Biomedical subjects

Jindrich Kopecek

Publications and source records attributed to Jindrich Kopecek.

39 records · Page 3Linked to original sources

PubMedDate not supplied

HPMA copolymer-bound doxorubicin induces apoptosis in human ovarian carcinoma cells by a Fas-independent pathway.

The mechanism of cell death in A2780 human ovarian carcinoma cells induced by free doxorubicin (DOX) and N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-bound DOX [P-(GFLG)-DOX] was investigated. In particular, the involvement of the Fas receptor system in drug-induced apoptosis was evaluated. P-(GFLG)-DOX was shown to effect apoptosis-induced tumor cell death as manifested by positive Annexin V-FITC staining, cleavage of procaspase 3 and its physiological substrate, poly(ADP-ribose) polymerase (PARP), and cleavage of procaspase 8. Using the fluorochrome-labeled caspase inhibitor assay, it was found that both free DOX and P-(GFLG)-DOX activated caspases 3 and 9, but both forms of DOX did not have an effect on the activity of caspase 8, when compared to untreated cells. It was shown that free DOX and P-(GFLG)-DOX upregulated Fas receptor expression at the cell membrane in a time-dependent manner. Triggering the drug-induced Fas receptor with an exogeneous soluble Fas ligand (sFasL) resulted in an increase in the extent of apoptotic cell death, indicating that the Fas signaling pathway remained functionally active. Also, antagonistic anti-Fas ZB4 antibody blocked the increase in the level of apoptosis following the application of sFasL, but did not interfere with drug-induced apoptosis. The study of the functional activity of the Fas receptor and of the activation of the most proximal effector of the caspase cascade, caspase 8, indicated that the Fas receptor pathway was not decisive in the induction of cell death by free DOX and P-(GFLG)-DOX in A2780 cells. This study suggests further investigation of the involvement of the mitochondrial pathway in A2780 cell apoptotic death, induced by free and HPMA copolymer-bound DOX.

Acrylamides↗

PubMedDate not supplied

HPMA copolymer-bound doxorubicin induces apoptosis in ovarian carcinoma cells by the disruption of mitochondrial function.

N-(2-Hydroxypropyl)methacrylamide (HPMA) copolymer-bound doxorubicin has showed greater potency than free doxorubicin in the treatment of ovarian cancer in vivo and in vitro. The promising activity of the conjugate demonstrated in clinical trials has generated considerable interest in understanding the mechanism of action of this macromolecular therapeutic. In this study, the involvement of the mitochondrial pathway in HPMA copolymer-bound doxorubicin-induced apoptosis in the human ovarian cancer cell line A2780 was investigated. Through a series of in vitro assays, including confocal microscopy, flow cytometry, and spectrofluorimetry, a significant decrease in mitochondrial membrane potential in A2780 cells treated with HPMA copolymer-bound doxorubicin was found. The most dramatic changes in mitochondrial membrane potential were observed between 2 and 12 h of continuous drug exposure. The potential of the mitochondrial membrane remained collapsed when drug treatment continued up to 24 h. For the first time, it was shown that HPMA copolymer-bound doxorubicin induces apoptosis in ovarian cancer cells by simultaneous activation of both caspase-dependent and caspase-independent pathways of DNA damage. This was determined by monitoring the translocation of the mitochondrial proteins cytochrome c and apoptosis-inducing factor to cytosol. The altered balance between anti-apoptotic and pro-apoptotic members of the Bcl-2 family of proteins was responsible for the mitochondrial function distraction. HPMA copolymer-bound doxorubicin induced a time-dependent decrease in the expression of the anti-apoptotic Bcl-2 and Bcl-xL proteins, which control cell survival. At the same time, the expression level of pro-apoptotic members (Bax, Bad) of the Bcl-2 family was increased under the chosen experimental conditions. Altogether, these results indicate that HPMA copolymer-bound doxorubicin induced apoptosis in ovarian cancer cells through the mitochondrial pathway.

Acrylamides↗

PubMedDate not supplied

Pharmacokinetic and biodistribution studies of a bone-targeting drug delivery system based on N-(2-hydroxypropyl)methacrylamide copolymers.

Osteotropicity of novel bone-targeted HPMA copolymer conjugates has been demonstrated previously with bone histomorphometric analysis. The pharmacokinetics and biodistribution of this delivery system were investigated in the current study with healthy young BALB/c mice. The 125I-labeled bone-targeted and control (nontargeted) HPMA copolymers were administered intravenously to mice, and their distribution to different organs and tissues was followed using gamma counter and single photon emission computed tomography (SPECT). Both the invasive and noninvasive data further confirmed that the incorporation of D-aspartic acid octapeptide (D-Asp8) as bone-targeting moiety could favorably deposit the HPMA copolymers to the entire skeleton, especially to the high bone turnover sites. To evaluate the influence of molecular weight, three fractions (Mw of 24, 46, and 96 kDa) of HPMA copolymer-D-Asp8 conjugate were prepared and evaluated. Higher molecular weight of the conjugate enhanced the deposition to bone due to the prolonged half-life in circulation, but it weakened the bone selectivity. A higher content of bone-targeting moiety (D-Asp8) in the conjugate is desirable to achieve superior hard tissue selectivity. Further validation of the bone-targeting efficacy of the conjugates in animal models of osteoporosis and other skeletal diseases is needed in the future.

Animals↗