The Head-off Environmental Asthma in Louisiana (HEAL) study--methods and study population

BACKGROUND

In the city of New Orleans, Louisiana, and surrounding parishes (NOLA), children with asthma were perilously impacted by Hurricane Katrina as a result of disrupted health care, high home mold and allergen levels, and high stress.

OBJECTIVES

The Head-off Environmental Asthma in Louisiana (HEAL) study was conducted to examine relationships between the post-Katrina environment and childhood asthma in NOLA and assess a novel asthma counselor intervention that provided case management and guidance for reducing home mold and allergen levels.

METHODS

Children (4-12 years old) with moderate-to-severe asthma were recruited from NOLA schools. Over 1 year, they received two clinical evaluations, three home environmental evaluations, and the asthma intervention. Quarterly end points included symptom days, medication use, and unscheduled emergency department or clinic visits. A community advisory group was assembled and informed HEAL at all phases.

RESULTS

Of the children (n = 182) enrolled in HEAL, 67% were African American, and 25% came from households with annual incomes < $15,000. HEAL children were symptomatic, averaging 6.6 symptom days in the 2 weeks before baseline, and had frequent unscheduled visits to clinics or emergency departments (76% had at least one unscheduled visit in the preceding 3 months). In this report, we describe study design and baseline characteristics of HEAL children.

CONCLUSIONS

Despite numerous challenges faced by investigators, study staff, and participants, including destroyed infrastructure, disrupted lives, and lost jobs, HEAL was successful in terms of recruitment and retention, the high quality of data collected that will provide insight into asthma-allergen relationships, and the asthma intervention. This success was attributable to using an adaptive approach and refining processes as needed.

Indoor environmental exposures for children with asthma enrolled in the HEAL study, post-Katrina New Orleans

BACKGROUND

Rain and flooding from Hurricane Katrina resulted in widespread growth of mold and bacteria and production of allergens in New Orleans, Louisiana, which may have led to increased exposures and morbidity in children with asthma.

OBJECTIVES

The goal of the Head-off Environmental Asthma in Louisiana (HEAL) study was to characterize post-Katrina exposures to mold and allergens in children with asthma.

METHODS

The homes of 182 children with asthma in New Orleans and surrounding parishes were evaluated by visual inspection, temperature and moisture measurements, and air and dust sampling. Air was collected using vacuum-pump spore traps and analyzed for > 30 mold taxa using bright field microscopy. Dust was collected from the children's beds and bedroom floors and analyzed for mouse (Mus m 1), dust mite (Der p 1), cockroach (Bla g 1), and mold (Alternaria mix) allergens using ELISA.

RESULTS

More than half (62%) of the children were living in homes that had been damaged by rain, flooding, or both. Geometric mean indoor and outdoor airborne mold levels were 501 and 3,958 spores/m3, respectively. Alternaria antigen was detected in dust from 98% of homes, with 58% having concentrations > 10 µg/g. Mus m 1, Der p 1, and Bla g 1 were detected in 60%, 35%, and 20% of homes, respectively, at low mean concentrations.

CONCLUSIONS

Except for Alternaria antigen in dust, concentrations of airborne mold (ratio of indoor to outdoor mold) and dust allergens in the homes of HEAL children were lower than measurements found in other studies, possibly because of extensive post-Katrina mold remediation and renovations, or because children moved into cleaner homes upon returning to New Orleans.

Implementation of evidence-based asthma interventions in post-Katrina New Orleans: the Head-off Environmental Asthma in Louisiana (HEAL) study

BACKGROUND

Childhood asthma morbidity and mortality in New Orleans, Louisiana, is among the highest in the nation. In August 2005, Hurricane Katrina created an environmental disaster that led to high levels of mold and other allergens and disrupted health care for children with asthma.

OBJECTIVES

We implemented a unique hybrid asthma counselor and environmental intervention based on successful National Institutes of Health asthma interventions from the National Cooperative Inner City Asthma (NCICAS) and Inner-City Asthma (ICAS) Studies with the goal of reducing asthma symptoms in New Orleans children after Hurricane Katrina.

