Biomedical subjects

Halina Ostrowska

Publications and source records attributed to Halina Ostrowska.

5 recordsLinked to original sources

PubMed2006

Immuno-proteasome subunit LMP7 is up-regulated in the ischemic kidney in an experimental model of renovascular hypertension.

Immuno-proteasome is thought to be responsible for the processing of intracellular antigens and is induced when cells are treated with the inflammatory cytokines promoting cellular immunity. We tested the possibility that immuno-proteasome can be up-regulated in renal cells exposed to a long-lasting ischemia and inflammation in an experimental model of two-kidney, one-clip renovascular hypertension in the rat. Western blotting showed that immuno-proteasome subunit, LMP7, was up-regulated in the clipped ischemic kidney that was atrophic, but not in the contralateral unclipped kidney that underwent compensatory hypertrophy. Immunohistochemical analysis revealed that LMP7 was highly expressed in cortical epithelial and endothelial cells of the ischemic kidney. Surprisingly, the second immuno-subunit, LMP2, was almost undetectable, indicating that renal ischemia may induce exclusively the LMP7 subunit. We also found that renal ischemia neither reduced the SDS-stimulated proteasomal activity nor affected a high level of the PA28 activator. Thus, the results provide evidence that LMP7 immuno-subunit is induced in renal cells exposed to a long-lasting renal ischemia and inflammation, and that there is a direct link between LMP induction and renal atrophy. This opens an opportunity to study a role for LMP-containing proteasomes in the kidneys and other organs undergoing reduction in mass in diseases accompanied by a long-lasting ischemia and inflammatory responses.

Animals↗

PubMed2005

Ebelactone B, an inhibitor of extracellular cathepsin A-type enzyme, suppresses platelet aggregation ex vivo in renovascular hypertensive rats.

The present study was undertaken to investigate whether ebelactone B, an inhibitor of bradykinin and angiotensin I hydrolysis by serine carboxypeptidase Y-like enzymes, could influence platelet aggregation ex vivo in renovascular hypertensive rats (2-kidney, 1-clip Goldblatt model, 2K1C). We found that ebelactone B (5 mg/kg) administrated subcutaneously once a day for 5 days, 5 weeks after the development of hypertension, or a single dose of ebelactone B (0.5 mg/kg) injected intravenously into 2K1C hypertensive rats before the induction of arterial thrombosis, both markedly suppressed collagen-induced platelet aggregation in whole blood. In contrast, inhibition of collagen-induced platelet aggregation was not evident in vitro after pretreatment of the blood with ebelactone B, indicating that ex vivo the antiaggregatory action of this compound can proceed through an indirect mechanism. The injection of ebelactone B did not affect the mean blood pressure of 2K1C hypertensive rats but lowered an elevated extracellular serine carboxypeptidase cathepsin A-like activity. Thus, the data indicate that ebelactone B may be a promising antiaggregatory agent in renovascular hypertension and suggest that 1 of the possible mechanisms through which it exerts this effect may be related to the suppression of cathepsin A-like activity released locally during the development of renovascular hypertension.

Animals↗

PubMed2004

Proteasome inhibitor prevents experimental arterial thrombosis in renovascular hypertensive rats.

