PhotoPoint Photodynamic Therapy Promotes Stabilization of Atherosclerotic Plaques and Inhibits Plaque Progression

Photodynamic Therapy for Atherosclerosis

Atherosclerosis, which currently contributes to 31% of deaths globally, is of critical cardiovascular concern. Current diagnostic tools and biomarkers are limited, emphasizing the need for early detection. Lifestyle modifications and medications form the basis of treatment, and emerging therapies such as photodynamic therapy are being developed. Photodynamic therapy involves a photosensitizer selectively targeting components of atherosclerotic plaques. When activated by specific light wavelengths, it induces localized oxidative stress aiming to stabilize plaques and reduce inflammation. The key advantage lies in its selective targeting, sparing healthy tissues. While preclinical studies are encouraging, ongoing research and clinical trials are crucial for optimizing protocols and ensuring long-term safety and efficacy. The potential combination with other therapies makes photodynamic therapy a versatile and promising avenue for addressing atherosclerosis and associated cardiovascular disease. The investigations underscore the possibility of utilizing photodynamic therapy as a valuable treatment choice for atherosclerosis. As advancements in research continue, photodynamic therapy might become more seamlessly incorporated into clinical approaches for managing atherosclerosis, providing a blend of efficacy and limited invasiveness.

Characterization of a Novel Amphiphilic Cationic Chlorin Photosensitizer for Photodynamic Applications

A novel amphiphilic cationic chlorin e₆ derivative was investigated as a promising photosensitizer for photodynamic therapy. Two cationic -N(CH₃)₃⁺ groups on the periphery of the macrocycle provide additional hydrophilization of the molecule and ensure its electrostatic binding to the mitochondrial membranes and bacterial cell walls. The presence of a hydrophobic phytol residue in the same molecule results in its increased affinity towards the phospholipid membranes while decreasing its stability towards aggregation in aqueous media. In organic media, this chlorin e₆ derivative is characterized by a singlet oxygen quantum yield of 55%. Solubilization studies in different polymer- and surfactant-based supramolecular systems revealed the effective stabilization of this compound in a photoactive monomolecular form in micellar nonionic surfactant solutions, including Tween-80 and Cremophor EL. A novel cationic chlorin e₆ derivative also demonstrates effective binding towards serum albumin, which enhances its bioavailability and promotes effective accumulation within the target tissues. Laser confocal scanning microscopy demonstrates the rapid intracellular accumulation and distribution of this compound throughout the cells. Together with low dark toxicity and a rather good photostability, this compound demonstrates significant phototoxicity against HeLa cells causing cellular damage most likely through reactive oxygen species generation. These results demonstrate a high potential of this derivative for application in photodynamic therapy.

Cathepsin B-Cleavable Polymeric Photosensitizer Prodrug for Selective Photodynamic Therapy: In Vitro Studies

Cathepsin B is a lysosomal cysteine protease that plays an important role in cancer, atherosclerosis, and other inflammatory diseases. The suppression of cathepsin B can inhibit tumor growth. The overexpression of cathepsin B can be used for the imaging and photodynamic therapy (PDT) of cancer. PDT targeting of cathepsin B may have a significant potential for selective destruction of cells with high cathepsin B activity. We synthesized a cathepsin B-cleavable polymeric photosensitizer prodrug (CTSB-PPP) that releases pheophorbide a (Pha), an efficient photosensitizer upon activation with cathepsin B. We determined the concentration dependant uptake in vitro, the safety, and subsequent PDT-induced toxicity of CTSB-PPP, and ROS production. CTSB-PPP was cleaved in bone marrow cells (BMCs), which express a high cathepsin B level. We showed that the intracellular fluorescence of Pha increased with increasing doses (3-48 µM) and exerted significant dark toxicity above 12 µM, as assessed by MTT assay. However, 6 µM showed no toxicity on cell viability and ex vivo vascular function. Time-dependent studies revealed that cellular accumulation of CTSB-PPP (6 µM) peaked at 60 min of treatment. PDT (light dose: 0-100 J/cm2, fluence rate: 100 mW/cm2) was applied after CTSB-PPP treatment (6 µM for 60 min) using a special frontal light diffuser coupled to a diode laser (671 nm). PDT resulted in a light dose-dependent reduction in the viability of BMCs and was associated with an increased intracellular ROS generation. Fluorescence and ROS generation was significantly reduced when the BMCs were pre-treated with E64-d, a cysteine protease inhibitor. In conclusion, we provide evidence that CTSB-PPP showed no dark toxicity at low concentrations. This probe could be utilized as a potential imaging agent to identify cells or tissues with cathepsin B activity. CTSB-PPP-based PDT results in effective cytotoxicity and thus, holds great promise as a therapeutic agent for achieving the selective destruction of cells with high cathepsin B activity.

Targeted theranostic photoactivation on atherosclerosis

Background

Photoactivation targeting macrophages has emerged as a therapeutic strategy for atherosclerosis, but limited targetable ability of photosensitizers to the lesions hinders its applications. Moreover, the molecular mechanistic insight to its phototherapeutic effects on atheroma is still lacking. Herein, we developed a macrophage targetable near-infrared fluorescence (NIRF) emitting phototheranostic agent by conjugating dextran sulfate (DS) to chlorin e6 (Ce6) and estimated its phototherapeutic feasibility in murine atheroma. Also, the phototherapeutic mechanisms of DS-Ce6 on atherosclerosis were investigated.

Results

The phototheranostic agent DS-Ce6 efficiently internalized into the activated macrophages and foam cells via scavenger receptor-A (SR-A) mediated endocytosis. Customized serial optical imaging-guided photoactivation of DS-Ce6 by light illumination reduced both atheroma burden and inflammation in murine models. Immuno-fluorescence and -histochemical analyses revealed that the photoactivation of DS-Ce6 produced a prominent increase in macrophage-associated apoptotic bodies 1 week after laser irradiation and induced autophagy with Mer tyrosine-protein kinase expression as early as day 1, indicative of an enhanced efferocytosis in atheroma.

Conclusion

Imaging-guided DS-Ce6 photoactivation was able to in vivo detect inflammatory activity in atheroma as well as to simultaneously reduce both plaque burden and inflammation by harmonic contribution of apoptosis, autophagy, and lesional efferocytosis. These results suggest that macrophage targetable phototheranostic nanoagents will be a promising theranostic strategy for high-risk atheroma.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01084-z.

Oxygen-generating glycol chitosan-manganese dioxide nanoparticles enhance the photodynamic effects of chlorin e6 on activated macrophages in hypoxic conditions

This study aimed to investigate the use of glycol chitosan (GC) for the synthesis of MnO₂ nanoparticles (NPs) and to evaluate whether the prepared GC-MnO₂ NPs enhance the light-triggered photodynamic effects of chlorin e6 (Ce6) via the generation of oxygen and alleviation of hypoxia in lipopolysaccharide (LPS)-activated macrophages (RAW 264.7), which produce excessive amounts of reactive oxygen species (ROS). GC-MnO₂ NPs were synthesized by a simple reaction between GC and KMnO₄ in water. The prepared GC-MnO₂ NPs were spherical in shape, with a mean diameter of approximately 60 nm. The particles effectively generated oxygen via H₂O₂-induced degradation under hypoxic conditions, which led to an increase in the singlet oxygen levels upon laser irradiation. Furthermore, GC-MnO₂ NPs significantly enhanced the light-triggered photodynamic effects of Ce6 on activated macrophages under hypoxic conditions, as shown by the increased levels of cell death and cell membrane damage in activated macrophages. Therefore, these results suggest that GC can be used as an alternative natural polymer for the synthesis of MnO₂ NPs and that oxygen-generating GC-MnO₂ NPs enhance the light-triggered photodynamic effects of Ce6 on activated macrophages by alleviating hypoxia.

