Effects of enhanced consumption of fruit and vegetables on plasma antioxidant status and oxidative resistance of LDL in smokers supplemented with fish oil

OBJECTIVE

To determine whether consumption of five portions of fruit and vegetables per day reduces the enhancement of oxidative stress induced by consumption of fish oil.

SUBJECTS

A total of 18 free-living healthy smoking volunteers, aged 18-63 y, were recruited by posters and e-mail in The University of Reading, and by leaflets in local shops.

DESIGN

A prospective study.

SETTING

Hugh Sinclair Unit of Human Nutrition, School of Food Biosciences, The University of Reading, Whiteknights PO Box 226, Reading RG6 6AP, UK.

INTERVENTION

All subjects consumed a daily supplement of 4 x 1 g fish oil capsules for 9 weeks. After 3 weeks, they consumed an additional five portions of fruits and vegetables per day, and then they returned to their normal diet for the last 3 weeks of the study. Fasting blood samples were taken at the ends of weeks 0, 3, 6 and 9.

RESULTS

The plasma concentrations of ascorbic acid, lutein, beta-cryptoxanthin, alpha-carotene and beta-carotene all significantly increased when fruit and vegetable intake was enhanced (P<0.05). Plasma concentrations of alpha-tocopherol, retinol and uric acid did not change significantly during the period of increased fruit and vegetable consumption. Plasma oxidative stability, assessed by the oxygen radical absorbance capacity (ORAC) assay, also increased from weeks 3-6 (P<0.001) but not in association with increases in measured antioxidants. Lag phase before oxidation of low-density lipoprotein (LDL) significantly decreased in the first 3 weeks of the study, reflecting the incorporation of EPA and DHA into LDL (P<0.0001). Subsequent enhanced fruit and vegetable consumption significantly reduced the susceptibility of LDL to oxidation (P<0.005).

CONCLUSION

Fish oil reduced the oxidative stability of plasma and LDL, but the effects were partially offset by the increased consumption of fruit and vegetables.

Tumor-derived expression of vascular endothelial growth factor is a critical factor in tumor expansion and vascular function

There is considerable controversy concerning the importance of tumor-derived angiogenic factors to the neovascularization of solid tumors. Tumor, endothelial, and stromal expression of vascular endothelial growth factor (VEGF) have been hypothesized to be critical for tumor angiogenesis. To determine the relative contribution of tumor versus nontransformed tissue expression of VEGF to tumor growth, we used gene targeting and cre-loxP recombination to generate embryonic stem cell lines in which VEGF can be conditionally deleted. These lines were used to derive mouse embryonic fibroblast lines with null mutations in both alleles of VEGF. Upon immortalization and H-ras transformation, we used these VEGF null fibroblasts to make fibrosarcomas in immunocompromised mice. We report that tumorigenic VEGF expression is critical for ras-mediated tumorigenesis, and the loss of tumorigenic expression causes dramatic decreases in vascular density and vascular permeability and increases in tumor cell apoptosis.

mAngiogenin-3, a target gene of oncoprotein E2a-Pbx1, encodes a new angiogenic member of the angiogenin family

Angiogenins are proteins in the pancreatic ribonuclease superfamily that utilize their ribonuclease activity to induce formation of new blood vessels. Recently we identified a new member of the angiogenin gene family, mouse angiogenin-3, by virtue of its transcriptional activation in NIH3T3 fibroblasts coincident with transformation by the chimeric leukemia oncogene, E2a-Pbx1. Here we have isolated the cDNA encoding mouse angiogenin-3 and used it to produce the protein in E. coli. We demonstrate that mouse angiogenin-3 is a ribonuclease whose activity and specificity towards tRNA and dinucleotide substrates differ from those of mouse angiogenin or of mouse angiogenin-related protein, a non-angiogenic factor. Mouse angiogenin-3 induced angiogenesis in both the chicken embryo chorioallantoic membrane assay and the rat cremaster muscle. Electron microscopy revealed that endothelial cells within vessels induced by both mouse angiogenin-3 and mouse angiogenin contain fenestrations similar to those observed in endothelial cells from neovasculature induced by vascular endothelial growth factor and basic fibroblast growth factor. Mouse angiogenin-3 also induced other molecular events typical of rapidly proliferating endothelial cells, such as increases in rough endoplasmic reticulum, polysomes, and mitochondria.

Influence of host microvascular environment on tumour vascular endothelium

This review will focus on the tumour microvascular endothelium; how it is derived, modulated by angiogenic factors, and how the structure and function is influenced by the host tissue microenvironment.

