Violet/blue light activates Nrf2 signaling and modulates the inflammatory response of THP-1 monocytes.

Several studies suggest that light in the UVA range (320-400 nm) activates signaling pathways that are anti-inflammatory and antioxidative. These effects have been attributed to Nrf2-mediated upregulation of "phase 2" genes such as heme oxygenase-1 (HO-1) that neutralize oxidative stress and metabolize electrophiles. Proteomics analysis previously had shown that small doses of blue light (400-500 nm) increased levels of peroxiredoxin phase 2 proteins in THP-1 monocytes, which led to our hypothesis that blue light activates Nrf2 signaling and thus may serve as an anti-inflammatory agent. THP-1 monocytes were treated with doses of blue light with and without lipopolysaccharide (LPS) inflammatory challenge. Cell lysates were tested for Nrf2 activation and HO-1 production. Treated cells were assessed for viability/mitochondrial activity via trypan blue exclusion and MTT assay, and secretion of two major pro-inflammatory cytokines, interleukin 8 (IL8) and tumor necrosis factor alpha (TNFα) was measured using ELISA. Blue light activated the phase 2 response in cultured THP-1 cells and was protective against LPS-induced cytotoxicity. Light pre-treatment also significantly reduced cytokine secretion in response to 0.1 µg ml-1 LPS, but had no anti-inflammatory effect at high LPS levels. This study is the first to report these effects using a light source that is approved for routine use on dental patients. Cellular responses to these light energies are worth further study and may provide therapeutic interventions for inflammation.

Dentin hypersensitivity and oxalates: a systematic review.

Treatment of dentin hypersensitivity with oxalates is common, but oxalate efficacy remains unclear. Our objective was to systematically review clinical trials reporting an oxalate treatment compared with no treatment or placebo with a dentin hypersensitivity outcome. Risk-of-bias assessment and data extraction were performed independently by two reviewers. Standardized mean differences (SMD) were estimated by random-effects meta-analysis. Of 677 unique citations, 12 studies with high risk-of-bias were included. The summary SMD for 3% monohydrogen-monopotassium oxalate (n = 8 studies) was -0.71 [95% Confidence Interval: -1.48, 0.06]. Other treatments, including 30% dipotassium oxalate (n = 1), 30% dipotassium oxalate plus 3% monohydrogen monopotassium oxalate (n = 3), 6% monohydrogen monopotassium oxalate (n = 1), 6.8% ferric oxalate (n = 1), and oxalate-containing resin (n = 1), also were not statistically significantly different from placebo treatments. With the possible exception of 3% monohydrogen monopotassium oxalate, available evidence currently does not support the recommendation of dentin hypersensitivity treatment with oxalates.

Response of THP-1 monocytes to blue light from dental curing lights.

Blue light curing units (wavelengths of 400-500 nm) are a mainstay of restorative dentistry, and several high-intensity light sources have been developed to polymerize resin composites more rapidly. The biological safety of visible light has been assumed, but some reports of adverse biological effects of blue light in non-dental contexts support further evaluation of the biological safety of high-intensity blue light. The current study tested the hypothesis that blue light provokes cell stress responses resulting in the secretion of cytokines or expression of heat-shock proteins (HSP) in monocytes. Human monocytic cells were irradiated with three light sources (quartz-tungsten-halogen, plasma-arc and laser), then cellular proliferation, secretion of the inflammatory cytokine TNFalpha and induction of HSP72 were measured. Results indicated that although all three light sources significantly inhibited proliferation of monocytes, the secretion of TNFalpha was not induced following exposure to blue light and was not potentiated with administration of the activator lipopolysaccharide. Similarly, treatment with the plasma-arc light, which caused the largest temperature increase in previous studies, did not induce HSP72. The current results do not support activation of monocytes by blue light as an inflammatory risk factor in dental tissues during curing of composites. However, the results of the current study should be further verified in primary monocytes and an animal model before decisions about clinical risks are made.

Cytotoxicity of endodontic materials over 6-weeks ex vivo.

