Rationally designed upconversion nanoparticles for NIR light-controlled lysosomal escape and nucleus-based photodynamic therapy.

Cell nucleus-based photodynamic therapy is a highly effective method for cancer therapy, but it is still challenging to design nucleus-targeting photosensitizers. Here, we propose the "one treatment, multiple irradiations" strategy to achieve nucleus-based photodynamic therapy using the photosensitizer rose bengal (RB)-loaded and mesoporous silica-coated upconversion nanoparticles with the surface modification of amine group (UCNP/RB@mSiO2-NH2 NPs). After implementation into cancer cells, the rationally designed UCNP/RB@mSiO2-NH2 NPs could be specifically accumulated in the acidic lysosomes due to their amino group-decorated surface. Upon a short-term (3 min) irradiation of 980 nm near-infrared light, the reactive oxygen species produced by RB through the Förster resonance energy transfer between the upconversion nanoparticles and RB molecules could effectively destroy lysosomes, followed by the release of the UCNP/RB@mSiO2-NH2 NPs from the lysosomes. Subsequently, these released UCNP/RB@mSiO2-NH2 NPs could be transferred into the cell nucleus, where a second 980 nm light irradiation was conducted to achieve the nucleus-based photodynamic therapy. The rationally designed UCNP/RB@mSiO2-NH2 NPs showed excellent anticancer performance in both two-dimensional and three-dimensional cell models using the "one treatment, multiple irradiations" strategy.

Extracts Prepared from a Canadian Toxic Plant Induce Light-Dependent Perinuclear Vacuoles in Human Cells.

We are investigating plant species from the Canadian prairie ecological zone by phenotypic cell assays to discover toxins of biological interest. We provide the first report of the effects of extracts prepared from the shrub Symphoricarpos occidentalis in several human cell lines. S. occidentalis (Caprifoliaceae) extracts are cytotoxic, and, strikingly, treated cells undergo light-dependent vacuolation near the nucleus. The range of irradiation is present in standard ambient light and lies in the visible range (400-700 nm). Vacuolization in treated cells can be induced with specific wavelengths of 408 or 660 nm at 1 J/cm2 energies. Vacuolated cells show a striking phenotype of a large perinuclear vacuole (nuclear associated vacuole, NAV) that is distinct from vesicles observed by treatment with an autophagy-inducing agent. Treatment with S. occidentalis extracts and light induces an intense lamin A/C signal at the junction of a nuclear vacuole and the nucleus. Further study of S. occidentalis extracts and vacuolation provide chemical tools that may contribute to the understanding of nuclear envelope organization and human cell biology.

Photobiomodulation therapy can change actin filaments of 3T3 mouse fibroblast.

The purpose of this study was to investigate the effects that photobiomodulation therapy might produce in cells, in particular, related to their structure. Thus, this paper presents the results of morphological changes in fibroblasts following low-intensity light illumination. Mouse fibroblasts were grown on glass coverslips on either 4 kPa or 16 kPa gels, to mimic normal tissue conditions. Cells were photo-irradiated with laser light at either 625 nm or 808 nm (total energies ranging from 34 to 47 J). Cells were fixed at 5 min, 1 h, or 24 h after photo-irradiation, stained for both actin filaments and the cell nucleus, and imaged by confocal microscopy. A non-light exposed group was also imaged. A detailed analysis of the images demonstrated that the total polymerized actin and number of actin filaments decrease, while the nucleus area increases in treated cells shortly after photo-irradiation, regardless of substrate and wavelength. This experiment indicated that photobiomodulation therapy could change the morphological properties of cells and affect their cytoskeleton. Further investigations are required to determine the specific mechanisms involved and how this phenomenon is related to the photobiomodulation therapy mechanisms of action.

Extract of Deschampsia antarctica (EDA) Prevents Dermal Cell Damage Induced by UV Radiation and 2,3,7,8-Tetrachlorodibenzo-p-dioxin.