METHODS

Children (4-12 years old) with moderate-to-severe asthma (n = 182) received asthma counseling and environmental intervention for approximately 1 year. HEAL was evaluated employing several analytical approaches including a pre-post evaluation of symptom changes over the entire year, an analysis of symptoms according to the timing of asthma counselor contact, and a comparison to previous evidence-based interventions.

RESULTS

Asthma symptoms during the previous 2 weeks decreased from 6.5 days at enrollment to 3.6 days at the 12-month symptom assessment (a 45% reduction, p < 0.001), consistent with changes observed after NCICAS and ICAS interventions (35% and 62% reductions in symptom days, respectively). Children whose families had contact with a HEAL asthma counselor by 6 months showed a 4.09-day decrease [95% confidence interval (CI): 3.25 to 4.94-day decrease] in symptom days, compared with a 1.79-day decrease (95% CI: 0.90, 2.67) among those who had not yet seen an asthma counselor (p < 0.001).

CONCLUSIONS

The novel combination of evidence-based asthma interventions was associated with improved asthma symptoms among children in post-Katrina New Orleans. Post-intervention changes in symptoms were consistent with previous randomized trials of NCICAS and ICAS interventions.

The Environmental Polymorphism Registry: a unique resource that facilitates translational research of environmental disease

BACKGROUND

Dissecting complex disease has become more feasible because of the availability of large-scale DNA resources and advances in high-throughput genomic technology. Although these tools help scientists identify potential susceptibility loci, subjects with relevant genotypes are needed for clinical phenotyping and toxicity studies.

OBJECTIVE

We have developed a resource of subjects and their DNA to use for translational research of environmental disease.

METHODS

More than 15,000 individuals of diverse sex, age, race, and ethnicity were recruited from North Carolina. DNA was isolated from their blood and coded with personal identification numbers linked to their identities. This linked resource of subjects and their DNA-the Environmental Polymorphism Registry (EPR)-allows scientists to screen for individuals with genotypes of interest and invite them to participate in follow-up studies.

DISCUSSION

The EPR is a phenotype-by-genotype resource designed to facilitate translational studies of environmental disease. Based on their genotypes, subjects are invited to participate at all levels of research, from basic laboratory ex vivo cell phenotyping experiments that require viable tissue to in vivo observational studies and clinical trials. Here we report on progress of the EPR since 2008. We also describe a major effort at the National Institute of Environmental Health Sciences (NIEHS) to investigate susceptibility loci in 87 environmental response genes and gene × environment interactions using EPR resources.

CONCLUSION

The EPR is a unique and novel resource and is ideal for genotype-driven translational research of environmental disease. We expect that it will serve as a model for future resources. Such tools help scientists attain their ultimate goals: to identify at-risk populations and develop strategies for preventing and treating human disease.

The Feasibility of Creating a Population-Based National Twin Registry in the United States

Between 4 to 6 million twins exist in the US today who offer scientists a valuable potential resource for conducting behavioral and biomedical research. However, unlike many other countries, there is no national system in the US for identifying twins and eliciting their participation in these important research programs. Therefore, the National Institute of Environmental Health Sciences (NIEHS) is conducting a study to determine the feasibility of creating a national, population-based twin registry in the US. The major goal is to estimate the potential size and characteristics of a national twin registry based on the current twin population in the US, our ability to ascertain and enrol them, and their willingness to participate. Existing US twin cohorts are also being examined in this study as well as alternatives for improving US twin resources should a national twin registry be deemed infeasible. The various options will be compared in terms of possible source populations, generalizability and adequacy for statistically powering various types of etiological studies. Two expert advisory panels have been assembled to assist in the conduct of this study. The Scientific Advisory Panel is charged with providing expertise concerning study goals, design and methodology, and evaluating the study's conclusion. A separate Ethics Advisory Panel is charged with providing expertise on the ethical, legal, and social issues that might be encountered if a national twin registry is ultimately pursued. Having a national population-based twin registry in the US would be advantageous to US scientists and those worldwide. It would provide ample numbers of twin pairs to conduct various types of environmental genomic studies currently not possible with existing US twin resources. It would also allow US scientists to select for characteristics (race, ethnicity, environments, and so on) inherent in our own population. Finally and foremost, it would help to meet the worldwide demand for twin resources which is expected to increase over time, as new genomic and analytical tools become available and new hypotheses emerge concerning the complex interplay between genes, lifestyles and environment.

