Single cell analysis of PKC activation during proliferation and apoptosis induced by laser irradiation

Effect of Photobiomodulation on Atrophic-Erosive Clinical Forms of Oral Lichen Planus: A Systematic Review

INTRODUCTION

Oral lichen planus is a chronic autoimmune inflammatory disease of unknown origin, characterized by various clinical forms of which the atrophic-erosive causes patients the greatest symptomatology. For this reason, there are different treatments that improve the associated signs and symptoms. One of these therapies is photobiomodulation (PBM), which, although new, has a high level of acceptance in dentistry based on evidence. However, there are inconsistent results in its application against lichen planus. The aim of this review was to evaluate the effect of photobiomodulation and its effectiveness as a therapeutic alternative for atrophic-erosive lesions.

MATERIAL AND METHODS

The databases PubMed, Google Scholar and Cochrane Library were searched to identify studies investigating the photobiomodulation treatment in atrophic-erosive lesions of oral lichen planus. A total of 294 articles were identified, published between 2017 and 2022, and then evaluated; 7 articles that met all the inclusion criteria were included in this study.

RESULTS

The type of laser light source used in PBM was the diode laser (four cases), the Nd-YAG laser at the same wavelength of 1064 nm (two cases) and the He-Ne laser (one case). The minimum and maximum wavelengths used were 630 nm and 1064 nm, respectively. Most studies used lesions treated with topical corticosteroids as a control group. The follow-up times of the studies were highly variable.

CONCLUSIONS

Photobiomodulation is a treatment that competently combats oral lichen planus lesions by improving signs and symptoms, with no known adverse reactions so far, which makes it more beneficial compared to more conventional therapies, such as corticosteroids, for which side effects have been found.

Photobiomodulation in 3D tissue engineering

SIGNIFICANCE

The method of photobiomodulation (PBM) has been used in medicine for a long time to promote anti-inflammation and pain-resolving processes in different organs and tissues. PBM triggers numerous cellular pathways including stimulation of the mitochondrial respiratory chain, alteration of the cytoskeleton, cell death prevention, increasing proliferative activity, and directing cell differentiation. The most effective wavelengths for PBM are found within the optical window (750 to 1100 nm), in which light can permeate tissues and other water-containing structures to depths of up to a few cm. PBM already finds its applications in the developing fields of tissue engineering and regenerative medicine. However, the diversity of three-dimensional (3D) systems, irradiation sources, and protocols intricate the PBM applications.

AIM

We aim to discuss the PBM and 3D tissue engineered constructs to define the fields of interest for PBM applications in tissue engineering.

APPROACH

First, we provide a brief overview of PBM and the timeline of its development. Then, we discuss the optical properties of 3D cultivation systems and important points of light dosimetry. Finally, we analyze the cellular pathways induced by PBM and outcomes observed in various 3D tissue-engineered constructs: hydrogels, scaffolds, spheroids, cell sheets, bioprinted structures, and organoids.

RESULTS

Our summarized results demonstrate the great potential of PBM in the stimulation of the cell survival and viability in 3D conditions. The strategies to achieve different cell physiology states with particular PBM parameters are outlined.

CONCLUSIONS

PBM has already proved itself as a convenient and effective tool to prevent drastic cellular events in the stress conditions. Because of the poor viability of cells in scaffolds and the convenience of PBM devices, 3D tissue engineering is a perspective field for PBM applications.

Changes in Cell Biology under the Influence of Low-Level Laser Therapy

Low-level laser therapy (LLLT) has become an important part of the therapeutic process in various diseases. However, despite the broad use of LLLT in everyday clinical practice, the full impact of LLLT on cell life processes has not been fully understood. This paper presents the current state of knowledge concerning the mechanisms of action of LLLT on cells. A better understanding of the molecular processes occurring within the cell after laser irradiation may result in introducing numerous novel clinical applications of LLLT and potentially increases the safety profile of this therapy.

Photoactivation of mitochondrial reactive oxygen species-mediated Src and protein kinase C pathway enhances MHC class II-restricted T cell immunity to tumours

High fluence low-level laser (HF-LLL), a mitochondria-targeted tumour phototherapy, results in oxidative damage and apoptosis of tumour cells, as well as damage to normal tissue. To circumvent this, the therapeutic effect of low fluence LLL (LFL), a non-invasive and drug-free therapeutic strategy, was identified for tumours and the underlying molecular mechanisms were investigated. We observed that LFL enhanced antigen-specific immune response of macrophages and dendritic cells by upregulating MHC class II, which was induced by mitochondrial reactive oxygen species (ROS)-activated signalling, suppressing tumour growth in both CD11c-DTR and C57BL/6 mice. Mechanistically, LFL upregulated MHC class II in an MHC class II transactivator (CIITA)-dependent manner. LFL-activated protein kinase C (PKC) promoted the nuclear translocation of CIITA, as inhibition of PKC attenuated the DNA-binding efficiency of CIITA to MHC class II promoter. CIITA mRNA and protein expression also improved after LFL treatment, characterised by direct binding of Src and STAT1, and subsequent activation of STAT1. Notably, scavenging of ROS downregulated LFL-induced Src and PKC activation and antagonised the effects of LFL treatment. Thus, LFL treatment altered the adaptive immune response via the mitochondrial ROS-activated signalling pathway to control the progress of neoplastic disease.

Transcranial Laser Photobiomodulation Improves Intracellular Signaling Linked to Cell Survival, Memory and Glucose Metabolism in the Aged Brain: A Preliminary Study

Aging is often accompanied by exacerbated activation of cell death-related signaling pathways and decreased energy metabolism. We hypothesized that transcranial near-infrared laser may increase intracellular signaling pathways beneficial to aging brains, such as those that regulate brain cell proliferation, apoptosis, and energy metabolism. To test this hypothesis, we investigated the expression and activation of intracellular signaling proteins in the cerebral cortex and hippocampus of aged rats (20 months old) treated with the transcranial near-infrared laser for 58 consecutive days. As compared to sham controls, transcranial laser treatment increased intracellular signaling proteins related to cell proliferation and cell survival, such as signal transducer and activator of transcription 3 (STAT3), extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), p70 ribosomal protein S6 kinase (p70S6K) and protein kinase B (PKB), also known as Akt that is linked to glucose metabolism. In addition, ERK is linked to memory, while ERK and JNK signaling pathways regulate glucose metabolism. Specifically, the laser treatment caused the activation of STAT3, ERK, and JNK signaling proteins in the cerebral cortex. In the hippocampus, the laser treatment increased the expression of p70S6K and STAT3 and the activation of Akt. Taken together, the data support the hypothesis that transcranial laser photobiomodulation improves intracellular signaling pathways linked to cell survival, memory, and glucose metabolism in the brain of aged rats.

Equivocal, explicit and emergent actions of PKC isoforms in cancer

The maturing mutational landscape of cancer genomes, the development and application of clinical interventions and evolving insights into tumour-associated functions reveal unexpected features of the protein kinase C (PKC) family of serine/threonine protein kinases. These advances include recent work showing gain or loss-of-function mutations relating to driver or bystander roles, how conformational constraints and plasticity impact this class of proteins and how emergent cancer-associated properties may offer opportunities for intervention. The profound impact of the tumour microenvironment, reflected in the efficacy of immune checkpoint interventions, further prompts to incorporate PKC family actions and interventions in this ecosystem, informed by insights into the control of stromal and immune cell functions. Drugging PKC isoforms has offered much promise, but when and how is not obvious.

