Showing papers by "László Vígh published in 2012"

Hydroximic Acid Derivatives: Pleiotropic Hsp Co-Inducers Restoring Homeostasis and Robustness

Abstract: According to the "membrane sensor" hypothesis, the membrane's physical properties and microdomain organization play an initiating role in the heat shock response Clinical conditions such as cancer, diabetes and neurodegenerative diseases are all coupled with specific changes in the physical state and lipid composition of cellular membranes and characterized by altered heat shock protein levels in cells suggesting that these "membrane defects" can cause suboptimal hsp-gene expression Such observations provide a new rationale for the introduction of novel, heat shock protein modulating drug candidates Intercalating compounds can be used to alter membrane properties and by doing so normalize dysregulated expression of heat shock proteins, resulting in a beneficial therapeutic effect for reversing the pathological impact of disease The membrane (and lipid) interacting hydroximic acid (HA) derivatives discussed in this review physiologically restore the heat shock protein stress response, creating a new class of "membrane-lipid therapy" pharmaceuticals The diseases that HA derivatives potentially target are diverse and include, among others, insulin resistance and diabetes, neuropathy, atrial fibrillation, and amyotrophic lateral sclerosis At a molecular level HA derivatives are broad spectrum, multi-target compounds as they fluidize yet stabilize membranes and remodel their lipid rafts while otherwise acting as PARP inhibitors The HA derivatives have the potential to ameliorate disparate conditions, whether of acute or chronic nature Many of these diseases presently are either untreatable or inadequately treated with currently available pharmaceuticals Ultimately, the HA derivatives promise to play a major role in future pharmacotherapy

The HSP co-inducer BGP-15 can prevent the metabolic side effects of the atypical antipsychotics

Abstract: Weight gain and dysfunction of glucose and lipid metabolism are well-known side effects of atypical antipsychotic drugs (AAPD). Here, we address the question whether a heat-shock protein (HSP) co-inducer, insulin sensitizer drug candidate, BGP-15, can prevent AAPD-induced glucose, lipid, and weight changes. We also examined how an AAPD alters HSP expression and whether BGP-15 alters that expression. Four different experiments are reported on the AAPD BGP-15 interventions in a human trial of healthy men, a rodent animal model, and an in vitro adipocyte cell culture system. Olanzapine caused rapid insulin resistance in healthy volunteers and was associated with decreased level of HSP72 in peripheral mononuclear blood cells. Both changes were restored by the administration of BGP-15. In Wistar rats, weight gain and insulin resistance induced by clozapine were abolished by BGP-15. In 3T3L1 adipocytes, clozapine increased intracellular fat accumulation, and BGP-15 inhibited this process. Taken together, our results indicate that BGP-15 inhibits multiple metabolic side effects of atypical antipsychotics, and this effect is likely to be related to its HSP co-inducing ability.

Lysosomal rerouting of Hsp70 trafficking as a potential immune activating tool for targeting melanoma.

Abstract: Tumor specific cell surface localization and release of the stress inducible heat shock protein 70 (Hsp70) stimulate the immune system against cancer cells. A key immune stimulatory function of tumor-derived Hsp70 has been exemplified with the murine melanoma cell model, B16 overexpressing exogenous Hsp70. Despite the therapeutic potential mechanism of Hsp70 transport to the surface and release remained poorly understood. We investigated principles of Hsp70 trafficking in B16 melanoma cells with low and high level of Hsp70. In cells with low level of Hsp70 apparent trafficking of Hsp70 was mediated by endosomes. Excess Hsp70 triggered a series of changes such as a switch of Hsp70 trafficking from endosomes to lysosomes and a concomitant accumulation of Hsp70 in lysosomes. Moreover, lysosomal rerouting resulted in an elevated concentration of surface Hsp70 and enabled active release of Hsp70. In fact, hyperthermia, a clinically applicable approach triggered immediate active lysosomal release of soluble Hsp70 from cells with excess Hsp70. Furthermore, excess Hsp70 enabled targeting of internalized surface Hsp70 to lysosomes, allowing in turn heat-induced secretion of surface Hsp70. Altogether, we show that excess Hsp70 expressed in B16 melanoma cells diverts Hsp70 trafficking from endosomes to lysosomes, thereby supporting its surface localization and lysosomal release. Controlled excess-induced lysosomal rerouting and secretion of Hsp70 is proposed as a promising tool to stimulate anti-tumor immunity targeting melanoma.

Nutritional lipid supply can control the heat shock response of B16 melanoma cells in culture

Abstract: The in vitro culture of cells offers an extremely valuable method for probing biochemical questions and many commonly-used protocols are available. For mammalian cells a source of lipid is usually provided in the serum component. In this study we examined the question as to whether the nature of the lipid could become limiting at high cell densities and, therefore, prospectively influence the metabolism and physiology of the cells themselves. When B16 mouse melanoma cells were cultured, we noted a marked decrease in the proportions of n-3 and n-6 polyunsaturated fatty acids (PUFAs) with increasing cell density. This was despite considerable quantities of these PUFAs still remaining in the culture medium and seemed to reflect the preferential uptake of unesterified PUFA rather than other lipid classes from the media. The reduction in B16 total PUFA was reflected in changes in about 70% of the molecular species of membrane phosphoglycerides which were analysed by mass spectrometry. The importance of this finding lies in the need for n-3 and n-6 PUFA in mammalian cells (which cannot synthesize their own). Although the cholesterol content of cells was unchanged the amount of cholesterol enrichment in membrane rafts (as assessed by fluorescence) was severely decreased, simultaneous with a reduced heat shock response following exposure to 42°C. These data emphasize the pivotal role of nutrient supply (in this case for PUFAs) in modifying responses to stress and highlight the need for the careful control of culture conditions when assessing cellular responses in vitro.

A novel insulin sensitizer drug candidate-BGP-15-can prevent metabolic side effects of atypical antipsychotics.

Abstract: Atypical antipsychotic drugs (AAPD) are widely used to treat severe psychiatric disorders, have well documented metabolic side effects such as disturbances in glucose metabolism, insulin resistance and weight gain. It has been shown that BGP-15, a hydroxylamine derivative with insulin sensitizing activity can prevent AAPD provoked fat accumulation in adipocyte cultures, and insulin resistance in animal experiments and in healthy volunteers. The aim of this study was to compare the preventive effect of BGP-15 with conventional oral antidiabetics on metabolic side effects of AAPDs. We found that BGP-15 that does not belong to either conventional insulin sensitizers or oral antidiabetics, is able to counteract insulin resistance and weight gain provoked by antipsychotic agents in rats while rosiglitazone and metformin were not effective in the applied doses. Our results confirm that BGP-15 is a promising new drug candidate to control the metabolic side effects of atypical antipsychotics. Data indicate that this rat model is suitable to analyze the metabolic side effects of AAPDs and the protective mechanism of BGP-15.

Evidence on Cholesterol-Controlled Lipid Raft Interaction of the Small Heat Shock Protein HSPB11

Abstract: Small heat-shock proteins (sHSPs) are members of the family of molecular chaperones. Their major cellular function is considered to be the prevention of irreversible protein aggregation during stress conditions and subsequent promotion of the folding of partially denatured proteins. However, sHSPs may also be associated with biological membranes and participate in cellular “stress management” by acting as membrane-stabilizing factors. In spite of the great potential significance in the development of therapeutic strategies, the mechanisms of the membrane (and lipid) association of sHSPs are still unknown. A novel 16.2 kDa human sHSP, HSPB11, inhibits H2O2, taxol and etoposide-induced cell death through stabilization of the mitochondrial membrane system, the activation of HSP90, the stabilization of lipid rafts and activation of the PI-3-kinase—Akt cytoprotective pathway. We show here that HSPB11 binds to lipid membranes via a specific cholesterol-mediated interaction. The affinity of HSPB11 demonstrates a very distinct cholesterol-dependent binding to cholesterol/sphingomyelin Langmuir monolayers: If the cholesterol concentration increases above a certain level, HSPB11 binds to membranes much more efficiently. The possible roles of HSPB11 and other sHSPs in protection against stress-induced hydrophobic membrane defects are discussed.

Insulin resistance occurs in parallel with sensory neuropathy in streptozotocin-induced diabetes in rats: differential response to early vs late insulin supplementation.

Abstract: We investigated whether progressive sensory neuropathy was accompanied by changes in whole-body insulin sensitivity (WBIS) in rats made diabetic by streptozotocin (STZ). The effects of early and late insulin supplementation were also studied. The STZ-treated rats failed to gain weight and exhibited stable hyperglycemia and low plasma insulin levels with a decrease in nerve conduction velocity (NCV) measured in A and C fibers of the saphenous nerve. A decreased sensory neuropeptide (SNP) release such as that of substance P, somatostatin, and calcitonin gene–related peptide determined from organ fluid of tracheal preparations subjected to electrical field stimulation also occurred in diabetic animals. These features were accompanied by a decrease in WBIS measured by hyperinsulinemic-euglycemic glucose clamping and a decrease in insulin-stimulated glucose uptake in cardiac and gastrocnemius muscle. When insulin supplementation with slow-release implants (2 IU/d) was started 4 weeks after STZ injection, blood glucose level normalized. Both insulin sensitivity and sensory nerve function reflected in either NCV or SNP release completely recovered by the 12th post-STZ week. When the insulin implants were applied from the eighth post-STZ week, both WBIS and glucose uptake remained significantly decreased, with a seriously impaired NCV and SNP release with strong hyperglycemia. Late insulin supplementation, however, even by using double implantation from the 10th post-STZ week, was unable to restore blood glucose, WBIS, NCV, and SNP release by the 12th week. Insulin resistance occurs in parallel with sensory neuropathy in STZ-diabetic rats. Both can be improved by early but not late insulin supplementation.