Different effects of photodynamic therapy and gamma-irradiation on vascular smooth muscle cells and matrix : implications for inhibiting restenosis

Combinations of Photodynamic Therapy with Other Minimally Invasive Therapeutic Technologies against Cancer and Microbial Infections

The rapid rise in research and development following the discovery of photodynamic therapy to establish novel photosensitizers and overcome the limitations of the technology soon after its clinical translation has given rise to a few significant milestones. These include several novel generations of photosensitizers, the widening of the scope of applications, leveraging of the offerings of nanotechnology for greater efficacy, selectivity for the disease over host tissue and cells, the advent of combination therapies with other similarly minimally invasive therapeutic technologies, the use of stimulus-responsive delivery and disease targeting, and greater penetration depth of the activation energy. Brought together, all these milestones have contributed to the significant enhancement of what is still arguably a novel technology. Yet the major applications of photodynamic therapy still remain firmly located in neoplasms, from where most of the new innovations appear to launch to other areas, such as microbial, fungal, viral, acne, wet age-related macular degeneration, atherosclerosis, psoriasis, environmental sanitization, pest control, and dermatology. Three main value propositions of combinations of photodynamic therapy include the synergistic and additive enhancement of efficacy, the relatively low emergence of resistance and its rapid development as a targeted and high-precision therapy. Combinations with established methods such as chemotherapy and radiotherapy and demonstrated applications in mop-up surgery promise to enhance these top three clinical tools. From published in vitro and preclinical studies, clinical trials and applications, and postclinical case studies, seven combinations with photodynamic therapy have become prominent research interests because they are potentially easily applied, showing enhanced efficacy, and are rapidly translating to the clinic. These include combinations with chemotherapy, photothermal therapy, magnetic hyperthermia, cold plasma therapy, sonodynamic therapy, immunotherapy, and radiotherapy. Photochemical internalization is a critical mechanism for some combinations.

An integrative review of nonobvious puzzles of cellular and molecular cardiooncology

Oncologic patients are subjected to four major treatment types: surgery, radiotherapy, chemotherapy, and immunotherapy. All nonsurgical forms of cancer management are known to potentially violate the structural and functional integrity of the cardiovascular system. The prevalence and severity of cardiotoxicity and vascular abnormalities led to the emergence of a clinical subdiscipline, called cardiooncology. This relatively new, but rapidly expanding area of knowledge, primarily focuses on clinical observations linking the adverse effects of cancer therapy with deteriorated quality of life of cancer survivors and their increased morbidity and mortality. Cellular and molecular determinants of these relations are far less understood, mainly because of several unsolved paths and contradicting findings in the literature. In this article, we provide a comprehensive view of the cellular and molecular etiology of cardiooncology. We pay particular attention to various intracellular processes that arise in cardiomyocytes, vascular endothelial cells, and smooth muscle cells treated in experimentally-controlled conditions in vitro and in vivo with ionizing radiation and drugs representing diverse modes of anti-cancer activity.

Tissue Reactions and Mechanism in Cardiovascular Diseases Induced by Radiation

The long-term survival rate of cancer patients has been increasing as a result of advances in treatments and precise medical management. The evidence has accumulated that the incidence and mortality of non-cancer diseases have increased along with the increase in survival time and long-term survival rate of cancer patients after radiotherapy. The risk of cardiovascular disease as a radiation late effect of tissue damage reactions is becoming a critical challenge and attracts great concern. Epidemiological research and clinical trials have clearly shown the close association between the development of cardiovascular disease in long-term cancer survivors and radiation exposure. Experimental biological data also strongly supports the above statement. Cardiovascular diseases can occur decades post-irradiation, and from initiation and development to illness, there is a complicated process, including direct and indirect damage of endothelial cells by radiation, acute vasculitis with neutrophil invasion, endothelial dysfunction, altered permeability, tissue reactions, capillary-like network loss, and activation of coagulator mechanisms, fibrosis, and atherosclerosis. We summarize the most recent literature on the tissue reactions and mechanisms that contribute to the development of radiation-induced cardiovascular diseases (RICVD) and provide biological knowledge for building preventative strategies.