Exposure to natural and artificial light and environmental pollutants are the main factors that challenge skin homeostasis, promoting aging or even different forms of skin cancer through a variety of mechanisms that include accumulation of reactive oxygen species (ROS), engagement of DNA damage responses, and extracellular matrix (ECM) remodeling upon release of metalloproteases (MMPs). Ultraviolet A radiation is the predominant component of sunlight causative of photoaging, while ultraviolet B light is considered a potentiator of photoaging. In addition, different chemicals contribute to skin aging upon penetration through skin barrier disruption or hair follicles, aryl hydrocarbon receptors (AhR) being a major effector mechanism through which toxicity is exerted. Deschampsia antarctica is a polyextremophile Gramineae capable of thriving under extreme environmental conditions. Its aqueous extract (EDA) exhibits anti- photoaging in human skin cells, such as inhibition of MMPs, directly associated with extrinsic aging. EDA prevents cellular damage, attenuating stress responses such as autophagy and reducing cellular death induced by UV. We demonstrate that EDA also protects from dioxin-induced nuclear translocation of AhR and increases the production of loricrin, a marker of homeostasis in differentiated keratinocytes. Thus, our observations suggest a potential use exploiting EDA's protective properties in skin health supplements.

Comparison of two different laser photobiomodulation protocols on the viability of random skin flap in rats.

To identify the best low level laser photobiomodulation application site at the same irradiation time to increase the viability of the skin flap in rats. Eighteen male rats (Rattus norvegicus: var. Albinus, Rodentia Mammalia) were randomly distributed into three groups (n = 6). Group I (GI) was submitted to simulated laser photobiomodulation; group II (GII) was submitted to laser photobiomodulation at three points in the flap cranial base, and group III (GIII) was submitted to laser photobiomodulation at 12 points distributed along the flap. All groups were irradiated with an Indium, Galium, Aluminum, and Phosphorus diode laser (InGaAlP), 660 nm, with 50 mW power, irradiated for a total time of 240 s in continuous emission mode. The treatment started immediately after performing the cranial base random skin flap (10 × 4 cm2 dimension) and reapplied every 24 h, with a total of five applications. The animals were euthanized after the evaluation of the percentage of necrosis area, and the material was collected for histological analysis on the seventh postoperative day. GII animals presented a statistically significant decrease for the necrosis area when compared to the other groups, and a statistically significant increase in the quantification of collagen when compared to the control. We did not observe a statistical difference between the TGFß and FGF expression in the different groups evaluated. The application of laser photobiomodulation at three points of the flap cranial base was more effective than at 12 points regarding the reduction of necrosis area.

Co-loading of photothermal agents and anticancer drugs into porous silicon nanoparticles with enhanced chemo-photothermal therapeutic efficacy to kill multidrug-resistant cancer cells.

The development of nanoparticles-based drug delivery systems with a high therapeutic efficacy is necessary to treat multidrug-resistant (MDR) cancer cells. Herein, photothermal agents (IR820 dyes) and anticacner drugs (doxorubicin, DOX) were successively incorporated into amino-terminated porous silicon nanoparticles (NH2-PSiNPs) via electrostatic attractions, to prepare DOX/IR820/NH2-PSiNPs nanocomposites with a high loading amount of DOX (13.3%, w/w) and IR820 (18.6%, w/w), respectively. Meanwhile, DOX molecules were also directly loaded into NH2-PSiNPs to form DOX/NH2-PSiNPs nanocomposites (DOX, 18.7%, w/w). Compared with low release percentage (20.3%) of DOX molecules from DOX/NH2-PSiNPs in acidic environments under NIR laser irradiation, DOX/IR820/NH2-PSiNPs had dual pH/NIR light-triggered release and their release percentage could reach 88.1% under the same conditions. Furthermore, cellular interactions tests demonstrated that DOX/IR820/NH2-PSiNPs could delivery more DOX molecules into the nuclei of MDR cancer cells, with efficient intracellular release triggered by NIR light, in contrast to DOX/NH2-PSiNPs. Finally, DOX/IR820/NH2-PSiNPs exhibited an enhanced chemo-photothermal therapeutic efficacy (cell viability, 38.4%) of killing MDR cancer cells in vitro, compared with 85.4% of free DOX and 75.9% of DOX/NH2-PSiNPs. Therefore, based on PSiNPs-based nanocarriers conjugated with photothermal agents and anticancer drugs, NIR light-triggered drug delivery system with higher efficacy of combined chemo-photothermal therapy would have important potential on MDR cancer treatments in future.