AIM: To test the hypothesis that extending the time of a traditional ex vivo cytotoxicity test helps to identify trends in the behaviour of root core materials and sealers, which could ultimately aid in predicting their clinical safety and performance. METHODOLOGY: Endodontic sealers and core specimens were initially tested in direct contact with L929 fibroblasts for 72 h. Cell response was estimated by measuring cellular succinate dehydrogenase activity relative to Teflon controls. Cytotoxicity (% of more active cells) was reassessed after 1, 3, 4 and 6 weeks, with the specimens stored in a physiologically balanced salt-solution between tests. RESULTS: Distinct trends in cytotoxicity among both core materials and sealers were observed over the 6-week test. Four of the six sealers and two of the three core materials showed cell viabilities of <30% of Teflon after 6 weeks (>70% cytotoxicity). CONCLUSIONS: The current results suggest that some endodontic materials have an elevated biological risk for extended intervals.

Long-term sealing ability of Pulp Canal Sealer, AH-Plus, GuttaFlow and Epiphany.

AIM: To evaluate the long-term sealing ability of four contemporary endodontic sealers [Pulp Canal Sealer (PCS), AH-Plus, GuttaFlow and Epiphany] using a fluid filtration technique. METHODOLOGY: The palatal roots of 40 human maxillary molar teeth were selected and the root canal was prepared using a crown-down technique (apical size 40, 6% taper). Roots were irrigated with 3% NaOCl, 17% EDTA solution and rinsed with distilled water. Canals were filled with either PCS, AH-Plus, GuttaFlow or Epiphany using a single-cone technique (n = 8). Twenty-four hours after filling, the roots were connected to an automatic flow-recording device (Flodec System) filled with double-distilled water under pressure (0.2 bar) to measure leakage. Flow rates were assessed at 6, 12 or 24-h and after 1-year of storage. RESULTS: None of the materials fully prevented fluid flow. Fluid flow decreased after 6 h and decreased further after 12 h. After 24 h, PCS and AH-Plus allowed significantly more fluid flow than GuttaFlow and Epiphany. After 1 year, PCS allowed significantly more fluid flow than the other materials. No significant changes in leakage occurred between 24 h and 1 year. CONCLUSIONS: GuttaFlow and Epiphany allowed less fluid movement along filled straight roots.

In vitro biological effects of sodium titanate materials.

UNLABELLED: Monosodium titanate (MST) particles effectively bind specific metals and are therefore promising compounds for delivery or sequestration of metals in biological contexts. Yet, the biological properties of MST are largely unexplored. Our previous study showed that the cytotoxicity of these compounds was mild, but the nature of the dose response curves suggested that residual titanates in culture may have interfered with the assay. In the current study, we assessed the importance of these artifacts, and extended our previous results using fibroblasts for biological evaluation. We also assessed the biological response to a new type of titanate (referred to as amorphous peroxo-titanate or APT) that shows more promising metal binding properties than MST. METHODS: The degree of titanate-induced interference in the MTT (mitochondrial activity assay) was estimated by means of cell-free assays with and without a final centrifugation step to remove residual titanate particulate. Cytotoxic responses to titanates were assessed by measuring succinate dehydrogenase activity (by MTT) in THP1 monocytes or L929 fibroblasts after 24-72 h exposures. Monocytic activation by APT was assessed by TNFalpha secretion (ELISA) from monocytes with or without lipopolysaccharide (LPS) activation. RESULTS: We confirmed that residual titanate particulates may alter the SDH activity assay, but that this effect is eliminated by adding a final centrifugation step to the standard MTT procedure. Addition of MST or APT at concentrations up to 100 mg/L altered succinate dehydrogenase activity by < 25% in both monocytes and fibroblasts. Fibroblasts displayed time-dependent adaptation to the MST. APT did not trigger TNFalpha secretion or modulate LPS-induced TNFalpha secretion from monocytes. CONCLUSIONS: Although further in vitro and in vivo assessment is needed, MST and APT exhibit biological properties that are promising for their use as agents to sequester or deliver metals in biological systems.

Initial cytotoxicity of novel titanium alloys.