Bidirectional myofiber transition through altering the photobiomodulation condition

Despite remarkable advancements in modern medicine, muscular atrophy remains as an unsolved problem. It is well known that pathological characteristics of different atrophy types could vary according to the pathophysiological causes. In fact, the lesion of atrophy is not always homogenously distributed but often predominantly evident in either fast or slow myofibers. As the focalization of the atrophic lesions, the existence and the functional impairment of each fast and slow progenitor/satellite cell (SC) are suspected though there are still controversies about this hypothesis. In this study, we isolated Pax7 positive (Pax7^+ve) SCs from the tibia anterior (fast) and soleus (slow) muscles respectively and successfully demonstrated, for the first time, the difference between optimal exposure durations of photobiomodulation (PBM) which was known as low level laser irradiation (LLLI) in promoting proliferation of Pax7^+ve SC which were acquired from fast and slow muscles respectively. Moreover, a hypertrophy-accompanied bidirectional change in myofiber composition with neuromuscular junction alteration, either from slow to fast or fast to slow, were achieved by applying different PBM durations. Simultaneously, PBM exhibited a synergistic effect with muscle exercise on the increase in myofiber size. Our data suggested the existence of at least two different populations of Pax7^+ve SC which possess distinct sensitivities towards PBM. As our data revealed the capability of PBM in bidirectional changes of skeletal muscle composition and neuromuscular junction constitution thereby strengthen its contractility through altering the irradiation condition, we believe PBM showed the potential to be as a promising clinical treatment for muscular atrophy.

Percutaneous Exposures of volunteers to polychromatic light (480-3400 nm) trigger systemic mechanism of the human myeloma cells growth delay without any effect on bortezomib cytotoxicity in vitro

Background and aim

Polychromatic light is actively used in medicine. However, its oncological safety and effect against cytotoxic therapy remains poorly studied. Multiple myeloma (MM) develops in the bone marrow and therefore malignant plasma cells are inaccessible to direct exposure to light. The aim of our work was to study the influence of polychromatic visible and infra-red light (pVIS + pIR) on growth and sensitivity of the myeloma cells to the cytotoxic effect of drug bortezomib (BTZ) through systemic mechanism.

Materials and methods

We explored the effect of volunteers blood sera after their 4-daily irradiations with pVIS + pIR light (480-3400 nm) on growth and viability of the human myeloma RPMI 8226 cells in the presence of BTZ at its application in 2 modes: short-term (1 h, 300 nM) and long-term ( 96 h, 5 nM). Viability and proliferative activity of cells was evaluated by MTT assay.

Results

It was found that photomodified blood sera delayed growth of myeloma RPMI 8226 cells (by 25 % in 48 h and 23 % in 96 h) but had no effect on spontaneous and mitogen-induced proliferation of autologous peripheral blood T- and B-lymphocytes. We also revealed that pVIS + pIR did not change RPMI 8226 cells sensitivity to BTZ.

Conclusion

The results suggest the systemic mechanism of polychromatic light and argue in favor of its oncological safety during/after BTZ therapy of MM patients without effect on the drug cytotoxicity.

Cell-cycle-dependences of membrane permeability and viability observed for HeLa cells undergoing multi-bubble-cell interactions

Microbubble-mediated sonoporation is a promising strategy for intracellular gene/drug delivery, but the biophysical mechanisms involved in the interactions between microbubbles and cells are not well understood. Here, HeLa cells were synchronized in individual cycle phases, then the cell-cycle-dependences of the membrane permeability and viability of HeLa cells undergoing multi-bubble sonoporation were evaluated using focused ultrasound exposure apparatus coupled passive cavitation detection system. The results indicated that: (1) the microbubble cavitation activity should be independent on cell cycle phases; (2) G₁-phase cells with the largest Young's modulus were the most robust against microbubble-mediated sonoporation; (3) G₂/M-phase cells exhibited the greatest accumulated FITC uptake with the lowest viability, which should be mainly attributed to the chemical effect of synchronization drugs; and (4) more important, S-phase cells with the lowest stiffness seemed to be the most susceptible to the mechanical effect generated by microbubble cavitation activity, which resulted in the greatest enhancement in sonoporation-facilitated membrane permeabilization without further scarifying their viability. The current findings may benefit ongoing efforts aiming to pursue rational utilization of microbubble-mediated sonoporation in cell-cycle-targeted gene/drug delivery for cancer therapy.

Hepatitis B core antigen regulates dendritic cell proliferation and apoptosis through regulation of PKC/NF‑κB signaling pathway

Hepatitis B core antigen (HBcAg) possesses unusual immunologic features. However, the biological roles and mechanisms of HBcAg in dendritic cell proliferation and apoptosis remain to be elucidated. In the present study, DC2.4 cells were treated with different concentrations of HBcAg (10, 20 and 30 µg/ml). MTT assay and flow cytometry (Annexin V/propidium iodide analysis) were performed to investigate changes in cell proliferation and apoptosis. Western blot analysis was conducted to examine the changes in nuclear factor (NF)‑κB and protein kinase C (PKC) signaling pathways. NF‑κB inhibitor pyrrolidine dithiocarbamate (PDTC) and PKC inhibitor Chelerythrine were used to block these two signaling pathways. It was identified that HBcAg increased proliferation and decreased apoptosis in a dose‑dependent manner. Western blotting results demonstrated that HBcAg upregulated p‑PKC, p‑IκB, p‑P65, tumor necrosis factor‑α and B‑cell lymphoma 2 (Bcl‑2) levels, and downregulated cleaved caspase 3, demonstrating that HBcAg activated the PKC and NF‑κB signaling pathways. NF‑κB inhibitor PDTC reduced the effects of HBcAg on DC2.4 proliferation (0.6 fold vs. 0.25 fold) and apoptosis (0.43 fold vs. 0.17 fold), and on Bcl‑2 expression levels. PKC inhibitor Chelerythrine reduced the biological effects of HBcAg; it reduced proliferation (0.67 fold vs. 0.23 fold) and upregulated apoptosis (0.43 fold vs. 0.13 fold). Chelerythrine also blocked NF‑κB activity and the HBcAg‑induced Bcl‑2 increase, suggesting the effect on Bcl‑2 from HBcAg was dependent on the PKC/NF‑κB signaling pathway. In conclusion, HBcAg promoted proliferation and inhibited apoptosis through the PKC/NF‑κB/Bcl‑2 signaling pathway in DC2.4 cells.