Host microvasculature influence on tumor vascular morphology and endothelial gene expression

We have previously demonstrated that vascular endothelial growth factor-165 (VEGF), a tumor-secreted angiogenic factor, can acutely and chronically induce fenestrations in microvascular endothelium (Cancer Res 1997, 57:765-772). Because the morphology and function of microvascular endothelium differs from tissue to tissue, we undertook studies to examine whether the neovasculature in tumors also differed depending upon tumor location. Four tumor types implanted in the brain or subcutis in nude mice were studied: a murine rhabdomyosarcoma (M1S), a murine mammary carcinoma (EMT), and two human glioblastomas (U87 and U251). In addition, we studied Chinese hamster ovary cells stably transfected with human VEGF165. As previously reported, tumors grown in the subcutaneous space had a microvasculature that was fenestrated and had open endothelial gaps. The identical tumors when grown in the brain also had fenestrated endothelium and vessels with open endothelial gaps, but they were drastically reduced in occurrence. Open endothelial gaps were not seen in all tumors implanted in the brain (EMT and M1S), although fenestrated endothelium was always seen. VEGF and VEGF receptors were measured in tumors from both locations by immunoblotting and competitive polymerase chain reaction, respectively. VEGF amount was not significantly different between the tumor locations. Interestingly, total tumor vascular mRNA expression of both Flk-1 and Flt-1 was greater in tumor vessels derived from the brain compared with tumor vessels derived from subcutaneous tissues. These results demonstrate that the host microvascular environment determines the morphology and function of the tumor vasculature and that endothelia from different tissues vary in their ability to express the VEGF receptors given identical stimuli.

Regulation of transport pathways in tumor vessels: role of tumor type and microenvironment

Novel anti-neoplastic agents such as gene targeting vectors and encapsulated carriers are quite large (approximately 100-300 nm in diameter). An understanding of the functional size and physiological regulation of transvascular pathways is necessary to optimize delivery of these agents. Here we analyze the functional limits of transvascular transport and its modulation by the microenvironment. One human and five murine tumors including mammary and colorectal carcinomas, hepatoma, glioma, and sarcoma were implanted in the dorsal skin-fold chamber or cranial window, and the pore cutoff size, a functional measure of transvascular gap size, was determined. The microenvironment was modulated: (i) spatially, by growing tumors in subcutaneous or cranial locations and (ii) temporally, by inducing vascular regression in hormone-dependent tumors. Tumors grown subcutaneously exhibited a characteristic pore cutoff size ranging from 200 nm to 1.2 microm. This pore cutoff size was reduced in tumors grown in the cranium or in regressing tumors after hormone withdrawal. Vessels induced in basic fibroblast growth factor-containing gels had a pore cutoff size of 200 nm. Albumin permeability was independent of pore cutoff size. These results have three major implications for the delivery of therapeutic agents: (i) delivery may be less efficient in cranial tumors than in subcutaneous tumors, (ii) delivery may be reduced during tumor regression induced by hormonal ablation, and (iii) permeability to a molecule is independent of pore cutoff size as long as the diameter of the molecule is much less than the pore diameter.

Immunoisolation and partial characterization of endothelial plasmalemmal vesicles (caveolae)

Plasmalemmal vesicles (PVs) or caveolae are plasma membrane invaginations and associated vesicles of regular size and shape found in most mammalian cell types. They are particularly numerous in the continuous endothelium of certain microvascular beds (e.g., heart, lung, and muscles) in which they have been identified as transcytotic vesicular carriers. Their chemistry and function have been extensively studied in the last years by various means, including several attempts to isolate them by cell fractionation from different cell types. The methods so far used rely on nonspecific physical parameters of the caveolae and their membrane (e.g., size-specific gravity and solubility in detergents) which do not rule out contamination from other membrane sources, especially the plasmalemma proper. We report here a different method for the isolation of PVs from plasmalemmal fragments obtained by a silica-coating procedure from the rat lung vasculature. The method includes sonication and flotation of a mixed vesicle fraction, as the first step, followed by specific immunoisolation of PVs on anticaveolin-coated magnetic microspheres, as the second step. The mixed vesicle fraction, is thereby resolved into a bound subfraction (B), which consists primarily of PVs or caveolae, and a nonbound subfraction (NB) enriched in vesicles derived from the plasmalemma proper. The results so far obtained indicate that some specific endothelial membrane proteins (e.g., thrombomodulin, functional thrombin receptor) are distributed about evenly between the B and NB subfractions, whereas others are restricted to the NB subfraction (e.g., angiotensin converting enzyme, podocalyxin). Glycoproteins distribute unevenly between the two subfractions and antigens involved in signal transduction [e.g., annexin II, protein kinase C alpha, the G alpha subunits of heterotrimeric G proteins (alpha s, alpha q, alpha i2, alpha i3), small GTP-binding proteins, endothelial nitric oxide synthase, and nonreceptor protein kinase c-src] are concentrated in the NB (plasmalemma proper-enriched) subfraction rather than in the caveolae of the B subfraction. Additional work should show whether discrepancies between our findings and those already recorded in the literature represent inadequate fractionation techniques or are accounted for by chemical differentiation of caveolae from one cell type to another.