We assessed the biological response to several novel titanium alloys that have promising physical properties for biomedical applications. Four commercial titanium alloys [Super-TIX(R) 800, Super-TIX(R) 51AF, TIMETAL(R) 21SRx, and Ti-6Al-4V (ASTM grade 5)] and three experimental titanium alloys [Ti-13Cr-3Cu, Ti-1.5Si and Ti-1.5Si-5Cu] were tested. Specimens (n = 6; 5.0 x 5.0 x 3.0 mm(3)) were cast in a centrifugal casting machine using a MgO-based investment and polished to 600 grit, removing 250 mum from each surface. Commercially pure titanium (CP Ti: ASTM grade 2) and Teflon (polytetrafluoroethylene) were used as positive controls. The specimens were cleaned and disinfected, and then each cleaned specimen was placed in direct contact with Balb/c 3T3 fibroblasts for 72 h. The cytotoxicity [succinic dehydrogenase (SDH) activity] of the extracts was assessed using the MTT method. Cytotoxicity of the metals tested was not statistically different compared to the CP Ti and Teflon controls (p > 0.05). These novel titanium alloys pose cytotoxic risks no greater than many other commonly used alloys, including commercially pure titanium. The promising short-term biocompatibility of these Ti alloys is probably due to their excellent corrosion resistance under static conditions, even in biological environments.

Radicals produced by blue-light-resin interactions alter the redox status of THP1 human monocytes.

Resin composites are widely used in dentistry, and are polymerized in situ using a blue-light activated, free-radical polymerization mechanism. Blue light (400-500nm) is used to activate camphoroquinone (CQ), which decomposes to form free radicals that are stabilized by dimethyl-p-toludine (DMPT). CQ and DMPT are applied near tooth pulpal tissues and are irradiated during restorative procedures, suggesting that pulpal cells are exposed to free radicals. Because glutathione is a major component of the cellular redox management system, we tested the hypothesis that blue light irradiation would shift cellular glutathione redox balance of cells exposed to CQ and DMPT. We also measured NFkappaB activation, a redox-sensitive transcription factor that regulates inflammatory responses and glutathione synthetic enzyme levels. THP1 human monocytes were exposed to sublethal levels of CQ (0.4 mM) or DMPT (1.0 mM), with or without blue light exposure (25 J/cm(2)) from a quartz-tungsten-halogen source. The ratio of reduced to oxidized glutathione was measured using as assay based on 5,5'-dithio-bis(2-nitrobenszoic acid). NFkappaB transactivation was measured by transfection of an NFkappaB-containing plasmid linked to a luciferase reporter. Our results showed that blue light, CQ, or DMPT alone had no significant effect on cellular glutathione redox balance, but that the combination of these agents induced a marked oxidative bias, and reduced total glutathione levels up to 50%. On the other hand, light, CQ, and DMPT alone or in combination suppressed NFkappaB transactivation by >70%. Our results suggest that CQ and DMPT pose risks to pulpal tissues with or without blue light irradiation, and that multiple, interacting mechanisms shape the response to these agents.

Cytokine secretion from monocytes persists differentially after activator removal-One mechanism of long-term biological response to implants.

Biomedical implants significantly improve the quality of life in an ever-increasing number of patients. However, inflammation of tissues around implants remains a long-term, post-placement sequelae that may contribute to implant failure. Infection-mediated failure is partly a consequence of inappropriate host response and chronic inflammation, and is mediated primarily by the secretory products of monocytes and macrophages. Although the secretion of inflammatory mediators from activated monocytes is well characterized, the resolution of mediator levels post-activation is relatively unstudied. The current study defines the time course of cytokine secretion by activated human monocytes after the activator has been removed. THP1 human monocytes were activated by LPS, and cytokine secretion was monitored over time after LPS removal using enzyme-linked immunosorbent assays (TNFalpha or IL8) or a cytokine array. The release of cytokines was compared with conditions without LPS removal. As expected, secretion of nearly all cytokines was reduced when LPS was removed, but the amount of the reduction was highly cytokine-dependent. Furthermore, levels of cytokines were stable in medium alone but not in cell-culture, suggesting an active process to either degrade or internalize secreted cytokines. Our results are consistent with clinical experience that inflammation resolves rapidly after treatment to remove bacteria or inflamed tissue. However, the differential cytokine regulation indicates a sophisticated coordination of cytokine levels probably associated with management of the wound healing response after removal of the bacterial insult. This wound healing response is one critical component of the long-term success of biomedical implants.