Curcumin-mediated photodynamic therapy inhibits the phenotypic transformation, migration, and foaming of oxidized low-density lipoprotein-treated vascular smooth muscle cells by promoting autophagy

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Vascular smooth muscle cells (VSMCs) are becoming a hot spot and target of atherosclerosis research. This study aimed to observe the specific effects of curcumin (CUR)-mediated photodynamic therapy (CUR-PDT) on oxidized low-density lipoprotein (ox-LDL)-treated VSMCs and confirm whether these effects are mediated by autophagy. In this study, the mouse aortic smooth muscle cell line and A7r5 cell lines were used for parallel experiments. VSMC viability was evaluated by Cell Counting Kit-8 assay. VSMCs were treated with ox-LDL to establish a model of atherosclerosis in vitro. The autophagy level and the expression of proteins related to phenotypic transformation were detected by western blotting. The migration ability of the cells was detected by using transwell assay. The presence of intracellular lipid droplets was detected by Oil Red O staining. The results showed that VSMCs transformed from the contraction phenotype to the synthetic phenotype when stimulated by ox-LDL, during which autophagy was inhibited. However, CUR-PDT treatment significantly promoted the level of autophagy and inhibited the process of phenotypic transformation induced by ox-LDL. In addition, ox-LDL significantly promoted VSMC migration and increased the number of lipid droplets, whereas CUR-PDT treatment significantly reduced the ox-LDL-induced increase in the migration ability of, and lipid droplet numbers in, VSMCs. When the VSMCs were pretreated with the autophagy inhibitor 3-methyladenine for 24 hours, the effects of CUR-PDT were reversed. Therefore, our study indicated that CUR-PDT can inhibit the phenotypic transformation, migration, and foaming of ox-LDL–treated VSMCs by inducing autophagy.

An update in clinical utilization of photodynamic therapy for lung cancer

Lung cancer is one of the leading causes of cancer-related death worldwide, with nearly 1.8 million-diagnosis and 1.59 million deaths. Surgery, radiotherapy, and chemotherapy in individual or combination are commonly used to treat lung cancers. Photodynamic therapy (PDT) is a highly selective method for the destruction of cancer cells by exerting cytotoxic activity on malignant cells. PDT has been the subject of numerous clinical studies and has proven to be an effective strategy for cancer therapy. Clinical studies revealed that PDT could prolong survival in patients with inoperable cancers and significantly improve quality of life. For inoperable lung cancer cases, PDT could be an effective therapy. Despite the clinical success reported, PDT is still currently underutilized to treat lung cancer and other tumors. PTD is still a new treatment approach for lung cancer mainly due to the lack of enough clinical research evaluating its' effectiveness and side effects. In this review, we discuss the current prospects and future potentials of PDT in lung cancer treatment.

In Vitro Photodynamic Effects of the Inclusion Nanocomplexes of Glucan and Chlorin e6 on Atherogenic Foam Cells

Macrophage-derived foam cells play critical roles in the initiation and progression of atherosclerosis. Activated macrophages and foam cells are important biomarkers for targeted imaging and inflammatory disease therapy. Macrophages also express the dectin-1 receptor, which specifically recognizes β-glucan (Glu). Here, we prepared photoactivatable nanoagents (termed Glu/Ce6 nanocomplexes) by encapsulating hydrophobic chlorin e6 (Ce6) within the triple-helix structure of Glu in aqueous condition. Glu/Ce6 nanocomplexes generate singlet oxygen upon laser irradiation. The Glu/Ce6 nanocomplexes were internalized into foam cells and delivered Ce6 molecules into the cytoplasm of foam cells. Upon laser irradiation, they induced significant membrane damage and apoptosis of foam cells. These results suggest that Glu/Ce6 nanocomplexes can be a photoactivatable material for treating atherogenic foam cells.

Smart Dual-Functionalized Gold Nanoclusters for Spatio-Temporally Controlled Delivery of Combined Chemo- and Photodynamic Therapy

We report the preparation of gold nanoclusters (AuNCs) as a delivery vehicle for the clinically approved photodynamic and chemotherapeutic agents Protoporphyrin IX (PpIX) and doxorubicin (DOX), respectively, and their effect on tumor cells. DOX was attached to the gold nanoclusters through a singlet oxygen-cleavable linker and was therefore released after PpIX irradiation with red light, contributing, synergistically with singlet oxygen, to induce cell death. The doubly functionalized AuNCs proved more effective than a combination of individually functionalized AuNCs. Unlike free DOX, the photoactive nanosystem was non-toxic in the absence of light, which paves the way to introduce a spatiotemporal control of the anticancer therapy and could contribute to reducing the undesirable side effects of DOX.

Clinical Trials and Basic Research in Photodynamic Diagnostics and Therapies from the Center for Laser Diagnostics and Therapy in Poland

The purpose of this review is to present an overview of the development of photodiagnostic and photodynamic therapy (PDD and PDT) techniques in Poland. The paper discusses the principles of PDD, including fluorescent techniques in determining precancerous conditions and cancers of the skin, digestive tract, bladder and respiratory tract. Methods of PDT of cancer will be discussed and the current state of knowledge as well as future trends in the development of photodynamic techniques will be presented, including the possibility of using photodynamic antimicrobial therapy. Research pioneers in photodynamic medicine such as Thomas Dougherty are an inspiration for the development of methods of PDD and PDT in our Clinic. The Center for Laser Diagnostics and Therapy in Bytom, Poland, promotes the propagation of PDD and PDT through the training of clinicians and raising awareness among students in training and the general public. Physicians at the Center are engaged in photomedical research aimed at clinical implementation and exploration of new avenues in photomedicine while optimizing existing modalities. The Center promotes dissemination of clinical results from a wide range of topics in PDD and PDT and serving as representative authorities of photodynamic medicine in Poland and Europe.

Rapid inhibition of atherosclerotic plaque progression by sonodynamic therapy

Aims

Currently, efficient regimens to reverse atherosclerotic plaques are not available in the clinic. Herein, we present sonodynamic therapy (SDT) as a novel methodology to rapidly inhibit progression of atherosclerotic plaques.

Methods and results

In atherosclerotic rabbit and apoE-deficient mouse models, SDT efficiently decreased the atherosclerotic burden within 1 week, revealing a decrease in the size of the atherosclerotic plaque and enlarged lumen. The shrunken atherosclerotic plaques displayed compositional alterations, with a reduction in lesional macrophages and lipids. The rapid efficacy of SDT may be due to its induction of macrophage apoptosis, enhancement of efferocytosis, and amelioration of inflammation in the atherosclerotic plaque. Compared with atorvastatin, the standard of care for atherosclerosis, SDT showed more significant plaque shrinkage and lumen enlargement during 1 week treatment. Furthermore, SDT displayed good safety without obvious side effects. In a pilot clinical trial recruiting the patients suffering atherosclerotic peripheral artery disease, combination therapy of SDT with atorvastatin efficiently reduced progression of atherosclerotic plaque within 4 weeks, and its efficacy was able to last for at least 40 weeks.