Low-Level Laser Therapy Stimulates Proliferation in Head and Neck Squamous Cell Carcinoma Cells

Objectives: Low-level laser therapy (LLLT) is a promising non-invasive treatment option for oropharyngeal mucositis, which is a common side effect of many oncological treatments. LLLT is known for its wound healing properties due to the stimulation of cellular processes, such as proliferation, migration and differentiation. Controversy exists on the possible stimulatory effect of LLLT on head and neck cancer (HNSCC) cells in patients treated with radiotherapy. The aim of this study was to evaluate the biostimulatory effect together with the underlying mechanisms of LLLT on HNSCC cancer cells and normal epithelial cells. Materials and methods: HNSCC cell lines (SCC154, SQD9, and SCC61) and human tonsil epithelial cells were exposed to a Gallium-Aluminum-Arsenide diode laser (830 nm, 150 mW) with energy densities of 0, 1, and 2 J/cm2. The proliferation potential of the cells was assessed by Sulforhodamine B assay, immunoblotting (mitogenic pathways), immunocytochemistry (Ki67), and flow cytometry (PI cell cycle staining). Results: Cell proliferation was increased in HNSCC cell lines after laser irradiation with 1 J/cm2, whereas no significant increase was seen after laser irradiation with 2 J/cm2. In contrast, no effect on cell proliferation was seen in the human tonsil epithelial cells after laser irradiation with any of the energy densities. The increased proliferation was associated with elevated levels of pAKT, pERK, and Ki67 protein expression and cell cycle progression. Conclusion: Our results show that LLLT increases cell proliferation in a dose-dependent manner in HNSCC cells but not in normal epithelial tonsil cells. These results suggest that LLLT has to be used with caution when treating oropharyngeal mucositis in HNSCC patients since tumor cells present in the LLLT irradiation field could be triggered by LLLT.

Effects of Er:YAG and Diode Laser Irradiation on Dental Pulp Cells and Tissues

Vital pulp therapy (VPT) is to preserve the nerve and maintain healthy dental pulp tissue. Laser irradiation (LI) is beneficial for VPT. Understanding how LI affects dental pulp cells and tissues is necessary to elucidate the mechanism of reparative dentin and dentin regeneration. Here, we show how Er:YAG-LI and diode-LI modulated cell proliferation, apoptosis, gene expression, protease activation, and mineralization induction in dental pulp cells and tissues using cell culture, immunohistochemical, genetic, and protein analysis techniques. Both LIs promoted proliferation in porcine dental pulp-derived cell lines (PPU-7), although the cell growth rate between the LIs was different. In addition to proliferation, both LIs also caused apoptosis; however, the apoptotic index for Er:YAG-LI was higher than that for diode-LI. The mRNA level of odontoblastic gene markers-two dentin sialophosphoprotein splicing variants and matrix metalloprotease (MMP)20 were enhanced by diode-LI, whereas MMP2 was increased by Er:YAG-LI. Both LIs enhanced alkaline phosphatase activity, suggesting that they may help induce PPU-7 differentiation into odontoblast-like cells. In terms of mineralization induction, the LIs were not significantly different, although their cell reactivity was likely different. Both LIs activated four MMPs in porcine dental pulp tissues. We helped elucidate how reparative dentin is formed during laser treatments.

Tumor Size-Dependent Anticancer Efficacy of Chlorin Derivatives for Photodynamic Therapy

Photodynamic therapy (PDT) with a suitable photosensitizer molecule is a promising anticancer treatment. We evaluated two chlorin molecules as potential photosensitizers, methyl pyropheophorbide a (MPPa) and N-methoxyl purpurinimide (NMPi), against A549 human lung adenocarcinoma cells in vitro as well as in A549 tumor-bearing mice in vivo. Cell viability, microscopy, and fluorescence-activated cell sorting (FACS) analyses were performed for the in vitro studies. MPPa and NMPi showed high phototoxicity in vitro, which was dependent on the concentration of the photosensitizers as well as the light irradiation time. In the animal study, tumor volume change, tumor surface alterations, and hematoxylin & eosin (H&E) and terminal deoxyribonucleotidyl transferse-mediated dUTP nick-end labelling (TUNEL) staining analyses were performed and compared between small (tumor volume of <50 mm³) and large (tumor volume of >50 mm³) size of initial tumors. MPPa and NMPi showed high anticancer efficacy against small-size tumors, indicating that early treatment with PDT is effective. Especially, repeated two times PDT with NMPi allowed almost complete eradication against small-size tumors. However, MPPa and NMPi were not effective against large-size tumors. In conclusion, the two chlorin derivatives, MPPa and NMPi, show good anticancer efficacy as promising photosensitizers for PDT in vitro and in vivo. Moreover, their activity in vivo was significantly dependent on the initial tumor size in mice, which confirms the importance of early cancer treatment.

The Effects of Low-Power Laser Irradiation on Inflammation and Apoptosis in Submandibular Glands of Diabetes-Induced Rats

Diabetes can lead to dysfunction of the secretory capacity in salivary glands. Activation of the receptor for advanced glycation end products (RAGE) and its ligands has been suggested to participate in chronic disorders such as diabetes and its complications. In this study, the expression of RAGE, high mobility group box 1 (HMGB1) and advanced glycation end products (AGE), as well as the effects of low-power laser irradiation (LPLI) in salivary glands of diabetic rats were evaluated, and the mechanisms involved were characterized. The expression of RAGE and HMGB1 at the protein and mRNA levels was observed in submandibular glands (SMGs) of streptozotocin-induced diabetic rats. A diode laser was applied at 660 nm, 70 mW, 20 J/cm², 0.56 J/point, with a spot area of 0.028 cm² and its in vivo effects and the pathways involved were evaluated. Immunohistochemistry and western blotting analysis were performed for inflammatory and apoptosis markers. Diabetes up-regulates HMGB1/AGE/RAGE axis gene expression in SMGs that is associated with activation of the nuclear factor kappa B (NF-κB) pathway. Interestingly, LPLI suppresses NF-κB activation induced by inflammation. LPLI also reduces diabetes-induced apoptosis. That effect was accompanied by decreased levels of Bax, and cleaved caspase 3, which were up-regulated in diabetes. Taken together, our data suggest that LPLI reduces diabetes-induced inflammation by reducing the induction of HMGB1, ultimately leading to inhibition of apoptosis in submandibular glands of diabetic rats.

Hypocrellin B and paclitaxel-encapsulated hyaluronic acid-ceramide nanoparticles for targeted photodynamic therapy in lung cancer

To increase the therapeutic efficacy of photodynamic therapy (PDT) in treating lung cancer, we developed both photosensitizer and anticancer drug encapsulated hyaluronic acid-ceramide nanoparticles. Based on our previous study, a co-delivery system of photosensitizers and anticancer agents greatly improves the therapeutic effect of PDT. Furthermore, hyaluronic acid-ceramide-based nanoparticles are ideal targeting carriers for lung cancer. In vitro phototoxicity in A549 (human lung adenocarcinoma) cells and in vivo antitumor efficacy in A549 tumor-bearing mice treated with hypocrellin B (HB)-loaded nanoparticles (HB-NPs) or hypocrellin B and paclitaxel loaded nanoparticles (HB-P-NPs) were evaluated. Cell viability assay, microscopic analysis and FACS analysis were performed for the in vitro studies and HB-P-NPs showed enhanced phototoxicity compared with HB-NPs. In the animal study, the tumor volume change and the histological analysis was studied and the anticancer efficacy improved in the order of free HB<HB-NPs<HB-P-NPs. In conclusion, the combination therapy of PDT and chemotherapy, and hyaluronic acid-ceramide nanoparticle-based targeted delivery improved the effects of PDT in lung cancer in mice.