Solanum tuberosum ZPR1 encodes a light-regulated nuclear DNA-binding protein adjusting the circadian expression of StBBX24 to light cycle.

ZPR1 proteins belong to the C4-type of zinc finger coordinators known in animal cells to interact with other proteins and participate in cell growth and proliferation. In contrast, the current knowledge regarding plant ZPR1 proteins is very scarce. Here, we identify a novel potato nuclear factor belonging to this family and named StZPR1. StZPR1 is specifically expressed in photosynthetic organs during the light period, and the ZPR1 protein is located in the nuclear chromatin fraction. From modelling and experimental analyses, we reveal the StZPR1 ability to bind the circadian DNA cis motif 'CAACAGCATC', named CIRC and present in the promoter of the clock-controlled double B-box StBBX24 gene, the expression of which peaks in the middle of the day. We found that transgenic lines silenced for StZPR1 expression still display a 24 h period for the oscillation of StBBX24 expression but delayed by 4 h towards the night. Importantly, other BBX genes exhibit altered circadian regulation in these lines. Our data demonstrate that StZPR1 allows fitting of the StBBX24 circadian rhythm to the light period and provide evidence that ZPR1 is a novel clock-associated protein in plants necessary for the accurate rhythmic expression of specific circadian-regulated genes.

Thymus vulgaris alleviates UVB irradiation induced skin damage via inhibition of MAPK/AP-1 and activation of Nrf2-ARE antioxidant system.

Solar ultraviolet (UV) radiation-induced reactive oxidative species is mainly responsible for the development of photoageing. Rosmarinic acid was one of the main bioactive components detected in Thymus vulgaris (TV) we extracted. In this study, UVB-induced skin damages have been shown to be ameliorated by treatment with TV in hairless mice (HR-1) skin, demonstrated by decreased matrix metalloproteinases (MMPs) and increased collagen production. However, the underlying molecular mechanism on which TV acted was unclear. We examined the photoprotective effects of TV against UVB and elucidated the molecular mechanism in normal human dermal fibroblasts. Thymus vulgaris remarkably prevented the UVB-induced reactive oxygen species and lactate dehydrogenase. Dose-dependent increase in glutathione, NAD(P)H: quinone oxidoreductase1 and heme oxygenase-1, by TV was confirmed by increased nuclear accumulation of Nrf2. Furthermore, 5-Methoxyindole-2-carboxylic acid was introduced as a specific inhibitor of dihydrolipoyl dehydrogenase (DLD). We demonstrated that Nrf2 expression was regulated by DLD, which was a tricarboxylic acid cycle-associated protein that decreased after UVB exposure. Besides, TV significantly diminished UVB induced phosphorylation of mitogen activated protein kinases pathway, containing extracellular signal-regulated kinase, Jun N-terminal kinase and p38, which consequently reduced phosphorylated c-fos and c-jun. Our results suggest that TV is a potential botanical agent for use against UV radiation-induced oxidative stress mediated skin damages.

Sodium valproate prevents radiation-induced injury in hippocampal neurons via activation of the Nrf2/HO-1 pathway.