Conclusion

SDT is a non-invasive and efficacious regimen to inhibit atherosclerotic plaque progression.

Pyropheophorbide-α methyl ester-mediated photodynamic therapy induces apoptosis and inhibits LPS-induced inflammation in RAW264.7 macrophages

BACKGROUND

This study aimed to determine the effect of pyropheophorbide-α methyl ester (MPPa)-mediated photodynamic therapy (MPPa-PDT) on the apoptosis and inflammation of murine macrophage RAW264.7 cells.

METHODS

Uptake and subcellular localization of MPPa was detected by flow cytometry and confocal fluorescence microscope. Cell viability was assessed by CCK-8; ROS levels were assessed by DCFH-DA. Cell apoptosis was measured by flow cytometry and Hoechst 33342 staining, whereas mitochondrial membrane potential was detected by JC-1 staining. Secretion of tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) was determined using ELISA kits. Caspase-3, cleaved caspase-3, procaspase-9, cleaved caspase-9, PARP, cleaved PARP, Bcl-2, Bax, NF-κB p-p65, p-IKKα/β, and p-IκBα were measured by western blotting. Nuclear factor κB (NF-κB)-p65 nuclear translocation was observed by immunofluorescence.

RESULTS

MPPa -PDT influenced cell viability in a light dose-dependent manner. It induced ROS formation and RAW264.7 cell apoptosis. It also increased the expression of cleaved caspase-3, cleaved caspase-9, cleaved PARP and Bax, decreased the expression of Bcl-2. While TNF-α, IL-1β, and IL-6 increased in LPS group (model of inflammation), it deceased in LPS-MPPa-PDT group. NF-κB p-p65, p-IKKα/β, and p-IκBα had higher expression in LPS group while that reduced in LPS-MPPa-PDT group. Simultaneously, MPPa-PDT inhibited nuclear translocation of NF-κB-p65 caused by LPS.

CONCLUSIONS

MPPa-PDT can induce apoptosis and attenuate inflammation in mouse RAW264.7 macrophages, thereby suggesting a promising therapy for atherosclerosis.

Exogenous imaging contrast and therapeutic agents for intravascular photoacoustic imaging and image-guided therapy

Intravascular photoacoustic (IVPA) imaging has been developed in recent years as a viable imaging modality for the assessment of atherosclerotic plaques. Exogenous imaging contrast and therapeutic agents further enhance this imaging modality and provide significant benefits. Imaging contrast agents can significantly increase photoacoustic signal, resulting in enhanced plaque detection and characterization. The ability to use these particles to molecularly target markers of disease progression makes it possible to determine patient-specific levels of risk and plan treatments accordingly. With improved diagnosis, clinicians will be able to use therapeutic agents that are synergistic with IVPA imaging to treat atherosclerotic patients. Pre-clinical and clinical studies with relevance to IVPA imaging have shown promise in the area of diagnosis and therapeutics. In this review, we present a variety of imaging contrast agents that are either designed for or are compatible with IVPA imaging, cover uses of therapeutic agents that compliment this imaging modality, and discuss future directions of research in the field.

Sonodynamic therapy: A potential treatment for atherosclerosis

Atherosclerosis (AS), a chronic arterial disease, is one of the major causes of morbidity and mortality worldwide. Several treatment modalities have been demonstrated to be effective in treating AS; however, the mortality rate due to AS remains high. Sonodynamic therapy (SDT) is a promising new treatment using low-intensity ultrasound in combination with sonosensitizers. Although SDT was developed from photodynamic therapy (PDT), it has a stronger tissue-penetrating capability and exhibits a more focused effect on the target lesional site requiring treatment. Furthermore, SDT has been demonstrated to suppress the formation of atheromatous plaques, and it can increase plaque stability both in vitro and in vivo. In this article, we critically summarize the recent literature on SDT, focusing on its possible mechanism of action as well as the existing and newly discovered sonosensitizers and chemotherapeutic agents for the treatment of AS.

Progression and Characterization of the Accelerated Atherosclerosis in Iliac Artery of New Zealand White Rabbits: Effect of Simvastatin

OBJECTIVE

Although atherosclerosis is described in New Zealand White rabbit's iliac artery, yet details of time-dependent atherosclerosis progression are not well known. Further, a well characterized accelerated model of atherosclerosis is also required for the screening of candidate drugs to target specific steps of atherosclerosis development. The present study extensively characterizes the time-dependent plaque composition and functional responses of the atherosclerosis in rabbit iliac artery and its modification by simvastatin.

METHODS

Atherosclerosis was induced with a combination of balloon injury and atherogenic diet (AD) (1% cholesterol, 6% peanut oil) in rabbit's iliac artery. Atherosclerosis progression was evaluated on days 8, 10, 15, 21, 35, and 56 after AD feeding. The plaque characterization was done using histology, real-time reverse transcription-polymerase chain reaction, and vasoreactivity experiments. The standard anti-hyperlipidemic drug, simvastatin (5 mg·kg·d), was used to investigate its effect on atherosclerotic changes.

RESULTS

Plasma lipids were elevated in a progressive manner after AD feeding from days 8 to 56. Similarly, arterial lipids, Monocyte Chemoattractant Protein-1 (MCP-1) level along with infiltration of macrophages in the lesion area were also increased from day 15 onward. This resulted in a significant increase in the plaque area and intimal-medial thickness ratio in contrast to normal animals. Inflammatory milieu was observed with a significant increase in expression of pro-inflammatory regulators like MCP-1, Tumor Necrosis Factor-α (TNF-α) and Vascular Cell Adhesion Molecule-1 (VCAM-1), whereas anti-inflammatory cytokine interleukin 10 decreased as disease progressed. Endothelial dysfunction was also observed, specifically Acetylcholine (ACh)-induced vasorelaxation was reduced from day 8 onward, whereas the phenylephrine-induced vasoconstriction response was progressively reduced from day 15 in the iliac artery. Ground substances including proteoglycans, α-actin, and collagen content along with metalloproteinase-9 and Tissue inhibitor of metalloproteinases-1 (TIMP-1) inhibitors were significantly augmented at later time points, day 21 onward. Simvastatin treatment for 35 days, at a dose having no significant effect on plasma lipid levels, significantly reduced atherosclerotic progression as evident by reduced macrophage content, inflammatory burden, and extracellular matrix component like proteoglycans and metalloproteinase-9.

CONCLUSIONS

The authors observed that AD feeding with balloon injury in the rabbit iliac artery accelerated the progression of atherosclerosis and exhibited predominant features of type III human lesion within 8 weeks (56 days). Simvastatin treatment for 35 days exhibited anti-atherosclerotic efficacy without significantly lowering the circulating lipids. The current study thus provides an insight into the time-dependent atherosclerotic progression in rabbit iliac artery and highlights its utility for anti-atherosclerotic evaluation of the candidate drugs.

Using X-rays in photodynamic therapy: an overview

Photodynamic therapy is a therapeutic option to treat cancer and other diseases.

