Chlorhexidine-induced apoptosis or necrosis in L929 fibroblasts: A role for endoplasmic reticulum stress

Cytotoxicity evaluation of Chlorhexidine and Blue®M applied to a human gingival fibroblast (HGF-1) and keratinocytes (NOK-SI): In vitro study

Chlorhexidine (CHX) is a prime choice to control the oral microbiota. However, it's a chemical agent leading to side effects such as teeth strains, taste disturbance, and desquamation of oral mucosa. Alternatively, the lactoferrin and oxygen-based Blue®M has been introduced as an alternative to the CHX, not disturbing tissue repair. Therefore, the study aimed to evaluate the effects of Blue®M and CHX on oral human fibroblasts (HGF-1) and keratinocytes (NOK-SI). Cell cultures using HGF-1 and NOK-SI evaluated cell proliferation, cell cycle, apoptosis and necrosis, and migration. In the dose-effect test, Blue®M reduced the HGF-1 sample in a 4-fold concentration than CHX (CHX: 173.07 ±10.27; Blue®M: 43.86 ±3.04). The proliferation test revealed an eightfold reduction of the sample for CHX, while for Blue®M, the proliferation rate was eighteen times lower. The apoptosis and necrosis rates increased by 25% (p<0.0001) for HGF-1 for both substances. In NOK-SI, the apoptosis rates increased by 10% (p=0.02) and 15% (p=0.001) for CHX and Blue®M, respectively. Furthermore, the fibroblast had a lower capacity for wound closure in the Scratch Assay (monolayer cell migration) for Blue®M. Despite the limitations of this in vitro study, the results of the lactoferrin and oxygen-based Blue®M demonstrated cytotoxicity in doses over the Minimum inhibitory concentration and Minimum bactericidal concentration for Oral fibroblasts (HGF- 1) and Keratinocytes (NOK-SI).

Effect of amoxicillin and clindamycin on the gene expression of markers involved in osteoblast physiology

Background/purpose

Amoxicillin and clindamycin are the most effective decontaminants for intraoral bone grafts before their application in bone regeneration without cytotoxic effects on osteoblasts, but their effects on the gene expression of markers involved in osteoblast growth and differentiation remain unclear. The study objective was to determine the effects of amoxicillin and clindamycin on the gene expression of markers involved in osteoblast growth and differentiation.

Materials and methods

Real-time polymerase chain reaction (RT-PCR) was performed to explore the effect of 150 μg/mL clindamycin or 400 μg/mL amoxicillin on the gene expression by primary human osteoblasts (HOBs) of runt-related transcription factor 2 (Runx-2), osterix (OSX), alkaline phosphatase (ALP), osteocalcin (OSC), osteoprotegerin (OPG), receptor activator for nuclear factor κ B ligand (RANKL), type I collagen (Col-I), bone morphogenetic proteins 2 and 7 (BMP-2 and BMP-7), TGF-β1 and TGF-β receptors (TGF-βR1, TGF-βR2, and TGF-βR3), and vascular endothelial growth factor (VEGF).

Results

Treatment with 150 μg/mL clindamycin significantly increased the gene expression of TFG-β1, TGF-βR1, TGF-βR2, TGF-βR3, RUNX-2, Col-1, OSX, OSC, BMP-2, BMP-7, ALP, VEGF, and RANKL by HOBs. Treatment with 400 μg/mL amoxicillin significantly increased the gene expression of TGF-β R1, Col-I, OSC, RANKL, and OPG alone.

Conclusion

These findings suggest that 150 μg/mL clindamycin is the decontaminant of choice to treat intraoral bone grafts before their application in bone regeneration. The osteogenic and antibacterial properties of clindamycin can favor and accelerate the integration of bone grafts in the oral cavity.

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.

Research methods assessing sodium hypochlorite cytotoxicity: A scoping review

Sodium hypochlorite (NaOCl) cytotoxicity has been assessed using different methodologies, which has led to arbitrary interpretations. This scoping review aimed to discuss the different methodological protocols for assessing NaOCl cytotoxicity. A literature review performed in the PubMed and Embase databases up to July 2023 identified manuscripts reporting NaOCl cytotoxicity. The dataset identified 546 publications, further screened by 2 reviewers. Ninety studies were identified and mined methodologically to collect information on cell type, cytotoxicity assay, NaOCl dilution solutions, presence of fetal bovine serum (FBS), and NaOCl exposure time. The culture medium used in cytotoxicity assays contains buffering substances that neutralize the pH of NaOCl, thus reducing its cytotoxicity, an approach that may lead to bias when solutions with different pH are compared. For short exposure periods, as in simulations to evaluate the contact between irrigant and periapical tissue cells during chemo-mechanical preparation, NaOCl dilution should be performed with saline, which does not buffer the irrigant. For long exposure periods, as in simulations of irrigant extrusions, NaOCl should be diluted in the culture medium, to reproduce the expected buffering effect occurring in extrusions. The presence of FBS in culture medium can decrease NaOCl toxicity. There is no standardization of NaOCl cytotoxicity methodologies. This poses the risk of arriving at incorrect results and, therefore, pertinent tests must be refined.

Calcium hypochlorite cytotoxicity mechanism in fibroblasts and effect on osteoblast mineralization

AIM

To determine the cytotoxicity mechanism of 2.5% calcium hypochlorite [Ca(OCl)2 ] in L929 fibroblasts and the effect of this solution on human osteoblast-like cells (Saos-2) mineralization, compared to that of 2.5% sodium hypochlorite (NaOCl).

METHODOLOGY

L929 fibroblasts were exposed to Ca(OCl)2 and NaOCl at different dilutions for 10 min. Cell metabolism was assessed by methyl-thiazole-tetrazolium (MTT); lysosome integrity, by neutral red (NR) assay; type of cell death, by flow cytometry (apoptosis/necrosis); cytoskeleton, by actin and α-tubulin fluorescence and cell ultrastructure, by transmission electron microscopy (TEM). The alkaline phosphatase (ALP) activity and mineralized nodule formation were determined in Saos-2 by thymolphthalein release and alizarin red staining (ARS), respectively. The data were analysed by two-way anova and Bonferroni's post-test (α = .05).

RESULTS

Ca(OCl)2 promoted higher cell viability and a lower percentage of apoptosis and necrosis than NaOCl (p < .05). Ca(OCl)2 and NaOCl decreased cell metabolism and lysosome integrity, induced the breakdown of microtubules and actin filaments, promoted alterations of rough endoplasmic reticulum and disruption of mitochondrial cristae. Additionally, Ca(OCl)2 did not induce ALP activity and had no effect on mineralized nodules formation.

CONCLUSIONS

Although Ca(OCl)2 and NaOCl promoted the same cytotoxicity mechanism, Ca(OCl)2 was less cytotoxic than NaOCl. As for ALP activity, no differences were observed between NaOCl and Ca(OCl)2 . The production of mineralized nodules induced by Ca(OCl)2 was lower than those induced by NaOCl, but was not different from those induced by the control group.

In vitro cytotoxicity and antibacterial activity of hypochlorous acid antimicrobial agent

Background/purpose

Bacteria-associated oral diseases such as dental caries and periodontitis are widespread epidemics that cause oral pain and loss of function. The purpose of this study was to evaluate the in vitro cytotoxicity and antibacterial activity of different concentrations of hypochlorous acid (HOCl).

Materials and methods

Five different concentrations (100, 200, 300, 400, and 500 ppm) of HOCl were evaluated for their antimicrobial efficacy against Gram-negative (A. actinomycetcmcomitans and P. gingivalis) and Gram-positive bacteria (S. mutans and S. sanguinis) after treatment for 1 and 10 min. Sodium hypochlorite (NaOCl) and chlorhexidine (CHX) were used as positive controls. In addition, HOCl was examined for L929 cytotoxicity and RAW 264.7 growth.

Results

The bacteriostatic ratio of NaOCl was comparable to that of CHX and significantly (P < 0.05) higher than that of all HOCl solutions. Higher HOCl concentration had significantly (P < 0.05) higher antibacterial effect, and the bacteriostatic ratio of 10 min treatment was slightly higher than that of 1 min treatment. CHX and NaOCl seeded into L929 cells resulted in low cell viability with only 30-39%, much significantly (P < 0.05) lower than all HOCl groups (greater than 80%). All HOCl solutions met the recommendations of ISO 10993-5 and showed no cytotoxicity, although there was a concentration-dependent decrease in cell viability. All antimicrobial agents showed the same trend of response to RAW 264.7 as L929.

Conclusion

Within the limit of this study, 400 ppm HOCl disinfectant may be a potential antimicrobial candidate for mouthwash, endodontic irrigants, and periodontitis treatment.

Efficacy of hypochlorous acid as an alternative oral antimicrobial agent on human gingival fibroblasts, Aggregatibacter actinomycetemcomitans, and Candida albicans biofilms in vitro

This study compared the cytotoxicity and antimicrobial activity of hypochlorous acid (HOCl) at 50 ppm and 200 ppm and 0.2% chlorhexidine (CHX) at various time intervals, in vitro. Cell viability and cytotoxicity of human gingival fibroblasts (HGF) were evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test and the lactate dehydrogenase assay. Antimicrobial effects on Aggregatibacter actinomycetemcomitans and Candida albicans were determined using the time-kill method. All solutions exhibited a significant impact on HGFs in a dose- and time-dependent manner. 50 ppm HOCl demonstrated the highest cell viability, followed by 200 ppm HOCl. Both HOCl solutions were less cytotoxic to HGFs than 0.2% CHX. 50 ppm and 200 ppm HOCl demonstrated stronger efficiencies than CHX against A. actinomycetemcomitans and C. albicans. The data suggest that HOCl solutions have potential as an alternative antiseptic to CHX due to their lower cytotoxicity and superior antimicrobial activity, but optimal dosage of HOCl requires further investigations.

Phenotypic Modulation of Adipose-Derived Stem Cells and Fibroblasts Treated with Povidone-Iodine and Chlorhexidine in Mono and Coculture Models

Topical antiseptics are essential in wound treatment, and adipose-derived stem cells (ADSCs) have recently been proven to facilitate healing. However, the impact of antiseptics on ADSCs has not been fully elucidated, especially in relation to other relevant cell types present in the wound microenvironment, e.g., fibroblasts. This study evaluated the effects of chlorhexidine and povidone-iodine on four cellular constructs in 2D and 3D in vitro culture systems. Cell constructs were treated with two concentrations of each antiseptic, after which cell migration activity, α-SMA, and Ki67 marker expressions were assessed and compared. Both tested concentrations of povidone-iodine impaired migration and sprouting compared to chlorhexidine, which had minimal effects when used in low concentrations. The gap in the wound healing assay did not close after 24 h of povidone-iodine treatment, although, at the lower concentration, cells started to migrate in a single-cell movement pattern. Similarly, in 3D culture systems, sprouting with reduced spike formation was observed at high povidone-iodine concentrations. Both antiseptics modulated α-SMA and Ki67 marker expressions at 5 days following treatment. Although both antiseptics had cytotoxic effects dependent on drug concentration and cell type, povidone-iodine contributed more substantially to the healing process than chlorhexidine, acting especially on fibroblasts.

Preparation of Citrus reticulata peel nano-encapsulated essential oil and in vitro assessment of its biological properties

Dental caries is the most common biofilm-dependent oral disease. Streptococcus mutans is among the main microorganisms responsible for the development of dental caries. Nano-suspension of Citrus reticulata (tangerine) peel essential oil in 0.5% (v/v) concentration was prepared and its antibacterial effect on S. mutans in planktonic and biofilm forms as well as its cytotoxic and antioxidant effects were assessed and compared with chlorhexidine (CHX). The minimum inhibitory concentration (MIC) of free essential oil, nano-encapsulated essential oil, and CHX was 5.6% (v/v), 0.0005% (v/v), and 0.0002% (w/v), respectively. The percentage of biofilm inhibition by the free essential oil, nano-encapsulated essential oil, and CHX at half-MIC was 67.3%, 24%, and 90.6%, respectively. The nano-encapsulated essential oil had no cytotoxicity and showed significant antioxidant effects in different concentrations. Nano-encapsulation of tangerine peel essential oil significantly enhanced its biological activities in much lower concentrations than the free essential oil (11,000 times diluted). It also showed lower cytotoxicity and higher antibiofilm effects in sub-MICs compared with CHX, indicating the optimal potential of tangerine nano-encapsulated essential oil for incorporation in the composition of organic antibacterial and antioxidant mouth rinses.

Development, characterization and antimicrobial activity of multilayer silica nanoparticles with chlorhexidine incorporated into dental composites

OBJECTIVE

In this study a dentistry nanocomposite with prolonged antibacterial activity using silica nanoparticles (SNPs) loaded with chlorhexidine (CHX) was developed.

METHODS

SNPs were coated with the Layer-by-Layer technique. Dental composites were prepared with organic matrix of BisGMA/TEGDMA and SNPs with or without CHX (0, 10, 20 or 30% w/w). The physicochemical properties of the developed material were evaluated and agar diffusion method was used to test the antibacterial. In addition, the biofilm inhibitory activity of the composites was evaluated against S. mutans.

RESULTS

SNPs were rounded with diameters about 50 nm, the organic load increased with increasing deposited layers. Material samples with SNPs loaded with CHX (CHX-SNPs) showed the highest values of post-gel volumetric shrinkage, that ranged from 0.3% to 0.81%. Samples containing CHX-SNPs 30% w/w showed the highest values of flexural strength and modulus of elasticity. Only samples containing SNPs-CHX showed growth inhibition against S. mutans, S. mitis and S. gordonii in a concentration-dependent manner. The composites with CHX-SNPs reduced the biofilm formation of S. mutans biofilm at 24 h and 72 h.

SIGNIFICANCE

The nanoparticle studied acted as fillers and did not interfere with the evaluated physicochemical properties while providing antimicrobial activity against streptococci. Therefore, this initial study is a step forward to the synthesis of experimental composites with improved performance using CHX-SNPs.

Application of antimicrobial, potential hazard and mitigation plans

The tremendous rise in the consumption of antimicrobial products had aroused global concerns, especially in the midst of pandemic COVID-19. Antimicrobial resistance has been accelerated by widespread usage of antimicrobial products in response to the COVID-19 pandemic. Furthermore, the widespread use of antimicrobial products releases biohazardous substances into the environment, endangering the ecology and ecosystem. Therefore, several strategies or measurements are needed to tackle this problem. In this review, types of antimicrobial available, emerging nanotechnology in antimicrobial production and their advanced application have been discussed. The problem of antimicrobial resistance (AMR) due to antibiotic-resistant bacteria (ARB)and antimicrobial resistance genes (AMG) had become the biggest threat to public health. To deal with this problem, an in-depth discussion of the challenges faced in antimicrobial mitigations and potential alternatives was reviewed.

The antibacterial effect of Plectranthus scutellarioides (L.) R.Br. leaves extract against bacteria associated with peri-implantitis

Background and aim

The present study investigates Plectranthus scutellarioides (L.) R.Br. as potential antibacterial oral rinse against bacteria associated with peri-implantitis to prevent the initial infection as well as disease progression.

Experimental procedure

Phytochemical screening was done on P. scutellarioides lyophilized extract to identify the presence of chemical constituent by using mass-based identification. The extract was screened for its antibacterial activity against 4 Gram-positive aerobes (early colonizer) and 5 Gram-negative facultative anaerobes as well as obligate anaerobes (late colonizer) using disc diffusion method. The extract was tested for minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), its cytotoxicity effects on human gingival fibroblast cell (HnGF) as well as bacteria morphological changes by scanning electron microscopy (SEM).

Results and conclusion

Four flavonoid compounds were identified namely quercetin-3-glucoside, quercitrin, quercetin 3-(6″-acetylglucoside) and quercetin 3-O-acetyl-rhamnoside. The sensitivity test revealed that P. scutellarioides extract was effective against all the bacteria tested. MIC concentrations for the Gram-positive aerobes were in the range of 1.56–12.50 mg/mL, and the MBC concentrations were within 3.13–12.50 mg/mL. For Gram-negative obligate anaerobes, the MIC concentration were within 3.13–12.50 mg/mL and MBC within 6.25–200.00 mg/mL. The ethanolic extract did not have any cytotoxic effect on HnGF cells at the tested concentrations. SEM images showed bacterial cell wall disruption for all the bacteria tested. The results showed that P. scutellarioides extract exerts its antibacterial property by disrupting the cell wall of all the bacteria tested. Hence, P. scutellarioides may benefit from further investigations on its safety for oral use as an adjunctive treatment for peri-implantitis.

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The quercetin derivatives reported in this study were the first been identified for this plant species.

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The optimize method used for the mass-based identification can be reproducible and applied for the future isolation, identification and characterizations of the plant chemical compounds.

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The plant extract was effective against all the bacteria tested and note that, there were no studies have been carried out on the effects of this plant on oral bacteria especially the obligate anaerobes.

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The plant extract also was not toxic towards HnGF.

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The SEM image showed the plant extract have exert its antibacterial activity through cell wall destruction.

An in vitro comparison of antimicrobial efficacy and cytotoxicity between povidone-iodine and chlorhexidine for treating clinical endometritis in dairy cows

This study aimed to assess the in vitro antimicrobial effects of chlorhexidine (CHX) and povidone-iodine (PI) on clinical isolates of Escherichia coli (E. coli) and Trueperella pyogenes (T. pyogenes) from the vaginal discharge of dairy cows, as well as to compare the cytotoxicity effects of CHX and PI on bovine endometrial epithelial cells (BEnEpC). In Experiment 1, 12 E. coli and 10 T. pyogenes were isolated from the vaginal discharge of cows with a uterine infection. The MIC and MBC against CHX and PI were analyzed in vitro. In Experiment 2, the cytotoxicity effects of CHX and PI on BEnEpC were analyzed using a Viability/Cytotoxicity Kit, wound scratch healing assay, and the expression of pro-inflammatory cytokine genes (IL-6, IL-8, and TNF-α). In Experiment 1, the MIC and MBC values of CHX against E. coli were 0.0002% and 0.0002 to 0.00025%, respectively. The MIC and MBC values of PI were 1.25 to 2.5% and 1.25 to 5%, respectively. For T. pyogenes, the MIC and MBC values of CHX were 0.00002%. The MIC and MBC values of PI were 1.25%. In Experiment 2, the cell viability significantly decreased, and wound closures were significantly inhibited after treatment with ≥ 0.002% CHX and ≥ 0.025% PI. The expression of IL-6, IL-8, and TNF-α significantly increased after treatment with PI. Only IL-6 showed a significant increase after cells were treated with 0.00002% and 0.0002% CHX. The results suggested that both CHX and PI had high antibacterial effects. However, veterinarians and farmers should be aware of their cytotoxicity, which decrease viability of endometrial epithelial cells and inhibit wound healing in vitro.

Impact of glycine and erythritol/chlorhexidine air-polishing powders on human gingival fibroblasts: an in vitro study

BACKGROUND

Supra- and subgingival air-polishing has been used in periodontitis and gingivitis therapy for years. Low-abrasive types of powders have facilitated the application in subgingival areas. In this study, the cellular effects of a glycine powder and an erythritol/chlorhexidine (CHX) powder on human gingival fibroblasts (HGF) were investigated.

METHODS

HGF were obtained from sound gingiva of three healthy donors. After 12hours and 24hours of incubation time, cell viability testing and, after 24hours and 48hours, a cell proliferation assay was conducted. Additionally, the individual components erythritol and CHX were investigated for cell viability. In vitro wound healing was monitored for 48hours and scanning electron microscopy (SEM) analysis was performed after 24hours. Statistical analysis was accomplished by ANOVA and post hoc Dunnett's and Tukey's tests (p < 0.05) were performed.

RESULTS

Erythritol/CHX powder and in a lower extent, glycine powder decreased cell viability and cell proliferation. The negative effect of erythritol/CHX was mainly based on the CHX component. In vitro wound healing was negatively influenced in both types of powders compared to control. Cell size was altered in both test groups, whereas cell morphology was affected only in the erythritol/CHX group.

CONCLUSIONS

The investigated powders for subgingival air-polishing can influence cell viability, morphology, and proliferation, as well as wound closure in vitro. These actions on fibroblasts are discernible, with the cytotoxic effect of erythritol/CHX powder being very clear and mainly due to the CHX component. Our results suggest that subgingivally applied powders can exert direct effects on gingival fibroblasts.

Effect of Three Chlorhexidine-Based Mouthwashes on Human Gingival Fibroblasts: An In Vitro Study

Mouthwashes containing chlorhexidine (CHX) are deemed to be associated with dose-dependent side effects, including burning sensation and taste alteration. To overcome these drawbacks, mouthwashes with CHX at lower concentrations with or without adjunctive agents are proposed. The aim of this in vitro study was to investigate the effects of three CHX-based mouthwashes on human gingival fibroblasts (HGFs). After 3 days of cell culture, groups were randomly treated for 30 s, 60 s or 120 s with (a) CHX 0.05% in combination with cetylpyridnium chloride (CPC) 0.05%; (b) CHX 0.1%; (c) CHX 0.2%; or (d) NaCl as control. Cell viability, cytotoxicity and apoptosis were evaluated at 2 h, 3 days and 6 days after the exposure to the different solutions. Similar cell viability values were found among the test groups at all time points. At day 0, higher cytotoxicity was measured in the group treated with CHX 0.02%, in particular after long application time (120 s), while no significant difference was found between CHX + CPC and the control group. All the investigated mouthwashes were well tolerated by HGF cells for the tested application times. The highest cytotoxic effect was observed for CHX 0.2%; therefore, clinicians should consider limiting its usage to carefully selected clinical situations.

Real-Time Analysis of Antiproliferative Effects of Mouthwashes Containing Alcohol, Sodium Fluoride, Cetylpyridinium Chloride, and Chlorhexidine In Vitro

Objectives

In this study, the cytotoxic responses of six different over-the-counter mouthwashes on L929 cells were analyzed by two different techniques: the traditional colorimetric tetrazolium-based reduction assay (MTT) and the modern impedance-based real-time cell analysis (RTCA) system to investigate their biocompatibility in vitro. Thus, the investigation of the antiproliferative effects of the specified materials via different techniques is vital to reach this goal.

Materials and Methods

First, L929 mouse fibroblasts were exposed to the dilutions of mouthwashes for 2 minutes. After incubation, the tetrazolium reduction method was used to assess the metabolic viability of cells measured by colorimetric MTT assay and morphological inspection of cells was performed via phase-contrast microscopy. Furthermore, the effect of each mouthwash on the proliferation, morphology, and adhesion of L929 cells was monitored continuously by a noninvasive and label-free RTCA system for 140 h.

Results

Our data showed that all of the mouthwashes had varying cytotoxic effects on fibroblasts compared to the control group in MTT assay. In addition to that, RTCA technology has provided the growth kinetic profiles that can be used to analyze if the treatment is causing antimitotic or DNA-damaging effect on cells. Thus, analysis via this system can tell us the mechanism of toxicity behind the cell growth inhibition in vitro. Here, we found that only mouthwash 1 moderately maintained the viability of the L929 cells, yet displaying antimitotic effects and the other mouthwashes (mouthwash 2-mouthwash 6) showed toxicity via DNA-damaging effects.

Conclusions

Of the six types of mouthwash tested, the most biocompatible result was obtained from a mouthwash containing alcohol (i.e., mouthwash 1). On the other hand, sodium fluoride- (NaF-) and cetylpyridinium chloride- (CPC-) containing mouthwash (i.e., mouthwash 2) showed the most cytotoxic effect.

In Vitro Gingival Wound Healing Activity of Extracts from Reynoutria japonica Houtt Rhizomes

Rhizomes of Reynoutria japonica Houtt. are a traditional Chinese medicinal herb (Polygoni cuspidati rhizoma, hu zhang) used for treatment of numerous diseases including wound healing support. The aim of this study was to provide evidence for the value of this herbal drug’s traditional use as a gingival healing treatment as well as to obtain the most active extract. In vitro studies were performed using primary human gingival fibroblasts (HGFs) with determination of viability (MTT assay), cell proliferation (the confocal laser scanning microscope (CLSM) was used to visualize histone 3 expression), cell migration (wound healing assay), and evaluation of the expression of collagen type III (immunocytochemical staining) after incubation with extracts from R. japonica rhizomes (25% or 40% ethanol or 60% acetone). In addition to these extracts, commercial dental rinse (containing chlorhexidine digluconate 0.2%) was tested as the gold standard of choice for gum healing in dental practice. The studied extracts were qualitatively and quantitatively characterized using the validated HPLC/DAD/ESI-HR-QTOF-MS method. Total phenols and tannins content were determined using the Folin–Ciocalteu assay. Low concentration of all extracts after 24 h incubation caused significant increase in HGF viability. This effect was most pronounced at a concentration of 50 µg/mL, which was selected for further experiments. All extracts (at 50 µg/mL) stimulated HGF to proliferate, migrate, and increase collagen III synthesis, but with different strength. The highest stimulated proliferation and migration activity was observed after incubation with 25% EtOH, which according to phytochemical analysis may be related to the highest content of resveratrol and an appropriate composition of procyanidins. The 25% EtOH extract from R. japonica rhizomes appears to be a promising gingival wound healing agent worthy of animal and clinical trials.

Effect of Chlorhexidine Digluconate in Early Wound Healing of Human Gingival Tissues. A Histological, Immunohistochemical and Biomolecular Analysis

Chlorhexidine digluconate (CHX) is considered the gold standard for oral cavity antiseptic treatment. Nevertheless, several in vitro studies have reported detrimental effects in oral tissue repair. The aim of the present study was to evaluate the in vivo effect of post-surgical CHX mouth rinse on gingival tissue (G) 24 h after injury. G biopsies were obtained in three patients 24 h after surgery with the indication of post-surgical 0.12% CHX use and were compared with those obtained from the same patients without any antiseptic use. Changes in collagen production, cell proliferation, and apoptosis were examined by histological and Ki-67/P53 immunohistochemical analysis. Fibrotic markers (COL1A1, αSMA), proapoptotic protein (BAX) expression, and wound healing-related gene modulation (RAC1, SERPINE1, TIMP1) were analyzed by quantitative real-time PCR analysis. CHX was able to reduce cellular proliferation and increase collagen deposition, proapoptotic molecule and fibrotic marker expression, and myofibroblast differentiation, reduce expression of RAC1 and trigger expression of SERPINE1 and TIMP1, showing “scar wound healing response” pattern. This study assessed for the first time the in vivo effects of CHX on gingival tissue. The demonstration of a CHX-induced fibrotic transformation, leading to scar repair, supports the need for new post-surgical clinical protocols based on a strategic and personalized use of CHX.

