Role of thromboxane and prostacyclin release on photodynamic therapy-induced tumor destruction.

Thromboxane and prostacyclin levels in serum were measured following photodynamic therapy (PDT) to assess the role of these vasoactive agents on vascular damage and tumor destruction. Sprague Dawley rats were given injections i.v. of Photofrin II doses ranging from 0 to 25 mg/kg. Twenty-four h later, the right hindlimbs of animals bearing chondrosarcoma tumor or controls were exposed to 0-135 J/cm2 630 nm light. Serum concentrations of thromboxane and prostacyclin were determined by radioimmunoassay. A dose-response relationship was established between the amount of photosensitizer administered and the light dose delivered with the release of thromboxane immediately following PDT. Treatment of tumor induced higher levels of thromboxane than did the treatment of tumor-free tissue, suggesting that tumor is more sensitive to PDT-induced damage. The porphyrin and light doses found to induce the release of thromboxane into serum were the same as those required to evoke vascular stasis and tumor destruction. Prostacyclin release was not altered by PDT. The administration of indomethacin (10 mg/kg, i.p.) 3 h before light treatment was found to suppress the intravascular release of thromboxane at the highest porphyrin and light doses studied. Indomethacin treatment also inhibited PDT-induced vascular stasis and tumor destruction, suggesting that the release of thromboxane is linked to these events. Since prostacyclin levels in serum were unchanged following PDT treatment of tumor and controls, thromboxane release appears to be a specific response to PDT and may mediate the vascular stasis observed following PDT.

Effects of photodynamic therapy using mono-L-aspartyl chlorin e6 on vessel constriction, vessel leakage, and tumor response.

The effect of photodynamic therapy using mono-L-aspartyl chlorin e6 (NPe6) on both direct cytotoxicity and vascular damage was examined. Sprague-Dawley rats bearing chondrosarcoma tumor were given i.v. injections of 5 or 10 mg/kg NPe6 and exposed to 135-J/cm2 664-nm laser light either 4 or 24h after NPe6 injection. The percentage of viable tumor cells was estimated either immediately after the completion of light treatment or 24 h after treatment using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Measurements of arteriole constriction and venule leakage in normal cremaster tissues were made during and 1 h after the light treatment. Tumor response was evaluated for the 4 different NPe6 dose and time combinations. Both direct tumor cytotoxicity and vascular stasis were observed during light treatment. Vessel leakage did not occur. Blood flow stasis was a result of platelet aggregation and the mechanical obstruction of flow rather than vessel constriction. The magnitude of direct cytotoxicity and vascular response was dependent on both the amount of NPe6 delivered and the delay between injection and light treatment. Tumor cure was found in animals either when given high NPe6 doses or when treated early after NPe6 injection. Treatment regimens which maximized the effect of both vascular stasis and direct tumor cytotoxicity were found to produce the best tumor response. Dose combinations which produced vascular stasis with minimal early cytotoxicity did not result in cure. The combined mechanisms of damage after photodynamic therapy using NPe6 suggests that this photosensitizer may have specific advantages for clinical use and provides a benchmark for the development of new photosensitizers.

The role of microvascular damage in photodynamic therapy: the effect of treatment on vessel constriction, permeability, and leukocyte adhesion.

