[Soluble P-selectin - a marker of platelet activation and vessel wall injury: increase of soluble P-selectin in plasma of patients with myocardial infarction, massive atherosclerosis and primary pulmonary hypertension]

AIM

A comparative analysis of the content of the soluble form of cell adhesion protein P-selectin in the blood plasma of patients with acute myocardial infarction (AMI), massive atherosclerosis (MA) and primary pulmonary hypertension (PPH), investigation of the relationship between plasma content of P-selectin and known markers of platelets and endothelial cells activation, preliminary assessment of the prognostic value of P-selectin determination.

MATERIALS AND METHODS

This study included 16 patients with AMI, 20 patients with MA, 21 patients with PPH and 18 healthy donors. The follow-up was 1-5 years. End-points in the group of patients with AMI were recurrent acute coronary syndrome and coronary artery by-pass operation, in the group with MA--thrombotic complications (acute coronary syndrome, ischemic stroke) and in the group with PPH--death. P-selectin was measured by ELISA and platelet factor 4 (PF4), thromboxane B2 (TXB2), endothelin-I and stable prostacyclin metabolite 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) by means of commercial ELISA kits.

RESULTS

Mean level of P-selectin in blood plasma of patients with AMI (1 day) (361 +/- 18 ng/ml), MA (410 +/- 31 ng/ml) and PPH (627 +/- 83 ng/ml) was increased in comparison with the group of healthy donors (269 +/- 12 ng/ml) (everywhere p < 0.001). In AMI, P-selectin was increased on day 1 only, on days 2, 3 and 10-14 of the disease the level of P-selectin was significantly lower than on day 1 and did not differ from the control level in the group of donors. In patients with MA a significant correlation was detected between plasma content of P-selectin and platelet activation marker PF4 (r = 0.606, P = 0.007) and in patients with PPH between the content of P-selectin and another platelet activation marker TXB2 (r = 0.622, p = 0.013). However, no correlation was found in PPH patients between the content of P-selectin and markers of endothelial activation and/or damage (endothelin-1 and 6-keto-PGF1 alpha). Difference in the concentration of P-selectin in patients with or without end-points during the follow-up period was detected in patients with AMI (353 +/- 14 ng/ml and 451 +/- 24 ng/ml, p = 0.009) and PPH (477 +/- 58 ng/ml and 927 +/- 184 ng/ml, p = 0.017) but not with MA (426 +/- 37 ng/ml and 361 +/- 24 ng/ml, p = 0.295).

CONCLUSION

The level of P-selectin in plasma was increased in patients with acute thrombosis (AMI, 1 day) as well as in patients without clinical signs of thrombosis but with a massive injury of the vasculature (MA and PPH). The increase of P-selectin was, presumably, caused by its secretion from activated platelets since its concentration in plasma correlated with platelet concentration but not endothelial activation markers. Preliminary data indicate that blood plasma soluble P-selectin may be considered as a potential prognostic marker in AMI and PPH.

[Effect of age and radiation exposure on the frequency of translocations and dicentrics detected by FISH method in human lymphocytes]

The frequencies of translocations and dicentrics detected by "chromosome painting" in lymphocytes were estimated in 115 healthy donors and in 273 people exposed to uncontrolled irradiation at low doses 1-4 years ago. Age responses of both types of exchanges at the age range from 3 to 85 years fit to quadratic model. The frequency of translocations grew faster with age than the frequency of dicentrics. The yields of stable exchanges in exposed people was significantly higher than those in control donors of corresponding ages.

Production of soluble P-selectin by platelets and endothelial cells

The distribution of a soluble form of a cell adhesion molecule, P-selectin, in human platelets and cultivated endothelial cells has been studied by enzyme-linked immunosorbent assay (ELISA). The concentration of soluble P-selectin in the blood plasma of healthy donors and patients with abnormal platelet count has also been determined. P-selectin was measured in the Triton X-100 lysate of platelets and endothelial cells (total P-selectin), in the 100,000g supernatant obtained after sedimentation of the membrane fraction from the homogenate of sonicated platelets and endothelial cells (intracellular soluble P-selectin), in the supernatant of activated and nonactivated platelets, and in the culture medium of endothelial cells. A soluble form of P-selectin which did not coprecipitate with the membrane fraction was detected in platelets and accounted for approximately 10% of the total P-selectin. Platelet activation by thrombin, ADP, or a thromboxane A2 analog resulted in the secretion of 30-50% of the intracellular soluble P-selectin. Measurements of P-selectin in endothelial cell culture revealed that endothelium from aorta contained about twofold more P-selectin than endothelium from umbilical vein. Intracellular soluble P-selectin was identified in both types of endothelial cells. In endothelial cells from the umbilical vein this form made up approximately 10% of the total P-selectin. Soluble P-selectin was also detected in the medium of cultivated endothelial cells, where its content correlated with the total cellular P-selectin. Concentration of P-selectin in blood plasma strongly correlated with the platelet count in the blood of healthy donors and patients with thrombocytosis and thrombocytopenia. These data indicate that platelets serve as one of the main source of plasma P-selectin. However, the presence of P-selectin in the plasma of patients with severe thrombocytopenia suggests that endothelium can also be involved in plasma P-selectin production. Thus, in vitro experiments as well as measurements of plasma P-selectin have shown that both platelets and endothelial cells can produce a soluble form of the protein. Platelet-derived soluble P-selectin and plasma P-selectin were shown to react with antibodies against the cytoplasmic domain of P-selectin. These data prove that at least part of soluble P-selectin is produced by synthesis employing special mRNA which lacks the sequence encoding the transmembrane domain, but not by the proteolytic shedding of the extracellular portion of membrane P-selectin.

