In vitro response of human gingival epithelioid S-G cells to minocycline

In vitro evaluation of BMSCs early proliferation on minocycline-loaded electrospun nanofibers membrane

BACKGROUND

Electrospun nanofibers could simulate the natural extracellular matrix (ECM) of the host bone, while minocycline (MINO) is a broad-spectrum tetracycline antibiotic which has been found to have multiple non-antibiotics biological effects that promotes osteogenesis in vitro and in vivo.

OBJECTIVE

The present study aims at constructing a polylactic acid (PLA) electrospun nanofiber membrane loaded with MINO to enhance Bone marrow mesenchymal stem cells (BMSCs) adhesion and proliferation for early clinical treatment.

METHODS

The MINO-PLA membrane were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and in vitro drug release study. The antibacterial ability was also investigated. In addition, in vitro cellular proliferation experiment was performed to verify whether the PLA electrospun nanofibers membrane loaded with MINO enhance BMSCs adhesion and proliferation.

RESULTS

Analyzing the drug release and cell growth results, it was found that only the effective concentration of MINO-PLA could help the growth of BMSCs in the short term. This is related to the drug release rate of MINO-PLA and the initial concentration of MINO.

CONCLUSION

This study shows that by controlling the concentration and release rate of MINO with electrospinning PLA, BMSCs could proliferate on it, and a new bone repair material had been made in this study.

Cytotoxic Effects on Gingival Mesenchymal Stromal Cells and Root Surface Modifications Induced by Some Local Antimicrobial Products Used in Periodontitis Treatment

(1) Background: this study aims to test the cytotoxicity of three antimicrobial products used in periodontitis treatment on gingival mesenchymal stem cells (gMSCs) and their influence on root surfaces and gMSC adhesion. We tested the null hypothesis that the effects of the antimicrobials did not differ. (2) Methods: the commercial products based on sulphonic/sulphuric acids, sodium hypochlorite and silver nanoparticles, in five different concentrations, were added to culture medium for growing gMSCs. Cell proliferation capacity was tested using the Cell Counting Kit-8 (CCK8) and their viability was determined by succinate dehydrogenase activity (MTT) assay. Scanning electron microscopy evaluated the adhesion of gMSCs on root samples treated mechanically and with commercial products. (3) Results: the products induced a dose-dependent cytotoxicity in terms of reduced proliferation and viability of gMSCs, as well as cell shape modifications. Significant differences in CCK8 values between the different commercial products were observed. Based on proliferation tests, the null hypothesis was rejected. When MTT values of the three products were compared with each other, no significant differences were observed for any of the five concentrations (p = 0.065, p = 0.067, p = 0.172, p = 0.256, p = 0.060). (4) Conclusions: the three antimicrobials had a certain degree of cytotoxicity on gMSCs. gMSCs repopulated treated root surfaces.

Effects of curing lights on human gingival epithelial cell proliferation

BACKGROUND

Light-emitting diode (LED) and quartz-tungsten-halogen (QTH) curing lights are used commonly in clinics. The aim of this study was to assess the effect of these lights on the proliferation of human gingival epithelial cells.

METHODS

Smulow-Glickman (S-G) cells were exposed to a VALO LED (Ultradent) or an XL3000 QTH (3M ESPE) light at 1 millimeter or 6 mm distance for 18, 39, 60, and 120 seconds. Untreated and Triton X-100 treated cells were used as controls. At 24, 48, and 72 hours after light exposure, cell proliferation was evaluated via a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

RESULTS

The authors first evaluated the performances of these 2 lights. Both LED and QTH lights generated heat. The LED light generated less heat than the QTH light and could save approximately two-thirds of the curing time. When used for 18 seconds at a 6 mm distance, the LED light did not inhibit the proliferation of S-G cells. However, if the exposure time was longer (for example, 39, 60, or 120 seconds), the LED light inhibited cell proliferation. The inhibitory effect increased when the exposure time was increased to 39, 60, or 120 seconds. The QTH light did not inhibit S-G cell proliferation if the exposure time was less than 120 seconds.

CONCLUSIONS

Prolonged exposure to a blue curing light (both LED and QTH) inhibits the proliferation of gingival epithelial cells and may cause damages to oral soft tissues.

PRACTICAL IMPLICATIONS

In dental practices, a balance should be struck in consideration of curing time not only to cure the composites completely but also to minimize unnecessarily prolonged light exposure.

