8-Methoxypsoralen and longwave ultraviolet irradiation are a novel antiproliferative combination for vascular smooth muscle

8-Methoxypsoralen Induces Apoptosis by Upregulating p53 and Inhibits Metastasis by Downregulating MMP-2 and MMP-9 in Human Gastric Cancer Cells

Furanocoumarin 8-methoxypsoralen (8-MOP) is the parent compound that naturally occurs in traditional medicinal plants used historically. 8-MOP has been employed as a photochemotherapeutic component of Psoralen + Ultraviolet A (PUVA) therapy for the treatment of vitiligo and psoriasis. Although the role of 8-MOP in PUVA therapy has been studied, little is known about the effects of 8-MOP alone on human gastric cancer cells. In this study, we observed anti-proliferative effect of 8-MOP in several human cancer cell lines. Among these, the human gastric cancer cell line SNU1 is the most sensitive to 8-MOP. 8-MOP treated SNU1 cells showed G1-arrest by upregulating p53 and apoptosis by activating caspase-3 in a dose-dependent manner, which was confirmed by loss-of-function analysis through the knockdown of p53-siRNA and inhibition of apoptosis by Z-VAD-FMK. Moreover, 8-MOPinduced apoptosis is not associated with autophagy or necrosis. The signaling pathway responsible for the effect of 8-MOP on SNU1 cells was confirmed to be related to phosphorylated PI3K, ERK2, and STAT3. In contrast, 8-MOP treatment decreased the expression of the typical metastasis-related proteins MMP-2, MMP-9, and Snail in a p53-independent manner. In accordance with the serendipitous findings, treatment with 8-MOP decreased the wound healing, migration, and invasion ability of cells in a dose-dependent manner. In addition, combination treatment with 8-MOP and gemcitabine was effective at the lowest concentrations. Overall, our findings indicate that oral 8-MOP has the potential to treat early human gastric cancer, with fewer side effects.

Defined Small Molecules Produced by Himalayan Medicinal Plants Display Immunomodulatory Properties

Plant-derived compounds that modulate the immune responses are emerging as frontline treatment agents for cancer, infectious diseases and autoimmunity. Herein we have isolated 40 phytochemicals from five Bhutanese Sowa Rigpa medicinal plants-Aconitum laciniatum, Ajania nubegina, Corydalis crispa, Corydalis dubia and Pleurospermum amabile-and tested 14 purified compounds for their immunomodulatory properties using a murine dendritic cell (DC) line, and cytotoxicity against a human cholangiocyte cell line using xCELLigence real time cell monitoring. These compounds were: pseudaconitine, 14-veratryolpseudaconitine, 14-O-acetylneoline, linalool oxide acetate, (E)-spiroether, luteolin, luteolin-7-O-β-d-glucopyranoside, protopine, ochrobirine, scoulerine, capnoidine, isomyristicin, bergapten, and isoimperatorin. Of the 14 compounds tested here, scoulerine had adjuvant-like properties and strongly upregulated MHC-I gene and protein expression whereas bergapten displayed immunosuppressive properties and strongly down-regulated gene and protein expression of MHC-I and other co-stimulatory molecules. Both scoulerine and bergapten showed low cytotoxicity against normal healthy cells that were consistent with their immunoregulatory properties. These findings highlight the breadth of immunomodulatory properties of defined compounds from Bhutanese medicinal plants and show that some of these compounds exert their mechanisms of action by modulating DC activity.

Crystal structure of tetra-hydro-seselin, an angular pyran-ocoumarin

In the title compound, tetra-hydro-seselin, C14H16O3, a pyran-ocoumarin [systematic name: 8,8-dimethyl-3,4,9,10-tetra-hydro-2H,8H-pyrano[2,3-f]chromen-2-one] obtained from the hydrogenation of seselin in the presence of Pd/C in MeOH at room temperature, the dihedral angle between the central benzene ring and the best planes of the outer fused ring systems are 6.20 (7) and 10.02 (8)°. In the crystal, mol-ecules show only very weak inter-molecular C-H⋯O inter-actions.