PURPOSE: To investigate the neuroprotective role of sodium valproate (VPA) in a hippocampal neuronal cell line (HT22) and the hippocampus of zebrafish after exposure to radiation. METHODS: We investigated whether VPA could protect HT22 hippocampal neurons and the hippocampus of zebrafish from radiation-induced injury. We measured the generation of reactive oxygen species (ROS), the mitochondrial membrane potential, the levels of glutathione (GSH) and malondialdehyde (MDA), and the activity of superoxide dismutase (SOD). The expression of nuclear factor (erythroid-derived 2)-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) was also measured. The cognitive behavior of the zebrafish was evaluated 1month after radiation exposure. RESULTS: VPA treatment improved the survival rate (300 mg/kg body weight (BW) VPA: 76.67%; 100 mg/kg BW VPA: 56.7%) of zebrafish 1 month after exposure to a lethal dose of whole-body irradiation (P<0.01). VPA treatment decreased the ROS generation (P<0.01), decreased the MDA levels (P<0.01), increased the GSH levels (P<0.01) and increased the SOD activity (P<0.01). VPA treatment activated the Nrf2/HO-1 pathway, increased the nuclear translocation of Nrf2 and increased the mRNA (P<0.01) and protein expression of HO-1 to prevent radiation-induced neuronal injury. SiRNA knockdown of the Nrf2 gene prevented the VPA-induced attenuation of radiation injury in the HT22 neuronal cells that was found in the control cells (40.09±1.76% vs. 41.14±1.09%, P>0.05). VPA also improved the zebrafish cognitive behavior after radiation-induced neuronal injury as measured by the exploration test (control 5.74±1.42min vs. radiation therapy 16.39±4.03min vs. radiation therapy plus VPA 7.18±1.79min, P<0.05). CONCLUSIONS: ROS generation after radiation exposure contributes to DNA damage in the zebrafish brain. VPA inhibits ROS generation by activating the Nrf2/HO-1 pathway, which improves cognitive behavior following radiation-induced neuronal injury.

Inhibitory effects of Enteromorpha linza polysaccharide on micronucleus of Allium sativum root cells.

In this study, the antimutagenic function of the polysaccharide from Enteromorpha linza with the micronucleus test of Allium sativum root cells induced by sulfur dioxide and ultraviolet was studied. The concentration-effect relation of the two inducers was firstly evaluated. The results showed that an increase of genotoxicity damage was demonstrated and micronuclei frequency induced by sulfur dioxide and ultraviolet displayed dose dependent increases. All the doses of polysaccharide did affect the micronuclei frequency formation compared with the negative control. And also, the significant increase in inhibition rate of micronuclei frequency was observed with the increase of the dose of polysaccharide. It was showed maximum inhibition of micronuclei frequency cells (71.74% and 66.70%) at a concentration of 200g/mL in three experiments. The low molecular weight polysaccharide showed higher inhibition rate than raw polysaccharide at the higher concentration (50g/mL) in the absence of sulfur dioxide and ultraviolet. It was confirmed to be a good mutant inhibitor.

Low-concentration uranium enters the HepG2 cell nucleus rapidly and induces cell stress response.

This study aimed to compare the cell stress effects of low and high uranium concentrations and relate them to its localization, precipitate formation, and exposure time. The time-course analysis shows that uranium appears in cell nuclei as a soluble form within 5 min of exposure, and quickly induces expression of antioxidant and DNA repair genes. On the other hand, precipitate formations began at the very beginning of exposure at the 300-µM concentration, but took longer to appear at lower concentrations. Adaptive response might occur at low concentrations but are overwhelmed at high concentrations, especially when uranium precipitates are abundant.

Photo-activated psoralen binds the ErbB2 catalytic kinase domain, blocking ErbB2 signaling and triggering tumor cell apoptosis.

