Sandor Bernath

BGP-15 — a novel poly(ADP-ribose) polymerase inhibitor — protects against nephrotoxicity of cisplatin without compromising its antitumor activity

Nephrotoxicity is one of the major dose limiting side effects of cisplatin chemotherapy. The antitumor and toxic effects are mediated in part by different mechanisms, thus, permitting a selective inhibition of certain side effects. The influence of O-(3-piperidino-2-hydroxy-1-propyl)nicotinic amidoxime (BGP-15) - a poly(ADP-ribose) polymerase (PARP) inhibitor - on the nephrotoxicity and antitumor efficacy of cisplatin has been evaluated in experimental models. BGP-15 either blocked or significantly reduced (60-90% in 100-200 mg/kg oral dose) cisplatin induced increase in serum urea and creatinine level in mice and rats and prevented the structural degeneration of the kidney, as well. The nephroprotective effect of BGP-15 treatment was revealed also in living mice by MRI analysis manifesting in the lack of oedema which otherwise developed as a result of cisplatin treatment. The protective effect was accompanied by inhibition of cisplatin-induced poly-ADP-ribosylation and by the restoration of the disturbed energy metabolism. The preservation of ATP level in the kidney was demonstrated in vivo by localized NMR spectroscopy. BGP-15 decreased cisplatin-induced ROS production in rat kidney mitochondria and improved the antioxidant status of the kidney in mice with cisplatin-induced nephropathy. In rat kidney, cisplatin caused a decrease in the level of Bcl-x, a mitochondrial protective protein, and this was normalized by BGP-15 treatment. On the other hand, BGP-15 did not inhibit the antitumor efficacy of cisplatin in cell culture and in transplantable solid tumors of mice. Treatment with BGP-15 increased the mean survival time of cisplatin-treated P-388 leukemia bearing mice from 13 to 19 days. PARP inhibitors have been demonstrated to diminish the consequences of free radical-induced damage, and this is related to the chemoprotective effect of BGP-15, a novel PARP inhibitor. Based on these results, we propose that BGP-15 represents a novel, non-thiol chemoprotective agent.

Reduction of acute photodamage in skin by topical application of a novel PARP inhibitor

The ultraviolet (UV) components of sunlight induce damage to the DNA in skin cells, which is considered to be the initiating step in the harmful biological effects of UV radiation. Repair of DNA damage results in the formation of single-strand DNA breaks, which activate the nuclear poly(ADP-ribose) polymerase (PARP). Overactivation of PARP worsens the oxidative cell damage and impairs the energy metabolism, raising the possibility that moderation of PARP activation following DNA damage may protect skin cells from UV radiation. The topical effects of the novel PARP inhibitor O-(3-pyperidino-2-hydroxy-1-propyl) pyridine-3-carboxylic acid amidoxime monohydrochloride (BGP-15M) were investigated on UV-induced skin damage in a hairless mouse model. For evaluation of the UV-induced acute photodamage to the skin and the potential protective effect of BGP-15M, DNA injury was detected by measuring the formation of single-strand DNA breaks and counting the resulting sunburn (apoptotic) cells. The ADP-ribosylation of PARP was assessed by Western blot analysis and then quantified. In addition, the UV-induced immunosuppression was investigated by the immunostaining of tumor necrosis factor alpha and interleukin-10 expressions in epidermal cells. The signs of inflammation were examined clinically and histochemically. Besides its primary effect in decreasing the activity of nuclear PARP, topically applied BGP-15M proved to be protective against solar and artificial UV radiation-induced acute skin damage. The DNA injury was decreased (P<0.01). An inhibition of immunosuppression was observed by down-regulation of the epidermal production of cytokines IL-10 and TNFalpha. In the mouse skin, clinical or histological signs of UV-induced inflammation could not be observed. These data suggest that BGP-15M directly interferes with UV-induced cellular processes and modifies the activity of PARP. The effects provided by topical application of the new PARP-regulator BGP-15M indicate that it may be a novel type of agent in photoprotection of the skin.

Inhibitory effect of ionized free intracellular calcium enhanced by ruthenium red and m-chloro-carbonylcyanide phenyl hydrazon on the evoked release of acetylcholine

In order to understand the relationship between the free ionized calcium concentration in the axon terminals and the transmitter release we have investigated the effect of ruthenium red (RuR) and m-chloro-carbonylcyanide phenyl hydrazon (CCCP), mitochondrial uncoupler agents on the liberation of acetylcholine from myenteric plexus of guinea-pig ileum. Both compounds are able to enhance intracellular free Ca2+. In the presence of RuR and CCCP the spontaneous release of radioactivity from isolated myenteric-plexus preparation, previously loaded with (methyl-3H)-choline chloride was significantly enhanced while that evoked by electrical stimulation was decreased. Atropine did not affect the electrically evoked release in the presence of CCCP, indicating that in the effect of CCCP the presynaptic muscarinic receptors mediated negative feedback modulation does not play any role. Our findings are consistent with the hypothesis that the enhanced level of intracellular free Ca2+ enhances the spontaneous while depresses the electrically evoked release of transmitter.

Dihydropyridine Derivatives Modulate Heat Shock Responses and have a Neuroprotective Effect in a Transgenic Mouse Model of Alzheimer's Disease

Heat shock proteins (Hsps) have chaperone activity and play a pivotal role in the homeostasis of proteins by preventing misfolding, by clearing aggregated and damaged proteins from cells, and by maintaining proteins in an active state. Alzheimer’s disease (AD) is thought to be caused by amyloid-β peptide that triggers tau hyperphosphorylation, which is neurotoxic. Although proteostasis capacity declines with age and facilitates the manifestation of neurodegenerative diseases such as AD, the upregulation of chaperones improves prognosis. Our research goal is to identify potent Hsp co-inducers that enhance protein homeostasis for the treatment of AD, especially 1,4-dihydropyridine derivatives optimized for their ability to modulate cellular stress responses. Based on favorable toxicological data and Hsp co-inducing activity, LA1011 was selected for the in vivo analysis of its neuroprotective effect in the APPxPS1 mouse model of AD. Here, we report that 6 months of LA1011 administration effectively improved the spatial learning and memory functions in wild type mice and eliminated neurodegeneration in double mutant mice. Furthermore, Hsp co-inducer therapy preserves the number of neurons, increases dendritic spine density, and reduces tau pathology and amyloid plaque formation in transgenic AD mice. In conclusion, the Hsp co-inducer LA1011 is neuroprotective and therefore is a potential pharmaceutical candidate for the therapy of neurodegenerative diseases, particularly AD.

Inhibition by p-nitrophenylphosphate of acetylcholine release induced by Na+-deprivation

The effect of p-nitrophenylphosphate (p-NPP) on the release of acetylcholine evoked by drugs and ionic environments known to inhibit Na+, K+-ATPase was studied in isolated cortical slices of rat brain and longitudinal muscle strip of guinea-pig ileum. p-NPP inhibited the release of acetylcholine induced by sodium deprivation provided that the circumstances were in favour of the function of the K+-activated part of ATPase. However, it failed to antagonize the increase in the acetylcholine release elicited by omission of K+ or by administration of ouabain. Therefore it is concluded that the K+-stimulated phosphatase moiety of the Na+, K+-ATPase might be involved in the release of acetylcholine.