The feasibility of creating a population-based national twin registry in the United States

Between 4 to 6 million twins exist in the US today who offer scientists a valuable potential resource for conducting behavioral and biomedical research. However, unlike many other countries, there is no national system in the US for identifying twins and eliciting their participation in these important research programs. Therefore, the National Institute of Environmental Health Sciences (NIEHS) is conducting a study to determine the feasibility of creating a national, population-based twin registry in the US. The major goal is to estimate the potential size and characteristics of a national twin registry based on the current twin population in the US, our ability to ascertain and enroll them, and their willingness to participate. Existing US twin cohorts are also being examined in this study as well as alternatives for improving US twin resources should a national twin registry be deemed infeasible. The various options will be compared in terms of possible source populations, generalizability and adequacy for statistically powering various types of etiological studies. Two expert advisory panels have been assembled to assist in the conduct of this study. The Scientific Advisory Panel is charged with providing expertise concerning study goals, design and methodology, and evaluating the study's conclusion. A separate Ethics Advisory Panel is charged with providing expertise on the ethical, legal, and social issues that might be encountered if a national twin registry is ultimately pursued. Having a national population-based twin registry in the US would be advantageous to US scientists and those worldwide. It would provide ample numbers of twin pairs to conduct various types of environmental genomic studies currently not possible with existing US twin resources. It would also allow US scientists to select for characteristics (race, ethnicity, environments, and so on) inherent in our own population. Finally and foremost, it would help to meet the worldwide demand for twin resources which is expected to increase over time, as new genomic and analytical tools become available and new hypotheses emerge concerning the complex interplay between genes, lifestyles and environment.

Cooperation of cyclooxygenase 1 and cyclooxygenase 2 in intestinal polyposis

Membrane arachidonic acid is converted by cyclooxygenase (COX) into prostaglandin (PG) G(2) and then to PGH(2) which is subsequently metabolized to PGE(2) by PGE synthase (PGES). Both COX-1 and COX-2 play critical roles in intestinal polyp formation, whereas COX-2 is also expressed in cancers of a variety of organs. Likewise, inducible microsomal PGES (mPGES-1) is expressed in several types of cancer, although its role in benign polyp formation has not been investigated. We demonstrated recently that most COX-2-expressing cells in the polyps are stromal fibroblasts. Here we show colocalization of COX-1, COX-2 and mPGES in the intestinal polyp stromal fibroblasts of Apc(Delta 716) mice, a model for familial adenomatous polyposis. Contrary to COX-2 that was induced only in polyps >1 mm in diameter, COX-1 was found in polyps of any size. In polyps >1 mm, not only COX-2 but also mPGES was induced in the stromal fibroblasts where COX-1 had already been expressed. Although polyp number and size were markedly reduced in COX-1 (-/-) or COX-2 (-/-) compound mutant Apc mice, both COX-2 and mPGES were induced in the COX-1 (-/-) polyps, whereas COX-1 was expressed in the COX-2 (-/-) polyps. We found also in human familial adenomatous polyposis polyps that COX-2 and mPGES were induced in the COX-1-expressing fibroblasts. On the basis of these results, we propose that COX-1 expression in the stromal cells secures the basal level of PGE(2) that can support polyp growth to approximately 1 mm, and that simultaneous inductions of COX-2 and mPGES support the polyp expansion beyond approximately 1 mm by boosting the stromal PGE(2) production.

Breast-feeding and the prevalence of asthma and wheeze in children: analyses from the Third National Health and Nutrition Examination Survey, 1988-1994

BACKGROUND

Asthma prevalence has increased dramatically in recent years, especially among children. Breast-feeding might protect children against asthma and related conditions (recurrent wheeze), and this protective effect might depend on the duration and exclusivity of the breast-feeding regimen.

OBJECTIVE

We sought to determine whether there is an association between breast-feeding and asthma, recurrent wheeze, or both in children up to 72 months of age and whether the duration and exclusivity of breast-feeding affect this association.

METHODS

Data were from the third National Health and Nutrition Examination Survey, a nationally representative cross-sectional survey conducted from 1988 to 1994. We tested for significant associations between breast-feeding and physician-diagnosed asthma and recurrent wheeze (> or =3 episodes in the past 12 months) before and after adjusting for potential confounders.

