Pharmacological modulation of the heat shock response

Cardioprotective Exercise and Pharmacologic Interventions as Complementary Antidotes to Cardiovascular Disease

Exercise and pharmacologic therapies to prevent and treat cardiovascular disease have advanced largely through independent efforts. Understanding of first-line drug therapies, findings from preclinical animal studies, and the need for research initiatives related to complementary cardioprotective exercise-pharma interventions are reviewed from the premise that contemporary cardioprotective therapies must include adjunctive exercise and lifestyle interventions in addition to pharmacologic agents.

Nonlinear effects of nanoparticles: biological variability from hormetic doses, small particle sizes, and dynamic adaptive interactions

Researchers are increasingly focused on the nanoscale level of organization where biological processes take place in living systems. Nanoparticles (NPs, e.g., 1-100 nm diameter) are small forms of natural or manufactured source material whose properties differ markedly from those of the respective bulk forms of the "same" material. Certain NPs have diagnostic and therapeutic uses; some NPs exhibit low-dose toxicity; other NPs show ability to stimulate low-dose adaptive responses (hormesis). Beyond dose, size, shape, and surface charge variations of NPs evoke nonlinear responses in complex adaptive systems. NPs acquire unique size-dependent biological, chemical, thermal, optical, electromagnetic, and atom-like quantum properties. Nanoparticles exhibit high surface adsorptive capacity for other substances, enhanced bioavailability, and ability to cross otherwise impermeable cell membranes including the blood-brain barrier. With super-potent effects, nano-forms can evoke cellular stress responses or therapeutic effects not only at lower doses than their bulk forms, but also for longer periods of time. Interactions of initial effects and compensatory systemic responses can alter the impact of NPs over time. Taken together, the data suggest the need to downshift the dose-response curve of NPs from that for bulk forms in order to identify the necessarily decreased no-observed-adverse-effect-level and hormetic dose range for nanoparticles.

Brain endothelial HSP-70 stress response coincides with endothelial and pericyte death after brain trauma

OBJECTIVES

Our objective was to characterize the heat shock response (HSR) in a model of traumatic brain injury (TBI) and to determine the association of HSR to cell death.

METHODS

We used immunofluorescent detection of HSP-70 to characterize HSR and TUNEL labeling to determine the pattern of cell death.

RESULTS

HSP-70 immunofluorescence revealed a steady increase from 4 to 48 hours following TBI, culminating in a ubiquitous expression with the capillary bed 48 hours post-TBI. TUNEL labeling revealed a small subset of endothelial cell death and a most robust staining of putative pericyte cell death.

DISCUSSION

Our results show that while injury causes a detectable stress response, cell death is not a direct consequence of the HSR.

Heat shock proteins are therapeutic targets in autoimmune diseases and other chronic inflammatory conditions

INTRODUCTION

Exploitation of antigen-specific regulatory T cells (Tregs) as critical regulators in the control of chronic inflammatory diseases is hampered by the obscure nature of most disease-relevant autoantigens. Heat shock proteins (Hsp) are possible targets for Tregs due to their enhanced expression in inflamed (stressed) tissues and there is evidence that Hsp can induce anti-inflammatory immunoregulatory T-cell responses.

AREAS COVERED

Recent publications showing that exogenous administration of stress proteins has induced immunoregulation in various models of inflammatory disease have also been shown to be effective in first clinical trials in humans. Now, in the light of a growing interest in T-cell regulation, it is of interest to further explore the mechanisms through which Hsp can be utilized to trigger immunoregulatory pathways, capable of suppressing such a wide and diversified spectrum of inflammatory diseases.

EXPERT OPINION

Therapeutic approaches via exploitation of antigen-specific Tregs will benefit from tailor-made combination therapies. Combining current therapeutic approaches with Hsp-specific therapies thereby enhancing natural immune regulation might expedite the entry of antigen-specific regulatory T cells into the therapeutic arsenal of the anti-inflammatory therapeutics.

Heat shock proteins are important mediators of skeletal muscle insulin sensitivity

Endogenous heat shock proteins (HSP) are decreased in disease states associated with insulin resistance and aging. Induction of HSPs has been shown to decrease oxidative stress, inhibit inflammatory pathways, and enhance metabolic characteristics in skeletal muscle. As such, HSPs have the potential to function as an important defense system against the development of insulin resistance and type 2 diabetes.