Photo-activation of psoralen with UVA irradiation, referred to as PUVA, is used in the treatment of proliferative skin disorders. The anti-proliferative effects of PUVA have been largely attributed to psoralen intercalation of DNA, which upon UV treatment, triggers the formation of interstrand DNA crosslinks (ICL) that inhibit transcription and DNA replication. Here, we show that PUVA exerts antitumor effects in models of human breast cancer that overexpress the ErbB2 receptor tyrosine kinase oncogene, through a new mechanism. Independent of ICL formation, the antitumor effects of PUVA in ErbB2+ breast cancer models can instead be mediated through inhibition of ErbB2 activation and signaling. Using a mass spectroscopy-based approach, we show for the first time that photo-activated 8MOP (8-methoxypsoralen) interacts with the ErbB2 catalytic autokinase domain. Furthermore, PUVA can reverse therapeutic resistance to lapatinib and other ErbB2 targeted therapies, including resistance mediated via expression of a phosphorylated, truncated form of ErbB2 (p85(ErbB2)) that is preferentially expressed in tumor cell nuclei. Current ErbB2 targeted therapies, small molecule kinase inhibitors or antibodies, do not block the phosphorylated, activated state of p85(ErbB2). Here we show that PUVA reduced p85(ErbB2) phosphorylation leading to tumor cell apoptosis. Thus, in addition to its effects on DNA and the formation of ICL, PUVA represents a novel ErbB2 targeted therapy for the treatment of ErbB2+ breast cancers, including those that have developed resistance to other ErbB2 targeted therapies.

Overexpression of rice OsREX1-S, encoding a putative component of the core general transcription and DNA repair factor IIH, renders plant cells tolerant to cadmium- and UV-induced damage by enhancing DNA excision repair.

Screening of 40,000 Arabidopsis FOX (Full-length cDNA Over-eXpressor gene hunting system) lines expressing rice full-length cDNAs brings us to identify four cadmium (Cd)-tolerant lines, one of which carried OsREX1-S as a transgene. OsREX1-S shows the highest levels of identity to Chlamydomonas reinhardtii REX1-S (referred to as CrREX1-S, in which REX denotes Required for Excision) and to yeast and human TFB5s (RNA polymerase II transcription factor B5), both of which are components of the general transcription and DNA repair factor, TFIIH. Transient expression of OsREX1-S consistently localized the protein to the nucleus of onion cells. The newly generated transgenic Arabidopsis plants expressing OsREX1-S reproducibly displayed enhanced Cd tolerance, confirming that the Cd-tolerance of the initial identified line was conferred solely by OsREX1-S expression. Furthermore, transgenic Arabidopsis plants expressing OsREX1-S exhibited ultraviolet-B (UVB) tolerance by reducing the amounts of cyclobutane pyrimidine dimers produced by UVB radiation. Moreover, those transgenic OsREX1-S Arabidopsis plants became resistant to bleomycin (an inducer of DNA strand break) and mitomycin C (DNA intercalating activity), compared to wild type. Our results indicate that OsREX1-S renders host plants tolerant to Cd, UVB radiation, bleomycin and mitomycin C through the enhanced DNA excision repair.

Photobiomodulation by low-power laser irradiation attenuates Aß-induced cell apoptosis through the Akt/GSK3ß/ß-catenin pathway.

Apoptosis induced by amyloid ß peptide (Aß) is thought to associate with the pathogenesis of Alzheimer disease (AD). Accumulating evidence shows that low-power laser irradiation (LPLI) is capable of reducing Aß-induced apoptosis. However, the underlying mechanisms remain unclear. In this study, we report a novel molecular mechanism by which LPLI attenuates Aß(25-35)-induced apoptosis through the Akt/GSK3ß/ß-catenin pathway. We found that Akt activated by LPLI interacted with GSK3ß and phosphorylated it on Ser9 in the presence of Aß(25-35), which resulted in the inhibition of GSK3ß. Furthermore, LPLI increased the nuclear translocation of ß-catenin and enhanced its T cell factor/lymphocyte enhancer factor-dependent transcriptional activity via the Akt/GSK3ß pathway to promote cell survival upon treatment with Aß(25-35.) Our data demonstrate that LPLI has a prosurvival effect on Aß-induced apoptosis and may be an effective therapeutic strategy in treating AD by targeting GSK3ß.

Far-infrared therapy induces the nuclear translocation of PLZF which inhibits VEGF-induced proliferation in human umbilical vein endothelial cells.