RESULTS

Crude analyses showed that breast-feeding was associated with significantly reduced risks for asthma and recurrent wheeze in children 2 to 71 months of age, but after adjusting for potential confounders, these overall protective associations attenuated and were no longer statistically significant. However, 2 new and important associations were revealed after adjusting for confounders: (1) compared with never breast-fed children, ever breast-fed children had significantly reduced odds of being diagnosed with asthma and of having recurrent wheeze before 24 months of age, and (2) among children 2 to 71 months of age who had been exposed to environmental tobacco smoke, those who had ever been breast-fed had significantly reduced risks of asthma and wheeze compared with those who had never been breast-fed.

CONCLUSIONS

Breast-feeding might delay the onset of or actively protect children less than 24 months of age against asthma and recurrent wheeze. Breast-feeding might reduce the prevalence of asthma and recurrent wheeze in children exposed to environmental tobacco smoke.

Susceptibility of cyclooxygenase-2-deficient mice to pulmonary fibrogenesis

The cyclooxygenase (COX)-2 enzyme has been implicated as an important mediator of pulmonary fibrosis. In this study, the lung fibrotic responses were investigated in COX-1 or COX-2-deficient (-/-) mice following vanadium pentoxide (V(2)O(5)) exposure. Lung histology was normal in saline-instilled wild-type and COX-deficient mice. COX-2(-/-), but not COX-1(-/-) or wild-type mice, exhibited severe inflammatory responses by 3 days following V(2)O(5) exposure and developed pulmonary fibrosis 2 weeks post-V(2)O(5) exposure. Western blot analysis and immunohistochemistry showed that COX-1 protein was present in type 2 epithelial cells, bronchial epithelial cells, and airway smooth muscle cells of saline or V(2)O(5)-exposed wild-type and COX-2(-/-) mice. COX-2 protein was present in Clara cells of wild-type and COX-1(-/-) terminal bronchioles and was strongly induced 24 hours after V(2)O(5) exposure. Prostaglandin (PG) E(2) levels in the bronchoalveolar lavage (BAL) fluid from wild-type and COX-1(-/-) mice were significantly up-regulated by V(2)O(5) exposure within 24 hours, whereas PGE(2) was not up-regulated in COX-2(-/-) BAL fluid. Tumor necrosis factor-alpha was elevated in the BAL fluid from all genotypes after V(2)O(5) exposure, but was significantly and chronically elevated in the BAL fluid from COX-2(-/-) mice above wild-type or COX-1(-/-) mice. These findings indicate that the COX-2 enzyme is protective against pulmonary fibrogenesis, and we suggest that COX-2 generation of PGE(2) is an important factor in resolving inflammation.

Genetic disruption of Ptgs-1, as well as Ptgs-2, reduces intestinal tumorigenesis in Min mice

Two isoforms of cyclooxygenase (COX) are known, and to date most studies have implicated COX-2, rather than COX-1, as the isoform involved in colon carcinogenesis. In the present study, we show that homologous disruption of either Ptgs-1 or Ptgs-2 (genes coding for COX-1 or COX-2, respectively) reduced polyp formation in Min/+ mice by approximately 80%. Only COX-1 protein was immunohistochemically detected in normal intestinal tissue, whereas both COX-1 and variable levels of COX-2 protein were detected in polyps. Prostaglandin E2 was increased in polyps compared with normal tissue, and both COX-1 and COX-2 contributed to the PGE2 produced. The results indicate that COX-1, as well as COX-2, plays a key role in intestinal tumorigenesis and that COX-1 may also be a chemotherapeutic target for nonsteroidal anti-inflammatory drugs.