Design of a flexible cell-based assay for the evaluation of heat shock protein 70 expression modulators

Heat shock protein 70 (Hsp70) is a chaperone protein that helps protect against cellular stress, a function that may be co-opted to fight human diseases. In particular, the upregulation of Hsp70 can suppress the neurotoxicity of misfolded proteins, suggesting possible therapeutic strategies in neurodegenerative diseases. Alternatively, in cancer cells where high levels of Hsp70 inhibit both intrinsic and extrinsic apoptotic pathways, a reduction in Hsp70 levels may induce apoptosis. To evaluate and identify, in a single assay format, small molecules that induce or inhibit endogenous Hsp70, we have designed and optimized a microtiter assay that relies on whole-cell immunodetection of Hsp70. The assay utilizes a minimal number of neuronal or cancer cells, yet is sufficiently sensitive and reproducible to permit quantitative determinations. We further validated the assay using a panel of Hsp70 modulators. In conclusion, we have developed an assay that is fast, robust, and cost efficient. As such, it can be implemented in most research laboratories. The assay should greatly improve the speed at which novel Hsp70 inducers and inhibitors of expression can be identified and evaluated.

A novel heat-shock protein coinducer boosts stress protein Hsp70 to activate T cell regulation of inflammation in autoimmune arthritis

OBJECTIVE

Stress proteins, such as members of the heat-shock protein (HSP) family, are up-regulated by cells in inflamed tissue and can be viewed functionally as "biomarkers" for the immune system to monitor inflammation. Exogenous administration of stress proteins has induced immunoregulation in various models of inflammation and has also been shown to be effective in clinical trials in humans. This study was undertaken to test the hypothesis that boosting of endogenous HSP expression can restore effective immunoregulation through T cells specific for stress proteins.

METHODS

Stress protein expression was manipulated in vivo and in vitro with a food component (carvacrol), and immune recognition of stress proteins was studied.

RESULTS

Carvacrol, a major compound in the oil of many Origanum species, had a notable capacity to coinduce cellular Hsp70 expression in vitro and, upon intragastric administration, in Peyer's patches of mice in vivo. As a consequence, carvacrol specifically promoted T cell recognition of endogenous Hsp70, as demonstrated in vitro by the activation of an Hsp70-specific T cell hybridoma and in vivo by amplified T cell responses to Hsp70. Carvacrol administration also increased the number of CD4+CD25+FoxP3+ T cells, systemically in the spleen and locally in the joint, and almost completely suppressed proteoglycan-induced experimental arthritis. Furthermore, protection against arthritis could be transferred with T cells isolated from carvacrol-fed mice.

CONCLUSION

These findings illustrate that a food component can boost protective T cell responses to a self stress protein and down-regulate inflammatory disease, i.e., that the immune system can respond to diet.

Hsp70 expression and induction as a readout for detection of immune modulatory components in food

Stress proteins such as heat shock proteins (Hsps) are up-regulated in cells in response to various forms of stress, like thermal and oxidative stress and inflammation. Hsps prevent cellular damage and increase immunoregulation by the activation of anti-inflammatory T-cells. Decreased capacity for stress-induced Hsp expression is associated with immune disorders. Thus, therapeutic boosting Hsp expression might restore or enhance cellular stress resistance and immunoregulation. Especially food- or herb-derived phytonutrients may be attractive compounds to restore optimal Hsp expression in response to stress. In the present study, we explored three readout systems to monitor Hsp70 expression in a manner relevant for the immune system and evaluated novel Hsp co-inducers. First, intracellular staining and analysis by flow cytometry was used to detect stress and/or dietary compound induced Hsp70 expression in multiple rodent cell types efficiently. This system was used to screen a panel of food-derived extracts with potent anti-oxidant capacity. This strategy yielded the identity of several new enhancers of stress-induced Hsp70 expression, among them carvacrol, found in thyme and oregano. Second, CD4(+) T-cell hybridomas were generated that specifically recognized an immunodominant Hsp70 peptide. These hybridomas were used to show that carvacrol enhanced Hsp70 levels increased T-cell activation. Third, we generated a DNAJB1-luc-O23 reporter cell line to show that carvacrol increased the transcriptional activation of a heat shock promoter in the presence of arsenite. These assay systems are generally applicable to identify compounds that affect the Hsp level in cells of the immune system.

Expression of heat shock proteins after ultrasound exposure in HL-60 cells

One of the important cellular defense mechanisms against stress is the induction of heat shock proteins (HSPs). We have recently demonstrated that a low frequency electromagnetic field is unable to induce the heat shock response (HSR). In the present study, we expanded our investigations to the induction of HSPs, particularly Hsp72, by ultrasound (US). Human promyelocytic leukemia HL-60 cells were exposed in suspension to US at 1, 3 and 10 MHz, as well as combinations of two of these frequencies. The ability of US to induce Hsp72 was tested for different frequencies, intensities and exposure times. In addition, the water bath temperature was varied from 30 to 36 degrees C. The Hsp72 protein expression was determined 4 and 24 h after treatment. We found that the amount of Hsp72 increased with increasing US frequency, reaching its highest level of about 1800%, induced by 10 MHz. After increasing the temperature of the water bath, the amount of Hsp72 in the treated cells was also increased, whereas no induction was observed at 30 degrees C. For all treatment conditions, ultrasound of 1 MHz was unable to significantly induce Hsp72. At 10 MHz, the exposure time was varied from 0 to 20 min. We found that the induction of Hsp72 took place after 5 min of exposure. For a fixed level of absorbed US energy, the continuous regime, as well as a pulsation of 1:2 (5 ms on and 5 ms off) induced the same Hsp72 level. Pulsation of 1:5 (2 ms on and 8 ms off) and 1:10 (1 ms on and 9 ms off) did not show any effect. A single sonication of 20 min, as well as a fractionated sonication of two 10 min exposures induced the same level of Hsp72, whereas four exposures of 5 min reduced the Hsp72 level. At the optimum exposure conditions (10 MHz, 10 min), the concentration of other HSPs was also determined. Hsp27 showed no effect but Hsp32, Hsp40 and Hsp72 were induced. Taken together, these results suggest a synergistic interaction between heat and US.

Complementation of a pathogenic IFNGR2 misfolding mutation with modifiers of N-glycosylation

Germline mutations may cause human disease by various mechanisms. Missense and other in-frame mutations may be deleterious because the mutant proteins are not correctly targeted, do not function correctly, or both. We studied a child with mycobacterial disease caused by homozygosity for a novel in-frame microinsertion in IFNGR2. In cells transfected with the mutant allele, most of the interferon γ receptor 2 (IFN-γR2) protein was retained within the cell, and that expressed on the cell surface had an abnormally high molecular weight (MW). The misfolding mutation was not gain-of-glycosylation, as it created no new N-glycosylation site. The mutant IFNGR2 allele was null, as the patient's cells did not respond to IFN-γ. Based on the well-established relationship between protein N-glycosylation and protein quality control processes, we tested 29 compounds affecting maturation by N-glycosylation in the secretory pathway. Remarkably, up to 13 of these compounds reduced the MW of surface-expressed mutant IFN-γR2 molecules and restored cellular responsiveness to IFN-γ. Modifiers of N-glycosylation may therefore complement human cells carrying in-frame and misfolding, but not necessarily gain-of-glycosylation, mutations in genes encoding proteins subject to trafficking via the secretory pathway. Some of these compounds are available for clinical use, paving the way for clinical trials of chemical complementation for various human genetic traits.

Sodium arsenite induces heat shock protein 70 expression and protects against secretagogue-induced trypsinogen and NF-kappaB activation

Heat shock proteins (HSPs), induced by a variety of stresses, are known to protect against cellular injury. Recent studies have demonstrated that prior beta-adrenergic stimulation as well as thermal or culture stress induces HSP70 expression and protects against cerulein-induced pancreatitis. The goal of our current studies was to determine whether or not a non-thermal, chemical stressor like sodium arsenite also upregulates HSP70 expression in the pancreas and prevents secretagogue-induced trypsinogen and NF-kappaB activation. We examined the effects of sodium arsenite preadministration on the parameters of cerulein-induced pancreatitis in rats and then monitored the effects of preincubating pancreatic acini with sodium arsenite in vitro. Our results showed that sodium arsenite pretreatment induced HSP70 expression both in vitro and in vivo and significantly ameliorated the severity of cerulein-induced pancreatitis, as evidenced by the markedly reduced degree of hyperamylasemia, pancreatic edema, and acinar cell necrosis. Sodium arsenite pretreatment not only inhibited trypsinogen activation and the subcellular redistribution of cathepsin B, but also prevented NF-kappaB translocation to the nucleus by inhibiting the IkappaBalpha degradation both in vivo and in vitro. We also examined the effect of sodium arsenite pretreatment in a more severe model of pancreatitis induced by L-arginine and found a similarly protective effect. Based on our observations we conclude that, like thermal stress, chemical stressors such as sodium arsenite also induce HSP70 expression in the pancreas and protect against acute pancreatitis. Thus, non-thermal pharmacologically induced stress can help prevent or treat pancreatitis.

Innate immunity meets with cellular stress at the IKK complex: regulation of the IKK complex by HSP70 and HSP90

Several research models have shown that if cellular stress induces the heat shock response then this will suppress the NF-kappaB-mediated inflammatory response. The NF-kappaB signaling pathway mediates both stress signals and innate immunity signals. Heat shock proteins HSP70 and HSP90 regulate several signaling cascades to maintain cellular homeostasis. Recent studies have revealed that HSP70 and HSP90 proteins regulate the function of the IKK complex which is the major activator of the NF-kappaB complex. The heat shock response can cause the dissociation of the IKK complex, composed of protein kinase subunits IKKalpha and IKKbeta and the regulatory unit NEMO, and inhibit the activation of NF-kappaB signaling. Suppression of immune signaling during cellular stress may be a useful feedback response for helping cells to survive tissue injury. Furthermore, IKKalpha and IKKbeta kinases are important activators of tumorigenesis and hence the inhibition of long-term activation of the IKK complex by HSP70 and HSP90 proteins may prevent cancer development during chronic inflammation.

Protein stress and stress proteins: implications in aging and disease

Environmental stress induces damage that activates an adaptive response in any organism. The cellular stress response is based on the induction of cytoprotective proteins,the so called stress or heat shock proteins. The stress response as well as stress proteins are ubiquitous,highly conserved mechanism, and genes, respectively, already present in prokaryotes. Chaperones protect the proteome against conformational damage, promoting the function of protein networks. Protein damage takes place during aging and in several degenerative diseases, and presents a threat to overload the cellular defense mechanisms. The preservation of a robust stress response and protein disposal is indispensable for health and longevity. This review summarizes the present knowledge of protein damage, turnover, and the stress response in aging and degenerative diseases.

Heat shock protein 70 regulates cellular redox status by modulating glutathione-related enzyme activities

Heat shock protein (Hsp) 70 has been reported to protect various cells and tissues from ischemic damage. However, the molecular mechanisms of the protection are incompletely understood. Ischemia induces significant alterations in cellular redox status that plays a critical role in cell survival/death pathways. We investigated the effects of Hsp70 overexpression on cellular redox status in Madin-Darby canine kidney (MDCK) cells under both hypoxic and ischemic conditions with 3 different approaches: reactive oxygen species (ROS) measurement by a fluorescence probe, redox environment evaluation by a hydroxylamine spin probe, and redox status assessment by the glutathione/glutathione disulfide (GSH/GSSG) ratio. Results from each of these approaches showed that the redox status in Hsp70 cells was more reducing than that in control cells under either hypoxic or oxygen and glucose deprivation (OGD) conditions. In order to determine the mechanisms that mediated the alterations in redox state in Hsp70 cells, we measured the activities of glutathione peroxidase (GPx) and glutathione reductase (GR), two GSH-related antioxidant enzymes. We found that OGD exposure increased GPx and GR activities 47% and 55% from their basal levels (no stress) in Hsp70 cells, compared to only 18% and 0% increase in control cells, respectively. These data, for the first time, indicate that Hsp70 modulates the activities of GPx and GR that regulate cellular redox status in response to ischemic stress, which may be important in Hsp70's cytoprotective effects.

Mechanisms of resistance to cisplatin and carboplatin

While cisplatin and carboplatin are active versus most common cancers, epithelial malignancies are incurable when metastatic. Even if an initial response occurs, acquired resistance due to mutations and epigenetic events limits efficacy. Resistance may be due to excess of a resistance factor, to saturation of factors required for tumor cell killing, or to mutation or alteration of a factor required for tumor cell killing. Platinum resistance could arise from decreased tumor blood flow, extracellular conditions, reduced platinum uptake, increased efflux, intracellular detoxification by glutathione, etc., decreased binding (e.g., due to high intracellular pH), DNA repair, decreased mismatch repair, defective apoptosis, antiapoptotic factors, effects of several signaling pathways, or presence of quiescent non-cycling cells. In lung cancer, flattening of dose-response curves at higher doses suggests that efficacy is limited by exhaustion of something required for cell killing, and several clinical observations suggest epigenetic events may play a major role in resistance.