Intravital microscopy of the rat cremaster muscle was used to evaluate changes in vessel constriction, vessel permeability, and leukocyte adhesion during and after photodynamic therapy (PDT). Animals were given Photofrin doses of 0-25 mg/kg i.v. 24 h before treatment. Cremaster muscles were exposed to 135 J/cm2 light at 630 nm. Animals given 5 mg/kg Photofrin showed no vessel constriction or increase in vessel permeability to albumin. Doses of 10 and 25 mg/kg Photofrin caused a dose-related constriction of arterioles which was observed within the first minutes of illumination at the higher drug dose. After the initial constriction, arteriole response to PDT was biphasic in nature, with some vessels relaxing to nearly control levels while others remained fully constricted. Constriction of venules occurred only at the highest porphyrin dose studied (25 mg/kg) and was delayed in comparison to arteriole constriction. Photofrin doses which produced arteriole constriction also caused an increase in venule permeability to albumin, which occurred shortly after the start of light treatment and was progressive with time. Leakage began at specific sites along the venule wall but became uniform along the entire length of the venule by 1 h after treatment. Changes in the adherence of polymorphonuclear leukocytes to venule endothelium were also observed with PDT. Photofrin doses of 25 mg/kg and 45 J/cm2 light were sufficient to cause polymorphonuclear leukocytes to become adherent to the vessel wall. A second group of animals was given indomethacin trihydrate to examine the involvement of cyclooxygenase products such as thromboxane in vessel response to PDT. Animals given 5 mg/kg indomethacin intraarterially 1 h before light treatment showed no constriction of arterioles or venules at all Photofrin and light doses studied. No increases in venule permeability to albumin were seen in this group of animals. This suggests that cyclooxygenase products including thromboxane are important in causing vessel constriction and changes in permeability during PDT. The initiating event which causes the release of these vasoactive agents remains unknown.

Photodynamic therapy using a protoporphyrinogen oxidase inhibitor.

The use of endogenously created porphyrins as an alternative to photosensitizer injection for photodynamic therapy is a rapidly evolving area of study. One common method to induce porphyrin synthesis and accumulation in cells is the topical, oral, or parenteral administration of 5-aminolevulinic acid, a precursor for heme biosynthesis. Porphyrin accumulation may also be elicited by the use of enzyme inhibitors of the heme biosynthetic pathway. Groups of DBA/2 mice bearing SMT-F mammary tumors were placed on a diet containing 0-4000 ppm of a protoporphyrinogen oxidase inhibitor, FP-846. This agent blocks a critical step in porphyrin metabolism and results in elevated intracellular levels of protoporphyrin IX. Light treatment of tumors produced both initial and long-term regression that was dependent on the amount of inhibitor, the duration of inhibitor exposure to animals, and the amount of light used in PDT. Tumor regression occurred without significant destruction of normal tissues in the treatment field and without initial vascular constriction or blood flow stasis. Tumor cure in animals given 4000 ppm FP-846 in feed for 3 days and 300 J/cm2 602-670 nm light (23% cure) was similar to the response in animals given 10 mg/kg Photofrin and the same light dose (20%).

Photodynamic therapy using mono-L-aspartyl chlorin e6 (Npe6) for the treatment of cutaneous disease: a Phase I clinical study.

The activity of a new photosensitizer, mono-L-aspartyl chlorin e6 (Npe6), was assessed in an ascending dose Phase I study for patients with superficial tumor. Eleven patients, with a total of 14 tumor sites, were treated with photodynamic therapy (PDT) using Npe6. Lesions included recurrent adenocarcinoma of the breast, basal cell carcinoma, and squamous cell carcinoma. The phototherapy protocol consisted of a single i.v. injection of 0.5-3.5 mg/kg Npe6, followed 4 h later by 25-100 j/cm2 at 664 nm of light. PDT using Npe6 caused no significant toxicity with the exception of temporary generalized skin photosensitivity. In all cases, light treatment caused immediate tissue blanching, followed by a marked necrosis of the tumor mass. Regression of tumor occurred over 24-48 h after the light treatment and was followed by the formation of a heavy eschar over the tumor site. Tumor regression was short-lived at Npe6 doses of 1.65 mg/kg and below. In two of three patients, tumor regression was either incomplete or tumors recurred within the 12-week observation period. Increasing the Npe6 dose to 2.5 or 3.5 mg/kg combined with 100 J/cm2 of light energy resulted in better control of tumor regrowth with 66% (6/9) of sites remaining tumor-free through 12 weeks observation. This increased tumor response came at the expense of the tissue selectivity observed at Npe6 doses of 1.65 mg/kg and below. There was no apparent selectivity for destruction of tumor compared with normal skin at Npe6 doses of 2.5 mg/kg and above. These data demonstrate that Npe6 is both an effective and safe photosensitizer for use in PDT and provide the impetus for continued study in Phase II clinical trials.