Pathological effects of ionizing radiation: endothelial activation and dysfunction

The endothelium, a tissue that forms a single layer of cells lining various organs and cavities of the body, especially the heart and blood as well as lymphatic vessels, plays a complex role in vascular biology. It contributes to key aspects of vascular homeostasis and is also involved in pathophysiological processes, such as thrombosis, inflammation, and hypertension. Epidemiological data show that high doses of ionizing radiation lead to cardiovascular disease over time. The aim of this review is to summarize the current knowledge on endothelial cell activation and dysfunction after ionizing radiation exposure as a central feature preceding the development of cardiovascular diseases.

Effect of cobalt(II) chloride hexahydrate on some human cancer cell lines

The present study investigates the anti-proliferative and apoptosis inducing mechanism of CoCl2·6H2O in PC-3 cancer cell line. Preliminary, three different forms of cobalt i.e., cobaltous (CoCl2·6H2O), macro-Co(II,III) oxide and nano-Co(II,III) oxide were screened for antiproliferative activity in PC-3 cell line. The CoCl2·6H2O being the most effective antiproliferative agent, hence it was further tested against lung (A549), prostrate (PC-3) and brain (IMR-32) cell lines. Human embryonic kidney cell line (293T) was used as a normal cell line to compare the toxicity of CoCl2·6H2O. The CoCl2·6H2O induced morphological and anatomical changes in PC-3 cancer cell which were studied using light, confocal and scanning electron microscopy. The lactate dehydrogenase was estimated which showed mild necrotic mode of cell death. The Annexin/PI staining confirmed the apoptotic mode of cell death in PC-3 cells. Further, production of reaction of reactive oxygen species and changes in mitochondrial membrane potential was also assessed spectrofluorimetrically. The cell cycle arrest was also investigated using flow cytometery. Finally, the caspase activity was estimated in CoCl2·6H2O treated PC-3 cancer cell line. Interestingly, it was found that CoCl2·6H2O induces more cell death in cancerous cells as compared to normal non-cancerous cells. These findings presented CoCl2·6H2O as potential antiproliferative agent.

Low-pH-induced apoptosis: role of endoplasmic reticulum stress-induced calcium permeability and mitochondria-dependent signaling

The acidic microenvironment around tumor cells is a major determinant in cancer growth, metabolism, and metastasis. However, its role in cancer physiology is still not clearly understood. In the present investigation, an attempt has been made to explore the effect of acidic environment on physiology of cancer cells. Exposure of Raji cells to extracellular acidic environment was associated with enhanced cytosolic calcium level and endoplasmic reticulum stress response. X-box binding protein 1 (XBP1) splicing, CCAAT/enhancer-binding protein homologous protein (CHOP), and glucose-regulated protein 78 kDa (GRP78) upregulation suggested endoplasmic reticulum stress generation. On the other hand, real-time-based upregulation of Bax gene expression and flow cytometric analysis of cytochrome c release as well as enhanced active caspase-3 further confirmed mitochondrion-mediated events leading to induction of apoptosis. The expression of TP53 and p21 was upregulated. These observations collectively strongly suggest that both endoplasmic reticulum stress-mediated calcium release and Bax targeting might be altering mitochondrion membrane potential which in turn could induce secondary apoptotic signals; subsequently, endoplasmic reticulum stress can also lead to nuclear localization of Nuclear factor-κB (NF-κB) which in turn favors p53 mediated apoptotic signals.

