes the newest knowledge about QAC and their role in hypersensitivities. After describing the different QAC, their structure and use, the most relevant studies about the effects of QAC on the immune system will be reviewed and discussed.

Cetylpyridinium chloride inhibits human breast tumor cells growth in a no-selective way

OBJECTIVE

Analyze the antitumor capacity of cetylpyridinium chloride (CPC) on human breast tumor cells, and the possible action mechanism.

MATERIAL AND METHODS

The human breast tumor cells MCF-7 and no-tumor breast cells MCF-10A were exposed to CPC under various condition (concentration and duration). Cell viability was measured with MTT assay, the LIVE/DEAD assay, and fluorescence microscopy. Membrane permeability after CPC exposure was evaluated by Calcein AM assay, mitochondrial morphology with a MitoView staining, and genotoxicity with the comet assay and fluorescence microscopy.

RESULTS

CPC was cytotoxic to both MCF-7 and MCF-10A as of a 24-h exposure to 0.1 µM. Cytotoxicity was dose-dependent and reached 91% for MCF-7 and 78% for MCF-10A after a 24-h exposure to 100 µM CPC, which outperformed the positive control doxorubicin in effectiveness and selectivity. The LD50 of CPC on was 6 µM for MCF-7 and 8 µM for MCF-10A, yielding a selectivity index of 1.41. A time response analysis revealed 64% dead cells after only 5 min of exposure to 100 µM CPC. With respect to the action mechanisms, the comet assay did not reveal genome fragmentation. On the other hand, membrane damage was dose-dependent and may also affect mitochondrial morphology.

CONCLUSION

Cetylpyridinium chloride inhibits MCF-7 cell growing in a non-selective way as of 5 min of exposure. The action mechanism of CPC on tumor cells involves cell membrane damage without change neither mitochondrial morphology nor genotoxicity.