In vitro study on the safety of near infrared laser therapy in its potential application as postmastectomy lymphedema treatment

Clinical studies demonstrated the effectiveness of laser therapy in the management of postmastectomy lymphedema, a discomforting disease that can arise after surgery/radiotherapy and gets progressively worse and chronic. However, safety issues restrict the possibility to treat cancer patients with laser therapy, since the effects of laser radiation on cancer cell behavior are not completely known and the possibility of activating postmastectomy residual cancer cells must be considered. This paper reports the results of an in vitro study aimed to investigate the effect of a class IV, dual-wavelength (808 nm and 905 nm), NIR laser system on the behavior of two human breast adenocarcinoma cell lines (namely, MCF7 and MDA-MB361 cell lines), using human dermal fibroblasts as normal control. Cell viability, proliferation, apoptosis, cell cycle and ability to form colonies were analyzed in order to perform a cell-based safety testing of the laser treatment in view of its potential application in the management of postmastectomy lymphedema. The results showed that, limited to the laser source, treatment conditions and experimental models used, laser radiation did not significantly affect the behavior of human breast adenocarcinoma cells, including their clonogenic efficiency. Although these results do not show any significant laser-induced modification of cancer cell behavior, further studies are needed to assess the possibility of safely applying NIR laser therapy for the management of postmastectomy lymphedema.

Downregulation of tumorogenicity and changes in the actin cytoskeleton of murine hepatoma after irradiation with polychromatic visible and IR light

OBJECTIVE

This study evaluated the function and structural consequences of direct exposure of murine hepatoma MH-22a cells to polychromatic polarized light, to determine potential risk of malignancy following irradiation.

BACKGROUND DATA

Visible (VIS) and infrared (IR) light have been actively used for prevention and treatment of complications developed after conventional tumor therapy. However, the safety associated with this irradiation has not been determined.

MATERIALS AND METHODS

Polychromatic light (480-3400 and 385-750 nm), were used at different doses (4.8-38.4 J/cm(2)) to determine the viability, proliferation, and actin cytoskeleton in vitro by flow cytometry and confocal microscopy. Tumorogenic properties of cells were studied in vivo after transplantation in C3HA mice.

RESULTS

Polychromatic light of a wide range of doses did not change the viability and proliferation of cells. After transplantation of cells irradiated with VIS-IR light (4.8 and 9.6 J/cm(2)) and VIS light (38.4 J/cm(2)) the tumor volume was lower in the treated group than in the control group in vivo. Transplantability of the irradiated cells also decreased, whereas survival of tumor-bearing mice increased. Three cell populations with different cytoskeleton structure were identified. After irradiation, the reorganized part of the actin cytoskeleton changed its localization to the submembranous area.

CONCLUSIONS

A decrease of tumorigenicity in cells irradiated with polychromatic light used in non-damaging doses correlated with an increase in the number of cells with reorganized actin in the submembranous area. The results of the present study argue in favor of the oncological safety of polychromatic VIS-IR light (480-3400 nm).

Assessment of the effect of laser irradiations at different wavelengths (660, 810, 980, and 1064 nm) on autophagy in a rat model of mucositis

It is known that high-dose radiation has an effect on tissue healing, but tissue healing does not occur when low dose radiation is applied. To clarify this issue, we compare the treatment success of low dose radiation with programmed cell death mechanisms on wounded tissue. In this study, we aimed to investigate the interactions of low and high-dose radiation using an autophagic mechanism. We included 35 adult Wistar-Albino rats in this study. All animals were injected with 100 mg/kg of 5-fluorouracil (5-FU) on the first day and 65 mg/kg of 5-FU on the third day. The tips of 18-gauge needles were used to develop a superficial scratching on the left cheek pouch mucosa by dragging in a linear movement on third and fifth days. After mucositis formation was clinically detected, animals were divided into five groups (n = 7). Different wavelengths of laser irradiations (1064 nm, Fidelis Plus, Fotona, Slovenia; 980 nm, FOX laser, A.R.C., Germany; 810 nm, Fotona XD, Fotona, Slovenia; 660 nm, HELBO, Medizintechnik GmbH, Wels, Austria) were performed on four groups once daily for 4 days. The laser irradiation was not performed on the control group. To get the tissue from the left cheek at the end of fourth day from all animals, oval excisional biopsy was performed. Molecular analysis assessments of pathological and normal tissue taken were performed. For this purpose, the expression analysis of autophagy genes was performed. The results were evaluated by normalization and statistics analysis. We found that Ulk1, Beclin1, and Atg5 expression levels were increased in the rats when the Nd:YAG laser was applied. This increase showed that a 1064-nm laser is needed to activate the autophagic mechanism. However, in the diode applications, we found that Beclin1, Atg10, Atg5, and Atg7 expressions numerically decreased. Atg5 is responsible for the elongation of autophagosome. Becn1 is a control gene in the control mechanism of autophagy. The reduction of the expression of these genes leads us to think that it may depend on the effect of drug (5-FU) used to form model. Expressions of therapeutic genes increase to ensure hemostasis, but in our study, expressions were found to decrease. More detailed studies are needed.

Laser-induced osteoblast proliferation is mediated by ROS production

Low-level laser therapy (LLLT) is widely used in regenerative medicine and in dental therapy by virtue of its beneficial effects in a plethora of pathological conditions. In this study, the effect of a 980 nm diode laser on pre-osteoblasts proliferation has been evaluated, along with reactive oxygen species (ROS) production. We hypothesized that ROS were a key factor in LLLT-induced pre-osteoblasts proliferation, as it is known that ROS can induce the activation of many biological pathways, leading to cell proliferation, differentiation or apoptosis. Murine pre-osteoblasts MC3T3 cells were irradiated with different energy outputs (1-50 J) in the absence or presence of the antioxidant N-Acetyl-L-cysteine (NAC). Laser treatment, in the absence of NAC, was able to induce a fluence-dependent statistically significant increase in ROS generation, while the presence of NAC strongly inhibited it. Cell proliferation, measured after laser stimulation, was significantly increased both at low and higher energy, with a peak at 10 J in the absence of the antioxidant. On the contrary, in the presence of NAC, laser irradiation was not able to induce any cell proliferation, suggesting a crucial role of ROS in this laser-induced cell effect. These results suggest that LLLT may be a useful tool for bone regeneration therapy and an effective range of fluences to be used is indicated.

Activation of nuclear estrogen receptors induced by low-power laser irradiation via PI3-K/Akt signaling cascade

Low-power laser irradiation (LPLI) has been shown to exert promotive effects on cell survival and proliferation through activation of various signaling pathways. Estrogen receptors (ERs, ERα, and ERβ) are ligand-activated transcription factors, which regulate target gene expression, promote cell proliferation, and resist apoptosis. However, it is unclear whether LPLI could induce ligand-independent activation of ERs. In the present study, we investigated the subcellular pools, nuclear redistribution, and transcriptional activity of ERs under LPLI (1.2 J/cm(2), 633 nm) treatment using single-molecule fluorescence imaging and dual-luciferase reporter assay. We found that ERs were not only localized to nucleus, but also existed in mitochondria. Moreover, we found that LPLI induced nuclear redistribution and transcriptional activity of ERs in a ligand-independent manner. Our further investigation showed that PI3-K/Akt signaling cascade was involved in LPLI-induced activation of ERs. Wortmannin, a PI3-K inhibitor, or triciribine (API-2), a specific Akt inhibitor, potently suppressed the nuclear redistribution and transcriptional activity of ERs induced by LPLI, revealing that PI3-K/Akt signaling cascade was required for the activation of ERs induced by LPLI. Collectively, we demonstrated the first time that LPLI induced the ligand-independent nuclear redistribution and transcriptional activity of ERs, which were dependent on the activity of PI3-K/Akt. Our findings provide direct evidence for the molecular mechanisms of LPLI-induced transcription factor activation.

