Differential heat shock gene hsp70-1 response to toxicants revealed by in vivo study of lungs in transgenic mice

Profiling protein targets of cellular toxicant exposure

Environmental agents of exposure can damage proteins, affecting protein function and cellular protein homeostasis. Specific residues are inherently chemically susceptible to damage from individual types of exposure. Amino acid content is not completely predictive of protein susceptibility, as secondary, tertiary, and quaternary structures of proteins strongly influence the reactivity of the proteome to individual exposures. Because we cannot readily predict which proteins will be affected by which chemical exposures, mass spectrometry-based proteomic strategies are necessary to determine the protein targets of environmental toxins and toxicants. This review describes the mechanisms by which environmental exposure to toxins and toxicants can damage proteins and affect their function, and emerging omic methodologies that can be used to identify the protein targets of a given agent. These methods include target identification strategies that have recently revolutionized the drug discovery field, such as activity-based protein profiling, protein footprinting, and protein stability profiling technologies. In particular, we highlight the necessity of multiple, complementary approaches to fully interrogate how protein integrity is challenged by individual exposures.

Effects of coenzyme Q10 on reproductive performance of laying Japanese quail (Coturnix japonica) under cadmium challenge

Japanese quail is an increasingly important bird of economic importance for commercial egg and meat production, particularly in developing countries. There is a need for research aimed at improving efficiency of these birds during stressful challenges, such as oxidative stress. Coenzyme Q10 (CoQ10), a highly functional antioxidant, protects cells against oxidative stress. This study was conducted to determine the effects of CoQ10 on reproductive performance of Japanese quail under cadmium (Cd) challenge. A total of 216 six-wk-old Japanese quail were randomly allocated into 3 groups for an 8 wk experimental trial. The treatments include a negative control (NC): feeding basal diet; a positive control (PC): feeding basal diet and cadmium administration (1 mg/100 g BW, at 10 and 11 wk of age), and (CdQ10): feeding CoQ10 supplemented (900 mg/kg diet) basal diet and Cd administration. At 11 and 13 wk of age, egg production, body weight, mortality, oviduct, and ovarian biometry, were recorded. Histology and histopathology of isthmus and magnum, fertility, hatchability, hatchling quality, and HSP70 mRNA transcript abundance in the utero-vaginal junction (UVJ) were evaluated. Positive control and CdQ10 group had no significant effect on live body weight, stroma weight, follicle size, hatchability, and fertility; however, Cd administration increased (P < 0.01) mortality rate in the PC group compared to the NC and CdQ10 groups. CdQ10 quail produced more eggs and had a higher hatchling quality compared to the PC group (P < 0.01). The thickness and height of isthmus and magnum folds in the CdQ10 group was increased compared to the PC group (P < 0.01) and overall oviduct weight was increased with CoQ10 supplementation (P < 0.01). Compared to PC, the CdQ10 group had a reduction in infiltration of inflammatory cells. Relative abundance of HSP70 mRNA in UVJ was influenced by interactive effect of treatment × time (P < 0.05). In conclusion, dietary supplementation of CoQ10 showed beneficial effects on some reproduction characteristics of female Japanese quail under Cd-induced oxidative stress.

The functions and regulation of heat shock proteins; key orchestrators of proteostasis and the heat shock response

Cells respond to protein-damaging (proteotoxic) stress by activation of the Heat Shock Response (HSR). The HSR provides cells with an enhanced ability to endure proteotoxic insults and plays a crucial role in determining subsequent cell death or survival. The HSR is, therefore, a critical factor that influences the toxicity of protein stress. While named for its vital role in the cellular response to heat stress, various components of the HSR system and the molecular chaperone network execute essential physiological functions as well as responses to other diverse toxic insults. The effector molecules of the HSR, the Heat Shock Factors (HSFs) and Heat Shock Proteins (HSPs), are also important regulatory targets in the progression of neurodegenerative diseases and cancers. Modulation of the HSR and/or its extended network have, therefore, become attractive treatment strategies for these diseases. Development of effective therapies will, however, require a detailed understanding of the HSR, important features of which continue to be uncovered and are yet to be completely understood. We review recently described and hallmark mechanistic principles of the HSR, the regulation and functions of HSPs, and contexts in which the HSR is activated and influences cell fate in response to various toxic conditions.

Differential correlations between changes to glutathione redox state, protein ubiquitination, and stress-inducible HSPA chaperone expression after different types of oxidative stress

In primary bovine fibroblasts with an hspa1b/luciferase transgene, we examined the intensity of heat-shock response (HSR) following four types of oxidative stress or heat stress (HS), and its putative relationship with changes to different cell parameters, including reactive oxygen species (ROS), the redox status of the key molecules glutathione (GSH), NADP(H) NAD(H), and the post-translational protein modifications carbonylation, S-glutathionylation, and ubiquitination. We determined the sub-lethal condition generating the maximal luciferase activity and inducible HSPA protein level for treatments with hydrogen peroxide (H2O2), UVA-induced oxygen photo-activation, the superoxide-generating agent menadione (MN), and diamide (DA), an electrophilic and sulfhydryl reagent. The level of HSR induced by oxidative stress was the highest after DA and MN, followed by UVA and H2O2 treatments, and was not correlated to the level of ROS production nor to the extent of protein S-glutathionylation or carbonylation observed immediately after stress. We found a correlation following oxidative treatments between HSR and the level of GSH/GSSG immediately after stress, and the increase in protein ubiquitination during the recovery period. Conversely, HS treatment, which led to the highest HSR level, did not generate ROS nor modified or depended on GSH redox state. Furthermore, the level of protein ubiquitination was maximum immediately after HS and lower than after MN and DA treatments thereafter. In these cells, heat-induced HSR was therefore clearly different from oxidative stress-induced HSR, in which conversely early redox changes of the major cellular thiol predicted the level of HSR and polyubiquinated proteins.

Synergistic effects of toxic elements on heat shock proteins

Heat shock proteins show remarkable variations in their expression levels under a variety of toxic conditions. A research span expanded over five decades has revealed their molecular characterization, gene regulation, expression patterns, vast similarity in diverse groups, and broad range of functional capabilities. Their functions include protection and tolerance against cytotoxic conditions through their molecular chaperoning activity, maintaining cytoskeleton stability, and assisting in cell signaling. However, their role as biomarkers for monitoring the environmental risk assessment is controversial due to a number of conflicting, validating, and nonvalidating reports. The current knowledge regarding the interpretation of HSPs expression levels has been discussed in the present review. The candidature of heat shock proteins as biomarkers of toxicity is thus far unreliable due to synergistic effects of toxicants and other environmental factors. The adoption of heat shock proteins as "suit of biomarkers in a set of organisms" requires further investigation.

Biocompatibility and genotoxicity studies of polyallylamine hydrochloride nanocapsules in rats

PAH nanocapsule studies in rats showed that it is biocompatible and nongenotoxic for furtherin vivodrug-delivery studies.

Mild hypothermia facilitates the expression of cold-inducible RNA-binding protein and heat shock protein 70.1 in mouse brain

An appropriate thermal control system is essential for maintaining brain homeostasis. Hypothermia is a decrease in core body temperature that occurs when the thermoregulatory responses of homeothermic animals are impaired by environmental and situational influences, such as cold ambience and anesthesia. In recent years, hypothermia has been used for medical treatment, i.e., therapeutic hypothermia, for patients with stroke, traumatic brain injury, and heart surgery. However, the target molecules acting during hypothermia have not been identified. To understand the molecular mechanisms, we generated a mouse model of mild hypothermia (1°C-2°C below normal), and analyzed the expression of several genes. After mice were exposed to cold for 24 and 48 h, their rectal temperature reached 33°C-35°C. Then, using real-time quantitative PCR, we analyzed the mRNA expression levels of c-fos, cold-inducible RNA-binding protein (CIRP), heat shock protein (hsp) 70.1, oxytocin, and representative inflammatory cytokines, i.e., tumor necrosis factor (TNF)-α and interleukin (IL)-6 in target organs. Importantly, we found that the expression levels of CIRP and hsp70.1 were elevated in the olfactory bulb within 48 h. In the hypothalamus, CIRP expression levels increased and were followed by an increase in hsp70.1 expression. Meanwhile, TNF-α and IL-6 expression decreased gradually over 24 and 48 h in the olfactory bulb and hypothalamus. These specific expression profiles, i.e., enhanced CIRP and hsp70.1 expression and depressed cytokine expression, suggest that they could regulate apoptosis related to the cytokine signaling.

Identification of candidate genes downstream of TLR4 signaling after ozone exposure in mice: a role for heat-shock protein 70

BACKGROUND

Toll-like receptor 4 (TLR4) is involved in ozone (O3)-induced pulmonary hyperpermeability and inflammation, although the downstream signaling events are unknown.

OBJECTIVES

The aims of our study were to determine the mechanism through which TLR4 modulates O3-induced pulmonary responses and to use transcriptomics to determine potential TLR4 effector molecules.

METHODS

C3H/HeJ (HeJ; Tlr4 mutant) and C3H/HeOuJ (OuJ; Tlr4 normal) mice were exposed continuously to 0.3 ppm O3 or filtered air for 6, 24, 48, or 72 hr. We assessed inflammation using bronchoalveolar lavage and molecular analysis by mRNA microarray, quantitative RT-PCR (real-time polymerase chain reaction), immunoblots, immunostaining, and ELISAs (enzyme-linked immunosorbent assays). B6-Hspa1a/Hspa1btm1Dix/NIEHS (Hsp70-/-) and C57BL/6 (B6; Hsp70+/+ wild-type control) mice were used for candidate gene validation studies.

RESULTS

O3-induced TLR4 signaling occurred through myeloid differentiation protein 88 (MyD88)-dependent and -independent pathways in OuJ mice and involved multiple downstream pathways. Genomewide transcript analyses of lungs from air- and O3-exposed HeJ and OuJ mice identified a cluster of genes that were significantly up-regulated in O3-exposed OuJ mice compared with O3-exposed HeJ mice or air-exposed controls of both strains; this cluster included genes for heat-shock proteins (e.g., Hspa1b, Hsp70). Moreover, O3-induced inflammation, MyD88 up-regulation, extracellular-signal-related kinase-1/2 (ERK1/2) and activator protein-1 (AP-1) activation, and kerotinocyte-derived chemokine (KC) protein content were significantly reduced in Hspa1a/Hspa1btm1Dix (Hsp70-/-) compared with Hsp70+/+ mice (p < 0.05).

CONCLUSIONS

These studies suggest that HSP70 is an effector molecule downstream of TLR4 and is involved in the regulation of O3-induced lung inflammation by triggering similar pathways to TLR4. These novel findings may have therapeutic and preventive implications for inflammatory diseases resulting from environmental exposures.

Pulse duration determines levels of Hsp70 induction in tissues following laser irradiation

Induction of heat shock protein (Hsp) expression correlates with cytoprotection, reduced tissue damage, and accelerated healing in animal models. Since Hsps are transcriptionally activated in response to stress, they can act as stress indicators in burn injury or surgical procedures that produce heat and thermal change. A fast in vivo readout for induction of Hsp transcription in tissues would allow for the study of these proteins as therapeutic effect mediators and reporters of thermal stress∕damage. We used a transgenic reporter mouse in which a luciferase expression is controlled by the regulatory region of the inducible 70 kilodalton (kDa) Hsp as a rapid readout of cellular responses to laser-mediated thermal stress∕injury in mouse skin. We assessed the pulse duration dependence of the Hsp70 expression after irradiation with a CO(2) laser at 10.6 μm in wavelength over a range of 1000 to 1 ms. Hsp70 induction varied with changes in laser pulse durations and radiant exposures, which defined the ranges at which thermal activation of Hsp70 can be used to protect cells from subsequent stress, and reveals the window of thermal stress that tissues can endure.

HSFs and regulation of Hsp70.1 (Hspa1b) in oocytes and preimplantation embryos: new insights brought by transgenic and knockout mouse models

Gene encoding heat shock protein (Hsps) are induced following a thermal stress thanks to the activation of heat shock transcription factor (HSF) which interacts with heat shock elements (HSE) located within the sequence of Hsp promoters. This cellular and protective response (heat shock response (HSR)) is well known and evolutionarily conserved. Nevertheless, HSR does not function in all the cells produced during the life of a multicellular organism, e.g., early mouse embryos. Taking advantage of mouse transgenic and knockout models, we investigated the roles of trans (HSF 1 and 2) and cis (HSE) regulatory elements in the control of Hsp70.1 (Hspa1b) through several developmental steps from oocytes to blastocysts. Our studies confirm that, even in absence of any stress, HSF1 regulates Hsp70.1 in oocytes and early embryos. Our data emphasize the role of maternal and paternal HSFs in the developmentally regulated expression of Hsp70.1 observed when the zygotic genome activation occurs. Furthermore, in this unstressed developmental condition, affinity and binding to HSEs might be more permissive than in the stress response. Finally, submitting blastocyst to different stress conditions, we show that HSF2 is differentially required for Hsp expression and cell survival. Taken together, our findings indicate that the role of heat shock trans and cis regulatory elements evolve along the successive steps of early embryonic development.

[Behçet's disease in obstetrics and gynecology]

Behçet's disease is a multisystemic disease of unknown origin characterized by a recurrent bipolar aphtosis (oral and genital) associated with vascular, digestive or articular symptoms. Gynecologists can be faced to this disease at any time of the life of their patients, including during the pregnancy. Given that the first demonstrations of the disease can be genital, they are in the front line to evoke this diagnosis. They thus have to know the main characteristics of the disease to make the diagnosis and to organize a multidisciplinary management. During pregnancy, the treatment of the disease is to be adapted to avoid teratogenic drugs, and adapt the doses of the treatment.

