New Light on an Old Problem

Atherosclerosis Treatment with Stimuli-Responsive Nanoagents: Recent Advances and Future Perspectives

Atherosclerosis is the root of approximately one-third of global mortalities. Nanotechnology exhibits splendid prospects to combat atherosclerosis at the molecular level by engineering smart nanoagents with versatile functionalizations. Significant advances in nanoengineering enable nanoagents to autonomously navigate in the bloodstream, escape from biological barriers, and assemble with their nanocohort at the targeted lesion. The assembly of nanoagents with endogenous and exogenous stimuli breaks down their shells, facilitates intracellular delivery, releases their cargo to kill the corrupt cells, and gives imaging reports. All these improvements pave the way toward personalized medicine for atherosclerosis. This review systematically summarizes the recent advances in stimuli-responsive nanoagents for atherosclerosis management and its progress in clinical trials.

Photosensitization mechanism of Cu(ii) porphyrins

This work presents the mechanism of the photoinduced generation of reactive oxygen species (ROS) by paramagnetic copper porphyrins in aqueous solution. Electronic structure calculations within the framework of the (time-dependent) density functional theory, (TD)DFT, reveal the details regarding the development of the atomistic and electronic structures of the copper porphyrin in solution along the set of chemical reactions accessible upon photoactivation. This study identifies the key parameters controlling the feasibility of the various reaction pathways that drive the formation of specific reactive oxygen species, ROS, i.e. superoxide, peroxyl and hydroxyl radicals. An important outcome of our results is the rationalization of how the water solvent molecules play a crucial role in most steps of the overall reaction. The present study is illustrated by focusing on one specific copper porphyrin for which precise experimental data have recently been measured, and can readily be generalized to the whole family of paramagnetic porphyrins. The conclusions of this work shed light on the rational design of metalloporphyrins as photosensitizers for photodynamic therapy.

Photodynamic Therapy

Photodynamic therapy is a clinical technique for the treatment of cancers, microbial infections and other medical conditions by means of light-induced generation of reactive oxygen species using photosensitising drugs. The intrinsic fluorescence of many such drugs make them potential theranostic agents for simultaneous diagnosis and therapy. This chapter reviews the basic chemical and biological aspects of photodynamic therapy with an emphasis on its applications in theranostics. The roles of nanotechnology is highlighted, as well as emerging trends such as photoimmunotherapy, image-guided surgery and light- and singlet-oxygen dosimetry.

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.

Manipulating tumor hypoxia toward enhanced photodynamic therapy (PDT)

This mini-review summarizes various methods for overcoming or utilizing hypoxia for enhanced PDT.

Atherosclerotic disease and management challenges with nanomedicine: EU FP7 NMP funded “NanoAthero” and “CosmoPHOS-nano” large-scale projects

Atherosclerosis is the most important arterial wall disease that causes arterial stenosis and may lead to the clinical manifestations of angina, heart attack and stroke. There is a demanding unmet medical need for new approaches for early diagnosis and improved/novel targeted therapies and therapy monitoring of atherosclerosis. This is the focus of two European large scale projects, the NanoAthero and the CosmoPHOS-nano by using nanomedicine. The aim is to demonstrate that nanotechnology-enabled systems can be successfully developed and clinically proven to be safe and effective in tackling cardiovascular diseases.

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.

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.