In vitro cytotoxicity of dental composites based on new and traditional polymerization chemistries.

UNLABELLED: The biological response to dental restorative polymer composites is mediated by the release of unpolymerized residual monomers. Several new composite formulations claim to reduce unpolymerized residual mass. The current study assessed the cytotoxic responses to several of these new formations and compared them with more traditional formulations. Our hypothesis predicted that if these new polymerization chemistries reduce unpolymerized residual mass, the cytotoxicity of these materials also should be reduced relative to traditional formulations. METHODS: Materials (HerculiteXRV, Premise, Filtek Supreme, CeramxDuo, Hermes, and Quixfil) were tested in vitro in direct contact with Balb mouse fibroblasts, initially, then after aging in artificial saliva for 0, 1, 3, 5, or 8 weeks. The toxicity was determined by using the MTT assay to the estimate SDH activity. Knoop hardness of the materials also was measured at 0 and 8 weeks to determine whether surface breakdown of the materials in artificial saliva contributed to cytotoxic responses. RESULTS: Materials with traditional methacrylate chemistries (Herculite, Premise, Filtek Supreme) were severely (>50%) cytotoxic throughout the 8-week interval, but materials with newer chemistries or filling strategies (Hermes, CeramXDuo, and Quixfil) improved over time of aging in artificial saliva. Hermes showed the least cytotoxicity at 8 weeks, and was statistically equivalent to Teflon negative controls. Hardness of the materials was unaffected by exposure to artificial saliva. CONCLUSIONS: Newer polymerization and filling strategies for dental composites show promise for reducing the release of unpolymerized components and cytotoxicity.

Intra- and extracellular reactive oxygen species generated by blue light.

Blue light from dental photopolymerization devices has significant biological effects on cells. These effects may alter normal cell function of tissues exposed during placement of oral restorations, but recent data suggest that some light-induced effects may also be therapeutically useful, for example in the treatment of epithelial cancers. Reactive oxygen species (ROS) appear to mediate blue light effects in cells, but the sources of ROS (intra- versus extracellular) and their respective roles in the cellular response to blue light are not known. In the current study, we tested the hypothesis that intra- and extracellular sources of blue light-generated ROS synergize to depress mitochondrial function. Normal human epidermal keratinocytes (NHEK) and oral squamous cell carcinoma (OSC2) cells were exposed to blue light (380-500 nm; 5-60 J/cm(2)) from a dental photopolymerization source (quartz-tungsten-halogen, 550 mW/cm(2)). Light was applied in cell-culture media or balanced salt solutions with or without cells present. Intracellular ROS levels were estimated using the dihydrofluorescein diacetate (DFDA) assay; extracellular ROS levels were estimated using the leucocrystal violet assay. Cell response was estimated using the MTT mitochondrial activity assay. Blue light increased intracellular ROS equally in both NHEK and OSC2. Blue light also increased ROS levels in cell-free MEM or salt solutions, and riboflavin supplements increased ROS formation. Extracellularly applied ROS rapidly (50-400 muM, <1 min) increased intracellular ROS levels, which were higher and longer-lived in NHEK than OSC2. The type of cell-culture medium significantly affected the ability of blue light to suppress cellular mitochondrial activity; the greatest suppression was observed in DMEM-containing or NHEK media. Collectively, the data support our hypothesis that intra- and extracellularly generated ROS synergize to affect cellular mitochondrial suppression of tumor cells in response to blue light. However, the identity of blue light targets that mediate these changes remain unclear. These data support additional investigations into the risks of coincident exposure of tissues to blue light during material polymerization of restorative materials, and possible therapeutic benefits.

Dynamics of composite polymerization mediates the development of cuspal strain.