Leukotrienes in ulcerative colitis: results of a multicenter trial of a leukotriene biosynthesis inhibitor, MK-591

BACKGROUND & AIMS

Leukotrienes (LTs) are believed to be important in the pathogenesis of ulcerative colitis (UC). The aim of this study was to determine whether inhibition of LT biosynthesis with a 5-lipoxygenase inhibitor (MK-591) induces remission in patients with mild to moderate UC.

METHODS

One hundred eighty-three patients with mild to moderately active UC enrolled in this randomized parallel group, double-blind study. Patients received placebo or MK-591 at a dose of 12.5, 50, or 100 mg twice daily for 8 weeks. A subset of patients underwent rectal dialysis to determine LTB4 concentration.

RESULTS

MK-591 reduced LTB4 concentrations in rectal dialysate at the final determination. The median percent of baseline LTB4 concentration for 100 mg taken twice daily was 1.4% (n = 4); for 50 mg taken twice daily, 16.5% (n = 6); for 12.5 mg taken twice daily, 12% (n = 6); and for placebo, 78% (n = 6). There was no correlation between reduction of LTB4 and remission. Patients in remission at week 8 were as follows: placebo, 9 of 44 (20.5%); 100 mg taken twice daily, 11 of 43 (25.6%); 50 mg taken twice daily, 8 of 49 (16.3%); and 12.5 mg taken twice daily, 4 of 47 (8.5%) (P > 0.10).

CONCLUSIONS

MK-591 markedly inhibited LT biosynthesis, but it did not differ significantly from placebo in clinical efficacy. Inhibition of LT biosynthesis was not effective as a single therapeutic modality in active UC.

Neovasculature induced by vascular endothelial growth factor is fenestrated

We have reported previously that topical administration of vascular endothelial growth factor165 (VEGF) to a microvascular bed supplied with a continuous endothelium can rapidly induce the formation of endothelial fenestrations (W. G. Roberts and G. E. Palade, J. Cell Sci., 108: 2369-2379, 1995). From these results, we hypothesized that tumor vasculature, in general, may also be fenestrated because it has been reported that tumor secretion of VEGF causes the surrounding host vasculature to invade and feed the growing tumor. Using electron microscopy to characterize the endothelial cell morphology in tumor vessels from either the periphery or the core of the tumor and immunoblotting to detect secreted VEGF, we analyzed the vasculature of human and murine neoplastic tumors grown s.c. in male nude mice. To clarify the role of VEGF165 two models were used: (a) Chinese hamster ovary (CHO) cells stably transfected with hu VEGF165 and injected into mice (VEGF:CHO tumors); and (b) slow-release pellets containing purified VEGF or basic fibroblast growth factor implanted on the rat cremaster muscle. All tumors had vessels with fenestrated endothelium, open interendothelial junctions, and clustered fused caveolae. From all of the peripheral tumor vessels observed, fenestrated endothelium was observed in 41% from EMT, 35% from M1S, 37% from U87, and 56% from VEGF:CHO tumors, whereas surrounding skin and muscle, from which tumor vessels were derived, had fenestrated endothelium in 2 and 0% of all vessels, respectively. Additionally, further analysis revealed a substantial decrease in the anionic glycocalyx on the luminal face of the fenestral diaphragms in endothelium from tumors (especially VEGF:CHO) when compared to intestine or pancreas. Because the host tissue microvascular endothelium which supplies the tumor is not fenestrated, tumors can transform nonproliferating, nonfenestrated vessels into proliferating vessels, many of which have fenestrated endothelium. These data provide evidence that chronic VEGF exposure can induce fenestrations in nonfenestrated endothelium similar to the fenestrated endothelium found in tumor vessels.

Acid suppression by famotidine 20 mg twice daily or 40 mg twice daily in preventing relapse of endoscopic recurrence of erosive esophagitis

Control of esophageal acid exposure is important in treating patients with gastroesophageal reflux disease (GERD). After complete healing of esophagitis, most patients will relapse within 6 months if left untreated. This multicenter, randomized, double-masked, placebo-controlled trial, conducted in the United States, examined whether two famotidine dosing regimens are effective in extending the time in remission for patients with moderate-to-severe erosive esophagitis. Of 172 patients enrolled, 31 received placebo, 69 received famotidine 20 mg twice daily (BID) , and 72 received famotidine 40 mg BID. Endoscopy was scheduled at baseline and at months 3 and 6. Patients assessed global heartburn and symptom relief at months 3 and 6 relative to the start of the study. Life table (Kaplan-Meier) relapse rates at 6 months were 22% (P < 0.001 vs placebo) for famotidine 20 mg BID, 11% (P < 0.001 vs placebo) for famotidine 40 mg BID, and 62% for placebo. Compared with placebo, patients in the famotidine groups were significantly less likely to note global symptomatic deterioration, as measured by the distribution of global assessment responses. The incidence of clinical and laboratory adverse experiences was similar among treatment groups. For maintenance treatment of GERD, famotidine 20 mg BID and 40 mg BID are more effective than placebo in extending the time in remission.

Increased microvascular permeability and endothelial fenestration induced by vascular endothelial growth factor

The vascular endothelial growth factor (VEGF) was originally described as vascular permeability factor due to its ability to increase microvascular permeability to plasma proteins. However, the vessel types (arteriolar, venular, and capillary) affected by VEGF and the modification of endothelial morphology in response to increased permeability induced by VEGF in vivo have not been precisely documented. By topical application or intradermal injection of recombinant human VEGF-165 we find that VEGF increases the permeability of postcapillary venules as well as muscular venules and capillaries. Surprisingly, we also find that endothelia of small venules and capillaries become fenestrated within 10 minutes of VEGF application. Fenestrations appeared in vascular beds which do not normally have fenestrated endothelium, namely the cremaster muscle and skin. Histamine, saline, and heat-inactivated VEGF do not cause fenestrations. Increased permeability is completely inhibited when VEGF is cleared by immunoprecipitation with anti-VEGF monoclonal antibodies. The VEGF effect on permeability is unlike that of any other mediator described to date since both muscular venules and capillaries are affected.

Inositol polyanions. Noncarbohydrate inhibitors of L- and P-selectin that block inflammation

Selectins are cell adhesion molecules known to support the initial attachment of leukocytes to inflamed vascular endothelium through their recognition of carbohydrate ligands such as the tetrasaccharide sialyl Lewisx (Neu5Ac alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc-). In the present study, we describe the inhibition of L- and P-selectin function by inositol polyanions, simple 6-carbon ring structures that have multiple ester-linked phosphate or sulfate groups. In a purified component competition assay, binding of L- and P-selectin-Ig fusion proteins to immobilized bovine serum albumin-sialyl Lewisx neoglycoprotein was inhibited by inositol hexakisphosphate (InsP6, IC50 = 2.1 +/- 1.4 microM and 160 +/- 40 microM), by inositol pentakisphosphate (InsP5, IC50 = 1.4 +/- 0.2 and 260 +/- 40 microM), and by inositol hexakissulfate (InsS6, IC50 = 210 +/- 80 microM and 2.8 +/- 0.9 mM); E-selectin-Ig binding was unaffected. Inositol polyanions diminished the adhesion of LS180 colon carcinoma cells to plates coated with L- and P-selectin-Ig but not with E-selectin-Ig. Inositol polyanions blocked polymorphonuclear leukocyte (PMN) adhesion to COS cells expressing recombinant transmembrane P-selectin but not to those expressing E-selectin. In addition, inositol polyanions diminished PMN adhesion to activated endothelial cells under rotation-induced shear stress, a process known to require L-selectin function. In vivo, the effects of inositol polyanions were studied in two murine models of acute inflammation. Intravenously administered InsP6 (two doses of 40 mumol/kg) inhibited PMN accumulation in thioglycolate-induced inflammation (55 +/- 10% inhibition) and in zymosan-induced inflammation (61 +/- 4% inhibition). InsP5 and InsS6 also inhibited inflammation in these models, although higher doses were required for InsS6. In conclusion, inositol polyanions are noncarbohydrate small molecules that inhibit L- and P-selectin function in vitro and inflammation in vivo.

Heparin oligosaccharides bind L- and P-selectin and inhibit acute inflammation

Initial attachment of leukocytes to the vessel wall at sites of inflammation is supported by a family of carbohydrate-binding adhesion molecules called the selectins. Selectin ligands include sialyl-Lewis x (sLex, Neu5Ac alpha 2-3Gal beta 1-4[Fuc alpha 1-3]GlcNAc--) and related structures. We report here that defined heparin oligosaccharides interact with the selectins. Heparin chains containing four or more monosaccharide residues inhibited the function of L- and P-selectin, but not E-selectin, in vitro. In a competition enzyme-linked immunosorbent assay measuring inhibition of solution-phase selectin-Ig fusion proteins (selectin-Ig) binding to immobilized bovine serum albumin-sLex neoglycoprotein, a heparin-derived tetrasaccharide mixture inhibited 50% of L- and P-selectin-Ig binding (IC50) at 200 +/- 40 mumol/L and 850 +/- 110 mumol/L, respectively. A single hexasulfated tetrasaccharide (delta UA2S alpha 1-4GlcNS6S alpha 1-4IdoA2S alpha 1-4GlcNS6S) was particularly active against L- and P-selectin-Ig (IC50 = 46 +/- 5 mumol/L and 341 +/- 24 mumol/L). By comparison, the tetrasaccharide sLex was not inhibitory at concentrations up to 1 mmol/L. In cell adhesion assays, heparin tetrasaccharides reduced binding of neutrophils to COS cells expressing P-selectin but not to COS cells expressing E-selectin. They also blocked colon cancer cell adhesion to L- and P-selectin but not E-selectin. In a model of acute inflammation, intravenously administered heparin tetrasaccharides diminished influx of neutrophils into the peritoneal cavities of thioglycollate-treated mice. We conclude that heparin oligosaccharides, including non-anticoagulant tetrasaccharides, are effective L- and P-selectin inhibitors in vitro and have anti-inflammatory activity in vivo.