Crystal structure of di-bromo-meth-oxy-seselin (DBMS), a photobiologically active pyran-ocoumarin

The title compound, C15H14Br2O4 [systematic name: rac-(9S,10R)-3,9-dibromo-10-methoxy-8,8-dimethyl-9,10-dihydropyrano[2,3-h]chromen-2(8H)-one], is a pyran-ocoumarin derivative formed by the bromination of seselin, which is a naturally occurring angular pyran-ocoumarin isolated from the Indian herb Trachyspermum stictocarpum. In the mol-ecule, the benzo-pyran ring system is essentially planar, with a maximum deviation of 0.044 (2) Å for the O atom. The di-hydro-pyran ring is in a half-chair conformation and the four essentially planar atoms of this ring form a dihedral angle of 4.6 (2)° with the benzo-pyran ring system. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds, forming chains propagating along [010]. In addition, π-π stacking inter-actions, with centroid-centroid distances of 3.902 (2) and 3.908 (2) Å, link the hydrogen-bonded chains into layers parallel to (001).

Crystal structure of a photobiologically active brominated angular pyran-ocoumarin: bromo-hy-droxy-seselin

The title compound, C₁₄H₁₃BrO₃ [systematic name: rac-(9S,10R)-9-bromo-10-hy-droxy-8,8-dimethyl-9,10-di-hydro-2H,8H-pyrano[2,3-f]chromen-2-one], is a substituted pyran-ocoumarin, obtained by bromination of seselin [8,8-dimethyl-2H,8H-pyrano[2,3-f]chromen-2-one], which was isolated from the Indian herb Trachyspermum stictocarpum (Aajmod). The pyrano ring has a distorted half-chair conformation and its mean plane is inclined to the coumarin mean plane by 1.6 (2)°. In the crystal, mol-ecules are linked by pairs of O-H⋯O hydrogen bonds, forming inversion dimers with an R²₂(16) ring motif. The dimers stack along the a-axis direction and are linked by offset π-π inter-actions, forming columns [inter-centroid distance = 3.514 (4) Å].

Crystal structure of bergapten: a photomutagenic and photobiologically active furan-ocoumarin

The title compound, C12H8O4, is a furan-ocoumarin [systematic name: 4-meth-oxy-7H-furo[3,2-g]chromen-7-one], which was isolated from the Indian herb T. stictocarpum. The mol-ecule is almost planar with an r.m.s. deviation of 0.024 Å for the hetero atoms of the fused-ring system. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds, forming a three-dimensional framework. There are offset π-π inter-actions present involving the coumarin moieties stacking along the a-axis direction [shortest inter-centroid distance = 3.717 (3) Å].

Mechanisms Underlying the Antiproliferative and Prodifferentiative Effects of Psoralen on Adult Neural Stem Cells via DNA Microarray

Adult neural stem cells (NSCs) persist throughout life to replace mature cells that are lost during turnover, disease, or injury. The investigation of NSC creates novel treatments for central nervous system (CNS) injuries and neurodegenerative disorders. The plasticity and reparative potential of NSC are regulated by different factors, which are critical for neurological regenerative medicine research. We investigated the effects of Psoralen, which is the mature fruit of Psoralea corylifolia L., on NSC behaviors and the underlying mechanisms. The self-renewal and proliferation of NSC were examined. We detected neuron- and/or astrocyte-specific markers using immunofluorescence and Western blotting, which could evaluate NSC differentiation. Psoralen treatment significantly inhibited neurosphere formation in a dose-dependent manner. Psoralen treatment increased the expression of the astrocyte-specific marker but decreased neuron-specific marker expression. These results suggested that Psoralen was a differentiation inducer in astrocyte. Differential gene expression following Psoralen treatment was screened using DNA microarray and confirmed by quantitative real-time PCR. Our microarray study demonstrated that Psoralen could effectively regulate the specific gene expression profile of NSC. The genes involved in the classification of cellular differentiation, proliferation, and metabolism, the transcription factors belonging to Ets family, and the hedgehog pathway may be closely related to the regulation.

Molecular atherectomy for restenosis

Receptors for basic (b) and acidic (a) fibroblast growth factor (FGF) are upregulated in activated smooth muscle cells. These cells, which proliferate in response to bFGF, can thus be killed by a conjugate of bFGF and the ribosome-inactivating enzyme, saporin (which, by itself, does not enter the cells). Quiescent smooth muscle cells and other cells that have few FGF receptors are not killed. In vivo, bFGF-saporin transiently inhibits smooth muscle cell proliferation and neointimal accumulation after balloon injury to the rat carotid artery. Delivery of saporin, diagnostic imaging agents, or antisense oligodeoxynucleotides might be made even more selective by linking these substances to antibodies against the extracellular domains of the putative FGF receptor isoform specific for activated smooth muscle cells.