Photobiomodulation by low-power laser irradiation attenuates Aβ-induced cell apoptosis through the Akt/GSK3β/β-catenin pathway

Apoptosis induced by amyloid β peptide (Aβ) is thought to associate with the pathogenesis of Alzheimer disease (AD). Accumulating evidence shows that low-power laser irradiation (LPLI) is capable of reducing Aβ-induced apoptosis. However, the underlying mechanisms remain unclear. In this study, we report a novel molecular mechanism by which LPLI attenuates Aβ(25-35)-induced apoptosis through the Akt/GSK3β/β-catenin pathway. We found that Akt activated by LPLI interacted with GSK3β and phosphorylated it on Ser9 in the presence of Aβ(25-35), which resulted in the inhibition of GSK3β. Furthermore, LPLI increased the nuclear translocation of β-catenin and enhanced its T cell factor/lymphocyte enhancer factor-dependent transcriptional activity via the Akt/GSK3β pathway to promote cell survival upon treatment with Aβ(25-35.) Our data demonstrate that LPLI has a prosurvival effect on Aβ-induced apoptosis and may be an effective therapeutic strategy in treating AD by targeting GSK3β.

Low-level laser therapy regulates microglial function through Src-mediated signaling pathways: implications for neurodegenerative diseases

BACKGROUND

Activated microglial cells are an important pathological component in brains of patients with neurodegenerative diseases. The purpose of this study was to investigate the effect of He-Ne (632.8 nm, 64.6 mW/cm2) low-level laser therapy (LLLT), a non-damaging physical therapy, on activated microglia, and the subsequent signaling events of LLLT-induced neuroprotective effects and phagocytic responses.

METHODS

To model microglial activation, we treated the microglial BV2 cells with lipopolysaccharide (LPS). For the LLLT-induced neuroprotective study, neuronal cells with activated microglial cells in a Transwell™ cell-culture system were used. For the phagocytosis study, fluorescence-labeled microspheres were added into the treated microglial cells to confirm the role of LLLT.

RESULTS

Our results showed that LLLT (20 J/cm2) could attenuate toll-like receptor (TLR)-mediated proinflammatory responses in microglia, characterized by down-regulation of proinflammatory cytokine expression and nitric oxide (NO) production. LLLT-triggered TLR signaling inhibition was achieved by activating tyrosine kinases Src and Syk, which led to MyD88 tyrosine phosphorylation, thus impairing MyD88-dependent proinflammatory signaling cascade. In addition, we found that Src activation could enhance Rac1 activity and F-actin accumulation that typify microglial phagocytic activity. We also found that Src/PI3K/Akt inhibitors prevented LLLT-stimulated Akt (Ser473 and Thr308) phosphorylation and blocked Rac1 activity and actin-based microglial phagocytosis, indicating the activation of Src/PI3K/Akt/Rac1 signaling pathway.

CONCLUSIONS

The present study underlines the importance of Src in suppressing inflammation and enhancing microglial phagocytic function in activated microglia during LLLT stimulation. We have identified a new and important neuroprotective signaling pathway that consists of regulation of microglial phagocytosis and inflammation under LLLT treatment. Our research may provide a feasible therapeutic approach to control the progression of neurodegenerative diseases.

Low-power laser irradiation (LPLI) promotes VEGF expression and vascular endothelial cell proliferation through the activation of ERK/Sp1 pathway

Angiogenesis, the growth of new blood vessels from pre-existing vessels, represents an excellent therapeutic target for the treatment of wound healing and cardiovascular disease. Herein, we report that LPLI (low-power laser irradiation) activates ERK/Sp1 (extracellular signal-regulated kinase/specificity protein 1) pathway to promote VEGF expression and vascular endothelial cell proliferation. We demonstrate for the first time that LPLI enhances DNA-binding and transactivation activity of Sp1 on VEGF promoter in vascular endothelial cells. Moreover, Sp1-regulated transcription is in an ERK-dependent manner. Activated ERK by LPLI translocates from cytoplasm to nuclear and leads to increasing interaction with Sp1, triggering a progressive phosphorylation of Sp1 on Thr453 and Thr739, resulting in the upregulation of VEGF expression. Furthermore, selective inhibition of Sp1 by mithramycin-A or shRNA suppresses the promotion effect of LPLI on cell cycle progression and proliferation, which is also significantly abolished by inhibition of ERK activity. These findings highlight the important roles of ERK/Sp1 pathway in angiogenesis, supplying potential strategy for angiogenesis-related diseases with LPLI treatment.

Inhibition of Aβ(25-35)-induced cell apoptosis by low-power-laser-irradiation (LPLI) through promoting Akt-dependent YAP cytoplasmic translocation

Deposition of amyloid-β-peptide (Aβ) in the brain is considered a pathological hallmark of Alzheimer's disease (AD). Our previous studies show that Yes-associated protein (YAP) is involved in the regulation of apoptosis induced by Aβ(25-35) through YAP nuclear translocation and its pro-apoptotic function is mediated by its interaction with p73. In the present study, we first found that Low-power laser irradiation (LPLI) promoted YAP cytoplasmic translocation and inhibited Aβ(25-35)-induced YAP nuclear translocation. Moreover, the cytoplasmic translocation was in an Akt-dependent manner. Activated Akt by LPLI phosphorylated YAP on ser127 (S127) and resulted in decreasing the interaction between YAP and p73, and in suppressing the proapoptotic gene bax expression following Aβ(25-35) treatment. Inhibition of Akt expression by siRNA significantly abolished the effect of LPLI. More importantly, LPLI could inhibit Aβ(25-35)-induced cell apoptosis through activation of Akt/YAP/p73 signaling pathway. Therefore, our findings first suggest that YAP may be a therapeutic target and these results directly point to a potential therapeutic strategy for the treatment of AD through Akt/YAP/p73 signaling pathway with LPLI.

Protective effect of autophagy in laser-induced glioma cell death in vitro

BACKGROUND AND OBJECTIVE

Laser phototherapy could be potentially used for cancer treatment, but the mechanisms of laser-induced cell death are not completely understood. Autophagy is the process in which the damaged cellular proteins and organelles are engulfed by and destroyed in acidified multiple-membrane vesicles. The aim of the present study was to investigate the role of autophagy in laser-induced tumor cell death in vitro.

STUDY DESIGN/MATERIALS AND METHODS

The monolayers of U251 human glioma tumor cells were exposed to 532 nm laser light from a single mode frequency-doubled Nd-YVO4 laser. A flattened Gaussian radial profile of laser beam (0.5-4 W) was used to uniformly illuminate entire colony of cells for various amounts of time (15-120 seconds) in the absence of cell culture medium. The cells were grown for 24 hours and the cell viability was determined by crystal violet or MTT assay. The presence of autophagy was assessed after 16 hours by fluorescence microscopy/flow cytometric analysis of acridine orange-stained autophagolysosomes and Western blot analysis of the autophagosome-associated LC3-II protein. The concentration of the principal pro-autophagic protein beclin-1 was determined after 6 hours by cell-based ELISA.

RESULTS

The intracytoplasmic accumulation of autophagic vesicles, increase in LC3-II and up-regulation of beclin-1 expression were clearly observed under irradiation conditions that caused approximately 50% cytotoxicity. Post-irradiation addition of three different autophagy inhibitors (bafilomycin A1, chloroquine, or wortmannin) further increased the laser-induced cytotoxicity, without affecting non-irradiated cells.