Allergic lung responses are increased in prostaglandin H synthase-deficient mice

To investigate the function of prostaglandin H synthase-1 and synthase-2 (PGHS-1 and PGHS-2) in the normal lung and in allergic lung responses, we examined allergen-induced pulmonary inflammation and airway hyperresponsiveness in wild-type mice and in PGHS-1(-/-) and PGHS-2(-/-) mice. Among nonimmunized saline-exposed groups, we found no significant differences in lung function or histopathology, although PGE(2) was dramatically reduced in bronchoalveolar lavage (BAL) fluid from PGHS-1(-/-) mice, relative to wild-type or PGHS-2(-/-) mice. After ovalbumin sensitization and challenge, lung inflammatory indices (BAL cells, proteins, IgE, lung histopathology) were significantly greater in PGHS-1(-/-) mice compared with PGHS-2(-/-) mice, and both were far greater than in wild-type mice, as illustrated by the ratio of eosinophils in BAL fluid (8:5:1, respectively). Both allergic PGHS-1(-/-) and PGHS-2(-/-) mice exhibited decreased baseline respiratory system compliance, whereas only allergic PGHS-1(-/-) mice showed increased baseline resistance and responsiveness to methacholine. Ovalbumin exposure caused a modest increase in lung PGHS-2 protein and a corresponding increase in BAL fluid PGE(2) in wild-type mice. We conclude that (a) PGHS-1 is the predominant enzyme that biosynthesizes PGE(2) in the normal mouse lung; (b) PGHS-1 and PGHS-2 products limit allergic lung inflammation and IgE secretion and promote normal lung function; and (c) airway inflammation can be dissociated from the development of airway hyperresponsiveness in PGHS-2(-/-) mice.

Disruption of the mouse cyclooxygenase 1 gene. Characteristics of the mutant and areas of future study

Surprisingly, disruption of the COX-1 gene resulted in generally healthy mice. This is in spite of the fact that prostaglandin levels in the tissues examined were reduced by greater than 99%. The results obtained to date with the COX-1 deficient mice indicate that some of the physiological roles previously attributed to COX-1 may not be entirely correct. Ongoing studies with the COX deficient mice are aimed at better defining the physiological roles of the cyclooxygenases and concomitantly the mechanisms by which NSAIDs cause their biological effects.

Differential inhibition of murine prostaglandin synthase-1 and -2 by nonsteroidal anti-inflammatory drugs using exogenous and endogenous sources of arachidonic acid

Mouse embryonic fibroblasts (10T1/2) and Chinese hamster ovary (AS52) cell lines that stably express murine prostaglandin G/H synthase (PGHS)-1 or -2 were used to compare the effects of exogenous and endogenous arachidonic acid (AA) on isozyme-selective inhibition by acetylsalicylic acid, indomethacin, and N-[2-cyclohexyloxyl-4-nitrophenyl] methanesulfonamide (NS-398). The rationale for developing in vitro systems that identify PGHS-2-selective inhibitors is the belief that inhibition of this isoform accounts for the therapeutic benefits of nonsteroidal anti-inflammatory drugs (NSAIDs). Conversely, inhibition of PGHS-1 is believed to cause the toxic effects of NSAIDs, such as gastric and renal damage. When exogenous AA was used, acetylsalicylic acid was a 5- to 10-fold more potent inhibitor of PGHS-1, whereas indomethacin was a 4- to 5-fold more potent inhibitor of PGHS-2. Within the dose range tested (1 x 10(-6) microM to 100 microM), NS-398 was highly selective for PGHS-2. When calcium ionophore A23187 was used to mobilize endogenous AA, acetylsalicylic acid and indomethacin equipotently inhibited both PGHS-1 and PGHS-2 isozymes. NS-398 remained highly selective for PGHS-2 in 10T1/2 and AS52 cells but also effectively (100%) inhibited PGHS-1 in AS52 cells. Pharmacological data derived using endogenous AA correlated better with the anti-inflammatory efficacy of these NSAIDs in laboratory animals and with the therapeutic/toxic activities of these NSAIDs in rheumatoid arthritic patients. Therefore, screening for PGHS-selective NSAIDs may best be conducted in intact cells that express high levels of each isozyme using endogenous sources of AA.