Cellular stress response pathway system as a sentinel ensemble in toxicological screening

High costs, long test times, and societal concerns related to animal use have required the development of in vitro assays for the rapid and cost-effective toxicological evaluation and characterization of compounds in both the pharmaceutical and environmental arenas. Although the pharmaceutical industry has developed very effective, high-throughput in vitro assays for determining the therapeutic potential of compounds, the application of this approach to toxicological screening has been limited. A primary reason for this is that while drug candidate screens are directed to a specific target/mechanism, xenobiotics can cause toxicity through any of a myriad of undefined interactions with cellular components and processes. Given that it is not practical to design assays that can interrogate each potential toxicological target, an integrative approach is required if there is to be a rapid and low-cost toxicological evaluation of chemicals. Cellular stress response pathways offer a viable solution to the creation of a set of integrative assays as there is a limited and hence manageable set (a small ensemble of 10 or less) of major cellular stress response pathways through which cells mount a homoeostatic response to toxicants and which also participate in cell fate/death decisions. Further, over the past decades, these pathways have been well characterized at a molecular level thereby enabling the development of high-throughput cell-based assays using the components of the pathways. Utilization of the set of cellular stress response pathway-based assays as indicators of toxic interactions of chemicals with basic cellular machinery will potentially permit the clustering of chemicals based on biological response profiles of common mode of action (MOA) and also the inference of the specific MOA of a toxicant. This article reviews the biochemical characteristics of the stress response pathways, their common architecture that enables rapid activation during stress, their participation in cell fate decisions, the essential nature of these pathways to the organism, and the biochemical basis of their cross-talk that permits an assay ensemble screening approach. Subsequent sections describe how the stress pathway ensemble assay approach could be applied to screening potentially toxic compounds and discuss how this approach may be used to derive toxicant MOA from the biological activity profiles that the ensemble strategy provides. The article concludes with a review of the application of the stress assay concept to noninvasive in vivo assessments of chemical toxicants.

Molecular imaging, an innovative methodology for whole-body profiling of endocrine disrupter action

Endocrine disrupters (EDs) are environment and food contaminants known to alter metabolic functions of mammals by interfering with specific endocrine pathways. Many EDs act on steroid hormone target cells by interacting with intracellular receptors (IRs) like estrogen receptors, androgen receptors, and thyroid hormone receptors; other receptors may be engaged. IRs are ligand-operated transcription factors acting in concert with general or cell-specific coregulators. The newly acquired awareness on the panoply of IR functions has increased the concern on potential, unsought, harmful effects of EDs on human health and has questioned the capability of currently available methodologies to identify and study EDs in the environment and in the food chain. Indeed, current in vivo and in vitro methodologies restrict the analysis to very specific organs or cell systems, with obvious limitations in predicting the systemic metabolic consequences of ED exposure. The emphasis recently laid by Regulatory Authorities, including European Center for the Validation of Alternative Methods, on the generation of in vitro model systems for toxicological analyses discouraged the development of models suitable to envision the whole spectrum of ED body actions required when studying compounds acting through IRs. Molecular imaging now provides the opportunity to quantify ED effects in living organisms enabling, for the first time, to acquire a full comprehension of the systemic effects of acute and prolonged exposure to EDs, solving the issue of the potential harm due to repeated low-dose exposure. The systems here reviewed are of unquestionable toxicological relevance and need to be taken into consideration to improve the methodology currently available and in use.

Fluoro-edenite fibers induce expression of Hsp70 and inflammatory response

Many asbestos-like mineral fibers have been detected in the air of mountainous and volcanic areas of Italy and other parts of the world. These fibers have been suspected to be the cause of increased incidences of lung cancer and other lung diseases in these areas. However, the mechanisms of the cellular response and defense following exposure to these microscopic fibers have not been characterized. We continue to study these mechanisms to be able to propose preventive strategies in large populations. The objective of the present study was to determine comparatively biological responses of mesothelial Met-5A and monocyte-macrophage J774 cells following exposure to two types of fluoro-edenite fibers having low and high iron content (labeled 19 and 27, respectively) obtained from Biancavilla (Sicily, Italy). The reference fiber was a non-iron fibrous tremolite from Val di Susa (Piemonte, Italy). The cells were treated with 5, 50, and 100 μg of fibrous matter per 1 ml for 72 hr. We identified several key mechanisms by which cells responded and counteracted the injury induced by these fibers. The fibers caused induction of the heat shock protein 70 (Hsp70), stimulated formation of reactive oxygen species (detected by using DCFH-DA as a fluorescent probe) and NO^• (measured as nitrite). Exposure of cells to the fibers induced lactate dehydrogenase activity and decreased viability. The fluoro-endenite type 27 was the most potent fiber tested, which indicated that iron and possibly manganese contribute significantly to this fiber toxicity. The J774 cells were more sensitive to fluoro-edenite than Met-5A cells suggesting that the primary site of the fiber-induced inflammatory response could be the macrophage rather than the pulmonary epithelium. Fluoro-edenite produces more biological alterations with respect to non-iron tremolite. Hsp70 and free radicals could be important factors in the context of mineral fiber-induced acute lung injury leading possibly to mutagenic effects. We anticipate that pharmacological blockade of the fiber-dependent cellular responses could in long term offer preventive approach to combat lung diseases induced by these fibers.

Molecular-genetic imaging based on reporter gene expression

Molecular imaging includes proteomic, metabolic, cellular biologic process, and genetic imaging. In a narrow sense, molecular imaging means genetic imaging and can be called molecular-genetic imaging. Imaging reporter genes play a leading role in molecular-genetic imaging. There are 3 major methods of molecular-genetic imaging, based on optical, MRI, and nuclear medicine modalities. For each of these modalities, various reporter genes and probes have been developed, and these have resulted in successful transitions from bench to bedside applications. Each of these imaging modalities has its unique advantages and disadvantages. Fluorescent and bioluminescent optical imaging modalities are simple, less expensive, more convenient, and more user friendly than other imaging modalities. Another advantage, especially of bioluminescence imaging, is its ability to detect low levels of gene expression. MRI has the advantage of high spatial resolution, whereas nuclear medicine methods are highly sensitive and allow data from small-animal imaging studies to be translated to clinical practice. Moreover, multimodality imaging reporter genes will allow us to choose the imaging technologies that are most appropriate for the biologic problem at hand and facilitate the clinical application of reporter gene technologies. Reporter genes can be used to visualize the levels of expression of particular exogenous and endogenous genes and several intracellular biologic phenomena, including specific signal transduction pathways, nuclear receptor activities, and protein-protein interactions. This technique provides a straightforward means of monitoring tumor mass and can visualize the in vivo distributions of target cells, such as immune cells and stem cells. Molecular imaging has gradually evolved into an important tool for drug discovery and development, and transgenic mice with an imaging reporter gene can be useful during drug and stem cell therapy development. Moreover, instrumentation improvements, the identification of novel targets and genes, and imaging probe developments suggest that molecular-genetic imaging is likely to play an increasingly important role in the diagnosis and therapy of cancer.

Development of a bicistronic vector for multimodality imaging of estrogen receptor activity in a breast cancer model: preliminary application

PURPOSE

The aim of this study was to develop a cellular model for the concurrent imaging of reporter genes expression by using positron emission tomography (PET) and bioluminescence imaging (BLI) for the assessment of estrogen receptor activity in vivo in a breast cancer model.

METHODS

Two reporters were chosen: a mutated form of the dopaminergic D2 receptor (D(2)R80A) for PET imaging, and the Firefly Luciferase for BLI. The presence of an IRES sequence between the two reporters ensured the coordinated expression driven by the same regulatory sequence containing an estrogen responsive element (ERE). To prevent chromatin effects on reporter expression, the construct was flanked by insulator sequences (Matrix Attachment Region, MAR).

RESULTS

In vitro studies showed that the vector was efficient in coordinating the expression of the two genes. Moreover, stably transfected cells implanted in recipient animals maintained their capacity to express the reporters and react to systemic treatments permitting the in vivo study of ERs activity by PET and BLI imaging. In vitro expression analysis after long-term treatments showed different behaviour of the two reporter proteins in monitoring estrogen-dependent transcription outlining the importance of multi-reporter systems. With this model, PET and BLI can be applied to the concurrent evaluation of gene expression induced by estrogen and its analogues by using a bicistronic construct.

CONCLUSION

The combined features of rapid, sensitive, sequential BLI and tomographic and quantitative PET imaging will allow the use of this strategy for the in vivo evaluation of molecular processes also for pharmacodynamic studies.

Cell death, stress-responsive transgene activation, and deficits in the olfactory system of larval zebrafish following cadmium exposure

Cadmium (Cd) is a well-described environmental pollutant known to have adverse effects in fish, including behavioral deficits. We have previously reported the development of an in vivo system that utilizes hsp70 gene activation as a measure of acute 3 h cadmium toxicity in whole living transgenic zebrafish larvae carrying a stably integrated hsp70-enhanced green fluorescent protein (eGFP) reporter gene. Here, we report that activation of this transgene in olfactory epithelium of zebrafish larvae during 96 h sublethal Cd exposure is predictive of cadmium-induced cell death, altered histological and surface organization of the epithelium, and changes in olfactory dependent behavior. The transgene is first activated in the olfactory epithelium at concentrations below those giving rise to significant defects, but exhibits a more robust response following exposure to Cd at concentrations that begin to cause significant cell death, morphological alterations, and behavioral deficits. Further, the data show that Cd-induced olfactory deficits reported previously in juvenile and adult fish can also occur during larval stages of fish development, and that such behavioral deficits are closely associated with cell death and structural alterations in the olfactory epithelium.

Cadmium: cellular effects, modifications of biomolecules, modulation of DNA repair and genotoxic consequences (a review)

Cadmium is an important toxic environmental heavy metal. Occupational and environmental pollution with cadmium results mainly from mining, metallurgy industry and manufactures of nickel-cadmium batteries, pigments and plastic stabilizers. Important sources of human intoxication are cigarette smoke as well as food, water and air contaminations. In humans, cadmium exposures have been associated with cancers of the prostate, lungs and testes. Acute exposures are responsible for damage to these organs. Chronic intoxication is associated with obstructive airway disease, emphysema, irreversible renal failure, bone disorders and immuno-suppression. At the cellular level, cadmium affects proliferation, differentiation and causes apoptosis. It has been classified as a carcinogen by the International Agency for Research on Cancer (IARC). However, it is weakly genotoxic. Indirect effects of cadmium provoke generation of reactive oxygen species (ROS) and DNA damage. Cadmium modulates also gene expression and signal transduction, reduces activities of proteins involved in antioxidant defenses. Several studies have shown that it interferes with DNA repair. The present review focuses on the effects of cadmium in mammalian cells with special emphasis on the induction of damage to DNA, membranes and proteins, the inhibition of different types of DNA repair and the induction of apoptosis. Current data and hypotheses on the mechanisms involved in cadmium genotoxicity and carcinogenesis are outlined.

Transcriptome response to heavy metal stress in Drosophila reveals a new zinc transporter that confers resistance to zinc

All organisms are confronted with external variations in trace element abundance. To elucidate the mechanisms that maintain metal homeostasis and protect against heavy metal stress, we have determined the transcriptome responses in Drosophila to sublethal doses of cadmium, zinc, copper, as well as to copper depletion. Furthermore, we analyzed the transcriptome of a metal-responsive transcription factor (MTF-1) null mutant. The gene family encoding metallothioneins, and the ABC transporter CG10505 that encodes a homolog of 'yeast cadmium factor' were induced by all three metals. Zinc and cadmium responses have similar features: genes upregulated by both metals include those for glutathione S-transferases GstD2 and GstD5, and for zinc transporter-like proteins designated ZnT35C and ZnT63C. Several of the metal-induced genes that emerged in our study are regulated by the transcription factor MTF-1. mRNA studies in MTF-1 overexpressing or null mutant flies and in silico search for metal response elements (binding sites for MTF-1) confirmed novel MTF-1 regulated genes such as ferritins, the ABC transporter CG10505 and the zinc transporter ZnT35C. The latter was analyzed in most detail; biochemical and genetic approaches, including targeted mutation, indicate that ZnT35C is involved in cellular and organismal zinc efflux and plays a major role in zinc detoxification.

Ozone induces oxidative stress in rat alveolar type II and type I-like cells

Ozone is a highly reactive gas present in urban air, which penetrates deep into the lung and causes lung injury. The alveolar epithelial cells are among the first cell barriers encountered by ozone. To define the molecular basis of the cellular response to ozone, primary cultures of rat alveolar type II and type I-like cells were exposed to 100 ppb ozone or air for 1 h. The mRNA from both phenotypes was collected at 4 and 24 h after exposure for gene expression profiling. Ozone produced extensive alterations in gene expression involved in stress and inflammatory responses, transcription factors, antioxidant defenses, extracellular matrix, fluid transport, and enzymes of lipid metabolism and cell differentiation. Real-time reverse transcription-polymerase chain reaction and Western blot analysis verified changes in mRNA and protein levels of selected genes. Besides the increased stress response, ozone exposure downregulated genes of cellular differentiation. The changes were more prominent at 4 h in the type I-like phenotype and at 24 h in the type II phenotype. The type I-like cells were more sensitive to ozone than type II cells. The genome-wide changes observed provide insight into signal pathways activated by ozone and how cellular protection mechanisms are initiated.