The Rabbit Model of Accelerated Atherosclerosis: A Methodological Perspective of the Iliac Artery Balloon Injury

Acute coronary syndrome resulting from coronary occlusion following atherosclerotic plaque development and rupture is the leading cause of death in the industrialized world. New Zealand White (NZW) rabbits are widely used as an animal model for the study of atherosclerosis. They develop spontaneous lesions when fed with atherogenic diet; however, this requires long time of 4 - 8 months. To further enhance and accelerate atherogenesis, a combination of atherogenic diet and mechanical endothelial injury is often employed. The presented procedure for inducing atherosclerotic plaques in rabbits uses a balloon catheter to disrupt the endothelium in the left iliac artery of NZW rabbits fed with atherogenic diet. Such mechanical damage caused by the balloon catheter induces a chain of inflammatory reactions initiating neointimal lipid accumulation in a time dependent fashion. Atherosclerotic plaque following balloon injury show neointimal thickening with extensive lipid infiltration, high smooth muscle cell content and presence of macrophage derived foam cells. This technique is simple, reproducible and produces plaque of controlled length within the iliac artery. The whole procedure is completed within 20 - 30 min. The procedure is safe with low mortality and also offers high success in obtaining substantial intimal lesions. The procedure of balloon catheter induced arterial injury results in atherosclerosis within two weeks. This model can be used for investigating the disease pathology, diagnostic imaging and to evaluate new therapeutic strategies.

Porphyrin photosensitizers in photodynamic therapy and its applications

In 1841, the extraction of hematoporphyrin from dried blood by removing iron marked the birth of the photosensitizer. The last twenty years has witnessed extensive research in the application of photodynamic therapy (PDT) in tumor-bearing (or other diseases) animal models and patients. The period has seen development of photosensitizers from the first to the third generation, and their evolution from simple to more complex entities. This review focuses on porphyrin photosensitizers and their effect on tumors, mediated via several pathways involved in cell necrosis, apoptosis or autophagic cell death, and the preventive and therapeutic application of PDT against atherosclerosis.

Photodynamic therapy for the treatment of atherosclerotic plaque: Lost in translation?

Acute coronary syndrome is a life-threatening condition of utmost clinical importance, which, despite recent progress in the field, is still associated with high morbidity and mortality. Acute coronary syndrome results from a rupture or erosion of vulnerable atherosclerotic plaque with secondary platelet activation and thrombus formation, which leads to partial or complete luminal obstruction of a coronary artery. During the last decade, scientific evidence demonstrated that when an acute coronary event occurs, several nonculprit plaques are in a "vulnerable" state. Among the promising approaches, several investigations provided evidence of photodynamic therapy (PDT)-induced stabilization and regression of atherosclerotic plaque. Significant development of PDT strategies improved its therapeutic outcome. This review addresses PDT's pertinence and major problems/challenges toward its translation to a clinical reality.

Cysteine proteases in atherosclerosis

Atherosclerosis predisposes patients to cardiovascular diseases, such as myocardial infarction and stroke. Instigation of vascular injury is triggered by retention of lipids and inflammatory cells in the vascular endothelium. Whereas these vascular lesions develop in young adults and are mostly considered harmless, over time persistent inflammatory and remodeling processes will ultimately damage the arterial wall and cause a thrombotic event due to exposure of tissue factors into the lumen. Evidence from human tissues and preclinical animal models has clearly established the role of cathepsin cysteine proteases in the development and progression of vascular lesions. Hence, understanding the function of cathepsins in atherosclerosis is important for developing novel therapeutic strategies and advanced point of care diagnostics. In this review we will describe the roles of cysteine cathepsins in different cellular process that become dysfunctional in atherosclerosis, such as lipid metabolism, inflammation and apoptosis, and how they contribute to arterial remodeling and atherogenesis. Finally, we will explore new horizons in protease molecular imaging, which may potentially become a surrogate marker to identify future cardiovascular events.

Plaque Rupture and Thrombosis: the Value of the Atherosclerotic Rabbit Model in Defining the Mechanism

Persistent inflammation and mechanical injury associated with cholesterol crystal accretion within atherosclerotic plaques typically precedes plaque disruption (rupture and/or erosion) and thrombosis--often the terminal events of atherosclerotic cardiovascular disease. To elucidate the mechanisms of these events, the atherosclerotic rabbit model provides a unique and powerful tool that facilitates studies of atherogenesis starting with plaque buildup to eventual disruption. Examination of human coronary arteries obtained from patients who died with myocardial infarction demonstrates evidence of cholesterol crystals perforating the plaque cap and intimal surface of the arterial wall that can lead to rupture. These observations were made possible by omitting ethanol, an avid lipid solvent, from the tissue processing steps. Importantly, the atherosclerotic rabbit model exhibits a similar pathology of cholesterol crystals perforating the intimal surface as seen in ruptured human plaques. Local and systemic inflammatory responses in the model are also similar to those observed in humans. The strong parallel between the rabbit and human pathology validates the atherosclerotic rabbit model as a predictor of human pathophysiology of atherosclerosis. Thus, the atherosclerotic rabbit model can be used with confidence to evaluate diagnostic imaging and efficacy of novel anti-atherosclerotic therapy.

Intra-Arterial Drug and Light Delivery for Photodynamic Therapy Using Visudyne®: Implication for Atherosclerotic Plaque Treatment

Photodynamic therapy (PDT), which is based on the activation of photosensitizers with light, can be used to reduce plaque burden. We hypothesized that intra-arterial photosensitizer administration and photo-activation will lead to high and rapid accumulation within the plaque with reduced systemic adverse effects. Thus, this "intra-arterial" PDT would be expected to have less side effects and due to the short time involved would be compatible with percutaneous coronary interventions.

AIM

We characterized the dose-dependent uptake and efficacy of intra-arterial PDT using Liposomal Verteporfin (Visudyne®), efficient for cancer-PDT but not tested before for PDT of atherosclerosis.

METHODS AND RESULTS

Visudyne® (100, 200, and 500 ng/ml) was perfused for 5-30 min in atherosclerotic aorta isolated from ApoE(-/-) mice. The fluorescence Intensity (FI) after 15 min of Visudyne® perfusion increased with doses of 100 (FI-5.5 ± 1.8), 200 (FI-31.9 ± 1.9) or 500 ng/ml (FI-42.9 ± 1.2). Visudyne® (500 ng/ml) uptake also increased with the administration time from 5 min (FI-9.8 ± 2.5) to 10 min (FI-23.3 ± 3.0) and 15 min (FI-42.9 ± 3.4) before reaching saturation at 30 min (FI-39.3 ± 2.4) contact. Intra-arterial PDT (Fluence: 100 and 200 J/cm(2), irradiance-334 mW/cm(2)) was applied immediately after Visudyne® perfusion (500 ng/ml for 15 min) using a cylindrical light diffuser coupled to a diode laser (690 nm). PDT led to an increase of ROS (Dihydroethidium; FI-6.9 ± 1.8, 25.3 ± 5.5, 43.4 ± 13.9) and apoptotic cells (TUNEL; 2.5 ± 1.6, 41.3 ± 15.3, 58.9 ± 6%), mainly plaque macrophages (immunostaining; 0.3 ± 0.2, 37.6 ± 6.4, 45.3 ± 5.4%) respectively without laser irradiation, or at 100 and 200 J/cm(2). Limited apoptosis was observed in the medial wall (0.5 ± 0.2, 8.5 ± 4.7, 15.3 ± 12.7%). Finally, Visudyne®-PDT was found to be associated with reduced vessel functionality (Myogram).

CONCLUSION

We demonstrated that sufficient accumulation of Visudyne® within plaque could be achieved in short-time and therefore validated the feasibility of local intravascular administration of photosensitizer. Intra-arterial Visudyne®-PDT preferentially affected plaque macrophages and may therefore alter the dynamic progression of plaque development.