Relative activities of retrovirally expressed murine prostaglandin synthase-1 and -2 depend on source of arachidonic acid

We have developed derivatives of mouse embryonic fibroblasts (10T1/2) and Chinese hamster ovary (AS52) cells that stably express high levels of murine prostaglandin synthase-1 or -2 (PGHS-1 or -2). The cDNAs were transferred using retroviral vectors and the resulting G418-resistant clones were analyzed for prostaglandin E2 (PGE2) production. Specific expression was confirmed by Western and Northern analyses. Enzyme activities, protein, and message levels peaked 1 (10T1/2) or 2 (AS52) days after seeding but decreased as cells became density arrested. Upon subculturing, enzyme activities returned to their initial high levels. With 10 microM exogenous arachidonic acid (AA) as the substrate, PGHS-1 activities were approximately 3- to 5-fold higher than PGHS-2 activities. Conversely, when exogenous AA was left out of the medium and only endogenous AA was available as substrate, enzyme activities were lower; but PGHS-2 activities were 5-fold (10T1/2) or 1.5-fold (AS52) higher than PGHS-1 activities. Following phorbol ester treatment to stimulate endogenous AA release, PGHS-2 activities increased over time and by 6 hours, were 4-fold (10T1/2) or 2-fold (AS52) higher than PGHS-1 activities. However, when calcium ionophore A23187 was used to stimulate endogenous AA release, maximum PGHS activities occurred within 30 min of treatment; PGHS-1 activities were equal to (10T1/2) or 2-fold higher (AS52) than PGHS-2 activities. Because these cell lines allow us to measure specific PGHS activity in intact cells, we were able to demonstrate that the relative activities of the two PGHS isozymes depend on the source of AA (exogenous versus endogenous) or biochemical stimulus used to mobilize endogenous AA (A23187 versus phorbol ester). These data suggest that PGHS-1 and PGHS-2 preferentially utilize different pools of AA and may be modulated through different stimulus-initiated pathways.

Prostaglandin synthase 1 gene disruption in mice reduces arachidonic acid-induced inflammation and indomethacin-induced gastric ulceration

Cyclooxygenases 1 and 2 (COX-1 and COX-2) are key enzymes in prostaglandin biosynthesis and the target enzymes for the widely used nonsteroidal anti-inflammatory drugs. To study the physiological roles of the individual isoforms, we have disrupted the mouse Ptgs1 gene encoding COX-1. Homozygous Ptgs1 mutant mice survive well, have no gastric pathology, and show less indomethacin-induced gastric ulceration than wild-type mice, even though their gastric prostaglandin E2 levels are about 1% of wild type. The homozygous mutant mice have reduced platelet aggregation and a decreased inflammatory response to arachidonic acid, but not to tetradecanoyl phorbol acetate. Ptgs1 homozygous mutant females mated to homozygous mutant males produce few live offspring. COX-1-deficient mice provide a useful model to distinguish the physiological roles of COX-1 and COX-2.

Retroviral mediated expression of human cytochrome P450 2A6 in C3H/10T1/2 cells confers transformability by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)

In order to develop more efficient in vitro systems for the study of pro-mutagenic or pro-carcinogenic chemicals, we have produced transgenic C3H/10T1/2 cell lines expressing human cytochrome P450 (CYP) 2A6. A retroviral vector containing the cDNA was packaged in psi-2 cells, and used to infect C3H/10T1/2 cells. From 100 G418-resistant clones initially isolated, three cell lines were chosen for further study based upon their morphologies, growth rates and CYP2A6-dependent coumarin 7-hydroxylase activities. Infected clone 10T1/2-04, like the 10T1/2 cells, had no detectable CYP2A6 enzyme activity, while clones 10T1/2-10 and 10T1/2-29 had microsomal CYP2A6 enzyme activities within the range found in human liver microsomes. CYP2A6 protein levels were in agreement with the observed enzyme activities. Southern blots revealed that cells from clone 10T1/2-04 contained a vector lacking the CYP2A6 cDNA, while cells from clones 10T1/2-10 and 10T1/2-29 contained multiple full-length inserts. Southern analysis also indicated the presence of an endogenous CYP2A6 ortholog in the four cell lines. All cell lines exhibited about equal sensitivity to induction of cytotoxicity and conversion to ouabain resistance by the direct acting mutagen N-methyl-N'-nitro-N-nitrosoguanidine. The four lines were also about equally sensitive to transformation by benzo[a]pyrene, a chemical requiring metabolic activation. However, only clones 10T1/2-10 and 10T1/2-29, which express CYP2A6 activity, were mutated and morphologically transformed by the tobacco specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone.