Human and environmental health challenges for the next decade (2010–2020).

The public health and environmental communities will face many challenges during the next decade. To identify significant issues that might be addressed as part of the International Life Sciences Institute (ILSI) Health and Environmental Sciences Institute (HESI) scientific portfolio, an expert group of key government, academic, and industry scientists from around the world were assembled in 2009 to map the current and future landscape of scientific and regulatory challenges. The value of the scientific mapping exercise was the development of a tool which HESI, individual companies, research institutions, government agencies, and regulatory authorities can use to anticipate key challenges, place them into context, and thus strategically refine and expand scientific project portfolios into the future.

Maximizing safe design of engineered nanomaterials: the NIH and NIEHS research perspective.

Estimating potential risk of an emerging technology as its products are being developed offers the greatest potential for success of the technology. The National Nanotechnology Initiative was launched in 2000 to provide a federal framework to support safe and responsible development of nanotechnology.Within this framework, the National Institutes of Health (NIH) focuses resources and expertise on both the biomedical applications of nanotechnology and the possibility of adverse health effects, or implications research. NIH developed the NanoHealth and Safety Enterprise Initiative by identifying shared research needs across the nanotechnology applications and implications research communities to create an integrated research strategy to maximize resources and expedite the development of engineered nanomaterials (ENM) that are safe by design. The central goal of this program is to decipher the fundamental principles of ENM interactions with biological systems that are relevant to human exposure and physiological response. Program components include materials science, basic biology, pathobiology, and informatics, as well as a cross-disciplinary training program for new nanotechnology scientists. The magnitude of this program will be best supported by flexible, dynamic funding and research mechanisms including the formation of public-private partnerships that span the expertise and interests of government, industry, academia, public interest, and other stakeholders. It is through such innovative, integrated, and cross-disciplinary programs that the full promise of nanotechnology may be realized while ensuring that this emerging field does not succumb to hidden perils.

Genetic determinants of sensitivity to beryllium in mice.

Chronic beryllium disease (CBD), an irreversible, debilitating granulomatous lung disease is caused by exposure to beryllium. This occupational hazard occurs in primary production and machining of Be-metal, BeO, beryllium - containing alloys, and other beryllium products. CBD begins as an MHC Class II-restricted, T(H)1 hypersensitivity, and the Human Leukocyte Antigen, HLA-DPB1E(69), is associated with risk of developing CBD. Because inbred strains of mice have not provided good models of CBD to date, three strains of HLA-DPB1 transgenic mice in an FVB/N background were developed; each contains a single allele of HLA-DPB1 that confers a different magnitude of risk for chronic beryllium disease: HLA-DPB1*0401 (OR approximately 0.2), HLA-DPB1*0201 (OR approximately 3), and HLA-DPB1*1701 (OR approximately 46). The mouse ear swelling test (MEST) was employed to determine if these different alleles would support a hypersensitivity response to beryllium. Mice were first sensitized on the back and subsequently challenged on the ear. In separate experiments, mice were placed into one of three groups (sensitization/challenge): C/C, C/Be, and Be/Be. In the HLA-DPB1*1701 mice, the strain with the highest risk transgene, the Be/Be group was the only group that displayed significant maximum increased ear thickness of 19.6% +/- 3.0% over the baseline measurement (p < 0.05). No significant changes were observed in the other transgenic strains for any treatment condition. In addition, inter-strain differences in response to beryllium in seven inbred strains were investigated through use of the MEST, these included: FVB/N, AKR, Balb/c, C3H/HeJ, C57/BL6, DBA/2, and SJL/J. The FVB/N strain was least responsive, while the SJL/J and C57/BL6 strains were the highest responders. Our results suggest that the HLA-DPB1*1701 transgene product is an important risk factor for induction of the beryllium-sensitive phenotype. This model should be a useful tool for investigating beryllium sensitization.

Determination of in vivo dose response and allergen-specific T cells in subjects contact-sensitized to squaric acid dibutyl ester.