Animal models for photodynamic therapy (PDT)

Photodynamic therapy (PDT) combines visible light and photosensitizing dyes. Different animal models have been used to test PDT for cancer, infectious disease and cardiovascular disease. Mouse models of tumours include subcutaneous, orthotopic, syngeneic, xenograft, autochthonous and genetically modified.

Photodynamic therapy (PDT) employs non-toxic dyes called photosensitizers (PSs), which absorb visible light to give the excited singlet state, followed by the long-lived triplet state that can undergo photochemistry. In the presence of ambient oxygen, reactive oxygen species (ROS), such as singlet oxygen and hydroxyl radicals are formed that are able to kill cancer cells, inactivate microbial pathogens and destroy unwanted tissue. Although there are already several clinically approved PSs for various disease indications, many studies around the world are using animal models to investigate the further utility of PDT. The present review will cover the main groups of animal models that have been described in the literature. Cancer comprises the single biggest group of models including syngeneic mouse/rat tumours that can either be subcutaneous or orthotopic and allow the study of anti-tumour immune response; human tumours that need to be implanted in immunosuppressed hosts; carcinogen-induced tumours; and mice that have been genetically engineered to develop cancer (often by pathways similar to those in patients). Infections are the second biggest class of animal models and the anatomical sites include wounds, burns, oral cavity, ears, eyes, nose etc. Responsible pathogens can include Gram-positive and Gram-negative bacteria, fungi, viruses and parasites. A smaller and diverse group of miscellaneous animal models have been reported that allow PDT to be tested in ophthalmology, atherosclerosis, atrial fibrillation, dermatology and wound healing. Successful studies using animal models of PDT are blazing the trail for tomorrow's clinical approvals.

Rapid stabilisation of atherosclerotic plaque with 5-aminolevulinic acid-mediated sonodynamic therapy

5-Aminolevulinic acid-mediated sonodynamic therapy (ALA-SDT) effectively induces the apoptosis of atherogenic macrophages, but whether it can stabilise atherosclerotic plaque in vivo is unclear. Here, we used an animal model to evaluate the effects of ALA-SDT on plaque stabilisation. Sixty rabbits were induced atherosclerotic plaques in the femoral artery with a combination of silastic tube placement with atherogenic diet, and randomly assigned into control (n = 12) and SDT (n = 48) groups. In the SDT group, after intravenous injected with ALA (60 mg/kg) animals underwent the treatment of ultrasound with intensities of 0.75, 1.00, 1.50 and 2.00 W/cm(²) (n = 12 for each intensity). Seven days after the treatment, the plaque disruption assay was performed to test plaque stability. We found that ALA-SDT with ultrasound intensity of 1.5 W/cm(²) showed the strongest efficacy to stabilise plaques. Under this condition, the frequency of plaque disruption decreased by 88% (p<0.01), positive area of macrophages reduced by 94% (p<0.001) and percentage content of lipids dropped by 60% (p < 0.001), while percentage content of collagens increased by 127% (p<0.001). We also found that the plaque stabilisation by ALA-SDT was associated with increased macrophage apoptosis and apoptotic cell clearance. Moreover, ALA-SDT decreased the contents and activities of matrix metalloproteinase-2,9 and increased the levels of tissue inhibitors of matrix metalloproteinase-1,2 in plaques. Our studies demonstrate that ALA-SDT promotes plaque stabilisation by inducing macrophage elimination and inhibiting matrix degradation. This method might be a promising regimen for atherosclerosis therapy.

Upconversion nanoparticle-mediated photodynamic therapy induces THP-1 macrophage apoptosis via ROS bursts and activation of the mitochondrial caspase pathway

Atherosclerosis (AS) is the most vital cardiovascular disease, which poses a great threat to human health. Macrophages play an important role in the progression of AS. Photodynamic therapy (PDT) has emerged as a useful therapeutic modality not only in the treatment of cancer but also in the treatment of AS. The purpose of this study was to determine the molecular mechanisms underlying the activity of PDT, using mesoporous-silica-coated upconversion fluorescent nanoparticles encapsulating chlorin e6 (UCNPs-Ce6) in the induction of apoptosis in THP-1 macrophages. Here, we investigated the ability of UCNPs-Ce6-mediated PDT to induce THP-1 macrophage apoptosis by facilitating the induction of reactive oxygen species (ROS) and regulation of mitochondrial permeability transition pore (MPTP) to depolarize mitochondrial membrane potential (MMP). Both Bax translocation and the release of cytochrome C were examined using immunofluorescence and Western blotting. Our results indicated that the levels of ROS were significantly increased in the PDT group, resulting in both MPTP opening and MMP depolarization, which led to apoptosis. In addition, immunofluorescence and Western blotting revealed that PDT induced both Bax translocation and the release of cytochrome C, as well as upregulation of cleaved caspase-9, cleaved caspase-3, and cleaved poly(ADP-ribose) polymerase. Therefore, we demonstrated that UCNPs-Ce6-mediated PDT induces apoptosis in THP-1 macrophages via ROS bursts. The proapoptotic factor Bax subsequently translocates from the cytosol to the mitochondria, resulting in the MPTP opening and cytochrome C release. This study demonstrated the great potential of UCNPs-Ce6-mediated PDT in the treatment of AS.

The efficacy and mechanism of apoptosis induction by hypericin-mediated sonodynamic therapy in THP-1 macrophages

Purpose

To investigate the sonoactivity of hypericin (HY), together with its sonodynamic effect on THP-1 macrophages and the underlying mechanism.

Materials and methods

CCK-8 was used to examine cell viability. Confocal laser scanning microscopy was performed to assess the localization of HY in cells, reactive oxygen species (ROS) generation, and opening of the mitochondrial permeability transition pore (mPTP) after different treatments. Apoptosis was analyzed using Hoechst–propidium iodide and transmission electron microscopy. Mitochondrial membrane potential (ΔΨm) collapse was detected via fluorescence microscopy. Lipoprotein oxidation was determined in malondialdehyde (MDA) assays. Western blotting was conducted to determine the translocation of BAX and cytochrome C and the expression of apoptosis-related proteins.

Results

HY was sublocalized among the nuclei and the mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosome in the cytosol of THP-1 macrophages. Under low-intensity ultrasound irradiation, HY significantly decreased cell viability and induced apoptosis. Furthermore, greater ROS generation, higher MDA levels, and greater ΔΨm loss were observed in the sonodynamic therapy (SDT) group. Both ROS generation and MDA levels were significantly reduced by the ROS scavenger N-acetyl cysteine (NAC) and the singlet oxygen scavenger sodium azide. Most of the loss of ΔΨm was inhibited by pretreatment with NAC, sodium azide, and the mPTP inhibitor cyclosporin A (CsA). mPTP opening was induced upon SDT but was reduced by pretreatment with bongkrekic acid, 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid disodium, CsA, and NAC. Western blot analyses revealed translocation of BAX and cytochrome C, downregulated expression of Bcl-2, and upregulated expression of cleaved caspase-9, cleaved caspase-3, and cleaved poly(ADP-ribose) polymerase in the SDT group, which were reversed by NAC.