OBJECTIVES: In the current study, we used electronic speckle pattern interferometry (ESPI) to measure tooth deformation in response to polymerization of five resin composites with a range of polymerization shrinkage. Our hypothesis was that composites with higher polymerization shrinkage should cause more cuspal strain as measured by ESPI. METHODS: Standardized MOD cavities were prepared and placed into the ESPI apparatus before the cavities were filled with composites (n=10). The ESPI apparatus was constructed to measure the out-of-plane displacement of the lingual cusps of the teeth during the polymerization of the restorative material. A thermocouple was attached to the specimen to monitor thermal changes throughout the polymerization process. RESULTS: Experiments with empty preparations demonstrated that the ESPI technique was temporally responsive and sensitive to dimensional changes. However, the correlation between polymerization shrinkage of composite resins and ESPI-measured tooth deformation was not straightforward. In particular, a flowable material did not deform the tooth significantly more that a conventional hybrid. Further, an experimental silorane material (with the lowest axial shrinkage) induced the least tooth deformation. SIGNIFICANCE: We concluded that ESPI is a viable method for assessing cuspal strain induced by shrinkage of bonded composite restorations, but that polymerization shrinkage data may overestimate shrinkage-induced tooth deformation. The rate of polymerization shrinkage appeared to mediate the development of cuspal strain.

Adsorption of biometals to monosodium titanate in biological environments.

Monosodium titanate (MST) is an inorganic sorbent/ion exchanger developed for the removal of radionuclides from nuclear wastes. We investigated the ability of MST to bind Cd(II), Hg(II), Au(III), or the Au-organic compound auranofin to establish the utility of MST for applications in environmental decontamination or medical therapy (drug delivery). Adsorption isotherms for MST were determined at pH 7-7.5 in water or phosphate-buffered saline. The extent of metal binding was determined spectroscopically by measuring the concentrations of the metals in solution before and after contact with the MST. Cytotoxic responses to MST were assessed using THP1 monocytes and succinate dehydrogenase activity. Monocytic activation by MST was assessed by TNFalpha secretion (ELISA) with or without lipopolysaccharide (LPS) activation. MST adsorbed Cd(II), Hg(II), and Au(III) under conditions similar to those in physiological systems. MST exhibited the highest affinity for Cd(II) followed by Hg(II) and Au (III). MST (up to 100 mg/L) exhibited only minor (<25% suppression of succinate dehydrogenase) cytotoxicity and did not trigger TNFalpha secretion nor modulate LPS-induced TNFalpha secretion from monocytes. MST exhibits high affinity for biometals with no significant biological liabilities in these introductory studies. MST deserves further scrutiny as a substance with the capacity to decontaminate biological environments or deliver metals or metal compounds for therapeutic applications.

Au(III), Pd(II), Ni(II), and Hg(II) alter NF kappa B signaling in THP1 monocytic cells.

The transcription factor NFkappaB plays a key role in the tissue inflammatory response. Metal ions released into tissues from biomaterials (e.g., Au, Pd, Ni, Hg) are known to alter the binding of NFkappaB proteins to DNA, thereby modulating the effect of NFkappaB on gene activation and, ultimately, the tissue response to biomaterials. Little is known about the effect of these metals on key signaling steps prior to NFkappaB-DNA binding such as transcription factor activation or nuclear translocation, yet these steps are equally important to modulation of the pathway. Oxidative stress is known to alter NFkappaB proteins and is suspected to play a role in metal-induced NFkappaB signaling modulation. Our aim in the current study was to assess the effects of sublethal levels of Ni, Hg, Pd, and Au ions on NFkappaB activation and nuclear translocation in the monocyte, which is acknowledged as an important orchestrator of the biological response to materials and the pathogenesis of chronic disease. Sublethal concentrations of Au(III), Ni(II), Hg(II), and Pd(II) were added to cultures of human THP1 monocytic cells for 72 h. In parallel cultures, lipopolysaccharide (LPS) was added for the last 30 min to activate the monocytic cells. Then cellular cytoplasmic and nuclear proteins were isolated, separated by electrophoresis, and probed for IkappaBalpha degradation (activation) and NFkappaB p65 translocation. Protein levels were digitally quantified and statistically compared. The levels of reactive oxygen species (ROS) in the monocytic cells were measured as a possible mechanism of metal-induced NFkappaB modulation. Only Au(III) activated IkappaBalpha degradation by itself. Au(III) and Pd(II) enhanced LPS-induced IkappaBalpha degradation, but Hg(II) and Ni(II) suppressed it. Au(III), Ni(II), and Pd(II) activated p65 nuclear translocation without LPS, and all but Ni(II) enhanced LPS-induced translocation. Collectively, the results suggest that these metal ions alter activation and translocation of NFkappaB, each in a unique way at unique concentrations. Furthermore, even when these metals had no overt effects on signaling by themselves, all altered activation of signaling by LPS, suggesting that the biological effects of these metals on monocytic function may only be manifest upon activation. None of the metal ions elevated levels of ROS at 72 h, indicating that ROS were probably not direct modulators of the NFkappaB activation or translocation at this late time point.

