Enhanced expression of a high-molecular-weight protein in arteriosclerotic plaques

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).

Quantitative alteration of some aortic intima proteins in fatty streaks and fibro-fatty lesions

Proteins from grossly and histologically normal human aortic intimas and human aortic intima with fatty streaks or fibro-fatty lesions were extracted with 9 M urea mixture. Protein extracts were mixed with an internal absorbance calibrator (carbonic anhydrase) and subsequently separated by two-dimensional gel electrophoresis, silver stained, and quantitated by a laser beam densitometer. The vascular-origin proteins actin, tropomyosin-like proteins, tubulin, glycoprotein G35, and two myosin light chains were present in the highest amounts in normal aortic intima (27-year-old male). Quantitation of vascular-origin proteins in aortic intima with a fibro-fatty lesion from the same subject showed a slight decrease in relative amount of these proteins as compared to the normal intima. Several polypeptides (P15, P18, P60, P110b) and plasma-derived proteins not observed in the normal intima were found in fibro-fatty lesion (albumin, haptoglobin beta-chain, fibrinogen beta-chain, alpha 1-HS-glycoprotein). Other proteins which were present in very low amounts in the normal intima (transferrin, alpha 1-antitrypsin, apolipoprotein A-1, P56, P190) were found to be major proteins of intima with fibro-fatty lesion. Differences in relative amount of plasma-derived and vascular-origin proteins between normal intima and intima with fatty streaks, studied in a large number of specimens from 38 thoracic intimas and 18 paired abdominal intimas (16-34 years old) were less prominent. Statistically significant increases of the albumin/actin ratio were found in fatty streaks as compared to paired normal intimas as well as in the mean value of albumin/actin ratio in the group of fibro-fatty lesions (mean = 6.1) as compared to the group of fatty streaks (mean = 1.7) or normal intima (mean = 0.7). Several lesion unique proteins were observed; however, the frequency of the occurrence of these proteins in 41 specimens with lesion was low. No significant differences were observed in intima protein pattern and quantities of selected intima proteins between paired thoracic and abdominal aortas.

Modulation of aortic protein phosphorylation by benzo(a)pyrene: implications in PAH-induced atherogenesis

The toxicity of polycyclic aromatic hydrocarbons such as benzo(a)pyrene, 7,12-dimethylbenz(a)anthracene, and 3-methylcholanthrene has been associated with alterations in the proliferation of vascular smooth muscle cells and the development of lesions of mesenchymal origin. Because phosphorylation of endogenous substrates plays a central role in the regulation of smooth muscle cell growth, the present studies were conducted to evaluate the phosphorylation pattern of medial aortic protein upon repeated in vivo exposure of Japanese quail to benzo(a)pyrene (BaP). Medial aortic homogenates from quail treated for 10 weeks with 10 mg/kg benzo(a)pyrene or vehicle were processed for in vitro measurements of protein phosphorylation. In vitro phosphorylation of endogenous or exogenous proteins stimulated in vitro by phorbol myristate acetate/phosphatidylserine or cyclic AMP, known activators of protein kinase C and cyclic AMP-dependent protein kinase, respectively, was examined in the cytosolic and particulate fractions of homogenates from control and treated animals. Benzo(a)pyrene treatment significantly enhanced the basal phosphorylation of M(r) 113, 35, and 23 kDa proteins in the cytosolic fraction. Modest increases in the phosphorylation of M(r) 71, 52, and 38 kDa were also observed under basal conditions. No changes in the basal phosphorylation of particulate proteins were observed. Phosphorylation of endogenous protein substrates by protein kinase C in the cytosolic fraction was not altered by benzo(a)pyrene treatment. In contrast, inhibition of C-kinase-mediated phosphorylation of endogenous M(r) 272, 72, and 45 kDa proteins was observed in the particulate fraction of aortic homogenates from benzo(a)pyrene-treated quail relative to controls. Exogenous histone phosphorylation by PKC in the particulate, but not cytosolic fraction, was decreased by benzo(a)pyrene treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Human aortic intima protein composition during initial stages of atherogenesis

Protein extracted from 24 human aortic intimas (6-33 years old) with 9 M urea mixture, were studied after separation by two-dimensional gel electrophoresis (2-DE) and silver staining. The protein composition of normal intima in 4 cases, each without any gross changes in the thoracic aorta, displayed similarity. In each 2-DE protein pattern of these intimas about 150 polypeptide spots were detectable/mg of wet tissue. Major and medium polypeptides were described by relative molecular weight Mr in kilodaltons (kDa) and relative charge Cr. Major proteins found were actin (P44-18; Mr = 44 kDa; Cr = -18), tropomyosin-like proteins (P34-29, P35-28.5, P36-31) and two glycoproteins (G35-21, G35-23.5). Several new major and medium extracellular proteins were demonstrated in fibro-fatty lesions as well as in the lesion-free intimas adjacent to lesion in 3 cases. Many of these proteins appeared to originate from plasma: albumin, IgG, alpha 1-antitrypsin, transferrin, haptoglobin beta-chain, apo A-I, apo A-II, fibrinogen beta-chain, alpha 2-HS glycoprotein and alpha 1-antichymotrypsin. Visual comparison of intimal protein patterns from 17 different cases with varying degree of fatty streaks in the thoracic aorta, showed variability in 2 polypeptides P32-17.8 and P32-19.8 as well as 4 plasma proteins albumin, alpha 1-antitrypsin, transferrin and apo A-I. This study suggests that changes in protein composition may occur in the human aortic intima during the initial histological stages of atherogenesis providing potentially useful markers for their identification and pathophysiological evaluation.