Chloroaluminum sulfonated phthalocyanine partitioning in normal and intimal hyperplastic artery in the rat. Implications for photodynamic therapy

Photodynamic therapy, the light activation of photosensitizers into cytotoxic mediators, has been a successful treatment for experimental intimal hyperplasia (IH). To understand the basis of the photosensitizer chloroaluminum sulfonated phthalocyanine (CASPc)-mediated photoinhibition of intimal hyperplasia in the rat common carotid artery model, we studied photosensitizer partitioning in hyperplastic as compared to normal arterial tissue. Serum clearance of CASPc is exponential with, a half-life of 300 minutes. Laser-induced fluorescence and spectrofluorimetric analyses of artery tissue demonstrated an approximately 60% lower uptake and retention of CASPc by normal arterial tissue as compared to arteries with IH; the differences become more pronounced at 24 h. Fluorescent microscopy of arterial tissue demonstrated increased uptake of the CASPc by the artery with IH. However, by 24 h it is primarily the IH tissue that has retained the CASPc, with clearance of the dye from the media of normal or hyperplastic arteries. These data demonstrate that IH, like neoplastic tissue, has an increased accumulation of CASPc compared to normal artery. The preferential partitioning into hyperplastic tissue has implications for therapeutic targeting of this cellular population with photodynamic therapy.

Tumor-secreted vascular permeability factor/vascular endothelial growth factor influences photosensitizer uptake

The role of vascular permeability in the preferential accumulation of photosensitizers in tumor tissue was investigated. Two murine tumors [experimental mammary tumor carcinoma (EMT-6) and methylcholanthrene-induced rhabdomyosarcoma (M1S)] and a human bladder carcinoma (EJ) were grown s.c. on the flank in athymic nude mice and analyzed for in vivo vessel permeability, vascular permeability factor (VPF) secretion, and accumulation of the photosensitizer, chloroaluminum sulfonated phthalocyanine. In vivo tumor vessel permeability and vascular volume were quantitated by measuring Evans blue extravasation and accumulation of a high molecular weight fluoresceinated dextran, respectively. VPF was isolated from serum-free tumor cell conditioned medium using heparin-Sepharose affinity chromatography. Dot and Western blots stained with anti-VPF antiserum positively identified VPF in samples from each tumor. Chloroaluminum sulfonated phthalocyanine pharmacokinetics in tumor-bearing mice were measured using a fiber-based spectrofluorometer. In vivo vessel permeability was found to be greatest in M1S tumors, next in EMT-6 tumors and finally in EJ tumors. Consistent with in vivo data, M1S and EMT-6 tumor cells in culture secrete significantly more VPF than EJ tumor cells. Chloroaluminum sulfonated phthalocyanine accumulation was approximately 2 times greater in M1S and EMT-6 tumors compared to EJ tumors. Our data present evidence that photosensitizer accumulation can be correlated to in vivo tumor vessel permeability and VPF secretion of that tumor. Taken together, the data support the hypothesis that vascular permeability differences among tumors play a significant role in the uptake and retention of photodynamic agents.

Photodynamic therapy of arteries. A novel approach for treatment of experimental intimal hyperplasia

BACKGROUND

Photodynamic therapy (PDT) uses light activation of otherwise nontoxic dyes for the production of reactive oxygen species that cause cell injury and death.

METHODS AND RESULTS

The inhibition of intimal hyperplasia (IH) by PDT was studied in the balloon injury model of the rat carotid artery. Chloroaluminum-sulfonated phthalocyanine (CASPc) was the drug chosen for PDT because it does not produce skin photosensitivity and has a high absorption peak of light at 675 nm, a wavelength with good tissue penetration. A pilot study indicated that CASPc administration with laser radiant exposure of 100 J/cm2 resulted in a homogeneous, circumferential effect on the whole artery. Male Sprague-Dawley rats received the balloon catheter injury to the left common carotid artery (day 0) and were equally divided into two groups. Nine rats received either CASPc (5 mg/kg i.v., n = 6) or saline (n = 3) at day 2, before IH was present, and nine rats received CASPc or saline in the same manner on day 7, when IH was already present. Twenty minutes after drug injection, the distal left common carotid artery was irradiated under saline with 675-nm laser light at 100 mW/cm2 for 10(3) seconds (100 J/cm2). At this low laser irradiance, there are no thermal effects, but photoactivation of CASPc occurs. The rats were killed at day 14 after balloon injury when IH reaches a maximum. The arteries were harvested after perfusion-fixation for light microscopy, histological and computerized morphometric evaluation, and transmission electron microscopy (TEM) analysis. The cross-sectional areas of the neointima were measured in the PDT-treated arteries and in the laser-only control arteries. There was a significant mean +/- SD decrease of IH in the PDT-irradiated segments of the arteries (0.06 +/- 0.05 mm2) versus the laser-only control ones (0.17 +/- 0.07 mm2) (t test, p less than 0.001), with no statistical difference between the day 2 and day 7 treated rats. Lack of IH was correlated in 90% of cases with histological absence of medial smooth muscle cells or inflammatory cells, but no other structural injury was identified. TEM analysis showed early evidence of PDT-mediated cytotoxic effects at 4 hours and the absence of collagen or elastic tissue structural alterations.

CONCLUSIONS

These data demonstrated that PDT can effectively inhibit the IH response when it is used before or during induction of cellular proliferation in this acute model. Although the long-term implications of PDT in arteries need to be defined, this technique may offer a new method for understanding and treating IH.

Role of neovasculature and vascular permeability on the tumor retention of photodynamic agents

A variety of photodynamic sensitizers (chloroaluminum sulfonated phthalocyanine, tetraphenyl porphine sulfonate, mono-L-aspartyl chlorin e6, Photofrin, chlorin e6, and Uroporphyrin dihydrochloride I) were characterized by their ability to be retained in EMT-6 tumors growing in BALB/c mice. Two properties uniquely associated with tumors, proliferating neovasculature and vascular permeability, were tested for their relative importance in retaining the photosensitizer. A chick embryo model was used to compare photosensitizer uptake/retention in proliferating and nonproliferating neovasculature with retention in proliferating nonvascular tissue. Our results provide evidence that photosensitizers which are preferentially retained by tumors have a selective affinity for proliferating neovasculature. The chloroaluminum sulfonated phthalocyanine and tetraphenyl porphine sulfonate compounds possess the greatest affinity for proliferating neovasculature relative to nonvascular tissue, while the phthalocyanine has the largest tumor/normal differential in vivo of all the photosensitizers tested. Chlorin e6 and uroporphyrin dihydrochloride I were the only photosensitizers which were not retained in greater amounts by tumor tissues relative to normal tissues. Using a delayed-type hypersensitivity reaction, extended and constant vascular permeability was induced in BALB/c mice. Vascular permeability was quantitated by Evans blue extraction from the delayed-type hypersensitivity sites. Interestingly, leaky vessels alone did not result in photosensitizer retention, as seen with tumors. These data demonstrate that tumor-retained photosensitizers possess a selective affinity for proliferating neovasculature and that vascular permeability alone is not sufficient to retain these sensitizers.

Photodynamic therapy of spontaneous cancers in felines, canines, and snakes with chloro-aluminum sulfonated phthalocyanine

This is the first report on the photodynamic treatment with a second-generation sensitizer, chloro-aluminum sulfonated phthalocyanine (CASPc) of spontaneously arising tumors and on the photodynamic therapy (PDT) of snake neoplasms. Each of 10 cats, 2 dogs, and 3 snakes presenting with a variety of tumor types (squamous cell carcinoma, mast cell malignant tumor, and mixed carcinoma/sarcoma) was given an intravenous injection of 1 mg of CASPc per kilogram body weight 48 hours prior to irradiation with 675-nm light. Some larger tumors (greater than 1.5 cm deep) were surgically debulked prior to PDT. No significant systemic toxicity or skin photosensitization was observed in any animal. The tumor responses were comparable to those seen with conventional cryotherapy, hyperthermia, or surgery. PDT with CASPc of these cases led to 67% (12 of 18) complete response, 22% (4 of 18) partial response, and 11% (2 of 18) no response (less than 50% reduction in tumor size). Four cases could not be evaluated. Since the overall tumor response to CASPc is very good, and the problem of skin photosensitivity is nonexistent, it is expected that using CASPc-PDT to eradicate human tumors would also yield comparable results. Further studies with long-term follow-up are necessary to optimize the use of CASPc-PDT in veterinary and human medicine.

Prevalence of cryptosporidiosis in patients undergoing endoscopy: evidence for an asymptomatic carrier state

PURPOSE

We sought to determine the presence of the parasite cryptosporidium in the duodenal aspirates of patients undergoing routine upper gastrointestinal endoscopy.

PATIENTS AND METHODS

The study consisted of 169 patients undergoing upper endoscopy or endoscopic retrograde cholangiopancreatography. Immunocompromised patients were not included in the study population. Samples were aspirated from the second portion of the duodenum. Biopsy specimens were also obtained. Three randomly passed stool samples were obtained from 75% of the patients who were found to have cryptosporidium in the duodenum.