Efficacy and safety of a topical gel formulation of recombinant human platelet-derived growth factor-BB (becaplermin) in patients with chronic neuropathic diabetic ulcers. A phase III randomized placebo-controlled double-blind study.

OBJECTIVE: To compare the efficacy and safety of topically applied recombinant human platelet-derived growth factor-BB (rhPDGF-BB) (becaplermin) with placebo gel in patients with chronic diabetic neuropathic ulcers of the lower extremities. RESEARCH DESIGN AND METHODS: This multicenter double-blind placebo-controlled phase III trial included 382 patients with type 1 or type 2 diabetes and chronic ulcers of at least 8 weeks' duration. After sharp debridement of the ulcer, patients were randomized to receive becaplermin gel 30 micrograms/g, becaplermin gel 100 micrograms/g, or placebo gel, in conjunction with a standardized regimen of good wound care until complete wound closure was achieved or for a maximum of 20 weeks. Moist saline-soaked gauze dressings were changed twice daily with study medication applied by patients or caregivers at the evening dressing change. Safety was assessed by monitoring adverse events (AEs) and by clinical laboratory evaluations. RESULTS: Compared with placebo gel, becaplermin gel 100 micrograms/g significantly increased the incidence of complete wound closure by 43% (50 vs. 35%, P = 0.007) and decreased the time to achieve complete wound closure by 32% (86 vs. 127 days; estimated 35th percentile, P = 0.013). AEs reported during treatment or during a 3-month follow-up period were similar in nature and incidence across all treatment groups. CONCLUSIONS: Becaplermin gel 100 micrograms/g, in conjunction with good wound care, significantly increased the incidence of complete wound closure and significantly reduced the time to complete closure of chronic diabetic neuropathic ulcers. The safety profile of becaplermin gel was similar to that of placebo gel.

A comparison of the effects of photodynamic therapy on normal and tumor blood vessels in the rat microcirculation.

The effects of light activation of the tumor photosensitizer dihematoporphyrin ether (DHE) were studied in the microcirculation of the rat cremaster muscle. Arterioles and venules in an implanted chondrosarcoma were studied by in vivo television microscopy and were compared to normal vessels of the same size elsewhere in the preparation and in control preparations. Activation with green light (530-560 nm, 200 mW/cm2, 120 J/cm2) 48 h after intraperitoneal injection of DHE (10 mg/kg body wt) resulted in significant narrowing of diameters of red blood cell columns in tumor arterioles and venules. The response in normal and control arterioles and venules was not significantly different from that seen in the tumor vessels except that the control arterioles did not remain significantly constricted during the treatment period. Treatment resulted in stasis of blood flow in 90% of tumor and normal arterioles at the completion of light activation. In venules, stasis of blood flow was observed in 75% of tumor and 70% of normal vessels. Vasoconstriction was the primary response in arterioles, while thrombosis predominated in venules. Morphologic assessment of light-activated vessels in the cremaster preparation by transmission electron microscopy revealed platelet aggregation with damage to endothelial cells and smooth muscle cells. Perivascular effects observed included interstitial edema and damage to skeletal muscle cells. In the tumor-bearing preparation, no direct cytotoxic effect on the tumor cells was shown. The surrounding vessels exhibited similar vascular stasis, but the lining cells appeared minimally affected. Photoactivation of DHE results in significant changes in the microcirculation which lead to stasis of blood flow. In this model, the response was similar for the normal microvasculature and for the microcirculation of an implanted chondrosarcoma. These effects may account, in part, for the mechanism of action of photodynamic therapy.

Use of endoscopic retrograde cholangiopancreatography in the management of biliary complications after laparoscopic cholecystectomy.