In vitro photodynamic therapy with chlorin e6 leads to apoptosis of human vascular smooth muscle cells

Percutaneous coronary intervention has become the most common and widely implemented method of heart revascularization. However, the development of restenosis remains the major limitation of this method. Photodynamic therapy (PDT) recently emerged as a new and promising method for the prevention of arterial restenosis. Here the efficacy of chlorin e6 in PDT was investigated in vitro using human vascular smooth muscle cells (TG/HA-VSMCs) as one of the cell types crucial in the development of restenosis. PDT-induced cell death was studied on many levels,including annexin V staining, measurement of the generation reactive oxygen species (ROS) and caspase-3 activity,and assessment of changes in mitochondrial membrane potential and fragmentation of DNA. Photosensitization of TG/HA-VSMCs with a 170 lM of chlorin e6 and subsequent illumination with the light of a 672-nm diode laser(2 J/cm2) resulted in the generation of ROS, a decrease in cell membrane polarization, caspase-3 activation, as well as DNA fragmentation. Interestingly, the latter two apoptotic events could not be observed in photosensitized and illuminated NIH3T3 fibroblasts, suggesting different outcomes of the model of PDT in various types of cells. The results obtained with human VSMCs show that chlorin e6 may be useful in the PDT of aerial restenosis, but its efficacy still needs to be established in an animal model.

A novel lignan composition from Cedrus deodara induces apoptosis and early nitric oxide generation in human leukemia Molt-4 and HL-60 cells

AP9-cd, a standardized lignan composition from Cedrus deodara consisting of (-)-wikstromal, (-)-matairesinol, and dibenzyl butyrolactol, showed cytotoxicity in several human cancer cell lines reported earlier. An attempt was made in this study to investigate the mechanism of cell death in human leukemia Molt-4 and HL-60 cells. It inhibited Molt-4 cell proliferation with 48-h IC(50) of approximately 15 microg/ml, increased sub-G0 cell fraction with no mitotic block, produced apoptotic bodies and induced DNA ladder formation. Flow cytometric analysis of annexinV-FITC/PI-stained cells showed time-related increase in apoptosis and post-apoptotic necrosis. All these biological end-points indicated cell death by apoptosis. Further, initial events involved massive nitric oxide (NO) formation within 4 h with subsequent late appearance of peroxides in cells; measured by flow cytometry using specific fluorescent probes. Persistently high levels of NO and peroxide appeared to decrease mitochondrial membrane potential (Psi(mt)) which was recovered by cyclosporin A in Molt-4 cells. AP9-cd caused 2-fold activation of caspase-3 in Molt-4 and 5-fold activation in HL-60 cells. Also caspases-8 and -9 were activated in HL-60 cells. Ascorbate suppressed the enhanced caspases activities indicating a pro-oxidant effect of AP9-cd. Further, caspase-3 activation correlated with NO generation that was partially impaired by nitric oxide synthase (NOS) inhibitors and ascorbate suggesting a role of pro-oxidant species in caspase-3 activation. AP9-cd produced no cytotoxicity in primary rat hepatocyte culture at the concentrations used. The studies indicated that AP9-cd mediated early NO formation leads to caspases activation, peroxide generation, and mitochondrial depolarization which may be responsible for mitochondrial-dependent and -independent apoptotic pathways involved in the killing of leukemia cells by AP9-cd.

Radiation therapy induced modulation of wound healing at experimental vein graft anastomoses

OBJECTIVES

The aim of this study was to investigate if radiation therapy (RT) favorably modulates wound healing at vein graft anastomoses.

MATERIALS AND METHODS

Jugular vein grafts were sewn into carotid arteries in 32 rats which were randomly divided into two groups: RT (gamma source, 14 Gray, n=16) and control (C, sham irradiation, n=16). Grafts and adjacent arteries were analyzed at 2 (n=8) and 8 weeks (n=8) by histology, immunohistochemistry, and morphometry.

RESULTS

Although, RT did not reduce the overall occurrence of intimal hyperplasia, the distribution differed. RT led to a reduction of intimal hyperplasia in arterial segments (median: C: 41.873 microm2; RT: 6.452 microm2, p < 0.0007). In contrast, RT augmented intimal hyperplasia in vein grafts (median: C: 30.287 microm2; RT: 90.455 microm2, p < 0.014). Vein graft diameters after RT were enlarged (median: C: 2.098 microm; RT: 3.381, p < 0.031). Over 80% of the cells were of mesenchymal origin in both groups.