Recent studies indicate that highly selective proteasome inhibitors can be useful in prevention of some cardiovascular events. Here we demonstrate that proteasome inhibitor, Z-Ile-Glu (Ot-Bu) Ala-Leucinal (PSI), is active in the prevention of platelet-dependent arterial thrombosis induced in renovascular hypertensive rats (two-kidney, one clip Goldblatt model, and 2K1C, n=5). The administration of PSI intravenously at a single dose of 0.3 mg/kg before induction of arterial thrombosis markedly increased carotid final flow rate, as compared to control (vehicle) group (10.36 +/- 1.8 ml/min and 1.2 +/- 1.2 ml/min, respectively), significantly decreased the wet (1.23 +/- 0.23 mg and 4.1 +/- 0.94 mg, respectively), and dry (0.46 +/- 0.145 mg and 1.46 +/- 0.39, respectively) thrombus weight, and completely prevented arterial occlusion. Moreover, platelets from PSI - treated thrombotic 2K1C rats, showed in response to collagen a significant inhibition of aggregation in the whole blood (10.26 +/- 0.6 ohms vs. 15.51 +/- 0.91 ohms in the control group). In contrast, collagen-induced platelet aggregation was not inhibited in vitro, after pre-treatment of the blood with PSI at the concentration of 10 microM that effectively inhibited the 20S proteasome activity in platelets, indicating that ex vivo anti-aggregatory effect of PSI proceeds through an indirect mechanism not associated with suppression of 20S proteasome activity in platelets. In conclusion, our in vivo findings demonstrate that proteasome inhibitor, Z-Ile-Glu(Ot-Bu)Ala-Leucinal, prevents the development of arterial thrombosis in renovascular hypertensive rats and effectively suppresses platelet aggregation by an indirect mechanism. Thus the data provide a new insight into the potential role for the proteasome-dependent pathway in cardiovascular events.

Animals↗

PubMed2003

Human platelet 20S proteasome: inhibition of its chymotrypsin-like activity and identification of the proteasome activator PA28. A preliminary report.

Earlier studies have demonstrated that human platelets contain the 20S proteasome, and its protein activator. However, understanding the potential role of the proteasome in human platelets requires a detailed knowledge about its chymotryptic-like activity, a crucial one for protein degradation in all eukaryotic cells. In this communication we have shown that human platelet 20S proteasome exhibited chymotryptic-like activity towards succinyl-Leu-Leu-Val-Tyr-7-amido-4-methylcoumarin as substrate at a broad pH range, with optimum between pH 7.5-8.0 and 5.0-5.5. These two activities were markedly inhibited by a 10 micromol/l concentration of two structurally unrelated proteasome inhibitors: lactacystin/beta-lactone or benzyloxycarbonyl-Ile-Glu(O-tert.-butyl)-Ala-leucinal, but not by ebelactone B, an inhibitor of lysosomal cathepsin A/deamidase. The chymotryptic-like activity of the 20S proteasome against succinyl-Leu-Leu-Val-Tyr-7-amido-4-methylcoumarin was also significantly inhibited in platelets, after exposure of platelet-rich plasma to 10 micromol/l lactacystin and benzyloxycarbonyl-Ile-Glu(O-tert.-butyl)-Ala-leucinal for up to 60 min. This indicates that these inhibitors can enter platelets and selectively inhibit 20S proteasome activity. We also demonstrated for the first time by Western blot analysis that human platelets contain a proteasome activator, PA28, which is known to play a key role in antigen processing by significant stimulation of the proteasomal chymotryptic-like activity. Since the platelet 20S proteasome was also present in a latent form, this suggests that its activity may be regulated in vivo in human platelets. All these results can therefore be beneficial in future studies on the role of the 20S proteasome in platelet biology.

Acetylcysteine↗

PubMed2003

Lysosomal high molecular weight multienzyme complex.

Three acidic glycosidases: beta-galactosidase (beta-GAL, EC 3.2.1.23), alpha-neuraminidase (NEUR, sialidase, EC 3.2.1.18), N-acetylaminogalacto-6-sulfate sulfatase (GALNS, EC 3.1.6.4) and serine carboxypepidase cathepsin A (EC 3.4.16.1) form a functional high molecular weight complex in the lysosomes. The major constituent of this complex is cathepsin A, the so-called "lysosomal protective protein" (PPCA). By forming a multienzyme complex, it protects the glycosidases from rapid intralysosomal proteolysis, and it is also required for the intracellular sorting and proteolytic processing of their precursors. In man, a deficiency of cathepsin A leads to a combined deficiency of beta-GAL and NEUR activities, called "galactosialidosis". Multiple mutations identified in the cathepsin A gene are the molecular basis of this lysosomal storage disease. This review describes the structural organization of the lysosomal high molecular weight multienzyme complex and the importance of the protective protein/cathepsin A in physiology and pathology.

Cathepsin A↗