BACKGROUND: Current options in the management of bile duct injuries caused by laparoscopic cholecystectomy include diagnostic and therapeutic endoscopic retrograde cholangiopancreatography (ERCP) and open laparotomy with direct repair. The goal of this review was to clarify the role and evaluate the potential of endoscopic techniques to diagnose and treat bile duct injuries. METHODS: The records of all patients undergoing biliary tract surgery at our hospitals for the period from December 1989 to February 1993 were reviewed. Twenty-five patients were identified with bile duct injuries during laparoscopic cholecystectomy. RESULTS: ERCP was performed for diagnostic or therapeutic purposes in 22 of the 25 patients; successful opacification of the biliary tree was achieved in 21 (95%) of the 22 patients. In these 21 patients the location and nature of the injury were identified correctly in 19 (90%). In six of the 25 cases, interventional ERCP was used as the primary treatment of these injuries. Successful treatment was achieved in five (83%) of the six cases, although laparotomy was required in two to drain the abscess cavity better. Open surgical repair was performed as the primary treatment in the remaining 19 patients. Interventional ERCP with stenting was required in six and transhepatic stenting in one of these patients as an adjunctive treatment for stricture or persistent fistula. Six (86%) of these seven patients have been treated successfully to date in this manner. CONCLUSIONS: ERCP is a uniquely helpful diagnostic and therapeutic technique in the management of laparoscopic biliary complications. Open surgical repair remains the procedure of choice for patients with loss of bile duct tissue or long complex strictures. ERCP with sphincterotomy, balloon dilatation, and stenting is an accepted alternative approach for bile leaks (fistulas) and treatment of shorter strictures resulting from either the initial laparoscopic injury or the initial repair.

The treatment of malignant endobronchial obstruction with laser ablation.

BACKGROUND: We compared a new endoscopic treatment for malignant endobronchial obstruction known as photodynamic therapy (PDT) with the more established therapy of neodymium: yttrium-aluminum garnet laser (Nd:YAG) therapy. METHODS: A retrospective review was conducted of the medical records at our institution from 1988 to 1999 of patients treated for bronchial obstruction by thermal laser vaporization (Nd:YAG) or by PDT using the tunable dye laser in combination with a light-sensitive dye (PDT). The Nd:YAG procedure vaporized the obstructing neoplasm, whereas the PDT procedure photoablated the obstruction. Thirty-day mortality and morbidity rates were analyzed for both treatment groups using chi-square analysis. RESULTS: Of the 102 patients who were suitable for review, 83 received treatment with the Nd:YAG laser and 19 patients received treatment with PDT. Morbidity rates were comparable in both groups (22% for Nd:YAG vs 31% for PDT; P > .05). Equally common complications in both groups were respiratory failure and hypoxemia. Five Nd:YAG patients (6%) died within 30 days after treatment (3 of respiratory failure, 2 of massive hemoptysis), whereas 2 patients (10%) in the PDT group (1 of massive hemoptysis, 1 of acute myocardial infarction) died (P > . 05). CONCLUSIONS: PDT and Nd:YAG have similar mortality and morbidity rates. In our experience, PDT is a better choice for the treatment of malignant bronchial obstruction because it is technically easier, potentially safer, and does not require general anesthesia.

The effect of photodynamic therapy on tumor oxygenation.

Oxygen microelectrodes were used to measure tumor partial pressure of oxygen (PO2) before and after photodynamic therapy (PDT) in a rat transplantable subcutaneous chondrosarcoma. Before PDT there was a gradient of PO2 from the superficial layers of the tumor (PO2 = 46 +/- 6 mm Hg) toward the center of the tumor (PO2 = 10 +/- 1 mm Hg). Mean tumor PO2 (21 +/- 2 mm Hg) was significantly reduced to 3 +/- 1 mm Hg 1 hour after PDT, and this reduction in PO2 persisted 4 hours (8 +/- 2 mm Hg) and 24 hours (6 +/- 1 mm Hg) after PDT. The largest percentage decrease in PO2 occurred at a depth of only 50 microns into the tumor. Inasmuch as PDT has been shown to decrease blood flow, our data suggest that PDT actions on blood vessels in the peripheral areas of the tumor are of major importance for eliciting the tumor hypoxia that contributes to tumor necrosis after PDT.