CONCLUSIONS

These data indicate that beclin-1-dependent induction of autophagy can protect glioma cells from laser-mediated cytotoxicity.

Survivin mediates self-protection through ROS/cdc25c/CDK1 signaling pathway during tumor cell apoptosis induced by high fluence low-power laser irradiation

Survivin, an important member of inhibitor-of-apoptosis (IAP) family, can be up-regulated by various pro-apoptotic stimuli, such as UV, photodynamic therapy (PDT) and cisplatin. High fluence low-power laser irradiation (HF-LPLI) is a newly discovered pro-apoptotic stimulator. The anti-apoptotic mechanism of survivin during HF-LPLI-induced apoptosis is still not investigated. Here, we report that HF-LPLI up-regulates survivin activity through reactive oxygen species (ROS)/cdc25c protein phosphatase (cdc25c)/cyclin-dependent kinase (CDK1) signaling pathway in human lung adenocarcinoma cells (ASTC-a-1). The up-regulation of survivin activity can reduce HF-LPLI-induced apoptosis, while down-regulation of the activity can promote the apoptosis. In addition, activated survivin delays mitochondrial depolarization, cytochrome c release, caspase-9 and Bax activation, all of which are typical pro-apoptotic events of cell apoptosis induced by HF-LPLI. On the basis of the present studies, we conclude that survivin can mediate self-protection during tumor cell apoptosis caused by HF-LPLI.

LPLI inhibits apoptosis upstream of Bax translocation via a GSK-3beta-inactivation mechanism

Low-power laser irradiation (LPLI), a non-damage physical therapy, which has been used clinically for decades of years, is shown to promote cell proliferation and prevent apoptosis. However, the underlying mechanisms that LPLI prevents cell apoptosis remain undefined. In this study, based on real-time single-cell analysis, we demonstrated for the first time that LPLI inhibits staurosporine (STS)-induced cell apoptosis by inactivating the GSK-3beta/Bax pathway. LPLI could inhibit the activation of GSK-3beta, Bax, and caspase-3 induced by STS. In the searching for the mechanism, we found that, LPLI can activate Akt, which was consistence with our former research, even in the presence of STS. In this anti-apoptotic process, the interaction between Akt and GSK-3beta increased gradually, indicating Akt interacts with and inactivates GSK-3beta directly. Conversely, LPLI decreased the interaction between GSK-3beta and Bax, with the suppression of Bax translocation to mitochondria, suggesting LPLI inhibits Bax translocation through inactivating GSK-3beta. These results were further confirmed by the experiments of co-immunoprecipitation. Wortmannin, an inhibitor of phosphatidylinositol 3'-OH kinase (PI3K), potently suppressed the activation of Akt and subsequent anti-apoptotic processes induced by LPLI. Taken together, we conclude that LPLI protects against STS-induced apoptosis upstream of Bax translocation via the PI3K/Akt/GSK-3beta pathway. These findings raise the possibility of LPLI as a promising therapy for neuron-degeneration disease induced by GSK-3beta.

Low-level laser therapy attenuates creatine kinase levels and apoptosis during forced swimming in rats

Studies suggest that high-intensity physical exercise can cause damage to skeletal muscles, resulting in muscle soreness, fatigue, inflammatory processes and cell apoptosis. The aim of this study was to investigate the effects of low-level laser therapy (LLLT) on a decrease in creatine kinase (CK) levels and cell apoptosis. Twenty male Wistar rats were randomly divided into two equal groups: group 1 (control), resistance swimming; group 2 (LLLT), resistance swimming with LLLT. They were subjected to a single application of indium gallium aluminum phosphide (InGaAlP) laser immediately following the exercise for 40 s at an output power of 100 mW, wavelength 660 nm and 133.3 J/cm(2). The groups were subdivided according to sample collection time: 24 h and 48 h. CK was measured before and both 24 h and 48 h after the test. Samples of the gastrocnemius muscle were processed to determine the presence of apoptosis using terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP) nick end labeling. (There was a significant difference in CK levels between groups (P < 0.0001) as well as between the 24 h and 48 h levels in the control group, whereas there was no significant intra-group difference in the LLLT group at the same evaluation times. In the LLLT group there were 66.3 +/- 13.2 apoptotic cells after 24 h and 39.0 +/- 6.8 apoptotic cells after 48 h. The results suggest that LLLT influences the metabolic profile of animals subjected to fatigue by lowering serum levels of CK. This demonstrates that LLLT can act as a preventive tool against cell apoptosis experienced during high-intensity physical exercise.

Intravital imaging of tumor apoptosis with FRET probes during tumor therapy

PURPOSE

The aim of the study is to dynamically and non-invasively monitor the apoptosis events in vivo during photodynamic therapy (PDT) and chemotherapy.

PROCEDURES

A FRET probe, SCAT3, was utilized to determine activation of caspase-3 during tumor cell apoptosis in mice, induced by PDT, and cisplatin treatments. Using this method, dynamics of caspase-3 activation was observed both in vitro and in vivo.

RESULTS

Analysis of the fluorescent missions from tumor cells indicated that the caspase-3 activation started immediately after PDT treatment. In contrast, the caspase-3 activation started about 13 and 36 h after cisplatin treatment in vitro and in vivo, respectively.

CONCLUSIONS

FRET could be used effectively to monitor activation of caspase-3 in living organism. This method could be used to provide rapid assessment of apoptosis induced by anti-tumor therapies for improvement of treatment efficacy.

H-Ras and PI3K are required for the formation of circular dorsal ruffles induced by low-power laser irradiation

The formation of circular dorsal ruffles upon growth factor stimulation facilitates the static cells for subsequent motility. Low-power laser irradiation (LPLI) has been shown to exert some promotive effects on migration and proliferation in various cell types. It is unclear whether LPLI could induce the formation of circular ruffles. In this study, using confocal fluorescence microscope, we for the first time demonstrated that LPLI could induce the production of circular ruffle structures in COS-7 cells. These structures were proved to be actin-based and originated from membrane microdomains enriched in cholesterol. Ras was shown to be activated by LPLI and expression of YFP-H-Ras (N17), a dominant negative H-Ras, blocked the generation of circular ruffles induced by LPLI. Wortmannin, PI3K inhibitor, potently suppressed the formation of LPLI-induced circular ruffles in a dose-dependent manner. However, blocking the activation of PKC, which was activated during LPLI-induced cell proliferation in our previous study, had no effect on the formation of circular ruffles. Thus, both H-Ras and PI3K were required for the formation of circular ruffles induced by LPLI and the generation of circular ruffles provides new information for the mechanisms of biological effects of LPLI. J. Cell. Physiol. 219: 535-543, 2009. (c) 2009 Wiley-Liss, Inc.

