In vitro human cell responses to a low-dose photodynamic treatment vs. mild H2O2 exposure

Investigation of Impact of Oxidative Stress on Human Periodontal Ligament Cells Exposed to Static Compression

Oxidative stress (OS) is a common feature of many inflammatory diseases, oral pathologies, and aging processes. The impact of OS on periodontal ligament cells (PDLCs) in relation to oral pathologies, including periodontal diseases, has been investigated in different studies. However, its impact on orthodontic tooth movement (OTM) remains poorly understood. This study used an in vitro model with human PDLCs previously exposed to H2O2 to investigate the effects of OS under a static compressive force which simulated the conditions of OTM. Human PDLCs were treated with varying concentrations of H2O2 to identify sub-lethal doses that affected viability minimally. To mimic compromised conditions resembling OTM under OS, the cells were pretreated with the selected H2O2 concentrations for 24 h. Using an in vitro loading model, a static compressive force (2 g/cm2) was applied for an additional 24 h. The cell viability, proliferation, and cytotoxicity were evaluated using live/dead and resazurin assays. Apoptosis induction was assessed based on caspase-3/7 activity. The gene expression related to bone remodeling (RUNX2, TNFRSF11B/OPG, BGLAP), inflammation (IL6, CXCL8/IL8, PTGS2/COX2), apoptosis (CASP3, CASP8), and autophagy (MAP1LC3A/LC3, BECN1) was analyzed using RT-qPCR. This study suggests an altering effect of previous OS exposure on static-compression-related mechanosensing. Further research is needed to fully elucidate these mechanisms.

Positive effects of low-dose photodynamic therapy with aminolevulinic acid or its methyl ester in skin rejuvenation and wound healing: An update

In dermatology, photodynamic therapy (PDT) is widely used in skin tumors, infections, etc., because of the killing effect triggered by toxic reactive oxygen species (ROS). However, the ROS concentration is determined by various photosensitizer concentrations and formulations, as well as various irradiation parameters. Low-dose PDT leads to sufficiently low ROS level, which results in biological effects that are the exact opposite of the killing potency. Therefore, in recent years, low-dose PDT has been exploited in improving aging and wound. Low-dose ALA/MAL PDT might improve aging through promoting the proliferation of fibroblasts, blocking DNA damage, counteracting oxidative stress, inhibiting melanogenesis, and remodeling lymphatic vessels in aged skin. Promoting fibroblasts and epidermal stem cells proliferation and migration, promoting granulation tissue formation and angiogenesis and regulating the inflammatory process might be the mechanisms of low-dose ALA/MAL PDT in wound healing. Nevertheless, the positive effects of low-dose PDT have not been thoroughly investigated in dermatology, and high-quality studies are still needed to fill the relevant vacancy.

Genetic Material Manipulation and Modification by Optical Trapping and Nanosurgery-A Perspective

Light can be employed as a tool to alter and manipulate matter in many ways. An example has been the implementation of optical trapping, the so called optical tweezers, in which light can hold and move small objects with 3D control. Of interest for the Life Sciences and Biotechnology is the fact that biological objects in the size range from tens of nanometers to hundreds of microns can be precisely manipulated through this technology. In particular, it has been shown possible to optically trap and move genetic material (DNA and chromatin) using optical tweezers. Also, these biological entities can be severed, rearranged and reconstructed by the combined use of laser scissors and optical tweezers. In this review, the background, current state and future possibilities of optical tweezers and laser scissors to manipulate, rearrange and alter genetic material (DNA, chromatin and chromosomes) will be presented. Sources of undesirable effects by the optical procedure and measures to avoid them will be discussed. In addition, first tentative approaches at cellular-level genetic and organelle surgery, in which genetic material or DNA-carrying organelles are extracted out or introduced into cells, will be presented.

Lipid Peroxidation Assay Using BODIPY-Phenylbutadiene Probes: A Methodological Overview

The assessment of reactive oxygen species has increasing importance in biomedical sciences, due to their biological role in signaling pathways and induction of cell damage at low and high concentrations, respectively. Detection of lipid peroxidation with sensing probes such as some BODIPY dyes has now wide application in studies using fluorescent microplate readers, flow cytometry, and fluorescence microscopy. Two phenylbutadiene derivatives of BODIPY are commonly used as peroxidation probes, non-oxidized probes and oxidized products giving red and green fluorescence, respectively. Peculiar features of lipoperoxidation and BODIPY dye properties make this assessment a rather complex process, not exempt of doubts and troubles. Color changes and fluorescence fading that are not due to lipid peroxidation must be taken into account to avoid misleading results. As a characteristic feature of lipoperoxidation is the propagation of peroxyl radicals, pitfalls and advantages of a delayed detection by BODIPY probes should be considered.

Direct 1O2 optical excitation: A tool for redox biology

Molecular oxygen (O2) displays very interesting properties. Its first excited state, commonly known as singlet oxygen (1O2), is one of the so-called Reactive Oxygen Species (ROS). It has been implicated in many redox processes in biological systems. For many decades its role has been that of a deleterious chemical species, although very positive clinical applications in the Photodynamic Therapy of cancer (PDT) have been reported. More recently, many ROS, and also 1O2, are in the spotlight because of their role in physiological signaling, like cell proliferation or tissue regeneration. However, there are methodological shortcomings to properly assess the role of 1O2 in redox biology with classical generation procedures. In this review the direct optical excitation of O2 to produce 1O2 will be introduced, in order to present its main advantages and drawbacks for biological studies. This photonic approach can provide with many interesting possibilities to understand and put to use ROS in redox signaling and in the biomedical field.

Establishing the subcellular localization of photodynamically-induced ROS using 3,3'-diaminobenzidine: A methodological proposal, with a proof-of-concept demonstration

The critical involvement of reactive oxygen species (ROS) in both physiological and pathological processes in cell biology makes their detection and assessment a fundamental topic in biomedical research. Established methodologies to study ROS in cell biology take advantage of oxidation reactions between the ROS and a reduced probe. After reacting the probe reveals the presence of ROS either by the appearance of colour (chromogenic reaction) or fluorescence (fluorogenic reaction). However current methodologies rarely allow for a site-specific detection of ROS production. Here we propose a colorimetric reaction driven by the oxidation of 3,3'-diaminobenzidine (DAB) by photodynamically-produced ROS that allows for fine detection of the ROS production site. The introduced methodology is fast, easy to implement and permits cellular resolution at the submicrometric level. Although the basic protocol is proved in a photodynamic model of ROS generation, the principle is applicable to many different scenarios of intracellular ROS production. As a consequence this proposed methodology should greatly complement other techniques aiming at establishing a precise subcellular localization of ROS generation.