Conclusion

HY mediated SDT-induced apoptosis in THP-1 macrophages via ROS generation. Then, the proapoptotic factor BAX translocated from the cytosol to the mitochondria, increasing the ratio of BAX/Bcl-2, and the mPTP opened to release cytochrome C. This study demonstrated the great potential of HY-mediated SDT for treating atherosclerosis.

Aminolevulinic acid with gold nanoparticles: a novel theranostic agent for atherosclerosis

5-Aminolevulinic acid gold nanoparticles functionalized with polyethylene glycol were synthesized and administered to rabbits to evaluate their use in clinical practice as theranostic agents for atherosclerosis.

Photodynamic therapy: current status and future directions

Photodynamic therapy (PDT) is a minimally invasive therapeutic modality used for the management of a variety of cancers and benign diseases. The destruction of unwanted cells and tissues in PDT is achieved by the use of visible or near-infrared radiation to activate a light-absorbing compound (a photosensitizer, PS), which, in the presence of molecular oxygen, leads to the production of singlet oxygen and other reactive oxygen species. These cytotoxic species damage and kill target cells. The development of new PSs with properties optimized for PDT applications is crucial for the improvement of the therapeutic outcome. This review outlines the principles of PDT and discusses the relationship between the structure and physicochemical properties of a PS, its cellular uptake and subcellular localization, and its effect on PDT outcome and efficacy.

Regulated necrosis in HeLa cells induced by ZnPc photodynamic treatment: a new nuclear morphology

Photodynamic therapy (PDT) is a cancer treatment modality based on the administration of a photosensitizer (PS), which accumulates preferentially in tumor cells. Subsequent irradiation of the neoplastic area triggers a cascade of photochemical reactions that leads to the formation of highly reactive oxygen species responsible for cell inactivation. Photodynamic treatments in vitro are performed with the PS, zinc-phthalocyanine (ZnPc). The PS is near the plasma membrane during uptake and internalization. Inactivation clearly occurs by a necrotic process, manifested by nuclear pyknosis, negative TUNEL and Annexin V assays and non-relocation of cytochrome c. In contrast, by increasing the incubation time, ZnPc is accumulated in the Golgi apparatus and produces cell inactivation with characteristics of apoptosis and necrosis: TUNEL positive, relocated cytochrome c and negative Annexin V assay. This type of death produces a still undescribed granulated nuclear morphology, which is different from that of necrosis or apoptosis. This morphology is inhibited by necrostatin-1, a specific inhibitor of regulated necrosis.

Ultrasonography of lower limb vascular angiopathy and plaque formation in type 2 diabetes patients and finding its relevance to the carotid atherosclerotic formation

Objective: One of the major complications of diabetes is blood vessel disease, termed angiopathy, which is characterized by abnormal angiogenesis. The objective of this study was to discuss the characteristics of lower limb vascular angiopathy and plaque formation in type 2 diabetes patients and finding its relevance to the carotid atherosclerotic plaque formation, thus directing the clinical diagnosis and treatment.

Methods: The ultrasonography was used to monitor the patients with carotid artery and lower limb artery.

Results: Compared with the control group, decreased blood flow to lower limb and lower limb angiopathy occurred more obviously in dorsal artery of foot than in popliteal artery. The study revealed that the detection rate of the prevalence of carotid atherosclerosis plaque and lower limb arterial plaque and the combination of plaque both carotid and lower limb arteries in diabetic patients was 369:342:296 (about 1.25:1.15:1) and that the prevalence of carotid plaque and lower limb arterial plaque in all subjects with plaque was 71.3%. The risk of plaque formation also had positive correlation with patient’s age. Color Doppler ultrasound had a clinical significance in the early diagnosis and curative effect observation in type 2 diabetes with lower limb angiopathy. The risk of simultaneous plaque formation in both carotid artery and lower extremity artery was greater in type 2 diabetes than that of control subjects, but they were not necessarily to occur simultaneously. The symptoms were inconspicuous in the early course of diabetes.

Conclusion: The application of ultrasound monitoring in patients with carotid artery and lower limb artery might play a role in early warning, delaying the occurrence of macrovascular diseases, and slowing down the development of macroangiopathy such as cerebral infarction and diabetic foot and so on, thus providing a significant basis for clinical diagnosis and treatment.

Intravascular photoacoustics for image-guidance and temperature monitoring during plasmonic photothermal therapy of atherosclerotic plaques: a feasibility study

Recently, combined intravascular ultrasound and photoacoustic (IVUS/IVPA) imaging has been demonstrated as a novel imaging modality capable of visualizing both morphology (via IVUS) and cellular/molecular composition (via IVPA) of atherosclerotic plaques, using both endogenous tissue absorbers and exogenous contrast agents. Plasmonic gold nanoparticles were previously utilized as IVPA contrast agents which co-localize with atherosclerotic plaques, particularly phagocytically active macrophages. The present work demonstrates the use of IVUS/IVPA imaging as a tool for localized temperature monitoring during laser heating. The temperature dependent change in IVPA signal intensity of silica-coated gold nanorod contrast agents absorbing within the near-infrared optical wavelength range is evaluated and shown to have a linear relationship, with a slope greater than that of endogenous tissue. A continuous wave laser was subsequently incorporated into the IVUS/IVPA integrated catheter and utilized to selectively heat the nanoparticles with simultaneous IVPA temperature monitoring. IVUS/IVPA, therefore, provides a platform for detection and temperature monitoring of atherosclerotic plaques through the selective heating of plasmonic gold nanoparticle contrast agents.

ROS-responsive activatable photosensitizing agent for imaging and photodynamic therapy of activated macrophages

The optical properties of macrophage-targeted theranostic nanoparticles (MacTNP) prepared from a Chlorin e6 (Ce6)-hyaluronic acid (HA) conjugate can be activated by reactive oxygen species (ROS) in macrophage cells. MacTNP are nonfluorescent and nonphototoxic in their native state. However, when treated with ROS, especially peroxynitrite, they become highly fluorescent and phototoxic. In vitro cell studies show that MacTNP emit near-infrared (NIR) fluorescence inside activated macrophages. The NIR fluorescence is quenched in the extracellular environment. MacTNP are nontoxic in macrophages up to a Ce6 concentration of 10 μM in the absence of light. However, MacTNP become phototoxic upon illumination in a light dose-dependent manner. In particular, significantly higher phototoxic effect is observed in the activated macrophage cells compared to human dermal fibroblasts and non-activated macrophages. The ROS-responsive MacTNP, with their high target-to-background ratio, may have a significant potential in selective NIR fluorescence imaging and in subsequent photodynamic therapy of atherosclerosis with minimum side effects.

Effect of molecular characteristics on cellular uptake, subcellular localization, and phototoxicity of Zn(II) N-alkylpyridylporphyrins

Tetra-cationic Zn(II) meso-tetrakis(N-alkylpyridinium-2 (or -3 or -4)-yl)porphyrins (ZnPs) with progressively increased lipophilicity were synthesized to investigate how the tri-dimensional shape and lipophilicity of the photosensitizer (PS) affect cellular uptake, subcellular distribution, and photodynamic efficacy. The effect of the tri-dimensional shape of the molecule was studied by shifting the N-alkyl substituent attached to the pyridyl nitrogen from ortho to meta and para positions. Progressive increase of lipophilicity from shorter hydrophilic (methyl) to longer amphiphilic (hexyl) alkyl chains increased the phototoxicity of the ZnP PSs. PS efficacy was also increased for all derivatives when the alkyl substituents were shifted from ortho to meta, and from meta to para positions. Both cellular uptake and subcellular distribution of the PSs were affected by the lipophilicity and the position of the alkyl chains on the periphery of the porphyrin ring. Whereas the hydrophilic ZnPs demonstrated mostly lysosomal distribution, the amphiphilic hexyl derivatives were associated with mitochondria, endoplasmic reticulum, and plasma membrane. A comparison of hexyl isomers revealed that cellular uptake and partition into membranes followed the order para > meta > ortho. Varying the position and length of the alkyl substituents affects (i) the exposure of cationic charges for electrostatic interactions with anionic biomolecules and (ii) the lipophilicity of the molecule. The charge, lipophilicity, and the tri-dimensional shape of the PS are the major factors that determine cellular uptake, subcellular distribution, and as a consequence, the phototoxicity of the PSs.

Modifications of microvascular EC surface modulate phototoxicity of a porphycene anti-ICAM-1 immunoconjugate; therapeutic implications

Inflammation and shear stress can upregulate expression of cellular adhesion molecules in endothelial cells (EC). The modified EC surface becomes a mediating interface between the circulating blood elements and the endothelium, and grants opportunity for immunotherapy. In photodynamic therapy (PDT), immunotargeting might overcome the lack of selectivity of currently used sensitizers. In this study, we hypothesized that differential ICAM-1 expression modulates the effects of a drug targeted to surface ICAM-1. A novel porphycene-anti-ICAM-1 conjugate was synthesized and applied to treat endothelial cells from macro and microvasculature. Results show that the conjugate induces phototoxicity in inflamed, but not in healthy, microvascular EC. Conversely, macrovascular EC exhibited phototoxicity regardless of their state. These findings have two major implications; the relevance of ICAM-1 as a modulator of drug effects in microvasculature, and the potential of the porphycene bioconjugate as a promising novel PDT agent.

Photodynamic Therapy Using a Protease-Mediated Theranostic Agent Reduces Cathepsin-B Activity in Mouse Atheromata In Vivo

Objective—

To investigate whether an intravenously injected cathepsin-B activatable theranostic agent (L-SR15) would be cleaved in and release a fluorescent agent (chlorin-e6) in mouse atheromata, allowing both the diagnostic visualization and therapeutic application of these fluorophores as photosensitizers during photodynamic therapy to attenuate plaque-destabilizing cathepsin-B activity by selectively eliminating macrophages.

Approach and Results—

Thirty-week-old apolipoprotein E knock-out mice (n=15) received intravenous injection of L-SR15 theranostic agent, control agent D-SR16, or saline 3× (D0, D7, D14). Twenty-four hours after each injection, the bilateral carotid arteries were exposed, and Cy5.5 near-infrared fluorescent imaging was performed. Fluorescent signal progressively accumulated in the atheromata of the L-SR15 group animals only, indicating that photosensitizers had been released from the theranostic agent and were accumulating in the plaque. After each imaging session, photodynamic therapy was applied with a continuous-wave diode-laser. Additional near-infrared fluorescent imaging at a longer wavelength (Cy7) with a cathepsin-B–sensing activatable molecular imaging agent showed attenuation of cathepsin-B–related signal in the L-SR15 group. Histological studies demonstrated that L-SR15–based photodynamic therapy decreased macrophage infiltration by inducing apoptosis without significantly affecting plaque size or smooth muscle cell numbers. Toxicity studies (n=24) showed that marked erythematous skin lesion was generated in C57/BL6 mice at 24 hours after intravenous injection of free chlorin-e6 and ultraviolet light irradiation; however, L-SR15 or saline did not cause cutaneous phototoxicity beyond that expected of ultraviolet irradiation alone, neither did we observe systemic toxicity or neurobehavioral changes.

Conclusions—

This is the first study showing that macrophage-secreted cathepsin-B activity in atheromata could be attenuated by photodynamic therapy using a protease-mediated theranostic agent.

Effects of 5-aminolevulinic acid-mediated sonodynamic therapy on macrophages

BACKGROUND

Inflammatory cells exhibit an elevated level of protoporphyrin IX (PpIX) after the administration of 5-aminolevulinic acid (ALA). Here, we investigate the sonodynamic effects of ALA-derived PpIX (ALA-PpIX) on macrophages, which are the pivotal inflammatory cells in atherosclerosis.

METHODS AND RESULTS

Cultured THP-1 macrophages were incubated with ALA. Fluorescence microscope and fluorescence spectrometer detection showed that intracellular PpIX increased with the concentration of ALA in the incubation solution in a time dependent manner; the highest level of intracellular PpIX was observed after 3-hour incubation. 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assays demonstrated that lower concentrations (less than 2 mM) of ALA have no influence on cell viability (more than 90% of cells survived), but sonodynamic therapy (SDT) with a low concentration of ALA significantly decreased the survival rate of cells, and the effect was increased with both ALA concentration and ultrasound exposure time. Cell apoptosis and necrosis induced by ALA-mediated SDT (ALA-SDT) were measured using Hoechst 33258 and propidium iodide assay. ALA-SDT induced both cell apoptosis and necrosis, and the maximum apoptosis/necrosis ratio was observed at 6 hours after SDT with 1 mM of ALA and 5 minutes of ultrasound exposure. Flow cytometry analysis showed that ALA-SDT significantly increased late stage apoptotic cells (about 10-fold control). Furthermore, ALA-SDT induced reactive oxygen species generation in THP-1 macrophages immediately after the treatment and a conspicuous loss of mitochondrial membrane potential (MMP) at 6 hours compared with that of the control, ALA alone, and ultrasound alone groups.

CONCLUSION

ALA-SDT exhibited synergistic apoptotic effects on THP-1 macrophages, involving excessive intracellular reactive oxygen species generation and MMP loss. Therefore, ALA-SDT is a potential treatment for atherosclerosis.

The sonodynamic effect of curcumin on THP-1 cell-derived macrophages

Curcumin is extracted from the rhizomes of the traditional Chinese herb Curcuma longa and has been proposed to function as a photosensitizer. The potential use of curcumin as a sonosensitizer for sonodynamic therapy (SDT) requires further exploration. This study investigated the sonodynamic effect of curcumin on macrophages, the pivotal inflammatory cells in atherosclerotic plaque. THP-1-derived macrophages were incubated with curcumin at a concentration of 40.7 μmol/L for 2 h and then exposed to pulse ultrasound irradiation (2 W/cm² with 0.86 MHz) for 5–15 min. Six hours later, cell viability was decreased in cells that had been treated with ultrasound for 10 and 15 min. After ultrasound irradiation for 15 min, the ratio of apoptotic and necrotic cells in SDT group was higher than that in ultrasound group, and the ratio of apoptotic cells was higher than that of necrotic cells. Both loss of mitochondrial membrane potential and morphological changes of cytoskeleton were apparent 2 h after treatment with curcumin SDT. These findings support that curcumin had sonodynamic effect on THP-1-derived macrophages and that curcumin SDT could be a promising treatment for atherosclerosis.