BACKGROUND: Squaric acid dibutyl ester (SADBE) is a known contact sensitizer, but dose-response data are not defined. OBJECTIVE: To determine the relationship between sensitization dose and contact hypersensitivity (CHS) response to SADBE in human volunteers. The study also aimed to investigate whether SADBE-reactive blood T cells could be detected using ex vivo mature dendritic cells (DCs) as antigen-presenting cells. METHOD: Forty healthy volunteers were sensitized to either 12.5, 25, 50, or 250 microg of SADBE in a 48 microL volume. This was followed by elicitation 2 weeks later with five doses (0, 0.2, 2, 20, and 200 microg in 20 microL). An additional 10 subjects received the elicitation doses without prior sensitization. Blood samples obtained after sensitization were purified into T cells and mature DCs. RESULTS: A direct relationship between sensitization dose and in vivo CHS response was observed. The SADBE dose that effectively sensitized 50% of the population (ED50) was 22 microg/cm2. Significant SADBE-specific T-cell proliferation in vitro was not observed 2 weeks after sensitization but became evident after elicitation. CONCLUSION: This study establishes the in vivo dose-response characteristics of immune reactivity to SADBE and antigen-specific T-cell reactivity.

Ethics in nanomedicine.

As the science and technology of nanomedicine speed ahead, ethics, policy and the law are struggling to keep up. It is important to proactively address the ethical, social and regulatory aspects of nanomedicine in order to minimize its adverse impacts on the environment and public health and also to avoid a public backlash. At present, the most significant concerns involve risk assessment, risk management of engineered nanomaterials and risk communication. Although in vivo animal experiments and ex vivo laboratory analyses can increase our understanding of the interaction of engineered nanomaterials in biological systems, they cannot eliminate all of the uncertainty surrounding the exposure of a human subject to nanomedicine products in clinical trials. Significant risks can still materialize after a product has cleared the Phase I hurdle and is in Phase II or III clinical trials. Furthermore, as the use of engineered nanomaterials in nanomedicine increases, questions of social justice, access to healthcare and the use of nanotechnology for physical enhancement become increasingly important.

Ethical issues in clinical trials involving nanomedicine.

Nanomedicine shows tremendous promise for improving medical diagnosis, treatment, and prevention, but it also raises a variety of ethical concerns. Because of the paucity of data on the physicochemical properties of nanoscale materials in biological systems, clinical trials of nanomedicine products present some unique challenges related to risk minimization, management and communication involving human subjects. Although these clinical trials do not raise any truly novel ethical issues, the rapid development of nanotechnology and its potentially profound social and environmental impacts, add a sense of urgency to the problems that arise.

Beryllium exposure: dermal and immunological considerations.

OBJECTIVE: People exposed to beryllium compounds are at increased risk of developing beryllium sensitization and chronic beryllium disease (CBD). The purpose of this short communication is to present information regarding the potential importance of skin exposure to beryllium, an exposure and alternate immune response pathway to the respiratory tract, which has been largely overlooked in epidemiologic and exposure assessment studies. METHODS: We reviewed the published literature, including epidemiologic, immunologic, genetic, and laboratory-based studies of in vivo and in vitro models, to assess the state of knowledge concerning skin exposure to beryllium. RESULTS: Reduction in inhalation exposure to beryllium has not resulted in a concomitant reduction in the occurrence of beryllium sensitization or CBD, suggesting that continued prevalence may be due, in part, to unchecked skin exposure to beryllium-containing particles. CONCLUSIONS: Recent developments in our understanding of the multiple exposure pathways that may lead to beryllium sensitization and CBD suggest that a prudent approach to worker protection is to assess and minimize both skin and inhalation exposures to beryllium.

Electrostatic potential on human leukocyte antigen: implications for putative mechanism of chronic beryllium disease.

The pathobiology of chronic beryllium disease (CBD) involves the major histocompatibility complex class II human leukocyte antigen (HLA). Although occupational exposure to beryllium is the cause of CBD, molecular epidemiologic studies suggest that specific (Italic)HLA-DPB1(/Italic) alleles may be genetic susceptibility factors. We have studied three-dimensional structural models of HLA-DP proteins encoded by these genes. The extracellular domains of HLA-DPA1*0103/B1*1701, *1901, *0201, and *0401, and HLA-DPA1*0201/B1*1701, *1901, *0201, and *0401 were modeled from the X-ray coordinates of an HLA-DR template. Using these models, the electrostatic potential at the molecular surface of each HLA-DP was calculated and compared. These comparisons identify specific characteristics in the vicinity of the antigen-binding pocket that distinguish the different HLA-DP allotypes. Differences in electrostatics originate from the shape, specific disposition, and variation in the negatively charged groups around the pocket. The more negative the pocket potential, the greater the odds of developing CBD estimated from reported epidemiologic studies. Adverse impact is caused by charged substitutions in positions 55, 56, 69, 84, and 85, namely, the exact same loci identified as genetic markers of CBD susceptibility as well as cobalt-lung hard metal disease. These findings suggest that certain substitutions may promote an involuntary cation-binding site within a putatively metal-free peptide-binding pocket and therefore change the innate specificity of antigen recognition.

Skin as a route of exposure and sensitization in chronic beryllium disease.

Chronic beryllium disease is an occupational lung disease that begins as a cell-mediated immune response to beryllium. Although respiratory and engineering controls have significantly decreased occupational beryllium exposures over the last decade, the rate of beryllium sensitization has not declined. We hypothesized that skin exposure to beryllium particles would provide an alternative route for sensitization to this metal. We employed optical scanning laser confocal microscopy and size-selected fluorospheres to demonstrate that 0.5- and 1.0- micro m particles, in conjunction with motion, as at the wrist, penetrate the stratum corneum of human skin and reach the epidermis and, occasionally, the dermis. The cutaneous immune response to chemical sensitizers is initiated in the skin, matures in the local lymph node (LN), and releases hapten-specific T cells into the peripheral blood. Topical application of beryllium to C3H mice generated beryllium-specific sensitization that was documented by peripheral blood and LN beryllium lymphocyte proliferation tests (BeLPT) and by changes in LN T-cell activation markers, increased expression of CD44, and decreased CD62L. In a sensitization-challenge treatment paradigm, epicutaneous beryllium increased murine ear thickness following chemical challenge. These data are consistent with development of a hapten-specific, cell-mediated immune response following topical application of beryllium and suggest a mechanistic link between the persistent rate of beryllium worker sensitization and skin exposure to fine and ultrafine beryllium particles.

Differential regulation of sensitizer-induced inflammation and immunity by acute restraint stress in allergic contact dermatitis.

Previously, we demonstrated that restraint stress applied before chemical sensitization modulates allergic contact dermatitis (ACD) differently than restraint applied before challenge. In this study, we asked if these dichotomous restraint-induced changes reflect modulation of the cutaneous microenvironment or changes in development of antigen-specific immunity in the lymph node (LN) of BALB/c mice. Our data confirm that restraint suppresses T cell-dependent immunity in ACD when applied prior to sensitization or prior to challenge and demonstrate that the stress-induced increase in ear swelling is due to heightened inflammation associated with ACD and is dependent upon the sensitization status of the mouse.

Acute stress modulates the irritant component of sensitizers in allergic contact dermatitis: implications for exposure assessment.

Exposure of skin to noxious environmental stimuli can cause allergic contact dermatitis (ACD), which is a major health risk. Epidemiological studies have determined that 40% of workers report that their jobs are very, or extremely, stressful, and the number of chemicals to which workers are exposed increases each year. We hypothesized that combined exposure to a workplace stressor and a sensitizing chemical would alter the time course and magnitude of the skin immune response. We assessed the mixed exposure of chemical and restraint stress using three potent skin sensitizers, 2,4 dinitrofluorbenzene (DNFB), dicyclohexylcarbodiimide (DCC), and oxazolone, (OXA) on the ear swelling response in stress-susceptible BALB/c mice. Quantitative analyses showed that the dose-response relationship for each chemical followed a cubic trend. Although stress did not alter the shape of the curve, application of restraint stress on day 1 or on day 6 diminished the ear swelling response to 0.1% DNFB. However, if the concentration of the challenge dose was increased to a more irritating concentration, 0.25% DNFB, ear swelling was enhanced. Restraint stress applied on day 6 also increased ear swelling in response to the highly irritating sensitizer DCC, but not to the low-irritancy chemical OXA. These data support the hypothesis that dose-response relationships exist for sensitization with chemical and that restraint stress modulation of the ear swelling response is both chemical specific and dependent on the irritancy potential of the chemical.