CONCLUSIONS

RT reduced intimal hyperplasia in arterial segments. However, RT led to graft dilatation and increased intimal hyperplasia in vein grafts. RT did not favorably modulate the vascular wound healing response in this model.

Evaluation of radioprotective activities of Rhodiola imbricata Edgew – A high altitude plant

The present study reports the radioprotective properties of a hydro-alcoholic rhizome extract of Rhodiola imbricata (code named REC-7004), a plant native to the high-altitude Himalayas. The radioprotective effect, along with its relevant superoxide ion scavenging, metal chelation, antioxidant, anti-lipid peroxidation and anti-hemolytic activities was evaluated under both in vitro and in vivo conditions. Chemical analysis showed the presence of high content of polyphenolics (0.971 +/- 0.01 mg% of quercetin). Absorption spectra analysis revealed constituents that absorb in the range of 220-290 nm, while high-performance liquid chromatography (HPLC) analysis confirmed the presence of four major peaks with retention times of 4.780, 5.767, 6.397 and 7.577 min. REC-7004 was found to lower lipid oxidation significantly (p < 0.05) at concentrations viz., 8 and 80 microg/ml respectively as compared to reduced glutathione, although the optimally protective dose was 80 microg/ml, which showed 59.5% inhibition of induction of linoleic acid degradation within first 24 h. The metal chelation activity of REC-7004 was found to increase concomitantly from 1 to 50 microg/ml. REC-7004 (10-50 microg/ml) exhibited significant metal chelation activity (p < 0.05), as compared to control, and maximum percentage inhibition (30%) of formation of iron-2,2'-bi-pyridyl complex was observed at 50 microg/ml, which correlated well with quercetin (34.9%), taken as standard. The reducing power of REC-7004 increased in a dose-dependent manner. The absorption unit value of REC-7004 was significantly lower (0.0183 +/- 0.0033) as compared to butylated hydroxy toluene, a standard antioxidant (0.230 +/- 0.091), confirming its high reducing ability. Superoxide ion scavenging ability of REC-7004 exhibited a dose-dependent increase (1-100 microg/ml) and was significantly higher (p < 0.05) than that of quercetin at lower concentrations (1-10 microg/ml), while at 100 microg/ml, both quercetin and REC-7004 scavenged over 90% superoxide anions. MTT assay in U87 cell line revealed an increase in percent survival of cells at doses between 25 and 125 microg/ml in case of drug + radiation group. In vivo evaluation of radio-protective efficacy in mice revealed that intraperitoneal administration of REC-7004 (maximally effective dose: 400 mg/kg b.w.) 30 min prior to lethal (10 Gy) total-body gamma-irradiation rendered 83.3% survival. The ability of REC-7004 to inhibit lipid peroxidation induced by iron/ascorbate, radiation (250 Gy) and their combination [i.e., iron/ascorbate and radiation (250 Gy)], was also investigated and was found to decrease in a dose-dependent manner (0.05-2 mg/ml). The maximum percent inhibition of formation of MDA-TBA complex at 2 mg/ml in case of iron/ascorbate, radiation (250 Gy) and both i.e., iron/ascorbate with radiation (250 Gy) was 53.78, 63.07, and 51.76% respectively and were found to be comparable to that of quercetin. REC-7004 (1 microg/ml) also exhibited significant anti-hemolytic capacity by preventing radiation-induced membrane degeneration of human erythrocytes. In conclusion, Rhodiola renders in vitro and in vivo radioprotection via multifarious mechanisms that act in a synergistic manner.

Gamma-irradiation modulates vascular smooth muscle cell and extracellular matrix function: Implications for neointimal development

OBJECTIVE

Migration of vascular smooth muscle cells (SMCs) into the subintimal space, and their proliferation and resultant deposition of extracellular matrix are key processes in the development of intimal hyperplasia, leading to vascular recurrent stenosis. The purpose of this study was to investigate the effects of clinically administered doses of gamma-radiation on SMCs and extracellular matrix proteins in vitro, to better understand how it impinges on cellular and extracellular components of recurrent stenosis.