The nitroxide TEMPO is an efficient scavenger of protein radicals: cellular and kinetic studies

Protein oxidation occurs during multiple human pathologies, and protein radicals are known to induce damage to other cell components. Such damage may be modulated by agents that scavenge protein radicals. In this study, the potential protective reactions of the nitroxide TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl radical) against Tyr- and Trp-derived radicals (TyrO./TrpN.) have been investigated. Pretreatment of macrophage cells with TEMPO provided protection against photo-oxidation-induced loss of cell viability and Tyr oxidation, with the nitroxide more effective than the hydroxylamine or parent amine. Pulse radiolysis was employed to determine rate constants, k, for the reaction of TEMPO with TyrO. and TrpN. generated on N-Ac-Tyr-amide and N-Ac-Trp-amide, with values of k~10(8) and 7×10(6)M(-1)s(-1), respectively, determined. Analogous studies with lysozyme, chymotrypsin, and pepsin yielded k for TEMPO reacting with TrpN. ranging from 1.5×10(7) (lysozyme) to 1.1×10(8) (pepsin)M(-1)s(-1). Pepsin-derived TyrO. reacted with TEMPO with k~4×10(7)M(-1)s(-1); analogous reactions for lysozyme and chymotrypsin TyrO. were much slower. These data indicate that TEMPO can inhibit secondary reactions of both TyrO. and TrpN., though this is protein dependent. Such protein radical scavenging may contribute to the positive biological effects of nitroxides.

Effects of vascular photodynamic therapy in a newly adapted experimental rat aortic aneurysm model

The hypothesis driving this study was that photodynamic therapy (PDT) may limit abdominal aortic aneurysm growth due to matrix changes. The aortas of 12 rats were incubated with elastase using a newly modified experimental aneurysm model (3.5 mg/ml). Rats were allocated to an elastase-only group (n = 6) to study the elastase-induced aneurysm growth and an elastase ± PDT group to evaluate if PDT limited aneurysm growth (n = 6). PDT was performed with the photosensitizer methylene blue, and thermoneutral laser light (660 nm) was applied (120 J/cm(2), 100 mW/cm(2)) using a diode laser. Four untreated rats served as controls. The arteries were analysed after 4 weeks based on histology, immunohistochemistry and morphometry. This modified rat elastase model led to reproducible aneurysm development with no elastase-induced mortality compared with control animals (circumference, controls: 2.9 ± 0.2 vs. elastase: 5.5 ± 0.9 mm; P < 0.01). PDT after elastase incubation did not inhibit inflammatory cell infiltration. No significant change in the circumference was observed between elastase incubation and PDT treatment after elastase incubation (circumference, elastase: 5.5 ± 0.9 vs. elastase and PDT: 6.1 ± 0.8 mm; P < 0.01). Despite a PDT-induced resistance to protease digestion, PDT did not reduce aortic dilatation in the elastase-treated rat aorta. These findings suggest that PDT may not be a useful modality to prevent aneurysm growth.

Sonodynamic effect of an anti-inflammatory agent--emodin on macrophages

Emodin has been used as an anti-inflammatory agent and inflammation is a crucial feature of atherosclerosis. Here, we investigated the sonodynamic effect of emodin on macrophages, the pivotal inflammatory cells in atherosclerotic plaque. THP-1 derived macrophages were cultured with emodin and exposed to ultrasound. Six hours later, unlike the cells treated for 5 and 10 min, the viability of cells treated for 15 min decreased significantly and the cells showed typical apoptotic chromatin fragmentation. The percentage of apoptotic and necrotic cells in the sonodynamic therapy (SDT) group was higher than that in the ultrasound group. Two hours after treatment for 15 min, the cytoskeleton lost its original features as the filaments dispersed and the cytoskeletal proteins aggregated. The percentage of cells with disturbed cytoskeletal filaments in the SDT group was higher than that in the ultrasound group. These results suggest emodin has a sonodynamic effect on macrophages and might be used as a novel sonosensitizer for SDT for atherosclerosis.

Atorvastatin and clopidogrel interfere with photosensitization in vitro

Photodynamic therapy (PDT) has been used to eliminate undesired cells by using a combination of photosensitizers and light illumination to generate reactive oxygen species. There is great interest in applying PDT to atherosclerosis; preferential destruction of pro-inflammatory macrophages in atheromata might attenuate plaque growth or rupture-prone vulnerability. Here, we report on a previously unknown interaction between cardiovascular drugs that are commonly prescribed for atherosclerosis patients and the cytolytic effects of photodynamic therapy using Cathepsin B activatable photosensitizer L-SR15 on murine macrophage Raw 264.7 cells in culture. Atorvastatin and clopidogrel significantly interfered with in vitro photosensitization effect while aspirin did this to a lesser extent; these drugs did not change the efficiency of cellular uptake of L-SR15 after in vitro photosensitization. A photosensitization interference effect of atorvastatin and clopidogrel was also observed when using a conventional photosensitizer free Ce6 or NCI-H1299 cancer cells. Considering the clinical implications of PDT, our study merits further investigation in clinical settings as well as in animal models.

Waterproof AlInGaP optoelectronics on stretchable substrates with applications in biomedicine and robotics

Inorganic light-emitting diodes and photodetectors represent important, established technologies for solid-state lighting, digital imaging and many other applications. Eliminating mechanical and geometrical design constraints imposed by the supporting semiconductor wafers can enable alternative uses in areas such as biomedicine and robotics. Here we describe systems that consist of arrays of interconnected, ultrathin inorganic light-emitting diodes and photodetectors configured in mechanically optimized layouts on unusual substrates. Light-emitting sutures, implantable sheets and illuminated plasmonic crystals that are compatible with complete immersion in biofluids illustrate the suitability of these technologies for use in biomedicine. Waterproof optical-proximity-sensor tapes capable of conformal integration on curved surfaces of gloves and thin, refractive-index monitors wrapped on tubing for intravenous delivery systems demonstrate possibilities in robotics and clinical medicine. These and related systems may create important, unconventional opportunities for optoelectronic devices.

High dietary methionine plus cholesterol stimulates early atherosclerosis and late fibrous cap development which is associated with a decrease in GRP78 positive plaque cells

The role of homocysteine, or its precursor methionine, in the formation of fibrous caps and its association with endoplasmic reticulum (ER) stress is unclear. Homocysteine can stimulate collagen accumulation and upregulate the ER stress chaperone glucose regulated protein 78 (GRP78). The aim of this study was to determine if high dietary methionine would increase fibrous caps, and that removal of an atherogenic diet would decrease the amount of ER stressed cells. New Zealand white rabbits were fed for 2, 4, or 12 weeks an atherogenic diet [1% methionine + 0.5% cholesterol (2MC, 4MC or 12MC)]; for 4 or 12 weeks a 0.5% cholesterol diet (4Ch, 12Ch); and to study plaque regression, an MC diet for 2 or 4 weeks accompanied by 10 weeks of a normal diet (2MCr, 4MCr). Endothelial function, atherosclerosis and GRP78 positive cells were studied. Endothelial function was abolished in 4MC and atherosclerosis increased 17-fold (P < 0.05) compared with 4Ch. Fibrous caps composed 48% of total plaque area in 12MC vs. 10% in 12Ch (P < 0.01), and 12MC expressed less GRP78 plaque cells vs. 12Ch (P < 0.01). Four MCr had less plaque GRP78 cells than 12MC (P < 0.05) and less endothelial GRP78 cells (P < 0.01). In addition, GRP78 positive cells were the highest in 4MC, but decreased in all other groups (P < 0.01). GRP78 positive cells within the fibrous cap inversely correlated with cap size (r(2) = 0.9). These studies suggest that high dietary methionine could be beneficial for plaque stabilisation, and a normal diet also stabilises plaque and decreases the number of stressed plaque cells.