Dental adhesive compounds alter glutathione levels but not glutathione redox balance in human THP-1 monocytic cells.

The use of hydrophilic dental monomers in dentin bonding agents has vastly improved resin-dentin bond strengths, but incomplete polymerization of these monomers and their leaching into adjacent (pulpal) oral tissues has raised concerns about their biocompatibility. The sublethal effects of these resins are virtually unknown, but their electrophilic nature led to the hypothesis that they may alter cellular oxidative stress pathways. Glutathione balance between reduced (GSH) and oxidized (GSSG) is a major mechanism by which cells maintain redox balance and was therefore the focus of the current investigation. THP-1 human monocytic cells were exposed to hydroxyethyl methacrylate (HEMA), benzoyl peroxide (BPO), camphorquinone (CQ), or triethyelene glycol dimethacrylate (TEGDMA) for 24 h at sublethal doses, then GSH and GSSG levels were measured by means of Ellman's method adapted for cell culture. The results indicate that these dental resin compounds act at least partly via oxidative stress by increasing GSH levels at sublethal concentrations. However, the GSH-GSSG ratio was relatively unaffected. Only BPO altered the GSH-GSSG ratio at 24 h, again at sublethal levels (7.5-15 micromol/L). The results support the hypothesis that resin monomers act, at least in part, via oxidative stress, and that oxidative-stress pathways should be one focus of future investigations of monomer biocompatibility.

Anti-rheumatic gold compounds as sublethal modulators of monocytic LPS-induced cytokine secretion.

The objective of this study was to quantify the ability of sublethal concentrations of several gold compounds to differentially modulate the monocytic secretion of key cytokines that are important in the etiology of rheumatic diseases. Human THP1 monocytic cells were exposed to the anti-rheumatic drugs auranofin (AF), gold sodium thiomalate (GSTM) or HAuCl4 (Au(III)) for 24-72 h. Succinate dehydrogenase (SDH) activity of the monocytes was used to determine sublethal concentrations. Monocytes were then exposed to sublethal concentrations of gold compounds for 72 h, and the activator lipopolysaccharide (LPS) was added (or not) to cultures for the last 6h. The secretion of IL6, IL8, IL10, and TNFalpha were measured in cell supernatants using ELISA. Cytokine secretion was compared among concentrations and gold compounds. SDH experiments established a sublethal concentration range of 0-75 microM for GSTM and Au(III) and 0-0.5 microM for AF. In cytokine experiments, none of the compounds alone activated secretion of any of the cytokines, but all differentially (50-440%, p<0.05) increased LPS-induced secretion of IL6 and IL8 over TNFalpha and IL10. In conclusion, sublethal concentrations of AF, GSTM, and Au(III) all may differentially modulate activation of monocytic cells, and this differential modulation may be important in the mechanisms of action of these compounds.

Future directions in bonding resins to the dentine-pulp complex.

Resin-based materials are rapidly becoming the primary restorative material to replace tooth structure and the low percentage of biological problems reported for resin-based restorations is testimony to their relative biocompatibility. Despite considerable advances in the understanding of the mechanisms, which govern the integration of resin composite materials with the dentine-pulp complex, considerable potential for improvement remains. Most of these improvements centre around a better understanding of the biological and microbiological risks of resin materials and will only be possible with improved in vitro and in vivo models. There are also a number of possible future developments in materials, clinical techniques and diagnostic methods that may improve the long-term success and reliability of resin-based restorations. The remainder of this paper describes the most likely avenues for future improvements.

Cytotoxicity of commercial and novel binary titanium alloys with and without a surface-reaction layer.

Titanium-based alloys form a surface reaction layer when cast. This study investigated the effect of the surface reaction layer on the cytotoxicity of novel Ti-based binary alloys. The cytotoxicities of the novel alloys were compared with commercially pure titanium, Ti-6Al-4V and Ti-6Al-7Nb. Cast discs with or without the reaction layer were first tested for cytotoxicity, then for elemental release into cell-culture medium. The elements released into the extracts were measured by means of an inductively coupled plasma atomic emission spectrometer. The commercial and novel binary Ti-based alloys showed no statistically significant cytotoxicity, although some trends were noted for several alloys. The presence of the reaction layer did not significantly alter the cytotoxicity. These favourable biocompatibility results show that these novel alloys have promise for use in dental restorations.

Blue light differentially modulates cell survival and growth.

Previous studies have reported that blue light (400-500 nm) inhibits cell mitochondrial activity. We investigated the hypothesis that cells with high energy consumption are most susceptible to blue-light-induced mitochondrial inhibition. We estimated cell energy consumption by population doubling time, and cell survival and growth by succinate dehydrogenase (SDH) activity. Six cell types were exposed to 5 or 60 J/cm(2) of blue light from quartz-tungsten-halogen (QTH), plasma-arc (PAC), or argon laser sources in monolayer culture. Post-light SDH activity correlated positively with population doubling time (R(2) = 0.91 for PAC, 0.76 for QTH, 0.68 for laser); SDH activity increased for cell types with the longest doubling times and was suppressed for cell types with shorter doubling times. Thus, light-induced exposure differentially affects SDH activity, cell survival, and growth, depending on cell energy consumption. Blue light may be useful as a therapeutic modulator of cell growth and survival.

Metal ions alter lipopolysaccharide-induced NF kappa B binding in monocytes.

Metals are components of a variety of biomaterials used in orthopedic and dental appliances; however, their biocompatibility with the surrounding tissues is not completely understood. Monocytes are important immune cells that respond to inflammatory stimuli by rapidly producing a variety of inflammatory proteins. Regulation of this response often involves activation of the transcription factor NF kappa B. The current study was designed to determine whether monocyte activation of NF kappa B in response to bacterial lipopolysaccharide (LPS) is affected by pretreatment with metal ions. Concentrations of metal ions that affected cell number after 24 h of exposure were first determined. Then THP-1 human monocytes were cultured for 2 h in media containing metal ions at concentrations below levels that altered cell growth. Parallel cultures were treated with 10 microg/mL Escherichia coli LPS, and all samples were cultured an additional 2 h. Nuclear proteins were extracted and normalized amounts were incubated with [(32)P]-end-labeled NF kappa B consensus oligonucleotide. NF kappa B-DNA complexes were identified and quantified by electrophoretic mobility shift analysis. The extent of NF kappa B-DNA complex formation after metal ion pretreatment with or without LPS induction was compared to no treatment or LPS-only treated controls. Finally, LPS-induced IL1 beta secretion was measured from palladium-treated and control cells. Concentrations were identified for each metal ion (Ag(+), Co(2+), Cu(2+), Hg(2+), Ni(2+), and Pd(2+)) that did not reduce cell number after 24 h of exposure (ranging from 5 microM for Ag(+) and Hg(2+) to 200 microM for Ni(2+)). Exposures of 2 h at these concentrations did not alter cell morphology, staining with trypan blue, or cell number. LPS exposure had no effect on cell number with or without metal ions after 2 h. When metal treatment alone was assessed, none of the metal ions had a significant effect on NF kappa B-DNA binding. However, pretreatment with Co(2+), Ni(2+), Ag(1+), Hg(2+), and Pd(2+) significantly decreased NF kappa B-DNA binding by 40-70% versus LPS alone. Only Cu(2+) had no effect on LPS-induced NF kappa B-DNA complex formation. Pd(2+) lowered, but did not abolish, IL1 beta secretion at concentrations comparable to those that altered NF kappa B-DNA binding. These results suggest that many commonly used metals alter monocyte function at concentrations that are not overtly toxic, and that protein levels controlled in part by NF kappa B also may be altered.