Minocycline-loaded PLGA electrospun membrane prevents alveolar bone loss in experimental peridontitis

Minocycline (MINO) is a tetracycline antibiotic effective against most of the bacteria microorganisms related to periodontal disease. Additionally, MINO promotes bone in vitro and in vivo. The objective of the present study was to establish the protocol for the preparation of MINO-loaded poly (lactic-co-glycolic acid) (MINO-PLGA) electrospun membranes and to evaluate their effect on osteogenesis in vitro and in a rat model of periodontitis. The characterization of MINO-PLGA electrospun membranes was assessed by scanning electron microscopy, laser scanning confocal microscopy, and contact angle measurement. The drug release study showed a sustained diffusion of MINO from electrospun membranes over a period of 40 d. The MINO-PLGA membranes containing 2% of the drug exhibited better support of osteoblast proliferation and adhesion and was subsequently used in vivo in an experimental periodontitis model. Its therapeutic potential was evaluated by the measurement of alveolar bone loss (ABL), bone volume analysis, histological analysis, and immunohistochemistry. MINO-PLGA membrane increased alveolar crest height in the periodontitis model, inhibited the expression of the ligand of the receptor activator for nuclear factor-κB (RANKL), and promoted the expression of its inhibitor, osteoprotegerin. The study demonstrated that MINO-PLGA electrospun membranes may be applied to stimulate bone regeneration in periodontitis.

A Novel Small Molecule, ZY354, Inhibits Dental Caries-Associated Oral Biofilms

Biofilm control is a critical approach to the better management of dental caries. Antimicrobial small molecules have shown their potential in the disruption of oral biofilm and control of dental caries. The objectives of this study were to examine the antimicrobial activity and cytotoxicity of a newly designed small-molecule compound, ZY354. ZY354 was synthesized, and its cytotoxicity was evaluated in human oral keratinocytes (HOK), human gingival epithelial cells (HGE), and macrophages (RAW) by CCK-8 assays. Minimal inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), minimum biofilm inhibition concentrations (MBICs), and minimum biofilm reduction concentrations (MBRCs) of ZY354 against common oral streptococci (i.e., Streptococcus mutans, Streptococcus gordonii, and Streptococcus sanguinis) were determined by microdilution method. The exopolysaccharide (EPS)/bacterium ratio and the dead/live bacterium ratio in the ZY354-treated multispecies biofilms were determined by confocal laser scanning microscopy, and the microbial composition was visualized and quantified by fluorescent in situ hybridization and quantitative PCR (qPCR). The demineralizing activity of ZY354-treated biofilms was evaluated by transverse microradiography. The results showed that ZY354 exhibited low cytotoxicity in HOK, HGE, and RAW cells and exhibited potent antimicrobial activity against common oral streptococci. The EPS and the abundance of S. mutans were significantly reduced after ZY354 treatment, along with an increased dead/live microbial ratio in multispecies biofilms compared to the level with the nontreated control. The ZY354-treated multispecies biofilms exhibited reduced demineralizing activity at the biofilm/enamel interface. In conclusion, the small-molecule compound ZY354 exhibits low cytotoxicity and remarkable antimicrobial activity against oral streptococci, and it may have a great potential in anticaries clinical applications.

The effect of doxycycline hyclate, chlorhexidine gluconate, and minocycline hydrochloride on osteoblastic proliferation and differentiation in vitro

BACKGROUND

The purpose of this study was to determine the effect of the active substance of three types of local delivery systems, doxycycline hyclate 10% (DOXY), chlorhexidine gluconate, 2.5 mg (CHX), and minocycline hydrochloride, 1 mg (MINO), on osteoblastic cell proliferation and differentiation.

METHODS

There were four groups: control osteoblastic cells (OB) alone, OB + DOXY, OB + CHX, and OB + MINO. Trypan blue and MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assays were used to test osteoblastic cell viability. Cell differentiation was tested by measuring alkaline phosphatase levels. Osteoblast morphology was investigated by light and scanning electron microscopy.

RESULTS

At a concentration of 0.5 mg/ml, the Trypan blue test showed that DOXY, MINO, and CHX had significant toxicity effects on osteoblast cells compared to the control group, with a mean cell viability of 84%, 74%, and 51%, respectively (P <0.05). The MTT test showed that the control and DOXY groups were statistically significantly different (P <0.05) compared to CHX and MINO groups. The DOXY group showed a significantly higher alkaline phosphatase activity ( approximately 56%) than the control and MINO groups, and it was nearly 178% higher than the CHX group (P <0.05). The morphology of the osteoblasts seemed to be slightly altered when they were incubated with DOXY; however, with MINO, they appeared rounded with minimal attachment. In the CHX group, the osteoblasts assumed a shape of a very thin filopodia with a volcano-like nucleus.

CONCLUSIONS

At a concentration of 0.5 mg/ml, CHX and, to a lesser extent, MINO had a cytotoxic effect on osteoblast proliferation in vitro. However, DOXY seemed to enhance maturation and differentiation rather than proliferation. In addition to DOXY's beneficial effect as an adjunctive therapy to mechanical debridement in the treatment of periodontal disease, it may have an effect on periodontal regeneration.

Development of an in vitro assay for the investigation of metabolism-induced drug hepatotoxicity

In a number of adverse drug reactions leading to hepatotoxicity drug metabolism is thought to be involved by generation of reactive metabolites from nontoxic drugs. In this study, an in vitro assay was developed for measurement of the impact of metabolic activation of compound on the cytotoxicity toward a human hepatic cell line. HepG2 cells were treated for 6 h with compound in the presence or absence of rat liver S9-mix, and the viability was measured using the MTT test. The cytotoxicity of cyclophosphamide was substantially increased by S9-mix in the presence of NADPH. Three NADPH sources were tested: NADPH (1 mmol/L) or NADPH regenerating system with either NADP(+)/glucose 6-phosphate (G6P) or NADP(+)/isocitrate. All three NADPH sources increased the cytotoxicity of cyclophosphamide to a similar extent. Eight test compounds known to cause hepatotoxicity were tested. For these, only the cytotoxicity of diclofenac was increased by S9 enzymes when an NADPH regenerating system was used. The increased toxicity was NADPH dependent. Reactive drug metabolites of diclofenac, formed by NADPH-dependent metabolism, were identified by LC-MS. Furthermore, an increase in toxicity, not related to enzymatic activity but to G6P, was observed for diclofenac and minocycline. Tacrine and amodiaquine displayed decreased toxicity with S9-mix, and carbamazepine, phenytoin, bromfenac and troglitazone were nontoxic at all tested concentrations, with or without S9-mix. The results show that this method, with measurement of the cytotoxicity of a compound in the presence of an extracellular metabolizing system, may be useful in the study of cytotoxicity of drug metabolites.

Inhibitory effect of minocycline on amyloid beta fibril formation and human microglial activation

Minocycline, a derivative of the antibiotic tetracycline, displays neuroprotective properties in various models of neurodegenerative diseases and is now used in clinical trials, because of its relative safety and tolerability. Minocycline passes the blood-brain barrier and is presumed to inhibit microglial activation. In Alzheimer's disease brain, a number of proteins, including serum amyloid P component (SAP) and complement factors such as C1q, accumulate in amyloid beta (Abeta) plaques. In a previous study, SAP and C1q were found to be required for clustering of activated microglia in Abeta plaques. Furthermore, SAP and C1q enhanced Abeta fibril formation and Abeta mediated cytokine release by human microglia in vitro. In the present study, we report that tetracycline and minocycline dose-dependently reduce TNF-alpha and IL-6 release by adult human microglia upon stimulation with a combination of Abeta, SAP, and C1q. In addition, minocycline and to a lesser extent tetracycline inhibit fibril formation of Abeta as determined in a thioflavin-S-based fluorescence test. This inhibitory effect was observed with Abeta alone as well as with Abeta in combination with SAP and C1q. Our data suggest that minocycline and tetracycline at tolerable doses can inhibit human microglial activation. This activity in part is exerted by inhibition of (SAP and C1q enhanced) Abeta fibril formation.

In vitro cytotoxicity to human cells in culture of some phenolics from olive oil

The neutral red in vitro cytotoxicity assay was used to evaluate the comparative responses of human cells isolated from tissues of the oral cavity to olive oil phenolics. The cell lines used included normal gingival fibroblasts, immortalized, nontumorigenic gingival epithelial cells, and carcinoma cells from the salivary gland. No differences in the relative sensitivities to the phenolics amongst the three cell types were noted. In general, for all cell types, the sequence of increasing cytotoxicity was: oleuropein aglycone>oleuropein glycoside, caffeic acid>o-coumaric acid>cinnamic acid>>tyrosol, syringic acid, protocatechuic acid, vanillic acid. Cytotoxicity was noted only at phenolic concentrations far exceeding those attainable after habitual consumption, thus indicating that consumption of phenol-rich olive oil is safe.