Many studies suggest that far-infrared (FIR) therapy can reduce the frequency of some vascular-related diseases. The non-thermal effect of FIR was recently found to play a role in the long-term protective effect on vascular function, but its molecular mechanism is still unknown. In the present study, we evaluated the biological effect of FIR on vascular endothelial growth factor (VEGF)-induced proliferation in human umbilical vein endothelial cells (HUVECs). We found that FIR ranging 3∼10 µm significantly inhibited VEGF-induced proliferation in HUVECs. According to intensity and time course analyses, the inhibitory effect of FIR peaked at an effective intensity of 0.13 mW/cm(2) at 30 min. On the other hand, a thermal effect did not inhibit VEGF-induced proliferation in HUVECs. FIR exposure also inhibited the VEGF-induced phosphorylation of extracellular signal-regulated kinases in HUVECs. FIR exposure further induced the phosphorylation of endothelial nitric oxide (NO) synthase (eNOS) and NO generation in VEGF-treated HUVECs. Both VEGF-induced NO and reactive oxygen species generation was involved in the inhibitory effect of FIR. Nitrotyrosine formation significantly increased in HUVECs treated with VEGF and FIR together. Inhibition of phosphoinositide 3-kinase (PI3K) by wortmannin abolished the FIR-induced phosphorylation of eNOS and Akt in HUVECs. FIR exposure upregulated the expression of PI3K p85 at the transcriptional level. We further found that FIR exposure induced the nuclear translocation of promyelocytic leukemia zinc finger protein (PLZF) in HUVECs. This induction was independent of a thermal effect. The small interfering RNA transfection of PLZF blocked FIR-increased PI3K levels and the inhibitory effect of FIR. These data suggest that FIR induces the nuclear translocation of PLZF which inhibits VEGF-induced proliferation in HUVECs.

Micronucleated erythrocytes in preterm newborns exposed to phototherapy and/or oxygentherapy.

Preterm newborns (PNBs) have an immature antioxidant defense system, and this makes them more susceptible to oxidative stress generated by postnatal treatments. The objective was to determine whether micronucleated erythrocytes increase in PNB by postnatal treatments such as oxygentherapy and phototherapy. We counted micronucleated erythrocytes and micronucleated polychromatic erythrocytes as DNA damage in 72 blood samples of PNB at 26-36 weeks of gestation, taken between 1 and 84 h after birth. We assume that more time passed between sampling and birth would correspond to greater time of exposure to oxygen (37 cases) and phototherapy plus oxygen (35 cases). In the PNB only exposed to oxygen, the differences were not significant, while there was a significant increase in micronucleated polychromatic erythrocytes with increasing exposure time in those treated with phototherapy plus oxygen. In conclusion, our results suggest that the MN increase from phototherapy can be observed in peripheral blood erythrocytes of PNB.

Laser microsurgery in Caenorhabditis elegans.

Laser killing of cell nuclei has long been a powerful means of examining the roles of individual cells in C. elegans. Advances in genetics, laser technology, and imaging have further expanded the capabilities and usefulness of laser surgery. Here, we review the implementation and application of currently used methods for target edoptical disruption in C. elegans.

GATA3 expression is decreased in psoriasis and during epidermal regeneration; induction by narrow-band UVB and IL-4.