RESULTS

Overall, cryptosporidium oocysts were identified in 12.7% of patients. There was no significant difference in the prevalence of the parasite in any subgroup of procedure or symptom complex. Half of those (46.7%) with positive aspirates had demonstrable cryptosporidium in stool samples, although none of the patients had diarrhea. No patient had detectable cryptosporidium in biopsy samples of the duodenum.

CONCLUSION

The findings suggest a surprisingly high asymptomatic carrier rate for cryptosporidium.

Singlet oxygen generation of porphyrins, chlorins, and phthalocyanines

The production of singlet oxygen was measured indirectly for three classes of photosensitizers: porphyrins (Photofrin II, TPPS4), chlorins (MACE, DACE), and a phthalocyanine (CASPc). Buffered solutions of sensitizers and singlet oxygen acceptors were irradiated with a CW dye laser and the oxygen depletion was monitored electrochemically with a Clark-type microelectrode. A comparison of oxygen-depletion rate constants and quantum efficiencies yields the order of efficiency of the sensitizers: TPPS4 greater than MACE greater than PII greater than DACE greater than CASPc. For singlet oxygen acceptors the order was: furfuryl alcohol greater than imidazole greater than tryptophan. CHO cell suspensions were also used as acceptors. Here the order of efficiency (per absorbed photon) was PII greater than MACE approximately CASPc. Expressed in terms of oxygen depletion per cell the order was CASPc approximately PII greater than MACE. When performing cell clonogenicity studies the order of efficiencies, expressed as percentage cell kill per unit weight of sensitizer, was CASPc greater than PII greater than MACE approximately DACE. The discrepancy between the efficiencies of sensitizers to generate singlet oxygen and their cytotoxicity was explained in terms of photodegradation (for the chlorins), intracellular localization (for PII), and contributions from a Type I mechanism (for CASPc).

Skin photosensitivity and photodestruction of several potential photodynamic sensitizers

The major side effect associated with porphyrins (Photofrin II) in clinical photodynamic therapy is skin photosensitivity. In order to avoid this deleterious reaction, patients must remain out of the sunlight for approximately 1 month. A possible procedure to reduce the amount of skin photosensitivity is to photodegrade (photobleach) the compound in the skin. In this study, we report a series of experiments describing the photodegradation rates of two photosensitizers currently receiving attention due to their potential for use in PDT (mono L-aspartyl chlorin e6 and chloroaluminum sulfonated phthalocyanine). These compounds are compared to Photofrin II (PfII). Experiments consisted of determining photodegradation rates and efficiencies of the sensitizers in (i) phosphate buffered saline (PBS), (ii) PBS with fetal calf serum (to enhance absorption and simulate cellular binding or deaggregation), (iii) Chinese Hamster Ovary cells, and (iv) Balb/c mice. We performed two standardized skin sensitivity assays using the Hartely albino guinea pig irradiated with a UV blue point lamp and Balb/c mice irradiated with the therapeutic wavelength of each sensitizer. In addition, we performed a cell clonogenicity assay comparing photodegraded and fresh PfII on CHO cells. The photodegraded PfII exhibited significant phototoxicity, although the fluorescence was bleached by more than 70%. The results show that PfII causes major skin photosensitization and that the other compounds produce no substantial skin sensitivity. Our studies suggest that photodegradation of PfII with 630 nm light has little influence on the phototoxicity of the compound. In addition, skin sensitivity was not alleviated with prior photobleaching with 405 nm light.

In vitro photosensitization I. Cellular uptake and subcellular localization of mono-L-aspartyl chlorin e6, chloro-aluminum sulfonated phthalocyanine, and photofrin II

The mechanisms of cellular uptake, subcellular localization, and cellular retention kinetics of the photosensitizers photofrin II (PfII), mono-L-aspartyl chlorin e6 (MACE), and chloro-aluminum sulfonated phthalocyanine (CASPc) are reported in this paper. Each photosensitizer's cellular uptake mechanism was determined by preferentially inhibiting endocytosis by chilling cells to 2 degrees C, while allowing diffusion across the membrane. Subcellular localization was studied by computer-enhanced low-light level video fluorescence microscopy, while flow cytometry was used to determine uptake and retention kinetics. The results indicate that PfII enters the cell primarily by diffusion across the membrane, whereas MACE and CASPc enter the cell through endocytosis.

In vitro photosensitization II. An electron microscopy study of cellular destruction with mono-L-aspartyl chlorin e6 and photofrin II

Primary sites of subcellular destruction with photofrin II (PfII) and mono-L-aspartyl chlorin e6 (MACE) were determined by transmission electron microscopy (TEM). Potorous tridactylus (PTK2) cells were grown in Rose chambers and incubated for 24 hr with a sensitizer concentration sufficient to provide 100% mortality. Cells were irradiated with laser light and fixed and processed for electron microscopy at various times post-irradiation. The results indicate that PfII initially destroys mitochondria, whereas MACE destroys lysosomes. Both conclusions are consistent with fluorescence subcellular localization studies.