Restraint stress and corticotropin releasing hormone modulation of murine cutaneous POMC mRNA.

The skin is a unique immunological defense barrier that protects the organism from occupational and environmental exposures and provides a model system in which to evaluate the interaction of the central nervous system with the peripheral immune response. In the studies presented here, we tested mild, acute restraint stress activation of the cutaneous corticotropin releasing hormone-pro-opiomelanocortin (CRH-POMC) axis. We verified that 2 h restraint stress increased the serum concentration of corticosterone and alpha-melanocyte stimulating hormone. We report for the first time that CRH upregulates POMC mRNA expression in mouse skin in vitro. We also demonstrated, by RT-PCR, that 2,4 di-nitrofluorobenzene (DNFB) upregulates cutaneous POMC mRNA expression, the production of which is suppressed by restraint stress. These data confirm the presence and functionality of two hormones of the hypothalamo-pituitary axis in the skin and suggest that activation of the central hypothalamo-pituitary-adrenal axis may over ride activation of the cutaneous CRH-POMC mechanism in the development of DNFB-stimulated allergic contact dermatitis.

Genetic factors modify the risk of developing beryllium disease.

Chronic beryllium disease (CBD) is a debilitating, granulomatous lung disease that occurs in 1 to 5% of exposed workers. Beryllium stimulates a major histocompatibility Class II-restricted, TH1, CD4+ T cell-mediated immune response. The immunological component of the illness, coupled with the small subset of beryllium workers who develop disease, led researchers to hypothesize that genetic factors modify risk of disease. Analysis of human leukocyte antigen (HLA) genes, the T cell receptor, and tumor necrosis factor (TNF)-alpha focused on three critical steps in the development of beryllium specific immunity. Molecular epidemiological analysis of the association of HLA-DP, -DR, and -DQ has implicated HLA-DPB1E69 allelic variants in disease; however, its role in sensitization is unclear. A single report suggested association between HLA-DQB1G86 and progression from sensitization to disease. A beryllium-specific binding motif was identified in CBD-derived T cell clones. Beryllium-stimulated proliferation using HLA-DPB1*0201 and TCRAV22S1/TCRBVb3 T cell receptors (TCRs) confirmed beryllium specificity of these molecules. The G/A transition at -308 in the TNF-alpha promoter was associated with high concentrations of TNF-alpha in bronchoalveolar lavage and to disease severity. Although these studies are continuing, the data confirm the role of genetic factors in the cellular response to beryllium.

Insights into the quantitative relationship between sensitization and challenge for allergic contact dermatitis reactions.

The ability of chemical or pharmaceutical agents to induce allergic contact dermatitis (ACD) is of major health and regulatory concern. As such, tests to identify their sensitizing capacity, such as the guinea pig maximization test and the more recently developed local lymph node assay, are broadly used. Ideally, for risk assessment it is useful to translate results from animal data into establishing safe or no-effect levels for occupational or environmental agents. This, of course, would require consideration of the quantitative relationships between sensitizing and challenge doses as well as other exposure conditions. In the present studies, we modeled two sensitizers, 2,4-dinitrochlorobenzene and squaric acid dibutyl ester, over a large range of concentrations using the LLNA and more traditional tests that measure both sensitization and elicitation responses. Both the sensitization and challenge phases provided similar dose-response curves, demonstrating a threshold followed by a shallow linear increase and eventual plateau at increasing doses. Extending earlier studies by P. S. Friedmann (1994, Immunotoxicology and Immunopharmacology, pp. 589-616, Raven Press, New York) in humans, we observed that the minimum dose required to elicit sensitization or challenge was not static, but rather reflected a "sliding-scale." That is, as the sensitization dose was increased, the concentration required to elicit a challenge response was decreased. Correspondingly, as the challenge dose was increased, the dose required for sensitization was lessened. Taken together, these findings indicate that there is a need to consider dose-response relationships for sensitization and challenge in establishing minimum exposure levels for chemicals that cause ACD.