Hematoporphyrin binding to cultured aortic smooth muscle cells from spontaneously atherosclerotic turkey

Identification of a variant collagen alpha 3 (VI) in early-stage avian arteriosclerotic plaques

A 170 kD protein, prominent in soluble extracts of rooster arteriosclerotic plaques, has been partially characterized. The protein was eluted from a size exclusion column in a broad molecular weight fraction > 100 kD. Concanavalin A and a murine polyclonal antibody raised against the isolated 170 kD protein reacted with the protein on Western blots. The 170 kD protein had an isoelectric point of approximately 5.4 and was digested by collagenase treatment. Amino acid analysis of a 70 kD fragment of the protein closely resembled that for chick collagen alpha 3 (VI). A 13 amino acid sequence within this 70 kD fragment had 69% identity and 85% homology to chicken collagen alpha 3 (VI). Soluble protein extracts from cultured plaque smooth muscle cells (SMC), and from healthy artery SMC, contained low levels of the protein. These cellular extracts also reacted with the polyclonal antibody described above. Although the protein lacks absolute amino acid sequence identity with collagen alpha 3 (VI) it shares with it many biochemical features, suggesting that the 170 kD protein is a variant species of chick collagen alpha 3 (VI).

Determining the optimal dose of Photofrin in miniswine atherosclerotic plaque

The purpose of this study was to determine the lowest dose of Photofrin (P) that would produce a 3:1 or greater ratio between atherosclerotic (AS) and control arterial walls. Aortoiliac AS was created in 24 Yucatan miniswine by a combination of balloon endothelial injury and 2% cholesterol and 15% lard diet for 7 weeks. Arteriography was then performed to demonstrate AS lesions. Following this, swine were given intravenously P in one of the following single dosages: 2.5, 1.0 or 0.5 mg/kg. Twenty-four hours later, swine were sacrificed and aortoiliac and control carotid artery segments removed and photographed with ultraviolet light to differentiate fluorescent from nonfluorescent areas. Arterial specimens were submitted for histologic analysis and chemical extraction for determination of fluorescence using a spectrofluorometer. Tissue concentration (ng/g tissue) of P from AS vessels were: Group I, 130.4 +/- 82.7; Group II, 10.0 +/- 1.2; and Group III, 9.1 +/- 0.6, respectively (P < 0.05). Ratios of P concentration in AS: control vessels were: Group I, 8.1 +/- 13.7; Group II, 1.1 +/- 0.2; and Group III, 0.9 +/- 0.1, respectively (P < 0.05). These results demonstrated that a P dose of 2.5 mg/kg provided at least a 3:1 ratio between AS: control artery wall.

Assessing Photofrin uptake in atherosclerosis with a fluorescent probe: comparison with photography and tissue measurements

The purpose of this study was to assess Photofrin porfimer sodium (P*) concentration in atherosclerotic plaque (ASP) using a fluorescence detector (Fluoroprobe) compared with fluorescent photography and chemical extraction of P*. ASP was created in the aortoiliac segments of Yucatan miniswine by a combination of balloon endothelial injury and 2% cholesterol and 15% lard diet for 7 weeks. At that time, swine were given P* I.V. in one of the following single dosages: Group I, 2.5; Group II, 1.0; or Group III, 0.5 mg/kg. Swine were sacrificed 24 hours later and aortoiliac and control carotid artery segments removed. Fluorescence was determined from these segments using photographic techniques, the Fluoroprobe, and a spectrofluorometer after chemical extraction. ASP were identified in all swine using photography and the Fluoroprobe. The intensity of fluorescence measured with the Fluoroprobe for Groups I to III was 1,098 +/- 524, 471 +/- 337, and 295 +/- 173 units, respectively (P < 0.01). The tissue concentration of P* in ASP from each group was 130.4 +/- 82.7, 10.0 +/- 1.2, and 9.1 +/- 0.6 ng/g, respectively (P < 0.01). There was a linear correlation between the fluorescence intensity measured with the Fluoroprobe and the extracted tissue concentration (r = 0.88, P < 0.0001). This study showed that a fluorescent detector such as the Fluoroprobe accurately detects the uptake of P* into atherosclerotic plaque.

In vitro uptake of dicarboxylic porphyrins by human atheroma. Kinetic and analytical studies

Human atheromatous aorta segments as well as presumably disease-free control aorta were obtained at autopsy. They were incubated with solutions of various purified dicarboxylic porphyrins including hematoporphyrin (HP) and hydroxyethylvinyldeuteroporphyrin (HVD), and with solutions of Photofrin. Selective labelling of the atheroma was shown by macroscopic and microscopic observations of the characteristic porphyrin fluorescence associated with the atheromatous plaques. The time dependence of the uptake, monitored by absorption spectrophotometry or by high performance liquid chromatography, was inferred from the disappearance of the porphyrins in the incubation medium. Significant binding was observed in the absence of albumin or serum proteins. The uptake of HP was less than that of the more hydrophobic compounds HVD or Photofrin when these porphyrins were used alone. The presence of albumin or serum drastically reduces atheroma labelling. Some competition between HP and HVD for binding sites is also seen. The present results do indicate that hydrophobic porphyrins have an intrinsic affinity for atheroma and that they can be taken up through passive processes. Taking into account previous data on animal models (Photochem. Photobiol. (1989), 731-737), it appears however that, in vivo, interactions with proteins and pharmacokinetics will primarily determine plaque labelling.