PMMA bone cement containing long releasing silica-based chlorhexidine nanocarriers

Prosthetic joint infections (PJI) are still an extremely concerning eventuality after joint replacement surgery; growing antibiotic resistance is also limiting the prophylactic and treatment options. Chlorhexidine (a widely used topical non-antibiotic antimicrobial compound) coatings on silica nanoparticles capable of prolonged drug release have been successfully developed and characterised. Such nanocarriers were incorporated into commercial formulation PMMA bone cement (Cemex), without adversely affecting the mechanical performance. Moreover, the bone cement containing the developed nanocarriers showed superior antimicrobial activity against different bacterial species encountered in PJI, including clinical isolates already resistant to gentamicin. Cytocompatibility tests also showed non inferior performance of the bone cements containing chlorhexidine releasing silica nanocarriers to the equivalent commercial formulation.

The Effects of Three Chlorhexidine-Based Mouthwashes on Human Osteoblast-Like SaOS-2 Cells. An In Vitro Study

Several decontamination methods for removing biofilm from implant surfaces during surgical peri-implantitis treatment have been reported, including the intraoperative usage of chlorhexidine (CHX)-based antiseptics. There is a lack of information on possible adverse effects on bone healing. The study aimed to examine the impact of three CHX-based mouthwashes on osteoblast-like cells (SaOS-2) in vitro. Cells were cultured for three days in 96-well binding plates. Each well was randomly treated for either 30, 60 or 120 s with 0.05% CHX combined with 0.05% cetylpyridinium chloride (CPC), 0.1% CHX, 0.2% CHX or sterile saline (NaCl) as control. Cell viability, cytotoxicity and apoptosis were assessed at day 0, 3 and 6. Cell viability resulted in being higher in the control group at all time points. At day 0, the CHX 0.2 group showed significantly higher cytotoxicity values compared to CHX 0.1 (30 s), CHX + CPC (30 s, 60 s and 120 s) and control (60 s and 120 s), while no significant differences were identified between CHX + CPC and both CHX 0.1 and NaCl groups. All test mouthwashes were found to induce apoptosis to a lower extent compared to control. Results indicate that 0.2% CHX presented the highest cytotoxic effect. Therefore, its intraoperative use should be carefully considered.

Inhibition of the Human Hsc70 System by Small Ligands as a Potential Anticancer Approach

Simple Summary

High levels of Heat shock proteins (Hsps) in specific cancers are usually linked to a poor prognosis, tumor progression, invasiveness, and resistance to treatment. Chaperone inhibition could therefore be toxic for cancer cells due to their high dependence on chaperone activity to survive. This study shows the potential to repurpose the small chemical compound pinaverium bromide, currently used to treat functional gastrointestinal disorders, as a possible antitumor drug since it displays a marked toxicity against two melanoma cell lines without affecting the viability of fibroblast and primary melanocytes. This compound interacts with structural regions shared by representatives of the Hsp70 and Hsp110 families, inhibiting the substrate remodeling ability of the Hsp70 system in vitro and in a cellular context.

Abstract

Heat shock protein (Hsp) synthesis is upregulated in a wide range of cancers to provide the appropriate environment for tumor progression. The Hsp110 and Hsp70 families have been associated to cancer cell survival and resistance to chemotherapy. In this study, we explore the strategy of drug repurposing to find new Hsp70 and Hsp110 inhibitors that display toxicity against melanoma cancer cells. We found that the hits discovered using Apg2, a human representative of the Hsp110 family, as the initial target bind also to structural regions present in members of the Hsp70 family, and therefore inhibit the remodeling activity of the Hsp70 system. One of these compounds, the spasmolytic agent pinaverium bromide used for functional gastrointestinal disorders, inhibits the intracellular chaperone activity of the Hsp70 system and elicits its cytotoxic activity specifically in two melanoma cell lines by activating apoptosis. Docking and molecular dynamics simulations indicate that this compound interacts with regions located in the nucleotide-binding domain and the linker of the chaperones, modulating their ATPase activity. Thus, repurposing of pinaverium bromide for cancer treatment appears as a promising novel therapeutic approach.

Characterization of ionic liquid cytotoxicity mechanisms in human keratinocytes compared with conventional biocides

The ability to chemically modify ionic liquids (ILs) has led to an expansion in interest in their use in a diversity of applications, not least as antimicrobials and biocides. Relatively little is known about cytotoxicity mechanisms of ILs in comparison to other biocides currently in widespread use, as well as their practical significance for the ecological environment and human health. Using NCTC 2544 and HaCat human keratinocyte cells, this study aimed to characterize cytotoxicity rates and mechanisms of a range of ILs. Using both lactate dehydrogenase (LDH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) based cytotoxicity assays, it was confirmed that at biocide-relevant concentrations, ILs with longer alkyl chains exhibited greater biocidal activity than those with shorter alkyl chains, with comparable activity to the commonly used biocides chlorhexidine, benzalkonium chloride and cetylpyridinium chloride, at relevant in-use biocide concentrations. Mode of cell death, measured using fluorescence-activated cell sorting (FACS) and caspase 3/7 activity, determined necrosis to be the primary cytotoxic mechanism at higher concentrations of the biocides stated above, and with ILs [C₁₄MIM]Cl and [C₁₄quin]Br, with apoptosis observed at borderline necrotic concentrations. Perhaps most interestingly, modification of anion had a significant effect on cytotoxicity. The use of N[SO₂CF₃] as an anion to [C₁₆MIM] attenuated cytotoxicity 10-fold in comparison to other anions, suggesting cytotoxicity may also be a tuneable property when using ILs as biocides.

Synthesis of multifunctional chlorhexidine-doped thin films for titanium-based implant materials

Our goal was to create bio-functional chlorhexidine (CHX)-doped thin films on commercially pure titanium (cpTi) discs using the glow discharge plasma approach. Different plasma deposition times (50, 35 and 20 min) were used to create bio-functional surfaces based on silicon films with CHX that were compared to the control groups [no CHX and bulk cpTi surface (machined)]. Physico-chemical and biological characterizations included: 1. Morphology, roughness, elemental chemical composition, film thickness, contact angle and surface free energy; 2. CHX-release rate; 3. Antibacterial effect on Streptococcus sanguinis biofilms at 24, 48 and 72 h; 4. Cytotoxicity and metabolic activity using fibroblasts cell culture (NIH-F3T3 cells) at 1, 2, 3 and 4 days; 5. Protein expression by NIH-F3T3 cells at 1, 2, 3 and 4 days; and 6. Co-culture assay of fibroblasts cells and S. sanguinis to assess live and dead cells on the confocal laser scanning microscopy, mitochondrial activity (XTT), membrane leakage (LDH release), and metabolic activity (WST-1 assay) at 1, 2 and 3 days of co-incubation. Data analysis showed that silicon films, with or without CHX coated cpTi discs, increased surface wettability and free energy (p < 0.05) without affecting surface roughness. CHX release was maintained over a 22-day period and resulted in a significant inhibition of biofilm growth (p < 0.05) at 48 and 72 h of biofilm formation for 50 min and 20 min of plasma deposition time groups, respectively. In general, CHX treatment did not significantly affect NIH-F3T3 cell viability (p > 0.05), whereas cell metabolism (MTT assay) was affected by CHX, with the 35 min of plasma deposition time group displaying the lowest values as compared to bulk cpTi (p < 0.05). Moreover, data analysis showed that films, with or without CHX, significantly affected the expression profile of inflammatory cytokines, including IL-4, IL-6, IL-17, IFN-y and TNF-α by NIH-F3T3 cells (p < 0.05). Co-culture demonstrated that CHX-doped film did not affect the metabolic activity, cytotoxicity and viability of fibroblasts cells (p > 0.05). Altogether, the findings of the current study support the conclusion that silicon films added with CHX can be successfully created on titanium discs and have the potential to affect bacterial growth and inflammatory markers without affecting cell viability/proliferation rates.