Ultraviolet A regulates adipogenic differentiation of human adipose tissue-derived mesenchymal stem cells via up-regulation of Kruppel-like factor 2

Adipocyte dysfunction is strongly associated with the development of obesity, which is a major risk factor for many disorders, including diabetes, hypertension, and heart disease. This study shows that ultraviolet A (UVA) inhibits adipogenic differentiation of human adipose tissue-derived mesenchymal stem cells and its action mechanisms. The mRNA levels of peroxidase proliferator-activated receptor (PPAR) γ and CCAAT/enhancer-binding protein α (C/EBPα), but not CCAAT/enhancer-binding protein ((C/EBP) β and δ, were reduced by UVA. Moreover, the mRNA levels of PPAR γ target genes (lipoprotein lipase (LPL), CD36, adipocyte protein (aP2), and liver X receptor α (LXR)) were down-regulated by UVA. Additionally, attempts to elucidate a possible mechanism underlying the UVA-mediated effects revealed that UVA induced migration inhibitory factor (MIF) gene expression, and this was mediated through activation of AP-1 (especially JNK and p42/44 MAPK) and nuclear factor-κB. In addition, reduced adipogenesis by UVA was recovered upon the treatment with anti-MIF antibodies. AMP-activated protein kinase phosphorylation and up-regulation of Kruppel-like factor 2 (KLF2) were induced by UVA. Taken together, these findings suggest that the inhibition of adipogenic differentiation of human adipose tissue-derived mesenchymal stem cells by UVA occurs primarily through the reduced expression of PPAR γ, which is mediated by up-regulation of KLF2 via the activation of MIF-AMP-activated protein kinase signaling.

Effectiveness of narrow-band ultraviolet-B phototherapy for prevention of intimal hyperplasia in a rat carotid balloon injury model

BACKGROUND AND OBJECTIVE

Narrow-band ultraviolet-B light (NBUVB) (313 nm) is known to have anti-proliferative effects, implying a potential treatment for intimal hyperplasia, but it remains to be ascertained. We assessed the effects of NBUVB irradiation for prevention of intimal hyperplasia.

STUDY DESIGN/MATERIALS AND METHODS

The rat carotid arteries were irradiated with NBUVB after balloon injury (BI), and the degree of intimal hyperplasia was histopathologically assessed. The anti-proliferative effects using cultured human smooth muscle cells were evaluated by flow cytometry and immunoblot analysis.

RESULTS

NBUVB (0.3-4.5 J/cm(2)) irradiation immediately after BI reduced the degree of intimal hyperplasia at 14 and 28 days after BI (P<0.001) without any obvious complications. Neither an increase in the number of medial cells nor upregulation of proliferating cell nuclear antigen was observed in the irradiated arteries. NBUVB irradiation at 2 or 14 days after BI significantly suppressed further intimal hyperplasia (P<0.01). NBUVB-irradiated cultured cells showed inhibited proliferation involved with G(1) and G(2)/M arrests. Increased expression of p53 and inhibition of retinoblastoma protein (pRB) phosphorylation were also seen in the NBUVB-irradiated cells.

CONCLUSIONS

These data suggest that NBUVB irradiation is an effective method for preventing intimal hyperplasia. The anti-proliferative effect is partly due to the cell cycle arrest caused by p53 expression and inhibited pRB phosphorylation.

Psoralen derivatives and longwave ultraviolet irradiation are active in vitro against human melanoma cell line

Cutaneous malignant melanoma is a very serious form of skin cancer that arises from melanocytes. Currently there is no effective treatment for metastatic melanoma so intense clinical trials are evaluating new drugs for this human malignancy. Psoralens are a group of compounds that bind to DNA in rapidly dividing cells and with ultraviolet light in the A band (UVA) cause DNA crosslinking, thereby preventing cellular division. They are used in the treatment of psoriasis and cutaneous T-cell lymphoma among other skin and blood diseases. We have investigated the cytotoxic potential of three psoralen derivatives plus UVA exposure (PUVA) on a established cell line of human melanoma. Cells were treated with different concentrations of 8-methoxypsoralen (8-MOP), 4,5',8-trimethylpsoralen (TMP) and 7-methylpyridopsoralen (MPP), for 1 h and after exposure to UVA light (0.3 J/cm(2)) were allowed to recover over a 24-72 h period. Viability was assessed by the microculture 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay. Cisplatin, one of the most important drugs in the chemotherapy of melanoma, was included for comparative studies. All the psoralen derivatives tested were markedly cytotoxic in a dose and post-exposure-time dependent manner. The IC(50) values for 72 h of post-exposure time were as follows: MPP=0.05+/-0.01, TMP=0.13+/-0.003 and 8-MOP=10.79+/-1.85 micromol/L. Regardless of the limitations of the in vitro model, our results suggested that the lower IC(50) values of TMP and MPP might be of clinical importance.

