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1

Strategies for overcoming ABC-transporters-mediated multidrug resistance [MDR] of tumor cells

100%
Borowski E., Bontemps-Gracz M. M., Piwkowska A.
Acta Biochimica Polonica
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2005
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tom 52
|
nr 3
The development of multidrug resistance (MDR) of tumors is a major cause of failure in antitumor chemotherapy. This type of crossresistance is due to the expression of ABC transporter glycoproteins actively effluxing the drug from the cells against the concentration gradient at the expense of metabolic energy, thus preventing the accumulation in cells of therapeutic concentration of active agents. In this review strategies for overcoming this adverse phenomenon are discussed. They comprise the control of expression of MDR glycoprotein transporters and control of the functioning of the expressed transporter proteins. The latter approach is discussed in more detail, comprising the following general strategies: (i) development of compounds that are not substrates of efflux pump(s), (ii) use of agents that inactivate (inhibit) MDR proteins, (iii) design of cytostatics characterized by fast cellular uptake, surpassing their mediated efflux, (iv) use of compounds competing with the drug for the MDR protein-mediated efflux. Positive and negative aspects of these strategies are analysed, with special attention put on strategy based on the use of MDR modulators in combination therapy, allowing the restoration of cytotoxic activity of clinical cytostatics towards resistant tumor cells.
2

Changes in short-term potentiation of hypoglossal activity by modulators of nitric oxide production in the rabbit

84%
Budzinska K., Wojtal E.
Acta Neurobiologiae Experimentalis
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2001
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tom 61
|
nr 4
3

In search for effective modulators of the proteasome activity

67%
Karpowicz P., Stoj J., Gaczynska M., Osmulski P., Jankowska E.
Acta Neurobiologiae Experimentalis
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2013
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tom 73
|
nr 1
Proteasome is a multi-activity enzyme involved in a ubiquitin-dependent turnover of cytoplasmic and nuclear proteins. It recognizes and digests short-lived regulatory proteins, influencing cellular processes as crucial as progression of the cell cycle, transcription, oncogenesis and flux of substrates through metabolic pathways. The enzyme is responsible also for the housekeeping chores, degrading misfolded or oxidatively damaged proteins. Defects in the proteasome action play a causal role in development of a number of diseases, among which are cerebral ischemia and neurodegenerative disorders such as Huntington’s, Alzheimer’s, and Parkinson’s diseases. Being a multifunctional proteolytic machinery, the proteasome must act under a strict control to prevent massive degradation of all intracellular proteins, which would result in a cell death. One of the levels of such a control is the proteasome structure itself. The core particle called 20S proteasome is a barrel-like structure made up of four rings of seven subunits each. The outer (α) rings play predominantly a structural role forming a kind of a gated channel leading to the proteolytic chamber. The inner-β-rings harbor six active sites, concealed inside the cavity formed by the β subunits. So far, the only proteasome-targeting agents used in clinics are competitive inhibitors, directly blocking the enzyme’s active sites. However, the multi-subunit barrel-like structure of the 20S proteasome encourages to test compounds which can target allosteric interactions between subunits and influence the gating mechanism, involved in the control of the substrates’ uptake. Such modulators may provide a precise and substrate-specific regulation of the proteasome catalytic performance. Additionally, targeting the allosteric interactions may enable not only inhibition but also stimulation of the proteasome, which is crucial in managing disorders connected with the proteasome not sufficient activity, such as neurodegenerative diseases. A variety of protein ligands, interacting with the outer ring of the 20S proteasome and modulating its activity, is already known. They can serve as templates for design of putative small-molecule allosteric drugs. In an effort to find synthetic compounds able to enhance or suppress the performance of the proteasome active centers we utilize one of such protein ligands – HIV-1 Tat protein. The protein is known to inhibit the core proteasome and to interfere with the physiological PA28 activator in its binding to the 20S. G48RKKRRQRRRPS59 fragment of HIV-1 Tat (Tat1) occurred to be very efficient in the 20S proteasome inhibition. By single and multiple alanine substitutions we have recognized “hot spots” in the sequence of Tat1. NMR and molecular dynamics calculations allowed us to correlate these putative pharmacophores with the structural turns. By introduction of a non-peptide turn-inducing modification to the Tat1 sequence we have obtained the derivatives highly toxic for human cultured cancer cells HeLa.S3. The work was supported by grants: NCN 2011/01/B/ST5/06616 and DS/8440-4-0172-2
4
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Leptin is the modulator of HSP60 gene expression in AR42J cells

67%
Bonior J., Jaworek J., Konturek S. J., Pawlik W. W.
Journal of Physiology and Pharmacology. Supplement
|
2006
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tom 57
|
nr 7
135-143
Leptin, circulating protein involved in the control of body weight and energy expenditure received attention as a modulator of immune response of the organism. Leptin receptors have been detected in the pancreas and experimental studies have shown that leptin protects the pancreas against the damage induced by caerulein overstimulation. Heat shock proteins (HSP) are endogenous proteins produced by various cells exposed to high temperature or to the noxious agents. HSP protect the cells against various environmental and endogenous stressors. The implication of HSP60 in the leptin-induced pancreatic protection has not been examined yet. The aim of this study was: to investigate the changes of HSP60 mRNA signal in the pancreatic AR42J cells subjected to caerulein and leptin. AR42J cells were incubated in standart medium at 37°C for: 0, 1, 3, 5, 12 or 24 h, under basal conditions. Incubation time of 3 h was selected for the next experiments. AR42J cells were incubated in presence of caerulein (10-11, 10-9 or 10-7M), leptin (10-8 or 10-6M), or combination of above. Gene expression for HSP60 was determined by RT-PCR. The mRNA signal for HSP60 has been observed in AR42J pancreatic cells under basal conditions. Incubation of AR42J cells in presence of leptin (10-8 or 10-6M) resulted in the significant increase of gene expression for HSP60 in both groups of AR42J cells. Caerulein stimulation reduced mRNA signal for HSP60. The strongest mRNA signal for HSP60 has been observed after the exposition of AR42J cells to combination of leptin and caerulein. We conclude that: 1. Gene expression for HSP60 has been detected in pancreatic AR42J cells under basal conditions. 2. HSP60 gene expression was significantly increased in pancreatic AR42J cells stimulated by leptin whereas caerulein reduced this signal. 3. The strongest gene expression for HSP60 has been detected in the cells incubated with combination of caerulein and leptin.
5

NANC transmission in intestines and its pharmacological modulation

59%
Bauer V.
Acta Neurobiologiae Experimentalis
|
1993
|
tom 53
|
nr 1
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