Mechanism of tumor destruction following photodynamic therapy with hematoporphyrin derivative, chlorin, and phthalocyanine

The effect of photodynamic therapy on the tumor microvasculature in the first few hours after treatment was studied at the light and electron microscopy levels. BALB/c mice with EMT-6 tumor received ip injections of hematoporphyrin derivative, chlorin, or phthalocyanine, and 24 hours later, the tumors were treated with light at 100 J/cm2 at the appropriate therapeutic wavelength for each photosensitizer. Animals were killed and their tumors removed at time 0, 30 minutes, 1 hour, and 2, 4, 6, 8, 12, 16, and 24 hours after treatment. The results indicate that for all three sensitizers the effects of photodynamic therapy leading to rapid necrosis of tumor tissue are not the result of direct tumor cell kill but are secondary to destruction of the tumor microvasculature. The first observable signs of destruction occur in the subendothelial zone of the tumor capillary wall. This zone, composed of dense collagen fibers and other connective tissue elements, is destroyed in the first few hours after phototherapy. However, the ultrastructural changes seen in this zone are different for the hematoporphyrin derivative, compared with chlorin and phthalocyanine. Binding of photosensitizers to the elements in this zone as well as altered permeability and transport through the endothelial cell layer because of the increased intraluminal pressure may be key features of tumor destruction.

In vitro effects of the long-acting somatostatin analogue SMS 201-995 on electrolyte transport by the rabbit ileum

We have investigated the in vitro properties of SMS 201-995, a long-acting somatostatin analogue, on electrolyte transport in rabbit ileum. Similar to native somatostatin, serosal addition of this compound inhibits electrogenic anion secretion and stimulates neutral sodium and chloride absorption. Both compounds have similar maximal effects on ion transport; however, the ED50 of SMS 201-995 (2.4 X 10(-10) M) was 60 times less than that for somatostatin. In addition, unlike somatostatin, no inherent tachyphylaxis was observed in response to SMS 201-995. The antisecretory profile of SMS 201-995 was also compared with that of epinephrine. Unlike treatment with epinephrine, pretreatment of tissues with SMS 201-995 did not directly inhibit electrogenic anion secretion stimulated by vasoactive intestinal polypeptide, calcium ionophore A23187, and bethanechol. In contrast, this agent blocked vasoactive intestinal polypeptide and bethanechol inhibition of net sodium absorption. We conclude that SMS 201-995 has several unique in vitro properties that may explain its greater biologic activity compared with that of somatostatin. Its effects on secretagogue-stimulated electrogenic anion secretion and electroneutral NaCl absorption appear to differ.

In vitro characterization of monoaspartyl chlorin e6 and diaspartyl chlorin e6 for photodynamic therapy

The characteristics of two new chlorin photosensitizers were studied in cell culture by determining phototoxicity, subcellular localization, and photophysical properties. Monoaspartyl chlorin e6 (MACE) and diaspartyl chlorin e6 (DACE) are new photosensitizers that show promise for use in photodynamic therapy. These chlorins are pure, monomeric compounds as determined by high-pressure liquid chromatography. Both compounds absorb substantially at a longer wavelength (664 nm) than does dihematoporphyrin ether-ester (DHE). Tumor diagnosis with the use of fluorescence should be facilitated due to the purity of the compounds and the single fluorescence emission peak. Phototoxicity dose-response curves of the sensitizers were completed using a standard clonogenic assay to determine cell viability. The chlorins showed good sensitizing capabilities with light. In addition, subcellular localization of MACE, DACE, and DHE was studied using fluorescence microscopy. Whereas DHE was located throughout the cytoplasm, the primary site of localization of the chlorins appeared to be in the lysosome. The results demonstrate that MACE and DACE are effective photosensitizing agents in vitro and compare favorably to DHE.

In vivo studies on the utilization of mono-L-aspartyl chlorin (NPe6) for photodynamic therapy

The in vivo photosensitizing efficacy of mono-L-aspartyl chlorin has been studied by determining the percentage of BALB/c mice cured at varying doses of drug. Using an EMT-6 tumor model, animals received i.p. injections of mono-L-aspartyl chlorin (0.5-100 mg/kg) and then were subsequently exposed to light at 664 nm. Tumor biopsies were taken from selected animals sacrificed at 24 h after treatment and routine histopathological sections made. The other animals remained in the dark for a period of 6 weeks to determine the cure rate. Our results show that mono-L-aspartyl chlorin is an effective tumor localizer that brings about the selective degradation of tumor tissue following light exposure.