METHODS

The effects of gamma-irradiation (10, 20 Gy) on SMC migration into three-dimensional collagen matrix gels was quantitated by calibrated light microscopy, and the release of metalloproteinases into conditioned media was investigated with an enzyme-linked immunosorbent assay and zymography. Collagen production was assayed with [(3)H]-proline incorporation, and SMC phenotype changes with confocal microscopy with a fluorescent alpha-actin antibody. The effect of gamma-irradiation on extracellular matrix was investigated by quantitating untreated SMC proliferation ((3)H-thymidine incorporation) on irradiated endothelial cell-derived matrix and by assessing structural collagen matrix changes with sodium dodecylsulfate polyacrylamide gel electrophoresis. All groups were compared with nonirradiated control groups.

RESULTS

SMC vertical migration was significantly decreased by gamma-irradiation (48% and 55%, respectively; P <.0001). Irradiation did not generate measurable matrix protein crosslinks, nor did it alter the production of metalloproteinases or collagen synthesis. However, gamma-irradiation decreased the ability of extracellular matrix to induce nonirradiated SMC proliferation (15% reduction; P =.0028). Moreover, gamma-irradiation reversed the secretory phenotype of cultured SMCs to a contractile type.

CONCLUSIONS

The gamma-irradiation-induced reduction of cellular migration, changes in SMC phenotype, and functional activity of matrix-bound factors, and no measurable effects on the production of extracellular matrix proteins, may in part explain the diverse effects of gamma-irradiation on the restenotic response.

Radiation protection of HepG2 cells by Podophyllum hexandrum Royale

Radioprotection by an aqueous extract of Podophyllum hexandrum (RP-1) was investigated in HepG2 cells by evaluating colony forming efficacy (CFE), redox status of mitochondria, reactive oxygen species (ROS), generation of nitric oxide (NO), peroxidation of lipids and intracellular glutathione. Lower concentrations of RP-1 (0.1 and 1 microg/ml) rendered maximum radioprotection when administered 1 or 2 h before irradiation. Higher concentrations (5 and 10 microg/ml) however were less effective when administered 1 or 2 h before irradiation, but were more effective with increased time intervals (4 or 8 h) between RP-1 administration and irradiation. RP-1 pre-treatment also significantly inhibited radiation-induced MTT reduction in a concentration and time-dependent manner by decreasing gamma radiation-induced leakage of electrons from electron transport chain. Pre-irradiation administration of RP-1 significantly reduced both ROS and NO generation and enhanced glutathione levels, thereby inhibiting lipid peroxidation.

Restenosis: Intracoronary Brachytherapy

Though interventional strategies have revolutionized the management of patients with symptomatic coronary artery disease, in-stent restenosis has emerged as the single most important limitation of long-term success following percutaneous coronary intervention. Once present, in-stent restenosis is extraordinarily difficult to treat, with conventional revascularization techniques failing in 50% to 80% of patients. Intracoronary radiation, or brachytherapy, targets cellular proliferation within the culprit neointima. Clinical trials have demonstrated that brachytherapy is a highly effective treatment for in-stent restenosis, reducing angiographic restenosis by 50% to 60% and the need for target vessel revascularization by 40% to 50%. The benefits of intracoronary brachytherapy may be particularly pronounced in certain patient subgroups (eg, those with diabetes, long lesions, or lesions in saphenous vein bypass grafts), but comes at the cost of an increased rate of late stent thrombosis and the need for extended antiplatelet therapy. The role of brachytherapy in the arsenal of the interventional cardiologist will continue to evolve, particularly in light of the unprecedented recent advances with the use of drug-eluting stents for restenosis prevention.

Endovascular photodynamic therapy using mono-L-aspartyl-chlorin e6 to inhibit Intimal hyperplasia in balloon-injured rabbit arteries

BACKGROUND AND OBJECTIVE

Intimal hyperplasia (IH) leading to restenosis is a major complication of arterial revascularization. The purpose of this study was to investigate the effect of photodynamic therapy (PDT) using mono-L-aspartyl chlorin e6 (NPe6) as a photosensitizer and intraluminal radial irradiation for inhibition of IH experimentally.