Low-power laser irradiation promotes cell proliferation by activating PI3K/Akt pathway

Low-power laser irradiation (LPLI) can stimulate cell proliferation through a wide network of signals. Akt is an important protein kinase in modulating cell proliferation. In this study, using real-time single-cell analysis, we investigated the activity of Akt and its effects on cell proliferation induced by LPLI in African green monkey SV40-transformed kidney fibroblast cells (COS-7). We utilized a recombinant fluorescence resonance energy transfer (FRET) Akt probe (BKAR) to dynamically detect the activation of Akt after LPLI treatment. Our results show that LPLI induced a gradual and continuous activation of Akt. Moreover, the activation of Akt can be completely abolished by wortmannin, a specific inhibitor of PI3K, suggesting that the activation of Akt caused by LPLI is a PI3K-dependent event. Src family is involved in Akt activation as demonstrated by the part inhibition of Akt activity in samples treated with PP1 (an inhibitor of Src family). In contrast, loading Gö 6983, a PKC inhibitor, did not affect this response. Further experiments performed using GFP-Akt fluorescence imaging and Western blot analysis demonstrate that, the activation of Akt is a multi-step process in response to LPLI, involving membrane recruitment, phosphorylation, and membrane detachment. LPLI promotes cell proliferation through PI3K/Akt activation since the cell viability was significantly inhibited by PI3K inhibitor. All these studies create a concernful conclusion that PI3K/Akt signaling pathway is well involved in LPLI triggered cell proliferation that acts as a time- and dose-dependent manner. J. Cell. Physiol. 219: 553-562, 2009. (c) 2009 Wiley-Liss, Inc.

High fluence low-power laser irradiation induces mitochondrial permeability transition mediated by reactive oxygen species

High fluence low-power laser irradiation (HF-LPLI) can induce cell apoptosis via the mitochondria/caspase-3 pathway. Here, we further investigated the mechanism involved in the apoptotic process in human lung adenocarcinoma cells (ASTC-a-1) at a laser irradiation fluence of 120 J/cm(2) (633 nm). Cytochrome c release was ascribed to mitochondrial permeability transition (MPT) because the release was prevented by cyclosporine (CsA), a specific inhibitor of MPT. Furthermore, mitochondrial permeability for calcein (approximately 620 Da) was another evidence for the MPT induction under HF-LPLI treatment. A high-level intracellular reactive oxygen species (ROS) generation was observed after irradiation. The photodynamically produced ROS caused onset of MPT, as the ROS scavenger docosahexaenoic acid (DHA) prevented the MPT. However, CsA failed to prevented cell death induced by HF-LPLI, indicating the existence of other signaling pathways. Following laser irradiation, Bax activation occurred after mitochondrial depolarization and cytochrome c release, indicating Bax activation was a downstream event. In the presence of CsA, Bax was still activated at the end-stage of apoptotic process caused by HF-LPLI, suggesting that Bax was involved in an alternative-signaling pathway, which was independent of MPT. Under HF-LPLI treatment, cell viabilities due to pre-treatment with DHA, CsA, or Bax small interfering RNA (siRNA) demonstrated that the MPT signaling pathway was dominant, while Bax signaling pathway was secondary, and more importantly ROS mediated both pathways. Taken together, these results showed that HF-LPLI induced cell apoptosis via the CsA-sensitive MPT, which was ROS-dependent. Furthermore, there existed a secondary signaling pathway through Bax activation. The observed link between MPT and triggering ROS could be a fundamental phenomenon in HF-LPLI-induced cell apoptosis.

Molecular mechanisms of cell proliferation induced by low power laser irradiation

Low power laser irradiation (LPLI) promotes proliferation of multiple cells, which (especially red and near infrared light) is mainly through the activation of mitochondrial respiratory chain and the initiation of cellular signaling. Recently, the signaling proteins involved in LPLI-induced proliferation merit special attention, some of which are regulated by mitochondrial signaling. Hepatocyte growth factor receptor (c-Met), a member of tyrosine protein kinase receptors (TPKR), is phosphorylated during LPLI-induced proliferation, but tumor necrosis factor alpha (TNF-alpha) receptor has not been affected. Activated TPKR could activate its downstream signaling elements, like Ras/Raf/MEK/ERK, PI3K/Akt/eIF4E, PI3K/Akt/eNOS and PLC-gamma/PKC pathways. Other two pathways, DeltaPsim/ATP/cAMP/JNK/AP-1 and ROS/Src, are also involved in LPLI-induced proliferation. LPLI-induced cell cycle progression can be regulated by the activation or elevated expressions of cell cycle-specific proteins. Furthermore, LPLI induces the synthesis or release of many molecules, like growth factors, interleukins, inflammatory cytokines and others, which are related to promotive effects of LPLI.

Low-power laser irradiation activates Src tyrosine kinase through reactive oxygen species-mediated signaling pathway

Low-power laser therapy in medicine is widespread but the mechanisms are not fully understood. It has been suggested that low-power laser irradiation (LPLI) could induce photochemical reaction and activate several intracellular signaling pathways. Reactive oxygen species (ROS) are considered to be the key secondary messengers produced by LPLI. Here, we studied the signaling pathway mediated by ROS upon the stimulation of LPLI. Src tyrosine kinases are well-known targets of ROS and can be activated by oxidative events. Using a Src reporter based on fluorescence resonance energy transfer (FRET) and confocal laser scanning microscope, we visualized the dynamic Src activation in Hela cells immediately after LPLI. Moreover, Src activation by LPLI was in a dose-dependent manner. The increase of Src phosphorylation at Tyr416 was detected by Western blotting. In the presence of vitamin C, catalase alone, or the combination of catalase and superoxide dismutase (SOD), the activation of Src by LPLI is significantly abolished. In contrast, Gö6983 loading, a PKC inhibitor, did not affect this response. Treatment of Hela cells with exogenous H(2)O(2) also resulted in a concentration-dependent activation of Src. These results demonstrated that it was ROS that mediated Src activation by LPLI. Cellular viability assay revealed that laser irradiation of low doses (</=25 J/cm(2)) promoted Hela cells viability while high doses impaired. Therefore, LPLI induces ROS-mediated Src activation which may play an important role in biostimulatory effect of LPLI.

Bim(L) displacing Bcl-x(L) promotes Bax translocation during TNFalpha-induced apoptosis

Bcl-2 family proteins are implicated as essential regulators in tumor necrosis factor-alpha (TNFalpha)-induced apoptosis. Bim(L), a BH3-only member of Bcl-2 family, can directly or indirectly activate the proapoptotic Bax and the subsequent mitochondrial apoptotic pathway. However, the molecular mechanism of Bim(L) activating Bax activation during TNFalpha-induced apoptosis is not fully understood. In this study, the role of Bim(L) in Bax activation during TNFalpha-induced apoptosis was investigated in differentiated PC12 and MCF7 cells, with real-time single-cell analysis. The experimental results show that Bax translocated to mitochondria and cytochrome c (Cyt c) released from mitochondria after TNFalpha treatment. Furthermore, SP600125 (specific inhibitor of JNK) could inhibit the Cyt c release from mitochondria. Co-immunoprecipitation results show that, the interaction between Bcl-x(L) and Bax decreased after TNFalpha treatment, while that between Bcl-x(L) and Bim(L) increased. Bax did not co-immunoprecipitate with Bim(L) before or after the TNFalpha treatment. In addition, the increased interaction between Bim(L) and Bcl-x(L) was dynamically monitored by using fluorescence resonance energy transfer (FRET) technique. Most importantly, there was no evidence of Bim(L) redistribution to mitochondria until cell apoptosis. By comprehensively analyzing these data, it is concluded that Bim(L) displaces Bcl-x(L) in the mitochondria and promotes Bax translocation during TNFalpha-induced apoptosis.