Psoriasis is characterized by hyperproliferation of keratinocytes and by infiltration of activated Th1 and Th17 cells in the (epi)dermis. By expression microarray, we previously found the GATA3 transcription factor significantly downregulated in lesional psoriatic skin. Since GATA3 serves as a key switch in both epidermal and T helper cell differentiation, we investigated its function in psoriasis. Because psoriatic skin inflammation shares many characteristics of epidermal regeneration during wound healing, we also studied GATA3 expression under such conditions.Psoriatic lesional skin showed decreased GATA3 mRNA and protein expression compared to non-lesional skin. GATA3 expression was also markedly decreased in inflamed skin of mice with a psoriasiform dermatitis induced with imiquimod. Tape-stripping of non-lesional skin of patients with psoriasis, a standardized psoriasis-triggering and skin regeneration-inducing technique, reduced the expression of GATA3. In wounded skin of mice, low GATA3 mRNA and protein expression was detected. Taken together, GATA3 expression is downregulated under regenerative and inflammatory hyperproliferative skin conditions. GATA3 expression could be re-induced by successful narrow-band UVB treatment of both human psoriasis and imiquimod-induced psoriasiform dermatitis in mice. The prototypic Th2 cytokine IL-4 was the only cytokine capable of inducing GATA3 in skin explants from healthy donors. Based on these findings we argue that GATA3 serves as a key regulator in psoriatic inflammation, keratinocyte hyperproliferation and skin barrier dysfunction.

Tea polyphenols protect against irradiation-induced injury in submandibular glands' cells: a preliminary study.

AIM: To study the protective effect of tea polyphenols (TPs) on submandibular glands affected by radiation injury. METHODS: Sixty rats were randomly divided into radiation group (R-group, N = 30) and TP-pre-treated-radiation group (TPR-group, N = 30). The rats were intragastrically administered with TP or normal sodium from 14 days before radiation, continuously daily, until the experiment. All the rats in both groups were irradiated with a single exposure dose of 15 Gy gamma rays that were delivered to the head and neck areas. Ten rats of each group were anatomised on the 3rd, 6th and 30th day after irradiation, respectively. The submandibular glands of the rats were removed for the study. The morphologic changes of the submandibular glands were observed by transmission electron microscopy (TEM). The terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP)-biotin nick-end labelling (TUNEL) method was used to detect apoptosis of the submandibular glands' cells. RESULTS: Electron microscope observation of the submandibular glands showed that the lesions of the TPR-group were mild. Change in apoptosis of the cells was not obvious compared with the R-group. The cell apotosis was typical after irradiation in the R-group. Apoptosis index that was detected in the cells of submandibular glands of the TPR-group was statistically significantly decreased compared with the R-group (P < 0.01) on the 3rd, 6th and 30th day after irradiation. CONCLUSION: TP could protect submandibular glands from radiation injuries, and the protection mechanism may be realised by anti-apoptosis.

High fluence low-power laser irradiation induces apoptosis via inactivation of Akt/GSK3ß signaling pathway.

High fluence low-power laser irradiation (HF-LPLI) is a newly discovered stimulus through generating reactive oxygen species (ROS) to trigger cell apoptosis. Activation of glycogen synthase kinase 3ß (GSK3ß) is proved to be involved in intrinsic apoptotic pathways under various stimuli. However, whether the proapoptotic factor GSK3ß participates in HF-LPLI-induced apoptosis has not been elucidated. Therefore, in the present study, we investigated the involvement of GSK3ß in apoptosis under HF-LPLI treatment (120 J/cm2, 633 nm). We found that GSK3ß activation could promote HF-LPLI-induced apoptosis, which could be prevented by lithium chloride (a selective inhibitor of GSK3ß) exposure or by GSK3ß-KD (a dominant-negative GSK3ß) overexpression. We also found that the activation of GSK3ß by HF-LPLI was due to the inactivation of protein kinase B (Akt), a widely reported and important upstream negative regulator of GSK3ß, indicating the existence and inactivation of Akt/GSK3ß signaling pathway. Moreover, the inactivation of Akt/GSK3ß pathway depended on the fluence of HF-LPLI treatment. Furthermore, vitamin c, a ROS scavenger, completely prevented the inactivation of Akt/GSK3ß pathway, indicating ROS generation was crucial for the inactivation. In addition, GSK3ß promoted Bax activation by down-regulating Mcl-1 upon HF-LPLI treatment. Taken together, we have identified a new and important proapoptotic signaling pathway that is consisted of Akt/GSK3ß inactivation for HF-LPLI stimulation. Our research will extend the knowledge into the biological mechanisms induced by LPLI.