Molecular imaging: a new way to study molecular processes in vivo

Non-invasive imaging of reporter gene expression using different imaging modalities is increasing its role for the in vivo assessment of molecular processes. Multimodality imaging protocols overcome limitations to a single imaging modality and provide a thorough view of specific processes, often allowing a quantitative measurement and direct visualization of the process in a specific target organ or tissue. The use of the right reporter gene for the development of animal models and the characterization of its expression in different conditions and tissues is fundamental for basic, translational and future pharmacological applications of a given model. This paper summarizes the major steps in the development and evaluation of a specific animal model for in vivo molecular imaging studies and describes the first example of an animal model designed for the in vivo assessment of a specific receptor activity and its possible evolution towards multimodality imaging analysis.

Increased heat shock protein 70 expression following toxicant-mediated cytotoxicity: a ubiquitous marker of toxicant exposure?

The up-regulation of heat shock protein (HSP) expression has been proposed as a general biomarker of cellular protection against various environmental stresses and chemicals. The present study investigated the possibility of using HSP70 up-regulation as a biomarker of toxicant exposure in vitro. Cells of a rat hepatoma cell line (FGC4) were exposed to concentrations of 1,3-dichloroacetone, duroquinone, diquat dibromide, menadione, hydrogen peroxide, cadmium chloride (CdCl2) and sodium (meta)arsenite (NaAsO2) that elicited 20-50% cytotoxicity over a 24-hour period, and HSP70 levels were measured by ELISA. Up-regulation of HSP70 expression was demonstrated following treatment with menadione, CdCl2 and NaAsO2, but not with the other chemicals tested. A shorter exposure time (6 hours) and/or the use of non-toxic concentrations reduced the level of HSP70 up-regulation with menadione, CdCl2 and NaAsO2, but did not uncover any up-regulation with the other chemicals. Although the toxicity of the majority of the chemicals tested is believed to involve an oxidative stress component, the results of this study clearly demonstrate that up-regulation of HSP70 expression cannot be used as a general biomarker of toxicant exposure in vitro.

Oxidative stress as a multiple effector in Fanconi anaemia clinical phenotype

Fanconi anaemia (FA) is a genetic disease characterised by bone marrow failure with excess risk of myelogenous leukaemia and solid tumours. A widely accepted notion in FA research invokes a deficiency of response to DNA damage as the fundamental basis of the 'crosslinker sensitivity' observed in this disorder. However, such an isolated defect cannot readily account for the full cellular and clinical phenotype, which includes a number of other abnormalities, such as malformations, endocrinopathies, and typical skin spots. An extensive body of evidence pointing toward an involvement of oxidative stress in the FA phenotype includes the following: (i) In vitro and ex vivo abnormalities in a number of redox status endpoints; (ii) the functions of several FA proteins in protecting cells from oxidative stress; (iii) redox-related toxicity mechanisms of the xenobiotics evoking excess toxicity in FA cells. The clinical features in FA and the in vivo abnormalities of redox parameters are here reconsidered in view of the pleiotropic clinical phenotype and known biochemical and molecular links to an in vivo prooxidant state, which causes oxidative damage to biomolecules, resulting in an excessive number of acquired abnormalities that may overwhelm the cellular repair capacity rather than a primary deficiency in DNA repair. FA may thus represent a unique model disease in testing the integration between the acquisition of macromolecular damage as a result of oxidative stress and the ability of the mammalian cell to respond effectively to such damage.

Gene expression pattern in spontaneously hypertensive rats exposed to urban particulate matter (EHC-93)

Epidemiological studies show associations of short-term exposure to particulate matter with morbidity and mortality. Although many studies investigate the health effects of ambient particulate matter, the associated mechanisms, and the causality, they often focus on classical parameters. The objective of the present study was to gain insight into the roles of a wide range of genes in this process. Particular attention has been paid to immediate oxidative stress in the lung. We isolated total lung RNA from spontaneously hypertensive male rats 2-40 h after exposure to reference EHC-93 (10 mg/kg). Our results show that exposure to particulate matter generates a time-dependent pattern of gene expression. From the 8799 genes or expressed sequence tags tested, we see that 132 genes were up- or downregulated shortly after exposure (i.e., 2-6 h), whereas after 15-21 h and 24-40 h, 46 and 56 genes showed altered expression, respectively. Focusing on the earliest point, 99 of the 132 genes were identified as unique. They include genes involved in an oxidative stress response (hemeoxygenase-1, metallothioneins, and thioredoxin reductase), an inflammatory response macrophage inflammatory protein-2, and tumor necrosis factor alpha), transcription factors belonging to the activating protein-1 family, and genes involved in cardiovascular functions. The present study, although not representing an ambient situation, is used to identify the biological pathways implicated in the initial injury response to PM exposure. Using Affymetrix chips, this study shows time-dependent gene expression, it identifies many genes that can be affected by exposure to particulate matter, and it confirms the involvement of oxidative stress in particulate-matter-related effects.