Antimicrobial Effect of Natural Berry Juices on Common Oral Pathogenic Bacteria

(1) Background: Antimicrobial agents such as chlorhexidine (CHX) are commonly used in oral plaque control. However, sometimes those agents lack antimicrobial efficiency or cause undesired side effects. To identify alternative anti-infective agents, the present study investigated the antibacterial activity of all-fruit juices derived from blackcurrant, redcurrant, cranberry and raspberry on common oral pathogenic gram-positive and gram-negative bacteria (Streptococcus mutans, Streptococcus gordonii, Streptococcus sobrinus, Actinomyces naeslundii, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Enterococcus faecalis). (2) Methods: Antibacterial efficiency was evaluated by agar diffusion assay and in direct contact with bacteria in planktonic culture. Furthermore, cytotoxicity on human gingival fibroblasts was determined. (3) Results: Blackcurrant juice was most efficient at suppressing bacteria; followed by the activity of redcurrant and cranberry juice. Raspberry juice only suppressed P. gingivalis significantly. Only high-concentrated blackcurrant juice showed minimal cytotoxic effects which were significantly less compared to the action of CHX. (4) Conclusion: Extracts from natural berry juices might be used for safe and efficient suppression of oral pathogenic bacterial species.

Antimicrobial, antibiofilm and cytotoxic effects of a colloidal nanocarrier composed by chitosan-coated iron oxide nanoparticles loaded with chlorhexidine

OBJECTIVES

This study evaluated the antimicrobial and antibiofilm effects of a colloidal nanocarrier for chlorhexidine (CHX) on Candida glabrata and Enterococcus faecalis, as well as tested its cytotoxic effect on murine fibroblasts.

METHODS

Iron oxide nanoparticles (IONPs) were coated with chitosan (CS) and loaded with CHX at 31.2, 78 and 156 μg/mL. Antimicrobial effects were assessed by determining the minimum inhibitory concentration (MIC), using the broth microdilution method, and fractional inhibitory concentration index (FICI). Preformed biofilms (48 h) were treated with different concentrations of the nanocarrier (24 h) and quantified by colony-forming units (CFUs), total biomass and metabolic activity. For cytotoxicity, the viability of L929 cells was evaluated by MTT assay after 24 and 48 h of exposure to the nanocarrier. Data were submitted to ANOVA and Fisher LSD or Tukey post-hoc tests (α = 0.05).

RESULTS

MIC and FICI results showed an indifferent interaction among the components of the nanocarrier for all strains evaluated. CHX alone and nanocarrier containing 156 μg/mL CHX did not differ from each other in reducing the number of CFUs. However, the nanocarrier containing 156 μg/mL CHX promoted the highest reductions in total biofilm biomass and metabolism, surpassing the effect of CHX alone. After 24 and 48 h of exposure, the nanocarrier reduced CHX toxicity to the L929 cell at low concentrations.

CONCLUSION

These findings suggest that the CHX nanocarrier has potential to be used in the control of oral diseases associated with C. glabrata and E. faecalis.

CLINICAL RELEVANCE

CHX has improved the antibiofilm effect and reduced the cytotoxicity (at low concentrations) when conjugated to CS-coated IONPs. This new colloidal formulation has potential as an alternative antimicrobial agent to pure CHX for the control of biofilm-related oral diseases, such as oral candidiasis and endodontic infections.

Effects of octenidine applied alone or mixed with sodium hypochlorite on eukaryotic cells

AIM

To assess the effects of octenidine dihydrochloride (OCT) on eukaryotic cells and the cytotoxicity of OCT associated with sodium hypochlorite - NaOCl (NaOCl/OCT).

METHODOLOGY

L929 fibroblasts and human osteoblast-like cells (Saos-2) were exposed to 0.1% OCT, 2% CHX, 2.5% NaOCl, 5.25% NaOCl and mixtures of 5.25% NaOCl and 0.1% OCT (NaOCl/OCT) at 90 : 10, 80 : 20 and 50 : 50 ratios. Cell viability was assessed by methyl-thiazol-tetrazolium (MTT) and neutral red (NR) assays; type of cell death, by flow cytometry; cytoskeleton, by actin and α-tubulin fluorescence; and alkaline phosphatase (ALP) activity, by thymolphthalein release. The data were analysed by two-way ANOVA and Bonferroni tests (α = 0.05).

RESULTS

MTT and NR assays revealed that 0.1% OCT had the lowest cytotoxicity (P < 0.05), followed by 2% CHX (P < 0.05). The 2.5% NaOCl, NaOCl/OCT 80 : 20 and NaOCl/OCT 50 : 50 solutions had intermediate cytotoxicity. NaOCl 5.25% and NaOCl/OCT 90 : 10 had the highest cytotoxicity (P < 0.05). The OCT group had a higher percentage of viable cells than the NaOCl and CHX groups (P < 0.05), and induced apoptosis at higher doses. The cytoskeleton alterations were observed at 0.12%, 0.6% and 2.02% for the NaOCl, CHX and OCT groups, respectively. The solutions did not induce ALP activity.

CONCLUSION

Octenidine dihydrochloride was less cytotoxic, induced apoptosis at higher doses, caused few changes in the cytoskeleton and did not induce alkaline phosphatase activity. In addition, octenidine dihydrochloride reduced the cytotoxicity of 5.25% NaOCl when combined at 20 and 50%.