Photochemotherapy of vascular cells with 8-methoxypsoralen and visible light: differential effects on endothelial and smooth muscle cells

BACKGROUND

The long-term efficacy of percutaneous transluminal coronary angioplasty is limited by the restenosis which occurs in approximately 40% of patients, usually within 6 months of the procedure.

PURPOSE

The present study was designed to evaluate the effects of 8-methoxypsoralen (8-MOP) activated with visible light on the properties of bovine aortic smooth muscle cells (SMC) and endothelial cells (EC) in vitro.

METHODS

Cells were seeded in polystyrene wells, allowed to attach over a 24-h period, incubated with 1, 20, or 50 microg/ml 8-MOP and then exposed to 12 J/cm2 visible light (447 nm). Cell counts were performed for up 14 days (n = 4-6 wells per time point), and each experiment was performed in triplicate. Cellular migration, morphology, and size were also analyzed.

RESULTS

The lowest 8-MOP dose (1 microg/ml) had no significant effect on SMC proliferation, while the highest dose (50 microg/ml) induced cytostasis. An intermediate dose of 8-MOP (20 microg/ml) produced a transient and reversible inhibition of proliferation. There was no significant effect on proliferation of EC at lowest dose of 8-MOP (1 microg/ml). However, in contrast to the SMC experiments, a transient and reversible inhibition of EC proliferation was seen at both 20 and 50 microg/ml 8-MOP.

CONCLUSIONS

These experiments demonstrate that while 8-MOP photoactivated with 447 nm visible light can reversibly inhibit the proliferation of both SMC and EC in a dose-dependent fashion, SMC are more sensitive to the treatment than EC.

UVB-activated psoralen reduces luminal narrowing after balloon dilation because of inhibition of constrictive remodeling

In this study we have explored the potential of PUVB (8-MOP + UVB) therapy for the reduction of luminal narrowing after arterial injury. In 15 rabbits, balloon dilation of iliac arteries was performed. In 20 arteries, dilation was combined with the delivery of pulsed ultraviolet light B (UVB) irradiation with 10 arteries being previously subjected to sensitizer infusion. Changes in vessel diameter, proliferation and extracellular matrix protein content at 6 weeks were evaluated by means of angiography and histomorphometry-immunohistochemistry. We found that PUVB, applied at the time of dilation, induced reduction in late loss (LL) at 6 weeks (percutaneous transluminal angioplasty vs UVB vs PUVB: 0.64 +/- 0.15 mm vs 0.61 +/- 0.05 mm vs 0.29 +/- 0.05 mm; p = 0.018). The same holds true for constrictive remodeling (0.53 +/- 0.15 mm vs 0.45 +/- 0.06 mm vs 0.15 +/- 0.05 mm; p = 0.016). In the irradiation groups, LL was independent of acute gain (AG), as opposed to the control. Collagen content increased significantly after PUVB in media and adventitia, without increased cellular proliferation in all vessel layers. Thus, PUVB at the time of dilation reduced luminal narrowing at follow-up without effecting proliferation. This effect was independent of AG and was associated with increased collagen content in media and adventitia.

Inactivation of WBCs in RBC suspensions by photoactive phenothiazine dyes: comparison of dimethylmethylene blue and MB

BACKGROUND

The transfusion of blood components containing WBCs can cause unwanted complications, which include virus transmission, transfusion-associated GVHD, alloimmunization, febrile reactions, and immunomodulation. Phototreatment with 4 microM of dimethylmethylene blue (DMMB) and 13 J per cm(2) of white light irradiation has previously been shown to be an effective way to inactivate different models of enveloped and nonenveloped viruses in RBC suspensions, with minimum damage to RBCs. The present study compares WBC photoinactivation in buffy coat after DMMB or MB phototreatment under virucidal conditions.

STUDY DESIGN AND METHODS

Buffy coat diluted to 30-percent Hct was treated with the dye and white light. Isolated WBCs were assayed for cell proliferation and viability by an assay using a tetrazolium compound, limiting dilution analysis, DNA fragmentation, and flow cytometry assays.

RESULTS

DMMB and 2.5 J per cm(2) of light phototreatment can inactivate T cells to the limit of detection by limiting dilution analysis (>4.76 log reduction). No WBC proliferation activity was observed after DMMB and 3.8 J per cm(2) of light. DNA degradation after DMMB phototreatment was light dependent. In addition, DMMB phototreatment induced apoptosis in WBCs. In contrast, MB phototreatment under virucidal conditions did not cause significant changes in the viability of WBCs. Neither DNA degradation nor signs of apoptosis were observed after MB phototreatment.

CONCLUSION

DMMB phototreatment inactivates T-lymphocytes, the cells that cause GVHD.

Psoralen and long wavelength ultraviolet radiation as an adjuvant therapy for prevention of intimal hyperplasia and constrictive remodeling after balloon dilation: a study in the rabbit iliac artery

BACKGROUND AND OBJECTIVE

Restenosis after balloon angioplasty is the summated effect of intimal hyperplasia and arterial shrinkage, both caused by hyperproliferation. In the present study, the potential of a photochemotherapeutic modality (Psoralen + UVA: PUVA) for the prevention of angioplasty induced proliferation was explored.

STUDY DESIGN/MATERIALS AND METHODS

In rabbit iliac arteries, balloon dilation followed by PUVA-therapy (H = 1 J/cm2) was performed (n = 15). Contralateral arteries served as control. After 2 and 28 days of survival, the contribution of intimal hyperplasia and remodeling to lumen loss was determined by means of angiography and histological analysis.

RESULTS

After 2 days, large parts of the media had become acellular, while proliferation was occurring predominantly in the adventitia in both groups. After 28 days, late loss, arterial shrinkage, but not intimal hyperplasia were larger in the PUVA group (P < 0.05).

CONCLUSION

PUVA-therapy did not prevent intimal hyperplasia following balloon dilation but enhanced luminal narrowing by augmented constrictive remodeling.

Pretreatment with continuous-wave ultraviolet irradiation to prevent the development of delayed vasospasm in the rabbit common carotid artery model

OBJECT

Ultraviolet (UV) light irradiation can lead to immunomodulation. The purpose of this study was to determine the preventive effect of UV light on cerebral vasospasm by using a rabbit common carotid artery (CCA) model.

METHODS

Rabbit CCAs were constricted for a long period by application of autologous blood within a silicon sheath. Before immersion in blood, the CCAs were adventitiously exposed to UV light emitted from a helium-cadmium laser (wavelength 325 nm) yielding an irradiation energy of 10 mJ/mm2. The occurrence of vasospasm was evaluated using angiography 48 hours after blood exposure in this model. The UV light treatment significantly reduced the degree of vasospasm. Compared with luminal diameters measured on Day 0, prior to treatment, the luminal diameters of UV light-treated arteries (six animals) decreased by only 6%, whereas that of the sham-treated arteries (eight animals) significantly decreased by 26% (p<0.001). Histological examination of UV light-treated CCAs revealed no endothelial damage and extended smooth-muscle cells, in which some fragmented nuclei were confirmed by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling. Twenty-eight days after blood exposure, examination of UV light-treated CCAs revealed only myointimal proliferation, similar to that of the sham-treated CCAs.

CONCLUSIONS

These results are the first to provide evidence of a prophylactic effect of UV light on vasospasm and are suggestive of involvement of apoptosis in the mechanism of this effect.

Psoralen activity and binding sites in melanotic and amelanotic human melanoma cells

The biological activity and specific binding sites of 8-methoxypsoralen (8-MOP) are assayed using two human melanoma cell lines, melanotic SK-Mel 28 and amelanotic C32TG. Long-term (72 hr) treatment with 8-MOP at a concentration of 10(-4)M results in an increase in melanogenesis and a decrease in proliferation, similar in both cell lines. Daily exposure of these cells to ultraviolet A (UVA) irradiation (1.28 mJ/cm(2)) does not enhance the response to the compound. Daily pulse application (30 min daily) of 8-MOP does not promote any response. However, in combination with UVA, 8-MOP pulse treatment becomes as effective as the long-term treatment. A decrease in cell proliferation in the constant presence of 8-MOP is not coupled with apoptosis, since no increase in the number of apoptotic nuclei was observed after the treatment. The flow cytometry indicates that 8-MOP arrests the cells at the G0/G1 phase, irrespective of the presence or absence of UVA light. In view of the lack of epidermal growth factor (EGF) receptors in both cell lines, it is not likely that such an arrest is associated with the down-regulation of EGF receptors by 8-MOP. It is noted that this compound elicits a biphasic cell response, since cell proliferation increases after the first 24-hr treatment, whereas it decreases in the subsequent 48 hr and thereafter. Competition binding assays using 3H-8-MOP disclosed: 1) the specific binding of the compound in both cell lines occurs in the presence or absence of UVA light, and 2) a higher binding rate at low concentrations of the compound is in SK-Mel 28 (72%) rather than C32TG (58%) cells. The competition assays in the presence of UVA suggest a possible occurrence of covalent bindings between psoralen and receptor, as DNA covalent binding accounted to only 3-5% of the total binding in both cell lines.

Effects of ultraviolet light in vascular cells in vitro and in intact atherosclerotic explants: potential role of apoptosis in vascular biology

Complex cell-to-cell interactions are known to participate during vascular injury and remodeling, resulting in smooth muscle cell proliferation. Mechanical interventions have yielded little benefit in limiting this process and several site-specific genetic therapies are not yet clinically available. The aim of this study was to delineate the effect of very short wavelength ultraviolet (UVC) light therapy on the viability of macrophage and smooth muscle cells. Vascular cells were both treated in vitro and in intact explanted atherosclerotic aortic segments ex vivo with UVC light. Brief exposure to short wavelength UVC light in the absence of photosensitizers elicited a differential temporal and functional response among treated cells. However, dramatic reduction in both cellular viability and proliferative capacity with eventual cell demise was observed in all UVC-treated cells. Flow cytometry and immunohistochemical analyses revealed the presence of extensive DNA fragmentation, suggestive of apoptosis as a predominant pathway of cell death in these cells exposed to UVC light. We hypothesize that selective induction of apoptosis, in contrast to necrosis, with UVC light may represent a beneficial approach to interdict the complex biologic cascade of messengers that participate in the restenotic response to vascular injury.

Prevention of restenosis after coronary angioplasty: towards a molecular approach?

Restenosis after coronary angioplasty, the main limitation of interventional cardiology, remains an unsolved issue. The failure to-date of all pharmacological attempts at prevention has prompted the development of alternative strategies. A mechanistic approach to the problem of restenosis is based on the assumption that creating a more satisfactory acute angioplasty result would reduce the development of restenosis. With the exception of coronary stenting, however, none of the new angioplasty devices have convincingly reached this goal. Furthermore, recent advances in the field of vascular biology have opened new avenues for a molecular approach of restenosis. Better understanding of the pathophysiology of restenosis, in conjunction with high-pace development of catheter, polymer, and virus technologies, provide opportunities to deliver agents--drugs, genes, or antisense oligonucleotides--locally, at the site of angioplasty to interfere specifically with the restenosis process. Some of these molecular strategies are currently being investigated in animal models. Clinical application of a molecular approach to prevent restenosis, however, will require close collaboration between physicians, molecular biologists, and bio-engineers.

Preventing intimal hyperplasia with photodynamic therapy using an intravascular probe

The purpose of this study was to determine the efficacy of intravascular photodynamic therapy (PDT) to prevent the development of intimal hyperplasia. Anesthetized New Zealand white rabbits underwent placement of Fogarty balloon catheters introduced via femoral artery cutdowns. Catheters were passed retrograde 10 cm into the lower abdominal aorta, inflated six times, and withdrawn toward the inguinal ligament. Rabbits were then randomly assigned to one of the following groups: group 1, drug with no light; group 2, no drug with 240 joules of light; group 3, drug plus 120 joules of light; or group 4, drug plus 240 joules of light. Uninjured carotid arteries served as negative control vessels (N) and injured but non-PDT-treated iliac artery segments served as positive controls (P). Porfimer sodium (photofrin) was administered in a dose of 5.0 mg/kg. Light was provided by a fiberoptic probe with a 1 cm cylindric diffuser attached to an argon pumped dye laser tuned to 630 nm to provide 1 W of laser light for 120 or 240 seconds. One month after PDT, rabbits were killed, perfusion fixed with glutaraldehyde, and vessels removed and examined microscopically. Intimal thickness (mean +/- SD) was calculated and expressed as ratios of the intima/media at four equal positions. Results for N, P, and groups 1, 2, 3, and 4 were 0.02 +/- 0.00, 1.18 +/- 0.71, 0.76 +/- 0.33, 0.96 +/- 0.43, 0.14 +/- 0.22, and 0.36 +/- 0.16, respectively. Intimal thickness was significantly reduced in groups 3 and 4 when compared with P, group 1, and group 2 (p < 0.001, ANOVA). These results showed that intravascular PDT was effective in reducing intimal hyperplasia following arterial injury. This may be a practical method of delivering light for PDT.

Prospects for site-specific delivery of pharmacologic and molecular therapies

The local delivery of therapeutic agents to the arterial wall represents a new strategy for the treatment of vascular diseases, including restenosis. Approaches for local, intravascular, site-specific delivery include 1) direct deposition of therapeutic agents into the vessel wall through an intravascular delivery system; 2) systemic administration of inactive agents followed by local activation; and 3) systemic administration of fusion toxins that have a specific affinity to proliferating smooth muscle cells at the angioplasty site. In addition to conventional drugs, new therapeutic agents based on molecular mechanisms, including recombinant genes and antisense oligonucleotides, are now under investigation. Although development of intravascular drug delivery devices, including those tailored to accommodate novel therapeutic agents, offers new treatment options for restenosis and other vascular diseases, certain issues that currently limit the safety and efficacy of these approaches remain to be addressed.

Photodynamic therapy inhibition of experimental intimal hyperplasia: acute and chronic effects

PURPOSE

Intimal hyperplasia (IH) is a focal arterial problem that still eludes successful therapy. We have previously demonstrated the feasibility of use of photodynamic therapy (PDT) for the acute treatment of experimental IH with light to activate an otherwise biologically inert photosensitizer. The purpose of this study was to determine the acute and long-term effects of PDT inhibition of IH on the artery wall.

METHODS

Segmental IH was induced by balloon injury localized to the cervical common carotid artery of 33 rats. The photosensitizer chloroaluminum sulfonated phthalocyanine (5 mg/kg) for the experimental group or saline solution for the control group was administered intravenously. Twenty-four hours later, all instrumented portions of arteries were irradiated at 675 nm to induce cytotoxic injury in the PDT-treated arteries as compared with laser only-treated arteries for controls. Animals were killed at 1, 2, 4, and 16 weeks.

RESULTS

There were no untoward side effects in either group. All PDT-treated arteries were devoid of smooth muscle or inflammatory cells in the treated media. There was no evidence of arterial degeneration of PDT-treated arteries. Only three arteries in the PDT group developed IH, whereas it was universal in all controls. In control arteries, immunocytochemistry with bromodeoxyuridine revealed maximal intimal and medial cell proliferation at 1 week, and morphometric analysis demonstrated a maximal IH at 2 weeks. Immunocytochemistry staining for smooth muscle cell actin was positive for the IH in control and when present in PDT-treated arteries, whereas the adventitia of PDT-treated arteries were positive after 2 weeks. Electron microscopy demonstrated early myofibroblast migration to the adventitia, and at 16 weeks occasional myofibroblasts were noted in the media of PDT-treated arteries. There was complete reendothelial cell covering of the intima by 4 weeks.

CONCLUSIONS

These in vivo data demonstrate that PDT is an effective local method for the treatment of experimental IH. There is no evidence of significant recurrence of IH or arterial degeneration. Further studies with PDT may provide novel approaches to the understanding and treatment of arterial IH.

Cardiovascular applications of laser technology

Laser technology has been evaluated for the treatment of coronary artery disease, ventricular and supraventricular arrythmias, hypertrophic cardiomyopathy, and congenital heart disease. Developments in laser angioplasty, laser thrombolysis, transmyocardial laser revascularization, photochemotherapy, laser treatment of arrhythmias and/or laser diagnostics are directed at improving upon conventional non-laser approaches, and providing new therapeutic and diagnostic options. This review will summarize the current status of the multiple applications of laser technology for cardiovascular diagnosis and therapy.