Spatio-Temporal Dynamic Analysis of Bid Activation and Apoptosis Induced by Alkaline Condition in Human Lung Adenocarcinoma Cell

Activation of initiator and effector caspases and Bid cleavage are apoptotic characteristic features. They are associated with cell alkalization or acidification in some models of apoptosis. The alteration of culture conditions such as extracellular pH value and the overexpression of Bid plasmids may induce cell apoptosis. In present report, we used fluorescence confocal imaging and fluorescence resonance energy transfer (FRET) techniques based on green fluorescent proteins (GFPs) to monitor the spatio-temporal dynamics of Bid translocation and caspase-3 activation in real time in living human lung adenocarcinoma (ASTC-a-1) cells under neutral (pH 7.4) and alkaline (pH 8.0) conditions. The cells transfected with Bid-CFP plasmid did not show apoptotic characteristics for 96 hours under an atmosphere of 95% air, 5% CO(2) at pH 7.4 and 37 degrees C, implying that the overexpression of Bid-CFP plasmid does not induce cell apoptosis. However, all the cells underwent apoptosis after being placed in the alkaline culture (pH 8.0). The dynamic results in single living cell showed that the alkaline condition at pH of 8.0 induced Bid cleavage and tBid translocation to mitochondria at about 1.5 hour, and then induced the caspase-3 activation and cell apoptosis. These results show that the alkaline sondition (pH=8.0) induces cell apoptosis by activating caspase-8, which cleaves Bid to tBid, tBid translocation to mitochondria, and then activating the caspase-3 in the ASTC-a-1 cells.

Calpain-mediated pathway dominates cisplatin-induced apoptosis in human lung adenocarcinoma cells as determined by real-time single cell analysis

Cisplatin is an efficient anticancer agent. Cisplatin-based chemotherapy is believed to involve different signal transduction pathways, among which calpain activation has been proposed as an important factor in the induced apoptosis. In our study, based on real-time single cell analysis, we investigated the molecular involvement of calpain in cisplatin-induced apoptosis in living human lung adenocarcinoma cells. After cisplatin treatment, calpain was activated, resulting in Bid cleavage at 4-5 hr, followed by Bid translocation and cytochrome c release, leading to cell death. Calpeptin and PD150606, specific inhibitors of calpain, blocked Bid activation completely; however, cytochrome c release was delayed by more than 2 hr, which was associated with the delay of caspase-3 activation and cell death. Remarkably, calpain-mediated release of cytochrome c and cell death was significantly compromised in the Bid knockdown cells. Z-IETD-fmk and Z-VDVAD-fmk were used to block the activation of caspase-8 and caspase-2, respectively; however, the progression of apoptosis were not affected, suggesting that caspase-8 and caspase-2 were not involved in this experimental model. Taken together, the data demonstrate that calpain mediated cisplatin-induced apoptosis in human lung adenocarcinoma cells through activating Bid, which then regulated the mitochondrial apoptotic pathway. The delays of cytochrome c release, caspase-3 activation and subsequent cell death by inactivating calpain or silencing Bid exclude other earlier or parallel pathways, strongly suggesting that the calpain-mediated pathway is the kinetically earliest one, which dominates the cisplatin-induced apoptosis.

Bid is required in NPe6-PDT-induced apoptosis

Photodynamic therapy (PDT) employing photosensiter N-aspartyl chlorin e6 (NPe6) can induce lysosome disruption and initiate the intrinsic apoptotic pathway. Yet the precise signal transduction pathway remains poorly understood. In this study, we have investigated the molecular mechanism in NPe6-PDT-induced apoptosis in human lung adenocarcinoma cells (ASTC-a-1). A recombinant fluorescence resonance energy transfer (FRET) Bid probe was utilized to determine the kinetics of Bid cleavage. The results show that cleavage of the Bid-FRET probe occurred 150 +/- 5 min after NPe6-PDT treatment, and this process lasted for 45 +/- 5 min. The Bid cleavage coincided with a translocation of tBid from cytoplasm to mitochondria. Remarkably, a significant protection against cell death was observed by using small interfering RNA for Bid. Therefore, our study clearly showed the dynamics of Bid activation and redistribution during NPe6-PDT-induced apoptosis by using real-time analysis in living cells, and the inhibition of cell death by silencing Bid with interference strongly suggested that activation of Bid is required for inducing apoptosis in this experimental model.

Bid is not required for Bax translocation during UV-induced apoptosis

UV irradiation triggers apoptosis through both the membrane death receptor and the intrinsic apoptotic signaling pathways. Bax, a member of the Bcl-2 family of proteins, translocates from the cytosol to the mitochondrial membrane during UV-induced apoptosis, but the regulation of Bax translocation by UV irradiation remains elusive. In this study, we show that Bax translocation, caspase-3 activation and cell death by UV irradiation are not affected by Z-IETD-fmk (caspase-8 inhibitor), but delayed by Pifithrin-alpha (p53 inhibitor), although Bid cleavage could be completely abolished by Z-IETD-fmk. Co-transfecting YFP-Bax and Bid-CFP into human lung adenocarcinoma cells, we demonstrate that translocation of YFP-Bax precedes that of Bid-CFP, there is no significant FRET (fluorescence resonance energy transfer) between them. Similar results are obtained in COS-7 cells expressing YFP-Bax and Bid-CFP. Furthermore, using acceptor photobleaching technique, we observe that there is no interaction between YFP-Bax and Bid-CFP in both healthy and apoptotic cells. Additionally, during UV-induced apoptosis there is downregulation of Bcl-x(L), an anti-apoptotic protein. Overexpression of Bcl-x(L) in cells susceptible to UV-induced apoptosis prevents Bax translocation and cell death, repression of Bid protein with siRNA (small interfering RNA) do not inhibit cell death by UV irradiation. Taken together, these data strongly suggest that Bax translocation by UV irradiation is a Bid-independent event and inhibited by overexpression of Bcl-x(L).

Real-time monitoring full length bid interacting with Bax during TNF-alpha-induced apoptosis

Bid, a member of the pro-apoptotic Bcl-2 protein family, is activated through caspase-8-mediated cleavage into a truncated form (p15 tBid) during TNF-alpha(tumor necrosis factor alpha)-induced apoptosis. Activated tBid can induce Bax oligomerization and translocation to mitochondria, triggering the release of cytochrome c, caspase-3 activation and cell apoptosis. However, it is debatable that whether Bid and tBid can interact directly with Bax in living cells. In this study, we used confocal fluorescence microscope, combined with both FRET (fluorescence resonance energy transfer) and acceptor photobleaching techniques, to study the dynamic interaction between Bid and Bax during TNF-alpha-induced apoptosis in single living cell. In ASTC-a-1 cells, full length Bid induced Bax translocation to mitochondria by directly interacting with Bax transiently in response to TNF-alpha treatment before cell shrinkage. Next, we demonstrated that, in both ASTC-a-1 and HeLa cells, Bid was not cleaved before cell shrinkage even under the condition that caspase-8 had been activated, but in MCF-7 cells Bid was cleaved. In addition, in ASTC-a-1 cells, caspase-3 activation was a biphasic process and Bid was cleaved after the second activation of caspase-3. In summary, these findings indicate that, FL-Bid (full length-Bid) directly regulated the activation of Bax during TNF-alpha-induced apoptosis in ASTC-a-1 cells and that the cleavage of Bid occurred in advanced apoptosis.