Three-dimensional human skin model infected with Staphylococcus aureus as a tool for evaluation of bioactivity and biocompatibility of antiseptics

In the light of pandemic spreads of multi-drug-resistant micro-organisms, alternative antimicrobial strategies to the use of antibiotics are the focus of research attention. As a prerequisite for medical application, the aim of this study was to develop a three-dimensional full skin infection model to evaluate the bioactivity and biocompatibility of antiseptics in application-relevant concentrations. A three-dimensional (3D) full skin model consisting of collagen-embedded fibroblasts as dermis and a fully differentiated epidermis built from keratinocytes was infected with Staphylococcus aureus. Infected skin models were treated for 24 h with the antiseptics polihexanide, octenidine dihydrochloride, chlorhexidine digluconate and povidone-iodine. Infection resulted in detrimental effects, a strong immune response with increased secretion of lactate dehydrogenase and pro-inflammatory cytokines, and increased gene expression of pro-inflammatory cytokines and antimicrobial peptides after 24 h. Application of antiseptics protected the skin models from damage due to S. aureus infection while demonstrating good biocompatibility. The best ratio of bioactivity to biocompatibility was observed for polihexanide. Polihexanide also enhanced the innate immune response by increasing the gene expression levels of antimicrobial peptides such as human β-defensin 2, human β-defensin 3, psoriasin and ribonuclease 7. The developed model provides an excellent tool to investigate the response of human cells to microbial infections in a complex 3D structure. Furthermore, the infection model is appropriate for evaluation of bioactivity and biocompatibility of antiseptics. As such, the model presented in this study is a promising approach to evaluate the mechanisms and effectiveness of new antimicrobial strategies.

Effects of octenidine mouth rinse on apoptosis and necrosis of human fibroblasts and epithelial cells - an in vitro study

This study aimed at comparing the cytotoxicity of a new octenidine mouth rinse (MR) on gingival fibroblasts and epithelial cells using different established MRs. Octenidol (OCT), Chlorhexidine 0.2% (CHX), Meridol (MER), Oral B (OB), and control (PBS only) were used. Human primary gingival fibroblasts (HGFIBs) and human primary nasal epithelial cells (HNEPCs) were cultivated in cell-specific media (2 × 10⁵ cells/well) and treated with a MR or PBS for 1, 5, and 15 min. All tests were performed in duplicate and repeated 12 times. The apoptosis and necrosis were determined using a Caspase-3/7 assay and LDH assay, respectively. The data were analyzed using two-way analysis of variance with subsequent Mann-Whitney U-test. No significant differences could be found between the incubation times of the MR, neither for apoptosis nor necrosis (p > 0.05). Regarding apoptosis of HGFIBs, MRs had no influence at all. In HNEPCs, OCT induced relevantly lower apoptosis than CHX (p = 0.01). Considering necrosis, MER showed the lowest numbers of necrotic HGFIBs and HNEPCs, whereas OB induced the highest number of necrotic cells. The differences between both MR were statistically relevant (p < 0.01). OCT did neither differ from the other MRs nor from the control (PBS) in induction of necrosis in both cell types. In conclusion, the slightly negative effect of OCT considering apoptosis and necrosis of HGFIBs and HNEPCs is nearly the same or even lower compared to the established MRs included in this study. The results confirm that OCT is a potential alternative to CHX.

Endoplasmic reticulum stress is involved in 2,4-dichlorophenol-induced hepatotoxicity

2,4-Dichlorophenol (2,4-DCP) is an environmental pollutant exhibiting a wide spectrum of toxic effects. We investigated the toxic effects and potential mechanisms underlying 2,4-DCP-induced hepatotoxicity. In vitro, 2,4-DCP caused hepatotoxicity manifested by a decrease in cell viability and inhibition of colony formation. Bip and CHOP expression was up-regulated at the mRNA and protein levels. Moreover, 2,4-DCP induced eIF2α phosphorylation and Xbp1 mRNA splicing, indicating that endoplasmic reticulum (ER) stress was activated after exposure of HL7702 cells to 2,4-DCP for 12 hr. Furthermore, the mitochondrial membrane potential collapsed and apoptosis was triggered after exposure to 2,4-DCP for 24 hr. In vivo, 2,4-DCP caused histological changes in the liver, and dramatically elevated the serum alanine transaminase (ALT) and aspartate aminotransferase (AST) levels of mice. ER stress was also triggered in the liver of mice on days 1 and 3. The ER stress inhibitor TUDCA could partly relieve the liver damage, as indicated by the restoration of serum ALT and AST levels. Taken together, our results demonstrated that ER stress may serve as an early warning mechanism against 2,4-DCP-induced hepatotoxicity, and severe ER stress may lead to apoptosis.

In vitro evaluation of wound healing and antimicrobial potential of ozone therapy

Although ozone therapy is extensively applied when wound repair and antimicrobial effect are necessary, little is known about cellular mechanisms regarding this process. Thus, this study aimed to evaluate ozone cytotoxicity in fibroblasts (L929) and keratinocytes (HaCaT) cell lines, its effects on cell migration and its antimicrobial activity. Cells were treated with ozonated phosphate-buffered saline (8, 4, 2, 1, 0.5 and 0.25 μg/mL ozone), chlorhexidine 0.2% or buffered-solution, and cell viability was determined through MTT assay. The effect of ozone on cell migration was evaluated through scratch wound healing and transwell migration assays. The minimum inhibitory concentrations for Candida albicans and Staphylococcus aureus were determined. Ozone showed no cytotoxicity for the cell lines, while chlorhexidine markedly reduced cell viability. Although no significant difference between control and ozone-treated cells was observed in the scratch assay, a considerable increase in fibroblasts migration was noticed on cells treated with 8 μg/mL ozonated solution. Ozone alone did not inhibit growth of microorganisms; however, its association with chlorhexidine resulted in antimicrobial activity. This study confirms the wound healing and antimicrobial potential of ozone therapy and presents the need for studies to elucidate the molecular mechanisms through which it exerts such biological effects.

Cytocompatibility testing of cyclodextrin-functionalized antimicrobial textiles-a comprehensive approach

Functionalized textiles can be used in wound management to reduce the microbial burden in the wound area, to prevent wound infections, and to avoid cross-contamination between patients. In the present study, a comprehensive in vitro approach to enable the assessment of antibacterial activity of functionalized textiles and cytotoxicity of cyclodextrin (CD)-complexes with chlorhexidine diacetate (CHX), iodine (IOD), and polihexanide (PHMB) is suggested to evaluate their properties for supporting optimal conditions for wound healing. For all β-CD-antiseptic functionalized cotton samples a strong antibacterial effect on the Gram-positive bacteria Staphylococcus aureus and Staphylococcus epidermidis as well as on the Gram-negative bacteria Klebsiella pneumoniae and Escherichia coli was proven. In addition, β-CD-CHX and β-CD-PHMB were effective against the yeast Candida albicans. The growth of Pseudomonas aeruginosa could be reduced significantly by β-CD-IOD and β-CD-PHMB. The established comprehensive testing system for determination of biocompatibility on human HaCaT keratinocytes is suitable for obtaining robust data on cell viability, cytotoxicity and mode of cell death of the β-CD-antiseptic-complexes. The promising results of the high antimicrobial activity of these functionalized textiles show the high potential of such materials in medical applications.