Evidence for a role of heat shock factor 1 in inhibition of NF-κB pathway during heat shock response-mediated lung protection

Heat shock transcription factor (HSF)-1 is recognized as a central component of the heat shock response, which protects against various harmful conditions. However, the mechanisms underlying the protection and the role of HSF-1 in these mechanisms have not yet been clearly elucidated. Using HSF-1 knockout mice ( Hsf1−/−), we examined whether heat shock response-mediated lung protection involved an inhibition of the proinflammatory pathway via an interaction between HSF-1 and NF-κB, in response to cadmium insult. The HSF-1-dependent protective effect against intranasal instillation of cadmium (10 and 100 μg/mouse) was demonstrated by the higher protein content (1.2- and 1.4-fold), macrophage (1.6- and 1.9-fold), and neutrophil (2.6- and 1.8-fold) number in bronchoalveolar fluids, higher lung wet-to-dry weight ratio, and more severe lung damage evaluated by histopathology in Hsf1−/−compared with wild-type animals. These responses were associated with higher granulocyte/macrophage colony-stimulating factor (GM-CSF; 1.7-fold) but not TNF-α concentrations in bronchoalveolar fluids of Hsf1−/−mice compared with those of wild-type animals, indicating that HSF-1 behaved as a repressor of specific cytokine production in our model. To further investigate the mechanism of GM-CSF repression, we analyzed the NF-κB activity and IκB stability. The DNA binding NF-κB activity, in particular p50 homodimer activity, was higher in Hsf1−/−mice than in wild-type mice after cadmium exposure. These results provide a first line of evidence that mechanisms of lung protection depending on HSF-1 involve specific cytokine repression via inhibition of NF-κB activation in vivo.

Techniques: Reporter mice – a new way to look at drug action

During the past decade remarkable progress in molecular genetics and the possibility of manipulating cells so that the expression of genes can directly 'report' on drug activity has produced major changes in drug development strategies. The recent description and pharmacological validation of reporter mice for in vivo analysis of hormone receptor activity opens new horizons for drug discovery. These novel animal models, in association with in vivo imaging technologies, provide a global view of the target tissues of drug action following acute and repeated drug treatment, thus enabling the prediction of potential side-effects in the early phase of preclinical studies. It is anticipated that further improvements of transgene architecture will lead to models that combine pharmacokinetic, pharmacodynamic and toxicological studies in a single step, which should provide a tremendous saving in time and, paradoxically, the number of animals to be sacrificed in the development of novel pharmacologically active molecules.

Use of Hsf1−/− mice reveals an essential role for HSF1 to protect lung against cadmium-induced injury

Cadmium (Cd) is known to activate heat shock (HS) response, which is characterized by overexpression of heat shock proteins (Hsps) under the control of heat shock factor 1 (HSF1). The potential protection provided by the HS response, induced by increasing the body temperature of animals before Cd exposure or by Cd itself, against pathophysiological changes occurring after Cd intranasal instillation (1 to 100 microg/mouse) was examined. HSF1-deficient mice were used to evaluate the role of this factor in lung protection. Cd instillation caused dose- and time-dependent changes in the respiratory pattern measured by plethysmography (Penh), and significant increases in lactate dehydrogenase (LDH) activity as well as macrophage and neutrophil counts in bronchoalveolar lavage fluids. HS preconditioning induced Hsp overexpression and reduced the Penh (-30%), LDH (-25%), and neutrophil (-55%) responses to subsequent administration of the highest Cd doses (50 and 100 microg) in wild-type mice. HSF1 deficiency abolished the HS response and its protective effect. In the absence of preconditioning, Hsf1(-/-) mice exhibited higher values of Penh (+70%) and LDH activity (+42%) compared with wild-type animals when exposed to the lowest Cd doses. Higher macrophage (+80%) and neutrophil counts (+115%) were recorded whatever the dose. Western blot analyses indicated that lung protection might be related to the kinetics of HSF1-dependent Hsp70 expression. Altogether, our data demonstrate that HS response elicited both by prior HS and by Cd itself moderates pulmonary injuries due to Cd instillation, and that HSF1 is a major mediator in this protection.