STUDY DESIGN/MATERIALS AND METHODS

Study of laser transmission through the blood indicated that exclusion of blood is a prerequisite for intraluminal PDT. For homogeneous radial laser irradiation to the vessel wall, we used a newly developed cylindrical diffusing balloon laser fiber. Injuries were induced by pulling a balloon catheter through the right iliac artery of rabbits. One and 6 hours after the NPe6 injection (5mg/kg i.v.), drug distribution was examined by fluorescence microscopy. Nineteen rabbits received NPe6 at the time of injuries and PDT was performed with 664-nm laser at 30 and 10 J/cm(2) (20, 30, 40 mW/cm(2)) 1 hour after the injuries. The arteries were harvested at 2 days. In a second group of rabbits, PDT was given at 30 mW/cm(2) (30 J/cm(2)). Two weeks after treatment, the arteries were removed and examined histologically.

RESULTS

NPe6 was found to be distributed selectively in the injured media. Endovascular NPe6-PDT showed complete depletion of smooth muscle cells even with 10 J/cm(2) at 2 days. IH was significantly inhibited at 14 days after PDT.

CONCLUSIONS

Endovascular PDT of injured artery using NPe6 can prevent IH in this model of arterial wall injury and may become clinically useful for the prophylaxis of IH.

Origin of neointimal endothelium and alpha-actin-positive smooth muscle cells in transplant arteriosclerosis

The development of transplant arteriosclerosis (TA) is today's most important problem in clinical organ transplantation. Histologically, TA is characterized by perivascular inflammation and progressive intimal thickening. Current thought on this process of vascular remodeling assumes that neointimal vascular smooth muscle (VSM) cells and endothelium in TA are graft-derived, holding that medial VSM cells proliferate and migrate into the subendothelial space in response to signals from inflammatory cells and damaged graft endothelium. Using MHC class I haplotype-specific immunohistochemical staining and single-cell PCR analyses, we show that the neointimal alpha-actin-positive VSM cells in rat aortic or cardiac allografts are of recipient and not of donor origin. In aortic but not in cardiac allografts, recipient-derived endothelial cells (ECs) replaced donor endothelium. Cyclosporine treatment prevents neointima formation and preserves the vascular media in aortic allografts. Recipient-derived ECs do not replace graft endothelium after cyclosporine treatment. We propose that, although it progresses beyond the needs of functional repair, TA reflects the activity of a normal healing process that restores vascular wall function following allograft-induced immunological injury.

Photodynamic therapy induces apoptosis in intimal hyperplastic arteries

Photodynamic therapy (PDT) generates free radicals through the absorption of light by photosensitizers. PDT shows promise in the treatment of intimal hyperplasia, which contributes to restenosis, by completely eradicating cells in the vessel wall. This study investigates the mechanisms of PDT-induced cell death. PDT, using the photosensitizer chloroaluminum-sulfonated phthalocyanine (1 mg/kg) and laser light (lambda = 675 nm) 100 J/cm(2) was administered to rat carotid arteries after balloon injury-induced intimal hyperplasia. Apoptosis was determined by cell morphology with light microscopy and transmission electron microscopy, DNA cleavage by terminal dUTP nick-end labeling staining, and nucleosomal fragmentation (ladder pattern) by DNA agarose gel electrophoresis. Four hours after PDT, apoptosis was observed in vascular cells, as evidenced by terminal dUTP nick-end labeling staining and transmission electron microscopy. Within 24 hours no cells were present in the neointima and media. Immunofluorescence using an alpha-smooth muscle cell actin antibody confirmed the disappearance of all neointimal and medial cells within 24 hours. No inflammatory cell infiltrate was observed during this time frame. Apoptosis was sharply confined to the PDT treatment field. These data demonstrate that vascular PDT induces apoptosis as a mechanism of rapid, complete, and precise cell eradication in the artery wall. These findings and the lack of inflammatory reaction provide the basis for understanding and developing PDT for a successful clinical application in the treatment of hyperplastic conditions such as restenosis.