2,4-dichlorophenol induces ER stress-mediated apoptosis via eIF2α dephosphorylation in vitro

2,4-Dichlorophenol (2,4-DCP) has been widely used to produce herbicides and pharmaceutical intermediates, which exhibits various toxic effects including apoptosis. However, the mechanisms underlying 2,4-DCP-induced apoptosis, especially mediated by endoplasmic reticulum (ER) stress, are still unknown. In the present study, the mouse embryonic fibroblasts (MEFs) were used as an in vitro model system to figure out whether 2,4-DCP could induce ER stress, and further to elucidate the role of ER stress in 2,4-DCP-induced apoptosis. The results showed that 2,4-DCP dramatically caused the decrease of cell viability, the increase of apoptotic cells, the collapse of mitochondrial membrane potential (MMP) and the activation of caspase-3, suggesting that 2,4-DCP did induce apoptosis. Meanwhile, 2,4-DCP acted similarly as ER stress agonist tunicamycin (Tu) to activate all three branches (IRE1α, ATF6 and eIF2α) of ER stress. Furthermore, repression of ER stress or inhibition of eIF2α dephosphorylation significantly alleviated 2,4-DCP-induced apoptosis. Taking these results together, the present study firstly showed that 2,4-DCP induced ER stress-mediated apoptosis via eIF2α dephosphorylation in mammalian cells. These findings will provide new insights into the mechanisms underlying apoptosis after chlorophenols exposure.

Carboxymethylcellulose films containing chlorhexidine–zirconium phosphate nanoparticles: antibiofilm activity and cytotoxicity

Hybrid composite films of carboxymethylcellulose and chlorhexidine intercalated nanosized zirconium phosphate result able to reduce the formation of biofilms on wound surface.

Melatonin as a candidate therapeutic drug for protecting bone cells from chlorhexidine-induced damage

BACKGROUND

Melatonin was proposed for use in periodontitis and peri-implantitis therapy due to its bone-supportive effects. This issue is of interest because standard adjuvant antiseptics, namely chlorhexidine (CHX), prove damaging for osteoblasts. Thus, the aim of this study is to investigate if melatonin is suitable as an auxiliary agent for protecting osteoblasts from CHX damage.

METHODS

MC3T3 osteoblast response was determined following administration of various CHX concentrations in the absence or presence of melatonin. Osteoblast morphology was evaluated, total reactive oxygen species (ROS) and superoxide levels were quantified, ratios of apoptotic and necrotic cells were identified by flow cytometry, metabolic activity of remaining cells was assessed, and effects were calculated with repeated measures analysis and post hoc P value adjustment.

RESULTS

CHX led to poor morphology, increased total ROS and superoxide levels, and rigorously diminished the number of vital and metabolic active osteoblasts in a concentration-dependent manner. However, simultaneous melatonin supply supported cell morphogenesis and growth, reduced ROS and superoxide generation, shifted the percentage of CHX-damaged cells from necrotic/late to early apoptotic events, and modulated metabolic activity in osteoblasts.

CONCLUSION

These data reveal that melatonin protects osteoblasts in the CHX context, thereby implicating melatonin as a promising drug in periodontitis and peri-implantitis treatment.

Xanthan gum protects rabbit articular chondrocytes against sodium nitroprusside-induced apoptosis in vitro

We have previously reported that intra-articular injection of xanthan gum (XG) could significantly ameliorate the degree of joint cartilage degradation and pain in experimental osteoarthritis (OA) model in vivo. In this present study, we evaluated the protective effect of XG against Sodium nitroprusside (SNP)-induced rabbit articular chondrocytes apoptosis in vitro. Rabbit articular chondrocytes were incubated with various concentrations of XG for 24h prior to 0.5mmol/L SNP co-treatment for 24h. The proliferation of chondrocytes was analyzed using MTT assay. The chondrocytes early apoptosis rates were evaluated using Annexin V-FITC/PI flow cytometry. The morphology of apoptosis chondrocytes were observed by scanning electron microscopy (SEM). The loss/disruption of mitochondrial membrane potential was detected using rhodamin 123 by confocal microscope. The concentration of prostaglandin E2 (PGE2) in cell culture supernatants was evaluated using ELISA assay. The results showed that XG could significantly reverse SNP-reduced cell proliferation and inhibited cell early apoptosis rate in a dose-dependent manner. XG alleviated loss/disruption of mitochondrial membrane potential and decreased the PGE2 level of chondrocytes cell culture supernatants in SNP-induced chondrocytes. These results of the present research strongly suggest that XG can protect rabbit articular chondrocytes against SNP-induced apoptosis in vitro.

Sex differences in liver toxicity-do female and male human primary hepatocytes react differently to toxicants in vitro?

There is increasing amount of evidence for sex variation in drug efficiency and toxicity profiles. Women are more susceptible than men to acute liver injury from xenobiotics. In general, this is attributed to sex differences at a physiological level as well as differences in pharmacokinetics and pharmacodynamics, but neither of these can give a sufficient explanation for the diverse responses to xenobiotics. Existing data are mainly based on animal models and limited data exist on in vitro sex differences relevant to humans. To date, male and female human hepatocytes have not yet been compared in terms of their responses to hepatotoxic drugs. We investigated whether sex-specific differences in acute hepatotoxicity can be observed in vitro by comparing hepatotoxic drug effects in male and female primary human hepatocytes. Significant sex-related differences were found for certain parameters and individual drugs, showing an overall higher sensitivity of female primary hepatocytes to hepatotoxicants. Moreover, our work demonstrated that high content screening is feasible with pooled primary human hepatocytes in suspension.

Chlorhexidine-loaded hydroxyapatite microspheres as an antimicrobial delivery system and its effect on in vivo osteo-conductive properties

Hydroxyapatite (HA) has been investigated as a delivery system for antimicrobial and antibacterial agents to simultaneously stimulate bone regeneration and prevent infection. Despite evidence supporting the bactericidal efficiency of these HA carriers, few studies have focused on the effect of this association on bone regeneration. In this work, we evaluated the physico-chemical properties of hydroxyapatite microspheres loaded with chlorhexidine (CHX) at two different concentrations, 0.9 and 9.1 μgCHX/cm2 HA, and characterized their effects on in vitro osteoblast viability and bone regeneration. Ultraviolet-visible spectroscopy, scanning and transmission electron microscopy associated with energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy were used to characterize the association of CHX and HA nanoparticles. The high CHX loading dose induced formation of organic CHX plate-like aggregates on the HA surface, whereas a Langmuir film was formed at the low CHX surface concentration. Quantitative evaluation of murine osteoblast viability parameters, including adhesion, mitochondrial activity and membrane integrity of cells exposed to HA/CHX extracts, revealed a cytotoxic effect for both loading concentrations. Histomorphological analysis upon implantation into the dorsal connective tissues and calvaria of rats for 7 and 42 days showed that the high CHX concentration induced the infiltration of inflammatory cells, resulting in retarded bone growth. Despite a strong decrease in in vitro cell viability, the low CHX loading dose did not impair the biocompatibility and osteoconductivity of HA during bone repair. These results indicate that high antimicrobial doses may activate a strong local inflammatory response and disrupt the long-term osteoconductive properties of CHX-HA delivery systems.