[Distribution of Cs-137 in bodies of inhabitants of the Vitebsk Region]

The content of 137Cs in the whole human body and certain internal organs has been determined using gamma-spectrometry method for inhabitants of Vitebsk Region. The average activity of 137Cs in the whole human body was obtained to be 0.038 mkCu. The unevenness of radiocesium accumulation in the investigated internal organs has been noted. The average annual doses from 137Cs for some human organs have been calculated.

[Sulfated polysaccharides as inhibitors of receptor activity of P-selectin and P-selectin-dependent inflammation]

The inhibitory effects of sulfated polysaccharides-fucoidan and heparin on P-selectin-ligand interaction in vitro and on the ability of fucoidan to inhibit the leukocyte extravasation in rat peritonitis were studied. The lectin activity of P-selectin in vitro was based on its ability to bind lectin-labeled synthetic ligand, Sialyl-Lea/x, conjugated with polyacrylamide (PAA). Fucoidan and heparin inhibited binding of labeled ligand to both purified P-selectin and the activated platelets expressing P-selectin on their surface. The inhibitory effect of fucoidan 100-fold higher than that of heparin. As P-selectin plays an important role at an earlier stage of the inflammation process, the antiinflammatory action of fucoidan on P-selectin-dependent peritonitis in rats was studied. Peritonitis was induced by intraperitoneal injection of the peptone solution and was characterized by an increase in total cell number and neutrophil percentage in rat peritone exudate. Intravenous injection of fucoidan was found to cause a dose- and time-dependent reduction of neutrophil extravasation into inflamed peritoneum. The minimal dose of fucoidan, that was able to produce 96.8 +/- 2.9% inhibition of neutrophil extravasation--if administered within the first 15 min after peptone-B was 0.8 mg per rat. Significant effect of fucoidan injection (about 80% inhibition) was also obtained 1.5 h after the induction of inflammation. Fucoidan administered 2.5 h after peptone had virtually no effect on neutrophil extravasation. The data obtained show that fucoidan blocks the inflammation process at its earlier stages--most probably at the expense of its interaction with P-selectin.

[The nephron microanatomy of the kidney in the lamprey Lampetra fluviatilis L. before and after metamorphosis]

Isolated nephrons from premetamorphic lamprey larvae and adult animals were obtained using microdissection and kidney collagenase treatment methods. Significant differences in the architectonics of kidney tubules were found in larvae as compared with adults. The position of larval kidney was cranial while that in adult lampreys was caudal. The absence of nephron loop was noted in larval kidney. Distal and proximal tubules were shifted one from another in mediolateral direction. Distal tubule was significantly larger than proximal one. Mesonephric duct was located laterally near the glomus. Kidney tubules morphogenesis and nephron population number increase was observed at premetamorphic stage of larval kidney development.

[The differential diagnosis of fatal outcomes in patient treatment with lidocaine]

A method for isolation, identification, and measurement of lidocaine is proposed for investigations of biological specimens. The presence of lidocaine is confirmed by common alkaloid reactions, chromatography in a thin layer of adsorbent, and color test. Lidocaine concentration is measured by extraction photoelectrocolorimetry. A formula is proposed, permitting a tentative assessment of the injected lidocaine dose. The threshold identification value is 0.2 mg%, threshold detection value 0.5 mg%.

Fucoidan inhibits leukocyte recruitment in a model peritoneal inflammation in rat and blocks interaction of P-selectin with its carbohydrate ligand

Neutrophil recruitment into systemic inflammatory sites in vivo is thought to be initiated by selectin-mediated endothelial adherence. The effect of fucoidan (natural sulfated polymer of L-fucose) on the selectin dependent PMN migration into rat peritoneum following the induction of inflammation by peptone injection was studied. Peritonitis was characterized by an increase in the total cell number (from 45.3 x 10(6) to 91.6 x 10(6)/rat), and by highly elevated PMN content (from 0.2% to 58%) in the rat peritoneal cavity 3 h after peptone injection. Intravenous administration of fucoidan was found to reduce, in a dose-dependent manner, neutrophil migration into peritoneum. Fucoidan in a dose as low as 0.8 mg per rat caused 96.8% reduction of neutrophil extravasation. The inhibitory effect of fucoidan was also dependent on the time intervals between the peptone and fucoidan injections. The maximal inhibitory effect of fucoidan was observed within the first 15 min after the induction of peritonitis and it was maintained at a level of 80% during 1.5 h. Administration of fucoidan 2.5 h after peptone injection had practically no effect on PMN extravasation. Since P-selectin is known to play a key role at the earlier stages of PMN extravasation, it was suggested that the inhibitory effect of fucoidan was mostly due to its interaction with P-selectin. The in vitro experiments demonstrated the high affinity of fucoidan for both isolated P-selectin and P-selectin in plasma membranes of activated platelets.

[Treatment of pulmonary thromboembolism with small doses of streptokinase combined with heparin, nitroglycerin, and prednisolone]

The efficiency of method worked out by the authors for pulmonary thromboembolism management surpasses the existing routine schemes of treatment by standard doses of streptokinase. The opportune application of this method gives positive results in considerable percentage of cases, i.e. in massive and submassive thromboembolism with acute or recidivating course.