Effect of photodynamic therapy on blood flow in normal and tumor vessels.

The aim of this series of experiments was to determine the dynamic blood flow changes that occur in normal and neoplastic tissues during photodynamic therapy. Mice bearing SMT-F tumors and rats with transplanted chondrosarcomas were injected with graded doses of dihematoporphyrin ether. Studies of changes in single-vessel and whole-tumor blood flow were carried out with 630 nm light activation. A helium neon laser Doppler velocimeter was used to stimulate dihematoporphyrin ether, as well as to measure changes in flow velocity in both single-vessel and whole-tumor models. There was a reduction of flow velocity in all vessels and tumors in animals injected with 1 to 40 mg/kg dihematoporphyrin ether intraperitoneally. The extent of flow reduction was related to drug dose administered. Decreases in blood flow began within 10 seconds of light stimulation and were maximal within 5 minutes. Both normal and tumor vessels responded similarly. We conclude that photodynamic therapy leads to significant microcirculatory changes that may be pertinent to the mechanism of tumor necrosis.

Metatarsal head resection for diabetic foot ulcers.

Twenty-five diabetic patients underwent 34 metatarsal head resections for chronic neuropathic ulceration. All ulcers were located on the plantar surface beneath the metatarsophalangeal joints. The ulcers had been present for a mean of 9.0 +/- 7.8 months before operation, yet they healed in a mean of 2.4 +/- 1.6 months postoperatively. None recurred during the mean follow-up time of 13.8 +/- 11.0 months. Moderate peripheral vascular disease, impaired renal function, and retinopathy did not affect the time required for ulcer healing. There were two complications: one wound infection and one hematoma. No extremities were lost, and none of the patients suffered any long-term sequelae. We recommend metatarsal head resection to achieve the healing of chronic diabetic foot ulcers under the metatarsophalangeal joints.

The influence of renal function on diabetic foot ulceration.

We examined the effect of renal function on the formation, severity, and outcome of diabetic foot lesions. Information was collected from a retrospective hospital chart survey and analyzed by univariate and multivariate linear regression analysis. Creatinine clearance, peripheral neuropathy, and peripheral vascular disease were all found to be independently associated with formation of foot lesions, indicating that each of these acts by distinct biologic mechanisms. Renal function had no bearing on the severity of lesions or on their eventual healing. We conclude that foot ulcers are more likely to develop in diabetic patients who also suffer from renal impairment, but they are no less likely to heal than are those in patients with normal renal function. We further conclude that attempts to preserve functional limbs in these patients are justified.

Diversion of duodenal contents: its effect on the production of experimental gastric cancer.

Diversion of duodenal contents after gastroenterostomy and vagotomy did not protect 240 laboratory rats from increased risk of gastric carcinoma. They were divided into three groups of 80: group 1 received 0.9 mg of 3-methylcholanthrene injected submucosally into the gastric antrum; groups 2 and 3 had bilateral truncal vagotomy and gastroenterostomy, with carcinogen injected into the gastric submucosa near the anastomosis; group 3 also had total duodenoenteric diversion. Blind histopathologic examination of surviving rats during necropsy eight months later disclosed that cancer had developed in six of 60 (10%) group 1 rats, in 23 of 71 (33%) group 2 rats, and in seven of 27 (22%) group 3 rats. Compared with group 1, groups 2 and 3 had an increased incidence of gastric cancer but did not differ from one another in this regard.

The effects of aspirin on microvasculature after photodynamic therapy.

The effects of aspirin (acetylsalicylic acid: ASA) on vessel behavior and tumor response were measured during and after photodynamic therapy (PDT). Changes to vessel constriction, macromolecular leakage, tumor interstitial pressure, and tumor response were examined. Animals were randomly placed into treatment groups and injected with 0-25 mg/kg Photofrin and given 0 or 135 J/cm2 light treatment. The light treatment was standardized to 75 mW/cm2 at 630 nm over a 30 min treatment interval (135 J/cm2). The treatment groups were further subdivided to receive Photofrin alone or Photofrin plus 100 mg/kg ASA. A cremaster muscle model in Sprague-Dawley rats was used to directly observe microvascular response and changes in vessel permeability to macromolecules. A tumor interstitial pressure model was designed to measure pressure changes in a chondrosarcoma tumor over time. This model indirectly measures macromolecular leakage, among other factors, in the tumor tissue. Groups of 10-20 rats were implanted subcutaneously with chondrosarcoma and were subjected to PDT to assess tumor response to the various treatments. Statistically significant differences in vessel leakage and changes in interstitial pressure were observed between animals given ASA plus PDT as compared to animals given PDT alone. The administration of ASA significantly inhibited venule leakage of albumin and reduced increases in interstitial pressure after treatment. The use of ASA had no effect on vessel constriction or tumor response after PDT. These findings suggest that the increases in vessel permeability observed during and after PDT, using Photofrin, do not significantly contribute to tumor response.

Changes in tumor interstitial pressure induced by photodynamic therapy.

This study has examined the changes in tumor interstitial pressure exhibited during and after photodynamic therapy (PDT). The kinetics of these changes are marked by an initial decrease, followed by a rapid rise in tumor interstitial pressure. We have also employed two inhibitory agents to evaluate the different components of the pressure curve. Specially designed pressure chambers were seeded with chondrosarcoma and implanted subcutaneously in rats. Animals were injected with 0-50 mg/kg Photofrin II (i.v.) 7 days post-implantation and tumors were exposed to 0-540 J/cm2 630 nm 24 h later. Interstitial pressure was monitored via a transducer connected to the implanted chamber. Additional groups of animals were injected with either indomethacin (an inhibitor of thromboxane synthesis) or Ketanserin (a serotonin antagonist) before light treatment. Porphyrin doses of 10 mg/kg and above (135 J/cm2), or light doses of 135 J/cm2 and above (25 mg/kg Photofrin II) were effective in modifying interstitial pressure. Porphyrin doses greater than 25 mg/kg, or light doses greater than 270 J/cm2 produced no further increases in interstitial pressure. Animals given indomethacin (10 mg/kg i.p.) exhibited the initial decrease in pressure during light treatment, but showed no increase past baseline levels. Animals given Ketanserin (10 mg/kg i.p.) demonstrated no decrease in pressure during PDT, but showed the same elevations in pressure as controls. This suggests that two independent mechanisms account for the different components of the pressure curve, and that serotonin release may occur during PDT.

The effects of thrombocytopenia on vessel stasis and macromolecular leakage after photodynamic therapy using photofrin.

Several studies have reported thrombus formation and/or the release of specific vasoactive eicosanoids, suggesting that platelet activation or damage after photodynamic therapy (PDT) may contribute to blood flow stasis. The role of circulating platelets on blood flow stasis and vascular leakage of macromolecules during and after PDT was assessed in an intravital animal model. Sprague-Dawley rats bearing chondrosarcoma on the right hind limb were injected intravenously (i.v.) with 25 mg/kg Photofrin 24 h before light treatment of 135 J/cm2 at 630 nm. Thrombocytopenia was induced in animals by administration of 3.75 mg/kg of rabbit anti-rat platelet antibody i.v. 30 min before the initiation of the light treatment. This regimen reduced circulating platelet levels from 300,000/mm3 to 20,000/mm3. Reductions in the luminal diameter of the microvasculature in normal muscle and tumor were observed in control animals given Photofrin and light. Venule leakage of macromolecules was noted shortly after the start of light treatment and continued throughout the period of observation. Animals made thrombocytopenic showed none of these changes after PDT in either normal tissues or tumor. The lack of vessel response correlated with the absence of thromboxane release in blood during PDT. These data suggest that platelets and eicosanoid release are necessary for vessel constriction and blood flow stasis after PDT using Photofrin.

The effects of thromboxane inhibitors on the microvascular and tumor response to photodynamic therapy.

Vascular stasis and tissue ischemia are known to cause tumor cell death in several experimental models after photodynamic therapy (PDT); however, the mechanisms leading to this damage remain unclear. Because previous studies indicated that thromboxane release is implicated in vessel damage, we further examined the role of thromboxane in PDT. Rats bearing chondrosarcoma were injected with 25 mg/kg Photofrin (intravenously) 24 h before treatment. Light (135 J/cm2, 630 nm) was delivered to the tumor area after injection of one of the following inhibitors: (1) R68070: a thromboxane synthetase inhibitor; (2) SQ-29548: a thromboxane receptor antagonist; and (3) Flunarizine: an inhibitor of platelet shape change. Systemic thromboxane levels were determined. Vessel constriction and leakage were evaluated by intravital microscopy. Tumor response was assessed after treatment. Thromboxane levels were decreased more than 50% with SQ-29548 as compared to controls. Thromboxane levels in animals given R68070 and Flunarizine remained at baseline levels. SQ-29548 and R68070 reduced vessel constriction compared to controls, while Flunarizine totally prevented vessel constriction. R68070 and SQ-29548 inhibited vessel permeability compared to PDT controls; Flunarizine did not. Animals given these inhibitors showed markedly reduced tumor cure. These results indicate that the release of thromboxane is linked to the vascular response in PDT.

The microvascular effects of photodynamic therapy: evidence for a possible role of cyclooxygenase products.

Photodynamic therapy (PDT) of malignant tumours may involve the interruption of tumor and peritumor microcirculation. We have studied the effect of light activation of the photosensitizing drug dihematoporphyrin ether (DHE) on rat subcutaneous arterioles and the modulation of these effects by cyclooxygenase inhibitors indomethacin and acetyl salicylic acid (ASA). Animals received DHE 48 h prior to light activation and additionally either indomethacin, ASA or saline 3 h prior to treatment. Light activation (630 nm, 60 J/cm2) resulted in a significant reduction to 62 +/- 2% SEM of initial blood flow. This effect was inhibited by ASA (98 +/- 8% SEM) and indomethacin (87 +/- 8% SEM). Results from the administration of various doses of both compounds indicate that this inhibition is dose related. The data presented here show that PDT causes a significant reduction in blood flow in normal arterioles and that this effect was inhibited by ASA and indomethacin indicating that prostaglandins or thromboxane A2 may play an important role in the microvascular response to PDT.

The effects of photodynamic therapy using differently substituted zinc phthalocyanines on vessel constriction, vessel leakage and tumor response.

The effects of four different zinc phthalocyanines were studied during and after photodynamic therapy (PDT). Measurements of vessel constriction, vessel leakage, tumor interstitial pressure, eicosanoid release, and tumor response of chondrosarcoma were made in Sprague-Dawley rats. Animals were injected intravenously with 1 mumol/kg of mono-, di-, or tetrasulfonated zinc phthalocyanine, or 1 mumol/kg of a zinc phthalocyanine substituted with four tertiary butyl groups. Tissues were exposed to 400 J/cm2 670 nm light 24 h after photosensitizer injection. An additional group of animals was given indomethacin before treatment. The use of the monosulfonated and tertiary butyl substituted zinc phthalocyanines in PDT caused the release of specific eicosanoids, caused vessel constriction, and induced venule leakage and increases in tumor interstitial pressure. Tumor cures of 27% and 7% were observed. Photodynamic therapy using the disulfonated zinc phthalocyanine did not induce vessel constriction or the release of eicosanoids, however, tumor cure was 43%. The use of the tetrasulfonated zinc phthalocyanine caused intermediate effects between the mono- and disulfonated compounds. The administration of indomethacin to animals completely inhibited the effects of PDT using the monosulfonated compound but had minimal effects on treatment using the disulfonated compound. This suggests that the monosulfonated and disulfonated compounds act by different mechanisms of destruction.